Copper-selective electrochemical filling of macropore arrays for through-silicon via applications

Abstract

In this article, the physico-chemical and electrochemical conditions of through-silicon via formation were studied. First, macropore arrays were etched through a low doped n-type silicon wafer by anodization under illumination into a hydrofluoric acid-based electrolyte. After electrochemical etching, 'almost' through-silicon macropores were locally opened by a backside photolithographic process followed by anisotropic etching. The 450 × 450-μm2 opened areas were then selectively filled with copper by a potentiostatic electrochemical deposition. Using this process, high density conductive via (4.5 × 105 cm-2) was carried out. The conductive paths were then electrically characterized, and a resistance equal to 32 mΩ/copper-filled macropore was determined. © 2012 Defforge et al.