Bulk Micromachining Technology Research Articles

A C-shaped hinge for displacement magnification in MEMS rotational structures

The design, analysis, fabrication, and characterization of two distinct MEMS rotational structures are provided; these structures include a classical symmetrical lancet structure and a novel symmetrical C-shaped structure provided with a tilted arm, and both are actuated by thermal actuators. Our proposed C-shaped structure implemented a curved beam mechanism to enhance the movement delivered by the thermal actuators. The geometrical parameters of our proposed device were optimized using the design of experiment (DOE) method. Furthermore, the analytical modeling based on Castigliano’s second theorem and the simulations based on the finite element method (FEM) were used to predict the behavior of the symmetrical C-shaped structure; the results were in good agreement with each other. The MEMS-based rotational structures were fabricated on silicon-on-insulator (SOI) wafers using bulk micromachining technology and deep reactive ion etching (DRIE) processes. The fabricated devices underwent experimental characterization; our results showed that our proposed MEMS rotational structure exhibited a 28% improvement in the delivered displacement compared to the symmetrical lancet structure. Furthermore, the experimental results showed good agreement with those obtained from numerical analysis. Our proposed structures have potential applications in a variety of MEMS devices, including accelerometers, gyroscopes, and resonators, due to their ability to maximize displacement and thus enhance sensitivity.

Design and Fabrication of a High-Temperature SOI Pressure Sensor with Optimized Crossbeam Membrane.

This paper presents a SOI piezoresistive pressure sensor with the crossbeam membrane. The roots of the crossbeam were widened, which solved the problem of the poor dynamic performance of small-range pressure sensors working at a high temperature of 200 °C. A theoretical model was established to optimize the proposed structure, which combined the finite element and the curve fitting. Using the theoretical model, the structural dimensions were optimized to obtain the optimal sensitivity. During optimization, the sensor nonlinearity was also taken into consideration. The sensor chip was fabricated by MEMS bulk-micromachining technology, and Ti/Pt/Au metal leads were prepared to improve the sensor ability of high-temperature resistance over a long time. The sensor chip was packaged and tested, and the experimental results show the sensor achieved an accuracy of 0.241% FS, nonlinearity of 0.180% FS, hysteresis of 0.086% FS and repeatability of 0.137% FS at the high temperature. Given the good reliability and performance at the high temperature, the proposed sensor provides a suitable alternative for the measurement of pressure at high temperatures.

Development and Research of the Sensitive Element of the MEMS Gyroscope Manufactured Using SOI Technology

In this article, based on the developed methodology, the stages of designing the sensitive element of a microelectromechanical gyroscope with an open-loop structure are considered. This structure is intended for use in control units for mobile objects such as robots, mobile trolleys, etc. To quickly obtain a ready-made gyroscope, a specialized integrated circuit (SW6111) was selected, for the use of which the electronic part of the sensitive element of the microelectromechanical gyroscope was developed. The mechanical structure was also taken from a simple design. The simulation of the mathematical model was carried out in the MATLAB/Simulink software environment. The mechanical elements and the entire structure were calculated using finite element modeling with ANSYS MultiPhysics CAD tools. The developed sensitive element of the micromechanical gyroscope was manufactured using bulk micromachining technology−silicon-on-insulator−with a structural layer thickness equal to 50 μm. Experimental studies were carried out using a scanning electron microscope and a contact profilometer. Dynamic characteristics were measured using a Polytec MSA-500 microsystem analyzer. The manufactured structure has low topological deviations. Calculations and experiments showed fairly accurate results for the dynamic characteristics, with an error of less than 3% for the first iteration of the design.

Fabrication and flow rate characterization of a DRIE process based valveless piezoelectric micropump

