Bonding wire for semiconductor device

Abstract

Bonding wire for a semiconductor device, comprising: a Cu alloy core material; and a Pd plating layer formed on a surface of the Cu alloy core material, wherein the bonding wire contains at least one or more first elements selected from As and Te, a concentration of the first elements in total is 0.1 ppm by mass or more and 100 ppm by mass or less relative to the total wire, and satisfies at least one of the following conditions: (i) a concentration of As is 2.5 ppm by mass or more when the bonding wire contains As; and (ii) a concentration of Te is 0.2 ppm by mass or more when the bonding wire contains Te, and the bonding wire further contains at least one or more second elements selected from Ni, Zn, Rh, In, Ir, Pt, Ga and Ge, and a concentration of each of the second elements is 0.011 mass% or more and 1.2 mass% or less relative to the entire wire.

Description

Technical FieldThe present invention relates to a bonding wire for a semiconductor device used to connect electrodes on a semiconductor device, and wiring of a circuit board such as outer wires.Background ArtAs a bonding wire for a semiconductor device that connects electrodes on a semiconductor device and external wires (hereinafter referred to as "a bonding wire"), a thin wire having a wire diameter of about 15 to 50 μm is used nowadays. For a bonding method using a bonding wire, a thermal pressure bonding method using ultrasonic waves is generally used in which a general bonding device, a capillary tool used for bonding by passing a bonding wire, and the like are used. A bonding method of a bonding wire is performed by heating and melting a wire tip by arc heat that is fed to form a ball by surface tension (FAB); press-bonding the ball part to an electrode of the semiconductor device that is heated to a range of 150 to 300° C. (hereinafter referred to as "ball bonding"); forming a loop; and finally press-bonding a wire part to an electrode of the outer lead (hereinafter referred to as wedge bonding (wedge bonding)). For the electrode on the semiconductor device as an object to be bonded with the bonding wire, an electrode structure is used in which a thin alloy layer mainly containing Al is formed on a Si substrate. For the electrode of the external lead, an electrode structure with Ag plating or Pd plating is used.Although Au was mainly used as a material of the bonding wire, in the large scale integration (LSI) use, replacement of Au with Cu is mainly performed. In view of the large increase of electric vehicles and hybrid vehicles, needs for replacing Au with Cu also increase when used in the vehicle.As for a Cu bonding wire, it has been proposed to use a wire having high purity Cu (purity: 99.99% by mass or more, for example, JP S61-48 543 A). Cu has a disadvantage of being more sensitive to oxidation than Au, and has a problem in that reliability of bonding, moldability of the ball, and wedge bondability are inferior. As a method for preventing surface oxidation of a Cu bonding wire, a structure in which a surface of the Cu core material is coated with a metal such as Au, Ag, Pt, Pd, Ni, Co, Cr, and Ti has been proposed (JP 2005-167 020 A). A structure has also been proposed in which a surface of Cu core material is coated with Pd and its surface is coated with Au, Ag, Cu, or an alloy thereof (JP 2012-364 90 A). US 2012 / 0 118 610 A1 discloses a bonding wire for semiconductors, comprising: a core wire made of copper or a copper alloy, a palladium-containing coating layer, the coating layer being formed on a surface of the core wire and having a thickness of 10 to 200 nm; and an alloy layer containing a noble metal and palladium, the alloy layer being formed on a surface of the coating layer and having a thickness of 1 to 50 nm, the noble metal being gold or silver, and a concentration of the noble metal in the alloy layer being not less than 10% and not more than 75% by volume.SUMMARY OF THE INVENTIONProblem to be Solved by the InventionCompared to general electronic devices, on-vehicle devices require connection reliability in a severe high-temperature and high-humidity environment. In particular, durability of connection of a ball-bonded part formed by bonding a wire ball to an electrode is of greatest importance. Some methods are developed to evaluate bond reliability in a high temperature and high humidity environment, and a representative evaluation method includes a highly accelerated temperature and humidity stress (HAST) test (a test of exposure to a high temperature and high humidity environment). When a connection reliability of a ball bonded part is evaluated by HAST, a ball bonded part to be evaluated is exposed to a high-temperature and high-humidity environment having a temperature of 130° C. and a relative humidity of 85%, and then the durability of the connection of the ball bonded part is evaluated by measuring temporal changes in a resistance value of the bonded part or by measuring temporal changes in the shear strength of the ball bonded part. Recently, the durability of the connection in HAST among such connections of 100 hours or more has been demanded.It has been disclosed that the connection durability of the ball bonded part can be less than 100 hours in a case where conventional Cu bonding wire having a Pd plating layer is used to perform a bonding operation with a pure Al electrode in which the first bonding is ball bonding and the second bonding is wedge bonding, followed by a sealing operation with an epoxy resin and evaluation of a resultant ball bonded part under the above-mentioned HAST condition, and its connection reliability is not sufficient for in-vehicle devices.An object of the present invention is to provide a Cu bonding wire having a Pd plating layer on its surface, which improves connection reliability of a ball bonded part in a high-temperature and high-humidity environment and is suitable for in-vehicle devices.Means for Solving the ProblemThe present invention achieves this object by a bonding wire for a semiconductor device according to claim 1.Result of the InventionThe present invention is a bonding wire for a semiconductor device, including a Cu alloy core material and a Pd plating layer formed on a surface of the Cu alloy core material. The bonding wire contains at least one or more elements selected from As and Te in an amount of 0.1 to 100 mass ppm, and thereby the present invention increases a connection durability of a ball-bonded part in a high-temperature and high-humidity environment and can improve connection reliability.Embodiment for Carrying Out the InventionThe bonding wire of the present invention is a bonding wire for a semiconductor device, comprising a Cu alloy core material and a Pd plating layer formed on a surface of the Cu alloy core material, the bonding wire containing at least one or more elements selected from As and Te in a total amount of 0.1 to 100 mass ppm. The bonding wire of the present invention having the specific configuration can improve connection reliability of a ball-bonded part in a high-temperature and high-humidity environment required for in-vehicle devices.Although details will be described below, when a ball is formed by arc discharge using the bonding wire of the present invention, during the process when the bonding wire melts and solidifies, an alloy layer having a higher Pd concentration than an inside of the ball is formed in a surface of the ball. Such a ball is used to connect to an Al electrode, and a high-temperature and high-humidity test that allows Pd to be concentrated at a bonding interface is performed. A concentrated layer formed by the concentrated Pd may reduce diffusion of Cu and Al at a bonding interface during the high temperature and high humidity test, and may reduce a growth rate of a corrodible compound. It is thus capable of significantly improving the connection reliability of a ball bonded part in a high-temperature and high-humidity environment.The alloy layer having a high Pd concentration formed on a surface of the ball has excellent oxidation resistance, and thereby can reduce defects such as a deviation of a ball formation position relative to a center of the bonding wire at the time of ball formation.In order to improve connection reliability in view of increasing connection longevity of a ball-bonded part in a high-temperature and high-humidity environment having a temperature of 130° C. and a relative humidity of 85%, the concentration of the at least one or more elements selected from As and Te is 0.1 mass ppm or more, preferably 0.5 mass ppm or more, more preferably 1 mass ppm or more, and further preferably 1.5 mass ppm or more, 2 mass ppm or more, 2.5 mass ppm or more, or 3 mass ppm or more in total relative to the entire bonding wire.A molding resin (an epoxy resin) as a package of a semiconductor device contains chlorine (Cl) in its molecular skeleton. In a high-temperature and high-humidity