GB2212933A

GB2212933A - A positive-working photoresist composition

Info

Publication number: GB2212933A
Application number: GB8827542A
Authority: GB
Inventors: Hidekatsu Kohara; Yoshiyuki Satoh; Mitsuo Yabuta; Yoshiaki Arai; Nobuo Tokutake; Koichi Takahashi; Toshimasa Nakayama
Original assignee: Tokyo Ohka Kogyo Co Ltd
Current assignee: Tokyo Ohka Kogyo Co Ltd
Priority date: 1987-11-27
Filing date: 1988-11-25
Publication date: 1989-08-02
Anticipated expiration: 2008-11-25
Also published as: DE3839906A1; KR910004844B1; GB2212933B; KR890008606A; GB8827542D0

Description

1 11 221293,3 A POSITIVE-WORKING PHOTORESIST COMPOSITION The present

invention relates to a positiveworking photoresist composition or, more particularly, to a a positive-working photoresist composition suitable for use as a resist material to form a highly heat- resistant and finely patterned resist layer with an excellent dimensional accuracy and good pattern configuration in the manufacture of various kinds of semiconductor electronic devices such as ICs, LSIs and the like.

Together with the rapidly growing demand for various kinds of electronic instruments such as industrial computers, personal computers, electronic instruments for automation of offices and the like in recent years, the technology of semiconductor-based electronic devices is also rapidly progressing.towards higher and higher density of integration. With regard to the fineness in patterning in the manufacture of semiconductor-based integrated circuits, for example, the line widths of patterning for 256 kilobits DRAM ICs, 1 megabit DRAM ICs and 4 megabits DRAM ICs are about 2 ym, about 1.0-1.3 pm and about 0.7-08 pm, respectively, so that there is an urgent need to develop a technology of fine working in the submicron range.

As is well known, patterning in semiconductor technology is performed by the photolithographic method in which positive-working photosensitive compositions are generally used when the resist pattern is to have a fineness of about 2mm or even smaller line width.

The basic ingredients in a positive-working photosensitive composition include an alkali-soluble novolac resin and a photosensitve or photodecomposable compound termed a photosenisitizer. Various types of alkalisoluble novolac resins are used for this purpose, including phenol formaldehyde novolac resins taught in U.S. Patent No. 3,402,044 and cresol novolac resins taught in "Electrochemistry and Industrial Physical Chemistry", volume 48, page 584 (1980). Furthermore, it is taught in Japanese Patent Kokai 58-17112 and 62-35439 that the sensitivity of the positive-working photosensitive composition or dimensional accuracy of the resist pattern formed therefrom can be improved when the cresol novolac resin is prepared from a mixture of creseol isomers in an appropriate mixing ratio. on the other hand, the proper selection of the photosensitizer is also important for obtaining a photosensitive composition with a high performance. Photosensitizers of a type widely used include the sulfonate esters of a naphthoquinone diazide sulfonic acid as the photodecomposable constituent and a compound having phenolic hydroxy groups as taught in U.S. Patents No. 3,046,118, No. 3, 106,465 and No. 20 3,148,983 and Japanese Patent Publication 62-28457. Another factor for obtaining a desired accuracy or precision of patterning with a submicron fineness is the equipment for pattern-wise exposure of the resist layer to light. The types of equipment currently used for this purpose are those of the minifying projection exposure type, referred to as steppers hereinbelow, utilizing a light of the socalled G-line having a wavelength of 436 nm. Although the G-line steppers are useful for patterning when the line width of the pattern is 0.8-1.0 pm or larger, they are not suitable when patterning in a finer line width is desired to comply with the trend toward a higher and higher density of integration in the semiconductor devices of recent years. Therefore, developments are now under way for a stepper utilizing light of a shorter wavelength v V than the G-line, in which the light for exposure is the so-called I-line having a wavelength of 365 nm emitted from mercury lamps.

