Biometric Sensor PIN Photodiode Composite Insulation
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Solution Overview
Problem
Existing detection apparatuses with inorganic insulating films face reduced reliability and detection sensitivity due to increased parasitic capacitance and thinner film coverage, which affects the performance of biometric sensors like fingerprint and vein sensors.
Innovation Solution
A detection apparatus with a substrate featuring PIN photodiodes, transistors, and a layered insulating structure comprising a first inorganic insulating film, a first organic insulating film, and an upper conductive layer, where the photodiodes have regions with direct contact between semiconductor layers and separate regions, reducing parasitic capacitance and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inorganic insulating film is made thinner to reduce parasitic capacitance, then detection sensitivity is improved, but the covering property is lowered and reliability is reduced
Solution Approach 1:
The patent employs a composite insulating structure combining inorganic insulating film (e.g., silicon oxide, silicon nitride) and organic insulating film (e.g., polyimide, acrylic resin). This composite approach allows the inorganic film to provide thin coverage for reduced parasitic capacitance while the organic film provides thicker coverage for enhanced reliability and protection, resolving the contradiction between thin-film benefits and thick-film reliability.
2Reliability
If the photodiodes are thickly formed to improve coverage, then the covering property is improved, but parasitic capacitance increases and detection sensitivity is lowered
Solution Approach 1:
The dual-layer insulating structure allows the inorganic film to be thin (reducing parasitic capacitance) while the organic film provides the necessary thickness for good covering property. This composite approach simultaneously achieves both low parasitic capacitance for high sensitivity and adequate coverage for reliability.
Solution Approach 2:
The patent changes the material parameters of the insulating films, selecting specific inorganic materials (silicon oxide, silicon nitride) and organic materials (polyimide, acrylic resin) with appropriate dielectric properties and thickness characteristics to optimize both parasitic capacitance reduction and covering property.
3Measurement precision
If the inorganic insulating film is used to cover photodiodes, then the detection function is maintained, but parasitic capacitance increases between upper electrode and substrate structures
Solution Approach 1:
The composite insulating film structure provides effective electrical isolation between the upper electrode and substrate while minimizing parasitic capacitance. The inorganic film's low dielectric constant and thin thickness reduce capacitance, while the organic film ensures complete coverage, maintaining detection function.
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 layered insulating structure effectively reduces parasitic capacitance, improving the detection sensitivity and reliability of biometric sensors by optimizing the coverage and thickness of insulating films.
Implementation Method 1
a plurality of photodiodes that are arranged on the substrate and each includes a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer stacked on the substrate
Data Source
AI summary
A detection apparatus includes: a substrate; photodiodes each including a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer; transistors provided for the respective photodiodes; an insulating film provided so as to cover the transistors; a first inorganic insulating film provided so as to cover the photodiodes; a first organic insulating film provided on the upper side of the first inorganic insulating film; and an upper conductive layer provided on the upper side of the first organic insulating film and electrically coupled to the photodiode. Each photodiode includes: first regions in each of which the p-type semiconductor layer, the i-type semiconductor layer, and the n-type semiconductor layer are directly in contact with one another; and a second region in which the p-type semiconductor layer and the i-type semiconductor layer are separate from each other. The adjacent first regions are coupled together by the p-type semiconductor layer.