Abstract:
A process and structure for copper damascene interconnects including a tungsten-nitride (WN 2 ) barrier layer formed by atomic layer deposition is disclosed. The process method includes of forming a copper damascene structure by forming a first opening through a first insulating layer. A second opening is formed through a second insulating layer which is provided over the first insulating layer. The first opening being in communication with the second opening. A tungsten-nitride (WN 2 ) layer is formed in contact with the first and second openings. And, a copper layer is provided in the first and second openings. Copper is selectively deposited by a CVD process and/or by an electroless deposition technique at low temperature to provide improved interconnects having lower electrical resistivity and more electro/stress-migration resistance than conventional interconnects. Additionally, metal adhesion to the underlying substrate materials is improved and the amount of associated waste disposal problems is reduced.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to the field of semiconductors and, in particular, to a method of forming damascene structures in semiconductor devices.  
         BACKGROUND OF THE INVENTION  
         [0002]    The integration of a large number of components on a single integrated circuit (IC) chip requires complex interconnects. Ideally, the interconnect structures should be fabricated with minimal signal delay and optimal packing density. The reliability and performance of integrated circuits may be affected by the quality of their interconnect structures. Advanced multiple metallization layers have been used to accommodate higher packing densities as devices shrink below sub-0.25 micron design rules. One such metallization scheme is a dual damascene structure formed by a dual damascene process. The dual damascene process is a two-step sequential mask/etch process to form a two-level structure, such as a via connected to a metal line situated above the via.  
           [0003]    FIGS.  1 A- 1 C illustrate a sequence of fabrication steps for a known dual damascene process as applied to interconnect formation. As shown in FIG. 1A, the process begins with the deposition of a first insulating layer  140  over a first level interconnect metal layer  120 , which in turn is formed over or within a semiconductor substrate  100 . A second insulating layer  160  is next formed over the first insulating layer  140 . An etch stop layer  150  is typically formed between the first and second insulating layers  140 ,  160 . The second insulating layer  160  is patterned by photolithography with a first mask (not shown) to form a trench  170  corresponding to a metal line of a second level interconnect. The etch stop layer  150  prevents the upper level trench pattern  170  from being etched through to the first insulating layer  140 .  
           [0004]    As illustrated in FIG. 1B, a second masking step followed by an etch step are applied to form a via  180  through the etch stop layer  150  and the first insulating layer  140 . After the etching is completed, both the trench  170  and the via  180  are filled with metal  122 , which is typically copper (Cu), to form a damascene structure  125 , as illustrated in FIG. 1C.  
           [0005]    If desired, a second etch stop layer (not shown) may be formed between the substrate  100  and the first insulating layer  140  during the formation of the dual damascene structure  125 . In any event, and in contrast to a single damascene process, the via and the trench are simultaneously filled with metal. Thus, compared to the single damascene process, the dual damascene process offers the advantage of process simplification and low manufacturing cost.  
           [0006]    In an attempt to improve the performance, reliability and density of the interconnects, the microelectronics industry has recently begun migrating away from the use of aluminum (Al) and/or its alloys for the interconnects. As such, advanced dual damascene processes have begun using copper (Cu) as the material of choice because copper has high conductivity, extremely low resistivity (about 1.7 μΩcm) and good resistance to electromigration. Unfortunately, copper diffuses rapidly through silicon dioxide (SiO 2 ) or other interlayer dielectrics, such as polyimides and parylenes, and copper diffusion can destroy active devices, such as transistors and capacitors, formed in the IC substrate. In addition, metal adhesion to the underlying substrate materials must be excellent to form reliable interconnect structures but the adhesion of copper to interlayer dielectrics, particularly to SiO 2 , is generally poor.  
           [0007]    The introduction of copper conductors in integrated circuits has recently received wide publicity. As mentioned above, copper interconnect is the most promising metallization scheme for the future generation high-speed ULSI, primarily because of lower electrical resistivity (1.7 vs. 2.3 μΩcm) and electro/stress-migration resistance than the conventional aluminum-based materials. Recently, IBM and Motorola introduced full, 6-level copper wiring in a sub-0.25 μm CMOS ULSI technology (D. Edelstein, et al., “Full Copper Wiring in a sub-0.25 μm CMOS ULSI technology”,  Technical Digest of  1997  IEDM , p. 773-776 (1997); S. Vankatesan, et al., “A High Performance 1.8 v, 0.2 μm CMOS Technology with Copper Metallization”, ibid, p. 769-772); J. G. Ryan, et al., “Copper Interconnects for Advanced Logic and DRAM”,  Extended Abstracts of the  1998  International Conference on Solid State Devices and Materials , p. 258-259 (1998)). Again, however, as mentioned above copper atoms easily diffuse into silicon device, and act as recombination centers and spoil device performance. Copper also diffuses into commonly used dielectric materials SiO 2  and certain polymers. As a result, in order to adopt copper interconnects for ULSI, a suitable diffusion barrier is needed.  
