Polarizing Element for Lithography Mark Position Measurement
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Solution Overview
Problem
Conventional imprint apparatuses face measurement errors due to scattered light from mark edges, which degrades the accuracy of relative position measurement between the mold and substrate, as unnecessary light mixes with the detection light, causing noise in the moiré fringe signal.
Innovation Solution
A measurement apparatus with a polarizing element that generates different polarization directions for light from the first and second marks, preventing scattered light from interfering with the detection and improving the signal-to-noise ratio by ensuring only relevant light is used for mark position measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single image capturing element is used to capture both X mark and Y mark, then the device complexity is reduced, but measurement precision deteriorates due to scattered light from mark edges
Solution Approach 1:
The patent divides the detection function into two separate image capturing elements: one dedicated to capturing the X mark and another to capturing the Y mark. This segmentation allows each detector to focus on a specific mark, preventing scattered light from one mark from interfering with the detection of the other mark, thereby maintaining high measurement precision while using a relatively simple overall structure.
Solution Approach 2:
The patent introduces a beam splitter as an intermediary optical element that separates the light paths from the X mark and Y mark to different image capturing elements. The beam splitter acts as a mediator that directs light from the X mark to the first image capturing element and light from the Y mark to the second image capturing element, preventing cross-interference and ensuring accurate position measurements for both marks.
2Ease of operation
If scattered light from mark edges is allowed to reach the image capturing element, then the ease of operation is maintained, but measurement precision deteriorates due to noise in detection signal
Solution Approach 1:
The patent extracts and removes the harmful scattered light from the detection path by using separate image capturing elements for each mark. By dedicating one detector to the X mark and another to the Y mark, the scattered light from each mark only reaches its corresponding detector, not the other detector. This extraction of harmful interference maintains operational simplicity while significantly improving measurement precision.
3Productivity
If multiple marks are illuminated simultaneously by a single light source, then productivity is improved, but measurement precision deteriorates due to light interference between marks
Solution Approach 1:
The patent segments the detection system into two independent detection channels, each with its own image capturing element. This allows simultaneous illumination and detection of multiple marks (X mark and Y mark) without cross-interference, as each mark's light is directed to a dedicated detector. This segmentation maintains high productivity through simultaneous detection while ensuring measurement precision by preventing light interference between marks.
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 solution enhances the accuracy of mark position measurement by reducing noise from scattered light, allowing for precise alignment and positioning of the mold and substrate, thereby improving the overall imprint process.
Implementation Method 1
a polarizing element configured to generate different polarization directions from each other in light from the first mark and in light from the second mark which are incident on the image capturing unit
Data Source
AI summary
The present invention provides a measurement apparatus that measures a position of an object which includes a first mark and a second mark, comprising: an image capturing unit configured to capture the first mark and the second mark in a state in which the first mark and the second mark are contained in a field of view; and a polarizing element configured to generate different polarization directions from each other in light from the first mark and in light from the second mark which are incident on the image capturing unit.