JP2022092771A - Workpiece processing method - Google Patents

Abstract

To provide a workpiece processing method capable of appropriately modifying a workpiece without damaging a device even when a portion on a surface side of the workpiece is provided with the device and a light-shielding film.SOLUTION: A workpiece processing method includes a first holding step, a first modified layer forming step, a second holding step, and a second modified layer forming step. The first holding step supports a portion on a surface side of the workpiece without sucking it and holds the workpiece by griping a frame by a first clamp mechanism. The first modified layer forming step forms a modified layer along division schedule lines in an outer peripheral region. The second holding step sucks an adhesive tape stuck to a portion on a rear side of the workpiece and holds the workpiece by griping the frame by a second clamp mechanism. The second modified layer forming step forms a modified layer along division schedule lines in a device region.SELECTED DRAWING: Figure 2

Description

The present invention relates to a work piece processing method applied when processing a plate-shaped workpiece.

In electronic devices such as mobile phones and personal computers, device chips equipped with devices having various functions are indispensable components. In the device chip, for example, a wafer made of a material such as silicon is divided into a plurality of regions by a planned division line (street), a device is formed in a portion on the surface side of each region, and then along the planned division line. Obtained by splitting the wafer.

When a plate-shaped workpiece such as a wafer is divided into a plurality of chips, for example, a laser beam having a wavelength transmitted through the workpiece is focused on a planned division line of the workpiece to separate the workpiece. Reform at the planned division line. After that, when a force is applied to the workpiece from the outside, the workpiece is divided into a plurality of chips at the boundary of the modified and fragile division schedule line.

By the way, when a film having a light-shielding property such as a metal film is provided on the surface side portion of the work piece, the work piece can be sufficiently provided even if the work piece is irradiated with a laser beam from the position on the surface side. Not modified to. Therefore, a method has been proposed in which a work piece is modified by irradiating the work piece with a laser beam from a position on the back surface side where a light-shielding film is not provided (see, for example, Patent Document 1).

In this method, first, the work piece is held by the holding table so that the back surface side portion is exposed by sucking the front surface side portion of the workpiece with the holding table (chuck table). Then, the laser beam is irradiated from the position opposite to the holding table (the position on the back surface side of the workpiece) toward the portion on the back surface side of the workpiece to modify the workpiece.

Japanese Unexamined Patent Publication No. 2007-173475

However, when the above method is applied to a workpiece provided with a device such as a structurally fragile thin film type MEMS (Micro Electro Mechanical System), there is a high possibility that the device will be damaged by the suction force of the holding table.

Therefore, an object of the present invention is to process a workpiece that can appropriately modify the workpiece without damaging the device even when the device and the light-shielding film are provided on the surface side portion of the workpiece. To provide a method.

According to one aspect of the present invention, the plurality of devices provided on the surface side portion of the device region partitioned by the scheduled division line and the outer peripheral region surrounding the device region and partitioned by the scheduled division line. Adhesive tape is attached to the portion of the plate-shaped workpiece opposite to the front surface, which is provided on the front surface side and has a light-shielding film overlapping the planned division line, and accommodates the work piece. A method for processing a workpiece in which the adhesive tape is fixed to an annular frame provided with an opening, and the workpiece is irradiated with a laser beam to modify the workpiece at the planned division line. , The surface side portion of the work piece is supported by the holding surface of the first holding table without suction through a protective member that protects the surface side portion of the work piece, and the first holding table is supported. A first holding step for holding the workpiece by gripping the frame with a first clamp mechanism provided around it, and after the first holding step, from a position opposite to the first holding table. By irradiating the planned division line in the outer peripheral region with a laser beam and modifying the workpiece at the planned division line in the outer peripheral region, the modified layer along the planned division line is formed in the outer peripheral region. After the first modified layer forming step and the first modified layer forming step, the adhesive tape attached to the back surface side portion of the workpiece so as to expose the front surface side portion is applied. The workpiece is brought into contact with the holding surface of the second holding table, the adhesive tape is sucked by the holding surface, and the frame is gripped by a second clamp mechanism provided around the second holding table. After the second holding step and the second holding step, a laser beam is irradiated to the planned division line in the device region from a position opposite to the second holding table, and the inside of the device region. Provided is a method for processing a workpiece including a second modified layer forming step of forming a modified layer along the planned division line in the device region by modifying the workpiece on the planned division line. Will be done.

