Imprint Alignment Calibration for Parallax Error Compensation
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Solution Overview
Problem
Imprint lithography faces challenges in accurately aligning stamps and substrates due to parallax errors caused by non-perpendicular illumination and large gaps, which complicate correction of alignment issues.
Innovation Solution
A method and system for determining a detection angle using a calibration substrate with markers, allowing for non-perpendicular illumination to calculate and compensate for parallax errors, enabling accurate alignment by calculating the detection angle and adjusting the camera position if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If non-perpendicular illumination is used to enable alignment detection, then alignment detection capability is provided, but parallax errors occur causing measurement inaccuracy
Solution Approach 1:
The patent changes the detection angle parameter from perpendicular to non-perpendicular (oblique) illumination. By deliberately introducing an angle parameter α between 0° and 90°, the system enables alignment detection while calculating parallax errors through the relationship between detected marker positions and the known vertical separation, allowing accurate alignment determination despite the non-perpendicular detection angle
2Ease of operation
If a large gap exists between stamp and substrate during alignment, then alignment can be performed before contact, but parallax errors increase due to the large distance
Solution Approach 1:
The patent implements a feedback mechanism by calculating the detection angle α based on the measured parallax displacement and the known vertical separation between markers. This calculated angle serves as feedback information that is used to correct the measured marker positions, allowing the system to maintain high alignment accuracy even when a large gap exists between stamp and substrate during the alignment phase
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 precise alignment of stamps and substrates by compensating for parallax errors, ensuring accurate imprinting processes even with non-perpendicular illumination, thereby improving the alignment accuracy and reducing misalignment issues.
Implementation Method 1
illuminating the pair of markers by a light source; detecting, by a detector having an optical axis, light redirected from the first marker and the second marker
Implementation Method 2
determining the first detection angle based on the refractive index n of the substrate and the first detected lateral displacement between the first and second marker
Data Source
AI summary
A method of detecting a detection angle in a lithographic apparatus, the method comprising using a calibration substrate having a refractive index n and having a first pair of markers, the pair of markers having a predetermined lateral displacement from each other, the first marker in the pair of markers being at a first predetermined vertical position within the calibration substrate and the second marker in the pair of markers being at a second predetermined vertical position within the calibration substrate, the calibration substrate resting on its first surface, illuminating the pair of markers by a light source, detecting, by a detector having an optical axis, light redirected from the first marker and the second marker to determine a first detected lateral displacement between the first marker and the second marker, wherein the optical axis of the detector is at a detection angle, α1, relative to the normal of the substrate of less than 90° and determining the first detection angle based on the first detected lateral displacement between the first and second marker.