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• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C5/00—Alloys based on noble metals
  • C22C5/04—Alloys based on a platinum group metal
• • 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
  • C22C9/06—Alloys based on copper with nickel or cobalt as the next major constituent
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  • H10W20/45—Interconnections external to wafers or substrates, e.g. back-end-of-line [BEOL] metallisations or vias connecting to gate electrodes characterised by their insulating parts
  • H10W20/48—Insulating materials thereof
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  • H10W70/01—Manufacture or treatment
  • H10W70/05—Manufacture or treatment of insulating or insulated package substrates, or of interposers, or of redistribution layers
  • H10W70/093—Connecting or disconnecting other interconnections thereto or therefrom, e.g. connecting bond wires or bumps
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  • H10W70/00—Package substrates; Interposers; Redistribution layers [RDL]
  • H10W70/40—Leadframes
  • H10W70/464—Additional interconnections in combination with leadframes
  • H10W70/465—Bumps or wires
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  • H10W72/01—Manufacture or treatment
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  • H10W72/01551—Changing the shapes of bond wires
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  • H10W72/071—Connecting or disconnecting
  • H10W72/075—Connecting or disconnecting of bond wires
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  • H10W72/071—Connecting or disconnecting
  • H10W72/075—Connecting or disconnecting of bond wires
  • H10W72/07511—Treating the bonding area before connecting, e.g. by applying flux or cleaning
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  • H10W72/071—Connecting or disconnecting
  • H10W72/075—Connecting or disconnecting of bond wires
  • H10W72/07541—Controlling the environment, e.g. atmosphere composition or temperature
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  • H10W72/075—Connecting or disconnecting of bond wires
  • H10W72/07541—Controlling the environment, e.g. atmosphere composition or temperature
  • H10W72/07555—Controlling the environment, e.g. atmosphere composition or temperature changes in materials
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  • H10W72/521—Structures or relative sizes of bond wires
  • H10W72/522—Multilayered bond wires, e.g. having a coating concentric around a core
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  • H10W72/521—Structures or relative sizes of bond wires
  • H10W72/522—Multilayered bond wires, e.g. having a coating concentric around a core
  • H10W72/523—Multilayered bond wires, e.g. having a coating concentric around a core characterised by the structures of the outermost layers, e.g. multilayered coatings
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  • H10W72/00—Interconnections or connectors in packages
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  • H10W72/531—Shapes of wire connectors
  • H10W72/536—Shapes of wire connectors the connected ends being ball-shaped
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  • H10W72/531—Shapes of wire connectors
  • H10W72/5363—Shapes of wire connectors the connected ends being wedge-shaped
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  • H10W72/551—Materials of bond wires
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  • H10W72/551—Materials of bond wires
  • H10W72/552—Materials of bond wires comprising metals or metalloids, e.g. silver
  • H10W72/5522—Materials of bond wires comprising metals or metalloids, e.g. silver comprising gold [Au]
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  • H10W72/551—Materials of bond wires
  • H10W72/552—Materials of bond wires comprising metals or metalloids, e.g. silver
  • H10W72/5525—Materials of bond wires comprising metals or metalloids, e.g. silver comprising copper [Cu]
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  • H10W72/551—Materials of bond wires
  • H10W72/552—Materials of bond wires comprising metals or metalloids, e.g. silver
  • H10W72/5528—Intermetallic compounds
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  • H10W72/551—Materials of bond wires
  • H10W72/555—Materials of bond wires of outermost layers of multilayered bond wires, e.g. material of a coating
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  • H10W72/59—Bond pads specially adapted therefor
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  • H10W72/90—Bond pads, in general
  • H10W72/921—Structures or relative sizes of bond pads
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  • H10W72/951—Materials of bond pads
  • H10W72/952—Materials of bond pads comprising metals or metalloids, e.g. PbSn, Ag or Cu
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  • H10W74/00—Encapsulations, e.g. protective coatings

Definitions

• the present invention relates to a bonding wire for a semiconductor device used for connecting an electrode on a semiconductor element and a wiring of a circuit wiring board such as an external lead.
• bonding wires fine wires having a wire diameter of about 15 to 50 ⁇ m are mainly used as bonding wires for semiconductor devices (hereinafter referred to as “bonding wires”) for bonding between electrodes on semiconductor elements and external leads.
• the bonding wire bonding method is generally an ultrasonic combined thermocompression bonding method, and a general-purpose bonding apparatus, a capillary jig used for connection through the bonding wire, or the like is used.
• the bonding process of the bonding wire involves heating and melting the wire tip with arc heat input, forming a ball (FAB: Free Air Ball) by surface tension, and then heating it on the electrode of the semiconductor element heated within the range of 150 to 300 ° C.
• FAB Free Air Ball
• This ball part is bonded by pressure bonding (hereinafter referred to as “ball bonding”), then a loop is formed, and then the wire part is bonded by pressure bonding (hereinafter referred to as “wedge bonding”) to the electrode on the external lead side.
• the electrode on the semiconductor element that is the bonding partner of the bonding wire has an electrode structure in which an alloy mainly composed of Al is formed on a Si substrate, and the electrode on the external lead side has an electrode structure in which Ag plating or Pd plating is applied. Used.
• Patent Document 1 one using high purity Cu (purity: 99.99 mass% or more) has been proposed (for example, Patent Document 1).
