Cutting apparatus and wafer processing method

A cutting apparatus includes a line sensor unit that applies a laser beam in a band shape elongated in a radial direction of a wafer to a region inclusive of a peripheral portion of the wafer held on a chuck table, and detects reflected light, and an information calculation section that calculates the position of the wafer and the height of the front surface of the wafer from the reflected light of the laser beam detected by the line sensor unit in a state in which the chuck table is rotated before the wafer is cut to form a stepped portion, and that calculates the width and the height of the stepped portion from the reflected light of the laser beam detected by the line sensor unit after the wafer is cut to form the stepped portion.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a cutting apparatus for cutting a wafer and a wafer processing method in which the cutting apparatus is used.

Description of the Related Art

In recent years, for realizing small-type lightweight devices, processing for thinning a wafer formed of such a material as silicon has come to be conducted more frequently. For instance, a device such as an integrated circuit (IC) is formed in each of regions of a wafer partitioned by division lines (streets), then the wafer is thinned by such a method as grinding and is divided along the division lines, whereby device chips corresponding to the devices are obtained.

Of the wafer used for manufacture of the device chips as above, a peripheral portion is normally chamfered in order to prevent chipping or cracking from occurring due, for example, to a shock exerted on the wafer during carrying thereof. However, when the thus chamfered wafer is thinned by grinding or the like method, the peripheral edge of the wafer becomes sharp like a knife edge and brittle, leading to rather easier occurrence of chipping or cracking.

In view of this problem, there has been proposed a processing method called edge trimming in which the chamfered portion is cut and removed before grinding (see, for example, Japanese Patent Laid-Open No. 2014-33152). When a cutting blade is made to cut into the wafer from the front surface side of the wafer to preliminarily cut and remove the chamfered portion, it is ensured that even if the wafer is ground from the back surface side, the peripheral edge of the wafer is prevented from becoming sharp like a knife edge and brittle.

SUMMARY OF THE INVENTION

In the edge trimming, for example, the cutting blade is made to cut into the chamfered portion of the wafer held by the chuck table from the front surface side, and, in this condition, the chuck table is rotated. For appropriate cutting and removal of the chamfered portion, therefore, it has been necessary to acquire information on the position of the wafer relative to the chuck table and on the position of the cutting blade relative to the wafer, and to accurately adjust the positional relations of them.

In addition, there are cases where it is desired to acquire information related to the width and the height of a step (stepped portion) formed by the cutting and removal of the chamfered portion, for the purpose of confirming the accuracy of edge trimming, the state of the cutting blade, and so on. In the conventional cutting apparatus, however, a plurality of sensors are mounted for acquiring such kinds of information, which leads to a complicated structure and makes it difficult to reduce cost.

It is therefore an object of the present invention to provide a cutting apparatus which is simple in structure and is able to acquire various kinds of information, and a wafer processing method using the cutting apparatus.

In accordance with an aspect of the present invention, there is provided a cutting apparatus including a chuck table that holds by a holding surface a wafer chamfered at a peripheral portion and that is rotatable, a cutting unit that cuts the peripheral portion of the wafer held on the chuck table from a front surface side by a cutting blade mounted to a spindle, to form on the front surface side of the wafer an annular stepped portion along the peripheral portion, a line sensor unit that applies a laser beam in a band shape elongate in a radial direction of the wafer to a region inclusive of the peripheral portion of the wafer held on the chuck table, and detects reflected light of the laser beam reflected on the region, and an information calculation section that calculates a position of the wafer and a height of the front surface of the wafer from the reflected light of the laser beam detected by the line sensor unit in a state in which the chuck table is rotated before the wafer is cut to form the stepped portion, and that calculates the width and the height of the stepped portion from the reflected light of the laser beam detected by the line sensor unit after the wafer is cut to form the stepped portion.

In a mode of the present invention, preferably, the cutting apparatus further includes a threshold comparison section that compares the width and the height of the stepped portion calculated by the information calculation section with thresholds for the width and the height of the stepped portion, and that determines whether or not consumption amount and a change in shape of a tip of the cutting blade are within allowable ranges.

