射频MEMS开关的制作工艺研究及其直流特性测试
摘要
射频MEMS开关与目前射频系统中所使用的PIN二极管开关和MESFET开关相比,具有更低的插入损耗、更高的隔离度、更好的线性、更低的功耗和可应用频带更宽。利用射频MEMS开关可制作移相器、开关式滤波器、开关阵列等,应用于雷达、卫星通信、无线通信等系统中。
本课题主要研究接触式射频MEMS开关的制作工艺及其直流特性。对接触式射频MEMS开关的电极、波导、触点、牺牲层、悬梁的制作工艺进行了研究,制作出射频MEMS开关样品,对开关的直流特性进行了测试和研究。
研究金属的淀积和剥离工艺,解决了厚金的剥离问题,制作出金的厚度为2μm,信号线与地线之间的间距为8μm的波导;研究PECVD法生长氮化硅工艺,在牺牲层聚酰亚胺上生长出厚度为1μm的氮化硅,解决了在聚酰亚胺上生长氮化硅薄膜破裂的问题;研究ICP刻蚀氮化硅和等离子体刻蚀聚酰亚胺的工艺,成功地制作出悬梁,解决了释放牺牲层出现粘连的问题。
本文用共聚焦显微镜测试氮化硅薄膜悬梁悬起的高度,确定出最适合接触式射频MEMS开关中使用的氮化硅生长工艺条件。用手动探针台测试接触式射频MEMS开关的通断特性,用显微镜测试开关的驱动特性,确定出开关的阈值电压为22-27V。用共聚焦显微镜测试开关加直流电压后的下拉高度,研究开关的悬梁在驱动电压下的弯曲程度及下降达到的最低位置。本文制作出的开关由于悬梁中存在残余应力,开关在加直流电压后触点不能下降到所需的高度与下电极接触,尚未实现开关的“导通”。
RF MEMS switches have an advantage over PIN diodes and MESFETs in isolation, insertion loss, linearity, power dissipation and can be used in broader frequency band. RF MEMS switches can be used to make phase shifter, filter, switch array, etc. The main application areas of MEMS switches are radar systems, satellite communication systems and wireless communication systems.
The fabrication processes of metal-metal contact RF MEMS switch and the test of its DC property are the main content of this thesis.Metal-metal contact switch includes electrode, waveguide, contact,sacrificial layer and suspended beam.We study the fabrication processes and optimize the process parameters and succeed in making the switch. We test the pull-down voltage of the switch and its height change between down and up state.
The fabrication processes of metal-metal contact switch include the following steps. Electrode, waveguide and contact are made through lift-off process. Sacrificial layer is made through rotational spread. The structure of suspended beam is made through PECVD process. The moving parts are released by selectively etching an underlying sacrificial layer through ICP dry etching and oxygen plasma etching.We succeed in depositing and lifting-off gold of 2 micrometer in thickness, plasma enhanced vapor depositing silicon nitride on polymide of 1 micrometer in thickness and releasing the suspended beam.
We test the height of silicon nitride suspended beam from different depositing condition in laser-scanning microscope and decide the most proper depositing condition for RF MEMS switch.we research the on and off state of the switch, observe the pull-down property of the assembled sample in microscope and test its pull-down height when applied DC voltage. The pull-down voltage of the switch is from 22 volt to 27volt. The metal contact cannot touch the down electrode when the switch is applied DC voltage due to the residual stress in the thin film, so the signal cannot transmit.
本课题主要研究接触式射频MEMS开关的制作工艺及其直流特性。对接触式射频MEMS开关的电极、波导、触点、牺牲层、悬梁的制作工艺进行了研究,制作出射频MEMS开关样品,对开关的直流特性进行了测试和研究。
研究金属的淀积和剥离工艺,解决了厚金的剥离问题,制作出金的厚度为2μm,信号线与地线之间的间距为8μm的波导;研究PECVD法生长氮化硅工艺,在牺牲层聚酰亚胺上生长出厚度为1μm的氮化硅,解决了在聚酰亚胺上生长氮化硅薄膜破裂的问题;研究ICP刻蚀氮化硅和等离子体刻蚀聚酰亚胺的工艺,成功地制作出悬梁,解决了释放牺牲层出现粘连的问题。
本文用共聚焦显微镜测试氮化硅薄膜悬梁悬起的高度,确定出最适合接触式射频MEMS开关中使用的氮化硅生长工艺条件。用手动探针台测试接触式射频MEMS开关的通断特性,用显微镜测试开关的驱动特性,确定出开关的阈值电压为22-27V。用共聚焦显微镜测试开关加直流电压后的下拉高度,研究开关的悬梁在驱动电压下的弯曲程度及下降达到的最低位置。本文制作出的开关由于悬梁中存在残余应力,开关在加直流电压后触点不能下降到所需的高度与下电极接触,尚未实现开关的“导通”。
RF MEMS switches have an advantage over PIN diodes and MESFETs in isolation, insertion loss, linearity, power dissipation and can be used in broader frequency band. RF MEMS switches can be used to make phase shifter, filter, switch array, etc. The main application areas of MEMS switches are radar systems, satellite communication systems and wireless communication systems.
