AVS 45th International Symposium
    Plasma Science and Technology Division Monday Sessions
       Session PS-MoP

Paper PS-MoP15
In-situ Cleaning of GaAs and Al@sub x@Ga@sub 1-x@As Surfaces and Production of Ohmic Contacts Using an Atomic Hydrogen Source Based on a Reflected Arc Discharge

Monday, November 2, 1998, 5:30 pm, Room Hall A

Session: Plasma Science and Technology Poster Session
Presenter: V.A. Kagadei, Research Institute of Semiconductor Devices, Russia
Authors: V.A. Kagadei, Research Institute of Semiconductor Devices, Russia
D.I. Proskurovsky, Institute of High Current Electronics, Russia
Correspondent: Click to Email
The existence of a thin-metal-film - semiconductor interface containing no contaminant is a necessary condition for the formation of high-quality ohmic contacts. Chemical treatment of the surface of a semiconductor is insufficient to provide an interface free from oxide. This is most pronounced for semiconductors showing high rates of oxidation of the surface, e.g., for Al@sub x@Ga@sub 1-x@As. A technology for production of ohmic contacts with n-type GaAs and n-type and p-type Al@sub x@Ga@sub 1-x@As has been proposed, such that the surface cleaning in a flow of atomic hydrogen (AH) and the deposition of a metal film are accomplished in a unified vacuum cycle. A feature of this technology is that the processes are conducted in a vacuum deposition system with a residual pressure of 3 10@super -6@ Torr for GaAs and (3-7) 10@super -7@ Torr for AlxGa1-xAs. The AH flow was produced by a reflected-arc-discharge-based source with a hollow cathode and a self-heating element. In the course of cleaning, the hydrogen pressure was 10@super -4@ Torr. The specimen temperature and the treatment time were varied in the range as follows: T = 100 - 400 C and t = 0.5 - 90 min. AuGe/GaAs interfaces have been produced with the contaminant content being below the sensitivity threshold of the method of Auger electron spectroscopy (AES). With some technological procedures having been executed, an AuGe/Al@sub 0.6@Ga@sub 0.4@As interface has been produced with the oxygen content less than 1% and the contents of other impurities below the AES sensitivity threshold. A comparative examination has been carried out for ohmic contacts produced using the technology proposed and the conventional technology based on "wet" chemical cleaning. The contacts produced by the proposed technology show a better morphology of the surface and of the contact area edge, high adhesion, and a low contact resistant; the process of their production features good reproducibility. Performance data of devices made using the new technology are reported. The technology developed is promising for production of shallow-lying contacts with GaAs and contacts with AlxGa1-xAs having a high Al content.