往年博士学位优秀论文精选-中英文(18)

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　　高性能MEMS射频无源器件与三维硅微机械加工技术

　　作者姓名：顾磊

　　论文题目：高性能MEMS射频无源器件与三维硅微机械加工技术

　　作者简介：顾磊，男1980年4月出生，2004年4月师从中国科学院上海微系统与信息技术研究所李昕欣研究员，于2007年7月获博士学位。

　　中文摘要

　　片上集成电感、互感和可调电容是射频集成电路中三种最重要的射频无源元件，在整个电路系统中起着决定性的作用，是单片RF

　　集成电路如压控振荡器(VCOs)、低噪声放大器(LNAs)及无源滤波器中的关键性部件，在个人移动通讯、全球定位系统(GPS)以及卫星信号接收等高频电路系统中占有重要的地位。利用微机械技术研究射频无源器件是目前MEMS研究领域的热点之一。体微机械、表面微机械以及LIGA技术是MEMS领域重要的三种加工手段，几种加工方式的融合与实现片上集成也是目前MEMS加工领域的发展方向。

　　本论文工作主要研究硅基三维微机械结构制造及射频关键器件的研制技术。一方面针对目前电讯用RFIC的高性能无源元件，如电感、互感和可变电容。所开发的低温工艺可以与射频CMOS工艺相兼容，同时利用MEMS技术解决了硅衬底损耗等问题，实现了高性能的RF电感、互感和可变电容等关键元件，另一方面还针对微纳操纵和精确定位系统需求的X-Y微移动平台，用深沟侧壁隔离(Trench-sidewall)

　　MEMS工艺形成具有微米级移动范围和纳米级定位精度的高性能X-Y微移动载台，为微米电子机械系统进入到纳米电子机械系统研究提供了基本的操作平台，同时新型的电绝缘技术使该微平台可以在普通硅片上制作实现，替代SOI硅片，大大降低了制造成本。主要研究工作和成果分项归纳为：

　　1)在国际上首次报道一种采用低温CMOS兼容工艺制造的嵌入式悬浮螺管 (Concave- Suspended Solenoid)

　　结构电感和互感(L.Gu, X.Li, IEEE Trans. Electron Devices 54，2007，pp.882;L.Gu, X.Li,IEEE

　　Trans. Microwave Theory Tech.

　　55，2007，pp.1237)。为了便于封装以及后续加工，电感或互感线圈嵌入在硅片内部，电感线圈周围的硅材料被XeF2气体各向同性腐蚀去除，整个线圈结构通过两边伸出的二氧化硅薄膜支撑(发明专利CN200610029276.8李昕欣,顾磊)。由于线圈周围的硅都被腐蚀移除，电感的衬底损耗极低，大大提高器件的高频性能。而采用铜电镀工艺又显著降低线圈的欧姆损耗。上面两个因素使得新型电感和互感的Q值和谐振频率得到显著提高。两边二氧化硅膜支撑也使得整个悬浮结构更加结实，制作的器件在10000g加速度冲击试验下完好无损。利用有限元分析软件ANSYS仿真100g的环境加速度以及80摄氏度环境温度改变下的电感值变化，分析得到的变化值比目前国际上报道最好的悬浮结构还要低一个量级。针对该创新结构嵌入式悬浮螺管电感和互感，建立了集总和准分布两种电路模型，模型与测量结果相吻合，能够指导电感或互感的优化设计

　　(L.Gu, X.Li, IEEE J-MEMS

　　16，2007，pp.1162)。电感高频性能测量结果表明2.47nH电感的Q值在2GHz时高达54，自谐振频率超过15GHz，优于已发表的各种CMOS兼容微机械片上电感。在电感制造基础上进一步工艺创新，设计制造出双螺旋结构悬浮互感，建立了器件模型(L.Gu,

　　X.Li,IEEE Trans. Microwave Theory Tech.

