The Ion Distribution Function in Weakly Collisional Sheaths

Low-temperature, partially ionized plasmas are widely used in the fabrication of VSLI (Very-Large-Scale Integration) circuits. As electronic technology advances and size of integrated circuits dwindles, anisotropy requirement in plasma processing becomes increasingly important. In recent years, high-density, low-pressure plasmas of low collisionality have shown promising characteristics in improving anisotropy in many of the state-of-the-art process tools including ECR (Electron Cyclotron Resonance) devices. In such fabrication tools, the outcome of the process strongly depends on the nature of plasma sheaths located between the bulk plasma and the processed material. A quantitative understanding of plasma sheaths is thus of practical importance in controlling the fabrication processes.