Ž . Applied Surface Science 156 2000 76–84 www.elsevier.nlrlocaterapsusc High selectivity Inductively Coupled Plasma etching of GaAs over InGaP D.C. Hays a , H. Cho a , J.W. Lee b , M.W. Devre b , B.H. Reelfs b , D. Johnson b , J.N. Sasserath b , L.C. Meyer c , E. Toussaint c , F. Ren c , C.R. Abernathy a , S.J. Pearton a, ) a Department of Materials Science and Engineering, UniÕersity of Florida, P.O. Box 116400, 132 Rhines Hall, GainesÕille, FL 32611, USA b Plasma Therm, St. Petersburg, FL 33716, USA c Department of Chemical Engineering, UniÕersity of Florida, GainesÕille, FL 32611, USA Received 15 July 1999; accepted 21 August 1999 Abstract The dry etch selectivity of GaAs over InGaP in BCl rSF discharges with additives of He, Ar, or Xe under Inductively 3 6 Coupled Plasma conditions was examined. Selectivities over 200 were achieved in BCl rSF or BCl rSF rHe at low ion 3 6 3 6 energies and moderate ion fluxes. The mechanism for achieving selective etching was studied with Electron Spectroscopy for Chemical Analysis, and is due to formation of non-volatile InCl and InF reaction products. The key to achieving high X X selectivity is to minimize sputter-induced desorption of these reaction products. Ion-induced damage in the InGaP was also minimized at low ion energies and moderate ion fluxes. q 2000 Elsevier Science B.V. All rights reserved. Keywords: GaAs; InGaP; Inductively Coupled Plasma 1. Introduction In Ga P is lattice-matched to GaAs and has 0.5 0.5 many attractive properties compared with AlGaAs, which forms the other major lattice-matched het- erostructure with GaAs. InGaPrGaAs has a larger Ž . valence band discontinuity D E s 0.3 eV , leading V to improved carrier injection efficiency in hetero- junction bipolar transistors, lower densities of DX centers, lower surface recombination velocity, and is w x less prone to oxidation 1–21 . These attributes are ) Corresponding author. Tel.: q 1-352-8461086; fax: q 1-352- 8461182. Ž . E-mail address: spear@mse.ufl.edu S.J. Pearton . attractive not only for HBTs, but also for high Ž . w x electron mobility transistors HEMTs 4–19 . The InGaAlP system as a whole displays a wide Ž . range of bandgaps from In Ga P 1.9 eV to 0.5 0.5 Ž . Ž . Al Ga In P 2.3 eV suitable for visible X 1yX 0.5 0.5 w x light-emitting diodes and lasers 20,21 . In the fabrication of all of these devices, a critical step is the formation of mesas by selectively etching GaAs and stopping at an underlying InGaP layer. Ž . High selectivity ) 100:1 is possible for GaAsrIn- w x GaP with wet chemical etch solutions 22 , but cre- ation of small lateral dimension devices requires dry etching for acceptable pattern transfer. While con- Ž . ventional reactive ion etching RIE can produce Ž . good selectivity ) 100 , the high ion energies in- Ž . volved typically G 200 eV create damage in the 0169-4332r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0169-4332 99 00363-3