Breakdown Voltage And ESD Protection Of RF-LDMOS

Lateral high-voltage power device LDMOS has advantages of high voltage, large gain, high transconductance, wide dynamic range, low distortion and compatibility with low-voltage circuit process. LDMOS is more and more widely used in power radio frequency integrated 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. Nowadays, LDMOS has developed to the fifth generation, designers try their best to improve the whole performances through altering device structure and changing process. Therefore, the hot spot of this article concentrate on reliability of LDMOS when frequency behavior and electrical behavior meet application requirement.In the paper, the structure and model of RF-LDMOS had been established; the relations of the breakdown voltage to the substrate concentration,drift doses and channel concentration 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.We research the reliability of RF-LDMOS from two aspects. Firstly, breakdown voltage. Breakdown voltage is an important electrical parameter, and is also an important reliability parameter of RF-LDMOS. We mainly improve device structure and make breakdown voltage meet application requirement, analyse the theory of the FRESUF technology, and discuss the relationship the breakdown voltage to the substrate concentration, drift doses and channel concentration. Secondly, ESD protection. Local electro-thermal breakdown caused by ESD is also an important reliability parameter of RF-LDMOS. We mainly study the basic local electro-thermal breakdown mechanism and the function which all kinds of structures of LDMOS can increase maximum second breakdown current, if device measure is not increased.Under 2D-device simulation software ISE, we propose a new lateral double diffused MOSFET with embedded SCR which based on RESURF technology, what we called is ESCR-LDMOS. we simulate frequency parameter RF-LDMOS (ft, gm), electrical parameter(Vt, Idss, BVds), avalanche breakdown voltage (BVds) and maximum second breakdown current(It2) which can reflect reliability. We mainly disscuss avalanche breakdown voltage, local electro-thermal breakdown mechanism, maximum second breakdown current by ESD and frequency characteristic of ESCR-LDMOS, at last we give the simulation results of every electrical parameter. Under 1GHZ operation frequency, 3.8V threshold voltage, the second current of the new structure with the same length of the device measure, drift region and 40V breakdown voltage is 7.5 times than convenional LDMOS, and with excellent RF character.