AVS 45th International Symposium
    Thin Films Division Thursday Sessions
       Session TF-ThM

Paper TF-ThM8
Advanced Deposition Technique for Producing Thin Films of Polycrystalline Silicon

Thursday, November 5, 1998, 10:40 am, Room 310

Session: Thin Films for Flat Panel Applications
Presenter: J.B.O. Caughman, Oak Ridge National Laboratory
Authors: J.B.O. Caughman, Oak Ridge National Laboratory
D.B. Beach, Oak Ridge National Laboratory
G.L. Bell, Oak Ridge National Laboratory
Correspondent: Click to Email
An improved plasma enhanced chemical vapor deposition technique has been demonstrated for depositing poly-crystalline silicon thin films for flat panel display applications. The technique combines a high density radio frequency (rf) inductively coupled plasma source with downstream gas injection that has resulted in device quality films deposited at high rates. Unlike conventional rf reactors, inductively coupled sources have high plasma and atomic species density along with low ion energies hitting the film surface during growth. Our system uses a planar induction coil for the plasma coupling that creates a dense hydrogen plasma over a large area (30 cm diameter). The hydrogen plasma serves as a source of large quantities of atomic hydrogen that aid in the deposition process. For better control of the plasma chemistry, silane (100%) is injected downstream, where the precursors needed for film growth are separated from the ionization region. The films are deposited on quartz samples on a heated substrate (< 400 degrees C). The power coupling mechanism (inductive vs. capacitive coupling) has been analyzed by using an rf sensor (located after the matching network) to determine processing conditions favorable for polysilicon growth. Deposition rates increase substantially with the amount of inductive power coupling and reach values of 60-80 nm/min. Increasing the coupled power beyond 1 kW eventually leads to a decrease in the net deposition rate, possibly due to increased etching of the deposited film by the hydrogen. Deposition results show that the conductivity (10@super -7@ S/cm) and the crystallinity (>80% based on the Raman spectrum) of the films are good. Analysis of the X-ray diffraction spectrum shows a highly preferred grain orientation in the <110> plane. Details of the deposition conditions and the power coupling mechanism will be discussed. @FootnoteText@ Research sponsored by the Laboratory Directed Research and Development Program of ORNL, managed by Lockheed Martin Energy Research Corp. for the U.S. Department of Energy under contract no. DE-AC05-96OR22464.