JP2009291807A - Laser beam machining apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining apparatus that prevents refraction of a laser beam emitted along a liquid beam jetted from a nozzle. <P>SOLUTION: The laser beam machining apparatus is equipped with a chuck table, a laser beam irradiation means that emits a laser beam to a workpiece held on the chuck table, and a feeding-of-work means for performing chuck table feeding-of-work, wherein the laser beam irradiation means includes a laser beam oscillation means and a machining head for converging the laser beam oscillated from the laser beam oscillation means. The machining head is composed of a liquid column forming means having an injection nozzle for jetting a liquid along the optical axis of the laser beam converged by a condensing lens, and composed of a gas curtain forming means forming a cylindrical gas curtain that surrounds the liquid column jetted from the injection nozzle. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus that performs laser processing on a workpiece by irradiating a laser beam along a liquid column injected from an injection nozzle.

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

In recent years, as a method for dividing a plate-like workpiece such as a semiconductor wafer, a laser processing groove is formed by irradiating a pulse laser beam along a street formed on the workpiece, and a mechanical processing is performed along the laser processing groove. A method of cleaving with a braking device has been proposed. (For example, refer to Patent Document 1.)
JP-A-10-305421

  When a laser processing groove is formed by irradiating a pulsed laser beam along the street of a semiconductor wafer using a laser processing apparatus, debris is generated by the irradiation of the laser beam on the semiconductor wafer, and this debris adheres to the surface of the device. There is a problem of degrading the quality of the device. Therefore, when forming a laser processed groove along the street of a semiconductor wafer, a surface of the semiconductor wafer is coated with a protective film in advance, and a laser beam is irradiated through the protective film. A process for coating the protective coating must be added, and productivity is poor. Further, when a semiconductor wafer is irradiated with a laser beam, the device is heated, so that there is a problem that the quality of the device is deteriorated.

As a laser processing method that eliminates the influence of debris generated by irradiating a laser beam and prevents the workpiece from being heated, a liquid column is sprayed from the spray nozzle, and the laser beam is irradiated along this liquid column. Laser processing methods have been proposed. (For example, see Patent Document 2.)
JP 2006-255769 A

  Thus, the liquid column ejected from the ejection nozzle collides with the upper surface of the workpiece and becomes a turbulent flow, which refracts the laser beam and lowers the machining accuracy.

  The present invention has been made in view of the above-mentioned facts, and its main technical problem is to provide a laser processing apparatus that prevents the laser beam irradiated along the liquid column ejected from the ejection nozzle from being refracted. It is in.

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 processing head comprising a processing feed means for relatively processing and feeding the laser beam irradiation means, the laser beam irradiation means including a laser beam oscillation means and a condensing lens for condensing the laser beam emitted from the laser beam oscillation means; In a laser processing apparatus comprising:
The processing head is disposed below the liquid column forming unit, with a liquid column forming unit having an ejection nozzle that ejects liquid along the optical axis of the laser beam condensed by the condensing lens. Gas curtain forming means for forming a cylindrical gas curtain surrounding the liquid column ejected from the ejection nozzle,
The gas curtain forming means includes a bottom wall having a first passage through which a liquid column ejected from the injection nozzle passes, and a lower end portion of the liquid column forming means that is formed upright from the outer periphery of the bottom wall. A first cylindrical body having an annular side wall that is fitted to the bottom wall, a second cylinder that protrudes from the bottom surface of the bottom wall and through which a liquid column ejected from the ejection nozzle passes, and the first cylinder A second cylinder that surrounds the body and forms a cylindrical gap with the outer peripheral surface of the first cylinder, and a gas supply means for supplying gas to the cylindrical gap. Has
A laser processing apparatus is provided.

The lower surface of the second cylindrical body is preferably formed as a tapered surface that is inclined downward from the inner periphery toward the outer periphery.
The gas curtain forming means preferably includes a gas introduction passage for supplying gas at a plurality of positions at equal angles with respect to the cylindrical gap.
Furthermore, an annular support shelf is provided on the outer peripheral portion of the upper surface of the bottom wall constituting the gas curtain forming means, and the space between the lower surface of the liquid column forming means and the upper surface of the bottom wall fitted with the annular side wall. It is desirable that an outside air introduction chamber be formed in the air.

