Aluminum bonding wire or aluminum bonding ribbon

Abstract

Provided is an aluminum bonding wire or an aluminum bonding ribbon that is required for a next-generation SiC power semiconductor, and that exhibits excellent high-speed temperature cycle reliability even in a high-speed temperature cycle test with a long cycle count. This aluminum bonding wire or aluminum bonding ribbon contains 3.0-20.0 mass % of Si. When the crystal orientation of the Al phase in an L cross-section (cross-section in the central axis direction, including the central axis) of the aluminum bonding wire or aluminum bonding ribbon is measured, the orientation ratio of the <100> crystal orientation, in which the angle difference is 15° or less with respect to a direction parallel to the central axis (RD direction), is 15-50%. When the number of Si phases, in which the equivalent circle diameter in the L cross-section is 0.5-0.8 μm, is designated as Ns and the number of Si phases, in which the equivalent circle diameter in the L cross-section is 0.5 μm or more, is designated as Nc, the ratio [Ns / Nc×100(%)] of Ns to Nc is 30-95%.

Description

Al bonding wire or Al bonding ribbon

[0001] The present invention relates to an Al bonding wire or an Al bonding ribbon, and further to a semiconductor device obtained using the Al bonding wire or the Al bonding ribbon.

[0002] In semiconductor devices, electrodes formed on a semiconductor chip are connected to electrodes on a lead frame or substrate using bonding wires (wire material) or bonding ribbons (strip material). Power semiconductor devices primarily use bonding wires or bonding ribbons made of aluminum (Al). The wire diameter of Al bonding wires is typically in the range of 100 μm to 600 μm, while Al bonding ribbons typically have widths in the range of 100 μm to 3000 μm and thicknesses in the range of 50 μm to 600 μm. Here, Al bonding wires and Al bonding ribbons are collectively referred to as Al connecting materials.

[0003] In power semiconductor devices, silicon (Si) is often used as the material for the semiconductor chip, and Al-Si alloys or Al-Cu alloys are often used as the materials for the electrodes formed on the semiconductor chip. Furthermore, power semiconductor devices using Al bonding wire or Al bonding ribbon are often used in high-power equipment such as air conditioners and solar power generation systems, as well as in-vehicle semiconductor devices.

[0004] There are two methods for joining Al bonding wire or Al bonding ribbon: first, with an electrode on a semiconductor chip, and second, with an electrode on a lead frame or substrate. Both methods use wedge bonding. Wedge bonding is a method in which ultrasonic vibration and load are applied to the Al bonding wire or Al bonding ribbon via a metal jig (tool), destroying the surface oxide film between the Al bonding wire or Al bonding ribbon and the electrode material, exposing a new surface, and performing solid-state diffusion bonding. This connection method is characterized by connecting in a solid state without melting the connecting material, and is a joining technique that differs from welding techniques that melt the connecting material.

[0005] Next-generation power semiconductor devices are required to operate stably for longer periods of time than general-purpose power semiconductor devices. Power semiconductor devices operate by repeatedly turning current on and off. When current is supplied to a Si semiconductor chip through an Al bonding wire or Al bonding ribbon, the temperature of the first junction rises. On the other hand, when the current supply is stopped, the temperature of the first junction drops. Thus, the first junction repeatedly rises and falls in temperature during power semiconductor operation. This repeatedly applies thermal stress to the first junction due to the difference in thermal expansion between the Al bonding wire or Al bonding ribbon and the semiconductor chip. When using a connecting material made solely of high-purity Al, the Al bonding wire or Al bonding ribbon breaks due to thermal stress in a relatively short period of time, making it difficult to meet the performance requirements of next-generation power semiconductor devices. Therefore, next-generation power semiconductors are required to improve the junction life (hereinafter also referred to as "temperature cycle reliability") associated with temperature rise and fall of the first junction.

[0006] In response to the demand for temperature cycle reliability, an Al bonding wire that focuses on improving mechanical strength has been proposed. As a method for improving the mechanical properties of the Al bonding wire, a method of adding a specific element to Al has been proposed.

[0007] Patent Document 1 discloses a bonding wire made of an Al alloy containing at least magnesium (Mg) and silicon (Si), and the total content of Mg and Si is 0.03 mass % or more and 0.3 mass % or less. This patent document describes the effect of increasing strength by solid solution strengthening of Mg and Si, and the effect of precipitated magnesium silicide (Mg ２ It is disclosed that the crack propagation suppression effect of Si) delays the decrease in the bond strength of the first bonded portion in a cold temperature cycle test in the temperature range of 70°C to 120°C.

[0008] Patent Document 2 discloses a bonding wire made of an alloy containing 0.01 to 0.2 mass% iron (Fe), 1 to 20 mass ppm silicon (Si), and the remainder being Al with a purity of 99.997 mass% or more, wherein the amount of Fe in solid solution is 0.01 to 0.06%, the amount of Fe precipitated is 7 times or less the amount of Fe in solid solution, and the bonding wire has a fine structure with an average crystal grain size of 6 to 12 μm. This patent document discloses that by uniformly dispersing intermetallic compound particles of Fe and Al in Al to improve the mechanical strength of the matrix and further refining the recrystallized grains, it is possible to suppress a decrease in the bonding strength of the first bonded portion in a thermal shock test in a temperature range of -50 ° C to 200 ° C.

[0009] Patent Document 3 discloses a bonding wire obtained by melting an Al-Si alloy containing 0.1 to 5 mass % silicon (Si) with the remainder being Al and impurities, and then forming the melted Al-Si alloy into a thin wire by rapid cooling. This patent document discloses that mechanical strength is improved by rapidly cooling the molten Al-Si alloy to finely and uniformly disperse the Si.

[0010] JP 2014-131010 A JP 2014-129578 A JP 59-57440 A

[0011] As described above, next-generation power semiconductor devices are required to withstand longer periods of use than general-purpose power semiconductor devices. During operation of a power semiconductor device, the temperature of the first bonded portion repeatedly rises and falls. As a result, because the Al bonding wire or Al bonding ribbon has a larger linear expansion coefficient than the semiconductor chip, thermal stress occurs at the first bonded portion due to the difference in linear expansion coefficients between the two, which ultimately leads to fatigue failure of the Al bonding wire or Al bonding ribbon. A temperature cycle test is one type of accelerated evaluation test for the life (temperature cycle reliability) of the first bonded portion as it rises and falls in temperature. The Al bonding wire or Al bonding ribbon used in next-generation power semiconductors is required to exhibit excellent temperature cycle reliability in a temperature cycle test.

[0012] However, when using an Al bonding wire that has been strengthened by adding Si or the like as disclosed in Patent Documents 1 to 3, in a temperature cycle test assuming use in a next-generation power semiconductor device, cracks propagate at a relatively fast rate in the Al alloy electrode, which has lower strength than the Al bonding wire. The inventors have confirmed that there is a problem that it is difficult to stably obtain good temperature cycle reliability.

[0013] On the other hand, conventional temperature cycle tests (hereinafter also referred to as "TCT (Temperature Cycle Test)") can be easily performed using commercially available test equipment. However, the temperature change rate in TCT is relatively slow, which raises concerns about discrepancies with the fast temperature change rate during operation of power semiconductor devices. Therefore, recently, high-speed temperature cycle tests (hereinafter also referred to as "high-speed TCT"), which increase the temperature change rate to approximate actual usage conditions, have been considered. The temperature change rate in conventional TCT is, for example, about 10°C / min, while in high-speed TCT, the temperature changes at a high speed of, for example, about 200°C / min. Regarding reliability evaluation of the bond of an Al bonding wire or Al bonding ribbon, the inventors have confirmed that even if the Al bonding wire or Al bonding ribbon does not show a decrease in reliability when evaluated using conventional TCT, evaluation using high-speed TCT may result in a decrease in bond strength and a shortened bond life. Therefore, there is a demand for an Al bonding wire or Al bonding ribbon that exhibits good bond reliability even in high-speed TCT, which is a more severe test that is closer to the conditions of actual use, and that provides excellent temperature cycle reliability. Hereinafter, the temperature cycle reliability in high-speed TCT may be referred to as "high-speed temperature cycle reliability."

[0014] Furthermore, it is predicted that the use of highly heat-resistant silicon carbide (SiC) will increase in next-generation power semiconductor elements, replacing the previously mainstream silicon (Si). Connections for SiC power semiconductors will require even stricter high-speed temperature cycle testing than currently available. For example, while the number of cycles in high-speed temperature cycle testing for Si semiconductors is approximately 10,000, for SiC semiconductors, this should be extended to approximately 20,000. Furthermore, while the upper temperature limit for Si semiconductors is approximately 150°C, which is a strict condition, for SiC semiconductors, excellent high-speed temperature cycle reliability is required under even harsher conditions, such as above 175°C. The inventors have discovered that even Al bonding wires or Al bonding ribbons that exhibit excellent high-speed temperature cycle reliability at approximately 10,000 cycles may experience a problem of deterioration in the strength of the Al bonding wire or Al bonding ribbon joint when subjected to high-speed temperature cycle testing for SiC semiconductors at 20,000 cycles. This may result in poor high-speed temperature cycle reliability. This is thought to be because the shape, location, and extension behavior of cracks occurring at the bonded portion of the Al bonding wire or Al bonding ribbon change as the number of temperature cycles increases. Therefore, when the number of cycles increases from 10,000 to 20,000, the rate of cracks occurring inside the Al bonding wire or Al bonding ribbon increases rapidly, which is thought to be a factor in accelerating the deterioration of reliability.

[0015] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an Al bonding wire or Al bonding ribbon that exhibits excellent high-speed temperature cycle reliability even in high-speed temperature cycle tests with a long number of cycles, which is required for next-generation SiC power semiconductors.

