Lithography Pattern Measurement with Region-Specific Sensor Sensitivity
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Solution Overview
Problem
Existing lithography processes face challenges in maintaining measurement accuracy due to variations in detection light intensity caused by reflectance differences between patterns in the same or different layers, leading to decreased productivity and measurement errors.
Innovation Solution
A measurement apparatus that adjusts the sensitivity of different image capturing regions to maintain a relative ratio of detection signal intensities within an allowable range, using a control unit to set image capturing regions for each pattern and adjust the image sensor's sensitivity to optimize signal intensity and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single image capturing region is used to capture multiple patterns, then the measurement process is simplified, but measurement accuracy decreases due to varying detection light intensity from reflectance differences
Solution Approach 1:
The image capturing region is divided into multiple first image capturing regions corresponding to different patterns. This segmentation allows each region to be optimized for its specific pattern's reflectance characteristics, enabling accurate measurement while maintaining process simplicity.
Solution Approach 2:
Different sensitivity values are assigned to different first image capturing regions based on the reflectance characteristics of patterns in those regions. This local quality adjustment ensures that each region captures detection light with appropriate sensitivity, compensating for reflectance differences and maintaining measurement accuracy across all patterns.
2Measurement precision
If the sensitivity is adjusted for each pattern individually, then measurement accuracy improves, but the device complexity and adjustment time increase
Solution Approach 1:
The sensitivity of the image sensor is adjusted by changing the sensitivity value parameter for each first image capturing region. This parameter-based approach allows flexible and precise control of detection light intensity for each pattern without complex mechanical or optical adjustments, improving measurement accuracy while keeping the adjustment mechanism simple.
3Measurement precision
If multiple measurements are performed with different light adjustments, then measurement accuracy improves, but productivity decreases due to increased measurement time
Solution Approach 1:
Sensitivity values for different first image capturing regions are determined in advance based on reflectance characteristics. This preliminary action allows the measurement system to capture all patterns with appropriate sensitivity in a single measurement process, eliminating the need for multiple sequential measurements with different light adjustments, thereby improving both accuracy and productivity.
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
Enables accurate measurement of pattern positions despite reflectance differences, enhancing productivity by minimizing measurement errors and reducing the need for multiple light adjustments, thus improving overall measurement efficiency.
Implementation Method 1
an image sensor including a plurality of pixels which detect light from the first pattern and light from the second pattern
Data Source
AI summary
The present invention provides a measurement apparatus for measuring a position of a first pattern and a position of a second pattern provided in a target object, the apparatus including an image capturing unit including a plurality of pixels which detect light from the first pattern and light from the second pattern, and configured to form an image capturing region used to capture the first pattern and the second pattern by the plurality of pixels, and a control unit configured to adjust the image capturing unit such that a relative ratio of an intensity of a detection signal of the first pattern generated based on an output from a first image capturing region and an intensity of a detection signal of the second pattern generated based on an output from a second image capturing region falls within an allowable range.