In another mode of the present invention, there is provided a wafer processing method for processing a wafer provided on a front surface side with a device region formed with devices and a peripheral marginal region surrounding the device region, the wafer chamfered at a peripheral portion thereof, by use of the aforementioned cutting apparatus. The wafer processing method includes a holding step of holding a back surface side of the wafer by the chuck table, a first calculation step of applying the laser beam to the region inclusive of the peripheral portion of the wafer held on the chuck table in a state in which the chuck table is rotated, and calculating a position of the wafer and a height of the front surface of the wafer from the reflected light of the laser beam reflected on the region, and a stepped portion forming step of causing the cutting blade to cut into the wafer from the front surface side of the peripheral portion, based on the position of the wafer and the height of the front surface of the wafer calculated in the first calculation step, to form the peripheral portion with the stepped portion having a predetermined width and a predetermined depth.

In another mode of the present invention, preferably, the wafer processing method further includes, after the stepped portion forming step, a second calculation step of applying the laser beam to the region inclusive of the peripheral portion of the wafer held on the chuck table, to calculate a width and a height of the stepped portion from the reflected light of the laser beam reflected on the region, and a determination step of comparing the width and the height of the stepped portion calculated in the second calculation step with thresholds for the width and the height of the stepped portion, to determine whether or not consumption amount and a change in shape of a tip of the cutting blade are within allowable ranges.

The cutting apparatus according to a mode of the present invention includes the line sensor unit that applies the laser beam in the band shape elongate in a radial direction of the wafer to a region inclusive of a peripheral portion of the wafer held by the chuck table and that detects reflected light of the laser beam reflected on the region, and the information calculation section that calculates the position of the wafer and the height of the front surface of the wafer and calculates the width and the height of the stepped portion, from the reflected light of the laser beam detected by the line sensor unit. Therefore, it is unnecessary to mount a plurality of sensors for the purpose of calculating the position of the wafer and the height of the front surface of the wafer and calculating the width and the height of the stepped portion. In this way, according to the present invention, it is possible to provide a cutting apparatus which is simple in structure and which is able to acquire various kinds of information.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment according to one mode of the present invention will be described referring to the attached drawings.FIG. 1is a perspective view depicting schematically a configuration example of a cutting apparatus2according to the present embodiment. As depicted inFIG. 1, the cutting apparatus2has a base4that supports each structure. An upper surface of the base4is formed with an opening4ain the shape of a rectangle elongate in an X-axis direction (a front-rear direction, a processing feed direction) in plan view, and a first carrying unit6that carries a wafer11as an object to be processed is disposed in the opening4a.

The wafer11is formed in a disk-like shape from a semiconductor material such as silicon, for example, and its front surface11aside is divided into a device region on a central side and a peripheral marginal region surrounding the device region. The device region is further partitioned into a plurality of regions by division lines (streets) arranged in a grid pattern, and a device13such as an IC is formed in each of the regions. In addition, a peripheral portion11c(seeFIG. 2Aand the like) of the wafer11is chamfered. Note that while the disk-shaped wafer11formed of a semiconductor material such as silicon is used in the present embodiment, there are no limitations as to the material, shape, structure, size or the like of the wafer. For example, a wafer formed of other material such as semiconductor, ceramic, resin, or metal can also be used. In addition, there are also no limitations as to the kind, number, shape, structure, size, layout or the like of the device or devices.

Cassettes8aand8bthat accommodate wafers11are placed in an area on one side of the opening4ain regard of a Y-axis direction (a left-right direction, an indexing feed direction). A centering table10is disposed in an area on the opposite side of the opening4afrom the region where the cassettes8aand8bare mounted. The centering table10adjusts, for example, the position of the center of the wafer11carried from the cassettes8aand8bby the first carrying unit6. In an area on a further lateral side (on the opposite side of the opening4a) than the centering table10, there is formed an opening4bin the shape of a rectangle elongate in the X-axis direction in plan view. An X-axis moving table12, an X-axis moving mechanism (not depicted) that moves the X-axis moving table12in the X-axis direction, and a dustproof and droplet-proof cover14covering the X-axis moving mechanism are provided in the opening4b.

The X-axis moving mechanism includes a pair of X-axis guide rails (not depicted) parallel to the X-axis direction, and the X-axis moving table12is slidably mounted to the X-axis guide rails. A nut section (not depicted) is provided on a lower surface side of the X-axis moving table12, and an X-axis ball screw (not depicted) parallel to the X-axis guide rails is in screw engagement with the nut section. An X-axis pulse motor (not depicted) is coupled to one end portion of the X-axis ball screw. With the X-axis ball screw rotated by the X-axis pulse motor, the X-axis moving table12is moved in the X-axis direction along the X-axis guide rails.

