It refers to an architecture where the pixel sensor array and the readout or logic circuitry are fabricated on separate dies and joined vertically, typically through hybrid bonding or through-silicon vias, rather than laid out on a single planar chip. Claims in this space usually specify the interconnect pitch, the layer order (pixel chip over logic chip, or the reverse), and sometimes a rerouting layer that reconciles different pitches between the two dies. The representative record in this landscape, US20170309667A1, is a clean example of that last pattern. Reviewing a claim for this feature means checking whether it recites a specific pitch relationship or interconnect structure, since that is usually where infringement turns.

The assignee ranking behind this landscape returns only 8 companies, and it is heavily concentrated: the leading filer holds 43 of the ranked records, compared with 2 at fifth place. That is a steep drop rather than a gradual tail, which means a competitive review should weight the leader's portfolio far more heavily than the rest of the ranked list. Because the ranking is small, it should not be described as a top-50 or top-100 list — it is the whole set the data returns.

Filing activity peaked at 6 records in 2020, held near that level in 2021, and fell to 0 by 2024 — a -100% swing over that three-year span. However, publication lags filing by roughly 18 months, so 2025 and 2026 figures in any dataset are still incomplete and will revise upward as more records publish. The honest read is that the pace has cooled through the last complete year on record, not that the technology area has ended.

In this dataset, 54.3% of the 81 records in scope carry an A61B (diagnosis and surgery) classification alongside the core sensor-stacking classes. That overlap points to compact endoscopic and surgical camera modules as a major commercial driver for stacked sensor interconnect work, since those applications need small footprint, high readout rate sensors packed into a scope tip. A filer targeting industrial or consumer imaging should treat this as evidence that some of the most-cited prior art may be drafted with medical-device claim language, which affects how directly it reads onto a non-medical product.

Relative to the dense core claims around hybrid bonding pitch and readout architecture, this landscape shows thinner direct coverage in areas like thermal coupling management across stacked dies, stacking yield loss detection, and power-per-frame optimization specifically for in-sensor processing. These are still connected to the core technology but are not where the bulk of the 81 records concentrate their claim language. A narrowly drafted claim in one of these branches has a better chance of clearing the existing art than another claim aimed squarely at interconnect pitch, which is already crowded by the leading assignee's portfolio.