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MICROSTRUCTURAL AND ELECTRONIC PROPERTIES OF HYDROGENATED AMORPHOUS SILICON FILMS DEPOSITED BY MAGNETRON REACTIVE SPUTTERING. MUSTAFA PINARBASI, NAGI MALEY, ALAN MYERS, IGOR SZAFRANEK, JOHN R. ABELSON, JOHN A. THORNTON *. Department of Materials Science and Engineering, the Coordinated Science Laboratory, and the Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801. *"In memory of John A. Thornton" ABSTRACT Hydrogenated amorphous silicon (a-Si:H) films have been deposited by dc magnetron reactive sputtering in an Ar+H working gas. In this process, the hydrogen content A controlled by two independent variables: the substrate temperature and the hydrogen partial pressure in the deposition chamber. For a wide range of deposition conditions studied, it is shown that total hydrogen content of the films, as inferred from IR absorption, is uniquely related to the hydrogen bonding and the microstructure. We report films 0of high electronic quality, deposited between 200-300 C, in which hydrogen bonding varies from predominantly SiH to mixed SiH and SiH modes as the hydrogen content is increased. This struciral change is reflected in hydrogen evolution spectra. In addition to peaks at "500 0 and -600 C, a low-temperature peak (350-400 C) has been observed for the films which have high hydrogen content and consequently are rich in SiH2 . The low temperature peak is absent in SiH dominant films. However, the low-temperature peak is not associated with a columnar morphology because SEM images of fracture cross-sections are featureless for SiH dominant films and have a "bumpy" texture for high SiH2 content films. We propose that in our SiH2 rich films, excess hydrogen leads to a void rich but non-columnar morphology. Preliminary measurements of the Staebler-Wronski effect using AM-1 light show a low susceptibilty to degradation in both types of films. The different electronic properties of the films indicate that the quality of magnetron sputtered films does not necessarily correlate with the IR absorption peaks in a simple manner. INTRODUCTION Hydrogen is the key constituent which gives amorphous silicon its high electronic quality through the passivation of dangling bonds, and by facilitating structural relaxation in the random covalent network. To understand the incorporation and bonding of hydrogen and its effect on microstructure and film properties, independent control of hydrogen during film growth is essential. One of the major advantages of reactive sputtering is that it offers control of hydrogen content in the films independent of other deposition parameters[l,2,3]. We have studied the microstructural and electronic properties of the films as a Mat. Res. Soc. Syrup. Proc. Vol. 118.

1988 Materials Research Society

538

function of substrate temperature, and hydrogen content by varying the hydrogen partial pressure in the chamber. EXPERIMENTAL The deposition of a-Si:H is done in a UHV chamber by dc magnetron reactive sputtering as described elsewhere[l]. The films are gro