EUV Mirror Thermal Diffusion Layer Design
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Solution Overview
Problem
Existing extreme ultraviolet (EUV) light generation systems face challenges in managing heat distribution and stability due to the high-energy laser interactions with mirrors, leading to uneven heat dissipation and potential deformation, which affects the optical performance and longevity of the mirrors.
Innovation Solution
Incorporating a thermal diffusion layer with high thermal conductivity, such as diamond, on the surface of the mirror substrate, which diffuses and efficiently releases heat away from the high-reflection film, thereby reducing surface deformation and enhancing thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional mirror substrate is used without a thermal diffusion layer, then the mirror structure is simple and manufacturing is easier, but heat concentration occurs leading to surface deformation and reduced optical performance
Solution Approach 1:
The mirror employs a composite structure consisting of a substrate, a thermal diffusion layer made of high-thermal-conductivity material (such as diamond, graphite, or cubic boron nitride), and a reflective layer. This composite material approach enables efficient heat dissipation through the thermal diffusion layer while maintaining the reflective function of the reflective layer, thereby resolving the contradiction between heat dissipation performance and structural simplicity.
Solution Approach 2:
The mirror is segmented into three distinct functional layers: the substrate providing mechanical support, the thermal diffusion layer dedicated to heat dissipation, and the reflective layer for optical reflection. This segmentation allows each layer to perform its specific function optimally, with the thermal diffusion layer specifically addressing the heat concentration problem without compromising the other functions.
2Productivity
If high-energy laser beams are focused on the mirror, then EUV light generation efficiency is improved, but heat concentration causes surface deformation and reduces mirror stability
Solution Approach 1:
The invention converts the harmful heat concentration effect into a beneficial outcome by introducing a thermal diffusion layer that actively manages the heat generated during high-energy laser operation. The high-thermal-conductivity material in this layer transforms the concentrated heat into distributed thermal energy, preventing surface deformation while allowing continued high-efficiency EUV light generation.
Solution Approach 2:
The thermal diffusion layer acts as an intermediary between the substrate and the reflective layer, mediating the heat transfer process. It receives concentrated heat from the laser-irradiated reflective layer and distributes it across the substrate, thereby protecting the mirror's surface stability while enabling sustained high-power operation for improved EUV generation efficiency.
3Strength
If the reflective layer is directly placed on the substrate, then the mirror structure is simpler, but thermal conductivity is insufficient leading to heat accumulation and deformation
Solution Approach 1:
The invention introduces a composite layer structure where the thermal diffusion layer, composed of materials with exceptionally high thermal conductivity (diamond, graphite, or cubic boron nitride), is positioned between the substrate and the reflective layer. This composite structure enhances thermal stability by providing a dedicated heat dissipation pathway, preventing heat accumulation at the reflective layer-substrate interface while maintaining structural integrity.
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 implementation of a thermal diffusion layer significantly reduces heat concentration and deformation, improving the mirror's thermal stability and optical performance, even when exposed to high-energy light, while allowing for cost-effective and processable substrate materials.
Implementation Method 1
a thermal diffusion layer provided on a principal surface of the substrate, the thermal diffusion layer having a higher thermal conductivity than the substrate
Implementation Method 2
a reflective layer provided on the thermal diffusion layer, the reflective layer having a lower thermal conductivity than the thermal diffusion layer, wherein the reflective layer includes any of gold, molybdenum, and silver
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
A mirror is provided which may include: a substrate (111); a thermal diffusion layer (112) provided on a principal surface of the substrate, the thermal diffusion layer having a higher thermal conductivity than the substrate; and a reflective layer (113) provided on the thermal diffusion layer, the reflective layer having a lower thermal conductivity than the thermal diffusion layer.