Photomask Detection Mark Placement via Light Suppression
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Solution Overview
Problem
The existing photomask inspection techniques face challenges in achieving high accuracy due to restrictions on the placement of detection marks, leading to poor measurement accuracy and difficulty in manufacturing precise photomasks for fine microstructures.
Innovation Solution
A photomask design that includes a substrate with a film portion and detection marks, where the intensity of light transmitted through the detection marks is suppressed to prevent their transfer to the target, allowing for accurate inspection and placement without restricting the position of the detection marks, thereby improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the detection mark is transferred to the light exposure surface of the wafer for inspection, then the photomask accuracy and superposition accuracy can be inspected, but the position for forming the detection mark is significantly restricted
Solution Approach 1:
The patent extracts the detection mark from the pattern formation process by using a specific optical configuration where the detection mark is illuminated separately from the pattern transfer process. This allows the detection mark to be inspected without being transferred to the wafer, thereby removing the restriction on its placement position while maintaining inspection accuracy.
Solution Approach 2:
The patent introduces an intermediary optical system that selectively illuminates the detection mark through the photomask without transferring it to the wafer. This intermediary mechanism enables separate inspection of the detection mark from the pattern transfer process, allowing flexible placement of detection marks without affecting pattern fidelity.
2Manufacturing precision
If the detection mark position is restricted to ensure non-transfer to wafer, then pattern accuracy is maintained, but inspection measurement accuracy deteriorates
Solution Approach 1:
The patent segments the illumination and inspection process from the pattern transfer process. By using separate optical paths and illumination conditions, the detection mark can be positioned in areas that would normally be restricted, while still maintaining both pattern transfer accuracy and detection mark inspection accuracy through dedicated inspection lighting that does not cause mark transfer.
3Object-generated harmful factors
If detection marks are placed in restricted positions to avoid transfer, then unwanted transfer is prevented, but it becomes difficult to manufacture photomask with high accuracy
Solution Approach 1:
The patent creates a separate inspection copy of the detection mark by illuminating it through the photomask with specific optical conditions that prevent actual transfer to the wafer. This copying mechanism allows the detection mark to be placed in positions that would normally cause transfer, while the inspection process captures an optical copy without physical transfer, thereby simplifying manufacturing.
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 approach enhances the inspection and manufacturing accuracy of photomasks by allowing flexible placement of detection marks, improving positional accuracy and cumulative correction of pattern placement errors, while preventing unwanted transfer to the target.
Implementation Method 1
The film portion 3 has a light transmittance lower than light transmittance of the substrate 2
Data Source
AI summary
According to one embodiment, a photomask includes a substrate, a film portion, a pattern, and a plurality of detection marks. The film portion is provided on a surface of the substrate. The film portion has a light transmittance lower than light transmittance of the substrate. The pattern is provided in a surface of the film portion. The pattern is configured to be transferred to a transfer target. The plurality of detection marks is provided in the film portion, with intensity of light transmitted through the detection marks being suppressed so as to suppress transfer the detection marks to the transfer target.