Laser processing method

Abstract

To provide a laser processing method with which it is possible to suppress debris that occurs when a workpiece having an image sensor element as a device is laser-processed.SOLUTION: The laser processing method comprises: a holding step 101 in which the reverse side of a workpiece is held by a holding table so that the surface side of the workpiece is exposed; and a laser irradiation step 102 in which a laser beam is radiated from a laser beam irradiation unit along a scheduled divide line from the surface side of the workpiece being held by the holding table. In the laser irradiation step 102, a laser beam is radiated while changing a laser beam irradiation position on the surface of the workpiece by a laser beam scanning unit located between an oscillator for oscillating the laser beam and a collector for collecting the beams from the oscillator.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a laser processing method for laser-processing along a planned division line of a workpiece having an image sensor element.

Background Art

[0002] As a method for dividing a workpiece such as a semiconductor wafer along a planned division line, a method of dividing by laser-processing the planned division line is known (for example, see Patent Document 1). In such laser processing, the workpiece is continuously processed along the planned division line by the thermal energy generated in the irradiated area of the workpiece by the irradiation of the laser beam.

[0003] However, in the laser processing disclosed in Patent Document 1 described above, debris (processing chips) may be generated due to the concentration of thermal energy in the irradiated area of the workpiece, and there is a problem that this debris adheres to the surface of the workpiece and deteriorates the quality. Therefore, a laser processing method has been proposed in which a water-soluble protective film is formed on the surface of the workpiece and the workpiece is irradiated with a laser beam through the protective film (for example, see Patent Document 2). After the laser processing, the protective film is washed with water to remove the protective film together with the debris adhering to the protective film, and the surface of the workpiece can be protected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when laser processing a planned division line of a workpiece having an image sensor element as a device, a defect such as a mark caused by laser irradiation on a part of the sensor element portion (commonly known as surface burning) may occur. This mark occurs when the debris generated by the laser beam is relatively large.

[0006] From this, it is presumed that when large debris is floating in the air and the laser beam of the next pulse hits this debris, the laser beam scatters, and the scattered light irradiates the sensor element portion, leaving a mark. For the purpose of solving this problem, in order to reduce the size of the generated debris, it is conceivable to reduce the laser irradiation spot or lower the pulse energy, etc., but there is a problem that the productivity decreases.

[0007] Therefore, when laser processing a workpiece having an image sensor element as a device, there is a problem that a laser processing method should be provided that can relatively reduce the size of the debris generated by the laser beam.

[0008] The present invention has been made in view of such problems, and its object is to provide a laser processing method capable of suppressing debris generated when laser processing a workpiece having an image sensor element as a device.

Means for Solving the Problem

[0009] In order to solve the above-described problems and achieve the object, a laser processing method of the present invention is a laser processing method for performing laser processing along a planned division line on a workpiece in which a plurality of devices are formed in regions partitioned by a plurality of planned division lines intersecting each other on the surface, wherein the device has an image sensor element, and a holding step of holding the back surface side of the workpiece with a holding table so that the surface side of the workpiece is exposed, and a laser irradiation step of irradiating a laser beam from a laser beam irradiation unit along the planned division line from the surface side of the workpiece held by the holding table. The laser irradiation step irradiates the laser beam while changing the irradiation position of the laser beam on the surface of the workpiece by a laser beam scanning unit disposed between an oscillator that oscillates the laser beam and a condenser that condenses the light from the oscillator.

[0010] In the laser processing method, the laser beam scanning unit may include a galvanometer scanner, a resonant scanner, an acousto-optic polarization element, or a polygon mirror.

[0011] In the laser processing method, the laser irradiation step may irradiate a pulsed laser beam from the oscillator, and the irradiation energy for each irradiation region on the surface of the workpiece may be 10 μJ or less.

[0012] In the laser processing method, the laser irradiation step may irradiate a pulsed laser beam from the oscillator, and the pulse frequency may be 1 MHz or more.

Effect of the Invention

[0013] The present invention has an effect of being able to suppress debris generated when laser-processing a workpiece having an image sensor element as a device.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

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DETAILED DESCRIPTION OF THE INVENTION

[0015] Embodiments (embodiments) for carrying out 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. In addition, the constituent elements described below include those that can be easily assumed by those skilled in the art and substantially identical ones. Furthermore, the configurations described below can be combined as appropriate. Also, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[0016] 〔Embodiment 1〕 The laser processing method according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a workpiece to be processed by the laser processing method according to Embodiment 1. The laser processing method according to Embodiment 1 is a method of laser processing the workpiece 1 shown in FIG. 1.

