The ranking covers 100 companies across 574 records, with the leading assignee holding 75 records — well ahead of the fifth-place figure of 19. That gap indicates one incumbent has built substantially deeper coverage than the rest of the field, though the top 5 combined still account for only 28.0% of all records, leaving most filings spread across a long tail of smaller players. Anyone assessing competitive position should look at both the leader’s portfolio and the broader tail rather than assuming the field is a two-horse race.

Filings grew sharply from 5 in 2021 to 23 in 2024, a +360% increase over that span and the fastest growth window in the dataset’s coverage. The two most recent years appear lower in the raw trend, but that reflects the roughly 18-month lag between filing and publication rather than an actual drop in activity. Based on the 2021–2024 trajectory, the technology area was still accelerating as of the most recent complete filing year.

US6184154B1 covers a method for processing the backside of a wafer — such as etching it or applying a back seal — inside the same epitaxial reactor chamber used to deposit the front-side layer, without removing the wafer between steps. It blocks designs that combine backside processing and front-side epitaxial deposition within a single chamber cycle using the described sealing or etching approaches. Designs that process the backside in a separate chamber, or use a materially different sealing mechanism, sit outside its core claim scope, but a detailed claim chart is needed to confirm design-around viability for any specific reactor configuration.