Deposition system with shield mount

A deposition system and a method of operation thereof are disclosed. A PVD chamber is disclosed comprising a plurality of cathode assemblies, a rotating shield below the plurality of cathode assemblies to expose one of the plurality cathode assemblies through the shroud and through a shield hole of the shield, the shield comprising a top surface including a raised peripheral frame. A shield mount sized and shaped to engage with the raised peripheral frame to secure the shield mount to the shield.

TECHNICAL FIELD

The present disclosure relates generally to substrate processing systems, and more specifically, to deposition systems with multiple cathode assemblies (multi-cathodes) having a shield mount for a rotating shield.

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 wafer 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.

During deposition in a PVD chamber with multiple cathode assemblies, a rotating shield is utilized to expose one of the cathode assemblies at a time and protect other cathode assemblies from cross-contamination. Current shield designs do not uniformly hold the weight of the shield, especially for larger shields, which results in vibrations, reduced process control and defects generated during deposition. Thus, there is a need for deposition systems that include a mounting assembly that securely holds the weight of the shield, reduces vibrations and prevents generation of defects during deposition.

SUMMARY

According to one embodiment of the disclosure, a physical vapor deposition (PVD) chamber comprises a plurality of cathode assemblies; a rotating shield below the plurality of cathode assemblies to expose one of the plurality of cathode assemblies through a shield hole of the rotating shield, the rotating shield comprising a top surface including a raised peripheral frame; and a shield mount sized and shaped to engage with the raised peripheral frame to secure the shield mount to the shield.

In another embodiment, a physical vapor deposition (PVD) chamber comprises a plurality of cathode assemblies; a rotating shield below the plurality of cathode assemblies to expose one of the plurality cathode assemblies through a shield hole of the rotating shield, the rotating shield comprising a top surface including a raised peripheral frame; a shield mount sized and shaped to engage with the raised peripheral frame to secure the shield mount to the shield; a collet secured to the shield mount; and a shield motor shaft secured to the collet and secured to a motor that rotates the shield motor shaft and the shield.

Another embodiment pertains to a method of depositing a material layer comprising placing a substrate in a PVD chamber; rotating a shield below the plurality of cathode assemblies to expose one of the plurality cathode assemblies through a shield hole of the shield, the shield comprising a top surface including a raised peripheral frame, the shield secured to a shield mount sized and shaped to engage with the raised peripheral frame on the shield to secure the shield mount to the shield; and depositing the material layer on the substrate.

Certain embodiments of the disclosure have other features or elements in addition to or in place of those mentioned above.

DETAILED DESCRIPTION

The term “on” indicates that there is direct contact between elements. The term “directly on” indicates that there is direct contact between elements with no intervening elements.

Those skilled in the art will understand that the use of ordinals such as “first” and “second” to describe process regions do not imply a specific location within the processing chamber, or order of exposure within the processing chamber.

Embodiments of the disclosure pertain to a magnet design for a deposition system, for example a physical vapor deposition (“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).

Referring now toFIG. 1, a side view of a portion of a deposition system in the form of a PVD chamber100is shown. The deposition system in the form of a PVD chamber in some embodiments is a multi-cathode PVD chamber100including a plurality of cathode assemblies102. The multi-cathode PVD chamber100includes a multi-target PVD source configured to manufacture an MRAM (magnetoresistive random access memory) or a multi-target PVD source configured to manufacture an extreme ultraviolet (EUV) mask blank.

The multi-cathode PVD chamber comprises a chamber body101, comprising a source adapter107configured to hold multiple cathode assemblies102in place in a spaced apart relationship. While the chamber body101is shown as being generally cylindrical and having the source adapter107having a dome portion109that is angled to provide a raised dome, the PVD chamber100of the present disclosure is not limited to the configuration shown. For example, the dome portion109does not have to be angled, and the dome portion has a profile that is generally flat. Furthermore, the chamber body can be shapes other than cylindrical, including elliptical, square or rectangular. The source adapter107holds any number of the cathode assemblies102. As a specific example, the source adapter107supports twelve cathode assemblies102. However, in some embodiments, the source adapter107supports one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen or twenty cathode assemblies102.

The source adapter107in some embodiments is mounted onto a base adapter111, which is conical, cylindrical or any other shape such as square or rectangular. Both the source adapter107and the base adapter111enclose an inner volume119(shown inFIG. 3) which is an area where a substrate or carrier108is processed according to one or more embodiments.

