Abstract:
A novel interchangeable spin chuck system is provided that allows the user to quickly change substrate sizes and spin chuck styles without any extra tools. This system has a two-piece design and overcomes many of the drawbacks of previous spin chuck designs, such as difficulty in seating the spin chuck and ensuring that the spin chuck is at a consistent flatness and height. Furthermore, this spin chuck system allows the spin chucks to be manufactured at a lower cost. Thus, rather than restricting users to “make do” with incorrect spin chucks due to budget limitations, this economical design gives users access to a wider range of spin chuck sizes and styles.

Description:
RELATED APPLICATION 
       [0001]    This application claims the priority benefit of U.S. Provisional Patent Application No. 62/001,430, entitled MULTI-SIZE ADAPTABLE SPINCHUCK SYSTEM, filed May 21, 2014, each of which is incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]    1. Field of the Invention 
         [0003]    The present invention is directed to a novel spin chuck system having interchangeable spin chucks of varying sizes. The system is designed for easy adaptation to accommodate the wide variety of substrates utilized in spin-coating processes. 
         [0004]    2. Description of the Prior Art 
         [0005]    When spin coating substrates, especially microelectronic substrates, the substrate must be held securely while spinning. Typically, this is achieved by using a spin chuck (also called a “spin coater chuck”), which holds the substrate in place using vacuum and/or physical tension. Vacuum is transferred to the substrate via grooves or holes in the spin chuck that are connected to a vacuum source, usually through an opening in the spindle of the spin coater. 
         [0006]    It is often beneficial to be able to use multiple sizes of spin chucks on a single spin coater. This allows multiple-sized substrates to be coated on the same piece of equipment. Different spin coater models use different methods to enable the user to change the spin chuck on the tool. Some spin chucks use a screw in the center of the spin chuck to attach the spin chuck to the top of the spindle. Often, this screw has a hole through the middle that allows vacuum to be pulled across the surface of the spin chuck and down through the spindle of the spin coater. This design requires a screwdriver or allen wrench in order to change the spin chuck, and also creates a recessed area in the center of the spin chuck that can cause a dimple in the center of the substrate when vacuum is pulled. Because the specialized screw is also easily lost, especially down the drain port of the spin coater, the screw itself can cause delays. Other spin chucks slip over the spindle and use some sort of mechanism for locking it to the spindle and/or o-rings in order to transfer vacuum and hold the spin chuck in place. However, these designs have drawbacks because it can be difficult to see if a spin chuck is seated correctly, and chemical or wear damage to the o-rings can cause vacuum or process failure. Additionally, different spin chucks may be machined to different heights or may sit at different heights due to the installation technique, potentially causing variations in coating quality and thickness. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a novel spin chuck assembly that overcomes the foregoing problems. The assembly comprises a base having upper and lower ends, with the base having an opening at the lower end. The opening is configured to allow a spindle to be positioned therein. The spin chuck has upper and lower sides, with the upper side being configured to support a substrate, and the lower side being removably connected to the base upper end. The spin chuck is not removable from the base by a force of less than about 5 in·lbs being applied to one of the spin chuck and base. 
         [0008]    A method of utilizing an adaptable spin chuck assembly is also provided. The method comprises attaching a base having upper and lower ends to a spindle. The base has an opening at the lower end, and the opening receives the spindle therein. A spin chuck having upper and lower sides is attached to the base upper end. A substrate is placed on the spin chuck upper surface. 
         [0009]    In a further embodiment, a spin chuck assembly kit is also provided. The kit comprises a base having upper and lower ends, with the base having an opening at the lower end. The opening is configured to receive a spindle therein. The kit also comprises a plurality of spin chucks that are configured to support a substrate. The spin chucks each have lower sides that are similarly configured to be removably connected to the base upper end. Finally, the kit comprises a storage area, with the base and each spin chuck being contained in the storage area. 
