Fingerprint Sensor PIN Structure for Noise-Resistant Light Collection
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Solution Overview
Problem
Current fingerprint sensors in display devices face challenges in effectively authenticating fingerprints due to noise light interference and the need for improved semiconductor layer structures that enhance light collection efficiency.
Innovation Solution
A fingerprint sensor design featuring a thin film transistor, insulating layers, and a semiconductor layer with a PIN structure comprising N-type, I-type, and P-type semiconductor layers, where the P-type semiconductor layer is closer to the surface for better light collection, and a second sensing electrode with a width matching the P-type semiconductor layer, optimized through surface polishing to prevent leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional semiconductor layer structure is used, then the device complexity is reduced, but the light collection efficiency deteriorates
Solution Approach 1:
The semiconductor layer is segmented into multiple distinct layers (first semiconductor layer, second semiconductor layer, third semiconductor layer) with different doping types and characteristics. Each layer serves a specific function in the light detection process, with the first layer collecting light signals, the second layer providing intermediate processing, and the third layer handling signal output, thereby improving overall light collection efficiency through functional segmentation
Solution Approach 2:
Each semiconductor layer is assigned different local qualities through varying doping concentrations and material compositions. The first semiconductor layer has higher doping concentration optimized for light absorption, while subsequent layers have progressively lower doping concentrations optimized for signal processing, creating local quality variations that enhance overall device performance
2Measurement precision
If the P-type semiconductor layer is positioned closer to the surface, then the light collection efficiency is improved, but the noise light interference increases
Solution Approach 1:
The patent converts the potentially harmful effect of noise light by positioning the P-type semiconductor layer closer to the surface where it can collect both signal light and noise light. However, the subsequent N-type and I-type layers are configured to selectively process and filter the collected signals, transforming the noise collection into a benefit by enabling differential signal processing that enhances signal-to-noise ratio through selective detection
Solution Approach 2:
The patent employs a composite semiconductor structure combining P-type, N-type, and I-type layers in a specific configuration. This composite structure leverages the complementary properties of different semiconductor materials with varying bandgaps and doping characteristics, allowing the system to collect light efficiently while the layered composite structure provides natural filtering and signal processing capabilities that reduce noise interference
3Area of stationary object
If the second sensing electrode width is increased, then the light collection area is improved, but the leakage current increases
Solution Approach 1:
The second sensing electrode is configured with a specific local quality through its width being matched to the P-type semiconductor layer dimensions. This localized sizing ensures that the electrode collects light signals from the optimal area while maintaining appropriate electrical isolation, preventing excessive leakage current by limiting the electrode area to match the active semiconductor region rather than maximizing overall electrode size
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 enhances light collection efficiency and reduces noise light interference, improving fingerprint authentication accuracy and reliability in display devices.
Implementation Method 1
a sensing semiconductor layer disposed in the opening of the second insulating layer and on the first sensing electrode, and including an N-type semiconductor layer, an I-type semiconductor layer, and a P-type semiconductor layer
Data Source
AI summary
A fingerprint sensor includes: a thin film transistor disposed on a substrate; a first insulating layer disposed on the thin film transistor; a first sensing electrode disposed on the first insulating layer and connected to the thin film transistor; a second insulating layer disposed on the first sensing electrode and including an opening exposing the first sensing electrode; a sensing semiconductor layer disposed in the opening of the second insulating layer and on the first sensing electrode, and including an N-type semiconductor layer, an I-type semiconductor layer, and a P-type semiconductor layer; and a second sensing electrode disposed on the sensing semiconductor layer. An upper surface of the sensing semiconductor layer and an upper surface of the second insulating layer are coplanar.