  In the laser processing apparatus according to the present invention, the gas curtain forming means for forming the cylindrical gas curtain surrounding the liquid column ejected from the spray nozzle is disposed below the liquid column forming means constituting the machining head. The liquid column ejected from the ejection nozzle collides with the surface of the workpiece held on the chuck table and tends to become turbulent, but the outer peripheral surface of the first cylinder constituting the gas curtain forming means and the first The cylindrical gas curtain ejected from the cylindrical gap between the two cylindrical bodies presses the liquid that is going to be turbulent and flows over the surface of the workpiece. Therefore, since the pulse laser beam irradiated along the liquid column is not refracted, it is irradiated accurately at a predetermined position.

  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, a chuck table mechanism 3 that is disposed on the stationary base 2 so as to be movable in a machining feed direction indicated by an arrow X, and holds a workpiece. The laser beam irradiation unit support mechanism 4 is movably disposed in an index feed direction indicated by an arrow Y orthogonal to the direction indicated by the arrow X in FIG. And a laser beam irradiation unit 5 disposed in the.

  The chuck table mechanism 3 includes a pair of guide rails 31, 31 arranged in parallel along the machining feed direction indicated by the arrow X on the stationary base 2, and the arrow X on the guide rails 31, 31. A first slide block 32 movably disposed in the processing feed direction; and a second slide block 33 disposed on the first slide block 32 movably in the index feed direction indicated by an arrow Y; A cover table 35 supported by a cylindrical member 34 on the second sliding block 33 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 disk-shaped wafer as 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 that supports the wafer via a protective tape as will be described later.

  The first sliding block 32 is provided with a pair of guided grooves 321 and 321 fitted to the pair of guide rails 31 and 31 on the lower surface thereof, and in the index feed direction indicated by an arrow Y on the upper surface thereof. A pair of guide rails 322 and 322 formed in parallel with each other are provided. The first sliding block 32 configured in this way is processed by the arrow X along the pair of guide rails 31, 31 when the guided grooves 321, 321 are fitted into the pair of guide rails 31, 31. It is configured to be movable in the feed direction. The chuck table mechanism 3 in the illustrated embodiment includes a machining feed means 37 for moving the first sliding block 32 along the pair of guide rails 31 and 31 in the machining feed direction indicated by the arrow X. 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, when the male screw rod 371 is driven to rotate forward and backward by the pulse motor 372, the first sliding block 32 is moved along the guide rails 31, 31 in the machining feed direction indicated by the arrow X.

  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 is for moving the second slide block 33 along the pair of guide rails 322 and 322 provided in the first slide block 32 in the index feed direction indicated by the arrow Y. First index 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, when the male screw rod 381 is driven to rotate forward and reversely by the pulse motor 382, the second slide block 33 is moved along the guide rails 322 and 322 in the index feed direction indicated by the arrow Y.

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

  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 direction indicated by the arrow Z (Z-axis direction).

  The laser beam irradiation unit 5 in the illustrated embodiment includes a moving means 53 for moving the unit holder 51 along the pair of guide rails 423 and 423 in the direction indicated by the arrow Z (Z-axis direction). The moving 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. By driving the male screw rod (not shown) in the forward and reverse directions by the motor 532, the unit holder 51 and the laser beam irradiation means 52 are moved along the guide rails 423 and 423 in the direction indicated by the arrow Z (Z-axis 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 laser beam irradiation means 52 will be described with reference to FIGS.
The laser beam irradiation means 52 in the illustrated embodiment includes a cylindrical casing 521 that is fixed to the unit holder 51 and extends substantially horizontally, pulse laser beam oscillation means 6 disposed in the casing 521, and the casing 521. A machining head 7 is provided which is attached to the tip and collects the laser beam emitted from the pulsed laser beam oscillation means 6. The pulse laser beam oscillation means 6 comprises a pulse laser beam oscillator 61 composed of a YAG laser oscillator or a YVO4 laser oscillator, and a repetition frequency setting means 62 attached thereto. The thus configured pulse laser beam oscillation means 6 oscillates a pulse laser beam having a wavelength of 532 nm, a repetition frequency of 50 kHz, and an average output of 10 W, for example.

  As shown in FIG. 2, the processing head 7 includes a head housing 71, a direction changing mirror 72 that is disposed in the head housing 71 and changes the direction of the laser beam oscillated from the pulse laser beam oscillation means 6 downward, A condensing lens 73 for condensing the laser beam whose direction has been changed by the direction changing mirror 72 is provided. A liquid column forming unit 74 is disposed below the head housing 71, and a gas curtain forming unit 75 is disposed below the liquid column forming unit 74.

