JPH0656487B2 - Composition for positive photoresist - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a positive photoresist composition. More specifically, the present invention relates to a positive photoresist composition for forming a fine pattern with high dimensional accuracy, which is preferably used for manufacturing a semiconductor integrated circuit device such as a VLSI.

2. Description of the Related Art Recently, in the semiconductor industry, industrial computers,
Demand for office automation, personal computers, etc. has expanded exponentially, and its technology has continued to develop rapidly. Along with this, semiconductor integrated circuit devices are rapidly becoming denser and highly integrated. It is progressing.
Also, in fine pattern formation, 256 kilobit DRA
The pattern width of the semiconductor integrated circuit device for M is about 2 μm, 1
Megabit DRAM 1.0 to 1.3 μm, 4 megabits
As DRAM is integrated at 0.7 to 0.8 μm, so-called submicron order fine processing technology is required.

Currently, pattern formation in semiconductor integrated circuit device manufacturing is performed by photolithography, and positive photoresists are widely used for fine processing with a pattern width of 1 to 2 μm.

This positive photoresist is usually composed of an alkaline solution-soluble novolak resin and a photolytic component called a photosensitizer. Examples of the photosensitizer include naphthoquinone diazide sulfonic acid which is a photolytic agent and a phenolic property. Sulfonic acid esters with compounds having a hydroxyl group are used (US Pat. No. 3,40
2,044 specification). Further, various kinds of such esters have been disclosed so far (US Pat. No. 3,046,
No. 118, No. 3,106,465, No. 3,148,983
Specification).

On the other hand, regarding the alkaline solution soluble novolak resin,
For example, the use of phenol-formaldehyde novolak resin has been disclosed (U.S. Pat. No. 3,402,044), and examples of use of cresol novolak resin have been reported ["Electrochemistry and Industrial Physical Chemistry", Vol. 48,
Page 584, (1980)]. Further, it is also known that a high-sensitivity positive photoresist can be obtained by appropriately selecting the compounding ratio of the cresol isomers at the time of producing the cresol novolak resin for the purpose of increasing the sensitivity of the photoresist (JP-A-58). -17112).

By the way, as a photoresist exposure method, there are two types of methods, a contact exposure method and a reduction projection exposure method. In the former contact exposure method, since the mask pattern is brought into close contact with the resist surface provided on the wafer for exposure, there is an advantage that the contrast of light and dark is good and a high resolution pattern is easily obtained, but the mask is damaged. In addition to the fact that a mask pattern of the original size is required for the pattern, and an extremely expensive mask with high dimensional accuracy is required in the submicron order, it is necessary to handle it carefully and maintain the mask considerably. There are problems such as requiring the cost of.

On the other hand, in the reduction projection exposure method, since a mask pattern having a size 5 to 10 times larger than the pattern size is used, a relatively inexpensive mask pattern with good dimensional accuracy can be used. This reduction projection exposure method is extremely advantageous for obtaining a resist pattern of an order. However, such a reduction projection exposure method has a drawback in that the contrast ratio of light and dark between the exposed portion and the unexposed portion is significantly inferior to the contact exposure method. Therefore, a photoresist having high sensitivity to low contrast is required.

In the conventional positive photoresist, the minimum exposure amount required to selectively remove the photoresist in the exposed portion by the development process differs depending on the width of the exposed portion pattern,
For example, the minimum exposure amount required to resolve a pattern width of 2 μm is 1.2 to 1.3 times as much as 1.0 μm for a pattern of 1.5 μm width.
An m-width pattern requires an exposure dose of 1.5 to 1.7 times.
Therefore, when circuit patterns of various widths are complicatedly combined like the pattern of semiconductor integrated circuit elements such as VLSI, a desired pattern cannot be obtained due to insufficient exposure in a narrow pattern area. , Or overexposure in a thick pattern area, the pattern is removed more than necessary, and it is difficult to obtain a pattern faithful to the mask pattern. Since the formed pattern tends to be thick, it is difficult to perform fine processing in the submicron order with good reproducibility. In order to solve such a problem, a photoresist whose dimensional change is small with respect to the change of the exposure amount is required.

