IE64507B1 - Resist compositions and use - Google Patents

Abstract

The present invention relates to a masking composition, characterized in that it comprises, by weight: A) 100 parts of an organic solvent; and B) from 5 to 85 parts of solids. A method for forming a composite masking structure with design and substrate, characterized in that it comprises the steps of: 1) treating a substrate with a masking composition to produce a composite masking-substrate structure; 2) Bake the structure at a temperature on the scale of approximately 35 to 180 degrees C; 3) irradiate the applied masking in the form of a design; 4) heat the irradiated masking at a temperature in the approximate range of 35 to 185 degrees C; and 5) reveal the irradiated masking to produce a composite masking-substrate structure.

Description

RESIST COMPOSITIONS AND USE Prior to the present invention as shown by L.F.

Thompson et al. Introduction to Microlithography, ACS Symposium Series 219. American Chemical Society, 1983, page <. 111, novolak-based positive resists based on dissolution inhibition, generally utilize substituted 1,2-diazonaphtho- <4 quinones as dissolution inhibitors to render a novolac resin insoluble to development by dilute aqueous base. Upon irradiation, the diazonaphthoquinone undergoes rearrangement and those portions of the resist which have received irradiation by image-wise exposure are rendered soluble to dilute aqueous base. While these photoresists are widely used, they are generally limited to the near UV above 366 nm based on the absorbtion characteristics of the diazonaphthoquinone .

As taught by Ito et al, U.S. Patent No. 4,491,628, positive and negative working resist compositions are provided which can be used in the deep UV region (200-300 nm), as a result of employing diaryliodonium salts, or triarylsulfonium salts as photoinitiators. These ' photoinitiators are used with vinylic polymer containing recurrent labile pendant groups. The vinylic polymers undergo acidolysis to produce products which are very different in solubility from their precursors.

DE-A-2306248 discloses resist compositions comprising water insoluble organic compounds having acid labile pendant groups and light decomposable acid generator. A base-soluble resin is used as a binder.

Journal of Imaging Technology 11 (1985) 4, 146-157 discloses similar compositions discloses novolak resins together with onium salts.

Although effective results can be achieved with the resist compositions of Ito et al, the vinylic polymers and their acid labile substituted monomeric precursors are - 1 64507 not commercially available. In addition, the performance of the resulting photoresist is sometimes impaired due to excessive crosslinking resulting from the use of aryl onium salts upon exposure of the photoinitiator under normal operating conditions. Improved results can sometimes be achieved by incorporating stabilizers into the photoresist composition.

The present invention is based on our discovery that photoresist compositions sensitive to electron beam, X-ray and UV over the range of 600 to 200 nm can be made using commercially available polymer as the base resin. The photoresist can be converted from the insoluble to soluble state by the use of commercially available polymers in combination with a dissolution inhibitor having chemically combined acid labile groups, as defined hereinafter, and an aryl onium salt. Although the photoresist dissolution mechanism is not completely understood, it is believed that a chemical amplification effect is achieved upon the generation of acid from the irradiated aryl onium salt. The transformation of the dissolution inhibitor to the soluble state is effected by the acidolysis of the acid labile . groups which solubilizes exposed photoresist: areas.

A resist composition comprising by weight (A) 100 parts of organic solvent, and (B) from 5 to 85 parts of solids admixed with (A) comprising by weight (1) 100 parts of a water, or aqueous base soluble organic polymer having an average MW of from 200 to 20,000. (2) 5 to 100 parts of an acid labile group 30 substituted simple compound which is a dissolution inhibitor for (1), which is insoluble in water or aqueous base has a boiling point of at least l00°C, and is selected from tertiary butyl esters, aryl tertiary butyl ethers, aryl tertiary butyl carbonates, compound having trityl group, compound having benzyl group, compound having benzhydryl group, 1-trimethylsiloxy naphthalene, bis (1- 2 phenyl-l-methylethyl) terephthalate, alpha-phenethyl lnaphthoate, alpha-phenethyl 2-naphthoate, 3-cyclohexenyl benzoate, and 3,6-bis(benzoyloxy)cyclohexene, (3) an effective amount of an aryl onΐ™ salt.

