Henry Baltes | Swiss Federal Institute of Technology (ETH) & University of Zurich (original) (raw)
Papers by Henry Baltes
Proceedings 2000 ICRA. Millennium Conference. IEEE International Conference on Robotics and Automation. Symposia Proceedings (Cat. No.00CH37065)
The rst micromachined bimorph organic ciliary array with on-chip CMOS circuitry is presented. Thi... more The rst micromachined bimorph organic ciliary array with on-chip CMOS circuitry is presented. This device is composed o f a n 8 8 array of cells each having four orthogonally oriented actuators in an overall die size of 9:4mm 9:4mm. The polyimide based actuators were fabricated directly above the selection and drive circuitry. Selection and activation of actuators in this array shows that integration was successful. The integration of CMOS electronics and MEMS micromechanisms allows the implementation of new tasklevel micromanipulation strategies. New low-level control algorithms actuator gaits were also demonstrated. The array was programmed t o p erform several kinds of manipulation tasks, including linear translation, diagonal motion, as well as vector eld operations such as squeeze eld and radial eld orienting and centering. Preliminary experiments were also performed with the rst implementation of a universal eld" that uniquely positions and orients any non-symmetric part without programming or sensor feedback. All tasks were demonstrated using thin silicon dice o f a b out 3mm 3mm 0:5mm size as the object being moved.
Proceedings IEEE The Tenth Annual International Workshop on Micro Electro Mechanical Systems. An Investigation of Micro Structures, Sensors, Actuators, Machines and Robots
We developed a new packaging method based on flip-chip mounting, for integrated micro sensors. Th... more We developed a new packaging method based on flip-chip mounting, for integrated micro sensors. The technique is demonstrated with the fabrication, packaging, and characterization of CMOS anemometers. The sensors are produced using the commercial 2 pm CMOS process of EM Microelectronic-Marin SA, Switzerland, followed by bulk silicon micromachining. They consist of a membrane of the (CMOS dielectrics heated by integrated polysilicon resistors. Integrated thermopiles detect wind-induced temperature differences on the membrane. The sensor chip is flip-chip mounted on a ceramic substrate. An opening in the substrate is aligned with the sensor, and enables free advection. The electrical interconnections between the chip bumps and the substrate contact pads are soldered with PbIn,,. Concurrently a bump frame on the chip is soldered to a corresponding structure on the substrate. This bump frame seals the rest of the chip from the medium flowing over the sensor membrane. The sensor responses were characterized in a wind-tunnel as a function of sensor orientation, air velocity, and packaging parameters. The output signals increase monotonically with the air velocity up to 36 mV at 38 m i 1 (12 Beaufort) at a heating power of 4.7 mW. INTIRODUCTION A promising approach to microsystems is to cointegrate sensors, actuators, and electronic signal conditioning and read-out circuitry on the same chip by combining industrial CMOS technology and micromachining [ 1,2]. However this implies new challenges. In particular the packaging of the devices becomes a demanding task. The encapsulation has to fulfill the following conflicting requirements: (i) The system has to be electrically contacted. (ii) The electronic part of the system ought to be completely screened from the environment. (iii) The sensor needs protection against mechanical contact and undesired media. (iv) The encapsulation of the sensor must be partially transparent to the physical parameter to be sensed. (v) The solutions should be optimized for high reliability and low cost. We introduce a packaging method which successfully addresses these challenges. The number of steps needed to electrically contact and partially seal the MEMS 203
Microtechnology and Mems, 2002
Since its invention in 1986, the Atomic Force Microscope (AFM) [106] has evolved at an exceptiona... more Since its invention in 1986, the Atomic Force Microscope (AFM) [106] has evolved at an exceptional speed from a laboratory prototype to a commercial instrument utilized in several areas of research as well as in industrial applications, e.g. for quality control. These instruments have improved in quality and usability significantly over the last decade. Still, the drawback of commercially available AFM systems is their low throughput due to the serial nature of the involved scanning process and the limited scanning range, which makes the investigation of large samples laborious. Optical means are mostly employed to detect the displacement of the cantilever probe. Especially when operating in vacuum or in a hostile environment the adjustment of the cantilever and the optical detector is time consuming. Furthermore, the exchange of a damaged probe is complicated. The use of industrial CMOS processes helps to improve AFM sensors by making use of the integration of read-out circuitry and sensing and actuation elements on a single chip. Moreover, arrays of CMOS-based cantilevers can be fabricated on a single chip enabling parallel scanning and redundancy if one cantilever fails. In this chapter arrays of CMOS cantilevers for Parallel Scanning AFM are presented. The cantilevers have integrated piezoresistive read-out and thermal actuators. Two kinds of cantilever arrays have been realized: a 2-cantilever array and an improved 10-cantilever array. After an introduction into the field of Atomic Force Microscopy, the 2-cantilever array is discussed and experimental results are presented. Finite element simulations are described, that lead to a second improved cantilever design. The system design of the improved 10-cantilever array is discussed. The chapter concludes with experimental results obtained with the novel array.