• Cu has a defect that it is easily oxidized as compared with Au, and there is a problem that bonding reliability, ball forming property, wedge bonding property and the like are inferior.
• Patent Document 2 a structure in which the surface of the Cu core material is coated with a metal such as Au, Ag, Pt, Pd, Ni, Co, Cr, Ti has been proposed (Patent Document 2).
• Patent Document 3 A structure in which the surface of a Cu core material is coated with Pd and the surface is coated with Au, Ag, Cu, or an alloy thereof has been proposed (Patent Document 3).
• In-vehicle devices are required to have higher bonding reliability in harsh high-temperature and high-humidity environments than general electronic equipment.
• the bonding life of the ball bonding portion in which the ball portion of the wire is bonded to the electrode becomes the biggest problem.
• Several methods have been proposed for evaluating the bonding reliability in a high temperature and high humidity environment. As a representative evaluation method, HAST (Highly Accelerated Temperature and Humidity Stress Test) (high temperature and high humidity environment exposure test) There is.
• HAST Highly Accelerated Temperature and Humidity Stress Test
• the evaluation ball joint is exposed to a high-temperature and high-humidity environment at a temperature of 130 ° C.
• An object of the present invention is to provide a bonding wire suitable for a vehicle-mounted device by improving the bonding reliability of a ball bonding portion in a high-temperature and high-humidity environment in a Cu bonding wire having a Pd coating layer on the surface.
• the gist of the present invention is as follows. (1) In a bonding wire for a semiconductor device having a Cu alloy core material and a Pd coating layer formed on the surface of the Cu alloy core material, A bonding wire for a semiconductor device, wherein the bonding wire contains one or more elements selected from Ga and Ge, and the concentration of the element with respect to the whole wire is 0.011 to 1.5 mass% in total. (2) The bonding wire for a semiconductor device as described in (1) above, wherein the Pd coating layer has a thickness of 0.015 to 0.150 ⁇ m. (3) The bonding wire for a semiconductor device according to (1) or (2) above, further comprising an alloy skin layer containing Au and Pd on the Pd coating layer.
• the bonding wire further includes at least one element selected from Ni, Ir, and Pt, and the concentration of the element with respect to the entire wire is 0.011 to 1.2% by mass, respectively.
• the bonding wire further contains at least one element selected from B, P, and Mg, and the concentration of the element with respect to the entire wire is 1 to 100 ppm by mass.
• the abundance ratio of the crystal orientation ⁇ 111> having an angle difference of 15 degrees or less with respect to the longitudinal direction among the crystal orientations in the longitudinal direction of the bonding wire
• a predetermined amount of at least one selected from Ga and Ge is selected as the bonding wire.
• the bonding wire of the present invention has a Cu alloy core material and a Pd coating layer formed on the surface of the Cu alloy core material, and includes at least one selected from Ga and Ge, and Ga, Ge for the entire wire.
• the total concentration is 0.011 to 1.5% by mass.
• the bonding wire of the present invention can improve the bonding reliability of the ball bonding portion in a high-temperature and high-humidity environment required for a vehicle-mounted device.
• the alloy layer having a high Pd concentration formed on the surface of the ball is excellent in oxidation resistance, it is possible to reduce defects such as the ball forming position being shifted from the center of the bonding wire during ball formation. Can do.
• the total concentration of Ga and Ge in the entire wire is set to 0. 011 mass% or more, preferably 0.025 mass% or more, more preferably 0.031 mass% or more, still more preferably 0.050 mass% or more, 0.070 mass% or more, 0.090 mass% or more, It is 0.100 mass% or more, 0.150 mass% or more, or 0.200 mass% or more.
• the total concentration of Ga and Ge with respect to the entire wire is 0.100% by mass or more, it is possible to meet the demand for more stringent bonding reliability.
• the bonding wire of this invention contains Ge independently, it is preferable that the density
• Mold resin which is a package of a semiconductor device contains chlorine (Cl) in a molecular skeleton.
• Cl chlorine
• Cl in the molecular skeleton is hydrolyzed and eluted as chloride ions (Cl ⁇ ).
• Cu 9 Al 4 is easily corroded by halogens such as Cl, and corrosion progresses due to Cl eluted from the mold resin, leading to a decrease in bonding reliability.
• the bonding interface between the Pd coated Cu wire and the Al electrode has a structure of Cu / Pd enriched layer / Al. Therefore, compared to a Cu wire that does not have a Pd coating layer.
• the generation of Cu 9 Al 4 intermetallic compound is suppressed, the bonding reliability in a high-temperature and high-humidity environment required for in-vehicle devices is insufficient.
• the Pd-coated Cu bonding wire contains a predetermined amount of one or more elements selected from Ga and Ge as in the present invention
• the formation of Cu 9 Al 4 intermetallic compound at the joint is further suppressed. It seems that there is a tendency.
• Ga and Ge in the wire diffuse into the Pd coating layer.
• Ga and Ge present in the Pd enriched layer at the Cu and Al interface at the ball joint further enhance the effect of suppressing the mutual diffusion of Cu and Al by the Pd enriched layer, and as a result, it is easily corroded in a high temperature and high humidity environment. It seems to suppress the formation of Cu 9 Al 4 .
• Ga and Ge contained in the wire may have an effect of directly inhibiting the formation of Cu 9 Al 4 .
