原子層沈積技術之奈米複合阻氣薄膜研究

Abstract

本論文研究原子層沈積（Atomic Layer Deposition, ALD）奈米複合阻氣薄膜的機制，探討材料與結構對於薄膜氣體穿透率與抗撓曲程度的影響。本論文選擇氧化鋁/氧化鉿（Al2O3/HfO2,以下簡稱AHO）與新開發的氧化鋁/氧化鋅(Al2O3/ZnO, 以下簡稱AZO) 等兩種奈米複合阻氣薄膜。本研究發現在不同Al2O3/HfO2與Al2O3/ZnO比例下，奈米複合薄膜之氣體滲透率會隨著HfO2與ZnO含量增加而提高，而其可撓曲度則隨之下降。此是由於HfO2與ZnO皆為結晶性材料，因此當其於奈米複合薄膜結構中含量增加時，會於薄膜中產生大量晶界，使氣體滲透率上升；同時，該等結晶亦使薄膜容易在撓曲後受到破壞，因此可撓曲度較差。在AHO與AZO比較之比較方面，本研究發現AZO之氣體滲透率一般較AHO為高，此乃因ZnO較HfO2易結晶，因此較易產生氣體可快速通過之晶界；然而，當ZnO與HfO2的含量低時，AZO的氣體滲透率反而較AHO低，此是因為ZnO與HfO2兩種材料於複合薄膜中層數過少，尚不足以形成結晶，而ZnO成長時的立體障礙較小，能形成較緻密的結構。在經過結構與成膜條件的最佳化後，本研究所製備之AZO與AHO薄膜的水氣穿透率(WVTR)與氧氣穿透率（OTR）皆達到低於儀器量測極限(WVTR: 5×10-4g/m2/day; OTR: 2×10-2 c.cc/m2/day)的水準。此外，該等AHO與AZO薄膜具有穩定之阻氣效能，其阻氣效能經空氣中儲存超過1500小時或經撓曲2000次後皆不會有變化。

This study developed nano-laminated gas-permeation barriers with atomic layer deposition (ALD) to achieve low gas permeability, high flexibility/bendability, and in-air stability. Two material systems were investigated: Al2O3/HfO2 (AHO) and Al2O3/ZnO (AZO), the latter of which was a novel material for gas barrier applications. The barrier performance and flexibility of the nano-laminates were significantly dependent upon the Al2O3/HfO2 (A/H) and Al2O3/ZnO (A/Z) ratios: they both deteriorated with increasing A/H and A/Z ratios. This was attributed to the crystalline nature of HfO2 and ZnO, which increased the susceptibility to bending of the nano-laminates and provided grain boundaries for rapid gas permeation. Comparing AZO and AHO with the same A/Z and A/H ratios, we found that AZO was generally poorer gas barriers than AHO, likely as a result of ZnO’s greater tendency to crystallize; however, at lower ratios, AZO had lower gas permeability than AHO, likely as a result of better surface coverage enabled by the lower steric hindrance of the ZnO organometallic precursor. Upon optimizations of the composition and ALD conditions, both the AZO and AHO films achieved low water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) (WVTR < 5×10-4 g /m2/day; OTR < 2×10-2 c.c./m2/day) and remained stable upon storage in air for > 1500 h or bending for 2000 times.