EP3191894A1 - Method for controlling the defect rate in films obtained with mixtures of block copolymers and polymers - Google Patents

Abstract

The present invention concerns a method for controlling the defect rate in films obtained using a composition comprising a mixture of block copolymers and polymers deposited on a surface. The polymers comprise at least one monomer identical to those present in either block of the block copolymers.

Description

 A method of controlling the defect rate in films obtained with blends of block copolymers and polymers. The present invention relates to a method for controlling the defect rate in films obtained using a composition comprising a mixture of block copolymers and polymers deposited on a surface. The polymers comprise at least one monomer identical to those present in one or the other block of block copolymers.

Because of their ability to nanostructure, the use of block copolymers in the fields of materials and electronics or optoelectronics is now well known. This new technology allows access to advanced nano-lithographic object manufacturing and preparation processes with resolutions in terms of domain size ranging from a few nanometers to several tens of nanometers.

In particular, it is possible to structure the arrangement of the blocks constituting the copolymers at scales much smaller than 100 nm. Unfortunately it is difficult to obtain films free of defects.

Some authors have studied the effect of adding one or more homopolymers to the block copolymer. In Macromolecules 1991, 24, 6182-6188 Winey K. et al. discuss this effect on lamellar morphologies, in particular the thickness of lamellae and layers, in a polystyrene-b-polyisoprene system in the presence of homopolystyrene.

In Macromolecules, 1995, 28, 5765-5773, Matsen M. studies by SCFT (self-consistent-field-theory) simulation the behavior of mixtures of block copolymers with a (co) -polymer. These simulations show that the addition of homopolymer influences the final morphology of the mixture, which can go as far as a stabilization of the hexagonal morphology.

In Macromolecules 1997, 30, 5698-5703, Torikai N. et al., Still in lamellar morphologies, have a similar study where they show the effect that the molecular weight of the homopolymer added can have. The system studied is polystyrene-b-polyvinylpyridine in the presence of polystyrene or polyvinylpyridine.

In Adv. Mater. 2004, 16, No. 6, 533-536, Russel et al demonstrate that the addition of poly-methyl methacrylate (PMMA) to a polystyrene-b-polymethyl methacrylate (PS-b-PMMA) copolymer, with a size of the poly-methyl methacrylate homopolymer slightly higher than that of the poly-methyl methacrylate block of the corresponding block copolymer makes it possible to obtain a perpendicular cylindrical morphology independent of the thickness of the film.

More recently, in Langmuir, 2007, 23, 6404-6410, Kitano H. et al. report a favored perpendicular control of cylindrical domains by adding homopolymers of polystyrene to polystyrene-b-poly-methyl methacrylate. They suggest that this property comes from the decrease the constraint of hexagonal symmetry when adding polystyrene. The same effect is demonstrated by the addition of poly-methyl methacrylate. In Soft Matter., 2008, 1454-1466, Up Ahn D. et al. also present a similar discussion by focusing their work on the effect of the molecular weight of the homopolymer added to the block copolymer on the size, stability and periodicity of the rolls.

Finally, in Macromolecules 2009, 42, 5861-5872, Su-Mi Hur et al study simulations of morphologies resulting from mixtures of block copolymers and homopolymers. They demonstrate that the addition of copolymer makes it possible to achieve a stable tetragonal symmetry, which is not the case with the pure block copolymer.

If these studies show an effect of the presence of a polymer (homopolymer or copolymer) on the behavior of the film obtained, none of these studies gives any indication as to the quantification of the defects, much less the optimal way of minimizing them. Moreover, no study is concerned with the reduction of distance defects, of coordination or improvement of the UDC (critical dimension uniformity).

Indeed, the nanostructuration of a block copolymer of a surface treated by the process of the invention can take the forms such as cylindrical (hexagonal symmetry (symmetry of hexagonal network primitive "6mm") according to the notation of Hermann-mauguin , or tetragonal / quadratic ("4mm" tetragonal lattice symmetry), spherical (hexagonal symmetry ("6mm" or "6mmmm") hexagonal lattice symmetry), or tetragonal / quadratic (symmetry of 4 mm primitive tetragonal network), or cubic ("i¾n" network symmetry), lamellar, or gyroid. Preferably, the preferred form of nanostructuring is of the hexagonal cylindrical type.

