Workpiece division process

Abstract

Workpiece dividing method for dividing a plate-shaped workpiece (1) into several individual chips, the workpiece dividing method comprising: a workpiece preparation step of preparing the plate-shaped workpiece (1), wherein at least one side of the workpiece (1) is formed as a matte surface having irregularities and a surface roughness; a holding step of holding the workpiece (1) on a holding surface (21) of a chuck table (2) in a state in which the matte surface of the workpiece (1) is exposed; a cutting groove forming step of cutting the matte surface of the workpiece (1) held on the holding surface (21) of the chuck table (2) using a cutting blade (42), to thereby form a cutting groove (12) with a residual portion (15) having a predetermined thickness as measured from a back side of the workpiece (1); and a laser cutting step of applying a laser beam (7) having an absorption wavelength with respect to the workpiece (1) along the cutting groove (12) formed in the cutting groove forming step to thereby cut the remaining portion (15); wherein chipping, which may occur when cutting a front side of the workpiece (1) using the cutting blade (42), is suppressed by the matte surface; and a deposit generated in the laser cutting step is received in the cutting groove (12) to suppress exposure of the deposit on the front side of the workpiece (1).

Description

Background of the inventionField of the invention

[0001] The present invention relates to a workpiece dividing method. Description of the state of the art

[0002] A wafer having semiconductor devices such as ICs and LSIs or optical devices such as LDs and LEDs formed on the front surface is divided by applying a laser beam along dividing lines with a laser machining apparatus to form laser-machined grooves on the front surfaces of the wafer, thereby obtaining individual devices used as memories, CPUs, LEDs, etc. (see, for example, Japanese Patent Publication No. HEI 10-305420). Such a method using a laser beam to form a laser-machined groove has an advantage in that the width of a machined area when dividing the wafer can be reduced, compared with the case of cutting the wafer using a cutting blade.Consequently, in the case of manufacturing a chip with a device having a small size, it is possible to increase the number of chips that can be manufactured from a wafer as a workpiece.

[0003] Further information helpful for understanding the present invention can be found in the following documents: US 2006 / 0 169 680 A1 relates to the singulation of integrated circuits and in particular to a system for singulating integrated circuits by mechanical cutting and by laser cutting. DE 60 2005 005 872 T2 relates to a method for producing an adhesive sheet material for laser separation. Summary of the invention

[0004] However, in the case of applying a laser beam to the workpiece to form a laser-machined groove on the front surface of the workpiece, deposits as molten material generated from the workpiece by the laser beam are deposited on the opposite sides of the laser-machined groove in proportion to the amount removed from the workpiece by the laser beam. For example, in the case of forming a deep groove by applying a laser beam to divide the workpiece, the amount of deposits increases, so the width of the deposits deposited on the front surface of the workpiece is also increased. As a result, the advantage of being able to narrow the width of a surface area by laser machining may not be sufficiently achieved.

[0005] It is therefore an object of the present invention to provide a workpiece dividing method with which the width of a surface area that is machined during the division of the workpiece can be reduced.

[0006] According to one aspect of the present invention, there is provided a workpiece dividing method for dividing a plate-shaped workpiece into a plurality of individual chips, the workpiece dividing method comprising: a workpiece preparing step of preparing the plate-shaped workpiece, at least one side of which is formed as a matte surface having irregularities and surface roughness; a holding step of holding the workpiece on a holding surface of a chuck table in a state where the matte surface of the workpiece is exposed; a cutting groove forming step of cutting the matte surface of the workpiece held on the holding surface of the chuck table using a cutting blade to thereby form a cutting groove having a remaining portion having a predetermined thickness as measured from the back side of the workpiece;and a laser cutting step of applying a laser beam having an absorption wavelength relative to the workpiece along the cutting groove formed in the cutting groove forming step, thereby cutting the remaining portion; wherein chipping that occurs when cutting the front side of the workpiece using the cutting blade is prevented or reduced by the matte surface; and deposits generated in the laser cutting step are accommodated in the cutting groove to prevent or reduce exposure of the deposits on the front side of the workpiece.

