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High Temperature SOI ProcessThe high temperature SOI CMOS process uses SOI substratesfor the production of ASICs that operate at temperatures ofup to 250 C.Only fully CMOS compatible process steps are used to manufacture not only standard CMOS circuit elements, includingEEPROM, but also silicon based sensors, actuators and powerdevices.Power DevicesIn close cooperation with industrial partners, Fraunhofer IMSprovides a 600V-CMOS-process for half and full bridge driverchips for IGBTs.CMOS FabricationFraunhofer IMS provides numerous semiconductor productionservices in its 200 mm CMOS production line. The professionally managed class 10 clean room has more than 1300 m2floor space. The 24 hour, 7 days a week operation ensures theuniform quality of our products.The Fraunhofer IMS production line especially caters to theproduction of smaller and medium quantities of ASICs.The production line operates under an ISO 9001:2000 andTS 16949 certified quality management system, assuringstability and reliability of products and production. Timely,reliable and customer-oriented production is our and ourcustomers key to success.13

R E S E A R C H A n D D E V E l O P M E n T AT T H EFRAunHOFER InSTITuTE FOR MICROElECTROnIC CIRCuITS AnD SySTEMS2. SensorsCMOS Image SensorsFraunhofer IMS image sensors are based on CMOS technol-Pressure Sensorsogy, which enables the monolithic integration of sensor andThe basic element of our pressure sensors is a surfacecircuit elements on a single chip. This integration is usedmicromechanical sensor that is fabricated using standarde.g. to control the sensitivity of each individual pixel to avoidCMOS processing equipment. These sensors can be realizedblooming. Fraunhofer IMS has developed a dedicated 0,35 µmfor a wide range of pressures, sharing a single chip with allOpto CMOS process.electronic devices available in a CMOS process, e.g. MOSFETs,capacitors or EEPROMs. The sensors can be configured asA wide range of CMOS image sensors has been developed forabsolute with capacitive readout. The necessary signal conver-our customers and in research projects. The realized sensorssion, linearization and amplification circuits are realized on theinclude high dynamic range sensors, high speed sensors –same chip, effectively eliminating interference on sensor wiringwhich deliver 1000 high quality images per second – andthat is a major issue for discrete solutions. We have alreadyhigh-resolution sensors with “region of interest” function forcreated a variety of innovative products using this monolithicfaster readout of subsections of the pixel array. The CMOSintegration of sensors and signal processing functions likeimage sensors suppress smearing and blooming effects andprogrammable amplifiers, sensor linearization, temperaturealways deliver sharp images. Electronic high-speed shutters en-compensation or wireless interfaces.able the realization of 3D imagers base on laser pulsed basedtime-of-flight measurement.The layout of the sensor element determines its pressurerange, which may be situated between 0.5 to 250 bar, asthe sensor diameter controls the stiffness of the membrane:Smaller and stiffer membranes shift the pressure rangeto higher pressures. Thus the sensors are suitable for themeasurement of pressures ranging from blood, air, and tirepressure all the way to hydraulic oil pressure. The small sizeof the sensor and its associated electronics enables innovativemedical applications for the in vivo measurement of the pressures of blood, brain, eye or other body fluids.14Fraunhofer IMS Annual Report 2011

CMOS Image SensorCMOS Camera15

R E S E A R C H A n D D E V E l O P M E n T AT T H EFRAunHOFER InSTITuTE FOR MICROElECTROnIC CIRCuITS AnD SySTEMSInfrared SensorThe demand for uncooled infrared focal plane arrays (IRFPA)for imaging applications is constantly increasing. Examples forthe application of IRFPAs are thermography, pedestrian detection for automotive, firefighting and infrared spectroscopy.IRFPAs consist of an array of microbolometers located on topof a CMOS substrate which comprehends the readout circuit.Typcal array sizes are for lowcost applications 160 x 120or 320 x 240 pixels. State-of-the-art IRPGAs achieve VGAresolution with 640 x 480 pixels.The microbolometer is a special infrared sensor. TheIR-sensitive sensorelement based on the principle for a microbolometer is fabricated by post-processing on CMOS wafers.The microbolometer converts the infrared radiation into heartenergy and this induces a temperature rise resulting in achange of the electrical resistance. Typical microbolometershave pixel pitch values of 35 µm or 25 µm.BiosensorsBiosensors for point-of-care and home diagnostics are increasingly asked for. Therefore Fraunhofer IMS advances in thedevelopment of a new generation of biosensors. These specialsensors are developed in the Microsystems Technology Labwhere standard CMOS circuits are prepared for or – in future –combined with bioactive layers. Typically, additional metalsor oxides are added, as well as special surface treatment andactivation or the dispension of anchor chemistry for lateranalyte receptor immobilization. This new technology is calledpost-processing and it enables the production of differentsensors for different applications by joining biosensitive layerswith CMOS electronic readout circuitry. This “Bio to CMOS“processing leads to Biohybrid Systems.16Fraunhofer IMS Annual Report 2011

