Plasma Assisted DC Magnetron Sputtering Research Articles

Properties of tungsten thin film deposited using inductively coupled plasma assisted sputtering for next-generation interconnect metal

Tungsten (W) is actively investigated as one of the future metallization materials which can replace Cu for the metal thickness lower than tens of nanometer due to its sfmall electron mean free path of 19 nm and high melting temperature of 3673 K. In this study, inductively coupled plasma (ICP) assisted DC magnetron sputtering of W has been investigated for the lower resistivity of nm scale W film (30 nm). When the characteristics of W thin films deposited with and without ICP assistance were investigated, the decrease of the W thin film resistivity with the increase of deposition rate was observed as the ICP power is increased regardless of substrate heating. The decrease of W thin film resistivity by the ICP assisted DC sputter deposition was related to the change of crystal structure from A-15 to BCC, decreased oxygen incorporation in the film, decreased surface roughness, and increased grain size due to the increased ion flux to the substrate.

Reducing N2O induced cross-talk in a NDIR CO2 gas sensor for breath analysis using multilayer thin film optical interference coatings

Carbon dioxide (CO2) gas sensing is an important aspect in the biomedical field of capnography, where cheap, fast and accurate measurement of exhaled CO2 vs. time is crucial in the evaluation of lung and tracheal function during surgical anaesthesia and is an under-used bio-marker for underlying respiratory conditions. Current detection methods do not adequately meet these requirements and suffer from considerable cross-talk associated with the commonly used anaesthetic gas nitrous oxide (N2O). In this work, we report how cross-talk can be reduced in a commercially available, low power (35mW) non-dispersive infrared (NDIR) CO2 gas sensor using thin film multilayer optical filters. Current sensor spectral response, spans 2500nm–5000nm via use of a pentanary alloy LED/photodiode optopair grown by molecular beam epitaxy (MBE), resulting in sensor sensitivity to gases with absorption bands in this region, including N2O. To reduce the effective spectral response of the sensor, capturing only CO2, a multilayer thin film optical interference bandpass filter has been designed and deposited directly onto the diode epi-structures using microwave plasma assisted DC magnetron sputtering. Three different coating configurations have been explored; LED-only coated, photodiode only coated and both coated. Gas sensor response to N2O for each coating configuration has been explored. It was found that application of an optical bandpass filter onto both the sensor LED and photodiode only was the most effective method of reducing sensor response to N2O, however no signal was observed in one of the two “LED and PD coated”, therefore optimal coating configuration for cross-talk reduction is subject to further investigation.

Characterisation of Cu2O/CuO thin films produced by plasma-assisted DC sputtering for solar cell application

For large-scale implementation of devices magnetron sputtering is a practical method of producing metal oxides, however sputtered copper oxides tend to form as a mixture of Cu2O, Cu4O3, and CuO, with Cu2O being particularly difficult to produce reliably in pure form. In this study, nanostructured thin films of Cu2O, Cu4O3, and CuO were prepared using a novel reactive sputtering system, based on plasma-assisted DC magnetron sputtering with deposition and plasma assisted reaction zones spatially separated enabling separate control of film oxidation. X-ray diffraction, optical spectroscopy, and Raman spectroscopy were used to characterise the physical and optical properties and it is shown that plasma-assisted DC sputtering is a suitable technique for reliable production of CuO and Cu2O films in large areas at room temperature without the necessity of further processing. The results also indicate that solar cell performance may relate positively to the presence of crystalline Cu4O3 (200) and/or Cu2O (111) over other crystalline forms of copper oxide or amorphous copper oxide thin films.

Properties of IGZO Film Deposited by Ar/O2 Inductively Coupled Plasma Assisted DC Magnetron Sputtering

Properties of IGZO Film Deposited by Ar/O₂ Inductively Coupled Plasma Assisted DC Magnetron Sputtering

Measurement of energy flux to a substrate by thermal and Langmuir probes during inductively coupled plasma assisted DC magnetron sputtering

To understand the deposition mechanism during the inductively coupled plasma (ICP) assisted DC magnetron sputter-deposition of transparent conductive Al-doped ZnO (AZO) films, energy flux to a substrate was investigated. The total energy flux to a substrate (Jtotal) was measured by two types of thermal probes: one for the absolute value measurement of Jtotal at a fixed position, and the other for the spatial distribution measurement of Jtotal. The contribution due to charged species (Jch) was evaluated by the Langmuir probe measurements of plasma parameters. As a result, it was found that i) Jtotal was about 3000 W m−2 for the typical deposition condition and this value was about one order of magnitude larger than those of conventional planar magnetron sputtering, and ii) most of Jtotal was contributed by plasma charged species.

