Laser processing equipment

Abstract

To provide a laser machining device that is configured to make it unnecessary for an operator to calculate the number of spots which are positioned in a width direction and the number of paths to which pulse laser beams should be emitted, every time when machining work-pieces with different thicknesses.SOLUTION: The laser machining device is provided with a path number calculating part 106 that multiples a value determined by dividing a thickness H memorized in a thickness memorizing part 101 by a limit value R memorized in a limit-machining depth memorizing part 102, by the number of paths P memorized in a path number memorizing part 103, and multiples the value by the number of spots St determined from a spot diameter S of a pulse laser beam LB, an overlapping rate W of spots and a machining width V, so as to calculate path number Pt of the pulse laser beam LB which should be emitted to a cross section in the machining width V. Control means 100 emits the pulse laser beam LB, at the path number P calculated by the path calculating part 106 with respect to the machining width V, to a non-product region B selected by a selecting part 108 on the basis of an X coordinate and a Y coordinate memorized in a machining locus memorizing part 107.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a laser processing apparatus that performs a desired process on a workpiece held on a chuck table. [Background technology]

[0002] Wafers with multiple devices such as ICs and LSIs formed on their surface along planned dividing lines are then separated into individual device chips using dicing equipment and laser processing equipment, and are used in electrical devices such as mobile phones and personal computers.

[0003] The laser processing device is generally composed of a chuck table that holds the wafer, an imaging means that images the wafer held on the chuck table and detects the area to be processed, a laser beam application means that irradiates the wafer held on the chuck table with a pulsed laser beam, and a processing feed means that feeds the chuck table and the laser beam application means relative to each other, and is capable of processing wafers with high precision (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-085347 Summary of the Invention [Problem to be solved by the invention]

[0005] When the laser processing apparatus described in Patent Document 1 is used to form grooves of a desired depth by irradiating a pulsed laser beam of a wavelength that is absorbed by the wafer, there is a problem in that, even if the focal point of the pulsed laser beam is positioned on the intended dividing line, the number of passes to be irradiated is set, and the pulsed laser beam is repeatedly irradiated, the desired processing cannot be performed because of the limit on the processing depth relative to the spot size.

[0006] Therefore, the applicant considered the limit value of the processing depth for the spot diameter of the pulsed laser beam and the thickness of the wafer to be divided, calculated the number of spots to be positioned in the width direction of the planned division line and the number of passes to be made by irradiating the pulsed laser beam, and inputted the necessary processing information into a laser processing device to form grooves of the desired depth.

[0007] However, it has become clear that the operator must perform the above calculations each time a wafer of a different thickness is processed, which is troublesome, and furthermore, a calculation error can prevent proper laser processing, resulting in damage to the wafer. Such problems are not limited to processing the dividing lines of a wafer in which a plurality of devices are divided by dividing lines and formed on the surface, but can also occur when cutting a plate-like object into a desired shape.

[0008] The present invention has been made in view of the above-mentioned facts, and its main technical object is to provide a laser processing apparatus that can solve the problem that, when a pulsed laser beam is irradiated onto a workpiece to form a groove of a desired depth, an operator must calculate the number of spots to be positioned in the width direction and the number of passes to be made with the pulsed laser beam each time a workpiece of different thickness is processed, which is an unbearable hassle. [Means for solving the problem]

[0009] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a laser processing apparatus comprising: a chuck table having a holding surface defined in X-axis and Y-axis directions for holding a workpiece; laser beam application means for irradiating a pulsed laser beam onto the workpiece held on the chuck table; and control means, wherein the laser beam application means comprises an oscillator for oscillating a pulsed laser beam, and a condenser for focusing the pulsed laser beam oscillated by the oscillator onto the workpiece held on the chuck table, and the control means comprises a processing path memory unit for storing X- and Y-coordinates of a processing path to be formed on the workpiece held on the chuck table, a thickness memory unit for storing the thickness of the workpiece, a limit processing depth memory unit for storing the spot diameter and limit value of the processing depth of the pulsed laser beam, a pass number memory unit for storing the number of passes of the pulsed laser beam that reaches the limit value of the processing depth, an overlap rate memory unit for storing an overlap rate of the spot, and a control means for storing a product area and a non-product area. a processing width calculation unit that calculates a processing width by multiplying the spot diameter by a value obtained by dividing the thickness stored in the thickness memory unit by the limit value stored in the limit processing depth memory unit; and a pass number calculation unit that multiplies the value obtained by dividing the thickness stored in the thickness memory unit by the limit value stored in the limit processing depth memory unit by the number of passes stored in the pass number memory unit, and calculates the number of passes of the pulsed laser beam to be irradiated onto a cross section in the processing width by multiplying the spot diameter of the pulsed laser beam, the spot overlap rate stored in the overlap rate memory unit, and the number of spots calculated from the processing width calculated by the processing width calculation unit, wherein the control means irradiates the pulsed laser beam onto the non-product region selected by the selection unit based on the X and Y coordinates stored in the processing locus memory unit, for the number of passes calculated by the pass number calculation unit for the processing width calculated by the processing width calculation unit, thereby performing desired processing on a workpiece held on the chuck table.