           [0008]    Finally, as mentioned above, of the several schemes proposed for fabricating copper interconnects, the most promising method appears to be the Damascene process shown in FIGS.  1 A-C. Using this method, the trenches for conductors and vias are patterned in blanket dielectrics, and then the desired metal is deposited into the trenches and holes in one step. Chemical mechanical polishing (CMP) is used to remove the unwanted surface metal, while leaving the desired metal in the trenches and holes. This leaves a planarized surface for subsequent metallization to build multi-level interconnect. Unfortunately, this technology not only uses a large amount of expensive consumables for the CMP process and the associated waste disposal problem, but also is a very wasteful copper process. Typically, the conductors and via holes in the given metallization level occupies only a few percent, and the bulk of the deposited thick high-purity copper is removed by polishing operation, and becomes very expensive.  
           [0009]    Accordingly, there is a need for an improved damascene process which reduces production costs and increases productivity. There is also a need for a method of increasing the adhesion of copper to underlying damascene layers as well as a method of decreasing copper diffusion in such layers.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention provides a method for fabricating a copper damascene interconnect structure in a semiconductor device which requires fewer processing steps and reduces the diffusion of copper atoms to underlying damascene layers, improves metal adhesion to the underlying substrate materials, and reduces the amount of associated waste disposal problems.  
           [0011]    In one embodiment of the present invention, a process and structure for copper damascene interconnects including a tungsten-nitride (WN 2 ) barrier layer formed by atomic layer deposition is disclosed. The process method includes of forming a copper damascene structure by forming a first opening through a first insulating layer. A second opening is formed through a second insulating layer which is provided over the first insulating layer. The first opening being in communication with the second opening. A tungsten-nitride (WN 2 ) layer is formed in contact with the first and second openings. Hence, trenches and vias are formed according to damascene processing, subsequent to which a thin tungsten-nitride (WN 2 ) diffusion barrier layer is formed by an atomic layer deposition inside the trenches and vias. A copper layer is provided in the first and second openings. Copper is selectively deposited by a CVD process and/or by an electroless deposition technique at low temperature to provide improved interconnects having lower electrical resistivity and more electro/stress-migration resistance than conventional interconnects. Additionally, the adhesion of copper atoms to the underlying layers is increased, while the diffusion of copper atoms into adjacent interconnect layers is suppressed and the amount of associated waste disposal problems is reduced.  
           [0012]    Additional advantages of the present invention will be more apparent from the detailed description and accompanying drawings, which illustrate preferred embodiments of the invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1A is a cross-sectional view of a conventional dual damascene formation process for a semiconductor device at a preliminary stage of production.  
         [0014]    [0014]FIG. 1B is a cross-sectional view of the semiconductor device of FIG. 1A at a subsequent stage of production.  
         [0015]    [0015]FIG. 1C is a cross-sectional view of the semiconductor device of FIG. 1B at a subsequent stage of production.  
         [0016]    FIGS.  2 A- 2 K are cross-sectional views illustrating a sequence of fabrication steps for forming a dual damascene copper interconnect in association with a semiconductor device according to the teachings of the present invention.  
         [0017]    FIGS.  3 A- 3 B are cross-sectional views illustrating a sequence of fabrication steps for forming a dual damascene copper interconnect in association with a semiconductor device in accordance with a second embodiment of the present invention.  
         [0018]    [0018]FIG. 4 is a cross-sectional view of a multilayer damascene copper interconnect in association with a semiconductor device constructed in accordance with a third embodiment of the present invention.  
         [0019]    [0019]FIG. 5 illustrates an electronic system having a memory cell with a copper damascene structure according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0020]    In the following detailed description, reference is made to various specific embodiments in which the invention may be practiced. These embodiments are described with sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be employed, and that structural and electrical changes may be made without departing from the spirit or scope of the present invention.  
