Abstract:
The present invention relates to metallic interconnect having an interlayer dielectric thereover, the metallic interconnect having an upper surface substantially free from oxidation. The metallic interconnect may have an exposed upper surface thereon that is passivated by a nitrogen containing compound.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a divisional of U.S. patent application Ser. No. 09/293,188, filed Apr. 16, 1999, now U.S. Pat. No. 7,279,414, which will issue Oct. 9, 2007, which application is a continuation of U.S. patent application Ser. No. 09/143,289, filed on Aug. 28, 1998, titled “PLASMA TREATMENT OF AN INTERCONNECT SURFACE DURING FORMATION OF AN INTERLAYER DIELECTRIC,” now U.S. Pat. No. 6,150,257, issued Nov. 21, 2000, which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to semiconductor chip processing. More particularly, the present invention relates to electrically conductive interconnects covered with interlayer dielectrics. In particular, the present invention relates to electrically conductive interconnects having a passivation layer thereon that protects the interconnects such that the formation of oxide husks thereon is substantially eliminated. 
   BACKGROUND 
   In the microelectronics industry, a substrate refers to one or more semiconductor layers or structures that include active or operable portions of semiconductor devices. In the context of this document, the term “semiconductive substrate” is defined to mean any construction comprising semiconductive material including, but not limited to, bulk semiconductive material such as a semiconductive wafer, either alone or in assemblies comprising other materials thereon, and semiconductive material layers, either alone or in assemblies comprising other materials. The term “substrate” refers to any supporting structure including, but not limited to, the semiconductive substrates described above. 
   Semiconductor chip processing technology involves miniaturizing a plurality of semiconductive devices and placing them side-by-side upon a wafer. As miniaturization technology progresses, it has become expedient to stack semiconductive devices in order to retain a small chip footprint. It is also necessary to connect stacked devices by way of formation of an interconnect corridor and by filling of the interconnect corridor with electrically conductive material, such as a tungsten stud. Metallization lines are formed that make electrical connection to the tungsten stud. These metallization lines need to be electrically isolated from semiconductive devices that are formed above an existing layer of semiconductive devices. To this end, an interlayer dielectric (ILD) such as an oxide or nitride is formed. 
     FIG. 1  is a cross-sectional view of a semiconductor structure  10  that depicts interconnects  12  within a dielectric layer  14 . Semiconductor structure  10  has an upper surface  16  upon which an interlayer dielectric (ILD) layer  18  has been formed. The left half of  FIG. 1  depicts an initial effect of formation of ILD layer  18  according to the prior art. It can be seen that the portion of interconnect  12  that was exposed as part of upper surface  16  of semiconductor structure  10  has formed an oxide husk  20  upon interconnect  12 . Oxide husk  20  is formed either after planarization to form upper surface  16 , such as by chemical-mechanical planarization (CMP) or during the deposition of ILD layer  18 . Where interconnect  12  is a tungsten plug, oxide husk  20  forms into tungsten oxide (WO 3 ). 
   Further processing of semiconductor structure  10 , including thermal processing, causes complications that arise in the prior art. The right half of  FIG. 1  depicts one prior art problem. It can be seen that, due to a large stress between oxide husk  20  and interconnect  12 , oxide husk  20  has delaminated from interconnect  12  due to adhesion failure, and pushed upwardly to form a void  22  immediately above interconnect  12 . Void  22  causes planarity problems and can also lead to underetched trenches prior to metal fill. The delamination of oxide husk  20  is an indication of a relatively thick oxide over interconnect  12 . The thickness of oxide husk  20  can range from about 10 Å to about 500 Å. Oxide husk  20  needs to be removed prior to deposition of a metal line. The presence of void  22  causes a prominence in the ILD topology. The prominence can lead to underetched trenches prior to metal fill, resulting in the metal line not making sufficient electrical contact with interconnect  12 . In addition, the prominence caused by the formation of void  22  can be formed during ILD deposition. Additionally, the prominence formed due to void  22  could cause some imaging problems because of a departure from substantial planarity of the upper surface of the ILD. 
   The delamination of oxide husk  20  from upper surface  16  immediately above interconnect  12  creates significant yield problems and device failure both during device testing and in the field. 