Integrated thermal sensors can be made by industrial CMOS IC technology combined with subsequent ... more Integrated thermal sensors can be made by industrial CMOS IC technology combined with subsequent bulk or surface micromachining for thermal insulation. We review recent work on CMOS-based thermal radiation, AC power, mass flow, and pressure sensors with on-chip signal conditioning circuitry. We discuss diagnostic microstructures for the measurement of process-dependent thermal properties of CMOS materials.
Sensors and Actuators A: Physical, 1992
With 'photo-ASKS' comprlsmg hght-sensitive structures, hght-emmmg devices and analog and chgtal c... more With 'photo-ASKS' comprlsmg hght-sensitive structures, hght-emmmg devices and analog and chgtal clrcults, complete optlcal metrology systems can be Integrated on a smgle chip We report the reahzatlon of key components of such photo-ASICs usmg an mdustrual IC CMOS process We achieve photodlodes with an external quantum efficiency of 50-80% m the visible spectrum and posItIon-sensltlve devices (PSDs) with a spatial non-hneanty of around 0 3% We demonstrate surface-channel CCDs with a charge-transfer efficiency of 99 8% at room temperature, as well as bucket-bngade devices (BBDs) with a lower charge-transfer efficiency of 96% Light-emlttmg diodes (LEDs) are reahzed, emlttmg Infrared hght at 1160 nm (forward blased) and broadband vlslble yellow light with a spectral maximum at 640 nm (reverse biased) We discuss simple apphcatlons of passive photo-ASKS, such as a centrmd detector, a 3-D camera, a motion detector and a focus sensor, used to obtam a relative measure for the local focus of an optically Imaged scene, for example, m a photographic camera
This thesis describes the conception, design, implementation and ex¬ perimental characterization ... more This thesis describes the conception, design, implementation and ex¬ perimental characterization of ultrasound micro-systems. Such systems are intended for ultrasound control applications in industrial automa¬ tion, which so far relied on costly and bulky piezo-ceramic transducers. Two examples are discussedan ultrasound barrier detector micro¬ system and a miniaturized range finder. Both application make use of micromachinecl silicon membrane transducers, which are fabricated in a standard bipolar, CMOS or BiCMOS circuit technology. The mem¬ branes are about 1mm by lmm of size and can be excited thermally to emit ultrasound power at 80-100 kHz. They can also be stimulated by incident ultrasound waves and the resulting membrane vibrations are detected by a piezo-resistive Wheatstone bridge. The barrier detector micro-system is intended for the presence de¬ tection of liquid, transparent or light sensitive objects, especially at places where space is limited. It consists of an ultrasound transmit¬ ter/receiver pair facing each other at a distance up to 10 cm. No wired connection exists between transmitter and receiver in order to allow high flexibility within the application. The challenge in the design of the barrier detector is how to secure reliable operation of the system despite the non-idealities of the membrane transducers. Among oth¬ ers these are in particular the temperature and process dependence of the narrow bandwidth (quality factor Q-100) mechanical resonance and the weak sensor signals. An elegant solution is found to provide best performance of the transmitter. By embedding the membrane into the loop of an electro-mechanical oscillator, the hitter's oscillation fre¬ quency is always determined by the membrane resonance, where the emitted ultrasound power is maximum. For the receiver a simple and efficient self-calibration concept is developed, which is used to maximize the receiver sensitivity. It consists of a high gain (70 clB), ac-coupled amplification stage to boost the extremely weak sensor signals to a suf¬ ficient level. A subsequent tuning/tracking circuit automatically tunes vu Vlll Abstract the membrane resonator in order to find and track the highest possible sensitivity. Objects can be detected within 10 ms when they interrupt the sound-path between transmitter and receiver. The miniaturized range finder system uses the silicon membranes as transmitter/receiver for contact-less short range distance measurement in air. It can determine the distance from an object to the membrane surface up to 10 cm with a 5 mm precision and features an extremely small blind space of 1 cm, where the measurement is not possible. For the micro-system a novel quasi continuous-wave measurement proce¬ dure called A/ phase shift method is developed to enable the short range measurement despite the slow thermal excitation of the silicon membrane transducers. The new method, however, requires a coherent beam of ultrasound waves. This is performed by applying the concept of a phase locked loop circuit (PLL) to the tunable membrane resonator. The resulting electro-mechanical PLL is able to lock the emitted ultra¬ sound waves to the electrical signal and hence generates the required coherent beam. The same unique concept is used for the self-calibrating receiver to guarantee zero degree electrical phase shift and at the same time maximum sensitivity. Experimental and theoretical investigations Ansteuerclcktronik zulässt (monolithisches Mikrosystem). Die Systemarchitcktur ist in beiden Fällen so gewählt, class alle Funktionen vollstän¬ dig integriert werden können und class insbesondere eine effiziente Kom¬ bination von Sender und Empfänger im selben Chip ermöglicht wird. Ein Mikrosystem mit einer derartigen Architektur wird dann zu einer kostengünstigen, flexiblen und daher attraktiven Konkurrenz für viele bestehende piezo-keramische Lösungen.
