Bonding Wire

Abstract

The present invention provides a novel alloy-coated Cu bonding wire that provides a good FAB shape, has good initial bondability of the 2nd bond, including adhesion of the 2nd bond, and suppresses galvanic corrosion in a high-temperature environment to provide good bonding reliability of the 2nd bond. The alloy-coated Cu bonding wire includes 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 Pd and Ni of 90 atomic % or more, In the 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, Concentration of Pd at all measurement points in the coating layer, C Pd (atomic%) and Ni concentration C Ni (atomic %) ratio C Pd / C Ni When the average value of the above is X, the average value X is 0.1 or more and 35.0 or less, the total number of measurement points in the coating layer having an absolute deviation of 0.3X or less from the average value X is 50% or more of the total number of measurement points in the coating layer; It is characterized by satisfying the following condition (A). (A) Contains one or more elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Sn, Ta, W, Os, Ir, Pt, Au, and Bi (hereinafter referred to as "first additional element"), and the total concentration of the first additional element in the entire wire is 5 mass ppm or more and 450 mass ppm or less.

Description

[Technical field]

[0001] The present invention relates to a bonding wire. [Background technology]

[0002] A bonding wire is used to connect between an electrode formed on a semiconductor chip and an electrode on a lead frame or a substrate. The bonding wire connection process is completed by first bonding to an electrode on a semiconductor chip using a cylindrical bonding tool (capillary) through which the bonding wire is passed, forming a loop, and then second bonding of the wire portion to an external terminal such as an electrode on a lead frame or a substrate. In the first bonding, the tip of the wire portion (hereinafter also referred to as "tail") protruding from the capillary is heated and melted by arc heat input, forming a free air ball (FAB: Free Air Ball; hereinafter also simply referred to as "ball") by surface tension, and then bonding the ball portion to an electrode on the semiconductor chip by pressure bonding (hereinafter also referred to as "ball bonding"). In the second bonding, ultrasonic waves and a load are applied from the capillary to the wire portion to bond it to an external terminal by pressure bonding (hereinafter also referred to as "wedge bonding") without forming a ball.

[0003] Until now, gold (Au) has been the mainstream material for bonding wire, but it is increasingly being replaced by copper (Cu), mainly for LSI applications (for example, Patent Documents 1-3). In addition, with the recent spread of electric and hybrid vehicles, it is expected that Cu, which has high efficiency and reliability, will be used as a replacement for Au in in-vehicle device applications and also in power devices (power semiconductor devices) in high-power equipment such as air conditioners and solar power generation systems, due to its high thermal conductivity and fusing current.

[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).In addition, 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 bonding portion (Patent Document 5). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 61-48543 [Patent Document 2] Special Publication No. 2018-503743 [Patent Document 3] International Publication No. 2017 / 221770 [Patent Document 4] JP 2005-167020 A [Patent Document 5] International Publication No. 2017 / 013796 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, bonding wires are required to exhibit good bonding reliability even in harsh high-temperature environments.

[0007] The present inventors conducted an evaluation based on such recent demands, and found that in a conventional Cu bonding wire having a Pd coating layer, the Pd coating layer partially peels off during the wire connection process, exposing the Cu core material, and the contact area between the coated Pd part and the exposed Cu part is exposed to an environment containing oxygen, water vapor, and sulfur compound-based outgassing generated from the sealing resin in a high-temperature environment, causing local corrosion of Cu, i.e., galvanic corrosion, and insufficient bonding reliability at the 2nd joint. On the other hand, for bare Cu bonding wires not having a Pd coating layer, although galvanic corrosion does not occur, the FAB shape is poor, and the bondability at the 1st joint is therefore insufficient.

[0008] In the process of addressing the above-mentioned problems, it was confirmed that an alloy-coated Cu bonding wire, in which the surface of a Cu core material is coated with an alloy containing Ni and Pd, exhibits good results in terms of FAB shape and bonding reliability in a high-temperature environment, depending on the composition of the alloy coating. However, it was found that there is room for improvement in the adhesion between the wire and the terminal at the 2nd joint (hereinafter simply referred to as "adhesion of the 2nd joint"). Hereinafter, in this specification, the adhesion of the 2nd joint and the initial bonding strength of the 2nd joint are collectively referred to as the initial bondability of the 2nd joint.

[0009] The present invention provides a novel alloy-coated Cu bonding wire that provides a good FAB shape, has good initial bondability of the 2nd joint, including adhesion of the 2nd joint, and suppresses galvanic corrosion in high-temperature environments, resulting in good bonding reliability of the 2nd joint. [Means for solving the problem]

[0010] As a result of extensive investigations 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 comprising a core material made of Cu or a Cu alloy and a coating layer formed on a surface of the core material, the coating layer having a total concentration of Pd and Ni of 90 atomic % or more, In the 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, Concentration of Pd at all measurement points in the coating layer C Pd (atomic%) and Ni concentration C Ni (atomic %) ratio C Pd / C Ni When the average value of the above is X, the average value X is 0.1 or more and 35.0 or less, the total number of measurement points in the coating layer having an absolute deviation of 0.3X or less from the average value X is 50% or more of the total number of measurement points in the coating layer; A bonding wire that satisfies the following condition (A): (A) Contains one or more elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Sn, Ta, W, Os, Ir, Pt, Au, and Bi (hereinafter referred to as "first additional element"), and the total concentration of the first additional element in the entire wire is 5 mass ppm or more and 450 mass ppm or less. <2> A bonding wire comprising a core material made of Cu or a Cu alloy and a coating layer formed on a surface of the core material, the coating layer having a total concentration of Pd and Ni of 90 atomic % or more, In the 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, Concentration of Pd at all measurement points in the coating layer C Pd (atomic%) and Ni concentration C Ni (atomic %) ratio C Pd / C Ni When the average value of the above is X, the average value X is 0.1 or more and 35.0 or less, the total number of measurement points in the coating layer having an absolute deviation of 0.3X or less from the average value X is 50% or more of the total number of measurement points in the coating layer; A bonding wire that satisfies the following conditions (A) and (B). (A) One or more elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Sn, Ta, W, Os, Ir, Pt, Au, and Bi (hereinafter referred to as "first additive element") are included, and the total concentration of the first additive element in the entire wire (however, the concentration of Au is the concentration in the core material portion) is 5 mass ppm or more and 450 mass ppm or less. (B) The surface of the wire contains Au, and the concentration of Au in the entire wire is 0.5 mass% or less. <3> The total number of measurement points in the coating layer with an absolute deviation of 0.2X from the average value X is 50% or more of the total number of measurement points in the coating layer. <1> or <2> The bonding wire according to claim 1. <4> For all measurement points on the coating layer, C Pd Or C Ni is linearly approximated by the least squares method, the difference between the maximum value and the minimum value of the approximate line in the depth range of the coating layer is 20 atomic % or less. <1> ~ <3> 13. The bonding wire according to claim 12. <5> The concentration profile in the depth direction of the wire is measured by AES under the following conditions while digging from the surface of the wire by Ar sputtering. <1> ~ <4> 13. The bonding wire according to claim 12. <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. <6> The wire contains one or more elements selected from the group consisting of B, P, and Mg (hereinafter referred to as "second additional element"), and the total concentration of the second additional element in the entire wire is 1 ppm by mass or more and 100 ppm by mass or less. <1> ~ <5> 13. The bonding wire according to claim 12. <7> The wire contains one or more elements selected from the group consisting of Se, Te, As, and Sb (hereinafter referred to as "third additive elements"), and the total concentration of the third additive elements in the entire wire is 1 ppm by mass or more and 100 ppm by mass or less. <1> ~ <6> 13. The bonding wire according to claim 12. <8> The wire includes one or more elements selected from the group consisting of Ga and Ge (hereinafter referred to as the "fourth additional element"), and the total concentration of the fourth additional element in the entire wire is 0.011% by mass or more and 1.5% by mass or less. <1> ~ <7> 13. The bonding wire according to claim 12. <9> The wire contains one or more elements selected from the group consisting of In and Ag (hereinafter referred to as "fifth additional element"), and the total concentration of the fifth additional element in the entire wire is 1 ppm by mass or more and 500 ppm by mass or less. <1> ~ <8> 13. The bonding wire according to claim 12. Effect of the Invention