The method for self-assembly of block copolymers on a treated surface according to the invention is governed by thermodynamic laws. When the self-assembly leads to a morphology of cylindrical type, each cylinder is surrounded by 6 equidistant neighboring cylinders if there is no defect. Several types of defects can thus be identified. The first type is based on the evaluation of the number of neighbors around a cylinder constituted by the arrangement of the block copolymer, also called coordination defects. If five or seven cylinders surround the cylinder considered, it will be considered that there is a lack of coordination. The second type of defect considers the average distance between the cylinders surrounding the cylinder considered. [W.Li, F.Qiu, Y.Yang, and ACShi, Macromolecules 43, 2644 (2010); K. Aissou, T. Baron, M. Kogelschatz, and A. Pascale, Macromol. 40, 5054 (2007); RA Segalman, H. Yokoyama, and EJ Kramer, Adv. Matter. 13, 1152 (2003); RA Segalman, H. Yokoyama, and EJ Kramer, Adv. Matter. 13, 1152 (2003)]. When this distance between two neighbors is greater than two percent of the average distance between two neighbors, it will be considered that there is a fault. To determine these two types of defects, Voronoi constructions and associated Delaunay triangulations are conventionally used. After binarization of the image, the center of each cylinder is identified. The Delaunay triangulation then makes it possible to identify the number of first-order neighbors and to calculate the average distance between two neighbors. It is thus possible to determine the number of defects.

 This counting method is described in the article by Tiron et al. (J. Vac Sci Technol B 29 (6), 1071-1023, 2011.

A last type of defect concerns the angle of cylinders of the block copolymer deposited on the surface. When the block copolymer is no longer perpendicular to the surface, it will be considered that a defect of orientation appears.

The method of the invention makes it possible to obtain nanostructured assemblies in the form of films with a minimum of defect in orientation, coordination or distance over large monocrystalline surfaces.

Finally, the method of the invention allows the preparation of films with an improved critical dimension uniformity parameter.

Critical dimension uniformity (CDU) in a block copolymer film having a cylindrical morphology corresponds to the roll size uniformity of the rolls. In the ideal case, all the cylinders must have the same diameter, because any variation of this diameter will induce variations on the performances (conductivity, characteristics of the transfer curves, evacuated thermal power, resistance, etc.) for the applications. considered.

The Applicant has found that mixtures comprising block copolymers and polymers which comprise at least one monomer identical to those present in one or the other block of the block copolymers allows a significant reduction of the aforementioned defects accompanied by optimum as regards the mass of the polymers mixed with the block copolymers and the ratio of the masses of the polymers and the masses of the block copolymers.

Summary of the invention

 The invention relates to a method for controlling the defect rate of orientation, coordination or distance defects on large monocrystalline surfaces with an improvement of the CDU of a nano - structured assembly in the form of a copolymer blending film. blocks and polymers, this mixture comprising n block copolymers and m polymers which comprise at least one monomer identical to those present in one or the other block of the block copolymers comprising the following steps:

Mixture comprising block copolymers and polymers in a solvent.

-Deposit of this mixture on a surface, -recuit Detailed description:

By surface is meant a surface that can be flat or non-planar.

Annealing means a heating step for evaporation of the solvent when it is present, and allowing the establishment of the desired nano-structuring. Any block copolymer, whatever its associated morphology, may be used in the context of the invention, be it diblock copolymer, linear or star triblock, linear multiblock, comb or star. Preferably, these are diblock or triblock copolymers, and more preferably diblock copolymers.

 The polymers will be either homopolymers or random copolymers.

Within the scope of the invention, it will be possible to mix n polymeric block copolymers, n being an integer between 1 and 10, inclusive. Preferably, n is between 1 and 5, inclusive, and preferably n is between 1 and 2 inclusive, and more preferably n is 1, m being an integer between 1 and 10, terminals included. Preferably, m is between 1 and 5, inclusive, and preferably m is between 1 and 2 inclusive, and more preferably m is equal to 1.

