Apparatus and method for planarizing a workpiece and a workpiece handling wand for use in the method

Abstract

A work piece carrier head for the chemical mechanical planarization of a work piece includes a backing plate that is capable of being extended beyond the lower surface of the carrier head during a work piece loading operation. The exposed lateral surface of the backing plate in the extended position provides a reference surface to enable a work piece handling wand to align itself prior to loading the work piece into the carrier head. The work piece handling wand is configured to grip a work piece between a concave cradle and a moveable gripping finger. A work piece held by the wand can be centered relative to the backing plate prior to loading the work piece into the work piece carrier head by registering the wand to the exposed lateral surface of the extended backing plate.

What is claimed is:  
     
         1 . Apparatus for planarizing a surface of a work piece comprising: 
 a work piece carrier housing having a first surface and a bore extending inwardly from the first surface of the housing;    a plate slidably disposed within the bore, the plate having a front surface and a back surface, the front surface facing outwardly from the work piece carrier housing, the plate being moveable axially within the bore between an extended position in which the front surface extends beyond the first surface and a retracted position in which the front surface is retracted to a position above the first surface;    an internal passage within the plate; and    at least one aperture opening extending from the front surface to the internal passage and providing fluid communication between the at least one aperture and a source of pressurized fluid.    
     
     
         2 . The apparatus of  claim 1  further comprising: 
 a chamber formed by the back surface of the plate and the bore; and  
 a source of pressurized fluid configured to communicated with the chamber and capable of urging the plate between the extended and retracted positions by fluid pressure in the chamber.  
 
     
     
         3 . The apparatus of  claim 2 , further comprising: 
 an elastomeric diaphragm extending between the plate and the work piece carrier housing forming a flexible seal between the bore and the plate.    
     
     
         4 . The apparatus of  claim 1  further comprising: 
 a rigid mechanical limit stop operatively engaging the plate for positively limiting axial motion of the plate between the extended position and the retracted position.  
 
     
     
         5 . The apparatus of  claim 4  wherein the rigid mechanical limit stop comprises: 
 a radially extending groove formed in the bore; and  
 a radially extending flange formed in the plate, the radially extending flange extending into the radially extending groove, the flange and groove cooperating to provide an upper limit stop and a lower limit stop to limit axial motion of the plate relative to the bore.  
 
     
     
         6 . The apparatus of  claim 1  further comprising: 
 a bearing supporting the housing for rotation about an axis parallel to the bore; and  
 a motor coupled to the housing for rotating the housing about the axis.  
 
     
     
         7 . The apparatus of  claim 1  further comprising a lateral surface extending between the front surface and the back surface, at least a portion of the lateral surface being exposed beyond the first surface when the plate is in the extended position.  
     
     
         8 . The apparatus of  claim 7  wherein the lateral surface comprises a circular cross section having a diameter dimension substantially equal to a diameter dimension of the work piece.  
     
     
         9 . The apparatus of  claim 8  further comprising a work piece handling wand configured to convey a work piece to a position proximate the front surface.  
     
     
         10 . The apparatus of  claim 9  wherein the work piece handling wand comprises: 
 a cradle portion; and  
 a movable finger portion spaced apart from the cradle portion.  
 
     
     
         11 . The apparatus of  claim 10  wherein the cradle portion comprises a raised wall portion having a concave surface with a radius of curvature substantially equal to a diameter dimension of the work piece.  
     
     
         12 . The apparatus of  claim 11  wherein the movable finger portion comprises a raised wall portion.  
     
     
         13 . The apparatus of  claim 12  wherein the movable finger portion comprises a movable finger portion slideably coupled to the cradle portion on a support rail.  
     
     
         14 . The apparatus of  claim 13  wherein the movable finger portion is coupled to an actuator configured to move the movable finger portion on the support rail.  
     
     
         15 . The apparatus of  claim 14  wherein the movable finger portion is configured to move on the support rail to a position spaced apart from the cradle portion by a distance substantially equal to the diameter of the work piece.  
     
