Integrated Fabrication Process Research Articles

Fabrication Process for Monolithic Integration of a Nitride Superconductor-Based Superconducting Qubit with a Single Flux Quantum Control Circuit

We developed a process for fabricating nitride superconductor-based superconducting qubits monolithically integrated with a single flux quantum (SFQ)-based readout and control circuits. Since we used a Josephson junction (JJ) made of an NbN/AlN/NbN tri-layer, including a critical current density ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) of 50 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> as the suitable material for superconducting qubits and SFQ readout/control circuits operating at 20 mK, the JJs for both the qubits and the SFQ circuits could simultaneously be fabricated. The device structure was also composed of three superconductive layers, comprising two superconductive layers as wiring layers and other layers as the top ground plane. Then, we used a Pd film as the resistive layer, which is required as the shunt resistors and the bias resistors for the SFQ control circuits, followed by an investigation of the properties of NbN/AlN/NbN epitaxial junctions and evaluation of the sheet inductance of the base NbN and wiring NbTiN layer. Our results showed the successful fabrication of a JJ with a sufficiently low leakage current and a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> of around 50 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which was close to the target value. Furthermore, the evaluated sheet inductance exceeded 1 pH, which was several times larger than the values obtained for Nb-integrated circuits.

Stochastic magnetic tunnel junction with easy-plane dominant anisotropy

Super-paramagnetic fluctuation of a nanomagnet, when confined by a strong easy-plane anisotropy, can yield GHz speed random signal. A magnetic tunnel junction converts such moment movement into conductance fluctuation, and is useful as an entropy source for modern computing circuits. Here, the authors experimentally explore the base-line behavior of easy-plane magnetic tunnel junctions in the super-paramagnetic limit, using a CMOS back-end integrated fabrication process, and introduce some measurement methodologies to identify factors in device materials and fabrication in need of future optimization.

Polymer Ring-Flexure-Membrane Suspended Gate FET Gas Sensor: Design, Modelling and Simulation.

This work reports the design, modelling, and simulation of a novel polymer MEMS gas sensor platform called a ring-flexure-membrane (RFM) suspended gate field effect transistor (SGFET). The sensor consists of a suspended polymer (SU-8) MEMS based RFM structure holding the gate of the SGFET with the gas sensing layer on top of the outer ring. During gas adsorption, the polymer ring-flexure-membrane architecture ensures a constant gate capacitance change throughout the gate area of the SGFET. This leads to efficient transduction of the gas adsorption-induced nanomechanical motion input to the change in the output current of the SGFET, thus improving the sensitivity. The sensor performance has been evaluated for sensing hydrogen gas using the finite element method (FEM) and TCAD simulation tools. The MEMS design and simulation of the RFM structure is carried out using CoventorWare 10.3, and the design, modelling, and simulation of the SGFET array is carried out using the Synopsis Sentaurus TCAD. A differential amplifier circuit using RFM-SGFET is designed and simulated in Cadence Virtuoso using the lookup table (LUT) of the RFM-SGFET. The differential amplifier exhibits a sensitivity of 2.8 mV/MPa for a gate bias of 3 V and a maximum detection range of up to 1% hydrogen gas concentration. This work also presents a detailed fabrication process integration plan to realize the RFM-SGFET sensor using a tailored self-aligned CMOS process adopting the surface micromachining process.

Facile Fabrication of Oxygen‐Enriched MXene‐Based Sensor and Their Ammonia Gas‐Sensing Enhancement

AbstractVarious sensing materials have been demonstrated to increase the precision of sensing technology. Nevertheless, this complicates the fabrication process for materials integration to obtain devices that can simultaneously accommodate various gas detectors, like electronic nose. The study here focuses on exploring the sensing response of different functionalization of specific sensing materials to provide an alternative way to achieve selective response to multiple gases. Triethoxysilylpropyl succinic anhydride silane (TESPSA) was introduced on 2D material MXene‐Ti3C2Tx to form carboxylic acid terminated MXene (COOH‐Ti3C2Tx) and alternately coated with polyaniline (COOH‐Ti3C2Tx/PANI). This modification doubled up the gas binding sites and improved the binding strength of the Ti3C2Tx surface to NH3 gas molecules. The 5CC‐COOH‐Ti3C2Tx/PANI sensor prepared from five coating cycles showed the highest sensitivity (214.70 %) with fast gas response rate at 80 ppm NH3 (1.75 % s‐1). Therefore, the different signal responses from specific functionalization of the same sensing material functionalization will allow the possible sensor array fabrication to achieve fingerprint‐like sensing map recognition in the presence of mixed gases.

