Reflective EUV Mask With Etch-Formed Backside Protection
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Solution Overview
Problem
Existing EUV photo masks face damage to the backside conductive layer due to exposure to EUV radiation, which affects their performance and durability.
Innovation Solution
Incorporating a low thermal expansion glass substrate with a multilayer Mo/Si stack, a capping layer, an absorber layer, and a backside conductive layer, along with additional elements like Si, B, Ge, Al, As, Sb, Te, Se, and Bi to form a protective layer during etching, preventing damage to the backside conductive layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional photo mask structure is used for EUV lithography, then the mask can perform photolithography operations, but the backside conductive layer suffers damage from EUV radiation exposure
Solution Approach 1:
The patent introduces a backside protective layer as an intermediary between the EUV radiation environment and the backside conductive layer. This protective layer absorbs or blocks the harmful EUV radiation before it reaches the conductive layer, preventing damage while allowing the mask to function normally in photolithography operations
Solution Approach 2:
The backside protective layer is formed in advance on the backside of the substrate before the mask undergoes EUV exposure during photolithography operations. This preliminary protective measure ensures the conductive layer is already protected when EUV radiation is applied, preventing damage before it can occur
2Manufacturing precision
If the absorber layer is etched to form patterns, then the desired circuit patterns are created, but three-dimensional effects cause manufacturing precision issues
Solution Approach 1:
The patent applies a protective layer specifically to the sidewalls of the absorber layer during the etching process. This localized protection ensures that the top and bottom surfaces of the absorber layer can be etched with different selectivities, compensating for three-dimensional effects and achieving more accurate pattern dimensions
Solution Approach 2:
The protective layer is formed on the absorber layer sidewalls before the final etching steps are completed. This preliminary protection allows subsequent etching processes to achieve better dimensional control by preventing over-etching or undercutting that would otherwise be caused by three-dimensional effects
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 enhances the durability and performance of EUV photo masks by suppressing damage to the backside conductive layer, maintaining reflectivity, and reducing three-dimensional effects in the absorber layer patterns.
Implementation Method 1
Incorporating a low thermal expansion glass substrate with a multilayer Mo/Si stack, a capping layer, an absorber layer, and a backside conductive layer, along with additional elements like Si, B, Ge, Al, As, Sb, Te, Se, and Bi to form a protective layer during etching, preventing damage to the backside conductive layer
Implementation Method 2
The photo mask is an important component in photolithography operations. It is critical to fabricate EUV photo masks having a high contrast with a high reflectivity part and a high absorption part
Data Source
AI summary
A reflective mask includes a substrate, a reflective multilayer disposed on the substrate, a capping layer disposed on the reflective multilayer, and an absorber layer disposed on the capping layer. The absorber layer includes a base material made of one or more of a Cr based material, an Ir based material, a Pt based material, or Co based material, and further contains one or more additional elements selected from the group consisting of Si, B, Ge, Al, As, Sb, Te, Se and Bi.