Μm Pixel Pitch Research Articles

Teledyne's high‐performance 4 K × 4 K infrared detectors

AbstractWe present the test results of science grade 4 K × 4 K HgCdTe H4RG‐15 and H4RG‐10 SWIR 2.5 μm sensor chip assemblies (SCAs). Teledyne's 4 K × 4 K, 15 and 10 μm pixel pitch infrared arrays are developed for space and era of Extremely Large Telescopes. They are currently being used in new instrumentation on existing telescopes and missions. We report data on H4RG‐15 and H4RG‐10 arrays that have achieved science grade performance. For H4RG‐15 and H4RG‐10: very low dark current (<0.005 e−/pixel/s at 80 K and <0.01 e−/pixel/s at 95 K), high quantum efficiency >70–90%, single CDS readout noise <20 e−, operability >99%, total crosstalk <1.5%, well capacity >70 ke−, and power dissipation less than 4 mW are routinely achieved. These SCAs are substrate‐removed HgCdTe, which simultaneously detect visible and infrared light, enabling spectrographs to use a single SCA for visible‐IR sensitivity. Larger focal plane arrays can be constructed by assembling mosaics of individual arrays.

Development of a high-speed line-scanning fluorescence lifetime imaging microscope for biological imaging.

We report the development of a novel line-scanning microscope capable of acquiring high-speed time-correlated single-photon counting (TCSPC)-based fluorescence lifetime imaging microscopy (FLIM) imaging. The system consists of a laser-line focus, which is optically conjugated to a 1024 × 8 single-photon avalanche diode (SPAD)-based line-imaging complementary metal-oxide semiconductor (CMOS), with 23.78 µm pixel pitch at 49.31% fill factor. Incorporation of on-chip histogramming on the line-sensor enables acquisition rates 33 times faster than our previously reported bespoke high-speed FLIM platforms. We demonstrate the imaging capability of the high-speed FLIM platform in a number of biological applications.

Development of novel single-die hybridisation processes for small-pitch pixel detectors

Hybrid pixel detectors require a reliable and cost-effective interconnect technology adapted to the pitch and die sizes of the respective applications. During the ASIC and sensor R&D phase, especially for small-scale applications, such interconnect technologies need to be suitable for the assembly of single dies, typically available from Multi-Project-Wafer submissions. Within the CERN EP R&D programme and the AIDAinnova collaboration, innovative hybridisation concepts targeting vertex-detector applications at future colliders are under development. Recent results of two novel interconnect methods for pixel pitches of 25 µm and 55 µm are presented in this contribution — an industrial fine-pitch SnAg solder bump-bonding process adapted to single-die processing using support wafers, as well as a newly developed in-house single-die interconnection process based on Anisotropic Conductive Film (ACF). The fine-pitch bump-bonding process is qualified with hybrid assemblies from a recent bonding campaign at Frauenhofer IZM. Individual CLICpix2 ASICs with 25 µm pixel pitch were bump-bonded to active-edge silicon sensors with thicknesses ranging from 50 µm to 130 µm. The device characterisation was conducted in the laboratory as well as during a beam test campaign at the CERN SPS beam-line, demonstrating an interconnect yield of about 99.7%. The ACF interconnect technology replaces the solder bumps by conductive micro-particles embedded in an epoxy film. The electro-mechanical connection between the sensor and ASIC is achieved via thermocompression of the ACF using a flip-chip device bonder. The required pixel pad topology is achieved with an in-house Electroless Nickel Immersion Gold (ENIG) plating process. This newly developed ACF hybridisation process is first qualified with the Timepix3 ASICs and sensors with 55 µm pixel pitch. The technology can be also used for ASIC-PCB/FPC integration, replacing wire bonding or large-pitch solder bumping techniques. This contribution introduces the two interconnect processes and presents preliminary hybridisation results with CLICpix2 and Timepix3 sensors and ASICs.

