SiGe Etching Selectivity in GAA MOSFETs
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Solution Overview
Problem
Conventional wet chemical etching solutions for silicon-germanium alloys in semiconductor manufacturing lack selectivity and compatibility, particularly when removing sacrificial SiGe layers in GAA MOSFETs, leading to inadequate control over the etching process and unintended substrate recessing.
Innovation Solution
An aqueous etching composition comprising water, an oxidizer (hydrogen peroxide), a fluoride ion source (ammonium fluoride), and a surfactant (polyethyleneimine), which provides enhanced selectivity and control over the etching of silicon-germanium relative to silicon, allowing for precise removal of SiGe layers without recessing the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional wet chemical etching solutions (H2O2/CH3COOH) are used for SiGe etching, then selectivity towards Si1-xGex over Si is improved with smoothness, but the etching process is not effective for vertical stacks and is not compatible with nitride/oxide masks
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by replacing acetic acid with formic acid and adding isopropanol, creating a new composition (H2O2/CH3OH/HCOOH) that maintains high selectivity while improving compatibility with vertical stack geometries and nitride/oxide masks used in advanced semiconductor manufacturing processes
Solution Approach 2:
The patent creates a composite etching chemistry by combining hydrogen peroxide (oxidizer), formic acid (buffer and etchant), and isopropanol (solvent and modifier) in specific proportions, resulting in a synergistic solution that overcomes the limitations of conventional single-chemistry approaches for vertical FinFET and GAA structures
2Manufacturing precision
If H2O2/CH3COOH mixture is used for SiGe oxidation, then selectivity towards Si1-xGex over Si is improved, but the solution does not provide effective control over etching in vertical stacks
Solution Approach 1:
The patent modifies the etching solution parameters by changing from acetic acid to formic acid and adding isopropanol, which alters the etching kinetics to provide better control over vertical stack etching while maintaining high selectivity, enabling precise removal of SiGe sacrificial layers in FinFET and GAA structures
3Productivity
If selective etching of SiGe layers is performed to remove sacrificial layers, then SiGe layers are removed, but trenches are inadvertently recessed into the bulk substrate due to material similarity
Solution Approach 1:
The patent changes the chemical composition parameters by using H2O2/CH3OH/HCOOH instead of conventional etchants, achieving enhanced selectivity that enables complete removal of SiGe sacrificial layers while preventing unwanted etching of the silicon substrate, thereby eliminating substrate recess issues
Solution Approach 2:
The patent uses the etching solution to selectively remove sacrificial SiGe layers that are structurally identical to the final desired nanowire channels, allowing the process to create the exact channel structure needed while leaving the silicon substrate intact through superior material selectivity
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 composition achieves a selectivity of silicon-germanium over silicon of greater than 10, enabling effective removal of SiGe layers with improved process control, reducing substrate recessing and enhancing the formation of nanowire channels in GAA MOSFETs.
Implementation Method 1
Conventional wet chemical etching solutions for etching SiGe alloys typically employ an oxidizer and an oxide removal agent. The most common solutions are HF for silicon oxide etching and a solution of hydrogen peroxide (H2O2) and acetic acid (CH3COOH) for SiGe oxidation.
Implementation Method 2
Conventional wet chemical etching solutions for etching SiGe alloys typically employ an oxidizer and an oxide removal agent. The most common solutions are HF for silicon oxide etching
Implementation Method 3
An aqueous etching composition comprising water, an oxidizer (hydrogen peroxide), a fluoride ion source (ammonium fluoride), and a surfactant (polyethyleneimine)
Data Source
Figure 1A~1B
AI summary
Described herein is an etching solution comprising water; oxidizer; water-miscible organic solvent; fluoride ion source; and optionally, surfactant. Such compositions are useful for the selective removal of silicon-germanium over poly silicon from a microelectronic device having such material(s) thereon during its manufacture.