Abstract:
A microelectronic contact structure, e.g., a contact structure for a capacitor electrode of a DRAM, comprises a first dielectric layer on a substrate, a conductive region disposed on a first dielectric layer, a second dielectric layer on the first dielectric layer and contacting the conductive region at a sidewall of the conductive region, and an etch-stopping dielectric region disposed on the conductive region and having a sidewall in contact with the second dielectric layer. The etch-stopping dielectric region extends laterally beyond the sidewall of the conductive region and has an etching selectivity with respect to the second dielectric layer. A third dielectric layer is disposed on the second dielectric layer and etch-stopping dielectric region. A conductive plug extends through the third dielectric layer and along the sidewall of the etch-stopping dielectric region. For example, the conductive plug may contact a conductive pad formed on a source/drain region of an underlying substrate, and a capacitor may be disposed on the conductive plug, thus providing a capacitor memory cell.

Description:
RELATED APPLICATIONS 
     The present application is a divisional U.S. application Ser. No. 10/172,760, filed Jun. 14, 2002, now U.S. Pat. No. 6,710,466 entitled Method of Fabricating Integrated Circuit Having Self-Aligned Metal Contact Structure, the disclosure of which is hereby incorporated herein by reference. 
    
    
     RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 2001-34139, filed on Jun. 16, 2001, the contents of which are herein incorporated by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to integrated circuit devices and fabrication methods, and more particularly, to self-aligned contact structures and methods of fabricating the same. 
     As integrated circuit memory devices, such as dynamic random access memories (DRM) have become more highly integrated and their storage capacity has expanded, the size of features on chips have generally decreased. For example, processes performed according to a design rule less than 0.13 μm have recently been developed for DRAM cell manufacture. Processes for reducing the size of peripheral circuit features have also been developed. 
     However, a reduction in the design rule and chip size of DRAM cells can result in a failure to establish a sufficient process margin and desirable operational characteristics for devices. To solve these problems, processes for forming a capacitor-over-bit (COB) line structure, a self-aligned contact plug, a P+/N+ bit-line coincident-contact plug and a bit-line stud pad, have been developed. 
     In particular, for a DRAM cell with a COB structure, a one-cylinder storage node (OCS) structure has been used with a dielectric layer having a high dielectric constant to obtain sufficient cell capacitance. Also, active areas of a capacitor electrode have been increased by increasing the height of a storage node. However, increased storage node height can produce an undesirably large step difference between a cell domain and peripheral circuit domain. This can reduce a photolithography process margin for formation of a metal interconnection. Therefore, a process including forming an interlayer dielectric layer after the upper electrode of a capacitor is formed and planarizing the interlayer dielectric layer through a chemical mechanical polishing (CMP) process, has been suggested. 
     However, due to the height of the storage node and use of the CMP process, the thickness of the interlayer dielectric layer to be etched can exceed 3 μm when a contact hole for a metal contact plug is formed. If the thickness of the interlayer dielectric layer is increased, the contact hole may not be completely open due to a loading effect arising from differences in etching selectivity between a wide contact hole and a narrow contact hole, and between domains having a thick contact hole and a thin contact hole. In particular, the contact hole may become narrower towards the bottom, and therefore, a contact area between the metal contact plug and a bit line may become smaller, thereby potentially increasing contact resistance. An increase in contact resistance may increase signal degradation and increase power consumption. Further, as the design rule decreases, a short due to reduced alignment margin between the metal contact plug and a gate electrode can occur. Chip size of a DRAM cell can also be reduced by forming a P+/N+ contact plug of a bit-line contact plug instead of the existing contact plug when a sense amplifier is formed. 
     As described above, to solve the problems caused by a phenomenon in which the thickness of the interlayer dielectric layer increases when the contact hole is formed and apply the P+/N+ bit line coincident-contact plug, the metal contact plug can be made on the bit line stud pad by forming the bit line stud pad in contact with the bit line contact plug. In this case, as design rules decrease, the width of the bit line stud pad may need to be increased to secure an adequate alignment margin between the metal contact plug and the bit line stud pad. However, an increase in the width of the bit line stud pad can reduce a margin in the depth of focus for the photolithography used on patterning the bit line stud pad. As a result, problems, such as bridging, can occur. 