environment having a temperature of 130° C. and a relative humidity of 85% as a HAST evaluation condition, Cl hydrolyses in the molecular skeleton as a chlorine ion (Cl -). When a Cu / Al bonding interface is disposed in a high temperature in a case where a Cu bonding wire having no plating layer is bonded to an Al electrode, Cu and Al mutually diffuse, and finally, Cu 9 Al 4 is formed as an intermetallic compound. Cu 9 Al 4 is liable to be corroded by a halogen and is liable to be corroded by chloride dissolved from the molding resin, resulting in deterioration in connection reliability. In a case where a Cu wire has a Pd plating layer, a bonding interface between the Pd plated Cu wire and the Al electrode has a structure of a Cu / Pd concentrated layer / Al, whereby formation of the Cu 9 Al 4- intermetallic compound is reduced as compared with a case of the Cu wire without a plating layer, but its connection reliability in a high-temperature and high-humidity environment required for in-vehicle devices is still insufficient.In contrast, it is considered that when a Pd-coated Cu bonding wire contains at least one or more elements selected from As and Te in a certain amount as in the present invention, formation of a Cu 9 Al 4- intermetallic compound in the bonded part tends to be further reduced. When a ball is formed in a case where these elements are contained in a certain amount, the interfacial stress between Cu of the core material and Pd of the coating layer decreases, and then the interfacial wettability improves, which allows Pd to be more concentrated in a ball-bonded interface. It can thus be estimated that an effect of reducing mutual diffusion of Cu and Al through the Pd concentrated layer is further improved, and as a result, formation of Cu 9 Al 4, which is likely to corrode by the effect of Cl, is reduced, and then the connection reliability of the ball bonded part in a high-temperature and high-humidity environment is significantly improved.In the present invention comprising a Cu alloy core material, a Pd cladding layer on the surface of the Cu alloy core material, and further, as required, an alloy skin layer containing Au and Pd on its surface, as described below, when diffusion heat treatment or annealing heat treatment is performed, Cu of the core material diffuses through the cladding layer and the alloy skin layer by grain boundary diffusion or the like, thereby allowing Cu to reach an outermost surface of the wire and allowing Cu to be present in the outermost surface. Thus, in the present invention, Cu may be present at an outermost surface of the bonding wire.Further, in a case where a Pd-coated bonding wire contains As, Te, Sn, Sb, Bi, and Se in a certain amount, if Cu is present in an outermost surface of the bonding wire, the formation of the Cu 9 Al 4- intermetallic compound in a bonded part tends to be further reduced. Further, in the Pd-coated Cu bonding wire containing As, Te, Sn, Sb, Bi, and Se in a certain amount, when Cu is present at an outermost surface of the bonding wire, the interaction between As, Te, Sn, Sb, Bi, and Se and Cu contained in the bonding wire promotes concentration behavior of Pd on a surface of a FAB during formation of the FAB, allowing Pd to be concentrated at a more substantial concentration in a ball-bonded interface. It can thus be estimated that an effect of reducing mutual diffusion of Cu and Al through the concentrated Pd layer is further improved and, as a result, a formation amount of Cu 9 Al 4, which is likely to corrode by the effect of Cl, is reduced, and then the connection reliability of the ball-bonded part in a high-temperature and high-humidity environment is significantly improved.When a surface of the bonding wire is measured by an Auger electron spectroscopy device, and when Cu is detected on the surface, it can be determined that Cu is present at the outermost surface, and the above effect can be exhibited. In addition, since an improving effect of connection reliability of a ball bonded part can be securely exhibited in a high-temperature and high-humidity environment, it is preferable that a concentration of Cu be 1 at % or more relative to metallic elements constituting the outermost surface of the bonding wire. In view of further improving connection reliability of a ball-bonded part in a high-temperature and high-humidity environment, a concentration of Cu relative to metallic elements forming the outermost surface of the bonding wire is preferably 1.5 at % or more, and further preferably 2 at % or more, 2.5 at % or more, or 3 at % or more. From the viewpoint of reducing deterioration of oxidation resistance and sulfur resistance of the wire surface, which deteriorates durability of the bonding wire, a concentration of Cu relative to metallic elements constituting the outermost surface of the bonding wire is preferably 50 at % or less, more preferably 45 at % or less, and further preferably 40 at % or less, 35 at % or less, or 30 at % or less.The effect due to the presence of Cu on a surface tends to be exhibited when a purity of Cu of the core material is low (for example, 3N or less), and in particular, tends to be exhibited more significantly when the purity of Cu is 2N or less.The effect of improving the connection reliability of a ball-bonded part in a high-temperature and high-humidity environment due to the presence of Cu in an outermost surface of the bonding wire is unique to the bonding wire of the present invention containing As and Te in a certain amount. A general Pd-coated Cu bonding wire containing none of these elements does not achieve the improvement effect in connection reliability of a ball-bonded part in a high-temperature and high-humidity environment as in the present invention. In contrast, the presence of Cu at the outermost surface of the bonding wire deteriorates the oxidation resistance and the sulfur resistance of the wire surfaces and reduces the durability of the bonding wire in the general Pd-coated Cu bonding wire containing neither of these elements. In addition, eccentricity of the FAB often occurs and a spherical shape is likely to be deteriorated. In addition, wedge bondability tends to deteriorate.In the bonding wire of the present invention, the effect due to the presence of Cu appears at an outermost surface of the bonding wire both in a case where a Pd plating layer is an outermost surface and a case where an alloy skin layer containing Au and Pd is an outermost surface.The outermost surface refers to a region of the surface of the bonding wire to be measured by an Auger electron spectroscopy device without performing sputtering of the like.In view of obtaining the favorable FAB form and thus obtaining a favorable ball bondability, a concentration of the elements in the wire in total is 100 mass ppm or less, preferably 95 mass ppm or less, 90 mass ppm or less, 85 mass ppm or less, 80 mass ppm or less. When a concentration of Sn or Sb exceeds 10 mass %, or when a concentration of Bi exceeds 1 mass ppm, a FAB form becomes defective. Therefore, it is preferable for further improving a FAB form that Sn≤10 mass ppm, Sb≤10 mass ppm, and Bi≤1 mass ppm. In addition, a concentration of Se of 4.9 mass ppm or less is more advantageous in that a FAB shape and a wedge bondability can further improve.As for addition of As and Te into a bonding wire, the effect of the invention can be exhibited by using both a method of adding these elements into a Cu core material and a method of adding these elements therein by depositing these elements on a Cu core material or a surface of the wire. An amount of these elements to be added is minute and allows a wide variety of methods of addition, and the effect is exhibited by any addition method as long as the components are contained in the intended concentration range.In the bonding wire of the present invention, a thickness of the Pd plating layer is preferably 0.015 μm or more, more preferably 0.02 μm or more, still more preferably 0.025 μm or more, 0.03 μm or more, 0.035 μm or more, 0.04 μm or more, 0.045 μm or more, or 0.05 μm or more, in view of further improving connection reliability of a ball-bonded part in a high-temperature and high-humidity environment required for in-vehicle devices. From the viewpoint of obtaining an advantageous FAB shape, a thickness of the Pd plating layer is preferably 0.150 μm or less, more preferably 0.140 μm or less, 0.130 μm or less, 0.120 μm or less, 0.110 μm or less, or 0.100 μm or less.The definition of the Cu alloy core material and the Pd plating layer of the bonding wire will be described. A boundary between the Cu alloy core material and the Pd plating layer was determined based on a concentration of Pd. The boundary was set to be a position where a concentration of Pd was 50 at %, and a region where a concentration of Pd was 50 at % or more was determined as the Pd plating layer, and a concentration where a concentration of Pd was less than 50 