Low-damage Preparation of SiO 2 Dielectric Thin Film by the Photo-assisted Oxidation Processing
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Low-damage Preparation of SiO2 Dielectric Thin Film by the Photo-assisted Oxidation Processing Takehito Kodzasa, Sei Uemura, Kouji Suemori, Manabu Yoshida, Satoshi Hoshino, Noriyuki Takada and Toshihide Kamata National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, JAPAN. ABSTRACT We have already reported that low-temperature (about 170 oC) preparation technique of silicon dioxide (SiO2) dielectric thin film that has high resistivity and extremely smooth surface by the photo oxidation process. In this paper, we have developed a low-damage preparation technique to fabricate a SiO2 thin film by the photo-assisted low temperature oxidation process in order to apply this process to the flexible electronics using for convenient plastic films. We have reported that the SiO2 dielectric thin film with a high insulation performance can be prepared by the low temperature processing below 100oC by improving the pre-processing of the photo oxidation of thin film. INTRODUCTION In order to prepare thin film transistor (TFT) by low-temperature processing, it is needed that not only active layer (semiconductor thin film) but also passive layer (gate insulator thin film or electrodes) are prepared by the low-temperature processing. Some of organic polymer materials have been studied for the low-temperature processible insulator materials. However as most organic polymer has poor dielectric durability, it is not good to apply them for the gate insulator in the TFT devices. On the other hand, it is well known that SiO2 is the most superior for the insulator thin film because of low leakage current, high breakdown intensity and good thermal stability. We have already reported about the preparation of SiO2 insulator thin film with high resistivity and surface flatness same as thermal oxidized silicon by the solution process below 200 oC [1-2]. However, in order to apply the fabrication technique of SiO2 thin film for largescale flexible electronic, it needs to prepare it by the lower temperature processing than glass transition temperature of conventional polymer films such as polystyrene, polyethylene terephthalate or poly (methyl methacrylate). Table 1 shows glass transition temperature (Tg) of conventional polymer materials. Tg of most conventional polymer materials are less than 100 oC. Thus, in order to apply the fabrication technique for the flexible sheet devices such as electronic paper, RF-ID tag, display and power transmitter, it needs to be prepared by the low-temperature processing less than 100oC. In this paper, we show that SiO2 thin film with high insulation performance can be obtained with no damage against light irradiation. And we show that the SiO2 dielectric thin film having high insulating property is prepared by the low-temperature processing below 100 oC by improving the pre-heating of the photo-assisted oxidation.
Table 1 Tg of conventional polymer films. polymer films
Poly styrene
Poly (methyl methacrylate)
Polyethylene terephthalate
Polyethylene naphthalate
Polyether sulphone
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