JP2017217673A - Inspection method of laser beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately inspect deviation between an optical axis of an optical system and an optical axis of a laser beam.SOLUTION: An inspection method of a laser beam includes: a preparation step S1 of laminating a plate-like object for inspection and a support base material through a resin layer molten when irradiated with a laser beam having a wavelength transmitting through the plate-like object for inspection to prepare a workpiece unit; a modified layer formation step S2 of exposing the plate-like object for inspection and holding the workpiece unit to a holding surface of a chuck table, irradiating the plate-like object for inspection with the laser beam so as to condense the laser beam inside of the plate-like object for inspection from an exposure surface of the object to form a modified layer inside of the plate-like object for inspection; and an inspection step S3 of performing the modified layer formation step, and then inspecting a state of a molten mark formed on a resin layer by the laser beam having transmitted through the plate-like object for inspection.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a laser beam inspection method.

  For optical device wafers and glass substrates such as semiconductor wafers, sapphire substrates, SiC substrates, etc., there is known a laser processing method in which a modified layer is formed inside, and the modified layer is ruptured and divided (for example, (See Patent Document 1).

Japanese Patent No. 3408805

  When the optical axis of the optical system and the optical axis of the laser beam coincide with each other, the energy of the laser beam becomes maximum and the laser beam can be efficiently used for processing. However, if the optical axis of the optical system and the optical axis of the laser beam are deviated, the energy of the laser beam is biased and a modified layer in a desired state may not be obtained.

  Therefore, a laser beam inspection method that can accurately inspect the deviation between the optical axis of the optical system and the optical axis of the laser beam has been desired.

  The present invention has been made in view of the above, and an object thereof is to provide a laser beam inspection method capable of accurately inspecting a deviation between an optical axis of an optical system and an optical axis of a laser beam. .

  In order to solve the above-described problems and achieve the object, the laser beam inspection method of the present invention irradiates the inspection plate and support substrate with a laser beam having a wavelength that passes through the inspection plate. And a preparatory step of preparing a workpiece unit, exposing the inspection plate-like object, holding the workpiece unit on the holding surface of the chuck table, and emitting the laser beam. A modified layer forming step of irradiating the exposed surface of the inspection plate so as to collect light inside the inspection plate, and forming a modified layer inside the inspection plate; And an inspection step of inspecting a state of a melt mark formed in the resin layer by the laser beam transmitted through the inspection plate after the modified layer forming step is performed.

  According to the laser beam inspection method of the present invention, the optical axis of the optical system and the optical axis of the laser beam are shifted by inspecting the state of the melt mark formed in the resin layer by the laser beam transmitted through the inspection plate. Can be accurately inspected.

FIG. 1 is a perspective view showing a laser processing apparatus inspected by a laser beam inspection method according to an embodiment. FIG. 2 is a perspective view for explaining a workpiece unit used in the laser beam inspection method according to the embodiment. FIG. 3 is a block diagram showing laser beam irradiation means of the laser processing apparatus shown in FIG. FIG. 4 is a flowchart for explaining a laser beam inspection method according to the embodiment. FIG. 5 is an exploded perspective view for explaining a preparation step of the laser beam inspection method according to the embodiment. FIG. 6 is a schematic diagram for explaining a modified layer forming step of the laser beam inspection method according to the embodiment. FIG. 7 is a schematic diagram for explaining inspection steps of the laser beam inspection method according to the embodiment. FIG. 8 is a diagram for explaining inspection steps of the laser beam inspection method according to the embodiment. FIG. 9 is a schematic diagram illustrating inspection steps of the laser beam inspection method according to the embodiment. FIG. 10 is a schematic diagram for explaining inspection steps of the laser beam inspection method according to the embodiment. FIG. 11 is a diagram for explaining inspection steps of the laser beam inspection method according to the embodiment. FIG. 12 is a schematic diagram for explaining inspection steps of the laser beam inspection method according to the embodiment. FIG. 13 is a diagram for explaining inspection steps of the laser beam inspection method according to the embodiment.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the structures described below can be combined as appropriate. In addition, various omissions, substitutions, or changes in the configuration can be made without departing from the scope of the present invention.

