Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/06—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of metallic material
  • C23C16/16—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of metallic material from metal carbonyl compounds
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/06—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of metallic material
  • C23C16/18—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of metallic material from metallo-organic compounds
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  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/28—Manufacture of electrodes on semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/268
  • H01L21/283—Deposition of conductive or insulating materials for electrodes conducting electric current
  • H01L21/285—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation
  • H01L21/28506—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers
  • H01L21/28512—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers on semiconductor bodies comprising elements of Group IV of the Periodic Table
  • H01L21/28556—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers on semiconductor bodies comprising elements of Group IV of the Periodic Table by chemical means, e.g. CVD, LPCVD, PECVD, laser CVD
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  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
  • H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
  • H01L21/76802—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics
  • H01L21/76807—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics for dual damascene structures
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  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
  • H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
  • H01L21/76829—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing characterised by the formation of thin functional dielectric layers, e.g. dielectric etch-stop, barrier, capping or liner layers
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  • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
  • H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
  • H01L21/76829—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing characterised by the formation of thin functional dielectric layers, e.g. dielectric etch-stop, barrier, capping or liner layers
  • H01L21/76831—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing characterised by the formation of thin functional dielectric layers, e.g. dielectric etch-stop, barrier, capping or liner layers in via holes or trenches, e.g. non-conductive sidewall liners
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  • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
  • H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
  • H01L21/76829—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing characterised by the formation of thin functional dielectric layers, e.g. dielectric etch-stop, barrier, capping or liner layers
  • H01L21/76832—Multiple layers
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  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
  • H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
  • H01L21/76829—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing characterised by the formation of thin functional dielectric layers, e.g. dielectric etch-stop, barrier, capping or liner layers
  • H01L21/76834—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing characterised by the formation of thin functional dielectric layers, e.g. dielectric etch-stop, barrier, capping or liner layers formation of thin insulating films on the sidewalls or on top of conductors
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  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
  • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
  • H01L21/76841—Barrier, adhesion or liner layers
  • H01L21/76843—Barrier, adhesion or liner layers formed in openings in a dielectric
  • H01L21/76849—Barrier, adhesion or liner layers formed in openings in a dielectric the layer being positioned on top of the main fill metal
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  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
  • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
  • H01L21/76841—Barrier, adhesion or liner layers
  • H01L21/76853—Barrier, adhesion or liner layers characterized by particular after-treatment steps
  • H01L21/76855—After-treatment introducing at least one additional element into the layer
  • H01L21/76858—After-treatment introducing at least one additional element into the layer by diffusing alloying elements
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  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
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  • H01L21/76841—Barrier, adhesion or liner layers
  • H01L21/76853—Barrier, adhesion or liner layers characterized by particular after-treatment steps
  • H01L21/76861—Post-treatment or after-treatment not introducing additional chemical elements into the layer
  • H01L21/76864—Thermal treatment
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  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
  • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
  • H01L21/76841—Barrier, adhesion or liner layers
  • H01L21/76871—Layers specifically deposited to enhance or enable the nucleation of further layers, i.e. seed layers
  • H01L21/76873—Layers specifically deposited to enhance or enable the nucleation of further layers, i.e. seed layers for electroplating
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  • H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
  • H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
  • H01L23/532—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body characterised by the materials
  • H01L23/53204—Conductive materials
  • H01L23/53209—Conductive materials based on metals, e.g. alloys, metal silicides
  • H01L23/53228—Conductive materials based on metals, e.g. alloys, metal silicides the principal metal being copper
  • H01L23/53238—Additional layers associated with copper layers, e.g. adhesion, barrier, cladding layers
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  • H01L2221/10—Applying interconnections to be used for carrying current between separate components within a device
  • H01L2221/1005—Formation and after-treatment of dielectrics
  • H01L2221/101—Forming openings in dielectrics
  • H01L2221/1015—Forming openings in dielectrics for dual damascene structures
  • H01L2221/1036—Dual damascene with different via-level and trench-level dielectrics
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  • H01L2924/0001—Technical content checked by a classifier
  • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Definitions

• Copper is replacing aluminum as the material of choice for wiring of microelectronic devices, such as microprocessors and memories.
