用于MEMS封装的纳米多孔硅气敏特性分析
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摘要
采用双槽(自制)电化学腐蚀法在p型单晶硅表面制备多孔硅(PS)层,利用AFM技术分析多孔硅的表面形貌。研究分析了电流密度为20~60 mA/cm2时,多孔硅的孔径、孔深和孔隙率,并分析测试了多孔硅对高浓度乙醇的气敏特性。结果表明,在不同的电流密度腐蚀下,孔径都在10 nm左右;随着电流密度的增加,多孔硅的孔深和孔隙率增大且腐蚀的均匀性较好。当电流密度大于40 mA/cm2后,腐蚀的均匀性开始变差,灵敏度波动较大。通过对多孔硅气体吸附灵敏度的分析,在电流密度为40 mA/cm2时,对各浓度的乙醇气体的灵敏度相对稳定,均值达到2.24×106 kΩ,因此该类样品更适用于MEMS高真空封装的纳米吸气剂。
The porous silicon(PS)layers were formed by the electrochemical etching method using the home-made double-tank setup on the surface of the p-type monocrystalline silicon.The surface morphologies of the PS layers were analyzed by the AFM technology.The pore diameter,pore depth and porosity of the PS were analyzed at the current density of 20-60 mA/cm2,and the gas sensing properties of the PS were analyzed and tested by the high concentrate ethyl alcohol.The results show that the pore diameter is all about 10 nm at different corrosion current densities.The pore depth and the porosity of the PS increase with the increase of the current density,and the etching uniformity is better.While the current density is more than 40 mA/cm2,the etching uniformity begins to deteriorate and the fluctuation of the sensitivity is greater.By the analysis of the gas adsorption sensitivity for the PS,the sensitivities of different concentration ethanol gases are relatively stable,and the average value reaches 2.24×106 kΩwhen the current density is 40 mA/cm2.Thus,the sample is more suitable for the nanogetters of the MEMS high vacuum packaging.
The porous silicon(PS)layers were formed by the electrochemical etching method using the home-made double-tank setup on the surface of the p-type monocrystalline silicon.The surface morphologies of the PS layers were analyzed by the AFM technology.The pore diameter,pore depth and porosity of the PS were analyzed at the current density of 20-60 mA/cm2,and the gas sensing properties of the PS were analyzed and tested by the high concentrate ethyl alcohol.The results show that the pore diameter is all about 10 nm at different corrosion current densities.The pore depth and the porosity of the PS increase with the increase of the current density,and the etching uniformity is better.While the current density is more than 40 mA/cm2,the etching uniformity begins to deteriorate and the fluctuation of the sensitivity is greater.By the analysis of the gas adsorption sensitivity for the PS,the sensitivities of different concentration ethanol gases are relatively stable,and the average value reaches 2.24×106 kΩwhen the current density is 40 mA/cm2.Thus,the sample is more suitable for the nanogetters of the MEMS high vacuum packaging.
引文
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[2]SPARKS D R,MASSOUND-ANSARI S,NAJAFI N.Chiplevel vacuum packing of micromachines using nanogetters[J].IEEE Transactions on Advanced Packing,2003,26(3):277-282.
[3]陈松平,孙道恒.用于MEMS真空封装中的纳米吸气剂[J].功能材料与器件学报,2008,14(1):9-13.
[4]WANG Y,WU Y C,CUI J W,et al.Ag nanoparticles decorated TiO2nanotube arrays for ultrasensitive gas sensing[J].Journal of Nanoscience and Nanotechnology,2013,13(2):1453-1455.
[5]WAJIHUDDIN M,CHESTER W,VILLE K.Introducing porous silicon as a getter using the self aligned maskless process to enhance the quality factor of packaged MEMS resonators[C]//Proceedings of Frequency Control and the European Frequency and Time Forum(FCS),Joint Conference of the IEEE International.San Fransisco,CA,2011:1-4.
[6]LEWIS S E,DEBOBER J R,GOLE J L,et al.Sensitive,selective,and analytical improvements to a porous silicon gas sensors[J].Sensors Actuators:B,2005,110(1):54-65.
[7]孙凤云,胡明,孙鹏,等.多孔硅的I-V特性及NO2气敏特性研究[J].传感技术学报,2009,22(3):316-319.
[8]胡小华,施琼玲,魏锡文,等.多孔硅的表面吸附性能的研究[J].功能材料,2012,43(21):3006-3009.
[9]SUJATHA L,BHATTACHARYA E.Composite Si/PS membrane pressure sensors with micro and macro-porous silicon[J].Sadhana-Academy Proceeding in Engineering Sciences,2009,34(4):643-650.
[10]张聚华.溶质挥发性对稀溶液沸点的影响[J].北京服装学院学报,2010,30(4):63-66.