TW201935549A - Wafer processing method which does not change the control system of the laser processing device to smoothly divide a wafer configured with bumps - Google Patents

Abstract

A wafer is smoothly divided to form a functional layer including Low-k is formed. The disclosure has: a grinding and cutting step of grinding and cutting a rear surface of the wafer; and a laser processing groove forming step of irradiating first laser beam having absorptive wavelength relative to the functional layer on the surface of the wafer to form a laser processing groove so as to divide the function layer; and a modification layer forming step of focusing a second laser beam having transmittance wavelength relative to the wafer at a specific depth position to form a modification layer inside the wafer. In the grinding and cutting step, an outer peripheral remaining region drops toward downward direction relative to the device region. Afterward it is ground and cut from the rear surface side, the thickness of the wafer is thickened toward the outer peripheral edge from an inter peripheral edge of the outer peripheral surplus region. In the laser processing groove forming step, the first laser beam is condensed at a height position of the surface of the outer peripheral edge of the outer peripheral surplus region to form the deeper laser processing groove approaching the outer peripheral edge from the inter peripheral edge.

Description

Processing method of wafer

The present invention relates to a method for processing a wafer on which a device is formed on a surface.

On the surface of a device wafer such as an IC wafer on which a semiconductor device is mounted, functional layers including various layers constituting the device are laminated. This functional layer includes various layers such as a wiring layer that transmits electric signals, or an interlayer insulation layer that insulates each wiring layer. In recent years, in order to reduce parasitic capacitance formed between wiring layers, a so-called Low-k film having a low dielectric constant is used as an interlayer insulating layer included in a functional layer, in order to improve the processing capability of a device wafer and the like.

When the device wafer is manufactured, a plurality of intersecting planned division lines are set on the surface of the disc-shaped semiconductor wafer, and a device is formed in each area divided by the planned division line, and then divided along the predetermined division line. Wafer. However, the Low-k film is very fragile. When the wafer is divided together with the Low-k film, the Low-k film may be peeled from the wafer and the device may be damaged.

Then, the functional layer is removed by etching in advance, and a processing groove is formed along a predetermined division line. When performing the ablation process, a laser beam having an absorptive wavelength with respect to the functional layer is focused on the surface of the wafer, and the wafer and the laser processing unit are relatively moved along a predetermined division line.

Then, the wafer is irradiated with a laser beam having a wavelength penetrating to the wafer from the back surface side, and the light is focused on the inside of the wafer along the predetermined division line to form a modified layer by a multiphoton absorption process. After that, when the crack is extended from the modified layer at the bottom of the processing groove, the wafer containing the Low-k film can be appropriately divided. When using this method, the functional layer is not divided when the wafer is divided. Therefore, peeling of the Low-k film or damage to the device is suppressed.

However, as a semiconductor packaging technology, bumps made of metal or the like that are electrically connected to the device are formed on the surface of the device, and the surface and bumps of the wafer are covered and sealed with a sealing material to divide the wafer into individual devices. Wafer technology is put into practical use. This packaging technology is called WL-CSP (Wafer-level Chip Size Package). In the WL-CSP, the size of the device wafer formed by the wafer division is the size of the package as it is, which contributes to miniaturization and weight reduction of the device.

Furthermore, in order to form a thin device wafer, the wafer before being divided is ground from the back surface. When the grinding is performed, the wafer is transferred to a chuck mounting table provided in the grinding apparatus, and the rotating grinding wheel is brought into contact with the back surface of the wafer. At this time, the surface side of the wafer on which the protruding bumps are provided and the upper surface of the pan mounting table face each other.

The surface side of the wafer includes a device region where a device is formed, and a remaining area around the periphery without a device. The bumps are provided in the device region of the wafer, and are not provided in the remaining peripheral region. Therefore, during wafer grinding, the device area of the wafer is supported on the chuck mounting table via the bumps, and the remaining area on the periphery is not supported. In this way, when the wafer is placed on the disk mounting table, the remaining area of the outer periphery sags relative to the device area (see Patent Document 1).

When the backside of the wafer is ground in a state where the remaining area of the outer periphery is drooping, the thickness of the ground wafer after the grinding is thicker than the remaining area of the device. In this state, when processing grooves are formed on the front side of the wafer, and a laser beam is irradiated from the back side to form a reforming layer inside the wafer, the processing grooves and reforming are performed in the remaining peripheral area than the device area. The distance between the layers becomes larger. When the distance between the processing groove and the modified layer becomes larger, it is difficult for cracks to reach the processing groove when the wafer is divided, and it is difficult for the wafer to break in the remaining area of the periphery.