[0010] The laser processing apparatus includes an X-axis feed means for relatively feeding the chuck table and the laser beam application means in the X-axis direction for processing, and a Y-axis feed means for relatively feeding the chuck table and the laser beam application means in the Y-axis direction for processing, and the control means controls the oscillator and the X-axis feed means and the Y-axis feed means to perform the processing. The laser beam application means includes an X-axis optical scanner for guiding the pulsed laser beam in the X-axis direction and a Y-axis optical scanner for guiding the pulsed laser beam in the Y-axis direction, and the condenser is configured to include an fθ lens, and the control means controls the oscillator and the X-axis optical scanner and the Y-axis optical scanner to perform the processing. [Effects of the Invention]

[0011] The laser processing apparatus of the present invention is a laser processing apparatus comprising: a chuck table having a holding surface defined in the X-axis and Y-axis directions for holding a workpiece; laser beam application means for irradiating a pulsed laser beam onto the workpiece held on the chuck table; and control means, wherein the laser beam application means comprises an oscillator for oscillating a pulsed laser beam and a condenser for condensing the pulsed laser beam oscillated by the oscillator onto the workpiece held on the chuck table; and the control means controls the X-axis and Y-axis of a processing locus to be formed on the workpiece held on the chuck table. a machining path memory unit that stores a target Y coordinate; a thickness memory unit that stores the thickness of a workpiece; a limit machining depth memory unit that stores the spot diameter of a pulsed laser beam and a limit value of the machining depth; a pass number memory unit that stores the number of passes of the pulsed laser beam that reaches the limit value of the machining depth; an overlap rate memory unit that stores an overlap rate of the spot; and a selection unit that selects a product area and a non-product area. The machining width calculation unit calculates a machining width by multiplying a value obtained by dividing the thickness stored in the thickness memory unit by the limit value stored in the limit machining depth memory unit by the spot diameter. a pass number calculation unit that calculates the number of passes of the pulse laser beam to be irradiated onto the cross section in the processing width by multiplying a value obtained by dividing the limit value stored in the limit processing depth storage unit by the limit value stored in the limit processing depth storage unit, and multiplying the value obtained by dividing the limit value by the limit value stored in the limit processing depth storage unit by the number of passes stored in the pass number storage unit, and multiplying the spot diameter of the pulse laser beam, the spot overlap rate stored in the overlap rate storage unit, and the number of spots obtained from the processing width calculated by the processing width calculation unit, and the control means is provided with a Since the desired processing is performed on the workpiece held on the chuck table by irradiating the pulsed laser beam with the number of passes set, the control means calculates the number of spots to be positioned in the width direction of the desired processing locus and the number of passes to irradiate the pulsed laser beam, taking into account the limit value of the processing depth for the spot diameter of the pulsed laser beam and the thickness of the workpiece to be divided, and these are reflected in the laser processing performed by the control means, so it is no longer necessary for the operator to calculate the above-mentioned parameters each time and input them into the laser processing device to set them so that a groove of the desired depth is formed,This eliminates the need to perform the above-mentioned complicated calculations each time a workpiece of different thickness is machined, which can be unbearable. It also eliminates the problem of damage to the workpiece due to calculation errors. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an overall perspective view of a laser processing apparatus according to an embodiment of the present invention; [Figure 2] 2 is a block diagram showing an optical system of a laser beam application means disposed in the laser processing apparatus shown in FIG. 1. FIG. [Figure 3] 1. FIG. 4 is a block diagram showing an optical system of another embodiment of the laser beam application means disposed in the laser processing apparatus shown in FIG. [Figure 4] 2 is a perspective view of a wafer to be processed by the laser processing apparatus shown in FIG. 1. [Figure 5] 2 is a block diagram showing details of a control means disposed in the laser processing apparatus shown in FIG. 1. FIG. [Figure 6] 2(a) is a schematic cross-sectional view of a groove formed by the laser processing device shown in FIG. 1, and FIG. 2(b) is a schematic cross-sectional view of a dividing groove formed by the groove shown in FIG. [Figure 7] FIG. 5 is an enlarged plan view showing a part of the wafer shown in FIG. [Figure 8] FIG. 2 is a perspective view showing an embodiment of laser processing according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a laser processing apparatus configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0014] 1 shows an overall perspective view of a laser processing apparatus 1 of this embodiment. The laser processing apparatus 1 is disposed on a base 2 and is equipped with a holding means 3 including a chuck table 35 for holding a wafer 10 shown in the figure, a laser beam application means 6 for irradiating a pulsed laser beam onto the wafer 10 held on the chuck table 35, and a control means 100.