         [0021]    The term “substrate” used in the following description may include any semiconductor-based structure that has a semiconductor surface. The term should be understood to include silicon, silicon-on insulator (SOI), silicon-on sapphire (SOS), doped and undoped semiconductors, epitaxial layers of silicon supported by a base semiconductor foundation, and other semiconductor structures. The semiconductor need not be silicon-based. The semiconductor could be silicon-germanium, germanium, or gallium arsenide. When reference is made to a “substrate” in the following description, previous process steps may have been utilized to form regions or junctions in or on the base semiconductor or foundation.  
         [0022]    The term “copper” is intended to include not only elemental copper, but also copper with other trace metals or in various alloyed combinations with other metals as known in the art, as long as such alloy retains the physical and chemical properties of copper. The term “copper” is also intended to include conductive oxides of copper.  
         [0023]    FIGS.  2 A- 2 K are cross-sectional views illustrating a sequence of fabrication steps for forming a dual damascene copper interconnect in association with a semiconductor device according to the teachings of the present invention. FIG. 2A depicts a portion of an insulating layer  251  formed over a semiconductor substrate  250 , on or within which a metal layer  252  has been formed. The metal layer  252  represents a lower metal interconnect layer which is to be later interconnected with an upper copper interconnect layer. The metal layer  252  may for formed of copper (Cu), but other conductive materials, such as tungsten (W) or aluminum (Al) and their alloys, may be used also.  
         [0024]    [0024]FIG. 2B illustrates the structure following the next series of processing steps. As shown in FIG. 5, a first intermetal insulating layer  255  is formed overlying the insulating layer  251  and the metal layer  252 . In an exemplary embodiment of the present invention, the first intermetal insulating layer  255  is blanket deposited by spin coating to a thickness of about 2,000 Angstroms to 15,000 Angstroms, more preferably of about 6,000 Angstroms to 10,000 Angstroms. The first intermetal insulating layer  255  may be cured at a predefined temperature, depending on the nature of the material. Other known deposition methods, such as sputtering by chemical vapor deposition (CVD), plasma enhanced CVD (PECVD), or physical vapor deposition (PVD), may be used also for the formation of the first intermetal insulating layer  255 , as desired.  
         [0025]    In one embodiment, the first intermetal insulating layer  255  is be formed of a conventional insulating oxide, such as silicon oxide (SiO 2 ). In alternative embodiments, the first intermetal insulating layer  255  is formed of a low dielectric constant material such as, for example, polyimide, spin-on-polymers (SOP), parylene, flare, polyarylethers, polytetrafluoroethylene, benzocyclobutene (BCB), SILK, fluorinated silicon oxide (FSG), NANOGLASS or hydrogen silsesquioxane, among others. The present invention is not limited, however, to the above-listed materials and other insulating and/or dielectric materials known in the industry may be used also.  
         [0026]    [0026]FIG. 2C illustrates the structure following the next series of processing steps. As shown in FIG. 2C, a second intermetal insulating layer  257  is formed overlying an etch stop layer  256  and below a copper metal layer that will be formed subsequently. According to the teachings of the present invention, the second intermetal insulating layer  257  can be formed, for example, by deposition to a thickness of about 2,000 Angstroms to about 15,000 Angstroms, more preferably of about 6,000 Angstroms to 10,000 Angstroms. Other deposition methods, such as the ones mentioned above with reference to the formation of the first intermetal insulating layer  255  can also be used. The second intermetal insulating layer  257  can be formed of the same material used for the formation of the first intermetal insulating layer  255  or a different material. The etch stop layer  256  can be formed of conventional materials such as silicon nitride (Si 3 N 4 ) for example.  
         [0027]    [0027]FIG. 2D illustrates the structure following the next series of processing steps. As shown in FIG. 2D, a first photoresist layer  258  is formed over the second intermetal insulating layer  257  to a thickness of about 2,000 Angstroms to about 3,000 Angstroms. The first photoresist layer  258  is then patterned with a mask (not shown) having images of a via pattern  259 . Thus, as shown in FIG. 2E, a via  265  can be formed by first etching through the photoresist layer  258  and into the second intermetal insulating layer  257  with a first etchant, and subsequently etching into the first intermetal insulating layer  255  with a second etchant. As one of ordinary skill in the art will understand upon reading this disclosure, the etchants (not shown) can be selected in accordance with the characteristics of the first and second insulating materials  255 ,  257 , so that the insulating materials are selectively etched until the second etchant reaches the metal layer  252 .  
