WO2011042882A2

WO2011042882A2 - HIGH DEPOSITION RATE OF SiO2 USING ATOMIC LAYER DEPOSITION AT EXTRA LOW TEMPERATURE

Info

Publication number: WO2011042882A2
Application number: PCT/IB2010/054544
Authority: WO
Inventors: Katsuko Higashino; Kazutake Yanagita
Original assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 2009-10-07
Filing date: 2010-10-07
Publication date: 2011-04-14
Anticipated expiration: 2012-04-07
Also published as: WO2011042882A3

Abstract

Disclosed are low temperature atomic layer deposition processes to form SiO₂ films using a silicon chloride precursor, an oxidant, and a base.

Description

HIGH DEPOSITION RATE OF Si0₂ USING ATOMIC LAYER DEPOSITION

AT EXTRA LOW TEMPERATURE

Cross-Reference to Related Applications

This application claims the benefit under 35 U.S.C. § 1 19(e) to provisional application No. 61/249,522, filed October 7, 2009, the entire contents of which are incorporated herein by reference.

Technical Field

Background

Generally speaking, the SiO₂ film is one of the most common thin films in an integrated circuit (IC). As technology requires smaller and smaller ICs, the film deposition methods used to manufacture the ICs have gradually changed from chemical vapor deposition (CVD) to atomic layer deposition (ALD) methods in order to control the film thickness and step coverage at an atomic layer level. At the same time, extra low deposition temperatures are required to prevent oxidation of the interface and the decomposition of thermally unstable substrates. Conformal Si0₂ films at low temperature may be used as sacrificial layers for double patterning masks. However, ALD processes at lower temperatures tend to produce slower deposition rates than higher temperature process, resulting in lower throughput.

US Pat No 7,084,076 to Park et al. provides results from the catalytic atomic layer deposition at both 75°C and 105°C of SiO₂ using

hexachlorodisiloxane or hexachlorosilane, H₂O, and amines. The results indicate that the films formed from the hexachlorodisiloxane precursor exhibit superior properties to those formed from hexachlorosilane.

The need remains for higher-throughput process ALD Si0₂ depositions. Notation and Nomenclature

Certain abbreviations, symbols, and terms are used throughout the following description and claims and include: the term "alkyl group" refers to saturated functional groups containing exclusively carbon and hydrogen atoms. Further, the term "alkyl group" refers to linear, branched, or cyclic alkyl groups. Examples of linear alkyl groups include without limitation, methyl groups, ethyl groups, propyl groups, butyl groups, etc. Examples of branched alky!s groups include without limitation, f-butyl. Examples of cyclic alkyl groups include without limitation, cyclopropyl groups, cyclobutyl groups, cyclopentyl groups, cyclohexyl groups, etc.

The standard abbreviations of the elements from the periodic table of elements are used herein. It should be understood that elements may be referred to by these abbreviations (e.g., Si refers to silicon, Ar refers to argon, etc).

As used herein, the term "independently" when used in the context of describing R groups should be understood to denote that the subject R group is not only independentiy selected relative to other R groups bearing the same or different subscripts or superscripts, but is also independently selected relative to any additional species of that same R group. For example in the formula MR _X {NR²R³)₍₄-_X)! where x is 2 or 3, the two or three R¹ groups may, but need not be identical to each other or to R² or to R³. Further, it should be understood that unless specifically stated otherwise, values of R groups are independent of each other when used in different formulas.

Summary

Disclosed are ALD methods to deposit a Si0₂ films at low temperature. Step a) of the method comprises simultaneously supplying into a reaction chamber a pulse of a first base and a silicon chloride precursor. The silicon chloride precursor has the formula Si_aH_bCl_c, wherein b+c=2a+2. The first base and the silicon chloride precursor are each supplied at a flow rate of approximately 1 seem to approximately 100 seem. In step b), the reaction chamber is purged. A pulse of a second base and an oxidant selected from ozone or remote plasma activated 0₂ are simultaneously supplied into the reaction chamber in step c). The second base is supplied at a flow rate of approximately 1 to approximately 100 seem. The oxidant is suppiied at a flow rate of approximately 10 to approximately 500 seem. In step d), the reaction chamber is purged. The disclosed methods may include one or more of the following aspects:

• repeating steps a) through d);

• the silicon chloride precursor being selected from the group consisting of dichlorosi!ane (SiH₂Cb), trichiorosilane (SiHCI₃), tetrachlorosilane (SiCI ), hexachlorodisilane (SbCle), and mixtures thereof;

