Patent Publication Number: US-2022212234-A1

Title: Substrate cleaning brush

Description:
TECHNICAL FIELD 
     The present invention relates to a substrate cleaning brush which, when used, is attached to a substrate cleaning apparatus that performs brush cleaning on a substrate. 
     BACKGROUND ART 
     Patent Literature 1 discloses a substrate cleaning brush configured to hold a brush body in a brush holder including an upper attachment part and a lower holding part. The upper half of the brush body is a large diameter part while the lower half is a small diameter part smaller in diameter than the large diameter part. The brush body is made of a porous material that has continuous pores formed therein, is hydrophilic, and exhibits good flexibility and elasticity when moistened. On a center portion of the upper surface of the upper attachment part of the brush holder, a locking portion for attaching the substrate cleaning brush to a brush rotation shaft of a substrate cleaning apparatus is integrally provided in a protruding fashion. The inner diameter of the lower holding part of the brush holder is slightly larger than the outer diameter of the large diameter part of the brush body, and an annular support is integrally formed on the inner peripheral surface of the lower holding part near its lower end. The inner diameter of the annular support is slightly larger than the outer diameter of the small diameter part of the brush body and smaller than the outer diameter of the large diameter part. 
     To mount the brush body in the brush holder, the small diameter part of the brush body is inserted into the circular hole in the annular support of the lower holding part to thereby accommodate the brush body in the lower holding part, and then a fitting portion of the upper attachment part is fitted to an upper end portion of the lower holding part. This leads to a state where the brush body is held in the brush holder and the lower end surface of the brush body sticks out downward from the lower end of the lower holding part. 
     The substrate cleaning is performed by attaching the substrate cleaning brush to the brush rotation shaft on a brush holding arm of the substrate cleaning apparatus, rotating the substrate held by a spin chuck about a vertical axis with a cleaning liquid, such as pure water, supplied onto the substrate, lowering the substrate cleaning brush while causing it to rotate to thereby bring the lower surface of the brush body into contact with the surface of the substrate and, in this state, moving the substrate cleaning brush along the surface of the substrate from a center portion of the substrate toward a peripheral edge portion thereof. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Application Publication No. Hei 9-181025 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the cleaning with the substrate cleaning brush of Patent Literature 1, the lower surface of the small diameter part of the brush body moves over the surface of the substrate, and the soft small diameter part is elastically deformed in the radial direction in such a way as to slope relative to the rotation axis (vertical axis). For this reason, the contact pressure of the small diameter part on the surface of the substrate also varies according to the elastic deformation of the small diameter part in the radial direction. Thus, if the length, in the up-down direction, of the small diameter part that can be elastically deformed in the radial direction is excessively large, the contact pressure of the small diameter part will be large as well, which will make it difficult to evenly clean the cleaning target surface of the substrate. Hence, in order to evenly clean the cleaning target surface, the length, in the up-down direction, of the small diameter part that can be elastically deformed in the radial direction is preferably minimized within such a range as not to impair the cleaning effect of the small diameter part (a range within which elastic deformation occurs so as to bring about a desired cleaning effect). 
     However, the substrate cleaning brush of Patent Literature 1 is such that the small diameter part penetrates through the circular hole in the thin plate-shaped annular support, and the length of the circular hole in the up-down direction is significantly small as compared to the protruding length of the small diameter part from the large diameter part. Thus, the length, in the up-down direction, of the small diameter part that can be elastically deformed in the radial direction is excessively large. This may result in failure to evenly clean the cleaning target surface. 
     In view of the above, an object of the present invention is to provide a substrate cleaning brush suitable for evenly cleaning an entire cleaning target surface of a substrate. 
     Solution to Problem 
     To achieve the above object, a first aspect of the present invention provides a substrate cleaning brush that cleans a substrate by rotating together with a brush rotation shaft of a substrate cleaning apparatus whose axis extends in an up-down direction, and includes a brush holder and a brush body. 
