Hugo Bender

10×10nm 2 Hf/HfO x crossbar resistive RAM with excellent performance, reliability and low-energy operation

We report on worlds smallest HfO2-based Resistive RAM (RRAM) cell to date, featuring a novel Hf/HfOx resistive element stack, with an area of less than 10×10 nm2, fast ns-range on/off switching times at low-voltages and with a switching energy per bit of <0.1pJ. With excellent endurance of more than 5.107cycles, large on/off verified-window (>50), no closure of the on/off window after 30hrs/200C and failure-free device operation after 30hrs/250C thermal stress, the major device-level nonvolatile memory requirements are met. Furthermore, we clarify the impact of film crystallinity on cell operation from a scalability viewpoint, the role of the cap layer and bring insight into the switching mechanisms.

Nanometer‐scale magnetic MnAs particles in GaAs grown by molecular beam epitaxy

Spherical MnAs ferromagnetic particles with controllable diameters (5–30 nm) are embedded in a high quality GaAs matrix. The particles are formed in a two step process consisting of the epitaxy of a homogeneous Ga1−xMnxAs layer at low temperatures using molecular beam epitaxy followed by phase separation upon annealing. During the annealing step, the excess arsenic in the as‐grown film forms magnetic MnAs precipitates with the Mn from the Ga1−xMnxAs lattice. Structural and room‐temperature magnetic properties of the heterogeneous GaAs:MnAs films are described. The magnetic MnAs rich layers can be incorporated into semiconductor heterostructures as demonstrated by growing (GaAs/AlAs) multiple quantum well structures in combination with GaAs:MnAs layers.

Three-dimensional observation of the conductive filament in nanoscaled resistive memory devices.

The basic unit of information in filamentary-based resistive switching memories is physically stored in a conductive filament. Therefore, the overall performance of the device is indissolubly related to the properties of such filament. In this Letter, we report for the first time on the three-dimensional (3D) observation of the shape of the conductive filament. The observation of the filament is done in a nanoscale conductive-bridging device, which is programmed under real operative conditions. To obtain the 3D-information we developed a dedicated tomography technique based on conductive atomic force microscopy. The shape and size of the conductive filament are obtained in three-dimensions with nanometric resolution. The observed filament presents a conical shape with the narrow part close to the inert-electrode. On the basis of this shape, we conclude that the dynamic filament-growth is limited by the cation transport. In addition, we demonstrate the role of the programming current, which clearly influences the physical-volume of the induced conductive filaments.

Undoped and in-situ B doped GeSn epitaxial growth on Ge by atmospheric pressure-chemical vapor deposition

In this letter, we propose an atmospheric pressure-chemical vapor deposition technique to grow metastable GeSn epitaxial layers on Ge. We report the growth of defect free fully strained undoped and in-situ B doped GeSn layers on Ge substrates with Sn contents up to 8%. Those metastable layers stay fully strained after 30 min anneal in N2 at 500 °C; Ge-Sn interdiffusion is seen at 500 °C but not at lower temperature. B is 100% active in the in-situ GeSn:B layers up to a concentration of 1.7 × 1019 cm−3. GeSn:B provides slightly lower Hall hole mobility values than in pure p-type Ge especially for low B concentrations.

Materials aspects, electrical performance, and scalability of Ni silicide towards sub-0.13 μm technologies

Ni-silicide phase formation with and without a Ti capping layer was studied by sheet resistance, x-ray diffraction and transmission electron microscopy. Ni monosilicide is found to be the stable phase in a temperature range from 400 to 600 °C. At lower temperatures the Ni2Si phase is found to be present. For temperatures higher than 700 °C NiSi is converted into NiSi2. Pyramidal NiSi2 precipitates were found to grow epitaxially along the Si〈111〉 planes for annealing temperatures as low as 310 °C. The epitaxial NiSi2 grains were found to disappear when the annealing temperature is increased. Stress buildup during Ni silicidation was measured in situ and could be correlated to the formation of the different Ni-silicide phases. The stress induced by Ni-monosilicide formation compares favorably to the stress induced by Co disilicide and Ti disilicide. The average silicon consumption required to obtain a certain sheet resistance was found to be 35% lower for Ni monosilicide compared for Co disilicide. It was f...

