Scanning Probe Microscope Array Ultrasonic Sub-Surface Imaging
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Solution Overview
Problem
Existing scanning probe microscopy systems face challenges in accurately detecting sub-surface features in semiconductor samples due to low signal-to-noise ratio (SNR) and limitations in mechanical properties and optical accessibility.
Innovation Solution
The method involves emitting multiple plane waves at different angles using an array of probes in a scanning probe microscopy system, which significantly enhances the signal-to-noise ratio (SNR) and allows for more accurate imaging of sub-surface features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ultrasound imaging methods are used at GHz to THz frequencies, then sub-surface imaging capability is provided, but the signal-to-noise ratio becomes low making imaging difficult
Solution Approach 1:
The invention divides the imaging process into multiple sequential plane wave transmissions at different angles. Each plane wave provides a partial view of the sub-surface, and by combining multiple angled views, the system achieves high-resolution imaging with improved signal-to-noise ratio. This segmentation of the imaging process allows accurate detection of sub-surface features without requiring high-frequency single-shot ultrasound that would suffer from low SNR.
2Measurement precision
If optical methods are used for surface scanning, then high surface resolution is achieved, but detection of sub-surface features is limited by opaque layers
Solution Approach 1:
The invention merges the advantages of optical methods (high surface resolution through scanning probe microscopy) with acoustic methods (sub-surface penetration capability). The same scanning probe that provides high-resolution surface topography is also used to transmit and detect plane waves for sub-surface imaging. This combination allows the system to maintain high surface resolution while gaining the ability to detect sub-surface features through opaque layers that would block optical methods alone.
3Device complexity
If a single probe is used for scanning, then device simplicity is maintained, but measurement speed and productivity are limited
Solution Approach 1:
The invention uses periodic transmission of plane waves at multiple different angles in sequence. Rather than using multiple probes simultaneously (which would increase complexity), the system periodically switches between different transmission angles, with each angle providing complementary information about sub-surface features. This periodic multi-angle scanning approach maintains single-probe simplicity while achieving comprehensive sub-surface characterization that would otherwise require multiple probes operating in parallel.
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 enables improved sub-surface characterization and defect detection in semiconductor samples by enhancing the SNR and allowing for the accurate measurement of dimensions such as depth, size, height, and width of subsurface features.
Implementation Method 1
successive measurements in which the cantilevers are vibrated for emitting successive ultrasonic tilted planar waves in the sample
Implementation Method 2
a corresponding return signal is retrieved by means of the cantilevers in response to said emitted ultrasonic tilted planar waves
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3(a)~3(b)
AI summary
A method and system for performing sub-surface measurements on a sample, the system being a scanning probe microscope comprising a sensor head including an array of probes with a plurality of probes each comprising a cantilever and a probe tip arranged on the cantilever. The system is configured to perform the steps of: moving the array of probes towards a surface of the sample for enabling contact between the probe tips of the array of probes and the surface, and performing successive measurements in which the cantilevers are vibrated for emitting successive ultrasonic tilted planar waves in the sample, and a corresponding return signal is retrieved by means of the cantilevers in response to said emitted ultrasonic tilted planar waves, and wherein the planar waves are emitted consecutively at a plurality of different angles of inclination with respect to the surface of the sample.