JP6649705B2 - Laser processing method - Google Patents

Description

  The present invention relates to a laser processing method for forming a laser processing groove by irradiating a workpiece such as a glass plate or a semiconductor wafer with a laser beam.

  In a semiconductor device manufacturing process, a plurality of regions are divided by a plurality of planned dividing lines formed in a lattice on the surface of a substantially disk-shaped silicon substrate, and devices such as ICs and LSIs are divided into the divided regions. Form. Then, the semiconductor wafer is cut along the dividing lines to divide the region where the devices are formed, thereby manufacturing individual devices.

  As a method of dividing a wafer such as a semiconductor wafer described above along a planned dividing line, a laser beam having an absorptive wavelength is applied to the wafer along the planned dividing line to perform ablation processing to form a laser-processed groove. The forming technology has been put to practical use.

  As described above, a laser processing apparatus that irradiates a wafer with a laser beam having an absorptive wavelength to a wafer includes a workpiece holding unit that holds a workpiece, and a workpiece held by the workpiece holding unit. Laser beam irradiating means for irradiating a laser beam, and a moving means for relatively moving the workpiece holding means and the laser beam irradiating means are provided. It can be processed into a complicated shape (for example, see Patent Document 1).

JP 2007-275962 A

  As described above, when a workpiece is irradiated with a laser beam having an absorptive wavelength and subjected to ablation processing, cracks occur on both sides of the laser processing groove formed by the ablation processing and the quality of the product deteriorates. There is a problem of causing.

  The present invention has been made in view of the above facts, and a main technical problem thereof is to provide a laser processing method capable of removing a crack generated along a laser processing groove formed by ablation processing. is there.

In order to solve the main technical problem, according to the present invention, a workpiece holding means for holding a workpiece, and a laser beam oscillated by a pulse laser beam oscillator on the workpiece held by the workpiece holding means. A laser processing method using a laser processing apparatus comprising: a laser beam irradiating unit having a condenser for condensing and irradiating the laser beam; and a moving unit for relatively moving the workpiece holding unit and the laser beam irradiating unit. And
A laser beam having a wavelength that is absorptive to the workpiece is oscillated by the pulse laser beam oscillator along a processing line set on the workpiece held by the workpiece holding means, and collected by the condenser. A first processing step of forming a first laser processing groove on a workpiece along a processing line by performing ablation processing by irradiating light;
After performing the first processing step, a converging spot of a laser beam oscillated by the pulsed laser beam oscillator condensed by the concentrator is positioned adjacent to the first laser processing groove. By performing ablation by irradiating a laser beam along the laser processing groove, the processing is performed separately from the first processing step of forming a second laser processing groove along the first laser processing groove on the workpiece. A second processing step to be performed,
The second processing step includes irradiating the converging spot onto the first laser processing groove to irradiate the first laser processing groove, and a product area in which a workpiece becomes a product with the first laser processing groove interposed therebetween. It is those divided into a waste area for disposal and, second processing step is the laser processing how to practice the product area side is provided.

  In the second processing step, the condensed spot of the laser beam is polymerized and irradiated to the first laser processing groove in a range of 10 to 90%.

In the laser processing method according to the present invention, the pulse laser beam oscillator oscillates a laser beam having a wavelength that is absorptive to the workpiece along a processing line set on the workpiece held by the workpiece holding means. A first processing step of forming a first laser processing groove on a workpiece along a processing line by performing ablation processing by condensing and irradiating the light with the light collector; and the first processing step. Is performed, the converging spot of the laser beam oscillated by the pulsed laser beam oscillator condensed by the concentrator is positioned adjacent to the first laser processing groove, and the laser beam is irradiated along the first laser processing groove. And performing ablation processing, thereby forming a second laser processing groove along the first laser processing groove in the workpiece, separately from the first processing step. It includes a second processing step is carried out, a step of processing the second is intended to irradiation by polymerizing condensed spot on the first laser groove, and, the workpiece is first be those divided into a waste area for discarding the product to become the product area across the laser processed groove, the second processing step Runode be carried in the product area side, a first formed in the workpiece Cracks generated along the laser processing groove disappear by being ablated in the second processing step, and the energy of the laser beam irradiated in the second processing step is absorbed by the first laser processing groove to generate a crack. Is suppressed. Therefore, cracks do not occur along the second laser processing grooves, and the problem that cracks cause deterioration in product quality is solved.

