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This study introduces the direct electrodeposition of Cu on Ru-Al2O3 layers, which is a promising material to replace Cu seed, and Ta diffusion barrier layers at once. Ru-Al2O3 layers are deposited by atomic layer deposition (ALD), and their compositions are manipulated by varying the cycle numbers of Ru and Al2O3 ALD. The addition of Al2O3 induces the development of nanocrystalline Ru, instead of columnar structure, enhancing the characteristics as a diffusion barrier without losing a role of the seed layer for Cu electrodeposition. The native oxide of Ru is electrochemically eliminated by the coulometric reduction method (CRM) prior to Cu electrodeposition. The influences of both applied potential and the composition of Ru-Al2O3 layer on Cu film properties are clarified. Furthermore, the ability of Ru-Al2O3 layer to inhibit Cu diffusion is assessed, and it is confirmed that Ru-Al2O3 layer perfectly inhibits Cu diffusion during the annealing carried out at the temperature of 550°C for 30 min with the layer thickness of 7.5 nm. [ABSTRACT FROM AUTHOR]

Ruthenium (Ru) thin films were grown on thermally-grown SiO2 substrates by thermal atomic layer deposition (ALD) using a .sequential supply of a zero metal valence precursor, isopropyl-methylbenzene-cyclohexadienc Ru(O) (IMBCHRu, C16,H22Ru) and molecular oxygen (O2) at substrate temperatures ranging from 185 to 310 °C. The growth rate at 185 C was approximately 0.059 nm/cycle but its resistivity was >3000 μΩ cm. When the deposition was done at 200° C, the resistivity was decreased drastically to ~100 μΩ cm, and the film growth rate increased to 0.075 nm/cycle. An ALD temperature window from 225 to 270 °C was observed. A high growth rate of 0.086-0.089 nm/cycle was obtained at this ALD temperature window. The film deposited at 270°C showed a minimum resistivity of ~30 μΩ cm and a high density of 11.7 g/cm3 and with no impurities in the film, such as oxygen and carbon. At 310°C, the growth rate increased to 0.136 nm/cycle due to a partial decomposition of the precursor. In addition, the film resistivity increased slightly to ~40 μΩ cm with the incorporation of carbon and the formation of a less-dense film. The step coverage of the ALD-Ru film was dependent on the dimensions of the contact and deposition temperature. At the contact with an aspect ratio of ~4.6 (top opening diameter: 80 nm), the step coverage was excellent irrespective of the deposition temperature. However, at the contact with an aspect ratio of ~25. the step coverage of the film deposited at 310° C (or above ALD temperature window) was degraded, even though those prepared within ALD temperature window were ~100%. Finally, ALD-Ru film was used successfully as a seed layer for Cu electroplating. [ABSTRACT FROM AUTHOR]

The effect of the Al distribution on the electrical properties of Al-doped ZnO (AZO) films deposited by atomic layer deposition (ALD) is investigated. In order to control the Al distribution, the pulsing time of trimethylaluminum (TMA) is varied from 2 (within an ALD window) to 0.1 s. As a result, the areal density of Al atoms incorporated in a single dopant layer decreases from 3.3 × 1014 to 1.2 × 1014 cm-2. Hall measurements reveal that the minimum resistivity of the ALD-AZO films is decreased from 3.2 × 10-3 to 1.7 × 10-3 Ωcm as a result of reducing the TMA pulsing time from 2 to 0.1 s. This decrease is due to the obvious increase of the carrier concentration from 1.4 × 1020 to 4.7 × 1020 cm-3. It is suggested that both the improved doping efficiency (from 13 to 58%) and the insertion of more dopant layers within the ZnO matrix are responsible for the increase of the carrier concentration. [ABSTRACT FROM AUTHOR]

Ruthenium (Ru) thin films were successfully grown on the TiN substrate using plasma enhanced atomic layer deposition (PEALD) by using a zero metal valence precursor, IMBCHRu [(6-1-Isopropyl-4-MethylBenzene)(4-CycloHexa-1,3-diene) Ruthenium(0)] and direct plasma of ammonia (NH3) as a reactant at the substrate temperature ranging from 140 and 400°C. The wide atomic layer deposition (ALD) temperature window from 225 to 400°C was shown and a high growth rate of 0.094 nm/cycle at the ALD temperature window was obtained, which is twice that of PEALD Ru results deposited by Cp (Cyclopentaldienyl)-based Ru precursors previously reported. No incubation cycle for the growth on the TiN underlayer was observed, indicating the fast nucleation of Ru. The PEALD-Ru films formed polycrystalline and columnar grain structures with a hexagonal-close-packed phase that was confirmed by X-ray diffractometry and transmission electron microscopy analysis. Its resistivity was dependent on the microstructural features characterized by grain size and crystallinity as well as its density, which could be controlled by varying the deposition parameters such as deposition temperature and reactant pulsing condition. Resistivity of ~12 μ cm was obtained at the deposition temperature as low as 225°C by optimizing (NH3) plasma power and pulsing time [ABSTRACT FROM AUTHOR]