Preferably, the protective member contacts the surface side portion of the workpiece without being adhered to the surface side portion to protect the surface side portion.

In the work piece processing method according to one aspect of the present invention, the work piece is formed by irradiating a portion of the work piece on the back surface side from a position opposite to the first holding table with a laser beam to form a modified layer along a planned division line. Since the surface side portion of the workpiece is not sucked by the holding surface of the first holding table when it is formed in the outer peripheral region of the above, the device is not damaged by the suction force acting from the holding surface.

In addition, when a laser beam is applied to the surface side portion of the workpiece from a position opposite to the second holding table to form a modified layer along the planned division line in the device region of the workpiece, the workpiece is formed. Since the adhesive tape attached to the back surface side is sucked by the holding surface of the second holding table, the workpiece will not be cracked even if the tension of the adhesive tape changes during the processing of the workpiece.

As described above, according to the work piece processing method according to one aspect of the present invention, even when the device and the light-shielding film are provided on the surface side portion of the work piece, the device is not damaged. Workpieces can be modified appropriately.

FIG. 1 is a perspective view showing a workpiece or the like before being processed. FIG. 2 is a cross-sectional view showing the first holding step. FIG. 3 is a cross-sectional view showing the first modified layer forming step. FIG. 4 is a cross-sectional view showing the second holding step. FIG. 5 is a cross-sectional view showing a second modified layer forming step. FIG. 6 is a perspective view showing a workpiece or the like after being processed.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view showing a work piece 11 and the like before being processed by the work piece processing method according to the present embodiment. The workpiece 11 processed in the present embodiment has a wafer made of a semiconductor such as silicon as a base portion, and is formed in a disk shape.

The workpiece 11 is divided into a device region 13 located inside in the radial direction and an annular outer peripheral region 15 surrounding the device region 13, and these two regions are divided into a plurality of planned division lines (streets) that intersect each other. It is further divided into a plurality of small areas by 17. A device 19 such as a thin film type MEMS (Micro Electro Mechanical System) is formed on a portion of each small region included in the device region 13 on the surface 11a side. That is, a plurality of devices 19 are provided on the portion of the device region 13 on the surface 11a side.

On the other hand, the portion of the outer peripheral region 15 on the surface 11a side is an annular structure made of a metal such as an Al—Cu alloy that absorbs or reflects the laser beam used for modifying the base portion of the workpiece 11. A light-shielding film (metal film) 21 is provided. That is, the light-shielding film 21 is provided so as to overlap the scheduled division line 17, and has a property (light-shielding property) of not transmitting the laser beam used for modifying the base portion.

For example, an adhesive tape (dicing tape) 31 having a diameter larger than that of the work piece 11 is attached to the portion on the back surface 11b side of the work piece 11. Further, the outer peripheral side portion of the adhesive tape 31 is fixed to an annular frame 33 provided with a circular opening 33a capable of accommodating the work piece 11. As described above, in the present embodiment, the workpiece 11 is processed while being supported by the frame 33 via the adhesive tape 31.

In the present embodiment, a disk-shaped wafer made of a semiconductor such as silicon is used as the base portion of the workpiece 11, but the material, shape, structure, size, etc. of the base portion of the workpiece 11 are limited. do not have. According to the work piece processing method according to the present embodiment, for example, the work piece 11 having a base portion made of a material such as another semiconductor, ceramics, resin, or metal can be processed.

Similarly, there are no major restrictions on the type, quantity, shape, structure, size, arrangement, etc. of the device 19 provided on the workpiece 11, and the material, shape, arrangement, etc. of the light-shielding film 21. For example, the light-shielding film 21 may be provided at least on the surface 11a side of the outer peripheral region 15 so as to overlap with the planned division line 17.