FIG. 1 is a perspective view of a laser processing apparatus for performing a laser processing method according to the present invention. FIG. 2 is a block diagram of a laser beam irradiation unit provided in the laser processing apparatus shown in FIG. 1. FIG. 2 is a block configuration diagram of control means provided in the laser processing apparatus shown in FIG. 1. FIG. 2 is a perspective view showing a glass plate as a workpiece and a state in which the glass plate is attached to a protective tape mounted on an annular frame. FIG. 5 is an explanatory diagram showing a relationship with a coordinate position in a state where the glass plate shown in FIG. 4 is held at a predetermined position on a chuck table of the laser processing apparatus shown in FIG. 1. FIG. 2 is an explanatory view showing a first processing step in the first embodiment of the laser processing method according to the present invention, which is performed by the laser processing apparatus shown in FIG. 1. FIG. 6 is a plan view of a glass plate on which a first processing step is performed in the first embodiment of the laser processing method according to the present invention shown in FIG. 6 and an explanatory diagram showing a state of a first laser processing groove formed in the glass plate. . FIG. 4 is an explanatory view showing a second processing step in the first embodiment of the laser processing method according to the present invention. FIG. 4 is a perspective view showing a semiconductor wafer as a workpiece and a state where the semiconductor wafer is attached to a protective tape attached to an annular frame. FIG. 2 is an explanatory view showing a first processing step in a reference example of the laser processing method according to the present invention, which is performed by the laser processing apparatus shown in FIG. 1. FIG. 11 is a plan view of a semiconductor wafer on which a first processing step is performed in the reference example of the laser processing method according to the present invention shown in FIG. 10 and an explanatory diagram showing a state of a first laser processing groove formed in the semiconductor wafer. Explanatory drawing which shows the 2nd processing process in the reference example of the laser processing method by this invention.

  Hereinafter, preferred embodiments of the laser processing method according to the present invention will be described in more detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a laser processing apparatus for performing a laser processing method according to the present invention. A laser processing apparatus 1 shown in FIG. 1 includes a stationary base 2, a chuck table mechanism 3 movably disposed in the X-axis direction indicated by an arrow X on the stationary base 2 to hold a workpiece, and a stationary base 2. A laser beam irradiating unit 4 as a laser beam irradiating means disposed on the table 2;

  The chuck table mechanism 3 includes a pair of guide rails 31, 31 disposed in parallel on the stationary base 2 along the X-axis direction, and movably disposed on the guide rails 31, 31 in the X-axis direction. A first sliding block 32 provided; a second sliding block 33 disposed on the first sliding block 32 so as to be movable in a Y-axis direction indicated by an arrow Y perpendicular to the X-axis direction; A cover table 35 supported by a cylindrical member 34 on a second sliding block 33 and a chuck table 36 as workpiece holding means are provided. The chuck table 36 has a suction chuck 361 formed of a porous material, and holds a workpiece on a holding surface, which is an upper surface of the suction chuck 361, by operating a suction unit (not shown). ing. The chuck table 36 configured as described above is rotated by a pulse motor (not shown) provided in the cylindrical member 34. The chuck table 36 is provided with a clamp 362 for fixing an annular frame that supports the workpiece via a protective tape.

  The first sliding block 32 has a pair of guided grooves 321, 321 fitted on the pair of guide rails 31, 31 on the lower surface, and is formed in parallel on the upper surface along the Y-axis direction. A pair of guide rails 322 and 322 are provided. The first sliding block 32 configured as described above moves in the X-axis direction along the pair of guide rails 31, 31 by the guided grooves 321 being fitted into the pair of guide rails 31, 31. It is configured to be possible. The illustrated chuck table mechanism 3 includes an X-axis direction moving means 37 for moving the first sliding block 32 along the pair of guide rails 31 in the X-axis direction. The X-axis direction moving means 37 includes a male screw rod 371 disposed in parallel between the pair of guide rails 31 and 31 and a drive source such as a pulse motor 372 for driving the male screw rod 371 to rotate. I have. One end of the male screw rod 371 is rotatably supported by a bearing block 373 fixed to the stationary base 2, and the other end is operatively connected to the output shaft of the pulse motor 372. Note that the male screw rod 371 is screwed into a through female screw hole formed in a female screw block (not shown) provided to project from the lower surface of the central portion of the first sliding block 32. Accordingly, the first sliding block 32 is moved in the X-axis direction along the guide rails 31, 31 by driving the male screw rod 371 to rotate forward and reverse by the pulse motor 372.

