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Scheme of mechanical cleavage transfer of Si onto glass with SU-8 as a bonding and stress-induced layer. (a) Annealing the SU-8 bonded wafers at for to initiate the crack at edge of bonded substrate, and (b) cleavage propagation. Figures shown are the optical micrographs (top) and cross-sectional sketches (bottom).
Transferred thickness of the donor wafers versus distance beyond the initiated crack front: (A) (100) Si [●], (B) (111) Si [엯], and (C) [▵]. Optical micrograph pairs shown are the donor wafer (top) and handle wafer (bottom).
Specimen and crack geometry used for (a) Drory’s analysis and (b) present analysis. is the thermal residual stress in the film due to thermal expansion mismatch. is the bending moment due to thermal mismatch between two substrates and the film. The substrate bending moment between glass and silicon substrate tends to constrain the bending moment due to stress in film, resulting in a smaller shear mode contribution to crack propagation mechanism.
Comparison of -dependent transferred thickness of the donor wafers based on normalized experimental values and the prediction using the criterion. The uncertainties due to the elastic moduli are from reported values obtained from literature (Ref. 16–18 ). The error bars of the transferred thickness are the uncertainty of the measurement taken from 2 to 5 measurements.
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