Physical vapor deposition apparatus and method thereof

A PVD method includes tilting a first magnetic element over a back side of a target. The first magnetic element is moved about an axis that extends through the target. Then, charged ions are attracted to bombard the target, such that particles are ejected from the target and are deposited over a surface of a wafer. By tilting the magnetic element relative to the target, the distribution of the magnetic fields can be more random and uniform.

BACKGROUND

Integrated chips are formed by complex fabrication processes, during which a workpiece is subjected to different steps to form one or more semiconductor devices. Some of the processing steps may include forming a thin film onto a semiconductor substrate. Thin films can be deposited onto a semiconductor substrate in a low-pressure processing chamber using physical vapor deposition.

DETAILED DESCRIPTION

FIG. 1is a schematic diagram of a physical vapor deposition (PVD) apparatus100according to some embodiments of the present disclosure. As shown inFIG. 1, the PVD apparatus100includes a processing chamber110, a target holder120, a power supply130, a thickness detector140, a gas system150, a pedestal160, a vacuum system170, and a controller180. The target holder120is disposed in the processing chamber110and is configured to hold a target200. The power supply130is electrically connected to the target200and is configured to apply a bias voltage to the target200. The thickness detector140is disposed in the processing chamber110and is configured to detect a thickness TK of the target200. For example, the thickness detector140can be a supersonic detector, a thermos-detector, an X-ray detector, an eddy current thickness gauge, or the like. The gas system150is configured to introduce a sputtering gas G into the processing chamber110. The pedestal160is disposed in the processing chamber110and is configured to hold a wafer210. The controller180is configured to manage and control the PVD apparatus100.

The pedestal160is disposed in the processing chamber110and is configured to support the wafer210. In some embodiments, the pedestal160may be or include a chuck configured to hold the wafer210. For example, the pedestal160may include a mechanical chuck, a vacuum chuck, an electrostatic chuck (“e-chuck”), combinations thereof, or the like. The mechanical chuck may include one or more clamps to secure the wafer210to the pedestal160. The vacuum chuck may include a vacuum aperture coupled to a vacuum source to hold the wafer210to the pedestal160. The e-chuck relies on an electrostatic force generated by an electrode energized by a direct current (DC) voltage source to secure the wafer210to the chuck. In some embodiments, a temperature controlling device is connected to the pedestal160and is configured to adjust the pedestal temperature, and therefore the wafer temperature. In some embodiments, the pedestal160may be vertically movable through a shaft to allow the wafer210to be transferred onto the pedestal160through a load lock valve in a lower portion of the processing chamber110and thereafter raised to a deposition or processing position.

Since the sputtering of the target200is easily influenced by impurities, particularly oxidizing agents such as oxygen and water moisture, the processing chamber110is evacuated to a pressure lower than the atmospheric pressure by the vacuum system170before the sputtering of the target200starts. In this way, the impurities like oxygen and water moisture can be removed. In some embodiments, the vacuum system170creates the vacuum environment by pumping away gas inside the processing chamber110.

The gas system150introduces the sputtering gas G into the processing chamber110. The sputtering gas G in the processing chamber110is a kind of plasma, which is in fact a partially ionized gas. The partially ionized gas includes various kinds of electrons, ions, uncharged molecules, and radicals. In the case that the PVD apparatus100is operated to deposit titanium nitride onto the wafer210, the sputtering gas G may include, for example, nitrogen.

When the bias voltage is applied to the target200by the power supply130, the target200is electrically charged and becomes a cathode in the processing chamber110. In some embodiments, the power supply130is a radio frequency (RF) power source and is applied at a very high frequency (VHF) for forming the plasma from the sputtering gas and ionizing atoms or particles sputtered from the target200by the plasma. The sputtering gas may include one or more inert gases, such as a noble gas, or other inert gases. For example, non-limiting examples of suitable sputtering gases may include argon (Ar), helium (He), xenon (Xe), neon (Ne), hydrogen (H2), nitrogen (N2), combinations thereof, or the like. In some embodiments, the power supply130includes an additional direct current (DC) power source that may also be applied to the target200to increase the rate at which material is sputtered from the target200. In some embodiments, the DC power source may be applied to the target200to direct the plasma towards the target200.

