Syed Zeeshan Ali

• Cambridge CMOS Sensors Ltd

We present a miniaturised thermal acoustic gas sensor, fabricated using a CMOS microhotplate and MEMS microphone. The sensing mechanism is based on the detection of changes in the thermal acoustic conversion efficiency which is dependent on the physical properties of the gas. An active sensing element, consisting of a MEMS microphone, is used to de...

We propose a numerical model for efficient design and optimization of a novel infrared (IR) detector array, fabricated on a single micro-electro-mechanical system (MEMS) membrane based on silicon on insulator (SOI) technology. The model is based on a finite element method (FEM) and is used to investigate the effect of heat transfer, at pixel scale,...

The gas sensor market is growing fast, driven by many socioeconomic and industrial factors. Mid-infrared (MIR) gas sensors offer excellent performance for an increasing number of sensing applications in healthcare, smart homes, and the automotive sector. Having access to low-cost, miniaturized, energy efficient light sources is of critical importan...

The gas sensor market is growing fast, driven by many socioeconomic and industrial factors. Mid-infrared (MIR) gas sensors offer excellent performance for an increasing number of sensing applications in healthcare, smart homes, and the automotive sector. Having access to low-cost, miniaturized, energy efficient light sources is of critical importan...

Low-cost infrared (IR) thermal cameras are powering a rising market of industrial and consumer applications. Complementary metal-oxide-semiconductor (CMOS)-based thermopile arrays are proven thermal imagers that can be monolithically integrated into low-cost and low-power-consumption formats for high-volume manufacturability. Here we present a simp...

We present a new experimental technique to characterise the crosstalk of a thermopile-based thermal imager, based on bi-directional electrical heating of thermopile elements. The new technique provides a significantly simpler and more reliable method to determine the crosstalk, compared to a more complex experimental setup with a laser source. The...

This paper presents the high temperature thermal characterization of a Micro-Electro-Mechanical Systems (MEMS) infra-red (IR) thermal source, using non-contact optical approaches, based on IR and thermo-incandescence microscopy. The IR thermal source was fabricated using a CMOS based processing technology and consists of a miniature micro-heater, f...

We present a novel single-chip thermopile sensor array for mid-infrared room temperature imaging. The array is fabricated on a single complementary metal-oxide-semiconductor (CMOS) dielectric membrane, composed of single-crystal silicon (Si) and elements, and standard CMOS tungsten metal layers for thermopile cold junction heatsinking, significantl...

This work reports on the transfer of randomly oriented nanowire networks based on ZnO and Al-doped zinc oxide (AZO) encapsulated ZnO nanowires onto a complementary metal oxide semiconductor (CMOS) micro electro mechanical system (MEMS) platform. The substrate consists of an embedded tungsten micro-heater with gold interdigitated electrodes on top o...

Minimizing conductive heat losses in Micro-Electro-Mechanical-Systems (MEMS) thermal (hot-film) flow sensors is the key to minimize the sensors’ power consumption and maximize their sensitivity. Through a comprehensive review of literature on MEMS thermal (calorimetric, time of flight, hot-film/hot-film) flow sensors published during the last two d...

This study presents high-temperature characterisation of a novel infra-red (IR) emitter chip based on CMOS technology, using IR thermal microscopy. The performance and reliability of the thermal source are highly dependent on the operating temperature and temperature uniformity across the micro-heater which is embedded within the silicon dioxide me...

CMOS-based devices and the control of the materials properties by nanotechnology enabled significant progresses in the field of metal chemiresistors for gas sensing applications both in terms of miniaturization and performances (e.g., gas sensitivity). In this regard, ink-jet printing is a powerful technique to achieve high-volume production and me...

We present a novel thermopile-based infrared (IR) sensor array fabricated on a single CMOS dielectric membrane, comprising of poly-silicon p⁺ and n⁺ elements. Processing of the chip is simplified by fabricating the entire array on a single membrane and by using standard CMOS Al metal layers for thermopile cold junction heatsinking. On a chip area o...

Temperature monitoring and thermal management of CMOS circuits / sensors is often required for long term circuit reliability and sensors temperature compensations. The ideal solution is to co-fabricate the temperature sensors along with the CMOS circuits and other sensors using CMOS materials and the same CMOS processes. In this paper we therefore,...

In this paper, we study the recovery of onmembrane semiconductor components, such as N-type Field-Effect Transistors (FETs) available in two different channel widths and a Complementary Metal-Oxide-Semiconductor (CMOS) inverter, after the exposure to high dose of proton radiation. Due to the ionizing effect, the electrical characteristics of the co...

