EUV Photomask Border Region Formation via Laser Treatment
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Solution Overview
Problem
Existing EUV lithography techniques face challenges with contamination by foreign particles and the need for costly and time-consuming etching processes to create low-reflectivity border regions in photomasks.
Innovation Solution
The proposed solution involves constructing the border region of the EUV photomask with a solid structure of low EUV reflectivity, achieved through ultrafast laser treatment with tuned parameters, eliminating the need for etching and minimizing heat-affected zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional etching processes are used to create low-reflectivity border regions, then the border region can be formed, but the process becomes costly and time-consuming
Solution Approach 1:
The patent replaces the mechanical etching process with a laser-based approach. The laser directly writes the border region pattern onto the mask substrate, eliminating the need for photoresist coating, exposure, and etching steps. This substitution of mechanical/chemical processes with optical processing achieves the same border region formation function while dramatically improving manufacturing efficiency and reducing costs.
Solution Approach 2:
The laser writing process directly creates the low-reflectivity border region on the mask substrate without requiring additional processing steps. The laser energy locally modifies the substrate material properties to achieve the desired low-reflectivity characteristic, making the system self-sufficient and eliminating dependency on complex multi-step manufacturing processes.
2Manufacturing precision
If traditional etching processes are used to create border regions, then low-reflectivity regions can be formed, but the process becomes complex and time-consuming
Solution Approach 1:
The patent replaces the complex mechanical and chemical etching system with a laser-based optical system. The laser directly modifies the mask substrate material through localized energy deposition, creating the low-reflectivity border region in a single step. This eliminates the need for photoresist application, alignment, exposure, development, and etching processes, thereby dramatically simplifying the manufacturing process while maintaining precise reflectivity control.
Solution Approach 2:
The patent controls the reflectivity of the border region by adjusting laser processing parameters such as laser power, scanning speed, and number of passes. By changing these parameters, the laser induces different degrees of material modification (such as carbonization or structural changes) in the mask substrate, thereby achieving the desired low-reflectivity characteristic without complex process steps.
3Object-affected harmful factors
If larger border regions are created to ensure low reflectivity, then contamination is reduced, but the usable imaging area is reduced
Solution Approach 1:
The patent applies local quality by creating low-reflectivity border regions only where needed at the periphery of the mask, while maintaining high reflectivity in the central imaging area. The laser writing process enables precise spatial control, allowing the border region to be formed with minimal width and exact geometric definition. This localized treatment ensures that contamination is mitigated at the borders without sacrificing usable imaging area in the center.
Solution Approach 2:
The patent addresses the border region function by transitioning from a planar approach to a three-dimensional material modification approach. The laser processing creates localized material changes (such as carbonized layers or structural modifications) with controlled depth and lateral dimensions. This dimensional control allows the border region to achieve low reflectivity with minimal lateral extent, thereby preserving maximum imaging area while still providing effective contamination protection.
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 reduces the occupied area of the border region, maximizes the usable area of the imaging region, and mitigates debris-induced contamination, while maintaining desired aerial image contrast and improving critical dimension control.
Implementation Method 1
achieved through ultrafast laser treatment with tuned parameters
Implementation Method 2
minimizing heat-affected zones
Implementation Method 3
a reflective layer including molybdenum layers and silicon layers
Data Source
AI summary
A photomask and a method of manufacturing a photomask are provided. According to an embodiment, the method includes: providing a substrate; depositing a reflective layer including molybdenum layers and silicon layers over the substrate, the reflective layer including a first area and a second area laterally surrounding the first area from a top-view perspective; depositing a capping layer over the reflective layer; depositing an absorption layer over the capping layer; and causing an energy to pass through the absorption layer, the capping layer and the reflective layer within the second area for forming molybdenum silicide in a border region of the reflective layer and keeping the absorption layer and the capping layer substantially intact.