National MEMS Technology Roadmap - Markets, Applications and Devices

MEMS teknologiaa on jo pitkään käytetty lukuisien eri laitteiden valmistamiseen. Osa näistä laitteista on ollut markkinoilla jo useita vuosia, kun taas osa on vasta kehitysvaiheessa. Jotta tutkimus ja kehitystyötä osattaisiin jatkossa kohdistaa oikeille painopistealueille, on tärkeää tietää mihin suuntaan kehitys on menossa. Tämä työ on osa kansallista MEMS teknologioiden tiekartta -projektia ja sen tavoitteena oli selvittää MEMS laitteiden kehityksen suuntaa. Työ toteutettiin laajana kirjallisuustutkimuksena. Lisäksi tulosten tueksi haastateltiin asiantuntijoita Suomen MEMS teollisuudesta. Työssä tarkasteltiin lukuisia jo markkinoilta löytyviä ja vasta kehitteillä olevia MEMS laitteita ja analysoitiin niitä sekä teknisestä että kaupallisesta näkökulmasta. Tutkimuksen perusteella kävi ilmi, että MEMS markkinat ovat pitkään muodostuneet vakiintuneista laitteista kuten mustesuihkupäistä, kiihtyvyysantureista, paineantureista sekä RF suotimista. Lisäksi mikrofonit, gyroskoopit ja optiset laitteet ovat olleet kaupallisesti saatavilla jo pitkään. Markkinat ovat hiljattain alkaneet tehdä tilaa myös uusille MEMS laitteille, joita tulee ulos nopeaa vauhtia. Viimeisimpänä markkinoille tulleita laitteita ovat erilaiset mikrofluidistiikka laitteet, mikrobolometrit sekä yhdistelmäanturit. Pian kaupallisesti saatavia laitteita ovat magnetometrit, automaattitarkennuslaitteet sekä MEMS oskillaattorit. Näiden laitteiden lisäksi kehitteillä on monia uusia MEMS laitteita, jotka saattavat tarjota merkittäviä mahdollisuuksia tulevaisuudessa. Kehitteillä olevia laitteita ovat erilaiset lääketieteelliset laitteet, atomikellot, mikrojäähdyttimet, mikrokaiuttimet, energiantuottolaitteet sekä RFID-laitteet. Kaikki kehitteillä olevista laitteista eivät välttämättä tule menestymään kaupallisesti, mutta jatkuva tutkimustyö osoittaa, että monilla MEMS laitteilla on potentiaalia useissa eri sovelluksissa. Markkinanäkökulmasta tarkasteltuna suurin potentiaali piilee kuluttajaelektroniikka markkinoilla. Muita tulevaisuuden kannalta potentiaalisia markkinoita ovat lääketieteelliset ja teollisuusmarkkinat. Tutkimus osoitti että MEMS laitteiden tutkimukseen ja kehitykseen liittyy monia potentiaalisia painopistealueita tulevaisuudessa. Käyttömahdollisuuksien parantamiseksi monet jo vakiintuneet laitteet kaipaavat vielä parannuksia. Toisaalta, jo olemassa olevia laitteita voidaan hyödyntää uusissa sovelluksissa. Lisäksi monet uusista ja kehitteillä olevista MEMS laitteista vaativat vielä kehitystyötä.MEMS technology has long been applied to the fabrication of various devices from which some have already been in use for several years, whereas others are still under development. In order to find future focus areas in research and development activities in the industry, it is important to know where the development is going. This thesis was conducted as a part of National MEMS technology roadmap, and it aimed for determining the evolution of MEMS devices. The work was conducted as an extensive literature review. In addition, experts from the Finnish MEMS industry were interviewed in order obtain a broader insight to the results. In this thesis various existing and emerging MEMS devices were reviewed and analyzed from technological and commercial perspectives. The study showed that the MEMS market has long been composed of established devices, such as inkjet print-heads, pressure sensors, accelerometers and RF filters. Also gyroscopes, microphones and optical MEMS devices have already been on the market for a long time. Lately, many new devices have started to find their place in the markets. The most recently introduced commercial devices include microfluidic devices, micro bolometers, and combo sensors. There are also a few devices including magnetometers, MEMS oscillators, and auto-focus devices that are currently crossing the gap from R&D to commercialization. In addition to the already available devices, many new MEMS devices are under development, and might offer significant opportunities in the future. These emerging devices include various bioMEMS devices, atomic clocks, micro-coolers, micro speakers, power MEMS devices, and RFID devices. All of the emerging devices might not find commercial success, but the constant stream shows, that there are numerous applications, where MEMS devices could be applied in. From a market point of view, the greatest potential in the future lies in consumer electronics market. Other highly potential markets include medical and industrial markets. The results of the thesis indicate that there are many potential focus areas in the future related to MEMS devices, including improvements of the existing devices in order to gain better utilization, application of the existing devices in new areas, and development work among the emerging devices

