Direct Bonding of Diamond Substrate at Low Temperatures under Atmospheric Condition

A monocrystalline diamond substrate was bonded with a Si substrate employing a direct bonding technique. The diamond and Si surfaces were functionalized with hydroxyl (–OH) groups and subsequently bonded by the thermal dehydration reaction across the bonding interface. When a diamond (111) surface was treated with a mixture of H2SO4 and H2O2, it generated an atomic bond of C–O–Si with an oxygen-plasma-irradiated Si substrate. The bonding technique of diamond using the H2SO4/H2O2 mixture is expected to contribute to the future integration of diamond and semiconductor substrates because it allows low-temperature bonding in atmospheric air with negligible crystallinity damage.