Needless to say, the performance of the improved steppers mentioned above can be fully exhibited only when the equipment is used in combination with a photosensitive composition suitable for fine patterning of the submicron order. It is known that conventional positive-working photosensitive compositions developed for photolithographic works utilizing a G-line stepper are generally usable in the works with an I-line stepper as is taught in Solid State Technology, Japanese edition, 1977, February issue, pages 34-38. Because of the larger absorption of the I-line light than of the G-line light by the photosensitive composition, however, a difficulty is encountered in adapting a positiveworking photosensitive composition for the G-line for use with I-line steppers. This is because the quantity of the light energy absorbed by the resist layer is sometimes excessively large, thus causing overexposure so that the contrast of the resist layer is decreased and, in particular, the line pattern of the resist layer has a cross-sectional configuration deviating from the desirable rectangular or orthogonal form, thereby affecting the fidelity of pattern production. Accordingly, it is highly desirable to develop a positive-working photosensitive composition capable of giving a high- quality resist pattern irrespective of the type of stepper used which may be a G-line stepper or an I-line stepper.

In the manufacture of semiconductor devices by the photolithographic method, it is usual that the substrate surface is etched utilizing the patterned resist layer formed thereon as a mask after being exposed to light using a G-line or I-line stepper followed by development. The current technology for the etching treatment is to use a dry plasma etching process in view of the smaller amount of undesirable side etching than in wet processes. In this dry etching method, the patterned resist layer is also subject to a gradual decrease in thickness as a result of the attack of the plasma, while it is essential that the fidelity of the pattern reproduction on the substrate surface by etching is not affected by the decrease in the thickness of the resist layer. The decrease in thickness of a resist layer can be reduced by increasing the temperature of the post-baking treatment of the patterned resist layer after development. Therefore, it is also a desirable property of a photosensitive composition that the resist layer formed therefrom has a high heat resistance, together with the requirement for the orthogonal cross-sectional form of the line pattern. None of the conventional prior art positive- working photosensitive compositions is satisfactory because of the deficiency in one of the above described requirements.

We have now developed a positive-working photosensitive composition capable of giving a very finely patterned photoresist layer having a high heat resistance and an excellent dimensional accuracy as well as a good orthogonal cross-sectional configuration of the line patterns.

Accordingly, the present invention provides a positive-working photosensitive composition which comprises, in admixture:

(A) a cresol novolac resin comprising from io to 45% by weight or by mole of the m-cresol moiety and from 90 to 55% by weight or by mole of the pcresol moiety; and (B) a photosensitizer, which is a sulfonate ester or a combination of sulfonate esters of a polyhydroxy benzophenone selected from 2,3,4-trihydroxy benzophenone, 2,3,4,41-tetrahydroxy benzophenone or 2,21,4,49-tetrahydroxy benzophenone and a sulfonic 5 acid selected from 1,,2-naphthoquinonediazide-4sulfonic acid or 1,2naphthoquinonediazide5-sulfonic acid in which at least 80% by mole of the polyhydroxy benzophenone has three or four of the hydroxy groups in the molecule thereof esterified with the sulfonic acid.

In particular, it is preferred that the sulfonic acid is a combination of from 20 to 80% by weight of 1,2-naphthoquinonediazide-4-sulfonic acid and from 80 to 20% by weight of 1,2-naphthoquinonediazide5-sulfonic acid.

As described above, the essential ingredients in the inventive positiveworking photosensitive composition include component (A) which is a specific film-forming cresol novolac resin and component (B) which is a photosensitizer which is a sulfonate ester of a polyhydroxybenzophenone with a naphthoquinonediazide sulfonic acid.