[0007] Preferably, the surface roughness Ra of the matte surface of the workpiece is set to a range of 0.5 to 5.0 µm.

[0008] As described above, the workpiece dividing method according to the present invention is a method for dividing a plate-shaped workpiece into a plurality of individual chips, and this method includes a workpiece preparation step of preparing the plate-shaped workpiece, at least one side of which is formed as a matte surface, a holding step of holding the workpiece on a holding surface of a chuck table in a state where the matte surface of the workpiece is exposed, a cutting groove forming step of cutting the matte surface of the workpiece held on the holding surface of the chuck table using a cutting blade to thereby form a cutting groove with a residual portion having a predetermined thickness as measured from the back of the workpiece, and a laser cutting step of applying a laser beam.having an absorption wavelength relative to the workpiece, along the cutting groove formed in the cutting groove forming step, thereby cutting the remaining portion. Consequently, chipping of the front surface of the workpiece using the cutting blade during cutting through the matte surface is suppressed. Furthermore, deposits generated in the laser cutting step are absorbed in the cutting groove, thereby suppressing exposure of the deposits on the front surface of the workpiece.

[0009] The workpiece dividing method according to the present invention can have an effect that the width of a surface area machined when dividing the workpiece can be reduced.

[0010] The above and other objects, features and advantages of the present invention and the manner in which the same may be carried out will become more apparent and the invention itself will be best understood from a study of the following description and the appended claims with reference to the attached drawings which show preferred embodiments of the invention. Short description of the drawings Fig. 1 is a perspective view of a workpiece to be divided by a workpiece dividing method according to a preferred embodiment of the present invention; Fig. 2 is a side sectional view illustrating a cut groove forming step in the workpiece dividing method according to the preferred embodiment; and Fig. 3 is a side sectional view illustrating a laser cutting step in the workpiece dividing method according to the preferred embodiment. Detailed description of the preferred embodiment

[0011] A workpiece dividing method according to a preferred embodiment of the present invention will be described below with reference to the drawings. The present invention is not limited to this embodiment. Some elements in this preferred embodiment may be adopted from the prior art by those skilled in the art.

[0012] The preferred embodiment is described below with reference to the Fig. 1 to 3. The preferred embodiment relates to a workpiece dividing method. Fig. 1 is a perspective view of a workpiece 1 to be divided by the workpiece dividing method according to the preferred embodiment, Fig. Fig. 2 is a side sectional view showing a cutting groove forming step in the workpiece dividing method according to the preferred embodiment, and Fig. 3 is a side sectional view illustrating a laser cutting step in the workpiece dividing method according to the preferred embodiment. As shown in Fig. 1, the workpiece 1 is a plate-shaped member and is formed, for example, from a circular ceramic substrate made of AlTiC. A notch 1a is formed on the outer periphery of the workpiece 1. A plurality of chips (devices) are formed on the front surface 11 of the workpiece 1. A plurality of intersecting dividing lines for dividing the workpiece 1 into a plurality of chips are formed on the front surface 11 of the workpiece 1. The workpiece dividing method according to the preferred embodiment is a method for dividing the plate-shaped workpiece 1 into individual chips, and this method includes a workpiece providing step, a holding step, a cutting groove forming step, and a laser cutting step. (Workpiece preparation step)

[0013] The workpiece preparation step is a step of preparing the plate-shaped workpiece 1, at least one side of which is formed as a matte surface. That is, at least one of the front and back surfaces of the workpiece 1 is formed as a matte surface. The matte surface is a surface having a certain surface roughness. For example, the workpiece 1 is manufactured by firing, and the matte surface of the workpiece 1 is a surface that is not subjected to a gloss finish. In this preferred embodiment, only the front surface 11 of the workpiece 1 is formed as a matte surface. As a modification, both the front surface 11 and the back surface 14 of the workpiece 1 may be formed as matte surfaces.

