One assignee leads the field with 458 of the 1,833 records in scope, well ahead of the fifth-ranked filer at 56. The top five filers combined hold 43.5% of all records, and the top ten hold 54.9%, so the field is concentrated among a small group of semiconductor equipment and device makers rather than spread evenly. Anyone assessing competitive position should check both the single leader and this wider top-ten group, since freedom-to-operate risk is not limited to just the top name.

Filing peaked in 2021 at 133 records and had fallen 29% to 94 by 2024, the most recent year the trend can be treated as complete. That is a real pullback from peak, but it is not evidence the field has stopped: publication lags filing by roughly 18 months, so 2025 and 2026 figures in any dataset will always look artificially low and should not be read as a continued decline until later data fills in.

US6830853B1, assigned to Taiwan Semiconductor Manufacturing Company, claims a photomask-forming method that pairs dry anisotropic etching around pattern elements needing tight critical-dimension control with wet isotropic etching for the remaining opaque material. It is specific to combining these two etch modes within a single mask-patterning workflow, so it primarily constrains photomask fabrication approaches that mix anisotropic and isotropic steps for CD control and defect reduction, not selective etch chemistry generally. New filings on nanosheet release or gas-phase silicon-germanium removal outside mask fabrication sit outside this claim’s direct path, but any mask-process claim mixing etch modes for CD versus defect trade-offs should be checked against it.