Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
  • C25C1/12—Electrolytic production, recovery or refining of metals by electrolysis of solutions of copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C9/00—Alloys based on copper
• • 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
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/34—Sputtering
  • C23C14/3407—Cathode assembly for sputtering apparatus, e.g. Target
  • C23C14/3414—Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
  • C25C7/06—Operating or servicing
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • 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

• the present invention relates to high purity copper and a method of producing high purity copper based on electrolysis.
• the high purity copper produced with the method of the present invention can be used to produce high purity copper alloy by adding the necessary alloy elements.
• the present invention covers all of the above.
• % and ppm as used in this specification respectively represent mass % and mass ppm.
• purity represents the purity excluding C, O, N, and H as gas components.
• protrusions would arise on the target surface in the process of forming a thin film by way of sputtering, and particles would arise due to the rupture or the like of the protrusions (nodules) caused by an abnormal discharge. Generation of particles causes the percent defective of the semiconductor device to deteriorate.
• the recognition was that other causes had a greater influence on the generation of the foregoing particles or the rupture of the bonding wire, and the recognition that minute and trace amounts of inclusions existing in the high purity copper target were the cause was low.
• the sputtering method forms a film on a substrate by utilizing the phenomenon where atoms configuring the target are discharged into space and accumulated on the opposing substrate based on the momentum exchange that occurs when the accelerated charged particles collide with the target surface.
• the sputtering target is usually in the shape of a discoid or rectangular plate, and is used as the sputter source for forming, by way of sputtering, an electrode, gate, element, insulating film, protective film and the like of various semiconductor devices.
• an aluminum and aluminum alloy target a copper and copper alloy target, a high melting point metal and alloy target, a metal silicide target and the like are used.
• an important target is a copper and copper alloy target that is used in forming a copper wiring as an alternative of a conventional aluminum wiring.
• nodules In the deposition based on sputtering, protrusions having a size of several ⁇ m to several mm referred to as nodules sometimes arise on the eroded portion of the sputtering target. There is a problem in that such nodules will burst as a result of colliding with the charged particles in the sputtering process, and thereby cause to generate particles (cluster-shaped coarse fragments) on the substrate.
• the generation of particles will increase in proportion to the number of nodules on the eroded surface of the target, and a major issue is to prevent the generation of nodules in order to reduce the problematic particles.
• particles directly adhere to the thin film that is formed on the substrate, or once adhere to and accumulate on the circumferential wall or component of the sputtering device and thereafter flake off and adhere to the thin film again, and cause problems such as the disconnection or short circuit of the wiring.
• the generation of particles is becoming a major problem pursuant to the advancement of higher integration and miniaturization of the electronic device circuit as described.
• Patent Document 1 describes cleaning electrolyte based on solvent extraction.
• Patent Document 2 describes eliminating Sb and Bi with chelate resin.
• Patent Document 3 describes adding a diaphragm and glue in copper electrolysis to smooth the electrolyzed surface, and thereby reducing the uptake of impurities.
• Patent Document 4 describes causing anolite to come in contact with activated carbon in copper electrolysis to eliminate glue.
• Patent Document 5 describes performing electrolysis once again in copper electrolysis.
• Patent Document 6 describes smoothing the electrode surface based on periodic reverse current electrolysis in copper electrolysis to prevent the inclusion of suspended matter and electrolyte.
• Patent Document 7 describes adding a macromolecular additive to improve the surface condition in copper electrolysis and using electrolyte containing urea to produce high purity copper with a low silver and sulfur content.
• Patent Document 8 describes that the three metallurgical characteristics of a sputtering target that affect the performance of a target are the uniformity of the material (no precipitate, void, inclusion and other defects), crystal particle size (finer crystal particle size is generally more preferable than coarse crystal particle size), and texture (texture relates to the strength of a specific crystallographic orientation; a “weak” texture includes substantially random distribution of the crystallographic orientation, and a “strong” texture includes a preferential crystallographic orientation in the distribution of the crystallographic orientation), and further states that, generally speaking, it is necessary to reduce defects such as inclusions in the target.
