Conditioner apparatus for chemical mechanical polishing

Information

  • Patent Grant
  • 6293853
  • Patent Number
    6,293,853
  • Date Filed
    Friday, January 7, 2000
    25 years ago
  • Date Issued
    Tuesday, September 25, 2001
    23 years ago
Abstract
In one aspect, an apparatus and a method for use in substrate polishing are described wherein a conditioner head is provided for receiving an end effector for conditioning a polishing pad surface; the conditioner head is supported above the polishing pad surface to be conditioned; and the conditioner head is driven with an actuating force from a position that lies along a line that is substantially normal to the polishing pad surface to be conditioned so that an end effector attached to the conditioner head can condition the surface of the polishing pad. In another aspect, pneumatic pressure is supplied through the conditioner head support arm to apply actuating force to the conditioner head so that an end effector attached to the conditioner head can condition the surface of the polishing pad. In yet another aspect, the conditioner head support arm has a fluid channel extending therein and a fluid port, wherein the fluid channel is constructed to receive rinsing fluid and fluid port is constructed to direct rinsing fluid from the fluid channel toward the polishing pad surface to be conditioned.
Description




BACKGROUND OF THE INVENTION




The invention relates to substrate polishing techniques, including chemical mechanical polishing (CMP).




Chemical mechanical polishing is a process by which a substrate surface is smoothed (planarized) to a uniform level by a polishing pad and an abrasive slurry. A substrate to be polished is usually mounted on a rotatable carrier head and pressed against a rotating polishing pad. The polishing pad typically consists of a disk with a roughened surface. An abrasive chemical solution (slurry) is deposited onto the polishing pad to achieve a desired substrate surface finish. Over time, the polishing process glazes the polishing pad and creates irregularities in the polishing pad surface that can adversely affect the substrate surface finish. The polishing pad surface is typically “conditioned,” whereby the polishing pad surface is deglazed and surface irregularities are removed, by scouring the polishing pad surface with an abrasive device known as an end effector.




SUMMARY OF THE INVENTION




In one aspect, the invention features an apparatus and a method for use in substrate polishing according to which a conditioner head is provided for receiving an end effector; the conditioner head is supported above the polishing pad surface to be conditioned; and the conditioner head is driven with an actuating force from a position that lies along a line that is substantially normal to the polishing pad surface to be conditioned so that an end effector attached to the conditioner head can condition the surface of the polishing pad.




In another aspect, the invention features an apparatus and a method for use in substrate polishing according to which pneumatic pressure is supplied through the conditioner head support arm to apply actuating force to the conditioner head so that an end effector attached to the conditioner head can condition the surface of the polishing pad.




In yet another aspect, the invention features an apparatus and a method for use in substrate polishing according to which the conditioner head support arm has a fluid channel extending therein and a fluid port, wherein the fluid channel is constructed to receive rinsing fluid and fluid port is constructed to direct rinsing fluid from the fluid channel toward the polishing pad surface to be conditioned.




Embodiments may include one or more of the following features. The conditioner may be supported above the polishing pad surface by a support arm, and an actuating force may be applied to the conditioner head by a driver. The driver may apply to the conditioner head actuating force that lies along a line that is substantially normal to the polishing pad surface to be conditioned. The driver may comprise a drive shaft coupled between the conditioner head and the support arm, and the drive shaft may be linearly actuatable toward and away from the polishing pad to be conditioned along a drive shaft axis that is substantially normal to the polishing pad surface. The driver may comprise a fluid membrane coupled between the drive shaft and an interior cavity, wherein the fluid membrane seals fluid within the interior cavity of the support arm as the drive shaft is linearly actuated. The drive shaft may be constructed to rotate the conditioner head. A gimbal mechanism may be coupled between the drive shaft and the conditioner head to allow the conditioner head to rotate and to tilt at an angle relative to the drive shaft axis. The support arm may have another end coupled to a base that is constructed to move the conditioner head over the polishing pad surface to be conditioned.




When a driving force is applied to a conditioner head from a position that does not lie along a line that is normal to a polishing pad surface, the driving force and the responsive normal force may result in the generation of torque that tends to raise the conditioner head off the polishing pad surface; such a torque may lead to instability and thereby reduce the ability to uniformly apply force against polishing pad surface. By driving the conditioner head with an actuating force from a position that lies along a line which is substantially normal to a polishing pad surface, in accordance with one aspect of the invention, the normal force and the driving force both lie along the same line and little or no torque is generated. The invention therefore allows force to be controllably and stably applied against a polishing pad surface, improving the uniformity with which a polishing pad surface can be conditioned and thereby improving the overall polishing process. Supplying rinsing fluid to the polishing pad surface through the support arm, in accordance with another aspect of the invention, allows the overall size of the polishing apparatus to be reduced and improves the ability to control the delivery of rinsing fluid.