TRANSDUCERS '03. 12th International Conference on Solid-State Sensors, Actuators and Microsystems. Digest of Technical Papers (Cat. No.03TH8664), 2003
A monolithic gas sensor system is presented, which includes on a single chip an array of three me... more A monolithic gas sensor system is presented, which includes on a single chip an array of three metal-oxide covered microhotplates, each of which is individually addressable and can be operated at a defined temperature. The monolithically co-integrated circuitry consists of three independent temperature control loops for the microhotplates and an on-chip temperature sensor. An innovative design of a circular-shape microhotplate has been realized. Temperature homogeneity and thermal efficiency of the membrane were optimized for use with thick films of nanocrystalline metal oxides as sensitive layers. A SnO 2based sensing material with noble metal doping was operated at different temperatures as well as in temperature pulsing mode. Chemical sensor measurements have been conducted with, e.g., CO to show the system performance.
Microtechnology and MEMS, 2007
The use of general descriptive names, registered names, trademarks, etc. in this publication does... more The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.
Technical Digest. MEMS 2002 IEEE International Conference. Fifteenth IEEE International Conference on Micro Electro Mechanical Systems (Cat. No.02CH37266)
We present a magnetic actuation scheme combined with a piezoresistive MOS-transistor sensing tech... more We present a magnetic actuation scheme combined with a piezoresistive MOS-transistor sensing technique for CMOS-integrated resonators. It was developed for a cantilever resonator with on-chip amplifier, but is broadly applicable. The high efficiency of electromagnetic actuation significantly reduces the required operation power and allows for the use in portable devices. By use of stress-sensitive PMOS-transistors as active loads, the size of the piezoresistive Wheatstone bridge is significantly reduced. Thirdly, the post-processing sequence of the cantilever resonator has been optimized, so that only one photolithography step is necessary to release the whole mechanical structure. This facilitates the fabrication, increases yield and, thus, reduces fabrication cost.
Sensors Update, 2003
Sensor arrays based on industrial CMOS-technology combined with post-CMOS micromachining (CMOS ME... more Sensor arrays based on industrial CMOS-technology combined with post-CMOS micromachining (CMOS MEMS) are a promising approach to low-cost sensors. In the first part of this article [1], the state of research on CMOS-based gas sensor systems was reviewed, and a platform technology for monolithic integration of three different transducers on a single chip was described. In this second part, the transduction principles of three polymer-based gas sensors are detailed and the read-out circuitry is portrayed. The first transducer is a micromachined resonant cantilever. The absorption of analyte in the chemically sensitive polymer causes shifts in resonance frequency as a consequence of changes in the oscillating mass. The cantilever acts as the frequency-determining element in an oscillator circuit, and the resulting frequency change is read out by an on-chip counter. The second transducer is a planar capacitor with polymer-coated interdigitated electrodes. This transducer monitors changes in the dielectric constant upon absorption of the analyte into the polymer matrix. The sensor response is read out as a differential signal between the coated sensing capacitor and a passivated reference capacitor, both of which are incorporated into the input stage of a switched capacitor second-order RD-modulator. The third transducer is a thermoelectric calorimeter, which detects enthalpy changes upon ab-/desorption of analyte molecules into a polymer film located on a thermally insulated membrane. The enthalpy changes in the polymer film cause transient temperature variations, which are detected via polysilicon/aluminum thermocouples (Seebeck effect). The small signals in the lVrange are first amplified with a low-noise chopper amplifier, then converted to a digital signal using a RD-A/D-converter and finally decimated and filtered with a digital decimation filter.
Smart Structures and Materials 1999: Smart Electronics and MEMS, 1999
We review selected micro-and nano-systems developed recently at the Physical Electronics Laborato... more We review selected micro-and nano-systems developed recently at the Physical Electronics Laboratory of ETh Zurich using industrial CMOS technology in combination with post-processing micromachining and film deposition: (i) an infrared sensor microsystem for presence detection of persons, (ii) calorimetric, capacitive, and gravimetnc chemical sensor microsystems for detection of volatile organic compounds in air, and (iii) a parallel scanning AFM chip. The microsystems combine sensor structures and read-out circuitry on a single chip.
IEEJ Transactions on Sensors and Micromachines, 2000
Distributed Manipulation, 2000
The rst micromachined bimorph organic ciliary array with on-chip CMOS circuitry is presented. Thi... more The rst micromachined bimorph organic ciliary array with on-chip CMOS circuitry is presented. This device is composed of an 8 8 array of cells each h a ving four orthogonally oriented actuators in an overall die size of 9:4mm 9:4mm. The polyimide based actuators were fabricated directly above the selection and drive circuitry. Selection and activation of actuators in this array shows that integration was successful. The array was programmed to perform several kinds of manipulation tasks, including linear translation, diagonal motion, as well as vector eld operations such a s squeeze eld and radial eld orienting and centering. Preliminary experiments were also performed with the rst implementation of a universal eld" that uniquely positions and orients any non-symmetric part without programming or sensor feedback. All tasks were demonstrated using thin silicon dice of about 3mm 3mm 0:5mm size as the object being moved.
