Abstract:
A wafer level integration module and method for forming are disclosed. A construction includes semiconductor functional device fabrication carried out after interconnect structures are processed on a bare wafer. Interconnect structures are formed in a first side of the wafer. An insulation layer is deposited on the first side of the wafer to insulate walls of the interconnect structures. A conductive layer is deposited on the insulation layer filling the interconnect structures so as to contact the insulation layer on the walls of the interconnect structures. The conductive layer forms interconnection contacts on the first side of the wafer and interconnection vias extending into the wafer. The first conductive layer including the interconnection contacts is exposed on the first side of the wafer and a semiconductor functional device is formed on the first side of the wafer. The semiconductor functional device is interconnected with the interconnection contacts during the fabricating. At least portions of the conductive layer associated with the interconnection vias are exposed from the second side of the wafer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a Continuation of U.S. patent application Ser. No. 12/991,545 entitled “WAFER LEVEL INTEGRATION MODULE WITH INTERCONNECTS” filed on Nov. 8, 2010, which is a National Stage Application of International Application PCT/SG2009/000164 filed on 6 May 2009, which claims priority to Singapore Application No. 200803479-5 filed 6 May 2008 by Gautham Viswanadam. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to an integrated circuit (IC) device and a method of manufacturing an IC device. More particularly, this invention relates to an IC device including one or more dies arranged in an array configuration within the defined wafer geometry, and to a method of manufacturing such an IC device. 
       BACKGROUND OF THE INVENTION 
       [0003]    With the miniaturization of electronic products, there is a continuous need to reduce the size of devices and to add more functionality so that more IC devices can be accommodated area on a substrate. In prior IC device fabrication, an IC device has a foot print approximately the size of a die of the IC device. Multiple dies with multiple interconnection pads on each die are processed together to form a semiconductor wafer first. The devices that have been arrayed on the wafer are then packaged in many ways. Two such conventional packaging methods include separating the dies from the arrayed wafer prior to packaging, and packaging the arrayed dies on the semiconductor wafer while the arrayed dies are still in wafer form. After packaging, the arrayed dies are then separated, and the IC devices under conventional packaging methods are typically used in the desired application as a wafer level package device. 
         [0004]    Referring to  FIG. 1A-1F , different configurations are shown of prior wafer level package and chip scale packages of IC devices.  FIG. 1A-1F  show typical IC devices that are fabricated in conventional wafer level configurations. For example the IC wafer level package devices that are shown in  FIG. 1A-1F  have interconnects formed after wafer configuration.  FIG. 1A  shows solder interconnects  4  formed after layers  3  of functional devices and I/O  2  are formed on a wafer substrate  1 .  FIG. 1B  shows holes  5  with conductive material that are processed for the I/O.  FIG. 1C  shows three dimensional connector for internally connecting backside with drilling to connect I/O pad.  FIG. 1D  shows I/O connector  7  along side wall after device fabrication.  FIG. 1E  shows holes processed like holes shown in  FIG. 1B  to connect I/O pad  8 .  FIG. 1F  shows holes processed like holes shown in  FIG. 1B  with solder ball and wire bonding  9 . Each individual device is packaged while the devices are still available in wafer form, prior to the wafer dicing process to obtain chip sized package. Many packaging process steps are added directly on a device wafer to realize these chip sized packages, which are of small form factor and reduced weight. However, the resulting IC device that is fabricated by the conventional processes is limited by I/O density as the chip size determines the package I/O density. 
         [0005]    For example, U.S. Pat. No. 6,040,235 and U.S. Pat. No. 6,117,707 disclose two processes that are conventional. U.S. Pat. No. 6,040,235 discloses an IC device having a footprint approximately the size of a die of the IC device. The steps for manufacturing the IC device in such a conventional process includes providing a wafer that includes multiple dies wherein each die includes multiple connection pads; sandwiching the wafer between two protective layers; cutting notches through one of the protective layers along outlines of the dies to expose portions of the connection pads; forming metal contacts on the surface of the notched protective layer that are electrically connected to the exposed portions of the connection pads; and separating the dies to form individual dies. The step of cutting notches is sequential and therefore is time-consuming, and also requires an accurate fixed angular shaped cutting blade for cutting the notches. As cutting produces debris, the cutting step has to be performed outside of a clean room to prevent contamination and damage of the device. A cut wafer is then transported into the clean room for further processing, making handling of the wafer cumbersome. Additionally, the two protective layers on a resultant die also increase the cost of fabrication. 
