Al bonding line or Al bonding strip

Abstract

An Al bonding wire or Al bonding strip is provided that exhibits excellent high-speed temperature cycling reliability in high-speed temperature cycling tests required for next-generation SiC power semiconductors with high upper temperature limits. The Al bonding line or Al bonding band contains 3.0% by mass or more and 20.0% by mass or less Si. A closed curve representing the outer periphery of a section perpendicular to the central axis of the Al bonding line or Al bonding band is designated as S0. A closed curve of similar shape, which is 2 / 3 times that of S0, is designated as S1. A closed curve of similar shape, which is 1 / 3 times that of S0, is designated as S2. S0, S1, and S2 are configured such that their centroids coincide with the centroid of the section perpendicular to the central axis of the Al bonding line or Al bonding band. The region enclosed by S0 and S1 is designated as the surface portion, and the region enclosed by S2 is designated as the core portion. When the volume fraction of voids in the core with an equivalent sphere diameter of 1 μm or more and less than 10 μm, as determined by X-ray CT analysis, is designated as Rd, and the volume fraction of voids in the surface portion with an equivalent sphere diameter of 1 μm or more and less than 10 μm is designated as Rf, the ratio (Rf / Rd) is 0.005 or more and 0.50 or less.

Description

Technical Field

[0001] This invention relates to Al bonding lines or Al bonding strips. Furthermore, it relates to semiconductor devices obtained using Al bonding lines or Al bonding strips. Background Technology

[0002] In semiconductor devices, bonding wires (wire materials) or bonding strips (strip materials) connect electrodes formed on a semiconductor chip to electrodes on a lead frame or substrate. Power semiconductor devices primarily use bonding wires or bonding strips made of aluminum (Al). Al bonding wires typically have a diameter ranging from 100 μm to 600 μm, while Al bonding strips generally have a width ranging from 100 μm to 3000 μm and a thickness ranging from 50 μm to 600 μm. Here, Al bonding wires or Al bonding strips are collectively referred to as Al bonding materials.

[0003] In power semiconductor devices, silicon (Si) is mostly used as the semiconductor chip material, and Al-Si alloys or Al-Cu alloys are mostly used as the electrode materials formed on the semiconductor chip. In addition, power semiconductor devices using Al bonding wires or Al bonding strips are mostly used in high-power equipment such as air conditioning or solar power generation systems, as well as automotive semiconductor devices.

[0004] Regarding the bonding methods for Al bonding wires or Al bonding strips, there are first bonding with electrodes on semiconductor chips and second bonding with electrodes on lead frames or substrates, both employing wedge bonding. Wedge bonding refers to a method where ultrasonic vibration and load are applied to the Al bonding wire or Al bonding strip using a metal clamp (appliance), breaking down the surface oxide film of the Al bonding wire or Al bonding strip and the electrode material to expose a newly formed surface, thus achieving solid-state diffusion bonding. This bonding method is characterized by bonding in a solid-state state without melting the bonding materials, and is a bonding technique different from welding techniques that melt the bonding materials.

[0005] In next-generation power semiconductor devices, stable operation over extended periods is required compared to general-purpose power semiconductor devices. Power semiconductor devices operate by repeatedly switching current on and off. When current is supplied to a Si semiconductor chip via Al bonding wires or Al bonding strips, the temperature of the first junction rises. Conversely, when the current supply is stopped, the temperature of the first junction drops. Thus, during the operation of the power semiconductor, the first junction repeatedly heats up and cools down. This subjects the first junction to repeated thermal stress caused by the difference in thermal expansion between the Al bonding wires or Al bonding strips and the semiconductor chip. When using bonding materials composed solely of high-purity Al, the Al bonding wires or Al bonding strips are damaged in a short time due to thermal stress, making it difficult to meet the performance requirements of next-generation power semiconductor devices. Therefore, in next-generation power semiconductors, it is necessary to improve the junction lifetime (hereinafter also referred to as "temperature cycling reliability") accompanying the heating and cooling of the first junction.

[0006] To address the requirements for temperature cycling reliability, Al bonding wires with a primary focus on improving mechanical strength were proposed. As a method to enhance the mechanical properties of Al bonding wires, the addition of specific elements to Al was proposed.

[0007] Patent Document 1 discloses a bonding wire made of an Al alloy containing at least magnesium (Mg) and silicon (Si), wherein the combined content of Mg and Si is more than 0.03% by mass and less than 0.3% by mass. This patent document discloses a high-strength effect achieved through solid solution strengthening of Mg or Si, or an effect of inhibiting crack propagation through precipitated magnesium silicide (Mg2Si), thereby delaying the decrease in bonding strength of the first joint during cold temperature cycling tests in a temperature range of 70°C to 120°C.

[0008] Patent Document 2 discloses a bonding wire characterized by being composed of an alloy containing 0.01 to 0.2% by mass of iron (Fe), 1 to 20 ppm by mass of silicon (Si), and the remainder being Al with a purity of 99.997% by mass or higher. The Fe solid solution content is 0.01 to 0.06%, the Fe precipitation is less than 7 times the Fe solid solution content, and the average crystal grain size is 6 to 12 μm, forming a fine microstructure. This patent document discloses a method to uniformly disperse intermetallic compound particles of Fe and Al within Al, thereby improving the mechanical strength of the matrix, and further refining the recrystallized particles, thereby suppressing the decrease in the bonding strength of the first bonding portion during thermal shock testing in a temperature range of -50°C to 200°C.

[0009] Patent document 3 discloses a bonding wire made by melting an Al-Si alloy containing 0.1 to 5% by mass of silicon (Si), with the remainder consisting of Al and impurities, then spraying and rapidly cooling the melted alloy to form a fine wire. This patent document discloses that by rapidly cooling the molten Al-Si alloy and dispersing the Si finely and uniformly, the mechanical strength is improved.

[0010] Prior art literature

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 2014-131010

[0013] Patent Document 2: Japanese Patent Application Publication No. 2014-129578

[0014] Patent Document 3: Japanese Patent Application Publication No. 59-57440 Summary of the Invention

[0015] The technical problem that the invention aims to solve

[0016] As mentioned above, next-generation power semiconductor devices are required to withstand longer operating times compared to general-purpose power semiconductor devices. During operation, the temperature of the first junction repeatedly rises and falls. As a result, the Al bonding wires or Al bonding strips, due to their larger coefficient of linear expansion than the semiconductor chip, experience thermal stress at the first junction caused by the difference in their coefficients of linear expansion, potentially leading to fatigue failure. Temperature cycling testing is one method to accelerate the evaluation of the junction's lifespan (temperature cycling reliability) during the temperature rise and fall associated with this first junction. Al bonding wires or Al bonding strips used in next-generation power semiconductors are required to exhibit excellent temperature cycling reliability in temperature cycling tests.

[0017] However, in the case of using Al bonding wires with high strength by adding Si, as disclosed in Patent Documents 1-3, the following technical problem was identified in temperature cycling tests envisioned for use in next-generation power semiconductor devices: cracks propagate faster in Al alloy electrodes with lower strength than Al bonding wires, making it difficult to obtain stable and good temperature cycling reliability.

[0018] On the other hand, existing temperature cycling tests (hereinafter also referred to as "TCT (Temperature Cycle Test)") can be easily conducted using commercially available testing equipment. However, since the temperature change rate in TCT is relatively slow, there are concerns about discrepancies with the faster temperature change rate during the operation of power semiconductor devices. Therefore, recently, in order to approximate actual usage conditions, high-speed temperature cycling tests (hereinafter also referred to as "high-speed TCT") that accelerate the temperature change rate are being investigated. Regarding the temperature change rate, conventional TCTs have a rate of, for example, around 10°C / minute, while in high-speed TCTs, the temperature change is performed at a high speed, for example, around 200°C / minute. Regarding the reliability evaluation of Al bonding wires or Al bonding strips, the inventors have confirmed that even Al bonding wires or Al bonding strips whose reliability does not decrease when evaluated by existing TCTs sometimes experience a decrease in bonding strength and a reduction in bonding life when evaluated by high-speed TCTs. Therefore, there is a need for Al bonding wires or Al bonding strips that exhibit good bonding reliability and provide excellent temperature cycling reliability in high-speed TCTs, which are more stringent tests that approximate actual usage conditions. Hereinafter, the temperature cycling reliability in high-speed TCT is sometimes referred to as "high-speed temperature cycling reliability".

[0019] Furthermore, the use of silicon carbide (SiC), with its high heat resistance, is predicted to develop in next-generation power semiconductor devices that will replace silicon (Si), which has been the mainstream technology so far. In the interconnection of SiC power semiconductors, more stringent high-speed temperature cycling tests are required than those currently available. For example, the temperature range for high-speed temperature cycling tests of Si semiconductors is -40°C to 150°C, while in contrast, SiC semiconductors require high-speed temperature cycling reliability in the range of -40°C to 175°C due to the harsh temperature conditions. Moreover, as for next-generation SiC power semiconductors used in high-output applications that utilize the heat resistance of SiC, excellent high-speed temperature cycling reliability is required even under more stringent test conditions with an upper limit temperature of 185°C. Here, if the upper limit temperature of the high-speed TCT increases from 175°C to 185°C, the temperature difference in thermal cycling increases by 10°C, and the aforementioned difference in thermal expansion at the junction of Al bonding lines or Al bonding bands widens, accelerating fatigue failure. In addition, due to the high temperature, the bonding state of the interface before the test becomes a cause of fatigue failure, so it is necessary to improve the initial bonding state.

[0020] The present invention was made in view of the above-mentioned problems, and its object is to provide Al bonding wires or Al bonding strips that exhibit excellent high-speed temperature cycling reliability in high-speed temperature cycling tests with high upper temperature limits required for next-generation SiC power semiconductors.

[0021] Technical means for solving technical problems

[0022] The inventors conducted in-depth research on the aforementioned technical problems and discovered that the following Al bonding line or Al bonding strip can solve these problems. Based on this insight, further research was conducted, resulting in the present invention. Specifically, an Al bonding line or Al bonding strip containing 3.0% by mass to 20.0% by mass of Si, wherein the volume fraction of voids with an equivalent sphere diameter of 1 μm or more and less than 10 μm in the core, as determined by X-ray CT (Computed Tomography), is set as Rd, and the volume fraction of voids with an equivalent sphere diameter of 1 μm or more and less than 10 μm in the surface portion is set as Rf, and the ratio (Rf / Rd) is within a specific range.

[0023] That is, the present invention includes the following.

[0024] <1>

[0025] An Al bonding wire or Al bonding strip is an Al bonding wire or Al bonding strip containing 3.0% by mass and 20.0% by mass of Si.

[0026] S0 is defined as the closed curve representing the outer periphery of a section perpendicular to the central axis of the Al joint line or Al joint band; S1 is defined as a closed curve of a similar shape that is 2 / 3 times the size of S0; and S2 is defined as a closed curve of a similar shape that is 1 / 3 times the size of S0. S0, S1, and S2 are configured such that their centroids coincide with the centroid of the section perpendicular to the central axis of the Al joint line or Al joint band. The area enclosed by S0 and S1 is designated as the surface portion, and the area enclosed by S2 is designated as the core portion.

