Effects of crystallization mechanism on the electrical characteristics of green continuous-wave-laser-crystallized polycrystalline silicon thin film transistors

Abstract

Thin film transistors (TFTs) with amorphous silicon films crystallized via continuous-wave green laser at a wavelength of 532 nm exhibit very different electrical characteristics in various crystallization regions, corresponding to the Gaussian energy density distribution of the laser beam. In the center region subjected to the highest energy density, the full melting scheme led to the best crystallinity of the polycrystalline silicon film, resulting in the highest field-effect mobility of 500 cm2 V−1 s−1. In contrast, the edge region that resulted in solid phase crystallization exhibited the worst mobility of 48 cm2 V−1 s−1 for the polycrystalline silicon TFTs.

High-Performance Single-Crystal-Like Strained-Silicon Nanowire Thin-Film Transistors via Continuous-Wave Laser Crystallization

“…is also marked. Additionally, the grain size is observed about 2 μm×20 μm, and the direction of grain growth is parallel the CW laser scanning direction and channel direction of the CLC poly-Si TFTs [7]. Fig.…”

“…The highquality crystalline silicon is formed in the scanned center region with a width of about 120 μm. In addition, the width of the worst polygonal grain in the transition region and the small grain in the edge region are about 70 μm and 60 μm under single scanned beam profile, respectively [7]. We used the overlapping method, the second scan of center region over the first scan of transition and edge region, to enhance uniformity and quality.…”

“…Various technologies, including solid-phase crystallization, metalinduced crystallization, excimer laser crystallization (ELC), and continuous-wave laser crystallization (CLC), have been proposed to enlarge grain size for improving the LTPS TFTs [3]- [7]. Among the LTPS technologies, the grain size and quality of polycrystalline silicon (poly-Si) films via CLC process are the largest and the best, hence metaloxide-semiconductor field-effect transistors (MOSFETs) fabricated by CLC opened up the field of silicon-oninsulator (SOI) [9], [10].…”

“…However, grain boundaries still affect the performance of LTPS TFTs, such as the device uniformity, subthreshold swing (S.S.), on/off ratio, mobility, etc. Therefore, a number of articles reported about the methods of nanowire (NW) channel processing to enhance the performance and uniformity of devices [3]- [5], [7]. On the other hand, for advanced large-scale integration circuits, strained-Si technologies are increasingly important when device size is scaling down.…”

Impact of substrate composition on the morphology and conductivity of laser-crystallized silicon films

“…A significant amount of ongoing material-processing research is being directed at thin-film silicon, which is being driven largely by potential applications in flexible and lightweight electronics, such as thin-film transistors and solar cells [1][2][3][4][5]. Traditional top-down processing approaches for reducing the thickness of crystalline silicon (c-Si) wafers (i.e., grinding, polishing, or chemical etching) can only produce films that are 10-100 lm in thickness, and these still require additional chemical-based polishing to remove the cracks and dislocations incurred through mechanical processing.…”