Multi-Aperture Optical Arrangement for Stitch-Free Metrology
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Solution Overview
Problem
Prior metrology systems in semiconductor manufacturing rely on quad non-polarizing beam splitters, which limit the field of view and require image stitching, leading to alignment errors that hinder meeting future specifications.
Innovation Solution
An optical arrangement for a metrology system that eliminates the use of a quad non-polarizing beam splitter by employing an illumination mode selector with shaped apertures and reflective portions in the pupil plane, allowing for simultaneous illumination and detection without image stitching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a quad non-polarizing beam splitter is used in prior metrology systems, then illumination intensity is enhanced, but field of view is limited and image stitching is required
Solution Approach 1:
The beam splitter is divided into four separate apertures arranged in a quad configuration, where each aperture independently transmits a portion of the beam. This segmentation allows the system to maintain a wide field of view while providing sufficient illumination intensity through the combined effect of multiple apertures, eliminating the need for image stitching.
Solution Approach 2:
The solution transitions from a single large aperture to multiple smaller apertures arranged in a two-dimensional quad pattern. This dimensional rearrangement enables the system to achieve both wide field of view and adequate illumination intensity by distributing the beam across multiple spatial locations rather than relying on a single aperture.
2Area of stationary object
If image stitching is used to expand field of view, then field of view is increased, but alignment errors are introduced
Solution Approach 1:
By segmenting the beam splitter into four apertures that simultaneously illuminate the entire field of view, the system eliminates the need for image stitching operations. This segmentation approach provides complete field coverage in a single shot, thereby avoiding alignment errors that would arise from stitching multiple images together.
3Productivity
If a quad non-polarizing beam splitter is used, then system throughput is optimized, but device complexity increases
Solution Approach 1:
The four apertures are integrated into a single beam splitter component rather than requiring four separate optical elements. This merging approach maintains the high system throughput provided by the quad configuration while reducing optical complexity by consolidating multiple functions into one element.
Solution Approach 2:
The beam splitter is designed to simultaneously perform multiple functions: it acts as both an illumination element and a beam distribution element. The quad aperture configuration enables the single component to control both the intensity and spatial distribution of the beam, reducing the need for additional optical elements and simplifying the overall system.
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
The new optical design enhances system throughput by optimizing illumination and detection light intensity, eliminating alignment errors, and enabling low-cost high-photon efficiency dual objective sensing.
Implementation Method 1
transmit portions of radiation through the transmissive portions of the at least one multi-aperture pattern toward a diffraction grating target; and reflect, with the reflective portions of the at least one multi-aperture pattern, diffracted radiation from the diffraction grating target
Implementation Method 2
reflect, with the reflective portions of the at least one multi-aperture pattern, diffracted radiation from the diffraction grating target along a second optical path toward a detector
Data Source
AI summary
An optical arrangement eliminates the use of a quad non polarized beam splitter (QNPBS) and the need for image stitching. The optical arrangement provides an enhanced transmission gain as with a QNPBS to optimize system throughput. A metrology system (600) includes an illumination mode selector (IMS) (650) comprising a multi-aperture pattern having transmissive portions and reflective portions. The IMS (650) is positioned in a pupil plane (655) of the system (600), and configured to: transmit portions (671) of radiation (604) toward a diffraction grating target (610); and reflect diffracted radiation from the target (610) along a second optical path (631) toward a detector (662). Area decoupling of transmissive and reflective portions on the IMS (650) optimizes the illumination and detection light intensity simultaneously. Plus and minus first diffraction order diffracted radiation from the target (610) may be reflected by two reflective quadrants of the multi-aperture pattern, the two reflective quadrants located on a back or non-radiation source facing side (651) of the IMS (650).