Back-to-back substrate wafer bonding: A new approach to the fabrication of double-side coated wafers

Abstract

We present a novel method for fabrication of double side coated wafers by back-to-back Direct Wafer Bonding (DWB). Two 3 inch sapphire wafers (R-cut) were coated each with YBa\(_2\)Cu\(_3\) O\(_{7-\delta}\) by laser ablation on one side. The wafers were then directly bonded with their uncoated sides together in a microcleanroom. Subsequent heating increased the bond energy up to energies sufficient for fabrication of hybrid devices working at cryogenic temperatures. TEM cross sections reveal direct contact of the two sapphire lattices.