  The liquid column forming means 74 disposed under the head housing 71 includes a liquid chamber forming housing 740 that forms a liquid chamber 741. The liquid chamber forming housing 740 includes a cylindrical side wall 742, and an upper wall 743 and a lower wall 744 that block the upper and lower surfaces of the side wall 742, respectively. A transparent plate 745 is disposed on the upper wall 743 constituting the liquid chamber forming housing 740. An injection nozzle 746 is formed at the center of a circular lower wall 744 constituting the liquid chamber forming housing 740. In addition, the injection port 746a of the injection nozzle 746 is formed on the optical axis of the laser beam while the convergence point condensed by the condenser lens 73 is positioned.

  A liquid introduction port 741 a that opens to the liquid chamber 741 is formed in the side wall 742 constituting the liquid chamber forming housing 740, and this liquid introduction port 741 a is connected to the liquid supply means 76. The liquid supply means 76 includes a liquid supply source 761 such as water, a pipe 762 connecting the liquid supply source 761 and the liquid inlet 741a provided in the side wall 742 constituting the liquid chamber forming housing 740, and the pipe. And an electromagnetic on-off valve 763 disposed in the area 762. The electromagnetic on-off valve 763 blocks communication between the liquid supply source 761 and the liquid introduction port 741a in the deenergized (OFF) state, and when energized (ON), the liquid supply source 751 and the liquid introduction port. 741a is communicated. Note that the liquid supply means 76 configured in this manner supplies a liquid having a pressure of, for example, 13 MPa to the liquid chamber 741 through the liquid inlet 741a. The liquid supplied to the liquid chamber 741 by the liquid supply means 76 becomes a liquid column 70 from the injection port 746a of the injection nozzle 746 and is jetted toward the gas curtain forming means 75 described later. The diameter of the liquid column 70 is set to φ0.05 mm in the illustrated embodiment.

  The gas curtain forming means 75 disposed below the liquid column forming means 74 includes a bottom wall 751 having a first passage 751a through which the liquid column 70 ejected from the ejection nozzle 746 passes, and the bottom An annular side wall 752 that is formed upright from the outer periphery of the wall 751 and fits to the lower end of the liquid chamber forming housing 740 that constitutes the liquid column forming means 74, and is formed to protrude from the lower surface of the bottom wall 751. A first cylinder 753 having a second passage 753a through which the liquid column 70 ejected from 746 passes, and an outer peripheral surface of the first cylinder 753 which is disposed to surround the first cylinder 753 And a second cylindrical body 755 that forms a cylindrical gap 754 therebetween, which are formed of stainless steel in the illustrated embodiment. An annular support shelf 751 b is provided on the outer peripheral portion of the upper surface of the bottom wall 751 constituting the gas curtain forming means 75. Therefore, when the annular side wall 752 constituting the gas curtain forming means 75 is fitted to the lower end portion of the liquid chamber forming housing 740 constituting the liquid column forming means 74, the lower end of the liquid chamber forming housing 740 is attached to the annular support shelf 751b. In contact with each other, an outside air introduction chamber 750 is formed between the lower surface of the liquid chamber forming housing 740 and the upper surface of the bottom wall 751. Further, as shown in FIG. 3, four female screw holes 752a are formed at an interval of 90 degrees on the annular side wall 752 constituting the gas curtain forming means 75, and fastening bolts 77 are provided in the four female screw holes 752a. It is designed to be screwed together. Therefore, the gas side wall 752 is fitted to the lower end of the liquid chamber forming housing 740 constituting the liquid column forming means 74, and the tightening bolt 77 is screwed to tighten the gas curtain forming means 75 to form the liquid chamber. It is attached to the lower end of the housing 740.

