EUV Resist Etch Durability and Pattern Collapse Mitigation
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Solution Overview
Problem
In sub-22nm half-pitch patterns, pattern collapse and insufficient etch resistance of EUV resist layers pose challenges for transferring resist feature patterns into underlying layers, as reducing resist thickness to lower aspect ratios limits etch resistance and feature transfer.
Innovation Solution
A method involving the use of intermediate high etch resistance materials for pattern reversal, such as image reversal materials with enhanced etch resistance, to replace the original resist layer before etching, allowing for low aspect ratio feature patterns with improved etch resistance and reduced pattern collapse, utilizing techniques like diffusion-limited etch-back and slimming processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If resist thickness is reduced to achieve lower aspect ratio, then pattern collapse is mitigated, but etch resistance is insufficient for full pattern transfer
Solution Approach 1:
The patent segments the originally single resist layer into two distinct functional layers: a first EUV resist layer optimized for lithographic patterning with lower etch resistance, and a second EUV resist layer optimized for etch resistance with higher durability. This segmentation allows each layer to be independently optimized for its specific function, resolving the contradiction between pattern stability and etch resistance.
Solution Approach 2:
The patent introduces a vertical dimensionality change by stacking two resist layers with different thicknesses and properties. The first layer has thickness optimized for lithography (e.g., 10-20 nm) while the second layer has greater thickness optimized for etch resistance (e.g., 20-50 nm). This multi-layer vertical structure enables simultaneous optimization of both patterning fidelity and etch durability.
2Strength
If resist thickness is increased to improve etch resistance, then pattern transfer capability is enhanced, but aspect ratio increases promoting pattern collapse
Solution Approach 1:
The patent divides the total resist thickness into two segments with different functional optimizations. The first segment (first EUV resist layer) is optimized for lithographic resolution with thinner profile, while the second segment (second EUV resist layer) provides additional etch resistance. This segmentation eliminates the need for a single thick resist layer that would cause pattern collapse.
Solution Approach 2:
The patent applies local quality by giving each resist layer different material compositions and properties tailored to its specific location and function. The first layer uses materials optimized for lithographic contrast and resolution, while the second layer uses materials with higher etch resistance. This local optimization allows the structure to achieve both low aspect ratio and high etch resistance.
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
Enables full transfer of feature patterns into underlying layers with reduced risk of pattern collapse, allowing for further device scaling by maintaining sufficient etch resistance and lowering resist thickness, thereby overcoming the limitations of EUV photo-lithography.
Implementation Method 1
the second EUV resist layer has a greater etch resistance than the first EUV resist layer to the etch process
Implementation Method 2
exposure of the radiation-sensitive material to a pattern of electromagnetic (EM) radiation using, for example, a photo-lithography system
Data Source
Figure 1A~1C
Figure 1D~1G
Figure 2A~2C
AI summary
A method for patterning a substrate is described. The patterning method includes receiving a first patterned layer overlying a material layer to be etched on a substrate, wherein the first patterned layer is composed of a resist material having (i) material properties that provide lithographic resolution of less than about 40 nanometers when exposed to extreme ultraviolet radiation lithography, and (ii) material properties that provide a nominal etch resistance to an etch process condition. The first patterned layer is over-coated with an image reversal material such that the image reversal material fills and covers the first patterned layer. The patterning method further includes removing an upper portion of the image reversal material such that top surfaces of the first patterned layer are exposed, and removing the first patterned layer such that the image reversal material remains resulting in a second patterned layer.