Patent Publication Number: US-2020288857-A1

Title: Hybrid material post-cmp brushes and methods for forming the same

Description:
BACKGROUND 
     The present disclosure relates to brushes for cleaning substrates, and more particularly, to hybrid material post-CMP brushes and methods for forming the same. 
     In the semiconductor manufacturing industry and other industries, brushes are used to remove contaminants from surfaces, such as from semiconductor wafers. Conventional brushes are not received from the manufacturer in a condition to be used immediately. Instead, brushes are typically conditioned (or “broken in”) before use on the intended products to remove particulates from the brush. 
     Limitations and disadvantages of conventional brushes will become apparent to one of skill in the art, through comparison of such approaches with some aspects of the present method and system set forth in the remainder of this disclosure with reference to the drawings. 
     SUMMARY 
     The present disclosure discloses hybrid material post-CMP brushes and methods for forming the same, substantially as illustrated by and described in connection with at least one of the figures, and as set forth more completely in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings. 
         FIG. 1  illustrates an example illustration of a hybrid brush cleaning a surface, in accordance with aspects of this disclosure. 
         FIG. 2A  illustrates a cross-section view of an example hybrid brush, in accordance with aspects of this disclosure. 
         FIG. 2B  illustrates a cross-section view of another example hybrid brush, in accordance with aspects of this disclosure. 
         FIG. 3  illustrates an example arrangement of adjacent layers of the hybrid brush of  FIG. 2A , in accordance with aspects of this disclosure. 
         FIG. 4  illustrates another example arrangement of adjacent layers of the hybrid brush of  FIG. 2A , in accordance with aspects of this disclosure. 
         FIG. 5  illustrates a flow diagram of an example method of forming a hybrid brush, in accordance with aspects of this disclosure. 
         FIG. 6  illustrates a flow diagram of an example method of forming a hybrid brush, in accordance with aspects of this disclosure. 
         FIG. 7  illustrates a flow diagram of an example method of forming a hybrid brush, in accordance with aspects of this disclosure. 
         FIG. 8  illustrates a flow diagram of an example method of forming a hybrid brush, in accordance with aspects of this disclosure. 
     
    
    
     The figures are not necessarily to scale. Where appropriate, similar or identical reference numbers are used to refer to similar or identical components. 
     DETAILED DESCRIPTION 
     Various applications may benefit from physical cleaning of a surface. For example, in semiconductor manufacturing a semiconductor wafer may be cleaned to remove potentially destructive contaminants during one or more stages of fabricating electronic circuits on the wafer. The cleaning can be provided by, for example, a brush that comes in contact with the surface to be cleaned. Other surfaces of devices used in electronic systems may also benefit from cleaning. This may be, for example, where one layer needs to be cleaned before another layer can be put on top of it. For example, display screens and/or touch screens may make use of a cleaning process before adding a next layer. 
     Accordingly, while it should be understood that various embodiments of the disclosure may be used for different applications, example references in this disclosure will be made to brushes for cleaning a surface of a semiconductor wafer for ease of description. 
     During a manufacturing process for a semiconductor wafer, a large number of contaminants may be found on the semiconductor wafer surface in the form of, for example, organic and/or inorganic particles. These contaminants may lead to device failure and poor wafer yields. Moreover, with each new semiconductor technology node, the critical size of the defects on the semiconductor wafer and the tolerable number of defects on the semiconductor wafer becomes smaller. 
     The semiconductor industry may use post-chemical mechanical planarization (pCMP) cleaning in the manufacture of semiconductor devices where brushes, such as, for example, polyvinyl acetate (PVAc) brushes, may be used in combination with application-specific cleaning agents and/or chemicals to remove particles from the semiconductor wafer surface. 
     The various brush types, including PVAc brushes, by nature of the material itself and/or the brush manufacturing/shipping process, will naturally release particles (organic or inorganic) when flushed and/or exposed to a fluid such as, for example, deionized water (DIW) and/or cleaning agents/chemicals. The quantity of particles released can be related to the nature of the fluid (DIW, cleaning agent, etc.) that the brush is exposed to, as well as the process conditions that the brush is used for (e.g., fluid flow rates, brush rotational speeds, etc.). 
