This paper reports the infrared spectral responses of 17 and 35 μm uncooled bolometers fabricated at INO. They are measured by making use of an external readout circuit along with a monochromator. As expected, the spectral absorption strongly depends on the bolometer stack as well as the pixel layout. By proper selection of design parameters, the spectral response can be made flat from 3 to 14 μm without significant deterioration of the detector figure of merit.
This paper reviews recent developments in customized packaged bolometers at INO with an emphasis on their applications. The evolution of INOs bolometer packages is also presented. Fully packaged focal plane arrays of broadband microbolometers with expanded absorbing range are shown, for applications in spectroscopic and THz imaging. This paper also reports on the development of customized packaged bolometer focal plane arrays (FPAs) for space applications such as a multispectral imaging radiometer for fire diagnosis, a far infrared radiometer for in-situ measurements of ice clouds and a net flux radiometer for Mars exploration.
Microfabrication for integrated MEMS is the art of combining micro electronic circuits with micro optics, mechanics, fluidics, sensing and other technologies. To meet the diversified requirements for MEMS (Micro Electro Mechanical Systems) and MOEMS (Micro Opto Electro Mechanical Systems), a broad spectrum of materials and fabrication processes must be available. INO is the only entity offering MEMS foundry-type services in Canada. These services include design, prototyping, fabrication of mini-series, packaging and testing of various MEMS.
This paper reports on the development of a fully packaged focal plane array of broadband microbolometers. The detector makes use of a gold black thin film to expand its absorption range from 3 to 14 μm. A low temperature packaging process was developed to minimize sintering of the gold black absorber during vacuum sealing of the bolometer array package. The gold black absorber was also laser trimmed to prevent lateral diffusion of heat and promote a better MTF. The resulting FPAs show a NETD lower than 25 mK at a frame rate of 50 Hz
This paper reports the NETD values of various uncooled bolometers fabricated at INO. They are measured using an
external readout circuit that emulates the readout scheme of a commercial ROIC. The measured NETD values range
between 6 and 75 mK, depending on the pixel pitch and response time. Pixel pitches of 12, 17 and 35 μm are considered.
The figure of merit of the characterized detectors is below 350 mK*ms.
This paper reports on the deposition of vanadium oxide thin films with sheet resistance uniformity better than 2.5% over a 150 mm wafer. The resistance uniformity within the array is estimated to be less than 1%, which is comparable with the value reported for amorphous silicon-based microbolometer arrays. In addition, this paper also shows that the resistivity of vanadium oxide, like amorphous silicon, can be modeled by Arrhenius' equation. This result is expected to significantly ease the computation of the correction table required for TEC-less operation of VOx-based microbolometer arrays.
In recent years, smart phone applications have both raised the pressure for cost and time to market reduction, and the
need for high performance MEMS devices. This trend has led the MEMS community to develop multi-die packaging of
different functionalities or multi-technology (i.e. wafer) approaches to fabricate and assemble devices respectively. This
paper reports on the fabrication, assembly and packaging at INO of various MEMS devices using heterogeneous
assembly at chip and package-level. First, the performance of a giant (e.g. about 3 mm in diameter), electrostatically
actuated beam steering mirror is presented. It can be rotated about two perpendicular axes to steer an optical beam within
an angular cone of up to 60° in vector scan mode with an angular resolution of 1 mrad and a response time of 300 ms. To
achieve such angular performance relative to mirror size, the microassembly was performed from sub-components
fabricated from 4 different wafers. To combine infrared detection with inertial sensing, an electroplated proof mass was
flip-chipped onto a 256×1 pixel uncooled bolometric FPA and released using laser ablation. In addition to the microassembly
technology, performance results of packaged devices are presented. Finally, to simulate a 3072×3 pixel
uncooled detector for cloud and fire imaging in mid and long-wave IR, the staggered assembly of six 512×3 pixel FPAs
with a less than 50 micron pixel co-registration is reported.
