JP2013035003A - Laser beam machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam machining device that can form a laser-machined groove having an unprescribed machining width through a single machining step by optionally adjusting the machining groove.SOLUTION: The laser beam machining device includes: a laser beam irradiator for irradiating a workpiece 100 held on a chuck table 36 with laser beam; a machining feed unit for moving the chuck table and the laser beam irradiator relatively in a machining feed direction, namely, in an X-axis direction; and an indexing feed unit for moving them relatively in an indexing feed direction, namely, in a Y-axis direction, perpendicular to the X-axis direction. The laser beam irradiator includes: a laser beam-oscillating unit for oscillating the laser beam; and a light collector 7 for collecting the laser beam thus oscillated. The light collector includes: an elliptical spot-forming unit for forming a light-collecting spot elliptically; and a machining width-adjusting unit for adjusting the angle θ to an X-axis direction of a long axis in the formed elliptical light-collecting spot.

Description

  The present invention relates to a laser processing apparatus capable of arbitrarily adjusting the processing width of a laser processing groove formed by irradiating a laser beam.

  As is well known to those skilled in the art, in a semiconductor device manufacturing process, a semiconductor in which a plurality of devices such as ICs and LSIs are formed in a matrix by a laminated body in which an insulating film and a functional film are laminated on the surface of a semiconductor substrate such as silicon. A wafer is formed. 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 along the streets of a semiconductor wafer 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 fixed by electroforming, for example, diamond abrasive grains having a grain size of about 3 μm, and the thickness is 20 μm. It is formed to the extent.

  Recently, in order to improve the processing capability of semiconductor chips such as IC and LSI, inorganic films such as SiOF and BSG (SiOB) and polymers such as polyimide and parylene are used 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 as a film and a functional film for forming a circuit is laminated has been put into practical use. Yes.

  Since the Low-k film described above is different from a material of a semiconductor substrate such as silicon, it is difficult to cut simultaneously with a cutting blade. In other words, the low-k film is very brittle like mica, so when cutting along the street with a cutting blade, the low-k film peels off, and this peeling reaches the circuit, causing fatal damage to the semiconductor chip. There is a problem of giving.

  In order to solve the above problem, two laser-processed grooves are formed along the streets formed in the semiconductor wafer to divide the laminate, and a cutting blade is positioned between the two laser-processed grooves. A wafer dividing method has been proposed in which a semiconductor wafer is cut along a street by moving a cutting blade and a semiconductor wafer relative to each other. (For example, refer to Patent Document 1.)

JP-A-2005-64231

  Thus, the method of dividing the laminate by forming two laser-processed grooves along the streets formed on the semiconductor wafer described above is to locate the laser beam condensing spots on both sides of the streets to form the laser-processed grooves. There is a problem that it must be formed and productivity is poor. Also, in the method of dividing the laminate by forming two laser-processed grooves along the street formed in the semiconductor wafer, the laminate remains in the central portion of the street sandwiched between the two laser-processed grooves. Therefore, there is also a problem that the straightness of the cutting blade is impaired and the device is damaged. Furthermore, the method of dividing the laminate by forming two laser-processed grooves along the streets formed on the semiconductor wafer is different depending on the wafer, with the width of the street being 30 to 100 μm. The interval must be adjusted each time, which further deteriorates productivity.

  The present invention has been made in view of the above-mentioned facts, and its main technical problem is to form a laser processing groove having an arbitrary processing width by a single processing step by making the processing width arbitrarily adjustable. It is providing the laser processing apparatus which can do.

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 A machining feed means for moving the laser beam irradiation means relative to the machining feed direction (X-axis direction), and an index feed direction (Y-axis) orthogonal to the chuck table and the laser beam irradiation means for the machining feed direction (X-axis direction). In a laser processing apparatus comprising an indexing feed means for relative movement in the direction),
The laser beam irradiation means comprises a laser beam oscillation means for oscillating a laser beam, and a condenser for condensing the laser beam oscillated by the laser beam oscillation means,
The concentrator adjusts the angle of the major axis with respect to the X-axis direction in an elliptical spot forming unit that forms an elliptical shape of the focused spot and an elliptical focused spot formed by the elliptical spot forming unit. Processing width adjustment means,
A laser processing apparatus is provided.