Readout electronics for microbolometer infrared focal plane array

Ph.DDOCTOR OF PHILOSOPH

Near Infrared Thermal Imaging for Process Monitoring in Additive Manufacturing

This work presents the design and development of a near infrared thermal imaging system specifically designed for process monitoring of additive manufacturing. The overall aims of the work were to use in situ thermal imaging to develop methods for monitoring process parameters of additive manufacturing processes. The main motivations are the recent growth in use of additive manufacturing and the underutilisation of near infrared camera technology in thermal imaging. The combination of these two technologies presents opportunities for unique process monitoring methods which are demonstrated here. A thermal imaging system was designed for monitoring the electron beam melting process of an Arcam S12. With this system a new method of dynamic emissivity correction based on tracking the melted material is shown. This allows for the automatic application of emissivity values to previously melted areas of a layer image. This reduces the potential temperature error in the thermal image caused by incorrect emissivity values or the assumption of a single value for a whole image. Methods for determining materials properties such as porosity and tensile strength from the in situ thermal imaging are also shown. This kind of analysis from in situ images is the groundwork for allowing part properties to be tuned at build time and could remove the need for post build testing that would determine if it is suitable for use. The system was also used to image electron beam welding and gas tungsten arc welding. With the electron beam welding of dissimilar metals, the thermal images were able to show the preheating effect that the melt pool had on the materials, the suspected reason for the process’s success. For the gas tungsten arc welding process analysis methods that would predict weld quality were developed, with the aim of later integrating these into the robotic welding process. Methods for detecting the freezing point of the weld bead and tracking slag spots were developed, both of which could be used as indicators of weld quality or defects. A machine learning algorithm was also applied to images of pipe welding on this process. The aim of this was to develop an image segmentation algorithm that could be used to measure parts of the weld in process and inform other analysis, like those above

Photodetectors

In this book some recent advances in development of photodetectors and photodetection systems for specific applications are included. In the first section of the book nine different types of photodetectors and their characteristics are presented. Next, some theoretical aspects and simulations are discussed. The last eight chapters are devoted to the development of photodetection systems for imaging, particle size analysis, transfers of time, measurement of vibrations, magnetic field, polarization of light, and particle energy. The book is addressed to students, engineers, and researchers working in the field of photonics and advanced technologies

Developing thermal infrared imaging systems for monitoring spatial crop temperatures for precision agriculture applications

