Direct observation of intra-grain defect formation during local solid-phase epitaxy.

Area of Science:

• Materials Science
• Solid-State Physics
• Nanotechnology

Background:

• Achieving defect-free polycrystalline films via solid-phase crystallization (SPC) is a persistent challenge in semiconductor fabrication.
• Understanding intermediate processes during crystal growth is key to suppressing defects in polycrystalline silicon (poly-Si) films.

Purpose of the Study:

• To directly observe and analyze the elementary processes of crystal growth at local crystalline Si (c-Si)/amorphous Si (a-Si) interfaces.
• To identify the mechanisms responsible for defect formation within Si grains during SPC.

Main Methods:

• In situ high-resolution transmission electron microscopy (HRTEM) was employed to observe Si thin film crystallization.
• Sequential atomic plane formation was analyzed with a time resolution of 10 milliseconds.

Main Results:

• Two distinct crystal growth modes were identified at c-Si/a-Si interfaces: continuous solid-phase epitaxy (SPE) and a newly discovered discontinuous SPE.
• Continuous SPE resulted in defect-free Si grains, while discontinuous SPE led to internal uncrystallized regions, initiating intra-grain defects.

Conclusions:

• Intra-grain defects in poly-Si films originate from abnormal atomic plane growth dynamics during crystallization.
• The newly identified discontinuous SPE mode is a primary source of defects, degrading electrical properties of poly-films.