JP6998178B2 - Laser processing equipment - Google Patents

Description

The present invention relates to a laser processing apparatus that irradiates a plate-shaped workpiece with a laser beam to process it.

A wafer in which a plurality of devices such as ICs and LSIs are partitioned by a scheduled division line and formed on the surface is divided into individual devices by a laser processing device and used for electric devices such as mobile phones, personal computers, and lighting devices. ..

The laser processing device is a type that forms a groove that becomes the starting point of division by ablation processing in which the condensing point of the laser beam having a wavelength that is absorbent to the workpiece is positioned on the surface of the workpiece and irradiated. For example, refer to Patent Document 1), a condensing point of a laser beam having a wavelength that is transparent to the work piece is positioned inside the work piece and irradiated, and the inside of the work piece is used as a starting point of division. A type that forms a modified layer (see, for example, Patent Document 2), a focusing point of a laser beam having a wavelength that is transparent to the workpiece is positioned at a required position of the workpiece. A type that irradiates from the front surface to the back surface of the workpiece to form a shield tunnel composed of pores that are the starting points of division and amorphous surrounding the pores (see, for example, Patent Document 3). And, and the laser processing apparatus is appropriately selected according to the type of the workpiece, the processing accuracy, and the like.

Among the above-mentioned laser processing devices, especially in the type to be ablated, debris (laser processing waste) generated when the surface of the workpiece (wafer) is irradiated with a laser beam is generated on the surface of the device formed on the wafer. Before performing laser processing, the surface of the wafer is coated with a liquid resin that transmits the laser beam used for processing to prevent debris from adhering, as it may scatter and adhere, degrading the quality of the device. It has been proposed to remove the liquid resin after laser processing (see, for example, Patent Document 4).

Japanese Unexamined Patent Publication No. 10-305420 Japanese Patent No. 3408805 Japanese Unexamined Patent Publication No. 2014-221483 Japanese Unexamined Patent Publication No. 2004-188475

According to the technique described in Patent Document 4, the liquid resin coating can prevent debris from adhering to the surface of the device, and the processing quality is ensured. However, there is a problem in productivity because a step of applying the liquid resin and a step of removing the liquid resin after processing are required. Further, the liquid resin has a problem of being uneconomical because it cannot be used repeatedly.

Further, a technique has been proposed in which the wafer is submerged in water and irradiated with a laser beam to suspend the debris in water to prevent the wafer from adhering to the surface of the wafer. However, when the wafer is irradiated with a laser beam while the wafer is submerged, fine bubbles are generated from the irradiated portion of the wafer, and these bubbles hinder the progress of the laser beam, so that desired processing cannot be performed. There is a problem.

The present invention has been made in view of the above facts, and its main technical problem is that when a plate-shaped workpiece is irradiated with a laser beam and processed, the irradiation of the workpiece with the laser beam is hindered. The purpose is to provide laser processing equipment without the need for laser processing.

In order to solve the above-mentioned main technical problem, according to the present invention, a laser beam provided with a holding means for holding a plate-shaped workpiece and a condenser for irradiating the workpiece held by the holding means with a laser beam. It is a laser processing device including at least an irradiation means, a processing feed means for relatively processing and feeding the holding means and the concentrator, and is positioned directly under the concentrator and to be processed. A liquid layer generator for generating a liquid layer on the upper surface of an object is provided, and the liquid layer generator includes a transparent plate that allows the passage of a laser beam irradiated by the concentrator, and a top wall containing the transparent plate. A housing composed of a side wall having a lower end portion that hangs from the outside of the top wall and forms a gap between the work piece and a housing, and a liquid is supplied to the internal space of the housing to make the internal space liquid. The internal space of the housing is composed of a liquid supply unit to be filled, and the liquid introduced from the liquid supply unit is jetted into the internal space toward the irradiation position of the laser beam irradiated to the workpiece. A laser processing apparatus is provided in which a liquid injection nozzle is arranged, and the liquid injection nozzle injects a liquid in a direction orthogonal to a processing feed direction .

The laser beam irradiating means may be provided with an oscillator that oscillates the laser beam, and may be provided with a dispersion means that disperses the laser beam oscillated from the oscillator.

