JP6917727B2 - Laser processing equipment - Google Patents

Description

The present invention relates to a laser processing apparatus that disperses the irradiation direction of a laser beam by a polygon mirror and irradiates a plurality of laser beams to a processing point.

A wafer formed on the surface of a plurality of devices such as ICs and LSIs separated by a planned division line is divided into individual devices by a cutting device equipped with a rotatable cutting blade, and is used for electric devices such as mobile phones and personal computers. It will be used.

Further, in a wafer in which a device is formed by a functional layer in which a low dielectric constant insulating film (Low-k film) is laminated on the upper surface of a semiconductor substrate such as silicon, when a cutting blade is used to cut a planned division line, Since the functional layer laminated on the planned division line peels off like a mica and deteriorates the quality of the device, the planned division line is divided by a laser processing device before cutting the planned division line with a cutting blade. A technique for removing a film has been proposed by the applicant (see Patent Document 1).

Further, when the low-k film is removed by ablation processing by irradiating the planned division line with a laser beam to form a dividing groove, the melt of the Low-k film is not discharged and is filled in the groove formed by the laser beam. Since there is a possibility that a dividing groove of the required width will not be formed by returning, it is necessary to irradiate the laser beam many times along the planned dividing line in order to secure a dividing groove of sufficient width, which is said to be poor in productivity. There's a problem. In order to deal with this problem, the applicant has developed and already proposed a laser machining apparatus in which a laser beam is dispersed between a laser oscillator and a condenser in the machining direction and a plurality of laser beams are irradiated to the machining point. (See Patent Document 2).

Japanese Unexamined Patent Publication No. 2005-064231 Japanese Unexamined Patent Publication No. 2015-085347

According to the invention described in Patent Document 2, a laser beam is dispersed between the laser oscillator and the condenser in the processing direction so that a plurality of laser beams are irradiated to the processing point, which is efficient. It is possible to disperse the laser beam in the processing direction and irradiate the processing point with a plurality of laser beams. However, in order to improve productivity while maintaining the processing direction and the dispersion direction of the laser beam in a predetermined relationship, when a forward-rotating polygon mirror and a reverse-rotating polygon mirror are installed to reciprocate the wafer. In addition, the configuration is such that the polygon mirror that rotates in the forward direction is switched to the polygon mirror that rotates in the reverse direction, which includes a problem that the configuration becomes complicated and a failure is induced.

The present invention has been made in view of the above facts, and its main technical problem is that a laser capable of maintaining a predetermined relationship between a processing direction and a laser beam dispersion direction by a polygon mirror even with a simple configuration. The purpose is to provide processing equipment.

In order to solve the above-mentioned main technical problem, according to the present invention, in the laser processing apparatus, a holding means for holding the workpiece and a laser beam irradiating means for irradiating the workpiece held by the holding means with a laser beam. The holding means and the laser beam irradiating means are processed and fed relative to each other in the X direction, and the holding means and the laser beam irradiating means are processed relative to the Y direction orthogonal to the X direction. The laser beam irradiating means includes at least a Y-direction moving means for feeding, a laser oscillator that oscillates a laser beam, a polygon mirror that disperses the laser beam oscillated by the laser oscillator at a predetermined dispersion angle, and scans in the X direction. A condenser that concentrates the laser beam scanned in the X direction on the workpiece held by the holding means, and an inversion that is arranged between the polygon mirror and the condenser and reverses the scanning direction of the laser beam. The reversing device is composed of at least a device, and the reversing device includes an image rotation prism, a driving unit that rotates the image rotation prism 90 degrees around the center of the dispersion angle, a polygon mirror, and the image rotation prism. A first relay lens arranged between the laser beams dispersed at the dispersion angle to correct the laser beam into parallel light, and parallel arranged between the image rotation prism and the condenser and passing through the image rotation prism. A second relay lens that returns light to the dispersion angle, and at least when the workpiece held by the holding means is irradiated with a laser beam and processed on the outward path and when processed on the return path. the image rotation prism 90 degrees by rotating laser beam laser processing apparatus scanning direction Ru is inverted is provided.