Therefore, a processing method has been proposed in which the relative moving speed of the disk mounting table and the laser processing unit is changed during the implementation of the ablation processing (see Patent Document 2). In this processing method, when the laser beam is irradiated, the relative moving speed is reduced as it approaches the outer periphery. In this way, as the outer periphery is approached, the ablation processing is performed at a high intensity to form a deep processing groove. Therefore, in the remaining area of the outer periphery, it is easy to extend the crack from the modified layer to the processing groove, and the remaining area of the outer periphery can be fractured in the same manner as the device area.
[Prior technical literature]
[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2013-21017
[Patent Document 2] Japanese Patent Laid-Open No. 2017-45965

[Problems to be Solved by the Invention]

In this processing method, although it is necessary to appropriately change the relative movement speed of the disk mounting table and the laser processing unit during laser beam irradiation, it is not easy to control the relative movement speed with high accuracy. Furthermore, since the configuration of a system capable of appropriately controlling the change in the relative moving speed is complicated, it is necessary to introduce the system into a laser processing apparatus at a high cost.

The present invention was created in view of such a problem, and an object thereof is to provide a processing method of a wafer that can smoothly divide a wafer provided with bumps without applying a change to a control system of a laser processing apparatus.

[Means to solve the problem]

According to one aspect of the present invention, a method for processing a wafer is provided, which is formed by laminating a functional layer on the surface to the surface, forming a device region including a plurality of devices including the functional layer, and surrounding the device. The remaining area outside the device area, and the intersecting plural division line is set on the surface side so that the device is divided into a plurality and the surface is provided with a plurality of crystals which are electrically connected to a plurality of bumps of each device. A circle is processed along the predetermined dividing line together with the functional layer, and is characterized in that it includes a grinding step in which a crystal is placed in a grinding device provided with a disk mounting table with the surface facing downward. The circle is held on the disk mounting table, and the wafer is thinned by grinding the back side of the wafer; the laser processing groove forming step is performed after the grinding step, and will have an absorptive wavelength with respect to the functional layer The first laser beam is irradiated on the surface of the wafer to form a laser processing groove to cut off the functional layer; and a reforming layer forming step is performed after the laser processing groove forming step is performed. The second laser beam having a transmissive wavelength of the wafer is condensed at a specific depth position from the back side of the wafer along the predetermined division line, and is formed inside the wafer to form a division of the wafer. The modified layer of the starting point, in the grinding step, when the wafer is held on the reel mounting table, the device region of the wafer is supported on the reel mounting table via the bump, and thereafter, according to By the grinding unit being ground from the back side, the thickness of the wafer becomes thicker from the inner peripheral edge toward the outer peripheral edge of the remaining peripheral region. In the laser processing groove forming step, the first laser beam is focused on The laser processing groove is formed at a height position of the surface on the outer periphery of the remaining region of the outer periphery and is irradiated along the predetermined division line to form a deeper portion of the remaining region of the periphery as the inner periphery approaches the outer periphery.

In the step of forming the laser processing groove, before or after condensing the first laser beam at a height position on the surface outside the peripheral edge of the outer peripheral area and irradiating along the predetermined division line, It is preferable that the first laser beam is condensed at a height position on the surface of the device region of the wafer and irradiated along the predetermined division line.

[Inventive effect]

In the method for processing a wafer related to one aspect of the present invention, in the laser processing groove forming step, a first laser beam having an absorptance with respect to the functional layer is irradiated along a predetermined division line. When the surface of the wafer is irradiated with the first laser beam, the wafer is ablated and a laser processing groove is formed on the surface.

Here, the smaller the difference between the height position of the surface of the wafer irradiated with the first laser beam and the height position of the light-condensing point of the first laser beam, the higher the intensity of the ablation process, and the formed laser process The ditch becomes deeper. In the laser processing groove forming step, since the first laser beam is focused on the height position of the surface of the wafer on the outer periphery of the remaining peripheral region, the laser processing groove is formed on the outer periphery of the remaining peripheral region. deep.

The difference is when the first laser beam is irradiated onto the surface of the wafer from the outer periphery to the inner periphery of the remaining area of the outer periphery along the predetermined division line without changing the height of the focusing point of the first laser beam. Gradually becoming larger, the intensity of the ablation process is gradually weakening, and the laser processing groove is gradually becoming shallower. In the device region, a relatively shallow laser-processed groove is formed as it is.

When the laser processing trench is formed in the laser processing trench forming step, the height position of the bottom of the laser processing trench is relatively uniform over the entire length of the laser processing trench. Therefore, the distance between the modified layer formed in the modified layer forming step and the laser processing groove is relatively uniform. Therefore, the crack is also easily extended from the modified layer to the laser-processed groove over the entire length of the divided predetermined line.

In the laser processing groove forming step, the wafer and the laser processing unit can be relatively moved at a certain speed. In this case, it is not necessary to change the height of the focused light of the first laser beam. That is, it becomes extremely easy to control the laser processing unit or the disk mounting table, and wafers can be smoothly divided without applying a change to the control system of the laser processing apparatus.

Therefore, the present invention can smoothly divide a wafer processing method of a wafer provided with bumps without applying a change to a control system of a laser processing apparatus.

