Detection method and processing apparatus

Abstract

To detect local thickness abnormality in a wafer.SOLUTION: A method for detecting a thickness abnormality in a wafer includes a measuring step for measuring the thickness of the wafer at a plurality of locations in the wafer by relatively moving a sensor head of a thickness measuring device for measuring the thickness of the wafer without contacting the wafer and a first holding table for holding the wafer on a first holding surface within a predetermined plane, and a detection step for detecting the thickness abnormality in the wafer using a measurement result from the measuring step.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a detection method for detecting abnormal thickness of a wafer, a holding table, and a processing unit including a spindle and capable of processing a wafer held on a holding surface of the holding table with a processing tool attached to a lower end portion of the spindle.

Background Art

[0002] When thinning a wafer by grinding the back surface of the wafer held by a chuck table with a grinding wheel, in order not to damage the device formed on the surface on the side opposite to the back surface, the surface may be protected by attaching a protective tape to the surface (see, for example, Patent Document 1).

[0003] Even when a protective tape is attached to the surface of the wafer, the outer surface of the protective tape is not necessarily flat, and the unevenness of the device may be reflected on the outer surface of the protective tape. In this case, before grinding the wafer, the protective tape may be cut and flattened with a surface planer (also referred to as a bite cutting device) so that the unevenness on the outer surface of the protective tape is not reflected on the ground wafer (see, for example, Patent Document 2).

[0004] The surface planer includes a chuck table and a spindle, and a bite tool is attached to a lower end portion of the spindle. When cutting the protective tape with the bite tool, first, the protective tape is exposed upward, and the wafer is sucked and held by the chuck table in a manner such that the holding surface of the chuck table and the wafer are in contact with each other.

[0005] At this time, for example, (i) particles such as cutting chips, and (ii) burrs generated during self-grinding for correcting the shape of the holding surface may be present on the holding surface, causing the protective tape to bulge locally. When the outer surface of the protective tape is flattened by cutting in this state, after cutting, the protective tape becomes locally thinner at the bulging portion of the protective tape.

[0006] Similarly, when there are local depressions on the holding surface, the wafer and the protective tape are suction-held so as to follow the shape of the holding surface. Therefore, after cutting, the protective tape becomes locally thicker at the locations where the holding surface was depressed.

[0007] Thus, even though the outer surface of the protective tape has been flattened by cutting, if a local thickness abnormality of the protective tape occurs, in the subsequent grinding process, the wafer is ground while the outer surface of the protective tape is suction-held so that the back surface of the wafer is exposed. As a result, a local thickness abnormality is also formed in the wafer at the location of the local thickness abnormality of the protective tape.

[0008] Also, even when there is no local thickness abnormality in the protective tape, if there are local irregularities formed on the holding surface of the chuck table of the grinding device, local thickness abnormalities will be formed in the wafer thinned by grinding.

[0009] Furthermore, when the wafer is suction-held by the chuck table of the grinding device in a manner such that the wafer and the holding surface are in direct contact without attaching the protective tape to the wafer, if there are local irregularities formed on the holding surface of the chuck table of the grinding device, local thickness abnormalities will similarly be formed in the wafer thinned by grinding.

[0010] Local thickness abnormalities in the wafer may affect the device chips formed by singulating the wafer into individual devices, and may also lead to processing defects in the manufacturing process after the grinding process.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0012] The present invention has been made in view of such problems, and an object thereof is to detect a local thickness abnormality of a wafer.

Means for Solving the Problems

[0013] According to one aspect of the present invention, there is provided a detection method for detecting a thickness abnormality of a wafer, including a sensor head of a thickness measuring instrument that measures the thickness of the wafer without contacting the wafer, and a first holding table that holds the wafer on a first holding surface. A measuring step of measuring the thickness of the wafer at a plurality of locations on the wafer by relatively moving them in a predetermined plane, and a detecting step of detecting an abnormality in the thickness of the wafer using the measurement results in the measuring step. A detection method is provided.

[0014] Preferably, the measuring step includes measuring the thickness of the wafer on a first circumference having a first diameter while rotating the first holding table that holds the wafer with the position of the sensor head fixed in the predetermined plane.

[0015] Also, preferably, the measuring step includes measuring the thickness of the wafer on a second circumference having a second diameter smaller than the first diameter and on a third circumference having a third diameter larger than the first diameter while rotating the first holding table that holds the wafer with the position of the sensor head fixed in the predetermined plane.

[0016] Also, preferably, in the detecting step, an abnormality in the thickness of the wafer is detected by comparing the difference between the maximum value and the minimum value of the thickness of the wafer measured in the measuring step with a predetermined threshold value.

[0017] Preferably, the detection method further includes a grinding step of holding the first surface of the wafer by the first holding table and grinding the second surface of the wafer, which is located on the side opposite to the first surface in the thickness direction of the wafer, with a grinding wheel, and starting the grinding step before the measuring step.

[0018] Preferably, in the detection step, an abnormality in the thickness of the wafer is detected by comparing the difference between the maximum value and the minimum value of the thickness of the wafer measured in the measuring step with a predetermined threshold value that is larger than the undulation value of the thickness of the wafer after the grinding step.

[0019] Preferably, in the grinding step, by grinding the second surface of the wafer, a circular recess having a depth that does not reach the first surface in the thickness direction from the second surface and a ring-shaped reinforcing portion surrounding the outer peripheral portion of the circular recess are formed.

[0020] Preferably, the detection method further includes an attaching step of attaching a protective tape to the first surface so as to cover the first surface of the wafer before the grinding step, and moving a turning tool having a cutting edge linearly along a predetermined direction with respect to the spindle while rotating the cutting edge around the spindle and fixing the cutting edge at a predetermined height, and holding the wafer by a second holding surface so that the protective tape is exposed, thereby cutting the protective tape with the turning tool to flatten the protective tape.

[0021] According to another aspect of the present invention, there is provided a processing apparatus including: a holding table having a holding surface for holding a wafer; a rotation drive mechanism including a first motor for rotating a rotation axis of the holding table disposed at a central portion of the holding surface; a first moving mechanism having a second motor for moving the holding table along a first direction; a processing unit having a spindle and capable of processing the wafer held on the holding surface with a processing tool attached to a lower end portion of the spindle; a thickness measuring device having a sensor head for measuring a thickness of the wafer without contacting the wafer; a second moving mechanism having a third motor for relatively moving the sensor head with respect to the holding table along a second direction intersecting the first direction; a third moving mechanism having a fourth motor for pivoting the sensor head relative to the holding table within a predetermined plane defined by the first direction and the second direction; one or both of the above; and a controller having a processor and a memory for controlling the rotation drive mechanism, the processing unit, the thickness measuring device, the first moving mechanism, the second moving mechanism, and the third moving mechanism. The controller includes a determination unit for determining an abnormality in the thickness of the wafer by executing a program stored in the memory with the processor. The determination unit determines an abnormality in the thickness of the wafer based on measurement results obtained by measuring the thickness of the wafer at a plurality of locations on a predetermined circumference around the rotation center of the rotation axis.

[0022] According to still another aspect of the present invention, there is provided a processing apparatus including: a holding table having a holding surface for holding a wafer; a rotation driving mechanism including a first motor for rotating a rotation axis of the holding table disposed at a central portion of the holding surface; a first moving mechanism having a second motor for moving the holding table along a first direction; a processing unit having a spindle and capable of processing the wafer held on the holding surface with a processing tool attached to a lower end portion of the spindle; a thickness measuring device having a sensor head disposed directly above a moving path of a center of the holding surface and for measuring a thickness of the wafer without contacting the wafer; and a controller having a processor and a memory and for controlling the rotation driving mechanism, the processing unit, the thickness measuring device, and the first moving mechanism, wherein the controller includes a determination unit for determining an abnormality in the thickness of the wafer by executing a program stored in the memory with the processor, and the determination unit determines the abnormality in the thickness of the wafer based on measurement results obtained by measuring the thickness of the wafer at a plurality of locations on a predetermined circumference around a rotation center of the rotation axis.

