Bonding wire for semiconductor devices

Abstract

The present invention provides a novel Cu bonding wire which enables the achievement of good bonding reliability at a 1st bonding part in a high-temperature high-humidity environment. This bonding wire for semiconductor devices is characterized by comprising a core material that is formed of Cu or a Cu alloy, and a coating layer that is formed on the surface of the core material, while containing a conductive metal other than Cu, and is also characterized in that: the coating layer contains Ni and Pd; and the ratio CNi / CPd of the concentration CNi (% by mass) of Ni to the concentration CPd (% by mass) of Pd in the entirety of the wire is 0.02 to 0.7 inclusive. This bonding wire for semiconductor devices is also characterized in that: with respect to the concentration profile in the depth direction of the wire as determined by Auger electron spectroscopy (AES), the position at which the Ni concentration is maximum is within the region from the wire surface to the depth of 0.5d, if d (µm) is the thickness of the coating layer; and the maximum concentration of Ni is 10% by atom or more. This bonding wire for semiconductor devices is further characterized in that if a free air ball (FAB) is formed using this bonding wire, in the concentration profile in the depth direction from the front end surface of the FAB, the average concentration of Ni is 0.3% by atom or more if the total concentration of Cu, Pd and Ni is taken as 100% by atom in a region A that extends from 20 nm to 200 nm in the depth direction from the front end surface of the FAB.

Description

Bonding wire for semiconductor devices

[0001] The present invention relates to a bonding wire for a semiconductor device, and further to a semiconductor device including the bonding wire.

[0002] In semiconductor devices, electrodes formed on a semiconductor chip are connected to electrodes on a lead frame or substrate using bonding wires. The bonding wire connection process is completed by first bonding to an electrode on the semiconductor chip, then forming a loop, and then second bonding the wire portion to an external electrode on the lead frame or substrate. The first bonding involves heating and melting the tip of the wire with arc heat input, forming a free air ball (FAB) using surface tension, and then crimping the ball portion to the electrode on the semiconductor chip (hereinafter referred to as "ball bonding"). The second bonding involves crimping the wire portion to the external electrode by applying ultrasonic waves and a load (hereinafter referred to as "wedge bonding") without forming a ball. The electrodes on the semiconductor chip, which are the bonding partners of the bonding wire, generally have an electrode structure in which an Al-based alloy film is formed on a Si substrate, while the electrodes on the lead frame or substrate generally have an electrode structure in which Ag or Pd plating is applied. After the connection process, the joints are sealed with a sealing resin material to obtain a semiconductor device.

[0003] Until now, gold (Au) has been the mainstream material for bonding wire, but copper (Cu) is increasingly being used instead, primarily for LSI applications (see, for example, Patent Documents 1 to 3). Furthermore, with the recent spread of electric and hybrid vehicles, it is expected that Cu, which has high thermal conductivity and fusing current, will be used in automotive devices and also in power devices (power semiconductor devices) for high-power equipment such as air conditioners and solar power generation systems. Cu is therefore expected to be a highly efficient and reliable alternative.

[0004] Cu has the disadvantage of being more easily oxidized than Au, and as a method of preventing the surface oxidation of Cu bonding wire, a structure in which the surface of the Cu core material is coated with a metal such as Pd has been proposed (Patent Document 4). Also, a Pd-coated Cu bonding wire has been proposed in which the surface of the Cu core material is coated with Pd and Pd and Pt are further added to the Cu core material to improve the bonding reliability of the first joint (Patent Document 5).

[0005] Japanese Patent Application Laid-Open No. 61-48543 Japanese Patent Application Laid-Open No. 2018-503743 International Publication No. 2017 / 221770 Japanese Patent Application Laid-Open No. 2005-167020 International Publication No. 2017 / 013796

[0006] Automotive devices and power devices tend to be exposed to higher temperatures and humidity during operation than general electronic devices, and the bonding wires used are required to exhibit good bonding reliability under harsh high-temperature environments and harsh high-temperature, high-humidity environments.

[0007] At the first bonding point where the Cu bonding wire is ball-bonded to the electrode on the semiconductor chip, an interface is formed where the Cu of the wire and the Al of the electrode are bonded. When the Cu / Al bonding interface is exposed to high temperatures, the Cu and Al interdiffuse, eventually forming an intermetallic compound, Cu. ９ Al ４ On the other hand, when the sealing resin material used in semiconductor devices is placed under high temperature and humidity, chloride ions and sulfide ions are generated due to hydrolysis etc. ９ Al ４ is prone to corrosion due to reaction with chloride ions and sulfide ions, and therefore, in Cu bonding wire, it is required to improve the bonding reliability of the first bonding portion in a high-temperature, high-humidity environment.

[0008] In this regard, in Cu bonding with a Pd coating layer, an alloy layer with a higher Pd concentration than the inside of the ball is formed on the surface of the ball during the process of melting and solidifying the bonding wire during ball formation. When this ball is used to bond to an electrode, the presence of an alloy layer with a high Pd concentration at the bonding interface suppresses the diffusion of Cu and Al at the bonding interface even in a high-temperature, high-humidity environment, and the above-mentioned Cu ９Al ４ It has been confirmed that this method can reduce the rate of production of such easily corrosive compounds and improve the bonding reliability of the first bonded portion to some extent in a high-temperature, high-humidity environment.

[0009] However, when evaluation was carried out in a high-temperature, high-humidity environment based on the characteristics required for automotive devices and power devices, it was found that there was room for improvement in the bonding reliability of the first bonded portion of the conventional Cu bonding wire having a Pd coating layer.

[0010] Even when looking at the second joint that is wedge-bonded to the external electrode, with a conventional Cu bonding wire having a Pd coating layer, there are cases where sufficient bonding reliability cannot be obtained in a high-temperature environment, as follows: That is, during the wire connection process, the Pd coating layer partially peels off, exposing the Cu core material, and the contact area between the coated Pd portion and the exposed Cu portion is exposed to an environment containing oxygen, water vapor, and sulfur compound-based outgassing generated from the sealing resin material in a high-temperature environment, which causes local corrosion of the Cu, i.e., galvanic corrosion, and there are cases where sufficient bonding reliability cannot be obtained at the second joint.

[0011] Furthermore, Pd is a rare metal, and in recent years, exhaust gas regulations have led to increased demand for it as a catalyst for purifying automobile exhaust gases, which has caused its price to skyrocket, creating a strong demand for alternative materials.

[0012] The present invention provides a novel Cu bonding wire that provides good bonding reliability of a first bonded portion even under a harsh high-temperature, high-humidity environment, and also provides good bonding reliability of a second bonded portion even under a harsh high-temperature environment.

[0013] As a result of extensive research into the above problems, the present inventors have found that the above problems can be solved by providing the following configuration, and have completed the present invention.

[0014] That is, the present invention includes the following: [1] A bonding wire for a semiconductor device, comprising a core material made of Cu or a Cu alloy and a coating layer containing a conductive metal other than Cu formed on the surface of the core material, wherein the coating layer contains Ni and Pd, and the Ni concentration C of the entire wire is Ｎｉ (mass%) and Pd concentration C ＰｄRatio C (mass%) Ｎｉ / C Ｐｄ [1] A bonding wire for a semiconductor device, wherein the Ni concentration is 0.02 or more and 0.7 or less, and in a concentration profile in the depth direction of the wire obtained by Auger electron spectroscopy (AES), when the thickness of the coating layer is d (nm), the position showing the maximum Ni concentration is within a range of 0.5d from the wire surface and the maximum Ni concentration is 10 atomic % or more, and when a free air ball (FAB) is formed using the bonding wire, in a concentration profile in the depth direction from the surface of the tip of the FAB, in a region A from 20 nm to 200 nm deep from the surface of the tip of the FAB, the average Ni concentration is 0.3 atomic % or more when the total concentration of Cu, Pd, and Ni is 100 atomic %. [2] The bonding wire according to [1], wherein in region A, the average total concentration of Pd and Ni is 2.0 atomic % or more when the total concentration of Cu, Pd, and Ni is 100 atomic %. [3] In region A, the concentration C of Pd Ｐｄ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｄ / C ＮｉThe bonding wire according to [1] or [2], wherein the average value of (a) is 0.8 or more and 27.6 or less. [4] The bonding wire according to any of [1] to [3], wherein the coating layer has a region containing Pd as a main component on the core material side in the thickness direction of the coating layer, and a region containing Ni and Pd within a range of a depth of 0.5d from the wire surface, where the thickness of the coating layer is d (nm). [5] The bonding wire according to any of [1] to [4], wherein the thickness d of the coating layer is 10 nm or more and 130 nm or less. [6] The bonding wire according to any of [1] to [5], wherein the concentration profile in the depth direction of the wire is obtained by measuring by AES under the following <conditions> while digging in the depth direction from the surface of the wire by Ar sputtering. [Conditions] The wire is positioned so that the center of its width is the center of the width of the measurement surface, and the width of the measurement surface is 5% to 15% of the wire diameter, and the length of the measurement surface is 5 times the width of the measurement surface. [7] A bonding wire according to any one of [1] to [6], wherein the concentration profile in the depth direction from the surface of the tip of the FAB is obtained by measuring by Auger electron spectroscopy (AES) under the following <Conditions> while digging in the depth direction from the surface of the tip of the FAB by Ar sputtering. <Conditions> The wire is positioned so that the distance between the center of the measurement surface and the apex of the tip of the FAB is within πD / 12, where D is the FAB diameter, and the width and length of the measurement surface are 0.05D to 0.2D, respectively. [8] A bonding wire according to any one of [1] to [7], wherein the wire surface contains Au. [9] A bonding wire according to [8], wherein the concentration of Au in the surface of the wire is 10 atomic % to 90 atomic %.

[10] The bonding wire according to [9], wherein the concentration of Au on the surface of the wire is measured by AES under the following conditions: The wire is positioned so that the center of its width is the center of the width of the measurement surface, and the width of the measurement surface is 5% to 15% of the wire diameter, and the length of the measurement surface is 5 times the width of the measurement surface.

[11] The bonding wire according to any one of [1] to

[10] , wherein, when a FAB is formed using the wire, the crystal orientation of a cross section of the FAB perpendicular to the crimp bonding direction is measured, and the proportion of <100> crystal orientations with an angle difference of 15 degrees or less with respect to the crimp bonding direction is 30% or more.

[12] The bonding wire according to any one of [1] to

[11] , which contains one or more elements selected from the group consisting of B, P, and Mg (hereinafter referred to as "first additional elements"), and the total concentration of the first additional elements relative to the entire wire is 1 mass ppm to 100 mass ppm.

[13] The bonding wire according to any one of [1] to

[12] , which contains one or more elements selected from the group consisting of Se, Te, As, and Sb (hereinafter referred to as "second additional elements"), and the total concentration of the second additional elements relative to the entire wire is 1 mass ppm to 100 mass ppm.

[14] The bonding wire according to any one of [1] to

[13] , which contains one or more elements selected from the group consisting of Ga, Ge, and In (hereinafter referred to as "third additional elements"), and the total concentration of the third additional elements relative to the entire wire is 0.011 mass% to 1.5 mass%.

[15] A semiconductor device including the bonding wire according to any one of [1] to

[14] .

[0015] According to the present invention, a novel Cu bonding wire can be provided that provides good bonding reliability of the first bonded portion even in a harsh high-temperature, high-humidity environment and good bonding reliability of the second bonded portion even in a harsh high-temperature environment.

[0016] Fig. 1 is a schematic diagram for explaining the position and dimensions of a measurement plane when performing composition analysis by AES to obtain a concentration profile in the depth direction of a wire. Fig. 2 is a schematic diagram for explaining the position and dimensions of a measurement plane when performing composition analysis by AES to obtain a concentration profile in the depth direction from the surface of the tip of a FAB. Fig. 3 is a schematic diagram for explaining a cross section perpendicular to the compression bonding direction of the FAB. Fig. 4 is a schematic diagram of a wire bonding structure. Fig. 4 is also a schematic diagram for explaining the position and dimensions of a measurement line when performing composition analysis to determine the presence or absence of region B near the bonding surface between an electrode and a ball bond.

[0017] The present invention will be described in detail below with reference to preferred embodiments. While the description may refer to drawings, each drawing merely shows the shape, size, and arrangement of components to the extent that the invention can be understood. The present invention is not limited to the following embodiments and examples, and can be modified and implemented as desired within the scope of the claims of the present invention and their equivalents.

[0018] [Bonding Wire for Semiconductor Device] The bonding wire for semiconductor device of the present invention (hereinafter also referred to simply as "wire of the present invention" or "wire") includes a core material made of Cu or a Cu alloy, and a coating layer containing a conductive metal other than Cu formed on the surface of the core material, wherein the coating layer contains Ni and Pd, and the concentration C of Ni relative to the entire wire is Ｎｉ (mass%) and Pd concentration C Ｐｄ Ratio C (mass%) Ｎｉ / C Ｐｄ is 0.02 or more and 0.7 or less; in a concentration profile in the depth direction of the wire obtained by measurement using Auger electron spectroscopy (AES), when the thickness of the coating layer is d (nm), the position showing the maximum Ni concentration is within a range of 0.5d depth from the wire surface and the maximum Ni concentration is 10 atomic % or more; and when a free air ball (FAB) is formed using the bonding wire, in a concentration profile in the depth direction from the surface of the tip of the FAB, in a region A at a depth of 20 nm or more and 200 nm or less from the surface of the tip of the FAB, the average Ni concentration is 0.3 atomic % or more when the total concentration of Cu, Pd, and Ni is 100 atomic %.

