TECHNICAL FIELD
The invention relates to an apparatus and method for both securing and removing a semiconductor workpiece from within a fixture or chuck. More specifically, the invention relates to an apparatus and method for securing a workpiece within a chuck prior to processing of the workpiece, and removing the workpiece from the chuck upon completion of the processing steps.
BACKGROUND OF THE INVENTION
State of the art electronics (e.g., cellular phones, personal digital assistants, and smart cards) demand thinner integrated circuit devices (“ICD”). In addition, advanced packaging of semiconductor devices (e.g., stacked dies or “flip-chips”) provide dimensional packaging constraints which also require an ultra-thin die. Moreover, as operating speeds of ICDs continue to increase heat dissipation becomes increasingly important. This is in large part due to the fact that ICDs operated at extremely high speeds tend to generate large amounts of heat. That heat must be removed from the ICD to prevent device failure due to heat stress and to prevent degradation of the frequency response due to a decrease in carrier mobility. One way to enhance thermal transfer away from the ICD, thereby mitigating any deleterious temperature effects, is by thinning the semiconductor wafer from which the ICD is fabricated. Other reasons for thinning the semiconductor wafer include: optimization of signal transmission characteristics; formation of via holes in the die; and minimization of the effects of thermal coefficient of expansion between an individual semiconductor device and a package.
Semiconductor wafer thinning techniques have been developed in response to this ever increasing demand for smaller, higher performance ICDs. Typically, semiconductor devices are thinned while the devices are in wafer form. Wafer thicknesses vary depending on the size of the wafer. For example, the thickness of a 150 mm diameter silicon semiconductor wafer is approximately 650 microns, while wafers having a diameter of 200 or 300 mm are approximately 725 microns thick. Mechanical grinding of the back side of a semiconductor is one standard method of thinning wafers. Such thinning is referred to as “back grinding.” Generally, the back grinding process employs methods to protect the front side or device side of the semiconductor wafer. Conventional methods of protection of the device side of the semiconductor wafer include application of a protective tape or a photoresist reinforcing layer to the device side of the wafer. The back side of the wafer is then ground until the wafer reaches a desired thickness.
However, conventional back grinding processes have drawbacks. Mechanical grinding induces stress in the surface and edge of the wafer, including micro-cracks and edge chipping. This induced wafer stress can lead to performance degradation and wafer breakage resulting in low yield. In addition, there is a limit to how much a semiconductor wafer can be thinned using a back grinding process. For example, semiconductor wafers having a standard thickness (as mentioned above) can generally be thinned to a range of approximately 250-150 microns.
Accordingly, it is common to apply a wet chemical etch process to a semiconductor wafer after it has been thinned by back grinding. This process is commonly referred to as stress relief etching, chemical thinning, chemical etching, or chemical polishing. The aforementioned process relieves the induced stress in the wafer, removes grind marks from the back side of the wafer and results in a relatively uniform wafer thickness. Additionally, chemical etching after back grinding thins the semiconductor wafer beyond conventional back grinding capabilities. For example, utilizing a wet chemical etch process after back grinding allows standard 200 and 300 mm semiconductor wafers to be thinned to 100 microns or less. Wet chemical etching typically includes exposing the back side of the wafer to an oxidizing/reducing agent (e.g., HF, HNO3, H3PO4, H2SO4) or alternatively to a caustic solution (e.g., KOH, NaOH, H2O2). Examples of wet chemical etching processes may be found in co-pending U.S. patent application Ser. No. 10/631,376, filed on Jul. 30, 2003, and assigned to the assignee of the present invention. The teachings of application Ser. No. 10/631,376 are incorporated herein by reference.
Although methods for thinning semiconductor wafers are known, they are not without limitations. For example, positioning a semiconductor wafer in a submount or “chuck” (as it is commonly known) so that the wafer can be thinned requires expensive coating and bonding equipment and materials, increased processing time, and the potential for introducing contaminates into the process area. Additionally, adhesives for bonding a wafer to a chuck that may be useful in a mechanical grinding process will not withstand the chemical process fluids used in wet chemical etching. Furthermore, the current use of a photoresist or adhesive tape fails to provide mechanical support for very thin wafers either during the back grind process or in subsequent handling and processing. The use of tape also creates obstacles in the removal process. For example, tape removal may subject a wafer to unwanted bending stresses. In the case of a photoresist, the material is washed off the device side of a wafer with a solvent, adding to the processing time and use of chemicals, and increasing the risk of contamination. The use of taping and protective polymers are also costly, since both equipment and materials are necessary to apply and remove the protective media.
Further, thinned semiconductor wafers are prone to warping and bowing. And because thinned semiconductor wafers can be extremely brittle, they are also prone to breakage when handled during further processing. Thinned semiconductor wafers (e.g., below 250 microns) also present complications in automated wafer handling because, in general, existing handling equipment has been designed to accommodate standard wafer thicknesses (e.g., 650 microns for 150 mm wafer and 725 microns for 200 and 300 mm wafers).
Accordingly there is a need for a process and equipment for producing thinner semiconductor workpieces. At the same time, there is a need to provide thinner workpieces that are strong enough to minimize the risk of breakage, yet remain compatible with conventional automated semiconductor wafer handling equipment. Finally, it would be advantageous to develop a system that reduces the number of processing steps for thinning a semiconductor workpiece.
SUMMARY OF THE INVENTION
The present invention provides an apparatus and method for automatically securing a workpiece within a chuck (prior to processing) and removing the workpiece from the chuck upon completion of the process steps. Upon securing the workpiece in the chuck, the workpiece can be subjected to a desired process, e.g., a wet chemical etch process without the need for the use of tape or reinforcing films applied to the workpiece. Further, the chuck can be used as a carrier for transporting the thinned workpiece throughout a fab during subsequent processing. As a result, the workpiece is less susceptible to damage during the various processing steps and during handling, either prior to or subsequent to the thinning process. Moreover, by eliminating the need for applying a tape or reinforcing film to the workpiece, the apparatus and method of the present invention reduces: (i) process time; (ii) chemical consumption; and (iii) risk of contamination of the workpiece. Accordingly, the apparatus and method of the present invention improve wafer thinning yields and overall process efficiency.
