JP2017199717A - Processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method of a device wafer capable of preventing damage of a device.SOLUTION: A processing method of a device wafer in which respective devices are formed in a region partitioned by a plurality of crossing division schedule lines on a front face comprises: a modified layer formation step in which laser beam of a wavelength permeable to the device wafer is irradiated with the device wafer along the division schedule line from a rear side of the wafer to form a modified layer in the device wafer and a crack is extended from the modified layer to at least the front face side; a division step in which the device wafer is divided into respective device chips by applying external force to the device wafer after performing the modified layer formation step; and a guide groove formation step in which a groove guiding an extension direction of the crack extending from the modified layer to the front face side is formed from the front face of the wafer along the division schedule line before performing the modified layer formation step.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for processing a device wafer in which devices are respectively formed in regions partitioned by a plurality of division lines that intersect on the surface.

  In the manufacturing process of semiconductor device chips, a grid-like division line called street is set on the surface of a wafer made of silicon or a compound semiconductor, and devices such as IC and LSI are formed in each area partitioned by the division line. Is done. These wafers are divided along the division lines, and individual semiconductor device chips are manufactured.

  In order to divide the device wafer having the device pattern formed on the surface along the planned dividing line, for example, a modified layer serving as a starting point of the dividing is formed inside the device wafer along the planned dividing line, and then the device An external force is applied to the wafer. When such a modified layer is provided inside the device wafer, the external force required for dividing the device wafer can be made relatively small, and the load on the device formed on the device wafer is also reduced.

  The modified layer is formed by irradiating a laser beam so as to collect light at a predetermined depth inside the device wafer using a condensing lens, and forming the modified layer at the position by multiphoton absorption. Is known (see, for example, Patent Document 1). When the device wafer is irradiated with a laser beam by this method, almost no absorption occurs on the surface of the device wafer, so that the region other than the region where the laser beam is focused does not melt.

  After the modified layer is formed inside the device wafer, an external force is applied to the device wafer to extend a crack from the modified layer in the vertical direction (thickness direction). When the crack extends and penetrates the device wafer vertically, the device wafer is divided. In the following description, the vertical direction refers to the thickness direction of the device wafer.

JP 2002-192370 A

  However, when the crack is extended from the modified layer, the crack may not extend linearly in the vertical direction. Since the device wafer has a plurality of division lines in the vertical and horizontal directions, the total extension of the division lines is several to several tens of times the diameter of the wafer. It is not always easy to correctly extend the cracks vertically from the modified layer in all the lengths.

  Also, the direction in which the crack extends may change while the crack extends. The probability that the extending direction changes as the distance for extending the cracks increases, but when the wafer is made thin in order to keep the probability low, the strength of the wafer itself is lowered and the handling property is lowered.

  Further, for example, when a film formed on the surface of the device wafer is removed by a method such as laser ablation, distortion due to heat or the like may occur in the vicinity of the surface of the device wafer. If a modified layer is formed inside the device wafer in the state in which the strain is generated and then an external force is applied to extend the crack, the crack may extend out of the vertical direction.

  Then, if the crack goes off the division line and reaches the device formation region, the device is damaged, which causes a problem. If the width of the planned division line is set wide in advance, damage to the device formation region can be prevented even if the crack progresses to some extent in an unexpected direction, but in that case, it is used for the device formation region of the device wafer. The area that can be reduced.

  Furthermore, when an external force is applied to extend the crack, the external force does not only extend the crack, but may cause damage to the device. In order to extend the crack, an external force of a certain level or more is necessary, but if the external force is too large, the device is damaged. Therefore, it is preferable that the magnitude of the external force required for extending the crack is as small as possible.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a device wafer processing method capable of reducing the possibility of damaging the device as compared with the prior art.

  According to one aspect of the present invention, there is provided a device wafer processing method in which a device is formed in each of regions divided by a plurality of division lines intersecting with each other, the wavelength of the device wafer being transparent. A modified layer forming step of forming a modified layer inside the device wafer by irradiating a laser beam from the rear surface side of the wafer along the division line and extending a crack from the modified layer to at least the front surface side of the wafer. Then, after the modified layer forming step is performed, an external force is applied to the device wafer to divide the device wafer into individual device chips, and the modified layer forming step is performed before the modified layer forming step. Grooves that guide the extending direction of cracks extending from the quality layer to the surface side are formed from the surface of the wafer along the planned dividing line. Processing method of the device wafer, characterized in that it comprises the id groove forming step, is provided.

