SiGe Etching Composition for Selective Removal Over Germanium
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Solution Overview
Problem
Conventional aqueous etching solutions for silicon-germanium alloy films in semiconductor manufacturing lack selectivity and compatibility with nitride/oxide masks, leading to inefficient removal of sacrificial SiGe layers and surface roughness issues during the fabrication of Ge nanowire channels in GAA MOSFETs.
Innovation Solution
An aqueous etching solution comprising a quinone oxidizer, fluoride ion source, water-miscible solvent, corrosion inhibitor, and surfactant, which provides enhanced selectivity and compatibility, allowing for the selective removal of silicon-germanium over germanium with controlled etch rates and surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional aqueous etching solutions (HF/H2O2/CH3COOH) are used for SiGe etching, then etch selectivity towards SiGe over Si is improved, but compatibility with nitride/oxide masks deteriorates due to high etch rate on oxide and nitride
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by replacing the conventional HF/H2O2/CH3COOH chemistry with a novel composition containing ammonium bifluoride, hydrobromic acid, and hydrogen peroxide. This parameter change achieves both high SiGe etch selectivity (greater than 2:1 over Ge) and compatibility with nitride/oxide masks by controlling the etch rates of all materials involved
Solution Approach 2:
The patent uses a composite etching solution formulation combining multiple chemical components (ammonium bifluoride, hydrobromic acid, hydrogen peroxide, and water) that work synergistically. This composite chemistry provides selective SiGe removal while protecting masks, resolving the contradiction between selectivity and mask compatibility
2Ease of manufacture
If conventional etching solutions are used for SiGe removal, then etching process is simplified, but surface roughness increases leading to poor nanowire quality
Solution Approach 1:
The patent modifies the chemical composition parameters to include specific concentrations of ammonium bifluoride (0.1-10 wt%), hydrobromic acid (1-50 wt%), and hydrogen peroxide (0.1-10 wt%). These parameter adjustments enable the etching process to maintain simplicity while producing smooth surfaces with minimal roughness, ensuring high nanowire quality
3Productivity
If high etch rate chemistry is used for rapid SiGe removal, then productivity increases, but selectivity control deteriorates making it difficult to prevent substrate trench recession
Solution Approach 1:
The patent optimizes the concentration parameters of the etching components to achieve the right balance: ammonium bifluoride (0.1-10 wt%) provides etching power while hydrobromic acid (1-50 wt%) and hydrogen peroxide (0.1-10 wt%) enhance selectivity. This parameter optimization enables both high productivity through rapid SiGe removal and precise selectivity control to prevent unwanted substrate trench recession
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
The solution achieves selective etching of silicon-germanium with a selectivity greater than 2, compatibility with nitride/oxide masks, and prevents surface roughness, ensuring successful fabrication of Ge nanowire channels with minimal chemical contamination.
Implementation Method 1
The composition comprises: water; oxidizer; water-miscible organic solvent; fluoride ion source
Implementation Method 2
A H2O2/CH3COOH/HF mixture is highly selective towards Si1-xGex over Si
Implementation Method 3
The composition may also comprise at least one surfactant
Implementation Method 4
The composition may also comprise at least one corrosion inhibitor
Data Source
Figure 1A~1B
AI summary
Described herein is an etching solution comprising water; an oxidizer; a water-miscible organic solvent; a fluoride ion source; a corrosion inhibitor and optionally, a surfactant, optionally a buffer, optionally a chelating agent. Such compositions are useful for the selective removal of silicon-germanium over germanium from a microelectronic device having such material(s) thereon during its manufacture.