These block copolymers and polymers may be synthesized by any techniques known to those skilled in the art among which mention may be made of polycondensation, ring-opening polymerization, anionic, cationic or radical polymerization these techniques can be controlled or not, and combined or not. When the copolymers are prepared by radical polymerization, they may be controlled by any known technique such as NMP ("Nitroxide Mediated Polymerization"), RAFT ("Reversible Addition and Fragmentation Transfer"), ATRP ("Atom Transfer Radical Polymerization") , INIFERTER ("Initiator-Transfer- Termination "), RITP (" Reverse Iodine Transfer

Polymerization "), ITP (" Iodine Transfer Polymerization).

According to a preferred form of the invention, the block copolymers and the polymers are prepared by controlled radical polymerization, more particularly by nitroxide-controlled polymerization, in particular N-tert-butyl-1-diethylphosphono-2, 2-nitroxide. dimethylpropyl.

According to a second preferred form of the invention, the block copolymers and the polymers are prepared by anionic polymerization. When the polymerization is carried out in a radical manner, the constituent monomers of the block copolymers and polymers will be chosen from the following monomers: at least one vinyl, vinylidene, diene, olefinic, allylic or (meth) acrylic monomer. This monomer is chosen more particularly from vinylaromatic monomers such as styrene or substituted styrenes, in particular alpha-methylstyrene, silylated styrenes, acrylic monomers such as acrylic acid or its salts, alkyl acrylates and cycloalkyl acrylates. or aryl such as methyl acrylate, ethyl acrylate, butyl acrylate, ethylhexyl acrylate or phenyl acrylate, hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate, alkyl ether acrylates such as 2-methoxyethyl acrylate, alkoxy- or aryloxy-polyalkylene glycol acrylates such as methoxypolyethylene glycol acrylates, ethoxypolyethylene glycol acrylates, methoxypolypropylene glycol acrylates, methoxypolypropylene glycol acrylates, polyethylene glycol-polypropylene glycol or mixtures thereof, aminoalkyl acrylates such as 2- (dimethylamino) ethyl acrylate (ADAME), fluorinated acrylates, silyl acrylates, phosphorus acrylates such as alkylene glycol phosphate acrylates, glycidyl acrylates, dicyclopentenyloxyethyl acrylates, methacrylic monomers such as methacrylic acid or its salts, alkyl, cycloalkyl, alkenyl or aryl methacrylates such as methyl methacrylate (MMA), lauryl, cyclohexyl allyl, phenyl or naphthyl, hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate, ether alkyl methacrylates such as 2-ethoxyethyl methacrylate, methacrylates of alkoxy- or aryloxy-polyalkyleneglycol such as methoxypolyethylene glycol methacrylates, ethoxypolyethylene glycol methacrylates, methacrylates of m thoxypolypropylene glycol, methoxypolyethylene glycol-polypropylene glycol methacrylates or mixtures thereof, aminoalkyl methacrylates such as 2- (dimethylamino) ethyl methacrylate (MADAME), fluorinated methacrylates such as 2,2,2-trifluoroethyl methacrylate, silylated methacrylates such as 3-methacryloylpropyltrimethylsilane, phosphorus methacrylates such as alkylene glycol phosphate methacrylates, hydroxyethylimidazolidone methacrylate, hydroxyethylimidazolidinone methacrylate, 2- (2-oxo-l) methacrylate imidazolidinyl) ethyl, acrylonitrile, acrylamide or substituted acrylamides, 4-acryloylmorpholine, N-methylolacrylamide, methacrylamide or substituted methacrylamides, N-methylolmethacrylamide, methacrylamido-propyltrimethyl ammonium chloride (MAPTAC), glycidyl, dicyclopentenyloxyethyl methacrylates, itaconic acid, maleic acid or its salts, maleic anhydride, alkyl or alkoxy- or aryloxypolyalkyleneglycol maleates or hemimaleate, vinylpyridine, vinylpyrrolidinone, (alkoxy) poly (alkylene glycol) vinyl ether or divinyl ether, such as methoxy poly (ethylene glycol) vinyl ether, poly (ethylene glycol) divinyl ether, olefinic monomers, among which mention may be made of ethylene, butene, hexene and 1-octene, diene monomers including butadiene, isoprene and fluorinated olefinic monomers, and vinylidene monomers, among which mention may be made of vinylidene fluoride, alone or as a mixture at least two monomers mentioned above.

