Emmanouel Hourdakis

Submicron gap capacitor for measurement of breakdown voltage in air

We have developed a new method for measuring the value of breakdown voltage in air for electrode separations from 400nmto45μm. The electrodes used were thin film Au lines evaporated on sapphire. The resulting capacitors had an area of 80×80μm2. We demonstrate the ability to deduce the value of the separation of the plates by the value of the capacitance. The data acquired with this method do not agree with Paschen’s law for electrode separations below 10μm, as expected from previous experiments. Amongst the improvements of our method are the measurement of plate separation and the very small surface roughness (average of 6nm).

Why the long-term charge offset drift in Si single-electron tunneling transistors is much smaller (better) than in metal-based ones: Two-level fluctuator stability

A common observation in metal-based (specifically, those with AlOx tunnel junctions) single-electron tunneling (SET) devices is a time-dependent instability known as the long-term charge offset drift. This drift is not seen in Si-based devices. Our aim is to understand the difference between these, and ultimately to overcome the drift in the metal-based devices. A comprehensive set of measurements shows that (1) brief measurements over short periods of time can mask the underlying drift, (2) we have not found any reproducible technique to eliminate the drift, and (3) two-level fluctuators (TLFs) in the metal-based devices are not stable. In contrast, in the Si-based devices the charge offset drifts by less than 0.01e over many days, and the TLFs are stable. We also show charge noise measurements in a SET device over four decades of temperature. We present a model for the charge offset drift based on the observation of nonequilibrium heat evolution in glassy materials, and obtain a numerical estimate in go...

Electrical breakdown in the microscale: Testing the standard theory

We present breakdown voltage measurement data in air taken with a technique we have recently developed and present calculations that show that the common assumption that one protrusion is responsible for the observed current is not warranted. The data suggest that below 10μm of electrode separation the dominant effect is field emission of electrons. Analyzing the data in that regime, using the theory of standard field emission and field amplification on the surface of a conductor, we come to a prediction about the geometry of the surface protrusions on the electrodes. We look for these protrusions using an atomic force microscope. We find several reasons why the standard theory does not appear to explain our data and conclude that the standard theory is not sufficient.

Error mechanisms and rates in tunable-barrier single-electron turnstiles and charge-coupled devices

Si-based single-electron tunneling (SET) devices have of late become an important alternative to the metal-based ones, both for ultralarge scale integration (ULSI) electronics and for electrical metrology. We have very recently been designing, fabricating, and measuring SET turnstiles, pumps, and charge-coupled devices using tunable barriers in silicon. Having shown the potential of these devices, we wish to understand the error mechanisms which may manifest themselves, and to predict the level of these errors, in order to decide how feasible these devices will be. In this paper, we devote a substantial amount of analysis to the consideration of the “dynamical” error mechanism. This particular error considers how electrons split up as the barrier is raised, or alternatively how the Coulomb blockade is formed. We then consider a wide variety of other errors, including thermal, frequency, leakage, and heating errors. We show the dependence of the error rate on each of those mechanisms, and predict maxima or...

Direct resistance comparisons from the QHR to100 M/spl Omega/ using a cryogenic current comparator

Measurements of room-temperature 100 M/spl Omega/ standard resistors and cryogenic thin-film resistors based directly on a quantized Hall resistance standard have been made with a cryogenic current comparator (CCC) bridge. This 15 496:2 ratio CCC attains a current sensitivity of 10.7 fA/Hz/sup 1/2/ in measurements of cryogenic thin-film resistors, without extensive shielding or filtering. A resistive primary winding helps the CCC maintain stability in the presence of external noise. The resistive-winding technique may be useful for the absolute measurement of small currents delivered by single-electron tunneling devices.

Lack of charge offset drift is a robust property of Si single electron transistors

One of the challenges that single-electron transistors (SETs) face before they can be considered technologically useful is the charge offset drift. Recently, two different types of Si SETs were shown to have a drift of only 0.01e (the fundamental charge) over several days. Those devices came from one fabrication source. Here, we present the results for Si SETs fabricated by our group (a different source) demonstrating their operation as SETs. We confirm that the charge offset drift is less than 0.01e, demonstrating the lack of charge offset drift is generic to Si devices and not dependent on the fabrication source.