   What is needed in the art is a method of overcoming the prior art problems. What is also needed in the art is a method of forming an ILD layer without the formation of an oxide husk and the subsequent formation of a void between the top of the interconnect and the ILD layer. What is needed in the part is a method of preventing or reducing the oxidation of the upper surface of a metallic interconnect during the formation of an interlayer dielectric. 
   SUMMARY OF THE INVENTION 
   The present invention relates to the formation of an ILD layer while preventing or reducing oxidation of the upper surface of an electrically conductive interconnect or contact. Prevention or reduction of oxidation of the upper surface of an interconnect or contact is achieved according present invention by passivating the exposed upper surface of the interconnect or contact prior to formation of the ILD. It is to be understood that “interconnect” and “contact” can be interchangeable in the inventive method and structures. 
   In order to avoid the oxidation of an upper surface of an interconnect during the formation of an ILD layer, an in situ passivation of the upper surface of the interconnect, immediately prior to or simultaneously with the formation of the ILD layer, avoids the problems of the prior art. 
   A preferred embodiment of the present invention comprises providing a semiconductor structure including a dielectric layer. Following the formation of the dielectric layer, a depression is formed in the dielectric layer. The depression terminates at an electrically conductive structure therebeneath. The depression is then filled with an interconnect that is composed of an electrically conductive material, such as a refractory metal, and preferably tungsten. After filling of the depression with the interconnect, an upper surface of the interconnect and dielectric layer is formed by a method such as chemical-mechanical planarization (CMP). 
   Following the formation of the upper surface, a chemical composition is reacted with at least one monolayer of the upper surface of the interconnect to form a chemical compound having a higher resistance to oxidation than the interconnect. 
   Preferably, the chemical composition will be a nitrogen-containing chemical compound such as ammonia, NH 3 . Where the interconnect is a refractory metal, such as tungsten, the at least one monolayer forms a tungsten nitride-type composition or adsorbed complex. Following formation of the at least one monolayer upon the upper surface of the interconnect, formation of the ILD layer may be carried out by such methods as a deposition by the decomposition of tetra ethyl ortho silicate (TEOS), or by chemical vapor deposition (CVD) of oxides, nitrides, carbides, and the like. 
   In order to form an ILD layer using lower processing temperatures, it is preferred that a CVD be carried out under plasma-enhanced (PE) conditions, i.e., PECVD. 
   Formation of the ILD layer may be carried out in a manner that introduces materials to form the ILD layer simultaneously with the introduction of the ammonia plasma to create a passivation layer upon the upper surface of the interconnect. 
   Next, formation of the ILD layer with substantially like materials is carried out under conditions where the ILD layer substantially absorbs the passivation layer and the passivation layer is sufficiently thick to resist substantial formation of the oxide husk. 
   Alternative compositions to ammonia may be used during plasma treatment of the upper surface of the interconnect. For example, nitrogen-containing compositions that are preferred for the inventive method include ammonia, diatomic nitrogen, nitrogen-containing silane, and the like. 
   These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order to illustrate the manner in which the above-recited and other advantages of the invention are obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
       FIG. 1  is a cross-sectional view of a semiconductor structure comprising a dielectric layer and a metallic interconnect according to the prior art. It can be seen in  FIG. 1  that two stages of processing are illustrated, whereby an oxide husk upon the interconnect expands to create a void and a substantially non-planar topology for subsequently deposited layers. 
       FIG. 2  is a cross-sectional view of a semiconductor structure being manufacturing according to the inventive method, where a contact corridor has been opened in a dielectric layer and a liner layer has been deposited upon the dielectric layer and within the contact corridor. 
       FIG. 3  is a cross-sectional view of the semiconductor structure depicted in  FIG. 2  after further processing, wherein a metal nitride layer has been formed upon the liner layer, an electrically conductive stud or interconnect has been filled into the depression, and wherein an upper surface has been created by a technique such as planarization. The upper surface includes both the dielectric layer and the interconnect, and wherein a passivation layer has been formed upon the upper surface. 
       FIG. 4  is a cross-sectional view of the semiconductor structure depicted in  FIG. 3  after further processing, wherein an ILD layer has been formed upon the upper surface according to the inventing methods such that the passivation layer has substantially protected the electrically conductive stud such that oxidation has been substantially resisted. 
