JP2019125598A - Wafer division method - Google Patents

Abstract

To provide a wafer division method capable of preventing a division failure of chips and variation in distance among the chips by difference in an elongation amount of a tape.SOLUTION: A method for dividing a wafer 100 for dividing the wafer 100 along orthogonal scheduled division lines 102 includes: a modified layer formation step for irradiating laser beams of wavelength having penetrability to the wafer 100 along the scheduled division lines 102 to form modified layers 120 inside the wafer 100; a sticking step for sticking an expanded tape in which a first direction 13 is more stretchable than a second direction 14 perpendicular to the first direction 13 to the wafer 100; and a division step for expanding an interval between chips while expanding the expanded tape to perform division to chips. In the modified layer formation step, modified layers 120 formed on scheduled division lines 102 parallel with the first direction 13 are more than modified layers 120 formed on scheduled division lines 102 parallel with the second direction 14.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a wafer dividing method for dividing a wafer into individual chips.

  In general, a laser beam of a wavelength having transparency to the wafer is irradiated along a planned dividing line of the wafer to form a modified layer inside the wafer, and the modified layer is used as a break starting point to form individual chips. The division method to divide into is known (for example, refer to patent documents 1). In this type of dividing method, an expanded tape (hereinafter referred to as a tape) is attached to the wafer on which the modified layer is formed, and the tape is expanded by an expansion device, so that the modified layer becomes a break starting point. It is divided.

JP, 2013-207170, A

  By the way, the tape to be attached to the wafer is usually used by feeding a long tape wound in a roll and cutting it for a predetermined length in the longitudinal direction. In this type of tape, a perpendicular direction (TD: Transverse Direction (second direction)) in which the machine direction (MD: Machine Direction (first direction)), which is the longitudinal direction of the tape, is perpendicular to the flow direction. Easier to stretch than). When the wafer is attached to the tape, the directions of the intended dividing lines of the wafer are roughly associated with the flow direction (first direction) and the vertical direction (second direction) and attached to the tape. There are many cases. For this reason, when the tape is expanded and divided concentrically by the same force, the amount of elongation of the tape differs depending on the direction, so that the modified layer is not partially broken and chip division failure or divided chips There has been a problem that the distance between them (kerf width) varies.

  The present invention has been made in view of the above, and an object of the present invention is to provide a wafer dividing method capable of preventing chip division failure and variation in the distance between chips due to the difference in the elongation amount of the tape.

  In order to solve the problems described above and to achieve the object, the present invention divides a wafer on a surface of which a plurality of devices partitioned by a plurality of dividing lines are formed along the dividing lines. Forming a modified layer in the interior of the wafer by irradiating the wafer with a laser beam of a wavelength having transparency to the wafer along the planned dividing line, the first direction being the first direction A sticking step of sticking an expandable tape which is more extensible than a second direction orthogonal to the direction 1 to the wafer, and a dividing step of expanding the expandable tape and dividing it into chips while widening the distance between the chips; The modified layer formed in the planned dividing line parallel to the first direction in the modifying layer forming step is formed on the planned planned line parallel to the second direction. It is characterized in that more than reforming layer.

  According to this configuration, the modified layer formed in the planned dividing line extending along the second direction that is less likely to extend than the first direction is formed on the planned dividing line extending along the first direction. Since the number of layers is larger than that of the expanded tape, even if the expanded tape is expanded concentrically with the same force by differentiating the degree of formation of the modified layer depending on the first direction and the second direction of the expanded tape, the first direction And an equal amount of elongation in the second direction. As a result, it is possible to prevent chip division failure and variation in the distance between the divided chips. Here, that the number of modified layers is large means that the ratio of the modified layers in the region corresponding to the planned dividing line is large.

  In the modified layer forming step, a modified layer is formed on the dividing line parallel to the first direction up to the outer periphery of the wafer, and the dividing line parallel to the second direction is arbitrary. The modified layer may be formed leaving the unprocessed area. According to this configuration, it is possible to easily form the modified layers having different degrees of formation on the planned dividing lines extending along the first direction and the second direction.

  In the modified layer forming step, the planned dividing line parallel to the first direction has a larger power of the laser beam irradiated from the planned dividing line parallel to the second direction, in the thickness direction of the wafer. It may be configured to include at least any one of the conditions that the number of the modified layers formed is large or the overlapping ratio of the irradiation marks of the laser beam is high. According to this configuration, it is possible to easily form the modified layers having different degrees of formation on the planned dividing lines extending along the first direction and the second direction.

