JP2013121598A - Method for cutting workpiece, and laser machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a workpiece cutting method that can prevent debris from adhering to the surface of the workpiece, and to provide a laser machining device suitable for implementing the cutting method.SOLUTION: The workpiece cutting method for cutting a workpiece along scheduled cutting lines by irradiating the workpiece, which is provided with a plurality of scheduled cutting lines crossing each other on a surface thereof, with a laser beam, and dividing the workpiece into individual chips, includes: a holding step of holding the workpiece by a holding tool with a predetermined space provided below the scheduled cutting lines of the workpiece; and a cutting step of cutting the workpiece along the scheduled cutting lines to produce a plurality of chips by forming a liquid column by jetting liquid along the scheduled cutting lines of the workpiece after the holding step, and irradiating the workpiece with a laser beam along the cutting lines of the workpiece by guiding the laser beam into the liquid column.

Description

  The present invention relates to a workpiece cutting method for irradiating a workpiece with a laser beam and cutting the workpiece into a plurality of chips, and a laser processing apparatus for cutting the workpiece.

  In a semiconductor device manufacturing process, a plurality of regions are defined by planned cutting lines called streets formed in a lattice shape on the surface of a semiconductor wafer having a substantially disk shape, and devices such as IC and LSI are defined in the 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).

  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 has been proposed a laser processing apparatus (water jet laser processing apparatus) that performs desired processing by irradiating a workpiece with a laser beam that has been irradiated with light (for example, Japanese Patent Publication No. Hei 2-1621, JP 2001- No. 321977 and Japanese Patent Application Laid-Open No. 2011-41962).

  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 2011-41962 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. Part of the generated debris is taken up in the liquid forming the liquid column.

  However, as the liquid column colliding with the processing point is scattered on the surface of the workpiece, there is a problem that debris generated in the processing included in the liquid forming the liquid column adheres to the surface of the workpiece.

  The present invention has been made in view of the above points, and an object of the present invention is to implement a cutting method of a workpiece capable of preventing debris from adhering to the surface of the workpiece, and the cutting method. It is providing the laser processing apparatus suitable for this.

  According to the first aspect of the present invention, a workpiece having a plurality of intersecting scheduled cutting lines set on the surface is irradiated with a laser beam to cut the workpiece along the scheduled cutting lines into individual chips. A method of cutting a workpiece to be divided, the holding step of holding the workpiece with a holding means in a state where a predetermined space is provided below the line to be cut of the workpiece, and the holding step is performed. Thereafter, liquid is ejected along the planned cutting line of the workpiece to form a liquid column, and the laser beam is guided along the planned cutting line by guiding the laser beam into the liquid column. A cutting method for irradiating a workpiece and cutting the workpiece along the planned cutting line to form a plurality of chips is provided.

  According to a second aspect of the present invention, there is provided a laser processing apparatus for cutting a workpiece having a plurality of intersecting scheduled cutting lines set on the surface along the scheduled cutting line, and holding means for holding the workpiece. And laser beam irradiation means for irradiating the workpiece held by the holding means with a laser beam, the laser beam irradiation means being generated from the laser beam generation means and the laser beam generation means. A processing head having a condensing lens that condenses a laser beam, and a liquid ejecting unit that ejects a liquid onto a workpiece and forms a liquid column through which the laser beam condensed by the condensing lens is guided. The holding means includes a liquid column escape groove that divides a plurality of chip holding areas corresponding to the cutting lines of the workpiece, suction holes respectively formed in the chip holding areas, and Suction hole The laser processing apparatus is provided which is characterized by having a suction line connected to a suction source communicating.

  In the cutting method of the present invention, the workpiece is held in a state where a predetermined space is provided below the line to be cut. Thereafter, a liquid is ejected along a planned cutting line to form a liquid column, and the workpiece is irradiated with a laser beam guided into the liquid column.

  The liquid forming the liquid column flows out into the space below the workpiece through the cut groove of the workpiece cut by the laser beam. Accordingly, since the liquid forming the liquid column is not scattered on the surface of the workpiece, debris taken in the liquid is prevented from adhering to the surface of the workpiece.

  Furthermore, because the liquid that forms the liquid column flows out into the space below the workpiece, so-called recasting that causes debris to adhere to the cut side surface of the workpiece can be prevented, so even thicker workpieces can be cut. It becomes.