  A laser processing apparatus 1 shown in FIG. 1 is an apparatus that divides a wafer W as an inspection plate-like object, on which a device D is formed, along a planned division line L. FIG. 1 is a perspective view showing a laser processing apparatus inspected by a laser beam inspection method according to an embodiment.

  As shown in FIG. 2, the wafer W is attached to the surface of the adhesive tape T attached to the annular frame F with the back surface Wb facing up. FIG. 2 is a perspective view for explaining a workpiece unit used in the laser beam inspection method according to the embodiment. In the present embodiment, the wafer W is a semiconductor wafer or an optical device wafer having a disk-shaped glass substrate.

  Returning to FIG. 1, a laser processing apparatus 1 that inspects by the inspection method of the laser beam LB according to the present embodiment will be described. The laser processing apparatus 1 includes a main body 2, a wall 3 standing upward from the main body 2, and a support column 4 projecting forward from the wall 3.

  The laser processing apparatus 1 includes a chuck table 10 that holds a workpiece unit U including a wafer W, and an X-axis moving unit 20 that relatively moves the chuck table 10 and a laser beam irradiation unit (laser beam irradiation unit) 50 in the X-axis direction. A Y-axis moving unit 30 that relatively moves the chuck table 10 and the laser beam irradiation unit 50 in the Y-axis direction, a rotating unit 40 that rotates the chuck table 10 around a central axis parallel to the Z-axis direction, and the chuck table 10. The laser beam irradiation means 50, the imaging means 60, and the control means 100 which irradiate the wafer W hold | maintained by the laser beam irradiating with a pulse laser beam (henceforth "laser beam") LB are provided.

  The chuck table 10 has a holding surface 10 a that holds the wafer W. The holding surface 10 a holds the wafer W attached to the opening of the annular frame F via the adhesive tape T. The holding surface 10a has a disk shape made of porous ceramic or the like, and is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown). The holding surface 10 a sucks and holds the placed wafer W via the adhesive tape T. In the present embodiment, the holding surface 10a is a plane parallel to the X-axis direction and the Y-axis direction. Around the chuck table 10, a plurality of clamp portions 11 that sandwich the annular frame F around the wafer W are arranged.

  The X-axis moving unit 20 is a processing feed unit that moves the chuck table 10 in the X-axis direction by moving the chuck table 10 in the X-axis direction. The X-axis moving means 20 supports a ball screw 21 provided to be rotatable about an axis, a pulse motor 22 for rotating the ball screw 21 about the axis, and a chuck table 10 to be movable in the X-axis direction. And a guide rail 23.

  The Y-axis moving means 30 is an index feeding means for indexing and feeding the chuck table 10 by moving the chuck table 10 in the Y-axis direction. The Y-axis moving means 30 supports a ball screw 31 provided to be rotatable about an axis, a pulse motor 32 for rotating the ball screw 31 about the axis, and a chuck table 10 to be movable in the Y-axis direction. Guide rail 33 is provided.

  The rotating means 40 rotates the chuck table 10 around a central axis parallel to the Z-axis direction. The rotating means 40 is disposed on the moving table 12 that is moved in the X-axis direction by the X-axis moving means 20.

  The laser beam application means 50 performs laser processing on the wafer W held on the chuck table 10. More specifically, the laser beam irradiation means 50 irradiates the wafer W held on the chuck table 10 with a laser beam LB having a wavelength that is transmissive to the wafer W, thereby forming the modified layer K inside the wafer W. . As shown in FIG. 3, the laser beam irradiation unit 50 includes an oscillation unit 51 that oscillates the laser beam LB, an optical system 52, and a condensing unit 53 that collects the laser beam LB at a desired position on the wafer W. FIG. 3 is a block diagram showing laser beam irradiation means of the laser processing apparatus shown in FIG. The laser beam irradiation means 50 is attached to the tip of the support column 4.

  The oscillation means 51 includes, for example, a laser oscillator 511 that transmits a YAG laser beam or a YVO laser beam, a repetition frequency setting unit 512 that sets a repetition frequency of the laser beam LB, and a pulse width adjustment unit 513 that adjusts the output of the laser beam LB. .

  The laser beam LB oscillated from the laser oscillator 511 is a laser beam having a wavelength that is transmissive to the wafer W. The laser beam LB has a wavelength of 1064 nm, for example.

