Investigation on Electrical Degradation of High Voltage nLDMOS After High Temperature Reverse Bias Stress

The breakdown voltage (BV) and on resistance (R_dson) degradation of the 700-V n-type single-RESURF lateral double-diffused MOS (nLDMOS) after high-temperature reverse bias (HTRB) stress have been investigated in this work. A detail analysis that shows good agreement with the experiments is proposed based on electrostatic force microscope (EFM) testing, charge-pumping testing, and TCAD simulations. The BV degradation is caused by the generated positive ions from the device surface under HTRB stress. Not only the BV decreases but also the breakdown position migrates up from the body region to the surface region below the gate field plate of the device. Interface states are generated due to the hot carriers injected into the gate oxide and the field oxide below the gate field plate, which is the reason for the R_dson degradation. In order to avoid the degradation, reducing the drift doping is one of the effective methods, although it will sacrifice the conduction capability. The tradeoff between robustness and conduction capability is also presented.