Surface roughness & flatness
For many of the subsequent applications of glass-wafers a minimal surface roughness and a high surface flatness are necessary.
Classification of Surface Roughness,
measured with an Atomic Force Microscope
OP FineTech uses a state-of-the-art measuring facility (Zygo New View) as well as an atomic force microscope to measure surface roughness. Sample measurements of OP FineTech glass-wafers confirm that their surface roughness lies beneath 0,2 nm. This value is only marginally above the lowest super+ roughness-class.
measured with Zygo New View
As a matter of course surface flatness is also being gauged with the latest measuring devices. Measurement of TTV is related to the backside of the wafer because the chuck holding the wafer is defined as an ideal plane. In this case, TTV determines also the total surface flatness GBIR – (G)lobal (B)ackside (I)deal Focal Plane (R)ange – at the same time. With a GBIR of 0,430 μm the glass-wafer is extremely flat.
measured with Zygo GPI
Additionally, OP FineTech experts also check the warping of the wafer. The warp is defined as the difference between the maximum and minimum distances of the median surface of a free, unclamped wafer to a reference plane.
Surface Flatness: Warp,
measured with Corning-Tropel Flatmaster