NH3 Plasma Pretreatment Research Articles

Investigation of atomic layer deposition methods of Al2O3 on n-GaN

In this work, three atomic layer deposition (ALD) approaches are used to deposit an Al2O3 gate insulator on n-GaN for application in vertical GaN power switches: thermal ALD (ThALD), plasma-enhanced ALD (PEALD), and their stacked combination. The latter is a novel method to yield the most ideal insulating layer. Also, the influence of an in situ NH3 or H2 plasma pre-treatment is studied. Planar MIS capacitors are used to investigate the electrical properties and robustness of the gate insulators. In vacuo x-ray photoelectron spectroscopy (XPS) is used to study the changes in chemical composition after every surface treatment. XPS shows that all plasma pre-treatments efficiently remove all carbon contamination from the surface, but only NH3 plasma is observed to additionally remove the native oxide from the n-GaN surface. The water precursor step in the ThALD process does not completely remove the CH3 ligands of the trimethylaluminum precursor step, which might electrically be associated with a reduced forward bias robustness. The O2 plasma step in the PEALD process is associated with the removal of carbon and a tremendous increase of the O content in the GaN surface region. Electrically, this strongly correlates to an enhanced forward bias robustness and an increased forward bias hysteresis, respectively. The ThALD/PEALD stack method mitigates the shortcomings of both ALD processes while maintaining its advantages. Electrical measurements indicate that the stack method alongside NH3 plasma pretreatment provides the best characteristics in terms of hysteresis, threshold voltage, forward bias robustness, and interface trap density of states.

Scalable and highly tunable conductive oxide interfaces

Conducting oxide interfaces have attracted considerable attention, motivated by both fundamental science and potential for oxide electronic devices. An important gap for maturing such device technology is scalability and routes to control the electronic properties, which can narrow the device engineering space. Here, we demonstrate and explain the mechanisms of highly tunable conductive oxide interfaces. We synthesized amorphous–crystalline Al2O3/SrTiO3 interfaces using the scalable and industry-compatible atomic layer deposition (ALD) technique. An NH3 plasma pretreatment is employed in the ALD chamber, and its duration is used as a tuning parameter for the electrical properties, where a span of three orders of magnitude in the sheet resistance is observed at room temperature. For the most conductive sample, our results are comparable to the highest carrier density values reported for all-crystalline oxide interfaces prepared with state-of-the-art epitaxial growth techniques, such as pulsed laser deposition. We pinpoint the origin of conductivity to oxygen vacancies caused by the SrTiO3 reduction by the NH3 plasma pretreatment. These results present a simple, scalable, and industry-compatible route for realizing conductive oxide interfaces, with a broad parameter space, offering a versatile and flexible toolkit for oxide device engineering.

Bottom-up plasma-enhanced atomic layer deposition of SiO2 by utilizing growth inhibition using NH3 plasma pre-treatment for seamless gap-fill process

The design-rule shrinkage in semiconductor devices is a challenge at every step of the integration process. In the gap-fill process for isolation, the seam and void formation cannot be suppressed by using a deposition process, which even has excellent step coverage. To achieve seamless gap fill in the high-aspect-ratio structure, which has a non-ideal etch profile such as a negative slope, the deposition process should be able to realize the “bottom-up growth” behavior. In this work, the bottom-up growth of a SiO2 plasma-enhanced atomic layer deposition (PE-ALD) process in a trench structure was investigated by using a growth inhibition process employing plasma treatment. N2 and NH3 plasma pre-treatments were employed to suppress the growth of the SiO2 PE-ALD process without any contamination, and the inhibition mechanism was investigated by performing surface chemistry analyses using X-ray photoelectron spectroscopy. Furthermore, the gap-fill characteristics of the SiO2 PE-ALD process were examined, depending on the process conditions of NH3 plasma pre-treatment, by performing cross-sectional field emission scanning electron microscopy measurements. Finally, a seamless gap-fill process in a high-aspect-ratio trench pattern was achieved by the bottom-up growth behavior of SiO2 PE-ALD using NH3 plasma pre-treatment.

