JPH01179147A - Positive type photoresist composition - Google Patents

Abstract

PURPOSE:To obtain excellent dimensional accuracy, pattern shape and heat resistance by incorporating a specific cresol novolak resin and photosensitizer into the title compsn. CONSTITUTION:The cresol novolak resin is obtd. from a mixture composed of 10-45wt.% m-cresol and 90-55wt.% p-cresol. The photosensitizer is the resultant product of the esterification reaction of at least one kind of polyhydroxybenzophenone among 2,3,4-trihydroxybenzophenones, 2,3,4,4'- tetrahydroxybenzophenones, and 2,2',4,4'-tetrahydroxybenzophenones and naphthoquinone diazide sulfonic acid contg. 1,2-naphthoquinone diazide-4-sulfonic acids 1,2-naphthoquinone diazide-5-sulfonic acids at 20:80-80:20 weight ratios and the content of triester and higher polyester is specified to >=80mol.%. The application to steppers for both G rays and I rays is thereby enabled and excellent dimensional accuracy and pattern shape are obtd. The fine patterns having the good heat resistance are thus formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a positive photoresist composition, and more specifically, it is suitable for use in manufacturing semiconductor integrated circuit devices such as VLSIs and has excellent dimensional accuracy and The present invention relates to a positive photoresist composition for forming fine patterns that has excellent pattern shape and good heat resistance.

Conventional technology In recent years, in the semiconductor industry, industrial computers,
The demand for office automation, personal computers, etc. is rapidly expanding, and the technology continues to develop rapidly. Along with this, semiconductor integrated circuit devices are also rapidly becoming denser and more highly integrated. is progressing.

Furthermore, in forming fine patterns, the pattern width is approximately 2 μm for semiconductor integrated circuit elements for 256 kilobit DRAM.
m, 1.0 to 1.3 μm for 1 megabit DRAM,
Furthermore, as DRAMs (4 megapixels) are integrated with a size of 0.67 to 0.8 μm, microfabrication technology on the so-called submicron order is becoming necessary.

Currently, pattern formation in the manufacture of semiconductor integrated circuit devices is performed by photolithography, and positive photoresists are widely used for microfabrication with a pattern width of about 2 μm or less.

This positive photoresist is usually composed of an alkaline solution-soluble novolac resin and a photodegradable component called a photosensitizer. Examples of the alkaline solution-soluble novolak resin include phenol-formaldehyde novolak resin (US Pat. No. 3,402,044). No. specification) and cresol novolak resin [Electrochemistry and Industrial Physical Chemistry, Vol. 48, p. 584 (1980)] are used. Furthermore, by appropriately selecting the blending ratio of cresol isomers during the production of cresol novolac resin, we have developed a highly sensitive positive photoresist (Japanese Patent Laid-Open No. 58
It is also known that a positive type photoresist (Japanese Patent Application Laid-Open No. 62-35349) with excellent dimensional accuracy can be obtained.

On the other hand, as photosensitizers, for example, sulfonic acid esters of naphthoquinonediazide sulfonic acid, which is a photodegradable component, and a compound having a phenolic hydroxyl group are often used, and various esters have been proposed. (U.S. Pat. No. 3,046,118, U.S. Pat. No. 3,106.465, U.S. Pat. No. 3,1
48,983, Japanese Patent Publication No. 62-28457).

Several methods have been proposed to form submicron-order patterns using such positive photoresists, but the most common method is to use a reduction projection exposure system (hereinafter referred to as a stepper). However, this stepper currently uses G with a wavelength of 436 nm.
The mainstream is one using lines. However, although this G-line stepper can form patterns of approximately 0.8 to 1.0 μm, it cannot be used to meet the demand for smaller pattern widths due to the recent trend toward higher integration.
Therefore, recently, a stepper has been developed that outputs a mercury radiation wire with a wavelength shorter than that of the G-line, 365 nm.

In photolithography for forming such submicron-order patterns, in addition to improving the stepper as described above, the development of a positive photoresist compatible with the stepper is also an important theme.

