JP2019009199A - Wafer and processing method thereof - Google Patents

Abstract

To provide a wafer and a processing method thereof capable of efficiently and reliably performing division processing.SOLUTION: In a wafer (10) having planned dividing lines (L) set in a first direction (CH1) and a second direction (CH2) orthogonal to the first direction on the upper surface of a wafer substrate (11), the wafer substrate has a hexagonal crystal structure, and the first direction and the second direction of the planned dividing lines are set such that the angular differences with the crystal orientation of the wafer substrate are equal to each other. As a result, a force is equally applied to each of the dividing lines in the first direction and the second direction, such that efficient division can be realized without leaving an undivided portion.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wafer and a wafer processing method.

  As a wafer, for example, a GaN-based nitride semiconductor or the like laminated on a sapphire substrate is partitioned by dividing lines, and light emitting elements such as LEDs (light emitting diodes) are formed in each of the plurality of partitions on the sapphire substrate. Things are known. Such a wafer is divided into individual light emitting elements along a planned division line and used for various electronic devices such as portable devices, personal computers, and acoustic devices. Since the sapphire substrate has high Mohs hardness, it is difficult to apply mechanical dicing using a cutting blade. Therefore, a wafer dividing method using laser processing has been proposed (see, for example, Patent Document 1).

  In the dividing method described in Patent Document 1, a laser beam having a wavelength having transparency is applied to the wafer, and a modified layer is formed along the planned dividing line in the wafer. Then, by applying an external force to the modified layer in the wafer, the wafer is divided into individual devices starting from the modified layer. During the division, an external force is applied to the wafer by braking. In braking, the pressing blade is pressed onto the division line, and the pressing force of the pressing blade acts on the modified layer, whereby the wafer is divided into individual device chips.

JP 2008-6492 A

  However, if the wafer is divided line by line along the line to be divided by braking, the processing time becomes longer and the productivity becomes worse. In particular, in recent years, small chips of 1 mm square or less have also been developed, and there has been a problem that productivity is further deteriorated due to an increase in the number of lines to be divided due to the smaller chip size of the device.

  The present invention has been made in view of these points, and an object of the present invention is to provide a wafer and a wafer processing method that can perform division processing efficiently and reliably and have excellent productivity.

  The present invention is a wafer having a dividing line set in the first direction and a second direction orthogonal to the first direction on the upper surface of the wafer substrate, the wafer substrate has a hexagonal structure, The first direction and the second direction are characterized in that the angular differences from the crystal orientation of the wafer substrate are set to be equal to each other.

  The present invention is also a wafer processing method for dividing the wafer into a lattice shape along a division line, an adhesive tape attaching step for attaching an adhesive tape to the back surface of the wafer, and an adhesive tape attaching step. After performing the above, a modified layer forming step for forming a modified layer inside the wafer substrate by irradiating a laser beam having a wavelength transmissive to the wafer substrate along the division line, and a modified layer forming step And a tape expansion step of expanding the adhesive tape outward in the wafer radial direction and dividing the wafer along the planned division line starting from the modified layer.

  According to the wafer and wafer processing method described above, the tape expansion step (expanding) is performed to expand the adhesive tape by setting the intersecting (orthogonal) splitting lines in two directions so that the angle difference with the crystal orientation is equal. When braking), the force is evenly applied to the planned dividing lines in each direction. Accordingly, the division ratio is greatly improved as compared with the case where the two-way division lines are set to have different angle differences with respect to the crystal direction. In particular, the workability when dividing the wafer into small chips can be remarkably improved.

  The adhesive tape is an ultraviolet curable adhesive tape that cures the adhesive layer when irradiated with a predetermined cumulative amount of ultraviolet light. Before the tape expansion step is performed, the adhesive layer of the ultraviolet curable adhesive tape is irradiated with ultraviolet rays. It is preferable to carry out a pressure-sensitive adhesive layer curing step for curing.

  Before performing the adhesive tape sticking step, it is preferable to perform a UV cleaning step of UV cleaning the back surface of the wafer.

  According to the wafer and the wafer processing method of the present invention, the wafer can be divided efficiently and reliably, and the productivity of products produced from the wafer can be improved.

