광화학증착법에 의한 직접패턴 비정질 TiOx 박막의 제조 및 저항변화 특성
Resistive Switching Characteristic of Direct-patternable Amorphous TiOx Film by Photochemical Metal-organic Deposition
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초록
광화학증착법 (PMOD; photochemical metal-organic deposition)을 이용하여 photoresist 및 etching 공정없이pattern 된 TiOx resistive switching (RS) 소자를 제작 및 그 특성을 평가하였다. Ti(IV) 2-ethylhexanoate를 출발물질로 사용하였으며 UV 노출시간 10 min에 광화학반응이 완료됨을 FTIR 분석을 통하여 확인하였다. 200 oC 이하 저온공정에서직접패턴 된 20 nm 두께의 비정질 TiOx 박막의 균일한 두께의 패턴형성을 Atomic Force Microscopy를 통하여 확인하였다. 별도의 상형성을 위한 후 열처리 공정 없이 4 μm 선폭의 전극위에 형성된 20 nm 두께의 비정질 TiOx RS 소자는4V 동작전압에서 on/off ratio 20의 forming-less RS 특성을 나타내었다. Electrochemical migration에 영향을 미치는 grain boundary가 없어 소자간 신뢰성 향상이 기대되며, flexible 기판 또는 저온공정이 요구되는 메모리 소자 공정에서 PMOD 공정이 응용될 수 있음을 보여준다. Selector를 이용하여 crossbar array 구조를 도입할 경우 매우 간단한 구조의 저비용메모리 소자를 구현할 수 있을 것으로 기대 된다.
Abstract
This study demonstrates direct-patternable amorphous TiOx resistive switching (RS) device and the fabrication method using photochemical metal-organic deposition (PMOD). For making photosensitive stock solutions, Ti(IV) 2- ethylhexanoate was used as starting precursor. Photochemical reaction by UV exposure was observed and analyzed by Fourier transform infrared spectroscopy and the reaction was completed within 10 minutes. Uniformly formed 20 nm thick amorphous TiOx film was confirmed by atomic force microscopy. Amorphous TiOx RS device, formed as 6 x 6 μm square on 4 μm width electrode, showed forming-less RS behavior in ±4 V and on/off ratio ≈ 20 at 0.1 V. This result shows PMOD process could be applied for low temperature processed ReRAM device and/or low cost, flexible memory device.
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