[0027] When the volume fraction of voids in the core with an equivalent sphere diameter of 1 μm or more but less than 10 μm, as determined by X-ray CT (Computed Topograpy), is defined as Rd, and the volume fraction of voids in the surface portion with an equivalent sphere diameter of 1 μm or more but less than 10 μm is defined as Rf, the ratio (Rf / Rd) is 0.005 or more but less than 0.50.

[0028] <2>

[0029] like <1> The Al bonding line or Al bonding strip,

[0030] When the number of Si phases with an equivalent circle diameter of 0.5 μm to 0.8 μm in the L section (including the section in the direction of the central axis) is defined as Ns, and the number of Si phases with an equivalent circle diameter of 0.5 μm or more in the L section is defined as Nc, the ratio of Ns to Nc [Ns / Nc×100(%)] is 30% to 95%.

[0031] <3>

[0032] like <1> or <2> The Al bonding line or Al bonding strip,

[0033] It also contains one or more of Sr, Na, Eu, and P in total amounts of more than 10 ppm by mass and less than 800 ppm by mass.

[0034] <4>

[0035] like <1> ~ <3> Any of the Al bonding lines or Al bonding strips described in any one of them,

[0036] It also contains one or more of Ni, Ti, Fe, and Mg in a total amount of more than 100 ppm by mass and less than 1500 ppm by mass.

[0037] <5>

[0038] like <1> ~ <4> Any of the Al bonding lines or Al bonding strips described in any one of them,

[0039] The total concentration of elements other than Al, Si, Sr, Na, Eu, P, Ni, Ti, Fe, and Mg in the Al junction line or Al junction band is less than 0.5% by mass.

[0040] <6>

[0041] like <2> ~ <5> Any of the Al bonding lines or Al bonding strips described in any one of them,

[0042] The equivalent circle diameter and number of Si phases were determined using a SEM-EDS-EBSD instrument.

[0043] <7>

[0044] like <1> ~ <6> Any of the Al bonding lines or Al bonding strips described in any one of them,

[0045] It is used in semiconductor devices.

[0046] <8>

[0047] A semiconductor device, including as <1> ~ <7> Any of the Al bonding lines or Al bonding strips described herein.

[0048] Invention Effects

[0049] According to the present invention, it is possible to provide Al bonding wires or Al bonding strips that exhibit excellent high-speed temperature cycling reliability in high-speed temperature cycling tests with high upper temperature limits required for next-generation SiC power semiconductors, and semiconductor devices obtained using Al bonding wires or Al bonding strips. Attached Figure Description

[0050] Figure 1 This is a schematic diagram illustrating the measurement surface (inspection surface) used to determine the small-diameter ratio of the Si phase for Al junction lines. The measurement surface is a cross-section (L-section) that includes the central axis of the Al junction line.

[0051] Figure 2 This is a schematic diagram illustrating the measurement surface (inspection surface) used to determine the small diameter ratio of the Si phase in Al-bonded bands. The measurement surface is a cross-section (L-section) that includes the central axis of the Al-bonded band.

[0052] Figure 3 This is an example of a brightness histogram created in X-ray CT analysis to determine the brightness of voids or outer spaces and matter.

[0053] Figure 4 This is an example of a graph showing the quantity distribution of the equivalent circle diameter of the Si phase in section L.

[0054] Figure 5 This is a schematic diagram showing S0, S1, and S2 in the case of Al bonding lines, as well as the relationship between the core, intermediate part, and surface part.

[0055] Figure 6 This is a schematic diagram showing S0, S1, and S2 in the case of Al bonding, as well as the relationship between the core, intermediate part, and surface part. Detailed Implementation

[0056] Hereinafter, the present invention will be described in detail according to preferred embodiments. Reference is sometimes made to the accompanying drawings, but these drawings are only intended to schematically illustrate the shape, size, and arrangement of the constituent elements to a degree that allows for understanding of the invention. The present invention is not limited to the following embodiments and examples, and can be implemented in any manner without departing from the scope of protection of the present invention and its equivalents.

[0057] [Al bonding line or Al bonding strip]

[0058] The Al bonding wire or Al bonding strip of the present invention is an Al bonding wire or Al bonding strip containing 3.0% by mass or more and 20.0% by mass of Si, characterized in that...

[0059] S0 is defined as the closed curve representing the outer periphery of a section perpendicular to the central axis of the Al joint line or Al joint band; S1 is defined as a closed curve of a similar shape that is 2 / 3 times the size of S0; and S2 is defined as a closed curve of a similar shape that is 1 / 3 times the size of S0. S0, S1, and S2 are configured such that their centroids coincide with the centroid of the section perpendicular to the central axis of the Al joint line or Al joint band. The area enclosed by S0 and S1 is designated as the surface portion, and the area enclosed by S2 is designated as the core portion.

[0060] When the volume fraction of voids with an equivalent sphere diameter of 1 μm or more but less than 10 μm in the core, as determined by X-ray CT (Computed Tomograph) analysis, is defined as Rd, and the volume fraction of voids with an equivalent sphere diameter of 1 μm or more but less than 10 μm in the surface portion is defined as Rf, the ratio (Rf / Rd) (hereinafter also referred to as "void tilting rate") is 0.005 or more and 0.50 or less.

[0061] The Al bonding wires or Al bonding bands of the present invention contain 3.0% to 20.0% by mass of Si, and have an Al phase in which Si is dissolved in Al and a Si phase formed by Si crystallization or precipitation. Here, the Al phase may also contain other additive elements besides Si dissolved in it. Furthermore, the Si phase is a general term for Si crystallization and Si precipitates. Si crystallization is a coarse phase formed from the melt during solidification and has a size of about 1 to 25 μm. In contrast, Si precipitates are formed in a solid state and have a smaller size of about 0.1 to several μm. The coefficient of linear expansion of the Si phase is smaller than that of Al, which helps to reduce the difference in the coefficient of linear expansion between the Al bonding wires or Al bonding bands and the semiconductor chip, thereby reducing thermal stress and improving the reliability of high-speed temperature cycling.

[0062] In this invention, "wire" and "strip" are not classified by shape, but by their manufacturing method. That is, "wire" refers to "connecting material manufactured by drawing using a die," and "strip" refers to "connecting material manufactured by a rolling process." Generally, "wire" has a circular cross-sectional shape, and generally, "strip" has a rectangular or approximately rectangular cross-sectional shape.

[0063] That is, the central axis of the Al junction line, and the cross section (L section) containing the central axis direction, as shown below. Figure 1 As shown. Figure 1 The example shown is an Al joint line with a circular cross-sectional shape. However, in the case of an Al joint strip with a rectangular or approximately rectangular cross-sectional shape having a width W and a thickness T, the central axis refers to the axis that is the center of the width W and passes through the center of the thickness T. In addition, the L section refers to the section that includes the central axis in the direction of the central axis and is perpendicular to the direction of the width W. Figure 2Specifically, the central axis of the Al bonding strip and the cross section (L section) containing the central axis direction are as follows: Figure 2 As shown. When machining the cross-section to expose the L-section of the Al joint line, it is sometimes deviated from the central axis of the Al joint line. In this case, if the length of the L-section in the direction perpendicular to the central axis is more than 90% of the diameter of the Al joint line, it can be regarded as a cross-section including the central axis.

[0064] -Void tilting rate-

[0065] As mentioned above, when bonding materials composed solely of high-purity Al are used in temperature cycling tests, cracks propagate rapidly within the lines or bands, leading to reduced temperature cycling reliability. It has been confirmed that Al alloys with high Si concentrations can reduce the thermal expansion of the lines or bands, thus improving temperature cycling reliability. It has also been confirmed that in high-speed TCTs approaching real-world operating conditions, even Al bonding lines or bands that did not exhibit reduced reliability during conventional TCT evaluations sometimes experience decreased bond strength and shortened bond life. This is attributed to the increased thermal stress at the bonding joint due to the accelerated temperature change rate in high-speed TCTs. Furthermore, if the upper limit temperature of high-speed TCTs reaches high temperatures such as 185°C, the bond strength is prone to further reduction. To meet the high-speed temperature cycling reliability requirements of next-generation power semiconductor devices with high heat resistance, such as SiC, further improvements in high-speed temperature cycling reliability at high temperatures are needed.

[0066] As the upper limit temperature of high-speed temperature cycling tests increases, the thermal expansion difference between the Al bonding line / band and the SiC semiconductor widens, leading to increased thermal strain at the line / band junction. Forming a Si phase that reduces thermal expansion within the line / band of an Al alloy with a high Si concentration (hereinafter referred to as "high-concentration Al-Si alloy") reduces the overall thermal strain of the line / band, which helps suppress crack formation within the line / band (hereinafter referred to as "intra-line cracks"). However, when observing the defect patterns of high-speed TCTs with an upper limit temperature of 185°C, it was found that crack formation in the Al-based electrode film, which is the bonding target (hereinafter referred to as "intra-electrode cracks") is a cause of the defects. Since the Al-based electrode film is softer than the high-concentration Al-Si alloy line / band, the thermal stress of the high-temperature high-speed TCT propagates to the electrode, causing problems with the development of intra-electrode cracks. Because the defect mechanism of high-speed TCTs changes from general intra-line cracks to intra-electrode cracks, material design focusing on improving intra-electrode cracks is required.

[0067] In order to solve the above-mentioned problems, the inventors conducted in-depth research and discovered that forming tiny voids in high-concentration Al-Si alloy lines or strips, and thus creating an inclined structure in which the distribution of void volume in the lines or strips changes from the surface region to the central region, helps to suppress internal electrode cracks in high-temperature, high-speed TCT tests.

[0068] Specifically, the inventors discovered voids on the order of several μm in Al-Si alloy wires or strips, primarily forming around the Si phase. This is believed to be due to the formation of these voids during the wire drawing or rolling processes in the fabrication of Al-Si alloy wires or strips. During these processes, the hard Si phase inhibits deformation, while the Al phase surrounding the Si phase readily undergoes plastic deformation, thus allowing voids to form around the Si phase. Furthermore, the regions containing these voids effectively mitigate stress and strain within the wire or strip under high-speed TCT temperature changes. The close proximity of the Si phase and voids further enhances these effects, beyond the significant reduction in thermal expansion due to the Si phase's high thermal expansion reduction. The voids also buffer the thermal stress accompanying temperature changes, further strengthening the reduction in thermal expansion and stress. If the upper limit of the high-speed temperature cycling test reaches high temperatures, the difference in thermal expansion between the wire or strip and the semiconductor widens; therefore, the function of the voids in buffering thermal stress becomes even more crucial at high temperatures.

[0069] Furthermore, the smaller size of the voids locally improves strain propagation, thus enhancing the effect of mitigating crack propagation within the electrode. If the voids grow large or develop into cracks, they can become a cause of wire breakage during the wire drawing or rolling process. Therefore, regarding voids related to joint reliability, X-ray CT analysis was used to focus on voids with an equivalent sphere diameter of 1 μm or more but less than 10 μm.

