Stacked APD Pixel Architecture for Dense Photodetection Circuits
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Solution Overview
Problem
The existing configuration of photoelectric conversion devices with stacked substrates does not optimally distribute functional blocks for controlling and processing signals from avalanche photodiodes, hindering high integration and improved characteristics.
Innovation Solution
A photoelectric conversion device is configured by stacking at least three substrates, with avalanche photodiodes on one substrate, quenching circuits on another, and processing circuits on yet another, and including electrical connections between these substrates for signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If functional blocks are distributed across multiple substrates, then high integration and improved characteristics are achieved, but device complexity increases
Solution Approach 1:
The device is divided into three separate substrates: first substrate for APD arrays, second substrate for quenching circuits, and third substrate for processing circuits. This segmentation allows each functional block to be optimized independently while working together as an integrated system, resolving the contradiction by distributing functions across substrates to improve processing efficiency without creating unmanageable complexity on a single substrate
Solution Approach 2:
The patent transitions from a two-dimensional planar integration to a three-dimensional stacked architecture. By stacking substrates vertically, the system achieves higher integration density and improved signal processing characteristics without increasing the lateral footprint, effectively adding a spatial dimension to resolve the complexity-efficiency trade-off
2Measurement precision
If avalanche photodiodes are arranged in high density, then detection precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The APD arrays are fabricated on a separate first substrate with optimized photodiode spacing and arrangement for high detection precision. This segmentation allows the photodiode array to be manufactured with precise geometric specifications independently, then integrated with circuit substrates, thereby achieving high detection precision without compounding manufacturing precision requirements across all components
Solution Approach 2:
The first substrate acts as an intermediary carrier that holds the precisely arranged APD arrays. This intermediate substrate allows the photodiodes to be positioned with high precision during fabrication, then the entire first substrate is bonded to subsequent circuit substrates, transferring the precision-aligned photodiode array to the final integrated device without requiring subsequent precision alignment steps
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 configuration enables high integration and improved characteristics of pixel and peripheral circuits, allowing for high-density arrangement of photodiodes and efficient signal processing.
Implementation Method 1
a photoelectric conversion unit including an avalanche photodiode
Data Source
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AI summary
A photoelectric conversion device is configured by stacking a first substrate, a second substrate, and a third substrate and includes a plurality of pixels each including a photoelectric conversion unit including an APD and a signal processing unit that processes a signal output from the photoelectric conversion unit. The signal processing unit includes a quenching circuit connected to the APD and a processing circuit that processes a signal corresponding to incidence of light on the APD. The APD is arranged on the first substrate, at least a part of the quenching circuit is arranged on the second substrate, and at least a part of the processing circuit is arranged on the third substrate. Each of the plurality of pixels includes a plurality of electrical connection portions between the second substrate and the third substrate, a part of the plurality of electrical connection portions constitutes a part of an input signal line to the processing circuit, and another part constitutes a part of an output signal line from the processing circuit.