System and method for cleaning a wafer chuck

A wafer chuck is cleaned using a cleaning cap to remove processing residue and particulate matter. The cleaning cap is configured to overlie and align with the wafer chuck and includes a base and a first roller connected to the base and having wound therearound a cleaning cloth. The cleaning cap further includes a second roller connected to the base and having attached thereto a free end of the cleaning cloth. During use, the cleaning cloth winds upon the second roller from the first roller when the second roller rotates about its axis. The cleaning cap can be positioned relative the wafer chuck by way of a manipulator to ensure the cleaning cloth contacts the wafer chuck with sufficient force. The cleaning cloth rubs the wafer chuck with both translational motion and rotational motion.

BACKGROUND

Various processes in the manufacture of semiconductor devices involve the use of a wafer chuck, i.e., a device that is employed to hold a wafer in place, manipulate the wafer into or out of a processing chamber, rotate the wafer, align and orient the wafer, etc. It is known that a wafer chuck can become dirty during processing steps. Residues and particulate matter can contaminate a chuck and subsequently contaminate other wafers that are placed on the chuck. This contamination can lead to yield and reliability problems. Hence, it is required in the art to frequently remove a wafer chuck (and hence often an entire processing chamber or machine) from service in order to clean the chuck, resulting in the loss of productivity and hence increased costs.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1Aschematically illustrates a wafer processing device100. Device100includes a chamber2in which is located a wafer chuck4. As is known in the art, wafer chuck4is configured to have secured thereto a workpiece, such as a semiconductor wafer to securely hold the wafer thereon.

Wafer chuck4is attached to stage6, which as is known in the art, can position the wafer chuck, and hence a wafer placed upon the wafer chuck, into position, typically providing freedom of movement in three axes as well as providing for rotational movement as well. Wafer chuck4typically includes apparatus (not shown) for securing a wafer to the wafer chuck, such as retaining clips or springs, a retaining ring, vacuum orifices, and the like.

Device100also includes a cleaning cap8.FIG. 1Aillustrates the processing device100wherein cleaning cap8is in a first position removed from wafer chuck4. As illustrated, cleaning cap8may be positioned above wafer chuck4in the first position. Alternatively, cleaning cap8may be positioned outside chamber2, in a recess of a wall of chamber2(not shown), laterally displaced from a top surface of wafer chuck4, laterally and vertically displaced from the top surface of wafer chuck4, or any other location that will be apparent to those skilled in the art, informed by the present teaching and through routine experimentation. This first position is the position in which cleaning cap8may be stored or located when not in use. Preferably, cleaning cap8is stored or located, when not in use, in a position wherein cleaning cap8does impede or interfere with the operation of device100during its intended use.

FIG. 1Billustrates cleaning cap8in a second position wherein cleaning cap8is positioned on or closely adjacent wafer chuck4. In this second position, portions of cleaning cap8may be in contact with wafer chuck4as will be described in greater detail below. In some embodiments, cleaning cap8is moved between a first position and a second position by way of a manipulator10, such as a robotic arm, a turn screw mechanism, a spring loaded mechanism, or the like, which manipulator moves cleaning cap8between various positions, including the first and second positions described above. In alternative embodiments, cleaning cap8and wafer chuck4can be moved relative to one other by way of a manipulator attached to wafer chuck4(not shown) in lieu of or in addition to a manipulator10. In still other embodiments, cleaning cap8and wafer chuck4can be moved relative to one another by way of stage6having a degree of freedom in the z direction, in lieu of or in addition to manipulator10.

FIG. 2illustrates cleaning cap8in more detail. In some embodiments, cleaning cap8includes a base20made of plastic, ceramic, nylon, quartz, or other suitable material. In other embodiments, base20could be made of metal or a metallic compound. One skilled in the art will recognize, as a matter of routine experimentation, the type of material suited for the particular application.FIG. 2Aillustrates in plan view the surface27of cleaning cap8, being the surface that is proximate to or in contact with wafer chuck4when cleaning cap8is in the above-described described second position.FIG. 2Billustrates cleaning cap8in cross-section view along the line B-B′ inFIG. 2A.

Cleaning cap8includes a first roller22and a second roller24. In the illustrated embodiment, as shown inFIG. 2B, first roller22and second roller24are located within a recess26in bottom surface27of base20. As illustrated inFIG. 2B, by “within” a recess, it meant that the first roller22and second roller24are substantially within the recess, but that a portion of the roller may extend beyond or below bottom surface27.