[0014] As described above, the workpiece preparation step is a step of preparing the plate-shaped workpiece 1 having a matte surface on at least one side. This step may include a step of forming features on the workpiece 1, a step of machining the back surface 14 of the workpiece 1, a step of forming a protective film on the front surface 11 of the workpiece 1, and a step of placing the workpiece 1 into a cassette or the like of a cutting device 30 (see FIG. Fig. 2). (cutting device)

[0015] As it is in Fig. 2, the workpiece 1 is held on a holding surface 21 of a chuck table 2 provided in the cutting device 30. The cutting device 30 includes the chuck table 2 and a cutting means 4. The chuck table 2 serves to hold the workpiece 1 when cutting the workpiece 1 using the cutting means 4. The holding surface 21 (upper surface) of the chuck table 2 is, for example, a circular portion formed of a porous ceramic material. The chuck table 2 is connected to a vacuum source (not shown) via a vacuum line (not shown), whereby the back surface 14 of the workpiece 1 is held on the holding surface 21 under suction.

[0016] The cutting means 4 serves to cut the workpiece 1 by rotating a cutting blade 42. The cutting means 4 includes a spindle housing 41, the cutting blade 42, and a spindle 43. The cutting blade 42 is fixed to the spindle 43 so as to be rotatable therewith. The spindle 43 is rotatably supported by the spindle housing 41. The spindle housing 41 contains a drive source, such as a motor, for rotatably driving the spindle 43. The cutting blade 42 is a very thin abrasive element that is substantially annular, and this is rotated to cut the workpiece 1. The thickness t of the cutting blade 42 is, for example, in the range of 40 to 10 µm, preferably 30 to 20 µm.

[0017] The cutting device 30 further includes a transport mechanism for transporting the workpiece 1 to the holding surface 21 of the chuck table 2 and placing the workpiece 1 thereon, a Z-axis moving mechanism for relatively moving the chuck table 2 and the cutting means 4 in the direction (Z direction) perpendicular to the holding surface 21, an X-axis moving mechanism for relatively moving the chuck table 2 and the cutting means 4 in the X-direction (the direction perpendicular to the paper plane of the Fig. 2) and a Y-axis moving mechanism for relatively moving the chuck table 2 and the cutting means 4 in the Y direction. In this preferred embodiment, the Z direction is a vertical direction, and the workpiece 1 is placed on the support surface 21 of the chuck table 2 in a state where the front surface 11 of the workpiece 1 is oriented upward in the vertical direction.

[0018] Both the X-direction and the Y-direction are perpendicular to the Z-direction. Furthermore, the X-direction and the Y-direction intersect. In particular, in this preferred embodiment, the X-direction and the Y-direction are perpendicular to each other. The cutting device 30 further includes a Z-axis rotating mechanism for rotating the chuck table 2 about the Z-axis. The workpiece 1 is arranged on the holding surface 21 of the chuck table 2 such that the rotation axis of the chuck table 2 coincides with the axis of the circular workpiece 1. The cutting device 30 further includes a mechanism for retrieving and transporting the workpiece 1 to the next station after performing a cutting operation by the cutting device 30. Before arranging the workpiece 1 on the chuck table 2, a so-called "dicing tape" 3 is applied as an adhesive tape to the back 14 of the workpiece 1. (hold step)

[0019] The holding step is a step of holding the workpiece 1 on the holding surface 21 of the chuck table 2 in a state where the matte surface of the workpiece 1 is exposed. The conveying mechanism of the cutting device 30 serves to convey the workpiece 1, which is loaded in a cassette or the like, to the chuck table 2 and to place the workpiece 1 on the chuck table 2 in a state where the back surface 14 of the workpiece 1 faces the holding surface 21 via the dicing tape 3. In other words, the conveying mechanism of the cutting device 30 is configured to place the workpiece 1 on the chuck table 2 in a state where the front surface 11 (matte surface) of the workpiece 1 is exposed. Then, the back surface 14 of the workpiece 1 is held by suction onto the holding surface 21 of the chuck table 2 via the dicing tape 3. (orientation)