[0016] As a result of intensive research into the above-mentioned problems, the inventors discovered that the above-mentioned problems can be solved by an Al bonding wire or Al bonding ribbon containing 3.0 mass% or more and 20.0 mass% or less of Si, in which the orientation ratio of the <100> crystal orientation of the Al phase in the RD direction in the L cross section (a cross section in the central axis direction including the central axis) of the Al bonding wire or Al bonding ribbon, and the ratio of the number of Si phases having a circle equivalent diameter of 0.5 μm or more and 0.8 μm or less in the L cross section are within a specific range.Based on this finding, the inventors further researched and completed the present invention.

[0017] That is, the present invention includes the following: <1> An Al bonding wire or Al bonding ribbon containing 3.0 mass % or more and 20.0 mass % or less of Si, wherein, when the crystal orientation of the Al phase in an L cross section (a cross section in the central axis direction including the central axis) of the Al bonding wire or Al bonding ribbon is measured, the orientation ratio of <100> crystal orientations having an angular difference of 15° or less with respect to a direction parallel to the central axis (RD direction) is 15% or more and 50% or less, and where Ns is the number of Si phases having a circle equivalent diameter of 0.5 μm or more and 0.8 μm or less in the L cross section, and Nc is the number of Si phases having a circle equivalent diameter of 0.5 μm or more in the L cross section, the ratio of Ns to Nc [Ns / Nc × 100 (%)] is 30% or more and 95% or less. <2> The Al bonding wire or Al bonding ribbon according to <1>, wherein the ratio of Ns to Nc [Ns / Nc × 100 (%)] is 40% or more. <3> The Al bonding wire or Al bonding ribbon according to <1> or <2>, wherein, when the crystal orientation of the Si phase in the L cross section is measured, the total orientation ratio of the <100> crystal orientation and the <111> crystal orientation, which have an angular difference of 15° or less with respect to the direction perpendicular to the central axis (ND direction), is 20% or more and 60% or less. <4> The Al bonding wire or Al bonding ribbon according to any of <1> to <3>, wherein the average value of the ratio (e / f) of the short side length e to the long side length f of the Si phase in the L cross section is 0.20 or more and 0.70 or less. <5> The Al bonding wire or Al bonding ribbon according to any one of <1> to <4>, further containing a total of 10 mass ppm to 800 mass ppm of one or more of Sr, Na, Fe, and P. <6> The Al bonding wire or Al bonding ribbon according to any one of <1> to <5>, further containing a total of 100 mass ppm to 2000 mass ppm of one or more of Ti, Ni, Mg, and Cu. <7> The Al bonding wire or Al bonding ribbon according to any one of <1> to <6>, wherein the total concentration of elements other than Al, Si, Sr, Na, Fe, P, Ti, Ni, Mg, and Cu in the Al bonding wire or Al bonding ribbon is 0.5 mass% or less.<8> An Al bonding wire or Al bonding ribbon according to any one of <1> to <7>, wherein the orientation ratio of the crystal orientation, and the circle equivalent diameter and number of the Si phase are values ​​measured using a SEM-EDS-EBSD device. <9> An Al bonding wire or Al bonding ribbon according to any one of <4> to <8>, wherein the average value of the ratio (e / f) of the short side length e to the long side length f of the Si phase is a value measured using a SEM-EDS-EBSD device. <10> An Al bonding wire or Al bonding ribbon according to any one of <1> to <9>, which is for a semiconductor device. <11> A semiconductor device comprising the Al bonding wire or Al bonding ribbon according to any one of <1> to <10>.

[0018] According to the present invention, it is possible to provide an Al bonding wire or Al bonding ribbon that exhibits excellent high-speed temperature cycle reliability even in high-speed temperature cycle tests with long cycle numbers, which is required for next-generation SiC power semiconductors, and a semiconductor device obtained using the Al bonding wire or Al bonding ribbon.

[0019] FIG. 1 is a schematic diagram illustrating the measurement surface (inspection surface), RD direction, and ND direction when measuring the crystal orientation of the Al phase and Si phase, the small diameter ratio of the Si phase, and the shape of the Si phase for an Al bonding wire. The measurement surface is a cross section (L cross section) in the central axis direction including the central axis of the Al bonding wire. FIG. 2 is a schematic diagram illustrating the measurement surface (inspection surface), RD direction, and ND direction when measuring the crystal orientation of the Al phase and Si phase, the small diameter ratio of the Si phase, and the shape of the Si phase for an Al bonding ribbon. The measurement surface is a cross section (L cross section) in the central axis direction including the central axis of the Al bonding ribbon. FIG. 3 is a schematic diagram illustrating the short side length (e) and long side length (f) of the Si phase in the L cross section. FIG. 4 is an example of a graph showing the number distribution of the circle equivalent diameter of the Si phase in the L cross section.

[0020] The present invention will be described in detail below with reference to preferred embodiments. While the description may refer to drawings, each drawing merely shows the shape, size, and arrangement of components to the extent that the invention can be understood. The present invention is not limited to the following embodiments and examples, and can be modified and implemented as desired within the scope of the claims of the present invention and their equivalents.

[0021] [Al bonding wire or Al bonding ribbon] The Al bonding wire or Al bonding ribbon of the present invention is an Al bonding wire or Al bonding ribbon containing 3.0 mass% or more and 20.0 mass% or less of Si, wherein, when the crystal orientation of the Al phase in an L cross section (a cross section in the central axis direction including the central axis) of the Al bonding wire or Al bonding ribbon is measured, the orientation ratio of the <100> crystal orientation having an angle difference of 15° or less with respect to the direction parallel to the central axis (RD direction, Rolling Direction) (hereinafter also referred to as the "orientation ratio of the <100> crystal orientation of the Al phase in the RD direction") is 15% or more and 50% or less, When the number of Si phases having a circle-equivalent diameter of 0.5 μm or more and 0.8 μm or less in the L cross section is defined as Ns, and the number of Si phases having a circle-equivalent diameter of 0.5 μm or more in the L cross section is defined as Nc, the ratio of Ns to Nc [Ns / Nc×100(%)] is 30% or more and 95% or less.

[0022] As mentioned above, when a connecting material made solely of high-purity Al is used in a temperature cycle test, cracks propagate relatively rapidly within the connecting material, resulting in a decrease in temperature cycle reliability. It has been confirmed that Al alloys containing a high concentration of Si can reduce the thermal expansion of the wire and improve temperature cycle reliability. In a high-speed temperature cycle test (high-speed TCT) using a high temperature change rate similar to actual use conditions, it has been confirmed that even Al bonding wires or Al bonding ribbons that do not exhibit a decrease in reliability when evaluated using conventional TCT can experience a decrease in bond strength and a shortened bond life. Furthermore, Al bonding wires or Al bonding ribbons strengthened by the addition of Si or other additives have sometimes experienced internal cracks during their manufacture. Furthermore, as the number of temperature cycles in the high-speed TCT increases significantly, bond strength is more likely to decrease. Therefore, further improvements in high-speed temperature cycle reliability are required to meet the high-speed temperature cycle reliability required for next-generation power semiconductor devices, such as SiC, which have high heat resistance.

[0023] The inventors have demonstrated that the mode and causes of defects in wire or ribbon joints change with an increase in the number of cycles in high-speed temperature cycle testing. While this varies depending on the detailed conditions of the temperature history, cracks propagate predominantly within the wire or ribbon up to approximately 10,000 cycles. However, beyond 15,000 cycles, the progression of cracks at the joint interface and within the electrode occurs in a combined manner, reducing reliability. Although it can be difficult to distinguish between cracks at the joint interface and those within the electrode by observing the joint cross section, they have found that it is effective to distinguish between the two types of cracks observed during high-cycle testing and to clarify their relationship with the wire or ribbon structure.

[0024] Because high-speed TCT tends to concentrate stress at the bond interface, it has been confirmed that the incidence of cracks at the bond interface is higher than with standard TCT. In addition to suppressing cracks inside the wire or ribbon that occur at low cycles, when the test progresses to 20,000 cycles, it becomes important to simultaneously suppress cracks at the bond interface and inside the electrode. The number of cycles mentioned above is an example of a guideline value under certain conditions of high-speed TCT. The required number of cycles will vary depending on the high-speed TCT test conditions (temperature, time, temperature rise / fall rates) or the semiconductor device used.

[0025] As a result of intensive research to solve the above-mentioned problems, the inventors have found that an Al bonding wire or Al bonding ribbon containing 3.0 mass% to 20.0 mass% Si can improve reliability in high-speed TCT with a considerably long number of temperature cycles and contribute to a longer life by simultaneously adjusting the orientation ratio of the <100> crystal orientation of the Al phase parallel to the central axis (RD direction) in the L cross section and the number distribution of Si phases in regions with relatively small circle-equivalent diameters in the L cross section (the ratio of the number of Si phases with circle-equivalent diameters in a specific range to the total number of Si phases). By mutually controlling the structure from different perspectives, namely the crystal orientation of the Al phase and the number distribution of the Si phase, it is possible to improve high-speed temperature cycle reliability even in harsh high-speed TCT.

[0026] The Al bonding wire or Al bonding ribbon of the present invention contains 3.0 mass% or more and 20.0 mass% or less of Si, and has an Al phase in which Si is solid-solved in Al, and a Si phase formed by crystallization or precipitation of Si. Here, the Al phase may contain other additive elements in addition to Si as a solid solution. The Si phase is a general term for Si crystallized particles and Si precipitates. Si crystallized particles are formed from the melt during solidification and are coarse, measuring approximately 1 to 25 μm in size, while Si precipitates are formed from the solid state and are small, measuring approximately 0.1 to several μm in size.

[0027] In the present invention, "wire" and "ribbon" are not classified by shape, but by their manufacturing method. That is, "wire" refers to a "connecting material manufactured by wire drawing using a die," and "ribbon" refers to a "connecting material manufactured by a rolling process." A "wire" typically has a circular cross-sectional shape, and a "ribbon" typically has a rectangular or nearly rectangular cross-sectional shape.

