JP2011125871A - Laser beam machining apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining apparatus capable of preventing debris from sticking to a workpiece, wherein the debris is generated by irradiation of a laser beam guided in a liquid column. <P>SOLUTION: The laser beam machining apparatus is equipped with a cover liquid feeder by which a cover liquid is supplied to a workpiece to cover the upper face of the workpiece therewith. A machining head is composed of: a condensing lens for converging a laser beam generated by a laser beam generator; a liquid jetting tool that jets a liquid to the workpiece to form a liquid column through which the laser beam converged by the condensing lens is guided; an outer wall arranged so as to surround the liquid column for the purpose of controlling the inflow of the cover liquid into the machining point of the workpiece irradiated with the laser beam; a suction port arranged between the liquid column and the outer wall; and a sucking means including a sucking source connected to the suction port. The apparatus is characterized in that machining waste generated by the laser beam irradiation on the workpiece covered with the cover liquid is sucked together with the cover liquid by the suction tool and removed from the surface of the workpiece. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus having a laser beam irradiation means for irradiating a workpiece such as a semiconductor wafer with a laser beam, and in particular, a laser beam guided to a liquid column formed by being ejected from a liquid ejecting means. The present invention relates to a laser processing apparatus that performs laser processing.

  In a semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets formed in a lattice shape on the surface of a semiconductor wafer having a substantially disk shape, and devices such as ICs and LSIs are divided into these partitioned regions. Form. Each semiconductor device is manufactured by dicing the semiconductor wafer along the street.

  In recent years, as a method of dividing a plate-like workpiece such as a semiconductor wafer, a laser processing groove is formed on the workpiece by irradiating a pulse laser beam along a street formed on the workpiece, and this laser processing. A method of cleaving a workpiece along a groove by a mechanical braking device has been proposed (see, for example, Japanese Patent Laid-Open No. 10-305421).

  When a laser processing groove is formed in a wafer by irradiating a pulse laser beam along the street of the semiconductor wafer using a laser processing apparatus, debris is generated by irradiation of the laser beam on the wafer, and this debris is formed on the surface of the device. There is a problem that the quality of the device deteriorates due to adhesion.

  However, 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 degraded. Therefore, as a laser processing method for preventing the workpiece from being heated by irradiating the laser beam, a liquid column is formed by jetting a high-pressure liquid onto the workpiece, and the liquid column is transmitted (guided). There have been proposed laser processing apparatuses that perform desired processing by irradiating a workpiece with an irradiated laser beam (for example, Japanese Patent Publication No. 2-1621, Japanese Patent Application Laid-Open No. 2001-321977, Japanese Patent Application Laid-Open No. 2006). -255769).

  In these laser processing apparatuses, since the focused laser beam is guided to the workpiece through the thread-like liquid column, laser processing can be performed regardless of the focal position of the focusing lens. Furthermore, since the heat generated during laser processing is cooled by the liquid, there is a merit that deterioration of the quality of the workpiece due to heat can be prevented.

Japanese Patent Laid-Open No. 10-305421 Japanese Patent Publication No.2-1621 Japanese Patent Laid-Open No. 2001-321977 JP 2006-255769 A

  On the other hand, when a workpiece is irradiated with a laser beam, heat energy is concentrated in the irradiated region, and processing scraps called debris are generated. A portion of the generated debris is taken into the liquid forming the liquid column, but the debris that has not been taken into the liquid is fixed on the workpiece. Moreover, after the liquid containing debris stays on the workpiece, the debris is fixed to the workpiece by drying, and the debris cannot be removed even if the workpiece is washed after processing.

  The present invention has been made in view of the above points, and an object thereof is to prevent debris generated by irradiation of a laser beam guided in a liquid column from adhering to a workpiece. It is to provide a possible laser processing apparatus.

