Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
  • H01L21/67005—Apparatus not specifically provided for elsewhere
  • H01L21/67011—Apparatus for manufacture or treatment
  • H01L21/67155—Apparatus for manufacturing or treating in a plurality of work-stations
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/001—Apparatus specially adapted for electrolytic coating of wafers, e.g. semiconductors or solar cells
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/008—Current shielding devices
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/02—Tanks; Installations therefor
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/003—Electroplating using gases, e.g. pressure influence
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • 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
  • H01L21/288—Deposition of conductive or insulating materials for electrodes conducting electric current from a liquid, e.g. electrolytic deposition
  • H01L21/2885—Deposition of conductive or insulating materials for electrodes conducting electric current from a liquid, e.g. electrolytic deposition using an external electrical current, i.e. electro-deposition

Definitions

• the present invention relates to the field of fabrication of integrated circuits, and, more particularly, to electrochemically treating substrates during various steps of production to deposit and/or remove a metal on/from the substrate.
• the materials used in multilevel interconnect technology of integrated circuits are thin films of conductors and thin films of insulators.
• IC integrated circuits
• aluminum and aluminum alloys have been widely used in combination with silicon dioxide (Si0 2 ) as an insulator.
• Si0 2 silicon dioxide
• copper possibly in combination with a low-k dielectric material, is nowadays increasingly replacing aluminum and silicon dioxide.
• the use of the copper technology results in a reduction of the number of necessary metallization levels.
• plating in the form of electroplating and electroless plating, and the reverse process, also referred to as an electropolishing process, have become widely- used metal deposition/removing techniques.
• an inorganic acid is used as the main ingredient for the plating solution.
• Sulfuric acid or phosphoric acid is widely used in a variety of concentrations. Sulfuric acid and phosphoric acid are known to etch copper, irrespective of the concentration with which the sulfuric acid and phosphoric acid are provided. The etch rate is further increased when oxygen is readily available at the metal areas formed on semiconductor substrates, as is the case in a conventional plating process due to the oxygen contained in the ambient air.
• the present invention is directed to methods and apparatus to reduce the amount of oxygen and sulfur dioxide coming into contact with exposed metal surfaces before, during and after plating and/or electropolishing metal-containing substrates.
• a process tool for electrochemically treating a substrate comprises a plating reactor and a cover enclosing the plating reactor to define an internal volume containing an internal gas atmosphere.
• the cover is configured to substantially avoid a gas exchange with an ambient atmosphere.
• a process tool for electrochemically treating a substrate comprises a plating reactor and a gas supply system configured to provide a flow of inert gas to the plating reactor to reduce at least one of an oxygen concentration and a sulfur dioxide concentration in the plating reactor.
• a method of electrochemically treating a substrate comprises providing a process tool configured to electrochemically treat the substrate. Next, a gas atmosphere is established that surrounds the substrate, wherein the gas atmosphere has a lower oxygen concentration than an ambient atmosphere surrounding the process tool.
• Figure 1 shows a Pourbaix diagram of copper
• Figure 2a shows a simplified portion of a schematic view of a process tool for electrochemically treating a substrate according to one illustrative embodiment of the invention
• Figure 2b schematically shows a view of the process tool of Figure 2a including further process stations involved in electrochemically treating the substrate;
• Figure 2c shows a schematic view of the process tool with recirculated inert gas, according to the present invention.
• Figure 2d shows a schematic view of a system including the process tool of Figure 2a that allows improved process control according to another illustrative embodiment of the invention.
• copper is oxidized in air to form copper oxide.
• copper may form the so-called green copper carbonate.
• sulfur dioxide (S0 2 ) which may be present in air, copper may form a sulfate. Therefore, a copper layer on a substrate may most likely be subjected to various oxidation processes creating copper ions (Cu + or C ⁇ X) as part of a compound according to the relations given in Equation la. These reactions preferably take place in the presence of oxygen and water, which are commonly also present in the ambient air.
• Equation 2 2H + + 2e- -» H 2
• Equation 1 shows the chemical reaction resulting in the so-called oxygen corrosion.
• the equation shows that oxygen present in air or dissolved in water leads to an oxidation process.
• the electrons necessary in Equation 1 are spent, for example, by the process of Equation la and copper is transformed to Cu 2+ .
