Hye-Hyang Park

Design of Sequential Lateral Solidification Crystallization Method for Low Temperature Poly-Si Thin Film Transistors

Sequential lateral solidification (SLS) is known as a promising method for making low-temperature poly-Si thin film transistors (LTPS TFT) with superior performance for the fabrication of highly circuit-integrated flat panel displays such as TFT liquid crystal display (LCD) and TFT organic light Emitting diode (OLED). In this work we studied the dependence of TFT characteristics on SLS poly-Si grain width and suggested the methods of designing SLS mask pattern to achieve uniform TFT performance. We varied the width of the poly-Si grain by employing the 2-shot SLS mask pattern with different overlaps between the 1st and 2nd laser pulses. The width of the poly-Si grain decreased with decreasing the overlap. However, the measured TFT characteristics revealed that the width of the poly-Si grain negligibly influences the device properties. We could achieve the TFT mobility of approximately 350 cm2/Vs for the overlap of not less than 1 µm. We suggested that the SLS mask pattern (x, y) should be designed such that 2+y≤x (optical resolution), where x is the spacing of the laser-absorbed region and y is the spacing of the laser-nonabsorbed region on the substrate.

A Study of Parasitic Series Resistance Components in In–Ga–Zn–Oxide (a-IGZO) Thin-Film Transistors

We extracted the effective channel length and parasitic series resistance in a-IGZO inverted-staggered etch-stop (ES) TFTs. When there is an overlap between the drain or source electrode and the FET channel, the resistance of the channel underneath the overlapping regions is very low compared with other channel region resistance. As a result, the effective channel length is smaller than the physical length. The aforementioned definition of effective channel length in terms of device geometric parameters seems to be specific for ES a-IGZO TFTs.

P‐21: Investigation of Pattern‐Induced Brightness Non‐Uniformity in AMOLED Displays

We found that pattern-induced line type brightness non-uniformity is related to moire patterns that appear when primary grain boundaries in SLS processed poly-Si are aligned over repetitive TFT patterns such as metal lines. We propose a method to diminish the Moire pattern type non-uniformity by adopting black matrix and top emission TFT structure.

Uniformity improvement of SLS poly‐Si TFT AMOLED

Abstract In this study, we attempted to find the origin of brightness non‐uniformity in SLS poly‐Si TFT AMOLED. By developing a suitable SLS process with a compensation circuit, we successfully improved the non‐uniformity from 40% to 1.7%. In addition, we were able to fabricate 2.2? AMOLED display using SLS poly‐Si.