Patent Publication Number: US-2007105372-A1

Title: Conductive material patterning methods

Description:
FIELD OF THE INVENTION  
      The present invention relates to patterning methods. More particularly, the present invention pertains to the patterning of conductive materials, e.g., copper.  
     BACKGROUND OF THE INVENTION  
      Integrated circuits generally include conductive, semiconductive, and insulative materials. Although various metals are used in the metallization of large-scale integrated circuits, many of such metals are difficult to fabricate in fine patterns because of the lack of adequate or suitable etching methods.  
      For example, copper is a well-recogized conductor. However, few integrated circuits having fine line patterns integrate copper as the conductor for metallization purposes because it is difficult to fabricate fine patterns of copper. There is a strong incentive lo incorporate copper as a conductive material in integrated circuits because of its low resistivity, higher melting temperature relative to other metals, and higher electromigration resistance compared with other currently used conductive materials, such as aluminum alloys. As such, incorporation of copper as a conductive material in integrated circuits is desired so as to allow an increase in speed thereof.  
      One method of using copper for interconnect structures is by patterning the copper using a damascene-type method. Such a method employs the deposition of copper into predefined damascene trenches. Such a process, particularly when adjacent silicon-containing regions, requires that a diffusion barrier/liner layer be used within the trench. However, if the barrier thickness cannot be reduced as trench sizes become smaller, the impact on resistance of the conductor deposited in the trench is significant.  
      Further, the existing processing methods for patterning certain conductive materials, such as aluminum are often ineffective for other conductive materials such as copper. For example, dry etching methods are generally inadequate for providing thin copper conductor patterns.  
     SUMMARY OF THE INVENTION  
      The present invention provides patterning methods for patterning conductive materials in the fabrication of integrated circuits. For example, such methods are particularly advantageous for patterning hard to pattern conductive materials, such as copper, palladium, or platinum, or alloys thereof.  
      A patterning method according to the present invention includes providing a first material and transforming at least a surface region of the first material to a second material. One or more portions of the second material are converted to one or more converted portions of first material while one or more portions of the second material remain. One or more portions of the remaining second material are removed selectively relative to converted portions of first material.  
      In one embodiment of this method, providing the first material may include forming a first material comprising copper or an alloy thereof. Further, transforming at least a surface region of the first material to a second material may include transforming at least a surface region of the copper or copper alloy to a copper oxide material, e.g., oxidizing the first material.  
      In another embodiment of this method, converting the one or more portions of the second material may include exposing the one or more portions of the second material to radiation, e.g., using a broadband radiation source and a photo mask or using a scanning laser.  
      In yet another embodiment of the method, a layer thickness of the one or more converted portions of first material may be increased, e.g., electroplating material on the one or more converted portions of first material or electroless depositing of material on the one or more converted portions of first material. For example, such increasing of the thickness may be performed prior to or after removing the one or more portions of the remaining second material selectively relative to converted portions of first material  
      Another patterning method according to the present invention includes providing a layer on a substrate. The layer includes a first chemical composition and is treated to transform at least a region of the layer to a second chemical composition. The layer is then patterned by converting one or more portions of the transformed region including the second chemical composition to one or more converted portions including the first chemical composition with one or more portions including the second chemical composition remaining. The one or more remaining portions including the second chemical composition are removed selectively relative to the one or more converted portions including the first chemical composition.  
      In various embodiment of this method, for example, the layer including the first composition may be transformed to a metal oxide (e.g., by oxidation), one or more portions of the transformed region including the second chemical composition may be converted to one or more converted portions including the first chemical composition by exposing the one or more portions of the transformed region comprising the second chemical composition to radiation (e.g., using a broadband source and a photo mask or using a scanning laser), the first chemical composition may include an elemental metal which is transformed to a second chemical composition comprising a metal oxide, a thickness of one or more converted portions comprising the first chemical composition may be increased, and the first chemical composition may include copper and the second chemical composition may include copper oxide.  
      Another method according to the present invention includes providing metal oxide comprising material on a substrate and transforming one or more regions of the metal oxide comprising material to one or more regions of an elemental metal comprising material while leaving one or more remaining regions of the metal oxide comprising material. Thereafter, one or more of the remaining regions of the metal oxide comprising material are removed selectively relative to the one or more regions of the elemental metal comprising material to form conductors on the substrate.  