This research details the potential of a micro-hotplate photo sensor, based on a silicon-on-insulator (SOI) lateral PIN (P+/P-/N+) diode and a micro-heater, fabricated on a thin suspended membrane from a commercial 1.0 μm SOI complementary metal oxide semiconductor (CMOS) technology. A local annealing (30-minute micro-heating, at elevated temperatu...

In this paper, we investigate the recovery of some semiconductor-based components, such as N/P-type field-effect transistors (FETs) and a Complementary Metal-Oxide-Semiconductor (CMOS) inverter, after being exposed to a high total dose of gamma rays radiation. The employed method consists mainly in a rapid, low power and in-situ annealing mitigatio...

For the first time, we demonstrate the detection of carbon dioxide (CO 2) using a non-dispersive infra-red (NDIR) technique that does not require an expensive CMOS-incompatible optical filter. This is achieved by employing a differential IR thermopile detector with micro-engineered (plasmonic) optical properties, fabricated in a commercially availa...

In this work we investigate the characteristics and critical operating temperatures of on-membrane embedded MOSFETs from an experimental and analytical point of view. This study permits us to conclude the possibility of integrating electronic circuitry in the close vicinity of micro-heaters and hot operation transducers. A series of calibrations an...

Nanostructured metal oxide semiconductors have been widely investigated and are commonly used in gas sensing structures. After a brief review which will be fo-cused on chemiresistive oxygen sensing employing this type of sensing materials, for both room temperature and harsh environment applications (particularly, at high ambient temperature and hi...

Non-dispersive Infrared (NDIR) is one of the most reliable methods of measuring carbon dioxide (CO2) level in exhaled human breath. In this paper, we describe the application of infrared (IR) emitters and detectors manufactured on standard low cost CMOS silicon substrate with Deep Reactive Ion Etching (DRIE) process. Using these devices we have sho...

An SOI CMOS multi-sensor MEMS chip, which can simultaneously measure temperature, pressure and flow rate, has been reported. The multi-sensor chip has been designed keeping in view the requirements of researchers interested in experimental fluid dynamics. The chip contains ten thermodiodes (temperature sensors), a piezoresistive-type pressure senso...

This paper reports on the performance of a silicon-on-insulator photodiode suspended on a dielectric membrane. The micro-hotplate platform consists of a micro-heater and a thin-film lateral P+/P-/N+ (PIN) photodiode. Without optimizing the multilayer stack on top of the PIN diode, experimental responsivities of the suspended photodiodes at room tem...

Here we report on the mask-less deposition of Au-SnO2 nanocomposites with a silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) micro electro mechanical system (MEMS) platform through the use of dip pen nanolithography (DPN) to create a low-cost ethanol sensor. MEMS technology is used in order to achieve low power consumption,...

In this paper we present a temperature-modulated graphene oxide (GO) resistive humidity sensor that employs complementary-metal-oxide-semiconductor (CMOS) micro-electro-mechanical-system (MEMS) micro-hotplate technology for the monitoring and control of indoor air quality (IAQ). GO powder is obtained by chemical exfoliation, dispersed in water and...

In this paper, we report a lateral silicon-on-insulator (SOI) P+P−N+ (PIN) photodiode suspended on a micro-hotplate platform, with aluminum (Al) layer deposited on backside. Voltage applied to the Al back gate can modify the depletion condition in the intrinsic (I) region. The device output photocurrent reaches a maximum under fully-depleted (FD) c...

The application of plasmonics to thermal emitters is generally assisted by absorptive losses in the metal because Kirchhoff's law prescribes that only good absorbers make good thermal emitters. Based on a designed plasmonic crystal and exploiting a slow-wave lattice resonance and spontaneous thermal plasmon emission, we engineer a tungsten-based th...

In this paper, we present the design and characterization of a low-power low-cost infra-red emitter based on a tungsten micro-hotplate fabricated in a commercial 1-μm SOI-CMOS technology. The device has a 250-μm diameter resistive heater inside a 600-μm diameter thin dielectric membrane. We first present electro-thermal and optical device character...

We report on the integration of inkjet-printed graphene with a CMOS micro-electro-mechanical-system (MEMS) microhotplate for humidity sensing. The graphene ink is produced via ultrasonic assisted liquid phase exfoliation in isopropyl alcohol (IPA) using polyvinyl pyrrolidone (PVP) polymer as the stabilizer. We formulate inks with different graphene...

Dielectrophoretic alignment is found to be a simple and efficient method to deposit the solution prepared ZnO nanowires onto micro hot plate substrates. Due to the strong surface effects, positive temperature coefficient for resistance was encountered with ZnO nanowires in the high temperature range (>250 °C). The response to ammonia (NH3) was eval...

