JP2018042209A - Manufacturing method for surface elastic wave device chip - Google Patents

Abstract

The present invention provides a new method for manufacturing a surface acoustic wave device chip that allows surface acoustic wave device chips with good frequency characteristics to be obtained at a high yield. [Solution] A method for manufacturing a surface acoustic wave device chip, which includes a grinding step of grinding the back surface of a wafer in which surface acoustic wave devices are formed in each region on the front surface side divided by a plurality of intersecting division lines. and a dividing step of dividing the wafer into a plurality of surface acoustic wave device chips along the dividing line after performing the grinding step, and removing defective surface acoustic wave device chips from the plurality of surface acoustic wave device chips divided in the dividing step. A sorting step for sorting wave device chips, and a laser beam with a wavelength that absorbs the surface acoustic wave device chips is irradiated onto the back side of the surface acoustic wave device chips selected in the sorting step to suppress reflection of acoustic waves. a step of irradiating a laser beam to form irregularities on the back surface. [Selection diagram] Figure 3

Description

  The present invention relates to a method for manufacturing a surface acoustic wave device chip.

  In wireless communication devices such as mobile phones, bandpass filters that pass only electrical signals in a desired frequency band play an important role. As one of the band pass filters, a surface acoustic wave device (surface acoustic wave filter) using a surface acoustic wave (SAW) that propagates on the surface of a substance is known (for example, see Patent Document 1). ).

The surface acoustic wave device includes, for example, a crystalline wafer made of a piezoelectric material such as quartz (SiO ₂ ), lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), and comb teeth formed on the surface of the wafer. Electrode (IDT: Inter Digital Transducer), and passes only an electric signal in a frequency band determined according to the type of piezoelectric material, the distance between the electrodes, and the like.

JP 2010-56833 A

  By the way, in the surface acoustic wave device as described above, a part of the acoustic wave generated in the vicinity of the electrode on the input side may propagate inside the wafer and be reflected on the back side. When the reflected acoustic wave reaches the output-side electrode, the frequency characteristics of the surface acoustic wave device are degraded.

  In order to solve this problem, it is conceivable to suppress reflection of elastic waves on the back surface by forming a certain degree of unevenness on the back surface of the wafer by a method such as sand blasting or grinding. However, such a method cannot always provide a surface acoustic wave device chip with good frequency characteristics and good yield.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a new method of manufacturing a surface acoustic wave device chip that can obtain a surface acoustic wave device chip having good frequency characteristics with a high yield. It is.

  According to one aspect of the present invention, there is provided a method for manufacturing a surface acoustic wave device chip, the back surface of a wafer having surface acoustic wave devices formed in respective regions on the surface side defined by a plurality of intersecting scheduled lines. A grinding step for grinding the wafer, a dividing step for dividing the wafer into a plurality of surface acoustic wave device chips along the planned dividing line after performing the grinding step, and a plurality of the surfaces divided in the dividing step A selection step for selecting the defective surface acoustic wave device chip from the acoustic wave device chip, and a wavelength having absorptivity for the surface acoustic wave device chip on the back surface of the surface acoustic wave device chip selected in the selection step A laser beam irradiation step for irradiating the laser beam to form irregularities on the back surface to suppress reflection of elastic waves. The method of manufacturing a surface acoustic wave device chip is provided that.

  In one embodiment of the present invention, it is preferable to further include a polishing step of polishing the back surface of the wafer after performing the grinding step and before performing the sorting step.

  In the surface acoustic wave device chip manufacturing method according to one aspect of the present invention, defective surface acoustic wave device chips are selected from a plurality of surface acoustic wave device chips obtained by dividing a wafer, and then the selected surface elastic wave device chips are selected. Irregularities for suppressing reflection of elastic waves are formed by irradiating the back surface of the wave device chip with a laser beam, so that the surface acoustic wave device chip that is defective due to reflection of the elastic wave on the back surface can be reproduced. . That is, according to the method for manufacturing a surface acoustic wave device chip according to one aspect of the present invention, a surface acoustic wave device chip having good characteristics can be obtained with a high yield.

