Dopant distributions in n-MOSFET structure observed by atom probe tomography.

Area of Science:

• Materials Science
• Semiconductor Physics
• Nanotechnology

Background:

• Understanding dopant distribution is crucial for optimizing metal-oxide-semiconductor field-effect transistor (MOSFET) performance.
• Advanced characterization techniques are needed to precisely map dopant profiles in complex device structures.

Purpose of the Study:

• To analyze the three-dimensional dopant distributions of Arsenic (As), Phosphorus (P), and Boron (B) in an n-type MOSFET.
• To investigate dopant segregation at interfaces and grain boundaries within the MOSFET structure.

Main Methods:

• Atom probe tomography (APT) was employed for high-resolution, 3D elemental mapping.
• Analysis covered various regions of the MOSFET, including the gate, gate oxide, channel, source/drain extension, and halo regions.

Main Results:

• Phosphorus (P) atoms were observed to segregate at the poly-Si gate/gate oxide interface and along grain boundaries within the poly-Si gate.
• The poly-Si gate exhibited an elongated grain structure along the gate height.
• Boron (B) atom concentration was found to be enriched near the edge of the source/drain extension, coinciding with Arsenic (As) implantation areas.

Conclusions:

• The study provides critical insights into dopant segregation mechanisms in MOSFETs.
• These findings are essential for refining fabrication processes and improving device reliability and performance.