JP2013163216A - Laser beam machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam machining device equipped with a dust discharging unit, in which dust generated by an abrasion processing does not disturb the light path of a laser beam.SOLUTION: A laser beam machining device is equipped with a dust discharging means which sucks in and discharges dust generated in the vicinity of a processing point caused by the abrasion processing of a laser beam passing through the interior, being arrangedly provided in the lower end of a condenser, wherein the dust discharging means is equipped with a first chamber which is connected to the condenser through a laser beam transmission window, and a second chamber which sucks in and exhausts the dust, being communicated with the lower end of the first chamber. The ratio of air flow volume supplied to the first chamber from an air supply means and an exhaust flow volume which the dust suck-in/exhaust means sucks in through the second chamber is adjusted to be in the range of 1:10-1:30.

Description

  The present invention relates to a laser processing apparatus for irradiating a surface of a workpiece such as a wafer with a laser beam to form a laser processing groove by ablation processing.

  In a 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 ICs, LSIs, and the like are divided into the partitioned regions. Form the device. Each semiconductor chip is manufactured by dividing the semiconductor wafer by cutting the semiconductor wafer along the streets.

  In addition, an optical device wafer in which an optical device such as a light emitting diode (LED) or a laser diode (LD) is formed on the surface of a sapphire substrate is also divided into individual optical devices by cutting along the street, and the divided light Devices are widely used in electrical equipment.

  As a method of dividing a wafer such as a semiconductor wafer or an optical device wafer along the street, ablation processing is performed by irradiating a pulse laser beam having a wavelength that absorbs the wafer along the street formed on the wafer. There has been proposed a method of forming a laser processing groove and breaking the optical device wafer along the laser processing groove.

  However, in this laser processing process, when a semiconductor wafer or optical device wafer is irradiated with a laser beam, silicon or sapphire melts to generate fine dust called molten debris, or debris, which is scattered and formed on the wafer. There is a problem that the quality of the device is deteriorated by adhering to the surface of the formed device. Furthermore, there is a problem in that the scattered dust adheres to a condenser objective lens incorporated in a condenser that irradiates a laser beam, thereby hindering the irradiation of the laser beam.

  As a countermeasure, for example, a dust discharge means that includes a jet outlet that jets air along the optical axis of the condenser objective lens, and sucks debris from around the jet outlet to prevent debris from accumulating on the surface of the device. Has been proposed (see JP 2007-69249 A).

JP 2007-69249 A JP 2011-189400 A

  However, when laser processing is actually performed with the laser processing apparatus disclosed in Patent Document 1, the generated debris is sucked from the entire periphery so as to surround the laser beam, and thus is sucked by the suction means from the generation of the debris. By now, debris will cross the laser beam.

  As a result, there has been a situation in which the laser beam cannot be stably irradiated onto the workpiece, and the depth and width of the formed laser processing groove become unstable. As a result, there has been a problem that the wafer cannot be uniformly divided into individual devices.

  The present invention has been made in view of these points, and the object of the present invention is to allow dust generated by ablation to be sucked and exhausted without traversing the optical path of the laser beam. It is providing the laser processing apparatus provided with the dust discharge unit.

  According to the present invention, there is provided a chuck table for holding a workpiece, and a condenser for irradiating the surface of the workpiece held on the chuck table with a laser beam to form a laser processing groove by ablation processing. A laser beam irradiation means, and a dust discharge means for sucking and discharging dust generated near the processing point by ablation processing of the laser beam disposed at the lower end of the condenser and passing through the inside In the processing apparatus, the dust discharge means generates an airflow flowing from the collector side to the processing point side around the laser beam passing through the inside, and the dust is directed toward the collector side. A first supply chamber that communicates with a lower end of the first chamber, and a second chamber that sucks and exhausts the dust, and the first chamber communicates with a gas supply means. In Subsequently, a laser beam transmission window formed of a transparent member that allows transmission of the laser beam is disposed on the ceiling of the first room, and the second room is formed on the surface of the workpiece. And a suction exhaust passage communicating with the suction exhaust means, and the ratio of the gas flow rate supplied from the gas supply means and the exhaust flow rate suctioned by the suction exhaust means is 1:10 to 10. A laser processing apparatus characterized by being adjusted within a range of 1:30 is provided.