The compositions are useful as water or aqueous base soluble results; Some of the water or aqueous base soluble organic polymers which can be utilized in the practice of the present invention to make the above described compositions, referred to hereinafter as polymer” are, for example: phenol novolac resins, cresol novolac resins, chlorophenol novolac resins, melamine-formaldehyde-resins, water soluble starch, and cellulose polymers, e.g. carboxymethylhydroxyethyl cellulose, propoxylated celluloses, polyacrylamide, poly-2-hycroxyethylmethacrylate, polymethylvinyl ether, polyethylene oxide, copolymers of 4-hydroxyphenylmaleimide with a member selected from styrene,'stilbene, vinyl ethers, and 4-hydroxy styrene, and polymers such as poly-4-vinylphenol, poly-4-hydroxy-emethyl styrene, polyacryl acrylic acid, and polymethacrylic acid.

Among the acid labile group substituted simple compounds, or dissolution inhibitors referred to hereinafter as inhibitor which can be utilized in the practice of the present invention to make the water or aqueous base soluble resists are, for example: (CHj) jC-O^-^^-OO^CCOLj) «=3>2 (Ci3) 3C(0:3),- -OC(CH3)3 C(Ci3)3 ((=,) ,c-o-c-(c-:2) 4-c-o-c3) 3 (ο3,3 ^(^3,3 (Ci3>3 ((=3)3 CO2-C ((=3)3 G02-C ((=3)3 C ((=3)3 Preferably, the inhibitors of the present invention have a molecular weight of less than about 1000. They have acid labile pendant groups which are preferably tert-butyl esters of carboxylic acid, and tert-butyl carbonates of phenols. In addition, these acid labile groups can be trityl, benzyl, benzhydryl as well as other modifications illustrated in the inhibitors above.

Radiation decomposable initiators which can be utilised in the practice of the present invention to generate acid upon exposure referred to hereinafter as the inTator are, for example:Triarylsulfonium salts, diarylchloronium salts, diarylbromonium salts, triarylselenonium salts, thiopyrylium salts, xanthylium salts, imidazolium salts, dialkylphenacylsulfonium salts, dialkylhydroxyphenylsulfonitim salts, ferrocenium salts, diazonium-salts, triarylsulfoxoni'um salts, diaryliodoxonium salts, phenacyltriarylphosphonium salts, phenacyltrialkylammonium salts, phenacylpyridinium salts. Further examples are shown by H.-J. Timpe and H. Baumaxin, Adhesion 9, 9 - 5 (1984) and Crivello patents U.S. 4,058,400; 4,058,401; 4,069,055; and 4,151,175; assigned to the same assignee as the present invention and incorporated herein by reference.

The following constitute some additional examples of onium salts: The compositions can be made by blending organic solvent, polymer, inhibitor, and the irradiation decomposable initiator.

In forming the resist composition, the order of addition of the various ingredients is not critical. It has been found that effective results can be achieved if there is utilized from about 5 to about 100 parts of inhibitor and 0.5 part to about 25 parts of initiator, per hundred parts of the polymer. Preferably, there can be used from 5 to 70 parts of inhibitor, per hundred parts of polymer and 1 to 20 parts of initiator, per hundred parts of polymer.

There are included in the term organic solvent which hereinafter means an organic solvent or mixture of organic solvents, which can be utilized in the practice of the present invention to make the resist composition, solvents such as 1,2-dimethoxy ethane, di(2-methoxy ethyl)ether, l-methoxy-2-propyl acetate, chlorobenzene, 1,1,2,2-tetrachloroethane, l-methoxy-2-ethyl acetate, dioxane, methylisobutyl ketone, cyclohexanone, n-butanol, ethylene glycol, propylene gycol, amylacetate, and butylacetate.