[0012] According to the present invention, it is possible to provide a novel alloy-coated Cu bonding wire that not only provides a good FAB shape, but also has good initial bondability of the 2nd joint, including adhesion of the 2nd joint, and suppresses galvanic corrosion in high temperature environments, thereby providing good bonding reliability of the 2nd joint. [Brief description of the drawings]

[0013] [Figure 1] Fig. 1 is a schematic diagram for explaining the second bonded portion and the position of the evaluation surface (cross section) when evaluating the adhesion of the second bonded portion. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the second bonded portion taken along the dashed double-dashed line AA in FIG. [Diagram 3] FIG. 3 is a schematic diagram for explaining the position and dimensions of the measurement surface when performing composition analysis by AES. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention will be described in detail below based on preferred embodiments. Although the drawings may be referred to in the description, 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 may be modified and implemented as desired within the scope of the claims of the present invention 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") is A core material made of Cu or a Cu alloy; a coating layer formed on the surface of the core material, the coating layer having a total concentration of Pd and Ni of 90 atomic % or more; In the 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, Concentration of Pd at all measurement points in the coating layer C Pd (atomic%) and Ni concentration C Ni (atomic %) ratio C Pd / C Ni When the average value of the above is X, the average value X is 0.1 or more and 35.0 or less, the total number of measurement points in the coating layer having an absolute deviation of 0.3X or less from the average value X is 50% or more of the total number of measurement points in the coating layer; It is characterized by satisfying the following condition (A). (A) Contains one or more elements ("first additive elements") selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Sn, Ta, W, Os, Ir, Pt, Au, and Bi, and the total concentration of the first additive elements in the entire wire is 5 ppm by mass or more and 450 ppm by mass or less.

[0016] As mentioned above, in recent years, bonding wires are required to exhibit good bonding reliability in harsh high-temperature environments. For example, bonding wires used in in-vehicle devices are required to have bonding reliability in high-temperature environments exceeding 150 ° C. The present inventors conducted an evaluation based on the characteristics required in recent years and found that in a conventional Cu bonding wire having a Pd coating layer, galvanic corrosion occurs in a high-temperature environment, and the bonding reliability at the 2nd joint may not be sufficient. In addition, with respect to bare Cu bonding wires not having a Pd coating layer, although galvanic corrosion does not occur, the FAB shape is poor, and the crimp shape of the 1st joint is inferior, and the response to the narrow pitch connection required for high-density mounting is insufficient.

[0017] In contrast, the 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 Pd and Ni is 90 atomic % or more. 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 in the depth direction, the thickness of the coating layer is 10 nm or more and 130 nm or less, and the concentration C of Pd at all measurement points in the coating layer is Pd (atomic%) and Ni concentration C Ni (atomic %) ratio C Pd / C Ni The inventors have found that an alloy-coated Cu bonding wire in which the average value X is 0.1 to 35.0, 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, when the average value X is X, provides a good FAB shape and suppresses galvanic corrosion in a high-temperature environment, thereby providing good bonding reliability of the 2nd bond.

[0018] On the other hand, it has been found that there is room for improvement in the initial bondability of the second bonded portion, particularly the adhesion of the second bonded portion, with respect to such alloy-coated Cu bonding wire, as described below. As described above, in the second bonding, the wire is pressure-bonded onto the external terminal by applying ultrasonic waves and a load from the capillary to the wire portion. FIG. 1 shows a schematic view of a second bonding portion formed on an external terminal (not shown) as viewed directly from above in a direction perpendicular to the main surface of the external terminal. In FIG. 1, a second bonding portion 10 is formed at the tip of the wire 1. In the second bonding portion, it is desirable that the wire and the external terminal are sufficiently in close contact. However, with respect to the second bonding portion formed using the above-described alloy-coated Cu bonding wire, it has been confirmed that there is a certain proportion of locations where the wire and the external terminal are not in close contact, and the adhesion between the wire and the terminal may be inferior. FIG. 2 shows a schematic cross-sectional view of the second bonding portion when cut in a direction perpendicular to the main surface of the external terminal at the position indicated by the two-dot chain line A-A in FIG. 1. In FIG. 2, a second bonding portion 10 is formed on the external terminal 50. However, with respect to the second bonding portion formed using the above-described alloy-coated Cu bonding wire, the inventors have found that there is a tendency for there to be locations where the wire and the external terminal are not in close contact over a certain width from the ends of the second bonding portion (the left and right ends of the second bonding portion 10 in FIG. 2). Such a problem with the adhesion of the second bonding portion is considered to be a specific problem caused by adopting the above-specified alloy coating, since it has not been at least manifested in conventional bonding wires such as bare Cu bonding wires.

[0019] On the other hand, according to the bonding wire that adopts the above-specified alloy coating and satisfies the above condition (A), the inventors have found that the excellent effects achieved by adopting the specific alloy coating can be maintained, and the adhesion of the second bonding portion can be improved to achieve good initial bondability of the second bonding portion.

[0020] <Core material made of Cu or Cu alloy> The wire of the present invention includes a core material made of Cu or Cu alloy (hereinafter, also simply referred to as "Cu core material").

[0021] 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 constituting a conventional Pd-coated Cu wire known as a bonding wire may be used.

[0022] In the present invention, the concentration of Cu in the Cu core material can be, for example, at the center (axial core portion) of the Cu core material, 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 99.95 atomic % or more.

[0023] From the viewpoint of realizing an alloy-coated Cu bonding wire that improves the adhesion of the 2nd joint and provides good initial bondability of the 2nd joint, it is preferable that the Cu core material contains the first additive element so as to satisfy the above condition (A).

[0024] The Cu core material may also contain one or more dopants selected from the second, third, fourth, and fifth additional elements described below. The preferred contents of these dopants are as described below.

