Copper deposition in wafer level packaging of integrated circuits

A process for forming a copper feature over a semiconductor substrate in wafer level packaging for interconnecting an electronic circuit of a semiconductor device with a circuit external to the device, wherein the semiconductor assembly comprises a base structure bearing an under bump structure, the under bump structure comprising an under bump pad or under bump metal;

• the process comprising:
• supplying current to an aqueous electrodeposition composition in contact with a cathode comprising the under bump structure on the semiconductor assembly, said aqueous electrodeposition composition comprising:
• a) a source of copper ions,
• b) an acid,
• c) a suppressor, and
• d) a leveler, wherein the leveler comprises a quaternized poly(epihalohydrin), the quaternized poly(epihalohydrin compound comprising n repeating units corresponding to structure 1N and p repeating units corresponding to structure 1P:
• wherein Q has a structure corresponding to that which is obtained by reacting a pendent methylene halide group of poly(epihalohydrin) with a tertiary amine selected from the group consisting of:
• (i) an N-substituted and optionally further substituted heteroalicyclic amine wherein the N-substituent is selected from the group consisting of substituted or unsubstituted alkyl, alicyclic, aralkyl, aryl, and heterocyclic and (ii) a substituted or unsubstituted nitrogen-containing heteroaryl compound;
• and
• wherein n is an integer between 3 and 35, p is an integer greater than 0 and up to 25;
• X is a halo substituent;
• and X− is a monovalent anion;
• and
• e) an accelerator;
• wherein current is supplied in an electrolytic circuit comprising a direct current power source, the aqueous electrodeposition composition, the under bump pad or under bump metal in electrical communication with the negative terminal of said power source and in contact with the electrodeposition composition, and an anode in electrical communication with the positive terminal of the power source and in contact with said electrodeposition composition;
• wherein the current supplied in the electrolytic circuit is maintained at an average current density of at least 12 A/dm2;
• and
• wherein a copper bump or pillar is electrodeposited on the under bump structure.