Bonding wire

Abstract

The present invention provides a novel Cu bonding wire which yields a good free air ball (FAB) shape, and also yields good high-temperature and high-humidity reliability of a first junction part even in cases where post-curing accompanying sealing is performed in a short time at a low temperature. The Cu bonding wire is characterized in that: the Cu bonding wire includes a core material which is formed of Cu or a Cu alloy, and a coating layer which is formed on the surface of the core material and in which the total concentration of Pt and Ni is 90 at% or more; and in a concentration profile in the depth direction of the wire as obtained by measuring concentrations at 50 or more measurement points of the coating layer in the depth direction by Auger electron spectroscopy (AES), the thickness of the coating layer is 10 nm to 130 nm inclusive, the average value X, where X is the average value of the ratio CPt / CNi of the concentration CPt (at%) of Pt to the concentration CNi (at%) of Ni with respect to all the measurement points in the coating layer, is 0.3 to 20.0 inclusive, and the total number of measurement points at which the absolute deviation from the average value X is 0.3X or less in the coating layer is 50% or more with respect to the total number of measurement points in the coating layer.

Description

Bonding Wire

[0001] The present invention relates to a bonding wire, 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 an electrode on the semiconductor chip (hereinafter referred to as "ball bonding"). The second bonding involves crimping the wire portion to an external electrode by applying ultrasonic waves and a load to the wire portion (hereinafter referred to as "wedge bonding") without forming a ball. After the connection process, the semiconductor chip and bonding wire are encapsulated in a sealing resin material to obtain a semiconductor device.

[0003] Until now, gold (Au) has been the mainstream material for bonding wires, but copper (Cu) is increasingly being used, primarily for LSI applications (see, for example, Patent Documents 1 to 3). Cu has the disadvantage of being more easily oxidized than Au, and as a method of preventing surface oxidation of Cu bonding wires, a structure in which the surface of a Cu core material is coated with a metal such as Pd has been proposed (Patent Document 4). A Pd-coated Cu bonding wire has also 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, improving the bonding reliability of the first bond (Patent Document 5).

[0004] 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

[0005] In recent years, bonding wires are required to exhibit good bonding reliability in high-temperature and high-humidity environments.

[0006] When the bonding wire material is changed from Au to Cu, deterioration of the bonding reliability of the first bonded portion in a high-temperature, high-humidity environment (hereinafter also referred to as "high-temperature, high-humidity reliability of the first bonded portion") is likely to become a problem. In the bonding wire connection process, the first bond is performed by crimping a ball portion formed at the tip of the bonding wire to an Al electrode on a semiconductor chip. However, when a bonding wire made of Cu is used, an intermetallic compound of Cu and Al is formed at the bonded portion, and this intermetallic compound is prone to corrosion under high-temperature, high-humidity conditions. In addition, bonding wire made of Cu may have a poor FAB shape, which may result in an inferior crimped shape of the first bonded portion, and is therefore insufficient to support the narrow-pitch connections required for high-density packaging. Guidelines for addressing these issues have been presented, such as by adding elements to Cu wire or applying a Pd coating to Cu wire (e.g., Patent Documents 3 and 5).

[0007] As described above, in the manufacture of a semiconductor device, after the bonding wire connection process, the entire assembly, including the semiconductor chip and the bonding wires, is encapsulated with an encapsulating resin material. Examples of encapsulating methods include a method in which a solid encapsulating resin material is heated and melted, the molten resin is poured into a mold, and then pressure-molded and cured for encapsulation, and a method in which a liquid encapsulating resin material is used for encapsulation using a microsyringe or the like. After encapsulation, a post-cure is performed to promote the curing of the encapsulating resin material. However, when a liquid encapsulating resin material is used, the post-cure conditions tend to be lower temperature and shorter time than when a solid encapsulating resin material is used. Even when a solid encapsulating resin material is used, there is a trend toward lower temperature and shorter time for post-cure in order to improve productivity.

[0008] It has been found that when using a bonding wire made of Cu, if the post-cure conditions associated with sealing are low temperature and short time, deterioration of the high-temperature, high-humidity reliability of the first bonded portion is difficult to avoid, even by adding elements to the Cu wire or applying a Pd coating to the Cu wire. During the first bonding, ultrasonic vibration is applied to promote deformation of the ball portion, which introduces a large amount of strain into the bonded portion. When post-cure is performed at a relatively high temperature and for a long time, as in the case of using a solid sealing resin material, the strain in the bonded portion is released. However, when post-cure is performed at a low temperature and for a short time, as in the case of using a liquid sealing resin material, the strain remains in the bonded portion. When there is a large amount of residual strain, the corrosion reaction of the Cu and Al intermetallic compound is likely to progress, and it is presumed that previously reported methods such as adding elements to the Cu wire or applying a Pd coating to the Cu wire cannot suppress the deterioration of the high-temperature, high-humidity reliability of the first bonded portion.

[0009] The present invention provides a novel Cu bonding wire that not only provides a good FAB shape but also provides good high-temperature, high-humidity reliability of the first bonded portion even when post-curing associated with sealing is performed at a low temperature and in a short time.

[0010] 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.

