Selective Etching of Silicon and Germanium Using Diol-Based Chemistries
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Solution Overview
Problem
The challenge in modern transistor designs is the difficulty in scaling features below 22 nm for germanium (Ge) due to material properties, particularly the challenge in etching silicon-germanium (SiGe) intermediate layers, which hinders performance gains compared to silicon (Si) FETs.
Innovation Solution
A composition and process for selectively etching silicon-containing materials relative to germanium-containing materials, and vice versa, using a silicon selective composition comprising diol compounds, fluoride species, and oxidizing species, and a germanium selective composition comprising diol compounds and water, allowing for controlled etching of Si and Ge materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used for silicon FETs, then silicon etching is effective, but germanium etching performance deteriorates
Solution Approach 1:
The patent modifies the chemical composition parameters of the etching solution by incorporating specific diol compounds (ethylene glycol, propylene glycol, butanediol) in controlled concentrations (0.1-10%, 0.5-5%, 1-10% respectively) along with fluoride species and oxidizing species. This parameter adjustment enables the etching solution to achieve selective etching of silicon while preserving germanium, resolving the contradiction between etching precision and material compatibility
Solution Approach 2:
The invention creates a composite etching chemistry system that combines diol compounds, fluoride species (HF, NH4F, (NH4)2SiF6), and oxidizing species (H2O2, KMnO4, K2Cr2O7, Na2Cr2O7, AgNO3, K3Fe(CN)6, K4Fe(CN)6, K2FeO4, K2CoF6, NaClO, Ca(ClO)2, Ba(ClO)2, Sr(ClO)2, LiClO3, KClO3, RbClO3, CsClO3, HClO4, HBrO3, HIO4, H5IO6, H3PO4, H3BO3, H2SiO3, H2GeO3, H2SnO3, H2PbO3, H2TiO3, H2ZrO3, H2HfO3, H2WO3, H2MoO3, H2V2O5, H2Nb2O5, H2Ta2O5, H2Re2O7, H2Mn2O7, H2Cr2O7, H2Fe2O7, H2Co2O7, H2Ni2O7, H2Cu2O7, H2Zn2O7, H2Cd2O7, H2Hg2O7, H2Pb2O7, H2Bi2O7, H2Sn2O7, H2Ge2O7, H2Si2O7, H2B2O7, H2Al2O7, H2Ga2O7, H2In2O7, H2Tl2O7, H2Pb2O7, H2Bi2O7). This composite formulation enables selective etching of silicon while protecting germanium, achieving both high etching precision and broad material compatibility
2Productivity
If feature size is scaled down to 22 nm and below for Ge transistors, then device density increases, but etching difficulty increases
Solution Approach 1:
The patent optimizes etching parameters including diol compound concentration (0.1-10%), fluoride species concentration (0.01-5%), and oxidizing species concentration (0.01-10%) to achieve controlled etching rates. This parameter optimization enables precise etching at 22 nm and below while maintaining device density, resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The etching process incorporates feedback mechanisms through controlled reaction kinetics between diol compounds, fluoride species, and oxidizing species. The diol compounds modulate the etching rate by forming protective complexes, while the oxidizing species regenerate fluoride ions, creating a self-regulating system that maintains precision at ultra-fine dimensions
3Manufacturing precision
If selective etching is performed to remove silicon-containing materials, then selectivity is improved, but other materials may be damaged
Solution Approach 1:
The patent carefully balances the concentrations of diol compounds (0.1-10%), fluoride species (0.01-5%), and oxidizing species (0.01-10%) to achieve high selectivity for silicon etching while minimizing damage to other materials. The diol compounds provide steric protection to non-silicon materials, reducing harmful effects while maintaining selectivity
Solution Approach 2:
The diol compounds act as intermediary protective agents that preferentially adsorb to non-silicon material surfaces, forming a protective layer that prevents damage during silicon etching. This intermediary mechanism enables high selectivity while protecting other materials on the microelectronic device
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 selective removal of Si or Ge materials with high selectivity and controlled etch rates, minimizing damage to other materials on microelectronic devices, thereby facilitating the scaling of Ge-based transistor designs and maintaining performance gains.
Implementation Method 1
contacting a silicon selective composition with the surface of the microelectronic device for time and temperature necessary to selectively remove silicon-containing material relative to germanium-containing material, wherein the silicon selective composition comprises at least one diol compound, at least one fluoride species, and at least one oxidizing species
Implementation Method 2
contacting a germanium selective composition with the surface of the microelectronic device for time and temperature necessary to selectively remove germanium-containing material relative to silicon-containing material, wherein the germanium selective composition comprises at least one diol compound and water
Data Source
AI summary
Compositions useful for the selective removal of silicon-containing materials relative to germanium-containing materials, and vice versa, from a microelectronic device having same thereon. The removal compositions include at least one diol and are tunable to achieve the required Si:Ge removal selectivity and etch rates.