The laser processing apparatus of the present invention includes a holding means for holding a plate-shaped workpiece, a laser beam irradiating means provided with a condenser for irradiating the workpiece held by the holding means with a laser beam, and the holding means. A laser processing device including at least a processing feed means for relatively processing and feeding the concentrator, which is positioned directly under the concentrator and has a liquid layer on the upper surface of the workpiece. The liquid layer generator comprises a transparent plate that allows the passage of a laser beam irradiated by the concentrator, a top wall including the transparent plate, and hanging from the outside of the top wall. From a housing composed of a side wall having a lower end portion that forms a gap between the work piece and the work piece, and a liquid supply unit that supplies liquid to the internal space of the housing and fills the internal space with liquid. A liquid injection nozzle is provided in the internal space of the housing to inject the liquid introduced from the liquid supply unit into the internal space toward the irradiation position of the laser beam irradiating the workpiece. The liquid injection nozzle ejects a liquid in a direction orthogonal to the processing feed direction, so that a laser processing apparatus is provided in which irradiation of a work piece with a laser beam is not hindered. Further, when the present invention is applied to a laser processing apparatus that performs ablation processing, it is possible to suppress debris generated during laser processing from adhering to the device without coating the surface of the wafer with a liquid resin. , Prevents the processing quality of the device from deteriorating.

It is a perspective view of the laser processing apparatus which concerns on this embodiment. FIG. 3 is an exploded perspective view showing a part of the laser processing apparatus shown in FIG. 1 in an exploded manner. It is a perspective view of (a) a liquid layer generator attached to the laser processing apparatus shown in FIG. 1, and (b) an exploded perspective view which shows by disassembling the liquid layer generator. It is a block diagram for demonstrating the outline of the optical system of the laser beam irradiation means mounted on the laser processing apparatus shown in FIG. 1. It is a partially enlarged sectional view which shows the operating state at the time of processing about the liquid layer generator mounted on the laser processing apparatus shown in FIG.

Hereinafter, the laser processing apparatus according to the embodiment of the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 shows a perspective view of the laser processing apparatus 2 of the present embodiment and a plate-shaped workpiece (for example, a silicon wafer 10) processed by the laser processing apparatus 2. The laser processing device 2 is arranged on the base 21, a holding means 22 for holding a plate-shaped workpiece, a moving means 23 for moving the holding means 22, and a side of the moving means 23 on the base 21. A frame body 26 composed of a vertical wall portion 261 erected in the Z direction indicated by an arrow Z and a horizontal wall portion 262 extending in the horizontal direction from the upper end portion of the vertical wall portion 261, a liquid supply mechanism 4, and a laser beam irradiating means. It is equipped with 8. As shown in the figure, the wafer 10 is supported by the annular frame F via, for example, the adhesive tape T, and is held by the chuck table 34 of the holding means 22. The laser processing apparatus 2 described above is entirely covered with a housing or the like omitted for convenience of explanation, and is configured to prevent dust or the like from entering the inside.

FIG. 2 is a perspective view showing a state in which the liquid recovery pool 60 constituting a part of the liquid supply mechanism 4 is removed from the laser processing device 2 and disassembled with respect to the laser processing device 2 shown in FIG.

The laser processing apparatus 2 according to the present embodiment will be described in detail with reference to FIG. 2.
Inside the horizontal wall portion 262 of the frame body 26, an optical system constituting the laser beam irradiating means 8 for irradiating the wafer 10 held by the holding means 22 with a laser beam is housed. A light collector 86 that constitutes a part of the laser irradiation mechanism 8 is arranged on the lower surface side of the tip portion of the horizontal wall portion 262, and is adjacent to the light collector 86 in the direction indicated by the arrow X in the figure. The alignment means 88 is arranged at the position. The alignment means 88 is used to capture an image of the workpiece held by the holding means 22 to detect a region to be laser-processed, and to align the condenser 86 with the machining position of the workpiece. Will be done.

The alignment means 88 is provided with an image pickup device (CCD) that uses visible light to image the surface of the wafer 10. Depending on the material constituting the waha 10, an infrared irradiation means for irradiating infrared rays, an optical system for capturing infrared rays irradiated by the infrared irradiation means, and an image pickup element for outputting an electric signal corresponding to the infrared rays captured by the optical system ( It is preferable to include infrared CCD).

