2000 V SOI LDMOS with new drift structure for HVICs

A laterally diffused metal oxide semiconductor (LDMOS) has been fabricated on a 12.2 μm buried oxide (BOX) silicon-on-insulator (SOI) substrate, successfully achieving a breakdown voltage of over 2000 V. This paper describes the proposed drift structure for SOI LDMOS. The proposed LDMOS drift structure adopts SOI reduced surface electric field (SOI RESURF) technology, which uses the BOX layer to establish the breakdown voltage. SOI RESURF technology achieves a high breakdown voltage by enhancing the critical electric field of the SOI layer. The proposed drift structure is characterized by the formation of an N-type buried diffusion layer with a concentration gradient at the SOI layer/BOX layer interface that consists of eight levels from the source to the drain. This structure increases the critical electric field of the SOI layer to 0.55 MV/cm compared to the normal critical electric field of silicon (Si), which is typically 0.3 MV/cm. As a result, a breakdown voltage of over 2000 V was achieved with a 12.2 μm BOX layer.