And, for positive type photoresists, generally G
It is known that positive photoresists compatible with line steppers can also be used in single line steppers [Solid State Technology (5oll 5ta-
ze technology) 4 Japanese edition, February issue, pages 34-38 (1987)]. However, if the positive type photoresist conventionally used in GG-ray steppers is used in a 1-line stepper, X-rays are more easily absorbed in the positive-type photoresist than G-rays, and excessive absorption is more likely to occur. Reduces the contrast of photoresist, especially deteriorates the cross-sectional shape of the resist,
The problem has arisen that it is not possible to obtain a resist pattern with a cross-sectional shape that is vertical and has excellent pattern dimensions, and there is a strong demand for the development of a resist that can provide a cross-sectional shape that is effective and practical for both G-line steppers and single-line steppers. ing.

In addition, when etching a submicron-order substrate using a resist pattern formed on the substrate using a lithography technique using a G-line stepper or a 1-line stepper as a mask, plasma or the like, which has a small amount of side etching, is usually used. The dry etching method used has been carried out.

In this dry etching method, the resist pattern used as a mask is also damaged during etching of the substrate, and the film is gradually thinned out. However, even if the resist pattern is thinned, the etched substrate remains faithful to the mask pattern. It is necessary to form a correspondingly reproduced pattern. Normally, in order to reduce this film loss, it is effective to increase the post-bake temperature after development. Therefore, regarding the characteristics required of the resist used, the cross-sectional shape of the resist pattern is excellent, as well as heat resistance. It must also have the following.

However, conventional positive photoresists lack either of these required properties and cannot necessarily be said to be satisfactory.

Problems to be Solved by the Invention Under these circumstances, the present invention is applicable to both G-line steppers and single-line steppers, and has excellent dimensional accuracy and pattern shape, as well as good heat resistance. The purpose of this invention is to provide a positive photoresist composition capable of forming fine patterns.

Means for Solving the Problems As a result of extensive research by the present inventors to develop a positive photoresist composition having the above-mentioned excellent characteristics, the present inventors discovered that a specific cresol novolac resin and a specific photosensitizer were combined. The present inventors have discovered that the object can be achieved, and have completed the present invention based on this knowledge.

That is, the present invention provides a positive photoresist composition comprising (a) cresol novolac resin and (B) a photosensitizer containing naphthoquinonediazide sulfonic acid ester as a main component, in which (a) the cresol novolak resin is m -Cresol 10-45 weight ratio and p-
(2.3.4-) that the photosensitizer is obtained from a cresol mixture with 90 to 55% by weight of cresol;
IJ hydroxybenzophenone, 2,3,4.4'-tetrahydroxybenzophenone and 2.2', 4.4'
- at least one polyhydroxybenzophenone selected from tetrahydroxybenzophenones; 1.
2-su7toquinone diazido 4-sulfonic acid and 1.2
-naphthoquinonediazide-5-sulfonic acid at a weight ratio of 20
: 80 to 80 : An esterification reaction product with naphthoquinonediazide sulfonic acid containing in a ratio of 80 to 20, and the content of polyester of triester or higher is 8
The present invention provides a positive photoresist composition characterized in that it has a molarity of 0 or more.

The present invention will be explained in detail below.

In the composition of the present invention, the cresol novolac resin used as component (4) is m-cresol 10 to 45
It is necessary that it is obtained from a cresol mixture of 90 to 55 parts by weight of p-cresol and 90 to 55 parts by weight of p-cresol. This mixing ratio is an essential condition in order to obtain a positive photoresist with excellent heat resistance, dimensional accuracy, and pattern shape, and cresol novolac resins obtained from products with this ratio outside the above range are not suitable for practical use. However, it is not possible to obtain a composition that satisfies both the heat resistance and pattern cross-sectional shape of a photoresist.

In addition, the photosensitizer mainly composed of 7-toquinonediazide sulfonic acid ester used as component (B) in the composition of the present invention includes 2.3.4-trihydroxybenzophenone, 2.3.4.4'-tetra It is an esterification reaction product of at least one polyhydroxybenzophenone selected from hydroxybenzophenone and 2.2', 4.4'-tetrahydroxybenzophenone, and naphthoquinonediazide sulfonic acid. It is preferable that all the hydroxyl groups of the polyhydroxybenzophenone are esterified in the esterification reaction, but in reality, it can be used sufficiently if the content of triester or higher polyester is 80 mole or more. can. If this content is less than 80 molt, the dimensional accuracy and pattern shape of the resulting resist pattern will be reduced, and the heat resistance will also be significantly deteriorated.

