In this paper a systematic investigation of nitrided oxides obtained by Rapid Thermal Oxidation/Nitridation (RTO/RTN) in AMAT Centura System is reported. Two different aspects were considered: first the comparison between single wafers and batch technology, second the different possible oxide architecture achievable with RTO/RTN system (i.e. RTO + RTN, RTN + RTO, RTN + RTO + RTN). Both morphological and patterned wafers were processed. Physical and chemical characterizations were carried out by means of SIMS, XPS, ELYMAT, AFM and Etching Rate studies. Morphological results were then correlated to electrical data obtained on MOS capacitors. The film obtained performing a NO RTN nitridation of the native oxide followed by a ISSG (In Situ Steam Generation) oxidation exhibited very promising electrical properties that made it an appealing candidate as gate dielectric in CMOS and Flash memories applications.

The degradation and breakdown of thin silicon dioxide films has been analysed using a two-step stress method. This procedure allows the evaluation of the degradation induced by the electrical stress without any assumption about the microscopic nature of the degradation process. The method has been used to analyse and compare the degradation dynamics when constant-voltage (CVS) and constant-current stresses (CCS) are applied to the oxide. Moreover, it is shown that in the case of CVS, the fitting of the I-t characteristics can provide quantitative information about the degradation (degradation rate) and breakdown (mean-time-to-breakdown), without taking into account any degradation model.

The structure of ultrathin silicon oxynitride films, used as gate dielectrics in integrated circuits (ICs), is studied using analytical electron microscopy (AEM). Laterally homogeneous blanket films approximately 2 nm in thickness are characterized in cross section using a 300 keV field emission TEM/STEM. High resolution imaging (HRTEM) is used to investigate the accuracy and precision of film thickness measurements and their comparability to other techniques such as secondary ion mass spectrometry, spectroscopic ellipsometry, x-ray reflectivity, x-ray photoelectron spectroscopy, and medium energy ion scattering. A two dimensional magnification calibration scheme that fits a pair of basis vectors to experimental images is presented, and integrated intensity profiles are used to define film boundaries for measurement. These image processing tools simultaneously improve the repeatability of the measurements and remove subjective operator bias from the measurement process.

The one-dimensional Schridinger and Poisson equations have been numerically solved in metal-oxide-semiconductor devices using a three-point finite difference scheme with a non-uniform mesh size. The capacitance-voltage characteristic of the structure has been calculated via this self-consistent approach and results have been compared with data obtained from the resolution of Poisson equation using different approximated methods based on the Boltzmann statistic with and without a first order quantum effect correction or the exact Fermi-Dirac statistic. The present work permits to evaluate and quantify the errors made by these approximations in determining the thickness of ultra-thin oxides.

The thermally oxidized Si1−x−yGexCy thin films were grown on silicon substrates by Plasma-enhanced Chemical Vapor Deposition (PECVD) and then wet oxidized at 800°C for 20 minutes. Photoluminescence spectra of the samples were measured at room temperature under 250nm excitation. Two ultraviolet photoluminescence bands with the peaks at ∼370nm and ∼396nm were observed in the oxidized samples. Possible mechanism of this photoluminescence is discussed.

Earlier growth studies on the rapid thermal oxidation of silicon in NO (RTNO) were not sufficiently comprehensive and were limited by temperature measurement uncertainty and thermal non-uniformity across the wafer. Using a state-of-the-art rapid thermal processing (RTP) system, the RTNO growth characteristics at 100 and 760 Torr, from 900 to 1200°C and from 0 to 480 s were investigated. It was found that the initial growth rate anomalously decreasedwith temperature and pressure. These anomalies were correlated to the evolution of the XPS N 1s spectrum of the RTNO film with oxidation time, temperature and pressure.

This paper demonstrates optimized performance and reliability in ‘second generation’ gate dielectrics which include monolayer nitrided Si-SiO2 interfaces, and deposited silicon oxynitride alloy gate dielectrics. Devices with oxynitride alloy gate dielectrics with an approximate 2:1 ratio of N:O display reduced tunneling current, improved hole mobilities and improved reliability compared to devices with Si-nitride gate dielectrics and the same nitrided interface.

The dependence of the structures of the CeO2/YSZ (Y2O3-ZrO2)/Si multilayer thin films on the YSZ thickness was investigated by HRTEM. The CeO2/YSZ interface is semicoherent with misfit dislocations for the films with 110 nm and 30 nm YSZ thickness. On the other hand, the structure of the films with 0.5 nun YSZ layer are very muzzy since the YSZ is very disordered. However, the CeO2 layer on the 0.5 nm of the YSZ has the lowest mosaicity (highest quality) near the surface, although once the epitaxy is weakened in the YSZ layer and the CeO2 layer just above the YSZ. The mosaicity of the YSZ layer is thought not to be taken over into the CeO2 layer since the columnar structure of the thinner YSZ layer becomes obscure. Moreover, a YSZ layer of only 0.5 nm could inhibit the reduction of CeO2 by Si. The ultra thin YSZ layer of 0.5 nm is necessary because it inhibits the growth of the columnar structure and protects the protection of CeO2 layer from reduction.

