Laser processing device

Abstract

Laser processing device (2), comprising: a holding device (4) for holding a workpiece (W) and a laser beam application means (6) for performing ablation on the workpiece which is held by the holding means, wherein the laser beam application means comprises a laser beam oscillator means (37) for oscillating a laser beam and a processing head (36) for applying the laser beam, which is oscillated by the laser beam oscillator means, to the workpiece, wherein the processing head has a focusing lens (41) for focusing the laser beam which is oscillated by the laser beam oscillator and a collecting means which is provided between the focusing lens and the workpiece to collect foreign matter which is generated by the application of the laser beam focused by the focusing lens to the workpiece, wherein the collecting means has a suction source (80) for sucking up the foreign bodies and a suction line (78) of which one end is connected to the suction source and the other end opens to the front of the workpiece, wherein the laser processing device further comprises a cleaning fluid supply means (82, 82A) for supplying a cleaning fluid to the suction line, wherein the cleaning fluid supply means has a cleaning fluid reservoir (34) for storing the cleaning fluid, and The suction line is cleaned by immersing the processing head in the cleaning fluid reservoir with predetermined timing and activating the suction source in the state in which the processing head is immersed in the cleaning fluid reservoir.

Description

BACKGROUND OF THE INVENTIONTechnical field

[0001] The present invention relates to a laser processing apparatus for applying a laser beam to the front side of a workpiece, for example a wafer, to thereby perform ablation. State of the art

[0002] A plurality of semiconductor devices such as ICs (integrated circuits) and LSIs (large scale integrated circuits) are formed on the front surface of a semiconductor wafer, or a plurality of optical devices such as LEDs (light-emitting diodes) are formed on the front surface of an optical device wafer. Such a wafer, like the semiconductor wafer and the optical device wafer, has a plurality of intersecting dividing lines (streets) for dividing the devices. A laser beam is applied to the front surface of the wafer along the dividing lines using a laser processing device, thereby creating a plurality of laser-machined grooves on the front surface of the wafer along the dividing lines. An external force is applied to the wafer to maintain the laser-machined grooves along the dividing lines, thereby dividing the wafer into individual devices.These individual devices are installed in various electronic devices such as PCs (personal computers) and LED lights, thereby producing the electronic devices incorporating the devices.

[0003] It is known that when a laser beam with an absorption wavelength suitable for the wafer is applied to the wafer during the laser processing step, fine dust particles called foreign matter are generated and dispersed, adhering to the front surface of each device, resulting in deterioration of device quality. To address this problem, a processing method including the steps of forming a protective film on the wafer before laser processing and removing the protective film and the foreign matter deposited on the protective film after laser processing has been proposed.A laser processing apparatus has also been proposed, which includes a nozzle for blowing air along the optical axis of a focusing objective lens and a collecting means for absorbing foreign matter from the vicinity of the nozzle (see, for example, Japanese Patent Application Laid-Open Nos. 2007-69249 A and 2011-189400 A). DE 10 2010 054 036 A1 relates to a laser beam processing apparatus. US 2004 / 0197433 A1 relates to a film removal apparatus. JP 2011-249393 A relates to a method and apparatus for cutting a hard substrate. PRESENTATION OF THE INVENTION

[0004] However, the protective film itself is evaporated by the laser beam during the actual laser processing, and the foreign matter from the protective film settles on the foreign matter suction mechanism. In this case, the foreign matter must be removed to prevent it from falling onto the wafer, necessitating regular maintenance. Furthermore, the air blown along the optical axis of the focusing objective lens is insufficient, resulting in the deposition of foreign matter on the focusing objective lens and other optical components.

[0005] During continuous wafer processing, foreign matter containing the dispersed material from the protective film can settle on a suction line of the collection device and eventually solidify like a popsicle stick. Once the foreign matter has adhered to the suction line, it is difficult to remove it. Furthermore, the solid matter that has adhered to the suction line reduces the suction force in the suction line.

[0006] As a result, foreign matter generated on the wafer during laser processing cannot be adequately collected.

[0007] It is therefore an object of the present invention to provide a laser processing device which can prevent the deposition of foreign bodies, which arise during laser processing, on the optical components including the focusing means and the suction line.

[0008] It is another object of the present invention to provide a laser processing apparatus which can clean the suction pipe even if a part of the foreign matter adheres to the suction pipe, thereby preventing the foreign matter from adhering to the suction pipe.

