Hydrogen gettering and strain-induced platelet nucleation in tensilely strained Si0.4Ge0.6/Ge for layer exfoliation applications

We show that tensilely strained epitaxial layers getter interstitially dissolved hydrogen and accelerate the nucleation of platelets. Both of these result in subsurface crack propagation leading to surface blistering and eventual exfoliation of a H+-implanted semiconductor surface. In this work, a strained Si0.4Ge0.6 layer was used to enhance the exfoliation kinetics of relaxed Ge/Si1−xGex/Si virtual substrates by gettering hydrogen and providing a preferential nucleation site for platelets. Using platelet morphology and strain relaxation data, a nucleation and growth model was formulated accounting for both chemical and strain energy contributions to the free energy of platelet formation, revealing two kinetically limited growth regimes for platelets in tensilely strained Si0.4Ge0.6 films. Low-temperature (<200°C) annealing nucleates 1011-cm−2 platelets which grow in the strain-limited regime with minimal loss of hydrogen to surface effusion. At 250 °C, platelet growth is diffusion limited, requiring transport of H2 molecules to the strained layer. Subsequent annealing of strained Si0.4Ge0.6/Ge gettering structures at a temperature exceeding 300 °C results in significantly improved surface blistering kinetics over samples which do not contain a gettering layer. Incorporation of tensilely strained layers has the potential of reducing the implantation dose and annealing temperature necessary for layer transfer. Combined with virtual substrate bonding, they provide a promising solution for economical integration of high-performance semiconductors with silicon.