The laser processing apparatus configured by the present invention includes a holding means for holding a work piece, a laser beam irradiating means for irradiating a work piece held by the holding means with a laser beam, the holding means, and the laser beam irradiating means. Includes at least an X-direction moving means that processes and feeds the laser beam relative to the X direction, and a Y-direction moving means that processes and feeds the holding means and the laser beam irradiating means in the Y direction orthogonal to the X direction. The laser beam irradiating means includes a laser oscillator that oscillates a laser beam, a polygon mirror that disperses the laser beam oscillated by the laser oscillator at a predetermined dispersion angle and scans it in the X direction, and a holding means that holds the laser beam scanned in the X direction. a condenser for condensing the workpiece held in the inverter to be inverted scanning direction of the laser beam arranged between the polygon mirror and the condenser unit, at least consists of, said inverter Is disposed between the image rotation prism, a drive unit that rotates the image rotation prism by 90 degrees with the center of the dispersion angle as the rotation axis, and the polygon mirror and the image rotation prism, and is dispersed at the dispersion angle. A first relay lens that corrects the laser beam to parallel light, and a second relay that is arranged between the image rotation prism and the condenser and returns the parallel light that has passed through the image rotation prism to the dispersion angle. A laser beam is formed by rotating the image rotation prism by 90 degrees between when the workpiece, which is composed of at least the lens and is held by the holding means, is irradiated with a laser beam and processed on the outward path and when the object is processed on the return path. it can reverse the scanning direction of Runode, realized by a simple configuration of a laser processing apparatus capable of maintaining the dispersion direction of the working direction and the laser beam in a predetermined relationship by the polygon mirror.

It is an overall perspective view which shows one Embodiment of the laser processing apparatus configured based on this invention. It is a block diagram for demonstrating the laser beam irradiation means adopted in the laser processing apparatus shown in FIG. It is explanatory drawing for demonstrating the image rotation prism which constitutes the reversing device of the laser beam irradiation means shown in FIG. 2, the drive motor which drives the image rotation prism, and the reversing principle of the image rotation prism.

Hereinafter, embodiments of a laser processing apparatus configured based on the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 shows an overall perspective view of the laser machining apparatus 2 of the present embodiment and the wafer 10 as a workpiece. The laser processing device 2 sends a laser beam to the holding means 6 for holding the wafer 10, the moving means 8 arranged on the stationary base 2a to move the holding means 6, and the wafer 10 held by the holding means 6. From the laser beam irradiating means 24 to irradiate, the vertical wall portion 51 erected on the side of the moving means 8 on the stationary base 2a, and the horizontal wall portion 52 extending in the horizontal direction from the upper end portion of the vertical wall portion 51. It is provided with a frame body 50. The optical system of the laser beam irradiating means 24 is built in the horizontal wall portion 52 of the frame body 50, and the condenser 241 of the laser beam irradiating means 24 is arranged on the lower surface of the tip of the horizontal wall portion 52. ing. Further, an imaging means 26 is arranged at a position adjacent to the condenser 241 in the X direction. The holding means 6 holds the wafer 10 held by the adhesive tape T on the annular frame F enlarged in the drawing.

The holding means 6 has a rectangular X-direction movable plate 30 mounted on the base 2a so as to be movable in the X direction indicated by the arrow X in the drawing, and an X movablely movable in the Y direction indicated by the arrow Y in the drawing. A rectangular Y-direction movable plate 31 mounted on the directional movable plate 30, a cylindrical support plate 32 fixed to the upper surface of the Y-direction movable plate 31, and a rectangular cover plate 33 fixed to the upper end of the support column 32. And include. A bellows is arranged in the X direction on the cover plate 33 (not shown), and a circular workpiece extending upward through an elongated hole extending in the Y direction formed on the cover plate 33 is processed. A chuck table 34 that holds an object and is configured to be rotatable in the circumferential direction by a rotation driving means (not shown) is arranged. 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. The X direction is the direction indicated by the arrow X in FIG. 1, and the Y direction is the direction indicated by the arrow Y and is orthogonal to the X direction. The planes defined in the X and Y directions are substantially horizontal.

