Highly Conformal Amorphous W–Si–N Thin Films by Plasma-Enhanced Atomic Layer Deposition as a Diffusion Barrier for Cu Metallization

Atomic layer deposition (ALD) has recently received increasing attention for the growth of high-conformity silicon nitride (SiN) thin films. In particular, plasma enhanced ALD (PEALD) allows SiN deposition at substantially lower temperatures (< 400 °C) with better film properties, compared to thermal ALD. These advantages make PEALD more attractive for ultra large scale integrated circuit (ULSI) device fabrication where the growth of aspect ratio independent and high-quality conformal thin dielectric films is tremendously important. The PEALD of SiN films involves a repetitive two-step process: (1) adsorption and decomposition of silicon-containing precursors and ii) nitridation of the Si-rich surface by active N species emanating from the plasma. Halogenated silanes such as hexachlorodisilane, bis(tertiary-butyl-amino)- silane, and dicholorosilane (DCS, SiH2Cl2) have been utilized as Si precursors. Despite previous studies, the underlying reaction mechanisms of these Si precursors with a N-rich SiN surface during PEALD still remain uncertain. Parameters controlling the rate of growth and uniformity have been demonstrated experimentally, but without knowledge of the reaction mechanisms, direct contributions of specific process conditions cannot be explained. Using first-principles density functional theory (DFT) calculations combined with experimental characterization, we have examined and identified a novel mechanism for the adsorption and decomposition of DCS on a N-rich SiN surface. Our study predicts that the DCS adsorption and dissociation can occur by overcoming a moderate barrier (~ 0.3 eV), far lower than the prohibitively large barriers predicted for previously proposed mechanisms. Through a detailed electronic structure analysis of the reaction intermediates, we have also elucidated the principles underlying the reaction mechanism, notably the hypervalent nature of Si which permits the facile reaction of molecularly adsorbed DCS with primary and secondary amines on the surface, followed by simultaneous Cl release and deportation steps and subsequent HCl formation and desorption. We have examined the same mechanism utilizing alternative precursors and the predicted trends are found to be corroborated with the important properties of the system. Understanding these principles allows us to develop guidelines for processing conditions, such as the importance of maintaining the proper surface composition to facilitate Si precursor adsorption and dissociation. Our study provides insight into the SiN ALD process via chlorosilanes and guidelines to control the deposition for high-quality SiN films and provides a framework for future theoretical studies of surface reactions during ALD.

Atomic layer deposition of transition metals for silicide contact formation: Growth characteristics and silicidation

New class of Zr precursor containing boratabenzene ligand enabling highly conformal wafer-scale zirconium dioxide thin films through atomic layer deposition