In some embodiments, the negatively charged target200attracts the positively charged ions in the plasma to accelerate and bombard the target200. Due to the bombardment of the target200by the positively charged ions, particles or atoms are ejected from the target200. The ejected particles or atoms are deposited over the surface of the wafer210held by the pedestal160. During the operation of the PVD apparatus100, the sputtering of the target200occurs and thus the thickness TK of the target200gradually decreases. Once the thickness TK of the target200is monitored to be less than a predetermined thickness, the operator will terminate the operation and replace the target200with a new target200.

In order to achieve an even bombardment of the target200by the charged ions, the PVD apparatus100further includes a magnetron300that includes a magnetic element310and a motor320. The target holder120is disposed between the magnetron300and the target200. During sputtering, the magnetic element310is configured to generate a magnetic field. The magnetic field acts with a force on ions within the plasma to trap the ions close to the target200. The trapped ions collide with neutral gas particles near the target200, enhancing ionization of the plasma near the target200and leading to a higher sputter rate.

The motor320is configured to rotate the magnetic element310, such that the magnetic field generated by the magnetic element310moves over the top surface of the target200. Under the effect of the magnetic field, the bombardment of the target200by the ions can be carried out more evenly. However, the strength of the magnetic field of the magnetic element310is not uniform along the magnetic element310. The magnetic field is stronger around north poles and south poles of the magnetic element310. Consequently, due to the stronger magnetic field, the bombardment is more vigorous at the corresponding locations on the target200where the stronger magnetic field is in effect. Hence, the target200gets depleted the most at the corresponding location on the target200where the strongest magnetic field is in effect. In other words, the thickness TK of the target200is not uniform due to the uneven magnetic field distribution of the magnetic element310.

Reference is made toFIG. 2, which is a schematic side view of the magnetron300in operation according to some embodiments of the disclosure. The magnetron300includes the magnetic element310, the motor320, a telescopic arm assembly330, a rotational shaft340, a counter weight350, and a hinge mechanism360. The magnetic element310is located at an end of the telescopic arm assembly330, and the telescopic arm assembly330is connected to and rotated by the motor320, through the rotational shaft340.

The rotational shaft340extends substantially along an axis of rotation302that extends substantially through the center C of the target200. The motor320is connected to the rotational shaft340and is configured to turn the rotational shaft340. The magnetron300is located on a backside of the target200(i.e., a side of the target200facing away from the wafer210), such that the magnetic element310is configured to generate one or more magnetic fields312that extend through the target200to a region below the target200. The magnetic fields312operate upon ions within the processing chamber to enhance the ionization of plasma near the target200, leading to a higher sputter rate.

The magnetic element310may include any type or number of magnets. In some embodiments, the magnetic element310includes one or more permanent magnets (e.g., neodymium magnets). Furthermore, the magnetic element310may include magnets of any size. As shown inFIG. 2, in some embodiments, the magnetic element310includes a plurality of small magnets314each having a north pole and a south pole.

By placing small magnets314having opposite polarities next to one another, one or more magnetic fields312having a high density can be achieved below the target200. The high density of the magnetic fields312provides for good step coverage and good deposition symmetry over the surface of the wafer210. For example, the wafer210has a plurality of trenches212, and a thin film220is deposited to have symmetry between the deposited films on opposing sidewalls of the trenches212and to have a film thickness on the trench sidewalls that is approximately equal to the film thickness at the bottoms of the trenches212. In some embodiments, the film220may be a work function metal layer.

The telescopic arm assembly330is configured to have a variable length. The magnetic element310is connected to the telescopic arm assembly330. The telescopic arm assembly330connects the magnetic element310to the rotational shaft340, which is located approximately at the center C of the target200and is driven by the motor320. The telescopic arm assembly330is configured to be adjustable in length, thereby varying the distance from the rotational shaft340to the magnetic element310.

In some embodiments, the telescopic arm assembly330includes a linear actuator configured to control changes in the length of the telescopic arm assembly330. By changing the length of the telescopic arm assembly330, the position of the magnetic element310relative to the rotational shaft340is changed.

In some embodiments, the counter weight350is located at a position along the telescopic arm assembly330that is opposite to the position of the magnetic element310. For example, as shown inFIG. 2, the counter weight350and the magnetic element310are on opposite sides of the rotational shaft340. The counter weight350is configured to stabilize the magnetic element310by balancing the load of the magnetic element310. This compensates for the weight of the magnetic element310and maintains balance in a rotational plane of the magnetron300.