[0009] According to one aspect of the present invention, a laser processing apparatus is provided which comprises holding means for holding a workpiece and a laser beam application means for performing ablation on the workpiece held by the holding means, wherein the laser beam application means comprises a laser beam oscillation means for oscillating a laser beam and a processing head for applying the laser beam oscillated by the laser beam oscillation means to the workpiece, wherein the processing head has a focusing lens for focusing the laser beam oscillated by the laser beam oscillation means, and a collecting means provided between the focusing lens and the workpiece for collecting foreign matter generated by the application of the laser beam focused by the focusing lens to the workpiece.wherein the collecting means comprises a suction source for sucking the foreign matter and a suction line having one end attached to the suction source and the other end opening toward the front side of the workpiece, the laser processing apparatus further comprising a cleaning liquid supply means for supplying a cleaning liquid to the suction line.

[0010] Preferably, the cleaning liquid supply means includes a cleaning liquid nozzle opening to the suction line, a cleaning liquid source for supplying the cleaning liquid to the cleaning liquid nozzle, and a cleaning liquid supply line having one end connected to the cleaning liquid nozzle and the other end connected to the cleaning liquid source.

[0011] The cleaning liquid supply means comprises a cleaning liquid reservoir for storing the cleaning liquid, wherein the suction line is cleaned by immersing the machining head in the cleaning liquid reservoir for a predetermined time and actuating the suction source in the state in which the machining head is immersed in the cleaning liquid reservoir.

[0012] According to another aspect of the present invention, there is provided a cleaning method for the suction line in the laser processing apparatus according to the present invention, which comprises a processing step of performing ablation of a workpiece, a retracting step of retracting the processing head from the workpiece after performing the processing step, and a cleaning step of actuating the cleaning liquid supplying means to clean the suction line after performing the retracting step.

[0013] With the laser processing apparatus of the present invention, it is possible to prevent the deposition of foreign matter generated during laser processing on the optical components, including the focusing means and the suction line. Even if some of the foreign matter adheres to the suction line, the suction line can be cleaned by the cleaning fluid supplied by the cleaning fluid supplying means, thereby preventing the foreign matter from adhering to the suction line.

[0014] The above and other objects, features and advantages of the present invention and the mode for carrying them out will become more apparent and the invention itself will be best understood by studying the following description and the appended claims with reference to the accompanying drawings which show some preferred embodiments of the invention. SHORT DESCRIPTION OF THE FIGURES Fig. 1 is a perspective view of a laser processing apparatus according to a first preferred embodiment of the present invention; Fig. 2 is a schematic view showing the configuration of a laser beam application means and a chuck table included in the laser processing apparatus; Fig. 3 is a perspective view showing the configuration of a protective blowing means included in the laser processing apparatus; Fig. 4 is a cross-section taken along the line IV-IV in Fig. 3, which shows a second preferred embodiment of the present invention; and Fig. 5 is a flowchart showing a laser processing method using the laser processing apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Preferred embodiments of the present invention will now be described in detail with reference to the drawings. Fig. 1 is a perspective view of a laser processing apparatus 2 according to a first preferred embodiment of the present invention. The laser processing apparatus 2 shown in Fig. 1 is configured to have a protective film P (see Fig. 4) on a wafer W (corresponding to a workpiece), holds the wafer W on a chuck table 4 (corresponding to the holding means), applies a laser beam from the laser beam application means 6 to the wafer W held in the chuck table 4, and moves the chuck table 4 and the laser beam application means 6 relative to each other to thereby perform ablation (laser processing) on ​​the wafer W so that a processed groove S (see Fig. 4) is formed on the wafer W by the laser beam.

[0016] The laser processing apparatus 2 includes the chuck table 4 for holding the wafer W, a processing head 36 constituting the laser beam application means 6, an imaging means (not shown), a foreign matter ejection means 10 provided on the processing head 36, and a control means 12. The laser processing apparatus 2 further includes a cassette 14 for storing the wafer W before and after laser processing, a temporary placement means 16 for temporarily placing the wafer W before and after laser processing, and a protective film forming and cleaning means 18 for forming the protective film P on the wafer W before laser processing and removing the protective film P from the wafer W after laser processing.

[0017] The laser processing apparatus 2 further includes an X-axis moving means (not shown) for relatively moving the chuck table 4 and the laser beam applying means 6 in the X direction, a Y-axis moving means (not shown) for relatively moving the chuck table 4 and the laser beam applying means 6 in the Y direction, and a Z-axis moving means (not shown) for relatively moving the chuck table 4 and the laser beam applying means 6 in the Z direction.

