Abstract:
Computer controlled de-clip-shadow mask removal machine. The present disclosure describes a computer controlled, fully programmable de-clip-shadow mask removal method and system. This method and system is adapted to remove retaining clips (without human contact), separate a shadow mask from a semiconductor wafer after a metal evaporation process, and remove the shadow mask with greater accuracy. The system uses servomotors which precisely control all ranges of motion required to safely and efficiently remove the mask from the wafer thus minimizing potential damages incurred by human contact.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims benefit of Provisional application U.S. Serial No. 60/412,367, filed on Sep. 20, 2002, entitled “Computer Controlled De-Clip-Shadow Mask Removal Machine.” 
     
    
     
       TECHNICAL FIELD OF THE INVENTION  
         [0002]    The present invention relates to a Controlled Collapse Chip Connection (C4) manufacturer&#39;s ability to reduce operational expense during a delicate mask removal wafer handling process.  
           [0003]    A shadow mask is a mask that is utilized for disposing structures on a silicon substrate through metal evaporation. During fabrication, the silicon wafer and mask can be held together using a Top Ring Assembly (TRA). The TRA can be bound together by a plurality of expandable clips. When the clips are compressed, they provide enough force to secure the assembly together. During a metal evaporation process, the shadow mask becomes adhered to a silicon wafer. After the process, the operator can manually remove the metal clips that bind the TRA. Such manual removal typically results in safety and efficiency limitations because the clips are small, difficult to maneuver, and sharp. As such, these clips are difficult to handle and can possibly cut through an operator&#39;s clean room glove resulting in an injury to the operator&#39;s hand. In such a situation, the operator would have to exit the clean room, treat the wound, throw away the cut gloves and perform a re-qualification procedure to return back to the clean room.  
           [0004]    Further, it is believed that the current manual method yields a potential 1.5 to 3.0 million-dollar per/year loss in damaged products due to “kinking” of masks during the removal process.  
         BACKGROUND OF THE INVENTION  
         [0005]    Once the clips are removed, the mask must be separated from the wafer. The current method for doing so is a manual process in which the operator peels the mask from the wafer by hand. In the past, the thickness and hole density in the masks were not enough to cause much difficulty in removing the mask; the operator could manually remove them without much effort. As technology advanced, so did the trend to make components smaller and thinner, resulting in a less structurally sound and more delicate mask product. Delicate masks carry a greater expense and have proven to be easier to damage during the manual removal process. The more delicate masks have made the removal operation more difficult, creating new problems. Damaged shadow masks can greatly affect production costs due to limited availability or the requirement to have high inventories. It would be beneficial to automate both the clip removal and the mask removal process.  
         SUMMARY OF THE INVENTION  
         [0006]    An objective of the present invention is to automate the removal of the shadow mask from the silicon wafer after the metal evaporation process. The heretofore utilized manual process is replaced with an automated system as described by the present invention that encompasses a new compter controlled de-clip-shadow mask removal machine that overcomes the limitations and problems associated with the prior art method and systems. This removal machine includes an automated, computer controlled, fully programmable machine to remove retaining clips and separate a shadow mask from semiconductor wafer after a special metal evaporation process. Using such an invention, various industries (such as the semiconductor industry) could significantly reduce the amount of money lost in damaged products. With a controlled environment, twenty-four shifts could produce consistent, high-output results. The machine includes a designated location for the operator to place the TRA. Once the TRA is fully nested, stainless steel pushers can remove the clips at the receipt of a command (via, for example, a press of a button). The system employs two or three axis of motion to address the mask removal issues and accommodates a variety of different wafer sizes by slightly modifying a vacuum chuck, a de-clip station and a program described further below. Such wafer sizes range, for example, from about a 4 inch diameter to about a 12 inch diameter. An advantage to a computer-controlled machine will be that each action will have a higher degree of repeatable precision. The machine would further increase safety and virtually eliminate mask damage. Once acceptable parameters are established and programmed, the machine maybe integrated with existing systems to improve overall productivity.  