[0019] As mentioned above, bonding wires used in automotive devices and power devices are required to exhibit good bonding reliability even in harsh high-temperature and high-humidity environments. The inventors conducted evaluations under harsh high-temperature and high-humidity environments based on the characteristics required for automotive devices, etc., and confirmed that conventional Cu bonding wires having a Pd coating layer may not provide sufficient bonding reliability at both the first and second bonding sections. Furthermore, Pd is a rare metal, and its price has skyrocketed due to increased demand for it as an automotive exhaust gas purification catalyst due to recent exhaust gas regulations, creating a strong demand for alternative materials.

[0020] In contrast, a wire having a core material made of Cu or a Cu alloy and a coating layer containing a conductive metal other than Cu formed on the surface of the core material, the coating layer containing Ni and Pd, and a Ni concentration C Ｎｉ (mass%) and Pd concentration C Ｐｄ Ratio C (mass%) Ｎｉ / C Ｐｄ The present invention has been found to provide a wire having a Ni concentration profile of 0.02 to 0.7 inclusive, wherein, in a depth direction of the wire measured by AES, when the thickness of the coating layer is d (nm), the position showing the maximum Ni concentration is within a range of 0.5d from the wire surface, and the maximum Ni concentration is 10 atomic % or more. When a bonding wire is formed using the bonding wire, in a concentration profile in the depth direction from the tip surface of the FAB, in a region A at a depth of 20 nm to 200 nm from the tip surface of the FAB, the average Ni concentration is 0.3 atomic % or more when the total concentration of Cu, Pd, and Ni is 100 atomic %, thereby providing good bonding reliability of the first bonded portion even in a harsh high-temperature, high-humidity environment and good bonding reliability of the second bonded portion even in a harsh high-temperature environment. Furthermore, the wire of the present invention uses Ni, which is cheaper than Pd, and can reduce the amount of Pd used compared to conventional Cu bonding wires having a Pd coating layer. Therefore, the present invention significantly contributes to the practical application and promotion of Cu bonding wire in in-vehicle devices and power devices.

[0021] <Core Material Made of Cu or Cu Alloy> The wire of the present invention includes a core material made of Cu or a Cu alloy (hereinafter, also simply referred to as "Cu core material").

[0022] The Cu core material is not particularly limited as long as it is made of Cu or a Cu alloy, and a known Cu core material that constitutes a conventional Pd-coated Cu wire known as a bonding wire for semiconductor devices may be used.

[0023] In the present invention, the concentration of Cu in the Cu core material can be, for example, 97 atomic % or more, 97.5 atomic % or more, 98 atomic % or more, 98.5 atomic % or more, 99 atomic % or more, 99.5 atomic % or more, 99.8 atomic % or more, 99.9 atomic % or more, or 99.99 atomic % or more at the center (axial core portion) of the Cu core material.

[0024] The Cu core material may contain, for example, one or more dopants selected from the first additional element, the second additional element, and the third additional element described below. The preferred contents of these dopants are as described below.

[0025] In one embodiment, the Cu core material is composed of Cu and inevitable impurities. In another embodiment, the Cu core material is composed of Cu, one or more elements selected from the first additional element, the second additional element, and the third additional element described below, and inevitable impurities. Note that the term "unavoidable impurities" used in reference to the Cu core material also includes elements constituting the coating layer described below.

[0026] <Coating Layer Containing Conductive Metal Other Than Cu> The wire of the present invention includes a coating layer (hereinafter also simply referred to as "coating layer") that contains a conductive metal other than Cu and is formed on the surface of a Cu core material.

[0027] In order to provide good bonding reliability of the first bonded portion even in a high-temperature and high-humidity environment and to provide good bonding reliability of the second bonded portion even in a high-temperature environment, it is important that the coating layer of the wire of the present invention satisfies all of the following conditions (1) to (3): (1) Ni concentration C of the entire wire Ｎｉ (mass%) and Pd concentration C Ｐｄ Ratio C (mass%) Ｎｉ / C Ｐｄ(2) In a concentration profile of the wire in the depth direction measured by AES, when the thickness of the coating layer is d (μm), the position showing the maximum Ni concentration is within a range of 0.5d depth from the wire surface, and the maximum Ni concentration is 10 atomic % or more. (3) When a FAB is formed using the bonding wire, in a concentration profile of the wire in the depth direction from the surface of the tip of the FAB, in a region A at a depth of 20 nm to 200 nm from the surface of the tip of the FAB, the average Ni concentration is 0.3 atomic % or more when the total concentration of Cu, Pd, and Ni is 100 atomic %.

[0028] Condition (1) Condition (1) is the concentration C of Ni in the entire wire. Ｎｉ (mass%) and Pd concentration C Ｐｄ Ratio C (mass%) Ｎｉ / C Ｐｄ Regarding the range of.

[0029] By including a coating layer that satisfies condition (1) in combination with conditions (2) and (3), the wire of the present invention can provide good bonding reliability of the first bonded portion even in a high-temperature, high-humidity environment, and can also provide good bonding reliability of the second bonded portion even in a high-temperature environment. Furthermore, by including a coating layer that satisfies condition (1), the wire of the present invention is suitable because it is easy to achieve a good FAB shape.

[0030] Regarding condition (1), the ratio C Ｎｉ / C Ｐｄ From the viewpoint of realizing good bonding reliability of the first bonded portion even in a high-temperature and high-humidity environment, from the viewpoint of realizing good bonding reliability of the second bonded portion even in a high-temperature environment, and from the viewpoint of realizing a good FAB shape, the ratio C is 0.02 or more, preferably 0.04 or more, more preferably 0.05 or more, 0.06 or more, 0.08 or more, or 0.1 or more. Ｎｉ / C Ｐｄ If the ratio C is less than 0.02, the bonding reliability, particularly the bonding reliability of the second bonding portion in a high temperature environment, tends to be insufficient. Ｎｉ / C ＰｄFrom the viewpoint of realizing a good FAB shape, the upper limit of is 0.7 or less, preferably 0.65 or less, more preferably 0.6 or less, 0.55 or less, 0.5 or less, 0.48 or less, 0.46 or less, 0.45 or less, 0.44 or less, 0.42 or less, or 0.4 or less.

[0031] Ratio C under condition (1) Ｎｉ / C Ｐｄ is the Ni concentration C of the entire wire measured by the method described in [Measurement of element content] below. Ｎｉ (mass%) was measured in the same manner as the Pd concentration C Ｐｄ It can be calculated by dividing by (mass %).

[0032] Condition (2) Condition (2) relates to the position and maximum concentration value of the maximum Ni concentration in the concentration profile in the depth direction of the wire obtained by AES measurement (hereinafter simply referred to as the "concentration profile in the depth direction of the wire").

[0033] By including a coating layer that satisfies condition (2) in combination with conditions (1) and (3), the wire of the present invention can provide good bonding reliability of the first bonded portion even in a high-temperature, high-humidity environment, and can also provide good bonding reliability of the second bonded portion even in a high-temperature environment.

[0034] In condition (2), from the viewpoint of realizing good bonding reliability of the first bonded portion even in a high-temperature, high-humidity environment, and from the viewpoint of realizing good bonding reliability of the second bonded portion even in a high-temperature environment, when the thickness of the coating layer is d (nm; a calculation method based on the concentration profile in the depth direction of the wire will be described later), the position showing the maximum Ni concentration in the concentration profile in the depth direction of the wire is within a depth range of 0.5d from the wire surface, preferably within a depth range of 0.4d from the wire surface, and more preferably within a depth range of 0.3d from the wire surface.

[0035] Regarding condition (2), from the viewpoint of realizing good bonding reliability of the first bonded portion even in a high-temperature and high-humidity environment, and from the viewpoint of realizing good bonding reliability of the second bonded portion even in a high-temperature environment, the maximum concentration of Ni in the concentration profile in the depth direction of the wire is 10 atomic % or more, preferably 15 atomic % or more, more preferably 20 atomic % or more, and even more preferably 25 atomic % or more or 30 atomic % or more. The upper limit of the maximum Ni concentration is not particularly limited and may be 100 atomic %, but from the viewpoint of realizing good bonding properties at the second bonded portion, it is preferably 99 atomic % or less, 98 atomic % or less, 96 atomic % or less, 95 atomic % or less, 94 atomic % or less, 92 atomic % or less, or 90 atomic % or less.

[0036] The position and maximum concentration value of Ni under condition (2) can be confirmed and determined by performing composition analysis by AES while digging from the surface of the wire in the depth direction (toward the center of the wire) by Ar sputtering. In detail, by repeating 1) composition analysis of the wire surface, 2) sputtering with Ar, and 3) composition analysis of the surface after sputtering, the concentration change of each element in the depth direction (center) from the surface of the wire (so-called depth direction concentration profile) can be obtained, and the maximum concentration value and the position and maximum concentration value of Ni under condition (2) can be confirmed and determined based on the concentration profile. In the present invention, when obtaining the depth direction concentration profile, the unit of depth is SiO ２ (The same applies to obtaining a concentration profile in the depth direction from the surface of the tip of the FAB, which will be described later.)

[0037] When performing 1) compositional analysis of the wire surface or 3) compositional analysis of the surface after sputtering, the position and dimensions of the measurement surface are determined as follows. In the following, the width of the measurement surface refers to the dimension of the measurement surface in the direction perpendicular to the wire axis (wire thickness direction), and the length of the measurement surface refers to the dimension of the measurement surface in the wire axis direction (wire length direction). This will be further explained with reference to Figure 1. Figure 1 is a schematic plan view of a wire 1, in which the wire axis direction (wire length direction) corresponds to the vertical direction (up and down direction) in Figure 1, and the direction perpendicular to the wire axis (wire thickness direction) corresponds to the horizontal direction (left and right direction) in Figure 1. Figure 1 shows a measurement surface 2 in relation to the wire 1, and the width of the measurement surface 2 is the dimension w of the measurement surface in the direction perpendicular to the wire axis. ａ and the length of the measuring surface 2 is the dimension l of the measuring surface in the direction of the wire axis. ａ is.

[0038] When measuring by AES, the wire is positioned so that the center of its width in the direction perpendicular to the wire axis is the center of the width of the measurement surface, and the measurement surface is determined so that the width of the measurement surface is 5% to 15% of the wire diameter. The length of the measurement surface is set to be 5 times the width of the measurement surface. In Figure 1, the width of the wire is indicated by the symbol W, and the center of the wire width is indicated by the dashed line X. Therefore, the measurement surface 2 is positioned so that the center of its width coincides with the dashed line X, which is the center of the wire width, and the width w of the measurement surface is set to be 5 times the width of the measurement surface. ａ is determined to be 5% to 15% of the wire diameter (same value as the wire width W), that is, 0.05W to 0.15W. ａ Is, l ａ =5w ａ By determining the position and dimensions of the measurement surface as described above, it is possible to accurately measure whether condition (2) is met, which is suitable for providing good bonding reliability of the first bonded portion even in a high-temperature, high-humidity environment and for providing good bonding reliability of the second bonded portion even in a high-temperature environment.

[0039] The thickness d of the coating layer can be determined from the obtained concentration profile in the depth direction. First, the boundary between the Cu core material and the coating layer is determined based on the Cu concentration. The position where the Cu concentration is 50 atomic % is determined as the boundary, and the region where the Cu concentration is 50 atomic % or more is the Cu core material, and the region where the Cu concentration is less than 50 atomic % is the coating layer. In the present invention, the boundary between the Cu core material and the coating layer does not necessarily have to be a grain boundary. Then, the concentration profile is confirmed from the wire surface toward the wire center, and the thickness d can be determined as the distance from the wire surface position Z0 to the depth position Z1 where the concentration of the Cu core material first reaches 50 atomic %. In addition, it is preferable to obtain concentration profiles for multiple measurement surfaces (n≧3) spaced 1 mm or more apart in the wire axial direction and use the arithmetic average value.

[0040] The position or maximum concentration value of Ni under condition (2) can be determined from the position where the concentration is maximum by focusing on the increase or decrease in Ni concentration in the obtained concentration profile in the depth direction.

[0041] The position and maximum concentration value of the maximum Ni concentration under the above condition (2) are based on the results of measurements under the conditions described in the section "Analysis of coating layer thickness by Auger electron spectroscopy (AES)" below.

[0042] - Condition (3) - When a FAB is formed, in a concentration profile in the depth direction from the surface of the tip of the FAB (hereinafter simply referred to as "concentration profile in the depth direction of the FAB"), in a region A from a depth of 20 nm to 200 nm from the surface of the tip of the FAB, the coating layer is provided so that the average value of the Ni concentration is 0.3 atomic % or more when the total concentration of Cu, Pd, and Ni is 100 atomic %, thereby making it possible to achieve good bonding reliability of the first bonded portion even in a high-temperature, high-humidity environment.

