Lithography Optical Sensor Filtering for High-Rate Sampling
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Solution Overview
Problem
Conventional filter concepts in lithography apparatuses face limitations due to settling time requirements, restricting the maximum sampling rate and leading to undesirable aliasing effects when high sampling rates are used without filters.
Innovation Solution
An apparatus comprising an analogue-to-digital converter and a digital filter device, synchronized by a shared system clock, which filters digital sensor signals in a channel-specific manner, eliminating the need for analogue filters and allowing for higher sampling rates without aliasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional analogue filters are used for sensor signal processing, then filtering of sensor signals is achieved, but the maximum sampling rate is restricted due to settling time requirements
Solution Approach 1:
The patent replaces the mechanical analogue filter system with a digital filter system. The analogue filter, which has inherent settling time limitations, is substituted by a digital filter implemented in a microprocessor or digital signal processor. This substitution eliminates the physical settling time constraint of analogue filters while maintaining the filtering function, thereby enabling higher sampling rates without sacrificing signal processing quality.
2Productivity
If high sampling rates are used without filters, then the maximum sampling rate is achieved, but undesirable aliasing effects occur
Solution Approach 1:
The patent applies digital filtering as a preliminary action to the sampled sensor signals. By implementing the filter in the digital domain after sampling, the system can first capture signals at high sampling rates and then apply filtering to remove aliasing effects. This approach allows the system to achieve high sampling rates while subsequently eliminating the harmful aliasing artifacts through digital signal processing.
3Adaptability or versatility
If conventional filter concepts are used with multiplexed sensor signals, then multiple sensor signals can be processed, but only a greatly limited sampling rate can be used due to long filter settling time
Solution Approach 1:
The patent replaces the analogue filtering system with a digital filtering system that can efficiently handle multiplexed signals. The digital filter, implemented in software or digital logic, processes multiple sensor channels without the settling time penalties of analogue filters. This allows the system to maintain high sampling rates while processing multiple sensor signals through time-division multiplexing or parallel digital filter instances.
Data Source
AI summary
An apparatus provides sensor data from at least one sensor of an optical system of a lithography apparatus. The apparatus comprises an analogue-to-digital converter and a digital filter device connected downstream of the analogue-to-digital converter. The analogue-to-digital converter is configured to convert an analogue signal sequence, which is provided via a number N of channels and includes a number N of analogue sensor signals from the number N of sensors of the optical system, into a digital signal sequence including N digital sensor signals. The analogue-to-digital converter and the digital filter device have the same frequency-synchronized system clock. The digital filter device is configured to filter the N digital sensor signals of the digital signal sequence in a channel-specific manner for providing and storing a respective filtered digital sensor signal for each of the N channels.