We have observed that wafer splitting from hydrogen ion implantation into s
ilicon after low temperature direct bonding creates an expunged film with a
surface roughness that is similar to 1 nm (RMS). This result is an order o
f magnitude smoother than the previous work (similar to 10 nm RMS). The key
improvement is the use of low temperature bond in our work resulting in a
strong bond far below the cut temperature. The smooth as-split surfaces pro
duced using a:low temperature bond are very important for creation of very
thin (<50 nm) silicon-on-insulator (SOI), three-dimensional bonded structur
es and nanostructures that are split after processing.