Microelectromechanical Systems Process Research Articles

A Polyimide Composite-Based Electromagnetic Cantilever Structure for Smart Grid Current Sensing.

Polyimides (PIs) have been extensively used in thin film and micro-electromechanical system (MEMS) processes based on their excellent thermal and mechanical stability and high glass transition temperature. This research explores the development of a novel multilayer and multifunctional polymer composite electro-piezomagnetic device that can function as an energy harvester or sensor for current-carrying wires or magnetic field sensing. The devices consist of four layers of composite materials with a polyimide matrix. The composites have various nanoparticles to alter the functionality of each layer. Nanoparticles of Ag were used to increase the electrical conductivity of polyimide and act as electrodes; lead zirconate titanate was used to make the piezoelectric composite layer; and either neodymium iron boron (NdFeB) or Terfenol-D was used to make the magnetic and magnetostrictive composite layer, which was used as the proof mass. A novel all-polymer multifunctional polyimide composite cantilever was developed to operate at low frequencies. This paper compares the performance of the different magnetic masses, shapes, and concentrations, as well as the development of an all-magnetostrictive device to detect voltage or current changes when coupled to the magnetic field from a current-carrying wire. The PI/PZT cantilever with the PI/NdFeB proof mass demonstrated higher voltage output compared to the PI/Terfenol-D proof mass device. However, the magnetostrictive composite film could be operated without a piezoelectric film based on the Villari effect, which consisted of a single PI-Terfenol-D film. The paper illustrates the potential to develop an all-polymer composite MEMS device capable of acting as a magnetic field or current sensor.

An Ionization-Based Aerosol Sensor and Its Performance Study.

In recent years, with the rapid development of new energy vehicles, the safety issues of lithium-ion batteries have attracted attentions from all sectors of society. Research has found that during the thermal runaway process of lithium-ion batteries, aerosol emissions usually occur earlier than other gases. Accurate and timely measurement of these aerosol concentrations can help to warn the power battery pack fires. However, existing aerosol sensors are unable to meet the requirements of real-time monitoring and high precision. This article proposes an ionization mechanism based aerosol sensor that works at principles of field emission, field charging and gas discharge, and investigates its static and dynamic response characteristics. The sensor is manufactured and assembled using Microelectro Mechanical Systems processing technology. The sensor exhibits superior performances in terms of range, sensitivity, nonlinearity, repeatability, response time, and other aspects. The study provides a new solution for current aerosol detection with great potential for application.

Development of Highly Sensitive and Thermostable Microelectromechanical System Pressure Sensor Based on Array-Type Aluminum-Silicon Hybrid Structures.

In order to meet the better performance requirements of pressure detection, a microelectromechanical system (MEMS) piezoresistive pressure sensor utilizing an array-type aluminum-silicon hybrid structure with high sensitivity and low temperature drift is designed, fabricated, and characterized. Each element of the 3 × 3 sensor array has one stress-sensitive aluminum-silicon hybrid structure on the strain membrane for measuring pressure and another temperature-dependent structure outside the strain membrane for measuring temperature and temperature drift compensation. Finite-element numerical simulation has been adopted to verify that the array-type pressure sensor has an enhanced piezoresistive effect and high sensitivity, and then this sensor is fabricated based on the standard MEMS process. In order to further reduce the temperature drift, a thermodynamic control system whose heating feedback temperature is measured by the temperature-dependent structure is adopted to keep the working temperature of the sensor constant by using the PID algorithm. The experiment test results show that the average sensitivity of the proposed sensor after temperature compensation reaches 0.25 mV/ (V kPa) in the range of 0-370 kPa, the average nonlinear error is about 1.7%, and the thermal sensitivity drift coefficient (TCS) is reduced to 0.0152%FS/°C when the ambient temperature ranges from -20 °C to 50 °C. The research results may provide a useful reference for the development of a high-performance MEMS array-type pressure sensor.

Design of Acetaldehyde Gas Sensor Based on Piezoelectric Multilayer Microelectromechanical System Resonator.

