Simulation Research On Novel Trench MOS Pinched-off Schottky Rectifier

Power semiconductor devices and power Integrated Circuit (IC), which are important branches of the whole semiconductor industry, are widely applied to industrial and social utilities. Power rectifier is a vital component of power semiconductor devices. On the basis of traditional P-i-N diode and planar Schottky barrier diode (SBD), several types of non-planar SBD have been designed and fabricated, among which Trench MOS Barrier Schottky rectifier (TMBS) and Graded doping-TMBS (GD-TMBS) successfully improve device characteristics by using depletion region induced by MOS structure to pinch off the conducting channel. However, the high field peak locating at the mesa botton near the trench corner limits the improvement of breakdown voltage for both TMBS and GD-TMBS.Process simulation and device simulation are called in a joint IC-technology computer aided design (IC-TCAD). It is one of the few technologies that are able to shrink the time and cost of IC developing. Besides, IC-TCAD is able to offer information which experiments can not to strengthen the research on IC process and device physics. In this thesis, we use process simulator Csuprem and device simulator Apsys of Crosslight Inc. to simulate planar SBD, TMBS, and GD-TMBS, characteristics of which we have already known. By comparing our simulated results with the known results, the applicability and precision of physic models used in Csuprem and Apsys are verified. The credibility of these simulators is so established.An improved structure over TMBS, Trapezoid Mesa-TMBS (TM-TMBS) is proposed. By simulation several parameters are varied to study their influence on breakdown voltage. Qualitative explanations are given to these relationships, according to which the optimized structure is given. Designing rules are also given to select the optimal value of these parameters. Simulation results demonstrate that optimized TM-TMBS achieves a 6.3% higher breakdown voltage and a 26% lower reverse leakage current compared with TMBS. Although TM-TMBS shows a slightly weaker forward performance, it's still better than planar SBD.An improved structure over GD-TMBS, GD-Trapezoid Mesa-TMBS (GD-TM-TMBS) is proposed. Following most of the parametric values of 200 V GD-TMBS, we used Apsys to study the influence of mesa bottom angle y and mesa top width a on device characteristics. Qualitative explanations are given to these relationships. It is revealed that only using a trapezoid mesa can not increase the breakdown voltage. The bottleneck is that the mesa bottom is hard to be pinched off. A new doping profile is derivated analytically, fitting the requirement of GD-TM-TMBS. Qualitative analysis demonstrates that this new doping profile is able to overcome the difficulty of pinching off.Another improved structure over TMBS, Round Corner-TMBS (RC-TMBS) is proposed. Electric field distributions of three kinds of RC-TMBS under reverse bias are studied by using Csuprem and Apsys. Physical explanations about the field peak values are given.Ⅰ-Ⅴcharacteristics of these three kinds of RC-TMBS are compared with those of TMBS and TM-TMBS. The optimized Double-RC-TMBS achieves a 2.9% higher breakdown voltage and a 15.5% lower leakage current compared with TMBS. Although the optimized Double-RC-TMBS shows slightly weaker forward performance compared with TMBS, it is still better than TM-TMBS. Physical explanations about the forward performance are given. Double-RC-TMBS can be considered as a eclectic mix of TMBS and TM-TMBS.