Femtosecond Projection Lithography Over-Polymerization Control

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Solution Overview

Problem

Current two-photon lithography techniques, such as femtosecond projection TPL, face challenges with low throughput and defects like over-polymerization, especially in nanoscale features, due to limitations in photopolymer resist material properties and the need for tuning process parameters.

Innovation Solution

The method employs multiple temporally focused light sheets with reduced density to control over-polymerization defects without altering the photopolymer composition, using a tunable mask and optical modeling to simulate light intensity distribution, ensuring a flat and uniform top surface for 3D structures with aspect ratios between 1.2 and 2.0.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If femtosecond projection TPL is used to increase throughput, then manufacturing speed improves, but over-polymerization defects increase

Engineering Contradiction:

ImprovethroughputVSAvoidover-polymerization defects

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent divides the illumination process into multiple sequential light sheets, each illuminating a specific depth region. This segmentation allows control over the polymerization process at different depths, preventing over-polymerization while maintaining high throughput parallel processing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different illumination conditions to different spatial regions by using multiple light sheets with specific intensity distributions. Each light sheet is optimized for its target depth region, creating local quality variations that suppress over-polymerization defects while maintaining overall high-speed fabrication.

Inventive Principle:

Principle #3Local quality

2Productivity

If high light intensity is used to reduce processing time, then productivity improves, but over-polymerization defects increase

Engineering Contradiction:

Improveprocessing speedVSAvoidover-polymerization

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The total light energy is segmented across multiple light sheets with controlled intensity distributions. This allows the system to achieve high productivity through parallel processing while each individual light sheet uses optimized intensity to avoid generating over-polymerization harmful effects.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs periodic illumination with multiple light sheets sequentially processed. This periodic action allows control over the polymerization kinetics, enabling high throughput while preventing the continuous high-intensity exposure that causes over-polymerization defects.

Inventive Principle:

Principle #19Periodic action

3Manufacturing precision

If photopolymer resist composition is tuned to minimize over-polymerization, then manufacturing precision improves, but device complexity increases

Engineering Contradiction:

Improveover-polymerization controlVSAvoidprocess parameter tuning

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces chemical composition tuning with an optical control approach using multiple temporally focused light sheets. This substitution eliminates the need to modify photopolymer resist composition or tune complex material parameters, reducing device complexity while maintaining manufacturing precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the illumination parameters (multiple light sheets with controlled intensity and temporal focusing) rather than changing material parameters. This approach achieves over-polymerization control through process parameter optimization without requiring complex photopolymer composition tuning.

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 approach significantly reduces over-polymerization defects, enhances throughput, and maintains high-quality 3D printing of micro and nanoscale structures, making the process more robust and suitable for high-throughput manufacturing.

Implementation Method 1

Two-photon lithography (TPL) is a photopolymerization-based additive manufacturing technique that facilitates fabrication of millimeter scale complex three-dimensional (3D) structures with submicron features. TPL uses nonlinear photo-absorption from a focused light spot to generate sub-diffraction features through localized photopolymerization

Methodology Applied

Scientific EffectTwo-photon absorption:

Implementation Method 2

generating a first temporally focused light sheet onto or within a first region of a photopolymer resist material

Methodology Applied

Scientific EffectTemporal focusing: Focusing

Data Source

PatentUS20230194992A1System and method to control defects in projection-based sub-micrometer additive manufacturing

Publication Date: 2023.06.22 GEORGIA TECH RES CORP

AI summary

An exemplary optical projection method and system is disclosed, e.g., femtosecond projection two-photon lithography (FP-TPL) based operation, that applies multiple temporally focused light with reduced density of the projected mask to control over-polymerization defects (e.g., without need to tune the photopolymer composition) when certain aspect ratio of the submicron features are desired.