  As shown in FIG. 4, the bottom wall 751 constituting the gas curtain forming means 75 is provided with an outside air introduction port 751c that opens into the outside air introduction chamber 750 and an outside air introduction passage 751d that communicates the outside air introduction port 751c with the outside air. It has been. In addition, a recess 751e that forms a gas introduction chamber 756 is formed at the center of the lower surface of the bottom wall 751. A second cylinder 755 that surrounds the first cylinder 753 and forms a cylindrical gap 754 with the outer peripheral surface of the first cylinder 753 is disposed in the recess 751e. The second cylindrical body 755 includes a cylindrical portion 755a having an inner diameter larger than the outer diameter of the first cylindrical body 753, and a flange portion 755b that protrudes outward in the radial direction at the lower end portion of the cylindrical portion 755a. The outer peripheral portion of the flange portion 755b is joined to the peripheral portion forming the concave portion 751e of the bottom wall 751 by welding. In this way, a gap 755c is formed between the upper end surface of the cylindrical portion 755a constituting the second cylindrical body 755 attached to the bottom wall 751 and the bottom surface of the concave portion 751e formed in the bottom wall 751. . The lower surface of the second cylindrical body 755 configured as described above is formed into a tapered surface 755d that is inclined downward from the inner periphery toward the outer periphery. The bottom wall 751 constituting the gas curtain forming means 75 is formed with a plurality of gas introduction passages 755f that communicate with the gas introduction chamber 756 formed by the recess 751e as shown in FIGS. . The plurality of gas introduction passages 755f are provided in the illustrated embodiment, and are provided at equiangular positions (180 degrees in the illustrated embodiment). Gas is supplied by the gas supply means 78 to the gas introduction passage 755f formed in this way.

  The gas supply means 78 includes a gas supply source 781 such as air, a pipe 782 connecting the gas supply source 781 and the gas introduction passage 755f, and an electromagnetic opening / closing valve 783 disposed in the pipe 782. . The electromagnetic on-off valve 783 blocks communication between the gas supply source 781 and the gas introduction passage 755f when deenergized (OFF), and when energized (ON), the electromagnetic supply valve 783 and the gas introduction passage are disconnected. It is configured to communicate with 755f. The gas supply means 78 configured in this manner supplies, for example, 5 liters of gas such as air per minute to the gas introduction chamber 756 through the gas introduction passage 755f. Therefore, in the illustrated embodiment, the gas introduced into the gas introduction chamber 756 through the gas introduction passage 755f is in the recess 751e formed in the upper end surface and the bottom wall 751 of the cylindrical portion 755a constituting the second cylindrical body 755. 3 to 5 m / mm from the cylindrical gap 754 between the outer peripheral surface of the first cylindrical body 753 and the inner peripheral surface of the cylindrical portion 755a constituting the second cylindrical body 755, passing through the clearance 755c between the bottom surface. It is ejected at a speed of seconds. Note that a plurality of gas introduction passages 755f for introducing gas into the gas introduction chamber 756 are formed at equiangular positions so that the gas can be evenly supplied to the gas introduction chamber 756.

  Referring back to FIG. 1, the laser processing apparatus in the illustrated embodiment includes an imaging unit 11 that is disposed at a front end portion of the casing 521 and detects a processing region to be laser processed by the laser beam irradiation unit 52. Yes. The imaging means 11 is composed of optical means such as a microscope and a CCD camera, and sends the captured image signal to a control means (not shown).

The laser beam irradiation means 52 in the illustrated embodiment is configured as described above, and the operation thereof will be described below with reference to FIG.
When the electromagnetic on-off valve 763 of the liquid supply means 76 is energized (ON), the high pressure liquid is supplied from the liquid supply source 761 to the liquid chamber 740 of the liquid column forming means 74 constituting the machining head 7 via the pipe 762. The high-pressure liquid supplied to the liquid chamber 740 is ejected as a liquid column 70 from the ejection port 746 a of the ejection nozzle 746. The liquid column 70 is held on the chuck table 36 through the first passage 751a formed in the bottom wall 751 constituting the gas curtain forming means 78 and the second passage 753a formed in the first cylinder 753. Jetted toward the wafer W. On the other hand, the pulse laser beam LB oscillated from the pulse laser beam oscillating means 6 is guided to the condenser lens 73 by the direction conversion mirror 72, and is irradiated along the liquid column 70 through the transparent plate 745 while being condensed by the condenser lens 73. Is done. Accordingly, the spot of the pulse laser beam LB becomes the diameter of the liquid column 70.