The apparatus of the present invention includes a chucking station for automatically securing a workpiece in a chuck. The “chucked” workpiece can then be subjected to a desired process. The chuck is preferably an assembly of two primary components; a support body for supporting the workpiece and a retainer removeably connected to the support body. The workpiece is positioned between the support body and the retainer. The retainer is connected to the support body securing the workspace to the support body device side down and exposing the back side of the workpiece for processing. Chucks suitable for use with the present invention are disclosed in co-pending U.S. patent application Ser. Nos. 10/923,436, filed on Aug. 20, 2006 and 11/423,582, filed on Jun. 12, 2006, which are incorporated fully herein by reference.
The chucking station has a lower assembly and an upper assembly. An actuator assembly operably connects the upper and lower assemblies. The lower assembly includes a receiver cooperatively dimensioned for receiving the chuck and at least one sensor calibrated to sense the position of the chuck within the receiver. The upper assembly includes a plate that couples with the support body of the chuck when the upper and lower assemblies are moved from a closed position to an open position by the actuator assembly. The lower assembly has a separator element that resides within a cavity positioned radially outward of the receiver. With the chucking station in a closed position, an inflatable bladder moves the separator element into engagement with the support body of the chuck, exerting a separation force upon an outer periphery of the support body of the chuck. The separation force bends the support body causing the support body to disengage from the retainer. Upon disengagement, the support body of the chuck is coupled to the upper assembly via a vacuum. The actuator assembly then moves the upper assembly away from the lower assembly opening the chucking station. In the open position, the retainer (with the workpiece resting thereon) remains on the lower assembly.
The lower assembly includes a release pedestal that moves from a position below the lower assembly to a position above the lower assembly to lift the workpiece from the retainer so that the workpiece can be readily removed from the opened chuck by a robot end effector (or a hand held wand). The release pedestal resides within a cavity positioned inward of the separator element cavity and is actuated by an inflatable bladder. In order to avoid exerting any potentially harmful force to the workpiece (especially a thinned workpiece), the pedestal progressively engages a periphery of the workpiece essentially releasing the workpiece away from the retainer instead of applying a uniform force to the workpiece all at one time. In this manner, a workpiece can be automatically secured in a chuck for thinning and/or other processing and likewise automatically removed from the chuck when the desired processing is completed.
The chucking station of the present invention is well suited for use in a system for processing workpieces, and especially well suited for chucking and un-chucking workpieces for subsequent thinning to meet the ever increasing demand for thinner integrated circuit devices.
BRIEF DESCRIPTION OF THE DRAWINGS
To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which
FIG. 1 is a perspective view of a module having a chucking station according to the present invention;
FIG. 2 is a front view of the module, showing the chucking station positioned within the module;
FIG. 3A is a perspective view of the chucking station in an open position;
FIG. 3B is a perspective view of a receiver assembly of the chucking station;
FIG. 3C is an exploded view of the receiver assembly of the chucking station;
FIG. 3D is a perspective view of an upper assembly of the receiver assembly of the chucking station;
FIG. 3E is a cross-sectional view of the upper assembly of FIG. 3D;
FIG. 4A is a perspective view of a chuck with a semiconductor workpiece secured therein prior to processing;
FIG. 4B is a cross-sectional view of the chuck and workpiece shown in FIG. 4A;
FIG. 4C is a partial enlarged view of the chuck and workpiece shown in FIG. 4B, showing the cooperation between the chuck and the workpiece;
FIG. 4D is an exploded cross-sectional view of the chuck and workpiece shown in FIG. 4A;
FIG. 4E is a partial enlarged view of the chuck and workpiece section identified as X shown in FIG. 4D;
FIG. 5A is a cross-sectional view of another embodiment of a chuck, showing a workpiece secured therein prior to processing;
FIG. 5B is a partial enlarged view of the chuck and workpiece shown in FIG. 5A, showing the cooperation between the chuck and the workpiece;
FIG. 6 is a cross-sectional view of the chucking station in an inserted position of the chucking process;
FIG. 7A is a cross-sectional view of the chucking station in a closed position of the chucking process;
FIG. 7B is a partial cross-sectional view of the chucking station in a disengaged position of the chucking process;
FIG. 8A is a cross-sectional view of the chucking station in a disconnected position of the chucking process;
FIG. 8B is a cross-sectional view of the chucking station in a loaded position of the chucking process;
FIG. 9 is a flowchart showing the various steps in the chucking process of a chuck and a workpiece;
FIG. 10 is a flowchart showing the various steps in the un-chucking process of a chuck and a workpiece;
FIG. 11 is a cross-sectional view of the chucking station in an inserted position of the un-chucking process;
FIG. 12 is a cross-sectional view of the chucking station in a disengaged position of the un-chucking process;
FIG. 13A is a cross-sectional view of the chucking station in a removal position of the un-chucking process;
FIG. 13B is a partial cross-sectional view of the chucking station in the removal position of the un-chucking process; and,
FIG. 14 is a schematic of a system for handling and processing of workpieces, including a handling area, a thinning tool and a robot.
