JP2015085347A - Laser processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser processing device capable of preventing a scattered moltem object from being buried to a processing groove by ablation.SOLUTION: The laser processing device comprises: laser beam radiation means 5; processing feeding means 37 for moving a chuck table to a processing feeding direction; and indexing feeding means 38 for moving the chuck table to an indexing feeding direction orthogonal to the processing feeding direction. The laser beam radiation means has: laser beam oscillation means 51; a collector 53; polygon mirror means 56; and incident position change means 57 for changing an incident position to the polygon mirror means. The polygon mirror means has: first polygon mirror means 561 for rotating a first polygon mirror in a first rotation direction for scanning laser beam in an X axis direction; and second polygon mirror means 562 for rotating a second polygon mirror in an opposite direction of the first rotation direction for scanning laser beam in the X axis direction. The incident position change means positions the laser beam to the first polygon mirror or the second polygon mirror selectively.

Description

  The present invention relates to a laser processing apparatus that performs laser processing on a workpiece such as a semiconductor wafer held on a chuck table.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by division lines arranged in a lattice pattern on the surface of a substantially disc-shaped semiconductor wafer, and devices such as ICs and LSIs are formed in the partitioned regions. . Then, the semiconductor wafer is cut along the streets to divide the region in which the device is formed to manufacture individual semiconductor devices.

  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 polymer films such as polyimide and parylene are formed on the surface of a substrate such as silicon. A semiconductor wafer having a form in which a semiconductor device is formed by a functional layer in which a low dielectric constant insulator film (Low-k film) made of an organic film is laminated has been put into practical use.

  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. ing.

  However, the Low-k film described above is difficult to cut with a cutting blade. In other words, the low-k film is very brittle like mica, so when the cutting blade is cut along the planned dividing line, the low-k film is peeled off, and this peeling reaches the circuit, resulting in fatal damage to the device. There is a problem of giving.

  In order to solve the above problem, the laser beam is irradiated along the planned dividing line on both sides in the width direction of the planned dividing line formed on the semiconductor wafer, and two laser processing grooves are formed along the planned dividing line. Cut the semiconductor wafer along the planned dividing line by dividing the low-k film laminate and positioning the cutting blade between the two laser processing grooves and moving the cutting blade and the semiconductor wafer relative to each other. A wafer dividing method is disclosed in Patent Document 1 below.

JP-A-2005-64231

Thus, when the laser beam is formed by removing the low-k film laminate by irradiating a laser beam along the planned dividing line and performing ablation processing, the molten material scattered in the laminate becomes the laser processed groove. In order to form a laser processing groove having a sufficient width, there is a problem that the laser beam must be irradiated a plurality of times along the line to be divided, resulting in poor productivity.
Also, in the technology in which the wafer is divided into individual devices by ablation processing by irradiating the wafer with a laser beam having a wavelength that absorbs the wafer along the planned dividing line, the melt is divided into the dividing grooves. In order to form the dividing groove necessary for the division, the laser beam must be irradiated a plurality of times along the planned division line, resulting in poor productivity.

  The present invention has been made in view of the above-mentioned facts, and the main technical problem thereof is a laser processing apparatus that can effectively prevent the melted material scattered by ablation processing from being buried back into the laser processing groove. Is to provide.

In order to solve the main technical problem, according to the present invention, a chuck table for holding a workpiece, laser beam irradiation means for laser processing the workpiece held on the chuck table, the chuck table, and the laser beam Processing feed means for relatively moving the irradiation means in the processing feed direction (X-axis direction), and index feed direction (Y-axis direction) orthogonal to the machining feed direction (X-axis direction) for the chuck table and the laser beam irradiation means A laser processing apparatus comprising an indexing and feeding means that moves relative to
The laser beam irradiating unit includes a laser beam oscillating unit that oscillates a laser beam, a condenser that collects the laser beam oscillated from the laser beam oscillating unit and irradiates the workpiece held on the chuck table, and the laser beam oscillation unit A polygon mirror means disposed between the means and the condenser for dispersing the laser beam oscillated from the laser beam oscillating means, and the incident position of the laser beam oscillated from the laser beam oscillating means on the polygon mirror means is changed. Incident position changing means
The polygon mirror means comprises: a first polygon mirror means comprising a first polygon mirror and a first scan motor that rotates the first polygon mirror in a first rotation direction and scans a laser beam in the X-axis direction; A second polygon mirror and a second scan motor configured to rotate the second polygon mirror in a second rotation direction opposite to the first rotation direction and scan a laser beam in the X-axis direction. Polygon mirror means, and
The incident position changing means selectively positions the laser beam oscillated from the laser beam oscillation means on the first polygon mirror and the second polygon mirror.
A laser processing apparatus is provided.