• semiconductors such as silicon causes defects that can prevent the proper functioning of transistors formed in the semiconductor.
• Copper also increases the leakage of current through insulators, such as silicon dioxide, placed between the copper wires. Therefore use of copper wiring demands that efficient diffusion barriers surround the copper wires, to keep the copper confined to its proper locations.
• Copper also has a tendency to move in the direction that electrons are flowing in a circuit. This electromigration process can lead to increased electrical resistance, or even an open circuit if a sufficiently large void forms within a copper interconnection. Most of this unwanted motion takes place along the surface of the copper. Therefore it is critical to maintaining long lifetimes that the copper interconnections be surrounded by materials that inhibit electromigration. Tantalum metal (Ta) serves this function on the bottom and sides of currently-used copper interconnections. The top of copper wiring (those parts that do not connect to an upper level by a via) are covered by SiC or Si 3 N 4 , although these materials are not as effective as the Ta in preserving the copper against electromigration.
• Ta Tantalum metal
• the SiC or Si 3 N 4 also have the disadvantage that they have a higher dielectric constant than the rest of the insulator, so they increase the capacitance of the circuits and decrease the speed with which signals can be transmitted through the wiring.
• Improved lifetime against electromigration has been achieved by electroless deposition of cobalt-tungsten alloys containing phosphorous (CoWP) or boron (CoWB) selectively on top of the copper wires. This selective process is supposed to avoid any deposition of these electrically conductive alloys on the surface of the insulator. Thus it should lead to a self-aligned conductive diffusion barrier on top of all surfaces of the copper that were exposed by the CMP step.
• This MnO x layer is then removed along with the rest of the excess Cu during CMP.
• Mn impurity is present in the Cu during the anneal that is supposed to increase the grain size and thereby decrease the electrical resistance of the Cu. The presence of the Mn impurity during the anneal can restrict the grain growth and thereby increase the final resistance of the Cu over what it would have been without the presence of the Mn impurity.
• Another disadvantage of this process is that some Mn impurity may remain in the Cu even after the anneal, thereby increasing its electrical resistance over that of pure Cu.
• MnO x layer has very weak adhesion to copper, and therefore the electromigration lifetime of such a structure is undesirably short.
• This technology relates to copper interconnections used in microelectronics, and more particularly relates to materials and techniques to secure robust adhesion between the copper and the surrounding materials, providing barriers to prevent diffusion of copper out of the wiring, keeping oxygen and water from diffusing into the copper, and keeping the copper wires from being damaged by the electric current that they carry.
• a process is described for forming a self-aligned diffusion barrier in microelectronic devices without the disadvantage of having a metallic impurity present in the Cu during or after the anneal.
• a metal such as Mn, Cr or V is reacted with the surfaces of the insulator inside the vias and trenches prior to deposition of a Cu-containing seed layer.
• the Mn, Cr or V is delivered to the surfaces by a conformal chemical vapor deposition (CVD) process that does not involve the use any oxygen-containing co-reactant along with the precursor for Mn, Cr or V.
• CVD conformal chemical vapor deposition
• a Cu seed layer is deposited, preferably by CVD.
• the seed layer can also be deposited as a copper compound, such as copper oxide (Cu 2 O), copper nitride (Cu 3 N) or copper oxynitride (CuO z N w ), which is later reduced to Cu.
• Mn, Cr or V is deposited on the planar surface of a partially completed interconnect just after a CMP step.
• the Mn, Cr or V reacts with silicon and oxygen contained in the insulator to form an insulating metal silicate layer, e.g., a MnSi x O y layer where the metal is Mn.
• the Mn dissolves into the top layers of the Cu to form a Cu-Mn alloy.
• a blanket deposition of the insulator for the next higher level of insulator is formed over both the Cu-Mn and MnSi x O y regions.
• the Mn in the Cu-Mn surface layer diffuses upward to react with the insulator to form a MnSi x N y diffusion barrier between the Cu and the insulator, in the embodiment in which the initially- deposited part of this insulator is Si 3 N 4 .
• the presence of this MnSi x Ny layer also increases the adhesion between the Cu and the insulator above it.
