Micro-Nanometric Hierarchical Structures via Single-Step Optical Lithography

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Solution Overview

Problem

Existing methods for manufacturing micro-nanometric hierarchical structures are complex and difficult to implement on an industrial scale due to their multi-step processes.

Innovation Solution

A method involving optical lithography with a mask having regions with different area ratios and a pitch equal to the minimum resolution dimension of the Rayleigh criterion, followed by development and optional anisotropic etching, to create pillars and protrusions of varying heights and dimensions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If separate steps are used for manufacturing pillars and protrusions, then manufacturing precision can be maintained, but device complexity and manufacturing time increase significantly

Engineering Contradiction:

Improveprecision of pillars and protrusionsVSAvoidcomplexity of manufacturing process

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent combines the manufacturing of pillars and protrusions into a single optical lithography step. By using a mask with specific geometric features (opaque regions defining pillar locations and transparent regions defining protrusion locations), both structures are formed simultaneously in one exposure and development process, eliminating the need for separate manufacturing steps while maintaining precision

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The optical lithography process is made multi-functional by designing the mask to serve dual purposes: defining both pillar structures and protrusion structures in a single pattern transfer operation. This universal approach allows one process step to achieve what traditionally required multiple specialized steps

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Manufacturing precision

If multiple steps are used for manufacturing hierarchical structures, then manufacturing precision is maintained, but productivity decreases

Engineering Contradiction:

Improveprecision of hierarchical structureVSAvoidproduction speed of hierarchical structures

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent merges multiple manufacturing operations into a single optical lithography step, where pillars and protrusions are formed simultaneously through one exposure and development cycle. This consolidation dramatically reduces manufacturing time and increases productivity while the carefully designed mask geometry ensures that precision requirements are met for both structure types

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The mask is pre-designed with specific geometric features that encode both pillar and protrusion patterns. By preparing the mask in advance with the complete hierarchical pattern information, the actual manufacturing process can proceed rapidly in a single step without requiring intermediate alignment or multiple exposure operations

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If pitch is reduced to minimum resolution dimension, then area ratio control improves, but manufacturing precision becomes more challenging

Engineering Contradiction:

Improvecontrol of area ratioVSAvoidresolution limit of optical system

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The patent applies different geometric characteristics to different regions of the mask: opaque regions with specific dimensions define pillar locations and sizes, while transparent regions define protrusion locations and sizes. This local differentiation of mask properties allows precise control of area ratios and structure dimensions even at minimum pitch scales, as each region is optimized for its specific function

Inventive Principle:

Principle #3Local quality

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

Facilitates the simultaneous and precise formation of pillars and protrusions, enabling easy industrial scalability and controlled surface properties.

Implementation Method 1

exposure of a resist layer to an electromagnetic radiation by an optical lithography system comprising a mask crossed by the electromagnetic radiation

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

the pitch being equal, to within 10%, to the minimum resolution dimension of the Rayleigh criterion

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS20250321493A1Method for manufacturing a micro-nanometric hierarchical structure and micro-nanometric hierarchical structure obtained by such a method

Publication Date: 2025.10.16 STMICROELECTRONICS INT NV

AI summary

The present description concerns a manufacturing method comprising the exposure of a resist layer to a radiation by an optical lithography system comprising a mask, the mask comprising an array of pads opaque to radiation, spaced apart by a pitch, and distributed in at least two regions, the area ratios of the two regions being different, the pitch being equal, to within 10%, to the minimum resolution dimension of the Rayleigh criterion, and the development of the layer obtaining two pillars of different heights at the locations of the images of the two regions and of protrusions of nanometric heights at the top of each pillar at the locations of the images of the pillars.