Pulsed DC Power For Deposition Of Film

A vapor deposition system and methods of operation thereof are disclosed. The vapor deposition system includes a vacuum chamber; a dielectric target within the vacuum chamber, the dielectric target having a front surface and a thickness; a substrate support within the vacuum chamber, the substrate support having a front surface spaced from the front surface of the dielectric target to form a process gap; and a signal generator connected to the dielectric target to generate a plasma in the vacuum chamber, the signal generator comprises a power source, the power source configured to prevent charge accumulation in the dielectric target. The method includes applying power to a dielectric target within a vacuum chamber to generate a plasma in a process gap between the dielectric target and a substrate support and pulsing the power applied to the dielectric target to prevent charge accumulation.

TECHNICAL FIELD

Embodiments of the disclosure generally relate to methods for depositing a film on a substrate. In particular, embodiments of the disclosure are directed to methods of depositing a dielectric film on a substrate.

BACKGROUND

Sputtering, alternatively called physical vapor deposition (PVD), has long been used for the deposition of metals and related materials in the fabrication of semiconductor integrated circuits. Use of sputtering has been extended to depositing metal layers onto the sidewalls of high aspect-ratio holes such as vias or other vertical interconnect structures, as well as in the manufacture of extreme ultraviolet (EUV) mask blanks. In the manufacture of EUV mask blanks minimization of particle generation is desired, because particles negatively affect the properties of the final product.

Plasma sputtering may be accomplished using either DC sputtering or RF sputtering. Plasma sputtering typically includes a magnetron positioned at the back of the sputtering target including two magnets of opposing poles magnetically coupled at their back through a magnetic yoke to project a magnetic field into the processing space to increase the density of the plasma and enhance the sputtering rate from a front face of the target. Magnets used in the magnetron are typically closed loop for DC sputtering and open loop for RF sputtering.

In plasma enhanced substrate processing systems, such as physical vapor deposition (PVD) chambers, high power density PVD sputtering with high magnetic fields and high DC power can produce high energy at a sputtering target, and cause a large rise in surface temperature of the sputtering target. The sputtering target is cooled by contacting a target backing plate with cooling fluid. In plasma sputtering as typically practiced commercially, a target of the material to be sputter deposited is sealed to a vacuum chamber containing the substrate to be coated. Argon is admitted to the chamber. When a negative DC bias of several hundred volts is applied to target while the chamber walls or shields remain grounded, the argon is excited into a plasma. The positively charged argon ions are attracted to the negatively biased target at high energy and sputter target atoms from the target.

While advancements in PVD chamber design have been made, there remains a need of method depositing dielectric film and preventing excessive charge accumulation on dielectric target.

SUMMARY

One or more embodiments of the disclosure are directed to a vapor deposition apparatus. In one or more embodiments, the vapor deposition apparatus comprises a vacuum chamber, a dielectric target within the vacuum chamber, a substrate support within the vacuum chamber, and a signal generator connected to the dielectric target to generate a plasma in the vacuum chamber. In some embodiments, the dielectric target has a front surface and a thickness. In some embodiments, the substrate support has a front surface spaced from the front surface of the dielectric target to form a process gap. In some embodiments, the signal generator is configured to prevent charge accumulation in the dielectric target.

Another embodiment of the disclosure is directed to a method of depositing a dielectric film. In some embodiments, the method comprises applying power to a dielectric target within a vacuum chamber to generate a plasma in a process gap between the dielectric target and a substrate support, and pulsing the power applied to the dielectric target to prevent charge accumulation.

DETAILED DESCRIPTION

Embodiments of the disclosure generally relate to methods and apparatus for depositing a film using a physical vapor deposition (PVD) process. According to some embodiments of the disclosure, a PVD film comprises a dielectric film.

FIG. 1describes an exemplary method100for depositing a film. In some embodiments, the method comprises a vapor deposition method. In some embodiments, the vapor deposition method comprises a physical vapor deposition (PVD) process or a variant thereof.

In one or more embodiments, the method100includes an optional pre-treatment operation110. During the pre-treatment, a substrate is treated with any suitable pre-treatment known to the skilled artisan. Suitable pre-treatments include, but are not limited to, pre-heating, cleaning, soaking, native oxide removal, or deposition of an adhesion layer and/or barrier layer.