[0023] Preferably, the processing apparatus further includes a display whose operation is controlled by the controller, and when the determination unit determines that there is an abnormality in the thickness of the wafer, the controller causes the display to display one or both of a value of the thickness of the wafer determined to be abnormal and a message indicating that there is an abnormality in the thickness.

Advantages of the Invention

[0024] In a detection method according to one aspect of the present invention, a thickness of a wafer is measured at a plurality of locations of the wafer by relatively moving, within a predetermined plane, a sensor head of a thickness measuring device for measuring the thickness of the wafer without contacting the wafer and a first holding table holding the wafer on a first holding surface. Then, based on a measurement result in a measurement step, an abnormality in the thickness of the wafer can be detected.

[0025] In the processing apparatus according to another aspect of the present invention, based on measurement results obtained by measuring the thickness of the wafer at a plurality of locations on a predetermined circumference around the rotation center of the rotation axis of the holding table, a discrimination unit in the controller of the processing apparatus can discriminate an abnormality in the thickness of the wafer.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

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Figure 8

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DETAILED DESCRIPTION OF THE INVENTION

[0027] (First Embodiment) With reference to the accompanying drawings, an embodiment according to one aspect of the present invention will be described. FIG. 1 is a flowchart of a detection method for detecting thickness anomalies of a wafer 11 (see FIG. 8(B)) in the first embodiment.

[0028] In this embodiment, the steps are performed in the order of the sticking step S10, the cutting step S20, the grinding step S30, the measurement step S40, and the detection step S50. More specifically, after the completion of the sticking step S10, the cutting step S20 is started, and after the completion of the cutting step S20, the grinding step S30 is started.

[0029] However, as will be described in detail later, for the grinding step S30, the measurement step S40, and the detection step S50 in this embodiment, the measurement step S40 is started after the start and before the completion of the grinding step S30, and the detection step S50 is started after the start and before the completion of the measurement step S40.

[0030] That is, there is a time when the grinding step S30, the measurement step S40, and the detection step S50 are performed simultaneously in parallel. Of course, the present invention is not limited to this embodiment, and the thickness anomaly of the wafer 11 can also be detected by starting the measurement step S40 after the completion of the grinding step S30 and starting the detection step S50 after the completion of the measurement step S40.

[0031] First, with reference to FIG. 2, the wafer 11 to be processed and the protective tape 19 will be described. The wafer 11 of this embodiment is disk-shaped and mainly composed of a silicon (Si) single crystal substrate. However, a metal layer, an insulating layer, etc. are formed on the wafer 11, and impurities are doped inside the wafer 11.

[0032] The diameter of the wafer 11 is, for example, 4 inches (about 100 mm) or more and 12 inches (about 300 mm) or less. The thickness of the wafer 11 before the grinding process S30 varies according to the diameter of the wafer 11, but is, for example, in the range of about 500 μm to about 800 μm.

[0033] The wafer 11 has a circular front surface (first surface) 11a and a back surface (second surface) 11b, respectively. The back surface 11b and the front surface 11a are located on opposite sides in the thickness direction 11c of the wafer 11, and the distance from the back surface 11b to the front surface 11a is the thickness of the wafer 11.

[0034] Note that there are no restrictions on the material, shape, structure, size, etc. of the wafer 11. The material of the single-crystalline substrate constituting the wafer 11 may have other semiconductor materials other than silicon, such as gallium arsenide (GaAs), gallium nitride (GaN), and silicon carbide (SiC).

[0035] The front surface 11a of the wafer 11 is partitioned by a plurality of division planned lines (i.e., streets) 13 arranged in a grid pattern, and devices 15 such as ICs (Integrated Circuits) and LEDs (Light Emitting Diodes) are formed in each of the partitioned regions. Note that there are no restrictions on the type, quantity, shape, structure, size, arrangement, etc. of the device 15.

[0036] The wafer 11 has, on the front surface 11a side, a circular device region 17a in which a plurality of devices 15 are arranged, and an annular outer peripheral surplus region 17b surrounding the device region 17a. Note that in FIG. 2, for convenience of explanation, a broken line is attached to the boundary between the device region 17a and the outer peripheral surplus region 17b, but no clear boundary line is displayed on the actual wafer 11.

[0037] As will be described later, in the grinding process S30, the back surface 11b side of the circular region corresponding to the device region 17a is ground, but the back surface 11b side corresponding to the outer peripheral surplus region 17b is not ground. Therefore, the thickness of the outer peripheral surplus region 17b does not change before and after the grinding process S30.

[0038] After the grinding process S30, the outer peripheral surplus region 17b functions as a ring-shaped reinforcing portion 11e (see FIG. 8(B)) for reducing the deflection of the device region 17a thinned in the grinding process S30. The ring-shaped reinforcing portion 11e suppresses a significant decrease in the rigidity of the wafer 11, and facilitates the conveyance, processing, etc. of the wafer 11 as compared with the case where the ring-shaped reinforcing portion 11e is not present.

[0039] In the present embodiment, before grinding the wafer 11, a circular protective tape 19 is attached to the surface 11a of the wafer 11 in order to prevent damage to the device 15 during grinding. The protective tape 19 has a base material layer having substantially the same diameter as the wafer 11.

[0040] The base material layer has a thickness of, for example, 5 μm or more and 200 μm or less, and is formed of a resin such as polyolefin (PO), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), or the like.

[0041] An adhesive layer (i.e., glue layer) is provided substantially over the entire surface of one side of the base material layer. The adhesive layer is, for example, a layer of an adhesive resin that cures when irradiated with heat or ultraviolet rays and whose adhesive force decreases, and is formed of a silicone-based material, an acrylic-based material, an epoxy-based material, or the like.

[0042] The base material layer is exposed on the outer surface 19a of the protective tape 19, and the adhesive layer is exposed on the inner surface 19b of the protective tape 19. FIG. 2 is a diagram showing the attaching process S10. In the attaching process S10, the inner surface 19b of the protective tape 19 is attached to the wafer 11 so that the protective tape 19 covers substantially the entire surface 11a, thereby forming a wafer unit 21.

[0043] In the wafer unit 21, the outer surface 19a (i.e., the base material layer) is exposed, and the inner surface 19b (i.e., the adhesive layer) is in contact with the surface 11a. However, the present invention is not limited to this example, and the protective tape 19 may have only the base material layer without having an adhesive layer.

[0044] When the protective tape 19 has no adhesive layer, the protective tape 19 is heat-pressed onto the surface 11a, whereby the protective tape 19 is adhered to the wafer 11. In this case, even if the protective tape 19 is peeled off from the wafer 11, there is an advantage that no residue of the adhesive layer remains on the surface 11a.

[0045] In the sticking step S10, when the protective tape 19 is stuck to the surface 11a, the unevenness of the device 15 is reflected on the outer surface 19a. Therefore, in order to reduce the unevenness of the outer surface 19a, the outer surface 19a of the protective tape 19 is flattened by cutting the protective tape 19 using a surface planer 2 (see FIG. 3) (cutting step S20).

[0046] As shown in FIG. 3, the surface planer 2 has a disk-shaped chuck table (second holding table) 4. The X-axis direction (processing feed direction), Y-axis direction, and Z-axis direction (height direction) shown in FIG. 3 are orthogonal to each other.

