JP2011156551A - Laser beam machining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining device which can form a wide laser beam machined groove, and can perform effective machining along a machining line. <P>SOLUTION: The laser beam machining device includes: a chuck table 36 holding a workpiece W; a laser beam irradiation means 52 emitting a laser beam LB; and a machining feed means relatively moving both of them. The laser beam irradiation means includes: a laser beam oscillation means 53; and a condenser 6 condensing the laser beam. The condenser is constituted of: a laser beam separation means 62 disposed with a plurality of pieces of wavelength plates 621a, 622a producing a phase difference between polarizing components parallel to an optical axis and polarizing components vertical thereto in the laser beam and separators 621 and 622 composed of birefringence type beam splitters 621b, 622b separating the laser beam at a prescribed separation angle in series; and a condenser lens 63 condensing a plurality of laser beams, and the respective birefringence type beam splitters are set so as to have different separation angles. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus suitable for forming a laser processing groove by irradiating a laser beam along a street formed on the surface of a workpiece such as a semiconductor wafer.

  In the semiconductor device manufacturing process, a semiconductor wafer in which a plurality of devices such as ICs and LSIs are formed in a matrix is formed by a laminate in which an insulating film and a functional film are laminated on the surface of a semiconductor substrate such as silicon. In the semiconductor wafer formed in this way, the above devices are partitioned by dividing lines called streets, and individual devices are manufactured by dividing along the streets.

  Such division of the semiconductor wafer along the street is usually performed by a cutting device called a dicer. This cutting apparatus includes a chuck table for holding a semiconductor wafer as a workpiece, a cutting means for cutting the semiconductor wafer held on the chuck table, and a movement for relatively moving the chuck table and the cutting means. Means. The cutting means includes a rotating spindle that is rotated at a high speed and a cutting blade attached to the spindle. The cutting blade is composed of a disk-shaped base and an annular cutting edge mounted on the outer periphery of the side surface of the base. The cutting edge is formed by fixing diamond abrasive grains having a grain size of about 3 μm, for example, by electroforming. The thickness is, for example, 20 to 30 μm.

  Recently, in order to improve the processing capability of devices such as IC and LSI, inorganic films such as SiOF and BSG (SiOB) and polymer films such as polyimide and parylene are formed on the surface of a semiconductor substrate such as silicon. A semiconductor wafer having a form in which a semiconductor chip is formed by a laminate in which a low dielectric constant insulator film (Low-k film) made of an organic film and a functional film for forming a circuit is laminated has been put into practical use. .

  In addition, a semiconductor wafer that is configured to test the function of the circuit through a metal pattern before dividing the semiconductor wafer by partially arranging a metal pattern called a test element group (TEG) on the street of the semiconductor wafer is also practical. It has become.

  Since the Low-k film and the test element group (TEG) described above are different from the material of the wafer, it is difficult to simultaneously cut with a cutting blade. That is, since the Low-k film is very brittle like mica, when it is cut along the street with a cutting blade, the Low-k film is peeled off, and this peeling reaches the device, causing fatal damage to the device. There is a problem. In addition, since the test element group (TEG) is made of metal, burrs are generated when it is cut with a cutting blade.

  In order to solve the above problems, a low-k film forming a street and a test element group (TEG) disposed on the street are removed by irradiating a pulse laser beam along the street of the semiconductor wafer, and the removed A processing method has been proposed in which a cutting blade is positioned in a region for cutting. (For example, refer to Patent Document 1.)

  In addition, as a method of forming a laser processing groove along the street with high accuracy by irradiating a pulse laser beam along the street of the wafer, a condensing spot of the pulse laser beam is formed in an ellipse, and the elliptical condensing is performed. The following patent document discloses a laser processing method in which the long axis of the spot is positioned along the street, and the focusing spot and the wafer are relatively processed and fed along the street to increase the overlapping ratio of the focusing spot. 2 is disclosed.

