Microelectromechanical Systems Manufacturing Research Articles

Printing MEMS: Application of Inkjet Techniques to the Manufacturing of Inertial Accelerometers.

In the last few years, the manufacturing of microelectromechanical systems (MEMS) by means of innovative tridimensional and bidimensional printing technologies has significantly catalyzed the attention of researchers. Inkjet material deposition, in particular, can become a key enabling technology for the production of polymer-based inertial sensors characterized by low cost, high manufacturing scalability and superior sensitivity. In this paper, a fully inkjet-printed polymeric accelerometer is proposed, and its manufacturing steps are described. The manufacturing challenges connected with the inkjet deposition of SU-8 as a structural material are identified and addressed, resulting in the production of a functional spring-mass sensor. A step-crosslinking process allows optimization of the final shape of the device and limits defects typical of inkjet printing. The resulting device is characterized from a morphological point of view, and its functionality is assessed in performing optical readout. The acceleration range of the optimized device is 0-0.7 g, its resolution is 2 × 10-3 g and its sensitivity is 6745 nm/g. In general, the work demonstrates the feasibility of polymeric accelerometer production via inkjet printing, and these characteristic parameters demonstrate their potential applicability in a broad range of uses requiring highly accurate acceleration measurements over small displacements.

Overview of the technologies used in the fabrication of MEMS/NEMS actuators for space applications

Given the advantages in terms of weight, size and cost and because it can withstand severe shocks and temperature changes, the MEMS/NEMS sensors are widely used in the aerospace domain. This paper presents a brief history of the scientists who made reference to micro and nano technologies for the first time, followed by a synthesis of the leading technologies used in the manufacture of microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) intensively used in aerospace industry. After reviewing the latest technologies used in the manufacture of MEMS/NEMS sensors, the paper continues with predicting the current state regarding the development of NEMS and MEMS, respectively.

Multimode TED-tuned beam mass damper for low-g capacitive MEMS accelerometers VRE reduction

Capacitive Micro-Electro-Mechanical Systems (MEMS) accelerometers for quasi-static applications are susceptible to vibration rectification error (VRE) when the ambient AC vibration signals get rectified to DC. Studies to mitigate the VRE have relied on the sigma-delta filtering algorithm with closed-loop feedback as well as the adoption of vibration-insensitive frequency modulation (FM) instead of conventional amplitude modulation. In this study, we propose a novel solution to VRE caused by asymmetric railing introducing multimode thermoelastic damping (TED) tuned beam mass damper (TBMD) integrated into the MEMS accelerometer effectively functioning as a compensator. Our contribution breaks through the microfabrication limitation of damping elements by utilizing intrinsic TED in MEMS material. The damper elements were alternately tuned up to the third flexural mode due to MEMS manufacturing constraints. This was done through parametric sweeps in numerical simulations on single-axis capacitive MEMS accelerometer integrated with multimode TED-damped TBMD. According to simulation results, the higher the mode shapes of the TED-damped tuned beam mass damper, the higher the damping effect and the better the vibration rectification factor.

Thermal properties and pressure-dependent elastic constants of cadmium stannate as a substrate for MEMS: An ab initio study

Silicon carbide (SiC) has become a suitable replacement to silicon as a substrate for manufacture of microelectromechanical systems (MEMS) that operate in harsh environmental conditions, owing to its better mechanical properties such as excellent wear resistance. However, just like silicon, SiC is also brittle, a property that limits its application as a substrate for manufacture of flexible MEMS. In this study, we explored the thermal properties as well as the pressure-dependent elastic constants of cadmium stannate (Cd2SnO4) for the first time within the quantum espresso code. The result showed that the elastic constants of SiC are much higher than those of Cd2SnO4. The properties of SiC were found to be more sensitive to the applied pressure compared those of Cd2SnO4, implying that it is less mechanically and thermally stable with the applied pressure compared to Cd2SnO4, and therefore, less appealing compared to Cd2SnO4 for the manufacture of most MEMS.

