Investigation on safe operating area and ESD robustness in a 60-V BCD process with different deep P-Well test structures

Safe operating area (SOA) is one of the noticeable reliability concerns for power MOSFETs during the normal circuit operating conditions. Besides, electrostatic discharge (ESD) reliability is another important reliability issue for the power IC products. To save the silicon area of power IC with high-voltage (HV) devices, it is preferable for HV MOSFET to be self-protected without any additional ESD protection device, and to behave wide SOA region. In this work, the impact of deep P-Well (DPW) structure to the electrical SOA (eSOA) and ESD robustness of HV MOSFET has been investigated in a 0.25-μm 60-V BCD process. DPW structure is used to implement the RESURF (reduced surface field) in MOSFET, which make it be able to sustain the high operating voltage. From the experimental results in silicon chip, the ESD robustness and eSOA of HV MOSFET can be improved by the modified DPW structure.