JP5399829B2 - Polishing pad dressing method - Google Patents

Description

  The present invention relates to a polishing pad dressing method for polishing a workpiece such as a semiconductor wafer.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a substantially wafer-shaped semiconductor wafer, and devices such as ICs, LSIs, etc. are partitioned in these partitioned regions. Form. By dividing the semiconductor wafer on which a plurality of devices are formed in this way along the streets, individual devices are formed. In order to reduce the size and weight of a device, the semiconductor wafer is usually ground to the predetermined thickness by grinding the backside of the semiconductor wafer prior to cutting the semiconductor wafer along the street and dividing it into individual devices. ing. The grinding of the back surface of a semiconductor wafer is usually performed by pressing a grinding wheel formed by fixing diamond abrasive grains with an appropriate bond such as a resin bond against the back surface of the semiconductor wafer while rotating at high speed. When the back surface of the semiconductor wafer is ground by such a grinding method, a so-called processing strain is generated on the back surface of the semiconductor wafer, which causes a problem that the bending strength of the individually divided devices is lowered.

  In order to solve the above-described problem, a polishing apparatus that polishes the back surface of a ground semiconductor wafer to remove the grinding distortion is disclosed in Patent Document 1 below. A polishing apparatus disclosed in the following Patent Document 1 includes a chuck table that holds a workpiece, and a polishing unit that has a polishing pad that polishes the workpiece held on the chuck table. The workpiece surface of the workpiece is polished by pressing the workpiece while rotating the polishing pad while supplying the liquid.

JP-A-8-99265

  In the polishing apparatus described above, when the polishing pad is replaced with a new polishing pad, the polishing ability becomes unstable and it becomes difficult to control the thickness of the wafer. Therefore, the dummy wafer is polished and dressed. The polishing ability is stabilized. However, in order to stabilize the polishing ability of the replaced polishing pad, it is necessary to polish and dress the dummy wafer for about 1 hour, which causes a problem of poor productivity.

  The present invention has been made in view of the above facts, and a main technical problem thereof is to provide a polishing pad dressing method capable of stabilizing the polishing ability of the polishing pad in a short time.

In order to solve the above main technical problem, according to the present invention, a chuck table for holding a workpiece, a polishing means including a polishing pad for polishing the workpiece held on the chuck table, and the polishing pad A polishing pad dressing method in a polishing apparatus comprising a polishing liquid supply means for supplying a polishing liquid to
A dressing board holding step for holding a dressing board having a plurality of grooves formed on the surface of the hard substrate on the chuck table with the surface facing up;
A dressing step of rotating the chuck table to rotate the polishing pad and polishing the dressing board surface with the polishing pad while supplying a polishing liquid to the polishing pad.
A method of dressing a polishing pad is provided.

  The plurality of grooves formed on the surface of the hard substrate constituting the dressing board is formed in a lattice shape.

  In the polishing pad dressing method according to the present invention, since a plurality of grooves are formed on the surface of the hard substrate constituting the dressing board for dressing the polishing pad, the polishing liquid passes through the plurality of grooves and is applied to the polishing surface of the polishing pad. While being supplied evenly, the unevenness due to the plurality of grooves moderately roughens the polishing surface of the polishing pad, so that dressing is effectively performed. Therefore, the polishing ability of the polishing pad can be stabilized in a short time.

The perspective view which shows one Embodiment of the grinding | polishing apparatus comprised by this invention. The perspective view which shows the grinding | polishing tool which comprises the grinding | polishing unit with which the grinding | polishing apparatus shown in FIG. 1 is equipped. The perspective view which shows the state seen from the lower surface side of the grinding | polishing tool shown in FIG. The perspective view which shows the chuck table mechanism and chuck table moving mechanism with which the grinding | polishing apparatus shown in FIG. 1 is equipped. The perspective view of the dressing board used for the dressing method of the polishing pad by this invention. Explanatory drawing of the dressing process in the dressing method of the polishing pad by this invention.