1 is a perspective view of a laser processing apparatus according to an embodiment of the present invention. It is a block diagram of a laser beam generation unit. It is a surface side perspective view of a semiconductor wafer. It is sectional drawing of the state which attracted and held the semiconductor wafer with the chuck table. It is a longitudinal cross-sectional view of the chuck table holding the processing head and wafer during laser processing.

  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 mechanism 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 mechanism 22 including 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 machining feed mechanism 12 and the index feed mechanism 22. At the same time, it is rotated by a motor accommodated in the cylindrical support member 26.

  As shown in FIGS. 4 and 5, a plurality of suction grooves 23 and liquid column escape grooves 25 are formed on the surface of the chuck table 28. Reference numeral 32 denotes a water cover. A bellows (not shown) is connected to the water cover 32 to protect the processing feed mechanism 12 and the index feed mechanism 22 from liquids such as 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 unit 52 is attached to the front end 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.

  Referring to FIG. 3, there is shown a front side perspective view of a semiconductor wafer (hereinafter sometimes simply referred to as a wafer) 11 which is a kind of workpiece. The wafer 11 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of streets (scheduled lines) 13 are formed in a lattice shape on the surface 11a, and an IC is formed in each region partitioned by the plurality of streets 13. A device 15 such as an LSI is formed.

  The thus configured semiconductor wafer 11 includes a device region 17 in which the device 15 is formed and an outer peripheral surplus region 19 that surrounds the device region 17 in a flat portion on the surface thereof. An arc-shaped chamfered portion 11 e is formed on the outer peripheral portion of the semiconductor wafer 11. Reference numeral 21 denotes a notch as a mark indicating the crystal orientation of the silicon wafer.

  In order to cut the wafer 11 along the scheduled cutting line 13, the wafer 11 is sucked and held by the chuck table 28 of the laser processing apparatus 2 as shown in FIG. 4. The chuck table 28 has a plurality of chip holding areas 28 a corresponding to the devices 15 of the wafer 11, and a suction hole 23 is formed in each chip holding area 28 a. These suction holes 23 are selectively connected to a negative pressure suction source 54 via a suction path 27.

  The chuck table 28 further has a liquid column escape groove 25 that defines a plurality of chip holding regions 28 a corresponding to the scheduled cutting line 13 of the wafer 11. The depth of the liquid column escape groove 25, which is a predetermined space provided below the wafer 11, is preferably 3 mm or more.

  In the cutting method of the present invention, when the wafer 11 is mounted on the chuck table 28, the respective cutting scheduled lines 13 are positioned and mounted so as to correspond to the liquid column escape grooves 25. For this positioning, for example, a positioning pin or the like provided on the chuck table 28 is used.

  Next, a detailed structure of the machining head 42 and a method for cutting the wafer 11 will be described with reference to FIG. The pulsed laser beam 55 adjusted to a predetermined power by the power adjusting means 50 of the laser beam generating unit 38 enters the processing head 42 from the beam introduction port 58 formed in the housing 56 of the processing head 42 as shown in FIG. be introduced.

  A mirror 60 that reflects the laser beam and a condenser lens 62 that condenses the laser beam are disposed in the housing 56. A liquid chamber housing 68 that defines a liquid chamber 66 of the liquid ejecting means 64 integrally with the housing 56 is formed. The liquid chamber housing 68 includes a cylindrical side wall 70, and an upper wall 72 and a lower wall 74 that close the upper and lower surfaces of the side wall 70, respectively.

  A transparent window 78 is disposed on the upper wall 72 constituting the liquid chamber housing 68. An injection nozzle 80 is formed at the center of the lower wall 74 constituting the liquid chamber housing 68. A condensing point of the laser beam 55 collected by the condensing lens 62 is positioned at the ejection port 80a which is the lower end of the ejection nozzle 80.

  The cylindrical side wall 72 has a liquid inlet 76 communicating with the liquid chamber 66, and the liquid inlet 76 is connected to a liquid supply source 84 via a pump 82. The liquid supply source 84 stores a liquid such as pure water, and the liquid pressurized to a predetermined pressure by the pump 82 is supplied into the liquid chamber 66 through the liquid inlet 76. When the high-pressure liquid is supplied into the liquid chamber 66, the high-pressure liquid is ejected from the ejection port 80 a of the ejection nozzle 80 to form the liquid column 86.

  A block 88 is attached to the lower end portion of the liquid chamber housing 68. A through hole 89 is formed at the center of the block 88, and a pipe 90 is press-fitted into the through hole 89. The pipe 90 and the injection nozzle 80 are aligned, and the liquid column 86 formed by being injected from the injection nozzle 80 is positioned so as to pass through the pipe 90.