Acetaldehyde is a volatile organic compound that can cause damage at the cellular and genomic levels. The monitoring of acetaldehyde gas at low concentrations requires fast-response and low-cost sensors. Herein, we propose the design of an acetaldehyde gas sensor based on a low-cost Microelectromechanical System (MEMS) process. This sensor is formed by a single-clamped piezoelectric multilayer resonator (3000 × 1000 × 52.2 µm) with a simple operating principle and easy signal processing. This resonator uses a zinc oxide piezoelectric layer (1 µm thick) and a sensing film of titanium oxide (1 µm thick). In addition, the resonator uses a support layer of 304 stainless steel (50 µm thick) and two aluminum layers (100 nm thick). Analytical and Finite-Element Method (FEM) models are developed to predict the mechanical behavior of the gas sensor, considering the influence of the different layers of the resonator. The analytical results agree well with respect to the FEM model results. The gas sensor has a first bending frequency of 4722.4 Hz and a sensitivity of 8.22 kHz/g. A minimum detectable concentration of acetaldehyde of 102 ppm can be detected with the proposed sensor. This gas sensor has a linear behavior to detect different acetaldehyde concentrations using the frequency shifts of its multilayer resonator. The gas sensor design offers advantages such as small size, a light weight, and cost-efficient fabrication.

A Low-Power and Robust Micromachined Thermal Convective Accelerometer.

This paper presents a micromachined thermal convective accelerometer with low power and high reliability. This accelerometer comprises a heater and two thermistors. The central heater elevates the temperature of the chip above ambient levels while the symmetrically arranged thermistors monitor the temperature differentials induced by acceleration. The heater and thermistors are fabricated on a glass substrate using a standard micro-electromechanical systems (MEMS) process flow, and the fabricated sensor is installed on a rotation platform and a shaking table experimental setup to perform the experiment. The results indicate that the sensor has the capability to measure accelerations surpassing 80 m/s2, with an approximate linear sensitivity of 110.69 mV/g. This proposed thermal convective accelerometer offers promising potential for various applications requiring precise acceleration measurements in environments where low power consumption and high reliability are paramount.

Design and analysis of mode-matched decoupled mass MEMS gyroscope with improved thermal stability

This paper presents an efficient design approach for microelectromechanical systems (MEMS) gyroscope considering the design constraint of MEMSCAP’s Silicon-on-Insulator Multi-User MEMS Processes (SOIMUMPs). A design for a decoupled mass MEMS resonant gyroscope with tuning electrodes is presented to minimize cross-axis coupling and optimize the gyroscope’s performance. The device features a size of 1.8 ×2.772 mm2 . A decoupled mass MEMS gyroscope has been designed using a novel mechanical beam configuration that optimizes the structural design to reduce unwanted interactions between drive and sense axes motions. Mode order has been achieved by obtaining the first two modes as drive and sense modes at 9946.3 Hz and 10 202.7 Hz, respectively. Parallel plate electrostatic tuning electrodes have been added to adjust and match the drive and sense modes at the resonant frequencies of 9946 Hz. This mode matching is crucial for optimizing gyroscope performance, accuracy, and sensitivity. The effects of temperature variation on the performance of the designed decoupled mass MEMS gyroscope have been investigated, particularly in terms of its mode-matched operation achieved using tuning electrodes. Finite element method (FEM) simulations were conducted, demonstrating that thermal stability was achieved, and mode-matched operation was maintained within the temperature range of −40 °C to 80 °C. The gyroscope exhibits enhanced performance compared to existing MEMS gyroscopes under mode-matched conditions, featuring a lower temperature coefficient of frequency (TCF) at 0.0415 Hz °C−1 in the drive mode and 0.0165 Hz °C−1 in the sense mode. FEM analysis for the fabrication process tolerances has been done, where MEMS gyroscope’s resonant frequencies, output capacitance, output displacement, and sense mode quality factor have shown negligible changes to fabrication process tolerances. Transient analysis was conducted using CoventorWare MEMS+ 3D schematic, which was integrated with MATLAB Simulink to measure the MEMS gyroscope’s output response, which corresponded with the varying input angular velocity signal.

