垂直轉移矽奈米線陣列及其熱傳導係數量測技術開發研究

Abstract

本研究利用金屬輔助無電蝕刻的方式製作大面積、低成本且長度為200 m以上之矽奈米線陣列，其蝕刻時間為1小時50分鐘，其蝕刻溶液為氫氟酸HF [6M]和硝酸銀AgNO3 [0.026M]。為了能將此矽奈米線陣列應用於熱電元件，本研究以鉻薄膜當蝕刻終止層，利用前述條件在薄化的矽晶圓上蝕刻出矽奈米線，再填入聚合物做支撐，來發展出矽奈米線陣列垂直轉移與圖案化技術。

熱傳導性質為熱電元件重要性質之一，本研究以前述方法製作出矽奈米線陣列結構，再設計一方法量測其熱傳導係數，並配合模擬分析驗證量測數據之準確性。本研究首先建立單一矽奈米線模型，藉助ANSYS Icepak 14.0電腦軟體與傅立葉熱傳定律，模擬計算出單一矽奈米線模型的xy方向和z方向熱傳導係數。接著利用軸流法量測出聚合物之熱傳導係數以及矽與聚合物的界面熱阻。再利用Icepak模擬矽奈米線陣列模型，並搭配平行線法所衍生出的三線式金屬線結構，經過模擬與量測結果互相比對，最後得出本研究製備之矽奈米線陣列結構之熱傳導係數為90 ~ 120 之間，證實矽奈米線陣列的熱傳導係數低於矽塊材。Fabrication of silicon nanowire arrays was presented by utilizing metal-assisted electroless etching in this study.Large-area and low cost silicon nanowire arrays with a length above 200 m was fabricated in an aqueous solution of AgNO3 (0.026 M) and HF (6M) for 110 minutes. Thinned silicon wafer has been etched to obtain nanowires array, and then filling in polymer to support the structure of nanowires. To develop a vertical transfer and patterned technology of silicon nanowires arrays and apply it in thermoelectric device, a method utilizing Cr thin film as stop-etching layer to terminate the etching process has been adapted in this study.

Silicon nanowires structure has been prepared according to above process, and an innovative method was designed to measure its thermal conductivity, which is the one of important properties of thermoelectric device. Furthermore, simulation analysis by software was used to verify the accuracy of measuring data. To build a single silicon nanowire model to measure the thermal conductivity of silicon nanowire arrays, ANSYS Icepak 14.0 software and Fourier’s law of thermal conduction have been utilized in this study. The results of xy and z direction of thermal conductivity of single silicon nanowire model were simulated and calculated. Next, we utilized axial heat flow method to measure the thermal conductivity of polymer and the interface thermal resistance of Si/polymer. Finally, a sample of silicon nanowires array with three metal wires has been made to simulate and measure the thermal conductivity of silicon nanowires structure, which is about 90 ~ 120 . This result confirms that the thermal conductivity of silicon nanowire arrays is lower than silicon bulk’s.