　　55，2007，pp.1237)。互感有效带宽测量值为14Ghz到16GHz，有效增益(可以作为评价互感性能的综合指标)为0.89，在国际报道的片上集成互感中性能最好。该电感和互感创新技术

　　2006年入选著名的国际电子器件大会(IEDM)作报告 (L.Gu, X.Li, IEEE IEDM 2006，pp.521) 。

　　2)针对该创新结构，提出并实现了各种经常使用的电感或互感设计方法 (L.Gu, X.Li,IEEE MEMS

　　2007，pp.771)，针对更大的电感值，为节省芯片面积，首尾串联的紧密型电感结构是合适的选择;反之如果希望进一步提高性能但对芯片面积要求不高，则“S”型结构更加合适;为避免电感线圈形成的电磁场对周围电路的影响，提出并实现了一种闭合回路结构，HFSS软件分析表明该结构能够将磁力线几乎全部限制在线圈内部

　　(L.Gu, X.Li, Microelectron.

　　Eng.85，2008，pp.697)。此外，为了进一步提高电感或互感的性能及一致性，提出并实现了一种带有绝缘沟槽的微结构，通过精确限制XeF2气体腐蚀区域的技术，显著提高了器件性能的一致性。通过在焊盘底部放置厚二氧化硅层减少引线焊盘引入的寄生效应，使得器件在满足片上集成需要的之外还可以作为高性能分立器件倒装焊封装到SiP射频电路中

　　(L.Gu, X.Li, Microw. Opt. Technol. Lett. 50,2008,pp.2442)。

　　3)针对射频集成电路用微机械可变电容存在的问题，提出了一系列的解决办法和创新技术。为了减少串联电阻、降低工艺复杂度并与Post-CMOS工艺兼容，发明一种低应力多层金属电镀技术来制造悬浮可变面积及可变间距梳齿电容

　　(L.Gu, X.Li, Microw. Opt. Technol. Lett.

　　50,2008,pp.2469)。利用金属镍优异的机械性能，我们采用镍制作器件结构，在金属镍的表面电镀一薄层金用来降低串联电阻并防止镍在空气中氧化。为降低衬底损耗，可变电容结构底部硅用干法腐蚀去除，可动结构通过周围的二氧化硅锚点支撑固定。整个制造过程温度不超过120摄氏度，仅需两块光刻版

　　(发明专利CN200710044283.3，李昕欣、顾磊)。器件测量结果为：4V电压驱动下，电容值的可调比高达2.98:1，1GHz时的Q值为103，2GHz时的Q值为46.2，优于目前报道的各种

　　CMOS兼容片上集成微机械可变电容。

　　为了避免驱动电压端口对射频信号端口的影响，提出并实现了一种新的相互绝缘式可变电容结构 (L.Gu, X.Li, Electronics Lett.

　　43,2007,pp.808)。电容驱动端与敏感电容端通过二氧化硅薄膜桥实现机械上相连，但电学上相互绝缘。该结构消除了直流偏置电路对可变电容性能的影响，提高了可变电容在电路布局中的灵活性，测量得到4V电压驱动下，电容的可调比高达3.18:1，Q值在1GHz时为115.0，在2GHz时为40.2。

　　4)国际上首次提出并实现一种旋转式微结构可变电容，能够抵抗外界环境振动或冲击对可变电容稳定性的影响 (L.Gu, X.Li, IEEE

　　Electron Device Letters

　　29,2008,pp.195)。当施加静电驱动力时，梳齿电容的运动方向是沿着器件中心轴旋转。这种结构只有受到轴向力才会产生明显形变，而外界环境加速度的影响几乎都为水平单一方向，很少会产生沿中心轴旋转加速度的干扰，故该结构能够有效抑制移动通讯系统应用时环境振动冲击对器件的影响，显著提高了可靠性(发明专利CN200710045457.4,李昕欣、顾

　　磊)。该旋转结构在10g环境加速度下，电容的变化值比传统微机械可变电容(直向运动)的电容变化值低两个量级以上。性能测试得到12V电压下，可变电容可调比为2.1:1，Q值在2GHz时仍高达35.2。

　　以上MEMS片上可调谐电容的相关成果又一次入选2007年国际电子器件大会(IEDM)做报告(L.Gu, X.Li, IEEE IEDM

　　2007，pp.427)。

　　本论文在射频电路用高性能MEMS器件方面的研究成果得到国际同行高度重视，作为中国学者，首次被邀请在2008年IEEE

　　RFIC国际会议做特邀报告(X.Li, L.Gu，IEEE RFIC-2008，pp.163)。

　　5) 首次采用深沟侧壁(Trench-sidewall)MEMS集成工艺技术在单一硅片上成功制造微移动平台 (L.Gu,et al, J

　　Micromech. Microeng. 85,2008,pp.697)。采用的Trench- sidewall

　　MEMS技术能够取代价格昂贵的SOI衬底，将静电驱动，电容、压阻信号检测部分集成在单硅片上，并且能够对一些功能进行自检和反馈控制，提高的器件的精度和可靠性，降低制造成本