Some embodiments of the disclosure are directed to apparatus for depositing a film. In some embodiments, the physical vapor deposition process is performed in any suitable apparatus. In some embodiments, the suitable apparatus comprises a physical vapor deposition system.

In some embodiments, the physical vapor deposition system comprises a vacuum deposition system. In some embodiments, the vacuum deposition system is configured for magnetron sputtering, ion sputtering, pulsed laser deposition, cathode arc deposition, or a combination thereof. In some embodiments, the vacuum deposition system comprises a magnetron sputtering system configured to form a film on the substrate by magnetron sputtering.

In some embodiments, a variety of dielectric films can be deposited with a suitable target in the same chamber configuration. In some embodiments, the methods are performed in existing deposition chambers. Accordingly, embodiments of the disclosure advantageously provide methods that are versatile and do not require changing hardware to control target bias through anode/cathode area ratio tuning.

An exemplary physical vapor deposition system200, useful for the methods of one or more embodiments, is illustrated inFIG. 2. The physical vapor deposition system200comprises a vacuum chamber252, a target256within the vacuum chamber252, a substrate support280within the vacuum chamber252and a signal generator286connected to the target256.

The vacuum chamber252is arranged about a central axis254on which the target256is supported through an isolator258, which vacuum seals the target256to the vacuum chamber252. The isolator258electrically isolates the target256from the electrically grounded vacuum chamber252. A vacuum pump system (not shown) pumps the interior of the vacuum chamber252to a pressure in the low milliTorr range. In some embodiments, the vacuum chamber252has a pressure in a range of from 1 milliTorr to 30 milliTorr, from 5 milliTorr to 30 milliTorr, from 10 milliTorr to 30 milliTorr, from 20 milliTorr to 30 milliTorr, from 1 milliTorr to 20 milliTorr, from 5 milliTorr to 20 milliTorr, from 10 milliTorr to 20 milliTorr, from 1 milliTorr to 10 milliTorr, from 5 milliTorr to 10 milliTorr or from 1 milliTorr to 5 milliTorr.

In one or more embodiments, the shape of the front surface of the target256can be planar or generally concave with thicker outer peripheral edges than inner diameter portions. The target256includes a layer of material facing the interior of the vacuum chamber252and which typically contains no more than 5 atomic % of elements other than the material to be deposited to provide a source of sputtered material.

The signal generator286comprises a power source260. In some embodiments, the signal generator286further comprises a waveform generator267operatively connected to the power source260. In some embodiments, the signal generator286applies power to bias the target256. In some embodiments, the power source260comprises a DC power source. In some embodiments, the DC power source biases the target with respect to the grounded vacuum chamber252or grounded sidewall shield (not shown) to excite a plasma gas into a plasma. In some embodiments, the target256is more negatively biased than the vacuum chamber252or sidewall shield (not shown).

At120inFIG. 1, the method100comprises applying a power to the target256. In some embodiments, the power comprises a DC power. In some embodiments, the target256comprises dielectric target.

Without being bound by any specific theory of operation, it is believed that simple DC sputtering of dielectrics is not possible due to insulating nature of the target. The nature of the target256results in accumulation of charges on the target surface to produce high potential build-up between target surface, chamber walls and/or substrate. The arc can damage the film, substrate, vacuum chamber components and/or power supply.

A reactive pulsed DC sputtering may be considered as a type of alternating current (AC) sputtering with not necessarily equal positive and negative half cycles and having a square waveform instead of sinusoidal. Reactive pulsed DC sputtering uses alloy targets. However, reactive pulsed DC sputtering from alloy targets is difficult for stoichiometry control. Whereas, depositing using RF sputter deposition from compound targets can be difficult to control too, especially where precise control of target bias, film properties, etc. is required due to the difficulty in tuning RF plasma. Thus, there is need to provide apparatus and methods to achieve the stoichiometry close to a desired range

The present disclosure describes embodiments of method100, the method100comprises using pulsed DC waveform, wherein the ON and OFF voltage and/or duty cycles are independently controlled depending upon the impedance of the target and chamber geometry. In one or more embodiments, the disclosure provides methods of using dielectric targets and pulsed DC sputtering to produce a waveform. In some embodiments, the waveform is shaped by one or more of a voltage, a duty cycle or a frequency.

