Design and modeling of bulk and SOI power LDMOSFETs for RF wireless applications

This paper presents the design optimization of LDMOSFET structures for use as power amplifiers in mobile wireless applications. A detailed study has b een carried out to evaluate the influence of the device substrate on the RF performance. The performance of devices with bulk and Silicon-on-insulator (SOI) substrates has been compared for 50 V LDMOSFETs. In both cases, p-ty pe and n-type epitaxial layers were considered. Extensive two-dimensional s imulations have been performed to understand the device dynamics and to opt imize the devices for better RF performance. A simple physics-based circuit model has been developed to enable large signal simulations for RF charact erization. It is shown that bulk devices on n-type epitaxial layers yield t he highest output RF power for a given voltage and current rating. SOI devi ces offer comparable RF performance with less area for a given rating, but suffer from self-heating effects. Thick-film SOI is shown as a viable power amplifier technology for integrated RFIC applications. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.