  According to the present invention, even if the expand tape is expanded concentrically with the same force by making the degree of formation of the modified layer different according to the first direction and the second direction of the expand tape, the first Equal amounts of elongation can be obtained in the direction and in the second direction. As a result, it is possible to prevent chip division failure and variation in the distance between the divided chips.

FIG. 1 is a perspective view showing a wafer to be divided in the present embodiment. FIG. 2 is a perspective view showing an expanded tape attached to the wafer when the wafer is divided. FIG. 3 is a flow chart showing the procedure of the wafer dividing method. FIG. 4 is a perspective view showing a configuration example of a laser processing apparatus for forming a modified layer inside a wafer. FIG. 5 is a plan view schematically showing the modified layer formed inside the wafer. FIG. 6 is a side sectional view showing the configuration before grinding a wafer. FIG. 7 is a side sectional view showing the structure after grinding the wafer. FIG. 8 is a perspective view showing a wafer supported by an annular frame via an expand tape. FIG. 9 is a side sectional view showing the configuration before dividing the wafer. FIG. 10 is a side sectional view showing the configuration after dividing the wafer. FIG. 11 is a partially enlarged plan view showing the configuration before dividing the wafer. FIG. 12 is a partially enlarged plan view showing the configuration after dividing the wafer. FIG. 13 is a plan view schematically showing a modified layer formed inside a wafer according to another embodiment. FIG. 14 is a plan view schematically showing a modified layer formed inside a wafer according to another embodiment.

  A mode (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. Further, the components described below include those which can be easily conceived by those skilled in the art and those which are substantially the same. Furthermore, the configurations described below can be combined as appropriate. In addition, various omissions, substitutions, or modifications of the configuration can be made without departing from the scope of the present invention.

  The wafer dividing method according to the present embodiment will be described with reference to the drawings. FIG. 1 is a perspective view showing a wafer to be divided in the present embodiment. FIG. 2 is a perspective view showing an expanded tape attached to the wafer when the wafer is divided. FIG. 3 is a flow chart showing the procedure of the wafer dividing method. In the present embodiment, the wafer 100 to be divided is a disk-shaped semiconductor wafer that uses silicon as a base material, or an optical device wafer that uses sapphire, SiC (silicon carbide), or the like as a base material. As shown in FIG. 1, the wafer 100 has a front surface 101 and a rear surface 104, and devices 103 are formed in a plurality of regions divided by a plurality of lines to be divided 102 formed on the front surface 101, respectively. These division lines 102 are arranged in a lattice shape orthogonal to each other.

  As shown in FIG. 2, the expand tape 10 is formed to be long and is wound around the outer peripheral surface 12 of the roller 11 in a roll shape, for example, the heated resin moves along the first direction 13 As it is drawn, it is stretched in the first direction 13 and the second direction 14 orthogonal to the first direction 13 and wound around the outer peripheral surface 12 of the roller 11. Then, the expand tape 10 fed from the roller 11 is cut into a predetermined length and a predetermined shape, and the cut portion is adhered to the wafer 100 for use. In the present embodiment, the first direction 13 is a so-called flow direction (MD: Machine Direction direction), and the second direction 14 is a so-called vertical direction (TD: Transverse Direction direction). In the present embodiment, the expandable tape 10 has a property in which the first direction 13 is easier to expand (stretchable) than the second direction 14. Expanded tape 10 has heat shrinkability which shrinks when heated. Further, the expand tape 10 includes a resin layer made of a synthetic resin, and an adhesive layer which is laminated on the resin layer and which can be attached to the wafer 100.

  The wafer dividing method according to the present embodiment is a method of dividing the wafer 100 into device chips along the planned dividing lines 102 by radially expanding the expand tape 10 attached to the wafer 100. It is also a manufacturing method. The dividing method of the wafer 100 includes, as shown in FIG. 3, a modified layer forming step S1, a grinding step S2, an expanded tape sticking step S3, and a dividing step S4. Next, each step will be described.

