Apparatus and methods for measuring thermally induced reticle distortion

Patent metadata

Field	Value
Publication number	US-8994918-B2
Application number	US-201113277085-A
Country	US
Kind code	B2
Filing date	Oct 19, 2011
Priority date	Oct 21, 2010
Publication date	Mar 31, 2015
Grant date	Mar 31, 2015

Abstract

An apparatus and method for measuring thermo-mechanically induced reticle distortion or other distortion in a lithography device enables detecting distortion at the nanometer level in situ. The techniques described use relatively simple optical detectors and data acquisition electronics that are capable of monitoring the distortion in real time, during operation of the lithography equipment. Time-varying anisotropic distortion of a reticle can be measured by directing slit patterns of light having different orientations to the reticle and detecting reflected, transmitted or diffracted light from the reticle. In one example, corresponding segments of successive time measurements of secondary light signals are compared as the reticle scans a substrate at a reticle stage speed of about 1 m/s to detect temporal offsets and other features that correspond to spatial distortion.

First claim

The invention claimed is:

1. An apparatus for in situ measurement of reticle distortion, comprising:
a reticle stage that retains and moves a reticle;
at least one optical source that provides an optical beam that is directed to a pattern of the reticle;
at least one detector situated so as to receive at least a portion of the optical beam from the pattern of the reticle within a movement of the reticle relative to the optical beam, and to produce a corresponding signal; and…

Assignees

• Sogard Michael
• Nikon Corp

Inventors

• Sogard Michael

Classifications

• G03F7/7085

  Physics · mapped topic

• G01M11/02 Primary

  Physics · mapped topic

• G03F7/70783 Primary

  Physics · mapped topic

• G03F7/70875

  Physics · mapped topic

• G03F1/84 Primary

  Physics · mapped topic