The multi-cathode PVD chamber100includes multiple cathode assemblies102for PVD and sputtering. Each of the cathode assemblies102is connected to a power supply112(shown inFIG. 3) including direct current (DC) or radio frequency (RF). The cathode assemblies102have any number of different diameters. In some embodiments, the cathode assemblies102all have the same diameter. In other embodiments, the cathode assemblies102have two, three, four, five, six or more different diameters.

As shown inFIGS. 1 and 2, the cathode assemblies102are arranged in an inner ring113and an outer ring115. These rings (inner ring113and outer ring115) are also called races. All of the cathode assemblies102can be arranged in a single ring instead of the inner ring113, and the outer ring115shown. In one or more embodiments, the configuration in which there is the inner ring113and the outer ring115achieves a high level of uniformity of deposition without rotating the carrier108shown inFIG. 3.

Referring now toFIG. 3, a cross-sectional view of a deposition system in the form of the PVD chamber100is shown, taken along line3-3ofFIG. 2according to an embodiment of the present disclosure. The cross-sectional view depicts an example of a PVD chamber100including the chamber body101defining an inner volume119, where a substrate or carrier is processed.

The cathode assemblies102in the embodiment shown inFIGS. 1-3are used for sputtering different materials as a material layer103. The cathode assemblies102exposed through shield holes104of a rotating shield106, which are over the substrate or carrier108on a rotating pedestal110. There may be only one carrier108over or on the rotating pedestal110.

The substrate or carrier108is in one embodiment, a structure having a semiconductor material used for fabrication of integrated circuits. For example, the substrate or carrier108according to some embodiments comprises a semiconductor structure including a wafer. Alternatively, the carrier is another material, such as an ultra low expansion glass substrate used to form an EUV mask blank. The substrate or carrier108are any suitable shape such as round, square, rectangular or any other polygonal shape. The rotating shield106is formed with the shield holes104so that the cathode assemblies102are used to deposit the material layers103through the shield holes104.

A power supply112is applied to the cathode assemblies102. The power supply112in some embodiments includes a direct current (DC) or radio frequency (RF) power supply. In some embodiments, such as the embodiment shown inFIGS. 1-3, angular positions of the cathode assemblies102are changed to any desired angle. This design allows coaxial feed for power, such as the power supply112, to the cathode assemblies102.

The rotating shield106exposes one of the cathode assemblies102at a time and protect other cathode assemblies102from cross-contamination. The cross-contamination is a physical movement or transfer of a deposition material from one of the cathode assemblies102to another of the cathode assemblies102. The cathode assemblies102are positioned over targets114. A design of a chamber can be compact. The targets114are any suitable size. For example, each of the targets114are a diameter in a range of from about 4 inches to about 20 inches, or from about 4 inches to about 15 inches, or from about 4 inches to about 10 inches, or from about 4 inches to about 8 inches or from about 4 inches to about 6 inches.

According to some embodiments, the rotating pedestal110allows for the use of a variety of different materials in one chamber. Features of the multi-cathode PVD chamber100include a single rotating shield, such as the rotating shield106, without rotating components hidden behind the rotating shield106. In some embodiments, the rotating shield106provides an advantage of improving particle performance.

InFIG. 3, the substrate or carrier108is on the rotating pedestal110, which can vertically move up and down. Before the substrate or carrier108moves out of the chamber, the substrate or carrier108moves below a lower shield118. A telescopic cover ring120is shown as a structure that abuts the lower shield118. Then, the rotating pedestal110moves down, and then the carrier108is lifted up with a robotic arm before the carrier108moves out of the chamber.

When the material layers103are sputtered, the materials sputtered from the targets114are retained inside and not outside of the lower shield118. Telescopic cover ring120in some embodiments includes a raised ring portion122that curves up and has a predefined thickness. The telescopic cover ring120also includes a predefined gap124and a predefined length with respect to the lower shield118. Thus, the materials that form material layers103will not be below the rotating pedestal110thereby eliminating contaminants from spreading to the carrier108.

FIG. 3depicts individual shrouds126. The shrouds126are designed such that a majority of the materials from the targets114that does not deposit on the carrier108is contained in the shrouds126, hence making it easy to reclaim and conserve the materials. This also enables one of the shrouds126for each of the targets114to be optimized for that target to enable better adhesion and reduced defects. For example, the majority includes at least 80% of one of the materials.