　　(X.Li，L.Gu，IEEE Sensors Journal,

　　8,2008,pp.1992)。显微镜测量制造出的两维微位移载台，在23V驱动电压下载台移动范围为20×20微米2。为车辆载台的移动定位精度，一种加热SPM探针纳米压印方法被设计和用于测量。测量结果显示位移精度优于18nm，为将来的微电子机械系统研究进入到纳电子机械系统研究提供了必要的操作和测试平台工具。

　　本论文工作用原始创新的关键技术解决了三维MEMS结构集成制造的复杂难题。特别是与CMOS集成电路工艺兼容的片上集成高性能射频无源器件技术，所取得的成果获得国际学术界的认可，所开发的可实用化技术也在微电子产业界获得转让和推广应用。论文的相关学术成果两度发表在国际电子器件领域论文录取最为困难的“国际电子器件会议”(International

　　Electron Device Meeting,简称IEDM，在IEDM五十多年历史中我国被录取发表的论文仅寥寥数篇)。此外，论文多次发表在包括IEEE E-D

　　Lett., IEEE T-ED, IEEE J- MEMS, IEEE

　　T-MTT等电子信息领域国际核心期刊上，引起了国际同行的重视。相关成果受2008年领域国际著名会议 IEEE International RFIC

　　Symposium邀请作特邀报告，是我国首次在该会议获邀作邀请报告。另外包括 IEEE ED Society的副主席和IEEE

　　Fellow等国际著名学者纷纷主动就该成果进行高性能RF集成电路技术合作研发。论文成果中包括三项核心发明专利(一项授权，两项公开)。香港主版上市公司上海先进半导体制造有限公司(ASMC)等企业就本论文的成果已经与我们展开了专利技术转让来实现微电子制造产品技术。根据该技术应用研发内容，上海市科委近期确立了重点项目进行支持。这种用自主创新的技术来提升我国微电子企业的产业技术水平对推动我国微电子事业的发展具有重要意义。

　　本文所作的研究工作，在MEMS三维复杂集成结构制造方面取得了突破性成果，对于实现高性能射频集成电路、通讯系统以及纳米操纵等具有重要的学术价值和应用价值，有助于我国在信息技术领域取得突出的、有特色的进展，获得重大经济效益。

　　规定期限内相关成果形成的论文和专利列表如下：

　　论文：

　　1.Lei Gu, Xinxin Li, Variable Capacitors and Tunable LC- Tanks Formed by

　　CMOS- Compatible Metal MEMS for RF ICs, IEDM 2007 --- 53th IEEE International

　　Electron Device Meeting, Washington DC，USA, 10-13 Dec., 2007, pp.427-430.

　　2.Lei Gu, Xinxin Li, A Post-CMOS Concave- Suspending MEMS Process in

　　Standard Silicon Wafers for High-Performance Solenoidal-DNA-Configured

　　Micro-Transformers, IEDM 2006 --- 52th IEEE International Electron Device

　　Meeting 2006, San Francisco, CA, USA, Dec. 11-13, 2006, pp. 521-524.

　　3.Lei Gu, Xinxin Li, Rotational- driven RF Variable Capacitors with

　　Post-CMOS Processes, IEEE Electron Device Letters, Vol.29, No.2, 2008,

　　pp.195-197.

　　4.Lei Gu, Xinxin Li, High-Q Solenoid Inductors With a CMOS- Compatible

　　Concave-Suspending MEMS Process, IEEE Journal of Microelectromechanical Systems,

　　VOL. 16, NO. 5, 2007, pp.1162-1172.

　　5.Lei Gu, Xinxin Li, High-Performance CMOS- compatible Solenoidal

　　Transformers with a Concave-suspended Configuration, IEEE Transactions on

　　Microwave Theory and Techniques, VOL. 55, NO. 6, 2007, pp.1237-1245.

　　6.Lei Gu and Xinxin Li, Concave-suspended High- Q Solenoid Inductors with

　　an RFIC-compatible Bulk-micromachining Technology, IEEE Transactions on Electron

　　Devices, Vol.54, 2007, pp.882-885.

