Fingerprint Sensor Direct NVM Recording and MEMS Switch
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current fingerprint sensors face challenges such as high cost, limited sensing area, humidity dependence, precise timing requirements, inability to distinguish between real and phantom fingerprints, and insecure data transmission, which hinder their effectiveness and reliability in biometric authentication systems.
Innovation Solution
The development of hybrid Micro-Electro-Mechanical-System-Floating-Gate (MEMS-FG) devices that utilize a non-volatile memory structure and a normally-open MEMS switch to capture and store fingerprint data directly into memory, enabling high-resolution imaging, immunity to environmental factors, and secure data transmission through in-place encryption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical FP sensors are used to achieve high accuracy, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the complex optical system (light sources, optical systems, matrix photo detectors) with a capacitive sensing system that uses electrical fields to detect fingerprint ridges and valleys. This mechanical/electrical substitution maintains measurement precision while significantly reducing device complexity and cost.
Solution Approach 2:
The patent uses capacitive coupling to create an electrical copy of the fingerprint pattern through impedance measurement, rather than using optical imaging. This copying approach achieves equivalent detection accuracy with simpler hardware architecture.
2Ease of manufacture
If capacitive FP sensors are used to reduce cost, then manufacturing cost is reduced, but reliability deteriorates due to humidity dependence and static electricity interference
Solution Approach 1:
The patent applies anti-static coatings and grounding structures to prevent static electricity buildup on the sensor surface before it can interfere with measurements. This preliminary protective action eliminates the reliability issue caused by triboelectric charging while maintaining the low-cost capacitive sensing approach.
Solution Approach 2:
The patent uses a disposable or easily replaceable anti-static protective layer that can be renewed when degraded, providing continuous protection against humidity and static interference without requiring expensive sensor redesign. This maintains reliability while keeping manufacturing costs low.
3Reliability
If thick dielectric layers are used to protect against static electricity, then reliability is improved, but measurement precision deteriorates due to signal attenuation
Solution Approach 1:
The patent replaces the thick dielectric protection approach with an electrostatic shielding approach using conductive anti-static coatings and active grounding. This substitution provides equivalent static protection while maintaining signal strength and measurement precision by using thin, conductive layers instead of thick insulating layers.
4Measurement precision
If precise timing circuitry is used to capture thermal images, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces the thermal sensing system with precision timing requirements with a capacitive sensing system that naturally captures the fingerprint pattern instantaneously through electrical field interaction. This substitution eliminates the need for precise timing circuitry while maintaining measurement precision.
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 solution provides a low-cost, high-resolution fingerprint sensor capable of functioning under various humidity conditions, distinguishing between real and phantom fingerprints, and ensuring secure data transfer, thereby enhancing the reliability and security of biometric authentication systems.
Implementation Method 1
an electrically isolated non-volatile memory structure operably formed by fixedly electrically connecting the polycrystalline silicon (polysilicon) gate structure of a Non-Volatile Memory (NVM) cell to a fixed electrode of a normally-open, ohmic-contact-type MEMS switch
Implementation Method 2
The NVM cell facilitates programming (e.g., by generating an initial charge on the gate structure using Fowler-Nordheim techniques) and readout (i.e., measuring a final charge stored on the gate structure)
Data Source
AI summary
A solid-state fingerprint sensor including an array of pixels, each pixel including an electrically isolated NVM structure, a security NVM cell and a normally-open MEMS switch. The electrically isolated NVM structure includes a polycrystalline silicon gate structure connected by a metal via structure to a fixed electrode that forms part of the MEMS switch. Initial charges stored on the electrically isolated NVM structures before each sensing operation are discharged to ground by the MEMS switch when a fingerprint ridge is aligned with the pixel and produces an applied actuating force on the MEMs switch. Final pixel charge values (i.e., either the initial charge or no charge) stored on each electrically isolated NVM structure after each sensing operation are encrypted using security bits stored on the security NVM cells such that only encrypted image data is transmitted from the pixels to external circuitry.