Positive-Working Photosensitive Composition With Three Difference 1,2-Naphthoquinone Diazide Sulfonic Acid Esters to Include the Ester of Curcumin

In the following, examples are given, as preceded by the description of the synthetic procedure of the specific ester compound of curcumin used as the component (C) as well as the photosensitive compound as the component (B), to illustrate the positive-working photosensitive composition of the invention in more detail but not to limit the scope of the invention in any way.

A solution of 8 g of triethanol amine in 32 ml of dioxane was added dropwise to a mixture prepared by dissolving 10 g of curcumin and 7.2 g of 1,2-naphthoquinone diazide-5-sulfonyl chloride in 350 ml of dioxane under vigorous agitation at room temperature over a period of 1 hour. Thereafter, a diluted hydrochloric acid prepared by diluting 25 g of a 35% hydrochloric acid with 1000 g of deionized water was added to the reaction mixture to precipitate the reaction product. The precipitates were collected by filtration and thoroughly washed with deionized water, dehydrated and dried. The thus obtained product was an esterification product of curcumin of which the average degree of esterification of the starting curcumin was 50%.

The procedure for the preparation was substantially the same as in Preparation Example 1 described above except that the amount of 1,2-naphthoquinone diazide-5-sulfonyl chloride was decreased to 3.6 g. The thus obtained product was an esterification product of curcumin of which the average degree of esterification of the starting curcumin was 25%.

The procedure for the preparation was substantially the same as in Preparation Example 1 described above except that the amount of 1,2-naphthoquinone diazide-4-sulfonyl chloride was increased to 10.8 g. The thus obtained product was an esterification product of curcumin of which the average degree of esterification of the starting curcumin was 75%.

The procedure for the preparation was substantially the same as in Preparation Example 1 described above except that the amount of 1,2-naphthoquinone diazide-4-sulfonyl chloride was increased to 14.5 g. The thus obtained product was an esterification product of curcumin of which the average degree of esterification of the starting curcumin was approximately 100% corresponding to a substantially pure diester of curcumin.

A solution of 7.7 g of triethanol amine in 32 g of dioxane was added dropwise to a solution of 2.0 g of 2,3,4-trihydroxy benzophenone and 7.0 g of 1,2-naphthoquinone-diazido-5-sulfonyl chloride in 350 ml of dioxane under vigorous agitation over a period of 1 hour to effect the esterification reaction. In the next place, the reaction mixture was admixed with a diluted hydrochloric acid which was a mixture of 25 g of 35% hydrochloric acid and 1000 g of water to precipitate the reaction product The precipitates collected by filtration were thoroughly washed with water and dried to give an esterification product of 2,3,4-trihydroxy benzophenone of which the average degree of esterification was 90%.

The experimental procedure was substantially the same as in Preparation Example 5 described above except that the amount of 1,2-naphthoquinone diazido 5-sulfonyl chloride was decreased to 3.5 g. The thus obtained esterification product had an average degree of esterification of 50%.

The experimental procedure was substantially the same as in Preparation Example 5 described above except that 2,3,4-trihydroxy benzophenone was replaced with the same amount of 2,3,4,4'-tetrahydroxy benzophenone and the amount of 1,2-naphthoquinonediazido-5-sulfonyl chloride was decreased to 5.7 g. The thus obtained esterification product of 2,3,4,4'-tetrahydroxy benzophenone had an average degree of esterification of 65%.

A coating solution was prepared by admixing a commercial product of a solution-type positive working photoresist composition containing 27% by weight of the non-volatile matter composed of a phenol novolak resin and a photosensitizing ingredient including o-naphthoquinone diazide compound (OFPR-800, a product by Tokyo Ohka Kogyo Co.) with the esterification product obtained in Preparation Example 1 in an amount of 3% by weight relative to the non-volatile material therein followed by filtration through a membrane filter having a pore diameter of 0.2 .mu.m.

The thus prepared coating solution of the photosensitive composition was uniformly applied by using a spinner to the surface of a semiconductor silicon wafer of 4-inches diameter provided with a vapor-deposited aluminum coating layer and having a difference ;n the surface levels of 1.0 .mu.m. The coating layer of the photosensitive composition had a thickness of 2.0 .mu.m as dried. After evaporation of the solvent from the coating layer, the silicon wafer was mounted and prebaked for 90 seconds on a hot plate kept at 110.degree. C. to complete the coating layer of the photosensitive composition.