Integrated fabrication process with multiple optimized factors for high power density of IPMC actuator

ABSTRACT Ionic polymer-metal composites (IPMCs) are typical smart materials that are commonly used in bionic applications, including soft robots, bionic flapping aircraft, and bionic fish. However, their low output force seriously limits device performance. Stacking of multiple IPMC actuators to improve the overall performance of soft actuators is a strategy that is used in practical applications. Under the energy dissipation condition in the IPMC stacking structure, if each single IPMC in the structure has high power density, the structure will produce excellent performance with high efficiency that can greatly promote wider application of IPMC actuators. To meet this requirement, a method for fabrication process integration with multiple optimized factors was used to obtain IPMC materials in this paper. Carbon nanotube (CNT) doping, isopropyl alcohol-assisted plating, and hot pressing with a mesoscopic structural mold were selected as typical optimization methods for process integration and were initially investigated separately to determine the optimal process parameters. By combining the best process parameters in an integrated process, the IPMC treated by isopropyl alcohol-assisted plating and CNT doping process (No. AC7) showed excellent actuation performance and high work density (~9.71/12.36 gf, ~14.93/31.89 kJ/m3 under 3/4 VDC). The enhanced performance meets the requirements for practical bionic applications.

Robotic 3D printed lunar bionic architecture based on lunar regolith selective laser sintering technology

The lunar base is not only an experimental station for extraterrestrial space exploration but also a dwelling for humans performing this exploration. Building a lunar base presents numerous obstacles and requires environmental perception, feedback design, and construction methods. An integrated fabrication process that incorporates design, 3D printing workflow, and construction details to build a bionic, reconfigurable and high-performance lunar base prototype is presented in this paper. The research comprises the study of the lunar regolith 3D printing mechanism, the real-time control of powder laying and compaction procedure, and the development of a 3D printing tool end system. In this paper, many scientific questions regarding in situ fabrication on the lunar surface are raised and addressed with the proposal of a progressive optimization design method, the molding principle, and gradation strategy of lunar soil-polyaryletherketone (PAEK) hybrid powder, and the principle of dual-light field 3D laser printing. The feasibility of the technical strategy proposed in this paper is verified by the presented empirical samples.

Effects of High-${\rm{\beta }}$ on Phase-Locking Stability and Tunability in Laterally Coupled Lasers

Phase-locked laser arrays have been extensively investigated in terms of their stability and nonlinear dynamics. Specifically, enhancing the phase-locking stability allows laser arrays to generate high-power and steerable coherent optical beams for a plethora of applications, including remote sensing and optical communications. Compared to other coupling architectures, laterally coupled lasers are especially desirable since they allow for denser integration and simpler fabrication process. Here, we present the theoretical effects of varying the spontaneous emission factor <inline-formula><tex-math notation="LaTeX">$\beta $</tex-math></inline-formula>, an important parameter for micro- and nanoscale lasers, on the stability conditions of phase-locking for two laterally coupled semiconductor lasers. Through bifurcation analyses, we observe that increasing <inline-formula><tex-math notation="LaTeX">$\beta $</tex-math></inline-formula> contributes to the expanding of the in-phase stability region under all scenarios considered, including complex coupling coefficients, varying pump rates, and frequency detuning. Moreover, the effect is more pronounced for <inline-formula><tex-math notation="LaTeX">$\beta $</tex-math></inline-formula> approaching 1, thus underlining the significant advantages of implementing nanolasers with intrinsically high <inline-formula><tex-math notation="LaTeX">$\beta $</tex-math></inline-formula> in phase-locked laser arrays for high-power generation. We also show that the steady-state phase differences can be widely tuned &#x2013; up to <inline-formula><tex-math notation="LaTeX">$\pi $</tex-math></inline-formula> radians &#x2013; by asymmetrically pumping high-<inline-formula><tex-math notation="LaTeX">$\beta $</tex-math></inline-formula> coupled lasers. This demonstrates the potential of high-<inline-formula><tex-math notation="LaTeX">$\beta $</tex-math></inline-formula> nanolasers in building next-generation optical phased arrays requiring wide scanning angles with ultra-high resolution.