[0015] The laser processing apparatus 1 also includes a moving means 4 including an X-axis feed means 41 that moves the chuck table 35 in the X-axis direction and a Y-axis feed means 42 that moves the chuck table 35 in the Y-axis direction, a frame 5 that includes a vertical wall portion 5a erected on the side of the moving means 4 on the base 2 and a horizontal wall portion 5b extending horizontally from the upper end of the vertical wall portion 5a, and an imaging means 7 that images the wafer 10 held on the chuck table 35 to perform alignment, and an input means 8 and a display means (not shown) are connected to the control means 100. Note that the display means can also be used as the input means 8 by configuring the display means as a touch panel that allows touch input.

[0016] As shown in FIG. 1 , the holding means 3 includes a rectangular X-axis direction movable plate 31 mounted on the base 2 so as to be movable in the X-axis direction, a rectangular Y-axis direction movable plate 32 mounted on the X-axis direction movable plate 31 so as to be movable in the Y-axis direction, a cylindrical support 33 fixed to the upper surface of the Y-axis direction movable plate 32, and a rectangular cover plate 34 fixed to the upper end of the support 33. A chuck table 35 extending upward through an elongated hole formed in the cover plate 34 is disposed on the cover plate 34. The chuck table 35 is configured to be rotatable by a rotation drive means (not shown) housed in the support 33. A holding surface 36 made of a breathable porous material and defined by the X-axis and Y-axis directions is formed on the upper surface of the chuck table 35. The holding surface 36 is connected to a suction means (not shown) by a flow path passing through the support 33, and four clamps 37 used to hold the wafer 10 (described later) on the chuck table 35 are arranged at equal intervals around the holding surface 36. By operating the suction means, the wafer 10 can be suction-held on the holding surface 36 of the chuck table 35 .

[0017] The X-axis feed means 41 converts the rotational motion of the motor 43 into linear motion via a ball screw 44 and transmits it to the X-axis movable plate 31, moving the X-axis movable plate 31 in the X-axis direction along a pair of guide rails 2a, 2a arranged along the X-axis direction on the base 2. The Y-axis feed means 42 converts the rotational motion of the motor 45 into linear motion via a ball screw 46 and transmits it to the Y-axis movable plate 32, moving the Y-axis movable plate 32 in the Y-axis direction along a pair of guide rails 31a, 31a arranged along the Y-axis direction on the X-axis movable plate 31.

[0018] The horizontal wall 5b of the frame 5 accommodates an optical system constituting the laser beam application means 6 and an imaging means 7. A condenser 61 that constitutes part of the laser beam application means 6 and irradiates the wafer 10 with a pulsed laser beam LB is disposed on the underside of the tip of the horizontal wall 5b. The imaging means 7 is an imaging means that captures an image of the wafer 10 held on the chuck table 35 to detect the position and orientation of the wafer 10, the position to be irradiated with the pulsed laser beam, etc., and is disposed adjacent to the condenser 61 in the X-axis direction indicated by the arrow X in the figure.

