Analytical Study on a 700 V Triple RESURF LDMOS With a Variable High-<i>K</i> Dielectric Trench
Zhen Cao, Qian Wang, Licheng Jiao
Abstract
A novel 700 V triple REduced SURface Field (RESURF) lateral double-diffused MOSFETs (LDMOS) with a variable high- K (VHK) dielectric trench for smart power applications is proposed and studied by TCAD simulations. Compared with conventional triple RESURF (CTR) LDMOS, the new structure features a composite high- K (HK) dielectric trench embedded in the drain edge. First, a higher HK dielectric layer is in the upper trench to suppress the high electric field ( E-field) under the drain by dielectric RESURF. Second, a lower HK dielectric is at the bottom of the trench to promote the depletion of the N-buffer layer and P-substrate, which increases the N-buffer doping concentration and thus reduces ON-resistance. The overall vertical bulk E-field distribution is modulated by the E-field peak generated at the position of varying K dielectric, which greatly improves breakdown voltage (BV). An analytical model of BV and vertical E-field taking account of the influence of the VHK dielectric trench is presented. Simulation results show that the proposed VHK TR LDMOS is able to obtain a 30.2% higher BV and a lower 15.4% R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON, sp</sub> than the CTR LDMOS. Moreover, the figure of merit (BV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON,sp</sub> ) of VHK TR LDMOS has doubled further breaking the lateral silicon limit.