Apparatus and method for examining a surface of a mask

Patent metadata

Field	Value
Publication number	US-9910065-B2
Application number	US-201615158779-A
Country	US
Kind code	B2
Filing date	May 19, 2016
Priority date	May 20, 2015
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

The present invention relates to apparatuses and methods for examining a surface of a test object, such as e.g. a lithography mask. In accordance with one aspect of the invention, an apparatus for examining a surface of a mask comprises a probe which interacts with the surface of the mask, and a measuring apparatus for establishing a reference distance of the mask from a reference point, wherein the measuring apparatus measures the reference distance of the mask in a measurement region of the mask which is not arranged on the surface of the mask.

First claim

What is claimed is:

1. Apparatus for examining a surface of a mask, comprising:
a. a probe which interacts with the surface of the mask; and
b. a measuring apparatus for establishing a reference distance of the mask from a reference point, wherein
c. the measuring apparatus measures the reference distance of the mask in a measurement region of the mask which is not arranged on the surface of the mask,
wherein the measurement region is arranged on a side of the mask facing away from the surface.

2. The apparatus according to claim 1 , wherein the measurement region and a measurement point of the probe lie substantially opposite one another on different sides of the mask.

3. The apparatus according to claim 1 , wherein the reference distance of the mask from the reference point is a distance averaged over the measurement region.

4. The apparatus according to claim 1 , wherein the measuring apparatus operates according to the principle of optical interference and/or according to the principle of a capacitive distance measurement.

5. The apparatus according to claim 1 , wherein the reference point is a point of the measuring apparatus.

6. The apparatus according to claim 1 , wherein the measuring apparatus is mechanically coupled to the probe in such a way that a movement of the probe relative to the mask leads to a movement of the measuring apparatus relative to the mask.

7. Apparatus for examining a surface of a mask, comprising:
a. a probe which interacts with the surface of the mask;
b. a measuring apparatus for establishing a reference distance of the mask from a reference point, in which the measuring apparatus measures the reference distance of the mask in a measurement region of the mask that is arranged on a side of the mask facing away from the surface; and
c. a correlation unit, which is embodied to correlate a measurement signal from the probe and a measurement signal from the measuring apparatus with one another.

8. The apparatus according to claim 1 , furthermore comprising a disturbance source, which is configured to expose the apparatus to controllable disturbances.

9. The apparatus according to claim 1 , furthermore comprising a placement table for placing the mask and an actuator which is embodied to displace the placement table in at least one direction (x; y; z).

10. The apparatus according to claim 9 , wherein the actuator is configured to displace the placement table in such a way that a strength of the interaction between the probe and the surface is kept substantially constant.

11. The apparatus according to claim 9 , furthermore comprising a locator for determining a position of the placement table within a plane (xy-plane) defined by the placement table.

12. The apparatus according to claim 9 , wherein the apparatus is embodied to be calibrated by a displacement of the placement table and/or a displacement of the probe along a predetermined sequence of movements.

13. The apparatus according to claim 1 , furthermore comprising a displacement unit which is embodied to displace the probe in at least one direction (x; y; z).

14. The apparatus according to claim 13 , wherein the displacement unit is configured to displace the probe in such a way that a strength of the interaction between the probe and the surface is kept substantially constant.

15. The apparatus according to claim 13 , furthermore comprising a probe locator for determining a position of the probe within a predefined plane (xy-plane).

16. The apparatus according to claim 1 , furthermore comprising a compensation unit for compensating external disturbances by applying a compensation signal to a signal for controlling the apparatus.

17. The apparatus according to claim 16 in combination with claim 9 , wherein the signal serves to control the actuator and/or to control the displacement unit.

18. The apparatus according to claim 1 , wherein the examination of the surface comprises an examination of a topography of the surface.

19. An apparatus for examining a surface of a mask, comprising:
a. a probe which interacts with the surface of the mask;
b. a first measuring apparatus for establishing a first reference distance of the mask from a first reference point, in which the first measuring apparatus measures the first reference distance of the mask in a first measurement region of the mask that is arranged on a side of the mask facing away from the surface; and
c. a second measuring apparatus for establishing a second reference distance of the mask from a second reference point.

20. The apparatus according to claim 19 , wherein a first measurement region of the first measuring apparatus and a second measurement region of the second measuring apparatus do not completely overlap.

21. The apparatus according to claim 19 , wherein the first reference distance of the mask from the first reference point is a distance averaged over the first measurement region of the first measuring apparatus and/or the second reference distance of the mask from the second reference point is a distance averaged over a second measurement region of the second measuring apparatus.

22. The apparatus according to claim 19 , wherein the first measuring apparatus and/or the second measuring apparatus operate according to the principle of optical interference and/or according to the principle of a capacitive distance measurement.

23. The apparatus according to claim 19 , wherein the first reference point is a point of the first measuring apparatus and/or the second reference point is a point of the second measuring apparatus.

24. The apparatus according to claim 19 , wherein the probe is mechanically coupled to the first measuring apparatus in such a way that a movement of the probe relative to the mask leads to a movement of the first measuring apparatus relative to the mask and/or the probe is mechanically coupled to the second measuring apparatus in such a way that a movement of the probe relative to the mask leads to a movement of the second measuring apparatus relative to the mask.

25. The apparatus according to claim 19 , wherein the first measuring apparatus and/or the second measuring apparatus is embodied as a measuring apparatus according to claim 1 .

26. The apparatus according to claim 7 , wherein the measuring apparatus is embodied as a measuring apparatus according to claim 1 .

27. The apparatus according to claim 7 , wherein the correlation unit has a phase analyser, which is configured to establish a phase difference between the measurement signal from the probe and the measurement signal from the measuring apparatus.

28. The apparatus according to claim 7 , wherein the measuring apparatus is embodied as a first measuring apparatus and/or as a second measuring apparatus according to claim 19 .

29. Apparatus for examining a surface of a mask, comprising:
a. a probe which interacts with the surface of the mask; and
b. a measuring apparatus for establishing a reference distance of the mask from a reference point, wherein
c. the measuring apparatus measures the reference distance of the mask in a measurement region of the mask, and
d. wherein a measurement point of the probe lies within the measurement region.

30. The apparatus according to claim 29 , wherein the measuring apparatus has a beam path and wherein the probe is arranged in the beam pa

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Budach Michael
• Hofmann Thorsten
• Edinger Klaus
• Szych Pawel
• Baralia Gabriel

Classifications

• G01B11/14

  for measuring distance or clearance between spaced objects or spaced apertures (G01B11/26 takes precedence; rangefinders G01C3/00) · CPC title

• G03F1/84

  Inspecting · CPC title

• G01Q30/06

  for error compensation · CPC title

• G01Q30/02 Primary

  Non-SPM analysing devices, e.g. SEM [Scanning Electron Microscope], spectrometer or optical microscope · CPC title

• G01Q60/363

  Contact-mode AFM · CPC title