Patent Abstract:
A chip and a chip package can transmit information to each other by using a set of converters capable of communicating with each other through the emission and reception of electromagnetic signals. Both the chip and the chip package have at least one such converter physically disposed on them. Each converter is able to (1) convert received electromagnetic signals into electronic signals, which it then may relay to leads on the device on which it is disposed; and (2) receive electronic signals from leads on the device on which it is disposed and convert them into corresponding electromagnetic signals, which it may transmit to a corresponding converter on the other device. Not having a direct physical connection between the chip and the chip package decreases the inductive and capacitive effects commonly experienced with physical bonds.

Full Description:
TECHNICAL FIELD  
         [0001]    The present invention is related generally to semiconductor integrated circuits, and more specifically to a method and system for electrically coupling a semiconductor chip to a chip package.  
         BACKGROUND OF THE INVENTION  
         [0002]    During the manufacture of integrated circuit devices, such as memories and microprocessors, a semiconductor die or chip must be physically and electrically attached to a chip package. A chip is a small piece of semiconductor material, such as silicon, in which an integrated circuit is formed, and a chip package as used herein is a protective container, such as a plastic dual-in-line package (DIP), or printed circuit board to which the chip is coupled, as will be appreciated by those skilled in the art.  
           [0003]    To electrically couple a chip to a chip package, electrical connections are formed between regions on the chip known as bonding pads, and leads or corresponding bonding pads on the chip package. This process can entail the creation of hundreds of electrical connections between the chip and chip package. Three techniques are generally relied on to accomplish this task: (1) wire bonding; (2) flip chip/bump bonding; and (3) tape automated bonding.  
           [0004]    [0004]FIG. 1 is a diagram illustrating a chip  2  that is wire-bonded to a chip package  4 . Generally, in a wire bonding process a thin wire  6  (commonly between 0.7 to 1.0 mil) is used to connect a chip bonding pad  8  to an inner lead  10  on the chip package  4 . Each inner lead  10  is coupled to an outer lead (not shown) which, in turn, provides electrical connections to external circuits (not shown). Each wire  6  must be placed individually, which is time consuming, and each wire results in increased electrical resistance in the connection. In addition, the use of wires mandates the observance of minimum spacing requirements to avoid short circuiting wires and performance problems resulting from wires being too close to one another.  
           [0005]    [0005]FIG. 2 shows a chip package  4  that is electrically coupled with a chip  2  through flip chip/bump bonding. With flip chip/bump bonding, metal bumps  12  placed on each bonding pad  8  on the chip  2  are soldered to the inner leads  14  of the chip package  4 . This is usually done by placing the chip  2  in position on the chip package  4  and melting the metal bumps  12  to solder the bonding pads  8  to the inner leads  14 . In this way, all of the bonds necessary to electrically connect a chip  2  to a chip package  4  can be done essentially simultaneously, which reduces the time required to interconnect the chip  2  and chip package  4  when compared to wire bonding. Flip-chip bonding, however, requires precise alignment of the chip  2  and the chip package  4  to ensure proper interconnection. Moreover, great care must also be exerted to prevent soldered metal from causing short circuits by propagating from one bonding pad  8  to adjacent bonding pads. Additionally, given the orientation of the chip  2  and the chip package  4 , after bonding an efficient visual inspection of the bonds is not possible, and the nature of the bonding procedure mandates that the chip  2  be heated and exposed to pressure.  
           [0006]    Tape automated bonding (TAB) is accomplished through the use of a flexible strip of tape on which a metal lead system has been deposited. Initially a conductive layer is deposited on the tape, usually by methods including sputtering and evaporation. This conductive layer is then formed by mechanical stamping or patterning techniques, such as fabrication patterning, resulting in a continuous tape with multiple individual lead systems. In order to bond the tape to the chip, the chip is then placed on a holder and the tape is positioned over the chip with the inner leads of a lead system on the tape being situated exactly over corresponding bonding pads located on the chip. The inner leads and the bonding pads are then pressed together, creating physical and electrical bonds between the inner leads and the bonding pads. TAB requires very precise positioning of the tape and the chip. Even slight misalignment can result in multiple short circuits and missed connections between inner leads and chip pads, thus compromising the electrical connection of the chip to the chip package.  