Photonic Beamforming for 5G and Beyond: A Review of True Time Delay Devices Enabling Ultra-Wideband Beamforming for mmWave Communications

The next generations of wireless communications are promising high capacity, low latency, and high throughput, enabled by millimeter wave spectrum. Beamforming and beam steering are key requirements for millimeter wave systems due to the fundamental limitations of such high frequencies. Traditional phased array antennas are narrow band and conventional beamforming techniques are too bulky, energy hungry, and expensive to integrate into consumer electronics. Therefore, new approaches of beamforming and beamsteering are required for 5G and beyond due to shortcomings of existing technologies. Here we present a comprehensive review of the photonic true time delay units for application in beamforming of next generations of wireless communications. The prospects and progress of several photonic techniques are discussed here along with their challenges. The fundamental focus of this endeavor will be on the on-chip Silicon-on-Insulator based approaches which enable utilizing conventional CMOS fabrication process for integration with other optical components for compact photonic integrated circuit.

A CMOS-MEMS Accelerometer With U-Channel Suspended Gate SOI FET

There have always been demands for the development of microscale sensors with integrated miniature electronics circuitry. Requirement of external amplification for the conventional MEMS accelerometer poses limitation on scaling, design, fabrication and on-chip Integrated Circuit (IC) compatibility. These limitations could be surpassed by the implementation of integrated CMOS-MEMS architectures for sensors and actuators. Here a novel U-channel suspended gate silicon on insulator field effect transistor (USG-SOIFET) is proposed to circumvent the pseudo short channel effects (P-SCE) present in the suspended gate field effect transistor (SGFET). In the proposed USG-SOIFET, the source and drain are separated by an air-gap and thereby ensuring effective screening of drain electric field penetration into source region. The gate length (L) of USG-SOIFET is 4 times lower than the conventional planar channel SGFET for the same performance of the device. Since the same performance is achieved with a smaller length, this results in a smaller device. Finite Element Modeling (FEM) of USG-SOIFET z-axis accelerometer using CoventerMP1.3 and TCAD process, device modeling and simulation of the USG-SOIFET using Synopsys Sentaurus are presented here. The sensitivity of the accelerometer is 4.185 μA/g with a non-linearity of 4.96% for ± 5 g detection range. The bandwidth of the accelerometer is 100 Hz and the cross-axis sensitivity is found to be 3.52%. A fabrication process integration scheme for realizing USG-SOIFET has also been discussed along with process simulation to demonstrate the feasibility of realizing this new device architecture. This device platform is a potential candidate for monolithic integration with CMOS.

Impact of wet ceria abrasive size on initial step height removal efficiency for Isolated SiO2 film chemical mechanical planarization

In 3-dimensional memories such as NAND flash and cross-point memory, the integration fabrication processes face a notable initial-step-height of an isolated SiO2-film deposition, which is an extremely critical process removing such initial-step-height perfectly via chemical mechanical planarization (CMP). The SiO2-film polishing-rate difference was generated between upper and lower locations of initial-step-height and was evidently depended on the nano-ceria abrasive size in an isolated SiO2-film CMP slurry; that is, the polishing ratio of the upper location to lower location remarkably increased from 4.5:1 to 11.5:1, as the ceria abrasive size increased from 21.3 to 81.0 nm. The difference of polishing rate was associated with a local pressure difference between upper and lower locations of initial-step-height; that is, the local pressure at the upper location remarkably increased from 5.2 to 14.2 PSI, while it at the lower location very slightly decreased from 1.0 to 1.3 PSI, as the ceria abrasive size increase from 21.3 to 81.0 nm. Thus, a larger ceria abrasive size in an isolated SiO2-film CMP slurry led to better removal ability (i.e., a shorter polishing time of initial-step-height and a thicker remaining isolated SiO2-film thickness).