3. ASIC DesignOur customers benefit from our research in these areas, whichThe development of analog, digital and mixed analog-digitalprovides viable solutions for their applications – applicationsintegrated systems is a core competence of Fraunhofer IMS.that demand miniaturization, energy efficiency, cost optimi-Application specific integrated circuits (ASICs) enable ourzation and reliability.customers to provide cheaper and more powerful products.We offer the full spectrum from custom to IP-based ASIC4. Wireless Systems and Transponderssolutions.A core-competence of Fraunhofer IMS is the development andFull-custom ASICs are designed from scratch to accommodaterealization of wireless systems. Research and developmentthe specific requirements of the customer, providing a highlyfocuses, among other things, on wireless sensor networks.optimized product. The IP-based ASIC is based on provenThese networks comprise autonomous sensor modules that aregeneric components, with lower design time and cost. Using adistributed over a large area or volume, and measure physical,mix and match approach both design styles can be combinedchemical and other quantities. The measured values are trans-to leverage the benefits of both.ferred to a central agency, making use of intermediate nodesfor data transfer, or they can be used by similarly distributedThe close co-operation with our in house CMOS productionactor modules for decision-making and control processes.line provides a seamless and efficient path from concept toDevelopment in this field includes new methods for commu-series production. Our long experience in the developmentnication (e.g. protocol stacks, localization) and the realizationof integrated circuits, starting from concept through design,of cost-efficient, miniaturized components. The realization oflayout, and fabrication to testing ensures a short developmentnew products in an efficient and timely manner is facilitatedtime and a minimized design risk.by the use of modular hardware and software componentsthat allow a quick adaptation to application requirements.Our fields of design expertise are: Embedded microcontrollerImportant applications of wireless sensor networks are in High-temperature ASICsthe field of: Smart power integration Industrial automation, e.g. logistics and inventory control. Non-volatile memories Agriculture e.g. monitoring of air and soil parameters. Mixed-signal design Facility management, e.g. remote monitoring of buildings Sensor transponderand infrastructure elements.Beside standard ASIC solutions for all kinds of applications,ASICs with sensors and sensor signal processing integrated onOur customers face a number of challenges that are adresseda single chip have been realized.by our R&D activities. One set these activities addresses toolsfor network development, deployment and maintenance. Oth-These ASICs often combine our core competences in ASICers address the field of energy harvesting, the ability to extractdesign,module power from the environment and obviating the need System-on-Chip (SoC) solutions,for batteries or power cables. Mixed-signal signal processing and Integration of RF building blocks for wireless energy anddata transfer.17

R E S E A R C H A n D D E V E l O P M E n T AT T H EFRAunHOFER InSTITuTE FOR MICROElECTROnIC CIRCuITS AnD SySTEMSThe transponder systems unit at the Fraunhofer IMS offersoffering complete system solutions.system solutions for the integration of novel portable orThese transponder systems are used in smart buildings andstationary transponder read-write devices and base stationsvehicles, industrial automation, medical devices and logistics.into smart network-systems.It also provides base stations for transponder ASICs withintegrated micro sensors developed at Fraunhofer IMS, thusSensor-Transponder System for Medical ApplicationsEnergyCarrierData18Fraunhofer IMS Annual Report 2011

