EUV Lithography Mirror Position Sensor Using Modulated Light
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Solution Overview
Problem
Current position sensing methods in lithography apparatuses, particularly in EUV lithography, face challenges with noise susceptibility and power loss in determining the precise position of mirrors, which affects the accuracy and reliability of beam positioning due to thermal influences and high absorption of light by materials.
Innovation Solution
A sensor arrangement using modulated light beams, such as pulsed or sinusoidal light, is employed to improve position sensing accuracy, incorporating a light source, measuring unit with a reference pattern, detection unit with photodetectors, and an evaluation apparatus to generate high signal quality with reduced noise, and integrating the light source and signal-processing unit within a vacuum housing for efficient signal processing and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional position sensing methods are used in EUV lithography, then the system can determine mirror positions, but the measurement precision deteriorates due to noise susceptibility and high absorption of light by materials
Solution Approach 1:
The patent employs periodic modulation of the light beam (sinusoidal or pulsed modulation) to encode position information in the time domain. This periodic action allows the system to distinguish the desired position signal from random noise through synchronous detection, thereby improving measurement precision while reducing noise susceptibility in the harsh EUV environment
Solution Approach 2:
The patent changes the temporal parameters of the light beam by applying modulation frequencies that are optimized for the specific measurement task. By varying the modulation frequency and duty cycle, the system can maximize the signal-to-noise ratio and adapt to different operating conditions,ไป่ improving position sensing accuracy despite material absorption and noise
2Power
If continuous light exposure is used for position sensing, then sufficient signal strength is achieved, but power loss increases due to thermal influences and high absorption by materials
Solution Approach 1:
The patent uses periodic modulation of the light beam with specific duty cycles to deliver concentrated bursts of energy rather than continuous exposure. This approach maintains sufficient signal strength during the active modulation periods while minimizing average power consumption and reducing thermal influences and energy loss from material absorption over time
Solution Approach 2:
The system performs preliminary modulation of the light beam with known patterns before actual position measurement. This preliminary action allows the system to establish optimal exposure parameters and synchronize detection, enabling efficient use of light energy and reducing overall power loss while maintaining adequate signal strength for accurate measurement
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 modulated exposure method enhances signal-to-noise ratio and reduces power loss, enabling precise and reliable position determination of mirrors, thereby improving the accuracy and stability of beam positioning in EUV lithography systems.
Implementation Method 1
a light source (203) for exposing the measuring unit (201) with a modulated light beam
Implementation Method 2
a detection unit (204) having a plurality of photodetectors (205) for the output of an electrical position signal by detection of the provided optical position signal
Implementation Method 3
the measuring unit (201) has a reference pattern (212) for influencing the light beam
Implementation Method 4
and a mirror arrangement (213) for reflecting the influenced light beam
Data Source
AI summary
Sensor arrangements, methods for ascertaining a respective position of a number of mirrors of a lithography apparatus, projection systems of a lithography apparatus, and lithography apparatus are disclosed. The sensor arrangement includes at least one position sensor apparatus for providing a position signal for a mirror and an evaluation apparatus for ascertaining the position of the mirror depending on the position signal.