The first scan motor of the first polygon mirror means rotates the first polygon mirror to scan the laser beam in the (+) direction of the X axis direction,
The second scan motor of the second polygon mirror means rotates the second polygon mirror to scan the laser beam in the (−) direction of the X axis direction,
When the moving direction of the chuck table is the (+) direction in the X-axis direction, the incident position changing means positions the first polygon mirror at a light incident position where the laser beam enters and is held by the chuck table. When the workpiece is scanned with a laser beam in the (+) direction of the X axis and the movement direction of the chuck table is the (−) direction of the X axis, the laser beam enters the second polygon mirror. A laser beam is scanned in the (−) direction in the X-axis direction with respect to the work piece positioned at the light position and held on the chuck table.
The incident position changing means selectively moves the first polygon mirror means and the second polygon mirror means to the laser beam incident position by moving the first polygon mirror means and the second polygon mirror means in the Y-axis direction. Position.
Further, the incident position changing means changes the optical path of the laser beam oscillated from the laser beam oscillating means and selectively causes the laser beam to enter the first polygon mirror and the second polygon mirror.
Further, Y-axis direction scanning means for scanning the laser beam oscillated from the laser beam oscillation means in the Y-axis direction of the first polygon mirror and the second polygon mirror is provided.

  In the laser processing apparatus according to the present invention, the laser beam irradiating unit includes a laser beam oscillating unit that oscillates a laser beam, and a laser beam oscillating from the laser beam oscillating unit that irradiates the workpiece held on the chuck table. And a polygon mirror means disposed between the laser beam oscillating means and the condenser to disperse the laser beam oscillated from the laser beam oscillating means, and an incident position of the laser beam oscillated from the laser beam oscillating means on the polygon mirror means. And a first scan motor that rotates the first polygon mirror and the first polygon mirror in the first rotation direction and scans the laser beam in the X-axis direction. The first polygon mirror means, the second polygon mirror and the second And a second polygon mirror means comprising a second scan motor that rotates the second polygon mirror in a second rotation direction opposite to the first rotation direction and scans the laser beam in the X-axis direction. Since the position changing means is configured to selectively position the laser beam oscillated from the laser beam oscillating means on the first polygon mirror and the second polygon mirror, the forward path machining and chuck for moving the chuck table in one direction. In return path processing in which the table is moved in the other direction, processing can be performed under the same conditions and processing quality can be made the same, and a laser beam is scanned on the workpiece in a predetermined range in the X-axis direction. Therefore, since the laser beam is ablated on the workpiece in the X-axis direction, it is possible to effectively prevent the melt from being backfilled in the formed laser processing groove.

The perspective view of the laser processing apparatus comprised according to this invention. The block block diagram of the laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped. FIG. 3 is an explanatory diagram showing a relationship between polygon mirror means and Y-axis direction scanning means constituting the laser beam irradiation means shown in FIG. 2. The perspective view of the polygon mirror means and incident position change means which comprise the laser beam irradiation means shown in FIG. Explanatory drawing which shows the laser beam dispersion | distribution state by the polygon mirror means which comprises the laser beam irradiation means shown in FIG. Explanatory drawing which shows the state scanned on the workpiece by which the laser beam is hold | maintained at the chuck table by the laser beam irradiation means shown in FIG. The block block diagram of the control means with which the laser processing apparatus shown in FIG. 1 is equipped. The perspective view and principal part expanded sectional view of the semiconductor wafer as a to-be-processed object. The perspective view which shows the state which affixed the semiconductor wafer shown in FIG. 8 on the surface of the dicing tape with which the cyclic | annular flame | frame was mounted | worn. Explanatory drawing of the functional film removal process implemented with the laser processing apparatus shown in FIG. Explanatory drawing of the functional film removal process implemented with the laser processing apparatus shown in FIG. The block block diagram which shows other embodiment of the laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped.

  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. And a laser beam irradiation unit 4 as a laser beam irradiation means disposed on the base 2.

  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, and arranged on the first sliding block 32 so as to be movable in an index feed direction (Y-axis direction) indicated by an arrow Y orthogonal to the machining feed direction (X-axis direction). A second sliding block 33, a support table 35 supported on the second sliding block 33 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 made of a porous material, and holds, for example, a circular semiconductor wafer as a workpiece on a holding surface which is the upper surface of the suction chuck 361 by suction means (not shown). It is supposed to be. 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 that supports a workpiece such as a semiconductor wafer via a protective tape.

