EUV Photomask Multilayer Capping for Oxidation Resistance
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Solution Overview
Problem
Existing lithography techniques, such as EUV lithography, face challenges due to degradation or oxidation of reflective materials in photomasks, which affects their refractive index and performance, leading to reduced service life and operation cycles.
Innovation Solution
A photomask with an anti-oxidation layer formed over the multilayer structure, specifically the topmost Si layer, to prevent oxidation, combined with a capping layer to further protect against oxidation during mask patterning, and a light-absorbing structure to manage EUV radiation, enhancing reflectivity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a photomask is used for EUV lithography, then lithography performance is improved, but oxidation of reflective materials occurs reducing service life
Solution Approach 1:
The photomask employs a composite structure with multiple functional layers: a reflective layer (e.g., silicon or molybdenum) for EUV radiation reflection, and a protective overlay layer (e.g., silicon oxide, silicon nitride, or diamond-like carbon) that prevents oxidation. This composite design allows the mask to maintain both high lithography performance through effective radiation reflection and extended service life through oxidation protection, directly resolving the technical contradiction between reliability and duration of action.
2Productivity
If reflective materials are exposed to EUV radiation, then lithography function is achieved, but oxidation degrades refractive index
Solution Approach 1:
The protective overlay layer acts as an intermediary between the EUV radiation environment and the reflective layer. This intermediate layer prevents direct interaction between oxygen and the reflective materials, thereby maintaining the stability of the refractive index while still allowing the photomask to perform its lithography function effectively.
3Duration of action of stationary object
If protective layers are added to prevent oxidation, then service life is extended, but device complexity increases
Solution Approach 1:
The protective overlay is implemented as a thin film layer (typically nanometer to micrometer scale) that provides oxidation protection without significantly increasing the overall device complexity. The thin film approach allows the protective function to be integrated into the existing photomask structure with minimal additional complexity, while still extending operation cycles by preventing material degradation.
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 anti-oxidation layer significantly extends the service life and operation cycles of the photomask by reducing oxidation effects, improving lithography performance and maintaining reflectivity over repeated exposures to EUV radiation.
Implementation Method 1
an anti-oxidation layer is formed over the multilayer structure... to prevent oxidation
Implementation Method 2
A multilayer structure is formed over the substrate, wherein the multilayer structure includes a plurality of silicon layers and a plurality of molybdenum layers alternately arranged
Implementation Method 3
a light-absorbing layer is formed over the capping layer... to control irradiation of a substrate by EUV radiation
Data Source
AI summary
A method for manufacturing a semiconductor structure is provided. The method may include several operations. A substrate is provided, received or formed. A multilayer structure is formed over the substrate, wherein the multilayer structure includes a plurality of silicon layers and a plurality of molybdenum layers alternately arranged with the plurality of silicon layers. A nitride layer and an oxide layer are formed over the multilayer structure, wherein a total thickness of the nitride layer and a topmost silicon layer is substantially equal to a thickness of each of all other silicon layers of the plurality of silicon layers. A patterned layer is formed over the nitride layer. A semiconductor structure thereof is also provided.