5. Smart Room & Building-SolutionsOne main IMS focus lies on the development of new conceptsAt the Fraunhofer-inHaus-Center, Europe’s leading innova-and electronic systems that provide unobtrusive assistancetion center for smart homes and buildings, IMS cooperatesfor elderly and handicapped people in order to maintain awith six Fraunhofer-Institutes and nearly 100 industrial partnersself-determined life at nursery homes with commercial opera-to develop, test and demonstrate innovative solutions of alltion and to optimize the care service process. We concentratekinds for different application fields in smart buildings. Inespecially on solutions like microelectronic sensor networks indetail IMS offers research, development and complete systems-rooms with software interpretation of data to get benefits likesolutions to component and systems manufacturers, buildersautomatic detection of problems or emergency cases (ambientand operators of homes and commercial buildings for new andassisted living AAL).added value functions on the basis of electronics and software.Another main field of R&D in all inHaus-application segmentsAt the inHaus1-Facility (Smart Home-lab) new domoticis energy efficiency, like in the smart home field. In coopera-techniques to control lighting, doors and windows as welltion with component and systems manufacturers and alsoas heating and ventilation for energy efficiency in homes areenergy providers next-generation-metering and buildingdeveloped and tested. One focus lies on solutions for smartautomation technologies for energy efficiency are developed,metering for more transparency in energy consumption. In thetested and demonstrated.SmartHome-Segment we have also a lot of experience in thefield of user interface solutions for easyer control of technicalThe inHaus Center offers R&D and complete systems-solutionsequipment in homes. User acceptance tests in the smart hometo builders, modernizers or operators of homes and com-lab garantee the new industrial products to have a bettermercial buildings, to implement complete electronic and ITCsuccess chance on the market.systems for new and added value functions. This includes thefollowing aspects:At the inHaus2-Facility (Smart Building-lab) new technical Safety and securitysolutions for commercial properties are being developed, Multimediae.g. for new benefits in facility management and building Support for the elderlyoperation, in the operation process of nursery homes, hotels Energy savingand offices. Light management19

20Fraunhofer IMS Annual Report 2011

developMent of the IMsBudget IMS22Capital Investment IMS23Staff Members IMS2421

DEVElOPMEnTFRAunHOFER IMS2824622081012Fraunhofer IMS Annual Report 2011

608101223

DEVElOPMEnTFRAunHOFER IMS624081012Fraunhofer IMS Annual Report 2011

selected pRojectsof the yeAR 2011Selected Projects of the year 2011ICMOS Devices and Technology26II Silicon Sencors and Microsystems36III CMOS Circuits53IV Wireless Chips an Systems61V Systems an Applications8125

ReducIng the IMpAct of pRocessvARIAtIons on the sensItIvIty ofcMos photodIodesF. Hochschulz, S. Dreiner, H. Vogt, U. PaschenW he n st a nda rd C M O S i ma g e s e n s o rs a re empl oy ed i n appl i c ati ons that requi re the detec ti on of light w it ha v e r y sm a ll s p e ctra l wi d th , l i k e 3 D-ti m e -of-fl i ght i magi ng or other appl i c ati ons wi th l as er l i ght illum ina t ion, proble m s a ri s e , th a t a re n e g l i g i b l e i n s tandard i magi ng appl i c ati ons wi th broadband i l l u m inat ion.F or a giv e n wa v e l e n g th a s tro n g va ri a ti on of the s ens i ti v i ty upon s mal l proc es s rel ated v ari ations of t hedie le c t r ic st a ck o n to p o f th e p h o to d i o d es l eads to l arge di e to di e v ari ati ons of the s ens i ti v i ty .Theoretical Backgroundeffect modulates the QE periodically depending on twoEvery digital imaging method is based on the absorptionmain parameters: the wavelength and the thickness of theof the incident radiation by a substrate material. In case ofdielectric layers that cover the silicon [1]. The amplitude ofCMOS image sensors this material is silicon. Upon absorptionthe modulation depends on the reflectivity of the materialelectron hole pairs are created, which are then separated byboundaries and thus on their refractive indices.the built-in potential of the pn-junction of a photodiode. Inthe visible range of the spectrum one electron hole pair isMotivationcreated per absorbed photon. The amount of electrons thatFig. 1 shows a simulation of the quantum efficiency for twoare detected per incident photon determines the sensitivitydifferent thicknesses of the dielectric stack. As can be seenof a photodetector and is called quantum efficiency (QE). Inthere, the oscillations of the quantum efficiency as a functionCMOS image sensors the photodiodes are connected to theof wavelength are huge. The same is true for the quantumperipheral circuitry by metal interconnects, which are in turnefficiency at a fixed wavelength and a variation of the SiO2isolated from each other by dielectric layers, commonly madethickness. The assumed thickness difference between the twoof SiO2. As CMOS processes include multiple metal layers, thiscurves in Fig. 1 of 0.13 μm is only 2.6 % of the total SiO2SiO2 layer is typically several microns thick. Additionally a coat-thickness. Thickness variations of that magnitude can easilying made of approximately 750 nm silicon nitride is depositedoccur from process induced variations from wafer to wafer andon top of CMOS circuits, called passivation. This passivationon a single wafer from die to die. As image sensors tend to beacts as a diffusion barrier for ions and protects the surfacelarge, a significant thickness difference can even occur on afrom mechanical damage.single die, directly affecting the pixel response non-uniformity(PRNU). A measurement of the discussed photodiodes using aCurrently two different ways to design CMOS image sensorsdiffraction grating monochromator is shown in Fig. 2.are pursued. In front side illuminated (FSI) image sensors theIn standard imaging applications, where the spectral width oflight impinges from the same side as the metal interconnectsthe impinging radiation exceeds the period of the oscillationswhile in back side illuminated (BSI) image sensors the lightthe QE oscillations are mitigated and the QE appears to beimpinges from the back side of the silicon. Here, FSI imageflat. For narrow spectral width applications the exact shape ofsensors are treated.the QE graph and the spectrum of the illumination contributeto the actual sensitivity of the system. Thus, for narrowThe radiant flux that passes through the layers on top oflinewidth applications measures are required to smoothen thethe photo active area is determined by interference effectsdependency of the sensitivity on wavelength and/or thicknessof waves reflected at different material boundaries. Thisvariations of the dielectric stack on the photodiodes.26Fraunhofer IMS Annual Report 2011