[0047] The chuck table 4 has a disk-shaped frame body formed of a metal such as stainless steel. On the top surface of the frame body, a disk-shaped recess having a smaller diameter than the outer diameter of the outer periphery of the frame body is formed. A plurality of support pins arranged at substantially equal intervals are provided in this recess.

[0048] The longitudinal direction of each support pin is substantially parallel to the thickness direction of the chuck table 4. In FIG. 3, only a plurality of pins located closest to the front are shown in consideration of the visibility of the drawing, but a large number of pins also exist in the depth direction of the paper surface. Each support pin is also formed of a metal such as stainless steel.

[0049] In the frame body, a flow path is formed so as to penetrate the frame body at the central portion in the radial direction of the frame body. A suction source (not shown) such as a vacuum pump is connected to this flow path. The negative pressure generated by the suction source is transmitted to the gaps between the support pins.

[0050] A plating layer made of a metal such as nickel is formed on the top surface of the frame body and the top surface of each support pin. The top surface of the frame body and the top surface of each support pin are substantially flush with each other, and constitute a substantially flat holding surface (second holding surface) 4a along the XY plane.

[0051] Foreign substances 4b such as the above-mentioned particles and burrs may adhere to the holding surface 4a. In FIG. 3, the foreign substance 4b is shown exaggerated. The size of the foreign substance 4b is several micrometers. For example, when the holding surface 4a is taken as the reference position (zero micrometers) in the Z-axis direction, the position of the upper end of the foreign substance 4b in the Z-axis direction is from 2 μm to 3 μm.

[0052] The chuck table 4 is supported by an X-axis direction moving plate (not shown) via a support portion 6. The X-axis direction moving plate is slidably mounted on a pair of guide rails arranged along the X-axis direction respectively.

[0053] A nut portion (not shown) is fixed to the lower surface side of the X-axis direction moving plate. A screw shaft (not shown) arranged along the X-axis direction is rotatably attached to the nut portion via a plurality of balls (not shown).

[0054] A stepping motor (not shown) is attached to one end of the screw shaft. By operating the stepping motor, the X-axis direction moving plate moves along the X-axis direction together with the chuck table 4.

[0055] A columnar spindle housing (not shown) is provided above the holding surface 4a. The longitudinal direction of the spindle housing is arranged along the Z-axis direction. A Z-axis direction moving mechanism (not shown) having a ball screw is fixed to the spindle housing.

[0056] The height position of the spindle housing is adjusted by the Z-axis direction moving mechanism. A part of the columnar spindle 8 is rotatably accommodated in the spindle housing by using an air bearing or the like.

[0057] Near the upper end of the spindle 8, a motor (not shown) is provided. The rotor of this motor corresponds to the spindle 8. At the lower end of the spindle 8, a disk-shaped wheel mount 10 made of metal is fixed.

[0058] An annular cutting wheel (cutting tool) 12 is mounted on the lower surface side of the wheel mount 10. The cutting wheel 12 has an annular base 12a. At a part of the base 12a, the upper end of a rectangular parallelepiped-shaped shank 12b is attached.

[0059] The longitudinal direction of the shank 12b is arranged along the Z-axis direction. At the lower end of the shank 12b, a cutting edge 12c formed of diamond or the like is fixed. When the spindle 8 is rotated, the cutting wheel 12 rotates around the spindle 8.

[0060] FIG. 3 is a view showing a cutting step S20 of flattening the outer surface 19a of the protective tape 19 using the surface planer 2. In the cutting step S20, first, with the back surface 11b and the holding surface 4a in contact so that the protective tape 19 is exposed, a negative pressure is transmitted to the holding surface 4a to suck and hold the wafer 11 on the holding surface 4a.

[0061] Next, while rotating the spindle 8 and the cutting wheel 12, the position of the spindle housing in the Z-axis direction is adjusted and fixed so that the height of the lower end of the cutting edge 12c is slightly lower than the height of the outer surface 19a.

[0062] When adjusting the height of the cutting edge 12c, usually, it is unknown whether there is an abnormally protruding or sunken area on the outer surface 19a. Also, an abnormally protruding or sunken area is generally a very small part of the outer surface 19a. Therefore, in this embodiment, such an area is not taken into consideration when adjusting the height of the cutting edge 12c.

[0063] The distance Δ from the outer surface 19a to the lower end of the cutting edge 12c in the Z-axis direction corresponds to the thickness of the protective tape 19 removed by cutting. Therefore, the distance Δ is appropriately adjusted according to the finished thickness of the protective tape 19.

[0064] Next, with the height of the cutting edge 12c fixed, the tool wheel 12 is rotated and cutting water (not shown), such as pure water, is supplied from a nozzle (not shown) to the outer surface 19a while the chuck table 4 is moved along the X-axis direction.

[0065] That is, the chuck table 4 is linearly moved along the X-axis direction (predetermined direction) orthogonal to the Z-axis direction with respect to the spindle 8 arranged along the Z-axis direction. Thereby, the outer surface 19a side of the protective tape 19 is cut and flattened.

[0066] Note that what is cut in the cutting step S20 is the base material layer of the protective tape 19, and the adhesive layer is not cut. Also, in the cutting step S20, a certain thickness is left without removing all of the base material layer. FIG. 4(A) is a cross-sectional view of the wafer unit 21 and the like after the cutting step S20.

[0067] As shown in FIG. 4(A), the height of the outer surface 19a after the cutting step S20 is the same as the height of the lower end of the cutting edge 12c, so it becomes substantially flat. However, the protective tape 19 has a thinning region 19c having an amorphous shape like an amoeba that is locally thinned due to the presence of the foreign matter 4b.

[0068] FIG. 4(B) is a cross-sectional view of the wafer unit 21 and the like removed from the chuck table 4. When the suction holding on the holding surface 4a is released, the deformation of the wafer 11 is also eliminated. As shown in FIG. 4(B), in the cutting step S20, the protective tape 19 is locally thinned.

[0069] That is, in the cutting step S20, a thinning region 19c in which the protective tape 19 is locally thinned is formed at the raised portion of the protective tape 19 corresponding to the foreign matter 4b within the holding surface 4a.

[0070] In one example, the thickness of the protective tape 19 before the cutting step S20 is 255 μm, and the thickness of the protective tape 19 excluding the thinning region 19c after the cutting step S20 is 235 μm. After the cutting step S20, the back surface 11b side of the wafer 11 is ground using the grinding device 20.

[0071] First, the grinding device 20 will be described with reference to FIGS. 5 to 7. FIG. 5 is a perspective view of the grinding device (processing device) 20. The X-axis direction (first direction), Y-axis direction, and Z-axis direction (height direction) shown in FIG. 5 are perpendicular to each other.

[0072] Note that the grinding device 20 of the present embodiment is a manual type in which the loading and unloading of the wafer unit 21 and the like are performed by an operator, but it may also be a full-auto type that automatically performs loading, grinding, cleaning, and unloading.

[0073] The grinding device 20 has a base 22 that supports or houses components. On the upper surface of the base 22, a rectangular opening 22a having a long hand portion in the X-axis direction is formed. In a plan view of the grinding device 20, a disk-shaped chuck table (holding table, first holding table) 24 is provided in the opening 22a.

[0074] The chuck table 24 has a disk-shaped frame body formed of non-porous dense ceramics. On the top surface of the frame body, a disk-shaped recess having a smaller diameter than the outer diameter of the outer periphery of the frame body is formed. A disk-shaped porous plate having substantially the same diameter as the recess is fixed to this recess.

[0075] The porous plate is formed of porous ceramics. A suction source (not shown) such as a vacuum pump is connected to the porous plate via a flow path formed in the frame body. The negative pressure generated by the suction source is transmitted to the top surface of the porous plate.

