WO2025215127A1

WO2025215127A1 - Formulation of metal alkoxide as precursor of a metal oxide coating layer

Info

Publication number: WO2025215127A1
Application number: PCT/EP2025/059823
Authority: WO
Inventors: Simon SIEMIANOWSKI; Andreas BERKEFELD; Manuel HAMBURGER; Oliver Doll
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2024-04-12
Filing date: 2025-04-10
Publication date: 2025-10-16
Anticipated expiration: 2026-10-12

Abstract

The present invention relates to a formulation for preparing an optical layer containing a metal oxide. The formulation may exhibit at least one of properties as an advanced material or as a high performance material. The formulation may be used in the nanotechnology process to make semiconductor device/display device application, for example semiconductor chip, or a liquid crystal, quantum dot, OLED display fabricated on a substrate controlled by semiconductors.

Description

FORMULATION OF METAL ALKOXIDE AS PRECURSOR OF A METAL OXIDE COATING LAYER

Field of the invention

The present invention relates to a formulation for preparing an optical layer containing a metal oxide, method for preparing a formulation, use of a formulation, method for preparing a composite, a composite, an optical device and a display device.

Background Art

Leading-edge optical devices typically include optical gratings made from composite materials supported by a substrate, featuring complex interlaced patterns composed of various layers or stacks. Usually, the creation of such complex and interlaced patterns demands for structuring processes, which become increasingly challenging with decreasing size of structural dimensions to be prepared.

In addition to a wide range of possible uses in various fields of application, such as in spectrometers or in optical storage systems (CD, DVD, etc.), diffractive gratings are the core components of so-called XR devices, mostly glasses. In this context, R stands for the term reality and X denotes different attributes such as, for example, virtual, augmented, mixed and so forth. Hence, diffractive gratings form part of the core of the so-called optical engine in XR devices, specifically in augmented reality and mixed reality glasses. Virtual reality glasses, when built as a head mounted display, are often composed of a conventional liquid crystal (LC) organic light emitting diode (OLED) display being embedded in the device directly in front of the users’ eyes, and thus do not necessarily require diffractive gratings. In contrast, augmented and mixed reality glasses are designed that way to enable consumers to obtain visual impressions of their environment, at its best as if they would not wear any glasses at all.

However, they also make it possible to provide and serve digital information and to also project it into the field of vision of individuals. Additional digital information is gathered from recognizing and analyzing the environment, the individual inspects or is currently looking at. In order to convey and project supporting digital information into the eyes of an individual, the augmented or mixed reality glasses are equipped with an information supply unit, which is coupled to an optical waveguide system that transports the optically coded supporting information through it directly to the lens of the glasses. Here, the information passes a diffractive grating which couples the incident light into the lens and splits it according to its angular information and its spectral bands by diffraction. After incoupling of the light, the lens serves as waveguide enabling transport of the light to and into the pupil of an individual. The location of light incoupling is independent of any preferred position and thus of the implication of technical needs. The direction of traversal of light within the lenses is determined by the diffractive grating diffracting or splitting the light. At certain positions in the lens, a second and a third diffractive grating serves for changing the direction of light traversal and thereby enforcing the light to be projected into pupil of the user. The light traversal in the glasses is accomplished by total internal reflection (TIR) of the light, thus bouncing several times between the glass interfaces until reaching another diffractive grating, which changes the internal TIR direction of the light (see Figure 2). The second and third grating are geometrically aligned in different directions with respect to the first and incoupling grating, e. g. by a certain angular distortion of the longitudinal axis, thus allowing to change the direction of propagation of totally internally reflected light. Needless to say, the lens itself or the material of which lenses are made of shall not be absorbing. Otherwise, the supportive information never reaches the pupil of the user or only with strongly depleted light intensity. The process works regardless of the use of reflection or transmission gratings. Usually, the lenses are equipped with both types of gratings to properly guide the light. While there are differences in the optical performance of reflection and transmission gratings, these differences are not relevant to the current invention. The basic structure of the gratings is very similar, which is more important at this point.

Nevertheless, there are different designs and structures such as surface relief (SR) or volume phase holographic (VPH) gratings to achievewaveguiding. Both types are very similar in appearance. In the simplest case, the gratings are somehow mounted onto the surface of a waveguiding material, here the lens. The grating itself is composed of an array of fine structures, mostly trenches of a first material type Material 01 with a refractive index Rl 01 , however, not limited thereto. The geometrical shape of the trenches may be manifold, from rectangular, over V-shaped trenches, U-shaped and there like. The width, including structures with different widths, the geometrical form of the trenches, their pitch as well as their depth, including different depths, are specially designed to influence the diffraction pattern of the incident light to be diffracted.

In case of VPH gratings, the trenches or structures of a first material type (Material 01 ) having a refractive index (Rl 01 ) are filled by a second material type (Material 02) having a refractive index (Rl 02), wherein Rl 02 is incrementally different from Rl 01 (see Figures 1 and 3). For the sake of completeness, it should be mentioned that Material 01 or Material 02 may be composed of a stack of structured layers, each containing a different material composition with different refractive index, stacked on top of each other, thereby forming Material 01 or Material 02 having an effective or graded refractive index Rl 01 or Rl 02, respectively. Incidentally, the (effective or graded) refractive indices Rl 01 and Rl 02 depend on the refractive index of the waveguide or the lens from which the glasses are made of. If a glass lens with high refractive index (n03 > 1 .46) is used, the (effective or graded) refractive indices of Material 01 and Material 02 are considered to be higher than that of the lens itself, whereby a Rl value of 2.0 can be reached and exceeded. Surface relief (SR) gratings may look similar and may also include a second type of material as a filler for the trenches, but the trenches can also be just air. High performance gratings, especially those of VPH-type, may be manufactured using standard lithography and deposition techniques known from micro-fabrication such as, for example, the manufacturing of integrated circuits.

Such standard techniques typically include physical vapor deposition (PVD) or chemical vapor deposition (CVD) processes and often suffer from incomplete gap filling due to unfavourable deposition and/or layer growth deposition properties including increased deposition and/or growth rates at comers and edges. Such incomplete gap filling results in the formation of voids within the structures to be filled by the PVD- and CVD-materials. In addition to the formation of voids, the surface of the substrate is covered by a PVD and/or CVD layer that is almost as thick as the maximum depth of the deepest structure to be filled by the deposited gap filling material (see Figures 4 and 5). In some applications, however, it may be necessary to expose the surface of the substrate so that it is available for further processing. Consequently, undesired overburden layers from PVD or CVD need to be removed, for example by chemical mechanical planarization (CMP) without harming the original substrate surface underneath. Although CMP is very well established in the process of manufacturing integrated circuits, CMP is a time consuming and costly process and can be seen as a potential economic drawback for mass production of leading-edge optical devices, particularly the mass production of diffractive gratings. It would therefore be desirable to have a solution for an advanced and cost-efficient manufacturing of optical gratings where gap filling does not require CMP (see Figure 6).

