High Performance n- and p-channel Strained Single Grain Silicon TFTs using Excimer Laser
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High Performance n- and p-channel Strained Single Grain Silicon TFTs using Excimer Laser Alessandro Baiano, Ryoichi Ishihara and Kees Beenakker. Delft University of Technology, Delft Institute of Microsystems and Nanoelectronics (DIMES), Laboratory of Electronic Components, Technology and Materials (ECTM) Feldmannweg 17, P.O. Box 5053, 2600 GB Delft, the Netherlands. ABSTRACT In this paper we investigate the carriers mobility enhancement of the n- and p-channel singlegrain silicon thin-film transistors (SG-TFTs) by μ-Czochralski process at low-temperature process (< 350 °C). The high laser energy density nearby the ablation phenomenon that completely melts the silicon layer during the crystallization is responsible for high tensile strain and good crystal quality of the silicon grains, which lead carriers mobility enhancement. INTRODUCTION Thin-film electronics, such as thin-film transistors (TFTs) using amorphous silicon (a-Si) and low temperature polysilicon (LTPS) have been extensively employed for active matrix liquid crystal displays (AMLCDs), image sensors etc. A major reason for the success of these TFTcentric solution is that solution based on commercial silicon IC microelectronics would not be economically viable [1], beside the fact that it is based on high-temperature process not acceptable for unconventional electronics. Nowadays, many new applications have been coming up such as smart wireless systems that operate in the range of radio frequency fabricated on glass or even flexible substrates. 3D integrated circuits has also become an important research area causing many common interests between IC microelectronics and low-temperature TFTs technologies. Whereas 3D integration in package level and wafer level [2] can be made by the CMOS technology, 3D integration at device level (monolithic integration), which results in the largest decrease in interconnect length and so highest density of interconnects between nodes may only be approached by low-temperature TFTs process [3]. Many new recrystallization techniques have been developed to improve electrical performance, such as sequential lateral solidification (SLS) [4], CW-laser lateral crystallization (CLC) [5], selectively enlarging laser crystallization (SELAX) [6], phase modulated excimer laser annealing (PMELA) [7]. We have developed the μ-Czochralski process [8], which has many fundamental advantages over the aforementioned techniques in term of: 1) 2D locationcontrol of large (up to 8 micros) grains, 2) wide energy density windows in which the location control is obtained, 3) the high throughput owing to the one shot process, and 4) capability of crystallographic orientation control [9]. Single grain silicon TFTs (SG-TFTs) by the μCzochralski has obtained mobility as high as SOI counterpart [8]. Transit frequency fT in the range of 5 to 6 GHz has been obtained with a gate length of 1.5 μm. As a result, RF amplifiers have been attained well over 10 dB gain below 1 GHz [10]. However, the major goal of large-
area electronics is to crea
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