EUV Reticle Absorber Deposition for Lower Mask 3D Effects
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current EUV reticles face challenges such as Mask 3D effects, overlay problems, and high manufacturing costs due to the use of Ta-based absorber materials, which require complex processing techniques that can damage the multi-layer mirror and capping layer, and do not adequately mitigate shadowing and focus issues.
Innovation Solution
The method involves forming EUV reticles with EUV absorbing structures made from metallic materials like Ni, Co, Sb, Ag, In, and Sn, using electroless deposition to create straight, vertical, and smooth sidewalls with low internal stress, allowing for reduced thickness and improved compatibility with existing EUV reticle fabrication processes, thereby minimizing defects and maintaining the protective properties of the capping layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ta-based absorber material with typical thickness of 70 nm is used, then high extinction coefficient is achieved, but Mask 3D effects such as shadowing differences and focus shifts occur
Solution Approach 1:
The patent changes the material parameter from Ta-based absorber to alternative metal absorbers (such as Mo, W, Pt, Pd, Ir, Rh, Ru, Os, Ag, Au, Cu, Al, Ga, In, Tl, Zn, Cd, Hf, Ta, Nb, Bi, Po, and their alloys). This material substitution maintains high extinction coefficient while reducing the required thickness to below 70 nm, thereby mitigating Mask 3D effects and improving pattern accuracy without sacrificing light absorption performance
Solution Approach 2:
Instead of reducing the thickness of traditional Ta-based absorber material to mitigate Mask 3D effects (which compromises extinction coefficient), the patent inverts the approach by substituting the material itself with alternative metals that achieve high extinction coefficient at reduced thicknesses. This reversal simultaneously solves both the light absorption requirement and the pattern accuracy problem
2Manufacturing precision
If etch-back or CMP techniques are used to create absorber patterns, then desired pattern shapes are achieved, but damage occurs to the capping layer and multi-layer mirror
Solution Approach 1:
The patent extracts and eliminates the harmful etch-back and CMP steps from the fabrication process. By using alternative metal absorbers that can be directly deposited and patterned without requiring subsequent etch-back or CMP operations, the method removes the source of damage to the capping layer and multi-layer mirror while still achieving the desired absorber patterns with square profiles
Solution Approach 2:
The patent introduces a sacrificial layer (such as SiO2, Si3N4, or organic materials) that is temporarily used during fabrication to define the absorber pattern, then easily removed. This disposable layer enables precise pattern formation without needing damaging etch-back or CMP steps on the expensive mirror and capping layer
3Ease of manufacture
If blanket layer deposition or non-selective deposition methods are used, then absorber material is provided, but further processing steps are required increasing manufacturing cost
Solution Approach 1:
The patent employs selective deposition methods where the absorber material is deposited only in specific regions defined by a sacrificial layer or mask. This local deposition approach eliminates the need for blanket layer deposition followed by etch-back or CMP, directly creating the desired absorber patterns and reducing the total number of fabrication steps while maintaining manufacturing feasibility
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 approach results in EUV reticles with reduced shadowing effects, minimal damage to the mirror and capping layer, and lower manufacturing costs, enabling the creation of features as small as 6 nm on the wafer with improved stability and reliability, while maintaining the reflective properties of the EUV mirror.
Implementation Method 1
forming the EUV absorbing structure selectively in the cavity by electroless deposition
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A method for making an extreme ultraviolet reticle, comprising: a. providing an assembly comprising: (i) an extreme ultraviolet mirror (2); and (ii) a cavity overlaying at least a bottom part of the extreme ultraviolet mirror; b. filling the cavity with an extreme ultraviolet absorbing structure (8) by forming the extreme ultraviolet absorbing structure selectively in the cavity, with respect to any surface not forming part of the cavity.