DETAILED DESCRIPTION
With reference to FIGS. 1 and 2, there is shown a tool or module 5 having a chucking apparatus or station 100 that connects a chuck or fixture 10 to a workpiece 50 to form a combined unit prior to processing the workpiece 50, and disconnects the chuck 10 from the workpiece 50 after processing is completed. The module 5 includes a housing or cabinet 70 with at least one shelf 72 that supports the station 100. The cabinet 70 further includes at least one supply group or stack 71 of semiconductor workpieces 50, a storage rack 74 for empty or unloaded chucks 10, and at least one carrier assembly 76 for chucks 10 loaded with a workpiece 50. To increase the efficiency of loading and unloading chucks 10 and workpiece 50, as well as connecting and disconnecting chucks 10 and workpiece 50, the station 100 is positioned between the supply group(s) 71 of workpieces 50 and the carrier assemblies 76. Further, the cabinet 70 can have an opening 78 in a first cabinet side wall 80 associated with the supply group 71 of workpieces 50, and an opening 82 in a second cabinet side wall 84 associated with the carriers 76. The openings 78, 82 provide access for the drop-off and pick-up of the workpieces 50 and the carriers 76, respectively. The cabinet 70 also includes a high efficiency filter, such as ultra low penetration (ULPA) filter, that provide contaminant free, laminar air flow during the operation of the station 100. An operator may be positioned near the shelf 72 to operate the chucking station 100, including loading chucks 10 and workpieces 50 into the station 100 for connection, and subsequent to processing, loading connected chucks 10 and workpieces 50 for disconnection. Alternatively, an automated device, such as a robot, can be utilized to operate the chucking station 100.
Referring to FIGS. 3A-C, the chucking station apparatus 100 comprises a lower assembly 105, an upper assembly 110 and an actuator assembly 115. During the various steps to “chuck” or secure the workpiece within the chuck for subsequent processing and to “unchuck” or remove the workpiece from the chuck in the chucking process, the actuator assembly 115 moves one of the lower assembly 105 or the upper assembly 110 both towards and away from the other assembly 105, 110. Although shown without a housing, the chucking station 100 may include a housing that generally encloses the lower, upper and press assemblies 105, 110, 115.
The lower assembly 105 includes a base plate 116 and a plurality of elongated support legs 118 depending there from. The lower assembly 105 also includes a receiver assembly 120 comprising a flange 122 and a receiver 124 positioned radially inward of the flange 122, wherein the receiver 124 is cooperatively dimensioned with a portion of the chuck 10 for its reception. In one preferred embodiment, both the chuck 10 and the receiver 124 have a circular periphery. The receiver 124 includes a recessed central plate 125 with a central opening 125a. The receiver assembly 120, preferably the flange 122, has at least one sensor assembly 123 calibrated to sense the position of the chuck 10 within the receiver 124 and/or the position of the upper assembly 110 with respect to the lower assembly 105. The sensor 123 assembly ensures that the chuck 10 (and the workpiece 50 therein) is properly seated or nested within the receiver 124 prior to the moving the upper assembly 110 to the lower assembly 105. Referring to FIG. 3C, the sensor assembly 123 includes a sensor 123a, a mounting bracket 123b and at least one fastener 123c. The receiver assembly 120 also includes a vacuum system 140 having at least one port 142 in the receiver 124, a lower fitting portion 143a and an upper fitting portion 143b aligned with a port 142, and a suction element or cup 144 in fluid communication with the fitting portions 143a, b. Preferably, the vacuum system 140 includes a plurality of fittings 143a, b and suction cups 144 circumferentially arranged along the receiver 124. When activated during the various process steps, the vacuum system 140 provides suction to the suction cup 144 to releasably secure the retainer 14 to the receiver 124.
The receiver assembly 120 further includes a chuck separator assembly 160 comprising a separator element 162 and an inflatable bladder 164, wherein the bladder 164 displaces the separator element 162 into engagement with the support body 12 to disengage it from the retainer 14. A supply line 165 provides an inflation fluid, such as air, to the bladder 164 during operation. The receiver assembly 120 also includes a workpiece release assembly 170 having an annular or ring-shaped internal bladder 172 and a pedestal 174, wherein the bladder 172 displaces the pedestal 174 into engagement with the workpiece 50 to elevate the workpiece 50 from the retainer 14. A supply line 173 provides an inflation fluid, such as air, to the bladder 172 during operation. The pedestal 174 has an upwardly extending finger 175 with an upper edge 177 that engages the outer peripheral region of the device side 53 of the workpiece 50 in order to elevate the workpiece 50 from a seal 16 of the retainer 14, upon which the workpiece 50 resides. A retainer ring 178 is positioned radially inward of the pedestal 174 and is secured to the central plate 125 by at least one fastener 179. In a preferred embodiment, the height of the finger 175 varies along the periphery of the pedestal 174 such that the distance between the edge 177 and a lower portion of the pedestal 174 varies. Described in a different manner, the height of the finger 175 and the edge 177 from a central region 174a is not uniform and various along the edge 177 (see FIG. 3C). Consequently, when the pedestal 174 and the finger 175 are displaced by the bladder 172, the edge 177 does not engage the entire peripheral region of the non-device or back side 53 at the same time. Instead, the edge 177 progressively engages discrete segments of the periphery of the back side 53 to “peel” the workpiece 50 from the seal 16 of the retainer 14. The precise operation of the components of the receiver assembly 120 is provided below with the discussion of the various process steps.
Referring to FIGS. 3A, D and E, the upper assembly 110 includes at least one cross member 126 extending between end member 127, and a plate 128 secured to the cross member 126. Each end member 127 has a rail 130 that is operably connected to the actuator assembly 115 that vertically displaces one of the lower assembly 105 or the upper assembly 110 towards the other assembly 105, 110. The upper assembly 110 also includes a vacuum system 146 that supplies suction to at least one channel 148 in an inner surface 128a of the plate 128 to releasably secure the support body 12 to the plate 128 during movement of the upper assembly 110. An elastomeric seal, or O-ring 129 resides at the periphery of the plate 128 to facilitate the sealing between the inner surface 128a and the body 12. The vacuum systems 140, 146 may be in fluid communication with the same vacuum source (not shown), or each system 140, 146 may have dedicated source. The upper assembly 110 further includes a support body separator assembly 180 comprising a separator element 182 and an inflatable bladder 184. To disengage the support body 12 from the plate 128, the bladder 184 displaces the separator element 182 towards the lower assembly 105 and into engagement with the support body 12. Preferably, the separator element 182 has a projection 183 that slidingly engages the end wall of the plate 128 when the bladder 184 displaces the element 182. As shown in FIG. 3E, the separator element 182 may include an interior recess 182a and the end wall of the plate 128 may include a cooperatively dimensioned groove 128b, wherein the interaction between these two components limits the movement of the separator element 182 towards the lower assembly 105. A supply line 185 provides an inflation fluid, such as air, to the bladder 184 during operation. Preferably, the separator element 182 and the bladder 184 are positioned radially outward of the plate 128 and the seal 129.
