Multi-Wavelength Scatterometer Using Independent Modulation
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Solution Overview
Problem
Conventional scatterometers in lithographic processes can only perform measurements using a single wavelength of measurement radiation, which leads to variable measurement quality due to different behaviors of targets in different layers and processing-induced changes, making it desirable to individually tune the measurement radiation for each target or layer.
Innovation Solution
A measurement system that splits an input radiation beam into multiple components, applies independent modulation to each component, and illuminates a target with these components, allowing the detection system to distinguish between them based on the applied modulation, enabling simultaneous measurement with multiple wavelengths and improving measurement quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single wavelength of measurement radiation is used, then the device complexity is reduced, but the measurement precision varies due to different target behaviors in different layers
Solution Approach 1:
The measurement system segments the radiation beam into multiple wavelength components, with each component independently modulated and directed at the target. This allows different wavelength components to optimize measurements for different layers or target types, improving measurement precision while maintaining manageable system complexity through modular beam processing
Solution Approach 2:
The system changes the wavelength parameter of the measurement radiation by splitting the beam into multiple wavelength components. Each wavelength component can be independently selected and modulated to match the optimal wavelength for specific target layers or structures, thereby improving measurement precision across varied targets
2Productivity
If multiple wavelengths are used simultaneously, then the productivity increases by reducing measurement time, but the device complexity increases
Solution Approach 1:
The system merges multiple wavelength components into a single measurement process, allowing simultaneous illumination of the target with multiple wavelengths. This combination enables parallel measurement of different target layers or features, significantly reducing total measurement time and improving productivity
Solution Approach 2:
The system applies periodic modulation to different wavelength components at distinct frequencies. This periodic modulation allows the detection system to distinguish between different wavelength components through frequency discrimination, enabling simultaneous multi-wavelength measurement while maintaining signal integrity
3Measurement precision
If dark field scatterometry is used for small targets, then the measurement precision improves for sub-10 μm targets, but the device complexity increases due to additional optical components
Solution Approach 1:
The system applies dark field detection specifically to the scattered radiation components from small targets, using localized modulation and detection strategies optimized for sub-10 μm target dimensions. This targeted approach improves measurement precision for small targets while concentrating optical complexity only where needed for the specific measurement task
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 allows for high-quality, efficient measurements by optimizing the wavelength for each individual layer, enhancing the robustness of overlay measurements and reducing measurement time, thereby increasing fabrication productivity and accuracy.
Implementation Method 1
a first optical system configured to split an input radiation beam into a plurality of components
Implementation Method 2
a modulator configured to receive the plurality of components and apply a modulation to at least one of the components independently of at least one other of the components
Implementation Method 3
a second optical system configured to illuminate a target with the plurality of components and direct radiation scattered by the target to a detection system
Data Source
AI summary
A measurement system is disclosed in which a first optical system splits an input radiation beam into a plurality of components. A modulator receives the plurality of components and applies a modulation to at least one of the components independently of at least one other of the components. A second optical system illuminates a target with the plurality of components and directs radiation scattered by the target to a detection system. The detection system distinguishes between each of one or more components, or between each of one or more groups of components, of the radiation directed to the detection system based on the modulation applied to each component or each group of components by the modulator.