JP7515965B2 - Manufacturing method of porous plate, manufacturing method of chuck table and processing device - Google Patents

Description

The present invention relates to a method for manufacturing a porous plate used in a chuck table, and a processing device equipped with a chuck table having a porous plate manufactured by the manufacturing method.

Known types of grinding devices include those that use grinding wheels to grind workpieces such as silicon substrates, ceramic substrates, glass substrates, and resin package substrates, those that polish the workpieces with polishing pads, and those that cut the workpieces along the intended division lines.

Processing devices such as grinding devices, polishing devices, and cutting devices are equipped with a chuck table having a porous plate made of porous ceramics. The porous plate is connected to a suction source such as an ejector via a specified flow path, and when the negative pressure generated by the suction source is transmitted to the porous plate, negative pressure is generated on the upper surface (holding surface) of the porous plate.

When processing a workpiece with a processing device, the top side of the workpiece is processed while the bottom side (held surface) of the workpiece is suction-held by the holding surface of the porous plate. During processing of the workpiece, liquid such as pure water may be supplied to the top side of the workpiece for cooling and removal of processing debris.

The processing device may also be provided with a cleaning unit that cleans the workpiece after processing. The cleaning unit has a chuck table equipped with the above-mentioned porous plate. A nozzle is disposed above the chuck table for spraying a gas-liquid mixed fluid (two-fluid) that is a mixture of a liquid such as pure water and air.

When cleaning a workpiece in the cleaning unit, the bottom side of the workpiece is held by suction on the holding surface of the porous plate, and a gas-liquid mixture is sprayed from a nozzle onto the top side of the workpiece.

However, when processing and cleaning the workpiece, liquid may seep in between the holding surface and the underside of the workpiece, and the liquid may adhere to the underside of the workpiece. If a workpiece with liquid remaining on its underside is placed in a cassette, there is a risk that the liquid may drip from the workpiece and adhere to the workpiece placed in the cassette.

Therefore, before storing the processed or cleaned workpiece in the cassette, it is necessary to remove the liquid adhering to the underside of the workpiece. For this reason, it is known to add an air blow unit to the processing device, which sprays air onto the underside of the workpiece to remove the liquid (see, for example, Patent Document 1).

JP 2010-167519 A

However, when an air blow unit is added to a processing device, a certain amount of space inside the processing device is occupied by the air blow unit, and additional costs are incurred. The present invention was made in consideration of these problems, and aims to suppress adhesion of liquid to the underside (held surface) of the workpiece without providing an air blow unit to the processing device.

According to one aspect of the present invention, there is provided a method for manufacturing a porous plate for use in a chuck table, the method comprising: a mixture preparation step of preparing a mixture of a plurality of abrasive grains, a bond material which melts when heated and is cooled after melting to fix the plurality of abrasive grains, and a pore-forming material which has an average particle size of 50 μm or more and disappears when heated; a mixture molding step of molding the mixture to form a plate-shaped molded body; and a molded body firing step of firing the molded body to form a porous plate, the porous plate having pores formed by the disappearance of the pore-forming material and first gaps between the abrasive grains and the bond material which are different from the pores, the porosity of the porous plate being 40% or more and 55% or less, the pores and the gaps being connected, the pores being exposed on one side of the porous plate, and when liquid is supplied to the one side, the liquid is sucked into the pores and discharged from the pores to the gaps by capillary action. The gaps include second gaps between the abrasive grains and third gaps between the bond materials, and it is preferable that the volume ratio of the pores to the gaps (pores:gaps) is 1:2 to 1:4.

According to another aspect of the present invention, there is provided a method for manufacturing a chuck table having a porous plate manufactured by the porous plate manufacturing method described above, and a frame body supporting the porous plate and having a suction path for transmitting negative pressure from a suction source to the porous plate, the method including a fixing step of fixing the porous plate in a recess of the frame body with an adhesive.

The porous plate according to one embodiment of the present invention has pores formed by the disappearance of a pore-forming material having an average particle size of 50 μm or more, and gaps that are different from the pores and are formed by the abrasive grains and the bonding material. The pores and the gaps are connected, and the pores are exposed on one side of the porous plate. When liquid is supplied to one side of the porous plate, the liquid is sucked into the relatively large pores, and then discharged from the pores into the gaps by capillary action.

Therefore, even if liquid seeps between the workpiece and the porous plate while the workpiece is being suction-held on the holding surface of the porous plate, the liquid is easily sucked into the interior of the porous plate and discharged. This makes it possible to prevent the liquid from adhering to the held surface side of the workpiece.

Therefore, an air blow unit for drying the held surface side is not required , and furthermore, by omitting the air blow unit, the processing time required to remove liquid by the air blow unit is not required, so the processing time from when the workpiece is carried out from the cassette to when the processed workpiece is carried into the cassette can be shortened. In other words, more efficient processing is possible compared to when an air blow unit is provided.