There is further provided by the present invention, a method for making a patterned resist on a substrate, which comprises: -7(1) treating, which means spin coating, spraying, <. solution casting or dip coating, the substrate with the resist- composition of the present invention to produce a I resist-substrate composite, (2) baking the resist-substrate composite to a temperature in the range of from about 35°C to 180°C, (3) irradiating the applied resist in a patterned manner, (4) heating the irradiated resist to a temperature in the range of from about 35°C to 185°C, and (5) developing the irradiated resist to produce a patterned resist substrate composite.

Among the substrates which can be treated in accordance with the practice of the method of the present - invention to make resist-substrate composites are copper clad laminates, silicon wafers, silicon dioxide wafers, aluminum and gallium arsenide.

Some of the developers which can be used in the practice of the method of the invention are aqueous base solutions, e.g. aqueous solutions of NaOH, KOE, and . tetrabutylammonium hydrojcid^. Typical developers are made by Shipley Company of Newton, Massachusetts, Hunt Company of East Providence, Rhode Island, amd KTI Company of Wallingford, Connecticut.

It has been further found that the afore-described onium salts or initiators can be used in combination with various photosensitizers to enhance the absorption of a given wavelength of light or sensitize the onium salt to a region of a spectrum where it does not absorb. Typical sensitizers which can be used in combination with the afore-described initiators or mixtures thereof are, for example: benzophenone, 2-chlorothioxanthone, an thr one, 9-ethoxyanthracene, anthracene, pyrene, perylene, phenothiazine, benzil, acridine orange, benzoflavin. -8setoflavin-T, anthraquinone, 9,10-diphenylanthracene, 9-fluorenone, benzophenone, and coronene.

The above-described sensitizers also can be used in combination with the initiators utilized in the practice of the present invention to modify the response of the photoresist under electron beam and X-ray irradiation as well as visible or UV irradiation.

Some of the resist applications contemplated for the resist compositions of the present invention are, for example, manufacture of circuit boards, integrated circuits, multilayer resist structures, e.g. in combination with polymethylmethacrylate, and the like. There also can be used in the resist composition of the present invention, flow control agents, surface active agents, anti-reflection dyes and wetting agents.

In order that those skilled in the art will be better able to practice the present invention, the following examples are given by way of illustration and not by way of limitation. All parts are by weight.

EXAMPLE 1 Photoresist compositions were prepared utilizing 1.5 g of various commercially available phenolic resins having a molecular weight of about 1000, 0.5 g of di-t-butylterephthalate, 0.1 g of diphenyl-4-thiophenoxypheny1 sulfonium hexafluorophosphate, and 6 mL of l-methoxy-2-propyl acetate. The various photoresist compositions were spin coated onto silicon wafers which had been previously treated with hexamethyldisilazane. The treated wafers were then baked for 1/2 hour ar 90°C. The wafers were then exposed to imagewise irradiation using .a Suss MA 56 Contact/Proximity Printer operated in the proximity mode at 313 nm, using an -9exposure time of 10-40 seconds with an intensity'of 4.5 2 mW/cm . After exposure, the wafers were heated in a forced air oven for a period of 60 seconds at 110-130°C and then 1 developed using a mixture of water and KTI 351 Developer.

The following lists . the commercially available resins utilized Phenolic resin” along with the development mixture and type of development: Phenolic Resin Dev/Water meta-cresol novolac polyvinylphenol t-butylphenol novolac 1:1 :1 (immersion) 5:1 (immersion) The resists were developed and 2 to 3.5 urn features were resolved.

