Patent Publication Number: US-9902038-B2

Title: Polishing apparatus, polishing method, and semiconductor manufacturing method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior U.S. Provisional Patent Application No. 62/112,419 filed on Feb. 5, 2015, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present embodiments relate to a polishing apparatus, a polishing method, and a semiconductor manufacturing method. 
     BACKGROUND 
     In recent years, downscaling in manufacturing of a semiconductor device is approaching a physical limit. Accordingly, a semiconductor device has been progressively formed in three dimensions as a new method for increasing the density of chips. For example, development of a FinFET structure as a logic semiconductor and a three-dimensional memory structure as a semiconductor memory has been advanced. 
     However, there is a problem that loads on processes are greatly increased during formation of a three-dimensional semiconductor device. 
     For example, in a CMP (Chemical Mechanical Polishing) process to flatten a wafer, the amount of polishing is greatly increased as compared to that in conventional techniques and a required time for the CMP process is also increased due to increase in the polishing amount. Furthermore, when the number of processed wafers is increased, the state of a polishing surface of a polishing pad gradually changes and accordingly the polishing rate may change. For example, at the beginning of use of the polishing pad, a small quantity of abrasive grains remains on the polishing pad. However, when the number of processed wafers increases, the amount of abrasive grains remaining on the polishing pad increases and thus the polishing rate increases. 
     Accordingly, in the CMP process, it is required to increase the polishing rate while keeping the flatness and also to stabilize the polishing rate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view of a polishing apparatus  1  according to a first embodiment; 
         FIG. 2  is a side view of the polishing apparatus  1  shown in  FIG. 1 ; 
         FIG. 3  is a schematic cross-sectional view of a cylindrical member  131  and nozzles  132  of the polishing apparatus  1  shown in  FIG. 1 ; 
         FIG. 4  is a schematic cross-sectional view of a polishing method according to the first embodiment; 
         FIG. 5  is a schematic plan view of the polishing apparatus  1  according to a second embodiment; and 
         FIG. 6  is a cross-sectional view of a dresser  14  of the polishing apparatus  1  shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments will now be explained with reference to the accompanying drawings. The present invention is not limited to the embodiments. 
     According to an embodiment, a polishing apparatus comprises a polisher, a holder, and a supplier. The polisher polishes a semiconductor substrate or a polishing target film on a semiconductor substrate. The holder holds the semiconductor substrate and presses the semiconductor substrate or the polishing target film against the polisher to rub the semiconductor substrate or the polishing target film against the polisher. The supplier has a nozzle that is to be inserted to the inside of the polisher and that supplies a polishing solution to the inside of the polisher. 
     (First Embodiment) 
     First, an embodiment of a polishing apparatus that has nozzles protruding from a cylindrical member is explained as a first embodiment.  FIG. 1  is a schematic plan view of a polishing apparatus  1  according to the first embodiment.  FIG. 2  is a side view of the polishing apparatus  1  shown in  FIG. 1 .  FIG. 3  is a schematic cross-sectional view of a cylindrical member  131  and nozzles  132  of the polishing apparatus  1  shown in  FIG. 1 . 
     As shown in  FIG. 1 , the polishing apparatus  1  includes a polisher  11 , a holder  12 , a supplier  13 , and a dresser  14 . 
     The polisher  11  is, for example, a polishing pad that is made of a resin and that polishes a polishing target film  21  (see  FIG. 2 ) on a semiconductor substrate  2 . The polisher  11  has a circular polishing surface  111  that polishes the polishing target film  21 . The polisher  11  is capable of rotating in the direction of an arrow A 1  around the center of the polishing surface  111  as an axis. The polisher  11  polishes the polishing target film  21  while being rotated by drive force of a drive source D 1  (such as a motor) shown in  FIG. 2 . 
     The polisher  11  can directly polish the rear surface of the semiconductor substrate  2 . The polisher  11  can be formed of, for example, expanded polyurethane to have air holes (micro voids) therein. Because of having the air holes, the polisher  11  can easily hold therein abrasive particles (abrasive grains) of a polishing solution. The polishing solution is a liquid (a solution) to be used for polishing of the polishing target film  21  or the semiconductor substrate  2  and contains abrasive particles. The polishing solution is also called slurry. 
