A recent preprint on ArXiv https://arxiv.org/abs/2402.12516 titled presents a new CMOS image sensor designed to achieve sub-electron read noise and photon number resolving capability.
Skipper-in-CMOS: Non-Destructive Readout with Sub-Electron Noise Performance for Pixel Detectors
Abstract: The Skipper-in-CMOS image sensor integrates the non-destructive readout capability of Skipper Charge Coupled Devices (Skipper-CCDs) with the high conversion gain of a pinned photodiode in a CMOS imaging process, while taking advantage of in-pixel signal processing. This allows both single photon counting as well as high frame rate readout through highly parallel processing. The first results obtained from a 15 x 15 um^2 pixel cell of a Skipper-in-CMOS sensor fabricated in Tower Semiconductor's commercial 180 nm CMOS Image Sensor process are presented. Measurements confirm the expected reduction of the readout noise with the number of samples down to deep sub-electron noise of 0.15rms e-, demonstrating the charge transfer operation from the pinned photodiode and the single photon counting operation when the sensor is exposed to light. The article also discusses new testing strategies employed for its operation and characterization.
I think this is a fine non-peer reviewed paper/report and the approach is a good improvement compared to recent skipper-CCD. The noise, after 3000+ non-destructive reads at -100C is probably closer to 0.20e- rms based on the PCH valley-peak ratio. At 0.15e- rms read noise the valley minimum should go to zero. Hopefully in a peer-reviewed journal version more critical details will be provided.
ReplyDeleteThe full well and the CG is not mentioned. The CTE is 99.9999% or even higher？
DeleteRunning a one-sample PCH-EM characterization on the data in fig. 10 (bottom) yields a read noise of 0.185e-, which is in line with Eric's estimate of 0.2e- and the comments about peak overlap. A more accurate number can be obtained with the raw sensor data (I simply digitized the plot).
Deletewhat is the recent skipper-CCD please ? What are the improvements compared to ? Thanks!
ReplyDelete"Skipper" CCD was a name given to a CCD with non-destructive readout capability that was demonstrated by Janesick et al at NASA JPL for reducing read noise circa 1990. The basic idea is the the charge is sensed multiple times by a floating gate and the multiple reads are averaged together to improve SNR by averaging read noise. The noise decreases like the square root of N where N is the number of reads. Ultimately the noise then becomes limited by either dark current buildup or the SF 1/f noise. The drawback is that often N>1000 and this slows the readout rate. In fact, Janesick et al proposed that some uninteresting pixels or regions could be skipped in the multiple readout process shortening readout time. I think this is where the name "skipper" came from. Skipper CCDS have been used more recently for use in physics experiments such as the search for dark matter. Integration times are very long so the slow readout is not a big issue, relatively speaking and deep sub-electron readout noise has been demonstrated. The devices are operated at cold temperatures to reduce dark current. The reduction of read noise using non-destructive CCD readout goes back to the early days of CCDs. Try google scholar search for "skipper CCD"
DeleteWhat are the major improvements in this realization please, Eric? Thanks!
ReplyDeleteThe authors mention that with a stacked architecture, multiple sample non-destructive readout can take place in a pixel-parallel way, thus reducing readout time and perhaps widening the application space of this non-destructive readout approach beyond long integration time and long readout time.
DeleteThank you so much Eric !!
DeleteCheck out as well Boyd Fowler's paper presented at IISW2021 (paper R08)(www.imagesensors.org)
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