FIG. FIG. 2 is a partial cross-sectional side view showing a mixture preparation step. FIG. 4 is a partial cross-sectional side view showing the mixture molding step. FIG. 4 is a cross-sectional view showing a compact sintering step. FIG. 5(A) is a cross-sectional view showing the porous plate fixing step, and FIG. 5(B) is a cross-sectional view of the frame and the porous plate. FIG. 4 is a partial cross-sectional side view showing a porous plate grinding step. 3A and 3B are diagrams showing a cross section of a chuck table and an enlarged cross section of the vicinity of a holding surface. FIG. 4 is a flow diagram of a method for manufacturing the chuck table. 4 is a partial cross-sectional side view showing how a workpiece is cut by the cutting unit. FIG. 1 is a partial cross-sectional side view showing how a workpiece is cleaned in a cleaning unit. FIG.

An embodiment of the present invention will be described with reference to the attached drawings. FIG. 1 is a perspective view of a cutting device (processing device) 2. In FIG. 1, the X-axis direction (processing feed direction), the Y-axis direction (indexing feed direction), and the Z-axis direction (vertical direction, height direction) are mutually orthogonal.

The cutting device 2 includes a base 4 that supports each component. An opening 4a is provided at the front corner of the base 4. A cassette elevator 6a that is raised and lowered by a lifting mechanism (not shown) is provided within the opening 4a.

A cassette 6b is placed on the top surface of the cassette elevator 6a. The cassette 6b contains a plurality of workpieces 11. The workpieces 11 are, for example, disk-shaped wafers made of a semiconductor material such as silicon. There are no limitations on the material, shape, structure, size, etc. of the workpieces 11.

A number of mutually intersecting planned division lines (streets) are set on the surface 11a of the workpiece 11. Devices such as ICs (Integrated Circuits) are formed on the surface 11a of each area partitioned by the planned division lines.

In this embodiment, no dicing tape is attached to the back surface 11b (the surface opposite to the front surface 11a) of the workpiece 11. However, a dicing tape (not shown) having approximately the same diameter as the workpiece 11 may be attached to the back surface 11b.

Alternatively, the back surface 11b side may be attached to the center of a dicing tape having a diameter larger than the diameter of the workpiece 11, and a metal ring-shaped frame may be attached to the outer periphery of the dicing tape.

A rectangular opening 4b with its long side along the X-axis direction is formed on the side of the cassette elevator 6a. Inside the opening 4b, a table cover 10 and a bellows-shaped cover 12 that expands and contracts in the X-axis direction are provided. A chuck table 14 is provided on the table cover 10.

A rotation drive source (not shown), such as a motor, is disposed below the table cover 10 to rotate the chuck table 14 around a rotation axis that is roughly parallel to the Z-axis direction (vertical direction). The rotation shaft 10a (see FIG. 9) of the rotation drive source is connected to the underside of the chuck table 14.

A ball screw type X-axis movement mechanism (processing feed unit) (not shown) is provided below the rotary drive source. By operating the X-axis movement mechanism, the table cover 10 and the chuck table 14 move along the X-axis direction.

The structure of the chuck table 14 will now be briefly described with reference to Figure 9. The chuck table 14 has a disk-shaped frame 16 made of a metal such as stainless steel. A disk-shaped recess 16a is formed in the frame 16.

A porous plate 21 (described later) is fixed and supported in the recess 16a by adhesive or the like. A plurality of convex portions 16b arranged concentrically are provided at the bottom of the recess 16a. Each convex portion 16b has one or more notches (not shown) formed therein.

A ring-shaped or arc-shaped space 16c is formed between two adjacent protrusions 16b in the radial direction of the bottom surface of the frame body 16. Each of the multiple spaces 16c is spatially connected by the cutouts of the protrusions 16b.

Each space 16c is connected to a through hole 16d formed to penetrate the bottom surface of the frame body 16. A suction source 10b such as an ejector is connected to the through hole 16d via a predetermined flow path. The through hole 16d and the space 16c function as a suction path that transmits negative pressure from the suction source 10b.

An electromagnetic valve 10c is provided in the flow path between the through hole 16d and the suction source 10b. When the electromagnetic valve 10c is opened while the suction source 10b is operating, negative pressure is transmitted to the upper surface (one surface, the holding surface 14a) of the porous plate 21 through the through hole 16d and the space 16c.

Next, a method for manufacturing the chuck table 14 according to this embodiment will be described with reference to Figures 2 to 8. First, a method for manufacturing the porous plate 21 used in the chuck table 14 will be described with reference to Figures 2 to 4.

Then, a method for manufacturing the chuck table 14 in which the porous plate 21 and the frame 16 are integrated will be described with reference to Figures 5 to 7. Figure 8 is a flow diagram of the method for manufacturing the chuck table 14.

To manufacture the porous plate 21, first, the abrasive grains 13, the bond material 15, and the pore-forming material 17 are mixed to prepare a mixture 19 (mixture preparation step (S10)). Figure 2 is a partial cross-sectional side view showing the mixture preparation step (S10).