[0025] In one embodiment, the Cu core material is composed of Cu, a first additive element, and inevitable impurities. In another embodiment, the Cu core material is composed of Cu, a first additive element, one or more elements selected from a second additive element, a third additive element, a fourth additive element, and a fifth additive element described later, and inevitable impurities. The Cu core material may contain elements constituting the coating layer described later.

[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, in which the total concentration of Pd and Ni is 90 atomic % or more.

[0027] In order to provide a good FAB shape and to suppress galvanic corrosion in a high-temperature environment and provide good bonding reliability of the 2nd bond, it is important that the coating layer in 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 in the coating layer is 50 or more (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) Pd concentration C at all measurement points in the coating layer Pd (atomic%) and Ni concentration C Ni (atomic %) ratio C Pd / C Ni When the average value of X is X, the average value X is 0.1 or more and 35.0 or less. (3) The total number of measurement points in the coating layer that have an absolute deviation of 0.3X or less from the average value X 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 points in the depth direction are measured so that they are 50 or more in the coating layer. In general, since the analysis in the depth direction by AES can be performed at a measurement interval of the sub-nano order, it is relatively easy to make the measurement points 50 or more 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 lowering the sputtering speed or shortening the sputtering time so that the number of measurement points is 50 or more. In this way, the measurement points in the depth direction by AES are measured so that they are 50 or more in the coating layer, and the concentration profile in the depth direction of the wire can be obtained. Although it depends on the thickness of the coating layer, it is more preferable to determine the measurement point interval of the AES so that the total number of measurement points on 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 a concentration profile along the depth of the wire obtained by AES measurement at 50 or more measurement points along the depth of the coating layer.

[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 suppress galvanic corrosion in a high-temperature environment, provide good bonding reliability of the second bonded portion, and provide a good FAB shape, and therefore a good crimped shape of the first bonded portion.

[0030] Regarding condition (1), the thickness of the coating layer (a calculation method based on a concentration profile in the depth direction of the wire will be described later) is 10 nm or more from the viewpoint of realizing a good FAB shape, 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. If the thickness of the coating layer is less than 10 nm, eccentricity occurs during FAB formation, the FAB shape deteriorates, and the compression shape of the 1st bonded portion tends to deteriorate. In addition, the upper limit of the thickness of the coating layer is 130 nm or less from the viewpoint of realizing a good FAB shape, preferably 125 nm or less, 120 nm or less, 115 nm or less, or 110 nm or less. If the thickness of the coating layer exceeds 130 nm, deformation or poor melting occurs during FAB formation, the FAB shape deteriorates, and the compression shape of the 1st bonded portion tends to deteriorate.

[0031] -Condition (2)- Condition (2) is the Pd concentration C Pd (atomic%) and Ni concentration C Ni (atomic %) ratio C Pd / 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 suppress galvanic corrosion in a high-temperature environment to provide good bonding reliability of the 2nd bonded portion, and can also provide a good FAB shape, and thus a good crimped shape of the 1st bonded portion.

[0032] Regarding the condition (2), from the viewpoint of realizing good joint reliability of the second joint, the average value X is 35.0 or less, preferably 34.0 or less, and more preferably 32.0 or less, 30.0 or less, 28.0 or less, 26.0 or less, 25.0 or less, 24.0 or less, 22.0 or less, or 20.0 or less. Pd / C NiIf it exceeds 35.0, galvanic corrosion in a high-temperature environment cannot be suppressed, and sufficient high-temperature bonding reliability tends not to be obtained in the 2nd bonded portion. In addition, the lower limit of the average value X is 0.1 or more, preferably 0.2 or more, 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, more preferably 1.5 or more, 2.0 or more, 2.5 or more, or 3.0 or more, from the viewpoint of increasing the initial bonding strength of the 2nd bonded portion and realizing good initial bonding properties of the 2nd bonded portion. If the average value X is less than 0.1, sufficient initial bonding properties of the 2nd bonded portion tends not to be obtained.

[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 suppress galvanic corrosion in a high-temperature environment to provide good bonding reliability of the 2nd joint, and can also provide a good FAB shape and, ultimately, a good crimp shape of the 1st joint.

[0034] Condition (3), together with condition (2), indicates that the coating layer contains a high concentration of PdNi alloy containing Pd and Ni in a predetermined ratio while suppressing the fluctuation of the Pd / Ni ratio in the thickness direction of the coating layer. From the viewpoint of realizing better bonding reliability of the 2nd bonding part in a high temperature environment and from the viewpoint of realizing a better FAB shape, it is more preferable that the total number of measurement points in the coating layer whose absolute deviation from the average value X is within 0.2X (more preferably within 0.18X, 0.16X, or 0.15X) is 50% or more of the total number of measurement points in the coating layer.

[0035] From the viewpoint of realizing better bonding reliability of the 2nd bonded portion in a high temperature environment and from the viewpoint of realizing a 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 preferable 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.

[0036] From the viewpoint of further enjoying the effects of the present invention, in the concentration profile in the depth direction of the wire, the Pd concentration C Pd (atomic %) or Ni concentration C Ni When the average value X is less than 1, the difference between the maximum and minimum values ​​of the approximate line in the range of the depth (thickness) of the coating layer is preferably 20 atomic % or less, more preferably 15 atomic % or less, and even more preferably 10 atomic % or less, 8 atomic % or less, 6 atomic % or less, or 5 atomic % or less. Ni When the atomic percent of the coating layer is linearly approximated by the least squares method, it is preferable that the difference between the maximum and minimum values ​​of the approximated line in the depth range of the coating layer is within the above range. Also, when the average value X is 1 or more, C Pd When (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.

[0037] The thickness of the coating layer under condition (1), the average value X and the absolute deviation from the average value X under conditions (2) and (3), 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 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, 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 the concentration change of each element in the depth (center) direction from the surface of the wire (so-called concentration profile in the depth direction), and the thickness can be confirmed and determined based on the concentration profile. In the present invention, when obtaining the concentration profile in the depth direction, the unit of depth is SiO 2 This was converted.

[0038] When performing 1) compositional analysis of the wire surface and 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 direction of the wire axis (wire length direction). Further explanation will be given with reference to Figure 3. Figure 3 is a schematic plan view of a wire 1, in which the direction of the wire axis (wire length direction) corresponds to the vertical direction (up and down direction) of Figure 3, and the direction perpendicular to the wire axis (wire thickness direction) corresponds to the horizontal direction (left and right direction) of Figure 3. Figure 3 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 It is.

[0039] The wire is positioned so that its center of 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 FIG. 3, 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 its center of width coincides with the dashed line X, which is the center of the wire width, and the width w of the measurement surface is determined so that the center of width w of the measurement surface is 5% to 15% of the wire diameter. a is determined so that it is 5% to 15% of the wire diameter (same value as the wire width W), that is, 0.05W to 0.15W. In addition, the length of the measurement surface l a is,l a =5w a The relationship is satisfied. By determining the position and dimensions of the measurement surface as described above, it is possible to accurately measure the success or failure of conditions (1) to (3), which are suitable for providing good bonding reliability of the 2nd bonded portion in a high-temperature environment and realizing a good FAB shape. 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 axial direction and use the arithmetic average value.