Plasma Treatment As an Effective Way of Modifying Carbon-Based Electrocatalysts for an Enhanced Oxygen Reduction Reaction

Oxygen reduction reaction (ORR) is pivotal in renewable energy technologies such as in fuel cells and metal-air batteries. Precious metal-free electrochemical ORR is a critical component in designing cost-effective electrochemical energy conversion devices. In this report we demonstrate an efficient surface modification of carbon nanotubes (CNT) through one-step oxygen plasma irradiation that induces doping and charge redistribution around the doped heteroatom oxygen that promotes ORR activity. The defect sites generated owing to oxygen dopant in CNTs were confirmed by Raman spectra, X-ray photoelectron spectroscopy (XPS) surface composition and CHNO elemental analysis. The O-doped CNTs were thoroughly characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) measurements. Our research shows that plasma-treated single-walled carbon nanotubes (SWCNT) are more effective ORR catalyst compared to multi-walled carbon nanotubes (MWCNT) due to the inherent structure of SWCNT that can access more defects and surface functional groups than MWCNT.In the following study, plasma modification approach was implemented in the synthesis of a highly active robust Metal-Nitrogen-Carbon (M-N-C) catalysts through NH3-plasma pretreatment on high surface area black pearl carbon. Pre-treated FeNC/NH3-C contains Fe3C and Fe-Nx as catalytically active sites. XPS confirms the presence of a high surface concentration of pyrrolic to pyridinic nitrogen and ferrous sites on FeNC/NH3-C that promotes low oxygen reduction overpotential (0.80 V vs RHE in 0.5 M H2SO4 and 0.96 V vs RHE in 0.1 M KOH). Hence plasma activates the surface and incorporates nitrogen which forms stable Fe-N coordination for accelerating oxygen reduction. Importantly, FeNC/NH3-C shows lower peroxide yield at 0.6V/RHE (<20% in 0.5 M H2SO4 and <2 % in 0.1 M KOH) that can reduce the detrimental effect of H2O2 on the catalysts support and exhibits high stability, seen from thousands of potential cycling stability tests of FeNC/NH3-C in acid solutions. Thereby this plasma-based new synthetic approach can promote more active and stable non-precious metal catalysts.

34.5: Four‐mask process Architecture using NH3 plasma treatment technology for Image Sticking Improvement in 32‐inch TV Product

A new method to improve the interface of A‐Si and SiNx in A‐Si TFT process, the influence of H content in PECVD system equipment and the A‐Si remain to image sticking are studied in the paper. The suitable NH3 plasma pretreatment power and time or A‐Si remain can decease the leakage current and to overcome the image sticking in four‐mask process

Band alignment regulation of HfO2/SiC heterojunctions induced by PEALD with in situ NH3-plasma passivation

The efficient passivation of in situ NH3-plasma pre-treatment and its regulation of the band alignment between HfO2 and 4H-SiC have been investigated by XPS. With in situ NH3-plasma passivation by PEALD, a VBO of 0.72 eV and a CBO of 1.54 eV can be obtained across the HfO2/4H-SiC interface. The Si-O bonds components reduction in the passivated interface layers will lead to band bending or band shift at the interface and regulate the band alignments between HfO2 and 4H-SiC. The physical mechanism investigation of band alignments can be a cornerstone for the application of HfO2/4H-SiC heterojunctions in the high-power devices.

Impact of surface pre-treatment on Pt-nanodot formation induced by remote H2-plasma exposure

We evaluated the influence of the surface modification of ultrathin Pt films with remote plasma treatment using pure N2 or pure NH3 on the formation of Pt nanodots (NDs), which was induced by exposing Pt films on ultrathin SiO2 layers to remote H2 plasma. Well-defined Pt NDs were formed from pre-treated Pt films and, at a remote H2 plasma exposure time of 5 min, areal dot density was increased by factors of ∼2.3 for the remote NH3 plasma pre-treatment (5 min) and ∼3.5 for the N2 plasma pre-treatment (3 min), while the areal density of Pt NDs formed by remote H2 plasma for 5 min without the pre-treatment was 1.5 × 1011 cm−2. The results can be interpreted in terms of the surface migration length of Pt atoms being effectively reduced due to the chemisorption of N atoms on the Pt film surface. In addition, we also demonstrated the formation of high-density Pt NDs with an areal density as high as ∼9.0 × 1011 cm−2 by exposing the Pt film pre-treated with SiH4 to the remote H2 plasma.

