Fingerprint Sensor Circuit Layout for Low-Leakage Display Integration
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Solution Overview
Problem
Display devices face challenges in minimizing leakage current and improving sensitivity of fingerprint sensors, particularly in high-resolution structures with dense pixels, while also accommodating diverse design requirements.
Innovation Solution
A fingerprint sensor design incorporating specific transistor configurations and layer structures, including a shielding electrode and overlapping layers to minimize leakage current and enhance sensitivity, utilizing a phototransistor with a gate-source voltage greater than zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fingerprint sensor uses a conventional transistor configuration, then the device complexity is reduced, but the leakage current increases and sensitivity decreases
Solution Approach 1:
The fingerprint sensor divides the sensing function into multiple specialized transistors: a first sensor transistor for sensing, a second sensor transistor for resetting, a third sensor transistor for reading out, and a fourth sensor transistor for controlling leakage current. This segmentation allows each transistor to be optimized for its specific function, improving overall sensitivity while managing complexity through functional specialization.
Solution Approach 2:
The fourth sensor transistor acts as an intermediary component specifically designed to control leakage current flowing into the sensor node. By introducing this dedicated leakage control transistor, the patent achieves better sensitivity without requiring complete redesign of the entire sensor circuit,而是 adding a specialized intermediary element.
2Manufacturing precision
If the fingerprint sensor is integrated into high-resolution display with dense pixels, then the display quality is improved, but the leakage current of the fingerprint sensor increases
Solution Approach 1:
The patent applies local quality by giving the fourth sensor transistor specific electrical characteristics (gate-source voltage greater than zero) that are tailored to counteract the increased leakage current caused by high-resolution display integration. This localized optimization addresses the leakage problem specifically in the fingerprint sensor region without affecting the overall display performance.
Solution Approach 2:
The patent changes the electrical parameters of the fourth sensor transistor, specifically setting its gate-source voltage to be greater than zero. This parameter change enables the transistor to actively control and reduce leakage current, allowing the fingerprint sensor to maintain low leakage even when integrated into high-resolution displays with dense pixel structures.
3Reliability
If the fingerprint sensor uses more transistors to control leakage current, then the sensitivity is improved, but the device complexity increases
Solution Approach 1:
Each of the four sensor transistors is designed to perform multiple functions within its specific operational phase. For example, the first sensor transistor serves both as the primary sensing element and as part of the signal amplification chain. This multi-functionality reduces the need for additional dedicated components, thereby improving sensitivity while limiting the increase in overall device complexity.
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 design effectively reduces leakage current and enhances sensitivity of fingerprint sensors, even in high-resolution displays with dense pixels, thereby improving overall performance.
Implementation Method 1
a fourth sensor transistor comprising a gate electrode connected to a bias voltage line, a first electrode connected to the bias voltage line, and a second electrode connected to the sensor node
Data Source
AI summary
A fingerprint sensor comprises a read-out line disposed on a substrate and extending in a first direction, a first sensor transistor controlling a sensing current based on a voltage of a sensor node, a second sensor transistor supplying a reset voltage to the sensor node based on a reset signal, a third sensor transistor electrically connected a first electrode of the first sensor transistor and the read-out line based on a gate signal, and a fourth sensor transistor comprising a gate electrode connected to a bias voltage line, a first electrode connected to the bias voltage line, and a second electrode connected to the sensor node.