  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 manner 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 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. Therefore, the first slide block 32 is moved in the X-axis direction along the guide rails 31 and 31 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, whereby the chuck table 36 is moved in the X-axis direction. 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 Y-axis direction. The chuck table mechanism 3 in the illustrated embodiment includes an index feeding means 38 for moving the second sliding block 33 in the Y-axis direction along a pair of guide rails 322 and 322 provided on the first sliding block 32. It has. The index feeding 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. 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 index feed means 38, the drive pulse of the control means, which will be described later, that outputs a drive signal to the pulse motor 382 is counted, so that the chuck table 36 is moved in the Y-axis direction. The position can also be detected. Further, when a servo motor is used as the drive source of the 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 pulse signal input by the control means Can be detected to detect the position of the chuck table 36 in the Y-axis direction.

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

The laser beam irradiation means 5 will be described with reference to FIG.
The laser beam irradiation unit 5 includes a pulse laser beam oscillation unit 51, an output adjustment unit 52 that adjusts the output of the pulse laser beam oscillated from the pulse laser beam oscillation unit 51, and a pulse laser beam whose output is adjusted by the output adjustment unit 52. A condenser 53 is provided for collecting and irradiating the workpiece held on the chuck table 36. The pulse laser beam oscillating means 51 includes a pulse laser beam oscillator 511 and a repetition frequency setting means 512 attached thereto. The pulse laser beam oscillator 511 of the pulse laser beam oscillation means 51 oscillates a pulse laser beam LB having a wavelength of 355 nm in the illustrated embodiment. The condenser 53 includes a telecentric fθ lens 531 that condenses the pulse laser beam oscillated from the pulse laser beam oscillating means 51 and whose output is adjusted by the output adjusting means 52.

  The pulse laser beam LB oscillated from the pulse laser beam oscillating means 51 and the output adjusted by the output adjusting means 52 is a first direction conversion mirror 541, a second direction conversion mirror 542, a Y-axis direction scanning means 55, a polygon mirror means. The light is guided to the condenser 53 through 56. The first direction changing mirror 541 changes the direction of the pulse laser beam oscillated from the pulse laser beam oscillating means 51 and the output adjusted by the output adjusting means 52 downward in FIG. 2, and the second direction changing mirror 542 The direction of the pulse laser beam whose direction has been changed by the direction changing mirror 541 is changed in the horizontal direction and guided to the Y-axis direction scanning means 55.

  In the illustrated embodiment, the Y-axis direction scanning unit 55 is composed of an acousto-optic deflecting unit, and the pulse laser beam LB guided through the second direction conversion mirror 542 is indexed in the feeding direction (Y-axis direction). A deflecting acoustooptic element 551, an RF oscillator 552 that generates an RF (radio frequency) to be applied to the acoustooptic element 551, and an RF power generated by the RF oscillator 552 are amplified and applied to the acoustooptic element 551. An RF amplifier 553 and a deflection angle adjusting means 554 for adjusting the frequency of the RF generated by the RF oscillator 552. The acoustooptic device 551 can adjust the angle at which the optical axis of the laser beam is deflected in accordance with the frequency of the applied RF. The deflection angle adjusting unit 554 described above is controlled by a control unit described later.

The Y-axis direction scanning unit 55 in the illustrated embodiment is configured as described above, and the operation thereof will be described below with reference to FIGS. 2 and 3.
For example, a voltage of 5 to 15 V is applied to the deflection angle adjusting unit 554 of the Y-axis direction scanning unit 55 including the acoustooptic deflecting unit from a control unit described later, and an RF having a frequency corresponding to 5 to 15 V is applied to the acoustooptic element 551. Then, for example, the optical axis of the pulse laser beam LB is deflected in the Y-axis direction within the range from the one-dot chain line to the two-dot chain line in FIGS. The light is selectively incident on the mirror 561a or the second polygon mirror 562a in the Y-axis direction within a range of, for example, 50 μm. As described above, the laser beam deflected by the acoustooptic device 551 is deflected in the indexing and feeding direction (Y-axis direction) corresponding to the voltage applied to the deflection angle adjusting means 554. The Y-axis direction scanning unit 55 in the illustrated embodiment absorbs a laser beam that is not deflected by the acoustooptic device 551 as indicated by a broken line in FIG. 2 when RF is not applied to the acoustooptic device 551. Absorbing means 555 is provided.