Due to various applications in electronic and optical fields, considerable efforts have been made to develop ZnO based semiconducting materials. ZnO has a wide and direct band gap of 3.37 eV, large exciton binding energy (60 meV), high mechanical and thermal stabilities, and good electrical conductivity. Therefore, ZnO thin films are intensively investigated and applied in solar cells, piezoelectrical devices, gas and biological sensors, catalysts, and high-efficiency short-wavelength optoelectronic nanodevices. To further enhance the properties of ZnO, researchers have been synthesizing ZnO films doped with aluminum or indium. Al doped ZnO (AZO) thin films have been highly developed featuring non-toxicity, low material cost, good thermal stability, high optical transmittance, and good electrical conductivity. [1, 2, 3] Many techniques have been used to deposit AZO thin films currently, such as sol gel processing, magnetron sputtering, pulsed laser deposition (PLD), chemical vapor deposition (CVD), and atomic layer deposition (ALD). Among these film deposition methods, ALD has been extensively investigated for the deposition of thin films of metals, alloys, semiconductors, and oxides. Compared with other techniques, ALD is considered as a novel technique for the deposition of AZO films due to its characteristic feature of self-limiting surface saturating reactions in each ALD cycle. ALD technology consequently and accurately controls the layer thickness with unprecedented atomic level precision, as well as the stoichiometry, composition, uniformity of large areas and maintains excellent conformity over complex surface nanostructures. The other advantage of ALD technology is to introduce each ALD chemical precursor sequentially separated by time to react on the surface of the structure. The concentration of dopant in the ZnO films can be precisely controlled by the number of ALD cycles, so that the physical properties of AZO films, such as carrier density and conductivity, can be adjusted to meet the requirements of different applications. In this study, a Savannah 100 cross-flow thermal ALD reactor was used for the deposition of Al doped ZnO thin films. The precursors of aluminium, zinc and oxygen used in the ALD process for the synthesis of Al doped ZnO thin films were trimethylaluminium (TMA: Al2(CH3)6), diethylzinc (DEZ: (C2H5)2Zn) and DI water. The growth temperature of AZO thin films was maintained at 250 oC. The flow rate of N2, used as a carrier gas, was accurately controlled at 20 sccm. In order to deposit ALD AZO films with various percentages of aluminium, TMA cycles were introduced once in every 30 pulses of DEZ and H2O injection. After deposition, AZO films were annealed in air at 500 oC, 600 oC, and 700 oC for 30 min, respectively. X-ray diffraction (XRD) was performed to characterize the crystal structure of ALD ZnO and AZO films. Field emission scanning electron microscopy (FE-SEM) was used to inspect the morphology of AZO films before and after annealing. The surface roughness was analyzed by atomic force microscopy (AFM). The compositions of AZO thin films were analyzed by energy dispersive X-ray spectroscopy (EDS). The sheet resistivity of AZO films was determined by using four-point probe measurements. Raman spectroscopy and photoluminescence (PL) were used to investigate the properties and detect structures of ALD AZO films. The band gaps of AZO films prepared by the ALD process were analyzed from PL spectroscopy results. The materials property and defect structure of ALD AZO films were investigated by Raman spectroscopy.

Atomic layer deposition of WNx thin films using a F-free tungsten metal-organic precursor and NH3 plasma as a Cu-diffusion barrier

Atomic layer deposited Mo2N thin films using Mo(CO)6 and NH3 plasma as a Cu diffusion barrier

Nanostructured ZrO2 thin films were prepared by thermal atomic layer deposition (ALD) and by plasma-enhanced atomic layer deposition (PEALD). The effects of the deposition conditions of temperature, reactant, plasma power, and duration upon the physical and chemical properties of ZrO2 films were investigated. The ZrO2 films by PEALD were polycrystalline and had low contamination, rough surfaces, and relatively large grains. Increasing the plasma power and duration led to a clear polycrystalline structure with relatively large grains due to the additional energy imparted by the plasma. After characterization, the films were incorporated as electrolytes in thin film solid oxide fuel cells, and the performance was measured at 500 °C. Despite similar structure and cathode morphology of the cells studied, the thin film solid oxide fuel cell with the ZrO2 thin film electrolyte by the thermal ALD at 250 °C exhibited the highest power density (38 mW/cm2) because of the lowest average grain size at cathode/electrolyte interface.

Atomic layer deposition (ALD) of aluminum oxyfluoride (AlOxFy) thin films was demonstrated at 150 °C. Trimethyl aluminum, water, and HF were used as the aluminum, oxygen, and fluorine sources, respectively. In situ quartz crystal microbalance studies were utilized to monitor the AlOxFy deposition. Two deposition pathways were explored to grow the AlOxFy thin films based on the HF exchange method and the nanolaminate method. Linear AlOxFy growth was observed during both deposition methods. The HF exchange method is based on the thermodynamically favorable fluorination of Al2O3 by HF. Compositional control was achieved either by changing the HF pressure during the HF exposure or by varying the thickness of the underlying Al2O3 layer prior to the HF exposure. The nanolaminate method is based on the sequential deposition of Al2O3 ALD and AlF3 ALD layers. The ratio of the number of Al2O3 ALD cycles to the number of AlF3 ALD cycles is the main parameter used to control the O and F concentrations. Ex situ x-ray photoelectron spectroscopy (XPS) depth-profiling and Rutherford backscattering spectroscopy measurements were used to determine the composition of the AlOxFy thin films. The XPS depth-profile measurements confirmed the uniform distribution of Al, O, and F throughout the AlOxFy films using both deposition methods. Both techniques could obtain a wide range of compositional tunability between Al2O3 and AlF3. Physical sputtering rates were also observed to be dependent on the relative concentrations of O and F in the AlOxFy films. The physical sputtering rates at 3 keV varied from 0.03 to 0.28 Å/s for Al2O3 and AlF3, respectively.

