Abstract:
Disclosed are a vertical-type capacitor and a formation method thereof. The capacitor includes a first electrode wall and a second electrode wall perpendicular to a semiconductor substrate, and at least one dielectric layer on the substrate to insulate the first electrode wall from the second electrode wall. The first electrode wall includes a plurality of first conductive layers and a plurality of first contacts, the plurality of first conductive layers being interconnected with each other by each of the plurality of first contacts. The second electrode wall includes a plurality of second conductive layers and a plurality of second contacts, the plurality of second conductive layers being interconnected with each other by each of the plurality of second contacts.

Description:
[0001]     This application claims the benefit of priority of Korean Application No. 10-2004-0114797, filed on Dec. 29, 2004, which is incorporated by reference herein in its entirety.  
       BACKGROUND  
       [0002]     1. Technical Field  
         [0003]     The present invention generally relates to a semiconductor device manufacturing technology, and particularly to a capacitor structure formed in a semiconductor device, and a fabrication method thereof.  
         [0004]     2. Description of the Related Art  
         [0005]     A semiconductor device such as an integrated circuit (IC) generally has electronic circuit elements such as transistors, capacitors, and resistors fabricated integrally on a piece of semiconductor material. The various circuit elements are connected through conductive connectors to form a complete circuit that can contain millions of individual circuit elements. In particular, capacitors are used extensively in electronic devices for storing electric charge. Capacitors essentially comprise two conductive plates separated by an insulator such as a dielectric layer.  
         [0006]     Advances in technologies of integrating semiconductor devices have resulted in a reduced overall size of IC elements. A variety of techniques have been explored to minimize the occupied surface area of a capacitor while maintaining sufficient capacitance. One technique employs an ultra-thin film of dielectric material as a capacitor dielectric layer, but it may incur device reliability problems. Another technique utilizes a new dielectric material having a higher dielectric constant, but it may require additional processes for adapting normal semiconductor device manufacturing processes for the new material.  
         [0007]     Meanwhile, a metal-insulator-metal (MIM) capacitor, as shown in  FIG. 1 , is often used in integrated circuits. A MIM capacitor is a particular type of capacitor having two metal plates sandwiching a dielectric layer. The two metal plates and the dielectric layer are parallel to a semiconductor substrate.  
         [0008]     To form a MIM capacitor, a bottom electrode  13  and a dielectric layer  14  are formed and patterned, in sequence, on an interlevel dielectric layer  12  that insulates an upper metal layer (now shown) and a lower metal layer  11  on a semiconductor substrate  10 . A top electrode  15  is then formed by depositing a conductive material, and lithographically patterning and etching the conductive material. Thus, the MIM capacitor consists of the bottom electrode  13 , the dielectric layer  14 , and the top electrode  15 .  
         [0009]     Because the metal plates are parallel to the substrate, a conventional MIM capacitor can be several hundred micrometers wide, which is much larger than a transistor, a memory cell, or any other elements. Thus, conventional MIM capacitors are difficult to integrate in highly integrated semiconductor devices.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention provides a vertical-type capacitor structure, which can be formed by a normal metallization process, and does not require separate capacitor formation processes. The vertical-type capacitor structure occupies a minimum surface area of a semiconductor substrate and thus enables higher integration.  
         [0011]     A capacitor consistent with an embodiment of the present invention includes a first electrode wall and a second electrode wall perpendicular to a semiconductor substrate, and a at least one dielectric layer on the substrate to insulate the first electrode wall from the second electrode wall. The first electrode wall includes a plurality of first conductive layers and a plurality of first contacts, the plurality of first conductive layers being interconnected with each other by each of the first plurality of contacts. The second electrode wall includes a plurality of second conductive layers and a plurality of second contacts, the plurality of second conductive layers being interconnected with each other by each of the plurality of second contacts.  
         [0012]     The present invention also provides a method for forming a vertical-type capacitor, including the steps of: (a) forming a dielectric layer; (b) forming at least two trenches in the dielectric layer, the at least two trenches being separated from each other; and (c) filling a conductive layer in the at least two trenches.  
