Design and simulation of a microwave powered microplasma system for local area materials processing

A microwave powered microplasma source is developed and tested for materials processing on spatially localized areas. A small diameter stream of plasma (less than 2 mm in diameter) is created by focusing microwave energy inside a discharge tube. The discharge then flows out the end of the tube onto the surface being processed delivering ions and reactive radicals. The diameter of the plasma stream from the tube to the material being processed can be controlled by an aperture mounted at the end of the tube. The spot size of the localized plasma stream ranges from 2 mm down to 10's micrometers depending on the aperture size. The discharge is created by using 2.45 GHz microwave energy that is coupled into the discharge using a small foreshortened cylindrical cavity that has a hollow inner conductor and a small capacitive gap at the end of the cavity. A processing gas mixture is fed through a 2 mm inner diameter quartz tube which is located inside the hollow inner conductor of the cavity. This tube is exposed to a high electric field at the small gap end of the cavity thus generating a surface wave plasma. The length of the surface wave discharge in the tube can be extended by increasing the microwave power to the discharge so that the plasma reaches the aperture. The operating pressures range from 0.5 Torr to 100 Torr and the microwave power utilized ranges from a few Watts to 10's Watts.;Several properties of the discharge including plasma power density, electron density and electron temperature are measured. The power densities of argon and Ar/O2 plasma discharges vary from 10's to over 450 W/cm 3. The plasma density and electron temperature of argon discharges are measured using a double Langmuir probe placed in the materials processing area. The plasma densities are in the range of 1011 -- 1013 cm-3.;Computational modeling of the plasma discharge and the microwave excitation of the discharge is performed using a finite element analysis. The goal of the modeling study is to complement and understand the design, development and operation of the microwave powered microplasmas. A self-consistent model of the foreshortened cylindrical cavity and plasma discharge is presented with results compared to experimental measurements.;The microplasma system is incorporated into a micromanufacturing system that integrates the plasma source with an atomic force microscope for surface measurements and nanomanipulation of the surface. Selected applications of the micromachining system demonstrated include using the microplasma as a spatially localized etcher, free radical source, and ultraviolet light source. Silicon and ultrananocrystalline (UNCD) diamond etching is performed using Ar/SF6 and Ar/O2 discharges, respectively, with etching rates of 0.2 -- 2 mum/min and 0.6 -- 2 mum/hr. Localized removal of photoresist is done by using the microplasma as a free radical source and photoresist is exposed to ultraviolet light from the microplasma source to create spatially localized patterns.