Analog Circuit Design, 1997
This thesis is focused on sensors based on industrial integrated circuit technology (IC microsens... more This thesis is focused on sensors based on industrial integrated circuit technology (IC microsensors). This approach is driven by a market which demands aug¬ mented functionality and performance affordable for an increasing number of cus¬ tomers. The fabrication of sensors by integrated circuit technology offers the potential to exploit the unique features of microelectronics, namely cost effective batch fabrication, miniaturization with established reliability, and cointegration of circuits. Beside the efficient production of the sensor it must be ensured that the
Sensors and Actuators A: Physical, 1993
Two different unmodified mdustnal CMOS processes have been used for the mtegratlon of h&y mte-rdt... more Two different unmodified mdustnal CMOS processes have been used for the mtegratlon of h&y mte-rdtgttated pn structures Under forward bias these pn Junctions emlt narrow-band mfrared bght at 1160 nm Hrlth an electncal-to-opt& power conversion e.tkency of typically 10e4 The same Junctions show broad-band vlslble-hght ermsslon between 450 and 800 nm m the avalanche breakdown region under reverg has with effinencles of the order of lo-* ti 1s already enough for a first few practical applications as hght-enuttmg devices (LED@ No satisfactory explanation for this emlsslon effect, fitting all the expenmentally observed electro-optical and physical properties of our salmon LEDs, has been found yet
IEEJ Transactions on Sensors and Micromachines, 1999
This paper presents improved capacitive readout type sensor interface circuits designed for CMOS ... more This paper presents improved capacitive readout type sensor interface circuits designed for CMOS inte grated chemical sensors. The sensor is fabricated using a 0.8 ym CMOS IC process technology. Volatile organic compounds (VOCs) are detected by measuring the capacitance change of polymer coated interdigital capacitors due to analyte absorption. The delta-sigma modulation sensor interface uses a sensor capacitor and a reference capacitor as those for the input of the frontend switched capacitor integrator. An improved capacitance sensing scheme is proposed to improve the sensitivity.
SPIE Proceedings, 1998
Thermally-based transducer microsystems can be made by using CMOS IC technology, post-CMOS microm... more Thermally-based transducer microsystems can be made by using CMOS IC technology, post-CMOS micromachining or deposition, and flip-chip packaging. Technology steps, materials, and physical effects pertinent to thermal microtransducers are summarized together with microheater, thermistor, thermopile, thermal isolation, and heat sink structures. An infrared intrusion detector, a thermal air flow sensor, and thermally excited microresonators for acoustic and chemical sensing serve as demonstrators. We discuss the characterization of process-dependent properties of CMOS materials crucial for thermal microtransducer CAD.
Technical Digest. MEMS 2002 IEEE International Conference. Fifteenth IEEE International Conference on Micro Electro Mechanical Systems, 2002
The paper reviews the state-of-the-art in the field of CMOS-based microelectromechanical systems ... more The paper reviews the state-of-the-art in the field of CMOS-based microelectromechanical systems (MEMS). The different CMOS MEMS fabrication approaches, pre-CMOS, intermediate-CMOS, and post-CMOS, are summarized and examples are given. Two microsystems fabricated with post-CMOS micromachining are presented, namely a mass-sensitive chemical sensor for detection of organic volatiles in air and a 10-cantilever force sensor array for application in scanning probe microscopy. The paper finishes with a look into the future, discussing key challenges and future application fields for CMOS MEMS.
29th European Solid-State Circuits Conference, 2003
A novel monolithic differential thermal analyzer fabricated in industrial CMOS-technology combine... more A novel monolithic differential thermal analyzer fabricated in industrial CMOS-technology combined with post-CMOS micromachining is presented, which includes three micro-hotplates and all necessary driving and signal conditioning circuitry. Three on-chip proportional temperature controllers (one controller per micro-hotplate), regulate the micro-hotplate temperature up to 350°C with a steady-state error of less than 1% of the preset micro-hotplate temperature. A circular microhotplate design was developed to improve the hotplate power efficiency. The thermal analysis performance was assessed by melting point measurements of ammonium nitrate (melting point at 169.6°C).
PROCEEDINGS OF THE IEEE, 2003
Microfabrication processes for chemical and biochemical sensors are reviewed. Standard processing... more Microfabrication processes for chemical and biochemical sensors are reviewed. Standard processing steps originating from semiconductor technology are detailed, and specific micromachining steps to fabricate three-dimensional mechanical structures are described. Fundamental chemical sensor principles are briefly abstracted and corresponding state-of-the-art examples of microfabricated chemical sensors and biosensors are given. The advantages and disadvantages of either fabricating devices in IC fabrication technology with additional microfabrication steps, or of using custom-designed nonstandard microfabrication process flows are debated. Finally, monolithic integrated chemical and biological microsensor systems are presented, which include transducer structures and operation circuitry on a single chip.
