Abstract:
A surface excited device package and method for packaging a surface excited device provide a surface excited device having a small footprint, high reliability, low cost and high production volume. The surface excited device may be a Surface Acoustic Wave (SAW) device or a Micro Electromechanical System(MEMS) device. A substrate including multiple conductive patterns is bonded to a semiconductor die that includes a surface excited device area. The substrate includes multiple conductive patterns for connecting electrical connections of the die and terminals for connecting the surface excited device to external devices. The substrate further includes an aperture over the surface exited device area and a cover for covering the cavity formed by the aperture to protect the surface excited device area from the external environment.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to integrated circuit packaging and more specifically, to packaging methods and assemblies for packaging surface excited devices.  
         BACKGROUND OF THE INVENTION  
         [0002]    Surface excited piezoelectric devices such as Surface Acoustic Wave (SAW) devices and Micro Electro-Mechanical System (MEMS) devices are commonly used in electronic and electromechanical/electro-optical systems. Other piezoelectric transducers are in common use for buzzers, crystal oscillators and filters, and other applications.  
           [0003]    SAW devices provide a bandpass filter or comb filter function by converting electric signals into a surface acoustic wave, i.e. mechanical signal, through a substrate. The electrodes are inter-digitally arranged on a substrate and a piezoelectric effect generates acoustic waves on the surface of the substrate. Frequency and phase control is achieved through the design of the circuit electrodes.  
           [0004]    MEMS devices include miniature electromechanical actuators formed from individual piezoelectric elements formed on a substrate. They are used to position miniature mirrors and other optical components to form electro-optical systems as well as for other micro-mechanical systems.  
           [0005]    Surface excited devices provide advantages in high integration, low power, high reliability and low cost applications. Since the manufacturing process is similar to that for semiconductor processing, the device can be manufactured in groups on a wafer. Further, a plurality of surface excited devices, signal processing components and other electronic structures can be integrated within one semiconductor die, resulting in high efficiency, low cost, high reliability and high production volumes.  
           [0006]    In accordance with the recent trend of most electronic, mechanical and optical components towards more compact, high performance and low cost designs, the surface excited device has found application as a core technology within the fields of bio- technology, communication &amp; information processing, transportation &amp; aerospace, optics, robotics and others.  
           [0007]    However, in conventional semiconductor packaging, the substrate is much larger than the die and a surface excited device is much larger than a typical semiconductor die. Therefore, conventional semiconductor packaging of a surface excited device will result in a very large package.  
           [0008]    Further, as wire bonding, solder bump addition, encapsulating and other processes are conducted after the semiconductor dies are singulated, the larger package reduces the semiconductor package assembly throughput and increases the assembly cost.  
           [0009]    Therefore, it would be desirable to provide a package for a surface excited device having a reduced substrate area.  
         SUMMARY OF THE INVENTION  
         [0010]    The above stated objectives are achieved in a surface excited device package and a method for packaging a surface excited device. The device package includes a die including a surface excited device area and a substrate bonded to a surface of the die and including multiple conductive patterns. The substrate further defines a cavity the surface exited device area and the device package further includes multiple conductive connectors for connecting the conductive patterns of the substrate to the electrical terminals of the die. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1A is a sectional view illustrating a surface excited device according to an embodiment of the present invention;  
         [0012]    [0012]FIG. 1B is a plan view illustrating a surface excited device according to an embodiment of the present invention;  
         [0013]    [0013]FIG. 2 is a sectional view illustrating a surface excited device according to another embodiment of the present invention;  
         [0014]    [0014]FIG. 3 is a sectional view illustrating a surface excited device according to another embodiment of the present invention;  
         [0015]    [0015]FIG. 4 is a sectional view illustrating a surface excited device according to another embodiment of the present invention;  
         [0016]    [0016]FIG. 5 is a sectional view illustrating a surface excited device according to another embodiment of the present invention;  
         [0017]    [0017]FIG. 6 is a sectional view illustrating a surface excited device according to another embodiment of the present invention;  
         [0018]    [0018]FIG. 7A through FIG. 7F are pictorial diagrams depicting a method for manufacturing a surface excited device in accordance with an embodiment of the present invention;  
         [0019]    [0019]FIG. 8A through FIG. 8F are pictorial diagrams depicting a method for manufacturing a surface excited device in accordance with another embodiment of the present invention;  
         [0020]    [0020]FIG. 9A through FIG. 9E are pictorial diagrams depicting a method for manufacturing a surface excited device in accordance with another embodiment of the present invention; and  
         [0021]    [0021]FIG. 10A through FIG. 10D are pictorial diagrams depicting a method for manufacturing a surface excited device in accordance with another embodiment of the present invention.  