FIG. 1A is a perspective view schematically showing a configuration example of a wafer, and FIG. 1B is an enlarged perspective view of a part (region A) on the front surface side of the wafer. C) is an enlarged cross-sectional view of a part of the wafer. FIG. 2A is a side view for explaining the grinding step, and FIG. 2B is a side view for explaining the polishing step. FIG. 3A is a partial cross-sectional side view for explaining the dividing step, FIG. 3B is a partial cross-sectional side view for explaining the sorting step, and FIG. FIG. 5 is a partial cross-sectional side view for explaining a laser beam irradiation step. FIG. 4A is a perspective view schematically showing the surface side of the surface acoustic wave device chip, and FIG. 4B is a perspective view schematically showing the back side of the surface acoustic wave device chip.

  Embodiments according to one aspect of the present invention will be described with reference to the accompanying drawings. The surface acoustic wave device chip manufacturing method according to this embodiment includes a grinding step (see FIG. 2A), a polishing step (see FIG. 2B), a dividing step (see FIG. 3A), and a selection step. (See FIG. 3B) and a laser beam irradiation step (see FIG. 3C).

  In the grinding step, the back surface of the wafer having the surface acoustic wave device formed on the front surface side is ground. In the polishing step, the back surface of the wafer after grinding is polished. In the dividing step, the wafer is divided into a plurality of surface acoustic wave device chips along the division planned line. In the selection step, defective surface acoustic wave device chips are selected from the plurality of surface acoustic wave device chips obtained in the division step.

  In the laser beam irradiation step, the surface acoustic wave device chip is irradiated with a laser beam having an absorptive wavelength, and the back surface of the selected defective surface acoustic wave device chip is provided with unevenness to suppress reflection of the elastic wave. Form. Hereinafter, a method for manufacturing the surface acoustic wave device chip according to the present embodiment will be described in detail.

FIG. 1A is a perspective view schematically showing a configuration example of a wafer used in this embodiment, and FIG. 1B is an enlarged perspective view of a part (region A) on the front side of the wafer. FIG. 1C is an enlarged cross-sectional view of a part of the wafer. The wafer 11 according to the present embodiment is formed in a disc shape using a piezoelectric material such as quartz (SiO ₂ ), lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), or the like.

  The front surface 11a of the wafer 11 is divided into a plurality of regions by a plurality of division lines (streets) 13 set in a lattice shape. In each region, a surface acoustic wave device having a pair of comb-like electrodes (IDT: Inter Digital Transducer) 15 that are in mesh with each other is formed.

  A coating layer 17 is provided on the front surface 11 a side of the wafer 11. The covering layer 17 is formed so as to cover the entire surface 11a using, for example, a resin such as an epoxy resin, a polyimide resin, or a phenol resin. For example, an electrode pad (not shown) connected to the electrode 15 is disposed on the surface (upper surface) of the covering layer 17. Other structures, spaces (gap), etc. may be formed on the surface or inside of the coating layer 17.

  A plurality of surface acoustic wave device chips can be manufactured by dividing the wafer 11 configured as described above along the division line 13. In the method for manufacturing a surface acoustic wave device chip according to this embodiment, first, a grinding step of grinding the back surface 11b of the wafer 11 is performed. FIG. 2A is a side view for explaining the grinding step.

  The grinding step is performed using, for example, a grinding apparatus 2 shown in FIG. The grinding device 2 includes a chuck table 4 for sucking and holding the wafer 11. The chuck table 4 is connected to a rotation drive source (not shown) such as a motor, and rotates around a rotation axis substantially parallel to the vertical direction. A moving mechanism (not shown) is provided below the chuck table 4, and the chuck table 4 is moved in the horizontal direction by the moving mechanism.

  A part of the upper surface of the chuck table 4 serves as a holding surface 4 a that sucks and holds the surface 11 a side (the coating layer 17 side) of the wafer 11. The holding surface 4 a is connected to a suction source (not shown) through a suction path (not shown) formed inside the chuck table 4. The wafer 11 is sucked and held by the chuck table 4 by applying the negative pressure of the suction source to the holding surface 4a.

  A grinding unit 6 is disposed above the chuck table 4. The grinding unit 6 includes a spindle housing (not shown) supported by an elevating mechanism (not shown). A spindle housing is accommodated in the spindle housing, and a disc-shaped mount 10 is fixed to the lower end portion of the spindle 8.

