臺灣博碩士論文加值系統

本研究利用微機電系統技術發展具多孔矽及奈米特性之金屬氧化物氣體微感測器，應用於相對低溫環境（25℃∼60℃）感測低濃度(5ppm)NOx氣體。當待測氣體吸附於感測薄膜表面時，因蕭特基接觸而使元件產生電阻變化，藉由量測此電阻變化量，可獲得感測靈敏度。以溶膠－凝膠法製備氧化鎢與多層奈米碳管混合之感測薄膜，並利用電化學蝕刻法製作多孔矽質微結構，將感測薄膜沉積於微多孔結構上，提高待測氣體與感測薄膜接觸面積，增加表面化學反應。微感測器配合蔽蔭遮罩以熱蒸鍍法製作指叉狀鎳感測電極，促進氣體催化，利於氣體吸附於感測薄膜表面，提高量測靈敏度。氣體微感測器結合光微影和蝕刻製程製作之加熱器，有效提升元件操作性及加快反應時間。實驗探討WO3感測薄膜於不同操作溫度及NOx氣體濃度的靈敏度變化，及多孔矽尺寸與感測電極對反應機制的影響。結果顯示WO3感測薄膜於60℃感測5ppmNOx氣體時可達最高靈敏度，室溫環境可感測5ppmNOx氣體，氣體微感測器反應時間與回復時間隨溫度升高而縮短，最短分別為25及32秒。

This study presents the design of metal-oxide micro gas sensors based on MEMS technology with porous silicon and nano-properties for NOx gas sensing in low concentration(5ppm) at relative low temperature(25℃∼60℃). Sensitivity is defined by measuring the variation of resistance for sensing layers caused by Schottky contact when gas specimens adsorb on the surface of sensing films. It is proposed that sensing films deposited onto the porous silicon surface fabricated by electrochemical etching are mixed with WO3 and MWCNTs by a sol-gel technique in order to increase effective area and chemical reactions on which gas molecules can be adsorbed. Interdigitated Ni catalytic electrodes are deposited onto the sensing films with a shadow mask by evaporating to improve gas adsorption on the surface of sensing films and increasing sensitivity. The gas micro sensor is also integrated with a heater made via lithography and deep etching processes for enhancing the properties of operation and response time. Experiments reveal the highest sensitivity of WO3 films is occured in the 5ppm of NOx at 60℃ and it is possible to detect 5ppm of NOx in room temperature. The response and recovery time of gas micro sensors are decreased with rising temperature that are 25s and 32s at lowest respectively. The results investigate the variation of sensitivities for sensing layers at various operating temperatures and different concentrations of NOx. The influence of dimensions for porous silicon and catalytic electrode on sensing response is also discussed.

誌謝 i
摘要 ii
Abstract iii
目錄 iv
圖目錄 vii
表目錄 xi
第一章 緒論 1
1.1 前言 1
1.2 研究動機與目的 3
1.3 文獻探討 5
1.4 研究流程與架構 14
第二章 氣體微感測器原理 16
2.1 金屬氧化物氣體感測器 16
2.1.1 蕭特基接觸 16
2.1.2 金屬氧化物氣體感測器感測機制 18
2.1.3 金屬氧化物氣體感測器靈敏度分析 20
2.1.4 氧化鎢特性 22
2.2 奈米碳管 24
2.2.1 奈米碳管特性 24
2.2.2 奈米碳管氣體感測器的應用 25
2.3 多孔矽微結構 26
2.4 溶膠－凝膠法混成感測薄膜 27
第三章 微製程設計 29
3.1 微感測元件設計 29
3.2 多孔矽蝕刻設備 31
3.2.1 電化學蝕刻夾具設計 32
3.2.2 照光設備與電極材料選擇 33
3.3 非等向性蝕刻與夾具保護設計 34
3.4 氧化鎢感測薄膜製作 38
3.5 光罩設計 40
3.5.1 微結構圖形設計 40
3.5.2 光罩對準圖形設計 45
3.6 微感測元件製程規劃 48
第四章 微元件製作與量測分析 53
4.1 微感測元件製程 53
4.1.1 多孔矽與對準圖形微影製程 53
4.1.2 多孔矽預蝕刻 56
4.1.3 電化學蝕刻製作多孔矽 59
4.1.4 晶圓背向蝕刻 63
4.1.5 具多層奈米碳管之氧化鎢感測薄膜製作與分析 64
4.1.6 指叉狀感測電極製作 72
4.1.7 加熱器製作 73
4.2 量測與分析 74
4.2.1 量測架構 74
4.2.2 加熱器分析 75
4.2.3 感測性質量測 77
第五章 結論與未來工作 83
5.1 結論 83
5.2 未來發展 84
參考文獻 85

[1]李科杰，新編傳感器技術手冊，北京－國防工業出版社，2000年1月。
[2]M. L. Davis and D. A. Cornwell, Introduction to Environmental Engineering, 2nd Edition, McGraw-Hill, Inc. , New York, pp. 430-431, 1991.
