Abstract
摘要:近年來奈米矽晶薄膜在大面積光電與電子(large-area optoelectronics and electronics)領域的應用與日俱增,其應用範圍涵蓋薄膜太陽能電池、薄膜電晶體等,其製程也與當前蓬勃發展的軟性電子(flexible electronics )有極高的相容性。雖然過去十年來奈米矽晶材料在製程與相關元件的發展迅速,然而由於其結構複雜性高,且材料特性對於製程參數敏感度高,因此在其基礎物理特性上的研究仍有待加強,其中又以穩定性及可靠度等研究最為迫切。目前這方面的研究仍在初步發展階段,且大多穩定度測試都針對元件層級作探討,不同甚至相互矛盾的結果相繼被提出。 因此,從基礎物理層面來針對薄膜層級做奈米矽晶之電性、光學性質以及可靠度等之研究是相當重要的課題。
本計畫的研究目的在於針對奈米矽晶薄膜的製程參數、薄膜結構與結晶度、能帶間隙中的缺陷分佈及穩定度與可靠度間的相關性作系統性的研究與分析。整個計畫執行可區可分為三大部分:薄膜沉積、穩定度與可靠度實驗、薄膜分析檢測。首先是樣品製作部分,我們採用電漿輔助化學氣相沉積法來成長奈米矽晶薄膜,所使用的基板包括玻璃基板以及透明塑膠基板,藉由製程參數的調整沉積出一系列具有不同結晶度與結構的奈米矽晶薄膜。 接著則是可靠度與穩定度測試,主要實驗方法是透過外加電流、外加光照或機械應力的施加等方式來觀察奈米矽晶薄膜能帶間隙中缺陷分佈在測試前後下的變化,藉此了解其穩定性與結晶度的相關性。 而薄膜分析檢測部分則是利用X光繞射(X-ray diffraction)與拉曼光譜(Raman Spectroscopy)來分析奈米矽晶薄膜結構與結晶度 ; 並透過光學與電性量測方法,結合穿透/反射光譜量測與等光電流量測(Constant photocurrent measurement)來取得其吸收光譜,再由吸收光譜獲取能帶間隙中缺陷分佈的資訊。我們希望藉由此計畫能有系統性的分析出奈米矽晶薄膜結晶度與穩定性之間的相關性,進而建立一模型準則來協助
Abstract: Hydrogenated nanocrystalline silicon (nc-Si:H) is a promising candidate material for low temperature large-area electronics, such as thin film solar cells and thin film transistors. The fast growing interests in flexible electronics today also motivates the development of nc-Si:H technology on account of its potential advantages of compatibility with plastic substrates, capability of complementary metal-oxide-semiconductor operation, possibly improved stability against light-induced degradation, and compatibility with the well-established hydrogenated amorphous silicon (a-Si:H) technology. Even though the progress in the deposition techniques and device fabrication of nc-Si:H have been quite substantial in recent years, the study of the nc-Si:H stability is still insufficient and most of the researches were conducted in the device-level. In addition, because of the complexity of the nc-Si:H materials, inconsistent even conflict results have been drawn.
The goal of this project is to have a fundamental understanding of nc-Si:H by systematic study of the correlation among thin film structure/phase, subbandgap defect density distribution, and stability behavior of nc-Si:H. The research can be divided into three parts: (a) sample preparation, (b) stability/reliability experiments and (c) sample analysis. First, nc-Si:H thin films will be deposited at various deposition conditions by plasma enhanced chemical vapor deposition system (PE-CVD) on glass and clear plastic substrates. By properly adjusting the processing parameters, a series of nc-Si:H with different crystal volume fraction will be obtained. Next, we will perform stability/reliability experiments, such as electrical-bias stressing, light irradiation/soaking experiments, and micro-stretching experiments. The sample structure and crystallinity will mainly be investigated by Raman spectroscopy and X-ray diffraction. The optical properties, such as optical bandgap and index of refraction, and defect state distribution will be studied by optical transmission measurement along with constant photocurrent measurement prior and after the stability /reliability experiments. Through the experiments performed in the project, we expect to establish a systematic method to identify device-quality nc-Si:H thin film prior to device fabrication, which will be beneficial to the design and development of nc-Si:H devices.
Keyword(s)
奈米矽晶
結晶度
穩定度
定光電流量測
吸收光譜
nanocrystalline silicon
crystal volume fraction
stability
constant photocurrent measurement
absorption spectrum