　　7.Lei Gu, Xinxin Li, Haifei Bao, Bin Liu, Yuelin Wang, Min Liu, Zunxian

　　Yang, Baoluo Cheng, Single-Wafer-Processed Nano-Positioning XY-Stages with a

　　Trench-Sidewall Micromachining Technology, J. Micromech. Microeng., 16 (2006)

　　1349–1357.

　　8.L. Gu and X. Li, Post- CMOS micromachined RF varactor with

　　mutual-isolated large-tuning capacitor and low-voltage actuator, Electronics

　　Letters, Vol. 43, No. 15, 2007, pp.808-809.

　　9.Lei Gu, Xinxin Li, On-chip embedded toroidal- solenoid inductors and

　　transformers formed by post-CMOS micromachining techniques, Microelectronic

　　Engineering, Vol. 85, 2008, pp.697-703.

　　10.Lei Gu, Zhengzheng Wu, Xinxin Li, Post- CMOS compatibly micromachined

　　high-performance on-chip air-core solenoidal inductors, Microwave and Optical

　　Technology Letters, Vol. 50, 2008, pp.2442 – 2446.

　　11.Lei Gu, Zhengzheng Wu, Xinxin Li, Post- CMOS micromachined nickel

　　tunable-capacitors with a large tuning-range under low actuating voltage,

　　Microwave and Optical Technology Letters, Vol. 50, 2008, pp.2469 – 2472.

　　12.Lei Gu, Xinxin Li, An wide-range tunable on-chip radio- frequency

　　LC-tank formed with a post- CMOS compatible MEMS fabrication technique,

　　Microelectronics Journal, (论文已在网站上公开出版，日期为：Available online 23 July

　　2008，编号：doi:10.1016/j.mejo.2008.06.065，纸本期刊正在印刷中)

　　13.Lei Gu, Xinxin Li, CONCAVE-SUSPENDED HIGH-Q SOLENOID INDUCTORS WITH A

　　POST-CMOS MEMS PROCESS IN STANDARD SILICON WAFERS, IEEE MEMS-07 --- the 20th

　　IEEE International Conference on Micro Electro Mechanical Systems, Kobe, Japan,

　　Jan. 21-25, 2007, pp.771.

　　14.Lei Gu, Xinxin Li, Haifei Bao, Bin Liu, Yuelin Wang, Min Liu, Zunxian

　　Yang, Baoluo Cheng, A Single-Wafer-Processed XY-Stage Fabricated with

　　Trench-sidewall Doping and Refilled-Trench Isolating Technology, IEEE NEMS-06

　　--- the 1st IEEE International Conference on Nano/Micro Engineered and Molecular

　　Systems, Jan. 18-21, 2006, Zhuhai, China, pp.860-863.

　　15.(邀请报告) Xinxin Li, Lei Gu, (INVITED) Hi- Performance RF passives Using

　　Post- CMOS MEMS Techniques for RF SoC, IEEE RFIC- 2008 --- 2008 IEEE Radio

　　Frequency Integrated Circuits Symposium, June 15-17, 2008, Atlanta, GA, USA,

　　pp.163-166. (注：第一作者为申请者的导师)

　　16.Xinxin Li, Lei Gu, Yuelin Wang, Heng Yang, Single-wafer- processed

　　Self-testable High- g Accelerometers with Both Sensing and Actuating Elements

　　Integrated on Trench- sidewall, IEEE Sensors Journal, Vol. 8, 2008,

　　pp.1992-1999. (注：第一作者为申请者的导师)

　　17.Xinxin Li, Baoluo Chen,　Yuelin Wang,　Lei Gu,　Jian Dong,　 Xiaohong Ge，A

　　trench-sidewall single-wafer- MEMS technology and its typical application in

　　high- performance accelerometers，IEDM 2004---50th IEEE International Electron

　　Device Meeting, San Francisco, CA ,13-15 Decmber，2004，pp.43-46.

　　(注：第一作者为申请者的导师)

　　18.Xinxin Li, Wei Xu, Ying Chen, Le Luo, Lei Gu, Min Liu, Baoluo Cheng, and

　　Yuelin Wang, Single- wafer-processed trench- sidewall integration and its

　　application in a micro resonant detector for vacuum monitoring, J. Vac. Sci.