The abrasive grains 13 are made of silicon (Si), silicon carbide (SiC), alumina (Al ₂ O ₃ ), etc. The size of the abrasive grains 13 used for grinding, polishing, etc. is expressed in terms of grain size. Details of grain size are described in, for example, the JIS standard established by the Japanese Industrial Standards Committee (JISC).

The grain sizes described in this specification are in accordance with or similar to JIS R 6001-1:2017 (Grain sizes of abrasives for grinding wheels - Part 1: Coarse grains) and JIS R 6001-2:2017 (Grain sizes of abrasives for grinding wheels - Part 2: Fine grains), as well as the notations commonly used in the industry that manufactures and sells grinding wheels.

Details on how to determine the grain size are described in JIS R 6001-1:2017 and JIS R 6001-2:2017. The grain size of the abrasive grains is determined using a grain size distribution test method, such as a sieve analysis test method, an X-ray sedimentation test method, an electrical resistance test method, or a sedimentation tube test method.

In this embodiment, abrasive grains 13 with a grain size of F180 or more and F280 or less are used. The terms "more than" and "less than" in "more than F180 or more and F280 or less" indicate the lower and upper limits of the grain size. The smaller the number, the larger the maximum grain size, and the larger the number, the smaller the maximum grain size.

The particle size of F180 or more and F280 or less specifically refers to any of the particle sizes F180 and F220 specified in JIS R 6001-1:2017, and F230, F240, and F280 specified in JIS R 6001-2:2017.

The bonding material 15 is, for example, a powder, and includes a plurality of particles formed of a glass material such as quartz glass, soda glass, borosilicate glass, and alkali-free glass. Each particle may be, for example, spherical, or may be an irregular shape having one or more corners (so-called angular shape).

Also, spherical and irregular shapes may be mixed. In either case, the bond material 15 melts and deforms when heated during the firing process described below, and solidifies when cooled after melting, fixing the positions of the multiple abrasive grains 13.

The pore-forming material 17 is, for example, a powder, and is made up of multiple spherical particles made of an organic material such as acrylic resin or polystyrene foam. The particles that make up the pore-forming material 17 may also be hollow glass beads (i.e., fine glass spheres that contain air inside).

The shape of the particles that make up the pore-forming material 17 is not limited to a perfect sphere, but may be a sphere with multiple protrusions on the surface, or may be an irregular shape with one or more corners, as long as it is not elongated and needle-like. In any case, the pore-forming material 17 decomposes and disappears when heated during the firing process described below, and relatively large pores 17a (see Figure 7) are formed.

The average particle size of the particles that make up the pore-forming material 17 is 50 μm or more. For example, the average particle size of the pore-forming material 17 is selected from the range of 50 μm to 400 μm. By making the average particle size of the pore-forming material 17 50 μm or more, the pores 17a formed by the disappearance of the pore-forming material 17 can be made relatively large.

There are known methods for expressing particle size, such as geometric diameter and equivalent diameter. Geometric diameters include Feret diameter, maximum diameter in a specific direction (i.e., Krummbein diameter), Martin diameter, sieve diameter, etc., while equivalent diameters include diameter equivalent to a circle with a projected area (i.e., Heywood diameter), diameter equivalent to a sphere with equal surface area, diameter equivalent to a sphere with equal volume, Stokes diameter, light scattering diameter, etc.

As the pore-forming material 17 having an average particle diameter of 50 μm or more, for example, a pore-forming material 17 consisting of a plurality of particles having a median diameter (i.e., the particle diameter at which the cumulative frequency is 50%) of 50 μm or more, determined by either the geometric diameter or the equivalent diameter, is used.

The particle size of the pore-forming material 17 may be determined using a particle size distribution test method, similar to the particle size of the abrasive grains 13. For example, as a pore-forming material 17 having an average particle size of 50 μm or more, a pore-forming material 17 having an average diameter of 50 μm or more in a weight (or volume) standard distribution in a sieving test method, an X-ray transmission sedimentation test method, an electrical resistance test method, a sedimentation tube test method, etc. may be used.

The mixture 19 is obtained by mixing the abrasive grains 13, the bond material 15, and the pore-forming material 17. For example, an agitator 20 is used for mixing. The agitator 20 has a cylindrical container 22 with a bottom. One end of a shaft 24 of a rotary drive source (not shown) is fixed to the bottom surface of the cylindrical container 22.

The shaft 24 is tilted at a predetermined angle from the vertical direction (the direction of gravity). By tilting the shaft 24, mixing is performed efficiently when the cylindrical container 22 is rotated. After the mixture preparation step (S10), the mixture 19 is molded (mixture molding step (S20)).

