Chemical mechanical polishing conditioner

Information

  • Patent Grant
  • 6361423
  • Patent Number
    6,361,423
  • Date Filed
    Friday, December 22, 2000
    24 years ago
  • Date Issued
    Tuesday, March 26, 2002
    22 years ago
Abstract
A conditioner head for conditioning the polishing surface of a polishing pad. The conditioner head includes a drive element carried for rotation about a longitudinal axis and a disk backing element. The disk backing element carries an abrasive disk and holds the lower surface of the disk in engagement with the polishing pad. The conditioner head further includes a driven element coupling the disk backing element to the drive element to transmit torque and rotation therebetween. The driven element is longitudinally movable between retracted and extended positions. An annular diaphragm spans a gap between the drive element and the driven element and is coupled to the drive element and to the driven element to rotate therewith as a unit.
Description




BACKGROUND




1. Technical Field




This invention relates generally to the planarization of semiconductor substrates and, more particularly to the conditioning of polishing pads in slurry-type polishers.




2. Background Information




Integrated circuits are typically formed on substrates, particularly silicon wafers, by the sequential deposition of conductive, semiconductive or insulative layers. After each layer is deposited, the layer is etched to create circuitry features. As a series of layers are sequentially deposited and etched, the outer or uppermost surface of the substrate, i.e., the exposed surface of the substrate, becomes successively less planar. This non-planar outer surface presents a problem for the integrated circuit manufacturer as a non-planar surface can prevent proper focusing of the photolithography apparatus. Therefore, there is a need to periodically planarize the substrate surface to provide a planar surface. Planarization, in effect, polishes away a non-planar, outer surface, whether a conductive, semiconductive, or insulative layer, to form a relatively flat, smooth surface.




Chemical mechanical polishing is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head, with the surface of the substrate to be polished exposed. The substrate is then placed against a rotating polishing pad. The carrier head may also rotate and/or oscillate to provide additional motion between the substrate and polishing surface. Further, a polishing slurry, including an abrasive and at least one chemically-reactive agent, may be spread on the polishing pad to provide an abrasive chemical solution at the interface between the pad and substrate.




Important factors in the chemical mechanical polishing process are: substrate surface planarity and uniformity, and the polishing rate. Inadequate planarity and uniformity can produce substrate defects. The polishing rate sets the time needed to polish a layer. Thus, it sets the maximum throughput of the polishing apparatus.




It is important to take appropriate steps to counteract any deteriorative factors which either present the possibility of damaging the substrate (such as by scratches resulting from accumulated debris in the pad) or reduce polishing speed and efficiency (such as results from glazing of the pad surface after extensive use). The problems associated with scratching the substrate surface are self-evident. The more general pad deterioration problems both decrease polishing efficiency, which increases cost, and create difficulties in maintaining consistent operation from substrate to substrate as the pad decays.




The glazing phenomenon is a complex combination of contamination, thermal, chemical and mechanical damage to the pad material. When the polisher is in operation, the pad is subject to compression, shear and friction producing heat and wear. Slurry and abraded material from the wafer and pad are pressed into the pores of the pad material and the material itself becomes matted and even partially fused. These effects reduce the pad's roughness and its ability to apply fresh slurry to the substrate.




It is, therefore, desirable to continually condition the pad by removing trapped slurry, and unmatting or re-expanding the pad material.




A number of conditioning procedures and apparatus have been developed. Common are mechanical methods wherein an abrasive material is placed in contact with the moving polishing pad. For example, a diamond coated screen or bar may be used which scrapes and abrades the pad surface, and both removes the contaminated slurry trapped in the pad pores and expands and re-roughens the pad.




SUMMARY




In one aspect, the invention is directed to a conditioner head for conditioning the polishing surface of a polishing pad. The head includes a drive element carried for rotation about a longitudinal axis. The head further includes a disk backing element for carrying an abrasive disk and holding the lower surface of the disk in engagement with the polishing pad. A driven element couples the disk backing element to the drive element and transmits torque and rotation therebetween. The driven element is longitudinally movable between retracted and extended positions. An annular diaphragm spans a gap between the drive element and the driven element and is coupled to the drive element and the driven element so as to rotate therewith as a unit.




Implementations of the invention may include one or more of the following. The diaphragm may in part bound a pressure chamber which may be pressurized to shift the driven element from the retracted position to the extended position and depressurized to shift the driven element from the extended position to the retracted position. During transition between the retracted and extended positions a first surface of the diaphragm, exterior to the pressure chamber, rolls of a generally annular outer surface portion of the driven element traverses the gap and rolls onto a generally annular inner surface portion of the drive element.