Mechanical and Chemical Characterization of NbNxCoatings Deposited by ICP Assisted DC Magnetron Sputtering

Niobium nitride coatings have many potential thin film applications due to their chemical inertness, good mechanical properties, temperature stability and superconducting properties. In this study, NbN coatings were prepared by inductively coupled plasma (ICP) assisted DC magnetron sputtering method on the surface of AISI 304 austenitic stainless steels. Effects of target power were studied on mechanical and chemical properties of the coatings. The coating structure was analyzed by X-ray diffraction (XRD) and field emission scanning elec- tron microscopy (FESEM). The coating hardness was measured by micro-knoop hardness tester. The coating thickness was measured using a 3D profiler and wear characteristics were estimated using a ball-on-disk wear tester. The thickness of the NbN coatings increased linearly from 300 nm to 2000 nm as the Nb target power increased, and it showed over HK 4000 hardness above Nb target power of 300 W. Hexagonal δ'-NbN phase and cubic δ-NbN phase were observed in the coating films and the hardness of the NbN coatings was higher when these two peaks were mixed. The corrosion resistance increased with the increase of the Nb target power. (Received October 30, 2013; Revised November 6, 2013; Accepted November 15, 2013)

Characteristics of NbN Films Deposited on AISI 304 Using Inductively Coupled Plasma Assisted DC Magnetron Sputtering Method

Niobium nitride (NbN) films were deposited on AISI 304 stainless steels by inductively coupled plasma (ICP) assisted dc magnetron sputtering method at different ICP powers, and the effects of ICP power on the phase formation, mechanical and chemical properties of the films were investigated. X-ray diffraction analysis (XRD) and field emission scanning electron microscopy (FESEM) were used to analyze the crystal structure and micro-knoop hardness was used to measure the hardness of the films. Also, 3-D mechanical profiler and a ball-on-disk wear tester were used to measure the thickness of the films and to estimate wear characteristics, respectively. The thickness of the films decreased but their hardness increased with increasing ICP power, and it was confirmed that only cubic <TEX>${\delta}$</TEX>-NbN(200) remained at high ICP power. At lower ICP powers, a mixture of the hexagonal <TEX>${\delta}^{\prime}$</TEX>-NbN and cubic <TEX>${\delta}$</TEX>-NbN phases was obtained in the films and the hardness decreased. The corrosion potential value increased gradually with increasing ICP power, but the changes of ICP power did not significantly influence the overall corrosion resistance.

Growth of preferred orientation Ge film using inductively coupled plasma-assisted DC magnetron sputtering at low temperature

Growth of low-temperature metal-free crystallized Ge film was investigated using inductively coupled plasma-assisted DC magnetron sputtering. The films were deposited both without and with inductively coupled plasma. The films deposited by a conventional DC magnetron sputtering system had randomly oriented crystalline structures. However, the addition of inductively coupled plasma developed crystal phase from an amorphous to a preferred oriented crystalline with increasing sputtering power. The optical band gaps of the amorphous and crystalline phases were 0.96eV and 0.7eV, respectively.

Effect of organic-buffer-layer on electrical property and environmental reliability of Ga-doped ZnO films prepared by RF plasma assisted DC magnetron sputtering on plastic substrate

Ga-doped ZnO (GZO) transparent conductive films have been prepared by RF plasma assisted DC magnetron sputtering under a reductive atmosphere on organic-buffer-layer (OBL) coated polyethylene telephthalate (PET) substrates without intentionally heating substrates. Electrical and optical properties, crystallinity, and environmental reliability of the GZO films have been investigated. The distributional characteristic of resistivity is observed in the GZO film deposited on the OBL-coated PET substrates. The high resistivity at facing the erosion area in the source target is reduced by providing the RF plasma and H 2 gas near the substrate, resulting in a uniform distribution of the sheet resistance. It has been also found that the increase of resistivity by an accelerated aging test performed under a storage condition at 60 °C and at a relative humidity of 95% is suppressed by employing the OBL. The OBL suppresses the formation of cracks, which are induced by the aging test. These facts are thought to contribute to a high environmental reliability of GZO films on PET substrates. Values of resistivity, Hall mobility and carrier concentration are obtained: 5.0–20 × 10 −3 Ω cm, 4.0 cm 2/Vs, and 3.8 × 10 20 cm −3, respectively. An average transmittance of the GZO film including OBL and PET substrate is 78% in a visible region. The OBL enables to realize the practical use of GZO films on PET sheets.