     The brush holder has a holder upper part, a holder lower part, and a holder bottom plate part. The holder upper part is attached to a lower end of the brush rotation shaft. The holder lower part is in a cylindrical shape extending downward from the holder upper part in a holder attached state in which the holder upper part is attached to the brush rotation shaft. The holder bottom plate part is in a hollow disc shape protruding radially inward from an inner edge of a lower end of the holder lower part in the holder attached state. In the holder attached state, a lower surface of the holder upper part, an inner peripheral surface of the holder lower part, and an upper surface of the holder bottom plate part define a brush accommodating space, an inner peripheral edge of the holder bottom plate part defines a circular holder opening having a smaller diameter than an inner diameter of the holder lower part, and a center axis of the brush accommodating space and a center axis of the holder opening substantially coincide with the axis of the brush rotation shaft. 
     The brush body integrally has a held part and a cleaning part. The held part has a circular column shape that is incapable of penetrating through the holder opening and is accommodated and held in the brush accommodating space. The cleaning part has a circular column shape that is smaller in diameter than the held part and capable of penetrating through the holder opening, and penetrates through the holder opening and projects downward in a brush attached state in which the held part is held in the brush accommodating space in the holder attached state. In the brush attached state, the brush body lets a lower surface of the cleaning part contact the substrate from above to clean the substrate. 
     A top-to-bottom length of the holder opening of the brush holder is longer than or equal to 1/4 of a protruding length of the cleaning part of the brush body from the held part thereof and shorter than the protruding length of the cleaning part. Note that, considering the cleaning ability of the cleaning part, the top-to-bottom length of the holder opening is preferably 2/3 of the protruding length of the cleaning part or longer. 
     In the case of cleaning the cleaning target surface of the substrate, the lower surface of the cleaning part of the brush body rotating about the brush rotation shaft is pressed against the cleaning target surface from above and moved over the cleaning target surface. In this movement, the cleaning part is elastically deformed in the radial direction in such a way as to slope relative to the brush rotation shaft. 
     With the above configuration, the top-to-bottom length of the holder opening of the brush holder is longer than or equal to 1/4 of the protruding length of the cleaning part of the brush body from the held part thereof and shorter than the protruding length of the cleaning part. Thus, the held part side (upper end side) of the cleaning part of the brush body in a top-to-bottom length range of 1/4 of the protruding length of the cleaning part or longer is restricted from being elastically deformed in the radial direction by the holder opening. In this way, the length of the cleaning part in the up-down direction that can be elastically deformed in the radial direction can be minimized within such a range as not to impair the cleaning effect of the cleaning part (a range within which elastic deformation occurs so as to bring about a desired cleaning effect). Accordingly, the entire cleaning target surface can be evenly cleaned. 
     A second aspect of the present invention is the substrate cleaning brush according to the first aspect, in which the brush holder has a cylindrical brush deformation restricting part protruding downward from the inner peripheral edge of the holder bottom plate part in the holder attached state, and an inner peripheral surface of the brush deformation restricting part defines the holder opening with the inner peripheral edge of the holder bottom plate part. 
     With the above configuration, the brush deformation restricting part protruding downward from the inner peripheral edge of the holder bottom plate part is provided, and the holder opening is defined by the inner peripheral edge of the holder bottom plate part and the inner peripheral surface of the brush deformation restricting part. This eliminates the need to increase the thickness of the holder bottom plate part according to the top-to-bottom length of the holder opening. 
     A third aspect of the present invention is the substrate cleaning brush according to the first or second aspect, in which, on the inner peripheral surface of the holder lower part, a plurality of protrusions are formed which elastically deform part of an outer peripheral surface of the held part of the brush body accommodated in the brush accommodating space radially inward. 
     With the above configuration, the plurality of protrusions of the holder lower part can suppress rotation of the held part of the brush body relative to the brush holder. 
     Advantageous Effect of Invention 
     According to the present invention, it is possible to evenly clean an entire cleaning target surface of a substrate. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exploded perspective view of a substrate cleaning brush according to an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the substrate cleaning brush in a state where the brush body in  FIG. 1  is mounted in the brush holder in  FIG. 1 . 
         FIG. 3  is a set of horizontal cross-sectional views of  FIG. 2 , with  FIGS. 3( a ), 3( b ), 3( c ), and 3( d )  illustrating a cross section, a IIIb-IIIb cross section, a IIIc-IIIc cross section, and a IIId-IIId cross section, respectively. 
