EUV Sensor Reference Alignment via Spherical-Conical Contact
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Solution Overview
Problem
In EUV projection exposure apparatuses for semiconductor lithography, achieving precise alignment of sensor references with respect to optical elements is challenging due to manufacturing tolerances and adhesive drift issues, which affect the accuracy of mirror positioning and orientation.
Innovation Solution
A method involving determining the orientation of the referential surface, inserting a reference element with a spherical surface into a conical receiving element, and using mechanical contact and adhesive bonding to achieve precise alignment, with optional use of interferometers, coordinate measuring machines, and optical measuring systems to ensure accurate positioning and orientation within tight tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If adhesive layers of nonuniform thickness are used to align the reference element, then alignment flexibility is improved, but angular drift occurs during curing and over time
Solution Approach 1:
The reference element features a spherical contact surface that mates with a conical receiving element. This curved geometry provides self-centering and automatic alignment, eliminating the need for nonuniform adhesive layers while ensuring stable angular positioning. The spherical-conical interface naturally guides the reference element into the correct orientation, preventing both alignment difficulties and subsequent drift.
Solution Approach 2:
The patent replaces the chemical adhesive bonding system with a mechanical contact system. The spherical surface of the reference element directly contacts the conical surface of the receiving element, creating a rigid mechanical connection. This mechanical interface provides both precise alignment and long-term stability without the drift problems associated with adhesive curing and thermal expansion.
2Measurement precision
If linear encoders are used for sensor systems, then measurement resolution is improved, but the working distance becomes very small requiring a compact sensor frame
Solution Approach 1:
The patent transitions from linear encoders with very small working distances to interferometric measurement systems that operate in a different dimensional regime. Interferometers use optical paths that can extend over longer distances, allowing the sensor frame to be positioned further from the optical elements while maintaining picometer-level measurement precision. This dimensional change in the measurement approach resolves the conflict between resolution and frame compactness.
3Length of stationary object
If interferometers are used with compact sensor frames, then measurement range is improved, but the reference to main body alignment tolerance becomes extremely tight
Solution Approach 1:
The spherical contact surface and conical receiving element are precision-manufactured as integral parts of the reference element and main body, respectively. This preliminary precision manufacturing establishes a stable mechanical reference that defines the alignment before the interferometer measurement process begins. The mechanical interface pre-establishes the geometric relationship, reducing the sensitivity to subsequent alignment variations.
Solution Approach 2:
The patent changes the alignment parameter from angular tolerance (10-200 μrad) to a mechanical contact geometry defined by the spherical-conical interface. By transforming the alignment requirement into a physical contact relationship rather than an angular specification, the system achieves stable referencing without extremely tight tolerance requirements. The mechanical contact geometry naturally accommodates small variations while maintaining measurement accuracy.
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 method enables precise alignment of sensor references with orientation tolerances as low as 10-200 μrad, reducing drift and improving the imaging quality in EUV projection exposure apparatuses by ensuring stable mechanical contact and accurate positioning of optical elements.
Implementation Method 1
inserting a reference element with a spherical surface into a conical receiving element, and using mechanical contact and adhesive bonding to achieve precise alignment
Implementation Method 2
inserting a reference element with a spherical surface into a conical receiving element, and using mechanical contact and adhesive bonding to achieve precise alignment
Implementation Method 3
the use of interferometers for determining the position and orientation of the mirrors
Implementation Method 4
using optional use of interferometers, coordinate measuring machines, and optical measuring systems to ensure accurate positioning and orientation
Data Source
AI summary
A semiconductor lithography projection exposure apparatus includes a sensor reference including reference elements. The apparatus also includes an optical element, which includes a main body comprising receiving elements receiving the reference elements. The optical element further includes a referential surface that is an optically active surface of the optical element. The reference elements are arranged to determine a position and an orientation of the optical element. A method includes aligning a sensor reference with respect to a referential surface in a semiconductor lithography projection exposure apparatus.