Back Focal Plane Microscopy for Isolated Feature Characterization
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Solution Overview
Problem
Current optical metrology techniques face challenges in accurately characterizing isolated features on semiconductor wafers due to weak signal strength and background interference, particularly when measuring nanometer-scale structures, as they often overwhelm the signal from the feature of interest.
Innovation Solution
The implementation of Back Focal Plane Microscopy (BFM) in dark-field detection mode with pinhole masking, which allows for efficient focusing and isolation of the measurement spot, enabling the detection of scattering properties and characterization of isolated features by analyzing the scattering matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical metrology is applied to isolated features, then measurement capability is provided, but signal strength is weak and background interference overwhelms the signal
Solution Approach 1:
The patent segments the measurement process into distinct angular components using a position-sensitive detector that resolves reflected light by angle of incidence. By separating the measurement into angular segments, the system can identify and isolate the specific angular signature of the isolated feature from the background, enhancing measurement precision while filtering out overwhelming background interference.
Solution Approach 2:
The patent transitions from conventional spatial detection to angular space detection by using a position-sensitive detector that maps reflected light positions to angles of incidence. This dimensional transformation from real space to angular space allows the system to distinguish isolated features based on their unique angular scattering patterns, resolving the contradiction between detecting weak signals and filtering background noise.
2Power
If a measurement spot covers many identical elements, then strong reflected signals are obtained, but the isolated feature characteristics are lost
Solution Approach 1:
The patent resolves this contradiction by transforming the detection domain from real space to angular space. Even when a measurement spot covers multiple elements, the position-sensitive detector resolves the reflected light by angle of incidence, revealing the unique angular scattering signature of isolated features that differs from periodic structures. This angular dimension preservation allows simultaneous acquisition of strong signals and isolated feature characteristics.
Solution Approach 2:
The patent applies local quality by focusing the measurement on specific angular regions characteristic of isolated features. The system identifies and analyzes light reflected at specific angles that are unique to isolated feature scattering patterns, thereby extracting isolated feature information even from measurements that include multiple elements in the illumination spot.
3Manufacturing precision
If optical metrology is applied to nanometer-scale isolated structures, then feature measurement is enabled, but signal strength becomes significantly weaker
Solution Approach 1:
The patent compensates for weak signals from nanometer-scale features by transforming the detection to angular space using a position-sensitive detector. The angular resolution allows the system to identify and integrate signal components specific to nanoscale feature scattering patterns, effectively enhancing the detectability of weak signals while maintaining measurement capability for sub-wavelength dimensions.
Solution Approach 2:
The patent replaces conventional intensity-based detection with angular-resolved detection. Instead of relying on signal intensity alone, the system uses the angular distribution of reflected light as the primary measurement parameter, substituting the mechanical/intensity detection approach with an optical angular analysis approach that is more sensitive to nanoscale features.
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 significantly enhances signal-to-noise ratio (SNR) by isolating reflections from the feature of interest, providing accurate characterization of isolated features with high precision, even at sub-wavelength dimensions.
Implementation Method 1
Back Focal Plane Microscopy (BFM) measurements are applied to a structure... performing dark-field detection mode while applying pinhole masking to incident light propagating through an illumination channel towards the structure
Implementation Method 2
The pinhole mask... enables angular resolution of reflected light
Implementation Method 3
processing the measured data and obtaining data characterizing scattering of said incident light from an illuminated spot on the structure
Implementation Method 4
a position-sensitive detector is provided which resolves reflected light by angle of incidence
Data Source
AI summary
An optical method and system are presented for use in measurement of isolated features of a structure. According to this technique, Back Focal Plane Microscopy (BFM) measurements are applied to a structure and measured data indicative thereof is obtained, wherein the BFM measurements utilize dark-field detection mode while applying pinhole masking to incident light propagating through an illumination channel towards the structure, the measured data being thereby indicative of a scattering matrix characterizing scattering properties of the structure, enabling identification of one or more isolated features of the structure.