Biased Inter-Pixel Light Shielding for Backside Illumination Color Mixing

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Solution Overview

Problem

Backside illumination CMOS solid-state imaging devices face challenges in suppressing optical color mixing and magenta flare while maintaining sensitivity, as existing solutions like light shielding films can decrease sensitivity due to light blocking.

Innovation Solution

A solid-state imaging device with an inter-pixel light shielding unit strategically located at the boundary portions between different color pixels, connected to a fixed potential and formed using materials like metal, which blocks light effectively without being present at same-color pixel boundaries, and a signal processing circuit to correct output values based on sensitivity differences.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a light shielding film is provided at all boundary portions between adjacent pixels in backside illumination CMOS, then optical color mixing is suppressed, but sensitivity decreases due to unnecessary light blocking at same-color pixel boundaries

Engineering Contradiction:

Improveoptical color mixingVSAvoidsensitivity

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The light shielding film is selectively provided only at boundary portions between pixels of different colors, while being omitted at boundary portions between pixels of the same color. This local differentiation suppresses optical color mixing where needed (at different-color boundaries) while avoiding unnecessary light blocking at same-color boundaries, thereby maintaining sensitivity.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If a light shielding film is provided at all boundary portions between adjacent pixels in backside illumination CMOS, then optical color mixing is suppressed, but device complexity increases due to uniform shielding structure

Engineering Contradiction:

Improveoptical color mixingVSAvoidshielding structure complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If the inter-pixel light shielding unit is biasedly located at different color pixel boundaries, then optical color mixing is suppressed effectively, but manufacturing precision requirements increase

Engineering Contradiction:

Improveoptical color mixingVSAvoidlight shielding unit positioning

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The pixel array is designed with predetermined color arrangements (such as Bayer pattern or other color filter arrays) where the positions of different-color pixel boundaries are known in advance. This allows the light shielding film to be selectively formed at specific boundaries during the manufacturing process, reducing the complexity of real-time positioning while maintaining effective suppression of optical color mixing.

Inventive Principle:

Principle #10Preliminary action

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

Effectively suppresses optical color mixing and magenta flare while improving sensitivity by selectively applying light shielding only where necessary, reducing unnecessary light blocking and adjusting signal processing to account for sensitivity variations.

Implementation Method 1

an inter-pixel light shielding unit which is provided in a boundary portion between the pixels adjacent to each other... the inter-pixel light shielding units are biasedly located at the boundary portion of the combination of the different color pixels

Methodology Applied

Scientific EffectLight blocking: Absorption (EM radiation)

Implementation Method 2

A micro lens is formed for each pixel, corresponding to the photodiode configuring each pixel. The micro lens condenses the input light from the outside to a photodiode of corresponding pixel.

Methodology Applied

Scientific EffectLight condensation: Lens

Implementation Method 3

Each of the color filters is a filter portion of any color of, for example, red, green, and blue, and transmits light of each color component.

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Implementation Method 4

Each pixel which is arranged in the pixel region is configured by a photodiode as a light receiving element having a photoelectric conversion function

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS8736731B2Solid-state imaging device and electronic apparatus having biasedly located inter-pixel light shielding units to minimize color mixing

Publication Date: 2014.05.27 SONY GROUP CORP

AI summary

A solid-state imaging device which includes a pixel region which is provided on a semiconductor substrate, and in which a plurality of pixels including a photoelectric conversion unit having a photoelectric conversion function is arranged, a wiring layer which is provided at one plate surface of the semiconductor substrate, a color filter layer which is divided into a plurality of color filters provided corresponding to each pixel of the plurality of pixels which is arranged in the pixel region, and an inter-pixel light shielding unit which is provided in a boundary portion between the pixels adjacent to each other, between the semiconductor substrate and the color filter layer.