Improvement in GaAs Device Yield and Performance through Substrate Defect Gettering
Abstract
The use of mechanically-produced, back-surface damage as a means of gettering impurities and defects in GaAs wafers has been investigated. Comparative analyses have been done on both ion implantation and mechanical back-surface-damage-gettering techniques. The increased thermal stability of mechanically-produced damage has shown ion-implantation techniques to be less effective for gettering over long anneal periods at elevated temperatures. Stress gradients produced by graded dislocation distributions produce reductions in front-surface defect concentrations and effective gettering of Au and Cr at the back surfaces. Thermal stability times of back-surface damage at anneal temperatures of 700-800 C is typically on the order of 2 - 3 hours, corresponding to the point at which major back-surface microstructural damage is largely annealed. Increases in the thermal-stability period were attained by encapsulating the back surface with an As-doped SiO2 layer. Gettering of Cr by back-surface damage was also investigated at low temperatures (300 C - 400C) for anneal periods of 10 - 300 hrs. Measurable concentrations of Cr were detected with the process characterized by an activation energy of approximately 0.88 eV and a time-dependent term, exp (theta square root of t). Using the developed gettering procedures, FET structures were fabricated on VPE layers on pre- gettered GaAs wafers. Dramatic improvements in yield per wafer, noise figures at higher frequencies and input capacitance values were obtained on 'inscreened' wafers processed through a normal fabrication line.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1980
- Accession Number
- ADA087712
Entities
People
- Jing Peng
- M. Malbon
- R. A. Armistead
- R. Ormond
- T. J. Magee