JPH08190200A - Method of forming si-containing thin film and method of forming pattern of the thin film - Google Patents

Abstract

PURPOSE: To obtain a method of forming a Si-contg. thin film having excellent O2 -RIE resistance and its pattern without using an expensive film forming device by forming a film of a photosensitive resin compsn., exposing the film, and heat treating the film after exposure. CONSTITUTION: A film 12 of a photosensitive resin compsn. containing poly(siloxane) deriv. having alkoxy groups and an acid producing agent which produces acid by exposure is formed on a base body 10. When the film is exposed and heated, the C-O-Si bonds in alkoxy groups in the poly(siloxane) deriv. are cut to produce silanols in the exposed part. Since silanols are easily condensed, the exposed part of the photosensitive resin compsn. is gelled. Thereby, a thin film 12 changed into SiO2 is formed. Therefore, this method does not require any complicated conditions for an expensive vacuum sputtering device or CVD device conventionally used, the working processes are made extremely easy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a Si-containing thin film used for manufacturing semiconductor devices and the like, and a pattern forming method for the thin film.

[0002]

2. Description of the Related Art When manufacturing a semiconductor device, for example, a thin film containing Si (silicon) (ideally a SiO ₂ film) is often used as an interlayer insulating film or the like. Here, the Si-containing thin film used as an interlayer insulating film or the like has conventionally been generally formed by a plasma CVD method, a sputtering method, or the like. Also, in the multi-layer resist process, S
i-containing thin films have been utilized. For example, in a three-layer resist process, a Si-containing thin film by a sputtering method is used as an intermediate layer (Reference I (J. Vac. Scl. Techno.
L., Vol. 16, Nov./Dec. 1979). Further, in, for example, a two-layer resist process which is one of semiconductor device manufacturing techniques, a pattern of a thin film containing Si (silicon) (ideally a SiO ₂ film) is used as an upper layer resist pattern. As an example of forming an upper layer resist pattern on this thin film using a photosensitive resin containing Si, reference II (Journal
of Electrochemical Society: SOLID-STATE SCIENCE AND TECHNOLOGY, VOL.132, N
o.5,1985, pp.1178-1182). In this document II, poly (trimethylsilylmethylmethacrylate-
An example using a 3-oxymino-2-butanone) copolymer has been reported.

[0003]

However, when forming a Si-containing thin film by the plasma CVD method or the sputtering method, an expensive film forming apparatus is required, and for example, it takes time to depressurize the film forming chamber. There were problems such as.

Further, in the method of Document II for forming the pattern of the Si-containing thin film, the silicon content of the photosensitive resin composition used for the upper resist is as low as 9.6% by weight (see Table II of Document II, for example). ), The formed pattern has an etching rate by O ₂ -RIE of 15 nm /
It was fast and was not always satisfactory in terms of O ₂ -RIE resistance.

Therefore, there has been a demand for a method of forming a Si-containing thin film having excellent O ₂ -RIE resistance and a pattern thereof without using an expensive film forming apparatus.

[0006]

Therefore, according to the first invention of this application, in a method of forming a Si (silicon) -containing thin film on a substrate, a poly (siloxane) derivative having an alkoxy group is formed on the substrate. A step of forming a film of a photosensitive resin composition containing an acid generator that generates an acid upon exposure, a step of exposing this film, and a step of subjecting this exposed film to a heat treatment. Characterize.

According to the second invention of this application, in a method of forming a pattern of a Si (silicon) -containing thin film on a base, a poly (siloxane) derivative having an alkoxy group on the base and an acid are generated by exposure. A step of forming a film of a photosensitive resin composition containing an acid generator, a step of selectively exposing a portion of the film to be left exposed, a step of heat-treating the exposed film, and a step of heating the exposed film. And a step of developing the treated film.

Further, the poly (siloxane) derivative having an alkoxy group referred to in the first and second inventions is, for example, one represented by the above formula (1), one represented by the above formula (2) and the above. It may be one or more selected from the copolymers of the one represented by the formula (1) and the one represented by the above formula (2). However, (1)
Each of R ¹ , R ² , R ⁵ and R ^{6 in} formula (2) represents an alkyl group, and may be the same or different. Also,
m and n are positive integers indicating the degree of polymerization. As a specific example of such a poly (siloxane) derivative, for example, a compound proposed by the applicant of the present application in Japanese Patent Application No. 4-17588 (Japanese Patent Application Laid-Open No. 5-216237) can be mentioned. This compound can be obtained with good controllability up to a weight average molecular weight of about 500 to 100,000 by changing the polymerization conditions.