  In the laser processing apparatus according to the present invention, the laser beam application means for irradiating the workpiece held on the chuck table with the laser beam condenses the laser beam oscillation means for oscillating the laser beam and the laser beam oscillated by the laser beam oscillation means. An ellipse spot forming means for forming the shape of the condensing spot into an ellipse, and a long axis X-axis in the elliptical condensing spot formed by the ellipse spot forming means. Machining width adjusting means for adjusting the angle with respect to the direction, so that the machining width can be reduced by adjusting the angle of the major axis of the elliptical focused spot formed by the elliptical spot forming means with respect to the X-axis direction. A laser processing groove having an arbitrary processing width can be formed by one processing step. Can. Therefore, for example, when a laser processing groove is formed in order to remove the laminated body laminated on the surface of the semiconductor substrate along the street of the semiconductor wafer, it is formed with a desired processing width without leaving the laminated body in the central portion. Therefore, when the semiconductor wafer is cut by the cutting blade along the laser processing groove, the straightness of the cutting blade is maintained. Accordingly, it is possible to prevent the problem that the straightness of the cutting blade is lost and the device is damaged due to the laminate remaining in the central portion. Also, even if the width of the street formed on the wafer is different from 30 to 100 μm, the laser beam can be adjusted by adjusting the angle of the long axis of the elliptical focused spot of the laser beam irradiated from the collector with respect to the X-axis direction. The processing width of the processing groove can be easily changed.

The perspective view of the laser processing apparatus comprised according to this invention. The block diagram of a structure of the laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped. Explanatory drawing of the processing head provided with the condensing device in 1st Embodiment which comprises the laser beam irradiation means shown in FIG. FIG. 4 is a perspective view of the processing head shown in FIG. 3. FIG. 4 is a perspective view of a cylindrical lens unit constituting the condenser of the processing head shown in FIG. 3. The perspective view which decomposes | disassembles and shows the structural member of the cylindrical lens unit shown in FIG. Sectional drawing of the lens holding member holding the cylindrical lens which comprises the cylindrical lens unit shown in FIG. The perspective view of the space | interval adjustment mechanism with which the laser processing apparatus shown in FIG. 1 is equipped and which adjusts the space | interval of a condensing lens and a cylindrical lens unit. The perspective view which shows the state which set the cylindrical lens unit to the space | interval adjustment mechanism shown in FIG. FIG. 2 is a block diagram showing the configuration of control means provided in the laser processing apparatus shown in FIG. 1. Explanatory drawing which shows the state which forms the cross-section circular spot with the cylindrical lens which consists of a condensing lens and a convex lens. Explanatory drawing which shows the state which forms the elliptical condensing spot by the cylindrical lens which consists of a condensing lens and a convex lens. Explanatory drawing which shows the state which forms the elliptical condensing spot by the cylindrical lens which consists of a condensing lens and a concave lens. FIG. 7 is an explanatory diagram illustrating a state in which an elliptical condensing spot is rotated around an optical axis and an angle of a long axis is adjusted with respect to an X-axis direction by a processing width adjusting unit constituting the cylindrical lens unit illustrated in FIGS. 5 and 6. A control map showing the relationship between the number of drive pulses applied to the pulse motor of the processing width adjusting means constituting the cylindrical lens unit shown in FIGS. 5 and 6 and the angle θ of the major axis of the elliptical focused spot with respect to the X-axis direction. . The perspective view and principal part expanded sectional view of the semiconductor wafer as a to-be-processed object. FIG. 17 is a perspective view showing a state in which the semiconductor wafer shown in FIG. 16 is attached to a protective tape attached to an annular frame F. Explanatory drawing of the laser processing groove | channel formation process implemented with the laser processing apparatus shown in FIG.

  Hereinafter, a laser processing apparatus configured 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 as a processing apparatus configured 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 to the laser beam irradiation unit support mechanism 4 And a laser beam irradiation unit 5 disposed so as to be movable in a condensing point position adjustment direction (Z-axis direction) indicated by an arrow Z.

  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 disposed on the first sliding block 32 so as to be movable in the indexing feed direction indicated by an arrow Y, and the second sliding block 33 A cover table 35 supported by a cylindrical member 34 and a chuck table 36 as a workpiece holding means are provided. The chuck table 36 includes a suction chuck 361 formed of a porous material, and holds, for example, a disk-shaped semiconductor wafer, which is a workpiece, on the suction chuck 361 by suction means (not shown). . The chuck table 36 configured as described above 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 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 X-axis direction along the pair of guide rails 31, 31 when the guided grooves 321, 321 are fitted 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 sliding 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. Therefore, the first sliding block 32 is moved along the guide rails 31 and 31 in the X-axis direction by driving the male screw rod 371 forward and backward by the pulse motor 372.