[0076] The porous plate has a substantially flat bottom surface and a top surface having an annular recessed region around the center. That is, when the porous plate is viewed in a cross-section passing through the center of the bottom surface and perpendicular to the bottom surface, the top surface has a double concave shape in which the center of the top surface and the outer peripheral end of the top surface protrude compared to other regions.

[0077] For example, the annular recessed region on the top surface of the porous plate is recessed by a predetermined distance of 10 μm or more and 30 μm or less in the thickness direction of the chuck table 24 compared to the center and the outer peripheral end of the top surface. However, since the amount of recess is so small, in FIGS. 8(A) and 8(B) described later, the top surface of the porous plate is shown as being substantially flat.

[0078] The top surface of the frame body and the top surface of the porous plate are substantially flush with each other and function as a holding surface (first holding surface) 24a for sucking and holding the wafer unit 21 (that is, the wafer 11).

[0079] A first cover 26 having a substantially regular outer shape is disposed on the outer peripheral portion of the chuck table 24. On both sides of the first cover 26 in the X-axis direction, bellows-shaped second covers 28 that can expand and contract along the X-axis direction are provided.

[0080] As shown in FIG. 6, the chuck table 24 is rotatably supported by an annular table base 30 having bearings. A rotary shaft 24b of the chuck table 24 is inserted into a through hole (not shown) at the center of the table base 30. The rotary shaft 24b is disposed at the center in the radial direction of the chuck table 24. The table base 30 is supported by an inclination adjustment mechanism 32.

[0081] FIG. 6 is a diagram showing an inclination adjustment mechanism 32, a rotation drive mechanism 42, etc. of the chuck table 24. The inclination adjustment mechanism 32 adjusts the inclination of the table base 30 so that an arc-shaped region connecting the center 24a1, the recessed region, and the outer peripheral end in a cross-sectional view of the holding surface 24a meshes with the outer peripheral side surfaces of a plurality of grinding wheels 80b in a grinding wheel 80 described later (see FIG. 8(A)).

[0082] However, the inclination angle of the table base 30 with respect to the XY plane is extremely small. The inclination adjustment mechanism 32 has a fixed shaft 32a that supports a part of the table base 30 and a plurality of movable shafts 32b that support the other parts of the table base 30, respectively. The fixed shaft 32a and the two movable shafts 32b are arranged at substantially equal intervals along the circumferential direction of the table base 30.

[0083] In FIG. 6, the fixed shaft 32a and the two movable shafts 32b are shown in a simplified manner. The length of the fixed shaft 32a in the Z-axis direction is fixed, and the length of the movable shaft 32b in the Z-axis direction is adjustable. For example, the height position of the upper end of the movable shaft 32b is adjusted by the amount of screwing into the screw hole of the screw shaft that constitutes the movable shaft 32b.

[0084] The fixed shaft 32a and the two movable shafts 32b are supported by a moving plate 44. A servo motor (first motor) 34 that rotates the rotation shaft 24b of the chuck table 24 is fixed to the moving plate 44. A drive pulley 36 is fixed to the output shaft of the servo motor 34.

[0085] Also, a driven pulley 38 is fixed to the lower end of the rotation shaft 24b of the chuck table 24, and an endless belt 40 is wound around the drive pulley 36 and the driven pulley 38. When the servo motor 34 is operated, power is transmitted to the rotation shaft 24b.

[0086] As a result, the chuck table 24 rotates around the rotation shaft 24b. The servo motor 34, the drive pulley 36, the driven pulley 38, the endless belt 40, etc. constitute a rotational drive mechanism 42 for rotating the rotation shaft 24b.

[0087] Returning to FIG. 5, the moving plate 44 is slidably attached onto a pair of guide rails 46 arranged along the X-axis direction. A nut portion 48 is fixed to the lower surface side of the moving plate 44. A screw shaft 50 arranged along the X-axis direction is rotatably attached to the nut portion 48 via a plurality of balls (not shown).

[0088] At one end of the screw shaft 50, a stepping motor (second motor) 52 is attached. The nut portion 48, the screw shaft 50, the stepping motor 52, etc. constitute the first ball screw 54. The pair of guide rails 46, the nut portion 48, the screw shaft 50, the plurality of balls, the stepping motor 52, etc. constitute the first moving mechanism 56.

[0089] If the stepping motor 52 is operated, the moving plate 44, the tilt adjustment mechanism 32, and the chuck table 24 will move integrally along the X-axis direction. Note that the first moving mechanism 56 may move the moving plate 44 slidably mounted on the pair of guide rails 46 using a belt (not shown) instead of the first ball screw 54.

[0090] In this case, the first moving mechanism 56 has a stepping motor (second motor), a toothed pulley fixed to the output shaft of the stepping motor, and a toothed belt provided with ribs meshing with the toothed pulley on its inner surface (none of which are shown), and the power of the stepping motor is transmitted to the moving plate 44 via the toothed belt.

[0091] On the rear side of the base 22, a column 58 in the shape of a quadrangular prism is provided. On the front side surface of the column 58, a grinding feed mechanism 60 is provided. The grinding feed mechanism 60 has a pair of guide rails 62 fixed to the front side surface of the column 58. A moving plate 64 is slidably mounted on the pair of guide rails 62 along the Z-axis direction.

[0092] On the rear side surface of the moving plate 64, a nut portion (not shown) is provided. A screw shaft 66 is rotatably attached to the nut portion via a plurality of balls (not shown). A pulse motor 68 is connected to the upper end of the screw shaft 66.

[0093] If the screw shaft 66 is rotated by the pulse motor 68, the moving plate 64 will move along the Z-axis direction along the guide rail 62. On the front side surface of the moving plate 64, a grinding unit (processing unit) 70 is fixed. The grinding unit 70 has a bottomed cylindrical holding member 72.

[0094] Inside the holding member 72, a cylindrical spindle housing 74 is disposed. Inside the spindle housing 74, a part of a cylindrical spindle 76 (see FIG. 8(A)) disposed substantially parallel to the Z-axis direction is rotatably held. The longitudinal direction of the spindle 76 is disposed substantially parallel to the Z-axis direction.

[0095] In the vicinity of the upper end of the spindle 76 within the spindle housing 74, a rotational drive source (not shown) such as a servo motor is provided. The lower end 76a (see FIG. 8(A)) of the spindle 76 protrudes downward from the lower end of the spindle housing 74.

[0096] As shown in FIG. 8(A), a disk-shaped wheel mount 78 is fixed to the lower end 76a of the spindle 76. On the lower surface side of the wheel mount 78, a grinding wheel (processing tool) 80 capable of grinding (processing) the wafer 11 is mounted using a fixing member (not shown) such as a bolt.

[0097] The grinding wheel 80 has an annular base 80a formed of a metal material such as an aluminum alloy. On the lower surface side of the base 80a, a plurality of grinding grains 80b are disposed at substantially equal intervals along the circumferential direction of the base 80a. The outer side surfaces of the plurality of grinding grains 80b constitute a circle having a predetermined diameter corresponding to approximately half of the diameter of the wafer 11.

[0098] Each grinding grain 80b is formed, for example, by kneading abrasive grains such as diamond and cBN (cubic Boron Nitride) into a binder such as metal, ceramics, or thermosetting resin, and then through processes such as molding and firing. Note that the grinding wheel 80 is a consumable item and is appropriately replaced with a new one according to the degree of wear.

[0099] Therefore, in the grinding apparatus 20, the grinding wheel 80 is not always mounted on the lower end 76a of the spindle 76. For example, when manufacturing, transferring, etc. of the grinding apparatus 20, the grinding wheel 80 may not be mounted on the spindle 76.

[0100] Immediately below the spindle 76, a nozzle (not shown) for supplying grinding water such as pure water to the contact area between the wafer 11 and the grinding wheel 80b is provided during grinding (i.e., processing) of the wafer 11.