The moving means 8 includes an X-direction moving means 40 and a Y-direction moving means 41. The X-direction moving means 40 converts the rotational motion of the motor 40b into a linear motion via the ball screw 40a and transmits it to the X-direction movable plate 30, and moves the X-direction movable plate 30 along the guide rail on the base 2a. Move forward and backward in the X direction. The Y-direction moving means 41 converts the rotational motion of the motor 41b into a linear motion via the ball screw 41a, transmits it to the Y-direction movable plate 31, and transmits the Y-direction movable plate along the guide rail on the X-direction movable plate 30. 31 is moved forward and backward in the Y direction. Although not shown, position detecting means are provided in the X-direction moving means 40, the Y-direction moving means 41, and the rotation driving means, respectively, and the positions of the chuck table 34 in the X-direction and the Y-direction are arranged. The position and the rotational position in the circumferential direction are accurately detected, and the X-direction moving means 40, the Y-direction moving means 41, and the rotational driving means are driven based on a signal instructed from a control means (not shown), and the arbitrary position and the rotation driving means are driven. It is possible to accurately position the chuck table 34 at an angle.

Based on FIG. 2, the laser beam irradiating means 24 configured to realize the wafer processing apparatus of the present invention will be described more specifically. As shown in FIG. 2A, the laser beam irradiating means 24 provides a laser oscillator 242 for irradiating a laser beam having a wavelength of 532 nm, which has absorption with respect to a wafer 10 made of silicon (Si), from the condenser 241. I have. The laser beam LB oscillated from the laser oscillator 242 is incident on the attenuator 243 that adjusts the output of the laser beam by adjusting the transmittance. The laser beam LB adjusted to a desired output by the attenuator 243 is changed in the traveling direction by the reflection mirror 244, and the laser beam LB whose traveling direction is changed is irradiated to the polygon mirror 245. The polygon mirror 245 has a plurality of reflecting surfaces that disperse the reflection direction of the laser beam LB in the range of the laser beam LBa to LBb forming a predetermined dispersion angle by being rotated in the direction indicated by the arrow 245'in the drawing by a drive motor (not shown). It is equipped with 245a.

The laser beams LBa to LBb reflected by the reflecting surface 245a of the polygon mirror 245 are irradiated to the reversing device 246. As shown in the figure, the reversing device 246 is corrected to parallel light by a first relay lens 246a that corrects the laser beams LBa to LBb dispersed by the polygon mirror 245 to parallel light, and a first relay lens 246a. It is composed of an image rotation prism 246c which is irradiated with a laser beam and is rotatably configured by a drive motor 246b, and a second relay lens 246d which returns parallel light passing through the image rotation prism 246c to the dispersion angle. The image rotation prism 246c is configured to be rotated by 90 degrees by meshing the driven gear 246f arranged on the outer peripheral portion with the drive gear 246e of the drive motor 246b.

As shown in FIG. 2A, the reversing device 246 reverses the scanning direction D1 of the laser beams LBa to LBb accompanying the rotation of the polygon mirror 245 and emits the laser beam 246 as the scanning direction D2. As shown, it is possible to switch to a state in which the incident laser beams LBa to LBb are emitted in the scanning direction D2'as they are without changing the scanning direction D1. Then, as shown in FIG. 2A, when the scanning direction of the laser beams LBa to LBb is inverted to D2 by the reversing device 246, the laser beams LBa to LBb emitted from the reversing device 246 are transmitted by the reflection mirror 249. It is reflected, collected by the telecentric fθ lens 241a built in the concentrator 241 and irradiated onto the wafer 10 held on the chuck table 34. At this time, the laser beam emitted from the condenser 241 is scanned in the direction indicated by the arrow D3 in the range corresponding to the dispersion angle, that is, in the range indicated by the irradiation position P1 of the laser beam LBa to the irradiation position P2 of the laser beam LBb. NS. Further, as shown in FIG. 2B, when the scanning directions D1 of the laser beams LBa to LBb incident on the reversing device 246 are maintained without being reversed and emitted in the scanning direction D2', the reversing is performed. The laser beams LBa to LBb emitted from the vessel 246 are on the wafer 10 held by the chuck table 34 in a range corresponding to the dispersion angle, that is, from the irradiation position P1'of the laser beam LBa to the irradiation position P2'of the laser beam LBb. In the range of the indicated position, the scan is performed in the direction indicated by the arrow D3'. The dispersion angle provided by the polygon mirror 245 is set so that the distance from the irradiation position P1 (P1') of the laser beam irradiated on the chuck table 34 to the irradiation position P2 (P2') is 8 mm. ..