[0011] That is, the present invention includes the following: <1> A bonding wire including a core material made of Cu or a Cu alloy and a coating layer formed on the surface of the core material, the coating layer having a total concentration of Pt and Ni of 90 atomic % or more, wherein a concentration profile in the depth direction of the wire obtained by Auger electron spectroscopy (AES) measurement at 50 or more measurement points in the coating layer in the depth direction shows that the thickness of the coating layer is 10 nm or more and 130 nm or less, and the Pt concentration C Ｐｔ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｔ / C ＮｉWhen the average value of the above is X, the average value X is 0.3 or more and 20.0 or less, and the total number of measurement points in the coating layer where the absolute deviation from the average value X is within 0.3X is 50% or more of the total number of measurement points in the coating layer. <2> For all measurement points in the coating layer, Ｐｔ or C ＮｉThe bonding wire according to <1>, wherein, when the line approximation is performed by the least squares method, the difference between the maximum and minimum values ​​of the approximate line within the depth range of the coating layer is 20 atomic % or less. <3> The bonding wire according to <1> or <2>, wherein the concentration profile in the depth direction of the wire is obtained by measuring by AES under the following <conditions> while digging down from the surface of the wire in the depth direction 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. <4> The bonding wire according to any of <1> to <3>, wherein the surface of the wire contains Au. <5> The bonding wire according to <4>, wherein the concentration of Au on the surface of the wire is 10 atomic % to 90 atomic %. <6> The bonding wire according to <5>, 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. <7> The bonding wire according to any one of <1> to <6>, which contains one or more elements selected from the group consisting of B, P, and Mg (hereinafter referred to as "first additional element"), and the total concentration of the first additional element with respect to the entire wire is 1 ppm by mass to 100 ppm by mass. <8> The bonding wire according to any one of <1> to <7>, which contains one or more elements selected from the group consisting of Se, Te, As, and Sb (hereinafter referred to as "second additional element"), and the total concentration of the second additional element with respect to the entire wire is 1 ppm by mass to 100 ppm by mass. <9> The bonding wire according to any one of <1> to <8>, containing one or more elements (hereinafter referred to as "third additional elements") selected from the group consisting of Ga and Ge, and a total concentration of the third additional elements relative to the entire wire is 0.011 mass% to 1.5 mass%. <10> The bonding wire according to any one of <1> to <8>, containing one or more elements (hereinafter referred to as "fourth additional elements") selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Ag, In, Sn, Ta, W, Os, Ir, Pd, Au, and Bi.<11> The bonding wire according to any one of <4> to <6>, wherein the total concentration of the fourth additive element relative to the entire wire is 5 ppm by mass or more and 450 ppm by mass or less. <12> The bonding wire according to any one of <1> to <6>, wherein the total concentration of the fourth additive element relative to the entire wire is 5 ppm by mass or more and 450 ppm by mass or less. <13> The bonding wire according to any one of <1> to <6>, wherein the total concentration of the fourth additive element relative to the entire wire is 5 ppm by mass or more and 450 ppm by mass or less.

[0012] According to the present invention, a novel Cu bonding wire can be provided that not only provides a good FAB shape but also provides good high-temperature, high-humidity reliability of the first bonded portion even when post-curing associated with sealing is performed at a low temperature and in a short time.

[0013] FIG. 1 is a schematic diagram for explaining the position and dimensions of a measurement surface when performing composition analysis by AES.

[0014] 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 and their equivalents.

[0015] [Bonding Wire] The bonding wire of the present invention (hereinafter simply referred to as "the wire of the present invention" or "wire") includes a core material made of Cu or a Cu alloy, and a coating layer formed on the surface of the core material, in which the total concentration of Pt and Ni is 90 atomic % or more, and in a concentration profile in the depth direction of the wire obtained by Auger electron spectroscopy (AES) measurement at 50 or more measurement points in the coating layer in the depth direction, the thickness of the coating layer is 10 nm or more and 130 nm or less, and the Pt concentration C Ｐｔ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio CＰｔ / C Ｎｉ When the average value of the above is defined as X, the average value X is 0.3 or more and 20.0 or less, and the total number of measurement points in the coating layer whose absolute deviation from the average value X is within 0.3X is 50% or more of the total number of measurement points in the coating layer.

[0016] As mentioned above, in the manufacture of semiconductor devices, after the bonding wire connection process, the entire device, including the semiconductor chip and bonding wires, is encapsulated with an encapsulating resin material. Examples of encapsulation methods include a method in which a solid encapsulating resin material is heated and melted, the molten resin is poured into a mold, and then pressure-molded and cured for encapsulation, and a method in which a liquid encapsulating resin material is used for encapsulation using a microsyringe or the like. After encapsulation, a post-cure is performed to accelerate the curing of the encapsulating resin material. However, when a liquid encapsulating resin material is used, the post-cure conditions tend to be lower temperature and shorter time than when a solid encapsulating resin material is used (the post-cure conditions when a solid encapsulating resin material is used are typically 170°C or higher for 4 hours or more, whereas the post-cure conditions when a liquid encapsulating resin material is used are typically 100-150°C for 3 hours or less). Even when a solid encapsulating resin material is used, there is a trend toward lower temperature and shorter time for encapsulation in order to improve productivity.

[0017] In this regard, it has been found that when using a bonding wire made of Cu, if the post-cure conditions associated with sealing are low temperature and short time, deterioration of the high-temperature, high-humidity reliability of the first bonded portion is difficult to avoid, even by adding elements to the Cu wire or applying a Pd coating to the Cu wire. During the first bonding, ultrasonic vibration is applied to promote deformation of the ball portion, which introduces a large amount of strain into the bonded portion. When post-cure is performed at a relatively high temperature and for a long time, as in the case of using a solid sealing resin material, the strain in the bonded portion is released. However, when post-cure is performed at a low temperature and for a short time, as in the case of using a liquid sealing resin material, the strain remains in the bonded portion. When there is a large amount of residual strain, the corrosion reaction of the Cu and Al intermetallic compound is likely to progress, and it is presumed that the previously reported methods, such as adding elements to the Cu wire or applying a Pd coating to the Cu wire, cannot suppress the deterioration of the high-temperature, high-humidity reliability of the first bonded portion. Furthermore, as mentioned above, bonding wires made of Cu may have poor fabrication bond shapes, which in turn may result in poor crimping shapes at the first bonding portion, and are not adequate for the narrow-pitch connections required for high-density mounting.

[0018] In contrast, a wire comprising a core material made of Cu or a Cu alloy and a coating layer formed on the surface of the core material in which the total concentration of Pt and Ni is 90 atomic % or more, and in a concentration profile in the depth direction of the wire obtained by AES measurement at 50 or more measurement points in the coating layer, the thickness of the coating layer is 10 nm or more and 130 nm or less, and the Pt concentration C Ｐｔ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｔ / C Ｎｉ The inventors have found that a bonding wire in which, when the average value of X is 0.3 or more and 20.0 or less, and the total number of measurement points in the coating layer whose absolute deviation from the average value X is within 0.3X is 50% or more of the total number of measurement points in the coating layer, results in a good FAB shape and also results in good high-temperature, high-humidity reliability of the first bonded portion even when post-cure associated with sealing is performed at a low temperature and in a short time.

