Mirror Barrier Layer System for Microlithography
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Solution Overview
Problem
Grazing incidence mirrors in microlithographic projection exposure apparatuses face issues with hydrogen penetration leading to reflectivity loss and potential destruction due to the lack of interfaces in single-layer reflection systems, allowing hydrogen to diffuse and cause blistering.
Innovation Solution
A barrier layer system with alternating layers of different materials is introduced between the reflection layer and the mirror substrate to impede hydrogen penetration, providing multiple interfaces to block hydrogen diffusion and potentially serving as a substrate protection and layer stress reduction layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer reflection layer is used for grazing incidence mirrors, then the device complexity is reduced and manufacturing is simplified, but hydrogen penetration increases leading to reflectivity loss and potential destruction
Solution Approach 1:
The reflection layer is segmented into multiple alternating layers of different materials (e.g., Mo/Si, W/B4C) with distinct functions: some layers provide high reflectivity while others act as hydrogen barrier layers. This segmentation allows the system to simultaneously achieve low complexity in design concept while providing robust protection against hydrogen penetration through the multi-layer structure.
Solution Approach 2:
The reflection layer uses composite material structures where alternating layers of different materials (metallic layers for reflectivity and ceramic/oxide layers for hydrogen barrier properties) are combined. This composite approach enables the system to leverage the advantages of different materials to simultaneously achieve high reflectivity and hydrogen resistance without significantly increasing manufacturing complexity.
2Object-affected harmful factors
If hydrogen atmosphere is used to prevent contaminant ingress, then protection against contaminants is improved, but hydrogen penetration into the reflection layer increases causing delamination and reflectivity loss
Solution Approach 1:
The invention converts the harmful effect of hydrogen atmosphere into a beneficial protective mechanism by designing the reflection layer with alternating hydrogen-barrier layers that specifically target and block hydrogen penetration. The hydrogen atmosphere that was previously harmful is now managed through the barrier layer structure, which allows the protective atmosphere to continue functioning while preventing hydrogen from reaching the substrate and causing delamination.
Solution Approach 2:
The alternating barrier layers act as intermediary structures between the hydrogen-containing atmosphere and the reflection layer substrate. These intermediate layers (such as Mo, W, B4C, or oxide layers) mediate the interaction by providing a physical and chemical barrier that blocks hydrogen diffusion while allowing the system to maintain its hydrogen atmosphere for contaminant protection.
3Reliability
If multiple alternating barrier layers are introduced, then hydrogen penetration is reduced by at least a factor of 10, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The invention optimizes parameters such as layer thickness (typically 1-10 nm per layer), material composition, and layer sequence to achieve maximum hydrogen barrier effectiveness while minimizing manufacturing complexity. By carefully controlling these parameters, the system achieves at least 10x reduction in hydrogen penetration without requiring an excessive number of layers, thus balancing reliability improvement with 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 barrier layer system effectively reduces hydrogen penetration by a factor of at least 10, preventing delamination and maintaining reflectivity, while also offering additional functionalities like substrate protection and layer stress compensation.
Implementation Method 1
a barrier layer system, which is arranged between the reflection layer and the mirror substrate and comprises a sequence of alternating layer plies composed of a first material and at least one second material, wherein the barrier layer system reduces penetration of hydrogen atoms as far as the mirror substrate by at least a factor of 10
Implementation Method 2
such mirrors operated with grazing incidence are understood to mean mirrors for which the angles of reflection relative to the respective surface normal, which occur during the reflection of the EUV radiation, are at least 65°
Data Source
AI summary
A mirror, in particular for a microlithographic projection exposure apparatus or an inspection system, having a mirror substrate (205), a reflection layer (220), which is configured to have a reflectivity of at least 50% for electromagnetic radiation of a predefined operating wavelength that is incident on the optically effective surface (200a) of the mirror at an angle of incidence of at least 65° relative to the respective surface normal, and a barrier layer system (210), which is arranged between the reflection layer and the mirror substrate and has a sequence of alternating layer plies composed of a first material and at least one second material. The barrier layer system reduces penetration of hydrogen atoms that would otherwise penetrate the mirror substrate by at least a factor of 10.