Further, in the etching process of the submicron order, usually a dry etching method with a small amount of side etching is performed, but in this dry etching method, the resist mask is also damaged and the film gradually decreases,
Even if the resist mask is damaged, it is necessary to form a reproduced pattern faithfully corresponding to the mask pattern on the substrate to be etched.

For example, as shown in (a) of the accompanying drawings, it is preferable that the resist pattern has a cross-sectional shape in which the side surfaces are raised substantially vertically. On the other hand, in (b) and (c), the side surface is widened toward the bottom of the resist pattern in a soot-like shape, and in such a shape, the thin film portion is damaged by etching. It is not preferable because the dimensions of the resist pattern change greatly as the etching progresses and the etching progresses.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In response to such a demand, the present invention forms a resist pattern having high sensitivity and a convex portion of a rectangular cross section, which is suitably used for manufacturing a semiconductor integrated circuit device such as a VLSI. It is an object of the present invention to provide a positive photoresist composition for forming a fine pattern with high dimensional accuracy.

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the inventors have found that a substituted phenol novolac resin has m-cresol and a substituent at the o-position or p-position. Using a mixture of a phenol and a phenol having at least two substituents on the aromatic ring in specific proportions and a formaldehyde condensate, a photosensitizer is used for the substituted phenol novolak resin. It has been found that the object can be achieved by blending the ingredients in a predetermined ratio, and the present invention has been completed based on this finding.

That is, the present invention is a composition for a positive photoresist containing (A) a substituted phenol novolak resin and (B) a photosensitizer containing naphthoquinone diazide sulfonate as a main component, wherein the substituted phenol novolak resin is Is (i) m-cresol and the general formula (R ₁ in the formula is C ₁ to C 6 located in the o-position or p-position
Which is an alkyl group, an alkenyl group or an aryl group), and a content of m-cresol of 45% by weight or less.
0.0-99.5% by weight, and (b) general formula (In the formula, R ₂ and R ₃ are each an alkyl group, an alkenyl group or an aryl group having 1 to 6 carbon atoms, and they may be the same or different, but at least one of them is preferable. Is located at the 2-position or 4-position and is not a methyl group together, and R ₄ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group or an aryl group). 1 type 10.0 to 0.5
A composition for a positive photoresist, which is a condensate of mixed phenols containing 10% by weight and formaldehyde, and contains 20 to 60 parts by weight of the component (B) per 100 parts by weight of the component (A). Is provided.

The substituted phenol novolak resin used in the composition of the present invention comprises m-cresol and at least one of the phenols represented by the general formula (I),
Mixture containing less than 45% by weight of m-cresol 90.0-
What is obtained by condensing mixed phenols containing 99.5% by weight and 10.0 to 0.5% by weight of at least one kind of the phenols represented by the general formula (II) with formaldehyde is required. Heretofore, in a positive photoresist using a cresol or a novolak resin composed of cresol, other phenols and formaldehyde as a base resin, an cresol rich in m-cresol must be used in order to give a pattern having high sensitivity. However, in the present invention, the content of m-cresol is 45
It was completely unexpected that the composition had a high sensitivity and the pattern cross-sectional shape was remarkably improved by specifying the other component composition when the cresol mixture of less than or equal to wt% was used.

Then, in order to give a photoresist having such a good pattern cross-sectional shape and to obtain a photoresist exhibiting excellent sensitivity, it is necessary to satisfy the above content range.

Examples of the phenols represented by the general formula (I) include o- or p-cresol, o- or p-ethylphenol, o- or p-isopropylphenol, o-
Or, p-tert-butylphenol, o- or p-allylphenol, o- or p-phenylphenol and the like can be mentioned, and these phenols may be used alone or in combination of two or more kinds. You may use.

Examples of the phenols represented by the general formula (II) include 2-methyl-4-isopropylphenol,
2-methyl-4-tert-butylphenol, 2-methyl-5-ethylphenol, 2-methyl-4-phenyldimethylpropylphenol and the like can be mentioned, and these may be used alone or 2 You may use it in combination of 2 or more types.

As the component (A) of the present invention, it is necessary to use a substituted phenol novolac resin obtained by condensing the substituted phenols with formaldehyde, and the formaldehyde feedstock is an aqueous solution such as formalin. Polymers such as and paraformaldehyde can also be used.