         FIG. 4  is a set of cross-sectional views of substrate cleaning brushes in examples in which the brush body in  FIG. 1  is mounted in brush holders of other configurations, with  FIG. 4( a )  representing a first modification and  FIG. 4( b )  representing a second modification. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A substrate cleaning brush (hereinafter referred to simply as cleaning brush)  1  according to an embodiment of the present invention will be described with reference to  FIGS. 1 to 3 . 
     As illustrated in  FIG. 2 , the cleaning brush  1  includes a brush holder  10  and a brush body  30  and, when used, is attached to the lower end of a brush rotation shaft  2  of a substrate cleaning apparatus. An axis  3  of the brush rotation shaft  2  extends in an up-down direction (substantially vertical direction), and the cleaning brush  1  rotates together with the brush rotation shaft  2  to perform brush cleaning on a cleaning target surface  5  of a substrate  4  (substantially entire upper surface of the substrate  4 ). The substrate  4  to be cleaned is any of various substrates such, for example, as a semiconductor wafer, a glass substrate for a liquid crystal display apparatus or a photomask, and a substrate for an optical disk, and the substrate cleaning apparatus performs brush cleaning by holding the substrate  4  in a horizontal orientation and rotating it about a vertical axis (axis  3 ) with a cleaning liquid supplied onto the cleaning target surface  5 . 
     As illustrated in  FIGS. 1 to 3 , the brush holder  10  includes an upper holder (holder upper part)  11  and a lower holder  12 . The upper holder  11  and the lower holder  12  are made of a hard resin material, such as polypropylene, for example, and are combined together by assembling the lower holder  12  to the upper holder  11 . 
     The upper holder  11  integrally has a disc-shaped upper-holder large diameter part  13 , a disc-shaped upper-holder small diameter part  14  slightly smaller in diameter than the upper-holder large diameter part  13 , and a holder male screw part  15  with a male thread formed on its outer peripheral surface, and the upper-holder large diameter part  13 , the upper-holder small diameter part  14 , and the holder male screw part  15  are provided coaxially. The upper-holder small diameter part  14  protrudes downward from the lower surface of the upper-holder large diameter part  13 , and the holder male screw part  15  protrudes upward from the upper surface of the upper-holder large diameter part  13 . On the outer peripheral surface of the upper-holder small diameter part  14 , a plurality (two in this embodiment) of locking protrusions  16  are provided in a protruding fashion. In the upper surface of the holder male screw part  15 , a rectangular hole  17  with a closed bottom is formed to extend downward. 
     The upper holder  11  is attached to the lower end of the brush rotation shaft  2  by inserting a rectangular shaft (not illustrated) on the brush rotation shaft  2  side of the substrate cleaning apparatus into the rectangular hole  17  and screwing a nut (not illustrated) to the holder male screw part  15 , and rotates together with the brush rotation shaft  2 . 
     The lower holder  12  integrally has a cylindrical holder lower part  18 , a hollow disc-shaped holder bottom plate part  19 , a cylindrical brush cover part  20 , and a cylindrical brush deformation restricting part  21 , and the holder lower part  18 , the holder bottom plate part  19 , the brush cover part  20 , and the brush deformation restricting part  21  are provided coaxially. 
     The outer diameter of the holder lower part  18  is made substantially equal to the outer diameter of the upper-holder large diameter part  13 , and the inner diameter of the holder lower part  18  is made substantially equal to or slightly larger than the outer diameter of the upper-holder small diameter part  14 . In one end portion (upper end portion) of the holder lower part  18 , a plurality (two in this embodiment) of locking holes  22  are formed which the locking protrusions  16  of the upper-holder small diameter part  14  can be inserted into and engaged with. The lower holder  12  is fixedly attached to the upper holder  11  by inserting the lower end of the upper-holder small diameter part  14  into the holder lower part  18  from above and engaging the locking protrusions  16  with the locking holes  22 . 