The fabrication processes of metal-metal contact RF MEMS switch and the test of its DC property are the main content of this thesis.Metal-metal contact switch includes electrode, waveguide, contact,sacrificial layer and suspended beam.We study the fabrication processes and optimize the process parameters and succeed in making the switch. We test the pull-down voltage of the switch and its height change between down and up state.
The fabrication processes of metal-metal contact switch include the following steps. Electrode, waveguide and contact are made through lift-off process. Sacrificial layer is made through rotational spread. The structure of suspended beam is made through PECVD process. The moving parts are released by selectively etching an underlying sacrificial layer through ICP dry etching and oxygen plasma etching.We succeed in depositing and lifting-off gold of 2 micrometer in thickness, plasma enhanced vapor depositing silicon nitride on polymide of 1 micrometer in thickness and releasing the suspended beam.
We test the height of silicon nitride suspended beam from different depositing condition in laser-scanning microscope and decide the most proper depositing condition for RF MEMS switch.we research the on and off state of the switch, observe the pull-down property of the assembled sample in microscope and test its pull-down height when applied DC voltage. The pull-down voltage of the switch is from 22 volt to 27volt. The metal contact cannot touch the down electrode when the switch is applied DC voltage due to the residual stress in the thin film, so the signal cannot transmit.
引文
[1]云振新RF/ 微波无线系统中的MEMS 技术[J] . 微纳电子技术, 2002(2):6-11.
[2] 缪妟, 武国英. RF MEMS 器件的研究及其应用前景[J ].电子产品世界,2003(5):37-40.
[3] 茅惠兵,忻佩胜,胡梅丽,等.微机械微波/射频开关的制备和功能测量研究[J ].半导体技术,2002,27(11 ):11-14.
[4]朱健, 郁元卫, 陆乐,等.双膜桥微波MEMS 开关[J] .微纳电子技术2003 (7/ 8):382-384.
[5]Gabriel M. Rebeiz, Jeremy B. Muldavin, “RF MEMS Switches and Switch Circuits”,IEEE microwave magazine pp.59-71,December 2001.
[6] 张永华,丁桂甫,蔡炳初,等.发展中的RF MEMS 开关技术[J ]. 微纳电子技术,2003(5):28-32.
[7]孙建海,崔大付,苏波,等.宽带RF-MEMS 开关驱动电压的分析研究[J] . 微纳电子技术,2004(9):37-39.
[8]P.D. Grant, R.R. Mansour, and M.W. Denhoff, “A comparison between RF MEMS switches and semiconductor switches”,Can.J.Elect.Comput.Eng. Vol.27,No.1,January 2002,pp.33-39.
[9]Peterson K. Micromechanical membrane switches on silicon IBM J.RES.Develop.,1979,276-385.
[10]Larson L E, Hackett R H,Melendes M A,et al. Micromachined microwave actuator(MIMAC)technology-a new tuning approach for microwave integrated circuits. In: Microwave and Millimeter-Wave Monolithic Circuits Symposium Digest,Boston,MA,1991,27-30.
[11] Yao J J ,Chang M F. A surface micromachined miniature switch for telecommunication application with single freq. from DC up to 4 GHz. In :Proc. Transducer’95 ,June 1995 :384-387.
[12]Goldsmith C,Wu W R, Norvell B. Micromechanical Membrane Switches for Microwave Application.IEEE MTT-S Digest,1995,91-94.
[13]Goldsmith C , Randall J . Characteristics of micromachined switches at microwave frequencies. In :Proc. of Digest IEEE MTT International Microwave Symposium San Francisco ,USA ,1996 ,2 :1141-1144.
