JP5501098B2 - 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, by a laser beam guided from a water column generating means to a formed water column. 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 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.

  Therefore, when forming the laser processing groove along the street of the semiconductor wafer, the surface of the semiconductor wafer is previously coated with a water-soluble protective film, and a laser beam is irradiated through this protective film. A process for coating the surface of the wafer with a protective coating must be added, resulting in poor productivity. 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 lowered.

  Therefore, as a laser processing method for eliminating the influence of debris generated by irradiating the laser beam and preventing the workpiece from being heated, high pressure water is sprayed on the workpiece to form a water column. There has been proposed a laser processing apparatus that performs desired processing by irradiating a workpiece with a laser beam transmitted (guided) inside (for example, Japanese Patent Publication No. 2-1621, Japanese Patent No. 3871240, JP, 2006-255769, A).

  In these laser processing apparatuses, the heat generated during laser processing is cooled by water, so that it is possible to prevent degradation of the quality of the work piece due to heat, further suppress the scattering of debris, and the focus of the laser beam is a thread-like water. Therefore, a semiconductor wafer, which is a kind of workpiece, can be divided into individual devices with uniform processing quality even if the surface of the workpiece has waviness.

Japanese Patent Laid-Open No. 10-305421 Japanese Patent Publication No.2-1621 Japanese Patent No. 3871240 JP 2006-255769 A

  However, in a conventional laser processing apparatus using a water column formed by jetting from a jet port (water column generating port), when the laser beam is irradiated onto water, fine bubbles and heat are generated to refract the laser beam. There is a problem that the laser beam is not properly guided to the filamentous water column.

  The present invention has been made in view of these points, and an object of the present invention is to provide a laser processing apparatus that does not affect the optical path of a laser beam even if water bubbles and heat are generated by irradiation of the laser beam. It is.

  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. The means includes a laser beam generating means and a processing head. The processing head condenses the laser beam generated from the laser beam generating means, and the laser focused by the condensing lens. Water column generating means for generating a string of water-like water that guides the beam to the workpiece, the water column generating means comprising: a water source; a pump connected to the water source for delivering water; and water pumped by the pump A laminar flow chamber defined by the top, bottom, and sides that generate the incoming water into a laminar flow, and a thread-like water column formed at the bottom of the laminar flow chamber. Water sprayed on the workpiece A generating port, an outlet for generating water flow from the laminar flow chamber and crossing the water column generating port, and a laser formed at the top of the laminar flow chamber and focused by the condenser lens And a transmission window for receiving the beam.

  Preferably, the outlet is connected to a throttle valve, and the flow rate per unit time of the throttle valve and the flow rate per unit time of the water column generating port are substantially the same.

  In the present invention, since the outflow port is formed in the laminar flow chamber so as to generate a flow of water across the water column generating port for generating the filamentous water column, fine bubbles and heat are generated in the laminar flow chamber by irradiation of the laser beam. Even if these occur, they are not discharged from the outlet and do not refract the laser beam, and the laser beam can be properly guided to the water column.

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

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, an external perspective view of a laser processing apparatus according to an embodiment of the present invention is shown. The laser processing apparatus 2 includes a first slide block 6 mounted on a stationary base 4 so as to be movable in the X-axis direction.

  The first slide block 6 is moved in the machining feed direction, that is, the X-axis direction along the pair of guide rails 14 by the machining feed means 12 including the ball screw 8 and the pulse motor 10.

  A second slide block 16 is mounted on the first slide block 6 so as to be movable in the Y-axis direction. That is, the second slide block 16 is moved along the pair of guide rails 24 by the index feed means 22 constituted by the ball screw 18 and the pulse motor 20 in the index feed direction, that is, the Y-axis direction.

  A chuck table 28 is mounted on the second slide block 16 via a cylindrical support member 26, and the chuck table 28 can be moved in the X-axis direction and the Y-axis direction by the processing feed means 12 and the index feed means 22. At the same time, it is rotated by a motor accommodated in the cylindrical support member 26.

  The chuck table 28 is provided with a clamp 30 for clamping the semiconductor wafer sucked and held by the chuck table 28. 32 is a water cover, and a bellows (not shown) is connected to the water cover 32 to protect the processing feed means 12 and the index feed means 22 from water.

  A column 34 is erected on the stationary base 4, and a laser beam irradiation mechanism (laser beam irradiation means) 36 is attached to the column 34. The laser beam irradiation mechanism 36 includes a laser beam generation unit 38 housed in the casing 40 and a processing head 42 attached to the tip of the casing 40. An imaging means 52 is attached to the tip of the casing 40 in alignment with the machining head 42 in the X-axis direction.

  As shown in FIG. 2, the laser beam generating unit 38 includes a laser oscillator 44 that oscillates a YAG laser or a YVO4 laser, a repetition frequency setting unit 46, a pulse width adjusting unit 48, and a power adjusting unit 50. . Although not particularly shown, the laser oscillator 44 has a Brewster window, and the laser beam emitted from the laser oscillator 44 is a linearly polarized laser beam.

  The pulse laser beam adjusted to a predetermined power by the power adjusting means 50 of the laser beam generating unit 38 is introduced into the machining head 42 from a beam introduction port 57 formed in the housing 54 of the machining head 42 as shown in FIG. Is done.