Other features and advantages will become apparent from the following description, including the drawings and the claims.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1A

is a perspective view of a polishing apparatus.





FIG. 1B

is an 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 view of a driver applying force to a conditioner head from a position that does not lie along a line that is normal to a polishing pad surface.





FIG. 3B

is a diagrammatic view of a driver applying force to a conditioner head from a position that lies along a line that is normal to a polishing pad surface.





FIG. 4A

is a diagrammatic side view of a polishing pad conditioner which includes a carrier head in an extended position.





FIG. 4B

is a diagrammatic side view of a portion of the polishing pad conditioner of

FIG. 4A

with the carrier head in a retracted position.





FIG. 4C

is a diagrammatic side view of the carrier head of the polishing pad conditioner of FIG.


4


A.





FIG. 4D

is diagrammatic side view of gimbal mechanism coupling the carrier head to a conditioner drive shaft in the polishing pad conditioner of FIG.


4


A.





FIG. 4E

is a diagrammatic side view of the base of the polishing pad conditioner of FIG.


4


A.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




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 housing


12


is a substrate loading apparatus


22


that includes a tub


24


that contains a liquid bath


26


in which cassettes


28


of substrates


30


are immersed before polishing. 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 tub


24


and a substrate blade


40


for transferring substrates from tub


24


to transfer station


16


.




Carousel


18


has a support plate


42


with slots


44


through which shafts


46


of carrier heads


20


extend. Carrier heads


20


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


44


to achieve a uniformly polished substrate surface. Carrier heads


20


are rotated by respective motors


48


, which are normally hidden behind removable sidewalls


50


of carousel


18


. In operation, a substrate is loaded from tub


24


to transfer station


16


, from which the substrate is transferred to a carrier head


20


; carousel


18


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


14


and finally returns the polished substrate to transfer station


16


.




Each polishing station


14


includes a rotatable platen


52


, which supports a polishing pad


54


, and a pad conditioner


56


; platen


52


and conditioner


56


are both mounted to a tabletop


57


inside polishing apparatus


10


. Each pad conditioner


56


includes a conditioner head


60


, an arm


62


, and a base


64


for positioning conditioner head


60


over the surface of a polishing pad


54


to be conditioned. Each polishing station


14


also includes a cup


66


, which contains a fluid for rinsing conditioner head


60


.




Referring to

FIGS. 2A and 2B

, in one mode of operation, polishing pad


54


is conditioned by pad conditioner


56


while polishing pad


54


polishes a substrate which is mounted on carrier head


20


. Conditioner head


60


sweeps across polishing pad


54


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


20


across polishing pad


54


. For example, a carrier head


20


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


54


and conditioner head


60


may be immersed in a rinsing fluid contained within cup


66


. During polishing, cup


66


may pivot out of the way as shown by arrow


69


, and conditioner head


60


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


54


as shown by arrows


70


and


72


, respectively. Three water jets


71


,


73


, and


75


may direct streams of water toward polishing pad


54


to rinse slurry from the pad surface.




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 herein incorporated by reference.




Referring to

FIG. 3A

, it has been realized that when a driving force (F


driver


) is applied to a conditioner head


75


from a position that does not lie along a line that is normal to a polishing pad surface


76


, the driving force and the responsive normal force (F


normal


) result in a counterclockwise torque (T′) that tends to raise conditioner head


75


off polishing pad surface


76


. Such torque generation may lead to instability and thereby reduce the ability to controllably apply force against polishing pad surface


76


. As shown in

FIG. 3B

, when, in accordance with one aspect of the invention, actuating force is applied to conditioner head


60


from a position that lies along a line


82


which is substantially normal to polishing pad surface


76


, the normal force and the driving force both lie along the same line


82


and little or no torque is generated. The invention therefore allows force to be controllably and stably applied against polishing pad surface


76


, improving the uniformity with which a polishing pad surface can be conditioned and thereby improving the overall polishing process.