Next, the polygon mirror means 56 will be described with reference to FIGS.
The polygon mirror means 56 in the illustrated embodiment rotates the first polygon mirror 561a disposed on the support substrate 560 and the first polygon mirror 561a in the first rotation direction A as shown in FIG. A first polygon mirror means 561 comprising a first scan motor 561b that scans a laser beam in the X-axis direction, a second polygon mirror 562a, and the second polygon mirror 562a in a direction opposite to the first rotation direction A. And a second polygon mirror means 562 comprising a second scan motor 562b that rotates in the second rotation direction B and scans the laser beam in the X-axis direction. A notch 560a for allowing the laser beam reflected by the first polygon mirror means 561 and the second polygon mirror 562a to pass through is formed at the center of the support substrate 560. The first polygon mirror means 561 and the second polygon mirror means 562 configured as described above are configured such that the first polygon mirror 561a and the second polygon mirror 562a are adjacent in series with the axis center in the Y-axis direction. It is arranged.

  Continuing the description with reference to FIG. 4, the laser beam irradiation means 5 in the illustrated embodiment is oscillated from the pulse laser beam oscillation means 51, the output is adjusted by the output adjustment means 52, and the first direction changing mirror 541 and Incident position changing means 57 for changing the incident position of the pulse laser beam LB guided by the second direction conversion mirror 542 to the polygon mirror means 56 is provided. The incident position changing means 57 is formed by an air piston mechanism 570 that moves in the Y-axis direction a support substrate 560 provided with a polygon mirror means 56 including a first polygon mirror means 561 and a second polygon mirror means 562. The piston rod 571 is connected to the support substrate 560. The incident position changing means 57 composed of the air piston mechanism 570 configured as described above moves the support substrate 560 in the Y-axis direction, so that the first polygon mirror means 561 as shown in FIG. The first polygon mirror 561a is positioned at a first position facing the Y-axis direction scanning means 55, and the second polygon mirror 562a of the second polygon mirror means 562 is moved as shown in FIG. It is positioned at a second position facing the Y-axis direction scanning means 55.

The laser beam irradiation means 5 in the illustrated embodiment is configured as described above, and the operation thereof will be described below. First, a state where the first polygon mirror 561a of the first polygon mirror means 561 is positioned at the first position facing the Y-axis direction scanning means 55 will be described.
As shown in FIG. 2, the pulsed laser beam LB oscillated from the pulsed laser beam oscillating unit 51 and adjusted in output by the output adjusting unit 52 passes through the first direction conversion mirror 541 and the second direction conversion mirror 542 in the Y-axis direction. Guided to scanning means 55. As described above, the pulse laser beam LB guided to the Y-axis direction scanning unit 55 applies a voltage of, for example, 5 to 15 V to the deflection angle adjusting unit 554 for a predetermined time period (one reflecting surface formed on the first polygon mirror 561a). 3), the first polygon mirror 561a is made incident on the first polygon mirror 561a in the Y-axis direction within a range of 50 μm, for example, as shown in FIG. 3A. On the other hand, as shown in FIG. 5A, the first polygon mirror 561a is rotated in the direction indicated by the arrow A, so that the pulse laser beam LB incident on the first polygon mirror 561a is the first polygon mirror 561a. Each reflecting surface of the polygon mirror 561a is dispersed through a notch portion 560a formed in the support substrate 560 in a range indicated by a one-dot chain line to a two-dot chain line in FIG. 5A. The pulse laser beam LB dispersed in this way is collected by the telecentric fθ lens 531 of the condenser 53 and is focused on the upper surface of the workpiece W held on the chuck table 36 in the range of the focal points P1 to P2 in the X-axis direction. Irradiated with. In the illustrated embodiment, the example in which the reflection surface of the first polygon mirror 561a is formed with eight surfaces is shown. However, when the first polygon mirror 561a formed on the eighteen surfaces is used, the first polygon mirror 561a is formed in the direction indicated by the arrow A. When it is rotated, the range from the condensing points P1 to P2 is 8 mm. Therefore, the pulsed laser beam LB scans the workpiece W held on the chuck table 36 within a range of 8 mm in the (+) direction of the X axis. Since the pulse laser beam LB incident on the first polygon mirror 561a is moved in the Y-axis direction within a range of, for example, 50 μm by the Y-axis direction scanning unit 55 as described above, the pulse laser beam LB on the workpiece W is moved. As shown in FIG. 6, the scanning range is 50 μm in the Y-axis direction and 8 mm in the X-axis direction.

