CMOS technology has made visible imaging compact, low-power and affordable. Just about every smartphone now harbors a digital camera that’s capable of professional photography.
But, the needs of the market are changing. Applications such as augmented reality and face recognition, autonomous driving and food scanning require a shift from imaging to sensing – from taking a picture to acquiring information.
The challenge is to bring these new imaging applications within reach of the consumer technology market, by lowering their cost without compromising their resolution. This is the goal of imec’s Pixel Technology Explore research activities, which break new ground in NIR/SWIR sensing and 3D imaging.
Imec intends to develop technologies for companies with a roadmap in innovative image sensors, cameras and smart imaging applications.
Near-infrared (NIR) and short-wave infrared (SWIR) sensing
The sensitivity range of silicon-based sensors is fundamentally limited to below 1100 nm. That’s why infrared imaging has been dominated by III-V detectors that are flip-chip-bonded to silicon readout circuits. This both drives up the costs and limits the pixel pitch and resolution.
The Pixel Technology Explore activity is looking at two methods for cost-effective uncooled IR detection:
- thin film on silicon – Materials such as organic and colloidal quantum dots offer low-cost synthesis, compatibility with a variety of substrates and processing feasibility on a large area. This article gives you an in-depth view.
- hybrid infrared imagers – Both III-V hetero-epitaxy on silicon and III-V material transfer on silicon are compatible with processing in a silicon wafer fab and reduce the manufacturing costs of IR sensors.
Imec’s thin-film SWIR image sensors can be integrated in camera modules with standard or SWIR lenses.
Silicon-based pixels for 3D sensing
Making use of the third dimension is another way of extending picture content beyond visible photography. For 3D sensing, imec is exploring these research avenues:
- IR laser dot projection – This is addressed by the research topics above that look into uncooled IR detection.
- Continuous Wave (indirect) Time-of-Flight (CW-ToF) – This also relies on an NIR laser pulse but measures the reflected light phase difference within each pixel to get access to distance.
- Direct Time-of-Flight (D-ToF) – This combines an NIR laser pulse with high speed Single Photon Avalanche Diodes (SPAD) that measure the time for a photon to travel between the laser source and the imager.
Want to become our partner in developing new imaging technologies?
As our partner in the Pixel Technology Explore activity, you’re provided with:
- TCAD/optical simulations and pixel architectures
- device demonstrators with analog readout
- process integration at die and wafer level (200/300 mm)
- PCM testing and pixel characterization (PTC, QE, MTF, ...)
- material characterization (TEM, SEM, AFM, ...)
We can also assist you with the development of prototypes. Here, you can take advantage of imec’s unique combination of expertise regarding imaging R&D – from material research all the way up to camera integration.
- Article: Building low-cost infrared sensors with sub-micron films (registration required)
- Article: Make smartphones and autonomous vehicles see the impossible
- Blogpost: Imec PbS QD photodiodes for CMOS integration
- Blogpost: Imec Quantum Dot Sensor
Publications and conferences on infrared sensors and 3D imaging
- E. Georgitzikis et al. “Integration of PbS quantum dot photodiodes on silicon for NIR imaging”, IEEE Sensors Journal 2019
- P.E. Malinowski et al. “NIR/SWIR monolithic image sensors enabled by thin-film photodiode stacks”, SPIE Optics+Photonics 2019, San Diego, US (11th-15th Aug 2019)
- Y. Li et al. “Beyond BEOL Interconnect Wafer Level Monolithic Near-Infrared/Infrared Thin Film Photo Diode Image Sensor Integration”, IEEE IITC/MAM 2019, Brussels, BE (3rd-6th Jun 2019)
- E. Georgitzikis et al. “Optimization of Charge Carrier Extraction in Colloidal Quantum Dots Short‐Wave Infrared Photodiodes through Optical Engineering”, Advanced Functional Materials, Vol. 28 (42), (2018)
- F. Verstraeten et al. “Near-infrared organic photodetectors based on bay-annulated indigo showing broadband absorption and high detectivities up to 1.1 μm”, Journal of Materials Chemistry C, (2018)
- P.E. Malinowski et al. “Thin-Film Quantum Dot Photodiode for Monolithic Infrared Image Sensors”, MDPI Sensors 17(12), 2867, (2017)
- P.E. Malinowski et al. “Organic photodetectors with active layer patterned by lithography”, 2015 IEEE SENSORS, (2015)
- E. Georgitzikis et al. “Organic- and QD-based image sensors integrated on 0.13 μm CMOS ROIC for high resolution, multispectral infrared imaging”, IISW 2019, (2019)
- E. Georgitzikis et al. “NIR Sensors Based on Photolithographically Patterned PbS QD Photodiodes for CMOS Integration”, IEEE Sensors, (2018)
- P.E. Malinowski et al. “Monolithic Near Infrared Image Sensors Enabled by Quantum Dot Photodetector”, IISW, (2017)
- E. Georgitzikis et al. “Determining charge carrier extraction in lead sulfide quantum dot near infrared photodetectors”, SPIE Nanoscience + Engineering, (2017)
- P. E. Malinowski et al. “Organic photodetectors with active layer patterned by lithography”, IEEE Sensors, (2015)
- P. E. Malinowski et al. “Photolithographic patterning of organic photodetectors with a non-fluorinated photoresist system”, Organic Electronics 15 (10), (2014)