EUV Mirror Shape Accuracy via Barrier Layer and Annealing
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Solution Overview
Problem
EUV light multilayer mirrors face challenges in achieving high shape accuracy due to material reactions at interfaces, leading to wavelength shifts and decreased reflectance, and require complex temperature control mechanisms for shape correction.
Innovation Solution
A mirror manufacturing method involving a shape adjusting layer with heat-dependent thickness, a reflection layer with barrier layers to prevent material diffusion, and partial annealing to adjust the layer thickness profile, allowing for precise shaping without complex temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a multilayer mirror is formed by alternately stacking molybdenum and silicon layers, then high reflectance can be obtained at perpendicular incidence, but material reactions at interfaces cause wavelength shifts and decreased reflectance
Solution Approach 1:
A barrier layer made of boron carbide (B4C) or silicon oxide (SiO2) is introduced between the molybdenum and silicon layers to prevent material diffusion and chemical reactions at the interface. This intermediary layer maintains the optical performance and wavelength stability of the multilayer mirror structure.
2Manufacturing precision
If the shape of a mirror is corrected by thermal expansion using a heater, then shape accuracy can be improved, but the structure becomes complicated due to the indispensable temperature control mechanism
Solution Approach 1:
A shape adjusting layer with positive thermal expansion coefficient is deposited on the substrate before the reflection layer. By controlling the thickness profile of this shape adjusting layer, the mirror shape can be corrected through thermal expansion during the deposition process itself, eliminating the need for separate heaters and temperature control mechanisms.
Solution Approach 2:
The shape correction is performed in advance during the deposition process by pre-forming the shape adjusting layer with the appropriate thickness profile, rather than requiring post-manufacturing thermal adjustment mechanisms.
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
This approach enables the production of mirrors with excellent shape accuracy and simple configuration, maintaining high reflectance while minimizing the influence of material reactions and eliminating the need for intricate temperature control.
Implementation Method 1
a shape adjusting layer 12 having a layer thickness which changes by heat
Implementation Method 2
a barrier layer which is arranged between the first layer and the second layer, and prevents a diffusion of a material of the first layer and a material of the second layer
Implementation Method 3
a process of partially annealing the shape adjusting layer
Data Source
AI summary
A method of manufacturing a mirror includes a first step of arranging, on a substrate, a shape adjusting layer having a layer thickness which changes by heat, a second step of arranging, on the shape adjusting layer, a reflection layer including a first layer, a second layer, and a barrier layer which is arranged between the first layer and the second layer, and prevents a diffusion of a material of the first layer and a material of the second layer, and a third step of bringing a shape of the reflection layer close to a target shape by changing a layer thickness profile of the shape adjusting layer after the second step, the third step including a process of partially annealing the shape adjusting layer.