Microlithographic mask, method for determining edge positions of the images of the structures of such a mask and system for carrying out such a method

Patent metadata

Field	Value
Publication number	US-11256178-B2
Application number	US-202017004973-A
Country	US
Kind code	B2
Filing date	Aug 27, 2020
Priority date	Oct 26, 2017
Publication date	Feb 22, 2022
Grant date	Feb 22, 2022

Abstract

For the purposes of measuring structures of a microlithographic mask, a method for capturing absolute positions of structures on the mask and a method for determining structure-dependent and/or illumination-dependent contributions to the position of an image of the structures to be imaged, or of the edges defining this structure, are combined with one another. As a result of this, establishing an edge placement error that is relevant to the exposure of a wafer and, hence, a characterization of the mask can be substantially improved.

First claim

What is claimed is:

1. A method, comprising:
providing a mask which comprises:
a metrology marker, comprising:
an anchoring element configured so that its global position data on the mask are establishable via an optical method using a first measurement wavelength; and
a test structure comprising structure elements imageable on a wafer with radiation at an imaging wavelength when the mask is used, a maximum distance of the structure elements of the test structure from the anchoring element being no more than one tenth of a side length of the mask, and the mask is a microlithographic mask;

determining an absolute position of the anchoring element on the mask;
using an aerial imaging method to determine a relative position of an image of edges defining the test structure relative to the absolute position of an image of the anchoring element;
determining an absolute position of the image of the test structure from the absolute position of the anchoring elements and the relative position of the image of the test structure in relation thereto; and
determining a deviation of the absolute position of the image of the test structure from a setpoint position.

2. The method of claim 1 , wherein the maximum distance of the structure elements of the test structure from the anchoring element is no more than one hundredth of the side length of the mask.

3. The method of claim 1 , wherein the maximum distance of the structure elements of the test structure from the anchoring element is no more than one millimeter.

4. A method of determining edge positions of images of the structures of a microlithographic mask comprising a metrology marker which comprises an anchoring element and a test structure, the anchoring element configured so that its global position data on the mask are establishable via an optical method using a first measurement wavelength, the test structure comprising structure elements configured so that they are imageable on a wafer with radiation at an imaging wavelength when the mask is used, a maximum distance of the structure elements of the test structure from the anchoring element being no more than one tenth of a side length of the mask, the method comprising:
a) determining an absolute position of the anchoring element on the mask;
b) using an aerial imaging method to determine a relative position of an image of edges defining the test structure relative to the absolute position of an image of the anchoring element;
c) determining an absolute position of the image of the test structure from the absolute position of the anchoring elements and the relative position of the image of the test structure in relation thereto; and
d) determining a deviation of the absolute position of the image of the test structure from a setpoint position.

5. The method of claim 4 , further comprising establishing structure-dependent contributions when determining the image of the relative position of the test structure relative to the position of the image of the anchoring element.

6. The method of claim 4 , further comprising, when determining the deviation of the absolute position of the image of the test structure from the setpoint position, taking into account contributions that are compensatable via a projection exposure apparatus.

7. The method of claim 4 , comprising using a non-actinic method to determine the absolute position of the anchoring element.

8. The method of claim 4 , comprising using an actinic method to determine the relative position of the image of the test structure.

9. The method of claim 8 , further comprising selecting an imaging property according to the imaging properties of a scanner.

10. The method of claim 4 , further comprising performing b) a plurality of times, wherein a chief ray direction is varied in each case.

11. The method of claim 4 , further comprising imaging structures of the mask onto a radiation-sensitive layer of a wafer via a projection exposure apparatus.

12. The method of claim 4 , wherein the method is used to optimize an optical proximity correction.

13. The method of claim 8 , further comprising selecting an imaging property according to the imaging properties of a scanner.

14. A method of analyzing a plurality of masks configured to be used for multiple exposure of a wafer, the method comprising:
for each mask, measuring the mask by a method comprising:
a) determining an absolute position of an anchoring element on the mask;
b) using an aerial imaging method to determine a relative position of an image of edges defining a test structure of the mask relative to a position of an image of the anchoring element;
c) determining an absolute position of the image of the test structure from the absolute position of the anchoring elements and the relative position of the image of the test structure in relation thereto; and
d) determining a deviation of the absolute position of the image of the test structure from a setpoint position; and

determining a relative deviation of structure elements on different masks, which have, at least in regions, identical setpoint positions.

15. The method of claim 14 , comprising, for each mask, using a non-actinic method to determine the absolute position of the anchoring element.

16. The method of claim 14 , further comprising, for each mask, establishing structure-dependent contributions when determining the image of the relative position of the test structure relative to the position of the image of the anchoring element.

17. The method of claim 14 , further comprising, for each mask when determining the deviation of the absolute position of the image of the test structure from the setpoint position, taking into account contributions that are compensatable via a projection exposure apparatus.

18. The method of claim 14 , comprising using an actinic method to determine the relative position of the image of the test structure.

19. The method of claim 14 , further comprising, for each mask, performing b) a plurality of times, wherein a chief ray direction is varied in each case.

20. The method of claim 14 , further comprising, for each mask, imaging structures of the mask onto a radiation-sensitive layer of a wafer via a projection exposure apparatus.

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Hellweg Dirk

Classifications

• G03F9/7088

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

• G03F7/70258

  Projection system adjustments, e.g. adjustments during exposure or alignment during assembly of projection system · CPC title

• G03F7/70441 Primary

  Optical proximity correction [OPC] · CPC title

• G03F7/70775

  Position control, e.g. interferometers or encoders for determining the stage position · CPC title

• G03F1/84

  Inspecting · CPC title