         [0006]    U.S. Pat. No. 6,117,707 discloses another IC device having multiple dies similar to that disclosed in U.S. Pat. No. 6,040,235. The dies are arranged in a stacked configuration. Interconnections between the dies of such an IC device are formed only after the stacks of dies are separated to form individualized IC devices. Accordingly, the process of interconnecting the dies in a device is performed on a device level and increases fabrication time. 
         [0007]    The conventional fabricating methods disclose packaging/interconnection of the device IOs to the external system after the devices are pre-fabricated, which limits the number of IOs and functionality of device per square of silicon area. Also additional processes and packaging are required for routing of the interconnection lines across or within the chip to the IOs located peripherally around the chip to enable external interconnections. It is well known in the art of semiconductor industry that handling of devices once it is fabricated is a critical step. Risk involved in loosing wafer yields is highly dependent on the amount of handling and process stages the device wafer undergoes after the wafer reaches packaging and assembly houses. 
         [0008]    Such conventional fabrication methods typically require additional device packaging methods after the devices are fabricated at the semiconductor wafer fabrication facilities which results in exposing the processed device to increased risk of contamination and damage. Therefore, there is a need for a method of fabricating a functional IC device that alleviates the problems associated with prior fabrication methods. 
       SUMMARY OF THE INVENTION 
       [0009]    An aspect of the invention includes a method of fabricating a wafer level integration module according to a construction whereby semiconductor functional device fabrication is carried out only after interconnect structures are processed on a bare wafer. The interconnect structures can be formed in a first side of the wafer. A first insulation layer on the first side of the wafer can be deposited so as to insulate walls of the interconnect structures. A first conductive layer can be deposited on the insulation layer so as to fill the interconnect structures. The conductive layer is deposited so as to contact the first insulation layer on the walls of the interconnect structures and to form interconnection contacts on the first side of the wafer and interconnection vias extending into the wafer. The first conductive layer can also form interconnection contacts on the first side of the wafer. A semiconductor functional device can be fabricated on the first side of the wafer so as to be interconnected with the interconnection contacts during the fabricating thereof. At least portions of the first conductive layer associated with the interconnection vias can be exposed from the second side of the wafer. 
         [0010]    In an embodiment the conductive layer can be a high temperature conductive film. The conductive interconnect film may be exposed by chemical mechanical polishing. A substrate may be provided and attached to the first side of conductive interconnect film to protect the first side of the wafer. A conductive material may be deposited to the second layer conductive layer for contact with external devices. 
         [0011]    In an embodiment the semiconductor functional device may comprise depositing additional layers forming the functional device. The additional layers may form a plurality of functional devices. The additional layers may be formed in a stack formation. The plurality of dies may be formed on the wafer. The dies may be separated along separation zones the plurality of dies. The functional device may be a transistor and the plurality of functional devices may be transistors. 
         [0012]    In an embodiment the functionality of the semiconductor device may be tested after fabrication of the device tested. The testing of the semiconductor device comprises forming test pads on the first side of the wafer. The test pads may be removed after testing and before fabrication of a subsequent device. A fourth insulation layer may be deposited to protect the second conductive layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    In order that embodiments of the invention may be fully and more clearly understood by way of non-limitative example from the following description taken in conjunction with the accompanying drawings in which like reference numerals designate similar or corresponding elements, regions and portions, and in which: 
           [0014]      FIG. 1A-1F  shows different configurations of prior wafer level package and chip scale packages of IC devices. 