The acid generator is not specified as long as it is a substance that generates an acid upon exposure to light. For example, the following (3)
A sulfonium salt represented by the formula and an onium salt such as an iodonium salt represented by the formula (4), p-toluenesulfonate represented by the formula (5), a trichloromethyl-substituted triazine represented by the formula (6), The trichloromethyl-substituted benzene represented by the formula (7) can be used as an acid generator.

[0010]

Embedded image

[0011]

[Chemical 4]

These acid generators are commercially available, or can be prepared according to the method described in J. V. Synthesis method by Crivello et al. (For example, Reference III: Journal of Polymer Science, Polymer Chemistry Edition (J. Po.
lymer Sci. , Polymer Chem. E
d. , 18, 2677 (1980)) and T.W. Endo
(Eg, Document IV: Journal of
Polymer Science, Polymer Chemistry Edition (J. Polymer Sci., Polym
er Chem. Ed. , 23, 359 (1985))
Can be synthesized according to.

By appropriately selecting these acid generators, various exposure sources can be easily dealt with. This acid generator has a lower limit of 0.01%, preferably 0.05%, and an upper limit of 50%, based on the weight of poly (siloxane).
It is preferable to add in the range of 30%. If it is out of this range, a high temperature may be required for film formation of the radiation-sensitive resin composition, or the coating film may become brittle.

The photosensitive resin composition used in the first and second inventions may further contain a crosslinking agent. As the cross-linking agent, for example, one represented by the following formula (8) is suitable. This is because this cross-linking agent contains silicon, so that it is possible to suppress a decrease in the silicon content of the photosensitive resin composition due to the constitution including the cross-linking agent, as compared with the case of using the other one. However, in equation (8), j, k, and l (j) are j ≧ 1, 2 ≦
It represents a positive integer that satisfies k ≦ 2 (j + 1) and l = 2 (j + 1) −k. R ^A represents hydrogen, an alkyl group, an aryl group or an alkenyl group, and k R ^A may be the same or different. R ^B represents a monovalent hydrocarbon group or hydrogen,
The 1 (ell) R ^B may be the same or different.

(R ^A O) _k R ^B _l Si _j O _(jl) (8) Further, the lower limit of the cross-linking agent is 0.05% and the upper limit is based on the weight of the poly (siloxane) derivative used. It is good to add in the range of 50%, preferably 30%. If it is out of this range, high temperature is required for film formation of the radiation-sensitive resin composition, or the coating film becomes brittle. When the crosslinking agent is used, a highly sensitive photosensitive resin composition which cannot be achieved by the two-component system of poly (siloxane) derivative and acid generator is obtained.

When the photosensitive resin composition is used, when the composition is applied onto a substrate by spin coating to form this film on the substrate, a solvent for preparing a coating solution for that purpose is required. . Examples of the solvent include 2-methoxyethyl acetate, monochlorobenzene, xylene, dioxane, methyl isobutyl ketone (MIB
K), isoamyl acetate and the like can be mentioned.

The lower limit of the heating temperature in the heat treatment performed on the exposed Si-containing thin film before development in the first invention is 40 ° C., preferably 60 ° C. Further, the upper limit temperature is not particularly specified as long as it does not affect the base, and can be an arbitrary temperature according to the design. Lower limit 4
The temperature of 0 ° C. means that when the heating temperature is lower than 40 ° C., the reaction between the acid generated from the acid generator and the resin does not proceed efficiently.
Further, with an acid generator that efficiently reacts with the resin at a temperature lower than 40 ° C., the storage stability itself of the photosensitive resin composition becomes a problem.