[Modified Layer Forming Step S1]
FIG. 4 is a perspective view showing a configuration example of a laser processing apparatus for forming a modified layer inside a wafer. FIG. 5 is a plan view schematically showing the modified layer formed inside the wafer. In FIG. 5, for convenience of explanation, the modified layer 120 is drawn by a solid line, and the number of modified layers 120 is drawn in a simplified manner with the number being smaller than the number of planned dividing lines 102 in FIG. 1. In the modified layer forming step S1, a laser beam of a wavelength having transparency to the wafer 100 is irradiated from the back surface 104 along the planned dividing line 102 to form the modified layer 120 inside the wafer 100. A modified layer is a region in which density, refractive index, mechanical strength, and other physical properties are different from those of the surrounding base material, and, for example, a melt processing region, a crack region, a dielectric breakdown region, refraction It is a rate change area, an area in which these areas are mixed, and the like.

  The modified layer 120 is formed using a laser processing apparatus 20, as shown in FIG. The laser processing apparatus 20 includes a chuck table 21 for holding the wafer 100, and a laser irradiation unit 22 for irradiating the wafer 100 held on the chuck table 21 with a laser beam. In the wafer 100, a protective tape 110 for protecting the device 103 is attached to the front surface 101, and the wafer 100 is held by the chuck table 21 via the protective tape 110 such that the back surface 104 faces upward. The protective tape 110 has a resin layer and an adhesive layer and is flexible.

  The chuck table 21 is configured to suction and hold the wafer 100. In addition, the chuck table 21 is configured to be rotatable in parallel with the horizontal plane (XY plane), and for the laser irradiation unit 22, in the processing feed direction (X axis direction) and the index feed direction (Y axis direction). Each has a relatively movable movement mechanism (not shown).

  The laser irradiation unit 22 includes an oscillator 22A that oscillates a laser beam, and a condenser 22B that condenses the laser beam oscillated by the oscillator 22A. In the oscillator 22A, the frequency of the oscillating laser beam is appropriately adjusted in accordance with the processing form and the like. The condenser 22B includes a total reflection mirror for changing the traveling direction of the laser beam oscillated by the oscillator 22A, a condenser lens for condensing the laser beam, and the like. Further, the laser irradiation unit 22 is provided with focusing point position adjustment means (not shown) for adjusting the focusing point position of the laser beam focused by the focusing lens of the focusing device 22B.

  When forming the modified layer 120 inside the wafer 100 using the laser processing apparatus 20, the chuck table 21 is moved below the light collector 22B of the laser irradiation unit 22, and is moved in the indexing feed direction (Y-axis direction). The planned dividing line 102 (for example, the planned dividing line 102 at the end: FIG. 1) provided at a predetermined interval is positioned immediately below the light collector 22B. Then, the condensing point position adjusting means (not shown) is operated to locate the condensing point of the laser beam 22C condensed by the condensing lens of the condenser 22B inside the wafer 100 to position the condenser 22B. Move in the optical axis direction.

  When the condensing point of the laser beam 22C is positioned inside in the thickness direction of the wafer 100, the laser irradiation unit 22 is operated to irradiate the laser beam 22C from the condenser 22B to form the modified layer 120 inside the wafer 100. . That is, while irradiating the laser beam 22C of a wavelength having permeability to the wafer 100 from the condenser 22B along the planned dividing line 102 (FIG. 1), the processing direction of the chuck table 21 in FIG. ) At a predetermined feed rate. When the irradiation of the laser beam 22C to one division planned line 102 is finished, the chuck table 21 is moved relative to the laser irradiation unit 22 in the indexing feed direction (Y direction), and the adjacent division planned line 102 is moved. The laser beam 22C is emitted along the When the irradiation of the laser beam 22C to the parallel planned dividing line 102 is finished, the chuck table 21 is rotated by 90 °, and the laser beam 22C is irradiated to the planned dividing line 102 orthogonal to the planned dividing line 102 irradiated with the laser beam 22C. . Thereby, the modified layer 120 is formed inside the wafer 100 along the regions corresponding to the plurality of planned dividing lines 102 orthogonal to each other.