         [0010]    In yet a further embodiment, a spin chuck comprising upper and lower sides is provided. The spin chuck has an annular platform extending from the lower side, and the platform has an inner threaded surface that is configured to be screwed to a base having corresponding threads. The spin chuck upper side is configured to support and secure a substrate thereto during a spin-coating process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a partial sectional view of a base utilized in the inventive spin chuck system; 
           [0012]      FIG. 2  is a partial sectional view of a spin chuck utilized in the inventive spin chuck system; 
           [0013]      FIG. 3  is a schematic drawing demonstrating the installation of the inventive base onto a typical spin coater spindle assembly; 
           [0014]      FIG. 4  is a partial sectional view of the inventive base fully seated on the spindle assembly of  FIG. 3 ; 
           [0015]      FIG. 5  is a partial sectional view of the inventive base when it is not fully seated on the spindle assembly of  FIG. 3 ; 
           [0016]      FIG. 6  is a schematic drawing demonstrating the attachment of the inventive spin chuck to the fully-seated inventive base shown in  FIG. 4 ; 
           [0017]      FIG. 7  is a partial sectional view of the inventive spin chuck system fully attached to the spin coater spindle assembly; 
           [0018]      FIG. 8  is a schematic drawing depicting an alternative spin chuck that could be used in the present invention; 
           [0019]      FIG. 9  is a schematic drawing depicting a further alternative spin chuck that could be used in the present invention; 
           [0020]      FIG. 10  is a kit having a single base and multiple, interchangeable spin chucks according to the invention; and 
           [0021]      FIG. 11  is the kit of  FIG. 10 , but showing the storage arrangement of the base and various spin chucks. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    The present invention overcomes the problems of the prior art by providing a spin chuck system that can be more easily adapted to the particular process being run. 
         [0023]    Turning to  FIG. 1 , a base  10  comprising a pair of cylindrical bodies,  12 ,  14  is illustrated. 
         [0024]    Outer cylindrical body  12  has a wall  16  that has inner and outer surfaces  18 ,  20 , as well as upper and lower ends  22 ,  24 . An opening  26  passes longitudinally through the center of the outer cylindrical body  12 . Inner surface  18  has a section  28  that “steps in,” so as to present a section  16   a  of wall  16  that has an increased thickness as compared to the remainder  16   b  of wall  16 . This increased thickness at  16   a  results in a corresponding narrowing of the diameter of opening  26 . Wall  16  of outer cylindrical body  12  further comprises upper and lower surfaces  30 ,  32  that serve to join inner and outer surfaces  18 ,  20 . Upper surface  30  includes an annular groove  34 , where an o-ring (not shown) could be included to ensure a seal between base  10  and the particular spin chuck (described below). Finally, outer cylindrical body  12  includes a threaded region  35  on outer surface  20 , at upper end  22 . 
         [0025]    Outer cylindrical body  12  can be formed of any number of materials having sufficient rigidity, provided that the material will not react with the process chemicals to which it will be exposed during use. Suitable materials include those selected from the group consisting of aluminum, acetal resin, stainless steel, polyetheretherketone (PEEK), polytetrafluorethylene (PTFE), and polyvinylidene fluoride (PVDF). 
         [0026]    Inner cylindrical body  14  is a bushing that comprises a wall  36  that has inner and outer surfaces  38 ,  40 , as well as upper and lower ends  42 ,  44 . An opening  46  passes longitudinally through the center of the inner cylindrical body  14 . Wall  36  of inner cylindrical body  14  further comprises upper and lower surfaces  48 ,  50  that serve to join inner and outer surfaces  38 ,  40 . Inner surface  38  includes an annular groove  52 , near upper end  42 . An o-ring (not shown) could be included in groove  52  to ensure a seal between base  10  and the spindle (described below). Additionally, there is preferably a pin alignment slot  54  formed in inner surface  38 , near the lower end  44  of inner cylindrical body  14 . As shown in  FIG. 1 , inner cylindrical body  14  is positioned within outer cylindrical body  12 , so that the outer surface  40  of inner cylindrical body  14  is against the inner surface  18  of outer cylindrical body  12 . Outer and inner cylindrical bodies  12 ,  14  are positioned so that their respective upper surfaces  30 ,  48  lie substantially along the same plane. Additionally, the length and positioning of inner cylindrical body  14  is such that its lower surface  50  coincides with stepped-in section  28 , so that inner cylindrical body  14  is adjacent section  16   a  of wall  16  (i.e., adjacent the area of increased thickness). Inner cylindrical body  14  is typically formed of a metal, and tends to lend greater precision and stability on a spindle. 
