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 [1] 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 1.0mum with the same drift dose. Beyond this value quasisaturation 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 1.0mum. Under optimum RESURF condition, reducing buried oxide increases the quasi-saturation current dramatically.