An example of the configuration of the image rotation prism 246c and the drive motor 246b constituting the reversing device 246 will be described in more detail with reference to FIG. As shown in the figure, the image rotation prism 246c is generally known as a so-called image inversion prism. More specifically, as shown in FIG. 3B, an incident side prism 246c1 having an incident surface Q on which a laser beam is incident and an emitting side prism 246c2 having an emitting surface R are combined with each other. The incident surface Q and the exit surface R are combined so as to be parallel to each other while providing a slight gap 246c3 between the inner slope U of the 246c1 and the inner slope V of the exit side prism 246c2. It can be composed of a combination prism having surfaces S and T and having a substantially trapezoidal shape in a lateral view.

The principle that the scanning direction is reversed by the image rotation prism 246c will be described with reference to FIG. FIG. 3B is a schematic view showing a state in which the image rotation prism 246c is viewed from a side view in a trapezoidal shape, and the incident position of the laser beam on the incident surface Q is in the direction of arrow W1 (FIG. 3 (B). The ray paths a, b, and c when moving in the direction of the arrow d1 in a) are shown. The ray path b is incident from the center position of the incident surface Q, and the incident positions of the ray paths a and c are point-symmetrical positions centered on the incident position of the ray path b. Further, the case where the laser beam travels along the ray path a is shown by a solid line, the case where the laser beam travels along the ray path b is shown by a dotted line, and the case where the laser beam travels along the ray path c is shown by a alternate long and short dash line.

As shown in the figure, the laser beam is set to be incident at right angles to the incident surface Q, and the laser beam incident on the incident surface Q in the light path a is the inner slope U of the incident side prism 246c1 and further. It is reflected by the outer slope T and is incident on the inner slope V of the exit side prism 246c2 at right angles. Then, the laser beam that travels straight through the gap 246c3 and enters the exit-side prism 246c2 is reflected by the emission surface R, the outer slope S, and the inner slope V, and then is emitted from the exit surface R. Similarly, the light path paths b and c are reflected twice by the incident side prism 246c1 side and three times by the exit side prism 246c2, and are emitted from the position shown in FIG. 3 (b). As is clear from the figure, the light path a, b, and c incident from the incident surface Q are irradiated from the exit surface R in a state of being rotated 180 degrees around the light path b, and the incident surface Q is emitted. When the laser beam is scanned in the order of a, b, c on the side, that is, in the direction indicated by the arrow W1 in FIG. 3B, the scanning direction is reversed in the direction indicated by the arrow W2 on the exit surface R side. Further, when the laser beam is scanned in the direction indicated by the arrow d2 perpendicular to the arrow d1 at the center of the incident surface Q in FIG. 3 (a), the laser beam is at the position indicated by the ray path b in FIG. 3 (b). In addition, the incident position is moved in the direction perpendicular to the paper surface, and the emission position in that case is the position indicated by the light beam path b of the emission surface R in FIG. 3 (b) and in the direction perpendicular to the paper surface. Since it moves, the scanning direction of the incident laser beam is not inverted and is emitted as it is.

As described above, the reversing device 246 of the present embodiment includes the drive motor 246b, and is configured to be able to rotate the image rotation prism 246c by 90 degrees from the state shown in FIG. 3A. Therefore, when the scanning direction of the laser beam dispersed by the polygon mirror 245 is fixed as in the present embodiment, the driving motor 246b is driven to rotate the direction of the image rotation prism 246c by 90 degrees. , A state in which the direction D1 scanned on the incident surface Q of the image rotation prism 246c is matched with the direction in which the scanning direction is reversed by the reversing device 246 (the direction indicated by the arrow d1 in FIG. 3A). A state in which FIG. 2A) and the direction D1 scanned on the incident surface Q coincide with the direction in which the scanning direction is emitted without being reversed (the direction indicated by the arrow d2 in FIG. 3A) ( It can be switched with FIG. 2 (b)).