Proposed StructureWhen multiple optical path lengths are incorporated into asingle photo active area the resulting sensitivity is a superposition of the sensitivity of the sub-areas. By exploiting theLOCOS (local oxidation of silicon) processing step, which isusually used for the isolation between devices, two differentoptical path lengths can be realized without any additionalprocessing steps. A schematic drawing depicting photo diodescovered with either the thin gate oxide or the thick field oxideis shown in Fig. 3 together with the proposed structure, whereboth are combined on a photodiode. This proposed structureFigure 1: Simulation of the QE for two different SiO2thicknesses. The simulations were conducted usingmonochromatic light.has been filed for patent.Impact on wavelength dependent QE variationsThe oscillations of the QE of the two regions in the photodiode with different thicknesses are out of phase and theirsuperposition is smoother than the QE of each of the originalareas. For a wavelength of 757 nm the oscillations are exactlyout of phase. In this wavelength region the QE is especiallysmooth, as can be seen in Fig. 4 (blue solid line). A photodiodethat has been produced using this method has been measuredand is compared to a simulation in Fig. 5.Figure 2: Comparison of measurements (solid lines) and simulations (dotted lines) of photodiodes featuring a SiO2 thickness of approx. 5 μm. The thicknesses of the different layersused in the simulations have been obtained from scanningelectron microscopic cross sections. The spectrum of themeasurement system was assumed to be Gaussian shaped.The spectral width of the measurement system is 0.8% andhas been convoluted into the simulated QE.Figure 3: Schematic of the three investigated photo diodes.A photodiode under thin gate oxide (left), under thick fieldoxide (middle) and a photodiode according to the proposedstructure with half of its area under thin and the other halfunder thick thermal oxide (right) is shown.27

CMOS DEVICES AnD TECHnOlOgyR E D u C I n g T H E I M PA C T O F P R O C E S SVA R I AT I O n S O n T H E S E n S I T I V I T y O FCMOS PHOTODIODESImpact on process induced QE variationsEven more important than the reduction of the QE variationsfor different wavelengths is its reduction with respect toprocess induced thickness variations for a fixed wavelength.When assuming process variations for the SiO2 thickness of5 0.5 μm and for the SiN thickness of 750 100 nm andsimulating the QE for all thickness c

medical devices the TÜV Süd audited a hard- and software development of the Fraunhofer IMS. That marks a further development step for this medical application. 3 Under the direction of Dr. Tom Zimmermann the working group "Biohybrid Systems" has been enlarged. In this area