It is a perspective view in the state where adhesive tape was stuck on the wafer of this embodiment. It is a figure which shows the setting of the division | segmentation schedule line in the wafer of this Embodiment. It is a figure which shows an example of the setting of the division | segmentation schedule line in the wafer of a comparative example. It is a figure which shows the modified layer formation step of this Embodiment. It is a figure which shows the adhesion layer hardening step of this Embodiment. It is a figure which shows the change of the adhesive force of the adhesive tape by ultraviolet irradiation. It is a figure which shows the tape expansion step of this Embodiment. It is a figure which shows the tape expansion step of this Embodiment.

  Hereinafter, a wafer and a wafer processing method according to the present embodiment will be described with reference to the accompanying drawings. First, a wafer to be processed will be described. FIG. 1 and FIG. 2 are diagrams showing the setting of the wafer and the division line on the wafer according to the present embodiment, and FIG. 3 is a diagram showing the setting of the division line on the wafer of the comparative example.

  As shown in FIGS. 4, 5, 7, and 8, the wafer 10 has a light emitting layer 12 laminated by epitaxial growth on an upper surface of a wafer substrate 11 that is a crystal growth substrate such as sapphire. 4, 5, 7, and 8 show the wafer 10 with the light emitting layer 12 facing downward. As shown in FIG. 1, the light emitting layer 12 of the wafer 10 is partitioned by a grid-like division line L, and the light emitting layer 12 is partitioned to form an optical device P such as an LED.

  As shown in FIGS. 1 and 2, the division line L of the wafer 10 includes a plurality of parallel first channels CH <b> 1 (shown as broken lines inclined upward in FIG. 2) and a plurality of parallel second channels. Channel CH2 (shown as a broken line sloping downward in FIG. 2). The first direction in which the first channel CH1 extends and the second direction in which the second channel CH2 extends have a relationship orthogonal to each other. In FIG. 2, in order to make it easy to identify the division line L, the interval between the division lines L with respect to the size of the wafer 10 and the size of the optical device P are conceptually drawn larger than those in FIG. 1. Yes.

  The wafer substrate 11 has a hexagonal crystal structure, and an orientation flat 13 showing a crystal orientation is formed on the outer periphery of the wafer 10 (see FIGS. 1 and 2). In the lower right circled portion in FIG. 2, a continuous regular hexagon (bottom surface of a regular hexagonal column) representing the crystal structure of the wafer substrate 11 is conceptually shown. The wafer 10 according to the present embodiment was conceived with the focus on setting the direction of the division line L to improve the division workability of the wafer 10 in consideration of the influence of such a crystal structure on the division work. It is. That is, the division line L on the wafer 10 is set so that the respective angle differences between the first channel CH1 and the second channel CH2 with respect to the crystal orientation (direction of the orientation flat 13) of the wafer substrate 11 having a hexagonal structure are equal. Is set.

  More specifically, as shown in FIG. 2, in the regular hexagon (regular hexagonal column) constituting the hexagonal crystal structure of the wafer substrate 11, it passes through the center and extends in the thickness direction of the wafer substrate 11 (direction perpendicular to the paper surface of FIG. 2). The a1 axis, a2 axis, and a3 axis that connect the c axis and the c axis and each vertex of the regular hexagon are set. The first channel CH1 and the second channel CH2 of the planned division line L are set at angles of 45 degrees and 135 degrees with respect to the a1 axis, respectively. In other words, the first channel CH1 and the second channel CH2 have an inclination of 45 degrees forward and backward with respect to the a1 axis.

  A substrate having a crystal structure such as the wafer 10 has a property that a force to be divided along the crystal orientation is easily applied when an external force is applied. When the direction of the division line L is set as in the present embodiment (FIG. 2), when an external force is applied to the wafer 10 to expand radially outward, the angular difference from the crystal orientation is the same. A force is equally likely to act on the first channel CH1 and the second channel CH2. Therefore, it becomes possible to divide both the first channel CH1 and the second channel CH2 with equal efficiency without any deviation.

  In the comparative example shown in FIG. 3, the direction of the second channel CH2 'in the planned division line L' is set parallel to the a1 axis of the crystal structure. The first channel CH1 'is orthogonal to the a1 axis. When the division line L ′ is set in this way, the second channel CH2 ′ that is parallel to the a1 axis (there is no angular difference from the a1 axis) is cleaved when an external force that expands radially outward is applied to the wafer. Easy to be. On the other hand, a force hardly acts on the first channel CH1 ′ having a large angle difference with respect to the a1 axis (the angle difference is 90 degrees), and is not divided into the first channel CH1 ′ compared to the second channel CH2 ′. There may be many occurrences. A large external force is required to cleave all the first channels CH1 'satisfactorily. However, if the force applied at the time of division is excessive, there is a high risk of device characteristic failure.