Next, the state where the second polygon mirror 562a of the second polygon mirror means 562 is positioned at the second position facing the Y-axis direction scanning means 55 will be described.
As described above, the pulse laser beam LB guided to the Y-axis direction scanning unit 55 is applied to the deflection angle adjusting unit 554 with a voltage of, for example, 5 to 15 V for a predetermined period (formed on the second polygon mirror 562a). When one reflecting surface is applied for a time required to pass through the incident position of the pulse laser beam, the second polygon mirror 562a is applied to the second polygon mirror 562a in the Y-axis direction within a range of 50 μm, for example, as shown in FIG. Incident. On the other hand, as shown in FIG. 5B, the second polygon mirror 562a is rotated in the direction indicated by the arrow B, so that the pulsed laser beam LB incident on the second polygon mirror 562a is the second polygon mirror 562a. Each reflecting surface of the polygon mirror 562a is dispersed within the range indicated by the alternate long and short dash line in FIG. 5B. The pulse laser beam LB dispersed in this way is collected by the telecentric fθ lens 531 of the condenser 53 and is focused on the upper surface of the workpiece W held on the chuck table 36 in the range of the focal points P1 to P2 in the X-axis direction. Then, the light is irradiated through the notch 560a formed in the support substrate 560. In the illustrated embodiment, the example in which the reflection surface of the second polygon mirror 562a is formed with eight surfaces is shown. However, when the second polygon mirror 562a formed on the eighteen surface is used, the second polygon mirror 562a is formed in the direction indicated by the arrow B. When it is rotated, the range from the condensing points P1 to P2 is 8 mm. Accordingly, the pulsed laser beam LB scans the workpiece W held on the chuck table 36 within a range of 8 mm in the (−) direction of the X-axis direction. Note that the pulse laser beam LB incident on the second polygon mirror 562a is moved in the Y-axis direction within a range of, for example, 50 μm by the Y-axis direction scanning unit 55 as described above, and thus the pulse laser beam LB on the workpiece W is moved. As shown in FIG. 6, the scanning range is 50 μm in the Y-axis direction and 8 mm in the X-axis direction.

  The laser processing apparatus in the illustrated embodiment includes control means 8 shown in FIG. The control means 8 is constituted by a computer, and a central processing unit (CPU) 81 that performs arithmetic processing according to a control program, a read-only memory (ROM) 82 that stores a control program and the like, and a readable and writable memory that stores arithmetic results and the like. A random access memory (RAM) 83, an input interface 84 and an output interface 85 are provided. Detection signals from the X-axis direction position detection unit 374, the Y-axis direction position detection unit 384, the imaging unit 6 and the like are input to the input interface 84 of the control unit 8. From the output interface 85 of the control means 8, the processing feed means 37, the index feed means 38, the pulse laser beam oscillation means 51 and the output adjustment means 52 of the laser beam irradiation means 5, and the deflection angle adjustment means of the Y-axis direction scanning means 55. The control signal is output to 554, the first scan motor 561b, the second scan motor 562b, the incident position changing means 57, and the like.

The laser processing apparatus in the illustrated embodiment is configured as described above, and the operation thereof will be described below.
8A and 8B are a perspective view and an enlarged cross-sectional view of a main part of a semiconductor wafer as a workpiece. A semiconductor wafer 9 shown in FIGS. 8A and 8B includes a plurality of ICs each having a functional layer 91 in which an insulating film and a functional film for forming a circuit are laminated on a surface 90a of a substrate 90 such as silicon having a thickness of 150 μm. A device 92 such as an LSI is formed in a matrix. Each device 92 is partitioned by division lines 93 formed in a lattice shape (in the illustrated embodiment, the width is set to 50 μm). In the illustrated embodiment, the insulating film forming the functional layer 91 is an organic film such as a SiO2 film, an inorganic film such as SiOF or BSG (SiOB), or a polymer film such as polyimide or parylene. It consists of a low dielectric constant insulator film (Low-k film) made of a film, and the thickness is set to 10 μm.

A functional layer removing step for removing the functional layer 91 constituting the semiconductor wafer 9 described above along the planned division line 93 will be described.
First, a wafer support process is performed in which a dicing tape is attached to the back surface of the substrate 90 constituting the semiconductor wafer 9 and the outer peripheral portion of the dicing tape is supported by an annular frame. That is, as shown in FIG. 9, the back surface 90b of the substrate 90 constituting the semiconductor wafer 9 is adhered to the surface of the dicing tape T on which the outer peripheral portion is mounted so as to cover the inner opening of the annular frame F. Therefore, in the semiconductor wafer 9 adhered to the surface of the dicing tape T, the surface 91a of the functional layer 91 is on the upper side.

