Abstract:
An electronic module and a process for forming an electronic module are provided. Uniform and sealed air gaps are formed in a vertical direction between two or more electronic devices. The uniform and sealed air gaps are formed by arranging spacers between the electronic devices, where the height of the spacers is selected depending upon the operating characteristics of the particular type of electronic devices.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Today&#39;s semiconductor packages include a number of different electronic devices. These electronic devices can include, for example, integrated circuits (ICs), microelectronic machines (MEMs), and/or the like. The integration of different electronic devices into a device module typically requires a significant amount of horizontal space, and relatively high assembly and processing complexity and cost. Current techniques for integrating different electronic devices into a device module largely focus on minimizing two-dimensional (X,Y) area of the discrete electronic devices. The discrete devices are assembled separately into the modules, where each such module includes a separate lid. Additionally, the assembled discrete devices occupy at least as much area in the two-dimensional (X,Y) portion of the module as the combined two-dimension area of the individual devices.  
       SUMMARY OF THE INVENTION  
       [0002]     An electronic module and process for forming the same are provided. In accordance with exemplary embodiments of the present invention, a second electronic device is arranged above a first electronic device. Spacers are arranged between a first and second electronic device to form a uniform and sealed air gap between the electronic devices. The height of the spacers, and the resulting height of the air gap, is selected based upon the type of electronic device. For radio frequency electronic devices, the height of the spacers is selected to reduce radio frequency interference between the first and second electronic devices. In the case of microelectronic machines, the height is selected to allow sufficient clearance for operation of the machines.  
         [0003]     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0004]      FIG. 1  illustrates an exemplary electronic module in accordance with the present invention; and  
         [0005]      FIGS. 2   a - 2   h  illustrate an exemplary process for forming the electronic module of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0006]      FIG. 1  illustrates an exemplary electronic module  100  in accordance with the present invention. The electronic module  100  includes a substrate  102  and two or more electronic devices, each of which comprise a wafer, active device, contact pads, and gold or copper balls. The substrate  102  includes one or more thermal vias  106   a - 106   d , one or more input/output (I/O) lines  104   a  and  104   b , and integrated transmission lines and inductors. Substrate  102  can be a lead free (LF) laminate or ceramic substrate.  
         [0007]     A first electronic device includes a wafer  122 , active device  124 , gold or copper balls  126   a  and  126   b , and contact pads  128   a  and  128   b . The contact pads  128   a  and  128   b  are respectively coupled to the I/O lines  104   a  and  104   b  by bonding wires  160   a  and  160   b.    
         [0008]     A second electronic device is arranged on spacers  123   a  and  123   b  above the first electronic device, thereby forming a uniform and sealed air gap between the first and second electronic devices. Specifically, an adhesive layer  131  couples the spaces  123   a  and  123   b  to the second electronic device. The second electronic device includes a wafer  132 , active device  134 , gold or copper balls  136   a  and  136   b , and contact pads  138   a  and  138   b . The contact pads  138   a  and  138   b  are respectively coupled to the I/O lines  104   a  and  104   b  by bonding wires  162   a  and  162   b.    
         [0009]     Module  100  also includes a third electronic device arranged above the second electronic device on spacers  133   a  and  133   b . Specifically, spacers  133   a  and  133   b  are provided on wafer  132  of the second electronic device and the third electronic device is coupled to the spacers  133   a  and  133   b  by an adhesive layer  141 . The third electronic device includes an active device  144  and contact pads  148   a  and  148   b  on wafer  142 . Gold or copper balls  146   a  and  146   b  are respectively coupled to bonding wires  164   a  and  164   b , which in turn are coupled to I/O lines  104   a  and  104   b , respectively.  
         [0010]     A lid  150  is arranged above the uppermost electronic device, which in the illustrated embodiment is the third electronic device. Lid  150  can be composed of silicon, glass, ceramic or the like material. Lid  150  includes an adhesive layer  151  on the side facing the third electronic device. Spacers  143   a  and  143   b  are arranged on wafer  142  of the third electronic device and are coupled to the adhesive layer  151 .  