The formation of oxynitride films less than 2.0 nm by using oxygen and nitrogen radicals produced by an electron cyclotron resonance plasma in an ultrahigh-vacuum system has been studied. The nitrogen concentration of the films was evaluated by x-ray photoelectron spectroscopy, and the position of the N in the films was evaluated by secondary ion mass spectroscopy. The interface roughness was also investigated by using atomic force microscopy. We found that the N concentration can be controlled at values up to 22.5%, and that although the interface roughness tends to increase with increasing N concentration, supplying oxygen and nitrogen radicals simultaneously decreases the roughness of the film and increases its nitrogen concentration (N: 18.2%, RMS: 0.12 nm). We also found that the nitrogen profile can be controlled by using different processing sequences. Radical oxynitridation should thus be very useful for making ultrathin gate-insulator films.

The generation of leakage current across 3-6-nm thick thermal oxides on (100)Si under electrical stress or irradiation with 10-eV photons is compared with the radiation-induced defect generation in 35-66-nm thick SiO2 layers. The degradation of both ultrathin and conventional oxides appears correlated with the concentration of atomic hydrogen in the layer. Both the leakage currents and the irradiation-induced defects were found to have two components: one thermally unstable that correlates with the H-induced donor states, and another related to the permanent oxide network damage ascribed to H-assisted Si-O bond break. As both degradation processes involve a proton formed in the oxide, we suggest that H ionization either by electron emission or by trapping a hole triggers oxide degradation.

Metal Oxide Semiconductor (MOS) capacitors with ultra-thin oxides have been irradiated with ionising particles (8 MeV electrons or Si, Ni, and Ag high energy ions), featuring various Linear Energy Transfer (LET) ranging over 4 orders of magnitude. Different oxide fields (Fbias) were applied during irradiation, ranging between flat-band and 3 MV/cm. We measured the DC Radiation Induced Leakage Current (RILC) at low fields (3-6 MV/cm) after electron or Si ion irradiation. RILC was the highest in devices biased at flat band during irradiation. In devices irradiated with higher LET ions (Ni and Ag) we observed the onset of Soft-Breakdown phenomena. Soft-Breakdown current increases with the oxide field applied during the stress.

Ultra-thin silicon dioxide films can be formed at temperatures as low as 220°C by direct oxidation of Si, using active oxygen species generated by tungsten catalytic reaction in a catalytic chemical vapor deposition (Cat-CVD) system. The structural and electrical properties of such a films are investigated. It is found that the density of Si atoms in intermediate oxidation states and the density of films determined from etch rate in dilute HF solution were comparable to those of the films by a conventional thermal oxidation at 900°C. The electrical properties, breakdown electric field and leakage current were also comparable to those of thermally oxidized films.

Ultra-thin silicon nitride films are being studied for use as high-dielectric constant (highk) materials in future gate dielectric applications, as Complementary Metal-Oxide-Semiconductor (CMOS) transistors are scaled down to the sub-100nm regime. In this study, process modifications are proposed to reduce the total charge and interface trap densities in sub-3.5 nm-thick silicon nitride films, grown in NH3, in a conventional furnace at 900°C and 1 atm. It is shown that by employing a short (<1 min) oxynitridation step in NO, before nitridation, and oxynitridation/Ar-annealing steps, after nitridation, silicon nitride films can be thermally grown with a total charge density as low as about 2.5E10 q/cm2 and an interface trap density of about 2.1E11/(eV-cm2). Besides, the effect of using NO as opposed to N2O for oxynitridation steps is also discussed.

Dielectric layers of thin silicon carbon nitride (SiCxNy) films have been prepared by ion beam sputtering deposition (IBD). For submicron metal-insulator-Si (MIS) based device applications, a dielectric of low interface roughness, increased capacitance/area with lower leakage on decreasing scale is highly desirable. We address these aspects for the IBD SiCxNy films on p-type Si and present their structural, optical and electrical characteristics as a function of the deposition conditions. Ultraviolet-visible transmittance and spectroscopic ellipsometry were employed to study the optical properties of the SiCxNy films. For electrical measurements, Al gate electrodes were fabricated on SiCxNy films to form metal-nitride-silicon (MNS) diodes. Characteristic I-V and photoconductivity measurements of the MNS are presented.