  A grinding wheel 12 having the same diameter as that of the mount 10 is mounted on the lower surface of the mount 10. The grinding wheel 12 includes a wheel base 14 made of a metal material such as stainless steel or aluminum. A plurality of grinding wheels 16 are annularly arranged on the lower surface of the wheel base 14.

  A rotary drive source (not shown) such as a motor is connected to the upper end side (base end side) of the spindle 8, and the grinding wheel 12 is substantially parallel to the vertical direction by the force generated by this rotary drive source. Rotate around the axis of rotation. A nozzle (not shown) for supplying a grinding liquid such as pure water to the wafer 11 or the like is provided in or near the grinding unit 6.

  In the grinding step, first, the wafer 11 is sucked and held on the chuck table 4. In the present embodiment, a protective member 21 made of resin or the like is attached to the surface 11a side (the coating layer 17 side) of the wafer 11 before performing the grinding step. Thereby, the wafer 11 can be protected from an impact applied during the grinding step.

  When the wafer 11 is sucked and held on the chuck table 4, the protective member 21 attached to the wafer 11 is brought into contact with the holding surface 4 a of the chuck table 4 to apply a negative pressure of the suction source. Thereby, the wafer 11 is held on the chuck table 4 with the back surface 11b side exposed upward.

  Next, the chuck table 4 is moved below the grinding unit 6. Then, as shown in FIG. 2A, the spindle housing (spindle 8 and grinding wheel 12) is rotated while the chuck table 4 and the grinding wheel 12 are rotated to supply the grinding liquid to the back surface 11b and the like of the wafer 11. Lower.

  The descending speed (falling amount) of the spindle housing is adjusted to such an extent that the lower surface of the grinding wheel 16 is pressed against the back surface 11 b side of the wafer 11. Thereby, the back surface 11b side can be ground and the wafer 11 can be made thin. When the wafer 11 is thinned to a predetermined thickness (finished thickness), the grinding step ends.

  In this embodiment, the back surface 11b side of the wafer 11 is ground using one set of grinding units 6 (grinding grindstones 16), but the wafer 11 is ground using two or more sets of grinding units (grinding grindstones). It can also be ground. For example, rough grinding is performed using a grinding wheel composed of abrasive grains having a large diameter, and finishing grinding is performed using a grinding wheel composed of abrasive grains having a small diameter, thereby greatly reducing the time required for grinding. The flatness of the back surface 11b can be improved without increasing the length.

  After the grinding step, a polishing step for polishing the back surface 11b of the wafer 11 is performed. FIG. 2B is a side view for explaining the polishing step. The polishing step is performed using, for example, a polishing apparatus 22 shown in FIG.

  The polishing apparatus 22 includes a chuck table 24 for sucking and holding the wafer 11. The chuck table 24 is connected to a rotation drive source (not shown) such as a motor, and rotates around a rotation axis substantially parallel to the vertical direction. A moving mechanism (not shown) is provided below the chuck table 24, and the chuck table 24 is moved in the horizontal direction by the moving mechanism.

  A part of the upper surface of the chuck table 24 is a holding surface 24 a that sucks and holds the surface 11 a side (the coating layer 17 side) of the wafer 11. The holding surface 24 a is connected to a suction source (not shown) through a suction path (not shown) formed inside the chuck table 24. By applying the negative pressure of the suction source to the holding surface 24 a, the wafer 11 is sucked and held by the chuck table 24.

  A polishing unit 26 is disposed above the chuck table 24. The polishing unit 26 includes a spindle housing (not shown) supported by an elevating mechanism (not shown). A spindle 28 is accommodated in the spindle housing, and a disc-shaped mount 30 is fixed to the lower end portion of the spindle 28. A polishing pad 32 having substantially the same diameter as the mount 30 is attached to the lower surface of the mount 30. The polishing pad 32 includes a polishing cloth made of, for example, a nonwoven fabric or urethane foam.