EXAMPLE 2 Inhibitor, t-butylnaphthalene-2-carboxylate was prepared as follows: A mixture of 51.S g (0.3 mole) of 2-naphthoic acid, and 120 ml of thionylchloride was refluxed for one hour. Excess thionylchloride was removed. The resulting solid was dissolved in ISO mL of tetrahydrofurane and 40 grams (0.35 mole) of potassium t-butoxide was added in , increments. After the addition had been completed, the reaction mixture was refluxed for four hours, cooled, and then poured into water. The resulting solid was collected by filtration, washed with water and dried in vacuo. The product was recrystallized from n-hexane to produce a crystalline solid having a melting point of 88-90°C. Based on method of preparation, the product was t-butyl-10naphthalene-2-carboxylate which was obtained in a yield of 68%.

A photoresist composition was prepared in accordance with the procedure of Example 1, utilizing 1.5 g of meta cresol novolac resin, 0.5 g of t-butyl naphthalene-2-carboxylate, 0.1 g of diphenyl-4-thiophenoxyphenylsulfonium hexafluorophosphate, and 6 mL of l-methoxy-2-propyl acetate. Coated silicon wafers prepared in accordance with the procedure of Example 1 provided excellent positive images with well resolved 3.5 micrometers features after imagewise exposure to UV light utilizing a 15-40 second irradiation time.

EXAMPLE 3 Additional photoresist compositions were prepared utilizing commercially available meta cresol novolac resin with di-t-butylterephthalate or t-butylnaphthalene-2carboxylate. In preparing the photoresist using di-t-butylterephthalate dissolution inhibitor, there were utilized 1.5 g of meta cresol novolac resin, 0,5 g of inhibitor, 0.1 g of 4-methoxyphenylphenyliodonium trif luoromethyl sulfonate, and 0.03 g of 9-fluorenone, a photosensitizer.

The photoresist utilizing t-butylnaphthalene-2carboxylate was combined with 1.5 g of the meta cresol novolac resin, 0.5 g of the inhibitor, 0.1 g 4-methoxyphenylphenyliodonium trifluoromethylsulfonate, 0.01 >·» g of perylene photosensitizer, and 6 mL of l-methoxy-2-propyl acetate.

' The above photoresist compositions were then spin coated onto siicon wafers in accordance with the procedure of Example 1. A photoresist composition containing the di-t-butylterephthalate inhibitor and the 9-fluorenone -11photosensitizer was irradiated for five seconds at 313 nm, while the photoresist composition containing the t-butylnaphthalene-2-carboxylate and the perylene sensitizer 2 was irradiated for 5 seconds at 365 nm (6.3 mW/cm ) and 2 405-436 nm (8.1 mW/cm ). The following Table combines the inhibitors, photosensitizers and wave lengths which were used: Inhibitor Photosensitizer UVX(nm) di-t-butyl- 9-fluorenone 313 terephthalate t-butylnaphthalene-2- perylene 405-436 carboxylate 365 under the resolved.

The resists were processed in KTI conditions described above, and 1 350 developer vm features were EXAMPLE 4 Inhibitor t-buty1-2-naphthyl carbonate was prepared by the following procedure: There were added 3.9 g (0.035 mole) of potassium-t-butoxide to a solution of 5 g (0.35 mole) of 2-naphthol in 90 mL of tetrahydrofuran under a nitrogen atmosphere. The mixture was stirred for 5 minutes and 8.3 g (0.035 mole) of di-t-butyldicarbonate was added. The mixture was stirred for 2 hours. The mixture was then poured into ice water and extracted twice with ethylacetate. The combined organic layers were washed three times with J water followed by a saturated sodium chloride solution and then dried over anhydrous sodium sulfate. The mixture was -12then concentrated using a rotary evaporator. A crystalline solid was obtained and recrystallized from petroleum ether and then dried in vacuo. There was obtained 65% yield of t-butylnaphthyl carbonate having a melting point of 74-75°C A photoresist composition was prepared following the. procedure of Example 1 utilizing 1.2 g of commercially available meta cresol novolac resin, 0.8 g of t-butyl-2-naphthylcarbonate, 0.1 g of diphenyl-4thiophenoxyphenylsulfoniumhexafluorophosphate and 6 mL of l-methoxy-2-propylacetate. Wafers were spin coated and exposed for 20-40 seconds as described in Example 1 and baked at 125°C for 30-60 seconds. There were obtained clear 2 micrometer lines and spaces after the photoresist was developed for one minute in a 1:2.5 mixture of KT I 351 and water.