[0070] By forming a tilted structure with fewer voids on the surface of the line or strip compared to the core, it is advantageous under drastic temperature changes, resulting in a high degree of improvement in the bonding lifetime of high-speed TCT. This is believed to be because, with fewer voids in the surface region, the reduced thermal expansion and strain effects of the Si phase propagate more efficiently to the electrode side of the bonding interface. The detailed mechanism is unclear, but it is speculated that the void portions absorb thermal strain during rapid temperature changes.

[0071] Specifically, the cross-section is divided into three parts, distinguishing the core, middle, and surface regions from the center, and the volume fraction of voids in each region is compared. That is, a closed curve representing the outer periphery of the cross-section perpendicular to the central axis of the Al joint line or Al joint band is designated as S0; a closed curve with a similar shape that is 2 / 3 times that of S0 is designated as S1; and a closed curve with a similar shape that is 1 / 3 times that of S0 is designated as S2. S0, S1, and S2 are arranged such that their centroids coincide with the centroid of the cross-section perpendicular to the central axis of the Al joint line or Al joint band. The region enclosed by S0 and S1 is designated as the surface region, and the region enclosed by S2 is designated as the core region. Here, "closed curve S1 with a similar shape that is 2 / 3 times that of S0" means that S0 and S1 have a similarity ratio of 3:2. Similarly, "closed curve S2 with a similar shape that is 1 / 3 times that of S0" means that S0 and S2 have a similarity ratio of 3:1. Figure 5 This illustrates the relationship between S0, S1, and S2, and the core, intermediate portion, and surface portion in the case of an Al bonding line. In the case of an Al bonding line, if the radius of the section perpendicular to the central axis of the Al bonding line is defined as R, then the circular region inside the concentric circles of radius 1 / 3R is the core, and the hollow circular region surrounded by concentric circles of radius 2 / 3R and radius R is the surface portion. Furthermore, Figure 6 This indicates the relationship between S0, S1, and S2, as well as the core, intermediate, and surface portions, in the case of Al bonding.

[0072] Furthermore, when the volume fraction of voids in the core with an equivalent sphere diameter of 1 μm or more and less than 10 μm, as determined by X-ray CT analysis, is set as Rd, and the volume fraction of voids in the surface portion with an equivalent sphere diameter of 1 μm or more and less than 10 μm is set as Rf, the void tilt ratio (Rf / Rd) is 0.005 or more and 0.50 or less.

[0073] Here, the calculation of the void volume fraction is first performed using X-ray CT analysis to calculate the volume Vs of voids with an equivalent sphere diameter of 1 μm or more but less than 10 μm, the total volume Vg of all void sizes, and the volume Vm of the material. Next, the ratio (Vs / (Vg+Vm)) obtained by dividing Vs by the total volume of voids and material (Vg+Vm) is calculated as the void volume fraction. Following this method, the void volume fractions Rd and Rf of the core and surface portions are calculated respectively.

[0074] By achieving a void tilt ratio (Rf / Rd) of 0.005 to 0.50, excellent high-speed temperature cycling reliability is exhibited even in high-temperature cycling tests with high upper temperature limits. The reasons for this are explained below. A void tilt ratio (Rf / Rd) of 0.005 or higher prevents the adverse effects caused by an excessive difference in void volume fraction between the surface and core regions, and also facilitates industrial manufacturing. Furthermore, a void tilt ratio (Rf / Rd) of 0.50 or lower sufficiently increases the difference in void volume fraction between the surface and core regions, thereby fully achieving the improved performance in high-speed temperature cycling tests with high upper temperature limits.

[0075] Furthermore, the inventors have confirmed that the Al bonding line or Al bonding band of the present invention exhibits an excellent shear strength ratio. In evaluating the bonding strength of the first joint, it is difficult to accurately evaluate the bonding strength of high-strength materials when the bonding line or bonding band fractures internally during a shear test. Regarding this, as a method to evaluate the bonding strength while suppressing the influence of material strength, it is considered to determine the shear strength by standardizing it with the material strength. The inventors investigated the relationship between material strength and bonding strength, and found that the ratio (SH / PS, hereinafter referred to as "shear strength ratio") obtained by dividing the shear strength (SH) by the 0.2% yield strength (PS) of the tensile test is effective. If the main factors governing the apparent shear strength of the first joint are decomposed, they can be divided into net bonding strength and the deformation resistance of the line or band. The latter deformation resistance is related to the yield strength at which the line or band yields and begins plastic deformation during a shear test. Therefore, in order to evaluate the net bonding strength, the influence of the yield strength of the line or band is considered to be removed from the apparent shear strength. This yield strength is the strength value when the elongation of the tensile test is 0.2%, i.e., the 0.2% yield strength.

[0076] Specifically, the inventors discovered that by using a shear strength ratio (SH / PS) normalized to 0.2% of the yield strength (PS), the bond condition can be evaluated more accurately. A high shear strength ratio indicates a good bond at the joint interface. Using the shear strength ratio (SH / PS) as an indicator, lines or strips with a high shear strength ratio can achieve both good bond strength and reduced bond damage, thereby exhibiting excellent performance in temperature cycling reliability.

[0077] From the viewpoint of exhibiting excellent high-speed temperature cycling reliability even in high-speed temperature cycling tests with high upper limit temperatures, and from the viewpoint of exhibiting excellent shear strength ratio, the lower limit of the void tilt ratio (Rf / Rd) is 0.005 or more, preferably 0.008 or more, 0.010 or more, 0.015 or more, 0.020 or more, 0.030 or more, or 0.050 or more, more preferably 0.080 or more, or 0.10 or more, further preferably 0.12 or more, or 0.15 or more, and particularly preferably 0.18 or more, or 0.20 or more. From the viewpoint of exhibiting excellent high-speed temperature cycling reliability even in high-speed temperature cycling tests with high upper limit temperatures, and from the viewpoint of exhibiting excellent shear strength ratio, the upper limit of the void tilt ratio (Rf / Rd) is 0.50 or less, preferably 0.48 or less, or 0.45 or less, more preferably 0.42 or less, or 0.40 or less, further preferably 0.38 or less, or 0.35 or less, and particularly preferably 0.32 or less, or 0.30 or less.

[0078] -Si concentration-

[0079] A Si concentration in the range of 3.0% by mass to 20.0% by mass helps to improve the shear strength ratio and reduce the thermal strain of the joint, thereby improving high-speed temperature cycling reliability. Specifically, a Si concentration of 3.0% by mass or more can significantly improve the high-speed temperature cycling reliability. Furthermore, regarding the upper limit of the Si concentration, with advancements and optimizations in equipment / conditions for manufacturing and bonding wires, etc., adverse conditions such as wire breakage during processing, deterioration of surface properties, reduction in initial bond strength due to hardening, or damage to semiconductor chips can be suppressed, and higher values ​​are permissible. However, a Si concentration of 20.0% by mass or less effectively suppresses these adverse conditions and improves the shear strength ratio. From the viewpoint of obtaining good high-speed temperature cycling reliability, the Si concentration in the Al bonding wire or Al bonding strip of the present invention is 3.0% by mass or more, preferably 3.5% by mass or more, more preferably 4.0% by mass or more, and even more preferably 4.2% by mass or more, 4.4% by mass or more, 4.5% by mass or more, 4.6% by mass or more, 4.8% by mass or more, or 5.0% by mass or more. Furthermore, from the viewpoint of effectively suppressing adverse conditions such as reduced initial bonding strength and damage to the semiconductor chip caused by hardening, and improving the shear strength ratio, the Si concentration in the Al bonding wire or Al bonding strip of the present invention is 20.0% by mass or less, preferably 19.0% by mass or less, 18.0% by mass or less, 17.0% by mass or less, 16.0% by mass or less, 15.0% by mass or less, 14.5% by mass or less, 14.0% by mass or less, 13.5% by mass or less, 13.0% by mass or less, or 12.5% ​​by mass or less. Moreover, if the hardness of the Al bonding wire or Al bonding strip is high, damage to the semiconductor chip is easily generated during the first bonding process depending on the bonding conditions of ultrasonic vibration and load. From the viewpoint of obtaining good bonding strength under a wider range of bonding conditions, the Si concentration in the Al bonding line or Al bonding strip of the present invention is more preferably 12.0% by mass or less, further preferably 11.5% by mass or less or 11.0% by mass or less, and particularly preferably 10.8% by mass or less, 10.6% by mass or less, 10.5% by mass or less, 10.4% by mass or less, 10.2% by mass or less or 10.0% by mass or less.

[0080] In the concentration analysis of elements contained in the Al bonding lines or Al bonding bands of the present invention, for example, an ICP (Inductively Coupled Plasma) luminescence spectrophotometer or an ICP mass spectrometer can be used. When elements such as oxygen and carbon, pollutants from the atmosphere, are adsorbed on the surface of the Al bonding lines or Al bonding bands, it is effective to clean them with acid or alkali according to the adsorbed substances before analysis.

[0081] -Analysis of the gaps in X-ray CT-

[0082] In this invention, the void tilt ratio (Rf / Rd) is determined using X-ray CT analysis. X-ray CT analysis is excellent for non-destructively observing voids in materials, and by performing three-dimensional image analysis based on this data, minute voids in metals can be observed with high precision. The following example illustrates an analytical method for measuring the voids in an Al bonding wire with a diameter of 300 μm. The analytical conditions are not limited to this; appropriate analytical conditions can be selected depending on the apparatus and the sample. For example, a 3DX X-ray microscope, "Xradia 520 Versa" (manufactured by ZEISS), can be used as an X-ray CT apparatus. The main measurement conditions in X-ray CT are as follows: the X-ray voltage can be set to 40 kV, the X-ray output to 3 W, the wavelength limiting filter to LE1, and the magnification lens to 4x. Under these conditions, a transmission image with a transmittance of 30% to 70% can be obtained. To observe minute voids, the size of each pixel is approximately 0.7 μm / pixel, and the measurement field of view can measure an area of ​​approximately 700 μm × 700 μm × 700 μm. The sample is approximately 10 mm long. With the end of the sample fixed, X-rays can be transmitted around the sample's axis at a 360-degree rotation angle to measure CT projection images. After obtaining CT projection images at all angles, reconstruction processing, such as center offset processing, is performed to obtain three-dimensional image data.

[0083] Next, the 3D image data is analyzed using image analysis software. Avizo Inspection can be used as the image analysis software. Specifically, a brightness histogram is created using the measurement data. Figure 3 A threshold is set for the brightness value corresponding to the midpoint between two peak positions of the void or outer space and the material. Image data regions with brightness lower than the threshold are identified as voids or outer spaces (the environment surrounding the sample). Next, for the identified voids and outer spaces, a process is performed to select regions of the outer space and remove them from the image data region. This allows the identification of image data containing voids in the material within the measurement area of ​​the sample. Then, through the same process, image data with brightness higher than the threshold are identified as image data related to the material. This "material" is a substance having mass and volume, and in the Al bonding line or Al bonding band of the present invention, it includes Al, Si, the first element group, the second element group and other elements, as well as their alloys, oxides, intermetallic compounds, etc. Furthermore, in the X-ray CT analysis of the present invention, pixels showing brightness higher than the aforementioned threshold are considered to contain material.

