Lithographic Sensor Sampling With Transposed Pattern Marks
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Solution Overview
Problem
Existing lithographic apparatuses face challenges in accurately determining physical quantities such as optical aberrations and substrate alignment due to intensity noise in radiation, which affects the precision of image formation on substrates.
Innovation Solution
A method using a sensor system that samples multiple positions with object plane patterning devices having different orientations, generating multiple data sets to combine and correct for intensity noise, thereby enhancing the accuracy of aberration and alignment measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single data set is used for measurement, then the measurement process is simple, but the sensitivity to correlated intensity noise is high
Solution Approach 1:
The measurement process is segmented into multiple independent data sets by using different portions of the object plane patterning device and measuring in different directions. Each data set is then processed separately and combined, which segments the noise correlation and reduces its impact on the final measurement precision.
Solution Approach 2:
The measurement approach transitions from a single measurement dimension to multiple dimensions by measuring in different directions (first direction and second direction) and using different portions of the patterning device. This dimensional expansion allows the system to distinguish between signal and correlated noise more effectively.
2Reliability
If multiple data sets are collected from different portions and directions, then the sensitivity to correlated intensity noise is reduced, but the measurement process becomes more complex
Solution Approach 1:
The sensor system is designed with multi-functionality by incorporating multiple portions of the object plane patterning device that can be used for different measurement directions. This universal design allows a single sensor system to collect multiple data sets for different physical quantities (aberrations and alignment) without requiring separate dedicated systems for each measurement type.
Solution Approach 2:
The measurement system uses copies or replicas of the same patterning device structure arranged in different orientations and positions. These copies enable the system to measure the same physical quantity multiple times from different perspectives, thereby reducing the impact of correlated intensity noise while maintaining measurement reliability.
3Manufacturing precision
If transposed patterning devices are used in different orientations, then alignment accuracy is improved, but the device configuration becomes more complex
Solution Approach 1:
The object plane patterning device is designed with asymmetric or transposed portions that have different orientations. This asymmetry is intentionally introduced to provide distinct measurement signatures for different alignment directions, enabling the system to accurately determine alignment status in multiple directions simultaneously.
Solution Approach 2:
The patterning device configuration is designed to be dynamically selectable, where different portions can be activated for measurement in different directions. This dynamic capability allows the system to adapt its measurement configuration based on the specific alignment verification needed, maintaining manufacturing precision while managing device complexity through selective operation.
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
The method reduces the sensitivity to correlated intensity noise, allowing for more precise determination of physical quantities like optical aberrations and improved alignment in lithographic processes.
Implementation Method 1
using a sensor system configured to sample a plurality of positions
Implementation Method 2
Some of these sensor systems use a detector that outputs a periodically varying signal. Such a periodically varying signal may be obtained using a periodic structure, such as a grating.
Data Source
AI summary
A method of determining a physical quantity is disclosed. The method uses a sensor system configured to sample a plurality of positions in parallel, wherein sampling each position uses radiation incident on an object plane patterning device (mark) and an image plane sensor. Each mark comprises a first portion and a second portion, the first portion being different to the second portion, and wherein the first and second portions of at least one of the marks is transposed relative to the first and second portions of the other marks. Each mark corresponds to a different sampling position. The method comprises, for each portion of each mark: performing a first measurement in a first direction; and performing a second measurement in a second direction different to the first direction. Four data sets are determined and subsequently combined to determine the physical parameter.