     The holder lower part  18  extends downward from the upper holder  11  in a holder attached state in which the lower holder  12  is attached to the upper holder  11  and the upper holder  11  is attached to the brush rotation shaft  2 . In the holder attached state, the holder bottom plate part  19  protrudes radially inward from the inner edge of the lower end of the holder lower part  18 . The brush cover part  20  has a cylindrical shape with a diameter equal to that of the holder lower part  18  and, in the holder attached state, extends downward continuously from the lower end of the holder lower part  18 . The brush deformation restricting part  21  has a cylindrical shape with a diameter smaller than that of the brush cover part  20  and, in the holder attached state, protrudes downward from the inner peripheral edge of the holder bottom plate part  19 . The protruding height of the brush cover part  20  and the protruding height of the brush deformation restricting part  21  from the holder bottom plate part  19  can each be set as desired. In this embodiment, both are set at a substantially equal protruding height. 
     In the holder attached state, the lower surface of the upper holder  11 , the inner peripheral surface of the holder lower part  18 , and the upper surface of the holder bottom plate part  19  define a brush accommodating space  23 . Together with the inner peripheral surface of the brush deformation restricting part  21 , the inner peripheral edge of the holder bottom plate part  19  defines a circular holder opening  24  with a smaller diameter than the inner diameter of the holder lower part  18  (the diameter of the inner peripheral surface of the holder lower part  18 ). Also, the center axis of the brush accommodating space  23  and the center axis of the holder opening  24  substantially coincide with the axis  3  of the brush rotation shaft  2 . 
     The brush body  30  is made of a spongy porous material having hydrophilicity, and integrally has a circular column-shaped held part  31  and a circular column-shaped cleaning part  32  smaller in diameter than the held part  31 . The porous material is, for example, a porous material using PVA as its raw material (PVAt-based porous material). The PVAt-based porous material is manufactured by, for example, generating polyvinyl formal by a formalizing reaction in which formaldehyde is bonded to PVA with an acid as a catalyst, during which a pore generating agent is added to form pores, to thereby complete an insoluble porous substrate, and thereafter extracting the bubble generating agent. The brush body  30  made of the PVAt-based porous material has continuous pores formed in its entire body, is hydrophilic, has good flexibility and elasticity when moistened, and loses the elasticity and hardens when dried. 
     The held part  31  has such an outer diameter as to be incapable of penetrating through the holder opening  24  (an outer diameter larger than the holder opening  24 ), and is accommodated and held in the brush accommodating space  23 . The cleaning part  32  is smaller in diameter than the held part  31  and has such an outer diameter as to be capable of penetrating through the holder opening  24 , and penetrates through the holder opening  24  and projects downward in a brush attached state in which the held part  31  is held in the brush accommodating space  23  in the holder attached state. To mount the brush body  30  in the brush holder  10 , the upper holder  11  and the lower holder  12  are detached from each other, the cleaning part  32  is inserted into the holder opening  24  of the lower holder  12  and the held part  31  is also accommodated in the brush accommodating space  23 , and then the lower holder  12  is attached to the upper holder  11 . As a result, the held part  31  is sandwiched between and held by the lower surface of the upper holder  11  and the upper surface of the holder bottom plate part  19 . During brush cleaning with the brush body  30 , the lower surface of the cleaning part  32  contacts the cleaning target surface  5  of the substrate  4  from above. 
     On the inner peripheral surface of the holder lower part  18 , a plurality of protrusions  25  that elastically deform part of the outer peripheral surface of the held part  31  accommodated in the brush accommodating space  23  radially inward are integrally provided in a protruding fashion. In this embodiment,  12  protrusions  25  having a semicircular arc shape and extending in the up-down direction are formed at substantially equal intervals in the circumferential direction. 
     A top-to-bottom length L 2  of the holder opening  24  of the brush holder  10  is set to be longer than or equal to 1/4 of a protruding length L 1  of the cleaning part  32  of the brush body  30  from the held part  31  thereof and shorter than the protruding length L 1  of the cleaning part  32  (L 1 &gt;L 2 ≥L1/4). In this embodiment, in consideration of the cleaning ability of the cleaning part  32 , the top-to-bottom length L 2  of the holder opening  24  is set within a range of 1/4 to 2/3 of the protruding length L 1  of the cleaning part  32  (L 1 ×2/3≥L 2 ≥L1/4). 