An embodiment of the present invention will be described with reference to the attached drawings. First, a wafer to be processed, which is a processing method according to this embodiment, that is, a wafer is described using FIG. 1 (A). FIG. 1 (A) is a perspective view schematically showing a wafer on which a functional layer is formed on a surface. The wafer 1 is a substantially circular plate-shaped substrate made of, for example, silicon, SiC (silicon carbide), other semiconductor materials, or materials such as sapphire, glass, and quartz.

A functional layer 3 is laminated on the surface 1 a of the wafer 1. The functional layer 3 includes various layers such as a wiring layer that transmits electric signals, or an interlayer insulating layer that insulates each wiring layer. In order to reduce parasitic capacitance formed between wiring layers, a so-called Low-k film having a low dielectric constant is used as an interlayer insulating film or the like. Low-k film, known as inorganic film such as SiOF, SiOB (borosilicate glass), or polymer film such as polyimide-based, p-xylene-based, that is, organic film, very fragile membrane.

The surface 1a of the wafer 1 is divided into a plurality of areas by a plurality of predetermined division lines (cut lines) 9 arranged in a grid pattern. Each area divided by the plurality of predetermined division lines 9 is formed with an integrated circuit (IC)等 的 装置 11。 The device 11. The functional layer 3 is included in the device 11, and various layers included in the functional layer 3 are formed into a specific shape by a photolithography process or the like to exert a specific function. Finally, the wafer 1 is thinned and divided along a predetermined division line 9 to form each device wafer.

In order to reduce the manufacturing cost of the device wafer, as many devices 11 as possible are formed on the surface 1 a of the wafer 1. However, due to the shape of the wafer 1 and the device 11, and for the convenience of the manufacturing process of the device wafer, the remaining area 7 on the outer periphery of the non-formation device 11 is arranged near the outer periphery of the wafer 1. In this regard, a region surrounded by the remaining peripheral region 7 and forming the device 11 is referred to as a device region 5. However, the boundary 15 of the remaining peripheral area 7 and the installation area 5 does not have to be clear.

On the surface 1 a of the wafer 1, a plurality of protruding bumps 13 are formed to protrude as connection terminals of the device wafer. The bump 13 is formed of a metal such as gold or copper, and is electrically connected to the device 11. In addition, the bumps 13 are formed only in the device region 5 on the surface 1 a of the wafer 1, and are not formed in the remaining region 7 on the outer periphery of the device 11 where the device 11 is not formed.

Next, each processing device used in the processing method of the wafer 1 according to this embodiment will be described. In addition, this processing method is not limited to this, and a part or all of the processing apparatus described below may not be used.

FIG. 2 (A) schematically shows a grinding apparatus 2 for grinding the back surface 1b side of the wafer 1 and thinning the wafer 1. The grinding device 2 includes a reel mounting table 4 that sucks and holds a workpiece, that is, a wafer 1, and a grinding unit 6 that grinds the wafer 1 held on the reel mounting table 4.

The chuck mounting table 4 includes a porous member (not shown) exposed on the upper surface side and an attraction source (not shown) connected to the porous member. The upper surface of the porous member serves as a holder for holding the wafer 1. surface. When the wafer 1 is placed on the holding surface, and the negative pressure generated by the suction source is applied to the wafer 1 through the hole of the porous member, the wafer 1 is sucked and held on the disk mounting table 4. The disk mounting table 4 can be rotated around an axis perpendicular to the holding surface.

The grinding unit 6 includes a main shaft 10 in a direction perpendicular to the holding surface of the pan mounting table 4, a roller bracket 12 arranged at the lower end of the main shaft 10, and a grinding wheel 14 mounted on the roller bracket 12. The grinding wheel 14 includes a base 16 and a grinding stone 18 mounted below the base 16. When the main shaft 10 is rotated around the direction perpendicular to the holding surface, the grinding wheel 14 can be rotated. In addition, the grinding unit 6 can be raised and lowered in a direction perpendicular to the holding surface of the pan mounting table 4.

When the wafer 1 is held on the holding surface of the chuck table 4, the grinding wheel 14 and the chuck table 4 are rotated, the grinding unit 6 is lowered, and the grinding stone 18 is brought into contact with the wafer 1. Being ground.

FIG. 3 (B) schematically illustrates a first laser processing apparatus 20 that irradiates a first laser beam on the surface 1a side of the wafer 1 and forms a laser processing groove 19 on the wafer 1 by an ablation process. The first laser processing apparatus 20 includes a disk mounting table 22 that sucks and holds the wafer 1, and a first laser processing unit 24 that irradiates a first laser beam to the wafer 1 held on the disk mounting table 22. The chuck mounting table 22 is the same as the chuck mounting table 4 provided in the grinding apparatus 2 described above.