[14]Schiele I, Evers C,Hillerich B,et al. A Surface Micromachined Electrostatic Microrelay. In: Sensor 97.Vortag, 1997,87-91.
[15]Pacheco S, Nguyen C T C, Kethei L P B.Micromechanical electrostatic K-band switches. In: IEEE MTT-S Digest.Baltimore, 1998, 1569-1572.
[16]Dooyoung Hah, Euisik Yoon,A Low-Voltage Actuated Micromachined Microwave Switch Using Torsion Springs and Leverage IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 48, NO. 12, DECEMBER 2000 :2540-2545.
[17]Jae Y. Park, Geun H. Kim, Ki W. Chung1, etc, Monolithically integrated micromachined RF MEMS capacitive switches. Sensors and Actuators A 89 (2001):88-94 .
[18]梁春广RF MEMS 技术[J].微纳电子技术.2002(1) :6-8.
[19] 顾洪明,梁春广,高葆新. 微波微电子机械开关[J] .半导体技术,2000,25(11):29-32.
[20]朱健, 周百令, 郁元卫,等.高隔离度S波段MEMS膜桥开关[J ].固体电子学研究进展,2004,24(1):64-67。
[21]郑惟彬,黄庆安,李拂晓.低阈值电压RF MEMS 开关的力学模型[J ].固体电子学研究与进展, 2003,23(4):500-503.
[22]郭方敏,赖宗声,朱自强,等.悬臂式RF MEMS开关的设计与研制[J ]. 半导体学报,2003,24(11):1190-1195.
[23]魏华征. 郭方敏. 赖宗声. 等.射频微机械开关的计算机辅助设计[J].半导体学报2002,23(9):947-951.
[24]龙永福, 朱自强, 赖宗声,等.射频/微波MEMS Shunt开关的开启时间研究,电子学报,2002,30(8):1204-1206.
[25]龙永福. 赖宗声. 朱自强. 高电容比射频/微波MEMS 膜开关的理论分析和数值模拟[J].微波学报,2003,19(1):56-60.
[26]李炜, 石艳玲, 忻佩胜, 等.电容式MEMS 开关中弹性膜应力对驱动电压的影响[J].固体电子学研究与进展,2003,23(4):514-519.
[27]龙永福, 石艳玲, 赖宗声,等.偏置电压对射频/微波MEMS 电容开关寿命的影响[J].微电子学,2004,34(1):30-34.
[28]李成诗. 郭方敏. 赖宗声,等,基于ANSYS 悬臂式RFMEMS 开关的力学模拟和疲劳分析[J ].半导体技术,2004,29(10):22-26.
[29]徐欣. 郭方敏, 葛羽屏,等.MEMS 悬臂式开关的失效分析[J ].传感技术学报,2004 年9 月第3 期:492-496.
[30]F.M.Guo, Z.Q.Zhu, Y.F.Long, etc. “Study on low voltage actuated MEMS rf capacitive switches”,Sensors and Actuators A 108 (2003),pp.128-133.
[31]Ye Wang, Zhihong Li, Daniel T. McCormick, Norman C. Tien,”A Micromachined RF microrelay with electrothermal actuation”, Sensors and Actuators A 103(2003), pp.231-236.
[32]韩阶平,侯豪情,邵逸凯.适用于剥离工艺的光刻胶图形的制作技术及其机理讨论[J]. 真空科学与技术1994,14(3):215-219.
[33]闫桂珍,张大成,李婷,等.金属剥离与衬底腐蚀等平面自对准OHR 技术研究[J]. 微纳电子技术2002,01:40-43.
[34]王文如,杨正兵.微细金属图形制作中的剥离技术[J]. 压电与声光2001,23(1):68-73.
[35]刑素贤,程足捷,王中文.等平面和金属剥离工艺在低电容高可靠晶体管生产中的应用[J].辽宁大学学报自然科学版1997,24(2)46-50。
[36]Peng Yao. 3D Photolithography based on image reversal Proc. of SPIE Vol.5342:165-172
[37]庄同曾张安康黄兰芳集成电路制造技术——原理与实践[M] .
[38] 赵永军,王民娟,杨拥军等. PECVD SiNx 薄膜应力的研究[J].半导体学报,1999,20(3):183-187.
[39] 唐元洪.等离子体增强型化学气相淀积氮化硅的淀积[J]. 湖南大学学报1996,23(1):42-44.