In some embodiments, the telescopic arm assembly330and the rotational shaft340are connected by the hinge mechanism360, such that the telescopic arm assembly330is pivotally connected to the rotational shaft340. In some embodiments, the telescopic arm assembly330includes a first portion332and a second portion334, in which the magnetic element310is connected to the first portion332, the counter weight350is connected to the second portion334, and the first portion332and the second portion334are connected by the hinge mechanism360. An angle between the first portion332and the second portion334is adjustable, by the hinge mechanism360, and therefore a position and an orientation of the magnetic element310relative to the target200is also adjustable. For example, the first portion332of the telescopic arm assembly330and the magnetic element310can be tilted relative to the top (back) surface of the target200at a non-zero angle. When the magnetic element310of the magnetron300is tilted relative to the target200, the loops of the magnetic field are also tilted relative to the target200, such that the strength of the magnetic field, received by the target200, can be more uniform.

The telescopic arm assembly330and the hinge mechanism360are electrically connected to and controlled by the controller180(as shown inFIG. 1). The controller180is a computer with software for controlling the movements of the magnetic element310, such as motion of the magnetic element310radially relative to the rotational shaft340. Furthermore, the controller180controls the tilting of the magnetic element310and the telescopic arm assembly330. By changing the speed of rotation, the length of the telescopic arm assembly330, and the tilting angle of the magnetic element310, a substantially uniform consumption of the target200can be achieved.

Reference is made toFIGS. 3A and 3B, which are cross-sectional views of the telescopic arm assembly330taken along different directions according to some embodiments of the disclosure. In some embodiments, the linear actuator includes a first linear actuator370adisposed in the first portion332of the telescopic arm assembly330and a second linear actuator370bdisposed in the second portion334of the telescopic arm assembly330. The first linear actuator370ais configured to create a linear motion for the magnetic element310, and the second linear actuator370bis configured to create a linear motion for the counter weight350.

In some embodiments, the first and second linear actuators370aand370beach includes a nut372, a motor374, and a lead screw376. Each of the first and second portions332and334has a fixed cover331and a sliding tube333. The nut372is threaded onto the lead screw376. The nut372is connected to the sliding tube333. The motor374is connected to the fixed cover331. The magnetic element310or the counter weight350is disposed on the sliding tube333. The motor374is configured to rotate the lead screw376.

In each of the first and second linear actuators370aand370b, the motor374can be, for example, a DC brush motor, a DC brushless motor, a stepper motor, an induction motor, or the like. The lead screw376has a continuous helical thread machined on its circumference running along the length. The nut372may be a lead nut or ball nut with corresponding helical threads. The nut372is further coupled to the fixed cover331and is able to slide relative to the fixed cover331. For example, the nut372includes two flanges3722, and the fixed cover331includes two slits3312. The flanges3722of the nut372are coupled to the slits3312of the fixed cover331, such that the nut372interlocks with the fixed cover331to prevent the nut372from rotating with the lead screw376. Therefore, when the lead screw376is rotated, the nut372is driven along the threads. The direction of motion of the nut372depends on the direction of rotation of the lead screw376. The rotational motion of the lead screw376is converted to a linear motion of the sliding tube333when the lead screw376is driven by the motor374. In some other embodiments, the first linear actuator370aand/or the second linear actuator370bmay include other suitable linear actuators, such as mechanical actuators, hydraulic actuators, pneumatic actuators, piezoelectric actuators, twisted and coiled polymer (TCP) actuators, electro-mechanical actuators, or the like. In some embodiments, the first linear actuator370aand the second linear actuator370bare controlled by the controller180(as shown inFIG. 1).

Reference is made toFIG. 4AandFIG. 4B, which are schematic side views of the magnetron300in different operation states according to some embodiments of the disclosure. InFIG. 4A, the first portion332of the telescopic arm assembly and the magnetic element310are tilted relative to the top (back) surface of the target holder120at a tilting angle θ. That is, the first portion332of the telescopic arm assembly of the magnetron300(or a bottom surface of the magnetic element310) and the top (back) surface of the target holder120have the tilting angle θ therebetween. The tilting angle θ is greater than about 0 degree and is smaller than or equal to about 2 degrees. If the tilting angle θ is greater than about 2 degrees, the magnetron300might hit the process chamber; if the tilting angle θ is equal to about 0 degree, the magnet fields generated by the magnetron300are not tilted, and thus the consumption uniformity of the target200cannot be improved; if the tilting angle θ is smaller than about 0 degree, the magnetron300might hit the target holder120. A distance d between the bottom surface of the magnetic element310and the top (back) surface of the target holder120is greater than about 0 mm and is smaller than or equal to about 3 mm. If the distance d is greater than about 3 mm, the magnetron300might hit the process chamber; if the distance d is equal to about 0 mm, the magnet fields generated by the magnetron300are not tilted, and thus the consumption uniformity of the target200cannot be improved; if the distance d is less than about 0 mm, the magnetron300might hit the target holder120.

