Image Sensor Pixel Groove Passivation for Dark Current Suppression

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Solution Overview

Problem

In solid-state image pickup devices, dry etching for forming pixel separation grooves introduces crystal defects and dangling bonds, leading to increased dark current generation due to damaged surface interfaces.

Innovation Solution

A laminated fixed charge film comprising a first insulating film formed contiguously from the light-receiving surface to the wall and bottom surfaces of the pixel separation groove, and a second insulating film on the light-receiving surface, using different deposition methods like ALD or MOCVD for the first film and PVD for the second, to improve interface states and suppress dark current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If dry etching is used to form pixel separation grooves, then the groove structure is achieved, but crystal defects and dangling bonds are introduced on the surface

Engineering Contradiction:

Improvepixel separation groove structureVSAvoidinterface quality

Core Design Contradiction:

ShapeVSReliability

Solution Approach 1:

An insulating film is introduced as an intermediary layer between the semiconductor substrate and the external environment. This film passivates the crystal defects and dangling bonds created by dry etching, preventing harmful interactions while maintaining the groove structure for optical isolation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful crystal defects and dangling bonds generated by dry etching are converted into beneficial passivation sites by forming an insulating film. The same etched surfaces that cause interface states are transformed into stable, passivated interfaces that reduce dark current generation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If a fixed charge film is formed on the light-receiving surface, then dark current generation is suppressed, but interface states increase due to dry etching damage

Engineering Contradiction:

Improvedark current suppressionVSAvoidinterface state

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The physical and chemical parameters of the surface are changed by forming an insulating film. This transformation alters the electrical properties at the interface, converting high-density interface states into stable, passivated interfaces with reduced trap levels and improved electrical characteristics.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

A composite structure is formed by combining the semiconductor substrate with an insulating film layer. This composite material system leverages the electrical properties of the semiconductor for photoelectric conversion while utilizing the insulating properties of the film for surface passivation and interface state reduction.

Inventive Principle:

Principle #40Composite materials

3Object-affected harmful factors

If the groove is filled with insulating film to suppress optical color mixture, then optical isolation is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveoptical color mixtureVSAvoidmanufacturing process

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

Multiple functions are merged into a single insulating film layer: (1) filling the groove for optical isolation to prevent color mixture, (2) passivating the etched surfaces to reduce interface states, and (3) providing a base layer for subsequent fixed charge film formation. This consolidation simplifies the manufacturing process while achieving multiple objectives.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The insulating film is designed to perform multiple functions simultaneously: optical isolation, surface passivation, and interface state reduction. This multi-functional approach eliminates the need for separate processing steps for each function, reducing overall manufacturing complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The laminated fixed charge film enhances interfacial quality, reduces dark current generation, and provides antireflection effects, improving the sensitivity and performance of the image pickup element.

Implementation Method 1

a first insulating film which is provided contiguously from the light-receiving surface to a wall surface and a bottom surface of the pixel separation groove

Methodology Applied

Scientific EffectAtomic layer deposition: Chemical Vapour Deposition

Implementation Method 2

a second insulating film which is provided on a part of the first insulating film, the part corresponding to at least the light-receiving surface

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS12166058B2Image pickup element, method of manufacturing image pickup element, and electronic apparatus

Publication Date: 2024.12.10 SONY GROUP CORP

AI summary

An image pickup element includes: a semiconductor substrate including a photoelectric conversion section for each pixel; a pixel separation groove provided in the semiconductor substrate; and a fixed charge film provided on a light-receiving surface side of the semiconductor substrate, wherein the fixed charge film includes a first insulating film and a second insulating film, the first insulating film being provided contiguously from the light-receiving surface to a wall surface and a bottom surface of the pixel separation groove, and the second insulating film being provided on a part of the first insulating film, the part corresponding to at least the light-receiving surface.