Influence of physical parameters on the quasi-saturation of a power SOI RF LDMOS

In this work, the influence of top silicon thickness T_si, buried oxide thickness T_box and drift doping N_d on quasi-saturation in SOI RESURF LDMOS is investigated through extensive 2-D simulations. A physical insight on quasi-saturation in SOI structures with different top silicon thickness is provided. Furthermore the influence of Self-heating effect on quasi-saturation is also presented. The quasi-saturation current increases as the decrease in top silicon thickness up to T_si 1.0 μm with the same drift dose. Beyond this value quasi-saturation current remains unchanged with T_si. The analysis shows that the saturation of carrier velocity in the drift neutral region is the main cause for higher quasi-saturation current in SOI structures with T_si less than 1.0 μm. Under optimum RESURF condition, reducing buried oxide increases the quasi-saturation current dramatically.