The naphthoquinonediazide sulfonic acid used in the present invention is composed of 1,2-naphthoquinonediazide-4-sulfonic acid and 1,2-naphthoquinone-5-sulfonic acid in a weight ratio of 20:80 to 80:20°, preferably 40°. :60 to 60:40. If this mixing ratio deviates from the above range, a resist pattern with excellent heat resistance and cross-sectional shape of the pattern cannot be obtained.

Such photosensitizers are selected from 2.3.4-)lihydroxybenzophenone, 2.3,4.4'-tetrahydroxybenzophenone and 2.2',4.4'-tetrahydroxybenzophenone. per mole of at least one polyhydroxybenzophenone,
1,2-naphthoquinonediazide-4-sulfonyl chloride and 1,2-naphthoquinonediazide-5-sulfonyl chloride are added in a predetermined ratio, preferably such that the total amount is 2.5 times the mole or more, to form a dehydrochlorination catalyst. Alternatively, the polyhydroxybenzophenone (!:,
After reacting 1.2-naphthoquinonediazide-4-sulfonyl chloride and 1.2-naphthoquinonediazide-5-sulfonyl chloride separately in the same manner as above, the obtained esterification reaction product was reacted with a predetermined reaction product. It may also be produced by mixing in proportions.

The esterification reaction between polyhydroxybenzophenone and naphthoquinonediazide sulfonyl chloride is performed using a reaction solvent,
Since the esterification rate varies depending on the type and amount of acid catalyst used, it is desirable to select conditions appropriately depending on the combination of polyhydroxybenzophenone and naphthoquinonediazide sulfonyl chloride, which are the reaction raw materials, and also depending on the purification of the reaction product. It goes without saying that a desired esterified product can be selectively obtained. Note that the esterification rate can be quantitatively determined by liquid chromatography.

Regarding the blending ratio of the cresol novolak resin as the component (A) and the photosensitizer as the component (B) in the composition of the present invention, the component (B) should be added in an amount of 10 to 30 parts by weight per 100 parts by weight of the component (A). If I is less than 10 parts by weight, the dimensional accuracy, pattern shape, heat resistance, etc. may be poor, and the object of the present invention may not be fully achieved; if it exceeds 30 parts by weight, This is not preferred because the sensitivity tends to decrease.

The composition of the present invention is preferably used in the form of a solution by dissolving the cresol novolak resin (component (4)) and the photosensitizer (component 0) in a suitable solvent.

Examples of such solvents include ketones such as acetone, methyl ethyl ketone, cyclohexanone, isoamyl ketone; ethylene glycol, propylene glycol;
Polyhydric alcohols such as ethylene glycol monoacetate, diethylene glycol or monomethyl ether, monoethyl ether, motsubutyl ether, motsubutyl ether or monophenyl ether of diethylene glycol monoacetate, and their derivatives cyclic ethers such as nidioxane: and acetic acid. Esters such as methyl, ethyl acetate, and butyl acetate can be mentioned. These may be used alone or in combination of two or more.

The positive-working photoresist compositions of the present invention may further contain compatible additives, such as additional resins, plasticizers, stabilizers, or colorants to make the developed image more visible. You can add whatever you want.

To give one example of a preferred method of using the composition of the present invention, a solution of the above-mentioned cresol novolac resin and photosensitizer dissolved in a suitable solvent is applied onto a substrate such as silicone urethane using a spinner or the like. After drying to form a photosensitive layer, it is exposed to light through a required mask using a G-line or 1-line stepper. Next, when this is developed using a developer, for example, an aqueous solution of tetramethylammonium hydroxide or choline with a weight ratio of 2 to 5, the portions made solubilized by exposure are selectively dissolved and removed, creating an image faithful to the mask pattern. can be obtained.

Effects of the Invention The positive photoresist composition of the present invention uses a cresol novolac resin obtained from a mixed cresol in which the mixing ratio of m-cresol and p-cresol is within a specific range, and a specific ester. By using a mixed naphthoquinonediazide sulfonic acid ester having a chemical conversion rate, it is possible to obtain a resist pattern that can be applied to either a G-line or a single-line stepper, has excellent dimensional accuracy and pattern shape, and is also heat resistant. Super LS
It can be suitably used for molding semiconductor integrated circuit elements such as I.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Note that the physical properties shown on each side were evaluated by the following method. (1) Sensitivity: Expressed as the minimum exposure time (m8) required to completely resolve only the pattern in the exposed area with a width of 1.0 μm.

