EUV Mask Blank Multilayer Coating Defect Mitigation
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Solution Overview
Problem
Existing methods for depositing multilayer reflective coatings in EUV lithography fail to effectively mitigate the impact of concave defects on substrates, leading to defects in the coating and increased surface roughness, and often generate additional contamination or foreign particles.
Innovation Solution
The method involves controlling the angle of ion beam sputtering between 35° and 80° while rotating the substrate to deposit a multilayer reflective coating, which mitigates the effect of concave defects and reduces the size of such defects in the coating, thereby smoothing the substrate surface without generating new foreign particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ion beam sputtering is performed at a normal incidence angle (0°) to deposit a multilayer reflective coating, then the coating process is simple and efficient, but concave defects on the substrate are amplified and cause phase defects in the coating
Solution Approach 1:
The patent changes the incidence angle parameter of the ion beam sputtering from the conventional 0° (normal incidence) to an oblique angle range of 35°-80°. This parameter change fundamentally alters the deposition dynamics, causing sputtered particles to preferentially fill concave defects while reducing the amplification effect that occurs at normal incidence. The oblique angle enables the coating process to simultaneously achieve high efficiency and defect mitigation.
Solution Approach 2:
The patent introduces a new dimensional aspect to the deposition process by utilizing oblique angle incidence rather than normal incidence. This dimensional change in the angle of particle bombardment creates a geometric effect where particles can access and fill concave regions more effectively, transforming the deposition pattern from one that amplifies defects to one that mitigates them.
2Manufacturing precision
If the incidence angle of ion beam sputtering is increased to 35°-80° to reduce concave defects, then the smoothness of the coating is improved, but the deposition rate decreases
Solution Approach 1:
The patent optimizes the incidence angle parameter within the specific range of 35°-80° to achieve a balance between surface smoothness and deposition rate. Within this range, the oblique angle sufficiently mitigates concave defect amplification while maintaining acceptable deposition efficiency. The patent also optimizes other parameters such as ion beam power, gas pressure, and substrate rotation speed to compensate for the reduced deposition rate at oblique angles.
Solution Approach 2:
The patent introduces dynamic elements to the deposition process, including substrate rotation during oblique angle sputtering and dynamic adjustment of deposition parameters. The substrate rotation ensures uniform coating distribution while the oblique angle deposition dynamically fills concave regions, achieving both smooth surfaces and acceptable productivity through process optimization.
3Ease of manufacture
If conventional sputtering methods are used to deposit multilayer coating, then the process is straightforward, but foreign particles and contamination are generated on the substrate
Solution Approach 1:
The patent utilizes an inert gas environment (typically argon) during ion beam sputtering to prevent contamination and foreign particle generation. The ion beam process itself, combined with the controlled inert atmosphere, creates a clean deposition environment that minimizes the generation of foreign particles and contamination compared to conventional sputtering methods, while maintaining process feasibility.
Solution Approach 2:
The patent replaces conventional mechanical sputtering with ion beam-assisted sputtering performed at oblique angles. This substitution changes the deposition mechanism from simple physical sputtering to a more controlled process where ion bombardment activates the deposition, reducing contamination and foreign particle generation while maintaining ease of manufacture through standardized equipment.
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 effectively reduces the size of concave defects in the multilayer reflective coating, improving the smoothness and reducing the perturbation in the periodic structure, resulting in a higher quality EUV mask blank with minimized defects and reduced surface roughness.
Implementation Method 1
a method for depositing a multilayer film of a mask blank for EUV lithography by using an ion beam sputtering method
Data Source
AI summary
A method for depositing, by ion beam sputtering, a multilayer reflective coating of a reflective mask blank for EUV lithography on a substrate having a concave defect formed thereon, characterized in that the method comprises carrying out ion beam sputtering so that an absolute value of an angle α formed between a normal line of a substrate and sputtered particles landing on the substrate is maintained so as to satisfy the formula of 35°≦α≦80° while rotating the substrate about a central axis thereof.