EUV Lithography Mask Black Border Region Design
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Solution Overview
Problem
Conventional EUV lithography systems face field-to-field interference issues due to non-zero reflectivity at the edges of the main field region, leading to critical dimension problems and degraded semiconductor device performance.
Innovation Solution
A 'black border' region is introduced around the main field region, which is non-reflective to EUV light, formed by creating trenches that expose the low thermal expansion substrate or using inter-diffused film pairs to disrupt reflectivity, and passivation layers are applied to protect the mask from contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If EUV lithography is used to achieve smaller device sizes, then resolution is improved, but field-to-field interference occurs due to non-zero reflectivity at mask edges
Solution Approach 1:
The patent extracts the problematic reflective regions from the mask by creating a black border region that surrounds the main field region. This black border is formed by removing or modifying the multilayer structure in specific peripheral areas, effectively separating the useful imaging field from the harmful reflective edges that cause field-to-field interference.
Solution Approach 2:
The patent applies different structural qualities to different regions of the mask. The main field region maintains the full multilayer structure for high reflectivity and imaging performance, while the peripheral black border region has modified or removed multilayer structure to achieve low reflectivity and eliminate interference, creating spatially varying local qualities across the mask surface.
2Object-generated harmful factors
If the mask structure is modified to reduce edge reflectivity, then field-to-field interference is reduced, but mask durability may be compromised
Solution Approach 1:
The patent performs preliminary protective actions by forming passivation layers on the mask structure before the mask is put into service. These passivation layers are deposited in advance to protect the mask surface, particularly in the black border region, from hydrogen exposure and other contaminants that could damage the mask during subsequent lithography operations.
Solution Approach 2:
The patent introduces passivation layers as intermediary protective structures between the mask surface and the harsh lithography environment. These intermediate layers act as a barrier that protects the underlying mask structure from direct exposure to hydrogen and other damaging factors, thereby maintaining mask durability while allowing the black border to function in reducing interference.
3Duration of action of stationary object
If passivation layers are added to protect the mask, then mask lifespan is extended, but device complexity increases
Solution Approach 1:
The passivation layers serve multiple functions simultaneously: they protect the mask from hydrogen exposure, provide a barrier against contaminants, and maintain the structural integrity of the black border region. By combining these protective functions into a single layered structure, the patent avoids the need for multiple separate protective systems, thereby limiting the increase in 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
This solution reduces field-to-field interference, improves critical dimension accuracy, and extends the lifespan of the EUV mask by preventing damage from hydrogen exposure during lithography processes.
Implementation Method 1
A reflective structure is disposed over a first side of the substrate
Implementation Method 2
A substantially non-reflective material is located in the second region
Data Source
AI summary
A lithography mask includes a substrate, a reflective structure disposed over a first side of the substrate, and a patterned absorber layer disposed over the reflective structure. The lithography mask includes a first region and a second region that surrounds the first region in a top view. The patterned absorber layer is located in the first region. A substantially non-reflective material is located in the second region. The lithography mask is formed by forming a reflective structure over a substrate, forming an absorber layer over the reflective structure, defining a first region of the lithography mask, and defining a second region of the lithography mask. The defining of the first region includes patterning the absorber layer. The second region is defined to surround the first region in a top view. The defining of the second region includes forming a substantially non-reflective material in the second region.