Spectral Control System for Optical Metrology
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Solution Overview
Problem
Current optical metrology systems face limitations in spectral control due to a limited choice of spectral structures, which restricts measurement potential and precision, especially with modern targets requiring narrower spectral bands for accurate feature measurement.
Innovation Solution
A spectral control system comprising a dispersion path with dispersive elements and a spectral controller that disperses illumination into multiple spectral bands, allowing for selective filtering and recombination into coaxial illumination, enabling flexible spectral control through multiple paths and optical switches for enhanced configurability and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If filters are used to select spectral bands, then spectral control is achieved, but the number of available spectral structures is limited
Solution Approach 1:
The illumination spectrum is segmented into multiple discrete spectral bands using dispersive elements (prisms or gratings), which separate the continuous spectrum into distinct wavelength components. This segmentation enables independent control of each spectral band through spectral controllers, dramatically increasing the number of available spectral structures from a few to many possibilities.
Solution Approach 2:
The system employs dynamic spectral control where the spectral bands can be selectively transmitted or blocked in real-time based on measurement requirements. Optical switches and programmable spectral controllers enable dynamic reconfiguration of the spectral composition, allowing the system to adapt to different measurement tasks without physical reconfiguration.
2Measurement precision
If broader spectral bands are used, then measurement coverage is improved, but precision deteriorates due to reduced spectral resolution
Solution Approach 1:
By segmenting the illumination spectrum into multiple narrow, discrete spectral bands using dispersive elements, the system achieves high spectral resolution while maintaining the ability to select from multiple bands. Each spectral band can be independently controlled, allowing precise spectral measurement while providing flexibility in band selection for different measurement applications.
3Adaptability or versatility
If multiple spectral control paths are implemented, then configurability is improved, but device complexity increases
Solution Approach 1:
The spectral control system uses universal components (dispersive elements, spectral controllers, optical switches) that can be configured in multiple paths to achieve different spectral control functions. The same basic components serve multiple purposes: dispersion, selection, combination, and dynamic switching, reducing the need for separate dedicated components for each function.
Solution Approach 2:
The system pre-configures multiple spectral control paths with predetermined spectral characteristics, allowing rapid selection and switching between different spectral configurations. This preliminary configuration enables complex spectral control capabilities to be achieved through simple switching actions rather than complex real-time calculations or reconfiguration.
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 system enhances measurement sensitivity and accuracy by allowing for precise selection and control of spectral attributes, enabling improved angular and spectroscopic scatterometry measurements with increased resolution and reduced precision penalties, and potentially replacing spectrometers with simpler detectors.
Implementation Method 1
One or more dispersive elements disposed along a dispersion path are configured to receive at least a first portion of illumination directed along the dispersion path from at least one illumination source. The dispersive elements are further configured to disperse the first portion of the illumination into a first plurality of dispersed portions of illumination.
Implementation Method 2
One or more combination elements disposed along the combination path are configured to combine the transmitted selection of the first plurality of dispersed portions of illumination into substantially coaxial illumination directed along an illumination path.
Data Source
AI summary
The disclosure is directed to a system and method of controlling spectral attributes of illumination. According to various embodiments, a portion of illumination including an excluded selection of illumination spectra is blocked, while another portion of the illumination including a transmitted selection of illumination spectra is directed along an illumination path. In some embodiments, optical metrology is performed utilizing the spectrally controlled illumination to enhance measurement capability. For instance, the spectral attributes of illumination utilized to analyze different portions of a sample, such as different semiconductor layers, may be selected according to certain measurement characteristics associated with the analyzed portions of the sample.