JPH0769610B2 - Pattern formation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pattern forming method, and more particularly, to forming a fine resist pattern on a submicron level in the production of VLSI, ultrahigh speed transistor, magnetic bubble memory and the like. Regarding the method.

[Prior Art] In recent years, with the remarkable increase in the degree of integration of semiconductor elements and the like, there has been a demand for a method of highly accurately forming a pattern having an extremely small line width and a small space.

As the degree of integration is improved, a multilayer wiring structure is required more and more in semiconductor devices and the like, and unevenness that cannot be ignored in the photolithography process has appeared on the surface of a semiconductor substrate to be patterned. Such irregularities irregularly reflect the exposure light that has passed through the photoresist, causing a phenomenon in which a portion that should not be exposed is irradiated. In addition, a standing wave is generated based on the interference between the reflected light from the base substrate and the incident light.

Since any of these effects causes a reduction in resolution, it has become difficult to perform high-resolution fine processing on an actual element by the conventional method using a single-layer resist.

For the purpose of solving the above problems, various multilayer resist methods have been proposed, and recently, a first resist layer is formed on a substrate using a conventional photoresist to flatten the unevenness of the base, A two-layer resist method, in which a second resist layer is formed of a photo- and radiation-sensitive polymer composed of an organosilicon polymer, has been actively researched (for example, E. Ong and
ELHu, Solid State Technology, 160 (1984).

The outline of the linography process using such a two-layer resist method is shown in FIG. First, as shown in FIG. 1A, a first resist layer 2 and a second resist layer 3 are formed on a semiconductor substrate 1.
And irradiating light or radiation to a predetermined portion of the second resist layer 3, a pattern is formed by development as shown in FIG. 1 (b), and then treated with oxygen plasma.
In the remaining portion of the second resist layer 3, the surface is changed to SiO ₂ and etching does not proceed, while in the portion where the first resist layer 2 is exposed, the first resist layer is oxidatively removed by etching, and The state shown in FIG.

In this way, the unevenness of the base substrate is flattened, and the second substrate
Since the resist layer is thin and uniform, the exposure conditions are ideal and high-resolution pattern transfer is expected.

In order to achieve high resolution by using the above two-layer resist method, the following conditions are essential.

(1) The first resist layer sufficiently absorbs the light used for exposing the second resist layer, and the reflection from the base and the standing wave do not affect the second resist layer.

(2) The etching grade ratio by the oxygen plasma of the first resist layer and the second resist layer is sufficiently large.

(3) The first resist layer should not be immersed in the coating solvent, developing solvent, or rinse solvent for the second resist layer.

(4) The first resist layer must withstand dry etching of the substrate.

Various resist materials have been proposed as materials for the second resist layer to date in order to realize the above two-layer resist method (for example, E. Reichanis, G. Sm.
olinsky, and CW Wilkins, Jr., Solid State Technology
130 (1985)). All of these materials contain an organic silicon polymer, and Si atoms in the material are converted into SiO ₂ during oxygen plasma treatment to form an oxygen plasma resistant film on the resist surface. Utilizing this property, the first resist layer is processed as shown in FIG. By the way, most of these organosilicon resists are negative resists so far,
Since the photosensitive area is limited to Deep UV, X-ray, and electron beam,
Limited use. Further, in the case of a negative resist, there is a problem in the process that peeling is difficult at the end of the process because the irradiated part is generally highly crosslinked. On the other hand, although several types of positive resists are known, most of them still have a photosensitive area limited to Deep UV, X-rays, and electron beams. In addition, the O ₂ RIE (O ₂
In the process of reactive ion etching, that is, reactive ion etching using oxygen plasma,
In order to suppress the pattern conversion difference from the resist layer to the first resist layer as small as possible, the second resist layer is required to have extremely high oxygen plasma resistance. unacceptable.

As described above, from the viewpoint of practicality, the known organosilicon-based resist is not yet sufficient as the upper layer resist (the second resist layer in FIG. 1) of the two-layer resist method, and it requires significant improvement. I am trying.

In the lithography process of the current semiconductor process,
In principle, alkali-development positive resists, which are excellent in resolution and dry etch resistance, are the mainstream, and it is considered that this tendency will continue in the future. Therefore, taking practicality into consideration, the most promising two-layer resist process is a process in which a positive resist which is excellent in resolution, sensitivity and oxygen plasma resistance and which is an alkali developing type is used as the upper layer resist.

[Problems to be Solved by the Invention] As described above, in the conventional two-layer resist method, it is possible to obtain the one satisfying all the conditions of resolution, sensitivity, photosensitive wavelength region, and pattern transfer accuracy from the upper layer to the lower layer. Not not.

The object of the present invention is to use an alkali-developable positive-working organosilicon resist, which is extremely excellent in resolution / sensitivity and oxygen plasma resistance, as an upper layer resist, thereby satisfying the above-mentioned conditions and being a very practical two-layer resist. To provide the law.