In the work piece processing method according to the present embodiment, the work piece 11 is irradiated with a laser beam, and the work piece 11 is modified along the scheduled division line 17. Specifically, first, a first holding step of holding the workpiece 11 is performed so that the outer peripheral region 15 can be modified by a laser beam. FIG. 2 is a cross-sectional view showing the first holding step.

In the first holding step, the laser processing apparatus 2 shown in FIG. 2 is used. As shown in FIG. 2, the laser processing apparatus 2 includes a chuck table (first holding table, second holding table) 4 used for holding the workpiece 11. The chuck table 4 is formed in, for example, a disk-shaped frame 6 made of a metal typified by stainless steel and a recess 6a formed in a porous disk shape made of a material such as ceramics and opened on the upper surface of the frame 6. Includes the arranged holding plate 8.

The upper surface of the holding plate 8 functions as a holding surface 8a for holding the workpiece 11. The recess 6a of the frame body 6 is connected to a suction source (not shown) such as a vacuum pump via a flow path 6b or the like provided inside the frame body 6. Further, a valve (not shown) capable of controlling the flow of the fluid is provided in the flow path 6b or the like. Therefore, if the valve is opened with the suction source operated, the negative pressure generated by the suction source acts on the holding surface 8a of the holding plate 8.

A plurality of clamp mechanisms (first clamp mechanism, second clamp mechanism) 10 used for fixing the frame 33 are provided around the frame body 6. A rotation drive source (not shown) such as a motor is connected to the lower portion of the frame body 6, and the chuck table 4 can rotate around a rotation axis substantially perpendicular to the holding surface 8a described above, for example. Further, the frame body 6 is supported by a moving mechanism (not shown), and the chuck table 4 can move in a direction (horizontal direction) substantially parallel to the holding surface 8a described above, for example.

In the first holding step, first, the disk-shaped protective member 35 corresponding to the workpiece 11 is arranged on the holding surface 8a of the chuck table (first holding table) 4. The protective member 35 is typically a resin film, a substrate, or the like, and has flexibility suitable for protecting a portion of the workpiece 11 on the surface 11a side (that is, the device 19).

After arranging the protective member 35 on the holding surface 8a of the chuck table 4, the work piece 11 is placed on the protective member 35 so that the surface 11a of the work piece 11 is in contact with the upper surface of the protective member 35. In the work piece processing method according to the present embodiment, after the protective member 35 is arranged on the holding surface 8a, no negative pressure is applied to the holding surface 8a. That is, the protective member 35 is not sucked by the holding surface 8a of the chuck table 4.

If the protective member 35 is sucked by the holding surface 8a, the suction force also acts on the portion of the work piece 11 on the surface 11a side through the fine pores existing in the protective member 35, and the device 19 may be damaged. Because. As described above, in the present embodiment, the portion of the work piece 11 on the surface 11a side is supported by the holding surface 8a of the chuck table 4 without being sucked through the protective member 35.

Further, in the present embodiment, the upper surface of the protective member 35 is brought into contact with the portion of the workpiece 11 on the surface 11a side, but is not adhered. Therefore, unlike the case where the protective member 35 is adhered to the portion of the work piece 11 on the surface 11a side, the device 19 is not damaged when the protective member 35 is peeled off from the work piece 11.

After the portion of the work piece 11 on the surface 11a side is supported by the holding surface 8a of the chuck table 4, the frame 33 is gripped by the clamp mechanism (first clamp mechanism) 10 provided around the chuck table 4. The frame 33 may be gripped by the clamp mechanism 10 at the same time as the work piece 11 is mounted on the protective member 35, or before the work piece 11 is mounted on the protective member 35. As a result, the workpiece 11 is held so that the portion on the back surface 11b side faces up.

As described above, the workpiece 11 is supported by the frame 33 via the adhesive tape 31. Therefore, if the frame 33 is gripped by the clamp mechanism 10, the position of the work piece 11 with respect to the chuck table 4 does not deviate significantly even if the work piece 11 is not fixed to the chuck table 4 by using negative pressure.