• a ball part was formed using a Pd-coated Cu bonding wire containing a predetermined amount of at least one selected from Ga and Ge, and the FAB was observed with a scanning electron microscope (SEM). A large number of precipitates having a diameter of several tens of nm ⁇ were observed on the surface. When the precipitate was analyzed by energy dispersive X-ray analysis (EDS: Energy Dispersive X-ray Spectroscopy), it was confirmed that Ga and Ge were concentrated. Although the detailed mechanism is unknown from the above situation, this precipitate observed in the FAB is present at the bonding interface between the ball part and the electrode, so that the temperature is 130 ° C. and the relative humidity is 85%. It seems that the joint reliability of the ball joint in a wet environment has been greatly improved.
• EDS Energy Dispersive X-ray Spectroscopy
• the presence site of Ga and Ge is preferably in the Cu alloy core material, but a sufficient action and effect can also be obtained by being contained in a Pd coating layer or an alloy skin layer containing Au and Pd described later.
• the method of adding Ga and Ge to the Cu alloy core material facilitates accurate concentration control, and improves wire productivity and quality stability.
• by including a part of Ga and Ge in the Pd coating layer and the alloy skin layer by diffusion due to heat treatment, etc. it is possible to improve the adhesion at each layer interface and further improve the wire productivity. .
• the concentration of Ga and Ge with respect to the entire wire is 1.5% by mass or less in total.
• it is 1.4 mass% or less, More preferably, it is 1.3 mass% or less, or 1.2 mass% or less.
• Cu may exist on the outermost surface of the Pd coating layer. If the Cu concentration is 30 atomic% or more, the sulfidation resistance of the wire surface is lowered, and the service life of the bonding wire is reduced, which may not be suitable for practical use. Therefore, when Cu is present on the outermost surface of the Pd coating layer, the concentration of Cu is preferably less than 30 atomic%.
• the outermost surface refers to a region in which the surface of the bonding wire is measured by an Auger electron spectrometer without performing sputtering or the like.
• the thickness of the Pd coating layer suppresses the eccentricity of the FAB from the viewpoint of further improving the bonding reliability of the ball bonding portion in the high temperature and high humidity environment required for the in-vehicle device.
• it is preferably 0.015 ⁇ m or more, more preferably 0.02 ⁇ m or more, still more preferably 0.025 ⁇ m or more, 0.03 ⁇ m or more, 0.035 ⁇ m or more, 0.04 ⁇ m or more, and 0.0. It is 045 ⁇ m or more, or 0.05 ⁇ m or more.
• the thickness of the Pd coating layer is preferably 0.150 ⁇ m or less, more preferably 0.140 ⁇ m or less, 0.130 ⁇ m or less, 0.120 ⁇ m from the viewpoint of suppressing the FAB shrinkage and obtaining a good FAB shape.
• it is 0.110 ⁇ m or less, or 0.100 ⁇ m or less.
• the definition of the Cu alloy core material and the Pd coating layer of the bonding wire will be described.
• the boundary between the Cu alloy core material and the Pd coating layer was determined based on the Pd concentration.
• the region where the Pd concentration was 50 atomic% was determined as the boundary, the region where the Pd concentration was 50 atomic percent or more was determined as the Pd coating layer, and the region where the Pd concentration was less than 50 atomic percent was determined as the Cu alloy core material. This is because, if the Pd concentration in the Pd coating layer is 50 atomic% or more, the effect of improving the characteristics can be obtained from the structure of the Pd coating layer.
• the Pd coating layer may include a region of a single Pd layer, and a region where Pd and Cu have a concentration gradient in the depth direction of the wire.
• the reason why the region having the concentration gradient is formed in the Pd coating layer is that Pd and Cu atoms may be diffused by heat treatment or the like in the manufacturing process. Furthermore, the Pd coating layer may contain inevitable impurities.
• an alloy skin layer further containing Au and Pd may be formed on the Pd coating layer.
• the bonding wire of this invention can further improve wedge bondability.
• the definition of the alloy skin layer containing Au and Pd of the bonding wire will be described.
• the boundary between the alloy skin layer containing Au and Pd and the Pd coating layer was determined based on the Au concentration.
• the region where the Au concentration was 10 atomic% was defined as a boundary, and the region where the Au concentration was 10 atomic percent or more was judged as the Pd coating layer. Further, even if the Pd concentration is in the region of 50 atomic% or more, if Au is present in 10 atomic% or more, it was determined as an alloy skin layer containing Au and Pd. The reason for this is that if the Au concentration is within the above-described concentration range, the effect of improving the characteristics can be expected from the structure of the Au skin layer.
• the alloy skin layer containing Au and Pd is an Au—Pd alloy, and both the case where Au and Pd include a region having a concentration gradient in the depth direction of the wire and the case where the region having the concentration gradient is not included Is included.
• the alloy skin layer containing Au and Pd preferably includes a region having the concentration gradient. The reason why the region having the concentration gradient is formed in the alloy skin layer containing Au and Pd is that atoms of Au and Pd are diffused by heat treatment or the like in the manufacturing process. Furthermore, the alloy skin layer containing Au and Pd may contain unavoidable impurities and Cu.
• the alloy skin layer containing Au and Pd reacts with the Pd coating layer to increase the adhesion strength between the alloy skin layer containing Au and Pd, the Pd coating layer, and the Cu alloy core material, and the wedge Peeling of the Pd coating layer and the alloy skin layer containing Au and Pd at the time of joining can be suppressed.