at % was determined as the Cu alloy core material. This is because when a concentration of Pd in the Pd plating layer is 50 at % or more, an effect of improving characteristics can be expected from the structure of the Pd plating layer. The Pd plating layer may include a region of a single Pd layer and a region having concentration gradients of Pd and Cu in a wire depth direction. The reason why the region having the concentration gradients is formed in the Pd plating layer is that atoms of Pd and Cu can diffuse by a heat treatment or the like in a manufacturing process. In the present invention, the concentration gradient refers to the fact that a change degree of the concentration in the depth direction per 0.1 μm is 10 mol % or more. In addition, the Pd plating layer may contain inevitable impurities.The bonding wire of the present invention may further include an alloy skin layer containing Au and Pd on a surface of the Pd plating layer. With this configuration, the bonding wire of the present invention can further increase connection reliability and can improve wedge bondability.The definition of the alloy skin layer containing Au and Pd of the bonding wire will be described. A boundary between the alloy skin layer containing Au and Pd and the Pd plating layer was determined based on a concentration of Au. The boundary was set such that a position where a concentration of Au was 10 at % and a region where a concentration of Au was 10 at % or more were determined as the alloy skin layer containing Au and Pd, and a region where a concentration of Au was less than 10 at % was determined as the Pd plating layer. Even in the region where a concentration of Pd was 50 at % or more, a region where Au was present at 10 at % or more was determined as the alloy skin layer containing Au and Pd. These determinations are because when a concentration of Au falls within the above-mentioned range, an improving effect of the characteristics from the structure of the Au skin layer can be expected. The alloy skin layer containing Au and Pd is an Au-Pd alloy, and includes both a case where it contains a region having concentration gradients of Au and Pd in the wire depth direction and a case where it does not contain the region having the concentration gradients. It is preferable that the alloy skin layer containing Au and Pd contains the region having the concentration gradients. The reason why the region having the concentration gradients is formed in the alloy skin layer containing Au and Pd is that atoms of Au and Pd diffuse by the heat treatment or the like in the manufacturing method. In addition, the alloy skin layer containing Au and Pd may contain inevitable impurities and Cu.In the bonding wire of the present invention, the alloy skin layer containing Au and Pd reacts with the Pd plating layer to improve the adhesion strength between the alloy skin layer containing Au and Pd, the Pd plating layer, and the Cu alloy core material, and to prevent the Pd plating layer and the alloy skin layer containing Au and Pd from peeling at the time of wedge bonding. Consequently, the bonding wire of the present invention can improve wedge bondability. From the viewpoint of obtaining favorable wedge bondability, a thickness of the alloy skin layer containing Au and Pd is preferably 0.0005 μm or more, and more preferably 0.001 μm or more, 0.002 μm or more, or 0.003 μm or more. From the viewpoint of reducing eccentricity to achieve an advantageous FAB shape, a thickness of the alloy skin layer containing Au and Pd is preferably 0.050 μm or less, and more preferably 0.045 μm or less, 0.040 μm or less, 0.035 μm or less, or 0.030 μm or less. The alloy skin layer containing Au and Pd can be formed by a method similar to that of the Pd plating layer.A molding resin (an epoxy resin) as a package of a semiconductor device contains a silane coupling agent. The silane coupling agent has a function of improving adhesion between organic matter (resin) and inorganic matter (silicon or metal), and thereby can improve adhesion with a silicon substrate or metal. In a case where higher adhesiveness is required, such as a case of in-vehicle semiconductors requiring reliability at higher temperatures, a "sulfur-containing silane coupling agent" is added therein. Sulfur contained in the molding resin is not released at about 130° C. as a temperature condition of HAST, but is released when used under a condition of 175° C. or more, e.g., 175° C. to 200° C. When sulfur released at a high temperature of 175° C. or more comes into contact with Cu, Cu remarkably corrodes to generate a sulfide (Cu 2 S) or an oxide (CuO). When corrosion of Cu occurs in a semiconductor device using Cu bonding wire, connection reliability, particularly, a ball-bonded part, deteriorates.As a means for evaluating connection reliability of the ball bonded part in a high temperature environment at 170° C. or more, a high temperature bearing test (HTS) (a high temperature durability test) is performed. For a sample to be evaluated that has been exposed to a high temperature environment, a joining durability of a ball bonded part is evaluated by measuring temporal changes in a resistance value of the ball bonded part or by measuring temporal changes in the shear strength of the ball bonded part. For semiconductor devices in the vehicle, improvement of connection reliability of the ball bonded part in the HTS of 175° C. to 200° C. is required.It is preferable that the bonding wire of the present invention further contains at least one or more elements selected from Ni, Zn, Rh, In, Ir, Pt, Ga, and Ge, and a concentration of each of the elements is 0.011 to 1.2 mass % relative to the whole wire. When the bonding wire of the present invention further includes these elements, it is capable of improving the performance in the HTS at 175° C. or more of the connection reliability of the ball bonded part in a high temperature environment. From the viewpoint of improving connection reliability of a ball-bonded part in a high-temperature environment (in particular, performance in HTS at 175° C. or more), a concentration of each of the elements relative to the whole wire is preferably 0.011 mass % or more, more preferably 0.020 mass % or more, and still more preferably 0.030 mass % or more, 0.050 mass % or more, 0.070 mass % or more, 0.090 mass % or more, or 0.10 mass % or more, 0.15 mass % or more, or 0.20 mass % or more. From the viewpoint of obtaining an advantageous FAB shape and from the viewpoint of reducing the curing of the bonding wire to reduce the deterioration of the wedge bondability, a concentration of each of the elements relative to the whole wire is preferably 1.2 mass % or less, and more preferably 1.1 mass % or less. When the bonding wire of the present invention contains a plurality of elements selected from Ni, Zn, Rh, In, Ir, Pt, Ga, and Ge, a concentration of these elements in total is preferably 0.011 to 2.2 mass % relative to the total wire. From the viewpoint of improving connection reliability of a ball-bonded part in a high-temperature environment (particularly, performance in HTS at 175° C. or more), a concentration of the elements as a whole relative to the whole wire is preferably 0.011 mass % or more, more preferably 0.020 mass % or more, and still more preferably 0.030 mass % or more, 0.050 mass % or more, 0.070 mass % or more, 0.090 mass % or more, 0.10 mass % or more, 0.15 mass % or more, or 0.20 mass % or more. From the viewpoint of obtaining an advantageous FAB shape and from the viewpoint of reducing the curing of the bonding wire to reduce the deterioration of the wedge bondability, a concentration of the elements as a whole relative to the whole wire is preferably 2.5 mass % or less, 1.8 mass % or less, or 1.6 mass % or less.In the bonding wire of the present invention, it is also preferable that the Cu alloy core material contains Pd and a concentration of Pd contained in the Cu alloy core material is 0.05 to 1.2 mass %. With this structure, a result similar to the case containing Ni, Zn, Rh, In, Ir, Pt, Ga, and Ge can be obtained. In the bonding wire of the present invention, a concentration of Pd contained in the Cu alloy core material is preferably 0.05 mass % or more, 0.1 mass % or more, 0.2 mass % or more, 0.3 mass % or more, 0.4 mass % or more, or 0.5 mass % or more, in view of improving connection reliability of a ball-bonded part in a high temperature environment (particularly, performance in HTS at 175° C. or more). From the viewpoint of obtaining an advantageous FAB shape and from the viewpoint of reducing the hardening of the bonding wire, a concentration of Pd contained in the Cu alloy core material to reduce the deterioration of the wedge bondability is preferably 1.2% by mass or less, and more preferably 1.1% by mass or less. When the bonding wire of the present invention contains Ni, Zn, Rh, In, Ir, Pt, Ga, and Pd in the aforementioned range of amounts, it can improve