The holding means 22 is movable in the X-axis direction indicated by the arrow X in FIG. 2, and is movable in the Y-axis direction indicated by the rectangular X-axis direction movable plate 30 mounted on the base 21 and the arrow Y in FIG. A rectangular Y-axis movable plate 31 mounted on the X-axis movable plate 30, a cylindrical support 32 fixed to the upper surface of the Y-axis movable plate 31, and a rectangle fixed to the upper end of the support 32. Includes a cover plate 33 having a shape. The cover plate 33 is provided with a chuck table 34 extending upward through an elongated hole formed on the cover plate 33. The chuck table 34 holds a circular workpiece and is configured to be rotatable by a rotation driving means (not shown). On the upper surface of the chuck table 34, a circular suction chuck 35 formed of a porous material and extending substantially horizontally is arranged. The suction chuck 35 is connected to a suction means (not shown) by a flow path passing through the support column 32, and four clamps 36 are evenly arranged around the suction chuck 35. The clamp 36 grips the frame F that holds the wafer 10 when the wafer 10 is fixed to the chuck table 34. The X-axis direction is the direction indicated by the arrow X in FIG. 2, and the Y-axis direction is the direction indicated by the arrow Y and is orthogonal to the X-axis direction. The plane defined in the X-axis direction and the Y-axis direction is substantially horizontal.

The moving means 23 includes an X-axis direction moving means 50 and a Y-axis direction moving means 52. The X-axis direction moving means 50 converts the rotational motion of the motor 50a into a linear motion via the ball screw 50b and transmits it to the X-axis direction movable plate 30 along the guide rails 27, 27 on the base 21. The movable plate 30 in the X-axis direction is moved forward and backward in the X-axis direction. The Y-axis direction moving means 52 converts the rotational motion of the motor 52a into a linear motion via the ball screw 52b, transmits it to the Y-axis direction movable plate 31, and guide rails 37, 37 on the X-axis direction movable plate 30. The movable plate 31 in the Y-axis direction is moved back and forth in the Y-axis direction along the above. Although not shown, the X-axis direction moving means 50 and the Y-axis direction moving means 52 are respectively provided with position detecting means, and the position of the chuck table 34 in the X-axis direction and the position in the Y-axis direction. , The rotation position in the circumferential direction is accurately detected, the X-axis direction moving means 50, the Y-axis direction moving means 52, and the rotation driving means (not shown) are driven, and the chuck table 34 is accurately positioned at an arbitrary position and angle. Is possible. The X-axis direction moving means 50 described above is a machining feeding means for moving the holding means 22 in the machining feeding direction, and the Y-axis direction moving means 52 is an indexing feeding means for moving the holding means 22 in the indexing feed direction.

The liquid supply mechanism 4 will be described with reference to FIGS. 1 to 3. As shown in FIG. 1, the liquid supply mechanism 4 connects the liquid layer generator 40, the liquid supply pump 44, the filtration filter 45, the liquid recovery pool 60, the liquid layer generator 40, and the liquid supply pump 44. It includes a pipe 46a and a pipe 46b connecting the liquid recovery pool 60 and the filtration filter 45. It is preferable that the pipe 46a and the pipe 46b are partially or wholly formed of a flexible hose.

As shown in FIG. 3A, the liquid layer generator 40 is positioned directly under the light collector 86, and more specifically, is attached to the lower end portion of the light collector 86. An exploded view of the liquid layer generator 40 is shown in FIG. 3 (b). As can be seen from FIG. 3B, the liquid layer generator 40 includes a housing 42 and a liquid supply unit 43.

The housing 42 has a substantially rectangular shape in a plan view, and is composed of a top wall 421 and a side wall 422. The top wall 421 has a substantially square shape in a plan view, and a circular opening 421a into which the lower end portion of the condenser 86 is inserted and fixed is formed in the central portion. A transparent plate 423 that allows the passage of the laser beam LB, which will be described later, is disposed at the bottom of the circular opening 421a, and closes the bottom of the circular opening 421a. That is, the top wall 421 includes a transparent plate 423. The top wall 421 is provided with air bleeding holes 421b penetrating in the vertical direction (X-axis direction) at four locations so as to surround the circular opening 421a. The transparent plate 423 is formed of transparent glass, but is not limited to this, and may be, for example, a transparent plate made of a resin such as acrylic.

