The Study of GaAs Power MESFETs Passivated with Photo-CVD and PECVD Silicon Nitride Films

• Main Authors: Lin, Wen Chung, 林文中
• Other Authors: Edward Y. Chang
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/46147144040005861479

碩士 === 國立交通大學 === 材料科學與工程研究所 === 85 === This thesis described the passivation of GaAs power MESFETs using either Photo-CVD or PECVD silicon nitride films. In the photo-CVD passivation process, hydrogenated amorphous silicon nitride films were prepared by mercury sensitized decomposition of silane and ammonia using a low-pressure mercury lamp. Detail processing techniques including ion-implantation, annealing, mesa isolation, ohmic contact, gate recess, gate formation, passivation, airbridge and backside processing were reported. The photo-CVD silicon nitride film was first deposited for passivation of GaAs power MESFET. The effect of these twotypes of process on MESFET passivation was studied. Depending upon the device structure, the passivation process needs tobe tailored to achieve minimal drift in device performance. DC and RF performances were relatable to the underlying compositional effects through extensive characterization of these films and devices. The GaAs power MESFET fabricated with photo-CVD passivation exhibited an improvement in the breakdownvoltage without the degradation of the transfer characteristics of the device.The unstable depletion region formed on the channel surface due to the generation of surface charges (during the deposition process) and subsequent trapping of these charges was minimized by using the photo-CVD process.The use of the non-stoichiometric nitride film offered the potential to develop films with minimal surface charges, the excess electronic charges being tied up by hydrogen (H+) ions that are generated during this process. Photo-CVD can be a good candidate for passivation of GaAs power MESFET.