  The illustrated laser processing apparatus 1 includes an X-axis direction position detector 374 for detecting the position of the chuck table 36 in the X-axis direction. The X-axis direction position detecting means 374 includes a linear scale 374a disposed along the guide rail 31 and a reading disposed on the first sliding block 32 and moving along the linear scale 374a together with the first sliding block 32. And a head 374b. The reading head 374b of the X-axis direction position detecting means 374 sends a pulse signal of, for example, one pulse every 1 μm to a control means described later. Then, the control means described later detects the position of the chuck table 36 in the X-axis direction by counting the input pulse signals. When a pulse motor 372 is used as a drive source of the X-axis direction moving means 37, a drive pulse of a control means, which will be described later, which outputs a drive signal to the pulse motor 372, is counted. An axial position can also be detected. When a servomotor is used as a drive source of the X-axis direction moving means 37, a pulse signal output from a rotary encoder for detecting the number of rotations of the servomotor is sent to a control means described later, and the control means inputs the pulse signal. By counting the pulse signals, the position of the chuck table 36 in the X-axis direction can be detected.

  The second sliding block 33 has a pair of guided grooves 331 and 331 fitted on a lower surface thereof with a pair of guide rails 322 and 322 provided on the upper surface of the first sliding block 32. By fitting the guided grooves 331 and 331 into the pair of guide rails 322 and 322, the guide grooves 331 and 331 can be moved in the Y-axis direction. The illustrated chuck table mechanism 3 includes a Y-axis direction moving unit 38 for moving the second sliding block 33 in the Y-axis direction along a pair of guide rails 322 and 322 provided on the first sliding block 32. I have it. The Y-axis direction moving means 38 includes a male screw rod 381 disposed in parallel between the pair of guide rails 322, 322, and a drive source such as a pulse motor 382 for rotating the male screw rod 381. I have. One end of the male screw rod 381 is rotatably supported by a bearing block 383 fixed to the upper surface of the first sliding block 32, and the other end is operatively connected to the output shaft of the pulse motor 382. Note that the male screw rod 381 is screwed into a through female screw hole formed in a female screw block (not shown) provided to protrude from the lower surface of the central portion of the second sliding block 33. Accordingly, the second sliding block 33 is moved in the Y-axis direction along the guide rails 322 and 322 by driving the male screw rod 381 to rotate forward and reverse by the pulse motor 382.

  The illustrated laser processing apparatus 1 includes a Y-axis direction position detecting unit 384 for detecting the position of the second sliding block 33 in the Y-axis direction. The Y-axis direction position detecting means 384 includes a linear scale 384a provided along the guide rail 322 and a reading provided on the second sliding block 33 and moving along the linear scale 384a together with the second sliding block 33. And a head 384b. The read head 384b of the Y-axis direction position detecting means 384 sends a pulse signal of, for example, one pulse every 1 μm to a control means described later. Then, the control means described later detects the position of the chuck table 36 in the Y-axis direction by counting the input pulse signals. When the pulse motor 382 is used as a drive source of the Y-axis direction moving means 38, the Y-direction of the chuck table 36 is counted by counting a drive pulse of a control means which outputs a drive signal to the pulse motor 382, which will be described later. The axial position can also be detected. When a servomotor is used as a drive source of the Y-axis direction moving means 38, a pulse signal output from a rotary encoder that detects the number of rotations of the servomotor is sent to a control means described later, and the control means inputs the pulse signal. By counting the pulse signals, the position of the chuck table 36 in the Y-axis direction can be detected.

  The laser beam irradiation unit 4 includes a support member 41 provided on the stationary base 2, a casing 42 supported by the support member 41 and extending substantially horizontally, and a laser beam provided on the casing 42. The apparatus includes an irradiating unit 5 and an imaging unit 6 disposed at the front end of the casing 42 and detecting a processing region to be laser-processed. The imaging unit 6 includes an illumination unit that illuminates the workpiece, an optical system that captures an area illuminated by the illumination unit, an imaging device (CCD) that captures an image captured by the optical system, and the like. Then, the captured image signal is sent to the control means described later.

