Silicon Trench Fabrication via Metal Catalyst Etching
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Solution Overview
Problem
Current methods for fabricating silicon trenches, such as reactive ion etching, potassium hydroxide wet chemical etching, and laser-assisted direct imprint, are either expensive, limited in scale, or restricted by crystal orientation, failing to efficiently produce highly anisotropic trenches with dimensions ranging from nanometers to micrometers.
Innovation Solution
A low-cost method involving a silicon substrate with a patterned etching-barrier layer, metal catalysts, and sequential immersion in etching solutions to achieve anisotropic etching and subsequent detachment of silicon nanostructures, allowing for large-area fabrication of silicon trenches with micrometer-scale depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If reactive ion etching (RIE) is used to create highly anisotropic structures, then etching anisotropy is improved, but device complexity and cost increase due to expensive instruments and additional hard etching masks
Solution Approach 1:
The patent extracts and removes the silicon nanostructures after etching, leaving behind clean trenches without requiring additional hard masks or complex removal steps. The catalysts are selectively removed, taking the etched silicon structures with them, which simplifies the overall process compared to traditional RIE methods.
Solution Approach 2:
Metal catalysts serve as intermediaries that enable selective etching of silicon. The catalysts facilitate the etching process by mediating the chemical reaction between the etching solution and silicon, allowing highly anisotropic etching without requiring complex RIE equipment or additional masking layers.
2Ease of manufacture
If KOH wet chemical etching is used for large-area fabrication, then manufacturing cost is reduced, but etching direction is restricted due to crystal orientation
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by using metal catalysts that enable etching in directions not limited by silicon crystal orientation. The catalysts modify the etching chemistry to achieve highly anisotropic etching in the desired direction regardless of the underlying crystal structure, providing both low cost and directional flexibility.
3Productivity
If laser-assisted direct imprint (LADI) is used for rapid patterning, then productivity is improved, but line width and depth are limited to sub-micrometers
Solution Approach 1:
The patent performs preliminary patterning to define the etching areas before introducing metal catalysts. This preliminary structure definition allows subsequent deep etching to proceed rapidly while maintaining precise control over the final trench dimensions, overcoming the depth limitations of direct LADI methods.
Solution Approach 2:
The etching process continues uninterrupted until the desired depth is achieved, with the metal catalysts maintaining active etching throughout the process. This continuous action enables deep trench formation without the depth limitations that constrain LADI methods, while still maintaining high productivity.
4Adaptability or versatility
If deep silicon trenches with depths between 10 and 100 μm are required, then application versatility is improved, but conventional methods become impractical or require additional complex steps
Solution Approach 1:
The patent uses disposable metal catalysts that are removed after serving their etching function. These catalysts enable deep trench etching through a simple, low-cost process, and are subsequently removed along with the etched silicon structures, leaving clean trenches without requiring complex additional processing steps.
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 method enables the cost-effective production of highly anisotropic silicon trenches with micrometer-scale depths, enhancing etching rates and scalability compared to conventional techniques, suitable for applications in semiconductor devices and solar cells.
Implementation Method 1
immersing the silicon substrate in a first etching solution to etch silicon under the metal catalysts in an anisotropic direction
Implementation Method 2
immersing the silicon substrate in a second etching solution, resulting a side etching between the silicon nanostructures and the silicon substrate
Data Source
AI summary
A method for forming a silicon trench, comprises the steps of: defining an etching area at a silicon substrate; forming metal catalysts at the surface of the etching area; immersing the silicon substrate in a first etching solution thereby forming anisotropic silicon nanostructures in the etching area; immersing the silicon substrate in a second etching solution thereby resulting in the silicon nanostructures being side-etched and detached from the silicon substrate, thus forming the silicon trench.