• Figure 1 illustrates more clearly this situation, in which the so-called Pourbaix diagram of copper is depicted.
• the Pourbaix diagram shows the electrochemical potentials of copper, its oxides, Cu 2 0 and CuO, and of the copper ion (Cu ++ ) as a function of the pH value.
• the diagram shows four separate areas denoted as Cu, Cu 2 0, CuO and Cu 2+ .
• the areas are separated by lines representing the situation of equilibrium of the compounds of the neighboring areas. The equilibrium may exist between two compounds along a line in the diagram or between three compounds around an intersection of lines separating different pairs of compounds.
• the redox potentials of the oxygen reduction according to Equation 1 are also shown in the Pourbaix diagram of Figure 1. Over the entire pH area, the redox potentials of the oxygen reduction are above the copper equilibrium where Cu 0 and CuO is formed as a protective layer. As a consequence, in the presence of oxygen, according to Equation 1 , copper will be oxidized to form copper oxide (CuO) or copper ions (Cu ++ ), depending on the pH value. Another possible situation is demonstrated by Equation 2 and the corresponding electrochemical potential of this equation is also presented in the Pourbaix diagram of Figure 1. The process according to Equation 2 is generally addressed as hydrogen corrosion, which takes place by reducing 2H + to H 2 . As is known from electrochemical potentials, copper is more noble than hydrogen. This fact is represented by the redox function of Equation 2 in the Pourbaix diagram of Figure 1. Along the entire pH area, the redox potential curve, according to Equation 2, is within the area of elementary copper.
• Equation 3 4CuO + S0 2 + 3H 2 0 + 0,5 0 2 - CuS0 4 3Cu(OH) 2
• Equation 3 shows the formation of caustic copper in the presence of sulfur dioxide (S0 2 ), water and oxygen.
• Caustic copper has a good solubility in water. Therefore, the reaction according to Equation 3 removes the copper oxide (CuO) protective layer and may cause further attack of the copper layer.
• a carbonate of copper may be produced in the presence of humidity, oxygen and carbon dioxide (C0 2 ).
• the present invention is, therefore, based on the concept of creating a local ambient for a substrate to be subjected to a process sequence requiring an electrochemical treatment, in which the amount of sulfur dioxide and/or oxygen and/or carbon dioxide is considerably reduced to thereby shift the equilibrium in Equation 3 towards copper oxide (left side) and to reduce the copper oxidation according to Equations 1, 1a and 2.
• This may be accomplished by providing a substantially inert atmosphere around the substrate to be processed by supplying substantially inert gases, such as nitrogen, argon, and the like, to the process tool under consideration or at least to relevant portions of the process tool.
• the partial pressure over the substrate of sulfur dioxide and/or oxygen and/or carbon dioxide is significantly lowered compared to the ambient atmosphere and reduces the probability for the chemical reaction of an exposed metal surface with these reactive components. Reducing the partial pressure may also allow the removal, to a certain degree, of these ambient gases from process liquids, such as electrolytes, water, for example in the form of ultra pure water, and the like, in which these ambient gases may have dissolved during storing and handling of the process liquids.
• a portion of a process tool 200 for electrochemically treating a substrate comprises a plating reactor 210, which may be, in the present example, an electroplating reactor including a rotatable substrate holder 211 that is adapted to receive and hold a substrate 212, and an anode 213 having formed therein an inlet 214 for introducing electrolyte during the processing of the substrate 212.
• a diffuser element 215 may be arranged between the anode 213 and the substrate holder 212.
• the electroplating reactor 210 represents a so-called fountain-type electroplating reactor.
• the plating reactor 210 may be configured to define an internal volume
• the electroplating reactor 210 includes, during operation of the electroplating reactor 210, an internal gas atmosphere that contains, in conventional apparatus, a gas mixture substantially corresponding to the ambient atmosphere.
• the electroplating reactor 210 comprises a gas supply system
• the gas supply system 217 that is configured to supply an inert gas, such as nitrogen, argon, or a noble gas and the like, to the internal volume 216.
• the gas supply system 217 includes a first supply line 218 coupled at one end thereof to an inert gas source 220 and at the other end to the internal volume 216.
• a second supply line 219 may be provided, one end of which is coupled to the internal volume 216 and the other end thereof coupled to an exhaust source (not shown).
