Effect of Gradual Junction on Performance and Reliability of High Voltage MOS Transistors

Abstract

In the thesis special process manufactured high voltage metal-oxide-semiconductor field effect transistors (HV-MOSFET) with gradual junction was studied Devices’ breakdown voltage hot-carrier-induced degradation and lifetime were compared with high-voltage devices with traditional junction The different mechanism and device lifetime between the devices was investigated First the advantages and the usage of HVMOSFET were illustrated The motivation of further studying high-voltage device with gradual junction was presented Due to the fact that high voltage devices with gradual junction had better off-state breakdown voltage performance comparing with device with traditional junction Thus the mechanism of devices’ off-state breakdown relationship between hot carrier effect and device reliability and lifetime were performed in the thesis Also technology computer aid design (TCAD) was utilized to discuss the details of the devices Therefore the differential between high-voltage devices with traditional junction and gradual junction were presented in the second part of the thesis and the structure of the devices and the measurement methodology and setup were also described Including device current ID-VD linear region current ID-VG substrate current Isub-VG and off-state breakdown voltage VBD The main part of the thesis were focus in part three and part four In part three the observation of improvement of off-state breakdown voltage in devices with gradual junction was proved And also indicated that the improvement of off-state breakdown voltage was even better in bigger dimension devices with gradual junction As a result TCAD was used to analysis the mechanism between these two kinds of devices for instance the electric field contour impact ionization rate contour The reliability issue was discussed in part four which the hot carrier stress was applied to study the degradation of the devices The measurement setup and stress condition were presented TCAD simulation software was used to confirm the measurement data At the end the plot of devices’ lifetime versus substrate current was demonstrated It can be used to predict the lifetime of high-voltage devices’ lifetime if the structure is demanded in application

Date of Award	2015 Jul 1
Original language	English
Supervisor	Jone-Fang Chen (Supervisor)