           [0007]    In view of the above-mentioned processes, it is desirable to develop a new process for electrically interconnecting a chip and chip package.  
         SUMMARY OF THE INVENTION  
         [0008]    According to one aspect of the present invention, a chip and a chip package can transmit information to each other by using a set of converters capable of communicating with each other through the emission and reception of electromagnetic signals. Both the chip and the chip package have at least one such converter physically disposed on them. Each converter is able to (1) convert received electromagnetic signals into electronic signals, which it then may relay to leads on the device on which it is disposed; and (2) receive electronic signals from leads on the device on which it is disposed and convert them into corresponding electromagnetic signals, which it may transmit to a corresponding converter on the other device. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a cross-sectional view of a chip wire-bonded to a chip package.  
         [0010]    [0010]FIG. 2 is a cross-sectional view of a chip bonded by flip chip/bump technology to a chip package.  
         [0011]    [0011]FIG. 3 is a functional and cross-sectional view of a chip that is coupled to a chip package through electromagnetic signals.  
         [0012]    [0012]FIG. 4 is a functional and cross-sectional view of a chip and chip package placed into communication according to another embodiment of the invention.  
         [0013]    [0013]FIG. 5 is a block diagram of a memory device including a semiconductor memory chip coupled to a chip package through electromagnetic signals.  
         [0014]    [0014]FIG. 6 is a block diagram of a computer system including the memory devices of FIG. 5. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    [0015]FIG. 3 is a functional and cross-sectional view of a microelectronics package  30  including a chip  32  that is coupled to a chip package  34  through electromagnetic signals  42 , as will now be explained in more detail. By coupling the chip  32  to the chip package  34  through electromagnetic signals  42 , a direct physical connection between the two is eliminated, which can simplify the fabrication of the package  30  and reduce the adverse inductive and capacitive effects associated with conventional bonding techniques. The chip  32  includes electronic circuitry  36  coupled to bonding pads  38  which, in turn, are coupled to first converters  40 . It is also possible for the circuitry  36  to be directly coupled to the converters  40  without the use of intervening bonding pads  38 . The circuitry  36  in the chip  32  may be a memory device, a processor, or any other type of integrated circuitry.  
         [0016]    Each first converter  40  receives a corresponding electric signal  41  from the circuitry  36  via the bonding pad  38 , and converts the electric signal into an electromagnetic signal  42 . The converter  40  then transmits the electromagnetic signal  42  to a corresponding second converter  44  located on the chip package  34 . The second converter  44  receives the electromagnetic signal  42  and converts it to a corresponding electric signal  45  that is applied to an inner lead  46 . The first and second converters  40  and  44  may also communicate in the opposite direction, with the second converter  44  converting the electric signal  45  received from the inner lead  46  to the electromagnetic signal  42  which the second converter  40  receives and converts into the electric signal  41  that is applied to the circuitry  36 . The first and second converters  40  and  44  may transmit and receive the electromagnetic signals  42  having a wide range of frequencies, including visible light and infrared frequencies. Furthermore, even though FIG. 3 only illustrates a pair of first converters  40  and a pair of second converters  44 , more or fewer converters may be employed as desired.  
         [0017]    The microelectronics package  30  includes an intermediate layer  48  disposed between the chip  32  and the chip package  34 . The intermediate layer  48  has suitable physical characteristics to allow the electromagnetic signals  42  to propagate through the intermediate layer, and may be air, an adhesive layer physically coupling the chip  32  to the chip package  34 , or other suitable materials, as will be appreciated by those skilled in the art. The intermediate layer  48  may include regions  49  disposed between the converters  40  and  44 , that are formed from different materials than the other portions of the intermediate layer  48 . In another embodiment, the intermediate layer  48  is omitted and the chip  32  is physically positioned on the chip package  34  with the converters  40 ,  44  adjacent one another. An encapsulation layer  51  is typically formed over the chip  32  once the chip is attached to the chip package  34 , sealing the chip and chip package to prevent moisture and other contaminants from affecting the operation of the package  30 .  
