Joel Molina

High-quality spin-on glass-based oxide as a matrix for embedding HfO2 nanoparticles for metal-oxide-semiconductor capacitors

By using a low cost, simple, and reproducible spin-coating method, thin films of SOG (spin-on-glass)-based oxides with electrical characteristics resembling those of a dry thermal oxide have been obtained. The superior electrical characteristics of Metal-Oxide-Semiconductor (MOS) capacitors based on SOG-oxides come from both (1) reducing the organic content of the SOG solutions after dilution with deionized water and (2) passivation of the silicon surface by a thin chemical oxide. Fourier transform infrared spectroscopy analysis shows that the organic content in H2O-diluted SOG-oxides is reduced compared to undiluted SOG after N2 annealing. In addition, by chemically embedding HfO2 nanoparticles (np-HfO2) to these SOG-based oxides, an effective increase in the accumulation capacitance of MOS capacitors is observed and this is related to the increase in the final dielectric constant of the resulting oxide after annealing so that potential use of SOG as a glass matrix for embedding HfO2 nanoparticles and produce higher-k oxide materials is demonstrated.

Physical and electrical characteristics of atomic-layer deposition-HfO2 films deposited on Si substrates having different silanol Si-OH densities

In this work, ultrathin HfO2 films, less than 6 nm in thickness, are deposited by atomic-layer deposition (ALD) on Si substrates that have a variable density of silanol (Si-OH) chemical bonds after oxidizing the Si surface using hot H2O2. Given the surface chemistry needed for proper ALD growth of HfO2, OH-last surfaces are needed in order to react with the Hf-based precursor during half-cycle of this reaction. The later is important for proper nucleation and uniform growth of ultrathin HfO2 by ALD. Depending on the immersion time of an initially HF-last Si surface in hot H2O2, ultrathin and nonstoichiometric chemical oxides SiOx are formed presenting a variable density of Si-OH bonds which are measured after Fourier-transform infra red spectroscopy. Following SiOx formation, HfO2 is directly deposited on these surfaces by ALD using water (H2O) and tetrakis-dimethylamino-hafnium as precursors. Metal–insulator–semiconductor (MIS) capacitors are then formed using both HfO2/Si and HfO2/SiOx/Si stacked structures and their electrical characteristics are evaluated. It is found that a variable density of Si-OH chemical bonds have an impact on the physical and electrical characteristics of these MIS structures by reducing their atomic surface roughness (Rrms) and gate leakage current density (Jg), and at the same time, increasing their flat band voltage (Vfb) for the same immersion times in H2O2. Obtaining the lowest Rrms, Jg, and Vfb are possible by using intermediate H2O2 immersion times between 4 and 8 min, which is also directly related to an intermediate Si-OH bond density.In this work, ultrathin HfO2 films, less than 6 nm in thickness, are deposited by atomic-layer deposition (ALD) on Si substrates that have a variable density of silanol (Si-OH) chemical bonds after oxidizing the Si surface using hot H2O2. Given the surface chemistry needed for proper ALD growth of HfO2, OH-last surfaces are needed in order to react with the Hf-based precursor during half-cycle of this reaction. The later is important for proper nucleation and uniform growth of ultrathin HfO2 by ALD. Depending on the immersion time of an initially HF-last Si surface in hot H2O2, ultrathin and nonstoichiometric chemical oxides SiOx are formed presenting a variable density of Si-OH bonds which are measured after Fourier-transform infra red spectroscopy. Following SiOx formation, HfO2 is directly deposited on these surfaces by ALD using water (H2O) and tetrakis-dimethylamino-hafnium as precursors. Metal–insulator–semiconductor (MIS) capacitors are then formed using both HfO2/Si and HfO2/SiOx/Si stacked struct...

