Quantificational dependence of vertival breakdown voltage on top silicon and dielectric layer thickness for SOI high voltage devices

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 a_eff which is experimentally obtained by taking threshold energy epsiv_T into accounting for electron multiplying. By the proposed E_S,C, quantificational dependence of vertical breakdown voltage V_B,V of SOI high voltage devices on top silicon thickness t_s and dielectric layer thickness t_I is dicussed. For the same t_s, a thicker t_I brings on a higher V_B,V because of a stated E_S,C, V_B,V = 348 V, 509 V with t_S-1 mum for t_I=2 mum, 3 mum, respectively. For the same t_I, V_B,V increases with the decreasing of t_S because of a crescent E_S,C when t_S is thin, and with t_I=2 mum, V_B,V=852 V, 348 V for t_S of 0.1 mum and 1 mum, respectively. So an ultra thin t_S can be used to provide a high V_B,V for SOI devicces. In addition, relation of t_I on t_S leading to the minimum of V_B,V is given, which should be avoided when a SOI device is designed. 2-D simulative and some experimental results meet well with analytical results.