  A rotation drive source (not shown) such as a motor is connected to the upper end side (base end side) of the spindle 28, and the polishing pad 32 is substantially parallel to the vertical direction by the force generated by this rotation drive source. Rotate around the axis of rotation. A nozzle (not shown) for supplying a polishing liquid (slurry) in which abrasive grains are dispersed to the wafer 11 or the like is provided in or near the polishing unit 26.

  In the polishing step, first, the protective member 21 attached to the wafer 11 is brought into contact with the holding surface 24a of the chuck table 24, and a negative pressure of the suction source is applied. Thus, the wafer 11 is held on the chuck table 24 with the back surface 11b side exposed upward.

  Next, the chuck table 24 is moved below the polishing unit 26. Then, as shown in FIG. 2B, the spindle table (spindle 28, polishing pad 32) is moved while the chuck table 24 and the polishing pad 32 are rotated to supply the polishing liquid to the back surface 11b of the wafer 11, etc. Lower. The lowering speed (lowering amount) of the spindle housing is adjusted to such an extent that the lower surface of the polishing pad 32 is pressed against the back surface 11 b side of the wafer 11.

  Thereby, the back surface 11b of the wafer 11 can be further planarized. However, it is desirable that this polishing step be performed within a range in which fine irregularities formed on the back surface 11b are not completely removed during the above-described grinding step. This is because if the irregularities on the back surface 11b are completely removed, the elastic wave propagating inside the wafer 11 is reflected by the back surface 11b, making it difficult to obtain a surface acoustic wave device having high frequency characteristics.

  In this polishing step, dry polishing without using a polishing liquid may be employed. Further, when the necessary flatness can be obtained by the above-described grinding step, the polishing step can be omitted.

  After the polishing step, a division step is performed in which the wafer 11 is divided into a plurality of surface acoustic wave device chips along the division line 13. FIG. 3A is a partial cross-sectional side view for explaining the division step. The dividing step is performed by, for example, a cutting device 42 shown in FIG.

  After the polishing step (or a grinding step when no polishing step is performed), a dicing tape 31 having a diameter larger than that of the wafer 11 is attached to the back surface 11b of the wafer 11 as shown in FIG. . An annular frame 33 is fixed to the outer peripheral portion of the dicing tape 31. As a result, the wafer 11 is supported by the annular frame 33 via the dicing tape 31. The protective member 21 attached to the surface 11a side of the wafer 11 is peeled off and removed at this stage.

  The cutting device 42 includes a chuck table 44 for sucking and holding the wafer 11. The chuck table 44 is connected to a rotation drive source (not shown) such as a motor, and rotates around a rotation axis substantially parallel to the vertical direction. A machining feed mechanism (not shown) is provided below the chuck table 44, and the chuck table 44 is moved in the machining feed direction (horizontal direction) by the machining feed mechanism.

  A part of the upper surface of the chuck table 44 serves as a holding surface 44 a that sucks and holds the back surface 11 b side of the wafer 11. The holding surface 44 a is connected to a suction source (not shown) through a suction path (not shown) formed inside the chuck table 44. By applying a negative pressure of the suction source to the holding surface 44 a, the wafer 11 is sucked and held by the chuck table 44. A plurality of clamps 46 for fixing the annular frame 33 are provided around the chuck table 44.

  A cutting unit 48 for cutting the wafer 11 is disposed above the chuck table 44. The cutting unit 48 includes a spindle 50 that serves as a rotation axis substantially parallel to the horizontal direction. An annular cutting blade 52 is attached to one end side of the spindle 50. A rotation driving source (not shown) such as a motor is connected to the other end side of the spindle 50, and the cutting blade 52 mounted on the spindle 50 rotates by a force transmitted from the rotation driving source.

  The cutting unit 48 is supported by an elevating mechanism (not shown), and this elevating mechanism is supported by an index feed mechanism (not shown). Therefore, the cutting unit 48 is moved (lifted / lowered) in the vertical direction by the elevating mechanism, and is moved in the index feeding direction perpendicular to the machining feeding direction by the index feeding mechanism.

  In the dividing step, first, the dicing tape 31 attached to the wafer 11 is brought into contact with the holding surface 44a of the chuck table 44, and a negative pressure of the suction source is applied. In addition, the annular frame 33 is fixed by a plurality of clamps 46. As a result, the wafer 11 is held on the chuck table 44 with the surface 11a side (the coating layer 17 side) exposed upward.

