Optical Element Orientation via Crystal Surface Height Profile
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The production of optical elements for lithography apparatuses is hindered by stress-induced birefringence, which distorts polarization properties and limits resolution, due to material processing stresses and temperature gradients in crystal substrates like calcium fluoride, requiring complex methods to optimize rotary orientation.
Innovation Solution
A method involving detecting the height profile of the crystal substrate's surface and using it to ascertain the optimal orientation of the optical element within the lithography apparatus to minimize stress-induced birefringence, incorporating magneto-rheological polishing to create a surface structure that visualizes stress-induced birefringence, allowing for simpler determination of the optimal orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to detect optimal rotary orientation, then the orientation can be determined, but the process requires complex test setups and is inconvenient
Solution Approach 1:
The patent extracts the orientation information directly from the height profile data obtained during standard manufacturing processes, separating the orientation detection function from complex test setups. By analyzing the angular distribution of height values from the surface profile, the method obtains orientation information without requiring additional measurement equipment or complex test apparatus.
Solution Approach 2:
The patent uses the height profile (which is already measured during manufacturing for quality control) as a copy or surrogate for direct birefringence measurement. Instead of setting up complex optical tests to measure birefringence directly, the method copies the orientation information from the readily available height profile data, simplifying the detection process while maintaining accuracy.
2Ease of manufacture
If crystal substrates undergo material processing and temperature gradients, then the optical elements can be manufactured, but stress-induced birefringence occurs that distorts polarization properties
Solution Approach 1:
The patent performs preliminary action by determining the optimal rotary orientation before the optical element is installed in the lithography apparatus. By analyzing the height profile during manufacturing and calculating the angular distribution of height values, the method identifies the orientation that minimizes stress-induced birefringence effects in advance, allowing the element to be installed correctly from the start without requiring post-manufacturing adjustments or corrections.
Solution Approach 2:
The patent changes the parameter being measured from direct birefringence measurement to height profile analysis. By measuring the height profile (which reflects the physical state and stress distribution in the crystal) and deriving orientation information from the angular distribution of height values, the method indirectly characterizes the birefringence conditions without requiring complex optical measurement setups.
3Manufacturing precision
If the height profile is detected during conventional production, then surface quality can be controlled, but additional orientation information is not obtained
Solution Approach 1:
The patent makes the height profile measurement serve multiple functions. The same height profile that is already measured during conventional manufacturing for surface quality control is additionally used to determine the optimal rotary orientation by analyzing the angular distribution of height values. This multi-functional use of the measurement data eliminates the need for separate orientation detection processes and recovers orientation information that would otherwise be lost.
Solution Approach 2:
The height profile measurement process serves itself by providing dual purposes: traditional surface quality assessment and orientation determination. The data collected for one purpose (surface control) automatically provides information for another purpose (orientation optimization) without requiring additional measurements or processes, making the existing measurement system work harder and provide more value.
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 simplifies the identification of the optimal orientation for minimizing stress-induced birefringence, reducing distortion of polarization properties and enhancing the resolution of the lithography apparatus by visualizing stress-induced birefringence through surface profiling.
Implementation Method 1
the process of crystal growth, for example, can give rise to stresses owing to the material processing or a temperature gradient. These stresses can lead to stress-induced birefringence
Implementation Method 2
incorporating magneto-rheological polishing to create a surface structure that visualizes stress-induced birefringence
Data Source
AI summary
A method of producing an optical element for a lithography apparatus, comprising the steps of: a) detecting a height profile of a surface of a crystal substrate of the optical element, and b) ascertaining, using the height profile detected, an installed orientation (δ2, δ4, δ6) of the optical element in an optical system of the lithography apparatus in relation to a stress-induced birefringence on incidence of polarized radiation, where the installed orientation (δ2, δ4, δ6) is an orientation in relation to a rotation of the optical element about a center axis of the optical element that runs through the surface.