  In the processing method according to an aspect of the present invention, the device wafer includes a laminate on the surface, and the laminate dividing step of dividing the laminate along the division line is performed before the dividing step is performed. Furthermore, you may provide.

  In the device wafer processing method according to the present invention, before the modified layer forming step, the guide groove for guiding the extending direction of the crack extending from the modified layer to the surface side is provided from the wafer surface to the division planned line. A guide groove forming step to be formed along is performed.

  Thereby, since the crack extends toward the guide groove, the crack does not reach the device formation region, and the possibility of damaging the device is reduced as compared with the conventional case. In addition, since the crack extends toward the guide groove in the modified layer forming step, the external force required for dividing the device wafer in the dividing step is very small. For this reason, the probability of damage to the device wafer due to the external force is also reduced.

  Therefore, according to the present invention, there is provided a device wafer processing method capable of reducing the possibility of damaging the device as compared with the conventional case.

It is a perspective view which shows typically the device wafer in which the device was each formed in the area divided by the division line. 2A is a schematic cross-sectional view illustrating a guide groove forming step, and FIG. 2B is a schematic view illustrating a cross-section of the wafer after the guide groove forming step. FIG. 3A is a schematic cross-sectional view illustrating a modified layer forming step, and FIG. 3B is a schematic view illustrating a cross-section of the wafer after the modified layer forming step. FIG. 4A is a schematic cross-sectional view illustrating the device wafer and the wafer dividing apparatus before performing the dividing step, and FIG. 4B illustrates the device wafer and the wafer dividing apparatus after performing the dividing step. It is a cross-sectional schematic diagram to explain. FIG. 5A is a schematic cross-sectional view illustrating a device wafer on which a laminated body is formed, and FIG. 5B is a schematic cross-sectional view illustrating a device wafer before performing a laminated body cutting step. FIG. 5C is a schematic cross-sectional view for explaining the device wafer after the laminated body dividing step and before the guide groove forming step, and FIG. 5D is a schematic view of the device wafer after the guide groove forming step. FIG. FIG. 6A is a schematic cross-sectional view illustrating a modified layer forming step in a device wafer on which a laminate is formed, and FIG. 6B illustrates a cross section of the wafer after the modified layer forming step. It is a schematic diagram. FIG. 7A is a schematic cross-sectional view for explaining the device wafer and the wafer dividing apparatus before the dividing step is performed on the device wafer on which the laminated body is formed, and FIG. It is a cross-sectional schematic diagram explaining a device wafer and a wafer dividing apparatus.

  Embodiments according to the present invention will be described with reference to the accompanying drawings. First, a device wafer that is a workpiece according to this embodiment will be described. FIG. 1 is a perspective view schematically showing an example of a device wafer. The device wafer 1 is a substantially disk-shaped wafer made of a material such as silicon, sapphire, SiC (silicon carbide), or other compound semiconductor.

  As shown in FIG. 1, the surface 1 a of the device wafer 1 is divided into a central device formation region 3 and an outer peripheral surplus region 5 surrounding the device formation region 3. The device formation region 3 is further divided into a plurality of regions by the planned division lines 7 arranged in a lattice pattern, and a device 9 such as an IC is formed in each region. The device wafer 1 is finally divided into individual device chips along the division planned line 7. The outer periphery 1b of the device wafer 1 is chamfered and slightly rounded.

  Note that a film made of, for example, a low dielectric constant (low-k) material constituting the device may be formed on the entire surface of the device wafer, and the film is partially formed along the division line 7. It may be removed.

  Next, the processing method according to the present embodiment will be described. In the processing method according to the present embodiment, first, a guide groove forming step is performed. In this step, guide grooves are formed on the surface of the device wafer. The guide groove induces the direction in which the crack extends when the crack is extended in the vertical direction (thickness direction) from the modified layer formed inside the device wafer in a later step, and the crack is generated in an unexpected direction. It has a function to prevent extension. Hereinafter, the guide groove forming step will be described with reference to FIG.

  FIG. 2A is a schematic cross-sectional view showing the device wafer 1 and the laser processing apparatus 2 in the guide groove forming step. The laser processing apparatus 2 includes a holding unit 4 and a processing head 2 a facing the holding unit 4. The holding unit 4 and the processing head 2a are relatively movable in a direction parallel to the upper surface of the holding unit 4, and the irradiation position is changed while irradiating a laser beam from the processing head 2a toward the holding unit 4. be able to.

