Method for Automatically De-Skewing of Multiple Layer Wafer for Improved Pattern Recognition

• US 20090010529A1
• Filed: 09/10/2008
• Published: 01/08/2009
• Est. Priority Date: 10/09/2001
• Status: Active Grant

• Current Assignee: Onto Innovation Inc.
• Original Assignee: Nanometrics Incorporated (Onto Innovation Inc.)
• Inventors: Zhou, Jian, Chu, Hua
• Granted Patent: US 8,045,790 B2
• Time in Patent Office: Days
• US Class Current: 382/151
• CPC Class Codes: G06V 10/243 by compensating for image skew or non-uniform image deformations

Abstract

A method for processing wafers includes learning a first pattern at a de-skew site on a first wafer layer, saving the first patterns in a recipe for de-skewing wafers, learning a second pattern at the de-skew site a second wafer layer, and saving the second pattern in the same recipe for de-skewing wafers. Learning the first pattern may include determining a score of uniqueness for the first pattern. The method further includes finding the de-skew site on the second wafer layer using the first pattern before learning the second pattern. Finding the de-skew site includes determining a score of similarity between the first pattern and the second pattern. Learning the second pattern is performed when the score of similarity is less than a threshold value. A recipe for de-skewing wafers includes multiple patterns of a de-skew site of a wafer, wherein the patterns include a first pattern at the de-skew site on a first wafer layer and a second pattern at the de-skew site on a second wafer layer.

Claims

1. A method comprising:

receiving a pattern of a first de-skew site on a layer on a wafer;

finding a match of the pattern with one of a plurality of learned patterns in a recipe, wherein the recipe includes a first set of coordinates of the first de-skew site and the plurality of learned patterns includes learned patterns of the first de-skew site for different layers;

determining a second set of coordinates of a second de-skew site on the layer;

determining a transforming matrix from the first and the second sets of coordinates of the first and the second de-skew sites; and

using the transforming matrix to de-skew the wafer.

2. The method of claim 1, wherein the recipe further includes the second set of coordinates of the second de-skew site and a second plurality of learned patterns of the second de-skew site.

3. The method of claim 1, wherein the plurality of learned patterns includes at least one common learned pattern of the first de-skew site for a plurality of layers on the wafer.

4. The method of claim 3, further comprising:

receiving a second pattern of the first de-skew site on a second layer on the wafer;

finding a match of the second pattern with the common learned pattern in the recipe;

determining the second set of coordinates of the second de-skew site on the second layer;

determining a second transforming matrix from the first and the second sets of coordinates of the de-skew site on the second wafer layer; and

using the second transforming matrix to de-skew the wafer.

5. The method of claim 1, further comprising:

receiving a second pattern of the first de-skew site on a second layer on the wafer;

finding a match of the second pattern with one of the plurality of learned patterns in the recipe;

determining the second set of coordinates of the second de-skew site on the second layer;

determining a second transforming matrix from the first and the second sets of coordinates of the de-skew site on the second wafer layer; and

using the second transforming matrix to de-skew the wafer.

6. A method comprising:

receiving a de-skew pattern at a first de-skew site on a layer on a wafer;

finding a match of the de-skew pattern with a learned pattern in a recipe, wherein the recipe includes a first set of coordinates of the first de-skew site and the learned pattern, the learned pattern matching a plurality of patterns at the first de-skew site on a plurality of layers on the wafer;

determining a second set of coordinates of a second de-skew site on the layer;

determining a transforming matrix from the first and the second sets of coordinates of the first and the second de-skew sites; and

using the transforming matrix to de-skew the wafer.

7. The method of claim 6, wherein the recipe further includes the second set of coordinates of the second de-skew site and a second plurality of learned patterns of the second de-skew site.

8. The method of claim 6, wherein the learned pattern in the recipe is a first learned pattern, the recipe further includes at least one additional learned pattern matching the pattern at the first de-skew site on a layer of the wafer that is not matched by the first learned pattern.

9. The method of claim 8, further comprising:

receiving a second de-skew pattern at the first de-skew site on a second layer on the wafer;

finding a match of the second de-skew pattern with the at least one additional learned pattern in the recipe;

determining the second set of coordinates of the second de-skew site on the second layer;

determining a second transforming matrix from the first and the second sets of coordinates of the de-skew site on the second wafer layer; and

using the second transforming matrix to de-skew the wafer.

10. The method of claim 6, further comprising:

receiving a second de-skew pattern at the first de-skew site on a second layer on the wafer;

finding a match of the second de-skew pattern with the learned pattern in the recipe;

determining the second set of coordinates of the second de-skew site on the second layer;

determining a second transforming matrix from the first and the second sets of coordinates of the de-skew site on the second wafer layer; and

using the second transforming matrix to de-skew the wafer.