Can I use the In-Situ 4000 Process Monitor during substrate rotation?
Yes. Most substrate holders which rotate during deposition have some mechanical errors which cause the reflection angle to vary as the substrate rotates. This so-called “wobble tilt” causes a periodic change in reflection angle resulting in an error in the reflectance measurement and produces a variation in reflectance synchronized to the substrate rotation motion. The In-Situ 4000 Process Monitor system contains a special software sample and hold filter which accommodates even large amounts of wobble tilt. The reflectance is sampled once per rotation so that the measurement is correct, even when the wobble tilt is very large.