  In the housing 54, a mirror 56 for reflecting the laser beam and a condenser lens 58 for condensing the laser beam are disposed. A laminar flow chamber housing 62 that defines a laminar flow chamber 76 of the water column generating means 60 is formed integrally with the housing 54.

  The water column generating means 60 includes a water source 80 shown in FIG. 1, a pump 82 that is connected to the water source 80 and delivers water pressurized to a predetermined pressure, and a laminar flow chamber housing 62 that defines a laminar flow chamber 76. Consists of

  The laminar flow chamber housing 62 has a top (top wall) 64, a bottom (bottom wall) 66, and a pair of side walls 68 shown in FIG. The bottom 66 is formed with a water column generating port (spout port) 70 for generating a thread-like water column 71, and the top 64 is formed with a transmission window 72 for receiving the laser beam condensed by the condenser lens 58. Has been.

  The laminar flow chamber housing 62 further generates a flow of water that flows out from the laminar flow chamber 76 and crosses the water column generating port 70, and an inlet 74 that receives the water pressurized and delivered by the pump 82 to about 35 MPa. An outlet 78 is provided. The outlet 78 communicates with the drain 86 via the throttle valve 84.

  The laminar flow chamber 76 has a substantially square cross section, and the dimensions of one side of the inflow port 74 and the outflow port 78 are set to about 1 to 2 mm. The water column generating port 70 has a size of φ20 to 150 μm, and the inner diameter of the throttle valve 84 is also set to a size of φ20 to 150 μm.

  Hereinafter, the operation of the laser processing apparatus configured as described above will be described. A laser beam 55 having a wavelength that is absorptive with respect to the wafer W adjusted to a predetermined power by the power adjusting means 50 of the laser beam generating unit 38 is introduced into the machining head 42 from the beam introduction port 57 of the machining head 42. The light is reflected by the mirror 56 and collected by the condenser lens 58 between the upper end 70 a and the lower end 70 b of the water column generating port 70 formed at the bottom 66 of the laminar flow chamber housing 62.

  On the other hand, high-pressure water such as pure water supplied from the pump 82 is introduced into the laminar flow chamber 76 from the inlet 74 formed in the laminar flow chamber housing 62 of the water column generating means 60, and the bottom 66 of the laminar flow chamber 76. The water column 71 is ejected from the water column generating port 70 formed in the above manner to form a thread-like water column 71. At the same time, the high-pressure water in the laminar flow chamber 76 flows out from the outflow port 78 and is discharged to the drain 86 through the throttle valve 84.

  The amount of water per unit time passing through the throttle valve 84 is set to be substantially the same as the amount of water per unit time passing through the water column generating port 70. Since the laminar flow chamber housing 62 of the present embodiment has an outlet 78 for generating a flow of water across the water column generating port 70 in the laminar flow chamber 76, the laminar flow chamber housing 62 in the laminar flow chamber 76 is irradiated with the laser beam. Even if fine bubbles and heat are generated, these fine bubbles and heat are discharged from the outlet 78, so that the laser beam can be properly guided to the thread-like water column 71 without refracting the laser beam 55. .

  The water column 71 collides with the processing point S of the wafer W and scatters. The laser beam 55 collected by the condensing lens 58 is guided (guided) to the water column 71 and irradiated to the processing point S without widening the beam diameter to form a laser processing groove along the street of the wafer W. To do.

  According to the present embodiment described above, since the outlet 78 is formed in the laminar flow chamber housing 62 of the water column generating means 60 so as to generate a flow of water across the water column generating port 70 in the laminar flow chamber 76, the laser is generated. Even if fine bubbles and heat are generated in the laminar flow chamber 76 by the irradiation of the beam 55, these are positively discharged from the outlet 78. Therefore, the fine bubbles and heat generated in the laminar flow chamber 76 can appropriately guide the laser beam 55 to the water column 71 without refracting the laser beam 55.

2 Laser processing apparatus 28 Chuck table 36 Laser beam irradiation mechanism 38 Laser beam generating unit 42 Processing head 58 Condensing lens 60 Water column generating means 62 Laminar flow chamber housing 70 Water column generating port 71 Water column 72 Transmission window 74 Inlet port 76 Laminar flow chamber 78 Outlet 80 Water source 82 Pump 84 Throttle valve

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,
The laser beam irradiation means includes a laser beam generation means and a processing head,
The processing head generates a condensing lens that condenses the laser beam generated from the laser beam generating means, and a thread-like water column that guides the laser beam condensed by the condensing lens to a workpiece. Water column generating means,
The water column generating means includes a water source, a pump connected to the water source for sending water, an inlet for receiving the water sent out by the pump, a top, a bottom, and a side part for generating the flowing water into a laminar flow. A laminar flow chamber defined by the water flow, a water column generating port formed at the bottom of the laminar flow chamber to generate a thread-like water column and spraying it on the workpiece, An outlet for generating a flow of water across the water column generating port; a transmission window for receiving a laser beam formed on the top of the laminar flow chamber and collected by the condenser lens;
A laser processing apparatus comprising:   The laser processing according to claim 1, wherein the outlet is connected to a throttle valve, and the flow rate per unit time of the throttle valve and the flow rate per unit time of the water column generating port are substantially the same. apparatus.

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