Argon plasma uniformity in a low-pressure inductively coupled plasma source with planar coil

摘要

Summary form only given. Plasma uniformity is crucial for material processing applications. We report the results of experimental and theoretical studies of the influence of different factors on uniformity of low pressure Argon plasmas sustained by an RF inductive electric field from a planar coil. Two different experimental studies have been performed. In the first, 2-D spatial profiles of light emission intensity and plasma density were measured in an ICP driven by a 3.5 turn spiral coil placed on the top of a cylindrical plasma volume of radius R=11.5 cm and height L=14 cm. Significant changes in the emission profile were observed as pressure was varied from 10 to 100 mTorr, and power from 100 to 200 Watts. In the second study the effects of aspect ratio (R/L) on plasma density profile were examined in an ICP system with a single-turn circular antenna of radius 14 cm, chamber radius R=17 cm and the pressure range 5-20 mTorr. A shift in plasma density maximum from on-axis to a radial position near the antenna location was observed when L varied from 12 to 2.5 cm. The numerical model contains different modules which solve Maxwell equations for RF inductive field, Poisson equation for space charge density, fluid equations for ion density and Boltzmann equation for electron distribution function (EDF) in the two-term approximation.