• MnSi x Oy and MnSi x Ny layers provide highly conductive, strongly adherent and durable copper layers for, e.g., the production of electronic elements, circuits, devices, and systems.
• the present application describes a process for forming an integrated circuit interconnect structure.
• the process comprises: providing a partially-completed interconnect structure that includes an electrically insulating region and an electrically conductive copper-containing region, the partially-completed interconnect structure having a substantially planar surface; depositing a metal (M) selected from the group consisting of manganese, chromium and vanadium on or into at least a portion of the electrically conductive copper- containing regions; depositing an insulating film on at least a part of the deposited metal, wherein the region of the deposited insulating film in contact with said at least a part of the deposited metal is substantially free of oxygen; and reacting at least a part of the deposited metal with the insulating film to form a barrier layer, wherein the electrically conductive copper-containing region is substantially free of elemental metal (M).
• M metal
• the process includes: providing a partially- completed interconnect structure having a via or a trench, the via or trench including sidewalls defined by one or more electrically insulating materials and an electrically conductive copper-containing bottom region; depositing a metal (M) selected from the group consisting of manganese, chromium and vanadium on the partially-completed interconnect structure; forming second insulating sidewall regions through reaction of the deposited metal and said one or more electrically insulating materials; removing or diffusing away the metal from the bottom region to expose the electrically conductive copper-containing bottom region; and filling the via or trench with copper.
• M metal
• the manganese may be replaced by chromium or vanadium.
• Fig. 1 is a schematic cross section of the top of a partially completed interconnect wiring structure in accordance with the invention, after a Chemical Mechanical Polishing (CMP) step.
• Fig. 2 is the structure of Fig. 1 after a metal deposition.
• Fig. 3 is the structure of Fig. 2 after removal of metal silicate.
• Fig. 4 is the structure of Fig. 3 after a blanket insulator is deposited.
• Fig. 5 is the structure of Fig. 4 after lithography and etching of vias and trenches in the insulator.
• Fig. 6 is the structure of Fig. 5 after an anneal.
• Fig. 7 is the structure of Fig. 6 after another metal deposition.
• Fig. 8 is the structure of Fig. 7 after an anneal.
• Fig. 9 is the structure of Fig. 8 after seed layer deposition and filling with copper.
• Fig. 10 is the structure of Fig. 9 after Chemical Mechanical Polishing.
• Fig. 11 is a cross-sectional high-resolution transmission micrograph of the result of CVD Mn on a Cu / SiO 2 /Si substrate.
• Fig. 12 is a scanning electron micrograph of (a) Cu/SiO 2 /Si and (b)
• Fig. 13 shows capacitance-voltage curves for samples of (a) Cu/SiO 2 /Si and (b) Cu/MnSi x O y /SiO 2 /Si before and after annealing at 400 0 C.
• Fig. 14 shows capacitance-voltage curves for samples of (a) Cu/SiO 2 /Si and (b) Cu/MnSi x O y /SiO 2 /Si before and after annealing at 250 0 C under a 1 MV/cm electric field.
• Fig. 15 shows a cross-section of a MnSi x O y layer formed by CVD on a low-k insulator.
• FIG. 1 A partially completed multi-level wiring structure for a microelectronic device is shown in Fig. 1.
• This structure comprises a substantially planar surface comprising insulating areas 10, e.g., silica, and electrically conducting areas 20, e.g., copper, forming the top of a completed lower level of wiring, separated by a diffusion barrier 25.
• this diffusion barrier can comprise manganese silicate.
• the device at this stage has been processed by CMP followed by cleaning.
• Mn metal is deposited on the surface. The Mn reacts with the exposed areas of the insulator 10 to form an insulating MnSi x Oy layer marked 30 in Fig. 2.
• the Mn diffuses into the upper portion of the Cu to form a CuMn alloy 40.
• the location of the upper surface prior to deposition is indicated by arrows 45, 45'.
• Mn is deposited on a heated substrate. If the temperature of the substrate is high enough (typically over 150 0 C) and the deposition of Mn is slow enough, then the reaction and diffusion of the Mn may be complete by the end of the deposition. If the reaction with the insulator and the diffusion into the Cu are not complete during deposition, then a post-deposition anneal may be used to complete the reaction and diffusion.
