Avalanche Capability Improvement by Ion Implantation-induced Defects Control for Trench Power MOSFET

To improve the avalanche capability of trench power MOSFETs, the resistance of the base diffusion layer must be lowered. Generally, a P-type high concentration layer is formed at the bottom of the trench. To form this layer, it is necessary to perform high-dose, low-energy boron implantation and activate it by annealing. However, if the diffused boron reaches the MOSFET channel, the threshold voltage will increase. In addition, high-dose ion implantation may result in EOR defects. BF2 and B were used as ion species in the P-type layer. The B ion was used at half the BF2 dose to prevent defect formation. The electrical characteristics of the two samples were compared, and the threshold voltage, on-resistance, and avalanche capability were the same as those of the BF2-implanted sample.