a loop forming ability, that is, can reduce a tilt that becomes a problem for high-density mounting. This is because a yield strength of a bonding wire increases and deformation of the bonding wire can be reduced when the bonding wire includes these elements. Examples of a method for determining a concentration of Pd contained in the Cu alloy core material from a bonding wire product include a method that exposes a cross section of a bonding wire and performs concentration analysis of a region of the Cu alloy core material, and a method that performs concentration analysis of a region of the Cu alloy core material while removing the bonding wire from its surface in a depth direction by sputtering or the like. When the Cu alloy core material includes a region having a concentration gradient of Pd, for example, line analysis may be performed on a cross section of the bonding wire, and concentration analysis may be performed on a region having no concentration gradient of Pd (a region where a change degree in the Pd concentration in the depth direction is less than 10 mol % per 0.1 μm, for example). A method for concentration analysis will be described below.Further, by including Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, and Pd in the amount of the above-mentioned range, the bonding wire of the present invention can further improve the durability of the connection of a ball-bonded part in a high-temperature and high-humidity environment having a temperature of 130° C. and a relative humidity of 85%. It is considered that when the bonding wire of the present invention further contains Ni, Zn, Rh, In, Ir, Pt, Ga, Ge and Pd in a certain amount, the formation of a Cu 9 Al 4- intermetallic compound tends to be further reduced. When these elements are further included, the interfacial stress between Cu of the core material and Pd of the cladding layer further decreases, and a concentration behavior of Pd in the ball-bonded interface appears more pronounced. It can thus be estimated that an effect of reducing mutual diffusion of Cu and Al through the Pd concentrated layer is further improved, and as a result, a formation amount of Cu 9 Al 4, which is likely to corrode by the effect of Cl, is significantly reduced, and then the reliability of the ball bonded part in a high-temperature and high-humidity environment is further improved.It is preferable that the bonding wire of the present invention further contains at least one or more of the elements selected from B, P, Mg, Ca, and La, and that a concentration of each of the elements is 1 to 100 mass ppm relative to the whole wire. With this structure, a depressed shape of a ball-bonded part required for high-density mounting can be improved, that is, circularity of the shape of a ball-bonded part can be improved. It is considered that this is because clogging of elements may allow a size of a crystal grain in the ball to be fine and may reduce deformation of the ball. From the viewpoint of improving the depressed shape of a ball-bonded part, that is, improving circularity of the shape of the ball-bonded part, a concentration of each of the elements relative to the whole wire is preferably 1 mass ppm or more, more preferably 2 mass ppm or more, 3 mass ppm or more, 4 mass ppm or more, or 5 mass ppm or more.From the viewpoint of reducing the curing of the ball and reducing the chip damage at the time of ball bonding, a concentration of each of the elements relative to the whole wire is preferably 100 mass ppm of less and more preferably 95 mass ppm or less, 90 mass ppm or less, 85 mass ppm or less, or 80 mass ppm or less. When the bonding wire of the present invention contains a plurality of elements selected from B, P, Mg, Ca, and La, a concentration of these elements is preferably 1 to 100 mass ppm in total relative to the whole wire. From the viewpoint of improving the depressed shape of a ball-bonded part, that is, improving circularity of a ball-bonded part, a concentration of the elements as a whole relative to the whole wire is preferably 1 mass ppm or more, and more preferably 2 mass ppm or more, 3 mass ppm or more, 4 mass ppm or more, or 5 mass ppm or more. From the viewpoint of reducing the curing of the ball and reducing the chip damage at the time of ball bonding, a concentration of the elements in total relative to the whole wire is preferably 90 mass ppm or less, 80 mass ppm or less, or 70 mass ppm or less.For concentration analysis of the Pd plating layer and the alloy skin layer containing Au and Pd and concentration analysis of Pd in the Cu alloy core material, a method of performing analysis while removing the bonding wire from its surface in the depth direction by sputtering or the like, or a method of exposing a cross section of the wire and performing line analysis, point analysis, or the like thereon are effective. As an analyzer used for such concentration analysis, an Auger electron spectroscopy apparatus installed in a scanning electron microscope or a transmission electron microscope, an energy dispersive X-ray analyzer, and an electron probe micro analyzer, etc. can be used. As a method of exposing a wire section, mechanical polishing, ion etching, etc. may be employed. For microanalysis of As, Te, Sn, Sb, Bi, Se, Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, B, P, Mg, Ca and La in the bonding wire, a solution obtained by dissolving the bonding wire with a strong acid is analyzed using an ICP emission spectrometer or an ICP mass spectrometer, thereby enabling detection as the concentrations of elements contained in the whole bonding wire.In a preferred embodiment of the present invention, a crystal orientation <111> at an angle of 15 degrees or less to a longitudinal direction of the bonding wire in the form of an area percentage in a measurement result when measuring crystal orientations on a surface of the bonding wire is in a proportion of 30 to 100%. The embodiment can improve a loop forming ability, that is, improve a loop smoothness required for high density mounting and reduce variations in the loop height. This is because, when a surface crystal orientation is aligned, the bonding wire is resistant to lateral deformation and its lateral deformation is reduced, and thus inclination errors can be reduced.In view of the reduction of the inclination errors, the aforementioned crystal orientation <111> in terms of an area percentage has a proportion of more preferably 35% or more, and further more preferably 40% or more, 45% or more, 50% or more, or 55% or more.(Production Method)Next, a method of manufacturing the bonding wire according to the embodiment of the present invention will be described. The bonding wire is obtained by preparing a Cu alloy used for a core material, processing it into a thin wire, forming a Pd plating layer and an Au layer, and performing heat treatment. After forming the Pd plating layer and the Au layer, another wire drawing and heat treatment may be performed. A method for manufacturing the Cu alloy core material, a method for forming the Pd plating layer and an alloy skin layer containing Au and Pd, and a method for heat treatment will be described in detail.The Cu alloy core used for a core material is obtained by melting Cu as a starting material and filler elements together and solidifying them. An arc heating furnace, a high frequency heating furnace, a resistance heating furnace or the like may be used for melting. In order to prevent gases such as O 2 and H 2, from being mixed into them from air, melting is preferably performed in a vacuum atmosphere or an inert atmosphere such as Ar and N 2.A method of forming the Pd plating layer and the Au layer on a surface of the Cu alloy core material includes a plating method, a vapor deposition method, and a melting method. For a plating method, both an electroplating method and an electroless plating method can be used. Electroplating called a bar plating or flash plating has a high plating speed and is advantageous in adhesiveness to a substrate. A solution used for electroless plating is classified into a substitution type and a reduction type. Although only performing the substitution plating is sufficient for a smaller thickness, it is effective for a larger thickness to perform the reduction plating in a stepwise manner after the substitution plating.For a vapor deposition method, physical adsorption such as a sputtering method, an ion plating method, and a vacuum vapor deposition method, and chemical adsorption such as plasma CVD may be used. They are all dry methods and are free from the necessity of cleaning after the formation of the Pd plating layer and the Au layer and any fear of surface contamination and the like during cleaning.When a heat treatment is performed after the formation of the Pd plating layer and the Au layer, Pd in the Pd plating layer diffuses into the Au layer to form the alloy skin layer containing Au and Pd. Instead of forming the alloy skin