Photoresist composition for deep ultraviolet lithography comprising a mixture of photoactive compounds

1. A photoresist composition comprising;

a) a polymer containing an acid labile group; and,

b) a mixture of photoactive compounds, where the mixture comprises a lower absorbing compound selected from structure (1) and (2), and a higher absorbing compound selected from structure (4) and (5),

where R 1 and R 2 are independently C 1-20 straight or branched alkyl chain optionally containing one or more O atoms, C 5-50 aralkyl or C 5-50 monocyclic, bicyclic, or tricylic alkyl group; each of R 5 , R 6 , R 7 , R 8 , and R 9 are independently hydrogen, hydroxyl, C 1-20 straight or branched alkyl chain optionally containing one or more O atoms, C 5-50 aralkyl or C 5-50 monocyclic, bicyclic, or tricylic alkyl group; m=1–5; X − is an anion; and Ar is selected from naphthyl, anthryl, and structure (3),

where each of R 30 , R 31 , R 32 , R 33 , and R 34 are independently selected from hydrogen, hydroxyl, C 1-20 straight or branched alkyl chain optionally containing one or more O atoms, C 1-20 straight or branched alkoxy chain, C 5-50 monocyclic, bicyclic, or tricylic alkyl group, C 5-50 cyclic alkylcarbonyl group, C 5-50 aryl group, C 5-50 arylcarbonylmethylene group, phenyl group, naphthyl group, anthryl group, peryl group, pyryl group, thienyl group, C 5-50 aralkyl group, —O—C 5-50 monocyclic, bicyclic, or tricylic alkyl group, —O—C 5-50 aryl group, —O—C 5-50 aralkyl group, —O—C 5-50 arylcarbonylmethylene group, or —O—C(═O)—O—R 18 where R 18 is C 1-20 straight or branched alkyl chain optionally containing one or more O atoms, C 5-50 monocyclic, bicyclic, or tricylic alkyl group, C 5-50 aryl, or C 5-50 aralkyl group;

the C 1-20 straight or branched alkyl chain optionally containing one or more O atoms, C 1-20 straight or branched alkoxy chain, C 5-50 monocyclic, bicyclic, or tricylic alkyl group, C 5-50 cyclic alkylcarbonyl group, phenyl group, naphthyl group, anthryl group, peryl group, pyryl group, thienyl group, C 5-50 aralkyl group, C 5-50 aryl group, or C 5-50 arylcarbonylmethylene group being unsubstituted or substituted by one or more groups selected from the group consisting of halogen, C 1-10 alkyl, C 3-20 cyclic alkyl, C 1-10 alkoxy, C 3-20 cyclic alkoxy, di C 1-10 alkylamino, dicyclic di C 1-10 alkylamino, hydroxyl, cyano, nitro, oxo, aryl, aralkyl, oxygen, aryloxy, arylthio, and groups of formulae (II) to (VI):

wherein R 10 and R 11 each independently represent a hydrogen atom, a C 1-20 straight or branched alkyl chain optionally containing one or more O atoms, or a C 5-50 monocyclic, bicyclic, or tricylic alkyl group, or R 10 and R 11 together can represent an alkylene group to form a five- or six-membered ring,

R 12 represents a C 1-20 straight or branched alkyl chain optionally containing one or more O atoms, a C 5-50 monocyclic, bicyclic, or tricylic alkyl group, or a C 5-50 aralkyl group, or R 10 and R 12 together represent an alkylene group which forms a five- or six-membered ring together with the interposing —C—O—group, the carbon atom in the ring being optionally substituted by an oxygen atom,

R 13 represents a C 1-20 straight or branched alkyl chain optionally containing one or more O atoms or a C 5-50 monocyclic, bicyclic, or tricylic alkyl group,

R 14 and R 15 each independently represent a hydrogen atom, a C 1-20 straight or branched alkyl chain optionally containing one or more O atoms or a C 5-50 monocyclic, bicyclic, or tricylic alkyl group,

R 16 represents a C 1-20 straight or branched alkyl chain optionally containing one or more O atoms, a C 5-50 monocyclic, bicyclic, or tricylic alkyl group, a C 5-50 aryl group, or a C 5-50 aralkyl group, and

R 17 represents C 1-20 straight or branched alkyl chain optionally containing one or more O atoms, a C 5-50 monocyclic, bicyclic, or tricylic alkyl group, a C 5-50 aryl group, a C 5-50 aralkyl group, the group —Si(R 16 ) 2 R 17, or the group —O—Si(R 16 ) 2 R 17; and

Y is a single bond or (C 1 –C 6 )alkyl.

