Microfabrication

Fabrication of through-silicon via arrays by photo-assisted electrochemical etching and supercritical electroplating

[+] Author Affiliations
Ho-Chiao Chuang, Hsi-Min Yang, Cheng-Xiang Wu, Jorge Sanchez, Jenq-Huey Shyu

National Taipei University of Technology, Department of Mechanical Engineering, Taipei, Taiwan

J. Micro/Nanolith. MEMS MOEMS. 16(1), 014501 (Jan 28, 2017). doi:10.1117/1.JMM.16.1.014501
History: Received November 4, 2016; Accepted January 10, 2017
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Abstract.  This paper aims to fabricate high aspect ratio through silicon via (TSV) by photo-assisted electrochemical etching (PAECE) and supercritical CO2 copper electroplating. A blind-holed silicon array was first fabricated by PAECE. By studying the etching parameters, including hydrofluoric acid concentration, etchant temperature, stirring speed, tetrabutylammonium perchlorate (TBAP) content, and Ohmic contact thickness, an array of pores with a 145 aspect ratio (height=250  μm and diameter=5.5  μm) was obtained successfully. Moreover, TBAP and Kodak Photo-Flo (PF) solution were added into the etchant to acquire smooth sidewalls for the first time. TBAP was added for the first time to serve as an antistatic agent in deionized water-based etchant to prevent side-branch etching, and PF was used to degasify hydrogen bubbles in the etchant. The effect of gold thickness over Ohmic contact was investigated. Randomized etching was observed with an Au thickness of 200 Å, but it can be improved by increasing the etching voltage. The silicon mold of through-holes was filled with metal using supercritical CO2 copper electroplating, which features high diffusivity, permeability, and density. The TSV structure (aspect ratio=135) was obtained at a supercritical pressure of 2000 psi, temperature of 50°C, and current density of 30  mA/cm2 in 2.5 h.

© 2017 Society of Photo-Optical Instrumentation Engineers

Citation

Ho-Chiao Chuang ; Hsi-Min Yang ; Cheng-Xiang Wu ; Jorge Sanchez and Jenq-Huey Shyu
"Fabrication of through-silicon via arrays by photo-assisted electrochemical etching and supercritical electroplating", J. Micro/Nanolith. MEMS MOEMS. 16(1), 014501 (Jan 28, 2017). ; http://dx.doi.org/10.1117/1.JMM.16.1.014501


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