AlGaN/GaN high electron mobility transistors (HEMTs) grown on 4 in. silicon substrates were demonstrated using different treatments at the Schottky gate terminal, namely (i) a regular Schottky contact made of Pd/Ti/Au (HEMT), (ii) an Al-based metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) using 3 nm Al/Pd/Ti/Au, and (iii) a plasma oxidized 3 nm Al/Pd/Ti/Au (plasma treated MOS-HEMT). A high drain current density (Idsmax) of 1086 mA/mm and a transconductance (gmmax) of 209 mS/mm were obtained for Al-based MOS-HEMTs. In the process of plasma oxidized Al, the aluminum-based oxide formed was identified as Al2O3 by X-ray photoelectron spectrum measurements. For HEMTs with regular Schottky contact, a gate bias beyond +1.5 V leads to excess gate leakage limiting the gate bias application. However, for the MOS-HEMTs, a gate bias as high as +3.5 V could be applied without any gate leakage. Further, a low two-terminal gate leakage was observed for our MOS-HEMTs. A two dimensional electron gas channel at an increased depth was observed for the MOS-HEMTs because of an insulating oxide layer at the Schottky contact. The out-diffusion of oxide states at the AlGaN barrier layer into thin Al facilitates the formation of Al2O3 as a gate dielectric for AlGaN/GaN HEMTs. [ABSTRACT FROM AUTHOR]

Tungsten (W) thin films were deposited using the modified chemical vapor deposition (CVD), the so-called pulsed CVD, and their properties were characterized as nucleation layers for the chemical vapor deposited W (CVD-W) technology of sub-50 nm memory devices. W growth per cycle was extremely linear with a higher growth rate of ∼0.58 nm/cycle as compared to that (∼0.28 nm/cycle) of the atomic layer deposition (ALD) process using the same chemistry. From the X-ray diffractometry, the pulsed CVD-W film was formed as an amorphous structure, which was the same as the atomic layer deposited W. This led to the formation of a low resistivity bulk CVD-W film deposited on it with the grain size of ∼180 nm at 200 nm thick film, and its resistivity was further decreased with the B2H6 post-treatment before the deposition of bulk CVD-W film (∼13 μΩ cm at a 50 nm thick film). However, we found that the adhesion performances of CVD-W growing on the B2H6-based pulsed CVD-W nucleation layer were significantly degraded as both the deposition temperature of the nucleation layer and the B2H6 post- treatment time increased. High resolution transmission electron microscopy and energy-dispersive spectroscopy analysis clearly demonstrated that a discontinuous boron layer was formed at the bulk CVD-W/nucleation layer interface, which was dominantly due to the B2H6 decomposition during the B2H6 post-treatment. We strongly suggest that a boron-containing discontinuous layer degrades the adhesion properties of CVD-W films growing on it. Considering the thermodynamics of the B2H6 decomposition, we can improve the adhesion properties by increasing the H2 flow rate at the post-treatment step. [ABSTRACT FROM AUTHOR]

Diffusion barrier performances of atomic layer deposited (ALD)-Ru thin films between Cu and Si were improved with the use of an underlying 2 nm thick ALD-TaCN interlayer as diffusion barrier for the direct plating of Cu. Ru was deposited by a sequential supply of bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp)2] and NH3 plasma and TaCN by a sequential supply of (NEt2)3Ta = Nbut (tert-butylimido-trisdiethylarnido-tantalum), and H2 plasma. Sheet resistance measurements, X-ray diffractometry, and Auger electron spectroscopy analysis showed that the bilayer diffusion barriers of ALD-Ru (12 nm)/ALD-TaCN (2 nm) and ALD-Ru (4 nm)/ALD-TaCN (2 nm) prevented the Cu diffusion up to annealing temperatures of 600 and 550°C for 30 mm, respectively. This is because of the excellent diffusion barrier performance of the ALD-TaCN film against the Cu, due to its amorphous structure. A 5 nm thick ALD-TaCN film was even stable up to annealing at 650°C between Cu and Si. Transmission electron microscopy investigation, combined with energy-dispersive spectroscopy analysis, revealed that the ALD-Ru/ALD-TaCN diffusion barrier failed by the Cu diffusion through the bilayer into the Si substrate. This is due to the ALD-TaCN interlayer preventing the interfacial reaction between the Ru and Si. [ABSTRACT FROM AUTHOR]

