Large-grain polysilicon films with low intragranular defect density by low-temperature solid-phase crystallization

Solid phase crystallization (SPC) of a-Si:H at 600°C was investigated by transmission electron microscopy (TEM) and Raman spectroscopy in a cantilever structure, where the underlying SiO₂ was removed prior to the crystallization. The absence of the underlying oxide leads to both a higher grain size and a lower intragranular defect density. The grain size increases from 0.6 μm in regions with the underlying oxide to 3.0 μm without the underlying oxide, and the intragranular defect density decreases one order of magnitude from ∼ 10¹¹ cm^-2 to ∼ 10¹⁰ cm^-2. The improvements in material quality without the lower a-Si/SiO₂ interface are thought to be due to a lower nucleation rate and a lower tensile stress with an easier silicon atomic rearrangement at the lower silicon interface.