SiGe Etching Composition for High Selectivity at Low Ge Content
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing etching compositions for microelectronic devices, such as those containing HF, AA, and H2O2, face challenges including reduced selectivity for etching SiGe relative to silicon as the germanium content in SiGe decreases, long time to achieve stable etch rates, and excessive etching of materials like silicon nitride and silicon oxide.
Innovation Solution
The introduction of additional acids like formic acid, sulfuric acid, and lactic acid into the etching composition, which includes hydrogen fluoride, acetic acid, and hydrogen peroxide, enhances the selectivity and etch rates of silicon-germanium relative to silicon, while minimizing the etching of other materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional three-part etching composition (HF/AA/H2O2) is used, then good etching rate for SiGe is achieved, but selectivity for SiGe relative to silicon diminishes as germanium content decreases
Solution Approach 1:
The patent modifies the chemical composition parameters of the etching solution by adding formic acid, lactic acid, or sulfuric acid to the traditional HF/AA/H2O2 system. These parameter changes enable the etching composition to maintain high selectivity for SiGe relative to silicon even when germanium content is reduced, while preserving adequate etching rates.
Solution Approach 2:
The patent creates a composite etching composition by combining multiple acids (hydrofluoric acid, acetic acid, hydrogen peroxide, plus formic acid, lactic acid, and/or sulfuric acid) in specific ratios. This composite formulation synergistically enhances both selectivity and etching rate performance that cannot be achieved with traditional three-component systems alone.
2Reliability
If traditional three-part etching composition (HF/AA/H2O2) is used, then etching of SiGe is achieved, but long time is required to reach stable etch rate
Solution Approach 1:
The patent incorporates formic acid, lactic acid, and/or sulfuric acid into the etching composition before use, which preliminarily prepares the chemical environment to accelerate the formation of stable etch rates. These additional acids appear to catalyze or facilitate the chemical reactions that lead to stable etching conditions, reducing the induction period.
3Manufacturing precision
If traditional three-part etching composition (HF/AA/H2O2) is used, then SiGe etching is effective, but excessive etching of silicon nitride and silicon oxide occurs
Solution Approach 1:
The patent adjusts the chemical parameters of the etching system by adding specific acids (formic, lactic, sulfuric) which modify the etching chemistry to be more selective toward SiGe. This parameter modification reduces the aggressive nature of the etchant toward silicon nitride and silicon oxide, minimizing collateral damage while maintaining effective SiGe removal.
4Manufacturing precision
If high germanium content SiGe is used as sacrificial layer, then high etching selectivity is achieved, but lattice mismatch with silicon increases
Solution Approach 1:
The patent changes the parameters of the etching composition (adding formic acid, lactic acid, and/or sulfuric acid) to enhance selectivity, thereby enabling the use of lower germanium content SiGe layers. This allows achieving both good selectivity and lattice matching simultaneously by modifying the etching chemistry rather than relying on high Ge content.
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 improved etching compositions achieve increased selectivity and etch rates for silicon-germanium, reduce the time to reach a stable etch rate, and minimize the etching of silicon nitride and silicon oxide, thereby improving the efficiency and precision of microelectronic device fabrication.
Implementation Method 1
aqueous etching composition that contains about one part hydrofluoric acid HF, two parts hydrogen peroxide solution, and six parts acetic acid
Implementation Method 2
dissolved hydrogen peroxide
Data Source
AI summary
Compositions useful for the selective removal by etching of silicon-germanium-containing materials relative to silicon-containing materials, from a microelectronic device having features containing these materials at a surface, the compositions containing hydrofluoric acid, acetic acid, hydrogen peroxide, and at least one additional acid that will improve performance as measured by one or more of an etching rate or selectivity and are tunable to achieve the required Si:Ge removal selectivity and etch rates.