JP2667742B2 - Photosensitive resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention can be used as a constituent material of a resist used in the manufacture of semiconductor devices and the like.
The present invention relates to a novel photosensitive resin which is sensitive to radiation such as light, electron beam, X-ray or ion beam.

[0002]

2. Description of the Related Art Processing techniques on the order of submicrons have become necessary as LSIs become more highly integrated. For this reason,
For example, in an etching process in an LSI manufacturing process, a dry etching technology capable of performing highly accurate and fine processing is employed.

[0003] In the dry etching technique, a substrate to be processed is covered with a resist, the resist is patterned using light, an electron beam, or the like, and the resulting pattern is used as a mask to expose the substrate from the substrate mask by reactive gas plasma. This is a technique for etching a portion to be etched. Therefore, the resist used in the dry etching technique is made of a material having a resolution of submicron order and sufficient resistance to reactive gas plasma.

However, as the degree of integration of the LSI increases, the step of the substrate to be processed becomes larger, and a pattern with a high aspect ratio is formed on the substrate to be processed. For this reason, the thickness of the resist layer tends to be increased so that the steps can be flattened and the resist layer is maintained as a mask until the processing is completed. Therefore, when the resist is exposed with light, the depth of focus of the exposure optical system is significantly restricted, and when the exposure is performed with an electron beam, the electron scattering phenomenon is remarkably affected. With the resist layer, it is becoming difficult to process the substrate as desired.

Therefore, a resist process called a two-layer resist method has been studied as one of new resist processes. This includes a thick polymer layer (hereinafter referred to as a lower layer, usually a layer made of polyimide or a thermoset photoresist) for flattening a substrate step, and
A thin photoresist layer or an electron beam resist layer having O ₂ -RIE resistance formed on the polymer layer (hereinafter, referred to as an electron beam resist layer)
These layers are called upper layers. )). Specifically, assumes the role of the upper layer to obtain a high resolution pattern, the lower layer is the upper layer pattern as a mask O ₂
Patterning by RIE, and the lower layer pattern obtained by this serves as a mask for dry etching during substrate processing.

Since the resist for the upper layer needs to have higher O ₂ -RIE resistance than the resist for the lower layer, it is often formed of a silicon-based photosensitive resin composition. Specifically, a compound in which a photocrosslinking agent or a photopolymerization initiator is blended with a silicone resin as a binder is known, and this can be used as a negative resist.

[0007] As a conventional example of such a photosensitive resin composition, there is the following one.

The one disclosed in Japanese Patent Application Laid-Open No. 61-20030. This is a composition consisting of a resin having a double bond such as poly (acryloyloxymethylphenylethylsilsesquioxane) and bisazide, which can be used as a highly sensitive UV resist under a nitrogen atmosphere. Met.

Japanese Patent Publication No. 60-49647 discloses a photosensitive resin composition using polysilane as a photopolymerization initiator. Specifically, it has been shown that a composition comprising a poly (organosiloxane) having a double bond and dodecamethylcyclohexasilane has good properties as an ultraviolet curable resin.

Japanese Patent Application Laid-Open No. 55-127523 discloses a photosensitive resin composition using an organic peroxide as a photopolymerization initiator. Specifically, a composition using a poly (organosiloxane) having a double bond and a suitable organic peroxide (such as a peroxyester) can be uniformly cured by irradiating the composition with ultraviolet rays. It is shown to be a film.

Further, there has been described a photosensitive resin composition for an upper layer resist based on a completely different idea from the above-described compositions, as described below.

For example, the one disclosed in JP-A-61-144639. This is because a general-purpose positive photoresist such as OFPR-800 (resist manufactured by Tokyo Ohka Kogyo Co., Ltd.) is used for poly (phenylsilsesquioxane) and cis-resist.
(1,3,5,7-tetrahydroxy) -1,3,5
It is obtained by adding a small amount of 7-tetraphenylcyclotetrasiloxane, and can be used as a positive resist that can be alkali-developed.

The use of a substance other than poly (siloxane) as a binder has also been studied. For example, JP-A-61-198151 discloses a positive photosensitive resin composition having sensitivity to visible light using a novolak resin having a trialkylsilyl group together with a diazonaphthoquinone photosensitive agent.

[0014]

However, when the conventional photosensitive resin composition is used as an upper resist in a two-layer resist process, there are the following problems.

