AVS 46th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM1-ThA

Paper EM1-ThA8
Etching and Cleaning of Silicon Wafers using HF Vapor Process in the Monolayer Etching Regime

Thursday, October 28, 1999, 4:20 pm, Room 608

Session: Chemical Mechanical Planarization
Presenter: H.H. Sawin, Massachusetts Institute of Technology
Authors: Y.-P. Han, Massachusetts Institute of Technology
H.H. Sawin, Massachusetts Institute of Technology
Correspondent: Click to Email
We have studied the oxide etching mechanisms of a gas phase HF etching process in a condensed (liquid phase) and a 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. In the non-condensed regime, the oxide can be etched in both multilayer and monolayer adsorption states depending on process conditions. The gas phase mass transfer rate limits the etching rate in the multilayer adsorption regime while surface reactions are the rate limiting step in the monolayer regime. The rate limiting steps for etching have been studied at various conditions by changing the temperature of the reactor, the partial pressure of the reactants and the flow rate. In the monolayer etching regime, the etching kinetics can be described by a Langmuir-Hinshelwood adsorption mechanism with competitive adsorption between HF and water. The monolayer etching regime shows many advantages over other etching regimes. We have observed a smoother etched oxide surface, a low selectivity against TEOS, and uniform etching over entire 4" wafer. The native oxide grown on the silicon wafer is removed within a minute, as confirmed by contact angle measurement and XPS. Additionally, aluminum lines are not etched or corroded in the monolayer regime, which implies this process can be applied to metal layers. Since there is no condensed layer on the wafer and chamber wall, the pumping speed is rapid enough for use in a vacuum cluster tool under a hard vacuum environment. We believe that the monolayer HF vapor etching process is applicable to in situ contact cleaning and in situ polymeric residue removal process on metal layers.