Study on the Manipulation Strategy of Metallic Microstructures Based on Electrochemical-Assisted Method

Microcomponent manipulation (MCM) technology plays a decisive role in assembling complex systems at the micro- and nanoscale. However, the existing micromanipulation methods are difficult to widely apply in the manufacturing of microelectromechanical systems (MEMSs) due to the limited manipulation space and complex application objects, and the manipulation efficiency is relatively low, which makes it difficult to industrialize these micromanipulating systems. To solve the above problems, this paper proposes an efficient metal MCM strategy based on the electrochemical method. To verify the feasibility and repeatability of the strategy, the finite element model (FEM) incorporating the hydrodynamic and electrochemical theories is used to calculate the local stress distribution of the contact position during the dynamic pick-up process. Based on the simulation results, we defined the relationship between the parameters, such as the optimal manipulating position and angle for picking, transferring and releasing. The failure behaviors of pick-up are built to realize the efficient three-dimensional manipulation of microcopper wire of 300 μm. By establishing a theoretical model and experimental verification, it was concluded that the middle point was the best manipulating position when picking up the microcopper wire, the most efficient picking angle was between 45 and 60 degrees for the pipette, and the average time was 480 s in three sets of picking-release manipulation experiments. This paper provides an achievable idea for different types of micro-object manipulations and promotes the rapid application of micromanipulation techniques in MEMSs.

Micro 3D printing of a functional MEMS accelerometer

Microelectromechanical system (MEMS) devices, such as accelerometers, are widely used across industries, including the automotive, consumer electronics, and medical industries. MEMS are efficiently produced at very high volumes using large-scale semiconductor manufacturing techniques. However, these techniques are not viable for the cost-efficient manufacturing of specialized MEMS devices at low- and medium-scale volumes. Thus, applications that require custom-designed MEMS devices for markets with low- and medium-scale volumes of below 5000–10,000 components per year are extremely difficult to address efficiently. The 3D printing of MEMS devices could enable the efficient realization and production of MEMS devices at these low- and medium-scale volumes. However, current micro-3D printing technologies have limited capabilities for printing functional MEMS. Herein, we demonstrate a functional 3D-printed MEMS accelerometer using 3D printing by two-photon polymerization in combination with the deposition of a strain gauge transducer by metal evaporation. We characterized the responsivity, resonance frequency, and stability over time of the MEMS accelerometer. Our results demonstrate that the 3D printing of functional MEMS is a viable approach that could enable the efficient realization of a variety of custom-designed MEMS devices, addressing new application areas that are difficult or impossible to address using conventional MEMS manufacturing.

Design, fabrication, characterization and reliability study of CMOS-MEMS Lorentz-force magnetometers

This article presents several design techniques to fabricate micro-electro-mechanical systems (MEMS) using standard complementary metal-oxide semiconductor (CMOS) processes. They were applied to fabricate high yield CMOS-MEMS shielded Lorentz-force magnetometers (LFM). The multilayered metals and oxides of the back-end-of-line (BEOL), normally used for electronic routing, comprise the structural part of the MEMS. The most important fabrication challenges, modeling approaches and design solutions are discussed. Equations that predict the Q factor, sensitivity, Brownian noise and resonant frequency as a function of temperature, gas pressure and design parameters are presented and validated in characterization tests. A number of the fabricated magnetometers were packaged into Quad Flat No-leads (QFN) packages. We show this process can achieve yields above 95 % when the proper design techniques are adopted. Despite CMOS not being a process for MEMS manufacturing, estimated performance (sensitivity and noise level) is similar or superior to current commercial magnetometers and others built with MEMS processes. Additionally, typical offsets present in Lorentz-force magnetometers were prevented with a shielding electrode, whose efficiency is quantified. Finally, several reliability test results are presented, which demonstrate the robustness against high temperatures, magnetic fields and acceleration shocks.

Experimental Investigation on Ablation of 4H-SiC by Infrared Femtosecond Laser.

