On the dc and noise properties of the gate current in epitaxial Ge p-channel metal oxide semiconductor field effect transistors with TiN∕TaN∕HfO[sub 2]∕SiO[sub 2] gate stack (original) (raw)
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Appl Phys Lett, 2008
In this paper, we report the dc and noise properties of the gate current in epitaxial Ge p-channel metal oxide field effect transistors (pMOSFETs) with a Si passivated surface. The gate stack consists of HfO2/SiO2 dielectric with TiN /TaN metal gate. The observed temperature dependence of the gate current indicates that the dominant charge transport mechanism through the gate dielectric consists of Poole-Frenkel conduction. Gate current 1/f noise is more than two orders higher in the case of Ge pMOSFETs when compared to reference Si pMOSFETs. Ge outdiffusion into the gate oxide is the suspected cause for the enhanced Poole-Frenkel conduction and the high gate current 1/f noise in Ge pMOSFETs.
2008
In this paper, we report the dc and noise properties of the gate current in epitaxial Ge p-channel metal oxide field effect transistors ͑pMOSFETs͒ with a Si passivated surface. The gate stack consists of HfO 2 / SiO 2 dielectric with TiN / TaN metal gate. The observed temperature dependence of the gate current indicates that the dominant charge transport mechanism through the gate dielectric consists of Poole-Frenkel conduction. Gate current 1 / f noise is more than two orders higher in the case of Ge pMOSFETs when compared to reference Si pMOSFETs. Ge outdiffusion into the gate oxide is the suspected cause for the enhanced Poole-Frenkel conduction and the high gate current 1 / f noise in Ge pMOSFETs.
1/f noise in Si and si/sub 0.7/Ge/sub 0.3/ pMOSFETs
IEEE Transactions on Electron Devices, 2003
Strained layer Si 0 7 Ge 0 3 pMOSFETs were fabricated and shown to exhibit enhanced hole mobility, up to 35% higher for a SiGe device with 3-nm-thick Si-cap, and lower 1 noise compared to Si surface channel pMOSFETs. The 1 noise in the investigated devices was dominated by mobility fluctuation noise and found to be lower in the SiGe devices. The source of the mobility fluctuations was determined by investigating the electric field dependence of the 1 noise. It was found that the SiO 2 /Si interface roughness scattering plays an important role for the mobility fluctuation noise, although not dominating the effective mobility. The physical separation of the carriers from the SiO 2 /Si interface in the buried SiGe channel pMOSFETs resulted in lower SiO 2 /Si interface roughness scattering, which explains the reduction of 1 noise in these devices. The 1 noise mechanism was experimentally verified by studying 1 noise in SiGe devices with various thicknesses of the Si-cap. A too large Si-cap thickness led to a deteriorated carrier confinement in the SiGe channel resulting in that considerable 1 noise was generated in the parasitic current in the Si-cap. In our experiments, the SiGe devices with a Si-cap thickness in the middle of the interval 3-7 nm exhibited the lowest 1 noise.
Gate electrode effects on low-frequency (1/ f) noise in p-MOSFETs with high-κ dielectrics
Solid-state Electronics, 2006
The defects related to the gate-dielectric in high-j-MOSFETs are studied using the 1/f noise technique. Three different types of gate electrodes were used for this purpose -poly-Si, metal (TiN/TaN) and fully Ni Silicided (FUSI) electrodes with Hf-based oxides as the gate dielectric layer. All the three types of devices show a specific behavior near the gate electrode-dielectric interface when the trap profiles are assessed using f · S I spectra. The tunneling depths were calculated and it was found that the high-j oxide (bulk) layers are being probed. From the drain current spectra S I vs. drain current I D of the various gate material devices at given depths, it may be inferred that the concentration of oxygen-vacancy-related defects can significantly influence the 1/f noise performance, which can explain the differences observed in noise between the gate electrodes. Comparison of FUSI gated devices, with various percentages of Hf in the dielectric layer, shows comparable noise levels (S VG ), indicating a minor dependence on Hf-content in the gate dielectric layer.
