Low-temperature Fabrication of a Crystallized Si Film Deposited on a Glass Substrate using an Yttria-stabilized Zirconia
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1153-A05-05
Low-temperature Fabrication of a Crystallized Si Film Deposited on a Glass Substrate using an Yttria-stabilized Zirconia Seed Layer Sukreen Hana Herman and Susumu Horita School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Nomi, Ishikawa, 923-1292, Japan ABSTRACT By using yttria-stabilized zirconia (YSZ) layer as a crystallized stimulation layer, a silicon film deposited by electron-beam evaporation was crystallized directly during the deposition at 320 ~ 430 °C. The crystallization of the Si film was stimulated and induced by the YSZ layer, as confirmed by transmission electron microscopy. The yttria content and the surface treatment of the YSZ layer are the main factors to determine the crystallization of the Si film. INTRODUCTION Investigations on crystalline silicon (c-Si) thin films, particularly polycrystalline Si (polySi) on glass or plastic substrates have been done intensively due to its superior characteristics compared with amorphous silicon (a-Si). Various methods to crystallize the a-Si have been proposed to obtain c-Si films at low temperature, such as solid phase crystallization (SPC) [1,2], metal induced crystallization (MIC) [3,4], laser annealing (LA) [5,6] and others. However, each method has its own drawbacks. SPC method needs high process temperatures and long annealing times. MIC method has provided a lower temperature process and shorter annealing time than SPC, but the poly-Si film is subject to high leakage current caused by the remnant metals as impurities. LA method, on the other hand, is a promising method with the lowest process temperature and the largest grain size compared to the above methods. However, the poly-Si film has a serious problem of large surface roughness. In order to obtain c-Si films without impurity and surface roughness at low temperature, we have proposed a new method of low-temperature growth of a poly-Si film on a quartz substrate, in which a poly-YSZ (yttria-stabilized zirconia : (ZrO2)1-x(Y2O3)x) film is used as a seed layer to cover the whole surface of the amorphous substrate, as shown in the schematic diagram of Fig. 1. YSZ is a chemically and thermally stable material and is suitable for the seed layer owing to the small lattice mismatch with Si of only about 5%. In fact, it was reported that a YSZ film can be grown heteroepitaxially on an Si substrate [7]. Clean in ethanol
Clean in deionized water
Dip in 5%HF
Set 1: Rinse in ethanol
(a) (b) Figure 1. Schematic diagrams of the Si films deposited on the glass substrates by (a) the conventional direct deposition method and (b) the seed layer method.
Set 2: Rinse in deionized water
Figure 2. Two kinds of YSZ layer surface
treatment prior to Si film deposition.
We have reported that the crystallized Si film was obtained on the YSZ seed layer at 515 °C, and the Si film deposited directly on the glass substrate at the same deposition temperature was amorphous [8]. Further, we have reported that the Si film deposited on the HF-etched YSZ that was rinse
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