[Means for Solving the Problems] In order to achieve the above object, the inventors have studied various materials, and as a result, have found that a photosensitive material containing a certain kind of alkali-soluble organosilicon polymer and a photosensitive dissolution inhibitor as a main component. The inventors have found that the method of using a volatile resin composition as the second resist layer is effective and completed the present invention.

In the two-layer resist method, it is necessary to use, as the second resist layer, a polymer material having both photosensitivity and oxygen plasma resistance. As such a material, an organometallic polymer containing a metal atom in the molecule can be used. This is because, in general, the organometallic polymer film forms a metal oxide film derived from the metal element in the polymer on the surface by the oxygen plasma treatment, and this oxide film has remarkable resistance to oxygen plasma. is there. However, it has been difficult to impart photosensitivity to the organometallic polymer itself. Therefore, as a result of studying various possibilities, it is found that a method in which oxygen plasma resistance and photosensitivity are assigned to different substances and a composition obtained by mixing the two is used as the second resist layer is effective. I found it. That is, it was found that in a coating film composed of a mixture of an alkali-soluble organometallic polymer and a photosensitive dissolution inhibitor, only a light-irradiated portion was selectively solubilized in an alkali developing solution to obtain a positive resist pattern. Then, such a positive resist pattern was formed on a suitable organic polymer material film in the same manner as described above and subjected to O ₂ RIE treatment, and as shown in FIGS. 1 (b) to 1 (c),
It was confirmed that the lower layer of the organic polymer material film was etched and the pattern was transferred from the upper layer to the lower layer with high accuracy.

That is, the present invention provides a first resist layer on a substrate,
A second resist layer is formed on the first resist layer, and the second resist layer is exposed to light to expose a desired portion, and developed to form a pattern in which the desired portion of the first resist layer is exposed. In a method for forming a fine pattern by removing the exposed first resist layer portion by dry etching, an alkali-soluble polyorganosilsesquioxane in which all or part of a side chain is an organic group having a phenolic hydroxyl group A composition containing, as a main component, a system polymer and a photosensitive dissolution inhibitor is used as the photosensitive resin composition for forming the second resist layer.

Alkali-soluble organometallic polymer The alkali-soluble organometallic polymer which is one of the main components of the photosensitive resin composition used in the present invention will be described in detail.

Considering its role, it is desirable that the alkali-soluble organometallic polymer be efficiently converted into a dense metal oxide by contact with oxygen plasma, and therefore, the metal element is more likely to be present in the polymer side chain than the polymer side chain. It is advantageous if it is contained in the main chain. Further, as the metal element, Si,
Ge, Sn, Ti, etc. are conceivable, but considering the availability of raw materials, ease of synthesis, safety, etc., Si is the most powerful. To impart alkali solubility to the organometallic polymer, an acidic group such as a phenolic hydroxyl group or a carboxyl group may be introduced into the side chain of the polymer.

From the above viewpoints, as a result of examining various organosilicon polymers as the alkali-soluble organometallic polymer, the alkali-soluble polyorganosilsesquioxane-based polymer is preferable, and particularly, the alkali represented by the following general formula (1) It was revealed that the soluble polyorganosilsesquioxane polymer is excellent in all properties.

(R ₁ -SiO _3/2 ) _n (R ₂ -SiO _3/2 ) _m (R ₃ -SiO _3/2 ) ₁ (R ₄ -SiO _3/2 ) _o (R ₅ -SiO _3/2 ) _p (R ₆ -SiO _3/2 ) _q (1) Here, R ₁ R ₂ in the general formula (1) is an organic group having a phenolic hydroxyl group, for example, a hydroxyphenyl group or a dihydroxyphenyl group. And an organic group comprising a group and an alkylene group having 1 to 6 carbon atoms bonded to the phenyl group. The carbon number of the alkylene group is 1
More preferably, it is ˜2. Also, R ₃ , R ₄ , R ₅ ,
R ₆ is an organic group containing no phenolic hydroxyl group, and there is no particular limitation regarding these. n and m are positive integers including zero, except when both are zero. l,
o, p, and q are positive integers including zero, and (n + m) / (n + m + l + o + p is necessary to obtain sufficient alkali solubility.
+ Q)> 0.4 must be satisfied.

The side chain in the general formula (1) is specifically, for example, Is.

These alkali-soluble polyorganosilsesquioxane-based polymers are soluble in alkaline solutions, for example, tetramethylammonium hydroxide aqueous solution and sodium hydroxide aqueous solution, while general-purpose organic solvents, for example, alcohol-based and ether-based. It easily dissolves in organic solvents such as amide, ketone, ester, and cellosolve. Further, these alkali-soluble polyorganosilsesquioxane-based polymers show almost no film slippage in oxygen plasma and exhibit extremely high dry etching resistance.