Figure 3 is a partial cross-sectional side view showing the mixture molding step (S20). In the mixture molding step (S20), the mixture 19 is molded to form a disk-shaped (plate-shaped) molded body 19a. For example, a pressure molding device 30 is used to mold the mixture 19. The pressure molding device 30 has a disk-shaped mold frame 32.

The mold 32 is made of metal or ceramics, has a certain strength, and is a container that can withstand firing at high temperatures of 1300°C or higher. The mold 32 has a disk-shaped recess with approximately the same diameter as the porous plate 21.

After the mixture 19 is poured into the recess to a specified depth, a disk-shaped pressure plate 34 having approximately the same diameter as the recess is placed in the recess. Then, the pressure plate 34 is pressed downward with a specified stress using a columnar pressure shaft 36. This causes the mixture 19 to be compression molded, forming a disk-shaped molded body 19a.

After the mixture molding step (S20), a compact firing step (S30) is performed. In the compact firing step (S30), the compact 19a is fired to form a porous plate 21. FIG. 4 is a cross-sectional view showing the compact firing step (S30). When firing the compact 19a, for example, a firing furnace 38 is used.

In the compact firing step (S30), the mold 32 enclosing the compact 19a and the pressure plate 34 are placed in a firing furnace 38, and the firing furnace 38 is heated to fire the compact 19a. The firing is performed, for example, for about 10 hours at a predetermined temperature of 800°C or higher and 1000°C or lower.

This forms a disk-shaped porous plate 21. During the firing process, the pore-forming material 17 is vaporized by decomposition, combustion, etc., and is released from the porous plate 21. Therefore, pores 17a (see Figure 7) corresponding to the size of the pore-forming material 17 are formed in the porous plate 21.

After the compact firing step (S30), a porous plate fixing step (S40) is performed. FIG. 5(A) is a cross-sectional view showing the porous plate fixing step (S40). For example, an operator removes the porous plate 21 from the formwork 32 and fits it into the recess 16a of the frame 16. At this time, the porous plate 21 may be fixed to the recess 16a with an adhesive or the like.

The thickness of the porous plate 21 after firing (the length from the upper surface 21a to the lower surface 21b) is greater than the depth of the recess 16a. Therefore, the upper surface 21a of the porous plate 21 fixed to the recess 16a protrudes from the upper surface of the frame 16. Figure 5 (B) is a cross-sectional view of the frame 16 and the porous plate 21.

Next, the upper surface 21a of the porous plate 21 is ground to align the height of the upper surface 21a of the porous plate 21 with the upper surface of the frame 16 (porous plate grinding step (S50)). Figure 6 is a partially cross-sectional side view showing the porous plate grinding step (S50).

When grinding the upper surface 21a side, for example, a horizontal-axis type grinding device 40 is used. The horizontal-axis type grinding device 40 has a support table 42 that supports the object to be ground. A cylindrical spindle 44 is provided on the support table 42. The spindle 44 is positioned so that the rotation axis of the spindle 44 is approximately parallel to the upper surface of the support table 42.

A circular grinding wheel 46 is attached to the outer periphery of one end of the spindle 44. The other end of the spindle 44 is connected to a rotational drive source (not shown) such as a motor that rotates the spindle 44.

When grinding the upper surface 21a, first, the frame 16 is fixed onto the support table 42 so that the upper surface 21a is exposed upward. Next, the spindle 44 is rotated at high speed, and the lower part of the rotating grinding wheel 46 is brought into contact with the upper surface 21a of the porous plate 21.

At this time, the support base 42 and the spindle 44 are moved relative to each other in a direction along the upper surface 21a, and the lower part of the grinding wheel 46 is moved over the entire upper surface 21a. This grinds the entire upper surface 21a side, and makes the upper surface 21a of the porous plate 21 and the upper surface of the frame 16 flush with each other.

In this manner, the chuck table 14 is manufactured. In the porous plate grinding step (S50), the upper surface 21a of the porous plate 21 may be ground by infeed grinding to make the upper surface 21a of the porous plate 21 flush with the upper surface of the frame 16.

The grinding device used in infeed grinding is equipped with a chuck table (not shown) having a holding surface that suctions and holds the underside of the frame 16. A rotating shaft of a rotary drive source (not shown) such as a motor is connected to the lower part of the chuck table.

A cylindrical spindle (not shown) is disposed above the chuck table so as to be approximately parallel to the axis of rotation of the chuck table. An annular grinding wheel (not shown) is attached to the lower part of the spindle. On one side of the grinding wheel, multiple block-shaped grinding stones are disposed at approximately equal intervals along the circumference of the grinding wheel.

When grinding the porous plate 21, the chuck table and grinding wheel are rotated in the same direction while the frame 16 is held by suction on the holding surface. Then, the spindle is fed to the holding surface side of the chuck table for grinding while grinding water such as pure water is supplied to the upper surface 21a of the porous plate 21. The grinding wheel comes into contact with the upper surface 21a of the porous plate 21, and the upper surface 21a side is ground.