           [0015]      FIG. 2A-2R  shows a cross-sectional view of a silicon wafer during processing steps of fabricating a functional IC device on a silicon wafer in accordance with an embodiment of the invention; and 
           [0016]      FIG. 3A-3B  shows a cross-sectional view of the processed silicon wafer of  FIG. 2A-2R  showing fabrication of a functional IC device such as a transistor device in accordance with an embodiment of the invention; 
           [0017]      FIG. 4A-B  shows a cross-sectional view of the processed silicon wafer of  FIG. 2A-2R  showing fabrication of two functional IC devices such as two transistor devices in accordance with an embodiment of the invention; 
           [0018]      FIG. 5-7  shows cross-sectional views of a processed silicon wafer of  FIG. 2A-2R  with multiple layers of functional IC devices; 
           [0019]      FIG. 8A-C  shows cross-sectional views of a processed silicon wafer during processing steps of fabricating a silicon on insulation (SOI) structure in accordance with an embodiment of the invention; and 
           [0020]      FIG. 9  shows a flow chart of the processing steps of a method of fabricating a functional IC in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    According to an embodiment of the present invention, there is provided a method  200  of manufacturing an integrated circuit (IC) device  90 . According to the method, a wafer  10  is first provided having a first or top surface and a second or bottom surface. The wafer may be a blank polished or unpolished silicon wafer or the like. High aspect ratio micro-structures  16  that are specifically designed to provide a die level interconnect configuration and mapping, are provided on the first blank surface  12  of the wafer. The wafer with pre-formed conductive interconnect microstructures  16  are further processed for device fabrication, for example, at the wafer fabrication facilities. Once the front side  12  devices are fabricated, the silicon material  20  is then removed from a second side  14  of the device wafer  10 , opposite the first side, to expose the high temperature conductive interconnect microstructures  16 . Contacts are formed on the second side of the device wafer using conductive metal. These contacts are electrically connected to the interior of the microstructures and thereby electrically connect with the functional device  26 . The dies  90 ( 1 ), 90 ( 2 ) are separated along the separation zones  88  between the dies to produce individualized functional and packaged dies, each of which serves as a fully packaged IC device  90 . Embodiments of the invention calls for a predetermined I/O pad distribution on the raw silicon wafer prior to the device fabrication process is started. A high temperature conductive interconnect film is deposited on a raw silicon wafer with necessary dielectric insulation components to prevent electrical current leakage and circuit shorting to silicon substrate in use. Once the interconnections are made, the device under application is fabricated and the wafer further processed for interconnecting the same to the external printed circuit board. where the packaging interconnections are pre-formed on the blank wafer first prior to packaging. 
         [0022]    A method and apparatus for manufacturing an integrated circuit (IC) device  90  is disclosed. A wafer  10  is first provided having a first or top surface and a second or bottom surface. The wafer may be a blank polished or unpolished silicon wafer or the like. High aspect ratio micro-structures  16  that are specifically designed to provide a die level interconnect configuration and mapping, are provided on the first blank surface  12  of the wafer. The wafer with pre-formed conductive interconnect microstructures  16  are further processed for device fabrication, for example, at the wafer fabrication facilities. Once the front side  12  devices are fabricated, the silicon material  20  is then removed from a second side  14  of the device wafer  10 , opposite the first side, to expose the high temperature conductive interconnect microstructures  16 . Contacts are formed on the second side of the device wafer using conductive metal. These contacts are electrically connected to the interior of the microstructures and thereby electrically connect with the functional device  26 . The dies  90 ( 1 ), 90 ( 2 ) are separated along the separation zones  88  between the dies to produce individualized functional and packaged dies, each of which serves as a fully packaged IC device  90 . 