  According to the present invention, there is provided a laser processing apparatus comprising: a holding unit that holds a workpiece; and a laser beam irradiation unit that irradiates the workpiece held by the holding unit with a laser beam. Cover liquid supply means for supplying a cover liquid and covering the upper surface of the workpiece with the cover liquid is provided. The laser beam irradiation means includes a laser beam generating means and a processing head, and the processing head includes A condensing lens that condenses the laser beam generated from the laser beam generating means, and a liquid column that guides the laser beam condensed by the condensing lens by ejecting liquid onto the workpiece. A liquid ejecting means; an outer wall disposed to surround the liquid column to control the inflow of the cover liquid to a processing point of the workpiece irradiated with the laser beam; the liquid column; A suction port disposed between the outer wall and the suction wall; A suction means including a suction source connected to the mouth, and processing waste generated by irradiating the workpiece covered with the cover liquid with the laser beam is sucked together with the cover liquid by the suction means. Thus, there is provided a laser processing apparatus characterized by performing suction removal from the workpiece.

  According to the laser processing apparatus of the present invention, since the suction port of the suction means is formed adjacent to the processing point where the liquid column and the laser beam collide with the workpiece, the debris generated by the laser beam irradiation is immediately generated. Removed by suction.

  Furthermore, since the laser processing apparatus of the present invention includes the cover liquid supply means, the upper surface of the workpiece being processed can be covered with the cover liquid. Therefore, the debris that has not been removed by the suction means can be captured by the cover liquid and discharged together with the cover liquid from the workpiece by the suction means. Therefore, debris is prevented from adhering to the workpiece.

It is a schematic block diagram of the laser processing apparatus which concerns on this invention embodiment. It is a longitudinal cross-sectional view of a process head part. It is a block diagram of a laser beam generation unit.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a laser processing apparatus 2 according to an embodiment of the present invention. On the front side of the laser processing apparatus 2, operation means 4 is provided for an operator to input instructions to the apparatus such as processing conditions. In the upper part of the apparatus, there is provided a display means 6 such as a CRT for displaying a guidance screen for an operator and an image taken by an imaging means described later.

  A wafer 11 that is a workpiece is attached to a dicing tape T that is an adhesive sheet, and an outer peripheral edge portion of the dicing tape T is attached to an annular frame F. As a result, the wafer 11 is supported by the frame F via the dicing tape T, and a plurality of wafers (for example, 25 sheets) are accommodated in the wafer cassette 8 shown in FIG. The wafer cassette 8 is placed on a cassette elevator 9 that can move up and down.

  Behind the wafer cassette 8, a loading / unloading means 10 is provided for unloading the wafer 11 before processing from the wafer cassette 8 and loading the processed wafer into the wafer cassette 8. Between the wafer cassette 8 and the loading / unloading means 10, a temporary placement area 12, which is an area on which a wafer to be carried in / out, is temporarily placed, is provided. Positioning means 14 for positioning at a certain position is provided.

  In the vicinity of the temporary placement region 12, a transport means 16 having a turning arm that sucks and transports the frame F integrated with the wafer 11 is disposed, and the wafer 11 transported to the temporary placement region 12 is It is sucked by the transport means 16 and transported onto the chuck table 18 and is sucked by the chuck table 18 and is held on the chuck table 18 by fixing the frame F by a plurality of clamps 19.

  The chuck table 18 is configured to be rotatable and reciprocally movable in the X-axis direction. Above the movement path of the chuck table 18 in the X-axis direction, an alignment unit 20 that detects a street of the wafer 11 to be laser processed. Is arranged.

  The alignment unit 20 includes an imaging unit 22 that images the surface of the wafer 11 and can detect a street to be laser processed by processing such as pattern matching based on an image acquired by imaging. The image acquired by the imaging unit 22 is displayed on the display unit 6.

  On the left side of the alignment unit 20, a laser beam irradiation unit 24 that irradiates the wafer 11 held on the chuck table 18 with a laser beam is disposed. The laser beam irradiation means 24 includes a laser beam generation unit 25 shown in FIG. 3 housed in a casing 26 and a processing head 28.

  The laser beam irradiation means 24 is formed integrally with the alignment means 20, and both move in the Y-axis direction and the Z-axis direction in conjunction with each other. The casing 26 is provided with cover liquid supply means 32 connected to a cover liquid supply source 34.