　　Technol. B 24 (1), Jan/Feb 2006, pp16-19. (注：第一作者为申请者的导师)

　　专利：

　　1.一种CMOS工艺兼容的嵌入悬浮螺管结构电感或互感的制作方法, CN200610029276.8, 李昕欣、顾磊(已授权)

　　2.一种CMOS工艺兼容的悬浮式可变电容的制作方法，CN200710044283.3，李昕欣、顾磊

　　(法律状态：实质审查的生效;公开(公告)号：101110354;公开(公告)日：2008-01-23)

　　3.一种抗环境振动的适用于移动电信的MEMS片上可变电容，CN200710045457.4, 李昕欣、顾 磊

　　(法律状态：实质审查的生效;公开(公告)号：101154505;公开(公告)日：2008-04-02)

　　关键词：微电子机械系统，射频无源器件，电感，互感，可变电容,可调谐谐振器，X-Y两维微移动平台，微机械加工

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　　High-performance MEMS RF passive components and silicon micromachined

　　technology

　　Lei Gu

　　ABSTRACT

　　On-chip inductors, transformers and tunable capacitors are most important

　　passive components in RF integrated circuits and play key roles for designing

　　VCO (voltage control oscillator), LNA (low noise amplifier) and passive filter

　　or resonator. Besides, personal mobile communication, GPS (global position

　　system), and satellitic signal receiver also need these high-performance

　　devices, namely high Q-factor of inductors/tunable capacitors and high available

　　gain of transformers. Presently, it is a hotspot for studying RF passive

　　components by using MEMS technology. Bulk, surface micromachining and LIGA

　　technique are three essential method of fabrication. Several kinds of processes

　　infused and integrated are also the direction for further MEMS research.

　　In this dissertation, we mainly study the 3-D micromachined process based

　　on silicon substrate and research of key RF passive components. On the one hand,

　　some high performance RF components are implemented for telecommunications by

　　using a concise process, such as inductors, transformers and tunable capacitors.

　　The novel process could be compatible with CMOS process with low temperature.

　　Moreover, the substrate loss is suppressed deeply by selective removing silicon

　　surrounding the devices. On the other hand, a nano-precision XY-stage is

　　designed and fabricated with trench-sidewall technology. Moreover, the XY-stage

　　is formed on a single wafer instead of SOI wafer to reduce the cost of the

　　fabrication. The stage is an elementary operation method for further research

　　from MEMS (microelectricmechanical system) to NEMS (nanoelectricmechanical

　　system) research. The main work and contributions are as follows:

　　1) In order to improve the performance of inductors and transformers,

　　concave-suspended solenoid structures are proposed and formed by low temperature

　　CMOS compatible process. To our best knowledge, these structures are reported

　　firstly in the world. To facilitate the package and post-fabrication, the coils

　　of inductors or transformers are embedded into the silicon substrate. The

　　silicon surrounding the coils are etched and removed by gaseous XeF2. Therefore,

　　the substrate loss of the device is suppressed due to the silicon surrounding

　　coils removed. Moreover, the ohmic loss also reduced by using the copper plated

　　process. Both factors improve the Q-factor and resonant frequency. The whole

　　structure is sustained with protruding silicon oxide film on the both sides of

　　the structure. The robust structure can be survived even under a shock of 10000g

　　acceleration. By using finite element software ANSYS, the deformation of coil is

　　one order smaller than other suspended inductors under 100g acceleration and 80

　　centigrade temperature changed. According to these proposed concave-suspended

　　solenoid inductors and transformers, lumped and quasi-distributed circuit models

　　are given. The simulated results based on circuit model can agree well with the

　　measurement and be used to design and optimize the inductors and transformers.

　　The measured Q-factor, the inductance and resonant frequency of the

　　concave-suspended solenoid inductor are 54@2GHz, 2.47nH at low frequency and

　　more than 15GHz, respectively. These performances are better than most of other

　　micromachining inductors. We also fabricate some transformers which formed with

　　the similar process. For the transformer, available gain can be defined as the

　　ratio between the power delivered to the load and the power input to the

　　network. It can be considered as an important figure-of-merit for overall

　　evaluation of the RF transformers. The available gain of our present transformer

　　is as high as 0.89 which is better than all other reported transformers. The

　　available bandwidth is from 14 to 16GHz.

