Patent Publication Number: US-2009217953-A1

Title: Drive roller for a cleaning system

Description:
BACKGROUND OF THE DISCLOSURE 
     1. Field of the Invention 
     The present invention relates to an apparatus of a drive roller for a cleaning system, more specifically, a drive roller used in a semiconductor substrate cleaning for use in semiconductor manufacturing. 
     2. Description of the Background Art 
     In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting, and dielectric materials are deposited on or removed from a surface of a substrate. As layers of materials are sequentially deposited and removed, the substrate may become non-planar and require planarization, in which previously deposited material is removed from the substrate to form a generally even, planar or level surface. The process is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage and scratches. The planarization process is also useful in forming features on the substrate by removing excess deposited material used to fill the features and to provide an even or level surface for subsequent deposition and/or other integrated circuit fabrication process. 
     During planarization process, a polishing fluid, such as slurry, may polish away material from the substrate surface. Some contaminants or particles may be generated during the polishing process. The slurry contaminants and/or particles may be present on the substrate after polishing. Accordingly, a cleaning process is performed after the polishing process to remove the polishing residuals, particles, and contaminants from the substrate surface. In one type of conventional cleaning process, the substrate is rotated during cleaning to provide uniform cleaning across the entire wafer surface. In conventional practice, the substrate is typically positioned on a plurality of rollers in a rotation system. The rollers hold and rotate the substrate during cleaning. 
     During cleaning, the substrate may slip while in contact with the rollers, thereby causing substrate rotation to momentarily decelerate or cease. The change in rotation may not only causes uneven cleaning or processing across the substrate surface, but also generate particles which may potentially damage and contaminate the substrate. Furthermore, once the substrate has slipped from the roller, the substrate may become misaligned in the cleaner and be damaged when retrieved by a robot. Additionally, after a number of cleaning cycles, the material used to fabricate the roller may be eroded, deteriorated, or worn out by the chemicals utilized during cleaning the substrate. Erosion or gradual degradation of the roller material may create particles and reduce the frictional force between the roller and the substrate, thereby increasing the potential of substrate slippage and contamination during cleaning. 
     Therefore, there is a need for an improved roller. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved design and configuration of a drive roller for use in a semiconductor substrate cleaning system. In one embodiment, a drive roller includes an outer ring having a disk-shaped body, wherein the disk-shaped body has an inner cylindrical, an upper wall, and an outer cylindrical wall defining a cavity within the disk-shaped body. An inner ring is disposed within the cavity. A groove is formed along an outer side of the inner ring, wherein the groove faces an inner surface of the outer cylindrical wall of the outer ring. 
     In another embodiment, a drive roller disposed in a semiconductor substrate cleaning system is fabricated by a material selected from a group consisting of polytetrafluoroethylene (PTFE), polytetrafluoroethylene (PTFE) containing material and fluoroelastomer and polytetrafluoroethylene (PTFE) containing material. The drive roller is configured to rotate a substrate disposed in the cleaning system. 
     In yet another embodiment, a semiconductor substrate cleaning system includes a base adapted to receive a substrate, at least a drive roller fabricated from a first material arranged to rotate the substrate disposed on the base, at least one idler fabricated from a second material configured to engage the substrate toward the drive roller, wherein the second material has a hardness greater than the first material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
         FIG. 1  depicts a schematic view of one embodiment of a cleaning system in accordance with the invention; 
         FIG. 2A-2B  depict a cross sectional view of the roller of  FIG. 1 ; 
         FIG. 3A-3C  depict a top isometric, top and bottom view of a roller that may be used in the cleaning system of  FIG. 1 ; and 
         FIG. 4  depicts a schematic view of another embodiment of a cleaning system in accordance with the invention. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     DETAILED DESCRIPTION 
     The present invention provides a drive roller having an improved contact surface and rotation control. The drive roller is particularly suitable for use in a semiconductor substrate cleaning system. In one embodiment, the drive roller is fabricated from a material having high hardness, wear resistance, and chemical and temperature compatibility, thereby providing sufficient friction to enjoy good rotation control while engaged with a substrate during cleaning processes. The improved material and roller configuration increases the drive roller serve life, thereby advantageously reducing the overall cost of ownership of the semiconductor cleaning system. 
       FIG. 1  depicts a schematic view of one embodiment of a cleaning system  100  that may be used to clean a substrate. In one embodiment, the cleaning system  100  may be used to clean substrates after a planarization process, a deposition process, or other process as needed. For example, the substrate may be cleaned after a chemical mechanical planarization process (CMP), an electrochemical mechanical planarization process (ECMP), a electroplating or electroless plating process, and so on. 
