Ultrasonic Sensor Substrate Rear Surface Structuring
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Solution Overview
Problem
Ultrasonic sensors using active piezoelectric thin layers face interference from echoes generated by the carrier substrate, which reduces measurement accuracy, and existing solutions are either complex or not suitable for compact and flexible designs.
Innovation Solution
The rear surface of the ultrasonic sensor's carrier substrate is structured with needle-shaped elevations and depressions to cause diffuse scattering of ultrasonic waves, preventing echoes from interfering with the sensor unit, achieved through techniques like black silicon technology and reactive ion etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the carrier substrate is used directly without surface structuring, then the sensor design is simple, but disruptive echoes from the boundary layer reduce measurement accuracy
Solution Approach 1:
The patent applies surface structuring only to the rear side of the carrier substrate, creating needle-shaped elevations and depressions specifically at the echo-generating boundary layer interface, while leaving the front sensor surface unchanged. This localized modification suppresses disruptive echoes without affecting the overall sensor design simplicity
Solution Approach 2:
The patent introduces a new dimensional feature (surface relief structures) on the rear side of the substrate to address the echo problem. By creating three-dimensional needle-shaped elevations and depressions, the patent transforms the two-dimensional flat surface into a structured surface that scatters ultrasonic waves, thereby improving measurement accuracy without fundamentally redesigning the entire sensor
2Measurement precision
If the carrier substrate thickness is increased to suppress echoes, then measurement accuracy improves, but the sensor becomes less compact and flexible
Solution Approach 1:
Instead of increasing the overall substrate thickness, the patent creates localized surface structures (needle-shaped elevations and depressions) on the rear side of the substrate. These localized features scatter ultrasonic waves at the boundary layer interface, suppressing echoes without requiring increased substrate thickness, thereby maintaining sensor compactness
Solution Approach 2:
The patent introduces curved and irregular surface features (needle-shaped elevations and depressions) on the rear substrate surface. These non-planar structures cause diffuse scattering of ultrasonic waves, effectively suppressing echoes while maintaining a compact substrate thickness. The curved surface features create multiple reflection paths that prevent coherent echo formation
3Measurement precision
If air is used as the boundary layer to suppress echoes, then measurement accuracy improves, but the sensor design becomes less flexible for various applications
Solution Approach 1:
The patent creates surface structures specifically at the rear boundary layer interface where echoes are generated. This localized modification works with any boundary layer material (air, water, gel, etc.) and does not require the boundary layer to have specific acoustic properties, thereby maintaining application flexibility while improving measurement accuracy
Solution Approach 2:
The patent transforms the harmful echo-generating boundary layer interface into a beneficial echo-suppressing structure by adding surface relief features. Instead of trying to eliminate the boundary layer or use specific materials to suppress echoes, the patent uses the boundary layer interface itself as the location for echo suppression through surface structuring, making the previously harmful feature useful for a wide range of applications
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 effectively suppresses disruptive echoes, enhancing measurement accuracy and allowing for simpler, more compact, and flexible ultrasonic sensor designs suitable for active piezoelectric thin layers.
Implementation Method 1
The surface structure is designed in such a way that it causes diffuse scattering of the ultrasonic waves incident on the structured rear side from the direction of the sensor unit
Implementation Method 2
an ultrasonic sensor comprising a substrate and a piezoelectric sensor unit arranged on or on this substrate and/or connected to this substrate
Data Source
Figure 1
Figure 2
AI summary
The present invention relates to an ultrasonic sensor for detecting and/or scanning an object comprising a substrate and a piezoelectric sensor unit arranged on or attached to this substrate and/or connected to this substrate, characterized in that the rear side of the substrate facing away from the piezoelectric sensor unit has a surface structure comprising a plurality of protrusions and depressions, wherein this surface structure is designed such that it causes diffuse scattering of ultrasonic waves incident on the rear side from the direction of the sensor unit and/or that its protrusions and/or depressions have a mean lateral extent in the range of 0.05 µm to 1 mm, preferably from 0.1 µm to 200 µm, more preferably from 0.2 µm to 20 µm, and/or a mean lateral extent that is less than or equal to the wavelength of an ultrasonic wave that can be generated by the piezoelectric sensor unit.