[0017] (Workpiece) The workpiece 1 to be processed by the laser processing method according to Embodiment 1 is, as shown in FIG. 1, for example, a disk-shaped semiconductor wafer or the like having a substrate such as a silicon substrate, a sapphire substrate, a gallium substrate, or a SiC substrate. In Embodiment 1, as shown in FIG. 1, a plurality of devices 4 are formed in regions partitioned by a plurality of division planned lines 3 intersecting each other on the surface 2 of the workpiece 1.

[0018] The device 4 is an image sensor element, and in Embodiment 1, it is a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor device (also referred to as an imaging device). The workpiece 1 is subjected to laser processing along the division planned lines 3 and is divided into individual devices 4.

[0019] In Embodiment 1, as shown in FIG. 1, a disk-shaped adhesive tape 6 having a diameter larger than that of the workpiece 1 is attached to the back surface 5 on the back side of the surface 2 of the workpiece 1, and an annular frame 7 is attached to the outer edge portion of the adhesive tape 6 and is supported within the opening of the frame 7.

[0020] (Laser Processing Apparatus) The laser processing method according to Embodiment 1 is implemented by the laser processing apparatus 10 shown in FIG. 2. FIG. 2 is a perspective view schematically showing a configuration example of a laser processing apparatus for implementing the laser processing method according to Embodiment 1. FIG. 3 is a diagram showing a configuration example of a laser beam irradiation unit of the laser processing apparatus shown in FIG. 1.

[0021] As shown in FIG. 2, the laser processing apparatus 10 includes a holding table 20, a moving unit 30, a laser beam irradiation unit 40, an imaging unit 50, a cassette elevator 60, a cleaning unit 70, a transfer unit 80, and a control unit 100.

[0022] The holding table 20 is disk-shaped, and a flat holding surface 21 formed of porous ceramic or the like is formed along the horizontal direction for holding the workpiece 1. Further, the holding table 20 is movably provided over a processing region below the laser beam irradiation unit 40 by the moving unit 30 and a loading / unloading region where the workpiece 1 is loaded and unloaded while being separated from below the laser beam irradiation unit 40.

[0023] The holding table 20 is connected to a vacuum suction source (not shown), and by being suctioned from the vacuum suction source, the workpiece 1 placed on the holding surface 21 is suctioned and held. In Embodiment 1, the holding table 20 suctions and holds the back surface 5 side of the workpiece 1 via the adhesive tape 6. Further, as shown in FIG. 2, a plurality of clamping portions 22 for clamping the frame 7 are provided around the holding table 20.

[0024] The moving unit 30 relatively moves the holding table 20 and the laser beam irradiation unit 40. The moving unit 30 includes at least a Y-axis moving unit 31 which is an indexing feed unit that moves the holding table 20 in the Y-axis direction parallel to the horizontal direction, an X-axis moving unit 32 which is a processing feed unit that moves the holding table 20 in the X-axis direction parallel to the horizontal direction and orthogonal to the Y-axis direction, and a rotational moving unit 33 that rotates the holding table 20 around an axis parallel to the Z-axis direction parallel to the vertical direction.

[0025] The Y-axis moving unit 31 is installed on the apparatus main body 11, and moves the holding table 20 in the Y-axis direction by moving a moving plate 12 on which the X-axis moving unit 32 is installed in the Y-axis direction. The X-axis moving unit 32 is installed on the moving plate 12, and moves the holding table 20 in the X-axis direction by moving a second moving plate 13 on which the rotational moving unit 33 is installed in the X-axis direction. The rotational moving unit 33 is installed on the second moving plate 13 and supports the holding table 20, thereby rotating the holding table 20 around the axis.

[0026] The Y-axis movement unit 31 moves the moving plate 12, the X-axis movement unit 32, the second moving plate 13, the rotational movement unit 33, and the holding table 20 in the Y-axis direction. The X-axis movement unit 32 moves the rotational movement unit 33 and the holding table 20 in the X-axis direction for each second moving plate 13.

[0027] The Y-axis movement unit 31 and the X-axis movement unit 32 include a well-known ball screw rotatably provided around an axis, a well-known motor that rotates the ball screw around the axis, and a well-known guide rail that movably supports the moving plates 12 and 13 in the X-axis direction or the Y-axis direction. The rotational movement unit 33 includes a well-known motor or the like that rotates the holding table 20 around an axis.