　　2) Different layouts of inductors and transformers are proposed for

　　different applications. For the high inductance with small area occupation, a

　　compact structure made by connecting several one column inductors in series is

　　better choice. For the high inductance with high performance, an “S”shaped

　　structure is a suitable choice with a little bigger area occupation. In order to

　　eliminate the effect of electromagnetic interference and noise coupling with

　　neighboring RF components, several closed loop solenoid inductor are

　　implemented. With simulation of HFSS (Ansoft company software), these structure

　　can confine the magnetic flux into a close-path. The structure can also avoid

　　the flux intersecting with metals and semiconductor materials where eddy

　　currents are easily induced. In order to improve the uniformity of the

　　performance, a kind of structure with silicon oxide refilled trenches is given,

　　which can define the region for XeF2 gaseous etching. The oxide block beneath

　　the test pad can suppress the substrate parasitics. This structure can be used

　　not only on-chip integration but as an off-chip for flip-chip package.

　　3) Some new structures and process are presented for solving problems

　　existed in conventional MEMS tunable capacitors. In order to reduce the series

　　resistance and simply the fabrication, low stress multi-metal electroplated

　　technology (also called metal MEMS technology) is proposed and used to fabricate

　　the suspended tunable capacitor with comb drivers. Electroplated nickel is used

　　as the structure material due to its excellent mechanical properties. A thin

　　gold film is covered on the surface of the nickel for long-term antioxidation in

　　the air. After finishing the whole structure, the silicon substrate beneath the

　　capacitive combs is also removed by XeF2 dry etching to for the same reason of

　　suppressing the substrate loss. The structures are sustained by surrounding

　　silicon oxide anchors. A suspension gap distance from the silicon substrate is

　　formed. The temperature during the whole fabrication is below 120 centigrade.

　　Only two masked are required. Under 4V driving voltage, the tuning ratio is

　　2.98:1. The Q-factor is 103 at 1GHz and 46.2 at 2GHz, which is better than most

　　of micromachining tunable capacitor.

　　Most of the previously reported MEMS tunable capacitors share a common

　　electric terminal with the electrostatic actuator. This common-ground

　　configuration confines the flexibility of RFIC design. Moreover, the DC driving

　　voltage interferes with the input RF signal especially in high power

　　application. To overcome this limitation, the present technique electrically

　　isolates the two parts at the middle of the linking bars with a patterned SiO2

　　bridge. The bridge just connects the two terminals mechanically but isolates

　　each other electrically. This allows a greater flexibility in RF circuit layout.

　　Under 4V driving voltage, the tuning ratio is 3.18:1. The Q-factor is 115 at

　　1GHz and 40.2 at 2GHz

　　4) To date, a drawback of the developed micromachined tunable capacitors

　　lies in the mechanical instability induced by the straight-line-driven comb

　　structures. For achieving a large tuning ratio under a low driving voltage, the

　　researches have always designed the suspension springs as flexible as possible.

　　When used in a mobile system like cell phone, such a mechanically instable

　　capacitor will be inevitably influenced by the environmental

　　vibratory/acceleration. On the contrary, rigid suspended beams require high

　　driving voltage for getting wide tuning range. This is a dilemma in the design

　　of micromaching tunable capacitors. To solve this problem, this dissertation

　　develops, for the first time, a rotationally driven tunable capacitor. The

　　rotational structure features a low stiffness in tangential direction for

　　capacitance tuning but a much higher stiffness along radial directions for

　　anti-vibration, thereby, exhibiting both high tuning-range under low-voltage and

　　high resist against the axial vibration and acceleration. Generally, the

　　environmental acceleration is applied along the straight direction. Therefore,

　　the rotational structure can effectively suppress the environmental

　　vibratory/acceleration. By using ANSYS simulation, the comb moving distance

　　along the electrostatic driving direction is about two orders of magnitude lower

　　than that of the conventional straight-moving tunable capacitors. Under 12V

　　driving voltage, the tuning range of rotational capacitor is 2.1:1. The Q-factor

　　is 35.2 at 2GHz.