      In various embodiments of this method, for example, providing the metal oxide comprising material on a substrate may include forming an elemental metal comprising material on the substrate and oxidizing substantially all of the elemental metal comprising material to form the metal oxide comprising material, the elemental metal comprising material may be one of copper and a copper alloy and the metal oxide comprising material may include copper oxide, transforming the one or more regions of the metal oxide comprising material may include exposing the metal oxide comprising material to radiation, removing the one or more of the remaining regions of the metal oxide comprising material may includes etching one or more of the remaining regions of the metal oxide comprising material with an etchant (e.g., hexafluoroacetylacetone), a thickness of the conductors on the substrate may be increased, and a diffusion barrier material may be used therewith.  
      A metal conductor patterning method is also described according to the present invention. The method includes providing a layer of copper on a substrate, transforming at least a surface region of the copper to a copper oxide, converting one or more portions of the copper oxide to one or more converted portions of copper while at least other portions of the copper oxide remain, and removing substantially all of the portions of the copper oxide remaining relative to the copper resulting in copper conductors on the substrate. For example, converting the one or more portions of the copper oxide to one or more converted portions of copper may include photoreducing the one or more portions of copper oxide to copper. Further, the method may include increasing a thickness of the copper conductors such as by electroplating material on the one or more converted portions of copper or electroless depositing of material on the one or more converted portions of copper.  
      Yet another patterning method according to the present invention includes forming diffusion barrier material on a substrate, forming a first material on at least a portion of the diffusion barrier material and transforming at least a surface region of the first material to a second material. One or more portions of the second material are converted to one or more converted portions of first material while at least one or more portions of the second material overlying diffusion barrier material remain. One or more of the remaining portions of second material are removed selectively relative to the one or more converted portions of first material exposing diffusion barrier material thereunder and the exposed diffusion barrier material is removed selectively relative to the one or more converted portions of first material.  
      In various embodiments of this method, forming the diffusion barrier material may include depositing the diffusion barrier material on the substrate by chemical vapor deposition or may include forming the diffusion barrier material on the substrate by electroless deposition.  
      In another embodiment, this method may further include increasing a thickness of the one or more converted portions of first material. Further, an additional diffusion barrier layer may be formed over the one or more converted portions of first material having an increased thickness, e.g., forming the additional diffusion barrier layer by electroless deposition.  
      In yet another conductor patterning method according to the present invention, the method includes forming a diffusion barrier material including cobalt, tungsten, and phosphorus on a silicon-containing region of a substrate (e.g., by chemical vapor deposition or electroless deposition) and forming a first material comprising copper on the diffusion barrier material. At least a surface region of the first material comprising copper is oxidized to a second material comprising copper oxide. One or more portions of the second material comprising copper oxide is converted to one or more converted portions of first material comprising copper while leaving at least one or more portions of the second material comprising copper oxide remaining over underlying portions of the diffusion barrier material, e.g. photoreduction of the copper oxide. One or more of the remaining portions of second material comprising copper oxide are removed selectively relative to the first material comprising copper exposing underlying diffusion barrier material. Further, the exposed diffusion barrier material is removed.  
      In one embodiment of this method, a thickness of one or more converted portions of the first material comprising copper may be increased e.g., by electroplating material on the one or more converted portions comprising copper or by depositing material on the one or more converted portions of first material comprising copper by electroless deposition.  
      In another embodiment of this method, additional diffusion barrier material may be formed over the one or more converted portions of the first material comprising copper, or over the one or more converted portions of the first material comprising copper having an increased thickness, to provide a barrier completely about the converted portions. For example, the additional diffusion barrier material may include cobalt, tungsten, and phosphorus.  
      The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. Advantages, together with a more complete understanding of the invention, will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will be better understood from reading the following description of illustrative embodiments with reference to the attached drawings, wherein below:  
       FIGS. 1-5  are sectional views illustrating a patterning method according to the present invention.  
       FIG. 6  is a sectional view illustrating alternate processing steps for certain steps shown in  FIGS. 1-5 .  
