Mirror Assembly with Segmented Perimeter for EUV Thermal Control
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Solution Overview
Problem
In extreme ultraviolet (EUV) lithography systems, existing mirror coatings absorb a significant portion of the EUV beam, leading to heating and deformation of the mirror assembly, which adversely affects the reflected EUV beam and reduces image resolution.
Innovation Solution
A mirror assembly design featuring a mirror with a reflective surface and a back plate that maintains the mirror perimeter at a uniform temperature, while only the mirror mounting region experiences a temperature gradient, minimizing deformation and absorption of the EUV beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If existing mirror coatings are used to reflect the EUV beam, then the mirror assembly can direct the beam to the reticle, but the mirror assembly absorbs a significant portion of the EUV beam causing heating and deformation
Solution Approach 1:
The mirror assembly is segmented into distinct regions: a mirror perimeter region and a mirror mounting region. The mirror slot physically separates these regions, allowing independent thermal management. This segmentation enables the perimeter region to remain cool while the mounting region can tolerate temperature gradients, resolving the contradiction between maintaining reflection efficiency and controlling temperature.
Solution Approach 2:
Different regions of the mirror assembly are assigned different thermal properties and functions. The mirror perimeter region is designed to maintain uniform temperature for optimal beam reflection, while the mirror mounting region is designed to accommodate temperature gradients without affecting optical performance. This local differentiation resolves the contradiction by optimizing each region for its specific function.
2Stability of the object's composition
If the mirror assembly is cooled to maintain uniform temperature, then thermal deformation is reduced, but the complexity of the cooling system increases
Solution Approach 1:
The mirror slot extracts or removes the mirror perimeter region from the thermal influence of the mounting region. By creating this physical separation, the perimeter region can be cooled independently or passively maintained at uniform temperature without requiring a complex cooling system for the entire mirror assembly. This extraction reduces overall system complexity while maintaining dimensional stability.
3Strength
If the mirror mounting region is secured to the back plate, then the mirror is retained in position, but thermal gradients cause deformation of the mirror assembly
Solution Approach 1:
The mirror slot segments the mirror assembly into a mounted region and a free perimeter region. This segmentation allows the mounting region to be securely attached to the back plate for positional stability, while the perimeter region remains thermally isolated and shape-stable. The segmentation resolves the contradiction by localizing the thermal management function to specific regions.
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 design reduces the deformation of the mirror assembly and maintains a stable EUV beam reflection, enhancing the resolution and accuracy of the lithography process by minimizing thermal distortion.
Implementation Method 1
a first mirror and a back plate. In one embodiment, the first mirror includes a mirror body that defines a reflective, first surface that redirects the beam
Implementation Method 2
the back plate can include a circulation conduit for directing a circulation fluid through the back plate to control the temperature of the back plate
Data Source
AI summary
A mirror assembly (332) for directing a beam (28) from an illumination source (26) to a reticle (36) includes a mirror (352) and a back plate (350). The mirror (352) includes a mirror body (352A) that defines a reflective first surface (352B) that directs the beam (28), a mirror mounting region (370), a mirror perimeter region (372) that encircles the mirror mounting region (370), and mirror slot (374) that separates the mirror perimeter region (372) from the mirror mounting region (370). The back plate (350) retains and engages the mirror mounting region (370) of the mirror (352) with the mirror perimeter region (372) spaced apart from the back plate (350). Further, the mirror body (352A) can include a second surface (352C) that is substantially opposite the first surface (352B), and the mirror mounting region (370) extends between the second surface (352C) to near the first surface (352B). Further, the mirror slot (374) extends from the second surface (352C) to near the first surface (352B).