For that reason, more cost-effective production technology allowing for lower cost of ownership is required. Summary of the invention

The inventors newly have found that there are still one or more of considerable problems for which improvement is desired, as listed below: providing a printable formulation containing a metal alkoxide for preparing an optical layer/composite realizing a sufficiently high refractive index of a printed layer after curing; providing a formulation containing a metal alkoxide which enables to prepare an optical layer having improved density and/or crack-less or crack-free property, providing a formulation containing a metal alkoxide which show improved filling up of nano-scaled cavities, trenches or nano-scaled gaps after curing of the printed formulation; providing a formulation containing a metal alkoxide for preparing an optical layer, which enables good dispersion in the formulation; simpler and/or more cost efficient method for preparing an optical layer/composite with using a formulation containing a metal alkoxide; realizing a more stable formulation, zero or reduced decomposition of co-solvent in the formulation, zero or reduced viscosity change of the formulation, providing a suitable formulation for ink jetting and/or realizing continuous inkjet printing.

The inventors aimed to solve one or more of the above-mentioned problems.

Then, the present inventors have surprisingly found that one or more of the above-described technical problems can be solved by the features as defined in the claims.

Namely, it is found a novel formulation for preparing an optical layer containing a metal oxide, preferably for preparing a composite, more preferably for preparing a layered composite, comprising at least, essentially consisting of or consisting of;

- a metal alkoxide containing a metal element selected from the group consisting of group 1 elements of the periodic table, group 4 elements, group 5 elements, group 6 elements, group 12 elements, group 14 elements and group 15 elements of the periodic table;

- a solvent selected from one or more members of the group consisting of alcohols, glycols, esters and amides.

In another aspect, the present invention further relates to method for preparing a formulation of the present invention, containing at least, essentially consisting of, or consisting of, the following steps;

(X1 ) dissolving a metal alkoxide in solvent 1 to form a metal alkoxide solution (X1 ); wherein said metal alkoxide contains a metal element selected from the group consisting of group 1 elements of the periodic table, group 4 elements, group 5 elements, group 6 elements, group 12 elements, group 14 elements and group 15 elements of the periodic table;

(X2) optionally dissolving an acid in solvent 2, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids to form an acid solution;

(X3) optionally adding said acid solution obtained in step (X2) to the metal alkoxide solution (X1 ) to form metal alkoxide solution (X3);

(X4) mixing water and solvent 3 to form an aqueous solvent; and

(X5) adding said aqueous solvent to the metal alkoxide solution (X1 ) obtained in step (X1 ) or the metal alkoxide solution (X3);

(X6) optionally dissolving an acid and water in solvent 4, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids to form an acid solution to form an aqueous acid solution (X6);

(X7) optionally adding said aqueous acid solution (X6) to the metal alkoxide solution (X1 ),

- wherein at least one of the solvents 1 to 4 contains a solvent selected from one or more members of the group consisting of alcohols, glycols, esters and amides. In another aspect, the present invention also relates to use of the formulation of the present invention for preparing an optical layer containing a metal oxide.

In another aspect, the present invention further relates to a method for preparing a composite containing a metal oxide; comprising at least, essentially consisting of or consisting of, the following steps (a) and (b):

(a) providing the formulation of the present invention onto a surface of a substrate; and

(b) applying a thermal treatment to the formulation provided on the surface of the substrate to convert at least a part of the metal alkoxide of the formulation to a metal oxide.

In another aspect, the present invention further relates to a composite, preferably being a layered composite, derived from the formulation of the present invention.

In another aspect, the present invention further relates to a composite, preferably being a layered composite, obtained by the method of the present invention.

In another aspect, the present invention further relates to an optical device comprising at least the composite of the present invention, and a substrate comprising a patterned surface or an uneven surface.

In another aspect, the present invention further relates to a display device comprising at least one functional medium configured to direct and modulate a light or configured to emit light; and the composite of the present invention.

Technical effects of the invention

The present invention may provide one or more of following effects; providing a printable formulation containing a metal alkoxide for preparing an optical layer/composite realizing a sufficiently high refractive index of a printed layer after curing; providing a formulation containing a metal alkoxide which enables to prepare an optical layer having improved density and/or crack-less or crack-free property, providing a formulation containing a metal alkoxide which show improved filling up of nano-scaled cavities, trenches or nano-scaled gaps after curing of the printed formulation; providing a formulation containing a metal alkoxide for preparing an optical layer, which enables good dispersion in the formulation; simpler and/or more cost efficient method for preparing an optical layer/composite with using a formulation containing a metal alkoxide; realizing a more stable formulation, zero or reduced decomposition of co-solvent in the formulation, zero or reduced viscosity change of the formulation, providing a suitable formulation for ink jetting and/or realizing continuous inkjet printing.

Preferred embodiments of the present invention are described hereinafter and in the dependent claims.

Brief description of the figures

Fig. 1 : Schematic cross-sectional view of a VPH grating with a Material 01 and a Material 02, wherein the refractive index IR 01 of Material 01 is incrementally different to the refractive index IR 02 of Material 02.

Fig. 2 : Schematic cross-sectional view of a VPH grating enabling light diffraction (transmissive case) including propagation of diffracted light within waveguide (e.g. lens) by total internal reflection.

Fig. 3 : Schematic cross-sectional view of a VPH grating providing gaps (trenches) to be filled with a high refractive index material (Material 02), wherein the refractive index of Material 02 is incrementally different form the refractive index of Material 01 flanking the gaps (trenches).

Fig. 4: Schematic representation of PVD- or CVD-mediated gap filling process and removal of undesired overburden. Fig. 5 : Schematic representation of PVD- or CVD-mediated gap filling process creating and leaving voids within gaps and deposited layers.

Fig. 6 : Schematic representation of gap filling process using formulations containing inventive metal complex or formulations thereof being converted to metal oxides.

Fig 7 : shows the results of TEM analysis of samples 1 to 6.

Fig 8 : shows the results of TEM analysis of Working example 17(sample 7) Fig. 9a: shows the results of TEM analysis of Working example 18

Fig. 9b: shows the results of TEM analysis of Working example 19

List of reference signs

1. Material 02 with Rl 02

2. Material 01 with Rl 01

3. Substrate (e.g. glass)

4. Diffraction of incident light represented by broad arrow

5. Total internal reflection of light (TIR)

6. Waveguide

7. Structured layer stack with gaps (trenches)

8. Substrate (e.g. glass or silicon)

9. Overburden of material (e.g. high refractive index material or high etch resistant material)

10. Material (e.g. high refractive index material or high etch resistant material) providing gap fill

11 . Voids

12. Formulation (e.g. ink) of high refractive index material (e.g. metal oxide precursor)

13. High refractive index material (e.g. metal oxide) providing gap fill with optional concave geometry

14. Overburden layer (optional)

15. Energy Definition of the terms

In the context of the present invention, the plural term “formulation media” as used herein, denote one or more compounds serving as a solvent, suspending agent, carrier and/or matrix for the metal alkoxide and any other component included in the formulation. Formulation media are generally inert compounds that do not react with said metal alkoxide and said other components. Formulation media may be liquid compounds, solid compounds or mixtures thereof. Typically, formulation media are organic compounds.