The photosensitizer used in the composition of the present invention is mainly composed of naphthoquinone diazide sulfonic acid ester, which is naphthoquinone diazide sulfonic acid and phenolic hydroxyl group such as polyhydroxybenzophenone or alkyl gallate. It can be easily obtained as a reaction product by performing an esterification reaction with a compound having a.

The compound having a phenolic hydroxyl group, for example, in addition to the alkyl gallate, polyhydroxybenzophenone such as tetrahydroxybenzophenone, trihydroxybenzene, trihydroxybenzene monoethers, 2,2 ', 4, 4'-tetrahydroxydiphenylmethane, 4,4'-dihydroxydiphenylpropane, 4,4'-
Dihydroxydiphenyl sulfone, 2,2'-dihydroxy-1,1-dinaphthylmethane, 2-hydroxyfluorene, 2-hydroxyphenanthrene, polyhydroxyanthraquinone, purprogarin and its derivatives, phenyl 2,4,6-trihydroxy Examples thereof include benzoic acid ester.

Aromatic amines and the like can be used instead of these compounds having a phenolic hydroxyl group. In that case, instead of the naphthoquinone diazide sulfonic acid ester, the same sulfonic acid amide is used.

In the composition of the present invention, the photosensitizer whose main component is the naphthoquinone diazide sulfonic acid ester is 100 parts by weight of the substituted phenol novolak resin.
It is compounded in the range of 25 to 60 parts by weight. If this amount exceeds 60 parts by weight, the sensitivity of the photoresist is remarkably deteriorated, and if it is less than 25 parts by weight, it becomes difficult to obtain a preferable pattern cross-sectional shape.

The positive photoresist composition of the present invention is preferably used in the form of a solution prepared by dissolving the substituted phenol novolak resin and the photosensitizer in a suitable solvent.

Examples of such solvents include acetone, methyl ethyl ketone, cyclohexanone, isoamyl ketone and other ketones: ethylene glycol, ethylene glycol monoalkyl ether and its acetates, ethylene glycol monoacetate, diethylene glycol or diethylene glycol monoacetate monomethyl ether, monoether. Mention may be made of polyhydric alcohols such as ethyl ether, monopropyl ether, monobutyl ether or monophenyl ether and its derivatives: cyclic ethers such as dioxane: and esters such as methyl acetate, ethyl acetate, butyl acetate. . These may be used alone or in combination of two or more.

In the positive photoresist composition of the present invention, a more compatible additive such as an additional resin, a plasticizer, a stabilizer, or a colorant for making a developed image more visible is conventionally used. What is present can be added and contained.

To give an example of a suitable use of the composition of the present invention, first, on a support such as a silicon wafer,
A solution in which a substituted phenol novolak resin and a photosensitizer are dissolved in a suitable solvent is applied by a spinner or the like and dried to form a photosensitive layer. After that, exposure is performed through a required mask using a reduction projection exposure apparatus or the like. Next, this is developed using a developing solution, for example, an aqueous solution of tetramethylammonium hydroxide or choline of 2 to 5% by weight, and the portion solubilized by exposure is faithfully reproduced in the mask pattern. Image (resist pattern) can be obtained.

The positive photoresist composition of the present invention comprises a mixture of m-cresol and a phenol having a substituent at the o-position or the p-position, and a phenol having at least two substituents on the aromatic ring. A substituted phenol novolak resin obtained from mixed phenols and formaldehyde each containing a specific proportion of photosensitizer in a predetermined proportion, and by using such a composition In particular, in image formation by the reduction projection exposure method, it is possible to obtain a resist pattern having a high sensitivity and a cross-sectional shape in which the side surfaces are substantially vertical.

Therefore, the composition of the present invention can provide a resist pattern with high dimensional accuracy that is extremely faithful to a mask, and
It can be suitably used for forming a fine pattern necessary for manufacturing a semiconductor integrated circuit device such as an LSI.

EXAMPLES Next, the present invention will be described in more detail with reference to examples.