  The processing head 2 a has a function of irradiating a workpiece held by the holding unit 4 with a laser beam. The processing head 2a is, for example, a pulse laser oscillator that can oscillate a laser beam having a wavelength in the ultraviolet region. For example, a laser oscillator using Nd: YAG as a laser medium can be used.

  The holding unit 4 includes a chuck table 4a and a plurality of clamps 4b disposed on the outer periphery of the chuck table 4a. The plurality of clamps 4b sandwich and fix an annular frame 1e holding the tape 1d on which the device wafer 1 is placed from the outer periphery. A porous ceramic material is disposed at the center of the upper surface of the chuck table 4a. The chuck table 4a sucks and holds the device wafer 1 placed on the porous ceramic material by negative pressure via the tape 1d.

  The device wafer 1, which is a workpiece in the guide groove forming step, is held on a tape 1d that is mounted on an annular frame 1e and occupies the ring of the frame 1e. By using the tape 1d and the annular frame 1e, the device wafer can be easily handled.

  The back surface 1c of the device wafer 1 is used as a surface to be held, and is adhered to the tape 1d. That is, the surface 1a is a surface to be processed in the guide groove forming step. The tape 1d is sticky on the surface and has a function of holding the attached device wafer 1.

  In the guide groove forming step, first, an annular frame 1e holding the tape 1d to which the device wafer 1 is attached is placed on the holding unit 4, and the frame 1e is sandwiched and fixed from the outer periphery by a plurality of clamps 4b. Next, a negative pressure is applied from the chuck table 4a to suck and hold the device wafer 1 on the chuck table 4a via the tape 1d.

  Next, a guide groove is formed. In the processing method according to this embodiment, a case where a guide groove is formed using a laser beam will be described. However, the means for forming the guide groove is not limited to this. For example, the guide groove may be formed using a rotating cutting blade.

  When a laser beam is used as means for forming the guide groove, the surface 1a of the device wafer 1 is irradiated with a laser beam having a wavelength of 355 nm (output 1.0 W, repetition frequency 160 kHz) from the processing head 2a.

  While continuing the irradiation of the laser beam by the processing head 2a, the holding unit 4 holding the device wafer 1 and the processing head 2a are relatively moved along the planned division line 7 and guided along the planned division line 7. Grooves are formed. In FIG. 2A, for example, the device wafer 1 is moved in the direction of the arrow together with the holding unit 4.

  FIG. 2B shows a schematic cross-sectional view of the device wafer 1 in which a portion where the guide groove is formed is enlarged. As shown in FIG. 2B, the guide groove 11 is formed from the upper surface of the device wafer 1 to a predetermined depth along the division line 7.

  The guide groove 11 preferably has a width at the upper end of 5 μm to 20 μm and a depth from the upper end to the bottom of 5 μm to 20 μm. The cross-sectional shape of the guide groove 11 is closer to the bottom. A narrow and narrow shape is preferable. Since the crack can be linearly extended from the modified layer described later to the surface 1a side, such a width, depth and shape are preferable.

  When the guide groove 11 is formed on the surface of the device wafer 1, an extending crack is induced, and the crack is easily extended so as to reach the guide groove 11. Since the guide groove 11 is formed on the surface 1 a of the device wafer 1 along the division line 7, the possibility that the crack reaches the device 9 formed on the surface 1 a of the device wafer 1 can be reduced. That is, by forming the guide groove 11 on the surface 1a on which the device is formed, the possibility that the device 9 is damaged by a crack can be reduced.

  Conventionally, it has been necessary to increase the width of the planned dividing line 7 in order to cope with the expansion of cracks in an unexpected direction. However, if the extension direction of the cracks can be controlled, the possibility of the cracks extending in an unexpected direction can be reduced, so that the width of the division planned line 7 can be reduced. Accordingly, the area in which the device can be formed increases, so that the number of chips obtained from the device wafer 1 can be increased.

  Next, the modified layer forming step in the processing method according to the present embodiment will be described. In this step, the laser beam is focused inside the device wafer 1, and the modified layer 13 is formed at a predetermined depth along the division line 7. Furthermore, the crack is extended from the formed modified layer 13 toward at least the surface 1a side.

