Effect of Trench Bottom Implantation on the Performance of Trench MOSFET

A trench MOSFET with trench bottom implantation (TBI) is formed to improve the device performance and reliability. Devices with various TBI conductivity types are studied by numerical simulations in this paper. The N-channel trench MOSFETs with P-TBI region and N-TBI region are compared in the aspect of static and dynamical characteristics. It is found that N-MOSFET with P-TBI region alleviates the electric field of the bottom oxide at the off-state, and achieves a higher breakdown voltage than that with N-type TBI region due to space charge compensation. However, P-type TBI region narrows the current path and causes on-resistance degradation. Besides, when the device is turned on, P-type TBI region stores negative charge and results in higher electric field.