This paper presents a systematic study of the 1/f noise coefficient as a function of pixel geometry for microbolometer structures. Structures with various VOx widths, electrode gaps, electrode widths and via hole sizes were fabricated and characterized. The experimental results show that the 1/f noise coefficient is adversely affected by current non uniformity, in agreement with model predictions. Design parameters that significantly impact current non uniformity are identified and approaches to minimize their importance are proposed.
Terahertz is a field in expansion with the emergence of various security needs such as parcel inspection and through-camouflage vision. Terahertz wavebands are characterized by long wavelengths compared to the traditional infrared and visible spectra. However, it has recently been demonstrated that a 52 μm pixel pitch microscanned down to an efficient sampling pitch of 26 μm could provide useful information even using a 118.83 μm wavelength. With this in mind, INO has developed a terahertz camera core based on a 384x288 pixel 35 μm pixel pitch uncooled bolometric terahertz detector. The camera core provides full 16-bit output video rate.
Conventional guidelines and approximations useful in macro-scale system design can become invalidated when applied
to the smaller scales. An illustration of this is when camera pixel size becomes smaller than the diffraction-limited
resolution of the incident light. It is sometimes believed that there is no benefit in having a pixel width smaller than the
resolving limit defined by the Raleigh criterion, 1.22 λ F/#. Though this rarely occurs in today's imaging technology,
terahertz (THz) imaging is one emerging area where the pixel dimensions can be made smaller than the imaging
wavelength. With terahertz camera technology, we are able to achieve sub-wavelength pixel sampling pitch, and
therefore capable of directly measuring if there are image quality benefits to be derived from sub-wavelength sampling.
Interest in terahertz imaging is high due to potential uses in security applications because of the greater penetration depth
of terahertz radiation compared to the infrared and the visible. This paper discusses the modification by INO of its
infrared MEMS microbolometer detector technology toward a THz imaging platform yielding a sub-wavelength pixel
THz camera. Images obtained with this camera are reviewed in this paper. Measurements were also obtained using
microscanning to increase sampling resolution. Parameters such as imaging resolution and sampling are addressed. A
comparison is also made with results obtained with an 8-12 μm band camera having a pixel pitch close to the diffractionlimit.
A THz camera based on an uncooled microbolometer 160X120 pixel array with nominal pitch of 52 μm has been
developed at INO and initial transmission and reflection images showed promise. In the present paper, the
characterization of both standard infrared and THz-optimized uncooled microbolometer pixel arrays are presented at
both infrared and THz wavelengths. Measurements in the THz region has been performed using non-uniform low-power
quantum-cascade laser (QCL) and uniform high-power far-infrared laser (FIR laser) beams at 3 THz and 4.25 and 2.54
THz, respectively. A measurement comparison has been achieved in the infrared using a blackbody radiation. Different
methods for noise-equivalent power (NEP) measurements have been investigated. These characterization methods are
promising especially for non-uniform laser beams irradiated on pixel arrays. The NEP results obtained from the different
methods are in good agreement independent of the method used in the experiments. The results show a high sensitivity
of the THz-optimized pixel array in the THz region. Large beam area reflection imaging of obscured materials at 2.54
THz have been performed at video rates of 30 frames per second using the THz-optimized pixel array equipped with a
semi-custom fast THz objective, proving that the INO THz camera provides a promising solution for stand-alone
High absorptivity and low thermal mass are two important requirements for coatings applied to thermal infrared
detectors. Gold black coatings are very good candidates to ensure these characteristics in the broadband infrared
spectral range. A specific deposition system was designed and built at INO in order to provide gold-black coatings
for different broadband detection applications including the broadband radiometer (BBR) instrument for the
European Space Agency (ESA) EarthCARE satellite. A parametric study targeting uniform optical absorptance
within the spectral range from 0.2 μm to 50 μm was conducted. Specular reflectance lower than 10% was obtained
for extended wavelength range up to 100 μm. The coating thickness ranges typically between 20 μm and 35 μm,
with uniformity of about ± 3 μm over a sample surface of 10x10 mm2. The deposit density was typically ~0.3% of
the bulk density of gold. To singulate the blackened infrared detector pixels, a laser micromachining process was
developed. The setup exhibits a 1μm positioning accuracy and allows for ablation of 3 μm to 12 μm wide channels
through the gold-black thickness, while preserving the pixel and gold-black deposit integrity.
