Single Grain Si TFTs Fabricated at 100 o C for Microelectronics on a Plastic Substrate
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0989-A09-05
Single Grain Si TFTs Fabricated at 100oC for Microelectronics on a Plastic Substrate Ming He, R. Ishihara, T. Chen, J.W. Metselaar, and C.I.M. Beenakker Delft University of Technology, Delft Institute of Microelectronics and Submicrontechnology (DIMES), Delft, 2628CT, Netherlands ABSTRACT Single grain TFTs are fabricated at a maximum temperature of 100oC for macroelectronics on a plastic substrate, as Si channels are fabricated at 100oC by combination of excimer laser crystallization and sputtering. The gate oxide is formed at 80oC by inductively coupled plasma enhanced chemical vapor deposition. These TFTs have shown a smaller threshold swing of 0.49 V/dec. and a higher field-effect mobility of 290 cm2/V∑s, which can be used to directly fabricate system circuits or a high quality display on a plastic substrate. INTRODUCTION Macroelectronics [1,2] is an emerging field in which a remarkable progress has made in microelectronics on a flexible, large-area substrate with size much bigger than a microelectronic fab can handle. Macroelectronics have begun to show great promise. The research in this trend will open up new applications, which doesn't exist today and reshape the global large-area microelectronics. One desirable feature of macroelectronics is to realize system circuits (e.g., memory, CPU, ect.) on a flexible plastic substrate, which can be built directly on or within an interesting foreign object, to enable it to sense, control, compute, and communicate, ect.[2] These applications that require computation, control or communication functions cannot be addressed by today's TFTs. To achieve above abilities, it is pressing to improve TFT performance and to develop costefficient processes, which are compatible with a flexible substrate. Single grain TFT (SG-TFT), which is fabricated inside a location-controlled single grain, exhibits similar characteristics as SOI-FETs [3]. SG-TFTs are fabricated within locationcontrolled grains with µ-Czochraski process (grain filter) [4] at a low process temperature. However the maximum process temperature is 550oC, which is at deposition of α-Si by lowpressure chemical vapor deposition (LPCVD) and is much higher than resistant temperature of a plastic substrate. In this paper, IC-quality SG-TFT is fabricated at a maximum process temperature of 100oC, which can be applied to a direct formation of system circuits on plastics. First, single grain channel are formed at 100oC by patterning location-controlled grains, which are prepared by excimer laser crystallization of sputtered α-Si on top of grain-filters; Then, gate SiO2 is deposited at 80oC by inductively coupled plasma enhanced chemical vapor deposition (ICPECVD). SG-TFTs fabricated with the above gate oxide within location-controlled Si grains have shown high performance such as a field-effect mobility of 290 cm2/V∑s, a subthreshold slope of 0.49 V/decade, an on/off-current ratio larger than 106.
EXPRIMENTAL DETAILS Location-controlled Si grains The requirement of high-quality Si materials with an ultra-low pr
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