The laser processing apparatus 2 of the present invention generally has the above-described configuration, and the laser processing performed by the laser processing apparatus 2 will be described below.

As shown in FIG. 1, when laser machining is performed on a wafer 10 to be a work piece, the wafer 10 in which a plurality of devices 14 are formed on a functional layer on the surface side is annularly formed via a protective tape T. It is placed on the chuck table 34 while being supported by the frame F, and is sucked and held. Next, the chuck table 34 is positioned directly under the imaging means 26 arranged at a position adjacent to the condenser 241 in the X direction by the moving means 8. If the wafer 10 is positioned directly under the image pickup means 26, an image processing means such as pattern matching is executed, the condenser 241 and the processing position on the wafer 10 are aligned, and the result of the alignment is achieved. Is sent to and stored in a control means (not shown) (alignment step). When the alignment step is performed, the moving means 8 is operated to position one end side (machining start position) of the predetermined division scheduled line 12 of the wafer 10 on the chuck table 34 directly below the condenser 241. At this time, the condensing point of the laser beam emitted from the concentrator 241 is positioned near the upper surface of the functional layer on which the device 14 is formed, and the scanning direction of the image rotation prism 246c of the reversing device 246 is reversed in advance. The position is set by the control means.

Next, the laser beam oscillator 242 and the attenuator 243 are operated by the control means, and the polygon mirror 245 is operated by a motor (not shown) to rotate the chuck table 34 at a rotation speed of, for example, 5000 rpm. In a), the vehicle is moved in the outward route direction (from right to left in the figure) indicated by the arrow X at a predetermined processing feed rate, and so-called ablation processing is performed along the planned division line 12 to form a division groove. At this time, as shown in the figure, the scanning direction D3 on the wafer 10 is opposite to the outward direction in which the chuck table 34 indicated by the arrow X moves.

Laser machining is performed while moving the chuck table 34 in the outward direction, and when the other end side of the scheduled division line 12 reaches a position directly below the condenser 241, the irradiation of the laser beam is temporarily stopped and the chuck table 34 is temporarily stopped. Stop moving. In the above laser machining, due to the action of the polygon mirror 245, scanning is performed repeatedly in the direction of arrow X at a higher speed than the moving speed of the chuck table 34, so that the laser machining overlaps on the scheduled division line 12 of the waiha 10. The ablation process is repeatedly performed, and it is possible to effectively prevent the melt formed by the laser process from being backfilled in the divided groove.

The laser processing is performed under the following processing conditions, for example.
Wavelength of laser beam: 532 nm
Repeat frequency: 5MHz
Average output: 10W
Machining feed rate: 500 mm / sec

Further, the polygon mirror is configured as follows, for example.
Number of rotating mirrors: 10 rotations: 5000 rotations / sec Scan pulse: 100 pulses

Next, the control means operates the Y-direction moving means 41 to move the chuck table 34 in the Y direction (indexing feed direction) by the interval of the scheduled division lines 12 formed on the wafer 10, and the adjacent divisions. The other end side of the scheduled line 12 is positioned at the laser beam irradiation position of the condenser 241. At this time, the drive motor 246b of the reversing device 246 is operated to rotate the image rotation prism 246c by 90 degrees to obtain the state shown in FIG. 2 (b). That is, the scanning directions of the laser beams LBa to LBb incident on the incident surface Q are not reversed, and are emitted from the emitting surface R in the same direction D2'. Then, the condensing point of the laser beam emitted from the concentrator 241 is positioned near the surface on which the device 14 is formed on the scheduled division line 12, and the chuck table 34 is moved in the outward direction as described above. Irradiate a laser beam under laser processing conditions. At the same time, the chuck table 34 is moved at a predetermined machining feed rate in the return path direction (from left to right in the figure) indicated by the arrow X in FIG. 2 (b), and so-called ablation is performed along the scheduled division line 12. Processing is carried out to form a dividing groove. As shown in the figure, also in this case, the scanning direction D3'on the wafer 10 is opposite to the moving direction of the chuck table 34 indicated by the arrow X. In this way, laser machining is performed while moving the chuck table 34 also in the return direction, and when one end side of the scheduled division line 12 reaches a position directly below the condenser 241, the laser beam is irradiated. It stops once, and the movement of the chuck table 34 is stopped. In this laser processing as well, as in the case of moving in the outward direction, scanning is repeated within a range of 8 mm in the direction of arrow X, so that ablation processing is performed overlappingly on the scheduled division line 12 in the direction of arrow X. It is possible to effectively prevent the melt from being backfilled in the formed dividing groove by laser processing. After that, by appropriately operating the moving means 8 and the laser beam irradiating means 24, the same laser processing is performed on all the scheduled division lines 12 on the wafer 10, and the laser processing for forming the dividing groove is performed.