  During the laser beam irradiation described above, the electromagnetic on-off valve 783 of the gas supply means 78 is energized (ON) and opened. As a result, gas is introduced from the gas supply source 781 into the gas introduction chamber 756 through the gas introduction passage 755f of the gas curtain forming means 75 via the pipe 782. The gas introduced into the gas introduction chamber 756 passes through a gap 755c between the upper end surface of the cylindrical portion 755a constituting the second cylindrical body 755 and the bottom surface of the concave portion 751e formed in the bottom wall 751, and the gas in the first cylindrical body 753. A cylindrical gap 754 between the outer peripheral surface and the inner peripheral surface of the cylindrical portion 755a constituting the second cylindrical body 755 serves as a cylindrical gas curtain 79, and surrounds the liquid column 70 to the chuck table 36. It is ejected toward the wafer W to be held.

Here, the effect | action of the gas ejected from the gas curtain formation means 75 is demonstrated.
As described above, the liquid column 70 ejected from the ejection port 746a of the ejection nozzle 746 constituting the liquid column forming means 74 collides with the surface of the wafer W held by the chuck table 36 and becomes a turbulent flow. When a turbulent liquid flow occurs on the surface of the wafer W as described above, the pulse laser beam LB irradiated along the liquid column 70 is refracted and is not irradiated at a predetermined position, so that the processing accuracy is deteriorated. At this time, since the cylindrical gas curtain 79 ejected from the gas curtain forming means 75 surrounds the liquid column 70 and is ejected toward the surface of the wafer W, it collides with the surface of the wafer W and becomes a turbulent flow. The intended liquid is pressed by the gas forming the gas curtain 79 and flows on the surface of the wafer W as a laminar flow. Accordingly, the pulsed laser beam LB irradiated along the liquid column 70 is not refracted, and is thus accurately irradiated at a predetermined position. When the liquid column 70 collides with the surface of the wafer W, water droplets are scattered, and the scattered water droplets adhere to the lower surface of the second cylindrical body 755 constituting the gas curtain forming means 75, and the water droplets grow and become liquid. When the column 70 falls, the liquid column 70 is disturbed and the pulse laser beam LB cannot be accurately irradiated to a predetermined position. However, in the illustrated embodiment, the lower surface of the second cylindrical body 755 is formed on the tapered surface 755d that inclines downward from the inner periphery toward the outer periphery, so that it adheres to the lower surface of the second cylindrical body 755. Since the water droplet moves to the outer periphery along the tapered surface 755d and falls, the liquid column 70 is not affected. Further, when the liquid column 70 is ejected from the ejection nozzle 746 formed in the liquid chamber forming housing 740 constituting the liquid column forming means 74, a negative pressure is generated between the liquid chamber forming housing 740 and the gas curtain forming means 75. In the embodiment described above, the outside air introduction chamber 750 is formed between the lower surface of the liquid chamber forming housing 740 constituting the liquid column forming means 74 and the upper surface of the bottom wall 751 constituting the gas curtain forming means 75. Since the outside air is introduced into the outside air introduction chamber 750 via the outside air introduction passage 751d, a negative pressure state does not occur. Accordingly, it is possible to prevent an adverse effect on the liquid column 70 caused by the negative pressure generated between the liquid chamber forming housing 740 and the gas curtain forming means 75.

The laser processing apparatus in the illustrated embodiment is configured as described above, and the operation thereof will be described below.
As shown in FIG. 1, a semiconductor wafer W as a workpiece is conveyed onto an adsorption chuck 361 of a chuck table 36 while being adhered to the surface of a dicing tape T mounted on an annular frame F. It is sucked and held by the chuck 361. The semiconductor wafer W has a plurality of streets formed in a lattice shape on the surface, and devices such as ICs and LSIs are formed in a plurality of regions partitioned by the plurality of streets formed in the lattice shape. The chuck table 36 that sucks and holds the semiconductor wafer W in this way is moved along the guide rails 31 and 31 by the operation of the processing feed means 37 and is positioned directly below the imaging means 11.

  As described above, when the chuck table 36 is positioned immediately below the image pickup means 11, the street formed in a predetermined direction of the semiconductor wafer W by the image pickup means 11 and a control means (not shown) is aligned with the processing head 7. Image processing such as pattern matching is performed to perform processing region alignment (alignment step). In addition, the alignment of the processing region is similarly performed on the street formed in the semiconductor wafer W and extending at right angles to the predetermined direction.

