Normalized Noise Power Spectral Density Research Articles

Low-Frequency Noise-Based Mechanism Analysis of Endurance Degradation in Al/αTiOx/Al Resistive Random Access Memory Devices.

In this work, we analyze a resistive switching random access memory (RRAM) device with the metal-insulator-metal structure of Al/αTiOx/Al. The transport mechanism of our RRAM device is trap-controlled space-charge limited conduction, which does not change during the endurance test. As the number of resistive switching (RS) cycles increases, the current in the low-resistance state (LRS) does not change significantly. In contrast, degradation in the high-resistance state (HRS) is noticeably evident. According to the RS cycle, the current shift fits well with the stretched-exponential equation. The normalized noise power spectral density (Si/I2) measured in the HRS is an order of magnitude higher than that in the LRS owing to the difference in the degree of trap occupancy, which is responsible for the transition of resistance states. During the consecutive RS, the Si/I2 in the HRS rapidly decreases for approximately 100 cycles and then saturates. In contrast, in the LRS, the Si/I2 does not change significantly. Here we propose a model associated with the endurance degradation of the experimental device, and the model is verified with a 1/f noise measurement.

Noise spectroscopy of tunable nanoconstrictions: molecule-free and molecule-modified

Devices with metallic nanoconstrictions functionalized by organic molecules are promising candidates for the role of functional devices in molecular electronics. However, at the moment little is known about transport and noise properties of nanoconstriction devices of this kind. In this paper, transport properties of bare gold and molecule-containing tunable cross-section nanoconstrictions are studied using low-frequency noise spectroscopy. Normalized noise power spectral density (PSD) SI/I2 dependencies are analyzed for a wide range of sample resistances R from 10 Ohm to 10 MOhm. The peculiarities and physical background of the flicker noise behavior in the low-bias regime are studied. It is shown that modification of the sample surface with benzene-1,4-dithiol molecules results in a decrease of the normalized flicker noise spectral density level in the ballistic regime of sample conductance. The characteristic power dependence of normalized noise PSD as a function of system resistance is revealed. Models describing noise behavior for bare gold and BDT modified samples are developed and compared with the experimental data for three transport regimes: diffusive, ballistic and tunneling. Parameters extracted from models by fitting are used for the characterization of nanoconstriction devices.

Impact of Gate Stack Dielectric on Intrinsic Voltage Gain and Low Frequency Noise in Ge pMOSFETs

Concerning future high-performance applications, materials such as germanium (Ge) and III/V, have been extensively studied as alternative for the channel region instead of silicon. The high mobility makes Ge a promising channel material for both low power and high performance applications of advanced devices [1]. On the other hand, gate stack engineering is challenging in Ge devices, in view of the higher density of interface states typically observed [2]. This work analyses the influence of gate stack layers (GSL) on intrinsic voltage gain and low frequency noise in planar Ge pMOSFET devices. The GSL is composed of germanium oxide (GeOx), aluminum oxide (Al2O3) and hafnium oxide (HfO2), where both Al2O3 and HfO2film thicknesses were varied. There are also two different plasma powers under evaluation. Furthermore, the analog parameters were analyzed at high temperature, ranging from 25 to 150 °C. The devices used in this work have been fabricated on a p-type silicon substrate at Imec/Belgium. There are four wafers with different dielectric composition as shown in table 1. The planar device dimensions are channel width (W) of 10 µm and channel length (L) of 130, 250, 1 and 10 µm. The low frequency noise (LFN) was measured in linear operation showing no clear impact of the gate stack processing. From the normalized noise power spectral density versus drain current it is derived that the predominant flicker noise is due to trapping by border traps in the gate stack and more specifically in the GeOx layer. Representing the square root of the input-referred voltage noise spectral density (SVG 0.5) versus Id/gmyields the flat-band value (intercept) and the mobility scattering coefficient is obtained from the slope of a linear fit in Fig. 1. Among the studied wafers (figure 2), D20 (which has the thinnest Al2O3 thickness) presents the lowest value of the intrinsic voltage gain (AV) for the channel length range studied due to the degradation of the Early voltage (VEA). Furthermore, for the other wafers no significant AV variation betweem the wafers was observed. It suggests that neither the HfO2 thickness nor the plasma power presented a relevant influence on the AVvalue. Considering that the AV for all studied wafers, except D20, present the same trend at room temperature (figure 2), wafer D18 was chosen to investigate the analog basic parameter performances from 25 to 150 °C. In figure 3 is can be seen that the transconductance (gm) is strongly degraded as the temperature increases due to mobility degradation. On the other hand, the output conductance (gD) presented almost no difference with the temperature rise. Figure 4 focuses on the AV as a function of temperature. It can be seen that AVdecreases 5 dB as the temperature increases from 25 to 150 °C, due to the influence of the gm reduction. [1] J.-H. Han et al., Microelectronic Engineering, v.109, p. 266–269, 2013. [2] V.P.-H Hu et al.,TED, v.60, I. 10, p. 3596 – 3600, October, 2013. [3] S. Takagi et al., Microelectronic Engineering, v.109, p. 389–395, 2013. Figure 1

