Maskless excimer laser induced projection patterning of InP in Cl 2 etch gas

Abstract

A chlorine-based excimer laser (KrF, 248 nm) induced etch process has been developed with focus on etch rate, spatial resolution capability and morphology of etched surfaces. The thermal desorption of spontaneously formed chemical reaction products of Cl 2 on InP during the short laser pulse permits excellent spatial resolution of about 1μm. We demonstrate for the first time maskless micropatterning of a III–V semiconductor by projection etching of micron-wide waveguide structures in InP. Etch rates can exceed those of conventional dry etching processes by a factor of 10 to 20, resulting in processing times which are conveniently short but well controllable due to the pulsed nature of the present process. Regarding surface morphology, the process is apparently sensitive to the laser speckle pattern and etch gas or surface contaminations. However, under proper processing conditions, the influence of both can be sufficiently reduced so that a surface smoothness is achieved comparable to conventional dry etching.