layer containing Au and Pd by the heat treatment after forming the Au layer, the alloy skin layer containing Au and Pd may be deposited from the beginning.For forming the Pd plating layer and the alloy skin layer containing Au and Pd, both a method for forming them after performing wire drawing to a final diameter of the wire and a method for forming them on a Cu alloy core material having a large diameter and then performing wire drawing plural times until a target diameter is obtained are effective. In the former in which the Pd plating layer and the alloy skin layer containing Au and Pd are formed with the final wire diameter, manufacturing, quality control and the like are easy. In the latter, by performing wire drawing in combination with the formed Pd plating layer and the alloy skin layer containing Au and Pd, there is an advantage that adhesiveness with the Cu alloy core material improves. Specific examples of the respective forming methods include a method of forming the Pd plating layer and the alloy skin layer containing Au and Pd with a final diameter while the wire is successively drawn by a plating solution, and a method of forming the Pd plating layer and the alloy skin layer containing Au and Pd by immersing a Cu alloy core material with a large diameter in an electro- or electroless plating solution and then drawing the wire to achieve a final wire diameter.After forming the Pd plating layer and the alloy skin layer containing Au and Pd, the heat treatment may be performed. By performing the heat treatment, diffusion of atoms occurs between the alloy skin layer containing Au and Pd, the Pd plating layer, and the Cu alloy core material, which improves the adhesion strength therebetween and is effective in preventing the alloy skin layer containing Au and Pd and the Pd plating layer from peeling off during the processing and thus improving the productivity. In order to prevent O 2 from being mixed in from air, it is preferable to perform the heat treatment in a vacuum atmosphere or an inert atmosphere such as Ar or N 2.As described above, by setting a condition for the diffusion heat treatment or the annealing heat treatment applied to the bonding wire by grain boundary diffusion or the like, Cu of the core material diffuses through the Pd plating layer and the alloy skin layer containing Au and Pd, allowing Cu to reach an outermost surface of the bonding wire and allowing Cu to be present at an outermost surface. For a heat treatment for allowing Cu to be present on an outermost surface, a heat treatment for forming the alloy skin layer containing Au and Pd as described above may be used. When the heat treatment for forming the alloy skin layer is performed, the temperature and time for the heat treatment may be selected to allow Cu to be present on an outermost surface or allow Cu to be absent on an outermost surface. In addition, it is also possible to adjust a concentration of Cu at an outermost surface to a certain range, for example, a range of 1 to 50 at %. Alternatively, Cu may be diffused to an outermost surface by a heat treatment performed elsewhere than in the formation of the alloy skin layer.As for the addition of As and Te into the bonding wire as described above, the result of the invention can be shown by both the method of adding these elements into the Cu core material and the method of adding these elements by depositing these elements on the Cu core material or the wire surface. The same is intended to apply to Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, B, P, Mg, Ca and La.The simplest method of adding the components is a method of adding them to raw materials of the Cu alloy core material. For example, high purity copper and the above component element raw materials are weighed as starting raw materials, and then heated and melted in a high vacuum or in an inert atmosphere such as nitrogen and argon to produce a ingot in which the components having the concentration in the intended range have been added, thus obtaining the raw materials containing the component elements having the intended concentrations. Accordingly, in a preferred embodiment, the Cu alloy core material of the bonding wire of the present invention contains at least one or more elements selected from As and Te such that a concentration of the elements in total relative to the total wire is 0.01 to 100 mass ppm, and Sn≤10 mass ppm, Sb≤10 mass ppm, and Bi≤10 mass ppm. The preferred numerical range of the total concentration is as described above. In another preferred embodiment, the Cu alloy core material of the bonding wire of the present invention contains at least one or more elements selected from Ni, Zn, Rh, In, Ir, Pt, Ga, and Ge such that a concentration of each of the elements is 0.011 to 1.2 mass % relative to the whole wire. The preferred numerical concentration range is as described above. In a preferred embodiment, the purity of Cu of the Cu alloy core material is 3N or less (preferably 2N or less). In a conventional Pd-coated bonding wire, a Cu core material having high purity (4N or more) is used in view of bondability, and there is a tendency to avoid the use of a Cu core material having low purity. The bonding wire of the present invention containing the specific elements has achieved the connection reliability of a ball-bonded part in a high-temperature and high-humidity environment required for in-vehicle devices, particularly when the Cu alloy core material having low Cu purity as mentioned above is used. In another preferred embodiment, the Cu alloy core material of the bonding wire of the present invention contains at least one or more elements selected from B, P, Mg, Ca, and La such that a concentration of each of the elements is 1 to 100 mass ppm relative to the whole wire. The preferred numerical concentration range is as described above.The above components may also be incorporated by depositing them on a wire surface during a wire manufacturing process. In this case, the deposition may be incorporated in each part of the manufacturing method of the wire, and may be repeated a plurality of times. The deposition can also be incorporated into several methods. The components may be added to a Cu surface before Pd coating, or may be added to a Pd surface after Pd coating, or may be added to an Au surface after Au coating, or may be incorporated into any coating method. A deposition method may be selected from (1) applying an aqueous solution followed by drying and heat treatment, (2) plating (wet), and (3) vapor deposition (dry).When the method of applying an aqueous solution followed by drying and heat treatment is used, an aqueous solution having an appropriate concentration is first prepared with a water-soluble compound containing the component elements. The components can thus be incorporated into the wire material. The fabrication may be incorporated into each part of the wire manufacturing process and may be repeated multiple times. The preparation can be incorporated into several processes. It may be added to a Cu surface before Pd plating, or may be added to a Pd surface after Pd plating, or may be added to an Au surface after Au plating, or may be incorporated in any plating method.When plating (wet) is used, the plating may be both electroplating and electroless plating. In electroplating, plating called flash plating, which has a high plating speed and favorable adhesiveness to a substrate, can also be used besides normal electroplating. A solution used for electroless plating is classified into a substitution type and a reduction type. Although substitution plating is generally used for a smaller thickness and reduction plating is used for a larger thickness, both of them may be used. They may be selected depending on a concentration to be added and a plating solution concentration, and a time may be adjusted. Both electroplating and electroless plating may be incorporated into each part of the wire manufacturing process and may be repeated multiple times. Both electroplating and electroless plating can be incorporated into several processes. They may be added to a Cu surface before Pd plating, or may be added to the Pd surface after Pd plating, or may be added to an Au surface after Au plating, or may be incorporated in any plating method.The vapor deposition (dry) includes sputtering, ion plating, vacuum deposition, plasma CVD and the like. It has its advantages in that it is a dry process and eliminates pretreatment and post-treatment, with no fear of contamination. Although vapor deposition generally has a problem in that a capping speed of a target member is slow, it is one of suitable methods in view of the object of the present invention because an addition amount of the above component members is relatively low.The vapor deposition may be incorporated into each part of the wire manufacturing process and may be repeated multiple times. Vapor deposition can be incorporated into several