     The actual semiconductor layer being processed may dictate the tolerable levels and/or sizes of particles that are released from the brush, and, hence, the time required to condition a brush. The time required for conditioning a brush may range from 10 minutes to 24 hours or more. The resulting lost productivity and correspondingly higher running costs are detrimental to the end-user. Accordingly, a hybrid brush that reduces the conditioning time and/or release of particles during use may be useful. 
     Disclosed are example hybrid brushes that may release fewer contaminants, and example methods for manufacturing such hybrid brushes. 
       FIG. 1  illustrates an example illustration of a hybrid brush cleaning a surface, in accordance with aspects of this disclosure. Referring to  FIG. 1 , there is shown a cleaning system  100  comprising a hybrid brush  102 , where the hybrid brush  102  is cleaning a semiconductor substrate  106 . The hybrid brush  102  may be rotated by a motor (not shown) that is connected to an axle  104 . When the axle  104  rotates, the hybrid brush  102  also rotates, thereby cleaning the surface of the semiconductor substrate  106 . In various embodiments, fluid may be introduced via the axle  104  to flow outward to the surface of the hybrid brush  102 , the fluid may be introduced to a surface of the hybrid brush  102 , and/or the fluid may be introduced to a surface of the semiconductor substrate  106 . While not shown, a system may have two hybrid brushes  102  on either side of the semiconductor device  106  (or any other device) so that both sides can be cleaned at the same time. 
       FIG. 2A  illustrates a cross-section view of an example hybrid brush, in accordance with aspects of this disclosure. Referring to  FIG. 2A , there is shown an example hybrid brush  200  with a mandrel  202 , a first layer  204 , and a second layer  206 . The hybrid brush  200  may be used to implement the hybrid brush  102  in the cleaning system  100  of  FIG. 1 . The mandrel  202  has a central opening  203  that allows an axle, such as, for example, the axle  104 , to fit into the opening  203  such that when the axle  104  rotates, the hybrid brush  200  can also rotate. 
     The hybrid brush  200  may additionally be fastened to the axle  104  by a fastening mechanism such as, for example, a clip, the axle snapping into the opening  203 , a protrusion in the axle  104  and/or the opening  203  providing force against each other to keep the axle  104  and hybrid brush  200  together, nuts at one of ends of the hybrid brush  200  to hold it in place on the axle  104 , etc. 
     The example first layer  204  is formed or fastened onto the mandrel  202 , and the second layer  206  is formed or fastened on to the first layer  204 . In various embodiments, the second layer  206  may be denser or less compressible. The first layer  204  and the second layer  206  may be such that more force is required to compress the second layer  206  than the first layer  204 . In some embodiments, the two layers  204  and  206  may be formed of similar material except that the second layer  206  is formed to be denser than the first layer  204 . In some other embodiments the second layer  206  may be formed from another material that is denser than the first layer  204 . Accordingly, it may be said generally that the first layer  204  may compress with less force than the second layer  206 . 
     For example, the layers  204  and  206  may comprise different PVAc formulations, or two different materials such as, for example, PVAc for the second layer  206  and polyurethane (PU), polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene vinyl acetate (EVA), etc., for the first layer  204 . 
     In some embodiments, the second layer  206  includes a starch templating agent while the first layer  204  omits the starch templating agent. The starch templating agent may be useful, for example, in cleaning a surface of a substrate. However, the second layer  206  may also use other suitable material in place of starch. Furthermore, in some embodiments the first layer  204  may comprise material where a force needed to compress the molded first layer is substantially the same when the molded first layer is dry as when it is wet with a cleaning fluid used for cleaning the surface. The cleaning fluid may comprise, for example, deionized water or ultrapure water, or other suitable fluids for cleaning surfaces in general, or cleaning a specific surface in particular. 
