硅基MEMS三维结构湿法腐蚀技术研究
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摘要
为了满足MEMS发展的需求，依据Si的各向异性腐蚀特性所发展起来的湿法腐蚀工艺在制作MEMS器件的过程中发挥了巨大的作用。与干法刻蚀相比较，湿法刻蚀技术的加工成本更为低廉，且工艺制作过程也相对简单。本文对硅材料的各向异性腐蚀机理及特性进行了深入分析，并以此为基础进行了硅基MEMS湿法工艺技术研究。通过对BN-303光刻胶的工艺优化，发现BN-303光刻胶对前烘温度较为敏感，摸索出一套优化光刻工艺为：在其它光刻工艺条件固定的情况下，最佳前烘温度为80℃，保温30min，经深腐蚀后得出较好的图形，对于后序的掩膜和圆形阵列刻蚀起到至关重要的作用，也为微器件加工提供一些可靠的工艺参考。
在KOH与IPA混合腐蚀液腐蚀系统中，为了得出类圆形深槽MEMS三维结构，通过对不同导电类型及电阻率的实验分析与探讨，总结出对于N型导电类型，电阻率为3×10~(-3)～9×10~(-3)Ω.cm的硅基片，在腐蚀过程中，IPA抑制(110)面腐蚀速率，使(110)面成为腐蚀演进面，并且(100)底面平整。通过对不同含量IPA对三维结构的影响分析，在5M(mol／L)KOH溶液中，20vol％IPA是影响(110)面腐蚀速率的极值点，低于该值不能完全阻挡OH~-活性离子接近(110)，而高于该值，由于色散力的存在，削弱了IPA对(110)面的吸咐作用，不能抑制V_((110))。并且对不同浓度KOH、不同腐蚀时间对MEMS三维结构的影响作了深入分析与探讨。
利用各向异性腐蚀湿法工艺制作了类圆形阵列，尝试结合各向同性腐蚀技术的制造思想，具有制造圆槽阵列和圆台阵列的能力，从而克服了传统MEMS制造中三维加工能力不足的缺点，是制造三维结构的高效低成本的有效方法，为批量化加工研制生产硅基MEMS奠定基础。
In order to match the demand of MEMS development, the wet etching processing that is developed on base of the property of anisotropic etching is playing an important role on the fabrication of MEMS. The cost of wet etching is lower and the processing of fabrication is simpler than the dry etching. We deeply analyzed the mechanism and property of anisotropic etching of silicon and studied the technique of the wet etching of MEMS on the base of the theory. The results showed that the performance of BN-303 was susceptible to effect of soft-baking temperature, and an optimal processing parameter of photolither was the soft-baking temperature at 80℃and keeping for 30min under other fixed conditions in the mix solution of KOH and IPA which provides some reliable data for the processing of micro-devices.
In order to get the round figure of MEMS, We analyzed the effect of different conductivity of the substrate on the 3D structure of MEMS. The results showed that N type silicon substrate with low conductivity of 3～9×10~(-3) was easily etched to smooth (100) surface in the mixture of KOH and IPA and the (110) appeared in the sidewall. We also analyzed that the effect of IPA on the 3D structure of MEMS and the extremum of the proportion of the mix solution, which 20vol%IPA was the optimal proportion in 5mol/L KOH water solution. If the IPA proportion exceeded the 20vol%, the effect of IPA on the (110) was weakened because the force of molecule. And it was lower than 20vol%, IPA could not entirely stop the contact of active ion of OH~- to the (110) and could not low the rate of etching (110). As well as we analyzed the effect of the different concentration of KOH and the different etch time on the 3D structure of MEMS, the like round figure arry of MEMS were fabricated by the method of anisotropic etching.
The method of firstly combining with the method of isotropic etching improves the ability of fabricating the round figure of MEMS and overcomes the defect of the traditionary method. The method is efficient and low cost, and it is the foundation of the mass product of MEMS on the silicon substrate.
