JP2016025112A - Laser cutting method and laser processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser cutting method and a laser processing apparatus that divide a plate-like workpiece into individual chips without leaving any flaw under laser processing on a divided chip.SOLUTION: A laser cutting method for irradiating a plate-like workpiece (W) having a protection layer (95) on the surface thereof with a laser beam to cut the plate-like workpiece into chips comprises a parting groove forming step of irradiating the protection layer on the surface of the plate-like workpiece with a laser beam to form a parting groove (89) for parting the protection layer while the back surface of the plate-like workpiece is sucked and held, a change-over step of reversing the plate-like workpiece and suck and hold the surface of the plate-like workpiece, and a cutting step of irradiating the back surface of the plate-like workpiece along the parting groove to perfectly cut the plate-like work.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a laser cutting method and a laser processing apparatus for dividing an optical device wafer having a protective layer such as a silicone resin on its surface into individual chips.

  2. Description of the Related Art A wafer for an optical device in which a silicone resin is applied as a protective layer on a surface of an alumina ceramic substrate serving as a base material is known as a plate-shaped workpiece that is put into a laser processing apparatus. When a wafer for optical devices is mechanically cut with a cutting device, a cutting blade is caught on the silicone film, and the silicone film is peeled off from the alumina ceramic substrate starting from the cut portion of the silicone film. For this reason, there has been proposed a method of dividing a wafer into individual chips by ablation processing using a laser beam having a wavelength that absorbs the wafer (see, for example, Patent Document 1).

JP-A-10-305420

  At the time of cutting the wafer for optical devices by ablation processing, after the silicone film is cut with a laser beam having a predetermined output, the output is changed and the alumina ceramic substrate is cut. For this reason, the wafer is divided into individual chips without causing the silicone film to peel off from the alumina ceramic substrate. However, if the silicone film is also irradiated with the laser beam when the alumina ceramic substrate is irradiated with the laser beam, the silicone film is burned or burnt. For this reason, there has been a problem in that the chips after the wafer division remain damaged during laser processing.

  The present invention has been made in view of the above points, and provides a laser cutting method and a laser processing apparatus that can divide a plate-like workpiece into individual chips without leaving any damage during laser processing on the divided chips. The purpose is to provide.

  The laser cutting method of the present invention is a laser cutting method in which a plate-like workpiece having a protective layer on its surface is irradiated with a laser beam to cut the plate-like workpiece to form chips, which sucks the back surface of the plate-like workpiece. Holding and irradiating the surface of the protective layer with a laser beam to form a dividing groove for dividing the protective layer; and after the protective layer dividing step, the suction surface of the plate-like workpiece to be sucked and held A switching step in which the back surface of the switching plate-shaped workpiece is exposed from the back surface to the front surface, and the protective layer side is sucked and held. After the switching step, the back surface of the plate-shaped workpiece is irradiated with a laser beam to completely cut the plate-shaped workpiece. And a cutting process.

  According to this configuration, after the laser beam is irradiated from the front surface side of the plate-shaped workpiece to form the dividing groove in the protective layer, the laser beam is irradiated from the back surface side of the plate-shaped workpiece to completely cut the plate-shaped workpiece. Since the laser beam is irradiated from the back side of the plate-shaped workpiece when the plate-shaped workpiece is completely cut, the protective layer on the front surface side is not affected by the laser beam. It is possible to divide the plate-like workpiece into individual chips without suppressing the burning or scorching of the protective layer and leaving no damage during laser processing.

  In the laser cutting method of the present invention, the surface of the plate-like workpiece is provided with a convex hemispheric surface for each chip, and in the cutting step, at least the hemispheric surface formed on the surface of the plate-like workpiece is sucked and held. Yes.

  The laser processing apparatus of the present invention is a laser processing apparatus used in the above-described laser cutting method, and has a chuck table having a suction surface for sucking and holding a plate-like workpiece, and a plate-like workpiece that is sucked and held by the chuck table. A laser irradiation means for irradiating a laser beam; an output variable portion for changing a laser output irradiated by the laser irradiation means; and a concave hemisphere corresponding to a convex hemisphere formed on the surface of the plate-like workpiece. A holding plate that enables at least suction holding of the convex hemispherical surface, and a switching mechanism that switches between a front surface and a back surface of a plate-like workpiece that is sucked and held by the suction surface, and the holding plate is adjacent to the concave shape. A gap is formed between the hemispherical surfaces, and the suction surface sucks and holds the back surface of the plate-shaped workpiece when the dividing groove is formed in the protective layer, and completely cuts the plate-shaped workpiece. It is at least sucking and holding the convex semi-spherical surface formed on the surface of the plate-shaped workpiece through the holding plate.

