Abstract:
A method for manufacturing an acoustic wave device includes: adhering wafer-shaped first and second piezoelectric substrates to a front face of a first and second adhesive sheet respectively and dividing the first and the second piezoelectric substrates into rectangles; adhering a third and fourth adhesive sheet to the first and second piezoelectric substrates respectively and moving at least one divided portions of the first and second piezoelectric substrates selectively to the third and fourth adhesive sheet respectively; moving the first piezoelectric substrate on the first adhesive sheet to the fourth adhesive sheet; and moving the second piezoelectric substrate on the second adhesive sheet to the third adhesive sheet.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2011-116552, filed on May 25, 2011, the entire contents of which are incorporated herein by reference. 
     FIELD 
     A certain aspect of the present invention relates to a method for manufacturing an acoustic wave device. 
     BACKGROUND 
     An acoustic wave device is used for a filter, a duplexer or the like in a mobile communication terminal. The acoustic wave device is a Surface acoustic wave (SAW) resonator using a surface acoustic wave, a boundary acoustic wave resonator using a boundary acoustic wave, a film bulk acoustic wave resonator (FBAR) using a piezoelectric thin membrane or the like. Japanese Patent Application Publication No. 2008-227748 and Japanese Patent Application Publication No. 9-326447 disclose a technology sealing a piezoelectric substrate, on which an acoustic wave device is provided, with a sealing member made of a resin or the like as a method for protecting an acoustic wave device. And the documents disclose a wafer level package structure having a hollow structure for securing a functional region (a region for exciting an acoustic wave) in an acoustic wave device. 
     Japanese Patent Application Publication No. 2008-227748 discloses that piezoelectric substrates (chips) having an acoustic wave device having different filter characteristics are sealed with an identical sealing resin and are integrated, in a duplexer, a dual filter or the like structured with a plurality of acoustic wave filters. There is a method for dicing a wafer into chips, arraying the chips and integrating the chips by an interposer or the like, as a method for integrating different chips. 
     When a wafer is divided into chips by dicing and the chips are arrayed as a method of manufacturing an acoustic wave device including a plurality of acoustic wave filters, there is a problem that a manufacturing cost is increased if a device is miniaturized. And, there is little merit on forming a wafer level package having a hollow space, because an interposer forms a hollow space on a piezoelectric substrate. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, there is provided a method for manufacturing an acoustic wave device comprising: adhering a wafer-shaped first piezoelectric substrate, on which a first acoustic wave device is provided, to a front face of a first adhesive sheet and dividing the first piezoelectric substrate into rectangles; adhering a wafer-shaped second piezoelectric substrate, on which a second acoustic wave device is provided, to a front face of a second adhesive sheet and dividing the second piezoelectric substrate into rectangles; adhering a third adhesive sheet to the first piezoelectric substrate from an opposite side of the first adhesive sheet and moving at least one divided portions of the first piezoelectric substrate selectively to the third adhesive sheet; adhering a fourth adhesive sheet to the second piezoelectric substrate from an opposite side of the second adhesive sheet and moving at least one divided portions of the second piezoelectric substrate selectively to the fourth adhesive sheet; moving the first piezoelectric substrate on the first adhesive sheet to the fourth adhesive sheet by adhering the fourth adhesive sheet, on which the second piezoelectric substrate is adhered selectively, to a front face of the first piezoelectric substrate on the first adhesive sheet; and moving the second piezoelectric substrate on the second adhesive sheet to the third adhesive sheet by adhering the third adhesive sheet, on which the first piezoelectric substrate is adhered selectively, to a front face of the second acoustic wave device on the second adhesive sheet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic cross sectional view of an acoustic wave device in accordance with a first embodiment; 
         FIG. 2A  and  FIG. 2B  illustrate a method for manufacturing the acoustic wave device in accordance with the first embodiment; 
         FIG. 3A  and  FIG. 3B  illustrate a method for manufacturing the acoustic wave device in accordance with the first embodiment; 
         FIG. 4  illustrates a method for manufacturing the acoustic wave device in accordance with the first embodiment; 
         FIG. 5  illustrates a method for manufacturing the acoustic wave device in accordance with the first embodiment; 
         FIG. 6A  through  FIG. 6C  illustrate a method for manufacturing the acoustic wave device in accordance with the first embodiment; 
         FIG. 7  illustrates a method for manufacturing the acoustic wave device in accordance with the first embodiment; 
         FIG. 8  illustrates a method for manufacturing the acoustic wave device in accordance with the first embodiment; 
         FIG. 9A  and  FIG. 9B  illustrate a method for manufacturing the acoustic wave device in accordance with the first embodiment; 
         FIG. 10A  through  FIG. 10E  illustrate a method for manufacturing the acoustic wave device in accordance with the first embodiment; 
         FIG. 11A  through  FIG. 11D  illustrate a method for manufacturing the acoustic wave device in accordance with the first embodiment; 
         FIG. 12  illustrates a method for manufacturing the acoustic wave device in accordance with the first embodiment; 
         FIG. 13  illustrates a method for manufacturing the acoustic wave device in accordance with a modified embodiment; and 
         FIG. 14A  and  FIG. 14B  illustrate a method for manufacturing the acoustic wave device in accordance with the modified embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A description is now be given of embodiments with reference to the accompanying drawings. 
