焦耳熱選擇性修飾矽奈米元件於氫氣及濕度感測器研究

Abstract

本研究運用焦耳熱輔助原子層化學沉積系統 (Atomic Layer Chemical Vapor Deposition, ALCVD) 選擇性沉積鉑金屬 (Platinum) 於元件上做為氫氣感測器使 用，並成功利用焦耳熱效應行 self-heating在室溫下即時地測量不同濃度的氫氣。 首先透過設計電阻式元件的參雜濃度 (n + /n - /n + ) ，可精準的控制焦耳熱放熱區域， 同時低濃度參雜區域對閘極電位變化靈敏的特點有利於感測氣體。接著應用 COMSOL 多重物理偶合模擬 self-heating 時表面溫度分布，與供給不同電壓下鉑 金屬的沉積情形相互驗證。將製備好的元件置於 PDMS 製作的小腔體中進行氫 氣感測，比較不同形貌的鉑金屬偵測氫氣的效率，優化其沉積條件，也比較不同 操作電壓下對氫氣感測的影響，定出最佳的量測條件使大氣中可靈敏地偵測 1.5 ppm 氫氣。另外，我們也應用焦耳熱區域性地燒除光阻再濺鍍氧化鋅的方式製備 濕度感測器，並對氫氣感測器做濕度校正，提高偵測氫氣的準確性。我們相信利 用焦耳熱效應技術製備的氫氣感測器可提升元件在室溫下的應用以及偵測準確 性，並預期此技術對呼吸氫氣測試等高濕度環境下準確地偵測氫氣有重大的幫 助。

In this study, we report the experimental results of selective deposition of Platinum via localized joule heating assisted atomic layer deposition on nanodevices as real-time hydrogen sensors. The active channels of nanobelt devices were consisted of n+/n-/n+ structure, and localized joule heating was induced at local high resistance n- region. The surface temperature was estimated by COMSOL simulations for different biases. AFM was used to investigate the morphology of Pt deposition at various conditions. Prepared devices were settled in a small chamber made by PDMS to perform the hydrogen detection. The effect of different Pt morphology was also compared on hydrogen sensing characteristics so that the deposition conditions were optimized simultaneously. Furthermore, several self-heating voltages were applied to accelerate response time of hydrogen sensing. The detection limit under atmosphere is about 1.5 ppm. In addition, selective ZnO modifications were achieved via localized PMMA ablation with Joule heating as humidity sensors. The developed ZnO-based humidity sensors were prepared as reference sensors in order to compensate humidity interference to H2 sensors.