Back-Side Illumination Image Sensor Light-Cutting Portion

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Solution Overview

Problem

In back-side illumination image capturing apparatuses, the thinning of gate insulation films during etching poses a risk of exposing the photoelectric conversion portion, leading to contamination and dark current issues, especially when the interlayer and gate insulation films have similar etching rates, causing damage and color mixing between pixels.

Innovation Solution

The implementation of a light-cutting portion within the interlayer insulation film, with a separate insulating layer acting as an etching stopper, reduces damage to the photoelectric conversion portion by controlling the etching process and preventing light from reaching adjacent pixels, using a method that forms openings in the interlayer insulation film through selective etching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the gate insulation film is thinned during etching to improve light absorption, then light absorption efficiency is improved, but the photoelectric conversion portion may be exposed leading to contamination and dark current

Engineering Contradiction:

Improvelight absorption efficiencyVSAvoidphotoelectric conversion portion protection

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

A light-cutting portion made of a material with different etching characteristics than the gate insulation film is introduced as an intermediary layer. This layer is positioned between the interlayer insulation film and the gate insulation film, acting as a mediator that allows selective etching to reach the light-cutting portion while stopping before exposing the photoelectric conversion portion, thus preventing contamination and dark current while still enabling light absorption improvement

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If the interlayer and gate insulation films have similar etching rates, then manufacturing process is simplified, but selective etching becomes difficult causing damage to photoelectric conversion portion

Engineering Contradiction:

Improveinsulation film structureVSAvoidetching control precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The light-cutting portion is designed with locally different etching characteristics compared to the gate insulation film. This local quality difference allows the etching process to selectively remove the light-cutting portion while preserving the gate insulation film and photoelectric conversion portion, enabling precise manufacturing control even when the overall insulation film structure remains relatively simple

Inventive Principle:

Principle #3Local quality

3Use of energy by moving object

If light passes through the photoelectric conversion portion and is reflected by wiring layer, then light utilization is improved, but color mixing occurs between adjacent pixels

Engineering Contradiction:

Improvelight utilization efficiencyVSAvoidcolor mixing between pixels

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The light-cutting portion is strategically positioned to extract and block the reflected light paths that would otherwise cause color mixing between adjacent pixels. By removing or blocking these specific light paths while allowing other light to reach the photoelectric conversion portion, the solution maintains light utilization efficiency while eliminating the harmful color mixing effect

Inventive Principle:

Principle #2Taking out (Extraction)

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 solution effectively reduces damage to the photoelectric conversion portion and minimizes color mixing by ensuring precise control over the etching process, enhancing the manufacturing process for back-side illumination image capturing apparatuses and improving image quality.

Implementation Method 1

a light-cutting portion for cutting light, of the incident light, that has passed through the photoelectric conversion portion

Methodology Applied

Scientific EffectLight blocking: Absorption (EM radiation)

Implementation Method 2

the first insulating layer is located between the light-cutting portion and the semiconductor substrate

Methodology Applied

Scientific EffectEtching stopper effect:

Data Source

PatentUS10361231B2Image capturing apparatus, manufacturing method thereof, and camera

Publication Date: 2019.07.23 CANON KK

AI summary

A back-side illumination image capturing apparatus includes a semiconductor substrate having a first surface for receiving incident light and a second surface located on the opposite side as the first surface, and including a photoelectric conversion portion, and a gate electrode disposed above the second surface. The apparatus further includes a first insulating layer disposed above the second surface of the semiconductor substrate, an interlayer insulation film disposed on the first insulating layer, a contact plug connected to the gate electrode, and a light-cutting portion for cutting light, of the incident light, that has passed through the photoelectric conversion portion. The light-cutting portion passes through at least part of the interlayer insulation film. The first insulating layer is located between the light-cutting portion and the semiconductor substrate.