JP 2005-142398 A JP 2006-51517 A

Thus, when the low-k film or the test element group (TEG) is removed by irradiating a pulse laser beam along the wafer street as in the processing method disclosed in Patent Document 1, the cutting blade is It is necessary to form a laser processing groove having a width wider than the thickness. For this reason, when the condensing spot diameter of the laser beam is about 10 μm, there is a problem that the laser beam irradiation step of irradiating the laser beam along the street must be performed a plurality of times in the width direction, resulting in poor productivity.
In addition, the overlapping ratio of the focused spots can be increased by forming the focused spot of the laser beam in an elliptical shape as in the laser processing method disclosed in Patent Document 2 described above. Since the energy distribution of the laser beam in the major axis direction of the spot exhibits a Gaussian distribution, the effect of the elliptical focused spot cannot be substantially exhibited.

  The present invention has been made in view of the above-mentioned facts, and the main technical problem thereof is that a wide laser processing groove can be formed at the same time, and effective processing can be performed along a processing line. It is providing the laser processing apparatus which can be performed.

In order to solve the above main technical problems, according to the present invention, a chuck table for holding a workpiece, a laser beam irradiation means for irradiating a workpiece with a laser beam to the workpiece, a chuck table, and the chuck table In a laser processing apparatus comprising a processing feed means for relatively moving a laser beam irradiation means in a processing feed direction,
The laser beam irradiating means comprises a laser beam oscillating means for oscillating a laser beam, and a condenser for condensing the laser beam oscillated from the laser beam oscillating means and irradiating the workpiece held on the chuck table,
The condenser condenses the laser beam oscillated by the laser beam oscillating means with a predetermined separation between a wave plate that causes a phase difference between a polarized light component parallel to the optical axis and a polarized light component perpendicular to the optical axis, and the laser beam that has passed through the wave plate. A plurality of separators each including a birefringent beam splitter that separates at an angle, and a condensing lens that condenses a plurality of laser beams separated by the laser beam separating unit. And
Each birefringent beam splitter constituting the laser beam separating means is set to a different separation angle.
A laser processing apparatus is provided.

The laser beam separating means adjusts the number of laser beams or the interval between spots by changing the number or interval of the separators.
Further, the laser beam separating means is configured to position a condensing spot of a plurality of laser beams in a direction perpendicular to the processing feed direction.
The laser beam separating means is configured to position a condensing spot of a plurality of laser beams in the processing feed direction.

  In the laser processing apparatus according to the present invention, the condenser for condensing the laser beam oscillated from the laser beam oscillating means and irradiating the workpiece held on the chuck table with the laser beam oscillated by the laser beam oscillating means is an optical axis. A plurality of separators comprising a wave plate that causes a phase difference between a polarization component parallel to and perpendicular to the beam component, and a birefringent beam splitter that separates a laser beam that has passed through the wave plate at a predetermined separation angle. Each of the birefringent beam splitters constituting the laser beam separating means have different separation angles. The laser beam separating means arranged on the laser beam separating means and a condensing lens for condensing a plurality of laser beams separated by the laser beam separating means Multiple light separated by laser beam separation means It can be positioned in a direction perpendicular to the processing-feed direction or machining feed direction. Accordingly, by positioning a plurality of optical axes separated by the laser beam separating means in the machining feed direction or in a direction perpendicular to the machining feed direction, a wide laser machining groove can be formed at the same time, and separated by the laser beam separating means. By positioning the plurality of optical axes in the processing feed direction, the overlapping rate of the focused spots is increased and effective laser processing can be performed.