processes. It may be added to a Cu surface before Pd plating, or may be added to a Pd surface after Pd plating, or may be added to an Au surface after Au plating, or may be incorporated in any plating method.The proportion of the crystal orientation <111> at an angle of 15 degrees or less to a longitudinal direction of the bonding wire when measuring crystal orientations on a surface of the bonding wire can be set to a range of 30 to 100% according to the following method. That is, a processing rate after forming the Pd plating layer or after forming the Pd plating layer and the Au skin layer is made large, which allows a texture having directivity to be developed on a surface of the wire (a texture having a crystal orientation aligned with a wire drawing direction). Specifically, a processing rate after forming the Pd plating layer or after forming the Pd plating layer and the Au skin layer is set to 90% or more, which allows the proportion of the crystal orientation <111> at an angle of 15 degrees or less to a longitudinal direction of the bonding wire in terms of area percentage to be 30% or more when measuring crystal orientations on a surface of the bonding wire. The machining rate is represented by "machining rate (%)=(cross-sectional area of the wire before machining - cross-sectional area of the wire after machining) / cross-sectional area of the wire before machining×100".When measuring crystal orientations on a wire surface, the electron-back scattered diffraction (ESBD) method is preferably used. The EBSD method can be used to observe crystal orientations on an observation surface, and graphically shows an angular difference of the crystal orientations between adjacent measurement points. Further, the EBSD method can be used to easily observe the crystal orientations even for a thin wire such as the bonding wire with high accuracy.The present invention is not limited to the above embodiment, and appropriate changes can be made within the scope of the present invention.ExamplesThe bonding wire according to an embodiment of the present invention will be described in detail below with reference to examples.(Sample)First, a method for producing a sample will be described. For Cu as a raw material of a core material, Cu having a purity of 99.99% by mass or more and containing inevitable impurities as the balance was used. For As, Te, Sn, Sb, Bi, Se, Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, Pd, B, P, Mg, Ca and La, those containing inevitable impurities as the balance at a purity of 99% by mass or more were used. As, Te, Sn, Sb, Bi, Se, Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, Pd, B, P, Mg, Ca and La as additive elements to the core material are mixed such that the wire or the core material has a desired composition. As for the addition of As, Te, Sn, Sb, Bi, Se, Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, Pd, B, P, Mg, Ca and La, they may be individually mixed. Alternatively, they may be mixed using a Cu main alloy containing the additive elements prepared in advance so as to have a desired amount when the element as a single body has a high melting point or when the element is added in a minute amount.The Cu alloy for the core material was prepared by filling the starting materials into a carbon crucible worked into a cylindrical shape having a diameter of 3 to 6 mm, heating and melting the starting materials to 1090 to 1300° C. in vacuum or in an inert atmosphere such as N 2- or Ar gas using a high-frequency furnace, and performing furnace cooling. The obtained alloy having a diameter of 3 to 6 mm was drawn to produce a wire having a diameter of 0.9 to 1.2 mm. Thereafter, a wire having a diameter of 300 to 600 μm was produced by successively performing wire drawing and the like using a die. A commercially available lubricant was used for wire drawing, and a wire drawing speed was 20 to 150 m / min. In order to remove a thin oxide film on a wire surface, etching treatment with hydrogen chloride was performed, and a Pd plating layer of 1 to 15 μm was formed to cover the entire surface of the Cu alloy as the core material. In addition, for some wires, an alloy skin layer containing Au and Pd was formed at 0.05 to 1.5 μm on the Pd plating layer. Electroplating (electroplating) was used for forming the Pd plating layer and the alloy skin layer. A commercially available semiconductor plating solution was used as a plating solution. Then, heat treatment at 200 to 500° C. and wire drawing were repeatedly performed to perform the processing to a diameter of 20 μm. After the processing, a heat treatment was performed while flowing an N 2- or Ar gas so that an elongation at break is ultimately about 5 to 15%. A heat treatment method was performed while the wire was continuously drawn, and was performed while an N 2- or Ar gas flowed. A wire feed speed was 20 to 200 m / min, a heat treatment temperature was 200 to 600° C., and a heat treatment time was 0.2 to 1.0 second.By adjusting the processing rate after the formation of the Pd plating layer or after the formation of the Pd plating layer and the alloy skin layer containing Au and Pd, the proportion (area percentage) of the crystal orientation <111> was adjusted at an angle of 15 degrees or less to a longitudinal direction of the bonding wire when crystal orientations on a surface of the bonding wire are measured.For concentration analysis of the Pd plating layer and the alloy skin layer containing Au and Pd, Auger electron spectrometry was performed while the bonding wire was adjusted from its surface in the depth direction by sputtering or the like. From the obtained concentration profile in the depth direction, a thickness of the Pd plating layer and a thickness of the alloy skin layer containing Au and Pd were determined.Regarding the working examples 93 to 98 listed in Tables 1-5, Cu having a purity of 99.99% by mass or more was used for the core material, and As, Te, Sn, Sb, Bi, and Se were contained by being deposited on the wire surface by electroplating during a manufacturing process of the wire. In this regard, a column of "Methods for Adding Components" was provided in Table 1-5, and "Overcoat Layer" was registered for Working Examples 99 to 109. Regarding all of Table 1-1 to Table 1-4 and the examples for which "core material" was registered in the column "method for adding components" in Table 1-5, As, Te, Sn, Sb, Bi, and Se were contained in the core material.Regarding Working Examples 99 to 109 and Working Examples 99 to 109 and Comparative Examples 13 and 14 listed in Table 1-5, Cu is caused to be present at an outermost surface of the bonding wire. In this regard, a column of "Cu concentration of wire surface" is provided in Table 1-5, and results obtained by measuring a surface of the bonding wire by an Auger electron spectroscopy device were recorded therein. By selecting a temperature and time for the heat treatment of the bonding wire, Cu was caused to be present at an outermost surface in a certain concentration. With respect to all of Table 1-1 to Table 1-4 and examples for which the column "Cu concentration of wire surface" in Table 1-5 is empty, heat treatment conditions that caused Cu to be absent at an outermost surface were employed, and therefore no Cu was detected by the Auger electron spectroscopy apparatus.The configurations of the samples prepared according to the above method are listed in Table 1-1 to Table 1-5. Working examples 1 to 8, 22, 23, 24, 26, 27 to 40, 48 to 62, 63 to 74, 93, 94, 99, 100, 105 and 106 are inventive examples. [ Table 1-1] (continuation)[Table 1-1] (continuation)Work Ex.10,10,0191◯Δ δ Δ⊚⊚◯⊚20,150,0533⊚Δ δ Δ◯⊚◯◯30,01-57⊚Δ δ ΔΔ δ ΔΔ δ Δ◯⊚40,050,00196⊚Δ δ Δ⊚⊚◯⊚50,0150,000597◯Δ δ Δ◯◯◯⊚60,10,00133⊚Δ δ Δ⊚⊚◯◯70,150,00359⊚Δ δ Δ◯⊚◯⊚80,010,0189⊚Δ δ ΔΔ δ Δ⊚◯⊚90,0150,0538◯Δ δ Δ◯⊚◯◯100,05-58⊚Δ δ Δ⊚Δ δ Δ◯⊚110,10,000598⊚Δ δ Δ⊚◯◯⊚120,150,00130◯Δ δ Δ◯⊚◯◯130,0150,00361⊚Δ δ Δ◯⊚◯⊚140,050,0199⊚Δ δ Δ⊚⊚◯⊚150,10,0532◯Δ δ Δ⊚⊚◯◯160,150,00159⊚Δ δ Δ◯⊚◯◯170,0150,00390◯Δ δ Δ◯⊚◯⊚ ⊚180,050,0130⊚Δ δ Δ⊚⊚◯◯190,10,0562⊚Δ δ Δ⊚⊚◯⊚200,15-95⊚Δ δ Δ◯Δ δ Δ◯⊚ [ Table 1-3] (continuation)[Table 1-3] (continuation)Work Ex.270,10,0132⊚◯⊚⊚◯⊚280,150,0558⊚⊚◯⊚⊚⊚290,01-65⊚◯Δ δ ΔΔ δ Δ◯⊚300,010,000588⊚⊚Δ δ Δ◯◯⊚310,0150,00188⊚⊚◯⊚⊚⊚320,150,00366⊚◯◯⊚⊚⊚330,050,00131⊚◯⊚⊚⊚⊚340,015-30⊚◯◯Δ δ Δ◯⊚350,10,00162⊚⊚⊚⊚⊚⊚360,10,00330⊚⊚⊚⊚⊚⊚370,050,0599⊚⊚⊚⊚⊚⊚380,150,00390⊚⊚◯⊚⊚⊚390,10,000554⊚◯⊚◯⊚⊚400,010,0133⊚◯Δ δ Δ⊚◯⊚410,015-60⊚◯◯Δ δ Δ⊚⊚420,050,000589⊚◯⊚◯⊚⊚430,10,00130⊚◯⊚⊚◯⊚440,150,00362⊚⊚◯⊚⊚⊚450,010,0195⊚◯Δ δ Δ⊚⊚⊚460,150,0159⊚◯◯⊚⊚⊚470,0150,0535⊚◯◯⊚⊚⊚ [ Table 1-3] (continuation)[Table 1-3] (continuation)Work Ex.480,05-65⊚⊚⊚Δ δ Δ⊚⊚490,050,0594⊚◯⊚⊚⊚⊚500,10,000595⊚⊚⊚◯⊚⊚510,10,000529◯⊚⊚◯◯◯520,150,00130⊚◯◯⊚◯⊚530,010,00359⊚◯Δ δ Δ⊚⊚⊚540,150,00162⊚⊚◯⊚⊚⊚550,0150,0197⊚◯◯⊚◯⊚560,050,0532⊚◯⊚⊚⊚⊚570,1-61⊚⊚⊚Δ δ Δ⊚⊚580,10,0130⊚◯⊚⊚⊚⊚590,150,000596⊚◯◯◯⊚⊚600,010,00390⊚◯Δ δ Δ⊚⊚⊚610,010,00133⊚◯Δ δ Δ⊚⊚⊚620,0150,00362⊚⊚◯⊚⊚⊚ [ Table 1-4] (continuation)[Table 1-4] (continuation)Work