The term “optical device” as used herein, relates to a device containing one or more optical components for forming a light beam including, but not limited to, gratings, lenses, prisms, mirrors, optical windows, filters, polarizing optics, UV and IR optics, and optical coatings. Preferred optical devices in the context of the present invention are augmented reality (AR) glasses and/or virtual reality (VR) glasses.

The term “display device” as used herein, is a kind of an optical device configured to output/present information in visual or tactile form. Examples are Liquid crystal display (LCD), Light emitting diode display (LED display), organic light emitting display (OLED), micro-LED display, quantum dot display (QLED), AR/VR display, plasma (PDP) display, electroluminescent (ELD) display.

Detailed description of the invention

The present invention relates to a formulation for preparing an optical layer containing a metal oxide, preferably for preparing a composite, more preferably for preparing a layered composite, comprising at least, essentially consisting of or consisting of;

- a solvent selected from one or more members of the group consisting of alcohols, glycols, esters and amides, preferably it is selected from oligoglycols, more preferably it is selected from oligo-ethylene and oligopropylene glycols, even more preferably it is selected from one or more members of the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol, hexaethylene glycol, octaethylene glycol, dipropylene glycol, tripropylene glycol and tetrapropylene glycol.

- Metal alkoxides

According to the present invention, the formulation contains said metal alkoxide containing a metal element selected from the group consisting of group 1 elements of the periodic table, group 4 elements, group 5 elements, group 6 elements, group 12 elements, group 14 elements and group 15 elements of the periodic table.

As said metal alkoxide, publicly available one can be used.

In a preferred embodiment of the present invention, said metal alkoxide is represented by any one of following chemical formulae (I) to (VI):

M^a1OR^a1 - (I)

M^a2(OR^a1)(OR^a2) - (II)

M^a3(OR^a1)(OR^a2)(OR^a3) - (III)

M^a4(OR^a1)(OR^a2)(OR^a3)(OR^a4) - (IV)

M^a5(OR^a1)(OR^a2)(OR^a3)(OR^a4)(OR^a5) - (V)

M^a6(OR^a1)(OR^a2)(OR^a3)(OR^a4)(OR^a5)(OR^a6) - (VI) wherein

M^a1 is a monovalent alkali metal, preferably M^a1 is K, Na or Li;

M^a2 is a divalent metal, preferably M^a2 is selected from Zn or Sn;

M^a3 is a trivalent metal, preferably M^a3 is Bi; M^a4 is a quadrivalent metal selected from Zr, Ti or Hf;

M^a5 is a pentavalent metal selected from V, Nb or Ta;

M^a6 is Mo or W; and

R^a1 , R^a2, R^a3, R^a4, R^a5 and R^a6 are each independently selected from a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3-25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups and/or one or more adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, and where one or more H atoms may be replaced by D;

According to the present invention, the total amount of the metal alkoxide in the formulation is in the range from 0.1 to 40wt.% based on the total amount of the formulation, preferably it is in the range from 1 to 35wt%, more preferably from 2 to 30wt%, even more preferably from 3 to 28wt%.

-Solvent

According to the present invention, the solvent in the formulation is selected from one or more members of the group consisting of alcohols, glycols, esters and amides, preferably it is selected from oligo-glycols, more preferably it is selected from oligo-ethylene and oligo-propylene glycols, even more preferably it is selected from one or more members of the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol, hexaethylene glycol, octaethylene glycol, dipropylene glycol, tripropylene glycol and tetrapropylene glycol.

It is believed that by using these specific type of high Boiling Point solvents, reaction speed can be controlled after printing during heating. Also, the above-mentioned solvents have good compatibility with metal alkoxide used in the present invention. It is considered these solvents are also suitable for printing, and/or filling up of cavities and structures.

After printing, deposition and fill up of structures, at least a part of the material as the metal oxide precursor need to become converted into the respective metal oxides by any known means know to the persons skilled in the art (thermally, photochemically, etc.).

To further optimize formulation properties, another solvent preferably in aqueous alcoholic solution like PGME can be added. More details of the additional solvent is described below in the section of “Additional solvent”.

-Acid

According to the present invention, the formulation may additionally contain an acid selected from one or more members of the group consisting of sulfonic acids, amine hydrochlorides and carboxylic acids. It is believed that the acid can function as a reaction mediator, and it also works to generate sol-gel type formulation.

In a preferred embodiment of the invention, said sulfonic acid is represented by following chemical formula (I).

R^y1SO₃H - (I) wherein R^y1 is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups R^yx;

R^yx is at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents R^yx here may optionally form a mono- or polycyclic, aliphatic ring system with one another; said amine hydrochloride is represented by following chemical formula (II)

HCI - R^y2 - (II) wherein

R^y2 is selected from the group consisting of N2H4, ammonia, hydroxylamine, imidazole and 1 ,4-diazabicyclo[2.2.2]octane; and/or said carboxylic acid is represented by following chemical formula (III)

R^y3 - COOH - (III) wherein

R^y3 is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups R^yx; R^yx is at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents R^yx here may optionally form a mono- or polycyclic, aliphatic ring system with one another.

In some preferred embodiments, the acid is an amine hydrochloride represented by following chemical formula (II) HCI - R^y2 - (II) wherein

R^y2 is selected from the group consisting of N2H4, ammonia, hydroxylamine, imidazole and 1 ,4-diazabicyclo[2.2.2]octane. As such amine hydrochloride, hydrazinium monohydrochloride can be used preferably.

In some preferred embodiments, said acid is a sulfonic acid represented by following chemical formula (I).

R^y1SO₃H - (I) wherein

R^y1 is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups R^yx;

R^yx is at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents R^yx here may optionally form a mono- or polycyclic, aliphatic ring system with one another.

As such sulfonic acid, methane sulfonic acid (MSA), para-toluene sulfonic acid (p-TSA), benzene sulfonic acid (BSA) can be used preferably. It is believed that these sulfonic acids are particularly suitable for this invention to realize improved gap filling property and it works well even with small amount like described below ranges.

In a preferred embodiment of the present invention, the stoichiometric mole ratio of the acid and the metal alkoxide is in the range from 0.01 : 100 to 120:100, preferably from 0.5:100 to 100:100 (the stoichiometric mole amount of the acid: total amount of the metal alkoxide), more preferably the relative mole amount of the acid based on the total amount of the metal alkoxide is in the range from 1 : 100 to 50: 100, furthermore preferably 2: 100 to 10:100 (the relative mole amount of the acid: total amount of the metal alkoxide).