In the embodiment of FIG. 3A, two actuator assemblies 115 are positioned approximately 180 degrees apart (or at opposite ends of the cross member 126) and are configured to vertically move the upper assembly 110 relative to the lower assembly 105. Each actuator assembly 115 includes a linkage member 132 that connects with the rail 130, and vertical member 134 with an internal cylinder assembly 136, preferably pneumatically driven, that actuates the rail 130 via the linkage 132 for movement of the upper assembly 110. A mounting bracket 133 and at least one fastener 135 (see FIG. 6A) connect the vertical member 134 to the base 116. The internal cylinder assembly 136 includes a piston 137 and a block 139 operably connected to the piston 137 and the linkage 132. Vertical movement of the piston 137 and the block 139 cause the upper assembly 110, including the rail 130, the cross member 126, and the plate 128, to move with respect to the lower assembly 105. Preferably, the vertical member 134 has at least one elongated channel 138 that slidingly receives the rail 130 during movement of the upper assembly 110. The operation of, as well as additional structures of the lower, upper and actuator assemblies 105, 110, 115 are explained in detail after the following paragraphs in which the chuck 10 is discussed.
With reference to FIGS. 4A-E, there is shown a chuck 10 for supporting a semiconductor workpiece 50. The chuck 10 is generally comprised of a supporting body or member 12, a retainer member or ring 14, and sealing members 16, 24. The retainer 14 has two annular grooves or recesses 18, wherein the sealing member 16, 24 are positioned therein, respectively. The retainer 14 preferably has a ring configuration and is removeably attached to the supporting body 12. In use, the workpiece 50, which has a device side 51, a bevel (i.e., peripheral edge) 52 and a back side 53, is placed onto a supporting surface 18 of the supporting body 12 of chuck 50, device side 51 down. The retainer 14 is then attached to the outer periphery of the supporting body 12. As shown specifically in FIG. 4C, when the retainer 14 is engaged to the supporting body 12, the retainer 14 covers a peripheral portion of the back side 53 of the workpiece 50, securing the workpiece 50 in the chuck 10. Through the operation of the chucking station 10, the retainer 14 is joined to the body 12 to secure the workpiece 50 and define a connected position PC (see FIGS. 4B and C), and the retainer 14 is separated from the body 12 to provide access to the workpiece 50 and define a disconnected position PD (see FIGS. 4D and E). In the connected position PC, the chuck 10 and the workpiece 50 form a combined unit that facilities handling and protects the workpiece 50 during the various processing steps. In the disconnected position PD, the workpiece 50 can be removed from or inserted into the supporting body 12.
In the connected position PC of FIGS. 4B and C, the retainer 14 preferably covers only a small peripheral or outermost portion of the back side 53 of the workpiece 50, leaving a majority of the back side 53 of the workpiece 50 exposed. In a preferred embodiment, the back side 53 surface area covered by the retainer 14 extends inwardly from the bevel 52 for about a distance of approximately 1-10 mm, more preferably between about 1-5 mm, and especially between about 2-4 mm. Preferably, at least 95% (or even 97% or 99%) of the back side 53 surface area of the workpiece 50 is left exposed. Once the chuck 10 and the workpiece 50 reach the connected position PC, the workpiece 50 is ready for processing. During the processing of the workpiece 50, the exposed portion of the back side 53 may be subjected to a process fluid and thinned to a desired thickness. As a result of covering the peripheral portion of the back side 53 of the workpiece 50, during thinning, process fluid cannot interact with the periphery of the back side 53 of the workpiece 50. Accordingly, the periphery of the back side 53 of the workpiece 50 remains in substantially its same pre-thinning form, configuration and thickness. For purposes of this invention, the semiconductor material remaining at the periphery of the workpiece 50 after thinning is referred to as a rim. It is the rim that imparts strength to the thinned workpiece 50 and permits automated handling equipment to handle the thinned semiconductor workpieces 50 processed according to the present invention.
To facilitate connection of the retainer 14 to the supporting body 12, the retainer 14 has an engagement member 20 that is received within a recess 22 formed in the supporting body 12. Although not shown in FIGS. 4A-E, the present invention includes a configuration where the engagement member 20 extends from the supporting body 12 and cooperates with a recess 22 formed in the retainer 14 to achieve the connected position PC between the retainer 14 and supporting body 12. In either configuration, preferably the engagement member 20 and the recess 22 are positioned between the first and second sealing member 16, 24. Therefore, the engagement member 20 and the recess 22 are positioned radially outward of the peripheral edge 52 of the workpiece 50. With reference to FIGS. 4C and E, the retainer 14 has an outer peripheral end 30 with an angled surface 32. When the retainer 14 is attached to the supporting body 12, the angled surface 32 of the outer peripheral end 30 of the retainer 14 mates with an angled surface 34 at an outer peripheral end of the supporting body 12 to form a notch 36. As explained below, the notch 36 accepts a portion of the actuator assembly 115 to facilitate removal of the retainer 14 from the supporting body 12 to reach the disconnected position PD. An annular outer periphery 12a of the body 12 bends or flexes when a force is applied, and then returns to its original position when the force is removed. The flexing of the outer periphery 12a results in the disengagement of the engaging member 20 from the recess 22. As explained below, to move from the connected position PC, a portion of the actuator assembly 115 is displaced into the notch 36 and engages the body 12 to flex the outer periphery 12a and separates the engagement member 20 from the recess 22.
