SPAD Photodetector Layout With Integrated Avalanche Quenching
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Solution Overview
Problem
Existing photodetectors with SPAD photodiodes have bulky quenching circuits that occupy a large surface area, particularly in photodetectors with SPAD photodiode arrays, and lack precise control over the avalanche phenomenon.
Innovation Solution
A photodetector design that incorporates a SPAD photodiode and a quenching transistor, where the transistor's channel is formed by a common doped region with the SPAD photodiode, reducing the surface area and enabling more precise control over the avalanche.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistor is used as the quenching circuit, then the avalanche phenomenon can be controlled, but the surface area occupied by the quenching circuit becomes large
Solution Approach 1:
The quenching transistor shares a common doped region with the SPAD photodiode, merging two separate structures into one integrated design. This eliminates the need for separate quenching circuit components and reduces the overall surface area while maintaining avalanche control functionality.
Solution Approach 2:
The common doped region serves dual purposes: it forms part of the SPAD photodiode structure and simultaneously creates the channel for the quenching transistor. This multi-functional design allows a single structural element to fulfill multiple roles, reducing component count and surface area.
2Reliability
If a PMOS transistor with doped wells is used to quench the avalanche, then avalanche control is improved, but the surface area occupied by the quenching circuit increases
Solution Approach 1:
The quenching transistor shares a common doped region with the SPAD photodiode, merging two separate structures into one integrated design. This eliminates the need for separate quenching circuit components and reduces the overall surface area while maintaining avalanche control functionality.
Solution Approach 2:
The channel of the quenching transistor extends vertically along the depth of the substrate rather than horizontally across the surface. This vertical channel configuration allows the transistor to function with minimal surface area occupation, moving the functional element from the two-dimensional plane to the three-dimensional depth dimension.
3Ease of manufacture
If the channel extends along a plane parallel with the upper face of the substrate, then the transistor can be manufactured, but the quenching circuit occupies substantial surface area
Solution Approach 1:
The channel of the quenching transistor extends vertically along the depth of the substrate rather than horizontally across the surface. This vertical channel configuration allows the transistor to function with minimal surface area occupation, moving the functional element from the two-dimensional plane to the three-dimensional depth dimension.
Solution Approach 2:
The quenching transistor is nested within the substrate structure, with its channel extending vertically through the substrate depth. This nesting approach allows the transistor to be integrated within the existing substrate volume rather than occupying additional surface area.
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 proposed design reduces the surface area occupied by the quenching circuit and enhances the control over the avalanche phenomenon, making it particularly advantageous for photodetectors with pixel arrays.
Implementation Method 1
a gate electrically isolated from the substrate by a dielectric layer
Implementation Method 2
A SPAD photodiode is an extremely sensitive detector capable of detecting a single photon
Implementation Method 3
A photogenerated carrier is then accelerated by the electric field at a sufficient velocity to trigger an impact ionisation phenomenon, or avalanche phenomenon
Data Source
AI summary
The invention relates to a photodetector, including a SPAD type photodiode comprising, in a semiconductor substrate, a first doped region of a first conductivity type and a second doped region of a second conductivity type opposite the first conductivity type so as to produce a PN junction; a quenching transistor comprising, in the substrate, a channel of the second conductivity type, a gate electrically isolated from the substrate by a dielectric layer, a third doped region of the first conductivity type flush with an upper face of the substrate. The dielectric layer is inserted between the gate and the first doped region, the channel is delimited by the first doped region and the third doped region.