The first laser processing unit 24 can oscillate the first laser beam 26 a having a wavelength that is transparent to the functional layer 3. The first laser beam 26 a is focused by the processing head 26 to a specific height position. The first laser processing unit 24 can be raised and lowered in a direction perpendicular to the holding surface of the disk mounting table 22. When the first laser processing unit 24 is raised and lowered, the condensing height of the first laser beam 26a can be changed. The disk mounting table 22 and the first laser processing unit 24 relatively move in a direction parallel to the holding surface.

First, the first laser processing unit 24 is positioned at a specific height on an extension line of the planned division line 9 of the wafer 1. Then, the first laser processing unit 24 oscillates the first laser beam 26 a while the first laser processing unit 24 and the disk mounting table 22 are relatively moved along the planned division line 9. In this way, the ablation process is performed along the planned division line 9.

After processing is performed along one of the planned division lines 9, the disk mounting table 22 and the first laser processing unit 24 are relatively moved in a direction parallel to the holding surface and perpendicular to the planned division line 9, and along other divisions The predetermined line 9 is processed. After the processing is performed along the predetermined division line 9 in one direction, the disk mounting table 22 is rotated at a specific angle, and the processing is performed in the same manner along the divided alignment line 9 in the other direction. In this way, the laser processing grooves 19 can be formed along all the predetermined division lines 9.

FIG. 6 schematically shows that the second laser beam is condensed from the back surface 1b side of the wafer 1 to the inside of the wafer 1. Through the multi-photon absorption process, a modification that becomes the starting point of division is formed in the wafer 1 Layer of the second laser processing device 32. The second laser processing device 32 includes a disk mounting table 34 and a second laser processing unit 36. The chuck mounting table 34 is the same as the chuck mounting table 4 provided in the grinding apparatus 2 described above.

The second laser processing unit 36 can oscillate a second laser beam 38 a having a wavelength that is transparent to the functional layer 1. The second laser beam 38 a is focused by the processing head 38 to a specific height position inside the wafer 1. The second laser processing unit 36 can be raised and lowered in a direction perpendicular to the holding surface of the disk mounting table 34. When the second laser processing unit 36 is raised and lowered, the condensing height of the second laser beam 38a can be changed.

The second laser processing unit 36 and the disk mounting table 34 are relatively movable in a direction parallel to the holding surface of the disk mounting table 34. In the second laser processing device 32, similar to the first laser processing device 20, the second laser beam 38 can be irradiated to the inside of the wafer 1 along the predetermined division lines 9 of the wafer 1. In the multiphoton absorption process, a modified layer 27 is formed inside the wafer 1 along the predetermined division line 9.

Next, each step of the method for processing a wafer according to this embodiment will be described. First, in the grinding apparatus 2, a grinding step of grinding the back surface 1 b of the wafer 1 and thinning the wafer 1 is performed. Before the wafer 1 is carried into the grinding device 2, a protective member 17 that protects the surface 1 a side of the wafer 1 is adhered to the surface 1 a side of the wafer 1. FIG. 1 (B) is a perspective view schematically showing a protective member 17 attached to the surface 1 a of the wafer 1.

The protective member 17 includes an adhesive layer 17b having an adhesive surface (see FIG. 2 (A)), and a thin film-like base material layer 17A (see FIG. 2 (A)) supporting the adhesive layer 17b. The side of the adhesive layer 17b is adhered to The surface 1a side of the wafer 1. For example, as the base material layer 17a, PO (polyolefin), PET (polyethylene terephthalate), polyvinyl chloride, polystyrene, or the like is used. The adhesive layer 17b is made of, for example, silicone rubber, acrylic material, epoxy material, or the like.

When the protective member 17 is adhered to the surface 1a side, the adhesive layer 17b deforms following the uneven shape of the surface 1a. The adhesive layer 17b is, for example, an ultraviolet curable resin. When the protective member 17 is peeled from the wafer 1, the protective member 17 is irradiated with ultraviolet rays to harden the adhesive layer 17b, and the peeling becomes easy.

Fig. 2 (A) is a sectional view schematically showing a grinding step. In the grinding apparatus 2, the wafer 1 having the surface 1 a to which the protective member 17 is adhered is carried. With the surface 1a facing downward, the wafer 1 is placed on the holding surface of the pan mounting table 4 via the protective member 17, and the suction source of the pan mounting table 4 is actuated to hold the wafer 1 on the pan mounting. Mounting table 4. In this way, the ground surface of the wafer 1, that is, the back surface 1b is exposed to the upper side.

Next, while rotating the disk mounting table 4 and the grinding wheel 14 around an axis perpendicular to the holding surface, the grinding unit 6 is lowered toward the disk mounting table 4. In this way, the grinding stone 18 contacts the back surface 1b of the wafer 1, and grinding processing is started. Then, the grinding unit 6 is lowered to a specific height position so that the wafer 1 has a specific thickness. As a result, the wafer 1 is thinned to a specific thickness.