• Patent Document 9 describes a titanium sputtering target in which the number of inclusions of 1 ⁇ m or more existing at the crystal grain boundary of titanium configuring the target is 100 inclusions or less per 1 cm 2 of the target plane, and additionally describes that the inclusions existing at the crystal grain boundary of titanium are a composite compound based on a combination of one or more types among oxides, nitrides, carbides, sulfides, and hydrides of metal components of titanium or iron, nickel, chromium, aluminum, silicon, tungsten, and molybdenum, and that the oxides can be decomposed by heat treatment.
• Patent Document 10 and Patent Document 11 describe reducing the number of inclusions in an aluminum or aluminum alloy target to be 40 inclusions/cm 2 or less per unit area, that splashes can be reduced by causing the maximum length of the inclusions to be 20 ⁇ m or less, that reducing the inclusions in the sputtering target is particularly important in order to inhibit the generation of particles and splashes, and reducing inclusions by filtering molten metal with a ceramic filter.
• Patent Document 12 described a method of producing a high purity copper or copper alloy sputtering target having an oxygen content of 100 ppm or less, carbon content of 150 ppm or less, nitrogen [content] of 50 ppm or less, and sulfur content of 200 ppm or less, wherein used is a high purity copper or copper alloy ingot in which the oxygen content in the target is 100 ppm or less, the carbon content is 150 ppm or less, the nitrogen [content] is 50 ppm or less, and the sulfur content is 200 ppm or less, or the number of indications having a flat bottom hole diameter of 0.5 mm or more is 0.014 indications/cm 2 or less in an ultrasonic inspection performed from the target surface, and obtained by melting and casting based on electron beam melting or vacuum induction skull melting.
• the large inclusions detected in the ultrasonic inspection are not observed in current high purity copper targets.
• Patent Document 13 describes that the gas components of oxygen, nitrogen, and carbon contained in the copper alloy sputtering target form inclusions at the crystal grain boundary and cause the generation of particles, and that it is desirable to reduce such gas components as much as possible since they cause the unexpected generation of particles during the sputter life, and unavoidable impurities excluding gas components are reduced to 10 wtppm or less.
• Patent Document 1 Japanese Published Unexamined Patent Application No.H11-106842
• Patent Document 2 Japanese Published Unexamined Patent Application No.2000-107596
• Patent Document 3 Japanese Published Unexamined Patent Application No. S63-297583
• Patent Document 4 Japanese Published Unexamined Patent Application No. S64-55394
• Patent Document 5 Japanese Published Unexamined Patent Application No. H1-152291
• Patent Document 6 Japanese Published Unexamined Patent Application No. S64-8289
• Patent Document 7 Japanese Published Unexamined Patent Application No. 2005-307343
• Patent Document 8 Japanese Published Examined Patent Application No.2004-513228
• Patent Document 9 Japanese Published Unexamined Patent Application No. H5-214519
• Patent Document 10 Japanese Published Unexamined Patent Application No. H9-25564
• Patent Document 11 Japanese Published Unexamined Patent Application No. H11-315373
• Patent Document 12 Japanese Published Unexamined Patent Application No.2000-239836
• an object of this invention is to use high purity copper or high purity copper alloy from which harmful P, S, C, 0 -based inclusions have been reduced as the raw material and controlling the existence form of nonmetal inclusions, and thereby reduce the occurrence of rupture of a bonding wire and improve the reproducibility of mechanical properties, or reduce the percent defect of a semiconductor device wiring formed by sputtering a high purity copper target with favorable reproducibility.
• the present inventors made the following discovery. Specifically, the inventors discovered that, by reducing as much as possible the abundance of nonmetal inclusions having a particle size of 0.5 ⁇ m or more and 20 ⁇ m or less existing in the high purity copper and causing such amount to be 10,000 inclusions/g or less, it is possible to reduce the occurrence of rupture of a bonding wire, or reduce the percent defect of a semiconductor device wiring formed by sputtering a high purity copper or copper alloy target with favorable reproducibility.