It is essential that the cresol novolac resin as component (A) contains the cresol moiety which is composed of from 10 to 45% (by weight or by mole) of the m-cresol moiety and from 90 to 55% (by weight or by mole) of the p-cresol moiety. In other words, the cresol novolac resin is prepared by the condensation reaction of a mixture of from 10 to 45% of m-cresol and from 90 to 55% of p-cresol with formaldehyde. This condition in the isomeric proportion of cresols is essential in order to obtain a positiveworking photoresist having an excellent heat resistance as well as good dimensional accuracy and cross-sectional configuration of the patterned resist layers. When the cresol novolac resin is prepared from a single cresol isomer or an isomeric mixture of cresols not satisfying the abovementioned requirement, the positive-working photosensitive composition compounded with such a cresol novolac resin does not give a positive-working photoresist of practical value having an excellent heat resistance as well as good dimensional accuracy and cross- sectional configuration of the patterned resist layers.

Component (B) as a photosensitizer is a sulfonate ester of a polyhydroxybenzophenone and a naphthoquinonediazide sulfonic acid. In particular, it is a product of an esterification reaction of a polyhydroxy benzophenone compound selected from 2,3,4trihydroxy benzophenone, 2,3,4,41-tetrahydroxy benzophenone or 2,21,4,41-tetrahydroxy benzophenone and a sulfonic acid which is 1,2-naphthoguinonediazide-4-sulfonic acid, 1, 2-naphthoquinonediazide-5-sulfonic acid or a combination thereof, or sulfonyl chloride compounds derived from these sulfonic acids. Although it is desirable that all of the hydroxy groups in the polyhydroxy benzophenone compound or compounds are esterified with the sulfonic acid, substantially the same performance of the photosensitive composition can be obtained when at least 80% by mole of the polyhydroxy benzophenone compound or compounds has at least three of the hydroxy groups per molecule thereof esterified with the sulfonic acid compound. In other words, at least 80% by mole of the starting polyhydroxy benzophenone compound should have been converted into a triester and/or tetraester with the sulphonic acid compound. When the molar proportion of such highly esterified molecular species is below 80%, the positive-working photosensitive composition compounded with such a photosensitiser would not give a positive-working photoresist of practical value having an excellent dimensional accuracy and cross-sectional configuration of the patterned resist layer together with a great decrease in the heat resistance of the resist.

It is preferred that the sulfonic acid compound is a mixture of from 20 to 80% by weight of 1,2 naphthoquinonediazide-4-sulfonic acid or sulfonyl chloride, and from 90 to 20% by weight of 1,2 naphthoquinonediazide-5-sulfonic acid or sulfonyl chloride or, more preferably, from 40 to 60% by weight of the former compound and from 60 to 40% by weight of the latter compound in order to obtain the best results in respect of heat resistance as well as dimensional accuracy and cross-sectional configuration of the patterned resist layer obtained from the photosensitive composition of the invention.

The above described benzophenone diazide sulfonate ester as the photosensitizer can be prepared by an esterification reaction according to a known procedure from 1 mole of the polyhydroxy benzophenone compound or compounds and, preferably, at least 2.5 moles of 1,2naphthoquinonediazide-4sulfonyl chloride and/or 1,2naphthoquinonediazide5-sulfonyl chloride as the reactant dissolved in a suitable organic solvent in the presence of a hydrogen chloride acceptor. When the sulfonic acid compound is a combination of 1,2naphthoquinonediazide-4-sulfonic acid and 1,2-naphthoquinonediazide-5sulfonic acid in the proportions specified above, it is optional that the esterification reaction is conducted with a mixture of 1,2-naphthoguinonediazide-4-sulfonyl chloride and 1,2-naphthoquinonediazide-5-sulfonyl chloride or, alternatively, these two sulfonyl chloride compounds are separately esterified to give two esterification products which are mixed together subsequently in a calculated proportion.