Then, inFIG. 4B, the magnetic element310is moved radially relative to an axis. For example, the axis can be the axis of rotation302that extends through the center C of the target200. Therefore, the distance from the axis to the magnetic element310is increased or decreased. The counter weight350is moved in an opposite direction to balance the magnetic element310. In some embodiments, the step of moving the magnetic element310radially relative to the axis can be performed before or after tilting the magnetic element310. After the magnetic element310is tilted and is moved radially relative to the axis, the magnetic element310is moved about the axis of rotation302. In some embodiments, the distance from the axis of rotation302to the magnetic element310and the tilting angle of the magnetic element310are fixed when the magnetic element310is moved about the axis of rotation302.

By varying the distance from the axis of rotation302to the magnetic element310and the tilting angle of the magnetic element310, the moving path of the magnetic element310about the axis of rotation302can be changed. Such motion enables an adjustable magnetic track that provides good consumption uniformity of the target and a short deposition time.

Reference is made toFIG. 5, which is a schematic top view of a magnetron assembly400of a PVD apparatus according to some embodiments of the disclosure. In some embodiments, the magnetron assembly400of the PVD apparatus includes a source magnetron410and an auxiliary magnetron420. The source magnetron410includes a source magnetic element310a, a first telescopic arm assembly330a(including a first portion332aand a second portion334aas illustrated inFIG. 5), a first counter weight350a, and a first hinge mechanism360a. The source magnetic element310a, the first telescopic arm assembly330a, the first counter weight350a, and the first hinge mechanism360aare respectively similar to the magnetic element310, the telescopic arm assembly330, the counter weight350, and the hinge mechanism360ofFIG. 2and thus are not repeated herein.

The auxiliary magnetron420includes an auxiliary magnetic element310b, a second telescopic arm assembly330b, a second counter weight350b, and a second hinge mechanism360b. The auxiliary magnetic element310b, the second telescopic arm assembly330b(including a first portion332band a second portion334bas illustrated inFIG. 5), the second counter weight350b, and the second hinge mechanism360bare respectively similar to the magnetic element310, the telescopic arm assembly330, the counter weight350, and the hinge mechanism360ofFIG. 2and thus are not repeated herein.

The PVD apparatus also includes a processing chamber, a target holder configured to hold a target, a power supply, a thickness detector, a gas system, a pedestal, a vacuum system, and a controller. The processing chamber, the target holder, the power supply, the thickness detector, the gas system, the pedestal, the vacuum system, and the controller of the PVD apparatus and the target are respectively similar to the processing chamber110, the target holder120, the power supply130, the thickness detector140, the gas system150, the pedestal160, the vacuum system170, and the controller180of the PVD apparatus100and the target200ofFIG. 1and thus are not repeated herein.

One application of the magnetron assembly400is to sputter a barrier or liner layer over sides and a bottom of a via hole. To achieve deep penetration into the via hole, RF biases the wafer to attract the ions deep within the via hole to sputter etch the barrier layer at the bottom of the via hole. As such, the sputter etching and deposition at the bottom of the via hole can be balanced.

The uniformity of sputter etching and/or deposition can be improved by using both the source magnetron410and the auxiliary magnetron420. In some embodiments, the source magnetron410and the auxiliary magnetron420have similar but nonetheless different structures. For example, the source magnetron410is smaller than the auxiliary magnetron420, magnetically stronger than the auxiliary magnetron420, and is positioned nearer the edge of the target200. The auxiliary magnetron420is larger than the source magnetron410, magnetically weaker than the source magnetron410, and is located nearer the rotational shaft340. The source magnetron410and the auxiliary magnetron420are rotated about the rotational shaft340to flatten the radial ion flux profile. The flattened radial ion flux profile increases the uniformity of sputter etching and/or deposition.