• the present invention provides:
• High purity copper having a purity of 6N or higher, wherein content of each of the respective components of P, S, 0, and C is 1 ppm or less, and nonmetal inclusions having a particle size of 0.5 ⁇ m or more and 20 ⁇ m or less contained in the copper are 10,000 inclusions/g or less; and 2) The high purity copper according to 1) above, wherein inclusions of carbon or carbide having a particle size of 0.5 ⁇ m or more and 20 ⁇ m or less are 5,000 inclusions/g or less.
• the present invention additionally provides:
• a method of producing high purity copper based on electrolysis wherein electrolysis is performed by providing a partition between a cathode and an anode, and, upon supplying electrolyte extracted from an electrolytic cell on the anode side or additional electrolyte to an electrolytic cell on the cathode side, passing the electrolyte through an activated carbon filter immediately before supplying it to the electrolytic cell on the cathode side, and thereafter supplying the electrolyte to the electrolytic cell on the cathode side; 4) The method of producing high purity copper based on electrolysis according to 3) above, wherein a purity of 6N or higher, content of each of the respective components of P, S, 0, and C being 1 ppm or less, and nonmetal inclusions having a particle size of 0.5 ⁇ m or more and 20 ⁇ m or less contained in the copper being 10,000 inclusions/g or less are achieved based on electrolysis; and 5) The method of producing high purity copper based on electrolysis according to 3) above, wherein inclusion
• P, S, O, and C are particularly problematic as impurities that cause the generation of inclusions. Since the meltability of these elements in copper is extremely low, the bulk thereof becomes inclusions in copper. Particularly, in order to achieve the high purity of copper according to the present invention, it is taboo to add organic additives such as glue or polymer for smoothing or the like which have been conducted conventionally. This is because the addition of such additives will increase the existence of P, S, O, and C.
• electrolyte of a sulfuric acid system that particularly causes nonmetal inclusions, in particular S, to get mixed in was not used, but nitric or hydrochloric electrolyte was used. Nevertheless, even upon taking the foregoing measures, the inclusion of large amounts of P, S, O, and C as impurities was acknowledged. Thus, it was necessary to seek the cause of increase in impurities elsewhere; that is, other than the electrolyte itself.
• P, S, and O that are contained in the electrolyte exist as the suspended solids of CuP, CuS, and CuO, and it has also been discovered that the cathode sometimes causes these suspended solids to be included in the copper during the electrolysis, and that these suspended solids are the primary cause of contamination.
• the impurities are organic matter
• the electrolytic copper containing organic matter of several ppm or more in a high concentration is to be melted by way of high frequency melting in order to achieve high purity
• carbon (C) that is formed as a result of the decomposition of the organic matter will get mixed in as is in the melted copper.
• nonmetal inclusions refers to the solid matter existing in the copper structure. Once these solid matters get mixed in, they cannot be eliminated sufficiently in the melting process. Among the above, carbon or carbide having carbon as its component is particularly harmful. In addition, when carbon or carbide having carbon as its component get mixed in upon becoming a bonding wire or in the semiconductor production process, it becomes extremely difficult to eliminate such carbon or carbide.
• an important process is to pass the electrolyte through an activated carbon filter immediately before supplying such electrolyte to the cathode-side electrolytic cell, and thereafter supplying the electrolyte to cathode-side electrolytic cell to perform electrolysis.
• the inclusions cannot be eliminated if a standard polypropylene filter is used. Specifically, this means that the elimination of inclusions will be difficult depending on the type of filter. Moreover, if the electrolyte is supplied from the anode box to the cathode box through introduction using a piping or a pump, the reduction of inclusions is similarly difficult.
• the electrolytic production process for producing the high purity copper was described above, and the high purity copper of the present invention can only be obtained with the foregoing process.
• the starting material a commercially available high purity copper material having a purity level of 5N or less can be used. Nevertheless, this starting material contains metal components other than Cu, nonmetal components, P, S, O, C and their compounds (SiO 2 , Al 2 O 3 , CuP, CuS, CuO and so on) each in the amount of several ppm to several 1000 ppm.