Micropumps have become one of the major research topics in the field of microfluidics. Different actuators have been used in active micropumps including piezoelectric ones, which convert electrical energy to mechanical energy. In this study, a piezoelectric disc was designed as an actuator and was integrated into a fabricated piezoelectric micropump. Unlike wet etching methods, which is generally used to etch layers of relatively high thickness in the silicon wafer, dry etching was used in this study. Aluminum was used as a mask material during the fabrications-steps, and the fabrication process was shortened with the use of the masking steps. The etching process of the slot, in which the piezoelectric disc was placed, and etching of the inlet/outlet channels were performed simultaneously. Thus, the processing time was significantly shortened. The fabrication of this silicon-based valveless micropump was accomplished by using the DRIE (deep reaction-ion etching) technique, which provided controlled etching. Experiments were conducted on the fabricated micropump with the use of the bulk micromachining technology to deliver the desired pumping action. The leakage and the air entrapment between the consecutive micropump structural layers were satisfactorily eliminated. This micropump is capable of delivering a promising flow rate of 52 (µl min−1) for deionized water, which corresponds to a 150 [Hz] square wave type and a peak-to-peak voltage of 60 (V) Vp -p . No moving mechanical valves were included so that the risks of clogging, reduced performance, and reduced reliability due to wear and fatigue were minimized. Not only gases and liquids but also fluids containing particles could be used as the working fluid for this micropump. The piezoelectric micropump design was optimized to achieve a high time-averaged flow rate (>50 (µl min−1)) with a relatively low excitation voltage (<100 (V) Vp -p ) as opposed to the use of a high excitation voltage.

"Analytical Modelling of the Boron Diffusion and Etching Process for the Accurate Design and Fabrication by Bulk Micromachining Technology of the Silicon Capacitive Pressure Sensors for Biomedical Applications"

"Analytical Modelling of the Boron Diffusion and Etching Process for the Accurate Design and Fabrication by Bulk Micromachining Technology of the Silicon Capacitive Pressure Sensors for Biomedical Applications"

Simulation & analysis of PZT/ P (VDF-TrFE) cantilever beams for health monitoring of building and structures

The design of a piezoelectric PZT/P(VDF-TrFE) based Microelectromechanical system cantilever beams for a very low frequency applications, using silicon bulk-micromachining technology is described in this paper. The natural frequencies of cantilever beams were calculated using the COMSOL software. For signal output, the cantilever-beam structure contains a layer of PZT/P(VDF-TrFE) as well as chrome-gold interdigitated electrodes. According to the simulation results, the cantilever-beam with dimensions of 10mmx3mmx5µm has a lowest resonant frequency of 95.56 Hz, implying that PZT/P(VDF-TrFE) is an appropriate piezoelectric material for really low frequency uses such as building and structure health monitoring.

Recent Advances in Reactive Ion Etching and Applications of High-Aspect-Ratio Microfabrication.

This paper reviews the recent advances in reaction-ion etching (RIE) for application in high-aspect-ratio microfabrication. High-aspect-ratio etching of materials used in micro- and nanofabrication has become a very important enabling technology particularly for bulk micromachining applications, but increasingly also for mainstream integrated circuit technology such as three-dimensional multi-functional systems integration. The characteristics of traditional RIE allow for high levels of anisotropy compared to competing technologies, which is important in microsystems device fabrication for a number of reasons, primarily because it allows the resultant device dimensions to be more accurately and precisely controlled. This directly leads to a reduction in development costs as well as improved production yields. Nevertheless, traditional RIE was limited to moderate etch depths (e.g., a few microns). More recent developments in newer RIE methods and equipment have enabled considerably deeper etches and higher aspect ratios compared to traditional RIE methods and have revolutionized bulk micromachining technologies. The most widely known of these technologies is called the inductively-coupled plasma (ICP) deep reactive ion etching (DRIE) and this has become a mainstay for development and production of silicon-based micro- and nano-machined devices. This paper will review deep high-aspect-ratio reactive ion etching technologies for silicon, fused silica (quartz), glass, silicon carbide, compound semiconductors and piezoelectric materials.

ANALYTICAL MODELING AND SIMULATION OF THE CHEMICAL ETCHING PROCEss OF THE BORON-DOPED SILICON LAYERS FROM BBr3 SOURCE in the micromachining technology

The boron-doped silicon layers commonly used to fabricate various micro-mechanical elements, particularly silicon membranes, are efficient stop-etching barriers, so their control is crucial in the bulk micromachining technology. As the properties of the boron doped layers depends on the type of the doping source and on the diffusion depth in the silicon bulk, a particular analysis should be applied in each specific case. In this paper there are reported the results of an analytical modeling of the boron diffusion profile in silicon, which are applied to simulate the boron diffusion profile at high diffusion temperatures (1050°C, 1100°C, 1150°C and 1200°C), emphasizing a dependence of the diffusion coefficient as a square root of the boron diffusion concentration. It is shown that the comparison of the theoretical results and some experimental diffusion data after diffusion at 1050°C shows a very good agreement, well supporting the analytical modeling. On this basis, the chemical etching rate and the etching time are simulated as a function of the boron diffusion depth in silicon for various etching solutions and etching conditions, providing suitable guiding curves for practical applications in the bulk micromachining technology

