Improvement of trench MOS barrier Schottky rectifier by using high-energy counter-doping trench-bottom implantation

Abstract

A trench MOS barrier Schottky (TMBS) rectifier formed by using high-energy boron trench-bottom implantation has been proposed. As compared to the conventional TMBS rectifier, this proposed device can achieve much larger reverse blocking voltage without considerable degradation of forward characteristics. By this scheme, the large peak electric field near the trench corner can be largely reduced due to charge compensation. In addition, owing to the presence of the counter-doped region, the second peak electric field is created below the trench bottom. Higher trench-bottom implantation energy may form wider boron dopant distribution, which facilitate larger alleviation of the second peak electric field. However, too high boron implantation energy may considerably cause dopant encroachment into the mesa region, which would increase the second electric field. Hence, properly high trench-bottom implantation energy should be employed to simultaneously cause low peak electric field at regions near the trench corner and below the trench bottom, thus providing a relatively high blocking voltage for this TMBS rectifier.