In-process gap reduction of capacitive transducers

The development of a new sensor generation with a significant performance gain is mainly aimed at increasing the sensitivity. In addition to that, a variety of properties such as integrability, power consumption, robustness, reliability, cross-talk sensitivity, and others, can be equally important. Some properties scale directly with sensitivity, whereas others show trade-off characteristics. An overview of different approaches for new sensor generations with enhanced performance is presented and discussed in this article. The main focus is on new microelectromechanical systems (MEMS) elements, fabricated within a standard high-aspect-ratio micromachining process and capacitive working principle. Herein, a novel MEMS-based bandpass, a gap reduction technique, fluted electrodes for reduced damping, and a novel direct current/direct current (DC/DC) converter, is proposed. Acoustic emission sensing is chosen as example application to underline the challenging requirements for the design. Furthermore, the recent improvements in technology are presented. Based on bonding and deep reactive ion etching (BDRIE), it allows larger aspect ratios as well as through-silicon vias and low-pressure encapsulation. Consistent further miniaturization leads to the use of nanoscopic elements within MEMS as sensing component instead of the conventional electrostatic working principle. Unique properties of graphene rolls or carbon nanotubes (CNTs) enable promising sensitivity improvements if they are integrated at wafer-level. Therefore, a design concept and formal verification-tool is presented.

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“…Different approaches are distinguished between the in‐process and post‐process gap reduction (GR) techniques.…”

Section: Gap Reductionmentioning

confidence: 99%

Design, Modeling, Fabrication, and Verification of New Multifunctional MEMS/NEMS Components

Freitag

Sauppe

Auerswald

et al. 2019

Physica Status Solidi (a)

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“…The fabrication of sub-micron trenches [5][6][7][8][9][10] or structures with very high aspect ratios up to 100 [6] is advantageous for many applications. To increase the aspect ratio of the sensing electrode gap, different technologies for reduction of trench width of capacitive micro structures below the technological limitations have been proposed and demonstrated in recent years [11][12][13][14][15].…”

Section: Fabrication Technique Figure 1 Schematic Process Flows Of Tmentioning

confidence: 99%

“…Using ratchet structures or bistable mechanisms for locking the reduced gap are critical for the reliability of the transducers. An inprocess gap reduction approach [14] utilizes residual stress in microstructures, coated with silicon dioxide. However, the technique causes a high temperature sensitivity of the microstructures.…”

Section: Fabrication Technique Figure 1 Schematic Process Flows Of Tmentioning

confidence: 99%

Design, Manufacturing and Test of a High-Precision MEMS Inclination Sensor for Navigation Systems in Robot-Assisted Surgery

Arnold¹

2018

IJBSE

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Robot supported minimally invasive interventions are state of the art in operating theatres. To increase the accuracy of surgical instrument positioning, high-precision motion tracking systems are required. The miniaturization of microelectromechanical systems (MEMS) facilitates the placing of orientation detection sensors close to the mounting of the surgical instrument to enhance positioning accuracy. A high resolution inclination sensor was developed using the innovative approach of laser-micro-welding. Trench sizes down to 800 nm are fabricated with more than 6-fold increase in aspect ratios (structure depth to electrode gap) compared to sensors without gap reduction. Electrical and physical tests as well as finiteelement-simulations were performed. An increased sensitivity from 7.2 fF/° up to 60 fF/° was verified for the sensor with reduced electrode gap and a customized ASIC.

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“…However, fabrication restrictions limit the minimum size of the spacing between the electrodes. Therefore, the reduction of the trench width after patterning of the microstructures has been proposed and demonstrated by different groups in recent years [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

“…Using ratchet structures or bistable mechanisms for locking the reduced gaps could be critical for the reliability of the device. An in-process gap reduction approach, which has been developed recently in our group [4], utilizes residual stress in microstructures, coated with silicon dioxide. However, the technique causes a high temperature sensitivity of the microstructures.…”

Section: Introductionmentioning

confidence: 99%

Novel post-process gap reduction technology of high aspect ratio microstructures ultilizing micro welding

Nowack

Leidich

Reuter

et al. 2011

2011 16th International Solid-State Sensors, Actuators and Microsystems Conference

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This paper presents a novel post-process gap reduction technology of high aspect ratio microstructures. The gap reduction procedure uses the well known electrostatic deflection of a movable microstructure. In contrast to other solutions, micro welding is utilized to create the final, permanent locking. The fabrication technology, the functional principle of the gap reduction mechanism and the experimental set-up is presented. As a result the initial gap width between vertical comb electrodes was decreased from 4500 nm to 385 nm, leading to a final aspect ratio of 150.

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In-process gap reduction of capacitive transducers

Cited by 5 publications

References 7 publications

Design, Modeling, Fabrication, and Verification of New Multifunctional MEMS/NEMS Components

Design, Modeling, Fabrication, and Verification of New Multifunctional MEMS/NEMS Components

Design, Manufacturing and Test of a High-Precision MEMS Inclination Sensor for Navigation Systems in Robot-Assisted Surgery

Novel post-process gap reduction technology of high aspect ratio microstructures ultilizing micro welding

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