在KOH与IPA混合腐蚀液腐蚀系统中，为了得出类圆形深槽MEMS三维结构，通过对不同导电类型及电阻率的实验分析与探讨，总结出对于N型导电类型，电阻率为3×10~(-3)～9×10~(-3)Ω.cm的硅基片，在腐蚀过程中，IPA抑制(110)面腐蚀速率，使(110)面成为腐蚀演进面，并且(100)底面平整。通过对不同含量IPA对三维结构的影响分析，在5M(mol／L)KOH溶液中，20vol％IPA是影响(110)面腐蚀速率的极值点，低于该值不能完全阻挡OH~-活性离子接近(110)，而高于该值，由于色散力的存在，削弱了IPA对(110)面的吸咐作用，不能抑制V_((110))。并且对不同浓度KOH、不同腐蚀时间对MEMS三维结构的影响作了深入分析与探讨。
利用各向异性腐蚀湿法工艺制作了类圆形阵列，尝试结合各向同性腐蚀技术的制造思想，具有制造圆槽阵列和圆台阵列的能力，从而克服了传统MEMS制造中三维加工能力不足的缺点，是制造三维结构的高效低成本的有效方法，为批量化加工研制生产硅基MEMS奠定基础。
In order to match the demand of MEMS development, the wet etching processing that is developed on base of the property of anisotropic etching is playing an important role on the fabrication of MEMS. The cost of wet etching is lower and the processing of fabrication is simpler than the dry etching. We deeply analyzed the mechanism and property of anisotropic etching of silicon and studied the technique of the wet etching of MEMS on the base of the theory. The results showed that the performance of BN-303 was susceptible to effect of soft-baking temperature, and an optimal processing parameter of photolither was the soft-baking temperature at 80℃and keeping for 30min under other fixed conditions in the mix solution of KOH and IPA which provides some reliable data for the processing of micro-devices.
In order to get the round figure of MEMS, We analyzed the effect of different conductivity of the substrate on the 3D structure of MEMS. The results showed that N type silicon substrate with low conductivity of 3～9×10~(-3) was easily etched to smooth (100) surface in the mixture of KOH and IPA and the (110) appeared in the sidewall. We also analyzed that the effect of IPA on the 3D structure of MEMS and the extremum of the proportion of the mix solution, which 20vol%IPA was the optimal proportion in 5mol/L KOH water solution. If the IPA proportion exceeded the 20vol%, the effect of IPA on the (110) was weakened because the force of molecule. And it was lower than 20vol%, IPA could not entirely stop the contact of active ion of OH~- to the (110) and could not low the rate of etching (110). As well as we analyzed the effect of the different concentration of KOH and the different etch time on the 3D structure of MEMS, the like round figure arry of MEMS were fabricated by the method of anisotropic etching.
The method of firstly combining with the method of isotropic etching improves the ability of fabricating the round figure of MEMS and overcomes the defect of the traditionary method. The method is efficient and low cost, and it is the foundation of the mass product of MEMS on the silicon substrate.
引文
[1] J Bryzek. Impact of MEMS technology on society. Sensors and Actuators A, 1996, 56: 1-9
[2] 李德胜．MEMS技术及其应用．哈尔滨：哈尔滨工业大学出版社，2002
[3] 刘光辉，亢春梅．MEMS技术的现状和发展趋势．传感器技术，2001，20(1)：52-56
[4] 赵强．基于MEMS技术的微型泵的研究：[博士学位论文]．北京：中国科学院研究生院(电子学研究所)，2004
[5] 李庆祥，王东生，李玉和．现代精密仪表设计．北京：清华大学出版社，2004
[6] 朱骞彬．微型机械加工技术发展现状和趋势及其关键技术．精密制造与自动化，2002，(2)：9-11
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[8] 刘东栋，胡海波，唐衍哲等．基于体硅微机械工艺的光波导器件封装技术．机械强度，2001，23(4)：531-534
[9] 罗均，谢少荣，龚振邦．面向MEMS的微细加工技术．电加工与模具，2001，(5)：1-6
[10] 李志信，罗小兵，过增元．MEMS技术的现状及发展趋势．传感器技术，2001，20(9)：58-60
[11] 周兆英，李志宏．新世纪的新事业——中国MEMS调查．电子产品世界，2000，(7)：13-14