         [0013]     Consistent with the present invention, steps (a) to (c) may be repeated to form at least two electrode walls perpendicular to a main surface of the substrate, each electrode wall having multiple conductive layers stacked over each other. The corresponding conductive layers of the at least two electrode walls are separated from each other the corresponding dielectric layers. In addition, the conductive layers of each of the at least two electrode walls are interconnected by a plurality of contacts. The contacts are formed by forming a contact hole in each of the at least two trenches, and filling the conductive layer in the contact holes in the at least two trenches. The conductive layer may comprise Cu or other suitable metals.  
         [0014]     These and other aspects of the present invention will become evident by reference to the following description of the invention, often referring to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0015]     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the features, advantages, and principles of the invention.  
         [0016]     In the drawings,  
         [0017]      FIG. 1  is a cross-sectional view of a conventional metal-insulator-metal capacitor structure.  
         [0018]      FIG. 2  is a perspective view of a vertical-type capacitor structure consistent with the present invention.  
         [0019]      FIG. 3  is a top view of a vertical-type capacitor structure consistent with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]     Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
         [0021]      FIG. 2  is a perspective view of a vertical-type capacitor structure consistent with an embodiment of the present invention, and  FIG. 3  is a top view of the vertical-type capacitor structure.  
         [0022]     A first interlevel dielectric layer (not shown) is firstly formed on a semiconductor substrate (not shown). Then, a trench (not shown) is formed in the first interlevel dielectric layer by an etching process. A conductive material, such as copper (Cu), is formed on the first interlevel dielectric layer, filling the trench. Subsequently, the substrate is planarized to remove the conductive material by chemical-mechanical polishing (CMP), retaining a portion of the conductive material to form a first conductive layer  21 , as shown in  FIGS. 2 and 3 .  
         [0023]     The semiconductor substrate may include a variety of electronic circuit elements, as well as isolations such as shallow trench isolations that electrically isolate the electronic circuit elements from each other.  
         [0024]     First conductive layer  21  may be formed in the isolation regions to minimize parasitic capacitances between the circuit elements.  
         [0025]     Aluminum or aluminum alloys, which have low contact resistivity and relatively simple formation processes, are conventional conductive materials. However, as the integration density of semiconductor devices is increased, aluminum metallization may result in junction spiking and electromigration problems. Accordingly, alternative materials having a lower electric resistivity and adapted for a higher operational speed of the devices has been developed. For example, compared to aluminum and aluminum alloys, copper has a relatively low electric resistivity and no electromigration problems.  
         [0026]     However, because copper rapidly diffuses into silicon or other metal layer and is a refractory material, copper metallization layer is typically formed by a damascene process, particularly a dual damascene process. A dual damascene process for forming copper connectors involves forming a trench and via hole in a dielectric layer, filling the trench and via hole with copper, and removing or planarizing a portion of copper over the dielectric layer to form a copper interconnections.  
         [0027]     Therefore, first conductive layer  21  may comprise copper formed by a dual damascene process, which includes forming a trench and an underlying via hole, and simultaneously filling the trench and the via hole with a conductive material (e.g., copper) to form an interconnect line and an underlying via plug.  
         [0028]     After the formation of first conductive layer  21 , a second dielectric layer (not shown) is formed on the first dielectric layer and first conductive layer  21 . Then, the second dielectric layer is etched to form a trench and a contact hole exposing first conductive layer  21 . In particular, the trench and contact hole in the second dielectric layer preferably have the same dimension as first conductive layer  21 .  
         [0029]     Then, a barrier metal is deposited over the substrate, and another conductive material is then formed over the substrate, followed by a CMP process that planarized the substrate to retain a portion of the conductive material in the trench and contact hole in the second dielectric layer. Consequently, a first contact  22  and a second conductive layer  23  are formed and have the same dimension as first conductive layer  21 .  