FIG. 2 (B) is a cross-sectional view schematically showing an enlarged wafer 1 to be ground. The functional layer 3 is omitted in FIG. 2 (B). As shown in FIG. 2 (B), when the wafer mounting table 4 holds the wafer 1, the adhesive layer 17b of the protective member 17 deforms following the shape of the surface 1a side of the wafer 1. In addition, the device region 5 of the wafer 1 is supported on the reel mounting table 4 mainly via the bumps 13.

For this reason, no bump 13 is formed in the remaining area 7 of the outer periphery. Compared with the bumps 13, the adhesive layer 17 b has higher flexibility and has a weaker ability to support the wafer 1. Therefore, when the wafer 1 is placed on the disk mounting table 4, the remaining peripheral area 7 is in a state of being drooped relative to the device area 5. When the back surface 1b side of the wafer 1 is ground in a state where the outer peripheral area 7 is drooping, as shown in FIG. 2 (B), the thickness of the ground wafer 1 from the inner peripheral edge toward the outer peripheral area 7 Thickened.

In the processing method related to this embodiment, a laser processing groove forming step is performed next. The laser processing groove forming step is performed by the first laser processing apparatus 20 described above. In addition, before the wafer 1 is carried into the first laser processing apparatus 20, the protective member 17 adhered to the surface 1a side of the wafer 1 is peeled in advance.

FIG. 3 (A) is a perspective view schematically showing the protection member 17 peeled from the surface 1 a of the wafer 1. When the ultraviolet curable resin is used for the protective member 17, when ultraviolet rays are irradiated and the protective member 17 is cured, peeling becomes easy. Moreover, as shown in FIG. 3 (A), a dicing tape 21 is stuck on the back surface 1b side of the wafer 1. The dicing tape 21 is configured in the same manner as the protective member 17.

Fig. 3 (B) is a perspective view schematically showing a laser processing groove forming step. The wafer 1 with the surface 1a facing upward is placed on the holding surface of the disk mounting table 22 of the first laser processing apparatus 20, and the wafer 1 is sucked and held on the disk mounting table 22. In this way, the processed surface of the wafer 1, that is, the surface 1a is exposed upward. Then, the camera 28 of the first laser processing unit 24 is used to capture the planned division line 9 of the surface 1 a of the wafer 1, and the relative positions of the disk mounting table 4 and the first laser processing unit 24 are adjusted.

Next, the surface 1 a of the wafer 1 is irradiated with the first laser beam 26 a having an absorptive wavelength with respect to the functional layer 3 along the planned division line 9. In this way, the functional layer 3 is removed by the ablation process, and a laser processing groove 19 for separating the functional layer 3 is formed on the surface 1 a of the wafer 1. FIG. 4 (A) schematically shows the wafer 1 after the laser processing groove forming step. As shown in FIG. 4 (A), when the laser processing groove forming step is performed, a laser processing groove 19 is formed on the surface 1a side of the wafer 1.

FIG. 4 (A) is a cross-sectional view schematically showing a light-condensing position of the first laser beam 26a, and FIG. 4 (B) is a cross-sectional view schematically showing an outer peripheral area 7 in an enlarged manner. 4 (A) and 4 (B) show the height position of the processing head 26 when the first laser beam 26a is irradiated near the outer periphery of the outer peripheral remaining area 7. When the laser processing groove forming step is performed, the first laser processing unit 24 is set so that the light-condensing point 30 of the first laser beam 26a is aligned with the height position of the surface 1a on the outer peripheral edge of the remaining area 7 of the outer periphery. Height.

FIG. 4 (C) is a cross-sectional view schematically showing an enlarged device region 5. 4 (A) and 4 (C) show the height position of the processing head 26 when the device region 5 is irradiated with the first laser beam 26a. During the ablation process, the height position of the processing head 26 is maintained. Therefore, when the ablation process is performed on the device region 5 of the wafer 1, the light-condensing point 30 of the first laser beam 26 a is arranged at a height position that deviates from the height position of the surface 1 a of the wafer 1.

The smaller the difference between the height position of the surface 1a of the wafer 1 and the height position of the light spot 30 of the first laser beam 26a, the higher the intensity of the ablation processing, the deeper the laser processing groove 19 formed. Therefore, in the laser processing groove forming step, a deep laser processing groove 19 is formed on the outer periphery of the outer peripheral remaining area 7 and the laser processing groove 19 formed becomes shallower as it approaches the inner periphery from the outer periphery. In the device region 5, a shallow laser processing groove 19 is formed.

Therefore, when the laser processing trench forming step is performed, the laser processing trench 19 is formed to a depth corresponding to the thickness of the wafer 1 at the position where the laser processing trench 19 is formed. Therefore, the height position of the bottom of the laser processing groove 19 becomes the same height position over its entire length.

In the processing method related to this embodiment, a modified layer forming step is performed next. The modified layer forming step is performed by the second laser processing apparatus 32 described above. In addition, before the wafer 1 is carried into the second laser processing apparatus 32, an expansion tape is affixed in advance to the surface 1 a side of the wafer 1.