  Preferably, the gas flow rate supplied from the gas supply unit is 100 ml / min or less, and the exhaust flow rate sucked by the suction exhaust unit is 100 ml / min or more. Preferably, the second chamber of the dust discharging means includes a first flow path and a second flow path in the direction of both sides of the processing groove centering on the laser beam through the dust flow path from the processing point to the suction exhaust path through the bottom opening. A flow path branching section that branches into the flow path.

  According to the laser processing apparatus of the present invention, the ratio of the gas flow rate supplied from the gas supply unit to the first chamber of the dust discharge unit and the exhaust flow rate suctioned by the suction exhaust unit from the second chamber is 1:10 to 10. Since the adjustment is made within the range of 1:30, the dust generated by laser processing can be smoothly exhausted to the suction exhaust means without leaking without directing the dust to the collector side.

  If gas is supplied and exhausted outside the range of this ratio, turbulence will occur in the flow of dust to the suction and exhaust means, etc., so dust will adhere and accumulate in and near the dust discharge means, This accumulation causes a phenomenon that the flow of exhaust gas is further disturbed.

  However, if gas is supplied and exhausted at this ratio, it will succeed in significantly reducing the adhesion of dust to the dust discharge means by smooth exhaust while maintaining a good processing state. The effective cleaning interval can be greatly extended.

It is a perspective view of the laser processing apparatus which comprised the dust discharge unit. It is a block diagram of a laser beam irradiation unit. It is a perspective view of a dust discharge unit. It is a longitudinal cross-sectional view of a dust discharge unit. It is the VV 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, a perspective view of a laser processing apparatus 2 including a dust discharge unit 64 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 along the pair of guide rails 14 in the machining feed direction, that is, the X-axis direction, 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 in the indexing direction, that is, the Y-axis direction along the pair of guide rails 24 by the indexing feeding means 22 constituted by the ball screw 18 and the pulse motor 20.

  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. . The chuck table 28 is provided with a clamp 30 for clamping the semiconductor wafer sucked and held by the chuck table 28.

  A column 32 is erected on the stationary base 4, and a casing 35 for accommodating the laser beam irradiation unit 34 is attached to the column 32. As shown in FIG. 2, the laser beam irradiation unit 34 includes a laser oscillator 66 that oscillates a YAG laser or a YVO4 laser, a repetition frequency setting unit 68, a pulse width adjustment unit 70, and a power adjustment unit 72. .

  The pulse laser beam adjusted to a predetermined power by the power adjusting means 72 of the laser beam irradiation unit 34 is irradiated to the semiconductor wafer W held on the chuck table 28 by the laser processing head 36 attached to the tip of the casing 35. . The laser processing head 36 includes a condenser 62 having a mirror 74 and a condenser objective lens 76, and a dust discharge unit 64 connected to the condenser 62.

  An imaging unit 38 that detects a machining region to be laser machined in alignment with the laser machining head 36 and the X-axis direction is disposed at the tip of the casing 35. The image pickup unit 38 includes an image pickup element such as a normal CCD that picks up an image of a wafer processing region with visible light.

  The imaging unit 38 further includes an infrared irradiation unit that irradiates the semiconductor wafer with infrared rays, an optical system that captures the infrared rays irradiated by the infrared irradiation unit, and an infrared CCD that outputs an electrical signal corresponding to the infrared rays captured by the optical system. Infrared imaging means composed of an infrared imaging element such as the above is included, and the captured image signal is transmitted to a controller (control means) 40.

  The controller 40 includes a central processing unit (CPU) 42 that performs arithmetic processing according to a control program, a read-only memory (ROM) 44 that stores a control program, and a random read / write that stores arithmetic results. An access memory (RAM) 46, a counter 48, an input interface 50, and an output interface 52 are provided.

  A machining feed amount detection unit 56 includes a linear scale 54 disposed along the guide rail 14 and a reading head (not shown) disposed on the first slide block 6. Is input to the input interface 50 of the controller 40.