Remote plasma-enhanced atomic layer deposition of gallium oxide thin films with NH3 plasma pretreatment

High quality gallium oxide (Ga2O3) thin films are deposited by remote plasma-enhanced atomic layer deposition (RPEALD) with trimethylgallium (TMG) and oxygen plasma as precursors. By introducing in-situ NH3 plasma pretreatment on the substrates, the deposition rate of Ga2O3 films on Si and GaN are remarkably enhanced, reached to 0.53 and 0.46 Å/cycle at 250 °C, respectively. The increasing of deposition rate is attributed to more hydroxyls (–OH) generated on the substrate surfaces after NH3 pretreatment, which has no effect on the stoichiometry and surface morphology of the oxide films, but only modifies the surface states of substrates by enhancing reactive site density. Ga2O3 film deposited on GaN wafer is crystallized at 250 °C, with an epitaxial interface between Ga2O3 and GaN clearly observed. This is potentially very important for reducing the interface state density through high quality passivation.

In vitro study of sirolimus release from nonwoven PLLA matrices

Abstract Sirolimus incorporated nonwoven polymer matrices were fabricated via electrospinning. Release kinetics considering different fiber diameters and layer thicknesses were investigated. In vitro drug release profiles were evaluated by measuring the drug concentration in an established drug release medium (0.9% saline solution with additives, not buffered) at predetermined time points. Furthermore, an NH3-plasma pretreatment was examined to ensure complete wetting from the beginning of the study. In comparison to thin drug-loaded PLLA spray coatings it was shown that the release of sirolimus is diffusion- and degradation-controlled regardless of the surface-to-volume ratio, though fiber diameters or a hydrophilization can affect its release kinetics.

Atomic layer deposition of 1D and 2D nickel nanostructures on graphite

One-dimensional (1D) nanowires (NWs) and two-dimensional (2D) thin films of Ni were deposited on highly ordered pyrolytic graphite (HOPG) by atomic layer deposition (ALD), using NH3 as a counter reactant. Thermal ALD using NH3 gas forms 1D NWs along step edges, while NH3 plasma enables the deposition of a continuous 2D film over the whole surface. The lateral and vertical growth rates of the Ni NWs are numerically modeled as a function of the number of ALD cycles. Pretreatment with NH3 gas promotes selectivity in deposition by the reduction of oxygenated functionalities on the HOPG surface. On the other hand, NH3 plasma pretreatment generates surface nitrogen species, and results in a morphological change in the basal plane of graphite, leading to active nucleation across the surface during ALD. The effects of surface nitrogen species on the nucleation of ALD Ni were theoretically studied by density functional theory calculations. Our results suggest that the properties of Ni NWs, such as their density and width, and the formation of Ni thin films on carbon surfaces can be controlled by appropriate use of NH3.

Nitride passivation of the interface between high-k dielectrics and SiGe

In-situ direct ammonia (NH3) plasma nitridation has been used to passivate the Al2O3/SiGe interfaces with Si nitride and oxynitride. X-ray photoelectron spectroscopy of the buried Al2O3/SiGe interface shows that NH3 plasma pre-treatment should be performed at high temperatures (300 °C) to fully prevent Ge nitride and oxynitride formation at the interface and Ge out-diffusion into the oxide. C-V and I-V spectroscopy results show a lower density of interface traps and smaller gate leakage for samples with plasma nitridation at 300 °C.