The coating layer of the photosensitive composition on the substrate surface was exposed patternwise to ultraviolet light through a test-chart photomask on a minifying projection exposure equipment (Wafer Stepper Model 1505 G3A, manufactured by Nikon Co.) and subjected to a development treatment at 23.degree. C. taking 30 seconds by use of a 2.38% by weight aqueous solution of tetramethyl ammonium hydroxide to form a patterned photoresist layer on the surface. Electron microscopic examination of the thus formed photoresist pattern indicated that the pattern was a high-fidelity reproduction of the photomask pattern of 0 8 .mu.m line width with sharpness even on the raised areas at the level difference where the thickness of the photoresist layer was relatively small. The cross sectional profile of the line pattern was orthogonal on the substrate surface.

The photosensitivity of the photoresist layer was evaluated by determining the minimum exposure time by which a line-and-space pattern of the resist layer having a width of 1.0 .mu.m of the lines and spaces could be obtained with full fidelity to give a result of 150 m seconds.

Two cresol novolak resins I and II were prepared from a mixture of m- and p-cresols and formalin in the presence of oxalic acid as a catalyst according to a conventional procedure. The resin I, which had a weight-average molecular weight of 28,000, was prepared from a mixture of m- and p-cresols in a ratio of 60:40 and the resin II, which had a weight-average molecular weight of 2000, was prepared from a mixture of m- and p-cresols in a ratio of 40:60.

A photosensitive composition in the form of a solution was prepared by dissolving 25 parts by weight of the cresol novolak resin I, 75 parts by weight of the cresol novolak resin II, 30 parts by weight of a reaction product of 1.0 mole of 2,3,4-trihydroxy benzophenone and 1.6 moles of naphthoquinone-1,2-diazide sulfonyl chloride and the esterification product of curcumin obtained in Preparation Example 2 in an amount of 3% by weight based on the total amount of the above three ingredients together in 390 parts by weight of ethylene glycol monoethyl ether acetate followed by filtration through a membrane filter of 0.2 .mu.m pore diameter.

A patterned photoresist layer was formed on a silicon wafer in substantially the same manner as in Example 1 using the above prepared photosensitive composition. An electron microscopic examination indicated that the quality of the line-and-space pattern of the resist layer was as satisfactory as in Example 1. The minimum exposure time determined in the same manner as in Example 1 was 160 m seconds as a measure of the photosensitivity of the photosensitive composition.

A line-and-space pattern of a photoresist layer was formed on a silicon wafer in the same manner as in Example 1 except that the photosensitive composition used therefor was formulated by using, instead of 3% by weight of the esterification product of curcumin prepared in Preparation Example 1, a combination of 2% by weight of the esterification product of curcumin prepared in Preparation Example 3 and 1% by weight of 1-ethoxy-4-(4'-N,N-diethylaminophenylazo) benzene.

An electron microscopic examination indicated that the quality of the line-and-space pattern of the resist layer was as satisfactory as in Example 1. The minimum exposure time determined in the same manner as in Example 1 was 170 m seconds as a measure of the photosensitivity of the photosensitive composition.

A line-and-space pattern of a photoresist layer was formed on a silicon wafer in the same manner as in Example 1 except that the photosensitive composition used therefor was formulated by using, instead of 3% by weight of the esterification product of curcumin prepared in Preparation Example 1, 3% by weight of the esterification product of curcumin prepared in Preparation Example 4.

An electron microscopic examination of the thus formed patterned photoresist layer indicated that the quality of the pattern was satisfactory practically with no problems at least on the flat areas although a slight influence of halation in the lateral direction was noted at and in the vicinity of the boundary areas with a difference in the surface levels. The minimum exposure time determined in the same manner as in Example 1 was 160 m seconds as a measure of the photosensitivity of the photosensitive composition.

A line-and-space pattern of a photoresist layer was formed on a silicon wafer in the same manner as in Example 1 except that the photosensitive composition used therefor was formulated by using, instead of 3% by weight of the esterification product of curcumin prepared in Preparation Example 1, the same amount of curcumin.

An electron microscopic examination of the thus formed line-and-space pattern indicated that the patterned lines had a cross section with rounded shoulders so that the quality of the pattern was less satisfactory. The minimum exposure time determined in the same manner as in Example 1 was 170 m seconds as a measure of the photosensitivity of the photosensitive composition.

A cresol novolak resin having a weight-average molecular weight of 2000 was prepared from a mixture of m- and p-cresols in a ratio of 40:60 by the condensation reaction with formalin in a conventional manner. A photosensitive composition in the form of a solution was prepared by dissolving 100 parts by weight of the cresol novolak resin, 30 parts by weight of an ester of 2,3,4-trihydroxy benzophenone and naphthoquinone-1,2-diazide sulfonic acid and the esterification product of curcumin obtained in Preparation Example 1 in an amount of 3% by weight based on the total amount of the above two ingredients together in 390 parts by weight of ethylene glycol monoethyl ether acetate followed by filtration through a membrane filter of 0.2 .mu.m pore diameter.