• Mn may be deposited by any convenient method, including chemical and physical methods.
• Chemical methods include chemical vapor deposition (CVD) and atomic layer deposition (ALD).
• Physical methods include sputtering and evaporation. Because the substrate is planar, step coverage by the deposition method is not critical to this step. Thus physical methods, which have poor step coverage, are adequate for this deposition step. CVD can also be used in this step whether or not the specific CVD process has good step coverage.
• the MnSi x O y layer 30 can optionally be removed after Mn deposition, as is shown in Fig. 3.
• the MnSi x O y layer 30 formed in the last step is an electrical insulator, but its leakage current may be higher than desired in some applications. In such cases, this metal silicate layer 30 may be removed, in order to reduce the leakage current in devices.
• the silicate layer 30 may be removed by any convenient means, such as polishing, wet etching or dry etching. The removal may be non-selective, removing copper at the same rate as the silicate, thereby maintaining a flat surface. Alternatively, the silicate layer 30 may be removed selectively without removing copper, as is illustrated in Fig. 3. The resulting uneven surface requires a conformal method to deposit the blanket insulator in the next step.
• a blanket insulator layer 50 is next deposited on this structure, as shown in Fig. 4.
• the structure in Fig. 4 includes the silicate layer 30 above insulating layer 10. Any of the methods known in the art may be used to make this insulator layer, including plasma-enhanced CVD or spin coating. Insulator compositions comprising Si and O may be used. In certain embodiments, insulator compositions comprising Si but which is substantially free of O, such as SiN, SiC, SiCN, and the like, may be used. In certain embodiments, insulator layers can be built up by deposition of several sub-layers of insulating material, each adding a specific functionality to the overall insulating layer.
• a first insulating sub-layer 51 which enhances adhesion to the manganese-doped copper layer underneath it, such as a Si 3 N 4 , may be used.
• sub-layer 51 may be substantially free of oxygen.
• sub-layer 51 that is substantially free of oxygen may enhance adhesion to the manganese-doped copper layer over than that obtained by adhesion of a sub-layer 51 which comprises oxygen.
• an etch-stop sub-layer 52 such as silicon carbide, may be deposited on top of sub-layer 51. The etch- stop sub-layer 52 can help to define the proper depth for etching of the holes (vias).
• the next insulating sub-layer 53 may be a porous dielectric with a very low dielectric constant (typically k less than about 2.5).
• the final insulating sub-layer 54 may be a denser non-porous dielectric with a higher dielectric constant (k greater than about 2.5), which can help to protect the more fragile porous dielectric layer from mechanical damage, as well as keeping water from entering into the pores of the porous dielectric.
• sublayers 53 and 54 may contain Si and O. Another function of the sub-layer 53 may be as an etch- stop layer for defining the bottoms of trenches through the sub-layer 54.
• any reference to insulating layer 50 in the present application should be understood to encompass one or more of the sub-layers described herein.
• Lithography and etching are used to pattern holes (vias) 100 and trenches 110 into the insulator layer 50.
• a schematic cross section of the resulting structure is shown in Fig. 5.
• This structure is annealed to form a MnSi x Ny layer 60 (assuming the use of Si 3 N 4 as sub-layer 51) at the interface between the insulating silica layer 50 and the CuMn alloy layer 40, as shown in Fig. 6.
• the MnSi x N y layer 60 serves as a barrier against diffusion of Cu out of the layer 20 and also provides strong adhesion between the Cu 20 and the insulator 50.
• the MnSi x Ny can also serve to prevent diffusion of oxygen or water from the insulator layer 50 into the Cu layer 20.
• Mn from the Mn-Cu alloy layer 40 is located in the MnSi x Ny layer 60; however, some Mn may migrate during anneal to the upper surface of the layer 20 to form a manganese oxide layer (not shown). Any manganese oxide remaining on the Cu surface may be removed by directional sputtering, or by selective etching by a vapor such as formic acid or by a liquid acid solution. This is indicated by the slight recession 65 between the upper surface of Cu layer 20 and adjacent MnSi x N y layer 60.
• Another layer of Mn is deposited next, preferably by a conformal method such as CVD or ALD.
