GaN LED Fingerprint Sensor Integration via Trench Formation
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Solution Overview
Problem
Existing papillary impression sensors face challenges in aligning gallium nitride LEDs with photo-detectors, limiting their use due to precise alignment requirements, which are exacerbated in sensors with interlaced light-emitting devices and matrix photo-detectors.
Innovation Solution
A manufacturing method that allows for the production of gallium nitride LEDs with high alignment precision by forming trenches in an active stack on a substrate receiving control circuits, enabling interlacing with photo-detectors without overlap, and using CMOS technology to minimize control circuit size and optimize LED distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gallium nitride LEDs are positioned around the image sensor using conventional transfer methods, then the sensor can be manufactured, but alignment precision deteriorates due to the complexity of aligning multiple components (LEDs and photo-detectors)
Solution Approach 1:
The patent combines the LED array and photo-detector matrix into a single integrated structure where both components are formed on the same substrate. This merging eliminates the need for separate transfer and alignment operations, directly resolving the contradiction between achieving high alignment precision and managing assembly complexity.
Solution Approach 2:
The patent establishes reference marks and alignment structures during the initial substrate preparation phase, before the actual LED and photo-detector formation. This preliminary action ensures that subsequent components can be precisely positioned relative to each other without requiring complex real-time alignment procedures.
2Area of stationary object
If the pixel pitch is reduced to minimize sensor dimensions, then the sensor size decreases, but alignment precision requirements increase
Solution Approach 1:
The patent incorporates the vertical dimension by forming LEDs and photo-detectors at different depths within the substrate structure. This three-dimensional arrangement allows for smaller lateral pitch while maintaining adequate separation and alignment tolerance, effectively reducing the overall sensor footprint without compromising alignment precision.
3Measurement precision
If gallium nitride LEDs are used for high efficiency and small pixel pitch, then electrical consumption decreases and detection precision improves, but the alignment difficulty increases tenfold
Solution Approach 1:
The patent introduces intermediary alignment structures and reference marks that mediate between the LED positions and photo-detector positions. These intermediaries provide a common reference framework that simplifies the alignment process while enabling the precise positioning required for high-performance gallium nitride LED operation.
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 the creation of highly sensitive papillary impression sensors with gallium nitride LEDs at small pixel pitches, reducing sensor dimensions while maintaining performance and minimizing electrical consumption, and allowing for the detection of living tissue.
Implementation Method 1
papillary impression sensor comprising one or more gallium nitride LEDs, in particular one or more gallium nitride LEDs interlaced with the photo-detectors of a matrix photo-detector
Implementation Method 2
a matrix photo-detector, in particular a matrix photo-detector interlaced with the one or more gallium nitride LEDs
Data Source
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AI summary
The invention relates to a fingerprint sensor (100), comprising a light-emitting device and a matrix photodetector, distributed together in and/or above the same semiconductor substrate (110). According to the invention, the light-emitting device consists of at least one gallium nitride LED (140). This provides a fingerprint sensor in which the light-emitting device can occupy only a small area on the substrate, while still offering high illumination power. In an advantageous embodiment, a pyroelectric material is inserted between the gallium nitride LEDs to form the pixels of a thermal fingerprint sensor.