Porous Silicon Fabrication Process for Optical Reflectors

Ying Yue; Nian Zhen

Ying Yue Wuhan University of Technology
Nian Zhen Wuhan University of Technology

Keywords: Porous silicon, non-manhattan, high aspect ratio, MEMS, wet etching

Abstract

We describe the use of porous silicon fabrication technique for fabricating non-manhattan
structures in silicon using wet etching. The fabrication method is simple to set up, economical
and produces smooth etched surface. A solid source diffusion of N++ in a P type wafer with low
stress thermally grown silicon nitride is used as a masking layer. Comparison of porous silicon
etches with wafers solid source diffusion and implanted diffusion is presented. The result show
that areas where a solid source diffusion is used form an etch angle of 70-80°, however using an
implanted diffusion the etch angle is closer to 90°. The selectivity of the etch during porous
silicon fabrication using any of the above two as masking layer results in fabrication of high
aspect ratio non-manhattan structures. These structures since are wet etched do not have
surface roughness and can be used for optical applications.

Author Biographies

Ying Yue, Wuhan University of Technology

School of Material Science and Engineering

Nian Zhen, Wuhan University of Technology

School of Power Engineering

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