Hot-Carrier-Induced Degradation and Optimization for Lateral DMOS With Split-STI-Structure in the Drift Region

The lateral double-diffusion MOS with split shallow trench isolation structure (split-STI LDMOS) in the drift region has been investigated under two hotcarrier stresses including the maximum bulk current stress (I bulkmax ) and maximum operating gate stress (V gmax ). For the I bulkmax stress condition, the main damage point causing the degradation of RON is found at the STI corner closest to the source with the interface state generation. In addition, the hot hole injection is found at the edge of the shrinking poly-gate region. For the V gmax stress condition, the main damage point causing the degradation of R ON is found at the two STI corners with interface state generation. Due to the more serious degradation of R ON , the I bulkmax stress condition is regarded as the worst-case stress condition. The novel structure with the H-shape STI in the drift region is proposed. It is demonstrated that the H-shape STI structure is effectively helpful to alleviate the hot-carrier degradation without altering the tradeoff between the OFF-state breakdown voltage and specific ON-resistance.