The Effects of Plasma Induced Damage on The Channel Layers of Ion Implanted GaAs MESFETs during Reactive Ion Etching(RIE
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The Effects of Plasma Induced Damage on The Channel Layers of Ion Implanted GaAs MESFETs during Reactive Ion Etching(RIE) and Plasma Ashing Processes Hokyun Ahn, Honggu Ji, Jaekyoung Mun, Min Park and Haecheon Kim Wireless Communication Devices Department, Basic Research Laboratory Electronics and Telecommunications Research Institute (ETRI) 161, Kajong-Dong, Yusong-Gu, Taejon, Korea 305-600 ABSTRACT The gate length of GaAs MESFETs is required to be shorter for higher microwave frequency applications. The side-wall process using silicon nitride is one of the effective processes to fabricate short gate length GaAs MESFETs. The side-wall process consists of deposition and anisotropic etching of silicon nitride and delivers plasma induced damages on the channel layers of the devices. In this study, the effects of plasma induced damage on the channel layers of ion implanted GaAs MESFETs during reactive ion etching and plasma ashing processes have been investigated. The plasma induced damage was characterized by sheet resistance measurement, Xray photoelectron spectroscopy(XPS) and auger electron spectroscopy(AES) of different etched surfaces, compared with a chemically wet-etched reference surface. Also the effect of the plasma induced damage on the device performance was investigated. As a result, plasma ashing can deteriorate the plasma-induced damage by RIE. INTRODUCTION GaAs MESFETs have been widely used in the microwave frequency application. Recently, as a higher frequency application is demanded, shorter gate length GaAs MESFETs should be fabricated through appropriate processes such as the side wall process using silicon nitride. The side wall process includes plasma-related processes such as reactive ion etching (RIE) and plasma ashing which are generally used due to the advantages of anisotropic etching profile and clean surface. However, these processes are usually accompanied with the plasma induced damage and contamination on the channel layers, which cause the degradation of the device performance. In this paper, the damaged layer has been characterized by X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES). The effects of the plasma induced damage on the performance of GaAs based devices were also discussed.
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Mat. Res. Soc. Symp. Proc. Vol. 720 © 2002 Materials Research Society
EXPERIMENTAL DETAILS For the experiment, liquid-encapsulated-czochralski (LEC) grown semi-insulating GaAs (100) wafers were used. To get the abrupt and shallow channel layers, Be implantation was performed at 40KeV and 2×10-2cm-2 before Si implantation at 60KeV and 7×10-2 cm-2. Doped Si and Be were electrically activated by rapid thermal annealing at 900oC with the wafer capped by silicon nitride. All samples were dipped in HF solution to remove the silicon
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