  The laser processing apparatus of the present invention includes a second chuck table instead of the holding plate, and the upper surface of the second chuck table is adjacent to a concave hemispherical surface corresponding to the convex hemispherical surface. A gap formed between the concave hemispherical surfaces, and the switching mechanism switches between the front surface and the back surface of the plate-like workpiece held by suction on the suction surface and the upper surface of the second chuck table. The convex hemispherical surface formed on the surface of the wafer by the hemispherical surface is sucked and held to completely cut the wafer.

  Another laser processing apparatus of the present invention is a laser processing apparatus used in the laser cutting method described above, and includes a chuck table having a suction surface for sucking and holding a plate-like work, and a plate-like work that is sucked and held by the chuck table. A first table unit that holds and holds the back surface of the plate-like workpiece by a laser irradiation unit that irradiates the laser beam; and an output variable unit that varies a laser output irradiated by the laser irradiation unit. And a second table portion that sucks and holds the surface of the plate-like workpiece, and an opening and closing mechanism that opens and closes so that the upper surface of the first table portion and the upper surface of the second table portion face each other side by side or adjacent to each other. And the upper surface of the first table portion has a suction surface corresponding to the back surface of the plate-like workpiece, and the upper surface of the second table portion is a concave surface corresponding to the convex hemispherical surface. And a gap formed between the concave hemispheres adjacent to each other, and the opening / closing mechanism has the back surface of the plate-like workpiece on the first surface when the dividing groove is formed in the protective layer. When the plate-like workpiece is completely cut, the convex hemisphere formed on the surface of the plate-like workpiece is sucked and held by the concave hemisphere when the plate-like workpiece is completely cut. Open and close the first table portion and the second table portion.

  According to the present invention, the protective layer is divided by irradiating a laser beam from the front side of the plate-like workpiece, and then completely cut by irradiating the laser beam from the back side of the plate-like workpiece. The plate-like workpiece can be divided into individual chips without leaving a mark.

It is a perspective view of the laser processing apparatus which concerns on this Embodiment. It is a perspective view of the chuck table concerning this embodiment. It is a perspective view of a holding plate and a plate-like work concerning this embodiment. It is explanatory drawing of the laser cutting method which concerns on this Embodiment. It is a figure which shows an example of the switching process using the switching mechanism which concerns on this Embodiment. It is a figure which shows an example of the laser cutting method using the chuck table which concerns on a modification. It is sectional drawing of the 2nd chuck table which concerns on another modification.

  A laser processing apparatus to which a laser cutting method according to the present invention is applied will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view of the laser processing apparatus according to the present embodiment. The laser processing apparatus according to the present invention is not limited to the laser processing apparatus shown in FIG. The laser processing apparatus may be configured in any way as long as the laser cutting method according to the present invention is applied.

  As shown in FIG. 1, the laser processing apparatus 1 irradiates a rectangular plate-shaped plate-like workpiece W on the chuck table 20 with a laser beam, and cuts the plate-like workpiece W into individual chips C (see FIG. 4C). It is configured as follows. The substrate 94 of the plate-like workpiece W is formed of a rectangular alumina ceramic plate, and is divided into a plurality of regions by grid-like division scheduled lines 96 of the substrate 94. An optical device is formed in each area divided by the planned division lines 96. A transparent resin is applied to the surface of the base 94 to form a protective layer 95 that protects the optical device.

  The protective layer 95 has a convex (dome-shaped) hemispherical surface 93 corresponding to each optical device. The hemispherical surface 93 functions as a lens, and improves the luminance by diffusing the light irradiated from the optical device. The plate-like workpiece W is not limited to a workpiece for an optical device, but may be a workpiece for a semiconductor or various package substrates. Therefore, the base 94 may be a glass or sapphire inorganic material substrate, or a semiconductor substrate such as silicon or gallium arsenide. Moreover, the protective layer 95 of the plate-shaped workpiece W should just be formed with the material which can protect a device.

  A chuck table moving mechanism 30 for moving the chuck table 20 in the X-axis direction and the Y-axis direction is provided on the base 10 of the laser processing apparatus 1. The chuck table moving mechanism 30 includes a pair of guide rails 31 arranged on the base 10 and parallel to the X-axis direction, and a motor-driven X-axis table 32 slidably installed on the pair of guide rails 31. doing. The chuck table moving mechanism 30 includes a pair of guide rails 33 arranged on the X-axis table 32 and parallel to the Y-axis direction, and a motor-driven Y-axis table 34 slidably installed on the pair of guide rails 33. And have.