       FIGS. 7-11  are sectional views illustrating another alternate patterning method according to the present invention.  
       FIGS. 12-17  are sectional views illustrating yet another alternate patterning method wherein a diffusion barrier material is used according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
      Generally, according to the present invention, the patterning method described with reference to  FIGS. 1-5  includes forming a first material  30 , as illustrated in  FIG. 1 , and transforming at least a surface layer of the first material  30  to a second material  32 , as shown in  FIG. 2 . Thereafter, the method includes converting one or more portions of the second material  32  back to one or more converted portions  34  of first material as shown in  FIG. 3 . Upon such conversion, one or more portions of the second material  32  remain. Thereafter, the second material  32  is selectively removed relative to the converted portions  34  of first material. One potential use for such a method is in formation of a pattern of:the first material, e.g., a pattern of conductors.  
      With reference to  FIG. 1 , a semiconductor wafer portion  10  is shown to include a substrate  20  and a first material  30  formed thereon. First material  30  may be an elemental metal, e.g., copper, alloys thereof, as well as other materials. For example, first material  30  may include copper, palladium or platinum, or alloys thereof such as copper palladium alloy or copper platinum alloy. The present invention is particularly advantageous in the patterning of copper and/or copper alloys.  
      The invention is not limited in application to semiconductor wafers, however, wafer fabrication constitutes one particularly advantageous application. Although first material  30  is formed on substrate  20  in  FIG. 1 , first material  30  may instead comprise an entire article or a portion of an article without being formed on a substrate, such as substrate  20 . In the context of this document, the term “semiconductor substrate” is defined to mean any construction including semiconductive material, including, but not limited to, bulk semiconductive materials 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 semiconductor substrates described above.  
       FIG. 2  shows wafer portion  10  wherein first material  30  on substrate  20  is transformed to second material  32 . For example, second material  32  may include a metal oxide or a metal oxide-comprising material as well as other materials. In  FIG. 2 , the entire thickness of first material  30  is transformed to second material  32 . However, in an alternate process, less than the full thickness of first material  30  may be transformed to second material  32 . For example, transforming only a surface layer of first material  30  to second material  32  may be preferred particularly when first material  30  is not formed on a substrate. Transforming only a surface region is further discussed below with reference to  FIGS. 7-11 .  
      Transformation of first material  30  to second material  32  may be accomplished by oxidation, among other methods. Oxidation of a metal may be conducted by a variety of methods, however, one particular method is believed advantageous for copper. For example, a copper film having a thickness in the range of about 10 Å to about 500 Å may be formed on the substrate  20 . The copper film may be formed by any suitable method, such as evaporation, sputtering, or chemical vapor deposition processes. The copper may be exposed to a plasma including O 2 , O 3 , or, preferably, O 2  and O 3 . For example, at a temperature in the range of about 100° C. to about 400° C., preferably 200° C. or greater, an oxidation rate of 200 Å per minute or higher may be achieved. For a lower oxidation rate, temperature less than 200° C. may be used. It should be noted that if layer  30  is copper and is entirely converted to copper oxide, the copper oxide layer  32  resulting will be about  1 . 67  times as thick as the copper layer  30 . Such an oxidation method may also be applicable to different elemental metals, metal-comprising materials, and other materials.  
       FIG. 3  shows a portion of second material  32  converted back to portions  34  of first material, creating a patterned first material. Such conversion leaves other portions remaining as second material  32 , as shown in  FIG. 3 . Converting one or more portions of second material  32  back to the first material may include exposing second material  32  to radiation to reduce an oxidation state, e.g., photoreduction. For example, the oxidation state of second material  32  may be reduced by radiation exposure, yielding first material. Various illumination techniques may reduce a metal oxide-comprising material to an elemental metal-comprising material. It is also conceivable that other methods may be used to reduce a metal oxide or metal oxide-comprising material to an elemental metal or to convert a second material back to a first material.  