IEEE Transactions on Electron Devices, 2000
Low-frequency noise and hole mobility are studied in Si and SiGe surface channel pMOSFETs with various types of high-κ dielectric stacks () and TiN as gate electrode material. Comparisons are made with poly-SiGe-gated pMOSFETs as well as poly-Si/SiO 2 /Si references. The choice of channel material (strained SiGe or Si), gate material (TiN or poly-SiGe), and high-κ material (Al 2 O 3 , HfO 2 , HfAlO x ) is discussed in terms of mobility and low-frequency noise. A TiN gate in combination with a surface SiGe channel is advantageous both for enhanced mobility and low 1/f noise. The dominant sources of carrier scattering are identified by analyzing the mobility measured at elevated temperatures. The 1/f noise is studied from subthreshold to strong inversion conditions and at different substrate biases. The mobility fluctuation noise model and the number fluctuation noise model are both used to investigate the 1/f -noise origin.
Low frequency noise in nMOSFETs with subnanometer EOT hafnium-based gate dielectrics
Microelectronics Reliability, 2007
This paper focuses on the noise behavior of nMOSFETs with high-k gate dielectrics (SiON/HfO 2 ) with an equivalent oxide thickness of 0.92 nm and using metal (TiN/TaN) as gate material. From the linear dependence of the normalized drain noise on the gate voltage overdrive we conclude that the 1/f noise is dictated by mobility fluctuations. This behavior is mainly ascribed to the reduced mobility due to the low interfacial thickness of 0.4 nm and the Hf-related defects. The gate current is more sensitive to RTS noise with respect to the drain current noise. Cross-correlation measurements between drain and gate noise are used as a tool for discriminating between noise mechanisms which generate different fluctuation levels at the gate and drain terminal.
Applied Physics Letters, 2007
Article Title: Low temperature mobility in hafnium-oxide gated germanium p-channel metal-oxide-semiconductor field-effect transistors Year of publication: 2007 Link to published version: http://dx.Effective mobility measurements have been made at 4.2 K on high performance high-k gated germanium p-type metal-oxide-semiconductor field effect transistors with a range of Ge/gate dielectric interface state densities. The mobility is successfully modelled by assuming surface roughness and interface charge scattering at the SiO 2 interlayer/Ge interface. The deduced interface charge density is approximately equal to the values obtained from the threshold voltage and subthreshold slope measurements on each device. A hydrogen anneal reduces both the interface state density and the surface root mean square roughness by 20%.
2007
This paper focuses on the noise behavior of nMOSFETs with high-k gate dielectrics (SiON/HfO 2 ) with an equivalent oxide thickness of 0.92 nm and using metal (TiN/TaN) as gate material. From the linear dependence of the normalized drain noise on the gate voltage overdrive we conclude that the 1/f noise is dictated by mobility fluctuations. This behavior is mainly ascribed to the reduced mobility due to the low interfacial thickness of 0.4 nm and the Hf-related defects. The gate current is more sensitive to RTS noise with respect to the drain current noise. Cross-correlation measurements between drain and gate noise are used as a tool for discriminating between noise mechanisms which generate different fluctuation levels at the gate and drain terminal.
Solid-State Electronics, 2005
Carrier mobility and low-frequency noise were investigated in Si 0.8 Ge 0.2 surface channel pMOSFETs with ALD Al 2 O 3 gate dielectrics. The devices were annealed in H 2 O vapor, which reduced the negative charge in the gate dielectrics. The carrier mobility was characterized versus change in oxide charge, which allowed an estimation of the Coulomb scattering from the charge in the Al 2 O 3 . The low-frequency noise was measured between subthreshold and strong inversion conditions in the H 2 O annealed and the un-annealed devices. The combined number fluctuation and correlated mobility fluctuation noise model could successfully explain the observed 1/f noise. The mobility fluctuations were negatively correlated to the number fluctuations in the un-annealed devices, which contained a negative oxide charge. In the H 2 O annealed devices, on the other hand, a positive correlation could be observed. The maximum magnitude of the scattering parameter a was found to be around 1 · 10 4 Vs/C. The H 2 O annealing was used in this work as a non-destructive tool to modify the charge in the Al 2 O 3 , but it can also be a viable method to improve device performance by introducing/passivating charge.
Electrical characterization of germanium p-channel MOSFETs
IEEE Electron Device Letters, 2000
In this letter, we report germanium (Ge) p-channel MOSFETs with a thin gate stack of Ge oxynitride and low-temperature oxide (LTO) on bulk Ge substrate without a silicon (Si) cap layer. The fabricated devices show 2 higher transconductance and 40% hole mobility enhancement over the Si control with a thermal SiO 2 gate dielectric, as well as the excellent subthreshold characteristics. For the first time, we demonstrate Ge MOSFETs with less than 100-mV/dec subthreshold slope.