[0040] 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 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 based on the results of measurement under the conditions described in the section [Analysis of coating layer thickness by Auger electron spectroscopy (AES)] below.

[0041] 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, Pd and Ni tend to coexist in a high concentration at a constant ratio, that is, there is a region (coating layer) where the total concentration of Pd and Ni is 90 atomic % or more, and the Pd concentration C Pd (atomic%) and Ni concentration C Ni (atomic %) ratio C Pd / C NiWhen the average value of is 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 Pd and Ni tend to decrease and the concentration of Cu tends to increase. In such a concentration profile in the depth direction, the concentration of Pd, C Pd (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 obtained from the thickness of the region where the total concentration of Pd and Ni is 90 atomic % or more and the total number of measurement points. Pd / C Ni The average value X can be obtained by arithmetically averaging the values, and the total number of measurement points with an absolute deviation from the average value X within 0.3X can be obtained by checking the absolute deviation from the average value X for all measurement points of the coating layer. As 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 Pd and Ni from the surface of the wire to a very shallow position. In such a case, the concentration C of Pd Pd (atomic%) and Ni concentration C Ni Focusing on the atomic percent (atomic %), the thickness of the coating layer and the total number of measurement points of the coating layer can be obtained from the thickness of the region where the total is 90 atomic percent or more and the total number of measurement points, and the ratio C Pd / C Ni The average value X can be obtained by taking the arithmetic average of the above 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.

[0042] -Other suitable conditions for the coating layer- In the wire of the present invention, in addition to satisfying all of the above conditions (1) to (3), it is more preferable that the coating layer satisfies one or both of the following conditions (4) and (5) based on the concentration profile in the depth direction of the wire. (4) Pd concentration C at all measurement points in the coating layer Pd (atomic%) average value X Pd When the average value X of the coating layer is Pd Absolute deviation from 0.1XPd The total number of measurement points within the range is 50% or more of the total number of measurement points on the coating layer. (5) Ni concentration C at all measurement points of the coating layer Ni (atomic%) average value 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 on 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 relation to 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), the wire of the present invention can provide particularly good bonding reliability of the second bonded portion in a high-temperature environment and can achieve a particularly good FAB shape.

[0043] The coating layer may contain, for example, one or more dopants selected from the second additional element, the third additional element, the fourth additional element, and the fifth additional element described below. The preferred contents of these dopants are as described below.

[0044] The wire of the present invention may further contain Au on its surface. By further containing Au on the surface of the wire, the initial bondability of the 2nd bonded portion can be further improved. When the wire of the present invention further contains Au on its surface, the concentration of Au in the entire wire may be usually 0.5 mass% or less, preferably 0.3 mass% or less or 0.2 mass% or less, and the lower limit may be, for example, 0.05 mass% or more, 0.1 mass% or more, etc. Thus, in one embodiment, the wire of the present invention satisfies the following condition (B). (B) The surface of the wire contains Au, and the concentration of Au in the entire wire is 0.5 mass% or less.

[0045] In addition, when the wire of the present invention further contains Au on its surface, in determining whether the above condition (A) is satisfied, the concentration of Au as the first additive element is the concentration in the core part obtained by exposing the cross section of the wire and measuring the Cu core part with 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 first additive element in the entire wire" in the above condition (A) is read as "total concentration of the first additive element in the entire wire (however, the concentration of Au in the core part is used)."

[0046] In one embodiment, the wire of the present invention includes a coating layer that satisfies the above conditions (1) to (3) and also satisfies the following conditions (A) and (B). (A) Contains one or more elements ("first additive elements") selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Sn, Ta, W, Os, Ir, Pt, Au, and Bi, and the total concentration of the first additive elements in the entire wire (however, the concentration of Au is the concentration in the core material) is 5 ppm by mass or more and 450 ppm by mass or less. (B) The surface of the wire contains Au, and the concentration of Au in the entire wire is 0.5 mass% or less.

[0047] According to the alloy-coated Cu bonding wire of the present invention containing the first additive element at the above-mentioned specific concentration, even if the Au concentration on the wire surface is low, for example, less than 10 atomic %, 8 atomic % or less, 6 atomic % or less, 5 atomic % or less, 4 atomic % or less, or 2 atomic % or less, the adhesion of the 2nd bond can be improved and good initial bondability of the 2nd bond can be achieved.

[0048] 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 acquiring a concentration profile in the depth direction. That is, when performing the composition analysis of the wire surface by Auger electron spectroscopy (AES), the position and dimensions of the measurement surface are determined as follows.

[0049] 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 measurement surface width, 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 initial bondability of the 2nd bonded portion. 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 to use the arithmetic average value.

[0050] The above-mentioned Au concentration on the surface is based on the results of measurements performed under the conditions described in the section "Composition analysis of wire surface by Auger electron spectroscopy (AES)" below.

[0051] 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 Pd and Ni in the concentration profile in the depth direction of the wire. The position where the total concentration of Pd and Ni is 90 atomic % is determined as the boundary, and the region where the total concentration of Pd and Ni is less than 90 atomic % is the Cu core material, and the region where the total concentration of Pd 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 obtained by checking the concentration profile from the wire surface toward the wire center, and is the distance from the depth position Z1 where the total concentration of Pd and Ni first reaches 90 atomic % or more to the depth position Z2 where the total concentration of Pd and Ni first falls below 90 atomic % (however, Z2>Z1).

[0052] The wire of the present invention is characterized in that it includes a coating layer that satisfies the above conditions (1) to (3). The average value X and the 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-mentioned boundary judgment method, and are determined by the Pd concentration C Pd (atomic%) and Ni concentration C Ni It is determined by focusing on (atomic %).

[0053] In one embodiment, the coating layer is made of Pd and Ni; and unavoidable impurities. In another embodiment, the coating layer is made of Pd and Ni; one or more elements selected from Au and the first additional element; and unavoidable impurities. In another embodiment, the coating layer is made of Pd and Ni; one or more elements selected from the second additional element, the third additional element, the fourth additional element, and the fifth additional element described below; and unavoidable impurities. In another embodiment, the coating layer is made of Pd and Ni; one or more elements selected from Au and the first additional element; one or more elements selected from the second additional element, the third additional element, the fourth additional element, and the fifth additional element described below; and unavoidable impurities. The coating layer may contain the elements constituting the Cu core material described above.

[0054] The wire of the present invention is characterized by satisfying the following condition (A). (A) Contains one or more elements ("first additive elements") selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Sn, Ta, W, Os, Ir, Pt, Au, and Bi, and the total concentration of the first additive elements in the entire wire is 5 ppm by mass or more and 450 ppm by mass or less.

[0055] By including a coating layer that satisfies all of the above conditions (1) to (3) and also satisfies the above condition related to the first additive element, the wire of the present invention can provide a good FAB shape and good bonding reliability of the 2nd bond in a high temperature environment, and can improve the adhesion of the 2nd bond to achieve good initial bondability of the 2nd bond.