The perspective view of the laser processing apparatus comprised according to this invention. The block diagram which shows the laser beam oscillation means and light collector which comprise the laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped. Explanatory drawing which shows the separation state of the laser beam by the laser beam separation means which comprises the collector shown in FIG. Explanatory drawing which shows an example of the arrangement | sequence of the condensing spot of the laser beam isolate | separated by the laser beam separation means shown in FIG. The perspective view which shows other embodiment of the laser beam separation means which comprises the collector with which the laser processing apparatus shown in FIG. 1 is equipped. The disassembled perspective view of the laser beam separation means shown in FIG. Explanatory drawing which shows the separation state of the laser beam by the laser beam separation means shown in FIG. 5 and FIG. Explanatory drawing which shows the isolation | separation state of a laser beam when a part of separator which comprises the laser beam separation means shown in FIG. 5 and FIG. 6 is removed. The perspective view of the semiconductor wafer as a to-be-processed object. FIG. 10 is an enlarged partial sectional view of the semiconductor wafer shown in FIG. 9. FIG. 10 is a perspective view showing a state in which the semiconductor wafer shown in FIG. 9 is supported on an annular frame via a protective tape. FIG. 10 is an explanatory view of a laser beam irradiation step for forming a laser processing groove along the street of the semiconductor wafer shown in FIG. 9 by the laser processing apparatus shown in FIG. 1. FIG. 13 is an enlarged cross-sectional view of a laser processing groove formed in a semiconductor wafer by performing the laser beam irradiation process shown in FIG. 12. Explanatory drawing of the cutting process which cut | disconnects a semiconductor wafer along the laser processing groove | channel formed by the laser beam irradiation process shown in FIG. Explanatory drawing which shows the relationship between the laser processing groove | channel and cutting blade in the cutting process shown in FIG. Explanatory drawing which shows the cutting feed position of the cutting blade in the cutting process shown in FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a preferred embodiment of a laser processing apparatus configured according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a laser processing apparatus constructed according to the present invention. A laser processing apparatus shown in FIG. 1 includes a stationary base 2 and a chuck table mechanism 3 that is disposed on the stationary base 2 so as to be movable in a machining feed direction (X-axis direction) indicated by an arrow X and holds a workpiece. A laser beam irradiation unit support mechanism 4 disposed on the stationary base 2 so as to be movable in an indexing feed direction (Y axis direction) indicated by an arrow Y orthogonal to the X axis direction, and an arrow Z on the laser beam unit support mechanism 4 And a laser beam irradiation unit 5 disposed so as to be movable in the focus position adjustment direction (Z-axis direction).

  The chuck table mechanism 3 includes a pair of guide rails 31 and 31 disposed in parallel along the X-axis direction on the stationary base 2, and is arranged on the guide rails 31 and 31 so as to be movable in the X-axis direction. A first sliding block 32 provided, a second sliding block 33 movably disposed on the first sliding block 32 in the Y-axis direction, and a cylindrical member on the second sliding block 33 And a chuck table 36 as a workpiece holding means. The chuck table 36 is formed of a porous material and includes a workpiece holding surface 361. The chuck table 36 holds, for example, a disk-shaped semiconductor wafer as a workpiece by a suction unit (not shown). Yes. Further, the chuck table 36 is rotated by a pulse motor (not shown) disposed in the cylindrical member 34. The chuck table 36 is provided with a clamp 362 for fixing an annular frame that supports a semiconductor wafer described later.

  The first sliding block 32 has a pair of guided grooves 321 and 321 fitted to the pair of guide rails 31 and 31 on the lower surface thereof, and is parallel to the upper surface along the Y-axis direction. A pair of formed guide rails 322 and 322 are provided. The first sliding block 32 configured in this way moves in the Y-axis direction along the pair of guide rails 31, 31 when the guided grooves 321, 321 fit into the pair of guide rails 31, 31. Configured to be possible. The chuck table mechanism 3 in the illustrated embodiment includes a processing feed means 37 for moving the first slide block 32 along the pair of guide rails 31, 31 in the X-axis direction. The processing feed 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 rotationally driving the male screw rod 371. 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 connected to the output shaft of the pulse motor 372 by transmission. The male screw rod 371 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the first sliding block 32. Accordingly, when the male screw rod 371 is driven to rotate forward and reversely by the pulse motor 372, the first slide block 32 is moved along the guide rails 31 and 31 in the machining feed direction which is the X-axis direction.

  The second sliding block 33 is provided with a pair of guided grooves 331 and 331 which are fitted to a pair of guide rails 322 and 322 provided on the upper surface of the first sliding block 32 on the lower surface thereof. By fitting the guided grooves 331 and 331 to the pair of guide rails 322 and 322, the guided grooves 331 and 331 are configured to be movable in the Y-axis direction. The chuck table mechanism 3 in the illustrated embodiment has a first index for moving the second slide block 33 along the pair of guide rails 322 and 322 provided in the first slide block 32 in the Y-axis direction. A feeding means 38 is provided. The first index feed means 38 includes a male screw rod 381 disposed in parallel between the pair of guide rails 322 and 322, and a drive source such as a pulse motor 382 for rotationally driving the male screw rod 381. It is out. 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 connected to the output shaft of the pulse motor 382. The male screw rod 381 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the second sliding block 33. Therefore, by driving the male screw rod 381 forward and backward by the pulse motor 382, the second slide block 33 is moved along the guide rails 322 and 322 in the indexing feed direction which is the Y-axis direction.