Ternary rare-earth metal oxide high-k layers on silicon oxide

Ternary oxides, GdScO3, DyScO3, and LaScO3, deposited by pulsed laser deposition using ceramics targets of stoichiometric composition, were studied as alternative high-k gate dielectrics on (100) Si. Their physical characterization was done using Rutherford backscattering, spectroscopic ellipsometry, x-ray diffraction, and transmission electron microscopy on blanket layers deposited on (100) Si, and electrical characterization on capacitors. It is found that DyScO3 and GdScO3 preserve their amorphous phases up to 1000°C. Other encouraging properties for high k applications were demonstrated, including k-value ∼22, almost no hysteresis or frequency dispersion in C–V curves, and leakage current reduction comparable to that of HfO2 of the same equivalent oxide thickness.

Island growth in the atomic layer deposition of zirconium oxide and aluminum oxide on hydrogen-terminated silicon: Growth mode modeling and transmission electron microscopy

Atomic layer deposition (ALD) is used in applications where inorganic material layers with uniform thickness down to the nanometer range are required. For such thicknesses, the growth mode, defining how the material is arranged on the surface during the growth, is of critical importance. In this work, the growth mode of the zirconium tetrachloride∕water and the trimethyl aluminum∕water ALD process on hydrogen-terminated silicon was investigated by combining information on the total amount of material deposited with information on the surface fraction of the material. The total amount of material deposited was measured by Rutherford backscattering, x-ray fluorescence, and inductively coupled plasma–optical emission spectroscopy, and the surface fractions by low-energy ion scattering. Growth mode modeling was made assuming two-dimensional growth or random deposition (RD), with a “shower model” of RD recently developed for ALD. Experimental surface fractions of the ALD-grown zirconium oxide and aluminum oxid...

Experimental determination of the maximum post-process annealing temperature for standard CMOS wafers

This paper reports on the experimental determination of the maximum post-process annealing temperature for standard 0.35 /spl mu/m CMOS wafers with aluminum based interconnections and tungsten plugs, without introducing significant modifications to their standard characteristics. The impact of increasing the post-processing temperature from 475/spl deg/C to 575/spl deg/C, for periods varying between 30 and 90 min, on both the front and back end is analyzed. 0.35 /spl mu/m CMOS technologies with different Al alloys, Al-1wt%Si-0.5wt%Cu (AlSiCu) or Al-0.5wt%Cu (AlCu), and different back end structures are considered. It is illustrated that the maximum annealing temperature is a function of the structure and composition of the interconnection layers and their maximum allowable resistance increase. It is also demonstrated that the transistor characteristics, the silicide quality and the leakage currents are as good as unaffected by annealing for 90 min at temperatures up to 525/spl deg/C.

In situ transmission electron microscopy study of Ni silicide phases formed on (001) Si active lines

The formation of Ni silicides is studied by transmission electron microscopy during in situ heating experiments of 12 nm Ni layers on blanket silicon, or in patterned structures covered with a thin chemical oxide. It is shown that the first phase formed is the NiSi2 which grows epitaxially in pyramidal crystals. The formation of NiSi occurs quite abruptly around 400 °C when a monosilicide layer covers the disilicide grains and the silicon in between. The NiSi phase remains stable up to 800 °C, at which temperature the layer finally fully transforms to NiSi2. The monosilicide grains show different epitaxial relationships with the Si substrate. Ni2Si is never observed.The formation of Ni silicides is studied by transmission electron microscopy during in situ heating experiments of 12 nm Ni layers on blanket silicon, or in patterned structures covered with a thin chemical oxide. It is shown that the first phase formed is the NiSi2 which grows epitaxially in pyramidal crystals. The formation of NiSi occurs quite abruptly around 400 °C when a monosilicide layer covers the disilicide grains and the silicon in between. The NiSi phase remains stable up to 800 °C, at which temperature the layer finally fully transforms to NiSi2. The monosilicide grains show different epitaxial relationships with the Si substrate. Ni2Si is never observed.

Two-step room temperature grain growth in electroplated copper

Electroplated copper exhibits some surprising changes at room temperature in sheet resistance, stress, and microstructure. This behavior, now known as self-annealing, is shown here to be intimately linked to the composition of the plating bath and the resulting incorporation of organic additives in the Cu layer. Their addition is a necessary condition for self-annealing to occur, but slows down the process for higher concentrations. The phenomenon also depends critically on film thickness, showing an accelerated transformation when film thickness increases. This dependence is explained in terms of a very rapid primary crystallization from the top surface down just after deposition, followed by a slower lateral recrystallization producing large secondary grains. The stress and sheet resistance during recrystallization are identified as two noncorrelated variables.