SiGe Epitaxy Interface Control via Halogen Passivation
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Solution Overview
Problem
The formation of silicon germanium (SiGe) structures often results in undesirably thick interface layers due to germanium segregation during the epitaxial growth of silicon layers over SiGe layers, leading to low growth rates and reduced device performance in applications like FinFETS and GAA FETs.
Innovation Solution
A method involving a transition and/or passivation layer formed using a mixture of silicon-containing gases, including halogen-containing gases like chlorine, and silicon-hydrogen gases, which helps in forming a thin interface layer and allows for higher temperature growth of silicon layers, reducing germanium segregation and enhancing growth rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If DCS is used to grow SiGe layers at temperatures between 600°C and 700°C, then the SiGe layers can be formed, but the growth rate is relatively low (about 0.8 nm·min−1) and undesirably large interface layers are formed with subsequently grown Si layers
Solution Approach 1:
The patent changes the chemical parameters of the gas mixture by introducing a halogen-containing gas (such as HCl) alongside DCS and SiH4. This chemical parameter change modifies the surface reactions during epitaxial growth, reducing germanium segregation at the Si/SiGe interface and enabling thinner interface layers while maintaining higher growth rates.
Solution Approach 2:
The patent uses a composite gas mixture comprising DCS, SiH4, and a halogen-containing gas (e.g., HCl). This composite approach combines the benefits of DCS for SiGe layer formation with SiH4 for silicon layer growth and the halogen-containing gas for suppressing germanium segregation, achieving both thin interface layers and high growth rates simultaneously.
2Manufacturing precision
If SiH4 is used to grow the Si layer overlying the SiGe layer at temperatures lower than 580°C, then the Si layer can be formed, but the growth rate is relatively low (about 0.8 nm·min−1) and the interface layer is still undesirably thick
Solution Approach 1:
The patent changes the temperature parameter by enabling Si layer growth at higher temperatures (above 580°C, up to 700°C or higher) when using the halogen-containing gas mixture. This temperature increase dramatically improves the growth rate while the halogen-containing gas suppresses germanium segregation, allowing thin interface layers to be maintained despite the higher temperature.
Solution Approach 2:
The halogen-containing gas acts as an intermediary that mediates between the SiH4 and SiGe layer interaction. It suppresses germanium segregation at the interface, enabling higher growth rates and thinner interface layers that would otherwise not be achievable with SiH4 alone at lower temperatures.
3Manufacturing precision
If the surface of the SiGe layer is not passivated during the transition to the subsequent Si layer epitaxial growth, then Ge segregates to the surface, resulting in formation of an interfacial layer of a few tens of angstroms
Solution Approach 1:
The halogen-containing gas (e.g., HCl) serves as an intermediary that passivates the SiGe layer surface during the transition to Si layer growth. It forms volatile germanium halogen species that prevent germanium segregation, thereby maintaining an abrupt interface with minimal interfacial layer formation.
Solution Approach 2:
The patent converts the potentially harmful germanium segregation into a beneficial process by using the halogen-containing gas to form volatile germanium halogen species that desorb from the surface. This transforms the segregation problem into a controlled surface chemistry process that actually protects the interface quality.
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
This approach results in a thinner interface layer and faster growth rates of silicon layers over SiGe layers, improving the performance and density of electronic devices by maintaining an abrupt transition and reducing the thickness of interfacial layers.
Implementation Method 1
forming a transition and/or passivation layer on the layer comprising SiGe by providing a gas comprising a mixture of: a first silicon-containing gas, a halogen-containing (e.g., chlorine-containing) gas, and a second silicon-containing gas within the reaction chamber
Implementation Method 2
The first silicon gas and the halogen/chlorine-containing gas can provide desired Ge-halogen or Ge—Cl bonds on a surface of the SiGe layer
Implementation Method 3
The second silicon-containing gas can provide silicon to any vacant sites that may be on the surface
Data Source
AI summary
Methods for forming structures that include a layer comprising silicon germanium are disclosed. Exemplary embodiments of the disclosure provide improved methods of forming a transition layer on the layer comprising silicon germanium that can mitigate any formation of an interface layer between the layer comprising silicon germanium and a subsequently formed layer comprising silicon.