     In some examples, the first layer  204  and the second layer  206  each include pores, where the pores in the first layer  204  are different in size and/or have a different pore layout pattern than pores in the second layer  206 . For example, the first layer  204  may have larger pores and/or more numerous pores than the second layer  206 . The pore size and distribution may be designed, for example, to allow better fluid distribution in the first layer  204  versus the second layer  206 . The first layer  204  and the second layer  206  may also have different thicknesses depending on, for example, the amount of pressure the second layer  206  may be exposed to when cleaning a substrate such as, for example, the substrate  106 , the density of the second layer  206 , and other design and/or usage parameters. The thicknesses of the first layer  204  and the second layer  206  may be independent from each other. 
     The hybrid brush  200  may be manufactured in various ways. For example, the hybrid brush  200  may have both layers  204  and  206  molded, only one of the layers  204  and  206  molded and the other of the layers  204  and  206  fastened, or both layers  204  and  206  fastened. Fastening may use any suitable technology including, for example, adhesives, sewing, stretch fitting an outer layer over an inner layer, having hooks on an outer surface of the first layer  204  and loops on an inner surface of the second layer  206  or vice versa, or using another type of attachment method similar to the hook and loop method, etc. Additionally, while two layers  204  and  206  are disclosed for the hybrid brush  200 , various embodiments of the disclosure may comprise three or more layers for adhesion/fastening of two layers on either side of the adhesion/fastening layer, to facilitate cleaning of a surface, longevity of the hybrid brush  200 , etc. 
       FIG. 2B  illustrates a cross-section view of another example hybrid brush, in accordance with aspects of this disclosure. Referring to  FIG. 2B , there is shown an example hybrid brush  220  with a mandrel  202 , a first layer  204 , a second layer  206 , and a fastening layer  208 . The hybrid brush  220  may be used to implement the hybrid brush  102  in the cleaning system  100  of  FIG. 1 . 
     The hybrid brush  220  may be similar to the hybrid brush  200  of  FIG. 2A  except that there is a fastening layer  208  shown between the first layer  204  and the second layer  206 . The fastening layer  208  may comprise, for example, adhesive layer or other material attaching the first layer to the second layer  206 . For example, the fastening layer  208  may be an adhesive that fastens the first layer  204  and the second layer  206  directly. The fastening layer  208  may be one part of a 2-part (or more) adhesive, where the other of the two parts may be in a second fastening layer put on top of the first fastening layer, part of the first layer, or a part of the second layer. The fastening layer  208  may also be, for example, material that melts an outer portion of the first layer so that a second layer can be slipped on top of the first layer. When the melted portion solidifies, the first layer may then be securely adhered to the second layer. The fastening layer  208  may also comprise barbs on one or both sides to fasten onto the first layer  204  and/or the second layer  206 . The fastening layer  208  may have an adhesive on one side and barbs on the second side. The fastening layer  208  may have, for example, barbs on one or both sides to attach to loops formed on corresponding one or both of the first layer  204  and the second layer  206 . 
     Therefore, it can be seen that the fastening layer  208  may be one or more of many different materials that can firmly attach the first layer  204  to the second layer  206 . Accordingly, while some examples have been listed, various embodiments of the disclosure need not be limited by those examples. 
       FIG. 3  illustrates an example arrangement of adjacent layers of the hybrid brush of  FIG. 2A , in accordance with aspects of this disclosure. Referring to  FIG. 3 , there is shown the surface  300  with protrusions  302 . The surface  300  may be the outer surface of, for example, the mandrel  202  and/or the outer surface of the first layer  204 . The protrusions  302  may be provided, for example, to improve fastening between the mandrel  202  and the first layer  204  and/or between the first layer  204  and the second layer  206 . The protrusions  302  may taper such that the cross-section area of a base of a protrusion  302  at the surface  300  is larger than a cross-section area of the protrusion  302  above the surface  300 . 