A chuck table16for holding the wafer11is provided on the upper side of the X-axis moving table12. The chuck table16is coupled to a rotational drive source (not depicted) such as a motor, and is rotated about a rotational axis substantially parallel to a Z-axis direction (vertical direction). In addition, the chuck table16is moved between a carrying-in/out region on a front side and a processing region on a rear side by the aforementioned X-axis moving mechanism. Part (peripheral part) of an upper surface of the chuck table16is a holding surface16a(seeFIG. 2Aand the like) that holds the wafer11by suction. The holding surface16ais connected to a suction source20(seeFIG. 2Aand the like) through a suction passage16b(seeFIG. 2Aand the like) formed inside the chuck table16, a valve18(seeFIG. 2Aand the like) and the like.

A first support structure22in a gate form straddling the opening4bin the Y-axis direction is disposed on the upper surface of the base4. A first rail24substantially parallel to the Y-axis direction is provided on a front surface of the first support structure22, and a second carrying unit28is mounted to the first rail24through a first lift unit26.

The second carrying unit28is moved in the Y-axis direction along the first rail24, and is moved in the Z-axis direction by the first lift unit26. By the second carrying unit28, it is possible, for example, to receive the wafer11from the centering table10or the chuck table16, and to transfer the wafer11to the centering table10or the chuck table16. In other words, the wafer11on the centering table10can be held by the second carrying unit28and can be carried in to the chuck table16. In addition, by the second carrying unit28, the wafer11can be carried out from the chuck table16, and the wafer11can be transferred onto the centering table10.

A second rail30substantially parallel to the Y-axis direction is provided on the upper side of the first rail24, and a third carrying unit34is mounted to the second rail30through a second lift unit32. The second carrying unit34is moved in the Y-axis direction along the second rail30, and is moved in the Z-axis direction by the second lift unit32.

A second support structure38in a gate form is disposed on the rear side of the first support structure22, through a shutter36that partitions the carrying-in/out region and the processing region. Two sets of cutting units42are provided on a front surface of the second support structure38, through moving units40, individually. The cutting units42are moved in the Y-axis direction and the Z-axis direction by the moving units40.

Each of the cutting units42has a spindle (not depicted) serving as a rotational axis substantially parallel to the Y-axis direction. An annular cutting blade is mounted to one end side of the spindle. A rotational drive source (not depicted) such as a motor is connected to the other end side of the spindle, and the cutting blade is rotated by a force transmitted from the rotational drive source.

An imaging unit44for imaging the wafer11held by the chuck table16and the like is provided at a position adjacent to the cutting unit42. The imaging unit44is used, for example, in alignment for adjusting the orientation of the division lines of the wafer11, and is moved in the Y-axis direction and the Z-axis direction together with the cutting unit42by the moving unit40.

An opening4cwhich is circular in plan view is formed at a position on the opposite side of the opening4bfrom the centering table10. A cleaning unit46for cleaning the wafer11after processing is disposed in the opening4c. The wafer11processed by the cutting unit42is carried to the cleaning unit46by the third carrying unit34. The wafer11cleaned by the cleaning unit46is placed onto the centering table10by the second carrying unit28, and is thereafter accommodated into the cassette8aor8bby the first carrying unit6.

A line sensor unit48that applies a band-shaped (rectilinear) laser beam48a(seeFIG. 2Aand the like) and detects reflected light of the laser beam48ais provided in the carrying-in/out region of the cutting apparatus2. Specifically, the line sensor unit48is disposed on an upper side of a peripheral portion of the chuck table16in a state in which the chuck table16is positioned in the carrying-in/out region. As a result of this, a laser beam48acan be applied from the line sensor unit48toward the region inclusive of the peripheral portion11cof the wafer11held by the chuck table16, and reflected light of the laser beam48areflected on the region can be detected. Note that the line sensor unit48is disposed in such an orientation that the laser beam48aelongated in a radial direction of the wafer11can be applied, and that the reflected lights reflected at a plurality of positions along the radial direction can be detected at a time.

A processor unit50is connected to the line sensor unit48. The processor unit50includes, for example, an information calculation section50athat calculates such information as position, height and size from data (the results of detection of the reflected light) obtained by the line sensor unit48, and a threshold comparison section50bthat compares the information calculated by the information calculation section50awith thresholds. The details of the functions possessed by the information calculation section50aand the threshold comparison section50bwill be described later.