The current paper reports on a sonochemical synthesis method for manufacturing nanostructured (typical grain size of 50 nm) SrTi0.6Fe0.4O2.8 (Sono-STFO40) powder. This powder is characterized using X ray-diffraction (XRD), Mössbauer spectroscopy and Scanning Electron Microscopy (SEM), and results are compared with commercially available SrTi0.4Fe0....

In this paper we present a novel Silicon-on-Insulator (SOI) complementary metal oxide semiconductor (CMOS) micro-electro-mechanical-system (MEMS) thermal wall shear stress sensor based on a tungsten hot-wire and a single thermopile. Devices were fabricated using a commercial 1 μm SOI-CMOS process followed by a deep reactive ion etching (DRIE) back-...

The integration of one dimensional (1D) nanostructures of non-industry-standard semiconductors in functional devices following bottom-up approaches is still an open challenge that hampers the exploitation of all their potential. Here, we present a simple approach to integrate metal oxide nanowires in electronic devices based on controlled dielectro...

In this paper, the performances of a lateral thin-film PIN photodiode based on silicon-on-insulator technology are reported for applications from blue to red wavelengths. The platform consists of a micro-hotplate with a suspended heater and a photodiode. Responsivities of 0.01 to 0.05 A/W were obtained for 450–900 nm light range in reverse bias ope...

This paper reports on the novel deposition of zinc oxide (ZnO) nanorods using dip pen nanolithographic (DPN) technique on SOI (silicon on insulator) CMOS MEMS (micro electro mechanical system) micro-hotplates (MHP) and their characaterisation as a low-cost, low-power ethanol sensor. The ZnO nanorods were synthesized hydrothermally and deposited on...

In this letter, we present a fully complementary-metal-oxide-semiconductor (CMOS) compatible microelectromechanical system thermopile infrared (IR) detector employing vertically aligned multi-walled carbon nanotubes (CNT) as an advanced nano-engineered radiation absorbing material. The detector was fabricated using a commercial silicon-on-insulator...

In this letter, we present a fully complementary-metal-oxide-semiconductor (CMOS) compatible microelectromechanical system thermopile infrared (IR) detector employing vertically aligned multi-walled carbon nanotubes (CNT) as an advanced nano-engineered radiation absorbing material. The detector was fabricated using a commercial silicon-on-insulator...

High doses of fast neutrons is detrimental to the performance of most common solid-state devices such as diodes and transistors. The ionizing effect is observed in particular for diodes used as simple integrated temperature sensors, or thermodiodes, when their junction voltage is measured at constant current bias. In this work, we present a low-pow...

This paper presents the performance of a silicon-on-insulator (SOI) p+/p-well/n+ diode temperature sen-sor, which can operate in an extremely wide temperature range of 80 K to 1050 K. The thermodiode is placed underneath a tungsten micro-heater which is embedded in a thin dielectric membrane, obtained with a post-CMOS deep reactive ion etching proc...

The integration of one dimensional (1D) nanostructures of non-industry-standard semiconductors in functional devices following bottom-up approaches is still an open challenge that hampers the exploitation of all their potential. Here, we present a simple approach to integrate metal oxide nanowires in electronic devices based on controlled dielectro...

We report here the development of a resistive single wall carbon nanotubes (SWCNTs) sensor, based on a CMOS substrate that responds at ambient temperature to ppm levels of ammonia. The power efficient CMOS micro-hotplate is a thin membrane structure and comprises metal heater with an interdigitated electrode. The SWCNTs film was prepared first by t...

This paper presents an experimentally verified 3D FEM model to understand heat transfer mechanisms in membrane based thermal conductivity sensors developed using SOI CMOS MEMS technology. It aims to provide a structured methodology to design micro thermal conductivity sensors for gas detection. The reported model takes in to account heat transfer b...

This paper presents an experimentally verified geometry dependent predictive FEM model of a high temperature closed membrane thermal conductivity sensor. The sensor was developed using SOI CMOS MEMS technology. The FEM model presents a systematic approach to design thermal conductivity sensors by understanding heat transfer mechanisms between the s...

Gas sensors have a wide range of applications such as in environmental monitoring, biomedical, and security. Presently, commercially available gas sensors are power hungry (>100 mW) and expensive (>$20). Both academia and industry are thus striving to develop low power, low cost, gas sensing devices. Different technological approaches (e.g. sensors...