• the bonding wire of this invention can further improve wedge bondability. If the thickness of the alloy skin layer containing Au and Pd is less than 0.0005 ⁇ m, the above effect cannot be obtained, and if it is thicker than 0.050 ⁇ m, the FAB shape may be eccentric.
• the thickness of the alloy skin layer containing Au and Pd is preferably 0.0005 ⁇ m or more, more preferably 0.001 ⁇ m or more, 0.002 ⁇ m or more, or 0.003 ⁇ m or more.
• the thickness of the alloy skin layer containing Au and Pd is preferably 0.050 ⁇ m or less, more preferably 0.045 ⁇ m or less, 0.040 ⁇ m or less, 0.035 ⁇ m. Or 0.030 ⁇ m or less.
• the alloy skin layer containing Au and Pd can be formed by the same method as the Pd coating layer.
• Cu may exist on the outermost surface of the alloy skin layer containing Au and Pd. If the Cu concentration is 35 atomic% or more, the sulfidation resistance of the wire surface is lowered and the service life of the bonding wire is lowered, which may not be suitable for practical use. Therefore, when Cu is present on the outermost surface of the Au skin layer, the concentration of Cu is preferably less than 35 atomic%.
• the outermost surface refers to a region in which the surface of the bonding wire is measured by an Auger electron spectrometer without performing sputtering or the like.
• a mold resin (epoxy resin) which is a package of a semiconductor device contains a silane coupling agent. Since the silane coupling agent has a function of improving the adhesion between the organic substance (resin) and the inorganic substance (silicon or metal), the adhesion with the silicon substrate or the metal can be improved. Furthermore, when a high adhesion is required, such as a semiconductor for automobiles that requires higher temperature reliability, a “sulfur-containing silane coupling agent” is added. Sulfur contained in the mold resin is not liberated at a temperature as low as 130 ° C., which is a temperature condition in HAST, but is liberated when used at a temperature of 175 ° C. to 200 ° C. or higher.
• HTS High Temperature Storage Test
• HTS High Temperature Storage Test
• in-vehicle semiconductor devices have been required to improve the reliability of ball joints with HTS of 175 ° C. to 200 ° C.
• the bonding wire of the present invention preferably contains at least one element selected from Ni, Ir, and Pt, and the concentration of the element with respect to the entire wire is preferably 0.011 to 1.2% by mass.
• the concentration of these components in the bonding wire is less than 0.011% by mass, the above effect cannot be obtained.
• concentration is higher than 1.2% by mass, the FAB shape is deteriorated and the bonding wire becomes hard and the wire bonding portion. The deformation becomes insufficient, and the deterioration of the wedge bondability becomes a problem.
• the Cu alloy core material of the bonding wire contains Pd and the concentration of Pd contained in the Cu alloy core material is 0.05 to 1.2% by mass, the same effect as Ni, Ir and Pt is obtained. be able to. Furthermore, by containing Ni, Ir, Pt, and Pd in the above content range, loop formation can be improved, that is, leaning that becomes a problem in high-density mounting can be reduced. This is because when the bonding wire contains these elements, the yield strength of the bonding wire is improved and deformation of the bonding wire can be suppressed.
• the bonding life of the ball bonded portion in a high temperature and high humidity environment where the temperature is 130 ° C. and the relative humidity is 85% can be further improved. it can.
• the Pd-coated Cu bonding wire contains Ni, Ir, Pt, and Pd as in the present invention, it is considered that the formation of Cu 9 Al 4 intermetallic compound in the joint tends to be further suppressed.
• the interfacial tension between Cu of the core material and Pd of the coating layer decreases, and Pd concentration at the ball bonding interface appears more effectively. Therefore, the effect of suppressing the mutual diffusion of Cu and Al by the Pd enriched layer is further strengthened. As a result, the amount of Cu 9 Al 4 that is easily corroded by the action of Cl is reduced, and the high temperature and high humidity environment of the ball joint is reduced. It is presumed that the reliability in this will be improved.
• the concentration of the element with respect to the entire wire is more preferably 0.02% by mass or more, 0.05% by mass or more, It is 0.1 mass% or more, 0.2 mass% or more, 0.3 mass% or more, or 0.5 mass% or more.
• the concentration of Pd contained in the Cu alloy core material is more preferably 0.1 mass% or more, 0.2 mass% or more, 0 .3% by mass or more, or 0.5% by mass or more.
• a method of obtaining the concentration of Pd contained in the Cu alloy core material from the bonding wire product for example, a method of exposing the cross section of the bonding wire and analyzing the concentration of the Cu alloy core material region, from the surface of the bonding wire
• a method of analyzing the concentration of the Cu alloy core material region while cutting it in the depth direction by sputtering or the like for example, when the Cu alloy core material includes a region having a Pd concentration gradient, a cross-section of the bonding wire is subjected to a line analysis, and a region having no Pd concentration gradient (for example, a change in Pd concentration in the depth direction).
• the concentration analysis may be performed on a region whose degree is less than 10 mol% per 0.1 ⁇ m.
• the same method as described above may be used to determine the concentration of the element contained in the Cu alloy core material from the bonding wire product. The concentration analysis method will be described later.
• the bonding wire of the present invention further contains at least one element selected from B, P, and Mg, and the concentration of the element with respect to the entire wire is 1 to 100 ppm by mass, so that it is required for high-density mounting.