         [0028]    After the formation of the via  265  through the second and first intermetal insulating layers  257 ,  255 , a trench  267  is formed by photolithography techniques as shown in FIG. 2G. As such, a second photoresist layer  262 , as shown in FIG. 2E, is formed over the second intermetal insulating layer  257  to a thickness of about 2,000 Angstroms to about 3,000 Angstroms and then patterned with a mask (not shown) having images of a trench pattern  263 . According to the teachings of the present invention, the trench pattern  263  is then etched into the second intermetal insulating layer  257  using photoresist layer  262  as a mask to form trench  267 , as shown in FIG. 2G. The thickness of the first intermetal insulating layer  255  defines the depth of the via  265 , as shown in FIGS.  2 E- 2 G. The thickness of the second intermetal insulating layer  257  defines the depth of the trench  267  of FIG. 2G.  
         [0029]    The etching of the trench  267  may be accomplished using the same etchant employed to form the via  265 , as shown in FIG. 2E, or a different etchant.  
         [0030]    Subsequent to the formation of trench  267 , the second photoresist layer  262  is removed so that further steps to create the copper dual damascene structure  200 , shown in FIG. 2K, may be carried out.  
         [0031]    [0031]FIG. 2H illustrates the structure following the next sequence of fabrication steps. As shown in FIG. 2H, a diffusion barrier layer  272  is formed on the via  265  and the trench  267  to a thickness of about 50 Angstroms to about 200 Angstroms, more preferably of about 100 Angstroms.  
         [0032]    In one embodiment according to the teachings of the present invention, the diffusion barrier layer  272  is formed of tungsten-nitride (WN 2 ) by atomic layer deposition. One example of a method for tungsten-nitride (WN 2 ) by atomic layer deposition is described in an article by Krause, J. W. et al. entitled, “Atomic layer deposition of tungsten nitride films using sequential surface reaction”,  Journal of Electrochemical Soc.,  147:3, 1175-81 ( 2000 ). According to the teachings of the invention, a thin layer of WN 2  prepared by ALD is used as the diffusion barrier layer in building copper interconnects for semiconductor devices. According to one embodiment of the invention, the deposition of the tungsten nitride film as the diffusion barrier layer  272  is performed at a temperature of about 600 to 800 degrees Kelvin. In one embodiment according to the teachings of the present invention, a tungsten-nitride (WN 2 ) layer is formed as the diffusion barrier layer  272  such that the diffusion barrier layer  272  is less than five atomic layers thick. According to the teachings of the present invention, these atomic layers are so uniform that a vertical wall as well as a short side wall obtain an equal thickness. In these embodiments, x-ray photoelectron spectroscopy depth profiling experiments evidence that the film diffusion barrier layer  272  has a WN 2  stoichiometry with low C and O impurity concentrations. Further, x-ray diffraction investigation reveals that the tungsten nitride films serving as the diffusion barrier layer  272  are micro-crystalline. Atomic force microscopy measurements of the deposited film serving as the diffusion barrier layer  272  evidence a remarkably flat surface indicating smooth film growth for the diffusion barrier layer  272 .  
         [0033]    In one embodiment of the invention, the tungsten-nitride (WN 2 ) diffusion barrier layer  272  is simultaneously deposited in both the via  265  and the trench  267 . However, the invention is not limited to this embodiment. Thus, in an alternative embodiment, the tungsten-nitride (WN 2 ) diffusion barrier layer  272  is deposited first in the via  265  before the formation of the trench  267 , and then in the trench  267  after its respective formation. According to the teachings of the present invention, in the case of either embodiment, after the formation of the diffusion barrier layer  272 , horizontal portions of the tungsten-nitride (WN 2 ) material, serving as the diffusion barrier layer  272 , which formed above a top surface of the second insulating material  257  are removed by either an etching or a polishing technique to form the structure illustrated in FIG. 2I. In one embodiment according to the teachings of the present invention, chemical mechanical polishing (CMP) is used to polish away excess tungsten-nitride (WN 2 ) material above the second insulating material  257  and the trench  267  level. According to the teachings of the present invention, the second insulating material  257  acts as a polishing stop layer when CMP is used.  