Focus on test, measurement, quantum metrology, and analytical equipment

Focus on test, measurement, quantum metrology, and analytical equipment

Development of integration mode proton imaging with a single CMOS detector for a small animal irradiation platform

A novel irradiation platform for preclinical proton therapy studies foresees proton imaging for accurate setup and treatment planning. Imaging at modern synchrocyclotron-based proton therapy centers with high instantaneous particle flux is possible with an integration mode setup. The aim of this work is to determine an object’s water-equivalent thickness (WET) with a commercially available large-area CMOS sensor. Image contrast is achieved by recording the proton energy deposition in detector pixels for several incoming beam energies (here, called probing energies) and applying a signal decomposition method that retrieves the water-equivalent thickness. A single planar 114 mm × 65 mm CMOS sensor (49.5 µm pixel pitch) was used for this study, aimed at small-animal imaging. In experimental campaigns, at two isochronous cyclotron-based facilities, probing energies suitable for small-animal-sized objects were produced once with built-in energy layer switching and the other time, using a custom degrader wheel. To assess water-equivalent thickness accuracy, a micro-CT calibration phantom with 10 inserts of tissue-mimicking materials was imaged at three phantom-to-detector distances: 3 mm, 13 mm, and 33 mm. For 3 mm and 13 mm phantom-to-detector distance, the average water-equivalent thickness error compared to the ground truth was about 1% and the spatial resolution was 0.16(3) mm and 0.47(2) mm, respectively. For the largest separation distance of 33 mm air gap, proton scattering had considerable impact and the water-equivalent thickness relative error increased to 30%, and the spatial resolution was larger than 1.75 mm. We conclude that a pixelated CMOS detector with dedicated post-processing methods can enable fast proton radiographic imaging in a simple and compact setup for small-animal-sized objects with high water-equivalent thickness accuracy and spatial resolution for reasonable phantom-to-detector distances.

Using an acousto-optic modulator as a fast spatial light modulator.

High-speed spatial light modulators (SLM) are crucial components for free-space communication and structured illumination imaging. Current approaches for dynamical spatial mode generation, such as liquid crystal SLMs or digital micromirror devices, are limited to a maximum pattern refresh rate of 10 kHz and have a low damage threshold. We demonstrate that arbitrary spatial profiles in a laser pulse can be generated by mapping the temporal radio-frequency (RF) waveform sent to an acousto-optic modulator (AOM) onto the optical field. We find that the fidelity of the SLM performance can be improved through numerical optimization of the RF waveform to overcome the nonlinear effect of AOM. An AOM can thus be used as a 1-dimensional SLM, a technique we call acousto-optic spatial light modulator (AO-SLM), which has 50 µm pixel pitch, over 1 MHz update rate, and high damage threshold. We simulate the application of AO-SLM to single-pixel imaging, which can reconstruct a 32×32 pixel complex object at a rate of 11.6 kHz with 98% fidelity.

Flexible high-resolution thin micropolarizers for imaging polarimetry

More durable (with high impact force), lighter, and more compact flexible azo dye micropolarizers are attractive candidates for low-cost, simple polarization imaging systems. The liquid crystal polymer (LCP), as an emerging material developed by photo-alignment technology, is a potential material for organizing the long-range ordered structure of azo dyes. However, little research has been done on LCP aligned azo dyes. This paper points out and solves a key problem that restricts the fabrication of high-precision arrays in guest (azo dye)-host (LCP) systems: the doping of dyes leads to disorder of the LCP during curing. After solving the problem, the relationship between the thickness of the LCP and the extinction ratio of the polarizing film was investigated, which effectively improved the extinction ratio. Alignment of azo dye molecules in the range of 2 µm (0°–180°) and arrays of micropolarizers (0°, 45°, 90°, -45°) with 8 µm × 8 µm pixel pitch was achieved by laser direct writing technology. The bending cycle test demonstrates the mechanical stability of the ultrathin flexible polarizer. The flexible patterned polarizer with robust chemical and mechanical stabilities provides a flexible way to capture the polarization of the light and highly integrated advanced flexible optoelectronic devices.

Pixel detector hybridisation with anisotropic conductive films

Hybrid pixel detectors require a reliable and cost-effective interconnect technology adapted to the pitch and die sizes of the respective applications. During the ASIC and sensor R&D phase, and in general for small-scale applications, such interconnect technologies need to be suitable for the assembly of single-dies, typically available from Multi-Project-Wafer submissions. Within the CERN EP R&D programme and the AIDAinnova collaboration, innovative hybridisation concepts targeting vertex-detector applications at future colliders are under development. This contribution presents recent results of a newly developed in-house single-die interconnection process based on Anisotropic Conductive Film (ACF). The ACF interconnect technology replaces the solder bumps with conductive particles embedded in an adhesive film. The electro-mechanical connection between the sensor and the read-out chip is achieved via thermo-compression of the ACF using a flip-chip device bonder. A specific pad topology is required to enable the connection via conductive particles and create cavities into which excess epoxy can flow. This pixel-pad topology is achieved with an in-house Electroless Nickel Immersion Gold (ENIG) plating process that is also under development within the project. The ENIG and ACF processes are qualified with the Timepix3 ASIC and sensors, with 55 µm pixel pitch and 14 µm pad diameter. The ACF technology can also be used for ASIC-PCB/FPC integration, replacing wire bonding or large-pitch solder bumping techniques. This contribution introduces the ENIG plating and ACF processes and presents recent results on Timepix3 hybrid assemblies.

