Fabrication of silicon-on-diamond substrate with an ultrathin SiO2 bonding layer

We proposed and demonstrated a sputter etching method to prepare both a flat surface (root-mean-square surface roughness of approximately 0.2-0.3 nm) and an ultrathin SiO2 bonding layer at an accuracy of approximately 5 nm in thickness to fabricate a silicon-on-diamond substrate (SOD). We also investigated a plasma activation method on a SiO2 surface using various gases. We found that O-2 plasma activation is more suitable for the bonding between SiO2 and Si than N-2 or Ar plasma activation. We speculate that the concentration of hydroxyl groups on the SiO2 surface was increased by O-2 plasma activation. We fabricated the SOD substrate with an ultrathin (15nm in thickness) SiO2 bonding layer using the sputter etching and O-2 plasma activation methods. (C) 2018 The Japan Society of Applied Physics.