The side wall 422 is a member hanging from the outside of the top wall 421, and is formed so as to cover the side surface of the internal space 422a formed by the housing 42. As shown in FIG. 3B, the side wall 422 is connected to two first frame members 422b and 422b that face each other in the X-axis direction and extend in the Y-axis direction, and a liquid supply unit 43 that extends in the X-axis direction. It is composed of a second frame member 422c constituting the side wall, a third frame member 422d facing the second frame member 422c and extending in the X-axis direction, and a liquid injection nozzle 422e formed on the second frame member 422c. ..

A liquid introduction port 422g and 422g are formed on the side of the second frame member 422c to which the liquid supply portion 43 is connected. Inside the first frame member 422b and 422b, a liquid passage 422h and 422h extending in the Y-axis direction are formed and connected to the liquid introduction port 422g and 422g. Further, a liquid supply port 422i opened toward the internal space 422a is formed on the inner side surface of the two first frame members 422b, and the liquid supply port 422i is connected to the liquid passage 422h. That is, the liquid introduction port 422g is communicated with the internal space 422a via the liquid passage 422h and the liquid supply port 422i.

The liquid injection nozzle 422e is formed in the center of the second frame member 422c. An injection nozzle introduction port 422f is formed on the upper surface of the second frame member 422c, and the injection nozzle introduction port 422f is communicated with the internal space 422a via the liquid injection nozzle 422e. The passage formed by the injection nozzle 422e is formed so that the cross-sectional area of the passage gradually becomes narrower and toward the lower side of the internal space 422a. The operation of the liquid injection nozzle 422e will be described in detail later.

The liquid supply unit 43 includes a supply port 43a for introducing the liquid into the inside, an internal passage 43b formed inside, and a central discharge port 43c, a sub-discharge port 43d, and 43d communicated via the internal passage 43b. , Is equipped. As shown in FIG. 3B, when the liquid supply unit 43 is connected to the housing 42, the central discharge port 43c is connected to the injection nozzle introduction port 422f, and the sub discharge port 43d is connected to the liquid introduction port 422g. Be connected.

The liquid layer generator 40 has the above-mentioned configuration, and the supply port 43a of the liquid supply unit 43 has an internal passage 43b, a central discharge port 43c, a sub discharge port 43d, a liquid injection nozzle 422e, and a liquid passage 422h. It communicates with the internal space 422a of the housing 42 via the above.

Returning to FIGS. 1 and 2, the liquid recovery pool 60 will be described. As shown in FIG. 2, the liquid recovery pool 60 includes an outer frame body 61 and two waterproof covers 66.

The outer frame body 61 has a predetermined distance inside the outer wall 62a extending in the X-axis direction indicated by the arrow X in the figure, the outer wall 62b extending in the Y-axis direction indicated by the arrow Y in the figure, and the outer walls 62a and 62b. The inner side walls 63a and 63b are arranged in parallel with each other, and the outer walls 62a and 62b and the bottom wall 64 connecting the lower ends of the inner side walls 63a and 63b are provided. The outer side walls 62a, 62b, the inner side walls 63a, 63b, and the bottom wall 64 form a rectangular liquid recovery path 70 whose longitudinal direction is along the X-axis direction and whose lateral direction is along the Y-axis direction. An opening that penetrates vertically is formed inside the inner side walls 63a and 63b constituting the liquid recovery path 70. The bottom wall 64 constituting the liquid recovery path 70 is provided with a slight inclination in the X-axis direction and the Y-axis direction, and the corner portion (left corner in the figure) at the lowest position of the liquid recovery path 70 is provided. A liquid discharge hole 65 is provided in the portion). A pipe 46b is connected to the liquid discharge hole 65 and is connected to the filtration filter 45 via the pipe 46b. The outer frame 61 is preferably formed of a stainless steel plate that is resistant to corrosion and rust.

