Patent Grant
8968052
1. Field of the Invention
The present invention relates generally to wafer processing, and more specifically to wafer grinding.
2. Discussion of the Related Art
It is common, such as with some conventional semiconductor wafers on which circuit patterns are formed on one side (a front side), to be subjected to a grinding process so as to reduce the overall thickness of the wafer. Grinding is typically performed on the back surface of the wafer. The resultant thinning of the wafer allows for the production of thinner packaged electronic chips, microchips, and the like. In some instances, the thickness of a microchip cannot exceed a predefined thickness. Various other advantages are achieved by reducing the thickness of the wafers.
Backside wafer grinding is often accomplished using a grinding wheel that is applied to the backside of the wafer. Pressure is applied while grinding in attempts to achieve desired thicknesses.
Several embodiments advantageously address the needs above as well as other needs by providing grinding apparatuses and methods. Some embodiments provide grinding apparatus, comprising: a base casting; a rotary indexer positioned within the base casting, wherein the rotary indexer is configured to rotate within the base casting and about a first axis; a first work spindle secured with the rotary indexer; a first work chuck coupled with the first work spindle, wherein the first work spindle is configured to rotate the first work chuck about a second axis; a bridge casting rigidly secured relative to the base casting, wherein the bridge casting bridges across at least a portion of the rotary indexer and is supported on opposite sides of the rotary indexer structurally forming a closed stiffness loop; a grind spindle secured with the bridge casting; a first grind wheel cooperated with the grind spindle such that the grind spindle is configured to rotate the first grind wheel, wherein the bridge casting secures the grind spindle such that the first grind wheel is positioned over the rotary indexer to generally align with at least a portion of the first work chuck when the first work spindle is rotated by the rotary indexer into a corresponding position.
Other embodiments provide methods of wafer grinding. These methods comprise: rotating a rotary indexer about a first axis and rotationally orienting a work chuck and work spindle into a load position; applying a vacuum pressure to secure a wafer to the work chuck; rotating the rotary indexer to rotationally orient the work chuck and work spindle into a grind position such that the wafer is at least partially aligned with a coarse grind wheel; activating a grind spindle to apply the coarse grind wheel to the wafer to grind the wafer according to a coarse grind recipe; detecting that the wafer has been ground to a predefined coarse grind thickness; activating the grind spindle to apply a fine grind wheel to grind the wafer according to a fine grind recipe, wherein the fine grind wheel is nested with the coarse grind wheel such that the coarse and fine grind wheels are coaxially aligned about a second axis that is different than the first axis and around which the first and second grind wheels are rotated by the grind spindle; detecting that the wafer has been ground to a predefined fine grind thickness; and rotating, after the detecting that the wafer has been ground to the predefined fine grind thickness, the rotary indexer to the first position such that the work chuck is rotationally orienting into the load position allowing the wafer to be removed.
Still further embodiments provide methods of grinding a wafer comprising: rotating a rotary indexer positioning a work chuck and work spindle secured with the rotary indexer to a load position allowing ready access to position a wafer on the work chuck; rotating the rotary indexer and positioning the work spindle and work chuck to a grind position generally aligned with at least a portion of a grind wheel supported and rotated by a grind spindle; preventing a shifting of a center of gravity of the rotary indexer as the rotary indexer rotates the work chuck by securing a counter balance on the rotary indexer relative to the work spindle.
Additionally, some embodiments provide methods of grinding a wafer, comprising: rotating a rotary indexer positioning a work chuck and work spindle secured with the rotary indexer to a load position allowing ready access to position a wafer on the work chuck; rotating the rotary indexer and positioning the work spindle and work chuck to a grind position generally aligned with at least a portion of a grind wheel supported and rotated by a grind spindle; preventing a shifting of a center of gravity of the rotary indexer as the rotary indexer rotates the work chuck by securing a counter balance on the rotary indexer relative to the work spindle.
The above and other aspects, features and advantages of several embodiments of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.
The following description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of exemplary embodiments. The scope of the invention should be determined with reference to the claims.
Reference throughout this specification to “one embodiment,” “an embodiment,” “some embodiments,” “some implementations” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” “in some embodiments,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
Furthermore, the described features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of apparatuses, components of apparatuses, processes, control structures and methods, programming, software modules, user actions or selections, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
Some present embodiments provide for wafer grinding, including but not limited to semiconductor wafer backgrinding. For example, some embodiments provide for silicon wafer grinding for semiconductors and/or other relatively hard materials wafer grinding, including for example grinding for Light-Emitting Diode (LED) manufacture. The relatively hard materials can include sapphire, silicon carbide, Aluminum-Titanium Carbide (AlTiC) for giant magnetoresistive (GMR) hard disk drive (HDD) heads and other such relatively hard materials. In some instances, the grinding systems and/or processes can be implemented and/or cooperated with other systems and/or apparatuses, such as robotics, front-end modules, automation machines, thin wafer handling, in situ and ex situ wafer thickness monitoring grind force measurement, servicing access for grinder components (like grind wheels), and other such systems and/or automations.