[0028] As shown in FIG. 2, a part of the laser beam irradiation unit 40 is provided at the tip of a support column 15 whose base end is supported by a standing wall 14 erected from the end in the Y-axis direction of the apparatus main body 11. The laser beam irradiation unit 40 irradiates the workpiece 1 held by the holding table 20 with a laser beam 401 for laser processing. As shown in FIG. 3, the laser beam irradiation unit 40 includes a laser beam oscillation means 41, an optical system 42, a wavelength conversion element 43, a laser beam scanning unit 44, and a condenser 45.

[0029] The laser beam oscillation means 41 includes an oscillator 46 and a repetition frequency setting means 47. The oscillator 46 is a device that oscillates a laser beam having a predetermined wavelength. In Embodiment 1, a crystal such as YAG doped with neodymium (Nd) ions or the like is preferably used, which is excited by a laser diode (LD) to oscillate a laser beam having a wavelength of about 1 μm.

[0030] The repetition frequency setting means 47 is a means for setting the repetition frequency of the laser beam oscillated by the oscillator 46. In Embodiment 1, the repetition frequency is preferably set to double, and based on the laser beam having a wavelength of about 1 μm described above, a laser beam 400 having a wavelength of about 514 nm, which is the second harmonic, is oscillated.

[0031] In Embodiment 1, the laser beam oscillation means 41 is controlled by the control unit 100 to oscillate a pulsed laser beam having a repetition frequency of 100 kHz or more and 100 MHz or less, an average output of 1 W or more and 1000 W or less, and a pulse width of 20 ps or less.

[0032] The optical system 42 includes at least one of predetermined optical devices such as a beam diameter adjuster and an output adjuster, and transmits the laser beam 400 oscillated from the laser beam oscillation means 41. The wavelength conversion element 43 is an element that converts the wavelength of the laser beam 400 transmitted by the optical system 42. In Embodiment 1, the laser beam 400 having a wavelength of about 514 nm oscillated by the laser beam oscillation means 41 is converted into a laser beam 401 having a wavelength of about 355 nm, which is absorbable by the workpiece 1 and is the third harmonic of the laser beam having an original wavelength of about 1 μm. In the present invention, the wavelength conversion element 43 may also convert the laser beam into a second harmonic or a fourth harmonic laser beam.

[0033] In Embodiment 1, since the wavelength conversion element 43 is provided on the downstream side of the optical system 42 in the traveling direction of the laser beams 400 and 401, the wavelength of the laser beam 400 passing through the optical system 42 can be made longer than the wavelength of the finally irradiated laser beam 401, so that damage to the optical system 42 can be suppressed.

[0034] The laser beam scanning unit 44 is disposed between the oscillator 46 and the condenser 45 as shown in FIG. 3. More specifically, the laser beam scanning unit 44 is disposed further downstream than the optical system 42 and the wavelength conversion element 43 provided downstream of the laser beam oscillation means 41 including the oscillator 46. The laser beam scanning unit 44 displaces the irradiation position of the laser beam 401 in the XY plane on the holding surface 21 of the holding table 20.

[0035] In Embodiment 1, the laser beam scanning unit 44 includes a galvanometer scanner, a resonant scanner, an acousto-optic deflector, or a polygon mirror. The laser beam scanning unit 44 is controlled by the control unit 100 to swing the laser beam 401 in the X-axis direction and the Y-axis direction and guide it to the condenser 45.

[0036] The condenser 45 has a circular shape with a diameter equal to or larger than that of the holding surface 21 of the holding table 20 in the XY plane, and is provided so as to cover the upper part of the holding surface 21 of the holding table 20 when located below the laser beam irradiation unit 40. The condenser 45 condenses the pulsed laser beam 401 oscillated from the oscillator 46 and scanned by the laser beam scanning unit 44. In the present invention, the condenser 45 may be smaller than the holding surface 21 of the holding table 20.

[0037] Examples of the condenser 45 include a large Fθ lens having the above-described diameter or a large image-side telecentric objective lens having the above-described diameter. In either case, the optical axis is provided along the Z-axis direction. The condenser 45 irradiates the laser beam 401 parallel to the Z-axis direction, which is the optical axis direction, that is, orthogonal to the holding surface 21 of the holding table 20, regardless of the incident angle of the laser beam 401 guided from the laser beam scanning unit 44.