A 1Gpixel 10FPS CMOS image sensor using pixel array high-speed readout technology

In the very large array CMOS image sensor (CIS), the very large parasitic resistors and capacitors on the column bus cause very slow charging and discharging speeds and affect the readout speed seriously. In order to solve the problem, this work proposed a high-speed readout circuit that can be applied to the very large array of column parallel readout mechanism CIS. Based on 55 nm CIS special process, on the premise of not produce additional bus, by tracking the analog signal settling process in real time, self-acceleration is realized in the terminal of the column bus, then the speed of charging and discharging are improved greatly. In the work, the column bus parasitic parameters of 42,624 × 24,000 pixels CMOS image sensor with 4 μm pixel pitch are analyzed in detail and a method for establishing self-acceleration of column bus is proposed. The experimental results show that the charging time is shortened from 4μs to 790 ns, and the discharging time is shortened from 22.43μs to 1.17μs under 38.3 pF parasitic capacitance and 26.5 kΩ parasitic resistance in the column bus. On the one hand, the frame per second (FPS) of the 1Gpixel CMOS image sensor reach 10FPS, on the other hand, the column bus tail current can be reduced to 1.5 μA, which reducing the power consumption of pixel array, and the sampling interval time of the correlation double sampling (CDS) is compressed, so broadened the frequency of noise suppression. While realizing self-acceleration, the additional power consumption single column is less than 10 μA.

A CMOS Microelectrode Array System With Reconfigurable Sub-Array Multiplexing Architecture Integrating 24,320 Electrodes and 380 Readout Channels.

This article presents a CMOS microelectrode array (MEA) system with a reconfigurable sub-array multiplexing architecture using the time-division multiplexing (TDM) technique. The system consists of 24,320 TiN electrodes with 17.7 μm-pitch pixels and 380 column-parallel readout channels including a low-noise amplifier, a programmable gain amplifier, and a 10-b successive approximation register analog to digital converter. Readout channels are placed outside the pixel for high spatial resolution, and a flexible structure to acquire neural signals from electrodes selected by configuring in-pixel memory is realized. In this structure, a single channel can handle 8 to 32 electrodes, guaranteeing a temporal resolution from 5 kS/s to 20 kS/s for each electrode. A 128 × 190 MEA system was fabricated in a 110-nm CMOS process, and each readout channel consumes 81 μW at 1.5-V supply voltage featuring input-referred noise of 1.48 μVrms without multiplexing and 5.4 μVrms with multiplexing at the action-potential band (300 Hz-10 kHz).

Simultaneous in-situ x-ray beam profile and intensity measurements with a minimally invasive pixelated diamond monitor

Measuring x-ray beam position, profile, and intensity at synchrotron beamlines provides valuable information for all experiments. Sydor’s transparent x-ray camera (TXC), based on technology originally developed at Brookhaven National Laboratory[1], enables these measurements in-line with experiments for live feedback. The TXC has a low beam profile that fits within a standard vacuum flange width and is composed of diamond material for > 90% transmission of > 5 keV x-rays, minimizing disruption of beamline space and the x-ray beam itself. Standard device parameters include 32 x 32, 60 µm pitch pixels, linearity over a 107 – 1016 photons/s dynamic imaging range, < 40 pA noise floor, and total flux measurement mode. Device performance has been evaluated using a pinhole mask with a benchtop silver x-ray tube and during beam focusing tests at the XFP beamline at NSLS-II and flux characterization at the FAST beamline at CHESS. This work will highlight the features of this commercial beam diagnostic, test results, and future directions and applications of the technology.

