J.M. Rafí

Linear kink effect induced by electron valence band tunneling in ultrathin gate oxide bulk and SOI MOSFETS

In this paper, evidence will be provided for the existence of a new class of floating body effects, occurring in SOI and bulk MOSFETs in the linear operation regime and called here the linear kink effects (LKEs). It will be shown that for a sufficiently large front-gate voltage V/sub G/, the transconductance g/sub m/ exhibits a second peak, both for n- and p-channel devices. The effect is most pronounced for partially depleted (PD) n-MOSFETs or bulk MOSFETs at cryogenic temperatures. It occurs as well in fully depleted (FD) transistors, with the back-gate preferably biased into accumulation. Associated with the LKE in the drain current, there is a strong increase of the low-frequency noise spectral density S/sub I/. Similar as for the impact-ionization related noise overshoot, it is observed that the nature of the spectrum changes from 1/f-like to Lorentzian in the LKE region. It is finally shown that the switching off transients change their sign from negative to positive for V/sub G on/ above the LKE threshold, giving evidence for the presence of majority carriers in the film during the ON phase.

Electrical characteristics of metal-insulator-semiconductor structures with atomic layer deposited Al2O3, HfO2, and nanolaminates on different silicon substrates

In this work, the electrical characteristics of different atomic layer deposited high-permittivity dielectric films (Al2O3, HfO2, and a nanolaminate of them), with a physical thickness of about 10 nm, are evaluated. An extensive capacitance-voltage and current-voltage characterization at room temperature is carried out on metal-insulator-semiconductor structures fabricated on different p-type and n-type silicon substrates and with Al as metal gate. HfO2 layers are found to exhibit the higher dielectric constant, but they suffer from the largest hysteresis and leakage currents and the lowest breakdown voltages. The nanolaminate stacks, with an intermediate dielectric constant, are found to exhibit more similarities to the Al2O3 layers, withstanding the largest voltages of all the studied dielectric films. The electrical degradation of the layers is evaluated by means of consecutive current-voltage ramps and with constant voltage stress experiments. Results on n-type Si, with electron injection from the sub...

Deposition Temperature and Thermal Annealing Effects on the Electrical Characteristics of Atomic Layer Deposited Al2O3 Films on Silicon

Atomic layer deposition (ALD) of Al 2 O 3 is of interest for a wide range of micro-nanoelectronic applications, where the electrical properties of the deposited layers can be strongly affected by deposition conditions and post-deposition treatments. In this work, a mercury-probe capacitance-voltage characterization is carried out on Al 2 O 3 films deposited on silicon by ALD at different temperatures and subjected to various thermal treatments in N 2 ambient. Effective positive charges located at the semiconductor/dielectric interface are encountered for the films deposited at the lowest temperature (100°C). Positive V fb shifts are always registered after the different thermal annealing conditions studied; however, the impact of the thermal treatments is found to be different depending on the deposition temperature. A significant negative charges build-up is observed after a 30 min anneal at 450°C, where improved surface passivation properties are achieved. Interestingly, the hysteresis, as well as the V fb shifts, clearly diminish for higher deposition temperatures or after a thermal anneal. However, the highest temperature treatments (≥800°C) result in significant interface states generation. Finally, exploratory experiments about the stability of the Al 2 O 3 layers under UV-light irradiation (in the 200-300 nm wavelengths range) show that this can be responsible for a significant degradation of their electrical characteristics.

Comparison of radiation hardness of P-in-N, N-in-N, and N-in-P silicon pad detectors

The very high radiation fluence expected at LHC (Large Hadron Collider) at CERN will induce serious changes in the electrical properties of the silicon detectors that will be used in the internal layers of the experiments (ATLAS, CMS, LHCb). To understand the influence of the fabrication technology in the radiation-induced degradation, silicon detectors were fabricated simultaneously with the three different possible technologies, P-in-N, N-in-N, and N-in-P, on standard and oxygenated float-zone silicon wafers. The diodes were irradiated with protons to fluences up to 10/sup 15/ cm/sup -2/. The measurements of the electrical characteristics, current-voltage and capacitance-voltage, are presented for the detectors manufactured with the three technologies. In terms of alpha factor (leakage current) the three technologies behave similarly. In terms of beta factor (effective doping concentration) N-in-P devices show the best performances.

Impact of 7.5-MeV proton irradiation on front-back gate coupling effect in ultra thin gate oxide FD-SOI n-MOSFETs

The degradation of deep submicron (0.1 /spl mu/m) fully depleted (FD)-silicon-on-insulator (SOI) n-channel metal oxide semiconductor field effect transistors (MOSFETs) subjected to 7.5-MeV proton irradiation is reported. The radiation-induced damage is investigated by studying the static characteristics of devices with different geometries and bias conditions. Special attention is paid to the analysis of the front-back gate coupling effect by changing the back-gate bias V/sub BG/. The change of the front and back channel parameters, the impact of the gate coupling effect and the gate-induced floating body effect are clarified. A correction procedure is proposed for the extraction of the front- and back-interface and oxide trap charge contribution to the threshold voltage shift by accounting for the front-back gate coupling.