Note that when forming the modified layer 120, the processing conditions shown below are set.
Light source: YAG pulse laser or YVO4 pulse laser Wavelength: 1342 nm
Average power: 0.9 W to 1.4 W
Processing feed rate: 700 mm / sec

  By the way, as described above, the expandable tape 10 has a property that the first direction 13 which is the flow direction is easier to expand than the second direction 14 which is the vertical direction. Generally, when attaching the wafer 100 to the expand tape 10, the dividing planned lines 102 orthogonal to each other of the wafer 100 are attached roughly in correspondence with the first direction 13 and the second direction 14, respectively. . Therefore, when expanding the expanded tape 10 (105) by the same force radially and dividing it, the amount of expansion of the expanded tape 10 varies depending on the direction, and the modified layer 120 formed along the planned dividing line 102 is partially There is a problem that the chip division failure occurs and the variation of the distance (kerf width) between the divided chips occurs without being broken.

  Therefore, in the present configuration, the modified layer 120 formed on the planned dividing line 102 parallel to the first direction 13 of the expand tape 10 in the modified layer forming step S1 is parallel to the second direction 14. The number is larger than that of the modified layer 120 formed on the planned division line 102. Here, that the number of the modified layers 120 is large means that the ratio of the modified layers 120 in the region corresponding to the planned dividing line 102 is large, in other words, the improvement per unit volume in the region corresponding to the planned dividing line 102 It means that the volume (quantity) of the quality layer 120 is large. When the expansion is performed by the same force, the larger the ratio of the modified layer 120, the easier the division.

  Specifically, as shown in FIG. 5, an unmachined region 121 not irradiated with the laser beam 22C is provided at the edge (outer periphery) 100A of the wafer 100. In FIG. 5, the unprocessed area 121 is provided in the area corresponding to the three planned division lines 102 located at the center for convenience of drawing, but is provided in the area corresponding to all the planned division lines 102. There is. In the present embodiment, the size (length) of the unprocessed region 121 formed at the edge (outer periphery) 100 A of the wafer 100 is set larger by making the second direction 14 larger than the first direction 13. The ratio R1 of the modified layer 120 formed in the region corresponding to the planned dividing line 102 extending along the direction 13 of 1 is formed in the region corresponding to the planned dividing line 102 extending along the second direction 14 The ratio R2 of the reformed layer 120 can be made larger.

  In addition, the ratio R1 of the modified layer 120 formed in the region corresponding to all the planned dividing lines 102 extending along the first direction 13 is set to all the planned dividing lines 102 extending along the second direction 14. The ratio R2 of the modified layer 120 formed in the corresponding region is larger. That is, the minimum value of the ratio R1 of the modified layer 120 formed in the region corresponding to the planned dividing line 102 extending along the first direction 13 corresponds to the planned dividing line 102 extending along the second direction 14 Is larger than the maximum value of the ratio R2 of the reformed layer 120 formed in the Therefore, for example, when a radial tensile force is applied to the wafer 100, the planned dividing line 102 extending along the first direction 13 is smaller than the planned dividing line 102 extending along the second direction 14. It is divided by force. The ratio of the ratios R1 and R2 is determined based on, for example, the positive ratio of the expansion direction (elastic coefficient) of the first direction 13 of the expanded tape 10 to the second direction 14 of the elongation. According to this configuration, when the expand tape 10 is expanded by the same force, the wafer 100 to which the expand tape 10 is attached is formed of the planned dividing lines 102 extending in the first direction 13 and the second direction 14 respectively. The modified layer 120 can be broken almost simultaneously to divide the wafer 100.

[Grinding step S2]
Next, the wafer 100 is thinned by grinding to a predetermined thickness. This grinding step S2 may be performed before the reforming layer formation step S1. FIG. 6 is a side sectional view showing the configuration before grinding the wafer, and FIG. 7 is a side sectional view showing the configuration after grinding the wafer. Grinding of the wafer 100 is performed using a grinding apparatus 30, as shown in FIGS. The grinding apparatus 30 includes a holding table 31 for holding the wafer 100 and a grinding unit 32 for grinding the wafer 100 held by the holding table 31. The holding table 31 is configured to suction and hold the wafer 100 via the protective tape 110. In addition, the holding table 31 is configured to be rotatable around the rotation shaft 31A.

  The grinding unit 32 includes a spindle 32A, a disk-shaped wheel mount 32B mounted to the lower end of the spindle 32A, and a grinding wheel 32C mounted to the lower surface of the wheel mount 32B. The grinding wheel 32C has a large number of grinding wheels 32D, and these grinding wheels 32D are annularly arranged and fixed to the lower surface of the wheel mount 32B. The grinding unit 32 is disposed movably in the vertical direction with respect to the holding table 31.

