Unpredicted Internal Geometric Reconfiguration of an Enclosed Space Formed by Heteroepitaxy

Area of Science:

• Semiconductor materials science
• Epitaxial growth techniques
• Surface science

Background:

• Selective epitaxy growth (SEG) is crucial for semiconductor device fabrication.
• Epitaxial lateral overgrowth (ELO) over dielectric masks offers novel interface engineering possibilities.
• Understanding adatom diffusion is key to controlling epitaxial layer quality.

Purpose of the Study:

• To investigate unexplored epitaxial lateral overgrowth (ELO) over micron-scale dielectric masks.
• To characterize adatom diffusion and interface phenomena during selective epitaxy growth (SEG) of Ge on SiO2.
• To explore the formation of novel 3D geometric configurations at the Ge/SiO2 interface.

Main Methods:

• Selective epitaxy growth (SEG) of Germanium (Ge) on a Silicon (Si) (100) wafer with micron-scale SiO2 masks.
• In-situ observation and analysis of adatom diffusion and interface evolution.
• Microscopy and structural analysis to characterize cavity and tunnel formation.

Main Results:

• Demonstrated anomalous adatom diffusion and migration at the Ge/SiO2 interface during SEG.
• Observed the formation of polyhedral cavities or tunnels on the SiO2 layer, dependent on oxide strip length.
• Documented a thermally induced reconfiguration of Ge atoms forming a single tunnel from multiple cavities and tunnels.
• Achieved defect-free Ge epitaxy above the oxide strips after coalescence.

Conclusions:

• The study provides new insights into adatom migration mechanisms within enclosed spaces during semiconductor epitaxy.
• The observed cavities and tunnels represent the first known 3D geometric configurations in selective heteroepitaxial structures.
• This work opens avenues for engineering interfacial structures in advanced semiconductor materials.