The laser beam irradiation means 5 will be described with reference to FIG.
The illustrated laser beam irradiation unit 5 includes a pulse laser beam oscillation unit 51, an output adjustment unit 52 that adjusts the output of the pulse laser beam oscillated from the pulse laser beam oscillation unit 51, and a pulse whose output is adjusted by the output adjustment unit 52. A concentrator 53 for condensing the laser beam and irradiating the work held on the chuck table 36 with the laser beam is provided. The pulse laser beam oscillation means 51 includes a pulse laser beam oscillator 511 and a repetition frequency setting means 512 attached thereto. The pulse laser beam oscillator 511 of the pulse laser beam oscillator 51 oscillates a pulse laser beam LB having a wavelength of 355 nm in the illustrated embodiment. The condenser 53 includes a direction changing mirror 531 for changing the direction of the pulse laser beam oscillated from the pulse laser beam oscillating unit 51 and having its output adjusted by the output adjusting unit 52 downward in FIG. And a condensing lens 532 that condenses the pulse laser beam whose direction has been changed by the laser beam and irradiates the work W held on the chuck table 36. The focal point (focus spot) of the pulsed laser beam focused by the condenser 53 is set in a direction perpendicular to the holding surface, which is the upper surface of the chuck table 36, by a focal point position adjusting means (not shown). (Z-axis direction). The pulse laser beam oscillating means 51 and the output adjusting means 52 of the laser beam irradiating means 5 thus configured are controlled by a control means described later.

  The illustrated laser processing apparatus 1 includes a control unit 8 shown in FIG. The control means 8 is constituted by a computer, and has a central processing unit (CPU) 81 for performing arithmetic processing according to a control program, a read-only memory (ROM) 82 for storing a control program and the like, and a readable and writable memory for storing an arithmetic result and the like. It has a random access memory (RAM) 83, an input interface 84 and an output interface 85. Detection signals from the X-axis direction position detecting means 374, the Y-axis direction position detecting means 384, the imaging means 6, and the like are input to the input interface 84 of the control means 8. Then, a control signal is output from the output interface 85 of the control means 8 to the X-axis direction moving means 37, the Y-axis direction moving means 38, the pulse laser beam oscillation means 51 of the laser beam irradiation means 5, the output adjusting means 52, and the like.

A laser processing method according to the present invention, which is performed using the laser processing apparatus 1 configured as described above, will be described.
FIG. 4A shows a glass plate 10 as a workpiece to be processed by the laser processing method according to the first embodiment of the present invention. The glass plate 10 shown in FIG. 4A is formed in, for example, a square having a thickness of 200 μm, and a processing line 101 to be processed and a processing start position 101a are marked on the surface 10a. The coordinates of the processing line 101 and the processing start position 101a formed on the glass plate 10 are stored in a random access memory (RAM) 83 constituting the control means 8. The processing line 101 and the processing start position 101a do not necessarily need to be formed on the surface 10a of the glass plate 10, and the set coordinates of the processing line 101 and the coordinates of the processing start position 101a are stored in a random access memory constituting the control means 8. (RAM) 83 may be stored. As shown in FIG. 4B, the glass plate 10 thus configured is attached to the surface of the protective tape T having an outer peripheral portion attached so as to cover the inner opening of the annular frame F. (Workpiece support step).

  After the above-described workpiece support step is performed, the protective tape T side of the glass plate 10 is placed on the chuck table 36 of the laser processing apparatus 1 shown in FIG. Then, by operating a suction unit (not shown), the glass plate 10 is suction-held on the chuck table 36 via the protective tape T (workpiece holding step). Therefore, the surface 10a of the glass plate 10 held on the chuck table 36 is on the upper side. The annular frame F to which the protective tape T to which the glass plate 10 is attached is fixed by the clamp 362.

  As described above, the chuck table 36 holding the glass plate 10 by suction is positioned directly below the imaging unit 6 by the X-axis direction moving unit 37. When the chuck table 36 is positioned directly below the imaging unit 6, the imaging unit 6 and the control unit 8 execute an alignment step of detecting a processing region of the glass plate 10 to be laser-processed. That is, the imaging unit 6 and the control unit 8 execute an alignment process for positioning the processing start position 101a of the processing line 101 to be formed on the glass plate 10 at the predetermined coordinates (x1, y1). When the alignment process is performed in this manner, the glass plate 10 on the chuck table 36 is positioned at the coordinate position shown in FIG.