EXAMPLE 5 A photoresist composition was prepared in accordance with the procedure of Example 1 utilizing 1.2 g m-cresol novolac resin, 0.8 g 4-t-butoxy-p-biphenyl, 0.1 g diphenyl-4-thiophenoxy-l-phenyl sulfonium hexafluorophosphate, and 6 mL l-methoxy-2-propyl acetate. Cleared 3 vm lines· and spaces were obtained by exposing coated wafers to 313 nm UV for 20-40 seconds, a 30-60 second bake at 125°C and immersion in a 1:1 solution of KTI351 and water.

EXAMPLE 6 A photoresist composition was prepared utilizing 1.5 g of commercially available meta cresol novolac resin, 500 mg of t-butyl-lH-indene-3-carboxylate, 100 mg of diphenyl-4-thiophenoxyphenylsulfonium hexafluorophosphate and 6 mL of l-methoxy-2-propylacetate. The photoresist was -13spin coated and irradiated as described in Example 1. There was obtained clear 2.5 micron lines and spaces with irradiation at 313 nm for 15-20 seconds, a 30-60 second bake at 125°C and a development for one minute in a 1:1 solution of KTI 351 developer and water.

EXAMPLE 7 Photoresist compositions were prepared utilizing commercially available meta cresol novolac, t-butyladamantane-l-carboxylate, and various initiators and 10 l-methoxy-2-propylacetate. One of the photoresist compositions was made by blending together 1.5 g meta cresol novolac, 500 mg of* t-butyladamantane-l-carboxylate, 100 mg of diphenyl-4-thiophenoxyphenylsulfonium hexafluorophosphate and 6 mL of l-methoxy-2-propylacetate. Another photoresist formulation utilized 1.5 g of the meta cresol novolac resin, 500 mg of the inhibitor, 110 mg of 4-methoxyphenyl-iodoniumhex a fluorophosphate, and 6 mL of l-methoxy-2-propylacetate.

The various photoresist compositions were applied to silicon wafers as previously described and subjected to imagewise exposure at 313 nm for 10-15 seconds and at 254 nm for 2-3 2 sec at 5.22 mW/cm . The resists were processed in accordance with the procedure of Example 1. There were resolved 3 um features from the sulfonium containing photoresist and 2.5 micron features from the iodonium containing photoresist.

EXAMPLE 8 A photoresist composition consisting of 1.5 g m-cresol novolac resin (Schenectady Chemicals HRJ 2606), 500 mg di-t-butyladipate, 100 mg 4-methoxyphenylphenyliodonium hexafluorophosphate and 6 mL 1-methoxy-2-propyl acetate was spin coated onto silicon wafers which had been previously treated with hexamethyldisilazane and baked. A film coating .. of 2 micrometers was obtained. The photoresist coatings were exposed for 4-5 seconds using a Suss MA56 Contact/Proximity Printer operated in the proximity mode at 2 254 nm with an intensity of 5.22 mW/cm . After exposure, the wafers were postbaked for 30-60 seconds at 130°C, then developed for 60 seconds in a 1:1 mixture of KTI 351 and water. Cleared well-imaged patterns were obtained having 3.5 pm lines and spaces.

EXAMPLE 9 There was dissolved 3 g of the m-cresol novolac resin of Example 8 in 10 mL methyl ethyl ketone. There was added to the resulting solution, 1 g t-butyl-2-naphthalene carboxylate, 0.02 g perylene and 0.2 g 4-methoxyphenylphenyliodonium trif luor ome thane sulfonate.