         [0018]    [0018]FIG. 4 is a functional and cross-sectional view of a microelectronics package  400  including a silicon chip  402  and a chip package  404  that are electrically coupled through infrared signals  406  according to another embodiment of the invention. Though not shown in FIG. 4, the silicon chip  402  includes circuitry and bonding pads and the chip carrier  404  includes inner leads as previously described for the corresponding components in FIG. 3. A first converter  407  is disposed on a first side  408  of the chip  402 , opposite a second side  410  of the adjacent side  412  of the chip package  404 . The first converter  407  operates as previously described for the converters  40  of FIG. 3 to convert the infrared signals  406  to electrical signals and visa versa. The second side  410  of the silicon chip  402  may physically contact the side  412  of the chip package  404  or an intermediate layer (not shown) may be disposed between the two.  
         [0019]    With the first converter  407  disposed on the first side  408  of the chip  402 , the infrared signals  406  propagate though the silicon chip  402  to a second converter  414  disposed on the side  412  of the package  404 . Because the chip  402  is silicon, which is substantially transparent to infrared signals, the infrared signals  406  propagate through the chip with a relatively low signal loss. If an intermediate layer is disposed between the silicon chip  402  and the chip package  404 , this layer must, of course, have suitable physical characteristics to allow the propagation of infrared signals. In the embodiment of FIG. 4, the chip  402  may be formed from materials other than silicon and the frequency of the signals  406  varied accordingly to allow the signals to propagate through the chip, as will be appreciated by those skilled in the art.  
         [0020]    [0020]FIG. 5 is a block diagram of a memory device  99  including a semiconductor memory circuit  101  formed on a chip  100  and coupled to a chip package  102  through electromagnetic signals  104 ,  105 , and  107  that include address, control, and data signals, respectively, for transferring data to and from the memory circuitry, as will now be explained in more detail. The memory circuitry  101  includes an address decoder  106 , a control circuit  108 , and read/write circuitry  110 , all of which are conventional and known in the art. The address decoder  106 , control circuit  108 , and read/write circuitry  110  are all coupled to a memory cell array  112  and are also coupled to an address bus  114 , a control bus  116 , and a data bus  118 , respectively. The memory device  99  may be a synchronous or asynchronous dynamic random access memory or static random access memory, as well as a packetized memory, such as an SLDRAM or RAMBUS device. Moreover, the device  99  need not be a memory device, but may be another type of integrated circuit.  
         [0021]    An address converter  120  receives electromagnetic address signals  104  and converts these signals into corresponding electric address signals that are applied to the address decoder  106  over the address bus  114 . A control converter  122  receives electromagnetic control signals  105  and converts these signals into corresponding electric control signals that are applied to the control circuit  108  over the control bus  116 . A read/write converter  124  operates during write operations of the memory device  99  to receive electromagnetic data signals  107  and convert these signals into corresponding electric data signals that are then applied to the read/write circuitry  110  over the data bus  118 . The read/write converter  124  also operates during read data transfers of the memory device  99  to receive electric data signals on the data bus  118  and convert these signals into corresponding electromagnetic data signals  107 . A package address decoder  126  is mounted on the chip package  102  adjacent the address decoder  106 , and receives electric address signals  133  and converts these signals into the electromagnetic address signals  104 , and a package control converter  128  mounted on the chip package adjacent the control converter  122  operates in the same way to generate the electromagnetic control signals  105  in response to electric control signals  132  applied to the chip package. A package read/write converter  130  is mounted on the chip package  102  adjacent the converter  124  and operates during write operations to receive electric data signals  131  and generate the corresponding electromagnetic data signals  107 . During read operations, the package read/write converter  130  receives the electromagnetic data signals  107  and generates the corresponding electric data signals  131 .  
