低溫化學氣相成長高水氧阻隔性材料與應用

Abstract

由於其可撓性、可彎曲性、耐衝擊性…等好處，使軟性電子與軟性顯示器在科技發展上越來越重要。在軟性電子中，除了元件中的主動層外，找到適當的可撓曲介電材質是實現軟性電子的重要關鍵。如：TFT中需要高品質的介電層作為gate insulator；為了延長元件的使用壽命，所使用的阻擋水氣、氧氣的保護層也是不可或缺的。然而，由於可撓性基板較為脆弱且無法耐高溫，必須發展出低溫(接近室溫)製程技術，因此如何在低溫下成長出高品質的介電薄膜是軟性電子未來發展一大課題。 在本論文中，我們探討在ICP-CVD系統中，以前驅物Hexamethyldisiloxane (HMDSO)與O2在低溫下成長出高品質的介電物質。藉由調整HMDSO/O2氣體比例、製程氣壓、CVD功率等參數，可在低溫下(接近室溫)控制薄膜成為特性較偏矽氧樹脂(偏有機)或是偏二氧化矽(偏無機)，藉以符合製程的需求。當複合薄膜成長150 nm在E2K玻璃時，在可見光範圍內仍可具有相當不錯的透明度，穿透率可達90%以上。同時，薄膜具有高崩潰電場，可達5.1MV/cm，並有與高溫350℃下 PECVD所成長出的SiOx同等級的低漏電流，確保在未來能運用於軟性電子上。有機-無機複合薄膜具有相當不錯的水氧阻隔性，藉由Mocon Aquatran的量測，當在PEN基板上成長150 nm有機-無機複合薄膜時，其水氣穿透率小於5E-4g/m2-day ，已達到機台的量測極限，未來也可將薄膜運用於軟性電子的保護層與阻擋層。

Due to their various features and merits, flexible electronics and displays are becoming more and more important. In addition to active semiconducting materials, flexible and high-performance dielectric materials are also essential for fully realizing flexible electronics and displays. For instance, high-performance dielectrics are needed for gate insulators of TFTs. To prolong device reliability and lifetimes, passivation layers with low water and oxygen permeation are required. Yet these dielectric materials shall be deposited at low temperatures (or even room temperature) to be compatible with plastic substrates often used in flexible electronics. In this study, we investigated the ICP-CVD growth of high-performance dielectric materials at low temperatures from organosilicon precursor Hexamethyldisiloxane (HMDSO) and O2. By tuning HMDSO/O2 gas ratios, working pressure, and CVD power, organic-inorganic hybrid films were obtained at (or near) room temperature with characteristics tunable from silicone-like (more organic) to silica-like (more inorganic) characteristics. The hybrid films (e.g. 150-nm thick on E2K glass) are very transparent in visible-light region with transmittance >90%. The hybrid films can show high breakdown fields up to 5.1MV/cm and low leakage currents, which are comparable to characteristics of SiOx deposited by PECVD at 350℃ and are promising for flexible electronics. The 150-nm hybrid films on PEN plastic substrates exhibit good barrier properties, with water vapor transmission rate < 5E-4g/m2-day as measured by Mocon Aquatran (indeed beyond instrument limit), making it also promising for passivation and barrier applications of flexible electronics.