The drive element may include a drive shaft and a collar substantially fixed to the drive shaft and having a generally annular inner surface portion. The driven element may include a drive sleeve encircling at least a length of the drive shaft and having a generally annular outer surface portion. The annular diaphragm may extend between an outer periphery and an inner aperture and may be sealingly secured along the outer periphery to the collar and along the inner aperture to the drive sleeve. The generally annular outer surface portion of the drive sleeve may be a circular cylinder and the generally annular inner surface portion of the collar may be a circular cylinder. The diaphragm may in part bound a pressure chamber. The pressure chamber may be pressurized to shift the drive sleeve from the retracted position to the extended position and depressurized to shift the drive sleeve from the extended position to the retracted position. During transition between the retracted and extended positions, a first surface of the diaphragm, exterior to the pressure chamber, may roll off the generally annular outer surface portion of the drive sleeve. The first surface of the diaphragm may then traverse a gap between the generally annular outer surface portion of the drive sleeve and the generally annular inner surface portion of the collar and roll onto the generally annular inner surface portion of the collar. A fluid for inflating the pressure chamber may be introduced to the pressure chamber through a channel in the drive shaft. The head may include a housing substantially rigidly coupled to a conditioner arm for moving the head at least transverse to the longitudinal axis. The housing may include a first portion encircling at least the length of the collar, which first portion is coupled to the collar by a bearing system for permitting the collar to rotate relative to the first portion about the longitudinal axis. A web may be formed at the upper end of the drive shaft, the collar depending from the web. A pulley may be substantially fixed to the web for transmitting torque to the drive shaft. The collar may comprise a first piece depending from and fixed to the web and a second piece, separately formed from the first piece. The second piece may engage the bearing system and the diaphragm may be secured along the outer periphery to the collar between the first and second pieces. The diaphragm may be partially sandwiched between an outer cylindrical surface of an annular lip depending from the first piece and a generally annular inner surface of the second piece which forms the generally annular inner surface portion of the collar.




In another aspect, the invention is directed to a disk holder for holding a conditioning disk for conditioning a polishing pad. The disk holding element has a lower face for engaging an upper surface of the conditioning disk. The disk holding element defines a plurality of generally radially outward extending channels along the upper surface of the conditioning disk.




Implementations of the invention may include one or more of the following. The disk may comprise a central region, an outer perimeter, a plurality of radially extending spokes, and a plurality of webs. The spokes may extend from the central region to the outer perimeter, each spoke having a lower surface for engaging the upper surface of the conditioning disk. The webs, one such web between each adjacent pair of spokes, may each have a lower surface at least partially vertically recessed from the lower surfaces of the adjacent spokes so as to define one channel. Each web may extend from the central region and terminate at an outboard edge, radially recessed from the outer perimeter. The outer perimeter may be formed as a rim having a plurality of radially extending passageways. Each passageway may be generally aligned with an associated channel for permitting flow radially outward through the passageway from the associated channel when the disk holding element and disk are rotated about a central longitudinal axis while at least a lower surface of the disk is exposed to a liquid. Each of the radially extending passageways may be formed as a downwardly extending recess in the rim. The conditioning disk may be readily securable to and removable from the disk holding element. Each spoke may carry a magnet for attracting the conditioning disk. The conditioning disk may be readily securable to and removable from the disk holder element and the disk holder element may be readily securable to and removable from a rotating fixture. Each spoke may carry a magnet for securing the conditioning disk to the disk holder element and for securing the disk holder element to the rotating fixture. A first pin may depend from a first spoke and a second pin may depend from a second spoke, the first and second pins receivable by the conditioning disk for preventing rotation of the conditioning disk relative to the disk holder element. The central region, outer perimeter, plurality of radially extending spokes, and plurality of webs may be unitarily formed as a single piece of material. Each spoke may have a relatively narrow section extending outward from the central region and joining a relatively wider section adjacent the outer perimeter. Each web may have an upper surface substantially coplanar with the upper surfaces of adjacent spokes.




In another aspect, the invention is directed to a disk holder element for holding a conditioning disk used in association with a conditioner head of an apparatus for conditioning the polishing surface of a polishing pad. The disk holder element includes a lower surface magnetically engageable with an upper surface of the disk and an upper surface magnetically engageable with a lower surface of the head. The disk holder element may comprise a plurality of magnets securing the disk to the disk holder element and securing the disk holder element to the conditioner head.




In another aspect, the invention is directed to a conditioner head for conditioning the polishing surface of the polishing pad. The head includes a generally circular abrasive disk having upper and lower surfaces. The lower surface defining a disk plane. A drive element is carried for rotation about a longitudinal axis. A disk backing element carries the disk and holds the lower surface of the disk in engagement with the polishing pad and applies force and torque to the disk. The disk backing element has an upper member, fixed to the drive element, which upper member has a central downward facing socket having a spherical surface portion. The disk backing element further includes a lower member, fixed to the abrasive disk, which lower membrane has a central upward facing projection with a spherical surface portion in sliding engagement with the spherical surface portion of the socket. The disk backing element further includes at least one resilient member, coupling the upper member to the lower member so as to bias the lower member toward a neutral orientation. In the neutral orientation the disk plane is perpendicular to longitudinal axis. The resilient member permits tilting of the disk plane relative to the longitudinal axis and permits transmission of torque and rotation from the drive element to the disk. The upper member may comprises a central hub. The at least one resilient member may comprise a plurality of radially extending spokes extending radially outward from the central hub. Each spoke may be upwardly and downwardly flexible for permitting tilting of the disk plane relative to the longitudinal axis while transmitting rotation from the drive element to the rim. The spherical surface portions of the socket and projection may have a common center lying substantially within the disk plane.