Arsenic redistribution after solid phase epitaxial regrowth of shallow pre-amorphized silicon layers

The behavior of ultra shallow ion implants of arsenic in Si following solid phase epitaxial re-growth process is reported. A 16 nm amorphous layer was created by ion implantation of Si+ at energy 5 keV and a dose 1×1015 at/cm2. As ion were implanted at 2 keV using 3 different doses: 1×1014, 5×1014 and 1×1015 at/cm2. The resulting As distributions, confined in the amorphous layer, were thermally treated at 550°C for 5-300 s in order to electrically activate dopant atoms. Crystal re-growth and As redistribution was investigated by secondary ion mass spectrometry and medium energy ion scattering. A growth rate depending on the As concentration was observed, the rate being slower for higher As content. Arsenic re-distribution to the surface and at the end-of-range defects was observed and a segregation model was developed. Finally, the substitutional fraction of As atoms was related to sheet resistance measurements revealing a higher fraction of electrically active dopant atoms in pre-amorphized samples compa...

Reaching state-of-the art requirements for MIM capacitors with a single-layer anodic Al2O3 dielectric and imprinted electrodes

Metal-Insulator-Metal (MIM) capacitors with a high capacitance density and low non-linearity coefficient using a single-layer dielectric of barrier-type anodic alumina (Al2O3) and an imprinted bottom Al electrode are presented. Imprinting of the bottom electrode aimed at increasing the capacitor effective surface area by creating a three-dimensional MIM capacitor architecture. The bottom Al electrode was only partly nanopatterned so as to ensure low series resistance of the MIM capacitor. With a 3 nm thick anodic Al2O3 dielectric, the capacitor with the imprinted electrode showed a 280% increase in capacitance density compared to the flat electrode capacitor, reaching a value of 20.5 fF/μm2. On the other hand, with a 30 nm thick anodic Al2O3 layer, the capacitance density was 7.9 fF/μm2 and the non-linearity coefficient was as low as 196 ppm/V2. These values are very close to reaching all requirements of the last International Technology Roadmap for Semiconductors for MIM capacitors [ITRS, http://www.itrs...

Electrical and structural properties of ultrathin SiON films on Si prepared by plasma nitridation

The authors combined electrical and structural characterizations with analytical and spectroscopic measurements in order to fully analyze oxynitride nanofilms on Si that were produced in a minibatch type plasma nitridation reactor. The authors demonstrate that for the investigated samples the result of nitridation is different in the 2-nm-thick SiO2 films compared to the 5-nm-thick films. In the first case, nitridation results in an increase of the oxide film thickness compared to the non-nitrided film, with a consequent decrease in leakage current and an increase in the electrically measured equivalent oxide thickness (EOT). In contrast, nitridation of the 5-nm-thick SiO2 films leads to a reduction of both the leakage current and EOT. Finally, the authors demonstrate that the applied nitridation process results in the desired nitrogen profile with high nitrogen concentration near the top surface or the middle of the SiON film and low nitrogen concentration near the SiON/Si interface, which leads to a rel...

Comparison oF Electrical Measurements with Structural Analysis oF Thin High-k Hafnium-based Films

We present a detailed characterization of thin high-k Hf-based dielectric/SiO2 stacks on Si by electrical measurements (capacitance - voltage (C-V) and current-voltage (I-V)), structural analysis using transmission electron microscopy (TEM) and compositional analysis using medium energy ion scattering (MEIS). We show that the electrical results are consistent with and can be explained by the structural and compositional results. Specifically, the structural results show that the effect of nitridation of the films using a decoupled plasma nitridation method is an increase in SiO2 thickness, which results in a capacitance and leakage current decrease, revealed by the electrical measurements. Nitridation also reduces the density of interface traps for these samples. The reduction is more effective in the case of nonstoichiometric hafnium silicate films (HfSiOx) than in the case of HfO2.