In some embodiments, a pulsing power is applied to the target256. In some embodiments, the pulsing power comprises a pulsing DC power. In some embodiments, the target256is being applied the pulsing DC power. In some embodiments, the dielectric target comprises lead zirconate titanate (PZT), lead magnesium niobate-lead titanate (PMN-PT), aluminium oxide (Al2O3), lithium niobate (LiNbO3) or combination thereof. In some embodiments, the target256can be any suitable dielectric material known to one skilled in the art.

In some embodiments, the target256is maintained at a temperature in a range of from 0° C. to 60° C., from 20° C. to 60° C., from 40° C. to 60° C., from 0° C. to 40° C., from 20° C. to 40° C. or from 0° C. to 20° C.

Referring back toFIG. 2, in one or more embodiments, the signal generator286is configured to generate the pulsing DC power. In some embodiments, the pulsing DC power comprises a pulsed DC waveform. In some embodiments, the signal generator286is configured to prevent charge accumulation. In some embodiments, the pulsed DC waveform is generated at a frequency in a range of from 10 kHz to 500 kHz, from 50 kHz to 500 kHz, from 100 kHz to 500 kHz, from 250 kHz to 500 kHz, from 10 kHz to 250 kHz, from 50 kHz to 250 kHz, from 100 kHz to 250 kHz, from 10 kHz to 100 kHz, from 50 kHz to 100 kHz or from 10 kHz to 50 kHz. In some embodiments, the pulsed DC waveform has a duty cycle in a range of from greater than 0 to 0.6, from greater than 0 to 0.5, from greater than 0 to 0.4, from greater than 0 to 0.3, from greater than 0 to 0.2 or from greater than 0 to 0.1. In some embodiments, the pulsed DC waveform has a duty cycle in a range of from greater than 0 to less than 0.6, from greater than 0 to less than 0.5, from greater than 0 to less than 0.4, from greater than 0 to less than 0.3, from greater than 0 to less than 0.2 or from greater than 0 to less than 0.1. In some embodiments, the pulsed DC waveform comprises a plurality of ON pulses and OFF pulses. In some embodiments, each of the ON pulses has ON time. In some embodiments, each of the OFF pulses has OFF time.

In some embodiments, the pulsed DC power has an ON voltage and an OFF voltage. In some embodiments, the ON voltage is in a range of from greater than 9 V to 1500 V, from greater than 10 V to 1500 V, from greater than 50 V to 1500 V, from greater than 100 V to 1500 V, from greater than 500 V to 1500 V or from greater than 1000 V to 1500 V.

In some embodiments, the pulsed DC waveform has an ON time and an OFF time. In some embodiments, each of the ON time and the OFF time independently having in a range of from 1 μs to 50 μs, from 10 μs to 50 μs, from 25 μs to 50 μs, from 1 μs to 25 μs, from 10 μs to 25 μs or from 1 μs to 10 μs.

In some embodiments, the waveform generator267produces independently equal positive or negative half cycles. In some embodiments, the waveform generator267produces independently unequal negative half cycles. In some embodiments, the waveform generator267produces a square waveform. In some embodiments, the waveform generator267does not produce sinusoidal waveform.

At130, the power supplied by the DC power source260to the target256excites the plasma processing gas into a plasma. In some embodiments, the plasma is generated in a process gap. The process gap is a gap between the target256and the substrate support280. The plasma comprises positively charged ions of the plasma gas. In some embodiments, the plasma gas is supplied in the vacuum chamber252from a gas source262through a mass flow controller264. In some embodiments, the plasma gas is supplied in a range of from 2 sccm to 100 sccm, from 20 sccm to 100 sccm, from 50 sccm to 100 sccm, from 75 sccm to 100 sccm, from 2 sccm to 75 sccm, from 20 sccm to 75 sccm, from 50 sccm to 75 sccm, from 2 sccm to 50 sccm, from 20 sccm to 50 sccm or from 2 sccm to 20 sccm. In some embodiments, the plasma gas maintains a pressure inside the vacuum chamber252. In some embodiments, the plasma gas maintains a pressure inside the vacuum chamber252in a range of from 1 milliTorr to 30 milliTorr, from 5 milliTorr to 30 milliTorr, from 10 milliTorr to 30 milliTorr, from 20 milliTorr to 30 milliTorr, from 1 milliTorr to 20 milliTorr, from 5 milliTorr to 20 milliTorr, from 10 milliTorr to 20 milliTorr, from 1 milliTorr to 10 milliTorr, from 5 milliTorr to 10 milliTorr or from 1 milliTorr to 5 milliTorr. In some embodiments, the substrate support280is maintained at a temperature in a range of from 15° C. to 1000° C., from 50° C. to 1000° C., from 100° C. to 1000° C., from 250° C. to 1000° C., from 500° C. to 1000° C., from 750° C. to 1000° C., from 15° C. to 750° C., from 50° C. to 750° C., from 100° C. to 750° C., from 250° C. to 750° C., from 500° C. to 750° C., from 15° C. to 500° C., from 50° C. to 500° C., from 100° C. to 500° C., from 250° C. to 500° C., from 15° C. to 250° C., from 50° C. to 250° C., from 100° C. to 250° C., from 15° C. to 100° C., from 50° C. to 100° C. or from 15° C. to 50° C.

