Patent Publication Number: US-2020303172-A1

Title: Target assembly shield

Description:
BACKGROUND 
     Field 
     Embodiments described herein generally relate to semiconductor process chambers and, more particularly, to shields for use in target assemblies in semiconductor process chambers. 
     Description of the Related Art 
     Integrated circuits (IC) may include more than one million micro-electronic devices such as transistors, capacitors, and resistors. Modern ICs are manufactured in process chambers using a multitude of steps, such as sputter deposition. Sputter deposition is a physical vapor deposition (PVD) method of thin film deposition by sputtering. This involves ejecting material from a target onto a substrate such as a silicon wafer. Sputtered atoms ejected from the target have a wide energy distribution, typically up to tens of eV. The sputtered ions can ballistically fly from the target in straight lines and impact energetically on the substrates, vacuum chamber, or in other components of the process chamber. 
     Sputtering is used extensively in the semiconductor industry to deposit thin films of various materials in integrated circuit processing. Thin antireflection coatings on glass for optical applications are also deposited by sputtering. Because of the low substrate temperatures used, sputtering is an ideal method to deposit contact metals for thin-film transistors. Another familiar application of sputtering is low-emissivity coatings on glass, used in double-pane window assemblies. The coating is a multilayer containing silver and metal oxides such as zinc oxide, tin oxide, or titanium dioxide. 
     However, due to the high energies of the sputtered ions, redeposition is an unfortunate side effect of a standard sputtering process, in which scattered sputtered ions form redeposits in areas of the chamber beside the substrate. For example, unwanted redeposits can form back onto exposed surfaces and chamber components within the process chamber. The redeposited material can spall off as particles. 
     Accordingly, there is a need for a way to effectively shield exposed surfaces and chamber components within a process chamber from redeposits. 
     SUMMARY 
     One or more embodiments described herein generally relate to shields for use in target assemblies and process chambers for processing semiconductor substrates. 
     In one embodiment, a shield in a process chamber includes a shield body having an opening formed through a portion of the shield body, wherein the shield body has a plurality of alignment features formed therein, each of the alignment features configured to align with a pin for locating and aligning the shield, and wherein the shield body has a mounting hole formed therein and configured to secure the shield to the target assembly through one of the alignment features. 
     In another embodiment, a target assembly includes a mounting plate; a plurality of pins extending from the mounting plate; a target support secured to the mounting plate, the target support having a first diameter; a target supported by the target support; and a shield comprising: a shield body having an opening through a portion of the shield body, the opening having a second diameter that is larger than the first diameter, wherein the shield body has a plurality of alignment features formed therein, each of the alignment features configured to align with one of the plurality of pins such that the shield connects with the target support, and wherein the shield body has a mounting hole formed therein and configured to secure the shield to the target support through at least one of the plurality of pins. 
     In another embodiment, a process chamber includes a chamber body comprising a bottom wall, a top wall, and one or more side walls collectively defining a process region; an aperture plate extending from the one or more side walls, the aperture plate having an aperture therethrough; a source over the aperture plate; a movable support structure located within the process region; a plurality of target assemblies, each target assembly configured to sputter material through the aperture toward the substrate support, wherein each target assembly comprises: a mounting plate; a plurality of pins extending from the mounting plate; a target support secured to the mounting plate, the target support having a first diameter; a target supported by the target support; and a shield comprising: a shield body having an opening through a portion of the shield body, the opening having a second diameter that is larger than the first diameter, wherein the shield body has a plurality of alignment features formed therein, each of the alignment features configured to align with one of the plurality of pins such that the shield connects with the target support, and wherein the shield body has a mounting hole formed therein and is configured to secure the shield to the target support through at least one of the plurality of pins. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
         FIG. 1  is a schematic side view of a process chamber for processing a semiconductor substrate according to at least one embodiment described in the present disclosure; 
         FIG. 2  is a schematic side view of a target assembly according to at least one embodiment described in the present disclosure; 
         FIG. 3  is a perspective view of a target assembly according to at least one embodiment described in the present disclosure; 
         FIG. 4A  is a rear side view of a shield according to at least one embodiment described in the present disclosure; 
         FIG. 4B  is a front side view of the shield shown in  FIG. 4A  according to at least one embodiment described in the present disclosure; 
         FIG. 5  is a partial perspective view of the target assembly with a shield sliding across a target according to at least one embodiment described in the present disclosure; and 
         FIG. 6  is a partial side view of the target assembly shown in  FIG. 5  with the shield secured to the target support according to at least one embodiment described in the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth to provide a more thorough understanding of the embodiments of the present disclosure. However, it will be apparent to one of skill in the art that one or more of the embodiments of the present disclosure may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring one or more of the embodiments of the present disclosure. 
