带p埋层表面注入硅基LDMOS模型与优化

Analytical Model and Optimization of Bulk-Silicon Surface Implanted LDMOS with p Buried Layer

提出一种带p埋层的表面注入硅基LDMOS高压器件新结构,称为BSI LDMOS(surface implanted LDMOS with pburied layer).通过表面注入n+薄层降低导通电阻,p埋层不但改善横向表面电场分布,提高击穿电压,而且增大漂移区优化浓度.求解电势的二维Poisson方程,获得表面电场和击穿电压的解析式,研究结构参数对表面电场和击穿电压的影响,数值与解析结果吻合较好.结果表明:与常规结构相比较,BSI LDMOS大大改善了击穿电压和导通电阻的折衷关系.

A novel bulk-silicon surface implanted device with a p buried layer is proposed,and an analytical model for the surface electrical field distributions and breakdown voltage is developed. The on-resistance is decreased as a result of the surfaceimplanted n^＋ layer surface,and the p buried layer improves the surface electrical field distribution and increases the optimal drift region doping concentration. Based on the 2D Poisson＇s solution, the model gives the closed form solutions of the surface potential and electrical field distributions as functions of the structure parameters and drain bias. The dependence of breakdown voltage on structure parameters is also calculated. Analytical results are well verified by simulation results obtained by MEDICI,showing the validity of the model presented here. BSI structure allowed a significant improvement of breakdown voltage by about 16%, and reduction of on-resistance by about 31%, compared to conventional structures.