選擇性沉積氧化鋅在矽奈米元件之濕度感測應用

Selective Deposition of ZnO on Silicon Nanodevices for Humidity Sensing Application

許照玄(Chao-Hsuan Sheu)

指導教授 ： 李耀坤

國立交通大學/理學院/分子科學研究所/碩士(2019年)

摘要

本研究整合了原子層沉積技術(Atomic Layer Deposition, ALD)，並利用元件焦耳自熱效應在元件上選擇性沉積氧化鋅於雙接面（n+/n-/n+）多晶矽奈米帶(Polysilicon Nanobelt, PNB)的n- 區域上，最後做為相對濕度感測器。研究成功運用此技術在元件n- 區域上選擇性沉積了氧化鋅，並進而分析氧化鋅元件對濕度感測之反應。由於元件的n- 區低濃度參雜，也是對表面最變化感測最靈敏的區域，因此這樣的設計可充分利用奈米元件的高靈敏度特性。研究同時也運用多重物理耦合軟體(COMSOL Multiphysics)，來模擬元件在焦耳自熱下的溫度分布。另一方面也利用熱載台(Thermal chuck)進行外部加熱，來推算元件表面升溫時的電阻變化。綜合上述兩個方法即可準確估計元件在焦耳自熱下，電壓與元件表面溫度的關係。元件製備後置於聚二甲基矽氧烷(PDMS)小腔體中，在元件焦耳自熱下進行相對濕度感測。相對濕度的感測研究比較了不同操作電壓下(亦即元件工作溫度不同)的量測結果:研究觀察到相對濕度17%以上的響應呈現出電性響應反轉的現象。最後研究依水分子在氧化鋅表面的化學與物理吸附與電性響應的關係，提出選擇性修飾氧化鋅奈米元件之濕度感測機制模型。

關鍵字

原子層沉積技術 ； 焦耳自熱效應 ； 選擇性沉積 ； 氧化鋅 ； 相對濕度 ； 濕度感測 ； 多重物理耦合軟體 ； 多晶矽奈米帶

並列摘要

In this work, a novel n+/n-/n+ polysilicon nanobelt (PNB) device has been presented for selective deposition of ZnO on n- region via atomic layer deposition (ALD) and device localized Joule self-heating. The device surface temperature was estimated via the relationship between COMSOL Multiphysics simulations and thermal chuck I-V(T) measurements. The estimated temperature was also used for ALD selective deposition. The device surface morphology and thickness after ALD selective deposition were characterized by AFM. In humidity detection, ZnO-decorated devices were mounted in a small PDMS chamber to perform humidity detection. The sensing behaviors with respect to self-heating temperature were analyzed at various relative humidity. An anomalous n to p-type response transition during humidity detection was observed when relative humidity was over 17% at a device bias larger than 25 V. Finally, a humidity sensing model based on chemical and physical adsorption of water molecule adsorption proposed. This model fully explained the electrical responses under various relative humidity.

並列關鍵字

Atomic Layer Deposition ； Joule self-heating ； selective deposition ； Zinc oxide ； relative humidity ； humidity sensing ； COMSOL Multiphysics ； Polysilicon Nanobelt

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