HfO2/GeOxNy/Ge gate stacks with sub-nanometer capacitance equivalent thickness and low interface trap density by in situ NH3 plasma pretreatment

The native oxides on Ge substrates can be transformed into GeOxNy by in situ NH3 plasma pretreatment. The interfacial and electrical properties of HfO2 caps gate stacks on Ge with and without ultrathin GeOxNy barrier layers have been investigated thoroughly. HfO2/GeOxNy/Ge stacking structure shows a sharp and flat interface between HfO2 and Ge substrates without recognized interfacial layer. In situ NH3 plasma pretreatment effectively improves the electrical properties such as higher accumulation capacitance, smaller frequency dispersion, and lower interface trap density (Dit) than without NH3 plasma pretreatment. It is ascribed to that fact that the GeOxNy barrier layer between HfO2 and Ge substrates shows better thermal stability and suppresses the Ge outdiffusion. The 3-nm-thick HfO2 gate stacks on Ge with 60s NH3 plasma pretreatment exhibit a capacitance equivalent thickness of 0.96nm and a leakage current density of 1.12mA/cm2 at +1V gate bias with acceptable Dit value of 3.42×1012eV−1cm−2. These results indicate that the surface nitridation by in situ NH3 plasma pretreatment may be a promising approach for the realization of high quality Ge-based transistor devices.

Improvement of thermal stability of nickel silicide film using NH3 plasma treatment

In this study, the effects of NH3 plasma pre-treatment on the characteristics of NiSi films were investigated. Nickel film was deposited on a Si(100) substrate by meal-organic chemical vapor deposition (MOCVD) using Ni(iPr-DAD)2 as a Ni precursor and NH3 gas as a reactant. Before the Ni deposition, silicon substrate was treated by NH3 plasma with various flow rates to adjust the amount of inserted hydrogen and nitrogen atoms. The Ni films showed a considerable low sheet resistance around 12 Ω/□, irrespective of the NH3 plasma pre-treatment conditions. The sheet resistance of the all Ni films was decreased after annealing at 500 °C due to formation of a low resistive NiSi phase. NiSi films with a high flow rate of NH3 plasma pre-treatment exhibited a lower sheet resistance and smoother interface between NiSi and the Si substrate than the low flow rate of the NH3 plasma pre-treated NiSi films because lots of nitrogen atoms incorporated at grain boundary of NiSi which result in reduce total surface/interface energy of NiSi and enhancement interface characteristics.

Improved interface properties of an HfO2 gate dielectric GaAs MOS device by using SiNx as an interfacial passivation layer

A GaAs metal-oxide-semiconductor (MOS) capacitor with HfO2 as gate dielectric and silicon nitride (SiNx) as the interlayer (IL) is fabricated. Experimental results show that the sample with the SiNx IL has an improved capacitance—voltage characteristic, lower leakage current density (0.785 × 10−6 A/cm2 at Vfb + 1 V) and lower interface-state density (2.9 × 1012 eV−1 cm−2) compared with other samples with N2− or NH3—plasma pretreatment. The influences of post-deposition annealing temperature on electrical properties are also investigated for the samples with SiNx IL. The sample annealed at 600°C exhibits better electrical properties than that annealed at 500°C, which is attributed to the suppression of native oxides, as confirmed by XPS analyses.

Robust Data Retention and Superior Endurance of Silicon–Oxide–Nitride–Oxide–Silicon-Type Nonvolatile Memory with NH3-Plasma-Treated and Pd-Nanocrystal-Embedded Charge Storage Layer

In this study, we investigated an ammonia (NH3) plasma-pretreatment (PT) for suppressing the formation of interface states between metal nanocrystals (NCs) and the surrounding dielectric during the NC forming process with the aim of obtaining a highly reliable Pd NC memory. The discharge-based multipulse (DMP) technique was performed to analyze the distribution of trap energy levels in the Pd NCs/Si3N4-stacked storage layer. Through DMP analysis, it is confirmed that the NH3 PT not only significantly increases the quality of the surrounding dielectric of metal NCs but also effectively passivates shallow trap sites in the Si3N4 trapping layer. As compared with the sample without NH3 PT, the NH3-plasma-treated device exhibits better reliability characteristics such as excellent charge retention (only 5% charge loss for 104 s retention time) and very high endurance (no memory window narrowing after 105 program/erase cycles). In addition, the robust multilevel cell retention properties of the NH3-plasma-treated memory are also demonstrated.