  The condensing means 53 includes a total reflection mirror that changes the traveling direction of the laser beam LB oscillated by the laser oscillator 511, a condensing lens that condenses the laser beam LB, and the like. More specifically, the condensing unit 53 includes a mirror 531 that reflects the laser beam LB, a mask 532, a pinhole 533 formed in the mask 532, and a condensing lens 534.

  The laser beam LB oscillated from the laser oscillator 511 passes through the optical system 52 composed of a plurality of optical components such as a polarization beam splitter and is incident on the condensing means 53. The laser beam LB incident on the condensing means 53 is reflected by the mirror 531. The laser beam LB reflected by the mirror 531 passes through the pinhole 533 of the mask 532. The laser beam LB that has passed through the pinhole 533 is applied to the wafer W held on the chuck table 10 by a condenser lens 534 configured by combining a plurality of lens groups.

  The imaging means 60 images the wafer W held on the chuck table 10 from above. The imaging means 60 is attached to the tip of the support column 4. The imaging means 60 is disposed at a position parallel to the laser beam irradiation means 50 in the X-axis direction. The imaging unit 60 includes an imaging device such as a CCD (Charge-Coupled Device) that detects light in an infrared region that is difficult to be absorbed by the wafer W. The imaging unit 60 outputs the captured image to the control unit 100.

  The control unit 100 controls the above-described components to cause the laser processing apparatus 1 to perform a laser processing operation on the wafer W. The control means 100 includes a computer system. The control means 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a counter 104, an input interface 105, and an output interface 106.

  The CPU 101 of the control means 100 performs arithmetic processing according to a computer program stored in the ROM 102 and sends a control signal for controlling the laser processing apparatus 1 via the output interface 106 to the above-described configuration of the laser processing apparatus 1. Output to the element.

  The ROM 102 stores programs and data necessary for processing in the control unit 100. The RAM 103 stores processing conditions for processing the wafer W. The processing conditions include a position where the modified layer K is to be formed, in other words, a position where the laser beam LB is to be irradiated.

  The laser processing apparatus 1 configured as described above irradiates the wafer W held on the chuck table 10 with the laser beam LB.

  Next, an inspection method for the laser beam LB of the laser processing apparatus 1 according to the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart for explaining a laser beam inspection method according to the embodiment. The inspection method for the laser beam LB includes a preparation step S1, a modified layer formation step S2, and an inspection step S3.

  First, preparation step S1 is performed. The preparation step S1 will be described with reference to FIG. FIG. 5 is an exploded perspective view for explaining a preparation step of the laser beam inspection method according to the embodiment. In the preparation step S1, the operator prepares a workpiece unit U by laminating the wafer W and the support base B via a resin layer A that melts when irradiated with a laser beam LB having a wavelength that passes through the wafer W. To do. On the surface Wa of the wafer W, a plurality of devices D are formed in a region partitioned by a plurality of division lines L. Such a wafer W is processed by the laser processing apparatus 1 to form the modified layer K, so that the wafer is divided into individual devices D using the modified layer K as a starting point in the subsequent breaking step. Then, the operator attaches the support base B of the workpiece unit U to the adhesive tape T whose outer peripheral portion is attached to the annular frame F. In this manner, as shown in FIG. 2, the wafer W is supported by the annular frame F through the resin layer A, the support base B, and the adhesive tape T with the back surface (exposed surface) Wb exposed. The

  The support base material B is, for example, a silicon wafer. The resin layer A is made of a material that absorbs the laser beam LB used in the laser processing apparatus 1 and melts at a predetermined temperature or higher. The thickness of the resin layer A is thinner than the thickness of the wafer W and the support base material B.

  After performing the preparation step S1, the modified layer forming step S2 is performed. The modified layer forming step S2 will be described with reference to FIG. FIG. 6 is a schematic diagram for explaining a modified layer forming step of the laser beam inspection method according to the embodiment. In the modified layer forming step S2, the operator exposes the wafer W, holds the workpiece unit U on the holding surface 10a of the chuck table 10, and applies the laser beam LB from the surface Wa which is the exposed surface of the wafer W to the wafer W. Irradiation is performed so that light is condensed inside, and a modified layer K is formed inside the wafer W.

