Lithography Beam Measurement Using Movable Sensor
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Solution Overview
Problem
Current lithographic sensors face limitations in resolution due to the number of pixels and available space, leading to suboptimal aberration control and intensity distribution measurements, which are crucial for high-precision imaging in advanced lithographic tools.
Innovation Solution
A lithographic apparatus with a measurement unit that moves a sensing surface transverse to the optical axis between multiple positions, capturing a portion of the radiation beam's view smaller than 100% at each position, allowing for higher resolution measurements without increasing pixel size or sensor distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor uses more pixels to increase resolution, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent divides the measurement process into multiple sequential steps, where the sensor captures the radiation beam at different positions along the optical axis. Instead of requiring all pixels to capture the entire beam simultaneously, the measurement is segmented across multiple positions, allowing fewer pixels to achieve the same total measurement precision.
Solution Approach 2:
The patent adds the optical axis dimension to the measurement approach. By moving the sensor along the optical axis and capturing the beam at multiple positions, the system transforms a 2D spatial measurement problem into a 3D measurement problem, enabling high-resolution measurement with fewer pixels through temporal-spatial integration.
2Measurement precision
If the sensor is placed further from the beam to increase spot size, then resolution improves, but available space and device compactness are limited
Solution Approach 1:
The patent makes the sensor position dynamic along the optical axis rather than fixed. By implementing a movable sensor that can be positioned at multiple locations, the system achieves the benefits of variable distances without requiring a permanently large apparatus, thus improving resolution while maintaining device compactness.
Solution Approach 2:
The patent utilizes the optical axis dimension to resolve the spatial conflict. Instead of only moving the sensor in the plane perpendicular to the optical axis, the system moves the sensor along the optical axis itself, creating additional measurement dimensions that improve resolution without increasing the lateral footprint of the device.
3Measurement precision
If smaller pixels are used to increase resolution, then measurement precision improves, but pixel crosstalk increases and measurement quality deteriorates
Solution Approach 1:
The patent segments the beam measurement across multiple sensor positions, allowing each pixel to capture a larger effective area over time. By accumulating measurements from different positions, the system achieves high resolution without requiring small pixels that would suffer from crosstalk at any single position.
Solution Approach 2:
The patent implements continuous scanning of the sensor along the optical axis, ensuring that each pixel continuously captures useful measurement data as the beam passes through different positions. This continuous action maximizes the utilization of each pixel's area, reducing the need for small pixels and thereby minimizing crosstalk while maintaining measurement quality.
Data Source
AI summary
A lithographic apparatus including a projection system having an optical axis and configured to project a radiation beam. The apparatus includes a measurement unit arranged to measure the radiation beam projected by the projection system, the measurement unit having an opening through which the radiation beam passes in use, and a sensing surface extending transverse to the optical axis and arranged to measure the radiation beam passing through the opening. The apparatus is configured to move the sensing surface in a plane transverse to the optical axis between a plurality of measurement positions. The radiation beam defines a view in the plane, and the measurement unit is configured such that the sensing surface captures, in each measurement position, a portion of the view smaller than 100% of the view.