[0018] The cassette 14 is configured to store a plurality of wafers W, each wafer W being held to an annular frame F by an adhesive tape T. That is, each wafer W is attached to the adhesive tape T, which is temporarily held by the annular frame F. The laser processing apparatus 2 includes a body case 20 and a cassette lift 15 provided in the body case 20 so as to be vertically movable in the Z direction. The cassette 14 is placed on the cassette lift 15. The temporary placement means 16 includes a handling means 22 for taking out the wafer from the cassette 14 before laser processing and also for setting the wafer W into the cassette 14 after laser processing, and a pair of rails 24 for temporarily placing the wafer W thereon before and after laser processing.

[0019] The protective film forming and cleaning means 18 functions to form the protective film P on the wafer W before laser processing. The wafer W is placed on the pair of rails 24 before laser processing and is then transported to the protective film forming and cleaning means 18 by a first transfer means 26. The protective film forming and cleaning means 18 also functions to remove the protective film P from the wafer W after laser processing. The wafer W is placed on the chuck table 4 after laser processing and is then transported to the protective film forming and cleaning means 18 by a second transfer means 28. The protective film forming and cleaning means 18 includes a spinner table 30 for placing and holding the wafer W before and after laser processing. The spinner table 30 is connected to a spinner table drive source (not shown) provided in the body case 20 of the laser processing apparatus 2.

[0020] When forming the protective film P, the wafer W before laser processing is held on the spinner table 30, and the spinner table 30 is rotated by the spinner table drive source to thereby rotate the wafer W. In this rotating state, a liquid resin containing a water-soluble resin such as PVA, PEG, and PEO is sprayed onto the front surface WS of the rotated wafer W from a coating nozzle (not shown) constituting the protective film forming and cleaning agent 18. Thus, the liquid resin is applied to the front surface WS of the wafer W. When the liquid resin is cured, the protective film P is formed on the front surface WS of the wafer W.

[0021] When removing the protective film P, the wafer W after laser processing is held on the spinner table 30, and the spinner table 30 is rotated by the spinner table drive source to thereby rotate the wafer W. In this rotating state, a cleaning liquid is sprayed onto the front surface WS of the rotated wafer W from a cleaning nozzle (not shown) constituting the protective film forming and cleaning means 18. Thus, the protective film P is removed and the front surface WS of the wafer W is cleaned.

[0022] After the protective film P is formed on the wafer W by the protective film forming and cleaning agent 18 before laser processing, the wafer W is transported to the chuck table 4 by the second transporting means 28. Further, after the protective film P is removed from the wafer W by the protective film forming and cleaning agent 18 after laser processing, the wafer W is transported to the rails 24 of the temporary placement means 16 by the first transporting means 26.

[0023] The chuck table 4 functions to hold the wafer W transported by the spin table 30 of the protective film forming and cleaning device 18 after the protective film P is formed on the wafer W. The chuck table 4 has a circular upper surface as a holding surface formed of a porous ceramic or the like. This holding surface of the chuck table 4 is connected to a vacuum source (not shown) through a vacuum line (not shown), whereby the wafer W placed thereon is held by negative pressure.

[0024] The chuck table 4 is detachably supported on a table moving base (not shown) provided in the body case 20 of the laser processing apparatus 2. This table moving base is movable in the X direction by the X-axis moving means and also movable in the Y direction by the Y-axis moving means. This table moving base is also rotatable about its axis (parallel to the Z axis) by a base drive source (not shown). Further, a clamp 32 for fixing the annular frame F is provided in the vicinity of the chuck table 4. The clamp 32 is driven by an air actuator (not shown) to thereby fix the annular frame F holding the wafer W through the adhesive tape T.

[0025] The laser processing apparatus 2 according to the first preferred embodiment shown in Fig. 1 includes a cleaning fluid supply means 82 provided adjacent to the chuck table 4. The cleaning fluid supply means 82 includes a cleaning fluid reservoir 34 and a cleaning fluid supply nozzle 35 for supplying a cleaning fluid to the cleaning fluid reservoir 34. This cleaning fluid is stored in the cleaning fluid reservoir 34 and used to clean the machining head 36.

[0026] The laser beam application means 6 functions to generate a laser beam L (see Fig. 2) to the front side WS of the wafer W held on the chuck table 4, to thereby form the processing groove S by ablation. Fig. Fig. 2 is a schematic view showing the configuration of the laser beam application means 6 and the chuck table 4. The laser beam application means 6 includes the machining head 36 and a laser beam oscillation means 37 for oscillating the laser beam L.