FIG. 5 is a perspective view schematically showing that the expansion tape 23 is adhered to the surface 1 a side of the wafer 1. The expansion tape 23 is, for example, adhered to the ring-shaped frame 25 at the outer periphery, and is adhered to the surface 1 a of the wafer 1 inside the opening of the frame 25. The configuration of the expansion tape 23 is, for example, the same as that of the protective member 17 described above. The ring-shaped frame 25 is made of a material such as metal.

The wafer 1 is carried into the second laser processing apparatus 32 in a state where the expansion tape 23 and the frame 25 are integrated into the frame unit 33. Fig. 6 is a cross-sectional view schematically showing a step of forming a modified layer. With the surface 1 a side facing downward, the wafer 1 is placed on the holding surface of the pan mounting table 34 via the expansion tape 23, and the wafer 1 is sucked and held on the pan mounting table 34. In this way, the irradiated surface of the second laser beam 38 a of the wafer 1, that is, the back surface 1 b side faces upward.

Next, the second laser beam 38 a having a wavelength penetrating to the wafer 1 is focused on a predetermined height position of the wafer 1 along the predetermined division line 9 via the dicing tape 21. In this way, a modified layer 27 is formed in the vicinity of the light-concentrating point 40 of the second laser beam 38a by a multiphoton absorption process.

The dicing tape 21 may be peeled before the second laser beam 38a is irradiated. In this case, the second laser beam 38a is irradiated onto the wafer 1 without the dicing tape 21 interposed therebetween.

The modified layer 27 becomes the starting point of division when the wafer 1 is divided. That is, when an external force or the like is applied to the wafer 1 and a crack is extended from the modified layer 27 at the bottom of the laser processing groove 19, the wafer 1 may be divided along the planned division line 9. In addition, even if this crack and the formation of the modified layer 27 are extended simultaneously. Here, the height position of the bottom of the laser processing groove 19 is the same height as the entire length as described above. That is, the distance between the bottom of the laser processing groove 19 and the modified layer 27 is the same even at any portion of the planned division line 9.

When the crack is extended from the reforming layer 27 toward the laser processing groove 19, the appearance of the crack changes according to the distance between the reforming layer 27 and the laser processing groove 19. Furthermore, the larger the distance, the more difficult it is for the crack to properly extend, and the wafer 1 becomes more difficult to break.

Here, for comparison, a processing method related to a comparative example in which the height position of the bottom portion of the laser processing groove 19 does not become the same over the entire length will be described. FIG. 9 (A) is a cross-sectional view schematically showing the light-condensing position of the first laser beam 26a in the processing method related to the comparative example, and FIG. 9 (B) is a schematic view showing an enlarged peripheral area FIG. 9 (C) is a cross-sectional view schematically showing an enlarged device area.

In the processing method related to this comparative example, when the laser processing groove forming step is performed, as shown in FIG. 9 (C), the first laser processing device 20 gathers the first laser beam 26a. The light spot 30 is aligned at the height position of the surface 1 a of the wafer 1 in the device region 5.

In this case, since the light-condensing point 30 of the first laser beam 26a is positioned at a height position on the surface of the wafer 1 in the device region 5, the ablation processing is performed with a relatively strong intensity to form a relatively deep laser Processing groove 19. On the other hand, as shown in FIG. 9 (B), the difference between the height position of the spot 30 of the first laser beam 26a and the height position of the surface 1a of the wafer 1 is large in the remaining area 7 of the outer periphery. Abrasive processing is performed with a relatively weak strength to form a relatively shallow laser processing groove 19.

In the remaining peripheral region 7, the thickness of the wafer 1 is larger than the thickness of the wafer 1 in the device 5, and the formed laser processing trench 19 becomes shallower. Therefore, as shown in FIGS. 9 (B) and 9 (C), the height position of the bottom of the laser processing groove 19 does not become the same over its entire length. Therefore, when the reforming layer forming step is subsequently performed to form the reforming layer 27 inside the wafer 1, the distance between the bottom of the reforming layer 27 and the laser processing groove 19 will not be the same over the entire length of the dividing line. .

In particular, the distance varies greatly from the inner peripheral edge to the outer peripheral edge of the remaining peripheral area 7. Accordingly, it is difficult to appropriately extend the crack from the reforming layer 27 in the laser processing groove 19 near the outer periphery of the remaining peripheral region 7. When the wafer 1 is divided along the planned division line 9, the remaining peripheral region 7 Near the outer periphery, it becomes difficult for the wafer 1 to be appropriately broken.

On the other hand, in the processing method related to this embodiment, since the distance between the modified layer 27 and the laser processing groove 19 is the same over its entire length, the wafer 1 is appropriately included in the vicinity of the outer periphery of the remaining peripheral region 7 Was broken. Further, in the laser processing groove forming step, it is not necessary to change the relative speeds of the first laser processing unit 24 and the disk mounting table 22 during the implementation of the ablation processing. Therefore, the wafer 1 on which the bumps 13 are arranged can be smoothly divided without changing the control system of the laser processing apparatus.