(2) Cross-sectional shape: Cut the 1.0 μm wide pattern of the exposed area in the width direction, observe the cross section with a microscope, and compare it to Figures 1 to 3 of the attached drawings.
Classified and shown according to the diagram.

(3) Heat resistance: The resist pattern was gradually heated and the temperature just before it sagged was shown.

Reference Example 1 2.3.47) Lyhydroxybenzophenone in dioxane 300-2. Of and 1,2-naphthoquinonediazide-5-sulfonyl chloride20. Of 1.2-su7toquinone diazido 4-sulfonyl chloride 8.02
Add and dissolve 25% carbon dioxide as a catalyst, add 202% IJum aqueous solution, and heat at 25°C.
After reacting for an hour, add 35% hydrochloric acid 25% by weight to the reaction solution.
9 to ion exchange water 1,000 ? The reactant was precipitated by adding a diluted hydrochloric acid solution, and the resulting product was thoroughly washed with ion-exchanged water, dried, and purified. Naphthoquinone diazide sulfonic acid ester 7.5 y obtained fc.

Reference Example 2 A mixture (a) of naphthoquinone-1,2-diazido-5-sulfonyl chloride and naphthoquinone-1,2-diazide-4-sulfonyl chloride in a weight ratio of 70:30 or a mixture (b) in a weight ratio of 40:60. A naphthoquinonediazide sulfonic acid ester having a triester content of 90 mol was produced by carrying out an esterification reaction with 2,3.4-)rihydroxypenzophenone in the same manner as in Reference Example 1.

Reference Example 3 A mixture (a) of naphthoquinone-1,2-diazido-5-sulfonyl chloride and naphthoquinone-1,2-diazide-4-sulfonyl chloride in a weight ratio of 60:40, and a mixture (b) in a weight ratio of 30:70. Alternatively, using a mixture (C) at a weight ratio of 50:50, 2.3,4.4'-tetrahydroxybenzophenone 2. Of and the above a compound (a), (
28. of each of b) and (e). Naphthoquinonediazide sulfonic acid esters each having a triester content of 85 mol were produced by carrying out an esterification reaction in the same manner as in Reference Example 1, except that Of was used.

Reference Example 4 Using a mixture of naphthoquinone-1,2-diazido-5-sulfonyl chloride and naphthoquinone-1,2-diazide-4-sulfonyl chloride in a weight ratio of 50:50, 2.2
',4.4'-Tetrahydroxybenzophenone2. O
f and the above mixture 28. Reference example 1 except for using Of and
An esterification reaction was carried out in the same manner as above to produce naphthoquinone diazide sulfonic acid ester having a triester content of 90 mol.

Comparative Reference Example Using a mixture of naphthoquinone-1,2-diazide-5-sulfonyl chloride and naphthoquinone-1,2-diazide-4-sulfonyl chloride in a weight ratio of 50:50, 2,3
．． 4-) The amount of lyhydroxypenzophenone used is 2.
The esterification reaction was carried out in the same manner as in Reference Example 1 except that 52 was used to produce a 7-toquinonediazide sulfonic acid ester having a triester content of 75 mol.

Example 1 110 parts by weight of formalin and 5 parts by weight of oxalic acid were added to a mixture of 40 parts by weight of m-cresol and 60 parts by weight of p-cresol, and after heating and boiling for 100 minutes,
A cresol novolak resin was produced by dehydration and concentration under reduced pressure.

Next, the cresol novolac resin 1 obtained in this way
00 parts by weight, 20 parts by weight of the naphthoquinonediazide sulfonic acid ester obtained in Reference Example 1 was dissolved in 390 parts by weight of ethylene glycol monoethyl ether acetate, and this was filtered using a membrane filter with a pore size of 0.2 μm. A photoresist composition was prepared. This photoresist composition was uniformly coated on a 4-inch silicon wafer to a thickness of 1.3 μm using a resist coater model TR-4000 (manufactured by Tammo Co., Ltd.), and then dried on a hot plate at 110° C. for 90 seconds. Next, a G-ray reduction projection exposure device DSW-4800 model Taehar stepper (GC
G#! using a test chart mask (manufactured by Dai Nippon Printing Co., Ltd.) using A company M). After exposure, diluted with 2.38% by weight tetramethylammonium hydroxide aqueous solution, 23
Developed at ℃ for 60 seconds.

