An RF-MEMS Switch With Low-Actuation Voltage and High Reliability

"Both the authors and the Editor-in-Chief of Volume 15, number 6 of the IEEE/ASME JMEMS (December 2006, pp.1606-1611) of the paper numbered JMEMS 1743 have agreed that this paper, "An RF MEMS Switch with Low Actuation Voltage and High Reliability," should not have been published. The paper would have been withdrawn had this fact been discovered before the IEEE/ASME JMEMS print date for December 2006. The authors have indicated that they will work to provide a new version their paper that will be considered for publication if it is submitted in the future. For help in coming to this decision, I would like to thank those concerned individuals, including the authors, JMEMS editors, and highly respected researchers in the MEMS and microwave communities who contributed their time and consideration to help us assure the integrity of our journal." Richard S. Muller, Editor-in-Chief, IEEE/ASME JMEMS     

MEMS-Based Electronically Steerable Antenna Array Fabricated Using PCB Technology

In this paper, a MEMS-based electronically steerable antenna array (ESA) fabricated using printed circuit processing techniques is reported. A Kapton polyimide film is used as the structural layer for fabricating MEMS varactors. The MEMS varactors have been used in the bistable mode to design loaded- line-type MEMS phase shifters. These MEMS phase shifters have been monolithically integrated with the ESA on a Duroid substrate using printed circuit processing techniques. For proof-of-concept demonstration of the proposed MEMS-based ESA, a 3-bit MEMS phase shifter has been monolithically integrated with a two- element double-folded slot-antenna array on a Duroid substrate. An X-band ESA prototype with a beam steering angle of 20deg at 9.1 GHz is presented.     

Design and consideration of wafer level micropackaging for distributed RF MEMS phase shifters

A novel packaging structure which is performed using wafer level micropackaging on the thin silicon substrate as the distributed RF MEMS phase shifters wafer with vertical feedthrough is presented. The influences of proposed structure on RF performances of distributed RF MEMS phase shifters are investigated using microwave studio (CST). Simulation results show that the insertion loss (S₂₁) and return loss (S₁₁) of packaged MEMS phase shifters are −0.4–1.84 dB and under −10 dB at 1–50 GHz, respectively. Especially, the phase shifts have well linear relation at the range 1–48 GHz. At the same time, this indicated that the proposed pacakaging structure for the RF MEMS phase shifter can provide the maximum amount of linear phase shift with the minimum amount of insertion loss and return loss of less than −10 dB.     

MEMS variable‐capacitor phase shifters part I: Loaded‐line phase shifter

This article describes the design and characterization of a continuously variable loaded‐line phase shifter using micro‐electro‐mechanical system (MEMS) variable capacitors as phase shifting components. The design and characterization of micro‐electro‐mechanical system (MEMS) variable capacitors for operation at 26.5 GHz is described. A lumped‐element model is obtained from measurements and physical consideration. Experimental results show a capacitance‐tuning ratio of 3.7:1. The capacitor's characterization results are used for designing the phase shifter. A phase shift of 40.5° at 26.5 GHz for a loaded‐line type has been measured. There is good agreement between simulated and measured results. A companion article (Part II) describes the application of these variable capacitors to the design of reflection‐type phase shifters. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 321–337, 2003.     

A new design of multi-bit RF MEMS distributed phase shifters for phase error reduction

In this paper, the major source of phase error for multi-bit MEMS distributed phase shifters, the mismatch between adjacent bits, is investigated. A quantitative account of the phase deviation with the effect of mismatch considered is presented by the simulated results as well as theoretically calculated results. A novel multi-bit distributed MEMS phase shifter aimed to eliminate this error source is proposed. The basic concept for the structure is that, by controlling the phase shifter from the unit cell level, performance deterioration resulted from multiple reflection of the signal in the device in the phase state switching process is avoided. To verify the feasibility of the proposed structure, two X-band 5-bit distributed phase shifters are designed and simulated. Compared with the traditional structure, the average phase errors in all phase states of the two are improved by 28.22 and 36.52 % at 10 GHz. The average RMS phase errors in the bandwidth of 1–12-GHz of 56 frequency points are 1.23° and 1.85°. The improvements of the return loss and insertion loss are also exhibited. Furthermore, the aperiodic distributed phase shifter using different unit cells is introduced to demonstrate that the proposed structure can also be used to decrease the number of MEMS switches of multi-bit MEMS distributed phase shifters.     