[12] K E Petersen. Silicon as a mechanical material. Proceedings of the IEEE, 1982, 70(5): 420-457
[13] 苑伟政，马炳和．微机械与微细加工技术．西安：西北工业大学出版社，2000
[14] G T A Kovacs, N I Maluf, K E Petersen. Bulk Micromachining of Silicon. Proceedings of the IEEE, 1998, 86(8): 1536-1551
[15] 李志坚，周润德．ULSI器件、电路与系统．北京：科学出版社，2000
[16] E Steinsland, T Finstad, A Hanneborg. Etch rates of(100), (111) and (110) single crystal silicon in TMAH measured in situ by laser reflectance interferometry. Sensors and Actuators A, 2000, 86: 73～80
[17] 黄庆安．硅微机械加工技术．北京：科学出版社，1996
[18] 赵晓峰，温殿忠．MEMS研究与发展前景．黑龙江大学自然科学学报，2002，19(1)：64-69
[19] E D Palik, V M Bermudez, O J Glembocki. Ellipsonetric study of orientation dependent etching of silicon in aqueous KOH. J Electrochem. Soc., 1985, 132(4): 871-884
[20] H Seidel, L Csepregi, A Heuberger, H Baumgartel. Anisotropic etching of crystalline silicon in alkaline solutions. J Electrochem. Soc., 1990, 137(11): 3612-3626
[21] Peter J Hesketh, Chishein Ju, Sanjay Gowda et al. Surface Free Energy Model of Silicon Anisotropic Etching. J Electrochem. Soc., 1993, 140(4): 1080-1085
[22] Y Nemirovsky, A EI-Bahar. The non equilibrium band model of silicon in TMAH and in anisotropic electrochemical alkaline etching solutions. Sensors and Actuators A, 1999, 75: 205-214
[23] 姜岩峰，黄庆安，吴文刚等．硅在KOH中各项异性腐蚀的物理模型．半导体学报，2002，23(4)： 434-439
[24] 陈伟平，王东红，马国忠等．硅微机械加工的削角补偿技术．哈尔滨工业大学学报，1997，29(3)：33-35
[25] 沈桂芬，吴春瑜，姚朋军等．各向异性腐蚀技术研究与分析．传感技术学报，2001，6：1413-146
[26] M Elwenspoek. On the Mechanism of Anisotropic Etching of Silicon. J Electrochem. Soc., 1993, 140(7): 2075-2080
[27] 姚娉．单晶硅各向异性腐蚀的计算机微观模拟：[硕士学位论文]．大连：大连理工大学研究生院，2005
[28] 宋斌，曹培林．全势能线性Muffin-Tin轨道组合分子动力学方法及其在半导体团簇结构计算中的应用．物理学进展，2000，20(3)：276-290
[29] 张兴，黄如，刘晓彦．微电子学概论．北京：北京大学出版社，2000
[30] D Brambley, B Martin, P Prewet. Microlithography. Adv. Mater. Opt. Elec, 1994, 4: 55-74
[31] 李佐邦，朱普坤，冯威等．光敏聚酰亚胺的研究进展．高分子材料科学与工程，1994，(6)：6-9
[32] 蒋荣欣．微细加工技术．北京：电子工业出版社，1990
[33] 唐雄贵，郭永康，杜惊雷等．基于角谱理论的厚层光刻胶衍射光场研究．光学学报，2004，24(12)：1691-1696
[34] H Maeloba, P Helin. Self-aligned vertical mirror and V-grooves applied to an optical-switch modeling and optimization of bi-stable operation by electromagnetic actuation. Sensors and Actuators A, 2001, 87: 172-178
[35] Irena Zubel, Irema Barycka. Silicon anisotropic etching in alkaline solutions I: The geometric description of figures developed under etching Si(100) in various solutions. Sensors and Actuators A, 1998, 70: 250-259
[36] C Strandman, I Rosengren, H G Elderstig. Fabrication of mirrors together with well-defined v-grooves using wet anisotropic etching of silicon. Microelectro Mechanical System, 1996, 4: 213-219
[37] Irena Zubel, Malgorzata Kramkowska. The effect of isopropyl alcohol on etching rate and roughness of (100) Si surfaces etched in KOH and TMAH solution. Sensors and Actuators A, 2001, 93:138-147
[38] I Zubel, M Kramkowska. Etch rate and morphology of silicon (hkl) surfaces etched in KOH and KOH saturated with isopropanol solutions. Sensors and Actuators A, 2004,115: 549-556
[39]刘玉岭, 李薇薇,周健伟．微电子化学基础．北京：化学工业出版社,2005
[40] Irena Zubel. The influence of atomic configuration of (hkl) planes on adsorption processes associated with anisotropic etching of silicon. Sensors and Actuators A, 2001, 94: 76-86
