AVS 46th International Symposium
    Plasma Science and Technology Division Thursday Sessions
       Session PS2-ThA

Paper PS2-ThA7
Reduction and/or Elimination of Undesirable Topographic Differential Charging Effects in Semiconductor Processing by using Simultaneous Modulation of Source and Wafer RF

Thursday, October 28, 1999, 4:00 pm, Room 609

Session: Pulsed Plasmas
Presenter: N. Hershkowitz, University of Wisconsin, Madison
Authors: N. Hershkowitz, University of Wisconsin, Madison
M.K. Harper, Intel Corporation
B.-W. Koo, University of Wisconsin, Madison
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High aspect ratio features are predicted to exhibit a variety of undesirable effects associated with electron shadowing and the resulting differential charging of dielectrics in semiconductor etching and deposition. Examples include notching in line and space structures, aspect ratio dependent etching, sidewall bowing, microtrenching and charging damage. In agreement with previous work, our experiments with Cl2 plasma etching of poly-Si and C2H2F4 of SiO2 (in a helicon etch tool) have found that modulation of the 13.56 MHz RF source can eliminate topographic charging effects in the absence of RF wafer bias, but fails in the presence of CW RF wafer bias. Data are presented showing that simultaneous source and wafer (on-off) modulation eliminates topograhic-charging effects while preserving the advantages of bias voltage. RF frequency and modulation duty cycle effects are discussed together with discharge mechanisms.