Proceedings 2000 ICRA. Millennium Conference. IEEE International Conference on Robotics and Automation. Symposia Proceedings (Cat. No.00CH37065)
The rst micromachined bimorph organic ciliary array with on-chip CMOS circuitry is presented. Thi... more The rst micromachined bimorph organic ciliary array with on-chip CMOS circuitry is presented. This device is composed o f a n 8 8 array of cells each having four orthogonally oriented actuators in an overall die size of 9:4mm 9:4mm. The polyimide based actuators were fabricated directly above the selection and drive circuitry. Selection and activation of actuators in this array shows that integration was successful. The integration of CMOS electronics and MEMS micromechanisms allows the implementation of new tasklevel micromanipulation strategies. New low-level control algorithms actuator gaits were also demonstrated. The array was programmed t o p erform several kinds of manipulation tasks, including linear translation, diagonal motion, as well as vector eld operations such as squeeze eld and radial eld orienting and centering. Preliminary experiments were also performed with the rst implementation of a universal eld" that uniquely positions and orients any non-symmetric part without programming or sensor feedback. All tasks were demonstrated using thin silicon dice o f a b out 3mm 3mm 0:5mm size as the object being moved.
Proceedings IEEE The Tenth Annual International Workshop on Micro Electro Mechanical Systems. An Investigation of Micro Structures, Sensors, Actuators, Machines and Robots
We developed a new packaging method based on flip-chip mounting, for integrated micro sensors. Th... more We developed a new packaging method based on flip-chip mounting, for integrated micro sensors. The technique is demonstrated with the fabrication, packaging, and characterization of CMOS anemometers. The sensors are produced using the commercial 2 pm CMOS process of EM Microelectronic-Marin SA, Switzerland, followed by bulk silicon micromachining. They consist of a membrane of the (CMOS dielectrics heated by integrated polysilicon resistors. Integrated thermopiles detect wind-induced temperature differences on the membrane. The sensor chip is flip-chip mounted on a ceramic substrate. An opening in the substrate is aligned with the sensor, and enables free advection. The electrical interconnections between the chip bumps and the substrate contact pads are soldered with PbIn,,. Concurrently a bump frame on the chip is soldered to a corresponding structure on the substrate. This bump frame seals the rest of the chip from the medium flowing over the sensor membrane. The sensor responses were characterized in a wind-tunnel as a function of sensor orientation, air velocity, and packaging parameters. The output signals increase monotonically with the air velocity up to 36 mV at 38 m i 1 (12 Beaufort) at a heating power of 4.7 mW. INTIRODUCTION A promising approach to microsystems is to cointegrate sensors, actuators, and electronic signal conditioning and read-out circuitry on the same chip by combining industrial CMOS technology and micromachining [ 1,2]. However this implies new challenges. In particular the packaging of the devices becomes a demanding task. The encapsulation has to fulfill the following conflicting requirements: (i) The system has to be electrically contacted. (ii) The electronic part of the system ought to be completely screened from the environment. (iii) The sensor needs protection against mechanical contact and undesired media. (iv) The encapsulation of the sensor must be partially transparent to the physical parameter to be sensed. (v) The solutions should be optimized for high reliability and low cost. We introduce a packaging method which successfully addresses these challenges. The number of steps needed to electrically contact and partially seal the MEMS 203
Microtechnology and Mems, 2002
Since its invention in 1986, the Atomic Force Microscope (AFM) [106] has evolved at an exceptiona... more Since its invention in 1986, the Atomic Force Microscope (AFM) [106] has evolved at an exceptional speed from a laboratory prototype to a commercial instrument utilized in several areas of research as well as in industrial applications, e.g. for quality control. These instruments have improved in quality and usability significantly over the last decade. Still, the drawback of commercially available AFM systems is their low throughput due to the serial nature of the involved scanning process and the limited scanning range, which makes the investigation of large samples laborious. Optical means are mostly employed to detect the displacement of the cantilever probe. Especially when operating in vacuum or in a hostile environment the adjustment of the cantilever and the optical detector is time consuming. Furthermore, the exchange of a damaged probe is complicated. The use of industrial CMOS processes helps to improve AFM sensors by making use of the integration of read-out circuitry and sensing and actuation elements on a single chip. Moreover, arrays of CMOS-based cantilevers can be fabricated on a single chip enabling parallel scanning and redundancy if one cantilever fails. In this chapter arrays of CMOS cantilevers for Parallel Scanning AFM are presented. The cantilevers have integrated piezoresistive read-out and thermal actuators. Two kinds of cantilever arrays have been realized: a 2-cantilever array and an improved 10-cantilever array. After an introduction into the field of Atomic Force Microscopy, the 2-cantilever array is discussed and experimental results are presented. Finite element simulations are described, that lead to a second improved cantilever design. The system design of the improved 10-cantilever array is discussed. The chapter concludes with experimental results obtained with the novel array.
