A HIGH-PERFORMANCE SELF-ALIGNED UMOSFET WITH A VERTICAL TRENCH CONTACT STRUCTURE

We compare the electrical characteristics of a UMOSFET having a trench contact (TC-UMOS) for the source and the body regions with those of the conventional surface contact UMOSFET (SC-UMOS). For SC-UMOS, there exists an optimum cell pitch which gives the lowest on-resistance. Reducing the cell pitch beyond that point results in increased on-resistance because the source contact resistance increases as the cell pitch is further reduced. On the contrary, for TC-UMOS, the on-resistance decreases as the cell pitch is reduced because the source contact resistance does not change. These results show that TC-UMOS is more effective than SC-UMOS for reducing the on-resistance by scaling down of the cell pitch. The minimum specific on-resistance of TC-UMOS is 0.43 mOMEGA . cm2. Furthermore, the critical avalanche current of TC-UMOS is enhanced significantly compared with that of SC-UMOS because the base resistance of the parasitic npn-bipolar transistor of TC-UMOS is lower than that of SC-UMOS.