(A) In general, a photocuring reaction which proceeds through an organic radical is inhibited by oxygen. Therefore, in the case of a photosensitive resin composition which is photocured according to this principle (for example, a photopolymerization initiator using bisazide as a photopolymerization initiator) Kaisho 61-2003
In the case of the photosensitive resin composition disclosed in Japanese Patent Application Publication No. 0-205, high sensitivity could not be achieved unless exposure was performed in a nitrogen atmosphere. This problem also occurs in the case of the photosensitive resin composition disclosed in Japanese Patent Application Laid-Open No. 55-127023 in which the photopolymerization initiator is composed of an organic peroxide. Therefore, although the use of an organic peroxide improves the properties of the cured film, the composition requires a long curing time.

(B) Further, according to the knowledge of the inventor of the present application, the photosensitive resin composition disclosed in Japanese Patent Publication No. 60-49647 using polysilane as a photopolymerization initiator is based on a composition using bisazide. Although not as great, the presence of oxygen also hinders high sensitivity.

Due to the above-mentioned problems (a) and (b), throughput cannot be increased when exposure is performed in an oxygen atmosphere, and nitrogen is supplied to the vicinity of a wafer in order to perform exposure in a nitrogen atmosphere. This is a problem because it requires various facilities to do this.

(C) A photosensitive resin composition disclosed in Japanese Patent Application Laid-Open No. 61-144639 having a constitution in which a silicon compound is added to a general-purpose photoresist, and a composition other than poly (siloxane) is used as a binder. the photosensitive resin composition disclosed in JP-a-61-198151 discloses that used as the silicon content of the added silicon compound, has a low silicon content of the binder used, sufficient O ₂ -RI
Does not show E resistance.

The present invention has been made in view of such a point, and accordingly, an object of the present invention is to provide a high sensitivity and high O
An object of the present invention is to provide a novel photosensitive resin composition having _2- RIE resistance.

[0020]

In order to achieve this object, according to the photosensitive resin composition of the present invention, poly (silsesquioxane) is contained as a binder, and light or electron beam is used as a crosslinking agent. , An acid generator that generates an acid upon irradiation with radiation such as an X-ray or an ion beam, and a tetrafunctional silane as a crosslinking accelerator.

Poly (silsesquioxane) used as a binder is a kind of silicone resin and has a high silicon content, so that it gives the photosensitive resin composition O ₂ -RIE resistance. Here, there are various silicone resins, and these various silicone resins generally include four types of silane monomers, monofunctional silane, difunctional silane, trifunctional silane, and tetrafunctional silane, alone or It is produced by hydrolysis and condensation (or copolymerization) of a plurality to obtain desired physical properties. However, since a solid film needs to be formed on the substrate for the purpose of the present invention, the silicone resin used as the binder is a monofunctional silane or a linear siloxane obtained from a bifunctional silane. Inappropriate, poly (silsesquioxane) obtained from trifunctional silane is preferable because it becomes a solid. Therefore, in the photosensitive resin composition of the present invention, poly (silsesquioxane) is used as a binder.

The photosensitive resin composition of the present invention functions as a negative resist, and its patterning principle is based on the growth of siloxane chains. Therefore, the structure of the poly (silsesquioxane), that is, the substituent on the silicon atom is not particularly limited. However, in view of the fact that the synthesis technology has been established, it is preferable that poly (silsesquioxane) be a polysiloxane represented by the following formula (where R ¹ and R ² are alkenyl: A group, an alkyl group, a phenyl group or an alkoxyl group, which may be the same or different, and R ³ is hydrogen,
It is an alkyl group, a phenyl group or a trimethylsilyl group. N is a positive integer. ).

[0023]

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Such a poly (silsesquioxane)
For example, Japanese Patent Application Laid-Open No.
The compound can be synthesized according to the method disclosed in Japanese Patent Application No. 2-283128 (Japanese Patent Application No. 61-127638), the method disclosed in U.S. Pat. No. 4,826,943, and the like.

Poly (alkoxysilsesquioxane) in which R ¹ and R ² are alkoxyl groups undergoes partial alcoholysis of silicon tetrachloride in the presence of triethylamine.
Then, it is obtained by hydrolysis.

Furthermore, the poly (silsesquioxane) used can form a solid film, does not gel at the synthesis stage, and is soluble in a solvent for preparing a resist coating solution. Since it is necessary, those having a weight average molecular weight in the range of 1,000 to 3,000,000 are preferable, and from the viewpoint of improving resolution, the weight average molecular weight is in the range of 1,000 to 300,000. Are preferred.

