Correlation of plasma properties and etching performance in a 25-cm diameter microwave multi-cusp ECR plasma reactor

Microwave electron-cyclotron-resonance (ECR) plasmas are of considerable interest for etching because of their ability to attain directional etching with low ion energies. Advantages of low ion energies include a reduction in damage to the wafer and the potential to achieve high degrees of etching selectivity. Significant issues remain concerning the scale-up of the plasma reactor to improve etching performance over large area substrates. This study is concerned with an investigation of the correlation between plasma properties and etching performance in a multi-cusp ECR reactor with a 25-cm diameter plasma confinement area. Specifically this paper will discuss the argon plasma density distribution in the vicinity of the wafer processing region with the presence of a 19-cm diameter wafer holder. Results are compared to argon plasma characterization results reported earlier in the absence of the wafer holder. Additionally, the variation of plasma potential and incident ion energy with and without the substrate holder will be described. Both single and double Langmuir probe measurements are used to evaluate the plasma distribution and a multi-grid energy analyzer is used to measure the ion energy. Silicon etching is studied as a function of pressure using an SF
₆
/Ar discharge excited at 2.45 GHz. Plasma properties are measured as a function of radial position and will be compared with the etching performance, including etch rate and etch-uniformity, for multiple 3-inch and single 5-inch diameter wafers.