[3]T. Takashi, "Oxygen sensor," Sensors and Actuators, Vol. 14, No. 1, pp. 109-110, 1994.
[4]H. Pink, L. Treitinger and L. Vite, "Preparation of fast detecting SnO2 gas sensor," Japanese Journal of Applied Physics, Vol. 19, No. 3, pp. 513-517, 3 March 1980.
[5]W. G. Pfann and H. P. Baltes, "A CMOS magnetic filed sensor," IEEE J. of Solid-State Circuits, Vol. 18, pp. 426-428, 1983.
[6]N. Yamazoe and N. Miura, "Environmental gas sensing," Sensors and Actuators B, Vol. 20, pp. 95-102, 1994.
[7]G. Sberveglieri, L. Depero, S. Groppelli and P. Nelli, "WO3 sputtered thin films for NOx monitoring," Sensors and Actuators B, Vol. 26(1–3), pp. 89-92, 1995.
[8]P. J. Shaver, "Activated tungsten oxide gas detectors," Applied Physics Letters, Vol. 11, pp. 255-257, 1967.
[9]B. Ruhland, T. Becker and G. Muller, "Gas-kinetic interactions of nitrous oxides with SnO2 surfaces," Sensors and Actuators B, Vol. 50, pp. 85-94, 1998.
[10]D. S. Lee, J. W. Lim, S. M. Lee, J. S. Huh and D. D. Lee, "Fabrication and characterization of micro-gas sensor for nitrogen oxides gas Detection," Sensors and Actuators B, Vol. 64, pp. 31-36, 2000.
[11]D. G. Rickerby, N. Wachter, M. C. Horrillo, J. Gutierrez, I. Gracia and C. Cane, "Structural and dimensional control in micromachined integrated solid state gas Sensors," Sensors and Actuators B, Vol. 69, pp. 314-319, 2000.
[12]C. Moldovan, L. Hinescu, M. Hinescu, R. Iosub, M. Nisulescu, B. Firtat, M. Modreanu, D. Dascalu, V. Voicu and C. Tarabasanu, "Silicon micromachined sensor for gas detection," Materials Science and Engineering B, Vol. 101, pp. 227-231, 2003.
[13]P. Kreisl, A. Helwig, A. Friedberger, G. Muller, E. Obermeier and S. Sotier, "Detection of hydrocarbon species using silicon MOS capacitors operated in a non-stationary temperature pulse mode," Sensors and Actuators B, Vol. 106, pp. 489-497, 2005.
[14]S. Kandasamy, A. Trinchi, W. Wlodarski, E. Comini and G. Sberveglieri, "Hydrogen and hydrocarbon gas sensing performance of Pt/WO3/SiC MROSiC devices," Sensors and Actuators B, Vol. 111-112, pp. 111-116, 2005.
[15]G. Gorokh, A. Mozalev, D. Solovei, V. Khatko, E. Llobet and X. Correig, "Anodic formation of low-aspect-ratio porous alumina films for metal-oxide sensor application," Electrochimica Acta, Vol. 52, pp. 1771-1780, 2006.
[16]C. Lua, Z. Chena and K. Saito, "Hydrogen sensors based on Ni/SiO2/Si MOS capacitors," Sensors and Actuators B, Vol. 122, pp. 556-559, 2007.
[17]L. Yadav, N. C. Gupta, R. Dwivedi and R. S. Singh, "Sensing behavior and mechanism of titanium dioxide-based MOS hydrogen sensor," Microelectronics Journal, Vol. 38, pp. 1226-1232, 2007.
[18]E. H. Espinosa, R. Ionescu, B. Chambon, G. Bedis, E. Sotter, C. Bittencourt, A.
Felten, J. J. Pireaux, X. Correig and E. Llobet, "Hybrid metal oxide and multiwall carbon nanotube films for low temperature gas sensing," Sensors and Actuators B, Vol. 127, pp. 137-142, 2007.
[19]V. M. Arakelyan, V. E. Galstyan, K. S. Martirosyana, G. E. Shahnazaryan, V. M. Aroutiounian and P. G. Soukiassian, "Hydrogen sensitive gas sensor based on porous silicon/TiO2-x structure," Physica E, Vol. 38, pp. 219-221, 2007.
[20]S. Vallejos, V. Khatko, J. Calderer, I. Gracia, C. Cane, E. Llobet and X. Correig, "Micro-machined WO3-based sensors selective to oxidizing gases," Sensors and Actuators B, 2008.
[21]E. Massera, I. Nasti, L. Quercia, I. Rea and G. Di Francia, "Improvement of stability and recovery time in porous-silicon-based NO2 sensor," Sensors and Actuators B, Vol. 102, pp. 195-197, 2004.
[22]B. Mitu, S. Vizireanu, R. Birjega, M. Dinescu, S. Somacescu, P. Osiceanu, V. Parvulescu and G. Dinescu, "Comparative properties of ternary oxides of ZrO2–TiO2–Y2O3 obtained by laser ablation, magnetron sputtering and sol–gel Techniques," Thin Solid Films, Vol. 515, pp. 6484-6488, 2007.
