MEMS Reliability Research Articles

MEMS Reliability: On-Chip Testing for the Characterization of the Out-of-Plane Polysilicon Strength

Polycrystalline silicon is a brittle material, and its strength results are stochastically linked to microscale (or even nanoscale) defects, possibly dependent on the grain size and morphology. In this paper, we focus on the out-of-plane tensile strength of columnar polysilicon. The investigation has been carried out through a combination of a newly proposed setup for on-chip testing and finite element analyses to properly interpret the collected data. The experiments have aimed to provide a static loading to a stopper, exploiting electrostatic actuation to move a massive shuttle against it, up to failure. The failure mechanism observed in the tested devices has been captured by the numerical simulations. The data have been then interpreted by the Weibull theory for three different stopper sizes, leading to an estimation of the reference out-of-plane strength of polysilicon on the order of 2.8-3.0 GPa, in line with other results available in the literature.

The preparation of CNT/PMMA composite film on SiO2 substrates

Abstract Microelectromechanical system (MEMS) has been highly valued since the size of the MEMS structure is miniaturized, the spacing between the components is in the nanometer range, and the behaviors of friction and adhesion greatly affect the reliability of MEMS. An atomic force microscope (AFM) was used to observe the surface morphology of carbon nanotube (CNT)/polymethyl methacrylate (PMMA) film, and X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical state of typical elements on the surface of the film. The friction and wear properties of composite nano-films under macroscopic conditions were systematically studied. The research results show that the composite nano-film has excellent anti-friction and anti-wear properties.

Reliability of MEMS in Shock Environments: 2000-2020.

The reliability of MEMS in shock environments is a complex area which involves structural dynamics, fracture mechanics, and system reliability theory etc. With growth in the use of MEMS in automotive, IoT, aerospace and other harsh environments, there is a need for an in-depth understanding of the reliability of MEMS in shock environments. Despite the contributions of many articles that have overviewed the reliability of MEMS panoramically, a review paper that specifically focuses on the reliability research of MEMS in shock environments is, to date, absent. This paper reviews studies which examine the reliability of MEMS in shock environments from 2000 to 2020 in six sub-areas, which are: (i) response model of microstructure, (ii) shock experimental progresses, (iii) shock resistant microstructures, (iv) reliability quantification models of microstructure, (v) electronics-system-level reliability, and (vi) the coupling phenomenon of shock with other factors. This paper fills the gap around overviews of MEMS reliability in shock environments. Through the framework of these six sub-areas, we propose some directions potentially worthy of attention for future research.

Fatigue studies of CoCrFeMnNi high entropy alloy films using nanoindentation dynamic mechanical analyses

Films in the microelectromechanical systems are frequently subjected to the fatigue damage under cyclic loading, and the fatigue properties of the films greatly influence the reliability and life of MEMS. However, because of the small dimension of films, characterization of their fatigue properties is a daunting challenge. Nanoindentation dynamic mechanical analysis (DMA) provides a possible solution. However, the setting of loading cycles is crucial to the fatigue test. Using CoCrFeMnNi high entropy alloy films, we investigated the fatigue properties extracted using two different types of loading: fixed load ratio with different mean loads and fixed mean load with different load ratios. Our results showed that both types of fatigue loading were reliable for the evaluation of the fatigue properties of films and it was demonstrated by the fatigue strength coefficients and exponents extracted from the test results. For comparison, DMA was also performed on CoCrFeMnNi high entropy alloys. Compared to the bulk counterpart, the film had much higher fatigue lifetime because of the thickness confinement, the presence of high-density nanotwins and the much smaller grain size in the film.

Reliability of RF MEMS switches at cryogenic (liquid He) temperatures

This paper reports on the reliability of RF MEMS switches operating in a cryogenic (<6 K) environment while monitoring the repeatability of their contact resistance (Rc) over time. Series DC-contact switches were actuated with a bipolar waveform then checked for stiction every 100 thousand contacts, and after every million cycles Rc was measured 100 times. Device lifetimes were limited to under 10 million contacts. The dominant failure mechanism is believed to be charging of the substrate underneath the electrostatic MEMS switch leading to permanent hold down of the device.