Femtosecond laser ablation has become one of the important structural processing methods for the third-generation semiconductor material, silicon carbide (SiC), and it is gradually being employed in the manufacture of microelectromechanical systems and microelectronic devices. Experimental study has been performed on infrared single and multiple pulses (1035 nm) femtosecond laser ablation of SiC at various processing parameters. Diameters of laser ablation spots on 4H-SiC were measured to estimate the absorption threshold for material modification and structural transformation, which were 2.35 J/cm2 and 4.97 J/cm2, respectively. In the multiple-pulse scribing ablation for microgrooves, the ablation threshold dropped to 0.70 J/cm2 due to the accumulation effect when the effective pulse number reached 720. The calculated average of the thermally stimulated ablation depth of 4H-SiC is 22.4 nm, which gradually decreased with the raising of the effective pulse number. For obtaining square trenches with precise and controllable depths and a smooth bottom in 4H-SiC, the effects of processing parameters on the material removal rate and surface roughness are discussed. The ablation rate per pulse is almost constant, even if the effective pulse number varies. The reduction of laser spot overlapping ratio in x direction has a greater weakening effect on the material removal rate than that in y direction. The precise amount of material removal can still be controlled, while modulating the surface roughness of the ablated features by changing the hatch rotation angle. This research will help to achieve controllable, accurate, and high-quality machining results in SiC ablation, using infrared femtosecond laser.

Temperature-Dependent Elastic Constants of Substrates for Manufacture of Mems Devices

We present a comparative computational study of temperature-dependent elastic constants of silicon (Si), silicon carbide (SiC) and diamond as substrates that are commonly used in the manufacture of Micro-Electromechanical Systems (MEMS) devices. Also mentioned is Cd2SnO4, whose ground-state elastic constants were determined just recently for the first time. Si is the dominant substrate used in the manufacture of MEMS devices, owing to its desirable electrical, electronic, thermal and mechanical properties. However, its low hardness, brittleness and inability to work under harsh environment such as high-temperature environment, has limited its use in the manufacture of MEMS like mechanical sensors and bioMEMS. Mechanical sensors are fabricated on SiC and diamond due to their high Young’s moduli as well as high fracture strength, while the bioMEMS are fabricated on polymers. The effect of temperature on the elastic constants of these substrates will help in giving insight into how their performance vary with temperature.

A monolithic three-dimensional thermal convective acoustic vector sensor with acoustic-transparent heat sink.

An acoustic vector sensor can directly detect acoustic particle velocity based on the measured temperature difference between closely spaced heated wires. For the detection of velocity in three dimensions, an integrated three-dimensional (3 D) sensor is desired, but it remains challenging in MEMS (Micro-Electro-Mechanical System) manufacturing. Here, a novel monolithic 3 D acoustic vector sensor is proposed, which is constructed using in-plane distributed wires assembled with acoustically transparent heat sink. The planar MEMS structure of the proposed sensor makes it easy to be fabricated and packaged. This work offers a new method for the design of acoustic vector sensors and other thermal convection-based MEMS sensors.

Fabrication of Aluminum Nickel Reactive Bilayer by the Lift-Off Process

Semiconductor component and microelectromechanical system manufacturing requires metal patterning in an integrated circuit (IC), using the photoresist lift-Off process. Ideal advantages like cost-effectiveness, reduction of complexity and process maturity are associated with the lift-Off process. Alternatively, the choice of photoresist relies on factors such as cost, initial photoresist thickness and reliable processing parameters extraction. However, the availability of the cheap photoresist is still at question. For the case of the underlying study, a highly cheap photoresist E8015 of thickness 38-micrometer was developed for the purpose of edge profiling. Desirable extraction of the useful parameter range for dry resist processing is performed. Parameter variation like exposure energy and development time led to a successful undercut angle of 66° to 73°, while the straight edge profile of 90° was realized at various parameter combinations. Eventually, a metallic multilayer of 10-micrometer thickness is successfully lifted off on plain silicon. Controlled self-propagating reaction within these structured metallic layers may be employed for IC packaging hereafter.

