Investigation of hydrogen implantation-induced blistering in SiGe

Abstract

A systematic investigation of the hydrogen implantation-induced blister formation on the surface of Si 0.78Ge 0.22 when annealed in the temperature range of 300–700 °C was carried out. The strain-relaxed Si 0.78Ge 0.22 layers were grown epitaxially on 8-inch Si(1 0 0) substrates by reduced pressure chemical vapour deposition (RPCVD). These wafers were implanted with hydrogen, H 2 +, ions at 240 keV with a dose of 5 × 10 16 cm −2. The formation of optically detectable blisters on the surface was observed using an optical microscope in Nomarski contrast mode. The width and depth of the blisters was determined with a profilometer. The characterization of the hydrogen implantation-induced damage and defects inside the Si 0.78Ge 0.22 layer was performed using cross-sectional transmission electron microscopy (XTEM). The Arrhenius plot of blistering time versus annealing temperature revealed two different activation energies for the formation of blisters. In the low temperature regime (300–400 °C) an activation energy of 1.2 eV was obtained, while in the high temperature regime (400–700 °C) the activation energy was 0.38 eV. In analogy to the case in Si, the lower activation energy can be associated with the free atomic diffusion of hydrogen in Si 0.78Ge 0.22 and the higher activation energy can be related to the hydrogen diffusion limited by trapping-detrapping phenomena. The depth of the broken blisters and the depth of the hydrogen-induced microcracks inside Si 0.78Ge 0.22 came out to be around 1.05 μm, which matches quite well with the calculated (by Stopping and Ranges of Ions in Matter, SRIM code) concentration peak of the hydrogen distribution inside Si 0.78Ge 0.22 for the case of 240 keV H 2 + implantation.