Organic Photodiode Trenches for Quantum Efficiency

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Solution Overview

Problem

Existing image sensors using organic semiconductor materials suffer from low quantum efficiency and high dark current, necessitating the development of devices with improved quantum efficiency and reduced dark current.

Innovation Solution

The formation of trenches in the N-type layer and pixel electrode layer of organic photodiodes increases the PN junction interfacial area, combined with the use of organic P-type and hole transport layers, enhances quantum efficiency by effectively converting photons into charge carriers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If organic semiconductor materials are used in image sensors, then manufacturing cost is reduced and integration with CMOS is improved, but quantum efficiency is low and dark current is high

Engineering Contradiction:

Improvemanufacturing costVSAvoidquantum efficiency

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent introduces trenches into the photodiode structure, transforming the flat surface into a three-dimensional configuration with increased surface area. This dimensional change allows more photons to be captured while maintaining the organic semiconductor material benefits, thereby improving quantum efficiency without sacrificing ease of manufacture

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent applies different materials and structures to different regions of the photodiode: organic semiconductor materials in specific layers, trenches in strategic locations, and selective contact structures. This local differentiation optimizes photon absorption and charge carrier collection in specific areas, improving overall quantum efficiency while maintaining manufacturing feasibility

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If organic semiconductor materials are used in image sensors, then manufacturing cost is reduced and integration with CMOS is improved, but dark current is high

Engineering Contradiction:

Improvemanufacturing costVSAvoiddark current

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent extracts or removes unwanted charge carriers through selective contact structures and layered configurations. By taking out harmful dark current components while retaining useful photon-induced carriers, the device achieves low dark current performance while maintaining the cost advantages of organic semiconductors

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces intermediary layers and structures (such as electron transport layers, hole transport layers, and selective contacts) that mediate between the organic semiconductor active layer and the electrodes. These intermediaries selectively transport desired charge carriers while blocking unwanted dark current, resolving the contradiction between manufacturing ease and dark current suppression

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If trenches are formed in the N-type layer and pixel electrode layer, then quantum efficiency is improved by increasing PN junction interfacial area, but device complexity increases

Engineering Contradiction:

Improvequantum efficiencyVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the photodiode structure by introducing trenches that divide the active layer into multiple regions. This segmentation increases the PN junction interfacial area for better photon-to-charge conversion while organizing the complexity into manageable, repeating units that can be manufactured using standard lithographic processes

Inventive Principle:

Principle #1Segmentation

4Reliability

If trenches are formed in the N-type layer and pixel electrode layer, then quantum efficiency is improved by increasing PN junction interfacial area, but manufacturing precision requirements increase

Engineering Contradiction:

Improvequantum efficiencyVSAvoidtrench formation precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent optimizes the trench parameters (depth, width, spacing, and density) to achieve the desired quantum efficiency improvement while keeping the manufacturing precision requirements within acceptable ranges. By carefully selecting these parameters, the design balances performance gains with manufacturing feasibility

Inventive Principle:

Principle #35Parameter changes

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 improves quantum efficiency by up to 200% compared to photodiodes with flat surfaces, while maintaining low dark current levels, thereby enhancing the performance of image sensors.

Implementation Method 1

The image sensors in the image sensor chips generate electrical signals in response to the stimulation by photons

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS11404484B2Image sensors with organic photodiodes and methods for forming the same

Publication Date: 2022.08.02 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Embodiments of forming an image sensor with organic photodiodes are provided. Trenches are formed in the organic photodiodes to increase the PN-junction interfacial area, which improves the quantum efficiency (QE) of the photodiodes. The organic P-type material is applied in liquid form to fill the trenches. A mixture of P-type materials with different work function values and thickness can be used to meet the desired work function value for the photodiodes.