  Hereinafter, preferred embodiments of a dressing method for a polishing pad according to the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a perspective view of a polishing apparatus for carrying out a polishing pad dressing method according to the present invention.
The polishing apparatus comprises an apparatus housing, generally designated 2. The apparatus housing 2 has a rectangular parallelepiped main portion 21 that extends elongated, and an upright wall 22 that is provided at the rear end portion (upper right end in FIG. 1) of the main portion 21 and is disposed in the vertical direction. Yes. A pair of guide rails 221 and 221 extending in the vertical direction are provided on the front surface of the upright wall 22. The pair of guide rails 221 and 221 is mounted with a polishing unit 3 as a polishing means so as to be movable in the vertical direction.

  The polishing unit 3 includes a moving base 31 and a spindle unit 32 attached to the moving base 31. The movable base 31 is provided with a pair of legs 311 and 311 extending in the vertical direction on both sides of the rear surface. The pair of legs 311 and 311 is slidably engaged with the pair of guide rails 221 and 221. Guided grooves 312 and 312 are formed. As described above, a support portion 313 protruding forward is provided on the front surface of the movable base 31 slidably mounted on the pair of guide rails 221 and 221 provided on the upright wall 22. The spindle unit 32 is attached to the support portion 313.

  The spindle unit 32 includes a spindle housing 321 mounted on the support portion 313, a rotating spindle 322 rotatably disposed on the spindle housing 321, and a servo as rotation driving means for driving the rotating spindle 322 to rotate. And a motor 323. The lower end of the rotary spindle 322 protrudes downward beyond the lower end of the spindle housing 321, and a disk-shaped tool mounting member 324 is provided at the lower end. The tool mounting member 324 is formed with a plurality of bolt insertion holes (not shown) at intervals in the circumferential direction. A polishing tool 325 is mounted on the lower surface of the tool mounting member 324. As shown in FIGS. 2 and 3, the polishing tool 325 includes a circular support base 326 and a circular polishing pad 327. The support base 326 is made of an aluminum alloy, and as shown in FIG. 2, a hole 326a through which a polishing liquid having an inner diameter of about 10 mm is formed at the center. In addition, the support base 326 is formed with a plurality of blind screw holes 326b extending downward from the upper surface at intervals in the circumferential direction. The lower surface of the support base 326 forms a circular support surface, and a polishing pad 327 is attached with a double-sided adhesive tape.

  The polishing pad 327 mounted on the lower surface of the support base 326 is formed in a circular shape having a diameter of 450 mm by fixing felt with urethane, and a polishing portion having an inner diameter of about 10 mm at the center as shown in FIG. A hole 327a through which the liquid passes is formed. In addition, a plurality of grooves 327 b formed in a lattice shape are provided on the lower surface (polishing surface) of the polishing pad 327. In the illustrated embodiment, the plurality of grooves 327b have a width of 4 mm, a depth of 3 mm, and are formed at intervals of 18 mm. The polishing tool 325 configured as described above is positioned on the lower surface of the tool mounting member 324 fixed to the lower end of the rotary spindle 322, and is a support base for the polishing tool 325 through a through hole formed in the tool mounting member 324. The fastening bolt 328 (see FIG. 1) is screwed into the blind screw hole 326b formed in 326, so that the tool mounting member 324 is mounted. In addition, the hole 327a provided in the polishing pad 327 of the polishing tool 325 mounted on the tool mounting member 324 in this way is formed into a rotating spindle as shown in FIG. 1 through the hole 326a provided in the support base 326. The polishing liquid supply passage 322 a formed in the hole 322 communicates with the passage 322 a. Accordingly, when a polishing liquid supply means (not shown) is operated, abrasive grains such as colloidal silica are mixed into the hole 327a provided in the polishing pad 327 through the hole 326a provided in the polishing liquid supply passage 322a and the support base 326. The polished polishing liquid is supplied.