• This step forms a layer 80 on the walls of the vias and trenches, which can vary from MnSi x O y near the top and MnSi x N y near the bottom if using silica as sub-layer 54 and silicon nitride as sub-layer 51.
• This step can further form a top layer of MnSi x O y 90 on the upper surface of insulator layer 50, as shown in Fig. 7.
• a CuMn alloy layer 70 forms initially on the exposed copper surface of layer 20, but then the Mn diffuses to form more of the insulator surfaces such as layer 60. If the formation of these layers is not complete by the end of the deposition, an additional anneal and possibly an acid etch is used to form the structure shown in Fig. 8, in which the copper 20 layer is substantially free of Mn impurity.
• a seed layer of Cu is formed, preferably by a conformal method such as CVD, ALD or IPVD. Then the vias and trenches are filled by electroplating to form the structure shown in Fig. 9. This pure Cu layer 120 is annealed to increase the grain size and reduce the resistance.
• vapor deposition is used to deposit a metal M selected from the group of Mn, Cr and V.
• AMD is an amidinate ligand
• these compounds may have the following structure: in which R 1 , R 2 , R 3 , R 1 , R 2 and R 3 are groups made from one or more non-metal atoms, such as hydrogen, hydrocarbon groups, substituted hydrocarbon groups, and other groups of non-metallic atoms.
• a manganese amidinate vapor is brought into contact with a heated substrate.
• a CuMn alloy is formed.
• an insulating surface layer of MnSi x Oy is formed.
• the temperature of the heated surface should be sufficiently high, typically over 150 0 C, or preferably over 300 0 C.
• AMD is an amidinate
• m 2 or 3
• n can range from 1 to 3.
• R 1 , R 2 , R 3 , R 1 , R 2 and R 3 are groups made from one or more non-metal atoms, such as hydrogen, hydrocarbon groups, substituted hydrocarbon groups, and other groups of non-metallic atoms.
• R 1 , R 2 , R 3 , R 1 , R 2 and R 3 may be chosen independently from hydrogen, alkyl, aryl, alkenyl, alkynyl, trialkylsilyl, alkylamide or fluoroalkyl groups or other non-metal atoms or groups.
• Exemplary hydrocarbon groups include Ci-C 6 alkyl, C 2 -C 6 alkenyl and C 2 - C 6 alkynyl groups. They can be branched or unbranched.
• Alkyl group refers to a saturated hydrocarbon chain that may be a straight chain or branched chain or a cyclic hydrocarbon group, containing the indicated number of carbon atoms.
• Ci-C 6 indicates that the group may have from 1 to 6 (inclusive) carbon atoms in it.
• alkyl groups include, but are not limited to, ethyl, propyl, isopropyl, butyl, and tert-butyl groups.
• cyclic alkyl groups include, but are not limited to, cyclopropyl, cyclopropylmethyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclohexylmethyl, cyclohexylethyl, and cycloheptyl groups.
• C 2 -C 6 alkenyl group refers to a straight or branched chain unsaturated hydrocarbon containing 2-6 carbon atoms and at least one double bond.
• Examples of a C 2 -C 6 alkenyl group include, but are not limited to, groups derived by removing a hydrogen from ethylene, propylene, 1-butylene, 2-butylene, isobutylene, sec-butylene, 1-pentene, 2-pentene, isopentene, 1-hexene, 2-hexene, 3-hexene, and isohexene.
• C 2 -C 6 alkynyl group refers to a straight or branched chain unsaturated hydrocarbon group containing 2-6 carbon atoms and at least one triple bond.
• Examples of a C 2 -C 6 alkynyl group include, but are not limited to, groups derived by removing a hydrogen from acetylene, propyne, 1-butyne, 2-butyne, isobutyne, sec- butyne, 1-pentyne, 2-pentyne, isopentyne, 1-hexyne, 2-hexyne, and 3-hexyne.
• Substituted hydrocarbon group refers to a saturated or unsaturated, straight or branched chain hydrocarbon containing 1-6 carbon atoms that can be further substituted with other functional groups, such as halogen or boron, or boron- containing groups.
• Halogen refers to an atom of fluorine, chlorine, bromine, or iodine.
