Total Thickness Variation (TTV) is the difference between the minimum and maximum values of thickness over the complete wafer. TTV is identified in a scan pattern or by carrying through series of point measurements on the wafer. It is expressed in microns or mils.
A small TTV value implies a very homogenous wafer with regard to its thickness. As the wafer diameter increases it is getting more and more difficult to obtain a good TTV value.
Several examples of Interferometer Measurements of TTV
of 3 wafers, φ200×ｔ1.2mm, with extremely high precision
The company OP FineTech pays great importance to highest precision in manufacturing their glass-wafers. The example shows that this 200 mm (8”) wafer features a minimal Total Thickness Variation of only 0,430 μm – a value which lies between the best and the second best TTV classification. Precise quality is guaranteed with OP FineTech wafers!
Example: Interferometer Measurement of TTV
of one OP FineTech glass-wafer, φ200×ｔ1.2mm
* GBIR= (G)lobal (B)ackside (I)deal Focal Plane (R)ange