A distributed MEMS phase shifter on a low-resistivity silicon substrate

Distributed MEMS phase shifters using CMOS-grade low-resistivity silicon have been successfully developed. Kapton films were utilized as dielectric layers to reduce RF signal attenuation in the lossy silicon substrate. The scattering parameters were evaluated from DC to 26 GHz. The phase shifting reaches 43° and insertion losses are less than 1.4 dB. The manufacturing process is simple and compatible with CMOS and post CMOS processes.     

RF MEMS压控振荡器的研制及相位噪声特性研究

利用RF MEMS可变电容作为频率调节元件,制备了中心频率为2 GHz的MEMS VCO器件.RF MEMS可变电容采用凹型结构,其控制极板与电容极板分离,并采用表面微机械工艺制造,在2 GHz时的Q值最高约为38.462.MEMS VCO的测试结果表明,偏离2.007 GHz的载波频率100kHz处的单边带相位噪声为-107 dBc/Hz,此相位噪声性能优于他们与90年代末国外同频率器件.并与采用GaAs超突变结变容二极管的VCO器件进行了比较,说明由于集成了RF MEMS可变电容,使得在RF MEMS可变电容的机械谐振频率近端时,MEMS VCO的相位噪声特性发生了改变.     

RF MEMS packaged switch evaluation tests up to 25 GHz

This article presents the results of the series of experimental tests of a packaged RF MEMS switch manufactured as a chip on a silicon substrate in the Center for Materials and Microsystems of Fondazione Bruno Kessler. Experiments have been performed up to 25 GHz and included S-parameters check in different operation and environmental conditions, including variation of input power, ambient temperature and number of switching cycles. Presented RF MEMS SPST switch is a basic element of more complex reconfigurable networks such as SPxT switches, phase shifters, power attenuators etc.

     

A low cost approach for the fabrication of microwave phase shifter on laminates

This paper presents a simple and low cost fabrication approach using extended printed circuit board processing techniques for an electrostatically actuated phase shifter on a common microwave laminate. This approach uses 15???m thin copper foils for realizing the bridge structures as well as for a spacer. A polymeric thin film deposited by spin coating and patterned using lithographic process is used as a dielectric layer to improve the reliability of the device. The prototype of the phase shifter for X-band operation is fabricated and tested for electrical and electromechanical performance parameters. The realized devices have a figure of merit of 70°/dB for a maximum applied bias potential of 85?V. Since these phase shifters can be conveniently fabricated directly on microwave substrates used for feed distribution networks of phased arrays, the overall addition in cost, dimensions and processing for including these phase shifters in these arrays is minimal.     

MEMS variable‐capacitor phase shifters part II: Reflection‐type phase shifters

A novel design procedure for reflection‐type phase shifters using capacitive devices is developed. Using this approach, a phase shifter for operation at 26.5 GHz is developed using MEMS variable capacitors reported in Part I of this article. A design optimization procedure is discussed. Design of a CPW hybrid at 26.5 GHz (as needed for this phase shifter) is also discussed. Experimental results validate the design procedure and yield a phase shift of 179.30° at 26.5 GHz. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 415–425, 2003.     

A low cost approach for the fabrication of microwave phase shifter on laminates

This paper presents a simple and low cost fabrication approach using extended printed circuit board processing techniques for an electrostatically actuated phase shifter on a common microwave laminate. This approach uses 15 μm thin copper foils for realizing the bridge structures as well as for a spacer. A polymeric thin film deposited by spin coating and patterned using lithographic process is used as a dielectric layer to improve the reliability of the device. The prototype of the phase shifter for X-band operation is fabricated and tested for electrical and electromechanical performance parameters. The realized devices have a figure of merit of 70°/dB for a maximum applied bias potential of 85 V. Since these phase shifters can be conveniently fabricated directly on microwave substrates used for feed distribution networks of phased arrays, the overall addition in cost, dimensions and processing for including these phase shifters in these arrays is minimal.