         [0034]    [0034]FIG. 2J illustrates the structure following the next sequence of fabrication steps. As shown in FIG. 2J, a conductive material  280  comprising copper (Cu) is deposited to fill in both the via  265  and the trench  267 . In one embodiment according to the teachings of the present invention, the copper is selectively deposited by chemical vapor deposition (CVD) at a low temperature. Some examples of methods for selective deposition of copper by CVD at low temperature are described in an article by Kaloyeros et al., entitled “Blanket and Selective Copper CVD From Cu(fod) 2  For Multilevel Metallization,  Mat. Res. Soc. Symp. Proc ., Vol 181 (1990), and in an article by Eisenbraun et al., entitled “Selective and Blanket Low-Temperature Copper CVD for Multilevel Metallization”,  Materials Research Society Conference Proceedings , ULSI-VII, 397-401 (1992), the disclosures of which are incorporated by reference herein. In one embodiment according to the teachings of the present invention, copper films are deposited by selective CVD at temperature of about 300-400° Celsius in an atmosphere of pure H 2  from the β-diketonate precursor bis (6,6,7,8,8,8-heptafluoro-2,2-dimethyl 1-3,5-octanedino) copper (II), Cu(fod) 2 . In an alternative embodiment according to the teachings of the present invention, copper films are deposited by selective CVD at temperature of about 300-400° Celsius in an atmosphere of pure or Ar from the β-diketonate precursor bis (6,6,7,8,8,8-heptafluoro-2,2-dimethyl 1-3,5-octanedino) copper (II), Cu(fod) 2 . According to the teachings of the present invention, the reactor is first pumped down to a base pressure of less than 5×10 −7  torr. Then the source compound is introduced into the sublimator which is heated to between 40 and 75° Celsius. A mass flow controller is employed to control the flow of the mixed gas-precursor into the reactor. Deposition is carried out using argon and hydrogen as carrier gases. According to the teachings of the present invention, the substrates are heated from 300 to 400° Celsius. The pressure during deposition ranges between 1 and 10 torr, and gas flow ranges from 30 to 55 sccm.  
         [0035]    Since the temperatures involved in the embodiments of the present invention are relatively low, any low-k dielectric material including polymers, which can withstand the above temperature range (300-400° C.), can be readily used with this technology as interlayer dielectrics, e.g. the first and second insulating materials  255 ,  257 .  
         [0036]    [0036]FIG. 2K illustrates the structure following the next sequence of fabrication steps. According to the teachings of the present invention, as shown in FIG. 2K, after the deposition of the copper material  280 , excess copper formed above the surface of the second insulating material  257  may be removed by either an etching or a polishing technique to form the copper dual damascene structure  200 . In one embodiment of the present invention, chemical mechanical polishing (CMP) is used as the technique to polish away excess copper above the second insulating material  257  and the trench  267  level. In this manner, the second insulating material  257  acts as a polishing stop layer when CMP is used.  
         [0037]    As one of ordinary skill in the art will understand upon reading this disclosure, the above described embodiments for selectively depositing copper  280  by chemical vapor deposition (CVD) at a low temperature, according to the teachings of the present invention, helps to reduce the amount of wasted copper in the process.  
         [0038]    According to the teachings of the present invention, the selective deposition of copper by CVD described above is not the only method that can be employed for forming the conductive material  280 . According to another embodiment of the invention, copper can be selectively deposited by an electroless plating technique. In some instance, an electroless plating technique is more attractive than conventional electroplating methods. For example, in some embodiments electroless plating is more advantageous than electroplating because of the low cost of tools and materials. An example of a studies for electroless plating is provided in an article by Shacham-Diamand et al. entitled “Copper electroless deposition technology for ultra-large-scale-integration (ULSI) metallization,”  Microelectronic Engineering , Vol. 33, pp. 47-48 (1997), the disclosure of which is incorporated by reference herein. As will be understood by one of ordinary skill in the art upon reading this disclosure, electroless plating has a very high selectivity, excellent step coverage and good via/trench filling because of the very thin seed layers formed by the electroless plating method.  
         [0039]    In the article by Shacham-Diamand et al., three practical seeding methods for the electroless deposition of copper, which can be used with the present invention, are presented. The three practical seeding methods for the electroless deposition of copper are: (1) noble metal seeding, typically on gold, palladium or platinum; (2) copper seeding using an aluminum sacrificial layer; and (3) wet activation of surfaces using a contact displacement method. The article by Shacham-Diamand et al. demonstrates the successful use of the third method to deposit copper on Ti/TiN or TiN/AlCu at room temperature.  