Atomic layer deposition (ALD) has been shown as a powerful technique to build three-dimensional (3D) all-solid-state microbattery, because of its unique advantages in fabricating uniform and pinhole-free thin films in 3D structures. The development of solid-state electrolyte by ALD is a crucial step to achieve the fabrication of 3D all-solid-state microbattery by ALD. In this work, lithium phosphate solid-state electrolytes were grown by ALD at four different temperatures (250, 275, 300, and 325 °C) using two precursors (lithium tert-butoxide and trimethylphosphate). A linear dependence of film thickness on ALD cycle number was observed and uniform growth was achieved at all four temperatures. The growth rate was 0.57, 0.66, 0.69, and 0.72 Å/cycle at deposition temperatures of 250, 275, 300, and 325 °C, respectively. Furthermore, x-ray photoelectron spectroscopy confirmed the compositions and chemical structures of lithium phosphates deposited by ALD. Moreover, the lithium phosphate thin films deposited at 300 °C presented the highest ionic conductivity of 1.73 × 10−8 S cm−1 at 323 K with ∼0.51 eV activation energy based on the electrochemical impedance spectroscopy. The ionic conductivity was calculated to be 3.3 × 10−8 S cm−1 at 26 °C (299 K).

We propose a deposition method capable of independently controlling the spatial density and average size of Ru nanocrystals by using both plasma-enhanced and thermal atomic layer deposition (ALD). Plasma-enhanced ALD is used to promote the nucleation of Ru nanocrystals, while thermal ALD is used to assist their growth. By the rigorous selection of each stage, we can demonstrate the formation of Ru nanocrystals with a density variation from 3.5 X 10 11 to 8.4 X 10 11 cm -2 and sizes from 2.2 to 5.1 nm, which is in the optimum density and size range of nanocrystal floating-gate memory application.

Atomic layer deposition (ALD) is a well-established technique for depositing nanoscale coatings with pristine control of film thickness and composition. The trimethylaluminum (TMA) and water (H2O) ALD chemistry is inarguably the most widely used and yet to date, we have little information about the atomic-scale structure of the amorphous aluminum oxide (AlOx) formed by this chemistry. This lack of understanding hinders our ability to establish process-structure-property relationships and ultimately limits technological advancements employing AlOx made via ALD. In this work, we employ synchrotron high-energy X-ray diffraction (HE-XRD) coupled with pair distribution function (PDF) analysis to characterize the atomic structure of amorphous AlOx ALD coatings. We combine ex situ and in operando HE-XRD measurements on ALD AlOx and fit these experimental data using stochastic structural modeling to reveal variations in the Al-O bond length, Al and O coordination environment, and extent of Al vacancies as a function of growth conditions. In particular, the local atomic structure of ALD AlOx is found to change with the substrate and number of ALD cycles. The observed trends are consistent with the formation of bulk Al2O3 surrounded by an O-rich surface layer. We deconvolute these data to reveal atomic-scale structural information for both the bulk and surface phases. Overall, this work demonstrates the usefulness of HE-XRD and PDF analysis in improving our understanding of the structure of amorphous ALD thin films and provides a pathway to evaluate how process changes impact the structure and properties of ALD films.

