IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Wednesday Sessions
       Session PS-WeA

Paper PS-WeA2
Monitoring Plasma-Wall Interactions During Etching of Thin Film Stacks

Wednesday, October 31, 2001, 2:20 pm, Room 104

Session: Plasma Surface Interactions II
Presenter: S.J. Ullal, University of California, Santa Barbara
Authors: S.J. Ullal, University of California, Santa Barbara
H. Singh, Lam Research Corporation
J. Daugherty, Lam Research Corporation
V. Vahedi, Lam Research Corporation
E.S. Aydil, University of California, Santa Barbara
Correspondent: Click to Email
Surface reactions on plasma etching reactor walls affect the species concentrations in the discharge and plasma properties such as electron temperature and ion flux. Despite the importance of plasma-wall interactions, reactions occurring on surfaces in contact with the plasma are poorly understood and wall conditions are uncontrolled during etching. Often, a stack of thin films of different materials must be etched sequentially in the same reactor using different gases. Complex multi-layered films are deposited on the chamber walls during the etching of the stack and interaction between successive etching steps through the changing wall conditions may have deleterious effects. Thus, it is critical to monitor the wall conditions and the nature of the films and adsorbates that are deposited on the walls. We have developed a surface probe based on in situ multiple total internal reflection Fourier transform infrared (MTIR-FTIR) spectroscopy as a diagnostic to monitor the films and adsorbates on the walls of an inductively coupled plasma etching reactor. Using this probe we studied the shallow trench isolation etching of Si where a photoresist patterned stack of anti-reflection coating, Si@sub 3@N@sub 4@, SiO@sub 2@ and Si is etched sequentially using gases as varied as fluorocarbons, Cl@sub 2@, HBr, and O@sub 2@. During the fluorocarbon etching of Si@sub 3@N@sub 4@ and SiO@sub 2@, fluorocarbon films deposit on the chamber walls. During the subsequent etching of Si by Cl@sub 2@/O@sub 2@, etch products such as SiCl@sub x@ react with the O in the plasma and deposit a silicon oxychloride layer on the reactor walls on top of the fluorocarbon layer. In order to maintain etching reproducibility, these multi-layered films must be cleaned before the next wafer is etched in the chamber. Reactions occurring on the wall surfaces and strategies to remove these complex multi-layered films to maintain reproducibility of wall conditions and etching processes will be discussed.