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Silicon diffusion control in atomic-layer-deposited Al2O3/La2O3/Al2O3 gate stacks using an Al2O3 barrier layer
Xing Wang1, Hong-Xia Liu1, Chen-Xi Fei1
1Key Laboratory for Wide-Band Gap Semiconductor Materials and Devices of Education, School of Microelectronics, Xidian University, No. 2, South Taibai Road, Yanta Zone, Xi'an City, Shaanxi Province 710071 People's Republic of China.
Nanoscale Research Letters
|April 22, 2015
Summary
A thin aluminum oxide (Al2O3) barrier layer effectively prevents silicon diffusion into lanthanum oxide (La2O3) during rapid thermal annealing (RTA). This improves the dielectric properties and electrical performance of Al2O3/La2O3/Al2O3/Si stack structures.
Area of Science:
- Materials Science
- Electrical Engineering
- Semiconductor Physics
Background:
- High-k dielectric materials like lanthanum oxide (La2O3) are crucial for advanced semiconductor devices.
- Silicon (Si) diffusion into La2O3 during annealing degrades dielectric properties.
- Controlling interfacial diffusion is key to optimizing device performance.
Purpose of the Study:
- To investigate the impact of an aluminum oxide (Al2O3) barrier layer thickness on Al2O3/La2O3/Al2O3/Si stack characteristics.
- To understand how Al2O3 barrier layers influence silicon diffusion during rapid thermal annealing (RTA).
- To correlate barrier layer properties with electrical performance metrics.
Main Methods:
- Fabrication of Al2O3/La2O3/Al2O3/Si stack structures with varying Al2O3 barrier layer thicknesses.
- Rapid thermal annealing (RTA) treatment.
- Material characterization using Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and X-ray Photoelectron Spectroscopy (XPS).
- Electrical performance evaluation through Capacitance-Voltage (C-V) and Current-Voltage (J-V) measurements.
Main Results:
- An Al2O3 barrier layer (approx. 1.5 nm, 15 ALD cycles) significantly suppresses Si diffusion from the Si substrate into the La2O3 layer during RTA.
- Suppression of Si diffusion leads to improved properties of the La2O3 dielectric layer.
- The thickness of the Al2O3 barrier layer influences the flat band voltage (VFB) shift and gate leakage current density.
Conclusions:
- The Al2O3 barrier layer is critical for maintaining the integrity and performance of La2O3-based dielectric stacks.
- Optimizing Al2O3 barrier layer thickness is essential for controlling interfacial reactions and achieving desired electrical characteristics.
- This study provides insights into fabricating robust high-k dielectric structures for semiconductor applications.
