Low-frequency Noise Behavior Research Articles

Low-frequency noise measurements on submicrometre n-channel and p-channel MOSFETs at various operating regions

Silicon founders give in their MOS transistor card models some low-frequency noise parameters for SPICE-based circuit simulators corresponding to pure 1/f a or flicker noise, with a very close to unity. MOS transistors used in analogue circuit applications are usually devices with large channel length and width. In low-noise applications, methods such as correlated double sampling are used to suppress the low frequency noise generated by them. Nevertheless, the transistors presently are submicrometre devices exhibiting very different low-frequency noise behaviour. In this paper, experimental low-frequency noise results obtained at room temperature on NMOS and PMOS transistors fabricated using a 0.7 μm process are presented. Both large and small devices on the same process are considered. All regions of operation of transistors are considered. We show that the low-frequency noise behaviour of small area MOSFETs is very different from that of large area devices and that the spectrum is the summation of Lorentzian spectra generated by the switching of individual active traps.

Impact of 0.25 [micro sign]m dual gate oxide thickness CMOS process on flicker noise performance of multifingered deep-submicron MOS devices

The flicker noise performance of 0.25 µm thin gate oxide transistors from the dual gate oxide thickness process and the single gate oxide thickness process have been evaluated and compared. A total of 20 transistors have been measured. The results reveal that thin gate oxide transistors from the dual gate oxide thickness process show a maximum of an order reduction in the current noise spectra. This reduction can be attributed to the lower nitrogen concentration peak at the Si/SiO2 interface. Hence the dual gate oxide thickness process will be the state-of-the-art for the implementation of system-on-chip designs. In general, the low-frequency noise behaviour of the fabricated deep-submicrometre MOSFETs is best described by the number fluctuation with correlated mobility fluctuation model.

Impact of advanced processing modules on the low-frequency noise performance of deep-submicron CMOS technologies

Fundamental studies related to the low-frequency (LF) noise performance in semiconductors started more than 40 years ago. In 1957, McWhorter published the first model for the 1/ f noise in semiconductors, which is still in use. Whereas for many decades LF noise studies were mainly of fundamental and theoretical interests, in recent years, LF noise characterisation has become a very valuable diagnostic technique for the development of semiconductor materials and devices. Especially, the use of noise characterisation as a tool for reliability predictions has triggered the semiconductor engineering society. Not only the silicon starting material, but also many of the used process modules have a strong impact on the noise performance. This trend is becoming even more pronounced for the advanced deep-submicron technologies. For analog applications of scaled technologies, LF noise may even act as a showstopper. This review, therefore, focuses on the impact of advanced processing on the low-frequency noise behaviour. Both front- and back-end process modules are discussed.

Impact of cobalt silicidation on the low-frequency noise behavior of shallow p-n junctions

This work describes the low-frequency noise of forward biased shallow p-n junctions fabricated in epitaxial silicon substrates. Particular emphasis is on the effect of silicidation on the low-frequency noise spectral density S/sub I/. It is demonstrated that the observed 1/f noise is significantly larger in Co-silicided junctions compared with the nonsilicided ones. A detailed analysis of the current and geometry dependence of S/sub I/ leads to the conclusion that the 1/f noise is of the generation-recombination (GR) type, with the responsible GR centres homogeneously distributed over the device area. From the correlation with the forward current-voltage (I-V) characteristics, it is derived that GR fluctuations in the hole current through the n/sup +/ region cause the increased 1/f noise in the silicided devices.

Flicker noise in deep submicron nMOS transistors

This paper describes the low-frequency noise behaviour of n-channel MOSFETs fabricated in a 0.1 μm technology. It is shown that the spectra are predominantly of the 1/ f-type for some part of the frequency range investigated. For some devices, two 1/ f-type parts occur, one at low and another at “high” frequencies, separated by a plateau. A careful analysis of the drain current or gate bias dependence of the noise spectral density reveals that the low-frequency 1/ f-type noise is governed by the fluctuations in the series resistance region of the devices. The corresponding Hooge parameter α H is of the order of 10 −4. For the 1/ f-like noise occurring at “high” frequencies, it is observed that it can be ascribed to fluctuations in the channel, giving rise to a high value of α H of ∼10 −3 (from 2.5×10 −3–8×10 −3).

Low frequency noise behaviour of InP/InGaAs heterojunction bipolar waveguide phototransistors

In this paper we report on both the DC and low frequency noise (LFN) properties of InP/InGaAs heterojunction bipolar phototransistors (HPTs) featuring waveguide type illumination. Both DC and LFN measurements demonstrate the good quality of these devices. In particular, they exhibit a 1/ f noise figure-of-merit of 2·10 −8 μm 2, which is exceptionally very good in the field of the compound semiconductor HBTs, where values around 10 −7 μm 2 are usually reported.