  The laser beam irradiation unit support mechanism 4 is movable in the Y-axis direction on a pair of guide rails 41, 41 arranged in parallel along the Y-axis direction on the stationary base 2. The movable support base 42 is provided. The movable support base 42 includes a movement support portion 421 that is movably disposed on the guide rails 41, 41, and a mounting portion 422 that is attached to the movement support portion 421. The mounting portion 422 is provided with a pair of guide rails 423 and 423 extending in the Z-axis direction on one side surface in parallel. The laser beam irradiation unit support mechanism 4 in the illustrated embodiment includes a second index feed means 43 for moving the movable support base 42 along the pair of guide rails 41 and 41 in the Y-axis direction. The second index feed means 43 includes a male screw rod 431 disposed in parallel between the pair of guide rails 41, 41, and a drive source such as a pulse motor 432 for rotationally driving the male screw rod 431. It is out. One end of the male screw rod 431 is rotatably supported by a bearing block (not shown) fixed to the stationary base 2, and the other end is connected to the output shaft of the pulse motor 432. The male screw rod 431 is screwed into a female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the moving support portion 421 constituting the movable support base 42. For this reason, when the male screw rod 431 is driven to rotate forward and backward by the pulse motor 432, the movable support base 42 is moved along the guide rails 41, 41 in the index feed direction that is the Y-axis direction.

  The laser beam irradiation unit 5 in the illustrated embodiment includes a unit holder 51 and laser beam irradiation means 52 attached to the unit holder 51. The unit holder 51 is provided with a pair of guided grooves 511 and 511 that are slidably fitted to a pair of guide rails 423 and 423 provided in the mounting portion 422. By being fitted to the guide rails 423 and 423, the guide rails 423 and 423 are supported so as to be movable in the Z-axis direction.

  The illustrated laser beam application means 52 includes a cylindrical casing 521 that is fixed to the unit holder 51 and extends substantially horizontally. In the casing 521, a pulse laser beam oscillation means 53 is disposed as shown in FIG. The pulse laser beam oscillating means 53 includes a pulse laser beam oscillator 531 composed of a YAG laser oscillator or a YVO4 laser oscillator, and a repetition frequency setting means 532 attached thereto. The pulsed laser beam LB oscillated from the pulsed laser beam oscillating means 53 is guided to the condenser 6 attached to the tip of the casing 521.

  Continuing the description with reference to FIG. 2, the condenser 6 in the illustrated embodiment includes a direction conversion mirror 61, a laser beam separation means 62, and a condenser lens 63. The direction changing mirror 61 changes the direction of the laser beam LB oscillated from the pulse laser beam oscillating means 53 downward, that is, toward the laser beam separating means 62.

  The laser beam separating means 62 includes two separators 621 and 622 arranged in series in the embodiment shown in FIG. The two separators 621 and 622 include wave plates 621a and 622a and birefringent beam splitters 621b and 622b, respectively. The wave plates 621a and 622a cause the laser beam LB oscillated by the pulse laser beam oscillating means 53 and direction-converted by the direction conversion mirror 61 to cause a phase difference between the polarization component parallel to the optical axis and the polarization component perpendicular to the optical axis. The birefringent beam splitters 621b and 622b are made of Wollaston polarizer or the like, and separate the polarization component parallel to the optical axis of the pulsed laser beam LB that has passed through the wave plates 621a and 622a and the polarization component perpendicular to each other at a predetermined separation angle. To do. Note that the separation angles of the birefringent beam splitter 621b constituting the separator 621 and the birefringent beam splitter 622b constituting the separator 622 are set to different values. In the illustrated embodiment, the separation angle of the birefringent beam splitter 622b constituting the separator 622 is set to a value smaller than the separation angle of the birefringent beam splitter 621b constituting the separator 621. Here, a state where the pulse laser beam LB is separated into a plurality of optical axes by the laser beam separation means 62 will be described with reference to FIG. The laser beam LB oscillated by the pulse laser beam oscillating means 53 and redirected by the direction converting mirror 61 is separated into LB1x and LB1y by a separator 621 at a large separation angle, and LB1x and LB1y separated into two by the separator 621 are separated. 622 is divided into LB2x, LB2y and LB2x, LB2y with relatively small separation angles. By using the two separators 621 and 622 in this way, the laser beam LB oscillated by the pulse laser beam oscillation means 53 can be separated into four laser beams. Therefore, if three separators are used, the laser beam can be separated into eight laser beams. If four separators are used, the laser beam can be separated into 16 laser beams. If five separators are used, 32 laser beams can be separated. It can be separated into a laser beam of books.

