| 摘要 |
Methods and apparatus for calculating alignment of layers during semiconductor processing are described. In one embodiment, first and second alignment targets are formed over a substrate and include respective pairs of first and second alignment target edges. The second alignment target defines a point of reference. First and second distances are measured between the first alignment target edges and the second alignment target edges as respective first and second functions of the distance from the point of reference. The first and second functions are differenced to define a linear equation having a slope and ii an intercept which contains offset components in two different directions. In a preferred embodiment, third and fourth alignment targets are formed over the substrate, with the fourth alignment target defining a different point of reference. The third and fourth alignment targets include respective edges, and third and fourth distances are measured between different respective edges of the third and fourth alignment targets as respective functions of the distances from the different point of reference. The third and fourth functions are differenced to define a linear equation having a slope and a second intercept which contains offset components in the same two different directions as the first-mentioned intercept. Values are calculated for the offsets using the first and second intercepts.
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