  In the present embodiment shown in FIG. 2, there is no difference in the fragility of the first channel CH1 and the second channel CH2 when the crystal orientation of the wafer 10 is used as a reference, and the first channel CH1 in the comparative example of FIG. The problem that it is hard to break only a specific part like 'does not occur. Therefore, the wafer 10 of the present embodiment can divide all the division lines L easily and reliably as compared with the comparative example of FIG.

  Next, processing for dividing the wafer 10 configured as described above will be described. This processing includes a UV cleaning step, an adhesive tape attaching step (see FIG. 1), a modified layer forming step (see FIG. 4), an adhesive layer curing step (see FIGS. 5 and 6), a tape expanding step (FIG. 7, (See FIG. 8). In the following description of the processing method, the surface on the side to which the adhesive tape T to be described later is attached is the back surface of the wafer 10. In the present embodiment, the light emitting layer 12 side of the wafer 10 is an object to be adhered to the adhesive tape T, but it can be arbitrarily selected on which surface of the wafer the adhesive tape is adhered. Of these, an adhesive tape may be attached to the surface opposite to the light emitting layer 12.

  In the UV cleaning step, the back surface of the wafer 10 before the adhesive tape is attached is UV cleaned. Although the illustration of the cleaning apparatus used in the UV cleaning step is omitted, an ultraviolet lamp (such as a low-pressure mercury lamp) capable of irradiating the wafer 10 with ultraviolet rays is provided. The organic compound adhering to the wafer 10 is decomposed by irradiation with ultraviolet rays, and active oxygen separated from ozone generated by the ultraviolet rays is combined with the organic compound to become a volatile substance, whereby the wafer 10 is cleaned.

  The adhesive tape attaching step is carried out by transporting the wafer 10 to a tape mounter (not shown), and attaches the adhesive tape T to the back surface of the wafer 10. The adhesive tape T is stuck from below with the surface of the wafer 10 on which the light emitting layer 12 is formed facing downward. As shown in FIGS. 4, 5, 7, and 8, the adhesive tape T has a configuration in which an adhesive layer 16 is applied on a tape base material 15. The adhesive layer 16 is formed of an ultraviolet curable adhesive material.

  FIG. 1 shows a state where the adhesive tape attaching step is completed. As shown in FIG. 1, an annular ring frame F is attached to the outer periphery of the adhesive tape T, and the adhesive layer 16 of the adhesive tape T exposed inside the opening surrounded by the inner peripheral portion of the ring frame F The wafer 10 is attached. The wafer 10 is conveyed in the state of FIG. 1 supported by the ring frame F via the adhesive tape T.

  Subsequently, a modified layer forming step shown in FIG. 4 is performed. In the modified layer forming step, the wafer 10 supported by the ring frame F and the adhesive tape T is transported to the laser processing apparatus 20. The wafer 10 is held on the holding table 21 of the laser processing apparatus 20 via the adhesive tape T, and the ring frame F around the wafer 10 is held on the annular table 22 by the clamp portion 23.

  With respect to the wafer 10 held on the holding table 21, the exit of the processing head 24 of the laser processing apparatus 20 is positioned immediately above the planned division line L, and the laser beam LZ from the processing head 24 toward the wafer 10 is positioned. Is irradiated. The laser beam LZ has a wavelength that is transmissive to the wafer substrate 11 and is adjusted so as to be condensed inside the wafer substrate 11. The processing head 24 can move relative to the wafer 10 in the horizontal direction.

  And while the condensing point of the laser beam LZ is adjusted, the processing head 24 is moved relative to the holding table 21 with respect to the wafer 10, and thus along the division line L inside the wafer substrate 11. The modified layer 14 is formed. For example, first, the condensing point is adjusted to a position near the light emitting layer 12 in the wafer substrate 11, and laser processing is performed so that the first modified layer 14 is formed along all the division lines L. Then, the height of the condensing point is shifted to the side farther from the light emitting layer 12, and laser processing is repeated along all the planned division lines L to form the second-stage modified layer 14. In this way, a division starting point along the division planned line L (first channel CH1 and second channel CH2) is formed inside the wafer 10.

