Off-axis levelling in lithographic projection apparatus
First Claim
Patent Images
1. A method of calibrating a lithographic projection apparatus comprising:
- generating a first height map of a substrate by measuring a position in a first direction substantially perpendicular to a surface of said substrate of a plurality of points on said substrate surface and simultaneously measuring a position of a substrate holder using a first position detection system, at a measurement station of a lithographic system;
generating a second height map of said substrate by measuring a position in said first direction of said plurality of points on said substrate surface and simultaneously measuring a position of said substrate holder using a second position detection system, at an exposure station of the lithographic system; and
comparing said first and second height maps to calibrate said first and second position detection systems.
2 Assignments
0 Petitions
Accused Products
Abstract
In an off-axis levelling procedure a height map of the substrate is generated at a measurement station. The height map is referenced to a physical reference surface of the substrate table. The physical reference surface may be a surface in which is inset a transmission image sensor. At the exposure station the height of the physical reference surface is measured and related to the focal plane of the projection lens. The height map can then be used to determine the optimum height and/or tilt of substrate table to position the exposure area on the substrate in best focus during exposure. The same principles can be applied to (reflective) masks.
-
Citations
10 Claims
-
1. A method of calibrating a lithographic projection apparatus comprising:
-
generating a first height map of a substrate by measuring a position in a first direction substantially perpendicular to a surface of said substrate of a plurality of points on said substrate surface and simultaneously measuring a position of a substrate holder using a first position detection system, at a measurement station of a lithographic system;
generating a second height map of said substrate by measuring a position in said first direction of said plurality of points on said substrate surface and simultaneously measuring a position of said substrate holder using a second position detection system, at an exposure station of the lithographic system; and
comparing said first and second height maps to calibrate said first and second position detection systems. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
Specification