As shown in FIG. 4E, the supporting body 12 has an outer shoulder 25, preferably circumferential, radially inward of the outer angled surface 34 that engages a finger 23 of the retainer 14 in the connected position PC. Further, the supporting body has a lip or step 26, preferably circumferential, radially inward of the recess 22 that is adapted to register or guide the workpiece 50 as it is loaded into the chuck 10. When properly aligned, the workpiece 50 rests entirely on the supporting surface 28 of the supporting body 12. While the chuck 10 can be any shape (e.g., square, rectangular, circular, etc), as shown in FIGS. 4A-E, in a preferred embodiment the chuck is disk-shaped and will have a diameter slightly larger than the diameter of the workpiece 50 secured within the chuck 10 for processing.
An alternative embodiment of a chuck 10 is shown in FIGS. 5A and B. Similar to the chuck 10 shown in FIGS. 4A-E, the alternate chuck 10 includes a supporting body 12 and a retainer 14. In contrast to FIGS. 4A-E where the retainer 14 includes both sealing elements 16, 24, each of the supporting body 12 and the retainer 14 have a sealing element 16, 24. Specifically, the second sealing member 24, preferably an elastomeric O-ring, is disposed in a substantially annular groove 38 formed in the outer periphery 12a of the supporting body 12, instead of being formed in the retainer 14. The sealing element 24 resides radially outward of the recess 22 and engages an inner surface of the retainer 14. In contrast, the sealing element 16 of the retainer 14 resides radially inward of the engaging member 20 engages the back, non-device side 53 of the workpiece 50. The outer periphery 12a is a ring-shaped portion of the supporting body 12 that bends or flexes when a force is applied, and then returns to its original position when the force is removed. The flexing of the outer periphery 12a results in the disengagement of the engaging member 20 and the recess 22. As the number of chucking cycles increases (i.e., the number of times the supporting body 12, including the outer periphery 12a, flexes under force application and then returns to an unstressed state) the body 12 may slowly lose its ability to return to its original position or shape. By placing the sealing element 24 in the supporting body 12, preferably in the outer periphery 12a, the sealing element 24 provides memory to the body 12. That is, the sealing element 24 flexes to facilitate the return of the deformed outer periphery 12a back to its original position. It has been found that an elastomeric O-ring having a diameter in a range of 0.10 inch to 0.15 inch, and particularly an O-ring with a diameter of approximately 0.14 inch, is well suited for use as a second sealing member 24 in a chuck of the present invention. The retainer 14 in FIGS. 5A and B has a smaller outer diameter than the outer diameter of the supporting body 12, wherein the difference in diameter creates an outer step or shoulder 12b and a resultant gap 13. As explained below, to move from the connected position PC to the disconnected position PD, a portion of the lower assembly 105 is displaced into the gap 13 and engages the shoulder 12b to flex the outer periphery 12a and separates the engagement member 20 from the recess 22. In the connected position PC, a projection 20a of the engagement member 20 is received within a slot 22b of the recess 22 and contacts a finger 22a of the recess 22.
As shown in FIGS. 5A and B, the first sealing member 16 is disposed within an annular grove 17 that is substantially rectangular in cross-section and that is positioned proximate the engaging member 20. The first sealing member 16 includes a substantially rectangular portion 16a that is secured within groove 17 and an inwardly extending sealing portion 16b that forms a seal with the workpiece 50. In the embodiment of FIG. 5B, the sealing portion 16b has an oblong configuration with a curvilinear tip 16c. Alternatively, the sealing portion 16b may have a linear or angled tip 16c. The sealing portion 16b includes a downwardly sloped outer surface 60, which is configured to create an interface 62, which is the region of contact with the workpiece 50, that prevents stagnation of process fluid at the interface. To facilitate flow or distribution of fresh process fluid at the interface 62, the downwardly sloped surface 60 of the sealing member 16 and the workpiece 50 define an interface angle 66 of approximately 90 degrees, and more preferably an angle greater than 90 degrees as indicated in FIG. 15B. Without intending to be limited to theory, it is believed that the interface angle 66 aids in the refreshment of processing fluids during the wet chemical etching process at the interface 62 between the sealing member 16 and workpiece 50. This refreshment prevents the buildup of spent process fluids as noted above and results in a more uniform process fluid concentration across the entire back side of the workpiece. Consequently, the full exposed portion of the back side 53 of the workpiece 50 has a more uniform thickness after thinning.
Suitable materials for fabricating the chuck 10, including the support body 12 and the retainer 14, include a number of different polymer materials that are stable and highly chemically resistant. Preferably the supporting body 12 comprises polytetrafluoroethylene and the retainer 14 preferably comprises a fluoropolymer such as polyvinylidene fluoride sold by Atofina Chemicals under the KYNAR tradename. The retainer 14 is preferably formed from a material having a Durometer hardness less than that of a fluoropolymer, but greater than the elastomeric materials discussed below with respect to the sealing member. That is, a material compressible enough to form a seal with the workpiece 50, but stiff enough to provide structure to the retainer 14 for receiving the supporting body 12. In any embodiment of the present invention, in order to enhance the attachability of the retainer 14 to the supporting body 12, it is preferred that the supporting body 12 is comprised of a material having a Durometer hardness greater than the Durometer hardness of the material from which the retainer 14 is formed. The sealing members 16, 24 are preferably formed from a compressible material having a Durometer hardness equal to or greater than 50. Specific examples of suitable elastomeric materials include: a perfluoroelastomer sold by DuPont under the tradename Kalrez; a perfluoroelastomer sold by Greene, Tweed & Co. under the tradename Chemraz; fluoruelastomers sold by DuPont under the tradename Viton; and hydrocarbon elastomers sold under the tradename EPDM.
The present invention has been explained with reference to a particular chuck design which is not meant to limit the application of the present invention. Those having ordinary skill in the art will understand that the present invention can be used to secure workpieces to chucks having myriad designs.
As mentioned above, the chucking station 100, prior to processing of the workpiece 50, secures a workpiece 50 within the chuck or fixture 10 to arrive at the connected position PC, and then subsequent to workpiece 50 processing, disconnects the chuck 10 from the workpiece 50 to arrive at the disconnected position PD. The various steps of a chucking process 300 which secures the workpiece 50 within the chuck 10 for subsequent processing, and a unchucking process 400 which removes the workpiece 50 from the chuck 10 are explained in the following paragraphs.