[0084] The image data of the voids and material obtained in this way are analyzed. The method for calculating the volume fraction of voids with an equivalent sphere diameter of 1 μm or more but less than 10 μm is explained in detail. Using image analysis software, the total volume Vs of voids with an equivalent sphere diameter of 1 μm or more but less than 10 μm, the total volume Vg of voids of all sizes, and the volume Vm of the material are calculated. The ratio (Vs / (Vg+Vm)) obtained by dividing Vs by the total volume of voids and material (Vg+Vm) is taken as the void volume fraction. Based on this method, the volume fractions Rd and Rf of the voids in the core and surface are calculated respectively.

[0085] Distribution of the equivalent circle diameter of the Si phase in section L-

[0086] In high-speed TCT with high upper temperature limits, from the viewpoint of obtaining excellent high-speed temperature cycling reliability even with longer cycle numbers, when the number of Si phases with an equivalent circle diameter of 0.5 μm or more and 0.8 μm or less in the L-section of the Al bonding line or Al bonding band is set as Ns, and the number of Si phases with an equivalent circle diameter of 0.5 μm or more in the L-section is set as Nc, the ratio of Ns to Nc [Ns / Nc×100(%)] (hereinafter also referred to as "small diameter ratio of Si") is 30% or more and 95% or less. The lower limit of the small diameter ratio of Si [Ns / Nc×100(%)] is preferably 32% or more, 35% or more, 38% or more, 40% or more, 42% or more or 45% or more, more preferably 48% or more, further preferably 50% or more or 52% or more, and particularly preferably 55% or more or 60% or more. The upper limit of the small diameter ratio of Si [Ns / Nc×100(%)] is preferably 92% or less, 90% or less, 88% or less, or 85% or less, more preferably 82% or less or 80% or less, further preferably 78% or less or 75% or less, and particularly preferably 72% or less or 70% or less. In one embodiment, the small diameter ratio of Si [Ns / Nc×100(%)] is preferably 40% or more and 90% or less.

[0087] The reasons for emphasizing the proportion of Si phases with an equivalent circle diameter of 0.5 μm to 0.8 μm are as follows: Firstly, since the volume of Si phases with an equivalent circle diameter of 0.5 μm or more is sufficiently large, the effect of reducing thermal expansion can be sufficiently achieved. Secondly, from the viewpoint of analytical accuracy of current EDS and EBSD analytical apparatuses, targeting Si phases with an equivalent circle diameter of 0.5 μm or more is appropriate. On the other hand, in Si phases with an equivalent circle diameter of 0.8 μm or less, the stress and strain near the interface caused by the Si phase become sufficiently uniform. Furthermore, the reasons for achieving excellent high-speed temperature cycling reliability in high-speed TCT, even with longer cycle numbers, by having a Si phase small diameter ratio [Ns / Nc×100(%)] ranging from 30% to 95% are as follows: Firstly, when the Si phase small diameter ratio is 30% or more, the presence of Si phases with small equivalent circle diameters is sufficient, the distribution of thermal strain becomes uniform, and the high-speed temperature cycling reliability is stabilized. On the other hand, when the small diameter ratio of the Si phase is 95% or less, the total volume of the Si phase increases, which can maintain a high level of effectiveness in reducing the overall thermal expansion of the bonding region and significantly enhance the effect of improving high-speed temperature cycling reliability. In one embodiment, when the porosity ratio (Rf / Rd) of the Al bonding line or Al bonding strip of the present invention is 0.005 or more and 0.50 or less, the Al bonding line or Al bonding strip exhibits excellent high-speed temperature cycling reliability in a high-speed temperature cycling test with 10,000 cycles. However, when the small diameter ratio of the Si phase in the Al bonding line or Al bonding strip is 30% or more and 95% or less, the Al bonding line or Al bonding strip exhibits excellent high-speed temperature cycling reliability even in a high-speed temperature cycling test with 13,000 cycles.

[0088] Here, the Si phases are formed in a granular shape, and it is confirmed that the number of Si phase particles has a significant impact on the thermal strain at the interface. Therefore, the ratio of the number of Si phase particles can be used to determine high-speed temperature cycling reliability. On the other hand, the influence of coarse particles in the particle area is overestimated, making it difficult to accurately evaluate their correlation with high-speed temperature cycling reliability.

[0089] -Methods for determining the equivalent circle diameter of the Si phase and calculating the minor diameter ratio-

[0090] This paper describes a method for determining the equivalent circle diameter of the Si phase in the L-section of an Al junction line or Al junction band. The equivalent circle diameter of the Si phase in the L-section can be determined using a SEM-EDS-EBSD apparatus. Specifically, a method can be used that combines information on Al and Si concentrations obtained by SEM-EDS (Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy) with information on crystal orientation obtained by Electron Backscattered Electron Diffraction (EBSD). More specifically, in the measurement area where the L-section of the Al junction line or Al junction band is used as the inspection plane, the concentrations of Al and Si using EDS and the crystal orientation analysis using EBSD are performed simultaneously. Then, using the analysis software attached to the apparatus, the Al and Si phases are separated and extracted from the EDS measurement results. Specifically, it is preferable to utilize the Chi Scan function of the analysis software OIM Data Collection or OIM Analysis (both manufactured by TSLSolutions) attached to the FE-SEM (Field Emission-Scanning Electron Microscope) device. Then, for the region identified as the Si phase, the crystal orientation can be analyzed using the analysis software attached to the device. If the orientation difference between the measurement points is 15° or more, it is determined to be a grain boundary and the equivalent circle diameter is calculated. In the process of calculating the small diameter ratio of Si, the calculation excludes the parts where the crystal orientation cannot be measured or the parts where the orientation analysis is unreliable, although it can be measured. Therefore, in one embodiment, the small diameter ratio of the Si phase in the L section of the Al bonding line or Al bonding band of the present invention is calculated by the following steps (1) to (3).

[0091] (1) The L-section of the Al bonding line or Al bonding band is used as the inspection surface, and the concentration of Al and Si is determined using EDS and the crystal orientation is determined using EBSD.

[0092] (2) Using chemical-assisted scanning, Al and Si are separated and extracted. Specifically, based on the EDS measurement results of Si, a tolerance equivalent to the threshold of Si is set, thereby enabling the separation and identification of Al and Si. Using the crystallization information of Al and Si in the material file, the crystal orientation can be analyzed.

[0093] (3) For regions identified as Si phase, analyze the crystal orientation. If the orientation difference between measurement points is 15° or more, it is identified as a grain boundary, and the equivalent circle diameter of each grain is calculated. The total number of Si phase particles Nc is calculated by summing the number of grains identified as Si phase. Here, Si phases with an equivalent circle diameter of 0.5 μm or more are considered. Considering the analytical precision of current ESD and EBSD analysis devices, fine materials smaller than 0.5 μm are excluded from the scope. In addition, the number Ns of Si phases in the range of equivalent circle diameter of 0.5 μm to 0.8 μm is summed. Then, the ratio of Ns to Nc [Ns / Nc×100(%)] (small diameter ratio of Si phase) is calculated.

[0094] In step (2) above, the tolerance (%) can be set within the range of 20% to 40%, and in the standard analysis of the L-section of Al bonding line or Al bonding band, it is preferable to compare it with about 30%. Further explanation is provided regarding the step of adjusting this tolerance. Preferably, the tolerance value is selected or confirmed in a manner equivalent to the shape and size of the Si phase identified from the EDS image of Si elemental concentration analyzed by two-dimensional EDS, using the chemical-assisted scanning function.

[0095] In this invention, the small diameter ratio of the Si phase is set as the average (arithmetic mean) of the orientation ratios obtained from three or more measurements. When selecting the measurement area, from the viewpoint of ensuring the objectivity of the measurement data, it is preferable to obtain test samples from the Al bonding line or Al bonding band of the object being measured at intervals of 50 cm or more along the central axis direction of the Al bonding line or Al bonding band for measurement. Furthermore, in this invention, regarding the measurement area for crystal orientation using the EBSD method, it is preferable that the length of the Al bonding line or Al bonding band along the central axis direction is 300 μm or more and less than 800 μm, with the entire Al bonding line or Al bonding band extending in a direction perpendicular to the central axis of the Al bonding line or Al bonding band. However, in cases where the size is large and it is difficult to measure the entire area, adjustments can be made within a range of less than 600 μm.

[0096] An example of the measurement results is shown below. Figure 4 The horizontal axis represents the equivalent circle diameter of Si, with each interval represented by a width of 0.1 μm. The vertical axis represents the number of particles. A double-arrow line indicates the range from 0.5 μm to 0.8 μm, where the particle number ratio [Ns / Nc×100(%)] is 50%. High-speed temperature cycling tests confirmed that even when the maximum temperature was increased to 185°C, the strength reduction was minimal, demonstrating good high-speed temperature cycling reliability.

[0097] Addition of Sr, Na, Eu, and P-

[0098] The Al bonding wire or Al bonding strip of the present invention may also contain any one or more of Sr, Na, Eu, and P (hereinafter also referred to as "first element group"). The total concentration of the first element group can be 0 ppm by mass, preferably 1 ppm or more by mass, more preferably 3 ppm or more by mass, further preferably 5 ppm or more by mass, particularly preferably 8 ppm or more by mass, or 10 ppm or more by mass. The upper limit of the total concentration of the first element group is preferably 10,000 ppm or less by mass or 8,000 ppm or less by mass, more preferably 5,000 ppm or less by mass or 3,000 ppm or less by mass, further preferably 2,000 ppm or less by mass or 1,000 ppm or less by mass, and particularly preferably 900 ppm or less by mass or 800 ppm or less by mass. In one embodiment, the total concentration of the first element group is preferably 10 ppm or more by mass or 800 ppm or less by mass.

[0099] The Al bonding wire or Al bonding strip of the present invention further contains at least one of Sr, Na, Eu, and P in total amounts of 10 ppm to 800 ppm by mass, which can reduce the frequency of wire breakage during the wire drawing process of the Al bonding wire or Al bonding strip. Al alloys containing Si at high concentrations of 3.0% to 20.0% by mass tend to have an increased frequency of wire breakage during the wire drawing process. One reason is believed to be that Si phase particles crystallized during solidification cause stress concentration during wire drawing, leading to wire breakage. It is speculated that by adding the first element group, the stress concentration during wire drawing can be alleviated and wire breakage reduced through effects such as uniform distribution of granular Si phase and suppression of Si phase growth and coarsening. It is believed that the effect of alleviating stress concentration during wire drawing is improved by adding the first element group while controlling the porosity tilt rate.

[0100] From the viewpoint of reducing the frequency of wire breakage during wire drawing, the total concentration of the first element group in the Al bonding wire or Al bonding strip of the present invention is more preferably 20 ppm by mass or more, further preferably 30 ppm by mass or more, 40 ppm by mass or more, or 50 ppm by mass or more, and the upper limit is preferably 750 ppm by mass or less, more preferably 740 ppm by mass or less, 720 ppm by mass or less, or 700 ppm by mass or less, further preferably 680 ppm by mass or less, 650 ppm by mass or less, 620 ppm by mass or less, or 600 ppm by mass or less, and particularly preferably 580 ppm by mass or less, 550 ppm by mass or less, 520 ppm by mass or less, or 500 ppm by mass or less.