       FIG. 5  is a cross-sectional view of the semiconductor structure depicted in  FIG. 4  after further processing, wherein a second depression has been formed into the ILD layer according to damascene technology in order to allow a metallization trench to be formed, or an upper level contact to be electrically connected to the interconnect that is beneath the ILD layer. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made to the drawings wherein like structures will be provided with like reference designations. It is to be understood that the drawings are diagrammatic and schematic representations of the embodiment of the present invention and are not drawn to scale. 
   The present invention relates to the formation of an ILD layer while preventing or reducing oxidation of the upper surface of an interconnect or contact stud. Prevention or reduction of oxidation of the upper surface of an interconnect is achieved according to the present invention by passivating the exposed upper surface of the interconnect prior to formation of the ILD. 
   In reference to  FIG. 2 , prevention or reduction of the likelihood of oxidation of upper surface  16  of interconnect  12  is accomplished during the formation of ILD layer  18 . This is carried out by an in situ passivation of upper surface  16  of interconnect  12 , immediately prior to or simultaneously with the formation of ILD layer  18 , which avoids the problems of the prior art. 
   A preferred embodiment of the present invention, illustrated beginning at  FIG. 2 , comprises providing semiconductor structure  10  including a dielectric layer  14 . Following the formation of dielectric layer  14 , a depression  26  is formed in dielectric layer  14  so as to terminate at an electrically conductive structure therebeneath, such as a substrate  24 . Depression  26  is then filled with an interconnect  12  as seen in  FIG. 3 , composed of an electrically conductive material such as a refractory metal. Interconnect  12  can be a tungsten stud or the like. After filling of depression  26  with an electrically conductive material, upper surface  16  of interconnect  12  and upper surface  16  of dielectric layer  14  is formed by a method such as CMP as illustrated in  FIG. 3 . 
   Following the formation of upper surface  16 , a chemical composition is reacted with at least one monolayer of upper surface  16  of interconnect  12  to form a chemical compound having a higher resistance to oxidation than interconnect  12 . 
   The chemical compound is provided in an amount sufficient to substantially chemically cover upper surface  16  of interconnect  12  in order to chemically protect approximately the first 1-1,000 atomic lattice layers thereof. The chemical compound may be a nitride form of the metal of which interconnect  12  is composed. Where ammonia, a hydrated nitrogen compound or the like is used, a chemical structure such as M—N—H x  forms, where M represents the metal of which interconnect  12  is composed. 
   The chemical compound may be, by way of non-limiting example, the nitrogen-containing chemical compound such as ammonia that has been adsorbed onto upper surface  16  of interconnect  12  sufficiently to substantially chemically cover or ‘blind off’ substantially any chemically reactive portion of upper surface  16  of interconnect  12  during formation of ILD layer  18 . Use of preferred chemical compounds that are to be matched with specific materials comprising interconnect  12  can be selected by one of ordinary skill in the art using such data and equations as Langmuir&#39;s monolayer adsorption isotherm or those also taught by Brunauer, Emmett, or Teller. Of interest to selection of a particular chemical compound in connection with a preferred material for interconnect  12 , will be any one of the five types of adsorption isotherms as classified by Brunauer. 1    1  O. Hougen et al.,  Chemical Process Principles  2 nd Ed ., Chapter 10: Adsorption. John Wiley and Sons, Inc. (1954). 
   It is of interest in the present invention that the formation of a passivation layer  32 , as seen in  FIG. 3 , substantially protects upper surface  16  of interconnect  12  from oxidation to a degree wherein the formation of oxide husk  20  and void  22  are substantially eliminated. Passivation layer  32  may be achieved by formation of a chemical compound upon upper surface  16  of interconnected  12  by a chemical reaction with approximately the first 1-1,000 atomic lattice layers of interconnect  12  or it may be achieved by adsorption onto upper surface  16  of interconnect  12  according to any of the aforementioned types as taught by Brunauer. 
   Preferably, the chemical composition will be a nitrogen-containing chemical compound such as ammonia, NH 3 . Where interconnect  12  is a tungsten stud, the at least one monolayer reacts to form a tungsten nitride-type composition or adsorbed complex upon the at least one monolayer. Following reaction with the at least one monolayer of upper surface  16  of interconnect  12 , formation of ILD layer  18  may be carried out by various methods. One method is deposition by the decomposition of tetra ethyl ortho silicate (TEOS), or by CVD of oxides, nitrides, carbides, and the like. 