In the MEMS manufacturing world, the "fabless" model is getting increasing importance in recent years as a way for
MEMS manufactures and startups to minimize equipment costs and initial capital investment. In order for this model to
be successful, the fabless company needs to work closely with a MEMS foundry service provider. Due to the lack of
standardization in MEMS processes, as opposed to CMOS microfabrication, the experience in MEMS development
processes and the flexibility of the MEMS foundry are of vital importance.
A multidisciplinary team together with a complete microfabrication toolset allows INO to offer unique MEMS foundry
services to fabless companies looking for low to mid-volume production. Companies that benefit from their own
microfabrication facilities can also be interested in INO's assistance in conducting their research and development work
during periods where production runs keep their whole staff busy. Services include design, prototyping, fabrication,
packaging, and testing of various MEMS and MOEMS devices on wafers fully compatible with CMOS integration.
Wafer diameters ranging typically from 1 inch to 6 inches can be accepted while 8-inch wafers can be processed in some
instances. Standard microfabrication techniques such as metal, dielectric, and semiconductor film deposition and
etching as well as photolithographic pattern transfer are available. A stepper permits reduction of the critical dimension
to around 0.4 μm. Metals deposited by vacuum deposition methods include Au, Ag, Al, Al alloys, Ti, Cr, Cu, Mo,
MoCr, Ni, Pt, and V with thickness varying from 5 nm to 2 μm. Electroplating of several materials including Ni, Au and
In is also available. In addition, INO has developed and built a gold black deposition facility to answer customer's needs
for broadband microbolometric detectors. The gold black deposited presents specular reflectance of less than 10% in the
wavelength range from 0.2 μm to 100 μm with thickness ranging from 20 to 35 μm and a density of 0.3% the bulk
density of gold. Two Balzers thin-film deposition instruments (BAP-800 and BAK-760) permit INO to offer optical thin
film manufacturing. Recent work in this field includes the design and development of a custom filter for the James
Webb Space Telescope (JWST) as collaboration with the Canadian company ComDEV. An overview of the different
microfabrication foundry services offered by INO will be presented together with the most recent achievements in the
field of MEMS/MOEMS.
THz imaging is a very promising field rapidly growing in importance. This expanding field is at its early stage of
development but already a large number of applications are foreseen. THz imaging promises to be a key technology in
various fields, such as defense & security where it can be used to defeat camouflage. Based on its many years of
experience in uncooled bolometers technology, INO has developed, assembled and characterized a prototype THz
imager. The camera's 160 × 120 pixel array consists of pixels with a 52 μm pitch that have been optimized for the THz
region. Custom camera electronics and an F/1 THz lens barrel complete the imager design. Real-time imaging at video
rate of 30 frame/sec has been performed with a 3 THz quantum cascade laser set-up. THz images of numerous object-obscurant
combinations are presented, proving the feasibility of video imaging in security screening applications.
Packaging constitutes one of the most costly steps of MEMS/MOEMS manufacturing. The package protects the MEMS
devices and, in the case of MOEMS, it also provides light access to the device. In many cases, MEMS require a specific
atmosphere for their proper functioning. The atmosphere should be kept invariable during the lifetime of the package in
order to not degrade the performance of the device. Maintaining a constant atmosphere inside the package becomes more
challenging as the cavity volume is decreased to the microliter and nanoliter range. Other packaging requirements are
compatibility with wafer-level microfabrication techniques (cost reduction) and low temperature assembly in cases
where temperature sensitive devices are to be packaged.