      For copper oxide, ultraviolet photoreduction of copper oxide to copper metal may be performed with radiation, preferably, having a wavelength of less than or equal to about 468 nanometers (nm). Particularly advantageous results may be achieved when temperature is maintained in a range of about 10° C. to about 100° C. At a radiation intensity of approximately 1.0 Watt per square centimeter, a 50 Å copper oxide layer may be photoreduced to a copper layer in less than one minute. Generally, a radiation intensity of less than about 60 Watts per square centimeter may be sufficient to photoreduce most copper oxide layers. However, depending on the needs of a particular application, radiation intensity may be higher. Photoreduction of metal oxides is described in U.S. patent application Ser. No. 09/484,683, entitled “Removal of Copper Oxides From Integrated Interconnects” filed 17 Jan. 2000.  
      A variety of exposure techniques can accomplish converting one or more portions of second material  32  in  FIG. 2  back to portions  34  of first material while leaving other portions remaining as second material  32 . One illustrative method includes providing a mask over the layer  32  and illuminating the unmasked portions of the layer. For example, a patterned photoresist or other masking material is formed on or over second material  32 , e.g., copper oxide, with openings in areas where it is desired to convert second material  32  back to the first material, e.g., copper. Thereafter, a broadband UV source, either coherent or incoherent, may be used to illuminate the second material  32 , e.g., copper oxide.  
      Radiation may also be used to provide patterned material by numerous other methods without forming a photoresist or masking material on second material  32 . For example, a scanned, focused UV laser may accomplish the desired conversion of a portion of second material  32 . Two suitable lasers include a KrF (wavelength—248 nm) laser or an ArF (wavelength—193 nm) laser.  
       FIG. 4  shows wafer portion  10  after removal of second material  32  selectively relative to patterned first material  34 . To accomplish selective removal, second material  32  is preferably removed at a removal rate of about 200 Å/minute to about 1400 Å/minute producing a selectivity ratio greater than about 20:1 with respect to the removal rate of patterned first material  34 . The acceptability of a particular selectivity ratio depends on a variety of factors, including the type of application, the tolerance levels for removal of patterned first material  34  during removal of second material  32 , the intended function for patterned first material  34 , etc.  
      Removing second material  32  may include a variety of methods. One illustrative removal method includes etching second material  32  with a gaseous etchant. For example, for copper oxide, and perhaps other materials, the gaseous etchant may comprise hexafluoroacetylacetone (H(hfac)). The H(hfac) is believed to form a volatile copper compound [bis-hexafluoroacetylacetonate: Cu(hfac) 2 ] and water vapor when the gas is heated to a predetermined temperature and the copper oxide surface is at a predetermined temperature. The volatile composition and water vapor can then be carried off with the flow of the gaseous etchant, (H(hfac)). Therefore, the copper oxide is selectively removed relative to first material  34 , such as elemental copper. In one illustrative embodiment, the temperature of H(hfac) gas may be approximately 40° C. with a copper oxide surface temperature of approximately 200° C. However, the gas temperature may range from 30° C. to 250° C. and the copper oxide temperature may range from 50° C. to 400° C. The copper oxide removal rate may be greater than 200 Å/minute when using certain flow rates of gaseous etchant.  
      As the present invention has application in pattern forming methods, another aspect of the invention includes a patterned layer forming method wherein a layer is formed over a substrate, the layer includes a first chemical composition (e.g., copper). The method further includes first treating the layer to transform at least a portion of the layer to a second chemical composition (e.g., copper oxide) and then treating the layer to convert at least a portion of the second chemical composition back to the first chemical composition (e.g., copper). The layer may then be patterned by removing the second chemical composition (e.g., copper oxide) selectively relative to the first chemical composition (e.g., copper).  FIGS. 1-4  show one example of implementing such a method in the case of semiconductive wafer portion  10 . However, other implementations may be used.  
      One such implementation includes a metal patterning method. In one aspect of the invention, the metal patterning method includes providing a layer of a metal oxide-comprising material on a substrate. A region of the metal oxide-comprising material may be transformed to a metal-comprising material while leaving a remaining region of the metal oxide-comprising material. Removing at least some of the remaining region of the metal oxide-comprising material selectively relative to the metal-comprising material is conducted to form a pattern on the substrate comprising the metal-comprising material.  
