JP6111090B2 - Laser processing method - Google Patents

Description

  The present invention relates to a laser processing apparatus that processes a plate-like workpiece by laser processing.

  As a method of dividing a plate-like workpiece such as a semiconductor wafer along a street (division planned line), a method by laser processing is known (for example, see Patent Document 1). In the laser processing method, laser light is condensed and irradiated on an irradiation area of a semiconductor wafer, the thermal energy is concentrated, and silicon in the irradiation area is melted or pyrolyzed to be vaporized. In this process, what is called debris is generated. If the debris adheres to the pattern surface of the semiconductor wafer, there arises a problem that the quality of the divided semiconductor chip is adversely affected.

  Therefore, there is a method of forming a protective film on the pattern surface of the semiconductor wafer and performing laser processing (see, for example, Patent Document 2 and Patent Document 3). There is also a laser processing apparatus that removes foreign matter generated by laser processing by ejecting a fluid to a laser processing region and sucking the fluid (for example, see Patent Document 4).

JP-A-6-120334 JP 2006-198450 A JP 2008-6379 A Japanese Patent Laid-Open No. 10-99978

  In the method of forming a protective film on the pattern surface of a semiconductor wafer, a material for forming the protective film is required, so a process of forming a protective film is necessary before laser processing, and it is unnecessary after laser processing. A process of removing the protective film is necessary. In addition, it is necessary to discard the removed protective film. This increases the running cost associated with laser processing.

  Further, in the method of ejecting fluid to the laser processing region and sucking it, not all the generated debris can be removed, and there is a possibility that it adheres to the pattern surface of the semiconductor wafer.

  An object of the present invention is to prevent debris generated by laser processing from adhering to a pattern surface of a semiconductor wafer at a low running cost.

The laser processing method according to the present invention includes a processing table on which a plate-like workpiece having a scheduled division line is placed, and a laser beam along the scheduled division line from above the plate-like workpiece placed on the processing table. A first laser irradiation device for irradiating and cutting a plate-like workpiece; and a first laser irradiation device for irradiating a laser beam in parallel with the upper surface of the plate-like workpiece placed on the processing table and in parallel with the division line. and 2 of the laser irradiation apparatus, using a laser processing apparatus comprising, a laser processing method of laser processing a plate-like workpiece, comprising the steps of holding the plate-shaped workpiece in the processing table, the laser irradiation of the first Cutting the plate workpiece by irradiating a laser beam along a division line of the plate workpiece held on the processing table by the apparatus; and the first laser irradiation device. A step of irradiating a laser beam, to vaporize the debris by plate workpiece the laser irradiation apparatus of the second debris generated by the cutting of by,
Suctioning and exhausting the vaporized debris .

According to the laser processing method according to the present invention, the laser light emitted by the second laser irradiation device vaporizes the debris, so that it is possible to prevent the debris from adhering to the plate-like workpiece. Therefore, it is not necessary to cover the surface of the plate-shaped workpiece with a protective film, so that the running cost related to laser processing can be reduced.

  Furthermore, since the vaporized debris is sucked from the suction port, it is possible to prevent the debris from adhering to the plate-like workpiece. Since the debris sucked by the suction part is vaporized, the debris can be prevented from clogging the suction part.

The perspective view which shows the structure of a laser processing apparatus. The perspective view which shows a plate-shaped workpiece. Front view sectional drawing which shows the structure of a laser processing apparatus. The schematic diagram which shows the effect | action of a laser processing apparatus. The perspective view which shows the laser beam which a 2nd laser irradiation apparatus radiates | emits. FIG. 4 is a front cross-sectional view showing a comparative example 1; FIG. 6 is a front sectional view showing a comparative example 2;

  A laser processing apparatus 10 shown in FIG. 1 has a fixed base 11, and a first feed mechanism 21 that feeds a processing table 23 holding a plate workpiece to be processed in the X direction on an upper surface 111 thereof. ing.

