Novel Low-Resistance Current Path UMOS With High-K Dielectric Pillars

Abstract

A low specific on-resistance (Ron,sp) UMOS with high permittivity (HK) dielectric pillars underneath the p body region (HK UMOS) is proposed and investigated. Its drift region uniquely consists of two narrow and highly-doped n pillars and one lightly doped n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> pillar, which is parallel to the HK dielectric pillars. First, the highly-doped n pillars offer low resistance current paths in the ON-state while the n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> region sustains high voltage in the OFF-state. Second, the HK dielectric causes an enhanced self-adapted lateral assistant depletion of the n pillars, which allows to keep a higher doping concentration of the n pillars and thus further reduces the Ron,sp. Third, the HK dielectric enhances the vertical field strength in high-voltage blocking state, leading to an improved breakdown voltage (BV). Compared with a conventional UMOS at the highest figure-of-merit, the HK UMOS with kD=200 not only decreases the Ron,sp by 67%, but also increases the BV by 12%.