In some embodiments, as shown inFIG. 6, the first portion332aof the first telescopic arm assembly330aand the source magnetic element310aare tilted relative to the top (back) surface of the target holder120at a first tilting angle θ1. That is, the first portion332aof first telescopic arm assembly330a(or a bottom surface of the source magnetic element310a) and the top (back) surface of the target holder120have the first tilting angle θ1therebetween. The first tilting angle θ1is greater than about 0 degree and is smaller than or equal to about 2 degrees. If the first tilting angle θ1is greater than about 2 degrees, the source magnetron410might hit the process chamber; if the first tilting angle θ1is equal to about 0 degree, the magnet fields generated by the source magnetron410are not tilted, and thus the consumption uniformity of the target200cannot be improved; if the first tilting angle θ1is smaller than about 0 degree, the source magnetron410might hit the target holder120. A first distance d1between the bottom surface of the source magnetic element310aof the source magnetron410and the top (back) surface of the target holder120is greater than about 0 mm and is smaller than or equal to about 3 mm. If the first distance d1is greater than about 3 mm, the source magnetron410might hit the process chamber; if the first distance d1is equal to about 0 mm, the magnet fields generated by the source magnetron410are not tilted, and thus the consumption uniformity of the target200cannot be improved; if the first distance d1is less than about 0 mm, the source magnetron410might hit the target holder120.

In some embodiments, as shown inFIG. 7, the first portion332bof the second telescopic arm assembly330band the auxiliary magnetic element310bare tilted relative to the top (back) surface of the target holder120at a second tilting angle θ2. That is, the first portion332bof the second telescopic arm assembly330b(or a bottom surface of the auxiliary magnetic element310b) and the top (back) surface of the target holder120have the second tilting angle θ2therebetween. The second tilting angle θ2is greater than about 0 degree and is smaller than or equal to about 2 degrees. If the second tilting angle θ2is greater than about 2 degrees, the auxiliary magnetron420might hit the process chamber; if the second tilting angle θ2is equal to about 0 degree, the magnet fields generated by the auxiliary magnetron420are not tilted, and thus the consumption uniformity of the target200cannot be improved; if the second tilting angle θ2is smaller than about 0 degree, the auxiliary magnetron420might hit the target holder120. In some embodiments, the second tilting angle θ2is greater than the first tilting angle θ1to ensure that the auxiliary magnetic element310bis closer to the axis of rotation302than the source magnetic element310ais to the axis of rotation302. A second distance d2between the bottom surface of the auxiliary magnetic element310bof the auxiliary magnetron420and the top (back) surface of the target200is greater than about 0 mm and is smaller than or equal to about 3 mm. If the second distance d2is greater than about 3 mm, the auxiliary magnetron420might hit the process chamber; if the second distance d2is equal to about 0 mm, the magnet fields generated by the auxiliary magnetron420are not tilted, and thus the consumption uniformity of the target200cannot be improved; if the second distance d2is less than about 0 mm, the auxiliary magnetron420might hit the target holder120. In some embodiments, the second distance d2is greater than the first distance d1to ensure that the auxiliary magnetic element310bis closer to the axis of rotation302than the source magnetic element310ais to the axis of rotation302.

Reference is made toFIG. 6. The source magnetic element310ais moved in a first radial direction relative to the axis of rotation302. In some embodiments, the step of moving the source magnetic element310ain the first radial direction relative to the axis of rotation302can be performed before or after tilting the source magnetic element310a. After the source magnetic element310ais tilted and is moved in the first radial direction relative to the axis of rotation302, the source magnetic element310ais moved about the axis of rotation302. In some embodiments, the distance from the axis of rotation302to the source magnetic element310aand the tilting angle of the source magnetic element310aare fixed when the source magnetic element310ais moved about the axis of rotation302.

Reference is made toFIG. 7. The auxiliary magnetic element310bis moved in a second radial direction relative to the axis of rotation302. In some embodiments, the step of moving the auxiliary magnetic element310bin the second radial direction relative to the axis of rotation302can be performed before or after tilting the auxiliary magnetic element310b. After the auxiliary magnetic element310bis tilted and is moved in the second radial direction relative to the axis of rotation302, the auxiliary magnetic element310bis moved about the axis of rotation302. In some embodiments, the distance from the axis of rotation302to the auxiliary magnetic element310band the tilting angle of the auxiliary magnetic element310bare fixed when the auxiliary magnetic element310bis moved about the axis of rotation302.

