Observation and Utilization of Boron Segregation in Trench MOSFETs to Improve Figure of Merit (FOM)
We report the observation and utilization of boron segregation in trench MOSFETs (UMOS) to reduce on-resistance. A trenched LOCOS process has been applied to a UMOS structure to reduce the gate-to-source overlap capacitance (C gs), and it is observed that not only 40% reduction in C gs is achieved but also 45% reduction in specific on-resistance (R on, sp). Figure of merit is improved by 58%. TSUPREM-4 doping profile simulation at the silicon and oxide interface revealed the presence of boron segregation. On-resistance reduction is attributed by the shortened vertical channel length due to boron segregation.
A gate enhanced power U-shaped MOSFET integrated with a Schottky rectifier
An accumulation gate enhanced power U-shaped metal-oxide-semiconductor field-effect-transistor (UMOSFET) integrated with a Schottky rectifier is proposed. In this device, a Schottky rectifier is integrated into each cell of the accumulation gate enhanced power UMOSFET. Specific on-resistances of 7.7 mΩ·mm2 and 6.5 mΩ·mm2 for the gate bias voltages of 5 V and 10 V are achieved, respectively, and the breakdown voltage is 61 V. The numerical simulation shows a 25% reduction in the reverse recovery time and about three orders of magnitude reduction in the leakage current as compared with the accumulation gate enhanced power UMOSFET.
Three-dimensional elasticity problems for the prismatic bar
A general solution is given to the three-dimensional linear elastic problem of a prismatic bar subjected to arbitrary tractions on its lateral surfaces, subject only to the restriction that they can be expanded as finite power series in the axial coordinate z. The solution is obtained by repeated differentiation of the tractions with respect to z, establishing a set of sub-problems . A recursive procedure is then developed for generating the solution to from that for . This procedure involves three steps: integration of the stress and displacement fields with respect to z, using an appropriate Papkovich–Neuber (P–N) representation; solution of two-dimensional in-plane and antiplane corrective problems for the tractions in that are independent of z; and expression of these corrective solutions in P–N form. The method is illustrated by an example.