Dependence of breakdown voltage on drift length and buried oxide thickness in SOI RESURF LDMOS transistors

The dependence of avalanche breakdown voltage on the drift region length and buried oxide thickness of thin silicon-on-insulator (SOI) LDMOS transistors is reported. An ideal relationship between breakdown voltage and drift length is derived. Experimental SOI LDMOS transistors with near ideal breakdown voltages in the short-drift-length regime have been realized. Specifically, 380 V was achieved in a drift length of 20 μm. Thin buried oxides are shown to be a major cause of deviation from this ideal. Experimental results verify this finding. An 860-V LDMOS transistor made in a 0.2 μm-thick SOI layer is reported