Through wafer via hole by reactive ion etching of GaAs

Through wafer via hole connection has found applications in photonic and microelectronic devices. Such vias provide higher packing densities, improved gain and simplified device layout. In this paper, reactive ion etching of GaAs via hole has been systematically studied using CCl₂F₂ as the reactive gas. The effects of process pressure and r.f. power on the etch rate and the resultant etch profiles have been investigated. It was found that the etch rate increased linearly with the increase of process pressure for values below 50 mTorr. The process pressure had a significant influence on the etch profiles. At low process pressure, anisotropic profiles were observed. The etch rate increased as the r.f. power was increased due to the increased excitation of reactive species as well as higher ion energies and improved sputter desorption of the etch products. Reproducible, and good etch profiles with etch rate as high as 1.55 μm/min could be obtained at a process pressure and r.f. power of 50 mTorr and 150 W, respectively. Devices have been successfully fabricated which employed the via hole process developed in this study. The via hole connections for the grounding were found to be working very well as confirmed by DC measurements.