Vertically Integrated Image Sensor with Programmable Pinning Layers

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Solution Overview

Problem

Small pixel image sensors face challenges with poor quantum efficiency due to electrical conductor placement, low photodetector charge capacity, and grid distortions leading to color crosstalk, as well as inadequate global electronic shutter performance and infrared sensitivity.

Innovation Solution

A vertically integrated image sensor design featuring front-side and backside photodetectors with programmable pinning layers, allowing for adjustable electrostatic barriers to enhance charge transfer and separation, enabling high sensitivity and low noise global shutter operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If back-illuminated image sensor is used, then quantum efficiency performance is improved, but manufacturing complexity increases due to wafer bonding and thinning process

Engineering Contradiction:

Improvequantum efficiencyVSAvoidmanufacturing process

Core Design Contradiction:

Use of energy by moving objectVSEase of manufacture

Solution Approach 1:

The image sensor is divided into front-side photodetectors and backside photodetectors that are vertically integrated but functionally separable. The pinning layers are segmented into front-side and backside components that can be independently controlled through separate contact structures, allowing independent optimization of each photodetector type while simplifying the manufacturing process.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of using the conventional back-illuminated structure with complex wafer bonding and thinning, the patent inverts the approach by implementing a front-side illuminated sensor with vertically integrated photodetectors where the backside photodetectors are formed through standard CMOS processing without requiring wafer bonding or thinning operations.

Inventive Principle:

Principle #13The other way round (Inversion)

2Manufacturing precision

If small pixel design is used, then resolution is improved, but photodetector charge capacity decreases

Engineering Contradiction:

ImproveresolutionVSAvoidcharge capacity

Core Design Contradiction:

Manufacturing precisionVSQuantity of substance

Solution Approach 1:

The patent transitions from a two-dimensional planar photodetector design to a three-dimensional vertically integrated structure. By stacking front-side and backside photodetectors vertically, the charge capacity is increased without increasing the lateral pixel area, thereby maintaining high resolution while enhancing charge storage capability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The front-side photodetectors and backside photodetectors are merged into a single vertically integrated photodetector structure within each pixel. This combination allows the pixel to utilize the full depth of the substrate for charge generation and storage, effectively increasing charge capacity without increasing pixel footprint.

Inventive Principle:

Principle #5Merging (Combining)

3Use of energy by moving object

If back-illuminated image sensor is used, then quantum efficiency is improved, but color crosstalk increases due to grid distortions

Engineering Contradiction:

Improvequantum efficiencyVSAvoidcolor accuracy

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The color filter array is segmented into front-side color filters and backside color filters that are vertically aligned with their respective photodetectors. This segmentation, combined with the vertically integrated photodetector structure, maintains precise color alignment without requiring complex wafer bonding processes that cause grid distortions.

Inventive Principle:

Principle #1Segmentation

4Reliability

If large pixel architecture is used, then global electronic shutter performance is improved, but pixel area increases

Engineering Contradiction:

Improveglobal shutter performanceVSAvoidpixel area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent implements global electronic shutter functionality by utilizing the vertical dimension of the vertically integrated photodetector structure. Transfer gates are positioned vertically between the front-side and backside photodetectors, allowing charge transfer and shutter operation without requiring additional lateral space that would increase pixel area.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 design improves photodetector charge capacity, reduces color crosstalk, and enables high-performance global electronic shutter and mixed spectrum imaging, increasing sensitivity and reducing system complexity and cost.

Implementation Method 1

an electrostatic barrier is produced between the front-side photodetector and the backside photodetector by adjusting an adjustable and programmable potential on the backside pinning layer

Methodology Applied

Scientific EffectElectrostatic barrier: Electrostatics

Implementation Method 2

light-sensitive photodetectors that convert incident light into electrical signals

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS8736728B2Image sensor with controllable vertically integrated photodetectors

Publication Date: 2014.05.27 SEMICON COMPONENTS IND LLC

AI summary

An image sensor includes front-side and backside photodetectors of a first conductivity type disposed in a substrate layer of the first conductivity type. A front-side pinning layer of a second conductivity type is connected to a first contact. The first contact receives a predetermined potential. A backside pinning layer of the second conductivity type is connected to a second contact. The second contact receives an adjustable and programmable potential.