Nanostructured Silicon via Catalytic Deposition and Anisotropic Etching
Solution Overview
Problem
Existing methods for producing nanostructured silicon, such as bottom-up VLS and metal-assisted chemical etching, are less consistent, require additional deposition steps, and often necessitate masking processes, limiting reproducibility and efficiency.
Innovation Solution
A method involving catalytic chemical vapor deposition followed by anisotropic etching is used to create columnar polycrystalline silicon structures with amorphous silicon in between, which are then selectively etched to form nanostructured silicon without the need for masking, using a dry ion etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If bottom-up VLS or metal-assisted chemical etching methods are used to produce nanostructured silicon, then columnar structures with high aspect ratios can be formed, but additional deposition steps for metal particles or mask layers are required, increasing process complexity
Solution Approach 1:
The invention extracts and removes the metal particles after they have served their catalytic function in forming the columnar structures. This eliminates the need for subsequent mask deposition steps while maintaining the high aspect ratio structures, thereby reducing overall process complexity
Solution Approach 2:
Metal particles are deposited in advance as catalysts to form the columnar structures during chemical vapor deposition. These particles perform their function before being removed, eliminating the need for later mask deposition steps and reducing total process complexity
2Shape
If conventional lithography with anisotropic etching is used to form deep structures, then vertical edges can be achieved, but masking processes are required which reduce productivity and increase process steps
Solution Approach 1:
The polymerization process automatically forms protective layers on the sidewalls during the etching process itself, without requiring external masking steps. The system serves itself by generating the necessary protection during the etching operation, thereby eliminating separate masking steps and improving productivity
Solution Approach 2:
The etching and polymerization steps are alternatingly repeated in cycles. This periodic action allows the polymer to form protective layers during polymerization steps and etching to occur during etching steps, achieving vertical edges without conventional masking while maintaining productivity
3Productivity
If PECVD is used to deposit silicon layers, then higher deposition rates can be achieved, but the decomposition of starting materials depends on plasma energy which may affect material quality
Solution Approach 1:
The invention changes the energy source from thermal to plasma-based, allowing decomposition of silane at lower substrate temperatures while maintaining high deposition rates. The plasma energy parameters are optimized to achieve both high productivity and good material quality by controlling ionization and radical formation
4Area of stationary object
If the diameters of columnar structures are reduced and distance between them is decreased to increase surface area, then light absorption improves, but the structures become more difficult to fabricate with consistent dimensions
Solution Approach 1:
The polymerization process provides self-regulating feedback during etching. The polymer layers form on sidewalls and control the etching rate, automatically adjusting to maintain consistent column dimensions and spacing. This feedback mechanism ensures manufacturing precision even at small scales with high surface area
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 allows for the production of nanostructured silicon with high aspect ratios and increased surface area, eliminating the need for masking and enhancing reproducibility and efficiency.
Implementation Method 1
conducting a catalytic chemical vapor deposition using a Si-containing precursor and a carrier gas to generate on the substrate a silicon layer comprising columnar polycrystalline silicon structures and amorphous silicon containing material therebetween
Implementation Method 2
catalytic chemical vapor deposition
Implementation Method 3
conducting an anisotropic etching process of the silicon layer to remove the amorphous silicon containing material between the polycrystalline silicon columns
Implementation Method 4
dry ion etching process
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
A method of fabricating nanostructured silicon on a substrate comprises a step of conducting a catalytic chemical vapor deposition using a Si-containing precursor and a carrier gas to generate on the substrate a silicon layer comprising columnar polycrystalline silicon structures and amorphous silicon containing material therebetween. The method further comprises conducting an anisotropic etching process of the silicon layer to remove the silicon between the polycrystalline silicon columns in order to fabricate the nanostructured silicon on the substrate.