In one or more embodiments, the plasma gas comprises one or more of helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe). In some embodiments, the plasma gas comprises one or more of helium (He), neon (Ne), or argon (Ar).

At140, positively charged ions of the plasma are accelerated towards the target256and sputter material from the target256. The density of the plasma is increased by placing in back of the target256a magnetron266having an inner magnetic pole268of one magnetic polarity surrounded by an outer magnetic pole270of the opposed magnetic polarity. The poles268,270project a magnetic field into the vacuum chamber252parallel to the face of the target256to trap electrons and hence increase the plasma density and the resultant sputtering rate. To improve the sputtering uniformity and target utilization, the magnetic poles268,270are asymmetric about the central axis254but supported on an arm272connected to a shaft274extending along the central axis254. A motor276rotates the shaft274and hence the magnetron266about the central axis254to provide at least azimuthal uniformity.

In RF sputtering, the alternating nature of the power means the depleted electrons due to ion bombardment are replenished at periodic intervals and the plasma can be sustained. Due to the difference in mobilities of process gas ions and electrons in the plasma at the high frequencies, the target develops a net negative bias and attracts the positive gas ions towards its surface, which sputter the films. This approach involves using oversized chambers to adjust the anode/cathode ratio which dictates the negative self-bias developed on the target. However, RF plasma is difficult to control because magnitude of target self-bias is dependent on anode/cathode ratio and can change with impedance of chamber kits with time. Another approach includes use of pulsed laser deposition technology, which is still best-suited for lab-scale samples and difficult to scale up.

In some embodiments, the signal generator286produces pulsed DC sputtering. In some embodiments, the signal generator286further comprise process knobs. In some embodiments, the process knobs produce pulsed DC sputtering. In some embodiments, the process knobs comprise one or more of: (A) DC power level (ON); (B) DC power level (OFF); (C) ON pulse width (TON); (D) OFF pulse width (TOFF); (E) Duty Cycle (TON/(TON+TOFF)); and (F) Frequency of pulsing (1/(TON+TOFF)). In some embodiments, the (A) DC power level (ON), (B) DC power level (OFF), (C) ON pulse width (TON), and (D) OFF pulse width (TOFF) are independent variables. In some embodiments, (E) Duty Cycle (TON/(TON+TOFF)) and (F) Frequency of pulsing (1/(TON+TOFF)) are dependent on (C) ON pulse width (TON), and (D) OFF pulse width (TOFF).

At150inFIG. 1, the method100comprises depositing a film.FIG. 2shows a substrate support280within the vacuum chamber252supports a substrate282in opposition to the target256. The substrate282is deposited with the film of a material sputtered from the target256. In some embodiments, the substrate282can be any suitable material known to one skilled in the art. In some embodiments, the substrate comprises glass, sapphire, quartz, SrTiO3, LaAlO3, Si, SiO2-coated Si or combinations thereof. In some embodiments, the substrate comprises any suitable material known to one skilled in the art. In some embodiments, the substrate is maintained at a temperature in a range of from 15° C. to 1000° C., from 50° C. to 1000° C., from 100° C. to 1000° C., from 250° C. to 1000° C., from 500° C. to 1000° C., from 750° C. to 1000° C., from 15° C. to 750° C., from 50° C. to 750° C., from 100° C. to 750° C., from 250° C. to 750° C., from 500° C. to 750° C., from 15° C. to 500° C., from 50° C. to 500° C., from 100° C. to 500° C., from 250° C. to 500° C., from 15° C. to 250° C., from 50° C. to 250° C., from 100° C. to 250° C., from 15° C. to 100° C., from 50° C. to 100° C. or from 15° C. to 50° C.