• the first and second supply lines 218, 219 although shown to be connected to the electroplating reactor 210 at an upper side portion and a lower side portion, may be arranged in any appropriate manner, depending on the type of electroplating reactor 210 used in the process tool 200 to feed inert gas to the internal volume 216.
• an inert gas for example nitrogen
• an inert gas for example nitrogen
• an inert gas may be supplied from the inert gas source 220 via the first supply line 218 into the internal volume 216 to establish a substantially inert atmosphere within the electroplating reactor 210, thereby significantly reducing the amount of sulfur dioxide and oxygen.
• substantially inert gas atmosphere is to describe a gas atmosphere, the oxygen concentration of which deviates from that of the ambient atmosphere, usually the atmosphere in a clean room, by at least 20%, so that a maximum oxygen concentration is approximately 16%, and preferably less than
• the substrate 212 may be loaded into the electroplating reactor 210 and may be received by the substrate holder 21 1.
• the internal substantially inert atmosphere of the internal volume 216 may be in contact with the ambient atmosphere so that a certain amount of gas exchange may take place.
• a certain amount of overpressure is created by the gas supply system 217 to thereby establish a gas flow from the internal volume 216 towards an opening (not shown) from which the substrate 212 is loaded onto the substrate holder 21 1. In this way, the introduction of oxygen and sulfur dioxide from the ambient atmosphere into the internal volume 216 is minimized.
• a certain amount of overpressure, by establishing a continuous fluid flow, may be advantageously maintained in electroplating reactors 210 that are not configured to sufficiently seal the internal volume 216 from the ambient atmosphere during operation.
• the gas system 218 may be operated to purge the internal volume 216, for example, by means of the second supply line 219, to further reduce the amount of oxygen and of sulfur dioxide that may have been introduced during loading of the substrate 212 into the electroplating reactor 210.
• operation of the electroplating reactor 210 is started, wherein, contrary to conventional apparatus, the electroplating process takes place in a substantially inert internal gas atmosphere to thereby significantly reduce the corrosion process at the copper surface being plated on the substrate 212.
• FIG. 2b schematically shows the process tool 200 with additional process modules coupled to the electroplating reactor 210.
• the process tool 200 further comprises a rinse station 230 downstream of the electroplating reactor 210 and a dry station 250 downstream of the rinse station 230.
• the electroplatmg reactor 210, the rinse station 230 and the dry station 250 are connected by a plurality of substrate transport modules 260 that are configured to allow substrate transportation, as indicated by arrows 261.
• the process tool 200 further comprises a cover 201 that defines an internal volume 202.
• the cover 201 is configured to substantially prevent a gas exchange with the ambient atmosphere, whereas, in other embodiments, the cover 201 is designed to at least remarkably reduce a gas exchange of the internal volume 202 with the ambient atmosphere.
• the cover 201 may comprise a plurality of baffles 203 that allow a certain degree of separation between the individual process modules and stations.
• the gas supply system 217 additionally comprises a plurality of supply lines 204 arranged to provide inert gas to at least some of the process stations 210, 230, 250 and the transportation modules 260.
• one or more exhaust lines may be provided to establish a continuous gas flow, especially when the cover 201 substantially completely seals the internal volume 202 from the ambient atmosphere. It is to be noted that the embodiment depicted in Figure 2b is only of an illustrative nature and many variations and modifications may be carried out without departing from the scope of the present invention.
• the provision, the design and the arrangement of the baffles 203 may be altered in many ways, depending on the configuration of the process stations 210, 230, 250 and the transportation modules 260.
• the rinse station 230 and the dry station 250 are shown as "open" systems, whereas, in other embodiments, these stations may include process chambers that may have separate enclosures requiring the provision of additional supply lines, such as the supply lines 218, 219.
• the transportation modules 260 may include any type of wafer handling apparatus and, accordingly, the baffles 203 may be designed so as to allow loading and de-loading activities to and from the adjacent process stations, while reducing gas exchange between adjacent stations and modules.
• the baffles 203 may be completely omitted, especially when the rinse station 230 and the dry station 250 individually comprise a process chamber having an enclosure.
• the substrate 212 having a copper surface that is electroplated under conditions as described with reference to Figure 2a, is transferred to the process module 260 downstream of the electroplating reactor 210. Since a substantially inert gas atmosphere is established in the internal volume 202 by the supply lines 204, the wet and sensitive surface of the previously plated copper will be substantially prevented from coming into contact with oxygen and/or sulfur dioxide.
