Pulsed Reactive Sputtering Research Articles

Effects of duty cycle and oxygen flow rate on the formation and properties of vanadium oxide films deposited by pulsed reactive sputtering

Vanadium oxide (VOx) thin films were deposited on glass substrates at room temperature by pulsed DC reactive magnetron sputtering. The effects of the duty cycle of the pulsed power and oxygen flow on the surface morphology, deposition rate, composition and electrical properties of VOx films were systematically investigated. Experimental results revealed that decreasing the duty cycle or increasing the oxygen flow leaded to the decrease of the root mean square (RMS) roughness of VOx films. Moreover, the deposition rate decreased with the reduction of the duty cycle, and it also became more sensitive to the duty cycle at higher oxygen flow. Electrical measurements indicated that if the oxygen flow was increased from 3.1 sccm to 3.5 sccm, the resistivity and the temperature coefficient of resistivity (TCR) value of VOx films varied from 0.005 Ω cm to 0.409 Ω cm and from −0.209%/K to −1.485%/K, respectively. Particularly, by adjusting the duty cycle, the maximum value of the resistivity and TCR of VOx films can be achieved as 604.2 Ω cm and −2.864%/K, respectively. X-ray photoemission spectroscopy (XPS) analyses revealed that decrease of the duty cycle or increase of the oxygen flow enhanced the oxidation of vanadium. Therefore, with adjustment of the duty cycle in combination with regulation of the oxygen flow, the thermistor properties of VOx films can be well controlled.

Two-phase single layer Al-O-N nanocomposite films with enhanced resistance to cracking

The article reports on dc pulsed reactive sputtering of two-phase single layer Al-O-N nanocomposite films using dual magnetron in a mixture of N2+O2 with pulsed inlet of oxygen. Two kinds of nanocomposite films were sputtered: (1) nc-AlN/a-(Al-O-N) film and (2) nc-(γ-Al2O3)/a-(Al-O-N) nanocomposite film; here nc- and a- denotes the nanocrystalline and amorphous phase, respectively. The transition from the nc-AlN/a-(Al-O-N) nanocomposite to the nc-(γ-Al2O3)/a-(Al-O-N) nanocomposite was controlled by the length of the period of oxygen pulses TO2. It was found that both nanocomposites are highly elastic films with relatively high hardness H=15 to 20GPa, low effective Young's modulus E⁎ satisfying the condition that the ratio H/E⁎>0.1, high elastic recovery We>60% and high resistance to cracking in bending. Correlations between the film structure and its mechanical properties are discussed in detail.

Thermal decomposition and fractal properties of sputter-deposited platinum oxide thin films

Abstract

Elimination of Arcing in Reactive Sputtering of Al2O3 Thin Films Prepared by DC Pulse Single Magnetron

AbstractThe article reports on the elimination of arcing in the DC pulse reactive sputtering of Al2O3 thin films using a single unbalanced magnetron operating at relatively high target power density Wta ranging from ∼10 to ∼50 W/cm2; Wta is the target power density averaged over the pulse length. Correlations between pulse length τ, pulse‐off time toff, repetition frequency fr and arcing at the target surface were investigated in detail. Undesirable damage of sputtered alumina film due to arcing is demonstrated. It is shown that the length of pulse‐off time toff is of key importance for elimination of arcing in pulse reactive sputtering of electrically insulating compounds using a single magnetron. magnified image

Process optimization for the sputter deposition of molybdenum thin films as electrode for AlN thin films

Molybdenum thin films have been deposited on Ti/(100) Si substrates by dc sputtering. For process optimization, a design of experiments method was used with three input factors (target power, substrate temperature, and process gas flow). Deposition rate, resistivity, roughness, diffraction angle, and rocking curve width were analyzed as output responses using statistical analysis method. Subsequently, a process allowing the deposition of highly crystalline, smooth, and low resistivity Mo film was selected and tested against film thickness. The as-optimized sputtered molybdenum thin film was used as seeding electrode for the growth of highly c-axis textured AlN film by dc pulsed reactive sputtering.

Properties of SiO 2 and Al 2O 3 films for electrical insulation applications deposited by reactive pulse magnetron sputtering

Alumina and silica films have been deposited using pulse reactive sputtering. Film deposition was carried out by stationary sputtering using the Double Ring Magnetron with film thickness uniformity of up to ±1% across a 200 mm diameter. In the high rate deposition process using closed loop reactive gas control, the deposition rate of dielectric compounds is in the range of 50–400 nm/min. Electrical properties of the films such as breakdown field strength, resistivity and dielectric constant have been measured in relation to pulse mode, substrate bias, deposition rate and size of contact pads. Breakdown field strength of the as-deposited Al 2O 3 and SiO 2 films ranges from 4 to 9 MV/cm. Resistivity of the films is between 10 +15 and 10 +17 Ωcm measured by dc methods and between 10 +10 and 10 +12 Ωcm measured by ac methods (1 kHz). For the SiO 2 films, an improvement of film properties due to increased energetic substrate bombardment was found. This was shown for both using bipolar pulse mode and additional rf substrate bias to enhance energetic bombardment. The results have been compared to SiO 2 films deposited as reference films by conventional rf sputtering with the same arrangement at a deposition rate of 15 nm/min. Properties of the reactively deposited films with 1 order of magnitude higher deposition rate are close to those of the rf sputtered films. Results, therefore, are promising regarding the application of SiO 2 and Al 2O 3 films deposited by reactive pulse magnetron sputtering for various insulation purposes, for example sensors with thick insulation layers and breakdown voltage up to 1000 V.

