Abstract

A buried conductive layer in silicon has been created using wafer bonding technique, with a cobalt interracial layer. Co-coated silicon wafers were brought into contact with either similar or uncoated wafers at room temperature. CoSt2 was then formed through as01id-phase r action, during an anneal at 700 to 900 ~ A 700 A buried CoSi2-1ayer, with a resistivity of approximately 21 ~ cm, was achieved. Good adhesion, as measured by tensile strength testing, between the wafers was achieved. Transmission electron microscopic investigations (Co-coated wafer bonded to bare silicon) showed that the silicide has not grown into the opposite wafer, and that an amorphous layer exists between the silicide and the silicon surface. The presence of such a layer has been confirmed by electrical characterization. The possibility of having a conductive layer buried in high quality silicon is of great interest for new device con-cepts, both in microelectronics and micromechanical ap-plications. Buried layers made by growing CoSt2 epitax-tally on silicon has been shown to be useful in fabrication of high frequency devices like the permeable base transis-tor 1 and the metal base transistor. 2 It may also simplify the