2. The composition according to claim 1 , where for the compound of structure (1) Ar is structure (3).

3. The composition according to claim 2 , wherein R 32 is selected from hydrogen, —O—C 1-20 straight or branched alkyl chain optionally containing one or more O atoms, —O—C 5-50 monocyclic, bicyclic or tricyclic alkyl group, or —O—C(═O)—O—R 18 .

4. The composition of claim 3 wherein R 18 is C 1-20 straight or branched alkyl chain optionally containing one or more O atoms, or C 5-50 monocyclic, bicyclic, or tricylic alkyl group, the C 5-50 monocyclic, bicyclic, or tricylic alkyl group being unsubstituted or substituted by one or more groups selected from the group consisting of halogen, C 1-10 alkyl, C 3-20 cyclic alkyl, C 1-10 alkoxy, C 3-20 cyclic alkoxy, di C 1-10 alkylamino, dicyclic di C 1-10 alkylamino, hydroxyl, cyano, nitro, or aryl.

5. The composition according to claim 1 , wherein the compound of structure (1) is selected from a 4-methoxyphenyl-dimethylsulfonium salt, 3,5-dimethyl-4-methoxyphenyl-dimethyl sulfonium salt, 3,5-dimethyl-4-hydroxyphenyl-dimethyl sulfonium salt, 4-hydroxyphenyl-dimethyl sulfonium salt, 3,5-dimethyl-4-hydroxyphenyl-dimethyl sulfonium salt, 4-t-butyl acetoxy-3,5-dimethyl phenyl dimethyl sulfonium salt, and 4-(2-methyl-2-adamantyl acetoxy)-3,5-dimethyl phenyl dimethyl sulfonium.

6. The composition according to claim 1 , wherein the compound of structure (2) is selected from 4-methoxyphenyl-methyliodonium salt, 3,5-dimethyl-4-hydroxyphenyl-methyliodonium salt, 4-hydroxyphenyl-methyl iodonium salt and 3,5-dimethyl-4-methoxyphenyl-methyliodonium salt.

7. The composition according to claim 1 , wherein the compound of structure (4) is selected from a triphenyl sulfonium salt and its derivatives.

8. The composition according to claim 1 , wherein the compound of structure (5) is selected from a diphenyl iodonium salt and its derivatives.

9. The composition according to claim 1 , wherein the polymer is nonaromatic.

10. The composition according to claim 1 , wherein the molar ratio of the higher absorbing compound to the lower absorbing compound is from about 1:10 to about 10:1.

11. The composition according to claim 10 , wherein the molar ratio of the higher absorbing compound to the lower absorbing compound is from about 1:5 to about 5:1.

12. The composition according to claim 11 , wherein the molar ratio of the higher absorbing compound to the lower absorbing compound is from about 1:2 to about 2:1.

13. The composition according to claim 12 , wherein the molar ratio of higher absorbing compound to the lower absorbing compound is about 1:1.

14. A compound selected from 4-(2-methyl-2-adamantyl acetoxy)-3,5-dimethyl phenyl dimethyl sulfonium nonaflate, 4-hydroxy-3,5-dimethyl phenyl dimethyl sulfonium bis-perfluoromethane sulfonamide, 4-hydroxy-3, 5-dimethyl phenyl dimethyl sulfonium bis-perfluoroethane sulfonamide, 4-hydroxy-3,5-dimethyl phenyl dimethyl sulfonium bis-perfluorobutane sulfonamide, 4-hydroxy-3,5-dimethyl phenyl dimethyl sulfonium tris-perfluoromethane sulfonmethide, and 4-hydroxy-3,5-dimethylphenyldimethylsulfonium pentafluorobenzene-sulfonate.

15. A process for imaging a photoresist comprising the steps of:

a) coating a substrate with the photoresist composition of claim 1 ;

b) baking the substrate to substantially remove the solvent;

c) image-wise exposing the photoresist coating;

d) postexposure baking the photoresist coating; and

e) developing the photoresist coating with an aqueous alkaline solution.

16. The process of claim 15 , wherein the image-wise exposure wavelength is below 200 nm.

17. The process according to claim 15 , wherein the aqueous alkaline solution comprises tetramethylammonium hydroxide.

18. The process according to claim 15 , wherein the aqueous alkaline solution further comprises a surfactant.

19. The process according to claim 15 , wherein the substrate is selected from a microelectronic device and a liquid crystal display substrate.