[0101] Returning to FIG. 5, a contact type thickness measuring device 82 is provided near the opening 22a. The thickness measuring device 82 has a first height gauge 82a and a second height gauge 82b. Each of the first height gauge 82a and the second height gauge 82b has an arm.

[0102] The base end portion of each arm is connected to a columnar base portion, and a head portion is fixed to the tip end portion of each arm. The head portion has a hemispherical contact portion formed of diamond or the like at its lower end.

[0103] The position of the contact portion in the Z-axis direction with respect to a predetermined reference position is measured, for example, on the order of 0.1 μm by a pulse count method of optically or magnetically reading a scale, or by a linear variable differential transformer (LVDT).

[0104] Note that the base portion is movable by a lifting mechanism (not shown). The lifting mechanism lowers the base portion when measuring the thickness of the object to be measured. When the base portion is lowered, the contact portion of the first height gauge 82a contacts the object to be measured, and the contact portion of the second height gauge 82b contacts a part of the holding surface 24a (i.e., the top surface of the frame).

[0105] When measuring the thickness of the object to be measured by the thickness measuring device 82, the thickness of the object to be measured is calculated from the difference between the height of the contact portion of the first height gauge 82a with respect to the above-mentioned reference position and the height of the contact portion of the second height gauge 82b with respect to the same reference position.

[0106] On the other hand, when the thickness is not measured, the base is raised. When the base is raised, the contact portion of the first height gauge 82a moves away from the object to be measured, and the contact portion of the second height gauge 82b also moves away from the holding surface 24a.

[0107] In the vicinity of the contact type thickness gauge 82, a non-contact type thickness gauge 84 is provided. The thickness gauge 84 is a spectroscopic interference type gauge using infrared light, and is arranged so as not to interfere with the first height gauge 82a and the second height gauge 82b.

[0108] The thickness gauge 84 has an arm 84a. A columnar base 84b is fixed to the base end portion of the arm 84a. The arm 84a of the present embodiment is arranged substantially parallel to the XY plane, and is inclined by a predetermined angle of 30 degrees to 60 degrees (for example, 45 degrees) with respect to the X-axis direction.

[0109] In the present embodiment, a direction inclined by a predetermined angle with respect to the X-axis direction on the XY plane is referred to as a second direction 84d. As is clear from the definition of this second direction 84d, the X-axis direction and the second direction 84d constitute a predetermined plane parallel to the XY plane.

[0110] A columnar sensor head 84c is fixed to the tip of the arm 84a. A laser beam having a wavelength in the infrared band is emitted from the sensor head 84c. For example, the distance from the lower end of the sensor head 84c to the back surface 11b of the wafer 11 is set to about 80 mm, and the spot diameter of the laser beam is set to approximately 25 μm.

[0111] The laser beam emitted from the sensor head 84c is reflected by the wafer 11 and the protective tape 19, and enters the sensor head 84c. The light entering the sensor head 84c includes the first reflected light from the back surface 11b of the wafer 11 and the second reflected light from the front surface 11a of the wafer 11 (that is, the interface between the wafer 11 and the protective tape 19).

[0112] The interference light of the first reflected light and the second reflected light is received by a light receiving element such as a photodetector or a photodiode through a spectroscope (not shown) such as a diffraction grating. The intensity of the interference light increases at a wavelength corresponding to the thickness of the wafer 11.

[0113] By analyzing the signal from the light receiving element with (i) a computer having a predetermined program and a general-purpose processor (both not shown) for executing this program, and (ii) a dedicated circuit such as an ASIC (Application Specific Integrated Circuit), the thickness of the wafer 11 corresponding to the wavelength of the interference light is calculated.

[0114] The thickness measuring device 84, the spectroscope, the light receiving element, the computer, etc. constitute a non-contact thickness measuring system that measures the thickness of the wafer 11 (i.e., the distance from the front surface 11a to the back surface 11b at the irradiation position of the laser beam) without contacting the wafer 11.

[0115] Incidentally, as shown in FIGS. 7(A) and 7(B), the sensor head 84c of the present embodiment is configured to be linearly movable along the second direction 84d by the second moving mechanism 86. FIG. 7(A) is a partial cross-sectional side view of the second moving mechanism 86 that moves the sensor head 84c, and FIG. 7(B) is a top view of the thickness measuring device 84.

[0116] The second moving mechanism 86 has a moving plate 88 that supports the base 84b. The moving plate 88 is slidably attached onto a pair of guide rails 90 arranged along the second direction 84d. In FIG. 7(A), only one of the guide rails 90 is shown for the sake of convenience.

[0117] A nut portion 92 is fixed to the lower surface side of the moving plate 88. A screw shaft 94 arranged along the second direction 84d is rotatably attached to the nut portion 92 via a plurality of balls (not shown).

[0118] One end of the screw shaft 94 is attached with a stepping motor (third motor) 96. The nut portion 92, the screw shaft 94, the stepping motor 96, etc. constitute the second ball screw 98. By operating the stepping motor 96, the moving plate 88 and the sensor head 84c move along the second direction 84d relative to the chuck table 24.

[0119] In addition, instead of the second ball screw 98, the second moving mechanism 86 may move the moving plate 88 slidably mounted on the pair of guide rails 90 using a belt. In this case, the second moving mechanism 86 has a stepping motor (third motor), a toothed pulley fixed to the output shaft of the stepping motor, and a toothed belt provided with ribs meshing with the toothed pulley on the inner surface (none of which are shown in the figure), and the power of the stepping motor is transmitted to the moving plate 88 via the toothed belt.

[0120] Here, return to FIG. 5 again. An exterior panel is provided above the base 22, and the upper and side portions of the chuck table 24, the column 58, etc. are covered by the exterior panel. A touch panel display (display) 100 is provided on one surface of the exterior panel.

[0121] The touch panel display 100 functions as an input device for the operator to input instructions, and also functions as a display device for displaying a GUI (Graphical User Interface), processing conditions, the thickness of the wafer 11 measured by the thickness measuring instruments 82, 84, etc., and a warning display indicating that the thickness of the wafer 11 is abnormal.

[0122] Instead of the touch panel display 100, a display device (display) without the function of an input device may be provided. However, in this case, an input device (such as a keyboard, mouse, trackball, touch pad, digitizer, etc.) for the operator to input instructions is provided separately.

[0123] On the top surface of the exterior panel, an elongated cylindrical indicator lamp 102 is provided. The indicator lamp 102 has a base portion in which a speaker (not shown) is incorporated. Note that the speaker may be provided in the grinding device 20 separately and independently from the indicator lamp 102.

[0124] On the base portion, light emitting portions capable of emitting light in different colors are provided. The light emitting portions have a plurality of light emitting regions arranged to overlap in the Z-axis direction. Each of the plurality of light emitting regions includes an LED and a diffusing lens provided so as to surround the LED, and can be lit or blinked in predetermined different colors such as red, yellow, blue, and green.

[0125] The grinding device 20 has a controller 104 that controls the above-described rotation drive mechanism 42, grinding unit 70, nozzle, thickness measuring device 84, first moving mechanism 56, second moving mechanism 86, touch panel display 100, indicator lamp 102, and the like.

[0126] In FIG. 5, for convenience, the controller 104 is shown outside the exterior panel, but in actuality, the controller 104 is provided inside the exterior panel or inside the base 22.

[0127] The controller 104 is constituted by a computer including, for example, a processor 104a typified by a CPU (Central Processing Unit) and a memory 104b. Note that the memory 104b includes a main storage device such as a DRAM (Dynamic Random Access Memory) and an auxiliary storage device such as a flash memory, a hard disk drive, and a solid state drive.