[0043] The present inventors speculate that the wire of the present invention, which satisfies conditions (1) and (2) and has a coating layer in which, when a FAB is formed, the average Ni concentration is equal to or greater than a certain value in a region A from 20 nm to 200 nm deep from the surface of the tip of the FAB, can achieve better bonding reliability of the first bonded portion in a high-temperature, high-humidity environment than a conventional Pd-coated Cu bonding wire as follows. That is, when a ball formed using the wire of the present invention is ball-bonded to an electrode, a Pd-Ni-containing alloy layer containing Ni at a certain concentration or greater is present at the bonding interface. Here, Ni can neutralize impurity ions, such as chloride ions and sulfide ions, which have a significant impact on the corrosion reaction of Cu-Al alloys in a high-temperature, high-humidity environment, by preferentially reacting with the impurity ions. The Ni action, along with the suppression of Cu and Al diffusion at the bonding interface, prevents Cu from being present. ９ Al ４ This, together with the effect of Pd of slowing down the rate of production of such easily corrosive compounds, works synergistically to significantly suppress corrosion of the first bonded portion in a high-temperature, high-humidity environment, thereby improving the bond reliability.

[0044] From the viewpoint of providing better bonding reliability at the first bonded portion under high temperature and high humidity conditions, the average Ni concentration in region A is preferably 0.4 atomic % or more, more preferably 0.5 atomic % or more, 0.6 atomic % or more, or 0.8 atomic % or more, and even more preferably 1.0 atomic % or more, 1.2 atomic % or more, 1.4 atomic % or more, or 1.5 atomic % or more. From the viewpoint of providing a good FAB shape and thus a good compression-bonded shape at the first bonded portion, the upper limit of the average Ni concentration is preferably 8 atomic % or less, more preferably 6 atomic % or less, and even more preferably 5 atomic % or less.

[0045] In determining whether condition (3) is satisfied, the average Ni concentration in region A can be confirmed and determined by forming a FAB using a bonding wire, and then performing composition analysis by Auger electron spectroscopy (AES) while digging from the surface of the tip of the FAB in the depth direction (toward the center of the FAB) by Ar sputtering. Specifically, by repeating 1) composition analysis of the surface of the tip of the FAB, 2) sputtering with Ar, and 3) composition analysis of the surface after sputtering, the concentration change of each element in the depth direction (center) from the surface of the tip of the FAB (so-called depth direction concentration profile) can be obtained, and the average Ni concentration can be confirmed and determined based on this concentration profile.

[0046] To determine whether condition (3) is met, the FAB may be formed using a commercially available wire bonder as follows: The arc discharge conditions are set so that the discharge current is 30 to 75 mA and the FAB diameter is 1.5 to 1.9 times the wire diameter. The EFO gap is 762 μm, the tail length is 254 μm, and the N ２ +5% H ２ The FAB may be formed while the gas is flowing at a rate of 0.4 to 0.6 L / min.

[0047] When performing 1) compositional analysis of the surface of the FAB tip and 3) compositional analysis of the surface after sputtering, the position and dimensions of the measurement surface are determined as follows. The position and dimensions of the measurement surface are described below with reference to FIG. 2 . FIG. 2( a) is a schematic diagram of a wire 1 tip melted by arc heat input to form a FAB 10 by surface tension. Specifically, it is a planar schematic diagram of the FAB 10 when viewed from a direction perpendicular to the pressure bonding direction of the FAB (indicated by arrow Z in the figure). In the present invention, the FAB tip refers to the portion of the FAB on the pressure bonding side (the lower portion of the FAB in FIG. 2( a)) that forms the bonding surface with an electrode on a semiconductor chip. In FIG. 2( a), the apex of the FAB tip is indicated by symbol 10t. FIG. 2( b) is a planar schematic diagram of the FAB 10 when viewed from directly above the FAB tip apex 10t. FIG. 2B shows the measurement surface 2 in relation to the FAB 10. In the following description, the width of the measurement surface 2 is the dimension w of the measurement surface in the left-right direction of FIG. ａThe length of the measurement surface 2 is the dimension l of the measurement surface in the vertical direction in FIG. ａ and the center of the measurement surface 2 means the intersection of the center line of the width of the measurement surface and the center line of the length of the measurement surface.

[0048] When the diameter of the FAB is D, the measurement surface is positioned so that the distance between the center of the measurement surface and the apex of the tip of the FAB is within πD / 12 (where π is the ratio of the circumference of a circle to its circumference), and the measurement surface is determined so that the width and length of the measurement surface are each 0.05D to 0.2D. The distance between the center of the measurement surface and the apex of the tip of the FAB means the FAB surface distance (spherical distance) from the apex 10t of the tip of the FAB to the center of the measurement surface, and the position of the measurement surface is determined so that this distance is within πD / 12. This means that when a spherical coordinate system (r, θ, φ) is applied in which the Z axis is the direction of crimping and bonding of the FAB, and the X axis and Y axis are set at the position where the FAB shows the maximum dimension in the direction perpendicular to the direction of crimping and bonding of the FAB (the maximum diameter position of the FAB; the position of line A-A in FIG. 2A), in the spherical coordinate system, the coordinate indicating the center of the measurement surface satisfies r ≈ 0.5D in the radial coordinate r, satisfies θ≦30° in the first angular coordinate, i.e., the angle θ that the radial coordinate r makes with the Z axis, and satisfies 0°≦φ≦360° in the second angular coordinate, i.e., the angle φ that the projection of the radial coordinate r onto the X-Y plane makes with the X axis or the Y axis. In the case of Figure 2(a), the center of the measurement surface can be positioned on the surface of the tip of the FAB where θ is within 30°, and in the case of Figure 2(b), the center of the measurement surface can be positioned within 0.25D in plan view distance from the apex 10t of the tip of the FAB (corresponding to within πD / 12 in spherical distance). Note that, since deposits originating from the substrate during fabrication of the FAB sample are present near the apex 10t of the tip of the FAB, a clean location that avoids these deposits is selected as the measurement surface. By determining the position and dimensions of the measurement surface as described above, it is possible to accurately measure whether condition (3), which is suitable for achieving good bonding reliability of the first bonded portion in a high-temperature, high-humidity environment, is met.

[0049] In the obtained concentration profile in the depth direction of the FAB, the Cu concentration C Ｃｕ (atomic %), Pd concentration C Ｐｄ(atomic %), Ni concentration C Ｎｉ (atomic %), and these C Ｃｕ , C Ｐｄ and C Ｎｉ The Ni concentration is calculated when the sum of the above is taken as 100 atomic %. The average Ni concentration in region A can be calculated by arithmetically averaging the Ni concentrations calculated for each measurement point in region A. In the present invention, it is preferable to use the arithmetic mean of values ​​obtained by measuring three or more FABs as the average Ni concentration in region A.

[0050] In the present invention, when obtaining a concentration profile in the depth direction of the FAB by AES, it is preferable to measure so that the number of measurement points in the depth direction is 50 or more in region A. This makes it possible to accurately measure and determine whether condition (3) is met, which is preferable for achieving good bonding reliability of the first bonded portion in a high-temperature, high-humidity environment. Therefore, in a preferred embodiment, the wire of the present invention satisfies the above-mentioned condition (3) in the concentration profile in the depth direction of the FAB obtained by AES measurement so that the number of measurement points in region A is 50 or more.

[0051] From the viewpoint of providing better bonding reliability of the first bonded portion in a high-temperature, high-humidity environment, when a FAB is formed using the wire of the present invention, it is preferable that the concentration profile of the FAB in the depth direction further satisfies one or more of the following conditions (4) and (5) in addition to condition (3), and it is particularly preferable that both of them be satisfied. In the following conditions (4) and (5), "region A" means, as in condition (3), a region from a depth of 20 nm to 200 nm from the surface of the tip of the FAB in the concentration profile in the depth direction of the FAB. (4) In region A, when the total concentration of Cu, Pd, and Ni is taken as 100 atomic %, the average total concentration of Pd and Ni is 2.0 atomic % or more. (5) In region A, the Pd concentration C Ｐｄ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｄ / C Ｎｉ The average value is 0.8 or more and 27.6 or less.

[0052] Condition (4) Condition (4) relates to the average value of the total concentration of Pd and Ni in region A.

[0053] From the viewpoint of providing better bonding reliability of the first bonded portion in a high-temperature, high-humidity environment, in region A, when the total concentration of Cu, Pd, and Ni is taken as 100 atomic %, the average total concentration of Pd and Ni is preferably 2.0 atomic % or more, more preferably 2.5 atomic % or more, 3.0 atomic % or more, or 3.5 atomic % or more, and even more preferably 4.0 atomic % or more, 4.2 atomic % or more, 4.4 atomic % or more, 4.6 atomic % or more, 4.8 atomic % or more, or 5.0 atomic % or more. The upper limit of the average total concentration of Pd and Ni is not particularly limited and can be, for example, 40 atomic % or less, 30 atomic % or less, or 20 atomic % or less.

[0054] Condition (5) Condition (5) is the Pd concentration C in region A. Ｐｄ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｄ / C Ｎｉ Regarding the average value of

[0055] In order to provide better bonding reliability of the first bonded portion under a high-temperature and high-humidity environment, in the region A, the ratio C Ｐｄ / C Ｎｉ is preferably 0.8 or more and 27.6 or less, and the upper limit is more preferably 25.0 or less, still more preferably 24.0 or less, 22.0 or less, 20.0 or less, 18.0 or less, 16.0 or less, 14.0 or less, 12.0 or less, or 10.0 or less, and the lower limit is more preferably 1.0 or more or more than 1.0, and more preferably 1.2 or more, 1.4 or more, or 1.5 or more.

[0056] The average value and ratio C of the total concentration of Pd and Ni under conditions (4) and (5) Ｐｄ / C ＮｉThe average value of can be confirmed and determined by forming a FAB using a bonding wire, as in condition (3), and performing composition analysis by AES while digging from the surface of the tip of the FAB by Ar sputtering in the depth direction (toward the center of the FAB). That is, when performing composition analysis by AES, the position and dimensions of the measurement surface are determined so that the distance between the center of the measurement surface and the apex of the tip of the FAB is within πD / 12, where D is the diameter of the FAB, and the measurement surface is determined so that the width and length of the measurement surface are 0.05D or more and 0.2D or less. Then, in the obtained concentration profile in the depth direction of the FAB, for each measurement point in region A at a depth of 20 nm or more and 200 nm or less from the surface of the tip of the FAB, the total concentration of Pd and Ni when the total concentration of Cu, Pd, and Ni is 100 atomic % and the ratio C Ｐｄ / C Ｎｉ Then, by arithmetically averaging the values ​​calculated for each measurement point in region A, the average value of the total concentration of Pd and Ni in region A and the ratio C Ｐｄ / C Ｎｉ As in the condition (3), it is preferable to use the arithmetic mean value of the values ​​obtained by measuring three or more FABs.

[0057] The average value of the Ni concentration under the above condition (3), the average value of the total concentration of Pd and Ni under the conditions (4) and (5), and the ratio C Ｐｄ / C Ｎｉ The average value is based on the results of measurements performed under the conditions described in the section "FAB Depth Analysis by Auger Electron Spectroscopy (AES)" below.

[0058] Other Preferred Conditions for the Coating Layer In the wire of the present invention, the coating layer satisfies all of the above conditions (1) to (3), and preferably also satisfies one or both of the above conditions (4) and (5). From the viewpoint of easily satisfying these conditions (1) to (5) and from the viewpoint of being able to achieve further effects such as providing a good FAB shape, it is preferred that the coating layer in the wire of the present invention satisfies one or more of the following conditions (6) and (7): (6) In the thickness direction of the coating layer, there is a region containing Pd as a main component on the core material side, and there is a region containing Ni and Pd within a range of a depth of 0.5d from the wire surface, where the thickness of the coating layer is d (nm). (7) The thickness d of the coating layer is 10 nm or more and 130 nm or less.

[0059] Condition (6) Condition (6) relates to the coating layer having a region containing Pd as a main component on the core material side in the thickness direction of the coating layer, and also having a region containing Ni and Pd within a range of a depth of 0.5d from the wire surface, where d (nm) is the thickness of the coating layer.

[0060] By including a coating layer that satisfies the condition (6), it is easier to satisfy the conditions (2), (3) and the conditions (4), (5), and it is easier to achieve better bonding reliability of the first bonding part even in a high-temperature, high-humidity environment, and it is also easier to achieve better bonding reliability of the second bonding part even in a high-temperature environment, which is preferable.

