Control of axial direction electron temperature distribution by gradient DC magnetic field in inductively coupled plasma

Abstract

A gradient magnetic field was applied in the axial direction of an inductively coupled plasma by controlling the currents of the upper and lower coils of the Helmholtz coil, respectively. This control changed the magnetic field conditions of electron cyclotron resonance (ECR) along the axial position of the chamber. The experiment was conducted under a low-pressure (0.67 Pa) argon discharge with a driving frequency of 60 MHz and radio frequency power of 300 W. The axial distributions of the electron temperature and ion density in the chamber were measured using a floating harmonic probe (FHP). Due to the ECR effect, the electron temperature along the axial direction was controlled by the Helmholtz coil currents. Considering the direction of the planar antenna towards the chamber bias electrode as the positive direction, a higher ion density was observed at a positive gradient magnetic field. The distribution of ion flux on the surface of the bias electrode was measured using a two-dimensional (2D) FHP. Although the gradient magnetic field increased the ion flux, the 2D distribution profile remained unchanged. The variations in electron temperature and ion density under these magnetic field conditions were analyzed using plasma simulations based on the fluid approximation method. The study demonstrates how adjusting magnetic field conditions can enhance ion bombardment energy and etching rates in plasma processing.