Low-Temperature Silicon Films Deposition by Pulsed Cathodic Arc Process for Microsystem Technologies
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A9.38.1
Low-Temperature Silicon Films Deposition by Pulsed Cathodic Arc Process for Microsystem Technologies Hui Xia1, Yan Yang2, and Paul L. Bergstrom2 Department of Materials Science and Engineering, 2 Department of Electrical and Computer Engineering, Michigan Technological University, Houghton, MI 49931, U.S.A. 1
ABSTRACT The deposition of silicon films was investigated for the first time by the pulsed cathodic vacuum arc process. This method has been employed to take the advantages of its low deposition temperature, high deposition rate, and high-energy capabilities, coupled with its relatively low operational cost. Heavily doped silicon films were deposited on silicon and glass substrates at temperatures below 100°C with pulsed deposition rate of 0.2nm/A·s. Pulsed arc currents up to 400A in 1~5ms pulse width with 20~300 pulses per second were studied. Compared with the direct current (D.C.) cathodic vacuum arc, numerous possibilities exist for the pulsed arc deposition to suit specific targeted film growth. The characterization of the films was carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD) in terms of materials morphological and structural properties. The production of high quality silicon film materials at low temperature would further enable the integration of microsystems with microelectronics. INTRODUCTION The development of silicon thin films is attractive for many applications in the field of optoelectronics and micromechanics such as thin film transistors, solar cells device and structural elements in microeletromehanical system (MEMS) [1-4]. To meet a growing variety of device technology requirements, attention is given to the film processing methods to control materials growth and properties. As a technique for high quality film growth, cathodic vacuum arc deposition is characterized by low temperature, high deposition rate, relatively low cost and high-energy process capabilities due to the nature of arc plasma discharge [5, 6]. The direct current (D.C.) and pulsed current vacuum arc comprise two approaches implemented for film deposition. Compared with D.C. arc, pulsed arc has the advantages of higher ion energies and higher deposition rate as well as the reduction of macrodroplets intrinsically associated with the cathodic arc process. However, two main issues limit the utilization of cathodic vacuum arc on silicon material. One is that the arc cannot be initiated on the intrinsic silicon unless it is highly doped or is heated up to increase the electrical conductivity substantially. The other problem with silicon is its brittle mechanical behavior, which makes it not as robust as metals in this area. The local heating at cathode spots and the resulting thermal shock can cause the silicon target to crack. Previous reports of cathodic vacuum arc on silicon film deposition were focused on the D.C. arc operation only [7, 8]. We believe that pulsed technology is more appropriate for silicon cathodic arc film deposition. In this work, we present the efforts on experimen
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