Real-time reticle curvature sensing

Patent metadata

Field	Value
Publication number	US-9632429-B2
Application number	US-201314423082-A
Country	US
Kind code	B2
Filing date	Aug 1, 2013
Priority date	Aug 29, 2012
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

Abstract

A system and method that bends a reticle and senses a curvature of a bent reticle in real-time. The system includes movable reticle stage, reticle vacuum clamps, sensor systems, and reticle bender. The reticle bender comprises piezo actuators. The sensor systems comprises measurement targets and corresponding sensors. The sensors are attached to the movable reticle stage and the measurement targets are attached to the reticle clamps, the reticle bender, or on reticle surfaces. The system is configured to determine a width of the reticle or distance between measurement targets at opposing ends of the reticle, measure a first rotational angle at a first end of the reticle, and measure a second local rotational angle at a second end of the reticle that is opposite to the first end. Based on the width or distance and the first and second angles, a field curvature of the reticle is determined.

First claim

What is claimed is:

1. A lithographic system comprising:
a reticle support configured to hold a reticle, the reticle comprising:
two major opposing surfaces that are substantially planar and parallel to each other and are substantially parallel to a reference plane before operational use of the reticle, and
first and second edges between the two major opposing surfaces, the second edge being located opposite to and at a pre-determined distance from the first edge; and

a sub-system comprising:
a plurality of sensors and a corresponding plurality of measurement targets that are coupled to a surface of the reticle;
a first sensor system configured to sense, at the first edge, a first relative orientation of the reference plane and a first plane during operational use of the reticle, the first plane being tangent to one of the two major opposing surfaces substantially at the first edge; and
a second sensor system configured to sense, at the second edge, a second relative orientation of the reference plane and a second plane during operational use of the reticle, the second plane being tangent to the one of the two major opposing surfaces substantially at the second edge,

wherein the sub-system is configured to determine a curvature of the reticle based on the pre-determined distance, the first relative orientation, and the second relative orientation.

2. The lithographic system of claim 1 , wherein each of the first and second sensor systems comprises a sensor from among the plurality of sensors and a corresponding measurement target from among the corresponding plurality of measurement targets coupled to respective first and second surfaces of the reticle.

3. The lithographic system of claim 2 , wherein the plurality of sensors comprises capacitive sensors and the corresponding plurality of measurement targets comprises capacitive plates.

4. The lithographic system of claim 1 , further comprising a reticle bender configured to control field curvature focus of the reticle.

5. The lithographic system of claim 1 , wherein the reticle support is coupled to a movable reticle stage.

6. A lithographic system comprising:
a reticle support configured to hold a reticle, the reticle comprising:
two major opposing surfaces that are substantially planar and parallel to each other before operational use of the reticle, and
first and second edges between the two major opposing surfaces, the second edge being located opposite to and at a pre-determined distance from the first edge; and

a sub-system comprising:
a plurality of sensors and a corresponding plurality of measurement targets that are coupled to a surface of the reticle;
a first sensor system configured to sense, at the first edge, a first relative orientation of a reference plane and a first plane during operational use of the reticle, the reference plane being substantially parallel to the first edge before operational use of the reticle and the first plane being substantially parallel to the first edge; and
a second sensor system configured to sense, at the second edge, a second relative orientation of the reference plane and a second plane during operational use of the reticle, the second plane being substantially parallel to the second edge,

wherein the sub-system is configured to determine a curvature of the reticle based on the pre-determined distance, the first relative orientation, and the second relative orientation.

7. The lithographic system of claim 6 , wherein the corresponding plurality of measurement targets are coupled to a bottom surface of the reticle.

8. The system of claim 6 , wherein each of the first sensor system and the second sensor system comprises a sensor from among the plurality of sensors and a corresponding measurement target from among the corresponding plurality of measurement targets that are coupled to respective first and second surfaces of the reticle.

9. The system of claim 6 , wherein the plurality of sensors is configured to measure displacement of respective ones of the plurality of measurement targets.

10. The lithographic system of claim 6 , wherein:
the first sensor system, comprising a first set of measurement targets from among the corresponding plurality of measurement targets, is further configured to:
measure displacements of the first set of measurement targets, and
determine the first relative orientation based on a difference between the displacements of the first set of measurement targets; and

the second sensor system, comprising a second set of measurement targets from among the corresponding plurality of measurement targets, is further configured to:
measure displacements of the second set of measurement targets; and
determine the second relative orientation based on a difference between the displacements of the second set of measurement targets.

11. The lithographic system of claim 6 , wherein the reticle support is coupled to a movable reticle stage.

12. A lithographic system comprising:
a projection lens with a lens top;
a reticle support configured to hold a reticle, the reticle being configured for imparting a radiation beam with a pattern in a cross-section of the radiation beam so as to create a patterned radiation beam, the reticle comprising:
two major opposing surfaces substantially planar and parallel to each other before operational use of the reticle, and
first and second edges between the two major opposing surfaces, the second edge being located opposite to and at a pre-determined distance from the first edge; and

a sub-system, movably mounted with respect to the lens top of the projection lens, configured to:
determine a first quantity representative of a first angle between a reference plane and a first plane during operational use of the reticle, the reference plane being substantially parallel to the first edge before operational use of the reticle and the first plane being substantially parallel to the first edge; and
determine a second quantity representative of a second angle between the reference plane and a second plane during operational use of the reticle, the second plane being substantially parallel to the second edge; and
determine a curvature of the reticle based on the pre-determined distance, the first quantity, and the second quantity,

wherein the sub system comprises a plurality of measurement targets that are coupled to a surface of the reticle.

13. The lithographic system of claim 12 , wherein the sub-system comprises a first sensor system and a second sensor system.

14. The lithographic system of claim 13 , wherein:
the first sensor system is configured to measure the first quantity; and
the second sensor system is configured to measure the second quantity.

15. The lithographic system of claim 13 , wherein:
the first sensor system, comprising a first set of measurement targets from among the plurality of measurement targets, is configured to:
measure displacements of the first set of measurement targets, and
determine the first quantity based on a difference between the displacements of the first set of measurement targets; and

the second sensor system, comprising a second set of measurement targets from among the plurality of measurement targets, is further configured to:
measure displacements of the second set of measurement targets; and
determine the second quantity based on a difference between the displacements of the second set of measurement targets.

16. A method of determining a curvature of a reticle being held by a reticle support in a lithographic system, the method comprising:
holding the re

Assignees

• Asml Holding Nv
• Asml Netherlands N V
• Asml Netherlands Bv

Inventors

• Ward Christopher Charles
• Leenders Martinus Hendrikus Antonius
• Schuster Mark Josef
• Valentin Christiaan Louis

Classifications

• G03F7/24 Primary

  Curved surfaces {(G03F7/70 takes precedence)} · CPC title

• G03F7/7085

  Detection arrangement, e.g. detectors of apparatus alignment possibly mounted on wafers, exposure dose, photo-cleaning flux, stray light, thermal load · CPC title

• G03F1/14

  Physics · mapped topic

• G03F7/70616 Primary

  Monitoring the printed patterns · CPC title

• G03F7/70783

  Handling stress or warp of chucks, masks or workpieces, e.g. to compensate for imaging errors or considerations related to warpage of masks or workpieces due to their own weight · CPC title