  Nut portions (not shown) are formed on the back sides of the X-axis table 32 and the Y-axis table 34, and ball screws 35 and 36 are screwed into these nut portions. Then, the drive motors 37 and 38 connected to one end portions of the ball screws 35 and 36 are rotationally driven, so that the chuck table 20 is moved along the guide rails 31 and 33 in the X-axis direction and the Y-axis direction. On the Y-axis table 34, the chuck table 20 is rotatably provided via a θ table 39. The chuck table 20 is configured to be able to individually hold the chips C (see FIG. 4C) after the division of the plate-like workpiece W. Details of the chuck table 20 will be described later.

  Further, a standing wall portion 11 is erected on the base 10 behind the chuck table moving mechanism 30, and an arm 12 projects from the standing wall portion 11 toward the upper side of the chuck table 20. A laser irradiation means 50 for irradiating a laser beam along a planned division line 96 of the plate-like workpiece W is provided at the tip of the arm 12. Connected to the laser irradiation means 50 are a gas supply unit 52 for injecting an assist gas to an irradiation region of the laser beam and an output variable unit 53 for changing the laser output of the laser beam (see FIG. 4A).

  The processing of the plate-like workpiece W by the laser irradiation means 50 is performed by ablation processing using a laser beam having a wavelength that is absorptive with respect to the plate-like workpiece W. Ablation means that when the irradiation intensity of the laser beam exceeds a predetermined processing threshold, it is converted into electronic, thermal, photochemical and mechanical energy on the solid surface, resulting in neutral atoms, molecules, positive and negative ions. , A phenomenon in which radicals, clusters, electrons, and light are explosively emitted and the solid surface is etched. The assist gas according to the present embodiment is compressed air, and is appropriately changed to a gas such as oxygen or nitrogen according to the material of the plate-like workpiece W or the like.

  In the laser processing apparatus 1 configured as described above, a laser beam is irradiated from the laser irradiation unit 50 to the plate-like workpiece W, and an assist gas is injected into the irradiation region of the laser beam. The plate-like workpiece W is ablated along the division line 96 by moving the chuck table 20 in a state where the laser beam is irradiated. In addition, in this Embodiment, although it was set as the structure which processes the plate-shaped workpiece | work W by ablation processing, it is not limited to this structure. Any processing may be used as long as the processing can be performed while the plate-like workpiece W is melted by the laser beam.

  In order to divide the plate-like workpiece W according to the present embodiment, the laser output is changed between when the protective layer 95 made of silicone resin is processed and when the substrate 94 made of alumina ceramic is processed. In this case, when the protective layer 95 is irradiated with a laser beam to partially remove the protective layer 95 and then the substrate 94 exposed from the protective layer 95 is completely cut with the laser beam, the condensing position and output during these laser processings Depending on the difference, the protective layer 95 may be burnt or burnt. For this reason, after partially removing the protective layer 95 from the plate-like workpiece W, the plate-like workpiece W is turned over and the substrate 94 is completely cut from the back surface 98 side to divide the plate-like workpiece W into individual chips C. (See FIG. 4C).

  However, since the convex hemispherical surface 93 is formed on the protective layer 95 of the plate-like workpiece W, the plate-like workpiece W cannot be sucked and held by the normal suction surface of the chuck table 20. Therefore, in the present embodiment, when the plate-like workpiece W is completely cut from the back surface 98 side (see FIG. 4C), a porous hemispherical surface 63 is formed between the plate-like workpiece W and the chuck table 20. A quality holding plate 60 is interposed. As a result, the protective layer 95 side of the plate-like workpiece W having the convex hemispherical surface 93 is sucked and held by the chuck table 20 so that the plate-like workpiece W can be completely cut from the back surface 98 side.

  Hereinafter, the chuck table and the holding plate will be described with reference to FIGS. 2 and 3. FIG. 2 is a perspective view of the chuck table according to the present embodiment. FIG. 3 is a perspective view of the holding plate and the plate-like workpiece according to the present embodiment. 2A shows a state where the holding block is removed from the chuck table, and FIG. 2B shows a state where the holding block is attached to the chuck table.

  As shown in FIGS. 2A and 2B, the chuck table 20 is provided with a holding block 22 capable of individually holding each chip C (see FIG. 4C) after the division of the plate-like workpiece W on a base member 21 serving as a base. Is configured. The upper surface of the holding block 22 is partitioned in a lattice shape by clearance grooves 23 corresponding to the division lines 96 (see FIG. 3) of the plate-like workpiece W, and suction surfaces 24 corresponding to the individual chips C are formed. . A suction port 25 is formed at the center of each suction surface 24 so as to penetrate the holding block 22 vertically. Each suction port 25 communicates with a shallow groove 26 formed on the base member 21 by arranging the holding block 22 on the base member 21.