In other embodiments first roller22and second roller24could be located extending mostly or entirely below bottom surface27of base20, in which case base20need not include recess26. In the illustrated embodiment, cleaning cap8further includes a third roller22′ and a fourth roller24′ located within a second recess26′. This second set of rollers is optional, and one skilled in the art will recognize that any number and combination of rollers could be employed in various embodiments. Typically embodiments will include one, two, or four such rollers but this is provided by way of example and not by limitation. For clarity, only first roller22, second roller24and associated additional elements will be described. Corresponding elements such as third roller22′, fourth roller24′, and their respective associated elements, although illustrated, will not be described—it being understood that the below description applies equally to corresponding ones of these additional optional elements.

Cleaning cloth28, also shown inFIG. 2A, is typically a thin, dust-free, lint-free, flexible cloth such as polyvinyl alcohol, cotton, a reinforced paper, a synthetic material such as nylon, rayon, polyester, or the like. A first end of cleaning cloth28may be attached to first roller22, such as by an adhesive, a mechanical fastener such as a staple, by forming a pocket in cleaning cloth28in which first roller22is placed, or by any other means. Cleaning cloth28may further be wound around first roller22, similarly to winding a bolt of cloth around a rod. A second end of cleaning cloth28may be attached to second roller24using the same attachment scheme as provided for with first roller22or a different attachment scheme. In this way, by rotating second roller24, cleaning cloth28is unwound from first roller22and pulled toward and wound upon second roller24. During operation, and as cleaning cloth28is unwound from first roller22and wound onto second roller24, cleaning cloth28is stretched taut between the two rollers and rubs against a top surface of wafer chuck4. In this way, wafer chuck4is cleaned by operation of cleaning cloth28rubbing against it.

As shown inFIG. 2B, second roller24is maintained in place within recess26by way of axes30, which allow for rotation of second roller24. Likewise, although not illustrated, first roller22is held in place within recess26by axes. Axes30associated with second roller24and/or the axes associated with first roller22, and/or both sets of axes are driven by a drive motor (not shown), which drives axes30and in turn second roller24(and/or first roller22) to cause the rotational movement whereby cleaning cloth28moves from one roller to another. If only one roller, for example second roller24, is driven by a motor, then cleaning cloth28can extend in only one direction (i.e. unwinding from first roller22and onto second roller24). Once cleaning cloth28is completely unwound from first roller22onto second roller24, the assembly (e.g., first roller22, second roller24, and cleaning cloth28) will need to be replaced or else cleaning cloth28will need to be manually re-wound onto first roller22for future operations. In embodiments where both first roller22and second roller24are driven by a motor, cleaning cloth28can be employed numerous times, winding from one roller onto the other and back again, without replacement or manual intervention.

FIG. 2Balso illustrates a series of spring mechanisms32which operate to maintain second roller24, and hence cleaning cloth28, in contact with the surface to be cleaned of cleaning chuck4. One skilled in the art will recognize that various mechanisms can be employed to ensure that cleaning cloth28maintains in close contact with wafer chuck4and with sufficient downward pressure to ensure good scrubbing or polishing type action, without such pressure as to damage the surface. In some embodiments, the downward pressure applied is between about 10 and 200 Pa.

FIG. 3illustrates a portion of cleaning cap8in cross-section view along the line C-C′ inFIG. 2A.FIG. 3is shown in larger scale, relativeFIG. 2B, to further illustrate illustrative features of some embodiments. Note that inFIG. 3cleaning cap8is shown in the second position wherein cleaning cap8is in close proximity to wafer chuck4. In the illustrated embodiment, rollers22and24are located within a recess26and extend below the bottom surface27of base20of cleaning cap8. The amount by which rollers22and24extend below bottom surface27is not critical, but rather the goal is to ensure that cleaning cloth28establishes and maintains good contact with wafer chuck4in order to clean the surface of same. As discussed above, it may be desirable to have cleaning cloth28contact wafer chuck4with a downward pressure, which can be accomplished by way of spring mechanisms32described above, by way of manipulator10applying downward pressure on entire cleaning cap8, stage6applying upward pressure on wafer chuck4to engage with cleaning cloth28, or by other means that will become apparent to one skilled in the art informed by the present teaching and routine experimentation.