Further, the heating temperature in the heat treatment performed on the exposed Si-containing thin film before development in the second invention is preferably 40 to 300 ° C. This is because, as described above, when the heating temperature is lower than 40 ° C., the reaction between the acid generated from the acid generator and the resin does not proceed efficiently, and the acid generator which reacts efficiently with the resin at a temperature lower than 40 ° C. Then, the storage stability itself of the photosensitive resin composition becomes a problem. Also, the heating temperature is 300
This is because if the temperature is higher than ° C, the acid generator may be thermally decomposed, which may deteriorate the pattern or prevent the pattern formation.

[0019]

According to the first and second inventions of this application, a film of a photosensitive resin composition containing a poly (siloxane) derivative having an alkoxy group and an acid generator that generates an acid upon exposure is formed. By exposing and heating this film, the C—O—Si bond of the alkoxy group possessed by the poly (siloxane) derivative is cleaved in the exposed part to produce silanol. Since silanol easily condenses, the exposed portion of this photosensitive resin composition is gelled.
Therefore, in the first invention, a thin film made of SiO ₂ is formed.

In the second invention, the composition is selectively exposed to light, and then the sample is heat-treated. By this series of processing, the selectively exposed portion of the film of the photosensitive resin composition becomes insoluble in the developing solution. Also,
In this second invention, since the heat-treated film is developed, the portion of the photosensitive resin composition other than the insolubilized portion is removed. Therefore, a pattern of a SiO ₂ thin film is formed on the base.

[0021]

EXAMPLES Examples of the Si-containing thin film forming method of the first invention and the Si-containing thin film pattern forming method of the second invention of the present application will be described below. It should be noted that FIGS. 1, 2 and 3 merely schematically show the shapes, sizes and arrangement relationships of the respective constituents to the extent that the present invention can be understood. Therefore, the present invention is not limited to these examples. Further, the materials used and the numerical conditions such as the amount of the materials used, the processing time, the temperature, the film thickness, and the like described in the following description are only preferable examples within the scope of the invention. Therefore, it should be understood that the present invention is not limited to only these conditions.

[Method of Forming Si-Containing Thin Film of First Invention] First Embodiment of the First Invention A process diagram showing the first embodiment of the first invention with sectional views of FIGS. 1 (A) to 1 (C). Will be described with reference to.

First, a silicon (Si) wafer is used as the base 10. Hereinafter, the base 10 will be referred to as a Si wafer.
A film 12 of a photosensitive resin composition containing a poly (siloxane) derivative having an alkoxy group and an acid generator that generates an acid upon exposure is formed on the Si wafer 10. This first
In the examples, the coating liquid used for forming the film 12 of the photosensitive resin composition was prepared as follows. A weight average molecular weight of poly (di-t-butoxysiloxane) [see the following formula (9)] in which all terminals are hydroxyl groups and side chains are t-butoxy groups (t-Bu groups) as a kind of alkoxy group Is 1
190 g of 10,000 and triphenylsulfonium triflate (PH ₃ S ⁺ OTf ⁻ ) represented by the following formula (10), which is a kind of acid generator, 8.25 g (0.02)
mol) is dissolved in 1780 g of monochlorobenzene, and this solution is filtered through a membrane filter having pores with a pore size of 0.2 μm to prepare a coating solution of the photosensitive resin composition.

[0024]

Embedded image

Next, this coating solution is coated on the Si wafer 10 to a film thickness of 0.2 μm by the spin coating method to form the film 12 of the photosensitive resin composition ((A) of FIG. 1).

Next, the structure of FIG. 1A is prebaked on a hot plate at a temperature of 80 ° C. for 1 minute. Then, the film 12 of the photosensitive resin composition after prebaking is exposed. For the exposure at this time, a Xe-Hg lamp (CM25
Exposure is carried out over a relatively wide range using a 0 cold mirror attached). Here, exposing a relatively wide range means exposing a large area so that the IR spectrum can be measured later. Of course, the entire surface of the wafer may be exposed, or a part of the wafer surface may be exposed. May be. However, in the first embodiment, the entire surface of the wafer is exposed. The exposure amount at that time was 9 mJ / cm ² .

Next, the exposed film 12 is subjected to a heat treatment. In the first example, the heat treatment was performed at 100 ° C. for 2 minutes.

