ZnO Light-Emission Array Fabricated into Nanometer-scale Pits on Silicon Substrate
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ZnO Light-Emission Array Fabricated into Nanometer-scale Pits on Silicon Substrate Naoki Ohashi,1 Isao Sakaguchi,1 Takashi Sekiguchi,1 Hajime Haneda,1 Kazuyoshi Kobayashi,2 Hidetoshi Masauda,2 Hirokazu Chazono,2 Masayuki Fujimoto1,3 1 National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan 2 Taiyo Yuden Co., Ltd., Nakamuroda, Haruna-machi, Gunma 5607-2, Japan 3 Graduate School of Electronic Science and Technology, Shizuoka University, 3-5-1 Jyouhoku, Hamamatsu, 432-8561 Japan ABSTRACT A nanometer-scale ZnO light emission array device was fabricated using the multi-level metallization technique of the CMOS process. Square arrays of pits with an inverted pyramid shape made from {111}Si planes were formed on a (100)Si substrate using selective etching. ZnO was deposited on the substrate by chemical vapor deposition (CVD), and the surface of the deposited ZnO film was carefully polished by chemical mechanical planarization (CMP). As a result, ZnO-filled nanometer-scale arrays were obtained after removing the ZnO layer except for the ZnO in the pits by CMP. Cathodoluminescence (CL) from the ZnO arrays was observed. INTRODUCTION Zinc oxide (ZnO) is a well-known phosphor material that emits blue-green light, and it is used in vacuum fluorescence display (VFD) and field emission display (FED) panels of automobiles, industrial instruments, and home electronics because of its high emission efficiency under low energy electron irradiation, e.g., 20 eV, and good visual characteristics [1]. Zinc oxide has become important as a light emitting material with a wide band gap in the wake of the technological and commercial success of GaN LEDs [2-4], and it has led to remarkable research advances in regard to quantum effects in superlattices [5], laser emission [6-8], hetero-junction structures [9], phosphor [10,11], etc.. On the other hand, the patterning of the light emitting elements is of critical importance to obtaining a visually sharp image. In this regard, the conventional patterning methods of using ZnO phosphor for VFDs are restricted to screen-printing, see left side of Fig. 1. The use of such large phosphor grains has thus far limited the image resolution of VFDs and FEDs, and a micro-fabrication technology for silicon-based materials to enable high-density integration is desired. For instance, high-resolution visualization devices are of great importance in the field of virtual reality. To obtain high resolution with a ZnO phosphor pattern, direct patterning of ZnO using a self-assembled mono-layer (SAM) has actively been pursued. Izaki et al. [12,13] have developed an electroless deposition method for polycrystalline ZnO films, through the reduction of nitrate ions using dimethylamine borane. By immersing substrates in an aqueous solution maintained at about 60oC, crystalline ZnO was obtained on the Pd catalyst particles attached to the substrate. Saito et al. [14] have fabricated ZnO micro-patterns that can show patterned cathodoluminescence images. They used a photo-patter
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