High critical electric field of thin silicon film and its realization in SOI high voltage devices

Abstract

Taking threshold energy epsiv_T into accounting for electron multiplying, the formula of silicon critical electric field E_S,C is given as a function of silicon film thickness t_s from an effective ionization rate alpha_eff. E_S,C is increasing with the decreasing of t_s especially at thinner t_s. 2-D simulative and some experimental results as well as the comparing with several other familiar expressions of electric field proved the proposed E_S,C is valid for both thick and thin silicon film. Thin silicon film with high E_S,C can be used to enhance dielectric field E_I and increase vertical breakdown voltage V_B,V of SOI high voltage devices. A high voltage SOI device with 80 nm silicon layer and 0.4mum dielectric layer is designed. A high E_S,C of 134V/mum is obtained, which makes E_I and V_B,V reach to 416 V/mum and 178 V, respectively.