An investigation into the high strength bonding technology of wafer-to-wafer with large-scale au line

As well known, the sandwich-like construction is the classic unit construction of MEMS microthrusters, and these three layers should be bonded between the igniting circuit layer and the microchamber-array-layer, the microchamber-array-layer and the micronozzle-array-layer. It’s bonded by BCB between the igniting circuit layer and the microchamber-array-layer, and their bonding strength is the key factor to determine the reliability of MEMS microthruster-array-chips. And the failure is mostly discovered on the bonding surface of the igniting circuit layer and the microchamber-array-layer in ignition experiments. For solving the bonding failure, the failure reason will be analysed and the improved bonding technique is designed. Here, the bonding strength is externalized, and the average shear strength increase to 11.63MPa from 2.80Mpa, this is over 4times than before. The igniting experiments prove the Si3N4 layer can enhance the BCB bonding strength and this new bonding method does solve the bonding problem of MEMS microthruster-array-chips.

Probabilistic Physics of Failure (PPOF) Reliability Analysis of RF-MEMS Switches under Uncertainty

MEMS reliability analysis is a challenging area of research which comprises various physics of failure and diverse failure mechanisms. Reliability issues are critical in both design and fabrication phases of MEMS devices as their commercialization is still delayed by these problems. In this research, a hybrid methodology is developed for the reliability evaluation of MEMS devices. Its first step is the identification of dominant failure modes by FMEA, evaluation of failure mechanisms and an updated lifetime estimation by the Bayesian method. The reliability of MEMS devices is studied using probabilistic physics of failure (PPoF) by determining the dominant failure mechanism. Accordingly, a deterministic model is selected for the analysis of the life and reliability of the dominant failure mechanisms. To convert the deterministic model to a probabilistic model, the uncertainty sources affecting the dielectric lifetime are determined. This model is simulated by the utilization of the Monte Carlo method. In the final stage, the results of life estimation are updated using the Bayesian method. Considering wide application and advantages of RF MEMS capacitive switches, it has been selected as a case study. A framework is developed for reliability evaluation of these switches failures due to stiction mechanism. The results contain FMEA table, lifetime estimation in different voltages, number of duty cycles and at the end, updated results of life estimation using the Bayesian method.

Fabrication and Characterization of Capacitive RF MEMS Perforated Switch

In this paper, we have designed, simulated, fabricated, and characterized a clamped-clamped micro mechanical structure-based shunt capacitive RF MEMS switch. The clamped–clamped micromechanical structure is micromachined using a gold metal thickness of 500 nm. AlN is used as a dielectric material, and it is deposited using the dc sputtering PVD process. In the MEMS technology, particularly in devices fabrication, releasing the membrane is a difficult task, and here, we have presented a novel wet process to release the membrane. Primarily, the S1813 sacrificial layer is etched by using the piranha solution and cleaned with the IPA solution. Critical point drying is done after fabrication to reduce the stiction effect on the switch. Overall, the switch requires the pull-in voltage of 5.5 V for 1.8- $\mu \text{m}$ displacement. In the process of optimization, primarily, the switch is designed and simulated using finite-element method tools. The reliability of the capacitive RF MEMS switches depends on the stiction problem caused by dielectric charging, and the proposed capacitive switch dielectric charging behavior is characterized using the CV curve method.

Special issue on Design, Test, Integration and Packaging of MEMS and MOEMS (DTIP 2015), held in Montpellier, France, April 27–30, 2015

The 2015 edition of the Symposium on Design, Test, Integration and Packaging of MEMS and MOEMS (DTIP) was held in Montpellier, France, 27–30 April 2015. Established in 1999 by our colleague Dr Bernard Courtois, DTIP is definitively the premier MEMS scientific event in Europe. DTIP’2015 was the 17th edition and has been extremely appreciated by an hundred of attendees for the quality of both scientific and social programs. Oral and poster presentations were carefully selected by the Program Committee to insure a high scientific level and awesome plenary speakers have been invited. This Symposium brought together participants interested in manufacturing of microstructures and participants interested in design tools to facilitate the design of these microstructures. This special issue is composed of 20 extended versions of the best papers presented at the Symposium. Extended papers have been refereed, along the usual refereeing process in force at Microsystem Technologies. Selected papers cover a broad range of topics including compact thermal modelling, thermal testing, electrostatic and thermal actuation, simulation, accelerometers, electronic front-end for sensors, magnetic nanoparticles and materials, RF MEMS, Quantum dots, piezoelectric films, Micro-transducers, magnetometers, microfluidic devices, resonant sensors, micro-fabrication, wafer bonding, Packaging, flexible interconnects and MEMS reliability. We hope that you will enjoy these contributions as much as we did and if you want to join the DTIP community do not hesitate to attend our next event or to visit our website.

