Electric characterization of SiC Trench MOSFETs with DLTS and admittance spectroscopy

Abstract

SiC trench MOSFETs aim to meet the need for efficient power transistors in our modern technology based society. State of the art are devices with aluminum (Al) as dopant in the inversion channel area. However, previous studies have shown an Al-related defect that might cause a channel mobility reduction. To overcome this SiC MOSFETs with boron (B)-implanted inversion channels are fabricated and electrically investigated. Devices with 10% B, 30% B and 100% B channel implantation are compared to the reference sample implanted with 100% Al. Basic measurement techniques as well as cryogenic characterizations such as DLTS and admittance spectroscopy are used to characterize the samples. A comparison between the latter two is drawn. Furthermore, results from an admittance spectroscopy simulation are shown in relation to the actual measurement.Since the analyzed B samples were annealed at low temperatures in order to prevent B out-diffusion, a non negligible amount of B can be found in the channel area by admittance spectroscopy. However, the measurement results indicate a B concentration that is too low to ensure a working metal oxide semiconductor field effect transistor (MOSFET) device. An outlook for further implantation dosages and annealing temperatures is given, which might lead to functioning MOSFETs with B as a channel implant.This thesis was written in cooperation with KAI Kompetenzzentrum Automobil- und Industrieelektronik GmbH. This work was funded by the Austrian Research PromotionAgency (FFG, Project No. 881110).