10 April 1995 Microwave-assisted laser dry etching of silicon
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A combination of microwave excitation and a mask projection scheme is applied for laterally structured etching of silicon. The technology is based on polymerization of an inert overlayer, which protects the silicon surface from the etching gas. After ablating the polymer from the silicon surface with pulsed Excimer laser radiation the surface is exposed to an etching gas atmosphere. Different feed gases have been used, such as CF4, either nonactivated or activated in a microwave discharge. With these etching gases well-defined structures can be achieved with etching rates of 0.1 micrometers /min. Using a gas mixture of CF4 and CCl4 the etching rate can be increased to 1 micrometers /min. smooth etching profiles can be achieved with laser fluences < 0.6 J/cm2. Further, for the Si etching with MMA (methylmethacrylate) polymerization suitable processing variables for these competitive processes are obtained. The deposited polymer films and etched Si surfaces are characterized by ex-situ electron spectroscopies (XPS, AES) and the gas phase reactions are investigated with quadruple mass spectroscopy (QMS). The formation of ClF3 or ClF is discussed as a critical step within the microwave-assisted laser dry etching (MALDE) process. The presence of these species correlates with high Si etch rates.
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Wilhelm Pfleging, Wilhelm Pfleging, Ernst-Wolfgang Kreutz, Ernst-Wolfgang Kreutz, Martin Wehner, Martin Wehner, Friedrich G. Lupp, Friedrich G. Lupp, } "Microwave-assisted laser dry etching of silicon", Proc. SPIE 2403, Laser-Induced Thin Film Processing, (10 April 1995); doi: 10.1117/12.206282; https://doi.org/10.1117/12.206282

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