[0056] Condition (A) relates to the total concentration of one or more elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Sn, Ta, W, Os, Ir, Pt, Au, and Bi, i.e., the first additional element, in the entire wire. Here, as described above, when the wire of the present invention further contains Au on its surface, the "total concentration of the first additional element in the entire wire" in condition (A) should be read as the "total concentration of the first additional element in the entire wire (however, the concentration of Au is the concentration in the core material)."

[0057] Regarding condition (A), from the viewpoint of realizing an alloy-coated Cu bonding wire that improves the adhesion of the 2nd bond and provides good initial bondability of the 2nd bond, the total concentration of the first additive element relative to the entire wire is 5 mass ppm or more, preferably 10 mass ppm or more, 15 mass ppm or more, 20 mass ppm or more, or 25 mass ppm or more, more preferably 30 mass ppm or more, 40 mass ppm or more, 50 mass ppm or more, 60 mass ppm or more, or 80 mass ppm or more, and even more preferably 100 mass ppm or more, 110 mass ppm or more, 120 mass ppm or more, 130 mass ppm or more, 140 mass ppm or more, or 150 mass ppm or more. In particular, when the total concentration of the first additive element relative to the entire wire is 100 mass ppm or more, it is preferable because it is easy to realize a bonding wire that improves the adhesion of the 2nd bond and provides even better initial bondability of the 2nd bond.

[0058] Regarding condition (A), in order to realize an alloy-coated Cu bonding wire that improves the adhesion of the 2nd bonded portion and provides good initial bondability of the 2nd bonded portion, the total concentration of the first additive element is 450 mass ppm or less with respect to the entire wire. The upper limit of the total concentration of the first additive element may be 440 mass ppm or less, 420 mass ppm or less, 400 mass ppm or less, etc. In addition, when the first additive 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 "1a additive element"), the upper limit of the total concentration of the 1a additive element may be 200 mass ppm or less, 180 mass ppm or less, 160 mass ppm or less, or 150 mass ppm or less, etc. When the first additional element includes one or more elements selected from the group consisting of Zr, Nb, Mo, Ru, Rh, and Sn (hereinafter also referred to as "1b additional element"), the upper limit of the total concentration of the 1b 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, etc.

[0059] In the wire of the present invention, from the viewpoint of improving the adhesion of the second bond and realizing a bonding wire that exhibits better initial bondability of the second bond, it is preferable that the first additive element is contained in the Cu core material.

[0060] The wire of the present invention may further contain one or more elements ("second additive elements") selected from the group consisting of B, P, and Mg. When the wire of the present invention contains the second additive element, the total concentration of the second additive element in the entire wire is preferably 1 mass ppm or more. This makes it possible to realize a bonding wire that provides a better crimp shape of the 1st bonded portion. The total concentration of the second additive element in the entire wire is more preferably 2 mass ppm or more, and further preferably 3 mass ppm or more, 5 mass ppm or more, 8 mass ppm or more, 10 mass ppm or more, 15 mass ppm or more, or 20 mass ppm or more. From the viewpoint of suppressing hardening of the wire and reducing chip damage during 1st bonding, the total concentration of the second additive element is preferably 100 mass ppm or less, and more preferably 90 mass ppm or less, 80 mass ppm or less, 70 mass ppm or less, 60 mass ppm or less, or 50 mass ppm or less. Therefore, in a preferred embodiment, the wire of the present invention contains the second additional element, and the total concentration of the second additional element in the entire wire is 1 ppm by mass or more and 100 ppm by mass or less.

[0061] When the wire of the present invention contains the 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 a better crimp shape of the first bonded portion, it is preferable that the second additive element is contained in the Cu core material.

[0062] The wire of the present invention may further contain one or more elements ("third additive elements") selected from the group consisting of Se, Te, As, and Sb. When the wire of the present invention contains the third additive element, the total concentration of the third additive element in the entire wire is preferably 1 mass ppm or more. This can improve the bonding reliability of the 1st bonded portion in a high-temperature and high-humidity environment. The total concentration of the third additive element in the entire wire is more preferably 2 mass ppm or more, and further preferably 3 mass ppm or more, 5 mass ppm or more, 8 mass ppm or more, 10 mass ppm or more, 15 mass ppm or more, or 20 mass ppm or more. From the viewpoint of realizing a good FAB shape and a good crimped shape of the 1st bonded portion, the total concentration of the third additive element is preferably 100 mass ppm or less, and more preferably 90 mass ppm or less, 80 mass ppm or less, 70 mass ppm or less, 60 mass ppm or less, or 50 mass ppm or less. Therefore, in a preferred embodiment, the wire of the present invention contains a third additional element, and the total concentration of the third additional element in the entire wire is 1 ppm by mass or more and 100 ppm by mass or less.

[0063] 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. From the viewpoint of realizing a bonding wire that provides better bonding reliability of the first bonding portion in a high-temperature and high-humidity environment, it is preferable that the third additive element is contained in the coating layer.

[0064] The wire of the present invention may further contain one or more elements ("fourth additional element") selected from the group consisting of Ga and Ge. 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 0.011 mass% or more. This can improve the bonding reliability of the 1st bonding portion in a high-temperature environment. The total concentration of the fourth additional element in the entire wire is more preferably 0.015 mass% or more, and further 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 1st bonded portion, and a good initial bondability of the 2nd bonded portion, the total concentration of the fourth additional element is preferably 1.5 mass% or less, 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 fourth additional element, and the total concentration of the fourth additional element in the entire wire is 0.011 mass% or more and 1.5 mass% or less.

[0065] 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.

[0066] The wire of the present invention may further contain one or more elements selected from the group consisting of In and Ag ("fifth additional element"). When the wire of the present invention contains the fifth additional element, the total concentration of the fifth additional element in the entire wire is preferably 1 mass ppm or more. This can provide good bonding reliability of the 2nd bonded portion even in a harsher high-temperature environment (for example, 200°C). The total concentration of the fifth additional element in the entire wire is preferably 2 mass ppm or more, 3 mass ppm or more, 4 mass ppm or more, or 5 mass ppm or more, more preferably 6 mass ppm or more, 8 mass ppm or more, or 10 mass ppm or more, even more preferably 20 mass ppm or more, 30 mass ppm or more, or 40 mass ppm or more, and even more preferably 50 mass ppm or more, 60 mass ppm or more, or 70 mass ppm or more. The upper limit of the concentration of the fifth additional element in the entire wire may be, for example, 500 mass ppm or less, 480 mass ppm or less, 460 mass ppm or less, 450 mass ppm or less, etc., taking into consideration costs, etc., since the effect of improving the joint reliability of the 2nd joint in a high-temperature environment reaches a plateau even if the fifth additional element is contained above that amount. Therefore, in a preferred embodiment, the wire of the present invention contains the fifth additional element, and the total concentration of the fifth additional element in the entire wire is 1 mass ppm or more and 500 mass ppm or less.

[0067] When the wire of the present invention contains a fifth additive element, the fifth 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 exhibits good bonding reliability of the second bond portion under a harsh high-temperature environment, it is preferable that the fifth additive element is contained in the Cu core material.

