Lithographic Position Measurement Drift Compensation
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Solution Overview
Problem
Conventional position measurement systems in lithographic apparatuses require time-consuming calibration to compensate for drift, leading to downtime and reduced productivity due to inaccurate positioning caused by deformations or displacements of sensors or gratings.
Innovation Solution
A position measurement system with a computational unit that applies adjustments to position signals based on predetermined drift characteristics, including base shapes of the system components, to compensate for drift without the need for periodic recalibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If periodic calibration is performed to compensate for drift, then positioning accuracy is improved, but apparatus downtime increases and productivity decreases
Solution Approach 1:
The patent applies preliminary action by pre-determining drift characteristics and base shapes during the calibration phase, storing them for later use. This allows the system to compensate for drift in real-time during operation without requiring periodic recalibration, thus maintaining positioning accuracy while avoiding apparatus downtime that would reduce productivity
Solution Approach 2:
The system implements self-service by automatically compensating for drift using the predetermined drift characteristics and base shapes stored in memory. The computational unit continuously adjusts position measurements based on these pre-established parameters, enabling the apparatus to maintain accuracy autonomously without external intervention or periodic calibration, thereby eliminating productivity loss from recalibration downtime
2Measurement precision
If conventional calibration methods are used to compensate for drift, then positioning accuracy is improved, but calibration time increases
Solution Approach 1:
The patent performs the calibration action in advance by determining drift characteristics and base shapes during an initial calibration phase, then storing these parameters for repeated use. This preliminary calibration eliminates the need for time-consuming periodic recalibration while maintaining position reference accuracy through continuous application of the pre-determined parameters
Solution Approach 2:
The system creates a copy of the drift characteristics and base shapes during initial calibration and stores this information in memory. This copied data can be repeatedly applied during operation without requiring the original calibration process to be repeated, thus maintaining accuracy while minimizing calibration time and associated downtime
Data Source
AI summary
A position measurement system includes a first part and a second part for determining a position of a first member relative to a second member by providing a position signal representing a position of the first part relative to the second part, and a computational unit comprising an input terminal for receiving the position signal. The computational unit is configured to, in use, apply a conversion to the position signal to obtain a signal representing a position of the first member relative to the second member; and apply an adjustment to the conversion to at least partly compensate for a drift of the first part or the second part or both. The adjustment is based on a predetermined drift characteristic of the first part or the second part or both respectively. The predetermined drift characteristic includes one or more base shapes of the first part and/or the second part.