It is believed that when the stoichiometric mole ratio of the acid and the metal oxide precursor is in the above-mentioned range, it improves film stability, improves gap filing property and/or provides improved refractive index value.

Namely, the stoichiometric mole ratio of the acid and the metal alkoxide 100:100 (acid: metal alkoxide) or less is recommended from the viewpoint of better film stability and/or improved refractive index value of the obtained film. It is preferably 50:100 or less, more preferably 10:100 or less.

From the viewpoint of improved gap filling property, the stoichiometric mole ratio of the acid and the metal alkoxide 0.1 :100 (acid: metal alkoxide) or more is recommended. It is preferably 0.5:100 or more, more preferably 1 :100 or more.

-Additional solvent

In a preferred embodiment, the formulation further contains another solvent selected from secondary alcohols having no, one or two alkoxy groups or one or two alkyl groups where one or more non-adjacent groups of said alkyl group is replaced by oxygen atom, or secondary linear or branched >C3 alcohols, preferably it is selected from one or more members of 2- propanol, 2-butanol, 2-pentanol and 3-pentanol, preferably secondary linear or branched >C4 alcohols; preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3- dialkyl ethers or combination of propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers and glycerol 1 ,3-dialkyl ethers.

It is believed that the additional solvents described above has a good compatibility with the solvent of the formulation and does not disturb/prevents the technical effects of using solvent of the formulation. Namely said additional solvent has a good compatibility with the solvent of the formulation selected from one or more members of the group consisting of alcohols, glycols, esters and amides, preferably it is selected from oligoglycols, more preferably it is selected from oligo-ethylene and oligopropylene glycols, even more preferably it is selected from one or more members of the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol, hexaethylene glycol, octaethylene glycol, dipropylene glycol, tripropylene glycol and tetrapropylene glycol (high Boiling point solvents).

It is believed that said additional solvent may also chemically interact with the metal oxide precursor in the formulation and allows controlling the rate of formation of a continuous metal oxide material during formulation deposition and final thermal curing process. Also, the above-mentioned additional solvents have good compatibility with metal alkoxide used in the present invention. It is considered these additional solvents are also suitable for printing, and/or filling up of cavities and structures.

In a preferred embodiment, the formulation contains water, and the stoichiometric amount of water is in the range from 100 to 400 mol% based on the total amount of metal alkoxide, preferably the stoichiometric amount of water based on the total amount of the metal alkoxide is in the range from 150 to 300 mol%, even more preferably from 180 to 270 mol%.

It is believed that the conversion of the metal alkoxide to the corresponding high refractive index metal oxide becomes less sensitive to the water content of the environment, thereby resulting in a more reproducible and controlled process.

-Method for preparing a formulation

In another aspect, the present invention also relates to a method for preparing a formulation of the present invention. Said method comprises at least, essentially consisting of or consisting of, the following steps:

(X1 ) dissolving a metal alkoxide in solvent 1 , preferably said solvent 1 is dry or water-free solvent to form a metal alkoxide solution (X1 ); wherein said metal alkoxide contains a metal element selected from the group consisting of group 1 elements of the periodic table, group 4 elements, group 5 elements, group 6 elements, group 12 elements, group 14 elements and group 15 elements of the periodic table;

(X2) optionally dissolving an acid in solvent 2, preferably said solvent 2 is dry or water-free solvent, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids to form an acid solution;

(X4) mixing water and solvent 3 to form an aqueous solvent; and

(X6) optionally dissolving an acid and water in solvent 4, preferably said solvent 4 is dry or water-free solvent, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids to form an acid solution to form an aqueous acid solution (X6); (X7) optionally adding said aqueous acid solution (X6) to the metal alkoxide solution (X1 ),

- wherein at least one of the solvents 1 to 4 contains a solvent selected from one or more members of the group consisting of alcohols, glycols, esters and amides, preferably it is selected from oligo-glycols, more preferably it is selected from oligo-ethylene and oligo-propylene glycols, even more preferably it is selected from one or more members of the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol, hexaethylene glycol, octaethylene glycol, dipropylene glycol, tripropylene glycol and tetrapropylene glycol. preferably at least one of the solvents 1 to 4 contains a solvent selected from one or more members of the group consisting of propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and/or propylene glycol monopropyl ether; glycerol 1 ,3-dialkyl ethers, 1 ,3-dimethoxy-2-propanol, more preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers; a secondary linear or branched >C3 alcohols, preferably it is selected from 2-propanol, 2-butanol, 2-pentanol, 3-pentanol, more preferably it is a linear or branched secondary >C4 alcohol; preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers; or wherein the solvents 1 to 4 contains a solvent selected from one or more members of the group consisting of propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and/or propylene glycol monopropyl ether; glycerol 1 ,3-dialkyl ethers, 1 ,3-dimethoxy-2-propanol, more preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers; a secondary linear or branched >C3 alcohols, preferably it is selected from 2-propanol, 2-butanol, 2-pentanol, 3- pentanol, more preferably it is a linear or branched secondary >C4 alcohol; preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers; and wherein a solvent selected from one or more of members of the group consisting of diethylene glycol, triethylene glycol, hexaethylene glycol, octaethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol and glycerol; is added in any one of the steps (X1 ) to (X7).

Preferably, the total amount of the metal alkoxide added in step (X1 ) is set to be in the range from 0.1 to 40wt.% based on the total amount of the obtained formulation, preferably it is in the range from 1 to 35wt%, more preferably from 2 to 30wt%, even more preferably from 3 to 28wt%.

Preferably, said metal alkoxide is a metal alkoxide containing a group 4 and/or group 5 element of the periodic table as detailly described in the section of “metal alkoxide”.

Preferably, said acid selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids is an acid as described in the section of “Acid” above.

-Use

In another aspect, the present invention also relates to use of the formulation of the present invention for preparing an optical layer containing a metal oxide, preferably for preparing a composite, more preferably for preparing a layered composite.

-Method for preparing a composite containing a metal oxide

In another aspect, the present invention also relates to a method for preparing a composite containing a metal oxide, preferably said metal oxide is selected from metal dioxide, metal mono oxide, or a combination of these; comprising at least the following steps (a) and (b) preferably the following order:

(a) providing the formulation of the present invention onto a surface of a substrate or a surface of an underlayer, preferably by wet deposition process, more preferably by spin-coating or an area selective printing, preferably said area selective printing is an ink-jetting, even more preferably said wet deposition process is spin-coating; and

(b) applying a thermal treatment to the formulation provided on the surface of the substrate or on the surface of an underlayer to convert at least a part of the metal alkoxide of the formulation to a metal oxide.

Preferably said composite being a layered composite, more preferably said layered composite is an optical layer.

