高c軸排列AlN薄膜之製作及其在UV檢測器之應用

Fabrication of highly oriented c-axis AlN films and their application for UV photodetector

張褚峰(Chu-Fung Chang)

指導教授 ： 林啟瑞

國立臺北科技大學/機電學院/機電整合研究所/碩士(2010年)

https://doi.org/10.6841/NTUT.2010.00285

摘要

一個優良的紫外光檢測器必須具有高靈敏性、高精密性、低功率損耗及高熱穩定性等特點，俾應用於現今之科學、化學、工業及國防方面。近年來III-V族為熱門光電材料，其中氮化鋁具有光電導特性、寬能隙(~6.2eV)、高熱傳係數、高熱穩定性及高化學穩定性，最具潛力發展紫外光檢測器之候選材料。
本論文利用非平衡磁控濺鍍系統沉積於Si(100)及Sapphire(001)之基板上，研製氮化鋁薄膜之金屬-半導體-金屬光檢測器，其中改變不同之參數條件來成長具有c軸優選取向之氮化鋁薄膜，再搭配微影蝕刻、舉離法製作出指叉狀電極，為了讓電極與材料之間有較高靈敏性及低功率損耗，利用爐管退火，其製程壓力為2×10-2 torr、氬氣為20 sccm、退火溫度為500 ℃、持溫時間為10 min，達到歐姆接觸作為電流傳導的界面，成功備製出紫外光檢測器。
本研究中，首先為了成長出c軸優選取向之氮化鋁薄膜，藉由適當的製程參數控制，成長氮化鋁薄膜。研究結果顯示氮氣濃度比例及射頻功率對於氮化鋁薄膜成長c軸優選取向影響最為顯著，接著研究中改變沉積基板為Sapphire(001)，主要目的是探討基板效應之影響，雖然能因基板效應之影響成長出高AlN(002)面之繞射峰，但其薄膜屬於多晶氮化鋁。研究結果指出使用Si(100)為基板，在RF功率175 w、氮氣濃度比例50 %、工作壓力4 mtorr、沉積時間3小時，能在室溫下成長出c軸優選取向之AlN薄膜，其半高寬為0.2007°、膜厚為458.8 nm，其表面粗糙度皆<5 nm(Rms)，達到製作元件的平整度。研究最後是將c軸優選取向之氮化鋁薄膜製作成紫外光檢測器，進行光電流量測，探討其光電流之增益與頻率響應，研究結果指出，在外加偏壓 10V時，自製檢測器經照射UV光(250~400 nm)後，具有明顯的電流增益，增益值差為3 order。

關鍵字

c軸優選取向 ； 氮化鋁薄膜 ； 紫外光檢測器

並列摘要

Future missions for space astronomy, defense, science and technology required UV photodetector that possess high sensitivity, high precision, low power loss, and high thermal stability. Recently, aluminum nitride has attracted a worldwide attention for potential applications in UV photodetectors, as it possesses good photoconductive properties, including of wide bandgap (~ 6.2 eV), high thermal conductivity as well as high chemical stability.
In this study, to develop the applications metal - semiconductor – metal photodetectors, AlN thin films were deposited onto Si (100) and Sapphire (001) substrate by using unbalanced magnetron sputtering system. Effects of various parameters on properties of coated AlN were investigated to obtain the c-axis AlN films. The obtained AlN thin films were employed to fabricate the Inter Digital Transducer (IDT) by using lithography and lift-off methods. To achieve an Ohmic contact as a conduction current interface for UV detector, the films finally were annealed at 500 oC in argon atmosphere (20 sccm of flow rate), with working pressure of 2x10-2 torr for 10 min. The produced films were characterized by X-ray diffractometry, scanning electron microscopy (SEM), atomic force microscopy (AFM). From X-ray diffraction, nitrogen concentration and RF power have the most significant impact to the deposition of high C-axis AlN films. High C-axis AlN thin films were successfully deposited onto Si (100) substrate with 0.2007o of FWHM and 458.8 nm of thickness, as the RF power was 175 w, 50% of nitrogen concentration, 4 mTorr of working pressure and 3 hours process. The AFM results showed that the roughness were < 5 nm (Rms). The AlN films finally were employed to fabricate UV photodetector. From photoconductivity measurement, as the applied bias voltage was ±10V, the self-detector for UV light irradiation (250-400 nm) has a current gain increases about 3 orders.

並列關鍵字

c-axis preferred orientation ； Aluminum nitride thin films

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