Lithographic Apparatus Slip Compensation via Position Correlation
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Solution Overview
Problem
In lithographic apparatuses, increased scanning velocities and acceleration phases lead to unpredictable and variable slip between the mask and mask table, causing position errors in pattern projection due to inertia forces, which conventional calibration methods cannot adequately compensate for, especially under stringent accuracy requirements.
Innovation Solution
A lithographic apparatus equipped with a support position sensor and a patterning device position sensor to measure the positions of the support and patterning device relative to specific structures, allowing a control device to determine the correlation between these positions and derive the slip between the patterning device and the support, enabling appropriate compensation for slip during scanning movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If scanning velocity is increased to improve throughput, then productivity increases, but slip between patterning device and support increases due to inertia forces
Solution Approach 1:
The patent employs sensors to detect the position of the patterning device and support table, feeding this information back to a control system. The control system calculates slip based on the difference between measured positions and uses this feedback to compensate for positioning errors, allowing high scanning velocities to be maintained while preserving manufacturing precision.
Solution Approach 2:
The patent replaces reliance on mechanical friction alone (which fails under high inertia forces) with an optical/electronic measurement and control system. Position sensors and a control device substitute for purely mechanical coupling, enabling accurate position compensation even when mechanical slip occurs during high-speed scanning.
2Loss of time
If acceleration phases are increased to reduce cycle time, then productivity improves, but slip between mask and mask table becomes unpredictable and increases
Solution Approach 1:
The control system continuously monitors positions during acceleration phases using sensors, calculates slip in real-time, and applies compensation. This feedback mechanism makes the system reliable even during rapid acceleration and deceleration phases, eliminating the unpredictability of mechanical coupling under high inertia forces.
Solution Approach 2:
The system performs preliminary measurement of positions before slip occurs, allowing the control device to calculate expected slip and compensate for it proactively. This preliminary action enables the system to maintain positioning reliability during acceleration phases rather than reacting to slip after it occurs.
3Manufacturing precision
If conventional calibration methods are used to compensate for slip, then positioning accuracy can be maintained under low acceleration, but these methods fail under high acceleration conditions
Solution Approach 1:
The patent transitions from static calibration (fixed compensation values determined beforehand) to dynamic compensation (real-time calculation of slip based on actual measured positions). This dynamic approach allows the system to adapt to varying acceleration conditions, making positioning accuracy maintainable across all operating conditions rather than only under low acceleration.
Solution Approach 2:
The system changes the parameter used for compensation from fixed calibration values to dynamically calculated slip values based on real-time position measurements. This parameter change enables the system to adapt to different acceleration levels and maintain positioning accuracy across the full range of operating conditions.
Data Source
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AI summary
In a lithographic apparatus, a slip of a patterning device relative to a support, the support constructed to support the patterning device, may be provided by measuring a position of the support relative to a first structure of the lithographic apparatus; measuring a position of the patterning device relative to a second structure of the lithographic apparatus; determining a correlation between the position of the patterning device and the position of the support from the measured position of the support, the measured position of the patterning device, and the mutual positions of the first and second structures; and deriving from the correlation a slip of the patterning device relative to the support. The structure may include a projection system to project a radiation beam patterned by the patterning device. The projection system may be connected to a frame, such as a metrology frame of the lithographic apparatus.