LPCVD of tungsten by selective deposition on silicon

Tungsten has been deposited in a low pressure chemical vapor deposition (LP CVD) system by silicon reduction of WF6. Hydrogen passivation of the silico n was found essential to inhibit native oxide formation on the silicon. A s elf-limiting W thickness of 100 nm was achieved at a deposition temperature of 440 degreesC. A typical layer sheet resistance of 2 Omega/square was ob tained. Layers deposited at higher temperature yielded greater thickness, b ut showed the inclusion of higher resistivity beta phase W. WSi2 also obser ved, indicating solid phase reaction between the silicon and the deposited W. A reduced self-limiting thickness of W was observed when heavily doped s ingle-crystal substrates were employed. This reduction in thickness was als o observed when polycrystalline samples were employed. (C) 2001 Kluwer Acad emic Publishers.