  In the modified layer forming step S2, the operator exposes the back surface Wb of the wafer W, and the workpiece unit U is exposed with the support base B and the holding surface 10a of the chuck table 10 facing each other via the adhesive tape T. Is placed on the holding surface 10a. The operator operates the vacuum suction source to apply a negative pressure to the holding surface 10a. In this way, the workpiece unit U is sucked and held on the holding surface 10a.

  The control unit 100 moves the chuck table 10 with the X-axis moving unit 20 and the Y-axis moving unit 30 to position the wafer W held on the chuck table 10 below the laser beam irradiation unit 50. Then, the control unit 100 uses the laser beam irradiation unit 50 to position the condensing point P of the laser beam LB inside the wafer W and irradiate the laser beam LB from the back surface Wb of the wafer W. The control means 100 is an X-axis moving means 20 that feeds the chuck table 10 in the X-axis direction. By doing so, the modified layer K is formed inside the wafer W by multiphoton absorption.

  The laser beam LB that has not been absorbed in the vicinity of the condensing point P is emitted from the front surface Wa of the wafer W as a passing light (transmitted laser beam) LT. The exit light LT emitted from the surface Wa of the wafer W is incident on the resin layer A bonded to the surface Wa of the wafer W. The resin layer A absorbs the lost light LT. For this reason, the resin layer A is melted by the heat generated by absorbing the missing light LT, and a melt mark M is formed below the modified layer K.

  In the modified layer forming step S2, the control unit 100 moves the chuck table 10 and the laser beam irradiation unit 50 for irradiating the laser beam LB in the X axis direction and the Y axis direction by the X axis moving unit 20 and the Y axis moving unit 30. Move relative. Thereby, a modified layer K parallel to the X-axis direction and the Y-axis direction is formed inside the wafer W.

  After performing the modified layer forming step S2, the inspection step S3 is performed. In the inspection step S3, the state of the melted mark M formed in the resin layer A by the passing light LT transmitted through the wafer W is imaged and inspected through the wafer W. In the present embodiment, in the inspection step S3, the operator visually inspects the melt mark M to inspect the laser beam LB of the laser processing apparatus 1. The inspection step S3 includes the state of the melt mark M formed when the modified layer K parallel to the X-axis direction is formed on the cross section parallel to the XY plane in the resin layer A of the workpiece unit U, and the Y-axis. Each state of the melt mark M formed when the modified layer K parallel to the direction is formed is inspected.

  With reference to FIGS. 7 to 9, the melt mark M in a state where the optical axis of the laser beam LB of the laser processing apparatus 1 is not displaced will be described. FIG. 7 is a schematic diagram for explaining inspection steps of the laser beam inspection method according to the embodiment. FIG. 8 is a diagram for explaining inspection steps of the laser beam inspection method according to the embodiment. FIG. 9 is a schematic diagram illustrating inspection steps of the laser beam inspection method according to the embodiment. 7 and 9 show a state in which the modified layer K parallel to the X-axis direction is formed. FIG. 8 shows an image obtained by photographing the cross section parallel to the XY plane in the vicinity of the resin layer A of the workpiece unit U by the imaging means 60. The image is displayed on a display device (not shown) of the laser processing apparatus 1 via the output interface 106. As shown in FIG. 7, in a state where the optical axis of the laser beam LB is not deviated, the missing light LT absorbed in the resin layer A is evenly distributed without being biased in the Y-axis direction. For this reason, as shown in FIG. 8, the melt mark M is formed symmetrically in the Y-axis direction with respect to the center of the missing light LT indicated by a solid line in the drawing. The X coordinate and the Y coordinate of the center of the missing light LT are the same as the X coordinate and the Y coordinate of the position irradiated with the laser beam LB. In other words, the solid line in the figure indicates the position where the laser beam LB is irradiated on the XY plane. In other words, in this case, the melt mark M is formed immediately below the modified layer K.

  In this case, as shown in FIG. 9, it can be determined that the optical axis of the laser beam LB coincides with, for example, the center of the pinhole 533 formed in the mask 532 and the optical axis of the condenser lens 534. In other words, it can be determined that the optical system 52 and the light condensing means 53 are set optimally.