     

Design and process considerations for fabricating RF MEMS switches on printed circuit boards

Design considerations and process development for fabricating radio frequency microelectromechanical systems (RF MEMS) switches on microwave laminate printed circuit boards (PCBs) are presented in details in this work. Two key processes, high-density inductively coupled plasma chemical vapor deposition (HDICP CVD) for low-temperature silicon nitride deposition, and compressive molding planarization (COMP) have been developed for fabricating RF MEMS switches on PCB. The effects of process conditions of HDICP CVD on low-temperature nitride film are fully characterized for its use in RF MEMS switches on PCB. Not only can COMP planarize the surface of the photoresist for lithographic patterning over topologically complex surfaces, but also simultaneously create a membrane relief pattern on the surface of a MEMS structure. Several membrane-type capacitive switches have been fabricated showing excellent RF performance and dynamic responses similar to those on semiconductor substrates. This technology promises the potential of enabling further monolithic integration of switches with other RF components, such as antennas, microwave monolithic integrated circuits (MMICs), phase shifters, tunable filters, and transmission lines on the same PCBs reducing the losses due to impedance mismatching from components/system assembly and simplifies the design of the whole RF system. [1416].     

Low-actuation voltage RF MEMS shunt switch with cold switching lifetime of seven billion cycles

This paper investigates the performance and lifetime of a metal-to-metal shunt RF MEMS switch fabricated on an SI-GaAs substrate. The switch is a shunt bridge design that is compatible with standard microelectronic processing techniques. The RF performance of the switch includes actuation voltages of less than 15 V, isolation better than 20 dB from 0.25 to 40 GHz, and switching speeds of less than 22 /spl mu/s. Varying the geometry of the switch affects both switching voltage and reliability, and the tradeoffs are discussed. We have developed a cold switching test method to identify the root cause of sticking as a failure mechanism. The switch structure includes "separation posts" that eliminate sticking failure and has demonstrated lifetimes as high as 7/spl times/10/sup 9/ cold switching cycles. These results show that good reliability is possible with a metal-to-metal RF MEMS switch operated with a low actuation voltage.     

一种新型的分布式MEMS移相器的小型化设计

通过在共面波导信号线上贴敷低介电常数的薄层绝缘介质,使得MEMS金属桥与共面波导信号线在“关“态下形成MIM电容的方法,实现了提高“关““开“两种状态下的电容比,从而提高了单位长度上的相移量.与传统的设计方法相比,在达到同样相移量指标的情况下仅需少量的MEMS金属桥就可以实现,工作的可靠性得到提高,未封装MEMS移相器器件的总体尺寸可以减小60%左右,此外由于在“关“态下,金属桥直接贴敷在介质表面上而不会随着外界环境震动,因此移相器的相移精度显著的提高.     

A novel design of RF MEMS dual band phase shifter

In this paper a novel design of RF MEMS dual band phase shifter is presented. The new design is switched-line type phase shifter which has been constructed by distributed MEMS transmission line (DMTL). Since the constant phase of DMTL can be changed, the proposed design has capability for working at two or more frequencies. The performances of the new design are compared with conventional switched-line design that has been constructed by transmission line of coplanar waveguide. The results show the feasibility of the new design and also show the new design reduces the size and loss of the structure compared with conventional switched-line design. The proposed design is unique approach to achieve a dual band phase shifter using MEMS technology which has low loss and weight with high linearity respect to the other technologies. This dual band phase shifter has very small size than the other passive dual band phase shifters.     

基于分布式射频MEMS移相器电容开关的分析与设计

通过分析MEMS电容开关的工作原理,设计出一种适合分布式射频MEMS移相器电路的新型电容开关.采用Intel lisuiteTM软件优化电容开关的驱动电压、响应时间、释放时间和机械振动模式.结果表明,开关驱动电压为2.5 V、响应时间小于30μs,释放时间大于60 μs和所有振动模式固有频率都大于15 KHz.与普通开关结构比较,该新型电容开关结构具有优越射频机电性能和响应时间,同时也对电容开关的制备工艺进行分析.     