  The first feeding mechanism 21 moves the moving base 216 to an arbitrary position in the X direction with respect to the fixed base 11. In the first feed mechanism 21, when the drive unit 212 (X-axis motor) rotates the screw shaft 211 arranged in the direction in which the axial direction is parallel to the X direction, the moving base 216 is moved to the upper surface 111 of the fixed base 11. It is regulated by the fixed guide 214 and moves in the X direction with respect to the fixed base 11.

  The upper surface 111 of the fixed base 11 is provided with a second feeding mechanism 22 for feeding the first laser irradiation device 31 that performs laser processing to the plate-like workpiece in the Y direction (horizontal direction orthogonal to the X direction). . In the second feed mechanism 22, when the drive unit 222 (Y-axis motor) rotates the screw shaft 221 arranged in the direction in which the axial direction is parallel to the Y direction, the moving base 226 is moved to the upper surface 111 of the fixed base 11. It is regulated by the fixed guide 224 and moves in the Y direction with respect to the fixed base 11.

  The first laser support unit 12 is fixed to the moving table 226, and the first laser support unit 12 supports the first laser irradiation device 31, the imaging device 24, and the suction unit 41. The first laser irradiation device 31 has a function of emitting laser light 311 in a vertically downward direction, for example, includes a condenser lens (not shown), and condenses the laser light 311 at the focal point 312. The imaging device 24 detects a position to be laser processed by, for example, photographing a vertically downward direction. The suction part 41 has, for example, a truncated conical hollow box shape. The suction part 41 surrounds the part where the first laser irradiation device 31 emits the laser light 311. The suction port 411 (see FIG. 3) is a through hole provided in the lower surface of the suction unit 41 and is positioned in the direction in which the first laser irradiation device 31 emits the laser light 311. The laser beam 311 is radiated out of the suction part 41 through the suction port 411. The exhaust port 412 is a through hole provided in the upper surface of the suction unit 41 and is connected to an exhaust suction source 42 (such as a vacuum pump) that sucks the gas in the suction unit 41.

  The second laser support unit 13 is fixed to the moving table 226, and the second laser support unit 13 supports the second laser irradiation device 32. The second laser irradiation device 32 has a function of emitting a high-power laser beam 321 in a plane band shape in the X direction. The laser beam 321 includes a laser beam 311 emitted by the first laser irradiation device 31 and Intersect. For example, the second laser irradiation device 32 emits a plurality of parallel laser beams. Further, the second laser irradiation device 32 may be configured to cover a planar range by slightly irradiating the laser beam to be irradiated left and right at a high frequency.

  The processing table 23 is fixed to the movable table 216 and holds a plate-like workpiece placed on the placement unit 231. The processing table 23 is, for example, a chuck table. For example, when the suction source 234 illustrated in FIG. 3 is operated, the plate-like workpiece placed on the placement unit 231 is sucked and held. The processing table 23 is rotatable about an axis in the Z direction (direction perpendicular to the XY plane) passing through the center of the mounting portion 231. A holding and fixing portion 233 for fixing a frame that supports the plate-like workpiece is disposed around the placement portion 231.

  Since the processing table 23 is fixed to the moving table 216 of the first feeding mechanism 21, the first feeding mechanism 21 can move the processing table 23 to an arbitrary position in the X direction. Moreover, since the 1st laser support part 12 is being fixed to the moving stand 226 of the 2nd feed mechanism 22, the 2nd feed mechanism 22 moves the focus 312 of the laser beam 311 to the arbitrary positions of a Y direction. be able to. Thereby, the processing position on the plate-shaped workpiece | work hold | maintained at the processing table 23 can be moved to arbitrary positions in XY plane.

  The laser absorption plate 14 is fixed to the moving table 216 and absorbs the laser light 321 emitted by the second laser irradiation device 32. The width of the laser absorbing plate 14 is longer than the diameter of the mounting portion 231. The laser absorbing plate 14 is disposed on the opposite side of the second laser irradiation device 32 with the processing table 23 sandwiched so that the laser light 321 that has passed over the processing table 23 is incident.