Photosensitive Dissolution Inhibitor Next, the photosensitive dissolution inhibitor which is another main component of the photosensitive resin composition used in the present invention will be described.

The role of the photosensitive dissolution inhibitor in the alkali-developable photosensitive resin composition acts to inhibit the alkali solubility of the alkali-soluble organosilicon polymer in the unexposed area,
On the other hand, in the exposed area, it is converted into an alkali-soluble compound by photolysis or loses the effect of inhibiting alkali dissolution to make the exposed area alkali-soluble. As the light-sensitive dissolution inhibitor relating to the present invention, o-nitrobenzyl ester, diazomeldrum acid, o-quinonediazide and the like can be used. Particularly, those which are sensitive to UV light of 300 nm or more include 1,2-naphtho Quinone diazides are effective. As the 1,2-naphthoquinonediazides, those represented by the following general formula (2) are preferable.

(However, R ₇ is a monovalent organic group.) Specific examples include the compounds (I) to (XXIV) shown below.

Next, a method for forming a fine pattern by the two-layer resist method of the present invention using the above photosensitive resin composition will be described.

Alkali-soluble organosilicon polymers (these polymers may be used alone or in the form of a mixture) 70
70 to 95% by weight of a base polymer containing 100 to 100% by weight (an alkali-soluble organosilicon polymer can be mixed with a polymer which serves as a film forming aid such as a novolac resin in a range of 0 to 30% by weight. Specifically, if it exceeds this range, it is not preferable in terms of oxygen plasma resistance.) And 30 to 5% by weight of the photosensitive dissolution inhibitor (when an amount of the photosensitive dissolution inhibitor in excess of this range is used, In general, it is not preferable in terms of sensitivity and oxygen plasma resistance. The photosensitive dissolution inhibitor may be a single substance or a mixture of a plurality of substances.)
What was dissolved in a general-purpose organic solvent such as ethyl cellosolve acetate is used as the second layer resist solution.

Next, an outline of a two-layer resist method using the above photosensitive resin composition will be described. First, as the first resist layer of the two-layer resist method, a commercially available positive resist (for example, manufactured by Shipley Co., Ltd.
AZ1350J, Microposit 1300 series, Tokyo Ohka
Hard-baked CFPR-800 etc. or polyimide resin (eg Hitachi Chemical PIQ etc.) can be used. These base leveling materials sufficiently flatten the irregularities of the substrate, sufficiently absorb the exposure light of the second resist layer, and are not soaked at the time of coating, developing and rinsing the second resist layer. There is no.

The first resist layer is formed by spin-coating these base leveling materials and hard-baking them under predetermined conditions. On top of this,
The second layer resist solution is spin-coated and pre-baked under predetermined conditions to form a two-layer resist (FIG. 1 (a)). Next, the upper layer (second resist layer) is subjected to desired pattern exposure, and only an exposed portion is selectively dissolved using an alkali developing solution such as an aqueous solution of tetramethylammonium hydroxide to form a positive resist pattern. Form on the upper layer. When this is processed by dry etching using oxygen plasma (referred to as O ₂ reactive ion etching or O ₂ RIE), the lower layer (first resist layer) can be processed using the upper layer resist pattern as a mask. In this case, the underlying processing shape depending on the purpose, O ₂ RIE
It can be controlled by the oxygen gas pressure (Po ₂ ) inside. A relatively low oxygen gas pressure (Po ₂ <several mtorr) is desirable to obtain a high aspect ratio vertical shape, and a tapered etch shape is possible at a relatively high oxygen gas pressure (Po ₂ > several mtorr). is there. By the above two-layer resist process, submicron level fine processing can be easily performed with an aspect ratio of 3 or more.

[Operation] First, in the photosensitive resin composition of the present invention, one component, the alkali-soluble organosilicon polymer, forms a silicon oxide film in oxygen plasma, and thus functions as an O ₂ RIE resistant film. On the other hand, the other main component, a photosensitive dissolution inhibitor, inhibits the alkali solubilization of the alkali-soluble organosilicon polymer in the unexposed portion, and the inhibitor itself becomes alkali-soluble by photodegradation in the exposed portion, It functions to dissolve the entire exposed area in an alkaline developer. Therefore, the photosensitive resin composition composed of these two main components can be used as the upper layer resist (second resist) of the two-layer resist method. That is, a first resist layer made of an appropriate organic polymer material is formed on the surface of a semiconductor substrate, a second resist layer made of the above-mentioned photosensitive resin composition is formed on the first resist layer, and the second resist layer is formed as described above. When patterned to, the second resist layer has a high O ₂ RIE resistance, so the first resist layer is used as a mask for O ₂ RIE.
Can be dry-etched.

By the process described above, a submicron pattern having a high aspect ratio can be easily formed.

