Solid-State Image Pickup Element Dark Current Suppression

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Solution Overview

Problem

Existing solid-state image pickup elements face challenges in suppressing dark current generation due to interface states between silicon substrates and insulating layers, which restrict the characteristics of layers with negative fixed charges and require high-temperature processing for ion implantation, affecting the reliability and stability of the image pickup process.

Innovation Solution

A solid-state image pickup element is developed with a silicon oxide film formed using plasma, combined with a film having negative fixed charges, which allows for the accumulation of positive charges near the interface, suppressing dark current generation and enhancing the reliability of the image pickup process without the need for high-temperature processing or specific oxide material lamination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If ion implantation is performed at high temperature for proper diffusion and activation, then the characteristics of the solid-state image pickup element are improved, but the reliability is compromised due to insufficient time to ensure all characteristics

Engineering Contradiction:

Improvediffusion and activation of implanted ionsVSAvoidcharacteristics of solid-state image pickup element

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent changes the temperature parameter from high temperature to low temperature processing. By forming the insulating layer with negative fixed charges at low temperature, the need for high-temperature diffusion and activation is eliminated, resolving the contradiction between manufacturing precision and reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the thermal diffusion mechanism with an electric field mechanism. Instead of relying on thermal diffusion for ion activation, the insulating layer with negative fixed charges creates an electric field that accumulates positive charges (holes) at the interface, achieving the desired effect without high-temperature processing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Object-generated harmful factors

If an insulating layer with negative fixed charges is formed to accumulate positive charges and suppress dark current, then dark current generation is suppressed, but the characteristics of the insulating layer are restricted

Engineering Contradiction:

Improvedark current generationVSAvoidcharacteristics of insulating layer

Core Design Contradiction:

Object-generated harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent introduces a silicon oxide film as an intermediary layer between the semiconductor layer and the insulating layer with negative fixed charges. This intermediary layer facilitates charge accumulation at the semiconductor layer interface while allowing the insulating layer to maintain its essential characteristics, resolving the contradiction between suppressing dark current and maintaining insulating layer versatility

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-generated harmful factors

If a silicon oxide film is formed between the semiconductor layer and the insulating layer with negative fixed charges, then positive charges are accumulated near the semiconductor layer interface and dark current is suppressed, but the device complexity increases

Engineering Contradiction:

Improvedark current generationVSAvoidlayer structure

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent segments the insulating layer function into two separate layers: a silicon oxide film for charge accumulation and an insulating layer with negative fixed charges for suppressing dark current. This segmentation allows each layer to perform its specific function efficiently while maintaining overall system manageability

Inventive Principle:

Principle #1Segmentation

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 solution effectively suppresses dark current generation, ensuring high reliability and stable operation of the image pickup element, while relaxing material and method restrictions, thereby stabilizing the signal obtained through photoelectric conversion and improving image quality.

Implementation Method 1

a silicon oxide film formed on the semiconductor layer in a region having at least the photodiode formed therein by using plasma

Methodology Applied

Scientific EffectPlasma: Plasma

Implementation Method 2

photoelectric conversion being carried out in the photodiode

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Implementation Method 3

a film formed on the silicon oxide film and having negative fixed charges

Methodology Applied

Scientific EffectElectrostatic charge accumulation: Electrostatics

Data Source

PatentUS8709958B2Solid-state image pickup element, method of manufacturing the same, and image pickup apparatus including the same

Publication Date: 2014.04.29 SONY GROUP CORP

AI summary

An embodiment of the invention provides a solid-state image pickup element, including: a semiconductor layer having a photodiode, photoelectric conversion being carried out in the photodiode; a silicon oxide film formed on the semiconductor layer in a region having at least the photodiode by using plasma; and a film formed on the silicon oxide film and having negative fixed charges.