      One possible method for forming a layer of the metal oxide-comprising material includes forming a layer of elemental metal on the substrate and transforming substantially all of the elemental metal to the metal oxide-comprising material. It is also conceivable within the present invention that a layer of other than elemental metal may be formed on a substrate and transformed, at least in part, to metal oxide or a metal oxide-comprising material. Nevertheless, significant advantages may exist to using elemental metals, such as one or more of copper, palladium, or platinum.  
      For example, a copper conductor pattern may be formed by first forming a layer of elemental copper on a substrate. The copper layer may be approximately 50 Å but preferably ranges from about 10 Å thick to about 100 Å. As discussed below, the copper layer may even be more than 100 Å thick depending on the particular application. A less than 100 Å thickness may provide advantages in forming of the copper conductor pattern. For example, a thickness less than 100 Å allows for rapid and uniform formation of the oxide and easy conversion of the entire film to the oxide thereof. Further, for example, because of the thin nature of the layer, better pattern definition can be attained. However, other thicknesses may be preferred depending on the particular materials used or the ultimate structure to be formed therefrom. The copper layer may be transformed in part or in its entirety to copper oxide. One or more regions of the copper oxide may then be converted back to copper by chemical reduction (reducing an oxidation state), e.g., photoreduction. Selective removal of the copper oxide may then be performed, leaving behind a copper conductor pattern.  
      In yet another aspect of the present invention, the method may further comprise increasing a thickness of patterned first material  34  shown in  FIG. 4 . Increasing the layer thickness may occur after a selective removal of second material  32  relative to patterned first material  34 , as shown in  FIG. 5 , to produce an increased first material  34   a . However, increased first material  34   a  may also be formed prior to selective removal of second material  32  relative to first material  34  as shown in  FIG. 6 .  
      A variety of potential methods for increasing a thickness of patterned first material  34  may be used. For a conductive patterned first material  34 , such as metal conductors (e.g., copper), electroplating or electroless deposition may be used to increase a thickness of patterned first material  34 . Notably, increasing a thickness of a pattern comprising a first material may include adding material other than the first material on or over the first material. For example, increasing a layer thickness of a pattern comprising a first chemical composition may include forming additional material other than the first chemical composition over the pattern. For electroless deposition, the material chosen to increase the layer thickness may be one for which the patterned material comprises a suitable activator as known among those skilled in the art of electroless deposition. For example, copper as patterned first material  34  may comprise a suitable activator for subsequent electroless deposition of additional copper as well as other metals and other materials.  
      First material  30  may be formed directly on substrate  20  as shown in  FIG. 1 . However, depending on the material types of first material  30  and substrate  20 , other materials may also exist between first material  30  and substrate  20 . For example, if first material  30  may diffuse into substrate  20 , then a barrier layer may be provided between the materials to prevent such diffusion. For example, copper may diffuse into silicon or germanium substrates. As described further below, a diffusion barrier layer may be used when copper is formed on silicon-containing substrates. Other requirements may exist for formation of first material  30  on substrate  20  depending on the particular formation method. A few suitable methods for forming first material  30  on substrate  20 , particularly when first material  30  is a metal, such as copper, include evaporation, sputtering, and chemical vapor deposition. Such methods may be conducted according to the knowledge of those skilled in the art in light of the disclosure herein of the present invention.  
      In one alternate illustrative embodiment of the present invention, only a surface region of first material  30  is transformed to second material  32  as shown in  FIG. 7 . A variety of circumstances may exist wherein only a region of first material  30  is transformed as shown. For example, when first material  30  is copper, the copper may be converted into copper oxide as second material  32 . Depending on radiation source properties and copper oxide properties,  468  nm radiation may only partially penetrate, e.g., about 100 Å, into copper oxide. Therefore, it may be desired to transform only an upper region of the copper such that the transformed thickness can be completely converted back to copper. Accordingly, transforming at least a surface layer or at least an outer portion of first material  30  may include transforming substantially all of first material  30 , as shown in  FIG. 2 , or may include transforming less than substantially all of first material  30 , as shown in  FIG. 7 .  