     SUMMARY OF THE INVENTION 
     According to some embodiments of the present invention, an integrated circuit comprises conductive patterns formed on a semiconductor substrate. Dielectric patterns are disposed between the conductive patterns on the substrate, each having a cross-section with an upside-down T shape and having greater thickness than the conductive patterns. A nitride film liner lines trenches defined by the conductive patterns and the dielectric patterns. A dielectric layer is disposed on the nitride film liner, filling the trenches. At least one metal contact plug passes through the dielectric layer and the nitride film liner and is in contact with at least one of the conductive patterns. 
     According to further embodiments of the present invention, an integrated circuit comprises conductive patterns on a semiconductor substrate in first and second domains. Dielectric patterns are disposed between the conductive patterns on the semiconductor substrate, each having a cross-section which is an upside-down T shape and having a greater thickness than the conductive patterns. A nitride film liner lines trenches defined by the conductive patterns and the dielectric patterns. A dielectric layer fills the trenched in the second domain. Nitride film studs having insubstantial step difference with respect to the dielectric patterns are disposed on the first domain and cover upper surfaces of the conductive patterns. At least one capacitor is in contact with a conductive region of the semiconductor substrate and passes through the dielectric patterns. An intermetal dielectric layer is disposed on the capacitor and the dielectric layer. At least one metal contact plug is in contact with at least one of the conductive patterns and passes through the intermetal dielectric layer, the dielectric layer and the nitride film liner. 
     In some method embodiments of the present invention, conductive patterns are formed on a semiconductor substrate. Dielectric patterns are formed between the conductive patterns on the semiconductor substrate, each having a cross-section with an upside-down T shape and a thickness greater than the conductive patterns. Trenches defined by the conductive patterns and the dielectric patterns are lined with a nitride film. A dielectric layer is formed on the nitride film to thereby fill the trenches. At least one metal contact plug is formed that passes through the dielectric layer and the nitride film liner and is in contact with at least one of the conductive patterns. 
     In further embodiments of the present invention, conductive patterns are formed on a semiconductor substrate in first and second domains. Dielectric patterns are formed between the conductive patterns on the semiconductor substrate, each having a cross-section with an upside-down T shape and a thickness greater than the conductive patterns. Trenches defined by the conductive patterns and the dielectric patterns are lined with a nitride film. A dielectric layer is formed, filling the lined trenches. Nitride film studs having insubstantial step difference with respect to the dielectric patterns are formed, the nitride film studs covering upper surfaces of the conductive patterns. At least one capacitor is formed that passes through the dielectric patterns to contact a conductive region of the semiconductor substrate. An intermetal dielectric layer is formed on the capacitor. At least one metal contact plug is formed that passes through the dielectric layer and the nitride film liner to contact at least one of the conductive patterns. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1-10 are cross-sectional views illustrating an integrated circuit and operations for fabricating the same according to some embodiments of the present invention. 
     FIGS. 11-16 are cross-sectional views illustrating an integrated circuit and operations for fabricating the same according to further embodiments of the present invention. 
     FIG. 17 is a plan view of a cell domain of the integrated circuit of FIGS. 1-10. 
     FIG. 18 is a plan view of a cell domain of the integrated circuit of FIGS.  11 - 16 . 
    
    
     DETAILED DESCRIPTION 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thickness of layers and regions are exaggerated for clarity. Like numbers refer to like elements throughout. It will be understood that when an element such as a layer, region or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. Moreover, each embodiment described and illustrated herein includes its complementary conductivity type embodiment as well. Embodiments of the present invention can provide improvements to contact structures for integrated circuit devices, such as the integrated circuit memory devices described in U.S. patent application Ser. No. 09/889,588, the disclosure of which is incorporated herein by reference in its entirety. However, it will be appreciated that the invention is applicable to contact structures in integrated circuit devices other than memory devices. 