  The modified layer 14 is a region where the density, refractive index, mechanical strength and other physical characteristics of the wafer 10 are different from the surroundings due to the irradiation of the laser beam, and the strength is lower than the surroundings. Say. The modified layer 14 is, for example, a melt treatment region, a crack region, a dielectric breakdown region, or a refractive index change region, and may be a region where these are mixed. In the present embodiment, the two-stage modified layer 14 is formed inside the wafer 10, but the present invention is not limited to this configuration. The modified layer 14 only needs to be formed so as to be a starting point for dividing the wafer 10. For example, when the wafer 10 is thin, the modified layer 14 may be formed in only one stage. Three or more modified layers 14 may be formed.

  After the modified layer forming step, the adhesive layer curing step shown in FIG. 5 is performed. In the adhesive layer curing step, the wafer 10 supported by the ring frame F and the adhesive tape T is conveyed to the ultraviolet irradiation device 30. The wafer 10 is supported on the support table 31 of the ultraviolet irradiation device 30 via the adhesive tape T. The support table 31 is made of glass and has ultraviolet transparency. Then, UV light is irradiated to the adhesive layer 16 of the adhesive tape T from a UV irradiator 32 provided below the support table 31. Thereby, the adhesive force of the ultraviolet curable adhesive layer 16 decreases, and the adhesiveness between the wafer 10 and the adhesive tape T decreases. Further, the adhesive layer 16 is cured and the flexibility is lowered.

  The UV irradiator 32 has an irradiation surface that is slightly larger than the diameter of the wafer 10, and irradiates the portion of the adhesive layer 16 of the adhesive tape T where the wafer 10 is adhered with ultraviolet rays. Thereby, an ultraviolet-ray is not irradiated to the location stuck to the ring frame F among the adhesion layers 16 of the adhesive tape T, and the fall of the adhesive force of the adhesive tape T with respect to the ring frame F can be prevented. Therefore, the wafer 10 can be transported through the ring frame F without the ring frame F being detached from the adhesive tape T.

FIG. 6 is a graph showing changes in the adhesive strength of the adhesive layer 16 due to the irradiation of ultraviolet rays. The adhesive layer 16 has an adhesive force that decreases sharply until the integrated light amount of the irradiated ultraviolet rays reaches 160 [mJ / cm ² ], and when the integrated light amount exceeds 160 [mJ / cm ² ], the adhesive force gradually decreases. Decrease. For this reason, the adhesive layer 16 can be cured while securing the adhesive force of the adhesive layer 16 by irradiating the adhesive layer 16 with ultraviolet rays of 160 [mJ / cm ² ] or less and a predetermined integrated light amount or less. it can. For example, by irradiating 50 [mJ / cm ² ] ultraviolet rays, the adhesive layer 16 can be semi-cured while leaving a normal half adhesive force, and the wafer 10 from the adhesive tape T in the tape expansion step described later. Can be prevented. Thus, in the adhesive layer curing step, it is preferable to irradiate ultraviolet rays having a predetermined integrated light amount or less necessary for curing the adhesive layer 16.

  When the adhesive layer 16 is irradiated with ultraviolet rays until it reaches a predetermined integrated light amount, the adhesive force of the adhesive layer 16 is significantly reduced. However, in the tape expansion step, which will be described later, a force mainly acts in the radial direction of the adhesive tape T, and no strong force acts in the peeling direction of the adhesive tape T and the wafer 10. The degree of curing may be increased by irradiating the adhesive layer 16 with ultraviolet rays up to a value close to.

  After the adhesive layer curing step, a tape expansion step shown in FIGS. 7 and 8 is performed. In the tape expansion step, the wafer 10 supported by the ring frame F and the adhesive tape T is transported to the expanding device 40. As shown in FIG. 7, the ring frame F is held by the clamp portion 42 on the annular table 41 of the expanding device 40, and the expansion drum 43 is disposed below the adhesive tape T. The expansion drum 43 has a substantially circular outer peripheral shape when viewed from above, and the outer peripheral portion of the expansion drum 43 is located between the wafer 10 and the ring frame F. A plurality of rotatable rolling rollers 44 are provided on the outer periphery of the expansion drum 43. The expansion drum 43 is supported by a plurality of lifting mechanisms 45 so as to be lifted and lowered.