1/f γ noise in polycrystalline silicon thin-film transistors

Polycrystalline silicon thin-film transistors show a 1/fγ (with γ<1) low frequency noise behavior. The 1/fγ noise is explained by emission and trapping processes of carriers between trapping states located within an energy range of kT around the Fermi level and the exponential tail states. We have derived a simple relationship between the frequency index γ of the noise spectrum and the energy distribution parameter of the tail states. From the experimental noise data, the theoretical model allows us to determine the tail states energy distribution and the grain boundary trap density.

Avalanche-induced excess noise in polycrystalline silicon thin-film transistors

The low-frequency noise behavior of polycrystalline silicon thin-film transistors, operated in the avalanche multiplication region of the output characteristics, is investigated. The avalanche-induced current noise, originating from generation-recombination processes in the depletion region of the drain junction, can be described by the carrier number fluctuation model. Using a model for the excess noise in silicon-on-insulator metal-oxide-semiconductor field-effect transistors operated in the kink regime, an analytical expression for the avalanche-induced current noise is derived taking into account an exponential distribution of the gap states. Comparison of the experimental noise data with the theoretical model indicates that, in addition to the avalanche multiplication, hot-carrier effects contribute significantly to the current increase in the avalanche regime.

On the geometry dependence of the 1/f noise in CMOS compatible junction diodes

This paper examines in detail the low-frequency (LF) noise behavior of Si n/sup +/p junction diodes in forward operation. Diodes fabricated on various types of Si substrates (FZ, epitaxial, and Cz) and with different geometries are studied in the current range 0.1-250 /spl mu/A in order to investigate the impact of these parameters. It is demonstrated that different kinds of 1/f noise behavior can be distinguished which point toward a different origin. The nature of the 1/f noise is most clearly identified by inspecting the variation of the frequency exponent with forward bias. On the one hand, what could be called "peripheral" or "surface" 1/f noise shows a frequency exponent which reduces with increasing forward current, a trend which is also observed for the corresponding ideality factor. When the 1/f noise is predominantly generated in the volume of the material (bulk origin), a more or less constant frequency exponent is found. It is also concluded that in many cases, no unique area or perimeter dependence is found when comparing the noise power spectral density of diodes with a different geometry. It will finally be shown that there exists a close correlation between the different 1/f noise sources and the different reverse current components, which are a sensitive function of the starting material characteristics and processing details.

Hot carrier degradation mechanisms in sub-micron p channel MOSFETs: Impact on low frequency (1/f) noise behaviour

In this work we present new results which illustrate the impact of hot carrier (HC) degradation on the low frequency (1/f) noise behaviour of submicron p channel MOSFETs. Submicron p channel MOSFETs were subjected to HC stress at a range of gate bias conditions, and the response of the low frequency noise was recorded. The results obtained are in marked contrast to the reported influence of HC stress on nMOSFETs 1/f noise, and indicate that the measurement of 1/f noise is a useful tool for investigating HC induced aging effects in submicron p channel devices. The significance of these results to the use of pMOSFETs in analog applications is briefly discussed.

1/f noise investigations in small channel length amorphous silicon thin film transistors

Conduction and low-frequency noise are analyzed in hydrogenated amorphous thin film transistors with small channel length. From current–voltage characteristics a set of conduction parameters is extracted pointing out parasitic resistances in series with the active channel. The low-frequency noise behavior is studied by means of the small equivalent circuit of the device. Intrinsic channel noise is separated from access resistance noise. Channel noise variations versus device biases agree with Hooge’s theory (carrier mobility fluctuations) but the noise levels are greater than in crystalline metal-oxide-semiconductor transistors. For high drain current 1/f noise in access series resistances prevails and becomes the main noise source. So, the results show the important part taken by these resistances in conduction and noise. Some comments for the design of thin film transistors are given.

Low-frequency drain current noise behavior of InP based MODFET's in the linear and saturation regime

This paper describes a detailed experimental study of the low-frequency (LF) drain current noise behavior of InP based MODFET's in a broad operation regime, spanning both linear and saturation operation. The noise power spectral density S/sub lD/ of the predominantly 1/f noise is studied as a function of the gate and drain bias. The experimental noise behavior is compared with available analytical models. It is shown that there is a reasonable agreement between the data and the theoretical models in linear operation. However, no accurate theory exists for the saturation regime. Therefore, an empirical analytical description is proposed, which provides a good approximation for the measurement data base. Furthermore, it can be used as a starting point for phase noise simulations in high-frequency nonlinear circuits.

Empirical model for the low-frequency noise of hot-carrier degraded submicron LDD MOSFETs

This paper discusses the empirical low-frequency (LP) noise behavior of hot-carrier degraded Lowly-Doped Drain (LDD) n-MOSFETs, which have been fabricated in a 0.7-/spl mu/m CMOS technology. It is shown that the increase of the noise spectral density follows a t/sup 0.3/ power law dependence with stress time. Additionally, an empirical relationship will be shown between the input-referred noise spectral density S/sub VG/ and the transconductance g/sub m/ of the stressed devices. The practical consequences of this exponential dependence will be briefly discussed.