  The melt mark M in a state where the optical axis of the laser beam LB of the laser processing apparatus 1 is displaced will be described with reference to FIGS. FIG. 10 is a schematic diagram for explaining inspection steps of the laser beam inspection method according to the embodiment. FIG. 11 is a diagram for explaining inspection steps of the laser beam inspection method according to the embodiment. FIG. 12 is a schematic diagram for explaining inspection steps of the laser beam inspection method according to the embodiment. 10 and 12 show a state in which the modified layer K parallel to the X-axis direction is formed. FIG. 11 shows an image obtained by photographing the cross section parallel to the XY plane in the vicinity of the resin layer A of the workpiece unit U by the imaging means 60. The image is displayed on a display device (not shown) of the laser processing apparatus 1 via the output interface 106. As shown in FIG. 10, in a state where the optical axis of the laser beam LB is deviated, the missing light LT absorbed in the resin layer A is distributed in the Y-axis direction. For this reason, damage at the interface of the resin layer A is unevenly distributed in the Y-axis direction. As a result, as shown in FIG. 11, the melt mark M is formed asymmetrically in the Y-axis direction with respect to the center of the missing light LT indicated by a solid line in the drawing. In other words, in this case, the melt mark M is formed so as to be shifted in the Y-axis direction from directly below the modified layer K. For example, the melt mark M shown in FIG. 11 has an edge of the melt mark M formed at a position several μm away from the dotted line as compared to the melt mark M shown in FIG. For this reason, in the state in which the melt mark M in FIG. 11 is formed, the laser processing apparatus 1 can estimate that the optical axis is shifted by about several μm. Thus, it can be estimated from the captured image how much the optical axis of the laser processing apparatus 1 is shifted.

  In this case, as shown in FIG. 12, it can be determined that the optical axis of the laser beam LB does not coincide with the center of the pinhole 533 formed in the mask 532 or the optical axis of the condenser lens 534, for example. In other words, the optical system 52 can determine that various optical components need to be adjusted so that the optical axis of the laser beam LB matches the center of the pinhole 533 of the mask 532 and the optical axis of the condenser lens 534. .

  The relationship between the deviation of the optical axis of the laser beam LB of the laser processing apparatus 1 and the melting mark M will be described with reference to FIG. FIG. 13 is a diagram for explaining inspection steps of the laser beam inspection method according to the embodiment. FIG. 13 shows an image obtained by photographing the cross section parallel to the XY plane in the vicinity of the resin layer A of the workpiece unit U by the imaging means 60. The image is displayed on a display device (not shown) of the laser processing apparatus 1 via the output interface 106. In FIG. 13, when the optical axis of the laser beam LB is shifted by −500 μm, by −250 μm, by 500 μm, or by 250 μm in the Y-axis direction, the melt mark M in each case. It is shown. Formation of melted trace M with melt mark M when shifted by -500 μm, melt mark M when shifted by −250 μm, melt mark M when shifted by 500 μm, melt mark M when shifted by 250 μm The direction that has been made is opposite to the Y-axis direction. -500 μm misalignment between the melt mark M when misaligned by 500 μm, the melt mark M when misaligned by 500 μm, the melt mark M when misaligned by −250 μm, and the melt trace M when misaligned by 250 μm In this case, the melting mark M in the case where the deviation is 500 μm is formed so as to be largely shifted in the Y-axis direction. In other words, the knowledge that there is a correlation between the amount of deviation of the optical axis of the laser beam LB and the total area of the formed melt mark M is obtained. Thus, by comparing the size of the melt mark M, it is possible to estimate the magnitude of the deviation of the optical axis of the laser beam LB. Further, by comparing the direction in which the melt mark M is formed, the direction of deviation of the optical axis of the laser beam LB can be estimated.

  Similarly, the melt mark M formed when the modified layer K parallel to the X-axis direction in the resin layer A of the workpiece unit U is formed is also visually confirmed.

  In this way, in the inspection step S3, the deviation between the melt mark M formed in the X-axis direction and the Y-axis direction and the position irradiated with the laser beam LB causes the difference between the optical axis of the optical system 52 and the optical axis of the laser beam LB. Determine the direction of displacement.

