Adaptive Mirror Piezoelectric Actuator for EUV Lithography
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Solution Overview
Problem
Existing adaptive mirrors in EUV microlithographic projection exposure systems face challenges in correcting aberrations quickly while minimizing heat generation and complexity, particularly when dealing with rapid surface shape adjustments required in lithography processes.
Innovation Solution
The adaptive mirror design incorporates a piezoelectric layer with a locally varying deformation response, allowing for desired surface shape adjustments without the need for locally varying electrical voltages. This configuration reduces the complexity of the electrode arrangements and eliminates the need for a mediator layer, thereby minimizing heat generation and enabling faster surface shape setting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a mediator layer with low electrical conductivity is used to limit parasitic heat evolution, then heat generation is reduced, but the speed of surface shape adjustment becomes too slow for lithography processes
Solution Approach 1:
The patent removes the mediator layer from the mirror structure entirely. By extracting this problematic intermediate layer, the system eliminates the trade-off between heat generation and response speed, allowing both electrodes to directly contact the piezoelectric layer for fast actuation without parasitic heating.
Solution Approach 2:
The patent divides the electrode arrangement into multiple independently controllable electrodes instead of using a single mediator layer. This segmentation allows selective actuation of different mirror regions, enabling fast local surface shape adjustments without requiring current flow through a slow mediator layer.
2Adaptability or versatility
If multiple independently driveable electrodes are used to achieve desired surface shapes, then surface shape control flexibility is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by making the piezoelectric layer itself have spatially varying properties (different d33 coefficients in different regions) rather than relying on complex electrode patterns. This allows simple, uniform electrodes to achieve complex surface shapes through the inherently non-uniform piezoelectric response.
Solution Approach 2:
The patent changes the physical parameters of the piezoelectric layer (specifically the d33 coefficient distribution) to encode the desired surface shape control. By varying material properties in space rather than electrical configuration, the system achieves high adaptability with simpler device structure.
3Ease of manufacture
If a piezoelectric layer with uniform properties is used, then manufacturing is simplified, but the ability to achieve desired surface shapes with constant voltage is limited
Solution Approach 1:
The patent implements local quality by creating a piezoelectric layer with spatially varying d33 coefficients. Different regions of the piezoelectric layer have different piezoelectric sensitivities, allowing a constant voltage applied across simple electrodes to produce a non-uniform, desired surface shape profile.
Solution Approach 2:
The patent uses a composite piezoelectric layer structure with regions of different piezoelectric properties. This composite approach combines multiple material characteristics within a single layer, enabling complex surface shape control while maintaining a relatively simple single-layer fabrication process.
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 proposed adaptive mirror achieves reduced parasitic heat evolution and high-speed surface shape adjustments, effectively correcting aberrations with lower construction complexity, while maintaining performance in both thermal stabilization and rapid deformation scenarios.
Implementation Method 1
an actuator layer system situated between the first electrode arrangement and the second electrode arrangement, wherein said actuator layer system comprises a piezoelectric layer and, in reaction to an electrical voltage being applied between the first electrode arrangement and the second electrode arrangement, exhibiting a deformation response
Data Source
AI summary
A mirror, e.g. for a microlithographic projection exposure apparatus, includes an optical effective surface, a mirror substrate, a reflection layer stack for reflecting electromagnetic radiation incident on the optical effective surface, at least one first electrode arrangement, at least one second electrode arrangement, and an actuator layer system situated between the first and the second electrode arrangements. The actuator layer system is arranged between the mirror substrate and the reflection layer stack, has a piezoelectric layer, and reacts to an electrical voltage applied between the first and the second electrode arrangements with a deformation response in a direction perpendicular to the optical effective surface. The deformation response varies locally by at least 20% in PV value for a predefined electrical voltage that is spatially constant across the piezoelectric layer.