 Preferably the block copolymers consist of block copolymer one of which blocks comprises a styrene monomer and the other block comprises a methacrylic monomer; more preferably, the block copolymers consist of block copolymer one of which blocks comprises styrene and the other block comprises methyl methacrylate.

The polymers preferably comprise a styrene monomer or methacrylic monomer; preferably, the polymers comprise styrene or methyl methacrylate. In a preferred context of the invention, the polymers consist of styrene. In a preferred context of the invention for the synthesis of block copolymers and polymers there will be used an anionic polymerization process in an apolar solvent, and preferably toluene, as described in US Pat. patent EP0749987, and involving a micro-mixer. Monomers selected from the following entities will be preferred: at least one vinyl, vinylidene, diene, olefinic, allylic or (meth) acrylic monomer. These monomers are chosen more particularly from vinylaromatic monomers such as styrene or substituted styrenes, especially alpha-methylstyrene, silylated styrenes, acrylic monomers such as alkyl acrylates, cycloalkyl acrylates or aryl acrylates such as acrylate. methyl, ethyl, butyl, ethylhexyl or phenyl, ether alkyl acrylates such as 2-methoxyethyl acrylate, alkoxy- or aryloxy-polyalkyleneglycol acrylates such as methoxypolyethylene glycol acrylates, ethoxypolyethylene glycol acrylates, methoxypolypropylene glycol acrylates, methoxy-polyethylene glycol-polypropylene glycol acrylates or mixtures thereof, aminoalkyl acrylates such as 2- (dimethylamino) ethyl acrylate (ADAME), fluorinated acrylates, silylated acrylates , phosphorus acrylates such as alkylene glycol phosphate acrylates, glycidyl acrylates, dicyclopent alkyl, cycloalkyl, alkenyl or aryl methacrylates such as methyl methacrylate (MMA), lauryl, cyclohexyl, allyl, phenyl or naphthyl, alkyl ether methacrylates such as 2-ethoxyethyl methacrylate, alkoxy- or aryloxy-polyalkylene glycol methacrylates such as methoxypolyethylene glycol methacrylates, ethoxypolyethylene glycol methacrylates, methoxypolypropylene glycol methacrylates, methoxy-polyethylene glycol-polypropylene glycol methacrylates or mixtures thereof, methacrylates aminoalkyl such as 2- (methacrylate) (Dimethylamino) ethyl (MADAME), fluorinated methacrylates such as 2, 2, 2-trifluoroethyl methacrylate, silylated methacrylates such as 3-methacryloylpropyltrimethylsilane, phosphorus methacrylates such as alkylene glycol phosphate methacrylates, methacrylate d hydroxyethylimidazolidone, hydroxyethylimidazolidinone methacrylate, 2- (2-oxo-1-imidazolidinyl) ethyl methacrylate, acrylonitrile, acrylamide or substituted acrylamides, 4-acryloylmorpholine, N-methylolacrylamide methacrylamide or substituted methacrylamides, N-methylolmethacrylamide, methacrylamido-propyltrimethylammonium chloride (MAPTAC), glycidyl, dicyclopentenyloxyethyl methacrylates, maleic anhydride, alkyl or alkoxy maleates or hemimaleates or aryloxypolyalkylene glycol, vinylpyridine, vinylpyrrolidinone, (alkoxy) poly (alkylene glycol) vinyl ether or divinyl ther, such as methoxy poly (ethylene glycol) vinyl ether, poly (ethylene glycol) divinyl ether, olefinic monomers, among which mention may be made of ethylene, butene, hexene and 1-octene, the monomers dienics including butadiene, isoprene and fluorinated olefinic monomers, and vinylidene monomers, among which mention may be made of vinylidene fluoride, lactones, lactides, glycolides, cyclic carbonates, siloxanes, the protected cases to be compatible with the anionic polymerization processes, alone or as a mixture of at least two aforementioned monomers.

According to an alternative method of synthesis, block copolymers are prepared by anionic polymerization and the Polymers will be prepared by controlled radical polymerization.

The block copolymers used in the invention each have the following characteristics:

 A number-average molecular weight of between 500 g / mol and 500,000 g / mol and preferably between 20,000 g / mol and 150,000 g / mol, and a dispersity index of between 1 and 3 and preferably between 1 and 2.