Master of ScienceDepartment of Biological & Agricultural EngineeringAjay ShardaPrecise water application conserves resources, reduces costs, and optimizes plant performance and quality. Existing irrigation scheduling utilizes single, localized measurements that do not account for spatial crop water need; but, quick, single-point sensors are impractical for measuring discrete variations across large coverage areas. Thermography is an alternate approach for measuring spatial temperatures to quantify crop health. However, agricultural studies using thermography are limited due to previous camera expense, unfamiliar use and calibration, software for image acquisition and high-throughput processing specifically designed for thermal imagery mapping and monitoring spatial crop water need. Recent advancements in thermal detectors and sensing platforms have allowed uncooled thermal infrared (TIR) cameras to become suited for crop sensing. Therefore, a small, lightweight thermal infrared imaging system (TIRIS) was developed capable of radiometric temperature measurements. One-time (OT) and real-time (RT) radiometric calibrations methods were developed and validated for repeatable, temperature measurements while compensating for strict environmental conditions within a climate chamber. The Tamarisk® 320 and 640 analog output yielded a measurement accuracy of ±0.82°C or 0.62ºC with OT and RT radiometric calibration, respectively. The Tamarisk® 320 digital output yielded a measurement accuracy of ±0.43 or 0.29ºC with OT and RT radiometric calibration, respectively. Similarly, the FLIR® Tau 2 analog output yielded a measurement accuracy of ±0.87 or 0.63ºC with OT and RT radiometric calibration, respectively. A TIRIS was then built for high-throughput image capture, correction, and processing and RT environmental compensation for monitoring crop water stress within a greenhouse and temperature mapping aboard a small unmanned aerial systems (sUAS). The greenhouse TIRIS was evaluated by extracting plant temperatures for monitoring full-season crop water stress index (CWSI) measurements. Canopy temperatures demonstrated that CWSI explained 82% of the soil moisture variation. Similarly, validation aboard a sUAS provided radiometric thermal maps with a ±1.38°C (α=0.05) measurement accuracy. Due to the TIR cameras’ performance aboard sUAS and greenhouse platforms, a TIRIS provides unparalleled spatial coverage and measurement accuracy capable of monitoring subtle crop stress indicators. Further studies need to be conducted to produce spatial crop water stress maps at scales necessary for variable rate irrigation systems

Colloidal quantum dot (CQD) based mid-wavelength infrared optoelectronics

Colloidal quantum dot (CQD) photodetectors are a rapidly emerging technology with a potential to significantly impact today’s infrared sensing and imaging technologies. To date, CQD photodetector research is primarily focused on lead-chalcogenide semiconductor CQDs which have spectral response fundamentally limited by the bulk bandgap of the constituent material, confining their applications to near-infrared (NIR, 0.7-1.0 um) and short-wavelength infrared (SWIR, 1-2.5 um) spectral regions. The overall goal of this dissertation is to investigate a new generation of CQD materials and devices that advances the current CQD photodetector research toward the technologically important thermal infrared region of 3-5 ?m, known as mid-wavelength infrared (MWIR). In this dissertation, electronic and optoelectronic characteristics of Ag2Se CQD based devices are analyzed by different device architectures with detailed analysis of detector performance parameters. The first part of the dissertation includes the report on the fabrication of solution-processed lateral photoconductive photodetectors. Significant photoresponse is demonstrated in MWIR with the lateral photoconductor at room temperature. The detailed analysis on the effect of ligand exchange as well as temperature and spectral dependent photoresponses is presented. In the second device structure, vertically stacked quantum dot devices are demonstrated. In this device architecture, a barrier QD layer is placed in between mid-wavelength absorber intraband Ag2Se QD layer. The insertion of barrier layer reduces dark current significantly since 1Se Ag2Se QD-1Se PbS QD conduction offset serves as a potential barrier, blocking the transport of thermally generated electrons and holes. In addition, vertical device design improves detector performance parameters significantly at room temperature. At the last part of the dissertation, development of p-n heterojunction diode devices is presented as third device structure. High performance detectors can be realized using a traditional p-n junction device design, however, the heavily-doped nature of intraband quantum dots present a new challenge in realizing diode devices. To address this challenge, an unique trait of blending two different QDs is employed to control electrical property. The fabricated p-n junction devices demonstrate reduced noise current density due to reverse bias operation, which shows improvement in the specific detectivity of the detector at room temperature. Consequently, this dissertation presents the feasibility of uncooled, room-temperature photodetection in the MWIR with intraband silver selenide quantum dots that has the potential to impact numerous applications ranging from all-weather night vision, machine vision, biomedical imaging, to free-space optical communication

Evaluation of Thermal Imaging Camera Spot Temperature Measurements in Structure Fires

Fire service thermal imaging cameras (TICs) are utilized to provide an image of the environment when visibility is limited or impaired by absorbing infrared radiation (IR) emitted from solid objects within its field of view (FOV). This image is often accompanied by a temperature output that may mislead firefighters who do not have proper training of the limitations associated with such quantitative measurements. An evaluation of TIC spot temperature measurements was conducted to determine the TIC’s ability to quantify thermal hazards within an ambient and smoke-filled fire environment. During ambient conditions spot temperature measurements are a function of focal length. During fire experiments participating media (i.e., smoke) impact the IR received by TICs therefore affecting the temperature outputs. This research explores the impact of participating media on solid object temperature measurements from fire service TICs