Some embodiments provide systems and methods of wafer grinding that comprise several sub-systems and improvements over the prior systems and methods. Many of these sub-systems provide inventive features and processes, and the methods and/or processes of using each and the entire system provides methods to achieve levels of ground wafer quality not achievable by means of other equipment or methods.
A Lower Base Casting (1): The lower base casting, in some embodiments, comprises a rigid base upon which the grind engine can be mounted into a frame. Additionally the rigid base, which in some instances can be made out of cast iron, steel, polymer concrete or other relevant material, is designed to provide a rigid mounting for the lower components of the grind engine. For example, the lower base casting (1) is designed to accept a rotary indexer (2), described in detail below. The rotary indexer (2), in turn, provides for mounting of the lower grind chuck work air bearing spindle(s) (the “work spindle(s)). A porous chuck (the “work chuck,” which in some instances is a ceramic chuck) is mounted to the air bearing spindle, and wafers are affixed to the work chuck during grinding. The base also allows connection of a stiff bridge casting (3) which spans above much of the lower base casting.
A Rotary Indexer (2): The rotary indexer is mounted into the lower base casting. In some embodiments, the rotary indexer (2) can have a cylindrical cross-section. Further, the rotary indexer (2) is mounted with the lower base, for example, by way of a high precision preloaded sealed cross roller ring bearing (16), which provides for the ability to rotate the rotary indexer while increasing stiffness and in some instances maximizing stiffness in multiple or all planes and moment loading. In other embodiments, one or more air bearings can be used in cooperation with or in place of one or more cross roller bearings to support and index the rotary indexer. A servo controlled motor, gear reduction, and belt system can be used to index the rotary indexer to various positions.
An Upper Bridge Casting (3): A rigid casting that is secured (e.g., bolted) to the lower base casting. The upper bridge casting 3 is configured and positioned to mount the upper grind air bearing spindle 8 (the “grind spindle”). The bridge casting, in some embodiments, is made out of cast iron and provides for higher stiffness than previous cantilevered arm designs, while still providing desired access for servicing the machine. In some embodiments, the bridge casting 3 is rigidly secured relative to the base casting 1, and in some instances with the base casting 1. In some implementations the bridge casting 3 extends from the base casting 1 generally away from the rotary indexer 2. The bridge casting 3 bridges across at least a portion of the rotary indexer 1, and in some instances across a diameter of the rotary indexer, and is supported on opposite sides of the rotary indexer 2 by the base casting. The bridge casting 3 is rigidly secured relative to the base casting structurally forming a closed stiffness loop. Further, the bridge casting 3 rigidly secures the grind spindle 8 relative to the base casting 3 and rotary indexer 2 such that the first grind wheel is positioned over the rotary indexer to generally align with at least a portion of the work chuck 5 when the work spindle 6 is rotated by the rotary indexer 2 into a corresponding grind position.
A Grind Chamber (4): The lower base casting 2 and upper bridge castings 3, along with other sheet metal and machined components form the grind chamber (4), or the area where the grinding occurs. The grind chamber (4) can in some implementations be sealed during grinding with one or more lids or doors (15) to prevent the grind effluent and swarf from slinging outside of the chamber. Exhaust and drain connections are provided to the grind chamber to provide for the removal of humid air, grind effluent, swarf, deionized water and the like. In some instances, coolant and/or other liquids may be at atomized, which may result in a fog that can be evacuated through the exhaust. In some embodiments, the grind chamber air volume is exchanged about each 2-5 second intervals.
One or more Work Chucks (5) and Work Spindles (6): The work chuck 5 and/or work spindles 6 can be implemented, in some embodiments, through an air bearing type spindle, which can provide for an improved or maximum stiffness and precision alignment of the spindle. The work chuck 5, which in some embodiments is an assembly with a porous ceramic surface, is configured to affix a wafer via a vacuum force during grinding to an ultra flat (or precision shaped) surface during the grinding process. The air bearing spindle has an integrated motor used to rotate the work chuck and wafer during grinding. A force sensing device, previously described by U.S. Pat. No. 7,458,878, which is incorporated herein by reference, is integrated into the spindle to measure the amount of force imparted by the grind wheel against the wafer during grinding.