  After performing the inspection step S3, based on the confirmation result of the melt mark M, when there is a deviation between the optical axis of the optical system 52 and the optical axis of the laser beam LB, various optical components of the optical system 52 are adjusted. At that time, if the adjustment is performed based on the shift amount estimated from the captured image, the adjustment work can be performed efficiently. Then, the modified layer forming step S2 and the inspection step S3 are performed again. Then, the adjustment of the optical system 52 is repeated until the melt mark M of the resin layer A becomes a target with respect to the center of the light beam LT. Further, by comparing the melt marks M before and after adjustment of various optical components of the optical system 52, adjustment is performed while estimating the magnitude of the deviation of the optical axis of the laser beam LB and the direction of deviation of the optical axis of the laser beam LB. can do.

  As described above, according to the present embodiment, the optical axis of the optical system 52 and the optical axis of the laser beam LB are inspected by inspecting the state of the melt mark M formed in the resin layer A by the laser beam LB transmitted through the wafer W. Can be accurately inspected.

  On the other hand, in the conventional method, in order to inspect the deviation between the optical axis of the optical system 52 and the optical axis of the laser beam LB, adjustment is performed using a power meter so that the energy of the laser beam LB is maximized. . However, inspection and adjustment work for various optical components require advanced expertise and technology. For this reason, it was necessary to call a specialized maintenance / inspection worker to perform inspection and adjustment work.

  According to the present embodiment, it is possible to easily inspect the deviation between the optical axis of the optical system 52 and the optical axis of the laser beam LB, even if it is not a specialized maintenance / inspection operator. For this reason, for example, the operator can inspect the deviation between the optical axis of the optical system 52 and the optical axis of the laser beam LB without calling a specialized maintenance / inspection operator.

  In the present embodiment, the modified layer K is formed on the workpiece unit U, and the displacement between the position of the melt mark M formed on the resin layer A and the laser beam LB is visually confirmed. In this way, this embodiment can determine whether or not there is a deviation between the optical axis of the optical system 52 and the optical axis of the laser beam LB.

  In the present embodiment, the displacement direction and the displacement amount of the optical axis are detected by the displacement direction and the displacement amount by visually confirming the displacement between the melt mark M formed on the resin layer A and the position irradiated with the laser beam LB. Can do. For this reason, this embodiment can adjust the optical axis of the optical system 52 efficiently.

  In the present embodiment, a wafer W produced as a workpiece of the laser processing apparatus 1 can be used as the inspection plate. In this embodiment, since it is not necessary to prepare a substrate as a plate for inspection, the inspection can be easily performed.

  In the above embodiment, in the inspection step S3, the laser beam LB of the laser processing apparatus 1 is inspected by visually observing the melt mark M. However, even if the control means 100 inspects the laser beam LB of the laser processing apparatus 1, Good.

  Specifically, in the modified layer forming step S2, the control unit 100 causes the RAM 103 to store the coordinates on the holding surface 10a at the position where the laser beam LB is irradiated. In other words, the coordinates on the holding surface 10a of the position where the laser beam LB is irradiated include the X coordinate and the Y coordinate of the position where the laser beam LB is irradiated.

  In the inspection step S3, the control unit 100 irradiates the laser beam LB when there is a difference between the coordinates of the laser beam LB stored in the RAM 103 and the coordinates of the melt mark M formed on the resin layer A. It is determined that the laser beam LB is deviated from the optical axis of the irradiation means 50. More specifically, the control unit 100 determines whether or not there is a difference between the X coordinate and Y coordinate irradiated with the laser beam LB and the X coordinate and Y coordinate of the melt mark M calculated by, for example, image analysis of the melt mark M. Determine whether. The control means 100 determines whether or not the X coordinate and Y coordinate of the melt mark M are formed symmetrically in the Y axis direction with respect to the X coordinate and Y coordinate irradiated with the laser beam LB. In other words, when the control unit 100 determines that there is a shift, the control unit 100 determines that the laser beam LB is shifted with respect to the optical axis of the laser beam irradiation unit 50. When it is determined that there is no deviation, the control unit 100 determines that the laser beam LB is not shifted from the optical axis of the laser beam irradiation unit 50.

  Thus, by inspecting the laser beam LB with the control means 100, the laser beam LB can be inspected more accurately than when visually inspecting.

  Alternatively, in the inspection step S3, the laser beam LB of the laser processing apparatus 1 is inspected by visually observing the melt mark M, and the deviation direction of the laser beam LB with respect to the optical axis is determined. The deviation direction of the laser beam LB may be determined.