In another aspect, the invention is directed to a conditioner head for conditioning the polishing surface of a polishing pad using an abrasive conditioning disk. The conditioner includes a drive element carried for rotation about a longitudinal axis and a disk backing element for holding and applying torque to the abrasive conditioning disk. The disk backing element includes a central hub fixed to the drive element, an outer rim generally defining a rim plane, and a plurality of radially extending spokes. The spokes extend from the central hub to the outer rim. Each spoke is upwardly and downwardly flexible for permitting tilting of the rim plane relative to the longitudinal axis while transmitting rotation from the drive element to the rim. Each spoke may have a transversely extending wave for increasing the flexibility of the spoke. The spokes may be formed of steel. The head may further comprise a plate having a central upward facing projection having a spherical surface portion. The hub may have a central downward facing socket having a spherical surface portion in sliding engagement with the spherical surface portion of the projection.




In another aspect, the invention is directed to a process for conditioning a polishing pad. The process includes providing an abrasive conditioning disk carried by a disk carrier and having a lower surface engageable with a polishing surface of the polishing pad. The carrier is caused to rotate the conditioning disk and bring the lower surface of the conditioning disk into engagement with the polishing surface of the polishing pad. The carrier is caused to reciprocate in the path along the rotating polishing pad. A carrier is caused to disengage the conditioning disk form the polishing pad. The carrier is caused to rotate the conditioning disk and introduce the conditioning disk to a body of cleaning liquid so as to cause a flow of the cleaning liquid longitudinally upward from the lower surface of the conditioning disk, through the conditioning disk, and radially outward along an upper surface of the conditioning disk so as to clean the conditioning disk.




Implementations of the inventive process may include on or more of the following. A second liquid may be applied to the polishing surface of the polishing pad. The second liquid may be permitted to flow up through the lower surface of the conditioning disk, through the conditioning disk, and radially outward along the upper surface of the conditioning disk when the conditioning disk is engaged with the polishing surface of the polishing pad. The flow of the cleaning liquid along the upper surface of the conditioning disk may be through a plurality of generally radially outwardly extending channels defined by a disk holder.




Among the advantages which may be provided by the invention are improved sealing and reduced wear and particle generation. Since the diaphragm may be fixed at its inner aperture and outer periphery to the associated elements, it need not be in sliding engagement with those elements either during rotation or in translation of the end effector between retracted and extended positions. This lack of sliding engagement reduces wear and the associated particle generation between slidingly engaged surfaces and prevents contaminants from entering the pressure chamber between slidingly engaged surfaces.




Further advantages are provided by the end effector featuring a spoked flexure and spherical socket and projection joint. The joint permits the application of downward force from the head to the conditioning disk to maintain compression between the conditioning disk and polishing pad surface. The flexure transmits torque and rotation to the disk while permitting the disk plane to tilt relative to the axis of rotation allowing the disk to remain flat against the polishing pad during conditioning. The flexure may bias the disk into a neutral orientation with the disk plane substantially perpendicular to the axis of rotation. By forming the flexure with a plurality of thin flat spokes, a balance is achieved between the ability to transmit torque about the axis of rotation and the ability to flex to allow the disk plane to tilt relative to the axis of rotation. The sliding spherical surface joint, with a center of rotation located in the center of the lower surface of the disk, also allows for smooth tilting of the disk during operation.




Further advantages are provided by a disk holding element which defines a plurality of channels along the upper surface of the disk so that during conditioning of the pad or during rinsing of the disk, there is a flow of either slurry or cleaning fluid upward through the bottom surface of the disk, through the disk, and radially outward along the upper surface of the disk through the channels. The channels facilitate more efficient conditioning and cleaning of the disk.




A further advantage is provided by a disk holding element which is made readily removable from the backing element and from the disk. The holding element may first be secured to the disk and then the combined holding element and disk may be secured to the backing element. Alignment features on the disk holding element facilitate the precise registration of the disk and holder relative to the backing element without undue effort. To allow faster changeout and thus reduce downtime when a disk is replaced, while one disk is in the conditioning head, a fresh disk can be secured to a second disk holding element. The first disk and first holder may be removed from the head, and replaced with a second disk and second holding element and the conditioner restarted. The first disk may then be separated from the first disk holding element and the first disk holding element secured to a new disk to await subsequent use.




The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.











BRIEF DESCRIPTION OF DRAWINGS





FIG. 1A

is a perspective view of a polishing apparatus.





