A new structure and its analytical model for the electric field and breakdown voltage of SOI high voltage device with variable-k dielectric buried layer

A new SOI high voltage device structure with variable-k (permittivity) dielectric buried layer (VK SOI) is proposed in this paper. In this structure, the buried layer is made of two dielectrics, one of which is the low-k dielectric. The breakdown voltage is enhanced due to the modulation effect of the variable-k buried layer on the electric fields in the buried layer and drift region. An analytical model for the electric field and breakdown voltage in VK SOI is presented taking the modulation effect into account, from which the RESURF condition is derived. The dependences of the electric field distribution and breakdown voltage on the device parameters for VK SOI are investigated. Compared with the conventional SOI, the electric field of the buried layer and breakdown voltage of VK SOI with relative permittivity kI2 = 2 of the low-k dielectric are enhanced by 81% and 56%, respectively. The analytical results are in good agreement with those of 2D simulations. Finally, the proposed model and RESURF condition can be well applied to the conventional SOI and also extended to VT SOI (variable thickness buried layer SOI) devices.