  The shallow grooves 26 are formed so as to connect four rows of horizontal grooves 27 with one row of vertical grooves 28, and communicate with all the suction ports 25 of the holding block 22. The center of the vertical groove 28 communicates with a suction source (not shown) via a suction path 29 (see FIG. 4A) formed inside the base member 21. The suction surface 24 of the holding block 22 becomes negative pressure by the suction force from the suction source, whereby the plate-like workpiece W is sucked and held on the suction surface 24 of the holding block 22. As described above, the chuck table 20 can individually hold the chips C after the division of the plate-like workpiece W, so that the plate-like workpiece W is reversed and processed in two steps as in the present embodiment. The present invention is not limited to this case, and can be applied to a plate-shaped workpiece that is completely cut by one processing.

  As shown in FIG. 3, the holding plate 60 is formed in a plate shape with a porous material such as a porous ceramic material, and is interposed between the chuck table 20 and the plate workpiece W when the plate workpiece W is completely cut. The The surface of the holding plate 60 is partitioned in a lattice pattern by gaps 61 corresponding to the division lines 96 of the plate-like workpiece W, and suction areas 62 corresponding to the suction surfaces 24 (see FIG. 2A) of the holding blocks 22 are formed. Yes. In each suction area 62, a concave hemispherical surface 63 corresponding to the convex hemispherical surface 93 of the plate-like workpiece W is formed. When the convex hemispherical surface 93 of the plate-like workpiece W enters the concave hemispherical surface 63 of the holding plate 60, the protective layer 95 side of the plate-like workpiece W is sucked and held by the chuck table 20.

  Thereby, the suction area of the plate-like workpiece W by the holding plate 60 is widened, and the suction holding force is increased. Even when the assist gas is jetted together with the laser beam to the back surface 98 side of the plate-like workpiece W at the time of complete cutting of the plate-like workpiece W, chip fly after the division does not occur due to the momentum of the assist gas. In this case, the concave hemispherical surface 63 of the holding plate 60 is formed slightly larger than the convex hemispherical surface 93 of the plate-like workpiece W (see FIG. 4B), and the concave hemispherical surface 63 and the convex hemispherical surface are formed. A slight gap is provided between the surface 93. For this reason, the convex hemispherical surface 93 is not damaged by the inverted holding of the plate-like workpiece W.

  Further, the holding plate 60 is formed with a wall in which porous pores are closed with resin or the like in order to prevent leakage of suction force in the gap 61 and the outer peripheral surface 64 (see FIG. 4B). Thereby, leakage of the suction force from the gap 61 and the outer peripheral surface 64 of the holding plate 60 to the outside is prevented, and a decrease in the suction holding force in the suction region 62 is suppressed. Although the entire suction area 62 of the holding plate 60 is configured to suck and hold the protective layer 95 side of the plate-like workpiece W, the present invention is not limited to this structure. The holding plate 60 may be configured to suck and hold at least the convex hemispherical surface 93 of the plate-like workpiece W.

  Next, a laser cutting method using a laser processing apparatus will be described with reference to FIG. FIG. 4 is an explanatory diagram of the laser cutting method according to the present embodiment. 4A shows a protective layer dividing step, FIG. 4B shows a switching step, and FIG. 4C shows a cutting step. Further, the laser cutting operation shown in FIG. 4 is merely an example, and can be changed as appropriate.

  As shown in FIG. 4A, a protective layer dividing step is first performed. In the protective layer dividing step, the back surface 98 side of the plate-like workpiece W is sucked and held by the holding block 22 of the chuck table 20 with the protective layer 95 of the plate-like workpiece W directed upward. The chuck table 20 is moved below the laser irradiation means 50, and the laser irradiation means 50 is positioned on the division line 96 of the plate-like workpiece W. Then, a laser beam is irradiated from the laser irradiation means 50 to the protective layer 95 on the surface 97 side of the plate-like workpiece W, and an assist gas is blown to the irradiation region of the laser beam.

At this time, the laser irradiation means 50 is moved relative to the plate-like workpiece W while the condensing point of the laser beam is adjusted, so that the protective layer 95 of the plate-like workpiece W is divided along the division line 96. A dividing groove 89 is formed. The processing conditions in the protective layer dividing step are processing conditions corresponding to the silicone resin, and are set as follows, for example.
Laser type: CO2 laser Output: 20 [W]
Repetition frequency: 100 [kHz]
Feeding speed: 200 [mm / s]
By laser processing under such processing conditions, the protective layer 95 made of silicone resin is appropriately removed.