[Examples] Hereinafter, some of the examples of the present invention will be specifically described, but the present invention is not limited thereto. First, a synthesis example of the alkali-soluble polyorganosilsesquioxane-based polymer for forming the second resist layer used in the present invention will be given.

Synthesis Example 1 An alkali-soluble polyorganosilsesquioxane polymer in which the p-hydroxybenzyl group is an organic group having a phenolic hydroxyl group.

1.1 Synthesis of p-methoxybenzyltrichlorosilane A 5 l three-necked flask equipped with a stirrer, condenser, dropping funnel and hydrochloric acid trap is replaced with nitrogen. In a flask, 79 g (0.80 mol) of cuprous chloride and 1261 tri-n-propylamine were added.
Add g (8.80mol) and p-methoxybenzyl chloride
1256g (8.02mol) and trichlorosilane 1184g (8.74mol)
The above mixture is added dropwise over 5 hours while stirring under nitrogen pressure. After aging until the flask temperature returns to room temperature, hexane 1 is added to precipitate a salt. The salt was filtered and then distilled under reduced pressure to obtain 1182 g (4.62 mol) of the desired product. Yield 57.7%; Boiling point 92 ° C / 4mmHg; NMR (60MHz, CCL ₄ , CH ₂ Cl ₂ ,
δ5.33), δ2.93 (2H, s), δ3.83 (3H, s), δ6.86
(2H, d, J = 9Hz), δ7.15 (2H, d, J = 9Hz) 1.2 Synthesis of poly (p-methoxybenzylsilsesquioxane) Equipped with stirrer, cooling tube, dropping funnel and hydrochloric acid trap Add 2 liters of water to a 5 liter three-necked flask. 1182 g of p-methoxybenzyltrichlorosilane dissolved in toluene 1
(4.62 mol) was added dropwise over 1.5 hours with stirring, and then
Aging for 1.5 hours. The mixture is transferred to a separatory funnel and the toluene layer is separated. After removing toluene and water by distillation,
12 g of a 10 wt% methanol solution of potassium hydroxide is added to the above hydrolysis product and heated at 200 ° C. for 2 hours. By heating under reduced pressure, 797 g (4.60 mol) of the desired product was obtained. Yield 9
9.4%; number average molecular weight 1000 to 100000; NMR (60MHz, CDCl ₃ ,
CH ₂ Cl ₂ , δ5.33), δ1.95 (2H, br.s), δ3.83 (3H, b
rs), δ6.80 (4H, br.s); IR (νcm ^-1 ) 2940,2850,162
0,1520,1470,1305,1260,1190,1130,1040,845 1.3 Synthesis of poly (p-hydroxybenzylsilsesquioxane) 5l three-necked flask equipped with stirrer, cooling tube, dropping funnel and hydrochloric acid trap Is replaced with nitrogen. 797 g (4.60 mol) of poly (p-methoxybenzylsilsesquioxane) was dissolved in 600 ml of acetonitrile by heating and placed in a flask.
Then 1378 g (9.20 mol) of sodium iodide are added. While heating under reflux under nitrogen pressure, trimethylchlorosilane 999g
(9.20 mol) is added dropwise in 4 hours. After aging for 18 hours while heating under reflux under nitrogen pressure, slowly add 200 ml of water,
Then, water and acetonitrile are added, and the mixture is further heated under reflux for 6 hours. Separate the acetonitrile layer, then
The acetonitrile layer is washed with a mixed aqueous solution of sodium hydrogen sulfite and sodium chloride, added dropwise to water and reprecipitated. After drying by vacuum heating, 368 g (2.31 mol) of the desired product was obtained. Yield 50.2%;
Number average molecular weight 1000 to 100000; NMR (60MHz, DMSO-d ₆ , CH ₂ Cl
₂ , δ5.68), δ1.75 (2H, br.s), δ6.61 (4H, br.
s), δ8.93 (1H, br.s), IR (νcm ^-1 ) 3350,1620,1520,
1430,1250,1190,1130,1050,845,805,760 1.4 Poly (p-hydroxybenzylsilsesquioxane-co-p-methoxybenzylsilsesquioxane-co
-P-Trimethylsiloxybenzylsilsesquioxane) In the method for synthesizing poly (p-hydroxybenzylsilsesquioxane) described in the paragraph 1.3, a reaction reagent (trimethylchlorosilane and iodide) for converting a methoxy group into a trimethylsiloxy group. By reducing the amount of sodium) or shortening the aging time, the methoxy group can be left at an arbitrary ratio. Further, in the process of converting the trimethylsiloxy group to a hydroxyl group by hydrolysis, if the aging time is shortened, up to about 15% of the trimethylsiloxy group can be left as it is.