In recent years, INO has performed a great amount of work towards the development of uncooled IR microbolometer
detectors using VOx technology. Different pixel designs have been optimized for different applications. The bolometer
pixels require a vacuum atmosphere below 10 mTorr to be maintained during the lifetime of the device in order to
operate at their highest sensitivity. INO's micropackaging technology has been demonstrated to provide base pressures
below 5 mTorr. An equivalent flow rate of 2.5×10-14 Torr.l/sec has been obtained for a device packaged without any
getter. The advantages of INO's micropackaging technology are the possibility of achieving very low base pressures, the
low temperatures required for the assembly (the package device is never exposed to a temperature above 150 °C) and its
compatibility with hybrid wafer-level packaging. The technology has been developed for the micropackaging of INO's
160×120 pixel uncooled microbolometer FPA, but it is compatible with any other kinds of MOEMS-MEMS devices
requiring vacuum hermetic packaging. In order to increase the lifetime of the package, knowledge of the gases
outgassing inside the package is crucial. A hybrid approach has been chosen as it permits packaging only known-good
dies and saving considerable quantities of IR window material. In INO's hybrid wafer-level packaging, dicing is
performed only through one of the wafers, therefore reducing the risk of perturbing the vacuum during the separation of
the different dies.
Micro-Electro-Mechanical Systems (MEMS) packaging constitutes most of the cost of such devices. For the integration
of MEMS with microelectronics systems to be widespread, a drastic reduction of the overall price is required. Wafer-level-packaging allows a fundamental reduction of the packaging cost by combining wafer-level microfabrication
techniques with wafer-to-wafer bonding. To achieve the vacuum atmosphere required for the operation of many MEMS
devices, bonding techniques such as anodic bonding, eutectic bonding, fusion bonding and gold to gold thermocompression
bonding have been utilized, which require relatively high temperatures (>300°C) being in some cases
incompatible with MEMS and microelectronics devices. Furthermore, to maintain vacuum integrity over long periods of
time, getters requiring high activation temperatures are usually employed.
INO has developed a hybrid wafer-level micropackaging technology based on low temperature fluxless solder joints in
which the micropackaged MEMS device is not exposed to a temperature over 150°C. The micropackages have been
designed for 160×120 microbolometer FPAs. Ceramic spacers are patterned by standard microfabrication techniques
followed by laser micromachining. AR-coated floatzone silicon IR windows are patterned with a solderable layer. Both,
microbolometer dies and windows are soldered to the ceramic tray by a combination of solder paste stencil printing,
reflow and fluxless flip-chip bonding. A low temperature getter is also introduced to control outgassing of moisture and
CO2 during the lifetime of the package. Vacuum sealing is carried out by locally heating the vacuum port after bake out
of the micropackages. In this paper, the vacuum integrity of micropackaged FPA dies will be reported. Base pressures as
low as 5 mTorr and equivalent flow rates at room temperature of 4×10-14 Torr.l/s without getter incorporation have been
demonstrated using integrated micro-pressure gauges. A study of the influence of different packaging parameters on the
lifetime of micropackages will be presented.
A dual band thermal/visible weapon sight (TVWS) prototype was developed by INO in collaboration with
DRDC Valcartier. The TVWS operates in the 8-12 μm infrared (IR) and 300-900 nm visible wavebands for
enhanced vision capabilities in day and night operations. It is equipped with lightweight athermalized
coaxial catadioptric objectives, a bolometric IR imager operating in a microscan mode providing an
effective resolution of 320 x 240 pixels and a visible image intensifier of 768 x 493 pixels. The TVWS is
equipped with a miniature shutter for automatic offset calibration. Real-time imaging at 30 fps is available.