  As shown in FIG. 4B, the switching step is performed after the protective layer dividing step. In the switching step, the plate-like workpiece W is removed from the holding block 22 of the chuck table 20, and the holding plate 60 is placed on the holding block 22. Since the suction surface 24 of the holding block 22 is covered with the holding plate 60, the surface of the holding plate 60 functions as a suction surface for the plate-like workpiece W. Then, the plate-like workpiece W is placed on the holding plate 60 such that the protective layer 95 side of the plate-like workpiece W is directed downward and the convex hemispherical surface 93 of the plate-like workpiece W enters the concave hemispherical surface 63 of the holding plate 60. W is mounted again.

  At this time, since the concave hemispheric surface 63 of the holding plate 60 and the convex hemispheric surface 93 of the plate-like workpiece W are slightly spaced, the convex hemispheric surface 93 is not damaged. When a suction force is generated in the holding block 22 of the chuck table 20, the suction force also acts on the surface 97 (protective layer 95) of the plate-like workpiece W through the holding plate 60. Since the gap 61 of the holding plate 60 and the pores of the outer peripheral surface 64 are filled with resin, leakage of the suction force is suppressed and the plate-like workpiece W is appropriately sucked and held by the holding plate 60. In this way, the suction target surface of the plate-like workpiece W to be sucked and held is switched from the back surface 98 to the front surface 97, the back surface 98 of the plate-like workpiece W is exposed, and the protective layer 95 side is sucked and held.

  As shown in FIG. 4C, a cutting step is performed after the switching step. In the cutting step, the processing conditions corresponding to the protective layer 95 made of silicone resin are changed to the processing conditions corresponding to the substrate 94 made of alumina ceramic. Further, the laser irradiation means 50 is positioned on the planned division line 96 (divided groove 89) of the plate-like workpiece W with the back surface 98 of the plate-like workpiece W being exposed. Then, the assist gas is blown together with the laser beam from the laser irradiation means 50 to the back surface 98 of the plate-like workpiece W in a state where the laser output is increased by the output variable unit 53.

  Thereby, the base material 94 is cut | disconnected by a laser beam, while the processing waste produced by melt | dissolution of the plate-shaped workpiece | work W is blown away with assist gas. At this time, since the gap 61 of the holding plate 60 exists immediately below the irradiation region of the laser beam, the holding plate 60 is not heated by the laser beam. Therefore, the portion where the holding plate 60 and the protective layer 95 of the plate-like workpiece W are in contact with each other is not heated by the laser beam, and the protective layer 95 is not adversely affected. The plate-like workpiece W is completely cut by passing through the base material 94 and continuing to the dividing groove 89 of the protective layer 95.

Thus, since the irradiation of the laser beam to the protective layer 95 is suppressed when the plate-like workpiece W is completely cut, the protective layer 95 is not burned or burnt. The processing conditions in the cutting process are processing conditions corresponding to alumina ceramic, and are set as follows, for example. In this case, the processing conditions corresponding to the alumina ceramic are such that the laser output is increased and the feed rate is decreased with respect to the processing conditions corresponding to the silicone resin.
Laser type: CO2 laser Output: 50 [W]
Repetition frequency: 100 [kHz]
Feeding speed: 40 [mm / s]
In the cutting process, a fiber laser may be used instead of the CO2 laser.

  In the switching step, the operator may manually switch the suction surface of the plate-shaped workpiece from the back surface to the front surface, or may switch the suction surface of the plate-shaped workpiece from the back surface to the front surface with a dedicated device. Hereinafter, the structure which implements a switching process with an exclusive apparatus is demonstrated. FIG. 5 is a diagram illustrating an example of a switching process using the switching mechanism according to the present embodiment.

  As shown in FIG. 5A, the switching mechanism 70 grips both ends of the plate-like workpiece W with a pair of clamps 71, reverses the plate-like workpiece W upside down, and sucks and holds the workpiece with the suction surface 24 of the chuck table 20. The front surface 97 and the back surface 98 of W are switched. On the opposing surfaces of the pair of clamps 71 of the switching mechanism 70, a holding groove 73 formed in a concave shape is formed so that the side surface 99 of the plate-like workpiece W can be held. Further, the pair of clamps 71 are configured to be separated from or approach each other in the X-axis direction by the horizontal moving unit 74, lifted / lowered in the Z-axis direction by the lifting / lowering moving unit 75, and rotated around the X-axis by the rotating unit 76. Has been.

