Plasma Pulse Time Research Articles

Growth, physical and electrical characterization of nickel oxide thin films prepared by plasma-enhanced atomic layer deposition using nickelocene and oxygen precursors

Nickel oxide (NiO) thin films are prepared by plasma-enhanced atomic layer deposition using nickelocene (NiCp2) and oxygen (O2) precursors. The effects of process parameters on the growth rate of NiO film are investigated, including deposition temperature, NiCp2 pulse time, and O2 plasma pulse time. In terms of deposition temperatures between 225 and 275 °C, a stable growth rate of ∼0.17 Å/cycle is obtained, meanwhile, the deposited films contain Ni(II)−O, Ni(III)−O, Ni(II)−OH, C−C bonds and metallic Ni atoms, and exhibit a smooth surface with root-mean-square roughness of ≤0.37 nm. As the deposition temperature increases from 150 to 350 °C, the deposited NiO film changes from an amorphous state to a NiO (200) orientation-dominated texture and further to NiO (111) and (200) orientations concomitant polycrystalline one; at the same time, the transmittance of the film shows a decline tendency, and the optical band gap decreases from 3.69 to 3.48 eV. Furthermore, it is found that the deposited NiO film behaves like a dielectric rather than a semiconductor, and for the NiO film deposited at 250 °C, a dielectric constant of 16.7 is demonstrated together with a film composition of 51.6% Ni, 40% O and 8.4% C.

In situ real-time and ex situ spectroscopic analysis of Al2O3 films prepared by plasma enhanced atomic layer deposition

In situ real-time ellipsometry (irtE) with a very high time resolution of 24 ms was applied to monitor the inductively coupled plasma enhanced atomic layer deposition (ALD) process of Al2O3 thin films to precisely resolve each step of the ALD process and its complete cycle. The influence of plasma power, plasma pulse duration, and deposition temperature on the film growth characteristics was investigated. Ex situ ellipsometry [UV-VIS-NIR-SE (ultraviolet-visible-nearinfrared-spectroscopic ellipsometry) and IR-SE (infrared spectroscopic ellipsometry)] and x-ray photoelectron spectroscopy revealed the bulk properties (thickness, refractive index, chemical composition, and carbon incorporation) of the films, which together with the in situ results are compared to those of the films prepared by thermal ALD (T-ALD). The ICPEALD (inductively coupled plasma enhanced ALD) films were deposited at substrate temperatures between 80 and 250 °C and the role of plasma power (50–300 W) and its pulse duration (1–20 s) was investigated at 250 °C. The reference T-ALD layers were prepared at 200 °C. The ICPEALD process of Al2O3 shows an increased growth rate, and the produced films exhibit higher carbon contaminations than the T-ALD Al2O3 films. Plasma pulse times of up to 15 s further increase the content of carbon and CH species; at the same time, the refractive index decreases. The optical properties of ICPEALD deposited Al2O3 films are comparable with those of the T-ALD films for low plasma power and short plasma pulse durations. For the ICPEALD films, UV absorption is found and it is dependent on the deposition parameters. irtE resolves process effects that correlate with the bulk properties of Al2O3, such as impurities and oxygen deficiencies.

Electrical Properties of Molybdenum Metal Deposited by Plasma Enhanced – Atomic Layer Deposition of Variation Condition

Molybdenum is a low-resistivity transition metal that can be applied to silicon devices using Si-metal electrode structures and thin film solar cell electrodes. We investigate the deposition of metal Mo thin film by plasma-enhanced atomic layer deposition (PE-ALD). Mo(CO)6 and H2 plasma are used as precursor. H2 plasma is induced between ALD cycles for reduction of Mo(CO)6 and Mo film is deposited on Si substrate at 300℃. Through variation of PE-ALD conditions such as precursor pulse time, plasma pulse time and plasma power, we find that these conditions result in low resistivity. The resistivity is affected by Mo pulse time. We can find the reason through analyzing XPS data according to Mo pulse time. The thickness uniformity is affected by plasma power. The lowest resistivity is 176 μΩ·cm at Mo(CO)6 pulse time 3s. The thickness uniformity of metal Mo thin film deposited by PE-ALD shows a value of less than 3% below the plasma power of 200 W.