         [0040]    FIGS.  3 A- 3 B are cross-sectional views illustrating a sequence of fabrication steps for forming a dual damascene copper interconnect in association with a semiconductor device in accordance with a second embodiment of the present invention. FIGS.  3 A- 3 B are intended to cover an embodiment of the present invention which employs the above mentioned wet activation of surfaces using a contact displacement method. In the embodiment of FIG. 3A, according to the teachings of the present invention, contact displacement copper deposition is used to first selectively activate the tungsten-nitride (WN 2 ) material, serving as the diffusion barrier layer  372 , after which selective electroless copper deposition is employed to obtain a copper layer  381 . Copper deposition by contact displacement offers the advantage of room temperature processing, which in turn allows many low dielectric constant organic and/or inorganic materials to be used as the material of choice for interlayer dielectrics, such as the first and second intermetal insulating layers  355 ,  357 .  
         [0041]    After the deposition of the copper material  381 , as shown in FIG. 3A, excess copper formed above the surface of the second insulating material  357  can be removed by either an etching or a polishing technique to form a copper dual damascene structure  300 , as illustrated in FIG. 3B. In one embodiment of the present invention, chemical mechanical polishing (CMP) is used to polish away excess copper above the second insulating material  357  and the trench  367  level. In this manner, the second insulating material  357  acts as a polishing stop layer when CMP is used.  
         [0042]    Again, as one of ordinary skill in the art will understand upon studying this invention, the above described embodiments for deposition of the copper material  381  using an electroless plating technique also helps to reduce the amount of wasted copper in the process.  
         [0043]    Although only one copper dual damascene structure, e.g. structures  200  and  300 , is shown in FIG. 2K and FIG. 3B, respectively, it will be readily apparent to those skilled in the art that in fact any number of such copper dual damascene structures may be formed on the substrate. Also, although the exemplary embodiments described above refer to the formation of copper dual damascene structures,  200  and  300 , the invention is further applicable to other types of damascene structures.  
         [0044]    [0044]FIG. 4 thus illustrates an embodiment, according to the teachings of the present invention, for a triple damascene structure  400 . The triple damascene structure  400 , shown in FIG. 4, follow the same processing steps described above in connection with FIGS. 2 and 3. Thus, the triple damascene structure  400  of FIG. 4 will include a tungsten-nitride (WN 2 ) material, serving as a diffusion barrier layer  472  and copper  482  selectively deposited by the methods described in detail above. For example, FIG. 4 illustrates a triple damascene structure  400  with three intermetal insulating layers  455 ,  457 , and  459  (which can comprise same or different insulating materials) formed over the substrate  450  and in which vias  465  and trenches  467  have been formed and then simultaneously filled with the selectively deposited copper  482  by the methods described above.  
         [0045]    As one of ordinary skill in the art will understand from reading this disclosure, further steps to create a functional memory cell or other integrated circuit component having the interconnects of the present invention can be carried out. Hence, additional multilevel interconnect layers and associated dielectric layers can be formed to create operative electrical paths from any of the copper damascene structures  200 ,  300 , and  400  to appropriate regions of a circuit integrated on a substrate.  
         [0046]    [0046]FIG. 5 illustrates an embodiment of an electronic system  500  having such a memory cell with a copper damascene structure according to the present invention. As shown in FIG. 5, the electronic system  500  is a processor-based  544  system which includes a memory circuit  548 , for example a DRAM. According to the teachings of the present invention, either the processor  544 , the memory circuit  548 , or both contain damascene structures, such as the copper damascene structures described in connection with FIGS. 2, 3 and  4 . The electronic system  500  shown in FIG. 5 illustrates generally a computer system  500 . Such a computer system  500  generally comprises a central processing unit (CPU)  544 , such as a microprocessor, a digital signal processor, or other programmable digital logic devices, which communicates with an input/output (I/O) device  546  over a bus  552 . The memory  548  communicates with the system  500  over bus  552 .  
         [0047]    In the case of a computer system  500 , the processor-based system may include peripheral devices such as a floppy disk drive  554  and a compact disk (CD) ROM drive  556  which also communicates with CPU  544  over the bus  552 . According to the teachings of the present invention, memory  548  can be constructed as an integrated circuit, which includes one or more copper damascene structures as described above in connection with FIGS. 2, 3, and  4 .  100 ,  200 ,  300 . In one embodiment according to the teachings of the present invention, the memory  548  and the processor, for example CPU  544 , can be formed on a single chip as a single integrated circuit.  
         [0048]    The above description and drawings are only to be considered illustrative of exemplary embodiments which achieve the features and advantages of the present invention. Modification and substitutions to specific process conditions and structures can be made without departing from the spirit and scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description and drawings, but is only limited by the scope of the appended claims.