  Next, the chuck table 44 is rotated so that an arbitrary division line 13 is parallel to the machining feed direction. Further, the chuck table 44 and the cutting unit 48 are relatively moved so that the cutting blade 52 is aligned with an extension line of an arbitrary division planned line 13. Thereafter, the lower end of the rotated cutting blade 52 is lowered to a position lower than the back surface 11b of the wafer 11, and the chuck table 44 is moved in the processing feed direction.

  Thereby, the cutting blade 52 can be cut into the wafer 11, and the wafer 11 can be completely cut along the target division line 13 (full cut). The above-described operation is repeated, and when the wafer 11 is cut along all the planned dividing lines 13 and divided into a plurality of surface acoustic wave device chips 41, the dividing step is completed.

  After the dividing step, a selecting step for selecting defective surface acoustic wave device chips 41 from the plurality of surface acoustic wave device chips 41 obtained in the dividing step is performed. FIG. 3B is a partial cross-sectional side view for explaining the selection step. The selection step is performed by, for example, the inspection device 62 shown in FIG. The inspection apparatus 62 includes a chuck table 64 for sucking and holding a plurality of surface acoustic wave device chips 41 (wafer 11).

  A part of the upper surface of the chuck table 64 serves as a holding surface 64 a that sucks and holds the back surface side (the back surface 11 b side of the wafer 11) of the plurality of surface acoustic wave device chips 41. The holding surface 64 a is connected to a suction source (not shown) through a suction path (not shown) formed inside the chuck table 64. By applying the negative pressure of the suction source to the holding surface 64 a, the plurality of surface acoustic wave device chips 41 are sucked and held by the chuck table 64. A plurality of clamps 66 for fixing the annular frame 33 are provided around the chuck table 64.

  An inspection probe 68 for inspecting the characteristics of the surface acoustic wave device chip 41 is disposed above the chuck table 64. For example, the characteristics of the surface acoustic wave device chip 41 can be electrically inspected by bringing the inspection probe 68 into contact with an electrode pad formed on the surface of the coating layer 17 and inputting a predetermined electrical signal.

  In the selection step, first, the dicing tape 31 to which the plurality of surface acoustic wave device chips 41 are attached is brought into contact with the holding surface 64a of the chuck table 64, and a negative pressure of the suction source is applied. In addition, the annular frame 33 is fixed by a plurality of clamps 66. Thus, the plurality of surface acoustic wave device chips 41 are held on the chuck table 64 in a state where the surface side (the surface 11a side of the wafer 11 and the coating layer 17 side) is exposed upward.

  Next, the chuck table 64 and the inspection probe 68 are relatively moved to bring the inspection probe 68 into contact with the electrode pad of any surface acoustic wave device chip 41. In this state, for example, by inputting a predetermined electrical signal from the inspection probe 68 to the electrode pad, the electrical characteristics of the target surface acoustic wave device chip 41 can be examined.

  After the above operation is repeated and the characteristics of all the surface acoustic wave device chips 41 are examined, a defective surface acoustic wave device chip 41 for which sufficient characteristics are not obtained is separated from the dicing tape 31 into another dicing tape 51 (FIG. 3 (see (C)). Specifically, for example, a defective surface acoustic wave device chip 41 is picked up from the dicing tape 31, and the surface side (the surface 11 b side of the wafer 11) is brought into close contact with another dicing tape 51.

  Thereby, the back surface side (the back surface 11b side of the wafer 11) of the defective surface acoustic wave device chip 41 can be exposed upward. This transfer is performed using, for example, a pickup collet (not shown). When all the defective surface acoustic wave device chips 41 are transferred, the sorting step ends. An annular frame 53 (see FIG. 3C) is fixed to the outer peripheral portion of the dicing tape 51. The surface acoustic wave device chip 41 having sufficient characteristics is a finished product as it is.