The effect of NH3 plasma pulse time on atomic layer-deposited TiN films using tetrakis-(dimethylamino) titanium as a metal precursor

The growth of TiN films by plasma-enhanced atomic layer deposition is investigated using tetrakis-(dimethylamino) titanium and NH3. In particular, the influence of the NH3 plasma pulse time on the deposited film is discussed in detail. It is found that the film resistivity decreases monotonically to 4.6 × 10−4 Ω · cm by increasing the NH3 plasma pulse time to 25 s, then shows an increase. The former trend is ascribed to some competitive reactions dominated by N radicals and residual O2, i.e., more N radicals originating from longer NH3 plasma pulses produce more Ti–N bonds and restrain the formation of Ti–O and Ti–C bonds in the deposited film. The latter trend is attributed to the generation of additional Ti, N, and C active sites at the saturated bonding surface due to plasma ion bombardment; these can react with residual O2, producing more C–O and Ti–O bonds. Smooth, ultra-thin TiN films (<3 nm) are also successfully demonstrated.

Understanding the effect of nitrogen plasma exposure on plasma assisted atomic layer epitaxy of InN monitored by real time grazing incidence small angle x-ray scattering

The authors present an in situ study of the effect of nitrogen plasma pulse time on the temporal evolution of the surface morphology of InN growth on a-plane sapphire at 250 °C by plasma assisted atomic layer epitaxy (ALEp). The growth surface evolution was monitored in real-time using grazing incidence small angle x-ray scattering (GISAXS) measurements at an x-ray incidence angle of 0.8°. Nitrogen plasma pulse time (tp) was varied between 15 and 30 s in 5-s steps, and for all tp, the near specular scattering broadens and correlated peaks develop and evolve along the Yoneda Wing (YW). For tp ≥ 20 s, a YW with one correlated length scale evolves. At the end of the growth, the longest correlated length scale is 16.54 nm for tp = 25 s. Porod analysis of GISAXS intensity at high qy for tp = 25 s shows the formation of mounded shapes at the early stage of nucleation that transitioned to cylinders after about 3 unit cells of InN growth. Additionally, at tp = 25 s, the growth rate is highest with root mean square surface roughness and carbon impurity levels at or below atomic force microscopy and x-ray photoelectron spectroscopy sensitivity limits, respectively. At tp &amp;lt; 25 s, the growth surface may be undersaturated and at tp &amp;gt; 30 s, it appears that trimethylindium precursor molecules start to decompose, resulting in higher carbon content in the film. Thus, the nature of GISAXS correlated length scale directly correlates with the material quality. Additional ex situ characterizations reveal an electron mobility of 6–31 cm2/V s for a 3–5 nm thick InN film on a-plane sapphire, which is similar to the reported value of 30 cm2/V s for a 1300 nm thick InN film grown by molecular beam epitaxy directly on sapphire. Thus, the combination of in situ synchrotron x-ray analysis and ex situ characterization is a powerful approach to develop understanding of the growth mechanisms of ALEp of III-N materials in order to improve the quality by reducing impurities and broaden material applications.

Room-temperature plasma-enhanced atomic layer deposition of ZnO: Film growth dependence on the PEALD reactor configuration

Room-temperature plasma-enhanced atomic layer deposition (PEALD) of ZnO was studied by depositing the films using diethylzinc and O2 plasma from inductively-coupled plasma (ICP) and capacitively-coupled plasma (CCP) plasma source configurations. The CCP-PEALD was operated using both remote and direct plasma. It was observed that the films deposited by means of remote ICP and CCP were all highly oxygen rich, independently on plasma operation parameters, but impurity (H, C) contents could be reduced by increasing plasma pulse time and applied power. With the direct CCP-PEALD the film composition was closer to stoichiometric, and film crystallinity was enhanced. The ZnO film growth was observed to be similar on silicon, polycarbonate and poly(methyl methacrylate) substrates, but changes in polymer surface morphology indicate plasma-induced damage during the deposition due to exposure to ion bombardment when direct plasma was applied.