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a perspective front right isometric view of the machine according to the present invention;  
         [0008]    [0008]FIG. 2 is a perspective rear right isometric view of the machine of FIG. 1 according to the present invention;  
         [0009]    [0009]FIG. 3 is an exploded left isometric view of the de-clip station of FIG. 1 according to the present invention;  
         [0010]    [0010]FIG. 3A is an enlarged view of a portion of the apparatus shown in FIG. 3;  
         [0011]    [0011]FIG. 4 is a perspective left view of a horizontal (wedge) assembly according to the present invention; and  
         [0012]    [0012]FIG. 5 is an exploded left isometric view of a vertical slide assembly according to the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    Referring now to FIG. 1, there is illustrated a perspective front right isometric view of a computer controlled de-clip-shadow mask removal machine  90  according to the present invention. The rigid frame assembly  100 , with its clean room safe, anti-static ESD wheels  101 , makes this machine both stable and portable. The de-clip station  200  with its alignment pins  201  (FIG. 3) and alignment slots  202  (FIG. 3) make placement of the TRA  600  consistent and reliable. Position of the horizontal assembly  300  is shown as an example only and may be positioned in a variety of locations such as on either side of or behind the de-clip station  200 . The human-machine interface (HMI)  104  may be a monitor, such as a touch screen monitor, which interacts between an operator (not shown) and the machine  90 . The program displays graphics, instructions, and other information relevant to that particular stage. The operator may select an appropriate command via an input such as a “button” on a touch screen or a voice recognition system to advance to a next stage of operation. A quick-connect air inlet adapter  102  is used to supply air to the system. This single air standard 110-wall socket plug  103  can be used to supply power to the entire system  90  or a power source can be self-contained within the system. Further, the incoming power source for the machine  90  may vary to suit different plants.  
         [0014]    Referring now to FIG. 2, there is illustrated a perspective rear right isometric view of the machine  90 . A vacuum generator  105  creates a vacuum from the incoming air source coming through the inlet adapter  102  and supplies vacuum to a vacuum chuck  503  (FIG. 5). The machine  90  uses vacuum to hold the wafer  603  (FIG. 3) on the vacuum chuck  503  during rotation. A vacuum sensor  106  is computer controlled to insure proper pressure is maintained for each type of wafer  603  being processed.  
         [0015]    Referring now to FIG. 3 and FIG. 3A, there is illustrated an exploded left isometric view of the de-clip station  200 . The TRA  600  is placed on the de-clip station  200  and oriented by the alignment pins  201 . The TRA is comprised of a top ring  601  and a bottom clip  604 , between which are disposed a mask  602  over a wafer  603 . The rings  601  and  604  are held together by clips  605 . The alignment slots  202  act as a go-no-go gage helping to insure that the clips  605  are in the right orientation for removing. A number of actuators  205  (for example, about 2 about 12 and preferably 6), controlled by a valve  206 , push an equal number of the de-clip blocks  203  in an outward direction for removal thereof. Such de-clip blocks  203  include a slot  204  that can completely remove the clips  605  from the retaining pins  201 . The clip shield  210  prevents the removed clips  605  from being projected out of the nest area protecting the operator. The clips  605  can safely fall down the ramps  207  into a funnel  208  and to a removable clip tray  209 .  
         [0016]    Referring now to FIG. 4, there is illustrated a perspective left isometric of the horizontal assembly  300 . This axis consists of a horizontal slide  302 , which propels the de-masking wedge  303 . The de-masking wedge  303  makes contact with the mask  602 , (FIG. 3). The de-masking wedge  303  then moves towards the center to dislodge the wafer  603  from the mask  602 . Such movements may be performed at a plurality of speeds and preferably at a slower speed. The position of the de-masking wedge  303  may be programmed and precisely controlled by the servomotor  301 .  