     FIGS. 1-10 are cross-sectional views illustrating an integrated circuit device and operations for fabricating the same according to first embodiments of the present invention. FIG. 17 is a layout plane view illustrating a cell domain of the integrated circuit according to first embodiments of the present invention. The cross-section of a cell domain C shown in FIG.  1  and FIGS. 2-10 corresponds to a line I-I′ and a line II-II′, respectively, shown in FIG.  17 . 
     Referring to FIG. 1, a shallow trench isolation (STI) film is formed as an isolation film  90  on a semiconductor substrate  100 . The isolation film  90  defines the cell domain C and a peripheral circuit domain P and, further, separates elements formed on the domains C and P from each other. A first gate  105  and a first source/drain (not shown) and a second gate  106  and a second source/drain  111  are formed in the peripheral circuit domain P. A plurality of third gates  107  and a third source/drain  112  are formed in the cell domain C. A gate insulating layer  105   a  is interposed between the first, second and third gates  105 ,  106  and  107  and the semiconductor substrate  100 . The upper surfaces and sidewalls of depositions made of the gate insulating layer  105   a  and any one of the first, second and third gates  105 ,  106 ,  107 , are surrounded by a nitride-film spacer  105   b.    
     A first dielectric layer (not illustrated as an independent layer) is formed on the semiconductor substrate  100  having the first, second and third gates  105 ,  106 ,  107  and the source/drain  11  and  112 . Then the first dielectric layer is patterned to form a hole exposing the third source/drain  112 . After a conductive material for filling the hole is deposited, the upper surface of the resultant structure is planarized to form first and second conductive pads  120   a ,  120   b , which are separated from each other. 
     A second dielectric layer (not illustrated as an independent layer) is formed on the resultant structure. The second dielectric layer combines with the first dielectric layer to form a lower dielectric layer  115 . A first contact plug  125   a  in contact with the first gate  105  and a second contact plug  125   b  in contact with the second source/drain  111  are then formed, each passing through the lower dielectric layer  115 . A third contact plug  125   c  in contact with the upper surface of the second conductive pad  120   b  is also formed. The second and third contact plugs  125   b ,  125   c  function as bit line contact plugs. A conductive layer  130  is formed on the lower dielectric layer  115  having the first, second and third contact plugs  125   a ,  125   b ,  125   c  and a nitride film  135  is formed on the conductive layer  130 . 
     Referring to FIG. 2, the conductive layer  130  and the nitride film  135  are patterned to form conductive patterns  130   a  and nitride patterns  135   a  which contact the upper surfaces of the first, second and third contact plugs  125   a ,  125   b ,  125   c.    
     Referring to FIG. 3, a dielectric layer  140  is formed to have little or no step difference with respect to the structure composed of the conductive patterns  130   a  and the nitride patterns  135   a . The dielectric layer  140  is obtained by depositing a dielectric material to fill gaps between the patterns  130   a ,  135   a , and then performing a chemical mechanical polishing (CMP) such that the upper surfaces of the nitride patterns  135   a  are exposed. 
     Referring to FIG. 4, a predetermined thickness of the nitride patterns  135   a  is etched away to form remnant nitride patterns  135   b . It is preferable that the dielectric layer  140  undergoes little or no etching. The remnant nitride patterns  135   b  are preferably formed through an etching process in which the nitride film pattern  135   a  has a superior etching selectivity to the dielectric layer  140 . In a subsequent process, the remnant nitride patterns  135   b  are etched when a portion of the dielectric layer  140  is etched, thereby preventing the conductive patterns  130   a  from being etched. For this reason, the thickness of the remnant nitride patterns  135   b  preferably depends on the dielectric layer  140  to be etched. 