　　5) Besides the RF passive components, a XY-stage is firstly presented on a

　　single silicon wafer with trench-sidewall MEMS integrated technology. The

　　trench-sidewall technology can be used to integrated piezoresistive, capacitive

　　sensing and electrostatic actuator on a single silicon wafer instead of

　　expensive SOI or SOG wafer. Moreover, the reliability of device can be improved

　　by self-testing and feed back control. By using measured microscope, the moving

　　range of the XY-stage is tested as 20×20μm2 under a driving voltage of 23V. In

　　order to get a precision of movement, a nano-print system is designed and used

　　to measure the XY-stage. Limited by the radius of the nanometric tip, the

　　resolution of the tip position is about 18 nm. With this error bar denoted, all

　　five data are on the straight fitting line. Therefore, in the small displacement

　　region, the positioning precision of the stage can be considered better than the

　　resolution of the nano tip, i.e. better than ±18 nm. The XY-stage provides an

　　acceptable measured method for NEMS research.

　　The work of this thesis is creating innovation to develop 3-D MEMS

　　integrating fabrication technology that is well known a very difficult work.

　　Especially the CMOS-compatible integration technology for high-performance RF

　　passives has been highly appraised by international academic field. The

　　developed techniques have been transferred to microelectronics industry for

　　production applications. Two papers have been published in the famous

　　“International Electron Device Meeting (IEDM)”. Quite a number of papers are

　　also published in the top-level journals of the field, such as IEEE E-D Lett.,

　　IEEE T-ED, IEEE J-MEMS, IEEE T-MTT, etc. The related results are invited to

　　present as an invited paper on 2008 IEEE International RFIC Symposium. Based on

　　the related achievement. Some famous scientists, including the vice president of

　　IEEE ED Society and IEEE Fellow, have collaborated with us to develop RF Ics.

　　Three patents are now pending. Some microelectronics companies like ASMC have

　　collaborated with us, working on patent technology transfer for production

　　applications. Based on this R&D content, recently Shanghai government

　　granted an key project to support this industrial application research.

　　In conclusion, the investigation in this thesis realizes an important

　　breakthrough in integration of complicated MEMS 3-D structures. The achievements

　　are of great signification for getting high performance RF IC, telecommunication

　　and nano-operation. These efforts will bring remarkable and prominent

　　development in information and technology field and gain more economic

　　benefit.

　　Relative publication and patent list:

　　Publications：

　　19. Lei Gu, Xinxin Li, Variable Capacitors and Tunable LC- Tanks Formed by

　　CMOS- Compatible Metal MEMS for RF ICs, IEDM 2007 --- 53th IEEE International

　　Electron Device Meeting, Washington DC，USA, 10-13 Dec., 2007, pp.427-430.

　　20. Lei Gu, Xinxin Li, A Post-CMOS Concave-Suspending MEMS Process in

　　Standard Silicon Wafers for High-Performance Solenoidal-DNA-Configured

　　Micro-Transformers, IEDM 2006 --- 52th IEEE International Electron Device

　　Meeting 2006, San Francisco, CA, USA, Dec. 11-13, 2006, pp. 521-524.

　　21. Lei Gu, Xinxin Li, Rotational-driven RF Variable Capacitors with

　　Post-CMOS Processes, IEEE Electron Device Letters, Vol.29, No.2, 2008,

　　pp.195-197.

　　22. Lei Gu, Xinxin Li, High-Q Solenoid Inductors With a CMOS-Compatible

　　Concave-Suspending MEMS Process, IEEE Journal of Microelectromechanical Systems,

　　VOL. 16, NO. 5, 2007, pp.1162-1172.

　　23. Lei Gu, Xinxin Li, High-Performance CMOS-compatible Solenoidal

　　Transformers with a Concave-suspended Configuration, IEEE Transactions on

　　Microwave Theory and Techniques, VOL. 55, NO. 6, 2007, pp.1237-1245.

　　24. Lei Gu and Xinxin Li, Concave-suspended High-Q Solenoid Inductors with

　　an RFIC-compatible Bulk-micromachining Technology, IEEE Transactions on Electron

　　Devices, Vol.54, 2007, pp.882-885.

　　25. Lei Gu, Xinxin Li, Haifei Bao, Bin Liu, Yuelin Wang, Min Liu, Zunxian

　　Yang, Baoluo Cheng, Single-Wafer-Processed Nano-Positioning XY-Stages with a

　　Trench-Sidewall Micromachining Technology, J. Micromech. Microeng., 16 (2006)

　　1349–1357.

