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

Boron tribromide mixed with chlorine, BBr 3 / Cl 2 , 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 BBr 3 / Cl 2 mixtures while maintaining Al / SiO 2 and Al/photoresist etch rate ratios of 33:1 and 15:1, respectively. The achievable selectivities in a conventional mixture of BCl 3 / Cl 2 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 BBr 3 / Cl 2 etching of Al and Al 2 O 3 films. Scanning Auger microprobe analysis was performed on the postetched substrates. A kinetic model is proposed to account for variations between BBr 3 / Cl 2 and BCl 3 / Cl 2 RIE etching of Al and Al alloys.