Abstract
Polycrystalline silicon (poly-Si) thin film transistors (TFTs) fabricated by near-infrared femtosecond laser annealing (FLA) are demonstrated. The FLA-annealed poly-Si channels exhibit low tail-state, deep-state, and midgap-state densities of grain traps. Characteristics such as field-effect mobility, threshold voltage, and subthreshold slope for FLA-annealed poly-TFTs are comparable to those of conventional approaches. A wide process window for annealing laser fluences was confirmed by examining the changes in electrical parameters for transistors with various channel dimensions.
Highlights
Laser-induced crystallization and activation are widely recognized as useful techniques for fabrication of various devices [1,2,3,4,5,6]
Even at the lowest fluence we employed, the maximum Gm of thin film transistor (TFTs) fabricated by SPC was lower than that of TFTs annealed by femtosecond laser annealing (FLA)
As we have shown in a previous study [13], the grain sizes of FLA-annealed samples are comparable to those of excimer laser annealing (ELA)-annealed ones reported in the literature [22]
Summary
Laser-induced crystallization and activation are widely recognized as useful techniques for fabrication of various devices [1,2,3,4,5,6]. The excimer laser has been proved to be a powerful tool for annealing of amorphous silicon layers, activation of shallow junctions and fabrication of TFTs [9,10,11,12]. We reported near-infrared (λ= 800 nm) femtosecond laser annealing (FLA) for crystallization of amorphous silicon (a-Si) and activation of dopant atoms confined in ultra shallow junction regions [13,14]. The photoexcited electron systems weaken the lattice and lead to structural transformation such as re-crystallization. As confirmed by measurements of electrical parameters and grain trap-state densities were obtained for a wide process window of annealing laser fluences
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