Industrial-scale deposition of highly uniform and precise optical interference filters by the use of an improved cylindrical magnetron sputtering system

• Optical coatings were produced with a cylindrical magnetron sputter system.
• Process stability and uniformity could be improved by compound target sputtering.
• Non-uniformity was ± 0.15% over 200 mm diameter for different carriers and batches.
• 12 layer broad-band AR-coatings were accurately produced by time-control only.

The manufacture of precision optical interference coatings requires a process with sufficient accuracy, precision, uniformity, and stability to produce economic quantities of coatings with acceptable yield. This paper compares the capabilities of the plasma assisted reactive magnetron sputtering (PARMS) process with the compound-assisted reactive sputtering process (CARS). Compared with PARMS, CARS exhibited superior process accuracy, stability and uniformity by being less sensitive to equipment and process temperatures, and to cathode and machine conditioning. A uniformity deviation of less than ± 0.15% is demonstrated for different optical multilayer filters over substrates of 200 mm diameter. The CARS process stability and precision are also demonstrated using many coating runs of a sensitive, broadband antireflective coating without the need for optical monitoring. Thus, it is shown that CARS combines the advantages of the Metamode (high stability) and the PARMS process (low optical absorption).