• the collapsed shape of the ball joint portion can be improved, that is, the roundness of the ball joint portion shape can be improved. This is because the crystal grain size of the ball can be reduced and the deformation of the ball can be suppressed by adding the element. If the concentration of the element with respect to the whole wire is less than 1 mass ppm, the above effect cannot be obtained. If the concentration exceeds 100 mass ppm, the ball becomes hard and chip damage at the time of ball bonding becomes a problem, which may not be suitable for practical use. .
• the concentration of the element with respect to the entire wire is more preferably 3 ppm by mass or more, or 5 ppm by mass or more.
• the concentration of the element with respect to the entire wire is more preferably 95 ppm by mass or less, 90 ppm by mass or less, 85 ppm by mass or less, or 80 ppm by mass or less.
• a method of performing analysis while scraping from the surface of the bonding wire in the depth direction by sputtering or the like, or A method of performing line analysis, point analysis, etc. by exposing the cross section of the wire is effective.
• an analysis apparatus used for concentration analysis an Auger electron spectroscopic analysis apparatus, an energy dispersive X-ray analysis apparatus, an electron beam microanalyzer, or the like provided in a scanning electron microscope or a transmission electron microscope can be used.
• a method for exposing the cross section of the wire mechanical polishing, ion etching, or the like can be used.
• the loop The formability can be improved, that is, the straightness of the loop required for high-density mounting can be improved, and the variation in the height of the loop can be reduced. This is because, if the surface crystal orientations are aligned, it becomes strong against lateral deformation and the lateral deformation is suppressed, so that leaning defects can be suppressed.
• the crystal orientation ⁇ 111> having an angle difference of 15 degrees or less with respect to the longitudinal direction among the crystal orientations of the bonding wire longitudinal direction.
• the abundance ratio is 30 to 100% in area ratio.
• the abundance ratio of the crystal orientation ⁇ 111> is an area ratio, more preferably 35% or more, and still more preferably 40% or more.
• the bonding wire can be obtained by manufacturing a Cu alloy used as a core material, then processing it into a wire shape, forming a Pd coating layer and an Au layer, and performing a heat treatment. In some cases, after forming the Pd coating layer and the Au layer, wire drawing and heat treatment are performed again.
• the production method of the Cu alloy core material, the Pd coating layer, the formation method of the alloy skin layer containing Au and Pd, and the heat treatment method will be described in detail.
• the Cu alloy used for the core material is obtained by dissolving and solidifying Cu as a raw material and the element to be added together.
• an arc heating furnace, a high-frequency heating furnace, a resistance heating furnace, or the like can be used.
• the method for forming the Pd coating layer and the Au layer on the surface of the Cu alloy core includes a plating method, a vapor deposition method, a melting method, and the like.
• a plating method either an electrolytic plating method or an electroless plating method can be applied.
• electroplating called strike plating or flash plating, the plating rate is high and the adhesion to the substrate is good.
• the solutions used for electroless plating are classified into substitutional type and reduction type. If the thickness is thin, substitutional plating alone is sufficient, but if the thickness is thick, reduction type plating is used after substitutional plating. It is effective to apply stepwise.
• vapor deposition method physical adsorption such as sputtering, ion plating, and vacuum deposition, and chemical adsorption such as plasma CVD can be used. All of them are dry, and cleaning after forming the Pd coating layer and Au layer is unnecessary, and there is no concern about surface contamination during cleaning.
• the alloy skin layer containing Au and Pd may be deposited from the beginning.
• the Pd coating layer and the alloy skin layer containing Au and Pd For the formation of the Pd coating layer and the alloy skin layer containing Au and Pd, a method of forming after drawing to the final wire diameter, and a plurality of times until the target wire diameter is formed after forming the thick Cu alloy core material. Both of these methods are effective. In the case of forming the Pd coating layer and the alloy skin layer containing Au and Pd with the former final diameter, manufacturing, quality control and the like are simple. The combination of the latter Pd coating layer, the alloy skin layer containing Au and Pd, and wire drawing is advantageous in that the adhesion to the Cu alloy core material is improved.
• each forming method a method of forming a Pd coating layer and an alloy skin layer containing Au and Pd while continuously sweeping a wire in an electrolytic plating solution on a Cu alloy core material having a final wire diameter, Alternatively, after a thick Cu alloy core is immersed in an electrolytic or electroless plating bath to form a Pd coating layer, an alloy skin layer containing Au and Pd, the wire is drawn to reach the final wire diameter Etc.
• heat treatment may be performed.
• atoms diffuse between the alloy skin layer containing Au and Pd, the Pd coating layer, and the Cu alloy core material to improve the adhesion strength. Therefore, the alloy skin layer containing Au and Pd during processing or Pd This is effective in that the peeling of the coating layer can be suppressed and the productivity is improved.
• the core Cu may diffuse in the Pd coating layer or the skin alloy layer containing Au and Pd and reach the outermost surface of the bonding wire.
• the degree of diffusion of Cu in the core material can be adjusted according to the conditions of the heat treatment and annealing (heat treatment temperature and time). .
• any of these methods can be used: a method of containing these elements in the Cu core material, a method of adhering the Cu core material or the wire surface, and including them.
• the effects of the present invention can be exhibited. The same applies to Ni, Ir, Pt, B, P, and Mg.
• the simplest method is to add the component elements to the Cu raw material.
• Cu is added with the above-described components in a target concentration range by heating and dissolving in a high vacuum or an inert atmosphere such as nitrogen or argon.