[0038] Further, the above-described laser beam irradiation unit 40 sets a condensing point on the surface 2 of the workpiece 1 held by the holding table 20, and irradiates the workpiece 1 with a laser beam 401 having a wavelength that is absorbable by the workpiece 1 along the planned division line 3, performs ablation processing on the planned division line 3 of the workpiece 1, and divides the workpiece 1 into individual devices 4. In Embodiment 1, the laser beam irradiation unit 40 irradiates the workpiece 1 with a laser beam 401 having an irradiation energy of 0.01 μJ or more and 10 μJ or less for each condensing point (corresponding to one irradiation region) on the surface 2 of the workpiece 1. This is because if the irradiation energy of the condensing point is less than 0.01 μJ, no processing will occur, and if the irradiation energy of the condensing point exceeds 10 μJ, defects such as marks where the laser beam 401 is irradiated on a part of the device 4 (commonly known as surface burning) will occur.

[0039] Also, in Embodiment 1, the laser beam irradiation unit 40 has a repetition frequency (corresponding to the pulse frequency) of the laser beam 401 of 1 MHz or more and 100 MHz or less. This is because if the repetition frequency of the laser beam 401 is less than 1 MHz, the productivity will decrease due to a decrease in the number of irradiations, and if the repetition frequency of the laser beam 401 exceeds 100 MHz, in order to cause processing, it is necessary to increase the output of the laser beam, that is, the cost will increase and the laser oscillator will become larger.

[0040] The imaging unit 50 is disposed at a position aligned with the condenser 45 of the laser beam irradiation unit 40 in the X-axis direction at the tip of the support column 15. The imaging unit 50 includes an imaging element that images the region to be divided of the workpiece 1 before laser processing held by the holding table 20. The imaging element is, for example, a CCD (Charge-Coupled Device) imaging element or a CMOS (Complementary MOS) imaging element. The imaging unit 50 images the workpiece 1 held by the holding table 20, obtains an image for performing alignment for aligning the workpiece 1 and the condenser 45 of the laser beam irradiation unit 40, and outputs the obtained image to the control unit 100.

[0041] The cassette elevator 60 is configured to install a cassette 61 containing the workpiece 1 before and after laser processing and move the cassette 61 in the Z-axis direction. In Embodiment 1, the cassette elevator 60 is disposed at an end of the apparatus main body 11 on the loading / unloading region side in the X-axis direction and at an end away from the standing wall 14 in the Y-axis direction.

[0042] The cleaning unit 70 is configured to clean the workpiece 1 after laser processing. The cleaning unit 70 is disposed at an end of the apparatus main body 11 on the loading / unloading region side in the X-axis direction and at an end closer to the standing wall 14 in the Y-axis direction.

[0043] The transfer unit 80 is configured to transfer the workpiece 1 between the cassette 61, the holding table 20, and the cleaning unit. The transfer unit 80 includes a pair of guide rails 81 on which the workpiece 1 to be inserted into and removed from the cassette 61 is placed, and a transfer arm 82 that inserts and removes the workpiece 1 into and from the cassette 61 and transfers the workpiece 1 between the guide rails 81, the holding table 20, and the cleaning unit 70.

[0044] The control unit 100 controls each component of the laser processing apparatus 10 to cause the laser processing apparatus 10 to perform a processing operation on the workpiece 1. The control unit 100 is a computer having an arithmetic processing unit with a microprocessor such as a CPU (central processing unit), a storage device having a memory such as a ROM (read only memory) or a RAM (random access memory), and an input / output interface device. The arithmetic processing unit of the control unit 100 performs arithmetic processing according to a computer program stored in the storage device and outputs a control signal for controlling the laser processing apparatus 10 to each component of the laser processing apparatus 10 via the input / output interface device.

[0045] The control unit 100 is connected to a display unit (not shown) composed of a liquid crystal display device or the like that displays the state and image of the processing operation, and an input unit (not shown) used when an operator registers processing content information or the like. The input unit is composed of at least one of a touch panel provided on the display unit and an external input device such as a keyboard.

[0046] (Laser processing method) Next, the laser processing method according to Embodiment 1 will be described. FIG. 4 is a flowchart showing the flow of the laser processing method according to Embodiment 1. FIG. 5 is a side view schematically showing a holding step of the laser processing method shown in FIG. 4 in a partial cross-section. FIG. 6 is a side view schematically showing a laser irradiation step of the laser processing method shown in FIG. 4 in a partial cross-section.