         [0017]    Referring now to FIG. 5, there is illustrated an exploded left isometric view of both the vertical assembly  400  and the rotation assembly  500 . The vertical assembly  400  consists of a vertical slide  402  and servomotor  401  mounted underneath the de-clip station  200  to provide controlled vertical motion for the vacuum chuck  503 . The o-ring  504  on the vacuum chuck  503  seals both the mask  602  and the wafer  603  via the vacuum generator  105  (FIG. 2) through the vacuum distributor  502 . The vertical position of the vacuum chuck  503 , relative to the de-masking wedge  303  (FIG. 4) may be programmed and precisely controlled by servomotor  401 . The speed at which the rotation assembly  500  spins the vacuum chuck  503  is programmed and precisely controlled by servomotor  501 . The positional bearing  211  (FIG. 3) stabilizes the position of the rotation assembly  500 .  
         [0018]    Operational Flow  
         [0019]    The following describes the operation of the de-mask station, it being understood that the steps in the operation may be performed either in the presented order or in any other order according to the present invention. Initially, the operator follows the computer images and instructions on the HMI  104 . The HMI  104  may prompt the operator to select the mask type with which to run for the current operation. The operator may then be prompted to manually place a top ring assembly  600  on top of the de-clip station  200  using the alignment pins  201  as a guide and the alignment slots  202  as a gage to insure proper repeatability. The machine  90  can simultaneously remove all the clips  605  from the TRA  600  based on an appropriate received command. This action frees the top ring  601  from the bottom ring  604 . The machine&#39;s computer or controller  107  can send a signal to activate the onboard vacuum generator  105  to secure the wafer  603  to the vacuum chuck  503  via the vacuum distributor  502 . The operator may then manually remove the top ring  601  from the TRA  600 . An appropriate command, shown on the display of the HMI  104 , may then be input by the operator to advance to the next step.  
         [0020]    At the next step, in response to changing images and brief descriptions on the display of the HMI  104  that are presented to the operator, the machine  90  may perform a series of steps that may not require operator intervention. The machine  90  will lift the wafer  603  and the mask  602  up to a particular position at a particular speed with the assembly  400  (which may be programmed, set by the operator, static and/or dynamic, for example), using a computer driven vertical slide  402 . The machine&#39;s horizontal servomotor  301  can then move the horizontal slide  302  to a particular position at a particular speed (which may be programmed, set by the operator, static and/or dynamic, for example) thus placing the de-masking wedge  303  slightly under the rotating mask  602 . The machine&#39;s rotation servomotor  501  can spin the computer driven rotation axis  500  at a particular speed (which may be programmed, set by the operator, static and/or dynamic, for example). The vertical assembly  400  can lower the vacuum chuck  503  to a particular position at a particular speed (which may be programmed, set by the operator, static and/or dynamic, for example).  
         [0021]    After positioning th de-masking wedge  303  as noted, the de-masking wedge  303  may move toward the center of the mask  602  at a particular speed (which may be programmed, set by the operator, static and/or dynamic, for example). The de-masking wedge  303  can peel the mask  602  from the wafer  603  until it is completely separated from the wafer  603 . Once the mask  602  is free, the machine&#39;s computer or controller  107  will stop all motors in motion. The HMI  104  can prompt the operator to then remove the mask  602  from the wafer  603 . Following the images and instructions on the display, the operator initiates the appropriate commands, which send the de-masking wedge  303  back to a horizontal retract position. The machine&#39;s vertical servomotor  401  lowers the vacuum chuck  503  to a vertical retract position. The machine&#39;s computer or controller  107  will turn off the vacuum generator  105  to enable the operator to remove the wafer  603  and the bottom ring  604  from the de-clip station  200 . Speeds for initial and retract positions may vary. The HMI  104  will prompt the operator to change the mask type, re-run the same mask type, or to completely end the cycle.  