The mixture was coated onto a copper-clad epoxy-glass circuit board and dried to remove the solvent. The dried circuit board was covered with a Mylar resin photographic negative. A GE E-3T7 medium pressure mercury arc lamp ballasted at 800 W was used to irradiate the negative for 30 seconds at a distance of 8 inches. Following imaging, the circuit board was baked for 3 minutes at 100°C and then developed in a 1:1 mixture of KTI 351 and water. The pattern was then etched into the circuit board using,an aqueous ferric chloride solution giving a clear positive image of the mask.

Although the above results are directed to only a few of the very many variables which can be utilized in the practice of the present invention, it should be understood < that the present invention is directed to the use of a much broader variety of polymers, inhibitor, and initiators, in the description preceding these examples.

Claims (10)

1. A resist composition comprising by weight (A) 100 parts of organic solvent, and (B) from 5 to 85 parts of solids admixed with (A) comprising by weight (1) 100 parts of a water, or aqueous base soluble

2. (2) 5 to 100 parts of an acid labile group substituted simple compound which is a dissolution -inhibitor for (1), which is insoluble in water or aqueous 10 base has a boiling point of at least 100°C, and is selected from tertiary butyl esters, aryl tertiary butyl ethers, aryl tertiary butyl carbonates, compound having trityl group, compound having benzyl group, compound having benzhydryl group, 1-trimethylsiloxy naphthalene, bis (115 phenyl-1-methylethyl) terephthalate, alpha-phenethyl 1naphthoate, alpha-phenethyl 2-naphthoate, 3-cyclohexenyl benzoate, and 3,6-bis (benzoyloxy) cyclohexene, (3) an effective amount of an aryl onium salt. 20 2. A spinnable or solution castable composition in accordance with Claim 1, where the organic polymer is a novolak resin.

3. A spinnable or solution castable composition in 25 accordance with Claim 1, where the aryl onium salt is a sulfonium salt.

4. A spinnable or solution castable composition in accordance with Claim 1, where the aryl onium salt is an iodonium salt. 5. Described herein by way of Example. ) 15. A method in accordance with claim 10 for making a composite, and • substantially as described herein by way of Example. 5 7. A spinnable or solution castable composition in accordance with Claim l, where the onium salt is diphenyl4-thiophenoxyphenylsulfonium hexaf luorophosphate.

5. A spinnable or solution castable composition in accordance with. Claim 1 containing a photosensitizer. - 16

6. A spinnable or solution castable composition in accordance with Claim l, where the onium salt is tr ipheny lsu If onium hexafluoroantimonate. 5 organic polymer having an average MW of from 200 to 20,000.

7. 14. A resist composition in accordance with claim 1, and substantially as

8. A spinnable or solution castable composition in 10 accordance with Claim 1, where the onium salt is 4methoxypheny Ipheny liodonium hexaf luorophosphate.

9. A spinnable or solution castable composition in accordance with Claim 1, where the onium salt is 415 methoxyphenylphenyliodonium trifluoromethane sulfonate. 10. A method for making a patterned resist substrate composite which comprises (1) treating a substrate with the resist composition 20 of Claim 1 to produce a resist-substrate composite, (2) baking the resist-substrate composite to a temperature in the range of from about 35°C to 180°C, (3) irradiating the applied resist in a patterned manner, 2g (4) heating the irradiated resist to a temperature in the range of from about 35®C to 185°C, and (5) developing the irradiated resist to produce a patterned resist substrate composite. 30 11. A composite comprising a substrate and a resist composition made in accordance with the method of Claim 10. 12. A composite in accordance with Claim 11, where the substrate is a silicon wafer. - 17 13. A composite in accordance with claim 11, where the substrate is a copper-clad laminate.

10. 16. A composite whenever made in accordance with the method of claim 15.