AVS 46th International Symposium
    Electronic Materials and Processing Division Monday Sessions
       Session EM-MoA

Paper EM-MoA4
Inductively Coupled Plasma-Induced Etch Damage of GaN p-n Junctions

Monday, October 25, 1999, 3:00 pm, Room 608

Session: Nitride Processing and Characterization
Presenter: R.J. Shul, Sandia National Laboratories
Authors: R.J. Shul, Sandia National Laboratories
L. Zhang, Sandia National Laboratories
A.G. Baca, Sandia National Laboratories
C.G. Willison, Sandia National Laboratories
J. Han, Sandia National Laboratories
S.J. Pearton, University of Florida
F. Ren, University of Florida
Correspondent: Click to Email
The fabrication of a wide variety of GaN-based photonic and electronic devices depends on dry etching through a p-n junction. Examples of these devices include laser diodes, light-emitting diodes, heterojunction bipolar transistors, p-i-n photodiodes and junction field effect transistors. The majority of dry etching methods used to pattern such devices rely on ion-assisted removal of the substrate material. Due to the relatively high bond energy (8.92 eV/atom) of GaN, the threshold ion energy for the onset of dry etching is typically on the order of 25 eV. Under conditions of both high ion flux and ion energies above this threshold, etch rates > 5,000Å/min are readily achieved for GaN in Inductively Coupled Plasma (ICP) or Electron Cyclotron Resonance (ECR) etch systems. However, under such conditions, the potential for plasma-induced damage is significant. Attempts to minimize such damage by reducing the ion energy or increasing the chemical activity in the plasma often results in a loss of etch rate or anisotropy which significantly limits critical dimensions and reduces the utility of the process for device applications requiring vertical etch profiles. It is therefore necessary to develop plasma etch processes which couple anisotropy for critical dimension and sidewall profile control and high etch rates with low-damage for optimum device performance. In this study, GaN p-i-n mesa diodes were formed by Cl@sub 2@/BCl@sub 3@/Ar etching at different ion energies and plasma fluxes. Reverse bias leakage currents were measured to evaluate damage created during plasma etch. Despite the increase in GaN etch rates observed with increasing ion energy and flux, damage was able to accumulate ahead of the etch front. Techniques to recover device performance will also be discussed. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-ACO4-94AL85000.