TaCx Thin Films Prepared by Atomic Layer Deposition as Diffusion Barriers for Cu Metallization

TaCx films were deposited by atomic layer deposition (ALD) using tris (neopentyl) tantalum dichloride, (Ta[CH2C(CH3)3]3Cl2) and H2 plasma as the precursor and reactant, respectively, at substrate temperatures ranging from 200°C to 400°C. The ALD–TaCx films with the formation of nanocrystalline structures and a rock‐salt phase were confirmed by X‐ray and electron diffraction. The ALD temperature window was found to be 225°C–300°C with a growth rate of ~0.11 nm per cycle. The resistivity of the ALD–TaCx films was dependent on the microstructural features, such as the grain size and crystallinity, as well as their composition (C/Ta ratio), and the presence of impurities in the films, which could be controlled by varying the deposition parameters, such as the deposition temperature and reactant pulse conditions. With increasing deposition temperature and reactant pulse time, Ta‐rich films with a low Cl impurity concentration and larger grain size were obtained. The film with a resistivity less than 400 μΩ cm was obtained at 300°C, which was within the ALD temperature window, by optimizing the H2 plasma pulse time. The step coverage of the film deposited at 300°C was approximately 100% over the trench structure (top opening width of 25 nm) with an aspect ratio of ~4.5. The performance of the ALD–TaCx films deposited under the optimized conditions was evaluated as a diffusion barrier for the Cu interconnects. The structure of Cu (100 nm)/ALD–TaCx (5 nm)/ Si was stable without the formation of copper silicide after annealing at 600°C for 30 min.

Studies on Formation of Carborane Film Prepared by Using a Deuterium Glow Discharge Method

Carborane powders (C2B10H12) were deposited on silicon substrates and the physical properties of the films were investigated as functions of the distance of the sample from the electrode, the carborane mass, and the plasma-pulse. To obtain the optimum thickness of the films, three silicon substrates were positioned at 6.5, 16.5, and 36.5 cm from the electrode, and the thickness of the samples was analyzed by using XRD, TEM, and SEM. For the deposition, the carborane powder was warmed to 80 degrees C in 10 minutes and was applied a DC-power pulse of 900 W (150 volts, 6 amps) for 2 hours. The mass of carborane and the on-time sequence were varied during the deposition. The combined results of XRD and TEM studies revealed that the structure of the deposited film is an amorphous phase. A careful analysis of the SEM images show that the thickness of the carborane films increased as increasing the mass of the flown carborane while it remained constant when a plasma-pulse time was varied. The thickest film of 353 A was achieved from the samples placed closest to the carborane inlet and the thickness became thinner as farther from the source suggesting that the density of the evaporated carborane powder in a chamber decreased as increasing the distance of the sample from the carborane inlet.

Electrical Properties of Ta(Si)N Films Prepared by Atomic Layer Deposition from Tert-Butylimido-Tris-Diethylamido Tantalum, Silane and Hydrogen Plasma

Ta(Si)N films were prepared by atomic layer deposition (ALD) from tert-butylimido-tris-diethylamido tantalum (TBTDET), triethylsilane, and activated hydrogen. Triethylsilane was used as an ancillary reducing agent and as a silicon precursor. The effects of the addition of the triethylsilane at different hydrogen plasma pulse times and power on the electrical properties, particularly stability in air, were investigated. Longer plasma pulse times with high power were effective in decreasing resistivity and increasing stability in air. However, introduction of silane resulted in an increase in resistivity of the films regardless of the hydrogen plasma conditions.