The SiOG-based single-crystalline silicon (SCS) RF MEMS switch with uniform characteristics

This paper details single-crystalline silicon (SCS) direct contact radio frequency microelectromechanical systems (RF MEMS) switch designed and fabricated using an SiOG (silicon-on-glass) substrate, so as to obtain higher fabrication and performance uniformity compared with a conventional metal switch. The mechanical and electrical performances of the fabricated silicon switch have been tested. In comparison with a conventional metallic MEMS switch, we can obtain higher productivity and uniformity by using SCS, because it has very low stresses and superior thermal characteristics as a structural material of the switch. Also, by using the SiOG substrate instead of an SOI substrate, fabrication cost can be significantly reduced. The proposed switch is fabricated on a coplanar waveguide (CPW) and actuated by electrostatic force. The designed chip size is 1.05 mm/spl times/0.72 mm. Measured pull-in voltage and actuation voltage were 19 V and 26 V, respectively. Eighteen identical switches taken randomly throughout the wafer showed average and standard deviation of the measured pull-in voltage of 19.1 and 1.5 V, respectively. The RF characteristics of the fabricated switch from dc to 30 GHz have been measured. The isolation and insertion loss measured on the four identical samples were -38 to -39 dB and -0.18 to -0.2 dB at 2 GHz, respectively. Forming damping holes on the upper electrode leads to a relatively fast switching speed. Measured ON and OFF time were 25 and 13 /spl mu/s, respectively. In the switch OFF state, self-actuation does not happen up to the input power of 34 dBm. The measured holding power of the fabricated switch was 31 dBm. Stiction problem was not observed after 10/sup 8/ cycles of repeated actuation, but the contact resistance varied about 0.5-1 /spl Omega/ from the initial value.     

Differential phase shifters based on Schiffman type‐C and type‐F networks with wide phase shift range

This study proposes a class of differential phase shifters based on the Schiffman type‐C and type‐F networks with wide phase shift range. After the phase and bandwidth properties of these two distinct networks are numerically analyzed, two unique advantages of wide phase shift range and wide phase shift bandwidth are revealed. Next, the optimal design parameters for different phase shift values up to 405° are presented to allow for a quick design process. To verify the proposed approach, a 180° differential phase shifter is designed, fabricated and measured. Good performance is achieved with an impedance ratio of 1.959 and 3.7° phase deviation over a phase shift bandwidth of 61%.     

MEMS tunable capacitors with fragmented electrodes and rotational electro-thermal drive

This paper reports on the design, simulation and fabrication of tunable MEMS capacitors with fragmented metal (AlSi 4%) electrodes. We examine a rotational electro-thermal actuation. An analytic model of the rotational effect thermal actuator was established in order to show the periodicity of the capacitance when the angle increases. Evaluation of the impact of fringing fields on the capacitance has been carried out using finite element analysis (FEA). The MEMS capacitors were fabricated using metal surface micromachining with polyimide sacrificial layer. The maximum rotation, corresponding to a maximum angle of 7°, was obtained near 1.2 V and 299 mA. The proposed capacitor has a practical tuning range of 30%. FEA has shown that this figure can be improved with design optimization. The MEMS architecture based on rotational effect and fragmented electrodes does not suffer from the pull in effect and offers a practical solution for future above-IC capacitors.     

串联电容式RF MEMS开关设计与制造研究

介绍了一种串联电容式RF MEMS开关的设计与制造。所设计的串联电容式RF MEMS开关利用薄膜淀积中产生的内应力使MEMS桥膜向上发生翘曲,从而提高所设计的开关的隔离度,克服了串联电容式RF MEMS开关通常只有在1GHz以下才能获得较高隔离度的缺点。其工艺与并联电容式RF MEMS开关完全相同,解决了并联电容式RF MEMS开关不能应用于低频段(<10GHz)的问题。其插入损耗为-0.88dB@3GHz,在6GHz以上,插入损耗为-0.5dB;隔离度为-33.5dB@900MHz、-24dB@3GH和-20dB@5GHz,适合于3~5GHz频段的应用。