-Step (a)

According to the present invention, said formulation may preferably be provided onto a surface of a substrate by wet deposition process. Said wet deposition process is drop casting, coating, or printing. A more preferred coating method is spin coating, spray coating, slit coating, or slot-die coating. A more preferred printing method is flexo printing, gravure printing, inkjet printing, EHD printing, offset printing, or screen printing. Furthermore preferred printing method is spray coating and inkjet printing and the most preferred one is inkjet printing.

Thus, in a preferred embodiment, the formulation is applied onto a surface of a substrate by spin-coating or ink-jetting in step (a). From a viewpoint of cost effective, ink-jetting can preferably be used.

In a preferred embodiment of the present invention, the formulation provided in step (a) of the method is an ink formulation being suitable for inkjet printing. Typical requirements for ink formulations are surface tensions in the range from 20 mN/m to 30 mN/m and viscosities in the range from 5 mPa s to 30 mPa s. Depending on the specific problem to be solved, the formulation needs to be deposited either as a homogeneous, dense and thin layer covering the entire surface of the substrate by a coating method or the formulation needs to be deposited locally in a structured manner, thus requiring a printing method. Both, coating and printing methods require formulations to be formulated in an adequate manner to comply with the physico-chemical needs of the respective coating and printing method as well as to comply with certain needs regarding the surface of the substrate to be coated or printed.

In a preferred embodiment of the method of the present invention, the surface of the substrate is pre-treated by a surface cleaning process. Preferred surface cleaning processes are silicon wafer cleaning processes such as described in W. Kern, The Evolution of Silicon Wafer Cleaning Technology, J. Electrochem. Soc., Vol. 137, 6, 1990, 1887-1892 and in New Process Technologies for Microelectronics, RCA Review 1970, 31 , 2, 185-454. Such silicon wafer cleaning processes include wet cleaning process involving cleaning solvents (e.g. isopropanol (IPA)); wet etching processes involving hydrogen peroxide solutions (e.g. piranha solution, SC1 , and SC2), choline solutions, or HF solutions; dry etching processes involving chemical vapor etching, UV/ozone treatments or glow discharge techniques (e.g. O2 plasma etching); and mechanical processes involving brush scrubbing, fluid jet or ultrasonic techniques (sonification). The surface of the substrate can also be pre-treated by silanization or an atomic layer deposition (ALD) process. The pre-treatment of the surface of the substrate serves to modify the hydrophobicity/hydrophi licity of the surface. This can improve the adhesion and filling characteristics of the optical metal oxide layer on the surface of the substrate.

In a more preferred embodiment, a wet cleaning process involving cleaning solvents (e.g. isopropanol (IPA)) is combined with one or more of a wet etching process involving hydrogen peroxide solutions (e.g. piranha solution, SC1 , and SC2), choline solutions, or HF solutions; dry etching process involving chemical vapor etching, UV/ozone treatments or glow discharge techniques (e.g. O2 plasma etching); and mechanical process involving brush scrubbing, fluid jet or ultrasonic techniques (sonification).

In a most preferred embodiment, a wet cleaning process involving cleaning solvents (e.g. isopropanol (IPA)) is combined with a mechanical process involving brush scrubbing, fluid jet or ultrasonic techniques (sonification) and with a wet etching process involving hydrogen peroxide solutions (e.g. piranha solution, SC1 , and SC2) or HF solutions;

Thus, in a preferable embodiment, in step (a), the formulation is applied to a surface of a substrate by spin-coating or ink-jetting.

In a preferable embodiment, the formulation is at least partly converted on the surface of the substrate to a composite, wherein said composite contains a metal oxide, preferably selected from metal dioxide and/or metal mono oxide; and a metal salt precursor.

In a preferable embodiment, the substrate is a patterned substrate comprising topographical features on the surface thereof.

-Step (b)

It is believed that metal alkoxide in the formulation is at least partly converted in step (b) on the surface of the substrate to a metal oxide to form a composite by exposure to thermal treatment. Said composite is preferably a layered composite. And said solvent is usually removed in step (b). Preferred thermal treatment includes exposure to elevated temperature from 50 to 300 °C, preferably it is from 80 to 250°C, more preferably from 100 to 200°C.

Thermal treatment is not limited to any specific thermal treatment methods or times. Depending on the type of substrate and formulation, a person skilled in the art can determine suitable thermal treatment methods.

In some embodiments of the method for preparing an optical metal oxide layer according to the present invention, the formulation is converted in step (c) on the surface of the substrate to an optical metal oxide layer by prebaking (soft baking) at a temperature from 40 to 150 °C, preferably from 50 to 120 °C, more preferably from 60 to 100 °C; and then baking (hard baking, sintering or annealing) at a temperature from 100 to 600 °C, preferably from 125 to 450 °C, more preferably from 150 to 250 °C.

Pre-baking (soft baking) serves the purpose to remove volatile and low boiling components such as e.g. volatile and low boiling formulation media or additives from the drop casted, coated or printed films. Pre-baking is preferably carried out for a period of 1 to 10 minutes. After pre-baking, layers of substrate adhering films of metal oxide precursor or metal oxide precursor mixtures are obtained. The films may still comprise residual formulation media or additives.

In an alternative preferred embodiment of the method for preparing an optical metal oxide layer according to the present invention, pre-baking is omitted so that the formulation is converted in step (c) on the surface of the substrate to an optical metal oxide layer directly by baking (hard baking, sintering or annealing) at a temperature from 100 to 600 °C, preferably from 125 to 450 °C, more preferably from 150 to 250 °C. Baking (hard baking, sintering or annealing) serves the purpose to convert the material as the metal oxide precursor or metal oxide precursor mixture layers on the substrate into a metal oxide layer. Moreover, the final properties of the metal oxide layer may be adjusted by the baking treatment. Baking is preferably carried out for a period of 1 to 300 minutes, preferably 1 to 60 minutes to achieve a refractive index (Rl) of > 1 .7, preferably > 1.8, more preferably > 1.9, even more preferably > 1.9, most preferably > 2.0.

Pre-baking and baking may be carried out under ambient atmosphere or atmospheres with increased oxygen content in order to decompose unwanted organic components, which can lead to a lower activation energy when the composite is formed.

In a preferred embodiment of the method of present invention, the substrate is a patterned substrate comprising topographical features on the surface thereof, and the layered composite, preferably it is an optical layer, forms a coating layer covering the surface of the substrate and filling said topographical features. As a result, the topographical features are filled by said composition, achieving a leveled surface.