[0028] In the present invention, the "ND direction" refers to a direction that satisfies both "a direction perpendicular to the central axis" and "a direction perpendicular to the rolled surface." In the case of wire, since forces are applied from all directions during wire drawing using a die, there is flexibility in how the ND direction is taken, and there is also flexibility in how the L cross section (a cross section in the central axis direction including the central axis) is taken, but it is common to take the L cross section so that it is perpendicular to the ND direction, and this approach is also adopted in the present invention. In the case of ribbon, the "ND direction" is uniquely determined by the definition of "a direction perpendicular to the rolled surface." On the other hand, there are two ways to take the L cross section in ribbon: "a cross section perpendicular to the width W direction" and "a cross section perpendicular to the thickness T direction." However, in order to emphasize ease of cross-section polishing and EBSD analysis, the "cross section perpendicular to the width W direction" is defined as the L cross section (Figure 2).

[0029] That is, the central axis of the Al bonding wire, the cross section (L cross section) in the central axis direction including the central axis, the RD direction, and the ND direction are as shown in FIG. 1. FIG. 1 shows the case of an Al bonding wire having a circular cross section, but in the case of an Al bonding ribbon having a rectangular or approximately rectangular cross section with a width W and a thickness T, the central axis refers to the axis passing through the center of the width W and the center of the thickness T, and the L cross section refers to a cross section in the central axis direction including the central axis and perpendicular to the width W direction (FIG. 2). Specifically, the central axis of the Al bonding ribbon, the cross section (L cross section) in the central axis direction including the central axis, the RD direction, and the ND direction are as shown in FIG. 2. When processing the cross section to expose the L cross section of the Al bonding wire, there may be a deviation from the central axis of the Al bonding wire. In this case, if the length of the L cross section in the direction perpendicular to the central axis is 90% or more of the wire diameter of the Al bonding wire, it can be considered to be a cross section including the central axis.

[0030] The reason why the Al bonding wire or Al bonding ribbon of the present invention can provide excellent reliability even in a high-speed temperature cycle test with a considerably large number of cycles is presumed to be as follows.

[0031] First, regarding high-speed temperature cycle reliability, the Si phase has a smaller linear expansion coefficient than Al, which contributes to reducing the difference in linear expansion coefficient between the Al bonding wire or Al bonding ribbon and the semiconductor chip, thereby potentially reducing thermal stress. It is also believed that the particulate Si phase can suppress the growth of cracks inside the Al bonding wire or Al bonding ribbon. Up to about 10,000 cycles of high-speed TCT, utilizing the effect of the Si phase in lowering the linear expansion coefficient and adjusting the crystal orientation of the Al bonding wire or Al bonding ribbon to enhance this effect are effective in improving reliability. On the other hand, as the number of temperature cycles increases beyond 15,000 cycles, the location and behavior affected by thermal strain accumulated inside the Al bonding wire or Al bonding ribbon bonding interface and the electrode to which it is bonded change. Therefore, in a joint that can withstand 20,000 cycles, it is believed that the effects of the Al phase crystal orientation and Si phase particle size distribution, which respectively affect the cracks at the Al bonding wire or Al bonding ribbon bonding interface and the cracks inside the electrode, become stronger. Specifically, when measuring the crystal orientation of the Al phase in the L cross section, the orientation ratio of the <100> crystal orientation, which has an angle difference of 15° or less with respect to the direction parallel to the central axis (RD direction), is 15% or more and 50% or less, thereby mitigating the increase in stress in the Al bonding wire or Al bonding ribbon during high-speed TCT, thereby enhancing the effect of suppressing the propagation of cracks in the electrode. Furthermore, when the number of Si phases having a circular equivalent diameter of 0.5 μm or more and 0.8 μm or less in the L cross section is Ns, and the number of Si phases having a circular equivalent diameter of 0.5 μm or more in the L cross section is Nc, the effect of suppressing the propagation of cracks at the wire or ribbon bonding interface is enhanced by the ratio of Ns to Nc [Ns / Nc × 100 (%)] being 30% or more and 95% or less.

[0032] The present invention is characterized by the mutual interaction between the crystal orientation of the Al phase in the RD direction and the number distribution of the circle-equivalent diameter of the Si phase, enhancing the effect. These effects will be explained separately. When the orientation ratio of the <100> crystal orientation of the Al phase in the RD direction is in the range of 15% to 50%, the increase in stress within the wire or ribbon due to temperature rise and fall is alleviated, and this effect extends to adjacent electrodes, thereby suppressing crack propagation within the electrode. Furthermore, simultaneously satisfying the number distribution of the Si phase with a small circle-equivalent diameter makes it possible to uniformize the distribution of thermal strain near the bonding interface, thereby enhancing the role of suppressing crack propagation at the bonding interface. In other words, by simultaneously combining the effect of reducing crack growth primarily within the electrode by controlling the <100> crystal orientation of the Al phase in the RD direction and the effect of reducing crack growth at the bonding interface by controlling the number distribution of the Si phase with a small circle-equivalent diameter, it is possible to extend the time until failure of the bonded joint occurs under harsh test conditions of approximately 20,000 temperature cycles in high-speed TCT. Simply controlling the <100> orientation of the Al phase in the RD direction has the effect of suppressing cracks inside the wire or ribbon, and simply controlling the number distribution of Si phases with small circle equivalent diameters has the effect of suppressing the progression of cracks inside the electrode, but controlling both of these simultaneously can enhance the synergistic effect.

[0033] Stress and strain may occur around Si phases with large equivalent circle diameters, and the Si phases themselves may become crack initiation sites. The effects of these stress concentrations and strains are exacerbated by the more drastic temperature changes in high-speed TCT than in conventional TCT. On the other hand, it is believed that reducing the size of the Si phase grains can reduce stress concentrations and strains relatively uniformly near the bond interface. Therefore, controlling the distribution of the number of Si phases with small equivalent circle diameters relative to the total number of Si phases is effective for extending the life of high-speed temperature cycle tests. Under conditions that suppress crack propagation within the wire or ribbon during low-cycle tests, the average equivalent circle diameter of the Si phases has some effect. However, in long-cycle tests such as 20,000 cycles, controlling the distribution of the number of Si phases with small equivalent circle diameters relative to the total number of Si phases can suppress test result variability and stably improve high-speed temperature cycle reliability.

[0034] As described above, it is presumed that the Al bonding wire or Al bonding ribbon of the present invention can provide excellent high-speed temperature cycle reliability as described above, as a result of the factors that contribute to improving temperature cycle reliability in high-speed temperature cycle tests being appropriately controlled over a wide range of cycle numbers.

[0035] -Si Concentration- A Si concentration in the range of 3.0% by mass or more and 20.0% by mass or less helps reduce thermal distortion at the bonded portion and improve high-speed temperature cycle reliability. Specifically, a Si concentration of 3.0% by mass or more can significantly improve high-speed temperature cycle reliability. Furthermore, with advances and optimization of the equipment and conditions used in the manufacture and bonding of wires, etc., higher upper limits for the Si concentration have become permissible while suppressing defects such as wire breakage during processing, deterioration of surface properties, reduction in initial bond strength due to hardening, and damage to semiconductor chips. However, a Si concentration of 20.0% by mass or less effectively suppresses these defects and achieves the desired high-speed temperature cycle reliability. From the viewpoint of obtaining good high-speed temperature cycle reliability, the Si concentration in the Al bonding wire or Al bonding ribbon of the present invention is 3.0 mass% or more, preferably 3.5 mass% or more, more preferably 4.0 mass% or more, and even more preferably 4.2 mass% or more, 4.4 mass% or more, 4.5 mass% or more, 4.6 mass% or more, 4.8 mass% or more, or 5.0 mass% or more. In addition, from the viewpoint of achieving the desired high-speed temperature cycle reliability while effectively suppressing defects such as a decrease in initial bond strength due to hardening and damage to the semiconductor chip, the Si concentration in the Al bonding wire or Al bonding ribbon of the present invention is 20.0 mass% or less, preferably 19.0 mass% or less, 18.0 mass% or less, 17.0 mass% or less, 16.0 mass% or less, 15.0 mass% or less, 14.5 mass% or less, 14.0 mass% or less, 13.5 mass% or less, 13.0 mass% or less, or 12.5 mass% or less. Furthermore, if the hardness of the Al bonding wire or Al bonding ribbon is high, damage to the semiconductor chip is more likely to occur during the first bonding 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 wire or Al bonding ribbon of the present invention is more preferably 12.0 mass% or less, even more preferably 11.5 mass% or less or 11.0 mass% or less, and particularly preferably 10.8 mass% or less, 10.6 mass% or less, 10.5 mass% or less, 10.4 mass% or less, 10.2 mass% or less, or 10.0 mass% or less.

[0036] For example, an ICP (Inductively Coupled Plasma) optical emission spectrometer or an ICP mass spectrometer can be used to analyze the concentration of elements contained in the Al bonding wire or Al bonding ribbon of the present invention. If elements derived from atmospheric contaminants such as oxygen or carbon are adsorbed on the surface of the Al bonding wire or Al bonding ribbon, it is effective to clean the surface with an acid or alkali depending on the adsorbed substance before analysis.

[0037] -Crystal orientation of the Al phase in the L cross section- From the viewpoint of obtaining excellent high-speed temperature cycle reliability even in high-speed TCT with a long number of cycles, when the crystal orientation of the Al phase in the L cross section of the Al bonding wire or Al bonding ribbon is measured, the orientation ratio of the <100> crystal orientation, which has an angle difference of 15° or less with respect to the direction parallel to the central axis (RD direction), is 15% or more, preferably 20% or more, more preferably 22% or more, 24% or more, 26% or more, or 28% or more, even more preferably 30% or more, and even more preferably 35% or more. From the viewpoint of obtaining excellent high-speed temperature cycle reliability even in high-speed TCT with a long number of cycles, the upper limit of the orientation ratio of the <100> crystal orientation of the Al phase in the RD direction is 50% or less, preferably 48% or less or 45% or less, more preferably 42% or less, and even more preferably 40% or less.