     FIG. 5 shows that a portion of the dielectric layer  140  and the remnant nitride patterns  135   b  are wet-etched. As a result of the wet etching, inverted T-shaped dielectric patterns  140   a  are formed between the conductive patterns  130   a . The dielectric patterns  140   a  and the conductive patterns  130   a  define trenches T 1  having widths greater than the conductive patterns  130   a . It is preferable that a portion of the dielectric layer  140  and the remnant nitride patterns  135   b  are etched through an etching process where the remnant nitride patterns  135   b  have little or no etching selectivity with respect to the dielectric layer  140 . 
     Referring to FIG. 6, a nitride film liner  145  is formed on the conductive patterns  130   a  and the dielectric patterns  140   a . The nitride film liner  145  is preferably formed so that the trench T 1  is not completely filled. For instance, the thickness of the nitride film liner  145  can be formed from 100 Å to 1000 Å. Next, another dielectric layer  150  is deposited to fill the trench T 1 . 
     Referring to FIG. 7, a photosensitive mask PR exposing the cell domain C is formed. The dielectric layer  150  is etched using the photosensitive film pattern PR as a mask, so that the nitride film liner  145  on the cell domain C is exposed. 
     Referring to FIG. 8, the photosensitive film PR is removed and a nitride layer is then deposited on the resultant structure, so that the trench T 1  is filled. The upper surface of the resultant structure is planarized to expose the dielectric patterns  140   a , preferably through an etch-back process. As a result, nitride film studs  147  having little or no step difference with respect to the dielectric patterns  140   a  are formed on the upper surfaces of the conductive patterns  130   a  in the cell domain C. During the etch-back process, the nitride film liner  145  is patterned to form well-shaped nitride film liner patterns  145   a.    
     Referring to FIG. 9, a dielectric layer  151  is formed on the resultant structure. Then a capacitor  190 , which is in contact with the upper surface of the first conductive pad  120   a , is formed. First, a storage node contact hole is formed by etching the dielectric layer  151 , the dielectric pattern  140   a  and the lower dielectric layer  115  using the nitride film studs  147  as a mask. The storage node contact hole is filled with a conductive material to form a storage node contact plug  190   a . Then, a lower electrode  190   b  is formed, contacting the storage node contact plug  190   a . An upper electrode  190   d  is obtained by forming a dielectric film on the lower electrode  190   b , depositing a conductive material thereon, and then planarizing the deposited conductive material. A planarized intermetal dielectric layer  152  may then be formed on the resultant structure. 
     Referring to FIG. 10, the intermetal dielectric layer  152  and the dielectric layers  150 ,  151  are partially etched through an etching process in which they exhibit etching selectivity with respect to the nitride film liner  145 , so that the nitride film liner  145  is exposed. Next, contact holes H 11  and H 12 , which expose the conductive patterns  130   a , are formed by etching the exposed portion of the nitride film liner  145 . 
     The holes H 11  and H 12  are then filled with metal. As a result, metal contact plugs  155   a  and  155   b  in contact with the conductive patterns  130   a  are formed, passing through the intermetal dielectric layer  152 , the dielectric layers  150  and  151  and the nitride film liner  145 . 
     In some conventional processes, an interlayer dielectric layer and a bit line mask silicon-nitride film of about 2000 Å are etched to form contact holes for a metal contact plug; In contrast, according to some embodiments of the present invention, contact holes can be more easily formed by etching the interlayer dielectric layer and the nitride film liner, which is thinner than the bit line mask silicon-nitride film. Further, the nitride film liner  145  is formed along with trenches defined by the conductive patterns  130   a  and the dielectric patterns  140   a , and therefore, has vertical and horizontal portions with respect to the semiconductor substrate  100 . As shown in FIG. 10, the contact hole H 12  can be self-aligned by the vertical portion of the nitride film liner  145 . In a subsequent process, metal wiring  160  may be formed on the upper surfaces of the metal contact plugs  155   a  and  155   b.    
     As shown in FIG. 10, it is possible to reduce contact resistance in the integrated circuit using the above-mentioned method, because there is a sufficient contact area between the conductive layer pattern, which is the bit line stud pad, and the metal contact plug. Further, the conductive layer pattern can be smaller. Therefore, for example, a desirable margin in the depth of focus of the photolithography for patterning the bit line stud pad can be obtained. 