  Reference numeral 60 denotes an index feed amount detection unit composed of a linear scale 58 disposed along the guide rail 24 and a read head (not shown) disposed on the second slide block 16. The detection signal is input to the input interface 50 of the controller 40.

  An image signal captured by the imaging unit 38 is also input to the input interface 50 of the controller 40. On the other hand, a control signal is output from the output interface 52 of the controller 40 to the pulse motor 10, the pulse motor 20, the laser beam irradiation unit 34, and the like.

  Next, the dust discharge unit 64 according to the embodiment of the present invention will be described in detail with reference to FIGS. 3 to 5. Referring to FIG. 3, a perspective view of the dust discharge unit 64 is shown.

  As shown in FIG. 2, the laser processing head 36 includes a condenser 62 having a mirror 74 and a condenser objective lens 76, and a dust discharge unit 64 connected to the condenser 62.

  Referring to FIG. 4, there is shown a longitudinal sectional view of the dust discharge unit 64 which is a sectional view taken along the line IV-IV in FIG. 5 is a cross-sectional view taken along line VV in FIG. The dust discharge unit 64 includes a casing 80 made of, for example, aluminum and integrally connected to the condenser 62. The lower end of the casing 80 is closed by a lid 82.

  Between the condenser 62 and the dust discharge unit 64, there is disposed a laser beam transmission window 84 made of glass or the like that transmits the laser beam. The dust discharge unit 64 generates a flow of air flowing from the collector 62 side around the laser beam 77 passing through the inside, and is defined by a casing 80 that prevents the dust from moving toward the collector 62 side. A room 86 is provided.

  As best shown in FIG. 3, a connection port 100 connected to a gas supply source such as compressed air is opened on the upper surface of the casing 80 adjacent to the first chamber 86. It is connected to a gas supply source via a conduit 102.

  A gas supply path 104 is formed around the first chamber 86, and the gas supplied from a gas supply source such as compressed air passes through the pipe 102, the connection port 100, and the gas supply path 104. An air flow that is supplied into the room 86 and flows from the condenser 62 side to the processing point 106 side is generated around the laser beam 77 as indicated by an arrow 105. This airflow prevents dust generated by laser processing from adhering to the laser beam transmission window 84 of the condenser 62.

  The dust discharge unit 64 further includes a second chamber 96 that is communicated with the first chamber 86 through the ceiling opening 88 and is long in the lateral direction for sucking and exhausting dust generated by laser processing. The second chamber 96 includes an upstream portion 96 a that communicates with the first chamber 86 via the ceiling opening 88 and a downstream portion 96 b that communicates with the suction exhaust path 98.

  Between the upstream portion 96a and the downstream portion 96b of the second chamber 96, a flow path branching portion 92 is provided, and the flow path of the dust 107 generated by laser processing by the flow path branching portion 92 is the first flow path. It branches into the flow path 94a and the 2nd flow path 94b.

  Therefore, the upstream part 96a and the downstream part 96b of the second chamber 96 are communicated with each other via the first flow path 94a and the second flow path 94b. The suction exhaust path 98 is connected to a suction exhaust means indicated by an arrow A.

  Hereinafter, the operation of the dust discharge unit 64 configured as described above will be described. From the laser oscillator 66 of the laser beam irradiation unit 34, for example, a pulse laser beam having a wavelength of 355 nm is oscillated, and the pulse laser beam adjusted to a predetermined power by the power adjusting means 72 is reflected by the mirror 74 of the condenser 62 and further collected. The light is condensed by the light objective lens 76 and irradiated onto the semiconductor wafer W held on the chuck table 28.

  As shown in FIG. 4, the laser beam 77 condensed by the condenser objective lens 76 is irradiated onto the semiconductor wafer W, and a laser processing groove 108 is formed by ablation processing. 4 and 5, T is a dicing tape, and the semiconductor wafer W is stuck to the dicing tape T and is sucked and held by the chuck table 28 through the dicing tape T.

