Separation of random telegraph signals from 1/f noise in MOSFETs under constant and switched bias conditions

The low-frequency noise power spectrum of small dimension MOSFETs is dominated by Lorentzians arising from random telegraph signals (RTS). The low-frequency noise is observed to decrease when the devices are periodically switched 'off'. The technique of determining the statistical lifetimes and amplitudes of the RTS by fitting the signal level histogram of the time-domain record to two-Gaussian histograms has been reported in the literature. This procedure is then used for analysing the 'noisy' RTS along with the device background noise, which turned out to be 1/f noise. The 1/f noise of the device can then be separated from the RTS using this procedure. In this work, RTS observed in MOSFETs, under both constant and switched biased conditions, have been investigated in the time domain, Further, the 1/f noise in both the constant and the switched biased conditions is investigated

1/f noise and switched bias noise measurement in p-MOSFET with varying gate oxide thickness

MOS transistors are notorious for their low frequency noise, which increases with decreasing device size. Using a new noise measurement set up, the power spectral density of 1/f noise in MOSFETs decreases, if the transistors are switched “off��? periodically (switched bias conditions)[1]. In this work, noise measurements on p-MOSFET are reported, with gate oxide thickness varying from 2 to 20 nm, keeping the electric field in the channel constant at 1.4 MV/cm. The switched bias noise and the reduction in the switched bias noise for p-MOSFET, are investigated as a function of the gate oxide thickness and the switching amplitude. Recently reported literature[2] on explanation for switched biased noise reduction is then compared with our measurement results and some explanations are proposed

Modeling of RTS noise in MOSFETs under steady-state and large-signal excitation

The behavior of RTS noise in MOSFETs under large-signal excitation is experimentally studied. Our measurements show a significant transient effect, in line with earlier reports. We present a new physical model to describe this transient behavior and to predict RTS noise in MOSFETs under large-signal excitation. With only three model parameters the behavior is well described, contrary to existing models

Separation of random telegraph signals from 1/f noise in MOSFETs

The low-frequency noise power spectrum of small dimension MOSFETs is dominated by Lorentzians arising from Random Telegraph Signals (RTS). The low-frequency noise is observed to decrease when the devices are periodically switched �off�. The amount of noise reduction is observed to be dependent on the amplitude of the switching gate signal. The time-domain technique of determining the statistical lifetimes and amplitudes of the RTS by fitting the signal level histogram of the time-domain record to two-Gaussian histograms is used for analysing the �noisy� RTS along with the device background noise. The device background noise or 1/f noise of the device can then be separated from the RTS using this procedure. In this work, the RTS and the corresponding 1/f noise observed in MOSFETs, under both constant and switched biased conditions, have been \ud investigated. Also, the noise reduction as a function of gate-switching amplitude during switched biased conditions is investigated

Analysis of 'Switched Biased' random telegraph signals in MOSFETs

With decreasing device dimensions of MOSFETs, the nature of the low-frequency noise spectrum is a Lorentzian. This type of spectrum is due to Random Telegraph Signals (RTS), whose origin can be attributed to the random trapping and de-trapping of mobile charge carriers in the channel in traps located at the Si- SiO2 interface or in the oxide. The low-frequency noise decreases, if the transistors are switched "off" periodically (switched biased conditions). In this work, we have studied both p-MOS and n-MOS devices. The small devices (W/L=10:0.3) have a few trapping states, which is proven by the Lorentzian nature of the power spectrum. The RTS were measured under both; constant biased and switched biased conditions. A clear change in the RTS parameters;the mean capture time (?c) and the mean emission time (?e), under switched biased conditions, has been observed, as compared to the values in the constant bias case

Constant and switched bias low frequency noise in p-MOSFETs with varying gate oxide thickness

The low-frequency noise power spectral density of MOSFETs is decreased if the MOSFETs are periodically switched "off" (switched bias conditions). The influence of the gate oxide thickness on fixed bias and switched biased low frequency drain current noise spectral density of PMOS devices has been experimentally investigated. Under constant bias conditions, it is observed that the current noise spectral density increases linearly with increase in the gate oxide thickness. The larger the measured low-frequency noise under constant bias, the larger is the noise reduction after periodically switching the P-MOSFETs off

Investigating Hot-Carrier Degradation in MOSFETs using Constant and Switched Biased Low-Frequency Noise measurements

Periodically switching the MOSFET ‘off’ (switched biasing), is known to reduce the low-frequency (LF) noise power spectrum. In this work, the constant and switched biased LF noise has been measured on devices before and after hot-carrier stress. The switched biased LF noise is more sensitive to hot-carrier degradation than the constant biased LF noise. The anomalous noise reduction, due to switched biasing, observed for fresh devices, gradually disappears as the devices are subjected to hot-carrier stress. Devices with a deuterium passivated SiO2/Si interface degrade significantly slower, as seen from our LF noise measurements

Low-Frequency noise in hot-carrier degraded MOSFETs

Low frequency (LF) noise in MOSFETs originates mainly from traps at the Si/SiO2 interface. As hot carrier (HC) stressing is known to increase the interface trap density, the LF noise is also expected to increase. In this paper we quantify the noise increase resulting from hot carrier degradation. Furthermore we investigate two methods that could reduce LF noise, bias switching and deuterium passivation. The impact of these two measures on noise after hot carrier stressing are quantified for the first time