Layout for measurement of overlay error
AssigneeMicron Technology, Inc.
InventorsPary Baluswamy, Tim H. Bossart
Life of this patent
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Abstract
In the manufacture of a multi-layer integrated circuit, a reference target is etched into a test wafer along with circuit features of a reference layer. As successive dependent layers are printed, successive dependent targets overlaying the same reference target are formed in photoresist. As each successive dependent target is printed, the degree to which it is registered with the reference target is used to determine the overlay error. After determination of overlay error for a layer, the layer's dependent target is removed, allowing the reference target to be matched with the dependent target of another layer.
Claims15
A method of laying out targets for an unfinished semiconductor product having an intermediate layer, said method comprising the steps of:
- providing a reference target in a reference layer on a test wafer, said reference target registering subsequent layers dependent on said reference layer;
- forming a dependent target in a dependant target location of the intermediate layer dependent on said reference layer;
- and
- removing said dependent target of said intermediate layer.
A method of measuring overlay error for an unfinished multi-layer integrated circuit, said method comprising the steps of:
- providing a reference target in a reference layer on a test wafer;
- providing a dependent target in a dependent target location area of an intermediate layer dependent on said reference layer;
- comparing said dependent target to said reference target to determine any registration errors between said subsequent layer and said intermediate layer;
- and
- removing said dependent target.
A method of making an unfinished multi-layer integrated circuit, said method comprising the steps of:
- providing a reference target in a reference layer on a test wafer, said reference target registering every intermediate layer dependent on said reference layer;
- forming intermediate layers dependent on said reference layer, each of said intermediate layers having a dependent target for comparison with said reference target;
- and
- removing said dependent targets from a prior one of said intermediate layers before having a succeeding one of said subsequent layers.
Dependencies are inferred from the claim text.