Reference is made toFIG. 6. The first counter weight350ais moved in a third radial direction relative to the axis of rotation302and opposite the first radial direction to balance the source magnetic element310a. Reference is made toFIG. 7. The second counter weight350bis moved in a fourth radial direction relative to the axis of rotation302and opposite the second radial direction to balance the auxiliary magnetic element310b. In some embodiments, the steps of moving the first counter weight350ain the third radial direction and moving the second counter weight350bin the fourth radial direction are respectively performed simultaneously with moving the source magnetic element310ain the first radial direction and moving the auxiliary magnetic element310bin the second radial direction. In some embodiments, the steps of moving the first counter weight350ain the third radial direction and moving the second counter weight350bin the fourth radial direction are performed prior to moving the source magnetic element310aand the auxiliary magnetic element310babout the axis of rotation302. In some embodiments, the distance from the axis of rotation302to the first counter weight350aand the distance from the axis of rotation302to the second counter weight350bare fixed when the source magnetic element310aand the auxiliary magnetic element310bare moved about the axis of rotation302.

Reference is made toFIG. 8, which is a flow chart of operating a PVD apparatus according to some embodiments of the disclosure. The method begins on step S10, in which a first magnetic element over a back side of a target is tilted. In some embodiments, the first magnetic element is connected to a hinge mechanism through an arm, and the first magnetic element is tilted by using the hinge mechanism.

In step S12, the first magnetic element is moved about an axis that extends through the target. In some embodiments, the hinge mechanism is connected to a rotational shaft, and the axis is the axis of rotation of the rotational shaft. In some embodiments, the first magnetic element is tilted prior to moving the first magnetic element about the axis. In some embodiments, a tilting angle of the first magnetic element relative to the target is fixed when the first magnetic element is moved about the axis.

In step S14, a plasma that includes charged ions is generated, and then in step S16, the charged ions are attracted to bombard the target, such that particles are ejected from the target and are deposited over a surface of a wafer. In some embodiments, the tilting angle of the first magnetic element relative to the target is also fixed when the charged ions are attracted to bombard the target.

Reference is made toFIG. 9, which is a flow chart of operating a PVD apparatus according to some other embodiments of the disclosure. The method begins on step S20, in which a first magnetic element over a back side of a target is moved in a first radial direction relative to an axis, wherein the axis extends through the target.

In step S22, a second magnetic element over the back side of the target is moved in a second radial direction relative to the axis. In some embodiments, the second magnetic element is closer to the axis than the first magnetic element is to the axis.

In step S24, after moving the first magnetic element in the first radial direction and moving the second magnetic element in the second radial direction, the first magnetic element and the second magnetic element are moved about the axis.

In step S26, a plasma that includes charged ions is generated, and then the charged ions are attracted to bombard the target, such that particles are ejected from the target and are deposited over a surface of a wafer.

The profile of the target after each PVD process varies because of the consumption of the target. By tilting the magnetic element relative to the target holder or the target and/or changing a distance from an axis of rotation to the magnetic element, the distribution of the magnetic fields can be more uniform, and thus the consumption of the target can be more uniform as well.

According to some embodiments of the disclosure, a method includes tilting a first magnetic element over a back side of a target. The first magnetic element is moved about an axis that extends through the target. A plasma including charged ions is generated. The charged ions are attracted to bombard the target, such that particles are ejected from the target and are deposited over a surface of a wafer.

According to some embodiments of the disclosure, a method includes moving a first magnetic element over a back side of a target in a first radial direction relative to an axis, wherein the axis extends through the target. The method includes moving a second magnetic element over the back side of the target in a second radial direction relative to the axis. After moving the first magnetic element in the first radial direction and moving the second magnetic element in the second radial direction, the first magnetic element and the second magnetic element are moved about the axis. A bias voltage is applied to the target. A plasma including charged ions is generated. The charged ions are attracted to bombard the target, such that particles are ejected from the target and are deposited over a surface of a wafer.

According to some embodiments of the disclosure, an apparatus includes a processing chamber configured to house a workpiece, a target holder in the processing chamber, a first magnetic element positioned over a backside of the target holder, a first arm assembly connected to the first magnetic element, a rotational shaft, and a first hinge mechanism connecting the rotational shaft and the first arm assembly.