Poly-Si Thin Film Formation Using a Novel Low Thermal Budget Process

Abstract

Polycrystalline silicon thin films were formed from the amorphous silicon thin film by the pulsed rapid thermal annealing process enhanced with a thin nickel seed layer through the vertical crystallization mechanism. In this paper, authors presented the results on the material properties of the crystallized film. The dopant and film thickness effects were also investigated. It has been demonstrated that a 2 μm thick amorphous silicon n+-i-p+ diode structure could be transformed into polycrystalline stack with a 4-pulse 1 sec 850°C heating and 5 sec cooling cycle process.

Polycrystalline Silicon Thin Film Formed By Multiple Pulsed Rapid Thermal Annealing – Intrinsic a-Si Film Thickness Effect

“…First, the Ni-induced crystallization is applicable to a-Si films of various thicknesses after the PRTA treatment even interrupted with the additional SiO 2 growth and stripping steps. This is consistent with the previous observation that the a-Si film could be crystallized in the horizontal or vertical direction after PRTA [7][8][9][10]. The crystallization process was initialized from the formation of crystalline NiSi 2 that has a lattice constant very close to that of the crystalline Si, i.e., 5.406Å vs. 5.430Å.…”

“…However, since there was a long delay between two PRTA procedures, i.e., for the strip of the old SiO 2 layer, the growth of the new SiO 2 layer, and dehydrogenation, the glass substrate was not exposed to the high temperature continuously for an extended period of time. The increase of the Si grain size may be from the merge or growth of small grains [10]. Another factor that contributes to the grain size change is that the thick Si film reduces the geometry limitation in the grain growth process [16,17].…”

“…Kuo, et al, [7,8] reported a low thermal budget pulsed rapid thermal annealing (PRTA) method that converted an a-Si thin film into a poly-Si film within a few seconds in the direction parallel to the substrate surface. This method was also used to crystallize a-Si in the vertical direction, i.e., perpendicular to the substrate surface [9,10]. For the original 100 nm thick a-Si film, the grain size in the crystallized poly-Si film was < 40 nm.…”