Backside Illumination CMOS Image Sensor Light Blocking Separation Film

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Solution Overview

Problem

In backside illumination CMOS image sensors with global shutter function, the separation of photo diodes and memories by dopants limits the area available for each component, leading to restricted saturation signal amounts and sensitivity, and incident light can cause aliasing by passing through the photo diode and being detected in the memory at unintended times.

Innovation Solution

Incorporating a light blocking or light absorbing film as a separation film between the photo diode and the memory to block or absorb incident light, allowing for increased space and improved sensitivity, and using a vertical transistor to transfer charge efficiently while maintaining the same pixel pitch.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a dopant is used to separate the photo diode and memory, then the photo diode and memory can be separated, but the area available for each component is limited

Engineering Contradiction:

Improveseparation effectivenessVSAvoidarea for photo diode and memory

Core Design Contradiction:

ReliabilityVSArea of moving object

Solution Approach 1:

A light blocking film is introduced as an intermediary layer between the photo diode and memory. This film effectively blocks light from reaching the memory while occupying minimal space, thus achieving reliable separation without limiting the area available for the photo diode and memory components

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention employs a thin light blocking film instead of thick dopant regions. This thin film structure provides effective light separation while minimizing the space consumed, thereby allowing larger areas for the photo diode and memory within the same pixel pitch

Inventive Principle:

Principle #30Flexible shells and thin films

2Reliability

If the photo diode and memory are separated by a dopant, then light can be blocked, but the saturation signal amounts and sensitivity are restricted

Engineering Contradiction:

Improvelight blocking capabilityVSAvoidsensitivity and saturation signal amounts

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The light blocking film serves as an effective intermediary that completely prevents light from reaching the memory, eliminating aliasing. This reliable light blocking enables the memory to be positioned closer to the photo diode, maximizing the usable area for signal accumulation and thereby improving saturation signal amounts and sensitivity

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If the photo diode and memory are disposed on the same plane, then the structure is simple, but incident light causes aliasing by entering the memory at unintended timing

Engineering Contradiction:

Improvestructural complexityVSAvoidaliasing

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The light blocking film is introduced as a mediator between the photo diode and memory. This film maintains the simple planar structure while effectively blocking incident light from entering the memory, thereby preventing aliasing without increasing structural complexity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

A thin light blocking film is used to maintain the simplicity of the planar structure. The film is thin enough to occupy minimal space while being sufficiently effective at blocking light, thus preventing aliasing while keeping the overall device structure simple and manufacturable

Inventive Principle:

Principle #30Flexible shells and thin films

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 effectively suppresses aliasing, increases the saturation signal amounts, and enhances the sensitivity of both the photo diode and memory by blocking or absorbing light that would otherwise interfere with the memory, thereby improving imaging performance.

Implementation Method 1

a separation film including one of a light blocking film and a light absorbing film between a memory and a photo diode

Methodology Applied

Scientific EffectLight blocking: Absorption (EM radiation)

Implementation Method 2

a separation film including one of a light blocking film and a light absorbing film between a memory and a photo diode

Methodology Applied

Scientific EffectLight absorbing: Absorption (EM radiation)

Implementation Method 3

incident light from the backside surface passes through the photo diode and an element separation film and enters the memory

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS10714519B2Solid-state imaging device, method of manufacturing a solid-state imaging device, and electronic apparatus

Publication Date: 2020.07.14 SONY GROUP CORP

AI summary

Provided is a solid-state imaging device including a lamination-type backside illumination CMOS (Complementary Metal Oxide Semiconductor) image sensor having a global shutter function. The solid-state imaging device includes a separation film including one of a light blocking film and a light absorbing film between a memory and a photo diode.