     FIGS. 11-16 are cross-sectional views illustrating an integrated circuit and operations for fabricating the same according to second embodiments of the present invention. FIG. 18 is a layout plane view illustrating a cell domain of the integrated circuit according to second embodiments of the present invention. Here, the cell domains C shown in FIGS.  11  and  12 - 16  correspond to a portion I-I′ and a portion II-II′ shown in FIG. 18, respectively. The second embodiments are similar to the above-described first embodiments, but form dielectric patterns in a different manner. 
     Referring to FIG. 11, a first gate  205 , a first source/drain (not shown), a second gate  206  and second sources/drains  211  are formed on a peripheral circuit domain P of a semiconductor substrate  200  as explained referring to FIG.  1 . Also, a plurality of third gates  207  and third sources/drains  212  are formed in the cell domain C of the semiconductor substrate  200 . The reference numerals  205   a  and  205   b  denote a gate insulating layer and a nitride film spacer, respectively. 
     First and second conductive pads  220   a ,  220   b , which are in contact with the third sources/drains  212 , are formed within a lower dielectric layer  215  formed on the first, second and third gates  205 ,  206 ,  207  and sources/drains  211 ,  212 . First and second contact plugs  225   a ,  225   b , which are bordered by the first gate  205  and the second sources/drains  211 , respectively, and pass through the lower dielectric layer  215  are formed. Next, a third contact plug  225   c  in contact with the upper surface of the second conductive pad  220   b  is formed. Then, a conductive layer  230  is formed on the resultant structure, and an oxide film  232  and a nitride film  235  are sequentially formed on the conductive layer  230 . 
     Referring to FIG. 12, the conductive layer  230 , the oxide film  232  and the nitride film  235  are patterned to form conductive patterns  230   a , oxide film patterns  232   a  and nitride patterns  235   a , which are in contact with the upper surfaces of the first, second and third contact plugs  225   a ,  225   b ,  225   c.    
     FIG. 13 shows a structure where a dielectric layer  240  is formed having little or no step difference with respect to the conductive patterns  230   a , the oxide film patterns  232   a  and the nitride patterns  235   a . A dielectric layer is formed, filling gaps between the conductive patterns  230   a , the oxide film patterns  232   a  and the nitride patterns  235   a  Next, a CMP process may be performed to expose the upper surfaces of the nitride patterns  235   a.    
     Referring to FIG. 14, the nitride patterns  235   a  are etched from the resultant structure shown in FIG. 13 to expose the oxide film patterns  232   a . Because the dielectric layer  240  is not etched, the nitride patterns  235   a  are preferably etched through an etching process in which they have superior etching selectivity with respect to the dielectric layer  240 . The oxide film patterns  232   a  are etched together with a portion of the dielectric layer  240  in a subsequent process, which can prevent etching of the conductive patterns  230   a.    
     Referring to FIG. 15, a portion of the dielectric layer  240  and the oxide film patterns  232   a  are wet-etched from the structure shown in FIG.  14 . As a result, dielectric patterns  240   a  are formed between the conductive patterns  230   a . The dielectric patterns  240   a  and the conductive patterns  230   a  define trenches T 2  with widths that are larger than the conductive patterns  230   a . It is preferable that a portion of the dielectric layer  240  and the oxide film patterns  232   a  are etched through an etching process in which the oxide film patterns  232   a  have little or no etching selectivity with respect to the dielectric layer  240 . 
     Processes for forming the structure of FIG. 16 are similar to those described for the first embodiments with reference to FIGS. 5-10. In particular, a nitride film liner  245 , nitride film studs  247  (including nitride film liner patterns  245   a ), dielectric layers  250 ,  251 , metal contact plugs  255   a ,  255   b , capacitors  290  (including electrodes  290   b ,  290   d  and dielectric  290   c ), intermetal dielectric layer  252 , and metal wiring  260  may be formed as described for corresponding structures in FIGS. 5-10. 
     In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.