[23]K. Hamamoto, Y. Fujishiro and M. Awano, "Gas sensing property of the electrochemical cell with a multilayer catalytic electrode," Solid State Ionics, Vol. 179, pp. 1648-1651, 2008.
[24]T. Ueda, S. Katsuki, K. Takahashi, H. A. Narges, T. Ikegami and F. Mitsugi, "Fabrication and characterization of carbon nanotube based high sensitive gas Sensors operable at room temperature," Diamond & Related Materials, Vol. 17, pp. 1586-1589, 2008.
[25]Ch. Y. Wang, M. Ali, T. Kups, C. C. Rohlig, V. Cimalla, T. Stauden and O. Ambacher, "NOx sensing properties of In2O3 nanoparticles prepared by metal organic chemical vapor deposition," Sensors and Actuators B, Vol. 130, pp. 589-593, 2008.
[26]Shalaka C. Navale, V. Ravia, D. Srinivas, I. S. Mulla, S. W. Gosavi and S. K. Kulkarni , "EPR and DRS evidence for NO2 sensing in Al-doped ZnO," Sensors and Actuators B, Vol. 130, pp. 668-673, 2008.
[27]V. V. Plashnitsa, T. Ueda, P. Elumalai and N. Miura, "NO2 sensing performances of planar sensor using stabilized zirconia and thin-NiO sensing electrode," Sensors and Actuators B, Vol. 130, pp. 231-239, 2008.
[28]K. Shimizu, K. Kashiwagi, H. Nishiyama, S. Kakimoto, S. Sugaya, H. Yokoi and A. Satsuma, "Impedancemetric gas sensor based on Pt and WO3 co-loaded TiO2 and ZrO2 as total NOx sensing materials," Sensors and Actuators B, Vol. 130, pp. 707-712, 2008.
[29]R. Triantafyllopoulou, S. Chatzandroulis, C. Tsamis and A. Tserepi, "Alternative micro-hotplate design for low power sensor arrays," Microelectronic Engineering
, Vol. 83, pp. 1189-1191, 2006.
[30]S. R. Morrision, "Chemical sensors" in Semiconductor Sensors, ed. S. M. Sze, John Wiley and Sons, New York, pp. 383, 1994.
[31]P. B. Weisz, "Effects of electronic charge transfer between adsorbate and solid on chemisorption and catalysis," The Journal of Chemical Physics, Vol. 21, No. 9, pp. 1531-1538, 1953.
[32]吳峰日，感測與轉換器，文笙書局，1990年五月。
[33]H. Windischmann and P. Mark, "A model for the operation of a thin film SnOx conductance-modulation carbon monoxide sensor," J. Electrochem. Soc. , Vol. 126, No. 4, pp. 627-633, 1979.
[34]S. R. Morrison, The Chemical Physics of Surfaces, 2nd, New York : Plenum Press, pp. 251, 1990.
[35]吳泉毅，楊宗燁，林鴻明，奈米半導體材料之氣體感測性質，物理雙月刊，25卷3期，2003年6月 。
[36]P. L. Andrew, "Temperature modulation in semiconductor gas sensing," Sensors and Actuators B, Vol. 60, pp. 35-42, 1999.
[37]P. T. Moseley, "Materials selection for semiconductor gas sensors," Sensors and Actuators B, Vol. 6, pp. 149-156, 1992.
[38]IRA N. Levine, Physical Chemistry, 4th edition, MsGraw-Hill, New York, pp. 443, 1995.
[39]N. Yamazoe, Y. Kurokawa and T. Seiyama, "Effects of additives on semiconductor gas sensors," Sensors and Actuators B, Vol. 4, pp. 283-289, 1983.
[40]S. R. Morrison, "Selectivity in semiconductor gas sensors," Sensors and Actuators B, Vol. 12, pp. 425, 1987.
[41]J. Tamaki, Z. Zhang, K. Fujimori, M. Akiyama, T. Harada, N. Miura and N. Yamazoe, "Grain-size effects in tungsten oxide-based sensor for nitrogen oxide," J. Electrochem. Soc. , Vol. 141, pp. 2207-2210, 1994.
[42]M. Penza, M. A. Tagliente, L. Mirenghi, C. Gerardi, C. Martucci and G. Cassano, "Tungsten trioxide (WO3) sputtered thin films for a NOx gas sensor," Sensors and Actuators B, Vol. 50, pp. 9-18, 1998.
[43]K. Bange, "Colouration of tungsten oxide films: A model for optically active coatings," Solar Energy Materials & Solar Cells, Vol. 58, pp. 1-131, 1999.
[44]丁志明，奈米科技－基礎、應用與實作，高立圖書有限公司，2005年2月。
[45]B. Y. Wei, M. C. Hsub, P. G. Su, H. M. Lin, R. J. Wu and H. J. Lai, "A novel SnO2 gas sensor doped with carbon nanotubes operating at room temperature," Sensors and Actuators B, Vol. 101, pp. 81-89, 2004.
[46]Marc J. Madou, Fundamemtals of Microfabrication: The Science of Miniaturization, CRC Press, March 2002.