  As shown in FIG. 8, in the tape expansion step, the lifting mechanism 45 is driven to move the expansion drum 43 upward to push up the adhesive tape T. Due to the difference between the central portion pushed up by the expansion drum 43 and the outer peripheral portion held by the annular table 41 and the clamp portion 42 and restricted in movement, a tensile force indicated by an arrow E in FIG. . Then, the portion of the adhesive tape T that is adhered to the wafer 10 is expanded radially outward. At this time, since the outer edge portion of the expansion drum 43 is in contact with the adhesive tape T via the rolling roller 44, the frictional force generated when the adhesive tape T is expanded and the load on the adhesive tape T are suppressed. Further, since the adhesive layer 16 of the adhesive tape T is cured as a result of the adhesive layer curing step (FIG. 5) performed previously, the adhesive tape is not greatly attenuated by the elongation of the adhesive layer 16 or the like. A tensile force is efficiently applied to the modified layer 14 of the wafer 10 via T. As a result, the wafer 10 is divided into device chips Q having individual optical devices P (FIG. 1) along the planned division line L, starting from the modified layer 14 whose strength has been reduced (see FIG. 8).

  Specifically, when the adhesive tape T is expanded radially outward, a tensile force acts on the adhesive layer 16 as the tape base material 15 is expanded. Since the adhesive layer 16 before being cured is highly flexible and the operation of the surface in contact with the tape base 15 and the surface in contact with the wafer 10 is low (easy to absorb external force), the tensile force is applied from the tape base 15. When this occurs, it is difficult to apply a sufficient external force to the modified layer 14 of the wafer 10. On the other hand, the pressure-sensitive adhesive layer 16 that has been cured by ultraviolet irradiation can easily transmit a tensile force from the tape base material 15 side to the wafer 10 side. For this reason, the adhesive layer 16 does not stretch and cracks and breaks, and a force that causes the wafer 10 supported on the adhesive layer 16 to expand outward in the radial direction acts strongly. Sufficient external force is applied to the quality layer 14.

  As a result, as shown in an enlarged view in FIG. 8, the wafer 10 is cracked starting from the modified layer 14 inside the wafer 10, and the dividing groove 17 along the division line L is formed. It is divided into individual device chips Q (see FIG. 8). At this time, in the previous adhesive layer curing step (FIG. 5), the adhesive layer 16 is irradiated with ultraviolet rays not more than a predetermined integrated light amount (see FIG. 6) necessary for curing the adhesive layer 16 so that the adhesive layer 16 has some adhesive force. By leaving it in a semi-cured state, it is possible to prevent the device chip Q from falling off the adhesive tape T during tape expansion. As described above, the ultraviolet irradiation process for weakening the adhesive force of the ultraviolet curable adhesive tape T to an appropriate degree is performed before the wafer 10 is divided, so that the wafer 10 can be easily divided at the tape expansion step.

  In the tape expansion step, since the wafer 10 is divided at a time by the expansion of the adhesive tape T, the tape expansion step can be performed in a shorter time compared to the division processing by braking on the individual division lines. Further, in the present embodiment, the angle difference between the first channel CH1 and the second channel CH2 with respect to the crystal orientation of the wafer 10 is set to be equal (see FIG. 2), so that it is radially outward with respect to the wafer 10 in the tape expansion step. When an external force is applied to the first channel CH1 and the second channel CH2, it is possible to uniformly apply the force to the first channel CH1 and the second channel CH2, and to divide all the planned division lines L evenly. Therefore, undivided portions are not easily generated on the wafer 10, and the productivity of the device chip Q can be improved.

  Further, in the present embodiment, the angle difference between the first channel CH1 and the second channel CH2 with respect to the crystal orientation of the wafer 10 is suppressed to a certain extent (for example, 45 degrees forward and backward with respect to the axis a1 in FIG. 2). Therefore, compared to the case where the angle difference with respect to the crystal orientation is large (the angle difference with respect to the axis a1 is 90 degrees) as in the first channel CH1 ′ of the comparative example shown in FIG. The tensile force of T can be small. That is, in the tape expansion step, the wafer 10 can be divided satisfactorily while suppressing the push-up amount of the adhesive tape T by the expansion drum 43 to be small, and in addition to improving productivity, labor saving and load reduction in the expander 40 can be achieved. Such effects can also be obtained.