Now, an example of a wafer processing method conducted using the aforementioned cutting apparatus2will be described below. In the wafer processing method according to the present embodiment, first, a holding step of holding a back surface11bside of the wafer11by the chuck table16of the cutting apparatus2is conducted. Specifically, for example, the wafer11the position of the center of which has been adjusted by the centering table10is carried in to the chuck table16by the second carrying unit28. More in detail, the back surface11bside of the wafer11is put in close contact with the holding surface16aof the chuck table16, such that the front surface11aside of the wafer11is exposed to the upper side. Then, the valve18is opened, whereby a negative pressure of the suction source20is made to act on the back surface11bside of the wafer11. As a result of this, the back surface11bside of the wafer11can be held by the chuck table16.

After the holding step, a first calculation step of calculating the position of the wafer11relative to the chuck table16and the height of the peripheral portion11con the front surface11aside is performed.FIG. 2Ais a sectional view depicting schematically the manner in which the laser beam48ais applied to the wafer11from the line sensor unit48, andFIG. 2Bis a plan view depicting schematically the manner in which the laser beam48ais applied to the wafer11from the line sensor unit48. Note that inFIG. 2A, some of components are depicted in the form of a functional block or the like. As depicted inFIGS. 2A and 2B, in the first calculation step, first, the chuck table16is rotated into an arbitrary orientation. In this state, the laser beam48ain a band shape elongate in a radial direction of the wafer11is applied from the line sensor unit48toward the region inclusive of the peripheral portion11cof the wafer11. Then, the reflected light of the laser beam48areflected on the front surface11aside of the wafer11is detected by the line sensor unit48.

FIG. 3Ais a sectional view depicting, in an enlarged form, a region of the wafer11to which the laser beam48ais applied, andFIG. 3Bis a graph depicting schematically the results of detection of the reflected light obtained by the line sensor unit48. Note that in the graph ofFIG. 3B, the axis of abscissas represents the position (r) in a radial direction of the wafer11, and the axis of ordinates represents height (Z). For example, when the reflected light of the laser beam48aapplied to the region depicted inFIG. 3Ais detected by the line sensor unit48, a graph as depicted inFIG. 3Bis obtained. In this graph, E corresponds to the position of a peripheral edge of the wafer11, and H corresponds to the height from the holding surface16aof the chuck table16to the front surface11aof the wafer11(namely, the thickness of the wafer11). The information calculation section50aof the processor unit50calculates the position of the peripheral edge of the wafer11and the height of the front surface11aof the wafer11, from H and E in the graph.

In the present embodiment, the reflected light of the laser beam48ais detected by the line sensor unit48while rotating the chuck table16; therefore, the graphs as depicted inFIG. 3Bare obtained correspondingly to a plurality of regions of the peripheral portion11c. In other words, the information calculation section50acan calculate the position of the peripheral edge and the height of the front surface11ain the plurality of regions of the wafer11. As a result, the positions of the profile of the wafer11become clear. Further, the information calculation section50amay calculate the position of the center of the wafer11, based on the information on the positions of the peripheral edge (the information on the positions of the profile) obtained from the plurality of regions of the wafer11. When the position of the wafer11and the height of the front surface11aof the wafer11are thus calculated, the first calculation step is finished.

After the first calculation step, a stepped portion forming step of partly cutting and removing the peripheral portion11cof the wafer11to form an annular stepped portion is carried out. Specifically, first, the chuck table16with the wafer11held thereon and the cutting unit42are relatively moved, to align the cutting blade to a position where the stepped portion is to be formed. Here, the position of the cutting blade (the position at which the cutting blade is made to cut into the wafer11) is determined based on the position of the wafer11calculated in the first calculation step in such a manner that an annular stepped portion with a predetermined width can be formed at the peripheral portion11c. Next, a lower end of the cutting blade is lowered to a position below the front surface11aof the wafer11. Simultaneously, the chuck table16is rotated. Here, the height of the cutting blade (the depth to which the cutting blade is made to cut into the wafer11) is determined based on the height of the front surface11aof the wafer11calculated in the first calculation step in such a manner that an annular stepped portion with a predetermined depth can be formed at the peripheral portion11c.