         [0022]    As a summary, the computer controlled de-clips-shadow mask removal machine of the present invention may comprise at least one of the following elements that may perform at least one of a following functions:  
         [0023]    1. a rigid frame constructed of welded fabrication and/or structural metal extrusion.  
         [0024]    2. a computer or controller to control the de-clip action and de-masking process.  
         [0025]    3. the computer or controller may store appropriate programmable speeds and position settings to accommodate various mask types, into separate subprogram(s) or receipt(s).  
         [0026]    4. a touch screen or push button HMI with graphic and/or text display to interact with operator(s).  
         [0027]    5. the computer or controller may store the speeds and position settings to accommodate various the mask types, into separate the subprograms or recipes.  
         [0028]    6. the de-clip station comprising at least one of a following elements from a group consisting of:  
         [0029]    at least one alignment pin and alignment slot for reliable removal of clips;  
         [0030]    a nesting area to secure a bottom ring;  
         [0031]    computer controlled actuators (pneumatic, electro-pneumatic or electronic) to proper de-clip blocks to remove the clips;  
         [0032]    the program to activate the computer controlled actuators to remove the clips;  
         [0033]    a clip shield to contain the clips after propelled from the nest area;  
         [0034]    ramps to guide the clips down funnel out of the de-clip station; and  
         [0035]    a removable tray located under the de-clip station to contain the clips after de-clip sequence.  
         [0036]    7. A vacuum chuck to hold the wafer by vacuum; the system shall regulate range of vacuum between, for example, 30 in/Hg to about −60.00 in/Hg, and preferably about −10 in/Hg to about −30.00 in/Hg.  
         [0037]    8. The system may employ three axis of motion to remove the mask from the wafer.  
         [0038]    a vertical axis to raise and lower the vacuum chuck to the programmable distance(s) from the wafer, ranging between, for example, −5.00 inches to about 10.00 inches, and preferably about −1.00 inches to about 2.99 inches traveling at speeds ranging between, for example, 0.50 inches per second to about 750.00 inches per second, and preferably about 5.00 inches per second to about 300.00 inches per second, best suited for safety of the wafer and efficiency for production.  
         [0039]    a rotation axis to spin the vacuum chuck at the programmable speeds ranging between, for example, 5.00 rpm to about 5000.00 rpm, and preferably about 25.00 rpm to about 2000.00 rpm, best suited to minimize friction force required for the wedge to remove the mask and efficiency for production.  
         [0040]    a horizontal axis to move the wedge in a horizontal direction between the mask and the wafer to separate the two, while simultaneously spinning the vacuum chuck; the programmable distance(s) from the wafer center, ranging between, for example, 0.005 inches to about 15.99 inches, and preferably about 0.05 inches to about 8.99 inches traveling at speeds ranging between, for example, 1.00 inches per second to about 500.00 inches per second, and preferably about 10.00 inches per second to about 250.00 inches per second, best suited for safety of the wafer and efficiency for production.  
         [0041]    The HMI  104 , may perform at least one of a following step from a group consisting of: (a) shall display images and/or instructions to prompt the operator(s) to follow entire sequence easily; (b), the interface will prohibit the operator(s) from accessing sensitive data; (c), only certified administrators will have access to the critical files/recipes and settings and (d) the operator(s) will select the subprogram(s) or recipe(s) for the appropriate the mask type; (e) the try will have a removable drawer for convenient storage of the clips once removed; (f) the vertical programmed positions will keep the wedge at a close, yet safe distance from the wafer to keep from inducing a stress that may kink the masks; (g) the vertical positions and speeds will be programmed in the recipes; (h) the rotation speeds will be programmed in the recipes; and (i) the horizontal positions and speeds will be programmed in the recipes, which shall be recalled in a program by the program to produce consistent results of high productivity in removing the clips and the mask from the wafer after the metal evaporation process.  
         [0042]    Although the preferred embodiment has been described in detail, it should be understood that various changes, substitutions and alterations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.