Cr-Based EUV Mask Absorber 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, along with a backside conductive layer made of tantalum boride, to enhance durability and prevent damage.
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:
The patent introduces an intermediate layer between the absorber layer and the backside conductive layer. This intermediate layer acts as a mediator that absorbs or blocks the harmful EUV radiation before it reaches the backside conductive layer, thereby protecting it from damage while allowing the mask to continue performing photolithography operations effectively.
Solution Approach 2:
The patent utilizes the harmful EUV radiation that would otherwise damage the backside conductive layer by introducing materials or structures that convert this harmful energy into a protective effect. The intermediate layer absorbs the harmful radiation, converting it into heat or other forms of energy that do not damage the conductive layer, thereby turning a harmful factor into a protective mechanism.
2Manufacturing precision
If the absorber layer is made more absorbing to improve contrast, then the reflectivity increases, but the damage to the backside conductive layer worsens
Solution Approach 1:
The patent divides the absorber layer into multiple segments or sub-layers with different compositions and thicknesses. This segmentation allows each sub-layer to contribute differently to the overall absorption and reflectivity, enabling fine-tuned control of optical properties while distributing the radiation load to minimize damage to the backside conductive layer.
Solution Approach 2:
The patent applies local quality by creating regions within the absorber layer with different material compositions and optical properties. Certain regions are optimized for high absorption to improve contrast, while other regions are designed with protective characteristics to reduce harmful radiation reaching the backside conductive layer, thereby achieving both high contrast and reduced damage locally.
3Ease of manufacture
If the mask structure is simplified to reduce manufacturing complexity, then the fabrication process becomes easier, but the protection against EUV radiation damage is reduced
Solution Approach 1:
The patent designs the intermediate layer to serve multiple functions simultaneously: it provides protection against EUV radiation damage to the backside conductive layer, contributes to the overall optical performance of the mask, and can be integrated into existing manufacturing processes. This multi-functionality allows the structure to be more complex in terms of protection but not necessarily in terms of manufacturing steps.
Solution Approach 2:
The patent employs composite materials in the intermediate layer that combine the protective properties needed to block EUV radiation with material characteristics that are compatible with standard semiconductor fabrication processes. These composite materials enable effective radiation protection while maintaining ease of manufacture through compatibility with existing deposition and patterning techniques.
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 effectively prevents damage to the backside conductive layer, maintaining the mask's performance and extending its lifespan by enhancing EUV absorption and reflectivity.
Implementation Method 1
a low reflective (high absorbing) absorber structure... to enhance durability and prevent damage... enhancing EUV absorption
Implementation Method 2
a reflective multilayer... enhancing EUV absorption and reflectivity
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.