EUV Photo Mask Alignment Marks with Sub-Resolution Assist Patterns
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current EUV lithography technologies face challenges in achieving high contrast and alignment accuracy due to the limitations of existing EUV photo masks, which struggle to effectively suppress background intensity and ensure precise alignment with EUV lithography tools.
Innovation Solution
The development of an EUV reflective photo mask with a multilayer Mo/Si stack, a capping layer, and an absorber layer, along with sub-resolution assist features (SRAFs) that include periodic patterns around the mask alignment marks to enhance signal contrast and alignment accuracy by suppressing background intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional EUV photo masks are used, then the basic photolithography function is maintained, but the background intensity cannot be effectively suppressed and alignment accuracy is insufficient
Solution Approach 1:
The photo mask is divided into multiple functional layers: a substrate, a multilayer reflective structure (Mo/Si stack), a capping layer, and an absorber layer. This segmentation allows each layer to perform its specific function - the multilayer structure provides reflectivity, the capping layer protects against oxidation, and the absorber layer creates high-contrast patterns while suppressing background intensity.
Solution Approach 2:
Different regions of the photo mask are designed with different properties: the multilayer Mo/Si stack provides high reflectivity in specific areas, while the absorber layer creates high absorption regions for pattern formation. The sub-resolution assist features are strategically placed around alignment marks to locally enhance signal contrast without affecting the overall mask structure.
2Measurement precision
If the multilayer Mo/Si stack with sub-resolution assist features is implemented, then signal contrast and alignment accuracy are significantly improved, but the device complexity increases
Solution Approach 1:
The photo mask employs a nested layered structure where the absorber layer is positioned over the capping layer, which in turn is over the multilayer Mo/Si stack, all on top of the substrate. This nesting allows complex functionality to be achieved through sequential layering rather than complex lateral arrangements, simplifying the overall device architecture while maintaining high signal contrast.
Solution Approach 2:
Instead of increasing lateral complexity to improve alignment accuracy, the invention adds vertical complexity by introducing multiple thin layers (substrate, Mo/Si stack, capping layer, absorber layer). This dimensional transition from 2D to 3D structuring enables high signal contrast and precise alignment without proportionally increasing lateral device complexity.
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 significantly improves signal contrast and alignment accuracy by effectively suppressing background intensity, thereby enhancing the performance of EUV lithography processes.
Implementation Method 1
a multilayer Mo/Si stack disposed over the substrate
Implementation Method 2
an absorber layer disposed over the capping layer
Data Source
AI summary
A photo mask for an extreme ultraviolet (EUV) lithography includes a mask alignment mark for aligning the photo mask to an EUV lithography tool, and sub-resolution assist patterns disposed around the mask alignment mark. A dimension of the sub-resolution assist patterns is in a range from 10 nm to 50 nm.