矽光伏特材料於低溫薄膜電晶體之應用

Abstract

大面積軟性電路展現新型態的電子裝置，快速的崛起在顯示、感應裝置、生醫及其他領域。除此之外軟性電子元件更具備許多優點，輕量化、可饒式、耐用、可以因應更多自由的設計。因為氫化非晶矽薄膜電晶體的成熟的低溫製程，現階段是最常被使用在液晶顯示器以及軟性電子，然而最大的缺點便是較低的電子遷移率、不穩定性以及較高的驅動電壓。近來研究發展顯示奈米或稱微晶矽的材料是具有取代氫化非晶矽成為新一代軟性電子及大面積電子元件潛力本篇論文中，利用高密度電漿化學氣相沉積系統及熱燈絲化學氣相沉積系統在低溫200oC 下沉積出高結晶性的氫化微晶矽薄膜以及低電阻率的n 型氫化微晶矽薄膜，並且藉由XRD 及SEM 確認氫化微晶矽薄膜，確認晶粒大小約100nm 等同於一般非晶矽藉由固相結晶法(Solid Phase Crystallization) 600℃退火24 小時的結晶性。使用簡單的自我對準式薄膜電晶體，藉由場效傳導法(Field Effect Conductance)取出缺陷密度(Density of states)從中了解不同結晶度對於缺陷密度分布之影響。最後將低缺陷密度之氫化微晶矽及n 型氫化微晶矽薄膜整合成功的製作出不需離子佈植、低成本、低溫、高結晶性的薄膜電晶體，開與關的電流差距超過105、開關速度達到S=100mV/decade，並且電子遷移率達到50 cm2/V-s 展現出極高的潛力應用於軟性電子元件。

Flexible, large area circuits exhibit a new form of electronics which have led to rapidly rising and promising applications in displays, sensors, medical devices and other areas. Besides flexible electronics on plastic substrates possess advantageous characteristics, being lightweight, flexible, and have the capacity to be manufactured in a variety of shapes, which leads to freedom of design. Currently, a-Si:H TFTs are used in AMLCD and compatible with flexible substrate due to low temperature process. However, low device mobility, higher drive voltage and electrical instability are the main disadvantages of a-Si TFT. Recent developments reveal that micro- or nanocrystalline silicon is a promising alternative for flexible display and largearea electronic applications. The charge carrier mobility exceeds the mobility of amorphous silicon significantly and compatible with flexible substrate. In this thesis, a high quality and low resistivity of intrinsic and n-type microcrystalline silicon films were developed at low temperature 200oC by High Density Plasma chemical vapor deposition system and Hot-Wire chemical vapor deposition system. First μc-Si:H film was analyzed by XRD and SEM. And the μc-Si:H with a grain sizes of ~50-100 nm was recognized. The grain size is the same with conventional SPC(600℃annealing 24hours)method. A self-aligned TFTs was demonstrated. After that, the density of state distribution was extracted from TFTs by FEC method. With these results we can understand the different crystallinity on the effect of defect density distribution. Finally a top-gate microcrystalline TFTs without S/D implantation was demonstrated. A high electron mobility exceeding 50 cm2/V-s, low subthreshold swing 0.1-0.3 V/decade and high current ON/OFF ratios more than 105 was obtained. It shows highly potential in flexible electronics application.