Design and Assembly of a Thin-Plate Mechatronic Atomizer by 3D Printing

Microfluidic structures and devices have been studied over decades for the transport of liquid through internal channels using versatile microfabrication schemes such as surface and bulk micromachining technologies. One challenge in consideration of the device design involves the breakthrough of microfluidic reservoir and channels being substantially limited in two-dimensional (2D) geometry. However, recent progress of the emerging 3D printing technologies has showed great potential to overcome this problem in a simple manner. This paper comprehensively reports an additive manufacturing of polylactic acid (PLA) layers to significantly improve the complexity in the formation of the 3D microfluidic structures as compared to conventional micro-manufacturing techniques. Moreover, a handheld mechatronic device with a small height of ~10 mm, assembled with a thin planar atomizer and a micro controller, was produced and demonstrated for generation of droplets (~6 μm in diameter). Both the analytical and experimental results indicated that the grids of channel microstructures were simply varied by different line widths (300–500 μm) and spacing (250–400 μm) 3D printed within the device, thereby providing the design capability for capillary flow. In this regard, a variety of complex micro devices fabricated via computer-aided design (CAD) and the 3D printing method could be applied for more applications than ever, such as microfluidic delivery of biomedical materials and health care devices of a small size.

Design and verification of a structure for isolating stress in sandwich MEMS accelerometer

In this paper, a structure for isolating packaging stress in a sandwich MEMS capacitive accelerometer is proposed and verified. The structure is designed and analyzed by finite element modeling (FEM) using ABAQUS. Two kinds of MEMS accelerometer, one with the stress isolation structure and the other without it, were simulated and compared. Simulation results show that the structure can reduce packaging stress and avoid uneven stress distribution. And then, MEMS accelerometers with and without the stress isolation structure are fabricated based on bulk micromachining technology and experimentally verified. The experimental results show that stabilities of the bias temperature coefficient and scale factor temperature coefficient of the MEMS accelerometer with the stress isolation structure are significantly improved. The comparison results demonstrate that the stress isolating structure is working and the packaging stress is successfully isolated.

Novel high-performance piezoresistive shock accelerometer for ultra-high-g measurement utilizing self-support sensing beams.

This study describes the design and implementation of a novel high-performance piezoresistive accelerometer for the measurement of shock acceleration of up to 100 000 g. The structure of the accelerometer sensing chip was implemented with piezoresistive self-support beams. The piezoresistors were made in piezoresistive sensing micro-beams, which were independent of support beams, to weaken the correlation between measuring sensitivity and resonant frequency. In this way, the measuring sensitivity of the proposed novel piezoresistive accelerometer could be increased without sacrificing resonant frequency. The optimization of structural dimensions of the sensing chip was conducted through finite element method simulations. The sensing chip was fabricated employing bulk-micromachining technology with a silicon-on-insulator wafer. The fabricated accelerometer was encapsulated in stainless shell and evaluated using the Hopkinson bar system. Results demonstrated the proposed accelerometer with the measuring sensitivity of 0.54 µV/g/V and the resonant frequency of 445 kHz.

Miniaturized langasite MEMS micro-cantilever beam structured resonator for high temperature gas sensing

In this paper, a miniaturized lanthanum gallium silicate (langasite, LGS, La3Ga5SiO14) micro-electromechanical systems (MEMS) micro-cantilever beam structured resonator is proposed for high temperature gas sensing applications. The proposed MEMS gas sensor is based on the thickness-shear vibration of the high temperature piezoelectric substrate, LGS, which is fabricated with bulk and surface micromachining technology. The fabrication process is optimized for better stability and integrity of the proposed LGS MEMS gas sensor. In order to improve the gas sensing sensitivity, the sample is further deposited with ZnO nanorods, where abundant gas molecules are expected to be adsorbed. Laboratory tests are subsequently carried out to validate the sensor’s response to various gas species, verify the adsorption mechanism, and investigate the sensitivity of the proposed gas sensor. Results show that compared to several resonator-based gas sensors, the proposed gas sensor displays a better sensitivity for CO2 sensing. The cross-sensitivity of ZnO nanorods between various gas species can be further addressed by principal component analysis technology, where important features can be extracted to distinguish between different gas species and/or concentrations. The proposed MEMS LGS resonator can be utilized for harsh environment applications, such as turbine-engine combustion chambers, nuclear power plants, and hazardous chemical industries, where high temperature can hamper most room temperature gas sensors. Combined with appropriate machine learning technology, the proposed gas sensor can be a good alternative to expensive, bulky gas chromatography devices.

