MEMS devices Analytical modeling and simulation with reference to cantilever-based MEMS devices

From the use of logic to integrated circuit (IC) technology, the area of electronics industry began to flourish. The manufacture of ICs encompasses 3D, 2D, and 1D surfaces that are enabled by fabrication processes and equipment. In the past, group 14 semiconductor silicon from period 3 was used as the wafer material owing to its exceptional electrical, elastic, and plastic limits. Microsensor and micro actuator devices made using MEMS include grippers, tweezers, and tongs (acoustic wave, biomedical, chemical, inertia, optical, pressure, radiation, and thermal sensors, for example) and valves, pumps, and microfluidics. Depending on the application, a microsystem created by coupling a MEMS microsensor and MEMS microactuator with a shared transduction unit will synergize sensing and actuating mechanisms.

Before sending them to the fabrication facility, MEMS-based goods must undergo a number of trials to be designed into real-time structures. The MEMS product designers will use simulation to validate several elements such as structural reliability and mode of operation. The MEMS device manufacturing process is expensive. To prevent architectural failures, particular consideration should be given to the material choice and the impact of surface pressures on the device. A science fiction software platform for modelling and simulating physics-based issues is called COMSOL Multiphysics. A FEA programme called COMSOL Multiphysics is used to create models with both 2D and 3D geometry. COMSOL Multiphysics excels at building complicated geometries by creating 2D geometries and extruding them into the necessary dimension on the third axis. The COMSOL Multiphysics programme can do more than just generate geometry; it can also correct sources, sinks, boundaries, and add materials to models. With the aid of the COMSOL Multiphysics programme, MEMS and NEMS-based device performance may be evaluated and examined prior to manufacture. The construction of a new physical interface based on the domain equation input by the user is the port fit benefit of utilising COMSOL. The MEMS application The Finite Element Method (FEM) analysis tool Intellisuite is used to design, model, and examine the properties of micro- and nanoscale components and devices. The programme can simulate MEMS devices at the system level utilising 2D and 3D models, as well as virtually fabricate devices that have been modelled using Intellisuite (1). For MEMS simulation, accuracy, capacity, and speed are the benchmarks.

Size, Piezo resistance (PZR), Temperature Coefficient of Resistance (TCR), Stiffness, Adhesion, Vibration, and Resonant Frequency are a few parameters taken into account while designing MEMS-based sensors and devices. Size: Due to

• High surface to volume ratio

• Very small size, mass, volume

• Very low power consumption

• Easy to integrate into systems or modify

• Low cost

• Can be highly resistant to harsh situations such vibration, shock and radiation

• Small thermal constant

• Batch fabricated in large arrays

• Parallelism

MEMS may be used in several applications. Bio-MEMS, a ground-breaking innovation, is bridging the gap between hitherto unconnected disciplines like biology and microelectronics. MEMS is used in a variety of industries, including transportation, consumer products, medical care, space travel, and manufacturing (4).

A few MEMS devices include airbag systems, anti-braking devices, vehicle security systems, inertial brake lights, headlight levelling, rollover detection, automatic door locks, and active suspension. There are several uses for accelerometers, including air bag deployment in contemporary vehicles to prevent crashes. Additionally, consumer gadgets like gaming controllers, portable media players, mobile phones, and specialised digital cameras also make use of accelerometers. When free-fall is detected, the hard disc head in PCs is moved into place. This guards against hard disc damage and data loss. MEMS gyroscopes are employed in contemporary automobiles for location and other purposes, such as to deploy a rollover bar or activate dynamic stability control, in order to detect yaw rotation. Examples of silicon pressure sensors are tyre pressure sensors for automobiles and disposable blood pressure monitors. A DLP-based projector's DMD chip contains several hundred thousand tiny mirrors on it. Data communications switching and alignment using optical switching technology. Applications of interferometric screen modulators (IMOD) in consumer electronics, particularly in displays for portable devices. With the development of RF-MEMS technology, inductors and capacitors have performed better (5).

Polymerase Chain Reaction (PCR) microsystems for DNA amplification and identification are used in Bio-MEMS antigen detection systems to discover infections in blood samples. STM (Scanning Tunnelling Microscope) tips that have been micromanufactured may be used to map the topography of tough microstructures. Biochips are utilised to find dangerous biological and chemical agents. Microsystems for selecting and screening drugs with high throughput. Lab-on-Chip, biosensor, and chemosensor development are all examples of how bio-MEMS are used in medical and health-related technology (6).

MEMS devices were utilised in the fields of signalling, location, and information transfer in space due to the many opportunities they offered.