  Specifically, in the modified layer forming step S2, the control unit 100 causes the RAM 103 to store the coordinates on the holding surface 10a at the position where the laser beam LB is irradiated.

  In the inspection step S3, the control unit 100 determines the laser beam LB with respect to the optical axis from the difference between the coordinates of the melt mark M formed in the X-axis direction and the Y-axis direction and the coordinates irradiated with the laser beam LB stored in the RAM 103. The direction of deviation is determined. More specifically, the control unit 100 has a difference between the X coordinate and Y coordinate of the melt mark M formed in the X axis direction and the Y axis direction, and the X coordinate and Y coordinate irradiated with the laser beam LB stored in the RAM 103. It is determined whether or not. When it is determined that there is a deviation, the control unit 100 determines the deviation direction of the laser beam LB with respect to the optical axis based on the magnitude of the deviation in the X axis direction and the Y axis direction. If the control unit 100 determines that there is no deviation, the control unit 100 determines that the laser beam LB is not shifted from the optical axis of the laser beam irradiation unit 50.

  Thus, by determining the deviation direction of the laser beam LB with respect to the optical axis by the control unit 100, the laser beam LB can be inspected more accurately than in the case where the determination is made visually.

  The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the scope of the present invention.

  In the above-described embodiment, the example in which the inspection method for the laser beam LB of the present invention is applied to the wafer W has been described. However, the workpiece is not limited to this. The inspection method of the laser beam LB can be similarly applied to other plate-like workpieces such as an optical device wafer. In the embodiment, the wafer W is a glass substrate, but it may be a silicon wafer. In that case, the melt mark M formed on the resin layer A may be imaged through the silicon wafer with an infrared camera. Further, the device may be formed on the support substrate instead of the wafer W, and the surface on which the device is formed may be laminated with the wafer W via a resin layer. In that case, since no device is formed on the wafer W, the molten mark M is formed without leakage light being blocked by the device layer, so that more accurate detection can be expected.

  The method for inspecting the laser beam LB is used for confirming the misalignment between the center of the laser beam LB and the center of the pinhole 533, as well as the misalignment between the various optical components of the optical system 52 and the center of the laser beam LB. You can also.

DESCRIPTION OF SYMBOLS 1 Laser processing apparatus 10 Chuck table 10a Holding surface 20 X-axis moving means 30 Y-axis moving means 50 Laser beam irradiation means (laser beam irradiation unit)
60 Image pickup means 100 Control means A Resin layer B Support base material D Device K Modified layer L Line to be divided LB Laser beam M Melt mark U Work piece unit W Wafer (Inspection plate)
Wa surface Wb Back surface (exposed surface)

Claims (4)

A step of preparing the workpiece unit by laminating the inspection plate and the supporting substrate through a resin layer that melts when irradiated with a laser beam having a wavelength that passes through the inspection plate;
The inspection plate is exposed to hold the workpiece unit on the holding surface of the chuck table, and the laser beam is condensed inside the inspection plate from the exposed surface of the inspection plate. A modified layer forming step of forming a modified layer inside the inspection plate,
An inspection step of inspecting a state of a melt mark formed in the resin layer by the laser beam transmitted through the inspection plate after the modified layer forming step is performed. Method. In the modified layer forming step, after storing the coordinates on the holding surface of the position where the laser beam is irradiated, the modified layer is formed,
In the inspection step, when there is a difference between the coordinates irradiated with the laser beam and the coordinates of the melt mark formed on the resin layer, the laser beam is irradiated with respect to the optical axis of the laser beam irradiation unit that irradiates the laser beam. The laser beam inspection method according to claim 1, wherein the laser beam is determined to be shifted. In the modified layer forming step, the chuck table and the laser beam irradiation unit for irradiating the laser beam are arranged in an X-axis direction parallel to the holding surface and a Y-axis direction parallel to the holding surface and perpendicular to the X-axis direction. Relative movement, forming a modified layer parallel to the X-axis direction and the Y-axis direction inside the inspection plate,
In the inspection step, a deviation direction of the laser beam with respect to the optical axis is determined from a deviation between the melt mark formed in the X-axis direction and the Y-axis direction and a position irradiated with the laser beam. The laser beam inspection method according to claim 2.   4. The laser beam inspection method according to claim 1, wherein the inspection plate is a glass substrate, and the support base is a silicon wafer.