The polymers used in the invention each have the following characteristics:

 A number-average molecular weight of between 500 g / mol and 500,000 g / mol and preferably between 20,000 g / mol and 150,000 g / mol, and a dispersity index of less than 3.

The mass copolymer block / polymer ratios will be between 99/1 and 1/99, preferably between 97/03 and 03/97, more preferably between 97/03 and 55/45 and ideally between 95/05 and 60/40.

In the preferred context of the invention using a block copolymer mixed with a polymer, the ratio of the molecular weight in nmobre of the polymer to the block copolymer is between 0.2 and 4, preferably between 1 and 3, and so still preferred between 1 and 2.

The invention particularly relates to the use of the method that is the subject of the invention for producing lithography masks or films, as well as the masks and films obtained. In the case of lithography, the desired structuring (for example, generation of domains perpendicular to the surface) nevertheless requires the preparation of the surface on which the polymer mixture is deposited in order to control the surface energy. Among the known possibilities, there is deposited on the surface a random copolymer whose monomers may be identical in whole or in part to those used in the block copolymer that is to be deposited. In a pioneering article Mansky et al. (Science, vol 275 pages 1458-1460, 1997) describes this technology well, now well known to those skilled in the art.

Among the preferred surfaces include surfaces made of silicon, silicon having a native or thermal oxide layer, germanium, platinum, tungsten, gold, titanium nitrides, graphenes, BARC (Bottom Anti Reflecting Coating) or any other anti-reflective layer used in lithography. Once the surface is prepared, a solution of the mixture of block copolymers is deposited and the solvent is evaporated according to techniques known to those skilled in the art such as the so-called "spin coating" technique, "Doctor Blade" "knife system" "Slot die System" but any other technique can be used such as a dry deposit, that is to say without going through a prior dissolution.

Subsequently, a heat treatment or solvent vapor (annealing), a combination of the two treatments, or any other treatment known to those skilled in the art which allows the mixture of block copolymers to be properly organized (preparation of 'nanostructuration). The surfaces may be said to be "free" (planar and homogeneous surface both from a topographic and chemical point of view) or to have guide structures for the "pattern" block copolymer, whether this guidance is of the chemical guidance type (called "guiding"). by chemistry-epitaxy ") or physical / topographical guidance (called" graphoepitaxial guidance ").

The following examples illustrate, without limitation, the scope of the invention:

These block copolymers are PS-fc-PMMA copolymers prepared according to a protocol described in EP0749987, EP0749987 and EP0524054, with recovery of the block copolymer considered by precipitation in a non-solvent at the end of the synthesis, such as a mixture 80 Of cyclohexane / heptane. The polymers are homopolymers of PS prepared according to the same protocol, the second step (PMMA) not being carried out, the living PS is deactivated by the addition of a methanol / hydrochloric acid mixture or any other proton donor.

They have the following characteristics

The molecular weights and the indices of dispersity corresponding to the ratio between weight-average molecular weight (Mw) and number-average molecular mass (Mn), are obtained by SEC (Size exclusion Chromatography), using 2 columns in series AGILENT 3ym ResiPore, in medium BHT stabilized THF at a flow rate of 1 mL / min at 40 ° C with samples concentrated at 1 g / L, with prior calibration with calibrated polystyrene samples using a prepared Easical PS-2 pack.

The mass ratio PS / PMMA is obtained by proton NMR on a Bruker 400 apparatus, integrating the 5 aromatic protons of the PS and the 3 protons of methoxy PMMA. The invention may also be carried out using other block copolymers and other PS from other sources.

Example 1

The solutions are deposited on a surface as follows:

 Preparation of the surface, grafting on Si 02:

The silicon wafers (crystallographic orientation {100}) are cut manually into pieces of 3x4 cm and cleaned by piranha treatment (H2 SO ₄ / H2O2 2: 1 (v: v)) for 15 minutes, then rinsed with water. ionized, and dried under nitrogen flow just before functionalization. The rest of the procedure is that described by Mansky et al. (Science, 1997, 1458), with only one modification (the annealing is done under ambient atmosphere and not under vacuum). PS-r-PMMA random mass copolymer molecular weight of 10,000 g / mol and PS / PMMA ratio 74/26, prepared by controlled radical polymerization using NMP technology, according to a protocol described in WO20121400383, Example 1 and Example 2 (copolymer 10), allowing the neutralization of the surface is dissolved in toluene to obtain solutions at 1.5% by weight. This solution is dispensed by hand over a freshly cleaned wafer, then spread by spin-coating at 700 rpm to obtain a film of about 40 nm thick. The substrate is then simply deposited on a heating plate, previously heated to the desired temperature, under ambient atmosphere for a variable time. The substrate is then washed by sonication in several toluene baths for a few minutes in order to remove the ungrafted polymer from the surface and then dried under a stream of nitrogen. It may be noted that throughout this procedure, toluene can be interchanged with PGMEA.

Any other copolymer may be used, typically a random copolymer P (MMA-co-Styrene) as used by Mansky provided the appropriate styrene and MMA composition is selected for neutralization.

The solution of the block copolymer or mixture of block copolymers and of polymer (1% by mass in propylene glycol-monomethyl ether acetate) is then deposited by "spin coating" on the previously treated surface and then 230 ° thermal annealing is carried out. C for at least 5 minutes to evaporate the solvent and allow time for the morphology to establish.

The procedure is such that the thickness of the block copolymer or block copolymer blend film is 40 nm. Typically the solution to be deposited (1% in the PGMEA) is deposited on a 2.7 × 2.7 cm sample by "spin coating" at 700 rpm.

Film thickness measurements were made on a Prometrix UV1280 ellipsometer.

The following mixtures are considered:

Witnesses: 13P16CL2, 13P13CG3

All block copolymer / homopolymer mixtures have a mass ratio of 9/1.

FIG. 1 shows the percentage of coordination defects among the number of cylinders detected as a function of the ratio of the number-average molecular masses of the polymer to the number-average molecular mass of the block copolymer. It is found that mixtures of block copolymers with polymers have fewer coordination defects and that an optimum is observed for number-average molecular weight ratios of the polymer over the number-average molecular weight of the block copolymer between 1 and 2.

Claims

 claims 1 Method for controlling the default rate of orientation, coordination or distance defects on large monocrystalline surfaces with an improvement of the CDU of a nano-structured assembly in the form of a mixture film of block copolymers and polymers this mixture comprising n block copolymers and m polymers which comprise at least one monomer identical to those present in one or the other block of the block copolymers comprising the following steps: Mixture comprising block copolymers and polymers in a solvent. -Deposit of this mixture on a surface, -recuit 2 The method of claim 1 wherein n is 1 and m is 1. The process of claim 2 wherein the block copolymer is a diblock copolymer. The process of claim 2 wherein the polymer is a random copolymer. The process of claim 2 wherein the polymer is a copolymer comprising methyl methacrylate. The process of claim 2 wherein the polymer is a copolymer comprising styrene. The method of claim 6 wherein the copolymer is a homopolymer of PS. The method of claim 3 wherein the block copolymers comprise a methacrylic monomer in one of the blocks and a styrene monomer in the other block. The process of claim 8 wherein the block copolymer is a PS-PMMA copolymer. The process of claim 1 wherein the number-average molecular weights of the block copolymers are from 500 to 500,000 g / mol. 11. The process as claimed in claim 1, in which the mass ratio of block copolymers / polymers is between 99/1 and 1/99. The process of claim 1 wherein the block copolymers are prepared by controlled radical polymerization. The process of claim 1 wherein the polymers are prepared by controlled radical polymerization. Process according to Claim 12 and 13, in which the controlled radical polymerization with nitroxides is carried out. The process of claim 14 wherein the controlled radical polymerization is conducted with N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide. The process of claim 1 wherein the block copolymers and the polymers are prepared by anionic polymerization. The process of claim 1 wherein the block copolymers are prepared by anionic polymerization and the polymers are prepared by controlled radical polymerization. The method of claim 1 wherein the thickness of the film is equal to or greater than 40 nm. The process of claim 2 wherein the ratio of number average molecular weight of the polymer to the block copolymer is 0.2 to 4. The method of claim 1 wherein the surface is free. The method of claim 1 wherein the surface is guided. Use of the method according to any one of the preceding claims for generating lithography masks or films. Mask of lithography or film obtained according to claim 22.