• An alloy ingot is produced. Therefore, in a preferred embodiment, the Cu alloy core material of the bonding wire of the present invention contains at least one element selected from Ga and Ge, and the total concentration of the elements with respect to the entire wire is 0.011 to 1.5. It contains so that it may become mass%.
• a suitable numerical range of the total concentration is as described above.
• the Cu alloy core material of the bonding wire of the present invention has at least one element selected from Ni, Ir, and Pt, and the concentration of the element with respect to the entire wire is 0.011 to 1 respectively. .2% by mass is included.
• a suitable numerical range of the concentration is as described above. Therefore, in one suitable embodiment, the purity of Cu of a Cu alloy core material is 3N or less (preferably 2N or less).
• a high purity (4N or more) Cu core material is used, and the use of a low purity Cu core material tends to be avoided.
• the ball bonding portion in a high-temperature and high-humidity environment required for a vehicle-mounted device is particularly preferable when a Cu alloy core material with low Cu purity is used as described above.
• the Cu alloy core material of the bonding wire of the present invention comprises one or more elements selected from B, P, and Mg, each having a concentration of 1 to 100 ppm by mass with respect to the entire wire. To be included. A suitable numerical range of the concentration is as described above.
• the above components can be added to the wire surface. In this case, it may be incorporated anywhere in the wire manufacturing process, or may be repeated a plurality of times. It may be incorporated into a plurality of processes. It may be added to the Cu surface before Pd coating, may be added to the Pd surface after Pd coating, may be added to the Au surface after Au coating, or may be incorporated in each coating process.
• the deposition method can be selected from (1) application of aqueous solution ⁇ drying ⁇ heat treatment, (2) plating method (wet method), and (3) vapor deposition method (dry method).
• an aqueous solution having an appropriate concentration is prepared using a water-soluble compound containing the above-described component elements.
• the said component can be taken in into a wire material. It may be incorporated anywhere in the wire manufacturing process or may be repeated multiple times. It may be incorporated into a plurality of processes. It may be added to the Cu surface before Pd coating, may be added to the Pd surface after Pd coating, may be added to the Au surface after Au coating, or may be incorporated in each coating process.
• the plating method can be applied to either an electrolytic plating method or an electroless plating method.
• a plating method called flash plating which has a high plating rate and good adhesion to the substrate, can be applied.
• Solutions used for electroless plating include a substitution type and a reduction type. Generally, substitutional plating is applied when the plating thickness is thin, and reduction plating is applied when the plating thickness is thick, but either can be applied. Select according to the concentration to be added, and adjust the plating solution concentration and time. .
• Both the electrolytic plating method and the electroless plating method may be incorporated anywhere in the wire manufacturing process, or may be repeated a plurality of times. It may be incorporated into a plurality of processes. It may be added to the Cu surface before Pd coating, may be added to the Pd surface after Pd coating, may be added to the Au surface after Au coating, or may be incorporated in each coating process.
• Examples of the evaporation method include a sputtering method, an ion plating method, a vacuum evaporation method, and plasma CVD. Since it is a dry process, pretreatment and post-treatment are unnecessary, and there is no concern about contamination. In general, the vapor deposition method has a problem that the addition rate of the target element is slow. However, since the concentration of the component elements is relatively low, it is one of the methods suitable for the purpose of the present invention.
• Each vapor deposition method may be incorporated anywhere in the wire manufacturing process, or may be repeated multiple times. It may be incorporated into a plurality of processes. It may be added to the Cu surface before Pd coating, may be added to the Pd surface after Pd coating, may be added to the Au surface after Au coating, or may be incorporated in each coating process.
• the ratio of the crystal orientation ⁇ 111> having an angle difference of 15 degrees or less with respect to the longitudinal direction of the crystal orientation in the longitudinal direction of the bonding wire is 30 in area ratio.
• the method of adjusting to 100% is as follows. That is, by increasing the processing rate after the formation of the Pd coating layer or after the formation of the Pd coating layer and the Au skin layer, a texture having directionality on the wire surface (a texture having a uniform crystal orientation in the wire drawing direction) ) Can be developed.
• the abundance ratio of the crystal orientation ⁇ 111> having an angle difference of 15 degrees or less with respect to the longitudinal direction can be 30% or more in terms of area ratio.
• processing rate (%) (wire cross-sectional area before processing ⁇ wire cross-sectional area after processing) / wire cross-sectional area before processing ⁇ 100” is expressed.
• EBSD backscattered electron diffraction
• the present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the gist of the present invention.
• Example 1 First, a method for manufacturing a sample is described.
• Cu used as the raw material of the core material was one having a purity of 99.99% by mass or more and the remainder composed of inevitable impurities.
• Ga, Ge, Ni, Ir, Pt, Pd, B, P, and Mg those having a purity of 99% by mass or more and the balance composed of inevitable impurities were used.
• Ga, Ge, Ni, Ir, Pt, Pd, B, P, and Mg, which are additive elements to the core material, are prepared so that the composition of the wire or the core material becomes the target.
• a Cu mother alloy containing an additive element may be prepared in advance and prepared so as to obtain a desired addition amount.