[0019] The reason why the bonding wire of the present invention having the above configuration can provide good high-temperature, high-humidity reliability of the first bonded portion is presumed to be as follows: When a ball is formed using the bonding wire of the present invention, a concentrated layer with a higher concentration of Pt and Ni than the interior is formed on the outer periphery of the ball, and Pt and Ni are concentrated at the bonded interface between the ball portion of the wire and the Al electrode during the first bond. It is presumed that when such a bonded portion is exposed to a high-temperature, high-humidity environment, Ni forms a stable oxide film on the surface of the Cu and Al intermetallic compound, thereby suppressing the progression of corrosion. Here, it has been confirmed that the presence of Pt at a predetermined concentration together with Ni is important for providing good high-temperature, high-humidity reliability of the first bonded portion. This is thought to be because Pt acts as a catalyst and promotes the formation of a stable oxide film by Ni.

[0020] Here, even when Pt is present together with Ni at a predetermined concentration, it may result in a poor FAB shape, and ultimately in an inferior crimped shape of the first joint. However, it has been found that the bonding wire of the present invention, in which Pt is present together with Ni at a predetermined distribution, can result in a good FAB shape, and ultimately in a good crimped shape of the first joint, and can be suitably adapted to the narrow pitch connections required for high-density mounting.

[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 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, 99.95 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, the third additional element, and the fourth 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, the third additional element, and the fourth additional element described below, and inevitable impurities. The Cu core material may contain elements that constitute the coating layer described below.

[0026] <Coating Layer> The wire of the present invention includes a coating layer (hereinafter simply referred to as "coating layer") formed on the surface of a Cu core material, the coating layer having a total concentration of Pt and Ni of 90 atomic % or more.

[0027] In order to obtain a good FAB shape and to obtain good high-temperature, high-humidity reliability of the first bonded portion even when post-curing associated with sealing is performed at a low temperature and in a short time, it is important that the coating layer of the wire of the present invention satisfies all of the following conditions (1) to (3) in the concentration profile in the depth direction of the wire obtained by AES measurement so that the number of measurement points in the depth direction is 50 or more in the coating layer (hereinafter simply referred to as the "concentration profile in the depth direction of the wire"). (1) The thickness of the coating layer is 10 nm or more and 130 nm or less. (2) The concentration C of Pt at all measurement points in the coating layer is Ｐｔ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｔ / C Ｎｉ (3) The total number of measurement points in the coating layer whose absolute deviation from the average value X is within 0.3X is 50% or more of the total number of measurement points in the coating layer.

[0028] In the present invention, when obtaining a concentration profile in the depth direction of the wire by AES, the measurement is performed so that the number of measurement points in the depth direction is 50 or more in the coating layer. Generally, depth analysis by AES can be performed at measurement intervals on the sub-nano order, so it is relatively easy to achieve 50 or more measurement points in relation to the thickness of the coating layer targeted by the present invention. If the number of measurement points is less than 50 as a result of the measurement, the measurement is performed again by reducing the sputtering rate or shortening the sputtering time, etc., so that the number of measurement points is 50 or more. This allows AES to measure 50 or more depth points in the coating layer, thereby obtaining a concentration profile in the depth direction of the wire. Although it depends on the thickness of the coating layer, it is more preferable to determine the AES measurement point interval so that the total number of measurement points in the coating layer is 70 (more preferably 100). Therefore, in a preferred embodiment, the coating layer of the wire of the present invention satisfies all of the above conditions (1) to (3) in the concentration profile in the depth direction of the wire obtained by measuring the coating layer by AES at 50 or more measurement points in the depth direction.

[0029] Condition (1) Condition (1) relates to the thickness of the coating layer. By including a coating layer that satisfies condition (1) in combination with conditions (2) and (3), the wire of the present invention can achieve good high-temperature, high-humidity reliability of the first bonded portion, even when post-curing associated with sealing is performed at a low temperature and in a short time, and can also achieve a good FAB shape and, ultimately, a good crimped shape of the first bonded portion.

[0030] Regarding condition (1), the thickness of the coating layer (a calculation method based on the concentration profile in the depth direction of the wire will be described later) is 10 nm or more, preferably 12 nm or more, 14 nm or more, 15 nm or more, 16 nm or more, 18 nm or more, or 20 nm or more, more preferably 25 nm or more, 30 nm or more, 40 nm or more, or 50 nm or more, and even more preferably 60 nm or more, 70 nm or more, 80 nm or more, or 90 nm or more, from the viewpoint of realizing good high-temperature, high-humidity reliability of the first bonded portion. If the thickness of the coating layer is less than 10 nm, the high-temperature, high-humidity reliability of the first bonded portion tends to deteriorate when post-cure associated with sealing is performed at a low temperature and in a short time, and the bond reliability of the first bonded portion in a high-temperature environment (hereinafter also referred to as "high-temperature reliability of the first bonded portion") tends to deteriorate. The upper limit of the thickness of the coating layer is 130 nm or less, preferably 125 nm or less, 120 nm or less, 115 nm or less, or 110 nm or less, from the viewpoint of realizing good high-temperature / high-humidity reliability of the first bonded portion and a good FAB shape. If the thickness of the coating layer exceeds 130 nm, deformation or poor melting may occur during FAB formation, deteriorating the FAB shape and the compression shape of the first bonded portion.

[0031] Condition (2) Condition (2) is the Pt concentration C Ｐｔ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｔ / C Ｎｉ By including a coating layer that satisfies condition (2) in addition to conditions (1) and (3), the wire of the present invention can achieve good high-temperature, high-humidity reliability of the first bonded portion even when post-curing associated with sealing is performed at a low temperature for a short time.

[0032] Regarding the condition (2), from the viewpoint of realizing good high-temperature and high-humidity reliability of the first bonded portion, the average value X is 20.0 or less, preferably 18.0 or less, more preferably 16.0 or less, 15.0 or less, 14.0 or less, 12.0 or less, or 10.0 or less, and further preferably 8.0 or less, 6.0 or less, 5.0 or less, 4.0 or less, 3.0 or less, or less than 3.0. Ｐｔ / C ＮｉIf X is more than 20.0, the high-temperature, high-humidity reliability of the first bonded portion tends to deteriorate when post-cure associated with sealing is performed at a low temperature for a short time. Furthermore, from the viewpoint of realizing good high-temperature, high-humidity reliability of the first bonded portion, the lower limit of the average value X is 0.3 or more, and preferably 0.4 or more, 0.5 or more, 0.6 or more, 0.8 or more, 1.0 or more, or more than 1.0. If X is less than 0.3, the high-temperature, high-humidity reliability of the first bonded portion tends to deteriorate when post-cure associated with sealing is performed at a low temperature for a short time.

