Abstract:
A fusible link between metallization layers of a semiconductor device comprises a tungsten plug deposited in a via interconnecting two aluminum metallization layers.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention pertains to semiconductor device structures, in general, and to a semiconductor structure having a link between metallization layers that is selectively, permanently openable, in particular. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the manufacture of some semiconductor devices, it is often desirable to provide the ability to permanently program the device by the use of links that may be permanently opened up. Such links are typically on a single metallization layer of the semiconductor device. 
         [0003]    It is often desirable to utilize multilayer metallization paths in semiconductor devices. 
         [0004]    It would be desirable to provide a link that may be utilized between metallization layers in semiconductor devices and which may be selectively, permanently opened up. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with the principles of the invention, an openable link is provided for permanently programming connections in a semiconductor device. The openable link is provided between metallization layers of a semiconductor device and comprises a tungsten plug deposited in a via interconnecting two aluminum metallization layers. 
         [0006]    A semiconductor device in accordance with the principles of the invention comprises a silicon substrate and a plurality of metal conductor paths separated by silicon dioxide. Each metal conductor paths is in a different plane. A tungsten link is disposed in a via extending through the silicon dioxide and connecting the plurality of metal conductor paths. The tungsten link may be permanently opened thereby opening the electrical connection between the conductor paths by applying a predetermined current level for a predetermined time through the metal conductor paths and tungsten link. 
         [0007]    Further in accordance with the principles of the invention, each of the plurality of metal conductor paths comprises aluminum. 
         [0008]    A method for providing factory customizable semiconductor devices includes providing fuse links in each semiconductor device. The method comprises the step of: depositing a first metallization layer on the device; depositing one or more insulating layers on the first metallization layer; providing a via in the one or more insulating layers; depositing a tungsten plug in the via; depositing a second metallization layer on the one or more insulating layers. The tungsten plug is in contact with and provides electrical connection between the first and second metallization layers. By applying a predetermined current across the tungsten plug for a predetermined time, the tungsten plug opens up whereby the electrical connection provided by the tungsten plug is permanently opened up. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0009]    The invention will be better understood from a reading of the following detailed description of the drawing in which like reference designators are used to identify like elements in the various drawing figures, and in which: 
           [0010]      FIG. 1  is a cross-sectional view of a portion of a semiconductor device in accordance with the principles of the invention; 
           [0011]      FIG. 2  is the same cross-sectional view of  FIG. 1 , but showing the effect of applying current to a tungsten link in the semiconductor device; and 
           [0012]      FIG. 3  is illustrates the relationship of the time it takes to open a link in accordance with  FIG. 1  with respect to maximum current levels through the tungsten link. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  illustrates a portion of a representative semiconductor device  100  in accordance with the principles of the invention. Device  100  is permanently programmable in accordance with predetermined parameters. 
         [0014]    Device  100  includes a silicon substrate  101 . Various electronic components are formed on substrate  101  utilizing known manufacturing techniques and processes. Device  100  includes a plurality of insulating silicon dioxide layers  111 ,  113 ,  115 ,  117 ,  119 ,  121 ,  123 ,  125 . There are a plurality of metallization layers  103 ,  105 ,  107 ,  109  formed in the silicon dioxide layers. Each metallization layer may include one or more separate metallization paths such as paths  107   a ,  107   b . Each metallization path in the illustrative embodiment of the invention is aluminum. 
         [0015]    To provide for electrical connections between metallization layers, vias are formed in insulating silicon dioxide layers  115 ,  117 ,  119 ,  123  and tungsten plugs are deposited therein. Of particular interest to the present invention is tungsten plug  131 . 
         [0016]    By applying a relatively large current through tungsten plug or link  131 , plug or link  131  acts similarly to a fuse and opens up. 
         [0017]    Turning to  FIG. 2 , the result of the application of link opening electrical current from metallization path  103   a  to metallization path  107   a  across tungsten plug  131  is shown.  FIG. 2  was obtained from an electron microphotograph of the device  100 . The composition of blobs  137 ,  139 ,  141  is not known. However, what is known is that the electrical connection between metallization paths  103   a  to metallization path  107   a  has been opened. 
         [0018]      FIG. 3  illustrates the relationship between applying specific maximum current levels across the tungsten plug  131  with the time it takes for the tungsten plug to open breaking the electrical connection between metallization paths in different metallization layers. 
         [0019]    The invention has been described in conjunction with a specific illustrative embodiment. It will be understood by those skilled in the art that various changes, substitutions and modifications may be made without departing from the spirit or scope of the invention. It is intended that all such changes, substitutions and modifications be included in the scope of the invention. It is not intended that the invention be limited to the illustrative embodiment shown and described herein. It is intended that the invention be limited only by the claims appended hereto, giving the claims the broadest possible scope and coverage permitted under the law.