Influences of Plasma Processed Interface Layers on Germanium MOS Devices with ALD Grown HfO2
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Influences of Plasma Processed Interface Layers on Germanium MOS Devices with ALD Grown HfO2 Takuya Sugawara1, Raghavasimhan Sreenivasan2, Yasuhiro Oshima2,3, and Paul C. McIntyre2 1 Leading-edge Process Development Center, Tokyo Electron Ltd., Nirasaki, 407-0192, Japan 2 Dept. of Materials Science and Engineering, Stanford University, Stanford, CA, 94305 3 Development Planning Department, Tokyo Electron America Inc., Santa Clara, CA, 95054 ABSTRACT Germanium and hafnium-dioxide (HfO2) stack structuresí physical and electrical properties were studied based on the comparison of germanium and silicon based metal-oxidesemiconductor (MOS) capacitorsí electrical properties. In germanium MOS capacitor with oxide/oxynitride interface layer, larger negative flat-band-voltage (Vfb) shift compared with silicon based MOS capacitors was observed. Secondary ion mass spectrum (SIMS) characteristics of HfO2-germanium stack structure with germanium oxynitride (GeON) interfacial layer showed germanium out diffusion into HfO2. These results indicate that the germanium out diffusion into HfO2 would be the origin of the germanium originated negative Vfb shift. Using Ta3N5 layer as a germanium passivation layer, reduced Vfb shift and negligible hysteresis were observed. These results suggest that the selection of passivation layer strongly influences the electrical properties of germanium based MOS devices.
INTRODUCTION Germanium and hafnium dioxide (HfO2) are attractive candidates for the materials of future metal-oxide-semiconductor (MOS) devices1,2. Maeda et al studied plasma nitrided germanium passivation layer electrical properties with HfO2 gate dielectrics and obtained improved interfacial properties3. Kita et al studied physical property differences between HfO2/Si and HfO2/Ge stack structure4. Although they showed excellent systematic study of the HfO2/Ge physical and electrical properties, the fundamental electrical property differences between Metal/HfO2/Si and Metal/HfO2/Ge MOS devices were not investigated. Therefore, in this study, we will try to study the germanium originated effects on electrical properties based on the comparison of germanium and silicon MOS devices. Also, various kinds of plasma processed interface layers between HfO2 and germanium ware studied to reveal its influences on MOS device electrical properties. EXPERIMENT In this study, we used atomic layer deposition (ALD)/remote plasma process system5,6. The system consists of Advanced Energy inductively coupled plasma (ICP) source and vacuumed chamber. In plasma oxidation and nitridation process, process gases such as Ar/N2/H2/NH3/O2 are introduced and excited in the ICP plasma source and emitted through a quartz tube to a sample surface. In ALD process, tetrakis-diethylamino hafnium (TDEAH) and water are introduced alternately to form HfO2. Using this system, we can do in-situ oxide/oxynitride layer formation followed by HfO2 deposition without evacuating the sample to atmosphere between these two processes. The experimental procedure is fo
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