Integration of feedback control and run-to-run control for plasma enhanced atomic layer deposition of hafnium oxide thin films

Low temperature growth of Beryllium Oxide thin films prepared via plasma enhanced atomic layer deposition

Elastomeric primer and adhesive systemSection:ChooseTop of pageElastomeric primer and ad... <<Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES Master Bond X21Med is a single-component elastomeric compound that passes ISO 10993-5 tests for cytotoxicity. It was developed as a primer to promote adhesion between polyolefins and other surfaces such as metals, ceramics, composites, and other kinds of plastics, but it can also bond two polyolefin materials. Easy to use, X21Med has a low viscosity of less than 250 cps. It cures at ambient temperatures; with heat, it cures more rapidly. It is serviceable from −51 °C to 93 °C. As a primer, X21Med should be applied in a thin layer to the surface and then the solvent allowed to evaporate. When used as an adhesive, it should be applied to both substrates and then mated. The maximum area of bonding effectiveness is about 1 inch squared. Once cured, the clear- to light-amber-colored product is tough but not rigid. It is a reliable electrical insulator and has a volume resistivity exceeding 1014 ohm-cm. The compound has applications in medical device, aerospace, electronics, specialty OEM, and other fields. It is available in pints, quarts, gallons, and five-gallon containers. Master Bond Inc, 154 Hobart St, Hackensack, NJ 07601, www.masterbond.com Atomic layer deposition plasma-processing systemSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p... <<Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES Oxford Instruments has announced the novel FlexAL-2D system for atomic layer deposition (ALD) of 2D transition-metal dichalcogenides for nanodevice applications. The FlexAL-2D system implements plasma-enhanced ALD to synthesize layers of 2D molybdenum disulfide films with tunable morphologies—namely, in-plane and vertically standing nanoscale architectures on CMOS-compatible silicon dioxide and silicon substrates. The wide parameter space offered by the ALD system allows 2D transition-metal dichalcogenides to be grown at lower temperatures than those used in chemical vapor deposition furnaces. With atoms, high temperatures can increase their diffusion on semiconductors and make it harder to place them at the right spot. According to the company, the FlexAL-2D system yields materials of high quality with precise digital thickness control over large-area, 200 mm wafers. Oxford Instruments plc, 300 Baker Ave, Ste 150, Concord, MA 01742, www.oxford-instruments.com Cold cathode vacuum transducerSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans... <<X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES The MKS Granville-Phillips 523 wide-range cold cathode vacuum transducer is suitable for applications that require an economical cold cathode with limited accuracy for simple, repeatable pressure measurement. It combines diverse materials and two types of discharge. The 523 covers a wide pressure range from 10−7 torr to atmosphere without the use of a conventional heat-loss Pirani sensor. A high-pressure discharge cell makes a second vacuum sensor unnecessary. The device can be mounted in any orientation, has a simple analog output, and complies with Restriction of Hazardous Substances and CE standards. Applications include analytical equipment such as mass spectrometers, scanning electron microscopes, industrial coating systems, and general vacuum-based pressure measurement apparatus. MKS Instruments Inc, 2 Tech Dr, Ste 201, Andover, MA 01810, www.mksinst.com X-ray fluorescence systemSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence system <<Precision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES Bruker has announced its S8 Tiger Series 2 wavelength dispersive x-ray fluorescence (WDXRF) system for advanced quantitative elemental analysis in academic and industrial research and materials quality control. Measurement times are reduced, sample throughput is increased, and time to result is improved, typically by 25% over the previous model. The S8 Tiger Series 2 features XRF2 small spot mapping for detailed maps of elemental distributions in materials. With a 300 µm spot size, XRF2 offers the highest spatial resolution available in WDXRF, according to Bruker. The system introduces the company’s novel HighSense technology, which offers a wide linear dynamic range to enable higher precision levels for process and quality control. The x-ray optics improves sensitivity and spectral resolution to benefit a wide range of applications, including recognition of foreign particles and analysis of material properties in metals, minerals, semiconductors, glass, ceramics, and nanotechnology. Bruker AXS GmbH, Oestliche Rheinbrueckenstr 49, 76187 Karlsruhe, Germany, www.bruker.com Precision UV mirrorsSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrors <<Solder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES Edmund Optics offers its TechSpec precision UV mirrors in deep-UV (DUV) and new vacuum-UV (VUV) enhanced coatings. They are suitable for use in numerous optical setups to reflect UV light, including fluorescence microscopy and spectrometry, and for various commercially available light sources. The mirrors with DUV coating offer excellent reflection from 190 nm to long-wave IR (LWIR), and the VUV-coated mirrors provide optimized reflection from 120 nm to LWIR. Designed for 0° angle of incidence, TechSpec precision UV mirrors exhibit greater than 78% reflectivity at their specified design wavelength. The mirrors are manufactured from a fused silica substrate and feature aluminum-based coatings for low polarization sensitivity. A surface flatness of λ/10 and a surface quality of 10-5provide for maximum precision. Six models are available in 12.5 mm, 25 mm, and 50 mm diameters. Edmund Optics Inc, 101 E Gloucester Pike, Barrington, NJ 08007-1380, www.edmundoptics.com Solder paste for fine-feature printingSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea... <<Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES Indium Corp has developed an air and nitrogen reflow, no-clean, lead-free solder paste to meet the fine-feature printing requirements of mobile manufacturers. The Indium11.8HF-SPR (T5-MC) paste is formulated for use with type 5 powder. It delivers high-stencil print-transfer efficiency on a broad range of processes while maintaining high reflow performance, and it is halogen