Highly selective dry etching of GaP in the presence of Al$_ extrm{x}$Ga$_{1- extrm{x}}$P

摘要

We present an inductively coupled-plasma reactive-ion etching process thatsimultaneously provides both a high etch rate and unprecedented selectivity forgallium phosphide (GaP) in the presence of aluminum gallium phosphide(Al$_\textrm{x}$Ga$_{1-\textrm{x}}$P). Utilizing mixtures of silicontetrachloride (SiCl$_4$) and sulfur hexafluoride (SF$_6$), selectivitiesexceeding 2700:1 are achieved at GaP etch rates above 3000 nm/min. A design ofexperiments has been employed to investigate the influence of the inductivelycoupled-plasma power, the chamber pressure, the DC bias and the ratio ofSiCl$_4$ to SF$_6$. The process enables the use of thinAl$_\textrm{x}$Ga$_{1-\textrm{x}}$P stop layers even at aluminum contents of afew percent.