The acid generator, which is another essential component of the photosensitive resin composition of the present invention, crosslinks only the irradiated portion of the photosensitive resin composition and insolubilizes the portion in a developing solution. In addition, in the case of a configuration in which a tetrafunctional silane is added, in addition to causing the above-described crosslinking, the acid-generating substance is combined with poly (silsesquioxane) only in the irradiated portion of the photosensitive resin composition. Condensation with the functional silane takes place.

As the acid generating substance, various known substances can be used. However, hydrohalic acid is not very suitable because of its weak catalytic action. A triarylsulfonium salt represented by the following formula and a diaryliodonium salt represented by the following formula are preferable because they generate an acid stronger than hydrohalic acid (provided that Ar in the formula and the formula is an aryl group; , X ^- is BF ₄ ^-,
PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , ClO ₄ ⁻ , those represented by the above formula or those represented by the above formula. ).

[0029]

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These triarylsulfonium salts are:
J. V. Researched by Crivello et al. (For example, Reference: Journal of Polymer Science., Polymer Chemistry Edition (J. Polymer).
Sci. , Polymer Chem. Ed. , 18,
2677 (1980)), and can be synthesized according to the synthesis method disclosed in this document, but some are now commercially available (eg, Midori Kagaku). Commercially available products can be used in carrying out the present invention.

Diaryliodonium salts are also described in J. Org. V. Researched by Crivello et al. (For example, references: J. Polymer Sci., Polymer)
rChem. Ed. , 22, 69 (1984)), which can be synthesized according to the synthetic method disclosed in this document, but some of them are commercially available. Commercially available products can be used in carrying out the present invention.

Further, as a suitable acid generator other than the above-mentioned triarylsulfonium salts and diaryliodonium salts, for example, benzoin tosylate represented by the following formula can be mentioned.

[0033]

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These acid-generating substances exhibit their effects when added in an amount of 0.05 to 50% by weight with respect to the binder. When trying to obtain high sensitivity,
The amount of the acid generator added is 0.5 to 50 with respect to the binder.
Preferably, the amount is in the range of weight percent.

The tetrafunctional silane to be added to the photosensitive resin composition is formed between the siloxane chains (-Si-O-Si-) or at the terminal (-) of the poly (silsesquioxane) by the action of an acid generator. (Si-O-Si-R) to form new crosslinkable points there. As a result of the formation of a large number of such cross-linking points in the poly (silsesquioxane), the radiation-irradiated portion of the photosensitive resin composition in this configuration becomes a polyfunctional polymer that can be condensed, and The action rapidly gels the three-dimensional skeleton because it spreads at an accelerated rate. That is, the sensitivity as the photosensitive resin composition can be further improved.

As the tetrafunctional silane, any one having the above-mentioned crosslinking promoting function can be used. However, tetraalkoxysilane, tetraaryloxysilane and the like are preferred because they are relatively stable to moisture. Further, in terms of being solid, tetraaryloxysilane represented by the following formula is more preferable (where Ar is an aryl group, and specifically, phenyl, 1-naphthyl, 2-naphthyl) Or a p-tolyl group).

(ArO) ₄ Si... The addition amount of the tetrafunctional silane is such that the crosslinking promoting function effectively occurs in the film of the photosensitive resin composition, and the film is not weakened. It is sufficient that the tetrafunctional silane does not precipitate from the film.
It is preferred that the amount be in the range of ５０50% by weight. However, if high sensitivity is to be obtained, the amount is preferably in the range of 1 to 50% by weight.

In using the photosensitive resin composition, the composition is applied on a substrate by spin coating to form a film on the substrate. For this reason, a solvent for preparing the coating solution is required. As this solvent,
For example, chlorobenzene, xylene, dioxane, methyl isobutyl ketone, isoamyl acetate, etc. can be mentioned.

When the photosensitive resin composition is used, the film of the composition is irradiated with radiation, and then the sample is subjected to a heat treatment, so that the irradiated portion of the film can be easily insolubilized in a developing solution. Become.

[0040]

EXAMPLES Examples of the photosensitive resin composition of the present invention will be described below. It should be noted that the materials used and the numerical conditions such as the amount of the materials used, the processing time, the temperature, and the film thickness described in the following description are only preferred examples within the scope of the present invention. Therefore, it should be understood that the present invention is not limited only to these conditions.