     
         16 . The apparatus of  claim 14  wherein the movable finger portion is configured to move on the support rail to a position spaced apart from the cradle portion by a distance substantially equal to the diameter of the circular cross section of the lateral surface.  
     
     
         17 . The apparatus of  claim 14  further comprising a position sensor configured to sense the location of the movable finger portion.  
     
     
         18 . The apparatus of  claim 10  wherein the work piece handling wand further comprises a protrusion extending from the cradle portion and configured to contact a physical reference surface on the work piece carrier housing.  
     
     
         19 . The apparatus of  claim 18  further comprising a wear ring positioned to surround the bore and wherein the physical reference surface comprises a surface of the wear ring.  
     
     
         20 . The apparatus of  claim 18  wherein the physical reference surface comprises a protrusion extending from the work piece carrier housing.  
     
     
         21 . Apparatus for planarizing a surface of a work piece comprising: 
 a work piece carrier housing;    a flexible diaphragm coupled to the work piece carrier housing, the flexible diaphragm comprising a horizontal portion against which a work piece can be positioned for planarization and a vertical portion having a substantially cylindrical shape extending upwardly from the horizontal portion; and    a wear ring having a lower surface, a substantially cylindrical inner surface, and a substantially cylindrical outer surface, the wear ring flexibly mounted to the work piece carrier housing and surrounding the flexible diaphragm, the wear ring configured to be moveable between a lowered position in which the lower surface is substantially coplanar with the surface of the work piece and a raised position in which at least a portion of the vertical portion is exposed.    
     
     
         22 . The apparatus of  claim 21  further comprising a work piece handling wand configured to convey a work piece to a position proximate the horizontal portion.  
     
     
         23 . The apparatus of  claim 22  wherein the work piece handling wand comprises: 
 a cradle portion; and  
 a movable finger portion spaced apart from the cradle portion.  
 
     
     
         24 . The apparatus of  claim 23  wherein the cradle portion comprises a raised wall portion having a concave surface with a radius of curvature substantially equal to a diameter dimension of the substantially cylindrical shape of the vertical portion.  
     
     
         25 . The apparatus of  claim 24  wherein the movable finger portion comprises a raised wall portion.  
     
     
         26 . The apparatus of  claim 25  wherein the movable finger portion comprises a movable finger portion slideably coupled to the cradle portion on a support rail and configured to move to a position spaced apart from the cradle portion by a distance substantially equal to the diameter of the work piece.  
     
     
         27 . The apparatus of  claim 25  wherein the movable finger portion comprises a movable finger portion slideably coupled to the cradle portion on a support rail and configured to move to a position spaced apart from the cradle portion by a distance substantially equal to the diameter of the substantially cylindrical shape of the vertical portion.  
     
     
         28 . The apparatus of  claim 23  wherein the work piece handling wand further comprises a protrusion extending from the cradle portion and configured to contact a physical reference surface on the work piece carrier housing.  
     
     
         29 . The apparatus of  claim 28  wherein the physical reference surface comprises a protrusion extending from the work piece carrier housing.  
     
     
         30 . The apparatus of  claim 23  wherein the work piece handling wand further comprises a protrusion extending from the cradle portion and configured to contact the substantially cylindrical inner surface of the wear ring.  
     
     
         31 . The apparatus of  claim 23  wherein the work piece handling wand further comprises a protrusion extending from the cradle portion and configured to contact the substantially cylindrical outer surface of the wear ring.  
     
     
         32 . The apparatus of  claim 23  wherein the substantially cylindrical shape of the vertical portion provides a reference surface to which the cradle portion can be aligned.  
     
     
         33 . The apparatus of  claim 21  further comprising a reference band attached to the vertical portion of the flexible diaphragm.  
     
     
         34 . A work piece handling wand for moving a substantially circular work piece to and in alignment with a planarizing apparatus, the work piece handling wand comprising: 
 a cradle portion;    a movable finger portion spaced apart from the cradle portion at the distal end of a longitudinal axis extending from the cradle portion to the movable finger portion, the cradle portion and the finger portion configured to confine a work piece therebetween; and    a reference surface configured to register with a reference surface on the planarizing apparatus to position the work piece in alignment with the planarizing apparatus.    
     
