Pockels Cell Arrays for Polarization Control in Microlithography
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Solution Overview
Problem
Microlithographic projection exposure apparatuses face challenges in flexibly setting different polarization distributions without the need for mirror arrangements with independently settable mirror elements.
Innovation Solution
An optical system comprising a polarization-influencing optical arrangement with transverse Pockels cells or Kerr cells, arranged in arrays successively in the light propagation direction, allowing for flexible polarization state settings, including combinations with diffractive optical elements to achieve arbitrary intensity and polarization distributions in the pupil plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mirror arrangements with independently settable mirror elements are used to set polarization distributions, then flexibility in setting different polarization states is improved, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical mirror arrangement system with an optical system using Pockels cells and diffractive optical elements. The Pockels cells use electro-optic effects to modulate polarization states through electric fields, eliminating the need for mechanically adjustable mirror elements while achieving the same flexibility in setting polarization distributions.
Solution Approach 2:
The invention changes the control parameter from mechanical mirror angles to electric field parameters applied to Pockels cells. By varying the electric field strength and orientation in the Pockels cells, different polarization states are achieved without mechanical movement, thereby reducing device complexity while maintaining adaptability.
2Adaptability or versatility
If mirror arrangements are used for polarization setting, then polarization control capability is improved, but intensity loss and ray shading effects increase
Solution Approach 1:
The patent substitutes mechanical mirror-based polarization control with an electro-optic system using Pockels cells. This substitution eliminates ray shading effects caused by mirror structures and reduces intensity loss by using transparent electro-optic materials that do not block or shade light paths.
Solution Approach 2:
The invention introduces Pockels cells as intermediary elements that interact with light through electro-optic effects rather than mechanical reflection. These cells act as transparent mediators that modify polarization states without the physical obstruction and shading inherent in mirror arrangements, thereby preserving light intensity.
3Device complexity
If Pockels cells are used instead of mirror arrangements, then device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent divides the polarization control function into separate modular Pockels cells, each responsible for specific polarization modulation tasks. This segmentation allows for standardized manufacturing of individual cells with precise specifications, making the overall system easier to manufacture and assemble while maintaining high precision through modular design.
Solution Approach 2:
The invention specifies precise manufacturing parameters for Pockels cells including crystal orientation, electrode positioning, and cell dimensions. By establishing well-defined parameter specifications during manufacturing, the system achieves the required precision through controlled production parameters rather than complex post-assembly adjustments.
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
Enables flexible and selectable polarization distributions in the pupil plane, reducing the need for mirror arrangements and minimizing intensity loss and ray shading effects, while allowing for efficient polarization switching and conversion between different polarization states.
Implementation Method 1
the first and second polarization-influencing elements are transverse Pockels cells
Implementation Method 2
the first and second polarization-influencing elements in each case have a birefringence that is dependent on the presence of an electric field
Implementation Method 3
the first polarization-influencing elements and the second polarization-influencing elements are transverse Pockels cells or transverse Kerr cells
Data Source
AI summary
The invention relates to an optical system for a microlithographic projection exposure apparatus, and to a microlithographic exposure method. An optical system for a microlithographic projection exposure apparatus comprises a polarization-influencing optical arrangement, wherein the polarization-influencing optical arrangement comprises at least one first array of first polarization-influencing elements and a second array of second polarization-influencing elements, wherein the first and second arrays are arranged successively in the light propogation direction, wherein the first and second polarization-influencing elements in each case have a birefringence that is dependent on the presence of an electric field, and wherein the first polarization-influencing elements and the second polarization-influencing elements are transverse Pockels cells.