[0061] In condition (6), the coating layer has a region containing Pd as a main component on the core material side in the thickness direction of the coating layer. In the present invention, the "region containing Pd as a main component" in the coating layer means a region in which the Pd concentration is 50 atomic % or more. The coating layer contains Ni in addition to Pd as a conductive metal other than Cu, and may further contain a conductive metal such as Au as described below. However, from the viewpoint of being able to further enjoy the effects of the present invention, the total concentration C of Pd, Ni, and Au in the entire wire is set to 50 atomic % or more. Ｍ (mass%) and Pd concentration C Ｐｄ Ratio C (mass%) Ｐｄ / C Ｍ It is preferable that the coating layer contains Pd so that the ratio C is preferably 0.5 or more, more preferably 0.6 or more, and even more preferably 0.7 or more or 0.8 or more.Ｐｄ / C Ｍ When the ratio C is in the above range, the bonding reliability of the first bonded portion in a high-temperature and high-humidity environment can be further improved, and the bondability of the second bonded portion can be further improved, which is preferable. Ｐｄ / C Ｍ The upper limit of is not particularly limited as long as conditions (1) to (3) are satisfied, and may be, for example, 0.98 or less, 0.96 or less, or 0.95 or less. In the wire of the present invention, when the thickness of the coating layer is d, it is preferable that the coating layer has a region containing Ni and Pd within a range of a depth of 0.5d from the wire surface. However, from the viewpoint of providing better bonding reliability of the first bonded portion in a high-temperature and high-humidity environment and from the viewpoint of providing better bonding reliability of the second bonded portion in a high-temperature environment, it is preferable that the total concentration C of Pd, Ni, and Au in the entire wire be 0.5d. Ｍ (mass%) and Ni concentration C Ｎｉ Ratio C (mass%) Ｎｉ / C Ｍ The coating layer preferably contains Ni so that the ratio C is preferably 0.01 or more, more preferably 0.02 or more, and even more preferably 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, or 0.08 or more. Ｎｉ / C Ｍ The upper limit of the ratio C is not particularly limited as long as it satisfies the conditions (1) to (3), and may be, for example, 0.4 or less, 0.35 or less, or 0.3 or less. Ｐｄ / C Ｍ Yahi C Ｎｉ / C Ｍ is the Pd concentration C of the entire wire measured by the method described in [Measurement of element content] below. Ｐｄ (mass%) and Ni concentration C Ｎｉ (mass%) was measured in the same manner as the total concentration C of Pd, Ni, and Au. Ｍ It can be calculated by dividing by (mass %).

[0062] Regarding condition (6), the coating layer has a region containing Pd as the main component on the core material side in the thickness direction of the coating layer, and when the thickness of the coating layer is d (nm; measurement and calculation methods are as described in relation to condition (2)), the coating layer has a region containing Ni and Pd within a range of 0.5d depth from the wire surface. This can be confirmed by performing composition analysis using Auger electron spectroscopy (AES) while digging from the wire surface in the depth direction (toward the wire center) using Ar sputtering, as described in relation to condition (2). In detail, after 1) performing composition analysis of the wire surface, 2) sputtering with Ar and 3) repeating composition analysis of the surface after sputtering obtain a concentration profile in the depth direction, and confirmation can be made from the concentration profile. The position and dimensions of the measurement surface when performing composition analysis by AES are also as described in relation to condition (2). By determining the position and dimensions of the measurement surface as described above, it is possible to accurately confirm the presence of regions in the coating layer that are mainly composed of Pd or that contain Ni and Pd, which is preferable from the viewpoint of easily satisfying conditions (2) and (3) and conditions (4) and (5).

[0063] In the present invention, the coating layer has a region containing Pd as a main component on the core material side in the thickness direction of the coating layer, and also has a region containing Ni and Pd within a range of 0.5d depth from the wire surface, based on the results of measurements performed under the conditions described in the section "Analysis of coating layer thickness by Auger electron spectroscopy (AES)" below.

[0064] The trend of the depth concentration profile obtained for a wire of the present invention according to a preferred embodiment is described below. A region containing Ni and Pd exists from the surface of the wire to a certain depth. In this region, the Ni concentration tends to decrease and the Pd concentration tends to increase from the surface of the wire toward the depth. Further in the depth direction, the Pd concentration reaches a maximum, then decreases and the Cu concentration tends to increase. The Pd concentration may exhibit a maximum concentration at a certain depth position (d1), or it may exhibit a maximum value over a certain depth range (d1 to d2). In such a concentration profile, by focusing on the increase or decrease in the Ni and Pd concentrations, it is possible to determine the presence and location of regions containing both Ni and Pd and regions containing Pd as the main component. Furthermore, by focusing on the increase or decrease in the Ni and Pd concentrations in such a concentration profile, the maximum Ni and Pd concentrations can be determined from the positions where their concentrations are maximum. As described below, when the coating layer contains Au on the wire surface side, there tends to be a region in the depth direction concentration profile where the Au concentration decreases and the Ni concentration increases from the wire surface to a very shallow position. Even in such cases, by focusing on the increase or decrease in the Ni and Pd concentrations in the coating layer, the presence of a region containing both Ni and Pd or a region mainly composed of Pd, the location of these regions, and the maximum concentrations of Ni and Pd can be determined. In the wire of the present invention, as long as there is a region containing Ni and Pd within a depth range of 0.5d from the wire surface, there may also be a region containing Ni and Pd at a depth greater than 0.5d from the wire surface. To determine the maximum concentrations of Ni and Pd in ​​the coating layer, it is preferable to obtain concentration profiles for multiple measurement surfaces (n≧3) spaced apart by 1 mm or more in the wire axial direction and use the arithmetic average value. The preferred range for the maximum Pd concentration will be described later. A "region mainly composed of Pd" can be determined when the maximum Pd concentration is 50 atomic % or more.

[0065] In a preferred embodiment, the position showing the maximum Ni concentration in the concentration profile in the depth direction of the wire is closer to the surface of the wire than the position showing the maximum Pd concentration.

[0066] From the viewpoint of further improving the bonding reliability of the first bonded portion in a high-temperature, high-humidity environment and realizing a good FAB shape, the maximum Pd concentration in the concentration profile in the depth direction of the wire is preferably 80 atomic % or more, more preferably 85 atomic % or more, and even more preferably 90 atomic % or more, more than 90 atomic %, 92 atomic % or more, 94 atomic % or more, or 95 atomic % or more. Furthermore, if the maximum Pd concentration in the coating layer is within the above range, it is preferable because it can further improve the second bondability (initial bondability of the second bonded portion). The upper limit of the maximum Pd concentration in the coating layer is not particularly limited and may be, for example, 100 atomic %.

[0067] Condition (7) Condition (7) relates to the thickness d of the coating layer. The method for measuring and calculating the thickness d of the coating layer is as explained in relation to condition (2).

[0068] In addition to the conditions (1) to (3), the inclusion of a coating layer satisfying the condition (7) provides better bonding reliability of the first bonded portion in a high-temperature, high-humidity environment, and also provides a better FAB shape, which in turn provides a better crimped shape of the first bonded portion. Furthermore, the inclusion of a coating layer satisfying the condition (7) is preferable because it can further improve the bondability of the second bonded portion.

[0069] Regarding condition (7), from the viewpoint of being able to enjoy the effects of the present invention, the thickness d of the coating layer is preferably 5 nm or more, more preferably 6 nm or more, 8 nm or more, 10 nm or more, 12 nm or more, even more preferably 14 nm or more, still more preferably 15 nm or more or 16 nm or more, and particularly preferably 18 nm or more or 20 nm or more. Furthermore, from the viewpoint of being able to enjoy the effects of the present invention, the upper limit of the thickness d of the coating layer is preferably 130 nm or less, more preferably 125 nm or less, 120 nm or less, 115 nm or less, 110 nm or less, 105 nm or less, 100 nm or less, 95 nm or less, or 90 nm or less. In a preferred embodiment, the thickness d of the coating layer is 10 nm or more and 130 nm or less.

[0070] The coating layer may contain, for example, one or more dopants selected from the first additional element, the second additional element, and the third additional element described below. The preferred contents of these dopants are as described below.

[0071] In the wire of the present invention, the coating layer may further contain Au on the wire surface side in the thickness direction of the coating layer. When the coating layer further contains Au, the bondability at the second bonded portion can be further improved.

[0072] From the viewpoint of further improving the bondability at the 2nd bonded portion, the Au concentration at the surface of the wire of the present invention is preferably 10 atomic % or more, more preferably 15 atomic % or more, even more preferably 20 atomic % or more, 22 atomic % or more, 24 atomic % or more, 25 atomic % or more, 26 atomic % or more, 28 atomic % or more, or 30 atomic % or more. From the viewpoint of realizing a good FAB shape and a good crimped shape of the 1st bonded portion, the upper limit of the Au concentration at the surface of the wire of the present invention is preferably 90 atomic % or less, more preferably 85 atomic % or less, even more preferably 80 atomic % or less, 78 atomic % or less, 76 atomic % or less, 75 atomic % or less, 74 atomic % or less, 72 atomic % or less, or 70 atomic % or less. Therefore, in a preferred embodiment, the Au concentration at the surface of the wire of the present invention is 10 atomic % or more and 90 atomic % or less.

[0073] In the present invention, the concentration of Au on the wire surface can be determined by performing composition analysis of the wire surface using Auger electron spectroscopy (AES) with the wire surface as the measurement surface, ignoring gas components such as carbon (C), sulfur (S), oxygen (O), and nitrogen (N), and nonmetallic elements.

[0074] The composition analysis of the wire surface can be performed under the same conditions as those of 1) the composition analysis of the wire surface, which was explained in relation to the method for obtaining a concentration profile in the depth direction. That is, when performing composition analysis of the wire surface by Auger electron spectroscopy (AES), the position and dimensions of the measurement surface are determined as follows.

[0075] The wire is positioned so that the center of the wire width in the direction perpendicular to the wire axis is the center of the width of the measurement surface, and the measurement surface is determined so that the width of the measurement surface is 5% to 15% of the wire diameter. The length of the measurement surface is set to be 5 times the width of the measurement surface. By determining the position and dimensions of the measurement surface as described above, the Au concentration on the wire surface can be measured with high accuracy, which is suitable for further improving the second bondability. In addition, it is preferable to perform measurements on multiple measurement surfaces (n≧3) spaced 1 mm or more apart from each other in the wire axis direction, and use the arithmetic average value.

[0076] The above-mentioned concentration of Au on the surface is based on the results of measurements performed under the conditions described in the section "Analysis of Wire Surface Composition by Auger Electron Spectroscopy (AES)" below.

[0077] When the coating layer contains Au on the surface side of the wire in the thickness direction of the coating layer, the position showing the maximum concentration of Au in the concentration profile in the depth direction of the wire is closer to the surface side of the wire than the position showing the maximum concentration of Ni or the position showing the maximum concentration of Pd.

[0078] In one embodiment, the coating layer is composed of Pd and Ni; and inevitable impurities. In another embodiment, the coating layer is composed of Pd and Ni; and one or more elements selected from Au, the first additional element, the second additional element, and the third additional element described below; and inevitable impurities. Note that the term "unavoidable impurities" used in reference to the coating layer also includes the elements that make up the Cu core material described above.

[0079] The wire of the present invention may further contain one or more elements ("first additional elements") selected from the group consisting of B, P, and Mg. When the wire of the present invention contains the first additional element, the total concentration of the first additional element relative to the entire wire is preferably 1 ppm by mass or more. This makes it possible to realize a bonding wire that provides a better crimped shape of the first bonded portion. The total concentration of the first additional element relative to the entire wire is more preferably 2 ppm by mass or more, and even more preferably 3 ppm by mass or more, 5 ppm by mass or more, 8 ppm by mass or more, 10 ppm by mass or more, 15 ppm by mass or more, or 20 ppm by mass or more. From the viewpoint of suppressing hardening of the wire and reducing chip damage during the first bonding, the total concentration of the first additional element is preferably 100 ppm by mass or less, and more preferably 90 ppm by mass or less, 80 ppm by mass or less, 70 ppm by mass or less, 60 ppm by mass or less, or 50 ppm by mass or less. Therefore, in one preferred embodiment, the wire of the present invention contains a first additional element, and the total concentration of the first additional element in the entire wire is 1 mass ppm or more and 100 mass ppm or less.

[0080] When the wire of the present invention contains a first additive element, the first additive element may be contained in either the Cu core material or the coating layer, or may be contained in both. When the wire of the present invention contains Au on its surface, the first additive element may be contained together with the Au. From the viewpoint of realizing a bonding wire that provides a better crimped shape of the first bonded portion, it is preferable that the first additive element be contained in the Cu core material.

[0081] The wire of the present invention may further contain one or more elements ("second additional elements") selected from the group consisting of Se, Te, As, and Sb. When the wire of the present invention contains the second additional elements, the total concentration of the second additional elements relative to the entire wire is preferably 1 ppm by mass or more. This can improve the bonding reliability of the first bonded portion in a high-temperature, high-humidity environment. The total concentration of the second additional elements relative to the entire wire is more preferably 2 ppm by mass or more, and even more preferably 3 ppm by mass or more, 5 ppm by mass or more, 8 ppm by mass or more, 10 ppm by mass or more, 15 ppm by mass or more, or 20 ppm by mass or more. From the viewpoint of realizing a good FAB shape and a good crimped shape of the first bonded portion, the total concentration of the second additional elements is preferably 100 ppm by mass or less, and more preferably 90 ppm by mass or less, 80 ppm by mass or less, 70 ppm by mass or less, 60 ppm by mass or less, or 50 ppm by mass or less. Therefore, in one preferred embodiment, the wire of the present invention contains a second additional element, and the total concentration of the second additional element in the entire wire is 1 mass ppm or more and 100 mass ppm or less.

[0082] When the wire of the present invention contains a second additive element, the second additive element may be contained in either the Cu core material or the coating layer, or may be contained in both. From the viewpoint of realizing a bonding wire that provides even better bonding reliability of the first bonded portion under high-temperature and high-humidity environments, it is preferable that the second additive element be contained in the coating layer. When the wire of the present invention contains Au on its surface, the second additive element may be contained together with the Au.