      Nevertheless, the present invention may proceed even though less than substantially all of first material  30  is transformed to second material  32 , as shown in  FIGS. 7-11 .  FIG. 8  shows one or more portions of second material  32  converted back to the first material to form patterned first material  34  while leaving other portions remaining as second material  32 . In such figures, the thickness difference between the transformed materials, e.g., second material  32 , relative to the patterned first material  34  is not shown as the thickness difference is very small.  FIG. 9  shows increasing a layer thickness of patterned first material  34  to form increased first material  34   a . As noted above, the method may instead include increasing a layer thickness of the pattern with a material other than the first material.  FIG. 10  shows second material  32  selectively removed relative to first material  30  and increased first material  34   a .  
      In the alternate illustrative embodiment shown by  FIGS. 7-11 , the substrate on which second material  32  is formed comprises first material  30 . Accordingly, the method may further comprise removing at least some of first material  30  formerly beneath the removed second material  32  to extend the pattern to the substrate as shown in  FIG. 11  Wafer portion  10  of  FIG. 10  may be processed by such a method with an anisotropic etch. For example, for removal of copper, such an etch may include ion milling, sputter etching using halides or oxidizing agents, or reactive ion etching using chlorine containing agents. Further, for example, copper may be etched as described in U.S. Pat. No. 4,352,716 to Schaible et al., entitled “Dry Etching of Copper Patterns” issued 5 Oct. 1982. Even though such an etch may reduce the thickness of increased first material  34   a , such thickness may be decreased by an amount roughly approximate the thickness of first material  30  formerly beneath the removed second material  32 . Accordingly, a sufficient portion of increased first material  34   a  may remain to provide a pattern of the first material. It is further conceivable that patterned first material  34  may be increased sufficiently in forming increased first material  34   a  to compensate for a subsequent blanket-etch.  
      Yet another aspect of the present invention may be further described by the following example:  
     EXAMPLE  
      A 50 Å copper film is deposited on a barrier layer over a monocrystalline silicon wafer by sputtering. The copper film is oxidized at approximately 200° C. with an O 2 /O 3  plasma for approximately 15 seconds. A photoresist mask is formed on the copper oxide and patterned by exposure to actinic energy through an exposure reticle. The resulting wafer is illuminated with a broad area source of 468 nm ultraviolet radiation at an intensity of about 1.0 Watt per square centimeter using the patterned photoresist mask. Such radiation converts the copper oxide exposed through the openings in the photoresist mask to metallic copper to a depth of approximately 50 Å after processing for approximately 1 minute. The photoresist is removed followed by removal of the unconverted copper oxide using H(hfac) gas at approximately 40° C. while maintaining the copper oxide surface at approximately 200° C. Selective copper oxide etching is completed after approximately 15 seconds. Electroless deposition of additional copper on the patterned copper is performed to form conductive copper patterns with a thickness of approximately 0.5 micrometers.  
      As described above, when certain materials are formed on other materials, diffusion therebetween may occur. As such, barrier layers must be provided to prevent such diffusion. For example, diffusion barrier materials are generally required when copper conductors are patterned on silicon substrates.  FIGS. 12-17  provide sectional views illustrating an embodiment of a patterning method when a diffusion barrier material is used. Generally, such a patterning method may be used in the formation of copper conductors on silicon. For example, a copper conductor pattern may be formed by locally exposing a uniform thin layer of copper oxide using either broad area WV source illumination and a photo mask or a scanned, focused UV laser as described previously herein. Such processing may include forming a diffusion barrier layer, e.g., CoWP, around the copper conductor. For example, such a diffusion barrier layer may be formed by electroless deposition.  
       FIG. 12  shows a wafer portion  110  wherein a diffusion barrier material  112  is formed on substrate  120 . A first material  130  is then formed on at least a portion of the diffusion barrier layer  112 . For example, the first material  130  may be an elemental metal or an alloy thereof. Further, for example, in one preferred embodiment of the present invention, the first material  130  is a copper-comprising material such as elemental copper or a copper alloy such as copper palladium or copper platinum. When the first material  130  is a copper-comprising material, one preferred diffusion barrier material includes cobalt, tungsten, and phosphorous.  