  FIG. 3A is a schematic cross-sectional view showing the device wafer 1 and the laser processing apparatus 6 in the modified layer forming step. In some cases, the laser processing apparatus 6 may be the laser processing apparatus 2 used in the guide groove forming step. In that case, the processing head 2 a of the laser processing apparatus 2 needs to be able to oscillate a laser beam having a wavelength that can pass through the device wafer 1. The apparatus configuration other than the processing head is the same in the laser processing apparatus 2 and the laser processing apparatus 6.

  That is, the laser processing apparatus 6 includes a holding unit 8 and a processing head 6 a facing the holding unit 8. The holding unit 8 and the processing head 6a are relatively movable in a direction parallel to the surface of the holding unit 8, and the irradiation position is changed while irradiating a laser beam from the processing head 6a toward the holding unit 8. be able to.

  The processing head 6a has a function of irradiating a workpiece held by the holding unit 8 with a laser beam. The processing head 6a is a pulse laser oscillator that can oscillate a laser beam having a wavelength in the near infrared region, for example.

  For example, an Nd: YAG laser has a fundamental wavelength in the near infrared region and a third harmonic wavelength in the ultraviolet region. Therefore, the laser processing apparatus using the Nd: YAG laser as the processing head can be used in both the guide groove forming step and the modified layer forming step.

  The holding unit 8 includes a chuck table 8a and a plurality of clamps 8b disposed on the outer periphery of the chuck table 8a. The plurality of clamps 8b sandwich and fix an annular frame 1g holding the tape 1f on which the device wafer 1 is placed from the outer periphery. In the chuck table 8a, a porous ceramic material is disposed at the center of the upper surface. The chuck table 8a sucks and holds the device wafer 1 placed on the porous ceramic material by a negative pressure via the tape 1f.

  The device wafer 1 as a workpiece in the modified layer forming step is held on a tape 1f mounted on an annular frame 1g and occupying the ring of the frame 1g. By using the tape 1f and the annular frame 1g, the device wafer 1 can be easily handled.

  The front surface 1a of the device wafer 1 is used as a surface to be held and adhered to the tape 1f, and the back surface 1c is used as the upper surface. In the modified layer forming step, a laser beam is irradiated from the back surface 1c side and condensed at a predetermined depth. The tape 1f has a function of holding the mounted device wafer 1 with a sticky surface.

  In the modified layer forming step, first, an annular frame 1g holding the tape 1f on which the device wafer 1 is placed is placed on the holding unit 8, and the frame 1g is sandwiched and fixed from the outer periphery by a plurality of clamps 8b. . Next, a negative pressure is applied from the chuck table 8a to suck and hold the device wafer 1 on the chuck table 8a via the tape 1f.

  Next, the modified layer 13 is formed. In order to form the modified layer 13, for example, a laser beam having a wavelength of 1064 nm (output 0.4 W, repetition frequency 60 kHz) that passes through the device wafer 1 is irradiated from the back surface 1 c side of the device wafer 1 to a predetermined depth. Collect light.

  Since the guide groove 11 is formed on the surface 1a side of the device wafer 1, when the laser beam is irradiated from the surface 1a side, the laser beam is scattered or refracted and a good modified layer cannot be formed. Therefore, the laser beam is irradiated from the back surface 1 c side of the device wafer 1.

  While continuing the irradiation of the laser beam by the processing head 6 a, the holding unit 8 holding the device wafer 1 and the processing head 6 a are relatively moved along the planned division line 7, and predetermined along the planned division line 7. The modified layer 13 is formed at a position at a depth of. In FIG. 3A, for example, the device wafer 1 is moved together with the holding unit 8 in the direction of the arrow.

  FIG. 3B is a schematic cross-sectional view of the device wafer 1 in which the portion where the modified layer 13 is formed is enlarged. As shown in FIG. 3B, the modified layer 13 is formed at a predetermined depth from the back surface 1 c side of the device wafer 1 along the division line 7.

  3A and 3B show the case where the modified layer 13 is formed at a single depth position, the multiple modified layers 13 are changed in depth. You may overlap and form in an up-down direction.

  In order for the extension direction of the crack to be stably induced by the guide groove 11 or the modified layer 13, it is preferable that the crack length is short. When the device wafer 1 is thick, if the modified layer 13 is formed only at a single depth, the cracks may not be sufficiently extended in the vertical direction.

