The process is intended to deliver an order of magnitude gain in manufacturing throughput and cost compared to processing today’s conventional IR imagers. At the same time, the process can offer multi-megapixel resolution.
Today’s infrared image sensors are manufactured using a hybrid technology: the crystalline semiconductor detector and the electronic readout are fabricated separately and then interconnected at pixel or chip periphery level.
Imec's IR imagers use a new thin-film photodetector pixel stack based on quantum dots deposited directly on top of an electronic readout. The imagers can then be built on a monolithic process compatible with wafer-based mass production. The pixels embed high-performance low bandgap quantum dot materials that match or even surpass the performance of inorganic light absorbers. The stacks have been carefully engineered and can be tuned to target a spectrum from visible light all the way up to 2µm wavelength. Test photodiodes on silicon substrate achieve an external quantum efficiency above 60 percent at 940nm wavelength, exceeding the state-of-the-art, and above 20 percent at 1450nm, allowing for uncooled operation with dark current comparable to commercial InGaAs photodetectors. The prototype imager has a resolution of 758x512 pixels and 5um pixel pitch.