Ex.630,10,0165⊚◯⊚⊚◯⊚640,150,0591⊚⊚◯⊚⊚⊚650,01-64⊚⊚Δ δ ΔΔ δ Δ◯⊚660,01-31⊚⊚Δ δ ΔΔ δ Δ◯⊚670,0150,00187⊚⊚◯⊚⊚⊚680,050,00159⊚◯⊚⊚⊚⊚690,050,000560⊚◯⊚◯◯⊚700,10,00329⊚⊚⊚⊚⊚⊚710,10,00192⊚⊚⊚⊚⊚⊚720,150,00331⊚⊚◯⊚⊚⊚730,050,0598⊚⊚⊚⊚⊚⊚740,010,0158⊚◯Δ δ Δ⊚◯⊚750,05-96⊚⊚⊚Δ δ Δ⊚⊚760,10,000532⊚⊚⊚◯⊚⊚770,150,00163⊚⊚◯⊚⊚◯780,010,00391⊚⊚Δ δ Δ⊚⊚⊚790,150,0158⊚◯◯⊚⊚⊚800,050,0135⊚⊚⊚⊚⊚⊚810,050,0595⊚⊚◯⊚⊚⊚820,10,0564⊚⊚⊚⊚◯⊚830,10,000530⊚⊚⊚◯◯⊚ [ Table 1-4] (continuation)[Table 1-4] (continuation)Work Ex.840,15-94⊚⊚◯Δ δ Δ⊚⊚850,150,00163⊚◯◯⊚⊚⊚860,010,000532⊚⊚Δ δ ΔO. O⊚⊚870,050,00159⊚⊚⊚⊚◯⊚880,10,00398⊚◯⊚⊚⊚⊚890,10,0131⊚⊚⊚⊚⊚⊚900,150,0131⊚⊚◯⊚⊚⊚910,010,00391⊚⊚Δ δ Δ⊚⊚⊚920,010,0562⊚⊚Δ δ Δ⊚⊚⊚ [ Table 1-5] (continuation)[Table 1-5] (continuation)Work Ex.93Overcoat Layer0,10,00191⊚Δ δ Δ⊚⊚◯⊚940,150,00332⊚Δ δ Δ◯⊚◯◯950,010,0163⊚Δ δ ΔΔ δ Δ⊚◯⊚960,050,0592⊚Δ δ Δ⊚⊚◯⊚970,1-34◯Δ δ Δ⊚Δ δ Δ◯◯980,150,000565⊚Δ δ Δ◯◯◯⊚99Core Material0,10,001725,4⊚ ⊚Δ δ Δ⊚◯◯◯1000,150,003305,2⊚ ⊚⊚◯◯◯⊚1010,010,015510⊚ ⊚Δ δ ΔΔ δ Δ◯◯⊚1020,050,057011⊚ ⊚⊚⊚◯◯⊚1030,1-3026⊚Δ δ Δ⊚Δ δ Δ◯◯1040,150,00055928⊚ ⊚◯◯Δ δ Δ◯⊚1050,01-301,1⊚ ⊚⊚Δ δ ΔΔ δ Δ◯⊚1060,050,0005601,4⊚ ⊚⊚⊚Δ δ Δ◯⊚1070,10,001725,2⊚⊚⊚◯◯⊚ Δ1080,150,003305,5⊚⊚◯◯◯1090,010,015512⊚ ⊚⊚Δ δ Δ◯◯⊚ [ Table 1-5] (continuation)[Table 1-5] (continuation)See, for example.10,008-20×Δ δ ΔΔ δ ΔΔ δ Δ◯Δ δ Δ20,20,0189×Δ δ Δ×⊚◯◯30,10,0110Δ δ ΔΔ δ Δ×⊚◯Δ δ Δ40,180,0162×Δ δ ΔΔ δ Δ⊚◯⊚5Core and core core rods0,20,0125×Δ δ Δ×⊚◯Δ δ Δ6material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material material0,0080,0112×Δ δ ΔΔ δ Δ⊚O. OΔ δ Δ70,10,0110Δ δ ΔΔ δ Δ×⊚◯Δ δ Δ80,20,0115⊚Δ δ Δ×⊚◯Δ δ Δ90,0080,0120⊚Δ δ Δ×⊚◯Δ δ Δ100,10,0112⊚Δ δ Δ×⊚◯Δ δ Δ110,1-62×Δ δ Δ⊚Δ δ Δ◯⊚120,10,00363×Δ δ Δ⊚⊚◯⊚130,1-635,4××××××140,10,0036411××××××(Evaluation Method)A crystal structure was evaluated with a wire surface as an evaluation surface. An electron back scattering diffraction (EBSD) method was used as an evaluation method. The EBSD method is characterized in that it can observe crystal orientations on an observation surface and graphically shows an angular difference of the crystal orientations between adjacent measurement points. The EBSD method can observe the crystal orientations also for a thin wire such as the bonding wire with high accuracy.When the EBSD method having a curved surface such as the wire surface is used as an object, care should be taken. When a region having a large curvature is measured, measurement with high accuracy is difficult. However, a bonding wire to be measured is fixed to a line on a plane, and a flat part near the center of the bonding wire is measured, whereby measurement can be performed with high accuracy. In particular, the following measurement region will work well. The size in the circumferential direction is 50% or less of the wire diameter having a center in the wire length direction as an axis, and the size in the wire length direction is 100 μm or less. Preferably, the size in the circumferential direction is 40% or less of the wire diameter and the size in the wire length direction is 40 μm or less, whereby the measurement efficiency can be improved by reducing a measurement time. In order to further improve the accuracy, it is desirable that three or more points be measured to obtain average information that takes variations into account. The measurement sites may be spaced apart by 1 mm or more so as not to be close to each other.The orientation ratio of <111> on the surface was determined as a population by calculating the ratio (area percentage) of the crystal orientation <111> at an angle of 15 degrees or less to the longitudinal direction of the bonding wire, all the crystal orientations being identified by dedicated software (for example, RIM analysis manufactured by TSL Solutions).The connection reliability of the ball bonded part in a high-temperature and high-humidity environment or a high-temperature environment was determined by preparing a sample for the evaluation of the connection reliability, performing HAST and HTS evaluation, and evaluating the connection durability of the ball bonded part in each test. The connection reliability evaluation sample was prepared by performing ball bonding on an electrode formed on a general metallic frame using a commercially available wire bonder and forming an alloy of Al-1.0%Si-0.5% Cu as a thin film having a thickness of 0.8 μm on an Si substrate, and sealing it with a commercially available epoxy resin. A ball was formed while flowing an N 2+ 5% H 2- gas at a flow rate of 0.4 to 0.6 L / min, and its size was in a diameter of a range of 33 to 34 μm.For the HAST evaluation, the prepared sample for the connection reliability evaluation using an unsaturated pressure cooker was exposed to a high-temperature and high-humidity environment having a temperature of 130° C. and a relative humidity of 85% and biased at 5 V. Every 48 hours, a shear test was performed for the ball-bonded part, and a time until a value of the shear strength became half of the initial shear strength was determined as the joining longevity of the ball-bonded part. The shear test after the high temperature and high humidity test was carried out after removing a resin by an acid treatment and exposing the ball bonded part.A tester manufactured by DAGE was used for a shear tester for HAST evaluation. An average of measurement values on 10 ball bonded parts selected at random was used for the value of shear strength. In the above evaluation, the link longevity of less than 96 hours was determined to be problematic in practice to be marked with a "cross" symbol, 96 hours or more and less than 144 hours was determined to be executable but somewhat problematic to be marked with a "triangle" symbol, 144 hours or more and less than 288 hours was determined to be practically no problem to be marked with a "circle" symbol, 288 hours or more and less than 384 hours was determined to be excellent to be marked with a "double circle" symbol, and 384 hours or more was determined to be particularly excellent to be marked with a symbol of a "pair of double circles" in the column "HAST" in Table 1.For the HTS evaluation, the sample prepared for the reliability evaluation was exposed to a high temperature environment of 200° C. using a high temperature thermostatic device. Every 500 hours, a shear test was performed on the ball bonded part, and a time until a value of the shear strength became half of the initial shear strength was determined as the joining longevity of the ball bonded part. The shear test after the high temperature and high humidity test was performed after removing a resin by acid treatment and exposing the ball bonded part.A tester manufactured by DAGE was used for a shear tester for HTS evaluation. An average of measurement values on 10 ball bonded parts selected at random was used for the value of shear strength. In the above evaluation, the link longevity of 500 or more to less than 1000 hours was determined to be feasible, but improvements were determined to be desirable to be marked with a "triangle" symbol, 1000 or more to 3000 hours was determined to be practically no problem to be marked with a "circle" symbol, and 3000 hours or more was determined to be particularly excellent to be marked with a "double circle" symbol.For evaluation of ball formability (FAB shape), a ball was collected and observed before performing bonding, and the presence or absence of voids on a surface of the ball, which is a perfect ball shape in the first place, was determined. The occurrence of each of the foregoing was determined to be erroneous. The formation of the ball was carried out while blowing an N 2- gas at a flow rate of 0.5 L / min to reduce oxidation in a melting process. The size of the ball was 34 μm. For one condition, 50 spheres were observed. An SEM was used for the observation. In the evaluation of the moldability of the sphere, a case where five or more defects occurred was determined to be problematic to be marked with a "cross" symbol, a case of three or four defects was determined to be executable but somewhat problematic to be marked with a "triangle" symbol, a case of one or two defects was determined to be no problem to be marked with a "circle" symbol, and a case where no defect occurred was determined to be excellent to be marked with a "double circle" symbol in the column of "FAB shape" in Table 1.Evaluation of wedge bondability to the wire-bonded part was determined by performing 1000 bonding parts on wires of a printed circuit board and evaluating the occurrence frequency of peeling of the bonded part. An Fe-42 at% Ni alloy printed circuit board plated with 1 to 3 μm of Ag was used for the printed circuit board. In this evaluation, harder bonding conditions are assumed to be normal, a holder temperature was set to 150° C., which was lower than a general target temperature range. In the above evaluation, a case where 11 or more errors occurred was determined to be problematic to be marked with a "cross" symbol, a case of 6 to 10 errors was determined to be