  When the above-described alignment work of the processing start position 101a of the processing line 101 to be formed on the glass sheet 10 is performed, the control means 8 operates the X-axis direction moving means 37 and the Y-axis direction moving means 38 to operate the chuck table 36. The processing start position 101a of the processing line 101 to be formed on the glass plate 10 held at the position is positioned immediately below the condenser 53 of the laser beam irradiation means 5. Next, by operating a not-shown condensing point position adjusting means, the condensed spot (s) of the pulsed laser beam LB condensed by the condensing lens 532 of the condensing device 53 as shown in FIG. Positioning on the front surface 10a (upper surface) (focusing spot positioning step).

  After the focusing spot positioning step is performed as described above, the laser beam irradiation means 5 is operated to irradiate the glass plate 10 with the pulsed laser beam LB having an absorptive wavelength from the light collector 53 to the X-axis direction. The moving means 37 and the Y-axis direction moving means 38 are operated to move the chuck table 36 along the processing line 101 to be formed on the glass plate 10 (first processing step). The movement of the chuck table 36 by the X-axis direction moving unit 37 and the Y-axis direction moving unit 38 is controlled based on the position information sent from the X-axis direction position detecting unit 374 and the Y-axis direction position detecting unit 384. When the processing start position 101a reaches just below the condenser 53, the irradiation of the pulse laser beam is stopped, and the operations of the X-axis direction moving means 37 and the Y-axis direction moving means 38 are stopped to move the chuck table 36. Stop. As a result, the glass plate 10 is ablated along the processing line 101, and a first laser processing groove 110 is formed along the processing line as shown in FIGS. 7A and 7B. As shown in FIGS. 7A and 7B, cracks 111 are formed on both sides of the first laser processing groove 110 in the glass plate 10 in which the first laser processing groove 110 is formed by the ablation processing. Occurs.

The processing conditions in the first processing step are set as follows.
Wavelength: 355 nm pulse laser Repetition frequency: 200 kHz
Average output: 3.7W
Focusing spot diameter: φ15 μm
Moving speed: 10mm / sec

  As described above, by performing the first processing step and forming the first laser processing groove 110 along the processing line 101 set in the glass plate 10, the first laser processing groove 110 is shown in FIGS. 7A and 7B. If the cracks 111 are formed on both sides of the laser processing groove 110 as described above, the quality of the product is degraded. Therefore, it is desirable to remove the crack 111 generated along the first laser processing groove 110. In order to remove the cracks 111 generated along the first laser processing groove 110, in the present invention, the pulse collected by the condenser lens 532 of the condenser 53 adjacent to the first laser processing groove 110 is used. The laser beam is irradiated along the first laser processing groove 110 to perform the ablation processing by positioning the laser beam focusing spot, and the second laser processing groove is formed along the first laser processing groove 110 on the glass plate 10. Is performed in the second processing step.

  As shown in FIGS. 7A and 7B, in the glass plate 10 in which the first laser processing groove 110 is formed along the processing line, the inside of the first laser processing groove 110 is defined as a product area 120. If the outside of the first laser processing groove 110 is divided as a discarded area 130, the crack 111 generated in the product area 120 along the first laser processing groove 110 is removed. Therefore, the second processing step of forming a second laser processing groove along the first laser processing groove 110 in the glass plate 10 is performed on the product area 120. That is, as shown in FIG. 8A, the focused spot (s) of the pulsed laser beam focused by the focusing lens 532 of the focusing device 53 is positioned adjacent to the first laser processing groove 110, and A second processing step of forming a second laser processing groove along the first laser processing groove 110 in the glass plate 10 by irradiating a laser beam along the first laser processing groove 110 and performing ablation processing is performed. carry out. At this time, the focused spot (s) of the pulse laser beam focused by the focusing lens 532 of the focusing device 53 is superimposed on the first laser processing groove 110. The ratio of overlapping the converging spot (s) with the first laser processing groove 110 is set to 40% in the illustrated embodiment. The ratio of the converging spot (s) overlapping the first laser processing groove 110 is preferably in the range of 10 to 90%.