The degree of esterification of the polyhydroxy benzophenone compound with the sulfonyl chloride depends on various parameters in the reaction including the types and amounts of the organic solvent as the reaction medium and the hydrogen chloride acceptor, so that these conditions should be appropriately selected depending on the combination of the particular polyhydroxy benzophenone and sulfonyl chloride. The esterification product may be subjected to a purification treatment to remove certain constituents in order to bring the degree of esterification of the resultant product to the level to meet the requirement for the photosensitizer used is in the composition of the invention. Liquid chromatography can be a useful means for the quantitative determination of the degree of esterification in the reaction product.

The photosensitive composition of the present invention can be prepared by mixing the above described cresol novolac resin as component (A) and the photosensitizer as component (B) in a suitable proportion preferably by dissolving them together in an organic solvent. The weight proportion of these components is preferably in such a range that 100 parts by weight of the cresol novolac resin are compounded with from 10 to 30 parts by weight of the photosensitizer. When the amount of the photosensitizer is too small, the photoresist layer obtained from the photosensitive composition may be somewhat inferior in respect of the heat resistance as well as the dimensional accuracy and crosssectional configuration of the patterned resist layer. on the other hand, when the amount thereof is excessively large, a decrease may be caused in the photosensitivity of the photosensitive composition.

1 The organic solvent used for dissolving the components (A) and (B) is not limited. Examples of suitable organic solvents include ketones, e.g., acetone, methyl ethyl ketone, cyclohexanone and isoamyl ketone, polyhydric alcohols and esters or ethers thereof, e.g., ethylene glycol, propylene glycol, ethylene glycol monoacetate, diethylene glycol monoacetate as well as monomethyl, monoethyl, monopropyl, monobutyl and monophenyl ethers thereof, cyclic ethers, e.g., dioxane, and esters, e.g., methyl acetate, ethyl acetate and butyl acetate. These organic solvents can be used either singly or as a mixture of two or more thereof.

It is of course optional that, in addition to the above described essential ingredients, the photosensitive composition of the present invention may be admixed with various kinds of known additives conventionally used in photosensitive compositions which are miscible therewith, such as auxiliary resins, plasticizers, stabilizers and colouring agents which serve to increase the visibility of the resist pattern after development.

The following is a description of a typical procedure for patterning by using the photosensitive composition of the present invention. A substrate such as a semiconductor silicon wafter is first coated with the photosensitive composition, which is a solution prepared by dissolving the cresol novolac resin and the photosensitizer in an organic solvent, by using a suitable coating machine such as a spinner followed by drying to form a layer of the photosensitive composition. Thereafter, the photosensitive layer is exposed pattern-wise to G-line or I-line light through a photomask bearing a desired pattern to form a latent image which is then developed by using an alkaline is developer solution such as an aqueous solution containing 2 to 5% by weight of an organic alkali, e.g., tetramethyl ammonium hydroxide and choline, to selectively dissolve away the photosensitive layer on the areas exposed to light where the photosensitive composition has been imparted with an increased solubility in the developer solution leaving the photosensitive layer on the unexposed areas to form a patterned resist layer.

To summarize the above description, the positiveworking photosensitive composition of the invention can be advantageously used in the manufacture of integrated semiconductor electronic devices such as LSIs and the like because the inventive composition, of which the essential ingredients are the specific cresol novolac resin and the specific photosensitizer described above in detail, can be used in both of the G- line and I-line steppers and the patterned resist layer obtained from the composition has excellent heat resistance as well as dimensional accuracy and cross sectional configuration of the line-wise patterned resist layer.

In the following, the positive-working photosensitive composition of the present invention is described in more detail by way of examples as preceded by the description of the preparation of the photosensitizers used in the examples although the scope of the invention should never be construed to be limited by these examples.

In the following examples, the photosensitive compositions were evaluated for the performance in respect of the photosensitivity thereof and cross sectional configuration and heat resistance of the patterned resist layer obtained therefrom according to the following procedures and criteria. 1. Photosensitivity The photosensitivity of a photosensitive composition was given in terms of the minimum exposure time in-milliseconds required for achieving complete resolution of a line pattern of 1.0 pm width on the exposed areas alone.