A novel correlative model of failure mechanisms for evaluating MEMS devices reliability

The failure behavior of MEMS can be regarded as the result of certain dependent failure mechanisms in accordance with device's internal attributes and external environment. However, the correlative effects among multiple mechanisms governing the failure process of MEMS have not been well characterized. This paper reviews significant failure mechanisms of MEMS products and proposes a new correlative model for MEMS reliability evaluation. Based on the nature of different failure mechanisms, dependent factors of these correlations are discussed and mathematical models are derived. With a case, reliability of a sort of RF switch is evaluated taking into account the failure mechanism correlative effects, and sensitivity analysis is conducted to assess the effects of the model parameters on reliability function R(t) and failure probability density function f(t).

Compact Lens-less Digital Holographic Microscope for MEMS Inspection and Characterization.

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and automotive. However, effective inspection and characterization metrology systems are needed to ensure the functional reliability of MEMS. This study presents a system based on digital holography as a tool for MEMS metrology. Digital holography has gained increasing attention in the past 20 years. With the fast development and decreasing cost of sensor arrays, resolution of such systems has increased broadening potential applications. Thus, it has attracted attention from both research and industry sides as a potential reliable tool for industrial metrology. Indeed, by recording the interference pattern between an object beam (which contains sample height information) and a reference beam on a CCD camera, one can retrieve the quantitative phase information of an object. However, most of digital holographic systems are bulky and thus not easy to implement on industry production lines. The novelty of the system presented is that it is lens-less and thus very compact. In this study, it is shown that the Compact Digital Holographic Microscope (CDHM) can be used to evaluate several characteristics typically consider as criteria in MEMS inspections. The surface profiles of MEMS in both static and dynamic conditions are presented. Comparison with AFM is investigated to validate the accuracy of the CDHM.

Compact Lens-less Digital Holographic Microscope for MEMS Inspection and Characterization

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and automotive. However, effective inspection and characterization metrology systems are needed to ensure the functional reliability of MEMS. This study presents a system based on digital holography as a tool for MEMS metrology. Digital holography has gained increasing attention in the past 20 years. With the fast development and decreasing cost of sensor arrays, resolution of such systems has increased broadening potential applications. Thus, it has attracted attention from both research and industry sides as a potential reliable tool for industrial metrology. Indeed, by recording the interference pattern between an object beam (which contains sample height information) and a reference beam on a CCD camera, one can retrieve the quantitative phase information of an object. However, most of digital holographic systems are bulky and thus not easy to implement on industry production lines. The novelty of the system presented is that it is lens-less and thus very compact. In this study, it is shown that the Compact Digital Holographic Microscope (CDHM) can be used to evaluate several characteristics typically consider as criteria in MEMS inspections. The surface profiles of MEMS in both static and dynamic conditions are presented. Comparison with AFM is investigated to validate the accuracy of the CDHM.

Multi-function optical characterization and inspection of MEMS components using stroboscopic coherence scanning interferometry

Abstract A Micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and automotive industries. However, effective inspection systems are also needed to ensure the functional reliability of MEMS. This study developed a stroboscopic coherence scanning Interferometry (SCSI) technique for measuring key characteristics typically used as criteria in MEMS inspections. Surface profiles of MEMS both static and dynamic conditions were measured by means of coherence scanning Interferometry (CSI). Resonant frequencies of vibrating MEMS were measured by deformation of interferogram fringes for out-of-plane vibration and by image correlation for in-plane vibration. The measurement bandwidth of the developed system can be tuned up to three megahertz or higher for both in-plane and out-of-plane measurement of MEMS.

