Microscopic 3D Structures via Frozen Precursor Layering
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Solution Overview
Problem
Existing methods for forming 3D structures on substrates are limited by the minimum thickness of the liquid layer, leading to unreliable wetting and non-uniform film thickness, and are restricted to materials that can solidify upon irradiation, preventing the creation of structures with overhanging features and limiting the range of usable materials.
Innovation Solution
A method involving a Scanning Electron Microscope with a Gas Injection System, where a substrate is cooled to apply a frozen layer of precursor fluid, which is then irradiated with an electron beam to form a stack of layers, allowing for the creation of 3D structures with overhanging features by controlling the temperature for evaporation of unprocessed precursor material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a thin layer of liquid precursor material is applied on the substrate surface, then the vertical resolution and dimensional control are improved, but the wetting reliability and film uniformity deteriorate
Solution Approach 1:
The patent changes the physical state parameter of the precursor material from liquid to gas, and controls the temperature parameter to condense the gas into a thin solid layer. This allows forming uniformly thin layers (5-50 nm) without the wetting problems that limit liquid-based methods, thereby achieving high vertical resolution while maintaining process reliability
Solution Approach 2:
The patent utilizes phase transitions of the precursor material: gas phase delivery followed by condensation to solid phase on the substrate. This phase transition approach enables controlled deposition of ultra-thin layers with uniform thickness, solving the fundamental limitation of liquid methods where thickness control below certain limits results in poor wetting and non-uniform films
2Productivity
If the penetration depth of particles is increased to convert precursor material through thicker layers, then the processing efficiency is improved, but the vertical resolution deteriorates
Solution Approach 1:
The patent segments the precursor material into multiple thin layers deposited sequentially, where each layer is thin enough (5-50 nm) that particle beams can penetrate completely through it. This segmentation allows using moderate particle energies that provide both sufficient penetration for complete conversion (maintaining productivity) and limited interaction volume (maintaining vertical resolution of 5-50 nm)
3Ease of manufacture
If conventional liquid precursor materials are used that solidify upon irradiation, then the process is simpler, but the material versatility and ability to create overhanging features are limited
Solution Approach 1:
The patent changes the delivery state from liquid to gas, allowing precursor materials to be delivered in vapor form and condensed to solid on the substrate. This enables using materials with high vapor pressures or low melting points that would be difficult to handle as liquids, expanding material versatility while maintaining a relatively simple process through gas injection systems
Solution Approach 2:
The patent introduces temperature control as an intermediary mechanism: the substrate temperature is controlled to be below the condensation point of the precursor gas, enabling condensation of gas-phase precursors into solid layers. This intermediary temperature control allows versatile material selection without requiring the materials to be liquids at room temperature
4Ease of operation
If the liquid precursor material is exposed to vacuum for electron beam irradiation, then the electron beam can reach the material, but the evaporation rate increases and liquid composition changes
Solution Approach 1:
The patent changes the precursor material state from liquid to gas, and delivers it through a gas injection system that operates in vacuum. Gas-phase precursors have much lower evaporation rates in vacuum compared to liquids, and their composition remains stable. The gas is delivered at controlled partial pressures, enabling electron beam irradiation without significant material loss or composition change
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 formation of structures with smaller dimensions and the use of various precursor materials, including those that do not solidify upon irradiation, by forming a sandwich of unconverted precursor material between converted and substrate layers, thus allowing for overhanging features and improved material versatility.
Implementation Method 1
converting part of the precursor material to another material or to another physical state by irradiating part of the layer with particles
Implementation Method 2
irradiating a part of the layer with particles, while the remaining part of the material stays on the surface
Implementation Method 3
the substrate is cooled below the freezing point of the precursor gas so that a frozen layer of the precursor gas can be applied to the substrate
Implementation Method 4
the temperature is raised so that the unprocessed precursor can evaporate
Data Source
AI summary
A method for forming microscopic 3D structures. In the method according to the invention a substrate (105) is placed in a Scanning Electron Microscope (SEM). The SEM is equipped with a Gas Injection System (GIS) (110) for directing a jet of precursor fluid to the substrate. The substrate is cooled below the freezing point of the precursor gas so that a frozen layer of the precursor gas can be applied to the substrate. By now repeatedly applying a frozen layer of the precursor to the substrate and irradiate the frozen layer with an electron beam (102), a stack of frozen layers (130) is built, each layer showing an irradiated part (131) in which the precursor is converted to another material. After applying the last layer the temperature is raised so that the unprocessed precursor (132) can evaporate. As a result 3D structures with overhanging features can be built.