AVS 45th International Symposium
    Manufacturing Science and Technology Group Monday Sessions
       Session MS-MoA

Paper MS-MoA10
Etching and Cleaning of Silicon Wafers using HF Vapor Process in the Non-Condensed Etching Regime

Monday, November 2, 1998, 5:00 pm, Room 317

Session: Contamination Free Manufacturing
Presenter: Y.-P. Han, Massachusetts Institute of Technology
Authors: Y.-P. Han, Massachusetts Institute of Technology
H. Sawin, Massachusetts Institute of Technology
Correspondent: Click to Email
We have studied oxide etching mechanisms of HF vapor etching process in two regimes: the condensed regime (liquid phase) and the non-condensed regime (gas phase). In the condensed regime, the etching rate of oxide is greatly affected by the flow rate of the reactant stream and the total pressure of reactor, which can change the mass transfer rates of both reactants and products. The rate limiting steps of the etch rate have been studied at various conditions by changing the temperature of the reactor, the partial pressure of the reactants and the flow rate. The etching rate of oxide in the non-condensed regime was mainly limited by the surface reaction rate at higher temperature, but the mass transfer rate became more important at lower temperature. We also have investigated the cleaning of Na from silicon wafer in HF vapor process. It was observed that Na contamination on thick thermal oxide films was typically removed by HF vapor process. On thinner oxide films, i.e. 1-2 nm native oxide, only part of the contaminated Na was typically removed by this process. The addition of SiF4 to the HF/H2O process, i.e. HF/H2O/SiF4 was found to improve the cleaning efficiency of Na from silicon surfaces. The volatile product is believed to be Na-OSiF3.