The two waterproof covers 66 include a fixing bracket 66a having a portal shape and a bellows-shaped resin cover member 66b to which the fixing bracket 66a is fixed to both ends. The fixing metal fitting 66a is formed with dimensions capable of straddling two inner side walls 63a of the outer frame body 61 arranged so as to face each other in the Y-axis direction. One of the fixing brackets 66a of the two waterproof covers 66 is fixed to the inner side wall 63b arranged so as to face each other in the X-axis direction of the outer frame body 61, respectively. The liquid recovery pool 60 configured in this way is fixed on the base 21 of the laser processing apparatus 2 by a fixture (not shown). The cover plate 33 of the holding means 22 is attached so as to be sandwiched between the fixing metal fittings 66a of the two waterproof covers 66. The end face of the cover member 33 in the X-axis direction has the same portal shape as the fixing bracket 66a, and has a dimension that straddles the inner side wall 63a of the outer frame body 61 in the Y-axis direction, similarly to the fixing bracket 66a. be. Therefore, the cover member 33 is attached to the waterproof cover 66 after the outer frame body 61 of the liquid recovery pool 60 is installed on the base 21. According to the above configuration, when the cover plate 33 is moved in the X-axis direction by the X-axis direction moving means 50, the cover plate 33 moves along the inner side wall 63a of the liquid recovery pool 60. The method of attaching the waterproof cover 66 and the cover member 33 is not limited to the above procedure. For example, before attaching the two waterproof covers 66 to the inner side wall 63b of the outer frame body 61, the cover member 33 is attached in advance. The waterproof cover 66 may be attached together with the cover member 33 to the outer frame body 61 previously attached to the base 21.

Returning to FIG. 1 and continuing the description, the liquid supply mechanism 4 has the above-described configuration, so that the liquid W discharged from the discharge port 44a of the liquid supply pump 44 passes through the pipe 46a and is a liquid layer. It is supplied to the generator 40. The liquid W supplied to the liquid layer generator 40 is ejected from the liquid injection nozzle 422e and the liquid supply port 422i of the housing 42 of the liquid layer generator 40 toward the internal space 422a. The liquid W ejected from the liquid layer generator 40 flows on the cover plate 33 or the waterproof cover 66, and flows down to the liquid recovery pool 60. The liquid W flowing down to the liquid recovery pool 60 flows through the liquid recovery path 70 and is collected in the liquid discharge hole 65 provided at the lowest position of the liquid recovery path 70. The liquid W collected in the liquid discharge hole 65 is guided to the filtration filter 45 via the pipe 46b, and the laser processing debris (debris), dust, dust, etc. are removed by the filtration filter 45, and the liquid supply pump is used. Returned to 44. In this way, the liquid W discharged by the liquid supply pump 44 circulates in the liquid supply mechanism 4.

FIG. 4 is a block diagram showing an outline of the optical system of the laser beam irradiating means 8. As shown in FIG. 4, the laser beam irradiating means 8 oscillates from an oscillator 82 that oscillates a pulsed laser beam LB, an attenuator (not shown) that adjusts the output of the laser beam LB oscillated by the oscillator 82, and an oscillator 82. It includes a reflection mirror (not shown) that appropriately changes the optical path of the laser beam LB, a polygon mirror 91 as a dispersion means for dispersing the irradiation direction of the laser beam LB, and a condenser 86. The oscillator 82 oscillates, for example, a laser beam LB having a wavelength that is absorbent to the workpiece.

The polygon mirror 91 arranged on the upper portion of the condenser 86 includes a motor (not shown) that rotates the polygon mirror 91 at high speed in the direction indicated by the arrow R. Inside the condenser 86, a condenser lens (fθ lens) 86a that concentrates the laser beam LB and irradiates the workpiece is disposed. As shown in the figure, in the polygon mirror 91, a plurality of mirrors M are arranged concentrically with respect to the rotation axis of the polygon mirror 91. The fθ lens 86a is located below the polygon mirror 91 described above, and collects the laser beam LB reflected by the polygon mirror 91 and irradiates the wafer 10 on the chuck table 34. By rotating the polygon mirror 91, the angle of the laser beam LB reflected by the mirror M changes within a predetermined range, and the laser beam LB is dispersed and irradiated in a predetermined range in the machining feed direction (X-axis direction) on the wafer 10. Will be done.