free, per the International Electrochemical Commission’s standard 61249-2-21 test method EN14582. It offers high transfer efficiency through small apertures less than or equal to 0.66 AR and a long stencil life greater than 12 h. Since the paste eliminates hot and cold slump, it inhibits bridging and solder-beading defects. An oxidation barrier avoids the potential for head-in-pillow and graping defects. Indium Corporation, 34 Robinson Rd, Clinton, NY 13323, www.indium.com Process for diamond-like coatingsSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ... <<Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES By incorporating plasma activation, Intlvac has enhanced the reaction kinetics of its diamond-like carbon (DLC) coating machines that use chemical vapor deposition technology. Coupling a dense plasma to carbon‐based precursor gases creates the favorable reaction energetics needed to form diamond-like material, including tantalum carbide ceramic microstructures. Using the company’s new process recipe, the machines produce hard, wear-and-abrasion-resistant DLC coatings to protect substrates, including temperature-sensitive ones, exposed to harsh environments. The smooth coatings are suitable for low-friction applications. They are chemically inert and appropriate for in situ biomedical uses. The standard Intlvac platform can produce DLC thicknesses from several microns to 10 nm on various substrate materials. Those include silicon, germanium, optical glasses, chalcogenides, sapphire, metals, and plastics. Intlvac Thin Film Corporation, 1401 Duff Dr, Unit 600, Fort Collins, CO 80524, www.intlvac.com Liquid transfer pumpSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pump <<New literatureEllipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES KNF has designed an economical solenoid-driven diaphragm pump for OEM users. The FL 10 pump features a nominal liquid flow rate of 100 mL/min against atmospheric pressure, simple linear flow rate adjustment, and a maintenance-free expected lifetime of 10 000 h. It can be operated to 14.5 psig (1 bar). Spring tension in the linear solenoid drive keeps the flow through the FL 10 tight in both directions when turned off and makes additional check valves unnecessary. Built to operate in demanding environments such as wet or dusty areas, the pump has an IP65 protection rating. Sealing between the pump housing and the linear drive ensures safe operation. In case of a ruptured diaphragm, liquid is kept away from other areas of the system. Chemically resistant flow-path materials in the FL 10 allow for reliable transportation of aggressive media. The company’s novel diaphragm technology transports liquid gently, so its pumps can handle sensitive fluids. KNF Neuberger Inc, 2 Black Forest Rd, Trenton, NJ 08691-1810, www.knfusa.com New literatureSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literature <<Ellipsometer for thin-fil...Specialized vacuum gauges...CITING ARTICLES Vacuum process monitoring brochure Hiden Analytical has released a brochure on its quadrupole mass spectrometers for vacuum process monitoring. Systems cover the full pressure range from UHV for background species and leak detection to the millibar regime for process monitoring and control. The HPR-30 system addresses the higher-pressure regimes. It features integrated dry vacuum pumping and overpressure protection and is configured to mount directly to the process chamber. The 300 amu mass range is applicable to most process environments, with alternative mass range options available for specialized applications. At lower pressures below 5 × 10−3 millibar, the dual-mode Hiden HMT residual gas analyzer (RGA) uses a Faraday detector for high-pressure operation. It works from low pressures to UHV with electron multiplier detection and offers partial pressure detection sensitivity to 2 × 10−13 millibar. The HALO and HAL RGA series operate at lower-pressure regimes with extensive mass range options up to 1000 amu and minimum detectable partial pressures down to 5 × 10−15 millibar. Hiden Analytical Inc, 37699 Schoolcraft Rd, Livonia, MI 48150, www.hideninc.com Ellipsometer for thin-film measurementsSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil... <<Specialized vacuum gauges...CITING ARTICLES According to Horiba Scientific, its Uvisel Plus modular ellipsometer includes a new generation of the FastAcq acquisition technology, which can measure thin-film samples faster and more accurately than previously possible. The technology features new electronic data processing and a high-speed monochromator. Samples from 190 nm to 2100 nm can be measured within 3 min at high resolution. The technology allows for continuous adjustment of the spectral resolution along the measurement range. The Uvisel series phase modulation technology can deliver pure, efficient polarization modulation for accurate and sensitive ellipsometric parameter measurements, such as critical thin transparent layers deposited onto glass substrates. The Uvisel Plus is considered a reference ellipsometer for materials science. It is suitable for thin-film thickness and optical constant measurements in materials research and processing, flat-panel displays, microelectronics, and photovoltaics. Horiba Scientific, 3880 Park Ave, Edison, NJ 08820, www.horiba.com Specialized vacuum gauges and controllersSection:ChooseTop of pageElastomeric primer and ad...Atomic layer deposition p...Cold cathode vacuum trans...X-ray fluorescence systemPrecision UV mirrorsSolder paste for fine-fea...Process for diamond-like ...Liquid transfer pumpNew literatureEllipsometer for thin-fil...Specialized vacuum gauges... <<CITING ARTICLES Edwards has released a range of passive gauges and controllers to meet the needs of users with specialized applications in the high-energy physics and UHV fields. The devices are suitable for a wide range of applications, from UHV systems to process industries, and for when an active gauge cannot be used. The passive gauges range from Pirani and Penning gauges to Bayard–Alpert and extractor ion gauge heads. They are used in conjunction with a passive gauge controller to display pressure and serve as an interface. Pressure ranges of 10−9 mbar to 1000 mbar are covered by the PGC201 controller together with Pirani and Penning gauges, and pressure ranges of 10−12 mbar to 1000 mbar are covered by the PGC202 controller together with an integrated Pirani and ion gauge. Edwards, Innovation Dr, Burgess Hill, West Sussex, RH15 9TW, UK, www.edwardsvacuum.com © 2017 American Institute of Physics.

