Multilayer CNT Coating for Hydrogen-Plasma-Resistant EUV Pellicles
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Solution Overview
Problem
In the semiconductor industry, particularly in EUV lithography, carbon nanotubes (CNTs) used in pellicle membranes are vulnerable to damage from hydrogen plasma, leading to reduced lifespan and increased defects in the transferred pattern.
Innovation Solution
A multilayer protective coating is applied to the CNTs, comprising a stress control layer and a hydrogen permeation barrier layer, which collectively reduce the influx of hydrogen ions and minimize damage from hydrogen plasma, thereby enhancing the reliability and lifespan of the pellicle membrane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If carbon nanotubes are used in pellicle membranes for EUV lithography, then high EUV transmittance is achieved, but the nanotubes are vulnerable to hydrogen plasma damage leading to reduced lifespan
Solution Approach 1:
The patent applies composite materials by coating carbon nanotubes with multiple protective layers including a first coating layer (e.g., silicon nitride, silicon oxynitride) and a second coating layer (e.g., aluminum oxide, hafnium oxide). This composite structure combines the high EUV transmittance of carbon nanotubes with the hydrogen plasma resistance of the coating materials, resolving the contradiction between transmittance and plasma resistance.
2Reliability
If protective coating is applied to carbon nanotubes to reduce hydrogen plasma damage, then reliability and lifespan are enhanced, but the complexity of the pellicle structure increases
Solution Approach 1:
The protective coating is segmented into multiple functional layers, each with specific thicknesses and material compositions optimized for different protective functions. The first coating layer provides initial protection while the second coating layer enhances hydrogen plasma resistance. This segmentation allows systematic optimization of protection without excessive complexity.
Solution Approach 2:
The patent optimizes parameters such as coating thickness (e.g., 1-10 nm for first layer, 0.5-5 nm for second layer) and material composition to achieve the desired balance between protection and transmittance. By carefully controlling these parameters, the coating provides effective protection while minimizing impact on EUV transmission and 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
The coated CNTs exhibit improved resistance to hydrogen plasma etching, resulting in enhanced durability, high EUV transmittance, and reduced defects in the semiconductor processing, thus extending the pellicle membrane's lifespan and maintaining high production efficiency.
Implementation Method 1
a hydrogen permeation barrier layer over the stress control layer
Implementation Method 2
The stress control layer is adapted to reduce the stress between the CNT and the outer layers of the protective coating
Implementation Method 3
directing a portion of the EUV light reflected from the photomask onto a photoresist layer on a substrate
Data Source
AI summary
A pellicle comprising a pellicle membrane with improved stability to hydrogen plasma is provided. The pellicle membrane includes a network of a plurality of carbon nanotubes. At least one carbon nanotube of the plurality of carbon nanotubes is surrounded by a multilayer protective coating that includes a stress control layer and a hydrogen permeation barrier layer over the stress control layer. The stress control layer and the hydrogen permeation barrier layer independently include an Me-containing nitride or an Me-containing oxynitride with Me selected from the group consisting of Si, Ti, Y, Hf, Zr, Zn, Mo, Cr and combinations thereof. The Me-containing nitride or the Me-containing oxynitride in the stress control layer has a first Me concentration, and the Me-containing nitride or the Me-containing oxynitride in the hydrogen permeation barrier layer has a second Me concentration less than the first Me concentration.