AVS 59th Annual International Symposium and Exhibition
    Plasma Science and Technology Tuesday Sessions
       Session PS1-TuA

Paper PS1-TuA10
Nano-crystalline Silicon Deposition using a Layer-by-layer Technique

Tuesday, October 30, 2012, 5:00 pm, Room 24

Session: Plasma Deposition and Plasma Enhanced ALD
Presenter: Z. Chen, University of Houston
Authors: Z. Chen, University of Houston
M.N. Iliev, University of Houston
J.A. Mucha, University of Houston
Y.K. Pu, Tsinghua University, China
D.J. Economou, University of Houston
V.M. Donnelly, University of Houston
Correspondent: Click to Email
Nano-crystalline silicon was deposited using a layer-by-layer technique in a novel reactor with two separate reaction regions for amorphous silicon deposition and nano-crystallization. Substrates were rotated between two internal plasma sources, with selectable processing times in each source. A capacitively-coupled plasma (CCP) with SiH4/He feed gas was used to deposit thin hydrogenated amorphous Si layers that were then immediately exposed to a H2 or D2 inductively-coupled plasma (ICP). The reaction of H or D atoms induced crystallization in the films. With 2 or 4 substrates on opposite sides of a circular susceptor, one substrate was in the SiH4 CCP, while another was in the H2 or D2 ICP. These two processes were performed sequentially and periodically to grow thin films. Raman spectroscopy was used to characterize the films and determine the fraction of crystalline (510 and 520 cm-1 peaks) material in the a-Si:H layer (480 cm-1 peak). For the same total exposure times in each plasma, nearly the same total thickness films were deposited. Many short exposures to both plasmas were more effective in producing nano-crystalline Si than with one long exposure to each plasma. In addition, the fraction of nano-crystalline Si increased with increasing ratio of H2 ICP-to-SiH4/He CCP exposure time. Mass spectrometry was also used to monitor products produced in the D2 plasma. During crystallization, etching was observed and SiDxHy peaks were detected, with the strongest coming at m/e=32 (SiD2+, SiH2D+). These signals decayed to a small background over times that depended on the exposure time in the SiH4/He CCP. The films were also characterized by spectroscopic ellipsometry and Fourier transform infrared absorption. By utilizing these characterization methods, the kinetics for crystallization was investigated and will be discussed.