[0038] Here, by setting the orientation ratio of the <100> crystal orientation of the Al phase in the RD direction to 15% or more, the length of cracks inside the electrode during high-speed temperature cycle testing is rapidly reduced. Furthermore, by setting the orientation ratio of the <100> crystal orientation of the Al phase in the RD direction to 50% or less, a good metal bond with the electrode can be obtained during bonding. Due to the influence of these two factors, when the orientation ratio of the <100> crystal orientation of the Al phase in the RD direction is set to 15% or more and 50% or less, the decrease in bond strength after 20,000 cycles in high-speed temperature cycle testing is significantly suppressed.

[0039] -Method for measuring the crystal orientation of the Al phase- The orientation ratio of the crystal orientation of the Al phase in the L cross section of an Al bonding wire or Al bonding ribbon can be measured using an SEM-EDS-EBSD device. Specifically, a method can be used in which information on the Al concentration and Si concentration obtained by SEM-EDS (Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy) is combined with information on the crystal orientation obtained by electron backscatter diffraction (EBSD). More specifically, in a measurement area in which the L cross section of the Al bonding wire or Al bonding ribbon is used as the inspection surface, Al and Si concentration measurement using EDS and crystal orientation analysis using EBSD are simultaneously performed. Next, the Al phase and Si phase are separated and extracted from the EDS measurement results using the analysis software provided with the device. Specifically, it is preferable to use the Chi Scan function, which is a function of the analysis software OIM Data Collection or OIM Analysis (both manufactured by TSL Solutions) provided with the FE-SEM (Field Emission-Scanning Electron Microscope) device. Then, for the region identified as Al phase, the orientation ratio of the <100> crystal orientation of the Al phase in the RD direction can be calculated using the analysis software provided with the device. To calculate the orientation ratio, a partial ratio is used, which is calculated as a population of the area of ​​only the crystal orientations that could be identified based on a certain reliability within the measurement area. The area ratio of the <100> crystal orientation in the RD direction with respect to the crystal orientation of the Al phase is defined as the orientation ratio of the <100> crystal orientation in the RD direction. Therefore, in one embodiment, the orientation ratio of the crystal orientation of the Al phase in the L cross section of the Al bonding wire or Al bonding ribbon of the present invention is calculated by the following procedures (1) to (3). (1) In a measurement area where the L cross section of the Al bonding wire or Al bonding ribbon is used as the inspection surface, Al and Si concentration measurements are performed using EDS and crystal orientation measurements are performed using EBSD simultaneously.(2) Using the Chi Scan function, Al and Si are separated and extracted. Specifically, by setting a tolerance equivalent to the Si threshold from the Si EDS measurement results, Al and Si can be separated and identified. The crystal orientation can be analyzed using the Al and Si crystal information in the material file. (3) For the region identified as an Al phase, the crystal orientation is analyzed and the orientation ratio of the <100> crystal orientation in the RD direction is calculated.

[0040] In the above procedure (2), the Tolerance (%) setting can be selected in the range of 20 to 40%, and in a standard analysis of the L cross section of an Al bonding wire or Al bonding ribbon, it is preferable to compare it at about 30%. The procedure for adjusting this Tolerance is explained below. It is preferable to select or confirm the Tolerance value so that the shape and size of the Si phase extracted and identified by the Chi Scan function are equivalent to those identified from the EDS map, which displays the Si element concentration in EDS analysis in two dimensions.

[0041] In the present invention, the orientation ratio of the <110> crystal orientation of the Al phase in the RD direction in the L cross section is the average (arithmetic mean) of the orientation ratio values ​​obtained by measuring three or more locations. When selecting the measurement area, in order to ensure the objectivity of the measurement data, it is preferable to obtain measurement samples from the Al bonding wire or Al bonding ribbon to be measured at intervals of 50 cm or more along the central axis of the Al bonding wire or Al bonding ribbon and provide them for measurement. Furthermore, in the present invention, the measurement area for the crystal orientation using the EBSD method has a length in the central axis direction of the Al bonding wire or Al bonding ribbon of 300 μm or more and less than 800 μm, and it is desirable that the entire Al bonding wire or Al bonding ribbon is included in the direction perpendicular to the central axis of the Al bonding wire or Al bonding ribbon. However, if the size is large and it is difficult to measure the entire area, it can be adjusted to a range of less than 600 μm.

[0042] -Distribution of circle-equivalent diameter of Si phase in L cross section- From the viewpoint of obtaining excellent high-speed temperature cycle reliability even in high-speed TCT with a long cycle number, when the number of Si phases having a circle-equivalent diameter of 0.5 μm or more and 0.8 μm or less in the L cross section of the Al bonding wire or Al bonding ribbon is Ns, and the number of Si phases having a circle-equivalent diameter of 0.5 μm or more in the L cross section is Nc, the ratio of Ns to Nc [Ns / Nc × 100 (%)] (hereinafter also referred to as the "small diameter ratio of Si phases") is 30% or more and 95% or less. The lower limit of the ratio [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, even more preferably 50% or more or 52% or more, and particularly preferably 55% or more or 60% or more. The upper limit of the ratio [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, even more preferably 78% or less or 75% or less, and particularly preferably 72% or less or 70% or less. In one embodiment, the ratio [Ns / Nc × 100(%)] is preferably 40% or more and 90% or less.

[0043] The reason why the proportion of Si phases having an equivalent circle diameter of 0.5 μm or more and 0.8 μm or less is important is considered as follows. Specifically, Si phases having an equivalent circle diameter of 0.5 μm or more have a sufficiently large volume, and therefore can sufficiently reduce thermal expansion. Furthermore, from the viewpoint of the analytical accuracy of current EDS and EBSD analysis devices, it is appropriate to target Si phases having an equivalent circle diameter of 0.5 μm or more. On the other hand, Si phases having an equivalent circle diameter of 0.8 μm or less sufficiently uniformize stress and strain near the bonding interface due to the Si phase. Furthermore, the reason why excellent high-speed temperature cycle reliability can be achieved even in high-speed TCT with a long number of cycles by setting the small diameter ratio of the Si phase [Ns / Nc × 100 (%)] in the range of 30% to 95% is considered as follows. Specifically, when the small diameter ratio of the Si phase is 30% or more, sufficient Si phases having small equivalent circle diameters are present, which uniformly distributes thermal strain and stabilizes high-speed temperature cycle reliability. 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, and the effect of reducing the thermal expansion of the entire bonding region can be maintained at a high level, thereby making it possible to sufficiently increase the effect of improving the reliability of high-speed temperature cycles.

[0044] Here, each Si phase is formed in a particle shape, and it has been confirmed that the number of Si phase particles has a large effect on thermal distortion at the bonding 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 effect of coarse particles is overestimated by the particle area, making it difficult to accurately evaluate the correlation with high-speed temperature cycling reliability.

[0045] - Average diameter of Si phase in L cross section - The Al bonding wire or Al bonding ribbon of the present invention preferably has an average diameter of Si phase in its L cross section of 0.8 μm or more and 4.0 μm or less. The average diameter of Si phase in the L cross section of the Al bonding wire or Al bonding ribbon of the present invention is more preferably 3.8 μm or less or 3.5 μm or less, even more preferably 3.4 μm or less, 3.2 μm or less, or 3.0 μm or less, and the lower limit is more preferably 1.0 μm or more or 1.1 μm or more, even more preferably 1.2 μm or more or 1.5 μm or more.

[0046] -Method for measuring the circle-equivalent diameter of the Si phase and method for calculating the minor diameter ratio- This section describes a method for measuring the circle-equivalent diameter of the Si phase in the L-section of an Al bonding wire or Al bonding ribbon. The circle-equivalent diameter of the Si phase in the L-section can be measured using a SEM-EDS-EBSD instrument. Specifically, similar to the measurement of the orientation ratio of the Al phase crystal orientation described above, a method can be used that combines information on the Al and Si concentrations obtained by SEM-EDS with information on the crystal orientation obtained by EBSD. More detailed procedures can be similar to those described above in relation to the measurement of the orientation ratio of the Al phase crystal orientation. That is, the crystal orientation of the region identified as the Si phase can be analyzed using the analysis software provided with the instrument. If the orientation difference between measurement points is 15° or more, it is determined to be a grain boundary, and the circle-equivalent diameter is calculated. The average of the circle-equivalent diameters of each Si phase is defined as the average diameter of the Si phase. In the process of determining the minor diameter ratio and average diameter of the Si phase, calculations are performed excluding areas where the crystal orientation cannot be measured, or areas where the crystal orientation can be measured but the reliability of the orientation analysis is low. Therefore, in one embodiment, the small diameter ratio and average diameter of the Si phase in the L-section of the Al bonding wire or Al bonding ribbon of the present invention are calculated by the following steps (1) to (3). (1) Using the L-section of the Al bonding wire or Al bonding ribbon as the inspection surface, Al and Si concentrations are measured using EDS and crystal orientation is measured using EBSD simultaneously. (2) Using the Chi Scan function, Al and Si are separated and extracted. Specifically, by setting a tolerance equivalent to the Si threshold from the Si EDS measurement results, Al and Si can be separated and identified. Crystal orientation can be analyzed using the Al and Si crystal information in the material file. (3) For the region identified as the Si phase, the crystal orientation is analyzed, and if the orientation difference between the measurement points is 15° or more, it is determined to be a grain boundary and the circle equivalent diameter of each crystal grain is calculated. The number of crystal grains identified as the Si phase is tallied to calculate the total number of Si phase particles Nc. Here, the target is a Si phase having a circle equivalent diameter of 0.5 μm or more. Taking into consideration the analytical accuracy of current ESD and EBSD analysis devices, fine particles of less than 0.5 μm are excluded.The number Ns of Si phases with a circle-equivalent diameter in the range of 0.5 μm to 0.8 μm is also counted. Then, the ratio of Ns to Nc [Ns / Nc × 100 (%)] (the small diameter ratio of the Si phase) is calculated. The circle-equivalent diameters of each crystal grain are averaged to calculate the average diameter of the Si phase. Here, for the average calculation, the average value obtained by area averaging (area-weighted averaging), which can be selected in the software provided with the device, is used.

