Photo-Excited Etching of Poly-Crystalline and Single-Crystalline Silicon in Cl₂ Atmosphere

Poly-Si etching under Hg-Xe lamp irradiation in a Cl 2 atmosphere was investigated. It was found that n + poly-Si is etched by chemical reaction with Cl radicals photodissociated in the gas phase, while undoped and p + poly-Si cannot be etched without irradiation by UV light. The primary effect of the photoirradiation is to produce electrons arising from electron-hole pair generation. The etch rates, etched features and etching products depend strongly on the electron concentration in the conduction band. The experimental results are explained by assuming that electron-attached Cl - ions penetrate into the Si lattice.