Yosef Koulik

Thin-Film Deposition With Refractory Materials Using a Vacuum Arc

Refractory metal plasma generated by a vacuum arc was used to deposit thin films with different arc currents I. The deposition rate Vdep was measured for electrode configurations including a planar Zr cathode and a planar W anode; cylindrical W or Mo electrode pairs and a cylindrical Nb cathode closed by a BN plate and a W or Nb shower-head cup anode or with one-hole Ta cup anode. Vdep for a Mo electrode pair with I = 275 A at a distance L = 110 mm from the electrode axis reached 2.2 μm/min, 60 s after arc ignition. For the W electrode pair Vdep was ~1 μm/min at 80 s (I = 200 A and L = 110 mm), while for W film deposition with shower-head anode Vdep was ~0.6 μm/min (I = 200 A and L = 60 mm). For Nb films deposited with the closed electrode configuration, Vdep was 0.3 μm/min at 30 s after arc ignition (I = 275 A and L = 80 mm from the anode front).

Temperature Distribution Dependence on Refractory Anode Thickness in a Vacuum Arc: Experiment

The time-dependent anode temperature was measured in a hot refractory anode vacuum arc (HRAVA) sustained between a consumed water-cooled cylindrical Cu cathode and nonconsumed cylindrical W anodes with thicknesses of separated by gaps of 5, 10, 15, and 20 mm. Arc currents of were applied for periods up to 210 s. The anode temperature was measured using high-temperature thermocouples at different points in the anode body. The visual radiation emitted by the plasma plume was recorded with a digital camera. The anode temperature increased with time, reaching a steady-state value which slightly increased with arc current. The anode temperature decreased with the gap and was higher for thinner anodes. When was increased from 5 to 30 mm, the time for the anode front-surface temperature to reach the steady state increased from 45 to 140 s, while this temperature decreased from 2525 to 2325 K . Thus, minimizing advantageously minimizes the start-up transient when using the radially expanding HRAVA plasma plume for thin-film deposition.

Evolution of a Plasma Plume From a Shower Anode in a Vacuum Arc With a Black-Body Electrode Configuration

The plasma plume extracted from a shower anode of a vacuum arc with a black-body assembly (VABBA) was imaged in various development stages. In the VABBA, cathode erosion products fill a closed chamber formed by the cathode and a refractory anode. The anode is heated by the arc and reevaporates any cathode material incident upon it. An expanding metallic plasma plume is extracted through small apertures in the shower anode. The plasma plume was utilized to deposit a Cu thin film on a relatively large substrate.

Ion current density measurements in a copper vacuum arc with different refractory anode thicknesses

The time-dependent ion current density was measured in a hot refractory anode vacuum arc (HRAVA) sustained between a consumed water-cooled cylindrical Cu cathode and non-consumed cylindrical W anodes with thickness d = 5, 10, 15, 20, or 30 mm separated by an h = 10 mm gap. Arc currents of I = 130, 150, 175, and 200 A were applied for a period of 90 s. Ion current density Ji extracted from the plasma was measured using a probe located at varying distances from the electrode axis. The active surface of the probe was oriented to be either perpendicular or parallel to the radially expanding plasma to measure the directed or random component of Ji, respectively. Ji started at arc ignition and grew slowly, passed through a peak, and reached a final steady state level. This level increased with arc current and decreased with probe distance. The time to reach the steady state decreased when d was decreased from 30 to 5 mm, for I = 200 A from 48 to 12 s and for I = 150 A from 69 to 20 s, and weakly depended on pro...

Anode temperature evolution in a vacuum arc with a black body electrode configuration

Anode temperature in a Vacuum Arc with a Black Body Assembly (VABBA) was measured as a function of time. The arc was ignited in an electrode assembly operated as a black body for the macroparticles (MPs). The cathode was a 30 mm diameter Cu rod and the refractory anode was 50 mm in diameter, and constructed from Ta. Plasma was ejected through an array of 250 holes of 0.6 mm diameter in the anode. The arc currents were I=175 & 225 A and the arc duration was 180 s. The anode temperature was measured using high-temperature thermocouples at two points (TC-top, TC-side) inside the anode body. The observed anode temperature increased sharply during a transient time of ~90 s and then it slightly increased with time up to 180 s reaching at TC-top 1650K (I=175 A) and 1850K (I=225 A). The anode temperature at the top surface exceeded that at side surface by ~150-200C.

Vacuum arc deposition using refractory electrodes

Refractory metal plasma generated by a vacuum arc was used to deposit thin films. The deposition rate Vdep was measured for different electrode configurations: (1) a planar Zr cathode and a planar W anode-both 60mm diam, (2) 32 mm diam cylindrical W or Mo electrode pairs, and a (3) Nb cylindrical cathode (32 mm diam) closed by a BN plate and a 50 mm diam W shower-head cup anode with either (a) an array of 1 mm diameter exit holes or (b) one 4 mm diam hole Ta cup anode. For Zr films, Vdep was 0.8 μm/min at a distance 110 mm from the electrode axis at 90 s after arc ignition. For W films at 60 s after ignition and the planar electrode configuration, Vdep was 0.6 μm/min at a distance of 60 mm from the electrode axis. For Nb films deposited with the closed electrode configuration, Vdep was 0.3 μm/min at distance 80 mm from the front shower anode surface at 30 s after arc ignition. For cylindrical Mo electrode pair Vdep was about 0.4 μm/min at a distance of 110 mm, 70 s after 200 A arc ignition.

Effective cathode voltage and ion current measurements in a Vacuum Arc with a Black Body Electrode Configuration

A new type of Vacuum Arc with a Black Body Assembly (VABBA) was studied to produce a directed plasma flux. The arc was contained in a closed cathode-anode assembly which confined and evaporated macroparticles (MPs) while the plasma was extracted through small anode apertures. Arc currents were I=175-250 A and arc time 90 s. The effective cathode voltage Ucef was determined by calorimetrically using a thermocouple probe. The ion current Ii was measured by an electrical probe. It was observed that Ucef increased with time from ~6.5 V for cold anodes (i.e for a conventional cathodic arc) to a steady state value of ~11.2-11.7 V when the anode was sufficiently hot and the arc operated in the VABBA mode. Ii decreased with distance from the anode. The expanding Cu plasma flux from a VABBA with a shower-head anode produced thin films on glass substrates with a deposition rate of 3μm/min.

Temperature distribution dependence on refractory anode thickness in a vacuum arc

The time dependent anode temperature was measured in a hot refractory anode vacuum arc (HRAVA) sustained between a consumed water-cooled cylindrical Cu cathode and nonconsumed cylindrical W anodes with d=5, 10, 15, 20 and 30 mm thickness. Arc currents of I=130, 150, 175 and 200 A were applied for periods up to 210 s and an inter-electrode gap of 10 mm. The anode temperature was measured using high-temperature thermocouples at different points in the anode body. The visual radiation emitted by the plasma plume was recorded with a digital camera. The anode temperature increased with time, reaching a steady state value which slightly increased with arc current. When d was increased from 5 to 30 mm, the time for the anode front surface to reach the steady state increased from 40 to 140 s, while this temperature decreased from 2525 to 2325 K (I=175 A). Thus minimizing d advantageously minimizes the start-up transient when using the radially expanding HRAVA plasma plume for thin film deposition.