Integrated thermal sensors can be made by industrial CMOS IC technology combined with subsequent ... more Integrated thermal sensors can be made by industrial CMOS IC technology combined with subsequent bulk or surface micromachining for thermal insulation. We review recent work on CMOS-based thermal radiation, AC power, mass flow, and pressure sensors with on-chip signal conditioning circuitry. We discuss diagnostic microstructures for the measurement of process-dependent thermal properties of CMOS materials.
Sensors and Actuators A: Physical, 1992
With 'photo-ASKS' comprlsmg hght-sensitive structures, hght-emmmg devices and analog and chgtal c... more With 'photo-ASKS' comprlsmg hght-sensitive structures, hght-emmmg devices and analog and chgtal clrcults, complete optlcal metrology systems can be Integrated on a smgle chip We report the reahzatlon of key components of such photo-ASICs usmg an mdustrual IC CMOS process We achieve photodlodes with an external quantum efficiency of 50-80% m the visible spectrum and posItIon-sensltlve devices (PSDs) with a spatial non-hneanty of around 0 3% We demonstrate surface-channel CCDs with a charge-transfer efficiency of 99 8% at room temperature, as well as bucket-bngade devices (BBDs) with a lower charge-transfer efficiency of 96% Light-emlttmg diodes (LEDs) are reahzed, emlttmg Infrared hght at 1160 nm (forward blased) and broadband vlslble yellow light with a spectral maximum at 640 nm (reverse biased) We discuss simple apphcatlons of passive photo-ASKS, such as a centrmd detector, a 3-D camera, a motion detector and a focus sensor, used to obtam a relative measure for the local focus of an optically Imaged scene, for example, m a photographic camera
This thesis describes the conception, design, implementation and ex¬ perimental characterization ... more This thesis describes the conception, design, implementation and ex¬ perimental characterization of ultrasound micro-systems. Such systems are intended for ultrasound control applications in industrial automa¬ tion, which so far relied on costly and bulky piezo-ceramic transducers. Two examples are discussedan ultrasound barrier detector micro¬ system and a miniaturized range finder. Both application make use of micromachinecl silicon membrane transducers, which are fabricated in a standard bipolar, CMOS or BiCMOS circuit technology. The mem¬ branes are about 1mm by lmm of size and can be excited thermally to emit ultrasound power at 80-100 kHz. They can also be stimulated by incident ultrasound waves and the resulting membrane vibrations are detected by a piezo-resistive Wheatstone bridge. The barrier detector micro-system is intended for the presence de¬ tection of liquid, transparent or light sensitive objects, especially at places where space is limited. It consists of an ultrasound transmit¬ ter/receiver pair facing each other at a distance up to 10 cm. No wired connection exists between transmitter and receiver in order to allow high flexibility within the application. The challenge in the design of the barrier detector is how to secure reliable operation of the system despite the non-idealities of the membrane transducers. Among oth¬ ers these are in particular the temperature and process dependence of the narrow bandwidth (quality factor Q-100) mechanical resonance and the weak sensor signals. An elegant solution is found to provide best performance of the transmitter. By embedding the membrane into the loop of an electro-mechanical oscillator, the hitter's oscillation fre¬ quency is always determined by the membrane resonance, where the emitted ultrasound power is maximum. For the receiver a simple and efficient self-calibration concept is developed, which is used to maximize the receiver sensitivity. It consists of a high gain (70 clB), ac-coupled amplification stage to boost the extremely weak sensor signals to a suf¬ ficient level. A subsequent tuning/tracking circuit automatically tunes vu Vlll Abstract the membrane resonator in order to find and track the highest possible sensitivity. Objects can be detected within 10 ms when they interrupt the sound-path between transmitter and receiver. The miniaturized range finder system uses the silicon membranes as transmitter/receiver for contact-less short range distance measurement in air. It can determine the distance from an object to the membrane surface up to 10 cm with a 5 mm precision and features an extremely small blind space of 1 cm, where the measurement is not possible. For the micro-system a novel quasi continuous-wave measurement proce¬ dure called A/ phase shift method is developed to enable the short range measurement despite the slow thermal excitation of the silicon membrane transducers. The new method, however, requires a coherent beam of ultrasound waves. This is performed by applying the concept of a phase locked loop circuit (PLL) to the tunable membrane resonator. The resulting electro-mechanical PLL is able to lock the emitted ultra¬ sound waves to the electrical signal and hence generates the required coherent beam. The same unique concept is used for the self-calibrating receiver to guarantee zero degree electrical phase shift and at the same time maximum sensitivity. Experimental and theoretical investigations Ansteuerclcktronik zulässt (monolithisches Mikrosystem). Die Systemarchitcktur ist in beiden Fällen so gewählt, class alle Funktionen vollstän¬ dig integriert werden können und class insbesondere eine effiziente Kom¬ bination von Sender und Empfänger im selben Chip ermöglicht wird. Ein Mikrosystem mit einer derartigen Architektur wird dann zu einer kostengünstigen, flexiblen und daher attraktiven Konkurrenz für viele bestehende piezo-keramische Lösungen.
