An Application of 3-D MEMS Packaging: Out-of-Plane Quadrupole Mass Filters

Massachusetts Inst. of Technol., Cambridge, MA
Journal of Microelectromechanical Systems (Impact Factor: 1.75). 01/2009; 17(6):1430 - 1438. DOI: 10.1109/JMEMS.2008.2006769
Source: IEEE Xplore


This paper reports the design, fabrication, and characterization of low-cost out-of-plane quadrupole mass filters that use commercially available dowel pins as electrode rods. The quadrupoles implement a 3-D MEMS packaging technology that relies on deep-reactive ion etching (DRIE)-patterned deflection springs for alignment. Quadrupoles with rod diameter ranging from 0.25 to 1.58 mm and aspect ratio of 30 to 60 were built and tested at RF frequencies of 1.44, 2.0, and 4 MHz. Assembled devices operated in the first stability region achieved a maximum mass range of 650 amu, while a minimum half-peak width of 0.4 amu at mass 28 was obtained in the second stability region. Operation in the second stability region provides a means to higher resolution, smoother peaks, and removed peak splitting at the expense of transmission. The ultimate resolution of the reported quadrupoles is also discussed.

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Available from: L. F. Velásquez-García, Oct 08, 2015
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    • "The rods were supported in a silicon frame, fabricated by deep reactive ion etching (DRIE) of bonded silicon-on-insulator (BSOI) material . Using a similar approach but with an out-of-plane geometry , a mass range of m/z = 614 and an estimated resolution of m/Δm ≈ 13 at 10% peak height was demonstrated at the Massachusetts Institute of Technology [86]. Recently, a new silicon-on-glass design from Microsaic Systems incorporating a prefilter achieved a mass range of m/z = 1200 and a resolution of m/Δm ≈ 150 at 10% peak height [87]. "
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    ABSTRACT: An electrospray-ionization mass spectrometer (ESI-MS) whose main components are all fabricated using silicon microelectromechanical systems (MEMS) techniques is demonstrated for the first time. The ion source consists of a microengineered alignment bench containing a V-groove mounting for a nanospray capillary, an ion-extraction electrode, and a pneumatic nebulizer. The vacuum interface consists of two plates, each carrying a 50-μm-diameter capillary, that are selectively etched and bonded together to provide a differentially pumped internal cavity. The quadrupole filter consists of a microfabricated frame that provides mountings for stainless-steel rods measuring 650 μm in diameter and 30 mm in length. Two different quadrupoles are compared: a first-generation bonded silicon device and a second-generation silicon-on-glass device with a Brubaker prefilter. Differential pumping of a MEMS component is demonstrated for the first time, atmospheric pressure ionization and ion transfer into vacuum are characterized, ESI-MS operation is demonstrated, and spectra are presented for a variety of compounds.
    Journal of Microelectromechanical Systems 01/2011; 19(6-19):1430 - 1443. DOI:10.1109/JMEMS.2010.2082501 · 1.75 Impact Factor
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    • "The dynamic range of the resolution with respect to N rf provides an indicator of the quality of the instrument and the resultant electric field [1]. For operation in zone 3, the value of K is much smaller with a typical maximum value of 1.43 [29], [30], resulting in a much greater resolution for a given N rf when compared with zone-1 operation. This increased resolution is due to the increased sharpness of the zone-3 stability region [31]. "
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    ABSTRACT: Size reduction in quadrupole mass spectrometers (QMSs) is an ongoing requirement driven by the needs of space exploration, portable, and covert monitoring applications. Microelectromechanical systems (MEMS) technology provides a method of achieving this size reduction. A quadrupole mass filter (QMF) is one component of a QMS and is suitable for microfabrication. MEMS manufacturing techniques are more suitable to the production of rectilinear electrodes, instead of the more widely used circular electrodes. Present understanding of the performance characteristics of rectilinear electrodes and the dependence of these characteristics on electrode geometry are not well documented. In this paper, we report on the performance characteristics of a square-electrode QMF. Both the predicted performances obtained by computer simulation and experimental data are presented for operation in stability zone 1 (0.236, 0.706) and zone 3 (3.16, 3.23). A comparison between these results and the simulated data for equivalent devices constructed using hyperbolic and circular electrodes for operation in zone 1 is also made. This comparison demonstrates that, although the field produced by square electrodes is far from the “ideal,” it is still possible to achieve useful filtering action. Our results also show that, for operation in zone 3, performance comparable with that of hyperbolic and circular electrodes operating in zone 1 is achievable.
    IEEE Transactions on Instrumentation and Measurement 10/2010; 59(9-59):2458 - 2467. DOI:10.1109/TIM.2009.2036346 · 1.79 Impact Factor
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    • "Prior work showed that we could reduce the effects of these nonideal terms by operating in the Fig. 4. Simulation of an Einzel lens with three sets of the unconventional lens elements in series. second stability region [53], [57]–[61], thus providing a means to address the expected performance loss associated with the square electrode geometry. "
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    ABSTRACT: We report the design, fabrication, and characterization of a new class of chip-scale quadrupole mass filter (QMF). The devices are completely batch fabricated using a wafer-scale process that integrates the quadrupole electrodes, ion optics, and housing into a single monolithic block. This process eliminates the electrode-to-housing misalignments inherent in other QMFs and enables the implementation of complex device architectures. To achieve the reported integration, 1 mm ?? 1 mm square electrodes of heavily doped silicon were utilized, resulting in quadrupoles with an effective aperture radius of 0.707 mm and a length of 30 mm. Mass filtering was demonstrated with this unconventional device showing a mass range of 650 amu and a resolution of ~30 at a drive frequency of 1.8 MHz. When operated in the second stability region at 2.0 MHz and a mass range of 50 amu, a peak width of 0.3 amu was achieved at mass 28, showing a resolution of ~90. This paper introduces operation in the second stability region as a reliable method for turning QMFs with less than ideal electrode geometries into high-performance devices.
    Journal of Microelectromechanical Systems 07/2010; 19(3-19):469 - 483. DOI:10.1109/JMEMS.2010.2046396 · 1.75 Impact Factor
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