[0083] The wire of the present invention may further contain one or more elements ("third additional element") selected from the group consisting of Ga, Ge, and In. When the wire of the present invention contains the third additional element, the total concentration of the third additional element relative to the entire wire is preferably 0.011 mass% or more. This can improve the bonding reliability of the first bonded portion in high-temperature environments. The total concentration of the third additional element relative to the entire wire is more preferably 0.015 mass% or more, and even more preferably 0.02 mass% or more, 0.025 mass% or more, 0.03 mass% or more, 0.031 mass% or more, 0.035 mass% or more, 0.04 mass% or more, 0.05 mass% or more, 0.07 mass% or more, 0.09 mass% or more, 0.1 mass% or more, 0.12 mass% or more, 0.14 mass% or more, 0.15 mass% or more, or 0.2 mass% or more. From the viewpoint of realizing a good FAB shape, a good crimped shape of the first bonded portion, and good bondability at the second bonded portion, the total concentration of the third additional element is preferably 1.5 mass% or less, and more preferably 1.4 mass% or less, 1.3 mass% or less, or 1.2 mass% or less. Therefore, in a preferred embodiment, the wire of the present invention contains the third additional element, and the total concentration of the third additional element with respect to the entire wire is 0.011 mass% or more and 1.5 mass% or less.

[0084] When the wire of the present invention contains a third additive element, the third additive element may be contained in either the Cu core material or the coating layer, or in both. When the wire of the present invention contains Au on its surface, the third additive element may be contained together with the Au.

[0085] The contents of the first additional element, the second additional element, and the third additional element in the wire can be measured by the method described later in [Measurement of element contents].

[0086] In the wire of the present invention, the total concentration of Cu, Ni, Au, and Pd can be, for example, 98.5 mass % or more, 98.6 mass % or more, 98.7 mass % or more, or 98.8 mass % or more.

[0087] Other Preferred Conditions Further preferred conditions that the wire of the present invention should satisfy will be described below.

[0088] When a FAB is formed using the wire of the present invention, the crystal orientation of a cross section of the FAB perpendicular to the crimp bonding direction is measured, and the proportion of <100> crystal orientations with an angle difference of 15 degrees or less with respect to the crimp bonding direction is preferably 30% or more. This allows for the realization of an exceptionally good crimp shape at the first bonded portion.

[0089] As mentioned above, the bonding wire connection process is completed by first bonding to an electrode on a semiconductor chip, then forming a loop, and then second bonding the wire portion to an external electrode on a lead frame or substrate. The first bonding involves heating and melting the tip of the wire with arc heat input, forming a fabricated ball (FAB) by surface tension, and then crimping (ball-bonding) the FAB to an electrode on the semiconductor chip. The inventors have found that, based on measurements of the crystal orientation of a cross section perpendicular to the crimp bonding direction of the FAB, a wire with a proportion of <100> crystal orientations at an angle of 15 degrees or less relative to the crimp bonding direction (hereinafter simply referred to as the "proportion of <100> crystal orientations in the cross section of the FAB") of 30% or more can achieve a particularly good crimp shape at the first bond.

[0090] From the viewpoint of realizing a better crimped shape of the first bonded portion, a wire having a <100> crystal orientation ratio of 35% or more in the cross section of the FAB is more preferably 40% or more, even more preferably 45% or more, and particularly preferably 50% or more, 55% or more, or 60%. In particular, a wire having a <100> crystal orientation ratio of 50% or more in the cross section of the FAB can realize an exceptionally good crimped shape of the first bonded portion. Therefore, in a preferred embodiment, the <100> crystal orientation ratio in the cross section of the FAB is 30% or more, more preferably 50% or more. The upper limit of the <100> crystal orientation ratio in the cross section of the FAB is not particularly limited, and may be, for example, 100%, 99.5% or less, 99% or less, 98% or less, or the like.

[0091] Referring to FIG. 3, a cross section perpendicular to the crimping direction of the FAB will be described. FIG. 3 shows a schematic diagram of the process in which the tip of the wire 1 is heated and melted by arc heat input, forming the FAB 10 by surface tension. The formed FAB 10 is crimped to an electrode (not shown) on a semiconductor chip. In FIG. 3, the crimping direction of the FAB 10 is the direction indicated by arrow Z (the vertical direction (up and down) in FIG. 3). The cross section perpendicular to the crimping direction Z is the cross section exposed by cutting the FAB along dotted line A-A perpendicular to the Z direction. Here, the dotted line A-A, which serves as the reference for cross sectioning, is set at the position where the diameter of the exposed cross section is maximum, i.e., the position where the diameter of the exposed cross section is D when the diameter of the FAB is D. During the cross sectioning process, it is possible for the line A-A to deviate from the target and the diameter of the exposed cross section to be smaller than D. However, as long as the diameter of the exposed cross section is 0.9D or greater, the effect of this deviation on the crystal orientation ratio is negligibly small and is therefore acceptable.

[0092] The crystal orientation of a cross section perpendicular to the FAB compression bonding direction can be measured using electron backscattered diffraction (EBSD). The device used for the EBSD method is composed of a scanning electron microscope and a detector attached thereto. The EBSD method is a technique in which the diffraction pattern of reflected electrons generated when a sample is irradiated with an electron beam is projected onto a detector and the diffraction pattern is analyzed to determine the crystal orientation at each measurement point. Dedicated software (such as OIM analysis by TSL Solutions, Inc.) can be used to analyze data obtained by the EBSD method. The proportion of a specific crystal orientation can be calculated by using the analysis software provided with the device and using the cross section perpendicular to the FAB compression bonding direction as the inspection surface.

[0093] In this invention, the percentage of the <100> crystal orientation in the cross section of the FAB is defined as the area of ​​the <100> crystal orientation relative to the measured area, expressed as a percentage. In calculating this percentage, only crystal orientations within the measurement surface that could be identified based on a certain reliability were used, and areas where the crystal orientation could not be measured, or areas where the crystal orientation could be measured but the reliability of the orientation analysis was low, were excluded from the measurement area and the area of ​​the <100> crystal orientation. If the excluded data here exceeds, for example, 20% of the total, there is a high possibility that the measurement target was contaminated in some way, and the measurement should be repeated from the cross section. Furthermore, in this invention, the percentage of the <100> crystal orientation in the cross section of the FAB was defined as the arithmetic average of the percentages obtained by measuring three or more FABs.

[0094] The inventors speculate as follows about the reason why a wire having a ratio of <100> crystal orientation of 30% or more in the cross section of the FAB can achieve a particularly good crimped shape of the first joint.

[0095] It is known that metals deform by sliding along specific crystal planes and crystal directions (these planes and directions are also referred to as "slip planes" and "slip directions"). The FAB formed using the wire of the present invention is primarily composed of a core material, Cu or a Cu alloy, and has a face-centered cubic crystal structure. When such a crystal structure is adopted, if the crystal orientation of the cross section perpendicular to the crimping direction is <100>, metal slip occurs in a direction 45 degrees to the crimped surface, causing deformation. The FAB deforms in a direction 45 degrees to the crimped surface and radially expands relative to the plane parallel to the crimped surface. It is believed that this results in a more circular crimped shape.

[0096] In the present invention, the proportion of the <100> crystal orientation in the cross section of the FAB tends to fall within a desired range by adjusting the thickness of the coating layer, the concentration ratio of Pd and Ni in the coating layer, and the Cu purity of the core material. For example, the inventors speculate as follows about the reason why the thickness of the coating layer affects the proportion of the <100> crystal orientation in the cross section of the FAB. Specifically, it is believed that during the melting stage, the Pd and Ni in the coating layer diffuse and mix appropriately toward the center of the FAB, and the Cu or Cu alloy containing this moderately diffused and mixed Pd and Ni in solid solution has a <100> crystal orientation oriented in the compression bonding direction. It is speculated that when the thickness of the coating layer is within a predetermined range, the diffusion and mixing of Pd and Ni during melting is appropriate, making it easier for the <100> crystal orientation to be oriented in the compression bonding direction. On the other hand, if the coating layer is too thin, it is likely to have a random crystal orientation without orientation, and if the coating layer is too thick, a different crystal orientation is likely to be preferred.

[0097] The diameter of the wire of the present invention is not particularly limited and may be determined appropriately depending on the specific purpose, but is preferably 15 μm or more, 18 μm or more, 20 μm or more, etc. The upper limit of the diameter is not particularly limited and may be, for example, 80 μm or less, 70 μm or less, or 50 μm or less.

[0098] <Method for Manufacturing Wire> An example of a method for manufacturing the bonding wire for semiconductor device of the present invention will be described.

[0099] First, raw copper of high purity (4N to 6N; 99.99 to 99.9999 mass % or more) is processed into a large diameter (diameter of about 3 to 6 mm) by continuous casting to obtain an ingot.

[0100] When dopants such as the first, second, and third additive elements are added, the addition method can be, for example, by incorporating them into the Cu core material, incorporating them into the coating layer, depositing them on the surface of the Cu core material, or depositing them on the surface of the coating layer. A combination of these methods may also be used. The effects of the present invention can be achieved regardless of the addition method. In the method of incorporating a dopant into the Cu core material, a copper alloy containing the dopant at the required concentration can be used as a raw material to produce the Cu core material. When adding a dopant to the raw material Cu to obtain such a copper alloy, a high-purity dopant component can be directly added to Cu, or a mother alloy containing about 1% of the dopant component can be used. In the method of incorporating a dopant into the coating layer, the dopant can be incorporated into a Pd or Ni plating bath (in the case of wet plating) or a target material (in the case of dry plating) used to form the coating layer. In the method of depositing on the surface of a Cu core material or on the surface of a coating layer, the surface of the Cu core material or the surface of the coating layer can be used as the deposition surface, and one or more deposition processes selected from (1) application of an aqueous solution ⇒ drying ⇒ heat treatment, (2) plating method (wet type), and (3) vapor deposition method (dry type) can be carried out.

[0101] A large diameter ingot is forged, rolled, and drawn to produce a wire (hereinafter also referred to as "intermediate wire") made of Cu or a Cu alloy and having a diameter of about 0.7 to 2.0 mm.

[0102] Although electrolytic plating, electroless plating, vapor deposition, and the like can be used as methods for forming a coating layer on the surface of a Cu core material, electrolytic plating, which can stably control the film thickness, is industrially preferred. For example, a coating layer may be formed on the surface of an intermediate wire. Alternatively, the coating layer may be formed on the surface of the Cu core material after the intermediate wire has been drawn and further thinned (e.g., after drawing to the final diameter of the Cu core material). The coating layer may be formed, for example, by providing a Pd layer on the surface of the Cu core material and then providing a Ni layer or a NiPd alloy layer containing Ni and Pd in ​​a predetermined ratio, or by providing a Ni layer or a NiPd alloy layer and then further providing a layer containing Pd. From the viewpoint of forming a coating layer with excellent adhesion to the Cu core material, a predetermined coating layer may be formed after strike plating of a conductive metal on the surface of the Cu core material.

[0103] When forming a coating layer having a region containing Au on the surface side of the wire, it can be formed by providing an Au layer on the surface side of the coating layer using the same method as described above.

[0104] The wiredrawing process can be performed using a continuous wiredrawing device that can accommodate multiple diamond-coated dies. If necessary, heat treatment can be performed during the wiredrawing process. The heat treatment can diffuse the constituent elements between the Ni layer or NiPd alloy layer on the wire surface and the underlying Pd layer, forming a region containing Ni and Pd within a depth of 0.5d from the wire surface. Furthermore, when forming a coating layer having an Au-containing region on the wire surface, the heat treatment can diffuse the constituent elements between the Au layer on the wire surface and the underlying Ni layer or NiPd alloy layer (or Pd-containing layer, if provided), forming an Au-containing region (e.g., an alloy region containing Au, Ni, and Pd) on the wire surface side of the coating layer so that the Au concentration on the wire surface falls within the above-mentioned preferred range. A preferred method for this is to continuously sweep the wire at a constant speed in an electric furnace at a constant furnace temperature to promote alloying, since this method allows the alloy composition, such as the maximum Ni concentration in the coating layer, to be controlled within the desired range. Instead of forming an Au layer on the surface of the coating layer and then forming a region containing Au by heat treatment, a method may be adopted in which an alloy region containing Au and one or more of Ni and Pd is deposited from the beginning.

[0105] The wire of the present invention can provide good bonding reliability of the first bonded portion even in a high-temperature, high-humidity environment, and can also provide good bonding reliability of the second bonded portion even in a high-temperature environment. Therefore, the bonding wire of the present invention can be suitably used, particularly as a bonding wire for automotive devices and power devices.

[0106] [Wire Bonding Structure] As described above, in the connection process using a bonding wire, the first bonding is performed by heating and melting the tip of the wire with arc heat input, forming a fabricated ball (FAB) by surface tension, and then crimping (ball bonding) the fabricated ball to an electrode on a semiconductor chip.