  As described above, if the focused spot (s) of the pulse laser beam focused by the focusing lens 532 of the focusing device 53 is positioned at 40% of the first laser processing groove 110, In the same manner as in the first processing step, the laser beam irradiating means 5 is operated to irradiate the glass plate 10 with a pulsed laser beam having an absorptive wavelength from the light collector 53 while the X-axis direction moving means 37 and the Y-axis direction. The moving means 38 is operated to move the chuck table 36 along the processing line 101 to be formed on the glass plate 10 (second processing step). As a result, a second laser processing groove 140 is formed along the first laser processing groove 110 on the outer peripheral portion of the product region 120 of the glass plate 10 as shown in FIG. In the second processing step, the condensed spot (s) of the pulsed laser beam condensed by the condensing lens 532 of the condensing device 53 is superimposed on the first laser processing groove 110 and irradiated. Cracks 111 (see FIG. 8A) generated along the first laser processing groove 110 on the outer peripheral portion of the product region 120 of the plate 10 are ablated by the second processing step to disappear and disappear. The energy of the pulsed laser beam applied in the processing step is absorbed by the first laser processing groove 110, and the generation of cracks is suppressed. Therefore, cracks do not occur along the second laser processing grooves 140, and the problem that cracks cause deterioration in product quality is solved. The processing conditions in the second processing step may be the same as the processing conditions in the first processing step.

  According to the experiment of the present inventor, in the above-described second processing step, if the ratio of the converging spot (s) of the pulsed laser beam to the first laser processing groove 110 is smaller than 10%, the first processing is performed. The ratio of the energy of the pulse laser beam absorbed in the laser processing groove 110 is small, and cracks are easily generated in the product region 120 of the glass plate 10. On the other hand, if the ratio of the converging spot (s) of the pulse laser beam to the first laser processing groove 110 is larger than 90%, the energy of the pulse laser beam applied to the product region 120 of the glass plate 10 is small. It has been found that it is difficult to eliminate the crack 111 generated along the first laser processing groove 110. Therefore, it is desirable that the ratio at which the focused spot (s) of the pulsed laser beam is superimposed on the first laser processing groove 110 is in the range of 10 to 90%.

Next, a reference example of the present invention will be described.
In (a) of FIG. 9 is a perspective view of a semiconductor wafer as a workpiece to be machined is indicated by the reference example of the present invention. The semiconductor wafer 20 shown in FIG. 9A is made of, for example, a silicon wafer having a thickness of 300 μm, and has a plurality of processing lines 21 formed in a grid on a surface 20a. Devices 22 such as ICs and LSIs are formed in a plurality of partitioned areas. As shown in FIG. 9B, the semiconductor wafer 20 thus configured has a back surface 20b attached to a front surface of a protective tape T having an outer peripheral portion attached so as to cover an inner opening of the annular frame F. (Workpiece supporting step). Accordingly, the surface of the semiconductor wafer 20 attached to the surface of the protective tape T is on the upper side.

  After the above-described workpiece support step is performed, the protection tape T side of the semiconductor wafer 20 is placed on the chuck table 36 of the laser processing apparatus 1 shown in FIG. Then, by operating a suction unit (not shown), the semiconductor wafer 20 is suction-held on the chuck table 36 via the protective tape T (workpiece holding step). Therefore, the surface 20a of the semiconductor wafer 20 held on the chuck table 36 faces upward. The annular frame F on which the protective tape T to which the semiconductor wafer 20 is attached is fixed by the clamp 362.

  As described above, the chuck table 36 holding the semiconductor wafer 20 by suction is positioned directly below the imaging unit 6 by the X-axis direction moving unit 37. When the chuck table 36 is positioned directly below the imaging unit 6, the imaging unit 6 and the control unit 8 execute an alignment step of detecting a processing region of the semiconductor wafer 20 to be laser-processed. In other words, the imaging means 6 and the control means 8 are used to align the pattern with the condenser 53 of the laser beam irradiating means 5 for irradiating a laser beam along the processing line 21 formed in a predetermined direction of the semiconductor wafer 20. Image processing such as matching is performed to perform an alignment step of detecting a laser beam irradiation position. Similarly, an alignment step of detecting a laser beam irradiation position is performed on a processing line 21 formed in a direction orthogonal to a predetermined direction formed on the semiconductor wafer 20.