FIG. 1B

is a partially exploded view of the polishing apparatus of FIG.


1


.





FIGS. 2A and 2B

are diagrammatic top views of a substrate being polished and a polishing pad being conditioned by the polishing apparatus of FIG.


1


.





FIG. 3A

is a diagrammatic cross-sectional view of a conditioner head with an end effector in a retracted position.





FIG. 3B

is a diagrammatic cross-sectional view of a conditioner head with an end effector in an extended position.





FIG. 4

is a diagrammatic cross-sectional view of the end effector of the conditioner head of

FIGS. 3A and 3B

.





FIG. 5

is a top view of a flexure of the end effector of FIG.


4


.





FIG. 6

is a top view of a backing plate of the end effector of FIG.


4


.





FIG. 7A

is a top perspective view of a disk holding member of the end effector of FIG.


4


.





FIG. 7B

is a top view of the disk holding member of FIG.


7


A.





FIG. 7C

is a bottom view of a disk holding member of FIG.


7


A.





FIG. 8

is a side view of the disk holding member along line


8





8


of FIG.


7


C.





FIG. 9

is a perspective view of a conditioning disk of FIG.


4


.





FIG. 10

is a diagrammatic cross-sectional view of a conditioner head with an end effector tilted to engage a polishing pad.





FIG. 11

is a diagrammatic cross-sectional view of a conditioner head with an end effector immersed in a cup of cleaning liquid.











Like reference numbers and designations in the various drawings indicate like elements.




DETAILED DESCRIPTION




Referring to

FIGS. 1A and 1B

, a polishing apparatus


10


includes a housing


12


that contains three independently-operated polishing stations


14


, a substrate transfer station


16


, and a rotatable carousel


18


which choreographs the operation of four independently rotatable carrier heads


20


. Attached to one side of the housing


12


is a substrate loading apparatus


22


that includes a tub


24


that contains a liquid bath


26


in which cassettes


28


containing substrates


30


are immersed. An arm


32


rides along a linear track


34


and supports a wrist assembly


36


, which includes a cassette claw


38


for moving cassettes


28


from a holding station


39


into the tub


24


and a substrate blade


40


for transferring substrates from the tub


24


to the transfer station


16


.




The carousel


18


has a support plate


42


with slots


44


through which shafts


46


of the carrier heads


20


extend. The carrier heads


20


can independently rotate and oscillate back-and-forth in the slots


44


to achieve a uniformly polished substrate surface. The carrier heads


20


are rotated by respective motors


48


, which are normally hidden behind removable sidewalls


50


of the carousel


18


. In operation, a substrate is loaded from the tub


24


to the transfer station


16


, from which the substrate is transferred to a carrier head


20


. The carousel


18


then transfers the substrate through a series of one or more polishing stations


14


and finally returns the polished substrate to the transfer station


16


.




Each polishing station


14


includes a rotatable platen


52


, which supports a polishing pad


54


, and a pad conditioner


56


. The platen


52


and conditioner


56


are both mounted to a table top


57


inside the polishing apparatus


10


. Each pad conditioner


56


includes a conditioner head


60


, an arm


62


, and a base


64


. The arm


62


has a distal end coupled to the conditioner head


60


and a proximal end coupled to the base


64


, which sweeps the conditioner head


60


across the polishing pad surface


76


to condition the surface


76


by abrading the surface to remove contaminants and retexturize the surface. Each polishing station


14


also includes a cup


66


, which contains a cleaning liquid for rinsing or cleaning the conditioner head


60


.




Referring to

FIGS. 2A and 2B

, in one mode of operation, a polishing pad


54


is conditioned by a pad conditioner


56


while the polishing pad polishes a substrate which is mounted on a carrier head


20


. The conditioner head


60


sweeps across the polishing pad


54


with a reciprocal motion that is synchronized with the motion of the carrier head


20


across the polishing pad


54


. For example, a carrier head


20


with a substrate to be polished may be positioned in the center of the polishing pad


54


and conditioner head


60


may be immersed in the cleaning liquid contained within the cup


66


. During polishing, the cup


66


may pivot out of the way as shown by arrow


69


, and the conditioner head


60


and the carrier head


20


carrying a substrate may be swept back-and-forth across the polishing pad


54


as shown by arrows


70


and


72


, respectively. Three water jets


74


may direct streams of water toward the polishing pad


54


to rinse slurry from the polishing or upper pad surface


76


.




For further details regarding the general features and operation of polishing apparatus


10


, please refer to co-pending application Ser. No. 08/549,336, filed, Oct. 27, 1995, by Perlov et al., entitled “Continuous Processing System for Chemical Mechanical Polishing,” and assigned to the assignee of the present invention, which is hereby incorporated by reference.