Example 1 * Preparation of Photosensitive Resin Composition First, the photosensitive resin composition of Example 1 is prepared by the following procedure.

As a poly (silsesquioxane), in this case R ¹ and R ² in the above formula are both allyl groups (C
0.5 g of poly (allylsilsesquioxane) having H ₂ = CHCH ₂ —), R ³ being hydrogen, and a weight average molecular weight M _w of 7,000 (M _w / M _n = 1.7); In this case, 0.019 g of benzoin tosylate of the above formula as a generating substance, and in this case, tetraphenoxysilane (formula (a) below) 0.1 as a tetrafunctional silane monomer
0 g was dissolved in 5 ml of chlorobenzene, and this solution was filtered through a Teflon filter having a hole having a diameter of 0.2 μm to prepare a coating solution of the photosensitive resin composition of Example 1. The poly (allylsilsesquioxane) is
The one synthesized by the synthesis method described in U.S. Pat. No. 4,826,943 to the applicant of this application is used, tetraphenoxysilane is manufactured by Shin-Etsu Chemical Co., Ltd., and benzoin tosylate is manufactured by Midori Chemical. Used.

[0043]

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* Measurement of Sensitivity and Contrast Next, the sensitivity and contrast of the photosensitive resin composition of Example 1 are measured by the following procedure.

First, a coating solution of the photosensitive resin composition of Example 1 was applied to a silicon substrate having a diameter of 3 inches by a spin coating method under a rotation condition of 1500 rpm.

Next, this sample was placed on a hot plate for 8 minutes.
Pre-bake for 1 minute at a temperature of 0 ° C.

Thus, a 0.24 μm thick film of the photosensitive resin composition of Example 1 can be formed on the silicon substrate.

Next, a chromium mask having a test pattern is brought into close contact with this sample, and thereafter, exposure is performed using a KrF excimer laser (wavelength: 248 nm) with various exposure amounts. In this case, a laser device called EMG201 manufactured by Lambda Physics was used for this exposure. This apparatus can perform exposure of 0.30 mJ / cm ² with one pulse.

Next, the exposed sample was baked at a temperature of 120 ° C. for 1 minute using a hot plate, and then methyl isobutyl ketone: isopropyl alcohol (IP
A) Develop with a mixed solution of 1: 1 (volume ratio) (this becomes a developer) for 30 seconds, and then rinse with IPA for 30 seconds.

Next, the remaining film thickness of the developed and rinsed sample was measured by a film thickness meter (in this case, Taly Step manufactured by Taylor Hobson Co., Ltd.), and the relationship between the exposure amount and the remaining film thickness was measured. Is obtained.

Thereafter, the sensitivity D _n ^{0.5 at which} the remaining film thickness becomes 50% of the initial film thickness (0.24 μm in this case) and the contrast γ of this composition are determined.

As a result, it was found that D _n ^0.5 was 1.3 mJ / cm ² and the contrast γ was 0.87.

[0053] * O ₂ measurements -RIE resistance is then measured O ² -RIE resistance of the photosensitive resin composition of Example 1 by the following procedure.

First, a photoresist (in this case, MP240 manufactured by Shipley Co., Ltd.) is formed on a silicon substrate by a spin coating method.
0) is applied and thermally cured to form a lower resist layer having a thickness of 2 μm on the silicon substrate.

Next, a coating solution of the photosensitive resin composition of Example 1 is applied on the lower resist layer under the same conditions as those for measuring the sensitivity and contrast.

Next, pre-bake, exposure, post-exposure bake, development, and rinsing are performed under the same conditions as those for measuring sensitivity and contrast except that the exposure amount is set to 10 mJ / cm ² .

When the pattern after rinsing was observed using a SEM length measuring machine, it was confirmed that the 0.5 μm line
The and space pattern was resolved, and the actual size of the line portion was found to be 0.52 μm.

Next, this sample was set in a reaction tank of a dry etching apparatus, called DEM451, manufactured by Nidec Anelva, and thereafter, the gas pressure in the reaction tank was set to 1.3 Pa, and the RF power density was set to 0. The lower resist layer is etched under the conditions of 12 W / cm ² and an O ₂ gas flow rate of 50 sccm.

When the sample after etching was observed using a SEM length measuring machine, it was found that the 0.5 μm line
It was found that the and space pattern had been resolved, and the actual size of the line portion was 0.49 μm.

