JP5610991B2 - Laser processing equipment - Google Patents

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. Individual semiconductor devices are manufactured by dicing the semiconductor wafer along the streets.

  In recent years, as a method of dividing a workpiece such as a semiconductor wafer, a laser processing groove is formed in the workpiece by irradiating a pulsed laser beam along a street formed on the workpiece, and along the laser processing groove. A method of cleaving a workpiece with a mechanical braking device has been proposed (see, for example, JP-A-10-305421).

  However, when a semiconductor wafer is irradiated with a laser beam, the device is heated, which causes 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.

  Further, in a laser processing apparatus that forms a liquid column by jetting a high-pressure liquid onto a workpiece, the liquid that has formed the liquid column locally remains on the workpiece. In the case of cutting an intersecting division line such as a semiconductor wafer with a laser processing apparatus, there is a problem that the liquid column is disturbed by the remaining liquid and the laser beam is refracted.

  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, the holding means for holding the workpiece, the laser beam irradiation means for irradiating the workpiece held by the holding means with the laser beam, and the laser beam irradiation means and the holding means are processed and fed. A processing feed means for relatively moving in a direction, wherein the laser beam irradiation means and the holding means are irradiated with a laser beam from the laser beam irradiation means to the work feed direction. Cover liquid supply means for supplying the cover liquid to the work piece from the downstream side to the upstream side in the direction in which the work proceeds on the work piece by relative movement to the work piece and covering the upper surface of the work piece with the cover liquid The laser beam irradiation means includes a laser beam generation means and a processing head, and the processing head collects the laser beam generated from the laser beam generation means. Liquid ejecting means for ejecting liquid onto the workpiece and forming a liquid column through which the laser beam condensed by the condensing lens is guided; and disposed on the outer peripheral side of the liquid column; And a prevention wall that surrounds the liquid column and forms a slight gap with the upper surface of the workpiece to prevent the flow of the cover liquid from colliding with the liquid column. There is provided a laser processing apparatus having an opening formed on the upstream side in the direction in which the processing in which the liquid forming the liquid column flows out.

  Preferably, the processing head surrounds the liquid column on the inner peripheral side of the prevention wall and supplies gas to the cover liquid in order to reduce the thickness of the cover liquid covering the upper surface of the workpiece on the inner peripheral side of the prevention wall. Gas ejecting means for ejecting is further provided.

  According to the laser processing apparatus of the present invention, since the upper surface of the workpiece being processed is covered with the cover liquid, debris generated by the processing is taken into the cover liquid and removed together with the cover liquid from the upper surface of the workpiece. Therefore, debris is prevented from adhering to the upper surface of the workpiece.

  In addition, since the cover liquid is prevented from colliding with the liquid column by the prevention wall disposed around the liquid column, the flow of the liquid column is not disturbed by the cover liquid, and the liquid column does not disturb the laser. The beam can be properly guided to the processing point.

  According to the invention described in claim 2, since the cover liquid covering the upper surface of the workpiece is thinned on the inner peripheral side of the prevention wall by the gas ejected by the gas ejecting means, the liquid column is disturbed by the cover liquid. The laser beam can be prevented from being refracted.

It is a schematic block diagram of the laser processing apparatus which concerns on 1st Embodiment of this invention. It is a longitudinal cross-sectional view of a process head part. It is a block diagram of a laser beam generation unit. It is a principal part expanded sectional view of the processing head shown in FIG. It is a cross-sectional view which shows the flow of the cover liquid of embodiment shown in FIG. FIG. 6 is a modification of the embodiment of FIG. 5, and is a cross-sectional view illustrating the flow of the cover liquid when the opening of the prevention wall is formed large. It is a schematic block diagram of the laser processing apparatus which concerns on 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration diagram of a laser processing apparatus 2 according to the first 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 image 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 21 of the alignment means 20 is provided with a cover liquid supply means 32 connected to a cover liquid supply source 34.

  In this embodiment, the cover liquid supply means 32 is composed of a pipe-shaped member having a plurality of pores for supplying the cover liquid, but the cover liquid supply means 32 covers the upper surface of the entire workpiece. Can be supplied to the workpiece, and the form is not limited to the pipe-shaped member.

  Reference numeral 31 denotes transport means for transporting the wafer 11 after laser processing to the spinner cleaning apparatus 30. The spinner cleaning apparatus 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. The condensing point of the laser beam 27 condensed by the condensing lens 50 is positioned at the upper end portion 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 nozzle 70 to form a liquid column 72.

  A pipe support block 74 is attached to the lower end portion of the liquid chamber housing 58. A through hole 75 is formed in the central portion 74 a of the pipe support block 74, and the 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.

  As best shown in the enlarged sectional view of FIG. 4, an annular prevention wall 78 and an annular inner peripheral wall 80 are fixed to the pipe support block 74. A gap G between the lower end of the annular prevention wall 78 and the upper surface of the wafer 11 is set to 0.1 to 1 mm.

  Compressed air from the air source 88 shown in FIG. 2 is introduced into the air passage 84 formed in the pipe support block 74 through the pipe 86, and is blown from the air jet port 90 as shown by an arrow 92 in FIG. .