  Therefore, a plurality of modified layers 13 may be formed so as to overlap in the vertical direction, and the plurality of modified layers 13 may be connected by cracks. In order to form the plurality of modified layers 13, when the laser beam is irradiated from the back surface 1 c side of the device wafer 1, first, the deepest from the back surface 1 c side among the planned formation positions of the plurality of modified layers 13. A laser beam is condensed and irradiated at a position (position close to the guide groove 11).

  After the modified layer 13 is formed along the planned dividing line 7 at the deepest position, the modified layer 13 is similarly formed at the next deepest position. In this way, the modified layer 13 is sequentially formed from a deep position (position close to the guide groove 11). If the modified layer 13 is not formed sequentially from a deep position, another modified layer 13 enters between the processing head 6a and the position where the laser beam is focused, and the laser beam is caused by the modified layer 13. This is because a good modified layer cannot be formed due to scattering or refraction.

  When determining the depth at which the modified layer 13 is formed and the number of the modified layers 13 to be formed, it is preferable to set the crack length so that it does not become too large. This is because if the length of the crack becomes too large, the crack is not correctly guided and the possibility of the crack extending in an unexpected direction increases.

  In order for the crack to be correctly guided in the vertical direction and to be elongated, for example, the distance between the modified layer 13 and the guide groove 11 may be determined to be 20 μm to 30 μm. Moreover, what is necessary is just to determine so that the distance of the modified layer 13 and the back surface 1c of the device wafer 1 may be 20 micrometers-40 micrometers. Depending on the size of the modified layer 13 itself, if it is difficult to satisfy the above condition with only one modified layer 13, the number of modified layers 13 necessary to satisfy the above condition is increased. What is necessary is just to pile up and down.

  Furthermore, when the output of the laser beam irradiated in the modified layer forming step is large, cracks can be extended from the modified layer to at least the surface side of the device wafer. By extending the cracks in this step, the device wafer is easily divided in the subsequent division step. In the dividing step, an external force is applied to divide the device wafer. However, the external force required for the division can be reduced, and the load applied to the device wafer can be reduced.

  Next, division steps in the processing method according to the present embodiment will be described with reference to FIG. FIG. 4 is a schematic cross-sectional view showing the device wafer 1 and the dividing apparatus 10 in the dividing step. FIG. 4A is a schematic cross-sectional view showing a state before division, and FIG. 4B is a schematic cross-sectional view showing a state after division. The dividing step is performed after the modified layer forming step. In the dividing step, an external force is applied to the device wafer 1 using the dividing apparatus 10 to divide the device wafer 1 into individual device chips 15.

  The device wafer 1 that is the workpiece of the dividing step is held on the tape 1f mounted on the frame 1g at the end of the modified layer forming step. The dividing step is performed as it is with the device wafer 1 held on the tape 1f. Alternatively, the device wafer 1 may be peeled off from the tape 1f, a new annular frame may be prepared, and the device wafer 1 may be stuck on the tape mounted on the annular frame to perform the dividing step.

  The dividing apparatus 10 includes a frame holding unit 12 that holds the annular frame 1g, and a tape expansion unit 16 that extends the tape 1f attached to the annular frame 1g held by the frame holding unit 12. The frame holding means 12 includes an annular frame holding member 18 and a plurality of clamps 20 as fixing means disposed on the outer periphery of the frame holding member 18. The annular frame 1 g is placed on a placement surface 18 a formed on the upper surface of the frame holding member 18.

  Then, the annular frame 1 g placed on the placement surface 18 a is fixed to the frame holding means 12 by the clamp 20. The frame holding means 12 configured as described above is supported by the tape expanding means 16 so as to be movable in the vertical direction.

  The tape expansion means 16 includes an expansion drum 22 disposed inside the annular frame holding means 12. The expansion drum 22 has an inner diameter smaller than the inner diameter of the annular frame 1g and larger than the outer diameter of the device wafer 1 attached to the tape 1f attached to the annular frame 1g.

  The tape expanding means 16 further includes a driving means 26 that moves the frame holding member 18 in the vertical direction. The driving means 26 is composed of a plurality of air cylinders 28, and the piston rod 30 is connected to the lower surface of the frame holding member 18. The driving means 26 has an annular frame holding member 12 between the reference position where the mounting surface 18a is substantially the same height as the upper end of the expansion drum 22 and the expansion position below the upper end of the expansion drum 22 by a predetermined amount. You can move up and down.