Figure 7 shows a cross section of the chuck table 14 and an enlarged cross section of the vicinity of the holding surface 14a. As shown in the enlarged cross section, pores 17a are formed inside the porous plate 21 due to the disappearance of the pore-forming material 17 with an average particle diameter of 50 μm or more.

The shape of the pores 17a roughly reflects the shape of the particles that make up the pore-forming material 17. The pores 17a are exposed on the holding surface 14a (i.e., the upper surface 21a of the porous plate 21 after grinding).

In addition, inside the porous plate 21, there are formed gaps 23 between the abrasive grains 13 and the bond material 15, gaps 23 between the abrasive grains 13, and gaps 23 between the bond materials 15, which are all different from the pores 17a. At least some of the gaps 23 communicate with the pores 17a.

When liquid is supplied to the holding surface 14a, the liquid is easily drawn into the pores 17a, which are larger than the gaps 23. The liquid drawn into the pores 17a is discharged from the pores 17a to the gaps 23 by capillary action.

Even when no negative pressure is applied to the porous plate 21, liquid supplied to the upper surface (one surface) 21a of the porous plate 21 is first sucked into the pores 17a, and then discharged from the pores 17a to the gaps 23 by capillary action.

Therefore, even if liquid seeps into the gap between the held surface of the workpiece 11 and the holding surface 14a while the workpiece 11 is being suction-held by the holding surface 14a, the liquid is easily sucked into and discharged from the inside of the porous plate 21. This makes it possible to prevent the liquid from adhering to the held surface.

The porosity, which is the ratio of the volume of the space including the pores 17a and the gaps 23 to the total volume of the porous plate, is adjusted to a predetermined value, for example, 30% or more and less than 60%. By setting the porosity to 30% or more, the discharge of liquid from the holding surface 14a to the inside of the porous plate 21 is promoted compared to when the porosity is less than 20%.

In addition, compared to when the porosity is 60% or more, the area of the pores 17a and gaps 23 exposed on the holding surface 14a is smaller, so when the workpiece 11 is cut, the shape of the pores 17a and gaps 23 exposed on the holding surface 14a is less likely to be transferred to the held surface of the workpiece 11. In addition, the size of chipping (defects) that may occur on the held surface side of the workpiece 11 during cutting can be reduced.

Returning to FIG. 1, other components of the cutting device 2 will now be described. A first conveying device 48 including a hand unit equipped with a suction pad is provided above the opening 4b. The first conveying device 48 conveys the workpiece 11 while sucking the workpiece 11 with the hand unit.

A gate-shaped support 4c is provided above the other end of the opening 4b, which is located on the opposite side to the one end in the X-axis direction, so as to straddle the opening 4b. A pair of processing unit movement mechanisms (indexing feed unit, cutting feed unit) 50 are provided on one side of the support 4c.

The pair of processing unit movement mechanisms 50 are provided with a pair of Y-axis guide rails 52 arranged on one surface of the support 4c and generally parallel to the Y-axis direction. Two Y-axis movement plates 54 are attached to the pair of Y-axis guide rails 52 in a manner that allows them to slide in the Y-axis direction.

A nut portion (not shown) is provided on one side of each Y-axis moving plate 54 (i.e., the support body 4c side). One Y-axis ball screw 56 that is generally parallel to the Y-axis guide rail 52 is rotatably connected to the nut portion of one Y-axis moving plate 54, and another Y-axis ball screw 56 is rotatably connected to the nut portion of the other Y-axis moving plate 54.

A Y-axis pulse motor 58 is connected to one end of each Y-axis ball screw 56. When the Y-axis pulse motor 58 rotates the Y-axis ball screw 56, each Y-axis moving plate 54 moves along the Y-axis guide rail 52.

A pair of Z-axis guide rails 60 that are generally parallel to the Z-axis direction are provided on the other side of each Y-axis moving plate 54 (i.e., the side opposite the support 4c). A Z-axis moving plate 62 is slidably attached to the pair of Z-axis guide rails 60.

A nut portion (not shown) is provided on one side of the Z-axis moving plate 62 (i.e., the support body 4c side), and a Z-axis ball screw 64 parallel to the Z-axis guide rail 60 is rotatably connected to this nut portion.

A Z-axis pulse motor 66 is connected to one end of the Z-axis ball screw 64. When the Z-axis pulse motor 66 rotates the Z-axis ball screw 64, the Z-axis moving plate 62 moves in the Z-axis direction along the Z-axis guide rail 60.

A cutting unit (processing unit) 70 that cuts (processes) the workpiece 11 is provided below each Z-axis moving plate 62. Each cutting unit 70 is arranged so that its longitudinal direction is aligned with the Y-axis direction.

The cutting unit 70 has a cylindrical spindle housing. The spindle housing partially accommodates the spindle 72 (see FIG. 9). The spindle 72 is supported in a rotatable manner within the spindle housing and is disposed approximately parallel to the Y-axis direction.