• the flow rate of the first base being greater than the flow rate of the silicon chloride precursor;

• each purge step occurring for the same duration as a preceding

supplying step;

• in the step of supplying the precursors, the reaction pressure being higher than purging them out;

• the reaction chamber having a pressure of approximately 0.1 to

approximately 10 Torr;

• the reaction chamber having a temperature approximately 50°C and approximately 200°C, preferably between approximately 50°C and approximately 150°C, and more preferably between approximately 50°C and approximately 100°C;

• the first and second base being independently selected from the group consisting of tertiary amines having the formula NRR'R", cyclic amines, and imines having the formula NR -R", wherein each of R, R\ and R" is an alkyl group which may be bonded each other; and the first and second base being independently selected from the group consisting of trimethylamine, triethy!amine, pyridine, and mixtures thereof.

Brief Description of the Figures

For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, wherein:

FIG 1 is a graph illustrating the difference in deposition rates between one embodiment of the disclosed method and the prior art; and

FIG 2 is a graph illustrating the difference in deposition rates between an alternate embodiment of the disclosed method and the prior art.

Detailed Description of Preferred Embodiments

Disclosed are processes that obtain high deposition rates of silicon dioxide films at extra low temperature (defined generally as temperatures between 50°C and 200°C, more preferably as temperatures less than 100°C). The methods have particular utility in depositing sacrificial layers for double patterning masks which, to reduce the design size, need to deposit S1O2 film at an extra low temperature.

The disclosed processes replace the commonly used oxidant H2O with ozone or remote plasma activated (RP) O2. Ozone and RP O2 have the advantage of stronger oxidative power and are easier to purge from the deposition chamber than H₂O. H₂O is difficult to purge, especially at lower temperatures, due to adsorption on the wall of the deposition chamber.

However, ozone and RP O₂ may be purged from the chamber easily. As a result, the disclosed processes are expected to improve the throughput dramatically.

The disclosed processes also result in greatly enhanced deposition rates. The disclosed processes form a silicon oxide layer on a substrate (e.g., a semiconductor substrate or substrate assembly) using an oxidant, a base, and a silicon chloride precursor. The processes may be useful in the manufacture of semiconductor, photovoltaic, LCD-TFT, or flat panel type devices.

The silicon chloride precursor has the formula Si_aH_bCl_c, wherein b+c-2a+2. Exemplary precursors include dichlorosilane (SiH₂CI₂),

trichlorosilane (SiHCi₃), tetrachlorosilane (SiCi₄), hexachlorodislane (Si₂CI₆), or mixtures thereof.

The selected base has an affinity with hydrogen chloride. The base may be a tertiary amine having the formula NRR'R", a cyclic amine, or an imine having the formula NR'=R", wherein each of R, R', and R" is

independently an alkyl group which may be bonded each other. Exemplary bases include trimethylamine, triethylamine, pyridine, or mixtures thereof.

As discussed above, the oxidant is ozone or remote plasma activated

(RP) 0₂.

The disclosed processes form a silicon-oxide layer on a substrate at low temperature using an atomic layer deposition process. The method includes simultaneously suppiying into a reaction chamber a pulse of a first base and the silicon chloride precursor, the first base and the silicon chloride precursor each being supplied at a flow rate of approximately 1 to

approximately 100 seem; purging the reaction chamber; simultaneously supplying into the reaction chamber a pulse of a second base and the oxidant, the second base being supplied at a flow rate of approximately 1 to

approximately 100 seem and the oxidant being supplied at a flow rate of approximately 10 to approximately 500 seem; and purging the reaction chamber. The first and second base may be the same, for example trimethyl amine. Alternatively, the first base may be trimethyl amine and the second base may be pyridine. This process may be repeated until a silicon oxide layer having the desired thickness is obtained. One of ordinary skill in the art will recognize that the desired thickness will vary depending upon the intended use of the silicon oxide layer.

The reaction chamber may be any enclosure or chamber within a device in which deposition methods take place such as, and without iimitation, a parallel-plate type reaction chamber, a cold-wall type reaction chamber, a hot-wall type reaction chamber, a single-wafer reaction chamber, a multi- wafer reaction chamber, or other types of deposition systems under conditions suitable to cause the precursors to react and form the layers.

The temperature and the pressure within the reaction chamber are held at conditions suitable for the deposition process. For instance, the pressure in the reaction chamber may be held between approximately 0.1 Torr and approximately 10 Torr, preferably between approximately 0.2 Torr and approximately 10 Torr, and more preferably between approximately 1 Torr and approximately 10 Torr, as required per the deposition parameters.