Further, the laser beam irradiating means 8 includes a focusing point position adjusting means (not shown). Although the specific configuration of the condensing point position adjusting means is omitted, for example, a ball screw whose nut portion is fixed to the condensing device 86 and extends in the Z direction indicated by the arrow Z is connected to one end of the ball screw. It may be configured to have a motor. With such a configuration, the rotary motion of the motor is converted into a linear motion, and the condenser 86 is moved along a guide rail (not shown) arranged in the Z direction, whereby the condenser 86 is moved. Adjusts the position of the focusing point of the laser beam LB focused by the lens in the Z direction.

The laser processing apparatus 2 of the present invention has substantially the same configuration as described above, and its operation will be described below.

When laser machining is performed by the laser machining device 2 of the present embodiment, a plate-shaped workpiece supported by an annular frame F via an adhesive tape T, for example, silicon (Si) having a device formed on its surface. Prepare a wafer 10 made of. When the wafer 10 is prepared, the wafer 10 is placed on the suction chuck 35 of the chuck table 34 shown in FIG. 1 with the surface on which the device is formed facing up, and fixed by a clamp 36 or the like. When the wafer 10 is fixed on the suction chuck 35, a suction source (not shown) is operated to generate a suction force on the suction chuck 35 to suck and hold the wafer 10.

When the wafer 10 is held by the suction chuck 35, the chuck table 34 is appropriately moved in the X-axis direction and the Y-axis direction by the moving means 23, and the wafer 10 on the chuck table 34 is positioned directly under the alignment means 88. If the wafer 10 is positioned directly below the alignment means 88, the alignment means 88 is used to image the top of the wafer 10. Next, based on the image of the wafer 10 captured by the alignment means 88, the wafer 10 and the condenser 86 are aligned by a method such as pattern matching. The condenser 86 is positioned above the processing start position on the wafer 10 by moving the chuck table 34 based on the position information obtained by this alignment. Next, the condenser 86 is moved in the Z direction by a condensing point position adjusting means (not shown), and the condensing point is positioned at the surface height of one end of the scheduled division line which is the irradiation start position of the laser beam LB of the wafer 10.

FIG. 5 shows a partially enlarged cross-sectional view of the liquid layer generator 40 cut in the Y-axis direction. As can be seen from FIG. 5, the liquid layer generator 40 is arranged at the lower end of the concentrator 86, and when the condensing point is positioned at the surface height of the wafer 10, the liquid layer generator 40 is arranged. A slight gap of, for example, about 0.5 mm to 2.0 mm is formed between the lower end of the liquid supply portion 43 constituting the 40 and the side wall 422 constituting the housing 42 and the surface of the wafer 10. It is set.

After the alignment between the condenser 86 and the wafer 10 is performed, the liquid supply mechanism 4 is replenished with the necessary and sufficient liquid W via the liquid recovery path 70 of the liquid recovery pool 60, and the liquid supply pump 44 is used. Operate. As the liquid W circulating in the liquid supply mechanism 4, for example, pure water is used.

Since the liquid supply mechanism 4 has the above-described configuration, the liquid W discharged from the discharge port 44a of the liquid supply pump 44 is supplied to the liquid layer generator 40 via the pipe 46a. As shown in FIG. 5, the liquid W supplied to the liquid layer generator 40 is supplied to the internal space 422 via the liquid supply unit 43, the liquid passage 422h of the housing 42, and the liquid supply port 422i. Further, the liquid W is injected from the tip of the liquid injection nozzle 422e into the internal space 422a. The gap formed between the lower end of the side wall 422 of the housing 42 and the wafer 10 is formed to be smaller than the passage cross-sectional area of the liquid passage 422h and the liquid injection nozzle 422e. Then, the air existing in the internal space 422a is gradually discharged from the air vent hole 421b formed in the top wall 421, so that the internal space 422a is gradually filled with the liquid W. .. The liquid W discharged from the gap between the lower end of the side wall 422 of the housing 42 and the wafer 10 and the air bleeding hole 421b is subsequently flowed down and collected in the liquid recovery pool 60. The liquid W flowing down in the liquid recovery pool 60 flows through the liquid recovery path 70 and is collected in the liquid discharge hole 65 provided at the lowest position of the liquid recovery path 70. The liquid W collected in the liquid discharge hole 65 is guided to the filtration filter 45 via the pipe 46b, cleaned by the filtration filter 45, and returned to the liquid supply pump 44. In this way, the liquid W discharged by the liquid supply pump 44 circulates in the liquid supply mechanism 4.