Referring to

FIGS. 4A and 4B

, support and


62


of pad conditioner


56


has one end coupled to conditioner head


60


and another end coupled to base


64


, which sweeps conditioner head


60


across a polishing pad surface. A driver


84


couples conditioner head


60


to arm


62


and drives conditioner head


60


between an extended position (

FIG. 4A

) and a retracted position (FIG.


4


B). As explained above, driver


84


applies an actuating force to conditioner head


60


from a position that lies along a line that is substantially normal to the polishing pad surface to be conditioned, so as to significantly reduce the amount of torque generated in polishing pad conditioner


56


.




Referring to

FIG. 4C

, driver


84


includes a housing


86


that defines an interior portion of a fluid cavity


88


. Fluid cavity


88


is further defined by a face plate


90


and a fluid membrane


92


, which is made of neoprene rubber with, for example, a hardness of about 40 durometer and a thickness of about 0.03 inch. Fluid membrane


92


has one end


93


that is attached to housing


86


by an annular clamp


94


and another end


96


that is attached to face plate


90


by an annular clamp


98


which is coupled to face plate


90


by bolts


100


,


102


. A flange


104


couples face plate


90


to a spline shaft


106


which is, in turn, coupled to a flange


108


of conditioner head


60


by a bolt


110


. In operation, fluid cavity


88


receives pressurized air through fluid channels


112


and


114


defined in driver housing


86


and through a fluid channel


116


which extends through and


62


and through base


64


to an inlet port


117


(FIG.


4


A). The build-up of air pressure inside fluid cavity


88


drives face plate


90


, spline shaft


106


, and conditioner head


60


in the direction indicated by arrow


118


. As air is evacuated from fluid cavity


88


, the reduction in air pressure in fluid cavity


88


causes face plate


90


, spline shaft


106


, and conditioner head


60


to retract in the direction indicated by arrow


120


.




Fluid channel


116


includes separate tubes for respectively receiving air and a rinsing solution, such as water. The rinsing solution tube is coupled to waterjets


71


,


73


, and


75


located along aim


62


(see

FIGS. 2A

,


2


B, and


4


A). The rinsing solution may be used to rinse a polishing pad surface before, during, or after polishing to prevent the build-up of slurry deposits.




Driver


84


also includes a toothed sheave


122


which is coupled to a spline nut


124


. Toothed sheave


122


and spline nut


124


are rotated by a toothed drive belt (not shown) which is driven by a motor in base


64


(discussed in detail below). Spline nut


124


engages spline shaft


106


and thereby causes spline shaft


106


and conditioner head


60


to rotate when driven by the drive belt. A pair of annular bearings


126


,


128


are held in place between arm


62


and spline nut


124


by an upper collars


130


,


131


and a lower collar


132


; annular bearings


126


,


128


are spaced apart by an annular spacer


134


. Annular bearings


126


,


128


allow spline nut


124


to rotate freely with respect to an


62


. A pair of bearings


136


,


138


allow spline nut


124


and spline shaft


106


to rotate freely with respect to face plate


90


.




Conditioner head


60


includes a face plate


140


which has an annular magnet


142


for holding in place an end effector (not shown) which is used to condition a surface of a polishing pad; pins


144


are used to engage and thereby transfer torque to an end effector held to face plate


140


. Face plate


140


and flange


108


are coupled together by a gimbal mechanism which includes a plurality of ball bearings


146


,


148


seated within holes in an annular cage


150


and positioned between an upper annular race


152


and a lower annular race


154


. Ball bearings


146


,


148


and springs


147


,


149


allow face plate


140


to mutate with respect to spline shaft


106


. The degree of nutation is limited by three torque transfer pins


156


which are mounted to flange


108


(only one torque transfer pin is shown in FIG.


4


B). Torque transfer pins


156


have protrusions


158


which extend into recesses


160


in face plate


140


and transfer rotational forces from flange


108


to face plate


140


. Each protrusion


158


includes an o-ring


162


with a hardness of about 40 durometer that limits the degree of nutation between face plate


140


and flange


108


. Although limited, this nutation allows face plate


140


to accommodate small features on the surface of a polishing pad so that one side of face plate


140


does not polish with greater force than another.




