The growth and physical properties of low pressure chemically vapour-deposited films of tantalum silicide on n+-type polycrystalline silicon

Abstract Bilayer films of tantalum silicide on n + -type polycrystalline silicon prepared by low pressure chemical vapour deposition (LPCVD) were fabricated from SiH 4 and TaCl 5 in a single standard hot-wall LPCVD reactor. The main advantages over conventional co-sputtered films are reduced wafer handling, improved conformal deposition, increased wafer throughput and the use of only one piece of process equipment. Both films of the bilayer structure are deposited at 575°C and annealing is carried out in the deposition reactor at 900°C. The amorphous deposited silicon films were doped in situ with PH 3 . The stoichiometry of the as-deposited tantalumrich Ta 5 Si 3 films is shifted to the desired low resistivity TaSi 2 during the annealing process, in which the additional silicon required is supplied from the underlying polycrystalline silicon. The resistivity of annealed LPCVD tantalum silicide films is 60–70μΩ cm which is comparable with that of films prepared by co-sputtering. The peak-to-valley surface roughness of 30 nm is at present typically a factor of 2 larger than that for co-sputtered films. Wet oxidation experiments indicate that there is no large difference in the thermal SiO 2 formation between LPCVD and co-sputtered tantalum silicide.