Fabrication of trench-gate power MOSFETs by using a dual doped body region

Fabrication of trench-gate power MOSFETs by using a dual doped body region has been proposed to further improve the device performance. For the usual scheme that employs a uniform doped body region, a device with a blocking voltage larger than 30 V and a specific on-state resistance of about 1.0 Ωcm can be obtained via the proper choice of trench depth, epitaxial thickness, and body doping concentration. On the other hand, a dual doped body region is produced by dual high-energy and low-energy implantation of boron dopant. By this scheme, a device with a blocking voltage larger than 30 V and a specific on-state resistance of about 0.8 Ωcm can be further achieved. Hence, with reducing the cell pitch size to be below 2 μm, this device fabrication scheme should be promising and practical for achieving a specific on-resistance smaller than 0.1 mΩcm² and a blocking voltage higher than 30 V.