Distributed electron cyclotron resonance in silicon processing: Epitaxy and etching

Abstract

The microwave multipolar plasma (MMP) is confined by a multipolar magnetic field and excited by a 2.45 GHz microwave electric field. The distributed electron cyclotron resonance (DECR) excitation uses the confinement magnets to obtain the resonant magnetic field necessary for ECR excitation. The major MMP asset for surface treatment is a substantial ion flux under controlled and low energy (down to a few eV). Unlike conventional ECR, the DECR ion flux onto the substrate is homogeneous and not influenced by magnetic fields. Silicon homoepitaxy by SiH4 DECR is achieved in the 400–800 °C range. The substrate is cleaned by an H2 or Ar plasma before deposition. Control of the ion energy during cleaning and deposition is paramount. Above 600 °C the defect density drops from 1010 to 105 cm−2. N‐type As doped layers are obtained by adding AsH3 to the plasma. The growth rate is almost independent of temperature and doping level. Abrupt As profiles are obtained when the ion impact energy is adjusted to 50 eV. Recent etching work concerns the study of etch rate and anisotropy in the etching of Si and SiO2 by MMP’s of fluorinated gases and halogen mixtures, and the etching of polymers in oxygen‐based MMPs.