Excess Low-Frequency Noise in Ultrathin Oxide n-MOSFETs Arising From Valence-Band Electron Tunneling

Abstract

Low-frequency flicker noise in analog n-MOSFETs with 15-A gate oxide is investigated. A new noise generation mechanism resulting from valence-band electron tunneling is proposed. In strong inversion conditions, valence-band electron tunneling from Si substrate to polysilicon gate takes place and results in the splitting of electron and hole quasi-Fermi-levels in the channel. The excess low-frequency noise is attributed to electron and hole recombination at interface traps between the two quasi-Fermi-levels. Random telegraph signals due to the capture of channel electrons and holes is characterized in a small area device to support our model.

Low-frequency noise in downscaled silicon transistors: Trends, theory and practice

“…Thus, the use of Shockley-Read-Hall process might be incorrect for the tunneling noise from oxide traps, since it is questionable whether the traps are in equilibrium. On the other hand, the capture and emission time constants in RTS noise in MOS transistors are found to follow Shockley-Read-Hall process [68,74,107,112,148,161,162]. Other issues related to the assumptions for superposition of tunneling events in gate oxide in creating 1/f noise are discussed in [4].…”

“…In fact, there is no standard procedure for analysis and compact model for RTS noise in MOS transistors. The RTS noise is also nonmonotonically bias-and temperature dependent [58,68,137,161,167], it varies between different time records captured from one sample [68,74], and between nominally identical samples [137,166]. On the other hand, the amplitudes of RTS noise can be large in sub-micron area MOS transistors [74,112,137] and RTS noise becomes important issue that the designs have to overcome, e.g.…”

Physics of fluctuation processes in downscaled silicon MOSFETs

“…The studies show that the presence of EVB currents stipulates not only the formation of the abovedescribes Lorentzian fluctuations, but also a drastic increase in 1/f noise [14,15].…”

“…However, for x max = x max 2 = 1.73 nm, we obtain f min = f min 2 = 50 Hz, i.e., the section of the 1/f spectrum should give place to the plateau even for a frequency of 50 Hz. Within the framework of the described model of 1/f noise, the mechanism of the noise rise detected under the conditions of strong inversion in the bulk n-channel field-effect MOS transistors with gate-oxide thickness equal to 1.5 nm [14,15] can be explained as follows. The tunnel EVB current initiates the occurrence of recombination processes near the gate surface of a silicon film, which are stipulated by the fact that part of the holes appearing on this surface for V * ≥ 1 V due to the EVB tunneling recombines with the electrons from the channel through the traps located in the gate oxide.…”

Linear kink effect Lorentzians in the noise spectra of n- and p-channel fin field-effect transistors processed in standard and strained silicon-on-insulator substrates

“…10 shows that the level of the plateau corresponding to the 1/f noise increases at V GF P 1 V where the LKE Lorentzians are observed and, hence, the EVB tunneling current is flowing. Such an increase can be explained by the fact that the EVB tunneling current provokes recombination processes at oxide and interface traps and these processes are the source of the additional 1/f noise [18,19].…”