CONTACTS TO MONOCRYSTALLINE N-TYPE AND P-TYPE SILICON BY WAFER BONDING USING COBALT DISILICIDE

Contacts to monocrystalline silicon have been prepared by wafer bonding using cobalt disilicide as an interfacial layer. Bonding has been carried out with three different structures: n(+)-CoSi2-(n+), p(+)-CoSi2-p(+) and p(+)-CoSi2-n(+). The intermediate cobalt disilicide layers had a thickness of either 700 Angstrom or 5250 Angstrom. The bonding interface was characterized by electrical measurement (IV) and Secondary-ion mass spectrometry (SIMS) of the formed contacts. The n(+)-CoSi2-n(+) and p(+)-CoSi2-p(+) bondings display an ohmic behaviour. The resistance of the bonded structures was in the range expected for the bulk silicon used (0.1-0.05 Omega cm). The p(+)-CoSi2-n(+) structures shows a non ohmic behaviour. An evaluation of the SIMS profiles reveals that the non-linear behaviour of the p(+)-CoSi2-interface is due to phosphorous diffusion from the n-doped region across the silicide to the p-doped area It is shown that the phosphorous compensates the boron dopant.