Fabrication of Metal Micropillars Array by Integrating Photo-Assisted Electrochemical Etching Through-Holes and Electroforming Techniques

[[abstract]]This research will integrate photo-assisted electrochemical etching (ECE) and electroforming techniques for fabricating high-density metal micropillars. This process is described as followed: high-density through holes in silicon are etched by photo-assisted electrochemical etching under various parameters; then the through holes are fully filled by copper electroforming technique to form high-density metal micropillars. The deveploed technology will be promising for the application of integrated probe array and wafer-level package in the further. Because of the above-mentioned, this research used the low-cost electrochemical etching (ECE) equipment developed by ourselves and got the best parameters of the related manufacture. The experiment results proved that the technology had been able to partially replace the dry etching technology. Using the ECE technology to fabricate high aspect of micro-pores array, we can get the structures of high aspect when the etching time reached 31.5 hours. Through-holes were formed by selective partial electropolishing in a 2.5wt.% HF electrolytic solution, using an N-type, (100)-oriented Si wafer as an anode, and a Pt plate as a cathode. The obtained holes were square through-holes of 40.mu.m side length, with an aspect ratio of 12.5. Metal micropillars were made by electroforming technology with pulse and reverse current. The height of metal micropillars achieve 500.mu.m and the aspect ratio can reach 12.5.