EUV Mask Defect Compensation via Digital Mapping
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Solution Overview
Problem
Existing lithography methods, particularly extreme ultraviolet (EUV) lithography, face challenges with phase defects in masks that increase fabrication costs and complexity, as current compensation methods are costly and inefficient.
Innovation Solution
A method involving the use of defect maps and large correction marks (DC marks) to accurately locate and hide phase defects underneath the absorber layer during the patterning process, utilizing tools like PROVE® for precise defect detection and positioning, allowing for effective EUV lithography without significant cost increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mask defects are repaired using conventional compensation methods, then fabrication defects in semiconductor devices are reduced, but mask fabrication time and cost significantly increase
Solution Approach 1:
The patent applies preliminary action by creating a defect map during the mask fabrication process itself, before the mask is used for lithography. This allows defects to be identified and documented in advance, enabling the IC design layout to be positioned to cover these defects during normal patterning, thereby eliminating the need for time-consuming post-fabrication repair operations
Solution Approach 2:
The patent extracts the defect information from the physical mask and creates a separate defect map that can be independently stored and processed. This extracted defect data is then used to generate correction instructions for the lithography process, separating the defect management function from the mask fabrication process and eliminating the need for costly repair operations
2Reliability
If mask defects are repaired using conventional compensation methods, then fabrication defects in semiconductor devices are reduced, but mask fabrication cost significantly increases
Solution Approach 1:
The patent treats the defect map as a disposable digital record that captures defect information once and is then used repeatedly during lithography processing. This eliminates the need for expensive physical mask repair operations, as the same defect information can be applied across multiple wafers and processing steps without additional cost
Solution Approach 2:
The patent creates a digital copy of the mask defect information in the form of a defect map, which can be stored, transmitted, and applied without the need for physical manipulation of the mask. This digital copying approach replaces costly physical repair operations with inexpensive data processing and pattern adjustment
3Productivity
If conventional lithography methods are used without defect compensation, then mask fabrication is simpler and faster, but phase defects in masks introduce fabrication defects in smaller IC devices
Solution Approach 1:
The patent performs preliminary defect mapping during mask fabrication, creating a digital record of defect locations before the mask is used for lithography. This preliminary action allows the lithography system to pre-calculate and apply corrective positioning of IC design layouts, ensuring high device fabrication quality without requiring complex post-processing or mask repair operations
Solution Approach 2:
The patent implements feedback by using the defect map information to adjust the IC design layout positioning during lithography. The system feeds back the defect locations detected during mask fabrication and uses this information to modify the patterning process, ensuring that defects do not translate into fabrication defects in the final semiconductor devices
Data Source
AI summary
A EUV mask comprises a low thermal expansion material (LTEM) substrate, a reflective multi-layer (ML) over the LTEM substrate, and a patterned absorber layer over the reflective ML. The reflective ML includes a defect. The EUV mask further comprises a mark associated with the defect. The mark is one of: a deposit over the patterned absorber layer at a distance offset from the defect, and a cavity into the patterned absorber layer in an area over the defect.