Stability and spatial characterization of electron cyclotron resonance processing plasmas

Abstract

This paper presents preliminary measurements of the spatial variation of the plasma density, electron temperature, plasma potential, and floating voltage within a divergent magnetic field electron cyclotron resonance (ECR) plasma processing reactor. The measurements are performed using an orbital-motion-limited cylindrical Langmuir probe designed specifically for use in these plasmas. A brief discussion of the stability and uniformity of divergent field plasmas in general, and qualitative techniques for the diagnosis of these properties, is also given. It was found that these plasmas generally occurred in distinct "modes," characterized by unique shapes and dependences on system variables, and between which discontinuous, noisy, and often bistable transitions occurred. Axially resolved probe measurements performed under ECR conditions showed that the plasma density exhibited a broadly peaked profile, while the electron temperature showed a sharp peak at ECR. The differences in these profiles leads to three qualitatively different plasma regions available for use in ECR processing. The variation of the plasma potential explains the origin of the axial ion beams that commonly occur in these systems.