A patterned photoresist layer was formed on a silicon wafer in substantially the same manner as in Example 1 using the above prepared photosensitive composition. An electron microscopic examination indicated that the quality of the line-and-space pattern of the resist layer was as satisfactory as in Example 1 with an orthogonal cross section of the line pattern. The minimum exposure time determined in the same manner as in Example 1 was 150 m seconds as a measure of the photosensitivity of the photosensitive composition.

The experimental procedure was substantially the same as in Example 5 except that 3% by weight of the esterification product of curcumin prepared in Preparation Example 1 was replaced with a combination of 1.5% by weight of the esterification product of curcumin prepared in Preparation Example 4 and 1.5% by weight of curcumin. An electron microscopic examination of the thus formed line-and-space pattern indicated that the quality of the line-and-space pattern of the photoresist layer was quite as satisfactory as in Example 1. The minimum exposure time determined in the same manner as in Example 1 was 160 m seconds as a measure of the photosensitivity of the photosensitive composition.

A line-and-space pattern of a photoresist layer was formed on a silicon wafer in the same manner as in Example 1 except that the photosensitive composition used therefor was formulated by using, instead of 3% by weight of the esterification product of curcumin prepared in Preparation Example 1, the same amount of 4-ethoxy-4'-diethylamino azobenzene.

An electron microscopic examination of the thus formed line-and-space pattern indicated that the patterned lines had a cross section with rounded shoulders so that the quality of the pattern was less satisfactory. The minimum exposure time determined in the same manner as in Example 1 was 450 m seconds as a measure of the photosensitivity of the photosensitive composition.

A cresol novolak resin was prepared by adding 110 parts by weight of a 30% formalin and 5 parts by weight of oxalic acid to a mixture of 40 parts by weight of m-cresol and 60 parts by weight of p-cresol and heating the mixture for 100 minutes under boiling followed by dehydration under reduced pressure. A coating solution of a photosensitive composition was prepared by dissolving 100 parts by weight of the thus prepared cresol novolak resin, 10 parts by weight of the esterification product prepared in Preparation Example 5, 20 parts by weight of the esterification product prepared in Preparation Example 7 and the esterification product of curcumin prepared in Preparation Example 1 in an amount of 3% by weight based on the solid content of the other ingredients in 390 parts by weight of ethylene glycol monoethyl ether acetate and filtering the solution through a membrane filter of 0.2 .mu.m pore diameter.

A silicon wafer was coated with this coating solution and the coating layer was patterned in the same manner as in Example 1. Electron microscopic examination of the thus formed pattern indicated that the pattern having a line width of 0.8 .mu.m was a reproduction of the photomask pattern with high fidelity even in the upside areas on the level difference lines where the coating layer had a relatively small thickness as compared with the downside areas. The cross sectional profile of the line pattern was precisely orthogonal rising upright on the substrate surface.

The photosensitivity of the photoresist layer was evaluated by determining the minimum exposure time by which a line-and-space pattern of the resist layer having a width of 1.0 .mu.m of the lines and spaces could be obtained with full fidelity to give a result of 200 m seconds.

The procedure in each of these Examples and Comparative Examples was substantially the same as in Example 7 excepting modification of the ratio of the m-cresol to p-cresol in the preparation of the cresol novolak resins, the kind and amount of the photosensitive compounds and the kind and amount of the esterification products of curcumin being shown in Table 1 below. In the Table, the photosensitive compounds IV, V and VI were each the product obtained in Preparation Examples 4, 5 and 6, respectively, and the esterification products of curcumin I, II, III and IV are each the product obtained in preparation Examples 1, 2, 3 and 4, respectively. The amount of the curcumin ester indicated in % by weight in Table 1 is based on the total amount of the cresol novolak resin taken in an amount of 100 parts by weight and the photosensitive compounds taken each in an amount indicated in parts by weight in Table 1 in the brackets. The table gives the results of the photosensitivity in m seconds determined in the same manner as in Example 1 and the cross sectional profile of the line pattern in each of the Examples and Comparative Examples. The cross sectional profile is shown by the symbols a, b or c corresponding to an upright-standing orthogonal form, an upright-standing form with rounded shoulders and a form with trailing skirts and rounded shoulders, respectively.