• Halogenated hydrocarbons include fluorinated, chlorinated or brominated alkyl.
• Exemplary fluorinated hydrocarbons include fluoroalkyl, fluoroalkenyl and fluoroalkynyl groups and combinations thereof.
• Groups of non-metallic atoms include nitrogen-containing and silicon- containing groups.
• Exemplary nitrogen-containing R groups include amines (NR'R"), in which R' and R" include one or more of H, Ci-C 6 alkyl, C 2 -C 6 alkenyl or C 2 -C 6 alkynyl group and combinations thereof.
• Exemplary silicon-containing R groups include silyl groups (SiR'R"R'"), in which R', R" and R'" include one or more of H, Ci-C 6 alkyl, C 2 -C 6 alkenyl or C 2 - C 6 alkynyl group and combinations thereof.
• R 1 , R 2 , R 3 , R 1 , R 2 and R 3 are each independently alkyl or fluoroalkyl or silylalkyl groups or alkylamide groups.
• the R n groups contain 1 to 4 carbon atoms.
• the manganese amidinate may comprise manganese(II) bis(7V,JV'-diisopropylpentylamidinate), corresponding to taking R 1 , R 2 , R 1 and R 2 as isopropyl groups, and R 3 and R 3 as n-butyl groups in the general formula 1.
• a CVD method bis( ⁇ /,N'-diisopropylpentylamidinato)manganese(II) vapor is flowed over a surface that has been heated to a temperatures of 100 to 500 0 C, or more preferably 150 to 400 0 C.
• a CuMn alloy is formed on the exposed copper surfaces.
• a MnSi x O y layer is formed as a diffusion barrier over the insulating areas.
• the manganese content of the MnSi x Oy layer and the CuMn layer is equivalent to a manganese metal film with thickness of 1 to 10 nm, or more preferably a thickness of 2 to 5 nm.
• the vapor is mixed with dihydrogen gas (H 2 ) at a temperature above 90 0 C and used for the CVD process.
• H 2 dihydrogen gas
• Manganese amidinates may be made by any conventional method. See, e.g., WO 2004/046417, which is incorporated by reference in its entirety.
• the metal precursor may include cyclopentadienyl and carbonyl ligands, corresponding to the general formula (Cp) q M r (CO) s where Cp is an cyclopentadienyl radical substituted by up to five groups, and q, r, and s can be any positive integer. These compounds may have the following structure:
• the Mn-containing precursor can be a manganese cyclopentadienyl tricarbonyl having the formula, (Cp)Mn(CO) 3 .
• Some of these compounds have a structure 2,
• R 1 , R 2 , R 3 , R 4 , and R 5 groups are made from one or more non-metal atoms, such as hydrogen, hydrocarbon groups, substituted hydrocarbon groups, and other groups of non-metallic atoms, as described herein above.
• R 1 , R 2 , R 3 , R 4 , and R 5 may be chosen independently from hydrogen, alkyl, aryl, alkenyl, alkynyl, trialkylsilyl or fluoroalkyl groups or other non-metal atoms or groups.
• R 1 , R 2 , R 3 , R 4 and R 5 are each independently alkyl or fluoroalkyl or silylalkyl groups or alkylamide groups.
• the R n groups contain 1 to 4 carbon atoms.
• a preferred compound of this type is commercially available methylcyclopentadienylmanganese tricarbonyl, (MeCp)Mn(C 0)3, in which R 1 is a methyl group and the other R n 's are hydrogen.
• the metal precursor may include two Cp ligands, with formula M(Cp) 2 where Cp is a cyclopentadienyl radical substituted by up to five groups.
• Thee compounds may have the following structure:
• the Mn-containing precursor can be a manganese cyclopentadienyl having the formula, Mn(Cp) 2 . Some of these compounds have the formula 3,
• R 1 , R 2 , R 3 , R 4 , R 5 , R 1' , R 2' , R 3' , R 4' and R 5' are groups made from one or more non-metal atoms, such as hydrogen, hydrocarbon groups, substituted hydrocarbon groups, and other groups of non-metallic atoms, as described herein above.