  A plate-like workpiece 90 shown in FIG. 2 is a semiconductor wafer, and a plurality of devices 92 are formed on the surface of the plate-like workpiece 90. Each device 92 is separated by dividing the plate-like workpiece 90 along a plurality of division lines 93a and 93b. The plurality of division lines 93a provided in the vertical direction are parallel to each other. The plurality of scheduled division lines 93b provided in the horizontal direction are parallel to each other and orthogonal to the scheduled division line 93a.

  The adhesive surface of the tape 82 is attached to the back surface (the surface opposite to the surface on which the device 92 is formed) of the plate-like workpiece 90, and the center is opened in the ring shape on the outer periphery of the adhesive surface. The formed frame 81 is attached. The tape 82 is affixed to the frame 81 so as to close the opening of the frame 81, and the plate-like work 90 is attached to the frame 81 via the tape 82 by attaching the back surface of the plate-like work 90 to the tape 82. Supported by

  As shown in FIG. 3, the plate-like workpiece 90 supported by the frame 81 is placed on the processing table 23, and for example, the planned dividing line 93 a is a direction in which the first feed mechanism 21 moves the processing table 23 (X direction). ) In parallel with.

  The lower surface of the suction part 41 is arranged at a position as close as possible to the surface of the plate-like workpiece 90 placed on the processing table 23. That is, the distance between the upper surface of the mounting portion 231 of the processing table 23 and the lower surface of the suction portion 41 is slightly longer than the total thickness of the thickness of the plate-like workpiece 90 and the thickness of the tape 82. .

  The second laser irradiation device 32 emits laser light 321 in parallel with the upper surface of the mounting portion 231. Therefore, the radiation direction of the laser light 321 is parallel to the surface of the plate-like workpiece 90 placed on the placement portion 231. The laser light 321 passes through the gap between the surface of the plate-like workpiece 90 and the lower surface of the suction part 41 and reaches the laser absorbing plate 14.

  When the plate-like workpiece 90 supported by the frame 81 is placed on the processing table 23, the holding and fixing portion 233 presses and fixes the frame 81 supporting the plate-like workpiece 90, and the suction source 234 operates to operate the plate-like workpiece. 90 is sucked and held on the processing table 23.

  Next, the drive units 212 and 222 move the moving bases 216 and 226 to positions where the plate-like workpiece 90 can be photographed, respectively. As the moving table 216 moves, the processing table 23 and the laser absorbing plate 14 move in the X direction, and as the moving table 226 moves, the laser irradiation devices 31 and 32 and the imaging device 24 move in the Y direction. The imaging device 24 images the plate-like workpiece 90 and detects a division planned line 93a to be processed.

  The drive units 212 and 222 move the movable bases 216 and 226 so that the focal point 312 (processing position) of the laser beam 311 is positioned at one end (or on an extension line) of one division planned line 93a to be processed. Move. Then, the exhaust suction source 42 is operated, the suction unit 41 starts suction from the suction port 411, the second laser irradiation device 32 starts emitting the laser light 311, and the first laser irradiation device 31 is the laser. The emission of light 321 is started.

  The drive unit 212 moves the moving table 216 in the X direction (machining feed direction). As a result, the focal point 312 of the laser beam 311 moves on the planned division line 93a, and the plate workpiece 90 is processed. When the focal point 312 of the laser beam 311 reaches the other end (or on the extension line) of the division line 93a, the drive unit 212 stops operating, the processing table 23 stops, and the first laser irradiation device 31 is stopped. Stops the emission of the laser beam 311, and the second laser irradiation device 32 stops the emission of the laser beam 321. In this way, processing of one division planned line 93a is performed.

  Next, the driving unit 222 moves the moving base 226 in the Y direction so that the focal point 312 of the laser beam 311 comes to the next division line 93a (or an extension thereof), and the second division line 93a is processed. do. By repeating this, all the division planned lines 93a are processed.

  After all the processing of the planned division line 93a is completed, the processing table 23 is rotated 90 degrees so that the planned division line 93b is parallel to the X direction, and the planned division line 93b is similarly processed.