RF switches, tunable filters, tunable mirror arrays for adaptive optics, micro-power sources, and turbines are all used to connect with base stations on the ground (7). About the launch vehicle, the regulation of thrust and attitude in satellite communication.

In all production-based sectors, hazardous gas detection and gas shutoff are important tasks that must be completed. Deep earth excavation is done in mining regions and stone-purchasing chambers. In such locations, hazardous gas limitations must be continuously monitored (8). Large machines must have their shock and vibration levels measured since these factors determine how well the equipment will hold up over time. Some industrial devices that monitor shock and tilt sensing are tested in harsh environments.

In all industries, from the automobile sector to the medical diagnostic business, developing micromachined components and devices is the focus of attention. Few failures arise as a result of incorrect selection of materials for devices and background operation (9). In Table 1, common MEMS technology failure mechanisms are given.

surfaces on moveable components or neighbouring layers for coherence in material qualities (10). Figure 1 displays a scanning electron microscope (SEM) picture of an adjacent layer mismatch that led to a chemical failure.

Figure 1: SEM image showing MEMS structures bending due to adjacent layer mismatch. Surface forces became a significant design parameter with the introduction of MEMS, although numerically they were mostly unknown due to their small levels. These stiction concerns are more interesting from the perspective of dependability evaluation. Surface forces and adhesion energy between surfaces are the primary causes of these stiction issues. Figure 2 shows the cantilever surfaces with no adhesion, lateral adhesion, and both lateral and vertical adhesions. The stiction may also be induced by both lateral and vertical adhesion (11).

Figure 2: (a) no adhesion (good release) ; (b) only lateral adhesion; and (c) lateral and vertical adhesion. (Courtesy of IOP Publishing Ltd).

The right materials must be used when developing any kind of MEMS construction in order to ensure mechanical dependability. Any structure's surrounding layers must be thoroughly examined for resemblance in material properties; otherwise, chemical failures may occur. By keeping adequate distances between buildings, surface forces acting on the lateral and vertical sides will be negated.

Surface stress adjustments allow for the determination of the bending in static mode, and the addition of mass allows for the measurement of the resonance frequency during dynamic mode transitions. Microcantilever defluxion calculations, resonance frequencies, and damping properties are among the sensors employed in touch and tapping modes of AFM (3). Static microcantilever deflections are caused by external pressures acting on the microcantilever (like in AFM) or intrinsic pressure created on the lifting surface and within the lifting device. While suspended beams may be produced virtually stress-free using microcantilever production techniques, additional stress is caused by physicochemical changes, thermal expansion, and interfacial activities. Microcantilever dynamic sensors depend on the mass and viscoelastic characteristics of the medium linked to them and are basically mechanical oscillators. For instance, the increased suspended mass of the resonator caused by the adsorption of analyte molecules on a resonant surface lowers the resonance frequency. A micro-species with a light weight and a high resonant rate should be employed to achieve excellent sensitivity in bulk detection. Systems that effectively detect masses in the zeptogram regions are being proposed right now, and nanosensor-based sensors have even been used to identify single molecules (12).

Piezo stimulation: In this method, MC is mounted atop a piezoactuator that is driven by a frequency generator. Electrostatic stimulation: In this approach, the microcantilever functions as an electrode in parallel electrodes. By supplying a potential difference between the driver plate and the microcantilever, a periodic force is provided to the microcantilever, enabling it. This works better in a vacuum since air dampens the resonator's movement. Electrostatic stimulation often works well when used in combination with capacitive detecting methods. electrostatic stimulation. At the top of the bottom sheet, there can be a gap between the electrodes. This voltage creates lateral stress, which destroys a microcantilever, and pulls both layers together, distorting the dielectric layer. Integrated piezoelectric stimulation: In this process, a silicon microcantilever is placed on a single-crystalline quartz after a piezoelectric film is pushed onto its two metal contacts. Utilizing a potential gap near the piezoelectric component, the microcantilever is constructed. Stimulation of resistive heat: In this method, the heating resistor is positioned above the microcantilever. Due to the stress of a local temperature rise near to the heating resistor, the microcantilever expands. Bimorph-effect stimulation: This method is similar to the previous one in that the predominant deflection occurs in the microcantilever due to differences in the thermal expansion coefficients of the microcantilever material and furnace (14).

An instrument known as a sensor converts a physical quantity into a corresponding electrical signal. MEMS heavily relies on sensors. The MEMS sensor is made up of a sensing component and related electronics that are used to extract the required electrical output. For multi-sensing applications, sensors may be combined with additional sensors. Three categories are used to categorise these MEMS sensors.