Next, the heated structure is developed with anisole for 20 seconds and then rinsed with xylene for 20 seconds. Subsequently, the structure containing the Si-containing thin film (SiO ₂ film) is heat-treated on a hot plate at 300 ° C. for 5 minutes. This heat treatment, which was performed after development,
It is preferable because it is possible to further promote the conversion of O ₂ and remove the residual solution. The temperature of this heat treatment performed after development is preferably high as long as it does not affect the base. Specifically, it may be determined according to the design.

An IR spectrum of the obtained thin film 12a was taken. In the spectrum, there were no peaks derived from an alkyl group or a silanol group, only the peak of SiO ₂ , and the thin film became SiO _2. Was confirmed.

Further, the obtained thin film 12a is DEM4
51 Parallel plate dry etcher (Nichiden Anelva Co., Ltd.)
O ₂ -RIE was performed for 15 minutes. However, in this etching, the O ₂ gas pressure is 1.0 Pa, the O ₂
Gas flow rate 20sccm, RF power density 0.12W
/ Cm ² It was performed under the conditions. The etching amount in this etching is 13 nm (1 in terms of etching rate)
3 / 15≈0.86 (nm / min)).

(Comparative Example) As a comparative example, plasma C is used.
When the NSG (non-doped silicate glass) film formed by the VD method was etched under the above O ₂ -RIE condition, the etching amount was 11 nm (11 / 15≈0.73 (nm / nm in terms of etching rate).
Minutes)).

Therefore, the thin film 12a formed in this embodiment.
According to the forming method of the first invention, since the etching rate is not so different from that of the NSG film formed by the plasma CVD method even when O ₂ -RIE is performed,
It is considered that the iO ₂ film is formed.

Second Embodiment of the First Invention The formation of a Si-containing thin film and its etching by O ₂ -RIE are carried out in the same procedure as in the first embodiment except that the developing treatment with anisole is not carried out in the constitution of the first embodiment. To do.
The etching amount in this etching was 13 nm. No significant difference was observed in this case with or without the use of developer. However, when contacted with the developer, the film 12
Since the carbon content can be removed, the O ₂ -RIE resistance is considered to be improved.

Third Embodiment of First Invention Formation of a Si-containing thin film and its O ₂ − by the same procedure as in the first embodiment except that the heat treatment after exposure was carried out at 40 ° C. in the constitution of the first embodiment. Etching by RIE is performed. Only the peak of SiO ₂ was observed in the IR spectrum of the film, and it was confirmed that this film was completely SiO ₂ .

Comparative Example A Si-containing thin film was formed without heat treatment after exposure in the configuration of the first embodiment. In this case, in the IR spectrum of the film Si
O ₂ and silanol peaks were observed, confirming incomplete SiO ₂ conversion.

[Method for Forming Pattern of Si-Containing Thin Film of Second Invention] Next, FIG. 2 and FIG. 3 for the embodiment of the second invention.
Will be described with reference to. Here, (A) to (C) of FIG. 2 and (A) to (B) of FIG. 3 show cross-sectional views of examples in which the second invention is applied to formation of an upper layer resist in a two-layer resist method.

First Embodiment of Second Invention A photoresist (MP2400 manufactured by Shipley Co., Ltd.) was spin-coated on a silicon substrate 11a, and then this sample was coated with 200.
The film thickness is 1.5μ when cured by heating in an oven at a temperature of ℃
A lower resist layer 11b of m is formed. Here, this structure constituted by the silicon substrate 11a and the lower resist layer 11b formed on the substrate 11a corresponds to the underlayer 13 referred to in the present invention in this embodiment ((A) of FIG. 2).

Next, a coating solution of the photosensitive resin composition prepared in the above-described first embodiment of the invention is applied on the lower layer resist 11b by a spin coating method to a film thickness of 0.2 μm to form a photosensitive resin composition. The material film 12 is formed ((B) of FIG. 2).

Next, pre-baking is performed under the same conditions as in the first embodiment of the invention, and then, in the first embodiment, the portion of the photosensitive resin composition film 12 to be left is selectively exposed by an electron beam exposure apparatus. To expose. The exposed portion of the film 12 is designated as 12x, and the unexposed portion is designated as 12y. Then, the exposed film 12 is processed by the same procedure as in the first embodiment of the invention.
x and 12y are heat-treated at a temperature of 100 ° C. for 2 minutes ((C) in FIG. 2).

