SPAD Pixel Wiring Layout for Higher Withstand Voltage
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Solution Overview
Problem
The existing photoelectric conversion apparatuses with SPAD pixels face challenges in ensuring withstand voltage between the first and second metal wirings, particularly in configurations and placement positions, which affect the reliability and efficiency of the photoelectric conversion process.
Innovation Solution
The apparatus includes a wiring structure with a first wiring positioned closest to the layer to supply voltage to the second conductivity type region and a second wiring that covers the first region, with the second wiring being closer to the layer than the first wiring, and is disposed in the same wiring layer as the first wiring, forming an opening with multiple sides to ensure effective voltage distribution and reduce the risk of dielectric breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first wiring is positioned closest to the layer to supply voltage to the second conductivity type region, then the voltage distribution is improved, but the withstand voltage between wirings may be compromised due to close spacing
Solution Approach 1:
The patent positions the first wiring in a different layer than the second wiring, utilizing the vertical dimension to separate high-voltage and low-voltage paths. This layer separation allows the first wiring to be close to the photodiode for good voltage distribution while maintaining adequate spacing for withstand voltage through the insulating layer.
Solution Approach 2:
An insulating layer is introduced as an intermediary between the first and second wirings. This insulating layer acts as a mediator that enables close proximity wiring configuration while maintaining electrical isolation and withstanding the voltage difference between the cathode and anode connections.
2Reliability
If the second wiring covers the first region and is disposed closer to the layer, then the photoelectric conversion sensitivity is improved, but the risk of dielectric breakdown increases due to reduced spacing
Solution Approach 1:
The insulating layer serves as a protective intermediary between the second wiring (closer to the layer) and the first wiring. This intermediary structure allows the second wiring to be positioned close to the photodiode for enhanced sensitivity while preventing dielectric breakdown through adequate electrical isolation.
Solution Approach 2:
The patent applies different properties to different regions: the second wiring is positioned close to the photodiode region for optimal photoelectric conversion, while the insulating layer provides localized electrical isolation where needed to prevent breakdown, creating a spatially differentiated structure with optimized local properties.
3Ease of manufacture
If multiple wirings are disposed in the same wiring layer, then the manufacturing process is simplified, but the withstand voltage between wirings becomes difficult to ensure
Solution Approach 1:
The patent transitions from a two-dimensional planar wiring arrangement to a three-dimensional multi-layer configuration. By disposing wirings in different vertical layers rather than the same layer, the invention maintains manufacturing simplicity while achieving adequate withstand voltage through vertical separation provided by insulating layers.
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 the withstand voltage and sensitivity of the photoelectric conversion apparatus, particularly for long-wavelength light, while maintaining reliability and improving the overall efficiency of the photoelectric conversion process.
Implementation Method 1
a photocarrier attributable to a single photon causes avalanche multiplication in a PN junction region within a semiconductor region
Implementation Method 2
a photocarrier attributable to a single photon causes avalanche multiplication in a PN junction region within a semiconductor region
Data Source
AI summary
An apparatus includes a layer that has a light incident surface and includes elements, and a wiring structure. Each of the elements includes a photodiode. The photodiode includes first and second regions of first and second conductivity types. A voltage is supplied to the second region through a second-conductivity-type region. The wiring structure includes a first wiring positioned closest to the layer among wirings to supply the voltage to the second-conductivity-type region, a plug connecting the first wiring and the second-conductivity-type region, and a second wiring supplying a voltage to the first region. The second wiring covers the first region when viewed in plan, and a distance between the second wiring and the layer is shorter than a distance between the first wiring and the layer.