Ga doped ZnO thin films prepared by RF plasma assisted DC magnetron sputtering under reductive atmosphere without heating substrates

AbstractGa doped ZnO (GZO) transparent conductive thin films have been prepared by RF plasma assisted DC magnetron sputtering under a reductive atmosphere without intentionally heating substrate. The resistivity of the GZO film facing the erosion area in the source target falls to about a 1/1000 value by providing the RF plasma, resulting in a uniform distribution of the sheet resistance. Currently obtained values of resistivity, Hall mobility, and carrier concentration are 1 x 10‐2 Ω‐cm, 4 cm2/Vs, and 3 x 1020 cm‐3, respectively. It has been also found that the crystallization of GZO films is also enhanced by the RF plasma. After the accelerated aging test (60 °C ‐ 95%RH) for 250 hrs, the sheet resistance maintains almost the same as the initial value for the GZO film prepared with RF plasma, though that increases by 15 times for the film prepared without RF plasma. (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Study of the inductively coupled plasma assisted DC magnetron sputtering (ICPDMS) during ITO deposition

An inductively coupled plasma (ICP) assisted DC magnetron sputtering (ICPDMS) method for the deposition of indium tin oxide (ITO) thin films was developed to satisfy the challenging requirements of a room temperature process and high temperature durability. The resistivity of ITO thin films deposited by ICPDMS at room temperature was improved to as low as 1.2 × 10 − 2 Ω cm by increasing the RF power of the ICP source to 1200 W. Due to the additional dissociation and ionization by the high density plasma in ICPDMS system, the ITO thin films have a higher portion of Sn and oxygen atoms and a lower initial carrier concentration, ~ 10 18 #/cm 3, at room temperature than conventional ITO. However, the carrier concentration could be rapidly increased up to 10 20 #/cm 3 by post-annealing to temperatures as high as 500 °C for 1 h under high vacuum conditions. Unlike conventional ITO, the electrical properties of ICPDMS–ITO were relatively unchanged after high temperature heat cycles, which is a very attractive property for high performance photovoltaic solar cell applications.

Structure and properties of Ti–Si–N films with ∼ 10 at.% Si deposited using reactive magnetron sputtering with high-flux low-energy ion assistance

Ti–Si–N films with about 10 at.% Si were deposited onto silicon (100) substrates using inductively coupled plasma-assisted dc magnetron sputtering of Ti 80Si 20 target in a mixture of argon and nitrogen. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and nanoindentation analysis were employed to investigate the effects of ion flux and ion energy on the structure and hardness of as-deposited films. It was found that (i) high-flux ion irradiation with energy of 20 eV caused microstructure to change from non-assisted amorphous columnar form to one where there are globular nanocrystallites of TiN (nc-TiN) embedded in amorphous Si 3N 4 (a-Si 3N 4) network; (ii) the hardness of this nc-TiN/a-Si 3N 4 nanocomposite film was approximately 35 GPa, significantly higher than that of monolithic TiN film of approximately 20 GPa; (iii) upon increasing ion energy the structure of Ti–Si–N film became columnar again and the hardness of film decreased markedly.

CrB 2 coatings deposited by inductively coupled plasma assisted DC magnetron sputtering

CrB 2 coatings were synthesized on high speed steel (HSS) substrates using inductively coupled plasma (ICP) assisted DC magnetron sputtering, and the structure and properties of the CrB 2 coating produced at different ICP powers and substrate biases were investigated. The hardness of the CrB 2 coatings increased from 30 GPa to 54 GPa by increasing the ICP power as well as the negative substrate bias. By increasing ICP power, the preferred orientation of the CrB 2 coating changed from (101) to (001). The CrB 2 coating showed excellent corrosion resistance. The corrosion resistance of the CrB 2 coatings was also found to be much better than that of the TiB 2 coatings. The adhesion strength of the film could be improved considerably after ICP nitriding of the substrate.

Deposition of TiO 2 Films by reactive Inductively Coupled Plasma assisted DC magnetron sputtering for high crystallinity and high deposition rate

TiO 2 films with high crystallinity were produced at a high deposition rate by inductively coupled plasma (ICP) assisted reactive magnetron sputtering. X-ray diffraction, UV–VIS spectrophotometer, and an α-step profilometer were used for the analysis of film characterization. The deposition rate was > 20 nm/min and the structure of the TiO 2 film changed with the deposition pressure. Anatase phase was obtained at 4 Pa without after-heat treatment, while amorphous and rutile phases were produced at < 2.67 Pa. The optical transmission was changed according to the target surface condition, and was as high as > 80% in the transition mode.

