Multi-Layered Resistive Element for SPAD Fill-Factor
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Solution Overview
Problem
Single-photon avalanche diode (SPAD) sensors fabricated on CMOS technology have limited fill-factors due to the occupation of valuable space by resistive elements, which are necessary to quench avalanche currents and prevent overheating, hindering further miniaturization and efficiency in imaging applications.
Innovation Solution
A multi-layered resistive element with a ReRAM structure is embedded over the photodiode region in the semiconductor substrate, providing quenching resistance while minimizing space usage, fabricated using CMOS-compatible processes to integrate with SPAD sensors and enhance photon detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional resistive elements are used in SPAD sensors, then avalanche current quenching is achieved, but valuable semiconductor substrate space is occupied, limiting fill-factor and device miniaturization
Solution Approach 1:
The resistive element is moved from the planar semiconductor substrate to the vertical dimension by forming it as an embedded structure within the substrate. This three-dimensional integration allows the resistive element to occupy volume rather than surface area, thereby maintaining the fill-factor while providing the necessary quenching function.
Solution Approach 2:
The resistive element is nested within the semiconductor substrate structure, specifically formed as an embedded region inside the photodiode region. This nesting approach allows the resistive element to be integrated within the existing device architecture without requiring additional lateral space, thus resolving the space occupation problem.
2Reliability
If resistive elements occupy valuable space on the semiconductor substrate, then avalanche current quenching is provided, but device miniaturization and photon detection efficiency are hindered
Solution Approach 1:
By transitioning the resistive element from a planar configuration to a vertical/embedded configuration, the photodiode surface area is maximized for photon detection while the quenching function is maintained through the embedded resistive structure. This dimensional change directly improves photon detection efficiency without sacrificing quenching capability.
3Area of stationary object
If multi-layered resistive elements are embedded in the semiconductor substrate, then space usage is minimized and fill-factor is improved, but device complexity increases
Solution Approach 1:
The resistive element is divided into multiple layers or segments that are formed sequentially within the substrate. This segmentation allows for controlled formation of the embedded structure using standard CMOS fabrication processes, managing the complexity through step-by-step construction rather than requiring a single complex processing step.
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 embedded multi-layered resistive element effectively quenches avalanche currents, maintaining sensor integrity under high reverse-biased voltage and allowing for higher photon detection efficiency and reduced power consumption, addressing the space constraints and performance limitations of traditional SPAD sensors.
Implementation Method 1
A resistive element is typically employed to provide a 'quenching' resistance to 'quench' the avalanche current by lowering the reverse-biased voltage to a level below the breakdown voltage of the SPAD sensor
Implementation Method 2
Imaging sensors typically include light sensors or photodetectors to detect electromagnetic radiation. In particular, photodiode sensors are semiconductor devices that are able to detect wavelengths in visible and infrared spectrum regions of the electromagnetic wave spectrum
Implementation Method 3
The SPAD sensor is based on a P-N junction operating under a high reverse-biased voltage that is above a breakdown voltage of the SPAD sensor. At this biased voltage, the SPAD sensor triggers a self-sustaining avalanche multiplication of charge carries after detecting a single photon
Data Source
AI summary
A sensor is provided, which includes a semiconductor substrate, a photodiode region, and a multi-layered resistive element. The photodiode region is arranged in the semiconductor substrate. The multi-layered resistive element is arranged over the semiconductor substrate and is coupled with the photodiode region.