AVS 45th International Symposium
    Thin Films Division Monday Sessions
       Session TF-MoA

Paper TF-MoA8
Surface Stress in Silicon Oxide Layer made by Plasma Oxidation with Applying Sample Bias

Monday, November 2, 1998, 4:20 pm, Room 310

Session: Mechanical Properties of Thin Films
Presenter: M. Kitajima, National Research Institute for Metals, Japan
Authors: A.N. Itakura, National Research Institute for Metals, Japan
T. Kurashina, University of Tsukuba, Japan
T. Narushima, University of Tsukuba, Japan
M. Kitajima, National Research Institute for Metals, Japan
Correspondent: Click to Email
We present the evolution of surface stress during plasma oxidation of Si(100) with applying bias voltage from -60V to +60V to the sample. The experiments were performed in a UHV condition. Oxide thickness was controlled from 0 to 3nm. The sample was a cantilever of Si(100) of dimensions 450µm x 50µm x 4µm. The bending of the lever due to stress was detected as a function of the oxidation time by a change in the reflection angle of laser beam from lever backside. Stress was calculated from the lever deflection using Stony's formula. The plasma was generated by RF discharge of oxygen gas at 13.56MHz. There has been observed three stages in the stress vs. time curve for the plasma oxidation of Si cantilever without applying sample bias. The first stage was rapidly building up of tensile stress and the second stage was the tensile stress decreasing slowly. In the last stage the stress changed to compressive. For the cases of oxidation with applying bias to the samples, stress curves showed different time dependence from that without bias. First, the stress curve showed a quick build-up of compressive stress, followed by a tensile stress formation, and the stress gradually changed to compressive one with further oxidation. The similar feature appeared in the curves with positive biases and negative biases. The stress values were not unique at same thickness but strongly depended on a bias voltage. We will discuss these stress changes in terms of the interface structure of silicon-oxide layer and silicon substrate.