[0107] The present invention also provides a wire bonded structure formed by ball-bonding the wire of the present invention to an electrode on a semiconductor chip. According to the wire bonded structure formed using the wire of the present invention having a coating layer that satisfies all of the above conditions (1) to (3), a Pd- and Ni-containing region containing Ni at a certain concentration or higher is present near the bonding surface of the ball bonded portion, thereby realizing good bonding reliability of the first bonded portion (ball bonded portion) even in a high-temperature, high-humidity environment.

[0108] In one embodiment, the wire bonding structure of the present invention includes a semiconductor chip having an Al electrode, a bonding wire, and a ball bond between the electrode of the semiconductor chip and the bonding wire, wherein the bonding wire includes a core material made of Cu or a Cu alloy and a coating layer containing a conductive metal other than Cu formed on the surface of the core material, the coating layer containing Ni and Pd, and the concentration C of Ni in the entire wire is Ｎｉ (mass%) and Pd concentration C Ｐｄ Ratio C (mass%) Ｎｉ / C Ｐｄ is 0.02 or more and 0.7 or less, and in a concentration profile in the depth direction of the wire obtained by AES measurement, when the thickness of the coating layer is d (nm), the position showing the maximum Ni concentration is within a range of 0.5d depth from the wire surface, and the maximum Ni concentration is 10 atomic % or more, and there is a region B in the vicinity of the joining surface of the electrode and the ball joining portion, where the Ni concentration is 1 mass % or more when the total concentration of Al, Cu, Pd, and Ni is 100 mass %.

[0109] Fig. 4 is a cross-sectional schematic diagram showing an example of a wire bonding structure. The wire bonding structure 100 shown in Fig. 4 is formed by ball-bonding a bonding wire 1 to an Al electrode 51 on a semiconductor chip 50. Fig. 4 shows a cross section of the wire bonding structure 100 taken along a plane passing through the wire axis L of the bonding wire 1 and parallel to the wire axis L (hereinafter, also simply referred to as a "cross section of the wire bonding structure"). The wire bonding structure 100 includes a semiconductor chip 50 equipped with an Al electrode 51, a bonding wire 1, and a ball bond 20 between the electrode 51 of the semiconductor chip and the bonding wire 1.

[0110] The ball bonding portion 20 is composed of a first ball compression portion 10a shown on the upper side (wire side) in Fig. 4 and a second ball compression portion 10b shown on the lower side (electrode side) in Fig. 4. In ball bonding, the FAB (10 in Fig. 3) formed at the tip of the bonding wire 1 is pressure-bonded to the electrode 51, but the first ball compression portion 10a is a portion that relatively maintains the shape of the FAB before ball bonding, and the second ball compression portion 10b is a portion that is formed by deforming the FAB so that it is crushed during pressure bonding. ｂ is the maximum width of the bonding surface 21 between the electrode 51 and the ball bonding portion 20 in a direction parallel to the bonding surface 21 (perpendicular to the wire axis L). H in Figure 4 is the maximum height of the second ball compression portion 10b relative to the bonding surface 21.

[0111] In the wire bonding structure 100 of the present invention, the bonding wire 1 is the wire of the present invention described above, and has a region B in which the Ni concentration is 1 mass % or more when the total concentration of Al, Cu, Pd, and Ni is 100 mass % near the bonding surface 21 between the electrode 51 on the semiconductor chip 50 and the bonding wire 1. Here, to determine whether or not the region B exists near the bonding surface, the vicinity of the bonding surface in the cross section of the wire bonding structure is subjected to composition analysis by energy dispersive X-ray spectroscopy (EDS), and the measurement line at that time (line P in FIG. 4) is １ , P ２ , P ３ The position and dimensions of the conductors 11 and 12 will be described later.

[0112] From the viewpoint of providing better bonding reliability of the first bonded portion under high-temperature and high-humidity environments, the average Ni concentration in region B is preferably 1.2 mass% or more, more preferably 1.4 mass% or more, and even more preferably 1.5 mass% or more. From the viewpoint of realizing a good crimped shape of the first bonded portion, the upper limit of the average Ni concentration is preferably 8 mass% or less, more preferably 6 mass% or less, and even more preferably 5 mass% or less.

[0113] From the viewpoint of achieving better bonding reliability of the first bonded portion in a high-temperature, high-humidity environment, when the total concentration of Al, Cu, Pd, and Ni is taken as 100 mass%, the average total concentration of Pd and Ni in region B is preferably 3 mass% or more, more preferably 3.5 mass% or more, and even more preferably 3.6 mass% or more, 3.8 mass% or more, or 4 mass% or more. The upper limit of the average total concentration of Pd and Ni is not particularly limited and may be, for example, 24 mass% or less, 18 mass% or less, or 15 mass% or less.

[0114] In order to provide better bonding reliability of the first bonded portion under a high-temperature and high-humidity environment, the Pd concentration C Ｐｄ (mass%) and Ni concentration C Ｎｉ Ratio C (mass%) Ｐｄ / C Ｎｉ is preferably 0.4 or more and 50 or less, and the upper limit is more preferably 40 or less, even more preferably 30 or less, 15 or less, or 10 or less, and the lower limit is more preferably 0.5 or more, more preferably 0.6 or more or 0.8 or more, even more preferably 1 or more, 1.2 or more, or 1.4 or more.

[0115] The presence or absence of region B, the average value of the total concentration of Pd and Ni in region B, and the ratio C Ｐｄ / C Ｎｉ The average value of can be confirmed and determined by EDS composition analysis of the vicinity of the bonding surface in the cross section of the wire bonded structure. Hereinafter, this will be explained with reference to Fig. 4. The composition analysis by EDS is performed by line analysis of the vicinity of the bonding surface 21 between the electrode 51 and the ball bonded portion 20 in the cross section of the wire bonded structure along a direction perpendicular to the bonding surface 21 (parallel to the wire axis L). In the cross section of the wire bonded structure shown in Fig. 4, three measurement lines for composition analysis are denoted by the symbols P １ , P ２ and P ３ Shown in.

[0116] In the present invention, the measurement line P for EDS composition analysis is １ , P ２ and P ３ The position and dimensions of the measurement line P are determined as follows:１ and P ２ is set so as to pass through the second point from the outside among the seven points that divide the maximum width Wb of the bonding surface 21 of the electrode 51 and the ball bonding portion 20 into six equal parts, and to extend in a direction perpendicular to the bonding surface 21 (measurement line P １ is the second point from the left in FIG. 4, the measurement line P ２ (The line P passes through the second point from the right in Figure 4.) ３ The measurement line P is set to pass through the middle point (fourth point from the outside) among the seven points that divide the maximum width Wb into six equal parts, and to extend in a direction perpendicular to the joining surface 21. １ , P ２ and P ３ The dimension (length) of the measurement line P may be determined appropriately depending on the dimension of the ball bonded portion (second ball compressed portion) in the wire bonded structure, and may be, for example, 5 μm or more, 10 μm or more, etc. １ , P ２ and P ３ The upper limit of the dimension (length) of can be, for example, 0.5H or less, 0.4H or less, or 0.3H or less, where H is the maximum height of the second ball compression portion 10b. By determining the position and dimension of the measurement line as described above, it is possible to accurately determine whether or not region B exists, which is suitable for providing good bonding reliability of the first bonded portion in a high-temperature, high-humidity environment. Note that a range of error associated with measurements, etc., is naturally allowed for the size and direction of each part in the wire bonding structure.

[0117] The measurement line P set in this way １ , P ２ and P ３ In the concentration profile for each measurement line obtained, the concentration C of Al is Ａｌ (mass%), Cu concentration C Ｃｕ (mass%), Pd concentration C Ｐｄ (mass%), Ni concentration C Ｎｉ (mass%) was calculated, and these C Ａｌ , C Ｃｕ , C Ｐｄ and C ＮｉThe Ni concentration is calculated when the total of the above is taken as 100 mass %. Ｎｉ The position of 1 mass% of Ni is determined as the boundary, and the concentration C Ｎｉ The region where the content of Cr is 1 mass % or more is defined as region B. The boundary of region B does not necessarily have to be a grain boundary.

[0118] The thickness of the region B is determined by checking the concentration profile from the bonding surface 21 side to the ball bonding portion side (wire side), and the Ni concentration C Ｎｉ From the position Z3 where the Ni concentration C Ｎｉ The thickness of region B can be determined as the distance to position Z4 where the content of the first bonded joint first falls to less than 1 mass %. From the viewpoint of achieving better bonding reliability of the first bonded joint under high-temperature and high-humidity environments, the thickness of region B in the concentration profile along measurement line P is preferably 0.6 μm or more, more preferably 0.8 μm or more, and even more preferably 1 μm or more. The upper limit of the thickness of region B is not particularly limited and may be, for example, 8 μm or less, 6 μm or less, or 4 μm or less.

[0119] The average Ni concentration in region B can be calculated by arithmetically averaging the Ni concentrations calculated for each measurement point in region B. In addition, the total concentration and ratio C of Pd and Ni calculated for each measurement point in region B can be calculated by arithmetically averaging the Ni concentrations calculated for each measurement point in region B. Ｐｄ / C Ｎｉ By arithmetically averaging the values ​​of each, the average value of the total concentration of Pd and Ni in region B and the ratio C Ｐｄ / C Ｎｉ In order to calculate these average values, the three measurement lines P are positioned so as to satisfy the above positions and dimensions. １ , P ２ and P ３ It is preferable to set these three measurement lines, perform composition analysis by EDS for these three measurement lines, and use the arithmetic mean value of the obtained values.

[0120] In the present invention, the presence or absence of region B in the wire bonding structure, the average value of the total concentration of Pd and Ni in region B, and the ratio C Ｐｄ / C ＮｉThe average values ​​are based on the results of measurements performed under the conditions described in the section "Composition analysis of wire bonded structure by energy dispersive X-ray spectroscopy (EDS)" below.

[0121] As described above, the wire bonding structure of the present invention is characterized in that the bonding wire included in the wire bonding structure is the wire of the present invention. That is, in the wire bonding structure of the present invention, the bonding wire includes a core material made of Cu or a Cu alloy and a coating layer containing a conductive metal other than Cu formed on the surface of the core material, and satisfies the above conditions (1) to (3). Details of the wire of the present invention, including preferred embodiments of the core material and coating layer, are as described above in the section "Bonding wire for semiconductor device."

[0122] In the wire bonding structure of the present invention, the semiconductor chip includes an Al electrode. The Al electrode may be, for example, an electrode formed by depositing an Al or Al-based alloy on a Si substrate. Examples of Al-based alloys include Al—Cu—Si alloys (such as an Al—Cu (0.2 to 0.9% by mass)-Si (0.5 to 1.5% by mass) alloys) and Al—Cu alloys (such as an Al—Cu (0.2 to 0.9% by mass)).

[0123] [Method for Manufacturing a Semiconductor Device] A semiconductor device can be manufactured by connecting electrodes on a semiconductor chip to electrodes on a lead frame or a circuit board using the bonding wire for a semiconductor device of the present invention.

[0124] In one embodiment, the semiconductor device of the present invention includes a circuit board, a semiconductor chip, and a bonding wire for electrically connecting the circuit board and the semiconductor chip, the bonding wire being the wire of the present invention. Here, it is preferable that the bonded portion between the semiconductor chip and the bonding wire be the wire bonded structure of the present invention.

[0125] In the semiconductor device of the present invention, the circuit board and semiconductor chip are not particularly limited, and known circuit boards and semiconductor chips that can be used to configure a semiconductor device may be used. Alternatively, a lead frame may be used instead of the circuit board. For example, a semiconductor device may be configured including a lead frame and a semiconductor chip mounted on the lead frame, as in the semiconductor device described in JP 2020-150116 A.

[0126] Examples of the semiconductor device include various semiconductor devices used in electrical appliances (e.g., computers, mobile phones, digital cameras, televisions, air conditioners, solar power generation systems, etc.) and vehicles (e.g., motorcycles, automobiles, trains, ships, aircraft, etc.).

[0127] The present invention will be specifically described below with reference to examples, although the present invention is not limited to the examples shown below.

[0128] (Sample) First, a method for preparing the sample will be described. The Cu used as the raw material for the Cu core material had a purity of 99.99% by mass or more (4N), with the remainder consisting of inevitable impurities. When the first additional element, second additional element, and third additional element were added, the purity of these elements was 99% by mass or more, with the remainder consisting of inevitable impurities, or a master alloy in which these additional elements were blended in high concentrations with Cu was used.

[0129] The core Cu alloy was first prepared by loading raw materials into a graphite crucible and heating them in a high-frequency furnace. ２The wire was heated to 1090-1500°C in an inert atmosphere of nitrogen or argon gas to melt it, and then continuously cast into ingots with diameters of approximately 3-6 mm. The resulting ingots were then drawn to produce intermediate wires with diameters of 0.7-2.0 mm. The wires were then continuously drawn using a die to reduce their diameter to the wire diameter to be coated. A commercially available lubricant was used for the wiredrawing process, and the wiredrawing speed was 20-150 m / min. The coating layer was formed by pickling with hydrochloric acid or sulfuric acid to remove the oxide film from the wire surface, followed by forming a Pd layer covering the entire surface of the Cu alloy core, and then forming a Ni layer on that surface. Furthermore, some wires (Examples Nos. 5-7) had an Au layer formed on the Ni layer. The Pd, Ni, and Au layers were formed using electroplating. Commercially available plating solutions were prepared and appropriately adjusted for use as Pd, Ni, and Au plating solutions.