Additively manufactured bi-material metamaterial to program a wide range of thermal expansion

The current research on bi-material diamond metamaterials, which can be used to program the coefficient of thermal expansion (CTE) over a wide range, mainly focuses on the theoretical design, while the corresponding experimental range of the CTEs is far narrower. In this study, a bi-material diamond metamaterial was additively manufactured using two polymers: nylon and polyvinyl alcohol (PVA). Without any need for extra processes such as bonding, welding, and mechanical fitting, the additively manufactured metamaterial integrated the nylon and PVA, providing an integrated fabrication process to ensure the expected programmable CTE. The experimentally measured CTEs agreed well with the theoretical predictions. When the material layout was selected as MAT-1 = PVA and MAT-2 = nylon, programmable CTEs ranging from 217.72 to 694.00 ppm/°C were obtained, which were larger than the CTEs of the nylon and PVA. When the material layout was MAT-1 = nylon and MAT-2 = PVA, even though both the nylon and the PVA had positive CTEs, a wide range of negative CTEs (varying from −25.02 to −369.01 ppm/°C) was obtained. The foregoing wide ranges of programmable CTEs are remarkably larger than the literature results, indicating the enhanced programmability of the bi-material metamaterial and stabilizing the foundation for the further design of multilevel and hierarchical metamaterials.

(Invited) Monolithic Integration of Zinc Tin Oxide Electronics

Oxide semiconductors’ unique properties – a wide bandgap, reasonably high electron mobility, and ease of bulk and thin film preparation – make them prime material candidates for a variety of electronic devices. In this talk, I will describe my group’s recent demonstration of amorphous zinc tin oxide (a-ZTO) electronic devices for thin film monolithic integration of comparatively high voltage (2 to 100 V) power electronics on top of low voltage (VDD ~ 1.2V) state-of-the-art silicon CMOS. We use an in-air solution process to synthesize a-ZTO semiconductor thin films. The resulting bottom-gate, top-contact transistors have field effect mobility of 8.3 cm2V-1s-1 and enhancement-mode behavior with turn-on near zero volts. By controlling ink dilution, we form homogeneous, amorphous channel layers less than 10 nm thick. When passivated with ozone-based atomic layer deposition of Al2O3 to stabilize the exposed top surface of the active layer, the transistors have excellent bias stress stability and sharp sub-threshold turn-on [1,2]. Next, we successfully integrated our thin film a-ZTO transistors directly on top of silicon finFET CMOS in the back end of line. The ZTO device fabrication process is fully compatible with finFET CMOS: after ZTO transistor formation, both the bottom silicon transistors and top a-ZTO transistors function well, with no degradation in performance. To expand the range of devices available for ZTO circuit design, we then developed several other device technologies. Using the Gibbs free energy of oxide formation and ionic radii of the bottom metal thin films as selection criteria, we chose metal contact layers and device structure to form multiple types of components – MISFETs, MESFETs, Schottky diodes, and resistive memory devices [3–5] – using one integrated fabrication process. With these devices, we demonstrate three applications. First, we make full-wave rectifiers that can harvest wireless power from commercial 13.56 MHz RFID signals and use the resulting d.c. voltage to switch underlying low voltage silicon finFETs. Second, we make logic inverters with low switching voltage window and single-transistor amplifiers with high gain by combining a depletion-mode MESFET device as a load and enhancement-mode MISFET devices as the drive transistor. Third, by incorporating a gate-drain offset into the MISFET design, we increase the TFT blocking voltage to above 100 V, enabling future 3-D monolithic integration of high voltage / low voltage interface power electronic circuits on top of silicon CMOS ICs [6].Thanks to G. A. Torres Sevilla and M. M. Hussain for providing silicon CMOS, N. Dasgupta and C. Huber for depositing alumina with ozone, and W. Hu, J. Li and J. Miller for help with TFT fabrication. This work was supported by SPAWAR through DARPA Young Faculty Award N66001-14-1-4046. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of DARPA or SPAWAR. Y.S. was supported in part by the Kwanjeong Educational Foundation. Portions of the work were performed in the Lurie Nanofabrication Facility, which is supported by the University of Michigan’s College of Engineering.[1] C. R. Allemang, R. L. Peterson, IEEE Electron Device Lett. 2019, 40, 1120; [2] Y. Son, A. Liao, R. L. Peterson, J Mater Chem C 2017, 5, 8071; [3] Y. Son, R. L. Peterson, in 2017 75th Annu. Device Res. Conf. DRC, 2017, pp. 1–2; [4] Y. Son, R. L. Peterson, Adv. Funct. Mater. 2019, 29, 1806002; [5] Y. Son, B. Frost, Y. Zhao, R. L. Peterson, Nat. Electron. 2019, 2, 540; [6] C. Allemang, R. L. Peterson, in 2017 75th Annu. Device Res. Conf. DRC, IEEE, South Bend, IN, 2017, pp. 1–2.