[41] H G Linde, L W Austin. Catalytic control of anisotropic silicon etching. Sensors and Actuators A, 1995, 49: 181-185
[42] C Moldovan, R Iosub, D Dascalu, G Nechifor. Anisotropic etching of silicon in complexant redox alkaline system. Sensors and Actuators B, 1999, 58: 438-449
[43] K Sato, M Shikida, T Yamashiro, M Tsunekawa. Anosotropic etching rates of single crystal silicon for TMAH water solution as a function of crystallographic orientation. Sensors and Actuators A, 1999, 73: 179-188
[44] C R Tellier, A Brahim-Bounab. Anisotropic etching of silicon crystals in KOH solution, Part II Theorietical two-dimensional etched shapes: discussion of the adequation slowness surface. Mater.Sci., 1994, 29: 6354-6378
[45] K Sato, MShikida, Y Matsuhima, T Yamashiro, K Asumi, Y Iriye, M Yamamoto. Characterization of orientation-dependent etching properties of single-crystals silicon: effects of KOH concentration. Sensors and Actuators, 1998, 64: 87-93
[46] M Shikida, K Sato, K Tokoro, D Uchikawa. Differences in anisotropic etching properties of KOH and TMAH solutions. Sensors and Actuators A, 2000, 80: 179-188
[47] M Alavi, Th Fabula, A Schumacher, H J Wagner. Monolithic micro-bridges in silicon using laser machining and anisotropic etching. Sensors and Actuators A, 1993, 37-38: 661- 665
[48] X Li, M Bao, S Shen. Maskless etching of three-dimensional silicon structures in KOH. Sensors and Actuators A, 1996, 57: 47-52
[49] B Kang, M R Haskard, N D Samaan Eds. A study of two-step silicon anisotropic etching for a polygon-shaped microstructure using KOH solution. Sensors and Actuators A, 1997, 62: 646-651
[50] C R Tellier, S Durand. Micromachining of (hkl) silicon structures: experiments and 3D simulation of etched shapes. Sensors and Actuators A , 1997, 60:168-175
[51] Irena Zubel. Silicon anisotropic etching im alkaline solutions III: On the possibility of spatial structure forming in the course of Si (100) anisotropic etching in KOH and KOH+IPA solutions. Sensors and Actuators A, 2000, 84: 116-125
[2] 李德胜．MEMS技术及其应用．哈尔滨：哈尔滨工业大学出版社，2002
[3] 刘光辉，亢春梅．MEMS技术的现状和发展趋势．传感器技术，2001，20(1)：52-56
[4] 赵强．基于MEMS技术的微型泵的研究：[博士学位论文]．北京：中国科学院研究生院(电子学研究所)，2004
[5] 李庆祥，王东生，李玉和．现代精密仪表设计．北京：清华大学出版社，2004
[6] 朱骞彬．微型机械加工技术发展现状和趋势及其关键技术．精密制造与自动化，2002，(2)：9-11
[7] 刘于．基于MEMS的微型电磁极化继电器设计：[硕士学位论文]．成都：电子科技大学，2003
[8] 刘东栋，胡海波，唐衍哲等．基于体硅微机械工艺的光波导器件封装技术．机械强度，2001，23(4)：531-534
[9] 罗均，谢少荣，龚振邦．面向MEMS的微细加工技术．电加工与模具，2001，(5)：1-6
[10] 李志信，罗小兵，过增元．MEMS技术的现状及发展趋势．传感器技术，2001，20(9)：58-60
[11] 周兆英，李志宏．新世纪的新事业——中国MEMS调查．电子产品世界，2000，(7)：13-14
[12] K E Petersen. Silicon as a mechanical material. Proceedings of the IEEE, 1982, 70(5): 420-457
[13] 苑伟政，马炳和．微机械与微细加工技术．西安：西北工业大学出版社，2000
[14] G T A Kovacs, N I Maluf, K E Petersen. Bulk Micromachining of Silicon. Proceedings of the IEEE, 1998, 86(8): 1536-1551
[15] 李志坚，周润德．ULSI器件、电路与系统．北京：科学出版社，2000
[16] E Steinsland, T Finstad, A Hanneborg. Etch rates of(100), (111) and (110) single crystal silicon in TMAH measured in situ by laser reflectance interferometry. Sensors and Actuators A, 2000, 86: 73～80
[17] 黄庆安．硅微机械加工技术．北京：科学出版社，1996
[18] 赵晓峰，温殿忠．MEMS研究与发展前景．黑龙江大学自然科学学报，2002，19(1)：64-69
[19] E D Palik, V M Bermudez, O J Glembocki. Ellipsonetric study of orientation dependent etching of silicon in aqueous KOH. J Electrochem. Soc., 1985, 132(4): 871-884
