Beryllium-Nitride EUV Pellicle Structure for Oxide-Free Transmittance
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Solution Overview
Problem
Existing EUV transmissive pellicles suffer from significant EUV transmittance loss due to natural oxide formation and reaction-induced membranes, which degrade their performance.
Innovation Solution
A three-layer configuration of metallic beryllium and nitride layers, with amorphous carbon layers on both sides, is used to prevent oxide and reaction-induced transmittance loss, allowing for high EUV transmittance by removing protective layers with hydrogen or oxygen plasma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is applied on the surface of the core material to prevent oxide formation, then the formation of transmittance-decreasing membranes is suppressed, but the EUV transmittance of the pellicle membrane decreases due to the lower transmittance of the protective layer
Solution Approach 1:
A carbon layer is introduced as an intermediary protective layer on the surface of the beryllium core material. This carbon layer prevents direct oxidation of the beryllium surface during storage and handling, while being removable via plasma treatment before EUV exposure to restore maximum transmittance. The carbon layer acts as a sacrificial mediator that protects during non-operational periods without permanently degrading EUV performance.
Solution Approach 2:
The surface properties of the protective layer are dynamically changed through plasma treatment. The carbon layer is in a removable state during fabrication and storage, then transformed into a removed state before EUV exposure by applying plasma conditions. This parameter change allows the system to have protection during storage and maximum transmittance during operation.
2Loss of energy
If no protective layer is applied, then the EUV transmittance remains high, but natural oxide membranes form on the surface causing significant transmittance loss
Solution Approach 1:
A carbon protective layer is applied in advance to the beryllium surface before any oxidation can occur. This preliminary protective action prevents the natural oxide formation that would otherwise degrade EUV transmittance during storage and handling. The protection is applied beforehand and can be removed just before use.
Solution Approach 2:
The carbon protective layer is treated as a temporary, disposable protective element. It is applied for storage and handling protection, then deliberately removed via plasma treatment before EUV exposure since it degrades transmittance. The layer serves its protective purpose temporarily and is discarded when no longer needed.
3Reliability
If a thick protective layer is used to ensure complete protection, then oxide formation is fully prevented, but the mechanical integrity and flexibility of the pellicle membrane are compromised
Solution Approach 1:
The protective function is localized to a thin carbon layer only on the surface of the beryllium core, rather than using a thick protective layer throughout. This thin local protective layer is sufficient to prevent oxidation during storage while maintaining the mechanical properties of the underlying beryllium core. The protection is applied locally where needed without compromising overall structure.
Solution Approach 2:
Instead of applying excessive protection thickness, a partial thin carbon layer is applied that provides sufficient protection against oxidation during storage and handling. This partial action is adequate for the protective purpose while avoiding the mechanical degradation that would result from excessive thickness. The protection is optimized to be just sufficient rather than excessive.
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 EUV transmissive membrane achieves an EUV transmittance of 88% or more at 13.5 nm, maintaining high performance by preventing transmittance loss and ensuring mechanical integrity.
Implementation Method 1
a first nitride layer that covers the first side of the beryllium layer... a second nitride layer that covers the second side of the beryllium layer
Implementation Method 2
removing protective layers with hydrogen or oxygen plasma
Implementation Method 3
the EUV transmissive membrane has an EUV transmittance of 88% or more at a wavelength of 13.5 nm
Data Source
AI summary
Provided is an EUV transmissive membrane having a three-layer configuration composed of a metallic beryllium layer (12) having a first side and a second side, a first nitride layer (14a) that covers the first side (12a) of the beryllium layer (12), wherein the first nitride layer includes at least one selected from the group consisting of silicon nitride, beryllium nitride, boron nitride, and zirconium nitride, and a second nitride layer (14b) that covers the second side (12b) of the beryllium layer (12), wherein the second nitride layer includes at least one selected from the group consisting of silicon nitride, beryllium nitride, boron nitride, and zirconium nitride. The EUV transmissive membrane (10) has an EUV transmittance of 88% or more at a wavelength of 13.5 nm.