Low frequency noise behaviors in the partially depleted silicon-on-insulator device

Low frequency noise in the partially depleted silicon-on-insulator (SOI) NMOS device is investigated in this paper. The experimental results show low frequency noise behaviors are in good consistence with classical noise model. Based on McWhorter model, the low frequency noise in the SOI device results from the exchange of carriers between channel and oxide. The densities of trapped charges in the front gate oxide and buried oxide are extracted. Due to the difference between manufacture processes, the extracted density of trapped charges in the buried oxide (Nt=8×1017 eV-1·cm-3) is larger than that in the gate oxide (Nt=2.767×1017 eV-1·cm-3), and the result is in good agreement with testing result of transfer characteristics in part 2. Based on the charge tunneling mechanism, the spatial distribution of trapped charges in the gate oxide and buried oxide are extracted by using the tunneling attenuation coefficient (λ=0.1 nm for SiO2) and time constant (τ0=10-10 s), and the result also proves that the trap in buried oxide is larger than that in gate oxide. In addition, the influence of channel length on the low frequency noise in the SOI device is discussed. The variations of normalized channel current noise power spectral density with channel length are investigated at four frequencies(10 Hz, 25 Hz, 50 Hz, and 100 Hz). The experimental results show that the normalized noise power spectral density decreases linearly with the increase of channel length, which indicates the low frequency noise of SOI device is mainly caused by the flicker noise in the channel, and the contribution of source/drain contact and parasitic resistances could be ignored. Finally, the dependences of back gate voltage on the front gate threshold voltage, front channel current and front channel noise are discussed by considering the charge coupling effect. The experimental results show the measured channel current and channel noise with applying front gate voltage and back gate voltage simultaneously are larger than those with applying the front gate voltage and back gate voltage separately.

A Unified Explanation of gm/ID-Based Noise Analysis

We present an unified explanation of the transconductance-to-drain current (gm/ID)-based noise analysis in this paper. We show that both thermal noise coefficient (γ) and device noise corner frequency (f co ) are dependent on the gm/ID of a transistor. We derive expressions to demonstrate the relationship between the normalized noise power spectral density technique and the technique based on γ and f co . We conclude this letter with examples to demonstrate the practical implication of our study. Our results show that while both techniques discussed in this letter can be used to compute noise numerically, using γ and f co to separate thermal noise from flicker noise provides additional insight for optimizing noise.

Border Traps in InGaAs nMOSFETs Assessed by Low-Frequency Noise

The low-frequency noise of n-channel InGaAs MOSFETs with Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> gate dielectric has been studied to assess the impact of a S-passivation treatment on the border trap (BT) density. It is shown that the spectra are predominantly \(1/f\) -like, while the normalized noise power spectral density (PSD) behaves according to the number fluctuations theory. The BT density derived from the input-referred voltage noise PSD exhibits a flat depth profile for the three processing conditions studied, with a pronounced reduction due to the S treatment. Additional excess \(1/f\) and generation-recombination noise sources are found as well, which are more related to the epitaxial material.

Low-frequency noise in amorphous indium–gallium–zinc oxide thin-film transistors with an inverse staggered structure and an SiO2 gate insulator

We report the low-frequency noise (LFN) behavior of amorphous indium–gallium–zinc oxide thin-film transistors with an inverse staggered structure and an SiO2 gate insulator. The normalized noise power spectral density depended on channel length, L, with the form 1/L2, and on the gate bias voltage, VG, and threshold voltage, VTH, with the form 1/(VG − VTH)β where 1.5 < β < 2.1. In addition, the scattering constant α was less than 105 Ω. These results suggest that the contact resistance has a significant role in the LFN behavior and the charge-carrier density fluctuation is the dominant origin of LFN.

Dependence of Hot Carrier Reliability and Low Frequency Noise on Channel Stress in Nanoscale n-Channel Metal–Oxide–Semiconductor Field-Effect Transistors

In this paper, the dependence of low-frequency (LF) noise, such as 1/f noise and random telegraph signal (RTS) noise, and the hot carrier reliability in n-channel metal–oxide–semiconductor field-effect transistors (NMOSFETs) on channel stress has been studied. The normalized noise power spectral density (SID /ID2) and RTS amplitude of NMOSFETs with compressive channel stress are greater than those with tensile channel stress because the active traps contributing to RTS noise with compressive stress are distributed closer to the Si/SiO2 interface. LF noise characteristics, as well as device performance are enhanced by introducing tensile channel stress to nanoscale NMOSFETs. However, it is shown that device degradation caused by tensile channel stress is greater than that caused by compressive channel stress under channel hot carrier (CHC) and drain avalanche hot carrier (DAHC) stress conditions. Therefore, concurrent consideration of reliability and LF noise characteristics as well as dc device performance is necessary in channel strain engineering for next generation complementary metal–oxide–semiconductor field-effect transistors (CMOSFETs) especially for analog or mixed signal integrated circuit applications.