[0047] An example of the measurement results is shown in Figure 4. The horizontal axis shows the circle equivalent diameter of the Si phase, with each section having a width of 0.25 μm, and the vertical axis shows the number of particles. The range of 0.5 μm or more and less than 0.8 μm is shown with a double-headed arrow, and the particle number ratio [Ns / Nc × 100 (%)] in this section is 50%. In a high-speed temperature cycle test of this Al bonding wire, strength degradation was kept low even after 20,000 cycles, confirming good high-speed temperature cycle reliability.

[0048] -Crystal orientation of Si phase in L cross section- When evaluating the bond strength of multiple Al bonding wires or Al bonding ribbons using high-speed TCT, it was confirmed that multiple bonded joints do not deteriorate simultaneously, but rather that there is variation in the deterioration of bond strength. That is, even when the number of cycles in high-speed temperature cycle testing increases and the average bond strength is roughly maintained, the strength begins to decrease at the joints of a small number of Al bonding wires or Al bonding ribbons, resulting in variation in the deterioration of bond strength. If the bond strength of even a small number of Al bonding wires or Al bonding ribbons deteriorates, there is a concern that the load on other Al bonding wires or Al bonding ribbons will increase at high currents, leading to sudden failures. To achieve the reliability required for next-generation power semiconductor devices, it is necessary not only to manage the lifespan based on the average bond strength during high-speed TCT, but also to control the variation in bond strength.

[0049] From the viewpoint of obtaining even better high-speed temperature cycle reliability in high-speed TCT with a long number of cycles and suppressing variations in bonding strength, when the crystal orientation of the Si phase in the L cross section of an Al bonding wire or Al bonding ribbon is measured, it is preferable that the total orientation ratio of the <100> crystal orientation and the <111> crystal orientation, which have an angular difference of 15° or less with respect to the direction perpendicular to the central axis (ND direction, Normal Direction) (hereinafter also referred to as the "total <100> + <111> ratio of the Si phase in the ND direction") be in the range of 20% or more and 60% or less. In addition to controlling the orientation ratio of the <100> crystal orientation of the RD Al phase and the small diameter ratio of the Si phase, by controlling the total ratio of <100> + <111> of the ND Si phase within this range, local stress concentrations are dispersed, reducing crack propagation at the bonding interface, resulting in reduced shear strength variation after severe high-speed TCT at 20,000 cycles or more. Furthermore, by aligning the <100> and <111> crystal orientations of the ND Si phase with the <100> crystal orientation of the RD Al phase, it is believed that the effect of suppressing local delamination at the bonding interface is realized even when the number of cycles during high-speed TCT, which has a rapid temperature change rate, is increased. The total ratio of the <100> + <111> Si phase in the ND direction is more preferably 25% or more, even more preferably 26% or more, 28% or more, or 30% or more, from the viewpoint of obtaining better high-speed temperature cycle reliability in high-speed TCT with a long number of cycles and suppressing variations in bond strength. The total ratio of the <100> + <111> Si phase is more preferably 58% or less, even more preferably 55% or less, 52% or less, 50% or less, 48% or less, or 45% or less, from the viewpoint of obtaining better high-speed temperature cycle reliability in high-speed TCT with a long number of cycles and suppressing variations in bond strength.

[0050] -Method for measuring the crystal orientation of the Si phase- The orientation ratio of the Si phase in the L-section of an Al bonding wire or Al bonding ribbon can be measured using a SEM-EDS-EBSD device. Specifically, as with the measurement of the orientation ratio of the Al phase, a method can be used that combines information on the Al and Si concentrations obtained by SEM-EDS with information on the crystal orientation obtained by EBSD. More detailed procedures can be similar to those described above in relation to the measurement of the orientation ratio of the Al phase. That is, for the region identified as the Si phase, the orientation ratio of the <100> crystal orientation and the <111> crystal orientation of the Si phase in the ND direction, as well as their total, can be calculated using the analysis software provided with the device. To calculate the orientation ratio, a partial ratio is used, calculated as a population of the area of ​​only the crystal orientations that could be identified with a certain level of reliability within the measurement area. Therefore, in one embodiment, the orientation ratio of the crystal orientation of the Si phase in the L-section of the Al bonding wire or Al bonding ribbon of the present invention is calculated by the following procedures (1) to (3). (1) In a measurement area where the L-section of the Al bonding wire or Al bonding ribbon is used as the inspection surface, Al and Si concentration measurements are performed using EDS and crystal orientation analysis is performed using EBSD simultaneously. (2) Using the Chi Scan function, Al and Si are analyzed separately. Specifically, by setting a tolerance equivalent to the Si threshold from the Si EDS measurement results, Al and Si can be separated and identified. The crystal orientation is analyzed using the Al and Si crystal information in the material file. (3) For the area identified as the Si phase, the crystal orientation is analyzed, and the orientation ratio of the <100> crystal orientation and the orientation ratio of the <111> crystal orientation of the Si phase in the ND direction are calculated.

[0051] In the present invention, the orientation ratio of the <100> crystal orientation and the orientation ratio of the <111> crystal orientation of the Si phase in the ND direction in the L cross section are the arithmetic mean values ​​of the orientation ratios obtained by measuring at least three locations. The tolerance setting range, the method for obtaining the measurement sample, and the measurement area of ​​the crystal orientation by the EBSD method in the above procedure (2) are as described above for the measurement of the orientation ratio of the crystal orientation of the Al phase.

[0052] -Shape of Si phase in L cross section- When bonding an Al bonding wire or Al bonding ribbon to an electrode on a conductor chip or an electrode on a lead frame or substrate, if a bonding failure such as peeling of the Al bonding wire or Al bonding ribbon from the electrode occurs, it can lead to product defects and reduced manufacturing yields, so it is necessary to obtain good bonding strength at each bond. In this regard, applying strong ultrasonic vibrations or loads to the first bonded portion to obtain good bonding strength can damage the semiconductor chip. In particular, when using an Al bonding wire or Al bonding ribbon that has been strengthened by adding Si or the like, its hardness can easily damage the semiconductor chip during the first bond. Adjusting the ultrasonic vibrations or load to reduce such damage can sometimes result in insufficient bonding strength at the first bonded portion (hereinafter simply referred to as "first bond strength") due to the high deformation resistance and unstable deformation direction, making it difficult to stably secure the bonding area. These problems during the initial bonding of the first joint can ultimately lead to reduced reliability and instability in high-speed temperature cycles, so it is more desirable for Al bonding wires or Al bonding ribbons that have been strengthened by adding Si or other elements to exhibit excellent first joint strength.

[0053] Here, the inventors discovered that by controlling the shape of the Si phase (the ratio (e / f) of the short side length e to the long side length f of the Si phase in the L cross section), the adhesion in the central axis direction of the interface between the Si phase and the Al phase is improved, interfacial slippage when ultrasonic vibration and load are applied is controlled, and the initial shear strength immediately after joining (first bond strength) can be increased. Furthermore, one of the effects of increasing the initial shear strength is that it can have the advantage of stabilizing the failure time (lifetime) in a high-speed temperature cycle test.

[0054] Specifically, the inventors conducted research on Al bonding wires or Al bonding ribbons containing 3.0% to 20.0% by mass of Si, in which the <100> ratio of the Al phase in the RD direction in the L cross section and the small diameter ratio of the Si phase are within specific ranges. They discovered that the shape of the Si phase in the L cross section affects the first bond strength. Specifically, they discovered that a ratio (e / f) of the short side length e to the long side length f of the Si phase in the L cross section, which is between 0.20 and 0.70, can suppress deterioration of the bond strength after high-speed TCT, improve the first bond strength, and ultimately reduce the variability of the bond strength. This ratio (e / f) is an index of flatness. This will be further explained with reference to FIG. 3. 3 is a schematic diagram of the Si phase in the L cross section of an Al bonding wire or Al bonding ribbon, with the central axis direction of the Al bonding wire or Al bonding ribbon corresponding to the horizontal direction (left-right direction) in FIG. 3 and the direction perpendicular to the central axis corresponding to the vertical direction (up-down direction) in FIG. 2. Regarding the Si phase in the L cross section, the above-mentioned "short side length e" corresponds to the dimension indicated by the symbol e in FIG. 3. Regarding the Si phase in the L cross section, the above-mentioned "long side length f" corresponds to the dimension indicated by the symbol f in FIG. 3. Hereinafter, the ratio (e / f) of the short side length e to the long side length f of the Si phase in the L cross section is also referred to as the "shape ratio (e / f) of the Si phase." The value of the shape ratio (e / f) of the Si phase can be obtained using the grain shape aspect ratio in the analysis software provided with the device.

[0055] The reason why the first bond strength can be improved by controlling the average value of the shape ratio (e / f) of the Si phase in the Al bonding wire or Al bonding ribbon of the present invention is presumed to be as follows. The reason why the first bond strength decreases is because cracks propagate inside the Al bonding wire or Al bonding ribbon or at the bond interface along the central axis direction of the Al bonding wire or Al bonding ribbon, or a direction close to it. Here, due to plastic processing by wiredrawing, the Si phase tends to be arranged so that the direction of its long side length f is the central axis direction of the Al bonding wire or Al bonding ribbon, or a direction close to it. When the average value of the shape ratio (e / f) of the Si phase is in the range of 0.20 to 0.70, the Si phase takes on a shape such as an ellipse or column, which exerts the effect of alleviating thermal stress in the central axis direction of the Al bonding wire or Al bonding ribbon, and thus it is thought that crack propagation along the central axis direction of the Al bonding wire or Al bonding ribbon, or a direction close to it, can be suppressed. In order to improve the first bonding strength, it is sufficient that the average value of the shape ratio (e / f) of the Si phase in the L cross section is within the above-mentioned preferred range, and it is not necessary that the shape ratio (e / f) of all the Si phases be in the range of 0.20 or more and 0.70 or less. For example, the Si phase may contain an Si phase having a shape ratio (e / f) of less than 0.20, or may contain an Si phase having a shape ratio (e / f) of more than 0.70.