As shown in the flowchart of FIG. 9, the first step 310 in the chucking process 300 involves moving the chucking station 10 to an open position PO (see FIG. 3) wherein the upper assembly 110 is spaced a distance from the lower assembly 105 to create a clearance that allows for the insertion of the chuck 10 (having no workpiece 50) into the receiver 124. Preferably, the actuator assembly 115 is pneumatically driven, wherein air is released or bled from the internal cylinder 136 which causes the upper assembly 110, including the rail 130, the cross member 126, and the plate 128, to move away from the lower assembly 105.
Once the chucking station 10 reaches the open position PO, the second step 320 involves inserting an empty chuck 10 into the receiver 124 to define an inserted position PI, which is shown in FIG. 6. The insertion can be performed either manually or by an automated device, such as a robot. The chuck 10 of FIGS. 5A and B is utilized to explain the chucking process 300, and the chuck 10 is loaded such that the retainer 14 is positioned against the receiver 124 and the support body 12 is positioned above the retainer 14. Described in a different manner, the retainer 14 is oriented towards the lower assembly 105 and the support body 12 is oriented towards the upper assembly 110. The inserted position PI is similar to the open position PO except for the inclusion of the chuck 10 in the receiver 124.
Next, the third step 330 involves utilizing the actuator assembly 115 to bring the lower and upper assemblies 105, 110 together. Air is supplied to the internal cylinder 136 of the actuator assembly 115, which causes the piston 137 and the block 139 to move away from a lower edge of the vertical member 134 thereby moving the rail 130 downward. This downward movement causes the upper assembly 110, including the cross member 126 and the plate 128, to move into engagement with the lower assembly 105 to define a closed position PCL of FIG. 7A. In the closed position PCL, a lower surface of the plate 128 engages an upper surface of the support body 12. To facilitate such engagement, the mounting bracket 133 includes a guide pin 150 and a pin mount 152, wherein the pin 150 is received within an aperture 154 of the cross member 126.
Once the closed position PCL is reached, the fourth step 340 involves disengaging the support body 12 from the retainer 14. Referring to FIG. 7B, the lower assembly 105 includes the separator assembly 160, wherein the separator element 162 and the bladder 164, are positioned within an annular cavity 166 of the plate 116 that is radially outward of the receiver 124. Once inflated, the bladder 164 displaces the separator element 162 into engagement with the support body 12, primarily the outer periphery 12a. Specifically, as the separator element 162 is displaced towards the support body 12, an inwardly-directed projection 162a of the element 162 engages the shoulder 12b to flex the outer periphery 12a and thereby separate the engagement member 20 from the recess 22. Described in a different manner, the separator element 162 exerts a separation force F (see FIG. 7B) upon the shoulder 12b and causes the outer periphery 12a to flex away from the retainer 14 whereby the recess 22 disengages the engagement member 20. As a result of the flexing, an intermediate extent 12c proximate the recess 22 acts as a hinge while the separation force F is applied. In addition to the projection 162a, the separator element 162 includes an outwardly extending leg 162b that engages a retainer 163 connected to the flange 116 to constrain movement of the separator element 162 and prevent over-extension of the element 162. To achieve the disengagement that defines a disengaged position PDE (see FIG. 7B), the outer periphery 12a must flex such that the recess finger 22a no longer contacts the engagement member projection 20a. Once the disengaged position PDE is reached, the separator element 162 is moved away from the support body 12 and back within the cavity 166 by deflating the bladder 164. Preferably, while the fourth step 330 of disconnecting the support body 12 from the retainer 14 occurs, the vacuum system 140 of the lower assembly 105 applies suction through the ports 142 to an outer surface of the retainer 14 to stabilize it within the receiver 124. Similarly, the vacuum system 146 of the upper assembly 110 applies suction through the ports 148 to an outer surface of the support body 12 to secure it to the upper plate 128.
After the engagement member 20 and the recess 22 are disengaged, the fifth step 350 involves moving the chucking station 10 to the disconnected position PD (see FIG. 8A) where both the upper assembly 110 and the support body 12 are spaced a distance from the lower assembly 105. Preferably, air is released from the internal cylinder 136 which causes the upper assembly 110, including the rail 130, the cross member 126 and the plate 128, as wells as the support body 12 to move away from the lower assembly 105. As mentioned above, the vacuum system 146 of the upper assembly 110 couples the support body 12 to the plate 128 such that the support body 12 moves with the plate 128 during movement away from the lower assembly 105. In the embodiment of FIG. 8, the upper assembly 110 and the support body 12 move vertically upward from the retainer 14 stationed in the receiver 124 of the lower assembly 105. Referring to FIGS. 8A and B, in the disconnected position PD, a clearance between the support body 12 and the retainer 14 allows for the sixth step 360—loading of the workpiece 50 into the retainer 14 supported by the receiver 124. The insertion of the workpiece 50 into the retainer 14 defines a loaded position PL. Referring to FIG. 8B, in the loaded position PL the workpiece 50 is horizontally supported by the sealing member 16 extending from the retainer 14.