2. Cross sectional configuration of line patterns A line pattern of 1.0 pm width formed on a substrate was cut perpendicularly to the longitudinal direction and the cross section of the line-wise patterned resist layer was microscopically examined. The results were given in three rating of A, Band C as rsham in Figure 1 corresponding to a cross section having complete orthogonality, a cross section having square shoulders but trailing skirts on the substrate surface and a cross section having rounded shoulders and trailing skirts 10 on the substrate surface, respectively. 3. Heat resistance of patterned resist layer A patterned resist layer on the substrate surface was heated to gradually increase the temperature and a measure of the heat resistance was given by the temperature just before appearance of dullness was noted in the cross sectional configuration of the patterned resist layer. Preparation 1.

An esterification reaction was performed at 25 'C for 2 hours by agitating a mixture of 2.0 g of 2,3,4-trihydroxy benzophenone, 3.5 9 of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 3.5 9 of 1,2-naphthoquinonediazide-4-sulfony1 chloride dissolved in 300 ml of dioxane with admixture of 20 g of a 25% by weight aqueous solution of sodium carbonate and then the reaction mixture was admixed with 25 g of a 35% by weight hydrochloric acid diluted with 1000 g of deionized water to precipitate the esterification product which was collected by filtration and thoroughly washed with deionized water and drying. Thus, 7. 5 g of an esterification product were obtained which was identified by analysis to be a mixture containing about 90% by moles of the triester of the starting 2,3, 4-trihydroxy benzophenone. Preparation 2.

The experimental procedure was substantially the same as in Preparation 1 except that the amounts of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 1,2-naphthoquinonediazide-4-sulfonyl chloride were 4.9 g and 2.1 9, respectively. The esterification product thus obtained contained about 90% by moles of the triester of the starting 2,3,4 trihydroxy benzophenone. Preparation 3.

The experimental procedure was substantially the same as in Preparation 1 except that the amounts of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 1,2-naphthoquinonediazide-4-sulfonyl chloride were 2.8 9 and 4.2 9, respectively. The esterification product thus obtained contained about 90% by moles of the triester of the starting 2,3,4- trihydroxy benzophenone. Preparation 4.

The experimental procedure was substantially the same as in Preparation 1 except that 2,3,4-trihydroxy benzophenone was replaced with the same amount of 2,3,4,4'-tetra- hydroxy benzophenone and the amounts of 1,2-naphthoquinonediazide-5- sulfonyl chloride and 1,2-naphthoquinonediazide4-sulfonyl chloride were 4. 2 g and 2.8 g, respectively. The esterification product thus obtained contained about 85% by moles of the triester of the starting 2,3,4,4'- tetrahydroxy benzophenone. Preparation 5.

The experimental procedure was substantially the same as in Preparation 4 except that the amounts of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 1,2-naphthoquinone- diazide-4-sulfonyl chloride were 2.1 g and 4.9 9, respectively. The esterification product thus obtained contained about 85% by moles of the triester of the starting 2,3,4,4'tetrahydroxy benzophenone. Preparation 6.

The experimental procedure was substantially the same as in Preparation 4 except that the amounts of 1,2-naphthoquinonediazide-5-sulfonyl chloride and 1,2-naphthoquinonediazide-4-sulfonyl chloride were each 3.5 9. The esterification product thus obtained contained about 85% by moles of the triester of the starting 2,3,4,4'-tetrahydroxy benzophenone.

!'L- Preparation 7.

The experimental procedure was substantially the same as in Preparation 1 except that 2,3,4-trihydroxy benzophenone was replaced with the same amount of 2,2',4,4'-tetra- hydroxy benzophenone and the amounts of 1,2-naphthoquinonediazide-5- sulfonyl chloride and 1,2-naphthoquinonediazide4-sulfonyl chloride were each 3.5 9. The esterification product thus obtained contained about 90% by moles of the triester of the start,ing 2,2',4,4'-tetrahydroxy benzo- phenone. Preparation 8.

