Solid-State Imaging Device Noise Reduction via Semiconductor Line Shielding

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Solution Overview

Problem

Conventional solid-state imaging devices suffer from noise charge generation due to unshielded light entering the charge storage region, which affects sensitivity and resolution.

Innovation Solution

A solid-state imaging device configuration that includes a semiconductor substrate with a photoelectric conversion film, a charge storage region, and a semiconductor material line that electrically connects the charge storage region to the amplification transistor, forming a light-shielding region to block unabsorbed light and reduce noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the photoelectric conversion film is laid over wiring layers and charge storage region in a layered structure, then the device achieves finer pixel design and higher resolution, but light that passes through the photoelectric conversion layer enters the charge storage region causing noise charge generation

Engineering Contradiction:

Improvepixel design precisionVSAvoidnoise charge

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

A light-shielding film is introduced as an intermediary layer between the photoelectric conversion film and the charge storage region. This mediator blocks harmful light from reaching the charge storage region while allowing the layered structure to maintain its fine pixel design capabilities.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The device structure is segmented into distinct functional layers: the photoelectric conversion film for light detection, the light-shielding film for noise prevention, and the charge storage region for signal accumulation. This segmentation allows each layer to perform its specific function without interference.

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If a light-shielding film is added to block light from entering the charge storage region, then noise charge generation is suppressed, but the device complexity and manufacturing steps increase

Engineering Contradiction:

Improvenoise chargeVSAvoidwiring layers

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The light-shielding film serves multiple functions: it blocks light from entering the charge storage region to prevent noise, provides structural support in the layered architecture, and can be integrated with existing wiring layers. This multi-functionality reduces the need for additional separate components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The light-shielding film is merged with the wiring layer structure, where the wiring layer itself serves as the light-shielding layer. This combination eliminates the need for a completely separate light-shielding component, reducing overall device complexity.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If metal material is used for contact plug to improve electrical connection, then conductivity is improved, but alloy formation with silicon creates crystal defects and noise

Engineering Contradiction:

Improveelectrical connectionVSAvoidcrystal defect

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

Polysilicon is used as a sacrificial or temporary material in the contact plug that can be easily deposited and removed or integrated without causing long-term harm. This material provides sufficient conductivity during operation without creating persistent crystal defects.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The material composition of the contact plug is changed from metal to polysilicon, altering its electrical and structural properties. This parameter change eliminates the alloy formation problem with silicon while maintaining adequate electrical conductivity for the application.

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 configuration suppresses noise charge generation, allows for finer pixel design without increasing wiring layers, and simplifies manufacturing by integrating the connection line with the contact plug, resulting in a low-cost, high-resolution imaging device.

Implementation Method 1

a photoelectric conversion film that is disposed above the pixel electrode and performs photoelectric conversion of light into a signal charge

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Implementation Method 2

the line is disposed so as to cover at least a portion of the charge storage region in a plan view of the solid-state imaging device

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS9935149B2Solid-state imaging device

Publication Date: 2018.04.03 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A solid-state imaging device according to the present disclosure includes: a charge storage region that stores a signal charge obtained through photoelectric conversion in a photoelectric conversion film; an amplification transistor that amplifies the signal charge stored in the charge storage region in a corresponding pixel; a contact plug that is electrically connected to the charge storage region and contains a semiconductor material; and a line that is disposed above the contact plug and contains a semiconductor material. The contact plug and the charge storage region are electrically connected, and the contact plug and a gate electrode of the amplification transistor are electrically connected via the line.