Aerial Image Measurement System for Semiconductor Mask Accuracy
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Solution Overview
Problem
Current aerial image measurement systems, such as scanning electron microscopes, are inefficient when measuring mask patterns on semiconductor substrates with multi-layer films or high and low patterns, leading to distortions and defects due to light scattering, which affects the accuracy of photolithography processes.
Innovation Solution
A measuring system and method utilizing a lighting unit, imaging unit, beam splitting unit, and reflecting unit to split and interfere illuminating light, forming interference light that accurately measures aerial images on substrates, improving measurement accuracy and avoiding development steps in photolithography processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scanning electron microscope (SEM) is used to measure mask patterns, then measurement capability is provided, but measurement efficiency deteriorates and measurement precision deteriorates due to light scattering in multi-layer films
Solution Approach 1:
The patent replaces the mechanical electron beam scanning system with an optical interference system. Instead of using SEM's electron beams to measure mask patterns, the invention uses light interference patterns (aerial images) that directly correspond to the mask pattern, eliminating the need for complex electron beam scanning and secondary electron detection mechanisms.
Solution Approach 2:
The patent creates an optical copy (aerial image) of the mask pattern through light interference. The measuring unit captures the aerial image formed by interfering light beams, which is a direct optical replica of the mask pattern, avoiding the need to physically scan or probe the actual mask structure with electron beams.
2Measurement precision
If SEM imaging measurement method is used for measuring mask pattern, then measurement capability is achieved, but measurement efficiency deteriorates
Solution Approach 1:
The patent performs preliminary action by pre-forming the aerial image through the optical system before measurement. The light interference pattern is created in advance and directly projected onto the measuring unit, eliminating the time-consuming sequential scanning process of SEM where electron beams must systematically traverse the entire mask pattern.
Solution Approach 2:
The aerial image serves as an instantaneous optical copy of the mask pattern, capturing the entire pattern information simultaneously in one measurement operation, rather than requiring time-consuming point-by-point scanning with electron beams.
3Productivity
If conventional aerial image measurement is performed on substrates with multi-layer films or high and low patterns, then measurement capability is provided, but measurement precision deteriorates due to light scattering
Solution Approach 1:
The patent converts the harmful effect of light scattering into a beneficial measurement mechanism. Instead of treating light scattering as a disturbance to be eliminated, the invention utilizes the scattered light as part of the interference pattern formation. The scattered light from multi-layer films and high-low patterns contributes to creating the aerial image that is then measured, transforming the previously harmful scattering effect into the basis 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 system enhances measurement accuracy by forming and measuring interference light, ensuring that the images on the substrate are the same as the actual mask images, thus reducing errors and saving time and costs in photolithography processes.
Implementation Method 1
providing illuminating light to pass through a mask to form initial light
Implementation Method 2
The beam splitting unit is configured for splitting the imaging light into projection light and reference light
Implementation Method 3
the substrate is configured for reflecting the projection light to form first reflected light onto the beam splitting unit
Implementation Method 4
The reflecting unit is configured for receiving the reference light to form second reflected light
Implementation Method 5
the second reflected light and the first reflected light interfering with each other to form interference light
Implementation Method 6
measuring the aerial image formed from the interference light
Data Source
AI summary
System and method for measuring an aerial image are provided. The system may include a lighting unit for providing illuminating light to pass through a mask to form initial light. An imaging unit is configured for imaging the initial light to form imaging light. A beam splitting unit is for splitting the imaging light into projection light and reference light. A projection light is projected to a substrate to form a mask image in the substrate, and the substrate reflects the projection light to form first reflected light onto the beam splitting unit. A reflecting unit is for receiving the reference light to form second reflected light, and for projecting the second reflected light onto the beam splitting unit, the second reflected light and the first reflected light interfering with each other to form interference light. A measuring unit is for measuring an aerial image formed from the interference light.