RF DELIVERY SYSTEM WITH DUAL MATCHING NETWORKS WITH CAPACITIVE TUNING AND POWER SWITCHING

Apparatus and method for delivering power to a substrate processing chamber may include a target and a substrate support pedestal disposed in the chamber, a pedestal impedance match device coupled between the substrate support pedestal and ground, wherein the pedestal impedance match device is configured to adjust a bias voltage on the substrate support pedestal, a target impedance match device coupled between the target and ground, wherein the target impedance match device is configured to adjust a bias voltage on the target, a switch electrically coupled to the pedestal impedance match device and the target impedance match device, a first RF power source coupled to the switch, wherein the switch is configured to direct high frequency voltage from the first RF power source to either the target or the substrate support pedestal, and a second RF power source coupled to the substrate support pedestal.

DETAILED DESCRIPTION

Embodiments of the present invention provide apparatus and methods to independently control a plasma density from during deposition and etch/resputtering processes in a PVD chamber. Specifically, in PVD chambers that operate in dual modes of deposition and etch, embodiments of the present invention advantageously provide power delivery apparatus and methods that use the same VHF generator for delivering power to either the target or pedestal via a high power/frequency switch. In addition, the plasma sheath voltage for a deposition process may be further controlled by a variable impedance to ground matching device coupled to the substrate support pedestal disposed in the PVD chamber, while the plasma sheath voltage for an etch process may be further controlled by a variable impedance to ground matching device coupled to a target disposed in the PVD chamber.

FIG. 1depicts a flow chart of a method100for processing a substrate in accordance with some embodiments of the present invention. The method100is described below with respect to the stages of depositing a metal-containing layer as depicted inFIG. 2. The method100may be performed in any suitable PVD process chamber having both DC and radio frequency (RF) power sources, such as process chamber300, described below and depicted inFIGS. 3 and 4.

The method100generally begins by providing a substrate200as shown inFIG. 2Ato a PVD chamber, for example the process chamber300. The substrate may include a blank substrate, such as having no features disposed thereon as illustrated inFIG. 2A. Alternatively, the substrate200may have features such as vias, trenches, or the like. In some embodiments the features may include a high aspect ratio feature201for, for example, as used in through silicon via (TSV) applications or the like, and as illustrated inFIG. 2B. As used herein, a high aspect ratio feature includes those features having a height to width aspect ratio of at least about 5:1. The substrate200may comprise one or more of silicon (Si), (SiO2), (SiN), or other dielectric materials, such as low k dielectric materials (i.e., k≦3.9), for example, such as ultra low k dielectric materials (i.e., k≦2.5). Further, the substrate200may comprise one or more of metals, metal alloys, or the like.

At102, RF power (such as from an RF power source318, described below) is applied at a VHF frequency to a target comprising metal disposed above the substrate200to form a plasma202from a plasma-forming gas. The target may be the target306discussed below. Further, the target may comprise one or more of metals, metal alloys, or the like, suitable for forming a metal-containing layer on the substrate200. For example, the target may comprise one or more of titanium (Ti), tantalum (Ta), copper (Cu), aluminum (Al), titanium nitride (TiN), aluminum nitride (AlN), aluminum oxide (Al2O3), cobalt (Co), tungsten (W), silicon (Si) or the like. The plasma-forming gas may include an inert gas, such as a noble gas, or other reactive gas. For example, non-limiting examples of suitable plasma-forming inert and and reactive gases may include argon (Ar), helium (He), xenon (Xe), neon (Ne), krypton (Kr), nitrogen (N2), oxygen (O2) or the like.

The RF power may be applied at a VHF frequency for one or more of forming the plasma from the plasma-forming gas and ionizing metal atoms sputtered from the target by the plasma. As used herein, a VHF frequency is a frequency in the range of from about 27 MHz to about 162 MHz. In some embodiments, the VHF frequency applied is about 60 MHz. Controlling the VHF frequency may facilitate control over the plasma density and/or the amount of ionization in metal atoms sputtered from the target. For example, increasing the VHF frequency may increase the plasma density and/or the amount of ionization in metal atoms sputtered from the target. The RF power applied to the target at102may be sufficient to sputter target material. However, optionally, at104, DC power may also be applied to the target to increase the rate at which material can be sputtered from the target, as discussed below.