  Referring back to FIG. 1, the polishing apparatus in the illustrated embodiment moves the polishing unit 3 in the vertical direction along the pair of guide rails 221 and 221 (in a direction perpendicular to the holding surface of the chuck table described later). A polishing feed means 4 is provided to be moved. The polishing feed means 4 includes a male threaded rod 41 disposed on the front side of the upright wall 22 and extending in the vertical direction. The male screw rod 41 is rotatably supported by bearing members 42 and 43 whose upper end and lower end are attached to the upright wall 22. The upper bearing member 42 is provided with a pulse motor 44 as a drive source for rotationally driving the male screw rod 41, and the output shaft of the pulse motor 44 is connected to the male screw rod 41 by transmission. A connecting portion (not shown) that protrudes rearward from the center portion in the width direction is also formed on the rear surface of the movable base 31, and a through female screw hole extending in the vertical direction is formed in this connecting portion, The male screw rod 41 is screwed into the female screw hole. Therefore, when the pulse motor 44 rotates in the forward direction, the moving base 31, that is, the polishing unit 3 is lowered or moved forward, and when the pulse motor 44 rotates in the reverse direction, the moving base 31, that is, the polishing unit 3 is raised or moved backward.

  Continuing the description with reference to FIGS. 1 and 4, the chuck table mechanism 5 is disposed in the main portion 21 of the housing 2. The chuck table mechanism 5 includes a support base 51 and a chuck table 52 disposed on the support base 51. The support base 51 is formed on a pair of guide rails 23 and 23 extending on the main portion 21 of the housing 2 in the direction indicated by the arrows 23a and 23b in the front-rear direction (the direction perpendicular to the front surface of the upright wall 22). A polishing tool which is slidably mounted and which constitutes the workpiece loading / unloading area 24 (position indicated by a solid line in FIG. 4) and the spindle unit 32 shown in FIG. 325 is moved between the polishing pad 327 and the polishing area 25 (position indicated by a two-dot chain line in FIG. 4).

  The chuck table 52 is made of an appropriate porous material such as porous ceramics, and is connected to a suction means (not shown). Therefore, by selectively communicating the chuck table 52 with a suction means (not shown), the workpiece placed on the holding surface which is the upper surface is sucked and held. In the illustrated embodiment, the chuck table 52 is configured to hold a wafer having a diameter of 300 mm. The chuck table 52 is rotatably supported by the support base 51. The chuck table 52 is rotated by a servo motor 53 as a rotation driving means connected to a rotation shaft (not shown) mounted at the lower end thereof. The illustrated chuck table mechanism 5 includes a cover member 54 having a hole through which the chuck table 52 is inserted and covering the support base 51 and the like. The cover member 54 is configured to be movable together with the support base 51. ing.

  4, the polishing apparatus in the illustrated embodiment moves the chuck table mechanism 5 along the pair of guide rails 23 in parallel with the holding surface which is the upper surface of the chuck table 52, using arrows 23a and 23b. The chuck table mechanism moving means 56 is provided for moving in the direction indicated by. The chuck table mechanism moving means 56 includes a male screw rod 561 that is disposed between the pair of guide rails 23 and extends parallel to the guide rail 23, and a servo motor 562 that rotationally drives the male screw rod 561. The male screw rod 561 is screwed into a screw hole 511 provided in the support base 51, and its tip is rotatably supported by a bearing member 563 attached by connecting a pair of guide rails 23, 23. ing. The servo motor 562 has a drive shaft connected to the base end of the male screw rod 561 by transmission. Therefore, when the servo motor 562 rotates in the forward direction, the moving base 53, that is, the chuck table mechanism 5 moves in the direction indicated by the arrow 23a. When the servo motor 562 rotates in the reverse direction, the support base 51, that is, the chuck table mechanism 5, moves in the direction indicated by the arrow 23b. It can be moved. The chuck table mechanism 5 that is moved in the directions indicated by the arrows 23a and 23b is selectively positioned in a workpiece loading / unloading area indicated by a solid line and a polishing area indicated by a two-dot chain line in FIG.

