Oversized 3D Lithographic Imprinting with Virtual Photomasks
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Solution Overview
Problem
Existing lithographic methods are limited in producing microstructures with structure heights exceeding 100 micrometers due to light absorption constraints and slow processing times, making it difficult to efficiently create large-area microstructures with high precision.
Innovation Solution
A lithographic process that subdivides a three-dimensional structural model into sequentially stacked substructures, each within the penetration depth of electromagnetic radiation, using computer-aided modeling and virtual photomasks to emboss oversized structures in a photostructurable carrier material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If single-photon laser lithography is used to expose photoresist, then individual points can be exposed with varying light doses for precise structuring, but the penetration depth is severely limited to maximum 100 micrometres due to exponential light absorption
Solution Approach 1:
The patent divides the single exposure step into multiple sequential exposure steps, each exposing a portion of the total structure height. By segmenting the exposure process into N steps with N virtual photomasks, the system can achieve total structuring depth exceeding the penetration depth of any single exposure step, while maintaining the precision benefits of controlled light dosing at each stage.
2Length of stationary object
If direct two-photon laser beam lithography is used to produce three-dimensional structures with structure heights in the millimetre range, then oversized structures can be created, but the writing speed is extremely slow at only around 3 mm2 per hour
Solution Approach 1:
The patent segments the three-dimensional structure into N two-dimensional layers, each corresponding to a virtual photomask. This allows parallel processing of multiple layers through sequential exposure steps, dramatically increasing productivity compared to sequential voxel scanning while maintaining the capability to produce millimetre-range structure heights.
Solution Approach 2:
The patent uses virtual photomasks that can be digitally generated and reused, allowing rapid reproduction of identical or modified layers. This copying approach enables efficient production of multiple layers with the same pattern, significantly boosting throughput compared to manual or sequential scanning methods.
3Length of stationary object
If the light dose is increased to overcome light absorption and achieve deeper penetration, then deeper structures can be exposed, but the photoresist is destroyed above a certain limit with current maximum light dose of 1200 mWs/cm2
Solution Approach 1:
The patent divides the total required light dose into N smaller doses applied sequentially across multiple exposure steps. Each virtual photomask exposes only the necessary portion at a safe light dose level, preventing photoresist destruction while collectively achieving the total energy deposition needed for deep structure formation.
Solution Approach 2:
The patent performs preliminary structuring in multiple steps, where each exposure step creates a portion of the final structure. By progressively building the structure layer by layer with controlled dosing, the system achieves deep penetration without exceeding the photoresist's maximum light dose tolerance at any single step.
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
Enables the production of microstructures with heights up to the sub-millimeter scale quickly and with high precision, overcoming limitations of current methods by allowing deeper penetration and faster processing.
Implementation Method 1
a lithographic process for embossing three-dimensional microstructures, which have oversized structure heights, in a photostructurable carrier material using an exposure device
Data Source
AI summary
The invention relates to a lithographic process for embossing three-dimensional microstructures, which have oversized structure heights, in a photostructurable carrier material using an exposure device, wherein an oversized structure height has a height which exceeds the value of the maximum nominal penetration depth. The process comprises the following process steps:applying a photostructurable carrier material (1) to a layer height (H.1) on a substrate carrier (2);performing computer-aided modelling of a virtual three-dimensional structural model (10) of the microstructure to be embossed, the total height (H.10) of which structural model is greater than the maximum nominal penetration depth during exposure into the carrier material (1);performing computer-aided subdivision of the total height (H.10) of the structural model (10) into a number of sequentially stacked substructures (11, 12, 13);calculating a virtual photomask (M.11, M.12, M.13) for each of the substructures (11, 12, 13);performing a structuring on the basis of the virtual photomasks (M.11, M.12, M.13) by means of exposure and development (E) of the carrier material (1), until layer by layer all virtual photomasks (M.11, M.12, M.13) have been structured;obtaining a finished structured carrier material (30) which contains a structuring corresponding to the entire structural model (S.10) and its total height (H.10).