When the liquid supply mechanism 4 starts operating and a predetermined time (about several minutes) elapses, the air in the internal space 422a of the housing 42 is completely discharged, and the layer of the liquid W is filled with the liquid W. It will be in a stable circulation state in the formed state.

In a state where the liquid W is stably circulated in the liquid supply mechanism 4, the chuck table 34 is moved in the machining feed direction (X-axis direction) by operating the X-axis direction moving means 50 while operating the laser beam irradiating means 8. ) At the specified movement speed. The laser beam LB emitted from the condenser 86 passes through the transparent plate 423 of the liquid layer generator 40 and the layer of liquid W filling the internal space 422a, and is irradiated to the work position (scheduled division line) of the wafer 10. To. When irradiating the wafer 10 with the laser beam LB, as described with reference to FIG. 4, the laser beam LB is dispersed and irradiated with respect to the wafer 10 in the X-axis direction, which is the processing feed direction, as the polygon mirror 91 rotates. To. After the predetermined mirror M is irradiated with the laser beam LB, the laser beam LB is irradiated to the next mirror M located on the downstream side in the rotation direction R of the polygon mirror 91, and the laser beam LB is continuously dispersed with respect to the weight 10. Is irradiated. The laser beam LB is oscillated from the oscillator 82, and such laser processing is repeated while the polygon mirror 91 is rotating. The number of mirrors M constituting the polygon mirror 91, the rotation speed of the polygon mirror 91, and the like are appropriately determined according to the workpiece.

The laser processing conditions in the laser processing apparatus 2 described above can be implemented under the following processing conditions, for example.
Wavelength of laser beam: 226nm, 355nm, 532nm, 1064nm
Average output: 10-100W
Repeat frequency: 0 to 300 MHz
Pulse width: 50fs to 1ns
Processing feed rate: 10 to 1000 mm / s

When the ablation process is performed in the above-mentioned state, bubbles are generated in the liquid W at the position where the laser beam LB of the wafer 10 is irradiated. On the other hand, in the present embodiment, as shown in FIG. 5, the liquid W is constantly flowed through the internal space 422a of the liquid layer generator 40 formed on the wafer 10 and is directed toward the irradiation position of the laser beam. The liquid W is ejected from the liquid vs. injection nozzle 422e. As a result, the bubbles generated in the vicinity of the irradiation position of the laser beam LB are quickly discharged to the outside of the housing 42 from the irradiation position of the laser beam on the wafer 10 and removed. In particular, according to the present embodiment, the liquid ejection nozzle 422e formed in the housing 42 ejects the liquid W from a direction orthogonal to the X-axis direction, which is the direction in which the laser beam LB is dispersed, that is, from the Y-axis direction. As a result, the wafer 10 can be irradiated with the laser beam LB while avoiding the bubbles generated by the ablation processing, and good ablation processing can be continuously performed.

Further, by continuously injecting the liquid W to the irradiation position of the laser beam LB on the wafer 10, the debris released into the liquid W is quickly removed from the wafer 10 together with the bubbles. As can be understood from FIG. 1, the liquid W containing the above-mentioned bubbles and debris flows on the cover plate 33 and the waterproof cover 66, and is guided to the liquid recovery path 70 of the liquid recovery pool 60. The liquid W guided to the liquid recovery path 70 flows while discharging the bubbles generated by the ablation process to the outside, and is discharged from the liquid discharge hole 65 formed at the bottom of the liquid recovery path 70. The liquid W discharged from the liquid discharge hole 65 is guided to the filtration filter 45 via the pipe 46b and is supplied to the liquid supply pump 44 again. As the liquid W circulates in the liquid supply mechanism 4 in this way, debris, dust, and the like are appropriately captured by the filtration filter 45, and the liquid W is maintained in a clean state.