The poly (p-hydroxybenzylsilsesquioxane-co-p-methoxybenzylsilsesquioxane-co-p-trimethylsiloxybenzylsilsesquioxane) synthesized as described above has m = o = q = 0, R1 is a p-hydroxybenzyl group, R3 is a p-methoxybenzyl group, and R5 is a p-trimethylsiloxybenzyl group, the general formula (1) (R ₁ -SiO _3/2 ) _n (R _2- SiO _3/2 ) _m (R ₃ -SiO _3/2 ) ₁ (R ₄ -SiO _3/2 ) _o (R
₅ -SiO _3/2 ) _p (R ₆ -SiO _3/2 ) _q can be expressed by the general formula (1). Table 1 shows poly (p-hydroxybenzylsilsesquioxane-) when the aging time was changed.
co-p-methoxybenzylsilsesquioxane-co-p
- shows a component ratio of trimethylsiloxy benzyl silsesquioxane) each structural unit in _{(R 1, R 3, R} 5).

Synthetic Example 2 Alkali-soluble polyorganosilsesquioxane-based polymer in which 2- (p-hydroxyphenyl) ethyl group is an organic group having a phenyl hydroxyl group 2.1 Synthesis of 2- (p-methoxyphenyl) ethyltrichlorosilane p- Place 36.7 g (0.274 mol) of methoxystyrene and 37.1 g (0.274 mol) of trichlorosilane in a Pyrex tube. Next, chloroplatinic acid 99.4 mg, tri-n-butylamine 81.0 mg
A few drops of a suspension consisting of 0.1888 g of p-methoxystyrene and p-methoxystyrene is added to the Pyrex tube and the tube is sealed. 80 ° C to 1 for sealed tube
40.0 g (0.148 mol) of the target product was obtained by putting the product in an oil bath at 00 ° C and reacting, then opening the sealed tube and distilling the contents.
Obtained. Yield 54%; Boiling point 84-85 ℃ / 2mmHg; NMR (60MHz, CC
l ₄ , TMS), δ1.48 to 1.76 (2H, m), δ2.62 to 2.88 (2H, m
m), δ3.6 (3H, s), δ6.61 (2H, d, J = 8.5Hz), δ6.9
2 (2H, d, J = 8.5Hz) 2.2 Synthesis of poly (2- (p-methoxyphenyl) ethylsilsesquioxane) In a 200ml three-necked flask equipped with a stirrer, cooling tube, dropping funnel and hydrochloric acid trap. Add 80 ml of water. Toluene 20m
21.6 g (80.0 mmol) of 2- (p-methoxyphenyl) ethyltrichlorosilane dissolved in 1 is added dropwise with stirring over 15 minutes and then aged for 1 hour. The mixture is transferred to a separatory funnel and the toluene layer is separated. After removing toluene and water by distillation, potassium hydroxide was added to the above hydrolysis product.
0.21 g of a 10 wt% methanol solution is added and the mixture is heated at 200 ° C. for 2 hours. The reaction mixture is dissolved in tetrahydrofuran,
The insoluble material was removed by filtration, and then tetrahydrofuran was distilled off to obtain 7.9 g (42 mmol) of the desired product. Yield 53
%; Number average molecular weight 1000 to 300000; NMR (60MHz, DMSO-d ₆ , TM
S), δ0.83 (2H, br.s), δ2.50 (2H, br.s), δ3.58
(3H, br.s), δ6.63 (4H, br.s) 2.3 Synthesis of poly (2- (p-hydroxyphenyl) ethylsilsesquioxane) Equipped with stirrer, cooling tube, dropping funnel and hydrochloric acid trap Replace the 100 ml three-necked flask with nitrogen. Poly (2-
(P-Methoxyphenyl) ethylsilsesquioxane)
7.9 g (42 mmol) was dissolved by heating in 20 ml of acetonitrile and placed in a flask, and then 18.9 g (0.126 g of sodium iodide).
mol) is added. While heating under reflux under nitrogen pressure, 13.7 g (0.126 mol) of trimethylchlorosilane was added dropwise over 15 minutes. 2
After aging for 4 hours, water and acetonitrile are added dropwise, and heating under reflux is continued for another 6 hours. After completion of the reaction, the acetonitrile layer is separated and washed with an aqueous sodium hydrogen sulfite solution.
An acetonitrile solution of the polymer is dropped into 20 times water and reprecipitated, and the polymer is filtered. Dry by heating under vacuum and target 5.
8 g (34 mmol) was obtained. Yield 81%; number average molecular weight 1000-3000
00; NMR (60MHz, DMSO-d ₆ , TMS), δ 0.93 (2H, br.s), δ
2.60 (2H, br.s), δ6.67 (4H, br.s), δ9.08 (1H, br.s)
s) 2.4 Poly (2- (p-hydroxyphenyl) ethylsilsesquioxane) -co-2- (p-methoxyphenyl) ethylsilsesquioxane-co-2- (p-trimethylsiloxyphenyl) ethylsilsesqui In the method for synthesizing poly (2- (p-hydroxyphenyl) ethylsilsesquioxane) described in section 2.3, a reaction reagent (trimethylchlorosilane and sodium iodide) for converting a methoxy group into a trimethylsiloxy group is used. By reducing the amount or shortening the aging time, the methoxy groups can be left at any ratio. Also, in the process of converting the trimethylsiloxy group to a hydroxyl group by hydrolysis, shortening the aging time will reduce the trimethylsiloxy group
You can leave it up to 15%.

