Failure Analysis And Redesign Of 60V Power U-MOSFET

The power MOSFET(Metal-Oxide-Semiconductor Field Effect Transistor) is recognized as a key component of power electronic systems. They determine the cost and efficiency of systems. In the word, at least 50 percent of the electricity is controlled by Power semiconductor devices. They are widely used in the consumer, industrial, medical, aerospace and transportation sectors. With increased awareness of the adverse impact on the environment resulting from carbon emissions, the efficiency and high performance of power device are demanded. U-MOSFET(Trench Metal-Oxide-Semiconductor Field Effect Transistor) widely favored by the market because it has a small chip area, low on-resistance, fast switching speed and other performance advantages.U-MOSFET optimal design, accurate failure analysis, and high reliability are academia and industry focus of the study. In this paper, the main task is to do failure analysis on a failure 60V U-MOSFET device, and complete high reliability design of 60V U-MOSFET device. The detail contents are described as following:(1) Through doing numerical statistical analysis on the failure 60V U-MOSFET device tape-out test data, on-resistance parameter is failure. Initially identified that 60V U-MOSFET device failure is chip layout design and cell design.(2) Doing failure analysis about layout design, combined with layout theory, the case of failure from layout is eliminated. Analysis the TEM(Transmission Electron Microscopy) of 60V U-MOSFET cell, established the cell physical model, derived the physical equations of on-resistance, combined with numerical simulation, we concluded that the case of 60V U-MOSFET failure is that Pbody from both sides of the trench gate occurs feed-through at the bottom of the trench. The on-resistance of epitaxial layer is increased, so that the total on-resistance of 60V U-MOSFET device is increased.(3) Based on the failure analysis of 60V U-MOSFET, we do the cell structure and termination structure re-design and optimization. We optimized the minimum on-resistance of 54353Ω, the threshold voltage of 2.947V, the blocking voltage of 81.2V of unit cell. The breakdown voltage of termination structure is 68V. Through setting the breakdown point at the Pbody zone between cell area and termination area, the oscillating is saluted effectively caused by the voltage transition from the cellular to the terminal.(4) After the layout of re-design 60V U-MOSFET device, we do the second tape out. Analysis the tape-out data, we succeed the re-design with threshold voltage of 2.959V, drain current of 140.649nA at 60V voltage, on-resistance of 2.77mΩ, breakdown voltage of 69.111V at 250μA drain current, gate forward leakage current o 18.509nA, gate reverse leakage current 10.305nA.