First light of MC[formula omitted]-1K, a 250 [formula omitted]m pixel pitch CdTe imaging spectrometer for hard X-ray astronomy

The next generation of hard X-ray space telescopes for astrophysics and solar physics requires the development of focal planes with high detection efficiency above 10 keV and enhanced spectroscopic imaging performance. We designed and produced MC2-1K, the first prototype of a new family of fine pitch hybrid detectors. It consists of a 32 × 32 pixel CdTe semiconductor detector point-to-point connected to the spectroscopic channels of a full-custom ASIC. The ASIC named D2R2 was produced in 2019 in the XFAB 0.18 μm technology and has the same 250 μm pixel pitch as the detector. We demonstrated a median equivalent charge noise of 54 e- RMS, equivalent to an energy resolution of 654 eV at 31 keV for a CdTe detector. We developed an acquisition system where the signals of D2R2’s 32 rows are encoded in parallel by a 32-channel ADC ASIC, OWB-1. The custom daughter board with the hybrid detector is placed in a thermally controlled vacuum chamber for a moderate cooling. This paper will present the characterization tests of the ASIC, the dedicated test set-up and the first spectroscopic measurements of the MC2-1K hybrid detector.

Compact athermalized LWIR objective lens

A new compact optical passive athermalized objective lens is designed with a focal length 120 mm and F-number 1.1. Its full field of view is 12.2°. The geometrical aberrations due to the large aperture and the wide field of view are well corrected as well as the chromatic aberration. Hence, the maximum RMS radius of the spot diagram over the full field of view is less than 17 µm and the Strehl ratio is 0.95 at 20 °C. The MTF is nearly limited in diffraction over the full F.O.V. This good correction of aberrations makes the optical system gain high resolution and suitable to work with a focal plane array detector with 17-µm pixel pitch. This performance is stable over a long temperature range from − 40 °C to + 65 °C. Moreover, the optical system is relatively compact “140 mm.” The total transmittance (after absorption consideration) of the optical system is enhanced from 6.6 to 94.07% at λ = 10 µm along the optical axis upon applying an anti-reflection coating.

Full-color micro-display by heterogeneous integration of InGaN blue/green dual-wavelength and AlGaInP red LEDs.

A full-color micro-display via bonding of a InGaN blue/green dual-wavelength light-emitting diode (LED) array and a AlGaInP red LED array is demonstrated. The micro-display has a 120 µm pixel pitch, and each pixel consists of 40 µm × 120 µm red/green/blue (R/G/B) subpixels. The red LED array was integrated with the blue/green dual-wavelength LED array by Au/In flip-chip bonding to achieve full-color emission. Full-color images presented by the micro-display have high brightness and a wide color gamut. This heterogeneous integration technology using conventional LED materials shows the feasibility of a cost-effective approach for reliable high-performance full-color LED micro-displays in virtual reality (VR) and augmented reality (AR) devices.

Performance of a complementary metal-oxide-semiconductor sensor for laser guide star wavefront sensing

The adaptive optics systems of future Extremely Large Telescopes (ELTs) will be assisted with laser guide stars (LGS) which will be created in the sodium layer at a height of ≈90 km above the telescopes. In a Shack–Hartmann wavefront sensor, the long elongation of LGS spots on the sub-pupils far apart from the laser beam axis constraints the design of the wavefront sensor (WFS) which must be able to fully sample the elongated spots without undersampling the non-elongated spots. To fulfill these requirements, a newly released large complementary metal oxide semiconductor sensor with 1100 × 1600 pixels and 9 μm pixel pitch could be employed. Here, we report on the characterization of such a sensor in terms of noise and linearity, and we evaluate its performance for wavefront sensing based on the spot centroid variations. We then illustrate how this new detector can be integrated into a full LGS WFS for both the European Southern Observatory’s ELT and the Thirty Meter Telescope.

Demonstration of 1280 × 1024 long-wavelength infrared FPA with 10 μm pixel pitch based on InAs/GaSb type-II superlattice

1280 × 1024 format long-wavelength infrared focal plane array with 10 μm pixel pitch was fabricated based on InAs/GaSb type-II superlattice. At 70 K, the single-element device shows a 50% cutoff wavelength of 10.0 μm, peak quantum efficiency of 45.04% and peak detectivity of 1.87 × 1011cm·Hz1/2·W−1 at 8.22 μm, the FPA infrared imaging performed an average noise equivalent temperature difference of 28.9 mK at 300 K background (F/3 optics) with an integration time of 1.12 ms and applied bias of −50 mV. The operability and non-uniformity of the FPA were 99.87% and 2.90% respectively, and it exhibits a stable residual non-uniformity below 0.1% of the dynamic range.