     The holder  12  is, for example, a platen (a jig) that has the semiconductor substrate  2  adhered thereto to hold the semiconductor substrate  2 . To enable the holder  12  to hold the entire circular semiconductor substrate  2 , the holder  12  has a disk shape with a larger diameter than that of the semiconductor substrate  2 . As shown in  FIG. 2 , the holder  12  holds the rear surface of the semiconductor substrate  2  and causes the front surface (the polishing target film  21 ) of the semiconductor substrate  2  to face the polisher  11 . The holder  12  presses the polishing target film  21  against the polisher  11  to which the polishing solution is supplied and rubs the polishing target film  21  against the polisher  11 , thereby polishing the polishing target film  21 . More specifically, the holder  12  polishes the polishing target film  21  while being rotated in the direction of an arrow A 2  by drive force of a drive source D 2  (such as a motor). The holder  12  is pressed in a downward direction dl by a pressing device (not shown), thereby applying polishing pressure to the polisher  11 . 
     The supplier  13  includes the cylindrical member  131 , and a plurality of nozzles  132  protruding at different positions from a surface  1311  of the cylindrical member  131  in order to supply the polishing solution to the polisher  11 . The cylindrical member  131  and the nozzles  132  can be formed of the same material (a metal such as stainless steel or a resin, for example) integrally and simultaneously or can be formed of different materials and then joined to each other. 
     As shown in  FIG. 1 , the cylindrical member  131  is positioned between a central portion of the polisher  11  and an end portion thereof and the central axis of the cylindrical member  131  is along a radial direction d 2  of the polisher  11 . The cylindrical member  131  is arranged at a position circumferentially shifted from the holder  12  not to interfere with the holder  12 . 
     A dimension in the direction of the central axis of the cylindrical member  131  is equal to or larger than the diameter of the semiconductor substrate  2 . The position of the cylindrical member  131  corresponds to the semiconductor substrate  2  held by the holder  12  in the circumferential direction of the polisher  11 . The nozzles  132  are arranged on the surface  1311  of the cylindrical member  131  over the entire range of the central axis direction and are arranged to be continuous in the circumferential direction. With this configuration of the cylindrical member  131  and the nozzles  132 , the polishing solution can be efficiently supplied to the entire area of the polisher  11  that is to be subjected to polishing of the semiconductor substrate  2  (hereinafter, also simply “the entire area of the polisher  11 ”) by rotating the cylindrical member  131  and the polisher  11  in a manner as described later. 
     As shown in  FIG. 2 , the cylindrical member  131  can be rotated around the central axis (in the direction of an arrow A 3 ) by drive force of a drive source D 3  (such as a motor). The cylindrical member  131  rotates on the polishing surface  111  with rotation of the polisher  11  while inserting the nozzles  132  to the inside of the polisher  11 . 
     As shown in  FIG. 3 , a hollow space  1312  that communicates with the nozzles  132  is provided inside the cylindrical member  131 . The polishing solution is supplied to the hollow space  1312  from a supply source S (see  FIG. 2 ) of the polishing solution through a pipe P. The cylindrical member  131  supplies the polishing solution supplied to the hollow space  1312  to the respective nozzles  132 . To ensure the rotation of the cylindrical member  131 , the pipe P and the cylindrical member  131  can be connected by a rotary joint or the like. 
     The nozzles  132  supply the polishing solution supplied from the cylindrical member  131  to the polisher  11 . Specifically, the nozzles  132  rotate integrally with the cylindrical member  131  and are moved to a position where the nozzles  132  are inserted to the inside of the polisher  11  (that is, at a lower end portion of the cylindrical member  131 ). The nozzles  132  having being inserted to the inside of the polisher  11  supply the polishing solution supplied from the hollow space  1312  to the inside of the polisher  11 . More specifically, the nozzles  132  form notches  112  (see  FIG. 4 ) on the polisher  11  and discharge the polishing solution at the notches  112  to the inside of the polisher  11 . 
