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When we look at the substrates or chips of semiconductor silicon or other types of materials, we often see technical indicators such as TTV, BOW, WARP, and perhaps even TIR, STIR, LTV, etc. What parameters do they represent?
TTV — Total Thickness Variation, Total Thickness Variation
BOW, bending
WARP – WARP degrees
TIR — Total Indicated Reading
STIR — Site Total Indicated Reading
LTV — Local Thickness Variation
Total thickness deviation — TTV
The difference between the maximum and minimum thickness of the wafer from the reference plane when the wafer is clamped tightly; Generally expressed in micron (m), generally expressed as ≤15 m.
Bending – BOW
The deviation between the minimum value and the maximum value of the surface of the central point of a wafer and the reference plane when the wafer is not closely attached. The deviation includes concave and convex cases. The concave bending is negative while the convex bending is positive. Generally expressed in micron (m), generally expressed as: ≤40 m.
WARP degrees – WARP
When a wafer is not attached closely, the back side of the wafer is usually taken as the reference plane. The deviation between the measured wafer surface and the minimum and maximum values of the reference plane includes the concave and convex cases. The concave bending degree is negative while the convex bending degree is positive. Generally expressed in micron (m), generally expressed as ≤30 m.
Total indicator reading — TIR
When a wafer is clamped tightly, the maximum and minimum distance deviations of the wafer surface from the reference plane are measured using the plane on which the sum of the intercepts of all the points in the qualified mass area of the wafer surface or the specified local area as the reference plane.