Inkjet Assisted Electroforming of Bioinspired Untethered Microrobots

In the last few decades, inkjet (IJ) printing evolved from a mere graphical and visual tool to a versatile methodology able to find application in a great number of industrial fields (e.g. electronics, display production, flexible electronics). The technology is based on the controlled emission of droplets from a nozzle. Such droplets, which contain the material of interest in the form of a solution or a dispersion, are deposited on a substrate, allowing thus controlled patterning. Thanks to its flexibility and efficiency, IJ proved to be one of the most promising technologies to pattern materials on a wide variety of rigid and flexible substrates. Recently, IJ found application also in the field of microfabrication. It was employed, for example, to manufacture microelectromechanical systems (MEMS) [1] or microelectronic components and sensors [2]. Another possible application of IJ, still not developed in the existing literature, is the production of magnetically guidable microrobots [3]. These can find application in a wide variety of fields, including for example micromanipulation, cell transport and drug delivery applications.Many applications of IJ in microfabrication, and microrobots production in particular, require the presence of conductive or magnetic layers to allow actuation or sensing. By employing IJ, however, it is difficult to obtain highly conductive and mechanically stable layers. From this point of view, the variety and the performances of IJ printed conductive and magnetic materials are in many cases limited. Metals IJ printing, for example, is normally based on the use of nanoparticle suspensions or on reactive IJ deposition [4]. Both methods, however, cannot outperform bulk metallic layers. To expand IJ applicability to micromanufacturing, we developed a novel approach to indirectly pattern bulk metallic microstructures by combining IJ printing and electroforming. The technique requires the presence of a conductive substrate. Initially, a layer of SU-8 photoresist is IJ printed [5] on the substrate to form a negative of the final pattern. Subsequently, the positive pattern is growth by mean of electrodeposition inside the negative SU-8 pattern. SU-8 is then removed, leaving an indirectly printed metal pattern. It is also possible to dissolve the substrate in a suitable aggressive solution, leaving thus freestanding electroformed planar structures. Moreover, this latter approach can be employed to transfer metal patterns on nonconductive substrates [6].We applied the approach described to the microfabrication of untethered functional microdevices inspired to the shape and behavior of water-striders (Gerridae). These insects exploit water surface tension to walk on the surface of shallow lakes and ponds. They are characterized by long legs, useful to distribute their weight on the water. Taking inspiration from Gerridae, we developed micromachined devices able to run on the air-water interface (insert in Figure 1). Initially, their negative pattern was printed on an aluminum substrate. Then, different metallic layers (Cu, NiFe and Cu) were sequentially electrodeposited inside. Copper was deposited to provide mechanical stability, while NiFe was deposited to allow magnetic actuation of the final devices. Subsequently, SU-8 was stripped from the surface and the aluminum substrate was dissolved in a NaOH solution. As a result, freestanding electroformed microdevices were obtained. They were morphologically characterized by mean of SEM and AFM. Finally, they were actuated by applying a controlled magnetic field gradient (Figure 1). The high level of precision achieved during the actuation tests performed suggests possible applications in the field of micromanipulation at the air-water interface.[1] G. K. Lau et al., Micromachines 8, 194 (2017)[2] N. K. Mani et al., “Bioelectrochemical Interface Engineering”, chapter 19, John Wiley & Sons (2020)[3] S. Palagi et al. Nat. Rev. Mater. 3(6), 113 (2018)[4] P. Calvert, “Reactive Inkjet Printing: A Chemical Synthesis Tool”, chapter 10, RSC publishing (2017)[5] R. Bernasconi et al., Polymer 185, 121933 (2019)[6] R. Bernasconi et al., IEEE Sensors 20(23), 14024 (2020)Figure 1. Visual appearance and speed vs. applied magnetic field gradient relationship for Cu/NiFe/Cu electroformed water striders. Figure 1