After the first holding step, the work piece 11 is irradiated with a laser beam from a position above the work piece 11 (the position opposite to the chuck table 4), and the work piece is formed at the planned division line 17 in the outer peripheral region 15. By modifying 11, a first modified layer forming step of forming a modified layer along the planned division line 17 in the outer peripheral region 15 is performed. FIG. 3 is a cross-sectional view showing the first modified layer forming step.

In the first modified layer forming step, the laser processing device 2 is continuously used. As shown in FIG. 3, a laser irradiation head 12 is arranged above the chuck table 4. The laser irradiation head 12 focuses the laser beam 23a generated by the laser oscillator (not shown) at a predetermined position. The laser oscillator includes, for example, a laser medium such as Nd: YAG and is configured to be capable of generating a pulsed laser beam 23a having a wavelength transmitted through the base portion of the workpiece 11.

In the first modified layer forming step, first, the angle around the rotation axis of the chuck table 4 is adjusted so that the planned division line 17 to be machined and the moving direction of the chuck table 4 are parallel to each other. Next, the chuck table 4 is moved to align the position of the laser irradiation head 12 with the position above the extension line of the scheduled division line 17 to be processed. Then, while irradiating the laser beam 23a from the laser irradiation head 12, the chuck table 4 is moved in a direction parallel to the target division scheduled line 17.

The position in the height direction of the condensing point for condensing the laser beam 23a is adjusted according to the position of the portion of the work piece 11 to be modified (the position in the thickness direction of the work piece 11). As a result, the work piece 11 can be modified by irradiating the scheduled division line 17 of the work piece 11 with the laser beam 23a from a position above the work piece 11 (a position opposite to the chuck table 4).

In the first modified layer forming step, as shown in FIG. 3, irradiation and non-irradiation of the laser beam 23a are switched so that the device region 13 of the workpiece 11 is not modified. That is, when the laser irradiation head 12 passes above the outer peripheral region 15, the work piece 11 is irradiated with the laser beam 23a, and when the laser irradiation head 12 passes above the device region 13, the workpiece 11 is irradiated. Do not irradiate the laser beam 23a.

After modifying the work piece 11 at the target division scheduled line 17 in the outer peripheral region 15 and forming the modified layer 25a along the planned division line 17 in the outer peripheral region 15, the same procedure is repeated and the outer peripheral region 15 is repeated. The modified layer 25a is formed on all the other scheduled division lines 17 in the above. When the modified layer 25a is formed on all the planned division lines 17 in the outer peripheral region 15, the first modified layer forming step is completed. In the first modified layer forming step, the modified layer 25a may be formed at each of a plurality of positions in the thickness direction of the workpiece 11.

After the first modified layer forming step, a second holding step of retaining the workpiece 11 is performed so that the device region 13 can be modified with a laser beam. FIG. 4 is a cross-sectional view showing the second holding step. The laser processing device 2 is still used in this second holding step.

In the second holding step, after removing the frame 33 from the clamp mechanism 10, the work piece 11 is turned upside down, and the adhesive tape 31 attached to the back surface 11b side of the work piece 11 is attached to the chuck table (second). The holding table) 4 is brought into contact with the holding surface 8a. After that, a negative pressure is applied to the holding surface 8a, and the adhesive tape 31 is sucked by the holding surface 8a.

After sucking the adhesive tape 31 on the holding surface 8a, the frame 33 is gripped by the clamp mechanism (second clamp mechanism) 10 provided around the chuck table 4. The frame 33 may be gripped by the clamp mechanism 10 at the same time as the adhesive tape 31 is brought into contact with the holding surface 8a, or before the adhesive tape 31 is brought into contact with the holding surface 8a. As a result, the workpiece 11 is held so that the portion on the surface 11a side is exposed upward.