A rotation drive source (not shown), such as a servo motor, is connected to one end of the spindle 72. A receiving flange portion 74 is fixed to the other end of the spindle 72. A cylindrical boss portion (not shown) is provided in the radial center of the receiving flange portion 74.

The opening of the annular cutting blade 76 is inserted into the boss portion. A pressing flange portion 78 is fixed to the cutting blade 76 on the side opposite the receiving flange portion 74. In this way, the cutting blade 76 is attached to the spindle 72 while being clamped between the receiving flange portion 74 and the pressing flange portion 78.

The cutting blade 76 shown in FIG. 9 is a hubless type (so-called washer type) blade with an annular cutting edge, but the cutting blade 76 may also be a hub type blade (not shown) with a cutting edge provided on the outer periphery of a circular metal base.

A pair of cooler nozzle units 80 are provided below the spindle 72 at a position sandwiching both sides of the cutting blade 76. Each cooler nozzle unit 80 supplies cutting water (liquid) 82 such as pure water toward the contact area (so-called processing point) between the cutting blade 76 and the workpiece 11.

The cutting unit 70 is also provided with a shower nozzle unit (not shown) that supplies cutting water 82 to the outer periphery of the cutting blade 76. Referring again to FIG. 1, a camera unit 84 for capturing an image of the workpiece 11 is provided adjacent to the cutting unit 70.

The camera unit 84 has an imaging element such as a CMOS image sensor or a CCD image sensor, and a predetermined optical system such as a lens for forming an image on the imaging element (neither shown). An opening 4d is provided at a position opposite opening 4b from opening 4a.

A cleaning unit (processing unit) 90 is provided in the opening 4d to clean (process) the workpiece 11 after processing. The cleaning unit 90 has a chuck table 94 that rotates while holding the workpiece 11.

As shown in FIG. 10, the chuck table 94 has a frame 96 similar to the frame 16 described above. The recesses 96a, protrusions 96b, spaces 96c, and through holes 96d of the frame 96 correspond to the recesses 16a, protrusions 16b, spaces 16c, and through holes 16d of the frame 16, respectively, and therefore will not be described.

The above-mentioned porous plate 21 is fixed to the recess 96a. A rotation shaft 92a of a rotation drive source (not shown) such as a motor is connected to the bottom of the frame 96. When the rotation drive source operates, the chuck table 94 rotates around a rotation axis that is roughly parallel to the Z-axis direction (vertical direction).

A suction source 92b such as an ejector is connected to the through hole 96d via a specified flow path. A solenoid valve 92c is provided in the specified flow path. When the solenoid valve 92c is opened while the suction source 92b is operating, negative pressure acts on the upper surface (retaining surface 94a) of the porous plate 21.

A nozzle 98 is disposed above the chuck table 94. The nozzle 98 is connected to a gas supply source (not shown) that supplies compressed air and a liquid supply source (not shown) that supplies a liquid such as pure water.

The gas supply source has, for example, a compressor, a tank that stores air compressed by the compressor, and a filter that removes water droplets and dust from the air. The liquid supply source has, for example, a tank that stores liquid such as pure water, and a pump for supplying liquid from the tank to the nozzle 98.

The air and liquid are mixed together to form cleaning water 100, which is a gas-liquid mixed fluid (two fluids), and is sprayed from the nozzle 98 toward the holding surface 94a. Note that the nozzle 98 is not limited to spraying a gas-liquid mixed fluid, and may spray only liquid such as pure water as the cleaning water 100.

The nozzle 98 is fixed to one end of a metal arm. A swing mechanism (not shown) is connected to the other end of the arm. The operation of the swing mechanism causes the arm to swing in the radial direction of the chuck table 94. In this case, the nozzle 98 moves back and forth along an arc-shaped path in a direction approximately horizontal to the holding surface 94a.

Next, the procedure for machining the workpiece 11 using the cutting device 2 will be described. First, one workpiece 11 is transported from the cassette 6b to the chuck table 14 using the first transport device 48 or the like. Then, the back surface 11b side of the workpiece 11 is suction-held by the holding surface 14a of the chuck table 14.

Next, the camera unit 84 captures an image of the surface 11a of the workpiece 11, and the chuck table 14 is rotated a predetermined amount so that the planned division line along the first direction is parallel to the X-axis direction.

Then, the cutting blade 76, which is rotating at high speed, is positioned on an extension of one of the planned division lines along the first direction. At this time, the processing unit movement mechanism 50 is operated to position the lower end of the cutting blade 76 at a height between the front surface 11a and the back surface 11b.

Then, the chuck table 14 is moved in the X-axis direction by the X-axis movement mechanism. As a result, a cutting groove 11c (a so-called half-cut groove) of a predetermined depth that does not reach the back surface 11b is formed on the front surface 11a side.

Figure 9 is a partial cross-sectional side view showing how the cutting unit 70 cuts the workpiece 11. During cutting, the workpiece 11 is cut while spraying cutting water 82 from the cooler nozzle unit 80 and the shower nozzle unit onto the workpiece 11.