Inkjet Deposition Assisted Electroforming of Functional Microstructures

Inkjet (IJ) printing is a materials deposition technology based on the controlled emission of droplets from a nozzle. Such droplets, which contain the material of interest in the form of a solution or a dispersion, are deposited on a substrate, allowing thus controlled patterning. In the last few decades, IJ evolved from a mere graphical and visual tool to a versatile methodology able to find application in a great number of industrial fields: electronics, displays production, ETC. IJ printing proved to be one of the most flexible and efficient technologies to pattern materials on a wide variety of rigid and flexible substrates.More recently, IJ found application also in the field of microfabrication. In particular, it was employed to manufacture microelectromechanical systems (MEMS) [1], microelectronic components and sensors [2]. Many of these applications require the presence of IJ printed conductive or magnetic layers to allow actuation or sensing. By employing IJ, however, it is difficult to obtain highly conductive and mechanically stable layers. This issue is connected to the nature of the IJ technology, which rely on the use of fluids, either solutions or dispersions. As a consequence, the variety of printable conductive and magnetic materials is limited. Metals IJ printing, in particular, is normally based on the use of nanoparticle suspensions or on reactive IJ deposition [3]. Both methods, however, cannot outperform bulk metallic layers. Conductive polymers IJ printing is possible as well, but final layers are characterized by limited mechanical properties and poor conductivity.To expand IJ applicability to micromanufacturing, we developed a novel approach to indirectly pattern bulk metallic microstructures by combining IJ printing and electroforming. The technique requires the presence of a conductive substrate. Initially, a layer of SU-8 photoresist is printed [4] on the substrate to form a negative of the final pattern. Subsequently, the positive pattern is growth by mean of electrodeposition inside the negative SU-8 pattern. SU-8 is then removed, leaving an indirectly printed metal pattern. It is also possible to dissolve the substrate in a suitable aggressive solution, leaving thus freestanding electroformed planar structures. Moreover, this latter approach can be employed to transfer metal patterns on nonconductive substrates. The methodology hereby presented can be potentially used for the production of MEMS, microelectronic components and microrobots.To provide an applicative example, we present the microfabrication of free-standing functional microdevices. In detail, a negative pattern was printed on an aluminum substrate. Then, different metallic layers (Cu, NiFe and Cu) were sequentially electrodeposited inside. Copper was deposited to provide mechanical stability, while NiFe was deposited to allow magnetic actuation of the final devices. Subsequently, SU-8 was stripped from the surface and the aluminum substrate was dissolved in a NaOH solution. As a result, freestanding electroformed microdevices were obtained. They were morphologically characterized by mean of SEM and AFM. Finally, they were actuated by applying a controlled magnetic field. The high level of precision achieved during the actuation tests performed suggests possible applications in the field of micromanipulation.[1] G. K. Lau et al., Micromachines 8, 194 (2017)[2] N. K. Mani et al., “Bioelectrochemical Interface Engineering”, chapter 19, John Wiley & Sons (2020)[3] P. Calvert, “Reactive Inkjet Printing: A Chemical Synthesis Tool”, chapter 10, RSC publishing (2017)[4] R. Bernasconi et al., Polymer 185, 121933 (2019)

