Lithography Measurement Stabilization via Active Vibration Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing measurement systems face challenges in maintaining accurate positioning of marks due to vibrations, leading to relative fluctuations between the stage and the measurement device, which can result in decreased measurement accuracy and increased measurement time, especially when the fluctuation period exceeds the image fetching time.
Innovation Solution
A measurement apparatus with an imaging unit fixed to a first member, a detector for stage position, and a control unit that synchronizes the stage with a second member to reduce relative position fluctuations, using active mounts and interferometers to stabilize the optical system and base frame, allowing for precise control of the reticle stage and imaging unit to compensate for vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the measurement device and stage are not supported by an identical housing, then the device complexity is reduced, but the measurement precision deteriorates due to relative fluctuation from floor vibrations
Solution Approach 1:
The patent employs feedback control by continuously monitoring the position of the first member (supporting the measurement device) and the stage using detectors, and actively adjusting their relative positions to compensate for vibrations. This feedback mechanism maintains measurement precision without requiring the device and stage to be housed together, thus avoiding increased device complexity.
Solution Approach 2:
The patent introduces a control unit as an intermediary that coordinates between the first member and the stage based on detection results. This intermediary processes vibration information and generates correction commands, enabling precise measurement without direct mechanical coupling between the measurement device and stage, thereby maintaining low device complexity while ensuring high measurement precision.
2Measurement precision
If the frequency of measurement is increased to match the fluctuation period, then the measurement precision is improved, but the measurement time period increases, resulting in deterioration of productivity
Solution Approach 1:
The patent performs preliminary action by pre-positioning the first member and stage to optimal locations before measurement begins, based on predicted vibration patterns. This preliminary positioning reduces the need for frequent measurements during the actual measurement process, thereby improving precision without sacrificing productivity.
Solution Approach 2:
The patent implements periodic action by measuring the vibration pattern and performing measurements at strategically selected periods within the vibration cycle rather than continuously. This periodic measurement approach captures sufficient data for high precision while minimizing total measurement time, thus maintaining productivity.
3Measurement precision
If the time period of fetching image signals is extended to capture full vibration cycles, then the measurement precision is improved, but the measurement time period increases, reducing productivity
Solution Approach 1:
The patent applies dynamics by making the measurement process adaptive to real-time vibration conditions. The system dynamically adjusts the measurement timing and duration based on detected vibration characteristics, allowing it to complete accurate measurements during favorable vibration phases rather than requiring extended fixed-time measurements, thus improving precision while reducing time loss.
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 solution enhances measurement accuracy and reduces measurement time by stabilizing the relative position of the mark, maintaining high precision even with longer fluctuation periods, thereby improving productivity.
Implementation Method 1
an imaging unit positioned with fixing with respect to a first member and configured to sense an image of the mark
Implementation Method 2
a first detector configured to detect a position of the stage with reference to a second member
Implementation Method 3
a second detector configured to detect fluctuation of a position of the first member with reference to the second member
Data Source
AI summary
A measurement apparatus includes: an imaging unit positioned with fixing with respect to a first member; a first detector configured to detect a position of a stage with reference to a second member; a second detector configured to detect fluctuation of a position of the first member with reference to the second member; and a control unit configured to obtain the position of the mark from an image of the mark sensed by the imaging unit while controlling a relative position of the stage relative to the second member so as to reduce fluctuation of a relative position of the mark relative to the imaging unit due to the fluctuation of the position of the first member based on detection results of the first and second detectors.