Mechanically induced Si layer transfer in hydrogen-implanted Si wafers

Abstract

Mechanically induced layer transfer of single-crystal silicon by hydrogen ion implantation, low-temperature wafer bonding, and subsequent mechanical splitting of the implanted wafer has been investigated. The bond strength measurements using the crack opening method in room environment yield a surface energy of ⩾2000 mJ/m2 after exposure to oxygen plasma and subsequent hydrophilic silicon/silicon dioxide bonding at 200 °C. Mechanically induced layer transfer was carried out for silicon wafers implanted to a dose of 5×1016 H2/cm2 at 100 keV and annealed for 2 h at 200 °C. No feature was observed by atomic force microscopy (AFM) measurements on the unbonded free surface after this heat treatment. For lower doses of implantation, annealing at higher temperatures is required to enable the mechanical transfer. AFM measurements on the split silicon surface indicate that low-temperature wafer bonding and mechanical transfer yield a root mean square surface roughness of 4 nm which is less than in the standard Smart-Cut® process.