Bow is the deviation of the center point of the median surface of a free, un-clamped wafer from the median surface to the reference plane. Where the reference plane is defined by three corners of equilateral triangle. This definition is based on now obsolete ASTM F534.
There are a number of factors that can affect the shape of a wafer be it Silicon carbide, GaAs or InP. While a wafer is at full thickness, it has the tensile strength to resist any external influences from changing its shape. However, as a wafer is thinned, external influences will cause a wafer to become concave or convex. Some of the more common influences is film type and thickness on the surface of wafer.
Concavity, curvature, or deformation of the silicon carbide wafer centerline independent of any thickness variation present.