After the modified layer forming step is performed, each device wafer is formed in order to divide the wafer 1, and the expansion tape 23 is expanded. When the expansion tape 23 is expanded, as shown in FIG. 7, the dicing tape 21 is peeled from the back surface 1 b side of the wafer 1. Then, the frame unit 33 including the wafer 1 is carried into an expansion device.

8 (A) is a cross-sectional view schematically showing a wafer carried into an expansion device, and FIG. 8 (B) is a cross-sectional view schematically showing an expansion state by the expansion device. The configuration of the expansion device 42 will be described. The expansion device 42 includes a cylindrical expansion drum 44 and a frame holding unit 46 that surrounds the expansion drum 44 from the outer peripheral side.

The expansion drum 44 includes a push-up portion 54 provided with an upper surface in contact with the expansion tape 23, a lever member 50 that supports the push-up portion 54 from below, and a cylinder 52 that lifts and lowers the lever member 50. . When the air cylinder 52 is actuated, the push-up portion 54 can be raised and lowered between the frame unit carry-in position 56 and the expanded position 58. The frame holding unit 46 includes a jig 48 that holds the frame 25 of the frame unit 33.

When the frame unit 33 is carried into the expansion device 42, as shown in FIG. 8A, the push-up portion 54 is arranged at the frame unit carry-in position 56, and the frame unit 33 is placed on the push-up portion 54. Then, the frame 48 is held by the harness 48.

Next, as shown in FIG. 8 (B), the air cylinder 52 is operated to raise the push-up portion 54 to the expanded position 58. In this way, the expansion tape 23 is expanded radially outward. In this way, the interval between the device wafers 31 formed by dividing the wafer 1 becomes wider, and it becomes easier to pick up the device wafers 31.

As described above, each of the device wafers 31 can be formed by smoothly dividing and forming the wafer 1 including the functional layer 3 of the Low-k film.

The present invention is not limited to the description of the above-mentioned embodiment, and can be implemented with various changes. For example, one aspect of the present invention is not limited to the case where the bottom of the laser processing groove 19 formed in the laser processing groove forming step becomes the same height position over the entire length of the predetermined division line 9. Depending on the irradiation conditions of the first laser beam 26a in the first laser processing device 20, the bottom of the formed laser processing groove 19 may not reach the same height position over the entire length of the predetermined division line 9. .

Even in this case, for example, from the inner peripheral edge to the outer peripheral edge of the remaining peripheral area 7, if the change in the height of the bottom of the laser processing groove 19 formed in the laser processing groove forming step is smaller than the change in thickness of the wafer 1 , Can also enjoy the effects of the present invention. That is, the wafer 1 in the remaining area 7 can be divided more smoothly.

Furthermore, in the above-mentioned embodiment, although in the laser processing groove forming step, the light-condensing point 30 of the first laser beam 26a is arranged at the height of the surface 1a of the wafer 1 in the remaining area 7 of the periphery, it is one of the present invention The appearance is not limited to this. For example, the light-condensing spot 30 may be arranged at a position higher than the height 1a of the surface 1a of the wafer 1 in the remaining peripheral region 7.

Even in this case, due to the ablation processing performed in the laser processing groove forming step, as the inner peripheral edge from the remaining area 7 of the outer periphery approaches the outer peripheral edge, the strength becomes higher, so the formed laser processing groove 19 follows from this The inner periphery becomes deeper toward the outer periphery.

In the laser processing groove forming step, when the first laser beam 26 a is focused at a height position of the surface 1 a of the wafer 1 on the outer periphery of the remaining peripheral region 7, there is no formation in the device region 5. In the case of a laser processing trench 19 having a sufficient depth. This is because, in the device region 5, the intensity of the ablation process becomes insufficient due to the reason that the distance between the light-condensing point 30 and the surface 1a of the wafer 1 becomes too large.

Therefore, even before or after the first laser beam 26 a is irradiated with the first laser beam 26 a focused on the surface 1 a of the wafer 1 at the outer periphery of the remaining peripheral region 7, it is further focused on the surface of the device region 5. The first laser beam 26a may be irradiated at the height position of 1a. That is, in the laser processing groove forming step, the first laser beam 26a is irradiated a plurality of times by changing the height of the light-condensing position to form a laser processing groove 19 having a uniform height at the bottom.

The structures, methods, and the like related to the above-described embodiments can be appropriately modified and implemented as long as they do not depart from the scope of the object of the present invention.