Pulsed-magnetron-sputtered low-temperature indium tin oxide films for flat-panel display applications

In this paper, indium tin oxide (ITO) thin films were prepared by unipolar and bipolar direct current (DC)-pulsed magnetron sputtering in a mixture of argon and oxygen onto unheated glass substrates. The target of ITO with 10 wt.% tin is used. The influences of polar modes (unipolar and bipolar); output frequencies (0 to 33 kHz); and times and off times on the optical, electrical, and structural properties of ITO films are investigated. The correlations between the deposition parameters and the film properties are discussed. It is found that the resistivity with 10-3 Ω-cm and transmittance with ≥90% of amorphous ITO films can be prepared by the reactive bipolar DC-pulsed sputtering with t-on between 45 µs and 85 µs (i.e., t-on/t+on is 9-17), and t+on, t-off and t+off are constant at 5 µs, 10 µs, and 5 µs, respectively. An optimal condition, based on the polar mode and frequency of reactive-pulsed sputtering, for obtaining the high transmittance and low resistivity of ITO films is suggested.

Dynamic simulations of pulsed reactive sputtering processes

In the reactive sputtering process numerous parameters interact in a complex and nonlinear way. Thus, if any parameter is changed during operation, it is not an easy matter to predict the response of the other involved parameters. The static behavior of the reactive sputtering process has previously been carefully investigated. However, studies of the time dependent behavior of this process are rare. It is important to study the dynamic behavior to gain a more complete understanding of the process. Furthermore, the increased use of pulsed power sources has set focus on the process dynamics. A model describing the time-dependent behavior of the pulsed reactive sputtering process is proposed in this work. The model suggests that the time to reach process equilibrium may vary substantially depending on the process history. This memory effect has been experimentally verified. Finally, the simulations clearly point out that for high repetition frequencies (>1 kHz) of the pulsed direct current (dc) reactive sputtering process there will be no time-dependent variations of the chemical compositions either at the target surface or at the growing film at the substrates. At these high frequencies the chemistry of the process will act identical as to the continuous dc reactive sputtering process having the average pulsed dc power supplied to the target.

ＰＲＳ法で作製したＦｅＳｉ／ＦｅＳｉＯ多層膜の軟磁気特性

The soft magnetic properties of Fe(Si)/Fe(Si)O multilayered films were investigated. The films were prepared by the pulse-reactive sputtering (PRS) method, which enables multilayered films to be deposited as fast as single films. The soft magnetic properties of the as-prepared films were improved by adding Si. The films show Bs of 1.82-1.87 T and μi' of around 1000 at 300 MHz. A film with Bs of 1.82 T shows μi' of around 1000 at 350 MHz, even after patterning into 18.5 μm-wide stripes.

Improvement of Thermal Stability of Metal/Oxide Interface for Electronic Devices

ABSTRACTThe nano-meter controlled iron/iron-oxide multilayer materials have been successfully obtained by the pulse reactive sputtering method with high deposition rate. These multilayer demonstrated a good thermal stability of its structure and magnetic properties up to 500°C when a small amount of Si was doped in the structure, whereas the non-doped multilayer degraded at above 300°C. The difference of the oxidation energy between Fe and Si increases the thermal stability of the interface between Fe and Fe-O layer.

Magnetic properties of nanostructure controlled FeAlSi/FeAlSiO multilayers

FeAlSi/FeAlSiO multilayers prepared by the pulse reactive sputtering were investigated. It was found that the layered structure had a high thermal stability over the ordering temperature of FeAlSi. In consequence, a saturation magnetic flux density of 1.4-1.5 T, a high isotropic initial permeability of 2000-10000 at 1 MHz were obtained even after the thermal annealing above 500/spl deg/C.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Iron-iron oxide layer films

Thin alternating layers of bcc Fe/amorphous Fe oxide were prepared by a new pulse reactive sputtering technique. The thickness of the Fe+(Fe oxide) periods varied from 8 to 540 Å. At room temperature, the films have soft magnetic properties with coercivities of 4–10 Oe. Samples cooled to 5 K in a saturating applied field show large coercive fields, displaced hysteresis loops and thermal irreversibility up to about 100 K. This low temperature behavior is evidence of exchange coupling between the ferromagnetic Fe and the amorphous Fe oxide.