Noise Overshoot Research Articles

The kink-related excess low-frequency noise in silicon-on-insulator MOST's

The phenomenology of the kink-related low-frequency (LF) noise overshoot in partially depleted (PD) silicon-on-insulator (SOI) MOS transistors is described in detail. The influence of various physical parameters is reported. Based on the observations, a comprehensive first-order theory for the feature is derived. The model is based on the charge fluctuations which are caused by deep-level assisted generation-recombination events in the depletion region of the transistor. It will be shown that the noise amplitude is proportional to the density of deep-level centers, while the peak position is a sensitive function of the saturation voltage. This follows from the postulated dependence of the capture time on the inverse substrate current. As will be shown, the standard expression for the multiplication current is in first order also valid for SOI MOST's, both at room temperature and at 77 K. Simulations demonstrate that the proposed model correctly predicts the dependence of the noise overshoot on the measurement frequency, on the gate voltage, the temperature and on the device length. Finally, the spectroscopic potential of the feature will be outlined and possible ways to render the technique truly quantitative are pointed out. >

The low-frequency noise overshoot in partially depleted n-channel silicon-on-insulator twin-MOST's

This paper investigates the effect of the so-called twin-MOST structure on the kink-related low-frequency (LF) noise overshoot, which is observed in partially depleted (PD) SOI nMOST's. It is demonstrated that a significant reduction of the noise overshoot amplitude may be achieved in such a configuration, compared with a single transistor having the same effective gate length. The observed reduction is stronger than the one predicted on purely geometrical grounds, indicating that the floating body effects are indeed successfully reduced by this structure.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Gate-length dependence of the low-frequency noise overshoot in partially depleted SOI n-MOSFET's

This letter investigates the effective gate-length L eff dependence of the low-frequency noise overshoot in partially-depleted Silicon-on-Insulator n-MOSFAT's. It will be demonstrated that the noise overshoot amplitude is proportional to 1 L eff andto the reciprocal noise frequency 1 f . The noise overshoot position is a linear function of the saturation voltage. These findings will be discussed in view of a recently developed model for the noise overshoot.

Low-frequency noise behavior of γ-irradiated partially depleted silicon-on-insulator n-channel metal-oxide-semiconductor transistors

This letter discusses the low-frequency noise behavior of partially depleted silicon-on-insulator n-channel metal-oxide-semiconductor transistors after γ irradiation to a total dose of 100 krad(Si). The noise characteristics both in linear operation and in saturation are investigated in detail. It is shown that the increase of the noise in the linear region is mainly due to the degradation of the sidewall isolation regions. In contrast, the so-called kink-related noise overshoot is hardly affected by the irradiation, indicating that its origin is most likely not interface related. This result will be discussed in view of a recently proposed model for the noise overshoot.

Kink-related low-frequency noise overshoot in Si NMOSTs at liquid helium temperatures

In this paper, the excess low-frequency noise observed in an Si MOSFET operating at liquid He temperatures is investigated in detail. More specifically, the influence of both temperature and bias voltage on the kink-related noise overshoot is reported and discussed in view of a recently proposed model. It will be demonstrated that the noise overshoot is drastically reduced for operation temperatures above 10 K, or if the device has a floating, or forward-biased substrate/well contact. For the first time, it will be shown that the magnitude of the “kink noise” has a hysteretic character, as does the drain current in the kink region. This is accompanied by a change in the nature of the low-frequency noise spectrum. A more refined model will be derived, relating the excess noise to the applied drain, gate and substrate bias. A good, qualitative agreement with the measurements is obtained by this approach.

A study of the kink-related excess low-frequency noise in silicon- on-insulator n-metal-oxide-semiconductor transistors operated at liquid helium temperatures

In this paper, the drain voltage dependence of the low-frequency (lf) noise of partially depleted silicon-on-insulator n-metal-oxide-semiconductor-transistors (n-MOSTs) is investigated in detail at liquid helium temperature. As will be shown, an increase in the noise spectral density is observed at the kink position, similar to bulk n-MOSTs operated at 4.2 K. This excess noise introduces a Lorentzian generation-recombination (GR) component in the lf noise spectrum. The physical mechanism underlying the GR noise is thought to be the same as for bulk transistors: ionization and capture in the depletion region of carriers, which are created at the drain. This generates a fluctuation in the depletion charge, which is translated into a fluctuation of the drain current via a change in the threshold voltage. A model will be proposed that is derived from the analysis previously established for the bulk case. Extension of the model to fully depleted, thin-film transistors and to higher temperatures (77 K, 300 K) will be briefly outlined. As will be demonstrated, a good overall agreement between theory and experiment is obtained whereby the key features of the noise overshoot, i.e., its position and amplitude, are consistently reproduced.

Kink-related noise overshoot in SOI n-MOSFETS operating at 4.2 K

The low frequency noise behaviour of SOI n-MOSFETs operated at 4.2 K is reported for the first time and compared with room temperature behaviour. It is shown that the noise level increases by a factor of 3-5, and the kink-related noise overshoot become much more pronounced on cooling. These results are compared with the noise overshoot observed in bulk devices operating at 4.2 K and a similar explanation for the phenomenon is proposed. >

Comments, with reply, on 'Modeling of the 1/f noise overshoot in short-channel MOSFETs locally degraded by hot-carrier injection' by B. Boukriss et al

It is pointed out that a letter by Boukriss et al. (see ibid., vol.10, p.433-6, 1989) contains no reference to the actual value of the characteristic exponent of the noise spectrum ( gamma ). This omission may result from the assumption that gamma is equal to one. Similar measurements by the present author indicate that gamma varies strongly following hot-carrier injection near the drain. The change in the characteristic component is caused by the injected carriers present in the oxide near the interface, rather than the increased number of traps. This injected charge has an effect on noise provided the channel is not pinched off. It is argued that to study only the amplitude of the noise and not gamma misses critical information, the scaling properties, and that if one is to measure noise amplitude, one should measure the characteristic exponent as well. In a reply, the original authors state that the 1/f noise was studied for a nonhomogeneous MOSFET. The 1/f noise level was investigated from weak to strong inversion.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Modeling of the 1/f noise overshoot in short-channel MOSFETs locally degraded by hot-carrier injection

On the basis of previous results concerning the 1/f noise in electrically stressed MOS transistors and the characterization of aged MOSFETs, the authors present a theoretical model for the flicker noise in nonhomogeneous short-channel MOS transistors operated in the ohmic region. When applied to hot-carrier-induced degradation, a simple two-region approximation of this model is shown to account for the existence of a noise peak (overshoot) near the threshold voltage, similar to the transconductance overshoot already observed. A two-dimensional simulation makes it possible to detail the influence of the gate bias, the distance over which the interface states (or traps) are generated, and their density. The 1/f noise overshoot appears to be more sensitive to aging conditions than transconductance overshoot. >