  The laser processing apparatus in the illustrated embodiment includes X-axis direction position detection means 374 for detecting the X-axis direction position of the chuck table 36. The X-axis direction position detecting means 374 is a linear scale 374a disposed along the guide rail 31, and a reading that is disposed along the linear scale 374a together with the first sliding block 32 disposed along the first sliding block 32. It consists of a head 374b. In the illustrated embodiment, the reading head 374b of the X-axis direction position detecting means 374 sends a pulse signal of one pulse every 1 μm to the control means described later. 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 for the machining feed means 37, the drive pulse of a control means, which will be described later, that outputs a drive signal to the pulse motor 372 is counted, so that the X direction of the chuck table 36 The position can also be detected. When a servo motor is used as a drive source for the machining feed means 37, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to a control means described later, and the pulse signal input by the control means. Can be detected to detect the position of the chuck table 36 in 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 indexing and feeding direction indicated by the arrow Y. The chuck table mechanism 3 in the illustrated embodiment has a first index for moving the second sliding block 33 in the Y-axis direction along a pair of guide rails 322 and 322 provided in the first sliding block 32. 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 Y-axis direction.

  The laser processing apparatus in the illustrated embodiment includes Y-axis direction position detecting means 384 for detecting the Y-axis direction position of the second sliding block 33. The Y-axis direction position detecting means 384 is a linear scale 384a disposed along the guide rail 322, and a reading which is disposed along the linear scale 384a together with the second sliding block 33 disposed along the second sliding block 33. And a head 384b. In the illustrated embodiment, the reading head 384b of the Y-axis direction position detecting means 384 sends a pulse signal of one pulse every 1 μm to the control means described later. 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 the drive source of the first indexing and feeding means 38, the drive table of the chuck table 36 is counted by counting the drive pulses of the control means to be described later that outputs a drive signal to the pulse motor 382. It is also possible to detect the position in the Y-axis direction. Further, when a servo motor is used as the drive source of the first index feed means 38, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to the control means described later, and the control means inputs By counting the number of pulse signals, the position of the chuck table 36 in the Y-axis direction can also be detected.

  The laser beam irradiation unit support mechanism 4 includes a pair of guide rails 41, 41 arranged in parallel along the indexing feed direction indicated by the arrow Y on the stationary base 2, and a Y axis on the guide rails 41, 41. A movable support base 42 is provided so as to be movable in the direction. 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 in the Y-axis direction along the pair of guide rails 41, 41. 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. Therefore, the movable support base 42 is moved in the Y-axis direction along the guide rails 41 and 41 by driving the male screw rod 431 forward and backward by the pulse motor 432.

  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 laser beam irradiation unit 5 in the illustrated embodiment includes a condensing point position adjusting means 53 for moving the unit holder 51 along the pair of guide rails 423 and 423 in the Z-axis direction. The condensing point position adjusting means 53 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 532 for rotationally driving the male screw rod. Thus, the unit holder 51 and the laser beam irradiation means 52 are moved along the guide rails 423 and 423 in the Z-axis direction by driving the male screw rod (not shown) by the pulse motor 532 in the normal direction and the reverse direction. In the illustrated embodiment, the laser beam irradiation means 52 is moved upward by driving the pulse motor 532 forward, and the laser beam irradiation means 52 is moved downward by driving the pulse motor 532 in reverse. Yes.

  The illustrated laser beam irradiation means 52 includes a cylindrical casing 521 that is fixed to the unit holder 51 and extends substantially horizontally. Further, as shown in FIG. 2, the laser beam irradiation means 52 is oscillated by the pulse laser beam oscillation means 522 provided at the tip of the casing 521 and the pulse laser beam oscillation means 522 and the output adjustment means 523 provided in the casing 521. And a processing head 6 for irradiating the workpiece held on the chuck table 36 with the pulsed laser beam. The pulse laser beam oscillation means 522 is composed of a pulse laser beam oscillator 522a composed of a YAG laser oscillator or a YVO4 laser oscillator, and a repetition frequency setting means 522b attached thereto. The output adjustment unit 523 adjusts the output of the pulse laser beam oscillated from the pulse laser beam oscillation unit 522.

  The processing head 6 includes a direction changing mirror 61 and a condenser 7 as shown in FIG. The direction conversion mirror 61 changes the direction of the pulse laser beam oscillated by the pulse laser beam oscillation unit 522 and irradiated through the output adjustment unit 523 toward the condenser 7. In the first embodiment shown in the figure, the condenser 7 is a condenser lens 8 that faces the workpiece held on the chuck table 36, and is upstream of the condenser lens 8 in the laser beam irradiation direction, that is, the condenser. A cylindrical lens unit 9 disposed between the lens 8 and the direction changing mirror 61, and a later-described interval adjusting mechanism for adjusting the interval between the condenser lens 8 and the cylindrical lens unit 9 are provided. The direction changing mirror 61, the cylindrical lens unit 9, and the interval adjusting mechanism, which will be described later, are disposed in a processing head housing 60 mounted at the tip of the casing 521 as shown in FIG. The condenser lens 8 is disposed in a lens housing 80 that is attached to the lower end of the processing head housing 60. The condenser lens 8 has a focal length of 40 mm in the illustrated embodiment. The condensing lens 8, the cylindrical lens 91, and the interval adjusting mechanism 10 function as an elliptical spot forming unit that forms a condensing spot into an elliptical shape as will be described later.

