Optical Fingerprint Sensor Layout With an Inorganic Diffusion Barrier
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Solution Overview
Problem
In optical fingerprint sensors, impurities can enter thin-film transistors during the formation of photoelectric conversion elements and electrodes, reducing the reliability of these transistors.
Innovation Solution
A detection device is designed with an insulating substrate, photoelectric conversion elements, first switching elements, and an inorganic insulating layer placed between the photoelectric conversion elements and the first switching elements, which acts as a barrier to prevent impurities from diffusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photoelectric conversion elements and electrodes are formed into a film on an insulating substrate, then the optical fingerprint sensor can be constructed, but impurities may enter the thin-film transistors causing reduction in reliability
Solution Approach 1:
An inorganic insulating layer is introduced as an intermediary barrier between the photoelectric conversion element and the thin-film transistor. This layer prevents impurities generated during photoelectric conversion element formation from diffusing into the thin-film transistor, thereby maintaining transistor reliability while allowing the optical fingerprint sensor structure to function.
Solution Approach 2:
The structure is segmented by introducing a dedicated inorganic insulating layer that separates the photoelectric conversion element region from the thin-film transistor region. This segmentation creates a physical barrier that blocks impurity diffusion pathways while maintaining the functional integrity of both components.
2Productivity
If thin-film transistors are used to drive photoelectric conversion elements, then the optical fingerprint sensor can operate, but impurity contamination during fabrication reduces transistor reliability
Solution Approach 1:
The inorganic insulating layer serves as a protective intermediary that allows the thin-film transistor to function as a driver for the photoelectric conversion element while shielding it from impurity contamination during the film formation process, thus maintaining both functionality and reliability.
Solution Approach 2:
The inorganic insulating layer is formed in advance before the photoelectric conversion element and electrode films are deposited. This preliminary action establishes a protective barrier that prevents subsequent impurity contamination of the thin-film transistor during the fabrication process.
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 configuration enhances the reliability of the thin-film transistors by preventing impurity diffusion, thereby improving the overall performance and accuracy of the optical fingerprint sensor.
Implementation Method 1
an inorganic insulating layer provided between the photoelectric conversion element and the first switching element in a normal direction of the insulating substrate
Implementation Method 2
a photoelectric conversion element that outputs a signal that changes with an amount of irradiating light
Data Source
AI summary
According to an aspect, a detection device includes: an insulating substrate; a plurality of photoelectric conversion elements that are arranged in a detection area of the insulating substrate, and each of which is configured to receive light and output a signal corresponding to the received light; a first switching element that is provided for each photoelectric conversion element and includes a first semiconductor, a source electrode, and a drain electrode; and an inorganic insulating layer provided between the photoelectric conversion element and the first switching element in a normal direction of the insulating substrate.