One or more Grind Wheels (7) and Coaxial Grind Spindle (8) (see also
Referring back to
In some embodiments, the grinding spindle 8 supporting the dual grind wheels 7a-b is vertically supported in the air bearing sleeve 13. The air bearing sleeve can be very close fitting and extends along a portion of a length the grind spindle 8 providing increased stability. The air bearing sleeve 13 can provide an air film under pressure firmly supporting the grind spindle 8, while still allowing rotational and axially movement of the grind spindle, which in some instances is virtually friction free. The air bearing provided by the air bearing sleeve 13 encircles the portion of the grind spindle 8. In some embodiments, the air bearing and/or air bearing sleeve are on the order of the same diameter as the grinding wheel and/or grind wheel assemblies, and accordingly resists moment load deflections due to grind forces. Some implementations include one or more precision balls or planetary lead screws that can be used to provide vertical spindle positioning. In some embodiments, the weight of the grind spindle 8 is substantially counter balanced, for example, through a plurality of rolling diaphragm air cylinders positioned on either side of and/or around the grind spindle 8.
Z-Axis Lead Screw Assembly (9): Infeed grinding movement is enabled via a servo controlled motor directly connected to a fine-pitch precision ground pre-loaded planetary roller or ball screw. As the motor turns the ball screw, the grind wheel air bearing grind spindle 8 is lowered or lifted. A very precise encoding device allows a controller or computer to track the rotation of the screw and implied z-axis displacement. The precision and force control, in at least some embodiments, is enabled through relatively friction free z-axis linear air bearings, thus eliminating at least the friction that produces a stick-slip phenomenon that can result in a loss of precision. The air bearings enable precision positioning and grind force measurements, and thereby control.
Measurement Probes (10): In some embodiments, the grind system or module includes one or more contact-type measurement probes 10, which can be mounted at a location above the grind position of the wafer and work chuck 5. Before a wafer is loaded onto the work chuck for grinding, probes, for example two probes, reference the distance to the surface of the work chuck. During grinding, one probe continues to monitor the position of the work chuck surface (just outside the outer diameter of the wafer) while the other probe monitors the thickness of the wafer while it is ground. The grinding process can be programmed to stop when a predetermined thickness is achieved or when a predetermined amount is removed.
One or more Grind Spindle Adjustment Screw Assemblies (11): Referring back to
In some embodiments, the adjustments screw assemblies 11 can be manually set (e.g., via a wrench). Further, some embodiments utilize a dual-threaded device. The combination of the two nested threads provides for very fine pitch, or movement per revolution. In other embodiments, the adjustment method is automated and controlled by feedback and a controller (e.g., feedback through one or more sensors, motors and the like to a computer). The adjustment screw assemblies, and in some instances the automated adjustment of these adjustment screw assemblies, can enable wafer shape control.
A Wheel Dresser (12): Referring back to
The grind engine includes the rotatable rotary indexer 2 (which in some embodiments is circular), to which the work spindle(s) 6 are mounted within.
In some embodiments, the rotary indexer 2 is driven by a geared servo motor 714 with a toothed pulley on an output shaft driving to a multipurpose pulley below the cross roller bearing by way of a positive drive belt (e.g., a Poly Chain® GT® Carbon™ Belt from Gates Corp.).
The rotary indexer movement also enables the positioning of the wafer in the correct spots for one or both coarse and fine grinding with the coaxial spindle arrangement, depending on implementation. Some embodiments employ nested coarse and fine grind wheels 7a-b, and with such nesting the coarse and fine grind wheels have slightly different diameters to allow for nesting. Accordingly, the rotary indexer 2 can index to a different position to place the center of the wafer beneath the teeth of the relevant grind wheel. In some instances, the center of the wafer is identified and/or aligned to correspond with the teeth, which can allow or simplify the grinding of the entire surface of the wafer. For example, the grind teeth can track through the center of the wafer. Some embodiments are configured to allow the rotary indexer 2 to be positioned to grind only an edge of a stacked or non-stacked wafer using one of the grind wheels or other edge grinder. The rotary indexer movement can also be used in combination with active grinding to step the grinding progressively from the outer diameter to the center of the wafer for stepped or incremental grinding of very hard materials.
Additionally or alternatively, more complex polar or Cartesian type measurements can be taken by coordinating rotary indexer and chuck rotations while the wafer is being measured by the single sensor. Some embodiments include a tool control system that allows for coordinated, multi-axis control for chuck and rotary indexer rotations, which enables precise and rapid mapping of the wafer thickness.