What Do We Know about Hydrogen-Induced Thermal Donors in Silicon?

The hydrogen-plasma-accelerated formation of shallow thermal donors in silicon has been studied for a wide range of doping concentration and interstitial oxygen content [O-i] by electrical and spectroscopic techniques. The plasma-hydrogenated material has been heat treated for different times in the temperature range of 275-500 degrees C. It is shown that, besides oxygen thermal donors (OTDs), hydrogen-related shallow thermal donors (STDHs) also play a crucial role in the hydrogen-assisted creation of excess carriers. The impact of different factors on the introduction rate of the shallow donors will be discussed, whereby a strong role is played by the doping concentration and type (i.e., the Fermi-level position during the thermal anneal in air). Generally, shallow donor formation is faster in p- compared to n-type Si, which is associated with the different charge state of H. From combined deep-level transient spectroscopy and Fourier transform infrared absorption spectroscopy, it is concluded that the additional free carriers are contributed by both STDH and OTD centers, so that H not only plays a catalytic role but actively takes part in the donor formation, depending on the experimental conditions. Finally, from our data some conclusions can be made regarding the nature of the STDHs, which is still a matter of debate.

Short-channel radiation effect in 60 MeV proton irradiated 0.13 /spl mu/m CMOS transistors

The impact of a 60 MeV proton irradiation on the static characteristics of 0.13 /spl mu/m CMOS transistors is investigated, as a function of the device length and width. It is shown that the degradation of the threshold voltage and of the transconductance exhibits a marked length dependence, with more pronounced changes for shorter devices. From the independence on the device width and the 2 nm gate dielectric (nitrided or reoxidized nitrided oxide), it is concluded that the basic damage mechanism is not related to the isolation or gate dielectric. The origin of the observed changes will be discussed in view of the two-dimensional doping profile, produced by lowly doped drain and pocket or halo implantations used to control the short-channel effects.

Explaining the parameters of the electron valence-band tunneling related Lorentzian noise in fully depleted SOI MOSFETs

The behavior of the Lorentzian noise overshoot time constant /spl tau/ and plateau amplitude is investigated in fully depleted silicon-on-insulator MOSFETs with the back gate in accumulation. It is shown that /spl tau/ is identical for long-channel nand p-MOSFETs in the gate overdrive voltage range studied. For shorter lengths (L = 0.12 /spl mu/m), a slight reduction of /spl tau/ for the p-MOSFETs and an increase for the short n-MOSFETs has been found. The observations will be explained by considering both the injection of majority carriers in the floating body through electron valence-band tunneling and the dynamic resistance of the source-body and gate-body junction.

Electrical characterization of high-k based metal-insulator-semiconductor structures with negative resistance effect when using Al2O3 and nanolaminated films deposited on p-Si

In this work, the results of the electrical behavior of metal-insulator-semiconductor (MIS) structures using Al2O3, HfO2, and nanolaminated layers as gate insulators are reported. The MIS structures were deposited by atomic layer deposition on several Si substrates. The authors observed different conduction mechanisms for these high-k based MIS structures depending on the bias regime. Direct tunneling, Fowler–Nordheim, Poole–Frenkel emission, and a negative resistance region have been observed at different gate voltage values. The tunneling conduction of majority and minority carriers assisted by defects located at the Al2O3/HfO2 and Al2O3/metal interfaces can explain the negative resistance behavior observed in Al2O3 and nanolaminated samples. In addition to current-voltage (I-V) measurements, MIS structures were also electrically characterized using capacitance-voltage (C-V), deep level transient spectroscopy, conductance transients (G-t), and flat-band voltage transient (VFB-t) techniques.

Impact of Direct Plasma Hydrogenation on Thermal Donor Formation in n-Type CZ Silicon

Institut de Microelectro`nica de Barcelona, Campus UAB, 08193 Bellaterra, SpainIn this paper, the role of a direct plasma hydrogenation treatment and a subsequent air annealing at 450°C in the formation ofthermal donors ~TDs! in n-type Czochralski~CZ! silicon is investigated by means of a combination of capacitance-voltage~C-V!and deep-level transient spectroscopy~DLTS!. The hydrogenation treatment is found to enhance the introduction rate of TDs at450°C for shorter annealing times, reaching its maximum acceleration after5handforthelongest plasma hydrogenation studied~2h!. For much longer annealing times, the TD introduction rate becomes independent of the presence of hydrogen in the material.DLTS detects only one donor level having an activation energy, which lowers with increasing doping density of the material, from0.106 to 0.093 eV. After activation energy correction for the Poole-Frenkel electric-field-enhanced emission, this trap is found tofit well with the conventional singly ionized oxygen thermal donor level. However, from C-V free carrier and DLTS trapconcentrations, it is derived that other shallower donors, created by the plasma hydrogenation and 450°C anneal should play animportant role in the free carrier concentration increase of the n-CZ silicon.© 2004 The Electrochemical Society. @DOI: 10.1149/1.1824039# All rights reserved.Manuscript submitted March 14, 2004; revised manuscript received May 5, 2004. Available electronically November 17, 2004.