Both the visible and IR images can be toggled with a single touch button and displayed on an integrated
color micro liquid crystal display (LCD). The TVWS also has a standard video output via a coaxial
connector. An integrated wireless analog RF link can be used to send images to a remote command control. The sight has an adjustable electronic crosshair and two manual focuses from 25 m to infinity. On-board
processing capabilities were added to introduce specific functionalities such as image polarity inversion
(black hot/white hot) and image enhancement. This TVWS model is also very lightweight (~ 1900 grams)
and compact (volume of 142 cubic inches). It offers human size target detection at 800 m and recognition at
200 m (Johnson criteria) with the IR waveband while offering the human recognition at up to 800 m with
the visible waveband. The TVWS is adapted for weaver or Picatinny rail mounting.
A rugged lightweight thermal weapon sight (TWS) prototype was developed at INO in collaboration with
DRDC-Valcartier. This TWS model is based on uncooled bolometer technology, ultralight catadioptric
optics, ruggedized mechanics and electronics, and extensive onboard processing capabilities.
The TWS prototype operates in a single 8-12 μm infrared (IR) band. It is equipped with a unique
lightweight athermalized catadioptric objective and a bolometric IR imager with an INO focal plane array
(FPA). Microscan technology allows the use of a 160 x 120 pixel FPA with a pitch of 50 μm to achieve a
320 × 240 pixel resolution image thereby avoiding the size (larger optics) and cost (expensive IR optical
components) penalties associated with the use of larger format arrays. The TWS is equipped with a
miniature shutter for automatic offset calibration. Based on the operation of the FPA at 100 frames per
second (fps), real-time imaging with 320 x 240 pixel resolution at 25 fps is available. This TWS is also
equipped with a high resolution (857 x 600 pixels) OLED color microdisplay and an integrated wireless
digital RF link. The sight has an adjustable and selectable electronic reticule or crosshair (five possible
reticules) and a manual focus from 5 m to infinity standoff distance. Processing capabilities are added to
introduce specific functionalities such as image inversion (black hot and white hot), image enhancement,
and pixel smoothing. This TWS prototype is very lightweight (~ 1100 grams) and compact (volume of 93
cubic inches). It offers human size target detection at 800 m and recognition at 200 m (Johnson criteria).
With 6 Li AA batteries, it operates continuously for 5 hours and 20 minutes at room temperature. It can
operate over the temperature range of -30oC to +40oC and its housing is completely sealed. The TWS is
adapted to weaver or Picatinny rail mounting. The overall design of the TWS prototype is based on
feedbacks of users to achieve improved user-friendly (e.g. no pull-down menus and no electronic focusing)
and ergonomic (e.g. locations of buttons) features.
Linear detector array formats are suitable for applications where relative motion between the detector and scene provides an intrinsic scanning mechanism, such as industrial inspection systems and satellite-based earth and planetary observation. The linear array format facilitates the introduction readout features not available in 2-D formats and when combined with low cost packaging approaches reduces sensor cost. We present two linear uncooled detector arrays based on VOx microbolometer technology and integrated CMOS readout electronics. The IRL256B is a linear array of 256 detectors on a 52 μm pitch. It includes a parallel array of 256 reference detectors to provide coarse offset correction and substrate temperature drift compensation. The IRL512A consists of 3 parallel lines of 512 pixels on a 39 μm pitch. It is particularly well suited to multi-spectral pushbroom imaging applications. Each pixel includes active and reference detectors to reduce pixel offset, eliminate common mode power supply noise and increase immunity to chip temperature drift. All pixels are integrated in parallel and the data are output in 14-bit digital format on three parallel output buses. The microbolometer detector design can be customized for selected wavelength ranges from NIR to VLWIR. The IRL256B has been integrated in industrial thermal line-scan imagers and spectrometers and may also be employed in uncooled airborne imaging and scanned surveillance or inspection systems. The IRL512A has been selected as the baseline detector for a number of future earth observation satellite missions.