         [0023]    With reference to  FIG. 2A-2R , a cross-sectional view of a silicon wafer during processing steps of fabricating a functional IC device on a silicon wafer in accordance with an embodiment of the invention.  FIG. 2A  is a schematic cross section of a blank silicon wafer  12 , which may be polished, unpolished, P-type, N-type, having a desired orientation for each application, or the like. It will be appreciated that other wafers would be suitable, such as for example a galium arsenide wafer, gallium indium wafer, germanium wafer, and the like.  FIG. 2B  shows the wafer  12  with microstructures  16  formed for the purpose of interconnections for the device under fabrication. The microstructures may have a dimension that is suitable for the specific application, for example, the microstructures may have an opening (X,Y) geometry of 0.5 μm (micron), and a depth of 10 μm (micron) which may be, for example, a minimum in an embodiment. The microstructures may be formed using any silicon removal method that is known in the art of semiconductor industry.  FIG. 2C  shows the wafer with insulated, passivated layer  18 . The passivation layer  18  may be a material such as SiO2, SiN, or the like. The passivation layer on the microstructures is to isolate the silicon walls of the microstructures from the conductive interconnect films/materials  20  shown in  FIG. 2D . The deposition of the passivation/insulation materials  18  may be performed using processes that are known in the art of semiconductor industry. The wafer is deposited with a conductive interconnect film  20  such as a high temperature interconnect film or material, or the like that is deposited at the microstructure walls for the purpose of providing interconnections with device under fabrication. These conductive films or materials  20  are deposited using methods that are known in the art of semiconductor industry. Doped conductive polysilicon or the like may be the material for electrical conductivity.  FIG. 2E  shows the wafer with a final passivation or insulation layer  22  that is deposited to protect the conductive interconnect films at the microstructures that are pre-formed for the purpose of interconnections with device under fabrication. The passivation layer  22  may be a material such as SiO2, SiN, or the like. It will be appreciated that in this embodiment the final passivation layer is to protect and provide additional protection of the underlying structures, however, in other embodiments since an oxide may form naturally over the polysilicon without any additional steps which acts to protect, the deposition of the passivation layer  22  may not be necessary. 
         [0024]      FIG. 2F  shows the processed wafer  24  after the removal of excess passivation films or materials  22  and excess conductive films or materials  20  that are deposited on the first side of the blank wafer  10  to expose the high temperature conductive interconnect film microstructures. The excess films or materials are removed by processes that are known in the art of semiconductor industry. 
         [0025]      FIG. 2G  shows the processed wafer  30  after at least one functional device is fabricated by layers  40 . In this embodiment, the functional device shown is a transistor, however it will be appreciated that the functional device may be configured differently and take different forms. For example the functional device may be transistors, resistors, capacitors, inductors, micro electro mechanical systems (MEMS), surface acoustic wave (SAW) devices, or the like. The layers  40  of the functional device are fabricated over the pre-formed microstructures  24 . The number of layers, for example layers  38 , 36 , 34 , 32  shown for the transistor example, depend on the type of device fabricated and the particular device design and in accordance with process guide lines. For example, the transistor devices are internally interconnected with the interconnection contacts located at the pre-formed microstructures of the wafers. The transistor device fabrication may be carried out at the wafer and device fabrication facilities.  FIG. 2H  shows test pads  94  formed on the front side of the wafer. The functionality of the fabricated device may be tested by providing corresponding test pads  94  on the front side of the wafers. The test pads may be a metal and formed in conventional manner. In an embodiment, after testing the functionality of the device the test pads may be removed, in particular if another device is to be fabricated on top of the tested device, since the metal of the test pads may not withstand the high temperatures in the fabrication process of the next device. 
         [0026]      FIG. 2I  shows the processed wafer that is attached with another substrate  70  on the front side of the silicon wafer to cover the functional device. The substrate  70  protects the functional device that has been fabricated on the front side from the handling, environment and other hazards that may damage the functional device. The protection substrate that is used on the first side of the device wafers could be of silicon, ceramic, glass, plastic molded or any substrate that is suitable for use in semiconductor device applications. 
