Demands for polycrystalline Si(poly-Si) are increasing for the application to electronic devices like thin film transistors(TFTs), solar cell and image sensors. Poly-Si thin films are generally fabricated by crystallizing amorphous Si(a-Si) because larger grains and smoother surfaces can be attained compare to direct deposition of poly-Si films. But sold phase crystallization generally takes tens of hours to crystallize a-Si at 600℃. The crystallization temperature has been lowered by annealing a-Si films in contact with various metals such as Au, Ag, Cu, Ni, Al, Pd, . And some metals, for example Ni and Pd, enhance the lateral crystallization of a metal free a-Si region , called silicide mediated lateral crysatallization.
In our study Ni was supplied by metal solution using the mixture of dilute acid solution for easy concentration control and viscous prophylene glycol for uniform coating. So low Ni concentration viscous can reduce metal contamination in MILC region. Poly-Si film crystallized with lower concentration of Ni showed larger grains with high angle grain boundaries and the defect at the impingement boundary of growth front was much smaller, compared to poly-Si film crystallized with higher concentration Ni. But the crystalliation time was increased.
High-temperature annealing of poly-Si crystallized by lateral growth was used to reduce the area of low angle boundary and improve the microstructure. After high-temperature annealing, low angle boundaries disappeared and the width of needle-like grain increased. And the defects in the grains are reduced. The surface roughness of poly-Si crystallized at 530℃ for 25h by furnace annealing was 6.09Å and it was improved to 4.22Å by additional rapid thermal annealing at 800℃ for 40min.
Effect of high-temperature annealing on the TFT characteristic of poly-Si was investiged. The field-effect mobility of TFT by high-temperature annealing increased to 94.7㎠/Vsec from 53.4㎠/Vsec of poly-Si TFT by lateral growth using low concentration Ni. And threshold voltage and sunthreshold slope of poly-Si TFT were also improved because the trap density decreased to 1.33×$10^{12}$/㎠ from 2.23×$10^{12}$/㎠ by high-temperature annealing.