Then, the development is carried out for 20 seconds with anisole in the same manner as in the first embodiment, followed by rinsing with xylene for 20 seconds ((A) in FIG. 3). Then, this sample is heat-treated on a hot plate at 300 ° C. for 5 minutes. The developed heating temperature is the same as that of the already described SiO ₂
As in the case of forming the contained thin film, it is preferable that the temperature is such that the formation of SiO _{2 in} the thin film can be promoted and the remaining solution can be removed. Therefore, it is considered that the heating temperature at this time is preferably high as long as it does not affect the base. Specifically, it is determined according to the design. Thereby, the pattern 12z of the Si-containing thin film according to the first embodiment of the second invention is obtained. The sensitivity (D _n ^0.5 ) of the photosensitive resin composition used here is 1.5 μC / c
m ² and 0.3 according to the method of the first embodiment.
It was found that the pattern of the Si-containing thin film of μm line and space (L / S) can be resolved. Further, the pattern 12z of the Si-containing thin film formed here cannot be measured for the IR spectrum because it is fine, but it is considered that it is a SiO ₂ pattern in view of the results of the first invention (each of the following embodiments). The same in the example).

Next, the structure shown in FIG. 3A is subjected to O ₂ -RIE treatment using a parallel plate type dry etcher (for example, model name DEM451 manufactured by Nichiden Anerva Co.), and the structure shown in FIG. ) Structure is obtained. Here, the lower layer resist portion left after etching is the lower layer resist pattern 11c.
Becomes The lower layer resist pattern 11c and the Si-containing thin film pattern 12z are collectively referred to as a two-layer resist pattern 14c.
Called. However, this etching is the first
As in the example, the O ₂ gas pressure was 1.0 Pa, the O ₂ gas flow rate was 20 sccm, and the RF power density was 0.12 W /
It was set to cm ² . By this etching, 0.3 μmL /
It was confirmed that the S two-layer resist pattern 14 was formed with an aspect ratio of 5.

Second Embodiment of Second Invention In the configuration of the first embodiment of the second invention, the exposure source is an Xe-Hg lamp (with CM250 cold mirror mounted) instead of the electron beam, and the exposure is tested. Similar to the first embodiment except that the exposure is performed through a mask,
A pattern of a Si-containing thin film is formed. However, the exposure amount is set to 9 mJ / cm ² . It was found that according to the method of the second embodiment, the pattern of the Si-containing thin film having the minimum size of the test mask of 0.5 μmL / S can be resolved.

Third Embodiment of the Second Invention Instead of the resin used in the first embodiment of the first invention, a poly (di-t-butoxysiloxane) having a t-butoxy group at the terminal [[11] ) Formula]] and having a weight average molecular weight of 10,000.

[0044]

[Chemical 6]

Except for this, a coating solution of the photosensitive resin composition is prepared in the same manner as in the first embodiment of the second invention, and the Si-containing thin film is patterned using this. The sensitivity (D _n ^0.5 ) of the photosensitive resin composition used here is 8 μC / cm ^2.
And according to the method of the third embodiment, 0.3 μm
It was found that the pattern of the line-and-space (L / S) Si-containing thin film can be resolved.

Fourth Embodiment of the Second Invention Instead of the resin used in the first embodiment of the first invention, poly (di-t-butoxylsesqui) which is a kind of poly (siloxane) having a ladder structure is used. Oxane) [(12) below
[See the formula] and has a weight average molecular weight of 10,000.

[0047]

[Chemical 7]

Other than that, a coating solution of the photosensitive resin composition is prepared in the same manner as in the first embodiment of the second invention, and the i-containing thin film is patterned using this. The sensitivity (D _n ^0.5 ) of the photosensitive resin composition used here is 3 μC / cm ² , and according to the method of the fourth embodiment, the Si-containing thin film of 0.3 μm line and space (L / S) is used. It was found that the pattern can be resolved.

Fifth Embodiment of the Second Invention In comparison with the structure of the first embodiment of the second invention, 8.0 g of tetraphenoxysilane [(PhO) ₄ Si] is used as a crosslinking agent.
(0.02 mol) A coating solution of the resin composition used in the fifth example is prepared in the same manner as in the first example except that it is further added. Then, a patterning experiment using this photosensitive resin composition is performed in the same procedure as in the first embodiment.
The photosensitive resin composition of the third embodiment used here has a sensitivity of 7.2 μC / cm ² , and a sensitivity of 0.3 μC.
It was found that the mL / S pattern can be resolved.