In some embodiments, the work spindle 6 is supported and/or suspended by a pressurized air bearing and held in position by journal and thrust bearings in a housing about a portion of the work spindle. One or more high resolution non-contact sensors and/or sensor gauges can be included in some embodiments to identify a location of the shaft within the housing. Grinding forces are transmitted to the wafer or work piece by the lead screw mechanism feeding the grinding wheel on to the wafer. Force can be calculated by a displacement along a length or central axis of the work spindle shaft within its housing. Feedback is then used to monitor or modify the feed rate to maintain an acceptable grind force against the wafer. In some instances, forces as small as one pound can be detected. The grind spindle linear air bearing can further enable this force resolution.
In some embodiments, the Upper Bridge Casting (3) can provide for superior stiffness while still providing access to the grind wheels for maintenance and wheel changes that are typically needed as the abrasive wheel element(s) wear. Access can be provided through a door (17) at the rear of the casting.
An angle of orientation of the rotatable grind wheel (7) to the rotatable wafer on the chuck (5) can determine a shape of the ground wafer. In many implementations the shape is extremely critical to the subsequent building of devices upon the wafer. Accordingly, some embodiments provide methods to determine the optimum grind-spindle angle and a device to mechanize the spindle angle adjustment.
The grind engine is capable of grinding wafers to a thickness of about 100 microns or less. For stacked wafer device manufacture (the semiconductor wafer is stacked via adhesive or other means upon a “carrier” wafer to add stiffness to the combination) the grind engine is configured to grind the top wafer to substantially thinner final thicknesses, such as less than 20 microns. Some embodiments, in achieving precision final thickness over the wafer for stacked wafer applications, employ metrology and software in combination with one or more contact probes (e.g., Heidenhain or Sony model) touching the top surface of the wafer. Additionally or alternatively, an Infrared interferometric sensor can be used that measures the height of the interface between the carrier and the top wafer that is being ground. In some instances, the contact probe and the Infrared sensor can be used in combination.
Cleaning the porous vacuum chuck that securely holds the wafer flat for grinding can be important for at least some thin wafer grinding implemented through the grind engine. Some systems clean the chuck with an automated abrasive wheel or a brush mounted to an arm. The abrasive wheel or brush processes, however, may leave small particles of abrasives or of porous chuck particle itself on the surface of the chuck, which then cause an impression or bump on the thin wafer to be ground, so that it is locally over ground. Some embodiments include a sharp blade scraping process, which can be performed after grinding the chuck, in addition to or alternatively to the brush and/or abrasive wheel, so as to dislodge small embedded particles protruding above the surface of the porous chuck.
The grind engine can be utilized and placed in alternative configurations and/or systems, depending upon the product to be manufactured, size and/or the diameter and the material of the wafer, and the precision of the final product required. For example:
Accordingly, the present embodiments provide methods and systems for use in grinding wafers and/or other such objects. These grinding methods and systems in part improve grind object geometry, increase throughput, and reduce cost of the tool.
Referring back to
In step 1414, the rotary indexer 2 is indexed to move the work chuck 5 and work spindle 6 to a load and/or unload position. In some implementations, the rotary indexer 2 is positioned or rotated to position the work chuck 5 relative to the door 15 of the grind chamber 4 to allow access to (manually or by robot) the work chuck for the placement or removal of a wafer to or from the work chuck. In step 1415, a wafer is placed on the work chuck 5. The placement of the wafer can be manually placed by the operator or technician, or by robot through partial or full automation. In step 1416, a vacuum is applied to and through the work chuck 5 to hold and secure the wafer against the work chuck. In step 1417, the grind chamber door(s) 15 is closed, and in some instances locked. Again, the door closing may be manual or part of the automated operation of the grind device.
In step 1418, the rotary indexer 2 is indexed to move the work chuck 5 and work spindle 6 to the coarse grind position. Typically, the rotary indexer rotates the work chuck such that at least a portion of the wafer supported on the work chuck 5 is aligned with at least a portion the coarse grind wheel secure with the grind spindle 8. In step 1419, the grind spindle 8 is activated to spin the coarse grind wheel according to the grind recipe and extends the coarse grind wheel to contact the wafer. In step 1420, the coarse grind recipe is executed to grind the wafer to a desired thickness. Often, this thickness is defined as a coarse grind thickness to within predefined thresholds. Again, the stiffness, rigidity and precision provided by the grind system allows that threshold to be extremely small, typically limited by the accuracy of the measurement probes and/or sensors of the system. With some current technologies, the thresholds can be as small as tens of micron, and in some instances a micron.
