Photodiode DTI Structure With Vertical Coupling for Smaller Pixels
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Solution Overview
Problem
Conventional photodiode designs face challenges in miniaturization and efficiency due to space occupation by doped regions within the pixel area, leading to increased pixel pitch and reduced fill factor, along with higher resistance and complexity in fabrication.
Innovation Solution
The introduction of deep trench isolation (DTI) structures and doped intermediate regions between vertical conductive layers, coupled with a single contact to metal wiring, reduces the need for doped regions within the pixel area, allowing for smaller pixel pitch and improved fill factor while maintaining photon detection probability and reducing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If doped regions are used within the pixel area to provide electrical coupling, then electrical connectivity is achieved, but the pixel pitch increases and fill factor decreases
Solution Approach 1:
The patent transitions from lateral electrical coupling within the pixel plane to vertical electrical coupling through the substrate thickness dimension. The doped intermediate region extends vertically from the first surface to the second surface, allowing electrical connectivity through the substrate rather than requiring lateral space within the pixel area, thereby reducing pixel pitch while maintaining connectivity.
Solution Approach 2:
The doped intermediate region acts as an intermediary element that provides electrical coupling between the first and second vertical conductive layers through the substrate. This intermediate doped region serves as a mediator that enables electrical connectivity without requiring direct lateral contact between conductive layers, thus saving pixel area.
2Reliability
If multiple contacts are used to provide electrical coupling between conductive layers, then electrical connectivity is achieved, but fabrication complexity increases
Solution Approach 1:
The patent merges the functions of multiple separate contacts into a single integrated doped intermediate region. Instead of requiring multiple discrete contact structures to establish electrical coupling between the first and second vertical conductive layers, a single doped intermediate region performs this function, thereby simplifying fabrication while maintaining electrical connectivity.
3Reliability
If doped regions are extended within the pixel area to reduce resistance, then electrical conductivity improves, but the pixel pitch increases
Solution Approach 1:
The patent extends the doped intermediate region through the substrate thickness dimension rather than expanding it laterally within the pixel plane. This vertical extension provides sufficient conductive path length to reduce resistance while avoiding lateral expansion that would increase pixel pitch, as the doped region utilizes the third dimension (substrate thickness) for its conductive pathway.
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 design enhances miniaturization, reduces pixel pitch, improves fill factor, and simplifies fabrication by eliminating the need for multiple contacts, thereby increasing reliability and maintaining dark current performance.
Implementation Method 1
a doped intermediate region between a contact at the first side of the layer of semiconductor material and a base of the DTI structure, and in direct contact with the contact and the first and second vertical conductive layers
Implementation Method 2
a deep trench isolation (DTI) structure between adjacent pixels of the plurality of pixels
Implementation Method 3
Semiconductor photodiodes are a category of photodetectors that use a P-N diode to convert incident photons into current
Implementation Method 4
Avalanche photodiodes are a highly biased photodiodes in which photo-generated carriers are multiplied by avalanche breakdown in the device. Single photon avalanche diodes (SPADs) are avalanche photodiodes which are sensitive enough to detect the incidence of a single photon
Data Source
AI summary
A photodiode device includes a plurality of pixels, each of the pixels including a diode structure on a first side of a layer of semiconductor material and a lens on a second side of the layer of semiconductor material, a deep trench isolation (DTI) structure between adjacent pixels of the plurality of pixels, a first vertical conductive layer over a first side of the DTI structure, a second vertical conductive layer over a second side of the DTI structure, and a doped intermediate region between a contact at the first side of the layer of semiconductor material and a base of the DTI structure, and in direct contact with the contact and the first and second vertical conductive layers.