         [0011]     Although  FIG. 1  illustrates an electronic module with three electronic devices, the electronic module can have more or less than three electronic devices. Active devices  124 ,  134  and  144  can be integrated circuits or microelectronic machines (MEMS). For example, in a radio frequency module, active devices  134  and  144  can be a transmitter and receiver filter, and active device  124  can be a switch. In a radio frequency module, I/O lines  104   a  and  104   b  can be coupled to an antenna, such as a low-gain antenna. In accordance with exemplary embodiments of the present invention, the spacers can be composed of polymer and have dimensions between 30 and 200 μm wide, and between 10 and 200 μm high. When the active devices  124 ,  134  and  144  are radio frequency devices, the height of the spacers and the resulting uniform and sealed air gap are selected to minimize interference between the active devices. In the case of microelectronic machines, the height of the spacers and the resulting uniform and sealed air gap are selected to provide sufficient clearance for the operation of the microelectronic machines.  
         [0012]     Arranging the various electronic devices vertically reduces the costs of the resulting electronic module, as the electronic devices share the same I/O line, and only one lid is required for all of the electronic devices. Additionally, the vertically arrangement can significantly reduce the X and Y dimensions, saving precious circuit board space and minimizing interconnect lengths and inductances. Moreover, the electronic module of the present invention can be pre-tested as a discrete component, thereby lowering the bill of materials and assembly costs, and providing a pre-testable component that can be sold to device manufacturers.  
         [0013]     Now that an overview of the electronic module has been presented, a process of manufacturing the electronic module will be described in connection with  FIGS. 2   a - 2   h . The process involves a wafer  200  with one or more active devices  134  and  144 , and corresponding contact pads. For each active device, two or more spacers  133   a  and  133   b  are arranged on the wafer  200  by spin or spray coating, and photo development or screen printing ( FIG. 2   a ). Since wafer  200  includes a second active device  144 , a second set of spacers  148   a  and  148   b  (not illustrated) are formed on the wafer. A set of spaces can be formed for each active device upon which another active device will be stacked in the electronic module.  
         [0014]     Next the device wafer is thinned from a full wafer thickness to a thickness between 50 and 200 μm using any conventional semiconductor back lapping process to form wafer  210  ( FIG. 2   b ). As illustrated in  FIG. 2   c , an adhesive  220 , such as a B-stage adhesive film, is formed on the side of the wafer  210  opposite to the active devices  134  and  144 , using, for example, a lamination or coating process. Next, the individual electronic devices are formed by a die singulation process ( FIG. 2   d ).  
         [0015]     As illustrated in  FIG. 2   e , the first electronic device, with the first active device  124 , is attached to substrate  102  using conventional die placement equipment. Spacers  123   a  and  123   b  are formed by spin or spray coating, and photo development or screen printing. Bonding wires  160   a  and  160   b  are respectively placed on gold or copper balls  126   a  and  126   b , and on I/O lines  104   a  and  104   b . The gold or copper balls  126   a  and  126   b  are heated, thereby mechanically and electrically coupling contact pads  128   a  and  128   b  to I/O lines  104   a  and  104   b , respectively. Next, the second electronic device is arranged above the first electronic device in such a way that the adhesive on the bottom of the second electronic device mates with the spacers  123   a  and  123   b  ( FIG. 2   f ). The second electronic device is wire bonded to the I/O lines  104   a  and  104   b  in a similar manner to that described above in connection with the first electronic device. As illustrated in  FIG. 2   g , the third electronic device is arranged above the second electronic device in a similar manner to that described above in connection with the second electronic device, and the third electronic device is wire bonded to the I/O lines  104   a  and  104   b.    
         [0016]     Lid  150  is arranged above the uppermost electronic device, which in the present description is the third electronic device, with adhesive layer  151  adjoining spacers  143   a  and  143   b  ( FIG. 2   h ). After the lid has been attached, the entire module is heated to a predetermined temperature (e.g., 150° C.) in a controlled environment for a predetermined amount of time (e.g., 1 hour) to cure the adhesive. The entire module is then encapsulated to form the electronic module illustrated in  FIG. 1 .  
         [0017]     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.