• R 1 , R 2 , R 3 , R 4 , R 5 , R 1' , R 2' , R 3' , R 4' and R 5' may be chosen independently from hydrogen, alkyl, aryl, alkenyl, alkynyl, trialkylsilyl or fluoroalkyl groups or other non-metal atoms or groups.
• R 1 , R 2 , R 3 , R 4 , R 5 , R 1 , R 2 , R 3 , R 4 and R 5 are each independently alkyl or fluoroalkyl or silylalkyl groups or alkylamide groups.
• the R n groups contain 1 to 4 carbon atoms.
• a seed layer of Cu may be deposited conformally by methods such as CVD or ALD.
• ALD methods are described, for example, by Zhengwen Li, Antti Rahtu and Roy G. Gordon in the Journal of the Electrochemical Society, volume 153, pages C787-C794 (2006) and by Zhengwen Li and Roy G. Gordon in the journal Chemical Vapor Deposition, volume 12, pages 435-441 (2006).
• CVD methods are described in the paper by Hoon Kim, Harish B. Bhandari, Sheng Xu and Roy G. Gordon, which was published in the Journal of the Electrochemical Society, volume 155, issue 7, pages H496-H503 (2008).
• smooth thin layers of copper oxynitride or copper oxide are first deposited using conventional vapor deposition techniques and then the deposited layers are reduced to smooth copper films by reduction with a hydrogen plasma at room temperature.
• Another method for reducing copper oxide films to copper metal is by reaction with liquid solutions of reducing agents such as dimethylamineborane or metal borohydrides.
• electrochemical deposition can be used to fill the trenches and vias with copper by techniques known in the art. Electrochemical deposition has the advantages that it can provide pure copper without voids or seams in a cost-effective process. [0060] In the foregoing description, the present invention has been described with respect to Mn metals. However, the present invention encompasses vanadium and chromium metals as well and these metals can be interchanged with manganese for the descriptions provided herein.
• the compound that served as a precursor for the manganese is called bis( ⁇ /,N'-diisopropylpropionamidinato)manganese(II), whose chemical formula is shown below.
• This compound was synthesized by the following method. All reactions and manipulations were conducted under a pure dinitrogen atmosphere using either an inert atmosphere box or standard Schlenk techniques. All glassware was stored in an oven at 150 0 C for over 12 h before carrying reactions. Diethyl ether was purified using an Innovative Technology solvent purification system, and was freshly used from the purification without any storage. Butyllithium (1.6 M in hexanes), N,N'- diisopropylcarbodiimide, and manganese(II) chloride (anhydrous beads) were purchased from Aldrich and used as received. Volume reduction and evaporation steps were performed in vacuo.
• Bis(N,N'- diisopropylpropionamidinato)manganese(II) is a pale yellow crystalline solid that immediately turns black when exposed to air.
• the liquid manganese precursor was evaporated at a temperature of 90 0 C into a flow of highly purified nitrogen (concentrations of water and oxygen less than 10 ⁇ 9 of the N 2 ). The vapor pressure of the precursor is estimated to be around 0.1 mbar at this temperature.
• the silica substrates were either thermally oxidized silicon or silica deposited ALD or by plasma-enhanced CVD.
• the CVD was carried out in a hot- wall tube reactor (diameter 36 mm) within a tube furnace at temperatures between 200 and 400 0 C and a total pressure of about 5 Torr.
• the flow rate of N 2 carrier gas was 60 seem.
• the amount of manganese deposited was measured by Rutherford backscattering spectroscopy (RBS).
• the MnSi x O y formation was evaluated by cross-sectional high-resolution transmission electron microscopy (HRTEM).
• HRTEM transmission electron microscopy
• the effectiveness of the MnSi x O y as a barrier to diffusion of Cu was tested in four ways: optical appearance, sheet resistance, Cu suicide formation and capacitance-voltage (CV) analysis of capacitors.
• layers of SiO 2 8 nm thick were grown on HF-etched silicon wafers by ALD at 215 0 C, followed by CVD Mn at 350 0 C for 10 min, which deposited an amount of Mn metal equivalent to a Mn metal film 2.3 nm thick, which reacted with the silica surface to form a thicker MnSi x Oy layer.