Poly (2- (p-hydroxyphenyl) ethylsilsesquioxane-co-2- (p
-Methoxyphenyl) ethylsilsesquioxane-co-
2- (p-trimethylsiloxyphenyl) ethylsilsesquioxane) has n = 1 = p = 0, and R ₂ is 2- (p
-Hydroxyphenyl) ethyl group, R ₄ is a 2- (p-methoxyphenyl) ethyl group, and R ₆ is a 2- (p-trimethylsiloxyphenyl) ethyl group, the general formula (1) (R ₁ -SiO _{3 / 2} ) _n (R ₂ -SiO _3/2 ) _m (R ₃ -SiO _3/2 ) _l (R ₄ -SiO _3/2 ) _o (R
₅ -SiO _3/2 ) _p (R ₆ -SiO _3/2 ) _q can be expressed by the general formula (1). Table 2 shows poly (2- (p-hydroxyphenyl) ethylsilsesquioxane-co-2- (p-methoxyphenyl) ethylsilsesquioxane-co-2- (p-) when the aging time was changed. trimethylsiloxy) ethyl silsesquioxane) each structural unit in the (R _2, R _4, shows a composition ratio of R _6).

Synthesis Example 3 Alkali-soluble polyorganosilsesquioxane-based polymer in which p-hydroxybenzyl group and 2- (p-hydroxyphenyl) ethyl group are organic groups having a phenolic hydroxyl group 3.1 Poly (p-methoxybenzylsilsesquioxy) Synthesis of Sun-co-2- (p-methoxyphenyl) ethylsilsesquioxane) 80 ml of water is placed in a 200 ml three-necked flask equipped with a stirrer, a condenser, a dropping funnel and a hydrochloric acid trap. Toluene 20m
1 (10.8 g (40 mmol) of 2- (p-methoxyphenyl) ethyltrichlorosilane and 10.2 g (40 mmol) of p-methoxybenzyltrichlorosilane dissolved in 1
Drip in 5 minutes, then age for 1 hour. The mixture is transferred to a separatory funnel and the toluene layer is separated. After removing toluene and water by distillation, 0.21 g of a 10 wt% methanol solution of potassium hydroxide is added to the above hydrolysis product, and the mixture is heated at 200 ° C. for 2 hours. The reaction mixture was dissolved in tetrahydrofuran, the insoluble material was removed by filtration, and the tetrahydrofuran was distilled off to obtain 5.3 g of the desired product. Number average molecular weight
1000-300000; NMR (60MHz, DMSO-d ₆ , TMS), δ 0.72 (2H.
br.s), δ1.97 (2H, br.s), δ2.37 (2H, br.s), δ3.
58 (6H, br.s), δ6.67 (8H, br.s). The ratio of 2- (p-methoxyphenyl) ethyl group to p-methoxybenzyl group was about 50:50.

3.2 Synthesis of poly (p-hydroxybenzylsilsesquioxane-co-2- (p-hydroxyphenyl) ethylsilsesquioxane) A 100 ml three-necked flask equipped with a stirrer, a cooling tube, a dropping funnel and a hydrochloric acid trap was installed. Replace with nitrogen. Poly (p-methoxybenzylsilsesquioxane-co-2) described in section 3.1
(P-Methoxyphenyl) ethylsilsesquioxane)
5.0 g of it is heated and dissolved in 15 ml of acetonitrile and placed in a flask, and then 13.0 g of sodium iodide is added. While heating and refluxing under nitrogen pressure, add 9.4 g of trimethylchlorosilane.
Drop in 15 minutes. After aging for 50 hours while heating under reflux under nitrogen pressure, 20 ml of water is added dropwise, then acetonitrile is added and the reaction mixture is heated under reflux for a further 6 hours. After completion of the reaction, the reaction mixture is transferred to a separating funnel and the acetonitrile layer is separated. Then, the acetonitrile layer is washed with an aqueous sodium hydrogen sulfite solution. The acetonitrile layer was added dropwise to a large amount of water, the polymer was filtered, and then heated in vacuum to obtain 3.9 g of the desired product.
Obtained. NMR (60MHz, DMSO-d ₆ , TMS), δ 0.78 (2H.br.
s), δ1.90 (2H, br.s), δ2.45 (2H, br.s), δ6.60
(8H, br.s), δ8.97 (2H, br.s) Number average molecular weight and p-hydroxybenzyl group and 2-
The ratio of (p-hydroxyphenyl) ethyl groups is the same as that of the precursor described in Section 3.1.