  After completion of the tape expansion step, the push-up operation of the expansion drum 43 is canceled and the expanding device 40 is returned to the state shown in FIG. Then, the adhesive tape T is peeled off from the wafer 10 (divided device chip Q). The adhesive tape T is easily peeled off by the adhesive layer 16 being cured in the previous adhesive layer curing step.

  The wafer 10 of the present embodiment is an optical device wafer in which an optical device P is formed on a wafer substrate 11 that is a sapphire substrate. However, a wafer to which the present invention is applied has a predetermined crystal structure and is divided. Any material other than the sapphire substrate may be used as long as processing can be performed. The device formed on the wafer may be other than an optical device.

  From the viewpoint of production efficiency, the tape expansion described above is suitable for the dividing process on the wafer, but the present invention can also be applied to a wafer divided by a method other than the tape expanding. When performing division processing by tape expansion, the UV cleaning step and the like in the present embodiment can be omitted. Further, the adhesive layer curing step can be omitted if a sufficient external force can be applied from the adhesive tape to the wafer in the tape expansion step without curing the adhesive layer of the adhesive tape.

  The apparatus configuration of the laser processing apparatus 20, the ultraviolet irradiation apparatus 30, the expanding apparatus 40, and the like in this embodiment is an example, and the wafer may be processed by a processing apparatus having a configuration other than this.

  Moreover, although each embodiment of the present invention has been described, as the other embodiment of the present invention, the above embodiment and modifications may be combined in whole or in part.

  The embodiments of the present invention are not limited to the above-described embodiments and modifications, and various changes, substitutions, and modifications may be made without departing from the spirit of the technical idea of the present invention. Furthermore, if the technical idea of the present invention can be realized in another way by technological advancement or another derived technique, the method may be used. Accordingly, the claims cover all embodiments that can be included within the scope of the technical idea of the present invention.

  As described above, according to the wafer and the wafer processing method of the present invention, the easiness of division based on the crystal orientation of the wafer substrate is equivalent in the first direction and the second direction of the division planned line. Therefore, it is excellent in the wafer splitting processability, and can contribute to the improvement of the productivity of products produced from the wafer.

DESCRIPTION OF SYMBOLS 10 Wafer 11 Wafer board | substrate 12 Light emitting layer 13 Orientation flat 14 Modified | denatured layer 15 Tape base material 16 Adhesive layer 17 Dividing groove 20 Laser processing apparatus 21 Holding table 22 Annular table 23 Clamp part 24 Processing head 30 Ultraviolet irradiation apparatus 31 Support table 32 UV Irradiator 40 Expanding device 41 Annular table 42 Clamp part 43 Expansion drum 44 Rolling roller 45 Lifting mechanism CH1 1st channel CH2 2nd channel F Ring frame L Line to be divided LZ Laser beam P Optical device Q Device chip T Adhesive tape (UV curing) Type adhesive tape)

Claims (4)

A wafer having division lines set on a top surface of a wafer substrate in a first direction and a second direction orthogonal to the first direction,
The wafer substrate has a hexagonal crystal structure, and the first direction and the second direction are set so that angular differences from the crystal orientation of the wafer substrate are equal to each other. Wafer to be used. A wafer processing method for dividing the wafer according to claim 1 into a lattice shape along the division line,
An adhesive tape attaching step for attaching an adhesive tape to the back surface of the wafer;
A modified layer that forms a modified layer inside the wafer substrate by irradiating the wafer substrate with a laser beam having a wavelength that is transparent to the wafer substrate after performing the adhesive tape attaching step. Forming step;
A tape expansion step of expanding the adhesive tape outward in the radial direction of the wafer after performing the modified layer forming step, and dividing the wafer along the planned dividing line from the modified layer as a starting point. A wafer processing method characterized by the above. The pressure-sensitive adhesive tape is an ultraviolet curable pressure-sensitive adhesive tape that cures the pressure-sensitive adhesive layer when irradiated with a predetermined cumulative amount of ultraviolet light,
The adhesive layer curing step of curing the adhesive layer by irradiating the adhesive layer of the ultraviolet curable adhesive tape with ultraviolet rays before the tape expansion step is performed. Wafer processing method.   4. The wafer processing method according to claim 2, wherein a UV cleaning step of UV cleaning the back surface of the wafer is performed before the adhesive tape attaching step.

Images