A preparation for a comparative purpose was undertaken in substantially the same manner as in Preparation 1 except that the amount of 2,3,4trihydroxy benzophenone was increased to 2.5 g and the amounts of 1,2-naphthoquinonediazide-5- sulfonyl chloride and 1,2-naphthoquinonediazide4-sulfonyl chloride were each 3.5 g. The esterification product thus obtained contained about 75% by moles of the triester of the starting 2,3,4-trihydroxy benzophenone.

Example 1._

A cresol novolac resin, which is referred to as the novolac I hereinafter, was prepared according to a conventional procedure from a mixture of 40 parts by weight of m-cresol and 60 parts by weight of p-cresol with addition of 110 parts by weight of a 30% formalin in the presence of 3 parts by weight of oxalic acid as a catalyst by heating the mixture for 100 minutes under boiling followed by dehydration under reduced pressure. A photosensitive composition was prepared by dissolving, in 390 parts by weight of ethylene glycol monoethyl ether acetate, 100 parts by weight of the above obtained novolac I and 15 parts by weight of a photosensitizer which was a reaction product obtained by the esterification reaction of 2.0 g of 2, 3,4-trihydroxy benzophenone and 7.0 g of 1,2-naphthoquinone-diazide-5-sul- fonyl chloride in the same manner as in Preparation 1 and containing about 98% by moles of the triester of the starting 2,3,4-trihydroxy benzophenone, which is referred to as the photosensitizer I hereinafter, followed by filtration through a membrane filter having a pore diameter of 0.2 pm.

A 4-inch silicon wafer was coated with the thus prepared photosensitive composition using a resist coater (Model TR-4000, manufactured by Tazmo Co.) to have a uniform thickness of the coating layer of 1.3 pm as dried followed by drying on a hot plate at 110 OC for 90 seconds to form a photoresist layer. The photoresist layer was then exposed pattern-wise to ultraviolet light through a test chart photomask (a product by Dai-Nippon Printing Co.) on a G-line wafer stepper for exposure by minifying projection (Model DSW-4800, manufactured by GCA Co.) followed by a development treatment at 23 OC for 60 seconds using a 2.38% by weight aqueous solution of tetramethyl ammonium hydroxide as the developer solution.

The minimum exposure time as a measure of the photosensitivity of the composition was 400 milliseconds. The linewise patterned resist layer had a cross sectional configuration of A and the temperature of heat resistance thereof was 140 OC. Examples 2 to 9 and Comparative Examples 1 to 3.

The experimental procedure in each of these Examples and Comparative Examples was substantially the same as in Example I except that the cresol novolac resin, which is referred to as the novolac II, III or IV hereinafter, was prepared from a mixture of m- and p-cresols in a different mixing ratio as shown below and the photosensitizer, which is referred to as the photosensitizer II, III, IV or V hereinafter, specified below added to 100 parts by weight of the cresol novolac resin in an amount of 15 or 20 parts by weight.

Cresol novolac resins Novolac II: m-cresol:p-cresol = 42.5:57.5 Novolac III: m-cresol:.p-cr.esol = 30:70 Novolac IV: m-cresol:p-cresol = 60:40 14 Photosensitizers Photosensitizer II: a reaction product of 2,3,4-trihydroxy benzophenone and 1,2-naphthoquinonediazide-5-sulfonyl chloride containing about 90% by moles of the triester Photosensitizer III: a reaction product of 2,3,4,4'-tetrahydroxy benzophenone and 1,2-naphthoquinonediazide-5-sulfonyl chloride containing about 95% by moles of the triester Photosensitizer IV: a reaction product of 2,2',4,4'-tetrahydroxy benzophenone and 1,2-naphthoquinonediazide-4sulfonyl chloride containing about 85% by moles of the triester Photosensitizer V: a reaction product of 2,3,4,4'-tetrahydroxy benzophenone and 1,2-naphthoquinonediazide-4-sulfonyl chloride containing about 70% by moles of the triester Table 1 below shows the formulation of each of the photosensitive compositions and the results of the evaluation tests thereof carried out in the same manner as in Example 1 including the corresponding data for the composi tion prepared in Example 1.

