Periodically Lateral Silicon Grains Fabricated by Excimer Laser Irradiation with a-Si Spacers for LTPS TFTs

Abstract

Low-temperature polycrystalline silicon ͑LTPS͒ thin-film transistors ͑TFTs͒ with a periodic lateral silicon grain structure have been demonstrated to exhibit high-performance electrical characteristics via the amorphous silicon spacers above the amorphous silicon film crystallized with excimer laser. Amorphous silicon spacers allowed the bottom of the under-layered amorphous silicon film to serve as seed crystals. The periodic grain structure could be artificially controlled via the super lateral growth phenomenon during excimer laser irradiation. Consequently, such periodically large and lateral grains in the TFTs would achieve high fieldeffect-mobility of 298 cm 2 /V s, as compared with the conventional ones of 128 cm 2 /V s. In addition, the uniformity of deviceto-device could be improved due to this location-manipulated lateral silicon grains.

Dependence of thin film transistor characteristics on low-angle grain boundaries of (100)-oriented polycrystalline silicon thin films

“…Recently, many crystallization technologies and structure optimization methods have been developed to improve the performance and uniformity of TFTs, however, they have not been satisfied for the applications in the FPDs and electronics. [1][2][3][4][5][6][7] Among these technologies, the uniformity has been obtained with excimer laser annealing that has been successfully applied to high-performance active-matrix TFTs in liquid crystal displays. However, electron mobility have been limited below 200 cm 2 V −1 s −1 owing to crystal grain size being smaller than 0.5 μm.…”

Uniform Square Polycrystalline Silicon Fabricated by Employing Periodic Metallic Pads and SiON Absorption Layer for Thin Film Transistors

“…If the grain size is regular and large, the grain boundaries in the channel can be fixed, and then, the uniformity and mobility of TFT can be improved. Several methods have been reported to improve the uniformity of the poly-Si film such as sequential lateral solidification [4], optical phase shift mask [5], grains controlled by floating structure [6], location control Si grain [7], µ-Czochralski method [8], and excimer laser irradiation with a-Si spacers [9].…”

“…1(a). The purpose of the Al metallic pads is to reflect the laser light and the Cr layer under Al metallic pads is to impede the Al diffusion into Si layer during ELA [9]. Next, the film is irradiated by high power excimer laser (KrF, pulse duration time of 28 ns, 840 mJ/cm 2 ) at room temperature, and the amorphous silicon region without metallic pads will be melted.…”

Effects of accumulated laser pulses on (Pb,Sr)TiO3 films post-excimer laser annealed at low temperatures

“…The crystallinity of films was improved by excimer laser annealing (ELA). The ELA technique is very attractive in terms of selective annealing area and local-high-temperature heating within very short time, which is feasible for fabrication of lowtemperature poly-silicon (LTPS) thin film transistor (TFT) [11][12][13][14][15]. Some studies about the properties of PZT and (Ba,Sr)TiO 3 (BST) films post-treated by ELA have been reported [16,17].…”