High density indium bumping using electrodeposition enhanced by megasonic agitation

Electrodeposition has been utilized to fulfill the demand of high density indium bumping used in high energy physics applications. Previous studies have shown the capability of electrodeposition to achieve high yield and high density indium bumps. The challenge exists to improve the bump height uniformity and consistency of electroplated indium bumps across the wafer at ultra-fine pitches with the highest yield. This paper reports progress towards the electroplating indium bumping process assisted by megasonic agitation. Electroplating of indium onto non-patterned substrates was initially conducted to investigate the performance of the solution with megasonic agitation. Further trials were carried out on 4 inch silicon dummy wafers to create indium bumps at 50 ¿m pitch. The results reflect that bubbles created during the plating process with megasonic agitation can affect the quality of the deposit and the yield of indium bumping, under the experimental conditions used in this study.