Gas Absorption in Package Using Au/Pt/Ti Bonding Layer

Vacuum packaging is required for the successful long-term operation of various kinds of micro-electromechanical system (MEMS) devices. The following points are important to complete and maintain encapsulated internal vacuum conditions: Degassing MEMS assemblies before packagingPackaging MEMS devices without leakageAbsorbing residual gases after packaging Our research group has developed a simplified MEMS packaging process using a Au/Ti layer (from top to bottom) as a bonding and gettering layer[1]. The assemblies were firstly metalized with thin Au/Ti films. The Au surfaces formed direct bonding without leakage even at room temperature. Moreover, when the packaged structure was annealed at 200 °C, the Ti atoms diffused to the inner surface of the package and absorbed residual gas molecules. This approach allows the simplification of the MEMS packaging process as the bonding and gettering layers can be simultaneously fabricated.However, we found that the Au/Ti film cannot form bonding after degas annealing at 200 °C because Ti oxides were formed on the surface. The annealing at 200 °C effectively removes the water molecules physi and chemi-sorbed on the MEMS assemblies, which deteriorate the packaged environment. The purpose of this study is to develop a metal multilayer that enables both the packaging after degassing at 200 °C and the absorption of residual gas at higher temperatures. The diffusion of Ti atoms can be controlled by fabricating a Pt barrier layer between the Au and Ti layers. A thick Pt layer enables bonding after degassing by preventing the diffusion of Ti during degassing. However, the gas absorption process requires a moderate thickness of the Pt layer because the Ti atoms should reach the surface at high temperatures. In this study, the packaging using thin Au/Pt/Ti multilayers were performed for the advanced MEMS packaging process.For the fabrication of packaged environments, a Si substrate with cavities was bonded with a flat Si substrate using the Au/Pt/Ti layers, as illustrated in Fig. 1. They were thermally oxidized before the bonding procedures. Firstly, the substrates were metalized with Au/Pt/Ti layers of 3/5/40 nm in thickness. The substrates were annealed at 200 °C under vacuum conditions for degassing. Immediately after degassing, the Au surfaces were brought in contact and pressed for the bond formation. Figure 2 shows the mapping of the interfacial gaps observed using a scanning acoustic microscope. Ultrasonic waves reflected in the bright areas, indicating the presence of unbonded areas at the interface. The bright square-shaped regions were due to the packaged areas. While particles on the surface were observed as tiny round voids, there was no leak path for the packages.For the absorption of residual gas molecules, the bonded specimens were annealed at 450 °C for 180 min. Figure 3 depicts the X-ray photoelectron spectra obtained from the inner surface of the annealed package. While the Ti atoms were absent on the surface before the high-temperature annealing step, Ti compounds were present after the high-temperature annealing. This is indicated that the Ti diffused through the Au and Pt layers and reacted with the residual gas molecules on the surface.These results suggested that the 3/5/40-nm-thick Au/Pt/Ti layers can form direct bonding after degassing and also absorb residual gas molecules in the package. We expect that this packaging technique would contribute to future MEMS manufacturing because high-vacuum sealing can be obtained by the simple metal multilayer structure.[1]. Y. Kurashima et al., 45th International Conference on Micro and Nano Engineering, 2019. Figure 1

Ab initio study of elastic properties of orthorhombic cadmium stannate as a substrate for the manufacture of MEMS devices

The elastic properties of the orthorhombic cadmium stannate (Cd2SnO4) were investigated using density functional theory, applying both energy-strain relationship (which is found in the literature) and stress-strain relationship (which we have developed in this study), both in the generalized gradient approximation and local density approximation (LDA) as implemented in the Quantum Espresso code. The results from both methods were found to be in good agreement with each other. However, the values for the stress-strain calculation were found to be relatively higher than those of the energy-strain and also, were those obtained from the LDA. The study found out that Cd2SnO4 possesses desirable elastic properties that are comparable to those of silicon, the dominant substrate material used in the manufacture of Microelectromechanical Systems. The bulk modulus was found to be nearly twice (more than 1.5 times) that of Si. Moreover, the material was found to be ductile, which when combined with the transparent nature that has been studied earlier and is available in the literature, can form a better substrate for the manufacture of transparent and flexible MEMS such as cardiopulmonary sensors, microbolometers, temperature and pressure sensors.

Numerical Simulation of an Entire Wafer Surface during Ozone-Based Wet Chemical Etching

In microelectromechanical system manufacturing and especially in the photovoltaic industry, wet-chemical baths are used for surface structuring, conditioning, and cleaning. Ozone-based wet-chemical...