[40] 徐泰然.MEMS和微系统——设计与制造[M] .机械工业出版社,2004:265.
[41]于映,陈跃.氮化硅介质薄膜内应力实验研究[J].真空科学与技术,2001,21(01):51-54.
[42] 周志烽, 范玉殿. 薄膜热应力的研究[J]. 真空科学与技术,1996,16(05):347-354.
[43] 曲喜新,杨邦朝,姜书俭等.电子薄膜材料[M].科学出版社
[44] 王玉玲,韩阶平.微细加工技术概述北京创威纳科技有限公司.
[45] stephen A.Campbell.微电子制造科学原理与工程技术[M].电子工业出版社.
[46] 胡耀志,黄光周,于继荣.机电产品微细加工技术与工艺[M].广东科技出版社.
[47] 厦门大学物理系半导体物理教研室.半导体器件工艺原理[M].人民教育出版社.
[48] 叶小琴. 许颖. 李艳等,PECVD 沉积氮化硅薄膜在退火过程中的特性变化及在太阳电池中的应用[J].北京师范大学学报(自然科学版),2004,40(2):221-223.
[2] 缪妟, 武国英. RF MEMS 器件的研究及其应用前景[J ].电子产品世界,2003(5):37-40.
[3] 茅惠兵,忻佩胜,胡梅丽,等.微机械微波/射频开关的制备和功能测量研究[J ].半导体技术,2002,27(11 ):11-14.
[4]朱健, 郁元卫, 陆乐,等.双膜桥微波MEMS 开关[J] .微纳电子技术2003 (7/ 8):382-384.
[5]Gabriel M. Rebeiz, Jeremy B. Muldavin, “RF MEMS Switches and Switch Circuits”,IEEE microwave magazine pp.59-71,December 2001.
[6] 张永华,丁桂甫,蔡炳初,等.发展中的RF MEMS 开关技术[J ]. 微纳电子技术,2003(5):28-32.
[7]孙建海,崔大付,苏波,等.宽带RF-MEMS 开关驱动电压的分析研究[J] . 微纳电子技术,2004(9):37-39.
[8]P.D. Grant, R.R. Mansour, and M.W. Denhoff, “A comparison between RF MEMS switches and semiconductor switches”,Can.J.Elect.Comput.Eng. Vol.27,No.1,January 2002,pp.33-39.
[9]Peterson K. Micromechanical membrane switches on silicon IBM J.RES.Develop.,1979,276-385.
[10]Larson L E, Hackett R H,Melendes M A,et al. Micromachined microwave actuator(MIMAC)technology-a new tuning approach for microwave integrated circuits. In: Microwave and Millimeter-Wave Monolithic Circuits Symposium Digest,Boston,MA,1991,27-30.
[11] Yao J J ,Chang M F. A surface micromachined miniature switch for telecommunication application with single freq. from DC up to 4 GHz. In :Proc. Transducer’95 ,June 1995 :384-387.
[12]Goldsmith C,Wu W R, Norvell B. Micromechanical Membrane Switches for Microwave Application.IEEE MTT-S Digest,1995,91-94.
[13]Goldsmith C , Randall J . Characteristics of micromachined switches at microwave frequencies. In :Proc. of Digest IEEE MTT International Microwave Symposium San Francisco ,USA ,1996 ,2 :1141-1144.
[14]Schiele I, Evers C,Hillerich B,et al. A Surface Micromachined Electrostatic Microrelay. In: Sensor 97.Vortag, 1997,87-91.
[15]Pacheco S, Nguyen C T C, Kethei L P B.Micromechanical electrostatic K-band switches. In: IEEE MTT-S Digest.Baltimore, 1998, 1569-1572.
[16]Dooyoung Hah, Euisik Yoon,A Low-Voltage Actuated Micromachined Microwave Switch Using Torsion Springs and Leverage IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 48, NO. 12, DECEMBER 2000 :2540-2545.
[17]Jae Y. Park, Geun H. Kim, Ki W. Chung1, etc, Monolithically integrated micromachined RF MEMS capacitive switches. Sensors and Actuators A 89 (2001):88-94 .
[18]梁春广RF MEMS 技术[J].微纳电子技术.2002(1) :6-8.
[19] 顾洪明,梁春广,高葆新. 微波微电子机械开关[J] .半导体技术,2000,25(11):29-32.
