Undoped Polycrystalline Si Research Articles

Crystallized Si films by low-temperature rapid thermal annealing of amorphous silicon

Low-temperature rapid thermal annealing has been used to crystallize both undoped and doped amorphous silicon (a-Si) films deposited at low temperatures. The polycrystalline films produced are completely crystallized with time temperature budgets such as 4 min at 700 °C. Unlike deposited polycrystalline Si films, the grain size in these crystallized films is not limited by film thickness. In the case of undoped a-Si films crystallized by this approach, the resulting conductivity is comparable to that achieved in undoped polycrystalline Si films produced by much higher processing temperatures. In the case of doped a-Si films, the resulting crystallized film yields a conductivity of 160 S/cm, a value which is comparable to the highest reported for doped polycrystalline and microcrystalline silicon. These doped films are found to have mobility values of ∼13 cm2/V s.

Dopant effect on intrinsic diffusivity in nickel silicide.

The effect of P on the diffusivity of Ni and Si in ${\mathrm{Ni}}_{2}$Si has been studied by analyzing the growth kinetics of ${\mathrm{Ni}}_{2}$Si on P-doped and undoped polycrystalline Si films using W markers. The growth of ${\mathrm{Ni}}_{2}$Si during the reaction of Ni and the P-doped Si films is faster than that of Ni and the undoped Si films. Marker analysis showed that the dopant does not affect the activation energies of diffusion; rather it increases greatly the preexponential factor of the diffusion of Si. The dopant effect has been examined in terms of the correlation factor and the entropy factor.

Characterization of short-range leakage currents in undoped polycrystalline Si by means of capacitance-voltage measurement

Metal-oxide-semiconductor capacitors with undoped polycrystalline Si (polysilicon) electrodes were studied and a model was developed to explain the voltage and frequency dependence of the capacitance and serial resistance. The model assumes random distribution of leaky paths in the polycrystalline Si layer which supply the charge to the polysilicon-oxide interface.

Implantation of carbon to stabilize TiSi 2 during thermal annealing

Vacuum annealing of TiSi 2 on undoped polycrystalline Si at temperatures above 850°C resulted in erosion of the polycrystalline layer and growth of large Si-crystallites in the silicide film. We found that Si grain growth and degradation of TiSi 2, can be greatly reduced by implanting carbon into the silicide film. The improvement of the thermal stability of TiSi 2 is attributed to strengthening the silicide film by second phase particles rather than reducing the mobility of Si in the silicide matrix.

Electrical characteristics of fast radiatively processed titanium silicides thin films

A fast radiative processing technique using quartz-halogen tungsten lamps is employed for the formation of titanium silicides on either high purity single crystal or undoped polycrystalline Si substrates. Characterization techniques such as four-point probe, x-ray diffraction, SEM, and backscattering spectrometry (BS) show complete TiSi2 formation after 17 s exposure to 18 W/cm2 radiation. Electrical characterization was performed by galvanomagnetic measurements. The results show a metallic and highly conductive silicide whose resistivity varies linearly with temperature in the temperature interval from 80 to 300 K. Films grown on (111) oriented single crystals and (110) textured polycrystalline Si showed both electrons and holes, with the holes as the predominant carriers at low temperature.

Selective Reactive Ion Beam Etching of SiO2 over Polycrystalline Si

Reactive ion beam etching experiments have been performed on and polycrystalline Si using , , and . The etch rate for using ions generated from fluorocarbon gases is enhanced over the rate obtained using argon ions, whereas the etch rate for Si is suppressed. Etch rates for thermal, LPCVD, and “Nitrox” oxides, and phosphorus‐doped and undoped polycrystalline Si are compared. LPCVD etches slightly faster than the other types of oxides while doped and undoped polycrystalline Si show little difference in etch rate. etch rates of greater than 600 Å/min have been observed with selectivities over Si of 6:1. The anisotropy of this technique is demonstrated by the formation of 0.5 μm diam contact windows in a 1 μm thick layer of on single crystal Si.