The shrouds126are designed to minimize cross-talk or cross-target contamination between the cathode assemblies102and to maximize the materials captured for each of the cathode assemblies102. Therefore, the materials from each of the cathode assemblies102would just be individually captured by one of the shrouds126over which the cathode assemblies102are positioned. The captured materials may not land on the substrate or carrier108.

The substrate or carrier108in some embodiments are coated with uniform material layer103deposited on a surface of the substrate or carrier108using the deposition materials including a metal from the targets114over the shrouds126. Then, the shrouds126are taken through a recovery process. The recovery process not only cleans the shrouds126but also recovers a residual amount of the deposition materials remained on or in the shrouds126. The uniformity of the material layer103relates to how evenly or smoothly the materials are deposited at a predetermined number of locations on the surface of the substrate or carrier108.

For example, there may be platinum on one of the shrouds126and then iron on another of the shrouds126. Since platinum is a precious metal that is more valuable than iron, the shrouds126with platinum are sent out for the recovery process. In one or more embodiments, rotating the rotating shield106to expose each of the cathode assemblies102through the shroud126and one of the shield holes104improves reliability without the cross-contamination between the cathode assemblies102. In some embodiments, rotating the rotating pedestal110improves the uniformity of the material layer103deposited from the targets114.

According to one or more embodiments, by varying the power to the cathode assemblies102, the amount of material deposited and the thickness of the material layer103can be varied. In some embodiments, varying the power controls the uniformity of the material layer103. In some embodiments, better uniformity is further be achieved by controlling the rotating pedestal110. Each of the cathode assemblies102applies different materials to form material layers103having different compositions. For example, a first cathode assembly and a second cathode assembly apply alternating layers of different materials in the formation of an extreme ultraviolet mask blank, for example, alternating layers of silicon deposited from a first target and cathode assembly102and molybdenum from a second target and cathode assembly102.

Referring now toFIG. 4, a top isometric view of one of the cathode assemblies102of the deposition system in the form of the multi-cathode PVD chamber100ofFIG. 1is shown. In some embodiments, an angular adjustment mechanism132provides an angular movement to change the angular positions of the cathode assemblies102. The angular adjustment mechanism132provides the angular positions by rotating a swing arm134of each of the cathode assemblies102with respect to or based on a pivot point136. The pivot point136is located at a bottom end of the swing arm134where the swing arm134is attached to a lower flange138. Water adapter blocks140are mounted on a top plate142. The top plate142is shown as over an upper flange144, which together with the lower flange138provides upper and lower support structures for an outer bellow assembly146.

FIG. 5is a cross-sectional view of one of the cathode assemblies102taken along line5-5ofFIG. 4. The cross-sectional view depicts an individual target source or one of the cathode assemblies102.FIG. 5depicts an assembly of one of the cathode assemblies102, in which a magnet-to-target spacing148is adjusted during the deposition process. The magnet-to-target spacing148is a distance between a magnet150of one of the cathode assemblies102and one of the targets114. The cathode assemblies102are adjusted manually or automatically. Each of the targets114is bonded or mounted to a backing plate152, which is similar to a structure with a vessel shape, the outer bellow assembly146having the lower flange138and the upper flange144. For example, both of the lower flange138and the upper flange144are welded with each other using flexible bellows with a conductive material including stainless steel (SST).

In some embodiments, each of the targets114is mounted inside the upper flange144. A grounded shield is formed with the lower flange138and the upper flange144grounded. A nonconductive ring154helps to electrically isolate the grounded shield from the targets114, which can be live due to connection with the power supply112.

For example, the nonconductive ring154includes an insulation material, such as ceramic or clay. The grounded shield is a part that is mounted on the inside of the lower shield118.

In some embodiments, the top plate142is bolted from a top surface of the top plate142to compress all O-rings including the nonconductive ring154to hold the targets114in place. As such, the vacuum as well as water leak sealing is achieved. Each source or each of the cathode assemblies102includes a number of manual motion mechanisms described below for improving the uniformity of the material layer103. For example, the bolted plate includes insulation, such as a type of an insulator material similar to fiberglass.