[0130] Thereafter, further wire drawing and other processes were carried out to process the wire into a final diameter of 20 μm. If necessary, intermediate heat treatment was carried out once or twice during the wire drawing process at 300 to 700°C for 2 to 15 seconds. When intermediate heat treatment was carried out, the wire was continuously swept and heated in N ２ After processing to the final wire diameter, the wire was continuously swept and N ２ The thermal refining treatment was performed while flowing nitrogen or Ar gas. The thermal refining treatment temperature was 200 to 600°C, the wire feed speed was 20 to 200 m / min, and the thermal refining time was 0.2 to 1.0 seconds. When the coating layer was thin or the Ni concentration was low, the thermal refining temperature was lowered and the wire feed speed was set to a higher value, and in the opposite cases, the thermal refining temperature was increased and the wire feed speed was set to a lower value.

[0131] (Test and Evaluation Methods) Test and evaluation methods will be described below.

[0132] [Composition Analysis of Wire Surface by Auger Electron Spectroscopy (AES)] For wires containing Au on their surface, the Au concentration on the wire surface was measured by Auger electron spectroscopy (AES) as follows, using the wire surface as the measurement surface. First, the bonding wire to be measured was fixed linearly to a sample holder. Next, the wire was positioned so that the center of the width of the wire in the direction perpendicular to the wire axis was the center of the width of the measurement surface, and the measurement surface was determined so that the width of the measurement surface was 5% to 15% of the wire diameter. The length of the measurement surface was 5 times the width of the measurement surface. Then, using an AES device (PHI-700 manufactured by ULVAC-PHI), composition analysis of the wire surface was performed at an acceleration voltage of 10 kV, and the surface Au concentration (atomic %) was determined. Note that the composition analysis by AES was performed on three measurement surfaces spaced 1 mm or more apart from each other in the wire axial direction, and the arithmetic average value was used. When determining the concentration of Au on the surface, gas components such as carbon (C), sulfur (S), oxygen (O), and nitrogen (N), non-metallic elements, etc. were not taken into consideration.

[0133] [Coating Layer Thickness Analysis by Auger Electron Spectroscopy (AES)] The thickness of the coating layer was analyzed by depth analysis using AES. Specifically, 1) composition analysis of the wire surface was performed using AES, and then 2) sputtering with Ar and 3) composition analysis of the surface after sputtering were repeated to obtain a concentration profile in the depth direction. The sputtering in 2) was performed using Ar. ＋ The measurements were performed using ions and an acceleration voltage of 2 kV. The surface composition analysis in 1) and 3) was performed using the same measurement surface dimensions and AES composition analysis conditions as those described in the "Analysis of Wire Surface Composition by Auger Electron Spectroscopy (AES)" section above. The depth concentration profile was obtained for three measurement surfaces spaced 1 mm or more apart along the wire axis.

[0134] - Thickness d of coating layer - In the obtained concentration profile in the depth direction, the concentration profile was confirmed from the wire surface toward the wire center, and the distance from the wire surface position Z0 to the depth position Z1 where the concentration of the core material Cu first reached 50 atomic % was obtained as the thickness of the measured coating layer. The thickness d of the coating layer was the arithmetic mean value of the values ​​obtained for the three measurement surfaces. The depth measured by AES analysis was obtained as the product of the sputtering rate and time. Generally, the sputtering rate is determined by the standard sample SiO ２ The depth analyzed by AES is measured using SiO ２ In other words, the unit of thickness of the coating layer is SiO ２ A conversion value was used.

[0135] - Maximum Pd and Ni Concentration in Coating Layer - In the obtained depth-direction concentration profile, the increase or decrease in the Pd and Ni concentrations was focused on, and the maximum Pd and Ni concentrations were determined from the positions where the concentrations were maximum. The arithmetic mean of the values ​​obtained for the three measurement surfaces was adopted as the maximum Pd and Ni concentrations. It was confirmed that the wire of the example had a region mainly composed of Pd on the core side, a region containing Ni and Pd within a depth range of 0.5d from the wire surface, the position showing the maximum Ni concentration was within a depth range of 0.5d from the wire surface, and the position showing the maximum Ni concentration was closer to the surface than the position showing the maximum Pd concentration. For the wire of the example provided with a coating layer containing Au on the wire surface side, it was confirmed that the position showing the maximum Au concentration was closer to the surface than the positions showing the maximum Ni concentration and the positions showing the maximum Pd concentration.

[0136] [FAB Depth Analysis by Auger Electron Spectroscopy (AES)] (1) Formation of FAB For the bonding wires produced in the examples and comparative examples, a commercially available wire bonder was used to perform FAB depth analysis, setting the current value to 30 to 75 mA, the EFO gap to 762 μm, and the tail length to 254 μm. ２ +5% H ２ The FAB was formed while the gas was flowing at a flow rate of 0.4 to 0.6 L / min. The diameter of the FAB was set to 1.5 to 1.9 times the wire diameter.

[0137] (2) Depth Analysis of FAB by AES Depth analysis of the tip surface of the formed FAB was performed using AES. Depth analysis by AES is a method of analyzing changes in composition in the depth direction by alternately performing composition analysis and sputtering, and it is possible to obtain concentration changes of each element in the depth (center) direction from the surface of the tip of the FAB (so-called concentration profile in the depth direction). Specifically, after 1) composition analysis of the surface of the tip of the FAB was performed by AES, 2) sputtering with Ar and 3) composition analysis of the surface after sputtering were repeated to obtain a concentration profile in the depth direction. The sputtering in 2) was performed using Ar. ＋ The surface composition analysis was performed using ions and an acceleration voltage of 2 kV. In the surface composition analysis of 1) and 3), the position and dimensions of the measurement surface were determined so that the distance between the center of the measurement surface and the apex of the tip of the FAB was within πD / 12 (where π represents the circumference ratio and D represents the FAB diameter (μm)). The width and length of the measurement surface were each 5 μm (a range of 5% to 20% of the FAB diameter). Since deposits originating from the substrate during fabrication of the FAB sample exist near the apex of the tip of the FAB, a clean area was selected as the measurement surface, avoiding the deposits. Then, using an AES device (PHI-700 manufactured by ULVAC-PHI) at an acceleration voltage of 10 kV, a concentration profile in the depth direction was obtained. To obtain the concentration profile in the depth direction using AES, 50 or more measurement points in the depth direction were measured in region A, which was 20 nm to 200 nm deep from the surface of the tip of the FAB. The concentration profile in the depth direction was obtained for three FABs.

[0138] -Average value of Ni concentration in region A- In the obtained concentration profile in the depth direction of the FAB, the Cu concentration C Ｃｕ (atomic %), Pd concentration C Ｐｄ (atomic %), Ni concentration C Ｎｉ (atomic %), and these C Ｃｕ , C Ｐｄ and C ＮｉThe Ni concentration was calculated when the total of the above was taken as 100 atomic %. The Ni concentrations calculated for each measurement point in region A were then arithmetically averaged to calculate the average Ni concentration in region A. The average Ni concentration in region A was the arithmetic mean of the values ​​obtained for the three FABs.

[0139] - Average value of total concentration of Pd and Ni in region A, ratio C Ｐｄ / C Ｎｉ In the concentration profile in the depth direction of the obtained FAB, for each measurement point in the region A whose depth from the surface of the tip of the FAB is 20 nm or more and 200 nm or less, C Ｃｕ , C Ｐｄ and C Ｎｉ The total concentration of Pd and Ni when the total is 100 atomic %, and the ratio C Ｐｄ / C Ｎｉ The values ​​calculated for each measurement point in region A were then arithmetically averaged to obtain the average value of the total concentration of Pd and Ni in region A and the ratio C Ｐｄ / C Ｎｉ The average value of the total concentration of Pd and Ni in region A and the ratio C Ｐｄ / C Ｎｉ The average value was the arithmetic mean value of the values ​​obtained for the three FABs.

[0140] [Composition Analysis of Wire Bonded Structure by Energy Dispersive X-ray Spectroscopy (EDS)] (1) Fabrication of Wire Bonded Structure For the bonding wires fabricated in the Examples and Comparative Examples, FABs were formed under the conditions described in the above section [FAB Depth Analysis by Auger Electron Spectroscopy (AES)], and a wire bonded structure was fabricated by ball bonding using a commercially available wire bonder to an electrode formed by depositing a 1.5 μm thick film of an Al-1.0 mass % Si-0.5 mass % Cu alloy on a silicon substrate on a general metal frame.

[0141] (2) Preparation of a cross-sectional sample of the wire bonded structure The wire bonded structure was sealed with a commercially available thermosetting epoxy resin. Then, a cross-sectional sample of the wire bonded structure was prepared so that the surface passing through the wire axis of the bonding wire and parallel to the wire axis was exposed.

[0142] (3) Composition Analysis of Wire Bonded Structure by EDS Line analysis by EDS was used for the composition analysis of the wire bonded structure. Specifically, in a cross-sectional sample of the wire bonded structure, line analysis was performed in the vicinity of the bonding surface between the electrode and the ball bond along a direction perpendicular to the bonding surface (parallel to the wire axis). The analysis was performed along three measurement lines P １ , P ２ and P ３ Measurement line P １ and P ２ was set to pass through the second point from the outside among the seven points that divide the maximum width of the bonding surface of the electrode and ball bonding part into six equal parts, and to extend in a direction perpendicular to the bonding surface (measurement line P in Figure 4). １ is the second point from the left, measurement line P ２ (The measurement line P is set to pass through the second point from the right.) ３ The measurement line P was set to pass through the middle point (fourth point from the outside) of the seven points that divide the maximum width of the joint surface into six equal parts, and to extend in a direction perpendicular to the joint surface. １ , P ２ and P ３ The dimensions (length) of the electrode were set to 15 μm (approximately 2 μm on the electrode side and approximately 13 μm on the ball bond side). Using an FE-SEM / EDS device (EDS detector: AztecEnergy manufactured by Oxford Instruments), line analysis was performed under conditions of an acceleration voltage of 15 kV and a measurement point interval of 0.2 μm, and the composition near the bonding surface of the electrode and ball bond was analyzed. The presence or absence of Region B was determined based on the presence or absence of a region where the Ni concentration was 1 mass % or more when the total concentration of Al, Cu, Pd, and Ni was taken as 100 mass %, and the total concentration and ratio C of Pd and Ni calculated for each measurement point in Region B were also determined. Ｐｄ / C Ｎｉ By arithmetically averaging the values ​​of each, the average value of the total concentration of Pd and Ni in region B and the ratio C Ｐｄ / C Ｎｉ The average value of the total concentration of Pd and Ni in region B and the ratio C Ｐｄ / C Ｎｉ The average value of the three measurement lines P １ , P２ and P ３ The arithmetic mean value of the obtained values ​​was adopted.

[0143] [Measurement of element content] The contents of the first additional element, the second additional element, and the third additional element in the wire were detected as the concentration of the elements contained in the entire wire by analyzing a solution obtained by dissolving the bonding wire in a strong acid using an ICP optical emission spectrometer and an ICP mass spectrometer. As the analyzer, an ICP-OES ("PS3520UVDDII" manufactured by Hitachi High-Tech Science Corporation) or an ICP-MS ("Agilent 7700x ICP-MS" manufactured by Agilent Technologies, Inc.) was used.

[0144] [Bonding Reliability of First Bonded Portion] The bonding reliability of the first bonded portion was evaluated by both a Highly Accelerated Temperature and Humidity Stress Test (HAST) and a High Temperature Storage Life Test (HTSL).

[0145] -HAST- A sample for testing the bond reliability of the first bond was prepared by ball-bonding a 1.5 μm-thick Al-1.0 wt% Si-0.5 wt% Cu alloy film formed on a silicon substrate mounted on a typical metal frame to an electrode using a commercially available wire bonder. The sample was then sealed with a commercially available thermosetting epoxy resin. The ball was formed under the conditions described in the "Fabrication Atomic Energy Spectroscopy (AES) Depth Analysis" section above. The prepared sample for bond reliability evaluation was exposed to a high-temperature, high-humidity environment of 130°C and 85% relative humidity using an unsaturated pressure cooker tester, and a 7 V bias was applied. The bond life of the first bond was determined by conducting a shear test on the ball bond every 48 hours, and the time until the shear strength value reached half of the initial shear strength. The shear strength value was the arithmetic mean value of measurements at 50 randomly selected ball bond locations. The shear test was performed after removing the resin using acid treatment to expose the ball bond. The evaluation was carried out according to the following criteria.

[0146] Evaluation criteria: ◎: Bonding life is 480 hours or more ○: Bonding life is 384 hours or more but less than 480 hours △: Bonding life is 288 hours or more but less than 384 hours ×: Bonding life is less than 288 hours

[0147] -HTSL- Samples for evaluating bonding reliability, prepared in the same manner as above, were exposed to an environment at a temperature of 175°C using a high-temperature incubator. The bonding life of the first bonding part was determined by conducting a shear test on the ball bonding part every 500 hours, and the time until the shear strength value became half of the initial shear strength was defined as the time. The shear strength value was the arithmetic mean value of measurements taken at 50 randomly selected points on the ball bonding part. The shear test after the high-temperature storage test was conducted after removing the resin by acid treatment to expose the ball bonding part. Evaluation was then performed according to the following criteria.