Research Reviews and Prospects of MEMS Reliability

Reliability of MEMS is essential to its successful application. This paper focused on the failure mode of MEMS, the reliability test and modeling of MEMS and the reliability test method of typical devices. Designing of MEMS reliability is discussed based on the review of MEMS reliability test and the failure model of MEMS reliability. In this paper, firstly, recent development in MEMS reliability field is elaborated. Secondly, research of MEMS reliability aimed at different typical MEMS mechanism and devices is summarized in three major areas: several common kinds of the failure mode of MEMS, MEMS reliability model and MEMS reliability test of typical MEMS mechanism and devices. Finally, the main direction of MEMS research and the research trend in the future is discussed.

Study on Reliability of Slanted Micro-Cantilever under Shock Stress

The reliability of MEMS has been a key issue for its application. Micro-cantilever is a basic structure of MEMS, which has a notable influence on its reliability. Basing on quasi-static theory, the response characteristic of the slanted Micro-cantilever under shock load is studied. Assume that the slanted micro-cantilever is a cantilever-mass system, whose maximal displacement and stress has been analyzed. Furthermore, the correction of theoretical analysis is validated by ANSYS simulation. Finally, experiments are carried out to validate the cantilever’s characteristic of shock response. The results can be used to guide the failure modes analysis of MEMS, and provide rules for MEMS reliability design.

MEMS packaging and reliability: An undividable couple

This paper reviews various approaches to package MEMS, illustrated mainly with examples from imec. Wafer-level or 0-level packaging is mostly dealt with. The role the package plays in achieving the required performance and reliability characteristics is elucidated. Package requirements, such as hermeticity and strength, are named, discussed and illustrated with examples. Considerations of reliability testing are presented. It is made conceivable that vacuum maintenance of tiny MEMS packages is a dominant reliability issue, something not at all obvious to achieve.

Special Section Guest Editorial: Reliability, Packaging, Testing, and Characterization of MOEMS and MEMS III

The <i>Journal of Micro/Nanopatterning, Materials, and Metrology</i> (JM3) publishes peer-reviewed papers on the core enabling technologies that address the patterning needs of the electronics industry.

Capacitive RF MEMS switch dielectric charging and reliability: a critical review with recommendations

This paper presents a comprehensive review of the reliability issues hampering capacitive RF MEMS switches in their development toward commercialization. Dielectric charging and its effects on device behavior are extensively addressed, as well as the application of different dielectric materials, improvements in the mechanical design and the use of advanced actuation waveforms. It is concluded that viable capacitive RF MEMS switches with a great chance of market acceptance preferably have no actuation voltage across a dielectric at all, contrary to the ‘standard’ geometry. This is substantiated by the reliability data of a number of dielectric-less MEMS switch designs. However, a dielectric can be used for the signal itself, resulting in a higher Con/Coff ratio than that one would be able to achieve in a switch without any dielectric. The other reliability issues of these devices are also covered, such as creep, RF-power-related failures and packaging reliability. This paper concludes with a recipe for a conceptual ‘ideal’ switch from a reliability point of view, based on the lessons learned.

Study on Designs of Stoppers for MEMS Devices in Shock Environment

Stoppers are commonly used to improve the shock resistance of MEMS devices. However, the collision between MEMS structure and stoppers in shock environment may lead to emergence of the stress wave, resulting in the failure of devices. Therefore, MEMS devices designed based on current statics theory is unreliable. After analyzing the method and principle for MEMS reliability design, the shock dynamics model was established. Based on the model, the response of the traditional design and designs with different stoppers to shock was researched. At last, protection performances of different stoppers were evaluated. Results showed that the use of stoppers could improve the shock resistance of the device obviously, but hard stoppers would cause to the emergence of the sharp stress wave. Elastic stoppers had excellent protection ability which could strengthen the shock resistance of the device greatly.

Stiction Failure Mechanisms of the Micromachined Electrostatic Comb-Drive Structures

Stiction is one of the most important and almost unavoidable problems in MEMS, which usually occurs when the restoring forces of the microstructures are unable to overcome the interfacial forces. Stiction could compromise the performance and reliability of the MEMS devices or may even make them malfunction. One of the pivotal process of advancing the performance and reliability of MEMS is to comprehend the failure modes and failure mechanisms of these microdevices. This article provides a critical investigation on the stiction failure mechanisms of the micromachined electrostatic comb-drive structures, which is significant to improve the reliability of microdevices, especially for microfilters, microgrippers, microaccelerometers, microgyroscopes, microrelays, and so on.