Photosensitive copolymer, photoresist comprising the copolymer, and method of forming an electronic device

1. A copolymer comprising the polymerized product of:

an acid-deprotectable monomer having the formula (I) and a comonomer:

wherein

c is 1, 2, 3, 4, or 5;

R a is H, F, —CN, C 1-10 alkyl, or C 1-10 fluoroalkyl;

R x is an unsubstituted or substituted C 1-10 linear or branched alkyl group, an unsubstituted or substituted C 3-10 cycloalkyl group, an unsubstituted or substituted C 3-10 alkenylalkyl group, or an unsubstituted or substituted C 3-10 alkynylalkyl group;

R y is fluorine-substituted C 3-6 linear alkyl, unsubstituted C 3-6 alkenylalkyl, or unsubstituted C 3-10 alkynylalkyl group; and

R z is a C 6-20 aryl group substituted with an acetal-containing group or a ketal-containing group, or a C 3 -C 20 heteroaryl group substituted with an acetal-containing group or a ketal-containing group, wherein the C 6-20 aryl group or the C 3 -C 20 heteroaryl group can, optionally, be further substituted.

2. The copolymer of claim 1 , wherein the acid-deprotectable monomer comprises at least two acid-deprotectable groups other than the acrylate ester.

3. The copolymer of claim 1 , wherein R y is fluorine-substituted C 3-6 linear alkyl.

4. The copolymer of claim 1 , wherein R z is

5. The copolymer of claim 4 , wherein R a is hydrogen or methyl.

6. The copolymer of claim 1 , wherein the comonomer comprises at least one of the following monomers:

an acid-deprotectable monomer having the formula (II), a lactone-containing monomer of the formula (III), a base-soluble monomer of formula (IV), a photoacid-generating monomer of the formula (V)

wherein

each R a is independently H, F, —CN, C 1-10 alkyl, or C 1-10 fluoroalkyl,

each R b is independently C 1-20 alkyl, C 3-20 cycloalkyl, C 6-20 aryl, C 3-20 heteroaryl, or C 7-20 aralkyl, and each R b is separate or at least one R b is bonded to an adjacent R b to form a cyclic structure,

L is a monocyclic, polycyclic, or fused polycyclic C 4-20 lactone-containing group,

W is a halogenated or non-halogenated, aromatic or non-aromatic C 2-50 hydroxyl-containing organic group having a pK a of less than or equal to 12,

Q is ester-containing or non-ester-containing and fluorinated or non-fluorinated and is C 1-20 alkylene, C 3-20 cycloalkylene, C 6-20 arylene, or C 7-20 aralkylene,

A is ester-containing or non-ester-containing and fluorinated or non-fluorinated and is C 1-20 alkylene, C 3-20 cycloalkylene, C 6-20 arylene, or C 7-20 aralkylene,

Z − is an anionic moiety comprising sulfonate, or an anion of a sulfonimide, and

G + is a sulfonium or iodonium cation.

7. A photoresist composition comprising the copolymer of claim 1 .

8. A method of forming an electronic device, comprising: (a) applying a layer of the photoresist composition of claim 7 on a substrate; (b) patternwise exposing the photoresist composition layer to activating radiation; and (c) developing the exposed photoresist composition layer to provide a resist relief image.

9. The method of claim 8 , wherein the activating radiation is extreme-ultraviolet or electron beam radiation.