Real Time Spectroscopic Ellipsometry Studies of the Solid Phase Crystallization of Amorphous Silicon

Abstract

ABSTRACTWe have introduced real time spectroscopic ellipsometry (RTSE) for characterization of the solid phase crystallization (SPC) of intrinsic and n-type amorphous silicon (a-Si:H) thin films. RTSE has several advantages in the study and design of SPC processes for thin film transistor and solar cell fabrication. These include the capability of obtaining (i) calibration data that yield the near surface temperature of the film during processing, (ii) the volume fraction of the crystalline Si component of the film continuously versus time during SPC, and (iii) a measurement of the grain size and quality of the final polycrystalline Si film. For the thin layers studied here (∼150-1000 Å), we demonstrate excellent fitting of the SPC dynamics to the Avrami-Johnson-Mehl theory for random nucleation and two-dimensional crystallite growth. For a-Si:H n-layers, the crystallization time over the range from 565 to 645°C appears to be weakly activated with an energy of 0.6 eV.