In step 1421, the one or more contract probes and other sensors monitor the thickness and pressures applied to provide feedback to the grind system. For example, a wafer contact probe monitors wafer thickness during grinding, typically in cooperation with a reference measurement of the work chuck surface provided by the work chuck contact probe. Additionally or alternatively, an IR sensor can be used in some embodiments, particularly when grinding a stacked wafer. Work chuck deflection can also be monitored by the chuck contact probe during grind. When the grind forces increase to a pre-defined limit, grinding can be paused and the coarse grind wheel can be automatically dressed. The grinding can then be resumed continuing to monitor the thickness and/or pressures (e.g., for further grind wheel dressing) until a desired wafer thickness and/or surface profile is achieved.
In step 1422, it is detected that the coarse removal target is achieved. In step 1423, the coarse grind wheel is refracted. Some embodiments include optional step 1424, where the rotary indexer 2 is indexed to move the work chuck 5 and wafer to a fine grind position when such movements are desired. In step 1425, the grind system executes the fine grind recipe, which can include steps similar to those of steps 1421-1422. Again, the fine grind is performed until a desired fine grind thickness is achieved to within predefined threshold. Similar to above, the fine grinding may be temporarily interrupted to dress the fine grind wheel, which can be activated in response to detected pressures. In step 1426, it is detected that the fine removal target is achieved.
In step 1427, the fine and/or coarse grind wheel(s) and/or grind spindle 8 are moved to a safe position relative to the wafer and/or work chuck 5. In optional step 1428, the rotary indexer 2 is indexed to move the work chuck 5 to a polish position and a polishing recipe is executed, when the grind system includes a polishing station and/or location. In step 1429, the rotary indexer is indexed to move the work chuck 5 to the load and/or unload position. In step 1430, the grind chamber door(s) are unlocked and opened, when one or more doors are present and/or locked. In step 1431, the wafer is removed from the grind chamber. Again, the removal may be manual or preformed by a robot (e.g., with end effectors).
Some embodiments further include a cleaning station or position. Accordingly, in some instances the process 1410 can include step 1432 where the rotary indexer is indexed to move chuck to chuck cleaning position. In step 1433, a chuck cleaner recipe is executed to clean the chuck 5. Other embodiments may not perform all of these steps, while other embodiments may perform additional steps. Further, some of these steps may be performed at separate devices and/or modules, such as a system cooperating multiple modules as described above and further below.
Further, some embodiments provide compact grinding systems. The compactness can be achieve, at least in part, by the cooperation of the one or more of the rotary indexer 2, the lower base casting 1, the bridge casting 3, the coaxial spindle configuration with dual, nested grind wheels (or single axis spindle combined with the extendable grind wheel apparatus, and other such relevant factors. For example, the use of the rotary indexer 2 contained within the base casting 1 and further configured with dimensions such that the work spindle 6 and work chuck 4 are mounted and rotated by the rotary indexer. The rotary indexer 2 can be configured, in accordance with some embodiments, with a diameter greater than a diameter of the work chuck 5 and a radius that is less than the diameter of the work chuck. In other configurations, the rotary indexer can be configured with a diameter that is greater than a diameter of the work chuck, and with a radius that is about equal to larger than the diameter of the work chuck. For example, in implementations where two work spindles and work chucks are secured with and rotated by the rotary indexer 2, the rotary indexer has a diameter greater than the two work chucks. Further, the rotation of the rotary indexer allows for the carousel movement of the work spindle and chuck into alignment with the one or more grind wheels and/or grind spindle.
The use of the nested, dual grind wheels on a single grind spindle 8 significantly reduced the size by, in part, reducing the number of grind spindles, areas for performing the separate coarse and fine grinding, the separate motors, control, bearings and other structures associated with multiple separate grind spindles. Further, the use of the bridge casting 3 allows for greater support of the grind spindle 8 than can typically be achieved with cantilever style mounting, which can allow reduced structural size and/or material to be used. Additionally, the bridge casting 3 allows for the enclosure of the rotary indexer 2 and grind wheels adding stiffness to the entire grind module with the structure providing a closed loop coupling the grind spindle to the work spindle.
