Multilayer Mirror Silicon Layer Modification for Lithography
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Solution Overview
Problem
Multilayer mirrors in lithographic apparatuses degrade over time due to harsh conditions, including high temperatures and hydrogen exposure, which affects their sputtering resistance and reactivity, leading to reduced lifespan and image quality issues.
Innovation Solution
A multilayer mirror design with modified silicon layers, where exposed regions are treated with implanted materials or passivation layers such as nitride, silicon nitride, or boron glass to enhance robustness against hydrogen reactivity and sputtering, while maintaining EUV radiation reflection and suppressing infrared radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multilayer mirrors are used in lithographic apparatuses, then EUV radiation reflection is achieved, but degradation occurs over time due to hydrogen exposure and high temperatures
Solution Approach 1:
The patent applies local quality by modifying only the exposed regions of the silicon layers with implanted materials or passivation layers, while leaving the bulk silicon layers unchanged. This localized modification provides targeted protection against hydrogen exposure and heat degradation without affecting the overall optical performance of the multilayer mirror structure.
Solution Approach 2:
The patent employs composite materials by combining silicon layers with implanted materials (such as boron, nitrogen, or nitride) and passivation layers to create a composite structure. This composite approach enhances the resistance of the silicon layers to hydrogen exposure and thermal degradation while maintaining the required optical properties for EUV radiation reflection.
2Reliability
If silicon layers are used in multilayer mirrors, then EUV radiation reflection is optimized, but sputtering resistance deteriorates under harsh conditions
Solution Approach 1:
The patent implements preliminary action by pre-modifying the exposed regions of silicon layers with implanted materials or passivation layers before the mirror is exposed to harsh conditions. This preventive measure creates a protective barrier that reduces sputtering degradation from the outset, rather than attempting to repair or protect after degradation occurs.
3Ease of manufacture
If exposed regions of silicon layers are left unmodified, then manufacturing is simpler, but robustness against hydrogen and sputtering is reduced
Solution Approach 1:
The patent applies local quality by modifying only the exposed regions of the silicon layers, which are the areas most vulnerable to hydrogen exposure and sputtering degradation. This selective modification approach provides targeted protection where needed while avoiding unnecessary modifications in regions that are already protected or not exposed to harmful conditions, thus balancing manufacturing complexity with reliability improvement.
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 modified multilayer mirrors exhibit improved resistance to hydrogen and sputtering, extending their lifespan and maintaining optical performance, thus enhancing the reliability of lithographic apparatuses.
Implementation Method 1
the multilayer mirror may be configured to reflect, or to preferentially reflect, EUV radiation. Alternatively or additionally, the multilayer mirror may be configured to suppress the reflection of infrared radiation
Implementation Method 2
A radiation system for producing EUV radiation may include a laser for exciting a fuel to provide the plasma... The plasma may be created, for example, by directing a laser beam at a fuel, such as particles of a suitable material (e.g., tin), or a stream of a suitable gas or vapour, such as Xe gas or Li vapour
Implementation Method 3
out-of-band radiation infrared radiation, for example the 10.6 μm radiation in some laser produced plasma sources, leads to unwanted and unnecessary heating of the patterning device, substrate, and optics within the lithographic apparatus
Data Source
AI summary
There is provided a multilayer mirror (80) comprising a layer of a first material (84) and a layer of silicon (82). The layer of the first material and the layer of silicon form a stack of layers. An exposed region of the layer of silicon comprises a modification that is arranged to improve the robustness of the exposed region of silicon.