A novel concept for low-cost, wafer-level packaging of MEMS is proposed and applied to vacuum packaging of INO's 160x120 pixel uncooled bolometric focal plane arrays, FPAs, based on vanadium oxide as thermistor material. The wafer-scale fabrication of both metallic and ceramic micropackages is described. In the former case, a nickel tray composed of several tens of micropackages is electroplated by using a thick negative resist as micromold. In the latter case, micropackages are fabricated from up to 1 mm-thick, polished, laser machined alumina wafers equipped with solderable layers and solder seals. FPA dies and infrared windows are then soldered to the main tray by thermo-compression bonding. Contrary to the conventional wafer-to-wafer bonding approach, assembly and vacuum sealing steps are dissociated. For that purpose, each micropackage is equipped with a pump-out hole for outgassing prior to vacuum sealing. To monitor in-situ pressure changes within the sealed microcavity, micromachined pressure sensors were specifically designed for thermal conductance measurements. The initial characterization of dies after assembly in the metallic micropackage is presented.
INO in collaboration with DRDC Valcartier has been involved in the design and development of uncooled IR bolometric detector technology since the early 1990s for a broad range of military and commercial applications. From the beginning, the strategy has been to develop small-size bidimensional detector arrays and specialty linear arrays, both equipped with on-chip readout electronics. The detector arrays have been implemented in various instruments for both imaging and non-imaging applications. This paper describes two TWS1 and TWS2 prototypes of single band thermal weapon sights (TWS) making use of a novel catadioptric, i.e. refractive/reflective, optics and INO's miniature IR cameras. These cameras employ a 160x120 pixel uncooled bolometric FPA with a 52 µm pitch and NETD at 50 mK, and modular electronics consisting of three boards stacked together to fit into a 3-inch cube volume. The ultra lightweight catadioptric objective is inherently athermalized in the -30°C to +40°C range. The TWS1 is also equipped with a miniature RF link allowing bi-directional video transmission. This TWS1 weighs only 900 g and has a total volume of about 75 in3. Its power consumption is 2 W. The experimental performance showed that human detection, recognition and identification could be achieved at 800 m, 200 m, and 120 m, respectively. Construction of an improved TWS2 model is in progress. The objective is the reduction of TWS2 model weight down to 700 g, its volume down to 50 in3, replacing the RF video link with a wireless digital link, and increasing resolution to 320x240 pixels.
A novel concept for low-cost, wafer-level packaging of MEMS is proposed and applied to vacuum packaging of INO’s 160x120 pixel uncooled bolometric focal plane arrays, FPAs, based on vanadium oxide thermistor material. A wafer-scale metallic tray composed of several tens of micropackages is electroplated by using the thick resist SU-8 as a micromold. FPA dies and infrared windows are then soldered to the main tray by flip-chip bonding. Contrary to the conventional wafer to wafer bonding approach, assembly and vacuum sealing steps are dissociated. For this purpose, each micropackage is equipped with a pump-out hole for outgassing under vacuum and at elevated temperature prior to vacuum sealing. The process flow for fabrication of micropackages is described. The influence of DC and pulse plating conditions on the stress and properties of deposited nickel packages was investigated. Results on the selective electroplating of indium solder on antireflection-coated IR window wafers and the formation of a solderable layer around the chip are presented.
We describe the fabrication process of silicon nitride (Si3N4) based two-dimensional photonic crystals. The fabrication process mainly involves e-beam direct-write lithography and reactive ion etching. The concerned photonic crystal structures consist of a periodic arrangement of sub-micrometric holes transferred into a suspended Si3N4 membrane using a poly-methylmethacrylate resist layer as a mask. Numerical simulations based on a plane wave expansion method for 2D photonic band gap approximation were conducted to determine the design parameters of the photonic crystal membranes. Flat and stress free photonic crystal membranes were achieved with very good control in sidewall profile and feature shape.
