What is the smallest substrate size I can use?
The standard In-Situ 4000 Process Monitor optics will measure a circular area of the substrate with diameter D/25 where D is the substrate to pyrometer distance. For example, if your substrate to pyrometer distance is 38 inches, then the area measured is a circle of 1.5 inch diameter. SVT Associates also offers an alternate version of the In-Situ 4000 Process Monitor which measures a smaller area corresponding to a diameter of D/90, with the consequence of an upward shift in the temperature measurement range to 500-1200°C. It is important that the substrate surface completely fill the measured area so that the measured radiation corresponds solely to the substrate and not filament heaters, or wafer mounting surfaces.