  The horizontal moving unit 74 extends in the X-axis direction, and an up-and-down moving unit 75 is installed on the horizontal moving unit 74 so as to be movable in the horizontal direction. The up-and-down moving unit 75 extends in the Z-axis direction, and a rotating unit 76 is installed in the up-and-down moving unit 75 so as to be able to move up and down. The rotating part 76 is composed of a rotating motor or the like, and a clamp 71 is attached to the output shaft of the rotating motor. In the switching process by the switching mechanism 70 configured as described above, the pair of clamps 71 are brought closer to each other by the horizontal moving unit 74 in a state where the pair of clamps 71 are lowered to a height at which the plate-like workpiece W can be gripped. . As a result, the side surface 99 of the plate-like workpiece W is gripped by the gripping grooves 73 of the pair of clamps 71.

  As shown in FIG. 5B, when the plate-like workpiece W is gripped by the pair of clamps 71, the pair of clamps 71 are raised by the up-and-down moving unit 75, and the plate-like workpiece W is sufficiently separated from the chuck table 20. Can be lifted up. Then, the holding plate 60 on which the concave hemispherical surface 63 is formed is placed on the holding block 22 of the chuck table 20 in a state where the plate-like workpiece W is lifted. Thereby, a suction surface capable of holding the convex hemispherical surface 93 on the protective layer 95 side of the plate-like workpiece W is formed on the holding plate 60 on the chuck table 20. The mounting of the holding plate 60 may be performed by a dedicated device or may be performed manually.

  As shown in FIG. 5C, when the holding plate 60 is placed on the chuck table 20, the pair of clamps 71 are rotated by the rotating unit 76 so that the plate-like workpiece W is turned upside down. As a result, the protective layer 95 of the plate-like workpiece W is directed downward, and the convex hemispherical surface 93 of the protective layer 95 faces the concave hemispherical surface 63 of the holding plate 60 in the vertical direction. As shown in FIG. 5D, the pair of clamps 71 are moved down by the up-and-down moving unit 75 so that the convex hemispherical surface 93 of the plate-shaped workpiece W fits into the concave hemispherical surface 63 of the holding plate 60. W is placed on the holding plate 60. Then, the pair of clamps 71 are separated from the plate-like workpiece W, and the protective layer 95 side of the plate-like workpiece W is sucked and held via the holding plate 60 by the suction force of the chuck table 20.

  As described above, according to the laser cutting method according to the present embodiment, after the laser beam is irradiated from the surface 97 side of the plate-like workpiece W to form the divided grooves 89 in the protective layer 95, The laser beam is irradiated from the back surface 98 side, and the plate-like workpiece W is completely cut. Since the laser beam is irradiated from the back surface 98 side of the plate workpiece W when the plate workpiece W is completely cut, the protective layer 95 on the front surface 97 side is not affected by the laser beam. The plate-like workpiece W can be divided into individual chips without suppressing the burning or scorching of the protective layer 95 and leaving no damage during laser processing. Further, since the holding plate 60 is interposed between the plate-like workpiece W and the chuck table 20 when the plate-like workpiece W is completely cut, the convex hemispherical surface 93 is formed on the plate-like workpiece W and the concave shape of the holding plate 60. The hemispherical surface 63 can be sucked and held.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  In the above switching step, the holding plate 60 is placed on the chuck table 20 so that the surface 97 side of the plate-like workpiece W can be held via the holding plate 60. However, the present invention is limited to this configuration. Not. It is also possible to perform the switching step using a chuck table 80 as shown in FIG. In addition, since the laser processing apparatus provided with the chuck table 80 which concerns on a modification has the structure similar to the laser processing apparatus 1 which concerns on the said embodiment except the chuck table 80, description is abbreviate | omitted.

  As shown in FIG. 6A, the chuck table 80 is configured by connecting a first table portion 81 and a second table portion 82 by an opening / closing mechanism 83 so as to be opened and closed. The first table portion 81 sucks and holds the back surface 98 of the plate-like workpiece W, and the upper surface of the first table portion 81 has a flat suction surface 84 corresponding to the back surface 98 of the plate-like workpiece W. ing. The second table unit 82 sucks and holds the surface 97 of the plate-like workpiece W, and the upper surface of the second table unit 82 is similar to the holding plate 60 (see FIG. 4B) of the present embodiment. A concave hemispherical surface 85 corresponding to the convex hemispherical surface 93 of the plate-like workpiece W and a gap 86 formed between adjacent concave hemispherical surfaces 85 are provided.