[0056] From the viewpoint of improving the first bond strength, thereby reducing the variation in bond strength in high-speed TCT, and further realizing the reliability required for next-generation power semiconductor devices, the average value of the shape ratio (e / f) of the Si phase in the L cross section of the Al bonding wire or Al bonding ribbon of the present invention is more preferably 0.25 or more, even more preferably 0.30 or more, and particularly preferably 0.32 or more, 0.34 or more, or 0.35 or more. From the viewpoint of improving the first bond strength, the upper limit of the average value of the shape ratio (e / f) of the Si phase is more preferably 0.65 or less, or 0.60 or less, and even more preferably 0.58 or less, 0.56 or less, or 0.55 or less.

[0057] -Method for Measuring the Shape Ratio (e / f) of the Si Phase- A method for measuring the shape ratio (e / f) of the Si phase in the L-section of an Al bonding wire or Al bonding ribbon will be described. First, similar to the above-mentioned crystal orientation measurement and measurement of the circle-equivalent diameter of the Si phase, measurement can be performed using an SEM-EDS-EBSD device. Specifically, a method can be used that combines information on the Al and Si concentrations obtained by SEM-EDS with information on the crystal orientation obtained by EBSD. More detailed procedures can be similar to those described above in relation to the measurement of the crystal orientation ratio. That is, the crystal orientation of the region identified as the Si phase can be analyzed using the analysis software provided with the device. If the orientation difference between measurement points is 15° or more, it is determined to be a grain boundary, and the shape ratio (e / f) is calculated. The average value of the shape ratios (e / f) of each Si phase is defined as the average value of the shape ratio (e / f) of the Si phase. In the process of calculating the shape ratio (e / f) of the Si phase, areas where the crystal orientation cannot be measured or where the crystal orientation analysis is unreliable are excluded from the calculation. Therefore, in one embodiment, the average value of the shape ratio (e / f) of the Si phase in the L-section of the Al bonding wire or Al bonding ribbon of the present invention is calculated by the following steps (1) to (3). (1) Using the L-section of the Al bonding wire or Al bonding ribbon as the inspection surface, Al and Si concentration measurements are performed using EDS and crystal orientation measurements are performed simultaneously using EBSD. (2) Using the Chi Scan function, Al and Si are separated and extracted. Specifically, by setting a tolerance equivalent to the Si threshold from the Si EDS measurement results, Al and Si can be separated and identified. The crystal orientation can be analyzed using the Al and Si crystal information in the material file. (3) For the region identified as the Si phase, the crystal orientation is analyzed, and if the orientation difference between the measurement points is 15° or more, it is determined to be a grain boundary, and the shape ratio (e / f) of each crystal grain is calculated. The shape ratios (e / f) of each crystal grain are then averaged to calculate the average shape ratio (e / f) of the Si phase. Here, the average value of the shape ratio (e / f) of the Si phase is the numerical value of the Grain Shape Aspect Ratio (hereinafter referred to as "grain shape aspect ratio") of the analysis software.This value is the average value obtained by averaging the grain shape aspect ratios of each crystal grain. The grain shape aspect ratio is calculated by determining the ratio (e / f) of the short side length (e) (grain shape minor axis) and long side length (f) (grain shape major axis) of one crystal grain. The average value obtained by area averaging (area-weighted average), which can be selected in the software provided with the device, is used for the average calculation. By using the average value obtained by area averaging, it is possible to accurately measure and determine whether the conditions related to the average value of the shape ratio (e / f) of the Si phase are met, which is suitable for reducing the variation in bonding strength in high-speed temperature cycle tests with a long number of cycles and further achieving the high-speed temperature cycle reliability required for next-generation power semiconductor devices.

[0058] When measuring the average value of the shape ratio (e / f) of the Si phase in the L cross section, the setting range of Tolerance in the procedure (2) above and the measurement area of ​​the crystal orientation by the EBSD method are as described above for the measurement of the orientation ratio of the crystal orientation of the Al phase.

[0059] In addition to the above, there are several other methods for measuring the circle-equivalent diameter of the Si phase and the shape ratio (e / f) of the Si phase, including binarization processing from an observed image of the L cross section. However, in the present invention, it is preferable to use the method of combining the information on the Al concentration and Si concentration obtained by SEM-EDS with the information on the crystal orientation obtained by EBSD, as described above, for reasons such as the fact that a number of measurement functions are provided and multiple characteristics such as the above-mentioned crystal orientation, the circle-equivalent diameter of the Si phase, and the shape ratio (e / f) of the Si phase can be obtained in a single measurement, automatic analysis is possible, and measurement is easy using widely used equipment and analysis techniques.

[0060] -Addition of Sr, Na, Fe, and P- The Al bonding wire or Al bonding ribbon of the present invention may further contain one or more of Sr, Na, Fe, and P (hereinafter also referred to as the "first element group"). The total concentration of the first element group may be 0 ppm by mass, preferably 1 ppm by mass or more, more preferably 3 ppm by mass or more, even more preferably 5 ppm by mass or more, and particularly preferably 8 ppm by mass or more or 10 ppm by mass or more. The upper limit of the total concentration of the first element group is preferably 10,000 ppm by mass or less or 8,000 ppm by mass or less, more preferably 5,000 ppm by mass or less or 3,000 ppm by mass or less, even more preferably 2,000 ppm by mass or less or 1,000 ppm by mass or less, and particularly preferably 900 ppm by mass or less or 800 ppm by mass or less. In one embodiment, the total concentration of the first element group is preferably 10 ppm by mass or more and 800 ppm by mass or less.

[0061] By further containing at least one of Sr, Na, Fe, and P in a total amount of 10 ppm by mass to 800 ppm by mass, the frequency of wire breakage during wiredrawing of the Al bonding wire or Al bonding ribbon can be reduced. Al alloys containing a high concentration of Si of 3.0% by mass to 20.0% by mass tend to have a higher frequency of wire breakage during the wiredrawing process. This is thought to be due in part to the fact that Si phase particles crystallized during solidification cause stress concentration during wiredrawing, inducing wire breakage. It is presumed that the addition of the first element group can uniformly distribute the particulate Si phase and inhibit the growth and coarsening of the Si phase, thereby alleviating stress concentration during wiredrawing and reducing wire breakage. It is believed that the addition of the first element group, along with controlling the orientation ratio of the crystal orientation of the Al phase in the RD direction in the L cross section and the small diameter ratio of the Si phase, enhances the effect of alleviating stress concentration during wiredrawing.

[0062] 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 ribbon of the present invention is more preferably 20 ppm by mass or more, even more 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, even more 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, 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.

[0063] When the Al bonding wire or Al bonding ribbon of the present invention contains one or more elements from the first element group, it may contain one element from the first element group, two elements from the first element group, three elements from the first element group, or all four elements from the first element group. Also, when the Al bonding wire or Al bonding ribbon of the present invention contains one or more elements from the first element group, it may contain Sr, Na, Fe, or P.

[0064] When the Al bonding wire or Al bonding ribbon of the present invention contains Sr from the first element group, the Sr concentration may be 0 ppm by mass, preferably 1 ppm by mass or more, 3 ppm by mass or more, 5 ppm by mass or more, or 8 ppm by mass or more. In addition, from the viewpoint of reducing the frequency of wire breakage during wire drawing, the Sr concentration is more preferably 10 ppm by mass or more, 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 wiredrawing, the Sr concentration is more preferably 800 ppm by mass or less, 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.

[0065] When the Al bonding wire or Al bonding ribbon of the present invention contains Na in the first element group, the Na concentration may be 0 ppm by mass, preferably 1 ppm by mass or more, 3 ppm by mass or more, 5 ppm by mass or more, or 8 ppm by mass or more. Furthermore, from the viewpoint of reducing the frequency of wire breakage during wire drawing, the Na concentration is more preferably 10 ppm by mass or more, 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 wiredrawing, the Na concentration is more preferably 800 ppm by mass or less, 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.

[0066] When the Al bonding wire or Al bonding ribbon of the present invention contains Fe from the first element group, the Fe concentration may be 0 ppm by mass, preferably 1 ppm by mass or more, 3 ppm by mass or more, 5 ppm by mass or more, or 8 ppm by mass or more. Furthermore, from the viewpoint of reducing the frequency of wire breakage during wire drawing, the Fe concentration is more preferably 10 ppm by mass or more, 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 Fe 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 wiredrawing, the Fe concentration is more preferably 800 ppm by mass or less, 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.

[0067] When the Al bonding wire or Al bonding ribbon of the present invention contains P from the first element group, the P concentration may be 0 ppm by mass, preferably 1 ppm by mass or more, 3 ppm by mass or more, 5 ppm by mass or more, or 8 ppm by mass or more. Furthermore, from the viewpoint of reducing the frequency of wire breakage during wire drawing, the P concentration is more preferably 10 ppm by mass or more, 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 wiredrawing, the P concentration is more preferably 800 ppm by mass or less, 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.

[0068] - Addition of Ti, Ni, Mg, Cu - The Al bonding wire or Al bonding ribbon of the present invention may further contain one or more of Ti, Ni, Mg, and Cu (hereinafter also referred to as the "second element group"). The total concentration of the second element group may be 0 mass ppm, preferably 1 mass ppm or more or 3 mass ppm or more, more preferably 5 mass ppm or more or 8 mass ppm or more, even more preferably 10 mass ppm or more or 30 mass ppm or more, particularly preferably 50 mass ppm or more, 80 mass ppm or more, or 100 mass ppm or more. The upper limit of the total concentration of the second element group is preferably 10,000 mass ppm or less, more preferably 8,000 mass ppm or less, even more preferably 5,000 mass ppm or less, particularly preferably 3,000 mass ppm or less or 2,000 mass ppm or less. In one embodiment, the total concentration of the second element group is preferably 100 ppm by mass or more and 2000 ppm by mass or less.