The cylindrical lens unit 9 will be described with reference to FIGS. FIG. 5 shows a perspective view of the cylindrical lens unit 9, and FIG. 6 shows an exploded perspective view of the cylindrical lens unit 9 shown in FIG.
The cylindrical lens unit 9 shown in FIGS. 5 and 6 includes a cylindrical lens 91, a lens holding member 92 that holds the cylindrical lens, and a frame 93 that holds the lens holding member 92.

  As shown in FIG. 7, the cylindrical lens 91 is a convex lens having a semicircular cross section. The cylindrical lens 91 has a focal length of 40 mm in the illustrated embodiment. In the illustrated embodiment, the lens holding member 92 that holds the cylindrical lens 91 is formed in a circular shape by a synthetic resin. The lens holding member 92 includes a lens holding portion 921 and a rotation shaft portion 922 formed to protrude from the center of the lower surface of the lens holding portion 921. The lens holding portion 921 is provided with a lens fitting hole 921a, and the cylindrical lens 91 is fitted and held in the lens fitting hole 921a. A laser beam insertion hole 922 a that communicates with a lens fitting hole 921 a provided in the lens holding portion 921 is formed in the rotation shaft portion 922 so as to penetrate in the axial direction.

  The frame 93 that holds the lens holding member 92 is formed in a rectangular shape as shown in FIG. 6, and a concave portion 931 in which the lens holding portion 921 of the lens holding member 92 is disposed is formed on the upper surface thereof. ing. In addition, a shaft hole 931b is provided in the bottom wall 931a of the recess 931 so that the rotation shaft 922 of the lens holding member 92 can be rotated. By disposing the lens holding portion 921 of the lens holding member 92 in the concave portion 931 of the frame body 93 configured in this manner and fitting the rotating shaft portion 922 into the shaft hole 931b, the lens holding portion 921 becomes a cylindrical lens. It is mounted so as to be rotatable about the optical axis of the laser beam passing through 91.

  The cylindrical lens unit 9 in the illustrated embodiment rotates the lens holding member 92 around the rotation shaft portion 922 and adjusts the angle of the long axis of the elliptical condensing spot with respect to the X-axis direction. 94. The machining width adjusting means 94 is composed of a pulse motor 941 and an endless belt 942 in the illustrated embodiment. The pulse motor 941 is mounted on the lower surface of the frame body 93, and its drive shaft 941 a is disposed so as to protrude into the recess 931. A pulley 943 is attached to the drive shaft 941a, and an endless belt 942 is wound around the pulley 943 and the outer periphery of the lens holding portion 921 of the lens holding member 92. Therefore, by applying a drive pulse to the pulse motor 941, the lens holding member 92 is rotated in a predetermined direction around the rotation shaft portion 922 via the pulley 943 and the endless belt 942. As will be described later, the processing width adjusting means 94 rotates an elliptical condensing spot formed by an elliptic spot forming means comprising the condensing lens 8, the cylindrical lens 91, and the interval adjusting mechanism 10 around the optical axis. The angle of the long axis of the elliptical focused spot with respect to the X-axis direction is adjusted.

The cylindrical lens unit 9 configured as described above is set in the interval adjusting mechanism 10 shown in FIG. Hereinafter, the interval adjusting mechanism 10 will be described.
8 is arranged so as to be movable in the vertical direction along the front surface of the support substrate 11, the condensing lens support plate 12 provided at the lower end of the support substrate 11, and the support substrate 11. The support table 13 is provided.

  The support substrate 11 includes a guide groove 111 formed in the vertical direction at the center of the front surface. A first adjustment plate 112 is fixed to the side surface intermediate portion of the support substrate 11. The condensing lens support plate 12 is formed so as to protrude perpendicularly to the front surface of the support substrate 11. The condensing lens support plate 12 has a hole 121 at the center. The lens housing 80 in which the condensing lens 8 is disposed at a position corresponding to the hole 121 on the lower surface of the condensing lens support plate 12 thus configured is mounted.