     In one embodiment, the cleaning system  100  includes a base  102 , one or more drive rollers and one or more idlers. At least one cleaning element  103 , shown in phantom, such as one or more brushes, fluid jets, sonic generators and the like, are positioned in the cleaning system  100  to engage and clean the substrate in a suitable manner. In the embodiment of  FIG. 1 , two drive rollers  106 ,  108  and two idlers  110 ,  112  are utilized. The base  102  is utilized to receive a substrate  104  thereon. Referring temporality to  FIG. 5 , the substrate  104  may include two major surfaces  502 ,  502 ′ and a substrate edge  504 . The edge  504  of the substrate  104  may include an outer edge  510  and bevels  512 ,  514 . The bevels  512 ,  514  meet at the outer edge  510  located in the edge region  504  of the substrate  104 . Referring back to  FIG. 1 , the cleaning system  100  may be utilized to clean the substrate edge region  504 , the outer edge  510 , two major surfaces  502 .  502 ′ and the bevels  512 ,  514 . 
     The drive rollers  106 ,  108  and the idlers  110 ,  112  are adapted to rotate the substrate  104  during cleaning. In one embodiment, the drive rollers  106 ,  108  may be actuated by drivers  114 ,  116 , such as motors, gears, belts or the like, to rotate the substrate  104  positioned on the base  102 . The idlers  110 ,  112  contact the substrate  104  and roll passively therewith so as to secure the rotation of the substrate  104  about a center axis. As the drive rollers  106 ,  108  are actuated to rotate, the drive rollers  106 ,  108  spin the substrate  104  in the direction imparted by the drive rollers  106 ,  108 . The idlers  110 ,  112  contact the substrate  104  from the opposing side of the substrate  104  relative to the drive rollers  106 ,  108  as to maintain the substrate in contact with the drive rollers  106 ,  108  while spinning. 
     In one embodiment, a sensor (not shown) may be interfaced with the idlers  110 ,  112 . The sensor may provide a signal indicative of idler and/or substrate rotation rate to a controller  120  of the cleaning system  100 . Based on the information provided by the sensor, the controller  120  may set the substrate rotation rate by using closed loop control to adjust the power supplied to drivers  114 ,  116  that control the rotation rate of the driver rollers  106 ,  108 . Since the idlers are free to spin with the substrate, and mismatch between the idler and drive roller rotation will be indicative of slippage between at least one of the drive rollers or idler. The controller  120  may be, for example, a microprocessor or microcontroller, programmable logic controller, or any suitable software, and/or hardware control device. 
     In one embodiment, the drive roller  106 ,  108  is mounted on appropriate shafts  122 ,  124  from the drivers  114 ,  116 . The shafts drivers  114 ,  116  may be selectively repositioned laterally to allow position adjustment of the drive rollers  106 ,  108  and then secured by clamp or fastener to retain the desired drive roller position. 
     Although the embodiment depicted in  FIG. 1  illustrates the cleaning system  100  holding the substrate  104  oriented in a horizontal plane, it is contemplated that the substrate  104  may be held and rotated in other planes, including a vertical plane, and/or be moved between different planes by the system  100  while rotating. 
       FIG. 2A  depicts a cross sectional view of one embodiment of the drive roller  106  of  FIG. 1 .  FIGS. 3A-C  which depict isometric, top and bottom views of the roller  106  may be referred to simultaneously for clarity of description. The drive roller  108  may be similarly configured. The drive roller  106  has an inner ring  212  at least partially surrounded by an outer ring  208 . The outer ring  208  has a disk-shaped body  220  having an inner cylindrical wall  280 , an upper wall  296 , and an outer cylindrical wall  292 . The inner cylindrical wall  280  defines a center opening  202  formed through the center of the disk-shaped body  220 . 
     The upper wall  296  of the outer ring  208  connects the inner cylindrical wall  208  to the outer cylindrical wall  292 , defining a cavity  298  within the disk-shaped body  220 . In one embodiment, the dimension of the cavity  298  is sized to accommodate the inner ring  212 , thereby allowing the inner ring  212  to be inserted within the cavity  298  of the outer ring  208 . 
