Indium electroplating compositions containing amine compounds and methods of electroplating indium
Indium electroplating compositions containing amine compounds in trace amounts to electroplate substantially defect-free uniform indium which has a smooth surface morphology. The indium electroplating compositions can be used to electroplate indium metal on metal layers of various substrates such as semiconductor wafers and as thermal interface materials.
1. A method comprising:
a) providing a substrate comprising a nickel layer;
b) contacting the substrate with an indium electroplating composition comprising one or more sources of indium ions, citric acid, salts thereof or mixtures thereof, and one or more amine compounds in amounts of 0.1 ppm to 100 ppm having a formula:
where R 1 is chosen from hydrogen; (CH 2 ) a NR 4 R 5 where R 4 and R 5 are independently chosen from hydrogen and linear or branched (C 1 -C 4 )alkyl and a is an integer of 1 to 4 (CH 2 CHR 6 —O) x H or salts thereof where R 6 is chosen from hydrogen or linear of branched (C 1 -C 4 )alkyl and x is an integer from 1 to 20; carboxy(C 1 -C 4 )alkyl or salts thereof; or (CH 2 CHR 6 —O) p (CH 2 CHR 9 —O) x H or salts thereof where R 9 is hydrogen or linear or branched (C 1 -C 4 )alkyl; R 2 is chosen from hydrogen; linear or branched (C 1 -C 4 )alkyl; (CH 2 CHR 6 —O) y H of salts thereof where R 6 is defined as above and y is an integer of 1 to 20; carboxy(C 1 -C 4 )alkyl or salts thereof; or (CH 2 CHR 6 —O) q (CH 2 CHR 10 —O) y H or salts thereof where R 10 is hydrogen or linear or branched (C 1 -C 4 )alkyl; R 3 is chosen from cocoalkyl; R′—O—(CH 2 ) m where R′ is chosen from linear or branched, saturated or unsaturated (C 1 -C 20 )alkyl, m is an integer of 1 to 4; (CH 2 ) m NR 7 R 8 where R 7 is (CH 2 CHR 6 —O) p (CH 2 CHR 9 —O) x H or salts thereof and R 8 is (CH 2 CHR 6 —O) q (CH 2 CHR 10 —O) y H or salts thereof; p and q are integers from 1-20; and G is (CH 2 CHR 6 —O) z H or salts thereof where z is an integer from 1 to 20 and n is 0 or 1; and wherein the indium electroplating composition is free of alloying metals; and
c) electroplating an indium metal layer on the nickel layer of the substrate with the indium electroplating composition.
2. The method of claim 1 , wherein the one or more amine compounds are in amounts of 5 ppm to 15 ppm.
3. The method of claim 1 , wherein the indium electroplating composition further comprises chloride ions.
4. The method of claim 3 , wherein a molar ratio of chloride ions to indium ions is at least 2:1.