Reactive Ion Etching of Aluminum/Silicon in BBr3 / Cl2 and BCl3 / Cl2 Mixtures

Abstract

Boron tribromide mixed with chlorine, , a novel gas mixture for dry etching of Al and Al alloys, has been studied in a hexagonal cathode reactive ion etching system. Etch rates, selectivities, profiles, and linewidth loss were determined as a function of feed gas composition, dc self‐bias, and reactor load in a Box‐Behnken experimental design. Response surface analysis indicates a window exists in the experimental parameter space where significant improvements in selectivity can be achieved without sacrificing anisotropic profiles. For example, anisotropic etching can be achieved with mixtures while maintaining and Al/photoresist etch rate ratios of 33:1 and 15:1, respectively. The achievable selectivities in a conventional mixture of were 13:1 and 2.5:1 for comparable anisotropic etching. Optical emission and mass spectrometry measurements were used to aid in an investigation of the kinetics of etching of Al and films. Scanning Auger microprobe analysis was performed on the postetched substrates. A kinetic model is proposed to account for variations between and RIE etching of Al and Al alloys.