EUV Reflective Mask Reference Marks for Contamination Control
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Solution Overview
Problem
The existing methods for forming reference marks on multilayer reflective films in EUV lithography face challenges such as contamination from dust during laser processing, poor cleaning resistance, and lengthy processing times, especially when using laser ablation or focused ion beam (FIB) techniques, which can lead to defects and accuracy issues in reflective masks.
Innovation Solution
A substrate with a multilayer reflective film featuring concave-shaped reference marks with grooves or protrusions, where the surface layer contains elements like Ru or Si for improved cleaning resistance, and a protective film is used to prevent contamination and enhance processing efficiency, allowing for precise defect location and pattern transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laser ablation is used to form reference marks on multilayer reflective film, then reference marks can be formed, but the surface may be contaminated by dust generated during processing
Solution Approach 1:
The reference mark formation process is segmented into two distinct steps: first forming a groove pattern, then filling it with material. This segmentation allows the harmful dust generation to be isolated to the groove formation step, while the filling step restores surface cleanliness, thus resolving the contradiction between ease of manufacture and surface contamination.
Solution Approach 2:
A filling material acts as an intermediary substance that is deposited into the grooves after they are formed by laser ablation. This intermediary material covers the contaminated groove surfaces and fills the voids, effectively masking the dust contamination while maintaining the reference mark's functional geometry.
2Ease of manufacture
If focused ion beam (FIB) is used to form reference marks, then reference marks can be formed, but processing time becomes excessively long
Solution Approach 1:
The patent replaces the mechanical FIB processing method with a thermal laser ablation process for groove formation, followed by a chemical vapor deposition filling process. This substitution eliminates the time-consuming FIB machining while achieving the same reference mark formation objective through a faster thermal and chemical process combination.
Solution Approach 2:
The laser groove formation is performed as a preliminary action before the material filling step. By pre-forming the groove structure with the fast laser process, the subsequent filling step only needs to deposit material into the pre-defined geometry, significantly reducing the total processing time compared to using FIB for the entire process.
3Productivity
If conventional defect inspection coordinates are used without reference marks, then inspection can be performed, but positional accuracy is low and detection varies between apparatuses
Solution Approach 1:
The reference marks serve as self-defined coordinate origins that enable each inspection apparatus to establish its own accurate reference frame. Instead of relying on external or approximate coordinate systems, the system uses the permanently etched reference marks on the substrate to self-calibrate and achieve high-precision defect location measurements that are consistent across different apparatuses.
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
The proposed solution prevents contamination and improves cleaning resistance, reducing defects and processing time, enabling accurate defect specification and efficient pattern transfer in reflective masks, thus enhancing the quality and precision of EUV lithography.
Implementation Method 1
a multilayer reflective film that reflects exposure light formed on a substrate
Implementation Method 2
an absorber film pattern that absorbs exposure light formed on the multilayer reflective film
Implementation Method 3
Laser ablation and a focused ion beam (FIB) are disclosed as methods for removing a portion of the multilayer reflective film
Data Source
AI summary
A substrate with a multilayer reflective film, a reflective mask blank, a reflective mask and a method of manufacturing a semiconductor device that can prevent contamination of the surface of the multilayer reflective film even in the case of having formed reference marks on the multilayer reflective film. A substrate with a multilayer reflective film contains a substrate and a multilayer reflective film that reflects EUV light formed on the substrate. Reference marks are formed to a concave shape on the surface of the substrate with the multilayer reflective film. The reference marks have grooves or protrusions roughly in the center. The shape of the grooves or protrusions when viewed from overhead is similar or roughly similar to the shape of the reference marks.