Use of organic reductants to lower brightener consumption in acid copper electroplating bath utilising catalytic anodes

Abstract

Catalytic anodes are an enabling technology for high speed, horizontal acid copper electroplating. However, their usage is associated with high additive oxidation rates which can be problematic in terms of cost and control of the electrolyte. The addition of certain 'organic reductants' to the electroplating solution has been found to have a dramatic effect on brightener consumption when catalytic anodes are employed. This paper reports an investigation of three such compounds having varying functionality with respect to brightener oxidation. It was found that the ability of a particular organic reductant to influence brightener oxidation was related to its electrochemical properties on a particular anode material. However, it is postulated that the species' mechanism of oxidation and its anti-oxidant properties may also be important factors.

Through-Hole Filling in a Cu Plating Bath with Functional Insoluble Anodes and Acetic Acid as a Supporting Electrolyte

“…= TZ 2+ (aq) + Diformazan 2− (aq) (disproportionation reaction) [16] Reaction 1 is the dissolution of TNBT in an aqueous solution. Reaction 2 is the protonation of TNBT in an acidic solution.…”

“…In contrast with the soluble anode, insoluble anodes perform well in the copper plating bath because of their low maintenance and excellent dimensional stability in surface area regarding uniform current distribution. However, the conventional insoluble or dimensionally stable anodes (DSA) [10][11][12][13][14] that are activated with IrO 2 /Ta 2 O 5 /Ti [15][16][17][18] have an anodic potential that is high enough to oxidize organic additives. Here, a special functional insoluble anode (DT) was employed rather than the conventional DSA to maintain bath stability by protecting the organic additives.…”