  Continuing the description with reference to FIG. 2, the four laser beams LB2x, LB2y and LB2x, LB2y from which the laser beam LB has been separated as described above are collected by the condenser lens 63 and held on the chuck table 36. The workpiece W is irradiated. In this way, the four laser beams LB2x, LB2y and LB2x, LB2y irradiated on the workpiece W are processed in the processing feed direction as shown in FIG. The arrangement direction of the separators 621 and 622 is set so as to be linearly positioned in the indexing feed direction (Y-axis direction) orthogonal to (X-axis direction).

Next, another embodiment of the laser beam splitting means 62 will be described with reference to FIGS.
The laser beam splitter 62 shown in FIGS. 5 and 6 includes five separators 621, 622, 623, 624, and 625. As shown in FIG. 6, the five separators 621, 622, 623, 624, and 625 include wave plates 621a, 622a, 623a, 624a, and 625a and birefringent beam splitters 621b, 622b, 623b, 624b, and 625b, respectively. Each of which is housed in a housing case 627. The storage case 627 is formed in a rectangular shape, and has an opening 627a provided on the top wall and the bottom wall (only the opening 627a provided on the top wall is shown in FIG. 6). Wave plates 621a, 622a, 623a, 624a, 625a constituting the separators 621, 622, 623, 624, 625 housed in the housing case 627 are rotatable around a horizontal plane, that is, around the optical axis of the laser beam passing therethrough. It is comprised so that rotation is possible. In addition, by rotating the wave plates 621a, 622a, 623a, 624a, and 625a, the ratio of the polarization component parallel to the optical component of the laser beam LB and the polarization component perpendicular to the optical axis can be changed. The birefringent beam splitters 621b, 622b, 623b, 624b, and 625b constituting the separators 621, 622, 623, 624, and 625 have different separation angles. In the illustrated embodiment, the separation angle of the birefringent beam splitter 621b is the largest, and the separation angles of the birefringent beam splitters 622b, 623b, 624b, and 625b are set to sequentially decrease. The separators 621, 622, 623, 624, and 625 configured as described above are accommodated in the separator unit case 628. Separator unit case 628 is formed in a rectangular parallelepiped shape that is long in the vertical direction. In the separator unit case 628, an opening 628c is provided in each of an upper wall 628a and a bottom wall 628b. The separator unit case 628 formed in this manner is partitioned between the upper wall 628a and the bottom wall 628b by four partition plates 628d, 628e, 628f, 628g, and the separators 621, 622, 623, There are five storage chambers 628h, 628i, 628j, 628k, and 628m that store 624 and 625. The four partition plates 628d, 628e, 628f, and 628g are formed with openings 628c having the same diameter as the openings 628c provided in the upper wall 628a and the bottom wall 628b, respectively. Separators 621, 622, 623, 624, and 625 are detachably accommodated in series in the five accommodating chambers 628h, 628i, 628j, 628k, and 628m of the separator unit case 628 thus configured.