The seventh step 370 involves moving the chucking station 100 from the disconnected position PD to the closed position PCL (similar to the third step 330 of FIG. 7A) in order to reach a connected position PC of the chuck 10. To reach closed position PCL the actuator assembly 115 brings the lower and upper assemblies 105, 110 into engagement, wherein the support body 12 remains coupled to the plate 128 of the upper assembly 110 during movement towards the lower assembly 105. Air is supplied to the internal cylinder 136 of the actuator assembly 115, which causes the piston 137 and the block 139 to move away from a lower edge of the vertical member 134 thereby moving the rail 130 downward. This downward movement causes the upper assembly 110, including the cross member 126, the plate 128 and the support body 12, to move towards the lower assembly 105 and brings the support body 12 into engagement with the retainer 14. The engagement between the lower and upper assemblies 105, 110, which is facilitated by the reception of the guide pin 150 in the aperture 154, defines the closed position PCL. Once there is sufficient engagement between the support body 12 and the retainer 14, meaning the engagement member 20 is received by the recess 22, the chuck 10 reaches the connected position PC. In the connected position PC, the workpiece 50 is secured between the joined support body 12 and the retainer 14 to form a combined chuck 10-workpiece 50 unit. After the connected position PC is attained, the vacuum system 146 of the upper assembly 110 is deactivated such that there is no suction between the support body 12 and the plate 128 of the upper assembly 110. Consequently, movement of the upper assembly 110 away from the lower assembly 105 and the chuck 10 will not involve the support body 12.
The eighth step 380 involves moving the chucking station 100 from the closed position PCL, wherein the chuck 10 and the workpiece 50 are in the connected position PC, to the open position PO (see FIG. 6). To reach the open position PO, air is released from the internal cylinder 136 of the actuator assembly 115, which causes the upper assembly 110, including the rail 130, the cross member 126, and the plate 128, to move away from the lower assembly 105. Due to the spacing between the lower and upper assemblies 104, 110, the chucking station 100 is in an open state. Because the vacuum system 146 is deactivated once the connected position PC is attained, movement of the upper assembly 110 does not involve the support body 12. Once the chucking station 100 reaches the open position PO, the chuck 10 and the workpiece 50 secured therein can be removed, either manually or by an automated tool, for processing of the workpiece 50 in another tool or module.
When the processing of the workpiece 50 is completed, the chuck 10 and the workpiece 50 are returned to chucking station 100 to “un-chuck” or remove the processed workpiece 50 from the chuck 10. The flowchart of FIG. 10 discloses the various step in the un-chucking process 400. Consistent with that explained above for opening the chucking station 100, the first step 410 involves separating the lower and upper assemblies 105, 110 a distance apart to define the open position PO. The second step 420 involves inserting a loaded chuck 10, meaning a chuck 10 with a workpiece 50 supported therein, into the receiver 124 to define an inserted position PI (see FIG. 11). The chuck 10 is loaded such that the retainer 14 is positioned against the receiver 124 and the support body 12 is positioned above the retainer 14. Described in a different manner, the retainer 14 is oriented towards the lower assembly 105 and the support body 12 is oriented towards the upper assembly 110. In the inserted position PI, the separator element 162 is positioned below the chuck 10 such that it does not make contact with either the retainer 14 or the support body.
After the both the chuck 10 and the workpiece 50 have reached the inserted position PI, the third step 430 involves utilizing the actuator assembly 115 to move the lower and upper assemblies 105, 110 into engagement to define the closed position PCL of FIG. 7A. As explained above, air is supplied to the internal cylinder 136 of the actuator assembly 115, which causes the piston 137 and the block 139 to move away from a lower edge of the vertical member 134 thereby moving the rail 130 downward. This downward movement causes the upper assembly 110, including the cross member 126 and the plate 128, to move into engagement with the lower assembly 105. In the closed position PCL, a lower surface of the plate 128 engages an upper surface of the support body 12. To facilitate such engagement, the guide pin 150 of the mounting bracket 133 is received within the aperture 154 of the cross member 126.
After the closed position PCL is attained, the fourth step 440 involves disengaging the support body 12 from the retainer 14. Referring to FIG. 12 and consistent with that explained above for the fourth step 340 of the chucking process 300, the inflatable bladder 164 displaces the separator element 162 towards into engagement with the support body 12. Specifically, as the separator element 162 is displaced towards the support body 12, an inwardly-directed projection 162a of the element 162 engages the shoulder 12b to flex the outer periphery 12a and thereby separate the engagement member 20 from the recess 22. The force applied to the shoulder 12b by the projection 162a causes the outer periphery 12a to flex away from the retainer 14 whereby the recess 22 disengages the engagement member 20. To achieve the disengagement that defines a disengaged position PDE, the outer periphery 12a must flex such that the recess finger 22a no longer contacts the engagement member projection 20a. Once the disengaged position PDE is reached, the separator element 62 is moved away from the support body 12 and back within the cavity 166 by deflating the bladder 164. Preferably, while the fourth step 430 of disconnecting the support body 12 from the retainer 14 occurs, the vacuum system 140 of the lower assembly 105 applies suction through the suction cup(s) 144 to an outer surface 14b of the retainer 14 to stabilize it within the receiver 124. Similarly, the vacuum system 146 of the upper assembly 110 applies suction through the ports 148 to an outer surface of the support body 12 to secure it to the upper plate 128.
Once the support body 12 is disengaged from the retainer 14, the fifth step 450 involves moving the chucking station 10 to the disconnected position PD (see FIG. 8A) where both the upper assembly 110 and the support body 12 are spaced a distance from the lower assembly 105 to expose the workpiece 50. Preferably, air is released from the internal cylinder 136 which causes the upper assembly 110, including the rail 130, the cross member 126 and the plate 128, as well as the support body 12 to move away from the lower assembly 105. Due to the spacing between the lower and upper assemblies 104, 110, the chucking station 100 is open. As mentioned above, the vacuum system 146 of the upper assembly 110 couples the support body 12 to the plate 128 to allow the support body 12 to move with the plate 128 during movement away from the lower assembly 105. In the embodiment of FIG. 8A, the upper assembly 110 and the support body 12 move vertically upward from the retainer 14 residing in the receiver 124 of the lower assembly 105 and thereby expose the device side 51 of the workpiece 50. Once the support body 12 is removed, the workpiece 50 is in the loaded position PL wherein the workpiece 50 is horizontally supported by the sealing member 16 extending from the retainer 14 (see FIG. 8B). The disconnected position PD is similar to the open position PO except for the attachment of the support body 12 to the plate 128.
