Top-Gate Organic Transistor Patterning via Photolithography

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Solution Overview

Problem

Current vertical organic field effect transistors (VOFETs) face challenges in achieving high on-current density, on/off ratio, operational stability, and uniformity, while their complex fabrication protocols limit compatibility with mass production techniques, and existing patterning methods like photolithography and etching are not suitable for organic semiconductor materials due to sensitivity and low yield.

Innovation Solution

A top-gate organic transistor design is introduced, compatible with mass production techniques, where the gate insulator acts as a degradation barrier, and electrodes are patterned using photo-lithography and etching, allowing for precise control and high-resolution patterning without the need for shadow masks, enabling the use of dopant materials and self-assembling layers for improved charge injection and mobility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If shadow masks are used for patterning electrodes on organic semiconductor, then high-resolution patterning can be achieved, but device complexity and fabrication complexity increase significantly

Engineering Contradiction:

Improvepatterning resolutionVSAvoidfabrication protocol complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical shadow mask system with a photo-lithography system that uses light to pattern electrodes directly on the organic semiconductor. This substitution eliminates the need for physical masks while achieving comparable or superior patterning resolution, thereby reducing fabrication complexity and device structure complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If photolithography and etching are used on organic semiconductor materials, then mass production compatibility is improved, but process yield decreases due to material sensitivity

Engineering Contradiction:

Improvemass production compatibilityVSAvoidprocess yield

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent uses photo-lithography to create a patterned photoresist layer that serves as a template or copy for the electrode pattern. This allows the electrode structure to be transferred onto the organic semiconductor through a gentle deposition process rather than aggressive etching, maintaining high yield while enabling mass production compatibility.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent introduces a photoresist layer as an intermediary between the patterning process and the organic semiconductor. This intermediary protects the sensitive organic material during processing while still allowing precise pattern transfer, thereby maintaining both high yield and mass production compatibility.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If lift-off process is used for electrode patterning, then photolithography freedom is achieved, but process yield and resolution are limited

Engineering Contradiction:

Improvephotolithography freedomVSAvoidprocess yield

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

Instead of using lift-off where material is deposited and then removed, the patent inverts the approach by depositing material only where needed through photo-lithographically defined masks. This direct patterning method achieves the versatility of photolithography while avoiding the yield and resolution limitations of lift-off processes.

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 design enhances current densities, stability, and uniformity, allowing for the production of transistors with high on/off ratios and reduced capacitance, facilitating the fabrication of complementary circuits and transistors with gain up to 20 times that of conventional thin-film transistors.

Implementation Method 1

the gate insulator acts as a degradation barrier

Methodology Applied

Scientific EffectPhysical barrier protection:

Implementation Method 2

electrodes are patterned using photo-lithography

Methodology Applied

Scientific EffectPhoto-lithography: Photography

Implementation Method 3

electrodes are patterned using photo-lithography and etching

Methodology Applied

Scientific EffectEtching:

Data Source

PatentEP2924754B1Method for producing an organic transistor and organic transistor

Publication Date: 2021.10.20 NOVALED GMBH

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AI summary

The invention refers to a method for producing an organic transistor, the method comprising steps of providing a first electrode (2) on a substrate (1), generating a source-drain insulator (3) assigned at least partially to the substrate (1) and/or at least partially to the first electrode (2), generating a second electrode (4) assigned to the source-drain insulator (3), depositing an organic semiconducting layer (5) on the first electrode (2), the second electrode (4), and the source-drain insulator (3), generating a gate insulator (6) assigned to the organic semiconducting layer (5), and providing a gate electrode (7) assigned to the gate insulator (6). Further, the invention relates to an organic transistor.