     
         35 . The work piece handling wand of  claim 34  wherein the cradle portion comprises: 
 a raised wall portion having a concave surface with a radius of curvature substantially equal to the curvature of the substantially circular work piece; and  
 a substantially flat floor portion intersecting with the raised wall portion.  
 
     
     
         36 . The work piece handling wand of  claim 35  wherein the raised wall portion is angled toward the longitudinal axis at an angle of less than 90° with respect to the longitudinal axis.  
     
     
         37 . The work piece handling wand of  claim 36  wherein the substantially flat floor portion is angled away from the longitudinal axis.  
     
     
         38 . The work piece handling wand of  claim 35  wherein the reference surface comprises the raised wall portion on the cradle portion.  
     
     
         39 . The work piece handling wand of  claim 34  wherein the reference surface comprises a protrusion extending outwardly from the cradle portion.  
     
     
         40 . The work piece handling wand of  claim 34  further comprising: 
 a second cradle portion; and  
 a second movable finger portion spaced apart from the second cradle portion at the distal end of the longitudinal axis, the second cradle portion and second movable finger portion positioned on the opposite side of the longitudinal axis from the cradle portion and the movable finger portion.  
 
     
     
         41 . A method for planarizing a work piece utilizing a work piece planarizing apparatus comprising a work piece carrier head, a wear ring, and a work piece carrier plate mounted therewith, the work piece carrier plate movable in a vertical direction from a retracted position to an extended position, the work piece carrier plate having a substantially planar surface with a plurality of apertures therethrough and a lateral edge, the lateral edge exposed when the work piece carrier plate is positioned in the extended position, and the wear ring positioned to surround the work piece carrier plate when the work piece carrier plate is positioned in the retracted position, the method comprising the steps of: 
 positioning the work piece carrier plate in the extended position;    transporting a work piece to a position proximate the substantially planar surface;    drawing fluid through the plurality of apertures; and    positioning the work piece in contact with the substantially planar surface so the fluid drawn through the plurality of apertures attracts and holds the work piece to the substantially planar surface.    
     
     
         42 . The method of  claim 41  wherein the step of transporting comprises the step of transporting the work piece on a work piece handling wand.  
     
     
         43 . The method of  claim 42  wherein the step of positioning the work piece comprises the step of centering the work piece relative to the work piece carrier plate by engaging a surface of the work piece handling wand with a surface of the work piece carrier head.  
     
     
         44 . The method of  claim 42  wherein the step of positioning the work piece comprises the step of centering the work piece relative to the work piece carrier plate by engaging a surface of the work piece handling wand with the lateral edge of the work piece carrier plate.  
     
     
         45 . The method of  claim 42  wherein the step of positioning the work piece comprises the step of centering the work piece relative to the work piece carrier plate by engaging a surface of the work piece handling wand with a surface of the wear ring.  
     
     
         46 . The method of  claim 42  wherein the step of centering the work piece relative to the work piece carrier plate comprises the step of engaging a surface of the work piece handling wand with an outer diameter surface of the wear ring.  
     
     
         47 . The method of  claim 42  wherein the step of centering the work piece relative to the work piece carrier plate comprises the step of engaging a surface of the work piece handling wand with an inner diameter surface of the wear ring.  
     
     
         48 . The method of  claim 42  wherein the step of centering the work piece relative to the work piece carrier plate comprises the step of engaging a surface of the work piece handling wand with an alignment feature coupled to the work piece carrier head.  
     
     
         49 . The method of  claim 42  wherein the step of transporting comprises the step of gripping the work piece between a raised cradle portion of the work piece carrier wand and a movable gripping finger of the work piece carrier wand position at a distal end of the work piece carrier wand.  
     
     
         50 . The method of  claim 41  further comprising the steps of: 
 moving the work piece carrier plate to the retracted position; and  
 lowering the work piece carrier head to place the work piece in contact with a polishing pad.  
 
