Overlay Error Detection Using Diffracted Light Position
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Solution Overview
Problem
Traditional diffracted light-based overlay measurement techniques require large overlay marks, which occupy excessive space in the exposure area, making them costly and unsuitable for in-field measurement, especially as photolithography patterns shrink to 22 nm or less, and are susceptible to illumination and transmission uniformity issues.
Innovation Solution
An apparatus and method for overlay error detection using positional information of diffracted light, where a light source, illumination system, and detector collect and analyze the main maximums of diffracted light components to measure overlay errors, allowing for smaller marks and reducing the influence of uniformity issues, with the illumination system including a collimator, filter, polarizer, and aperture stops to focus and direct light onto a pupil plane for accurate detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional diffracted light-based overlay measurement techniques are used, then overlay measurement accuracy can be achieved, but large overlay marks are required which occupy excessive space in the exposure area
Solution Approach 1:
The patent changes the measurement parameter from light intensity to light position. By detecting the positional information of diffracted light components on the detector, the system achieves overlay measurement without requiring large marks. The objective lens focuses diffracted light onto the detector, and the position of the light spots on the detector provides overlay information, eliminating the need for large mark areas.
2Measurement precision
If large overlay marks are used, then overlay measurement can be performed, but the cost of marks increases excessively
Solution Approach 1:
The patent changes the measurement parameter from light intensity to light position. By detecting the positional information of diffracted light components on the detector, the system achieves overlay measurement without requiring large marks. The objective lens focuses diffracted light onto the detector, and the position of the light spots on the detector provides overlay information, eliminating the need for large mark areas.
3Measurement precision
If large overlay marks are used, then overlay measurement can be performed, but in-field measurement becomes impossible
Solution Approach 1:
The patent changes the measurement parameter from light intensity to light position. By detecting the positional information of diffracted light components on the detector, the system achieves overlay measurement without requiring large marks. The objective lens focuses diffracted light onto the detector, and the position of the light spots on the detector provides overlay information, eliminating the need for large mark areas.
4Measurement precision
If overlay measurement is based on light strength signals of diffracted light, then overlay information can be obtained, but measurement accuracy becomes susceptible to system illumination uniformity and transmission uniformity
Solution Approach 1:
The patent changes the measurement parameter from light intensity to light position. By detecting the positional information of diffracted light components on the detector, the system achieves overlay measurement without requiring large marks. The objective lens focuses diffracted light onto the detector, and the position of the light spots on the detector provides overlay information, eliminating the need for large mark areas.
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 overlay error measurement using smaller marks, reducing costs and allowing in-field measurements, meeting the high accuracy requirements of new technical nodes by eliminating the impact of illumination and transmission uniformity, and allowing smaller overlay marks that take up less of the effective exposure area.
Implementation Method 1
the objective lens is configured to direct the measuring light onto an overlay mark, collect main maximums of diffracted light components diffracted from the overlay mark
Data Source
AI summary
A device including a light source, illumination system, objective lens, and detector. The light source produces measurement light beams, the illumination system directs measurement light beams into the objective lens, and the objective lens directs measurement light beams onto an overlay marker, collects main maximums of diffracted light beam diffracted from the overlay marker, and focuses main maximums of diffracted light beam onto a pupil plane of the objective lens. The detector is positioned on the pupil plane of the objective lens and used for detecting the position of each main maximums of diffracted light beam on the detector, to obtain the overlay error of said overlay marker. Diffracted-light position information is used to measure overlay error, and measurement signals are not affected by illumination uniformity, transmissivity uniformity, etc.