MEMS Mirror Tilt Sensing for EUV Lithography Pulse Disturbances
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Solution Overview
Problem
The use of MEMS mirrors in EUV lithography apparatuses leads to temporally and spatially varying current flows due to photon emission, which disturbs the monitoring of tilt angles, affecting the precision of micromirror positioning and the control loop.
Innovation Solution
A lithography apparatus with a detection device that measures tilt angles at a frequency greater than the radiation source repetition frequency, discarding specific signal values corresponding to radiation incidence times to provide a filtered tilt angle signal for precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If MEMS mirrors are used in EUV lithography apparatuses, then the installation space is reduced and integration is improved, but temporally and spatially varying current flows are generated that disturb tilt angle monitoring
Solution Approach 1:
The system performs preliminary identification of corrupted signal values by detecting current flow disturbances before they affect tilt angle measurements. The control loop proactively identifies and flags affected measurement values, allowing for their subsequent exclusion from position calculations, thus preventing measurement errors from propagating through the control system.
Solution Approach 2:
The system changes the parameter of measurement signal frequency to be greater than the radiation source repetition frequency. This frequency relationship ensures that multiple tilt angle measurements are taken during each radiation pulse cycle, allowing the system to identify and exclude corrupted measurements while maintaining continuous monitoring capability.
2Speed
If measurement signal frequency is increased to capture rapid tilt angle changes, then dynamic positioning accuracy is improved, but the impact of radiation-induced current flows on signal integrity is amplified
Solution Approach 1:
The system performs preliminary identification of corrupted signal values by detecting current flow disturbances before they affect tilt angle measurements. The control loop proactively identifies and flags affected measurement values, allowing for their subsequent exclusion from position calculations, thus preventing measurement errors from propagating through the control system.
Solution Approach 2:
The system discards corrupted tilt angle measurement values that are identified as being affected by radiation-induced current flows. By selectively excluding these problematic measurements from position calculations, the system recovers accurate mirror positioning information from the remaining valid measurements, maintaining control accuracy despite the presence of harmful current flows.
3Measurement precision
If continuous tilt angle monitoring is performed at high frequency, then positioning precision is improved, but signal corruption from radiation incidence increases
Solution Approach 1:
The system performs preliminary identification of corrupted signal values by detecting current flow disturbances before they affect tilt angle measurements. The control loop proactively identifies and flags affected measurement values, allowing for their subsequent exclusion from position calculations, thus preventing measurement errors from propagating through the control system.
Solution Approach 2:
The system discards corrupted tilt angle measurement values that are identified as being affected by radiation-induced current flows. By selectively excluding these problematic measurements from position calculations, the system recovers accurate mirror positioning information from the remaining valid measurements, maintaining control accuracy despite the presence of harmful current flows.
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 approach enhances the precision of micromirror positioning, improving the control loop accuracy and reducing disturbances caused by current fluctuations.
Implementation Method 1
a detection device that is configured to detect the tilt angle of the mirror based on a measurement signal
Implementation Method 2
The photons from the EUV radiation source in the lithography apparatus may trigger the emission of electrons from the mirror surfaces of the MEMS mirrors as a result of the photoelectric effect
Data Source
AI summary
A lithography system comprises: a radiation source for generating radiation having a specific repetition frequency; a mirror which is movable through a tilt angle for guiding the radiation in the lithography system; a measuring device which is designed to measure the tilt angle of the mirror based on a measurement signal having a measurement-signal frequency that is greater than the repetition frequency, in order to provide a time-discrete tilt-angle signal; and an analysis unit which is designed to discard specific signal values of the provided tilt-angle signal on the basis of a signal indicating the points in time at which the radiation impinged on the mirror surface of the mirror in order to provide a corrected time-discrete tilt-angle signal, and in order to determine the position of the mirror based on the corrected time-discrete tilt-angle signal.