Optional, yet advantageous, additional features are illustrated inFIG. 3. One such feature is solvent disperser34located adjacent first roller22. Solvent disperser34is located in such a way as to deliver a solvent/cleaning material to cleaning cloth28. In the illustrated embodiment, solvent disperser34is located above first roller22; in other embodiments, solvent disperser34may be located adjacent or below first roller22. In yet other embodiments, solvent disperser34may be located proximate to second roller24. In yet another embodiment, a first solvent disperser is located proximate first roller22and a second solvent disperser (not shown) is located proximate second roller24. Solvent disperser34communicates with a solvent reservoir (not shown) which delivers solvent at an appropriate temperature and pressure to solvent disperser34whereby the solvent is sprayed, poured, or otherwise delivered to cleaning cloth28. In currently anticipated embodiments, solvents such as water, distilled water, acetone, or the like are employed although the scope of the present invention is not limited to the particular solvent and or cleaner employed. In other embodiments, cleaning cloth28may be impregnated with a solvent such that a separate solvent disperser is not necessary. In yet other embodiments, solvent disperser34may be employed with a solvent-impregnated cleaning cloth28.

A brush36is illustrated adjacent second roller24. Brush36is situated relative second roller24so that particulate matter that is removed from wafer chuck4and adheres to cleaning cloth28can be removed through a brushing motion as cleaning cloth28passes under brush36. Is some embodiments, brush36is stationary, whereas in other embodiments, brush36is motor driven to provide additional movement relative cleaning cloth28. Vacuum orifice38is also located adjacent second roller24. In the illustrated embodiment, vacuum orifice38applies a vacuum in the immediate vicinity of brush36so that particulate matter brushed from cleaning cloth28is vacuumed into vacuum orifice38.

Also illustrated inFIG. 3are optional rollers40located interjacent first roller22and second roller24. Rollers40are included to further ensure that cleaning cloth28remains taut and tautly pressed against the surface of wafer chuck4during the cleaning process. Rollers40may be mounted fixed to base20or may be mounted using a spring mechanism (not shown) to provide downward pressure on cloth28. Two rollers40are shown in the illustrated embodiment although one, three, four, or more rollers could be employed. In other embodiments, rollers40could be replaced by one or more spring mechanisms that extend down and push against cleaning cloth28as cleaning cloth28slides beneath them.

Note that, as illustrated inFIG. 3, cleaning cap8extends beyond an outer edge of wafer chuck4. Such a configuration, while not mandatory, ensures that the outer edge of wafer chuck4will be contacted and hence cleaned by cleaning cloth28. In some embodiments, wafer chuck4is intended to hold a 450 mm diameter wafer and cleaning cap8has a diameter ranging from about 450 mm to about 900 mm.

FIG. 4Aillustrates the translational movement of cleaning cloth28in a linear direction as it is unwound from first roller22and wound onto second roller24. This is illustrated by arrow42. At the same time, cleaning cap8moves with rotational movement relative wafer chuck4, as illustrated by arrow46. By rotational movement relative to the chuck, it is meant that the motion can be the result of rotating cleaning cap8, rotating wafer chuck4, or rotating both. Hence, cleaning cloth28(and cleaning cloth28′ in the illustrated embodiment) rubs the surface of wafer chuck4in a linear fashion42(due to the movement from one roller to the next) while at the same time rubbing the surface of wafer chuck4in a rotational fashion46(due to the rotational movement of cleaning cap8relative wafer chuck4). This provides for a thorough cleaning operation in a relatively short period of time.

FIG. 4Billustrates another embodiment, in this case having 5 sets of first and second rollers and five cleaning cloths (28through28″″). Such an arrangement ensures that the entire wafer chuck surface is cleaned, not just the outer regions. In bothFIGS. 4A and 4B, the cleaning cloths28are illustrated as moving (linearly) in different directions. In other embodiments, the cleaning cloths28could move linearly in the same direction.

InFIG. 4Ca single cleaning cloth is illustrated, extending from the center of cleaning cap8towards its outer edge. During use, this cleaning cloth would rub wafer chuck4from the center toward the outer edge (the linear motion42) as it rotated about the wafer chuck (rotational motion46). Alternatively, cleaning cloth28would move from the outer edge toward the middle, and several such cloths could be employed, forming a star pattern.