In this work we report, for the first time, a silicon on insulator (SOI) complementary metal oxide semiconductor (CMOS) MEMS thermal wall shear stress sensor that uses CMOS tungsten metallization as sensing element, supported by a composite membrane comprising of silicon oxide and silicon nitride. The sensor was fabricated using a commercial 1 μm S...

In this paper we demonstrate the use of a CMOS infra-red emitter in a low power Non Dispersive Infra Red (NDIR) based carbon dioxide sensor for application in domestic boilers. Compared to conventional micro-bulbs as IR wideband sources, CMOS IR emitters offer several advantages: They are faster, smaller, have lower power consumption and can have i...

Abstract- This paper presents a multiphysic 3-D model of an SOI CMOS MEMS thermal wall shear stress sensor, considering all the physical domains involved and their interaction. After a brief introduction, the device is presented and its working principle explained. The numerical model and the validation process are then described.

This work presents for the first time a 3-D model of an SOI CMOS MEMS thermal wall shear stress sensor using multiphysics approach. The model involves three different physical domains and, when compared with the experimental results, shows an excellent agreement in every condition. After the validation process, the model has been used to perform a...

In this paper, we describe an infrared thermopile sensor comprising of single crystal silicon p+ and n+ elements, with an integrated diode temperature sensor fabricated using a commercial SOI-CMOS process followed by Deep Reactive Ion Etching (DRIE). The chip area is 1.16 mm × 1.06 mm. The integrated diode, being on the same substrate, allows a mor...

This abstract presents the development of a Silicon-on-Insulator (SOI) CMOS micro-electro-mechanical (MEMS) micro-hotplate based infra-red (IR) light source employing a vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) emission layer. Chips were batch fabricated using a standard SOI CMOS process with tungsten metalization followed by a d...

An infra-red (IR) device comprising a dielectric membrane formed on a silicon substrate comprising an etched portion; and at least one patterned layer formed within or on the dielectric membrane for controlling IR emission or IR absorption of the IR device, wherein the at least one patterned layer comprises laterally spaced structures.

Micro-hotplates are MEMS structures of interest for low-power gas sensing, lab-on-chips and space applications, such as micro-thrusters. Micro-hotplates usually consist in a Joule heater suspended on a thin-film membrane while thermopiles or thermodiodes are added as temperature sensors and for feedback control. The implementation of micro-hotplate...

A custom designed microelectromechanical systems (MEMS) micro-hotplate, capable of operating at high temperatures (up to 700 °C), was used to thermo-optically characterize fluorescent temperature-sensitive nanosensors. The nanosensors, 550 nm in diameter, are composed of temperature-sensitive rhodamine B (RhB) fluorophore which was conjugated to an...

Non-dispersive-infra-red (NDIR) sensors are believed to be one of the most selective and robust solutions for CO 2 detection, though cost prohibits their broader integration. In this paper we propose a commercially viable silicon-on-insulator (SOI) complementary metal-oxide (CMOS) micro-electro-mechanical (MEMS) technology for an IR thermal emitter...

In this paper we present for the first time, a novel silicon on insulator (SOI) complementary metal oxide semiconductor (CMOS) MEMS thermal wall shear stress sensor based on a tungsten hot-film and three thermopiles. These devices have been fabricated using a commercial 1 μm SOI-CMOS process followed by a deep reactive ion etch (DRIE) back-etch ste...

There is considerable demand for sensors that are capable of detecting ultra-low concentrations (sub-PPM) of toxic gases in air. Of particular interest are NO 2 and CO that are exhaust products of internal combustion engines. Electrochemical (EC) sensors are widely used to detect these gases and offer the advantages of low power, good selectivity a...

This paper presents for the first time the performance of a silicon-on-insulator (SOI) p+-n+ thermodiode, which can operate in an extremely wide temperature range of -200 °C to 700 °C while maintaining its linearity. The thermodiode is embedded in a thin dielectric membrane underneath a tungsten microheater, which allows the diode characterization...

In this paper, we demonstrate a micro-inkjet printing technique as a reproducible post-process for the deposition of carbon nanoparticles and fullerene adlayers onto fully CMOS compatible micro-electro-mechanical silicon-on-insulator infrared (IR) light sources to enhance their infrared emission. We show experimentally a significant increase in the...

We report a technique which can be used to improve the accuracy of infrared (IR) surface temperature measurements made on MEMS (Micro-Electro-Mechanical-Systems) devices. The technique was used to thermally characterize a SOI (Silicon-On-Insulator) CMOS (Complementary Metal Oxide Semiconductor) MEMS thermal flow sensor. Conventional IR temperature...