Preferred topographical features include, for example, gaps, grooves, trenches and vias. Topographical features may be distributed uniformly or non-uniform ly over the surface of the substrate. Preferably, they are arranged as an array or grating on the surface of the substrate. It is preferred that the topographical features exhibit variations in lengths, widths, diameters, and aspect ratios. It is preferred that said topographical features have an aspect ratio of 1 :20 to 20:1 , more preferably 1 :10 to 10:1 . The aspect ratio is defined as width of structure to its height (or depth). From the viewpoint of dimension, the depth of the topographical features is preferably in the range from 10 nm to 10 pm, more preferably 50 nm to 5 pm, and most preferably 100 nm to 1 pm. It is also preferred that the topographical features are inclined at a certain angle, such as an angle from 10 to 80°, preferably from 20 to 60°, more preferably from 30 to 50°, most preferably about 40°. Such inclined topographical features are also referred to as slanted or blazed topographical features.

It may also be necessary to fill topographical features locally with optical metal oxide layer, either completely or to a certain level, but not to cover adjacent surfaces of the substrate, where no topographical features to be filled are available.

The substrate is preferably a substrate of an optical device. Preferred substrates are made of inorganic or organic base materials, preferably inorganic base materials. Preferred inorganic base materials contain materials selected from the list consisting of ceramics, glass, fused silica, sapphire, silicon, silicon nitride, quartz, and transparent polymers or resins. The geometry of the substrate is not specifically limited, however, preferred are sheets or wafers.

In step (a) of the method, the formulation is applied onto a surface of a substrate, wherein said surface may be either a surface of a base material of the substrate or a surface of a layer of a material being different from the base material of the substrate, wherein such layer has been formed prior to applying said formulation.

In this way, sequences of different layers (layer stacks) can be formed on top of one another. Such layer stacks may also be structured, wherein such structures typically have dimensions in the nanometer scale, at least with respect to diameter, width and/or aspect ratio. Thus, in a preferable embodiment, in step (b), the formulation is at least partly converted on the surface of the substrate to a composite, preferably it being a layered composite, by baking it at a temperature from 100 to 600 °C, preferably it is from 125 to 450°C, more preferably from 150 to 250°C.

- Composite

In another aspect, the present invention relates to a composite, preferably being a layered composite, preferably said layered composite is an optical layer, obtained or obtainable by the method of the present invention.

In a preferred embodiment of the present invention, the composite comprises at least a metal oxide derived from the formulation and the metal alkoxide of the formulation as a non-converted part of the formulation used in step (a) of the method.

Thus, preferably said metal of the metal oxide is Ti or Zr. More preferably said metal oxide is selected from the group consisting of Titanium oxide, Zirconium oxide or a combination of these.

- Optical device

The present invention relates to an optical device comprising the composite of the present invention, which is preferably obtainable or obtained by the method of the present invention as described above. It is preferred that the optical device is a display device selected from an augmented reality (AR) and/or virtual reality (VR) device. Preferably said composite fills gap of said topographical features, more preferably said composite fills trench of the patterned substrate.

The present invention further relates to an optical device comprising the composite of the present invention, which is prepared by using the formulation according to the present invention as described above. It is preferred that the optical device is an augmented reality (AR) and/or virtual reality (VR) device. Preferably said composite fills gap of said topographical features, more preferably said composite fills trench of the patterned substrate.

- Display device

Finally, the present invention relates to display device comprising at least one functional medium configured to modulate a light or configured to emit light; and the composite, or an optical device of the present invention.

Examples of said display device is selected from a Liquid crystal display (LCD), Light emitting diode display (LED display), organic light emitting display (OLED), micro-LED display, quantum dot display (QLED), ARA/R display, plasma (PDP) display and an electroluminescent (ELD) display.

- Semiconductor device

The present invention also relates to a semiconductor device comprising at least one patterned layer or uneven layer, which is encapsulated by the composite of the present invention. Preferably said composite is directly attached onto the top part of the patterned layer or the top part of the uneven layer to form a void, and air or gas is in the void.

Semiconductor device according to this invention includes all types of semiconductor devices of WSTS (Worle semiconductor Trade Statistics) classification 2021 . It includes discretes, optoelectronics, sensors and actuators, Integrated Circuits (IC) and Total semiconductors of WSTS classification 2021 . Discretes include Diodes, small signal and switching transistors, power transistors, Power Diodes, thyristors, all other discretes. Optoelectoronics includes image sensors, light sensors, laser transmitters, laser pick-ups, couplers. Isolators & switches. IC includes analogs, MOS Micros, Total Logics (MOS & Bipolar), MOS Memories, Total application Specific ICs, Total ICs of the classification of WSTS 2021 . The present invention is further illustrated by the examples following hereinafter which shall in no way be construed as limiting. The skilled person will acknowledge that various modifications, additions and alternations may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims.

Examples

Zirconium tetra-n-butoxide (Zr(Obu)4)

Titanium tetra-n-butoxide (Ti(Obu)4)

Alternatively, Niobium pentaethoxide can also be used preferably.

Reference example 1 : Formulation Zr-0: Zirconium tetra-n-butoxide with 16.9 weight-% nominal solid content.

Formulation Zr-0 as reference example 1 is prepared as follows.

Zirconium tetra-n-butoxide is added to PGME (1 -methoxy-2-propanol: dried over molecular sieves) under argon atmosphere in two neck Schlenk flask connected to inert gas/vacuum line. The solution is stirred at room temperature and a solution of H2O and methanesulfonic acid (MSA) as an acid in PGME is added dropwise at room temperature, affording a clear solution that is stirred for another 60 mins.

The wt% of each components used for fabricating formulation Zr-0 is indicated in table 1 of Zr-0.

Reference example 2: Formulation Ti-0: Titanium tetra-n-butoxide with 15.4 weight-% nominal solid content.

Formulation Ti-0 as reference example 2 is prepared in the same manner as described above in Reference example 1 except for that Titanium tetra- n-butoxide is used instead of Zirconium tetra-n-butoxide.

The wt% and mol% of each component used for fabricating formulation Ti-0 are indicated in table 1 of Ti-0. Working examples 1 to 2: Formulations Zr-1 to Zr-2: Zirconium tetra-n- butoxide and TEG containing formulation

Formulations Zr-1 to Zr-2 are prepared in the same manner as described in Reference example 1 except for that the materials described in Table 1 (Zr- 1 to Zr-2) are used with the described amounts instead of the materials used in Reference example 1.

Working example 3: Formulation Zr-3: Zirconium tetra-n-butoxide, TEG and hydrazinium monohydrochloride containing formulation Formulations Zr-3 is prepared in the same manner as described in Reference example 1 above except for that the materials described in Table 1 (Zr-3) and hydrazinium monohydrochloride as an acid, are used with the described amounts instead of the materials used in Reference example 1 .

Working examples 4: Formulations Ti-1 : Titanium tetra-n-butoxide and TEG containing formulation Formulation Ti-1 is prepared in the same manner as described in Reference example 1 except for that the materials described in Table 1 (Ti-

1 ) are used with the described amounts instead of the materials used in Reference example 1.

Working examples 5: Formulation Ti-2: Titanium tetra-n-butoxide, TEG and hydrazinium monohydrochloride containing formulation Formulation Ti-2 is prepared in the same manner as described in Reference example 1 except for that the materials described in Table 1 (Ti-

2) and hydrazinium monohydrochloride as an acid, are used with the described amounts instead of the materials used in Reference example 1.