• the high purity copper of the present invention uses the foregoing starting material as the raw material, desirably, the high purity copper raw material has a purity of 6N or higher, content of the respective components of P, S, O, and C is 1 ppm or less, and nonmetal inclusions having a particle size of 0.5 ⁇ m or more are 10,000 inclusions/g or less.
• the foregoing nonmetal inclusions or the carbon system inclusions of carbon or carbide were measured with the “light scattering automatic particle counter for liquid” (manufactured by Kyushu RION Corporation).
• the measurement method is based on sorting the particle size in the liquid and measuring the particle concentration and particle count.
• the foregoing measuring equipment is also known as a “liquid particle counter” and is based on JIS B 9925 (this measuring equipment is hereinafter referred to as the “liquid particle counter”).
• the components of P, S, O, and C all become impurities in copper and form phosphides, sulfides, carbides, and oxides that do not become a solid solution in the copper, and may cause the formation of nonmetal inclusions. Thus, reducing these components to be 1 ppm or less will reduce the nonmetal inclusions and improve the characteristics of high purity copper.
• the nonmetal inclusions having a particle size of 0.5 ⁇ m or more and 20 ⁇ m or less contained in the copper are made to be 10,000 inclusions/g or less in the present invention, and the amount of such nonmetal inclusions is the problem. If the number of nonmetal inclusions exceeds 10,000 inclusions/g or less, they will become foreign matter in the thinned bonding wire, and it becomes easier for rupture to occur with such foreign matter as the source.
• the nonmetal inclusions in the target will reach a level of becoming problematic, become protrusive foreign matter during the erosion of the target, and abnormal discharge is easily generated to such protrustive foreign matter. This causes the generation of particles during sputtering.
• the numerical value of nonmetal inclusions having a particle size of 0.5 ⁇ m or more and 20 ⁇ m or less being 10,000 inclusions/g or less is not necessarily a large amount. This numerical value cannot be achieved simply by reducing the content of impurity elements configuring the nonmetal inclusions to be 1 ppm or less.
• the existence of inclusions of carbon or carbide is harmful, and it is desirable to reduce the carbon or carbide having a particle size of 0.5 ⁇ m or more and 20 ⁇ m or less to be 5,000 inclusions/g or less. Since the carbon or carbide is often a result of contamination from organic matter as described above, the use of organic matter in electrolysis must be avoided.
• a high purity copper alloy bonding wire or sputtering target can be produced by additionally adding an alloy element with the foregoing high purity copper as the base material.
• the sputtering target may be used upon adding 10% or less of one type or two types or more among the normally added elements of Al, Ag, B, Cr, Ge, Mg, Mn, Nd, Si, Sn, Ti, and Zr to the high purity copper.
• copper raw materials and alloy component materials may be used as the raw material for producing the high purity copper or high purity copper alloy of the present invention.
• radioactive elements such as U and Th as impurities affect the MOS with their radiation, alkali metals and alkali earth metals such as Na and K deteriorate the MOS interface characteristics, and transition metals or heavy metals such as Fe, Ni, and Co generate an interface state or cause a junction leak, and these elements may contaminate the semiconductor equipment through the copper film.
• a target is usually prepared by melting and casting the raw material, performing such plastic forming processes as forging and rolling as well as heat treatment in order to achieve the appropriate crystal structure, particle size and the like of the cast material, and performing finish processing to obtain the final target size in the shape of a disk or the like.
• the quality of the target such as its crystal orientation can be adjusted by appropriately combining the plastic forming process such as forging and rolling, and the heat treatment process.
• the primary inclusions in the copper and copper alloy are oxides, nitrides, carbides, and sulfides, and they are generated in the process of melting and casting the raw material.
• melting and casting are performed in a nonoxidizing atmosphere, or preferably in a vacuum for efficiently eliminating oxygen, nitrogen, and sulfur as the inclusion sources.
• electron beam melting using a water-cooled copper crucible, vacuum induction skull melting, or the use of a water-cooled copper mold is suitable for avoiding the contamination of carbon and oxygen from the graphite crucible used in conventional high frequency melting.