In each of the embodiments of the second invention described above, the second
An example of applying the invention to a two-layer resist process has been shown. However, it goes without saying that the second invention can be applied to the case of forming a pattern of a single-layer Si-containing thin film.

[0051]

As is apparent from the above description, according to the first and second inventions of this application, a film of a predetermined photosensitive resin composition is formed on a base, and then this film is formed. In the first invention, at least an exposure treatment and a heat treatment are carried out, and in the second invention, at least each treatment of a selective exposure, a heating and a development is carried out. For this reason, the silanol generated in the exposed portion of the film surely condenses, so that in the first invention, a SiO ₂ thin film can be obtained, and in the second invention, the SiO ₂ thin film. Pattern is obtained. Therefore, since complicated condition setting by a conventional expensive vacuum sputtering apparatus or CVD apparatus is not required, the working process becomes extremely simple.

Since a Si-containing thin film having a higher silicon content or a pattern thereof can be obtained by a simple method, a high O ₂ -RIE resistance can be obtained by using this Si-containing thin film or its pattern as a mask. To be

[Brief description of drawings]

1A to 1C are process drawings for explaining a process of an embodiment of the first invention.

FIG. 2A to FIG. 2C are process drawings for explaining the process of the embodiment of the second invention.

3A to 3B are process drawings for explaining the process following FIG.

[Explanation of symbols]

 10: Base 11a: Silicon substrate 11b: Lower resist layer 11c: Lower resist pattern 12: Photosensitive resin composition film 12a: Si-containing thin film 12x: Exposed part 12y: Unexposed part 12z: Si-containing thin film pattern 13: Base 14: Two-layer resist pattern

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01L 21/027

Claims (6)

[Claims] 1. A method of forming a Si (silicon) -containing thin film on a lower surface, comprising: (a) a photosensitive material containing a poly (siloxane) derivative having an alkoxy group on a base and an acid generator that generates an acid upon exposure. Formation of a Si-containing thin film, comprising: a step of forming a film of a resin composition; (b) a step of exposing the film; and (c) a step of subjecting the exposed film to a heat treatment. Method. 2. The method for forming a Si-containing thin film according to claim 1, wherein the poly (siloxane) derivative having an alkoxy group is represented by the following formula (1) or the following formula (2). And a copolymer of the following formula (1) and the following formula (2): 1
Or more of the the possible method for forming a Si-containing thin film characterized (provided that (1), (2) R ^1, R in the formula
Each of ² , R ⁵ and R ⁶ represents an alkyl group and may be the same or different. Further, m and n are positive integers indicating the degree of polymerization. ). Embedded image 3. The method for forming a Si-containing thin film according to claim 1, wherein the heat treatment temperature according to (c) is at least 40 ° C. or higher. . 4. A method for forming a pattern of a Si (silicon) -containing thin film on a lower surface, comprising: (a) a poly (siloxane) derivative having an alkoxy group on the base and an acid generator that generates an acid upon exposure. A step of forming a film of a photosensitive resin composition, (b) a step of selectively exposing a portion of the film to be left exposed, (c) a step of heat-treating the exposed film, (d) And a step of developing the heat-treated film, the method for forming a pattern of a Si-containing thin film. 5. The method for forming a pattern of a Si-containing thin film according to claim 4, wherein the poly (siloxane) derivative having an alkoxy group is represented by the following formula (1) or by the following formula (2): 1 selected from the copolymers represented by the following formula (1) and those represented by the following formula (2):
Or a plurality of Si-containing thin film pattern forming methods (wherein each of R ¹ , R ² , R ⁵ and R ^{6 in} the formulas (1) and (2) represents an alkyl group). ,
It may be the same or different. Further, m and n are positive integers indicating the degree of polymerization. ). Embedded image 6. The method for forming a pattern of a Si-containing thin film according to claim 4, wherein the heat treatment temperature in the step (c) is 40 to 300.
A method for forming a pattern of a Si-containing thin film, wherein the temperature range is ℃.