MILC PMOS Poly-Silicon TFT Circuits and Application in SOP

Abstract

Research towards thin film circuits is one of the most attractive directions of the large-area electronics and flexible electronics. In this work, the research on TFT shift register circuit which is critical for system integration on panel (SOP) is presented. The whole circuit is composed of MILC PMOS poly-Si TFTs. The TFT device exhibited field-effect mobility of 65.21cm 2 /Vs, threshold voltage of -3.5V and sub-threshold swing of 0.56V/dec. Some special design considerations were adopted to improve the robustness of the circuits. The whole shift register is composed of as many as 180 stages and exhibited well performance with frame frequency from 22Hz to 220Hz at the power supply voltage of 11V. No signal attenuation and distortion appeared from the first to the final stage. The effect of bootstrapping and dynamic behavior is analyzed. The fabrication and reliability analysis are also discussed in this paper. Overall, the high performance driver circuits based on our MILC PMOS process are possible and have the potential in the application of SOP. IntroductionTFT circuits have been studied widely because of the flexible and large area electronic applications for the last several years (1). There are many options which are polycrystalline silicon (poly-Si) TFT, amorphous silicon (a-Si) TFT, organic TFT and single crystalline silicon to realize TFT circuit (2). For a-Si silicon and organic TFT, there are some intrinsic limitations concerning integration of larger scale circuits, as a result of low mobility and high threshold voltage. During these years, several attempts of transferred single crystalline Si layers on glass substrate are reported (3). Also, some of recent literatures show that single-grain (SG) Si-TFT has the potential to develop a large scale digital and analogue circuit system by the special process (4). One of the most important concerns for TFT circuit is process variation and fabrication cost. To integrate high performance circuits of TFT devices, the low