[20] H Seidel, L Csepregi, A Heuberger, H Baumgartel. Anisotropic etching of crystalline silicon in alkaline solutions. J Electrochem. Soc., 1990, 137(11): 3612-3626
[21] Peter J Hesketh, Chishein Ju, Sanjay Gowda et al. Surface Free Energy Model of Silicon Anisotropic Etching. J Electrochem. Soc., 1993, 140(4): 1080-1085
[22] Y Nemirovsky, A EI-Bahar. The non equilibrium band model of silicon in TMAH and in anisotropic electrochemical alkaline etching solutions. Sensors and Actuators A, 1999, 75: 205-214
[23] 姜岩峰，黄庆安，吴文刚等．硅在KOH中各项异性腐蚀的物理模型．半导体学报，2002，23(4)： 434-439
[24] 陈伟平，王东红，马国忠等．硅微机械加工的削角补偿技术．哈尔滨工业大学学报，1997，29(3)：33-35
[25] 沈桂芬，吴春瑜，姚朋军等．各向异性腐蚀技术研究与分析．传感技术学报，2001，6：1413-146
[26] M Elwenspoek. On the Mechanism of Anisotropic Etching of Silicon. J Electrochem. Soc., 1993, 140(7): 2075-2080
[27] 姚娉．单晶硅各向异性腐蚀的计算机微观模拟：[硕士学位论文]．大连：大连理工大学研究生院，2005
[28] 宋斌，曹培林．全势能线性Muffin-Tin轨道组合分子动力学方法及其在半导体团簇结构计算中的应用．物理学进展，2000，20(3)：276-290
[29] 张兴，黄如，刘晓彦．微电子学概论．北京：北京大学出版社，2000
[30] D Brambley, B Martin, P Prewet. Microlithography. Adv. Mater. Opt. Elec, 1994, 4: 55-74
[31] 李佐邦，朱普坤，冯威等．光敏聚酰亚胺的研究进展．高分子材料科学与工程，1994，(6)：6-9
[32] 蒋荣欣．微细加工技术．北京：电子工业出版社，1990
[33] 唐雄贵，郭永康，杜惊雷等．基于角谱理论的厚层光刻胶衍射光场研究．光学学报，2004，24(12)：1691-1696
[34] H Maeloba, P Helin. Self-aligned vertical mirror and V-grooves applied to an optical-switch modeling and optimization of bi-stable operation by electromagnetic actuation. Sensors and Actuators A, 2001, 87: 172-178
[35] Irena Zubel, Irema Barycka. Silicon anisotropic etching in alkaline solutions I: The geometric description of figures developed under etching Si(100) in various solutions. Sensors and Actuators A, 1998, 70: 250-259
[36] C Strandman, I Rosengren, H G Elderstig. Fabrication of mirrors together with well-defined v-grooves using wet anisotropic etching of silicon. Microelectro Mechanical System, 1996, 4: 213-219
[37] Irena Zubel, Malgorzata Kramkowska. The effect of isopropyl alcohol on etching rate and roughness of (100) Si surfaces etched in KOH and TMAH solution. Sensors and Actuators A, 2001, 93:138-147
[38] I Zubel, M Kramkowska. Etch rate and morphology of silicon (hkl) surfaces etched in KOH and KOH saturated with isopropanol solutions. Sensors and Actuators A, 2004,115: 549-556
[39]刘玉岭, 李薇薇,周健伟．微电子化学基础．北京：化学工业出版社,2005
[40] Irena Zubel. The influence of atomic configuration of (hkl) planes on adsorption processes associated with anisotropic etching of silicon. Sensors and Actuators A, 2001, 94: 76-86
[41] H G Linde, L W Austin. Catalytic control of anisotropic silicon etching. Sensors and Actuators A, 1995, 49: 181-185
[42] C Moldovan, R Iosub, D Dascalu, G Nechifor. Anisotropic etching of silicon in complexant redox alkaline system. Sensors and Actuators B, 1999, 58: 438-449
[43] K Sato, M Shikida, T Yamashiro, M Tsunekawa. Anosotropic etching rates of single crystal silicon for TMAH water solution as a function of crystallographic orientation. Sensors and Actuators A, 1999, 73: 179-188
[44] C R Tellier, A Brahim-Bounab. Anisotropic etching of silicon crystals in KOH solution, Part II Theorietical two-dimensional etched shapes: discussion of the adequation slowness surface. Mater.Sci., 1994, 29: 6354-6378
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