Lithography Sensor System Noise Rejection
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Solution Overview
Problem
Conventional sensor systems in lithographic apparatuses face challenges in maintaining measurement reproducibility while achieving high throughput, as parallel detection arrangements can be affected by shared noise sources, leading to errors in pattern transfer processes.
Innovation Solution
A sensor system with multiple detectors sharing a noise source, where at least one detector responds differently to noise, allowing for improved measurement reproducibility by distinguishing between real position shifts and noise-induced shifts through phase and period differences in periodically varying signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a parallel detection arrangement with multiple detectors is used to reduce measurement time, then productivity is improved, but measurement precision deteriorates due to shared noise sources affecting all detectors
Solution Approach 1:
The patent applies local quality by making each detector's response to noise source-dependent. Different detectors are configured with different characteristics (e.g., different phases or periods in their periodic signals) so that while they all share the same noise source, their individual responses to the noise differ. This allows the system to distinguish between actual measurements and noise-induced variations, maintaining precision despite parallel operation.
Solution Approach 2:
The patent introduces an intermediary processing stage that analyzes the correlated noise patterns across multiple detectors. By examining how the shared noise source affects different detectors differently, the system can separate the noise component from the actual measurement signal, effectively mediating between the parallel detection arrangement and the final measurement results to maintain precision.
2Measurement precision
If measurement time is increased to improve measurement reproducibility, then measurement precision is improved, but productivity deteriorates due to throughput demands
Solution Approach 1:
The patent segments the measurement process by using multiple detectors operating in parallel to simultaneously measure different spatial locations or parameters. Each detector performs a portion of the measurement task independently, allowing the system to achieve high throughput while maintaining precision through the combined information from all detectors, which can distinguish signal from noise through their different noise responses.
Solution Approach 2:
The patent changes the parameters of the detectors' periodic signals (such as phase or period) to create distinguishable responses to the shared noise source. By modifying these parameters, the system enables noise rejection techniques that maintain measurement precision without requiring increased measurement time, thus preserving productivity.
Data Source
AI summary
A sensor system to measure a physical quantity, the system including a parallel detection arrangement with multiple detectors to allow measurements in parallel at different spatial locations, wherein the multiple detectors share a noise source, wherein the sensor system is configured such that the multiple detectors each output a signal as a function of the physical quantity, and wherein the sensor system is configured such that at least one detector responds differently to noise originating from the shared noise source than the one or more other detectors.