         [0027]      FIG. 2J  shows the processed silicon wafer after the removal of excess silicon materials from the second side of the wafer, to expose the insulation or passivation films  18  that are deposited at the pre-formed microstructures on the front side of the wafer. The passivation film material exposed may be SiO 2 , SiN, or the like as discussed. The silicon removal processes is any suitable process that is well known in the art of semiconductor industry. In  FIG. 2K , the processed silicon wafer after the deposition of new insulation/passivation films  74  on the second side of the silicon wafer to match and merge with the exposed insulation/passivation films  74  on the second side of the silicon device wafer. These films will ensure complete insulation of exposed silicon on the planar surface of the second side of the silicon wafer. In  FIG. 2L  the processed wafer is shown after patterning  76  and removal of insulation/passivation films to expose the high temperature conductive interconnection films  20  at the pre-formed microstructures from the second side of the wafer.  FIG. 2M  shows the processed wafer after the deposition of conductive interconnect films  78  at the second side of the silicon wafer to enable interconnections from the active devices to the second side of the silicon wafer. The conductive interconnect films may be a conductive material such as TiNi, Al, Cu, Au, and the like.  FIG. 2N  shows the processed wafer after the deposition of insulation/passivation films  80  at the planar surface of the second side to protect the interconnect films that form the interconnection between the active device to the external assemblies. Such insulation/passivation films may be materials such as SiO 2 , SiN, PI, BCB and the like.  FIG. 20  shows the processed wafer after the opening of insulation/passivation film via  82  to expose the interconnect films that form the part of interconnection channels with the active devices.  FIG. 2P  shows the processed wafer after the suitable conductive materials or films  84  that are deposited at the exposed inner interconnect films at the passivation/insulation opened via, to facilitate the board level interconnections during the external assemblies.  FIG. 2Q  shows the processed wafer after the deposition of solder materials  86  at the I/O bond pads to facilitate assembly of the device to the external circuit boards. 
         [0028]    In  FIG. 2R  a schematic cross section of the processed wafer after the dicing of the arrayed devices  90 ( 1  . . . n) to separate each device that has been interconnected to the corresponding I/O at the planar surface of the second side of the device. 
         [0029]      FIG. 5-7  shows cross-sectional views of a processed silicon wafer of  FIG. 2A-2R  with multiple layers of functional IC devices.  FIG. 3A-3B  shows a cross-sectional view of the processed silicon wafer of  FIG. 2A-2R  showing fabrication of a functional IC device such as a transistor device in accordance with an embodiment of the invention in greater detail than in  FIG. 2G .  FIG. 4A-B  shows a cross-sectional view of the processed silicon wafer of  FIG. 2A-2R  showing fabrication of two functional IC devices such as two transistor devices in accordance with an embodiment of the invention in more detail than shown in  FIG. 5 .  FIG. 6  and  FIG. 7  show three and four functional IC devices, respectively, in accordance with embodiments of the invention. It will be appreciated that any number of functional devices may be configured in stack configuration. Three dimensional stack devices  50 ,  130 ,  150  can be fabricated using this interconnect microstructure base wafer. Each device that may be same or different can be fabricated by deposition a layer of epitaxial silicon films  40 , 60 , 140 , 160  over the previously fabricated device and wafer. Thereby multiple functional devices in stack form are realized before the pre-formed microstructure wafer is processed for backside interconnections. The functionality of each single layer device and devices may be tested for functionality by depositing and patterning metal layers at the test pad locations and later removing the test pads prior to the second level devices are stacked and fabricated on the devices tested. 
         [0030]    Embodiments of the invention may be configured in a silicon on insulation (SOI) structure after the microstructures are fabricated, as shown in  FIG. 8A-C . This is formed by depositing a thin layer of silicon on the already deposited and exposed oxide or insulation thin films, giving rise to SOI structures of material such as SiO2 and the like. The SOI substrate is fabricated first on the pre-formed microstructures and later the devices are fabricated. 
