Cr-Based EUV Photo Mask Structure for Backside Layer 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
The EUV photo mask is designed with a low reflective (high absorbing) absorber structure, including a Cr-based absorber layer with controlled nitrogen concentration and optional antireflective and intermediate layers to enhance EUV absorption and protect the backside conductive layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional EUV photo mask structure is used, then the mask can perform photolithography operations, but the backside conductive layer suffers damage from EUV radiation exposure
Solution Approach 1:
An intermediate layer is introduced between the absorber layer and the substrate (containing the backside conductive layer). This intermediate layer acts as a mediator that absorbs or scatters the harmful EUV radiation before it reaches the backside conductive layer, thereby protecting it from damage while allowing the mask to function properly for photolithography operations.
Solution Approach 2:
The mask structure is segmented into multiple functional layers: the absorber layer for pattern definition, the intermediate layer for radiation protection, and the substrate with backside conductive layer for structural support and electrical functionality. This segmentation allows each layer to be optimized for its specific function, with the intermediate layer specifically designed to mitigate EUV radiation damage to the backside conductive layer.
2Manufacturing precision
If the absorber layer is made highly absorbing to improve contrast, then imaging quality improves, but more EUV radiation is absorbed and converted to heat affecting the backside conductive layer
Solution Approach 1:
The intermediate layer serves as a thermal management mediator by absorbing excess heat generated in the absorber layer and dissipating it away from the backside conductive layer. This allows the absorber layer to maintain high absorption for improved pattern contrast while the intermediate layer prevents excessive heat accumulation that would otherwise damage the backside conductive layer.
Solution Approach 2:
The intermediate layer is designed with specific thermal and optical parameters (such as thermal conductivity, thickness, and material composition) that enable it to efficiently manage heat flow. By optimizing these parameters, the system achieves high contrast imaging while controlling the thermal load on the backside conductive layer within acceptable limits.
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 design prevents damage to the backside conductive layer, maintaining the mask's performance and extending its lifespan by suppressing damage from EUV radiation.
Implementation Method 1
The absorber layer includes a Cr-based absorber layer with controlled nitrogen concentration to enhance EUV absorption
Data Source
AI summary
In a method of manufacturing a reflective mask, a photo resist layer is formed over a mask blank. The mask blank includes a substrate, a reflective multilayer on the substrate, a capping layer on the reflective multilayer, an absorber layer on the capping layer and a hard mask layer, and the absorber layer is made of Cr, CrO or CrON. The photo resist layer is patterned, the hard mask layer is patterned by using the patterned photo resist layer, the absorber layer is patterned by using the patterned hard mask layer, and an additional element is introduced into the patterned absorber layer to form a converted absorber layer.