Process control for low temperature reactive deposition of Al doped ZnO films by ICP-assisted DC magnetron sputtering

Al-doped ZnO (AZO) films were deposited by inductively coupled plasma (ICP) assisted DC magnetron sputtering at low temperatures. The AZO films were produced by sputtering a metallic target (Zn/Al) in a mixture of argon and oxygen gases. AZO films with an electrical resistivity of 6.3×10−4 Ω cm and an optical transmittance of 82% were obtained even at a low deposition temperature (<150 °C). In situ process control methods were used to obtain stable deposition conditions in the transition region without any hysteresis effect. The target voltage was changed using oxygen flow or DC power as control-parameter. It was found that the ratio of the oxygen to zinc emission intensity, I (O 777 nm)/I (Zn 481 nm) decreased with increasing the target voltage in the transition region.

Low temperature deposition of Al-doped zinc oxide films by ICP-assisted reactive DC magnetron sputtering

Al doped ZnO (AZO) films were synthesized by inductively coupled plasma (ICP) assisted DC magnetron sputtering at low temperatures (<150 °C). A two-turn rf coil was inserted in the process chamber between the substrate and magnetron to generate the ICP. In order to obtain the optimum film properties even at a low temperature, high-density plasma was used to activate the sputtered metals and oxygen. The deposition process could be stabilized by controlling the target voltage in the transition region. The electrical resistivity of the films was ∼10−3 Ω cm, and the optical transmittance in the visible range was >80%. As the working pressure was increased, the visible transmittance of films was increased but the low resistivity processing window became narrower.

Deposition of Ti–B–N films by ICP assisted sputtering

Ti–B–N coatings were prepared by inductively coupled plasma assisted DC magnetron sputtering using a TiB 2 target and a gas mixture of N 2 and Ar at 200 °C and a pressure of 60 mTorr. In addition to ICP, the effect of the substrate bias voltage on the structure and properties of the coating was investigated. By applying ICP the hardness of the TiB 2 coating was increased by more than 60 GPa, as a result of enhanced ionization in the plasma. By adding N 2 into the TiB 2 coating, the hardness decreased as reported previously. However, the hardness could be increased up to 76 GPa by applying ICP and a bias voltage to the substrate. The Ti–B–N coating, which had the highest hardness, showed the best surface uniformity and a very dense structure with a grain size of 3 nm. This sample also showed a high crystallinity compared to the coating prepared using other deposition parameters.

A study on the low temperature coating process by inductively coupled plasma assisted DC magnetron sputtering

Titanium nitride (TiN x ) was deposited on a plastic Acrylonitrile–butadiene–styrene substrate by inductively coupled plasma (ICP) sputtering. Many PVD coating processes, currently used in industry, are quite inefficient as there is a need for an extensive cooling time. However, the ICP technique is a high-density plasma technique, which allows deposition on substrates like plastics at low temperatures. Through the plasma diagnosis, the plasma density of the ICP sputtering system was superior to that of the other commercial PVD processes.

SYNTHESIS AND CHARACTERIZATION OF TERNARY AL-C-N COMPOUND

An attempt for modification of carbon nitride material by introduction of Al to form a ternary Al-C-N compound in a thin film deposited using inductively coupled plasma (ICP) assisted DC magnetron sputtering is reported. Optical emission spectroscopy (OES) is used for in-situ observation and identification of reactive species. The films were characterized using x-ray photoelectron spectroscopy (XPS) and x-ray diffraction spectroscopy (XRD). The results indicate that C-N bond is formed in the plasma. The XPS narrow scam spectra confirm the existence of C-Al, sp2C-N and sp3C-N bonds. Elemental proportion of carbon increases with the CH4/N2 flow rate ratio, and has a tendency to saturate. The film is dominated by c-AlN (111), mixed with Al4C3 and AlCN ternary compound.

NON-LINEAR EFFECTS OF Ti EMISSION ON TIN FILM DEPOSITION

Non-linear effects on Ti emission during TiN synthesis in an inductively coupled plasma assisted DC magnetron sputtering system have been investigated. TiN films are deposited on stainless steel 304 substrates, using N 2 + Ar mixture in the absence and presence of RF current variation. In-situ measurements of the optical emission collected during the deposition processes indicate differences in the intensities of the Ti species involved. Film characterizations indicate that such plasma non-linearity plays a pivotal role in the eventual film properties. Highly orientated (111) TiN films deposited under the same RF power were found to correspond to two different hardness values, one being 2240Hv and is 40% harder than the other.