         [0022]    The invention, as well as a preferred mode of use and advantages thereof, will best be understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings, wherein like reference numerals indicate like parts throughout. 
     
    
     DETAILED DESCRIPTION  
       [0023]    Referring to FIG. 1A and FIG. 1B, a surface excited device  100  according to the present invention is illustrated. An encapsulating portion  150  shown in FIG. 1A is omitted in FIG. 1B to provide a view of underlying features.  
         [0024]    As shown in the drawings, a semiconductor die  110  having a substantially planar first surface  111  and second surface  112  and side surfaces  113 , includes an surface excited device area  114  on second surface  112 . Surface excited device area  114  is generated with three-dimensional structures formed by a SAW technique or a MEMS technique. A plurality of input and output bond pads  115  are formed at the circumference of second surface  112  in the vicinity of the side surface  113 . The actual three-dimensional structures forming the surface excited device are not illustrated in FIG. 1A and FIG. 1B.  
         [0025]    An approximately planar substrate  130  is bonded to second surface  112  of semiconductor die  110  by an adhesive  120 . Substrate  130  comprises a flexible insulating layer  131  bonded to adhesive  120  and a plurality of conductive patterns  132  formed on flexible insulating layer  131 .  
         [0026]    Adhesive  120  may be a conventional double-sided adhesive tape and flexible insulating layer  131  may be a nonconductive polyimide or other insulating material such as flame retardant (FR) material FR- 5 , and conductive patterns  132  are formed from a conductive material such as copper foil. At least one cavity  133  is formed within a region of substrate  130  corresponding to surface excited device area  114  of semiconductor die  110  by an i aperture through insulating layer  131  and adhesive  120 . Cavity  133  is covered with a cover  134  to protect surface excited device area  114  from the external environment. Cover  134  may be made from the same material as conductive patterns  132  (e.g., copper foil) or alternatively may be made from a different material applied to insulating layer  131 .  
         [0027]    A slot  135  of predetermined size is formed at a region of adhesive  120  and substrate  130  corresponding to the input and output bond pads  115  of semiconductor die  110 . Semiconductor die  110  and substrate  130  are identical in length and width, with the exception of slot  135  region. Substrate  130  does not extend beyond side surface  113  of semiconductor die  110 .  
         [0028]    Input and output bond pads  115  of semiconductor die  110  are electrically and mechanically connected to conductive patterns  132  of the substrate  130  by conductive wires  140 , such as gold (Au) or aluminum (Al) wire. Further, input and output bond pads  115 , conductive wire  140 , a portion of conductive patterns  132  and slot  135  are encapsulated by an encapsulant  150  to protect them from the external environment. The side surface of encapsulant  150  is flush with side surface  113  of semiconductor die  110 . Accordingly, the area of the entire surface excited device package is no larger than the area of semiconductor die  110 . A plurality of conductive balls  160  are fused to the conductive patterns  132  to form terminals for connecting the packaged surface excited device to an external device. Thus a conductive path is established between an external device and the surface excited device  100  through conductive balls  160  to conductive patterns  132 , conductive wires and input and output bond pads  115  of semiconductor die  110 .  
         [0029]    Referring next to FIG. 2, a surface excited device  200  according to another embodiment of the present invention is illustrated. Since surface excited device  200  as shown in FIG. 2 is similar to surface excited device  100  of FIG. 1A, only those differences between the devices will be described below.  
         [0030]    A conductive bump  241  is fused to input and output bond pads  215  formed on a second surface  212  of a semiconductor die  210 . Conductive bump  241  may be a conventional gold or solder bump. A hardened conductive paste  242  is formed on the surface of conductive bump  241  and one side of conductive paste  242  is connected to conductive patterns  232  of substrate  230 . Thus conductive paste  242  forms an electrical connection to conductive bump  241  providing an electrical connection to semiconductor die  210 . The side surfaces of the conductive bump  241  and the conductive paste  242  are flush with side surface  213  of semiconductor die  210  and conductive bump  241  is exposed along the side surface of conductive paste  242 .  
         [0031]    Conductive paste protects input and output bond pads  215  of semiconductor die  210  and conductive bump  241  from the external environment. Conductive balls  260  may be optionally attached to conductive paste  242  for providing external electrical and mechanical connections or according to the another embodiment of the present invention they may be deleted and surface excited device  200  can be directly connected to an external device directly through conductive paste  242 .  