  After the selection step, a laser beam irradiation step is performed to form unevenness on the back surface of the defective surface acoustic wave device chip 41 (back surface 11b of the wafer 11) for suppressing reflection of the elastic wave. FIG. 3C is a partial cross-sectional side view for explaining the laser beam irradiation step. The laser beam irradiation step is performed using, for example, a laser processing apparatus 72 shown in FIG.

  The laser processing apparatus 72 includes a chuck table 74 for sucking and holding a plurality of surface acoustic wave device chips 41 (wafer 11). The chuck table 74 is connected to a rotation drive source (not shown) such as a motor, and rotates around a rotation axis substantially parallel to the vertical direction. A moving mechanism (not shown) is provided below the chuck table 74, and the chuck table 74 is moved in the horizontal direction by the moving mechanism.

  A part of the upper surface of the chuck table 74 serves as a holding surface 74a that sucks and holds the surface side of the surface acoustic wave device chips 41 (the surface 11a side of the wafer 11 and the coating layer 17 side). The holding surface 74 a is connected to a suction source (not shown) through a suction path (not shown) formed inside the chuck table 74. By applying a negative pressure of the suction source to the holding surface 74 a, the plurality of surface acoustic wave device chips 41 are sucked and held by the chuck table 74. A plurality of clamps 76 for fixing the annular frame 53 are provided around the chuck table 74.

  A laser irradiation unit 78 is disposed above the chuck table 74. The laser irradiation unit 78 irradiates and condenses a laser beam L pulsed by a laser oscillator (not shown) at a predetermined position. The laser oscillator is configured so as to be able to pulse-oscillate a laser beam L having a wavelength that absorbs the surface acoustic wave device chip 41 (particularly, the wafer 11) (wavelength that is difficult to transmit).

  In the laser beam irradiation step, first, the dicing tape 51 to which the plurality of surface acoustic wave device chips 41 are attached is brought into contact with the holding surface 74a of the chuck table 74 to apply a negative pressure of the suction source. In addition, the annular frame 53 is fixed by a plurality of clamps 76. As a result, the plurality of surface acoustic wave device chips 41 are held on the chuck table 74 with the back surface side (the back surface 11b side of the wafer 11) exposed upward.

  Next, the chuck table 74 is moved and rotated to align the laser processing unit 46 at an arbitrary processing start position. Then, as shown in FIG. 3C, a laser beam L having a wavelength that absorbs the surface acoustic wave device chip 41 (wavelength that is difficult to transmit) is applied from the laser processing unit 78 to the back surface of the surface acoustic wave device chip 41. The chuck table 74 is moved in the horizontal direction while irradiating toward the (back surface 11b of the wafer 11).

  Here, the laser beam L is condensed near the back surface of the surface acoustic wave device chip 41 (the back surface 11b of the wafer 11). In this way, by condensing the laser beam L having a wavelength that is easily absorbed by the surface acoustic wave device chip 41 in the vicinity of the back surface, the back surface side of the surface acoustic wave device chip 41 (the back surface 11b side of the wafer 11) is partially formed. A recess (unevenness) 19 (see FIG. 4B) for diffusing the elastic wave can be formed by melting and removing.

  A region in the vicinity of the concave portion 19 formed by such a method (ablation processing) is modified (for example, amorphized) through melting and resolidification. Therefore, the propagation characteristics of the acoustic wave propagating through the wafer 11 of the surface acoustic wave device chip 41 change in the region near the recess 19. That is, the traveling direction of the elastic wave also changes in the region near the recess 19. As described above, the elastic wave is appropriately diffused (scattered) in the concave portion 19 and a region in the vicinity thereof.

  In addition, there is no restriction | limiting in the aspect of the recessed part 19 formed. A continuous and integral recess 19 may be formed, or a discontinuous and discrete recess 19 may be formed. There is no limitation on the pitch and size of the recesses 19 when forming the discontinuous and discrete recesses 19. For example, a plurality of recesses 19 having a size (width and diameter) of 5 μm to 10 μm It is good to form with pitch.

For example, the conditions for forming the recess 19 in the wafer 11 made of lithium tantalate are set as follows.
Wavelength: 355nm (YAG pulse laser)
Repeat frequency: 200 kHz
Output: 1-2W

  When the recess 19 is formed on the back surface of the surface acoustic wave device chip 41 (the back surface 11b of the wafer 11) under such conditions, the laser beam irradiation step ends. In addition, there is no restriction | limiting in the irradiation conditions of the laser beam L. The irradiation conditions of the laser beam L can be arbitrarily set and changed according to the size, pitch, etc. of the recesses 19.