     Embodiments described herein generally relate to shields for use in target assemblies in semiconductor process chambers. The shields can be used to shield exposed surfaces and chamber components within a process chamber such that unwanted redeposits are prevented from forming back onto the exposed surfaces and chamber components. In some embodiments, the shields are electrically floating and are configured to cover the ends of the target. The target assembly has a target support secured to a mounting plate and a plurality of pins extending from the mounting plate. Each of the shields has a shield body with an opening. The shield body has alignment features configured to align with the plurality pins such that the shield connects with the target support. 
     In some embodiments, the diameter of the shield body opening is larger than the diameter of the target support, assuring protection of all mechanical parts of the target assembly from redeposits. Unlike conventional shields with sharp edges, shields as described herein can be made of smooth edges, helping to minimize particle generation and to prevent arcing. The shields can be made from ceramic material, which is thermally and structurally stable along with having a closer coefficient of thermal expansion (CTE) match to anticipated deposition materials. Additionally, the shields can be serviceable and recyclable, helping save costs and prevent waste. 
       FIG. 1  is a schematic side view of a process chamber  100  for processing a semiconductor substrate according to at least one embodiment described in the present disclosure. The process chamber  100  includes a plurality of target assemblies  120  (two shown here). Each target assembly  120  includes a target  122 , a shield  128 , and a mounting plate  130 . The shield  128  is mounted to the mounting plate  130  such that the shield  128  covers the ends of the target  122  and the target support  206  ( FIG. 2 ). The shield  128  can also be mounted to the target support  206 , which is described further below. In these embodiments, the shield  128  is electrically floating. The material of the target  122  can include a metal or a semiconductor, such as titanium (Ti), silicon (Si), or other similar materials. The target  122  includes a plurality of target magnets (not shown). The plurality of target magnets each has a fixed strength that can be different among the plurality of target magnets. In some embodiments, the plurality of target magnets are electromagnets. The powered target magnets cause sputtering of the target  122  through an electromagnetic interaction, which deposits material from the target  122  onto a substrate  117  through an aperture  126  below at a sputtering direction  124  as shown by the arrows in  FIG. 1 . The target  122  can be cylindrical, but can be other shapes as well. In these embodiments, the target  122  rotates which results in a more even erosion of the material from the target  122  on to the substrate  117 . As shown in  FIG. 1 , the targets  122  can be powered by target power sources  136 . 
     The process chamber  100  further includes a source  132 . The source  132  connects each of the mounting plates  130  to an aperture plate  134  and helps protect each of the target assemblies  120  from the environment. The aperture plate  134  contains the aperture  126  into which the sputtered material is deposited. The aperture plate  134  extends from one or more side walls  102  of a chamber body  101  of the process chamber  100 . The aperture plate  134  forms a portion of the top wall  103  of the chamber body  101 . The chamber body  101  also includes a bottom wall  105 . As such, the side walls  102 , the top wall  103 , and the bottom wall  105  collectively define a volume that includes a movable support structure  104 . 
     The movable support structure  104  includes a robot actuator  109 , a mounting flange  108  disposed on the bottom wall  105  of the process chamber  100 , a robot arm set  112 , and a halo  115 . The robot actuator  109  is configured to move the mounting flange  108 , and thus the robot arm set  112 . The robot arm set  112  can act to move the movable support structure  104  both horizontally and vertically. The combination of the horizontal and vertical motions allows for moving the movable support structure  104  in a three-dimensional space. The robot arm set  112  supports the halo  115 . 
     As shown, the substrate  117  can be placed on the substrate support  116 . The substrate support  116  can be made of a ceramic material, stainless steel, or other suitable materials. The deposition ring  114  surrounds the substrate support  116 , securing the substrate  117  to the substrate support  116 . The deposition ring  114  can be a dielectric material or other suitable materials. The halo  115  at least partially surrounds the deposition ring  114 . The halo  115  can be a metal, such as titanium (Ti) or stainless steel. The halo  115  can include a pattern and/or stiffening elements that reduces strain in the halo  115 , such as an X or cross shape. The halo  115  prevents unwanted deposition of material on the other components of the movable support structure  104  below. In some embodiments, the substrate support  116  includes a heater (not shown), and the heater heats the substrate support  116  and the substrate  117  disposed on the substrate support  116  to temperatures between about 20 degrees Celsius and about 400 degrees Celsius. The substrate support  116  can also include an electrostatic chuck (not shown). 
     The movable support structure  104  is configured to move the substrate  117  from a slot  118  to near the aperture  126  for sputtering of material onto the substrate  117 . The slot  118  allows for the substrate  117  to be placed easily within the process chamber  100  from outside the process chamber  100 . In some embodiments, the slot  118  is not at an ideal vertical position for sputtering onto the substrate  117 , and the movable support structure  104  moves the substrate  117  higher or lower than the slot  118  to begin deposition. Different areas of the substrate  117  that are not currently exposed by the aperture  126  can be reached by moving the substrate support  116  horizontally and/or vertically during deposition processes. During sputtering, the movable support structure  104  moves the substrate  117  along a movement path  106 , as shown by the arrows in  FIG. 1 . The movement path  106  can be a smooth motion without pauses, or the movement path  106  can include portions of the path wherein the substrate support  116  is stationary for portions of the movement path. In some embodiments, the movement path  106  can be a linear movement as shown in  FIG. 1 . The movement path  106  can be in one direction, a back and forth direction, or containing multiple passes. In some embodiments, the movement path  106  can be a circular rotation about the aperture  126 . The movement path  106  is such that the substrate support  116  is under the aperture  126  for at least a portion of the movement path  106  and is not under the aperture  126  for at least a portion of the movement path. 