Low Frequency Noise Behavior in Semiconductors

The low frequency behavior of the generation-recombination noise in the homogeneous semiconductors is investigated. The form of Lorentz law for spectral density of noise at low frequencies is made more precise. It is shown that at superlow frequencies the spectrum of generation-recombination noise changes into the 1/f-law. The characteristic frequency of this change depends on the temperature and dimensions of the sample.

The low-frequency noise behaviour of silicon-on-insulator technologies : E. Simoen and C. Claeys. Solid-State Electronics, 1996, 39(7), 949

The low-frequency noise behaviour of silicon-on-insulator technologies : E. Simoen and C. Claeys. Solid-State Electronics, 1996, 39(7), 949

Low temperature MBE grown AlInAs: Investigation of current voltage and low frequency noise behaviour of schottky diodes

The electrical characteristics of Schottky diodes fabricated on AlInAs layers grown on InP (100) substrates by molecular beam epitaxy in the temperature range 300 to 550°C were investigated by means of current-voltage and low frequency noise (LFN) measurements. Owing to the presence of deep level impurities in the layers, the decrease of the effective Schottky barrier height with measurement temperature below 160 K can be described by a two-step defect-assisted tunnelling process. The observed low frequency 1 f α (1 < α < 2) noise is attributed to the modulation of the Schottky barrier height arising from fluctuations in the occupancy of deep traps distributed within the AlInAs layers. From temperature dependent LFN measurements, we have identified two deep electron traps labelled L2 and L3, located respectively at 0.4 ± 0.1 eV and 0.66 ± 0.06 eV below the conduction band minimum.

The impact of oxide degradation on the low frequency ([formula omitted]) noise behaviour of P channel mosfets

Results are presented on the impact of hot carrier degradation on the low frequency (1f) noise behaviour of p channel MOSFETs. It is found that, in contrast to nMOSFETs, p channel devices exhibit no measurable change in the magnitude of the 1/f noise after severe device degradation at the condition of maximum gate current. The observations have been obtained on a range of device geometries and processes. The degradation results are analysed in conjunction with charge pumping characteristics to explain the insensitivity of the 1f noise to hot carrier degradation in the case of p channel devices. The significance of these results to the performance of p channel devices in analogue applications is discussed.

The low-frequency noise behaviour of Si n +p junction diodes fabricated on (1 0 0) and (1 1 1) substrates

This paper discusses the effect of the substrate orientation and crystal growth technique (Czochralski Cz and Float-Zone FZ) on the electrical characteristics of Si n +p junction diodes. More in particular, the influence on the static current-voltage and on the low-frequency noise in forward operation is investigated. As is shown, (111) oriented substrates yield diodes with a higher leakage current, a higher ideality factor and a higher noise, compared with (100) junctions. Combining diodes with a different area to perimeter ratio, the origin of the higher noise and leakage current is studied. It is concluded that the increase in noise for (111) substrates is correlated with the higher perimeter leakage current density. The latter is composed of an interface generation and a bulk generation component which are both affected by the orientation and the growth technique of the Si substrate.

Low excess noise of InAlAs/InP HFETs fabricatedusing selective dry recess etching

The low frequency noise (10 Hz-100 kHz) behaviour of InAlAs/InP HFETs fabricated using CH/sub 4//H/sub 2/ selective dry recess etching is reported. Devices from the same epitaxial structure fabricated using wet recess etching are also presented for comparison. The dry etching technique improves the drain noise spectral density. This improvement is attributed to the decrease in the source and drain resistance from 2.4 /spl Omega/ mm for the wet recess, to 1.6 /spl Omega/ mm For the dry recess. The equivalent series resistance fluctuations can explain the noise behaviour in both devices. No significant passivation of traps occurs during the CH/sub 4//H/sub 2/ etching process, as demonstrated by noise measurements on annealed dry etched devices.

High energy particle irradiation effects on the low-frequency noise of Czochralski silicon junction diodes

The effect of high energy particle irradiation on the low-frequency (LF) noise behavior of forward biased Czochralski (Cz) silicon p-n junction diodes is reported. It is shown that in the near-ideal diode region, the LF noise is hardly affected by up to 2×1011 cm−2 MeV proton (H+) and by up to 1015cm−2 MeV electron (e−) irradiations, respectively, and is therefore resistent to both bulk and ionization radiation damage. At higher injection levels, where the forward current and LF noise are series resistance dominated, a clear increase of the noise can be observed due to the high energy particle irradiation, which mainly creates displacement damage in the bulk of the wafer. The same noise observations hold for 60Co γ-irradiated Cz n+p diodes, which were performed for comparison purposes. In the latter case, the main degradation source is ionization damage in the peripheral lateral oxide isolation regions, as shown by reverse current and gated diode measurements.