Working examples 6 and 7: Formulations Ti-3 and Ti-4: Titanium tetra-n- butoxide and TEG containing formulation Formulations Ti-3 and Ti-4 are prepared in the same manner as described in Reference example 1 except for that the materials described in Table 1 (Ti-3 and Ti-4) are used with the described amounts instead of the materials used in Reference example 1.

Table 1 :

*Solvent 1 : PEG-4 (polyethylene glycol 200, from Merck), TEG: triethylene glycol

Solvent 2: PGME (1 -methoxyl-2-propanol. CAS No. 107-98-2, from Merck)

Reference example 3: preparation of Sample 1 (Zr-0 (50nm, R.T)) Formulation 0 from reference example 1 is spin coated onto an O2 plasma pretreated SisN4/Si substrate having 50nm width trenches to form a spin coated layer. Then the coated layer is baked at 150°C for 5m in. Finally Sample 0 (50nm, 150 °C) is obtained. Filling properties of the obtained sample is observed by TEM analysis. Reference examples 4 to 8: preparation of Sample 2(Zr-0 (150nm, R.T)), Sample 3 (Zr-0 (50nm, 100 °C/5min)), Sample 4 (Zr-0 (150nm, 100 °C/5min)), Sample 5 (Zr-0 (50nm, 200 °C/5min)) and Sample 6 (Zr-0 (150nm, 200 °C/5min))

The above-mentioned samples are fabricated in the same manner as described in Reference example 3 except for that the different conditions disclosed in table 2 are applied instead of the conditions of Reference example 3. Filing properties of the obtained samples are observed by TEM analysis.

Table 2:

According to the outcome of the TEM analysis, samples 1 to 6 all show airgap (the trenches of the substrate are covered by an encapsulation layer obtained from the formulation Zr-0 and within the trenches, air/gas are enclosed as shown in Fig.7.

Working example 17: preparation of Sample 7 (Zr-3(150nm, 100°C/5min)) Formulation Zr-3 from working example 3 (W.E.3) is spin coated onto an O2 plasma pretreated SisN4/Si substrate having 150nm width trenches on the surface. Then the coated layer is baked at 100°C for 5min. Finally, Sample 7 (Zr-3 (150nm, 100°C/5min)) is obtained. The obtained samples is observed by TEM analysis.

According to the outcome of the TEM analysis, Sample 7 (Zr-3 (150nm, 100°C/5min)) show airgap (the trenches of the substrate are covered by an encapsulation layer obtained from the formulation Zr-0 and within the trenches, air/gas are enclosed. Further, the trenches are partly filled by the encapsulation layer as shown in Fig. 8.

The results shows that by adding TEG solvent in working example 7 lead improved gap fill controlling (improved gap filing) even though high amount of a metal alkoxide is in a formulation which easily forms air gap (encapsulation layer).

Working example 18: preparation of Sample 8 (Ti-1 (50nm, 200°C/5min)) Formulation Ti-1 from working example 4 (W.E.4) is spin coated onto an O2 plasma pretreated SisN4/Si substrate having 50nm width trenches on the surface. Then the coated layer is baked at 200°C for 5min. Finally, Sample 8 (Ti-1 (50nm, 200°C/5min)) is obtained. The obtained sample is observed by TEM analysis.

According to the outcome of the TEM analysis, Sample 8 (Ti-1 (50nm, 200°C/5min)) shows airgap (the trenches of the substrate are covered by an encapsulation layer obtained from the formulation Ti-1 and within the trenches, air/gas are enclosed. Further, the trenches of the substrate are partly filled by the encapsulation layer as shown in Fig. 9a.

The results shows that by using TEG solvent in working example 8 leads improved gap fill controlling (improved gap filing) even though high amount of a metal alkoxide is in a formulation which easily forms air gap (encapsulation layer).

Working example 19: preparation of Sample 9 (Ti-2 (50nm, 200°C/5min)) Sample 9 (Ti-2 (50nm, 200°C/5min)) is prepared in the same manner as described in working example 18 except for that the Formulation Ti-2 is used instead of Formulation Ti-1 . The obtained sample is observed by TEM analysis. According to the outcome of the TEM analysis, Sample 9 (Ti-2 (50nm, 200°C/5min)) shows airgap (the trenches of the substrate are covered by an encapsulation layer obtained from the formulation Ti-2 and within the trenches, air/gas are enclosed. Further, the trenches of the substrate are partly filled by the encapsulation layer as shown in Fig. 9b.

The results shows that by using TEG solvent in working example 8 leads improved gap fill controlling (improved gap filing).

Working examples 20 to 22: preparation of Sample 10 (Ti-1 (150nm, 175°C/60min)), Sample 11 (Ti-1 (150nm, 200°C/5min)) and Sample 12(Ti-1 (150nm, 200°C/60min))

Sample 10 (Ti-1 (150nm, 175°C/60min)), Sample 11 (Ti-1 (150nm, 200°C/5min)) and Sample 12(Ti-1 (150nm, 200°C/60min)) are prepared in the same manner as described in Working example 18 except for that the SisN4/Si substrate having 150nm width trenches on the surface is used for fabricating samples 10, 11 and 12 and following different thermal conditions are applied instead of the SisN4/Si substrate and thermal conditions used in Working example 18.

Sample 10: formulation Ti-1 , SisN4/Si substrate having 50nm width trenches, 175°C/60min

Sample 11 : formulation Ti-1 , S isN4/S i substrate having 50nm width trenches, 200°C/5min

Sample 12: formulation Ti-1 , SisN4/Si substrate having 50nm width trenches, 200°C/60min

The obtained samples are observed by TEM analysis.

According to the outcome of the TEM analysis, Samples 10 to 12 all show improved gap filling properties comparing to Reference examples 3 to 8. Namely, Sample 12 shows the best gap filing properties. Working examples 23 to 25: preparation of Sample 13 (Ti-3 (150nm, 175°C/60min)), Sample 14 (Ti-3 (150nm, 200°C/5min)) and Sample 15(Ti-3 (150nm, 200°C/60min))

The samples 13 to 15 are fabricated in the same manner as described in working example 18 except for that the SisN4/Si substrate having 150nm width trenches on the surface is used for fabricating samples 13, 14 and 15 and following different thermal conditions are applied instead of the SisN4/Si substrate and thermal conditions used in Working example 18.

Sample 13: formulation Ti-3, SisN4/Si substrate having 50nm width trenches, 175°C/60min

Sample 14: formulation Ti-3, SisN4/Si substrate having 50nm width trenches, 200°C/5min

Sample 15: formulation Ti-3, SisN4/Si substrate having 50nm width trenches, 200°C/60min

The obtained samples are observed by TEM analysis.