Novel Fabrication Process for Integration of Microwave Sensors in Microfluidic Channels.

This paper presents a novel fabrication process that allows integration of polydimethylsiloxane (PDMS)-based microfluidic channels and metal electrodes on a wafer with a micrometer-range alignment accuracy. This high level of alignment accuracy enables integration of microwave and microfluidic technologies, and furthermore accurate microwave dielectric characterization of biological liquids and chemical compounds on a nanoliter scale. The microfluidic interface between the pump feed lines and the fluidic channels was obtained using magnets fluidic connection. The tube-channel interference and the fluidic channel-wafer adhesion was evaluated, and up to a pressure of 700 mBar no leakage was observed. The developed manufacturing process was tested on a design of a microwave-microfluidic capacitive sensor. An interdigital capacitor (IDC) and a microfluidic channel were manufactured with an alignment accuracy of 2.5 μm. The manufactured IDC sensor was used to demonstrate microwave dielectric sensing on deionized water and saline solutions with concentrations of 0.1, 0.5, 1, and 2.5 M.

Reusable, Non-Invasive, and Ultrafast Radio Frequency Biosensor Based on Optimized Integrated Passive Device Fabrication Process for Quantitative Detection of Glucose Levels.

The increase in the number of people suffering diabetes has been the driving force behind the development of glucose sensors to overcome the current testing shortcomings. In this work, a reusable, non-invasive and ultrafast radio frequency biosensor based on optimized integrated passive device fabrication process for quantitative detection of glucose level was developed. With the aid of the novel biosensor design with hammer-shaped capacitors for carrying out detection, both the resonance frequency and magnitude of reflection coefficient can be applied to map the different glucose levels. Meanwhile, the corresponding fabrication process was developed, providing an approach for achieving quantitative detection and a structure without metal-insulator-metal type capacitor that realizes low cost and high reliability. To enhance the sensitivity of biosensor, a 3-min dry etching treatment based on chlorine/argon-based plasma was implemented for realizing hydrophilicity of capacitor surface to ensure that the biosensor can be touched rapidly with glucose. Based on above implementation, a non-invasive biosensor having an ultrafast response time of superior to 0.85 s, ultralow LOD of 8.01 mg/dL and excellent reusability verified through five sets of measurements are realized. The proposed approaches are not limited the development of a stable and accurate platform for the detection of glucose levels but also presents a scheme toward the detection of glucose levels in human serum.

A broadband slant polarized cavity backed microstrip‐fed wide‐slot antenna array

This article deals with the design of a broadband cavity-backed microstrip-fed wide-slot antenna array for L-band applications. For verification purpose, a sample 1 × 4-element antenna array has been designed, manufactured and tested. Experimental results have shown satisfactory agreement with the simulation. The proposed antenna array exhibits a measured impedance bandwidth of 1.4 GHz (90%) with frequency of 0.85 to 2.25 GHz and the gain is higher than 11 dBi. The designed antenna has small size and low weight and can be fabricated using a low-cost fabrication process for easy integration with RF circuits and microwave components. This work is useful for some radar applications and radio frequency identification systems.

Fast and maskless nanofabrication for high-quality nanochannels

Nanochannels are critical components for the fundamental and applied studies of nanofluids. However, the intrinsic low efficiency and high cost of conventional bulk-/surface-/mold-machining methods severely hinder the wide application of nanochannels. Here, we reported a fast, low-cost and maskless fabrication strategy based on friction-induced selective etching in HF/HNO3 mixtures for controllable preparation of diversified and high-quality Si nanochannels. Owing to its distinct anisotropic etching characteristic to scratched area, this novel integrated fabrication process eliminated the limitation of HF/HNO3 mixtures in nanofabrication. Particularly, the etching efficiency and depth of scratched Si in HF/HNO3 mixtures are 12 and 2 times of those in HF solution, respectively. Furthermore, the effects of the volume ratio of HF and HNO3 as well as scratching parameters on nanochannel fabrication were investigated systematically. Cross-sectional transmission electron microscopy observation indicated that the as-fabricated nanochannels have no structural damage. Finally, the corresponding nanofluidic device was designed, fabricated and verified in sequence. The results demonstrate the feasibility of proposed approach for nanochannel fabrication in the area of nanofluids, particularly in analytical chemistry, biochemistry, liquid transport and metering, and energy conversion.