Effects of NH&lt;SUB&gt;3&lt;/SUB&gt; Plasma Pre-Treatment of Ta Substrate on Atomic Layer Deposition of Cu Thin Film

Cu has replaced Al as an interconnection material in ultra-large integrated circuits, reducing resistance capacitance delay and yielding higher electro-migration reliability. However, as the feature size decreases, it becomes more difficult to produce reliable Cu wiring. In this work, the Plasma Enhanced Atomic Layer Deposition (PEALD) of Cu seed layers deposited on Ta substrates (both with and without NH3 plasma pretreatment) was investigated. The Cu seed layers deposited on NH3 plasma-pretreated Ta substrates were found to have favorable properties compared to films deposited without plasma pretreatment because of an increase in the surface energy and of the Ta substrate, which resulted in improved surface wetting.

(Invited) Luminescence Properties of Silicon-Rich Silicon Nitride Films and Light Emitting Devices

Silicon-rich silicon nitride (SiNX) films have attracted enormous interests due to their promising luminescence properties and well compatibility with current CMOS technique. In this short review, the fabrication process of SiNX was addressed as well as their chemical composition and structure. The optical properties and future applications of the light emitting devices (LEDs) were also discussed. By analyzing the carrier conduction and combination mechanisms, electroluminescence (EL) intensity of LEDs was greatly improved through the following approaches: passivation of the interfacial states between SiNX films and Si substrates through NH3 plasma pre-treatment and post-annealing process; the balance of carrier injection via SiO2 electron accelerating layer; increase of the carrier-injection efficiency and light extraction efficiency and the enhancement of radiative recombination efficiency by surface plasmon.

Ultrathin GeOxNy interlayer formed by in situ NH3 plasma pretreatment for passivation of germanium metal-oxide-semiconductor devices

In situ NH3 plasma surface-nitridation treatments at 250 °C on both p- and n-type Ge(100) wafers were investigated. An ultrathin high quality GeOxNy interlayer was formed and exhibited dielectric breakdown for electric fields greater than 15 MV/cm. Well behaved capacitance-voltage characteristics were obtained for the complementary metal-oxide-semiconductor capacitors (CMOSCAPs) with HfO2(3 nm)/GeOxNy(1 nm) gate stacks. Gate leakage current density was below 5×10−7 A/cm2 at VFB±1 V for both MOSCAPs with an equivalent oxide thickness of 1.1 nm. Promising electrical properties of the CMOSCAPs indicate effective passivation of the Ge interface with GeOxNy interlayer formed by in situ NH3 plasma treatment.

(Invited) Reliability of Polycrystalline Silicon Thin-Film Transistors on the Glass Substrate

We have investigated electrical characteristics of laser-crystallized polycrystalline silicon thin film transistors (poly-Si TFTs) under various stresses such as bias, temperature, light illumination. The threshold voltage of short channel TFT (LCH=1.5μm) was significantly shifted to negative direction due to bias temperature stress (ΔVTH = -3.75V) compared with that of long channel TFT (ΔVTH = -0.32V) at 100{degree sign}C. We have also investigated the effects of light illumination on the laser-crystallized poly-Si TFT. In order to improve the reliability of laser-crystallized poly-Si TFT, a novel multiple-channel structure was proposed and fabricated without any additional processes. In addition, in order to enhance the electric characteristics and stability of alternating magnetic-field-enhanced rapid thermal annealing (AMFERTA) poly-Si TFTs, we have employed the NH3 plasma pretreatment prior to crystallization process. The NH3 plasma pretreatment process could effectively improve the reliability of AMFERTA poly-Si TFTs.

Significant Decrease of the Interface State Density by NH&lt;sub&gt;3&lt;/sub&gt; Plasma Pretreatment at 4H-SiC (000-1) Surface and its Bond Configuration

We have investigated NH3 plasma pretreatment for Si- and C-face 4H-SiC and characterized interface properties and bond configuration. It is revealed that the NH3 plasma pretreatment is effective to reduce interface state density on C-face. From X-ray photoelectron spectroscopy (XPS) measurements, N- and H-related C bonds were observed. N and H passivate C-related defects and dangling bonds, resulting in improved interface properties.