[0027] The processing head 36 includes a focusing means 38 for applying the laser beam L, which is oscillated by the laser beam oscillating means 37, to the front side WS of the wafer W and a collecting means 70 (see Fig. 3) collecting the foreign matter to be described below. The laser beam application means 6 further includes a repetition frequency adjusting means 43 for correctly adjusting the repetition frequency of the laser beam L to be oscillated by the laser beam oscillating means 37 according to the type of wafer W, the form of processing, and so on. For example, a YAG laser oscillator and a YVO4 laser oscillator can be used as the laser beam oscillating means 37. The focusing means 38 included in the processing means 36 includes a total reflection mirror 39 for changing the propagation direction of the laser beam L, thereby oscillating the laser beam oscillating means 37, and a focusing lens 41 for focusing the laser beam L reflected by the total reflection mirror 39.

[0028] The imaging means (not shown) functions to image the front side WS of the wafer W held on the chuck table 4. The imaging means is movable in the Z direction integrally with the laser beam application means 6 by the Z-axis moving means. The imaging means includes a CCD camera (not shown) for imaging the wafer W held on the chuck table 4 to obtain an image. The image obtained by the CCD camera is output from the imaging means to the control means 12.

[0029] Fig. Fig. 3 is a perspective view showing the configuration of a protective blowing means 8 included in the laser processing apparatus 2, and Fig. Figure 4 is a cross-sectional view taken along line IV-IV in Fig. 3, which shows a second preferred embodiment of the present invention. The protective blowing means 8 comprises a housing 44, which is connected via a clamp 42 (see Fig. 3) attached to the focusing means 38 of the laser beam application means 6, a transparent member 40 attached to the housing 44, and a protective blowing mechanism 46 for maintaining a positive pressure in the housing 44. The housing 44 has an upper opening 48 and a lower opening 50 to allow the passage of the laser beam L. The housing 44 has a funnel-shaped conical portion 52 that gradually tapers in diameter toward the lower opening 50. That is, the conical portion 52 of the housing 44 defines a funnel-shaped conical interior space.

[0030] The lower opening 50 of the housing 44 has an area that allows the passage of the laser beam L. For example, the diameter of the lower opening 50 is set to 4 mm. The housing 44 is constructed of a plurality of stacked flat plates 54 and a lowermost elongated plate 56. The transparent member 44 is provided to close the upper opening 48 of the housing 44 and can transmit the laser beam L. The transparent member 40 has an area that allows the passage of the laser beam L. That is, the transparent member 40 is formed of a material capable of transmitting the laser beam L and is a circular flat plate with a size suitable for closing the upper opening 48 of the housing 44.

[0031] The protective blowing mechanism 46 functions to blow a gas flowing from the side of the focusing means 38 toward one side of an operating point K around the laser beam L passing through the housing 44, thereby maintaining a positive pressure in the housing 44 to prevent an atmosphere containing the foreign matter from flowing into the housing 44 from the lower opening 50. As shown in Fig. 3 and Fig. 4, the protective blowing mechanism 46 includes a plurality of blowing ports 60, a gas supply line 62 (see Fig. 3) and a gas source (not shown). The plurality of blowing ports 60 are arranged around the transparent member 40 so as to be evenly spaced from each other in the circumferential direction of the transparent member 40. Each blowing port 60 has one end opening onto the inner surface of the housing 44, and the other end opening into a communication space 64 formed in the housing 44.

[0032] The gas to be blown from the blow ports 60 is directed in the direction of the laser beam L passing through the housing 44, so that it is slightly inclined downward from a horizontal plane so that the gas does not touch the transparent member 40. That is, one end of each blow port 60, which opens to the inner surface of the housing 44, is arranged below the transparent member 40, and each blow port 60 extends slightly obliquely downward from the other end to its one end. For example, eight blow ports 60 are provided. The gas supply line 62, which is Fig. 3, is connected to the plurality of blowing ports 60 through the connecting space 64. The gas source is connected to the plurality of blowing ports 60 through the gas supply line 62, whereby a pressurized gas is supplied to the plurality of blowing ports 60.

[0033] The foreign matter ejection means 10 is provided below the housing 44 of the protective blowing means 8 to eject the foreign matter by suction. As shown in Fig. 3 and Fig. 4, the foreign matter ejection means 10 includes a partition wall 66 (see Fig. 4) integral with the housing 44, an air curtain blowing mechanism 68 and a collecting means 70. The partition 66 is designed to form a scattering surface (shown by a dotted line in Fig. 4) that surrounds the foreign matter generated at the operating point K. The partition wall 66 is formed on the lowermost elongated plate 56 forming the housing 44. The partition wall 66 is configured to surround the lower opening 50 of the housing 44.