  Reference numeral 32 denotes transport means for transporting the wafer 11 after laser processing to the spinner cleaning device 30. The spinner cleaning device 30 cleans the processed wafer 11 and blows air from an air nozzle to dry the wafer 11.

  Referring to FIG. 2, a longitudinal sectional view of the machining head 28 is shown. As described above, the laser beam irradiation means 24 of the laser processing apparatus includes the laser beam generation unit 25 and the processing head 28.

  As shown in FIG. 3, the laser beam generating unit 25 includes a laser oscillator 36 that oscillates a YAG laser or a YVO4 laser, a repetition frequency setting unit 38, a pulse width adjusting unit 40, and a power adjusting unit 42. .

  The pulsed laser beam 27 adjusted to a predetermined power by the power adjusting means 42 of the laser beam generating unit 25 is introduced into the machining head 28 from a beam introduction port 46 formed in the housing 44 of the machining head 28.

  A mirror 48 that reflects the laser beam 27 and a condenser lens 50 that condenses the laser beam 27 are disposed in the housing 44. A liquid chamber housing 58 that defines a liquid chamber 56 of the liquid ejecting means 52 integrally with the housing 44 is formed. The liquid chamber housing 58 includes a cylindrical side wall 60 and an upper wall 62 and a lower wall 64 that close the upper and lower surfaces of the side wall 60, respectively.

  A transparent window 68 is disposed on the upper wall 62 constituting the liquid chamber housing 58. An injection nozzle 70 is formed at the center of the lower wall 64 constituting the liquid chamber housing 56. A condensing point of the laser beam 27 collected by the condensing lens 50 is positioned at the ejection port 70 a that is the lower end of the ejection nozzle 70.

  A liquid inlet 66 communicating with the liquid chamber 56 is formed in the cylindrical side wall 60, and the liquid inlet 66 is connected to the high pressure liquid supply source 54. When a high-pressure liquid such as pure water is supplied from the high-pressure liquid supply source 54 into the liquid chamber 56 through the liquid inlet 66, the high-pressure liquid is ejected from the ejection port 70 a of the ejection nozzle 70 to form the liquid column 72. To do.

  A suction block 74 that defines an annular suction port 80 and a suction path 82 is attached to the lower end of the liquid chamber housing 58. A through hole 75 is formed at the center of the suction block 74, and a pipe 76 is press-fitted into the through hole 75. The pipe 76 and the spray nozzle 70 are aligned, and the liquid column 72 formed by spraying from the spray nozzle 70 is positioned so as to pass through the pipe 76.

  An annular outer wall 78 is formed on the outer periphery of the lower end of the suction block 74. The suction port 80 is formed in an annular shape so as to surround the liquid column 72 that collides with the processing point 11 a of the wafer 11, and is connected to the suction source 86 via an annular suction path 82 and a discharge port 84. The suction port 80, the suction path 82, and the suction source 86 constitute a suction means.

  Adjacent to the processing head 28, a cover liquid supply means 32 connected to the cover liquid supply source 34 shown in FIG. For example, pure water is used as the cover liquid. The cover liquid 33 supplied from the cover liquid supply means 32 covers the upper surface of the wafer 11, but an annular outer wall 78 having a slight gap from the upper surface of the wafer 11 is attached to the lower end portion of the processing head 28. The inflow of the cover liquid to the point 11a can be controlled to an appropriate amount by the annular outer wall 78, that is, to the extent that the vicinity of the processing point 11a is slightly covered with a small amount of cover liquid.

  Hereinafter, the operation of the laser processing apparatus configured as described above will be described. The laser beam 27 adjusted to a predetermined power by the power adjusting means 42 of the laser beam generating unit 25 is introduced into the machining head 28 from the beam introduction port 46 of the machining head 28, reflected by the mirror 48, and reflected by the condenser lens 50. The light is condensed on the ejection port 70 a of the ejection nozzle 70 formed in the liquid chamber housing 58 of the liquid ejection means 52.

