Lithographic Substrate Table Calibration via 2D Pattern Mapping
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Solution Overview
Problem
Conventional calibration methods for substrate table position in lithographic apparatuses are inadequate in addressing position-dependent errors caused by irregularities in the reflecting surfaces of the substrate table, particularly in multidimensional configurations, leading to inaccuracies in position measurement and calibration.
Innovation Solution
A calibration method that involves repeatedly irradiating a pattern onto the substrate surface, displacing the substrate table to create a two-dimensional arrangement of patterns, reading out these patterns to derive incremental position deviations, and using these deviations to calculate and correct for position errors based on the two-dimensional position of the substrate table.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration methods are used, then the calibration process is simple, but position-dependent errors caused by irregularities in reflecting surfaces are not addressed, leading to inaccurate position measurement
Solution Approach 1:
The patent extends calibration from one-dimensional to two-dimensional by creating a 2D array of patterns on the substrate. This allows simultaneous measurement of position errors in both X and Y directions, as well as rotation around the Z axis, thereby capturing position-dependent errors across the entire substrate table surface.
Solution Approach 2:
The calibration pattern is divided into multiple discrete patterns arranged in a 2D array on the substrate. Each pattern can be independently read out and processed to derive position deviations at different locations, enabling localized error analysis and calibration across the substrate table.
2Adaptability or versatility
If multiple interferometers are directed to different sides of the substrate table, then position information in multiple dimensions is provided, but irregularities in reflecting surfaces cause measurement errors in position
Solution Approach 1:
Instead of relying on the substrate table's reflecting surfaces, the patent uses a separate calibration pattern copied onto the substrate. This calibration pattern serves as a reference copy that can be read out to derive position deviations, eliminating the influence of surface irregularities on the measurement.
Solution Approach 2:
The calibration pattern on the substrate acts as an intermediary reference. By reading out this pattern and comparing its position against expected values, the system can derive position deviations without directly measuring the substrate table's reflecting surfaces, thus avoiding errors caused by surface irregularities.
3Measurement precision
If a two-dimensional arrangement of patterns is created on the substrate, then position-dependent errors in both X and Y dimensions are accounted for, but the calibration process becomes more complex
Solution Approach 1:
The calibration pattern is read out systematically across the 2D array, and position deviations are derived continuously from the readout data. This continuous processing allows efficient extraction of calibration information across all measurement points without requiring separate discrete measurements for each position.
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 method provides a more accurate calibration of the substrate table position, accounting for position-dependent errors in both X and Y dimensions, and up to 6 degrees of freedom, thereby enhancing the precision of position measurement and calibration in lithographic apparatuses.
Implementation Method 1
The interferometer is a type of optical measurement device which measures a distance towards a reference, commonly a mirror or other reflecting surface
Implementation Method 2
The encoder is a type of optical measurement device which measures a position of a reference by detecting an interaction of an optical beam of the interferometer with a pattern on the reference
Implementation Method 3
repeatedly irradiating a pattern onto a surface of the substrate, thereby displacing the substrate table between successive irradiations to irradiate the pattern onto different locations on the surface of the substrate
Data Source
AI summary
A calibration method to calibrate a substrate table position in a lithographic apparatus, the method including repeatedly irradiating a pattern onto a surface of the substrate so as to create a two dimensional arrangement of patterns on the surface of the substrate, the irradiating including displacing the substrate table between successive irradiations to irradiate the pattern onto different locations on the surface of the substrate, reading out the patterns in the two dimensions to obtain pattern read out results, deriving incremental position deviations from the read out results of neighboring patterns in dependency on the position of the substrate table in the two dimensions, deriving from the incremental position deviations a position error of the substrate table as a function of the two dimensional position of the substrate table and calibrating the position of the substrate table using the position dependent position error.