[0020] After holding the workpiece 1 on the holding surface 21 of the chuck table 2 as set forth above, an alignment process is performed. The alignment process is a process of aligning a specific division line of the workpiece 1 with the cutting blade 42. Since the front surface 11 of the workpiece 1 is a matte surface in this preferred embodiment, a transmitted light microscope using infrared radiation is not suitable for performing the alignment process. Therefore, any means other than the transmitted light microscope using infrared radiation may be used to perform the alignment process for the front surface 11 of the workpiece 1. Alternatively, the alignment process may be performed from the back surface 14 of the workpiece 1.Furthermore, the alignment process can be performed, for example, according to the notch 1a formed on the outer periphery of the workpiece 1 or an orientation flat. The cutting device 30 is configured to obtain orientation information and then adjust the relative positional relationship between the workpiece 1 (the chuck table 2) and the cutting means 4 in the X and Y directions. The orientation information can be obtained by imaging the front surface 11 of the workpiece 1 and processing an obtained image.

[0021] The cutting device 30 further operates the X-axis moving mechanism, the Y-axis moving mechanism, and the Z-axis rotating mechanism according to the alignment information obtained as described above to change the relative positional relationship between the chuck table 2 and the cutting means 4 in the X and Y directions, thereby positioning one end of the predetermined dividing line directly below the cutting blade 42. At this time, the alignment of the predetermined dividing line and the cutting blade 42 is provided such that the predetermined dividing line extends in the X direction. Further, the cutting device 30 operates the Z-axis moving mechanism to adjust the relative positional relationship between the workpiece 1 and the cutting means 4 in the Z direction. (Cutting groove formation step)

[0022] The cutting groove forming step is a step of cutting the front surface 11 (matte surface) of the workpiece 1 held on the holding surface 21 of the chuck table 2 using the cutting blade 42 to thereby form a cutting groove 12 with a residual portion 15 having a certain thickness measured from the back surface 14 of the workpiece 1. As shown in Fig. 2, the workpiece 1 is cut from the front surface 11 using the cutting blade 42 of the cutting device 30, thereby forming the cutting groove 12. To form the cutting groove 12 with the residual portion 15 having a certain thickness measured from the back surface 14 of the workpiece 1, the Z-axis moving mechanism of the cutting device 30 is operated to preliminarily adjust the relative positional relationship between the chuck table 2 and the cutting means 4 in the Z direction.

[0023] The depth d of the cutting groove 12, that is, the distance in the Z direction from the front surface 11 of the workpiece 1 to the bottom of the cutting groove 12, is set to half or more of the thickness h of the workpiece 1. For example, the depth d of the cutting groove 12 is set so that the thickness of the residual portion 15 described below (which is equal to the value obtained by subtracting the depth d of the cutting groove 12 from the thickness h of the workpiece 1) is less than or equal to 100 μm.

[0024] The X-axis movement mechanism of the cutting device 30 is actuated to move the chuck table 2 and the cutting blade 42 relative to each other in the X direction, thereby forming the cutting groove 12 along the predetermined dividing line extending in the X direction. After completing the formation of the cutting groove 12 along the predetermined dividing line, the Y-axis movement mechanism of the cutting device 30 is actuated to move the chuck table 2 and the cutting blade 42 relative to each other in the Y direction, thereby aligning the cutting blade 42 with the next dividing line, and then starting the formation of another cutting groove 12.In this way, the cutting device 30 alternately performs the formation of the cutting groove 12 and the alignment of the cutting blade 42 with the next dividing line, thereby sequentially forming a plurality of grooves 12 along all the dividing lines extending in the X direction on the front side 11 of the workpiece 1. After completing the formation of the cutting grooves 12 along all the dividing lines extending in a first direction (X direction in this case), the Z-axis rotating mechanism of the cutting device 30 is operated to rotate the chuck table 2 by 90°, and then, in the same manner, a plurality of cutting grooves 12 are formed in a direction intersecting the previously formed cutting grooves 12, for example, along all the dividing lines extending in a second direction perpendicular to the first direction.At the time of completion of the formation of the cut grooves 12 along all the dividing lines extending in the second direction, the cut groove forming step is terminated.

