Resistor structures to electrically measure unidirectional misalignment of stitched masks
An apparatus and method for matched variable resistor structures to electrically measure unidirectional misalignment of stitched masks for etched interconnect layers includes a first test pad and a second test pad for measuring resistance therebetween; a first resistive element electrically connected at a first end to the first test pad; and, a second resistive element electrically connected at a first end to the second test pad. The first resistive element and the second resistive element are electrically connected by a vertical offset. The resistance measured between the first test pad and the second test pad is variable in accordance with an alignment of the first resistive element and the second resistive element relative to the vertical offset. An indicator may optionally provide an indication that the resistive elements are in alignment.
1. A method of electrically measuring an alignment of a set of stitched masks, comprising:
providing a first mask comprising a first test pad, a second test pad, and a first resistive element electrically connected to a first end of the first test pad;
providing a second mask comprising a second resistive element;
electrically connecting the second resistive element to a first end of the second test pad;
connecting the first resistive element and the second resistive element together to opposite ends of a vertical offset; and
measuring a resistance between the first test pad and the second test pad.
2. The method according to claim 1 , further comprising:
determining whether the first resistive element and the second resistive element are in alignment by comparing the measured resistance with a predetermined resistance.
3. The method according to claim 2 , wherein an indicator indicates whether a measured resistance is within a predetermined limit.
4. The method according to claim 3 , wherein the indicator provides a visual indication.
5. The method according to claim 3 , wherein the indicator provides an audiological indication.
6. The method according to claim 1 , further comprising:
determining whether the first mask and the second mask are in alignment by comparing the measured resistance with a predetermined resistance.