Bulk-micromachined, SOI-based half-bridge silicon strain gauges for high pressure applications

This paper presents a new half-bridge silicon strain gauge fabricated on a silicon-on-insulator (SOI) substrate by MEMS bulk-micromachining technology. These gauges have holes etched through the wafer by deep reactive ion etching (DRIE) and a closed shape with four sides, unlike the current competitive devices with open structures. This unique design minimizes the shifting or rotation of gauge position and enhances the bonding strength during glass-frit bonding, leading to an improved sensor performance and yield, and hence, a reduction in sensor cost. The prototype half-bridge gauges were tested under strains ranging from −170 to 170 and were shown to have a linear output with a typical gauge factor of about 112 and an average hysteresis of 0.0192% FS. In addition, the full bridge output for 0–50 bar pressure shows a typical sensitivity of about 0.345 mV/V/bar, a maximum thermal zero shift of −7.33% FS, and a thermal sensitivity shift of −0.17% FS/°C.

Planar Air-Filled Terahertz Antenna Array Based on Channelized Coplanar Waveguide Using Hierarchical Silicon Bulk Micromachining

A planar air-filled terahertz antenna array based on channelized coplanar waveguide (CCPW) is proposed and fabricated using silicon bulk micromachining technology. Planar air-filled four-unit array composed of two silicon layers is verified at 300 GHz. Periodical field blocking stubs are loaded in the gaps of the CCPW alternatively to break the fringing field symmetry, generating an in-phase radiating aperture. The fabrication technology has two features: first, the silicon dielectrics are completely plated with gold, generating a purely air-filled antenna with high performance and second, the hierarchical micromachining method enables a single silicon layer to be divided into two sublayers, resulting in reduced antenna layers. The numerical result shows a simulated -10 dB impedance bandwidth of 71.1 GHz (25.95%, 238.4-309.5 GHz) and stable fan-shaped beams with broadside gains and radiation efficiencies higher than 10.6 dBi and 87.9%, respectively. Experiment of the fabricated prototype exhibits a bandwidth that totally covers the simulation and stable beams with broadside gains higher than 8.6 dBi. To the best of author's knowledge, this is the first time that a planar air-filled terahertz antenna array is proposed. Moreover, confirmation of the strategy demonstrates the antenna's distinguished suitability to realize antenna-in-package solution.

Amplitude- and Gas Pressure-Dependent Nonlinear Damping of High-Q Oscillatory MEMS Micro Mirrors

Silicon-based micro-electromechanical systems (MEMS) can be fabricated using bulk and surface micromachining technology. A micro mirror designed as an oscillatory MEMS constitutes a prominent example. Typically, in order to minimize energy consumption, the micro mirror is designed to have high quality factors. In addition, a phase-locked loop guarantees resonant actuation despite the occurrence of frequency shifts. In these cases, the oscillation amplitude of the micro mirror is expected to scale linearly with the actuation input power. Here, however, we report on an experimental observation which clearly shows an amplitude depletion that is not in accordance with any linear behaviour. As a consequence, the actuation forces needed to reach the desired oscillation amplitude are by multiples higher than expected. We are able to explain the experimental observations accurately by introducing a single degree-of-freedom model including an amplitude-dependent nonlinear damping term. Remarkably, we find that the nonlinear damping shows a clear gas pressure dependency. We investigate the concepts and compare our findings on two different micro mirror design layouts.

