濕式氧化法製備矽奈米線及其光偵測器之應用

Using a Wet Oxidation Method for Fabrication of Silicon Nanowires and Their Application in Photodetectors

高鵬曜(Peng-Yao Kao)

指導教授 ： 毛明華

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202003525

摘要

在本論文中，我們製作出水平式矽奈米線材料的金屬-半導體-金屬蕭特基接觸光偵測器。在製程上，使用濕式氧化法將黃光微影定義出的矽長直條尺度微縮至奈米等級，並與下方矽基板隔絕，達到與使用SOI基板製作有相同的隔絕效果，避免使用昂貴的基板。然後旋塗SU-8負阻劑進行平坦化，最後在上方進行二次黃光微影、e-gun鍍鋁及掀離(lift-off)步驟，完成元件製作。
在量測上，利用兩端點的電性量測方式，量測元件在405 nm光照射下不同光強度的電流-電壓表現，並將電性量測之數據套入公式中去計算響應率，做成響應率-雷射光功率密度關係圖，發現隨著光功率密度增強，響應率有下降並趨緩的現象。另外我們將元件放入真空系統中進行變溫的量測，發現在80 K至150 K時，元件的光電流大約維持在0.032 nA，但在150 K至300 K時，光電流卻有下降的趨勢。我們認為這是因為表面缺陷能態在溫度高於150K之後被活化，捕獲載子而造成載子濃度降低所致。

關鍵字

矽奈米線 ； 濕式氧化 ； 金屬-半導體-金屬 ； 蕭特基接觸 ； 光偵測器 ； 響應率

並列摘要

In this thesis, we have fabricated the lateral Si nanowire-based metal-semiconductor-metal Schottky-contact photodetectors. In the process, we used the wet oxidation method to fabricate the Si nanowires on Si substrate. It has the same isolation effect, and also costs less than the conventional use of the SOI substrate. And then we spin-coated SU-8 to planarize the structure. Finally, we completed fabrication of our devices by using second lithography, e-gun evaporation, and lift-off.
For the device characterization, we use the two-terminal method and a 405nm diode laser to measure electrical performance of our devices under different laser power density. We observe that responsivity decreases when laser power density increases. We also measure our devices under vacuum and different temperature. Photocurrent remains almost constant at 0.032 nA from 80K to 150K, but it decreases from 150 K to 300 K. We believe that this phenomenon is caused by surface states which are activated by thermal energy at this temperature range.

並列關鍵字

Si Nanowires ； Wet Oxidation ； Metal-Semiconductor-Metal ； Schottky contact ； Photosensors ； Responsivity

參考文獻

[1] S. Sze, D. Coleman Jr, and A. Loya, "Current transport in metal-semiconductor-metal (MSM) structures," Solid-State Electronics, vol. 14, no. 12, pp. 1209-1218, 1971.

[2] Bing-Chang Zhang, Jian-Sheng Jie, Zhi-Bin Shao, Si-Yi Huang, Le He, and Xiao-Hong Zhang, " One-step growth of large-area silicon nanowire fabrics for high performance multifunctional wearable sensors ," Nano Res. 2019, 12(11): 2723–2728.

[3] Sorin Cristoloveanu,"Introduction to Silicon On Insulator materials and devices," Microelectronic Engineering, Vol. 39, Issues1-4, Pages 145-154 (1997).

[4] Chii-Wen Chen, Wei-Qi Chen, " Silicon on Insulator Analysis and Application," Volume 32, Minghsin Journal, August 2006.

[5] H Elhadidy et al, "Symmetrical current–voltage characteristic of a metal–semiconductor–metal structure of Schottky contacts and parameter retrieval of a CdTe structure," Semicond. Sci. Technol. 27 (2012).