Referring to

FIG. 4D

, the gimbal mechanism is constructed so as to substantially reduce non-uniform conditioning of a surface of polishing pad


54


. The ball-and-socket joint created by ball bearings


146


,


148


and upper and lower races


152


,


154


is constructed so that the spherical center of symmetry


168


coincides with the center of frictional torque (F′) generated between an end effector


170


attached to conditioner head


60


and a polishing pad. The effective rotational center


168


is the point around which, when the compression and varying lateral consistency of the polishing pad and the end effector are taken into account, the rotational frictional forces between the polishing pad and the end effector produce substantially no net torque in the vertical direction relative to center point


168


. That is, the gimbal mechanism is constructed so that the resultant force (R′) needed to drag conditioner head


60


across a polishing pad appears in the plane at the interface between conditioner head


60


and the polishing pad; this is the same plane that contains the resultant frictional force (F′) between conditioner head


60


and the polishing pad. The resulting net torque generated between conditioner head


60


and the polishing pad is thereby substantially reduced because the resultant dragging force (R′) and the resultant frictional force (F′) lie in substantially the same plane, with little or no moment arm separating these resultant forces. This construction substantially reduces the tendency of the conditioner head to rotate which would otherwise cause conditioner head


60


to apply polishing pressure nonuniformly across polishing pad


54


.




Referring to

FIG. 4E

, base


64


includes a pivot support plate


180


, which is attached to arm


62


, and a motor bracket


182


, which is mounted onto tabletop surface


57


. Motor bracket


182


is attached to a harmonic drive


184


(e.g., a harmonic drive available from Harmonic Drive Technologies, Teijin Seiki Boston, Inc. of Peabody, Mass.). The high-speed, low-torque side of harmonic drive


184


is fixed to motor bracket


182


, and the low-speed, high-torque side is fixed by flanges


186


,


188


to pivot support plate


180


and arm


62


. A drive sweep motor


190


is mounted to motor bracket


182


underneath tabletop


57


. Drive sweep motor


190


has a drive shaft


192


which is coupled by a clamp


194


to a gear


196


that engages with a rim drive gear


198


of harmonic drive


184


. In operation, drive sweep motor


190


drives harmonic drive


184


which, in turn, rotates pivot support plate


180


, thereby sweeping arm


62


back-and-forth across a surface of a polishing pad. Bearings


199


allow pivot support plate


180


to rotate freely with respect to motor bracket


182


.




As mentioned above with respect to

FIG. 4C

, conditioner head


60


is rotated by driving spline shaft


106


and spline nut


124


with a toothed sheave


122


that engages with a toothed drive belt at one end of arm


62


. At the other end of arm


62


, shown in

FIG. 4D

, the toothed drive belt (not shown) engages with a corresponding toothed sheave


200


which is coupled to one end of a drive shaft


202


. The other end of drive shaft


202


has a gear


204


, which engages with a gear


206


coupled by a clamp


208


to a motor drive shaft


210


of a conditioner motor


212


. Gears


204


,


206


are contained within a gear housing


214


that is fixed to tabletop


57


. Rotation of motor drive shaft


210


drives shaft


202


which, in turn, rotates toothed sheave


122


and thereby rotates conditioner head


60


. Bearings


216


,


218


enable drive shaft


202


to rotate freely with respect to pivot support plate


180


and motor bracket


182


.




Air is introduced into and evacuated from pad conditioner


56


through a pneumatic input


117


that is coupled to an inner tube


222


which extends through drive shaft


202


and connects with fluid channel


116


. Fluid, such as water, used to rinse an end effector attached to conditioner head


60


is introduced into pad conditioner


56


through a fluid input


224


which is coupled to an annular channel defined between the outer surface of inner tube


222


and the interior surface of an outer tube


226


.




Polishing pad conditioner


56


can be used in a number of different ways. For example, pad conditioner


56


may be controlled by a software program running on a computer. A polishing pad can be conditioned before, during or after a substrate is polished. A variety of end effectors may also be used. In general, an end effector includes an abrasive surface, such as a diamond-impregnated surface, that is pressed against a polishing pad to deglaze the pad and remove any surface irregularities. The abrasive surface may have teeth or recesses depending upon the desired substrate surface finish. An end effector may have an adhesive surface for attaching the end effector to the conditioner head.




Other embodiments are within the scope of the claims.