         [0027]    Turning to  FIG. 2 , a spin chuck  56  is depicted. Spin chuck  56  can be formed of the same materials described above with respect to the outer cylindrical body  12 . The spin chuck  56  has a platform  58 , which has upper and lower sides  60 ,  62 . A lower mount  64  extends from lower side  62 . Lower mount  64  has an inner peripheral surface  66  that is equipped with threads  68 , designed to mate with threaded region  35  of base  10 . Upper side  60  has a surface  70  having a plurality of concentric vacuum grooves  72 , as well as radial grooves  74  that connect grooves  72 . Finally, the spin chuck  56  has a central vacuum opening  76  that runs the full thickness of platform  58 . 
         [0028]    Advantageously, the inventive spin chuck system can be used with conventional spin coating equipment. Referring to  FIG. 3 , a typical spin bowl  78  is shown. Spin bowl  78  is equipped with a spindle assembly  80 . Spindle assembly  80  includes base support  82  and spindle  84 . As illustrated, base support  82  has a top edge  83 , and encompasses spindle  84 . Spindle  84  includes an upper surface  85 , a vacuum port  86 , and an alignment pin  88 . 
         [0029]    In use, the base  10  is slid onto spindle assembly  80 , so that spindle  84  passes into opening  26  and then opening  46 . The height of the base support  82  of spindle assembly  80  corresponds to that of section  16   b  of wall  16 . Thus, when fully seated, the stepped-in section  28  will be positioned near, but not in contact with, the top edge  83  (see  FIG. 4 ). Additionally, alignment pin  88  will rest within pin alignment slot  54 , when properly seated. However, with prior art chucks, proper seating can be difficult to determine as these parts are not visible in use. The present invention remedies this problem by providing an easy visual indicator of proper seating. That is, if the base  10  is fully and properly seated on spindle assembly  80 , the upper surface  85  of spindle  84  will lie along substantially the same plane as upper surfaces  30 ,  48  on base  10 . 
         [0030]    In contrast to  FIG. 4 ,  FIG. 5  shows an improperly seated base  10 . In this instance, stepped-in section  28  is not resting on top edge  83 , nor is alignment pin  88  positioned within pin alignment slot  54 . However, because of the design of the present invention, the user can visually observe that the upper surface  85  of spindle  84  does not lie along substantially the same plane as upper surfaces  30 ,  48  on base  10 . That is, one can observe that the upper surface  85  is lower than the upper surfaces  30 ,  48 , and that adjustments need to be made to arrive at the  FIG. 4 , fully-seated version. 
         [0031]    Once the user has verified that the base  10  is fully and properly seated on spindle assembly  10 , the spin chuck  56  can be attached to base  10 . Any attachment mechanism can be utilized, provided it secures spin chuck  56  sufficiently to base  10 . The attachment should be sufficiently secure that it is not readily separated by a simple hand-pull. Thus, the spin chuck  56  should not be removable from base  10  by a force that is less than about 5 in·lbs, preferably not removable by a force that is less than about 10 in·lbs, and preferably not removable by a force that is less than about 20 in·lbs. Generally, the force required to remove spin chuck  56  from base  10  will be from about 10 in·lbs to about 30 in·lbs. This force can be measured by securing one of the base  10  or spin chuck  56  (such as in a jig or vise), and applying a force to the other of the base  10  and spin chuck  56  with a digital torque wrench, and observing the measurement at which separation occurs. The most preferred attachment mechanism is the use of the illustrated threads. 
         [0032]    Referring to  FIG. 6 , spin chuck  56  is lowered onto base  10 , so that lower mount  64  contacts threaded region  35  of base  10 . The spin chuck  56  is turned, causing the threads  68  on spin chuck  56  to interact with threaded region  35  on base  10 , thus causing the spin chuck  56  to be screwed onto base  10 , and to surround the upper end  22 .  FIG. 7  illustrates the inventive spin chuck system after fully assembled and attached to the spindle assembly  80 , creating spin chuck system  90 . At this stage, the desired spincoating process can be carried out by the user. For example, a substrate (not shown; e.g., microelectronic substrate, lens, slide, film) of the desired size can be placed on the platform  58 , a vacuum can be pulled through vacuum opening  76 , so as to secure the substrate to the platform  58 , and spinning and dispensing of the particular coating composition can be carried out. 