A new fabrication method for enhancing the yield of linear micromirror arrays assisted by temporary anchors

As one of the most common spatial light modulators, linear micromirror arrays (MMAs) based on microelectromechanical system (MEMS) processes are currently utilized in many fields. However, two crucial challenges exist in the fabrication of such devices: the adhesion of silicon microstructures caused by anodic bonding and the destruction of the suspended silicon film due to residual stress. To solve these issues, an innovative processing method assisted by temporary anchors is presented. This approach effectively reduces the span of silicon microstructures and improves the Euler buckling limit of the silicon film. Importantly, these temporary anchors are strategically placed within the primary etching areas, enabling easy removal without additional processing steps. As a result, we successfully achieved wafer-level, high-yield manufacturing of linear MMAs with a filling factor as high as 95.1%. Demonstrating superior capabilities to those of original MMAs, our enhanced version boasts a total of 60 linear micromirror elements, each featuring a length-to-width ratio of 52.6, and the entire optical aperture measures 5 mm × 6 mm. The linear MMA exhibits an optical deflection angle of 20.4° at 110 Vdc while maintaining exceptional deflection flatness and uniformity. This study offers a viable approach for the design and fabrication of thin-film MEMS devices with high yields, and the proposed MMA is promising as a replacement for digital micromirror devices (DMDs, by TI Corp.) in fields such as spectral imaging and optical communication.

Recent progress in piezoelectric thin films as self-powered devices: material and application

Piezoelectric materials have become a key component in sensors and actuators in many industrial fields, such as energy harvesting devices, self-powered structures, biomedical devices, nondestructive testing, owing to the novel properties including high piezoelectric coefficient and electromechanical coupling factors. Piezoelectric thin films integrated on silicon substrates are widely investigated for their high performance and low manufacturing costs to meet the requirement of sensor networks in internet of things (IoT). The aim of this work is to clarify the application and design structure of various piezoelectric thin films types, synthesis methods, and device processes. Based on latest literature, the process of fabricating thin film sensors is outlined, followed by a concise overview of techniques used in microelectromechanical systems (MEMS) processing that can integrate more complex functions to obtain relevant information in surrounding environment. Additionally, by addressing piezoelectric thin films sensors as a cutting-edge technology with the ability to produce self-powered electronic devices, this work delivers incisive conclusions on all aspects of piezoelectric sensor related features. A greater understanding of piezoelectricity is necessary regarding the future development and industry challenges.

Micro-hexapod robot with an origami-like SU-8-coated rigid frame

AbstractIn recent years, many microrobots have been developed for search applications using swarms in places where humans cannot enter, such as disaster sites. Hexapod robots are suitable for moving over uneven terrain. In order to use micro-hexapod robots for swarm exploration, it is necessary to reduce the robot’s size while maintaining its rigidity. Herein, we propose a micro-hexapod with an SU-8 rigid frame that can be assembled from a single sheet. By applying the SU-8 coating as a structure to the hexapod and increasing the rigidity, the substrate size can be reduced to within 40 mm × 40 mm and the total length when assembled to approximately 30 mm. This enables the integration of the micro electromechanical systems (MEMS) process into small and inexpensive hexapod robots. In this study, we assembled the hexapod with a rigid frame from a sheet created using the MEMS process and evaluated the leg motion.

Design, fabrication, and characterization of a high-sensitivity integrated quartz vibrating beam accelerometer.

This paper describes the design, fabrication, and characterization of a quartz vibrating beam accelerometer consisting of a metal spring-mass and quartz double-ended tuning forks (DETFs). In this approach, the inertial force of the proof mass pulls or compresses the DETFs, affecting their resonance frequency and, thus, enabling the quasi-digital measurement of acceleration. An isolation structure was specifically designed to prevent the external interference stress from transforming into the DETFs and to decrease the DETFs' thermal stress as the ambient temperature changes. A stress-free and high-precision wire-cut electrical discharge machining process was introduced to solve the fabrication problem of flexible hinges, and a femtosecond laser was used to release the proof mass, comprehensively considering the compatibility of the fabrication process and structural design. The oscillation excitation and detection of the DETFs were analyzed, and the DETFs were fabricated using a micro-electromechanical systems process. Sensor dimensions were optimized to improve sensor sensitivity. An accelerometer prototype was fabricated, and its performance was characterized. The tested scale factor was 157.28 Hz/g, and its stability was 16.54 ppm. The bias stability and 1g stability at 1h were 18 and 7.84 µg, respectively. The experimental results validated the feasibility of the sensor design.