After the second holding step, the work piece 11 is irradiated with a laser beam from a position above the work piece 11 (the position opposite to the chuck table 4), and the work piece is formed at the planned division line 17 in the device area 13. By modifying 11, a second modified layer forming step of forming a modified layer along the scheduled division line 17 in the device region 13 is performed. FIG. 5 is a cross-sectional view showing a second modified layer forming step. The laser processing device 2 is still used in the second modified layer forming step.

In the second modified layer forming step, first, the angle around the rotation axis of the chuck table 4 is adjusted so that the planned division line 17 to be machined and the moving direction of the chuck table 4 are parallel to each other. Next, the chuck table 4 is moved to align the position of the laser irradiation head 12 with the position above the extension line of the scheduled division line 17 to be processed. Then, while irradiating the laser beam 23b from the laser irradiation head 12, the chuck table 4 is moved in a direction parallel to the target division scheduled line 17.

The position in the height direction of the focusing point for condensing the laser beam 23b is the same as the modified layer 25a formed in the first modified layer forming step (the position in the thickness direction of the workpiece 11). Adjusted to be possible. As a result, the work piece 11 can be modified by irradiating the scheduled division line 17 of the work piece 11 with the laser beam 23b from a position above the work piece 11 (a position opposite to the chuck table 4).

In the second modified layer forming step, as shown in FIG. 5, irradiation and non-irradiation of the laser beam 23a are switched so that the device region 13 of the workpiece 11 is modified. That is, when the laser irradiation head 12 passes above the outer peripheral region 15, the work piece 11 is not irradiated with the laser beam 23a, and when the laser irradiation head 12 passes above the device region 13, the workpiece 11 is not irradiated. The laser beam 23a is irradiated to 11.

After modifying the workpiece 11 at the target division schedule line 17 in the device region 13 and forming the modification layer 25b along the division schedule line 17 in the device region 13, the same procedure is repeated and the device region 13 is repeated. The modified layer 25b is formed on all the other scheduled division lines 17 in the above.

When the modified layer 25b is formed on all the planned division lines 17 in the device region 13, the second modified layer forming step is completed. In this second modified layer forming step, the modified layer 25b is formed at each of a plurality of positions in the thickness direction of the workpiece 11 in accordance with the modified layer 25a formed in the first modified layer forming step. May be done.

FIG. 6 is a perspective view showing the work piece 11 and the like after being processed by the work piece processing method according to the present embodiment. In the present embodiment, the modified layer 25a in the outer peripheral region 15 and the modified layer 25b in the device region 13 are formed so as to be connected to each other along each planned division line 17. That is, a modified layer 25 composed of a modified layer 25a and a modified layer 25b is formed on the entire planned division line 17.

Therefore, by performing a division step of applying a force to the workpiece 11 after the second modified layer forming step, the workpiece 11 is broken at the planned division line 17 in which the modified layer 25 is formed, and a plurality of chips are formed. Can be divided into. In this division step, a force can be applied to the workpiece 11 by, for example, a method of expanding the adhesive tape 31 or a method of pressing a blade-shaped member.

As described above, in the work piece processing method according to the present embodiment, the laser beam 23a is irradiated to the portion on the back surface 11b side of the work piece 11 from the position opposite to the chuck table (first holding table) 4. When the modified layer 25a along the planned division line 17 is formed in the outer peripheral region 15 of the work piece 11, the portion of the work piece 11 on the surface 11a side is not sucked by the holding surface 8a of the chuck table 4, so that the modified layer 25a is not sucked from the holding surface 8a. The acting suction force does not damage the device 19.

Further, the modified layer 25b along the scheduled division line 17 is formed by irradiating the portion of the workpiece 11 on the surface 11a side from the position opposite to the chuck table (second holding table) 4 with the laser beam 23b. When the adhesive tape 31 attached to the back surface 11b side of the workpiece 11 is formed in the device region 13, the adhesive tape 31 is attracted by the holding surface 8a of the chuck table 4, so that the tension of the adhesive tape 31 during the processing of the workpiece 11 is achieved. Even if is changed, the workpiece 11 will not be cracked.