  Returning to FIG. 1, the explanation will be continued. On both sides of the support base 51 constituting the chuck table mechanism 5 in the moving direction, as shown in FIG. Bellows means 6 and 7 covering the rails 23 and 23, the male screw rod 561, the servo motor 562 and the like are attached. The bellows means 6 and 7 can be formed from any suitable material such as campus cloth. The front end of the bellows means 6 is fixed to the front wall of the rear half of the main portion 21 constituting the housing 2, and the rear end is fixed to the front end surface of the support base 51 of the chuck table mechanism 5. The front end of the bellows means 7 is fixed to the rear end surface of the support base 51 of the chuck table mechanism 5, and the rear end is fixed to the front surface of the upright wall 22 of the apparatus housing 2. When the chuck table mechanism 5 is moved in the direction indicated by the arrow 23a, the bellows means 6 is expanded and the bellows means 7 is contracted, and when the chuck table mechanism 5 is moved in the direction indicated by the arrow 23b, the bellows means. 6 is contracted and the bellows means 7 is extended.

  The description will be continued based on FIG. 1. On the front half of the main portion 21 of the apparatus housing 2, a first cassette 11, a second cassette 12, a workpiece temporary placing means 13, and a cleaning means are provided. 14, a workpiece conveying means 15, a workpiece carrying-in means 16 and a workpiece carrying-out means 17 are arranged. The first cassette 11 stores a workpiece before polishing and is placed in a cassette carry-in area in the main portion 21 of the apparatus housing 2. The workpiece to be accommodated in the first cassette 11 is, for example, a semiconductor wafer W and is accommodated with the back surface facing up with the protective tape T attached to the surface. The second cassette 12 is placed in a cassette unloading area in the main portion 21 of the apparatus housing 2 and stores the semiconductor wafer W after polishing. The workpiece temporary mounting means 13 is disposed between the first cassette 11 and the workpiece loading / unloading area 24, and temporarily mounts the semiconductor wafer W before polishing. The cleaning means 14 is disposed between the workpiece loading / unloading area 24 and the second cassette 12 and cleans the semiconductor wafer W after polishing. Workpiece conveying means 15 is disposed between the first cassette 11 and the second cassette 12, and the semiconductor wafer W accommodated in the first cassette 11 is carried out to the workpiece temporary placement means 13. At the same time, the semiconductor wafer W cleaned by the cleaning means 14 is transported to the second cassette 12. The workpiece carrying-in means 16 is disposed between the workpiece temporary placing means 13 and the workpiece carrying-in / out area 24, and is placed on the workpiece temporary placing means 13 before polishing. The semiconductor wafer W is transferred onto the chuck table 52 of the chuck table mechanism 5 positioned in the workpiece loading / unloading area 24. The workpiece unloading means 17 is disposed between the workpiece loading / unloading area 24 and the cleaning means 14, and is mounted on a chuck table 52 positioned in the workpiece loading / unloading area 24. The processed semiconductor wafer W is transported to the cleaning means 14. The polishing apparatus in the illustrated embodiment includes a cleaning water spray nozzle 18 that cleans the holding surface of the chuck table 52 at the center of the main portion 21 of the apparatus housing 2. The cleaning water spray nozzle 18 ejects cleaning water toward the chuck table 52 in a state where the chuck table mechanism 5 is positioned in the workpiece loading / unloading area 24.

  The first cassette 11 containing the semiconductor wafer W as a workpiece is placed in a predetermined cassette carry-in area in the main portion 21 of the apparatus housing 2. Then, when all the semiconductor wafers W before being polished that were accommodated in the first cassette 11 placed in the cassette carry-in area are unloaded, a plurality of semiconductor wafers W are accommodated in place of the empty cassette 11. A new cassette 11 is manually placed in the cassette carry-in area. On the other hand, when a predetermined number of polished semiconductor wafers W are loaded into the second cassette 12 placed in a predetermined cassette unloading area in the main portion 21 of the apparatus housing 2, the second cassette 12 is manually moved. It is unloaded and a new empty second cassette 12 is placed.

  The polishing apparatus in the illustrated embodiment is configured as described above, and the polishing pad 327 of the polishing tool 325 is replaced. As described above, the newly exchanged polishing pad has unstable polishing ability, and therefore needs to be dressed to stabilize the polishing ability of the polishing pad. Hereinafter, the dressing method of the polishing pad will be described.