         [0022]    The converters  120 - 124  on the chip  100  and converters  126 - 130  on the chip package  102  may communicate via any of a variety of suitable communication protocols, as will be understood by those skilled in the art. Moreover, each converter  120 - 124  and converter  126 - 130  may correspond to a number of converters with one converter handling conversion of a single address, control, or data signal. For example, where the data bus  118  is N bits wide, the converter  124  corresponds to N converters and the converter  130  similarly corresponds to N converters. Alternatively, a single converter  120 - 124  and  126 - 130  could multiplex and demultiplex a number of data, address, or control signals, as will also be appreciated by those skilled in the art.  
         [0023]    In operation, external circuitry (not shown) provides address, control and data signals to the respective leads  131 , 132 , 133  on the chip package  102 . These are transmitted to the respective chip package converters where the electric signals are converted into electromagnetic signals  107 , 105 , 104  and transmitted to the respective converters on the chip  100 . The converters on the chip may then convert the electromagnetic signals  107 , 105 , 104  to electric signals and transmit them over the address bus  114 , the control bus  116  and the data bus  118  to the address decoder  106 , the control circuit  108  and the read/write circuitry  110  respectively.  
         [0024]    In operation during a read cycle of the memory device  99 , external circuitry (not shown) provides a read command to the converter  128  in the form of the signals  132 , and the converters  128  and  122  operate in combination to apply the read command to the control circuit  108 . In response to the read command, the circuit  108  generates a plurality of control signals to control operation of the decoder  106 , circuitry  110 , and array  112  during the read cycle. The external circuit also provides a memory address to the converter  126  as the signals  133 , and the converters  126  and  120  operate in combination to apply the address bus  118  to the address decoder  106 . In response to the memory address, the address decoder  106  provides a decoded memory address to the memory-cell array  112  which, in turn, accesses the memory cells corresponding to the address and provides the data in the accessed cells to the read/write circuitry  110 . The read/write circuitry  110  then provides this data on the data bus  118  and the converters  124  and  130  operate in combination to output the data as the signals  131  from the chip package  102 .  
         [0025]    During a write cycle of the memory device  99 , external circuitry (not shown) provides a write command to the converter  128  in the form of the signals  132 , and the converters  128  and  122  operate in combination to apply the write command to the control circuit  108 . In response to the write command, the circuit  108  generates a plurality of control signals to control operation of the decoder  106 , circuitry  110 , and array  112  during the write cycle. The external circuit also provides data to the converter  130  as the signals  131 , and the converters  130  and  124  operate in combination to apply the data to the data bus  118 . The read/write circuitry  110  provides the data to the memory-cell array  112  which, in turn, places the data in addressed memory cells.  
         [0026]    [0026]FIG. 6 is a block diagram of a computer system  139  which includes the memory device  99  of FIG. 5. The computer system  139  includes a processor  140  for performing various computing functions, such as executing specific software to perform specific calculations or tasks. In addition, the computer system  139  includes one or more input devices  142 , such as a keyboard or mouse, coupled with the processor  140  to allow an operator to interface with the computer system  139 . Typically, the computer system  139  also includes one or more output devices  144  coupled to the processor  140 , such output devices typically being a printer or video terminal. One or more data storage devices  146  are also typically coupled to the computer processor  140  to store data or retrieve data from external storage media (not shown). Examples of typical storage devices  146  include hard and floppy disks, tape cassettes, and compact disk read only memories (CD-ROMs). The processor  140  is typically coupled to the memory device  99  through a control bus, a data bus, and an address bus to provide for writing to and reading from the memory device.  
         [0027]    It is to be understood that even though various embodiments and advantages of the present invention have been set forth in the foregoing description, the above disclosure is illustrative only, and changes may be made in detail, and yet remain within the broad principles of the invention. Therefore, the present invention is to be limited only by the appended claims.

Technology Classification (CPC): 7