[0101] When the Al bonding line or Al bonding strip of the present invention contains any one or more elements from the first element group, it may contain any one element, any two elements, any three elements, or all four elements from the first element group. Furthermore, when the Al bonding line or Al bonding strip of the present invention contains any one or more elements from the first element group, it may contain Sr, Na, Eu, or P.

[0102] When the Al bonding wire or Al bonding strip of the present invention contains Sr from the first element group, the concentration of Sr can be 0 ppm by mass, preferably 1 ppm or more, 3 ppm or more, 5 ppm or more, or 8 ppm or more. Furthermore, from the viewpoint of reducing the frequency of wire breakage during wire drawing, the concentration of Sr is more preferably 10 ppm by mass or more, and even more preferably 20 ppm by mass or more, 30 ppm by mass or more, 40 ppm by mass or more, or 50 ppm by mass or more. The upper limit of the Sr concentration is preferably 10,000 ppm by mass or less, 8,000 ppm by mass or less, 5,000 ppm by mass or less, 3,000 ppm by mass or less, 2,000 ppm by mass or less, 1,000 ppm by mass or less, or 900 ppm by mass or less. Furthermore, from the viewpoint of reducing the frequency of wire breakage during wire drawing, the concentration of Sr is more preferably 800 ppm by mass or less, and even more preferably 750 ppm by mass or less, 740 ppm by mass or less, 720 ppm by mass or less, 700 ppm by mass or less, 680 ppm by mass or less, 650 ppm by mass or less, 620 ppm by mass or less, 600 ppm by mass or less, 580 ppm by mass or less, 550 ppm by mass or less, 520 ppm by mass or less, or 500 ppm by mass or less.

[0103] When the Al bonding wire or Al bonding strip of the present invention contains Na from the first element group, the concentration of Na can be 0 ppm by mass, preferably 1 ppm or more, 3 ppm or more, 5 ppm or more, or 8 ppm or more. Furthermore, from the viewpoint of reducing the frequency of wire breakage during wire drawing, the concentration of Na is more preferably 10 ppm by mass or more, and even more preferably 20 ppm by mass or more, 30 ppm by mass or more, 40 ppm by mass or more, or 50 ppm by mass or more. The upper limit of the Na concentration is preferably 10,000 ppm by mass or less, 8,000 ppm by mass or less, 5,000 ppm by mass or less, 3,000 ppm by mass or less, 2,000 ppm by mass or less, 1,000 ppm by mass or less, or 900 ppm by mass or less. Furthermore, from the viewpoint of reducing the frequency of wire breakage during wire drawing, the concentration of Na is more preferably 800 ppm by mass or less, and even more preferably 750 ppm by mass or less, 740 ppm by mass or less, 720 ppm by mass or less, 700 ppm by mass or less, 680 ppm by mass or less, 650 ppm by mass or less, 620 ppm by mass or less, 600 ppm by mass or less, 580 ppm by mass or less, 550 ppm by mass or less, 520 ppm by mass or less, or 500 ppm by mass or less.

[0104] When the Al bonding wire or Al bonding strip of the present invention contains Eu from the first element group, the concentration of Eu can be 0 ppm by mass, preferably 1 ppm or more, 3 ppm or more, 5 ppm or more, or 8 ppm or more. Furthermore, from the viewpoint of reducing the frequency of wire breakage during wire drawing, the concentration of Eu is more preferably 10 ppm by mass or more, and even more preferably 20 ppm by mass or more, 30 ppm by mass or more, 40 ppm by mass or more, or 50 ppm by mass or more. The upper limit of the Eu concentration is preferably 10,000 ppm by mass or less, 8,000 ppm by mass or less, 5,000 ppm by mass or less, 3,000 ppm by mass or less, 2,000 ppm by mass or less, 1,000 ppm by mass or less, or 900 ppm by mass or less. Furthermore, from the viewpoint of reducing the frequency of wire breakage during wire drawing, the concentration of Eu is more preferably 800 ppm by mass or less, and even more preferably 750 ppm by mass or less, 740 ppm by mass or less, 720 ppm by mass or less, 700 ppm by mass or less, 680 ppm by mass or less, 650 ppm by mass or less, 620 ppm by mass or less, 600 ppm by mass or less, 580 ppm by mass or less, 550 ppm by mass or less, 520 ppm by mass or less, or 500 ppm by mass or less.

[0105] When the Al bonding wire or Al bonding strip of the present invention contains P from the first element group, the concentration of P can be 0 ppm by mass, preferably 1 ppm or more, 3 ppm or more, 5 ppm or more, or 8 ppm or more. Furthermore, from the viewpoint of reducing the frequency of wire breakage during wire drawing, the concentration of P is more preferably 10 ppm by mass or more, and even more preferably 20 ppm by mass or more, 30 ppm by mass or more, 40 ppm by mass or more, or 50 ppm by mass or more. The upper limit of the P concentration is preferably 10,000 ppm by mass or less, 8,000 ppm by mass or less, 5,000 ppm by mass or less, 3,000 ppm by mass or less, 2,000 ppm by mass or less, 1,000 ppm by mass or less, or 900 ppm by mass or less. Furthermore, from the viewpoint of reducing the frequency of wire breakage during wire drawing, the concentration of P is more preferably 800 ppm by mass or less, and even more preferably 750 ppm by mass or less, 740 ppm by mass or less, 720 ppm by mass or less, 700 ppm by mass or less, 680 ppm by mass or less, 650 ppm by mass or less, 620 ppm by mass or less, 600 ppm by mass or less, 580 ppm by mass or less, 550 ppm by mass or less, 520 ppm by mass or less, or 500 ppm by mass or less.

[0106] -Addition of Ni, Ti, Fe, and Mg-

[0107] The Al bonding wire or Al bonding strip of the present invention may also contain any one or more of Ni, Ti, Fe, and Mg (hereinafter also referred to as "second element group"). The total concentration of the second element group can be 0 ppm by mass, preferably 1 ppm or more or 3 ppm or more, more preferably 5 ppm or more or 8 ppm or more, further preferably 10 ppm or more or 30 ppm or more, particularly preferably 50 ppm or more, 80 ppm or more or 100 ppm or more. The upper limit of the total concentration of the second element group is preferably 10,000 ppm or less by mass, more preferably 8,000 ppm or less by mass, further preferably 5,000 ppm or less by mass, particularly preferably 3,000 ppm or less by mass, 2,000 ppm or less by mass, 1,800 ppm or less by mass, 1,600 ppm or less by mass, or 1,500 ppm or less by mass. In one embodiment, the total concentration of the second element group is preferably 100 ppm or more and 1,500 ppm or less by mass.

[0108] The Al bonding lines or Al bonding bands of the present invention further contain any one or more of Ni, Ti, Fe, and Mg in total of 100 ppm to 1500 ppm by mass, which can suppress damage and scraping on the surface of the Al bonding lines or Al bonding bands, forming a smooth surface. Al alloys containing a high concentration of Si (3.0% to 20.0% by mass) are prone to surface hardening and shedding of Si phases and Al oxides present on the surface, resulting in surface damage and scraping during wire drawing, leading to Al bonding lines or Al bonding bands with uneven surfaces. It is speculated that by adding a second element group, the stabilization of Al oxides on the surface of the Al bonding lines or Al bonding bands, the refinement of Al grain structure, and hardening can be improved, thereby reducing damage and scraping during wire drawing. It is believed that by adding a second element group while controlling the porosity tilt rate, the effect of suppressing damage and scraping on the surface of the Al bonding lines or Al bonding bands and forming a smooth surface is improved.

[0109] From the viewpoint of suppressing surface damage and scraping, and forming Al bonding lines or Al bonding bands with smooth surfaces, the total concentration of the second element group in the Al bonding lines or Al bonding bands of the present invention is more preferably 150 ppm by mass or more, further preferably 200 ppm by mass or more, 250 ppm by mass or more, or 300 ppm by mass or more, and the upper limit is more preferably 1200 ppm by mass or less, further preferably 1000 ppm by mass or less, 900 ppm by mass or less, or 800 ppm by mass or less, and particularly preferably 700 ppm by mass or less, 600 ppm by mass or less, or 500 ppm by mass or less.

[0110] When the Al bonding line or Al bonding strip of the present invention contains any one or more elements from the second group, it may contain any one element, any two elements, any three elements, or all four elements from the second group. Furthermore, when the Al bonding line or Al bonding strip of the present invention contains any one or more elements from the second group, it may contain Ni, Ti, Fe, or Mg.

[0111] When the Al bonding line or Al bonding band of the present invention contains Ni from the second element group, the concentration of Ni can be 0 ppm by mass, preferably 1 ppm or more, 3 ppm or more, 5 ppm or more, 8 ppm or more, 10 ppm or more, 30 ppm or more, 50 ppm or more, or 80 ppm or more. Furthermore, from the viewpoint of suppressing surface damage and scraping to form an Al bonding line or Al bonding band with a smooth surface, the concentration of Ni is more preferably 100 ppm or more, and even more preferably 150 ppm or more, 200 ppm or more, 250 ppm or more, or 300 ppm or more. The upper limit of the Ni concentration is preferably 10,000 ppm or less, 8,000 ppm or less, 5,000 ppm or less, or 3,000 ppm or less. Furthermore, from the viewpoint of suppressing surface damage and scraping, and forming Al bonding lines or Al bonding bands with smooth surfaces, the concentration of Ni is more preferably 2000 ppm by mass or less, and even more preferably 1800 ppm by mass or less, 1600 ppm by mass or less, 1500 ppm by mass or less, 1200 ppm by mass or less, 1000 ppm by mass or less, 900 ppm by mass or less, 800 ppm by mass or less, 700 ppm by mass or less, 600 ppm by mass or less, or 500 ppm by mass or less.

[0112] When the Al bonding line or Al bonding band of the present invention contains Ti from the second element group, the concentration of Ti can be 0 ppm by mass, preferably 1 ppm or more, 3 ppm or more, 5 ppm or more, 8 ppm or more, 10 ppm or more, 30 ppm or more, 50 ppm or more, or 80 ppm or more. Furthermore, from the viewpoint of suppressing surface damage and scraping to form an Al bonding line or Al bonding band with a smooth surface, the concentration of Ti is more preferably 100 ppm or more, and even more preferably 150 ppm or more, 200 ppm or more, 250 ppm or more, or 300 ppm or more. The upper limit of the Ti concentration is preferably 10,000 ppm or less, 8,000 ppm or less, 5,000 ppm or less, or 3,000 ppm or less. Furthermore, from the viewpoint of suppressing surface damage and scraping, and forming Al bonding lines or Al bonding bands with smooth surfaces, the concentration of Ti is more preferably 2000 ppm by mass or less, and even more preferably 1800 ppm by mass or less, 1600 ppm by mass or less, 1500 ppm by mass or less, 1200 ppm by mass or less, 1000 ppm by mass or less, 900 ppm by mass or less, 800 ppm by mass or less, 700 ppm by mass or less, 600 ppm by mass or less, or 500 ppm by mass or less.