In some embodiments, the manual motion mechanisms include the angular adjustment mechanism132using the swing arm134that pivots around the lower flange138. The swing arm134holds a linear slide156over the swing arm134and at a top portion of each of the cathode assemblies102. The swing arm134adjusts the targets114for +/−5 degrees with respect to the carrier108. The manual motion mechanisms include a source lift mechanism158with the swing arm134holding the linear slide156at the top portion of each of the cathode assemblies102. The linear slide156holds a source or the materials with a hollow shaft160. The linear slide156provides a source movement of the materials along the hollow shaft160as shown by a bidirectional vertical arrow.

The manual motion mechanisms of some embodiments include a knob adjustment mechanism162with a manual adjustment knob or the knob130at the top portion of each of the cathode assemblies102to provide a linear actuation. The knob adjustment mechanism162is designed to achieve a total stroke length. The total stroke length includes any numerical value. For example, the total stroke length is 2.5 inches.

The manual motion mechanisms of some embodiments include a magnet-to-target adjustment mechanism164to adjust the magnet-to-target spacing148. A permanent magnet is placed inside the source. An inner shaft166holds the magnet150inside the hollow shaft160. The inner shaft166can include any structure for holding the magnet150. As a specific example, the inner shaft166includes a Delrin® shaft.

An adjustment screw168on top of each of the cathode assemblies102provides a linear adjustment of the magnet-to-target spacing148. A side locking screw170holds the magnet150in position after achieving a predetermined value of the magnet-to-target spacing148. For example, a total adjustable stroke length for the magnet-to-target spacing148is 1 inch.

Referring now toFIGS. 6-9, an alternative embodiment of a deposition system according to an embodiment of the disclosure is shown. Similar to the embodiment shown inFIG. 1, the deposition system in the form of a PVD chamber is a multi-cathode PVD chamber200including a plurality of cathode assemblies202. The multi-cathode PVD chamber200includes a multi-target PVD source configured to manufacture an MRAM (magnetoresistive random access memory) or a multi-target PVD source configured to manufacture an extreme ultraviolet (EUV) mask blank.

The multi-cathode PVD chamber200comprises a chamber body201, comprising a source adapter207configured to hold multiple cathode assemblies102in place in a spaced apart relationship. As can be seen inFIGS. 6 and 7, the chamber body201is shown as being generally cylindrical and having the source adapter207having a dome portion209flatter than the dome109of the multi-cathode PVD chamber100shown inFIG. 1. The source adapter207holds any number of the cathode assemblies202. As a specific example, the source adapter207supports twelve cathode assemblies202. However, in some embodiments, the source adapter207supports one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen, twenty, twenty-one, twenty-two, twenty-three, twenty-four or twenty-five cathode assemblies202.

The source adapter207is mounted onto a base adapter211, which can be conical, cylindrical or any other shape such as square or rectangular. Both the source adapter207and the base adapter211enclose an inner volume, which is an area where a substrate or carrier108is processed according to one or more embodiments.

The multi-cathode PVD chamber200includes multiple cathode assemblies202for PVD and sputtering. Each of the cathode assemblies202is connected to a power supply (not shown) including direct current (DC) or radio frequency (RF). The cathode assemblies202can have any number of different diameters. In some embodiments, the cathode assemblies202all have the same diameter. In other embodiments, the cathode assemblies202have two, three, four, five, six or more different diameters. Similar to the embodiment shown inFIGS. 1 and 2, the cathode assemblies202are arranged in an inner ring213and an outer ring215. All of the cathode assemblies202are arranged in a single ring instead of inner and outer rings.

FIG. 7is a cross-sectional view of a portion of a multi-cathode PVD chamber according to an embodiment of the disclosure showing cathode assemblies202, chamber body201and shield206. The shield206is connected to a shield motor shaft300by collet302, and the shield motor shaft300is rotated by a shield motor assembly304.FIG. 8is cross-sectional view of one of the cathode assemblies202shown inFIG. 7. The cathode assembly202shown inFIG. 8according to one or more embodiments comprises a motor272, which drives a motor shaft276that rotates a magnet assembly290in the direction shown by arrow295. A coupler274couples the motor272to the motor shaft276. Bearings278surround the motor shaft to facilitate rotational motion in the direction of arrow295. The cathode assembly202further comprises an upper housing280and a lower housing288surrounding an insulator282, which surrounds a conductor284including a coolant channel286therethrough to cool the cathode assembly202during processing. The upper housing280and the lower housing288may be assembled together using any suitable fasteners or fastening system such as machine screws or bolts. The cathode further comprises an insulator ring292and an O-ring294at a base of the conductor284. Deposition barrier296is provided at the bottom of the cathode assembly202. Assembled to the motor shaft276are an insulator plate297and a mounting plate299for securing the magnet assembly to the motor shaft276. A target298comprising material to be sputtered (e.g., silicon or molybdenum, etc.) is at the bottom of the cathode assembly202.