• electrolysis was performed using nitric electrolyte.
• electrolysis was performed by separating the cathode and the anode with a diaphragm, extracting the Cu ion-containing electrolyte that was eluted from the anode, and passing it through an activated carbon filter with a sieve opening of approximately 0.1 ⁇ m immediately before being placed in the cathode box.
• Example 1 is able to produce high purity copper having a purity of 6N or higher, wherein content of each of the respective components of P, S, O, and C is 1 ppm or less, and nonmetal inclusions having a particle size of 0.5 ⁇ m or more and 20 ⁇ m or less contained in the copper are 10,000 inclusions/g or less.
• the electrolyte may be additionally passed through the activated carbon filter as needed.
• Example 2 Under the same conditions as Example 1, filtering was performed with a standard polypropylene filter (filtering rate of 0.5 ⁇ m). As a result of subjecting the obtained electrolytic copper to vacuum induction skull melting and measuring the obtained high purity copper with a liquid particle counter, approximately 20,000 inclusions/g of nonmetal inclusions having a particle size of 0,5 ⁇ m or more and 20 ⁇ m or less were detected. In addition, the P, S, O, and C contained in the electrodeposited copper were 2 ppm, 6 ppm, 10 ppm, and 10 ppm, respectively. Moreover, the inclusions of carbon or carbide were approximately 8,400 inclusions/g.
• Example 2 The conditions were the same as Example 1, but the Cu ion-containing electrolyte that was eluted from the anode was extracted without using a filter and placed in the cathode box.
• the activated carbon filter was placed immediately after the anode box and the electrolyte was passed therethrough, and returned to the cathode box via a piping and a pump.
• Example 1 prepared as described above was melted to produce a target.
• the nonmetal inclusions having a particle size of 0.5 ⁇ m or more and 20 ⁇ m or less were approximately 6,500 inclusions/g.
• the increase of nonmetal inclusions was acknowledged at the stage of producing the target. However, the amount was small.
• the number of particles having a particle size of 0.05 ⁇ m or more was 17 particles/square inch, and it was possible to obtain a favorable sputtered film.
• the processes of melting the high purity copper of Example 1, and additionally subjecting this to casting, forging, heat treatment and rolling (drawing) are performed.
• the process is basically the same as producing the foregoing target. Accordingly, it is effective to use the cold crucible melting method in order to prevent the inclusion of impurities in the melting process and obtain an ingot.
• the foregoing high purity copper was processed and subject to heat treatment to produce a target.
• the number of nonmetal inclusions having a particle size of 0.5 ⁇ m or more and 20 ⁇ m or less was approximately 30,000 inclusions/g or more.
• the increase of nonmetal inclusions was acknowledged in proportion to the raw material. Moreover, the amount of increase was significant. This may be caused by a result that the number of nonmetal inclusions contained in the raw material itself to be melted is great.
• the number of nonmetal inclusions having a particle size of 0.5 ⁇ m or more and 20 ⁇ m or less was similarly approximately 30,000 inclusions/g or more.
• the increase of nonmetal inclusions was acknowledged in proportion to the raw material. Moreover, the amount of increase was significant.
• the rupture off the bonding wire increased in proportion to the abundance of nonmetal inclusions.
• a high purity copper from which harmful P, S, C, O inclusions have been reduced is provided.
• As a result of controlling the existence form and amount of nonmetal inclusions it is possible to reduce the occurrence of rupture of a bonding wire and improve the reproducibility of the mechanical strength, or inhibit the generation of particles upon sputtering a high purity copper or high purity copper target, and a superior effect of being able to reduce the percent defective of the semiconductor device wiring is yielded.
• the present invention is effective as a high purity copper and high purity copper alloy target and a bonding wire that will not rupture easily which are suitable for forming a copper wiring or the like that is capable of preventing problems such as short circuits and disconnections.

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• 2009
  • 2009-09-24 US US12/996,949 patent/US20110123389A1/en not_active Abandoned
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