[0128] The auxiliary storage device stores software including a predetermined program. By operating a processing device or the like according to this software, the functions of the controller 104 are realized. Note that a program for analyzing the light reception signal measured using the thickness measuring device 84 may be executed by this processor 104a.

[0129] The controller 104 includes a discrimination unit 104c (see FIG. 9(A) etc.) that discriminates an abnormality in the thickness of the wafer 11 by executing a program stored in the memory 104b with the processor 104a.

[0130] The non-contact thickness measuring device 84 is electrically connected to the controller 104. The discrimination unit 104c discriminates an abnormality in the thickness of the wafer 11 by comparing the thickness of the wafer 11 measured by the thickness measuring device 84 with a predetermined threshold value.

[0131] The discrimination unit 104c of the present embodiment discriminates that the thickness of the wafer 11 is abnormal when the thickness of the wafer 11 is equal to or greater than a predetermined threshold value. However, the discrimination unit 104c may discriminate that the thickness of the wafer 11 is abnormal when the thickness of the wafer 11 is less than or equal to a predetermined threshold value.

[0132] When the wafer 11 is thinned to 200 μm or less by grinding, the thickness of the wafer 11 has undulations of about 0.3 μm to 0.5 μm, for example. However, in the present embodiment, the predetermined threshold value used when the discrimination unit 104c discriminates that the thickness of the wafer 11 is abnormal is larger than the value of the undulation of the wafer 11 after the grinding step S30.

[0133] That is, the predetermined threshold value in the present embodiment is larger than the value of the undulation of the wafer 11 after the thickness of the device region 17a has become the finished thickness. The predetermined threshold value is, for example, 2.0 μm or more and 5.0 μm or less, and in one example, it is 3.0 μm. Note that, in the case where a local thin thickness abnormality occurs in the wafer 11, the same threshold value may be used.

[0134] The discrimination unit 104c discriminates an abnormality in the thickness of the wafer 11 based on measurement results obtained by measuring the thickness of the wafer 11 at a plurality of locations on a predetermined circumference around the rotation center of the rotation shaft 24b of the chuck table 24.

[0135] Since the area that can be measured on one circumference is part of the device area 17a, it is preferable to measure the thickness of the wafer 11 over the entire back surface 11b corresponding to the device area 17a while changing the position of the sensor head 84c with respect to the holding surface 24a by the second moving mechanism 86.

[0136] The discrimination unit 104c compares, for example, the difference between the maximum value and the minimum value of the thickness of the wafer 11 and the above-described predetermined threshold value. When the discrimination unit 104c determines that there is an abnormality in the thickness of the wafer 11, the controller 104 causes the touch panel display 100 to display one or both of the value of the thickness of the wafer 11 determined to be abnormal and the fact that there is a thickness abnormality.

[0137] Note that the determination of the thickness abnormality is not limited to the above-described method. For example, the discrimination unit 104c may discriminate the thickness abnormality of the wafer 11 based on whether the difference between the average value of the measured thickness values on the circumference and each measured value is equal to or greater than a predetermined threshold value (or less than). In this case, the predetermined threshold value may be 1.0 μm or more and 2.5 μm or less (for example, 1.5 μm).

[0138] In addition to this, the discrimination unit 104c may discriminate the thickness abnormality of the wafer 11 by calculating the change rate of the measured thickness values on the circumference. In this way, the discrimination unit 104c can discriminate the thickness abnormality of the wafer 11 based on the measurement result of the thickness of the wafer 11.

[0139] Next, referring to FIGS. 8 to 11, the grinding step S30, the measurement step S40, and the detection step S50 will be described. Note that before the grinding step S30, the above-described sticking step S10 and cutting step S20 are completed.

[0140] FIG. 8(A) is a diagram showing the grinding step S30. In the grinding step S30, first, the front surface 11a of the wafer 11 is sucked and held by the holding surface 24a of the chuck table 24 through the thinned protective tape 19. Thereby, the back surface 11b is exposed upward.

[0141] Next, the back surface 11b of the wafer 11 is ground with a grinding wheel 80. In the grinding step S30 of the present embodiment, as described above, a circular region corresponding to the device region 17a is ground on the back surface 11b.

[0142] As a result, as shown in FIG. 8(B), a circular recess 11d having a depth that does not reach the front surface 11a in the thickness direction 11c of the wafer 11 from the back surface 11b, and a ring-shaped reinforcing portion 11e surrounding the outer peripheral portion of the circular recess 11d are formed.

[0143] FIG. 8(B) is a cross-sectional view of the wafer unit 21 thinned in the grinding step S30. In the grinding step S30, a local thickening region 11f is formed in the wafer 11 due to the local thinning region 19c of the protective tape 19 described above.

[0144] The thickening region 11f depends on the diameter of the wafer 11, the size of the foreign matter 4b, etc. For example, in a wafer 11 having a diameter of 12 inches, the diameter of the thickening region 11f is 50 mm.

[0145] In the grinding step S30, until the thickness of the wafer 11 reaches a predetermined thickness, the grinding of the wafer 11 is advanced while measuring the thickness of the wafer 11 in the device region 17a with a contact type thickness measuring device 82 (see FIG. 5). The predetermined thickness is, for example, a predetermined value of 150 μm or more and 250 μm or less.

[0146] In the grinding step S30, for example, the rotation speed of the spindle 76 is set to a predetermined value of 1000 rpm or more and 7000 rpm or less. Also, the downward grinding feed speed along the Z-axis direction is set to 0.5 μm / s or more and 1.0 μm / s or less, and the flow rate of the grinding water is set to 1.5 L / min or more and 4.0 L / min or less.

[0147] The rotation speed of the chuck table 24 is set to a predetermined value of 200 rpm or more and 400 rpm or less until the thickness of the wafer 11 reaches a predetermined thickness, and when the thickness of the wafer 11 becomes less than the predetermined thickness, it is set to a predetermined value of 60 rpm or more and 150 rpm or less.

[0148] During grinding, the sensor head 84c of the non-contact thickness measuring instrument 84 is also disposed above the device area 17a. However, until the thickness of the wafer 11 reaches a predetermined thickness, due to the performance of the thickness measuring instrument 84, the thickness of the wafer 11 cannot be measured.

[0149] On the other hand, for example, when the thickness of the wafer 11 becomes equal to or less than a predetermined thickness, measurement with the thickness measuring instrument 84 becomes possible. Therefore, while measuring the thickness of the wafer 11 with the thickness measuring instrument 84, the grinding of the wafer 11 is advanced. At this time, in order to suppress damage to the back surface 11b, the contact portion of the first height gauge 82a in the thickness measuring instrument 82 is separated from the wafer 11.

[0150] Thus, in the present embodiment, after proceeding with the grinding step S30 until the thickness of the wafer 11 in the device area 17a becomes a thickness measurable by the thickness measuring instrument 84 (i.e., the above-described predetermined thickness), the measuring step S40 is started.

[0151] More specifically, after the thickness of the wafer 11 in the device area 17a becomes a thickness measurable by the thickness measuring instrument 84 and before it reaches the target finish thickness, the measuring step S40 is started. That is, in the method for detecting an abnormal thickness of the wafer 11, the grinding step S30 is started before the measuring step S40.

[0152] FIG. 9(A) is a diagram showing the measuring step S40 on the first circumference. As shown in FIG. 9(A), in the measuring step S40, while fixing the position of the sensor head 84c in the XY plane (predetermined plane), the chuck table 24 that sucks and holds the wafer 11 is rotated, and the thickness of the wafer 11 is measured on the first circumference 23a having the first diameter 23a1.