  FIG. 5 shows a dressing board used for dressing a polishing pad. The dressing board 10 shown in FIG. 5 includes a circular hard substrate 100 having a diameter of 300 mm and a thickness of 5 mm. The hard substrate 100 can be formed of silicon, ceramics, or a glass plate. A plurality of grooves 101 are formed in a lattice pattern on the surface of the hard substrate 100. The plurality of grooves 101 have a width of 0.5 to 1 mm and a depth of 0.5 to 1 mm, and are formed at intervals of 5 mm.

  In order to dress the polishing pad 327 using the dressing board 10 described above, the dressing board 10 is placed on the holding surface of the chuck table 52 positioned in the workpiece loading / unloading area 24 in FIG. At this time, the dressing board 10 is placed with the surface of the hard substrate 100 (the surface on which the lattice-like grooves 101 are formed) facing upward. When the dressing board 10 is placed on the chuck table 52, the dressing board 10 is sucked and held on the chuck table 52 by operating a suction means (not shown) (dressing board holding step).

  When the above-described dressing board holding step is performed, the chuck table mechanism moving means 56 is operated to move the chuck table mechanism 5 in the direction indicated by the arrow 23 a and position the chuck table 52 in the polishing area 25. When the chuck table 52 is positioned in the polishing area 25 in this way, the polishing pad 327 is positioned so as to cover the surface of the dressing board 10 as shown in FIG. 6, and the chuck table 52 is set in the direction indicated by the arrow 52a, for example, at 505 rpm. Rotate at a rotation speed of. Further, a polishing liquid supply means (not shown) is operated, and colloidal silica is inserted into a hole 327 a provided in the polishing pad 327 via a polishing liquid supply passage 322 a formed in the rotary spindle 322 and a hole 326 a provided in the support base 326. The polishing tool 325 is driven in the direction indicated by the arrow 325a, for example, at 500 rpm while the servo motor 323 is driven while supplying a polishing liquid mixed with abrasive grains such as at a flow rate of 500 ml (500 ml / min) per minute. At the same time, the pulse motor 44 of the polishing feed means 4 is driven to rotate forward to lower or advance the polishing unit 3, and the polishing pad 327 is pressed against the dressing board 10 held by the chuck table 52 with a pressure of 25 kPa. As a result, the polishing surface of the polishing pad 327 is dressed by polishing the surface of the dressing board 10 (dressing process). At this time, since the lattice-like grooves 101 are formed on the surface of the hard substrate 100 constituting the dressing board 10, the polishing liquid is uniformly supplied to the polishing surface of the polishing pad 327 through the lattice-like grooves 101, The unevenness due to the lattice-like grooves 101 moderately roughens the polishing surface of the polishing pad 327, so that dressing is performed effectively. According to experiments by the present inventors, the polishing ability of the polishing pad 327 could be stabilized by performing the dressing for 10 minutes.

  When the dressing operation is completed as described above, the supply of the polishing station by the polishing liquid supply means (not shown) is stopped, the pulse motor 44 of the polishing feed means 4 is driven in reverse to raise the spindle unit 32 to a predetermined position. Then, the rotation of the polishing tool 325 is stopped, and further, the rotation of the chuck table 52 is stopped. Next, the chuck table 52 is moved to the workpiece loading / unloading area 24. Then, the suction holding of the dressing board 10 held on the chuck table 52 is released, and the dressing board 10 is taken out from the chuck table 52.

Next, a polishing operation performed by the polishing pad 327 dressed as described above will be briefly described mainly with reference to FIG.
The semiconductor wafer W as a workpiece before polishing, which is accommodated in the first cassette 11, is transported by the vertical movement and advancing / retreating operation of the workpiece conveying means 15 and is placed on the workpiece temporary placing means 13. The The semiconductor wafer W mounted on the workpiece temporary mounting means 13 is positioned in the workpiece loading / unloading area 24 by the turning operation of the workpiece loading means 16 after being centered here. Is mounted on the chuck table 52 of the chuck table mechanism 5. A semiconductor wafer W as a workpiece placed on the chuck table 52 is sucked and held on the chuck table 52 by operating a suction means (not shown).

