Effects of Substrate Temperature and Atomic Hydrogen Flow on the Mircocrystallinity of Evaporated Hydrogenated silicon F
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EFFECTS OF SUBSTRATE TEMPERATURE AND ATOMIC HYDROGEN FLOW ON THE MIRCOCRYSTALLINITY OF EVAPORATED HYDROGENATED SILICON FILMS
A.J. Stoltz, Whitney Mason, J.D. Benson, and J.H. Dinan Night Vision & Electronic Sensors Directorate, Ft. Belvoir, VA 22060 K. McCormack Institute for Defense Analysis, Alexandra, VA A. Kaleczyc E-OIR Measurements, Inc., Spotsylvania, VA 22553 As a first step toward an understanding of the chemical and structural role of hydrogen in hydrogenated amorphous silicon, we utilized electron beam evaporation in an ultra high vacuum environment to deposit films of amorphous silicon and systematically dosed these films with atomic hydrogen during deposition. Secondary Ion Mass Spectroscopy (SIMS) data indicated that hydrogen concentration can be varied from the detection limit of SIMS to a value in excess of 1021 atoms*cm-3. The intentional addition of hydrogen caused the concentration to fall from in an excess of 1021 atoms*cm3 to below 1018 atoms*cm-3.
Introduction There has been a long-standing interest in amorphous silicon (α-Si) due to its applications in solar cells and thin film transistors, and to flat panel display elements.[1]. More recently thin films of this material have found an important application in uncooled infrared detectors. Moreover, there has been an increasing interest in the use of silicon films that are microcrystalline rather than amorphous. Traditionally, films have been deposited by chemical vapor deposition (CVD) techniques such as plasma enhanced chemical vapor deposition (PECVD) and hot-wire chemical vapor deposition (HWCVD), and by sputtering. CVD techniques depend on the cracking of a SiH4 precursor molecule - to SiH3 for PECVD and to SiH2 or SiH1[2] for HWCVD. These hydrogen-containing molecules arrive at the surface of the substrate wafer and result in the incorporation of hydrogen in the film at a level fixed by the temperature of the substrate. At elevated temperatures, further cracking of chemisorbed SiH3 (or SiH2) can take place. This allows higher Si-Si bonding in the material with a decrease in the overall hydrogen in the material and a decrease in the coordination of Si to Hydrogen, more Si-H1 and Si-H2 bonds, than SiH3 bonding[1]. The existence of hydrogen in these films is known to have a strong influence on their structural and chemical characteristics. The limitation of chemically cracking is discussed by Ilsin An and et al [3]. To elucidate the role of hydrogen in α-Si, it is of interest to utilize a deposition technique that does not depend on a precursor molecule.
A19.9.1 Downloaded from https://www.cambridge.org/core. Access paid by the UCSB Libraries, on 15 Sep 2018 at 14:31:04, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-715-A19.9
Physical vapor deposition (PVD) of Si atoms is such a technique[4]. PVD depends on a much different mechanism that, in principle, can result in a hydrogen level that is set by the partial pressure of hydrogen species in the vacuum chamber.
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