     The dresser  14  notches the polisher  11  to prevent the polisher  11  from being clogged with the polishing solution, for example. The dresser  14  includes abrasive grains (not shown) for notching the polisher  11  on a lower end surface thereof that is in contact with the polisher  11 . The abrasive grains are, for example, diamond. The dresser  14  notches the polisher  11  while being rotated on the polisher  11  by drive force of a drive source (such as a motor, not shown). A rotation axis of the dresser  14  can be parallel to the rotation axis of the polisher  11 . 
     If the polishing solution is coated on the polisher  11  by rotation (centrifugal force) of the polisher  11 , the polishing solution hardly penetrates into the polisher  11  while spreading on the polishing surface  111  of the polisher  11 . In this case, it is difficult that the abrasive particles of the polishing solution are sufficiently held (kept) in the polisher  11  and accordingly quick and flat polishing of the polishing target film  21  is difficult. Even if grooves or recesses are formed on the polisher  11 , the number of grooves or recesses is limited and thus is insufficient to hold the abrasive particles evenly over the entire polisher  11 . Furthermore, even if the dresser  14  notches the polisher  11 , it is difficult to hold abrasive particles therein sufficiently. Because the polisher  11  is formed of a resin or the like to have elasticity, the notches are narrowed or closed before the abrasive particles enter therein. 
     On the other hand, according to the present embodiment, the polishing solution can be discharged through the nozzles  132  at the inside of the notches  112  when the notches  112  are formed by the nozzles  132 . Therefore, the abrasive particles can be reliably supplied to the inside of the polisher  11 . Accordingly, a sufficient number (quantity) of abrasive particles can be held in the polisher  11  and thus the polishing target film  21  can be polished quickly and flatly. Furthermore, because a high polishing rate can be ensured from the beginning of use of the polisher  11  regardless of the number of processed semiconductor substrates  2 , the polishing rate can be stabilized. 
     An example of a polishing method to which the polishing apparatus  1  shown in  FIG. 1  is applied is explained next with reference to also  FIG. 4 .  FIG. 4  is a schematic cross-sectional view of a polishing method according to the first embodiment. 
     First, the cylindrical member  131  is positioned on the polisher  11  by a moving mechanism (not shown) for the cylindrical member  131  and the nozzles  132  at the position of a lower end portion of the cylindrical member  131  are inserted to the inside of the polisher  11 . At that time, the cylindrical member  131  can be pressed in the downward direction dl (see  FIG. 2 ) by a moving mechanism or a pressing mechanism (not shown). 
     Next, as shown in  FIG. 2 , the polisher  11  is rotated in the direction of the arrow Al by the drive source D 1  and the cylindrical member  131  is rotated in the direction of the arrow A 3  by the drive source D 3 . Accordingly, the cylindrical member  131  rotates with rotation of the polisher  11  while inserting the nozzles  132  to the inside of the polisher  11 . At that time, the polishing solution is supplied from the supply source S (see  FIG. 2 ) into the hollow space  1312  (see  FIG. 3 ) of the cylindrical member  131  and the supplied polishing solution is further supplied to the nozzles  132 . 
     As shown in  FIG. 4 , the nozzles  132  inserted into the polisher  11  discharge the polishing solution (denoted by reference character L in  FIG. 4 ) supplied from the hollow space  1312  to the inside of the polisher  11  at lower end portions of the notches  112  formed by the insertion. The polishing solution can be thereby reliably supplied to the inside of the polisher  11 . 
     Because the polisher  11  and the cylindrical member  131  both rotate, supply of the polishing solution by the nozzles  132  to the inside of the polisher  11  can be achieved evenly over the entire area of the polisher  11 . 