This paper reviews and addresses certain aspects of Silicon-On-Insulator (SOI) technologies for a harsh environment. The paper first describes the need for specialized sensors in applications such as (i) domestic and other small-scale boilers, (ii) CO2 Capture and Sequestration, (iii) oil & gas storage and transportation, and (iv) automotive. We de...

This paper introduces a pressure sensing structure configured as a stress sensitive differential amplifier (SSDA), built on a Silicon-on-Insulator (SOI) membrane. Theoretical calculation show the significant increase in sensitivity which is expected from the pressure sensors in SSDA configuration compared to the traditional Wheatstone bridge circui...

In this paper we present a robust SOI-CMOS ethanol sensor based on a tungsten-doped lanthanum iron oxide sensing material. The device shows response to gas, has low power consumption, good uniformity, high temperature stability and can be manufactured at low cost and with integrated circuitry. The platform is a tungsten-based CMOS micro-hotplate th...

For more than 20 years researchers have been interested in developing micro-gas sensors based on silicon technology. Most of the reported devices are based on micro-hotplates, however they use materials that are not CMOS compatible, and therefore are not suitable for large volume manufacturing. Furthermore, they do not allow the circuitry to be int...

We report a technique which can be used to improve the accuracy of infrared (IR) surface temperature measurements made on MEMS (Micro-Electro-Mechanical-Systems) devices. The technique was used to thermally characterize a SOI (Silicon-On-Insulator) CMOS (Complementary Metal Oxide Semiconductor) MEMS thermal flow sensor. Conventional IR temperature...

Here we demonstrate a novel technique to grow carbon nanotubes (CNTs) on addressable localized areas, at wafer level, on a fully processed CMOS substrate. The CNTs were grown using tungsten micro-heaters (local growth technique) at elevated temperature on wafer scale by connecting adjacent micro-heaters through metal tracks in the scribe lane. The...

This paper reports for the first time on the performance and long-term stability of a silicon-on-insulator (SOI) thermodiode with tungsten metallization, suspended on a dielectric membrane,at temperatures beyond 300 degree C. The thermodiode has been designed and fabricated with minute saturation currents (due to both small size and the use of SOI...

Silicon diodes can be used for accurate temperature monitoring up to higher temperatures in a variety of sensors such as micro-machined resistive and calorimetric gas sensors, thermal flow sensors, exhausts, etc. This paper investigates the performance of a diode temperature sensor when operated at ultra high temperatures (up to 780°C ). A low lea...

This paper reports on the integration of zinc oxide nanowires (ZnO NWs) with a silicon on insulator (SOI) CMOS (complementary metal oxide semiconductor) micro-hotplate for use as an alcohol sensor. The micro-hotplates consist of a silicon resistive micro-heater embedded within a membrane (composed of silicon oxide and silicon nitride, supported on...

We report a technique which can be used to improve the accuracy of infrared (IR) surface temperature measurements made on micro-electro-mechanical systems (MEMS). In this work, a silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) MEMS thermal flow sensor was studied. The device consists of a meander-shaped resistive heater el...

This work reports on thermal characterization of SOI (silicon on insulator) CMOS (complementary metal oxide semiconductor) MEMS (micro electro mechanical system) gas sensors using a thermoreflectance (TR) thermography system. The sensors were fabricated in a CMOS foundry and the micro hot-plate structures were created by back-etching the CMOS proce...

In this paper we present a novel hydrogen gas sensor comprising a high temperature SOI-CMOS micro-hotplate and employing zinc oxide nanowires as the sensing material. The micro-hotplates were fabricated at a commercial SOI foundry followed by a backside deep reactive ion etch (DRIE) at a commercial MEMS foundry. Particular care was taken in designi...

This paper describes a mixed signal approach to micro-hotplate temperature control technique using digital On-off control logic. The novel micro-hotplate used for this purpose is based on standard 600 nm CMOS technology and contains a metal micro-heater, a (parasitic) bipolar transistor temperature sensor and an interdigitated electrode in a dielec...

In this paper, we review the work carried out at Cambridge University, in the UK, to develop a CMOS gas sensor. Special emphasis is put on the design of low power CMOS micro-hotplates and local growth of nanomaterials: carbon nanotubes (CNTs), CNT polymer composites and zinc oxide (ZnO) nanowires (NWs) on fully processed CMOS substrates. Finally so...

In this paper we discuss the combined use of integrated CMOS microhotplates employing nanomaterial sensing layers for intelligent, compact gas sensors with increased sensitivity, selectivity and fast response times. We first review the status of nanomaterial-based gas sensors, their operating principles, discussing growth issues and their compatibi...