Shielding Electrode Stabilizes Sensing Current in Display Fingerprint Sensors
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Solution Overview
Problem
Display devices face challenges in maintaining a stable sensing current for fingerprint authentication due to voltage changes in adjacent signal lines, which cause parasitic capacitance between the light sensor transistor and signal lines, leading to inaccurate fingerprint recognition.
Innovation Solution
The implementation of a shielding electrode structure around the gate electrode of the sensing transistor, including multiple shielding portions, minimizes parasitic capacitance by shielding voltage changes from adjacent signal lines, thereby stabilizing the sensing current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light sensor transistor is placed close to the light sensing element to minimize sensing current variation, then the sensing accuracy is improved, but the parasitic capacitance between the transistor and adjacent signal lines increases causing voltage changes that degrade sensing stability
Solution Approach 1:
A shielding electrode is introduced as an intermediary component between the light sensor transistor and adjacent signal lines. This shielding electrode acts as a mediator that blocks the harmful electromagnetic coupling, preventing voltage changes in signal lines from affecting the transistor's gate voltage and thus maintaining sensing stability while allowing the transistor to remain close to the light sensing element for high accuracy
2Measurement precision
If the gate electrode of the sensing transistor is positioned close to the light sensing element to improve sensing performance, then the light collection efficiency is improved, but the susceptibility to voltage changes from adjacent signal lines increases due to increased parasitic capacitance
Solution Approach 1:
The shielding electrode serves as a protective intermediary that allows the gate electrode to maintain its optimal position close to the light sensing element for high light collection efficiency, while simultaneously blocking the harmful voltage interference from adjacent signal lines by providing an electrostatic shield
3Reliability
If multiple shielding portions are added around the gate electrode to enhance protection from voltage changes, then the sensing stability is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The shielding electrode is segmented into multiple shielding portions, each positioned to protect against voltage changes from specific adjacent signal lines. This segmentation allows for targeted protection where needed while maintaining manufacturing feasibility by dividing the shielding function into discrete, manageable segments that can be fabricated using standard display manufacturing processes
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 effectively prevents changes in the sensing current caused by voltage changes in adjacent signal lines, enhancing the accuracy of fingerprint recognition and reducing noise signals, thus improving the reliability of fingerprint authentication.
Implementation Method 1
a light sensing element spaced apart from the light emitting element, the light sensing element that generates a photocurrent according to external light
Implementation Method 2
preventing or minimizing variation of a sensing current flowing through a transistor of a light sensor, which is caused by a voltage change of an adjacent signal line by minimizing parasitic capacitance between the transistor of the light sensor and the adjacent signal line
Data Source
AI summary
A display includes a light emitting element that emits light, a driving transistor that controls a driving current flowing through the light emitting element, a light sensing element spaced apart from the light emitting element and generating a photocurrent according to external light, a first sensing transistor that controls a sensing current flowing to a readout line according to a voltage of a gate electrode of the first sensing transistor, which is electrically connected to an electrode of the light sensing element, and a shielding electrode disposed around a side of the gate electrode of the first sensing transistor in plan view.