  When the wafer support step described above is performed, the dicing tape T side of the semiconductor wafer 9 is placed on the chuck table 36 of the laser processing apparatus shown in FIG. Then, the semiconductor wafer 9 is sucked and held on the chuck table 36 via the dicing tape T by operating a suction means (not shown) (wafer holding step). Therefore, in the semiconductor wafer 9 held on the chuck table 36 via the dicing tape T, the surface 91a of the functional layer 91 is on the upper side.

  As described above, the chuck table 36 that sucks and holds the semiconductor wafer 9 is positioned directly below the imaging unit 6 by the processing feed unit 37. When the chuck table 36 is positioned immediately below the image pickup means 6 in this way, an alignment operation for detecting a laser processing region of the semiconductor wafer 9 by the image pickup means 6 and the control means 8 is executed. That is, the image pickup means 6 and the control means 8 are a division line 93 formed in a predetermined direction of the semiconductor wafer 9 and a condenser 53 constituting the laser beam irradiation means 5 that irradiates a laser beam along the division line 93. Image processing such as pattern matching is performed for alignment with the laser beam, and alignment of the laser beam irradiation position is performed. The alignment of the laser beam irradiation position is similarly performed on the division line 93 formed in the semiconductor wafer 9 and extending in a direction orthogonal to the predetermined direction.

  When the alignment step described above is performed, the control means 8 operates the processing feed means 37 to irradiate the chuck table 36 with the laser beam irradiation where the condenser 53 of the laser beam irradiation means 5 is positioned as shown in FIG. Move to the area, and position a predetermined division line 93 directly below the condenser 53. At this time, as shown in FIG. 10A, the semiconductor wafer 9 is positioned so that one end of the division-scheduled line 93 (the right end in FIG. 10A) is located directly below the condenser 53. The control unit 8 operates the incident position changing unit 57 so that the first polygon mirror 561a of the first polygon mirror unit 561 is positioned at the first position facing the Y-axis direction scanning unit 55. Keep it. Then, the condensing point (P) of the pulse laser beam irradiated from the condenser 53 is positioned near the upper surface of the functional layer 91 in the division line 93. Next, the control means 8 controls the pulse laser beam oscillating means 51, the output adjusting means 52, and the Y-axis direction scanning means 55 as described above, and the first scan motor 561b as shown in FIG. A pulse laser beam having a wavelength that absorbs light from the condenser 53 to the functional layer 91 constituting the semiconductor wafer 9 as shown in FIG. The chuck table 36 is moved at a predetermined processing feed speed in the direction indicated by the arrow X (+) in FIG. 10A (outward function layer removing step) by operating the processing feed means 37. Then, as shown in FIG. 10B, when the other end of the planned division line 93 (the left end in FIG. 10B) reaches a position directly below the condenser 53, the irradiation of the pulse laser beam is stopped and the chuck is stopped. The movement of the table 36 is stopped.

In addition, the said functional layer removal process is performed on the following process conditions, for example.
Laser beam wavelength: 355 nm (YAG)
Repetition frequency: 80 MHz
Pulse width: 15ps
Average output: 17W
Processing feed rate: 500 to 5000 mm / sec

  In the functional layer removal step described above, the pulse laser beam is scanned and ablated within the range of 50 μm in the Y-axis direction as described above, so that the functional layer constituting the semiconductor wafer 9 as shown in FIG. 91 is removed along the planned dividing line 93 by a laser processing groove 910 having a width of 50 μm. Further, as described above, since the pulse laser beam scans in the range of 8 mm in the X-axis direction, the ablation processing is performed overlapping in the X-axis direction, so that the backfilling of the melt is effectively performed in the formed laser processing groove 910. Can be prevented. In the illustrated embodiment, the pulse laser beam scan direction (condensation in (a) of FIG. 5) depends on the moving direction (arrow X (+)) of the chuck table 36 and the rotation direction indicated by the arrow A of the first polygon mirror 561a. Since the points P1 to P2) are in the forward direction, compared to the case where the moving direction of the chuck table 36 and the scanning direction of the pulse laser beam are opposite directions, the scattering of the melt can be reduced and the processing quality can be improved.