     
     
         51 . A method for planarizing a work piece utilizing a work piece planarizing apparatus comprising a work piece carrier head, a flexible work piece support diaphragm coupled to the work piece carrier head, and a wear ring flexibly mounted to the work piece carrier head and surrounding the flexible work piece diaphragm, the method comprising the steps of: 
 retracting the wear ring to expose a lateral edge of the flexible work piece diaphragm;    centering a work piece to be polished in alignment with the flexible work piece diaphragm;    lowering the wear ring to position a lower surface thereof substantially coplanar with the work piece; and    lowering the work piece carrier head to place the work piece in contact with a polishing pad.    
     
     
         52 . The method of  claim 51  wherein the step of centering comprises the steps of: 
 gripping the work piece with a work piece handling wand; and  
 engaging a surface of the work piece handling wand with the lateral edge.  
 
     
     
         53 . A method for planarizing a work piece utilizing a work piece handling wand and a work piece planarizing apparatus comprising a work piece carrier head, a work piece support surface coupled to the work piece carrier head, and a wear ring coupled to the work piece carrier head and surrounding the work piece support surface, the method comprising the steps of: 
 gripping a work piece with the work piece handling wand;    aligning the work piece handling wand and the work piece to the work piece support surface;    transferring the work piece from the work piece handling wand to the work piece support surface; and    lowering the work piece carrier head to press the work piece into contact with a polishing surface.    
     
     
         54 . The method of  claim 53  wherein the step of aligning comprises the step of engaging a surface of the work piece handling wand with a surface of the work piece carrier head.  
     
     
         55 . The method of  claim 53  wherein the step of aligning comprises the step of engaging a surface of the work piece handling wand with a surface of the wear ring.  
     
     
         56 . The method of  claim 53  further comprising the step of raising the wear ring to expose a lateral surface of the work piece support surface.  
     
     
         57 . The method of  claim 56  wherein the step of aligning comprises the step of engaging a surface of the work piece handling wand with the lateral surface of the work piece support surface.  
     
     
         58 . The method of  claim 56  wherein the work piece handling wand comprises a concave raised cradle portion and a moveable gripping finger adapted for gripping a work piece and wherein the step of aligning comprises the step of gripping the lateral surface of the work piece support surface between the concave raised cradle portion and the moveable gripping finger.  
     
     
         59 . A work piece handling wand for picking and placing a work piece having a thin, substantially circular disk shape, the wand comprising: 
 an elongate frame having a proximal end and a distal end;    a cradle portion coupled to the proximal end, the cradle portion comprising a first floor portion and a first raised wall portion, the first raised wall portion having a concave surface opening in the distal direction, the concave surface having a radius of curvature sized to substantially match the radius of curvature of the work piece;    a gripping finger slidably coupled to the distal end and moveable toward and away from the proximal end, the gripping finger comprising a first base portion and a second raised wall portion, the second raised wall portion having a surface facing toward the cradle portion; and    an actuator mounted to the frame and attached to the gripping finger for moving the gripping finger toward and away from the proximal end.    
     
     
         60 . The work piece handling wand of  claim 59  further comprising a sensor capable of determining the position of the gripping finger relative to the proximal end.  
     
     
         61 . The work piece handling wand of  claim 59  wherein the top of the first raised wall portion of the cradle portion is canted toward the distal end.  
     
     
         62 . The work piece handling wand of  claim 61  wherein the first floor portion of the cradle portion extends away from the first raised wall portion at an angle greater than ninety degrees.  
     
     
         63 . The work piece handling wand of  claim 59  wherein the concave surface subtends an angle of at least sixty degrees.  
     
     
         64 . The work piece handling wand of  claim 59  wherein the concave surface subtends an angle of at least one hundred degrees.  
     