CAFM based spectroscopy of stress-induced defects in HfO 2 with experimental evidence of the clustering model and metastable vacancy defect state

In this study, we perform random telegraph noise (RTN) spectroscopy on ultra-thin HfÜ2 dielectric films using a conductive atomic force microscope (CAFM), enabling accurate assessment of single or cluster defect kinetics in very small area regions with an ultra-sharp tip having radius of 15±5 nm. Our characterization results show that bias-dependent RTN trends can be clearly detected at high spatial resolution using CAFM technique. Experimental evidence of the metastable nature of oxygen vacancy defects is presented and the nanoscale breakdown results provide further support to the time-dependent defect clustering model that is recently proposed for oxide breakdown [1,2]. Statistical plots of the CAFM breakdown voltage show a trimodal distribution that corresponds to evolution of percolation cores at the grain (G), grain boundary/triple point (GB/TP) sites and G-GB interface regions.

Reduction in the interface-states density of metal-oxide-semiconductor field-effect transistors fabricated on high-index Si (114) surfaces by using an external magnetic field

After fabrication of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) devices on high-index silicon (114) surfaces, their threshold voltage (Vth) and interface-states density (Dit) characteristics were measured under the influence of an externally applied magnetic field of B = 6 μT at room temperature. The electron flow of the MOSFETs channel presents high anisotropy on Si (114), and this effect is enhanced by using an external magnetic field B, applied parallel to the Si (114) surface but perpendicular to the electron flow direction. This special configuration results in the channel electrons experiencing a Lorentzian force which pushes the electrons closer to the Si (114)-SiO2 interface and therefore to the special morphology of the Si (114) surface. Interestingly, Dit evaluation of n-type MOSFETs fabricated on Si (114) surfaces shows that the Si (114)-SiO2 interface is of high quality so that Dit as low as ∼1010 cm−2·eV−1 are obtained for MOSFETs with channels aligned at specific orientation...

Performance of a MOHOS-type memory using np-HfO 2 and variable tunneling oxide thickness

We use HfO2 nanoparticles (np-HfO2 embedded in a spin-on glass SOG oxide matrix) as a charge trapping layer CTL in metal/oxide/high-k/oxide/silicon (MOHOS)-memories. This CTL is then deposited on ultra-thin layers of chemical oxide SiOx ≤2nm. Depending on the SiOx thickness, a trade-off in writing/erasing and data retention time characteristics is obtained.

Extraction of gate oxide quality and its correlation to the electrical parameters of MOS devices

Physical, chemical and electrical measurements are a useful tool to determine some of the most important parameters in MOS devices. Electrical and structural properties of MOS devices can be obtained from these measurements. Main chemical bonds and thickness of gate oxide, threshold voltage, flatband voltage, series resistance and channel length for MOS devices are some of the parameters that can be obtained by these measurements. MOS capacitors and MOSFET devices with a CMOS standard fabrication process in INAOE were measured. Stress voltage was applied in MOS devices to extract lifetime characteristics and therefore, their reliability. The results showed to have a high correlation with manufacturing specifications.

Progressive-degradation and breakdown of W-La 2 O 3 MOS structures after constant voltage stress

In this paper, we report the progressive electrical degradation and consequent breakdown (both soft and hard-breakdown regimes) of thin W-La2O3 stacked films deposited on silicon substrates and their influence on the electrical characteristics of metal-oxide-semiconductor (MOS) devices. Initial electrical degradation of the MOS devices results in an increase of the gate oxide leakage current (mostly known as Stress-Induced Leakage-Current, SILC), with the devices practical effect being a monotonous shift in threshold voltage (¿Vth) after constant voltage stressing. Following the initial degradation of the gate oxide, both soft and hard-breakdown modes are detected and their influence on the electrical characteristics of the MOS devices are also obtained and compared.

Reliability characteristics of W-La 2 O 3 structures compared with those of HfO 2 -based gate oxides

In this paper, we report and compare the reliability results obtained for W-La2O3 gated Metal-Oxide-Semiconductor (MOS) devices with those of HfO2-based systems reported in literature. Reliability issues like stress-induced leakage current (SILC), interface-states generation (Dit), threshold voltage shift (DeltaVth) and time to breakdown (tbd) were compared and analyzed for both dielectrics in order to obtain a more specific assessment of their resistance to electrical degradation and breakdown.