Abstract: A novel SOI high voltage device structure with a variable low k dielectric layer (VLkD) is proposed.The buried layer is made up of dielectrics with variable k.The vertical electric field of the buried layer and the vertical breakdown voltage are enhanced due to the low dielectric constant.An enhanced dielectric electric field principle is then proposed.The modulation effect of the buried dielectric layer with different k on the surface electric field increases the lateral breakdown voltage.The RESURF criterion for VLkD SOI is developed.The dependence of breakdown characteristics on the structure parameters of VLkD is researched by 2D device simulator.It is shown that an electric field of the buried layer of 248V/μm and breakdown voltage of 295V can be obtained for a VLkD structure with a 2μm thick Si layer and 1μm composite buried layer with kIL=2 and kIH=3.9.The electric field of the buried layer and breakdown voltage are enhanced by 93% and 64%,respectively, compared to conventional SOI with a 1μm buried oxide layer.

Key words: variable low k dielectric layer, vertical electric field, modulation, RESURF criterion, breakdown voltage