     The protrusions  302  may be used for various embodiments such as, for example, when the inner layer  204  is molded around the mandrel  202 . Similarly, the protrusions may be used when the outer layer  206  is molded around the inner layer  204 . Another embodiment may also have protrusions  302  on an outer surface of the inner layer  204  and corresponding depressions on an inner surface of an outer layer  206 , where the protrusions of one surface align with and are inserted into the corresponding depressions of a counterpart surface. 
     The surface  300  may also be an outer surface of any other layer that may be fastened to an adjacent layer. While the protrusions may be present as shown, it should be noted that various embodiments have, more, fewer, and/or different protrusions, or omit the protrusions. 
       FIG. 4  illustrates another example arrangement of adjacent layers of the hybrid brush of  FIG. 2A , in accordance with aspects of this disclosure. Referring to  FIG. 4 , there is shown the surface  400  with depressions  402 . The surface  400  may be the outer surface of, for example, the mandrel  202  and/or the outer surface of the first layer  204 . The depressions  402  may be provided, for example, to facilitate fastening between the mandrel  202  and the first layer  204  and/or between the first layer  204  and the second layer  206 . 
     The depressions  402  may be used for many embodiments such as, for example, when the inner layer  204  is molded around the mandrel  202 . Similarly, the protrusions may be used when the outer layer  206  is molded around the inner layer  204 . Another embodiment may also have depressions  402  on an outer surface of an inner layer and corresponding protrusions on an inner surface of an outer layer, where the protrusions may be inserted into the corresponding depressions  402 . The depressions  402  may taper such that the cross-section area of the depressions  402  at the surface  400  is larger than the cross-section area of the depressions  402  below the surface  400 . 
     The surface  400  may also be an outer surface of any other layer that may be fastened to an adjacent layer. While the depressions  402  may be present as shown, it should be noted that various embodiments need not have any depressions. 
       FIG. 5  illustrates a flow diagram of an example method of forming a hybrid brush, in accordance with aspects of this disclosure. Referring to  FIG. 5 , there is shown an example flow diagram  500  that describes forming a hybrid brush such as, for example, the hybrid brush  200  of  FIG. 2A . At block  502 , the mandrel  202 , is placed into a first mold. At block  504 , a first material is injected into the first mold to form the first layer  204 . The first mold may be formed to allow an outer surface of the first layer  204  to be smooth, or to have protrusions and/or depressions. Some embodiments may form an outer surface of the first layer  204  to have both protrusions and depressions. 
     At block  506 , the mandrel  202  and the first layer  204  are removed from the first mold. At block  506 , the mandrel  202  and the first layer  204  may be treated, for example, by removing extraneous material present from the molding process that may not be desired, chemically treating the first layer  204 , heat treating the first layer  204 , etc., to prepare the mandrel  202  and/or the first layer  204  for putting the mandrel and the first layer into the second mold. 
     At block  508 , the mandrel  202  and the first layer  204  are placed into a second mold. At block  510 , a second material may be injected into the second mold to form the second layer  206 . The second material may be denser than the first material, or less compressible than the first material. The second mold may be formed to allow an outer surface of the second layer  206  to be smooth, or to have protrusions and/or depressions. Some embodiments may form an outer surface of the second layer  206  to have both protrusions and depressions. 
     At block  512 , the hybrid brush  200  with the first and second layers  204  and  206  may be removed from the second mold. At block  514 , the hybrid brush  200  may be, for example, cleaned up by removing extraneous material present from the molding process that may not be desired in a finished hybrid brush. 
     In some embodiments, the first material may comprise a first polyvinyl acetate formulation and the second material may comprise a second polyvinyl acetate formulation. In other embodiments, the first material may be a material other than a polyvinyl acetate formulation, while the second material may be a polyvinyl acetate formulation. Additionally, the first and/or the second material, as the case may be, may be replaced with other material(s) that is suitable for the cleaning process for which the hybrid brush  200  is intended. 