Simulation study of a planar quadrupole mass filter for MEMS mass spectrometer

Micro-electro-mechanical system (MEMS) based mass spectrometry, MEMS mass spectrometry, emerges a new technique branch of miniature mass spectrometry. One of the main challenges hindering the development of MEMS mass spectrometry is the poor compatibility between the complex electrode structure of traditional ion optics and MEMS processes. This paper proposed a planar quadrupole mass filter utilizing a highly simplified stacked-layer structure and film electrodes, which is easy to fabricate with high precision by MEMS surface micromachining. The ion trajectory simulation model of the MEMS mass spectrometry chip involving all necessary ion optics was elaborated for investigating the preliminary performance of the planar quadrupole mass filter. By optimizing the crucial parameters such as the frequency of radio frequency voltage, the ratio of direct current voltage and radio frequency voltage, pre-pole length, main-pole length, and injection kinetic energy, the preliminary simulation result of planar quadrupole mass filter achieved a 1–2 Da peak width (at 50% of peak height) and 20–80% ion transmission efficiency. Importantly, the planar quadrupole mass filter demonstrated a maximum working pressure of 0.1 Pa (using air as the buffer gas), 100 times higher than that of conventional quadrupole mass filters, while maintaining a 0.7–1.8 Da peak width and ∼5% ion transmission efficiency. Additionally, to modify the theoretical formulas for the non-ideal quadrupolar field of planar quadrupole mass filter, a novel approach based on stability diagrams obtained by simulation was also introduced. The pretty good linearity (R2=1) between ion masses in the range of 10 to 100 Da and the corresponding radio frequency voltages was verified through the simulated mass spectra. Notably, the proportional coefficient of ion mass and radio frequency voltage exhibited a minimal 4% deviation between the simulated value (4.7132 V0P/Da) and the calculated value (4.9036 V0P/Da) through the modified formula. In conclusion, the preliminary simulation results demonstrated that the planar quadrupole mass filter possessed moderate performance, high-pressure tolerance, and excellent theoretical consistency, which proved it a promising technology of MEMS mass spectrometry. It can find applications in the fields of gas detection, including the rapid response to hazardous gas emissions and in situ detection of dissolved gases in the deep sea.

Gallium oxide cantilevered thin film-based solar-blind photodetector and its arc detection applications

The performance of gallium oxide (Ga<sub>2</sub>O<sub>3</sub>) thin film detector based on metal-semiconductor-metal (MSM) is highly dependent on the uniformity of the Ga<sub>2</sub>O<sub>3</sub> thin film, and the manufacturing process is quite sophisticated, which poses a challenge for the scale-up and mass production of thin film photodetectors. In this work, an MSM Ga<sub>2</sub>O<sub>3</sub> thin film solar-blind photodetector with five-finger interdigital electrodes is fabricated by physically depositing Ga<sub>2</sub>O<sub>3</sub> thin film on the surface of a mass-produced cantilevered thin film chip. Through the microelectromechanical system (MEMS) process, the cantilever electrode structure is prepared, which protects the internal circuit and the integrity of the thin film. The Ga<sub>2</sub>O<sub>3</sub> thin film treated by argon plasma at a low temperature is amorphous, but the photodetector still possesses considerable ultraviolet detection performance. At a bias voltage of 18 V, it approaches the detection performance of crystalline Ga<sub>2</sub>O<sub>3</sub> thin film, with a detectivity of 7.9×10<sup>10</sup> Jones, an external quantum efficiency of 1779%, rise time and decay time of 1.22 s and 0.24 s, respectively. Moreover, a system of arc detection is built in outdoor environments. Without any optical focusing system, this photodetector achieves sensitive detection of pulsed arc in an outdoor sunlight environments. For pulsed arcs with an output voltage of 100 kV, the photodetector is capable of sensitive detection at a distance of 25 cm. Besides, the maximum detection distance of 155 cm indicates that the photodetector will have a favorable potential application value in the field of solar-blind detection. This work develops a sensitive functional thin film deposition technology based on the cantilever electrode structure fabricated by the MEMS process, which avoids the influence of the large-area uniformity of the functional thin film on the etching circuit. It provides a new technical approach and process route for preparing MSM photodetectors.

Metal-organic framework-based high-performance column chip for micro gas chromatography: hybrid function for simultaneous preconcentration and separation of volatile organic compounds.