For instance, in the case where the height of the front surface11aof the wafer11calculated in the first calculation step varies in the circumferential direction, it is recommendable to vary the height of the cutting blade (the depth to which the cutting blade is made to cut into the wafer11) according to the rotation of the chuck table16, taking into account the height of the front surface11aof the wafer11. In addition, in the case where the positions of the profile of the wafer11calculated in the first calculation step are deviated from a reference range of the chuck table16(in the case where the center of the wafer11is deemed not to be in register with the rotational axis of the chuck table16), it is recommendable to move the cutting unit42in the Y-axis direction in accordance with the rotation of the chuck table16. As a result of this, the cutting blade can be made to cut into the peripheral portion11cof the wafer11from the front surface11aside of the wafer11, to partly cut and remove the peripheral portion11cfrom the front surface11aside, and thereby to form an annular stepped portion11d(seeFIG. 4Aand the like) having a predetermined width and a predetermined depth. When the stepped portion11dis formed, the stepped portion forming step is finished.

After the stepped portion forming step, a second calculation step of calculating the width and the height of the stepped portion11d(for example, the height from a bottom of the stepped portion11dto the front surface11a) is carried out.FIG. 4Ais a sectional view depicting schematically the manner in which the laser beam48ais applied to the wafer11from the line sensor unit48, andFIG. 4Bis a plan view depicting schematically the manner in which the laser beam48ais applied to the wafer11from the line sensor unit48. Note that inFIG. 4A, some of components are depicted in the form of a functional block or the like. As depicted inFIGS. 4A and 4B, in the second calculation step, first, the chuck table16is rotated into an arbitrary orientation. In this state, a laser beam48ain a band-like shape elongate in a radial direction of the wafer11is applied from the line sensor unit48toward a region inclusive of the peripheral portion11c(a region inclusive of the stepped portion11d) of the wafer11. Then, reflected light of the laser beam48areflected on the front surface11aside of the wafer11is detected by the line sensor unit48.

FIG. 5Ais a sectional view depicting in an enlarged form a region of the wafer11to which the laser beam48ais applied, andFIG. 5Bis a graph depicting schematically the results of detection of the reflected light reflected on the region depicted inFIG. 5A. Note that in the graph ofFIG. 5B, the axis of abscissas represents the position (r) in a radial direction of the wafer11, and the axis of ordinates represents the height (Z). For example, when the reflected light of the laser beam48aapplied to the region depicted inFIG. 5Ais detected by the line sensor unit48, a graph as depicted inFIG. 5Bis obtained. In this graph, w corresponds to the width of the stepped portion11d, and h corresponds to the height of the stepped portion11d(the height from the bottom of the stepped portion11dto the front surface11a). The information calculation section50aof the processor unit50calculates the width and the height of the stepped portion11dfrom w and h in the graph.

FIG. 6Ais a sectional view depicting, in an enlarged form, another region of the wafer11to which the laser beam48ais applied, andFIG. 6Bis a graph depicting schematically the results of detection of the reflected light reflected on the region depicted in FIG.6A. When the reflected light of the laser beam48aapplied to the region depicted inFIG. 6Ais detected by the line sensor unit48, a graph as depicted inFIG. 6Bis obtained. In this graph, Δ1corresponds to the height from the bottom of the stepped portion11dto the top of a projection11e. In this way, in the case where ruggedness (projections and recesses) is present at the bottom of the stepped portion11d, it is desirable for the information calculation section50aof the processor unit50to calculate Δ1as the difference of elevation. Similarly, in the graph ofFIG. 6B, Δ2corresponds to the height from the bottom of the stepped portion11dto the top of a corner portion11fconfigured in a curved surface shape. In this way, in the case where the corner portion11fof the stepped portion11dis configured in a curved surface shape, it is desirable for the information calculation section50aof the processor unit50to calculate Δ2as the height of the corner portion11f. When the width, height, and difference in elevation of the stepped portion11dand the height of the corner portion11fand the like are calculated, the second calculation step is finished.

After the second calculation step, a determination step is carried out in which thresholds for the width, height, and difference of elevation of the stepped portion11dand the height of the corner portion11fand the width, height, and difference of elevation of the stepped portion11dand the height of the corner portion11fthat are calculated in the second calculation step are compared with each other, and it is determined whether or not consumption amount and a change in shape of a tip of the cutting blade and the like are within allowable ranges. Specifically, the threshold comparison section50bof the processor unit50compares a threshold for the width of the stepped portion11d, a threshold for the height of the stepped portion11d, a threshold for the difference of elevation of the stepped portion11d, and a threshold of the height of the corner portion11fthat are preliminarily set with the width, height, and difference of elevation of the stepped portion11dand the height of the corner portion11fthat are calculated in the second calculation step.