  As described above, when the street formed on the semiconductor wafer W held on the chuck table 36 is detected and the processing area is aligned, the chuck table 36 holding the semiconductor wafer W is irradiated with the laser beam. Move to the processing area of the means 52. Then, a predetermined street formed on the semiconductor wafer W is positioned directly below the processing head 7. Then, as described above, the liquid supply means 76, the pulse laser beam oscillation means 6 and the gas supply means 78 constituting the laser beam irradiation means 52 are activated, and the machining feed means 37 is activated to feed the chuck table 36 (laser). Processing step). As a result, as shown in FIG. 2, the pulse laser beam LB emitted from the injection port 746 a of the injection nozzle 746 becomes a liquid column 70 toward the wafer W held on the chuck table 36 and is oscillated from the pulse laser beam oscillation means 6. Is irradiated along the liquid column 70 and between the outer peripheral surface of the first cylindrical body 753 constituting the gas curtain forming means 75 and the inner peripheral surface of the cylindrical portion 755a constituting the second cylindrical body 755. A cylindrical gas curtain 79 is formed from the cylindrical gap 754 and is ejected toward the wafer W held on the chuck table 36 while surrounding the liquid column 70. By performing the laser processing step in this manner, the pulse laser beam LB irradiated along the liquid column 70 is not refracted as described above, so that the semiconductor wafer W held on the chuck table 36 is along a predetermined street. Laser processed accurately.

The perspective view of the laser processing apparatus comprised by this invention. The block diagram of a structure of the pulse laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped. The top view of the gas curtain formation means which comprises the process head which comprises the pulse laser beam irradiation means shown in FIG. FIG. 4 is a cross-sectional view taken along line AA of the gas curtain forming means shown in FIG. 3.

Explanation of symbols

3: Chuck table mechanism 36: Chuck table 37: Processing feed means 38: First index feeding means 43: Second index feeding means 5: Laser beam irradiation unit 52: Laser beam irradiation means 6: Pulse laser beam oscillation means 7: Processing head 71: Head housing 72: Direction changing mirror 73: Condensing lens 74: Liquid column forming means 740: Liquid chamber forming housing 741: Liquid chamber 745: Transparent plate 746: Injection nozzle 75: Gas curtain forming means 750: Outside air introduction chamber 751 : Bottom wall 752: annular side wall 753: first cylinder 754: cylindrical gap 755: second cylinder 76: liquid supply means 761: liquid supply source 763: electromagnetic on-off valve 78: gas supply means 781: Gas supply source

Claims (4)

A chuck table for holding a workpiece, a laser beam irradiation means for irradiating a workpiece held on the chuck table with a laser beam, and a processing feed means for relatively processing and feeding the chuck table and the laser beam irradiation means A laser processing apparatus comprising: a laser beam oscillating unit; and a processing head including a condensing lens that condenses the laser beam oscillated from the laser beam oscillating unit.
The processing head is disposed below the liquid column forming unit, with a liquid column forming unit having an ejection nozzle that ejects liquid along the optical axis of the laser beam condensed by the condensing lens. Gas curtain forming means for forming a cylindrical gas curtain surrounding the liquid column ejected from the ejection nozzle,
The gas curtain forming means includes a bottom wall having a first passage through which a liquid column ejected from the injection nozzle passes, and a lower end portion of the liquid column forming means that is formed upright from the outer periphery of the bottom wall. A first cylindrical body having an annular side wall that is fitted to the bottom wall, a second cylinder that protrudes from the bottom surface of the bottom wall and through which a liquid column ejected from the ejection nozzle passes, and the first cylinder A second cylinder that surrounds the body and forms a cylindrical gap with the outer peripheral surface of the first cylinder, and a gas supply means for supplying gas to the cylindrical gap. Has
Laser processing equipment characterized by that.   2. The laser processing apparatus according to claim 1, wherein a lower surface of the second cylindrical body is formed as a tapered surface inclined downward from an inner periphery toward an outer periphery.   3. The laser processing apparatus according to claim 1, wherein the gas curtain forming means includes a gas introduction passage for supplying gas at a plurality of positions at an equal angle with respect to the cylindrical gap.   An annular support shelf is provided on the outer peripheral portion of the upper surface of the bottom wall constituting the gas curtain forming means, and between the lower surface of the liquid column forming means fitted with the annular side wall and the upper surface of the bottom wall. The laser processing apparatus according to any one of claims 1 to 3, wherein an outside air introduction chamber is formed.

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