  As described above, when the processing line formed on the semiconductor wafer 20 held on the chuck table 36 is detected and the alignment process of the laser beam irradiation position is performed, the chucking is performed as shown in FIG. The table 36 is moved to the laser beam irradiation area where the condenser 53 of the laser beam irradiation means 5 is located, and one end of the predetermined processing line (the left end in FIG. 10A) is positioned immediately below the condenser 53. Then, the focused spot (s) of the pulsed laser beam focused by the focusing lens 532 of the focusing device 53 is adjusted to the vicinity of the surface (upper surface) of the semiconductor wafer 20. Next, the chuck table 36 is moved in the direction indicated by the arrow X1 in FIG. 10A while irradiating the semiconductor wafer with a pulse laser beam having an absorptive wavelength from the collector 53 of the laser beam irradiation means 5. Move at speed. When the other end of the processing line 21 (the right end in FIG. 10B) reaches a position immediately below the condenser 53, the irradiation of the pulse laser beam is stopped and the movement of the chuck table 36 is stopped. As a result, as shown in FIGS. 10B and 10C, a first laser processing groove 210 is formed on the semiconductor wafer 20 along the processing line 21 (first processing step). . The processing conditions in the first processing step may be the same as the processing conditions in the first embodiment.

  The first processing step described above is performed along all the processing lines 21 formed on the semiconductor wafer 20. As a result, the semiconductor wafer 20 is subjected to ablation along all the processing lines 21, and first laser processing grooves 210 are formed along all the processing lines 21 as shown in FIG. In the semiconductor wafer 20 in which the first laser processing groove 210 is formed by the ablation processing in this manner, cracks 211 are formed on both sides of the first laser processing groove 210 as shown in FIG. 10C and FIG. appear. If cracks 211 occur on both sides of the first laser processing groove 210 formed on the semiconductor wafer 20, the quality of a device as a product is degraded. Therefore, it is desirable to remove the crack 211 generated along the first laser processing groove 210. Therefore, when both sides of the first laser processing groove 210 formed along the processing line 21 like the semiconductor wafer 20 become a product region as the device 22, both sides along the first laser processing groove 210 The generated crack 211 is removed.

  In order to remove cracks 211 generated on both sides along the first laser processing groove 210, first, the light is collected by the condenser lens 532 of the condenser 53 adjacent to one side of the first laser processing groove 210. The condensed spot of the pulsed laser beam to be emitted is positioned, and the laser beam is irradiated along the first laser processing groove 210 to perform ablation processing, so that the semiconductor wafer 20 is subjected to the second laser processing groove 210 along the first laser processing groove 210. A second processing step of forming a laser processing groove is performed. That is, as shown in FIG. 12A, the light is condensed on one side (the upper side in FIG. 12A) by the condenser lens 532 of the condenser 53 adjacent to the first laser processing groove 210. The laser beam is irradiated along the first laser processing groove 210 and ablation processing is performed by locating the focused spot (s) of the pulsed laser beam, and the semiconductor wafer 20 is irradiated with the laser light along the first laser processing groove 210. A second processing step for forming a second laser processing groove is performed. At this time, the focused spot (s) of the pulsed laser beam focused by the focusing lens 532 of the focusing device 53 is superimposed on the first laser processing groove 210. In the illustrated embodiment, the ratio at which the condensed spot (s) overlaps the first laser processing groove 210 is set to 40% as in the first embodiment. Note that the ratio of overlapping the condensed spot (s) with the first laser processing groove 210 is desirably in the range of 10 to 90% as described above.

  As described above, if the focused spot (s) of the pulsed laser beam focused by the focusing lens 532 of the focusing device 53 is positioned at 40% of the first laser processing groove 210, The chuck table 36 holding the semiconductor wafer 20 while irradiating the semiconductor wafer 20 with a pulse laser beam having an absorptive wavelength from the condenser 53 by operating the laser beam irradiating means 5 in the same manner as in the first processing step. It is moved at a predetermined moving speed (second processing step). As a result, a second laser processing groove 220 is formed on one side of the first laser processing groove 210 on the semiconductor wafer 20 along the first laser processing groove 210 as shown in FIG. You. In the second processing step, the condensed spot (s) of the pulsed laser beam condensed by the condensing lens 532 of the condenser 53 is superimposed on the first laser processing groove 210 and irradiated. Cracks 211 (see FIG. 12 (a)) generated along one side of the first laser processing groove 210 in the wafer 20 are ablated by the second processing step and disappear, and the second processing step is performed. The energy of the pulsed laser beam irradiated in the step (1) is absorbed by the first laser processing groove 210, and the generation of cracks is suppressed.

