Phase-Difference Pixel Isolation Layout for Wide-Angle Autofocus
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Solution Overview
Problem
Existing image-plane phase-difference autofocus systems face limitations in handling wide incident light angles due to reduced light incidence surface size, which narrows the angle-of-incidence range and affects phase-difference signal output.
Innovation Solution
The proposed photoelectric conversion apparatus features a substrate with pixels divided into first and second portions, each with a microlens, and isolation regions shifted to accommodate varying light angles, ensuring uniform light incidence surfaces and reducing crosstalk, thereby enhancing phase-difference AF performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light incidence surface size of a PD is reduced to shift the boundary of separate PDs, then the phase-difference signal output is improved, but the incident light angle range becomes narrower
Solution Approach 1:
The patent introduces a third dimension (depth direction) to resolve the contradiction. By configuring isolation regions at different depths - with a first isolation region near the light incidence surface and a second isolation region deeper in the substrate - the patent creates a three-dimensional isolation structure. This allows the light incidence surface to remain sufficiently large for wide angle coverage while the depth-direction isolation provides the necessary separation for phase-difference signal generation.
Solution Approach 2:
The patent implements nested isolation regions where the first isolation region (extending from the light incidence surface) and the second isolation region (extending from deeper in the substrate) overlap in plan view but are separated in the depth direction. This nested configuration allows both regions to coexist without interfering with each other, enabling the light incidence surface to maintain its size while achieving effective isolation for phase-difference detection.
2Measurement precision
If the boundary of separate PDs is shifted by reducing light incidence surface size, then the phase-difference AF performance is improved, but the angle-of-incidence range that can be handled is narrowed
Solution Approach 1:
The patent resolves this contradiction by moving the isolation function from the lateral dimension to the depth dimension. The first isolation region extends from the light incidence surface in the depth direction, while the second isolation region extends from deeper in the substrate, also in the depth direction. This three-dimensional arrangement provides effective isolation for phase-difference AF without reducing the lateral size of the light incidence surface, thereby maintaining wide angle-of-incidence coverage.
3Object-affected harmful factors
If isolation regions are configured to isolate adjacent pixels and intra-pixel portions, then crosstalk is reduced, but the light incidence surface area is reduced
Solution Approach 1:
The patent uses nested isolation regions where the first isolation region (starting from the light incidence surface) and the second isolation region (starting from deeper in the substrate) are positioned to overlap in plan view but are separated in the depth direction. This nested configuration provides comprehensive isolation against crosstalk while minimizing the impact on the light incidence surface area, as the isolation occurs primarily in the depth dimension rather than laterally.
Solution Approach 2:
The patent addresses the crosstalk isolation problem by introducing depth-direction isolation regions rather than relying solely on lateral isolation. The first isolation region extends downward from the light incidence surface, and the second isolation region extends upward from deeper in the substrate, creating isolation barriers in the depth dimension that effectively prevent crosstalk without significantly reducing the light incidence surface area.
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 allows for a wider incident light angle range and improved phase-difference signal output, enhancing autofocus accuracy and image quality by maintaining uniform charge accumulation and generation regions across pixels.
Implementation Method 1
Each of the plurality of pixels includes a first portion, a second portion, and a microlens
Implementation Method 2
image-plane phase-difference autofocus (AF) with a plurality of separate photodiodes (hereinafter, also abbreviated as PDs) in each pixel
Data Source
AI summary
An apparatus includes pixels on a substrate. Each pixel includes a first portion, a second, and a microlens. The substrate has a first surface on an incidence side and a second surface opposite to the first surface, and includes an inter-pixel portion isolating adjacent pixels from each other, and an intra-pixel portion isolating the first and second portions from each other. The inter-pixel portion includes a first region located adjacently to the first surface, and a second region located adjacently to the second surface. The intra-pixel portion includes a third region located adjacently to the first surface, and a fourth region located adjacently to the second surface. The first and third regions are shifted with respect to the second and fourth regions, respectively, in an identical direction that is a direction orthogonal to a longitudinal direction of the intra-pixel portion in plan view from the first surface.