         [0033]    To remove the spin chuck system  90  from the spindle assembly  80 , the user can simply unscrew the spin chuck  56  from the base  10 , and then remove the base  10 , if desired. Alternatively, the user could lift the entire spin chuck system  90  straight up and off the spindle assembly  80 . The spin chuck  56  could then be unscrewed from the base  10 , away from the spin coater. The user could then clean the spin chuck  56  or replace it with a new spin chuck. Importantly, special tools are not required for assembly or disassembly, nor are small, easily lost parts (e.g., screws) used in the process. 
         [0034]    The inventive spin chuck system offers a number of further variations that give it substantial benefits over the prior art. For example, although a typical circular vacuum spin chuck was shown as spin chuck  56 , any type of spin chuck can be adapted to work with the present system. For example,  FIG. 8  shows a recessed spin chuck  92  that could be formed with the above-described platform  58  and used with the same base  10 . Additionally, a captive spin chuck  94  (see  FIG. 9 ) could also be made with a platform  58  and used with the same base  10 . This creates a large number of variations that can be achieved using the same base  10 , making it much simpler and quicker for the user to make changes to the process while using the same spin coating equipment. In addition to different styles of spin chucks being possible, spin chucks of different sizes (e.g., from about ¼-inch diameter to about 12-inch diameter—typically 5/16-inch, ½-inch, 1-inch, 2.25-inch, or 4-inch diameters) and shapes can be utilized, thus accommodating a wide range of substrate sizes and shapes. In the case of a standard vacuum chuck, the surface area of the top surface of the spin chuck would be the same size or smaller than the substrate to be processed; however, for recessed or captive spin chucks, the surface area of the top surface of the spin chuck would be the same size or slightly larger than the substrate to be processed. 
         [0035]    Furthermore, towards the end of having a readily adaptable two-part system, the above-described base  10  can be provided as part of a kit  94 , with spin chuck  56 , as well as a wide variety of other spin chucks  56   a - 56   f  of varying sizes and surface types (see  FIGS. 10-11 ). Preferably, there are at least 3 spin chucks, more preferably at least 5 spin chucks, and more preferably at least 7 spin chucks. In one embodiment, no two spin chucks  56 ,  56   a - 56   f  are identical. These can be provided in a case  98  having recessed areas  10   e,    100 ,  100   a - 100   e,  which have shapes and sizes corresponding to the base  10  and chucks  56 ,  56   a - 56   f  chosen for the particular kit. Notably, all spin chucks  56 ,  56   a - 56   f  in the kit  94  include a threaded platform  58  that can be attached to the single base  10  included in the system, making the system interchangeable and adaptable. 
         [0036]    A significant advantage of the present kit system is that it overcomes prior art problems of different substrate heights. That is, with prior art systems, even after undertaking the cumbersome swapping from one spin chuck to another, the height of the substrate on the spin chuck often varied with each spin chuck. Thus, the distance from the dispense tip to the substrate surface was not consistent, leading to the need for further equipment adjustments or dealing with inconsistently applied compositions. With the present invention, the use of a single base with each spin chuck designed for that base presents a consistent spacing between the substrates and the dispenser tip. 
         [0037]    While the above describes a preferred system according to the invention, it will be appreciated that a number of variations can be employed. It was noted that different spin chucks can be utilized. Additionally, different types of spin chuck surfaces, such as a different groove layout or even no grooves but instead a flat surface, can be employed. Also, although the base  10  was shown to be cylindrical in shape, other shapes (including ones of varying diameter from top to bottom) that would fit over the type of spindle assembly being utilized could be employed, provided the shape is weighted so that it can rotate around its z-axis. Of course, the platform  58  of spin chuck  56  would need to be altered to accommodate the different shape of base  10 , and done so in a way that still achieves the desired fastened strength. 
         [0038]    Also, the above base  10  was described with separate inner and outer cylindrical bodies  12 ,  14  for certain applications. In other instances, an integrally formed base (i.e., the entire base is made from the same material) can be utilized instead of having two different materials. Suitable materials for this embodiment include those selected from the group consisting of aluminum, acetal resin, stainless steel, PEEK, PTFE, and PVDF, with a particularly preferred material being an acetal resin (e.g., the acetal homopolymer resin sold by DuPont™ under the name DELRIN®). 
         [0039]    Finally, while the above describes seating the base  10  and then securing the spin chuck  56  to the base  10 , the spin chuck  56  and base  10  could first be screwed together and then placed on the spindle assembly  80 . Of course, it would likely be more difficult to seat the base  10  correctly on the spindle assembly  80 , and certainly the visual cue described above would no longer be available.