An ultra high vacuum system for thin dielectric film deposition at low temperatures
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G. Griffiths CSIRO Division ofRadio Physics, P. O. Box 76, Epping, NSW 2121, Australia (Received 22 October 1985; accepted 24 May 1988)
An ultra high vacuum system has been designed and constructed for the purpose of depositing high-quality oxide films on well-characterized crystal surfaces at low temperatures. In particular, aluminum phosphorus oxide films have been deposited on both InP and Ge surfaces for the purpose of device application. Electrical measurements of metal-oxide-semiconductor structures show much improved interfacial properties with little or no hysteresis.
I. INTRODUCTION The success of silicon microelectronic devices is primarily based on the fact that the thermally grown silicon dioxide on silicon possesses a near-ideal interface. On the other hand, properties of deposited oxides on silicon have always proven to be much inferior. Studies on deposited oxides have shown that many factors contribute to the poor quality of the oxide-semiconductor interface. In a sputtering system, high-energy particles tend to damage the crystal surface that is the interface after oxide deposition. In a plasma deposition system, the crystal surface tends to be charged by the plasma species. Electron gun evaporation methods will also cause surface damage due to high-energy electrons and radiation. High-temperature annealing of the deposited films usually helps to remove these damages but will not render the interface ideal. Deposition of dielectric films on compound semiconducting surfaces is even more difficult due to the low incongruent melting temperatures of these materials. Recently, however, Chang et al.x have demonstrated a new deposition technique that uses beams of chemically active species. Using such a lowtemperature scheme, they have shown that much-improved interface properties can be achieved. In this article we report the operation of an ultra high vacuum (UHV) system for the purpose of depositing oxide films at low temperatures. We demonstrate how a crystalline surface can be prepared and characterized before film deposition. As an example, we show how aluminum-phosphorus oxide films are deposited on InP and Ge surfaces with improved interfacial properties. II. DESCRIPTION OF THE UHV DEPOSITION SYSTEM The primary function of the UHV system is to provide an ultraclean environment so the deposition steps J. Mater. Res. 3 (5), Sep/Oct 1988
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can be well characterized and controlled. In particular, we are interested in using this system to deposit dielectric films on compound semiconductors. From earlier research results it has been shown that the following features are necessary for the system: (1) a background pressure of 10 ~ 10 Torr in the deposition system to maintain a clean surface; (2) the ability to remove carbon contaminants as well as native oxide from the crystal surface without altering the surface stoichiometry of the crystal; (3) the ability to deposit dielectric films at low temperatures to avoid modification of the crystal surface; and (4) analytical tool
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