EUV Multilayer Mirror Reflectivity Optimization
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Solution Overview
Problem
Lithography techniques face challenges in achieving high reflectivity in EUV scanners due to the limited number of materials and periodicity in multilayer mirror structures, resulting in significant energy loss, particularly with reflectivity less than 70% across multiple reflectors, which hampers the accuracy and efficiency of patterning at scaled-down dimensions.
Innovation Solution
Increasing the number of materials used in reflective multilayers to three or more, such as incorporating ruthenium and strontium, and allowing arbitrary thickness and ordering of layers, combined with intelligent algorithms like stochastic path finding and machine learning, to enhance reflectivity beyond traditional two-material, two-thickness limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional two-material periodic multilayer mirror structures are used, then manufacturing simplicity is maintained, but reflectivity is limited to less than 70% causing significant EUV energy loss
Solution Approach 1:
The patent applies composite materials by using three or more different materials (e.g., Mo, Si, Ru, Sr) in alternating layers to create a multilayer mirror structure. This composite approach enables higher reflectivity (70-80% or more) for EUV radiation compared to traditional two-material structures, directly addressing the energy loss problem while accepting increased structural complexity as a trade-off.
Solution Approach 2:
The patent changes the parameters of the multilayer structure by allowing arbitrary thicknesses for each layer and varying the ordering sequences. By optimizing these parameters (thickness values, material sequences, layer counts), the system achieves enhanced reflectivity beyond the traditional periodic structure limitations, transforming the energy loss issue into an opportunity for improved performance.
2Manufacturing precision
If periodic multilayer structures with fixed thickness are used, then manufacturing process is simplified, but patterning accuracy at scaled-down dimensions is compromised
Solution Approach 1:
The patent introduces dynamic variability in the multilayer structure by allowing arbitrary thickness values and non-periodic ordering sequences. This dynamic approach enables optimization of each layer's properties for specific patterning requirements, improving manufacturing precision at scaled-down dimensions while accepting that the fabrication process becomes more complex and requires advanced deposition techniques.
Solution Approach 2:
The patent applies local quality by allowing different layers to have different thicknesses and material compositions tailored to their specific positions and functions in the optical path. This localized optimization enables enhanced reflectivity and patterning accuracy in critical regions while maintaining overall system performance, directly addressing the precision requirement at advanced technology nodes.
3Loss of energy
If limited number of materials is used in multilayers, then material selection and fabrication are simplified, but reflectivity cannot be enhanced beyond traditional limitations
Solution Approach 1:
The patent employs composite materials with three or more different elements (such as Mo, Si, Ru, Sr) arranged in alternating layers. This composite structure enables enhanced EUV reflectivity (70-80% or more) and improved energy throughput by optimizing the interaction of multiple materials with EUV radiation, directly resolving the energy loss problem while managing material selection complexity through systematic approaches.
Solution Approach 2:
The patent achieves multi-functionality by designing a universal multilayer structure framework that can accommodate various material combinations and thickness configurations. This universal design approach enables optimization for high reflectivity and energy throughput while providing flexibility to adapt to different operational requirements, effectively managing the complexity through standardized design principles.
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 approach significantly increases reflectivity, improving EUV energy throughput by up to 50% or more, leading to enhanced patterning accuracy and efficiency in semiconductor device fabrication at advanced technology nodes.
Implementation Method 1
a first reflector and a second reflector, each reflector including a reflective multilayer... the first and second reflectors being spaced apart by a first distance, the first reflector reflecting the EUV radiation onto the second reflector
Data Source
AI summary
A lithography exposure system includes a light source, a substrate stage, and a mask stage between the light source and the substrate stage along an optical path from the light source to the substrate stage. The lithography exposure system further comprises a reflector along the optical path. The reflector comprises: a first layer having a first material and a first thickness; a second layer having the first material and a second thickness different from the first thickness; and a third layer between the first layer and the second layer, and having a second material different from the first material.