[0019] 2 is a block diagram showing an example of the optical system of the laser beam application means 6. The laser beam application means 6 of this embodiment includes an oscillator 62 that oscillates a pulsed laser beam LB, an attenuator 63 that adjusts the output of the pulsed laser beam LB oscillated by the oscillator 62, a reflecting mirror 64 that redirects the optical path of the pulsed laser beam LB toward the chuck table 35, and a condenser 61 including a condensing lens 61a that focuses the pulsed laser beam LB on the wafer 10 held on the holding surface 36 of the chuck table 35. When the pulsed laser beam LB is applied to the wafer 10, which is the workpiece, by the laser beam application means 6, the control means 100 controls the X-axis feed means 41 and the Y-axis feed means 42, so that the pulsed laser beam LB can be applied to desired X- and Y-coordinate positions of the wafer 10 held on the chuck table 35.

[0020] The laser beam application means of the present invention is not limited to the laser beam application means 6 shown in Fig. 2 described above, and may be provided with another form of laser beam application means 6', for example, a laser beam application means 6' configured with an optical system as shown in Fig. 3. The laser beam application means 6' is provided with an oscillator 62 and an attenuator 63 similar to those described above, as well as an X-axis optical scanner 65 that guides the pulsed laser beam LB in the X-axis direction of the wafer 10 held on the holding surface 36 of the chuck table 35, a Y-axis optical scanner 66 that guides the pulsed laser beam LB in the Y-axis direction of the wafer 10 held on the chuck table 35, and a condenser 61' including an fθ lens 61a'. The X-axis optical scanner 65 and the Y-axis optical scanner 66 are configured by, for example, galvanometer scanners, and when the pulsed laser beam LB is irradiated onto the wafer 10, which is the workpiece, the X-axis optical scanner 65 and the Y-axis optical scanner 66 can be controlled by the control means 100 so that the pulsed laser beam LB can be irradiated onto a desired position on the wafer 10 held on the chuck table 35. Note that the X-axis optical scanner 65 and the Y-axis optical scanner 66 are not limited to the galvanometer scanners described above, and may also be scanners that use an acousto-optic element (AOE), a diffractive optical element (DOE), a polygon mirror, or the like.

[0021] Next, the configuration of the wafer 10, which is the workpiece of the laser processing apparatus 1 of this embodiment, and the control means 100 will be described below. Note that in the embodiment described below, the laser processing apparatus 1 will be described as being equipped with the laser beam application means 6 shown in FIG.

[0022] The workpiece to be processed by the laser processing apparatus 1 of this embodiment is, for example, a silicon (Si) wafer 10 shown in Fig. 4. The wafer 10 is a wafer having a surface 10a on which a plurality of devices 12 are formed by being partitioned by planned division lines, and is positioned in an opening Fa of an annular frame F having the opening Fa capable of accommodating the wafer 10, and is held to the frame F via adhesive tape T to form an integrated unit.

[0023] The control means 100 is configured by a computer and includes a central processing unit (CPU) that performs calculations according to a control program, a read-only memory (ROM) that stores the control program etc., a readable and writable random access memory (RAM) that temporarily stores calculation results etc., an input interface, and an output interface. The control means 100 is connected to the imaging means 7, input means 8, oscillator 62, X-axis feed means 41, Y-axis feed means 42, etc.

[0024] The laser processing apparatus 1 of this embodiment has roughly the configuration as described above, and the functions and actions of the laser processing apparatus 1 will be specifically described below.

[0025] The laser processing performed on the wafer 10 by the laser processing apparatus 1 of this embodiment is carried out by control means 100.

[0026] 5 and 6, the following will explain the various functional units 101 to 108 realized by the control program stored in the control means 100 and various storage memories. The control means 100 includes a thickness memory unit 101 that stores the thickness H of the wafer 10, which is the workpiece, a limit processing depth memory unit 102 that stores the spot diameter S of the pulsed laser beam LB and the limit value R of the processing depth, a pass number memory unit 103 that stores the number of passes P of the pulsed laser beam LB that reaches the limit value R of the processing depth, and an overlap ratio memory unit 104 that stores the overlap ratio W of the spot during laser processing.