      Preferably, diffusion barrier layer  112  including cobalt, tungsten, and phosphorous is formed on a silicon-containing substrate  120  by any suitable method. For example, such a base diffusion barrier layer  112  may be formed by either chemical vapor deposition or by electroless deposition. For example, CoWP barrier material and formation thereof is described in U.S. Pat. No. 5,695,810 to Dubin et al., entitled “Use of Cobalt Tungsten Phosphide as a Barrier Material for Copper Metallization” issued 9 Dec. 1997; in the article, “Thin Electroless Barrier for Copper Films,” by Lopatin et al.,  Part of the SPIE Conference on Multi - Level Internet Technology II , Santa Clara, Calif. (September 1998); and in the article entitled, “High Aspect Ratio Quarter-Micron Electroless Copper Integrated Technology,” by Shacham-Diamand et al.,  Microelectronic Engineering,  37/38 (1997), pp. 77-88. Preferably, for example, the base diffusion barrier layer  112  including cobalt, tungsten, and phosphorous is formed to a thickness in the range of about 20 Å to about 100 Å. Further, for example, preferably, the diffusion barrier layer includes cobalt, tungsten, and phosphorous, wherein the layer includes cobalt in the range of about 84% to about 88%, about 2% to about 4% of tungsten, and about 10% to about 12% of phosphorous. In one illustrative embodiment, the base diffusion barrier layer  112  is formed of cobalt at about 87%, tungsten at about 2%, and phosphorous at about 11%.  
      Thereafter, preferably, the first material  130  includes copper and is formed over the base difflusion barrier layer  112 . The copper is deposited over the difflusion barrier layer  112  by a suitable method. For example, the copper may be formed by evaporation, sputtering, or chemical vapor deposition as previously described herein. Further, the copper is preferably formed to a thickness in the range of about 10 Å to about 200 Å. Thereafter, just as described with reference to  FIG. 2 , the first material  130  is transformed to second material  132  as shown in  FIG. 13 . As shown in  FIG. 13 , the entire portion of first material  130  is transformed to second material  132 , however, as previously described herein, less than the full thickness of the first material  130  may be transformed to second material  132 . Further, as previously described herein, transformation of first material  130  may be accomplished by oxidation, among other methods. For example, with regard to forming copper conductors, the copper material  130  may be exposed to a plasma oxidation process. For example, the plasma may include O 2 , O 3 , or, preferably, O 2  and O 3 . For example, a copper material may be oxidized to copper oxide at a temperature in the range of about 100° C. to about 400° C., preferably at about 200° C. For example, such oxidation occurs as described in the article entitled, “Dry Etching of Copper Film With Hexafluoroacetylacetone Via Oxidation Process,” by Kang et al.,  J. Vac. Sci. Technol.,  B17(1) January/February 1999.  
      After the first material  130  is transformed to second material  1   32 , one or more portions of second material  132  is converted to one or more converted portions  134  of the first material as shown in  FIG. 14 . Such a conversion leaves other portions of second material  132  remaining. Any suitable method of converting portions of the second material  132  to the converted portions  134  of first material may be used according to the present invention. Preferably, as previously described herein, the second material  132  is an oxide of the first material  130  which is formed of at least one metal material.  
      More specifically, with regard to the formation of patterned copper conductors, first material  130  includes copper and second material  132  includes copper oxide. The one or more portions of second material  132 , e.g., copper oxide, are converted to converted portions  134  of copper by exposure to radiation to reduce an oxidation state of the copper oxide, e.g., photoreduction. Such a conversion process for copper was previously described herein with reference to  FIGS. 1-6  and will not be further described in detail with reference to  FIGS. 12-17 . Generally, for example, such exposure to radiation may be provided by selectively exposing one or more portions of the copper oxide to a broad area UV source using a mask. For example, a source wavelength less than 486 nm and an intensity of approximately 1.0 Watt/cm 2  which illuminates copper oxide photoreduces the copper oxide to copper. Further, as previously described herein, the illumination may be incoherent or coherent. In addition, a scanned, focused laser may also be used to photoreduce one or more portions of the copper oxide. The result of the photoreduction of the copper oxide is shown in  FIG. 14  as the patterned converted portions  134  of copper.  