[0034] The air curtain blowing mechanism 68 functions to blow a gas in a direction parallel to the front side WS of the wafer W opposite to the direction of formation of the processing groove S (from the downstream side in the direction indicated by an arrow X1 in Fig. 4, which is the direction of relative movement of the laser beam L on the front side WS of the wafer W during laser processing), thereby covering the lower opening 50 of the housing 44 with this gas to prevent foreign matter from entering the housing 44. The air curtain blowing mechanism 68 includes a nozzle member 58 attached to the elongated plate 56, a blowing port 72 formed in the nozzle member 58, a gas supply line 74 connected to the blowing port 72, and a gas source (not shown) for supplying the gas through the gas supply line 74 to the blowing port 72.

[0035] The blowing port 72 is configured to open to the inner surface (inside) of the partition wall 66 formed on the nozzle member 58 in the vicinity of the lower opening 50 of the housing 44. The blowing port 72 extends parallel to the front side WS of the wafer W. The gas source is connected to the blowing port 72 through the gas supply line 74 formed in the housing 44, whereby a pressurized gas is supplied to the blowing port 72. Therefore, the pressurized gas (air flow) is blown from the blowing port 72.

[0036] The collecting means 70 is provided downstream of the flow of gas blown by the air curtain blowing mechanism 68 and functions to absorb the gas and foreign matter generated near the working point K. As shown in Fig. 4, the collecting means 70 includes a suction port 76 opening toward the partition wall 66, a suction line 78 connected to the suction port 76, and a suction source 80 connected to the suction line 78. The suction port 76 is provided below the housing 44 of the protective blowing means 8 so as to open toward the inner surface (inside) of the partition wall 66 formed on the lowermost elongated plate 56 of the housing 44. For example, the suction port 76 is disposed opposite the blowing port 72. That is, the collecting means 70 is disposed opposite the air curtain blowing mechanism 68 with respect to the laser beam L.

[0037] The suction line 78 is formed in the lowermost elongated plate 56 of the housing 44 and extends obliquely upward from the suction port 76 to communicate with the suction source 80. The suction source 80 is connected to the suction port 76 through the suction line 78 to suck the gas from the suction port 76. That is, the suction line 78 is arranged downstream of the flow of gas blown by the air curtain blowing mechanism 68 to suck in the gas and the foreign matter generated near the operating point K.

[0038] The suction line 78 of the collecting means 70 has one end connected to the suction source 80 and its other end opens to the upper surface (front side WS) of the wafer W. In the second preferred embodiment shown in Fig. 4, a cleaning liquid supply means 82A for supplying a cleaning liquid to the suction line 78 is provided around the suction line 78. As shown in Fig. 4, the cleaning liquid supply means 82A includes a plurality of cleaning liquid nozzles 84 opening toward the suction line 78, a cleaning liquid source 88 for supplying a cleaning liquid to the cleaning liquid nozzles 84, and a cleaning liquid supply line 86, one end of which is connected to each cleaning liquid nozzle 84 and the other end of which is connected to the cleaning liquid source 88.

[0039] The wafer W is a workpiece to be subjected to laser processing by the laser processing apparatus 2. For example, the wafer W is a disk-shaped semiconductor wafer or an optical device wafer formed from a substrate made of silicon, sapphire, gallium nitride, or the like. As shown in Fig. 1, a plurality of devices are formed on the front surface WS of the wafer W so as to be divided by a plurality of intersecting streets. Further, the back surface of the wafer W opposite to the front surface WS is attached to the adhesive tape T, and the annular frame F is further attached to the adhesive tape T so as to surround the wafer W. Thus, the wafer W is held by the adhesive tape T to the annular frame F in the state where the front surface F is exposed. Further, a so-called low-k film (not shown) formed of a low-k material (mainly a porous material) is formed as an interlayer dielectric material on the front surface WS of the wafer W.

[0040] The control means 12 functions to control the above-mentioned components of the laser processing device 2. The control means 12 controls the laser processing device 2 to apply the processing process to the wafer W. When performing the processing process on the wafer W, that is, when applying the laser beam L from the laser beam application means 6 to the front side WS of the wafer W, the control means 12 actuates the gas source of the protective blowing mechanism 36 to blow the gas from the blowing ports 60, also actuates the gas source of the air curtain blowing mechanism 68 of the foreign matter ejection means 10 to blow the gas from the blowing port 72, and also operates the suction source 80 of the collecting means 70 to suck the gas from the suction port 76.Further, the control means 12 controls the cleaning liquid supply means 82 or 82A at a predetermined timing to supply a cleaning liquid to the suction line 78, thereby cleaning the suction line 78.

