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

Paper TF-ThM4
Hydrogen Concentration Distribution in Plasma Deposited Hydrogenated Amorphous Silicon and Silicon Nitride Films

Thursday, November 5, 1998, 9:20 am, Room 310

Session: Thin Films for Flat Panel Applications
Presenter: B.F. Hanyaloglu, University of California, Santa Barbara
Authors: B.F. Hanyaloglu, University of California, Santa Barbara
D.C. Marra, University of California, Santa Barbara
E.S. Aydil, University of California, Santa Barbara
Correspondent: Click to Email
Understanding H distribution in plasma deposited hydrogenated amorphous silicon and silicon nitride (a-SiN:H) films as well as at the interfaces of these films is important for manufacturing of thin film transistors (TFTs) for flat panel display applications. Hydrogen concentration distribution and bonding in plasma deposited a-Si:H and a-SiN:H thin films were studied using in situ multiple internal reflection Fourier transform infrared spectroscopy in conjunction with in situ spectroscopic ellipsometry. The infrared spectra as a function of time were recorded both during deposition of the film and during etching with CF@sub 4@ plasma. The hydrogen concentrations as a function of depth below the film surface were obtained from the spectra recorded during the deposition and the etching experiments. Analysis of the spectra shows that the H distribution in a-Si:H and a-SiN:H films is surprisingly complex and far from uniform. The a-Si:H film consists of a very thin H rich layer at the surface that is primarily composed of SiH@sub 2@ and SiH@sub 3@. This H-rich surface layer is followed by a few 100 Angstrom thick subsurface region that is depleted in H compared to the bulk film. The bulk a-Si:H film grows beneath these two layers, which move up and stay at the surface during deposition. In a-Si:H deposition, there is evidence that H penetrates into the film through a process other than simple diffusion. We have also investigated H distribution and bonding in a-SiN:H films deposited on a-Si:H and a-Si:H films on a-SiN:H in order to study how the deposition sequence alters the chemical composition and structure of the a-Si:H/a-SiN:H interfaces. Implications of these experimental results on the differences in the peformance of top-gate and bottom-gate configuration TFTs will be discussed.