Here, the threshold for the width of the stepped portion11dand the threshold for the height of the stepped portion11dare determined, for example, in accordance with allowable ranges of consumption amount and a change in shape of the tip of the cutting blade. In the case where the width and the height of the stepped portion11dare not more than (are less than) the respective thresholds, the threshold comparison section50bdetermines that the consumption amount and the change in shape of the tip of the cutting blade are not in allowable ranges. On the other hand, in the case where the width and the height of the stepped portion11dare more than (are not less than) the respective thresholds, the threshold comparison section50bdetermines that the consumption amount and the change in shape of the tip of the cutting blade are within allowable ranges.

Similarly, the threshold for difference of elevation of the stepped portion11dand the threshold for the height of the corner portion11fare determined, for example, in accordance with an allowable range of the change in shape of the tip of the cutting blade. In the case where the difference of elevation of the stepped portion11dand the height of the corner portion11fare not more than (are less than) the respective thresholds, the threshold comparison section50bdetermines that the change in shape of the tip of the cutting blade is within the allowable range. On the other hand, in the case where the difference of elevation of the stepped portion11dand the height of the corner portion11fare more than (are not less than) the respective thresholds, the threshold comparison section50bdetermines that the change in shape of the tip of the cutting blade are not within the allowable ranges. Note that in the case where the height of the corner portion11fis more than (is not less than) the threshold, there is a problem that grinding of the wafer causes an edge to be processed in an eaves-like shape and be susceptible to chipping.

An operator is informed of the results of the determination step by such a method as display on a monitor (not depicted) or the like, turning ON (blinking) of an alarm lamp, or generation of an alarm sound. The operator can appropriately carry out such a process as replacement of the cutting blade, based on the results of determination in the determination step. Further, the cutting apparatus2may be configured so that the height, the position in the Y-axis direction and the like of the cutting blade can be automatically adjusted based on the results of the determination step. By this adjustment, it is possible to again process the wafer11as an object of determination, or to successively process another wafer11.

As has been described above, the cutting apparatus2of the present embodiment includes the line sensor unit48that applies the laser beam48ain a band-like shape elongated in a radial direction of the wafer11to the region inclusive of the peripheral portion11cof the wafer11held on the chuck table16and detects the reflected light of the laser beam reflected on the region. The cutting apparatus2of the present embodiment further includes the information calculation section50athat calculates the position of the wafer11and the height of the front surface11aof the wafer11, and calculates the width and the height of the stepped portion11d, from the reflected light of the laser beam48adetected by the line sensor unit48. Therefore, it is unnecessary to mount a plurality of sensors for calculating the height of the position of the wafer11and the height of the front surface11aof the wafer11as well as the width and the height of the stepped portion11d.

In addition, in the cutting apparatus2of the present embodiment, use is made of the line sensor unit48by which the reflected lights reflected at a plurality of positions can be detected at a time. Therefore, the time required for calculation of the position of the wafer11, the height of the front surface11aof the wafer11as well as the width and the height of the stepped portion11dcan be shortened, as compared to the cases where other sensor and/or other method is used.

Further, the cutting apparatus2of the present embodiment further includes the threshold comparison section50bthat compares the width and the height of the stepped portion11dcalculated by the information calculation section50awith the thresholds for the width and the height of the stepped portion11d, and determines whether or not the consumption amount and the change in shape of the tip of the cutting blade are within allowable ranges. Therefore, it is possible to appropriately determine whether or not the consumption amount and the change in shape of the tip of the cutting blade are within the allowable ranges, and to appropriately carry out such a process as replacement of the cutting blade.

Note that the present invention is not limited to the description of the above embodiment, but can be carried out with various modifications. For instance, in the wafer processing method according to the present embodiment, in the case where the positions of the profile of the wafer11calculated in the first calculation step are deviated from a reference range of the chuck table16, the cutting unit42is moved in the Y-axis direction in accordance with the rotation of the chuck table16in the subsequent stepped portion forming step. However, such a movement of the cutting unit42can be omitted, for example, if the wafer11is re-carried into the correct position on the chuck table16by the second carrying unit28before the stepped portion forming step.

In addition, in the wafer processing method according to the present embodiment, the chuck table16is rotated in the second calculation step. However, the chuck table16may not necessarily be rotated in the second calculation step. In this case, the width, height, and difference of elevation of the stepped portion11das well as the height of the corner portion11fand the like are calculated in regard of one region of the peripheral portion11c.