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In this study, a 2 in. Ni field aided lateral crystallization (FALC) polySi thinfilm transistor (TFT) (120 x 240) array was fabricated at the maximum process temperature of 500°C using an optimized current density distribution design. We investigated the correlation between crystallization and transistor characteristics in terms of transistor position in the array. Because an identical current density in the channel region of each pixel transistor was favorable to achieve uniform crystallization, an optimal common electrode design was chosen via Mathcad simulation. After the crystallization process, it was confirmed that the crystallinity variation in the transistor channels agreed well with the predicted simulation results. Furthermore, the positional variation in important transistor parameters in the array showed a good match with that of crystallization. The mean threshold voltage was 5.9 V (ΔVth = ± 0.2 V) while the mean mobility was 92.5 cm2 V1 s1 with a variation of 9.8%. These values suggested that the uniform NiFALC polySi TET arrays fabricated by the optimal design of the electrode were applicable to the active matrix organic light emitting display backplane. [ABSTRACT FROM AUTHOR]

Crystallization behavior of amorphous silicon (a-Si) using the field aided lateral crystallization (FALC) process was investigated. The lateral crystallization of a-Si was remarkably enhanced at the negative electrode side with the aid of an electric field, while it was retarded at the positive electrode side. FALC velocity using Ni was as high as 11 μm/h at 500 °C with an electric field of 4 V/cm. In addition, the nickel silicide phase, known to be a mediator for low temperature crystallization, can be driven from either the drain to source or source to drain in the active layer, depending on the bias conditions during crystallization. Thus, the defects originating from residual nickel silicide can be driven out from the channel region. Due to such an asymmetric location of the residual nickel silicide, the leakage current of the polycrystalline silicon thin film transistor (poly-Si TFT) using the FALC process showed a leakage current of approximately one order of magnitude lower when we reversed the probing polarity. Therefore, it was judged that the judicious selection of the bias condition during the FALC process can be useful in improving the electrical properties of poly-Si TFT. [Copyright &y& Elsevier]

Abstract: As a crystallization process, the field-aided lateral crystallization (FALC) technique has some outstanding advantages, such as high crystallization rate and low temperature. In this study, the electrical field was directly applied between source and drain areas of H shape patterns using the Mo–W interconnecting layer. The effects of the current density and electrical field strength on the crystallization behavior were investigated. Results show that the crystallization behaviors at different bias areas are different. The difference is attributed to the coexisting effects of electromigration and potential gradient. In addition, the dependence of the degree of crystallization on the current density was studied by Raman spectra and the microstructure crystallized by FALC was observed by a scanning electron microscope. [Copyright &y& Elsevier]

Abstract: The effect of the alternating field (AC voltage) instead of the static field (DC voltage) was investigated in the field-aided lateral crystallization process, which is one of the low temperature crystallization processes for the amorphous silicon films. Using a photolithography process, a 5-mm-wide bar-shaped photoresist (PR) pattern was formed on the a-Si. On the PR-patterned a-Si, a 2–3-nm-thick Cu catalyst layer was deposited by a DC sputtering, and then, the Cu layer on the PR pattern was lifted off. The silver electrodes were pasted at the opposite sides of the Cu-free bar pattern. Then, the patterned specimen was annealed at 500 °C in N2 ambient for 5 h with the application of various AC fields (ranging from 1 to 5 V/cm) along with a DC field of 30 V/cm. As compared with the case of a DC field of 35 V/cm only, the specimen from a mixed field of 30 V/cm DC and 5 V/cm AC resulted in 1.5 times faster crystallization rate, regardless of experimental frequency values ranging from 10 Hz to 50 MHz. Presumably, the enhancement of the crystallization rate under the combined field is associated with an increase in the flux of the crucial diffusion species, Cu atoms, which govern the overall crystallization rate due to the effect by the AC field. [Copyright &y& Elsevier]