Reflective Mask Blank Sputtering for Higher EUV Reflectance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current reflective mask blanks for EUV lithography have limitations in achieving high reflectance for EUV light, which affects the optical properties and throughput of the exposure process in semiconductor manufacturing.
Innovation Solution
A reflective mask blank with a multilayer reflection film formed using a sputtering method, where alternating layers of Si and Mo are deposited in two stages with different sputtering pressures, achieving a higher reflectance for EUV light by optimizing the layer thickness and surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional single-stage sputtering method is used to form the multilayer reflection film, then the manufacturing process is simple, but the reflectance for EUV light is insufficient
Solution Approach 1:
The sputtering process is segmented into two distinct stages: a first stage with higher sputtering pressure to form the initial layer structure, and a second stage with lower sputtering pressure to optimize the final layer quality and reflectance. This segmentation allows each stage to be optimized for its specific function, achieving high EUV light reflectance while managing process complexity.
Solution Approach 2:
The sputtering pressure parameter is changed between the two stages of layer formation. The first stage uses a higher sputtering pressure, and the second stage uses a lower sputtering pressure. This parameter change enables optimization of the multilayer reflection film structure to achieve reflectance of at least 66.5% for EUV light with wavelength of 13 to 14 nm.
2Productivity
If the multilayer reflection film has higher reflectance, then the exposure time can be reduced to improve throughput, but achieving high reflectance requires optimized multilayer structure with specific layer thicknesses and materials
Solution Approach 1:
The thickness of each layer in the multilayer reflection film is precisely controlled to optimize reflectance. By adjusting the thickness parameters of alternating high-refractive-index and low-refractive-index layers, the film achieves maximum reflectance for EUV light, enabling reduced exposure time and improved throughput.
Solution Approach 2:
The multilayer reflection film uses composite structure with alternating layers of materials having different refractive indices (high-refractive-index layers and low-refractive-index layers). This composite structure enhances the overall reflectance for EUV light, allowing for shorter exposure times and improved manufacturing throughput.
3Illumination intensity
If alternating layers with different refractive indices are used to form the multilayer reflection film, then the reflectance for EUV light is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The formation of alternating high and low refractive index layers is achieved through segmented sputtering stages. The first stage forms layers with one refractive index characteristic, and the second stage forms layers with the other characteristic. This segmentation simplifies the manufacturing process compared to attempting to form the complete multilayer structure in a single stage.
Solution Approach 2:
By changing the sputtering pressure parameter between stages, the process efficiently creates the alternating layer structure. The higher pressure in the first stage and lower pressure in the second stage naturally produce the desired layer characteristics, making the manufacturing process more manageable despite the complexity of the multilayer structure.
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 solution provides a reflective mask blank with enhanced reflectance, improving the exposure process efficiency and throughput by achieving a reflectance of at least 66.5% for EUV light, thereby supporting the formation of finer patterns in semiconductor devices.
Implementation Method 1
a multilayer reflection film for which a sputtering method is used to form first and second layers alternatively
Implementation Method 2
a multilayer reflection film that is formed on a substrate and reflects EUV light
Data Source
AI summary
A reflective mask blank including a substrate, a multilayer reflection film consisting of at least two first layers and at least two second layers that are laminated alternatively and having different optical properties each other, and an absorber film are manufactured by a sputtering method. Each layer is formed by two stages consisting of a first stage applied from when the forming of each layer is started and until a prescribed thickness is formed, and a second stage applied from when the prescribed thickness is formed and until the forming of each layer is completed, and a sputtering pressure of the first stage is set to higher than both a sputtering pressure at which the forming of the layer formed just before is completed, and a sputtering pressure of the second stage.