Thermal Evolution of Surface Blistering and Exfoliation in Hydrogen-Implanted Germanium with Post-Annealing Treatments

Hydrogen-induced surface blistering and exfoliation have become more useful index in assessing the mechanisms involved in the process of layer transfer in various semiconductor materials. This study focused specifically on determining the behaviors of germanium blistering and exfoliation induced by hydrogen molecular ion implantation. Germanium substrates were implanted with 200 keV H2+ ions to a fluence of 2.5 × 1016 ions/cm2 before undergoing furnace annealing (FA) treatments. Quantitative analysis using optical microscopy (OM) revealed a thermal evolution of optically-detectable blisters and craters, suggesting an optimal condition of 410°C, 1 hr. The mechanisms involved in the development of hydrogen blisters in germanium were also evidenced by hydrogen redistribution and microstructure evolution caused by thermal annealing. The measured effective activation energy levels necessary for blister and crater formation showed a noticeable increase in magnitude as compared to the previous result, which may be attributed to dose-dependent activation energy. Furthermore, in order to determine the effectiveness of the layer-splitting process at various post-annealing temperatures, characteristic time was defined based on the time evolution of the covered-area fraction of blisters and craters. The results indicated that a higher post-annealing temperature corresponds to a shorter characteristic time.