         [0032]    Referring now to FIG. 3, a surface excited device  300  according to another embodiment of the present invention is illustrated. Since surface excited device  300  as shown in FIG. 3 is similar to surface excited device  100  of FIG. 1A, only differences between the devices will be described below.  
         [0033]    Substrate  330  is formed at the periphery of input and output bond pads  315  of semiconductor die  310 . Accordingly, slot  335  is surrounded by substrate  330 . A conductive plating pattern  343  of a predetermined thickness is formed between input and output bond pads  315  and conductive pattern  332  of the substrate  330 . Input and output pad  315  and conductive pattern  332  are electrically connected through plating pattern  343 .  
         [0034]    Plating pattern  343  can be formed by a conventional electrolytic and/or a non-electrolytic plating technique. Alternatively, plating pattern  343  can be formed by a conventional electron ray deposition or sputtering technique and the present invention is not limited by method used to form plating pattern  343 . Plating pattern  343  may also be a conventional copper (Cu) or aluminum (Al) pattern. A hardened conductive paste  342  is formed on the surface of plating pattern  343  within slot  335 . Conductive ball  360  may be optionally formed on conductive pattern  332  and according to the one embodiment of the present invention no conductive ball  360  is used and the surface excited device  300  is be directly connected to an external device through conductive paste  342 .  
         [0035]    Referring to FIG. 4, a surface excited device  400  according to another embodiment of the present invention is illustrated. Since surface excited device  400  as shown in FIG. 4 is similar to surface excited device  100  of FIG. 1A, only those differences existing between the devices will be described below.  
         [0036]    A lead pattern  444  extends to input and output bond pads  415  of semiconductor die  410  from conductive pattern  432  of substrate  430 . Input and output bond pads  415  and the conductive pattern  432  are electrically connected together through lead pattern  444 . Lead pattern  444  can be connected to input and output bond pads  415  by a conventional TAB bond or lead bond method and lead pattern  444  can consist of the same material as the conductive pattern  432  or may be fabricated from a different material.  
         [0037]    Lead pattern  444  is encapsulated by an encapsulant  450  in order to protect lead pattern  444  from the external environment. A portion of metal pattern  432  and the entire slot  435  of substrate  430  are encapsulated by the encapsulant. Lead pattern  444  is fully covered with the encapsulant  450  similar to the encapsulation of conductive wire  140  as described above.  
         [0038]    Referring next to FIG. 5, a surface excited device  500  according to another embodiment of the present invention is illustrated. Since surface excited device  500  as shown in FIG. 5 is similar to surface excited device  200  of FIG. 2, only differences between the devices will be described below.  
         [0039]    Substrate  530  is formed at a periphery of input and output bond pads  515  of semiconductor die  510 . Slot  535  is surrounded by substrate  530  and a hardened conductive paste  542  is formed in slot  535 . Conductive bump  541  is fused to input and output bond pads  515  of semiconductor die  510 . Conductive ball may be optionally formed on conductive pattern  532  of substrate  530 . Alternatively, surface excited device  500  can be directly connected to an external device through conductive paste  542 .  
         [0040]    Referring now to FIG. 6, a surface excited device  600  according to another embodiment of the present invention is illustrated. Since surface excited device  600  as shown in FIG. 6 is similar to surface excited device  500  of FIG. 5, only differences existing between the devices will be described below.  
         [0041]    An inside surface  616  further formed by machining an upper part of side surface  613  of semiconductor die  610  to a predetermined depth. Inside surface  616  is flush with the side surface of substrate  630 . The inside surface  616  of semiconductor die  610  and the side surface of the substrate  630  are surrounded by an encapsulant  650 . The side surface of encapsulant  650  is flush with side surface  613  of the semiconductor die  610 . The top surface of encapsulant  650  is flush with the top surface of the substrate  630 . Although it is not shown in the figure, encapsulant  650  forms a rectangular ring along the edge of the top surface of semiconductor die  610 .  
         [0042]    Since inside surface  616  is formed at side surface  613  of semiconductor die  610  and is surrounded by the encapsulating portion  650  as described above, water cannot enter the interface between substrate  630  and the semiconductor die  610 , preventing de-lamination of the substrate.  
         [0043]    Referring to FIG. 7A through FIG. 7F, a method for packaging a surface excited device of the present invention is illustrated. As shown in FIG. 7A, a substrate strip  170  having a plurality of substrate units  130  connected with a boundary of slots  135  is provided. Substrate unit  130  includes an insulating layer  131 , an adhesive  120  bonded to the bottom surface of insulating layer  131 , and a plurality of conductive patterns  132  formed on the top surface of insulating layer  131 . A cavity  133  is formed at a region corresponding to a surface excited device area  114  of semiconductor die  110 , as will be described below, by an aperture formed through the insulating layer  131  and the adhesive  120 . Cavity  133  is covered with a cover  134 . Adhesive  120  is not a structural element(s) of the substrate strip  170 . Adhesive  120  is bonded to the substrate strip  170  during the manufacturing process of the surface excited device.  
