After devices or circuits are fabricated on a semiconductor wafer and similar substrates, the individual devices or circuits may be separated by scribing the wafer with a scribing tool, such as a sharply pointed scribe tip, and cleaving the wafer along the scribed lines.
Current apparatus used to scribe a semiconductor wafer do not include a means or method of determining where the outer peripheral edge of the wafer is located before starting to scribe the wafer. Exemplary of prior art approaches are U.S. Pat. No. 3,094,785 and U.S. Pat. No. 5,820,006.
In these and similar apparatus, the scribe tip is placed outside the edge of the wafer and at a height just lower than the height of the wafer. The scribe tip is moved laterally relative to the wafer until it comes into contact with the wafer edge. It then continues across the wafer, forming a scribe line until it falls off the other side of the wafer.
Using this approach to wafer scribing causes two problems. First, when the scribe tip hits the leading edge of the wafer, damage to the wafer in the form of chips or cracks can occur. The second problem is that when the scribe tip hits the edge of the wafer it is knocked upward by the edge of the wafer and then oscillates up and down as the mechanism tries to dampen the mechanical perturbations in an attempt to maintain a constant scribe force.