We report on the deposition properties of W nucleation layers prepared using a sequential supply of B2H6 and WF6 and their effects on the growth of the subsequent chemical vapor deposited (CVD)-W. The structural properties of the W nucleation layers such as their phase, crystallinity, and grain size depended on the deposition temperature, B2H6 flow rate, and B2H6 pulsing time. The formation of an amorphous and two forms of crystalline W film [primitive cubic β-phase and body-centered-cubic (bcc) α-one] was observed, depending on the deposition temperature. X-ray diffractometry and transmission electron microscopy diffraction analysis showed that the amorphous W was dominantly deposited at temperatures of up to 350°C and that when the deposition temperature was increased to 395°C, the film formed the β-phase. At a deposition temperature of 425°C, the phase of the film started to be transformed into a-phase and was completely transformed to single phase a-W with a very large grain size of approximately 120-180 nm at 450°C. We were also able to deposit the a-phase W film at 395°C with a lower B2H6 flow rate, but its grain size was only approximately 20-30 nm. The W nucleation layers had a significant effect on the final grain size and resistivity of the CVD-W films deposited on them. The minimum resistivity of the 50 nm thick CVD-W film with the optimized B2H6-based nucleation layer was ~ 10 μΩ cm, while the conventional CVD-W film with a SiH4-based nucleation layer showed a resistivity of 25 μΩ cm at the same thickness. [ABSTRACT FROM AUTHOR]

Tungsten nitride (WNx) thin films were grown by atomic layer deposition (ALD) within the temperature range of 200–350°C from diborane (B2H6), tungsten hexafluoride (WF6), and ammonia (NH3) for application to a contact barrier layer in dynamic random access memory (DRAM). Herein, B2H6 was used as an additional reducing agent to produce a low-resistivity ALD-WNx film, and its resistivity was in the range of 300–410 μΩ cm, depending on the deposition conditions for the ~10 nm thick film. An increase in the growth rate was observed with increasing deposition temperature, but an almost constant growth rate of ~0.28 nm/cycle was obtained in the temperature range from 275 to 300°C. The properties of the as-deposited film, including the resistivity, W/N ratio, density, B and F impurity content, and phase, were affected by the deposition temperature and B2H6 flow rate during the process. As the deposition temperature and B2H6 flow rate increased, the WIN ratio and film density increased and the impurity content decreased, leading to a reduction in the resistivity of the film. An increased W/N ratio was found to be favorable to the formation of a face-centered-cubic β-W2N phase. Excellent step coverage was obtained even on a 0.14 μm diameter contact hole with an aspect ratio of 16:1. The ALD-WNx film in this study was thermally stable to annealing at 800°C for 30 min, but after annealing at 900°C, it converted to body-centered-cubic α-W with the accompanying release of N. The ALD-WNx film was evaluated as a barrier layer for W-plug deposition for 70 nm design-rule DRAM. The results showed that the integration scheme with ALD-WNx showed lower contact resistance than metallorganic chemical vapor deposition TiN or TiCl4-based chemical vapor deposited TiN. [ABSTRACT FROM AUTHOR]

Data reduction and calibration procedures are introduced for a novel rotating-analyser-type spectral imaging ellipsometer. Using a monaxial power spectrograph, we developed a unique spectral imaging ellipsometer. It combines one-dimensional imaging ellipsometry with spectroscopic ellipsometry, and enables real-time measurement of the optical parameters and dimensional structures of patterned or multilayered thin film. It also has more calibration factors than conventional ellipsometers. We therefore present a method using Jones matrices for describing the polarization sensitivity of the spectrograph and random noise of the CCD array. For a patterned SiO2 layer on a silicon wafer, we used the spectral imaging ellipsometer to obtain a one-dimensional thickness profile. [ABSTRACT FROM AUTHOR]

As a new class of thermally activated actuators based on polymeric fibers, we investigated polyethylene terephthalate (PET) yarns for the development of a twisted-coiled polymer fiber actuator (TCA). The PET yarn TCA exhibited the maximum linear actuation up to 8.9% by external heating at above the glass transition temperature, 160 °C–180 °C. The payload of the actuator was successfully correlated with the preload and training-load conditions by an empirical equation. Furthermore, the PET-based TCA was electrically driven by Joule heating after the PET surface was metallization with silver. For the fast and precise control of PET yarn TCA, electroless silver plating was conducted to form electrical conductive layers on the PET fiber surface. The silver plated PET-based TCA was tested by Joule heating and the tensile actuation was increased up to 12.1% (6 V) due to the enhanced surface hardness and slippage of PET fibers. Overall, silver plating of the polymeric yarn provided a fast actuation speed and enhanced actuation performance of the TCA actuator by Joule heating, providing a great potential for being used in artificial muscle for biomimetic machines including robots, industrial actuators and powered exoskeletons. [ABSTRACT FROM AUTHOR]