Optical Polarization Evaluation in Microlithographic Projection Exposure
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Solution Overview
Problem
Microlithographic projection exposure apparatuses face challenges in evaluating and optimizing optical polarization properties, which affect the contrast and minimum size of structures produced, especially in high numerical aperture systems, due to polarization-dependent interference phenomena and birefringence effects in optical materials.
Innovation Solution
A method involving the determination of Jones vectors at the exit pupil, described as a linear superposition of predetermined vector modes with scalar superposition coefficients, allows for the evaluation and improvement of optical polarization properties by identifying and correcting imaging errors attributed to polarization effects, using polarization manipulators and optimized optical elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If projection objectives with high numerical apertures are used to generate smaller structures, then productivity and integration density are improved, but polarization-dependent interference effects worsen imaging quality and contrast
Solution Approach 1:
The patent applies parameter changes by systematically varying polarization state parameters (s-polarization, p-polarization, circular polarization, elliptical polarization) and numerical aperture parameters to optimize the balance between productivity and imaging quality. The method evaluates imaging quality as a function of these parameters and selects optimal combinations that maintain high integration density while compensating for polarization-dependent interference effects through calculated parameter adjustments.
2Manufacturing precision
If the polarization state is optimized for s-polarization to improve contrast, then imaging quality is improved, but the system becomes more sensitive to polarization-dependent effects in high numerical aperture configurations
Solution Approach 1:
The patent implements universality by developing a comprehensive evaluation method that handles multiple polarization states (s-polarization, p-polarization, circular polarization, elliptical polarization) within a single unified framework. This multi-functional approach allows the system to evaluate and optimize imaging quality across all polarization conditions, making the method universally applicable regardless of which polarization state is used, thereby reducing sensitivity to polarization-dependent effects while maintaining contrast optimization.
3Manufacturing precision
If a comprehensive evaluation method for polarization properties is implemented, then imaging quality can be improved, but device complexity increases
Solution Approach 1:
The patent applies mechanics substitution by replacing complex physical measurement systems with a computational evaluation method. Instead of requiring additional hardware to measure and evaluate polarization properties, the invention uses mathematical models and calculations to determine imaging quality as a function of polarization state and numerical aperture. This computational approach significantly reduces device complexity while maintaining the ability to evaluate and optimize imaging quality across different polarization conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables straightforward and physically informative evaluation of optical polarization conditions, facilitating the improvement of imaging properties by separating rotationally symmetric and azimuthally varying components, and allowing for precise correction of polarization-induced errors, thereby enhancing the capability to produce smaller structures with improved contrast.
Implementation Method 1
the reticle diffracts the transmitted projection light into different diffraction orders, which interfere in the image plane and thereby produce the image of the reticle
Implementation Method 2
different diffraction orders, which interfere in the image plane and thereby produce the image of the reticle
Implementation Method 3
Many of the optical materials used in projection objectives are furthermore intrinsically birefringent or have induced birefringence, and therefore also modify the polarization state of the projection light
Implementation Method 4
every optical interface alters to a greater or lesser extent the polarization state of light which does not arrive perpendicularly on the interface
Data Source
AI summary
In a method for describing, evaluating and improving optical polarization properties of a projection objective of a microlithographic projection exposure apparatus, the Jones or Stokes vectors are firstly determined at one or more points in the exit pupil of the projection objective. These are then described at least approximately as a linear superposition of predetermined vector modes with scalar superposition coefficients. The optical polarization properties can subsequently be evaluated on the basis of the superposition coefficients.