Directed self-assembly pattern formation methods and compositions

1. A method of forming a pattern by directed self-assembly, comprising:

(a) providing a semiconductor substrate comprising one or more layers to be patterned;

(b) applying a crosslinkable underlayer composition over the one or more layers to be patterned to form a crosslinkable underlayer, wherein the crosslinkable underlayer composition comprises a crosslinkable polymer comprising a first unit formed from a monomer of the following general formula (I-A) or (I-B):

wherein: P is a polymerizable functional group; L is a single bond or an m+1-valent linking group; X 1 is a monovalent electron donating group; X 2 is a divalent electron donating group; Ar 1 and Ar 2 are trivalent and divalent aryl groups, respectively, and carbon atoms of the cyclobutene ring are bonded to adjacent carbon atoms on the same aromatic ring of Ar 1 or Ar 2 ; m and n are each an integer of 1 or more; and each R 1 is independently a monovalent group; wherein the first unit is present in the crosslinkable polymer in an amount of from 3 to 10 mol %, based on the polymer;

(c) heating the crosslinkable underlayer to form a crosslinked underlayer;

(d) patterning the crosslinked underlayer;

(e) forming a self-assembling layer comprising a block copolymer over the patterned crosslinked underlayer; and

(f) annealing the self-assembling layer.

2. The method of claim 1 , wherein the patterned crosslinked underlayer is formed by photolithography and etching, wherein recesses exposing the substrate are disposed between adjacent patterns of the crosslinked underlayer.

3. The method of claim 2 , further comprising forming a brush layer in the recesses between adjacent patterns, wherein the self-assembling layer is formed on the patterns and the brush layer.

4. The method of claim 1 , wherein the patterns are formed by chemically altering selected regions of the crosslinked underlayer.

5. The method of claim 1 , wherein the polymerizable functional group P is chosen from the following general formulae (II-A) and (II-B):

wherein R 4 is chosen from hydrogen, fluorine, C 1 -C 3 alkyl and C 1 -C 3 fluoroalkyl; and A is oxygen or is represented by the formula NR 5 , wherein R 5 is chosen from hydrogen and substituted and unsubstituted C 1 to C 10 linear, branched and cyclic hydrocarbons; and

wherein R 6 is chosen from hydrogen, fluorine, C 1 -C 3 alkyl and C 1 -C 3 fluoroalkyl; and wherein L is chosen from optionally substituted linear or branched aliphatic and aromatic hydrocarbons, and combinations thereof, optionally with one or more linking moiety chosen from —O—, —S—, —COO—, —CONR 3 —, —CONH— and —OCONH—, wherein R 3 is chosen from hydrogen and substituted and unsubstituted C 1 to C 10 linear, branched and cyclic hydrocarbons.

6. The method of claim 1 , wherein the first unit is formed from a monomer of the general formula (I-A), wherein X 1 is chosen from C 1 -C 10 alkoxy, amine, sulfur, —OCOR 9 , wherein R 9 is chosen from substituted and unsubstituted C 1 to C 10 linear, branched and cyclic hydrocarbons, —NHCOR 10 , wherein R 10 is chosen from substituted and unsubstituted C 1 to C 10 linear, branched and cyclic hydrocarbons, and combinations thereof.

7. The method of claim 1 , wherein the first unit is formed from a monomer of the general formula (I-B), wherein X 2 is —O—, —S—, —COO—, —CONR 11 —, —CONH— and —OCONH—, wherein R 11 is chosen from hydrogen and substituted and unsubstituted C 1 to C 10 linear, branched and cyclic hydrocarbons, and combinations thereof.

8. The method of claim 1 , wherein the first unit is formed from a monomer chosen from one or more of the following monomers:

9. The method of claim 1 , wherein the polymer further comprises a second unit chosen from general formulae (III) and (IV):

wherein R 7 is chosen from hydrogen, fluorine, C 1 -C 3 alkyl and C 1 -C 3 fluoroalkyl, R 8 is chosen from optionally substituted C 1 to C 10 alkyl, and Ar 3 is an optionally substituted aryl group.