  A dividing step of the device wafer 1 performed using the dividing apparatus 10 configured as described above will be described. As shown in FIG. 4A, the annular frame 1g that supports the device wafer 1 via the tape 1f is placed on the placement surface 18a of the frame holding member 18, and the frame holding member 18 is fixed by the clamp 20. To do. At this time, the frame holding member 18 is positioned at a reference position where the mounting surface 18 a is substantially the same height as the upper end of the expansion drum 22.

  Next, the air cylinder 28 is driven to lower the frame holding member 18 to the extended position shown in FIG. As a result, the annular frame 1g fixed on the mounting surface 18a of the frame holding member 18 is also lowered, so that the tape 1f attached to the annular frame 1g abuts on the upper end edge of the expansion drum 22 and mainly in the radial direction. To be expanded.

  As a result, a tensile force acts radially on the device wafer 1 attached to the tape 1f. When a pulling force is applied to the device wafer 1 in a radial manner in this way, the modified layer and cracks formed along the planned division lines become the starting points of the division, and the device wafer 1 is cleaved along the planned division lines. Divided into device chips 15.

  In the processing method according to the present embodiment, a guide groove, one or a plurality of modified layers, and cracks extending from the modified layers are formed on the device wafer 1. Therefore, in the division step, the device wafer 1 is cleaved with high accuracy in the vertical direction along the division line, and is divided into individual device chips 15. At that time, since it is easily divided by a relatively small external force, the impact caused by the cleaving is small, and the crack does not reach the device formation region. Therefore, the possibility of damaging the device can be reduced as compared with the conventional case.

  Note that the processing method according to one embodiment of the present invention is also applied to a device wafer in which a low dielectric constant insulator film (Low-k film) is formed on the entire surface as a film included in a stacked body constituting a device. it can. A processing method according to a modification of the present invention applied to such a device wafer will be described below.

  In the processing method according to the modification of the present invention, a laminate is formed as a pattern for forming a circuit of a device on a device wafer. The laminate includes a low dielectric constant insulator film (Low-k film), and the low dielectric constant insulator film (Low-k film) is an inorganic film such as SiOF or BSG (SiOB) or a polyimide film. It consists of an organic film that is a polymer film such as a parylene film.

  In the device wafer having the laminated body formed on the surface, the laminated body cutting step is performed. The laminated body cutting step will be described with reference to FIGS. 5 (A) to 5 (D). FIG. 5A is a schematic cross-sectional view showing the device wafer 1 in which the laminated body 17 is formed on the surface 1a. As shown in FIG. 5A, a laminated body 17 constituting the device is formed on the surface 1a of the device wafer 1.

  The laminated body dividing step in the processing method according to this modification may be performed in a state where the device wafer 1 is held on a tape (not shown) mounted on an annular frame (not shown). Moreover, the laser beam cutting apparatus which has the structure similar to the laser beam machining apparatus 2 or the laser beam machining apparatus 6 demonstrated in this specification can be used for this laminated body parting step. Therefore, the description about a laser processing apparatus is abbreviate | omitted.

  In the laminated body dividing step, as shown in FIG. 5B, first, the laminated bodies 17 at both ends of the planned dividing line 7 are removed to form a pair of grooves 19 a that are part of the laminated body dividing grooves 19. FIG. 5B is a diagram schematically showing a cross-sectional structure of the device wafer 1 after the grooves 19a are formed. The laminated body 17 between the pair of grooves 19a is removed later, and the groove 19a is formed to prevent the removal 17 from affecting the laminated body 17.

  As a means for forming the groove 19a, ablation processing using a laser processing apparatus or cutting using a rotating cutting blade can be applied. In any means, since the groove 19a is relatively small, the burden on the device wafer 1 and the laminated body 17 when the groove 19a is formed is limited.

  Next, the laminated body 17 between the grooves 19a is removed, and a laminated body dividing groove 19 is formed at the position of the planned dividing line 7. FIG. 5C schematically shows a cross-sectional structure of the device wafer 1 when the laminated body dividing groove 19 is formed. The laminated body dividing groove 19 can be formed by cutting with a blade or ablation with a laser beam, but the latter is particularly preferable because the time required for the process can be reduced.

  In addition, when the laminated body 17 is partially removed by the ablation process by a laser beam, the peripheral part of the area | region to be removed may receive the influence of the heat which arises by this process. When the influence extends around the laminated body separating groove 19, for example, the laminated body 17 may be partially peeled from the device wafer 1 or the device 9 may be damaged.

