- 學位論文
Silicon Nanocrystal Photosensor Integrated on Low-Temperature Poly-Silicon Display Panel
整合於低溫複晶矽顯示器面板上之矽奈米晶粒光感測器
摘要
Recently, the topic of in-cell photosensors integrated into TFT-LCDs has received considerable attention. By integrating an optical sensor or a sensor array on a display panel, additional functions such as backlight control for power saving, or optical touch screen, can be achieved on a TFT-LCD. With the feature of high carrier mobility, the low-temperature poly-silicon (LTPS) technology enables photodetectors to be incorporated into high performance poly-silicon thin-film transistor (TFT) circuits. That makes it self-contained to realize photo-sensing applications on an LTPS TFT-LCD. However, the conventional lateral p-i-n photodiodes on an LTPS display panel suffer from strong backlight noise and limitations in geometrical design. Besides, the grain boundaries in poly-silicon thin films markedly influence the reliability of the p-i-n photodiodes. In order to overcome the drawbacks, a novel photo-sensing device, using nanocrystalline silicon buried in an SiO2 film sandwiched between bottom metal and top indium-thin-oxide (ITO) electrodes is proposed to be realized on LTPS display panels. In this dissertation, the fabrication of the Si-nanocrystal photosensor by adopting excimer-laser-annealing (ELA) in LTPS technology is described. The mechanisms of quantum confinement, dielectric confinement and photo-carrier generation and transportation within the Si nanocrystals are comprehensively investigated as well as the non-linear optical properties due to the interface effect between the Si quantum dots and the dielectric layer. An embedded ambient light sensor of the Si-nanocrystal photosensor is entirely characterized with performance comparisons to the p-i-n photodiode that reveals better optical performances and device reliability in the Si-nanocrystal ambient light sensor. An analytical SPICE model of the Si-nanocrystal photosensor is built for simulations of active sensor circuits designed for photo-sensing applications. A small-sized active sensor array is successfully demonstrated with the ability of image detection for an optical touch panel development. In addition, a backlight modulated readout scheme with a digital pixel output is studied in this work, which can filter out the ambient light noise and ensure the touch functionality under dark operational environment.
並列摘要
近年來，將光學感測器整合於薄膜電晶體液晶顯示器(TFT-LCD)上是相當受到關注的研究主題，藉由整合單一個光感應器或一個感測器陣列於顯示器面板上，一些有用的附加功能，例如利用控制背光源來節省電力的消耗，亦或是光學式的觸控面板等，可以實現在薄膜電晶體液晶顯示器上以提升其價值；低溫複晶矽(LTPS)技術擁有高載子遷移率，可於高效能的複晶矽(poly-Si)薄膜電晶體電路中整合光學感測器，以開發各種不同的應用；然而，在LTPS顯示器面板上，傳統側向式的p-i-n感光二極體會因為強烈背光源的照射影響其特性，且其結構在幾何設計與效能最佳化上面受到先天的限制。除此之外，複晶矽薄膜中的晶粒邊界存在著許多缺陷導致p-i-n感光二極體的元件可靠度低；為了決解這些缺點，本論文提出一個新式的光測器架構，將矽奈米晶體(Si nanocrystal)嵌入於一富矽氧化薄膜中，此氧化薄膜夾在不透光的金屬下電極與透明的銦錫氧化物(ITO)上電極之間做為一光感測元件，整合此新式矽奈米晶光感測器，可在LTPS顯示器面板上開發嵌入式環境光感測器以及光學反射式觸控面板。 本論文中將詳述利用LTPS製程中的準分子雷射退火技術來製造矽奈米晶光感測器的方法，並討論此矽奈米晶光感測器的量子侷限效應以及光激載子的產生與傳輸等機制，更進一步地討論由於矽量子點與介電層的介面效應所造成的非線性光響應特性。本論文將詳細分析此嵌入式矽奈米晶環境光感測器的特性並將之與傳統p-i-n感光二極體之環境光感應器做比較，由實驗的結果可得知矽奈米晶光感測器有較好的光感測效能和元件可靠度。本論文在SPICE的環境中建立了一個矽奈米晶光感測器的模型，利用此光感測器模型可精確的預測被動式或主動式矽奈米晶光感測架構的光電反應；本論文亦成功實做一小型主動式感測器陣列並展示其影像偵測的能力，以利評估光學式觸控面板的開發，並提出一背光調變式的讀取方法，此讀取電成功地濾除了環境光的雜訊，並確保光感應式觸控螢幕不受環境光的影響，於各種操作環境下都能維持正常功能。
參考文獻
延伸閱讀
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