• the substrate 212 typically comprises a thin film of electrolyte upon completion of the plating process and the substantially inert gas atmosphere in the internal volume 202 may reduce the probability for the corrosion of the newly-plated copper surface during transportation to the rinse station 230. Since the substrate 212 is processed in the rinse station 230 and the dry station 250, including transportation between these process stations, in a substantially inert gas atmosphere, corrosion of copper is also minimized during the post-plating processes.
• the process tool 200 may comprise a greater number of process modules, as shown in Figure 2b, in accordance with process requirements.
• the rinse station 230 may represent any cleaning station required for the processing of substrates, including sophisticated metallization layers.
• other embodiments, especially those process stations involving a "wet" processing of the substrate 202 may include an exhaust line, such as the second supply line 219 of the electroplating reactor 210, to continuously reduce the humidity in the corresponding local atmosphere.
• a modular structure, as shown in Figure 2b, further allows the individual accessing of process stations and/or transportation modules without unduly affecting the gas atmosphere of adjacent process stations and modules.
• the modular configuration of the process tool 200 allows for loading and de-loading of substrates from and to the process tool 200, for example, by means of the first and the last transportation modules 260, without unduly compromising the inert gas atmosphere in the remaining internal volume 202.
• Figure 2c schematically shows a further illustrative embodiment of the present invention, wherein the gas supply system 217 of the process tool 200 comprises a reactor 221 that is configured to remove oxygen and/or sulfur dioxide from an inert gas.
• the reactor 221 may be any type of chemical and/or physical reactor, including, for example, a catalyst, that allows the removal of oxygen and/or sulfur dioxide, in a manner as is well-known in the art.
• This embodiment is especially advantageous when the process tool 200 requires the supply of large amounts of inert gases or the supply of relatively expensive inert gases, such as argon or other noble gases, since the main amount of the inert gas may be reworked and reused.
• the cover 201 is preferably configured to minimize leakage of inert gas to the ambient atmosphere.
• Figure 2d schematically shows a further variation of the process tool 200.
• the process tool 200 comprises a plurality of sensor elements 271 that are connected to a control unit 270, which, in turn, is operatively coupled to the gas supply system 217 including the inert gas source 220.
• the sensor elements 271 may include a pressure sensor, an oxygen concentration sensor, a sulfur dioxide concentration sensor, and the like.
• the sensor elements 271 may be provided in one or more of the process stations 210, 230, 250 and the transportation modules 260.
• the control unit 270 may be configured to receive the signals output by the sensor elements 271 and to perform process control on the basis of the received sensor signals.
• the gas supply system 217 may comprise suitable means to adjust the fluid flow through the supply line 204 or the supply lines 218 and 219.
• Corresponding means are well-known in the art and may include valve elements, pumps, fans, and the like.
• the control unit 270 may then correspondingly adjust one or more of these flow-adjusting means to control fluid flow in the supply lines 204, 218, 219, thereby also controlling the atmosphere within the internal volume 202.
• the substantially inert gas atmosphere in the other process stations 230, 250 and transportation modules 260 may be controlled.
• the amount of inert gas supplied to the process tool 200 may be reduced to the actually required amount, thereby saving resources.
• the present invention efficiently allows one to reduce the probability for the formation of copper corrosion in processes involved in electrochemically treating a substrate, such as electroplating, electropolishing and the like, wherein a substantially inert gas atmosphere is established around the substrate by a continuous gas flow and/or by providing a cover defining an internal volume with a substantially inert gas atmosphere within the process tool or at least within a part of the process tool.
• a substantially inert gas atmosphere is established around the substrate by a continuous gas flow and/or by providing a cover defining an internal volume with a substantially inert gas atmosphere within the process tool or at least within a part of the process tool.
• other processes associated with electrochemically treating the substrate such as loading, transportation, cleaning, drying and temporarily storing of the substrate, are also performed within a substantially inert atmosphere.

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• 2003
  • 2003-06-24 AU AU2003248809A patent/AU2003248809A1/en not_active Abandoned
  • 2003-06-24 TW TW92117062A patent/TWI286355B/zh not_active IP Right Cessation
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  • 2003-06-24 EP EP03762324A patent/EP1540044A2/de not_active Withdrawn
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