  In the vicinity of the boundary between the multilayer body 17 and the multilayer body separation groove 19, the influence of heat generated by processing becomes the largest. Therefore, by forming the groove 19a, the influence can be prevented from propagating to the laminated body 17 constituting the device 9, and the peeling of the laminated body 17 and the damage of the device 9 can be prevented.

  However, the device wafer 1 is also affected by the ablation processing by the laser beam. In particular, the influence is large in the portion immediately below the laminate separation groove 19. Specifically, it is altered by heat and causes distortion and the like. Therefore, when the laminated body separation groove 19 is formed along the planned division line 7, a portion having distortion is formed along the planned division line 7.

  The device wafer 1 is cracked in the vertical direction along the planned dividing line 7 and is divided to form individual device chips 15. However, the crack is difficult to extend linearly in the vertical direction particularly in a portion having distortion. . Therefore, in order to reduce the influence of the distortion, a guide groove 11 is formed along the planned dividing line 7, and a laser beam is condensed and irradiated from the back side to form a modified layer 13 to induce cracks. The extending method is particularly effective.

  Next, the guide groove 11 is formed. FIG. 5D schematically shows a cross-sectional structure of the device wafer 1 when the guide groove 11 is formed. As shown in FIG. 5D, the guide groove 11 is formed at a part of the bottom of the laminated body separating groove 19 along the planned dividing line 7.

  Next, in the processing method according to this modification, a modified layer forming step is performed. FIG. 6 shows a cross-sectional structure of the device wafer 1 when the modified layer forming step is performed. The modified layer forming step in the modification is performed in the same manner as the modified layer forming step described in the embodiment.

  Next, in the processing method according to this modification, a division step is performed. FIG. 7 is a schematic cross-sectional view showing the device wafer 1 and the dividing apparatus 10 in the dividing step. FIG. 7A is a schematic cross-sectional view showing a state before division, and FIG. 7B is a schematic cross-sectional view showing a state after division. Note that the division step in the modification is performed in the same manner as the division step described in the embodiment.

  As described above, the processing method according to another aspect of the present invention has been described in the case where a laminate including a pattern for forming a circuit of a device is formed on a device wafer. Even in such a case, it is possible to divide the device wafer by linearly extending cracks in the vertical direction of the device wafer without being affected by the distortion of the device wafer that occurs during the formation of the laminated body separation groove. .

  In addition, this invention is not limited to description of the said embodiment, A various change can be implemented. For example, in the above embodiment, the case where the device wafer is divided using the dividing apparatus has been described. However, if the crack is extended in the vertical direction so as to penetrate the device wafer by performing the modified layer forming step, the dividing step can be omitted.

  In addition, the structure, method, and the like according to the above-described embodiment can be appropriately modified and implemented without departing from the scope of the object of the present invention.

DESCRIPTION OF SYMBOLS 1 Device wafer 1a Front surface 1b Outer periphery 1c Back surface 1d Tape 1e Frame 1f Tape 1g Frame 3 Device formation area 5 Peripheral surplus area 7 Line to be divided 9 Device 11 Guide groove 13 Modified layer 15 Device chip 17 Laminated body 19 Laminated body dividing groove 19a Groove 2 Laser processing device 2a Processing head 4 Holding unit 4a Chuck table 4b Clamp 6 Laser processing device 6a Processing head 8 Holding unit 8a Chuck table 8b Clamp 10 Dividing device 12 Frame holding means 16 Tape expanding means 18 Frame holding member 18a Mounting surface 20 Clamp 22 Expansion drum 26 Driving means 28 Air cylinder 30 Piston rod

Claims (2)

A device wafer processing method in which devices are respectively formed in regions divided by a plurality of scheduled division lines intersecting each other,
A laser beam having a wavelength that is transmissive to the device wafer is irradiated from the back side of the wafer along the division line to form a modified layer inside the device wafer, and at least the surface of the wafer from the modified layer A modified layer forming step for extending cracks on the side;
After performing the modified layer forming step, a dividing step of applying an external force to the device wafer to divide the device wafer into individual device chips;
Before carrying out the modified layer forming step, a guide groove forming step for forming a groove that guides the extending direction of a crack extending from the modified layer to the surface side from the surface of the wafer along the division line. When,
A device wafer processing method comprising: The device wafer has a laminate on the surface;
2. The device wafer processing method according to claim 1, further comprising a laminated body dividing step of dividing the laminated body along the scheduled division line before the dividing step is performed.