Controlling the Carrier Injection Efficiency in 3D Nanocrystalline Silicon Floating Gate Memory by Novel Design of...

Area of Science:

• Materials Science
• Electrical Engineering
• Computer Engineering

Background:

• Three-dimensional (3D) NAND flash memory offers superior big data processing capabilities compared to traditional von Neumann architectures, particularly for in-memory computing.
• High carrier injection efficiency is crucial for enhancing the performance of 3D NAND flash memory.
• Nanocrystalline silicon (nc-Si) floating gates are a key component in advanced memory technologies.

Purpose of the Study:

• To investigate and report the carrier injection efficiency of 3D NAND flash memory utilizing an nc-Si floating gate.
• To demonstrate how a novel control layer design influences carrier injection efficiency.
• To establish a correlation between capacitance-voltage (C-V) hysteresis direction and carrier injection efficiency.

Main Methods:

• Fabrication of nc-Si floating-gate Metal-Oxide-Semiconductor (MOS) structures with varying control layer thicknesses.
• Measurement and analysis of C-V hysteresis characteristics under different scanning bias conditions.
• Utilizing an energy band model to elucidate the carrier transfer mechanisms and hysteresis direction transitions.

Main Results:

• The C-V hysteresis direction of the nc-Si floating-gate MOS structure serves as a reliable indicator of carrier injection efficiency.
• A control layer thickness of 25 nm consistently resulted in counterclockwise C-V hysteresis, indicating efficient carrier injection.
• Reducing the control layer thickness to 22 nm induced a transition to clockwise C-V hysteresis, attributed to carrier injection into the SiNx control layer defects.

Conclusions:

• Thicker SiNx control layers effectively block unwanted carrier transfer from the top electrode, significantly improving carrier injection efficiency from the Si substrate to the nc-Si layer.
• The observed C-V hysteresis direction transitions are explained by the energy band model, clarifying the underlying carrier injection mechanisms.
• This research provides critical insights for optimizing 3D NAND flash memory performance, paving the way for enhanced in-memory computing applications.