[0033] Condition (3) Condition (3) relates to the total number of measurement points in the coating layer having an absolute deviation of 0.3X or less from the average value X being 50% or more of the total number of measurement points in the coating layer. By including a coating layer that satisfies condition (3) in combination with conditions (1) and (2), the wire of the present invention can achieve good high-temperature, high-humidity reliability of the first bonded portion, as well as a good FAB shape, and ultimately a good crimped shape of the first bonded portion, even when post-cure associated with sealing is performed at a low temperature and in a short time.

[0034] Condition (3), together with condition (2), indicates that the coating layer contains a PtNi alloy containing Pt and Ni in a predetermined ratio in a high concentration in the thickness direction of the coating layer while suppressing fluctuations in the Pt / Ni ratio. Even when post-cure associated with sealing is performed at a low temperature and in a short time, from the viewpoint of realizing good high-temperature and high-humidity reliability of the first bonded portion and realizing an even better FAB shape, the total number of measurement points in the coating layer whose absolute deviation from the average value X is within a predetermined range (the preferred range is as described above) is preferably 55% or more or 60% or more, more preferably 65% ​​or more, 70% or more or 75% or more, and even more preferably 80% or more, of the total number of measurement points in the coating layer.

[0035] In order to realize a good high-temperature, high-humidity reliability of the first bonded portion and, in particular, to realize a good FAB shape, the concentration profile in the wire depth direction is set to the Pt concentration C Ｐｔ (atomic %) or Ni concentration C ＮｉWhen the average value X is less than 1, the difference between the maximum and minimum values ​​of the approximate line in the depth (thickness) range of the coating layer is preferably 20 atomic % or less, more preferably 18 atomic % or less, 16 atomic % or less, or 15 atomic % or less, and even more preferably 14 atomic % or less, 12 atomic % or less, 10 atomic % or less, 8 atomic % or less, 6 atomic % or less, or 5 atomic % or less. Ｎｉ When the average value X of the coating layer is 1 or more, it is preferable that the difference between the maximum and minimum values ​​of the approximate line in the depth range of the coating layer is within the above range when the average value X of the coating layer is 1 or more. Ｐｔ When the atomic percentage (atomic %) is linearly approximated by the least squares method, it is preferable that the difference between the maximum and minimum values ​​of the approximate line within the depth range of the coating layer is within the above range.

[0036] The thickness of the coating layer under condition (1), the average value X and absolute deviation from the average value X under conditions (2) and (3), the total number of measurement points where the absolute deviation falls within a predetermined range, and the ratio of the total number of measurement points where the absolute deviation falls within a predetermined range to the total number of measurement points of the coating layer can be confirmed and determined by performing composition analysis using AES while digging from the surface of the wire in the depth direction (toward the center of the wire) using Ar sputtering. In detail, 1) after performing composition analysis of the wire surface, 2) sputtering with Ar and 3) composition analysis of the surface after sputtering are repeated to obtain concentration changes of each element in the depth direction (center) from the surface of the wire (so-called depth concentration profile), and confirmation and determination can be made based on this concentration profile. In the present invention, when obtaining the depth concentration profile, the unit of depth is SiO ２ It was converted.

[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] 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 The relationship of (a) and (b) is satisfied. By determining the position and dimensions of the measurement surface as described above, a good FAB shape can be obtained, and even when post-cure associated with sealing is performed at a low temperature and in a short time, it is possible to accurately measure the success or failure of conditions (1) to (3), which are suitable for realizing good high-temperature, high-humidity reliability of the first bonded joint. In addition, it is preferable to measure multiple points (n≧3) of the measurement surface spaced 1 mm or more apart in the wire axial direction and use the arithmetic average value.

[0039] The thickness of the coating layer under the above condition (1), the average value X and the absolute deviation from the average value X under the conditions (2) and (3), the total number of measurement points where the absolute deviation falls within a predetermined range, and the proportion of the total number of measurement points where the absolute deviation falls within a predetermined range to the total number of measurement points of the coating layer 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.

[0040] The trend of the concentration profile in the depth direction obtained for the wire of the present invention according to one embodiment will be described below. From the surface of the wire to a certain depth position, Pt and Ni tend to coexist at a high concentration in a constant ratio, i.e., there is a region (coating layer) where the total concentration of Pt and Ni is 90 atomic % or more, and the Pt concentration C Ｐｔ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｔ / C Ｎｉ When the average value of the Pt concentration C is taken as X, there tends to be a certain number of measurement points whose absolute deviation from the average value X is within 0.3X. Further in the depth direction, the concentrations of Pt and Ni tend to decrease and the concentration of Cu tends to increase. In such a concentration profile in the depth direction, the Pt concentration C Ｐｔ (atomic %) and Ni concentration C Ｎｉ Focusing on the ratio C (atomic %), the thickness of the coating layer and the total number of measurement points of the coating layer can be calculated from the thickness of the region where the total concentration of Pt and Ni is 90 atomic % or more and the total number of measurement points. Ｐｔ / C Ｎｉ The average value X can be determined by arithmetically averaging the values, and the total number of measurement points whose absolute deviation from the average value X is within 0.3X can be determined by checking the absolute deviation from the average value X for all measurement points on the coating layer. As will be described later, when Au is further contained on the surface of the wire, the concentration profile in the depth direction tends to show a decrease in the Au concentration and an increase in the concentrations of Pt and Ni from the surface of the wire to a very shallow position. In such a case, the concentration C of Pt Ｐｔ (atomic %) and Ni concentration C ＮｉFocusing on the ratio (atomic %), the thickness of the coating layer and the total number of measurement points of the coating layer can be calculated from the thickness of the region where the total is 90 atomic % or more and the total number of measurement points. Ｐｔ / C Ｎｉ The average value X can be obtained by arithmetically averaging the values, and the total number of measurement points whose absolute deviation from the average value X is within 0.3X can be obtained by checking the absolute deviation from the average value X for all measurement points on the coating layer.

