On-the-Fly Opto-Acoustic Microscopy Using Fixed Pump-Probe Delay
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Solution Overview
Problem
Conventional opto-acoustic metrology systems are slow due to the need to vary time delays between pump and probe pulses at each measurement point, limiting throughput and acquisition time for detecting buried structures in samples.
Innovation Solution
Implementing a fixed time delay between pump and probe pulses, allowing for continuous scanning and signal acquisition without varying delays, using a multi-channel detector array and line-shaped illumination spots to detect buried structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If variable time delay between pump and probe pulses is used at each measurement point, then time resolved reflectance measurements can be obtained to detect buried structures, but measurement acquisition time increases significantly
Solution Approach 1:
The patent implements continuous scanning of the sample without discrete move/stop/acquire cycles. The pump and probe beams continuously scan across the sample surface while maintaining a fixed time delay, enabling uninterrupted data acquisition and eliminating idle time between measurements.
Solution Approach 2:
The patent establishes a fixed pump-probe time delay configuration before measurement begins, eliminating the need to dynamically adjust delays during scanning. This preliminary setup allows the system to proceed directly with continuous measurement without time-consuming delay variations at each point.
2Measurement precision
If discrete move/stop/acquire process is used at each measurement point, then detailed reflectance measurements can be obtained, but throughput decreases
Solution Approach 1:
The system performs continuous scanning and measurement without discrete stop-and-go cycles. The pump and probe beams move continuously across the sample while maintaining fixed time delay, enabling uninterrupted data acquisition that significantly improves throughput compared to discrete move/stop/acquire processes.
3Loss of time
If fixed time delay between pump and probe pulses is used, then measurement acquisition time is reduced, but ability to obtain time resolved reflectance measurements is compromised
Solution Approach 1:
The patent transitions from time-domain resolution (varying delays) to spatial-domain resolution (continuous scanning with fixed delay). By continuously scanning the sample with fixed pump-probe delay, the system captures spatial variations in reflectance that encode information about buried structures, effectively trading temporal resolution for spatial mapping capability.
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 reduces acquisition time by eliminating the need for discrete move/stop/acquire processes, enabling rapid detection and imaging of buried structures with improved throughput and sensitivity.
Implementation Method 1
Opto-acoustic metrology, in general, uses a pump beam and a probe beam with a varying time delay between light pulses in each of the pump and probe beams. The light pulses in the pump beam produce an acoustic response within the sample under test that propagates to the surface of the sample, which is detected by the probe beam.
Implementation Method 2
The acoustic response, for example affects the reflectivity of the material in the sample or deflection of the probe beam.
Data Source
AI summary
An opto-acoustic measurement device detects and images buried structures in a sample, such as voids or other underlying structures, using a fixed delay time between pulses in the pump beam and pulses in the probe beam, while continuously scanning the sample over multiple measurements locations. The signals acquired at a fixed pump-probe time delay from a plurality of measurements locations has sufficient information and sensitivity to discriminate the presence or absence of a buried structure, such as a void, inclusion or solid structure, in a sample. The pump and probe beams may be focused in a line shaped illumination spot that is oriented orthogonally to that direction of travel during the scan, and a multi-channel linear detector array may detect signals at a plurality of locations along the line shaped illumination spot. Non-acoustic transient perturbations may be detected using two fixed pump-probe delay times.