Reactively sputtered aluminum nitride in GaAs processing

Abstract

Reactively sputtered aluminum nitride (AlN) has been investigated as a manufacturable method of preventing surface etching and damage while minimizing surface state density on GaAs based electronic devices. Deposition conditions to obtain a film with high selectivity to fluorine etch chemistries were broad, however other preferred characteristics such as low film stress required optimization of the process conditions related to the deposition equipment. Using AlN as an etch stop during critical PECVD oxide or nitride reactive ion etches resulted in measurable device performance improvements. Most notable were a reduction in transient behavior and a reduction in across wafer variation of many device and process control monitor parameters. The AlN module process capability was further enhanced by the development of a robust wet etch removal. A high flow diluted NH 4OH was found to completely remove all AlN despite possible film changes. These compositional changes and reactions with oxide dielectrics were found to occur depending upon the type of applications.