Research Of Power Mosfet With High-K Dielectric Trench

Based on the researches of VDMOS, Super Junction and High-K materials, fourkinds of power VDMOS devices with trenches filled of High-K material have beendiscussed in this thesis, aiming at optimizing breakdown voltage and specificon-resistance characteristics.（1） Super Junction VDMOS with a trench filled of HK material （HK SJ VDMOS）,this device features a trench filled of HK material under the trench gate. An MIScapacitance is formed by trench gate, HK trench and drift region. Assistant depletion isbrought in, doping concentration is highly increased so that specific R_on,spdecreases,lateral electric field component decreases, so that the E-field distribution is optimized.And also the charge imbalance problem is allievated. By simulation, we’ve gotBV=180V, increased by12%compared with conventional SJ VDMOS, R_on,sp=1.58mΩ·cm²decreased by50%compared with Con. SJ VDMOS. Feasible fabricationprocess with angled ion implantation is developed.（2） Trench gate VDMOS with a trench filled of HK material （HK TG VDMOS）,the charge imbalance problem is avoided and it can be developed for smaller cell-pitch.We’ve got BV=172V, increased by15%compared with Con. TG VDMOS, R_on,sp=0.85m Ω·cm²decreased by67%compared with Con. TG VDMOS.（3） VDMOS with a Semi-HK trench （Semi-HK VDMOS）, highly doped narrow Nand lowly doped N-pillars are beside the HK trench in this device instead of SJstructure. And there is N-buffer region under the HK trench, the N-buffer thickness isdefined with the consideration of BV and process. Assistant depletion and optimizedE-field distribution are brought in. Meanwhile, there is no need to worry about thecharge imbalance problem. We’ve got BV=620V, increased by33%compared with Con.Semi-SJ VDMOS, R_on,sp=10.8m Ω·cm²decreased by12%compared with Con. Semi-SJVDMOS.（4） N/N-pillar VDMOS with trenches filled of HK material （HK N/N-VDMOS）,HK material can lead to bigger gate-drain capacitance Cgd, so that switchingcharacteristics are badly influenced. Focusing on this problem, we’ve given a brief introduction of this new device. We’ve got BV=176V, increased by20%compared withconventional SJ VDMOS, R_on,sp=1.16m Ω·cm²decreased by58%compared with Con.SJ VDMOS.