  As shown in FIG. 6, the wafer 100 is placed on the holding table 31 via the protective tape 110 so that the back surface 104 of the wafer 100 faces upward. With the holding table 31 rotated, the grinding unit 32 presses the grinding wheel 32D against the back surface 104 of the wafer 100 held by the holding table 31 while rotating the grinding wheel 32C via the spindle 32A. The back surface 104 of the wafer 100 is ground. Then, as shown in FIG. 7, when the wafer 100 is thinned to a predetermined thickness, the operation of the grinding unit 32 is stopped.

[Expand tape sticking step S3]
Next, the modified layer 120 is formed, and the wafer 100 thinned to a predetermined thickness is attached to the expand tape. FIG. 8 is a perspective view showing a wafer supported by an annular frame via an expand tape. While peeling off the protective tape 110 (FIG. 4) stuck on the front surface 101 side of the wafer 100, the expand tape 105 is stuck on the back surface 104 of the wafer 100 and the annular frame 106. The expanded tape 105 is obtained by cutting the expanded tape 10 shown in FIG. 2 into a predetermined length and a predetermined shape. The wafer 100 is supported inside the annular frame 106 by the expand tape 105.

  When the wafer 100 is attached to the expand tape 105, the first direction 13 of the expand tape 105 corresponds to a large planned division line 102 of the ratio R1 of the modified layer 120, and the modified layer 120 of the second direction 14 The small division lines 102 with the ratio R2 are associated with each other. As a result, in the wafer 100, the planned dividing line 102 having a large ratio R1 of the modified layer 120 extends along the first direction 13 in which the expand tape 105 is easy to expand, and the second line Along the direction 14, the dividing line 102 of the ratio R2 of the modified layer 120 smaller than the ratio R1 extends.

[Division step S4]
After the expanding tape bonding step S3, a dividing step S4 is performed to expand the gap between the device chips while expanding the expanded tape 105 bonded to the wafer 100 to divide the wafer 100 into device chips. FIG. 9 is a side sectional view showing the configuration before dividing the wafer, and FIG. 10 is a side sectional view showing the configuration after dividing the wafer. FIG. 11 is a partial enlarged plan view showing the configuration before dividing the wafer, and FIG. 12 is a partial enlarged plan view showing the configuration after dividing the wafer. The division of the wafer 100 is performed using the expansion division apparatus 40, as shown in FIGS. The expanding and dividing apparatus 40 includes a support structure 41 for supporting the wafer 100 and the annular frame 106, and a cylindrical expanding drum 42 for expanding the expand tape 105. The inner diameter of the expansion drum 42 is larger than the diameter of the wafer 100, and the outer diameter of the expansion drum 42 is smaller than the inner diameter of the annular frame 106.

  The support structure 41 comprises a frame support table 43 for supporting the annular frame 106. The upper surface of the frame support table 43 is a support surface for supporting the annular frame 106. The outer peripheral portion of the frame support table 43 is provided with a plurality of clamps 44 for fixing the annular frame 106.

  Below the support structure 41, an elevating mechanism 45 for moving the support structure 41 up and down with respect to the expansion drum 42 is provided. The elevating mechanism 45 includes a cylinder case 46 fixed to a lower base (not shown) and a piston rod 47 inserted into the cylinder case 46. A frame support table 43 is fixed to an upper end portion of the piston rod 47. The lifting mechanism 45 moves the upper surface (supporting surface) of the frame support table 43 between a reference position at a height substantially equal to the upper end of the extension drum 42 and an extended position below the upper end of the extension drum 42. The support structure 41 is raised and lowered. In the present embodiment, the elevating mechanism 45 for raising and lowering the frame support table 43 (support structure 41) is provided with respect to the upper surface of the extension drum 42. However, the present invention is not limited to this. A raising and lowering mechanism for raising and lowering 42 may be provided, and the extension drum 42 may be configured to be raised and lowered with respect to the upper surface of the frame support table 43.