A user configurable data acquisition and signal processing system for high-rate, high channel count applications

Real-time signal processing in plasma fusion experiments is required for control and for data reduction as plasma pulse times grow longer. The development time and cost for these high-rate, multichannel signal processing systems can be significant. This paper proposes a new digital signal processing (DSP) platform for the data acquisition system that will allow users to easily customize real-time signal processing systems to meet their individual requirements.The D-TACQ reconfigurable user in-line DSP (DRUID) system carries out the signal processing tasks in hardware co-processors (CPs) implemented in an FPGA, with an embedded microprocessor (μP) for control. In the fully developed platform, users will be able to choose co-processors from a library and configure programmable parameters through the μP to meet their requirements.The DRUID system is implemented on a Spartan 6 FPGA, on the new rear transition module (RTM-T), a field upgrade to existing D-TACQ digitizers.As proof of concept, a multiply-accumulate (MAC) co-processor has been developed, which can be configured as a digital chopper-integrator for long pulse magnetic fusion devices. The DRUID platform allows users to set options for the integrator, such as the number of masking samples. Results from the digital integrator are presented for a data acquisition system with 96 channels simultaneously acquiring data at 500kSamples/s per channel.

Density and temperature measurements of pulsed plasma produced inside a curved vacuum chamber

Recent experimental evidence suggests the importance of fast radial plasma transport in the scrape-off-layer (SOL) of tokamaks. The outward transport appears to be convective rather than diffusive, extends into the far SOL, and can produce significant recycling from the main-chamber walls, partially by passing the divertor. A plausible theoretical mechanism to explain this phenomenon is the radial transport of locally dense plasma created by turbulent processes. In our experiment a blob of plasma is produced using a plasma-gun and injected radially to the curved vacuum chamber. In this paper we report the measurement of electron density and temperature of the plasma blob produced by the plasma-gun inside the curved vacuum chamber using cylindrical Langmuir probes. The probes are moved both radially and transversely to flow direction. The electron density and temperature are measured ~ 1016 m-3 and 10-1 eV respectively for radial flow at constant discharging potential, base pressure as well as plasma pulse time.

Plasma-Assisted Atomic Layer Deposition of Conductive Hafnium Nitride Using Tetrakis(ethylmethylamino)hafnium for CMOS Gate Electrode Applications

Conductive hafnium nitride films were deposited from a plasma-assisted atomic layer deposition (PA-ALD) process using a metallorganic hafnium precursor, tetrakis(ethylmethylamino)hafnium (TEMAH), using plasma as a reducing agent, at a substrate temperature of . The effects of radio frequency plasma pulse time and power on film resistivity, composition, and microstructure were investigated. The deposited films consisted of cubic phase as shown by X-ray diffraction analysis, and the resistivity ranged from to depending on the plasma conditions. The most conductive films were observed to result from conditions of higher plasma power, which is attributed to microstructural modifications as well as a decrease in ratio, which approached unity at the highest plasma powers employed. Carbon incorporation in the form of phase was shown to be beneficial in terms of improving both post-rapid-thermal-anneal stability and electrical conductivity. A midgap work function was obtained for a electrode structure integrated into a metal-oxide-semiconductor capacitor featuring a dielectric.

Preparation of TaN Thin Film by H2 Plasma Assisted Atomic Layer Deposition Using Tert-Butylimino-Tris-Ethylmethylamino Tantalum

The plasma assisted atomic layer deposition (ALD) of tantalum nitride (TaN) thin films were conducted using tert-butylimino-tris-ethylmethylamino tantalum (TBTEMAT) and hydrogen plasma at 250 degrees C. The effects of H2-plasma pulse time and RF power on the film properties, such as resistivity, surface roughness, step coverage and stability in air, were examined. The film growth rate (thickness/cycle) was in the range of 0.05-0.08 nm/cycle and the resistivity of the films varied from 490 to 70,000 microomega cm, depending on the plasma conditions. Longer plasma pulse times and increasing RF power yielded films of lower resistivity along with improving the stability. The films were smooth and the conformality of the films deposited in 0.28 microm holes with an aspect ratio of 7:1 was 100%.