In some embodiments, a reverse bias source284is operatively connected to the substrate support280. In some embodiments, the reverse bias source284is an AC power, a DC power or an RF power. In some embodiments, the substrate support280is conductive. In some embodiments, the substrate support280acts as an electrode. In some embodiments, the reverse bias source284applies reverse bias to the substrate support280. The negative DC bias on the substrate support280causes sputtered ions to accelerate towards the substrate282and their trajectories enter deep within any high aspect-ratio holes or features formed in the substrate282. In some embodiments, the reverse bias is applied in a range of from 0 V to 225 V, 0 V to 200 V, from 20 V to 200 V, from 50 V to 200 V, from 100 V to 200 V, from 150 V to 200 V, from 0 V to 150 V, from 20 V to 150 V, from 50 V to 150 V, from 100 V to 150 V, from 0 V to 100 V, from 20 V to 100 V, from 50 V to 100 V, from 0 V to 50 V, from 20 V to 50 V or from 0 V to 20 V.

Operation of the physical vapor deposition system200is controlled by a controller240. The controller240is coupled to one or more of the motor276, the DC power source260, the signal generator286, the wave generator267or the mass flow controller264. In some embodiments, there are more than one controller240connected to the individual components and a primary control processor is coupled to each of the separate processors to control the physical vapor deposition system200. The controller240may be one of any form of general-purpose computer processor, microcontroller, microprocessor, etc., that can be used in an industrial setting for controlling various chambers and sub-processors.

The at least one controller240can have a processor242, a memory244coupled to the processor242, input/output devices246coupled to the processor242, and support circuits248for communication between the different electronic components. The memory244can include one or more of transitory memory (e.g., random access memory) and non-transitory memory (e.g., storage).

The memory244, or computer-readable medium, of the processor may be one or more of readily available memory such as random access memory (RAM), read-only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The memory244can retain an instruction set that is operable by the processor242to control parameters and components of the physical vapor deposition chamber200. The support circuits248are coupled to the processor242for supporting the processor in a conventional manner. Circuits may include, for example, cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like.

Processes may generally be stored in the memory as a software routine that, when executed by the processor, causes the process chamber to perform processes of the present disclosure. The software routine may also be stored and/or executed by a second processor (not shown) that is remotely located from the hardware being controlled by the processor. Some or all of the method of the disclosure may also be performed in hardware. As such, the process may be implemented in software and executed using a computer system, in hardware as, e.g., an application specific integrated circuit or other type of hardware implementation, or as a combination of software and hardware. The software routine, when executed by the processor, transforms the general purpose computer into a specific purpose computer (controller) that controls the chamber operation such that the processes are performed.

In some embodiments, the controller240has one or more configurations to execute individual processes or sub-processes to perform the method. The controller240can be connected to and configured to operate intermediate components to perform the functions of the methods. For example, the controller240can be connected to and configured to control one or more of gas valves, actuators, motors, slit valves, vacuum control, etc.

The controller240of some embodiments has one or more configurations selected from: a configuration to rotate shaft274; a configuration to bias the target256; a configuration to bias the substrate282; a configuration to apply a waveform to the substrate bias; or a configuration to control the flow of the plasma gas.

At decision160, the thickness of the deposited film, or number of duty cycles is considered. If the deposited film has reached a predetermined thickness or a predetermined number of duty cycles have been performed, the method100moves to an optional post-processing operation160. If the thickness of the deposited film or the number of duty cycles has not reached the predetermined threshold, the method100returns to operation120, and continuing.

