Apparatus and method for shielding a wafer from charged particles during plasma etching

Abstract

A plasma etching system having a wafer chuck with a magnet that applies a magnetic field over a wafer to shield the wafer from charged particles. The magnetic field is parallel with the wafer, and is strongest near the wafer surface. The magnetic field may be straight, or circular. In operation, electrons are deflected from the wafer by the Lorentz force, the wafer acquires a positive charge, and ions are deflected by electrostatic repulsion. Neutral species are allowed through the magnetic field, and they collide with the wafer. Neutral species generally provide more isotropic and material-selective etching than charged particles, so the present magnetic field tends to increase etch isotropy and material selectivity. Also, the magnetic field can protect the wafer from seasoning processes designed to clean unwanted films from the chamber surface as seasoning processes typically rely on etching by charged particles.

Dependencies are inferred from the claim text.