[0068] The contents of the first additional element, the second additional element, the third additional element, the fourth additional element, and the fifth additional element in the wire can be measured by the method described later in [Measurement of element contents].

[0069] In the wire of the present invention, the total concentration of Cu, Ni, 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.

[0070] The diameter of the wire of the present invention is not particularly limited and may be appropriately determined depending on the specific purpose, but is preferably 13 μm or more, 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.

[0071] The wire of the present invention provides a good FAB shape, has good initial bondability of the second bond, including adhesion of the second bond, and can suppress galvanic corrosion in a high-temperature environment to provide good bonding reliability of the second bond. Therefore, the bonding wire of the present invention can be suitably used to connect between an electrode on a semiconductor chip and an external terminal such as an electrode on a lead frame or a substrate.

[0072] <Wire manufacturing method> An example of the method for producing the bonding wire of the present invention will be described.

[0073] The raw copper used has a purity of 4N (99.99% by mass or more) or higher, and an ingot containing each dopant is obtained by the method described below.

[0074] The above-mentioned first additive element and, when added, the second additive element, the third additive element, the fourth additive element, the fifth additive element, and other dopants can be added by, for example, including a method of including them in the Cu core material, a method of including them in the coating layer, a method of depositing them on the surface of the Cu core material, a method of depositing them on the surface of the coating layer, and combinations of these methods, and these methods can be appropriately selected. In the method of including the dopant in the Cu core material, the dopant component may be directly added to Cu, or a mother alloy containing about several percent of the dopant component may be used. In the method of including the dopant in the coating layer, the dopant may be included in the Pd or Ni plating bath (in the case of wet plating) or the target material (in the case of dry plating) when forming 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.

[0075] The above-mentioned ingot is forged, rolled and drawn to produce a wire made of Cu or a Cu alloy having a diameter of about 0.7 to 2.0 mm (hereinafter also referred to as "intermediate wire").

[0076] As a method for forming a coating layer on the surface of the Cu core material, electrolytic plating, electroless plating, vapor deposition, etc. can be used, but it is industrially preferable to use electrolytic plating, which can stably control the film thickness. For example, a coating layer may be formed on the surface of the intermediate wire. The coating layer may also be applied at the ingot stage, or the coating layer may be formed on the surface of the Cu core material after the intermediate wire is drawn and further thinned (for example, after drawing to the final wire diameter). The coating layer may be formed, for example, by providing a PdNi alloy layer containing Pd and Ni in a predetermined ratio on the surface of the Cu core material, or from the viewpoint of forming a coating layer having excellent adhesion to the Cu core material, by providing a PdNi alloy layer containing Pd and Ni in a predetermined ratio after applying strike plating of a conductive metal to the surface of the Cu core material. In addition, after forming a PdNi alloy layer containing Pd and Ni in a predetermined ratio, a layer containing one or more of Pd and Ni (for example, a Pd layer, a Ni layer, a PdNi alloy layer) may be further provided.

[0077] When forming a wire containing Au on its surface, it can be formed by providing an Au layer on the surface of the coating layer using the same method as described above.

[0078] In the wire drawing process, the wire is drawn to the final wire diameter (diameter of about 13 to 80 μm) using a wire drawing device using diamond dies. As for the heat treatment, in addition to the thermal refining heat treatment performed at the final wire diameter, intermediate heat treatment performed in the middle of the wire drawing process may be performed.

[0079] [Semiconductor Devices] A semiconductor device can be manufactured by using the semiconductor device bonding wire of the present invention to connect electrodes on a semiconductor chip to external terminals such as electrodes on a lead frame or a circuit board.

[0080] In one embodiment, a 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.

[0081] In the semiconductor device of the present invention, the circuit board and the semiconductor chip are not particularly limited, and a known circuit board and a semiconductor chip 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, the semiconductor device may be configured to include a lead frame and a semiconductor chip mounted on the lead frame, as in the semiconductor device described in JP 2020-150116 A.

[0082] Examples of the semiconductor device include various semiconductor devices used in electrical products (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.). EXAMPLES

[0083] The present invention will be specifically described below with reference to examples, although the present invention is not limited to the examples shown below.

[0084] (sample) First, the method for preparing the samples will be described. The raw material Cu used had a purity of 4N (99.99% by mass or more) or higher. The first additive element, and if added, the second additive element, the third additive element, the fourth additive element, and the fifth additive element had a purity of 3N or higher, or the mother alloy contained a few percent of these additive elements in Cu.

[0085] The core Cu alloy is first prepared by loading the raw materials into a graphite crucible and heating them in a high-frequency furnace with N 2The wire was heated to 1090-1800°C in an inert atmosphere such as nitrogen gas or Ar gas to melt it, and then an ingot with a diameter of 3-6 mm was produced by continuous casting. Next, the obtained ingot was subjected to wire drawing to produce an intermediate wire with a diameter of 0.7-2.0 mm. In the wire drawing, a commercially available lubricant was used, and the wire drawing speed was 20-150 m / min. The coating layer was formed by electrolytic plating. Some of the wires (Examples Nos. 5, 9, 15, 27, 33, and 36) had an Au layer on the PdNi alloy layer. A Pd-Ni plating solution and an Au plating solution were prepared and appropriately adjusted for use.

[0086] After that, further wire drawing and other processes were performed to process the wire into a final wire diameter of φ20 μm. If necessary, intermediate heat treatment was performed once or twice during the wire drawing process at 300 to 700 °C for 2 to 15 seconds. When intermediate heat treatment was performed, the wire was continuously swept and heated with 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, the thermal treatment temperature was lowered and the wire feed speed was set to a higher value, and when the coating layer was thick, the thermal treatment temperature was increased and the wire feed speed was set to a lower value.

[0087] (Testing and Evaluation Methods) The test and evaluation methods are explained below.

[0088] [Composition analysis of wire surface by Auger electron spectroscopy (AES)] For wires containing Au on the surface thereof, the Au concentration on the wire surface was determined by measuring the wire surface as the measurement surface by Auger electron spectroscopy (AES) as follows. First, the bonding wire to be measured was fixed in a straight line on the sample holder. Next, the wire was positioned so that the center of the wire width 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 set to 5 times the width of the measurement surface. Then, using an AES device (ULVAC-PHI PHI-700), composition analysis of the wire surface was performed at an accelerating voltage of 10 kV to determine the surface Au concentration (atomic %). The composition analysis by AES was performed on three measurement surfaces separated by at least 1 mm in the axial direction of the wire, and the arithmetic average value was used. In determining the concentration of Au on the surface, gas components such as carbon (C), sulfur (S), oxygen (O), and nitrogen (N), and nonmetallic elements were not taken into consideration.