Example 1 40% by weight of m-cresol and 50% by weight of p-cresol
And 2-methyl-4-isopropylphenol 10% by weight, formalin was added thereto, and 100 parts by weight of cresol novolak resin obtained by condensation by a conventional method using an oxalic acid catalyst and naphthoquinone-1,2 -Dissolve 2,3,4-trihydroxybenzophenone ester of diazide-5-sulfonic acid in 30 parts by weight of ethylene glycol monoethyl ether acetate in 390 parts by weight, and use this with a membrane filter having a pore size of 0.2 µm. Filtered
A photoresist composition was prepared.

This photoresist composition was applied uniformly on a 4-inch silicon wafer to a thickness of 1.3 μm using a resist coater (TR-4000, manufactured by Tatsumo Co., Ltd.), and then dried at 110 ° C. for 90 seconds on a hot plate. Then, using a reduction projection exposure apparatus (manufactured by GCA, DSW-4800 type wafer stepper), UV exposure was carried out through a test chat mask (manufactured by Dai Nippon Printing Co., Ltd.), and then, using a 2.38 wt% tetramethylammonium hydroxide solution, It was developed at 30 ° C. for 30 seconds.

The shortest exposure time required to completely remove only the pattern of the 1.0 μm wide exposed portion was 800 ms. In addition, the resist pattern had a good cross-sectional shape as shown in (a) of the accompanying drawings, in which the side surfaces were raised almost vertically.

Examples 2 to 4, Comparative Examples 1 to 3 The weight ratio of m-cresol to the phenols represented by the general formula (I) and the phenols represented by the general formula (II) (2-methyl-4-isopropylphenol) was measured. Change
A photoresist composition having the composition shown in the attached table was prepared, and then a pattern was formed in the same manner as in Example 1. The results are shown in the table.

In the table, the weight% [(value)] of m-cresol and phenols represented by the general formula (I) in the mixed phenols used in Examples 2 to 4 are as follows.

Example 2 m-cresol (40) + p-cresol (5
0) 〃 3 m-cresol (45) + o-cresol (5
0) 〃 4 m-cresol (45) + p-cresol (5
3) In Comparative Examples 1 to 3, m-cresol and p-
A novolak resin obtained by condensation polymerization of cresol and formalin was used.

Example 5 Instead of the test chart mask in Example 1, 1.
The exposure and development treatment was carried out in exactly the same manner as in Example 1 except that a test cherreticle having a line and space pattern of 25 μm width and a line and space pattern of 2.0 μm width was used. A line and space pattern was obtained.

Comparative Example 4 In Comparative Example 1, instead of the test chart mask, 450 ms of exposure was carried out with ultraviolet rays through the test chart reticle used in Example 5, and development processing was carried out. A line and space pattern of 1.25 μm was obtained. , 2.0 μm
In the line and space pattern section, a 1.6 μm line pattern and a 2.4 μm space pattern were used.

[Brief description of drawings]

FIG. 1 is a sectional view of different examples of photoresist patterns.

Front page continuation (72) Inventor Hisasa Nakayama 26-404 Takamura housing complex, 26-404 Takamura housing complex, Hiratsuka city, Kanagawa prefecture (56) ) JP-A-60-176034 (JP, A) JP-A-60-159846 (JP, A)

Claims (1)

[Claims] 1. A positive photoresist composition comprising (A) a substituted phenol novolac resin and (B) a photosensitizer containing naphthoquinone diazide sulfonate as a main component, wherein the substituted phenol novolac resin is ( B) m-cresol and general formula (R ¹ in the formula is C ¹ to C 6 located in the o-position or p-position
Which is an alkyl group, an alkenyl group or an aryl group), and a content of m-cresol of 45% by weight or less.
0.0-99.5% by weight, and (b) general formula (In the formula, R ₂ and R ₃ are respectively an alkyl group, an alkenyl group or an aryl group having 1 to 6 carbon atoms, and they may be the same or different, but at least one of them is At least two of the phenols located at the 2-position or 4-position and not both methyl groups, R ₄ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group or an aryl group) Species 10.0-0.5
It is a condensate of mixed phenols and formaldehyde containing 100% by weight, and per 100 parts by weight of component (A),
(B) A positive photoresist composition containing 20 to 60 parts by weight of component.