研究目的
Investigating the use of atomic layer deposited Tm2O3 as a high-k dielectric for Ge-based gate stacks and the effects of post-deposition anneals on interface state density and fixed charge density.
研究成果
The study concludes that Tm2O3 deposition by ALD increases interface state density in high-quality Ge/GeO2 interfaces, but optimized O2 post-deposition anneal can reduce it to below 5·1011 cm-2eV-1 without increasing the equivalent oxide thickness. However, this anneal also increases the fixed charge density, suggesting that the defects introduced during ALD are responsible for both interface states and fixed oxide charge.
研究不足
The study shows that while O2 post-deposition anneal can reduce interface state density, it also increases the fixed charge density, which could be a limitation for device performance. The optimal annealing conditions were found to be a trade-off between reducing interface state density and minimizing the increase in fixed charge density.
1：Experimental Design and Method Selection:
The study involves the fabrication of MOS capacitors to evaluate the electrical properties of Ge/GeOx/Tm2O3 gate stacks. The process includes thermal oxidation and subsequent Tm2O3 deposition, followed by post-deposition anneals in various ambients and temperatures.
2：Sample Selection and Data Sources:
n-type Ge (100) substrates with a doping concentration of ~1015 cm-3 were used. Samples were cleaned and prepared for oxidation and Tm2O3 deposition.
3：List of Experimental Equipment and Materials:
Equipment includes a rapid thermal anneal (RTA) chamber, atomic layer deposition (ALD) chamber, and physical vapor deposition for Al gate metal. Materials include TmCp3 and H2O as precursors for Tm2O3 deposition.
4：Experimental Procedures and Operational Workflow:
The process involves cleaning the Ge substrates, oxidizing them in the RTA chamber, depositing Tm2O3 via ALD, performing post-deposition anneals, and characterizing the MOS capacitors with capacitance-voltage (CV) measurements.
5：Data Analysis Methods:
Interface state density was evaluated from CV curves, and some samples were investigated by X-ray photoelectron spectroscopy (XPS) to analyze the Ge 3p spectra.
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