         [0031]    A method  200  of the invention in accordance with an embodiment is shown in the flow chart of  FIG. 9 . The steps of front side process  210  and back side process  230  are shown on a wafer provided  202 . The front side process comprises forming microstructures  210  and then deposition of an insulation layer  214 , conductive interconnect film  216 , such as high temperature conductive film, and second insulation layer  218 . The conductive interconnect film is exposed  220  by for example chemical mechanical polishing (CMP). The fabrication of the functional device is performed  222 . After device fabrication, the backside of the wafer is processed  230 . The back side process comprises protecting the frontside by attaching another substrate  232 , and exposing the backside microstructures  234 . An insulation or passivation layer is deposited  236  and the conductive interconnect layer is exposed  238 . Conductive interconnect film is deposited  240  for example patterned on the exposed interconnect film at the microstructures. Insulation or passivation film is deposited  242  to protect the conductive interconnect film. Inner conductive films are exposed  244  by for example etching process. Conductive material is deposited  246  for facilitating connection of the functional IC device to external circuitry. In an embodiment, after the device fabrication  222  and before the backside process, the functionality of the functional device may be tested  224 , 226 . Test pads may be formed  224  on the front side of the wafer and the device may be tested  226 . In an embodiment, in particular if another device is to be fabricated on the tested device, the test pads may be removed  228  after testing the functionality of the device since the material of the test pads may not withstand the high temperatures in the fabrication process of the next device. It will be appreciated another device may be fabricated, and any number of devices may be fabricated  222  accordingly, prior to the backside process  230 . 
         [0032]    Embodiments of the invention, the interconnect microstructures are formed first on the blank silicon wafer, and then the device is fabricated over the preformed interconnect microstructures. 
         [0033]    With this configuration, the device design may be optimized with minimal routing and ease of design while minimizing noise, maximizing device speed, and maximizing I/O pad flexibility. Additionally, the device configuration allows more functionality for reduced silicon area which results in minimized silicon cost since no peripheral bond pads are required. This allows for minimizing size of devices and silicon costs as the scribe line geometry is minimized. The functional space for the devices or more chips per wafer are maximized which also minimizes cost. As no bond pads are exposed, there are no atmospheric corrosion issues, which increase device reliability. Additionally, as no three-dimensional channels at the backside of the device are required, no thin film stress related to the three dimensional films is introduced. 
         [0034]    Embodiments of the invention may be adapted to any device of interest and no limitations are envisaged. The thickness of the devices may be minimized, for example in the order of 10 to 50 micron with minimal interconnect channels resulting in maximized device speed, and minimized overall form factors. This approach allows fabrication of build up layers using multi layer metal, passivation layers at the back side of the device within the wafer fabrication facilities, which minimizes risk of wafer damage or contamination. This results in increased wafer yields as no handling or assembly processes are carried out on the processed wafers. Embodiments of the invention allows pre-fabrication of standard gate I/O microstructures on the wafers prior to the device fabrication, allowing a flexibility to design and use only the required I/O microstructures for designs such as gate array metal interconnects that are popular in ASIC device fabrication. Multiple devices using same or different functions can be processed on top of each previously fabricated device wafer in stack format using an epitaxial silicon intermediate film, if required. Required I/Os may also be processed as an integral part of the device fabrication that may facilitate the multiple stack die interconnections to the second side of the active device wafer. 
         [0035]    Embodiments of the present invention virtually eliminates the packaging and assembly activities for the devices as the interconnections are carried out prior to the device fabrication during the wafer fabrication process at the wafer fabs. Embodiments of the invention offer advantages such as elimination of the requirement of bond pads at the peripheral of the devices. This gives rise to reduced silicon area and more functionality on a given silicon size, thus reducing the silicon cost. Another advantage is that circuitry for interconnection of the IOs with in the chip is minimized, which improves speed of the device and contributes to minimizing in interconnect routing noise. This contributes to the overall improvement on performance of the devices. Additionally, since no packaging such as die bonding, wire bonding, and the like is required, the cost on packaging is completely eliminated. As the I/O are predetermined before the devices are fabricated, there is no limitation on the I/O pitch with in the chip and hence high density interconnect chips can be fabricated using this process. An embodiment of the invention allows all the primary interconnections and test pads to be located within the chip without running any interconnect lines to device peripherals. Since no peripheral bond pads are involved in embodiments of invention, the scribe lines can be minimized, such as for example down to as small as 20 to 30 micron, which will allow additional silicon for additional device accommodation, thus further reducing the cost of silicon per device. The resulting reduction in street between the devices fits well into the existing laser dicing processes with optimal silicon scribe areas. 
         [0036]    While embodiments of the invention have been described and illustrated, it will be understood by those skilled in the technology concerned that many variations or modifications in details of design or construction may be made without departing from the present invention.