Crystalline Silicon Wet Etching With Agitation-Switched Directionality
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Solution Overview
Problem
Current wet chemical etching techniques for crystalline silicon (c-Si) lack the ability to selectively switch etch directions between the (100) and (110) crystallographic planes without changing the etching solution, temperature, or concentration, which limits the fabrication of well-defined vertical circular nanowires required for advanced transistor designs.
Innovation Solution
A method involving sample agitation in a potassium hydroxide (KOH) solution with <10% concentration at 20-30°C, where the etching solution contacts the c-Si parallel to the (110) plane, applying an oscillatory force to increase the removal rate of etching byproducts, allowing for controlled switching of etch directions between the (100) and (110) planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional wet chemical etching techniques are used with fixed etching solution and conditions, then the etching process is simple and easy to operate, but the etch direction cannot be selectively switched between (100) and (110) crystallographic planes
Solution Approach 1:
The patent applies dynamics by making the etching system adaptable through real-time control of agitation conditions. By dynamically adjusting the agitation state (stirred vs. quiescent) during etching, the system can switch between etching along (100) planes and (110) planes using the same etching solution, thereby achieving versatile etch direction control without changing solution composition or temperature
Solution Approach 2:
The patent changes physical parameters of the etching system by controlling agitation state rather than chemical parameters. By varying the agitation condition (stirred or quiescent) of the etching solution, the etch direction can be switched between crystallographic planes. This approach achieves parameter change through mechanical agitation control instead of chemical composition modification
2Manufacturing precision
If dry etching is used to produce vertical nanowire structures, then the nanowires can be produced with precise dimensions, but surface damage is caused to the silicon structure
Solution Approach 1:
The patent replaces the mechanical/physical process of dry etching with a chemical wet etching process. By using chemical reactions between the etching solution and silicon surface, the material removal is achieved through chemistry rather than physical sputtering, thereby eliminating surface damage while maintaining the ability to produce precise vertical nanowire structures through controlled anisotropic etching
3Speed
If etching solution temperature or concentration is increased to change etch direction, then the etch rate increases, but the process complexity and energy consumption increase
Solution Approach 1:
The patent employs self-service by utilizing the natural response of the etching system to agitation conditions. The etching solution automatically adjusts its etching behavior based on whether it is stirred or quiescent, without requiring external control of temperature or concentration. This self-adjusting mechanism allows etch direction switching through simple agitation control rather than energy-intensive parameter modification
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 sub-10-nm diameter monocrystalline vertical Si nanowires with circular profiles, achieving precise isotropic etch profiles and overcoming surface damage issues associated with dry etching, facilitating the development of vertical GAAFETs.
Implementation Method 1
the surface atoms are removed through a direct chemical reaction of the surface atoms with the etchant
Implementation Method 2
increasing the rate of removal of etching byproducts from the (110) crystallographic plane of the wet-etched c-Si by agitating the etching solution
Data Source
AI summary
This document describes a system and method for selectively switching the fast-wet-etching direction of crystalline silicon, c-Si, nanostructures between the (100) and the (110) crystallographic planes of c-Si by a simple method of sample agitation. This method effectively allows the invention to achieve anisotropic and isotropic wet-etching of c-Si.