Moiré Overlay Mark Layout for Low-Noise Misalignment Measurement
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Solution Overview
Problem
Conventional overlay mark forming methods for semiconductor devices face challenges in maintaining precision for grating patterns, leading to difficulties in accurately measuring misalignment between pattern layers and amplifying noise in Moire patterns.
Innovation Solution
The proposed solution involves an overlay mark configuration with pairs of grating patterns having different pitches, which are rotationally symmetrical and partially overlapping, forming Moire patterns with larger pitches than the optical resolution of the measurement apparatus, allowing for increased precision and reduced noise by simplifying grating patterns into single pitches with wider areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional overlay mark configuration with different pitches is used, then overlay measurement is possible, but precision is difficult to maintain and noise is amplified
Solution Approach 1:
The patent applies local quality by configuring grating patterns with different characteristics in different regions of the overlay mark. Specifically, the first grating pattern has a first pitch while the second grating pattern has a second pitch different from the first, allowing each region to serve its specific function in overlay measurement while maintaining overall precision
Solution Approach 2:
The patent transitions from conventional single-pitch or simple multi-pitch configurations to a two-dimensional rotational symmetry configuration. The grating patterns are arranged with rotational symmetry around a center point, adding a dimensional aspect that improves measurement reliability and reduces noise by providing multiple measurement paths
2Ease of manufacture
If grating patterns with different pitches are used, then Moire pattern formation is enabled, but noise in Moire patterns is amplified
Solution Approach 1:
The patent uses asymmetric pitch values between the first and second grating patterns to generate the Moire effect. The first pitch and second pitch are deliberately made different to create the interference pattern, while maintaining rotational symmetry in the overall arrangement to reduce noise
Solution Approach 2:
The patent converts the potential harm of noise amplification into a benefit by using the noise-reducing effect of rotational symmetry. The symmetric arrangement of grating patterns with different pitches causes noise to cancel out while preserving the Moire pattern signal, thus converting the harmful noise amplification into a beneficial noise reduction
3Productivity
If conventional overlay mark configuration is used, then overlay measurement can be performed, but measurement accuracy is reduced due to precision difficulties
Solution Approach 1:
The patent performs preliminary action by pre-configuring the grating patterns with specific pitch relationships and rotational symmetry before the actual overlay measurement takes place. This pre-arranged configuration ensures that when measurement occurs, the precision requirements are already met through the deliberate design of the grating pattern geometry
Solution Approach 2:
The patent makes the overlay mark configuration universal by creating a multi-functional structure where the grating patterns serve multiple purposes: forming Moire patterns for measurement, providing rotational symmetry for noise reduction, and maintaining different pitches for sensitivity. This multi-functionality improves both productivity and precision simultaneously
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 configuration enhances the precision of grating patterns, reduces noise, and enables accurate measurement of overlay errors between pattern layers, improving the reliability of semiconductor device manufacturing by amplifying small misalignment movements in Moire patterns.
Implementation Method 1
a first Moire pattern MA1 formed by overlapping the first grating pattern and the second grating pattern; and a second Moire pattern MA2 formed by overlapping the first grating pattern and the third grating pattern
Data Source
AI summary
An overlay mark forming a Moire pattern, an overlay measurement method using the overlay mark, an overlay measurement apparatus using the overlay mark, and a manufacturing method of a semiconductor device using the overlay mark are provided. The overlay mark for measuring an overlay based on an image is configured to determine a relative misalignment between at least two pattern layers. The overlay mark includes a first overlay mark including a pair of first grating patterns which has a first pitch along a first direction and which is rotationally symmetrical by 180 degrees, and includes a second overlay mark including a pair of second grating patterns and a pair of third grating patterns. The second grating patterns partially overlap the first grating patterns and are rotationally symmetrical by 180 degrees, and the third grating patterns partially overlap the first grating patterns and are rotationally symmetrical by 180 degrees.