TRANSDUCERS '03. 12th International Conference on Solid-State Sensors, Actuators and Microsystems. Digest of Technical Papers (Cat. No.03TH8664), 2003
A monolithic gas sensor system is presented, which includes on a single chip an array of three me... more A monolithic gas sensor system is presented, which includes on a single chip an array of three metal-oxide covered microhotplates, each of which is individually addressable and can be operated at a defined temperature. The monolithically co-integrated circuitry consists of three independent temperature control loops for the microhotplates and an on-chip temperature sensor. An innovative design of a circular-shape microhotplate has been realized. Temperature homogeneity and thermal efficiency of the membrane were optimized for use with thick films of nanocrystalline metal oxides as sensitive layers. A SnO 2based sensing material with noble metal doping was operated at different temperatures as well as in temperature pulsing mode. Chemical sensor measurements have been conducted with, e.g., CO to show the system performance.
Microtechnology and MEMS, 2007
The use of general descriptive names, registered names, trademarks, etc. in this publication does... more The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.
Technical Digest. MEMS 2002 IEEE International Conference. Fifteenth IEEE International Conference on Micro Electro Mechanical Systems (Cat. No.02CH37266)
We present a magnetic actuation scheme combined with a piezoresistive MOS-transistor sensing tech... more We present a magnetic actuation scheme combined with a piezoresistive MOS-transistor sensing technique for CMOS-integrated resonators. It was developed for a cantilever resonator with on-chip amplifier, but is broadly applicable. The high efficiency of electromagnetic actuation significantly reduces the required operation power and allows for the use in portable devices. By use of stress-sensitive PMOS-transistors as active loads, the size of the piezoresistive Wheatstone bridge is significantly reduced. Thirdly, the post-processing sequence of the cantilever resonator has been optimized, so that only one photolithography step is necessary to release the whole mechanical structure. This facilitates the fabrication, increases yield and, thus, reduces fabrication cost.
Sensors Update, 2003
Sensor arrays based on industrial CMOS-technology combined with post-CMOS micromachining (CMOS ME... more Sensor arrays based on industrial CMOS-technology combined with post-CMOS micromachining (CMOS MEMS) are a promising approach to low-cost sensors. In the first part of this article [1], the state of research on CMOS-based gas sensor systems was reviewed, and a platform technology for monolithic integration of three different transducers on a single chip was described. In this second part, the transduction principles of three polymer-based gas sensors are detailed and the read-out circuitry is portrayed. The first transducer is a micromachined resonant cantilever. The absorption of analyte in the chemically sensitive polymer causes shifts in resonance frequency as a consequence of changes in the oscillating mass. The cantilever acts as the frequency-determining element in an oscillator circuit, and the resulting frequency change is read out by an on-chip counter. The second transducer is a planar capacitor with polymer-coated interdigitated electrodes. This transducer monitors changes in the dielectric constant upon absorption of the analyte into the polymer matrix. The sensor response is read out as a differential signal between the coated sensing capacitor and a passivated reference capacitor, both of which are incorporated into the input stage of a switched capacitor second-order RD-modulator. The third transducer is a thermoelectric calorimeter, which detects enthalpy changes upon ab-/desorption of analyte molecules into a polymer film located on a thermally insulated membrane. The enthalpy changes in the polymer film cause transient temperature variations, which are detected via polysilicon/aluminum thermocouples (Seebeck effect). The small signals in the lVrange are first amplified with a low-noise chopper amplifier, then converted to a digital signal using a RD-A/D-converter and finally decimated and filtered with a digital decimation filter.
Smart Structures and Materials 1999: Smart Electronics and MEMS, 1999
We review selected micro-and nano-systems developed recently at the Physical Electronics Laborato... more We review selected micro-and nano-systems developed recently at the Physical Electronics Laboratory of ETh Zurich using industrial CMOS technology in combination with post-processing micromachining and film deposition: (i) an infrared sensor microsystem for presence detection of persons, (ii) calorimetric, capacitive, and gravimetnc chemical sensor microsystems for detection of volatile organic compounds in air, and (iii) a parallel scanning AFM chip. The microsystems combine sensor structures and read-out circuitry on a single chip.
IEEJ Transactions on Sensors and Micromachines, 2000
Distributed Manipulation, 2000
The rst micromachined bimorph organic ciliary array with on-chip CMOS circuitry is presented. Thi... more The rst micromachined bimorph organic ciliary array with on-chip CMOS circuitry is presented. This device is composed of an 8 8 array of cells each h a ving four orthogonally oriented actuators in an overall die size of 9:4mm 9:4mm. The polyimide based actuators were fabricated directly above the selection and drive circuitry. Selection and activation of actuators in this array shows that integration was successful. The array was programmed to perform several kinds of manipulation tasks, including linear translation, diagonal motion, as well as vector eld operations such a s squeeze eld and radial eld orienting and centering. Preliminary experiments were also performed with the rst implementation of a universal eld" that uniquely positions and orients any non-symmetric part without programming or sensor feedback. All tasks were demonstrated using thin silicon dice of about 3mm 3mm 0:5mm size as the object being moved.