Claims
  • 1. An apparatus for use in substrate polishing, comprising:a conditioner head constructed to receive an end effector for conditioning a surface of a polishing pad; and a support arm for supporting the conditioner head above the polishing pad surface to be conditioned, the support and having a fluid channel extending essentially longitudinally therein and a fluid port, wherein the fluid channel is constructed to receive rinsing fluid and the fluid port is constructed to direct rinsing fluid from the fluid channel toward the polishing pad surface to be conditioned.
  • 2. The apparatus of claim 1, wherein the fluid channel comprises a tube for receiving the rinsing fluid and a tube for receiving air.
  • 3. The apparatus of claim 2, wherein the tube for receiving the rinsing fluid is coupled to one or more water jets.
  • 4. The apparatus of claim 1, wherein the support arm is coupled to a base and the fluid channel extends through the base.
  • 5. The apparatus of claim 1, wherein the fluid channel is constructed to supply air to a fluid cavity, wherein the build-up and release of air pressure within the fluid cavity extends and retracts the conditioner head toward and away from the polishing pad surface to enable the end effector to condition the surface of the polishing pad.
  • 6. The apparatus of claim 1, wherein the end effector includes a diamond-impregnated surface.
  • 7. The apparatus of claim 1, wherein a surface of the end effector includes teeth.
  • 8. The apparatus of claim 1, wherein a surface of the end effector includes recesses.
  • 9. An apparatus for use in substrate polishing, comprising:a conditioner head constructed to receive an end effector for conditioning a surface of a substrate polishing pad; a support arm extending horizontally over the surface of the polishing pad and having one end coupled to the conditioner head for supporting the conditioner head above the polishing pad surface to be conditioned, the support arm having a channel constructed to convey fluid; and a pneumatic driver coupled between the support arm and the conditioner head and constructed to receive fluid through the support arm channel and thereby to apply an actuating force to extend and retract the conditioner head toward and away from the polishing pad surface, whereby an end effector attached to the conditioner head can condition the surface of the polishing pad.
  • 10. The apparatus of claim 9 wherein the driver is coupled between the support arm and the conditioner head to apply an actuating force to the conditioner head from a position that lies along a line that is substantially normal to the polishing pad surface to be conditioned.
  • 11. The system of claim 9 further comprising a fluid line that extends through the support arm to supply rinsing fluid to the polishing pad surface.
  • 12. A method for use in substrate polishing, comprising:providing a conditioner head constructed to receive an end effector for conditioning a surface of a polishing pad; supporting the conditioner head above the polishing pad surface to be conditioned with a support arm that extends horizontally over the surface of the polishing pad; and supplying pneumatic pressure through the support arm to a pneumatic driver coupled between the conditioner head and the support arm to apply an actuating force to extend and retract the conditioner head toward and away from the polishing pad surface to enable an end effector attached to the conditioner head to condition the surface of the polishing pad.
  • 13. The method of claim 12 wherein the conditioner head is driven with an actuating force that lies along a line from a position that is substantially normal to the polishing pad surface to be conditioned.
  • 14. An apparatus for use in substrate polishing, comprising:a machine base; a rotatable substrate carrier constructed to receive a substrate for polishing; a rotatable platen mounted on the machine base to support a polishing pad for polishing a surface of the substrate; a conditioner head constructed to receive an end effector for conditioning a surface of the polishing pad; a support arm having one end mounted on the machine base and another end coupled to the conditioner head to support the conditioner head above the polishing pad surface to be conditioned; and a driver coupled between the conditioner head and the support arm to apply, from a position that lies along a line that is substantially normal to the polishing pad surface to be conditioned, an actuating force for extending and retracting the conditioner head toward and away from the polishing pad surface, whereby an end effector attached to the conditioner head can condition the surface of the polishing pad.
  • 15. The apparatus of claim 14 wherein the driver is pneumatically-driven.
Parent Case Info

This application is a con't of Ser. No. 08/890,781 filed Jul. 11, 1997, now U.S. Pat. No. 6,036,583.

US Referenced Citations (10)
Number Name Date Kind
5216843 Breivogel et al. Jun 1993
5245796 Miller et al. Sep 1993
5308438 Cote et al. May 1994
5456627 Jackson et al. Oct 1995
5486131 Cesna et al. Jan 1996
5531635 Mogi et al. Jul 1996
5626509 Hayashi May 1997
5643067 Katsuoka et al. Jul 1997
5833519 Moore Nov 1998
6036583 Perlov et al. Mar 2000
Foreign Referenced Citations (2)
Number Date Country
0 774 323 A2 May 1997 EP
0 770 455 A1 May 1997 EP
Continuations (1)
Number Date Country
Parent 08/890781 Jul 1997 US
Child 09/479046 US