Yokoyama et al. from Tower Semiconductor have posted a preprint titled "Charge Domain Type 2.2um BSI Global Shutter Pixel with Dual Depth DTI Produced by Thick-Film Epitaxial Process":
Abstract: We developed a 2.2um Backside Illuminated (BSI) Global Shutter (GS) pixel with true charge-domain Correlated Double Sampling (CDS). A thick-film epitaxial deep DTI (Deep Trench Isolation) process was implemented to enhance 1/PLS (Parasitic Light Sensitivity) using a dual depth DTI structure.
The thickness of the epitaxial substrate was 8.5 um. This structure was designed using optical simulation. By using a thick epitaxial substrate, it is possible to reduce the amount of light that reaches the memory node. Dual-depth DTI, which shallows the DTI depth on the readout side, makes it possible to read signals from the PD to the memory node smoothly. To achieve this structure, we developed a process for thick epitaxial substrate, and the dual-depth DTI can be fabricated with a single mask. This newly developed pixel represents the smallest ever charge-domain GS pixel to date. Despite its compact size, this pixel achieved high QE (83%) and 1/PLS of over 10,000. The pixel maintains 80% of its peak QE at ±15 degrees. 1/PLS is stable even when the F# is small.
Full paper: https://sciprofiles.com/publication/view/7ae02d55ce8f3721ebfc8c35fb871d97
This work was published also in IISW25, the papers (including the one above) are available here: https://imagesensors.org/2025-papers/. Also the slides of the IISW presentation of the paper are linked: https://imagesensors.org/Past%20Workshops/2025%20Workshop/2025%20Presentations/R01.4_Yokoyama_slides.pdf.
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