　　26. L. Gu and X. Li, Post-CMOS micromachined RF varactor with

　　mutual-isolated large-tuning capacitor and low-voltage actuator, Electronics

　　Letters, Vol. 43, No. 15, 2007, pp.808-809.

　　27. Lei Gu, Xinxin Li, On-chip embedded toroidal-solenoid inductors and

　　transformers formed by post-CMOS micromachining techniques, Microelectronic

　　Engineering, Vol. 85, 2008, pp.697-703.

　　28. Lei Gu, Zhengzheng Wu, Xinxin Li, Post-CMOS compatibly micromachined

　　high-performance on-chip air-core solenoidal inductors, Microwave and Optical

　　Technology Letters, Vol. 50, 2008, pp.2442 – 2446.

　　29. Lei Gu, Zhengzheng Wu, Xinxin Li, Post-CMOS micromachined nickel

　　tunable-capacitors with a large tuning-range under low actuating voltage,

　　Microwave and Optical Technology Letters, Vol. 50, 2008, pp.2469 – 2472.

　　30. Lei Gu, Xinxin Li, An wide-range tunable on-chip radio-frequency

　　LC-tank formed with a post-CMOS compatible MEMS fabrication technique,

　　Microelectronics Journal, (Available online 23 July 2008,

　　doi:10.1016/j.mejo.2008.06.065)

　　31. Lei Gu, Xinxin Li, CONCAVE-SUSPENDED HIGH-Q SOLENOID INDUCTORS WITH A

　　POST-CMOS MEMS PROCESS IN STANDARD SILICON WAFERS, IEEE MEMS-07 --- the 20th

　　IEEE International Conference on Micro Electro Mechanical Systems, Kobe, Japan,

　　Jan. 21-25, 2007, pp.771.

　　32. Lei Gu, Xinxin Li, Haifei Bao, Bin Liu, Yuelin Wang, Min Liu, Zunxian

　　Yang, Baoluo Cheng, A Single-Wafer-Processed XY-Stage Fabricated with

　　Trench-sidewall Doping and Refilled-Trench Isolating Technology, IEEE NEMS-06

　　--- the 1st IEEE International Conference on Nano/Micro Engineered and Molecular

　　Systems, Jan. 18-21, 2006, Zhuhai, China, pp.860-863.

　　33. Xinxin Li, Lei Gu, (INVITED) Hi-Performance RF passives Using Post-CMOS

　　MEMS Techniques for RF SoC, IEEE RFIC-2008 --- 2008 IEEE Radio Frequency

　　Integrated Circuits Symposium, June 15-17, 2008, Atlanta, GA, USA,

　　pp.163-166.

　　34. Xinxin Li, Lei Gu, Yuelin Wang, Heng Yang, Single-wafer-processed

　　Self-testable High-g Accelerometers with Both Sensing and Actuating Elements

　　Integrated on Trench-sidewall, IEEE Sensors Journal, Vol. 8, 2008,

　　pp.1992-1999.

　　35. Xinxin Li, Baoluo Chen,　Yuelin Wang,　Lei Gu,　Jian Dong,　 Xiaohong Ge，A

　　trench-sidewall single-wafer- MEMS technology and its typical application in

　　high- performance accelerometers，IEDM 2004---50th IEEE International Electron

　　Device Meeting, San Francisco, CA ,13-15 Dec. 2004，pp.43-46.

　　36. Xinxin Li, Wei Xu, Ying Chen, Le Luo, Lei Gu, Min Liu, Baoluo Cheng,

　　and Yuelin Wang, Single-wafer-processed trench-sidewall integration and its

　　application in a micro resonant detector for vacuum monitoring, J. Vac. Sci.

　　Technol. B 24 (1), Jan/Feb 2006, pp16-19.

　　专利：

　　4. A fabrication method for CMOS compatible concave-suspended solenoid

　　inductors and transformers, CN200610029276.8, X. Li and L. Gu (Granted)

　　5. A fabrication method for CMOS compatible suspended variable-capacitors,

　　CN200710044283.3, X. Li and L. Gu (Pending)

　　6. A kind of MEMS on-chip varactors with anti-vibration capability for

　　movable telecommunication, CN200710045457.4, X. Li and L. Gu (Pending)

　　Key words: MEMS, RF passive components, inductors, transformers, tunable

　　capacitors, Tunable LC-tank, XY-stage, micromaching process.

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