[0027] Furthermore, it is provided with a processing width calculation unit 105 that calculates a processing width V by multiplying a value obtained by dividing the thickness H stored in the thickness memory unit 101 by the limit value R stored in the limit processing depth memory unit 102, and the resulting value by the spot diameter S, and a pass number calculation unit 106 that multiplies a value obtained by dividing the thickness H stored in the thickness memory unit 101 by the limit value R of the processing depth stored in the limit processing depth memory unit 102, and the pass number P stored in the pass number memory unit 103, and multiplies the spot overlap rate W stored in the overlap rate memory unit 104 and the spot number N obtained from the processing width V calculated by the processing width calculation unit 105, to calculate the pass number Pt of the pulse laser beam LB to be irradiated onto the cross section in the processing width V. The control means 100 is equipped with a processing path memory unit 107 that stores coordinate information I of the X and Y coordinates of the processing path to be formed on the wafer 10 held on the chuck table 35, and a selection unit 108 that selects between the product area A and the non-product area B. Based on the information collected from the processing width calculation unit 105, the pass number calculation unit 106, the processing path memory unit 107, and the selection unit 108, a processing execution unit 109 that executes laser processing controls the oscillator 62, the X-axis feed means 41, and the Y-axis feed means 42, thereby achieving the desired laser processing.

[0028] Each functional unit of the control means 100 described above will now be described in more detail. The thickness H of the workpiece (wafer 10) stored in the thickness memory unit 101 is acquired and stored, for example, by an operator operating the input means 8 to input the thickness H or by reading barcode information formed on the wafer 10. In this embodiment, the thickness H of the wafer 10 is, for example, 300 μm, and the thickness memory unit 101 stores the thickness H of the wafer 10 as 300 μm.

[0029] The limit machining depth storage unit 102 stores a limit value R of the machining depth based on the spot diameter S of the pulsed laser beam LB applied by the laser beam application means 6. To explain this with reference to FIG. 6( a), for example, in this embodiment, the spot diameter S of the pulsed laser beam LB applied by the laser beam application means 6 is φ10 μm. By repeatedly applying the pulsed laser beam LB along a desired position, the depth of the machined groove 20 formed at the predetermined position gradually increases. However, the machining depth does not increase indefinitely in proportion to the number of times the pulsed laser beam LB is applied along the desired machining position (number of passes P). There is a limit value R beyond which the machining depth does not become deeper. In this embodiment, the limit machining depth storage unit 102 previously determines the limit value R of the machining depth based on the spot diameter S = φ10 μm set under the laser processing conditions of this embodiment (described below) through an experiment, and stores the actual measured value (100 μm in this embodiment) as the limit value R.

[0030] The pass number memory unit 103 stores the pass number P that reaches the limit value R of the machining depth actually measured in the limit machining depth memory unit 102, and in this embodiment, the pass number P = 8 is stored as the actually measured value. Also, the overlap rate memory unit 104 is means for storing the spot overlap rates in the X-axis direction and the Y-axis direction when the pulsed laser beam LB is irradiated to form the dividing grooves 18 with a plurality of machining grooves 20, as shown in Fig. 6(b), and in this embodiment, the overlap rate is set to 50% in both the X-axis direction and the Y-axis direction and stored.

[0031] The processing width calculation unit 105 calculates the processing width V required to form the division grooves 18 deep enough to completely divide the wafer 10. Specifically, the thickness H (300 μm) stored in the thickness storage unit 101 is divided by the limit value R (100 μm) stored in the limit processing depth storage unit 102, and the result is multiplied by the spot diameter S (10 μm), to calculate the width V as follows: Processing width V=(H / R)·S=(300 / 100)·10=30[μm] As a result, the processing width V=30 μm is calculated and stored.

[0032] The pass number calculation unit 106 calculates the number of passes Pt of the pulsed laser beam LB to be irradiated onto the cross section in the processing width V, and the number of passes Pt is the number of passes of the pulsed laser beam LB required to form division grooves 18 that completely divide the wafer 10 along the planned division lines 14 of the wafer 10. The number of passes Pt is calculated by multiplying a value obtained by dividing the thickness H (300 μm) stored in the thickness memory unit 101 by the limit value R (100 μm) stored in the limit processing depth memory unit 102 by the number of passes P (8 times) stored in the pass number memory unit 103, and also by multiplying the value by the spot overlap rate W (50%) stored in the overlap rate memory unit 104 and the number of spots St found from the processing width V (30 μm) calculated by the processing width calculation unit 105.

[0033] Here, the number of spots St of the pulsed laser beam LB irradiated in the processing width V is expressed as "St = 1 + x" where x is the number of pulsed laser beams LB irradiated in the width direction after the first spot, and x is (Spot diameter S)·{1+(100%-overlap rate W)·x}=Processing width V From the relation, 10·{1+(1-0.5)·x}=30 is obtained by solving for x (x=4), so the number of spots St irradiated for the processing width V=30 μm is “5” (see also FIG. 6(b)).