Numerous attempts have been made to replace commercial bulky gas chromatography (GC) systems with compact GC systems for monitoring volatile organic compounds in indoor air. However, recently developed compact GC systems are still too bulky in terms of user convenience, portability, and on-site analysis. Hence, an advanced miniaturization of compact GC systems is needed. Importantly, the small and high-performance gas pretreatment chip devices should be developed for compact GC systems. This paper reports the development of a metal-organic framework (MOF)-coated hybrid micro gas chromatography column chip (hybrid GC chip) capable of preconcentration and separation on harmful volatile organic compounds at low-concentration in one single chip device. The hybrid GC chip, 2 cm × 2 cm in size, was fabricated using a microelectromechanical systems process. The synthesized MOF-5 particles were coated on the inner wall of the fabricated hybrid GC chip and acted as an adsorbent and a stationary phase. The developed hybrid GC chip afforded high preconcentration factors with 1033-1237 and high separation resolutions with 3.8-13.3. The developed column showed good performance as a gas preconcentrator and separation column, and is the first device to perform both roles in one single chip device.

High-Performance SAW Resonator with Spurious Mode Suppression Using Hexagonal Weighted Electrode Structure.

Surface acoustic wave resonators are widely applied in electronics, communication, and other engineering fields. However, the spurious modes generally present in resonators can cause deterioration in device performance. Therefore, this paper proposes a hexagonal weighted structure to suppress them. With the construction of a finite element resonator model, the parameters of the interdigital transducer (IDT) and the area of the dummy finger weighting are determined. The spurious waves are confined within the dummy finger area, whereas the main mode is less affected by this structure. To verify the suppression effect of the simulation, resonators with conventional and hexagonal weighted structures are fabricated using the micro-electromechanical systems (MEMS) process. After the S-parameter test of the prepared resonators, the hexagonal weighted resonators achieve a high level of spurious mode suppression. Their properties are superior to those of the conventional structure, with a higher Q value (10,406), a higher minimum return loss (25.7 dB), and a lower ratio of peak sidelobe (19%). This work provides a feasible solution for the design of SAW resonators to suppress spurious modes.

Microheater with copper nanofiber network via electrospinning and electroless deposition

In this report, we present the development of a copper nanofiber network-based microheater, designed for applications in electron microscopes, gas sensing, and cell culture platforms. The seed layer, essential for electroless deposition, was fabricated through the electrospinning of a palladium-contained polyvinylpyrrolidone solution followed by a heat treatment. This process minimized the contact resistance between nanofibers. We successfully fabricated a microheater with evenly distributed temperature by controlling the electrospinning time, heat treatment conditions, and electroless deposition time. We assessed the electrical and thermal characteristics of the microheater by examining the nanofiber density, sheet resistance, and transmittance. The microheater’s performance was evaluated by applying current, and we verified its capacity to heat up to a maximum of 350 °C. We further observed the microheater’s temperature distribution at varying current levels through an infrared camera. The entire manufacturing procedure takes place under normal pressure, eliminating the need for masking or etching processes. This renders the method easily adaptable to the mass production of microdevices. The method is expected to be applicable to various materials and sizes and is cost-effective compared to commercially produced microheaters developed through microelectromechanical system processes, which demand complex facilities and high cost.

Triaxial tactile sensor utilizing standing laser-induced graphene cantilevers on polyimide film

Microelectromechanical systems (MEMS) multiaxial tactile sensors have been developed in various fields to leverage their small size, high accuracy, and high sensitivity. Although various measurement principles have been proposed, most tactile sensors are fabricated using conventional and complicated Si processes. Conversely, laser-induced graphene (LIG) has recently attracted significant attention as a material for fabricating physical sensors due to its high sensitivity as a piezoresistor through simple laser processing. Therefore, the application of LIG to MEMS processes is expected to yield unprecedented MEMS sensor devices. In this paper, we propose a triaxial tactile sensor using standing LIG cantilevers embedded in an elastic body. The proposed sensing element was fabricated using ultraviolet (UV) laser irradiation to shape a polyimide film into cantilever structures and CO2 laser irradiation to form LIG strain gauges. Subsequently, the flat LIG cantilevers were stood up using thermal deformation. These multiple three-dimensional LIG cantilever elements enable multiaxial force measurements. The cantilever and elastic body portion of the sensor had dimensions of 3 × 3 × 0.2 mm and 12.5 × 12.5 × 3 mm, respectively. The fabricated sensor response was evaluated, and its capability to independently measure triaxial forces was verified. Therefore, the proposed simple and reproducible fabrication process is useful for realizing compact multiaxial tactile sensors.