Impact of Nitrogen Incorporation on Low-Frequency Noise of Polycrystalline Silicon/TiN/HfO2/SiO2 Gate-Stack Metal–Oxide–Semiconductor Field-Effect Transistors

The impact of nitrogen incorporation into HfO2/SiO2 gate dielectrics in the gate-stack fabrication process on the low-frequency noise of the drain current of polycrystalline silicon (poly-Si)/TiN (10 nm)/HfO2/SiO2 gate-stack metal–oxide–semiconductor field-effect transistors (MOSFETs) is studied, considering the scaling of an equivalent oxide thickness with the reduction in interfacial layer SiO2 thickness and the plasma nitriding of gate dielectrics. The nitriding combined with nitrogen plasma and nitrogen diffusion from a 10-nm-thick TiN layer increases the normalized noise power spectral density owing to carrier mobility fluctuation, and decreases the slope γ of the 1/fγ noise spectrum owing to the increase in the number of trapped carriers at the bulk trap site in the gate dielectric layer. The reduction in SiO2 thickness from 1.5 to 0.8 nm showed less impact on the mentioned phenomena with TiN. These results suggest that nitrogen incorporation into HfO2/SiO2 gate dielectrics in the device fabrication process for poly-Si/metal nitride/HfO2/SiO2 gate stacks requires careful attention to suppress the power density of low-frequency noise.

Dependence of Hot Carrier Reliability and Low Frequency Noise on Channel Stress in Nanoscale n-Channel Metal–Oxide–Semiconductor Field-Effect Transistors

In this paper, the dependence of low-frequency (LF) noise, such as 1/f noise and random telegraph signal (RTS) noise, and the hot carrier reliability in n-channel metal–oxide–semiconductor field-effect transistors (NMOSFETs) on channel stress has been studied. The normalized noise power spectral density (SID/ID2) and RTS amplitude of NMOSFETs with compressive channel stress are greater than those with tensile channel stress because the active traps contributing to RTS noise with compressive stress are distributed closer to the Si/SiO2 interface. LF noise characteristics, as well as device performance are enhanced by introducing tensile channel stress to nanoscale NMOSFETs. However, it is shown that device degradation caused by tensile channel stress is greater than that caused by compressive channel stress under channel hot carrier (CHC) and drain avalanche hot carrier (DAHC) stress conditions. Therefore, concurrent consideration of reliability and LF noise characteristics as well as dc device performance is necessary in channel strain engineering for next generation complementary metal–oxide–semiconductor field-effect transistors (CMOSFETs) especially for analog or mixed signal integrated circuit applications.

High-Performance 90-nm Dual-Gate nMOSFETs With Field-Plate Technology

In this letter, high-performance 90-nm dual-gate nMOSFETs with field-plate (FP) metal were demonstrated for high-power and low-frequency noise device applications. The pro posed dual-gate nMOSFETs with FP metals had a higher maximum oscillation frequency (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> )>; a lower noise power spectral density, and a higher output power (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> ) than traditional dual gate architecture. These improvements were obtained because two extra FP-induced depletion regions were present, and the total electrical field was suppressed, yielding high output resistance and higher output power. These FP-induced depletion regions also pushed the carriers into deeper channels and reduced the number of opportunities for carriers to be trapped by surface states between gate and drain terminals. Based on the dependence of the normalized noise power spectral density (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ID</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) on the gate voltage, the FP dual gate had a low noise power spectral density and a low range of Hooge factors at high current.

Low-Frequency Noise in Amorphous Indium–Gallium–Zinc-Oxide Thin-Film Transistors

We have investigated the low-frequency noise (LFN) properties of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) as a function of frequency, bias, and channel length of devices. The measured noise power spectral density of drain current (S iD) shows that the low-frequency noise in a-IGZO TFTs obeys the classical 1/f noise theory, i.e., it fits well to a 1/f gamma power law with gamma ~ 1 in the frequency range of 10 Hz to 1 kHz. From the dependence of normalized noise power spectral density (S iD/ID 2) on the gate voltage, mobility fluctuation is considered as a dominant LFN mechanism in a-IGZO TFTs. The magnitude of S iD/ID 2 is inversely proportional to the channel length of devices, which indicates that contact noise is insignificant in a-IGZO TFTs.