         [0044]    Next, referring to FIG. 7B, a wafer  180  having a plurality of semiconductor dies  110  connected at a boundary defined by scribing lines  190  is bonded to substrate strip  170  by adhesive  120 . The semiconductor die includes a surface excited device area  114  formed by SAW or MEMS techniques and a plurality of input and output bond pads  115  formed at the circumference of surface excited device area  114 . The input and output bond pads  115  of each semiconductor die  110  are located inside slot  135  of substrate unit  130 . Scribing line  190  is also located at a region under slot  135  of each substrate unit  130 . Here, the scribing line  190  shown in the drawing is a phantom line, which is cut to separate the surface excited devices later in the manufacturing process. (In the drawings, reference numeral  111  represents a first surface of each semiconductor die and numeral  112  indicates a second surface of each semiconductor die.)  
         [0045]    Next, as shown in FIG. 7C, the input and output bond pads  115  of the semiconductor die  110  are electrically and mechanically connected to conductive patterns  132  of substrate  130  by a conductive wire  140 , such as a gold (Au wire) or an aluminum wire (Al wire).  
         [0046]    Next, as shown in FIG. 7D, conductive wires  140  are encapsulated by an encapsulant. Conductive wires  140 , input and output bond pads  115  and a portion of conductive pattern  132  of substrate  130  are encapsulated by encapsulant  150 . Slot  135  of substrate unit  130  is therefore fully filled by encapsulant  150 .  
         [0047]    Then, as shown in FIG. 7E, a plurality of conductive balls  160 , such as solder balls, are fused to each conductive pattern  132  of substrate unit  130 . Conductive balls  160  provide external terminals for connecting the surface excited device of the present invention to an external device.  
         [0048]    Finally, as shown in FIG. 7F, substrate strip  170  and wafer  180  are sawn along scribing line  190 , thereby separating the surface excited devices from substrate strip  170  and wafer  180  to form individual devices. Since encapsulating portion  150  and semiconductor die  110  are sawn together at scribing line  190 , side surface  113  of semiconductor die  110  is flush with the side of encapsulating portion  150 .  
         [0049]    Referring next to FIG. 8A through FIG. 8F, a method for packaging a surface excited device according to another embodiment of the present invention is illustrated.  
         [0050]    Since the method for manufacturing a surface excited device of FIG. 8A through FIG. 8F is similar to that of FIG. 7A through FIG. 7F, only those differences existing between the methods will be described below.  
         [0051]    First, as shown in FIG. 8A and FIG. 8B, a substrate strip  270  is provided and a wafer  280  is bonded in steps similar to those previously described for the steps illustrated in FIG. 7A and FIG. 7B.  
         [0052]    Next, as shown in FIG. 8C, a conductive bump  241  is formed at input and output bond pads  215  of each semiconductor die  210 . Conductive bump  241  is fused to input and output bond pads  215  on both sides of scribing line  290 . One conductive bump  241  is fused to two input and output bond pads  215  at a time and will be separated later in the manufacturing process. Conductive bump  241  may be a conventional gold or solder bump.  
         [0053]    Next, as shown in FIG. 8D, a conductive paste  242  is applied to slot  235  and over the conductive bump  241  and hardened. Conductive paste  242  is hardened through a reflow process, after filling slot  235  with conductive paste  242 . Therefore, input and output bond pads  215  of each semiconductor die  210  are electrically connected to conductive pattern  232  of each substrate unit  230  by conductive paste  242 .  
         [0054]    Next, as shown in FIG. 8E, a plurality of conductive balls  260 , such as a solder ball, are fused to conductive patterns  232  of each substrate unit  230 . Conductive ball  260  provides an external terminal to connect the surface excited device of the present invention to an external device. Alternatively, the step of fusing conductive balls may be skipped, since conductive paste  242  can be directly connected to the external device.  
         [0055]    Finally, as shown in FIG. 8F, substrate strip  270  and wafer  280  are sawn along scribing line  290 , separating the individual surface excited devices. Conductive paste  242  and conductive bump  241  are thereby sawn together at scribing line  290 . Therefore, side surface  213  of semiconductor die  210  is flush with the side of conductive paste  242  and conductive bump  241 . Conductive bump  241  is exposed to the outside under conductive paste  242 .  