   In order to form ILD layer  18  using lower processing temperatures, it is preferred that a CVD be carried out under plasma-enhanced conditions, i.e., PECVD. According to the inventive method, PECVD temperatures are used in a temperature range from about 100° C. to about 600° C. Preferably, the processing temperature will be in a range from about 150° C. to about 500° C., more preferably from about 200° C. to about 450° C., and most preferably 300° C. to about 400° C. 
   According to the present invention, a first example is set forth below. Following the formation of dielectric layer  14 , as illustrated in  FIG. 2 , depression  26  such as a contact corridor is formation therein, exposing semiconductor substrate  24  that may be, by way of non-limiting example, a metallization line. Following the exposure of semiconductor substrate  24 , a titanium liner layer  28  or the like is formed within depression  26 . Subsequently, a titanium nitride layer  30  or the like is formed upon titanium liner layer  28  as illustrated in  FIG. 3 . Titanium nitride layer  30  may be formed by thermal nitridation of a portion of titanium liner layer  28 , by deposition of titanium nitride thereupon, or by a combination thereof. 
   Interconnect  12  is next formed within depression  26 . A preferred material for interconnect  12  is tungsten or the like. Tungsten or the like may be formed within depression  26  by CVD, PECVD, or by physical vapor deposition (PVD). 
   Upper surface ′ 16 , as seen in  FIG. 3 , may be formed by such methods as CMP or an anisotropic etchback that has an etch recipe selectivity that is substantially the same for interconnect  12  as for dielectric layer  14 . By “substantially the same,” it is meant that selectivity favors leaving dielectric layer  14 , and favors it over interconnect  12  in a range from about 1.5:1, preferably about 1.2:1, more preferably 1.1:1, and most preferably 1.05:1. 
   Passivation of upper surface  16  of interconnect  12  is next carried out by placing semiconductor structure  10  within a tool such as a PECVD chamber and introducing and striking an ammonia plasma or the like therein. Treatment temperatures, as set forth above, are imposed upon semiconductor structure  10 . The plasma treats upper surface  16  for a time treatment in a range from about 1 to about 60 seconds, preferably from about 5 to about 45 seconds, more preferably from about 20 to about 40 seconds, and most preferably for about 30 seconds. 
   Formation of ILD layer  18 , as illustrated in  FIG. 4 , may be carried out in a manner that introduces materials to form ILD layer  18  simultaneously with the introduction of the ammonia plasma to create a passivation layer  32  upon upper surface  16  of interconnect  12 . Alternatively, after the formation of passivation layer  32  has been substantially accomplished, the deposition tool may be substantially evacuated of the ammonia plasma, and dielectric precursor materials may then be introduced to the deposition tool to form ILD layer  18 . Other materials may be used to form passivation layer  32  besides ammonia. For example, diatomic nitrogen or a nitrogen-containing silane may be used. The specific material that may be used will depend upon the particular application. 
   Next, formation of ILD layer  18  with substantially like materials is carried out under conditions where ILD layer  18  substantially absorbs passivation layer  32  and/or passivation layer  32  is sufficiently thick to resist substantial formation of oxide husk  20 . In this embodiment, it is preferred by way of non-limiting example that both passivation layer  32  be formed using NH 3  and ILD layer  18  be formed in a deposition by decomposition of TEOS. Other materials, however, may be chosen. 
   Completion of this example is carried out by the formation of second depression  34  in ILD layer  18 . Accordingly, a masking layer is patterned upon upper surface  36  of ILD layer  18  and an anisotropic etch is carried out to form second depression  34 . The etch recipe is selective to interconnect  12  as well as titanium liner layer  28 , titanium nitride layer  30 , and optionally to dielectric layer  14 . 