[0041] Other Preferred Conditions for the Coating Layer In the wire of the present invention, the coating layer more preferably satisfies one or both of the following conditions (4) and (5) based on the concentration profile in the depth direction of the wire, in addition to satisfying all of the above conditions (1) to (3): (4) The Pt concentration C at all measurement points in the coating layer Ｐｔ The average value of (atomic %) is X Ｐｔ When the average value X of the coating layer is Ｐｔ Absolute deviation from 0.1X Ｐｔ The total number of measurement points within the range is 50% or more of the total number of measurement points in the coating layer. (5) Ni concentration C for all measurement points in the coating layer Ｎｉ The average value of (atomic %) is X Ｎｉ When the average value X of the coating layer is Ｎｉ Absolute deviation from 0.1X Ｎｉ The total number of measurement points within the range is 50% or more of the total number of measurement points of the coating layer.In conditions (4) and (5), the coating layer, its thickness, and the total number of measurement points are as described above in connection with conditions (1) to (3).When the wire of the present invention includes a coating layer that satisfies one or both of conditions (4) and (5) in addition to conditions (1) to (3), it is possible to achieve particularly good high-temperature, high-humidity reliability of the first bonded portion and particularly good FAB shape, even when post-cure associated with sealing is performed at a low temperature and in a short time.

[0042] The coating layer may contain, for example, one or more dopants selected from the first additional element, the second additional element, the third additional element, and the fourth additional element described below. The preferred contents of these dopants are as described below.

[0043] The wire of the present invention may further contain Au on its surface, which can further improve the bondability at the second bonded portion.

[0044] 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.

[0045] In the present invention, the concentration of Au on the surface can be determined by performing composition analysis of the wire surface by Auger electron spectroscopy (AES) using the wire surface as the measurement surface, ignoring gas components such as carbon (C), sulfur (S), oxygen (O), and nitrogen (N), and nonmetallic elements.

[0046] 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.

[0047] The wire is positioned so that the center of the width of the wire 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 accurately measured, which is suitable for further improving the bondability at the second bond. In addition, it is preferable to perform measurements on multiple locations (n≧3) of measurement surfaces spaced 1 mm or more apart from each other in the wire axis direction and use the arithmetic average value.

[0048] 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.

[0049] When Au is contained on the surface of the wire, the position showing the maximum Au concentration in the concentration profile in the depth direction of the wire is closer to the surface of the wire than the positions showing the maximum Pt concentration and the maximum Ni concentration.

[0050] In the wire of the present invention, the boundary between the Cu core material and the coating layer is determined based on the total concentration of Pt and Ni in the concentration profile in the depth direction of the wire. The position where the total concentration of Pt and Ni is 90 atomic % is determined as the boundary, and the region where the total concentration of Pt and Ni is less than 90 atomic % is the Cu core material, and the region where the total concentration of Pt and Ni is 90 atomic % or more 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. The thickness of the coating layer can be determined by checking the concentration profile from the wire surface toward the wire center, and is the distance from depth position Z1 where the total concentration of Pt and Ni first reaches 90 atomic % to depth position Z2 where the total concentration of Pt and Ni first drops below 90 atomic % (where Z2 > Z1).

[0051] The wire of the present invention is characterized by including a coating layer that satisfies the above conditions (1) to (3). The average value X and absolute deviation from the average value X, the total number of measurement points where the absolute deviation is within a predetermined range, and the ratio of the total number of measurement points where the absolute deviation is within a predetermined range to the total number of measurement points of the coating layer are determined by the above boundary determination method, and the Pt concentration C Ｐｔ (atomic %) and Ni concentration C Ｎｉ The content is determined by taking into consideration the atomic percentage.

[0052] In one embodiment, the coating layer is composed of Pt and Ni; and inevitable impurities. In another embodiment, the coating layer is composed of Pt and Ni; and one or more elements selected from Au, the first additional element, the second additional element, the third additional element, and the fourth additional element described below; and inevitable impurities. The coating layer may contain the elements that constitute the Cu core material described above.

[0053] 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.

[0054] 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.

[0055] 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 further 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 a 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.

[0056] 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.

[0057] The wire of the present invention may further contain one or more elements ("third additional elements") selected from the group consisting of Ga and Ge. When the wire of the present invention contains the third additional element, the total concentration of the third additional element in the entire wire is preferably 0.011 mass% or more. This can improve the high-temperature reliability of the first bonded portion. The total concentration of the third additional element in 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.

[0058] 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 may be contained 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.

[0059] The wire of the present invention may further contain one or more elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Ag, In, Sn, Ta, W, Os, Ir, Pd, Au, and Bi (hereinafter referred to as "fourth additional element"). When the wire of the present invention contains the fourth additional element, the total concentration of the fourth additional element in the entire wire is preferably 5 ppm by mass or more. This can suppress peeling of the coating layer and breakage during wiredrawing. This is presumably because the inclusion of a predetermined concentration of the fourth additional element improves adhesion between the coating layer and the Cu core material by diffusing and segregating at the interface between the coating layer and the Cu core material during wiredrawing and heat treatment after the formation of the coating layer (PtNi alloy layer).

[0060] From the viewpoint of suppressing wire breakage during wire drawing, the total concentration of the fourth additional element in the entire wire is preferably 5 ppm by mass or more, more preferably 10 ppm by mass or more, 15 ppm by mass or more, 20 ppm by mass or more, or 25 ppm by mass or more, and even more preferably 30 ppm by mass or more, 40 ppm by mass or more, 50 ppm by mass or more, 60 ppm by mass or more, 80 ppm by mass or more, or 100 ppm by mass or more.

[0061] From the viewpoint of suppressing wire breakage during wiredrawing, the total concentration of the fourth additional element in the entire wire is preferably 450 ppm by mass or less, and may be 440 ppm by mass or less, 420 ppm by mass or less, 400 ppm by mass or less, etc. Therefore, in a preferred embodiment, the wire of the present invention contains a fourth additional element, and the total concentration of the fourth additional element in the entire wire is 5 ppm by mass or more and 450 ppm by mass or less. Note that when the fourth additional element includes one or more elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, and Zn (hereinafter also referred to as "fourtha additional element"), the upper limit of the total concentration of the fourtha additional element may be 200 ppm by mass or less, 180 ppm by mass or less, 160 ppm by mass or less, or 150 ppm by mass or less, etc. When the fourth additional element includes one or more elements selected from the group consisting of Zr, Nb, Mo, Ru, Rh, Ag, In, and Sn (hereinafter also referred to as "fourth b additional element"), the upper limit of the total concentration of the fourth b additional element may be 350 ppm by mass or less, 340 ppm by mass or less, 320 ppm by mass or less, or 300 ppm by mass or less.