Characterisation of a soft X-ray optimised CMOS Image Sensor

A prototype CMOS Image Sensor optimised for soft X-ray applications has been designed by the Centre for Electronic Imaging in partnership with Teledyne-e2v. The device features four different pixel variants (three variants of 40 μm pitch pixels, and one variant of 10 μm pixels) each covering a quarter of the 2 × 2 cm2 image area. The pixel designs feature fully depleted pinned photodiodes using reverse substrate bias and have been optimised for low noise operation, high responsivity and low image lag.The fabricated front-illuminated devices have been tested in a custom-built vacuum test setup at operating temperatures between -30°C and -40°C. The sensors feature less than 5 e- RMS readout noise and energy resolution of 142 eV at Mn-Kα (5.9 keV). The response to soft X-ray with different sensor parameters (e.g. pixel pitch, deep-depletion extension implant depth, and back-bias voltage) is also studied.

Two High-Precision Proximity Capacitance CMOS Image Sensors with Large Format and High Resolution.

This paper presents newly developed two high-precision CMOS proximity capacitance image sensors: Chip A with 12 μm pitch pixels with a large detection area of 1.68 cm2; Chip B with 2.8 μm pitch 1.8 M pixels for a higher resolution. Both fabricated chips achieved a capacitance detection precision of less than 100 zF (10−19 F) at an input voltage of 20 V and less than 10 zF (10−20 F) at 300 V due to the noise cancelling technique. Furthermore, by using multiple input pulse amplitudes, a capacitance detection dynamic range of up to 123 dB was achieved. The spatial resolution improvement was confirmed by the experimentally obtained modulation transfer function for Chip B with various line and space pattens. The examples of capacitance imaging using the fabricated chips were also demonstrated.

High-spatial resolution measurements with a GaAs:Cr sensor using the charge integrating MÖNCH detector with a pixel pitch of 25 μm

The aim of this project is to determine the imaging capabilities of a 25 μm pixel pitch GaAs:Cr sensor of 500 μm thickness bump-bonded to the charge integrating MÖNCH 03 readout chip (also called GaAs-MÖNCH assembly) and to assess the possibility to improve the spatial resolution by applying a position interpolation algorithm developed at PSI. Measurements were performed at the TOMCAT beamline of the Swiss Light Source (SLS) using photon beams in the energy range of 10–30 keV. The imaging experiments indicate the possibility to enhance the spatial resolution of the detector beyond its actual physical pixel pitch. We have quantified the spatial resolution of a GaAs-MÖNCH assembly by means of the modulation transfer function (MTF), achieving 10 μm at 10 keV and 12 μm at 20 keV photon energies. By applying a modified interpolation algorithm, a spatial resolution of ∼5 μm was obtained for 16 keV when binning to 2.5 μm virtual pixels, while with the silicon-MÖNCH assembly, we achieved a spatial resolution of 3.5 μm, which serves as gold standard. The results are promising because they open new possibilities to perform imaging measurements using the GaAs-MÖNCH assembly at photon energies above 15 keV, where silicon sensors suffer from a diminishing quantum efficiency.

Development of a Fringe Printer With 0.35 μm Pixel Pitch

The development of computational devices can provide computer-generated holograms (CGH) of over 100 Giga-pixel easily. The performance improvement of the graphical processing unit makes calculations faster with a normal personal computer. In contrast, the output device of CGH is not reported much. Since CGH is a fringe pattern, high resolution and fine pixel pitch are required for the output device. We have been developing a direct fringe printer, which consists of a laser, an X-Y stage, an SLM, and optical parts available on the market. Our previous report presented a liquid crystal panel, which was used for SLM that had full HD resolution and 7 μm pixel pitch. Since the Pixel pitch of the liquid crystal panel is not small enough for CGH, the optical setup works to demagnify the pixel pitch of the printed fringe pattern. To record high resolution CGH, the calculated fringe pattern is split and exposed in tiles by the X–Y stage. The results showed a 0.44 μm pixel pitch and over 100 Gpixel CGHs. However, to output more high-quality CGH, the development of pixel pitch and resolution is very important. In this paper, we review the optical system of a fringe printer that achieved an output of 0.35 μm pixel pitch CGH. We also investigate the performance of the new fringe printer.