   Where formation of passivation layer  32  is carried out at least in part by adsorption, and where ammonia is used by way of non-limiting example, an ammonia compound and its derivatives are substantially adsorbed upon upper surface  16  of interconnect  12 . By “substantially absorbed,” it is meant that passivation layer  32  does not volatilize during the time required to form ILD layer  18 . This means that volatilization is prevented to an extent that passivation layer  32  resists formation of oxide husk  20 , or a portion thereof. Of primary interest in the present invention is the achievement of an embodiment whereby passivation layer  32  sufficiently protects upper surface  16  of interconnect  12  such that during the formation of ILD layer  18 , ILD layer sufficiently adheres to upper surface  16  of interconnect  12  without causing structural failure as that experienced in the prior art. 
   Additionally and preferably, any component of passivation layer  32  that volatilizes during formation of ILD layer  18  will be soluble in the materials that form ILD layer  18  such that no immiscible gas bubbles form from volatilized materials of passivation layer  32 . 
   A second example of the inventive method is set forth below. Semiconductor structure  10  includes dielectric layer  14 , made of borophosphosilicate glass (BPSG). Dielectric layer  14  rests upon substrate  24 . In this example, substrate  24  can be an electrically conductive film that is typically used to wire semiconductive devices. 
   Following the formation of dielectric layer  14 , depression  26  is formed by an anisotropic dry etch that stops on substrate  24 . The anisotropic dry etch may include such techniques as ion beam milling or an etch recipe that mobilizes a portion of the masking layer such that the masking layer redeposits upon the sidewalls of depression  26  while it is being formed, thereby forming a substantially anisotropic etch. 
   Following the formation of depression  26 , titanium liner layer  28  is deposited upon dielectric layer  14  and substrate  24  preferably by PECVD. Titanium liner layer  28  is then partially treated in a thermal nitride environment in order to grow titanium nitride layer  30  thereupon. Although titanium nitride layer  30  is grown by thermal combination and conversion of a portion of the titanium in titanium liner layer  28  into titanium nitride layer  30 , titanium nitride layer  30  may alternatively be formed by deposition of titanium nitride by such techniques as PVD, PECVD, CVD, and the like. 
   Following the formation of titanium nitride layer  30 , interconnect  12  is formed by deposition of tungsten into depression  26 . The deposition of tungsten into depression  26  in order to form interconnect  12  may be facilitated by the presence of titanium nitride layer  30  and titanium liner layer  28 . Where the formation of interconnect  12  is formed by force-filling of tungsten into depression  26 , the presence of titanium nitride layer  30  and titanium liner layer  28  facilitate slippage of the tungsten material along the region of what will become upper surface  16  and into depression  26  so as to fill depression  26 . 
   Following the filling of depression  26  with tungsten or the like in order to form interconnect  12 , all tungsten that is not within depression  26  is removed by a technique such as CMP. Because CMP itself may form oxide husk  20 , upper surface  16 , particularly that portion of upper surface  16  that comprises interconnect  12 , may need to be cleaned by such techniques as an interconnect oxide etch that is selective to dielectric layer  14  and unoxidized portions of interconnect  12 . 
   Following the cleaning of upper surface  16 , semiconductor structure  10  is placed within a deposition tool and an ammonia plasma is struck therein. Alternatively, the cleaning of upper surface  16  may be carried out within the same deposition tool where the ammonia plasma is struck. Additionally, the cleaning of upper surface  16  may be carried out within a cluster tool previous to in situ transfer of semiconductor structure  10  into the deposition tool. The temperature of semiconductor structure  10  during this stage of the inventive method is in a range substantially the same as in the previous example. Preferably, the treatment time to form passivation layer  32  is less than about 30 seconds. According to this second example, a preferred composition of passivation layer  32  comprises nitrogen that has been adsorbed upon upper surface  16  of interconnect  12  according to Brunauer&#39;s Type V adsorption. As a preferred alternative embodiment, upper surface  16  of interconnect  12  is first treated in a nitrogen atmosphere at a temperature sufficient to create tungsten nitride and then under conditions sufficient to create Type V adsorption of several layers of nitrogen compounds upon the tungsten nitride. By several layers of nitrogen compounds, it is understood that the overall composite thickness of passivation layer  32  is about 50 Å, preferably about 20 Å, more preferably about 10 Å, and most preferably about 5 Å. 
