ENCAPSULATION PROPERTIES OF Al2O3/ZrO2 NANOLAMINATES DEPOSITED BY OZONE BASED ATOMIC LAYER DEPOSITION

Abstract

Nowadays, organic electronic devices have emerged as attractive alternatives for lighting and photovoltaic applications. Especially, organic light emitting diodes (OLEDs) require highly advanced encapsulation layer because organic materials are very sensitive to oxidative species such as water and oxygen, so they require encapsulation to protect them. As a representative encapsulation technique is to use the glass with UV-cured epoxy resin dispensed at the sides of the devices as glue with getter inside. However, it is not suitable for flexible device due to high brittleness of glass under the mechanical stress, so thin film encapsulation is considered as indispensable technique for future flexible electronics. In this study, thickness of 100 nm Al2O3/ZrO2 layers grown by ozone (O3) based atomic layer deposition (ALD) at low temperature (100 °C) have been investigated as a layer of thin film encapsulations (TFE). Electrical calcium (Ca) degradation test was performed at relative humidity (RH) of 50 °C and 50 % to derive the water vapor transmission rates (WVTR) of aluminum oxide (Al2O3), zirconium oxide (ZrO2), and Al2O3/ZrO2 laminated films. Al2O3/ZrO2 laminated films exhibited better permeation barrier properties compared to those of Al2O3 and ZrO2 single layer films. In Al2O3/ZrO2 laminated films, the permeation barrier properties are improved as the number of alternating layers increases. The permeation barrier properties are closely related with the actual number of interfaces because of ZrAlxOy phase which is formed at the interface between Al2O3 and ZrO2 sublayers. ZrAlxOy phase is denser than single phase of each Al2O3 and ZrO2, and it has homogeneous amorphous structure. The formation of ZrAlxOy phase in Al2O3/ZrO2 laminated film improves the permeation barrier properties effectively. |오늘날, 유기전자소자는 조명과 광전지의 응용을 위한 매력적인 대안으로 부각되고 있다. 특히 유기발광다이오드는 고도의 봉지기술을 요구하는데 이는 유기재료가 물과 산소와 같은 산화 종에 매우 민감하기 때문이다. 대표적인 봉지기술의 재료로써 유리가 사용되며, 소자의 측면에 에폭시를 발라 UV 경화시켜 서로 붙이며, 그 사이에 흡습제를 넣는 것이다. 그러나 유리는 기계적 응력에 깨지기 쉽기 때문에 유연소자에 적용하기에는 적합하지 않다. 따라서 유연소자를 위한 박막봉지기술이 필수이다. 이 연구에서는 박막봉지막에 적용하기 위해 저온(100 ℃)에서 오존 기반 원자층증착법으로 증착한 100 nm 두께의 산화알루미늄(Al2O3)/산화지르코늄(ZrO2) 막에 대해 연구하였다. 50 ℃, 50%의 조건에서 전기적 칼슘 테스트를 이용해 Al2O3, ZrO2, 그리고 Al2O3/ZrO2 라미네이티드 막의 투습율을 구하였다. Al2O3/ZrO2 라미네이트 막이 각각의 Al2O3와 ZrO2 단일막 보다 더 좋은 투습막 특성을 보였고, Al2O3/ZrO2 라미네이트 막에서는 Al2O3와 ZrO2의 막의 교대층이 많을수록 더 좋은 투습막 특성을 보였다. 투습막 특성은 Al2O3와 ZrO2 내부층 사이의 계면과 관련이 있는데, 그 이유는 Al2O3와 ZrO2 내부층의 계면에 생성되는 ZrAlxOy 상이 각각의 Al2O3와 ZrO2의 단일상보다 더 밀도가 높고, 균질한 비정질 구조를 가지기 때문이다. 따라서 계면의 수가 많을수록 투습막의 특성이 향상된다.; Nowadays, organic electronic devices have emerged as attractive alternatives for lighting and photovoltaic applications. Especially, organic light emitting diodes (OLEDs) require highly advanced encapsulation layer because organic materials are very sensitive to oxidative species such as water and oxygen, so they require encapsulation to protect them. As a representative encapsulation technique is to use the glass with UV-cured epoxy resin dispensed at the sides of the devices as glue with getter inside. However, it is not suitable for flexible device due to high brittleness of glass under the mechanical stress, so thin film encapsulation is considered as indispensable technique for future flexible electronics. In this study, thickness of 100 nm Al2O3/ZrO2 layers grown by ozone (O3) based atomic layer deposition (ALD) at low temperature (100 °C) have been investigated as a layer of thin film encapsulations (TFE). Electrical calcium (Ca) degradation test was performed at relative humidity (RH) of 50 °C and 50 % to derive the water vapor transmission rates (WVTR) of aluminum oxide (Al2O3), zirconium oxide (ZrO2), and Al2O3/ZrO2 laminated films. Al2O3/ZrO2 laminated films exhibited better permeation barrier properties compared to those of Al2O3 and ZrO2 single layer films. In Al2O3/ZrO2 laminated films, the permeation barrier properties are improved as the number of alternating layers increases. The permeation barrier properties are closely related with the actual number of interfaces because of ZrAlxOy phase which is formed at the interface between Al2O3 and ZrO2 sublayers. ZrAlxOy phase is denser than single phase of each Al2O3 and ZrO2, and it has homogeneous amorphous structure. The formation of ZrAlxOy phase in Al2O3/ZrO2 laminated film improves the permeation barrier properties effectively.