Likewise, the temperature in the reaction chamber may be held between approximately 50°C and approximately 200°C, preferably between

approximately 50°C and approximately 50°C, and more preferably between approximately 50°C and approximately 100°C.

The reaction chamber contains one or more substrates onto which the thin films will be deposited. The one or more substrates may be any suitable substrate used in semiconductor, photovoltaic, flat panel or LCD-TFT device manufacturing. Examples of suitable substrates include without Iimitation silicon substrates, silica substrates, silicon nitride substrates, silicon oxy nitride substrates, tungsten substrates, titanium nitride, tantalum nitride, or combinations thereof. Additionally, substrates comprising tungsten or noble metals (e.g. platinum, palladium, rhodium or gold) may be used. The substrate may also have one or more layers of differing materials already deposited upon it from a previous manufacturing step. The silicon chloride precursor, the base, and the oxidant may be obtained in gas form. Therefore, they may be directly introduced into the reaction chamber.

The remote piasma activated (RP) oxygen is produced by ionizing O2 in a remote plasma source which contains high voltage electrodes used to ionize oxygen gas. The remote plasma may be generated with a power ranging from approximately 1 kW to approximately 10 kW, more preferably from approximately 2.5 kW to approximateiy 7.5 kW. A mixture of oxygen and O radicals are introduced into the reaction chamber. The O ions remain trapped in the remote plasma source, thereby preventing any damage to the substrate. Remote plasma units are commercially available, such as the MKS instruments' R^*evoiution^® reactive gas generator.

Solid or liquid silicon chloride precursors may be supplied either in neat form or in a blend with a suitable solvent, such as ethyl benzene, xylenes, mesitylene, decane, dodecane. The silicon chloride precursor may be present in varying concentrations in the solvent.

The neat or blended silicon chloride precursor is supplied into the reaction chamber in vapor form. For liquid or solid silicon chloride precursors, the vapor form may be produced by vaporizing the neat or blended precursor solution through a conventional vaporization step such as direct vaporization, distillation, or by bubbling. The neat or blended precursor may be fed in liquid state to a vaporizer where it is vaporized before it is introduced into the reaction chamber. Alternatively, the neat or blended precursor may be vaporized by passing a carrier gas into a container containing the silicon chloride precursor or by bubbling the carrier gas into the silicon chloride precursor. The carrier gas may include, but is not limited to, Ar, He, N2,and mixtures thereof. Bubbling with a carrier gas may aiso remove any dissolved oxygen present in the neat or blended precursor solution. The carrier gas and silicon chloride precursor are then introduced into the reaction chamber as a vapor. if necessary, the container of silicon chloride precursor may be heated to a temperature that permits the precursor to be in its liquid phase and to have a sufficient vapor pressure. The container may be maintained at temperatures in the range of, for example, approximately 0°C to

approximately 1 50°C. Those skiiled in the art recognize that the temperature of the container may be adjusted in a known manner to control the amount of precursor vaporized.

The silicon chloride precursor and the base are simultaneously supplied into the reaction chamber. The silicon chloride precursor and the base may be mixed together prior to introduction into the reaction chamber. Alternatively, the base and the silicon chloride precursor may be separately, but simultaneously, introduced into the reaction chamber.

A pulse of the base and the silicon chloride precursor is supplied into the reaction chamber at a flow rate of approximately 1 to approximately 100 seem. The flow rate of the base may be greater than the flow rate of the silicon chloride precursor.

Excess base and precursor are then removed from the reaction chamber by purging with an inert gas, such as, for example, Ar. The purge may last for the same duration as the pulse of the base and the silicon chloride precursor.

The reaction pressure during the step of supplying the precursor may be higher than during the purge step.

The oxidant and the base are simultaneously supplied into the reaction chamber. The oxidant and the base may be mixed together prior to introduction into the reaction chamber. Preferably, the base and the oxidant are introduced separately, but simultaneously, into the reaction chamber.

A pulse of the base and the oxidant is supplied into the reaction chamber. The base is supplied at a flow rate of approximately 1 to

approximately 00 seem. The oxidant is supplied at a flow rate of

approximately 10 to approximately 500 seem. Excess base and oxidant are then removed from the reaction chamber by purging with an inert gas, such as, for example, Ar. The purge may last for the same duration as the pulse of the base and the oxidant.

Examples

The following non-limiting examples are provided to further illustrate embodiments of the invention. However, the examples are not intended to be all inclusive and are not intended to limit the scope of the inventions described herein.

