Influence of melt depth in laser crystallized poly-Si thin film transistors

Abstract

The influence of film thickness and incident excimer laser energy density on the properties of poly-Si thin film transistors has been investigated and a coherent pattern of behavior has been identified which establishes controlled melt-through of the film as a key condition for achieving high quality devices. The conditions were correlated with the appearance of large grains and gave consistent results from both n- and p-channel devices, with carrier mobilities of more than 150 and 80 cm2/V s, respectively, and leakage currents of less than 2×10−14 A/μm. From a study of static irradiations, using a semi-Gaussian laser beam, the results are shown to be consistent with the super lateral grain growth (SLG) model. The trailing edge of the beam, when used in a swept mode, has been demonstrated to play an important role in extending the size of the energy window for this effect by re-setting the material into the SLG regime.