     First Embodiment 
       FIG. 1  illustrates a schematic cross sectional view of an acoustic wave device in accordance with a first embodiment. An acoustic wave device  100  has a structure in which a first piezoelectric substrate  11  and a second piezoelectric substrate  21  are sealed with sealing members  13  and  23  and a sealing resin  30 . A first acoustic wave device  10  is provided on an upper face of the first piezoelectric substrate  11 . A second acoustic wave device  20  is provided on an upper face of the second piezoelectric substrate  21 . LaTiO 3  or the like may be used as the first piezoelectric substrate  11  and the second piezoelectric substrate  21 . 
     The first acoustic wave device  10  and wiring layers  12   a  and  12   b  coupled to the first acoustic wave device  10  are provided on the upper face of the first piezoelectric substrate  11 . The upper face of the first piezoelectric substrate  11  is covered with the sealing member  13 . The sealing member  13  includes a metal layer  14  and a resin layer  15 . The metal layer  14  covers an upper portion of the first acoustic wave device  10  so that a hollow space is formed above the first acoustic wave device  10 . When the metal layer  14  acts as a ground electrode of the first acoustic wave device  10 , an edge of the metal layer  14  is coupled to the wiring layer  12   a  on the side of the ground. An insulating membrane  16  insulates the metal layer  14  from the wiring layer  12   b  on the side of signal inputting. The resin layer  15  covers a whole of the metal layer  14 . The sealing member  13  including the resin layer  15  and the metal layer  14  forms a wafer level package structure having a hollow space in the first piezoelectric substrate  11 . 
     The second acoustic wave device  20  and wiring layers  22   a  and  22   b  are provided on the second piezoelectric substrate  21 , in common with the first piezoelectric substrate  11 . The sealing member  23  including a metal layer  24  and a resin layer  25  covers the second acoustic wave device  20  and the wiring layers  22   a  and  22   b . And, another wafer level package having a hollow space is formed. 
     The first piezoelectric substrate  11  and the second piezoelectric substrate  21  are integrally sealed with the sealing resin  30 . Thus, the first acoustic wave device  10  and the second acoustic wave device  20  having different filter characteristics may be provided in a single chip. For example, when one of the first acoustic wave device  10  and the second acoustic wave device  20  acts as a transmitting filter and the other acts as a receiving filter, a duplexer constituted of a plurality of acoustic wave filters is established. 
     A through hole  17  is formed in the resin layer  15  of the sealing member  13  and in the sealing resin  30 . A through hole  27  is formed in the resin layer  25  of the sealing member  23  and in the sealing resin  30 . A through hole electrode  18  is provided in the through hole  17 . A through hole electrode  28  is provided in the through hole  27 . When one of the through hole electrodes  18  is coupled to the metal layer  14  of the sealing member  13  acting as a ground, the other is coupled to the wiring layer  12   b  on the side of signal inputting. When one of the through hole electrodes  28  is coupled to the metal layer  24  of the sealing member  23  acting as a ground, the other is coupled to the wiring layer  22   b  on the side of signal inputting. Solder balls  19  and  29  for mounting are provided on the through hole electrodes  18  and  28  respectively. 
     As illustrated in  FIG. 1 , there is a method of arraying chips and integrating the chips with an interposer in order to arrange the second piezoelectric substrate  21  (the second acoustic wave device  20 ) adjacent to the first piezoelectric substrate  11  (the first acoustic wave device  10 ). However, when the chips are arrayed after dicing a wafer into the chips, there is a problem that the manufacturing cost is increased if a device is miniaturized. There is little merit on forming a wafer level package having a hollow space in advance, because an interposer forms a hollow space on a piezoelectric substrate. A description will be given of a manufacturing method of an acoustic wave device for solving the above-mentioned problem. 