The laser beam separating means 62 shown in FIGS. 5 and 6 is configured as described above, and the state of separating the laser beam into a plurality of optical axes will be described with reference to FIG.
The five separators 621, 622, 623, 624, and 625 separate the laser beam LB oscillated by the pulsed laser beam oscillation means 53 into two similarly to the separators 621 and 622 shown in FIGS. 2 and 3, respectively. The optical axis of the laser beam separated by the last separator 626 is 32. The 32 optical axes thus separated are linearly positioned in the indexing feed direction (Y-axis direction) orthogonal to the machining feed direction (X-axis direction). In order to position the plurality of separated optical axes linearly in the machining feed direction (X-axis direction), each separation housed in each housing chamber 628h, 628i, 628j, 628k, 628m of the separator unit case 628 is used. The containers 621, 622, 623, 624, and 625 may be stored in a state rotated 90 degrees around the optical axis of the laser beam passing through the state shown in FIGS.

Next, a separation state when the separators 622 and 623 in the laser beam separation means 62 shown in FIGS. 5 and 6 are removed from the separator unit case 628 will be described with reference to FIG.
The separators 622 and 623 are removed, and the laser beams separated by the separators 621, 624, and 625 as shown in FIG. 8 have four optical axes positioned on both sides, and there is no optical axis in the center. It becomes a form.
As described above, various forms using a plurality of optical axes can be formed by changing the number and arrangement of the separators. Therefore, it is possible to cope with various types of processing by combining the separator in various forms.

  Returning to FIG. 1, the description is continued. At the front end portion of the casing 521 constituting the laser beam irradiation means 52, an imaging means 7 for detecting a processing region to be laser processed by the laser beam irradiation means 52 is disposed. . The imaging unit 7 includes an illuminating unit that illuminates the workpiece, an optical system that captures an area illuminated by the illuminating unit, an imaging device (CCD) that captures an image captured by the optical system, and the like. The captured image signal is sent to a control means (not shown).

  The laser beam irradiation unit 5 in the illustrated embodiment includes moving means 8 for moving the unit holder 51 along the pair of guide rails 423 and 423 in the Z-axis direction. The moving means 8 includes a male screw rod (not shown) disposed between the pair of guide rails 423 and 423, and a drive source such as a pulse motor 82 for rotating the male screw rod. By driving the male screw rod (not shown) by the motor 82 to rotate forward or reverse, the unit holder 51 and the laser beam irradiation means 52 are moved along the pair of guide rails 423 and 423 in the focal position adjustment direction (Z-axis direction). In the illustrated embodiment, the laser beam irradiation means 52 is moved upward by driving the pulse motor 82 forward, and the laser beam irradiation means 52 is moved downward by driving the pulse motor 82 in the reverse direction. ing.

The laser processing apparatus in the illustrated embodiment is configured as described above, and the operation thereof will be described below.
Here, a semiconductor wafer as a workpiece to be processed by the laser processing apparatus will be described with reference to FIGS.
A semiconductor wafer 10 shown in FIG. 9 and FIG. 10 includes a plurality of devices 13 such as ICs and LSIs in a matrix form by a laminated body 12 in which an insulating film and a functional film for forming a circuit are laminated on the surface of a semiconductor substrate 11 such as silicon. Is formed. Each device 13 is partitioned by streets 14 formed in a lattice shape. In the illustrated embodiment, the insulating film forming the laminated body 12 is an SiO 2 film, an inorganic film such as SiOF or BSG (SiOB), or an organic film such as a polymer film such as polyimide or parylene. It consists of a low dielectric constant insulator film (Low-k film) made of a film. A method of dividing the semiconductor wafer 10 thus configured along the street 14 will be described.

  In order to divide the above-described semiconductor wafer 10 along the street 14, the semiconductor wafer 10 is attached to the surface of the protective tape T attached to the annular frame F as shown in FIG. At this time, the semiconductor wafer 10 is adhered to the protective tape T with the back surface side facing up.

Next, a laser beam irradiation process is performed in which a laser beam is irradiated along the street 14 of the semiconductor wafer 10 to remove the laminate 12 on the street.
In this laser beam irradiation step, first, the semiconductor wafer 10 supported by the annular frame F is placed on the chuck table 36 via the protective tape T on the chuck table 36 of the laser processing apparatus shown in FIG. The semiconductor wafer 10 is sucked and held via the protective tape T. Therefore, the semiconductor wafer 10 is held with the surface 10a facing upward. The annular frame F that supports the semiconductor wafer 10 via the protective tape T is fixed by a clamp 362.