  If the semiconductor wafer W is sucked and held on the chuck table 52, the chuck table mechanism moving means 56 is actuated to move the chuck table mechanism 5 in the direction indicated by the arrow 23a, and polishing is performed in the same manner as in the dressing shown in FIG. The pad 327 is positioned in the polishing area 24 so as to cover the semiconductor wafer W. When the chuck table 52 holding the semiconductor wafer is positioned in the polishing area 25, the polishing liquid supply means (not shown) is operated, and the polishing liquid supply passage 322 a formed in the rotary spindle 322 and the support base 326 are provided. A polishing liquid in which abrasive grains such as colloidal silica are mixed is supplied at a flow rate of 500 ml / min to the hole 327a provided in the polishing pad 327 through the hole 326a, as in the above dressing. Then, the chuck table 52 holding the semiconductor wafer W is rotated in a predetermined direction, for example, at 505 rpm similarly to the time of dressing, and the servo motor 323 is driven to move the polishing tool 325 in a predetermined direction, for example, 500 rpm. And the pulse motor 44 of the polishing feed means 4 is driven to rotate forward to lower or advance the polishing unit 3, and the polishing pad 327 of the polishing tool 325 is moved to the back surface (upper surface) of the semiconductor wafer W on the chuck table 52. Press at a pressure of 25 kPa. By performing the polishing operation in this way, the back surface of the semiconductor wafer W is polished by a predetermined amount, and residual processing strain is removed (polishing step). In this polishing step, since the polishing pad 327 of the polishing tool 325 is dressed as described above and the polishing capability is stable, the thickness control of the semiconductor wafer W becomes easy.

  When the polishing operation is completed as described above, the pulse motor 44 of the polishing feed unit 4 is driven in reverse to raise the spindle unit 32 to a predetermined position, and the rotation of the polishing tool 325 is stopped. Stop rotating. Next, the chuck table mechanism 5 is moved in the direction indicated by the arrow 23 b and is positioned in the workpiece loading / unloading area 24. If the chuck table mechanism 5 is positioned in the workpiece loading / unloading area 24, the suction holding of the polished semiconductor wafer on the chuck table 52 is released, and the semiconductor wafer W whose suction holding is released is processed. It is unloaded by the object unloading means 17 and conveyed to the cleaning means 14. The semiconductor wafer W transferred to the cleaning unit 14 is cleaned here and then stored in a predetermined position of the second cassette 12 by the workpiece transfer unit 15.

2: Device housing 3: Polishing unit 31: Moving base 32: Spindle unit 321: Spindle housing 322: Rotating spindle 323: Servo motor 324: Tool mounting member 325: Polishing tool 326: Support member 327: Polishing pad 4: Polishing unit Feed mechanism 44: Pulse motor 5: Chuck table mechanism 51: Support base 52: Chuck table 56: Chuck table moving mechanism 10: Dressing board 100: Hard substrate 11: First cassette 12: Second cassette 13: Work piece Temporary object placing means 14: Cleaning means 15: Workpiece conveying means 16: Workpiece carrying means 17: Workpiece carrying means 18: Washing water injection nozzle

Claims (2)

Polishing comprising a chuck table for holding a workpiece, a polishing means having a polishing pad for polishing the workpiece held on the chuck table, and a polishing liquid supply means for supplying a polishing liquid to the polishing pad A polishing pad dressing method in an apparatus,
A dressing board holding step for holding a dressing board having a plurality of grooves formed on the surface of the hard substrate on the chuck table with the surface facing up;
A dressing step of rotating the chuck table to rotate the polishing pad and polishing the surface of the dressing board with the polishing pad while supplying a polishing liquid to the polishing pad,
A polishing pad dressing method characterized by the above.   The polishing pad dressing method according to claim 1, wherein the plurality of grooves formed on the surface of the hard substrate constituting the dressing board are formed in a lattice shape.

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