[0089] [Coating layer thickness analysis by Auger electron spectroscopy (AES)] AES depth analysis was used to analyze the thickness of the coating layer. AES depth analysis is a method of analyzing the change in composition in the depth direction by alternating composition analysis and sputtering, and it is possible to obtain the concentration change of each element in the depth direction (center) from the wire surface (so-called concentration profile in the depth direction). Specifically, 1) compositional analysis of the wire surface was performed by AES, followed by 2) sputtering with Ar and 3) compositional analysis of the surface after sputtering to obtain a concentration profile in the depth direction. + The measurements were performed with ions and an accelerating voltage of 2 kV. In the surface composition analyses 1) and 3), the dimensions of the measurement surface, the composition analysis by AES, and the conditions for calculating the concentration of each element were the same as those explained in the above section [Composition analysis of wire surface by Auger electron spectroscopy (AES)]. When obtaining the concentration profile in the depth direction by AES, the measurements were performed at 50 or more points in the coating layer in the depth direction. 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.

[0090] -The thickness of the coating layer and the total number of measurement points of the coating layer- In the obtained concentration profile in the depth direction, the concentration profile from the wire surface to the wire center was confirmed, and the Pd concentration C Pd (atomic%) and Ni concentration C Ni From the depth position Z1 where the total of (atomic %) first reaches 90 atomic % or more, C Pd and C. Ni The distance to depth position Z2 (where Z2>Z1) where the sum of the first dropped below 90 atomic % was determined as the measured thickness of the 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 as the arithmetic average 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 wire of the example was 50 to 100. The depth measured by AES analysis is calculated as the product of the sputtering rate and time. Generally, the sputtering rate is calculated based on 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.

[0091] -The total number of measurement points whose average value X and absolute deviation from the average value X are within a specified range- In the obtained concentration profile in the depth direction, the Pd concentration C Pd (atomic%) and Ni concentration C Ni (atomic %) ratio C Pd / C Ni The average value X was calculated by arithmetically averaging the values. Then, the ratio C of all the measurement points of the coating layer was calculated. Pd / 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, and the total number of measurement points whose absolute deviation from the average value X was within 0.2X were calculated. The average value X was calculated as the arithmetic mean value of the values ​​obtained for the three measurement surfaces.

[0092] -C Pd Or C NiThe slope of the approximate straight 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 Pd (atomic %) or C Ni (atomic %) was linearly approximated by the least squares method, and the difference (atomic %) between the maximum and minimum values ​​of the approximate line in the depth range of the coating layer was calculated. Here, if the average value X was less than 1, the C Ni (atomic%) is linearly approximated by the least squares method, and if the average value X is 1 or more, C Pd The difference (atomic %) between the maximum and minimum values ​​of the approximation line within the depth range of the coating layer was the arithmetic average value of the values ​​obtained for the three measurement surfaces.

[0093] [Measurement of element content] The contents of the first, second, third, fourth, and fifth additional elements in the wire were detected as the concentration of the elements contained in the entire wire by analyzing the liquid obtained by dissolving the bonding wire in strong acid using an ICP optical emission spectrometer and an ICP mass spectrometer. The analytical equipment used was an ICP-OES ("PS3520UVDDII" manufactured by Hitachi High-Tech Science Co., Ltd.) or an ICP-MS ("Agilent 7700x ICP-MS" manufactured by Agilent Technologies, Inc.). For wires that further contained Au on their surface, the concentration of Au as the first additional element was obtained by exposing the cross section of the wire and measuring the Cu core part using an electron beam microanalyzer (EPMA) or secondary ion mass spectrometry (SIMS).

[0094] [FAB shape] The FAB shape was evaluated by creating a FAB on a lead frame using a commercially available wire bonder and observing it with a scanning electron microscope (SEM) (number of evaluations: N=100). The FAB was performed with a current value of 30 to 75 mA, an EFO gap of 762 μm, and a tail length of 254 μm. 2 +5%H 2The gas was flowed at a flow 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 bad if it had eccentricity, irregular shape, or poor melting. Evaluation was performed according to the following criteria.

[0095] Evaluation criteria: ◎: 5 or less defects ○: 6 to 10 defects (no practical problems) ×: 11 or more defects

[0096] [Initial jointability of 2nd joint] The initial bondability of the 2nd bond was evaluated by measuring and observing the bond strength and adhesion of the 2nd bond. In detail, the bond strength of the 2nd bond was measured by a pull test. The adhesion of the 2nd bond was evaluated by observing the cross section of the 2nd bond with a SEM.

[0097] -2nd joint strength- Using a commercially available wire bonder, 80 wires each in the top, bottom, left and right directions (320 wires in total) were bonded onto an Ag-plated Cu alloy lead frame to prepare an evaluation sample. A pull test was then carried out on the second joint. The pull strength was calculated by taking the arithmetic mean value of the measurements taken from 15 pieces in each direction (total of 60 pieces).

[0098] - Adhesion of 2nd joint - Using a commercially available wire bonder, 40 wires each in the top, bottom, left and right directions (160 wires in total) were bonded onto a PPF-plated Cu alloy lead frame to prepare an evaluation sample. Then, the cross section of the second bond was polished using an ion beam to prepare a sample for SEM observation. In detail, the evaluation sample was cut in a direction perpendicular to the main surface of the lead frame at a position where the width of the second bond is maximum when viewed from directly above in a direction perpendicular to the main surface of the lead frame, and the cross section was polished to prepare a sample for SEM observation. Here, the width of the second bond refers to the dimension in the left-right direction of the second bond 10 in FIG. 1, and the cross section polishing using the ion beam was performed in a direction perpendicular to the straight line passing through the center X of the width of the wire in FIG. 1 (along the two-dot chain line AA in FIG. 1) at a position where the width of the second bond is approximately maximum. For the obtained samples for SEM observation, the cross section of the 2nd bond was observed with an SEM, and the ratio of the width where the wire and the lead frame were in contact (L2 in Fig. 2) to the total width of the 2nd bond (L1 in Fig. 2), i.e., the adhesion rate (%) (= L2 / L1 x 100) was calculated. Three 2nd bond sections were observed and calculated, and the arithmetic average value was used.

[0099] The obtained second bonded portion was evaluated based on the bond strength (pull strength) and adhesion (adhesion rate) according to the following criteria.

[0100] Evaluation criteria: ◎◎: Adhesion rate 90% or more and pull strength 8gf or more ◎: Adhesion rate is 90% or more and pull strength is 6gf or more and less than 8gf, or pull strength is 12gf or more and adhesion rate is 80% or more and less than 90% ○: Adhesion rate is 80% or more but less than 90% and pull strength is 6gf or more but less than 12gf ×: Adhesion rate less than 80% or pull strength less than 6gf

[0101] [Second joint reliability] The bonding reliability of the second bonding portion was evaluated by a high temperature storage life test (HTSL).

[0102] A sample was wedge-bonded to the lead of the lead frame using a commercially available wire bonder, and was sealed with a commercially available thermosetting epoxy resin to prepare a sample for the joint reliability test of the 2nd joint. The lead frame was a Cu alloy lead frame with 1-3 μm Ag plating. The prepared sample for the joint reliability evaluation was exposed to an environment at a temperature of 175°C using a high-temperature thermostat. The joint life of the 2nd joint was determined by performing a pull test on the wedge joint every 500 hours, and the time when the pull strength value became 1 / 2 of the initial pull strength was used. The value of the pull strength was the arithmetic average value of the measured values ​​of 50 randomly selected wedge joints. The pull test after the high-temperature storage test was performed after removing the resin by acid treatment to expose the wedge joint. Evaluation was then performed according to the following criteria.