  Next, the control means 8 actuates the index feed means 38 to move the chuck table 36 in the index feed direction (Y-axis direction) by the interval of the scheduled division lines 93 formed in the semiconductor wafer 9, as shown in FIG. ), The adjacent division line 93 is moved to the laser beam irradiation area where the condenser 53 of the laser beam irradiation means 5 is located, and the other end of the division line 93 (the left end in FIG. 11A) is collected. Position it so that it is located directly under the optical device 53. The control unit 8 operates the incident position changing unit 57 to position the second polygon mirror 562a of the second polygon mirror unit 562 at a second position facing the Y-axis direction scanning unit 55. Then, the condensing point (P) of the pulse laser beam irradiated from the condenser 53 is positioned near the upper surface of the functional layer 91 in the division line 93. Next, the control unit 8 controls the pulse laser beam oscillation unit 51, the output adjustment unit 52, and the Y-axis direction scanning unit 55 as described above, and the second scan motor 562b as shown in FIG. 5B. A pulse laser beam having a wavelength that absorbs light from the condenser 53 to the functional layer 91 constituting the semiconductor wafer 9 as shown in FIG. 11A, rotating in the direction indicated by arrow B at a rotational speed of 30000 rpm. The chuck table 36 is moved at a predetermined machining feed rate in the direction indicated by the arrow X (−) in FIG. 11A (return function layer removing step) by operating the machining feed means 37. Then, as shown in FIG. 11B, when the other end of the planned dividing line 93 (the left end in FIG. 10B) reaches a position directly below the condenser 53, the irradiation of the pulse laser beam is stopped and the chuck is stopped. The movement of the table 36 is stopped.

  Also in this return path functional layer removal step, the scanning direction of the pulse laser beam (in FIG. 5B) according to the moving direction of the chuck table 36 (arrow X (−)) and the rotation direction indicated by the arrow B of the second polygon mirror 562a. Since the condensing points P1 to P2) are in the forward direction, the processing can be performed under the same conditions as those in the forward function layer removing process shown in FIG. 10, and the processing quality can be made the same. Compared with the case where the scanning direction is the reverse direction, the scattering of the melt is reduced, and the quality of the device can be improved. In the return path functional layer removal step shown in FIG. 11, the pulse laser beam is scanned and ablated in the range of 50 μm in the Y-axis direction as in the forward path functional layer removal step shown in FIG. ), The functional layer 91 constituting the semiconductor wafer 9 is removed by a laser processing groove 910 having a width of 50 μm along the planned division line 93. Further, since the pulse laser beam scans in the range of 8 mm in the X-axis direction as described above, the ablation processing is overlapped in the X-axis direction. Can be prevented.

Next, another embodiment of the laser beam irradiation means 5 will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same member as the structural member which comprises the laser beam irradiation means 5 shown in FIG. 2 thru | or FIG. 7, and the description saves labor.
In the laser beam irradiation means 5 shown in FIG. 12, the Y-axis direction scanning means 55 comprises a first Y-axis direction scanning means 55a and a second Y-axis direction scanning means 55b, and the first Y-axis direction scanning means 55a. Is disposed opposite to the first polygon mirror 561a of the first polygon mirror means 561, and the second Y-axis direction scanning means 55b is opposed to the second polygon mirror 562a of the second polygon mirror means 562. Arranged. The first Y-axis direction scanning unit 55a and the second Y-axis direction scanning unit 55b may have the same configuration as the Y-axis direction scanning unit 55 shown in FIG. Further, in the laser beam irradiation means 5 shown in FIG. 12, the incident position changing means 58 corresponding to the incident position changing means 57 shown in FIGS. 2 to 7 includes the first Y-axis direction scanning means 55a and the second Y-axis direction. Arranged upstream of the scanning means 55b. The incident position changing means 58 may have the same configuration as the Y-axis direction scanning means 55 shown in FIG. 2, and the pulse laser beam LB guided through the second direction conversion mirror 542 is indexed and sent in the Y-axis direction (Y-axis direction). ), An RF oscillator 582 that generates an RF (radio frequency) to be applied to the acoustooptic element 581, and an RF power generated by the RF oscillator 582 by amplifying the acoustooptic element 581. And an RF amplifier 583 to be applied to the RF and a deflection angle adjusting means 584 for adjusting the frequency of the RF generated by the RF oscillator 582. When RF having a frequency corresponding to, for example, 10 V is applied to the acoustooptic element 581, the pulse laser beam LB is guided to the first Y-axis direction scanning unit 55 a, and RF having a frequency corresponding to, for example, 50 V is applied to the acoustooptic element 551. The optical path is changed so that the pulse laser beam LB is guided to the second Y-axis direction scanning means 55b. Further, the incident position changing means 58 in the illustrated embodiment absorbs a laser beam for absorbing a laser beam that is not deflected by the acoustooptic device 581 as indicated by a broken line in FIG. 12 when RF is not applied to the acoustooptic device 581. Means 585 are provided.