  As described above, the chuck table 36 that sucks and holds the semiconductor wafer 10 is positioned immediately below the imaging unit 7 by the processing feed unit 37. When the chuck table 36 is positioned immediately below the image pickup means 6, an alignment operation for detecting a laser processing region of the semiconductor wafer 10 by the image pickup means 7 and a control means (not shown) is executed. That is, the imaging unit 7 and the control unit (not shown) align the street 14 formed in a predetermined direction of the semiconductor wafer 10 and the condenser 6 of the laser beam irradiation unit 52 that irradiates the laser beam along the street 14. Image processing such as pattern matching is performed to perform alignment of the laser beam irradiation position. The alignment of the laser beam irradiation position is similarly performed on the street 14 formed in the semiconductor wafer 10 and extending in a direction orthogonal to the predetermined direction.

  When the streets 14 formed on the semiconductor wafer 10 held on the chuck table 36 are detected as described above and the alignment of the laser beam irradiation position is performed, the chuck table as shown in FIG. 36 is moved to a laser beam irradiation region where the condenser 6 for irradiating the laser beam is located, and a predetermined street 14 is positioned immediately below the condenser 6. At this time, as shown in FIG. 12A, the semiconductor wafer 10 is positioned such that one end of the street 14 (the left end in FIG. 12A) is located directly below the condenser 6. In this state, as shown in FIG. 12 (b), the respective focused spots (s) of the four laser beams LB 2 x, LB 2 y and LB 2 x, LB 2 y irradiated from the condenser 6 are arranged in the width direction of the street 14. Positioned. Then, the moving means 8 is operated to adjust the height position of the laser beam irradiation means 52 so that the respective focused spots (s) of the four laser beams LB2x, LB2y and LB2x, LB2y are located on the surface of the street 14. .

  Next, the laser beam irradiating means 52 is operated to irradiate the four laser beams LB2x, LB2y and LB2x, LB2y from the condenser 6, and the chuck table 36 is predetermined in the direction indicated by the arrow X1 in FIG. It is moved at a processing feed rate of (laser beam irradiation process). Then, as shown in FIG. 12C, when the other end of the street 14 (the right end in FIG. 12C) reaches a position directly below the condenser 6, the irradiation of the pulse laser beam is stopped and the chuck table 36 is stopped. Stop moving.

In addition, the processing conditions in the said laser beam irradiation process are set as follows, for example.
Laser light source: YVO4 laser or YAG laser Wavelength: 355 nm
Output: 10W
Repetition frequency: 100 kHz
Pulse width: 1 ns
Condensing spot diameter: 8 μm
Processing feed rate: 100 mm / sec

  By setting the condensing spots (s) having a condensing spot diameter of 8 μm under the above-described processing conditions so as to contact each other as shown in FIG. As shown in FIG. 4, a laser processing groove 101 having a width (E) of 32 μm and deeper than the laminate 12 is simultaneously formed by the four laser beams LB2x, LB2y and LB2x, LB2y. In this way, the laser beam irradiation process described above is performed on all the streets 14 formed on the semiconductor wafer 10.

  If the above-described laser beam irradiation process is performed on all the streets 14 formed on the semiconductor wafer 10, a cutting process for cutting the semiconductor wafer 10 along the streets 14 is performed. That is, as shown in FIG. 14, the semiconductor wafer 10 on which the laser beam irradiation process has been performed is placed on the chuck table 161 of the cutting apparatus 16 with the surface 10a facing upward, and the semiconductor wafer 10 is placed on the chuck table 161 by suction means (not shown). Hold on. Next, the chuck table 161 holding the semiconductor wafer 10 is moved to the cutting start position in the cutting area. At this time, as shown in FIG. 14, the semiconductor wafer 10 is positioned such that one end (the left end in FIG. 14) of the street 14 to be cut is positioned to the right by a predetermined amount from just below the cutting blade 162. At this time, the cutting blade 162 having a thickness of 20 μm, for example, is positioned within the width (E) of the laser processing groove 101 as shown in FIG.