One of the reasons for the dominance of Si in microelectronics is the quality of the Si-SiO2 interface. In contrast, development of SiC-based MOSFETs for power applications is hampered primarily by poor carrier mobility at the SiC-SiO2 interface. Here we review recent calculations that elucidate the reasons of the contrasting properties of the two interfaces. In the case of Si, the interface energy is in fact lower when the interface is abrupt and smooth because of the intrinisic geometry of the Si (001) surface and the softness of the Si-O-Si angle. However, two energe ically degenerate phases are possible, leading to domain boundaries, that are the cause of subcxide bonds, steps, and dangling bonds. In principle, these effects may be avoidable by low-temperature deposition. In contrast, the geometry and bond lengths of SiC surfaces are not suitable for abrupt and smooth interfaces, requiring the existence of a nonstoichiometric interlayer that may be the cause of the reduced mobility.

We have investigated the initial oxynitridation of an atomically flat Si(001)-2×l surface by NO. We found that appropriate oxynitridation conditions, in which oxide decomposition does not occur, are required to suppress the roughness of the NO-reacted Si surface. Under these conditions, we investigated the growth behavior and chemical structure. The first oxynitridation, in which NO reacts with the first Si layer on the Si(001)-2×l surface, takes place in a layer-bylayer manner caused by two-dimensional nucleation. However, further oxynitridation for the second Si layer proceeds in a three-dimensional manner in which the atomic-scale roughness at the oxynitride/Si interface increases. In addition, under our oxynitridation conditions, N is incorporated as N ≡ Si3, even though the oxynitride is ultrathin.

Low temperature oxidation process of Si(100) substrates using atomic oxygen has been proposed. For the generation of atomic oxygen, microwave plasma remotely attached on the oxidation chamber was used. In the microwave plasma, the large amount of rare gas and a small amount of 02 gas mixture was supplied. The existence of the large amount of rare gas controls the plasma energy to some restricted values associated with the metastable states of the rare gas. Consequently, using Kr as mixed rare gas, atomic oxygen were efficiently generated instead of excited 02 molecules with any vibrational or ionized states. The oxidation kinetics of crystalline Si using this process was shown to be diffusion limiting, even if the oxide thickness was less than several nm. The activation energy of B, which is referred to as the parabolic rate constant, was found to be as low as 0.14eV In addition, lower interface trap density of 2.6 × 1011/cm2/eV at the mid gap could be achieved for the as-grown SiO2/Si(100) interface at the processing temperature of 500C.

The modification of the Si(001)/SiO2 interface and the related interface defect reduction by thermal treatments in nitric oxide (NO) have been studied by Electron Paramagnetic Resonance spectroscopy for 630Å thick and ultrathin (28Å) oxides. The effects of annealing temperature, annealing time and rapid (RTN) or furnace annealing have been explored. Our results show that an appropriate NO treatment can drastically reduce the defect densities if, in addition to N incorporation in the transition layer near the interface, the thermal relaxation of the nitrided oxide is allowed. Our results indicate that NO treatment can lead to “defect free” Si/SiO2 interfaces.

Microscopic properties of thin oxynitrides are investigated using a combination of the infrared ATR and ab-initio electronic structure methods. We use a theoretical structural model based on the Si-SiO2 interface with the oxide thickness of 0.8 nm. The interfacial region amounts to about 0.4 nm (the total thickness of the oxygen containing layer is 1.2 nm). The Quantum Molecular Dynamics simulations suggest that N accumulates at the interface. We have generated samples with the nitrogen concentrations from 1.69 × 1014 cm−2 to 6.78 × 1014 cm−2. The structural analysis of nitrogen containing cells indicates a significant improvement of the oxide layer and the strain reduction at the interface. We have performed a calculation of the vibrational density of states. A N-localized mode at 809 cm-1 has been identified. The experimental ifnrared ATR data is in qualitative agreement with the calculation. The valence band offset calculations reveal a 0.3 eV increase of the offset due to nitrogen at the highest nitrogen concentration considered. The valence band offset increase comes mainly from the structural change in the oxide layer. The interfacial dipole contributes 0.12 eV to the increase, while the structural change in the oxide layer gives additional 0.2 eV.

Electron spin resonance (ESR) spectroscopy is used to explore the origin of positive charges in silicon oxynitride thin films formed in a N2O ambient. A new type of paramagnetic center in as-grown oxynitrides appeared as a single peak in the ESR spectrum with a zero crossing g value of 2.0006. This value suggests that the paramragnetic center is a kind of E' center. We investigated the quantitative behavior of the positive charge center and the paramagnetic center through the density changes induced by vacuum ultraviolet irradiation and hydrogen annealing. Based on the similar behavior of both types of center, we argue that the paramagnetic centers can account for a significant part of the positive charges specific to oxynitrides. Since the spin density increased with the oxynitridation temperature, the paramagnetic center is closely related to nitrogen incorporation processes.