[0034] The number of passes Pt of the pulsed laser beam LB to be irradiated onto the cross section in the processing width V is calculated as follows: Pt=(H / R)·P·St=(300 / 100)·8·5=120

[0035] As can be understood by referring to FIG. 6(b), the number of passes Pt of the pulsed laser beam LB to be irradiated onto the cross section in the processing width V in this embodiment is determined as follows: first, in the processing width V (30 μm) on the wafer 10, at each of five spot positions positioned so as to overlap each other by 50% in the processing width direction, the number of passes P (8 times) of the pulsed laser beam LB reaching the limit value (100 μm) of the processing depth is irradiated to form the first groove 22 having a width of 30 μm and a depth of 100 μm (40 times); and after forming the first groove 22, This indicates the total number (Pt=120) of the number of times (40 times) that the focal point of the pulsed laser beam LB is positioned at the bottom of the first groove 22 and laser processing is performed in the same manner as above to form second grooves 23 having a width of 30 μm and a depth of 200 μm, and the number of times (40 times) that, after forming the first groove 22 and second groove 23, the focal point of the pulsed laser beam LB is positioned at the bottom of the second groove 23 and laser processing is performed in the same manner as above to form third grooves 24 having a width of 30 μm and a depth of 300 μm, i.e., which completely divides the wafer 10. By forming the first groove 22, second groove 23, and third groove 24 as described above, it is possible to form division grooves 18 that completely divide the wafer 10.

[0036] As described above, the control means 100 is provided with a machining locus memory unit 107 that stores coordinate information I of the X and Y coordinates of the machining locus to be formed on the wafer 10 held on the chuck table 35. The coordinate information I stored in this embodiment is coordinate information I of the X and Y coordinates that specifies the center line 16 along the planned dividing line 14 of the wafer 10, which is shown enlarged in FIG. 7, and indicates the machining locus. The coordinate information I of the X and Y coordinates of the center line 16 is registered and stored in the machining locus memory unit 107 in advance by the input means 8 described above.

[0037] Furthermore, the control means 100 includes a selection unit 108 that selects between the product area A and the non-product area B, as described above. In this embodiment, the product area A refers to the area including the device 12 or the device 12 and its outer edge where laser processing is not permitted, and the non-product area B refers to the area where laser processing is permitted. That is, referring to FIG. 7 , the area on the wafer 10 where the device 12 is located is selected as the product area A, and the area where the planned division lines 14 are formed is selected as the non-product area B, and these are stored in the selection unit 108. The division grooves 18 formed by the laser processing described above are in the area of ​​the non-product area B (planned division lines 14), and are formed in the planned processing area 18′ indicated by the dashed line along the center line 16 indicated by the dashed line. Based on the information stored in the selection unit 108, laser processing is prevented from accidentally extending into the product area A. In practice, the selection unit 108 may select only the product area A or the non-product area B, or the present embodiment may be implemented assuming that the other area is the other area (product area A or non-product area B). In this embodiment, the width of the planned division line 14 selected as the non-product area B is 70 μm as shown. If the processing width V calculated by the processing width calculation unit 105 exceeds 70 μm, even if an attempt is made to form the division groove 18 along the center line 16 of the planned division line 14, proper laser processing cannot be performed within the non-product area B (planned division line 14), and it is determined that processing is impossible. In this case, the laser processing conditions described below are adjusted.

[0038] As described above, the control means 100 acquires the processing width V, the number of passes Pt of the pulsed laser beam LB to be irradiated onto the cross section in the processing width V, and coordinate information I of the X and Y coordinates of the processing trajectory to be formed, and once the product area A and non-product area B are selected, laser processing is performed on the wafer 10 based on the processing execution unit 109 of the control means 100.

[0039] The laser processing conditions in this embodiment are set, for example, as follows. Wavelength: 355nm Repetition frequency: 50kHz Average output: 2W Pulse energy: 40μJ Pulse width: 10ps Spot diameter: φ10μm

[0040] 1, the wafer 10 is placed on the holding surface 36 of the chuck table 35 of the holding means 3 with the front surface 10a facing upward, and is sucked and fixed by the frame F being gripped by the clamps 37. The wafer 10 held on the chuck table 35 is imaged using the imaging means 7 arranged in the laser processing apparatus 1, and alignment is performed to detect the X and Y coordinates of the processing path to be processed stored in the processing path storage unit 107, and the position of the planned dividing line 14 on the front surface 10a of the wafer 10 is detected, and the wafer 10 is rotated by the rotation drive means to align the predetermined planned dividing line 14 in the X-axis direction.

