Metal-induced unilaterally crystallized polycrystalline silicon thin-film transistor technology and application to flat-panel displays

Abstract

High quality flat-panel displays (FPD) typically use active-matrix (AM) addressing, with the optical state of each pixel controlled by one or more active devices such as amorphous silicon (a-Si) thin film transistors (TFT). The successful examples are portable computer and liquid-crystal television (LC-TV). A high level of system on panel (SoP) electronic integration is required for versatile and compact systems. Meanwhile, many self-emitting display technologies are developing fast, active matrix for self-emitting display is typically current driven. The a-Si TFTs suffer from limited current driving capability, polycrystalline silicon (poly-Si) device technology is required. A new technology employing metal-induced unilateral crystallization (MIUC) is presently reported. The device characteristics are obviously better than those of rapid-thermal annealed (RTA) and solid-phase crystallization (SPC) TFTs and the fabrication equipment is much cheaper than excimer laser crystallization (ELC) technology. The field effect mobility (μ_FE) of p- and n-channel MIUC TFTs is about 100cm²/Vs. I_on/I_off is more than seven orders. Gate-induced leakage current in LT-MIUC poly-Si TFTs has been reduced by crystallization before heavy junction implantation to improve material quality and incorporating a gate-modulated lightly-doped drain (gamo-LDD) structure to reduce the electric field near the drain/channel junction region. Meanwhile, re-crystallized (RC) MIUC TFT was researched, with device characteristics being improved. The 6.6cm 120X160 active matrix for OLED display is fabricated using LT-MIUC TFT technology on glass substrate. This display has the advantages of self-emitting, large intrinsic view angle and very fast response. At the same time, 6.6cm 120X160 AM-reflective twist nematic (RTN) display is fabricated using RC-MIUC TFT technology. This display is capable of producing 16 grade levels, 10:1 contrast video image. The SoP display for AM-OLED was designed, fabricated and analysed. 30MHz peripheral driver circuits have been achieved using 5μm RC-MIUC TFTs.

Date of Award	2002
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology