Stacked SPAD Pixel Layout With Through-Vias and Quenching Isolation
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Solution Overview
Problem
Current photoelectric conversion apparatuses lack a suitable arrangement of through-regions and through-vias for single-photon avalanche diode (SPAD) pixels, which affects the imaging performance and signal processing efficiency.
Innovation Solution
A photoelectric conversion apparatus is designed with a multilayer structure, where a first substrate with avalanche photodiodes is stacked on a second substrate containing a quenching device and signal processing units, with through-electrodes and vias that electrically connect the substrates, optimizing the arrangement of signal processing units and quenching devices for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a through-region and through-via are formed in a photoelectric conversion apparatus with SPAD pixels, then electrical connection between substrates is achieved, but the arrangement suitability for SPAD pixels is insufficient
Solution Approach 1:
The patent transitions from a planar arrangement to a three-dimensional stacked configuration, placing the pixel region on the first substrate and the quenching device on the second substrate. Through-electrodes penetrate the first substrate to establish vertical electrical connections, effectively utilizing the depth dimension to resolve the contradiction between achieving reliable electrical connection and maintaining arrangement suitability for SPAD pixels.
Solution Approach 2:
The photoelectric conversion apparatus is divided into functionally independent components: a first substrate containing pixel regions with SPAD pixels, a second substrate containing quenching devices, and through-electrodes for electrical connection. This segmentation allows each component to be optimized independently for its specific function while maintaining overall system performance.
2Device complexity
If signal processing units are arranged on the same substrate as pixel regions, then wiring complexity is reduced, but the area available for signal processing is limited
Solution Approach 1:
The patent resolves the area limitation by moving signal processing units from the two-dimensional plane of the first substrate to the second substrate in a stacked configuration. This vertical arrangement maintains electrical connection through through-electrodes while providing sufficient area on the second substrate for accommodating quenching devices and signal processing circuits without increasing wiring complexity.
3Speed
If the quenching device is positioned close to the pixel region, then signal processing speed is improved, but characteristic variations in the quenching device affect performance
Solution Approach 1:
The patent segments the quenching device from the pixel region by placing them on separate substrates, reducing direct coupling and the impact of quenching device characteristic variations on pixel performance. The through-electrodes provide controlled electrical connection while maintaining physical separation, thus improving tolerance to variations while preserving signal processing speed through optimized wiring design.
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 enhances imaging performance by maximizing the area for signal processing, reducing cathode capacitance, and improving the tolerance to characteristic variations in quenching devices, leading to more efficient and stable signal processing.
Implementation Method 1
a pixel region in which a plurality of avalanche photodiodes are arranged
Implementation Method 2
single-photon avalanche diode (SPAD) pixels
Data Source
AI summary
A photoelectric conversion apparatus including: a first component including a first substrate (FS) having a first plane and a pixel region in which avalanche photodiodes are arranged, and a first wiring layer provided on a side where the first plane of the FS is provided; and a second component including a second substrate (SS), a quenching device, and a second wiring layer, the SS having a third plane, the second wiring layer being provided on a side where the third plane of the SS is provided. The SS has an insulating region, and the insulating region has a through-electrode provided in a through-region that penetrates through the SS. The quenching device is separated from another element by the insulating region. The first component and the second component are electrically connected to each other in a region that overlaps the pixel region in a plan view.