Modified thermal sensors have been produced and characterized for fingerprint recording applications. The sensors are derived from the IR imaging technology developed at INO. The sensor array is made of 160x120 pixel VOx based micro thermistors that provide an image of a surface area of 8.3 x 6.2 mm2 with a resolution of 488 dpi. The sensors were reinforced to withstand the mechanical pressure of the finger and the electrical discharges from the human skin. It is shown that despite their low thermal insulation, the sensors provide an image of the fingerprint pattern with relatively high contrast and resolution. With the acquisition electronics of an IR imager, the temprature of the sensor must be controlled. Measurements of the thermistor temperature were performed in order to access the intrinsic properties of the fingerprint sensors. The NETD is on the order of 2 10-3°C when the pass band of the filter is 330 kHz. The temporal behavior of the thermistor temperature shows that 10 ms after the finger has been brought into contact, with the sensor, the temperature difference between thermistors in ridge and valley areas of the fingerprint DTr,v may reach 80 10-3°C, for an initial temperature difference between the finger and the sensor of 1°C. Once the sensor reaches a steady thermal state after a long time, the same difference decreases to 1.9 10-3°C. The required temperature difference DTr,v, estimated to be 4.8 10-3°C to achieve an adequate signal to noise ratio, is relatively easy to reach at short and at long time periods. A modification to the method of acquisition is proposed to cancel the effect of the thermal drift of the sensor and to eliminate the need for the sensor temperature stabilization with a TEC. With this method, the recording of the fingerprint pattern may be achieved in 50 ms after the finger has been brought into contact. This leads to interesting gains in space, time and power consumption. Finally, for applications where the finger must remain in contact with the sensor, the same method may be efficient to reduce the need for thermal control.
MEMS (Micro Electro Mechanical Systems) technology has expanded widely over the last decade in terms of its use in devices and instrumentation for diverse applications. However, access to versatile foundry services for MEMS fabrication is still limited. At INO, the presence of a multidisciplinary team and a complete tool set allow us to offer unique MEMS foundry-type services. These services include: design, prototyping, fabrication, packaging and testing of various MEMS and MOEMS devices. The design of a device starts with the evaluation of different structures adapted to a given application. Computer simulation tools, like IntelliSuite, ANSYS or custom software are used to evaluate the mechanical, optical, thermal and electromechanical performances. Standard IC manufacturing techniques such as metal, dielectric and semiconductor film deposition and etching as well as photolithographic pattern transfer are available. In addition, some unique techniques such as on-wafer lithography by laser writing, gray-scale mask lithography, thick photoresist lithography, selective electroplating, injection moulding and UV-assisted moulding are available to customers. The hermetic packaging and a novel patented wafer-level micropackaging are also applied. This multifaceted expertise has been utilized to manufacturing of several types of MEMS devices as well as complex instruments including micromirror-type devices, microfilters, IR microbolometric detector arrays, complete cameras and multipurpose sensors.
INO has been active in microbolometer and FPA technology development since the early 1990s. Microbolometer detectors based on VO2 films with TCR above 3% are typically fabricated. VOx films with TCR above 2% have been developed for applications where FPA temperature is not stabilized. INO is continuing its development of high fill factor pixels with sizes down to 25 micrometers and new macro- and micro-packaging technology. All fabrication is done on six inch wafers in INOs newly expanded clean room facility. INO currently offers as standard products 256x1 and 160x120 pixel FPAs with 52 micrometers pixel pitch. Both arrays have simple, robust, and versatile CMOS readout integrated circuits (ROICs) that may be accessed in self-scanning or random access mode, and reference detectors for on-chip coarse offset and temperature drift compensation. Single frame NETDs (f/1, 300 K, 8-12 micrometers ) are on the order of 150 - 250 mK and may be reduced by frame averaging. Prototyping boards have been developed for both arrays, and the 160x120 FPA has been integrated in a number of thermal cameras and instruments. In collaboration with its clients, INO has developed several FPAs for specific space and terrestrial applications. Custom ROICs fabricated in several different CMOS processes from multiple foundries have been used. A 512x3 pixel microbolometer FPA with 39 micrometers pitch is being developed for the European Space Agency. The array is designed for multi-spectral pushbroom imaging applications and features a novel ROIC with very low 1/f noise, pixel by pixel offset and drift compensation, variable integration time, and digital output. Its single frame NETD (f/1, 300 K, 8-12 micrometers ) is nominally 80 mK.
