EUV Mask Set Defect Compensation via Complementary Functional Portions
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Solution Overview
Problem
EUV lithography requires defect-free multilayer reflector masks, which are difficult and costly to produce, and existing methods struggle to effectively compensate for defects in the masks during the imaging process.
Innovation Solution
A method involving the inspection of EUV mask blanks to identify defects, determining complementary functional portions on each mask that are free of defects, and using these portions to form a virtual image area, with the predefined mask pattern being imaged onto a target by controlling the illumination process to compensate for defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If strict defect-free mask blanks are required for EUV lithography, then image quality is improved, but manufacturing cost and complexity increase significantly
Solution Approach 1:
The mask blank is divided into multiple functional portions, each containing defects in different locations. By segmenting the mask usage into multiple masks that cover different defect-free regions, the system can achieve defect-free imaging without requiring each individual mask blank to be completely defect-free, thus reducing manufacturing complexity while maintaining image quality.
Solution Approach 2:
The system changes the parameter of mask usage from requiring each mask to be completely defect-free to allowing defects in individual masks as long as the combined functional portions across multiple masks provide complete defect-free coverage. This parameter change in the defect tolerance criterion reduces manufacturing stringency while maintaining imaging quality.
2Reliability
If more EUV mask blanks are produced to ensure defect-free masks, then reliability is improved, but productivity and cost efficiency worsen
Solution Approach 1:
Multiple masks with different defect patterns are merged into a coordinated system where their functional portions complement each other. By combining the defect-free regions of multiple masks through coordinated illumination, the system achieves high reliability without needing to produce excessive numbers of perfectly defect-free mask blanks, thus improving production efficiency.
Solution Approach 2:
Instead of discarding mask blanks with defects, the system converts the presence of defects into a benefit by using defect information to strategically assign functional portions across multiple masks. The defects that would normally render masks unusable are instead used to guide the creation of a complementary mask set, turning a harmful factor into a useful element for achieving reliability with fewer masks.
3Adaptability or versatility
If complete mask patterns are provided on each mask blank, then functionality is improved, but the impact of defects on image quality worsens
Solution Approach 1:
Instead of requiring each mask to have uniform defect-free quality across its entire surface, the system applies local quality by assigning specific defect-free functional portions to each mask based on its actual defect locations. Each mask provides high-quality imaging in its assigned regions while the system as a whole maintains complete functionality through the combination of multiple masks with complementary functional portions.
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 allows the use of otherwise unusable EUV mask blanks, reducing the number of masks needed and lowering costs by creating a virtual defect-free mask set, while maintaining image quality and reducing exposure time.
Implementation Method 1
EUV (Extreme Ultraviolet) lithography uses radiation in the spectral range between 10 and 15 nm, which is strongly absorbed in solid state bodies and requires reflective optics. A photolithographic mask for employing EUV lithography relies on a multilayer reflector deposited on a polished substrate.
Data Source
AI summary
An EUV mask set and method of manufacturing is disclosed. In one embodiment, a set of EUV mask blanks is inspected to obtain information about defects in each of the EUV mask blanks. From the obtained information, a set of complementary functional portions is determined, wherein each functional portion is assigned to one of the EUV mask blanks and does not contain any of the defects. The functional portions of the EUV mask blanks of the EUV mask blank set complement one another to form a virtual image area corresponding in size to image areas of the EUV mask blanks. A predefined mask pattern is provided on the EUV mask blanks. Information identifying position and shape of the functional portions is used to control an illumination process for imaging the predefined mask pattern onto a target.