ESD Reliability Improvement of an HV nLDMOS by the Bulk FODs Engineering

Abstract

The high voltage (HV) lateral double-diffused MOS (LDMOS) has a much lower on-resistance, a higher tolerance to breakdown voltage and a higher output power used for automotive ICs and high-frequency communication modules. However, its shortcomings are evident, including a high trigger voltage (V_t1), low holding voltage (V_h), low ESD discharge capability per unit length and multi-fingers unable to fully turn-on, which are serious impacted the ESD reliability capability. In this paper, the HV-nLDMOS device with adding field-oxide-devices (FODs) in the bulk area to make the trigger voltage effectively decreased, and in order to increase the ESD capability is investigated. Furthermore, the influence of bulk P⁺ area which was replaced by FODs in the bulk region on snapback parameters in a 0.25-μm 60-V high voltage process is evaluated. After that, the ESD capability has grate increased while the device with adding any FOD structures in the 0.25-μm 60-V high voltage process. The I_t2 value is > 7A and to be increased > 111.74% than that of a reference group. Noteworthy, this structure may make the trigger voltage (V_t1) too low to operate normally. Therefore, it should be careful considered that the problem of maximum FOD occupied ratio while using this methodology.