[0047] The laser processing method according to Embodiment 1 is a method of laser processing the workpiece 1 having the above-described configuration along the division planned line 3. Further, the laser processing method according to Embodiment 1 is also a processing operation of the laser processing apparatus 10 having the above-described configuration.

[0048] In the laser processing apparatus 10 according to Embodiment 1, processing conditions are registered in the control unit 100 by an operator or the like, and a cassette 61 containing the workpiece 1 is installed in the cassette elevator 60. When the control unit 100 receives an instruction to start the processing operation from an operator or the like, the laser processing apparatus 10 starts the processing operation, that is, the laser processing method according to Embodiment 1. The laser processing method according to Embodiment 1 includes a holding step 101 and a laser irradiation step 102, as shown in FIG. 4.

[0049] (Holding step) The holding step 101 is a step of holding the back surface 5 side of the workpiece 1 by the holding table 20 so that the surface 2 side of the workpiece 1 is exposed. In Embodiment 1, in the holding step 101, the laser processing apparatus 10 controls the conveyance unit 80 by the control unit 100 to take out one workpiece 1 from the cassette 61 and place it on a pair of guide rails 81.

[0050] In Embodiment 1, in the holding step 101, the laser processing apparatus 10 controls the conveyance unit 80 by the control unit 100 to position the back surface 5 side of the workpiece 1 on the pair of guide rails 81 on the holding surface 21 of the holding table 20 positioned in the loading / unloading area. In Embodiment 1, in the holding step 101, the laser processing apparatus 10 controls the vacuum suction source by the control unit 100 to suck and hold the back surface 5 side to the holding surface 21 of the holding table 20 via the adhesive tape 6 as shown in FIG. 5, expose the surface 2 side of the workpiece 1, and clamp the frame 7 with the clamp portion 22.

[0051] (Laser irradiation step) The laser irradiation step 102 is a step of irradiating a laser beam 401 from the laser beam irradiation unit 40 along the division planned line 3 from the surface 2 side of the workpiece 1 held by the holding table 20. In Embodiment 1, in the laser irradiation step 102, the laser processing apparatus 10 controls the moving unit 30 by the control unit 100 to move the holding table 20 toward the processing area, photograph the workpiece 1 with the imaging unit 50, and perform alignment based on the image obtained by the imaging unit 50.

[0052] In Embodiment 1, in the laser irradiation step 102, as shown in FIG. 6, the laser processing apparatus 10 controls the laser beam irradiation unit 40 and the like by the control unit 100, and while changing the irradiation position of the laser beam 401 on the surface 2 of the workpiece 1 by the laser beam scanning unit 44, sets the focus point of the laser beam 401 on the surface 2 of each division planned line 3 and irradiates it. In Embodiment 1, in the laser irradiation step 102, the laser processing apparatus 10 irradiates the laser beam 401 on all the division planned lines 3 of the workpiece 1 held by the holding table 20 to divide the workpiece 1 into individual devices 4.

[0053] In Embodiment 1, in the laser irradiation step 102, when the laser processing apparatus 10 divides the workpiece 1 held by the holding table 20 into individual devices 4, the control unit 100 controls the moving unit 30 to position the holding table 20 in the loading / unloading area, stops the suction holding of the holding table 20, and releases the clamping of the clamp portion 22. In Embodiment 1, in the laser irradiation step 102, the laser processing apparatus 10 controls the transport unit 80 by the control unit 100 to transport the workpiece 1 from the holding table 20 to the cleaning unit 70, and the control unit 100 controls the cleaning unit 70 to clean the workpiece 1 divided into individual devices 4.

[0054] In Embodiment 1, in the laser irradiation step 102, after the laser processing apparatus 10 controls the transport unit 80 by the control unit 100 to transport the workpiece 1 from the cleaning unit 70 onto the pair of guide rails 81, the laser processing apparatus 10 transports the workpiece 1 on the pair of guide rails 81 into the cassette 61. In Embodiment 1, the laser processing apparatus 10 sequentially performs laser processing on the workpieces 1 in the cassette 61. In Embodiment 1, when the laser processing of all the workpieces 1 in the cassette 61 is completed, the laser processing apparatus 10 ends the processing operation.