[0069] The Al bonding wire or Al bonding ribbon of the present invention further contains one or more of Ti, Ni, Mg, and Cu in a total amount of 100 mass ppm to 2000 mass ppm, thereby suppressing scratches and abrasion on the surface of the Al bonding wire or Al bonding ribbon and forming a smooth surface. Al alloys containing Si at a high concentration of 3.0 mass% to 20.0 mass% may harden the surface and cause the Si phase and Al oxide present on the surface to fall off, resulting in scratches and abrasion on the surface during wiredrawing, resulting in an Al bonding wire or Al bonding ribbon with large surface irregularities. It is presumed that the addition of the second element group stabilizes the Al oxide on the surface of the Al bonding wire or Al bonding ribbon, refines the structure of the Al crystal grains, and hardens them, thereby reducing scratches and abrasion during wiredrawing. It is believed that by controlling the orientation ratio of the crystal orientation of the Al phase in the RD direction in the L cross section and the small diameter ratio of the Si phase, as well as adding the second element group, the occurrence of scratches and abrasions on the surface of the Al bonding wire or Al bonding ribbon can be suppressed, thereby enhancing the effect of forming a smooth surface.

[0070] From the viewpoint of forming an Al bonding wire or Al bonding ribbon having a smooth surface by suppressing the occurrence of scratches and abrasions on the surface, the total concentration of the second element group in the Al bonding wire or Al bonding ribbon of the present invention is more preferably 150 mass ppm or more, even more preferably 200 mass ppm or more, 250 mass ppm or more, or 300 mass ppm or more, and the upper limit is preferably 1800 mass ppm or less, more preferably 1600 mass ppm or less, 1500 mass ppm or less, or 1200 mass ppm or less, even more preferably 1000 mass ppm or less, 900 mass ppm or less, or 800 mass ppm or less, and particularly preferably 700 mass ppm or less, 600 mass ppm or less, or 500 mass ppm or less.

[0071] When the Al bonding wire or Al bonding ribbon of the present invention contains one or more elements from the second element group, it may contain one element from the second element group, two elements from the second element group, three elements from the second element group, or all four elements from the second element group. Also, when the Al bonding wire or Al bonding ribbon of the present invention contains one or more elements from the second element group, it may contain Ti, Ni, Mg, or Cu.

[0072] When the Al bonding wire or Al bonding ribbon of the present invention contains Ti from the second element group, the Ti concentration may be 0 ppm by mass, preferably 1 ppm by mass or more, 3 ppm by mass or more, 5 ppm by mass or more, 8 ppm by mass or more, 10 ppm by mass or more, 30 ppm by mass or more, 50 ppm by mass or more, or 80 ppm by mass or more. In addition, from the viewpoint of suppressing the occurrence of scratches and scraping on the surface and forming an Al bonding wire or Al bonding ribbon having a smooth surface, the Ti concentration is more preferably 100 ppm by mass or more, even more preferably 150 ppm by mass or more, 200 ppm by mass or more, 250 ppm by mass or more, or 300 ppm by mass. The upper limit of the Ti concentration is preferably 10,000 ppm by mass or less, 8,000 ppm by mass or less, 5,000 ppm by mass or less, or 3,000 ppm by mass or less. Furthermore, from the viewpoint of suppressing the occurrence of scratches and abrasions on the surface and forming an Al bonding wire or Al bonding ribbon with a smooth surface, the Ti concentration is more preferably 2000 mass ppm or less, even more preferably 1800 mass ppm or less, 1600 mass ppm or less, 1500 mass ppm or less, 1200 mass ppm or less, 1000 mass ppm or less, 900 mass ppm or less, 800 mass ppm or less, 700 mass ppm or less, 600 mass ppm or less, or 500 mass ppm or less.

[0073] When the Al bonding wire or Al bonding ribbon of the present invention contains Ni from the second element group, the Ni concentration may be 0 ppm by mass, preferably 1 ppm by mass or more, 3 ppm by mass or more, 5 ppm by mass or more, 8 ppm by mass or more, 10 ppm by mass or more, 30 ppm by mass or more, 50 ppm by mass or more, or 80 ppm by mass or more. In addition, from the viewpoint of suppressing the occurrence of scratches and scraping on the surface and forming an Al bonding wire or Al bonding ribbon having a smooth surface, the Ni concentration is more preferably 100 ppm by mass or more, even more preferably 150 ppm by mass or more, 200 ppm by mass or more, 250 ppm by mass or more, or 300 ppm by mass. The upper limit of the Ni concentration is preferably 10,000 ppm by mass or less, 8,000 ppm by mass or less, 5,000 ppm by mass or less, or 3,000 ppm by mass or less. Furthermore, from the viewpoint of suppressing the occurrence of scratches and abrasions on the surface and forming an Al bonding wire or Al bonding ribbon with a smooth surface, the Ni concentration is more preferably 2000 mass ppm or less, even more preferably 1800 mass ppm or less, 1600 mass ppm or less, 1500 mass ppm or less, 1200 mass ppm or less, 1000 mass ppm or less, 900 mass ppm or less, 800 mass ppm or less, 700 mass ppm or less, 600 mass ppm or less, or 500 mass ppm or less.

[0074] When the Al bonding wire or Al bonding ribbon of the present invention contains Mg from the second element group, the Mg concentration may be 0 ppm by mass, preferably 1 ppm by mass or more, 3 ppm by mass or more, 5 ppm by mass or more, 8 ppm by mass or more, 10 ppm by mass or more, 30 ppm by mass or more, 50 ppm by mass or more, or 80 ppm by mass or more. Furthermore, from the viewpoint of suppressing the occurrence of scratches and abrasion on the surface and forming an Al bonding wire or Al bonding ribbon having a smooth surface, the Mg concentration is more preferably 100 ppm by mass or more, even more preferably 150 ppm by mass or more, 200 ppm by mass or more, 250 ppm by mass or more, or 300 ppm by mass. The upper limit of the Mg concentration is preferably 10,000 ppm by mass or less, 8,000 ppm by mass or less, 5,000 ppm by mass or less, or 3,000 ppm by mass or less. Furthermore, from the viewpoint of suppressing the occurrence of scratches and abrasions on the surface and forming an Al bonding wire or Al bonding ribbon with a smooth surface, the Mg concentration is more preferably 2000 mass ppm or less, even more preferably 1800 mass ppm or less, 1600 mass ppm or less, 1500 mass ppm or less, 1200 mass ppm or less, 1000 mass ppm or less, 900 mass ppm or less, 800 mass ppm or less, 700 mass ppm or less, 600 mass ppm or less, or 500 mass ppm or less.

[0075] When the Al bonding wire or Al bonding ribbon of the present invention contains Cu from the second element group, the Cu concentration may be 0 ppm by mass, preferably 1 ppm by mass or more, 3 ppm by mass or more, 5 ppm by mass or more, 8 ppm by mass or more, 10 ppm by mass or more, 30 ppm by mass or more, 50 ppm by mass or more, or 80 ppm by mass or more. In addition, from the viewpoint of suppressing the occurrence of scratches and scraping on the surface and forming an Al bonding wire or Al bonding ribbon having a smooth surface, the Cu concentration is more preferably 100 ppm by mass or more, even more preferably 150 ppm by mass or more, 200 ppm by mass or more, 250 ppm by mass or more, or 300 ppm by mass. The upper limit of the Cu concentration is preferably 10,000 ppm by mass or less, 8,000 ppm by mass or less, 5,000 ppm by mass or less, or 3,000 ppm by mass or less. Furthermore, from the viewpoint of suppressing the occurrence of scratches and abrasions on the surface and forming an Al bonding wire or Al bonding ribbon with a smooth surface, the Cu concentration is more preferably 2000 mass ppm or less, even more preferably 1800 mass ppm or less, 1600 mass ppm or less, 1500 mass ppm or less, 1200 mass ppm or less, 1000 mass ppm or less, 900 mass ppm or less, 800 mass ppm or less, 700 mass ppm or less, 600 mass ppm or less, or 500 mass ppm or less.

[0076] As the aluminum raw material for manufacturing the Al bonding wire or Al bonding ribbon of the present invention, it is preferable to use Al with a purity of 4N (Al: 99.99% by mass or more), and it is more preferable to use Al with a lower impurity content of 5N (Al: 99.999% by mass or more). In one embodiment, Al with a purity of 3N (Al: 99.9% by mass or more) may be used.

[0077] The Al bonding wire or Al bonding ribbon of the present invention may further 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" are elements other than Al, Si, Sr, Na, Fe, P, Ti, Ni, Mg, and Cu, and the Al bonding wire or Al bonding ribbon of the present invention may further contain elements other than Al, Si, Sr, Na, Fe, P, Ti, Ni, Mg, and Cu. The total concentration of other elements in the Al bonding wire or Al bonding ribbon is not particularly limited as long as it does not impair the effects of the present invention. The total concentration of the other elements may be, for example, 0.5% by mass or less, 0.4% by mass or less, 0.3% by mass or less, 0.2% by mass or less, 0.15% by mass or less, 0.1% by mass or less, 0.08% by mass or less, 0.06% by mass or less, 0.05% by mass or less, 0.04% by mass or less, 0.03% by mass or less, 0.025% by mass or less, 0.02% by mass or less, 0.018% by mass or less, 0.016% by mass or less, 0.015% by mass or less, 0.014% by mass or less, 0.012% by mass or less, or 0.01% by mass or less. The lower limit of the total concentration of the other elements is not particularly limited, and may be 0% by mass.

[0078] In one embodiment, the remainder of the Al bonding wire or Al bonding ribbon of the present invention consists of Al and other elements. Therefore, in a preferred embodiment, the Al bonding wire or Al bonding ribbon of the present invention consists of Al, Si, and other elements. In another preferred embodiment, the Al bonding wire or Al bonding ribbon of the present invention consists of Al, Si, one or more elements from the first element group, and other elements. In yet another preferred embodiment, the Al bonding wire or Al bonding ribbon of the present invention consists of Al, Si, one or more elements from the second element group, and other elements. In yet another preferred embodiment, the Al bonding wire or Al bonding ribbon of the present invention consists of Al, Si, one or more elements from the first element group, one or more elements from the second element group, and other elements.

