US 8,542,356 B2 · Measurement method and measurement system for measuring birefringence

Abstract

A method measuring the birefringence of an object. A measurement beam having a defined input polarization state is generated, the measurement beam being directed onto the object. Polarization properties of the measurement beam after interaction with the object are detected in order to generate polarization measurement values representing an output polarization state of the measurement beam after interaction with the object. The input polarization state of the measurement beam is modulated into at least four different measurement states in accordance with a periodic modulation function of an angle parameter α, and the polarization measurement values associated with the at least four measurement states are processed to form a measurement function dependent on the angle parameter α. A two-wave portion of the measurement function is determined and analysed in order to derive at least one birefringence parameter describing the birefringence, preferably by double Fourier transformation of the measurement function.

Claims20

Dependent claims

A measurement system for measuring birefringence of an optical measurement object comprising:

a beam generating unit configured to generate a measurement beam having a defined input polarization state, the measurement beam being directed onto the measurement object;
a detector unit configured to detect polarization properties of the measurement beam after interaction with the measurement object and to generate polarization measurement values representing an output polarization state of the measurement beam;
and
an evaluation unit configured to evaluate the polarization measurement values and to determine at least one birefringence parameter representing the birefringence of the measurement object,
wherein the beam generating unit is further configured to modulate the input polarization state of the measurement beam into at least four different measurement states in accordance with a periodic modulation function of an angle parameter α;
and
wherein the evaluation unit is further configured to process the polarization measurement values associated with the at least four measurement states, to form a measurement function dependent on the angle parameter α, to determine a two-wave portion of the measurement function and to analyze the two-wave portion, in order to derive the at least one birefringence parameter.

4 more elements

A projection exposure apparatus for exposing a radiation-sensitive substrate arranged proximate to an image surface of a projection objective with at least one image of a pattern of a mask arranged proximate to an object surface of the projection objective, comprising:

a primary light source configured to emit primary light;
an illumination system configured to receive the primary light and to generate an illumination beam directed onto the mask;
a projection objective configured to generate an image of the pattern proximate to the image surface of the projection objective;
and
a measurement system configured to measure the birefringence of an optical measurement object arranged between the primary light source and the image surface of the projection objective, the measurement system comprising:
a beam generating unit configured to generate a measurement beam having a defined input polarization state, the measurement beam being directed onto the measurement object;
a detector unit configured to receive the measurement beam after interaction with the measurement object and to generate polarization measurement values representing an output polarization state of the measurement beam;
and
an evaluation unit configured to evaluate the polarization measurement values and to determine at least one birefringence parameter representing the birefringence of the measurement object.

6 more elements

A measurement method for measuring birefringence of a reticle, comprising:

arranging the reticle in an installation position between an illumination system and a projection objective of a projection exposure apparatus proximate to an object surface of the projection objective;
and
measuring the birefringence of the reticle in the installation position with a measurement system for measuring the birefringence of an optical measurement object, wherein the measurement system is integrated into the projection apparatus;
wherein said measuring comprises:
generating a measurement beam having a defined input polarization state, the measurement beam being directed onto the reticle, the input polarization state being the polarization state of the measurement beam directly before the measurement beam enters into the reticle;
detecting polarization properties of the measurement beam after interaction with the reticle in order to generate polarization measurement values representing an output polarization state of the measurement beam after interaction with the reticle;
and
evaluating the polarization measurement values, to determine at least one birefringence parameter representing the birefringence of the reticle.

5 more elements

Dependencies are inferred from the claim text.

Measurement method and measurement system for measuring birefringence

Life of this patent

Measurement method and measurement system for measuring birefringence

Life of this patent

Abstract

Claims20