Experimental Study On LDMOS's Structure And ESD

Lateral high-voltage power device LDMOS has advantages of high voltage, large gain, wide dynamic range, low distortion and compatibility with low-voltage circuit process. With the development of semiconductor technology, LDMOS is more and more widely used in power integrated circuits and smart power circuits. LDMOS is the preferred device used in the RF amplifier of 3G base stations because of its high operating frequency up to P or L band and attractive ratio of performance and price. Therefore, it is very important to study and model electrical characteristic of LDMOS because of its practical application.In the paper, the structure of RF-LDMOS had been established; the relations of the breakdown voltage to the substrate concentration and drift doses had been discussed in detail with the software ISE. The theory of the FRESUF technology had been analyzed, the effect of the RESURF to the LDMOS had been proved. At last, the optimal structure of RF-LDMOS has been received after the simulations on the parameters of the RF-LDMOS. Lots of data have been received for the final design of RF-LDMOS.The relationship between gate-drain capacitance (Cgd) and gate - source capacitance (Cgs) of RF-LDMOS and gate-source voltage (Vgs) and drain-source voltage (Vds) is investigated with ISE. Effects of the thickness of gate oxide, implant dosages of the drift region, and the implant dosages of the channel region on Cgd are also discussed. We prove the bird's beak structure represent more excellent RF characteristic compared with the conventional.The breakdown mechanisms for the 60V-LDMOS transistor under ESD stress is discussed by two-dimensional device simulation, and the ESD protection structures of the LDMOS: the deep drain double RESURF structure, the SCR-LDMOS structure, the HST-LDMOS structure were compared in detail. Using characterization of the LDMOS transistor under ESD conditions with various gate and drain clamps, the design of ESD protect for us is established.This paper describes a new lateral double diffused trench gate MOSFET with double RESURF technology. We simulate the breakdown voltage and capacitance especially the influences of double RESURF technology to the breakdown voltage. Compared with the conventional LDMOS, the breakdown voltage of the new structure improves 60V with the same length of the drift region and on-state resistance, and excellent RF character.