An improved apparatus for bonding semiconductor structures includes equipment for treating a first surface of a first semiconductor structure and a first surface of a second semiconductor structure with formic acid, equipment for positioning the first surface of the first semiconductor structure directly opposite and in contact with the first surface of the second semiconductor structure and equipment for forming a bond interface between the treated first surfaces of the first and second semiconductor structures by pressing the first and second semiconductor structures together. The equipment for treating the surfaces of the first and second semiconductor structures with formic acid includes a sealed tank filled partially with liquid formic acid and partially with formic acid vapor. Opening an inlet valve connects the tank to a nitrogen gas source and allows nitrogen gas to flow through the tank. Opening an outlet valve allows a mixture of formic acid vapor with nitrogen gas to flow out of the tank. The mixture is used for treating the surfaces of the first and second semiconductor structures.