Analog Circuit Design, 1997
This thesis is focused on sensors based on industrial integrated circuit technology (IC microsens... more This thesis is focused on sensors based on industrial integrated circuit technology (IC microsensors). This approach is driven by a market which demands aug¬ mented functionality and performance affordable for an increasing number of cus¬ tomers. The fabrication of sensors by integrated circuit technology offers the potential to exploit the unique features of microelectronics, namely cost effective batch fabrication, miniaturization with established reliability, and cointegration of circuits. Beside the efficient production of the sensor it must be ensured that the
Sensors and Actuators A: Physical, 1993
Two different unmodified mdustnal CMOS processes have been used for the mtegratlon of h&y mte-rdt... more Two different unmodified mdustnal CMOS processes have been used for the mtegratlon of h&y mte-rdtgttated pn structures Under forward bias these pn Junctions emlt narrow-band mfrared bght at 1160 nm Hrlth an electncal-to-opt& power conversion e.tkency of typically 10e4 The same Junctions show broad-band vlslble-hght ermsslon between 450 and 800 nm m the avalanche breakdown region under reverg has with effinencles of the order of lo-* ti 1s already enough for a first few practical applications as hght-enuttmg devices (LED@ No satisfactory explanation for this emlsslon effect, fitting all the expenmentally observed electro-optical and physical properties of our salmon LEDs, has been found yet
IEEJ Transactions on Sensors and Micromachines, 1999
This paper presents improved capacitive readout type sensor interface circuits designed for CMOS ... more This paper presents improved capacitive readout type sensor interface circuits designed for CMOS inte grated chemical sensors. The sensor is fabricated using a 0.8 ym CMOS IC process technology. Volatile organic compounds (VOCs) are detected by measuring the capacitance change of polymer coated interdigital capacitors due to analyte absorption. The delta-sigma modulation sensor interface uses a sensor capacitor and a reference capacitor as those for the input of the frontend switched capacitor integrator. An improved capacitance sensing scheme is proposed to improve the sensitivity.
SPIE Proceedings, 1998
Thermally-based transducer microsystems can be made by using CMOS IC technology, post-CMOS microm... more Thermally-based transducer microsystems can be made by using CMOS IC technology, post-CMOS micromachining or deposition, and flip-chip packaging. Technology steps, materials, and physical effects pertinent to thermal microtransducers are summarized together with microheater, thermistor, thermopile, thermal isolation, and heat sink structures. An infrared intrusion detector, a thermal air flow sensor, and thermally excited microresonators for acoustic and chemical sensing serve as demonstrators. We discuss the characterization of process-dependent properties of CMOS materials crucial for thermal microtransducer CAD.
Technical Digest. MEMS 2002 IEEE International Conference. Fifteenth IEEE International Conference on Micro Electro Mechanical Systems, 2002
The paper reviews the state-of-the-art in the field of CMOS-based microelectromechanical systems ... more The paper reviews the state-of-the-art in the field of CMOS-based microelectromechanical systems (MEMS). The different CMOS MEMS fabrication approaches, pre-CMOS, intermediate-CMOS, and post-CMOS, are summarized and examples are given. Two microsystems fabricated with post-CMOS micromachining are presented, namely a mass-sensitive chemical sensor for detection of organic volatiles in air and a 10-cantilever force sensor array for application in scanning probe microscopy. The paper finishes with a look into the future, discussing key challenges and future application fields for CMOS MEMS.
29th European Solid-State Circuits Conference, 2003
A novel monolithic differential thermal analyzer fabricated in industrial CMOS-technology combine... more A novel monolithic differential thermal analyzer fabricated in industrial CMOS-technology combined with post-CMOS micromachining is presented, which includes three micro-hotplates and all necessary driving and signal conditioning circuitry. Three on-chip proportional temperature controllers (one controller per micro-hotplate), regulate the micro-hotplate temperature up to 350°C with a steady-state error of less than 1% of the preset micro-hotplate temperature. A circular microhotplate design was developed to improve the hotplate power efficiency. The thermal analysis performance was assessed by melting point measurements of ammonium nitrate (melting point at 169.6°C).
PROCEEDINGS OF THE IEEE, 2003
Microfabrication processes for chemical and biochemical sensors are reviewed. Standard processing... more Microfabrication processes for chemical and biochemical sensors are reviewed. Standard processing steps originating from semiconductor technology are detailed, and specific micromachining steps to fabricate three-dimensional mechanical structures are described. Fundamental chemical sensor principles are briefly abstracted and corresponding state-of-the-art examples of microfabricated chemical sensors and biosensors are given. The advantages and disadvantages of either fabricating devices in IC fabrication technology with additional microfabrication steps, or of using custom-designed nonstandard microfabrication process flows are debated. Finally, monolithic integrated chemical and biological microsensor systems are presented, which include transducer structures and operation circuitry on a single chip.