AVS 46th International Symposium
    Thin Films Division Monday Sessions
       Session TF-MoP

Paper TF-MoP15
Process Control and Properties of Aluminum Doped Zinc Oxide Films Deposited by High Rate Mid-frequency Reactive Magnetron Sputtering

Monday, October 25, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: N. Malkomes, Fraunhofer Institute for Surface Engineering and Thin Films, Germany
Authors: N. Malkomes, Fraunhofer Institute for Surface Engineering and Thin Films, Germany
M. Vergöhl, Fraunhofer Institute for Surface Engineering and Thin Films, Germany
B. Szyszka, Fraunhofer Institute for Surface Engineering and Thin Films, Germany
T. Matthée, Fraunhofer Institute for Surface Engineering and Thin Films, Germany
Correspondent: Click to Email
Aluminum doped Zinc oxide films are promising candidates for economic TCO applications. To reach high deposition rates (about 7 nm/s at 4.5 W/cm2) in combination with optimum TCO properties by reactive mid-frequency (MF) sputter technique, the process window has to be precisely controlled. In order to overcome the typical hysteresis problem the process stabilization was done by plasma impedance control for ease of use, enabling to stabilize the deposition process in any working point on the s-curve of the corresponding hysteresis loop. In addition the setpoints were characterized by partial pressure measurements, optical emission spectroscopy (OES), and with in-situ spectroscopic ellipsometry. The influence of deposition parameters (working point, pressure, temperature) on the electrical and optical properties as well as film growth and morphology were studied by photometry, Hall-measurements and in-situ and ex-situ spectroellipsometry, respectively. Due to the bandgap widening the optimum films show neutral color. The ellipsometric spectra could be well modelled without using interface layers indicating the dense structure of the films. Electrical measurement yield that the optimum resistivity of ZnO:Al films deposited on unheated substrates is about 2.5 times higher than at 200°C substrate temperature. In the latter case, a value of 290µOhm cm could be reached. In addition the process window of stoichiometric films is widened due to oxygen partial pressure limited forming of the film on the heated substrate. .