  When the chuck table 161, that is, the semiconductor wafer 10 is positioned at the cutting start position in the cutting region in this way, the cutting blade 162 is cut and fed downward from the standby position indicated by a two-dot chain line in FIG. As shown by the solid line, it is positioned at a predetermined cutting feed position. This cutting feed position is set to a position where the lower end of the cutting blade 162 reaches the protective tape T attached to the back surface of the semiconductor wafer 10 as shown in FIG.

  Next, as shown in FIG. 14, the cutting blade 162 is rotated at a predetermined rotational speed in the direction indicated by the arrow 162a, and the chuck table 161, that is, the semiconductor wafer 10, is rotated at the predetermined cutting feed speed in the direction indicated by the arrow X1 in FIG. Move it. When the chuck table 161, that is, the other end of the semiconductor wafer 10 (the right end in FIG. 14) reaches a predetermined amount to the left of the cutting blade 162, the movement of the chuck table 161 is stopped. The semiconductor wafer 10 is cut along the street 14 by cutting and feeding the chuck table 161 in this way.

  Next, the chuck table 161, that is, the semiconductor wafer 10 is indexed and fed by an amount corresponding to the interval between the streets 14 in a direction perpendicular to the paper surface (index feeding direction), and the street 14 to be cut next is a position corresponding to the cutting blade 162. Return to the state shown in FIG. And a cutting process is implemented similarly to the above.

In addition, the said cutting process is performed on the following processing conditions, for example.
Cutting blade: outer diameter 52mm, thickness 20μm
Cutting blade rotation speed: 40000 rpm
Cutting feed rate: 50 mm / sec

  The above-described cutting process is performed on all the streets 14 formed on the semiconductor wafer 10. As a result, the semiconductor wafer 10 is cut along the streets 14 and divided into individual devices 13.

  In the above-described embodiment, laser processing is performed by linearly positioning the optical axis of the laser beam separated into a plurality in the index feed direction (Y-axis direction) orthogonal to the process feed direction (X-axis direction). In this example, a laser processing groove having a predetermined width is simultaneously formed. However, the laser beam is focused by linearly positioning the optical axis of a plurality of separated laser beams in the processing feed direction (X-axis direction). Effective processing can be performed by increasing the overlapping ratio of spots.

2: stationary base 3: chuck table mechanism 36: chuck table 37: processing feeding means 38: first index feeding means 4: laser beam irradiation unit support mechanism 43: second index feeding means 5: laser beam irradiation unit 51: unit Holder 52: Laser beam irradiation means 53: Pulse laser beam oscillation means 6: Condenser 61: Direction conversion mirror 62: Laser beam separation means 621, 622: Separator 621a, 622a: Wave plate 621b, 622b: Birefringence beam splitter 628: Separator unit case 7: Imaging means 10: Semiconductor wafer (workpiece)
16: Cutting device 161: Chuck table 162 of the cutting device: Cutting blade

Claims (4)

A chuck table for holding a workpiece, a laser beam irradiation means for irradiating a workpiece held on the chuck table with a laser beam, and a machining feed means for relatively moving the chuck table and the laser beam irradiation means in a machining feed direction In a laser processing apparatus comprising:
The laser beam irradiating means comprises a laser beam oscillating means for oscillating a laser beam, and a condenser for condensing the laser beam oscillated from the laser beam oscillating means and irradiating the workpiece held on the chuck table,
The condenser condenses the laser beam oscillated by the laser beam oscillating means with a predetermined separation between a wave plate that causes a phase difference between a polarized light component parallel to the optical axis and a polarized light component perpendicular to the optical axis, and the laser beam that has passed through the wave plate. A plurality of separators each including a birefringent beam splitter that separates at an angle, and a condensing lens that condenses a plurality of laser beams separated by the laser beam separating unit. And
Each birefringent beam splitter constituting the laser beam separating means is set to a different separation angle.
Laser processing equipment characterized by that.   2. The laser processing apparatus according to claim 1, wherein the laser beam separating unit adjusts the number of laser beams or the interval between spots by changing the number or interval of the separators. 3.   3. The laser processing apparatus according to claim 1, wherein the laser beam separating unit is configured to position a focused spot of a plurality of laser beams in a direction orthogonal to the processing feed direction.   The laser processing apparatus according to claim 1, wherein the laser beam separating unit is configured to position a condensing spot of a plurality of laser beams in the processing feed direction.

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