Local Area Materials Processing using a Microstripline-Based Miniature Microwave Discharge

Summary form only given. Miniature discharges and their potential use for local area materials processing are investigated in this study. The objective of this study is to do materials processing steps including etching, surface activation, and plasma-assisted CVD on localized areas by applying a small discharge to only the region being processed. A miniature microwave plasma discharge applicator design based on microstripline technology is applied to create a miniature stream of plasma species. The diameter of the plasma stream considered in this study ranges from 1 millimeter down to 10´s microns. The miniature microwave plasma discharge is created using 2.45 GHz microwave energy inside a 1-2 mm tube with an aperture on the end. Through this aperture the plasma stream for materials processing is formed. The microwave plasma source used in this investigation has a microstripline coupling structure with the discharge created inside 1 mm and 2 mm inner diameter quartz tubes. The microwave energy couples to the discharge via the stripline. The stripline has a characteristic impedance of 50 ohms and is connected to a microwave power supply operating at 1 watt to 100 watts. The discharge tube is orientated perpendicular to the stripline conductor. The characteristics of this discharge have been measured with electron densities in the range of 10¹² to over 10¹⁴ cm^-3 depending on the pressure, power and feed gas composition. Two materials processing applications are investigated including etching and plasma-assisted CVD. Specifically, an argon/SF₆ feed gas mixture is used to create a plasma stream with radicals for silicon etching. And, an argon/methane feed gas mixture is used to create a plasma stream for amorphous carbon deposition. A CAD-guided automated path generation system is developed to assist manufacturing micro-structures/patterns automatically using the micro plasma applicator. Based on the CAD model of a micro-s- ructure/pattern and the model of the microwave plasma source, a path of the plasma applicator can be automatically generated. It is fed to the control system of an xyz positioning stage to generate relative motion between the substrate and the plasma applicator for either etching or plasma-assisted CVD process