  As shown in FIGS. 4 and 5, when the semiconductor wafer W is irradiated with a laser beam, dust 107 such as debris is generated from the laser processing point 106. By connecting the suction / exhaust passage 98 of the dust discharge unit 64 to the suction / exhaust means, the dust 107 generated by the laser processing is divided into the first branching by the flow path branching section 92 as best shown in FIG. The air is sucked into the downstream portion 96b of the second chamber 96 as indicated by an arrow 95 through the flow path 94a and the second flow path 94b, and further sucked into the suction / exhaust means through the suction / exhaust path 98.

  As described above, the suction of the dust 107 generated at the processing point 106 is performed on both sides of the optical path of the laser beam 77 and on both sides of the laser processing groove 108 to be formed. Since it is performed via the flow path 94b, the laser beam 77 irradiated to the wafer W does not cross the flow path of the dust 107. As a result, the laser beam 77 is not obstructed by the dust 107, and the wafer W A laser processing groove 108 having a constant depth and width can be formed on the surface.

  Next, in the dust discharge unit 64 having the above-described configuration, the flow rate of gas such as compressed air supplied from the gas supply source to the first chamber 86 via the gas supply path 104 and the suction / exhaust means are the second. The ratio of the exhaust flow rate sucked through the room 96 and the suction exhaust passage 98 was considered.

  As shown in Table 1, the ratio of the gas flow rate supplied from the gas supply source and the exhaust flow rate sucked by the suction / exhaust means is changed from 1: 2.5 to 1:30 to determine whether the gas is supplied and exhausted. Obtained a good result.

  The gas supply and exhaust quality determination is made according to whether the airflow seen from the X-axis direction and the Y-axis direction in FIG. 1 has a large vortex, the dust flow sucked into the suction exhaust passage is strong, or the dust flow Whether or not the laser beam was interrupted or whether there was no dust flow toward the first room was used as a criterion.

  In the determination results of Table 1, “x” indicates a defect, “Δ” indicates a slight problem, “◯” indicates good, and “◎” indicates the best. From Table 1, it is determined that the ratio between the gas flow rate supplied from the gas supply source and the exhaust flow rate suctioned by the suction exhaust means is preferably in the range of 1:10 to 1:30. Preferably, the gas flow rate supplied from the gas supply source is 100 ml / min or less, and the exhaust flow rate sucked by the suction / exhaust means is 100 ml / min or more.

2 Laser processing device 28 Chuck table 34 Laser beam irradiation unit 36 Laser processing head 62 Condenser 64 Dust discharge unit 80 Casing 86 First chamber 92 Channel branch portion 94a First channel 94b Second channel 96 First Room 2 of 96a Upstream part 96b Downstream part 106 Processing point 107 Dust 108 Laser processing groove

Claims (3)

Laser beam irradiation means comprising a chuck table for holding a workpiece, and a condenser for irradiating the surface of the workpiece held on the chuck table with a laser beam to form a laser processing groove by ablation processing And a dust discharging means that sucks and discharges dust generated near the processing point by ablation processing of a laser beam that is disposed at the lower end of the light collector and passes through the inside. ,
The dust discharging means is
A first chamber for generating an airflow flowing from the collector side to the processing point side around a laser beam passing through the interior, and preventing the dust from moving toward the collector side;
A second chamber that communicates with the lower end of the first chamber and sucks and exhausts the dust;
The first room is connected to a gas supply path that communicates with the gas supply means, and a laser beam transmission window formed of a transparent member that allows transmission of the laser beam is disposed on the ceiling of the first room. Has been
The second chamber includes a bottom opening that opens toward the surface of the workpiece, and a suction exhaust passage that communicates with the suction exhaust means.
A laser processing apparatus, wherein a ratio between a gas flow rate supplied from the gas supply unit and an exhaust flow rate suctioned by the suction / exhaust unit is adjusted within a range of 1:10 to 1:30. The gas flow rate supplied from the gas supply means is 100 ml / min or less,
The laser processing apparatus according to claim 1, wherein an exhaust flow rate sucked by the suction exhaust unit is 100 ml / min or more.   The second chamber of the dust discharge means has a first flow in the dust flow path from the processing point to the suction exhaust path through the bottom opening toward both sides of the processing groove with the laser beam as a center. The laser processing apparatus according to claim 1, further comprising a flow path branching portion that branches into a path and a second flow path.

Images