  While the second laser irradiation device 32 moves in the Y direction, the laser absorbing plate 14 is fixed to the moving base 216 that does not move in the Y direction, so the position where the laser light 321 is absorbed by the laser absorbing plate 14 is It changes depending on the position of the division planned line 93 to be processed. Thereby, it is possible to prevent deterioration of the laser absorbing plate 14 due to the laser beam 321 being continuously absorbed in the same position of the laser absorbing plate 14.

  As shown in FIG. 4, the plate-like workpiece 90 is processed by irradiating the plate-like workpiece 90 arranged at the focal point 312 of the laser beam 311 with the laser beam 311 emitted by the first laser irradiation device 31. In the process, debris 96 is generated. The debris 96 is obtained by vaporizing the plate-like workpiece 90 heated at the focal point 312 of the laser beam 311 and liquefying or solidifying the vapor generated in the air, or by suddenly vaporizing the plate-like workpiece 90 at the focal point 312. The plate-like workpiece 90 around the focal point 312 is blown off by the explosion that occurs. The debris 96 scatters upward from the focal point 312 of the laser light 311.

  The laser beam 321 emitted from the second laser irradiation device 32 is separated from the surface of the plate-like workpiece 90 by a distance 323 and is emitted in parallel to the surface of the plate-like workpiece 90. The laser beam 321 intersects with the laser beam 311 emitted by the first laser irradiation device 31 and passes immediately above the focal point 312 of the laser beam 311. When the laser beam 321 hits the debris 96 scattered upward from the focal point 312 of the laser beam 311, the debris 96 is heated. Since the laser beam 321 has a high output and the debris 96 is very small, the temperature of the debris 96 rapidly increases and vaporizes. The vaporized debris 96 is sucked into the suction part 41 together with the air sucked from the suction port 411 and discharged from the exhaust port 412.

Thereby, since it can prevent that the debris 96 adheres to the surface of the plate-shaped workpiece 90, it is not necessary to provide a protective film on the surface of the plate-shaped workpiece 90. For this reason, the process of forming a protective film and the process of removing are eliminated, and the running cost related to laser processing can be reduced. In addition, productivity is improved because the protective film is not attached or detached.
In addition, since the laser beam 321 is emitted in parallel to the surface from the lateral direction of the plate-like workpiece 90, the high-power laser beam 321 is not irradiated to the plate-like workpiece 90.

  As shown in FIG. 5, the laser light 321 emitted by the second laser irradiation device 32 is applied to a planar band-shaped range having a width 322 in the Y direction. The debris 96 shown in FIG. 4 scatters upward from the focal point 312 of the laser light 311. Accordingly, the range in which the debris 96 scatters is substantially circular with the focal point 312 as the center. Therefore, in order to reliably vaporize the scattered debris 96, the width 322 of the laser beam 321 is set to the diameter of the debris scatter range. It is desirable to make it larger.

  The distance 323 between the surface of the plate-like workpiece 90 and the laser beam 321 is preferably as small as possible, and it is desirable that the laser beam 321 be emitted to a position that does not hit the plate-like workpiece 90.

  The machining position on the plate-like workpiece 90 moves in the X direction along the scheduled division lines 93a and 93b. That is, the focal point 312 of the laser beam 311 moves in the X direction on the plate-like workpiece 90. Since the radiation direction of the laser beam 321 is parallel to the X direction, the laser beam 321 is applied not only to the debris 96 scattered from the current machining position but also to the debris 96 left at the already finished machining position. Irradiated. Thereby, the debris 96 remaining without being vaporized during the scattering can be vaporized and removed.

Comparative Example 1
As shown in FIG. 6, when the laser processing apparatus does not have the second laser irradiation apparatus 32 and the suction unit 41, the debris 96 adheres to the surface of the plate-like workpiece 90 and adversely affects the device 92. In order to prevent this, if the surface of the plate-shaped workpiece 90 is covered with a protective film, the running cost of the laser processing apparatus increases.

  On the other hand, since the laser processing apparatus 10 of this Embodiment does not need to provide a protective film, the running cost of laser processing can be reduced.