   Another example is set forth below. Processing is carried out as set forth in previous examples. The formation of passivation layer  32  is carried out in situ with the formation of ILD layer  18 . After an optional cleaning of upper surface  16 , semiconductor structure  10 , within a deposition tool, is fed with a mixture of ammonia and silane or the like. At the beginning of this step of the inventive process, the mixture comprises an ammonia rich feed such that initially passivation layer  32  begins to form upon upper surface  16 . 
   The removal of ammonia from the mixture may be carried out incrementally. For example, the elimination of ammonia from the mixture may be initiated by decreasing the ammonia portion of the mixture by a preferred percentage of the entire amount of ammonia over a period of time. Specifically, the amount of ammonia may be decreased every five seconds by about 5%, such that after about 100 seconds, the amount of ammonia in the feed mixture is reduced to about zero. Alternatively, the amount of ammonia may be decreased every five seconds by 10%, such that after about one minute, the amount of ammonia in the feed mixture is reduced to about zero. Alternatively, the amount of ammonia may be decreased by about 25% every five seconds such that after about twenty seconds, the amount of ammonia in the feed mixture has been reduced to about zero. Additionally, the amount of ammonia may be decreased by 50% every five seconds such that after about ten seconds, the amount of ammonia in the feed mixture is reduced to about zero. Finally, the amount of ammonia in the feed mixture may be reduced from 100% to about zero after any five-second time increment in a single step. 
   As an alternative embodiment and in connection with the reduction of the amount of ammonia in the mixture, processing conditions may be altered from conditions that are less likely to cause formation to oxide husk  20  to conditions that are more likely. For example, processing temperatures sufficient to form passivation layer  32  may be initiated with an ammonia-rich mixture under conditions not likely to cause formation of oxide husk  20 . As the amount of ammonia in the mixture is reduced, processing temperatures may be increased proportionally under conditions that are more likely to cause formation of oxide husk  20  than under conditions previously established when the amount of ammonia in the mixture is greater. The initial formation of some of passivation layer  32 , however, resists the formation of oxide husk  20 . Preferably, the processing temperature will be the same as the deposition temperature for ILD layer  18 . 
   Following the formation of passivation layer  32 , upper surface  16  is covered with ILD layer  18  in situ by a method as set forth above. During the deposition of ILD layer  18 , passivation layer  32  protects upper surface  16  of interconnect  12  and prevents the formation of oxide husk  20 . As a preferred alternative embodiment of the present invention, the materials comprising passivation layer  32  may react with ILD layer  18  material without causing unwanted oxidation of upper surface  16  of interconnect  12 . In this preferred alternative embodiment, the materials comprising passivation layer  32  and ILD layer  18  will interact to form a new compound that will have a lower stress than that of oxide husk  20 . 
   Alternative compositions to ammonia may be used during plasma treatment of upper surface  16  of interconnect  12 . For example, nitrogen-containing compositions that are preferred for the inventive method include ammonia, diatomic nitrogen, nitrogen-containing silane, and the like. 
     FIG. 4  illustrates further processing of semiconductor structure  10  as depicted in  FIG. 3 . It can be seen that ILD layer  18  has been formed upon upper surface  16  of semiconductor  10  according to the inventive method. The presence of passivation layer  32  has prevented formation on oxide husk  20  according to an object of the invention. It can be appreciated that passivation layer  32  may form exclusively upon interconnect  12  and alternatively onto titanium liner layer  28  and titanium nitride layer  30 . This means that passivation layer  32  may not substantially form upon upper surface  16  over dielectric layer  14  due to incompatible reaction chemistry that prevents any type of reactive material to form. 
   Following the formation of ILD layer  18 , further processing is carried out as illustrated in  FIG. 5 . Second depression  34  is formed into ILD layer  18  by patterning and etching thereof. In a damascene process such as that illustrated in  FIG. 5 , second depression  34  is formed substantially above interconnect  12 . Second depression  34  may be, by way of non-limiting example, a wiring trench such that metallization within second depression  34  would run in and out of the plane of  FIG. 5 . Additionally, second depression  34  may be a contact corridor such that metallization would run left to right, substantially within the plane of  FIG. 5  along the upper surface  36  of ILD layer  18  and filled into second depression  34  such that a metallization line with a contact is formed, whereby the contact is in electrical communication with interconnect  12 . 
   The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims and their combination in whole or in part rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.