Photoenhanced reactive ion etching of III-V nitrides in BCl3/Cl-2/Ar/N-2 plasmas

Gallium nitride (GaN) and boron nitride (BN) are known as superior semicond uctor materials for UV optoelectronic and high power, high temperature appl ications. As a result of their high molecular bond strength these materials are extremely difficult to etch. In this article, reactive ion etching (RI E) tests were performed on GaN and BN thin films using respectively BCl3/Cl -2/Ar and Cl-2/Ar chemistries. In order to improve the etch rates at lower rf powers and thus reduce ion bombardment-induced damage, a photoassisted R IE process was investigated. The same plasma chemistries in combination wit h a xenon are lamp were utilized. In an attempt to minimize surface nitroge n depletion, N-2 was used instead of Ar as dilution gas. Photoenhancement w as observed for both GaN and BN etching. As expected, the etch rate increas ed with rf power for both unassisted and photoassisted etching conditions. The combination of illumination and N-2 led to a nitrogen-rich surface for GaN. In the case of BN, photoassisted etching in Ar resulted in a slightly lower surface nitrogen depletion. Chlorine was also detected on both etched GaN and BN films under illumination at a content of less than 1.7% and 2.5 %, respectively. (C) 1999 American Vacuum Society. [S0734-2101(99)20704-X].