In an effort to leverage uncooled microbolometer technology, testing of bolometer performance in various nonimaging applications has been performed. One of these applications makes use of an uncooled microbolometer array as the sensing element for a laser beam analyzer. Results of the characterization of cw CO2 laser beams with this analyzer are given. A comparison with the results obtained with a commercial laser beam analyzer is made. Various advantages specific to microbolometer arrays for this application are identified. A second application makes use of microbolometers for absolute temperature measurements. The experimental method and results are described. The technique's limitations and possible implementations are discussed. Finally, the third application evaluated is related to the rapidly expanding field of biometry. It consists of using a modified microbolometer array for fingerprint sensing. The basic approach allowing the use of microbolometers for such an application is discussed. The results of a proof-of-principle experiment are described. Globally, the described work illustrates the fact that microbolometer array fabrication technology can be exploited for many important applications other than IR imaging.
Prototypes of VO2-based bolometric detectors with lateral dimensions of 25 X 25, 30 X 30, 35 X 35, 40 X 40 and finally 50 X 50 micrometers2 and fill factors approaching 90% are presented. These detectors are grouped in hardwired linear arrays as large as 512 X 1 pixels. Under DC biasing, the fabricated detectors, even the smallest ones, exhibit responsivities from 48,000 to 120,000 VW-1, detectivities in the range of 1.5 X 108 cm Hz1/2W-1 and response times in the range of 5 ms. These new bolometric detector structures contain hidden-legs placed completely underneath the bolometer platform. Results of simulations of the mechanical, optical and electrical properties of these new detector structures are presented. A complete detector fabrication process flow is described.
An uncooled IR camera making use of a 128 X 128 pixel bolometric FPA is presented. The reconfigurable bolometric focal plane array consist of 50 micrometer X 50 micrometer pixels and simple on-chip CMOS readout electronics which can be operated in random access, independent row and column clocking, and self-scanning modes. Depending on the selected pixel format and frame rate, the FPA's NETD varies from 0.52 degrees Celsius down to 0.10 degrees Celsius. The modular IR camera is software configured and provides RS170A analog video and 12-bit TTL format digital outputs.
Three types of uncooled IR bolometric detector arrays equipped with 256 X 1 and 256 X 40 VO2 thermistor pixels and on-chip readout electronics are presented. These reconfigurable arrays consist of 50 micrometer X 50 micrometer pixels and CMOS readout electronics that can be operated either in random access mode or in self-scanning mode. Depending on the operational conditions, the NETD of the arrays can be as low as 20 mK.
The construction of superconductor focal planes for infrared or millimeter wave imaging requires that the substrate of superconductor films be micromachined into thermal isolation structures or horn cavities. Wet etching was used to create cavities in the MgO substrate of high Tc BiPbSrCaCuO films. Processes for lithography of metal patterns on superconductor films were also devised. It was found that cavities with a wall angle of 55 - 60 degrees could be formed in (100) MgO using solutions of HNO3:CH3COOH or H3PO4. The MgO normal etch rates of these solutions were found to be respectively 117 and 27 micrometer/hour. Thermal evaporation and magnetron rf sputtering were used to prepare Au and Ag films on BiPbSrCaCuO and MgO; however, only the sputtered films showed adequate film adhesion. Electric contacts and dipoles made of Au or Ag could be created by wet etching in a solution of KI-I without apparent degradation of the superconductivity of BiPbSrCaCuO.