Novel Vertical Power MOSFET With Step Hk Insulator Close to Super Junction Limit Relationship Between Breakdown Voltage and Specific ON-Resistance by Improving Electric Field Modulation

Abstract

A new vertical double-diffused metal oxide semiconductor field effect transistor (MOSFET) is presented based on the high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> (Hk) MOSFET concept in this article with the step high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> insulator, named as step Hk vertical double-diffused metal oxide semiconductor (VDMOS), to improve the electric field modulation effect. For step Hk VDMOS, the depletion is increased by the electric field modulation effect of step Hk insulator, which decreases the specific on-resistance of step Hk VDMOS compared to the conventional Hk VDMOS. The various thickness of the Hk insulator modulates the vertical electric field distribution in the drift region, which increases the breakdown voltage (BV) of the step Hk VDMOS. Meanwhile, an analytical model for novel step Hk VDMOS is obtained by solving the 2-D Poisson equation in an N-type drift region, and the 2-D Laplace equation in the step Hk region, which can reasonably explain the modulation effect of the step Hk region on the electric field distribution. The results show that the BV of the step Hk VDMOS is increased from 639 V of the conventional Hk VDMOS to 736 V with the same drift length of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$42~\mu \text{m}$ </tex-math></inline-formula> . The theoretical results of the electrical characteristics are in good agreement with the results from numerical simulations.