The sixth step 460 in the un-chucking process 400 involves utilizing the workpiece release assembly 170 to elevate the processed workpiece 50 from the receiver 124 and the retainer 14 to define a workpiece removal position PR. Once the removal position PR is reached, the workpiece 50 is removed from the chucking station 100 either manually or by an automated device. Referring to FIGS. 13A and B, the workpiece release assembly 170 includes the annular or ring-shaped internal bladder 172 and a pedestal 174, wherein both are positioned within an annular cavity 176 that is located radially inward of both the separator assembly 160 and the periphery of the receiver 124. When inflated, the bladder 172 displaces the pedestal 174 into engagement with the workpiece 50 and displaces both structures away from the retainer 14. Specifically, as the pedestal 174 is displaced towards the workpiece 50, an upwardly extending finger 175 of the pedestal 174 engages the outer peripheral region of the back side 53 of the workpiece 50 in order to elevate the workpiece 50 above the receiver 124. The finger 175 has a tip or edge 177 that provides an engaging surface for the peripheral region of the back side 53 of the workpiece 50. In a preferred embodiment, the height of the finger 175 varies along the periphery of the pedestal 174 such that the distance between the edge 177 and a lower portion of the pedestal 174 varies. Therefore, when the pedestal 174 and the finger 175 are displaced by the bladder 172, the edge 177 does not engage the entire periphery of the back side 53 at the same time. Instead, the edge 177 progressively engages discrete peripheral segments of the back side 53 to disengage or “peel” the workpiece 50 from the seal 16 of the retainer 14. As a result, the edge 177 eventually makes contact with the entire periphery of the workpiece 50, however, that contact is progressive along the circumference of the back side 53 during the engagement cycle. The progressive engagement provided by the pedestal 174 and edge 17 reduce the likelihood of workpiece damage in the event the workpiece 50 resists disengagement from the seal 16.
As the bladder 172 continues to inflate, the elevation of the pedestal 174 presents the workpiece 50 for removal from the receiver 124. The workpiece 50 can then be removed from the lower assembly 105 by an operator utilizing a Bernoulli end effector or by automated means for further processing and/or handling. Preferably, while the sixth step 460 of elevating the processed workpiece 50 to reach the removal position PR occurs, the vacuum system 140 of the lower assembly 105 applies suction to a lower surface 14b of the retainer 14 to retain it within the receiver 124. Similarly, the vacuum system 146 of the upper assembly 110 applies suction through the ports 148 to an outer surface of the support body 12 to secure it to the upper plate 128.
After the processed workpiece 50 is removed as explained in the foregoing paragraphs, the chucking station 100 is in the open position PO and the empty chuck 10 residing therein is ready to receive an unprocessed workpiece 50. Alternatively, the empty chuck 10 is removed from the station 100 and either an empty chuck 10 for insertion of an unprocessed workpiece 50, or a chuck 10 containing a processed workpiece 50 may be loaded into the station 100. In this manner, the chucking station 10 is configured for continuous operation, meaning the chucking and/or un-chucking of numerous chucks 10 and workpieces 50.
FIG. 14 shows the chucking station 100 and the chucking tool 5 incorporated into a system 500 environment for handling and processing of workpieces 50. The system 500 includes a handling area 505 that interacts with a process tool 510 via a robot 515. The handling area 505 includes a robot 520, a carrier docking station 525, the chucking tool 5 and the chucking station 100, a chuck buffer 530, and depending upon the size of the workpiece 50, a chuck and/or wafer pre-aligner 535. In one embodiment, the various handling components are arranged about the robot 520 to facilitate interaction between the components. For example, the robot 520 is positioned on one side of the chucking tool 5, including the chucking station 100, and the chuck buffer 530 is positioned on the other side of the chucking too 5. Also, the carrier docking station 525 and the pre-aligners 535 are arranged about the robot 520. The chuck buffer 530 represents a holding area for processed and unprocessed carriers containing chucks 10 and workpieces 50 as they move between the chucking tool 5 and the process tool 510. Typically, the workpieces 50 are delivered, within a carrier or cassette, to the handling area 505 by an operator. The robot 520 then removes workpieces 50 from their carrier and aligns the workpieces 50, if necessary, with the pre-aligner 535. Next, the robot 520 inserts a workpiece 50 into the chucking station 100 wherein the workpiece 50 is “chucked” or inserted into a chuck 10 for processing within the processing tool 510. The robot 520 then delivers chucked workpieces 50 from the station 100 to the buffer 530. The robot 515 that interacts with the handling area 505 and the process tool 510, delivers the chucked workpieces 50 from the buffer 530 to the processing tool 510. After the processing in the tool 510 is completed, the robot 515 delivers the chucked workpiece 50 to the buffer 530. From there, the handling area robot 520 inserts chucked workpieces 50 into the chucking station 100 whereby the workpiece 50 is “unchucked” or removed from the chuck 10. The robot 520 then loads unchucked workpieces 50 into a carrier such that an operator can remove them from the handling area 505.
Preferably, the process tool 510 is a tool for thinning a workpiece 50 and includes a thinning chamber 540, which may employ mechanical (grinding) and/or chemical (etching) thinning processes to thin the workpieces 50, and a second chamber with a rinsing dryer 545, such as a spin release dryer with rinsing features. In one preferred embodiment, a thinning tool 540 for use in the system 500 of the present invention is disclosed in pending U.S. patent application Ser. No. 10/922,762, filed on Aug. 20, 2004, which is incorporated fully herein by reference. Although not shown, the system 500 may also include an additional processing tool that fabricates the microelectronic devices on the workpiece 50 and that can be incorporated into the system 500 prior to the handling area 505. An example of such a processing tool for use in the system of the present invention is disclosed in pending U.S. patent application Ser. Nos. 10/859,748 and 10/860,384, which are incorporated herein by reference.
Numerous modifications may be made to the foregoing invention without departing from the basic teachings thereof. Although the present invention has been described in substantial detail with reference to one or more specific embodiments, those of skill in the art will recognize that changes may be made thereto without departing from the scope and spirit of the invention.
Patent Application
20080232935