[0062] As described above, the wire of the present invention may contain Au on its surface. When the wire of the present invention contains Au on its surface, the concentration of Au as the fourth additional element is the concentration in the core portion obtained by exposing the cross section of the wire and measuring the Cu core portion using an electron probe microanalyzer (EPMA) or secondary ion mass spectrometry (SIMS). In other words, when the wire of the present invention further contains Au on its surface, the "total concentration of the fourth additional element in the entire wire" is read as the "total concentration of the fourth additional element in the entire wire (however, the concentration of Au is the concentration in the core portion)."

[0063] When the wire of the present invention contains a fourth additional element, the fourth additional element may be contained in either the Cu core material or the coating layer, or may be contained in both. From the viewpoint of further suppressing wire breakage during wire drawing, it is preferable that the fourth additional element be contained in the Cu core material.

[0064] The contents of the first additional element, the second additional element, the third additional element, and the fourth additional element in the wire can be measured by the method described later in [Measurement of element contents].

[0065] In the wire of the present invention, the total concentration of Cu, Ni, and Pt may be, for example, 98.5 mass % or more, 98.6 mass % or more, 98.7 mass % or more, or 98.8 mass % or more.

[0066] 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.

[0067] The bonding wire of the present invention can provide good high-temperature, high-humidity reliability of the first bonded portion even when post-curing associated with sealing is performed at a low temperature and in a short time, and can also provide a good FAB shape and ultimately a good crimped shape of the first bonded portion. Therefore, the bonding wire of the present invention can be suitably used to connect electrodes on a semiconductor chip to external terminals such as electrodes on a lead frame or substrate in the manufacture of semiconductor devices.

[0068] <Method for Manufacturing Wire> An example of a method for manufacturing the bonding wire of the present invention will be described.

[0069] 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.

[0070] When dopants such as the first, second, third, and fourth additional 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 the 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 Pt 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.

[0071] 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.

[0072] 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. The coating layer may also be applied at the stage of a large-diameter ingot, or may be formed on the surface of the Cu core material after the intermediate wire is drawn to be 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 PtNi alloy layer containing Pt and Ni in a predetermined ratio on the surface of the Cu core material. From the viewpoint of forming a coating layer with excellent adhesion to the Cu core material, the coating layer may also be formed by providing a PtNi alloy layer containing Pt and Ni in a predetermined ratio on the surface of the Cu core material after strike plating a conductive metal. Furthermore, after forming a PtNi alloy layer containing Pt and Ni in a predetermined ratio, a layer containing at least one of Pt and Ni (for example, a Pt layer, a Ni layer, or a PtNi alloy layer) may be further provided.

[0073] When forming a wire containing Au on the surface, it can be formed by providing an Au layer on the surface of the coating layer using the same method as described above.

[0074] The wiredrawing process can be performed using a continuous wiredrawing device that can accommodate multiple diamond-coated dies. Heat treatment can be performed during the wiredrawing process, if necessary. When forming a wire containing Au on its surface, heat treatment can be used to diffuse the constituent elements between the Au layer on the wire surface and the underlying PtNi alloy layer (or Pt, Ni, or PtNi alloy layer, if present), thereby forming an Au-containing region (e.g., an alloy region containing Au, Pt, and Ni) on the wire surface so that the Au concentration on the wire surface falls within the 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, as this allows for reliable control of the alloy composition and thickness. Instead of forming an Au-containing region by heat treatment after providing an Au layer on the surface of the coating layer, a method of initially depositing an alloy region containing Au and one or more of Pt and Ni may also be used.

[0075] [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 of the present invention.

[0076] 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, and the bonding wire is the wire of the present invention.

[0077] 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.

[0078] 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.).

[0079] The present invention will be specifically described below with reference to examples, although the present invention is not limited to the examples shown below.

[0080] (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, third additional element, and fourth 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.

[0081] 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 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 the diameter of the wire to the diameter required for coating. 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 PtNi alloy layer containing Pt and Ni in a predetermined ratio to cover the entire surface of the Cu alloy core. Furthermore, some wires (Examples Nos. 3, 7, 8, 15, 16, 47, and 48) had an Au layer on the PtNi alloy layer. The PtNi alloy layer and Au layer were formed using electroplating. Commercially available plating solutions were prepared as Pt-Ni plating solutions and Au plating solutions, and were prepared as appropriate.

[0082] Thereafter, further wire drawing and other processes were carried out to process the wire into a final diameter of 18 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 Alternatively, the refining heat treatment was performed under a flow of Ar gas. The heat treatment temperature for the refining heat treatment was 200 to 600°C, the wire feed speed was 20 to 200 m / min, and the heat treatment time was 0.2 to 1.0 seconds. When the coating layer was thin, the heat treatment temperature was lowered and the wire feed speed was set to a higher value, and when the coating layer was thick, the heat treatment temperature was increased and the wire feed speed was set to a lower value.

[0083] (Test and Evaluation Methods) Test and evaluation methods will be described below.

[0084] [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.

[0085] [Coating layer thickness analysis by Auger electron spectroscopy (AES)] Depth analysis by AES was used for the thickness analysis of the coating layer. Depth analysis by AES involves alternately performing composition analysis and sputtering to analyze changes in composition in the depth direction, and can obtain concentration changes of each element in the depth (center) direction from the wire surface (so-called depth direction concentration profile). Specifically, 1) composition analysis of the wire surface was performed by 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 with Ar. ＋ The analysis was performed using ions and an acceleration voltage of 2 kV. In the surface composition analysis of 1) and 3), the dimensions of the measurement surface and the conditions for the AES composition analysis were the same as those described in the above section [Composition Analysis of Wire Surface by Auger Electron Spectroscopy (AES)]. When obtaining a concentration profile in the depth direction using AES, the measurement points in the depth direction were measured so that there were 50 or more points in the coating layer. The concentration profile in the depth direction was obtained for three measurement surfaces spaced 1 mm or more apart from each other in the wire axial direction.