     When the polisher  11  made of a material having air holes is used, the polishing solution is discharged from the nozzles  132  into the air holes, thereby enabling the abrasive particles to remain in the air holes. Therefore, more abrasive particles can be held. When the polisher  11  having air holes is used, tip portions (discharge openings) of the nozzles  132  can be inserted to, for example, a depth of 1 to 200 micrometers to enable the tip portions to reach the air holes. Although not particularly limited, the flow rate of the polishing solution per one nozzle  132  can be, for example, 1 ml/min or lower. In this case, assuming that the number of the nozzles  132  is 100, the polishing solution can be supplied at a total flow rate not exceeding 100 ml/min and thus the flow rate of the polishing solution can be suppressed. 
     The nozzles  132  can also discharge the polishing solution outside the notches  112 . The polishing solution discharged outside the notches  112  can be supplied to the polishing surface  111 . 
     Next, the holder  12  rotates with the polishing target film  21  being pressed against the polisher  11  to which the polishing solution is supplied, thereby polishing the polishing target film  21 . Because a sufficient number of abrasive particles are held in the polisher  11  at that time, the polishing target film  21  can be polished quickly and flatly. 
     Therefore, according to the present embodiment, because the polishing solution can be reliably supplied to the inside of the polisher  11  at the notches  112  when the notches  112  are formed on the polisher  11  by the nozzles  132 , a sufficient number of abrasive particles can be held in the polisher  11 . The holder  12  can thereby polish the polishing target film  21  quickly and flatly at a stable polishing rate by using a sufficient number of abrasive particles. That is, according to the present embodiment, the polishing rate can be improved while the flatness is ensured and also the polishing rate can be stabilized. 
     The polishing apparatus  1  according to the present embodiment can be applied to flattening of an insulating film (an oxide film) or the like in a manufacturing process of a three-dimensional semiconductor device such as a three-dimensional stack memory. By applying the polishing apparatus  1  according to the present embodiment to the manufacturing process of the three-dimensional semiconductor device, the manufacturing efficiency can be improved while the quality of the three-dimensional semiconductor device is maintained. 
     (Second Embodiment) 
     An example of the polishing apparatus  1  having nozzles provided in a dresser according to a second embodiment is explained next. In the second embodiment explained below, constituent elements identical to those of the first embodiment are denoted by like reference characters and redundant explanations thereof will be omitted.  FIG. 5  is a schematic plan view of the polishing apparatus  1  according to the second embodiment.  FIG. 6  is a cross-sectional view of a dresser of the polishing apparatus  1  shown in  FIG. 5 . 
     The supplier  13  according to the second embodiment has a different configuration from that of the supplier  13  independent of the dresser  14  according to the first embodiment and is combined (integrated) with the dresser  14 . That is, the supplier  13  also functions as the dresser  14 . 
     Specifically, as shown in  FIG. 6 , the dresser  14  includes the nozzles  132  instead of the abrasive grains explained in the first embodiment. A hollow space  141  that communicates with the nozzles  132  is provided inside the dresser  14 . The hollow space  141  is connected to the supply source S of the polishing solution via the pipe P. Therefore, the dresser  14  can discharge the polishing solution supplied from the supply source S to the hollow space  141  through the nozzles  132 . 
     According to the present embodiment, the nozzles  132  form the notches  112  on the polisher  11  and the polishing solution can be supplied to the inside of the polisher  11  at the notches  112  similarly to the first embodiment. Therefore, also in the second embodiment, the polishing rate can be improved while the flatness is ensured and also the polishing rate can be stabilized. Furthermore, the number of components and the cost can be reduced by integrating the nozzles  132  and the dresser  14 . 
     In the first embodiment, the cylindrical member  131  can be supported to be capable of rotating instead of being driven by the drive source D 3 . In this case, rotation of the polisher  11  with the cylindrical member  131  being pressed against the polisher  11  enables the cylindrical member  131  to rotate following the rotation of the polisher  11 . Therefore, similarly to the configuration shown in  FIG. 1 , the cylindrical member  131  can rotate while inserting the nozzles  132  into the polisher  11  and thus the polishing solution can be supplied over the entire area of the polisher  11 . Furthermore, because the drive source D 3  can be omitted, the cost can be reduced. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.