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

Abstract

We present an inductively coupled-plasma reactive-ion etching process that simultaneously provides both a high etch rate and unprecedented selectivity for gallium phosphide (GaP) in the presence of aluminum gallium phosphide (Al${}_{\text{x}}$Ga${}_{1-\text{x}}$P). Utilizing mixtures of silicon tetrachloride (SiCl${}_4$) and sulfur hexafluoride (SF${}_6$), selectivities exceeding 2700:1 are achieved at GaP etch rates above 3000 nm/min. A design of experiments has been employed to investigate the influence of the inductively coupled-plasma power, the chamber pressure, the DC bias and the ratio of SiCl${}_4$ to SF${}_6$. The process enables the use of thin Al${}_{\text{x}}$Ga${}_{1-\text{x}}$P stop layers even at aluminum contents of a few percent.

21 pages, 9 figures