Controllable Ultrathin Nanoporous Silicon Film’s Fabrication Process For A “LAB-ON-SI CHIP” Biosensing Platform

Abstract

To fabricate a “lab-on-Si chip” biosensing platform we propose to use a nanoporous silicon (npSi) based light emitting element. High current densities and high concentrations of hydrofluoric acid are generally needed during the electrochemical etching process to fabricate high porosity nanostructured silicon films. However, short process time (non-controllability/uniformity of ultrathin films formation), and toxic (high HF vapor pressure), fluidity and aggressive reagents (etching Al layers and interconnections in the meanwhile) are serious concerns associated with it. Therefore, it is highly demanded to seek alternatives to fabricate ultrathin nanoporous Si films using lower current densities at low Fion concentrations. We have developed an ultrathin nanoporous silicon fabrication process by electrochemical etching in ammonia fluoride solution. It was shown that highly uniform and ultrathin high porosity nanoporous silicon films can be fabricated under very low current densities and fluorine ion concentration in a reproducible manner. Structural and electro optical properties of nanoporous silicon films are also discussed.