According to the outcome of the TEM analysis, all the samples show improved gap filling properties comparing to Reference examples 3 to 8.

Working examples 26 to 28: preparation of Sample 16 (Ti-4 (150nm, 175°C/60min)), Sample 17 (Ti-4 (150nm, 200°C/5min)) and Sample 18(Ti-4 (150nm, 200°C/60min))

The samples 16 to 18 are fabricated in the same manner as described in working example 18 except for that the SisN4/Si substrate having 150nm width trenches on the surface is used for fabricating samples 16, 17 and 18 and following different thermal conditions are applied instead of the SisN4/Si substrate and thermal conditions used in Working example 18.

Sample 16: formulation Ti-4, SisN4/Si substrate having 50nm width trenches, 175°C/60min

Sample 17: formulation Ti-4, SisN4/Si substrate having 50nm width trenches, 200°C/5min

Sample 18: formulation Ti-4, SisN4/Si substrate having 50nm width trenches, 200°C/60min The obtained samples are observed by TEM analysis.

Claims

1 . Formulation for preparing an optical layer containing a metal oxide, which is preferably used for preparing a composite, more preferably for preparing a layered composite, comprising at least;

2. Formulation of claim 1 , wherein said metal alkoxide is represented by any one of following chemical formulae (I) to (VI):

M^a1OR^a1 - (I)

M^a2(OR^a1)(OR^a2) - (II)

M^a3(OR^a1)(OR^a2)(OR^a3) - (III)

M^a4(OR^a1)(OR^a2)(OR^a3)(OR^a4) - (IV)

M^a5(OR^a1)(OR^a2)(OR^a3)(OR^a4)(OR^a5) - (V)

M^a6(OR^a1)(OR^a2)(OR^a3)(OR^a4)(OR^a5)(OR^a6) - (VI) wherein

M^a1 is a monovalent alkali metal, preferably M^a1 is K, Na or Li;

M^a2 is a divalent metal, preferably M^a2 is selected from Zn or Sn;

M^a3 is a trivalent metal, preferably M^a3 is Bi;

M^a4 is a quadrivalent metal selected from Zr, Ti or Hf; M^a5 is a pentavalent metal selected from V, Nb or Ta;

M^a6 is Mo or W; and

R^a1 , R^a2, R^a3, R^a4, R^a5 and R^a6 are each independently selected from a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3-25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups and/or one or more adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, and where one or more H atoms of the above-mentioned groups may be replaced by D;

3. Formulation of claim 1 or 2, contains an acid selected from one or more members of the group consisting of sulfonic acids, amine hydrochlorides and carboxylic acids.

4. Formulation of any one of preceding claims, said sulfonic acid is represented by following chemical formula (I).

R^y1SO₃H - (I) wherein

R^y1 is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH; and where one or more H atoms of the above- mentioned groups may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups R^yx;

HCI - R^y2 - (II) wherein

Ry² is selected from the group consisting of N2H4, ammonia, hydroxylamine, imidazole and 1 ,4-diazabicyclo[2.2.2]octane; and/or said carboxylic acid is represented by following chemical formula (III)

Rv³ - COOH wherein

Ry³ is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups R^yx;

5. Formulation of any one of preceding claims, wherein the acid is an amine hydrochloride represented by following chemical formula (II)

HCI - R^y2 - (II) wherein

R^y2 is selected from the group consisting of N2H4, ammonia, hydroxylamine, imidazole and 1 ,4-diazabicyclo[2.2.2]octane.

6. Formulation of any one of claims 1 to 4, wherein said acid is a sulfonic acid represented by following chemical formula (I).

R^y1SO₃H - (I) wherein

7. Formulation of any one of preceding claims, wherein the stoichiometric mole ratio of the acid and the metal alkoxide is in the range from 0.01 :100 to 120:100, preferably the relative mole amount of the acid based on the total amount of the metal alkoxide is in the range from 0.1 to 50, more preferably 1 to 10.

8. Formulation of any one of preceding claims, further contains another solvent selected from secondary alcohols having no, one or two alkoxy groups or one or two alkyl groups where one or more non-adjacent groups of said alkyl group is replaced by oxygen atom, or secondary linear or branched >C3 alcohols, preferably it is selected from one or more members of 2-propanol, 2-butanol, 2-pentanol and 3-pentanol, preferably secondary linear or branched >C4 alcohols; preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3- dialkyl ethers or combination of propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers and glycerol 1 ,3-dialkyl ethers.

9. Formulation of any one of preceding claims, wherein the formulation contains water, and the stoichiometric amount of water is in the range from 100 to 400 mol% based on the total amount of metal alkoxide, preferably the stoichiometric amount of water based on the total amount of the metal alkoxide is in the range from 150 to 300 mol%, even more preferably from 180 to 270 mol%.

10. Method for preparing a formulation of any one of the preceding claims, containing at least the following steps;

(X4) mixing water and solvent 3 to form an aqueous solvent; and (X5) adding said aqueous solvent to the metal alkoxide solution (X1 ) obtained in step (X1 ) or the metal alkoxide solution (X3); (X6) optionally dissolving an acid and water in solvent 4, preferably said solvent 4 is dry or water-free solvent, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids to form an acid solution to form an aqueous acid solution (X6);

- wherein at least one of the solvents 1 to 4 contains a solvent selected from one or more members of the group consisting of alcohols, glycols, esters and amides, preferably it is selected from oligo-glycols, more preferably it is selected from oligo-ethylene and oligo-propylene glycols, even more preferably it is selected from one or more members of the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol, hexaethylene glycol, octaethylene glycol, dipropylene glycol, tripropylene glycol and tetrapropylene glycol.

11 . Method for preparing a composite containing a metal oxide, preferably said metal oxide is selected from metal monoxide, metal dioxide or metal pentoxide, or a combination of these; comprising the following steps (a) and (b):

(a) providing the formulation of any one of claims 1 to 9 onto a surface of a substrate or a surface of an underlayer, preferably by wet deposition process, more preferably by spin-coating or an area selective printing, preferably said area selective printing is an ink-jetting, even more preferably said wet deposition process is spin-coating; and

12. Method according to claim 11 , wherein in step (b), the formulation is at least partly converted on the surface of the substrate to a composite, wherein said composite contains a metal oxide, preferably selected from metal monoxide, metal dioxide and/or metal pentoxide; and the metal alkoxide of the formulation.

13. A composite, preferably being a layered composite, preferably said layered composite is an optical layer, derived from the formulation of any one of claims 1 to 9.

14. An optical device comprising the composite of claim 13, and a substrate comprising a patterned surface or an uneven surface.

15. A display device comprising at least one functional medium configured to direct and modulate a light or configured to emit light; and the composite of claim 13, or an optical device of claim 14.

16. A semiconductor device comprising at least a patterned layer or an uneven layer; and said patterned layer or an uneven layer is encapsulated by the composite of claim 13.