[0025] As described above, the cutting groove forming step of the workpiece dividing method according to this preferred embodiment is performed using the cutting blade 42 to cut the workpiece 1 from the front surface 11 as a matte surface, thereby forming the cutting grooves 12 on the front surface 11 of the workpiece 1. Thus, the workpiece 1 is cut from the matte surface by means of the cutting blade 42, so that chipping that may occur during cutting of the workpiece 1 can be suppressed by the irregularities on the matte surface. It is believed that the reason is that the occurrence of chipping itself is suppressed by the irregularities on the matte surface, or that the magnification of small chips that occur is suppressed by the irregularities on the matte surface.

[0026] The surface roughness Ra of the matte surface of the workpiece 1 is preferably set in the range of 0.5 to 5.0 μm. The upper limit of the surface roughness Ra of the matte surface of the workpiece 1 is more preferably set to 3 μm. The surface roughness Ra (center line average roughness) can be replaced by Rz (ten-point average roughness) or Rmax (maximum height). The front surface 11 of the workpiece 1 can be machined in advance to have a desired surface roughness.

[0027] By suppressing chipping as described above, the width of a surface area machined by the cutting blade 42 can be reduced. For example, compared with the case of cutting the front surface 11 as a mirror-finished surface using the cutting blade 42 to form the cut grooves 12, the generation of chipping can be suppressed, thereby reducing the width of a machined surface area. Consequently, according to the preferred embodiment, the width of a surface area required for dividing the workpiece 1 can be reduced. The workpiece 1 thus machined to form the cut grooves 12 by performing the cut groove forming step is next taken off the chuck table 2 and transferred to a laser processing device 50 (see FIG. Fig. 3) transported by means of a transport mechanism or the like (not shown). (Laser processing device)

[0028] As it is in Fig. As shown in Fig. 3, the laser processing apparatus 50 includes a chuck table 5 and a laser processing means 6. For example, the chuck table 5 is constructed like the chuck table 2 of the above-mentioned cutting apparatus 30. That is, the chuck table 5 has a holding surface 51 for holding the workpiece 1 thereon. The workpiece 1 is held on the holding surface 51 of the chuck table 5 in a state where the front surface 11 of the workpiece 1 is exposed.

[0029] The laser processing means 6 is designed to apply a laser beam 7 to the workpiece 1 held on the clamping table 5. The laser processing means 6 includes a laser oscillator for oscillating the laser beam 7 and focusing means for applying the laser beam 7 oscillated by the laser oscillator to the front surface 11 of the workpiece 1. The laser oscillator is capable of adjusting the frequency (wavelength) of the laser beam 7 to be oscillated. The laser oscillator serves to oscillate the laser beam 7, which has an absorption wavelength with respect to the workpiece 1. For example, a YAG laser oscillator or a YVO4 laser oscillator can be used as the laser oscillator.The focusing means includes a total reflection mirror for changing the propagation direction of the laser beam 7 oscillated by the laser oscillator, and a focusing lens for concentrating the laser beam 7 reflected by the total reflection mirror.

[0030] The laser processing device 50 further includes a transport mechanism for transporting the workpiece 1 to the holding surface 51 of the chuck table 5 and placing the workpiece 1 thereon, a Z'-axis moving mechanism for relatively moving the chuck table 5 and the laser processing means 6 in the Z'-direction, an X'-axis moving mechanism for relatively moving the chuck table 5 and the laser processing means 6 in the X'-direction (the direction perpendicular to the paper plane of the Fig.3) and a Y'-axis moving mechanism for relatively moving the chuck table 5 and the laser processing means 6 in the Y' direction. The Z' direction is a direction perpendicular to the holding surface 51. In this preferred embodiment, the Z' direction is a vertical direction, and the workpiece 1 is placed on the holding surface 51 of the chuck table 5 in a state where the front surface 11 of the workpiece 1 is oriented upward in the vertical direction.