     In the case of attaching the cleaning brush  1  to the brush rotation shaft  2  of the substrate cleaning apparatus and performing brush cleaning on the cleaning target surface  5  of the substrate  4 , for example, the substrate  4  held by a spin chuck (not illustrated) is rotated about the vertical axis with a cleaning liquid, such as pure water, supplied onto the cleaning target surface  5  of the substrate  4 , and the cleaning brush  1  is lowered from an upper position while being caused to rotate to thereby bring the lower surface of the cleaning part  32  of the brush body  30  into contact with the cleaning target surface  5 , and in this state, the cleaning brush  1  is moved along the cleaning target surface  5  from a center portion of the substrate  4  toward a peripheral edge portion thereof. Since, as described above, the lower surface of the cleaning part  32  of the brush body  30  rotating about the axis  3  of the brush rotation shaft  2  is pressed against the cleaning target surface  5  from above and moved over the cleaning target surface  5 , the cleaning part  32  is elastically deformed in the radial direction in such a way as to slope relative to the brush rotation shaft  2  (axis  3 ). 
     In this embodiment, the top-to-bottom length L 2  of the holder opening  24  of the brush holder  10  is longer than or equal to 1/4 of the protruding length L 1  of the cleaning part  32  of the brush body  30  from the held part  31  thereof and shorter than the protruding length L 1  of the cleaning part  32 . Thus, the upper end side of the cleaning part  32  of the brush body  30  in a top-to-bottom length range of 1/4 of the protruding length L 1  of the cleaning part  32  or longer is restricted from being elastically deformed in the radial direction by the holder opening  24 . In this way, the length of the cleaning part  32  in the up-down direction that can be elastically deformed in the radial direction can be minimized within such a range as not to impair the cleaning effect of the cleaning part  32  (a range within which elastic deformation occurs so as to bring about a desired cleaning effect). Accordingly, the entire cleaning target surface  5  can be evenly cleaned. 
     Moreover, the brush deformation restricting part  21  protruding downward from the inner peripheral edge of the holder bottom plate part  19  is provided, and the holder opening  24  is defined by the inner peripheral edge of the holder bottom plate part  19  and the inner peripheral surface of the brush deformation restricting part  21 . This eliminates the need to increase the thickness of the holder bottom plate part  19  according to the top-to-bottom length L 2  of the holder opening  24 . 
     Furthermore, the plurality of protrusions  25  of the holder lower part  18  can suppress rotation of the held part  31  of the brush body  30  relative to the brush holder  10 . This can further improve the cleaning performance. 
     Note that the present invention is not limited to the embodiment exemplarily described above and its examples, and various changes can be made outside the above embodiment and the like according to the design and the like without departing from the technical idea of the present invention. 
     For example, as illustrated in  FIG. 4( a ) , the brush holder  10  may omit the brush cover part  20  (see  FIG. 2 ). Moreover, as illustrated in  FIG. 4( b ) , the brush cover part  20  and the brush deformation restricting part  21  (see  FIG. 2 ) may be omitted and the holder bottom plate part  19  may be formed thicker to extend the top-to-bottom length of the holder opening  24  to a desired length. 
     INDUSTRIAL APPLICABILITY 
     The present invention is useful as a substrate cleaning brush which, when used, is attached to a substrate cleaning apparatus that performs brush cleaning on a substrate. 
     REFERENCE SIGNS LIST 
     
         
           1  substrate cleaning brush 
           2  brush rotation shaft 
           3  axis of brush rotation shaft 
           4  substrate 
           5  cleaning target surface 
           10  brush holder 
           11  upper holder (holder upper part) 
           12  lower holder 
           13  upper-holder large diameter part 
           14  upper-holder small diameter part 
           15  holder male screw part 
           16  locking protrusion 
           17  rectangular hole 
           18  holder lower part 
           19  holder bottom plate part 
           20  brush cover part 
           21  brush deformation restricting part 
           22  locking hole 
           23  brush accommodating space 
           24  holder opening 
           25  protrusion 
           30  brush body 
           31  held part 
           32  cleaning part 
         L 1  protruding height of cleaning part 
         L 2  top-to-bottom length of holder opening