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Title :多孔質シリコン3次元周期構造作製その構造・特性評価
Title alternative :Fabrication of Porous Silicon 3-Dimensional Periodic Structures and Their Structural and Characteristic Evaluation
Authors :前濱, 剛廣
比嘉, 晃
曽根川, 富博
Authors alternative :Maehama, Takehiro
Higa, Akira
Sonegawa, Tomihiro
Issue Date :May-2004
Abstract :平成14年度~平成15年度科学研究費補助金(基盤研究C(2))研究成果報告書
研究概要:シリコンをHF溶液中において臨界電流密度以下で陽極化成すると多孔質シリコン層が形成される.その多孔質層は,多孔度に対応して屈折率も変化し,多孔度は陽極化成電流密度で容易に制御できる.この性質を利用して,電流密度を低・高と周期的に変調し,第1層の多孔質シリコンの格子パターンを下層に自己クローニングして作製する,屈折率孔質シリコン3次元周期構造(PS3DPS)の作製手法を確立し,3次元フォトニック結晶作製に応用することがこの研究の狙いである.本枡究での具体的な目標は,赤外領域の光に反応する1辺が約1μmサイズのPS3DPSの作製である. 1μmサイズのPS3DPSの作製の基礎データを得るため,1μm層厚の1次元周期構造の形成特性を,走査電子顕微鏡及びX線2結晶法で詳細に調べ,10mA/cm^2と50mA/cm^2を交互に流す周期的変調法でほぼ設計通りの1次元周期構造が形成できることを確認した.1μm〜20μmの正方格子ホトマスクを用いた選択陽極化成と,提案した自己クローニング法でPS3DPSの作製を行い,どこまでPS3DPSサイズの縮小化が実現できるか走査電子顕微鏡による断面観測で調べた.その結果,(1)選択陽極化成のレジストとしてポジ形フォトレジストは不適でネガ形フォトレジストが適していることがわかり,(2)PS3DPSのサイズは,5x5μm正方格子を1μmの層厚で7層目まで自己クローニングできることが確認できた.また、サイズの縮小化と自己クローニングの繰り返し数の増加の障害となっている主な原因は,多孔質シリコンが深さ方向だけでなく横方向へも成長するためであることがわかった. 今後は,多孔質シリコンの成長メカニズムを解明して,深さ方向に対する横方向成長比が小さくなる陽極化成条件を探索して,1μmサイズのPS3DPSを実現する研究をさらに進める必要がある.
研究概要:When a silicon substrate is anodized in HF solution at a current density lower than the critical current density porous silicon layers(PS) are formed on the silicon substrate. The porosity of the PS relating to the refractive index can be controlled easily by the formation current density. A PS-three dimensional periodic structure(PS3DPS) is fabricated at the surface layer of the silicon substrate by self-cloning a PS-square lattice pattern formed on the silicon substrate by the selective anodization method. The self-cloning is carried out by modulating the formation current density periodically. This PS3DPS is expected to be applied to three-dimensional photonic crystals. This project purpose is to reduce the size of square-lattice of PS3DPS to the wavelength of infrared region or about 1 micron meter and to develop the fabrication technique. In order to use the examination results for fabricating 1 micron-meter-size PS3DPS, the structures of the PS-one dimensional periodic structures(PS1DPS) were examined by scanning electron microscope and X-ray double-crystal method. PS1DPSs with the almost same periods as designed were fabricated by the current density modulation method in which the currents of 10mA/cm^2 and 50mA/cm^2 were periodically thrown. We fabricated the PS3DPSs by self-cloning method using the photomask of 1〜20μm square lattice and the current density modulation method developed for fabrication of PS1DPS. The structures of the PS3DPS were investigated by scanning electron microscope. The results are as follows : (1)Negative type photoresist was rather suitable as a resist mask for selective anodization than Positive type photoresist. (2)A 5μm-square-lattice PS3DPS of 3.5 periods or 7 layers and the each layer length of 1μm was able to fabricate. In the PS3DPS the structure changed to PS1DPS at deeper region than the seventh layer. The such fabrication trouble of PS3DPS was caused so that the PS grows not only depth direction but also lateral direction. In future, we need to find the fabrication conditions which reduce the ratio of the growth rate in lateral direction to the rate in depth direction studying the growth mechanism of PS so that we can fabricate 1μm-square-lattice PS3DPS with enough numbers of period to apply to photonic crystal.
Type Local :研究報告書
Publisher :前濱剛廣
URI :http://hdl.handle.net/20.500.12000/12007
Appears in Collections:Research Report (Faculty of Engineering)

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