The cutting water 82 flows along the front surface 11a to the outside of the chuck table 14. However, the used cutting water 82 that reaches the outer periphery of the front surface 11a may seep into the gap between the back surface 11b (held surface) and the holding surface 14a.

As described above, the porous plate 21 of this embodiment has pores 17a formed by the pore-forming material 17 with an average particle size of 50 μm or more. Therefore, the used cutting water 82 that has penetrated between the back surface 11b and the holding surface 14a is easily sucked into the inside of the porous plate 21 and discharged. This makes it possible to suppress adhesion of the cutting water 82 to the back surface 11b side.

After cutting the workpiece 11 along the other planned dividing line parallel to the first direction, the processing unit moving mechanism 50 is operated to index and feed the cutting unit 70. This positions the cutting blade 76 on an extension line of the other planned dividing line adjacent to the cut planned dividing line in the Y-axis direction. Then, in the same manner, the workpiece 11 is cut along the planned dividing line.

After cutting the workpiece 11 along all of the planned division lines parallel to the first direction in this manner, the rotary drive source is operated to rotate the chuck table 14 by 90 degrees. Then, a second direction perpendicular to the first direction is positioned parallel to the X-axis direction, and the workpiece 11 is similarly cut along all of the planned division lines parallel to the second direction.

After cutting is completed, the workpiece 11 is transported to the cleaning unit 90 while the front surface 11a of the workpiece 11 is held by suction using a second transport device (not shown). The back surface 11b of the workpiece 11 is then held by suction using the holding surface 94a of the chuck table 94.

Next, the chuck table 94 is rotated, and the nozzle 98 is moved back and forth along an arc-shaped path in a direction approximately horizontal to the holding surface 94a while spraying cleaning water 100 from the nozzle 98 onto the surface 11a. Figure 10 is a partial cross-sectional side view showing how the workpiece 11 is cleaned (processed) by the cleaning unit 90.

During cleaning, cleaning water 100 that reaches the outer periphery of front surface 11a may get into the gap between back surface 11b and holding surface 94a. However, cleaning water 100 that penetrates between back surface 11b and holding surface 94a is easily sucked into and discharged from the porous plate 21, so adhesion of liquid to the back surface 11b can be suppressed.

The workpiece 11 cleaned in the cleaning unit 90 is transported directly from the cleaning unit 90 to the cassette 6b using the first transport device 48 or the like. In this way, the cutting device 2 can omit the air blow unit for drying the back surface 11b.

Furthermore, since the processing time required to remove liquid using the air blow unit is eliminated, the processing time from when the workpiece 11 is removed from the cassette 6b to when the cut workpiece 11 is loaded into the cassette 6b can be shortened. In other words, more efficient processing is possible than when an air blow unit is provided.

Next, we will explain an experimental example that evaluates the relationship between the average particle size of the pore-forming material 17 and the amount of liquid remaining after cleaning. In this experimental example, the average particle size of the pore-forming material 17 was set to various values, and multiple porous plates 21 shown in Experimental Example 1 to Experimental Example 8 were manufactured.

Specifically, in the mixture preparation step (S10), SiC abrasive grains 13 with a grain size of F180, a borosilicate glass bond material 15, and a pore-forming material 17 with an average particle size of 20 μm to 400 μm were prepared. The average particle size of the pore-forming material 17 was measured using a particle size distribution measuring device using a laser diffraction/scattering method.

In the mixture preparation step (S10), the volume ratio of the abrasive grains 13 to the abrasive grains 13 and the bond material 15 was set to 50% or more and 80% or less. In addition, the weight ratio of the abrasive grains 13 to the pore-forming material 17 (abrasive grains:pore-forming material) was set to 4:1 to 5:1.

Then, eight porous plates 21 were manufactured according to steps S20 to S50 described above. The porosity of each porous plate 21 was 40% or more and 55% or less. The volume ratio of the pores 17a to the gaps 23 (pores:gaps) was 1:2 to 1:4.

Then, the above-mentioned cleaning was performed using the chuck table 94 equipped with the porous plate 21 of Experimental Example 1 to Experimental Example 8, and the remaining liquid after cleaning and the degree to which the unevenness of the holding surface 94a was transferred to the workpiece 11 were evaluated. The evaluation results are shown in [Table 1].

A silicon wafer with a diameter of 300 mm was used as the workpiece 11. During cleaning, the back surface 11b side was held by the holding surface 94a, and the chuck table 94 was rotated at 200 rpm. In addition, cleaning water 100 was sprayed from the nozzle 98 while the arm was oscillating. At this time, the air pressure was set to 0.2 MPa, and the flow rate of pure water was set to 200 (ml/min).