Editors' Choice—Development of Screen-Printed Flexible Multi-Level Microfluidic Devices with Integrated Conductive Nanocomposite Polymer Electrodes on Textiles

We present a flexible plastisol-based microfluidic process integrated with conductive nanoparticle composite polymer (C-NCP) electrodes for flexible active microfluidic devices on textile substrates. First, we characterize the stretchability and flexibility of both plastisol films and microfluidic channels. A maximum elongation increase of 37.5% is observed for plastisol films, and a maximum elongation increase of 17.5% is observed for microfluidic channels. We also demonstrate multiple levels of microfluidic channels. Using a new integrated fabrication process, a device that measures the conductivity of fluid between two electrodes is fabricated on a textile and successfully demonstrated and characterized. For this new fabrication process, flexible screen-printable Ag C-NCP, with resistivity of 2.12 × 10−6 Ω·m, is used for device electrodes. Commercial Ag epoxy, with resistivity of 1 × 10−6 ∼ 10 × 10−6 Ω·m, is also used to fabricate a second set of electrodes for comparison. The device is tested with saline solutions at different salt concentrations, and the current through each saline solution is measured at different voltages using both Ag C-NCP electrodes and Ag epoxy electrodes. The current increases linearly for a given voltage as the salt concentration increases, for devices with both Ag C-NCP electrodes and Ag epoxy electrodes.

Polyimide Fibers with High Strength and High Modulus: Preparation, Structures, Properties, and Applications.

High strength and high modulus polyimide (HSHMPI) fibers are a type of novel high-performance organic fiber with an initial modulus higher than 90 GPa and extremely high tensile strength over 2.5 GPa realizing broad applications in the fields of electronic, engineering, aerospace, and atomic energy industries. There are currently two synthetic pathways, i.e., one-step and two-step methods, developed for the manufacture of HSHMPI fibers. An integrated fabrication process involving wet-spinning followed by thermal imidization is accepted as a typical two-step synthetic route for industrialization of HSHMPI fibers. In this article, the classification, synthetic method and technology, molecular structure, morphology, microstructures, and properties of HSHMPI fibers are summarized extensively. The effects of molecular structure and synthetic technology on the microstructures and overall performance of HSHMPI fibers are discussed. In addition, the trend in development and the application prospect of HSHMPI fibers are analyzed accordingly.

Site-Specific Growth and in Situ Integration of Different Nanowire Material Networks on a Single Chip: Toward a Nanowire-Based Electronic Nose for Gas Detection.

A new method for the site-selective synthesis of nanowires has been developed to enable material growth with defined morphology and, at the same time, different composition on the same chip surface. The chemical vapor deposition approach for the growth of these nanowire-based resistive devices using micromembranes can be easily modified and represents a simple, adjustable fabrication process for the direct integration of nanowire meshes in multifunctional devices. This proof-of-concept study includes the deposition of SnO2, WO3, and Ge nanowires on the same chip. The individual resistors exhibit adequate gas sensing responses toward changing gas concentrations of CO, NO2, and humidity diluted in synthetic air. The data have been processed by principal component analysis with cluster responses that can be easily separated, and thus, the devices described herein are in principle suitable for environmental monitoring.

A modular and generic monolithic integrated MEMS fabrication process

A modular and generic, monolithic integrated MEMS fabrication process is presented to integrate microelectronics (CMOS) with mechanical microstructures (MEMS). The proposed monolithic integrated fabrication process is designed using an intra-CMOS approach (to fabricate the mechanical microstructures into trenches without the need of planarization techniques) and a CMOS module (to fabricate the electronic devices) with a 3 ?m length as minimum feature. The microstructures module is made up to three polysilicon layers, and aluminum as electrical interconnecting material. From simulation results, using the SILVACO® suite (Athena and Atlas frameworks), no significant degradation on the CMOS performance devices was observed after MEMS manufacturing stage; however, the thermal budget of the modules plays a crucial role, because it set the conditions for obtaining the complete set of devices fabricated near their optimal point. Finally, to evaluate and to support the development of the proposed integrated MEMS process, a modular test chip that includes electrical test structures, mechanical test structures, interconnection reliability test structures and functional micro-actuators, was also designed.