         [0056]    As an alternative, a conductive plating pattern of a predetermined thickness can be formed between input and output bond pads  215  and conductive pattern  232  of substrate unit  230  to electrically connect them (instead of conductive bump  241 ). Here, the plating pattern can be formed by a conventional electrolytic plating process, a non-electrolytic plating process, an electron ray deposition or sputtering technique or the like.  
         [0057]    As a second alternative, a lead pattern of substrate unit  230  can be extended to input and output bond pads  215  of semiconductor die  210  from the conductive pattern  232  of the substrate unit  230 . The input and output bond pad  215  and the conductive pattern  232  can be electrically connected to each other through the lead pattern (instead of conductive bumps  241 ). The lead pattern can be connected to the input and output pads  215  by a conventional TAB bond or a lead bond method.  
         [0058]    Referring to FIG. 9A through FIG. 9E, a method for packaging a surface excited device according to another embodiment of the present invention is illustrated.  
         [0059]    As shown in FIG. 9A, a substrate strip  570  having a plurality of substrate units  530  connected with a boundary of slots  535  is provided. The substrate unit  530  includes a flexible insulating layer  531 , an adhesive  520  bonded to the bottom surface of the insulating layer  531 , and a plurality of conductive patterns  532  formed on the top surface of the insulating layer  531 .  
         [0060]    A cavity  533  is formed at a region corresponding to a surface excited device area  514  of each semiconductor die  510 , by providing an aperture through insulating layer  531  and the adhesive  520 . The cavity  533  is covered with a cover  534 .  
         [0061]    Next, a wafer  580  having a plurality of semiconductor dies  510  connected with a boundary of scribing lines  590  is bonded to substrate  570  by adhesive  520 . Each semiconductor die  510  includes a surface excited device area  514  formed by SAW or MEMS techniques and a plurality of input and output bond pads  515  formed at the circumference of the surface excited device area  514 . Scribing line  590  is located outside of slot  535 , as opposed to the above-described embodiments.  
         [0062]    Then, as shown in FIG. 9C, conductive bumps  541  are fused to input and output bond pads  515  of each semiconductor die  510 . Conductive bumps  541  are formed at each of the input and outputs bond pads  515  located within slots  535  of substrate unit  530  using gold or solder or an equivalent.  
         [0063]    Next, as shown in FIG. 9D, slots  535  are filled with conductive paste  542  and hardened. Conductive paste  542  is hardened through a reflow process. Input and output bond pads  515  of each semiconductor die  510  are electrically connected to conductive pattern  532  of each substrate unit  530  by conductive paste  542 . Conductive paste  542  forms an external terminal to connect separated surface excited devices of the present invention to an external device.  
         [0064]    Finally, as shown in FIG. 9E, substrate strip  570  and wafer  580  are sawn along scribing line  590 , thereby separating the surface excited devices. Since substrate unit  530  and semiconductor die  510  are sawn together at scribing line  590 , side surface  513  of semiconductor die  510  is flush with the side of substrate unit  530 .  
         [0065]    Referring now to FIG. 10A through FIG. 10D, a method for packaging a surface excited device according to another embodiment of the present invention is illustrated.  
         [0066]    First, as shown in FIG. 10A, a surface excited device is provided. Since the method for manufacturing the surface excited device is similar to that of FIG. 9A through FIG. 9D, further description of prior steps is omitted here.  
         [0067]    Next, as shown in FIG. 10B, a wafer  680  is sawn along scribing line  690  to a predetermined depth by using a blade (not shown) having a predetermined thickness. Scribing line  690  of the wafer  680  and the portion of substrate strip  670  that overlaps scribing line  390  are sawn. An inside surface  616  is thus formed at the side surface of each semiconductor die  610  to the inside of scribing line  690 .  
         [0068]    Then, as shown in FIG. 10C, an encapsulant  650  is applied within the sawn region, covering each inside surface  616  of the wafer  680 . The top surface of the encapsulant  650  is flush with the top surface of substrate strip  670 .  
         [0069]    Finally, as shown in FIG. 10D, encapsulant  650  and the wafer  680  are sawn through along the scribing line  690 , thereby separating the surface excited devices into individual packages. The thickness of the blade used to make the cuts of FIG. 10D is much thinner than the thickness of the blade used to make the cuts of FIG. 10B.  
         [0070]    This disclosure provides exemplary embodiments of the present invention. The scope of the present invention is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification, such as variations in structure, dimension, type of material and manufacturing process may be implemented by one of skill in the art in view of this disclosure.