     
         65 . The work piece handling wand of  claim 59  wherein the cradle portion and the gripping finger are disposed on a first side of the elongate frame and the first and second raised wall portions thereof extend in a first direction, the work piece handling wand further comprising: 
 a second cradle portion coupled to the proximal end on a second side of the elongate frame opposite the first side, the second cradle portion comprising a second floor portion and a third raised wall portion having a concave surface opening in the distal direction, the third raised wall portion extending in a second direction opposite the first direction;  
 a second gripping finger slidably coupled to the distal end on the second side, the second gripping finger comprising a second base portion and a fourth raised wall portion, the fourth raised wall portion having a surface facing toward the second cradle portion, the fourth raised wall portion extending in the second direction; and  
 a second actuator mounted on the elongate frame and attached to the second gripping finger and capable of moving the second gripping finger toward and away from the second cradle portion.  
 
     
     
         66 . A method for planarizing a work piece by a process of chemical mechanical planarization comprising the steps of: 
 moving a work piece handling wand comprising a cradle having a raised concave wall portion with a radius of curvature substantially the same as the radius of curvature of the work piece and a moveable gripping finger having a raised wall portion and adapted for movement toward and away from the cradle to a position proximate the work piece;    moving the raised wall portion of the moveable gripping finger away from the raised concave wall portion of the cradle a distance greater than the diameter of the work piece;    positioning the work piece handling wand such that the work piece is between the raised wall portion of the moveable gripping finger and the concave wall portion of the cradle; and    moving the moveable gripping finger toward the cradle until the work piece is gripped between the raised wall portion of the moveable gripping finger and the concave wall portion of the cradle.    
     
     
         67 . The method of  claim 66  further comprising the step of sensing the position of the moveable gripping finger to confirm that a work piece has been gripped.  
     
     
         68 . The method of  claim 66  further comprising the steps of: 
 moving the work piece handling wand and the work piece gripped thereby to a location proximate a work piece carrier head of a chemical mechanical planarization apparatus, the work piece carrier head having a reference surface of substantially circular cross section;  
 moving the moveable gripping finger away from the cradle to increase the distance between the raised wall portion of the moveable gripping finger and the concave wall portion of the cradle whereby the increased distance is greater than the diameter of the substantially circular cross section of the reference surface;  
 moving the work piece handling wand toward the reference surface until at least a portion of the reference surface is positioned between the raised wall portion of the moveable gripping finger and the concave wall portion of the cradle; and  
 moving the moveable gripping finger toward the cradle until the reference surface is gripped between the raised wall portion of the moveable gripping finger and the concave wall portion of the cradle.  
 
     
     
         69 . The method of  claim 68  further comprising the step of transferring the work piece from the work piece handling wand to the work piece carrier head while the reference surface is gripped between the raised wall portion of the moveable gripping finger and the concave wall portion of the cradle.  
     
     
         70 . The method of  claim 68  further comprising the step of retracting a wear ring of the chemical mechanical planarization apparatus to expose the reference surface.  
     
     
         71 . The method of  claim 66  further comprising the steps of: 
 moving the work piece handling wand and the work piece gripped thereby to a location proximate a work piece carrier head of a chemical mechanical planarization apparatus, the work piece carrier head having a wear ring coupled thereto, the wear ring having a substantially cylindrical lateral outer surface; and  
 centering the work piece relative to the work piece carrier head by engaging a projection extending from the cradle with the lateral outer surface.  
 
     
     
         72 . The method of  claim 66  further comprising the steps of: 
 moving the work piece handling wand and the work piece gripped thereby to a location proximate a work piece carrier head of a chemical mechanical planarization apparatus, the work piece carrier head having a wear ring coupled thereto, the wear ring having a substantially cylindrical lateral inner surface; and  
 centering the work piece relative to the work piece carrier head by engaging a projection extending from the cradle with the lateral inner surface.  
 
     
     
         73 . The method of  claim 66  further comprising the steps of: 
 moving the work piece handling wand and the work piece gripped thereby to a location proximate a work piece carrier head of a chemical mechanical planarization apparatus, the work piece carrier head having a reference surface; and  
 centering the work piece relative to the work piece carrier head by engaging a surface of the work piece handling wand with the reference surface.