EUV Lithography Reflective Element Silicon Carbide Protection
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Solution Overview
Problem
Reflective optical elements in EUV lithography devices face reduced reflectivity and service life due to contamination from reactive hydrogen and other sources, leading to detachment of multilayer system layers.
Innovation Solution
A reflective optical element with a protective layer system featuring an uppermost layer of silicon carbide or ruthenium, with a thickness between 5 nm and 25 nm, effectively decelerates high-energy hydrogen and suppresses ultraviolet radiation, reducing layer detachment and maintaining high reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer of fluoride is applied to the reflective surface, then contamination by silicon dioxide, hydrocarbon, or metal deposition is reduced, but the protective layer becomes vulnerable to detachment under reactive hydrogen exposure
Solution Approach 1:
The patent applies a composite protective layer structure consisting of a fluoride layer (such as fluoromagnesium oxide, fluorosilicon oxide, or fluorocalcium oxide) combined with an additional protective material layer. This composite structure leverages the contamination resistance of fluoride materials while adding materials that provide resistance to reactive hydrogen-induced detachment, thus resolving the contradiction between contamination protection and layer stability.
Solution Approach 2:
The patent modifies the compositional parameters of the protective layer by introducing specific metal fluoride compounds (fluoromagnesium oxide, fluorosilicon oxide, fluorocalcium oxide) with controlled thickness ratios. By adjusting the composition and thickness parameters of different protective layers, the system achieves both contamination resistance and resistance to hydrogen-induced detachment without sacrificing either property.
2Reliability
If multiple reflective optical elements are arranged in sequence, then the optical system achieves sufficient total reflectivity, but contamination on each element significantly reduces the overall system performance
Solution Approach 1:
The patent applies a multi-component protective layer structure to the reflective optical elements before they are exposed to the operating environment. This preliminary protective coating prevents contamination from accumulating on the reflective surface during operation, thereby maintaining high reflectivity across multiple sequential optical elements without significant performance degradation.
3Ease of operation
If reactive hydrogen is used to clean carbon contaminations, then carbon residues are removed, but individual layers of the multilayer system become detached
Solution Approach 1:
The patent introduces a specially designed protective layer composition that acts as a cushion or barrier between the reactive hydrogen cleaning process and the underlying multilayer system. This protective structure absorbs or mitigates the damaging effects of reactive hydrogen exposure, allowing effective carbon contamination removal while preventing layer detachment through the buffering protective architecture.
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 protective layer system significantly reduces the penetration of reactive hydrogen, minimizing layer detachment and ensuring high reflectivity and extended service life of the optical elements, while also suppressing ultraviolet radiation for accurate exposures.
Implementation Method 1
the high energy hydrogen is decelerated in the protective layer system
Implementation Method 2
both in the case of an uppermost layer composed of silicon carbide, and of an uppermost layer composed of ruthenium, the radiation in the wavelength region between 300 nm and 100 nm which is emitted, in particular, in addition to the EUV and SX radiation by plasma radiation sources, is more effectively suppressed
Implementation Method 3
water molecules are dissociated by the EUV and/or SX radiation, and the resulting free oxygen radicals oxidize the optically active surfaces of the reflective optical elements
Implementation Method 4
the resulting free oxygen radicals oxidize the optically active surfaces of the reflective optical elements
Data Source
Figure 1
Figure 2a~2c
Figure 3
AI summary
In order to reduce the negative influence of reactive hydrogen on the lifetime of a reflective optical element, particularly inside an EUV lithography device, there is proposed for the extreme ultraviolet and soft X-ray wavelength region a reflective optical element (50) having a reflective surface with a multilayer system (51 ) and in the case of which the reflective surface (60) has a protective layer system (59) with an uppermost layer (56) composed of silicon carbide or ruthenium, the protective layer system (59) having a thickness of between 5 nm and 25 nm.