  Next, as shown in FIG. 12C, the light is collected by the condenser lens 532 of the condenser 53 adjacent to the other side of the first laser processing groove 210 (the lower side in FIG. 12C). The focused spot (s) of the pulsed laser beam to be emitted is positioned, and the laser beam is irradiated along the first laser processing groove 210 to perform ablation processing. To perform a second processing step of forming a second laser processing groove. At this time, the focused spot (s) of the pulse laser beam focused by the focusing lens 532 of the focusing device 53 is superimposed on the first laser processing groove 210. The ratio of the converging spot (s) overlapping the first laser processing groove 210 is set to 40% in the illustrated embodiment. Note that the ratio of the converging spot (s) overlapping the first laser processing groove 210 is preferably in the range of 10 to 90% as described above. In this manner, the ratio of the converging spot (s) of the pulse laser beam condensed by the converging lens 532 of the concentrator 53 to the first laser processing groove 210 is positioned at a position of 40%, By performing the second processing step as described above, the other side of the first laser processing groove 210 in the semiconductor wafer 20 is formed along the first laser processing groove 210 as shown in FIG. Thus, a second laser processing groove 230 is formed. In the second processing step, the condensed spot (s) of the pulsed laser beam condensed by the condensing lens 532 of the condenser 53 is superimposed on the first laser processing groove 210 and irradiated. Cracks 211 (see (a) and (c) of FIG. 12) generated along the other side of the first laser processing groove 210 in the wafer 20 are ablated by the second processing step to disappear and disappear. The energy of the pulsed laser beam applied in the second processing step is absorbed by the first laser processing groove 210, and the generation of cracks is suppressed.

  As described above, if the second processing step is performed adjacent to both sides of the predetermined first laser processing groove 210 formed on the semiconductor wafer 20, all the second processing steps formed on the semiconductor wafer 20 are performed. The second processing step is performed adjacent to both sides of one laser processing groove 210. As a result, by performing the first processing step, cracks 211 generated along both sides of the first laser processing groove 210 in the semiconductor wafer 20 are removed, and along the second laser processing grooves 220 and 230. Thus, the problem that cracks do not occur and the quality of the device is deteriorated due to the cracks is solved.

1: Laser processing apparatus 2: Stationary base 3: Chuck table mechanism 36: Chuck table 37: X-axis direction moving means 38: Y-axis direction moving means 4: Laser beam irradiation unit 5: Laser beam irradiation means 51: Pulsed laser beam oscillation means 52 : Output adjusting means 53: condenser 6: imaging means 8: control means 10: glass plate 101: processing line 110: first laser processing groove 140: second laser processing groove 111: crack 20: semiconductor wafer 21: Processing line 210: first laser processing groove 211: crack 220, 230: second laser processing groove
F: Ring frame
T: Protective tape

Claims (2)

A laser beam irradiating means comprising: a workpiece holding means for holding a workpiece; and a condenser for focusing and irradiating a laser beam oscillated by a pulse laser beam oscillator onto the workpiece held by the workpiece holding means. And, a laser processing method using a laser processing apparatus comprising a moving means for relatively moving the workpiece holding means and the laser beam irradiation means,
A laser beam having a wavelength that is absorptive to the workpiece is oscillated by the pulse laser beam oscillator along a processing line set on the workpiece held by the workpiece holding means, and collected by the condenser. A first processing step of forming a first laser processing groove on a workpiece along a processing line by performing ablation processing by irradiating light;
After performing the first processing step, a converging spot of a laser beam oscillated by the pulsed laser beam oscillator condensed by the concentrator is positioned adjacent to the first laser processing groove. By performing ablation by irradiating a laser beam along the laser processing groove, the processing is performed separately from the first processing step of forming a second laser processing groove along the first laser processing groove on the workpiece. A second processing step to be performed,
The second processing step includes irradiating the converging spot onto the first laser processing groove to irradiate the first laser processing groove, and a product area in which a workpiece becomes a product with the first laser processing groove interposed therebetween. and be one divided into a waste area for disposal, processing steps of said second laser processing how to practice the product area side.   2. The laser processing method according to claim 1, wherein in the second processing step, the condensed spot of the laser beam is polymerized and irradiated to the first laser processing groove in a range of 10 to 90%. 3.