       FIG. 2  is a schematic side view of a target assembly  200  according to at least one embodiment described in the present disclosure. The target assembly  200  can be similar to the target assemblies  120  described above in  FIG. 1 . In these embodiments, the target assembly  200  includes a mounting plate  210 . The mounting plate  210  is mounted to a source  212 . The source  212  is mounted to an aperture plate  214 . A target support  206  is secured to the mounting plate  210 . A target  202  is supported by the target support  206 . As described above in  FIG. 1 , material from the target  202  is sputtered at a direction  204  as shown by the arrows in  FIG. 2 . A shield  208  is configured be secured to and make face to face contact with the target support  206 , which will be described in more detail below. 
       FIG. 3  is a perspective view of a target assembly  300  according to at least one embodiment described in the present disclosure. In these embodiments, two shields  304  are shown, although any number of shields can be used. The shields  304  are configured to shield each end of a target  302  from redeposits. Similar to the embodiments described above, at least one of the shields  304  is configured to be secured to the target support  306 . The target support  306  is secured to a mounting plate  308 . 
       FIG. 4A  is a rear side view and  FIG. 4B  is a front side view of a shield  400  according to at least one embodiment described in the present disclosure. The shield  400  includes a shield body  402 . The shield body  402  can be made can be made of smooth edges, helping to minimize particle generation and to prevent arcing that occurs in conventional shield bodies. The shield body  402  can be made from ceramic material, which is thermally and structurally stable along with having a closer CTE match to anticipated deposition materials. In some embodiments, the surface of the shield body  402  can be texturized, grit blasted, arc sprayed, or prepared in other similar ways, which improves the adhesion of deposition of material. The shield body  402  has an opening  404  through a portion of the shield body  402 . The opening  404  can be sized such that goes through a majority of the shield body  402 . The shield body  402  includes a plurality of alignment features  408  and a mounting hole  406  formed therein. The alignment features  408  and the mounting hole  406  provides a configuration such that the shield  400  connects to a target support  506 , which will be described in more detail in  FIGS. 5 and 6  below. 
       FIG. 5  is a partial perspective view of the target assembly  500  with a shield  504  sliding across a target  502  according to at least one embodiment described in the present disclosure. The target assembly  500  includes a mounting plate  514 . A plurality of pins  510  extend from the mounting plate  514 . A target support  506  is secured to the mounting plate  514 . In these embodiments, the opening  404  ( FIG. 4 ) of the shield  504  is configured to mate with the target  502  such that the shield  504  can slide across the target  502 . 
     In these embodiments, the shield  504  has a plurality of alignment features  408  (shown in  FIG. 4 ) formed therein. In this embodiment, two alignment features  408  are used. Each of the alignment features  408  are configured to align with one of the plurality of pins  510  when the shield  504  slides in the direction  512  as shown by the arrows in  FIG. 5 . As the shield  504  continues to slide in the direction  512 , the shield  504  eventually mates with the target support  506 . The opening  404  has a diameter that is larger than the diameter of the target support  506 . The larger diameter of the opening  404  in relation to the target support  506  provides the advantage of protecting exposed surfaces and chamber components, such as the target support  506 , from redeposits forming on them. 
       FIG. 6  is a front side view of the target assembly  500  shown in  FIG. 5  with the shield  504  secured to the target support  506  according to at least one embodiment described in the present disclosure. In these embodiments, the mounting hole  406  ( FIG. 4 ) is configured to secure the shield  504  to the target support  506  through at least one of the plurality of pins  510  at a mounting point  602 . At least another one of the plurality of pins  510  rests against the surface of the target support  506 , also helping to stabilize and secure the shield  504  to the target support  506 , helping to protect the exposed surfaces and chamber components from redeposits occurring from sputtering processes. 
     The above embodiments provide several advantages. For example, these shields help protect exposed surfaces and other chamber components from redeposits. In some embodiments, the diameter of the shield body opening is larger than the diameter of the target support, assuring protection of all mechanical parts of the process chamber from redeposits. Additionally, shields as described herein can be made of smooth edges, helping to minimize particle generation and to prevent arcing. The shields can be made from ceramic material, which is thermally and structurally stable along with having a closer CTE match to anticipated deposition materials. Furthermore, the shields can be serviceable and recyclable, helping save costs and prevent waste. 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.