At104, optionally, DC power may be applied to the target to direct the plasma202towards the target, for example, from a DC power source320coupled to the target306as described below. In some embodiments, the DC power may range from about 1 to about 2 kilowatts (kW). In some embodiments, the DC power may be about 1-5 kW, or approximately 2 kW. The DC power may be adjusted to control the deposition rate of sputtered metal atoms on the substrate. For example, increasing the DC power can result in increased interaction of the plasma with the target and increased sputtering of metal atoms from the target.

At106, metal atoms204are sputtered from the target using the plasma while maintaining a first pressure in the PVD chamber sufficient to ionize a predominant portion of metal atoms being sputtered from the target. For example, a predominant portion of metal atoms may range from about 60 to about 90 percent of the total number of metal atoms being sputtered by the plasma. The first pressure, in addition to the first RF power and the DC power applied, may be dependent on process chamber geometry (such as substrate size, target to substrate distance, and the like). For example, the first pressure may range from about 6 to about 140 millitorr (mT) in a chamber configured with a target to substrate gap of about 60 to 90 millimeters (mm). In some embodiments, the first pressure is about 100 mTorr. The first pressure in the chamber may be maintained by the flow rate of the plasma-forming gas and/or the flow rate of an additional gas, such as a reactive gas, which may be co-flowed with the plasma-forming gas. The first pressure may provide a high density of gas molecules between the target and the substrate200with which sputtered metal atoms204may collide and become ionized metal atoms206. Pressure may be additionally utilized to control the amount of ionization of metal atoms sputtered from the target. For example, increasing pressure in the target to substrate gap may increase the number of collisions with metal atoms and increase the amount of ionized metal atoms206.

At108, the plasma sheath voltage between the plasma and the substrate may be controlled to form a metal-containing layer210on one or more surfaces of the feature201while limiting overhang of the metal-containing layer210across a mouth203of the feature. The plasma sheath voltage may be controlled by various methods. In some embodiments, the plasma sheath voltage may be controlled by controlling impedance between the substrate and ground. For example, the chamber impedance can be controlled by a capacitance tuner coupled between the substrate support and ground, such as the capacitance tuner364discussed below and illustrated inFIG. 3.

At110, after deposition of the target material onto the substrate is completed, the RF power applied to the target at VHF frequency may be redirected to apply power to the substrate support at a second frequency to facilitate high voltage etching/resputtering of the metal-containing layer210deposited on the substrate. In some embodiments, the second frequency is typically the same as the first frequency. In other embodiments, the first and second frequencies may be different. In some embodiments, the redirecting of the RF power applied at VHF frequency is accomplished via a high power/frequency switch disposed in a target impedance match network, such as switch392disposed in target impedance match network363discussed below and illustrated inFIG. 3. In other embodiments, redirecting of the RF power applied at VHF frequency may be done using an impendence matching device such as, for example, pedestal match device365. For example, redirecting may be accomplished by setting the impedance of the path between RF power supply318and the substrate support pedestal302to either a high impedance or low impendence using an impendence matching device disposed between the VHF power supply and the pedestal or target. In some embodiments, the VHF frequency may be set at one or more of about 27.12, 40.68, 60, 81 or 162 MHz.

At112, a second RF power source may apply low frequency energy (e.g., a third frequency that is different from the first and second frequencies described above) to the substrate to facilitate high voltage etching/resputtering. In some embodiments, the low frequency supplied by the second RF source may be about 2 to about 13.56 MHz. In some embodiments, the VHF power at110may control plasma density and stabilize the plasma sheath voltage, while the lower frequency power at112supplies high voltage acceleration of the material species ions doing the etching.

At114, the plasma sheath voltage may be controlled during the high voltage etching/resputtering process by various methods. In some embodiments, the plasma sheath voltage may be controlled by controlling impedance between the target and ground. For example, the chamber impedance can be controlled by a capacitance tuner coupled between the target and ground, such as the capacitance tuner361discussed below and illustrated inFIG. 3. In other embodiments, the plasma sheath voltage may be controlled by controlling impedance between the substrate support and ground. The substrate support may contain an electrode that is smaller than the target electrode. Typically, controlling impedance at the smaller electrode has a greater affect on the sheath voltage. For example, the chamber impedance can be controlled by a capacitance tuner coupled between the substrate support and ground, such as the capacitance tuner364discussed below and illustrated inFIG. 3.