[0041] Based on the information detected by the above-mentioned alignment, as shown in FIG. 8, the condenser 61 of the laser beam application means 6 is positioned at a predetermined processing start position in the processing area 18' (see also FIG. 7) where the division grooves 18 will be formed on the predetermined dividing line 14 in a predetermined direction, and the focal point of the pulsed laser beam LB is positioned on the surface 10a. The X-axis feed means 41 and the Y-axis feed means 42 are operated to feed the wafer 10 in the X-axis direction to perform the above-mentioned ablation processing along the processing area 18' on the predetermined dividing line 14 of the wafer 10, and the wafer 10 is fed in the Y-axis direction in accordance with the overlap rate W (50% in this embodiment), and laser processing is performed within the processing width V of the processing area 18' based on the above-mentioned laser processing conditions in accordance with the number of spots St (five in this embodiment). Then, by operating the laser beam application means 6, the X-axis feed means 41, and the Y-axis feed means 42, the above laser processing is repeatedly performed so that the above number of passes P (eight times in this embodiment) is applied to one spot, thereby forming a groove (first groove 22 in FIG. 6(b)) that is 30 μm wide and 100 μm deep along the planned division line 14. Note that the order in which the pulsed laser beam LB is applied with the number of passes P that reaches the limit value R of the processing depth, corresponding to each of the five spots in this embodiment, can be determined arbitrarily.

[0042] Next, the position of the focal point is lowered in the Z-axis direction indicated by the arrow Z in FIG. 8 to position the spot at the bottom of the groove, and laser processing is performed along the groove in the same manner as described above to form the second grooves 23 and 24. As a result, by irradiating the pulsed laser beam LB for a total number of passes Pt=120, division grooves 18 with a depth of 300 μm are formed along the predetermined division lines 14 in the processing regions 18′. After the division grooves 18 have been formed along the predetermined division lines 14 in this manner, the wafer 10 is indexed and fed by the distance between adjacent division lines 14 in the Y-axis direction, and the unprocessed division lines 14 are positioned directly below the collector 61. Then, in the same manner as described above, the focal point of the pulsed laser beam LB is positioned in the processing regions 18′ of the division lines 14 of the wafer 10, and the division grooves 18 are formed by irradiating the pulsed laser beam LB. Similarly, the wafer 10 is processed and fed in the X-axis direction and the Y-axis direction to form division grooves 18 along all of the division lines 14 along the X-axis direction. Next, the wafer 10 is rotated 90 degrees to align the unprocessed division lines 14 perpendicular to the division lines 14 along which division grooves 18 have already been formed, in the X-axis direction. Then, for all of the remaining division lines 14, the focusing point of the pulsed laser beam LB is positioned and the pulsed laser beam LB is irradiated in the same manner as described above to form division grooves 18 along all of the division lines 14 formed on the front surface 10a of the wafer 10.

[0043] According to the above-described embodiment, the control means 100 calculates the number of spots St to be positioned in the width direction of the division line 14 and the number of passes Pt to be irradiated with the pulsed laser beam LB, taking into account the limit value R of the processing depth for the spot diameter S of the pulsed laser beam LB and the thickness H of the wafer 10 to be divided, and these are reflected in the laser processing performed by the control means 100. This eliminates the need for the operator to calculate the above-described parameters each time and input them into the laser processing apparatus 1 to set the laser processing apparatus 1 so as to form division grooves 18 of the desired depth, and also eliminates the problem of the operator having to perform the above-described complicated calculations each time a different wafer of a different thickness is processed, which is unbearable. Furthermore, the problem of the wafer being damaged due to calculation errors is also eliminated.