     Furthermore, the first layer may have characteristics such that a substantially similar force is needed to compress the first layer when it is dry as when it is wet with a cleaning fluid used for cleaning a surface of the substrate, or a surface of another object. 
       FIG. 6  illustrates a flow diagram of an example method of forming a hybrid brush, in accordance with aspects of this disclosure. Referring to  FIG. 6 , there is shown an example flow diagram  400  that describes forming a hybrid brush such as, for example, the hybrid brush  220  of  FIG. 2B . At block  602 , a mandrel  202  is placed into a first mold. At block  604 , a first material is injected into the first mold to form the first layer  204 . The first mold may be formed to allow an outer surface of the first layer  204  to be smooth, to have protrusions, or to have depressions. Some embodiments may form an outer surface of the first layer to have both protrusions and depressions. At block  606 , the mandrel  202  and the first layer  204  are removed from the first mold. 
     At block  608 , a fastening layer  208  is put on the first layer  204 . At block  610 , a second layer  206  may be secured to the first layer via the fastening layer  208 . The fastening layer  208  may be, for example, a layer of adhesive or any other material suitable for firmly fastening the first layer  204  to the second layer  206 . 
     There may be additional processes such as, for example, cleaning/trimming excess material from the first layer  204  when the mandrel  202  and the first layer  204  are removed from the first mold. Another embodiment may comprise using a second mold, much as with respect to  FIG. 5 , after the fastening layer  208  is put on the first layer  204 . Still another embodiment may comprise putting the fastening layer  208  on an inner surface of the second layer  206  if the second layer  206  is pre-formed to be put onto the first layer  204 . 
       FIG. 7  illustrates a flow diagram of an example method of forming a hybrid brush, in accordance with aspects of this disclosure. The flow diagram  700  describes a process similar to  FIG. 6 , except that the fastening layer is not used. Rather, the second layer  206  is put directly on to the first layer  204 . The second layer  206  may be, for example, a tubular shape that is slid on the first layer  204 , or wrapped around the first layer  204  and fastened in place by adhering one end of the material for the second layer  206  to the other end, or by sewing the second layer  206  to the first layer  204 , etc. 
       FIG. 8  illustrates a flow diagram of an example method of forming a hybrid brush, in accordance with aspects of this disclosure.  FIG. 8  describes a process where molding is not used. At block  802 , the first layer  204  may be placed about the mandrel  202  similarly as the second layer  206  was described to be put around the first layer  204  in  FIG. 7 . At block  804 , the second layer  206  may be put on the first layer  204  using any appropriate method including those described above. 
     Additionally, various embodiments of the disclosure may use any combination of steps described previously. For example, the first layer  204  may be put around the mandrel  202  as in  FIG. 8 , and the second layer  206  may be molded around the first layer  204 , etc. Additionally, although not shown, the molding process and or the forming process of the various layers may be under machine control, where the machine may execute instructions stored in memory. 
     While some methods of forming the hybrid brush were described, it should be noted that various embodiments of the disclosure may use other suitable methods that have not been described to form the hybrid brush. 
     An aspect of the disclosure may be a hybrid brush for cleaning a surface, comprising a mandrel, a first layer that is molded about the mandrel, wherein the first layer comprises a first material, and a second layer molded about the first layer, where the second layer comprises a second material. The molded first layer may compress under less force than the molded second layer. The molded first layer may not comprise a starch templating agent while the molded second layer may comprise a starch templating agent. A respective outer surface of the molded first layer and/or the molded second layer may be substantially free of protrusions. Various embodiments may have a respective outer surface of the molded first layer and/or the molded second layer with protrusions and/or depressions. The molded first layer may comprise larger pores than the molded second layer. The molded first layer may have a first pore distribution that is different than a second pore distribution for the molded second layer. 
     The thickness of the molded first layer may be independent of the thickness of the molded second layer. The first material may comprise a first polyvinyl acetate formulation and the second material may comprise a second polyvinyl acetate formulation. There may be a third layer between the first layer and the second layer, where the third layer may facilitate securing the molded first layer to the molded second layer. 
