Mask Error Measurement Using Composite Image Generation
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Solution Overview
Problem
As semiconductor devices become more highly integrated, there is a growing need for precise measurement of mask errors due to finer mask pattern pitches, which existing technologies struggle to address effectively.
Innovation Solution
The development of a mask error measurement system using a stage for a reference mask and a target mask, a light source, a beam splitter, and an image sensor to generate and measure composite images, allowing for accurate determination of mask pattern errors by focusing both masks' images onto a single image sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single image sensor is used to measure both reference mask and target mask, then device complexity is reduced, but measurement precision deteriorates due to distance differences and image interference
Solution Approach 1:
The patent divides the measurement process into two sequential stages: first capturing the reference mask image, then capturing the target mask image. By segmenting the measurement into separate steps with intermediate processing (clearing previous images, adjusting distances), the system maintains high measurement precision while using a single image sensor, thus reducing device complexity without sacrificing accuracy.
2Productivity
If mask pattern pitch is reduced for higher integration, then productivity is improved, but measurement precision deteriorates due to finer pitch requirements
Solution Approach 1:
The patent performs preliminary alignment by capturing the reference mask image first, storing it as a reference, then using it to guide the subsequent target mask measurement. This preliminary action establishes a baseline that enables precise measurement of fine-pitch patterns, allowing higher integration density to be achieved while maintaining measurement accuracy through the reference-based comparison approach.
3Measurement precision
If distance between masks is reduced for better alignment, then measurement precision is improved, but image interference increases
Solution Approach 1:
The patent employs periodic action by sequentially capturing images at different time points: first the reference mask, then clearing the display, and finally the target mask. This periodic clearing and recapturing process eliminates image interference between the two masks, allowing precise measurement even when masks are positioned close together, thus resolving the contradiction between measurement precision and image interference.
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 system enhances measurement accuracy by compensating for distance differences between the masks and reduces interference, improving exposure precision in subsequent processes.
Implementation Method 1
a beam splitter configured to receive the first beam and split the first beam into a second beam and a third beam, the second beam being a portion of the first beam reflected by the reference mask, the third beam being a portion of the first beam reflected by the target mask
Data Source
AI summary
An apparatus for measuring a mask error and a method for measuring a mask error are provided. The apparatus for measuring a mask error includes a stage configured to accommodate a reference mask having a reference pattern, and a target mask adjacent to the reference mask such that a mask pattern of the target mask faces the reference pattern, a light source configured to irradiate the first beam onto the reference mask and the target mask, a light receiving unit including an image sensor, and the image sensor configured to receive a composite image including a first image generated from the reference pattern and a second image generated from the mask pattern, and generate a third image from the first image and the second image, and a measuring unit configured to measure an error of the mask pattern from the third image.