Referring to

FIGS. 3A and 3B

, a conditioner head


60


includes an actuation and drive mechanism


78


which rotates an end effector


80


carrying a diamond impregnated conditioning disk


82


(see also

FIG. 9

) about a central vertically-oriented longitudinal axis


300


of the head. The actuation and drive mechanism further provides for the movement of the end effector


80


and disk


82


between an elevated retracted position (

FIG. 3A

) and a lowered extended position (FIG.


3


B). In substantially the extended position, the lower surface


84


of the disk


82


may be brought into engagement with the polishing surface


76


of the pad


54


. Additionally, the end effector may be introduced to the cup


66


(

FIG. 2B

) for cleaning the disk or the disk may be replaced, both of which are described in further detail below.




The actuation and drive mechanism


78


includes a vertically-extending drive shaft


86


which, at its upper end, includes a unitarily-formed, radially-extending web


88


. In the exemplary embodiment, the drive shaft may be formed of heat treated


440


C stainless steel. A pulley


90


is secured to the web and carries a belt


92


which extends along the length of the arm


62


and is coupled to a remote motor (not shown) for rotating the shaft


86


about the longitudinal axis


300


. A rotary union


94


is secured to the upper end of the shaft for introducing and withdrawing air from an actuation chamber via a longitudinal channel


96


in the shaft. A collar, having upper and lower pieces


98


and


100


, respectively, coaxially encompasses the shaft, defining a generally annular space


102


therebetween. The upper collar piece


98


is fired to arch depends from the web


88


. In the exemplary embodiment, the pulley may be formed of aluminum and the collar may be formed of 303 stainless steel. Accordingly, the shaft, pulley, and collar form a generally rigid structure which rotates as a unit about the longitudinal axis


300


. To permit rotation, the shaft/pulley/collar unit is carried within the head by a bearing system


104


comprising upper and lower ball bearing units


104


A and


104


B. The bearing system


104


couples the lower collar


100


of the collar piece to an inner head housing


106


which is fixed to the structure of the arm. An annular clamp


114


is secured to the base of lower collar piece


100


so as to vertically clamp an inner portion of the bearing system


104


between the clamp


114


and upper collar piece


98


. The inner head housing


106


is held within a centrally-apertured cup-shaped outer head housing


108


and secured thereto to vertically clamp an outer portion of the bearing system


104


between the inner and outer head housings. The outer head housing


108


is secured to a lower arm housing


110


so that the arm


62


supports the head


60


. An upper arm housing


112


provides additional structural support. In the exemplary embodiment, the inner and outer head housings may be formed of 303 and 316 stainless steel, respectively, and the clamp may be formed of 303 stainless steel.




A generally-annular drive sleeve


120


couples the end effector


80


to the drive shaft


86


. The drive sleeve may be formed of 316 stainless steel. The drive sleeve


120


is accommodated within the annular space


102


between the collar and drive shaft. The drive sleeve


120


is keyed to the drive shaft


86


so as to permit relative longitudinal translation therebetween while preventing relative rotation. In the illustrated embodiment, this is achieved by a keying member


122


having an outwardly projected keying tab


124


. The keying member


122


is secured within a vertical slot


126


in the periphery of shaft


86


and the tab


124


rides within a vertical slot


128


in the interior of sleeve


120


and interacts with the sides of the slot


128


to prevent relative rotation of the shaft and sleeve. Thus the shaft transmits torque and rotation from the pulley to the sleeve


120


. To provide a smooth sliding vertical engagement between the drive shaft


86


and drive sleeve


120


, a bearing having a cage


130


and a plurality of balls


132


is interposed between the inner cylindrical surface of the sleeve


120


and the outer cylindrical surface of the shaft


86


.




A generally-annular elastomeric diaphragm


134


having an outer periphery


136


and an inner periphery


138


off an upper portion of the annular space


102


to form a pressure chamber


102


A. The diaphragm has an upper surface


140


A generally interior to the pressure chamber


102


A and a lower surface


140


B generally exterior to the pressure chamber. In an exemplary embodiment, the diaphragm is made of neoprene having a thickness of about 0.03 inches. Along its inner periphery


138


, the diaphragm is sealingly secured between an upward facing shoulder of the drive sleeve


120


and a lower face an annular internally threaded clamp


142


. The clamp


142


(which may be formed as a nut) is engaged to an externally threaded reduced diameter portion


144


at the upper end of the drive sleeve


120


. In the exemplary embodiment, the clamp may be formed of 6061-T6 aluminum. The diaphragm extends radially outward from between the clamp and shoulder and then curves downward along a round


146


formed between the shoulder and a cylindrical outer surface portion


148


of the drive sleeve. The diaphragm disengages the circular cylindrical outer surface portion and continues radially outward, traversing a gap (the annular space


102


) between the drive sleeve and the collar. Continuing and curving upwardly, the lower surface


140


B of the diaphragm engages a circular cylindrical inner surface


150


of the lower collar piece


100


and extends upward therealong. The diaphragm wraps over a round


152


formed between the cylindrical inner surface


150


and an upward facing shoulder of the lower collar piece and is clamped between the upward facing shoulder and a downward facing shoulder of the upper collar piece


98


. Inboard of the inner cylindrical surface


150


, an annular lip


154


projects downward from the upper collar piece, sandwiching a portion of the diaphragm between an outer cylindrical surface of the lip


154


and the inner cylindrical surface


150


of the lower collar piece.