     A force to compress the molded first layer may be substantially the same when the molded first layer is dry as when it is wet with a cleaning fluid used for cleaning the surface. 
     An aspect of the disclosure may be a method for forming a brush for cleaning a substrate, comprising placing a mandrel in a first mold, forming a first layer around the mandrel by injecting a first material into the first mold, removing the mandrel with the first layer from the first mold, placing the mandrel with the first layer into a second mold, and forming the second layer surrounding the first layer by injecting a second material into the second mold. 
     The method may further comprise forming a third layer surrounding the first layer, prior to forming the second layer. The first mold may form depressions on an outer surface of the first layer. A first cross-section area of each of the depressions at the outer surface of the first layer may be smaller than a second cross-section area of each of the depressions below the outer surface of the first layer. 
     The first layer may compress under less force than the second layer. The first material may comprise a first polyvinyl acetate formulation and the second material may comprise a second polyvinyl acetate formulation. In some embodiments, the first material may not comprise polyvinyl acetate formulation while the second material may comprise polyvinyl acetate formulation. In some embodiments, the first material may not have a starch templating agent. In some embodiments, the second material may have a starch templating agent. 
     The first layer may comprise larger pores than the second layer. The thickness of the first layer may be independent of the thickness of the second layer. A respective outer surface of the first layer and/or the second layer may be substantially free of protrusions. Other embodiments may have a respective outer surface of the first layer and/or the second layer have protrusions and/or depressions. The method may also comprise treating the first layer after the mandrel and the first layer are removed from the first mold. 
     An embodiment of the present methods and systems utilize hardware, software, and/or a combination of hardware and software. For example, hardware and/or software may be utilized to control making a hybrid brush, testing suitability of the hybrid brush, and/or analyzing effluents to determine effectiveness of the hybrid brush in usage. Any kind of computing system or other apparatus adapted for carrying out the methods described herein is suited. A typical combination of hardware and software may include a general-purpose computing system with a program or other code that, when being loaded and executed, controls the computing system such that it carries out the methods described herein. Another typical implementation may comprise one or more application specific integrated circuit or chip. Some implementations may comprise a non-transitory machine-readable (e.g., computer readable) medium (e.g., FLASH memory, optical disk, magnetic storage disk, or the like) having stored thereon one or more lines of code executable by a machine, thereby causing the machine to perform processes as described herein. As used herein, the term “non-transitory machine-readable medium” is defined to include all types of machine readable storage media and to exclude propagating signals. 
     As utilized herein the terms “circuits” and “circuitry” refer to physical electronic components (i.e. hardware) and any software and/or firmware (“code”) which may configure the hardware, be executed by the hardware, and or otherwise be associated with the hardware. As used herein, for example, a particular processor and memory may comprise a first “circuit” when executing a first one or more lines of code and may comprise a second “circuit” when executing a second one or more lines of code. As utilized herein, “and/or” means any one or more of the items in the list joined by “and/or.” As an example, “x and/or y” means any element of the three-element set {(x), (y), (x, y)}. In other words, “x and/or y” means “one or both of x and y”. As another example, “x, y, and/or z” means any element of the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means “one or more of x, y and z”. As utilized herein, the term “exemplary” means serving as a non-limiting example, instance, or illustration. As utilized herein, the terms “e.g.” and “for example” set off lists of one or more non-limiting examples, instances, or illustrations. As utilized herein, circuitry is “operable” to perform a function whenever the circuitry comprises the necessary hardware and code (if any is necessary) to perform the function, regardless of whether performance of the function is disabled or not enabled (e.g., by a user-configurable setting, factory trim, etc.). 
     While the present method and/or system has been described with reference to certain implementations, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present method and/or system. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from its scope. Therefore, the present method and/or system are not limited to the particular implementations disclosed. Instead, the present method and/or system will include all implementations falling within the scope of the appended claims, both literally and under the doctrine of equivalents.