A vision sensor for simultaneous imaging and distance sensing in real-time

A vision sensor for simultaneous imaging and distance sensing is proposed herein. This vision sensor uses two images with a depth of field by two different aperture sizes to extract distance data. The aperture was fabricated through the microelectromechanical systems process. The optical parameter related to making a blur was precisely selected to reduce the active voltage and response time. The aperture measurement result showed that the maximum displacement of 1170 µm was obtained when 12 V was applied which enlarge aperture size from 2.75 mm to 3.92 mm. The response time was 16.6 ms with a rising and falling time of 6.2 and 10.4 ms, respectively. The distance data was obtained using the depth from defocus method, which compares the blurriness of two images using the aperture size. Through deep learning, the image and distance information were simultaneously obtained in a single camera. The result of a three-dimensional depth map showed an average accuracy of 98.7% when sensing the maximum distance of 10 m. To examine the accuracy of the device, experiments were conducted for different colors, and the result showed that maximum and minimum error rates of 3.46% and 1.83% were achieved, respectively. In addition, the error rate according to brightness was investigated, and the average error rate was maintained at 2.64% between 10 000 and 200 lx. The proposed sensor can be installed in self-driving robots, drones, and various smart devices.

Emission measurements and in-situ observation of ionic liquid electrospray thrusters with longitudinally grooved emitters

An externally wetted emitter array with longitudinally grooved structures for ionic liquid electrospray thrusters was fabricated to improve ionic liquid transport to the emitter tips. Two grooved emitter shapes with different groove depths were successfully fabricated using microelectromechanical system processing techniques. We evaluated the current–voltage characteristics, measured the mass spectra using time-of-flight (ToF) spectrometry, and conducted in-situ observations using a high-speed microscope. The experimental results of ion emission show that the absolute emission current increases compared with that of our previous emitter without grooves. This tendency is strengthened with deeper grooves. Moreover, the slope of the current–voltage curve for the grooved emitters does not decrease even when high voltages are applied, indicating that the grooved structure improves the ionic liquid transport to the emitter tips. This improvement is attributed to the low hydraulic impedance of the emitter structure. However, deeper grooving also increases the percentage of current intercepted by the extractor electrode, and electrochemical reactions are not avoided at an alternation frequency of 1 Hz. Although the first current–voltage measurement tended to have unstable characteristics, the ToF results indicated that the emission in the center line was in the pure-ion regime, composed mostly of monomer and dimer ions, under all the measured conditions. High-speed microscope observations showed that too much ionic liquid deposited on the extractor causes ion emission from the extractor to the emitter, known as backspray, and implies that no large droplets are emitted for either grooved emitter structure, which is consistent with the ToF results.

Design and Fabrication of a Thin and Micro-Optical Sensor for Rapid Prototyping.

Optical sensing offers several advantages owing to its non-invasiveness and high sensitivity. The miniaturization of optical sensors will mitigate spatial and weight constraints, expanding their applications and extending the principal advantages of optical sensing to different fields, such as healthcare, Internet of Things, artificial intelligence, and other aspects of society. In this study, we present the development of a miniature optical sensor for monitoring thrombi in extracorporeal membrane oxygenation (ECMO). The sensor, based on a complementary metal-oxide semiconductor integrated circuit (CMOS-IC), also serves as a photodiode, amplifier, and light-emitting diode (LED)-mounting substrate. It is sized 3.8 × 4.8 × 0.75 mm3 and provides reflectance spectroscopy at three wavelengths. Based on semiconductor and microelectromechanical system (MEMS) processes, the design of the sensor achieves ultra-compact millimeter size, customizability, prototyping, and scalability for mass production, facilitating the development of miniature optical sensors for a variety of applications.

Improved topography measurement with a high dynamic range using phase difference sensing technology.

Phase difference sensing technology (PDST) is employed for topography measurement, and two interference structures are proposed to achieve upper-limit adjustment and high resolution in the measurement range: a dual-wavelength system with a single Fabry-Perot (FP) cavity and a single-wavelength system with dual FP cavities. The phase difference between the two interference signals is determined by an elliptic fitting algorithm (EFA), and this change in phase difference is utilized to characterize the step height. Experimental results indicate that the measurement upper-limit can be adjusted to either 410 µm, 187 µm, or 108 µm by varying the wavelength difference in the dual-wavelength system, which gives a measurement error of 2.96%. In contrast, while offering a measurement resolution of 3.47 nm, the single-wavelength system exhibits a measurement error of 5.38%. The proposed method is capable of satisfying the measurement requirements during micro-electromechanical system (MEMS) processing with proficiency.