Metrology Illumination Bandwidth Optimization for Photon Incidence
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Solution Overview
Problem
As targets in lithographic processes become smaller, ensuring sufficient illumination for measurement becomes challenging, leading to increased measurement time due to reduced photon incidence, which affects measurement quality and signal-to-noise characteristics.
Innovation Solution
A method is introduced to optimize the bandwidth of measurement illumination by performing reference measurements with a narrow bandwidth, comparing these to measurements with varied bandwidths, and selecting an optimal bandwidth that balances photon incidence with measurement quality, using a processor to adjust the bandwidth for each application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the target size is reduced to maximize space on the wafer, then the area occupied by targets decreases, but the number of photons incident on the target per second decreases leading to increased measurement time
Solution Approach 1:
The patent changes the bandwidth parameter of the measurement illumination to optimize the number of photons incident on the target. By increasing the bandwidth, more photons are available for measurement, which compensates for the reduced target area and maintains acceptable measurement time despite the smaller target size.
2Quantity of substance
If the bandwidth of measurement illumination is increased to provide more photons, then the number of photons incident on the target increases, but the measurement quality may deteriorate
Solution Approach 1:
The patent implements dynamic adjustment of the illumination bandwidth based on the specific measurement application. The system can vary the bandwidth parameter to optimize between photon quantity and measurement quality requirements for different measurement scenarios, rather than using a fixed bandwidth setting.
Solution Approach 2:
The patent systematically varies the bandwidth parameter to find the optimal value that balances photon quantity and measurement quality. By performing optimization measurements with different bandwidths and comparing them to reference measurements, the system identifies the bandwidth that provides sufficient photons while maintaining acceptable measurement quality.
3Device complexity
If a fixed bandwidth is used for all measurement applications, then the device complexity is reduced, but the ability to optimize for different measurement requirements is limited
Solution Approach 1:
The patent introduces dynamic bandwidth adjustment capability to the illumination system, allowing the bandwidth parameter to be changed based on different measurement applications. This dynamic control enables the system to adapt to various measurement requirements while maintaining a relatively simple overall device architecture.
Data Source
AI summary
Disclosed is method of optimizing bandwidth of measurement illumination for a measurement application, and an associated metrology apparatus. The method comprises performing a reference measurement with reference measurement illumination having a reference bandwidth and performing one or more optimization measurements, each of said one or more optimization measurements being performed with measurement illumination having a varied candidate bandwidth. The one or more optimization measurements are compared with the reference measurement; and an optimal bandwidth for the measurement application is selected based on the comparison.