Z-axis tuning fork gyroscope having a controlled anti-phase and freestanding architecture: design and fabrication

This paper reports the design and fabrication of a z-axis tuning fork gyroscope (TFG) having anti-phase controlled and freestanding architectures. The gyroscope is designed to suppress the in-phase sensing mode by using a self-rotation ring. To improve the performance of the TFG by limiting the influence of the squeeze-film damping, the driving and sensing parts of the gyroscope were designed to oscillate in plane. Furthermore, by removing the substrate underneath the device, the slide-film damping in the gap between the proof masses and the substrate is eliminated. The proposed architecture is analysed by finite element method using ANSYS software. The simulated frequencies of the driving and sensing modes are 9.788 kHz and 9.761 kHz, respectively, which determines the sensor bandwidth of 27 Hz. The frequency difference between the driving and sensing modes and the parasitic ones is obtained to be 57.5%. The sensing displacement and driving displacement of the gyroscope at resonance are 0.104 μm and 6.034 μm, respectively. The gyroscope was fabricated based on the bulk micromachining technology. It is shown that the quality factor of the gyroscope is 111.2. The measured sensitivity of the sensor is evaluated to be 11.56 mV/°/s.

Trace 2,4-dinitrotoluene detection using suspended membrane micro-hotplate based on heat absorption monitoring

Detection of trace explosive has become an outstanding research activity recently, and there is a demand for fast and reliable detection techniques. In this paper, the detection of trace 2,4-Dinitrotoluene (DNT) as a nitroaromatic explosive based on heat absorption monitoring (HAM) is introduced which employs heat absorption phenomenon during melting process of explosive particles. Thermodynamic analysis shows that the sensitivity of HAM sensor will be enhanced by increasing of heating efficiency; therefore, the sensor has been designed based on suspended-type membrane (STM) micro-hotplate with the small active area and narrow tethers to achieve high heating efficiency. The designed sensor is fabricated by a simple micro-fabrication process using bulk micromachining technology and the electrical and thermal characterization is performed. Experimental results demonstrate that the fabricated HAM sensor is capable of detecting DNT as little as 20 ppb within 72 ms by the applying power of 3.7 mW. Moreover, the fabricated sensor shows higher selectivity to DNT than other explosives when it is regulated to the melting point of DNT, and to detect DNT concentrations above 150ppb, run-to-run repeatability and device-to-device reproducibility are better than 4%–9%.

Investigation of CMOS Multiplexer Jet Matrix Addressing and Micro-Droplets within a Printhead Chip.

In this study, we demonstrate and investigate a new droplet injection design. We create a thermal inkjet (TIJ) printhead using an application-specific integrated circuit system and bulk micromachining technology (microelectromechanical systems). We design inkjet printhead chips with a new structure and investigate their properties. For the new structure, the integration of complementary metal-oxide-semiconductors (MOSs) and enhancement-mode devices, as well as power switches and a TIJ heater transducer, enables logic functions to be executed on-chip. This capability is used in the proposed design to address individual jets with even fewer input lines than in matrix addressing. A high number of jets (at least 896) can be addressed with only 11 input lines. E1 (Enable 1) and E2 (Enable 2) are set up dependently, and they have the ability to reverse their signals in relation to each other (i.e., if E1 is disabled, E2 is enabled and vice versa). The E1 and E2 signals each service 448 jets. If one of the MOSs is turned on, then it corresponds to a power line with a similar function. If an addressing gate terminal of the other MOS has a discharge action, then we can control a different heater to generate heating bubbles in the jet inks. The operating frequency for addressing these measurements is 18 kHz in normal mode, 26 kHz in draft mode, and 16 kHz in best mode.