  4A is a perspective view schematically showing the surface side of the surface acoustic wave device chip 41 after the laser beam irradiation step, and FIG. 4B is a surface acoustic wave device chip after the laser beam irradiation step. It is a perspective view which shows typically the back surface side of 41. FIG. As shown in FIGS. 4A and 4B, the propagation characteristics of the acoustic wave are changed on the back surface of the surface acoustic wave device chip 41 completed through the laser beam irradiation step (the back surface 11b of the wafer 11). A recess 19 is provided.

  Therefore, the acoustic wave propagating inside the surface acoustic wave device chip 41 (wafer 11) is diffused in the concave portion 19 and a region in the vicinity thereof and hardly reflected on the back surface (the back surface 11b of the wafer 11). Thereby, it is possible to prevent the reflected elastic wave from re-entering the electrode 15 and suppress deterioration of the frequency characteristics. The concave portion 19 can diffuse not only the elastic wave generated on the surface side and propagating through the inside, but also the elastic wave generated by other factors.

  As described above, in the surface acoustic wave device chip manufacturing method according to the present embodiment, defective surface acoustic wave device chips 41 are selected from a plurality of surface acoustic wave device chips 41 obtained by dividing the wafer 11, and thereafter Since the concave portion (unevenness) 19 for suppressing the reflection of the elastic wave is formed by irradiating the back surface of the selected surface acoustic wave device chip 41 with the laser beam L, it is caused by the reflection of the elastic wave on the back surface. The defective surface acoustic wave device chip 41 can be reproduced. That is, according to the method for manufacturing the surface acoustic wave device chip according to the present embodiment, the surface acoustic wave device chip 41 having good characteristics can be obtained with a high yield.

  In addition, this invention is not restrict | limited to description of the said embodiment, A various change can be implemented. For example, in the dividing step of the above embodiment, a method of cutting the wafer 11 with the cutting blade 62 and dividing it into a plurality of surface acoustic wave device chips 41 is shown. It can also be divided into surface acoustic wave device chips.

  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 2 Grinding device 4 Chuck table 4a Holding surface 6 Grinding unit 8 Spindle 10 Mount 12 Grinding wheel 14 Wheel base 16 Grinding wheel 22 Polishing device 24 Chuck table 24a Holding surface 26 Polishing unit 28 Spindle 30 Mount 32 Polishing pad 42 Cutting device 44 Chuck Table 44a Holding surface 46 Clamp 48 Cutting unit 50 Spindle 52 Cutting blade 62 Inspection device 64 Chuck table 64a Holding surface 66 Clamp 68 Inspection probe 72 Laser processing device 74 Chuck table 74a Holding surface 76 Clamp 78 Laser irradiation unit 11 Wafer 11a Surface 11b Back side 13 Scheduled line (street)
15 Electrode 17 Covering layer 19 Recessed portion
21 Protective member 31 Dicing tape 33 Frame 41 Surface acoustic wave device chip 51 Dicing tape 53 Frame

Claims (2)

A method for manufacturing a surface acoustic wave device chip, comprising:
A grinding step of grinding a back surface of a wafer in which a surface acoustic wave device is formed in each region on the front surface side defined by a plurality of dividing lines intersecting each other;
A division step of dividing the wafer into a plurality of surface acoustic wave device chips along the planned division line after performing the grinding step;
A selection step of selecting defective surface acoustic wave device chips from the plurality of surface acoustic wave device chips divided in the dividing step;
Irradiation of the back surface of the surface acoustic wave device chip selected in the selection step with a laser beam having a wavelength that is absorptive with respect to the surface acoustic wave device chip provides unevenness for suppressing reflection of the elastic wave. And a laser beam irradiation step to be formed on the surface acoustic wave device chip.   The method of manufacturing a surface acoustic wave device chip according to claim 1, further comprising a polishing step of polishing the back surface of the wafer after performing the grinding step and before performing the sorting step.