[0031] Both the X' direction and the Y' direction are perpendicular to the Z' direction. Furthermore, the X' direction and the Y' direction intersect. Specifically, in this preferred embodiment, the X' direction and the Y' direction are perpendicular to each other. The laser processing device 50 further includes a Z' axis rotation mechanism for rotating the chuck table 5 about the Z' axis. The workpiece 1 is arranged on the support surface 51 of the chuck table 5 so that the rotation axis of the chuck table 5 coincides with the axis of the circular workpiece 1. The laser processing device 50 further includes a mechanism for retrieving or recovering the workpiece from the chuck table 5, whereby the workpiece 1 is transported to the next station after the laser processing device 50 has performed a laser processing operation. (Laser cutting step)

[0032] The laser cutting step is a step of applying the laser beam 7, which has an absorption wavelength relative to the workpiece 1, along the cut grooves 12 formed in the cut groove forming step, thereby cutting the residual portion 15. Before performing this laser cutting step, the laser processing device 50 is operated to obtain alignment information for aligning a specific cut groove 12 (the parting lines) of the workpiece 1 relative to the laser beam 7 to be applied by the laser processing means 6. The alignment information can be obtained by imaging the front surface 11 of the workpiece 1 and processing an obtained image.

[0033] Next, the laser processing device 50 operates the X'-axis moving mechanism, the Y'-axis moving mechanism, and the Z'-axis rotating mechanism according to the alignment information obtained above to change the relative position between the chuck table 5 and the laser processing means 6, thereby positioning one end of the predetermined dividing line (cutting groove 12) directly under the focusing means of the laser processing means 6. At this time, the alignment of the predetermined dividing line and the focusing means is performed so that the predetermined dividing line extends in the X'-direction. Further, the Z'-axis moving mechanism of the laser processing device 50 is operated to adjust the relative position between the workpiece 1 and the laser processing means 6 in the Z'-direction, thereby setting the focal point of the laser beam 7 to be applied by the focusing means.

[0034] After completing the alignment between the workpiece 1 and the laser processing means 6, the laser processing device 50 starts the laser cutting step to apply the laser beam 7 from the laser processing means 6. At that time, the laser beam 7 is applied to the bottom of the predetermined cutting groove 15, that is, to the upper end of the predetermined remaining portion 15. The X'-axis moving mechanism of the laser processing device 50 is actuated to move the workpiece 1 (the chuck table 5) and the laser processing means 6 relative to each other in the X' direction as the laser beam 7 is applied, thereby forming a laser-machined groove 13 in the predetermined remaining portion 15. The laser-machined groove 13 has a depth reaching the back surface 14 of the workpiece 1. Consequently, the predetermined remaining portion 15 is cut by this laser-machined groove 13.That is, the workpiece 1 is divided into a portion positioned on one side of the laser-machined groove 13 and a portion positioned on the other side of the laser-machined groove 13 in the Y' direction. Cutting the determined residual portion 15 can be performed by applying the laser beam 7 in one pass or in multiple passes.

[0035] Compared with the case where the cutting blade 42 is used to completely cut the workpiece 1, chipping that may occur on the back surface 14 of the workpiece 1 can be suppressed by performing the laser cutting step to cut the residual portion 15. Furthermore, the width of a machined surface area on the back surface 14 can be reduced. When forming the laser-machined groove 13, deposits 8 are generated on the opposite sides of the laser-machined groove 13. When the generated deposits 8 are deposited on the front surface 11 of the workpiece 1, the width of a machined surface area increases.

[0036] In this preferred embodiment, however, the laser-machined groove 13 is formed by applying the laser beam 7 to the bottom of the corresponding cut groove 12. Consequently, the deposits 8 generated by the formation of the laser-machined groove 13 are deposited on the opposite side wall surfaces 12a and 12b of the cut groove 12. That is, the deposit 8 generated in the laser cutting step accumulates in the corresponding cut groove 12 and is prevented from being exposed to the outside of the cut groove 12 (the front side 11 of the workpiece 1). Consequently, with the workpiece dividing method according to this preferred embodiment, the problem of the deposit 8 being exposed to the front side 11 of the workpiece 1, thereby reducing the width of a machined area, can be avoided.

[0037] The depth d and the width w of the cut groove 12 are set so that at least a portion of the deposits 8 generated by forming the laser-machined groove 13 can accumulate in the corresponding cut groove 12, thereby suppressing the exposure of the deposits 8 to the outside of the corresponding cut groove 12. Specifically, the depth d and the width w may be set so that all of the generated deposits 8 accumulate in the corresponding cut groove 12, in other words, so that the height of the deposit 8 in the Z' direction is less than or equal to the depth d of the corresponding cut groove 12. Furthermore, the focal spot diameter (Y' direction) of the laser beam 7 applied by the laser processing means is set smaller than the width w of the corresponding cut groove 12.

