Fingerprint Sensor Electrode Protrusions for Sensitivity
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Solution Overview
Problem
Existing semiconductor capacitive fingerprint sensors suffer from low sensitivity due to small differences in capacitance values at ridges and valleys of fingerprints, and insufficient protection of the electrode layer by the dielectric structure, which affects the accuracy and sensitivity of fingerprint acquisition.
Innovation Solution
A method for fabricating fingerprint sensors involving a base substrate with pixel regions, forming a sensing dielectric structure and connection structure, creating electrode plates with protrusions through a bulging treatment process, and forming an insulation medium structure to increase capacitance values and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dielectric structure thickness is increased to protect the electrode layer, then the reliability is improved, but the capacitance values decrease resulting in lower sensitivity
Solution Approach 1:
The electrode layer is transformed from a flat structure to a three-dimensional protruding structure with spherical or hemispherical tops. This curvature increases the surface area of the electrode layer that interacts with the finger, thereby increasing capacitance values and sensitivity without requiring a thinner dielectric layer for protection.
2Measurement precision
If the electrode layer surface area is increased to improve capacitance values, then the sensitivity is improved, but the device complexity increases
Solution Approach 1:
The shape parameter of the electrode layer is changed from flat to protruding with controlled height and radius. By optimizing these geometric parameters, the patent achieves increased surface area and capacitance values while maintaining manufacturing feasibility and avoiding excessive structural complexity.
3Measurement precision
If the distance between ridges and electrode layer is decreased to improve sensitivity, then the measurement precision is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The protruding spherical or hemispherical shape of the electrode layer creates a more favorable geometric relationship with the finger ridges. This curvature naturally optimizes the interaction distance and contact area between the electrode layer and ridges, improving sensitivity while reducing the stringency of manufacturing precision requirements compared to flat electrode designs.
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 method enhances the sensitivity of fingerprint sensors by increasing the surface area of electrode plates, improving the accuracy of fingerprint acquisition by increasing capacitance values without affecting the distance differences between ridges and valleys, thus improving the overall performance.
Implementation Method 1
The semiconductor capacitive sensors mainly utilize capacitors to acquire fingerprints... the actual distances for the finger to make contact with the plate may be different at the ridge positions as compared to at the valley positions, resulting in different capacitance values at different positions of the fingerprint
Data Source
AI summary
A fingerprint sensor includes: a base substrate including a plurality of pixel regions; a sensing dielectric structure formed on the base substrate in the pixel regions; and a sensing connection structure formed in the sensing dielectric structure. The sensing dielectric structure exposes the sensing connection structure and the sensing connection structure is connected to the base substrate. The fingerprint sensor further includes a plurality of electrode plates formed on surfaces of the sensing dielectric structure and the sensing connection structure. A plurality of protrusions are formed on surfaces of the electrode plates. The fingerprint sensor further includes an insulation medium structure formed on the plurality of electrode plates.