[0113] When the Al bonding line or Al bonding band of the present invention contains Fe from the second element group, the concentration of Fe can be 0 ppm by mass, preferably 1 ppm or more, 3 ppm or more, 5 ppm or more, 8 ppm or more, 10 ppm or more, 30 ppm or more, 50 ppm or more, or 80 ppm or more. Furthermore, from the viewpoint of suppressing surface damage and scraping to form an Al bonding line or Al bonding band with a smooth surface, the concentration of Fe is more preferably 100 ppm or more, and even more preferably 150 ppm or more, 200 ppm or more, 250 ppm or more, or 300 ppm or more. The upper limit of the Fe concentration is preferably 10,000 ppm or less, 8,000 ppm or less, 5,000 ppm or less, or 3,000 ppm or less. Furthermore, from the viewpoint of suppressing surface damage and scraping, and forming Al bonding lines or Al bonding bands with smooth surfaces, the concentration of Fe is more preferably 2000 ppm by mass or less, and even more preferably 1800 ppm by mass or less, 1600 ppm by mass or less, 1500 ppm by mass or less, 1200 ppm by mass or less, 1000 ppm by mass or less, 900 ppm by mass or less, 800 ppm by mass or less, 700 ppm by mass or less, 600 ppm by mass or less, or 500 ppm by mass or less.

[0114] When the Al bonding line or Al bonding band of the present invention contains Mg from the second element group, the concentration of Mg can be 0 ppm by mass, preferably 1 ppm or more, 3 ppm or more, 5 ppm or more, 8 ppm or more, 10 ppm or more, 30 ppm or more, 50 ppm or more, or 80 ppm or more. Furthermore, from the viewpoint of suppressing surface damage and scraping to form an Al bonding line or Al bonding band with a smooth surface, the concentration of Mg is more preferably 100 ppm or more, and even more preferably 150 ppm or more, 200 ppm or more, 250 ppm or more, or 300 ppm or more. The upper limit of the Mg concentration is preferably 10,000 ppm or less, 8,000 ppm or less, 5,000 ppm or less, or 3,000 ppm or less. Furthermore, from the viewpoint of suppressing surface damage and scraping, and forming Al bonding lines or Al bonding bands with smooth surfaces, the concentration of Mg is more preferably 2000 ppm by mass or less, and even more preferably 1800 ppm by mass or less, 1600 ppm by mass or less, 1500 ppm by mass or less, 1200 ppm by mass or less, 1000 ppm by mass or less, 900 ppm by mass or less, 800 ppm by mass or less, 700 ppm by mass or less, 600 ppm by mass or less, or 500 ppm by mass or less.

[0115] As the aluminum raw material for manufacturing the Al bonding wire or Al bonding strip of the present invention, Al with a purity of 4N (Al: 99.99% by mass or more) is preferably used, and even more preferably Al with a purity of 5N (Al: 99.999% by mass or more) or more with fewer impurities is used. In addition, in one embodiment, Al with a purity of 3N (Al: 99.9% by mass or more) may also be used.

[0116] To the extent that it does not impair the effects of the present invention, the Al bonding line or Al bonding strip of the present invention may also contain elements other than Al, Si, the first element group and the second element group (hereinafter also referred to as "other elements"). That is, "other elements" refers to elements other than Al, Si, Sr, Na, Eu, P, Ni, Ti, Fe and Mg. The Al bonding line or Al bonding strip of the present invention may also contain elements other than Al, Si, Sr, Na, Eu, P, Ni, Ti, Fe and Mg. The total concentration of other elements in the Al bonding line or Al bonding strip is not particularly limited to the extent that it does not impair the effects of the present invention. The total concentration of the other elements may also be less than 0.5% by mass, less than 0.4% by mass, less than 0.3% by mass, less than 0.2% by mass, less than 0.15% by mass, less than 0.1% by mass, less than 0.08% by mass, less than 0.06% by mass, less than 0.05% by mass, less than 0.04% by mass, less than 0.03% by mass, less than 0.025% by mass, less than 0.02% by mass, less than 0.018% by mass, less than 0.016% by mass, less than 0.015% by mass, less than 0.014% by mass, less than 0.012% by mass, or less than 0.01% by mass. There is no particular limitation on the lower limit of the total concentration of the other elements; it may also be 0% by mass.

[0117] In one embodiment, the remaining portion of the Al bonding line or Al bonding strip of the present invention is composed of Al and other elements. Therefore, in a preferred embodiment, the Al bonding line or Al bonding strip of the present invention is composed of Al, Si, and other elements. In another preferred embodiment, the Al bonding line or Al bonding strip of the present invention is composed of Al, Si, any one or more of the first element group, and other elements. Furthermore, in another preferred embodiment, the Al bonding line or Al bonding strip of the present invention is composed of Al, Si, any one or more of the second element group, and other elements. Furthermore, in yet another preferred embodiment, the Al bonding line or Al bonding strip of the present invention is composed of Al, Si, any one or more of the first element group, any one or more of the second element group, and other elements.

[0118] In one embodiment, the remaining portion of the Al bonding line or Al bonding strip of the present invention is composed of Al and unavoidable impurities. Therefore, in a preferred embodiment, the Al bonding line or Al bonding strip of the present invention is composed of Al, Si, and unavoidable impurities. In another preferred embodiment, the Al bonding line or Al bonding strip of the present invention is composed of Al, Si, any one or more of the first element group, and unavoidable impurities. Furthermore, in another preferred embodiment, the Al bonding line or Al bonding strip of the present invention is composed of Al, Si, any one or more of the second element group, and unavoidable impurities. Furthermore, in yet another preferred embodiment, the Al bonding line or Al bonding strip of the present invention is composed of Al, Si, any one or more of the first element group, any one or more of the second element group, and unavoidable impurities.

[0119] In a preferred embodiment, the Al bonding line or Al bonding strip of the present invention does not have a coating with a metal other than Al as the main component on its outer periphery. Here, "coating with a metal other than Al as the main component" means a coating with a content of metal other than Al of 50% by mass or more.

[0120] The Al bonding wire or Al bonding strip of the present invention can be either an Al bonding wire or an Al bonding strip. When the present invention is an Al bonding wire, its wire diameter is not particularly limited, and can be, for example, 50 μm or more, 60 μm or more, 80 μm or more, 100 μm or more, 120 μm or more, 140 μm or more, 150 μm or more, 180 μm or more, or 200 μm or more. The upper limit of this wire diameter is not particularly limited, and can be, for example, 600 μm or less, 550 μm or less, 500 μm or less, 450 μm or less, or 400 μm or less. In one embodiment, the wire diameter of the Al bonding wire of the present invention can be in the range of 100 to 600 μm, preferably 200 to 400 μm. When the present invention is a bonding strip, the dimensions (width W × thickness T) of its rectangular or substantially rectangular cross-section are not particularly limited, for example, W can be 100 to 3000 μm, and T can be 50 to 600 μm.

[0121] The Al bonding wires or Al bonding strips of the present invention exhibit excellent high-speed temperature cycling reliability even in high-speed temperature cycling tests with high upper temperature limits. Therefore, the Al bonding wires or Al bonding strips of the present invention are suitable for use as Al bonding wires or Al bonding strips for semiconductor devices. In particular, the Al bonding wires or Al bonding strips of the present invention are suitable for use as Al bonding wires or Al bonding strips for power semiconductor devices, and are even more suitable for use as Al bonding wires or Al bonding strips for SiC power semiconductor devices.

[0122] -Manufacturing method of Al bonding wire or Al bonding tape-

[0123] An example illustrating a method for manufacturing the Al bonding wire or Al bonding strip of the present invention will be provided. Hereinafter, an example will be described based on the manufacturing of the Al bonding wire.

[0124] The higher the purity of Al and alloying elements used as raw materials, the better. Al preferably has a purity of 99.5% by mass or more, with the remainder consisting of unavoidable impurities; more preferably, a purity of 99.9% by mass or more, with the remainder consisting of unavoidable impurities; and even more preferably, a purity of 99.99% by mass or more, with the remainder consisting of unavoidable impurities. Si, the first element group, the second element group, and other elements used as alloying elements preferably have a purity of 99.9% by mass or more, with the remainder consisting of unavoidable impurities; more preferably, a purity of 99.99% by mass or more, with the remainder consisting of unavoidable impurities. Continuous casting can be used in the casting process for melting and solidifying the Al alloy used for Al bonding wires. In continuous casting, molten material containing melted Al and alloying elements is poured into a water-cooled mold, while the casting material (ingot) is continuously pulled out from below the mold. Regarding the furnace atmosphere during melting, an inert or reducing atmosphere is preferred to prevent excessive oxidation of Al or Si, the first element group, the second element group, and other elements constituting the melt. Regarding the maximum temperature reached by the molten metal during melting, considering both ensuring the fluidity of the molten metal and easily controlling the shape and size of the Si phase during solidification, a range of 800°C or higher and less than 1050°C is preferred. Cooling methods after melting can include water cooling, furnace cooling, air cooling, etc.

[0125] After the cylindrical ingot obtained by melting is subjected to solution treatment at high temperature, it is repeatedly drawn using a die to produce wire of the target diameter. The drawn wire is then subjected to final heat treatment in an electric furnace to be used as Al-bonded wire.

[0126] To control the porosity tilt rate and the small diameter ratio of the Si phase, it is effective to control the heat treatment conditions, such as solution treatment, homogenization treatment, and final heat treatment, as well as the wire drawing conditions. During wire drawing, using a lubricant is effective in ensuring the lubrication of the contact interface between the wire and the die.

[0127] <Control of Void Inclination Rate>

[0128] In particular, controlling the wire feed speed (drawing speed), die reduction rate, lubrication, and intermediate annealing atmosphere during the wire drawing process is effective in controlling the wire gap tilt rate. These will be explained separately below.

[0129] By controlling the wire conveying speed at a high speed according to the wire diameter during wire drawing processing to assist the deformation of the surface region, it is effective in promoting the concentration gradient of voids. As a specific example, in the process of wire drawing processing within the range from a wire diameter of 1 / 2 of the wire diameter at the start of wire drawing processing to the final wire diameter, it is preferable to set the average wire drawing speed to 20 m / minute or more and less than 50 m / minute.

[0130] Regarding the die area reduction rate of wire drawing processing, it is effective to perform wire drawing on a thick diameter with a high area reduction rate and on a thin diameter with a low area reduction rate. By wire drawing with a high area reduction rate in the first half, the processing strain is concentrated in the center of the wire, promoting the increase of voids in the core part. In the wire drawing with a low area reduction rate in the second half, by gently deforming the vicinity of the surface, the voids in the surface part can be reduced. As a specific example thereof, it is preferable to set the die area reduction rate from the wire diameter at the start of wire drawing processing to a wire diameter of 1 / 2 thereof to a range of 20% or more and less than 40%, and set the die area reduction rate from a wire diameter of 1 / 2 to the final wire diameter to a range of 10% or more and less than 25%. Here, if the wire area reduction rate of each die is set to P1, P1 is represented by the following formula.