  In FIG. 2, the arrow A indicates the machining feed direction of the chuck table 18, and the arrow B indicates the direction in which machining progresses on the wafer 11 by forming and feeding the chuck table 18 in the A direction while irradiating a laser beam (a laser machining groove is formed). Direction).

  The cover liquid supply means 32 is disposed downstream of the processing head 28 in the direction of processing indicated by arrow B, and supplies the cover liquid 33 to cover the upper surface of the wafer 11 with the cover liquid 33.

  The cover liquid supply means 32 may be disposed on the downstream side in the direction in which the processing proceeds with respect to the processing head 28, and the cover liquid supply pipe 96 is disposed at a position as shown in the second embodiment shown in FIG. You may set up.

  As shown in FIG. 7, it is preferable to provide an air blowing means such as an air blowing pipe 98 on the downstream side in the direction in which the processing of the cover liquid supply pipe 96 proceeds. This also applies to the first embodiment shown in FIG. 2, and it is preferable to provide an air blowing means on the downstream side in the direction in which the processing of the cover liquid supply means 32 proceeds. By providing this air blowing means, the flow of the cover liquid 33 can be effectively formed.

  As shown in FIG. 5, the annular prevention wall 78 has an opening 79 on the upstream side in the working direction, that is, on the downstream side of the cover liquid flow indicated by the arrow 94. The liquid forming the liquid column 72 is discharged through the opening 79 of the annular prevention wall 78 as indicated by an arrow C.

  As an alternative embodiment of the annular prevention wall 78, as shown in FIG. 6, the annular prevention wall 78A may have a large opening 79A formed on the upstream side in the processing progress direction. In the case of this embodiment, the cover liquid flow 94A is strengthened to some extent so that the cover liquid that flows from the downstream side to the upstream side in the processing progress direction does not enter the annular prevention wall 78A from the opening 79A of the annular prevention wall 78A. It is preferable to do this.

  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 upper end portion 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 pipe support 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.

  On the other hand, since the upper surface of the wafer 11 is covered with the cover liquid 33 supplied from the cover liquid supply means 32, the debris (processing waste) generated by the laser processing as shown by the arrow A in FIG. It is removed from the upper surface of the wafer 11 through the opening 79 of the annular prevention wall 78. Therefore, debris is prevented from adhering to the upper surface of the wafer 11.

  Further, the cover liquid 33 supplied from the cover liquid supply means 32 is prevented from colliding with the liquid column 72 by the annular prevention wall 78 disposed so as to surround the liquid column 72. The flow of the column 72 is prevented from being disturbed.

  Further, since the cover liquid 33 covering the upper surface of the wafer 11 is thinned by the air blow 92 ejected from the air ejection port 90 on the inner peripheral side of the annular prevention wall 78, the liquid column 72 is disturbed by the cover liquid 33. The laser beam 27 is not refracted, and the laser beam 27 is irradiated to the processing point 11 a at an appropriate position to form a laser processing groove on 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
Air volume: 5L / min

  When the cover liquid was not supplied, the liquid column was disturbed by the liquid that formed the liquid column that remained locally on the wafer 11, resulting in processing defects such as a laser processing groove not being formed in part. When processing was performed under the above processing conditions while supplying the cover liquid 33 from the cover liquid supply means 32 as in this example, satisfactory laser processing could be performed.

  In the present embodiment, the cover liquid 33 is supplied from the cover liquid supply means 32 and the inflow of the cover liquid 33 to the processing point 11a is controlled by the annular prevention wall 78. Therefore, the cover liquid containing debris is the liquid column 72. Since the liquid is discharged through the opening 79 of the annular prevention wall 78 together with the liquid formed, contamination of the wafer 11 can be kept to a minimum.

  In addition, since the wafer 11 is always 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 25 Laser beam generating unit 28 Processing head 32 Cover liquid supply means 33 Cover liquid 52 Liquid injection means 54 High pressure liquid supply source 70 Injection nozzle 72 Liquid column 74 Pipe support block 76 Pipe 78 Annular prevention Wall 88 Air source 90 Air outlet

Claims (2)

A holding means for holding the workpiece, a laser beam irradiation means for irradiating the workpiece held by the holding means with a laser beam, and the laser beam irradiation means and the holding means are moved relative to each other in the machining feed direction. A laser processing apparatus comprising a processing feed means,
By moving the laser beam irradiation means and the holding means relative to each other in the processing feed direction while irradiating the workpiece with the laser beam from the laser beam irradiation means, the downstream side in the direction in which the processing proceeds on the workpiece A cover liquid supply means for supplying a cover liquid to the work piece from the upstream side to cover the upper surface of the work piece 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 the workpiece and forming a liquid column through which a laser beam condensed by the condenser lens is guided;
The liquid column is disposed on the outer peripheral side to surround the liquid column, and a slight gap is formed between the liquid column and the upper surface of the workpiece to prevent the cover liquid flow from colliding with the liquid column. And prevent wall
The laser processing apparatus, wherein the prevention wall has an opening formed on an upstream side in a direction in which the processing in which the liquid forming the liquid column flows out.   The processing head surrounds the liquid column on the inner peripheral side of the prevention wall to reduce the thickness of the cover liquid covering the upper surface of the workpiece on the inner peripheral side of the prevention wall. The laser processing apparatus according to claim 1, further comprising gas jetting means for jetting gas.

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