EUV Lithography Multi-Layer Stack for Photoresist Sensitivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current EUV lithography techniques face challenges in enhancing photoresist sensitivity due to low absorption of EUV radiation, leading to reduced performance and increased line edge roughness, line width roughness, and resolution issues, while existing methods such as underlayers and photo-acid generators have limitations in effectively redirecting energy back to the photoresist layer.
Innovation Solution
A multi-layer stack composed of a self-organized di-block copolymer with alternating layers of materials having different refractive indexes is used between the EUV photoresist layer and the substrate, redirecting EUV photons back into the photoresist layer to increase absorption and sensitivity, thereby reducing the dose required at the scanner level and improving throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the photoresist layer is made thinner to maintain reasonable aspect ratio and avoid pattern collapse, then the aspect ratio is improved, but the EUV radiation absorption is reduced
Solution Approach 1:
An intermediate structure consisting of multiple layers with alternating high and low refractive indexes is introduced between the photoresist layer and the substrate. This intermediary structure reflects EUV photons back into the photoresist layer, increasing the effective absorption of EUV radiation without requiring an increase in photoresist thickness, thereby maintaining the desired aspect ratio while improving radiation absorption.
Solution Approach 2:
Instead of increasing photoresist thickness in the vertical dimension to improve absorption, the solution introduces a multi-layered intermediate structure that manipulates photon reflection and path length. This approaches the absorption problem from an optical path dimension rather than a physical thickness dimension, allowing enhanced absorption while maintaining thin photoresist profile.
2Loss of energy
If underlayer materials are used to redirect energy back to the photoresist, then the photoresist sensitivity is improved, but the line edge roughness and line width roughness increase
Solution Approach 1:
The invention changes the optical parameters of the intermediate structure by using materials with specifically selected refractive indexes. The alternating high and low refractive index layers are designed to optimize photon reflection while controlling photo-acid generation, thereby improving photoresist sensitivity without excessive roughness penalty. The refractive index contrast is carefully controlled to balance sensitivity enhancement with pattern quality.
3Stability of the object's composition
If the photoresist layer is made thinner to improve aspect ratio, then the aspect ratio is improved, but the resolution deteriorates
Solution Approach 1:
The intermediate multi-layer structure acts as an optical mediator that enhances the effective interaction between EUV radiation and the thin photoresist layer. By reflecting photons back into the photoresist, it compensates for the reduced absorption inherent in thin films, thereby maintaining resolution performance despite the reduced thickness required for acceptable aspect ratio.
4Productivity
If more EUV photons are absorbed by the substrate instead of the photoresist, then the throughput is improved, but the photoresist sensitivity is reduced
Solution Approach 1:
The intermediate structure creates an optical feedback mechanism by reflecting EUV photons that would otherwise be lost in the substrate back into the photoresist layer. This feedback loop increases the effective dose delivered to the photoresist without requiring increased scanner power or reduced throughput, as the same incident photons are utilized more efficiently through multiple passes through the photoresist.
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 multi-layer stack enhances EUV photoresist sensitivity, reducing line width roughness and photon shot noise, and can be used as both a hard mask and a layer for pattern transfer, improving the overall performance of EUV lithography without compromising resolution or introducing pattern collapse risks.
Implementation Method 1
The multi-layer stack is a self-organized di-block copolymer, and has an upper surface and consists of a first layer of a first material and a second layer of a second material. The first material and the second material have different refractive indexes and the first layer and the second layer are stacked alternatingly and repeatedly on one another.
Implementation Method 2
The first material and the second material have different refractive indexes and the first layer and the second layer are stacked alternatingly and repeatedly on one another
Data Source
Figure 1
Figure 2a~2c
Figure 3~4
AI summary
A method for performing an extreme ultraviolet (EUV) photo-lithographic processing, the method comprising obtaining a substrate to be patterned having an upper main surface, providing an EUV photoresist layer on the upper main surface, and forming at least one opening in the EUV photoresist layer, wherein the method further comprises, providing, sandwiched between the EUV photoresist layer and the upper main surface, a multi-layer stack having an upper surface and consisting of a first layer of a first material and a second layer of a second material, wherein the materials have a different refractive indexes, and the layers are stacked alternately and repeatedly on one another, and wherein the at least one opening exposes a part of the upper main surface of the multi-layer stack.