In recent years, the application of (In, Al, Ga)N materials in photovoltaic devices has attracted much attention. Like InGaN, it is a direct band gap material with high absorption at the band edge, suitable for high efficiency photovoltaic devices. Nonetheless, it is important to deposit high-quality GaN material as a foundation. Plasma-enhanced atomic layer deposition (PEALD) combines the advantages of the ALD process with the use of plasma and is often used to deposit thin films with different needs. However, residual oxygen during growth has always been an unavoidable issue affecting the quality of the resulting film, especially in growing gallium nitride (GaN) films. In this study, the NH3-containing plasma was used to capture the oxygen absorbed on the growing surface to improve the quality of GaN films. By diagnosing the plasma, NH2, NH, and H radicals controlled by the plasma power has a strong influence not only on the oxygen content in growing GaN films but also on the growth rate, crystallinity, and surface roughness. The NH and NH2 radicals contribute to the growth of GaN films while the H radicals selectively dissociate Ga-OH bonds on the film surface and etch the grown films. At high plasma power, the GaN film with the lowest Ga-O bond ratio has a saturated growth rate, a better crystallinity, a rougher surface, and a lower bandgap. In addition, the deposition mechanism of GaN thin films prepared with a trimethylgallium metal source and NH3/Ar plasma PEALD involving oxygen participation or not is also discussed in the study.