       FIG. 2A  through  FIG. 12  illustrate a method for manufacturing the acoustic wave device in accordance with the first embodiment.  FIG. 4  and  FIG. 12  illustrate a perspective view of a dicing process of a wafer in the manufacturing method. The others illustrate a schematic cross sectional view of the manufacturing method. In  FIG. 2B ,  FIG. 3B ,  FIG. 6B , FIG.  6 C and  FIG. 9B , a top view related to the cross sectional view is also illustrated. In the figures of the manufacturing method, the piezoelectric substrates  11  and  21  and the sealing members  13  and  23  are mainly illustrated. The others are omitted. 
     First, as illustrated in  FIG. 2A  and  FIG. 2B , the wafer-shaped first piezoelectric substrate  11  of which upper face is sealed with the sealing member  13  is adhered to a front face of a first adhesive sheet  40  acting as a dicing tape. The first adhesive sheet  40  is an adhesive sheet of which adhesive force is reduced by ultraviolet rays. For example, a dicing tape (UV series) made by TOYO ADTEC Ltd. may be used for the first adhesive sheet  40 . Next, as illustrated in  FIG. 3A  and  FIG. 3B , the first piezoelectric substrate  11  is cut in rectangles (dicing) from the sealing member  13  side. As illustrated in  FIG. 4 , in the dicing process, the first adhesive sheet  40  is arranged on a ring  50  for fixing, and a rolling blade  52  is pressed to the first piezoelectric substrate  11  from above. As illustrated in  FIG. 4 , the wafer is subjected to the dicing from a single direction. The first piezoelectric substrate  11  is cut into parallel rectangles. Thus, the first piezoelectric substrate  11  is divided into a plurality of rectangle-shaped piezoelectric substrates. 
     Next, as illustrated in  FIG. 5 , ultraviolet rays are radiated to a back face of the first adhesive sheet  40  (the opposite side of the first piezoelectric substrate  11 ). It is possible reduce the adhesive force of preferable areas of the first adhesive sheet  40  when the ultraviolet rays are radiated selectively through a ultraviolet-rays-shielding mask  54 , because the adhesive force of the first adhesive sheet  40  is reduced by the ultraviolet rays. A number “ 42 ” is added to areas of which adhesive force is reduced. 
     Next, the second piezoelectric substrate  21  is subjected to the same processes as those of  FIG. 2A  through  FIG. 5 . The second acoustic wave device  20  (illustrated in  FIG. 1 ) is provided on the upper face of the second piezoelectric substrate  21 . The sealing member  13  covers the second acoustic wave device  20 . The second piezoelectric substrate  21  is subjected to the dicing process after the second piezoelectric substrate  21  is adhered to a second adhesive sheet (not illustrated). And, ultraviolet rays are radiated to the back face of the second adhesive sheet selectively. 
     Next, as illustrated in  FIG. 6A , the front face of the first adhesive sheet  40  (the first piezoelectric substrate  11  side) is pressed to a third adhesive sheet  60 . Thus, the first piezoelectric substrates  11   b ,  11   d  and  11   f , of which adhesive force is reduced, included in the first piezoelectric substrates  11   a  through  11   f  move to the third adhesive sheet  60 . The first piezoelectric substrates  11   a ,  11   c  and  11   e  of which adhesive force is not reduced remain on the first adhesive sheet  40 .  FIG. 6B  illustrates a top view of the third adhesive sheet  60  after the movement.  FIG. 6C  illustrates a top view of the first adhesive sheet  40  after the movement. 
     The first piezoelectric substrates  11   b ,  11   d  and  11   f  may move as illustrated in  FIG. 7 . As illustrated in  FIG. 7 , the first adhesive sheet  40  loops around a first roller  56 , and the third adhesive sheet  60  loops around a second roller  58 . There is an interval corresponding to the thickness of the first piezoelectric substrate  11  including the sealing member  13  between the first roller  56  and the second roller  58 . And the first roller  56  and the second roller  58  rotate in a direction different from each other. In a region  59  between the first roller  56  and the second roller  58 , the first piezoelectric substrate  11  on the first adhesive sheet  40  is contact to the third adhesive sheet  60 . In this case, when the adhesive force of the first adhesive sheet  40  is reduced, the first piezoelectric substrate  11  moves to the third adhesive sheet  60  because of the adhesive force of the third adhesive sheet  60 . On the other hand, when the adhesive force of the first adhesive sheet  40  is not reduced, the first piezoelectric substrate  11  does not move and remains on the first adhesive sheet  40 . When the first piezoelectric substrate  11  moves to the third adhesive sheet  60  even if the adhesive force of the third adhesive sheet  60  is strong and the adhesive force of the first adhesive sheet  40  is not reduced, the first piezoelectric substrate  11  does not move and remains the first adhesive sheet  40  if a rotation axis of the first roller  56  is shifted upward and the interval of the regions  59  is enlarged when the first piezoelectric substrate  11  of which adhesive force is not reduced reaches the region  59 . 