  In the dividing step S4, as shown in FIG. 9, the annular frame 106 is placed on the upper surface of the frame support table 43 moved to the reference position, and the annular frame 106 is fixed by the clamp 44. Thereby, the upper end of the expansion drum 42 contacts the expand tape 105 between the wafer 100 and the annular frame 106. Next, the elevating mechanism 45 lowers the support structure 41 to move the upper surface of the frame support table 43 to the extended position below the upper end of the extension drum 42 as shown in FIG. As a result, the expansion drum 42 is raised relative to the frame support table 43, and the expand tape 105 is expanded radially so as to be pushed up by the expansion drum 42. A force (in the present embodiment, a force in the radial direction of the wafer 100) acts on the wafer 100 in a direction in which the expand tape 105 is expanded. Therefore, due to the force generated by the expansion of the expand tape 105, the wafer 100 is divided into a plurality of device chips 130 along the planned dividing line 102 (FIG. 8) on which the modified layer 120 is formed, and the device chips A gap (kerf) 140 is formed between 130 and 130.

  Here, in the present embodiment, as described above, the unmachined region 121 formed on the edge (outer periphery) 100A of the wafer 100 is formed by forming the second direction 14 larger than the first direction 13. The ratio R1 of the modified layer 120 formed in the region corresponding to the planned dividing line 102 extending along the first direction 13 is formed in the region corresponding to the planned dividing line 102 extending along the second direction 14 The ratio R2 of the reformed layer 120 is set larger. As a result, the expand tape 105 is more likely to expand in the first direction 13 than in the second direction 14, while the wafer 100 has the dividing line 102 along the first direction 13 as follows: It is easier to divide than the planned dividing line 102 along the second direction 14. Therefore, it is possible to adjust the force to expand the expanding tape 105 and the force to keep the wafer 100 undivided, and the wafer 100 shown in FIG. 11 is expanded concentrically with the same force. In this case, the expansion of the expand tape 105 can be made equal in the first direction 13 and the second direction 14. Therefore, as shown in FIG. 12, the gap 140 formed between the device chips 130 and 130 has a width (kerf width) W1 of the gap 140 extending along the first direction 13 and a second direction 14. The width (kerf width) W2 of the gap 140 that extends can be made to be approximately the same, and division defects of the device chip 130 and variations in the width of the gap 140 can be prevented.

  Next, another embodiment will be described. In the embodiment described above, the unmachined regions 121 are provided at the edge 100A of the wafer 100, and the sizes of the unmachined regions 121 are made different between the planned dividing lines 102 along the first direction 13 and the second direction 14. However, it is not limited to this. FIG. 13 is a plan view schematically showing a modified layer formed inside a wafer according to another embodiment. In this embodiment, as shown in FIG. 13, the reforming layer 220 is continuously formed on the planned dividing line 102 along the first direction 13 from the edge 100A of the wafer 100 to the opposite edge 100A. On the other hand, the modification layer 220 is intermittently formed on the planned dividing line 102 along the second direction 14 from the edge 100A of the wafer 100 to the opposite edge 100A, A processing area 221 is provided. Also in this configuration, the ratio of the modified layer 220 formed in the region corresponding to the planned dividing line 102 extending along the first direction 13 by intermittently providing the unprocessed region 221 in the second direction 14. R1 is set larger than the ratio R2 of the modified layer 220 formed in the region corresponding to the planned dividing line 102 extending along the second direction 14. In addition, since the unprocessed regions 221 are provided in the second direction 14 in a distributed manner, it is possible to suppress the concentration of the force that the wafer 100 tries to maintain unprocessed on one location.

  FIG. 14 is a plan view schematically showing a modified layer formed inside a wafer according to another embodiment. In this embodiment, as shown in FIG. 14, the reforming layer 320 is continuously formed on the planned dividing line 102 along the first direction 13 from the edge 100A of the wafer 100 to the opposite edge 100A. doing. On the other hand, at the dividing line 102 along the second direction 14, an unprocessed region 321 not irradiated with the laser beam 22 C is provided at the edge (outer periphery) 100 A of the wafer 100. Also in this configuration, by providing the unprocessed region 321 in the second direction 14, the ratio R1 of the modified layer 320 formed in the region corresponding to the planned dividing line 102 extending along the first direction 13 is The ratio R2 of the modified layer 320 formed in the region corresponding to the planned dividing line 102 extending along the second direction 14 is set larger.