Further, since the modified layer 25a is formed in the outer peripheral region 15 and then the modified layer 25b is formed in the device region 13, the modified layer 25b is formed in the device region 13 and then the modified layer 25b is formed in the outer peripheral region 15. As in the case of forming 25a, the modified layer is formed in the outer peripheral region 15 in an unstable state in which the work piece 11 in which the modified layer 25b is formed and the device region 13 is easily cracked is not sucked by the chuck table 4. It is not necessary to form 25a. Therefore, the tension of the adhesive tape 31 does not change during the formation of the modified layer 25a, and the device region 13 does not crack.

As described above, according to the work piece processing method according to the present embodiment, the device 19 is damaged even when the device 19 and the light-shielding film 21 are provided on the portion of the work piece 11 on the surface 11a side. The work piece 11 can be appropriately modified without causing the work piece 11.

The present invention is not limited to the description of the above-described embodiment, and can be modified in various ways. For example, in the above-described embodiment, one laser machining apparatus 2 is used in the first holding step and the first modified layer forming step, and the second holding step and the second modified layer forming step. , Multiple laser processing devices may be used.

That is, as in the above-described embodiment, the first holding table and the first clamp mechanism used in the first holding step and the first modified layer forming step are used in the second holding step and the second modified layer forming step. It may be used as a second holding table and a second clamping mechanism, or a second holding table and a second clamping mechanism different from the first holding table and the first clamping mechanism may be used in the second holding step and the second modified layer. It may be used in the forming step.

In addition, the structures, methods, and the like according to the above-described embodiments and modifications can be appropriately modified and carried out as long as they do not deviate from the scope of the object of the present invention.

11: Workpiece 11a: Front surface 11b: Back surface 13: Device area 15: Outer peripheral area 17: Scheduled division line (street)
19: Device 21: Light-shielding film (metal film)
23a: Laser beam 23b: Laser beam 25: Modified layer 25a: Modified layer 25b: Modified layer 31: Adhesive tape (dicing tape)
33: Frame 33a: Opening 35: Protective member 2: Laser processing device 4: Chuck table (first holding table, second holding table)
6: Frame body 6a: Recessed portion 6b: Flow path 8: Holding plate 8a: Holding surface 10: Clamp mechanism (first clamp mechanism, second clamp mechanism)
12: Laser irradiation head

Claims (2)

A plurality of devices provided on the surface side portion of the device region partitioned by the scheduled division line, and the surface side portion of the outer peripheral region surrounding the device region and partitioned by the scheduled division line. An annular frame with an opening in which an adhesive tape is affixed to the backside portion of the plate-like workpiece with a light-shielding film that overlaps the planned division line and opposite the front surface. It is a processing method of a workpiece in which the adhesive tape is fixed to the workpiece and the workpiece is irradiated with a laser beam to modify the workpiece at the planned division line.
The holding surface of the first holding table supports the surface side portion of the work piece without suction through a protective member that protects the surface side portion of the work piece, and around the first holding table. The first holding step for holding the workpiece by gripping the frame with the first clamp mechanism provided in the
After the first holding step, the work piece is irradiated with a laser beam from a position opposite to the first holding table to the planned division line in the outer peripheral region and at the planned division line in the outer peripheral region. The first modified layer forming step of forming a modified layer along the planned division line in the outer peripheral region by modifying
After the first modified layer forming step, the adhesive tape attached to the back surface side portion of the workpiece so as to expose the front surface side portion is brought into contact with the holding surface of the second holding table. A second holding step of holding the workpiece by sucking the adhesive tape on the holding surface and gripping the frame with a second clamping mechanism provided around the second holding table.
After the second holding step, the work piece is irradiated with a laser beam from a position opposite to the second holding table to the planned split line in the device region and at the scheduled split line in the device region. A method for processing a workpiece including a second modified layer forming step of forming a modified layer along the planned division line in the device region by modifying the above. The work piece processing method according to claim 1, wherein the protective member contacts the surface side portion without being adhered to the surface side portion of the work piece to protect the surface side portion.

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