[0153] For example, set the rotation speed of the chuck table 24 to be 60 rpm or more and 150 rpm or less, and set the sampling frequency of the non-contact thickness measurement system including the thickness measuring instrument 84 to 4 kHz. However, in order to avoid measuring the same location multiple times, it is preferable to determine at least one of the frequency and the rotation speed so that the value (f / R) obtained by dividing the frequency (f) by the rotation speed (R) is not an integer.

[0154] For example, when the rotation speed is set to a predetermined value of 60 rpm or more and 150 rpm or less, and the sampling frequency is set to 4 kHz, since the value obtained by dividing the frequency by the rotation speed is an integer, it is preferable to avoid rotation speeds of 125 rpm, 100 rpm, or 50 rpm.

[0155] By avoiding the case where the value obtained by dividing the frequency during measurement by the rotation speed of the chuck table 24 is an integer, compared to the case where the value obtained by dividing the frequency by the rotation speed is an integer, the number of locations for measuring the thickness on the same circumference can be increased, so that the thickened region 11f can be detected more reliably.

[0156] In the measurement step S40, the thickness of the wafer 11 is measured at a plurality of locations on the wafer 11 by relatively moving the sensor head 84c and the chuck table 24 holding the wafer 11 on the holding surface 24a within the XY plane (a predetermined plane).

[0157] In the present embodiment, the position of the sensor head 84c with respect to the wafer 11 is adjusted using the second moving mechanism 86. FIG. 9(B) is a diagram showing the measurement of the thickness of the wafer 11 on a plurality of circumferences concentric with the first circumference 23a.

[0158] The measurement step S40 includes measuring the thickness of the wafer 11 on a second circumference 23b having a second diameter 23b1 smaller than the first diameter 23a1 while rotating the chuck table 24 that sucks and holds the wafer 11 with the position of the sensor head 84c fixed within the XY plane.

[0159] Further, the measurement step S40 similarly includes measuring the thickness of the wafer 11 on a third circumference 23c having a third diameter 23c1 larger than the first diameter 23a1 while rotating the chuck table 24 with the position of the sensor head 84c fixed.

[0160] FIG. 10 is a more detailed flowchart of the measurement step S40 and the detection step S50. While grinding the wafer 11 or after the wafer 11 has been thinned to the finish thickness by grinding, the thickness of the wafer 11 on one circumference is measured in the region corresponding to the device region 17a.

[0161] Thereby, the maximum value and the minimum value of the thickness on the circumference are obtained (measurement step S40). If the difference between the maximum value and the minimum value is equal to or greater than the above-described threshold value (YES in S52), one or both of the abnormal thickness value and the presence of the thickness abnormality are displayed on the touch panel display 100 (S56).

[0162] On the other hand, if the difference between the maximum value and the minimum value is less than the threshold value (NO in S52), the position of the sensor head 84c with respect to the chuck table 24 is moved in the radial direction of the chuck table 24 (S54). Then, the process returns to S40.

[0163] Note that the rotation axis 24b of the chuck table 24 is not completely parallel to the Z-axis direction but is slightly inclined with respect to the Z-axis direction. However, since the inclination angle of the rotation axis 24b with respect to the Z-axis direction is extremely small, even if the sensor head 84c is moved along the second direction 84d, it can be regarded as moving the sensor head 84c in the radial direction of the chuck table 24.

[0164] S52, S54, and S56 correspond to a detection step S50 of detecting an abnormality in the thickness of the wafer 11 using the measurement results in the measurement step S40. In this way, in the detection step S50, an abnormality in the thickness of the wafer 11 can be detected.

[0165] In addition, when an abnormality in thickness is detected, self-grinding may be performed on the holding surface 4a of the chuck table 4 of the surface planer 2 (that is, the holding surface 4a may be cut with the cutting edge 12c) to correct the shape of the holding surface 4a.

[0166] (First Modified Example) By the way, the sensor head 84c may be pivotally moved instead of necessarily moving linearly. FIG. 11(A) is a side view of a third moving mechanism 118 that pivotally moves the sensor head 84c, and FIG. 11(B) is a top view of the pivotally moving sensor head 84c.

[0167] As shown in FIG. 11(A), a driven pulley 110 is fixed to the lower end of the base 84b of the thickness measuring device 84. Further, a stepping motor (fourth motor) 112 is fixed to the base 22 of the grinding device 20. The output shaft of the stepping motor 112 can rotate both clockwise and counterclockwise.

[0168] A driving pulley 114 is fixed to the output shaft of the stepping motor 112, and an endless belt 116 is wound around the driving pulley 114 and the driven pulley 110. When the stepping motor 112 is operated, the sensor head 84c pivotally moves with the base 84b as the rotation axis.

[0169] The driven pulley 110, the stepping motor 112, the driving pulley 114, and the endless belt 116 constitute a third moving mechanism 118 that pivotally moves the sensor head 84c relative to the chuck table 24 in the XY plane (a predetermined plane). The third moving mechanism 118 is also controlled by the above-described controller 104.

[0170] FIG. 12(A) is a top view showing the wafer 11 held by the holding surface 24a and the sensor head 84c, and FIG. 12(B) is a view showing the measurement step S40 on the first circumference 23a, the second circumference 23b, and the third circumference 23c. As shown by the double-headed arrows, the sensor head 84c can pivot within a predetermined angular range.

[0171] (Second Modification Example) Note that, instead of adopting only one of the second moving mechanism 86 and the third moving mechanism 118, both of them may be adopted in combination. FIG. 13 is a side view showing the combination of the second moving mechanism 86 and the third moving mechanism 118.

[0172] The second moving mechanism 86 has been described with reference to FIG. 7, and the third moving mechanism 118 has been described with reference to FIG. 11(A), so the description thereof will be omitted. A columnar support portion 120 having a bearing for rotatably supporting the driven pulley 110 is fixed on the moving plate 88.

[0173] In this example, the sensor head 84c can perform linear movement in the XY plane by the second moving mechanism 86 and turning movement in the XY plane by the third moving mechanism 118.

[0174] (Second Embodiment) Incidentally, the second moving mechanism 86 and the third moving mechanism 118 may be omitted, and the sensor head 84c may be relatively moved with respect to the chuck table 24 in the XY plane by using only the first moving mechanism 56 that moves the chuck table 24 along the X-axis direction.

[0175] FIG. 14(A) is a view showing the sensor head 84c disposed directly above the center 24a1 of the holding surface 24a. In the second embodiment, the sensor head 84c is disposed directly above the movement path 24a2 of the center 24a1 of the holding surface 24a by the first moving mechanism 56.

[0176] Since the chuck table 24 is rotatable around the rotation axis 24b, by disposing the sensor head 84c directly above the movement path 24a2 of the center 24a1 by the first moving mechanism 56, it is possible to scan substantially the entire wafer 11 with the laser beam from the sensor head 84c even without the second moving mechanism 86 and the third moving mechanism 118.

[0177] FIG. 14(B) is a diagram showing a measurement step S40 on a first circumference 23a, a second circumference 23b, and a third circumference 23c according to the second embodiment. In addition, the structures, methods, etc. according to the above-described embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention.

[0178] For example, the protective tape 19 is not essential, and when grinding the wafer 11 without the protective tape 19 attached, the detection method for detecting the above-described thickness abnormality can also be executed. Further, in the grinding step S30, it is not limited to so-called TAIKO grinding for grinding the region corresponding to the device region 17a, and the entire back surface 11b may be uniformly ground.

[0179] In the above-described embodiment, the case where the thickness of the thickened region 11f is equal to or greater than the threshold value has been described. However, instead of the thickened region 11f, even in the case of a thinned region (not shown) where the wafer 11 is locally thinned, in the detection step S50, for example, whether or not the difference between the maximum value and the minimum value is equal to or greater than the threshold value can be used to detect a thickness abnormality.