[0044] In the above-described embodiment, an example has been described in which the laser processing apparatus 1 processes the wafer 10, on whose surface 10a a plurality of devices 12 are partitioned by the planned division lines 14, to form grooves of a desired depth, but the present invention is not limited thereto. For example, in a case where a circular silicon plate is processed as the workpiece and a product of a desired shape, such as a rectangular silicon plate, is to be obtained from the circular silicon plate, as specified by the X and Y coordinates of the processing path to be formed stored in the processing path memory unit 107, the selection unit 108 selects the desired rectangular area as product area A and selects an area surrounding the product area A as non-product area B, and performs the above-described laser processing on the non-product area B along the outer edge of the product area A to form division grooves 18, thereby obtaining the desired rectangular silicon plate as a product. [Explanation of symbols]

[0045] 1: Laser processing equipment 2: Base 3: Holding means 31:X-axis movable plate 32: Y-axis direction movable plate 33: Strut 34: Cover plate 35: Chuck table 36: Holding surface 4. Transportation 41: X-axis feed means 42: Y-axis feed means 43: Motor 44: Ball screw 45: Motor 46: Ball screw 5:Frame body 5a: Vertical wall 5b:Horizontal wall part 6, 6': Laser beam irradiation means 61, 61': Concentrator 61a: Condenser lens 61a': fθ lens 62: Oscillator 63: Attenuator 64: Reflective mirror 65: X-axis optical scanner 66: Y-axis optical scanner 7: Imaging means 8: Input method 100: Control means 101: Thickness memory unit 102: Limit machining depth memory section 103: Path number memory unit 104: Overlap rate memory unit 105: Machining width calculation section 106: Path number calculation unit 107: Machining trajectory memory section 108: Selection section 109: Processing execution unit A: Product area B: Non-product area H: Thickness of workpiece S: Spot diameter St: Number of spots R: Limit value of machining depth P: Number of passes of the pulsed laser beam LB to reach the limit value R of the processing depth Pt: Number of passes of the pulsed laser beam LB to be irradiated on the cross section in the processing width V V: Machining width W: Spot overlap rate I: Coordinate information of X and Y coordinates of the machining path LB: Pulsed laser beam

Claims

1. A laser processing apparatus including a chuck table having a holding surface defined in the X-axis direction and the Y-axis direction for holding a workpiece, a laser beam application means for applying a pulsed laser beam to the workpiece held on the chuck table, and a control means, the laser beam application means comprises an oscillator that oscillates a pulsed laser beam, and a condenser that condenses the pulsed laser beam oscillated by the oscillator onto the workpiece held on the chuck table; the control means comprises a machining path memory unit that stores the X and Y coordinates of a machining path to be formed on the workpiece held on the chuck table, a thickness memory unit that stores the thickness of the workpiece, a limit machining depth memory unit that stores the spot diameter of the pulsed laser beam and the limit value of the machining depth, a pass number memory unit that stores the number of passes of the pulsed laser beam that reaches the limit value of the machining depth, an overlap rate memory unit that stores the spot overlap rate, and a selection unit that selects a product area and a non-product area, a processing width calculation unit that calculates a processing width by multiplying a value obtained by dividing the thickness stored in the thickness storage unit by the limit value stored in the limit processing depth storage unit and the spot diameter; a pass number calculation unit that calculates the number of passes of the pulsed laser beam to be irradiated onto the cross section in the processing width by multiplying a value obtained by dividing the thickness stored in the thickness storage unit by the limit value stored in the limit processing depth storage unit by the number of passes stored in the pass number storage unit, and multiplying the spot diameter of the pulsed laser beam, the spot overlap rate stored in the overlap rate storage unit, and the number of spots obtained from the processing width calculated by the processing width calculation unit, The control means irradiates a pulsed laser beam onto the non-product region selected by the selection unit based on the X and Y coordinates stored in the processing path memory unit, for the processing width calculated by the processing width calculation unit, with the number of passes calculated by the pass number calculation unit, thereby performing desired processing on the workpiece held on the chuck table.

2. an X-axis feed means for relatively feeding the chuck table and the laser beam application means in the X-axis direction for processing, and a Y-axis feed means for relatively feeding the chuck table and the laser beam application means in the Y-axis direction for processing, 2. The laser processing apparatus according to claim 1, wherein said control means controls said oscillator, and also controls said X-axis feed means and said Y-axis feed means to carry out said processing.

3. the laser beam application means includes an X-axis optical scanner that guides the pulsed laser beam in an X-axis direction, and a Y-axis optical scanner that guides the pulsed laser beam in a Y-axis direction; The condenser includes an fθ lens, 2. The laser processing apparatus according to claim 1, wherein said control means controls said oscillator and also controls said X-axis optical scanner and said Y-axis optical scanner to perform said processing.

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