     Next, a second adhesive sheet (not illustrated) adhered to the second piezoelectric substrate  21  is subjected to the same processes as those of  FIG. 6A  through  FIG. 6C  and  FIG. 7 . That is, when a fourth adhesive sheet  70  (illustrated in  FIG. 9A  and  FIG. 9B ) is pressed to the front face of the second adhesive sheet (the second piezoelectric substrate  21  side), the second piezoelectric substrate  21  of which adhesive force with respect to the second adhesive sheet is reduced may be moved to the fourth adhesive sheet  70  selectively. 
     Next, as illustrated in  FIG. 8 , ultraviolet rays are radiated to the back face of the first adhesive sheet  40  on which some first piezoelectric substrate  11  are removed. Being different from  FIG. 5 , ultraviolet rays are radiated to whole face of the first adhesive sheet  40  without the ultraviolet-rays-shielding mask  54 . Through the process, the adhesive force of the whole face of the first adhesive sheet  40  is reduced. The second adhesive sheet (not illustrated) of which some second piezoelectric substrate  21  are removed is subjected to the same process as  FIG. 8 . 
     Next, as illustrated in  FIG. 9A , the fourth adhesive sheet  70  is pressed to the front face of the first adhesive sheet  40 . Thus, the first piezoelectric substrate  11  remaining on the first adhesive sheet  40  moves to the fourth adhesive sheet  70 . The movement of the first piezoelectric substrate  11  is established through a method using a roller as well as  FIG. 7 . The second piezoelectric substrate  21  is adhered to the fourth adhesive sheet  70  selectively in advance through the same process as  FIG. 6A  through  FIG. 6C . Through the movement, as illustrated in  FIG. 9B , the rectangle-shaped first piezoelectric substrate  11  and the rectangle-shaped second piezoelectric substrate  21  are arrayed on the fourth adhesive sheet  70  alternately. 
     The second adhesive sheet (not illustrated) is subjected to the same process as  FIG. 9A  and  FIG. 9B . That is, the third adhesive sheet  60  on which the first piezoelectric substrate  11  is adhered selectively in advance is pressed to the front face of the second adhesive sheet of which adhesive force is reduced. And, the second piezoelectric substrate  21  remaining on the second adhesive sheet moves to the third adhesive sheet  60 . Thus, the rectangle-shaped first piezoelectric substrate  11  and the rectangle-shaped second piezoelectric substrate  21  are arrayed alternately on the third adhesive sheet  60  as well as  FIG. 9B . 
     Next, as illustrated in  FIG. 10A , the first piezoelectric substrate  11  and the second piezoelectric substrate  21  on the fourth adhesive sheet  70  are adhered to a fifth adhesive sheet  80 . In the process, ultraviolet rays are radiated to the whole of the back face of the fourth adhesive sheet  70 , and thereby the adhesive force of the fourth adhesive sheet  70  is reduced. The fifth adhesive sheet  80  is pressed to the first piezoelectric substrate  11  and the second piezoelectric substrate  21  from the front face side of the fourth adhesive sheet  70 . And, the first piezoelectric substrate  11  and the second piezoelectric substrate  21  move to the fifth adhesive sheet  80 . Thus, as illustrated in  FIG. 10B , the first piezoelectric substrate  11  and the second piezoelectric substrate  21  are in contact to the fifth adhesive sheet  80 . 
     Next, as illustrated in  FIG. 10C , the first piezoelectric substrate  11  and the second piezoelectric substrate  21  are covered with the resin sheet  30  from the front face side of the fifth adhesive sheet  80 . Thus, the first piezoelectric substrate  11  and the second piezoelectric substrate  21  are sealed with a resin. Next, as illustrated in  FIG. 10D , ultraviolet rays are radiated to the back face of the fifth adhesive sheet  80 . Thereby, the adhesive force of the fifth adhesive sheet  80  is reduced, and the fifth adhesive sheet  80  is peeled. Next, as illustrated in  FIG. 10E , the resin sheet  30  is hardened by heat and is converted into the sealing resin  30 . Thus, the first piezoelectric substrate  11  and the second piezoelectric substrate  21  are integrated by the sealing resin  30 . The third adhesive sheet  60  is subjected to the above-mentioned processes. Thus, as illustrated in  FIG. 10E , the first piezoelectric substrate  11  and the second piezoelectric substrate  21  integrated by the sealing resin  30  is provided. 
