Back-Illuminated Imaging Device Pixel Separation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In back-illuminated solid-state imaging devices, the formation of narrow pixel separation p-wells using high-energy ion implantation is challenging due to mask thickness and aperture width issues, leading to crosstalk and deteriorated color reproducibility.

Innovation Solution

A method involving the formation of a mask with wider apertures and reversing the polarity of the pixel separation region by implanting p-type impurity ions into an n-type doped semiconductor layer, allowing for deeper ion implantation and separate formation of n-wells as pixel separation regions, preventing crosstalk and improving color reproducibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If high-energy ion implantation is used to form narrow pixel separation p-wells, then pixel separation is achieved, but mask fabrication becomes extremely difficult with narrow apertures and thick masks

Engineering Contradiction:

Improvepixel separation precisionVSAvoidmask fabrication ease

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

Instead of implanting ions from the front surface to create narrow p-wells, the patent inverts the approach by implanting from the back surface. This allows the use of wider mask apertures while achieving the same pixel separation effect, resolving the contradiction between precision and manufacturability.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the dimension of ion implantation from front-surface (top-down) to back-surface (bottom-up) approach. This dimensional change allows wider mask apertures to be used while still achieving precise pixel separation, eliminating the need for extremely narrow and thick masks.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If mask aperture is narrowed and mask is thickened to withstand high energy, then ion implantation precision is improved, but mask material stays behind on narrow aperture preventing complete p-well formation

Engineering Contradiction:

Improveion implantation precisionVSAvoidp-well formation completeness

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

By inverting the implantation direction to approach from the back surface, the patent avoids the mask material deposition problem that occurs with narrow front-surface apertures. The wider back-surface apertures prevent material buildup while maintaining implantation precision and ensuring complete p-well formation.

Inventive Principle:

Principle #13The other way round (Inversion)

3Manufacturing precision

If pixel separation p-well is formed by front side ion implantation, then pixel separation is achieved, but ion scattering at back side causes p-well extension and increases crosstalk

Engineering Contradiction:

Improvepixel separationVSAvoidcrosstalk

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent inverts the ion implantation direction from front-surface to back-surface approach. This eliminates the ion scattering problem that occurs when ions traverse the entire substrate thickness, as the implantation now stops at the back surface, preventing p-well extension and reducing crosstalk.

Inventive Principle:

Principle #13The other way round (Inversion)

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 approach enables high quantum efficiency and signal-to-noise ratio, even with miniaturized pixels, by preventing crosstalk and ensuring accurate pixel separation, resulting in high-resolution images with improved color reproducibility.

Implementation Method 1

implanting p-type impurity ions into an n-type doped semiconductor layer

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Implementation Method 2

incident light entering the light-receiving region in the Si layer generates photoelectrons

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Implementation Method 3

Part of the photoelectrons leak into adjacent pixels by thermal diffusion, causing crosstalk

Methodology Applied

Scientific EffectThermal diffusion: Diffusion

Data Source

PatentUS9876041B2Solid-state imaging device and method of manufacturing the same

Publication Date: 2018.01.23 SK HYNIX INC

AI summary

According to one embodiment, a method of manufacturing a back-illuminated solid-state imaging device including forming a mask with apertures corresponding to a pixel pattern on the surface of a semiconductor layer, implanting second-conductivity-type impurity ions into the semiconductor layer from the front side of the layer to form second-conductivity-type photoelectric conversion parts and forming a part where no ion has been implanted into a pixel separation region, forming at the surface of the semiconductor layer a signal scanning circuit for reading light signals obtained at the photoelectric conversion parts after removing the mask, and removing the semiconductor substrate and a buried insulating layer from the semiconductor layer after causing a support substrate to adhere to the front side of the semiconductor layer.