Examples 10 to 15 and Comparative Examples 4 and 5.

The experimental procedure in each of these Examples and Comparative Examples was substantially the same as in the preceding examples except that the apparatus for the pattern-wise ultraviolet exposure was an I-line exposure apparatus by minifying projection (Model NSR-101013, manufactured by Nikon Co.). The formulation of each photosensitive composition was as shown in Table 1. The cresol novolac resin was the novolac I, II, III or IV and the photosensitizer was the photosensitizer II, VI, VII or VIII, the latter three being specified below.

il Photosensitizers Photosensitizer VI: a reaction product of 2,3,4,4'tetrahydroxy benzophenone and 1,2-naphthoquinonediazide-5-sulfonyl chloride containing about 90% by moles of the triester Photosensitizer VII: a reaction product of 2,2',4,4'-tetrahydroxy benzophenone and 1,2naphthoquinonediazide-4-sulfonyl chloride containing about 90% by moles of the triester Photosensitizer VIII: a reaction product of 2,3,4,4'-tetrahydroxy benzophenone and 1,2-naphthoquinonediazide-5-sulfonyl chloride containing about 75% by moles of the triester Table 1 below shows the formulation of each of the photosensitive compositions and the results of the evaluation tests thereof.

T a b 1 e 1 Novolac Photosen- Ph'oto- Cross Temperature sitizer sensisection of heat (parts by tivity, of resistance, weight) ms pattern CC 1 (15) 400 A 140 11 (15) 300 A 135 11 (20) 350 A 140 111 (15) 250 A 140 111 (20) 300 A 145 IV (15) 600 A 140 IV (20) 800 A 145 11 (15) 350 A 135 111 (20) 400 A 135 11 (15) 350 A 135 11 (10) 300 A 140 11 (15) 450 A 135 VI (20) 350 A 145 VII (20) 900 A 140 Il (20) 350 A 140 11 (15) 180 C 130 V (15) 400 C 125 11 (40) 1000 A 140 VIII (20) 700 C 125 VI (20) 200 C 130 Exam- ple Comparative Example

II II II I I II 1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 1 2 3 4 I II I III I I I III II I II IV II II I I IV Examples 16 to 21 and Comparative Examples 6 and 7.

A photosensitive composition was prepared in each of these Examples and Comparative Examples in substantially the same manner as in the preceding examples from 100 parts by weight of one of the novolacs I to IV and 15 or20 parts by weight of one of the photosensitizers prepared in Preparation 1 to 8. The formulations of the compositions are shown in Table 2 below.

The procedure for the evaluation of these photosensi tive compositions was substantially the same as in Example 1 to give the results also shown in Table 2.

Examples 22 to 26.

A photosensitive composition was prepared in each of these Examples in substantially the same manner as in the preceding examples from 100 parts by weight of one of the novolacs I to IV and 15 or 20 parts by weight of one of the photosensitizers prepared in Preparations I to 7. The formulations of the compositions are shown in Table 2 below.

The procedure for the evaluation tests of these photo sensitive compositions was substantially the same as in Examples 10 to 15 to give the results also shown in Table 2. - T a b 1 e 2 Photosensi- Temper tizer prepar- Photo- Cross ature Novo- ed in Prepa- sensi- section of heat lac ration No. tivity, of resist (parts by ms pattern ance weight) 0 C 16 1 1' (20) 400 A 140 17 1 2 (20) 300 A 135 1 18 11 4 (20) 350 A 140 19 111 6 (20) 250 A 140 Exam- 20 11 3 (15) 300 A 145 21 1 5 (15) 400 A 140 ple 22 1 2 (20) 750 A 135 23 11 4 (20) 600 A 140 24 111 7 (20) 500 A 140 11 3 (15) 450 A 145 26 1 5 (15) 420 A 140 Com para- 6 11 8 (20) 1000 B 125 tive Exam ple 7 IV 6 (20) 180 C 130 Example 27.

