This landscape is built on 2,755 published records filed or published between 2015 and 2026, and the assignee ranking is counted in patent families rather than raw documents so repeat filings across jurisdictions do not inflate any one applicant's position. Because publication lags filing by roughly 18 months, the true count for 2025 and 2026 will keep rising as those applications publish. Treat the total as a snapshot at the 2026-08-31 data cut-off, not a final figure.

No — filing peaked at 63 in 2018 and has since declined; the most reliable recent comparison, 2021 to 2024, shows a drop from 57 to 35 filings, a 39% fall. That is a genuine deceleration in a process technology that has been in commercial use for decades, not evidence that the technology is being abandoned. Filings on adjacent hardware, such as electron-and-discharge-tube claims under H01J, have continued alongside the core coating claims, which suggests engineering effort is shifting toward chamber and source design rather than disappearing.

The ranking covers the leading 100 companies by family count within this dataset, with the top-ranked assignee holding 195 records and fifth place at 60. The top 5 combined hold 19.7% of all 2,755 records in scope, and the top 10 combined hold 28.0% — meaningful positions, but far short of control of the field. A long tail of lower-volume filers holds the remainder, so freedom-to-operate work needs to look well past the named leaders.

CA1242991A, granted in 1988 to Novellus Systems, claims a magnetron sputter source that uses an adjustable electromagnetic coil in place of fixed permanent magnets, letting a single source handle targets ranging from nonmagnetic to highly ferromagnetic. Its relevance today is as foundational prior art: any coil-driven or variable-magnetic-field magnetron source design should be checked against it and its citing family, since design-arounds for older permanent-magnet-only claims may not clear a coil-based approach. It is a citation anchor rather than an active blocking claim after this length of time, but it shapes how later coil-based claims were drafted.

Core coating claims under C23C appear in 98.7% of the 2,755 records, so that subclass is effectively saturated as a definition of the field rather than a differentiator. Narrower branches carry far lower density: H05H plasma-and-particle-accelerator claims sit in only 2.9% of records, and G02B optical-element claims in 4.2%, both well below the 34.7% carried by H01J chamber and discharge-tube claims. Those lower-density branches are the more promising starting points for a differentiated first claim, provided a prior-art search confirms the specific combination is genuinely open.