Low-frequency noise in monodisperse platinum nanostructures near the percolation threshold

The percolation threshold p 0 ≈ 0.6 is determined for monodisperse platinum nanostructures with 1.8-nm metallic particles deposited in a monolayer onto an insulating substrate through laser electrodispersion. It is shown that, in the “metallic” state (for p > p 0), both the magnitude of the noise and its temperature dependence are close to those of pure metallic Pt layers. The frequency dependence of the normalized noise power spectral density is described by the relationship S I /I 2 ∼ 1/f γ with the exponent γ close to unity. For current densities j ≥ 107−108 A/cm2, the noise power spectral density S I increases more rapidly with a further increase in the current as compared to I 2 because of the current generating excess defects. For p < p 0, the dependence of the conductivity σ on the temperature is adequately described by the standard relationship σ ∼ exp[−(T 0/T)1/2]. The normalized noise power spectral density S I /I 2 exceeds the corresponding value for a quasi-metallic structure by many orders of magnitude. The noise power spectral density S I is approximately proportional to the square of the current only for very low currents and increases steeply with a further increase in the current.

Low-frequency noise in La0.7Sr0.3Mn1-xFexO3 thin films

The low-frequency noise in epitaxial La0.7Sr0.3Mn1-xFexO3 thin films with x = 0, 0.08 and 0.12has been studied as a function of magnetic field (up to 1500 G). At zero external magneticfield (B = 0G), there is no appreciable peak in the normalized noise power spectral density (PSD)for x = 0thin films; however, a peak does appear for x = 0.08and 0.12 thin films near the metal–insulator transition temperature(Tp),which is below the Curie temperature. Unlike the resistivity,the noise PSD does not change with the doping level(x) at B = 0 G; however, at B = 1500 G the noise PSD decreaseswith x. At a low externalmagnetic field of B < 1500G, there is no or a small thermal hysteresis in the noisePSD for all three differently doped samples; however, at B = 1500G there appears a large thermal hysteresis for all samples. The contributionof magnetic domain fluctuations is a possible origin for the noise PSD.

Measurements of noise spectral densities for a high-Tc superconductor: Single-crystal Bi2Sr2CaCu2Ox.

The noise power spectral density for a ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{Ca}}_{1}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{\mathit{x}}$ single crystal has been examined as a function of magnetic field, temperature, and frequency. In the normal state, the normalized noise power spectral density ${\mathit{S}}_{\mathit{n}}$(f) was observed to be several orders of magnitude greater than that of normal metals. Near the superconducting transition temperature, we observed a marked increase in ${\mathit{S}}_{\mathit{n}}$(f) with and without an external magnetic field. Moreover, in this region, we observed an unusual frequency dependence of the noise power spectral density on the external magnetic field.

Enhancement of the noise spectral densities near the resistive transition region of YBCO micro-bridge

We have systematically measured the noise power spectral density ( S υ( f)) of the YBCO micro-bridge as a function of frequency, temperature and magnetic field. In all the cases above, S υ( f) shows V 2/ f α behaviour at the measured frequency range of 0.2 < f < 30 Hz, with V, the d.c. voltage across the sample and, α the fitting parameter to be determined. In the normal state, the normalized noise power spectral density ( S n ( f) = S υ ( f)/ V 2) is four or five orders of magnitude larger than that of the normal metals evaluated by Hooge's formula or thermal fluctuation model. Near the zero resistance temperature ( T c 0, S n( f) was found to further increase by eight orders of magnitude and α was shown to increase from 1 to 2 depending on the frequency range. Furthermore, once a magnetic field is applied, S n( f) showed a marked increase near T cO . This anomaly is attributed to magnetoic vortices coupled with the enhanced instability of space-time coherence associated with Cooper pair as a result of applied magnetic field.

Anomalously enhanced noise spectral densities of YBCO micro-bridge near the resistive transition region

We have systematically measured the normalized noise power spectral density (S n(f) = S v(f)/V 2) of the YBCO microbridge and found V 2/f α dependence. Near the zero resistance temperature (T czero), S n(f) increases more than eight orders of magnitude. Moreover, α changes from 1 to 2. Furthermore, once a magnetic field is applied, S n(f) showed a marked increase near T c,zero. This anomally is attributed to magnetic vortices coupled with the enhanced instability of space-time coherence associated with cooper pair as a result of applied magnetic field, in addition to the thermal fluctuation.

1/f noise in the resistive transition region of high-temperature superconductor YBCO microbridged thin films

The measurement of the normalized noise power spectral density (Sn(f)=Sv(f)/V2) of the YBCO microbridge sows 1/falpha dependence. The key features of the present measurements are as follows: in the normal state, Sn(f) is several orders of magnitude larger than the value predicted by Hooge (1969); near Tc, Sn(f) increases by several orders of magnitude and alpha approaches 2; the noise power increases in a magnetic field near Tc. This enhancement of Sn(f) seems to be related to fluctuation at the phase transition due to the instability of Cooper pair formation and breaking.