Microwave plasma etching of silicon and silicon dioxide

Abstract

Summary form only given. Studies are being conducted on the etching characteristics of silicon and silicon dioxide in a microwave plasma etching system, having a pulse modulated microwave source. The source can be adjusted for varying pulse widths and duty cycles. A slotted waveguide is used to radiate the microwaves from the source into a quartz chamber, where the process gas (a mixture of sulfur hexafluoride and oxygen) is ionized. Magnetic field coils around the quartz chamber set up a condition of electron-cyclotron resonance inside the chamber so that more efficient ionization can occur. The resulting plasma flows out of the bottom of the chamber and onto a biased platform where the silicon samples are placed. Etch characteristics that are being examined include etch rate, etch anisotropy, and etching selectivity between silicon and silicon dioxide. Etch rate may be affected positively by pulse modulation of the discharge. Possible reasons for this effect are a reduction in the amount of reaction products remaining on the surface during pulse modulated etching or an increased electron density in the plasma, which leads to greater ionization and dissociation of the neutral particles in the plasma