As can be understood from FIGS. 2A and 2B, according to the present embodiment, even when the chuck table 34 is moved in the return direction to perform laser machining, the laser is moved in the outward direction. It is possible to process under the same conditions as processing, and there are cases where laser processing is performed while moving in the outward direction and cases where laser processing is performed while moving in the return direction. The processing quality of the grooves can be made the same. Further, since the configuration for making the processing quality the same can be realized by the configuration in which the image rotation prism 246c in the reversing device 246 is rotated by 90 degrees, the configuration is not complicated or a failure is not induced, and maintenance is performed. The labor can be reduced.

The present invention is not limited to the above-described embodiment, and various modifications are assumed within the scope of the technical scope of the present invention. For example, in the above-described embodiment, by rotating the image rotation prism 246c by 90 degrees, the direction in which the laser beam is scanned is reversed regardless of whether the chuck table 34 moves in the outward path direction or the return path direction. The processing quality when the dividing groove is formed is the same, but the present invention is not limited to this, and the direction of the image rotation 246c set with respect to the direction in which the chuck table 34 moves is set in the opposite direction. By setting the scanning direction of the laser beam to be forward with respect to the moving direction of the chuck table 34, the processing quality when forming the dividing groove may be the same.

Further, in the present embodiment, the image rotation prism 246c used in the reversing device 246 is realized by combining the incident side prism 246c1 and the exit side prism 246c2, but the present invention is not limited to this, and the image inversion function is not limited to this. Other optical means such as a trapezoidal prism, a ladder prism, a dub prism, and the like can also be adopted.

2: Laser processing device 6: Holding means 8: Moving means 10: Wafer 12: Scheduled division line 14: Device 24: Laser beam irradiation means 241: Condenser 242: Laser oscillator 243: Attenuator 245: Polygon mirror 246: Inverter 246b : Drive motor 246c: Image rotation prism 26: Imaging means 40: X-direction moving means 41: Y-direction moving means

Claims (1)

It is a laser processing device
X that holds the workpiece, the laser beam irradiating means that irradiates the workpiece held by the holding means with a laser beam, and the holding means and the laser beam irradiating means that are relatively processed and fed in the X direction. At least a directional moving means and a Y-direction moving means for processing and feeding the holding means and the laser beam irradiating means in the Y direction orthogonal to the X direction are included.
The laser beam irradiating means uses a laser oscillator that oscillates a laser beam, a polygon mirror that disperses the laser beam oscillated by the laser oscillator at a predetermined dispersion angle and scans it in the X direction, and a laser beam scanned in the X direction as the holding means. It is composed of at least a concentrator that condenses on the held workpiece and a reversing device that is arranged between the polygon mirror and the concentrator and reverses the scanning direction of the laser beam .
The reversing device is arranged between an image rotation prism, a drive unit that rotates the image rotation prism by 90 degrees with the center of the dispersion angle as a rotation axis, and the polygon mirror and the image rotation prism, and the dispersion angle. A first relay lens that corrects the laser beam dispersed in the above to parallel light, and a second relay lens that is arranged between the image rotation prism and the condenser and returns the parallel light that has passed through the image rotation prism to the dispersion angle. Consists of at least two relay lenses,
And time of processing in the forward by irradiating a laser beam to the workpiece held by the holding means, a laser in the case of processing the return path, Ru rotate the image rotation prism 90 ° by inverting the scanning direction of the laser beam Processing equipment.

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