Metrology Apparatus with Dispersive Lens Array for Multi-Wavelength Lithography
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Solution Overview
Problem
Conventional metrology apparatuses in lithographic processes can only perform measurements using a single wavelength of measurement radiation, which limits measurement quality due to varying behavior of targets across different wavelengths and processing-induced changes, especially when measuring smaller targets surrounded by product features.
Innovation Solution
A metrology apparatus with an optical system that illuminates structures with measurement radiation comprising multiple non-overlapping wavelength bands, using a dispersive element to direct scattered radiation onto an array of lenses, allowing simultaneous detection of radiation in different wavelength bands, thereby optimizing wavelength selection for each layer and improving measurement robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single wavelength of measurement radiation is used, then the measurement process is simple, but measurement quality deteriorates due to varying target behavior across wavelengths and processing-induced changes
Solution Approach 1:
The measurement radiation is divided into multiple discrete wavelength bands (e.g., blue, cyan, green, yellow-green, yellow, orange) that are simultaneously directed onto different lenses of a lens array. Each wavelength band is processed separately through its dedicated lens, enabling independent optimization for different target layers while maintaining a unified measurement system.
Solution Approach 2:
The patent transitions from single-wavelength measurement to multi-wavelength measurement by adding the wavelength dimension. Multiple wavelengths are simultaneously measured across different lenses, creating a spectral dimension that enables optimized measurement for each layer without increasing sequential measurement time.
2Measurement precision
If multiple wavelengths are measured sequentially, then measurement quality can be optimized for each layer, but measurement time increases and productivity decreases
Solution Approach 1:
Multiple wavelength measurements are merged into a single simultaneous measurement process. The lens array directs different wavelength bands onto different lenses that all capture data at the same time, combining the benefits of wavelength-specific optimization with the efficiency of parallel processing.
Solution Approach 2:
The measurement system operates continuously by simultaneously capturing data across multiple wavelength bands in a single measurement event. There is no idle time between wavelength measurements since all wavelengths are measured in parallel, maintaining continuous productive action throughout the measurement process.
3Productivity
If a lens array with multiple lenses is used to simultaneously measure multiple wavelengths, then measurement efficiency improves, but device complexity increases
Solution Approach 1:
The lens array serves multiple functions simultaneously: it focuses different wavelength bands onto different lenses, enables parallel wavelength measurement, and maintains a compact integrated structure. This multi-functional design achieves high measurement efficiency without proportionally increasing system complexity.
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
Enables high-quality, efficient measurements by allowing simultaneous multilayer overlay measurements with optimal wavelength selection for each target, enhancing measurement accuracy and productivity by reducing the need for individual wavelength tuning and improving robustness against process variations.
Implementation Method 1
a dispersive element configured to direct scattered measurement radiation in each of a plurality of non-overlapping wavelength bands exclusively onto a different respective lens of the array of lenses
Implementation Method 2
an array of lenses configured to focus the scattered measurement radiation onto a sensor
Implementation Method 3
an optical system configured to illuminate the structure with measurement radiation and detect the measurement radiation scattered by the structure
Data Source
AI summary
Metrology apparatus and methods are disclosed. In one arrangement, a metrology apparatus comprises an optical system that illuminates a structure with measurement radiation and detects the measurement radiation scattered by the structure. The optical system comprises an array of lenses that focuses the scattered measurement radiation onto a sensor. A dispersive element directs scattered measurement radiation in each of a plurality of non-overlapping wavelength bands exclusively onto a different respective lens of the array of lenses.