      After the photoreduction of the second material  132  to the pattern  134  of first material, the remaining portions of second material  132  as shown in  FIG. 14  are removed. Such method of removal depends entirely upon the type of second material  132  present. For example, to remove second material  132  comprising copper oxide, preferably, exposure to a gaseous etchant (e.g., hexafluoroacetylacetone) is used in a manner as described previously with reference to  FIGS. 1-6 .  
      Upon removal of the remaining portions of second material  132  as shown in  FIG. 14 , portions of the diffusion barrier layer  112  underlying such portions now removed are exposed. With such portions of the diffusion barrier layer  112  exposed, a suitable process is used to remove such exposed material to the upper surface of the substrate  120 . The process will depend on the composition of the diffusion barrier material  112 .  
      In one preferred embodiment of the present invention, wherein the diffusion barrier material includes cobalt, tungsten, and phosphorous, the diffusion barrier material  112  not under the converted portions  134  of copper is removed. For example, a diffusion barrier material including cobalt, tungsten, and phosphorous may be removed by ion milling or sputter etching. For example, an energized argon plasma may be used to sputter the diffusion barrier material  
       FIG. 15  shows the resulting structure with the converted portions  134  of first material  130  stacked with diffusion barrier material  112 . The other portions of second material  132  are removed along with any diffusion barrier material  112  underlying such second material portions. Thereafter, in one embodiment of the present invention, a thickness of the patterned converted portions  134  of first material is increased as shown by the addition of material  134   a  in  FIG. 16 . Such an increase in thickness of the patterned converted portions  134  has been previously described herein with reference to  FIGS. 1-6  and shall not be described herein in detail with reference to  FIGS. 12-17 . However, in general, preferably, such an increase in thickness of the converted portions  134  is preferably accomplished by electroplating or electroless deposition. For example, in a case where converted portions  134  are copper conductors, such copper conductors  134  are increased in thickness preferably by electroless deposition. However, one skilled in the art will recognize that such increase in thickness is an optional processing step and converted portions  134  may function as conductors without any increase in thickness, if desired.  
      Generally, after an increase in thickness of the converted portions  134  comprising first material, a top diffusion barrier material  126  is formed. Preferably, the diffusion barrier material is formed to provide a barrier about the entire conductor, e.g., converted portion  134  and additional material  134   a . Further, preferably, the thickness of the diffusion barrier material  126  is in the range of about 20 Å to about 100 Å and conformally formed over the material of portions  134  and  134   a . Preferably, the diffusion barrier material is a material that can be electroless deposited. As such, the process of forming the diffusion barrier and at least portions of the materials encompassed thereby can be formed by electroless deposition. This is desirable because electroless deposition results in a more uniform and conformal barrier layer requiring fewer patterning and removal process steps.  
      Preferably, when the converted portions  134  and additional material  134   a  includes copper, the top diffusion barrier material  126  is the same as barrier material  112  and includes cobalt, tungsten, and phosphorous. Such materials are of the same type of composition as described previously with reference to  FIG. 12 . As a diffusion barrier material  126  including cobalt, tungsten, and phosphorous can be formed by electroless deposition, it is a preferred diffusion barrier material. However, other barrier materials which may be selectively deposited on the conductor material relative to the substrate  120 , e.g., electroless deposition on the converted portions  134  and additional material  134   a , can also be formed and are preferred over diffusion barrier materials that cannot be formed by selective deposition techniques.  
      As such, as shown in  FIG. 17 , and as described herein, conductors such as copper conductors or copper alloy conductors may be preferably formed according to the present invention. The copper conductor forming methods and diffusion barrier layer formation methods described herein can be employed as an alternative to methods wherein predefined damascene trenches are used to define copper conductor patterns in silicon-containing substrates.  
      All patents and references cited herein are incorporated in their entirety as if each were incorporated separately. This invention has been described with reference to illustrative embodiments and is not meant to be construed in a limiting sense. As described previously, one skilled in the art will recognize that various other illustrative applications may utilize the methods as described herein and that the various steps of the methods of alternate embodiments may be combined with steps of other embodiments to produce advantageous methods according to the present invention. Various modifications of the illustrative embodiments, as well as additional embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments that may fall within the scope of the present invention as defined by the accompanying claims.