In addition, the copolymer in which the ratio of the p-hydroxybenzyl group and the p-hydroxyphenylethyl group is changed is the ratio of p-methoxybenzyltrichlorosilane and 2- (p-methoxyphenyl) ethyltrichlorosilane at the time of hydrolysis. It was possible to change arbitrarily.

3.3 Poly (p-hydroxybenzylsilsesquioxane-co-2- (p-hydroxyphenyl) ethyl silsesquioxane-co-p-methoxybenzylsilsesquioxane-co-2- (p-methoxyphenyl) ethyl Synthesis of silsesquioxane-co-p-trimethylsiloxybenzylsilsesquioxane-co-2- (p-trimethylsiloxyphenyl) ethylsilsesquioxane) Poly (p-hydroxybenzylsilsesquioxane) according to item 3.2 -Co-2- (p-hydroxyphenyl) ethylsilsesquioxane), the amount of reaction reagents (trimethylchlorosilane and sodium iodide) for converting a methoxy group into a trimethylsiloxy group is reduced or the aging time is reduced. By making it short, the methoxy group can be left at an arbitrary ratio. Further, in the process of converting the trimethylsiloxy group to a hydroxyl group by hydrolysis, if the aging time is shortened, up to about 15% of the trimethylsiloxy group can be left as it is.

However, it cannot be specified whether the hydroxyl group, the methoxy group and the trimethylsiloxy group are attached to the benzyl group or the phenylethyl group.

In Table 3, the same polymer as described in 3.1 is used, and 3.2
The resulting poly (p
-Hydroxybenzyl silsesquioxane-co-2-
(P-Hydroxyphenyl) ethylsilsesquioxane-co-p-methoxybenzylsilsesquioxane-co-
2- (p-methoxyphenyl) ethylsilsesquioxane-co-p-trimethylsiloxybenzylsilsesquioxane-co-2- (p-trimethylsiloxyphenyl)
(Ethyl silsesquioxane) shows the hydroxyl content, methoxy group content, trimethylsiloxy group content, and the respective aging time dependencies.

Regarding the solubility of the above-mentioned polymer, as a result of examination with a typical general-purpose organic solvent, a polymer having a hydroxyl group content of 40% or more is methanol, tetrahydrofuran, N, N-dimethylacetamide, 2-methylcyclohexanone, acetic acid. It was soluble in isoamyl, methyl cellosolve, and dimethyl sulfoxide, but insoluble in toluene, hexane, and carbon tetrachloride. On the other hand, the aqueous solution was dissolved in a tetramethylammonium hydroxide aqueous solution and a sodium hydroxide aqueous solution.

Examination of Oxygen Plasma Resistance A 10% by weight solution of the above polymer in ethyl cellosolve was applied on a silicon substrate by spin coating, and the solution was applied at 100 ° C for 3 hours.
Pre-baking was performed for 0 minutes to form a polymer coating film having a thickness of about 0.2 μm. Then, using a barrel-type asher, it was exposed to oxygen plasma (conditions: oxygen pressure 0.5 torr, RF 300 W) for 20 minutes, but the above polymer did not cause any film sticking. However, parallel plate type O ₂ RIE system (condition: oxygen pressure 20mtorr, RF 200W (14
MHz) and a cathode bias voltage of −130 V), the film slip velocity of the polymer of Synthesis Example 1 was 23 Å / min, the polymer of Synthesis Example 2 was 40 Å / min, and the polymer of Synthesis Example 3 was 33 Å / min. Met. At this time, organic substances that are generally considered to have relatively high oxygen plasma resistance, such as PIQ (manufactured by Hitachi Chemical) and OFPR-
About 800 (made by Tokyo Ohka), AZ1350J (made by Hoechst), etc.
The film slip rate was 20Å / min. Further, the film slip rate of the polymer was hardly affected by the hydroxyl group content.

Next, a photosensitive resin composition using the alkali-soluble polyorganosilsesquioxane-based polymer of the above Synthesis Example (second
Examples of the photosensitive resin composition for resist layer) are shown below.

Composition Example 1 80% by weight of poly (p-hydroxybenzylsilsesquioxane) shown in Synthesis Example 1.3 and 20% by weight of the above-mentioned 1,2-naphthoquinonediazide derivative XII were dissolved in ethyl cellosolve acetate to give a solid product 27. A weight percent resist solution was prepared. Then, the above resist solution was spin coated on a silicon wafer and prebaked at 85 ° C. for 30 minutes to obtain 1.0 μm.
A m-thick resist film was formed. This was exposed to light of various different irradiation amounts, and the developer NMD-3 (2.38%
(Tetramethylammonium hydroxide aqueous solution) was developed with an alkaline developer diluted to 0.45% for 1 minute and then washed with water for 1 minute, and then the thickness of the residual resist film was measured. And
The residual film thickness (normalized) was plotted against the exposure dose (mJ / cm ² at 365 nm), and the minimum exposure dose at which the residual film rate was zero (this value was defined as sensitivity) was calculated to be about 30 mJ / It was cm ² , and it was confirmed that the photoresist was a high-sensitivity positive photoresist.