(Invited) How to Integrate MEMS on Foundry-Fabricated CMOS Backplanes

A large variety of new applications for Internet of Things (IoT), Industrie 4.0 and other consumer products are pushing volume and manufacturing of microelectromechanical systems (MEMS) into a new phase. Due to massive use of these sensors and actuators in mobile and industrial applications smaller systems combined with low power consumption and higher versatility are required. MEMS are transducers that sense or control physical, chemical or optical quantities creating devices for applications in the area of 3D-motion tracking, pressure sensing, light shaping or detection of irradiation. The combination of MEMS with an application specific integrated circuit (ASIC) based on CMOS technology enables the entire system to interact with outside world. These ASICs are providing required features such as analog-to-digital conversion, amplification, filtering, information processing and storage as well as communication to the outside world. There are different solutions available to combine MEMS with customized CMOS circuits. One choice known as system-in-package (SiP) is the manufacturing of MEMS and CMOS on separate wafers and its subsequent integration in a multi-chip module using interposer/ rewiring technologies. Key advatanges of this technique are high flexibility, high modularity and a complete decoupled manufacturing of CMOS and MEMS. This enables a rapid development and leads to low development costs. And, there is no impact of different sizes between CMOS and MEMS chip. In order to enhance the integration density, to drive system feature size down, to suppress potential parasitic capacitances and to reduce power consumption an integrated manufacturing on the same substrate is a must and known as system-on-chip (SoC) solution. On one hand this approach can be still realized by a multi-wafer processing and a final integration using bonding technologies. This technology is often named as heterogeneous integration. Key advantage of multi-wafer technology is the possibility to use high-performance MEMS materials such as monocrystalline silicon as actuation/sensing material and its integration on CMOS wafers. Disadvantages are the required alignment accuracies when using a metallic bond or limitation for integration densities when using via-last approach. A more consistent way is a complete monolithic integration of MEMS on CMOS substrates. Especially when large transducer arrays are required (e.g. bolometers, micro-mirror arrays, CMUT arrays) a monolithic integration of MEMS on CMOS is the best solution. All advantages are now on hand – high integration densities, low parasitic capacitances and an effective usage of CMOS area. Fraunhofer IPMS applies surface and bulk micromachining technologies for the integration of MEMS on customized CMOS backplanes. To reduce development costs and time-to-market IPMS combines standard CMOS processes offered from CMOS foundries with a subsequent integration of MEMS part in our MEMS fab. Due to the application specific design of the CMOS backplane this concept allows a perfect match between ASIC and MEMS functionalities. In a typical project flow CMOS and MEMS will be manufactured and tested in parallel to shorten development time. After ASIC design is finished it will be tested using Multi- Project- Wafer run (MPW) in a CMOS foundry. Using these MPW runs a complete characterization of CMOS functionality can be realized in an early project state at low costs. Parallel to CMOS testing an entire process development of MEMS part can be done on passive devices in our MEMS fab. If CMOS and MEMS characterization is completed the MEMS part will be monolithically integrated on these customized CMOS backplanes. But there are still some challenges for the integration of MEMS on foundry fabricated CMOS backplanes, e.g.: Modifications of last CMOS/ interconnect/ ILD layers to realize an appropriate interface to MEMS Clarification of PCM (process control monitoring) test environment, depth of test structures and possible arising contamination issues In-chip surface topology after interconnect processing to define necessary actions to achieve required planarity for further processing Tuning mix-and-match lithography to achieve high overlay accuracies (Picture 1: Reached overlay accuracy between last 0,18µm CMOS and first MEMS layer of about 30- 40nm after correction step using i-line stepper) Required chip design features when using sacrificial layer technology IPMS offers a wide range of surface and bulk micromachining technologies which are particularly suitable for the fabrication of sensors and actuators on pre-fabricated CMOS wafers using monolithic integration. Especially surface micromachining using inorganic sacrificial layer technology allows the realization of rather complex MEMS structures on CMOS backplanes. Based on examples such as spatial light modulators (SLM) and capacitive micromachined ultrasonic transducers (CMUT) we will present solutions for the integration of surface micromachined MEMS on customized CMOS substrates. Figure 1

Air-Filled Long Slot Leaky-Wave Antenna Based on Folded Half-Mode Waveguide Using Silicon Bulk Micromachining Technology for Millimeter-Wave Band

An air-filled long slot leaky-wave antenna (LWA) based on folded half-mode waveguide (FHMW) fabricated using silicon substrate is proposed for millimeter-wave application. As is well known, the high-permittivity silicon dielectric is not suitable for antenna design. Thanks to the through-wafer dry etching and gold-plating processes deriving from the silicon bulk micromachining technology, three purely air-filled structures including the vertical part of the FHMW that also acts as the leaky-wave long slot in the top layer, horizontal part of the FHMW and matching section in the middle layer, and coupling slot in the bottom layer constitute the high-performance air-filled long slot LWA. To the best of the authors’ knowledge, this is the first time that an FHMW is adopted for antenna design. Compared with the conventional half-mode waveguide, the profile is lowered, the required silicon layer number is fixed to three, and the design can be more flexible. Experiment of the fabricated prototype shows that the main beam can be scanned from 41° to 49° with a gain variation between 13.15 and 15.41 dBi in the frequency range from 56 to 64 GHz. Moreover, confirmation of the design strategy provides the feasibility to realize the system-in-package solution.