Still further, the use of the rotary indexer design and casting configurations provides enhanced stiffness of the grinding system, and thus allows for greater accuracy in thickness and surface shape while also allowing for very thin grinding. The higher levels of stiffness of the grind engine are provided, at least in part, by the rotary indexer 2 being mounted within the base casting 1 and supported at least near a perimeter of the rotary indexer by the highly stiff cross roller ring bearing 16. The lower base casting 1 fully contains the rotary indexer 2 and the ring bearing 16 providing a stiff base. Further, the rotary indexer 2 and the ring bearing 16 fully contain the one or more work spindles 6 and/or counter balance 14 within their diameters.
Additionally, the cooperation of the base casting 1 and the bridge casting 3 provides a rigid structure that in turn rigidly supports the work spindle 6 and the grind spindle 8. The rotary indexer 2 and cross roller bearing 16 are stiffly mounted in lower base casting 1. The mounting of the bridge casting 6 from the base casting to extend up from the base casting and over at least a portion of the rotary indexer 2 provides for a stiff mounting for the grind spindle 8 relative to the rotary indexer 2 and the work chuck when rotated into a grind position by the rotary indexer.
The present embodiments additionally provide enhanced throughput and/or wafer processing at least through the coaxial grind spindle combined with dual, nested grind wheels and the rotary indexer design. The rotary indexer 2 rotationally positions the work chuck and wafer in relevant locations within the single grind enclosure to achieve multiple operations (e.g., coarse grind, fine grind, polish, chuck cleaning, etc.). This combination minimizes travel and overhead time of the wafer between coarse and fine grind steps as well as polishing, and the cleaning of the work chuck. Further, by securing the two grinding wheels to the same rotational axis allow them to rotate in alignment with each other and further allow for a single alignment mechanism to align both grind wheels at the same time to the work spindle 6. This in part produces a more precise alignment, more compact assembly, faster alignment, and economy of a single alignment mechanism. As described above, some embodiments replace the spindle counterbalance 14 with a second grind spindle. This allows for wafer load/unload on one spindle while the other spindle is preparing for grinding and/or is grinding, which can further reduce overhead time.
Similarly, the grinding system of the present embodiments can provide enhanced processing capabilities. The higher level of stiffness in the grind system, in part, provides for improved process capabilities. For example, the enhanced stiffness allows the ability to grind wafers to an extreme thinness and accuracy of shape. The rigidity of the structure combined with the adjustment screw assemblies provide for the ability for superior alignment of the grind and work spindles. Better alignment allows the wafer to be ground to a more precise shape, and therefore thinner, without the fear of removing too much material in certain areas on the wafer. Superior rigidity also allows the grind module to better maintain spindle alignments, even while subjected to the forces created during grinding.
Improved processing is also provided, at least in part, through other aspects of the grind system. For example, the single spindle alignment for both the coarse and fine grind wheels via use of the coaxial spindle also allows for quicker, easier setup of the grind system. The cooperation of the two measurement probes (one to track the wafer thickness, and the other to track any chuck movement that may have occurred since the wafer was placed on the chuck, e.g., from thermal expansion of the spindle) further improves precision, accuracy and processing. Some implementations additionally or alternatively utilize an IR type probe that further improves the processing and throughput. Again, the IR probe allows for rapid and precise measurements of ground wafer thickness, particularly when performing stacked wafer grinding, instead of only being able to measure the full stack height of the carrier and ground wafer via a contact measurement probe.
The compact rotary indexer 2 further provides improved processing. The use of the rotary indexer 2 in combination with the counter balance (dummy spindle) or the inclusion of a second work spindle 6 balances the rotary indexer and prevents shifting of center of gravity during rotary indexer movement and/or minimizes structural deflections in the grind module, and to adjacent grind modules when cooperated with other grind modules. Further, the rotary indexer 2 allows for positioning, and in some instances oscillation, of the wafer beneath the grind wheels, and/or a post-grind stress relief polish head, pad or other structure. Similarly, the rotary indexer can positions and oscillate the work chuck 5 beneath a chuck cleaning system and/or device. Still further, the rotary indexer 2 can be utilized in some implementations to position and move a wafer beneath a single or multiple wafer measurement devices while the wafer is measured. The combination of rotary indexer and wafer chuck movement can allow for complete measurement of a wafer using only a single sensor.
As described above, the grinding system can be cooperated with one or more other systems and/or engines to provide a cooperative processing tool. Accordingly, in some embodiments, the grind system is provided in a modular design having a compact configuration. This compact configuration, however, still allows the grind system to execute a complete grind process, which can include coarse and fine grind steps and/or edge grinding, if desired, all within the same grind module. Further, the compact design allows the grind system or module to be cooperated or ganged together with one or more other multiple grind modules and/or other types of modules in a single tool. For example, one or more polish modules can be combined with one or more grind modules into a single automated tool. Conversely, the grind module can function all by itself, such as a manual load, laboratory type grinding tool.