• the core Cu alloy is loaded with raw material in a carbon crucible processed into a cylindrical shape with a diameter of 3 to 6 mm, and is used at 1090 to 1300 ° C. in a vacuum or in an inert atmosphere such as N 2 or Ar gas using a high frequency furnace. It was manufactured by performing furnace cooling after heating to dissolution. The obtained ⁇ 3 to 6 mm alloy is drawn to ⁇ 0.9 to 1.2 mm, and then continuously drawn using a die to obtain a ⁇ 300 to 600 ⁇ m wire. Was made. A commercially available lubricant was used for wire drawing, and the wire drawing speed was 20 to 150 m / min.
• a Pd coating layer having a thickness of 1 to 15 ⁇ m was formed so as to cover the entire surface of the core Cu alloy. Further, in some wires, an alloy skin layer containing Au and Pd was formed on the Pd coating layer in an amount of 0.05 to 1.5 ⁇ m. Electrolytic plating was used to form the Pd coating layer and the alloy skin layer containing Au and Pd. As the plating solution, a commercially available semiconductor plating solution was used. Thereafter, heat treatment at 200 to 500 ° C. and wire drawing were repeatedly performed to obtain a diameter of 20 ⁇ m.
• heat treatment was performed while flowing N 2 or Ar gas so that the elongation at break was about 5 to 15%.
• the heat treatment was performed while continuously sweeping the wire and flowing N 2 or Ar gas.
• the wire feed rate was 20 to 200 m / min
• the heat treatment temperature was 200 to 600 ° C.
• the heat treatment time was 0.2 to 1.0 seconds.
• Bonding wire longitudinal direction in the measurement result when the crystal orientation of the bonding wire surface is measured by adjusting the processing rate after forming the Pd coating layer or after forming the Pd coating layer and the alloy skin layer containing Au and Pd The abundance ratio (area ratio) of the crystal orientation ⁇ 111> having an angle difference of 15 degrees or less with respect to the longitudinal direction was adjusted.
• the concentration analysis of the Pd coating layer and the alloy skin layer containing Au and Pd was performed using an Auger electron spectrometer while sputtering with Ar ions from the surface of the bonding wire in the depth direction.
• the thicknesses of the coating layer and the skin alloy layer were determined from the obtained concentration profile in the depth direction (the unit of depth is converted to SiO 2 ).
• a region in which the concentration of Pd is 50 atomic% or more and the concentration of Au is less than 10 atomic percent is defined as a Pd coating layer, and the region in which the Au concentration on the surface of the Pd coating layer is in the range of 10 atomic percent or more Was used as an alloy skin layer.
• the thickness and composition of the coating layer and the alloy skin layer are shown in Tables 1 and 2, respectively.
• the concentration of Pd in the Cu alloy core material was measured by a method of performing line analysis, point analysis, etc. with an electron beam microanalyzer provided in a scanning electron microscope with the wire cross section exposed. As a method for exposing the wire cross section, mechanical polishing, ion etching, or the like was used.
• the concentration of Ga, Ge, Ni, Ir, Pt, B, P, and Mg in the bonding wire is analyzed by using a solution obtained by dissolving the bonding wire with a strong acid using an ICP emission spectroscopic analyzer and an ICP mass spectrometer. The concentration of elements contained in the entire wire was detected.
• Table 1 is an example of the present invention
• Table 2 is a comparative example.
• numerical values outside the scope of the present invention are underlined.
• the crystal structure was evaluated using the wire surface as the observation surface.
• As an evaluation method backscattered electron diffraction (EBSD) was used.
• the EBSD method has the feature that the crystal orientation of the observation surface can be observed, and the angle difference of the crystal orientation between adjacent measurement points can be illustrated. Even a thin wire such as a bonding wire is relatively simple and accurate. The crystal orientation can be observed.
• the size in the circumferential direction is 50% or less of the wire diameter with the center in the wire longitudinal direction as the axis, and the size in the wire longitudinal direction is 100 ⁇ m or less.
• the measurement efficiency can be improved by shortening the measurement time.
• the abundance ratio of the surface crystal orientation ⁇ 111> is based on the crystal orientation in the longitudinal direction of the bonding wire, with all crystal orientations specified by dedicated software (for example, OIM analysis manufactured by TSL Solutions, etc.) as the population. It calculated
• the bonding reliability of the ball bonding portion in a high temperature and high humidity environment or a high temperature environment was determined by preparing a sample for bonding reliability evaluation, performing HAST and HTS evaluation, and determining the bonding life of the ball bonding portion in each test.
• a sample for evaluating the bonding reliability is an electrode formed by forming an Al-1.0% Si-0.5% Cu alloy having a thickness of 0.8 ⁇ m on a Si substrate on a general metal frame.
• Ball bonding was performed using a commercially available wire bonder, and sealing was performed using a commercially available epoxy resin. The balls were formed while N 2 + 5% H 2 gas was flowed at a flow rate of 0.4 to 0.6 L / min, and the size was in the range of ⁇ 33 to 34 ⁇ m.
• the produced sample for evaluation of bonding reliability was exposed to a high-temperature and high-humidity environment with a temperature of 130 ° C. and a relative humidity of 85% using an unsaturated pressure cooker tester, and a bias of 7 V was applied. .
• the joint life of the ball joint was subjected to a shear test of the ball joint every 48 hours, and the shear strength value was set to be half the shear strength obtained at the initial stage.
• the shear test after the high-temperature and high-humidity test was conducted after removing the resin by acid treatment and exposing the ball joint.
• the test machine made by DAGE was used as the share test machine for HAST evaluation.
• As the value of the shear strength an average value of 10 measured values of randomly selected ball joints was used.