Advanced CMOS Integrated Circuit Design and Application

The recent development of various application systems and platforms, such as 5G, B5G, 6G, and IoT, is based on the advancement of CMOS integrated circuit (IC) technology that enables them to implement high-performance chipsets. In addition to development in the traditional fields of analog and digital integrated circuits, the development of CMOS IC design and application in high-power and high-frequency operations, which was previously thought to be possible only with compound semiconductor technology, is a core technology that drives rapid industrial development. This book aims to highlight advances in all aspects of CMOS integrated circuit design and applications without discriminating between different operating frequencies, output powers, and the analog/digital domains. Specific topics in the book include: Next-generation CMOS circuit design and application; CMOS RF/microwave/millimeter-wave/terahertz-wave integrated circuits and systems; CMOS integrated circuits specially used for wireless or wired systems and applications such as converters, sensors, interfaces, frequency synthesizers/generators/rectifiers, and so on; Algorithm and signal-processing methods to improve the performance of CMOS circuits and systems

Ultra Low Noise CMOS Image Sensors

CMOS Image Sensors (CIS) overtook the charge coupled devices (CCDs) in low noise performance. Photoelectron counting capability is the next step for CIS for ultimate low light performance and new imaging paradigms. This work presents a review of CMOS image sensors based on pinned photo diodes (PPDs). The latter includes the historical background, the PPD physics and the readout chain circuits used for low-noise performance. The physical mechanisms behind the random fluctuations affecting the signal at different levels of conventional CIS readout chains are reviewed and clarified. This thesis dedicates a particular focus to the readout circuit noise given that it precludes photoelectron counting in conventional CIS. A detailed analytical calculation of the temporal read noise (TRN) in conventional CIS readout chain is presented. The latter suggests different noise reduction techniques at process and circuit design level. Among the noise reduction techniques suggested by the analytical noise calculation, the increase of the oxide capacitance by using a thin oxide in-pixel amplifying transistor, for low 1/f noise, is suggested for the first time. A test chip designed in a 180 nm CIS process and embedding optimized readout chains exploiting the new pixels together with state-of-the-art 4T pixels optimized at process level for low 1/f noise. A mean input-referred noise of 0.4 e-rms has been measured. Compared with the state-of-the-art pixels, also present onto the test chip, the mean RMS noise is divided by more than 2. Based on these encouraging result, a full VGA (640H×480V) imager has been integrated in a standard CIS process. The presented imager relies on a 4T pixel of 6.5 µm pitch with a properly sized and biased thin oxide PMOS source follower. A full characterization of the proposed image sensor, at room temperature, is presented. The sensor chip features an input-referred noise histogram from 0.25 e-rms to a few e-rms peaking at 0.48 e-rms. This sub-0.5 electron noise performance is obtained with a full well capacity of 6400 e- and a frame rate that can go up to 80 fps. The VGA imager also features a fixed pattern noise as low as 0.77%, a lag of 0.1% and a dark current of 5.6 e-/s. Correlated multiple sampling (CMS) is a noise reduction technique commonly used in low noise CIS. This work presents an original design for CMS based on a passive switched-capacitor network, with a minimum number of capacitors. The proposed circuit requires no additional active circuitry, has no impact on the output dynamic range and does not need multiple analog-to-digital conversions. It was verified with transient noise simulations and shows a noise reduction in perfect agreement with ideal CMS. For a future perspective, the impact of the technology downscale on CIS sensitivity from an electronic read noise aspect is investigated. Active imaging in the Terahertz (THz) band is an emerging technology. Source modulation combined with a selective filtering can be used to reduce the noise in CMOS THz imagers. This work presents the first integration of a 1 kpixel CMOS THz imager integrating, in each pixel, a metal antenna with a MOS rectifier, low noise amplification and highly selective filtering, based on a switch-capacitor N-path filter combined with a broad band Gm-C filter. The latter has been tested successfully. An input-referred noise of 0.2 µV RMS corresponding to a total noise equivalent THz power of 0.6 nW at 270 GHz and 0.8 nW at 600 GHz