  The support table 13 includes a support portion 14 and a table portion 15 provided at the lower end of the support portion 14. The support portion 14 has a guided rail 141 that fits in the guide groove 111 formed in the support substrate 11 on the rear surface. When the guided rail 141 is fitted into the guide groove 111, the support table 13 is supported by the support substrate 11 so as to be movable in the vertical direction along the guide groove 111. Note that a second adjustment plate 142 located above the first adjustment plate 112 is fixed to the upper end of the support portion 14. The table portion 15 is formed to project at a right angle to the front surface of the support portion 14. The table portion 15 is provided with a hole 151 through which a laser beam passes in the central portion, and a hole 152 through which the pulse motor 941 of the processing width adjusting means 94 is inserted. In addition, positioning rails 153 and 154 extending at right angles to the front surface of the support substrate 11 are formed on both side ends of the table portion 15. The distance between the positioning rails 153 and 154 is set to a dimension corresponding to the width direction dimension of the frame body 93 constituting the cylindrical lens unit 9.

  Adjustment screw means 16 is disposed on the second adjustment plate 142. The adjustment screw means 16 includes a support cylinder 161 attached to the second adjustment plate 142, a measurement rod 162 disposed in the support cylinder 161 so as to be able to advance and retract, and an adjustment dial 163 for moving the measurement rod 162 forward and backward. It consists of the same mechanism as a micrometer. The adjustment screw means 16 configured in this way regulates the vertical position of the support portion 14 constituting the support table 13 by the tip (lower end) of the measuring rod 162 coming into contact with the upper surface of the first adjustment plate 112. To do. Therefore, by rotating the adjustment dial 163 in one direction or the other direction and moving the measuring rod 162 forward and backward, the table portion 15 provided at the vertical position of the support portion 14, that is, the lower end of the support portion 14, and the condenser lens support plate 12 can be changed. At this time, the distance between the table portion 15 of the support table 13 and the condenser lens support plate 12 is appropriately adjusted by adjusting the advance / retreat amount of the measuring rod 162 based on the scale formed on the support cylinder 161 and the adjustment dial 163. can do.

  As shown in FIG. 9, the cylindrical lens unit 9 is set on the table portion 15 that constitutes the support table 13 of the interval adjusting mechanism 10 configured as described above. That is, the frame 93 of the cylindrical lens unit 9 is placed between the positioning rails 153 and 154 in the table portion 15 that constitutes the support table 13. The cylindrical lens unit 9 placed at a predetermined position on the table portion 15 of the support table 13 is fixed to the table portion 15 of the support table 13 by an appropriate fixing means (not shown).

  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 17 for detecting a processing region to be laser processed by the laser beam irradiation means 52 is disposed. . The image pickup means 17 is composed of an image pickup device (CCD) or the like, and sends a picked up image signal to a control means described later.

  The laser processing apparatus in the illustrated embodiment includes a control means 20 shown in FIG. The control means 20 is constituted by a computer, and a central processing unit (CPU) 201 that performs arithmetic processing according to a control program, a read only memory (ROM) 202 that stores a control program and the like, and a design value of a workpiece to be described later. Read / write random access memory (RAM) 203 for storing data, operation results, and the like, a counter 204, an input interface 205, and an output interface 206. Detection signals from the X-axis direction position detection unit 374, the Y-axis direction position detection unit 384, the imaging unit 17, the input unit 210, and the like are input to the input interface 205 of the control unit 20. A control signal is output from the output interface 206 of the control means 20 to the pulse motor 372, pulse motor 382, pulse motor 432, pulse motor 532, laser beam irradiation means 52, pulse motor 941, and the like.

The laser processing apparatus in the illustrated embodiment is configured as described above, and the operation thereof will be described below.
The condensing spot shape of the laser beam irradiated by the laser beam irradiation means 52 mentioned above is demonstrated with reference to FIG. 11 and FIG.
First, as shown in FIGS. 11A and 11B, the distance (d1) between the cylindrical lens 91 and the condenser lens 8 is set to 40 mm, which is the same as the focal length (f2) of the cylindrical lens 91. explain. In this case, the laser beam L is not condensed in the Y direction by the cylindrical lens 91, but is condensed in the Y direction only by the condenser lens 8. That is, as shown in FIG. 11A, the laser beam L that has passed through the cylindrical lens 91 is condensed at a condensing point (P1) 40 mm below the focal length (f1) of the condensing lens 8.