  The opening / closing mechanism 83 rotates the second table portion 82 in the closing direction toward the upper surface of the first table portion 81 so that the upper surface of the first table portion 81 and the upper surface of the second table portion 82 are properly aligned. It is configured to be paired (see FIG. 6B). Further, the opening / closing mechanism 83 turns the second table portion 82 in the opening direction from the upper surface of the first table portion 81 so that the upper surface of the first table portion 81 and the upper surface of the second table portion 82 are arranged side by side. It is possible to make it adjoin. Further, when the first table portion 81 and the second table portion 82 are closed, an interval corresponding to the thickness of the plate-like workpiece W is provided, so that the first table is sandwiched between the plate-like workpieces W. The part 81 and the second table part 82 can be closed.

  In the chuck table 80 configured as described above, the plate-like workpiece W placed on the first table portion 81 is protected with the first table portion 81 and the second table portion 82 opened. A layer splitting process is performed. The back surface 98 of the plate-like workpiece W is sucked and held by the flat suction surface 84 of the first table portion 81, and the dividing groove 89 is formed in the protective layer 95 of the plate-like workpiece W by laser processing. At this time, the convex hemispherical surface 93 of the plate-like workpiece W is directed upward on the first table portion 81, and the concave hemispherical surface of the second table portion 82 adjacent to the first table portion 81. 85 is also directed upward.

  As shown in FIG. 6B, when the dividing groove 89 is formed in the plate-like workpiece W, the switching process is performed by opening and closing the first and second table portions 81 and 82 by the opening and closing mechanism 83. In this case, the second table portion 82 is turned in the closing direction with respect to the first table portion 81, and the convex hemispherical surface 93 of the plate-like workpiece W is changed to the concave hemispherical surface 85 of the second table portion 82. The 2nd table part 82 is mounted in the surface 97 of the plate-shaped workpiece W so that it may enter. As a result, the upper surface of the second table portion 82 faces the upper surface of the first table portion 81, and the plate-like workpiece W is sandwiched between the upper surfaces of the first and second table portions 81 and 82. Next, the protective layer 95 side of the plate-like workpiece W is sucked and held by the second table portion 82.

  At this time, a slight gap is provided between the concave hemispherical surface 85 of the second table portion 82 and the convex hemispherical surface 93 of the plate-like workpiece W, thereby preventing the convex hemispherical surface 93 from being damaged. Has been. Further, the gap 86 of the second table portion 82 has the outer pores filled with resin, so that leakage of suction force is suppressed, and the plate-like workpiece W is appropriately sucked and held on the second table portion 82. Has been. Subsequently, the suction holding of the plate-like workpiece W by the first table portion 81 is released, and the second table portion 82 is turned in the opening direction with the plate-like workpiece W sucked and held. As a result, the plate-like workpiece W is held by the second table portion 82 with the back surface 98 facing upward.

  As shown in FIG. 6C, a cutting process is performed on the plate-like workpiece W placed on the second table portion 82 in a state where the first table portion 81 and the second table portion 82 are opened again. Is done. The convex hemispherical surface 93 of the plate-like workpiece W is sucked and held by the concave hemispherical surface 85 of the second table portion 82, and the plate-like workpiece W is completely cut by laser processing. In this cutting step, similarly to the above-described embodiment, the laser output is increased and the feed rate is reduced as compared with the protective layer dividing step. As described above, even when the chuck table 80 according to the modified example is used, the switching process can be performed by opening and closing the first and second table portions 81 and 82.

  Further, as shown in FIG. 7, a second chuck table 90 may be provided in addition to the chuck table 20 according to the present embodiment. Similar to the holding plate 60 of the present embodiment, a gap 92 is formed between the concave hemispherical surface 91 and the adjacent concave hemispherical surfaces 91 on the upper surface of the second chuck table 90. Then, for example, the plate-like workpiece W is reversed from the chuck table 20 to the second chuck table 90 by the switching mechanism 70 shown in FIG.

  In the embodiment and the modification described above, the convex hemispherical surface 93 is formed on the protective layer 95 of the plate-like workpiece W. However, the present invention is not limited to this configuration. The plate-like workpiece W only needs to have the protective layer 95 formed on the base material 94, and the convex hemispherical surface 93 may not be formed on the protective layer 95. Even in such a plate-like workpiece W, the plate-like workpiece W can be divided into individual chips without causing burning or scorching in the protective layer 95 and leaving no damage during laser processing. .

  In the embodiment and the modification described above, the protective layer dividing step, the switching step, and the cutting step are performed by the single laser processing apparatus 1, but the present invention is not limited to this configuration, and each step is separately performed. It may be implemented in the apparatus.