The optional post-processing operation170can be, for example, a process to modify film properties (e.g., annealing) or a further film deposition process (e.g., additional ALD or CVD processes) to grow additional films. In some embodiments, the optional post-processing operation170can be a process that modifies a property of the deposited film. In some embodiments, the optional post-processing operation170comprises annealing the as-deposited film. In some embodiments, annealing is done at temperatures in the range of from 300° C. to 1000° C., from 500° C. to 1000° C., from 800° C. to 1000° C., from 300° C. to 800° C., from 500° C. or 800° C. or from 300° C. to 500° C. The annealing environment of some embodiments comprises one or more of an inert gas (e.g., molecular nitrogen (N2), argon (Ar)) or a reducing gas (e.g., molecular hydrogen (H2) or ammonia (NH3)) or an oxidant, such as, but not limited to, oxygen (O2), ozone (O3), or peroxides. In one or more embodiments, the oxidant comprises complex oxides. In some embodiments, the complex oxides comprises BaTiO3. Annealing can be performed for any suitable length of time. In some embodiments, the film is annealed for a predetermined time in the range of from 15 seconds to 6 hours, from 1 minute to 6 hours, from 30 minutes to 6 hours, from 1 hour to 6 hours, from 2 hours to 6 hours, from 4 hour to 6 hours, from 15 seconds to 4 hours, from 1 minute to 4 hours, from 30 minutes to 4 hours, from 1 hour to 4 hours, from 2 hours to 4 hours, from 15 seconds to 2 hours, from 1 minute to 2 hours, from 30 minutes to 2 hours, from 1 hour to 2 hours, from 15 seconds to 1 hour, from 1 minute to 1 hour, from 30 minutes to 1 hour, from 15 seconds to 30 minutes, from 1 minute to 30 minutes or from 15 seconds to 1 minute. In some embodiments, annealing the as-deposited film increases the density, increases the resistivity, decreases the resistivity and/or increases the purity of the film. In one or more embodiments, annealing can also with performed with a gas under plasma. In one or more embodiments, annealing the as-deposited film in the presence of a complex oxides decreases the resistivity of the film. In one or more embodiments, annealing the as-deposited film in the presence of a complex oxides decreases number of oxygen vacancies.

In one or more embodiments, the method100is run in a power mode with power being the set-points. In one or more embodiments, the method100is run in a current mode with current being the set-points. In one or more embodiments, the method100is run in a voltage mode with voltage being the set-points. In one or more embodiments, the method100is run in a power, a current or a voltage mode, with power, current or voltage being the set-points, respectively.

In one or more embodiments, the plasma may be generated remotely or within the processing chamber. In one or more embodiments, the plasma is an inductively coupled plasma (ICP) or a conductively coupled plasma (CCP). Any suitable power can be used depending on, for example, the reactants, or the other process conditions. In some embodiments, the plasma is generated with a plasma power in the range of from 10 W to 3000 W. In some embodiments, the plasma is generated with a plasma power less than or equal to 3000 W, less than or equal to 2000 W, less than or equal to 1000 W, less than or equal to 500 W, or less than or equal to 250 W.

In some embodiments, the dielectric film formed comprises dielectric. In some embodiments, the dielectric film consists essentially of dielectric. As used in this manner, the term “consists essentially of dielectric” means that the dielectric film has greater than or equal to 80%, 85%, 90%, 95%, 98%, 99% or 99.5% of dielectric on an volume basis. Measurements of the composition of the dielectric film refer to the bulk portion of the film, excluding interface regions where diffusion of elements from adjacent films may occur.

One or more embodiments of the disclosure are directed to methods of depositing dielectric films in high aspect ratio features. A high aspect ratio feature is a trench, via or pillar having a height:width ratio greater than or equal to 10, 20, or 50, or more. In some embodiments, the dielectric film is deposited conformally on the high aspect ratio feature. As used in this manner, a conformal film has a thickness near the top of the feature that is in the range of 80-120% of the thickness at the bottom of the feature.

Some embodiments of the disclosure are directed to methods for bottom-up gapfill of a feature. A bottom-up gapfill process fills the feature from the bottom versus a conformal process which fills the feature from the bottom and sides. In some embodiments, the feature has a first material at the bottom and a second material at the sidewalls. The dielectric film deposits selectively on the first material relative to the second material so that the metal film fills the feature in a bottom-up manner.

Embodiments of the disclosure pertain to a deposition system, for example a physical vapor deposition (“PVD”) chamber. In one or more embodiments, the PVD chamber comprising at least one cathode assembly, and in particular embodiments, a PVD chamber comprising multiple cathode assemblies (referred to herein as a “multi-cathode chamber).