As is clear from the results of this O ₂ -RIE experiment, the photosensitive resin composition of the present invention was produced by using O ₂ -RIE.
Slightly retreats (retreats about 5% in the example)
Therefore, it can be understood that it has excellent O ₂ -RIE resistance.

[0061]

[0062]

[0063]

(Example 2) In the same manner as in Example 1, except that the acid generating substance was changed to 0.021 g of a triarylsulfonium salt represented by the following formula (b) in place of benzoin tosylate in the structure of Example 1. Thus, the photosensitive resin composition of Example 2 is prepared.

[0065]

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Next, the sensitivity and contrast of the photosensitive resin composition of Example 2 are determined in the same procedure as in Example 1.

As a result, it was found that D _n ^0.5 was 0.35 mJ / cm ² and γ was 0.90.

[0068]

[0069]

[0070]

(Example 3) In the same manner as in Example 1, except that the acid generator was changed to 0.032 g of a diaryliodonium salt represented by the following formula (c) in place of benzoin tosylate. Thus, the photosensitive resin composition of Example 3 is prepared.

[0072]

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Next, the sensitivity and contrast of the photosensitive resin composition of Example 3 are determined in the same procedure as in Example 1.

As a result, it was found that D _n ^0.5 was 7.1 mJ / cm ² and γ was 1.3.

[0075]

[0076]

[0077]

Example 4 In the structure of Example 1, instead of poly (allylsilsesquioxane), R ¹ and R ² in the above formula were both tertiary butyl groups (CH ₃ ) ₃ C—. , poly (silsesquioxane) using the R ³ is hydrogen weight average molecular weight Mw of 1,700 (Mw / Mn = 1.05), the amount of acid generating material 0.
A photosensitive resin composition of Example 4 is prepared in the same manner as in Example 1 except that the amount is changed to 020 g.

Next, the sensitivity and contrast of the photosensitive resin composition of Example 4 are determined in the same procedure as in Example 1.

As a result, it was found that D _n ^0.5 was 2.5 mJ / cm ² and γ was 1.0.

[0081]

[0082]

[0083]

[0084]

[0085]

In order to clarify the differences in the composition and properties of the photosensitive resin compositions of the examples, the compositions and properties of the photosensitive resin compositions are shown in Table 1. In Table 1, the tetrafunctional silane monomer is abbreviated as Q monomer.

[0087]

[Table 1]

[0088]

Although the embodiments of the photosensitive resin composition of the present invention have been described above, the present invention is not limited to the above-described embodiments.

For example, in the above embodiment, the exposure light source is Kr
Although the F excimer laser is used, the photosensitive resin composition of the present invention is also sensitive to light sources other than the KrF excimer laser, for example, electron beams, X-rays, lasers of other wavelengths, etc., and exhibits the same effects as those of the examples.

Further, in the above-described embodiment, an example was described in which the photosensitive resin composition of the present invention was used as a constituent material of a resist for forming a pattern. However, the photosensitive resin composition of the present invention is used only for a resist. It is not limited to. For example,
It can also be used as a junction coating agent and a buffer coating agent for protecting semiconductor elements.

[0092]

As is clear from the above description, the photosensitive resin composition of the present invention has a constitution containing poly (silsesquioxane), an acid generator and a tetrafunctional silane monomer. A photosensitive resin composition having higher sensitivity than before and having excellent O ₂ -RIE resistance is obtained.

Thus, for example, a resist suitable as an upper layer resist of a two-layer resist process can be obtained. Therefore, application to manufacturing of a highly integrated semiconductor device can be expected.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-129642 (JP, A) JP-A-60-260947 (JP, A) JP-A-61-250056 (JP, A) JP-A-4- 184445 (JP, A) JP-A-3-166546 (JP, A) JP-A-3-28852 (JP, A) JP-A-4-159553 (JP, A)

Claims (1)

(57) [Claims] 1. A poly (silsesquioxane) represented by the following general formula (where R ¹ and R ² are alkenyl, alkyl, phenyl or alkoxyl groups, and R ³ is hydrogen, an alkyl group, a phenyl group, or a trimethylsilyl group, and n is a positive integer.) The weight average molecular weight is in the range of 1,000 to 3,000,000. And an acid generator that generates an acid upon irradiation with radiation, wherein the tetraaryloxysilane represented by the following formula is added in the range of 0.1 to 50% by weight based on the poly (silsesquioxane). Characteristic photosensitive resin composition. Embedded image