FIG. 3depicts a schematic, cross-sectional view of an exemplary physical vapor deposition chamber (process chamber300) in accordance with some embodiments of the present invention. Other PVD chambers may also be used with the inventive apparatus and methods disclosed herein. Examples of suitable PVD chambers are commercially available from Applied Materials, Inc., of Santa Clara, Calif. Other process chambers from other manufactures may also benefit from the inventive apparatus disclosed herein.

The process chamber300contains a substrate support pedestal302for receiving a substrate304thereon, and a sputtering source, such as a target306. The substrate support pedestal302may be located within a grounded enclosure wall308, which may be a chamber wall or a grounded shield.

In some embodiments, the process chamber may include an RF power source318to provide VHF power to either the target306or substrate support pedestal302(via switch392discussed below), a DC power source320to provide DC power to the target306, and a second RF bias power source362to provide low frequency power to the substrate support pedestal302. In some embodiments, RF energy supplied by the RF power source318may be a VHF frequency from about 27 MHz to about 162 MHz. For example, non-limiting frequencies of about 27 MHz, 40 MHz, 60 MHz, 81 MHz and 162 MHz (or other multiples of 13.56 MHz) can be used.

In some embodiments, the RF power supplied by the second RF bias power source362may range in frequency from about 0.5 MHz to about 13.56 MHz.

In some embodiments, the DC power source320may be utilized to apply a negative voltage, or bias, to the target306. The power supplied by DC power source320depends on the process running. For example, during an Etch process, DC power would not be supplied as it is not needed. In other processes, such as deposition processes for example, the DC power is used to help sputter the target material. In some embodiments, the DC power supplied may range from 100 Watts to about 2000 Watts. In some embodiments, the DC power supplied would be about a quarter of the RF power supplied for a given process.

In some embodiments, a plurality of RF power sources may be provided (i.e., two or more) to provide RF energy in a plurality of the above frequencies to each of the target306or the substrate support pedestal302. The RF and DC energy may be supplied to the target and/or substrate support pedestal via feed structures that may be fabricated from suitable conductive materials to conduct the RF and DC energy from the RF power sources318and362, and the DC power source320.

In some embodiments, the feed structure may have a suitable length that facilitates substantially uniform distribution of the respective RF and DC energy about the perimeter of the feed structure. For example, in some embodiments, the feed structure may have a length of between about 1 to about 12 inches, or about 4 inches. In some embodiments, the body may have a length to inner diameter ratio of at least about 1:1. Providing a ratio of at least 1:1 or longer provides for more uniform RF delivery from the feed structure (i.e., the RF energy is more uniformly distributed about the feed structure to approximate RF coupling to the true center point of the feed structure. The inner diameter of the feed structure may be as small as possible, for example, from about 1 inch to about 6 inches, or about 4 inches in diameter. Providing a smaller inner diameter facilitates improving the length to ID ratio without increasing the length of the feed structure.

RF power source318and DC power source320may be coupled to target306(via the feed structure) through target impedance match device363. The target impedance match device363may be coupled to the target for adjusting voltage on the target306and controlling the RF bias power of the target306. The target impedance match device363may include a variable capacitance tuner362to ground for controlling the impedance. In addition, in some embodiments, target impedance match device363may include a high power/frequency switch392that can direct VHF energy from RF power source318to either the target306(e.g., for a deposition process) or the substrate support pedestal302through a pedestal match device365(e.g., for an etch/resputtering process) as desired. Thus, as shown inFIG. 3, the target impedance match device363may be coupled to a pedestal match device365. A controller310(discussed below in more detail) may be used to control switch392to direct VHF energy from RF power source318to either the target306(e.g., for a deposition process) or the substrate support pedestal302(e.g., for an etch/resputtering process) as desired. Although switch392is shown as part of target impedance match device363, switch392may included in pedestal match device365, or disposed at any point between target impedance match device363and pedestal match device365.

In other embodiments, redirecting of the RF power applied at VHF frequency may optionally be done using pedestal match device365. For example, redirecting may be accomplished by setting the impedance of the path (e.g., path398inFIG. 3) between RF power supply318and the substrate support pedestal302to either a high impedance or low impendence using an impendence matching device disposed between the VHF power supply and the pedestal or target.