Comparative Example 2
As shown in FIG. 7, when the laser processing apparatus has the suction part 41 but does not have the second laser irradiation apparatus 32, the suction part 41 sucks the debris 96. It is possible to prevent the debris 96 from adhering to the surface. However, since the debris 96 is not vaporized, when the particle size of the debris 96 is large, the debris 96 becomes heavier. Therefore, the debris 96 is not necessarily sucked by the suction portion 41 and can adhere to the surface of the plate-like workpiece 90. There is sex. Further, once the debris 96 adheres to the plate-like workpiece 90, it cannot be removed. Further, when the debris 96 is sucked into the suction part 41 in a liquid or solid state, the suction part 41, the exhaust suction source 42, or the pipe connecting the suction part 41 and the exhaust suction source 42, etc. Debris 96 can become clogged.

  On the other hand, since the laser processing apparatus 10 of this embodiment irradiates the debris 96 with the laser beam 321 and vaporizes the debris 96 and sucks it into the suction portion 41, the debris 96 can be sucked efficiently. Adhesion to the surface of the plate-like workpiece 90 can be prevented. Further, even when the debris 96 remaining without being vaporized during the scattering adheres to the surface of the plate-like workpiece 90, the adhering debris 96 can be vaporized and removed. Further, since the debris 96 is vaporized, it is possible to prevent the debris 96 from clogging the suction part 41 and the like. Thereby, the maintenance cost of the laser processing apparatus 10 can be reduced.

  The laser processing apparatus 10 described above is an example, and the present invention is not limited to this. For example, the first laser irradiation device 31, the suction unit 41, and the imaging device 24 do not move, and the processing table 23 and the laser absorption plate 14 move not only in the X direction but also in the Y direction as the moving table 216 moves. The second laser irradiation device 32 moves in the X direction as the moving table 216 moves, but the position in the Y direction may be fixed. Moreover, the structure which moves the processing position on the plate-shaped workpiece | work 90 by fixing the processing table 23 and moving the laser irradiation apparatuses 31 and 32 to a X direction and a Y direction may be sufficient. Furthermore, the structure which moves both the process table 23 and the laser irradiation apparatuses 31 and 32 to a X direction and a Y direction may be sufficient.

  Further, the direction in which the second laser irradiation device 32 emits the laser light 321 does not have to be strictly parallel to the processing feed direction.

10 laser processing equipment, 11 fixing base, 111 upper surface,
12 1st laser support part, 13 2nd laser support part, 14 Laser absorption plate,
21 First feed mechanism, 22 Second feed mechanism,
211, 221 screw shaft, 212, 222 drive unit,
214, 224 guide, 216, 226 moving table, 22 second feed mechanism,
23 processing table, 231 placement section, 233 holding and fixing section, 234 suction source,
24 imaging device,
31 1st laser irradiation apparatus, 311 and 321 laser light, 312 focus,
32 Second laser irradiation device, 322 width, 323 distance,
41 suction part, 411 suction port, 412 exhaust port, 42 exhaust suction source,
81 frames, 82 tapes,
90 Plate work, 92 devices, 93a, 93b Divided lines, 96 debris

Claims (1)

A processing table on which a plate-like workpiece having a scheduled division line is placed, and cutting the plate-like workpiece by irradiating laser light along the scheduled division line from above the plate-like workpiece placed on the machining table. And a second laser irradiation apparatus that irradiates laser light in parallel with the upper surface of the plate-like workpiece placed on the processing table and in parallel with the planned division line. A laser processing method for laser processing the plate- like workpiece using a laser processing apparatus ,
Holding the plate-like workpiece on the processing table;
Cutting the plate-shaped workpiece by irradiating laser light along a planned division line of the plate-shaped workpiece held on the processing table by the first laser irradiation device;
Irradiating the debris generated by the cutting processing of the plate-like workpiece by the first laser irradiation device with a laser beam by the second laser irradiation device, and vaporizing the debris;
Sucking and exhausting the vaporized debris;
A laser processing method comprising:

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