以原子層沉積及分子束磊晶成長之高介電常數氧化物為閘極介電層之高效能氮化鎵金氧半場效電晶體之製作和研究

Fabrication and Investigation of High-Performance GaN MOSFETs using ALD and MBE Grown High-k Oxides as Gate Dielectrics

張耀中(Yao-Chung Chang)

指導教授 ： 洪銘輝 ； 郭瑞年

國立清華大學/工學院/材料科學工程學系/博士(2010年)

摘要

GaN, with a high electron saturation velocity, a large critical electrical field, good thermal conductivity, strong polarization fields, and epi-layer grown on Si, has been intensively investigated for applications in power RF electronics and high-temperature applications. In addition, the aggressive scaling of CMOS devices dramatically increases the horizontal electric field of the channel region. At this high electric field, GaN may outperform III-V and Si in high saturation velocity and resulted in better cutoff frequency and drain current. Therefore, GaN is now also being considered as a channel candidate for the next generation CMOS devices.
In this dissertation, high-performance accumulation-type and inversion-type GaN MOSFETs have been demonstrated by using atomic-layer-deposited (ALD) Al2O3 and HfO2, and molecular-beam-epitaxy grown (MBE) Ga2O3(Gd2O3) as gate dielectrics. For the first time, fabrication of inversion-type GaN MOSFETs were successfully achieved with ALD high k gate dielectrics which showed a normally-off characteristic with large threshold voltage (Vth > 2.5 V), a very low off-state drain current (Ioff) of 4×10-13 A/um as well as a high Ion/Ioff ratio. The device performances are markedly improved compared to the previous results of inversion-type GaN MOSFETs with high k gate dielectrics.
In addition, the accumulation-type GaN MOSFETs also exhibited outstanding device performances as compared to those of previously reported GaN MOSFETs. For example, the 4 um gate-length device exhibited the record high drain current density (Id) of 300 mA/mm at gate voltage of 8 V and drain voltage of 20 V. Compared to the state-of-the-art GaN HEMTs, the simply-designed GaN MOSFETs provide low gate leakage currents, negligible current collapses, and comparable drain currents, with the devices being normalized to the same gate lengths.
The crucial interfacial quality and microstructure between these high-k thin films and GaN were systematically investigated by using x-ray reflectivity (XRR), transmission electron microscope (TEM), x-ray photoelectron spectroscopy (XPS), and electrical characterizations. The electrical characterizations including capacitance-voltage (C-V) and gate leakage current-voltage (I-V) measurements were performed on the GaN MOS capacitors. The sharp interface with roughness < 0.5 nm, low interfacial density of states (Dit) in the range of 5×1011 eV-1cm-2, and a large conduction-band offset (ΔEc) of 1.85±0.1 eV at Al2O3/GaN interface have been extracted. These superior material and electrical properties, and the distinct merits of wide bandgap GaN contributed to the remarkable device performances of the GaN MOSFETs. The results clearly establish the potential of using these high-quality high- gate dielectric/GaN heterostructures for advanced CMOS, power RF electronics, and high-temperature application.

關鍵字

氮化鎵 ； 砷化鎵 ； 高介電係數介電層 ； 金氧半場效電晶體 ； 原子層沉積技術 ； 分子束磊晶技術 ； 氧化鋁 ； 氧化鉿

並列摘要

無資料

並列關鍵字

GaN ； GaAs ； High k dielectric ； MOSFET ； ALD ； MBE ； Al2O3 ； HfO2

參考文獻

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