executable but slightly problematic to be marked with a "triangle" symbol, a case of 1 to 5 errors was determined to be no problem to be marked with a "circle" symbol, and a case where no error occurred was determined to be excellent to be marked with a "double circle" symbol in the column of "wedge bondability" in Table 1.Evaluation of a depressed shape of the ball bonded part was determined by observing the ball bonded part from immediately above after bonding and evaluating its circularity. As an object to be bonded with the bonding wire, an electrode in which an Al-0.5%-Cu alloy was formed as a thin film having a thickness of 1.0 μm on a Si substrate was used. Observation was performed using an optical microscope, and 200 sites were observed for one condition. Elliptical with a large deviation from a perfect circle and anisotropic in deformation was determined to be defective in the indented shape of the ball bonded part. In the above evaluation, a case where six or more errors occurred was determined to be problematic to be marked with a "cross" symbol, a case of four or five errors was determined to be executable but slightly problematic to be marked with a "triangle" symbol, one to three were determined to be no problem to be marked with a "circle" symbol, and a case where a favorable perfect circle was obtained was determined to be excellent to be marked with a "double circle" symbol in the column of "depressed shape" in Table 1.[Inclination]For a printed circuit board for evaluation, 100 bonding parts having a loop length of 5 mm and a loop height of 0.5 mm were formed. As an evaluation method, an upright wire part was observed from a horizontal chip direction, and the evaluation was performed based on a clearance when a clearance between a perpendicular line passing through the center of the ball-bonded part and the upright wire part was maximized (tilt clearance). When the inclination clearance was smaller than the wire diameter, the inclination was determined to be favorable, while when the inclination clearance was larger, the upright portion was inclined, and thus the inclination was determined to be defective. One hundred bonded wires were observed with an optical microscope, and the number of tilt errors was counted. A case where seven or more errors occurred was determined to be problematic to be marked with a "cross" symbol, a case of four to six errors was determined to be executable but slightly problematic to be marked with a "triangle" symbol, a case of one to three errors was determined to be no problem to be marked with a "circle" symbol, and a case where no error occurred was determined to be excellent to be marked with a "double circle" symbol in the column "tilt" in Table 1.(Evaluation results)The bonding wires according to Working Examples 1 to 109 each include a Cu alloy core material and a Pd plating layer formed on the surface of the Cu alloy core material, and the bonding wire includes at least one or more elements selected from As, Te, Sn, Sb, Bi, and Se, a concentration of the elements being 0.1 to 100 mass ppm in total relative to the whole wire. It was found that the bonding wires according to Working Examples 1 to 109 having this structure can achieve the reliability of the ball bonded part in the HAST test in the high-temperature and high-humidity environment with a temperature of 130° C. and a relative humidity of 85%.In contrast, in Comparative Examples 1, 2, 4 to 6, and 11 to 14, a concentration of the elements was out of the lower limit, and the reliability of the ball bonded portion was not obtained in the HAST test. In Comparative Examples 3 and 7 to 10, a concentration of the elements was out of the upper limit, and the FAB shape was defective. In Comparative Examples 1, 3 and 5 to 10, the area ratio of the crystal orientation <111> was outside the preferred range of the present invention, and the evaluation result of the inclination was a "triangle" symbol.In the working examples further comprising an alloy skin layer containing Au and Pd on the Pd plating layer, it was found that excellent wedge bondability can be obtained when a thickness of the alloy skin layer containing Au and Pd is 0.0005 to 0.050 μm.In Working Examples 27 to 92, 100, 102, and 104 to 109, it was found that the high temperature reliability of the ball bonded part by the HTS evaluation is advantageous because the bonding wire further contains at least one or more of the elements selected from Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, and Pd, and a concentration of each of the elements other than Pd is 0.011 to 1.2 mass % relative to the whole wire, and a concentration of Pd contained in the Cu alloy core material is 0.05 to 1.2 mass %.In some of the working examples 28 to 92, the FAB shape was advantageous, and the wedge bondability was advantageous when the bonding wire further contains at least one or more elements selected from B, P, Mg, Ca, and La, and a concentration of each of the elements is 1 to 100 mass ppm relative to the whole wire.In Working Examples 99 to 109, the wire contains As, Te, Sn, Sb, Bi, and Se, and Cu was present at an outermost surface of the wire. With this configuration, the working examples 99, 101, 103, 105, 106, 108, and 109 had a symbol "of a pair of double circles" or a "double circle" symbol in the HAST evaluation results, which made clear the effect of causing Cu to be present at an outermost surface. In addition, in the working examples 100, 102, 104, and 107, the purity of Cu of the wire was as low as 2N or less, and all of them were highly advantageous in the HAST evaluation results, a symbol "a pair of double circles". In contrast, these working examples demonstrated a slight decrease in wedge bondability.In Comparative Examples 13 and 14, not only the HAST evaluation results but also the HTS evaluation results were erroneous, the FAB shape and the indented shape were erroneous, and further, wedge bondability and inclination also deteriorated because the wire contained no As, Te, Sn, Sb, Bi and Se while Cu was present at an outermost surface of the wire.

Claims

A bonding wire for a semiconductor device, comprising: a Cu alloy core material; and a Pd plating layer formed on a surface of the Cu alloy core material, wherein the bonding wire contains at least one or more first elements selected from As and Te, a concentration of the first elements is 0.1 mass ppm or more and 100 mass ppm or less in total relative to the whole wire, and satisfies at least one of the following conditions: (i) a concentration of As is 2.5 mass ppm or more when the bonding wire contains As; and (ii) a concentration of Te is 0.2 mass ppm or more when the bonding wire contains Te, and the bonding wire further contains at least one or more second elements selected from Ni, Zn, Rh, In, Ir, Pt, Ga, and Ge, and a concentration of each of the second elements is 0.011 mass % or more and 1.2 mass % or less relative to the whole wire.The bonding wire for a semiconductor device according to claim 1, wherein the bonding wire further includes at least one or more elements selected from Su, Sb, Bi, and Se, and wherein the concentration of the at least one or more elements selected from As, Te, Sn, Sb, Bi, and Se is 1 mass ppm or more and 100 mass ppm or less in total relative to the whole wire.The bonding wire for a semiconductor device according to any one of claims 1 to 2, wherein a thickness of the Pd plating layer is 0.015 μm or more and 0.150 μm or less.The bonding wire for a semiconductor device according to any one of claims 1 to 3, further comprising an alloy skin layer containing Au and Pd on the Pd plating layer.The bonding wire for a semiconductor device according to claim 4, wherein a thickness of the alloy skin layer containing Au and Pd is 0.0005 μm or more and 0.050 μm or less.The bonding wire for a semiconductor device according to any one of claims 1 to 5, wherein the Cu alloy core material contains Pd, and a concentration of Pd contained in the Cu alloy core material is 0.05 mass% or more and 1.2 mass% or less relative to the whole wire.The bonding wire for a semiconductor device according to any one of claims 1 to 6, wherein the bonding wire further includes at least one or more third elements selected from B, P, Mg, Ca, and La, and a concentration of each of the third elements is 1 mass ppm or more and 100 mass ppm or less relative to the whole wire.The bonding wire for a semiconductor device according to any one of claims 1 to 7, wherein in a measurement result when crystal orientations are measured on a surface of the bonding wire, a crystal orientation <111> having an angle of 15 degrees or less to a longitudinal direction of the bonding wire has a proportion of 30% or more and 100% or less.The bonding wire for a semiconductor device according to any one of claims 1 to 8, wherein Cu is present at an outermost surface of the bonding wire.

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