  As described above, the present invention has an effect that a plate-shaped workpiece can be divided into individual chips without leaving any damage during laser processing on the divided chips, and in particular, a silicone resin or the like. This is useful for a laser cutting method and a laser processing apparatus for dividing a wafer for an optical device having a protective layer into individual chips.

DESCRIPTION OF SYMBOLS 1 Laser processing apparatus 20, 80 Chuck table 50 Laser irradiation means 53 Output variable part 60 Holding plate 61 Holding plate clearance 63 Holding plate concave hemisphere 70 Switching mechanism 81 First table part 82 Second table part 83 Opening and closing Mechanism 84 First table portion suction surface 85 Second table portion concave hemisphere 86 Second table portion gap 89 Dividing groove 90 Second chuck table 91 Second chuck table concave hemisphere 92 Clearance of second chuck table 93 convex hemispherical surface of plate workpiece 95 protective layer 97 surface of plate workpiece 98 back surface of plate workpiece C chip W plate workpiece

Claims (5)

A laser cutting method for forming a chip that is cut into pieces by irradiating a plate-like workpiece having a protective layer on the surface with a laser beam and cutting the plate-like workpiece,
A protective layer dividing step for forming a dividing groove for dividing the protective layer by sucking and holding the back surface of the plate-like workpiece and irradiating the protective layer on the surface with a laser beam;
After the protective layer dividing step, the switching step of switching the suction surface of the plate-shaped workpiece to be sucked and held from the back surface to the front surface and exposing the back surface of the plate-shaped workpiece to suck and hold the protective layer side;
After the switching step, a cutting step of irradiating the back surface of the plate workpiece with a laser beam to completely cut the plate workpiece;
A laser cutting method comprising: The surface of the plate-like workpiece is provided with a convex hemisphere for each chip,
The laser cutting method according to claim 1, wherein in the cutting step, at least the hemispherical surface formed on the surface of the plate-like workpiece is sucked and held. A laser processing apparatus used in the laser cutting method according to claim 2,
A chuck table having a suction surface for sucking and holding a plate-like work, a laser irradiation means for irradiating a laser beam to the plate-like work sucked and held by the chuck table, and an output for changing a laser output emitted by the laser irradiation means A variable portion, a holding hemispherical surface corresponding to the convex hemispherical surface formed on the surface of the plate-like workpiece, and capable of holding at least the convex hemispherical surface by suction, and suction holding by the suction surface A switching mechanism for switching between the front surface and the back surface of the plate workpiece to be
The holding plate has a gap formed between the concave hemispheres adjacent to each other,
The suction surface sucks and holds the back surface of the plate-like workpiece when forming the dividing groove in the protective layer, and is formed on the surface of the plate-like workpiece via the holding plate when completely cutting the plate-like workpiece. A laser processing device that holds and holds at least a convex hemispherical surface. A second chuck table instead of the holding plate;
The upper surface of the second chuck table includes a concave hemispherical surface corresponding to the convex hemispherical surface, and a gap formed between the adjacent concave hemispherical surfaces,
The switching mechanism switches between the front surface and the back surface of the plate-like workpiece that is sucked and held by the suction surface and the upper surface of the second chuck table,
4. The laser processing apparatus according to claim 3, wherein the convex hemispherical surface formed on the surface of the wafer by the concave hemispherical surface is sucked and held to completely cut the wafer. A laser processing apparatus used for the laser cutting method according to claim 2,
A chuck table having a suction surface for sucking and holding a plate-like work, a laser irradiation means for irradiating a laser beam to the plate-like work sucked and held by the chuck table, and an output for changing a laser output emitted by the laser irradiation means A variable portion, and
The chuck table includes a first table portion that sucks and holds the back surface of the plate-like workpiece, a second table portion that sucks and holds the surface of the plate-like workpiece, an upper surface of the first table portion, and a second table portion. An open / close mechanism that opens and closes the top surface of the
The upper surface of the first table portion has a suction surface corresponding to the back surface of the plate-like workpiece,
The upper surface of the second table portion has a concave hemispherical surface corresponding to the convex hemispherical surface, and a gap formed between the adjacent concave hemispherical surfaces,
The opening / closing mechanism sucks and holds the back surface of the plate-like workpiece on the suction surface of the first table portion when forming the dividing groove in the protective layer, and the concave hemispherical surface when completely cutting the plate-like workpiece. A laser processing apparatus that opens and closes the first table portion and the second table portion so as to suck and hold the convex hemispherical surface formed on the surface of the plate-like workpiece.

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