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 hot-carrier stresses including the maximum bulk current stress ( ${I}_{\text {bulkmax}}$ ) and maximum operating gate stress ( ${V}_{\text {gmax}}$ ). For the ${I}_{\text {bulkmax}}$ stress condition, the main damage point causing the degradation of ${R}_{ \mathrm{\scriptscriptstyle ON}}$ 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 ${V}_{\text {gmax}}$ stress condition, the main damage point causing the degradation of ${R}_{ \mathrm{\scriptscriptstyle ON}}$ is found at the two STI corners with interface state generation. Due to the more serious degradation of ${R}_{ \mathrm{\scriptscriptstyle ON}}$ , the ${I}_{\text {bulkmax}}$ 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.