A photosensitive composition was prepared by dissolving, in 390 parts by weight of ethylene glycol monoethyl ether acetate, 100 parts by weight of the novolac 1, 5 parts by weight of the photosensitizer II and 5 parts by weight of another photosensitizer, which was a product of the esterification reaction of 2. 0 g of 2,3,4-trihydroxy benzophenone and 7.0 9 of 1,2- naphthoquinonediazide-4-sulfonyl chloride containing 90% by moles of the triester of the starting benzophenone compound, followed by filtration through a membrane filter of 0.2 pm pore diameter.

The results of the evaluation tests of this photosensitive composition undertaken in the same manner as in Example 16 using the G-line stepper were that: the minimum exposure time as a measure of photosensitivity was 480 milliseconds, the cross sectional configuration of the resist pattern was A and the temperature of heat resistance was 145 'C. Substantially the same results of evaluation tests were obtained when the pattern-wise exposure was conducted using the I-line stepper used in Examples 22 to 26 instead of the G-line stepper.

1 11 1

Claims

CLAIMS:

1. A positive-working photosensitive composition which comprises, in admixture:

(A) a cresol novolac resin comprising from 10 to 45% by weight or by mole of the m-cresol moiety and from 90 to 55% by weight or by mole of the pcresol moiety; and (B) a photosensitizer, which is a sulfonate ester or a combination of sulfonate esters of a polyhydroxy benzophenone selected from 2,3,4-trihydroxy benzophenone, 2,3,4,41-tetrahydroxy benzophenone or 2,21,4,41-tetrahydroxy benzophenone and a sulfonic acid selected from 1,2-naphthoquinonediazide-4 sulfonic acid or 1,2-naphthoquinonediazide 5-sulfonic acid in which at least 80% by mole of the polyhydroxy benzophenone has three or four of the hydroxy groups in the molecule thereof esterified with the sulfonic acid.

2. A positive-working photosensitive composition as claimed in claim 1 wherein the sulfonic acid is a mixture of from 20 to 80% by weight of 1,2-naphtho- quinonediazide-4-sulfonic acid and from 80 to 20% by weight of 1,2-naphthoquinonediazide-5-sulfonic acid.

3. A positive-working photosensitive composition as claimed in claim 2 wherein the sulfonic acid compound is a mixture of from 40 to 60% by weight of 1,2-naphthoquinonediazide-4-sulfonic acid and from 60 to 40% by weight of 1,2-naphthoquinonediazide-5sulfonic acid.

A positive-working photosensitive composition as claimed in any one of the preceding claims wherein the amount of the photosensitizer as component (B) is in the range of from 10 to 30 parts by weight per 100 parts by weight of the cresol novolac resin as component (A).

5. A method for forming a patterned photoresist layer on the surface of a substrate which comprises the steps of:

(a) coating the surface of the substrate with a positive-working photosensitive composition as claimed in any one of claims 1 to 4; (b) drying the coating layer; (c) exposing the coating layer of the photosensitive composition pattern-wise to ultraviolet light of a wavelength of mainly 365 nm to form a pattern-wise latent image; and (d) developing the latent image by dissolving away the photosensitive composition in the coating layer from the areas exposed to ultraviolet light with a developer solution.

6. A photosensitive composition as claimed in claim 1 and substantially as hereinbefore described with reference to the foregoing examples.

7. A method as claimed in claim 5 substantially as hereinbefore described with reference to the foregoing examples.

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