Lithographic Inspection Apparatus Using Multi-Configuration Target Measurements
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Solution Overview
Problem
Current lithographic processes face challenges in accurately monitoring focus and dose parameters due to the complexity of selecting suitable target geometries and the limitations of diffraction-based focus techniques, which often require sub-resolution features and large pitches that may contravene design rules.
Innovation Solution
A method involving acquiring first and second target measurements with varying measurement configurations, such as different wavelengths or polarization, to determine lithographic process parameters like focus and dose, using a first metric derived from these measurements, allowing for the use of conventional targets and obviating the need for specific DBF structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If diffraction-based focus techniques are used to monitor focus and dose parameters, then measurement capability is provided, but the method requires sub-resolution features and large pitches that may contravene design rules
Solution Approach 1:
The patent changes the measurement parameters by using multiple measurement configurations (different wavelengths, polarization states, or detection angles) to measure the same target. This allows conventional targets that comply with design rules to be measured effectively, eliminating the need for special sub-resolution features while maintaining measurement precision for focus and dose parameters
2Measurement precision
If asymmetry-based diffraction techniques are used to determine focus, then focus measurement is achieved, but complex target geometry selection is required to ensure desired asymmetry relationships
Solution Approach 1:
The patent creates a universal measurement method that works with conventional targets by using multiple measurement configurations. Instead of requiring specially designed asymmetric targets for each measurement type, the same target can be measured under different configurations (wavelengths, polarization, angles) to extract focus information, greatly simplifying target selection and design
Solution Approach 2:
By varying measurement parameters such as wavelength, polarization state, or detection angle between first and second measurements, the patent enables focus determination using conventional targets without requiring complex asymmetric geometries. The metric derived from comparing measurements under different parameters provides focus information while maintaining design rule compliance
3Reliability
If multiple measurements with different measurement configurations are performed, then reduced sensitivity to process and tool effects is achieved, but measurement time and complexity increase
Solution Approach 1:
The patent combines multiple measurements performed under different measurement configurations into a single integrated analysis. By measuring the same target with different wavelengths, polarization states, or detection angles and deriving a metric from the comparison, the method achieves reduced sensitivity to process and tool effects while minimizing the time penalty through efficient data processing and combined analysis
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 provides a robust and efficient method for monitoring focus and dose parameters, reducing sensitivity to process and tool effects, and eliminating the requirement for specific DBF structures, thereby improving the accuracy and consistency of lithographic processes.
Implementation Method 1
These devices direct a beam of radiation onto a target and measure one or more properties of the scattered radiation
Implementation Method 2
obtain a diffraction 'spectrum' from which a property of interest of the target can be determined
Implementation Method 3
wherein a first measurement is performed with a first wavelength and a second measurement is performed with a second wavelength
Data Source
AI summary
Disclosed is a method of monitoring a lithographic process parameter, such as focus and/or dose, of a lithographic process. The method comprises acquiring a first and a second target measurement using respectively a first measurement configuration and a second measurement configuration, and determining the lithographic process parameter from a first metric derived from said first target measurement and said second target measurement. The first metric may be difference. Also disclosed are corresponding measurement and lithographic apparatuses, a computer program and a method of manufacturing devices.