Patent ID: 7328517

Claim:
An apparatus for determining at least one warpage characteristic of a substantially planar substrate, comprising: a carrier configured for holding and positioning a substantially planar substrate in a plane, the substantially planar substrate having first and second substantially planar opposed surfaces parallel to the plane; a first linear measuring device including a first movable caliper disposed on one side of the plane and configured for measuring a plurality of first linear distances, each first linear distance being the distance from a zero point location to a location on the first surface of the substrate; a second linear measuring device including a second movable caliper disposed on an opposing side of the plane and configured for measuring a plurality of second linear distances, each second linear distance being the distance from a zero point location to a location on the second surface of the substrate, wherein the first movable caliper and the second movable calipers are each biased toward the plane; and a calculation device for calculating the plurality of first and second linear distances and the at least one warpage characteristic from the plurality of first and second linear distances.