  On the other hand, the laser beam L is condensed in the X direction by the cylindrical lens 91. That is, since the focal length (f1) of the cylindrical lens 91 is set to 40 mm, the condensing point P2 where the laser beam L is condensed in the X direction by the cylindrical lens 91 as shown in FIG. It becomes the center position of the optical lens 8. The laser beam L condensed at the central position of the condenser lens 8 in this way spreads toward the lower surface of the condenser lens 8 and is condensed again from the lower surface of the condenser lens 8 at the condensing point P1. It passes through the condenser lens 8 in a condensed state. As described above, when the distance (d1) between the cylindrical lens 91 and the condensing lens 8 is the same as the focal length (f1) of the cylindrical lens 91, the laser beam L having a circular cross section incident on the cylindrical lens 91 is converted into the cylindrical lens 91. Is condensed in the direction of the arrow X, and the direction of the arrow Y is condensed by the condenser lens 8, so that the condensing spot S1 having a circular cross section as shown in FIG. Is formed. Accordingly, by setting the workpiece at the position of the condensing point P1, the workpiece can be laser processed by the condensing spot S1 having a circular cross section.

  Next, when the interval (d1) between the cylindrical lens 91 and the condenser lens 8 is set to 20 mm, which is half the focal length (f1) of the cylindrical lens 91, as shown in FIGS. 12 (a) and 12 (b). Will be described. Also in this case, the laser beam L is not condensed in the Y direction by the cylindrical lens 91 but is condensed in the Y direction only by the condenser lens 8. That is, as shown in FIG. 12A, the laser beam L that has passed through the cylindrical lens 91 is condensed at a condensing point (P1) 40 mm below the focal length (f1) of the condensing lens 8.

  On the other hand, since the focal length (f2) of the cylindrical lens 91 is set to 40 mm, the laser beam L condensed in the X direction by the cylindrical lens 91 is being collected as shown in FIG. The light enters the condensing lens 8, is further condensed by the condensing lens 8, is condensed at the condensing point P <b> 3, and then spread in the direction indicated by the arrow X until reaching the workpiece. As a result, at the position of the condensing point P1, a condensing spot S2 having an elliptical cross section is formed as shown in an enlarged view in FIG. This elliptical condensing spot S2 is formed with the long axis D1 oriented in the direction indicated by the arrow X. The ratio of the long axis D1 and the short axis D2 of the elliptical condensing spot S2 can be adjusted by changing the distance (d1) between the condensing lens 8 and the cylindrical lens 91. Therefore, by setting the workpiece at the position of the condensing point P1, the workpiece can be laser processed by the condensing spot S2 having an elliptical cross section.

Next, the case where the cylindrical lens 91 which comprises the said cylindrical lens unit 9 is formed of the concave lens is demonstrated with reference to FIG. The case where the focal length (f2) of the cylindrical lens 91 made of a concave lens is set to −40 mm and the distance (d1) between the cylindrical lens 91 and the condenser lens 8 is set to 20 mm will be described.
Also in this case, the laser beam L is not condensed in the Y direction by the cylindrical lens 91 but is condensed in the Y direction only by the condenser lens 8. That is, as shown in FIG. 13A, the laser beam L that has passed through the cylindrical lens 91 is condensed at a condensing point (P1) 40 mm below the focal length (f1) of the condensing lens 8.

  On the other hand, since the focal length (f2) of the cylindrical lens 91 made of a concave lens is set to −40 mm, the laser beam L diffused in the X direction by the cylindrical lens 91 as shown in FIG. 8, but is diffused in the X direction by the cylindrical lens 91, and thus reaches the condensing point (P 1) that is the focal length (f 1) of the condensing lens 8 during condensing by the condensing lens 8. . As a result, at the position of the condensing point (P1), which is the focal length (f1) of the condensing lens 8, a condensing spot S2 having an elliptical cross section is formed as shown in FIG. Is done. This elliptical condensing spot S2 is formed with the long axis D1 oriented in the direction indicated by the arrow X. The ratio of the long axis D1 and the short axis D2 of the elliptical condensing spot S2 can be adjusted by changing the distance (d1) between the condensing lens 8 and the cylindrical lens 91. Therefore, by setting the workpiece at the position of the condensing point P1, the workpiece can be laser processed by the condensing spot S2 having an elliptical cross section.