[0131] P1={(R2 2 -R1 2 ) / R2 2}×100

[0132] In the formula, R2 represents the diameter (mm) of the wire before processing, and R1 represents the diameter (mm) of the wire after processing.

[0133] In addition, in the heat treatment at the final wire diameter or the intermediate heat treatment at a thin diameter close to the final wire diameter, by improving the lubricity in the aqueous solution of wire drawing processing, the deformation of the surface extending along the wire drawing direction is promoted, and the concentration gradient of voids in the surface region is assisted. The lubricating liquid used is preferably selected from liquids containing surfactants that reduce the friction coefficient in an aqueous system.

[0134] Even when performing an intermediate heat treatment carried out during wire drawing processing in an atmosphere of an inert gas such as N2 gas, the control of the concentration gradient of voids is effective. Controlling the oxidation of Si in Al during wire drawing can assist in maintaining a low concentration of Si near the surface, and thereby reduce the void volume ratio near the surface.

[0135] <Control of the small diameter ratio of the Si phase>

[0136] Optimizing intermediate and final heat treatment conditions in groups is effective in controlling the small diameter ratio of the Si phase. Specifically, when the intermediate heat treatment temperature closest to the final wire diameter is set to Tm (°C), and the final heat treatment temperature at the final wire diameter is set to Tc (°C), the small diameter ratio of the Si phase is easily adjusted to between 30% and 95% because the intermediate heat treatment temperature Tm is more than 50°C higher than the final heat treatment temperature Tc. Specifically, increasing the intermediate heat treatment temperature homogenizes the Si dissolved in the Al phase, and decreasing the temperature of the final heat treatment reduces the concentration of Si dissolved in the Al phase. This combination of temperatures increases the number of small Si phases, thus increasing the small diameter ratio of the Si phase. It is believed that adjusting the temperature of the final intermediate heat treatment is more effective among multiple intermediate heat treatments, promoting the increase of the number of small Si phases by utilizing dislocations and other factors added in subsequent processing steps.

[0137] Regarding the final heat treatment conditions, adjustments within a temperature range of 200°C to 360°C and a time range of 2 hours to 20 hours are effective. Through the final heat treatment, the recovery and recrystallization of the Al phase occur, and the amount of Si dissolved in the Al phase changes, as does the recrystallization temperature, depending on the heat treatment temperature. By adjusting the recrystallization induced by the final heat treatment, the small diameter ratio of the Si phase can be easily controlled. For example, adjusting the final heat treatment at a low temperature or for a short time tends to increase the small diameter ratio of the Si phase.

[0138] As described above, the above is a representative example of Al bonding wire or Al bonding strip, and an example of manufacturing Al bonding wire as a wire material has been explained. Al bonding strip, as a strip material, can also be manufactured using essentially the same steps. The temperature and time of the heat treatment can be used under conditions that are approximately the same as described above. Furthermore, when manufacturing Al bonding strip by rolling, it is only necessary to replace the reduction ratio of the die with the reduction ratio and adjust it accordingly.

[0139] [Semiconductor Devices]

[0140] Semiconductor devices can be manufactured by connecting electrodes on a semiconductor chip to external electrodes on a lead frame or substrate using the Al bonding wires or Al bonding strips of the present invention. That is, the semiconductor device of the present invention includes the Al bonding wires or Al bonding strips of the present invention. As described above, both the first bonding with the electrodes on the semiconductor chip and the second bonding with the electrodes on the lead frame or substrate utilize wedge bonding.

[0141] In one embodiment, the semiconductor device of the present invention is characterized by including a circuit substrate, a semiconductor chip, and an Al bonding line or Al bonding strip for making the circuit substrate and the semiconductor chip conductive, wherein the Al bonding line or Al bonding strip is the Al bonding line or Al bonding strip of the present invention.

[0142] In the semiconductor device of the present invention, the circuit board and the semiconductor chip are not particularly limited, and any known circuit board and semiconductor chip that can be used to construct a semiconductor device can be used. Alternatively, a lead frame can be used instead of a circuit board. For example, as described in Japanese Patent Application Publication No. 2020-150116, the structure of the semiconductor device may include a lead frame and a semiconductor chip mounted on the lead frame.

[0143] Examples of semiconductor devices include those used in electrical products (such as computers, mobile phones, digital cameras, televisions, air conditioners, solar power systems, etc.) and vehicles (such as motorcycles, automobiles, trams, ships, and aircraft, etc.), with power semiconductor devices (power semiconductor devices) being the most preferred.

[0144] Example

[0145] Hereinafter, embodiments of the present invention will be shown for detailed description. However, the present invention is not limited to the embodiments shown below.

[0146] (sample)

[0147] The sample preparation method is described. The Al used as raw material is Al with a purity of 4N (99.99% by mass or higher), with the remainder consisting of unavoidable impurities. The Si, Group I (Sr, Na, Eu, P), Group II (Ni, Ti, Fe, Mg), and other elements (Mn, Zn) used as alloying elements are alloying elements with a purity of 99.99% by mass or higher, with the remainder consisting of unavoidable impurities. Al alloys used for Al bonding lines or Al bonding bands are manufactured by filling a melting crucible with Al raw materials and alloying element raw materials, and then using a continuous casting furnace. The furnace atmosphere during melting is Ar atmosphere, and the maximum temperature reached by the molten liquid is 800°C or higher but less than 1050°C. The cooling method after melting is either air cooling (atmospheric cooling) or water cooling (water cooling).

[0148] A cylindrical ingot with a diameter of 6 mm was obtained by melting. After solution treatment and homogenization, the ingot was drawn using a die and subjected to intermediate heat treatment to produce an Al bonding wire with a diameter of 300 μm. This 300 μm Al bonding wire was then used as the starting material to produce an Al bonding strip with a thickness of 100 μm and a width of 600 μm through a two-stage rolling process. The solution treatment temperature range was above 500°C and below 550°C, and the time was above 2 hours and below 4 hours. After solution treatment, homogenization was continuously performed during cooling. The homogenization temperature range was above 250°C and below 350°C, and the time was above 2 hours and below 5 hours. The cooling method after homogenization was air cooling in the atmosphere.

[0149] The intermediate heat treatment is performed 3 to 4 times. Regarding the wire diameter after intermediate heat treatment relative to the final wire diameter, the first intermediate annealing is performed at a wire diameter of 6.5 to 7.0 times, the second at 4.0 to 5.0 times, and the third at 2.0 to 3.0 times. When performing 4 intermediate heat treatments, the intermediate annealing is performed at a wire diameter of 7.5 to 8.5 times the final wire diameter. Regarding the temperature range for intermediate heat treatment, the first and second treatments are at 300°C or higher but less than 370°C for 1 hour or more but less than 3 hours, while the third and fourth treatments are at 250°C or higher but less than 400°C for 2 hours or more but less than 40 hours.

[0150] Commercially available lubricant is used during wire drawing. The reduction rate of the wire area for each die during wire drawing is 10% or more but less than 30%. The reduction rate is adjusted according to the wire diameter of the die. The final heat treatment temperature range is 200°C or more but less than 350°C, and the final heat treatment time is 2 hours or more but less than 20 hours. The final heat treatment temperature (Tc) is selected within a temperature range 50 to 100°C lower than the temperature (Tm) of the third or fourth intermediate annealing mentioned above.

[0151] In some embodiments, a die with a die angle of 14° or more but less than 18° is used for wire drawing.

[0152] (Methods for determining elemental content)

[0153] For the concentration analysis of elements contained in Al junction lines or Al junction bands, the analytical apparatus used is ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer) (PS 3520 UVDDII manufactured by Hitachi Advanced Technology & Science Co., Ltd.) or ICP-MS (Inductively Coupled Plasma-Mass Spectrometer) (Agilent Technologies Co., Ltd.) to perform the analysis.

[0154] (X-ray CT analysis)

[0155] The apparatus used was a 3D X-ray microscope, "Xradia 520 Versa" (manufactured by ZEISS). The X-ray voltage was 40 kV, the X-ray output was 3 W, the wavelength limiting filter was LE1, and the magnification lens was 4x. Under these conditions, transmission images with a transmittance of 30%–70% were obtained. To observe minute gaps, each pixel was approximately 0.7 μm / pixel, and the measurement field was measured over an area of ​​approximately 700 μm × 700 μm × 700 μm. The sample length was approximately 10 mm, and the end of the sample was fixed. The X-rays were transmitted through the sample at a rotation angle of 360 degrees around its axis to measure the CT projection images. In this measurement, CT projection images were acquired at intervals of 0.225° relative to the 360° rotation angle (a total of 1601 images). Each CT projection image was observed with an exposure time of 30 seconds. After obtaining the full-angle CT projection images, reconstruction processing, including center offset processing, was performed to obtain three-dimensional image data. Additionally, beam hardening may be performed as needed.

[0156] Next, the three-dimensional image data was analyzed using image analysis software, specifically AvizoInspection. Three-dimensional image data is image data that reflects the density difference of the observed area as a three-dimensional distribution of brightness values. Relatively high-density lines or bands (materials) are considered high-brightness, while low-density voids or outer spaces are considered low-density. First, a brightness histogram was generated using measurement data obtained by graphically representing the brightness values ​​and frequencies of each voxel in the three-dimensional image data. Figure 3The brightness value at the midpoint of two peak positions corresponding to the voids or outer space and the material is set as a threshold. Image data regions with brightness below the threshold are identified as voids or outer space (the environment surrounding the sample). Next, for the identified voids and outer space, the outer space region is selected and removed from the image data region. This allows image data of voids in the material within the measurement area of ​​the sample to be identified. Then, through the same process, image data with brightness above the threshold is identified as image data related to the material.

[0157] The image data of the voids and materials obtained in this way are analyzed. The calculation method of void tilt rate is explained in detail. Using image analysis software, the total volume Vs of voids with an equivalent sphere diameter of 1 μm or more but less than 10 μm and the volume Vm of the material are calculated. The ratio (Vk / (Vk+Vg)) obtained by dividing Vk by the total volume of voids and materials with an equivalent sphere diameter of 1 μm or more but less than 10 μm is taken as the void volume fraction. Based on this method, the void volume fractions Rd and Rf of the core and surface parts are calculated respectively, and the void tilt rate (Rf / Rd) is calculated.

[0158] (Small diameter ratio of Si phase [Ns / Nc×100(%)])

[0159] The small diameter ratio [Ns / Nc×100(%)] of the Si phase in the L section was determined using a SEM-EDS-EBSD apparatus, employing a method that combines information on Al and Si concentrations obtained by SEM-EDS with information on crystal orientation obtained by EBSD. Specifically, the determination was performed according to the steps (1) to (3) below.

[0160] (1) In the measurement area where the L section of the Al bonding line or Al bonding band is used as the inspection surface, the concentration of Al and Si using EDS and the crystal orientation using EBSD are measured simultaneously.

[0161] (2) Al and Si are separated and extracted using the chemical-assisted scanning function of the EBSD analysis software. Specifically, based on the EDS measurement results of Si, a tolerance equivalent to the threshold of Si is set, thereby enabling the separation and identification of Al and Si. The crystallization information of Al and Si in the material file is used for crystal orientation analysis. Here, the tolerance condition is mainly set at 30%, and adjusted as needed.