  Further, in the above-described embodiment, the modified layers 120 to 320 formed in the planned dividing line 102 parallel to the first direction 13 can be formed in the second direction 14 by providing the unprocessed region not irradiated with the laser beam 22C. However, the configuration for increasing the number of modified layers is realized in addition to the configuration in which the above-described unprocessed region is provided. be able to. For example, the output (power) of the laser beam 22C irradiated to the planned dividing line 102 to form the modified layer is divided more parallel to the first direction 13 than the planned dividing line 102 parallel to the second direction 14 The schedule line 102 can also be made stronger. Since the amount of the modified layer generally tends to depend on the size of the output of the laser beam, by irradiating the laser beam with a higher output, it corresponds to the planned dividing line 102 extending along the first direction 13. The ratio R1 of the reformed layers formed in the region can be made larger than the ratio R2 of the reformed layers formed in the region corresponding to the planned dividing line 102 extending along the second direction 14.

  Similarly, the focal point of the laser beam 22C irradiated to the planned dividing line 102 is changed in the thickness direction of the wafer 100, and the modified layer formed in the thickness direction of the planned dividing line 102 parallel to the first direction 13. The number may also be greater than the number of modified layers formed in the thickness direction of the planned dividing line 102 parallel to the second direction 14. If the number of modified layers is increased, the ratio of modified layers is correspondingly increased, so the ratio R1 of the modified layers formed in the region corresponding to the planned dividing line 102 extending along the first direction 13 is The ratio R2 of the modified layer formed in the region corresponding to the planned dividing line 102 extending along the second direction 14 can be made larger. In addition, when the laser beam 22C is overlapped and irradiated along the dividing line 102, the ratio of the formed modified layer is increased accordingly. Therefore, the overlapping ratio of the irradiation marks of the laser beam 22C irradiated to the planned dividing line 102 parallel to the first direction 13 is the irradiation trace of the laser beam 22C irradiated to the planned dividing line 102 parallel to the second direction 14. It can also be made higher than the overlap rate of

  The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the scope of the present invention. In the above-described embodiment, although the protective tape 110 uses a tape different from the expand tape 10, the expand tape 10 can also be used. In this case, in the dividing step S4, the device chip 130 is singulated with the back surface side facing up, so that it is necessary to invert the top and bottom of the device chip in the next pickup step or die bonding step, for example. . At the time of laser beam irradiation, another protective tape is attached to the surface 101 of the wafer 100, and after irradiating the laser beam, the expand tape 10 is attached to the surface 101 and transferred, and then the division step S4 is performed. As well.

10, 105 Expanded tape 13 1st direction 14 2nd direction 20 Laser processing device 21 Chuck table 22 Laser irradiation unit 22C Laser beam 30 Grinding device 31 Holding table 32 Grinding unit 40 Extended division device 100 Wafer 100A Edge (periphery)
DESCRIPTION OF SYMBOLS 101 Surface 102 Division scheduled line 103 Device 104 Back surface 105 Expanded tape 106 Annular frame 110 Protective tape 120, 220, 320 Modified layer 121, 221, 321 Raw area 130 Device chip 140 Clearance

Claims (3)

A wafer dividing method for dividing a wafer on the surface of which a plurality of devices partitioned by a plurality of dividing lines is formed along the dividing lines,
Forming a modified layer inside the wafer by irradiating a laser beam of a wavelength having transparency to the wafer along the planned dividing line;
Attaching an expanded tape to the wafer, wherein the expand tape is easier to stretch in a second direction in which the first direction is orthogonal to the first direction;
And a dividing step of expanding the expanded tape and dividing it into chips while widening the distance between the chips.
In the modified layer forming step, the number of modified layers formed on the planned dividing line parallel to the first direction is larger than the number of modified layers formed on the planned planned line parallel to the second direction. Wafer dividing method characterized by In the modified layer forming step, a modified layer is formed on the dividing line parallel to the first direction up to the outer periphery of the wafer,
2. The wafer dividing method according to claim 1, wherein a modified layer is formed leaving any unprocessed area in the planned dividing line parallel to the second direction.   In the modified layer forming step, the planned dividing line parallel to the first direction is formed in the thickness direction of the wafer in which the power of the laser beam irradiated from the planned dividing line parallel to the second direction is large. 2. The method according to claim 1, further comprising at least one of the following conditions: a large number of the modified layers, or a high overlapping ratio of irradiation marks of the laser beam.

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