Highly Conductive HfN[sub x] Films Prepared by Plasma-Assisted Atomic Layer Deposition

Highly conductive and conformal hafnium nitride (HfN x ) thin films were prepared by plasma-assisted atomic layer deposition using tetrakis(dimethylamido)hafnium and hydrogen plasma. The effects of deposition temperature, plasma pulse time, radio frequency power, and the N 2 /H 2 ratio on the electrical characteristics of the films were investigated. The growth rate (thickness/ cycle) was in the range of 0.85- 1.45 nm/cycle, and the resistivity of the films varied from 4.0 to 1500 X 10 3 μΩ cm, depending on the deposition conditions. Higher deposition temperature combined with higher power and longer exposure time of the hydrogen plasma was effective in decreasing the film resistivity.

Stability of Plasma Posttreated TiN Films Prepared by Alternating Cyclic Pulses of Tetrakis-Dimethylamido-Titanium and Ammonia

The effect of plasma posttreatment on the resistivity and stability of tetrakis-dimethylamido-titanium (TDMAT)-based atomic layer deposition TiN films was investigated. Posttreatment with hydrogen plasma was effective for lowering the resistivity of the TiN films and also for improving their stability in air. Longer plasma pulse times with high power yielded films of lower resistivity aand increased stability in air. However, there was no noticeable improvement of the film's stability with nitrogen plasma gas.

Preparation of TiN films by plasma assisted atomic layer deposition for copper metallization

This paper describes the effect of plasma pulse time, power, and composition on the electrical properties of TiN prepared by plasma assisted atomic layer deposition. Longer plasma pulse times yielded films of lower resistivity with enhanced stability in air, but resistivity was observed to exponentially decrease to a certain saturated value. Film resistivity also decreased with increasing RF power along with improving the stability. At a fixed power and exposure time, resistivity of the films decreases with increasing hydrogen percentage until up to 40%, and then remained at that value at higher hydrogen percentages. However, the stability was better with samples prepared with low hydrogen percentage.

Characteristics of Tungsten Carbide Films Prepared by Plasma-Assisted ALD Using Bis(tert-butylimido)bis(dimethylamido)tungsten

Tungsten carbide thin films were prepared by plasma-assisted atomic layer deposition (ALD) using bis(tert-butylimido)bis(dimethylamido)tungsten at 250°C. The effects of plasma pulse time, radio frequency power, and the ratio on the film properties, such as resistivity, surface roughness, step coverage, and stability in air, were examined. The film growth rate (thickness/cycle) was in the range 0.04-0.07 nm/cycle and the resistivity of the films varied from 295 to 22,000 μΩ cm, depending on the plasma conditions. The films were smooth and the conformality of the films deposited in 0.15 μm holes with an aspect ratio of 15:1 was 100%. © 2003 The Electrochemical Society. All rights reserved.

Perinatal exposure to cannabinoids alters neurochemical development in rat brain

Room-temperature plasma-enhanced atomic layer deposition (PEALD) of ZnO was studied by depositing the films using diethylzinc and O2 plasma from inductively-coupled plasma (ICP) and capacitively-coupled plasma (CCP) plasma source configurations. The CCP-PEALD was operated using both remote and direct plasma. It was observed that the films deposited by means of remote ICP and CCP were all highly oxygen rich, independently on plasma operation parameters, but impurity (H, C) contents could be reduced by increasing plasma pulse time and applied power. With the direct CCP-PEALD the film composition was closer to stoichiometric, and film crystallinity was enhanced. The ZnO film growth was observed to be similar on silicon, polycarbonate and poly(methyl methacrylate) substrates, but changes in polymer surface morphology indicate plasma-induced damage during the deposition due to exposure to ion bombardment when direct plasma was applied.