2PD Image Sensor Pixel Separation to Limit Color Mixture

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Solution Overview

Problem

The 2PD scheme for on-sensor phase-difference AF in image sensors faces issues such as reduced photodiode volume, color mixture between divided pixels, and sensitivity loss due to pixel division, which affect autofocus precision and image quality.

Innovation Solution

A solid-state image pickup element with pixels having photoelectric conversion elements partitioned by different types of separating regions, including a first-type region formed by impurity ion implantation and a second-type region formed with a silicon dioxide film, to inhibit color mixture and maintain sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If photodiode is divided into two for 2PD scheme, then on-sensor phase-difference AF function is achieved, but photodiode volume is reduced

Engineering Contradiction:

Improveon-sensor phase-difference AF functionVSAvoidphotodiode volume

Core Design Contradiction:

Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The photodiode is divided into two separate photodiodes (first divided pixel and second divided pixel) to enable on-sensor phase-difference AF. This segmentation allows each divided pixel to capture light from different portions of the exit pupil, enabling focus detection while maintaining image quality through cumulation of outputs.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The separating portion is embedded within the pixel structure, with the first and second divided pixels nested around the separating portion. This nesting approach minimizes space occupation while achieving the division function, allowing dense layout of phase-difference pixels.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Measurement precision

If pixel is divided for phase-difference detection, then autofocus precision is improved, but color mixture between divided pixels occurs

Engineering Contradiction:

Improveautofocus precisionVSAvoidcolor mixture

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The separating portion is extracted and placed between the first and second divided pixels to physically isolate them. This extraction prevents color mixture by blocking light paths that would otherwise cause crosstalk between adjacent divided pixels, while maintaining autofocus precision.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The separating portion acts as an intermediary element between the first and second divided pixels. It mediates the light paths from different exit pupil portions while preventing unwanted light mixing, thus eliminating color mixture without compromising the phase-difference detection capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If pixel is divided into two for 2PD scheme, then phase-difference detection is enabled, but sensitivity is reduced

Engineering Contradiction:

Improvephase-difference detectionVSAvoidsensitivity

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

Each divided pixel is designed to perform multiple functions: capturing light for image formation and providing phase-difference detection signal. The cumulation of outputs from first and second divided pixels generates an output for one pixel that can be used for image forming, maintaining sensitivity while enabling phase-difference detection.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The optical characteristics of the separating portion are optimized by controlling its thickness to be equal to or less than a wavelength of blue light. This parameter change allows the separating portion to be transparent to visible light while maintaining its light-blocking function for preventing color mixture, thus preserving sensitivity.

Inventive Principle:

Principle #35Parameter changes

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 approach improves autofocus precision and image quality by reducing color mixture and sensitivity loss, while maintaining the dense layout of phase-difference pixels, thus addressing the limitations of the 2PD scheme.

Implementation Method 1

a first-type separating region formed by impurity ion implantation

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Implementation Method 2

a second-type separating region formed with a silicon dioxide film to inhibit color mixture

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS11749703B2Solid-state image pickup element, method of manufacturing solid-state image pickup element, and electronic apparatus

Publication Date: 2023.09.05 SONY GROUP CORP

AI summary

To solve at least one of various problems in an image sensor in a 2PD scheme. A solid-state image pickup element includes a plurality of pixels each including a photoelectric conversion element formed on a silicon substrate, in which some pixels in the plurality of pixels each have the photoelectric conversion element partitioned by a first-type separating region extending in a plate shape in a direction along a thickness direction of the silicon substrate, and other pixels in the plurality of pixels each have the photoelectric conversion element partitioned by a second-type separating region formed with a material different from a material of the first-type separating region, the second-type separating region extending in a plate shape in the direction along the thickness direction of the silicon substrate.