[0038] After completing the formation of the laser-machined groove 13 along the specified dividing line extending in the first direction, the Y'-axis moving mechanism of the laser machining device 50 is actuated to move the chuck table 5 and the laser machining means 6 relative to each other in the Y' direction, thereby performing alignment of the laser machining means 6 to the next dividing line, and then starting the formation of the next laser-machined groove 13. In this way, the laser machining device 50 alternately performs the formation of the laser-machined groove 13 (cutting the residual portion 15 by the laser beam 7) and the alignment of the laser machining means 6 to the next dividing line, thereby sequentially cutting the residual portions 15 along all the dividing lines extending in the first direction.

[0039] After completing the cutting of the remaining portions 15 along all the dividing lines extending in the first direction, the Z'-axis rotation mechanism of the laser processing device 50 is operated to rotate the chuck table 5 by 90°, and then similarly cut the remaining portions 15 in a direction that intersects the previously cut remaining portions 15, that is, along all the dividing lines extending in the second direction perpendicular to the first direction. At the time of completing the cutting of the remaining portions 15 along all the dividing lines extending in the second direction, the laser cutting step is terminated.

[0040] After completion of the laser cutting step, the workpiece 1 is removed from the chuck table 5 and then subjected to a pick-up step. In the pick-up step, each chip 16 obtained by dividing the workpiece 1 in the laser cutting step is peeled off the dicing tape 3. As described above, the deposits 8 on the front side 11 of the workpiece 1 are prevented from being exposed in this preferred embodiment. Consequently, it is possible to avoid the problem of the deposits 8 being sucked out by vacuum in the pick-up step.

[0041] In the present invention, the workpiece is not limited to a ceramic substrate. For example, any substrate made of inorganic material other than the ceramic substrate, and a semiconductor wafer such as a silicon wafer, can be used as the workpiece in the present invention. In the case of a silicon wafer, the matte surface of the workpiece is a surface that is not subjected to any processing, such as grinding, after cutting a silicon ingot.

[0042] While the cutting device 30 and the laser processing device 50 are separate devices in this embodiment, the cutting device 30 and the laser processing device 50 can be combined to construct an integral device. The contents disclosed in this preferred embodiment can be combined as appropriate.

[0043] The present invention is not limited to the details of the preferred embodiment described above. The subject matter of the invention is defined by the appended claims, and all changes and modifications that fall within the scope of equivalence of the subject matter of the claims are therefore encompassed by the invention.

Claims

[1] Workpiece dividing method for dividing a plate-shaped workpiece (1) into a plurality of individual chips, the workpiece dividing method comprising: a workpiece preparation step of preparing the plate-shaped workpiece (1), wherein at least one side of the workpiece (1) is formed as a matte surface having irregularities and a surface roughness; a holding step of holding the workpiece (1) on a holding surface (21) of a chuck table (2) in a state in which the matte surface of the workpiece (1) is exposed; a cutting groove forming step of cutting the matte surface of the workpiece (1) held on the holding surface (21) of the chuck table (2) using a cutting blade (42), to thereby form a cutting groove (12) with a residual portion (15) having a predetermined thickness as measured from a back side of the workpiece (1); and a laser cutting step of applying a laser beam (7) having an absorption wavelength with respect to the workpiece (1) along the cutting groove (12) formed in the cutting groove forming step to thereby cut the remaining portion (15); wherein chipping, which may occur when cutting a front side of the workpiece (1) using the cutting blade (42), is suppressed by the matte surface; and a deposit generated in the laser cutting step is received in the cutting groove (12) to suppress exposure of the deposit on the front side of the workpiece (1). [2] A workpiece dividing method according to claim 1, wherein the surface roughness Ra of the matte surface of the workpiece (1) is set to a range of 0.5 to 5.0 µm.

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