• the bonding life is less than 96 hours, it is judged that there is a problem in practical use. If it is x, it is practical if it is 96 hours or more and less than 144 hours, but it is slightly problematic, ⁇ mark, 144 hours or more 288 If it was less than the time, it was judged that there was no problem in practical use, and it was judged that it was particularly excellent if it was 288 hours or more, and it was marked as ⁇ , and it was written in the “HAST” column of Table 1.
• the produced sample for bonding reliability evaluation was exposed to a high-temperature environment at a temperature of 200 ° C. using a high-temperature incubator.
• the joint life of the ball joint was subjected to a shear test of the ball joint every 500 hours, and the shear strength value was set to a time that is 1 ⁇ 2 of the shear strength obtained in the initial stage.
• the shear test after the high-temperature and high-humidity test was conducted after removing the resin by acid treatment and exposing the ball joint.
• the test machine made by DAGE was used as the share test machine for HTS evaluation.
• As the value of the shear strength an average value of 10 measured values of randomly selected ball joints was used.
• the bonding life is 500 hours or more and less than 1000 hours, it can be practically used, but it is judged that there is a demand for improvement, and if it is 1000 hours or more and less than 3000 hours, it is judged that there is no practical problem. If it was 3000 hours or more, it was judged that it was particularly excellent and marked with ⁇ .
• Ball formation was evaluated by collecting and observing the balls before joining, and determining the presence or absence of bubbles on the ball surface and the presence or absence of deformation of the ball that was originally a true sphere. If any of the above occurred, it was judged as defective. Ball formation was performed while blowing N 2 gas at a flow rate of 0.5 L / min in order to suppress oxidation in the melting step. The size of the ball was 34 ⁇ m. 50 balls were observed for one condition. SEM was used for observation. In the evaluation of the ball formability, it is judged that there is a problem when 5 or more defects occur, and it is possible to use it if there are 3 or 4 defects. In the case of ⁇ 2 pieces, it was judged that there was no problem and was marked as ⁇ , and when no defect occurred, it was judged as excellent and marked as ⁇ , and it was shown in the “FAB shape” column of Table 1.
• the evaluation of the wedge bondability at the wire bonding portion was performed by performing 1000 bonding on the lead portion of the lead frame and determining the frequency of occurrence of peeling of the bonding portion.
• As the lead frame an Fe-42 atomic% Ni alloy lead frame plated with 1 to 3 ⁇ m of Ag was used.
• the stage temperature was set to 150 ° C., which is lower than the general set temperature range, assuming severer bonding conditions than usual.
• ⁇ mark 6 to 10 defects are practical.
• it was judged that there was no problem and was marked as ⁇ and when no defect occurred, it was judged as excellent and marked as ⁇ , and it was shown in the “wedge bondability” column of Table 1.
• the evaluation of the collapsed shape of the ball joint was made by observing the bonded ball joint from directly above and determining its roundness.
• an electrode in which an alloy of Al-0.5% Cu having a thickness of 1.0 ⁇ m was formed on a Si substrate was used. Observation was performed using an optical microscope at 200 locations for one condition. It was judged that the collapsed shape of the ball joint portion was poor for an oval shape having a large deviation from a perfect circle and an anisotropy in deformation.
• X mark if there are 4-5 defects, it can be used practically. In the case, it was judged that there was no problem, and the mark “ ⁇ ” was obtained.
• [Leaning] 100 leads were bonded to the evaluation lead frame with a loop length of 5 mm and a loop height of 0.5 mm.
• the wire upright portion was observed from the chip horizontal direction, and the evaluation was performed by the interval (leaning interval) when the interval between the perpendicular passing through the center of the ball joint portion and the wire upright portion was the maximum.
• the leaning interval was smaller than the wire diameter, the leaning was good, and when the leaning interval was large, the upright part was inclined, so that the leaning was judged to be bad.
• 100 bonded wires were observed with an optical microscope and the number of leaning defects was counted. If there are 7 or more defects, it is judged that there is a problem.
• the bonding wires according to Invention Examples 1 to 107 shown in Table 1 have a Cu alloy core material and a Pd coating layer formed on the surface of the Cu alloy core material, and the bonding wire is selected from Ga and Ge. One or more elements are contained, and the concentration of the elements with respect to the entire wire is 0.011 to 1.5 mass% in total. As a result, it was confirmed that the bonding wires according to the inventive examples 1 to 107 can obtain the ball joint reliability in the HAST test under the high temperature and high humidity environment where the temperature is 130 ° C. and the relative humidity is 85%.
• Comparative Examples 1 to 9 shown in Table 2 the Ga and Ge total concentrations were out of the lower limit, and the ball joint reliability was not obtained in the HAST test.
• the thickness of the Pd coating layer was outside the lower limit of the preferred range, and the FAB shape was x.
• Comparative Examples 1, 3, 6, and 8 the area ratio of the ⁇ 111> crystal orientation was outside the preferred range of the present invention, and the leaning was ⁇ .
• the concentration of the element other than Pd with respect to the entire wire is 0.011 to 1.2% by mass, Cu
• concentration of Pd contained in the alloy core material was 0.05 to 1.2% by mass, it was confirmed that the high-temperature reliability of the ball joint portion by HTS evaluation was good.
• the bonding wire further contains at least one element selected from B, P, and Mg
• the concentration of the element with respect to the entire wire is 1 to 100 ppm by mass, so Was good.

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