[0041] Next, a laser processing method for processing the wafer W using the laser processing apparatus 2 will be explained. Fig. 5 is a flowchart showing the laser processing method using the laser processing apparatus 2. First, the adhesive tape T is attached to the back side of the wafer W opposite the front side WS on which the devices are formed. Further, the annular frame F is attached to the adhesive tape T. The wafer W, thus held to the annular frame F by the adhesive tape T, is stored in the cassette 14.

[0042] A user inputs processing information into the control means 12. When the user inputs an instruction to start a processing operation, the laser processing device 2 begins the processing step. In this processing step, the control means 12 executes step ST1, which is shown in Fig. 5. In step ST1, the wafer W prior to laser processing is removed from the cassette 14 and transported by the handling means 22 to the preliminary placement means 16. That is, the wafer is temporarily placed on the pair of rails 24 of the preliminary placement means 16. Thereafter, the wafer W is transported by the first transport means 26 to the spin table 30 of the protective film forming and cleaning means 18. The wafer W is then held on the spin table 30.

[0043] Thereafter, the spinner table 30 is lowered and next rotates around its axis. During the rotation of the spinner table 30, the liquid plastic is sprayed from the coating nozzle onto the wafer W held on the spinner table 30. As a result, the liquid plastic is applied to the entire surface of the front side WS of the wafer W held on the spinner table 30 by centrifugal force. After a predetermined time has elapsed, the rotation of the spinner table 30 is stopped, and the application of the liquid plastic from the coating nozzle is also stopped. When the liquid plastic applied to the front side WS of the wafer W is cured, the protective film P formed from the liquid plastic is formed on the front side WS of the wafer W.

[0044] In this way, step ST1 is a protective film forming step in which the liquid resin is applied to the front surface WS of the wafer W to thereby form the protective film P. After completing the formation of the protective film P, the spin table 30 is lifted, and the wafer W is next transported from the spin table 30 to the chuck table 4 by the second transport means 28.

[0045] Then, the wafer W is held on the chuck table 4 and the control means 12 performs step ST2.

[0046] In step ST2, the chuck table 4 is moved by the X-axis moving means and the Y-axis moving means to move the wafer W held on the chuck table 4 under the imaging means. In this position, the wafer W is imaged by the imaging means. An image obtained by the imaging means is output to the control means 12. The control means 12 then performs image processing such as pattern matching to establish alignment between a predetermined street of the wafer W held on the chuck table 4 and the focusing means 38 of the laser beam applying means 6 for applying the laser beam L, thus performing the alignment process for aligning the focusing means 38 and the predetermined street in the X direction. After performing this alignment process, the control means 12 performs step ST3.

[0047] In step ST3, the clamping table 4 is moved by the X-axis moving means and the Y-axis moving means according to the alignment information detected in step ST2. Furthermore, the clamping table 4 is rotated about its axis by the base drive source to bring the predetermined line parallel to the X-direction (see Fig. 4). Thereafter, one end of the predetermined line is positioned immediately below the focusing means 38 of the laser beam application means 6, and the laser beam L is applied by the focusing means 38. At the same time, the chuck table 4, which supports the wafer W, is moved by the X-axis moving means in the X direction at a predetermined feed rate. That is, the laser beam L is relatively moved on the front side WS of the wafer W in the direction shown by an arrow X1 (see Fig. 4).

[0048] As a result, the wafer W and the protective film P are partially removed by the laser beam L along the predetermined road to thereby form the processed groove S as shown in Fig. 4. When the other end of the predetermined street reaches the position immediately below the focusing means 38, the application of the laser beam L from the focusing means 38 is stopped, and the movement of the chuck table 4 by the X-axis moving means is also stopped. Thereafter, the chuck table 4 is indexed in the Y direction by the Y-axis moving means to similarly move the laser beam L along the next street, thereby forming a similarly machined groove S along this street. This laser processing is similarly applied to all the streets of the wafer W to form a plurality of similarly machined grooves S along all these streets.

[0049] In this way, step ST3 is a processed groove forming step in which the laser beam L is applied to the front side WS of the wafer W along the streets from the protective film P side after step ST2 is performed, thereby forming the processed grooves S in the front side WS along the streets. Further, in step ST3 as the processed groove forming step, gas is blown from the ports 60 connected to the gas source of the protective blowing mechanism 46 of the protective blowing means 8 while applying the laser beam L. Consequently, the pressure inside the casing 44 is maintained at a positive pressure higher than the external pressure.

[0050] Each blowing port 60 extends slightly obliquely downward toward the inner surface of the casing 44, and the plurality of blowing ports 60 are arranged at equal intervals around the transparent member 40. Consequently, the gas blown from the plurality of blowing ports 60 flows downward toward the lower opening 50 of the casing 44 evenly around the transparent member 40. That is, a so-called downward flow is generated in the casing 44 of the protective blowing means 8, so that it flows downward toward the lower opening 50 evenly around the transparent member 40.

