Method and apparatus for fabricating wafer by calculating process correction parameters

1. An apparatus for fabrication of a wafer with a structural pattern comprising:

an exposure tool for exposure of the wafer;

an overlay measurement tool for measuring a subset of overlay deviations between lower first overlay marks and second overlay marks in a photoresist layer on the wafer; and

a process correction unit connected to the overlay measurement tool and accepting the measured subset of overlay deviations, calculating from the overlay deviations wafer fine model corrections parameters, for a plurality of overlay positions estimating overlay residuals from the wafer fine model correction parameters, and calculating a set of process correction parameters for the exposure tool from the overlay residuals and providing the set of process correction parameters to the exposure tool.

2. The apparatus of claim 1 , wherein the overlay measurement tool is adapted to select only those overlay marks within a specified distance to one of a plurality of exposure fields, for which the set of process correction parameters should be interpolated, the plurality of exposure fields being arranged on the wafer.

3. The apparatus of claim 2 , further comprising an etching unit for etching a pattern onto a surface of the exposed wafer.

4. A method for aligning and exposing a wafer with a structural pattern having overlay marks, comprising lower first overlay marks and second overlay marks, in an exposure tool, the method comprising:

feeding from an exposure controller the exposure tool with an initial overlay model;

coating the wafer having lower first overlay marks with a photoresist layer;

producing with the exposure tool a structure in a plurality of exposure fields incorporating second overlay marks on the photoresist layer;

measuring with an overlay measurement tool overlay deviations by comparing a subset of the first overlay marks with corresponding ones of the second overlay marks and calculating from the overlay deviations wafer fine model correction parameters;

passing the measured overlay deviations to a process correction unit;

estimating with the process correction unit overlay residuals for a plurality of overlay positions from the wafer fine model correction parameters, thereby generating a set of process correction parameters;

passing the set of process correction parameters to the exposure controller; and

feeding from the exposure controller the set of process correction parameters to the exposure tool.

5. The method of claim 4 , further comprising subjecting the photoresist layer to at least one of a chemical process or physical process to produce a structure on the wafer, wherein the structure incorporates the first overlay marks.

6. The method of claim 5 , further comprising

weighting the overlay deviations of the selected subset of the overlay marks based on the distance to the overlay position; and

calculating an overlay error from the weighted overlay deviations and thereby generating the amended overlay model, wherein said calculating comprises carrying out a least square fit for each one of the exposure fields for both the x-direction and y-direction.

7. The method of claim 4 , further comprising selecting the subset of overlay marks in dependence on a distance to one of the plurality of exposure fields, for which the set of process correction parameters should be interpolated, the plurality of exposure fields being arranged on the wafer.