Composition for cobalt electroplating comprising leveling agent

A composition for cobalt electroplating comprising:

• (a) metal ions consisting essentially of cobalt ions, and
• (b) a leveling agent,
• wherein the composition excludes a functional concentration of reducing agents,
• wherein the pH is within the range of 1 to 5,
• wherein the leveling agent is a compound of formula L1:
• [B]n[A]p (L1);
• or the leveling agent is a compound comprising a structural unit of formula L3a or L3b:
• or salts thereof,
• wherein
• R1 is selected from the group consisting of X1CO—O—R11, X1—SO2—O—R11, X1—PO(OR11)2, and X1—SO—O—R11;
• R31 is selected from the group consisting of R1, H, OR32 and R32,
• R32 is selected from the group consisting of (i) H and (ii) C1 to C6 alkyl,
• X1 is a divalent group selected from the group consisting of (i) a chemical bond (ii) aryl, (iii) C1 to C12 alkanediyl, which is optionally interrupted by 0 atoms, (iv) arylalkyl group —X11—X12—, (v) alkylaryl group —X12—X11—, and (vi) —(O—C2H3R12)m—O—,
• X2 is (i) a chemical bond or (ii) methanediyl,
• R11 is selected from the group consisting of H and C1 to C4 alkyl,
• R12 is selected from the group consisting of H and C1 to C4 alkyl,
• X12 is a divalent aryl group,
• X11 is a divalent C1 to C15 alkanediyl group,
• A is a co-monomer selected from the group consisting of vinyl alcohol, which is optionally (poly)ethyoxylated, and acrylamide,
• B is a unit of formula L1a:
• R2, R3, R4 are independently selected from the group consisting of R1 and (i) H, (ii) aryl, (iii) C1 to C10 alkyl (iv) arylalkyl, (v) alkylaryl, and (vi) —(O—C2H3R12)m—OH, wherein if one of R2, R3 or R4 is R1, remaining R2, R3 or R4 are different from R1,
• n is an integer from 2 to 10,000,
• m is an integer from 2 to 50,
• is an integer from 2 to 1000, and
• p is 0 or an integer from 1 to 10,000,
• wherein the composition is free of any dispersed particles.