Thick photo resist layer metrology target

Patent metadata

Field	Value
Publication number	US-11874102-B2
Application number	US-202016996699-A
Country	US
Kind code	B2
Filing date	Aug 18, 2020
Priority date	Dec 30, 2019
Publication date	Jan 16, 2024
Grant date	Jan 16, 2024

Abstract

A metrology target includes a first target structure formed within at least one of a first area and a third area of a first layer of a sample, where the first target structure comprises a plurality of first cells containing one or more first cell pattern elements; and a second target structure formed within at least one of a second area and a fourth area of a second layer of the sample, the second target structure comprising a plurality of second cells containing one or more second cell pattern elements.

First claim

What is claimed:

1. A metrology target comprising:
a first target structure configured in accordance with a metrology recipe, wherein the first target structure is formed within at least one of a first area and a third area of a first layer of a sample, the first target structure comprising two or more first cells each containing two or more first cell pattern elements arranged periodically; and
a second target structure configured in accordance with the metrology recipe, wherein the second target structure is formed within at least one of a second area and a fourth area of a second layer of the sample, the second target structure comprising two or more second cells containing two or more second cell pattern elements arranged periodically, wherein the second target structure is formed from a photoresist material with sufficient thickness to induce asymmetry in at least some of the second cell pattern elements when fabricated in accordance with the metrology recipe, wherein at least one of a size or a number the second cell pattern elements is selected in accordance with the metrology recipe to provide that an overlay value for the metrology target mitigates the asymmetry in the at least some of the second cell pattern elements when the overlay value is determined in accordance with the metrology recipe based on one or more images of the metrology target from an optical metrology tool by computing a difference between a center of gravity of the first layer and a center of gravity of the second layer based on averaged individual center of gravity values of each of the first cell pattern elements and the second cell pattern elements.

2. The metrology target of claim 1 , wherein the first target structure is two-fold rotationally symmetric to the second target structure about a common center of rotational symmetry on the sample.

3. The metrology target of claim 2 , wherein the plurality of first cells comprises one or more first periodically patterned grids, and wherein the one or more first periodically patterned grids include the one or more first cell pattern elements.

4. The metrology target of claim 2 , wherein the plurality of second cells comprises one or more second periodically patterned grids, and wherein the one or more second periodically patterned grids include the one or more second cell pattern elements.

5. The metrology target of claim 1 , wherein the one or more first cell pattern elements are compatible with an optical metrology mode.

6. The metrology target of claim 1 , wherein the one or more second cell pattern elements are compatible with an optical metrology mode.

7. The metrology target of claim 1 , wherein the thickness of the photoresist material is greater than 2 micrometers.

8. The metrology target of claim 1 , wherein the thickness of the photoresist material is greater than 15 micrometers.

9. A system comprising:
a controller communicatively couplable to one or more metrology sub-systems, wherein the controller including one or more processors, wherein the one or more processors are configured to execute a set of program instructions maintained in memory when implementing a metrology recipe, wherein the set of program instructions is configured to cause the one or more processors to:
receive, from the one or more metrology sub-systems, one or more images indicative of illumination emanating from one or more metrology targets of a sample when implementing the metrology recipe, wherein the one or more metrology targets of the sample comprise:
a first target structure configured in accordance with the metrology recipe, wherein the first target structure is formed within at least one of a first area and a third area of a first layer of a sample, the first target structure comprising two or more first cells containing two or more first cell pattern elements arranged periodically; and
a second target structure configured in accordance with the metrology recipe, wherein the second target structure is formed within at least one of a second area and a fourth area of a second layer of the sample, the second target structure comprising two or more second cells containing two or more second cell pattern elements arranged periodically, wherein the second target structure is formed from a photoresist material with sufficient thickness to induce asymmetry in at least some of the second cell pattern elements when fabricated.

determine a center of gravity for each of the two or more first cells based on averaging individual center of gravity positions of each of the associated first cell pattern elements from the one or more images;
determine a center of gravity of the first layer based on averaging the centers of gravity for the two or more first cells;
determine a center of gravity for each of the two or more second cells based on averaging individual center of gravity positions of each of the associated second cell pattern elements from the one or more images;
determine a center of gravity of the second layer based on averaging the centers of gravity for the two or more second cells;
determine an overlay value of the sample by computing a difference between the center of gravity of the first layer and the center of gravity of the second layer.

10. The system of claim 9 , wherein the first target structure is two-fold rotationally symmetric to the second target structure about a common center of rotational symmetry on the sample.

11. The system of claim 10 , wherein the plurality of first cells comprises one or more first periodically patterned grids, and wherein the one or more first periodically patterned grids include the one or more first cell pattern elements.

12. The system of claim 10 , wherein the plurality of second cells comprises a second plurality of periodically patterned grids, and wherein the second plurality of periodically patterned grids includes the one or more second cell pattern elements.

13. The system of claim 9 , wherein the one or more first cell pattern elements are compatible with an optical metrology mode.

14. The system of claim 9 , wherein the one or more second cell pattern elements are compatible with an optical metrology mode.

15. A method of measuring overlay of a sample, comprising:
illuminating a sample including one or more metrology targets when implementing a metrology recipe, the one or more metrology targets comprising:
a first target structure configured in accordance with the metrology recipe, wherein the first target structure is formed within at least one of a first area and a third area of a first layer of a sample, the first target structure comprising two or more a plurality of first cells containing two or more first cell pattern elements arranged periodically; and
a second target structure configured in accordance with the metrology recipe, wherein the second target structure is formed within at least one of a second area and a fourth area of a second layer of the sample, the second target structure comprising two or more a plurality of second cells containing two or more second cell pattern elements arranged periodically, wherein the second target structure is formed from a photoresist material with sufficient thickness to induce asymmetry in at least some of the second cell pattern elements when fabricated;

generating one or more images based on illumination emanating from the one or more metrology targets of the sample in accordance with the metrology recipe;
determining a center of gravity for each of the two or more first cells based on averaging individual center of gravity positions of each of the associated first cell pattern elements from the o

Assignees

• Kla Corp

Inventors

• Guo Lingyi
• Pei Jincheng

Classifications

• G03F9/708

  Mark formation · CPC title

• G03F7/706843

  Metrology apparatus · CPC title

• G03F9/7088

  Alignment mark detection, e.g. TTR, TTL, off-axis detection, array detector, video detection · CPC title

• G03F9/7076

  Mark details, e.g. phase grating mark, temporary mark · CPC title

• G01B11/272 Primary

  using photoelectric detection means · CPC title