Again, the grind system 1512 includes the rotary indexer 2, with the work chuck 5 cooperated with the rotary indexer allowing the rotary indexer to rotate the work chuck 5, and thus a wafer, into a grind position relative to the grind spindle (where the relative position of the grind spindle 8 relative to the work chuck is shown in
It is noted that in some instances other methods and systems may provide thicker wafers. These implementations can use corrective means after grind, such as selective etch and polish methods to modify wafer shape. These subsequent processes add production time and cost to the final product being made on the wafers (i.e. Back-Side Illumination image sensing chips (BSI) image sensors).
Further, some embodiments can provide grinding for Back-Side Illumination camera chips (BSI) and Thru-Silicon Vias (TSV) for 3D stacked wafers are currently being required to achieve more functionality for given chip cross-sectional area. Further, the systems and methods typically provide improved grinding, including grinding thin and/or stacked wafers.
One or more controllers and/or processors are included in the grinding engine and/or cooperated with the grinding engine to provide control over the grinding engine and/or the grinding. Typically the controller receives sensor data and controls the grinding accordingly. The controller or controllers can be implemented through one or more processors, controllers, central processing units, logic, software and the like. Further, in some implementations the controller(s) may provide multiprocessor functionality. Computer and/or processor accessible memory can be included in the controller and/or accessed by the controller. In some embodiments, memory stores executable program code or instructions that when executed by a processor of the controller cause the grinding engine to control the one or more components of the grinding engine and/or perform grinding. Further, the code can cause the implementation of one or more of the processes and/or perform one or more functions such as described herein.
The methods, techniques, systems, devices, services, servers, sources and the like described herein may be utilized, implemented and/or run on many different types of devices and/or systems. These devices and/or systems may be used for any such implementations, in accordance with some embodiments. One or more components of the system may be used for implementing any system, apparatus or device mentioned above or below, or parts of such systems, apparatuses or devices, such as for example any of the above or below mentioned controllers, as well as user interaction system, sensors, feedback, displays, controls, detectors, motors and the like. However, the use of one or more of these systems or any portion thereof is certainly not required.
The memory, which can be accessed by the processors and/or controllers, typically includes one or more processor readable and/or computer readable media accessed by at least the processors and/or controllers, and can include volatile and/or nonvolatile media, such as RAM, ROM, EEPROM, flash memory and/or other memory technology. Further, the memory can be internal to the system; however, the memory can be internal, external or a combination of internal and external memory. The external memory can be substantially any relevant memory such as, but not limited to, one or more of flash memory secure digital (SD) card, universal serial bus (USB) stick or drive, other memory cards, hard drive and other such memory or combinations of such memory. The memory can store code, software, executables, grind recipes, scripts, data, coordinate information, programs, log or history data, user information and the like.
Accordingly, some embodiments provide a processor or computer program product comprising a medium configured to embody a computer program for input to a processor or computer and a computer program embodied in the medium configured to cause the processor or computer to perform or execute steps comprising any one or more of the steps involved in any one or more of the embodiments, methods, processes, approaches, and/or techniques described herein. For example, some embodiments provide one or more computer-readable storage mediums storing one or more computer programs for use with a computer simulation, the one or more computer programs configured to cause a computer and/or processor based system to execute steps comprising: rotating a rotary indexer about a first axis and rotationally orienting a work chuck and work spindle into a load position; applying a vacuum pressure to secure a wafer to the work chuck; rotating the rotary indexer to rotationally orient the work chuck and work spindle into a grind position such that the wafer is at least partially aligned with a coarse grind wheel; activating a grind spindle to apply the coarse grind wheel to the wafer to grind the wafer according to a coarse grind recipe; detecting that the wafer has been ground to a predefined coarse grind thickness; activating the grind spindle to apply a fine grind wheel to grind the wafer according to a fine grind recipe, wherein the fine grind wheel is nested with the coarse grind wheel such that the coarse and fine grind wheels are coaxially aligned about a second axis that is different than the first axis and around which the first and second grind wheels are rotated by the grind spindle; detecting that the wafer has been ground to a predefined fine grind thickness; and rotating, after the detecting that the wafer has been ground to the predefined fine grind thickness, the rotary indexer to the first position such that the work chuck is rotationally orienting into the load position allowing the wafer to be removed.