Explanation of Reference Numerals

[0180] 2: Surface planer 4: Chuck table (second holding table), 4a: Holding surface (second holding surface), 4b: Foreign matter 6: Support portion, 8: Spindle, 10: Wheel mount 11: Wafer, 11a: Front surface (first surface), 11b: Back surface (second surface), 11c: Thickness direction 11d: Circular recess, 11e: Ring-shaped reinforcing portion, 11f: Thickened region 12: Cutting wheel (cutting tool) 12a: Base portion, 12b: Shank, 12c: Cutting edge 13: Scribing line, 15: Device, 17a: Device region, 17b: Outer peripheral surplus region 19: Protective tape, 19a: Outer surface, 19b: Inner surface, 19c: Thinned region 20: Grinding device (processing device), 22: Base, 22a: Opening 21: Wafer unit 23a: First circumference, 23a1: First diameter 23b: Second circumference, 23b1: Second diameter 23c: Third circumference, 23c1: Third diameter 24: Chuck table (holding table, first holding table) 24a: Holding surface (first holding surface), 24a1: Center, 24a2: Movement path, 24b: Rotation axis 26: First cover, 28: Second cover, 30: Table base 32: Tilt adjustment mechanism, 32a: Fixed axis, 32b: Movable axis 34: Servo motor (first motor), 36: Driving pulley, 38: Driven pulley 40: Endless belt, 42: Rotational drive mechanism 44: Moving plate, 46: Guide rail, 48: Nut part, 50: Screw shaft 52: Stepping motor (second motor), 54: First ball screw 56: First movement mechanism, 58: Column, 60: Grinding feed mechanism 62: Guide rail, 64: Moving plate, 66: Screw shaft, 68: Pulse motor 70: Grinding unit (processing unit), 72: Holding member 74: Spindle housing, 76: Spindle, 76a: Lower end 78: Wheel mount 80: Grinding wheel (processing tool), 80a: Base, 80b: Grinding wheel 82: Thickness measuring device, 82a: First height gauge, 82b: Second height gauge 84: Thickness measuring device, 84a: Arm, 84b: Base, 84c: Sensor head 84d: Second direction 86: Second movement mechanism, 88: Moving plate, 90: Guide rail, 92: Nut part 94: Screw shaft, 96: Stepping motor (third motor), 98: Second ball screw 100: Touch panel display (display), 102: Indicator lamp 104: Controller, 104a: Processor, 104b: Memory, 104c: Discrimination unit 110: Driven pulley, 112: Stepping motor (fourth motor) 114: Driving pulley, 116: Endless belt 118: Third moving mechanism, 120: Support part S10: Bonding process, S20: Cutting process, S30: Grinding process S40: Measuring process, S50: Detecting process, Δ: Distance

Claims

1. A detection method for detecting an abnormal thickness of a wafer, comprising: a sensor head of a thickness measuring instrument that measures the thickness of the wafer without contacting the wafer, and a first holding table that holds the wafer on a first holding surface, and moving them relatively in a predetermined plane, a measuring step of measuring the thickness of the wafer at a plurality of locations on the wafer; a detection step of detecting an abnormality in the thickness of the wafer using the measurement results in the measurement step; A detection method characterized by comprising the above.

2. The detection method according to claim 1, wherein the measurement step includes measuring the thickness of the wafer on a first circumference having a first diameter while rotating the first holding table holding the wafer with the position of the sensor head fixed in the predetermined plane.

3. The detection method according to claim 2, wherein the measurement step includes measuring the thickness of the wafer on a second circumference having a second diameter smaller than the first diameter and on a third circumference having a third diameter larger than the first diameter while rotating the first holding table holding the wafer with the position of the sensor head fixed in the predetermined plane.

4. In the detection step, an abnormality in the thickness of the wafer is detected by comparing the difference between the maximum value and the minimum value of the thickness of the wafer measured in the measurement step with a predetermined threshold value. The detection method according to claim 1.

5. The detection method according to any one of claims 1 to 4, further comprising a grinding step of holding a first surface of the wafer by the first holding table and grinding a second surface of the wafer located on the side opposite to the first surface in the thickness direction of the wafer with a grinding wheel, and starting the grinding step before the measurement step.

6. In the detection step, the difference between the maximum value and the minimum value of the thickness of the wafer measured in the measurement step is compared with a predetermined threshold value greater than the undulation value of the thickness of the wafer after the grinding step, thereby detecting an abnormality in the thickness of the wafer. The detection method according to claim 5, characterized in that.

7. In the grinding step, by grinding the second surface of the wafer, a circular concave portion having a depth that does not reach the first surface in the thickness direction of the wafer from the second surface, and a ring-shaped reinforcing portion surrounding the outer peripheral portion of the circular concave portion are formed. The detection method according to claim 5, characterized in that.

8. Before the grinding step, A pasting step of pasting a protective tape on the first surface so as to cover the first surface of the wafer; While rotating a cutting tool having a cutting edge around a spindle and fixing the cutting edge at a predetermined height, a second holding table that holds the wafer on a second holding surface so that the protective tape is exposed is linearly moved along a predetermined direction with respect to the spindle, thereby cutting the protective tape with the cutting tool and flattening the protective tape. A cutting step; The detection method according to claim 5, further comprising:

9. A holding table having a holding surface for holding a wafer; A rotation drive mechanism including a first motor that rotates a rotation axis of the holding table disposed at a central portion of the holding surface; A first moving mechanism having a second motor and moving the holding table along a first direction; A processing unit having a spindle and capable of processing the wafer held on the holding surface with a processing tool mounted at a lower end portion of the spindle; A thickness measuring device having a sensor head and measuring the thickness of the wafer without contacting the wafer; A second movement mechanism having a third motor and moving the sensor head relative to the holding table along a second direction intersecting the first direction, and a third movement mechanism having a fourth motor and pivoting the sensor head relative to the holding table within a predetermined plane defined by the first direction and the second direction, one or both of them, A controller having a processor and a memory and controlling the rotation drive mechanism, the processing unit, the thickness measuring device, the first movement mechanism, the second movement mechanism, and the third movement mechanism, is provided with The controller includes a determination unit that determines an abnormality in the thickness of the wafer by executing, by the processor, a program stored in the memory. The determination unit determines an abnormality in the thickness of the wafer based on measurement results obtained by measuring the thickness of the wafer at a plurality of locations on a predetermined circumference around the center of rotation of the rotation axis. A processing apparatus characterized by that.

10. A holding table having a holding surface for holding a wafer, A rotation drive mechanism including a first motor that rotates a rotation axis of the holding table disposed at the center of the holding surface, A first movement mechanism having a second motor and moving the holding table along a first direction, A processing unit having a spindle and capable of processing the wafer held on the holding surface with a processing tool attached to the lower end of the spindle, A thickness measuring device having a sensor head disposed directly above the movement path of the center of the holding surface and measuring the thickness of the wafer without contacting the wafer, A controller having a processor and a memory and controlling the rotation drive mechanism, the processing unit, the thickness measuring device, and the first movement mechanism, is provided with The controller includes a determination unit that determines an abnormality in the thickness of the wafer by executing, by the processor, a program stored in the memory. The discrimination unit discriminates an abnormality in the thickness of the wafer based on measurement results obtained by measuring the thickness of the wafer at a plurality of locations on a predetermined circumference around the center of rotation of the rotating shaft. A processing apparatus characterized by this.

11. It further includes a display whose operation is controlled by the controller, When the discrimination unit discriminates that there is an abnormality in the thickness of the wafer, the controller causes the display to display one or both of the value of the thickness of the wafer discriminated as abnormal and a message indicating that there is an abnormality in the thickness. The processing apparatus according to claim 9 or 10, characterized by this.

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