According to embodiments of the present disclosure, a shield mounting assembly305is provided for a rotating shield206in a multi-cathode chamber, the shield mounting assembly305providing reduced vibrations and a secure way of mounting the shield206.

FIG. 9Ais a partial cross-sectional view showing a shield mounting assembly305according to one or more embodiments, andFIG. 9Bis an enlarged partial perspective view of a portions of the shield mounting assembly305. The shield mounting assembly305includes a collet302, which is fastened to a shield motor shaft300and the shield206by shield mount308. In one embodiment, a ferrofluidic feedthrough313or magnetically coupled rotational feedthrough is provided to engage the motor shaft and pass rotational motion of the shield motor shaft300to the shield206.

According to one or more embodiments, the ferrofluidic feedthrough is advantageous because the ferrofluidic feedthrough313is a straight, direct drive that does not exhibit lag like a magnetic coupling for rotation of a large, bulky shield.FIG. 14shows a cross-section view of an example of a ferrofluidic feedthrough according to one or more embodiments. In some embodiments, the shaft of the ferrofluidic feedthrough313is always perpendicular to the flange313a, which eliminates offset and wobble. Furthermore, in some embodiments, the ferrofluidic feedthrough313eliminates exposure of foreign particles (e.g., grease) inside the PVD chamber under high vacuum. In some embodiments, the ferrofluidic feedthrough313uses the response of a magnetic fluid with an applied magnetic field. Rotary seal components include a ferrofluid, a permanent magnet, two pole pieces and a magnetically permeable shaft. A magnetic circuit employs stationary pole pieces and the rotating shaft and concentrates magnetic flux in the radial gap under each pole piece. When the ferrofluid is applied to this radial gap, it takes the shape of a liquid O-ring and produces a hermetic vacuum seal.

A tapered centering shaft310engages the collet302and the shield motor shaft300. A dowel314centers the shield206and the shield mount308. The tapered centering shaft310and the dowel314cooperate to center the shield mount308and the shield206.

FIG. 10is an enlarged cross-sectional view of the tapered centering shaft310according to one or more embodiments. The tapered centering shaft310has a tapered tip316that engages the shield motor shaft300and has a flared head318to secure the collet302to the shield motor shaft300.

Referring now toFIG. 11an exploded top perspective view of a shield206and a shield mount308according to one or more embodiments is shown.FIG. 12shows an assembled top perspective view of a shield and a shield mount according to one or more embodiments.FIG. 13shows an enlarged top perspective view of a portion of the mounting assembly and the shield according to one or more embodiments. Referring toFIGS. 11-13, the top surface206aof the shield206includes a receiving pocket320shaped to receive the shield mount308. Shield mount308and receiving pocket320are complementarily shaped, or, in other words have complementary geometric shapes. Stated another way, the shield mound defines a geometric shape that is received within a pocket of the shield to secure the shield mount to the shield. In the embodiment shown, the receiving pocket320and the shield mount308are star-shaped or in the shape of a pentagon having concave sides. The shape of the receiving pocket320and the shield mount are exemplary, and it will be understood that other complementarily shaped shield mount308and receiving pocket320combinations are possible, such as triangular, square, trapezoidal, rectangular, etc.

The receiving pocket320comprises a raised peripheral frame321defining the receiving pocket320. The shield mount308has edge projections322that are configured to be received under the raised peripheral frame321.FIG. 12shows the shield mount308fitted within the recess with the edge projections322engaged with the peripheral frame to secure or lock the shield mount308to the shield206.

One or more embodiments described herein are particularly useful in multi-cathode PVD systems with rotating magnets. The target assemblies described herein may be particularly useful in the manufacture of extreme ultraviolet (EUV) mask blanks. An EUV mask blank is an optically flat structure used for forming a reflective mask having a mask pattern. In one or more embodiments, the reflective surface of the EUV mask blank forms a flat focal plane for reflecting the incident light, such as the extreme ultraviolet light. An EUV mask blank comprises a substrate providing structural support to an extreme ultraviolet reflective element such as an EUV reticle. In one or more embodiments, the substrate is made from a material having a low coefficient of thermal expansion (CTE) to provide stability during temperature changes. The substrate according to one or more embodiments is formed from a material such as silicon, glass, oxides, ceramics, glass ceramics, or a combination thereof.