  The above-described laser beam irradiation means 5 shown in FIG. 12 has a first Y-axis direction scanning means 55a disposed opposite to the first polygon mirror 561a of the first polygon mirror means 561 and a second polygon mirror means. The second Y-axis direction scanning means 55b is disposed opposite to the second polygon mirror 562a of 562, and the incident position of the pulse laser beam LB oscillated from the pulse laser beam oscillation means 51 and the output adjusted by the output adjustment means 52 is provided. 2 to 7 is provided with incident position changing means 58 comprising acousto-optic deflecting means for selectively changing the first Y-axis direction scanning means 55a and second Y-axis direction scanning means 55b. The incident position where the polygon mirror means 56 composed of the first polygon mirror means 561 and the second polygon mirror means 562 shown in FIG. The change means 57 becomes unnecessary.

2: Stationary base 3: Chuck table mechanism 36: Chuck table 37: Processing feed means 374: X-axis direction position detection means 38: Indexing feed means 384: Y-axis direction position detection means 4: Laser beam irradiation unit 5: Laser beam irradiation means 51: Pulse laser beam oscillation means 52: Output adjustment means 53: Condenser 55: Y-axis direction scanning means 56: Polygon mirror means 561: First polygon mirror means 562: Second polygon mirror means 57: Incident position changing means 6: Imaging means 8: Control means 9: Semiconductor wafer F: Ring frame T: Dicing tape

Claims (5)

A chuck table for holding a workpiece, a laser beam irradiation means for laser processing the workpiece held on the chuck table, and the chuck table and the laser beam irradiation means relative to the machining feed direction (X-axis direction) A laser comprising: processing feed means for moving; and 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). A processing device,
The laser beam irradiating unit includes a laser beam oscillating unit that oscillates a laser beam, a condenser that collects the laser beam oscillated from the laser beam oscillating unit and irradiates the workpiece held on the chuck table, and the laser beam oscillation unit A polygon mirror means disposed between the means and the condenser for dispersing the laser beam oscillated from the laser beam oscillating means, and the incident position of the laser beam oscillated from the laser beam oscillating means on the polygon mirror means is changed. Incident position changing means
The polygon mirror means comprises: a first polygon mirror means comprising a first polygon mirror and a first scan motor that rotates the first polygon mirror in a first rotation direction and scans a laser beam in the X-axis direction; A second polygon mirror and a second scan motor configured to rotate the second polygon mirror in a second rotation direction opposite to the first rotation direction and scan a laser beam in the X-axis direction. Polygon mirror means, and
The incident position changing means selectively positions the laser beam oscillated from the laser beam oscillation means on the first polygon mirror and the second polygon mirror.
Laser processing equipment characterized by that. The first scan motor of the first polygon mirror means rotates the first polygon mirror to scan the laser beam in the (+) direction of the X axis direction,
The second scan motor of the second polygon mirror means rotates the second polygon mirror to scan a laser beam in the (−) direction of the X axis, and the incident position changing means When the moving direction is the (+) direction in the X-axis direction, the first polygon mirror is positioned at a light incident position where the laser beam is incident and the workpiece held on the chuck table is in the X-axis direction. When the laser beam is scanned in the (+) direction, and the movement direction of the chuck table is the (−) direction in the X-axis direction, the second polygon mirror is positioned at the light incident position where the laser beam enters. The laser processing apparatus according to claim 1, wherein a laser beam is scanned in the (−) direction in the X-axis direction with respect to the workpiece held on the chuck table.   The incident position changing means moves the first polygon mirror means and the second polygon mirror means in the Y-axis direction to select the first polygon mirror and the second polygon mirror as the laser beam incident positions. The laser processing apparatus according to claim 1, wherein the laser processing apparatus is positioned in a mechanical manner.   3. The incident position changing means changes the optical path of the laser beam oscillated from the laser beam oscillating means so that the laser beam is selectively incident on the first polygon mirror and the second polygon mirror. Laser processing equipment.   5. The apparatus according to claim 1, further comprising a Y-axis direction scanning unit that scans a laser beam oscillated from the laser beam oscillation unit in a Y-axis direction of the first polygon mirror and the second polygon mirror. Laser processing equipment.

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