         [0030]     After the formation of second conductive layer  23 , a third dielectric layer (not shown) is formed over the substrate, and a trench and a contact hole is formed therein by an etching process. The trench and contact hole in the third dielectric layer expose second conductive layer  23  and have the same dimension as second conductive layer  23 .  
         [0031]     Subsequently, a barrier metal is formed over the substrate, and a conductive material is formed on the barrier metal layer. A CMP process is performed to remove a portion of the conductive material and the barrier metal, with a portion of the conductive material and the barrier metal remaining in the trench and the contact hole in the third dielectric layer to form a second contact  24  and a third conductive layer  25 . Second contact  24  and third conductive layer  25  have the same dimension as first conductive layer  21 , first contact  22 , and second conductive layer  23 .  
         [0032]     A third contact  26  and a fourth conductive layer  27  are formed in the same manner as second contact  24  and third conductive layer  25 . Namely, a fourth dielectric layer (not shown) is formed over the substrate, and a trench and contact hole are formed therein and have the same dimension as third conductive layer  25 . Then, a barrier metal and a conductive material are formed and polished by a CMP process to form third contact  26  and fourth conductive layer  27 . Third contact  26  and fourth conductive layer  27  have the same dimension as third conductive layer  25 .  
         [0033]     As shown in  FIGS. 2 and 3 , first conductive layer  21 , first contact  22 , second conductive layer  23 , second contact  24 , third conductive layer  25 , third contact  26 , and fourth conductive layer  27  are stacked over each other to form a pattern having separate portions isolated by the first through the fourth dielectric layers. Each portion may be in a comb shape having multiple branches.  FIGS. 2 and 3  show a first electrode wall labeled as CTM and a second electrode wall labeled as CBM each comprising a portion of the pattern of first conductive layer  21 , first contact  22 , second conductive layer  23 , second contact  24 , third conductive layer  25 , third contact  26 , and fourth conductive layer  27  stacked over each other. The first and second electrode walls CTM and CBM are isolated from each other by the first through fourth dielectric layers. Thus, the first and second electrode walls CTM and CBM and the first to fourth dielectric layers form a vertical-type capacitor. Because the first and second electrode walls are perpendicular to the substrate, the surface area occupied by the vertical-type capacitor is minimized. In addition, the capacitance of the vertical-type capacitor can be controlled by adjusting the distance between the first and second electrode walls.  FIGS. 2 and 3  show that each of the first and second electrode walls has two branches that are interdigitated with each other. However, the first and second electrode walls can respectively comprise more than two branches, thus forming a greater capacitance of capacitor in a relatively simple manner.  
         [0034]     Conductive layers  21 ,  23 ,  25 , and  27 , and contacts  22 ,  24 , and  26  can be formed simultaneously with other metal contacts or interconnections in a normal multi-level metallization process. Accordingly, the present invention does not require separate processes for forming the vertical-type capacitor.  
         [0035]     While the first and second electrode walls consist of four conductive layers as shown in  FIGS. 2 and 3 , the number of conductive layers is not so limited. It should be understood that the first and second electrode walls could comprise more or less than four conductive layers, depending on the design rule of semiconductor devices. The effective areas of the vertical-type electrode walls CTM and CBM increase as the number of metallization layers increases, as a result of which the capacitance of the vertical-type capacitor also increases.  
         [0036]     As shown in  FIGS. 2 and 3 , the first and second electrode walls CTM and CBM respectively have a comb-form engaged with each other and are separated by the dielectric layers.  FIGS. 2 and 3  show that the first and second electrode walls respectively have two branches that are interdigitated with each other. However, the first and second electrode walls can respectively comprise more than two branches, thus forming a greater capacitance of capacitor in a relatively simple manner.  
         [0037]     In addition, while the conductive layers and contacts are formed by Cu dual damascene method, in the above-described embodiment, it should be understood that other materials, such as aluminum or tungsten, may be used as well.  
         [0038]     While the invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.