[0055] As described above, in Embodiment 1, in the laser irradiation step 102, the laser beam irradiation unit 40 having the above-described configuration irradiates the workpiece 1 with a laser beam 401 such that the irradiation energy per condensing point is 0.01 μJ or more and 10 μJ or less. Also, in Embodiment 1, in the laser irradiation step 102, the laser beam irradiation unit 40 having the above-described configuration irradiates the workpiece 1 with a pulsed laser beam 401 having a repetition frequency of 1 MHz or more and 100 MHz or less from the oscillator 46.

[0056] As described above, in the laser processing method according to Embodiment 1, in the laser irradiation step 102 of irradiating the planned division line 3 of the workpiece 1 with the laser beam 401, the irradiation position of the condensing point of the laser beam 401 on the surface 2 of the workpiece 1 is changed by the laser beam scanning unit 44 while irradiating the laser beam 401. For this reason, in the laser processing method according to Embodiment 1, since the irradiation position of the condensing point of the laser beam 401 is changed by the laser beam scanning unit 44, the scanning speed of the laser beam 401 increases, the overlap rate of the condensing points is decreased to reduce the irradiation energy, and the size of the generated debris can be made relatively small.

[0057] As a result, the laser processing method according to Embodiment 1 has an effect of being able to suppress debris generated when laser-processing the workpiece 1 having the image sensor element as the device 4. Note that the overlap rate is the ratio of the area where adjacent condensing points of the laser beam 401 overlap to the area of the condensing point of the laser beam 401.

[0058] In addition, in the laser processing method according to Embodiment 1, since laser processing is performed by irradiating a laser beam 401 with an irradiation energy of 10 μJ or less at the condensing point and a repetition frequency of 1 MHz or more, the irradiation energy of the laser beam 401 is reduced compared to the method of irradiating the laser beam 401 while relatively moving the workpiece 1 and the laser beam irradiation unit 40 with the moving unit 30. In particular, debris generated when laser-processing the workpiece 1 having the image sensor element as the device 4 can be suppressed.

[0059] In addition, in the laser processing method according to Embodiment 1, laser processing is performed by irradiating a laser beam 401 with an irradiation energy of 10 μJ or less at the condensing point and a repetition frequency of 1 MHz or more, the irradiation energy of the laser beam 401 is reduced, and debris generated during laser processing can be suppressed. Therefore, laser processing can be performed without covering the surface 2 of the workpiece 1 with a protective film before the laser irradiation step 102.

[0060] Note that the present invention is not limited to the above-described embodiment. That is, various modifications can be made without departing from the gist of the present invention. For example, in the present invention, before the laser irradiation step 102, a liquid water-soluble resin such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) (for example, HogoMax (registered trademark) manufactured by DISCO Corporation) may be applied to the surface 2 of the workpiece 1, and the liquid water-soluble resin may be dried to cover the entire surface 2 of the workpiece 1 with a water-soluble protective film.

Explanation of Reference Numerals

[0061] 1 Workpiece 2 Surface 3 Division planned line 4 Device 5 Back surface 20 Holding table 40 Laser beam irradiation unit 44 Laser beam scanning unit 45 Condenser 46 Oscillator 101 Holding Step 102 Laser Irradiation Step 401 Laser Beam (Pulsed Laser Beam)

Claims

1. A laser processing method for laser-processing a workpiece in which a plurality of devices are formed in regions defined by a plurality of planned division lines intersecting each other on the surface, along the planned division lines, comprising: the device has an image sensor element; a holding step of holding the back surface side of the workpiece with a holding table so that the surface side of the workpiece is exposed; a laser irradiation step of irradiating a laser beam from a laser beam irradiation unit along the planned division line from the surface side of the workpiece held by the holding table; comprising: the laser irradiation step irradiates a laser beam while changing the irradiation position of the laser beam on the surface of the workpiece by a laser beam scanning unit disposed between an oscillator that oscillates the laser beam and a condenser that condenses the light from the oscillator. The laser processing method is characterized in that.

2. The laser processing method according to claim 1, wherein the laser beam scanning unit includes a galvanometer scanner, a resonant scanner, an acousto-optic polarization element, or a polygon mirror.

3. The laser processing method according to claim 1, wherein the laser irradiation step irradiates a pulsed laser beam, and the irradiation energy for each irradiation region on the surface of the workpiece is 10 μJ or less.

4. The laser processing method according to any one of claims 1 to 3, wherein the laser irradiation step irradiates a pulsed laser beam, and the pulse frequency is 1 MHz or more.

Images