[0086] - Thickness of the coating layer and the total number of measurement points of the coating layer - In the acquired concentration profile in the depth direction, the concentration profile from the wire surface to the wire center side was confirmed, and the Pt concentration C Ｐｔ (atomic %) and Ni concentration C Ｎｉ From the depth position Z1 where the total of (atomic %) reaches 90 atomic % for the first time, C Ｐｔ and C Ｎｉ The distance to depth position Z2 (where Z2 > Z1) where the sum of the values ​​of the SiO 2 and the SiO 3 values ​​first fell below 90 atomic % was determined as the thickness of the measured coating layer. The total number of measurement points from depth position Z1 to depth position Z2 was determined as the total number of measurement points of the coating layer. The thickness of the coating layer was determined by the arithmetic mean value of the values ​​obtained for the three measurement surfaces. It was also confirmed that the total number of measurement points of the coating layer for the wires of the examples was between 50 and 100. The depth measured by AES analysis was determined as the product of the sputtering rate and time. Generally, the sputtering rate is determined by the SiO 2 value obtained from the standard sample. 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.

[0087] - The total number of measurement points where the average value X and the absolute deviation from the average value X are within a predetermined range - The concentration C of Pt at all measurement points of the coating layer in the acquired concentration profile in the depth direction Ｐｔ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｔ / C Ｎｉ The average value X was calculated by arithmetically averaging the values ​​of the coating layer. Ｐｔ / C Ｎｉ The absolute deviation from the average value X was calculated for each of the three measurement surfaces, and the total number of measurement points whose absolute deviation from the average value X was within 0.3X was determined. The average value X was the arithmetic mean value of the values ​​obtained for the three measurement surfaces.

[0088] -C Ｐｔ or C Ｎｉ The slope of the approximate line (the difference between the maximum and minimum values ​​in the depth range of the coating layer) - C for all measurement points of the coating layer Ｐｔ(atomic %) or C Ｎｉ The average value X (atomic %) was linearly approximated by the least squares method, and the difference (atomic %) between the maximum and minimum values ​​of the approximated line in the depth range of the coating layer was calculated. Ｎｉ (atomic %) is linearly approximated by the least squares method, and if the average value X is 1 or more, C Ｐｔ The difference (atomic %) between the maximum and minimum values ​​of the approximate line within the depth range of the coating layer was calculated by arithmetic average of the values ​​obtained for the three measurement surfaces.

[0089] [Measurement of element content] The contents of the first additional element, the second additional element, the third additional element, and the fourth additional element in the wire were determined by analyzing a solution obtained by dissolving the bonding wire in strong acid using an ICP optical emission spectrometer and an ICP mass spectrometer, and were detected as the concentration of the elements contained in the entire wire. As the analytical device, 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. Note that for wires further containing Au on their surface, the concentration of Au as the fourth additional element was determined by exposing the cross section of the wire and measuring the Cu core portion using EPMA or SIMS.

[0090] [Fab Shape] The fabrication bonder (FAB) was fabricated on a lead frame using a commercially available wire bonder and observed with a scanning electron microscope (SEM) (number of evaluations: N=100). The fabrication current was set to 30-75 mA, the EFO gap was set to 762 μm, and the tail length was set to 254 μm. ２ +5% H ２ The gas was flowed at a rate of 0.4 to 0.6 L / min, and the diameter was set to 1.5 to 1.9 times the wire diameter. The FAB shape was judged as good if it was perfectly spherical, and poor if it was eccentric, irregular, or had poor melting properties. Evaluation was based on the following criteria:

[0091] Evaluation criteria: ◎: 5 ​​or less defects ○: 6 to 10 defects (no practical problem) ×: 11 or more defects

[0092] [High Temperature and Humidity Reliability of First Bonded Portion] The high temperature and humidity reliability of the first bonded portion was evaluated by a Highly Accelerated Temperature and Humidity Stress Test (HAST).

[0093] Specifically, a sample was ball-bonded to an electrode formed by depositing a 1.5 μm-thick film of an Al-1.0 wt % Si-0.5 wt % Cu alloy on a silicon substrate mounted on a typical metal frame using a commercially available wire bonder. The sample was then sealed with a commercially available liquid sealing resin material and post-cured at 100°C for 1 hour, followed by 150°C for 3 hours to prepare a sample for reliability testing of the first bond. The ball was formed under the conditions described in the [FAB Shape] section above. The prepared sample for reliability testing of the first bond was exposed to a high-temperature, high-humidity environment of 130°C and 85% relative humidity using an unsaturated pressure cooker tester, and a 3V 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 became half of the initial shear strength. The shear strength value was the arithmetic average of measurements taken at 50 randomly selected ball bond locations. The shear test was carried out after removing the resin by acid treatment to expose the ball joint, and evaluation was made according to the following criteria.

[0094] Evaluation criteria: ◎: Bonding life is 192 hours or more ○: Bonding life is 96 hours or more but less than 192 hours ×: Bonding life is less than 96 hours

[0095] [Bonded Shape] The bonded shape of the first bonded portion (the crushed shape of the ball) was evaluated by forming a ball using a commercially available wire bonder under the conditions described in the [FAB Shape] section above, crimping it 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 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 poor if it was oval or petal-like. Evaluation was then performed according to the following criteria.

[0096] Evaluation criteria: ◎: 1 or less defects ○: 2 to 5 defects (no practical problems) ×: 6 or more defects

[0097]

[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 40 mA to 90 mA in 10 mA increments, and the vertical axis indicates the load during second bonding, with six levels ranging from 30 gf to 80 gf in 10 gf increments, to determine the number of conditions under which bonding was possible for a total of 36 second bonding conditions.

[0098]

[0099] 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 of non-adhesion or bonder stoppage was determined and evaluated according to the following criteria.

[0100] Evaluation criteria: ◎: 33 or more conditions ○: 25 to 32 conditions ×: 24 or less conditions

[0101] [Wiredrawability] Wiredrawing was performed to a final wire diameter of 18 μm, and the number of wire breakages was counted. The wiredrawing conditions, such as the feed rate and area reduction rate, were as described above, and the drawn wire length was 500,000 m. Evaluation was then performed according to the following criteria.

[0102] Evaluation criteria: ◎: 1 time or less 〇: 2 times ×: 3 times or more

[0103] [High Temperature Reliability of First Bonded Portion] The high temperature reliability of the first bonded portion was evaluated by a high temperature storage life test (HTSL).

[0104] Specifically, a sample for reliability testing of the first bonded portion, prepared using the same procedure as in the "High-Temperature, High-Humidity Reliability of the First Bonded Portion" section, was exposed to an environment at a temperature of 150°C using a high-temperature incubator. The bond life of the first bonded portion was determined by conducting a shear test on the ball bonded portion every 250 hours, and the time it took for the shear strength value to become half of the initial shear strength. The shear strength value was the arithmetic mean value of measurements taken at 50 randomly selected locations on the ball bonded portion. The shear test after the high-temperature storage test was conducted after removing the resin using an acid treatment to expose the ball bonded portion. Evaluation was then performed according to the following criteria.