Example 1

Si0₂ film was deposited by ALD using HCDS, ozone, and

trimethylamine (TMA). The reaction chamber was controlled at 2 Torr, 70°C, and 100 seem of Ar was continuously flowing. The deposition process included the following steps: 1 ) supply a pulse of 1 seem of HCDS and 15 seem of TMA to the reaction chamber for 10 seconds, 2) purge the excess precursors by slm of Ar for 0 seconds, 3) supply 4.6 seem of ozone/200 seem of O2 and 5 seem of TMA to the chamber for 20 seconds 4) purge excess precursors by 1 slm of Ar for 20 seconds. The sequence from 1 ) to 4) was repeated until the deposited layer achieved suitable thickness.

The method was repeated with water replacing ozone. The method was repeated with no trimethylamine. The results are provided in FIG 1 . The results show that higher deposition rates are achieved from the combination of ozone with trimethylamine as compared to water with trimethylamine and ozone alone. All values contain ~0.25A/cycle as natural oxide layer. The value of 0₃ without TMA is equal to non-tested sample.

Example 2

Si0₂ film was deposited by ALD using HCDS, remote plasma activated O2, and trimethylamine (TMA). The reaction chamber was controlled at 2 Torr, 70°C, and 100 seem of Ar was continuously flowing. The deposition process included the following steps: 1 ) supply a pulse of 1 seem of HCDS and 15 seem of TMA to the reaction chamber for 10 seconds, 2) purge the excess precursors by 1 slm of Ar for 10 seconds, 3) supply remote plasma activated 200 seem of 0₂ and 15 seem of TMA and 1 slm of Ar to the chamber for 20 seconds 4) purge the excess precursors by 1 slm of Ar for 20 seconds. The sequence from 1 ) to 4) was repeated until the deposited layer achieved suitable layer thickness.

The method was repeated with water replacing ozone. The method was repeated with no trimethylamine. The results are provided in FIG 2. The results show that higher deposition rates are achieved from the combination of activated 0₂ with trimethylamine as compared to water with trimethylamine and activated 0₂ alone. All values contain ~0.25A/cyc!e as natural oxide layer. The value of plasma activated 0₂ can oxidize Si substrate, so plasma activated 0₂ without TMA contains natural Si0₂ and oxidized substrate at interface.

It will be understood that many additional changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above and/or the attached drawings.

Claims

What is claimed is:

1 . An ALD method to deposit a Si0₂ film at low temperature, the method comprising the steps of:

a) simultaneous!y supplying into a reaction chamber a pulse of a first base and a silicon chloride precursor having the formula Si_aH_bCI_Cl wherein b+c=2a+2, the first base and the silicon ch!oride precursor each being supplied at a flow rate of approximately 1 seem to approximately 100 seem; b) purging the reaction chamber;

c) simultaneously supplying into the reaction chamber a pu!se of a second base and an oxidant selected from ozone or remote plasma activated 0₂, the second base being supplied at a flow rate of approximately 1 to approximately 100 seem and the oxidant being supplied at a flow rate of approximately 10 to approximately 500 seem; and

d) purging the reaction chamber.

2. The method of claim 1 , further comprising repeating steps a) through d).

3. The method of claim 1 or 2, wherein the silicon chloride precursor is selected from the group consisting of dichlorosilane (SiH₂C!₂)_! trichlorosilane (SiHCI₃), tetrachlorosiiane (SiCI₄), hexachlorodislane (Si₂CI₆), and mixtures thereof.

4. The method of any one of claims 1 to 3, wherein the flow rate of the first base is greater than the flow rate of the silicon chloride precursor.

5. The method of any one of claims 1 to 4, wherein each purge step occurs for a same duration as a preceding supplying step.

6. The method of any one of claims 1 to 5, wherein in the step of supplying the precursors, the reaction pressure is higher than purging them out.

7. The method of any one of claims 1 to 6, wherein the reaction chamber has a pressure of approximately 0.1 to approximately 10 Torr.

8. The method of any one of claims 1 to 7, wherein the reaction chamber has a temperature approximately 50°C and approximately 200°C, preferably between approximately 50°C and approximately 150°C, and more preferably between approximately 50°C and approximately 100°C.

9. The method of any one of claims 1 to 8, wherein the first and second base are independentiy selected from the group consisting of tertiary amines having the formula NRR'R" or NR'=R", cyclic amines, and imines, wherein each of R, R', and R" is an alkyl group which may be bonded each other.

10. The method of claim 9, wherein the first and second base are independently selected from the group consisting of trimethylamine, triethylamine, pyridine, and mixtures thereof.