• MEMS chemical sensors (Gas sensors, Cantilever array sensor)

• MEMS Inertial sensors (Gyroscopes, Accelerometers)

• MEMS pressure sensors

Use the COMSOL Multiphysics programme to simulate geometries into thorough 3D or 2D models or 1D plots using the finite element method (FEM). According to Figure 4, the procedure begins with the constructing geometry in the submicron or micrometre domain. After the geometry has been optimised, the suggested or created model's physics are implemented (15). A better understanding of the science behind the suggested design's functioning is required for assigning physics. Structure mechanics, thermal stress, diluted species movement, Joule

static and dynamic modes. Selection of the domain and assignment of materials come after the physics implementation. The materials might either be chosen from the built-in materials or from user-defined materials (16). Basic parameters like the young's modulus (E), poisson ratio (v), density (), and unique properties of the material must be known for the user-defined materials. The next step is to mesh the provided model using the user's constraints. To compensate for computational slowness and relative tolerance, free tetrahedral or free triangular elements with element sizes ranging from very coarse to extremely fine would be preferable. The simulation's last phase involves setting up a stationary solver or a user-defined setup with simulations to produce the desired results on 3D or 2D models in the software program's 3D graphics window.

Different sizes and materials have been used to build MEMS-based Microcantilevers. The corresponding displacement increases as beam length increases. Compared to polysilicon and silicon nitride, this material achieves the highest displacement.

1. Lee KB, Lin L & Cho. A closed form approach for tunable comb resonators with curved finger contour. Sensors and Actuators A, 2018; vol. 141: pp. 523-529. vol. 267, pp. 242-61. 3. Kaur, M & Prasad, M 2016, 'Development of double spiral MEMS hotplate using front-side etching cavity for gas sensors', in AIP Conference Proceedings, vol. 1724, p. 020053. 4. Gopinath, P, Anitha, V & Mastani, SA 2015, 'Microcantilever based biosensor for disease detection applications', J Med Bioeng, vol. 4, no. 4, p. 34. 5. Yen D, Kharjepour A & Mansour R. Design and modeling of MEMS bidirectional vertical thermal actuator Journal of micromechanical microengineering, 2014; vol. 14: pp. 841-845. 6. Sangeetha, P & Juliet, AV 2013, 'Simulation and Analysis of MEMS Cantilever Sensor for Tuberculosis Detection Based on Capacitive Sensing Readout Method', IUP Journal of Electrical & Electronics Engineering, vol. 6, no. 3. 7. Saxena, G & Paily, R 2013, 'Analytical modeling of square microhotplate for gas sensing application', IEEE Sensors Journal, vol. 13, no. 12, pp. 4851-9. 8. Bogue, R 2013, 'Recent developments in MEMS sensors: a review of applications, markets and technologies', Sensor Review, vol. 33, no. 4, pp. 300-4. 9. Sujatha, L, Aravind, VSS, Padamapriya, R & Preethi, B 2012, 'Design and Analysis of Micro-Heaters using COMSOL Multiphysics For MEMS Based Gas Sensor', in Excerpt from the Proceedings of the 2012 COMSOL Conference in Bangalore. 10. Ogando K, La Forgia JJ, Zarate H & Pastoriza. Designed characterization of a fully compliant out-of plane thermal actuator. Sensors and Actuators A, 2012; vol. 183: pp. 95-100. 11. Bazaz SA, Khan F & Shakoo RI. Design, Simulation and testing of electrostatic SOI MUMPs based microgripper integrated with capacitive contact sensor. Sensors and Actuators A, 2011; 167(1): pp. 44-53. 12. DOW AAB. Development and Modeling of an electrothermally MEMS microactuator with an integrated microgripper. 2011; vol. 21: pp. 1-8. 13. Sundaram, S, Tormen, M, Timotijevic, B, Lockhart, R, Overstolz, T, Stanley, RP & Shea, HR 2011, 'Vibration and shock reliability of MEMS: modeling and experimental validation', Journal of Micromechanics and Microengineering, vol. 21, no. 4, p. 045022. 14. Ananthasuresh GK. Electro Thermal-compliant Microactuator Hands on SOI MUMPs Workshop, June 17-18, 2011. 15. T Sun L, Chen L, Rong W & Li X. A hybrid type electrostatically driven Microgripper with an integrated vacuum tool. Sensors and resistance actuation. Journal of Micromechanics and microengineering, 2010; vol.20: pp.9.

Research Scholar, Shri Krishna University, Chhatarpur M.P.