The pedestal match device365may include a variable capacitance tuner364to ground that is coupled to the substrate support pedestal for adjusting a bias voltage on the substrate304.

FIG. 4depicts another schematic, cross-sectional view of an exemplary physical vapor deposition chamber (process chamber300) that may be used with embodiments the inventive apparatus and methods disclosed herein.

The target306may be coupled to source distribution plate422via conductive member427. The source distribution plate includes a hole424disposed through the source distribution plate422and aligned with a central opening of the feed structure. The source distribution plate422may be fabricated from suitable conductive materials to conduct the RF and DC energy from the feed structure. The source distribution plate422may be coupled to the target406via a conductive member425. The conductive member425may be a tubular member having a first end426coupled to a target-facing surface428of the source distribution plate422proximate the peripheral edge of the source distribution plate422. The conductive member425further includes a second end430coupled to a source distribution plate-facing surface432of the target306(or to the backing plate446of the target406) proximate the peripheral edge of the target306.

A cavity434may be defined by the inner-facing walls of the conductive member425, the target-facing surface428of the source distribution plate422and the source distribution plate-facing surface432of the target306. The cavity434is coupled to the central opening415of the body via the hole424of the source distribution plate422. The cavity434and the central opening415of the body may be utilized to at least partially house one or more portions of a rotatable magnetron assembly436as illustrated inFIG. 4and described further below. In some embodiments, the cavity may be at least partially filled with a cooling fluid, such as water (H2O) or the like.

A ground shield440may be provided to cover the outside surfaces of the lid of the process chamber300. The ground shield440may be coupled to ground, for example, via the ground connection of the chamber body. The ground shield440has a central opening to allow the feed structure to pass through the ground shield440to be coupled to the source distribution plate422. The ground shield440may comprise any suitable conductive material, such as aluminum, copper, or the like. An insulative gap439is provided between the ground shield440and the outer surfaces of the distribution plate422, the conductive member425, and the target306(and/or backing plate446) to prevent the RF and DC energy from being routed directly to ground. The insulative gap may be filled with air or some other suitable dielectric material, such as a ceramic, a plastic, or the like.

In some embodiments, a ground collar may be disposed about the body and lower portion of the feed structure. The ground collar is coupled to the ground shield440and may be an integral part of the ground shield440or a separate part coupled to the ground shield to provide grounding of the feed structure. The ground collar440may be made from a suitable conductive material, such as aluminum or copper. In some embodiments, a gap disposed between the inner diameter of the ground collar and the outer diameter of the body of the feed structure may be kept to a minimum and be just enough to provide electrical isolation. The gap can be filled with isolating material like plastic or ceramic or can be an air gap. The ground collar prevents cross-talk between the RF feed and the body, thereby improving plasma, and processing, uniformity.

An isolator plate438may be disposed between the source distribution plate422and the ground shield440to prevent the RF and DC energy from being routed directly to ground. The isolator plate438has a central opening to allow the feed structure to pass through the isolator plate438and be coupled to the source distribution plate422. The isolator plate438may comprise a suitable dielectric material, such as a ceramic, a plastic, or the like. Alternatively, an air gap may be provided in place of the isolator plate438. In embodiments where an air gap is provided in place of the isolator plate, the ground shield440may be structurally sound enough to support any components resting upon the ground shield440.

The target306may be supported on a grounded conductive aluminum adapter442through a dielectric isolator444. The target306comprises a material to be deposited on the substrate304during sputtering, such a metal or metal oxide. In some embodiments, the backing plate446may be coupled to the source distribution plate-facing surface432of the target306. The backing plate446may comprise a conductive material, such as copper-zinc, copper-chrome, or the same material as the target, such that RF and DC power can be coupled to the target306via the backing plate446. Alternatively, the backing plate446may be non-conductive and may include conductive elements (not shown) such as electrical feedthroughs or the like for coupling the source distribution plate-facing surface432of the target306to the second end430of the conductive member425. The backing plate446may be included for example, to improve structural stability of the target306.

The substrate support pedestal302has a material-receiving surface facing the principal surface of the target306and supports the substrate304to be sputter coated in planar position opposite to the principal surface of the target306. The substrate support pedestal302may support the substrate304in a central region448of the process chamber300. The central region448is defined as the region above the substrate support pedestal302during processing (for example, between the target306and the substrate support pedestal302when in a processing position).

