The RF noise in 0.18-/spl mu/m CMOS technology has been measured and modeled. In contrast to some other groups, we find only a moderate enhancement of the drain current noise for short-channel MOSFETs. The gate current noise on the other hand is more significantly enhanced, which is explained by the effects of the gate resistance. The experimental results are modeled with a nonquasi-static RF model, based on channel segmentation, which is capable of predicting both drain and gate current noise accurately. Experimental evidence is shown for two additional noise mechanisms: 1) avalanche noise associated with the avalanche current from drain to bulk and 2) shot noise in the direct-tunneling gate leakage current. Additionally, we show low-frequency noise measurements, which strongly point toward an explanation of the 1/f noise based on carrier trapping, not only in n-channel MOSFETs, but also in p-channel MOSFETs.

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Noise modeling for RF CMOS circuit simulation

Electrical noise and RTS fluctuations in advanced CMOS devices

An overview is given of recent theoretical concepts and experimental findings with respect to the flicker or 1/ f noise in advanced silicon MOSFETs. First, a summary will be given of the theoretical models which to date are being considered for modeling of the flicker noise phenomenon. These will be confronted with experimental evidence, from which the likely validity range of the different models and their possible limitations follow. Next, attention will be paid to the impact of technology scaling to submicron dimensions on the 1/ f noise. Finally, the effect of specific advanced processing steps, typical for submicron CMOS technology will be highlighted and guidelines for low-noise processing will be formulated.

On the flicker noise in submicron silicon MOSFETs

We investigated the reduction of current fluctuations in few-layer black phosphorus (BP) field-effect transistors resulting from Al2O3 passivation. In order to verify the effect of Al2O3 passivation on device characteristics, measurements and analyses were conducted on thermally annealed devices before and after the passivation. More specifically, static and low-frequency noise analyses were used in monitoring the charge transport characteristics in the devices. The carrier number fluctuation (CNF) model, which is related to the charge trapping/detrapping process near the interface between the channel and gate dielectric, was employed to describe the current fluctuation phenomena. Noise reduction due to the Al2O3 passivation was expressed in terms of the reduced interface trap density values Dit and Nit, extracted from the subthreshold slope (SS) and the CNF model, respectively. The deviations between the interface trap density values extracted using the SS value and CNF model are elucidated in terms of t...

Few-Layer Black Phosphorus Field-Effect Transistors with Reduced Current Fluctuation

Low-Frequency Noise in Advanced CMOS Devices begins with an introduction to noise, describing the fundamental noise sources and basic circuit analysis. The characterization of low-frequency noise is discussed in detail and useful practical advice is given. The various theoretical and compact low-frequency (1/f) noise models in MOS transistors are treated extensively providing an in-depth understanding of the low-frequency noise mechanisms and the potential sources of the noise in MOS transistors. Advanced CMOS technology including nanometer scaled devices, strained Si, SiGe, SOI, high-k gate dielectrics, multiple gates and metal gates are discussed from a low-frequency noise point of view. Some of the most recent publications and conference presentations are included in order to give the very latest view on the topics. The book ends with an introduction to noise in analog/RF circuits and describes how the low-frequency noise can affect these circuits.

Low-Frequency Noise in Advanced MOS Devices

An improved analysis of low frequency trapping noise in a MOS device is proposed. This analysis takes into account the supplementary fluctuations of the mobility induced by those of the interface charge. It enables an adequate description of the gate voltage dependence of the input equivalent gate voltage noise to be obtained in various actual situations. The outputs given by the Hooge mobility fluctuation model are also presented and discussed with respect to those obtained by the carrier number fluctuation model. In particular, the impact of the channel length or channel width, and the model type on the input gate voltage and drain current noise characteristics is studied and compared to typical experimental data. Finally, a procedure for the diagnosis of the low frequency noise sources in a MOS transistor is proposed.

Improved Analysis of Low Frequency Noise in Field‐Effect MOS Transistors

An investigation of the amplitude drain current RTS fluctuations in small area silicon MOS transistors is presented. A simple theoretical model for the interpretation of the RTS amplitude variations with gate and drain voltages is proposed. The limits of application of the model are established and discussed with respect to the experimental results.

Investigation of Drain Current RTS Noise in Small Area Silicon MOS Transistors

A theoretical analysis for the calculation of the conductance fluctuations in small area metal–oxide–semiconductor (MOS) devices is presented. This analysis relies essentially on the assumption that the trap region in the device channel can be approximated by a rectangular region inside which the sheet conductivity differs from that in the region of the channel outside the trap. The sheet conductivity shift in the trap region is evaluated using the concept of flat band voltage shift associated with the trapping of one elementary charge in the trap region. The approach of flat band voltage shift is then advantageously used to derive first-order analytic expressions of the random telegraph signal (RTS) amplitude. In particular, it is found both, analytically and numerically that, in the case of small sheet conductivity modulation, the RTS amplitude becomes independent of the trap size. The numerical simulations show that the maximum RTS amplitude occurring in weak inversion is not a monotonic function of the trap size. Indeed, the normalized conductance fluctuation does increase as the trap area is reduced, passes through a maximum and finally decreases towards zero. The comparison of the simulation results with typical experimental RTS data shows an overall good agreement. In particular, it is clearly demonstrated from the RTS measurements that the gate voltage dependence of the normalized RTS amplitude can be strongly correlated to that of the transconductance to drain current ratio gm/Id.



Eine theoretische Analyse fur die Berechnung der Leitfahigkeitsfluktuationen in kleinflachigen Metall–Oxid–Halbleiter(MOS)-Bauelementen wird angegeben. Diese Analyse beruht wesentlich auf der Annahme, das der Haftstellenbereich im Bauelementekanal durch einen rechteckigen Bereich genahert werden kann, indem die Schichtleitfahigkeit sich von der im Kanalbereich auserhalb der Haftstelle unterscheidet. Die Schichtleitfahigkeit im Haftstellenbereich wird mit dem Konzept der Flachbandspannungsverschiebung, die mit dem Anhaften einer elementaren Ladung im Haftstellenbereich verbunden ist, berechnet. Dieses Verfahren der Flachbandspannungsverschiebung wird dann vorteilhaft benutzt, um analytische Ausdrucke erster Ordnung fur die Amplitude des statistischen Telegraphensignals (RTS) abzuleiten. Insbesondere wird sowohl analytisch als auch numerisch gefunden, das im Falle einer geringen Schichtleitfahigkeitsmodulation die RTS-Amplitude unabhangig von der Haftstellengrose wird. Die numerischen Simulationen zeigen, das die maximale RTS-Amplitude, die in schwacher Inversion auftritt, keine monotone Funktion der Haftstellengrose ist. Tatsachlich nimmt die normierte Leitfahigkeitsfluktuation zu, wenn die Haftstellenflache verringert wird, geht durch ein Maximum und nimmt endlich auf null ab. Der Vergleich der Simulationsergebnisse mit typischen experimentellen RTS-Daten zeigt eine gute Gesamtubereinstimmung. Insbesondere wird aus den RTS-Messungen klar gezeigt, das die Gatespannungsabhangigkeit der normierten RTS-Amplitude streng mit der des Steilheits–Drainstromverhaltnisses gm/Id korreliert werden kann.

O. Roux

Papers

Improved Analysis of Low Frequency Noise in Field‐Effect MOS Transistors

Investigation of Drain Current RTS Noise in Small Area Silicon MOS Transistors

Modeling of contuctance fluctuations in small area metal–oxide–semiconductor transistors