When the above-mentioned ablation processing is performed on the predetermined division schedule line, by operating the moving means 23, one end of the unprocessed division schedule line adjacent to the already laser-processed division schedule line in the Y-axis direction. The light collector 86 is positioned in the above, and the same laser processing as the above-mentioned ablation processing is performed. Then, if ablation processing is performed on all the adjacent division schedule lines, the chuck table 34 is rotated by 90 degrees, so that the unprocessed division schedule line orthogonal to the previously processed division schedule line in the predetermined direction is performed. The same ablation process is performed on the surface. In this way, ablation processing can be performed on all the planned division lines on the wafer 10.

According to the present embodiment, the laser beam LB is irradiated to the wafer 10 through the transparent plate 423 and the layer of the liquid W disposed in the liquid layer generator 40 to perform laser processing, and the laser processing is performed from the surface of the wafer 10. Bubbles generated and debris generated by laser processing are quickly removed together with the liquid W. As a result, air bubbles generated from the surface of the wafer 10 do not interfere with laser processing, and debris does not adhere to the device after processing to prevent deterioration of processing quality.

In the above embodiment, the laser beam LB irradiated from the oscillator 82 is configured to be dispersed by the polygon mirror 91 and guided to the condenser lens 86, but the present invention is not limited to this, and the reflection direction is replaced with the polygon mirror 91. May be a fixed mirror. Further, in the above-described embodiment, the laser processing performed on the wayha 10 is an ablation processing, but a processing for forming a modified layer inside the workpiece (for example, the laser described in Patent Document 2). It does not prevent the application to processing), that is, processing for forming a so-called shield tunnel (for example, laser processing described in Patent Document 3).

2: Laser processing device 4: Liquid supply mechanism 8: Laser beam irradiation means 10: Wafer (plate-shaped workpiece)
21: Base 22: Holding means 23: Moving means 26: Frame body 261: Vertical wall part 262: Horizontal wall part 30: X-direction movable plate 31: Y-direction movable plate 33: Cover plate 34: Chuck table 35: Suction chuck 40: Liquid layer generator 42: Housing 421: Top wall 421a: Circular opening 421b: Air vent hole 422: Side wall 422a: Internal space 422b: First frame member 422c: Second frame member 422d: Third Frame member 422e: Liquid injection nozzle 422f: Injection nozzle supply hole 422g: Liquid introduction port 422h: Liquid passage 422i: Liquid supply port 423: Transparent plate 43: Liquid supply unit 43a: Supply port 43b: Internal passage 43c: Central discharge port 43d : Sub-discharge port 44: Liquid supply pump 45: Filter filter 50: X-direction moving means 52: Y-direction moving means 60: Liquid recovery pool 60A: Space 65: Liquid discharge hole 66: Bellows cover 70: Liquid recovery path 86: Condenser 88: Alignment means

Claims (2)

A laser beam irradiating means provided with a holding means for holding a plate-shaped workpiece and a condenser for irradiating the workpiece held by the holding means with a laser beam, and the holding means and the condenser are relative to each other. A laser machining apparatus configured to include at least a machining feed means for machining and feeding.
A liquid layer generator, which is positioned directly under the concentrator and generates a liquid layer on the upper surface of the workpiece, is provided.
The liquid layer generator is
A side wall having a transparent plate that allows the passage of a laser beam irradiated by the concentrator, a top wall including the transparent plate, and a lower end portion that hangs from the outside of the top wall and forms a gap between the workpiece. It is composed of a housing composed of, and a liquid supply unit that supplies a liquid to the internal space of the housing and fills the internal space with the liquid.
In the internal space of the housing, a liquid injection nozzle that ejects the liquid introduced from the liquid supply unit toward the irradiation position of the laser beam irradiating the workpiece is arranged in the internal space .
The liquid injection nozzle is a laser processing apparatus that injects liquid in a direction orthogonal to the processing feed direction . The laser processing apparatus according to claim 1, wherein the laser beam irradiating means is provided with an oscillator that oscillates a laser beam and a dispersion means that disperses the laser beam oscillated from the oscillator.

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