     The outer ring  208  includes a lip  210  extending outwardly from an outer surface  294  of a distal end the outer cylindrical wall  292 , defining a step  290  along the outer surface  294 . A plurality of the sloped flanges  204  are attached on the outer surface  294  of the outer cylindrical wall  292  above the lip  210 . As shown in the enlarged illustration of the sloped flange  204  in  FIG. 2B , the sloped flange  204  has an upper flat portion  250  and a tapered portion  252 . The tapered portion  252  extends from the upper flat surface  250  and slopes radially inward to contact the lip  210 . The sloped flange  204  has a width which is smaller than a width  272  of the lip  210 , thereby causing the substrate  104  to be urged securely against the step  290  defined by the flange  204  and the lip  250 . In one embodiment, the lip  210  may have the radial width  272  between about 0 millimeter (mm) and about 3 millimeter (mm), such as about 1.5 millimeter (mm). 
     In one embodiment, the outer ring  208  may be fabricated from a material with sufficient elasticity, flexibility and frictional force to grip the substrate  104  while having minimal wear or particle generation. Additionally, the material comprising the outer ring  208  may have certain degree of chemical and temperature resistance selected to prevent the outer ring  208  from damage or degradation after a number of processing cycles in the environment of the cleaner system  100 . In one embodiment, the outer ring  208  may be fabricated by a plastic material. In another embodiment, the outer ring  208  may be fabricated by a material selected from a group consisting of polytetrafluoroethylene (PTFE), polytetrafluoroethylene (PTFE) containing material, and fluoroelastomer and polytetrafluoroethylene (PTFE) containing material. The material of the outer ring  208  is configured to have hardness between about 50 Shore A and about 80 Shore A, such as between about 60 Shore A and about 65 Shore A. 
     The inner ring  212  has a groove  286  formed along an outer surface  270 . The groove  286  faces an inner surface  252  of the outer cylindrical wall  292 . The groove  286  has an upper surface  282  and a lower surface  284 . The lower surface  284  of the groove  286  is formed at a position substantially even with or coplanar with horizontal top surface  288  of the lip  210  upon fitting the inner ring  212  into the cavity  298 . In one embodiment, the material of the inner ring  212  may be selected from a material similar to the material used to fabricate the outer ring  208 . Alternatively, the inner ring  212  may be fabricated from a material having similar properties, such as sufficient elastic and frictional force and desired chemical and temperature resistance, but less expensive material for cost reduction concerns. In one embodiment, the materials for fabricating the inner ring  212  may be selected from a group consisting of polyurethane and polyvinyl difloride (PVDF). 
     In operation, the substrate  104  is positioned on the base  102  disposed on the cleaning system  100 , resting on the lip  210  of the drive rollers  106 ,  108 . As the drive rollers  106 ,  108  and the idlers  110 ,  112  are moved toward the substrate  104  (as shown by arrow  278 ), the drive rollers  106 ,  108  and the idlers  110 ,  112  contact the edge  504  of the substrate  104 . Upon contacting the substrate  104 , a reacting and/or counter force generated from the substrate  104  (as shown by arrow  276 ) may be transmitted to the drive rollers  106 ,  108  and the idlers  110 ,  112 . Elasticity and flexibility of the material comprising the drive rollers  106 ,  108  and the idlers  110 ,  112  allows the contacting surface of rollers  106 ,  108  and idlers  110 ,  112  to conform to the substrate for enhanced gripping. As the sloped flange  204  of the outer ring  208  has the tapered portion  252  that guilds the substrate  104  against the lip  250 , the sloped flange  204  provides a lateral force to assist the substrate  104  to be more securely gripped within the drive rollers  106 ,  108 . Furthermore, the groove  286  of the inner ring  212  allows the outer wall  292  to flex inwardly, thereby securely contouring to and gripping the substrate  104  (as shown by arrows  274 ) within the drive roller  106 ,  108  and preventing the substrate  104  from slipping during rotation. 
     In one embodiment, the materials utilized to fabricate the idler  110 ,  112  are selected to have hardness substantial similar to hardness of the material utilized to fabricate the drive roller  106 ,  108 . In one embodiment, the idler  110 ,  112  and the drive roller  106 ,  108  are both fabricated from a material selected from a group consisting of polytetrafluoroethylene (PTFE), polytetrafluoroethylene (PTFE) containing material, and fluoroelastomer and polytetrafluoroethylene (PTFE) containing material. 
     In another embodiment, the material s for fabricating the idler  110 ,  112  are selected to have hardness higher than the hardness of the materials selected to fabricate the drive rollers  106 ,  108 . As the idler  110 ,  112  moves to contact the substrate  104 , a force may be applied to the substrate  104 , providing a pushing pressure toward the substrate  104 . The pressure imparted to the substrate  104  is then transmitted from the substrate  104  to the drive rollers  106 ,  108 . The substrate  104  will deform and be gripped by the softer drive rollers  106 ,  108 . In one embodiment, material utilized to fabricate the idlers  110 ,  112  is selected to have hardness between about 10 Shore A and about 40 Shore A higher than the hardness of the material selected to fabricate the drive roller  106 ,  108 . In another embodiment, the material selected to fabricate the idlers  110 ,  112  has hardness between about 60 Shore A and about 90 Shore A, such as between about 80 Shore A and about 85 Shore A. Suitable examples of the materials that may be used to fabricate the idlers  110 ,  112  are selected from a group consisting of polyurethane and polyvinyl difloride (PVDF). 
