Hybrid MEMS-FG Device for Secure Fingerprint Sensing
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Solution Overview
Problem
Conventional fingerprint sensors face challenges such as high cost, complexity, humidity dependence, static electricity interference, and insecure data transmission, along with issues related to precise readout timing and distinguishing between real and phantom fingerprints.
Innovation Solution
A hybrid Micro-Electro-Mechanical-System-Floating-Gate (MEMS-FG) device with an electrically isolated non-volatile memory structure, where the polysilicon gate is connected to a fixed electrode of a normally-open MEMS switch, allowing direct-to-NVM storage of actuation data and secure encryption of fingerprint data for transmission.
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 simple capacitive sensing system that measures impedance changes directly through sensor plates, achieving accurate fingerprint detection without optical components
Solution Approach 2:
The patent uses a cost-effective capacitive sensor design with simple sensor plates that can be easily manufactured and replaced, providing an economical alternative to expensive optical sensors while maintaining sufficient accuracy for fingerprint identification
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 introduces a dielectric layer as an intermediary between the sensor plate and the environment, which protects the capacitive sensor from humidity and static electricity interference while allowing the sensing function to operate reliably under varying environmental conditions
Solution Approach 2:
The patent modifies the electrical parameters of the capacitive sensor by adjusting the dielectric properties and capacitance values to optimize performance, enabling the sensor to maintain reliable operation across different humidity levels and electromagnetic environments
3Reliability
If thick dielectric layers are used to protect capacitive sensors from static electricity, then reliability is improved, but measurement precision deteriorates due to reduced sensitivity
Solution Approach 1:
The patent optimizes the dielectric layer parameters (thickness, material properties, capacitance value) to achieve a balance between protection and sensitivity, selecting specific dielectric constants and thickness ranges that provide adequate static electricity protection while maintaining sufficient electrical field penetration for accurate fingerprint ridge detection
4Ease of operation
If conventional FP sensors are used without encryption, then ease of operation is maintained, but security deteriorates due to insecure data transmission
Solution Approach 1:
The patent implements self-service security by automatically encrypting fingerprint data at the sensor level using integrated encryption circuitry, so that data is protected during transmission without requiring additional operational steps or user intervention, maintaining simplicity while enhancing security
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 enables cost-effective, high-resolution fingerprint sensing with immunity to humidity and static electricity, and secure data transfer, eliminating the need for precise readout timing and improving the distinction between real and phantom fingerprints.
Implementation Method 1
an electrically isolated non-volatile memory structure operably formed by fixedly electrically connecting the polysilicon gate structure of a non-volatile memory cell to a fixed electrode of a normally-open, ohmic-contact-type MEMS switch
Implementation Method 2
contact of the moving electrode with the fixed electrode couples the electrically isolated structure to ground (or another suitable voltage potential), whereby any charge stored on electrically isolated structure is discharged
Data Source
AI summary
A hybrid Micro-Electro-Mechanical-System-Floating-Gate (MEMS-FG) device includes an electrically isolated non-volatile memory (floating) structure including a polysilicon gate structure connected by a metal via to a fixed electrode, where the polysilicon gate structure also forms the gate of an NVM cell, and the fixed electrode forms part of a lever-type or membrane-type ohmic MEMS switch. An initial charge is written before each sensing operation onto the floating structure by way of the NVM cell. During each sensing operation, sensor data is effectively written directly onto the NVM cell by way of either maintaining or discharging the initial charge, where discharge of the initial charge occurs when a predetermined event (e.g., contact by a fingerprint ridge) produces an actuating force that biases a movable electrode of the MEMS switch against the fixed electrode. The sensor data is read out from the NVM cell after each sensing operation.