In operation, the chamber


102


A may be inflated to move the drive sleeve


120


and end effector


86


from the retracted position (

FIG. 3A

) to the extended position (FIG.


3


B). The chamber may be deflated, such as by applying a vacuum through the rotary union


94


, move the drive sleeve and end effector from the extended position to the retracted position. Because gravity naturally biases the end effector and drive sleeve toward the extended position, vacuum is provided for retraction. During transition between the retracted and extended positions, the lower surface


140


B of the diaphragm rolls off the cylindrical outer surface


148


of the drive sleeve, traverses the gap formed by annular space


102


, and rolls onto the cylindrical inner surface


150


of the lower collar piece. The amount of downforce applied to the end effector will be proportional to the pressure applied to the chamber. Optionally, a spring (not shown) may be provided to bias the drive sleeve toward the retracted position and, thereby, eliminate or reduce the need for applying a vacuum to retract the end effector.




The drive sleeve couples the end effector to the drive shaft to transmit torque and rotation from the drive shaft and downforce from the pressure chamber to the end effector shown in FIG.


4


. The end effector


80


includes a backing element


156


for transmitting the torque, rotation, and downward force to the conditioning disk


82


. An optional removable disk holder


158


may intervene between the disk and the backing element. In the illustrated cross-sectional views, including

FIG. 4

, the section through the disk holder


158


is taken at an angle of 150° about the axis


300


. The remainder of the head is sectioned by a plane. A central cylindrical projection


160


depends from the base of the drive sleeve


120


and is received by a cylindrical well


162


in a hub


164


of the backing element


156


and is secured thereto by means such as screws (not shown). A centrally-apertured annular elastomeric membrane cover


166


prevents contaminants from falling into the interior of the backing element. The cover


166


is clamped at its aperture between a horizontal shoulder


168


of the drive sleeve base and an annular surface of the top of the hub


164


, outboard of the projection


160


and well


162


. In the exemplary embodiment, the cover may be formed of ethylene propylene diene terpolymer (EPDM) rubber. A central downward facing socket


170


having a concave spherical surface portion is formed in the bottom of the hub


164


. In the illustrated embodiment, the socket is a sector comprising approximately 63.5° degrees of arc. Extending radially outward from the hub


164


are four generally flat sheet-like spokes


172


(see also FIG.


5


), each oriented so as to have generally upper and lower surfaces. At the proximal end of each spoke, the spoke's upper surface is in contact with an annular downward facing shoulder


176


of the hub


164


radially outboard of the socket


170


. In the exemplary embodiment, the hub may be formed of 303 stainless steel. The spokes may be formed of 302 stainless steel with an exemplary thickness of 0.010 inches (0.25 mm). Each spoke's proximal end is secured to the hub


164


such as by rivets, screws, or other fastening means (not shown). The distal ends of the spokes are secured to an annular rim


178


which may be formed as a flat horizontal 303 stainless steel band to which the spokes are welded or otherwise secured.




With their low profile, the spokes


172


are resiliently flexible upward and downward so as to permit tilting of the rim, relative to the axis


300


from the otherwise neutral horizontal orientation. However, the configuration of the spokes makes them substantially inflexible transverse to the axis


300


, so that they effectively transmit torque and rotation about the axis


300


from the hub


164


to the rim


178


. Optionally, to increase vertical flexibility without compromising lateral strength and ability to transmit torque, the spokes may each be provided with a transversely extending wave or ruffle


180


. In the exemplary embodiment, the wave extends two cycles, each cycle having a length of approximately 0.22 inches (5.6 mm) and an amplitude of approximately 0.04 inches (1.0 mm). Three to five spokes are preferred to balance torque transmission and flexibility.




Immediately below the spokes, the backing element includes a rigid, generally disk-shaped, polyethylene terepthalate (PET) backing plate


182


. The backing plate has a central upward facing projection


184


having a convex spherical surface portion


186


(see also

FIG. 6

) of equal radius to and in sliding engagement with the concave spherical surface portion of the socket


170


. Interaction of the projection


184


and socket


170


can transmit compressive force between drive sleeve


120


and backing element


156


while permitting the backing element to rotate about axes orthogonal to the axis


300


. The backing plate


182


has a generally flat lower surface


188


in contact with an upper surface


190


of a body


192


of the disk holder


158


. The plate


182


extends radially outward to a generally annular rim section


194


. The rim section


194


is secured to the band


178


such as by screws extending through the band. The rim section


194


is also secured to the outer periphery of the cover


166


such as by screws extending through a clamp ring


198


clamping the cover


166


to the rim


194


. The plate rim


194


carries a generally-annular L-sectioned stainless steel ring


196


in an annular upwardly directed pocket. The pocket is sealed with a PET plug which is flush with the lower surface


188


of the backing plate


182


.




