Composition for cobalt or cobalt alloy electroplating

A composition for cobalt electroplating comprising

• (a) a cobalt ion,
• (b) an ammonium compound of formula (NR1R2R3H+)nXn−and
• (c) a suppressing agent of formula S1;
• wherein
• R1, R2, R3 are independently selected from H and linear or branched C1 to C6 alkyl,
• X is an n valent inorganic counter ion or n valent organic counter ion selected from the group consisting of chloride, sulfate, hydrogen sulfate, phosphate, hydrogen phosphate, dihydrogen phosphate, nitrate, C1 to C6 alkyl sulfonate, C1 to C6 carboxylates, phosphonate, and sulfamate,
• n is an integer selected from 1, 2 or 3,
• RS1 is XS—YS,
• RS2 is RS1 or RS3;
• XS is linear C1 to C10 alkanediyl, branched C1 to C10 alkanediyl, linear C2 to C10 alkenediyl, branched C2 to C10 alkenediyl, linear C2 to C10 alkynediyl, branched C2 to C10 alkynediyl, or (C2H3Rs6—O)m—H;
• YSis ORS3, NRS3RS4, N+RS3RS4RS5, or NH−(C=O)—RS3;
• RS3, RS4, and RS5 are independently (i) H, (ii) C5 to C20 aryl, (iii) C1 to C10 alkyl (iv) C6 to C20 arylalkyl, (v) C6 to C20 alkylaryl optionally substituted by OH, SO3H, COOH, or a combination thereof, or (vi) (C2H3RS6—O)n—H, RS3 and RS4 optionally together forming a ring system optionally interrupted by O or NRS7,
• m and n are independently integers in a range of from 1 to 30,
• RS6 is H or C1 to C5 alkyl,
• RS7 is RS6 or
• and
• wherein the composition is essentially boric acid free;
• wherein, if either nickel ions or iron ions are present, the molar ratio of nickel ions and iron ions, and the sum of nickel ions and iron ions, to cobalt ions is not greater than about 0.01;
• and
• wherein the composition is free of any functional concentration of reducing agents effective to reduce cobaltous ion (Co2+) to metallic cobalt (Co0).