[0051] Furthermore, the conical portion 52 of the housing 44 is formed like a funnel having a diameter that gradually tapers toward the lower opening 50. Consequently, the velocity of the downward flow gradually increases toward the lower opening 50. As a result, it is possible to prevent the problem that a foreign matter-containing atmosphere generated near the working point K by laser processing may enter the housing 44 from the lower opening 50.

[0052] Further, in step ST3 as the processed groove forming step, while the gas is blown from the blowing ports 60 of the protective blowing mechanism 46 of the protective blowing means 8, the gas is blown from the blowing port 72 of the air curtain blowing mechanism 68 of the foreign matter ejection means 10, and the gas is sucked into the suction port 76 connected to the suction source 80 of the collecting means 70. In this way, the gas is blown from the blowing port 72 of the air curtain blowing mechanism 68 of the foreign matter ejection means 10 so that the lower opening 50 of the housing 44 is covered with the gas blown from the blowing port 72. In addition, an atmosphere containing the foreign matter generated near the working point K is sucked from the suction port 76 through the suction line 78 to the suction source 80.

[0053] In the second preferred embodiment shown in Fig. 4, the control means 12 further controls the cleaning liquid supply means 82A to supply the cleaning liquid to the suction line 78, thereby cleaning the suction line 78. The predetermined time for cleaning the suction line 78 is not particularly limited. For example, after performing machining on the wafer W, the processing head 36 is preferably retracted from the wafer W, and the cleaning liquid supply means 82A is then operated to clean the suction line 78. As a modification, the cleaning liquid supply means 82A may always be operated to clean the cleaning line 78 during machining on the wafer W.

[0054] In the second preferred embodiment shown in Fig. As shown in Figure 4, the cleaning liquid supply means 82A is constructed of the cleaning liquid nozzles 84, the cleaning liquid supply line 86, and the cleaning liquid source 88. The cleaning liquid is supplied from the cleaning liquid source 88 to the cleaning liquid supply line 86 at the predetermined timing. The cleaning liquid supplied to the cleaning liquid supply line 86 is sprayed from the cleaning liquid nozzles 84, thereby cleaning the suction line 78.

[0055] In the first preferred embodiment shown in Fig. As shown in Fig. 1, the cleaning liquid supply means 82 is constructed of the cleaning liquid reservoir 34 and the cleaning liquid supply nozzle 35. The machining head 36 is immersed in the cleaning liquid reservoir 34 at a predetermined timing. In the state where the machining head 36 is immersed in the cleaning liquid reservoir 34, the suction source 80 is operated to supply (suck) the cleaning liquid from the cleaning liquid reservoir 38 to the suction line 78, thereby cleaning the suction line 78. Alternatively, the machining head 36 may be immersed in the cleaning liquid reservoir 34 during the operation of the suction source 80.

[0056] If the amount of cleaning liquid stored in the cleaning liquid reservoir 34 is insufficient, the cleaning liquid is supplied from the cleaning liquid supply nozzle 35 into the cleaning liquid reservoir 34. Therefore, the predetermined timing for cleaning in the first preferred embodiment is not particularly limited.

[0057] For example, cleaning may be performed at regular intervals or at intervals of a fixed number of wafers. If the cleaning liquid supply means 82 is provided in the laser processing apparatus 2, the cleaning liquid supply means 82A is not always necessary. Conversely, if the cleaning liquid supply means 82A is provided in the laser processing apparatus 2, the cleaning liquid supply means 82 is not always necessary. That is, only at least one of the cleaning liquid supply means 82 and the cleaning liquid supply means 82A is necessary in the laser processing apparatus 2.

[0058] Furthermore, the blowing port 72 is arranged downstream of the suction port 76 in the direction of arrow X1 as the direction of relative movement of the laser beam L on the front side WS of the wafer W during laser processing in step ST3 as the processed groove forming step. Consequently, the lower opening 50 is reliably covered with the gas blown from the blowing port 72, making it possible to reliably prevent the problem that an atmosphere containing foreign matter generated near the working point K by the laser processing may enter the casing 44 from the lower opening 50.

[0059] After forming the processed grooves S on the front side WS of the wafer W along all the streets, the chuck table 4 holding the wafer W is moved by the X-axis moving means to the home position shown in Fig.1. Thereafter, the wafer W is transported from the chuck table 4 by the second transport means 28 to the spin table 30 of the protective film forming and cleaning device 18. In the state where the wafer W is held on the spin table 30, the spin table 30 is lowered and then rotated about its axis. During the rotation of the spin table 30, the cleaning liquid is sprayed onto the wafer W from the cleaning nozzle. Since the protective film P is formed of a water-soluble resin, the protective film P is removed (washed off) from the front side WS of the wafer W by the cleaning liquid and centrifugal force, together with the foreign matter adhering to the wafer W during laser processing.

