奈米金塗佈於立體指叉狀電極之CMOS MEMS 氣體感測器

Abstract

本研究嘗試開發一種可應用於微氣相層析系統的氣體感測器，該感測器為阻抗式感測器。主要利用立體指叉狀電極的結構及單層有機分子膜包覆奈米金屬簇(Monolayer Protected nano-Au Cluster, MPCs)的感應物質作結合，其量測機制是透過感應物質對於不同氣體濃度會有相對應的阻抗變化。感測器使用CMOS-MEMS製程製作，以TSMC 0.35μm 2P4M製程為基礎加上MEMS後製程，並塗佈感應物質(MPC)後完成。其中電極是將1,3金屬層及2,4金屬層分別經由via相連形成立體指叉狀電極，此結構不但增加了單位感應面積，同時也透過金屬層的距離縮短電極間距至1μm，可降低量測阻值並增加靈敏度。在本研究中分別量測甲苯、丁醇、辛烷三種氣體，其濃度感測範圍為30ppm至5000ppm，並且成功證明其良好的量測靈敏度及線性度。

In this research, we developed a chemiresistive gas sensor for micro gas chromatography system. The sensing material, monolayer protected gold nano-cluster (MPC), was coated onto the three dimensional interdigitated electrodes (3D IDEs) of the sensor. The measuring principle of this sensitive material is based on the impedance variation corresponding to different gas concentrations. This chemiresistive sensor was realized by using CMOS-MEMS fabrication process is based on TSMC 0.35μm 2P4M (2 polysilicon 4 metal) process and post process. The device was completed after spreading the sensitive material MPC on its surface. The 3D IDEs are composed by the first and third layer of the metal on one side and the second and forth layer of the metal on the other side. Our 3D IDEs not only increased the sensing surface area at a given chip area but also decreased the gap distance between electrodes to 1μm. This reduced gap distance increased the sensitivity of the sensor as well as lowered the resistance of the deposited sensing material. In this research, the great linearity and sensitivity of the sensor were demonstrated with three compounds (Octane, Butanol, and Toluene) at different concentrations in the range of 30ppm to 5000ppm and manifested the good linearity and sensitivity. Our sensor with exceptional reliability was also demonstrated by a prolonged testing over three months with minimal drift.