The disk holder


158


, shown in FIG.


4


and in isolated perspective, top, bottom and side views in

FIGS. 7A

,


7


B,


7


C and


8


, respectively, has a central core or hub region


200


from which radiate six radially-extending spokes


202


. Each spoke has substantially flat lower surface


206


. Each spoke has a relatively narrow section extending outward from the core and diverging to form a relatively wide section


208


adjacent an outer perimeter rim


210


. In the illustrated embodiment, the rim


210


is formed as a generally annular band. A web


212


is formed between each adjacent pair of spokes


202


. Each web extends from the core


200


and terminates at an outboard edge


218


which is radially recessed from the rim


210


. Each web has a lower surface


214


which is vertically recessed from the lower surfaces of adjacent spokes. Each web also has a flat upper surface that is substantially coplanar with the upper surfaces of the adjacent spokes to form an upper surface


216


of the disk holder which contacts the lower surface


188


of the backing plate. Alternatively, the upper surface


216


of each web may be slightly recessed from the upper surface of the spoke to reduce the effects of slurry trapped between the disk holder and backing element. Associated and aligned with each web


212


is a downwardly extending recess


220


(

FIGS. 4 and 7

) in the upper edge of the rim


210


. Between each recess


220


, the rim


210


includes a projection


222


at the outer end of each spoke


202


. The projections


222


extend above the upper surfaces of the spokes. As shown in

FIG. 4

, when the disk holder is engaged to the backing plate, each projection


222


is received by a corresponding recess or cutout


224


in the rim


194


of the backing plate


182


(see FIG.


6


). The projections


222


fit securely within the recesses


224


to prevent relative rotation of the disk holder and backing element. Radially outward extending channels


223


are each defined by an adjacent pair of the spokes


202


, the lower surface


214


of the web


212


between such pair of spokes, and the upper surface


238


of the disk


82


. The role of these channels is described in further detail below.




In the illustrated embodiment, the core


200


, spokes


202


, webs


212


, and rim


210


are unitarily formed, preferably as a single molding of a polymer material such as PET.




A cylindrical blind bore is formed in the wide section of each spoke


202


adjacent the rim


210


. The bore accommodates a cylindrical magnet


230


and is plugged by a polyethylene terepthalate (PET) cylinder. In the illustrated embodiment, the bore extends down from the upper surface


204


of the spoke, and the cylinder is flush with the upper surface of the spoke. Magnetic attraction between the magnets


230


and the ring


196


vertically secures the disk holder to the backing element by magnetic attraction.




In each spoke of one diametrically opposed first pair of spokes, a drive pin


232


depends from the spoke immediately inboard of the magnet


230


. When the disk holder is mated to the disk


82


, the drive pins are received by associated bores


234


in the disk and serve to prevent rotation of the disk relative to the disk holder. The disk


82


(see also

FIG. 9

) may be formed of nickel-coated carbon steel having the lower surface


84


embedded with diamond particles for an abrasive. The magnets attract the disk, vertically securing the disk to the holding element with the upper surface


238


of the disk contacting the lower surfaces of the spokes


202


.




The flat lower surface


84


of the disk defines a disk plane


302


. In a neutral orientation, the disk plane is perpendicular to the longitudinal axis


300


which extends through the center of the disk. The concave and convex spherical surface portions of socket


170


and projection


184


, respectively, have a common center of curvature


304


at the intersection of the disk plane


302


with the longitudinal axis


300


. In operation, with the conditioner head located above the polishing pad as described above, the drive shaft


86


is caused to rotate, which rotation is transmitted to the disk


82


. The end effector


80


is then shifted from the retracted position to an extended position to bring the lower surface


84


of the disk into engagement with the polishing surface


76


of the pad. The downward force compressing the disk against the pad is controlled by modulating the pressure in the pressure chamber


102


A. The downward force is transmitted through the drive sleeve, the hub, between the concave and convex spherical surface portions to the backing plate, to the disk holder, and then to the disk. Torque to rotate the disk relative to the pad is supplied from the drive shaft to the drive sleeve, the hub, the spokes, the rim of the backing element, the holder, and then to the disk via the pins.




Precise perpendicular alignment between the axis


300


and the polishing surface


76


of the pad is not easily provided. Because of this, it is desirable that at least the disk be able to tilt to maintain its lower surface flat against the polishing surface of the pad as shown in FIG.