  On the other hand, high-pressure liquid such as pure water supplied from the high-pressure liquid supply source 54 is introduced into the liquid chamber 56 from the liquid inlet 66 formed in the liquid chamber housing 58 of the liquid ejecting means 52, and A liquid column 72 is formed by being ejected from an ejection nozzle 70 formed on the lower wall 64, and the liquid column 72 guides the laser beam 27.

  The liquid column 72 passes through the pipe 76 press-fitted into the through hole 75 of the suction block 74, collides with the processing point 11 a of the wafer 11, and scatters. The laser beam 27 collected by the condensing lens 50 is guided (guided) to a liquid column 72 passing through the pipe 76, and the beam 11 is irradiated to the processing point 11a without being widened, so that the wafer 11 is laser processed. Grooves are formed.

  Debris (processing waste) is generated with laser processing, but a part of the generated debris forms a liquid column, is taken in by the liquid that collides with the processing point 11a, and operates the suction source 86. It is immediately sucked from the suction port 80 and removed from the upper surface of the wafer 11.

  Further, the remaining debris that has not been taken into the liquid is taken into the cover liquid supplied in a minute amount in the vicinity of the processing point 11a, and the cover liquid containing debris passes through the suction port 80 formed around the processing point 11a. It is sucked and sucked to the suction source 86 through the suction path 82 and the discharge port 84 and removed from the upper surface of the wafer 11.

  An experiment was conducted using a silicon wafer as the wafer 11 under the following processing conditions.

Light source: LD excitation Q switch Nd: YVO4 laser Wavelength: 532 nm
Average output: 6.6W
Repetition frequency: 40 kHz
Nozzle diameter: φ50μm
Fluid pressure: 20 MPa
Distance between pipe outlet and wafer: 0.4mm
Pipe inner diameter: 0.5mm
Suction flow rate: 25L / min

  When processing was performed under the above processing conditions while supplying the cover liquid from the cover liquid supply means 32, the depth, width and depth stability of the laser processing groove was as good as that of the configuration in which the cover liquid was not supplied. Processing was possible.

  In the configuration in which the cover liquid is supplied and the inflow of the cover liquid to the processing point 11a is controlled by the annular outer wall 78, the cover liquid containing debris is sucked and removed by the suction means, so that the cover liquid containing debris is placed on the wafer 11. The contamination of the wafer 11 can be kept to a minimum without spreading.

  In addition, since the wafer 11 is covered with the cover liquid 33, it does not dry, and even slightly remaining debris does not adhere to the wafer 11, so that the spinner cleaning device 30 can wash it efficiently.

2 Laser processing apparatus 11 Semiconductor wafer 18 Chuck table 24 Laser beam irradiation means 25 Laser beam generating unit 28 Processing head 32 Cover liquid supply means 52 Liquid injection means 54 High pressure liquid supply source 70 Injection nozzle 72 Liquid column 74 Suction block 76 Pipe 78 Annular Outer wall 80 Suction port 86 Suction source

Claims (2)

A laser processing apparatus comprising: a holding unit that holds a workpiece; and a laser beam irradiation unit that irradiates the workpiece held by the holding unit with a laser beam,
A cover liquid supply means for supplying a cover liquid to the workpiece and covering the upper surface of the workpiece with the cover liquid;
The laser beam irradiation means includes a laser beam generation means and a processing head,
The processing head includes a condensing lens that condenses the laser beam generated from the laser beam generating unit;
Liquid ejecting means for ejecting liquid onto a workpiece and forming a liquid column through which the laser beam condensed by the condenser lens is guided;
An outer wall disposed so as to surround the liquid column to control the inflow of the cover liquid to a processing point of the workpiece irradiated with the laser beam;
A suction means including a suction port disposed between the liquid column and the outer wall, and a suction source connected to the suction port;
Processing laser generated by irradiating the workpiece covered with the cover liquid with the laser beam is sucked together with the cover liquid by the suction means to be removed by suction from the workpiece. Processing equipment.   The laser processing apparatus according to claim 1, wherein the suction port is annularly disposed so as to surround the liquid column.

Images