• MnSi x Oy layer shows that the CVD Mn metal diffused through the Cu layer and reacted with the SiO 2 to form an amorphous MnSi x Oy layer about 2 ⁇ 5 nm thick between the Cu and the SiO 2 .
• the MnSi x Oy layer is thicker near grain boundaries in the Cu, along which Mn diffusion is faster. This result is clear evidence of Mn metal deposition.
• MnSi x Oy As a copper barrier was evaluated using a sample structure PVD Cu(200 nm)/CVD Mn (2.3 nm)/ALD SiO 2 (8 nm)/Si. A MnSi x Oy layer was formed between the Cu and ALD SiO 2 layers. The shiny Cu color and sheet resistances of these samples were unchanged by anneals in nitrogen at 400 or 450 0 C. After a 500 0 C anneal, the control sample without Mn turned black and its sheet resistance increased by a factor of 200 because of massive diffusion of the Cu through the thin ALD SiO 2 into the silicon. The CVD Mn sample, by contrast, retained its shiny Cu color and showed only a slight increase in resistance even at 500 0 C.
• Fig. 12 shows the SEM results after a 500 0 C anneal for 1 hr.
• the few Cu-containing spots appear to be Cu suicide crystallites oriented by the crystal directions of the silicon.
• the control sample shows that the majority of its surface is covered by Cu suicide.
• the control sample showed a large Cu signal in EDX analysis that was stronger than the silicon signal, confirming that the thin ALD SiO 2 allowed diffusion of Cu.
• the CVD Mn-treated samples did not show Cu by large-area EDAX. A few small areas of the SEM image did show some Cu by EDAX, indicating some localized breakdown of the MnSi x Oy barrier at 500 0 C. These spots might arise from dust or other defects in the films, which were not processed in a clean-room environment.
• MnSi x Oy layers were also found to be good barriers to oxygen and water, which can corrode copper layers.
• commercial low-k porous insulator layers from Applied Materials was coated with manganese as described above, followed by CVD copper.
• the top surface of the copper was protected with 20 nm of ALD silica by the process described in Science, volume 298, pages 402 - 406 (2002).
• the sample was cut into pieces to expose the edges of the low-k insulator so that oxygen or water vapor could diffuse into the low- k layer. After exposure to dry air at 300 0 C for 24 hours, the sample maintained its shiny copper color.
• a cross-sectional transmission electron microscope (TEM) was used to make an image (Fig. 15) of a MnSi x Oy layer in the surface of a low-k insulator. This image shows the MnSi x Oy layer as a dark, featureless band, indicating that this layer is an amorphous glass. Conformality of the CVD Mn and CuON depositions in holes with aspect ratios up to 40:1 was confirmed by cross-sectional SEM and TEM studies.
• Example 1 is repeated with manganese cyclopentadienyl tricarbonyl, MnCp(CO) 3 , in place of bis(bis( ⁇ /, ⁇ f'-diisopropyl-pentylamidinato)manganese(II). Similar results are obtained.
• Example 1 is repeated with chromium in place of manganese. Similar results are obtained.
• Example 1 is repeated with vanadium in place of manganese. Similar results are obtained.
• the sheet resistance then returned to slightly less than 0.5 ohms per square because the manganese diffused to the surfaces or the interface.
• the out-diffusion of the manganese from the Cu film was confirmed by SIMS analysis.
• the adhesion energy was remarkably increased to greater than 12 J m "2 , because manganese diffused to the interface, and made an interface or reaction layer.
• the adhesion energy was greater than the 10.1 + 1 J m ⁇ 2 obtained in Example 1.
• the Mn capping process is able to maintains the insulation between Cu lines.
• comb test structures were prepared with long ( ⁇ 4 cm) parallel Cu interconnects separated by SiO 2 -based insulating lines 70 nm wide. The upper surfaces were prepared by chemical- mechanical polishing to be substantially flat. The leakage current between the lines was less than 10 "12 amperes when measured at 2 volts. After CVD of Mn as in Example 1 for 5 minutes and PECVD of 20 nm Si 3 N 4 , the leakage current remained at this low base-line level. The resistance along the length of the lines decreased slightly from its initial value, possibly because of growth in the size of the copper grains during the CVD processes.

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