Properties of polycrystalline silicon films obtained by rapid thermal processing for micromechanical sensors

The mechanical and structural properties of as-deposited polycrystalline Si films, grown by rapid thermal processing low-pressure chemical vapor deposition at a high deposition rate of 0.4 μm/min on oxidized Si wafer substrates, were investigated using Raman spectroscopy and transmission electron microscopy (TEM) measurements. The effect of high phosphorus doping using a spin-on technique has also been studied for applications in electrically conducting microstructures. The thermal treatment of the samples, with rapid thermal annealing at 1000 and 1050 °C, as well as with furnace annealing at 1000 °C, results in a reduction of the intra-grain defects in the films. Furthermore, spin-on-coated phosphorus was easily incorporated in the films resulting in an effective electrical activation. All films have shown an overall marginal compressive stress of about 20 MPa; however, the SiO2, in pad form, beneath the SOI structures, introduces a small (about 10 MPa) tensile stress. Finally, cantilever and doubly supported beams, of useful length with a deflection, out of the horizontal plane, of less than 0.1 μm, were fabricated using rapid thermal processing compatible with the standard silicon microelectronics technologies.