[0105] Evaluation criteria: ◎: Bonding life is 1000 hours or more ○: Bonding life is 500 hours or more but less than 1000 hours ×: Bonding life is less than 500 hours

[0106] The evaluation results of the examples and comparative examples are shown in Tables 2 to 4.

[0107]

[0108]

[0109]

[0110] All of the wires of Examples 1 to 48 were provided with coating layers that satisfied all of the specific conditions (1) to (3) of the present invention, and it was confirmed that they provided a good FAB shape and also provided good high-temperature, high-humidity reliability of the first bonded portion even when post-curing associated with sealing was performed at a low temperature and in a short time. Note that the wires of Examples 6, 16, 18 to 21, 25, 27, 29, 31, 34, 41 to 45, 47, and 48 achieved both exceptionally good FAB shapes and high-temperature, high-humidity reliability of the first bonded portion, but at least for the wires of these Examples, the C values ​​for all measurement points of the coating layer were Ｐｔ The average value of (atomic %) is X Ｐｔ When the average value X of the coating layer is Ｐｔ Absolute deviation from 0.1X Ｐｔ The total number of measurement points within the range is 50% or more of the total number of measurement points on the coating layer, and the C Ｎｉ The average value of (atomic %) is X Ｎｉ When the average value X of the coating layer is ＮｉAbsolute deviation from 0.1X Ｎｉ It was confirmed that the total number of measurement points within the range was 50% or more of the total number of measurement points on the coating layer. It was also confirmed that the wires of Example Nos. 3, 7, 8, 15, 16, 47, and 48, which contained Au on the surface, had exceptionally excellent bondability at the second bonded portion. Furthermore, it was confirmed that the wires of Example Nos. 15-17, 38-40, 44, 45, 47, and 48, which contained a total of 1 ppm by mass or more of the first additive element, provided exceptionally good crimped shapes at the first bonded portion. It was confirmed that the wires of Example Nos. 18-21, 38, 41, 42, and 44-48, which contained a total of 1 ppm by mass or more of the second additive element, provided exceptionally good bond reliability at the first bonded portion under high-temperature, high-humidity environments. It was confirmed that the wires of Example Nos. 18-21, 38, 41, 42, and 44-48, which contained a total of 0.011 mass% or more of the third additive element, provided exceptionally good bond reliability at the first bonded portion under high-temperature, high-humidity environments. It was confirmed that wires of Example Nos. 22 to 24, 39, 41, 43, 44, and 46 to 48 provided particularly good joint reliability of the first joint in a high-temperature environment. It was confirmed that wires of Example Nos. 25 to 37, 40, 42, 43, and 45 to 48, which contained a total of 5 ppm by mass or more of the fourth additional element, had particularly excellent wiredrawability. On the other hand, it was confirmed that wires of Comparative Example Nos. 1 to 5 had coating layers that did not satisfy at least one of the specific conditions (1) to (3) of the present invention, and that either the FAB shape or the high-temperature, high-humidity reliability of the first joint was poor.

[0111] 1 Bonding wire (wire) 2 Measurement surface X Center of wire width W Wire width (wire diameter) w ａ Measurement surface width l ａ Length of the measuring surface

Claims

1. A bonding wire comprising a core material made of Cu or a Cu alloy and a coating layer formed on the surface of the core material, the total concentration of Pt and Ni being 90 atomic % or more, wherein, in a concentration profile in the depth direction of the wire obtained by measuring 50 or more measurement points in the coating layer by Auger electron spectroscopy (AES), the thickness of the coating layer is 10 nm or more and 130 nm or less, and the Pt concentration C for all measurement points in the coating layer is Ｐｔ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｔ / C Ｎｉ a bonding wire in which, when the average value of X is X, the average value X is 0.3 to 20.0, and the total number of measurement points in the coating layer having an absolute deviation from the average value X within 0.3X is 50% or more of the total number of measurement points in the coating layer.

2. For all measurement points of the coating layer, C Ｐｔ Or C Ｎｉ 2. The bonding wire according to claim 1, wherein, when the above equation is linearly approximated by the least squares method, the difference between the maximum and minimum values ​​of the approximate line within the depth range of the coating layer is 20 atomic % or less.

3. The bonding wire according to claim 1 or 2, wherein the concentration profile in the depth direction of the wire is obtained by measuring with 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.

4. A bonding wire according to any one of claims 1 to 3, wherein the surface of the wire contains Au.

5. The bonding wire according to claim 4, wherein the concentration of Au on the surface of the wire is 10 atomic % or more and 90 atomic % or less.

6. The bonding wire according to claim 5, 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 its width on 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 described in any one of claims 1 to 6, comprising one or more elements (hereinafter referred to as "first additive elements") selected from the group consisting of B, P and Mg, and the total concentration of the first additive elements in the entire wire is 1 ppm by mass or more and 100 ppm by mass or less.

8. A bonding wire according to any one of claims 1 to 7, comprising one or more elements (hereinafter referred to as "second additive elements") selected from the group consisting of Se, Te, As and Sb, and the total concentration of the second additive elements in the entire wire is 1 mass ppm or more and 100 mass ppm or less.

9. A bonding wire described in any one of claims 1 to 8, comprising one or more elements (hereinafter referred to as the "third additive element") selected from the group consisting of Ga and Ge, and the total concentration of the third additive element in the entire wire is 0.011 mass% or more and 1.5 mass% or less.

10. The bonding wire according to any one of claims 1 to 3 and 7 to 9, comprising one or more elements (hereinafter referred to as "fourth additive element") selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Ag, In, Sn, Ta, W, Os, Ir, Pd, Au, and Bi, and having a total concentration of the fourth additive element in the entire wire of 5 ppm by mass or more and 450 ppm by mass or less.

11. The bonding wire according to any one of claims 4 to 6, comprising one or more elements (hereinafter referred to as "fourth additive element") selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Ag, In, Sn, Ta, W, Os, Ir, Pd, Au, and Bi, and having a total concentration of the fourth additive element in the entire wire (wherein the concentration of Au is the concentration in the core material portion) of 5 ppm by mass or more and 450 ppm by mass or less.

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