  As described above, the interval adjusting mechanism 10 that adjusts the interval (d1) between the condensing lens 8 and the cylindrical lens 91 functions as an elliptical spot forming means for forming the shape of the condensing spot into an ellipse. Then, the processing width adjusting means 94 for rotating the lens holding member 92 about the rotation shaft portion 922 rotates the condensing spot S2 whose section is elliptical about the optical axis, and the X of the long axis D1. Adjust the angle with respect to the axial direction. That is, as shown in FIG. 14A, when the major axis D1 of the elliptical condensing spot S2 is aligned with the X-axis direction, the processing width becomes the width of the minor axis D2, as shown in FIG. 14B. When the major axis D1 of the elliptical condensing spot S2 is turned 90 degrees from the state shown in FIG. 14A and aligned with the direction orthogonal to the X-axis direction (Y-axis direction), the processing width is equal to the major axis D1. It becomes length. Then, as shown in FIG. 14C, when the major axis D1 of the elliptical condensing spot S2 is positioned at an angle θ with respect to the X-axis direction, the processing width becomes D1sinθ. Thus, in order to adjust the processing width by adjusting the angle of the long axis D1 with respect to the X-axis direction in the elliptical condensing spot S2, the number of drive pulses applied to the pulse motor 941 of the processing width adjusting means 94 and the ellipse are adjusted. The relationship between the long axis D1 and the angle θ with respect to the X-axis direction in the shaped focused spot S2 is set as in the control map shown in FIG. The control map shown in FIG. 15 shows the angle θ with respect to the X-axis direction of the long axis D1 in the converging spot S2 where the horizontal axis is the number of drive pulses and the vertical axis is an ellipse, and the random access memory (RAM ) 203.

Next, a description will be given of a processing method for forming a laser processing groove on a workpiece using an elliptical condensing spot S2 as shown in FIGS. 12 and 13 in the laser processing apparatus shown in FIG.
FIG. 16A shows a perspective view of a semiconductor wafer as a workpiece, and FIG. 16B shows an enlarged cross-sectional view of the main part of the semiconductor wafer shown in FIG. . A semiconductor wafer 100 shown in FIGS. 16 (a) and 16 (b) includes a plurality of ICs, LSIs, and the like by a stacked body 102 in which an insulating film and a functional film for forming a circuit are stacked on the surface of a semiconductor substrate 101 such as silicon. The devices 103 are formed in a matrix. Each device 103 is partitioned by streets 104 formed in a lattice shape. In the illustrated embodiment, the insulating film forming the stacked body 102 is an SiO 2 film, an inorganic film such as SiOF or BSG (SiOB), or an organic film such as a polyimide film or a parylene film. It consists of a low dielectric constant insulator film (Low-k film) made of a film.

  In order to form the laser processing groove along the street 104 on the semiconductor wafer 100 described above and remove the laminated body 102, the semiconductor wafer 100 is affixed to the protective tape T attached to the annular frame F as shown in FIG. To wear. At this time, the semiconductor wafer 100 is adhered to the protective tape T with the front surface 100a facing up.

  In order to form the laser processed groove along the street 104 in the semiconductor wafer 100 and remove the stacked body 102, the operator inputs the input means 210 in order to set the groove width of the laser processed groove from which the stacked body 102 is removed. Then, the angle θ of the major axis D1 with respect to the X-axis direction in the elliptical condensing spot S2 is input. Thus, when the angle θ with respect to the X-axis direction of the long axis D1 in the elliptical condensing spot S2 is input, the control means 20 displays the control map shown in FIG. 15 stored in the random access memory (RAM) 203. The number of drive pulses to be applied to the pulse motor 941 of the machining width adjusting means 94 is determined with reference to output a drive pulse control signal to the pulse motor 941. As a result, as described above, the lens holding member 92 is rotated about the rotation shaft portion 922 via the pulley 943 and the endless belt 942 attached to the drive shaft 941a of the pulse motor 941, and the elliptical light collection is performed. The major axis D1 in the spot S2 is adjusted so as to have an angle θ with respect to the X-axis direction.

  As shown in FIG. 17, the semiconductor wafer 100 supported by the annular frame F via the protective tape T places the protective tape T side on the chuck table 36 of the laser processing apparatus shown in FIG. Then, by operating a suction means (not shown), the semiconductor wafer 100 is sucked and held on the chuck table 36 via the protective tape T. The annular frame F is fixed by a clamp 362. The chuck table 36 that sucks and holds the semiconductor wafer 100 in this way is positioned directly below the imaging unit 17 by the processing feed unit 37. When the chuck table 36 is positioned immediately below the image pickup means 17, the image pickup means 17 and the control means 20 execute an alignment operation for detecting a processing region to be laser processed on the semiconductor wafer 100. That is, the imaging unit 17 and the control unit 20 align the street 104 formed in the predetermined direction of the semiconductor wafer 100 with the condenser 7 of the laser beam irradiation unit 52 that irradiates the laser beam along the street 104. Image processing such as pattern matching is performed to align the laser beam irradiation position. In addition, the alignment of the laser beam irradiation position is similarly performed on the street 104 formed on the semiconductor wafer 100 and extending at right angles to the predetermined direction.