[20]朱健, 周百令, 郁元卫,等.高隔离度S波段MEMS膜桥开关[J ].固体电子学研究进展,2004,24(1):64-67。
[21]郑惟彬,黄庆安,李拂晓.低阈值电压RF MEMS 开关的力学模型[J ].固体电子学研究与进展, 2003,23(4):500-503.
[22]郭方敏,赖宗声,朱自强,等.悬臂式RF MEMS开关的设计与研制[J ]. 半导体学报,2003,24(11):1190-1195.
[23]魏华征. 郭方敏. 赖宗声. 等.射频微机械开关的计算机辅助设计[J].半导体学报2002,23(9):947-951.
[24]龙永福, 朱自强, 赖宗声,等.射频/微波MEMS Shunt开关的开启时间研究,电子学报,2002,30(8):1204-1206.
[25]龙永福. 赖宗声. 朱自强. 高电容比射频/微波MEMS 膜开关的理论分析和数值模拟[J].微波学报,2003,19(1):56-60.
[26]李炜, 石艳玲, 忻佩胜, 等.电容式MEMS 开关中弹性膜应力对驱动电压的影响[J].固体电子学研究与进展,2003,23(4):514-519.
[27]龙永福, 石艳玲, 赖宗声,等.偏置电压对射频/微波MEMS 电容开关寿命的影响[J].微电子学,2004,34(1):30-34.
[28]李成诗. 郭方敏. 赖宗声,等,基于ANSYS 悬臂式RFMEMS 开关的力学模拟和疲劳分析[J ].半导体技术,2004,29(10):22-26.
[29]徐欣. 郭方敏, 葛羽屏,等.MEMS 悬臂式开关的失效分析[J ].传感技术学报,2004 年9 月第3 期:492-496.
[30]F.M.Guo, Z.Q.Zhu, Y.F.Long, etc. “Study on low voltage actuated MEMS rf capacitive switches”,Sensors and Actuators A 108 (2003),pp.128-133.
[31]Ye Wang, Zhihong Li, Daniel T. McCormick, Norman C. Tien,”A Micromachined RF microrelay with electrothermal actuation”, Sensors and Actuators A 103(2003), pp.231-236.
[32]韩阶平,侯豪情,邵逸凯.适用于剥离工艺的光刻胶图形的制作技术及其机理讨论[J]. 真空科学与技术1994,14(3):215-219.
[33]闫桂珍,张大成,李婷,等.金属剥离与衬底腐蚀等平面自对准OHR 技术研究[J]. 微纳电子技术2002,01:40-43.
[34]王文如,杨正兵.微细金属图形制作中的剥离技术[J]. 压电与声光2001,23(1):68-73.
[35]刑素贤,程足捷,王中文.等平面和金属剥离工艺在低电容高可靠晶体管生产中的应用[J].辽宁大学学报自然科学版1997,24(2)46-50。
[36]Peng Yao. 3D Photolithography based on image reversal Proc. of SPIE Vol.5342:165-172
[37]庄同曾张安康黄兰芳集成电路制造技术——原理与实践[M] .
[38] 赵永军,王民娟,杨拥军等. PECVD SiNx 薄膜应力的研究[J].半导体学报,1999,20(3):183-187.
[39] 唐元洪.等离子体增强型化学气相淀积氮化硅的淀积[J]. 湖南大学学报1996,23(1):42-44.
[40] 徐泰然.MEMS和微系统——设计与制造[M] .机械工业出版社,2004:265.
[41]于映,陈跃.氮化硅介质薄膜内应力实验研究[J].真空科学与技术,2001,21(01):51-54.
[42] 周志烽, 范玉殿. 薄膜热应力的研究[J]. 真空科学与技术,1996,16(05):347-354.
[43] 曲喜新,杨邦朝,姜书俭等.电子薄膜材料[M].科学出版社
[44] 王玉玲,韩阶平.微细加工技术概述北京创威纳科技有限公司.
[45] stephen A.Campbell.微电子制造科学原理与工程技术[M].电子工业出版社.
[46] 胡耀志,黄光周,于继荣.机电产品微细加工技术与工艺[M].广东科技出版社.
[47] 厦门大学物理系半导体物理教研室.半导体器件工艺原理[M].人民教育出版社.
[48] 叶小琴. 许颖. 李艳等,PECVD 沉积氮化硅薄膜在退火过程中的特性变化及在太阳电池中的应用[J].北京师范大学学报(自然科学版),2004,40(2):221-223.