[0060] After the removal of the protective film P is completed, the rotation of the spin table 30 about its axis is stopped, and the supply of cleaning fluid from the cleaning nozzle is also stopped. Thereafter, the spin table 30 is raised, and the wafer W is then transported from the spin table 30 to the preliminary placement means 16 by the first transport means 26. The wafer W is then transported from the preliminary placement means 16 by the handling means 22 into the cassette 14 on the cassette lift 15.

[0061] According to the laser processing apparatus 2, a positive pressure can be maintained in the housing 4, and a downward flow can be generated in the housing 44 through the funnel-shaped conical portion 52 of the housing 44 and the protective blowing mechanism 46, so that it is possible to prevent an atmosphere containing foreign matter from entering the housing 44 from the lower opening 50. Furthermore, the suction line 78 can be cleaned by the cleaning liquid supply means 82 and 82A. Consequently, the focusing means 38 and the suction line 78 can be protected from the deposition of foreign matter, and it is possible to prevent clouding of the transparent member 40 due to the deposition of foreign matter in the atmosphere. Consequently, the foreign matter generated when performing laser processing can be prevented from adhering to the optical components including the focusing means 38 and the transporting member 40, as well as to the suction line 78.

[0062] While laser processing is performed after the formation of the protective film P on the wafer in each preferred embodiment, the present invention is not limited to this configuration, but the formation of the protective film P is not always necessary. Further, the protective film P is formed by applying the liquid resin containing the water-soluble resin, such as PVA, PEG, and PEO, to the front surface WS of the wafer W and then curing the applied liquid resin in each preferred embodiment. However, the applied liquid resin may be incompletely cured (dried) to form the protective film P, but abrasion may be performed on this protective film P in the incompletely dried state. In this case, a large amount of foreign matter may be generated from this protective film P in the incompletely dried state.But the entry of the foreign matter into the housing 44 can be prevented by the protective blowing agent 8, thereby avoiding the clouding of the transparent element 40.

[0063] The configurations of the X-axis moving means, the Y-axis moving means, and the Z-axis moving means can be appropriately modified in the present invention. Furthermore, the cleaning liquid reservoir 34 can be provided with a Z-axis moving means to be movable in the Z direction. The present invention is not limited by the above-described contents in the respective preferred embodiments. Furthermore, the components described above can include anything that can be easily assumed by those skilled in the art and also include substantially the same parts as those known in the art.

Claims

[1] Laser processing device (2), comprising: a holding means (4) for holding a workpiece (W) and a laser beam application means (6) for performing ablation on the workpiece held by the holding means, the laser beam application means comprising a laser beam oscillation means (37) for oscillating a laser beam and a machining head (36) for applying the laser beam oscillated by the laser beam oscillation means to the workpiece, wherein the machining head comprises a focusing lens (41) for focusing the laser beam oscillated by the laser beam oscillating means, and a collecting means provided between the focusing lens and the workpiece for collecting foreign matter generated by the application of the laser beam focused by the focusing lens to the workpiece, wherein the collecting means comprises a suction source (80) for sucking up the foreign bodies and a suction line (78), one end of which is connected to the suction source and the other end of which opens to the front of the workpiece, wherein the laser processing apparatus further comprises a cleaning liquid supply means (82, 82A) for supplying a cleaning liquid to the suction line, wherein the cleaning liquid supply means comprises a cleaning liquid reservoir (34) for storing the cleaning liquid, and the suction line is cleaned by immersing the machining head into the cleaning liquid reservoir at a predetermined timing and actuating the suction source in the state in which the machining head is immersed in the cleaning liquid reservoir. [2] The laser processing apparatus according to claim 1, wherein the cleaning liquid supply means comprises a cleaning nozzle (84) opening to the suction line, a cleaning liquid source (88) for supplying the cleaning liquid to the cleaning liquid nozzle, and a cleaning liquid supply line (86) having one end connected to the cleaning liquid nozzle and the other end connected to the cleaning liquid source. [3] A cleaning method for the suction line in the laser processing apparatus according to claim 1, comprising: a processing step of performing a removal on the workpiece, a retraction step of retracting the machining head from the workpiece after performing the machining step and a cleaning step of actuating the cleaning liquid supplying means to clean the suction line after performing the retracting step.

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