[0148] Evaluation criteria: ◎: Bonding life is 2000 hours or more ○: Bonding life is 1000 hours or more but less than 2000 hours ×: Bonding life is less than 1000 hours

[0149] [Bonding Reliability of Second Bonding Portion] The bonding reliability of the second bonding portion was evaluated by a high temperature storage life test (HTSL).

[0150] A sample was prepared for testing the bonding reliability of the second bond by wedge-bonding the lead portion of the lead frame using a commercially available wire bonder and sealing it with a commercially available thermosetting epoxy resin. The lead frame was an Fe-42 atomic % Ni alloy lead frame plated with 1 to 3 μm of Ni / Pd / Au. The prepared sample for evaluating bonding reliability was exposed to a 200°C environment using a high-temperature incubator. The bonding life of the second bond was determined by conducting a pull test on the wedge bond every 500 hours, and the time it took for the pull strength to reach half of the initial pull strength. The pull strength value was the arithmetic mean value of measurements taken at 50 randomly selected locations on the wedge bond. The pull test after the high-temperature storage test was performed after removing the resin by acid treatment to expose the wedge bond. Evaluation was then performed according to the following criteria.

[0151] Evaluation criteria: ◎: Bonding life is 2000 hours or more ○: Bonding life is 1000 hours or more but less than 2000 hours ×: Bonding life is less than 1000 hours

[0152]

[0111] The bondability of the second bond was evaluated by a second bond window test, in which the horizontal axis indicates the ultrasonic current during second bonding, with six levels ranging from 30 mA to 80 mA in 10 mA increments, and the vertical axis indicates the load during second bonding, with six levels ranging from 20 gf to 70 gf in 10 gf increments, to determine the number of conditions under which bonding was possible for a total of 36 second bonding conditions.

[0153]

[0154] In this test, 200 wires for each condition were bonded to the lead portion of a lead frame using a commercially available wire bonder for each of the examples and comparative examples. The lead frame was Ag-plated, and the stage temperature was 200°C, N ２ +5% H ２ Bonding was carried out under a gas flow of 0.5 L / min. The number of conditions under which continuous bonding was possible without problems such as non-adhesion or bonder stoppage was determined and evaluated according to the following criteria.

[0155] Evaluation criteria: ◎: 33 or more conditions ○: 30 to 32 conditions △: 26 to 29 conditions ×: 25 or less conditions

[0156] [Fab Shape] The fabrication sphere shape was evaluated by fabricating fabricated spheres on a lead frame using a commercially available wire bonder and observing them with a scanning electron microscope (SEM) (number of evaluations: N = 100). The fabricated spheres were fabricated under the conditions described in the above section [Fab Depth Analysis by Auger Electron Spectroscopy (AES)]. The fabricated sphere shape was evaluated as good, whereas eccentricity, irregular shape, or poor melting were evaluated as bad. The evaluation was performed according to the following criteria:

[0157] Evaluation criteria: ◎: 5 ​​or less defects ○: 6 to 10 defects (no practical problem) ×: 11 or more defects

[0158] [Measurement of Crystal Orientation in the Cross Section of the FAB] A commercially available wire bonder was used to form a FAB under the conditions described in the above section [Depth Analysis of the FAB by Auger Electron Spectroscopy (AES)], and the crystal orientation was measured using a cross section perpendicular to the FAB compression bonding direction as the measurement surface. In the present invention, the cross section perpendicular to the FAB compression bonding direction refers to the cross section exposed by cutting the FAB along the dotted line A-A shown in Figure 3, and the reference dotted line A-A was set at the position where the diameter of the exposed cross section was maximum. For the measurement, an EBSD method was used, and the proportion of the <100> crystal orientation was calculated using the analysis software provided with the device using the procedure described above. Three FABs were measured, and the arithmetic average of the obtained proportions was determined as the proportion of the <100> crystal orientation in the cross section of the FAB.

[0159] [Bonded Shape] The bonded shape of the first bonded portion (ball crushed shape) was evaluated using a commercially available wire bonder, forming a ball under the conditions described in the above section [FAB Depth Analysis by Auger Electron Spectroscopy (AES)], and bonding it to an electrode formed by depositing a 1.5 μm thick Al-1.0 mass% Si-0.5 mass% Cu alloy on a Si substrate, and observing it from directly above with an optical microscope (number of evaluations N = 100). The crushed shape of the ball was judged as good if it was close to a perfect circle, and as bad if it was oval or petal-like. Evaluation was then performed according to the following criteria.

[0160] Evaluation criteria: ◎: No defects ○: 1 to 3 defects (no practical problems) △: 4 to 5 defects (no practical problems) ×: 6 or more defects

[0161] [Chip Damage] Evaluation of chip damage was performed by forming a ball using a commercially available wire bonder under the conditions described in the above section [FAB Depth Analysis by Auger Electron Spectroscopy (AES)], crimping the ball to an electrode formed by depositing a 1.5 μm thick Al-1.0 mass % Si-0.5 mass % Cu alloy film on a Si substrate, dissolving the wire and electrode in a chemical solution to expose the Si substrate, and observing the Si substrate directly below the bonded portion with an optical microscope (evaluation number N=50). Evaluation was then performed according to the following criteria.

[0162] Evaluation criteria: ○: No cracks or bonding traces; △: No cracks, but bonding traces were found in some places (3 places or less); ×: Other than that

[0163] The evaluation results of the Examples and Comparative Examples are shown in Tables 2 and 3.

[0164]

[0165]

[0166] All wires of Example Nos. 1 to 19 have a coating layer that satisfies all of the specific conditions (1) to (3) of the present invention, and it was confirmed that they provide good bonding reliability of the first bonded portion even in high-temperature, high-humidity environments, as well as good bonding reliability of the second bonded portion even in high-temperature, high-humidity environments. Furthermore, it was confirmed that wires of Example Nos. 5 to 7, which contain Au on the surface, have particularly excellent initial bondability of the second bonded portion. Furthermore, it was confirmed that wires of Example Nos. 8, 11, 12, and 17 to 19, which contain a total of 1 ppm by mass or more of the first additional element, provide particularly good crimped shapes of the first bonded portion. It was confirmed that wires of Example Nos. 9 to 13, 18, and 19, which contain a total of 1 ppm by mass or more of the second additional element, provide particularly good bonding reliability of the first bonded portion even in high-temperature, high-humidity environments. Example Nos. 1 to 19, which contain a total of 0.011 mass% or more of the third additional element, provide particularly good bonding reliability of the first bonded portion even in high-temperature, high-humidity environments. It was confirmed that wires Nos. 14 to 19 provided particularly good bonding reliability of the first bonded portion in a high-temperature environment. On the other hand, it was confirmed that wires Nos. 1 to 4, which had coating layers that did not satisfy at least one of the specific conditions (1) to (3) of the present invention, had poor bonding reliability of at least one of the first bonded portion in a high-temperature, high-humidity environment and the second bonded portion in a high-temperature environment.

[0167] When a FAB was formed using a wire, the crystal orientation of the cross section of the FAB perpendicular to the bonding direction was measured. It was confirmed that a good crimped shape of the first bonded portion could be achieved when the proportion of the <100> crystal orientation, which has an angle difference of 15 degrees or less with respect to the bonding direction, was 30% or more (Examples 20, 21, and 23). In particular, it was confirmed that an exceptionally good crimped shape of the first bonded portion could be achieved when the proportion of the <100> crystal orientation was 50% or more (Example 23).

[0168] It was also confirmed that the wire-bonded structures produced using the wires of Examples 1 to 19 had a region B near the bonded surface between the electrode and the ball bond, where the Ni concentration was 1% by mass or more when the total concentration of Al, Cu, Pd, and Ni was 100% by mass. For example, for the wire-bonded structure produced using the wire of Example No. 6, the average Ni concentration in region B was 1.53% by mass. Furthermore, in region B, when the total concentration of Al, Cu, Pd, and Ni was 100% by mass, the average total concentration of Pd and Ni was 3.76% by mass, and the Pd concentration C Ｐｄ (mass%) and Ni concentration C Ｎｉ Ratio C (mass%) Ｐｄ / C Ｎｉ The average value was 1.45.

[0169] REFERENCE SIGNS LIST 1 Bonding wire (wire) 2 Measurement surface 10 FAB (ball) 10a First ball compression part 10b Second ball compression part 10t Tip apex of FAB 20 Ball bonding part 21 Bonding surface 50 Semiconductor chip 51 Al electrode D FAB diameter X Center of wire width W Wire width (wire diameter) w ａ Measurement surface width l ａ Length of measurement surface Z: Crimp bonding direction of FAB L: Wire axis of bonding wire W: ｂ Maximum width of the contact surface between the electrode and the ball P １ , P ２ , P ３ Measurement Line

Claims

1. A bonding wire for a semiconductor device, comprising a core material made of Cu or a Cu alloy and a coating layer containing a conductive metal other than Cu formed on a surface of the core material, The coating layer contains Ni and Pd, and the Ni concentration C Ｎｉ (mass%) and Pd concentration C Ｐｄ Ratio C (mass%) Ｎｉ / C Ｐｄ is 0.02 or more and 0.7 or less, In a concentration profile in the depth direction of the wire obtained by measurement using Auger electron spectroscopy (AES), when the thickness of the coating layer is d (nm), the position showing the maximum Ni concentration is within a range of a depth of 0.5d from the wire surface, and the maximum Ni concentration is 10 atomic % or more; A bonding wire for semiconductor device, wherein when a free air ball (FAB) is formed using the bonding wire, in a concentration profile in the depth direction from the tip surface of the FAB, in a region A having a depth from the tip surface of the FAB of 20 nm or more to 200 nm or less, the average Ni concentration is 0.3 atomic % or more when the total concentration of Cu, Pd, and Ni is 100 atomic %.

2. The bonding wire according to claim 1, wherein in region A, when the total concentration of Cu, Pd, and Ni is 100 atomic %, the average value of the total concentration of Pd and Ni is 2.0 atomic % or more.

3. In region A, the concentration of Pd is C Ｐｄ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｄ / C Ｎｉ The bonding wire according to claim 1 , wherein the average value of is 0.8 or more and 27.6 or less.

4. The bonding wire according to claim 1, wherein the coating layer has a region containing Pd as a main component on the core material side in the thickness direction of the coating layer, and has a region containing Ni and Pd within a range of a depth of 0.5d from the wire surface when the thickness of the coating layer is d (nm).

5. The bonding wire according to claim 1 , wherein the thickness d of the coating layer is 10 nm or more and 130 nm or less.

6. The bonding wire according to claim 1, wherein the concentration profile in the depth direction of the wire is obtained by measuring by AES under the following <conditions> while digging in the depth direction from the surface of the wire by Ar sputtering. <Conditions> The center of the wire width is positioned to be the center of the width of the measurement surface, and the width of the measurement surface is 5% to 15% of the wire diameter, and the length of the measurement surface is 5 times the width of the measurement surface.

7. The bonding wire according to claim 1, wherein the concentration profile in the depth direction from the surface of the tip of the FAB is obtained by measuring by Auger electron spectroscopy (AES) under the following <conditions> while digging in the depth direction from the surface of the tip of the FAB by Ar sputtering. <Conditions> When the diameter of the FAB is D, the distance between the center of the measurement surface and the apex of the tip of the FAB is within πD / 12, and the width and length of the measurement surface are 0.05D or more and 0.2D or less, respectively.

8. The bonding wire according to claim 1 , wherein the surface of the wire contains Au.

9. 9. The bonding wire according to claim 8, wherein the concentration of Au on the surface of the wire is 10 atomic % or more and 90 atomic % or less.

10. The bonding wire according to claim 9 , wherein the concentration of Au on the surface of the wire is measured by AES under the following conditions: <Conditions> The center of the wire width is positioned to be the center of the width of the measurement surface, and the width of the measurement surface is 5% to 15% of the wire diameter, and the length of the measurement surface is 5 times the width of the measurement surface.

11. 2. The bonding wire according to claim 1, wherein when a FAB is formed using the wire, a crystal orientation of a cross section of the FAB perpendicular to the bonding direction is measured, and the proportion of <100> crystal orientations having an angle difference of 15 degrees or less with respect to the bonding direction is 30% or more.

12. The bonding wire according to claim 1, comprising one or more elements (hereinafter referred to as "first additive elements") selected from the group consisting of B, P, and Mg, and a total concentration of the first additive element in the entire wire is 1 ppm by mass or more and 100 ppm by mass or less.

13. The bonding wire according to claim 1, further comprising one or more elements (hereinafter referred to as “second additive elements”) selected from the group consisting of Se, Te, As, and Sb, and a total concentration of the second additive elements relative to the entire wire is 1 ppm by mass or more and 100 ppm by mass or less.

14. The bonding wire according to claim 1, further comprising one or more elements (hereinafter referred to as “third additive elements”) selected from the group consisting of Ga, Ge, and In, and a total concentration of the third additive element with respect to the entire wire is 0.011% by mass or more and 1.5% by mass or less.

15. A semiconductor device comprising the bonding wire according to any one of claims 1 to 14.