Dispersant and polishing agent composition

A dispersant for chemical mechanical polishing that flattens a surface of at least one of an insulating layer and a wiring layer, the dispersant comprising:

• a block copolymer (P) having a polymer block A and a polymer block B, wherein
• the polymer block A and the polymer block B each have a structural unit having an ionic functional group selected from the group consisting of a carboxyl group, a sulfonic acid group, and a salt thereof,
• the block copolymer (P) is a polymer that satisfies at least one of condition I and condition II:
• condition I:
• the ionic functional group of the polymer block A and the ionic functional group of the polymer block B are different from each other, and
• condition II:
• a content of the ionic functional group of the polymer block A and a content of the ionic functional group of the polymer block B are different from each other, and
• a ratio (A/B) of the polymer block A to the polymer block B in the block copolymer (P) is 5/95 to 95/5 by mass ratio,
• wherein the polymer block A further comprises a structural unit UC having an alkyl group having 1 to 10 carbon atoms in a side chain moiety, in addition to the structural unit having the ionic functional group, and
• a content of the structural unit UC is 1% by mass or more and 70% by mass or less based on all constituent monomer units of the polymer block A.

A dispersant for chemical mechanical polishing that flattens a surface of at least one of an insulating layer and a wiring layer, the dispersant comprising:

• a block copolymer (P) having a polymer block A and a polymer block B, wherein
• the polymer block A and the polymer block B each have a structural unit derived from a vinyl monomer represented by formula (1):
• CH2═CR1—C(═O)—NR2—R3 . . . (1)
• where R1 is a hydrogen atom or a methyl group, and R2 and R3 are each independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group, or R2 and R3 are a group that forms a ring together with a nitrogen atom to which R2 and R3 are attached by being bonded to each other, and
• the vinyl monomer represented by the formula (1) is at least one selected from the group consisting of (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-ethyl-N-methyl(meth)acrylamide, 4-(meth)acryloylmorpholine, 2-hydroxyethylacrylamide, and 2-(meth)acrylamido-2-methylpropanesulfonic acid or a salt thereof, and
• a ratio (A/B) of the polymer block A to the polymer block B in the block copolymer (P) is 5/95 to 95/5 by mass ratio.