Eccentric reflective optical fiber MEMS micro-pressure sensor

An eccentric reflective optical fiber micro-electro-mechanical system (MEMS) micro-pressure sensor is proposed in this paper. The core part of the sensor consists of a dual fiber collimator (a fiber collimator with two pigtails) in an eccentric position and a sensitive silicon diaphragm. The sensitive silicon diaphragm adopts the BM (beam-membrane) structure with small structural parameters manufactured by MEMS manufacturing technology. Simulation results show that the BM structure has good sensitivity and high natural frequency. Overall structure of the sensor with the measurement range of 0 ∼ 10 kPa is designed. The way of intensity demodulation ensures the performance and stability of the sensor and makes the sensing system easier to process signals. By building a static test platform and conducting experiments, we can conclude that the sensitivity of the sensor is −0.32 dB kPa−1. Furthermore, the repeatability of the sensor is 1.26%FS (full-scale), the hysteresis of the sensor is 0.95%FS and the zero drift of the sensor is 0.615%FS h–1. By building a dynamic experimental platform and conducting experiments, it can be seen that the response time of the sensor is 0.47 ms (<1 ms), the sensor has good dynamic response.

A Review on Microscopic Visual Servoing for Micromanipulation Systems: Applications in Micromanufacturing, Biological Injection, and Nanosensor Assembly.

Micromanipulation is an interdisciplinary technology that integrates advanced knowledge of microscale/nanoscale science, mechanical engineering, electronic engineering, and control engineering. Over the past two decades, it has been widely applied in the fields of MEMS (microelectromechanical systems), bioengineering, and microdevice integration and manufacturing. Microvision servoing is the basic tool for enabling the automatic and precise micromanipulation of microscale/nanoscale entities. However, there are still many problems surrounding microvision servoing in theory and the application of this technology’s micromanipulation processes. This paper summarizes the research, development status, and practical applications of critical components of microvision servoing for micromanipulation, including geometric calibration, autofocus techniques, depth information, and visual servoing control. Suggestions for guiding future innovation and development in this field are also provided in this review.

SiC nanowire-based SU-8 with enhanced mechanical properties for MEMS structural layer design

In addition to being used for pattern transfer, the negative photoresist SU-8 is widely used as a structural material in microelectromechanical systems (MEMS). Due to its good photopatternability, SU-8 has lower manufacturing costs than many other materials, but its mechanical properties are relatively weak to some extent, which limits its performance. The mechanical properties of epoxy-like SU-8 can be enhanced by adding micro- or nano-fillers such as carbon nanotube, clay, and SiC nanowire, which have superior elastic modulus. In this study, SiC nanowires were used to improve the mechanical properties of SU-8 while the SU-8 retains its photopatternability. The SiC nanowires were uniformly dispersed in SU-8 by stirring and ultrasonication. SU-8 materials with different SiC nanowire contents were fabricated into dog bone samples by lithography. The elastic modulus, storage modulus, and damping factor of the samples were measured by the Dynamic mechanical analysis (DMA) Q800. The experiment result shows that the rigidity and toughness increased, and the damping reduced. The 2 wt% SiC nanowires-reinforced SU-8 had a 73.88% increase in elastic modulus and a 103.4% increase in elongation at break. Furthermore, a spring component made by SiC-doped SU-8 could withstand greater acceleration. The SiC nanowires-reinforced SU-8 has the potential to meet higher requirements in the design and manufacture of MEMS and greatly reduce the manufacturing costs of MEMS devices.

MEMS Fabrication of Silicon Microwire Targets.

Micro- and nano-structured surfaces can lead to increased absorption of incident laser pulses in high power laser experiments. Here we describe how MEMS (Micro-Electro-Mechanical System) manufacturing techniques (in this case, optical lithography, and deep silicon etching), have been used to create surface structured (“microwire”) laser targets consisting of 15um tall, regular arrays of 2um or 3um wide silicon microcolumns for a recent experimental campaign using the Vulcan laser at Rutherford Appleton Laboratory (RAL)