Abstract
This study reports a systematic investigation on a new method and mechanism to eliminate surface microdefect-degraded strength of silicon through nanotexturing at the silicon surface. The unavoidable occurrence of microdefects in silicon wafers increases the probability of catastrophic fracture of silicon-based devices, thus highlighting the need for a strengthening mechanism to minimize fractures resulting from defects. In this study, a novel mechanism for manufacturing silicon wafers was engineered on the basis of nanoscale reinforcement through surface nanotexturing. Because of nanotexturing, different defect depths, which were synthetically emulated as V-notches, demonstrated a bending strength enhancement by factors of 2.5, 3.2, and 6 for 2-, 7-, and 14-µm-deep V-notches, respectively. A very large increase in the number of fragments observed during silicon fracturing was also indicative of the strengthening effect. Nanotextures surrounding the V-notch reduced the stress concentration factor at the notch tip and became saturated as the nanotexture depth approached 1.5 times the V-notch depth. The stress reduction at the V-notch tip, as measured by micro-Raman spectroscopy, revealed that nanotextures reduced the effective depth of the defect. Therefore, the nanotextured samples were able to sustain a larger fracture force. The enhancement in Weibull modulus, along with an increase in bending strength in the nanotextured samples compared to polished single-crystal silicon (sc-silicon) samples, also demonstrated the reliability of the strengthening method. These results suggest that this method may be suitable for industrial implementation. This nanotexturing methodology was successfully implemented and demonstrated for achieving the high rupture resistive solar cells and rollable silicon IC wafers.