An EUV mask blank includes a multilayer stack, which is a structure that is reflective to extreme ultraviolet light. The multilayer stack includes alternating reflective layers of a first reflective layer and a second reflective layer. The first reflective layer and the second reflective layer form a reflective pair. In a non-limiting embodiment, the multilayer stack includes a range of 20-60 of the reflective pairs for a total of up to 120 reflective layers.

The first reflective layer and the second reflective layer are formed from a variety of materials. In an embodiment, the first reflective layer and the second reflective layer are formed from silicon and molybdenum, respectively. The multilayer stack forms a reflective structure by having alternating thin layers of materials with different optical properties to create a Bragg reflector or mirror. The alternating layers of, for example, molybdenum and silicon are formed by physical vapor deposition, for example, in a multi-cathode PVD chamber.

A first embodiment of the disclosure pertains to a physical vapor deposition (PVD) chamber comprising a plurality of cathode assemblies; a rotating shield below the plurality of cathode assemblies to expose one of the plurality of cathode assemblies through a shield hole of the rotating shield, the rotating shield comprising a top surface including a raised peripheral frame; and a shield mount sized and shaped to engage with the raised peripheral frame to secure the shield mount to the shield.

In a second embodiment, the PVD chamber of the first embodiment further comprises a target below each of the plurality of cathode assemblies; and a rotating pedestal carrier.

In a third embodiment, the first and second embodiment include the feature that the raised peripheral frame defines a pocket having a geometric shape that is complementary and the shield mount has a geometric shape that is complementary to the geometric shape of the pocket. In a fourth embodiment, the geometric shape of the pocket is a polygon. In a fifth embodiment, the geometric shape of the pocket is a pentagon. In a sixth embodiment, the geometric shape of the pocket is a pentagon with concave sides.

In a seventh embodiment, in any of the first through sixth embodiments, the shield mount comprises edge projections that are received by the raised peripheral frame. In an eighth embodiment, the PVD chamber of the first through seventh embodiments further comprises a collet secured to the shield mount and a shield motor shaft secured to the collet. In ninth embodiment, the shield motor shaft is engaged with a ferrofluidic feedthrough and a shield motor.

In a tenth embodiment, a physical vapor deposition (PVD) chamber comprises a plurality of cathode assemblies; a rotating shield below the plurality of cathode assemblies to expose one of the plurality cathode assemblies through a shield hole of the rotating shield, the rotating shield comprising a top surface including a raised peripheral frame; a shield mount sized and shaped to engage with the raised peripheral frame to secure the shield mount to the shield; a collet secured to the shield mount; and a shield motor shaft secured to the collet and secured to a motor that rotates the shield motor shaft and the shield.

In an eleventh embodiment, the PVD chamber of the tenth embodiment further comprises a ferrofluidic feedthrough engaged with the shield motor shaft to pass rotational motion of the shield motor shaft to the shield. In a twelfth embodiment, the tenth embodiment further comprises a tapered centering shaft engaging the collet and the shield motor shaft. In a thirteenth embodiment, the tenth embodiment includes a feature wherein the shield mount has a geometric shape that engages a peripheral frame on a top surface of the shield to secure the shield mount to the shield.

A fourteenth embodiment pertains to method of depositing a material layer comprising placing a substrate in a PVD chamber comprising a plurality of cathode assemblies; rotating a shield below the plurality of cathode assemblies to expose one of the plurality cathode assemblies through a shield hole of the shield, the shield comprising a top surface including a raised peripheral frame, the shield secured to a shield mount sized and shaped to engage with the raised peripheral frame on the shield to secure the shield mount to the shield; and depositing the material layer on the substrate. In a fifteenth embodiment of the method, the shield mount comprises a geometric shape that fits within a pocket defined by the raised peripheral frame. In a sixteenth embodiment of the method, the shield mount is in the shape of a pentagon. In any of the method embodiments, the substrate comprises an extreme ultraviolet mask blank. In such method embodiments, depositing multiple alternating materials layers comprises a first layer comprising molybdenum and a second layer comprising silicon.