As a result, the sensitivity was 400 ms. Further, the resist pattern had a good cross-sectional shape with vertically cut sides as shown in FIG. 1 of the attached drawings, and its dimensional accuracy was also excellent. Further, the heat resistance determined as the temperature immediately before the resist pattern shape sagged was 140°C.

Examples 2-6. Comparative Examples 1 to 2 Except that the mixing ratio of m-cresol and p-cresol and the type and mixing amount of naphthoquinonediazide sulfonic acid ester used were as shown in Table 1,
By repeating the same operations as in Example 1, a positive photoresist composition having the physical properties shown in Table 1 was obtained.

Examples 7 to 1 The mixing ratio of m-cresol and p-fragile 5 and the type and mixing amount of the 7-toquinonediazide sulfonic acid ester used were as shown in Table 2, and the exposure treatment was 1-line reduction projection exposure device N5R-1010
The sensitivity, cross-sectional shape of the pattern, and heat resistance of each photoresist composition were evaluated using the same operations as in Example 1, except for using i3 (manufactured by Nikon Corporation), and the results are shown in Table 2. It was shown to. As a result, the photoresist composition of the present invention can be effectively used in a one-line reduction projection exposure apparatus.
It was confirmed that the heat resistance and cross-sectional shape of the pattern were extremely excellent.

Example 12 m-cresol and p-cresol in a weight ratio of 40:6
100 parts by weight of a cresol novolak resin obtained by mixing formalin in a ratio of 0 to 2, followed by condensation using an oxalic acid catalyst in a conventional manner, and 2°3.4-)lyhydroxybenzophenone 2. ．． 5 parts by weight of 1,2-naphthoquinonediazide-5-sulfonic acid ester (containing triester) obtained by esterifying Of and 1,2-naphthoquinonediazide-5-sulfonyl chloride 7,Of by a known method. 190%) and hee 2,3.4-)! J Hydroxybenzophenone 2. 5 parts by weight of 1,2-naphthoquinonediazide-4-sulfonic acid ester obtained by esterifying Or and 7.02 parts of 1,2-naphthoquinonediazide-4-sulfonyl chloride (containing triester). (90 mol%) was dissolved in 390 parts by weight of ethylene glycol monoethyl ether acetate, and filtered using a membrane filter with a pore diameter of 2 μm to prepare a photoresist composition. When a resist pattern was formed using this photoresist composition in the same manner as in Example 1, the minimum exposure time required to completely resolve only the pattern in the 1.0 μm wide exposed area was 480 m.
It was s. The attached drawings show various cross-sectional shapes of resist patterns, and the resist pattern shape in this example has a good cross-sectional shape with vertical sides as shown in Figure 1, and its dimensional accuracy is also excellent. Ta. Further, the heat resistance determined as the temperature immediately before the resist pattern shape sagged was 145°C.

Example 13 The exposure device was a one-line reduction projection exposure device N5R-1010i.
When a resist pattern was formed by the same operations as in Example 12 except that a resist pattern (manufactured by Kon Co., Ltd.) was used in Example 12, the same results as in Example 12 were obtained.

[Brief explanation of the drawing]

FIG. 3 is a cross-sectional view showing different cross-sectional shapes. Figure 1 Figure 2 -Yo Figure 3

Claims (1)

[Scope of Claims] 1. A positive photoresist composition containing (A) a cresol novolac resin and (B) a photosensitizer containing naphthoquinonediazide sulfonic acid ester as a main component, wherein (a) the cresol novolac resin is (b) the photosensitizer is obtained from a cresol mixture of 10 to 45% by weight of m-cresol and 90 to 55% by weight of p-cresol, and (b) the photosensitizer is 2,3,4-trihydroxybenzophenone, At least one polyhydroxybenzophenone selected from 2,3,4,4'-tetrahydroxybenzophenone and 2,2',4,4'-tetrahydroxybenzophenone, and 1,2-naphthoquinonediazide-4- Sulfonic acid and 1,2-naphthoquinonediazide-5-sulfonic acid in a weight ratio of 20:80
A positive photoresist composition, which is an esterification reaction product with naphthoquinonediazide sulfonic acid containing in a ratio of 80:20 to 80:20, and the content of a triester or higher polyester is 80 mol% or more. thing.