In the "Liquid Remaining" section of Table 1, the operator visually inspected the back surface 11b after cleaning and rated the amount of remaining liquid on a three-point scale. × indicates that sufficient liquid remained on the back surface 11b. △ indicates that some liquid remained on the back surface 11b, and ◯ indicates that almost no liquid remained on the back surface 11b.

Considering the experimental results, in order to reduce the amount of liquid remaining on the back surface 11b, it is preferable to set the average diameter of the pore-forming material 17 to 30 μm or more, and more preferably 50 μm or more. However, if the average diameter of the pore-forming material 17 is made too large, the pores 17a exposed to the holding surface 94a will also become large.

Therefore, due to the suction force from the holding surface 94a acting on the back surface 11b, the unevenness of the holding surface 94a is transferred to the workpiece 11 during cutting. In the "Transfer of unevenness to the workpiece" item in [Table 1], the back surface 11b after cleaning was visually observed by an operator, and the unevenness of the back surface 11b was evaluated on a three-point scale.

× indicates that the unevenness was transferred to the entire back surface 11b side. △ indicates that the unevenness was transferred to a part of the back surface 11b side, and ◯ indicates that the unevenness was not transferred to the back surface 11b side. In view of the experimental results, from the viewpoint of reducing the transfer of unevenness, the average diameter of the pore-forming material 17 is preferably 300 μm or less, and more preferably 200 μm or less.

Furthermore, from the viewpoint of reducing residual liquid and reducing the transfer of unevenness, the average diameter of the pore-forming material 17 is preferably 30 μm or more and 300 μm or less, and more preferably 50 μm or more and 200 μm or less.

In addition, the structures, methods, etc. according to the above embodiments can be modified as appropriate without departing from the scope of the purpose of the present invention.

2: Cutting device 4: Base 4a, 4b, 4d: Opening 4c: Support 6a: Cassette elevator, 6b: Cassette 10: Table cover 10a: Rotating shaft, 10b: Suction source, 10c: Solenoid valve 11: Workpiece, 11a: Front surface, 11b: Back surface, 11c: Cutting groove 12: Bellows-shaped cover 13: Abrasive grain 14: Chuck table 14a: Holding surface 15: Bond material 16: Frame, 16a: Concave, 16b: Convex, 16c: Space, 16d: Through hole 17: Pore forming material, 17a: Pore 19: Mixture, 19a: Molded body 20: Agitator 21: Porous plate, 21a: Upper surface, 21b: Lower surface 22: Cylindrical container 23: Gap 24: Shaft 30: Pressure molding device 32: Mold 34 : Pressing plate 36 : Pressing shaft 38 : Baking furnace 40 : Grinding device 42 : Support table 44 : Spindle 46 : Grinding wheel 48 : First conveying device 50 : Processing unit moving mechanism 52 : Y-axis guide rail 54 : Y-axis moving plate 56 : Y-axis ball screw 58 : Y-axis pulse motor 60 : Z-axis guide rail 62 : Z-axis moving plate 64 : Z-axis ball screw 66 : Z-axis pulse motor 70 : Cutting unit 72 : Spindle 74 : Receiving flange portion 76 : Cutting blade 78 : Pressing flange portion 80 : Cooler nozzle unit 82 : Cutting water 84 : Camera unit 90 : Cleaning unit 92a: Rotating shaft, 92b: Suction source, 92c: Solenoid valve 94 : Chuck table, 94a: Holding surface 96 : Frame, 96a: Concave portion, 96b: Convex portion, 96c: Space, 96d: Through hole, 98: Nozzle, 100: Cleaning water

Claims (3)

A method for manufacturing a porous plate used in a chuck table, comprising:
a mixture preparation step of preparing a mixture of a plurality of abrasive grains, a bonding material which is melted by heating and cooled after melting to fix the plurality of abrasive grains, and a pore-forming material having an average particle size of 50 μm or more and disappearing by heating;
A mixture molding step of molding the mixture to form a plate-shaped body;
A molded body sintering step of forming a porous plate by sintering the molded body;
Equipped with
The porous plate has pores formed by the disappearance of the pore-forming material, and first gaps that are different from the pores and are between the abrasive grains and the bond material,
The porosity of the porous plate is 40% or more and 55% or less,
the pores and the gaps are in communication with each other, and the pores are exposed on one surface of the porous plate;
A method for manufacturing a porous plate, characterized in that when liquid is supplied to the one surface, the liquid is sucked into the pores and discharged from the pores into the gaps by capillary action. the gaps include second gaps between the abrasive grains and third gaps between the bond materials,
The method for manufacturing a porous plate according to claim 1, characterized in that the volume ratio of the pores to the gaps (the pores:the gaps) is 1:2 to 1:4. A method for manufacturing a chuck table including a porous plate manufactured by the method for manufacturing a porous plate according to claim 1 or 2, and a frame body supporting the porous plate and having a suction path for transmitting a negative pressure from a suction source to the porous plate, comprising:
A method for manufacturing a chuck table, comprising the step of fixing the porous plate in the recess of the frame with an adhesive.

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