[0103] Evaluation criteria: ◎◎: Bonding life more than 3000 hours ◎: Bonding life 2000 hours or more but less than 3000 hours ○: Bonding life 1000 hours or more but less than 2000 hours ×: Bonding life less than 1000 hours

[0104] [Reliability of the first joint] The bonding reliability of the first bonding portion was evaluated by both a High Temperature Storage Life Test (HTSL) and a Highly Accelerated Temperature and Humidity Stress Test (HAST).

[0105] -HTSL- A sample was prepared for the bonding reliability test of the 1st bonding part by forming a 1.5 μm thick film of an alloy of Al-1.0 mass% Si-0.5 mass% Cu on a silicon substrate on a general metal frame, bonding the ball to the electrode using a commercially available wire bonder, and sealing the electrode with a commercially available thermosetting epoxy resin. The ball was formed under the conditions described in the [FAB shape] column above. The prepared sample for the bonding reliability evaluation was exposed to an environment at a temperature of 175°C using a high-temperature thermostat. The bonding life of the 1st bonding part was determined by performing a shear test on the ball bonding part every 500 hours, and the time when the shear strength value became 1 / 2 of the initial shear strength was used. The shear strength value was the arithmetic average value of the measured values ​​of 50 randomly selected ball bonding parts. The shear test after the high-temperature storage test was performed after removing the resin by acid treatment to expose the ball bonding part. Evaluation was then performed according to the following criteria.

[0106] Evaluation criteria: ◎: Bonding life more than 2000 hours ○: Bonding life 1000 hours or more but less than 2000 hours ×: Bonding life less than 1000 hours

[0107] -HAST- A sample for evaluating the bonding reliability of the 1st bonding part, which was prepared in the same manner as above, was exposed to a high-temperature and high-humidity environment at a temperature of 130°C and a relative humidity of 85% using an unsaturated pressure cooker tester, and a bias of 7V was applied. The bonding life of the 1st bonding part was determined by conducting a shear test on the ball bonding part every 48 hours, and the time when the shear strength value became half of the initial shear strength value was used. The shear strength value was the arithmetic average value of the measurements of 50 randomly selected points on the ball bonding part. The shear test was performed after removing the resin by acid treatment to expose the ball bonding part. Evaluation was then performed according to the following criteria.

[0108] Evaluation criteria: ◎: Bonding life 384 hours or more ○: Bonding life 240 hours or more but less than 384 hours ×: Bonding life less than 240 hours

[0109] [Crimp shape] The bonded shape of the 1st bonded portion (ball crushed shape) was evaluated by forming a ball using a commercially available wire bonder under the conditions described in the [FAB Shape] column above, crimping it to an electrode made 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 bad if it was elliptical or petal-like. Evaluation was then performed according to the following criteria.

[0110] Evaluation criteria: ◎: No defects ○: 1 to 5 defects (no practical problems) ×: 6 or more defects

[0111] The evaluation results of the examples and comparative examples are shown in Tables 1 and 2.

[0112] [Table 1]

[0113] [Table 2] [Explanation of symbols]

[0114] 1 Bonding wire (wire) 2. Measurement surface 10 2nd joint 50 External terminal X Wire Width Center W Wire width (wire diameter) w a Measuring surface width l a Length of the measuring surface L1 Overall width of 2nd joint L2 Width where the wire and external terminal are in close contact at the 2nd joint

Claims

1. A bonding wire comprising a core material made of Cu or a Cu alloy and a coating layer formed on a surface of the core material, the coating layer having a total concentration of Pd and Ni of 90 atomic % or more, 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, Pd concentration C at all measurement points of the coating layer Ｐｄ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｄ / C Ｎｉ When the average value of the above is X, the average value X is 0.1 or more and 35.0 or less, the total number of measurement points in the coating layer having an absolute deviation of 0.3X or less from the average value X is 50% or more of the total number of measurement points in the coating layer; A bonding wire that satisfies the following condition (A): (A) Contains one or more elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Sn, Ta, W, Os, Ir, Pt, Au, and Bi (hereinafter referred to as "first additional element"). The total concentration of the first additional element in the entire wire is 5 ppm by mass or more and 450 ppm by mass or less.

2. A bonding wire comprising a core material made of Cu or a Cu alloy and a coating layer formed on a surface of the core material, the coating layer having a total concentration of Pd and Ni of 90 atomic % or more, 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, Pd concentration C at all measurement points of the coating layer Ｐｄ (atomic %) and Ni concentration C Ｎｉ (atomic %) ratio C Ｐｄ / C Ｎｉ When the average value of the above is X, the average value X is 0.1 or more and 35.0 or less, the total number of measurement points in the coating layer having an absolute deviation of 0.3X or less from the average value X is 50% or more of the total number of measurement points in the coating layer; A bonding wire that satisfies the following conditions (A) and (B). (A) One or more elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Zn, Zr, Nb, Mo, Ru, Rh, Sn, Ta, W, Os, Ir, Pt, Au, and Bi (hereinafter referred to as "first additive element") are included, and the total concentration of the first additive element in the entire wire (however, the concentration of Au is the concentration in the core material portion) is 5 ppm by mass or more and 450 ppm by mass or less. (B) The surface of the wire contains Au, and the concentration of Au in the entire wire is 0.5 mass % or less.

3. The bonding wire according to claim 1 or 2, wherein the total number of measurement points in the coating layer having an absolute deviation from the average value X within 0.2X is 50% or more of the total number of measurement points in the coating layer.

4. For all measurement points of the coating layer, C Ｐｄ Or C Ｎｉ 3. The bonding wire according to claim 1 or 2, 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.

5. The bonding wire according to claim 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 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.

6. The bonding wire according to claim 1 or 2, comprising one or more elements (hereinafter referred to as “second additive elements”) selected from the group consisting of B, P, and Mg, and a total concentration of the second additive elements in the entire wire is 1 ppm by mass or more and 100 ppm by mass or less.

7. The bonding wire according to claim 1 or 2, further comprising one or more elements (hereinafter referred to as “third additive elements”) selected from the group consisting of Se, Te, As, and Sb, and a total concentration of the third additive element relative to the entire wire is 1 ppm by mass or more and 100 ppm by mass or less.

8. The bonding wire according to claim 1 or 2, comprising one or more elements (hereinafter referred to as “fourth additive element”) selected from the group consisting of Ga and Ge, and a total concentration of the fourth additive element with respect to the entire wire is 0.011 mass% or more and 1.5 mass% or less.

9. The bonding wire according to claim 1 or 2, comprising one or more elements (hereinafter referred to as “fifth additional element”) selected from the group consisting of In and Ag, and a total concentration of the fifth additional element with respect to the entire wire is 1 ppm by mass or more and 500 ppm by mass or less.

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