유기발광소자용 투명전극 제작 및 형상 분석에 관한 연구

Abstract

In this study, optimal conditions for the fabrication process of ITO thin films were derived and transparent electrodes were fabricated by patterning on the ITO thin films through photolithography. The characteristics of the fabricated ITO thin films and its transparent electrode devices were measured by field emission-scanning electron microscopy(FE-SEM) and digital holography based on fiber optics and similar results were obtained. The ITO thin films were fabricated by varying the various process conditions. As a result, the ITO thin films were grown under the conditions: The pressure of Ar gas and O2 gas were adjusted to 90 and 0.1 sccm, respectively. the RF power was 300 W, the deposition temperature was 250℃, and deposition time was 1350 sec. The ITO thin films produced at this optimum condition had the thickness of 155 nm, the area resistance of 25.3 ohm/sq and the surface roughness uniformity of 9.1%. After post-treatment at 380℃, the light transmittance reached 97.1%, the surface roughness Rpv and Ra were 15.644 nm, and 1.708 nm. After the photolithography process for the transparent electrodes, the electrical characteristics of the ITO thin films and transparent electrodes device were measured and showed similar performance in electrical characteristics. In order to observe the topological characteristics of the fabricated ITO thin films and the transparent electrode devices, measurements were performed using high-resolution FE-SEM. After metal coating with Pt, the thickness of the ITO thin film was found to be in the range of 112~174 nm for each process condition. For the measurement of the topology of the ITO thin film and transparent electrodes, a transmission and reflection type digital holography system was implemented by using bulk optics. We also developed a digital holography capable of phase shifting based on fiber optics, and compared the feasibility of the proposed measurement technique by performing measurements on the same sample. In the proposed optical fiber-based digital holography, the degree of phase shift could be precisely controlled by the pump light, and it was confirmed that the interference fringe control for 4-step or 8-step phase shifting is desirable by using this optical phase control method. In addition, phase lock effect could be confirmed by controlling phase shift in real time. Thickness of the ITO thin film and the transparent electrode devices were measured by using the developed optical fiber-based digital holography system and the results were 159.6 nm and 57.8 nm, which showed the error of 3.3% and 3.6%, respectively, when comparing with the results measured by FE-SEM. However, considering the external vibration and the error in measurement, the optical fiber-based digital holography method, which can measure in an in-situ non-intrusive environment, can be improved the performance and it is expected to be an alternative technology.