Abstract: An electroless copper plating bath for depositing a copper or copper alloy layer on a surface of a substrate, including copper ions; a reducing agent; a complexing agent for copper ions; wherein the bath further includes at least one compound according to formula (1): in which Z1 and Z2 are independently selected from the group consisting of hydrogen; carboxylic acid; carboxylate; sulfonic acid; sulfonate; carboxamide; nitrile; nitro; trialkylammonium; 2-carboxyvinyl; 2-vinylcarboxylate; 2-(trialkylammonium)vinyl; hydroxamic acid; and oxime; provided at least one of Z1 and Z2 is not hydrogen; and in which R1, R2, R3 and R4 are: i. R1, R2, R3 and R4 are hydrogen; or ii. R1 with R2 form together an aromatic ring, R3 and R4 are hydrogen; or iii. R3 with R4 form together an aromatic ring, R1 and R2 are hydrogen; or iv. both R1 with R2 and R3 with R4 form together an aromatic ring, respectively.

Abstract: An electroless copper plating bath for depositing a copper or copper alloy layer on a surface of a substrate, including copper ions; a reducing agent; a complexing agent for copper ions; wherein the bath further includes at least one compound according to formula (1): in which Z1 and Z2 are independently selected from the group consisting of hydrogen; carboxylic acid; carboxylate; sulfonic acid; sulfonate; carboxamide; nitrile; nitro; trialkylammonium; 2-carboxyvinyl; 2-vinylcarboxylate; 2-(trialkylammonium)vinyl; hydroxamic acid; and oxime; provided at least one of Z1 and Z2 is not hydrogen; and in which R1, R2, R3 and R4 are: i. R1, R2, R3 and R4 are hydrogen; or ii. R1 with R2 form together an aromatic ring, R3 and R4 are hydrogen; or iii. R3 with R4 form together an aromatic ring, R1 and R2 are hydrogen; or iv. both R1 with R2 and R3 with R4 form together an aromatic ring, respectively.