10


. If the polishing surface of the pad is not perpendicular to the axis


300


, the disk, disk holder and backing element may tilt relative to the axis via sliding of the convex spherical surface of the projection


184


relative to the concave spherical surface of the socket


170


. The hub


164


remains fixed relative to the axis


300


. To accommodate the tilt, the spokes


172


flex either upward or downward depending on their location at any given point in time. The location of the common center


304


in disk plane


302


minimizes fluctuations in the compression force between the disk and the pad when the end effector


80


tilts to maintain engagement between the end effector and pad. The shear force applied to the disk by friction with the polishing pad is directed in the disk plane


302


and, thereby, does not exert a moment about the center


304


which would otherwise tend to pivot the disk and produce an uneven pressure distribution between the disk and pad. The cover


166


is free to flex and stretch to accommodate the tilting.




In operation, the lower surface of the rotating conditioning disk


82


, engaged with the polishing surface of the rotating polishing pad, is reciprocated in a path along the rotating polishing pad as described above. During this process, the bottom surface of the disk is immersed in the thin layer of a polishing slurry


299


atop the polishing pad. The rotation of the disk may induce a flow


248


of the polishing slurry longitudinally upward from the lower surface


84


of the disk, through an array of holes


242


in the disk, and radially outward along the upper surface of the disk through the channels


223


. The flow proceeds outward through radially-extending passageways in the rim


210


formed by the recesses


220


. Each passageway/recess


220


is generally aligned with an associated channel


223


. This flow of the slurry may increase the effectiveness of conditioning by helping to evacuate material from the pad surface.




As shown in

FIG. 11

, for cleaning the disk


82


, the end effector is raised, causing the disk to disengage from the polishing pad. The cup


66


may then be pivoted to a location below the head and the end effector extended so as to immerse the disk in a cleaning liquid


298


in the cup. The disk is rotated about the axis


300


within the body of cleaning liquid (the rotation need not have been altered since the disk was engaged to the pad). The rotation causes a flow


250


of the cleaning liquid longitudinally upward from the lower surface of the disk, through the holes


242


, through the disk, and radially outward along the upper surface of the disk through the channels


223


. Flow of the cleaning liquid, which may comprise deionized water, serves to clean the disk of contaminants including material worn from the pad, byproducts of the polishing etc.




A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, various features may be adapted for use with a variety of existing or future conditioner and polisher configurations other than those specifically shown. Although the exemplary end effector is shown constructed with particular components, various of the components may be combined or further subdivided. Additionally, various elements of these components or their subcomponents and their associated functions may be shifted to other components. Accordingly, other embodiments are within the scope of the following claims.



Claims
  • 1. A disk holder for holding a conditioning disk for conditioning a polishing pad, comprising:a lower face for engaging an upper surface of the conditioning disk and defining a plurality of generally radially outward extending channels along the upper surface of the conditioning disk.
  • 2. The disk holder of claim 1 further comprising:a central region; an outer perimeter; a plurality of radially extending spokes, extending from the central region to the outer perimeter, each said spoke having a lower surface for engaging the upper surface of the conditioning disk; and a plurality of webs, one such web between each adjacent pair of said spokes, each web having a lower surface at least partially vertically recessed from the lower surfaces of the adjacent spokes so as to define one said channel.
  • 3. The disk holder of claim 2 wherein each web extends from the central region and terminates at an outboard edge, radially recessed from the outer perimeter.
  • 4. The disk holder of claim 3 wherein the outer perimeter is formed as a rim and wherein the rim has a plurality of radially extending passageways, each passage generally aligned with an associated one of the channels for permitting flow radially outward through the passageway from the associated channel when the disk holder and disk are rotated about a central longitudinal axis while at least a lower surface of the disk is exposed to a liquid.
  • 5. The disk holder of claim 4 wherein each of the radially extending passageways is formed as a downwardly extending recess in the rim.
  • 6. The disk holder of claim 2 wherein the conditioning disk is readily securable to and removable from the disk holder and each spoke carries a magnet for attracting the conditioning disk.
  • 7. The disk holder of claim 2 wherein the conditioning disk is readily securable to and removable from the disk holder, and the disk holder is readily securable to and removable from a rotating fixture wherein each spoke carries a magnet for securing the conditioning disk to the disk holder and for securing the disk holder to the rotating fixture.
  • 8. The disk holder of claim 2 further comprising a first pin depending from a first one of said spokes and a second pin depending from a second one of said spokes, the first and second pins receivable by the conditioning disk for preventing rotation of the conditioning disk relative to the disk holder.
  • 9. The disk holder of claim 2 wherein the central region, outer perimeter, said spokes and said webs are unitarily formed as a single piece of material.
  • 10. The disk holder of claim 9 wherein each one of said spokes has a relatively narrow section extending outward from the central region and joining a relatively wider section adjacent the outer perimeter.
  • 11. The disk holder of claim 9 wherein each one of said webs has an upper surface, substantially coplanar with the upper surfaces of adjacent ones of said spokes.
Parent Case Info

This application is a division of U.S. application Ser. No. 09/052,798, filed Mar. 31, 1998, now U.S. Pat. No. 6,200,199 B1, which is incorporated herein by reference.

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