[0162] (3) For regions identified as Si phase, analyze the crystal orientation. If the orientation difference between measurement points is 15° or more, it is identified as a grain boundary, and the equivalent circle diameter of each grain is calculated. The total number of Si phase particles Nc is calculated by summing the number of grains identified as Si phase. Here, Si phases with an equivalent circle diameter of 0.5 μm or more are considered as the target. Considering the analytical precision of current ESD and EBSD analysis devices, fine materials smaller than 0.5 μm are excluded from the target. Next, the number Ns of Si phases in the range of equivalent circle diameter between 0.5 μm and 0.8 μm is summed. Then, the ratio of Ns to Nc [Ns / Nc×100(%)] (small diameter ratio of Si phase) is calculated.

[0163] The small diameter ratio of the Si phase is the average (arithmetic mean) of the values ​​obtained by the above steps (1) to (3) for the three measurement areas.

[0164] (Evaluation method for Al bonding lines or Al bonding bands)

[0165] The evaluation method for Al bonding wires is described. The Al bonding wires used in the evaluation have a diameter of Φ300μm. A Si semiconductor chip is used, and the electrodes on the semiconductor chip are obtained by forming an Al-0.5%Cu alloy film with a thickness of 4μm. The substrate is obtained by forming a Ni film of 5µm on an Al alloy. A commercially available wire bonder (manufactured by Ultrasonic Industries Co., Ltd.) is used for bonding the Al bonding wires. Both the first bonding (bonding to the aforementioned electrodes on the semiconductor chip) and the second bonding (bonding to the aforementioned substrate) are wedge bonding. A HESSE fully automatic bonding machine "BJ 955" equipped with a bonding head is used for bonding the Al bonding wires.

[0166] (Evaluation method for reliability of high-speed temperature cycling)

[0167] High-speed temperature cycling (HTCT) testing utilizes a commercially available high-speed thermal shock testing apparatus. In HTCT, hot air is rapidly blown onto the sample for heating. The sample undergoing HTCT is a structure with a semiconductor chip mounted on a substrate, and the electrodes on the semiconductor chip are connected to the electrodes on the substrate using Al bonding wires or Al bonding strips. For samples placed in the sample chamber of the HTCT apparatus, heating and cooling are repeated as a cycle, applying the thermal load repeatedly. The minimum cooling temperature is -40°C, and the maximum heating temperature is 185°C. The heating time, including the heating time, is 20 seconds, and the cooling time, including the cooling time, is 40 seconds. After 10,000 cycles, the sample is removed, and the shear strength of the first joint is tested. The shear strength of the first joint used in evaluating the reliability of HTCT is the average of the shear strengths at 10 randomly selected locations. The ratio (percentage) of the average shear strength after HTCT to the average shear strength before the test is used as the strength retention rate. A higher strength retention rate indicates better joint reliability. If the strength retention rate is above 70%, it is judged as excellent and indicated by "3"; if it is above 60% but below 70%, it is judged as excellent and indicated by "2"; if it is above 50% but below 60%, it is judged as needing improvement and indicated by "1"; if it is below 50%, it is considered to have a practical problem and indicated by "0". "3" and "2" are judged as acceptable, and "1" and "0" are judged as unacceptable. The evaluation results are recorded in the "High-speed temperature cycling reliability 10,000 cycles" column of the table.

[0168] (Evaluation of reliability over 13,000 high-speed temperature cycling cycles)

[0169] In the aforementioned high-speed temperature cycling test, the lower limit temperature was set to -40℃ and the upper limit temperature was set to 185℃, and the test was conducted for 13,000 cycles. A shear test was performed on the first joint. The average shear strength of five randomly selected locations at the first joint was calculated for the shear strength value used in the evaluation of high-speed temperature cycling reliability. The ratio of the shear strength after the temperature cycling test to the value before the test was evaluated as the joint strength retention rate. If the joint strength retention rate was less than 50%, it was judged as having a practical problem and represented by "0"; if it was above 50% but less than 60%, it was judged as needing improvement and represented by "1"; if it was above 60% but less than 70%, it was judged as excellent and represented by "2"; and if the joint strength retention rate was above 70%, it was judged as exceptionally excellent and represented by "3". The evaluation results are recorded in the "High-speed temperature cycling reliability 13,000 cycles" column of the table.

[0170] (Evaluation method for the shear strength ratio of the first joint)

[0171] The evaluation method for the shear strength ratio of the first joint is described. Regarding the joint conditions, the standard conditions for Al joint lines are used as a reference, and the ultrasonic output and load are set slightly higher to ensure the joint area. Shear strength is evaluated through a shear test to measure the shear strength of the first joint. Ten first joints are tested, and the average shear strength (SH) is measured. A commercially available micro shear strength testing machine (Nordson 4000-PLUS) is used for shear strength measurement. The shear speed is 200 μm / s, and the height of the shearing tool is 10 μm from the electrode surface. The shear strength is measured by fixing the substrate with the Al joint line or Al joint strip in a clamp. Additionally, tensile tests are performed on five specimens, and the average 0.2% yield strength (PS) is measured. An RTF-1225 tensile testing machine (A&D) is used, with a tensile speed of 10 mm / min. The ratio (SH / PS) obtained by dividing the shear strength (SH) by the 0.2% yield strength (PS) of the tensile test is used as the shear strength ratio. If the shear strength ratio is 5.2 or higher, the bond condition is considered excellent and rated "3"; if it is 4.5 or higher but less than 5.2, it is considered practically sound and rated "2"; if it is 3.5 or higher but less than 4.5, it is considered to require improvement and rated "1"; if it is less than 3.5, it is considered to have practical problems and rated "0". The evaluation results are recorded in the "Shear Strength Ratio" column of the table.

[0172] (Evaluation method for wire breakage during processing)

[0173] The evaluation method for wire breakage during processing is explained. Wire drawing is performed from wire diameters of 6mmφ to 0.3mmφ, and the number of wire breaks is recorded. The conveyor speed, reduction rate, and other processing conditions used for wire drawing are selected from the aforementioned conditions, and appropriate manufacturing conditions are adjusted or modified for each wire. The length of the Al-bonded wire after drawing is in the range of 100~200m, and the number of wire breaks is calculated per 100m. If the number of wire breaks is 0, it is judged as good and rated "3"; if it is 1, it is judged as being solvable by improving manufacturing conditions and rated "2"; if it is 2~4, the reduction in productivity is considered a problem and rated "1"; if it is 5 or more, it is judged as unusable and rated "0". The evaluation results are recorded in the "Wire Breakage During Processing" column of the table.

[0174] (Evaluation methods for surface damage and scraping)

[0175] Regarding the surface properties of the A1 bonding line or Al bonding band, evaluation focuses on damage and scratching. The diameter of the A1 bonding line is 0.3 mmφ. The A1 bonding band is 100 μm thick and 600 μm wide. Along the central axis of the A1 bonding line or Al bonding band, three measurement areas are randomly selected at intervals of more than 1 m. Three samples of approximately 2 cm in length are collected from each of the three areas, for a total of nine samples, which are then observed. The surface is observed using a SEM at magnifications ranging from 50 to 500 times. Damage exceeding 50 µm in length and scratching exceeding 30 µm in length are considered defective. The number of damaged or scratched areas is counted. If there are zero areas, it is considered good and rated as acceptable ("3"). If there are 1 to 2 areas, it is considered practically usable and rated as "2". If there are 3 to 7 areas, it is considered poor surface properties and rated as "1". If there are 8 or more areas, it is considered unusable and rated as "0". The evaluation results are recorded in the "Surface Properties" column of the table.

[0176] The evaluation results of the examples and comparative examples are shown in Tables 1 to 4. Examples 1 to 30 and Comparative Examples 1 to 6 in Tables 1 to 3 are results concerning Al bonding lines, and Examples B1 to B3 and Comparative Example B1 in Table 4 are results concerning Al bonding bands.

[0177] [Table 1]

[0178]

[0179] [Table 2]

[0180]

[0181] [Table 3]

[0182]

[0183] [Table 4]

[0184]

[0185] Explanation of reference numerals in the attached figures

[0186] 1 Al joint line

[0187] 10. Central axis

[0188] 11 L-section

[0189] 2 Al joint zone

[0190] 20 central axis

[0191] 21 L-section

[0192] Surface portion of 51 Al bonding line

[0193] 52 Al joint line middle section

[0194] 53 Al bonding wire core

[0195] 61 Al joint surface

[0196] 62 Al joint zone middle part

[0197] 63 Al bonding core

Claims

1. An Al bonding wire or Al bonding strip containing 3.0% by mass and 20.0% by mass of Si, S0 is defined as the closed curve representing the outer periphery of a cross section perpendicular to the central axis of the Al joint line or Al joint band; S1 is defined as a closed curve of a similar shape that is 2 / 3 times the size of S0; and S2 is defined as a closed curve of a similar shape that is 1 / 3 times the size of S0. S0, S1, and S2 are configured such that their centroids coincide with the centroid of the cross section perpendicular to the central axis of the Al joint line or Al joint band. The area enclosed by S0 and S1 is designated as the surface portion, and the area enclosed by S2 is designated as the core portion. When the volume fraction of voids in the core with an equivalent sphere diameter of 1 μm or more and less than 10 μm, as determined by X-ray CT analysis, is set as Rd, and the volume fraction of voids in the surface portion with an equivalent sphere diameter of 1 μm or more and less than 10 μm is set as Rf, the ratio Rf / Rd is 0.005 or more and 0.50 or less.

2. The Al bonding wire or Al bonding strip as described in claim 1, When the number of Si phases with an equivalent circle diameter of 0.5 μm to 0.8 μm in the L section (i.e., the section including the central axis in the direction of the central axis) is defined as Ns, and the number of Si phases with an equivalent circle diameter of 0.5 μm or more in the L section is defined as Nc, the ratio of Ns to Nc, Ns / Nc×100 (%), is 30% to 95%.

3. The Al bonding wire or Al bonding strip as described in claim 1 or 2, It also contains one or more of Sr, Na, Eu, and P in total amounts of more than 10 ppm by mass and less than 800 ppm by mass.

4. The Al bonding line or Al bonding strip as described in any one of claims 1 to 3, It also contains one or more of Ni, Ti, Fe, and Mg in a total amount of more than 100 ppm by mass and less than 1500 ppm by mass.

5. The Al bonding line or Al bonding strip as described in any one of claims 1 to 4, The total concentration of elements other than Al, Si, Sr, Na, Eu, P, Ni, Ti, Fe, and Mg in the Al junction line or Al junction band is less than 0.5% by mass.

6. The Al bonding line or Al bonding strip as described in any one of claims 2 to 5, The equivalent circle diameter and number of Si phases were determined using a SEM-EDS-EBSD instrument.

7. The Al bonding line or Al bonding strip as described in any one of claims 1 to 6, It is used in semiconductor devices.

8. A semiconductor device, Includes the Al bonding line or Al bonding strip as described in any one of claims 1 to 7.

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