Finger Biometric Sensor With Distributed Thin Film And Monocrystalline Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fingerprint sensors face challenges in reducing cost and size while maintaining performance, as smaller component geometries do not significantly reduce sensor die size or cost, and sliding sensors are prone to image distortion and inconvenient user paradigms.
Innovation Solution
A finger biometric sensor design utilizing a thin film substrate with a TFT layer and electric field sensing electrodes, combined with a monocrystalline integrated circuit for processing circuitry, allowing for low-cost production and effective imaging without the need for a large semiconductor substrate, and incorporating multiplexing techniques for efficient signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard CMOS integrated circuits are used on monocrystalline silicon substrates, then high-quality fingerprint sensing is achieved, but fabrication cost increases and die size becomes large
Solution Approach 1:
The patent divides the sensor into two separate substrates: a first substrate containing sensing electrodes and a second substrate containing signal conditioning electronics. This segmentation allows each substrate to be optimized independently - the sensing substrate can use cost-effective thin-film technology while the electronics substrate uses high-performance CMOS, resolving the contradiction between sensing quality and fabrication cost
Solution Approach 2:
The patent introduces an intermediary bonding interface between the first substrate (sensing electrodes) and the second substrate (electronics). This intermediary connection allows the two different substrate types to work together, enabling high-quality sensing without requiring the entire sensor to be fabricated on expensive monocrystalline silicon
2Device complexity
If smaller component geometries are used, then circuit size is reduced, but fingerprint sensor die size does not reduce significantly
Solution Approach 1:
The patent transitions from a planar single-substrate layout to a three-dimensional stacked architecture with two substrates bonded together. This dimensional change allows the sensing electrodes and electronics to occupy different spatial layers, effectively reducing the footprint area while maintaining all necessary circuit functions
3Area of stationary object
If sliding sensors are used to image larger skin areas, then sensor size can be smaller, but image distortion increases and user convenience decreases
Solution Approach 1:
The patent makes the sensor flexible and adaptable by allowing it to conform to different finger placements (both stationary and sliding). The separated substrate design with bonding interface provides mechanical flexibility, enabling the sensor to maintain image quality whether the finger is stationary or moving across the sensor surface
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
The solution enables the creation of a low-cost, high-quality fingerprint sensor that can generate accurate images with a small geometry, reducing costs and minimizing image distortion, while maintaining effective performance for both stationary and sliding finger placements.
Implementation Method 1
Capacitances resulting from individual finger surface portions in combination with sense electrodes are sensed by the sense circuit
Implementation Method 2
RF electric fields to develop an electronic representation of the fingerprint pattern
Data Source
AI summary
A finger biometric sensor may include a thin film substrate, a thin film transistor (TFT) layer on the thin film substrate, and an array of electric field sensing electrodes adjacent the TFT layer for receiving a finger adjacent thereto. The TFT layer may include a plurality of TFTs defining a respective TFT amplifier stage for each electric field sensing electrode. The sensor may further include a finger excitation electrode adjacent the array of electric field sensing electrodes, and at least one integrated circuit adjacent the thin film substrate. The integrated circuit may include a monocrystalline substrate and processing circuitry adjacent the monocrystalline substrate and connected to the TFT amplifier stages.