Uniform and linear variable doping ultra-thin PSOI LDMOS with n-type buried layer

A novel ultra-thin partial silicon-on-insulator (PSOI) LDMOS with n-type buried (n-buried) layer (NBL PSOI LDMOS) is proposed. The new PSOI LDMOS features an n-buried layer underneath the n-type drift (n-drift) region close to the source side, providing a large conductivity region for majority carriers to significantly improve the self-heating effect. A combination of uniform and linear variable doping (LVD) profile with highly initial concentration is utilised in the n-drift region, which alleviates the inherent tradeoff between specific on-resistance (R_on,sp) and breakdown voltage (BV), as well as achieving low power dissipation. With a 60-μm n-drift region length, the NBL PSOI LDMOS obtains a high BV of 940 V with a low maximum temperature (T_max) of 327 K at a power (P) of 1 mW/μm, which is reduced by around 56 K in comparison to the conventional SOI LDMOS using an LVD profile for the n-drift region (LVD SOI LDMOS). Moreover, R_on,sp of the NBL PSOI LDMOS is lower than that of the LVD SOI LDMOS for a wide range of BV from 400 to 900 V.