     Next, as illustrated in  FIG. 11A , the through hole  17  is formed in the sealing resin  30  from the side of the sealing member  13  of the first piezoelectric substrate  11 . And, the through hole  27  is formed in the sealing resin  30  from the side of the sealing member  23  of the second piezoelectric substrate  21 . Next, as illustrated in  FIG. 11B , the through hole electrodes  18  and  28  are formed in the through holes  17  and  27  respectively. After that, as illustrated in  FIG. 11C , the solder balls  19  and  29  for mounting are provided on the through hole electrodes  18  and  28  respectively. After that, as illustrated in  FIG. 11D , the sealing resin  30  is subjected to dicing and is divided into chips. 
     As illustrated in  FIG. 12 , in the dicing process, the first piezoelectric substrate  11  and the second piezoelectric substrate  21  integrated by the sealing resin  30  are adhered to a dicing tape  90 , and the rolling blade  52  is pressed to the sealing resin  30  from above. Being different from  FIG. 4 , the sealing resin  30  is subjected to the dicing from two directions having a right angle with each other. The sealing resin  30  is divided into chips acting as a single device. The sealing resin  30  after the dicing includes one of the first piezoelectric substrates  11  and one of the second piezoelectric substrate  21 . Through the processes, the acoustic wave device  100  illustrated in  FIG. 1  is fabricated. 
     With the method for manufacturing the acoustic wave device in accordance with the first embodiment, a wafer including acoustic wave devices having a different characteristics is divided into rectangles. Some of the rectangles are moved to an adhesive sheet selectively. Two adhesive sheets, to which a wafer including an acoustic wave device having different characteristics are adhered, are jointed to each other. Thus, rectangle-shaped wafers are adhered to a single adhesive sheet alternately. After that, sealing with a resin, forming a through hole, forming a through hole electrode, and forming a solder ball are performed together. At last, the overall structure is subjected to dicing and is divided into each acoustic wave device. Thus, the manufacturing process is simplified, and the manufacturing cost is reduced, compared to a case where piezoelectric substrates (chips) having a wafer level package are arrayed and are integrated. 
     In the first embodiment, as illustrated in  FIG. 6A  through  FIG. 6C , a pitch of the first piezoelectric substrates  11  on the first adhesive sheet  40  is equal to that of the first piezoelectric substrates  11  on the third adhesive sheet  60 . However, as illustrated in  FIG. 13 , the pitch of the first piezoelectric substrate  11  after the movement may be different from that before the movement. For example, the pitch can be changed easily, if the rotating speed of the two rollers is different from each other when the first piezoelectric substrate  11  are moved by the rollers illustrated in  FIG. 7 . There is a case where a size (width) of a device including the first piezoelectric substrate  11  is different from that of a device including the second piezoelectric substrate  21 . In this case, it is easy to arrange two piezoelectric substrates having a different size adjacent to each other by adjusting a pitch of piezoelectric substrate according to that of another piezoelectric substrate, if the pitch is changeable. 
     In the first embodiment, as illustrated in  FIG. 3A  and  FIG. 3B , the dicing is performed from the side of the sealing member  13 . In this case, a burr may be formed because of a resin during the dicing process. And, the burr may be adhered to a surface of an acoustic wave device because of static electricity. In this case, it is preferable that the side of the sealing member  13  is adhered to a dicing tape (the first adhesive sheet  40 ) as illustrated in  FIG. 14A , and after that the side of the first piezoelectric substrate  11  is subjected to the dicing process as illustrated in  FIG. 14B . Thus, even if a bun is formed, the formed burr is adhered to the dicing tape  40 . Therefore, adhesion of the bun to the surface of the acoustic wave device is restrained. And, the number of process is reduced even if the movement from the fourth adhesive sheet  70  to the fifth adhesive sheet  80  illustrated in  FIG. 10A  through  FIG. 10E  is not performed. 
     In the first embodiment, a description is given of an acoustic wave device having a wafer level package having a hollow space. However, the manufacturing method is not limited to the above-mentioned acoustic wave device. However, the wafer level package having a hollow space is appropriate for the case where two types of acoustic wave devices are arrayed and integrated in the embodiment, because the thickness of whole of the device tends to be increased. 
     In the first embodiment, an adhesive sheet (the first adhesive sheet  40  through the fifth adhesive sheet  80 ) of which adhesive force is reduced by ultraviolet rays is used, in order to establish a selective movement of the rectangle-shaped piezoelectric substrates. The movement method of the piezoelectric substrate is not limited to the case. However, with the above-mentioned method, the piezoelectric substrate is moved easily. 
     The present invention is not limited to the specifically described embodiments, but other embodiments and variations may be made without departing from the scope of the claimed invention.