Other embodiments provide one or more computer-readable storage mediums storing one or more computer programs configured for use with a computer simulation, the one or more computer programs configured to cause a computer and/or processor based system to execute steps comprising: rotating a rotary indexer positioning a work chuck and work spindle secured with the rotary indexer to a load position allowing ready access to position a wafer on the work chuck; rotating the rotary indexer and positioning the work spindle and work chuck to a grind position generally aligned with at least a portion of a grind wheel supported and rotated by a grind spindle; preventing a shifting of a center of gravity of the rotary indexer as the rotary indexer rotates the work chuck by securing a counter balance on the rotary indexer relative to the work spindle.
Some embodiments provide grinding apparatuses comprising: a base casting; a rotary indexer positioned within the base casting, wherein the rotary indexer is configured to rotate within the base casting and about a first axis; a first work spindle secured with the rotary indexer; a first work chuck coupled with the first work spindle, wherein the first work spindle is configured to rotate the first work chuck about a second axis; a bridge casting rigidly secured relative to the base casting, wherein the bridge casting bridges across at least a portion of the rotary indexer and is supported on opposite sides of the rotary indexer; a grind spindle secured with the bridge casting; a first grind wheel cooperated with the grind spindle such that the grind spindle is configured to rotate the first grind wheel, wherein the bridge casting secures the grind spindle such that the first grind wheel is positioned over the rotary indexer to generally align with at least a portion of the first work chuck when the first work spindle is rotated by the rotary indexer into a corresponding position.
Other embodiments provide grinding apparatuses comprising: a grind spindle; a first grind wheel coupled with the grind spindle, wherein the grind spindle is configured to rotate the first grind wheel; a work spindle; a work chuck coupled with the work spindle, wherein the work spindle is configured to rotate the work chuck about a first axis; a rotary indexer positioned relative to the grind spindle, wherein the work spindle is secured with the rotary indexer and wherein the rotary indexer is configured to rotate the work spindle about a second axis that is different than the first axis such that the work chuck is positioned generally in alignment with at least a portion of the first grind wheel; and a ring bearing having a circular, ring configuration, wherein the ring bearing supports the rotary indexer and is configured to aid the rotary indexer in rotating about the second axis, wherein the work spindle is secured with the rotary indexer within an inner diameter of the ring bearing.
Further, some embodiments provide method of wafer grinding, comprising: rotating a rotary indexer about a first axis and rotationally orienting a work chuck and work spindle into a load position; applying a vacuum pressure to secure a wafer to the work chuck; rotating the rotary indexer to rotationally orient the work chuck and work spindle into a grind position such that the wafer is at least partially aligned with a coarse grind wheel; activating a grind spindle to apply the coarse grind wheel to the wafer to grind the wafer according to a coarse grind recipe; detecting that the wafer has been ground to a predefined coarse grind thickness; activating the grind spindle to apply a fine grind wheel to grind the wafer according to a fine grind recipe, wherein the fine grind wheel is nested with the coarse grind wheel such that the coarse and fine grind wheels are coaxially aligned about a second axis that is different than the first axis and around which the first and second grind wheels are rotated by the grind spindle; detecting that the wafer has been ground to a predefined fine grind thickness; and rotating, after the detecting that the wafer has been ground to the predefined fine grind thickness, the rotary indexer to the first position such that the work chuck is rotationally orienting into the load position allowing the wafer to be removed.
While the invention herein disclosed has been described by means of specific embodiments, examples and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.
This application claims the benefit of U.S. Provisional Application No. 61/549,787, filed Oct. 21, 2011, for Walsh et al., entitled SYSTEMS AND METHODS OF WAFER GRINDING; U.S. Provisional Application No. 61/585,643, filed Jan. 11, 2012, for Walsh et al., entitled SYSTEMS AND METHODS OF PROCESSING SUBSTRATES; U.S. Provisional Application No. 61/708,146, filed Oct. 1, 2012, for Brake et al., entitled METHODS AND SYSTEMS FOR USE IN GRIND SHAPE CONTROL ADAPTATION; U.S. Provisional Application No. 61/708,165, filed Oct. 1, 2012, for Walsh et al., entitled METHODS AND SYSTEMS FOR USE IN GRIND SPINDLE ALIGNMENT; U.S. Provisional Application No. 61/632,262, filed Jan. 23, 2012, for Vogtmann et al., entitled METHOD AND APPARATUS FOR CLEANING GRINDING WORK CHUCK USING A SCRAPER; and U.S. Provisional Application No. 61/631,102, filed Dec. 28, 2011, for Michael Vogtmann, entitled METHOD AND APPARATUS FOR CLEANING GRINDING WORKCHUCK USING A VACUUM; each of which is incorporated in its entirety herein by reference.
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