  When the street 104 formed on the semiconductor wafer 100 held on the chuck table 36 is detected as described above and alignment of the laser beam irradiation position is performed, the chuck as shown in FIG. The table 36 is moved to a laser beam irradiation region where the condenser 7 of the laser beam application means 52 for irradiating the laser beam is located, and a predetermined street 104 is positioned immediately below the condenser 7. Next, the chuck table 36 is processed and fed at a predetermined feed speed in the direction indicated by the arrow X1 in FIG. The pulse laser beam emitted from the condenser 7 in this way is such that the long axis D1 of the elliptical condensing spot S2 is X on a predetermined street 104 extending in the X-axis direction as shown in FIG. It has an angle θ with respect to the axial direction. In this way, the chuck table 36 is processed and fed while irradiating the pulsed laser beam from the condenser 7, and as shown in FIG. 18C, other than the street 104 at the irradiation position of the laser beam emitted from the condenser 7. When the end (the right end in FIG. 18) reaches, 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 FIG. 18C and FIG. 18D, the laser processed groove 105 from which the stacked body 102 stacked on the surface of the semiconductor substrate 101 along the street 104 of the semiconductor wafer 100 is removed. It is formed (laser machining groove forming step). In the laser processing groove 105 formed in this way, the long axis D1 in the elliptical condensing spot S2 of the pulse laser beam irradiated from the condenser 7 has an angle θ with respect to the X-axis direction. A required processing width wider than the thickness of the cutting blade of the cutting blade described later can be obtained by one processing.

In addition, the said laser processing groove | channel formation process is performed on the following processing conditions, for example.
Laser light source: YVO4 laser or YAG laser Wavelength: 355 nm
Repetition frequency: 10 kHz
Average output: 7W
Spot shape: Ellipse with short axis (10 μm) and long axis (100 μm) Processing feed rate: 100 mm / sec

  If the laser processing groove forming step is performed on all the streets 104 extending in the predetermined direction of the semiconductor wafer 100 as described above, the chuck table 36 is rotated 90 degrees to be orthogonal to the predetermined direction. By performing the laser processing groove forming step along each street 104 extending in the direction, the laser processing groove 105 from which the stacked body 102 has been removed is formed along all the streets 104 formed in the semiconductor wafer 100. Can do.

  As described above, when the laser processed groove 105 is formed by removing the laminated body 102 along all the streets 104 formed in the semiconductor wafer 100, the semiconductor wafer 100 is formed in the laser processed groove 105 formed in the street 104. Are cut and cut into individual devices and conveyed to a cutting process. This cutting process is performed by a cutting apparatus having a cutting blade having a cutting edge with a thickness of about 20 μm. The width of the laser processing groove 105 is wider than the thickness of the cutting blade of the cutting blade, and the laminate 102 is formed at the center. Therefore, the straightness of the cutting blade is maintained. Accordingly, it is possible to prevent the problem that the straightness of the cutting blade is lost and the device is damaged due to the laminate remaining in the central portion. Even if the width of the street formed on the wafer is different from 30 to 100 μm, the angle θ of the long axis D1 with respect to the X axis direction in the elliptical focused spot S2 of the laser beam irradiated from the condenser 7 is adjusted. By doing so, the processing width of the laser processing groove 105 can be easily changed.

2: Stationary base 3: Chuck table mechanism 36: Chuck table 37: Processing feed means 374: X-axis direction position detection means 38: First index feed means 384: Y-axis direction position detection means 4: Laser beam irradiation unit support mechanism 42: Movable support base 43: Second index feeding means 5: Laser beam irradiation unit 51: Unit holder 52: Laser beam irradiation means 6: Processing head 61: Direction changing mirror 7: Condenser 8: Condensing lens 9: Cylindrical Lens unit 91: Cylindrical lens 92: Lens holding member 93: Frame body 94: Processing width adjustment means 10: Space adjustment mechanism 11: Support substrate 12: Condensing lens support plate 13: Support table 16: Adjustment screw means 100: Semiconductor wafer 101: Semiconductor substrate 102: Stacked body 103: Device 104 Street 105: laser processing groove
F: Ring frame
T: Protective tape

Claims (1)

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 the chuck table and the laser beam irradiation means relative to the machining feed direction (X-axis direction) A laser comprising: a processing feed means for moving the chuck table; and an index feed means for relatively moving the chuck table and the laser beam irradiation means in an index feed direction (Y-axis direction) orthogonal to the work feed direction (X-axis direction). In processing equipment,
The laser beam irradiation means comprises a laser beam oscillation means for oscillating a laser beam, and a condenser for condensing the laser beam oscillated by the laser beam oscillation means,
The concentrator adjusts the angle of the major axis with respect to the X-axis direction in an elliptical spot forming unit that forms an elliptical shape of the focused spot and an elliptical focused spot formed by the elliptical spot forming unit. Processing width adjustment means,
Laser processing equipment characterized by that.

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