Converts Thin Amorphous SiGe Films Through Thermal Oxidation to Uniform, Single-Crystal SiGe Layers on Silicon Structures
This oxidation-induced conformal epitaxy (OICE) process converts thin amorphous silicon-germanium (SiGe) films through thermal oxidation into uniform, single-crystal SiGe layers that can conformally coat three-dimensional silicon/SiGe nano-architectures. Semiconductor manufacturing is moving toward gate-all-around stacked nanosheet transistors for the 3nm node since these devices deliver higher drive current and tighter channel control. However, the performance of both n-FET and p-FET nanosheets depends on strained SiGe channels that must uniformly coat the three-dimensional silicon pillars. Conventional tools like MOCVD and CVD cannot reliably produce the conformal, single-crystal SiGe layers required for scaling high-aspect-ratio nanostructures, especially at the 3 nm node and beyond. This highlights an evident need for a reliable method to form conformal crystalline SiGe on complex geometries.
The global nanosheet GAA transistor market was valued at USD 1.2 billion in 2024 and is projected to grow rapidly, with major chip manufacturers adopting 3D architectures for sub-5 nm nodes. At the same time, the SiGe semiconductor materials market—valued at roughly USD 5 billion in 2025—is expected to triple by 2033, reflecting the growing importance of SiGe-based device engineering.
Researchers at the University of Florida, in collaboration with Sandia National Laboratories, developed an Oxidation-Induced Conformal Epitaxy (OICE) process for transforming a thin amorphous or polycrystalline Si/SiGe coating into a single-crystal SiGe layer via thermal oxidation. By matching the underlying silicon, the resulting SiGe lattice has the potential to conformally coat three-dimensional silicon pillars and nanosheets with a uniform strained channel. This OICE approach offers a promising low-cost approach for enabling next-generation semiconductor device architectures.
Application
Fabricates conformal, epitaxial SiGe layers on planar or 3D silicon structures using thermal oxidation for advanced logic transistors, strain-engineered devices, and Si/SiGe heterostructures for electronics and quantum technologies
Advantages
- Creates uniform, high-quality SiGe layers on both flat and 3D silicon surfaces, enabling smooth and conformal coverage for advanced device structures
- Transforms amorphous SiGe into single-crystal material during oxidation, resulting in improved electrical and structural performance compared to polycrystalline films
- Uses standard oxidation furnaces, making the process lower-cost and easier to scale than traditional epitaxy methods like MOCVD or CVD
- Naturally forms a thin silicon cap, ideal for integrating high-k dielectrics and improving compatibility with next-generation transistor designs
- Supports complex 3D device architectures, including nanosheets and nanowires, advancing future semiconductor technologies such as GAA transistors
Technology
Oxidation-Induced Conformal Epitaxy (OICE) is a fabrication process for creating smooth, high-quality SiGe layers on both flat and 3D silicon surfaces. It achieves this by first coating a silicon surface with an amorphous (non-crystalline) SiGe layer. This layer is easy to deposit at low temperatures and can cover flat surfaces as well as 3D shapes such as nanosheets, fins, or pillars.
After the coating is applied, the sample is placed in a thermal oxidation furnace, and the silicon begins to oxidize. As this happens, germanium is pushed out of the growing oxide layer and moves toward the silicon surface, causing the SiGe layer to slowly reorganize. This reorganization turns the originally amorphous film into a single-crystal layer that matches the crystal structure of the silicon underneath.
As oxidation continues, areas where native oxide dissolves allow crystal grains to align and grow. Over time, these well-aligned grains expand and take over the entire film, resulting in a smooth, uniform, single-crystal SiGe layer. This process uses standard oxidation equipment, making it cheaper and more scalable than traditional epitaxy methods, while still producing high-quality SiGe layers for advanced semiconductor devices.
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