       FIGS. 3A-C  depict a isometric, a top and a bottom view of one embodiment of the drive roller  106 . Referring first to  FIG. 3A , as discussed above the drive roller  106 ,  108  includes the outer ring  208  having the disk-shaped body  220 . The disk-shaped body  220  has the center opening  202  formed therethrough. The center opening  202  that allows the shaft  122 ,  124  to pass therethrough. The center opening  202  allows the drive roller  106 ,  108  to be mounted to the cleaning system  100  through the shafts  122 ,  124 . The drive roller  106 ,  108  has at least one sloped flanges  204  formed on the outer surface of disk-shaped body  220  above the lip  210 . In the embodiment depicted herein, a plurality of sloped flanges  204  is formed on the outer surface of the drive roller  106 ,  108 . 
       FIG. 3B  depicts a top view of the drive roller  106 ,  108  as depicted in  FIG. 3A  which has the center opening  202  formed within the disk-shaped body  220 .  FIG. 3C  depicts a bottom view of the drive roller  106 ,  108  having the center opening  202  formed through the disk-shaped body  220 . The inner ring  212  is capped and inserted within the cavity  298  defined within the outer ring  208 . 
       FIG. 4  depicts another embodiment of a cleaning system  400 . Similar to the cleaning system  100  of  FIG. 1 , the cleaning system  400  also includes the base  102 , one or more drive rollers  106 ,  108  and one or more idlers  110 ,  112 . In addition to the mechanical components as depicted in  FIG. 1 , one or more nozzles  402  may be positioned within the cleaning system  400 . In one embodiment, the nozzle  402  may be positioned at a location adjacent to the drive roller  106 ,  108 . The nozzle  402  may direct a fluid spray to the substrate  104 . After a number of cleaning cycles, some particles, contaminants, and process residual may be accumulated at the cut-out portion  206  and the sloped flange  204  of the drive roller  106 ,  108 . Accordingly, the nozzle  402  positioned close to the drive rollers  106 ,  108  may provide a fluid spray to the substrate  104  just prior to contacting the drive rollers  106 ,  108 . In the embodiment wherein the substrate  104  is rotated in a counter clockwise direction (as shown by the arrow  404  in  FIG. 4 ), the nozzle  402  may be positioned at a left side of the drive roller  106 ,  108 , viewing from direction relative to drive roller  106 ,  108 . 
     In one embodiment, the nozzle  402  may be adjusted to aim fluid supplied from the nozzle  402  at the edge  504  of the substrate  104 . The sprayed fluid cleans the substrate edge  504 , such as the outer edge  510 , and the upper  512  and lower bevel  514  of the substrate  104 , as shown in  FIG. 5 , to wash away the potential contaminant and residuals that may be remained on the substrate  104  prior to contacting the roller. Alternatively, the nozzle  402  may be adjusted and angled in different directions to clean other portions of the substrate  104 , including the substrate upper surface  502  or the lower surface  502 ′. 
     In one embodiment, the fluid provided from the nozzle  402  may be at least one of nitrogen containing gas, such as N 2 , NH 3 , N 2 O, and inert gas, such as Ar or He. In another embodiment, the fluid provided from the nozzle  402  may be a liquid with moderate chemical properties, such as H 2 O, DI water and the like. In the particular embodiment depicted in  FIG. 4 , the fluid supplied to the cleaning system  400  is N 2  gas. The fluid removes particles from the edge of the substrate  104 , thereby reducing roller wear. Additionally, the fluid, particularly when in gaseous form, allows the rollers to more securely grip the substrate, thereby reducing the likelihood of slippage. 
     Thus, the drive roller with improved material and design provides a good contact surface and rotation control while engaging with a substrate disposed in the cleaning system. The improved material of the drive roller increases the lifetime of the drive roller and lengthens the drive roller replacement cycle time, thereby advantageously reducing the overall manufacture cost. Additionally, the implement of a nozzle close to the drive roller also provide a source of purging a processing gas to an edge and/or bevel of the substrate, thereby promoting the cleaning efficiency of the substrate. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.