In some embodiments, the substrate support pedestal302may be vertically movable through a bellows450connected to a bottom chamber wall452to allow the substrate304to be transferred onto the substrate support pedestal302through a load lock valve (not shown) in the lower portion of processing the chamber300and thereafter raised to a deposition, or processing position. Chamber wall452may connected to ground394. One or more processing gases may be supplied from a gas source454through a mass flow controller456into the lower part of the chamber300. An exhaust port458may be provided and coupled to a pump (not shown) via a valve460for exhausting the interior of the process chamber300and facilitating maintaining a desired pressure inside the process chamber300.

A rotatable magnetron assembly436may be positioned proximate a back surface (e.g., source distribution plate-facing surface432) of the target306. The rotatable magnetron assembly436includes a plurality of magnets466supported by a base plate468. The base plate468connects to a rotation shaft470coincident with the central axis of the chamber300and the substrate304as illustrated inFIG. 4. However, this design of the magnetron assembly is merely one exemplary embodiment. For example, other designs may include a rotatable magnetron assembly that is disposed off axis with respect to the central axis of the chamber and the substrate.

A motor472can be coupled to the upper end of the rotation shaft470to drive rotation of the magnetron assembly436. The magnets466produce a magnetic field within the chamber300, generally parallel and close to the surface of the target306to trap electrons and increase the local plasma density, which in turn increases the sputtering rate. The magnets466produce an electromagnetic field around the top of the chamber300, and magnets466are rotated to rotate the electromagnetic field which influences the plasma density of the process to more uniformly sputter the target306. For example, the rotation shaft470may make about 0 to about 150 rotations per minute.

In some embodiments, the chamber300may further include a process kit shield474connected to a ledge476of the adapter442. The adapter442in turn is sealed and grounded to the aluminum chamber sidewall308. Generally, the process kit shield474extends downwardly along the walls of the adapter442and the chamber wall308downwardly to below an upper surface of the substrate support pedestal302and returns upwardly until reaching an upper surface of the substrate support pedestal302(e.g., forming a u-shaped portion484at the bottom). Alternatively, the bottommost portion of the process kit shield need not be a u-shaped portion484and may have any suitable shape. In some embodiments, process kit shield474may be grounded. A cover ring486rests on the top of an upwardly extending lip488of the process kit shield474when the substrate support pedestal302is in its lower, loading position but rests on the outer periphery of the substrate support pedestal302when it is in its upper, deposition position to protect the substrate support pedestal302from sputter deposition. An additional deposition ring (not shown) may be used to shield the periphery of the substrate304from deposition. In some embodiments, a capacitance tuner (not shown) may be coupled to the process kit shield for adjusting voltage on the shield474. The capacitance tuner (not shown) may be utilized, for example, to direct ion flow towards the shield474and/or in combination with the capacitance tuners364and/or361to control the energy and direction of ion flow.

In some embodiments, a magnet490may be disposed about the chamber300for selectively providing a magnetic field between the substrate support pedestal302and the target306. For example, as shown inFIG. 4, the magnet490may be disposed about the outside of the chamber wall308in a region just above the substrate support pedestal302when in processing position. In some embodiments, the magnet490may be disposed additionally or alternatively in other locations, such as adjacent the adapter442. The magnet490may be an electromagnet and may be coupled to a power source (not shown) for controlling the magnitude of the magnetic field generated by the electromagnet.

A controller310may be provided and coupled to various components of the process chamber300to control the operation thereof. The controller310includes a central processing unit (CPU)412, a memory414, and support circuits416. The controller310may control the process chamber300directly, or via computers (or controllers) associated with particular process chamber and/or support system components. The controller310may be one of any form of general-purpose computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory, or computer readable medium,434of the controller310may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, optical storage media (e.g., compact disc or digital video disc), flash drive, or any other form of digital storage, local or remote. The support circuits416are coupled to the CPU412for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. Inventive methods as described herein may be stored in the memory414as software routine that may be executed or invoked to control the operation of the process chamber300in the manner described herein. The software routine may also be stored and/or executed by a second CPU (not shown) that is remotely located from the hardware being controlled by the CPU412.