Composition Examples 2-36 Various compositions were investigated in the same manner as Composition Example 1. Specific values relating to the components of the composition, the compounding ratio, the developing conditions and the sensitivity are shown in Table 4 for the polymer of Synthesis Example 1, Table 5 for the polymer of Synthesis Example 2 and the polymer of Synthesis Example 3. Summarized them in Table 6.

Next, an example of the two-layer resist method will be described.

Example 1 First, OFPR-8 was used as a first resist layer on a silicon wafer.
00 (manufactured by Tokyo Ohka Co., Ltd.) is spin-coated to a thickness of 2 μm, and it is 30 at 90 ° C.
Min., Baked at 200 ° C. for 30 minutes (hereinafter, abbreviated as “hard bake OFPR-800”), and then the same composition as in the above-mentioned photosensitive resin composition example 1 was used as the second resist layer. And a film having a thickness of 1 μm was formed.

The patterning of the second resist layer was performed by contact exposure using COBILT AF2800H. Here, the developing solution used in the above-mentioned composition example 1 was used, and the developing time was 3 minutes. Also, the optimum exposure amount is 1 μm lines & spaces for convenience.
Is the exposure amount at which 1: 1 is transferred. In this example, the optimum exposure amount was 80 mJ / cm ² at 365 nm.

Next, using the pattern of the second resist layer as a mask,
The first resist layer is O ₂ RIE (parallel plate type RIE device: enzyme pressure 3 m
Patterning was performed with torr, RFPWR 0.64 mW / cm (7 MHz), 20 to 30 minutes). As a result, it was possible to accurately obtain a resist pattern having a vertical step shape with an aspect ratio of 3 or more with a pattern dimension of submicron level. At this time, the dimensional conversion difference from the second resist pattern to the first resist pattern is
It was 0.1 μm or less.

Examples 2-36 In the same manner as in Example 1, a two-layer resist method was tried using the photosensitive resin compositions shown in Tables 4, 5 and 6, and in all cases, the pattern size was at a submicron level. A fine resist pattern having a vertical step shape with an aspect ratio of 3 or more could be obtained. Examples 2-36 are summarized in Table 7.

[Effects of the Invention] As described above, according to the present invention, a fine resist pattern having a pattern dimension of a submicron level and a high aspect ratio can be accurately obtained. Moreover, since the alkali developing process, which is currently the mainstream in the semiconductor process, can be applied as it is, it is extremely advantageous in practical use and is a very effective technique for the manufacturing process of semiconductor elements and the like.

[Brief description of drawings]

FIG. 1 is a schematic view of a lithographic process using a two-layer resist method. 1 ... Semiconductor substrate, 2 ... Organic polymer material film (first resist layer), 3 ... Light and radiation sensitive polymer film (second resist layer).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Kazuo, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd. Inside the Institute of Industrial Science, Hitachi, Ltd. (56) References Kai 61-144639 (JP, A) JP 61-256347 (JP, A) JP 62-36661 (JP, A) JP 62-229136 (JP, A)

Claims (3)

[Claims] 1. A step of providing a first resist layer on a substrate, a step of forming a second resist layer using a photosensitive resin composition on the first resist layer, and the second resist layer. And exposing the desired part of the first resist layer to expose the desired part of the first resist layer, and forming a pattern by removing the exposed part of the first resist layer by dry etching with oxygen plasma. The photosensitive resin composition has a base polymer containing an alkali-soluble polyorganosilsesquioxane-based polymer and a photosensitive dissolution inhibitor, and the above-mentioned alkali-soluble polyorganosilsesquioxane-based polymer. The combination is poly (p-hydroxybenzylsilsesquioxane-co
-2- (p-hydroxyphenyl) ethylsilsesquioxane-co-p-methoxybenzylsilsesquioxane-co-2- (p-methoxyphenyl) ethylsilsesquioxane-co-p-trimethylsiloxybenzylsil Sesquioxane-co-2- (p-trimethylsiloxyphenyl) ethylsilsesquioxane). 2. The photosensitive resin composition according to claim 1, wherein the photosensitive polymer composition contains 70 to 95% by weight of the base polymer and 30 to 5% by weight of the photosensitive dissolution inhibitor. A pattern forming method comprising 70 to 100% by weight of the alkali-soluble polyorganosilsesquioxane polymer. 3. The pattern forming method according to claim 1, wherein the base polymer further contains 30% by weight or less of a novolac resin as a film forming agent.