  Hereinafter, the operation of the laser processing apparatus configured as described above will be described. The laser beam 55 adjusted to a predetermined power by the power adjusting means 50 of the laser beam generating unit 38 is introduced into the processing head 42 from the beam introduction port 58 of the processing head 42, reflected by the mirror 60, and reflected by the condenser lens 62. The light is condensed on the ejection port 80 a of the ejection nozzle 80 formed in the liquid chamber housing 68 of the liquid ejection means 64.

  On the other hand, a high-pressure liquid such as pure water pressurized to high pressure by the pump 82 is supplied into the liquid chamber 66 from the liquid inlet 76 formed in the liquid chamber housing 68 of the liquid ejecting means 64, and A liquid column 86 is formed by being ejected from an ejection nozzle 80 formed on the lower wall 74, and the liquid column 86 guides the laser beam 55.

  The liquid column 86 passes through the pipe 90 press-fitted into the through hole 89 of the block 88, collides with the processing point of the wafer 11 and scatters. The laser beam 55 condensed by the condensing lens 62 is guided (guided) to a liquid column 86 passing through the pipe 90, and the laser beam irradiates the processing point without penetrating the beam diameter and penetrates the wafer 11. A processing groove 29 is formed. The liquid forming the liquid column 86 flows out into the liquid column escape groove 25 which is a space below the wafer 11 through the laser processing groove 29 penetrating the wafer 11.

  Debris (machining waste) is generated along with the laser processing, but the generated debris 85 is taken into the liquid 87 forming the liquid column 86 and flows out into the liquid column escape groove 25. According to the present embodiment, since the liquid 87 forming the liquid column 86 is not scattered on the surface 11 a of the wafer 11, the debris 85 contained in the liquid 87 is prevented from adhering to the surface 11 a of the wafer 11. The

  Further, since the liquid 87 forming the liquid column 86 flows out into the liquid column escape groove 25 which is a space below the wafer 11, it is possible to prevent so-called recast that the debris 85 adheres to the cut side surface of the wafer 11. Even thicker workpieces can be cut.

  The laser processing conditions used in the cutting method of this embodiment are as follows, for example.

Light source: LD excitation Q switch Nd: YVO4 pulse laser Wavelength: 532 nm (second harmonic of YVO4 laser)
Average output: 6.6W
Repetition frequency: 40 kHz
Fluid pressure: 20 MPa

  In the above-described embodiments, the method for cutting a semiconductor wafer as a workpiece has been described. However, the workpiece is not limited to a semiconductor wafer, and an optical device wafer, a ceramic substrate, a resin having a sapphire substrate, a SiC substrate, or the like. The cutting method of the present invention can be similarly applied to a substrate or the like.

2 Laser processing apparatus 11 Semiconductor wafer 23 Suction hole 25 Liquid column escape groove 28 Chuck table 36 Laser beam irradiation unit 38 Laser beam generation unit 42 Processing head 64 Liquid injection means 80 Injection nozzle 82 Pump 84 Liquid supply source 86 Liquid column 90 Pipe

Claims (2)

A workpiece cutting method in which a workpiece having a plurality of intersecting scheduled cutting lines set on the surface is irradiated with a laser beam, the workpiece is cut along the scheduled cutting lines, and divided into individual chips. There,
A holding step of holding the workpiece by the holding means in a state in which a predetermined space is provided below the planned cutting line of the workpiece;
After performing the holding step, liquid is ejected along the planned cutting line of the workpiece to form a liquid column, and a laser beam is guided into the liquid column, thereby along the planned cutting line. A cutting step of irradiating the workpiece with the laser beam and cutting the workpiece along the planned cutting line to form a plurality of chips;
A method of cutting a workpiece, comprising: A laser processing apparatus for cutting a workpiece having a plurality of intersecting scheduled cutting lines set on the surface along the scheduled cutting lines,
Holding means for holding the workpiece;
Laser beam irradiation means for irradiating a workpiece held by the holding means with a laser beam,
The laser beam irradiation means includes:
Laser beam generating means;
A condensing lens for condensing the laser beam generated from the laser beam generating means and a liquid column for injecting a liquid onto the workpiece and guiding the laser beam condensed by the condensing lens are formed. A processing head having a liquid ejecting means,
The holding means communicates with the liquid column escape grooves that respectively correspond to the cutting lines of the workpiece and define a plurality of chip holding areas, suction holes formed in the chip holding areas, and the suction holes. And a suction path connected to the suction source.

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