Antireflective coating compositions

1. An antireflective coating composition comprising,

(i) a thermal acid generator;

(ii) a crosslinkable copolymer comprising at least one unit with structure (1) and at least one unit with structure (2) and further where the crosslinkable polymer is free of acrylate groups and where structure (1) and (2) are,

where, R is selected from H and C 1 -C 6 alkyl and R 1 is independently selected from H, hydroxyl, C 1 -C 6 alkyl, C 1 -C 6 alkylenehydroxy, C 1 -C 6 ester and C 1 -C 6 carboxylic acid, and n=1-5; and

where, R and R 10 are independently selected from H and (C 1 -C 6 )alkyl, and m is 1-5; and

(iii) a polymeric crosslinker comprising at least one unit of structure (6),

where R 11 to R 13 are independently selected from H, (C 1 -C 6 )alkyl and aromatic group, and, R 14 and R 15 are independently (C 1 -C 10 ) alkyl.

2. The composition of claim 1 , where the unit of structure (1) is further defined by structure (5),

where, R is selected from H and C 1 -C 6 alkyl and R 1 is independently selected from H, hydroxyl, C 1 -C 6 alkyl, C 1 -C 8 alkylenehydroxy, C 1 -C 6 ester and C 1 -C 6 carboxylic acid, and p=1-4.

3. The composition of claim 1 , where R 14 and R 15 are methyl.

4. The composition of claim 1 , where the polymeric crosslinker further comprises a styrenic or (meth)acrylate unit.

5. The composition of claim 1 , where the thermal acid generator is selected from iodonium salts, tosylates, derivatives of benzene sulfonic acid salts, and derivatives of naphthalene sulfonic acid salts.

6. The composition of claim 1 where the carbon content of the composition after curing is greater than 75% by weight.

7. A process for imaging a photoresist comprising the steps of,

a) forming a antireflective coating from an antireflective coating composition of claim 1 on a substrate;

b) forming a coating of a photoresist over an antireflective coating;

c) imagewise exposing the photoresist with an exposure equipment; and,

d) developing the coating with an aqueous alkaline developer.

8. The process according to claim 1 where radiation for imagewise exposure is selected from 248 nm, 193 nm and 157 nm.

9. The process according to claim 1 where the developer in an aqueous solution of tetramethyl ammonium hydroxide.

10. An antireflective coating composition comprising,

(i) a thermal acid generator;

(ii) a crosslinkable acrylate polymer comprising units of structure (3) and (4),

where, R 2 to R 7 are independently selected from H, C 1 -C 6 alkyl and C 1 -C 6 alkylenehydroxy, R 8 is an nonaromatic, and R 9 comprises an aromatic moiety group selected from unsubstituted phenyl; and,

(iii) a polymeric crosslinker comprising at least one unit of structure (6),

where R 11 to R 13 is independently selected from H, (C 1 -C 6 ) alkyl and aromatic group, and, R 14 and R 15 are independently (C 1 -C 10 ) alkyl.