1‧‧‧ wafer

1a‧‧‧ surface

1b‧‧‧ back

3‧‧‧functional layer

5‧‧‧ device area

7‧‧‧ Outer peripheral area

9‧‧‧ divided scheduled line

11‧‧‧ device

13‧‧‧ bump

15‧‧‧ Realm

17‧‧‧Protective member

17a‧‧‧ Substrate

17b‧‧‧Adhesive layer

19‧‧‧Laser processing trench

21‧‧‧ Cutting Tape

23‧‧‧Expansion Tape

25‧‧‧Frame

27‧‧‧Modified layer

29‧‧‧ crack

31‧‧‧device chip

33‧‧‧Frame Unit

2‧‧‧ Grinding device

4, 22, 34‧‧‧ 挟 tray mounting table

6‧‧‧grinding unit

10‧‧‧ Spindle

12‧‧‧ bracket

14‧‧‧grinding wheel

16‧‧‧ abutment

18‧‧‧ grinding grinding stone

20, 32‧‧‧laser processing equipment

24, 36‧‧‧laser processing unit

26, 38‧‧‧Processing head

26a, 38a ‧‧‧ laser beam

28‧‧‧ Camera Unit

30, 40 spotlight

42‧‧‧Expansion device

44‧‧‧Expansion drum

46‧‧‧Frame holding unit

48‧‧‧ harness

50‧‧‧ Rod

52‧‧‧ Cylinder

54‧‧‧ Push-up Department

56‧‧‧Frame unit moving position

58‧‧‧ expanded position

FIG. 1 (A) is a perspective view schematically showing a wafer on which a functional layer is formed on a surface, and FIG. 1 (B) is a perspective view schematically showing a protective member being adhered to the surface of the wafer.

FIG. 2 (A) is a cross-sectional view schematically showing a cutting step, and FIG. 2 (B) is a cross-sectional view schematically showing an enlarged wafer to be ground.

FIG. 3 (A) is a perspective view schematically showing peeling of the protective member from the surface of the wafer, and FIG. 3 (B) is a perspective view schematically showing a laser processing groove forming step.

FIG. 4 (A) is a cross-sectional view schematically showing a light condensing position of a laser beam at the time of forming a laser processing groove, and FIG. 4 (B) is a cross-sectional view schematically and enlargedly showing an enlarged peripheral remaining area. 4 (C) is a cross-sectional view schematically showing a device area.

FIG. 5 is a perspective view schematically showing a wafer to which an expansion tape is adhered.

Fig. 6 is a cross-sectional view schematically showing a step of forming a modified layer.

FIG. 7 is a perspective view schematically showing peeling of a dicing tape from a back surface of a wafer.

8 (A) is a cross-sectional view schematically showing a wafer carried into an expansion device, and FIG. 8 (B) is a cross-sectional view schematically showing an expansion state by the expansion device.

FIG. 9 (A) is a cross-sectional view schematically showing a light condensing position of a laser beam during a laser processing groove forming step in a processing method related to a comparative example, and FIG. 9 (B) is an enlarged view of an outer peripheral remaining region. 9 (C) is a cross-sectional view schematically showing an enlarged device area.

Claims (2)

A wafer processing method comprising laminating a functional layer on a surface on the surface, forming a device region including a plurality of devices including the functional layer, and a plurality of intersecting plural areas surrounding a remaining area around the device region. A predetermined division line is set on the surface side so that the device is divided into plural numbers, and wafers each having a plurality of bumps electrically connected to the respective devices are arranged on the surface side, along with the predetermined division line along with the function Layer processing, which is characterized by: The grinding step is performed in a grinding device provided with a reel mounting table, the wafer is held on the reel mounting table with the surface facing downward, and the back of the wafer is ground to make the wafer thin. Turn into The laser processing groove forming step is to irradiate a first laser beam having an absorptive wavelength with respect to the functional layer to the surface of the wafer after the grinding step is performed to form a laser processing groove to cut off the laser processing groove. Functional layer; and The modified layer forming step is performed after the laser processing groove forming step is performed, and a second laser beam having a wavelength penetrating with respect to the wafer is passed along the predetermined division line from the back side of the wafer. And condensing at a specific depth position, forming a modified layer inside the wafer that becomes the starting point of the division of the wafer, In the grinding step, when the wafer is held on the chuck mounting table, the device region of the wafer is supported on the chuck mounting table via the bump, and thereafter, according to the The back side is ground, and the thickness of the wafer becomes thicker from the inner peripheral edge toward the outer peripheral edge of the remaining peripheral area. In the laser processing groove forming step, the first laser beam is condensed at a height position of the surface on the outer periphery of the remaining peripheral region, and is irradiated along the predetermined division line to form the remaining peripheral region. The laser processing groove becomes deeper as it approaches the outer periphery from the inner periphery. The processing method of the wafer as described in claim 1, wherein In the laser processing groove forming step, before or after converging the first laser beam at a height position on the surface outside the peripheral edge of the outer peripheral area and irradiating along the predetermined division line, further, The first laser beam is condensed at a height position on the surface of the device region of the wafer and is irradiated along the predetermined division line.