Shared-Microlens APD Pixel Wiring Layout for Low Crosstalk
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Solution Overview
Problem
Existing photoelectric conversion apparatuses with avalanche photodiodes (APDs) face decreased sensitivity and increased crosstalk due to light penetration through wiring layers and suboptimal microlens positioning, particularly when metal wiring is used in conjunction with microlenses over multiple APDs.
Innovation Solution
The apparatus features a wiring layer with varying widths of wiring between APDs, where the width between adjacent APDs is greater than the width between other pixels, and in some configurations, the wiring is omitted between APDs sharing a microlens, optimizing light reflection and focusing to enhance sensitivity and reduce crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal wiring is provided on a plurality of pixels including APDs to improve sensitivity, then sensitivity is improved, but light penetrates into the wiring layer causing crosstalk and decreasing sensitivity
Solution Approach 1:
The wiring width is locally varied: narrow wiring is used between pixels to minimize light penetration and crosstalk, while wide wiring is used between APDs within the same pixel to maintain sensitivity enhancement. This local differentiation resolves the contradiction by optimizing wiring width for each specific functional requirement.
Solution Approach 2:
The wiring structure is segmented into different regions with different widths: inter-pixel wiring (narrow) and intra-pixel wiring (wide). This segmentation allows the system to simultaneously achieve low crosstalk between pixels and high sensitivity within pixels by treating different spatial regions differently.
2Adaptability or versatility
If one microlens is disposed on a plurality of APDs to enable phase difference detection, then phase difference detection is enabled, but the location of metal wiring relative to the light focusing position is not optimal causing decreased sensitivity and increased crosstalk
Solution Approach 1:
The microlens is positioned to focus light at a specific location between APDs, and the wiring width is locally optimized at this focusing position. The wiring between APDs under a shared microlens is made wide to capture reflected light at the focusing position, while wiring between different pixel groups is made narrow. This local optimization resolves the contradiction by adapting wiring configuration to the specific light distribution pattern created by shared microlenses.
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 improves sensitivity by efficient light reflection and reduces crosstalk, allowing for better phase difference detection and autofocusing capabilities in photoelectric conversion systems.
Implementation Method 1
a microlens disposed on the second surface side so as to be common to the first photodiode and the second photodiode
Implementation Method 2
a wiring layer disposed on a first surface side... improves sensitivity by efficient light reflection
Data Source
AI summary
An apparatus includes a plurality of pixels, a layer that has a first surface and a second surface opposite the first surface and that includes a plurality of photodiodes, a wiring layer that is disposed on a first surface side and that includes first wiring and second wiring. Each of the plurality of pixels includes a first photodiode, a second photodiode located adjacent to the first photodiode in a first direction, and a microlens disposed on the second surface side so as to be common to the first photodiode and the second photodiode, and a width of the first wiring disposed between the second wiring of the first photodiode and the second wiring of the second photodiode is greater than a width of the first wiring disposed between the plurality of pixels in the first direction.