[0079] In one embodiment, the remainder of the Al bonding wire or Al bonding ribbon of the present invention consists of Al and inevitable impurities. Therefore, in a preferred embodiment, the Al bonding wire or Al bonding ribbon of the present invention consists of Al, Si, and inevitable impurities. In another preferred embodiment, the Al bonding wire or Al bonding ribbon of the present invention consists of Al, Si, one or more elements from the first element group, and inevitable impurities. In yet another preferred embodiment, the Al bonding wire or Al bonding ribbon of the present invention consists of Al, Si, one or more elements from the second element group, and inevitable impurities. In yet another preferred embodiment, the Al bonding wire or Al bonding ribbon of the present invention consists of Al, Si, one or more elements from the first element group, one or more elements from the second element group, and inevitable impurities.

[0080] In a preferred embodiment, the Al bonding wire or Al bonding ribbon of the present invention does not have a coating mainly composed of a metal other than Al on the outer periphery of the Al bonding wire or Al bonding ribbon. Here, the term "coating mainly composed of a metal other than Al" refers to a coating in which the content of a metal other than Al is 50 mass % or more.

[0081] The Al bonding wire or Al bonding ribbon of the present invention may be an Al bonding wire or an Al bonding ribbon. When the present invention is an Al bonding wire, its wire diameter is not particularly limited and may 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 the wire diameter is not particularly limited and may 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 may be in the range of 100 to 600 μm, and preferably 200 to 400 μm. When the present invention is an Al bonding ribbon, the dimensions of its rectangular or approximately rectangular cross section (width W x thickness T) are not particularly limited, and for example, W may be 100 to 3000 μm and T may be 50 to 600 μm.

[0082] The Al bonding wire or Al bonding ribbon of the present invention can provide excellent high-speed temperature cycle reliability even in high-speed temperature cycle tests with a long number of cycles. Therefore, the Al bonding wire or Al bonding ribbon of the present invention can be suitably used as an Al bonding wire or Al bonding ribbon for semiconductor devices. The Al bonding wire or Al bonding ribbon of the present invention can be particularly suitably used as an Al bonding wire or Al bonding ribbon for power semiconductor devices, and more suitably used as an Al bonding wire or Al bonding ribbon for SiC power semiconductor devices.

[0083] -Method for manufacturing Al bonding wire or Al bonding ribbon- An example of a method for manufacturing an Al bonding wire or Al bonding ribbon of the present invention will be described below. Hereinafter, an example will be described in relation to the manufacture of an Al bonding wire.

[0084] The Al and alloying elements used as raw materials preferably have a high purity. Al preferably has a purity of 99.5% by mass or more, with the remainder consisting of inevitable impurities, more preferably a purity of 99.9% by mass or more, with the remainder consisting of inevitable impurities, and even more preferably a purity of 99.99% by mass or more, with the remainder consisting of inevitable impurities. The Si, first element group, 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 inevitable impurities, and more preferably a purity of 99.99% by mass or more, with the remainder consisting of inevitable impurities. The Al alloy used for Al bonding wire can be produced by loading the Al raw material and the alloying element raw material into a graphite or alumina crucible processed to obtain a cylindrical ingot and melting it using an electric furnace or high-frequency heating furnace. The diameter of the cylindrical ingot is preferably Φ6 mm or more and less than 8 mm, taking into account the workability in the subsequent processing steps. The atmosphere in the furnace during melting is preferably an inert or reducing atmosphere to prevent excessive oxidation of Al, Si, the first element group, the second element group, and other elements that constitute the wire. The maximum temperature that the molten metal reaches during melting is preferably in the range of 800°C or higher and lower than 1050°C, taking into consideration factors such as ensuring the fluidity of the molten metal and making it easier to control the shape and size of the Si phase during solidification. Cooling methods after melting can include water cooling, furnace cooling, and air cooling.

[0085] The cylindrical ingot obtained by melting is subjected to a solution treatment in which it is heated at a high temperature, and then repeatedly subjected to wire drawing using a die to produce a wire of the desired wire diameter. The wire after wire drawing can be used as an Al bonding wire by performing a final heat treatment using an electric furnace.

[0086] In order to control the crystal orientation of the Al phase, the small diameter ratio of the Si phase, the average diameter of the Si phase, and the crystal orientation of the Si phase in the L cross section, it is effective to control the heat treatment conditions such as solution treatment, homogenization treatment, and final heat treatment, as well as the wiredrawing conditions, etc. During the wiredrawing process, it is effective to use a lubricant to ensure lubrication at the contact interface between the wire and the die.

[0087] An example of manufacturing conditions for controlling the orientation ratio of the <100> crystal orientation of the Al phase in the RD direction in the L cross section to a range of 15% to 50% and for controlling the small diameter ratio of the Si phase to a range of 30% to 95% is shown below.

[0088] <Control of the <100> crystal orientation of the Al phase in the RD direction> With regard to the wiredrawing conditions, it is effective to set the wire area reduction rate per die used during wiredrawing to a range of 10% or more and less than 20%. Here, if the wire area reduction rate per die is P1, P1 is expressed by the following formula.

[0089] P1 = {(R ２ ２ -R １ ２ ) / R ２ ２}×100 where R ２ is the diameter of the wire before processing (mm), R １ represents the diameter (mm) of the wire after processing.

[0090] By controlling the average die area reduction rate within a range of 10% or more and less than 20%, it is possible to adjust the <100> crystal orientation of the Al phase in the RD direction. For example, increasing the area reduction rate to increase the processing strain is useful for controlling the ratio of the <100> crystal orientation of the Al phase in the RD direction, which is the recrystallized structure, when heat treatment is applied.

[0091] Adjusting the conditions for the intermediate heat treatment facilitates the adjustment of the orientation ratio of the <100> crystal orientation of the Al phase in the RD direction. The intermediate heat treatment is a heat treatment performed during the process of processing from the ingot to the final wire diameter. The number of intermediate heat treatments is preferably in the range of three to four, and the wire diameter to which the intermediate heat treatment is performed can be selected. In particular, performing intermediate heat treatment (intermediate annealing) at a temperature range of 250°C or higher but less than 400°C for a time period of one hour or longer but less than 48 hours at least once within a range of 4.0 to 5.5 times the final wire diameter and at least once within a range of 2.0 to 3.5 times the final wire diameter helps to adjust the orientation ratio of the <100> crystal orientation of the Al phase in the RD direction at the final wire diameter to a range of 15% to 50%. By performing intermediate heat treatment under these conditions, the processing strain of the Al phase is reduced and slight recrystallization occurs, thereby reducing the processed structure of the Al phase at the final wire diameter, and the subsequent heat treatment increases the progress of recrystallization of the Al phase and promotes the rotation of the crystal orientation, making it easy to adjust the orientation ratio of the <100> crystal orientation of the Al phase in the RD. On the other hand, if the intermediate heat treatment temperature is 400°C or higher, there is a concern that the orientation ratio of the <100> crystal orientation of the Al phase in the RD will become unstable.

[0092] <Control of the Small Diameter Ratio of the Si Phase> Optimizing the intermediate heat treatment conditions and the final heat treatment conditions as a set is effective in controlling the small diameter ratio of the Si phase. Specifically, if the temperature of the intermediate heat treatment for the wire diameter (final) closest to the final wire diameter is Tm (°C) and the temperature of the final heat treatment for the final wire diameter is Tc (°C), the intermediate heat treatment temperature Tm being 50°C or more higher than the final heat treatment temperature Tc makes it easy to adjust the small diameter ratio of the Si phase to 30% or more and 95% or less. Specifically, by increasing the intermediate heat treatment temperature, the Si dissolved in the Al phase can be homogenized, and by lowering the temperature of the final heat treatment step, the concentration of Si dissolved in the Al phase can be reduced. Combining these temperatures can increase the number of fine Si phases and increase the small diameter ratio of the Si phase. Among multiple intermediate heat treatments, adjusting the temperature of the final intermediate heat treatment is more effective, and it is thought that this can promote an increase in the number of fine Si phases by utilizing dislocations and the like increased in the subsequent processing steps.

[0093] Regarding the final heat treatment conditions, it is effective to adjust the temperature range to 200°C or higher and lower than 360°C, and the time range to 2 hours or higher and lower than 20 hours. The final heat treatment promotes recovery and recrystallization of the Al phase, and at the same time, the amount of Si dissolved in the Al phase changes depending on the heat treatment temperature, thereby changing the recrystallization temperature. By adjusting the progress of recrystallization by the final heat treatment, it becomes easy to control the small diameter ratio of the Si phase. For example, by adjusting the final heat treatment to a low temperature or for a short time, the small diameter ratio of the Si phase tends to increase. Furthermore, by adjusting the final heat treatment conditions, it becomes easy to control the average circle equivalent diameter of the Si phase (average diameter of the Si phase).

[0094] <Control of Shape Ratio (e / f) of Si Phase> In order to adjust the shape ratio (e / f) of the Si phase in the L cross section, it is effective to control the conditions of the above-mentioned two-stage heat treatment (solution treatment and homogenization treatment) and the final heat treatment.

[0095] The temperature range of the solution treatment of the ingot is 400°C or higher but lower than 550°C for 1 hour or higher but lower than 6 hours, and the subsequent homogenization treatment is preferably 250°C or higher but lower than 350°C for 2 hours or higher but lower than 6 hours. The solution treatment causes the division and growth of the Si phase crystallized during the solidification process, and the homogenization treatment causes solid solution and precipitation of Si at the interface of the Si phase, thereby controlling the shape of the Si phase. For example, when solution treatment is performed at a high temperature, the shape ratio (e / f) of the Si phase tends to decrease.

[0096] <Control of Crystal Orientation of Si Phase in ND Direction> In order to adjust the crystal orientation of the Si phase in the ND direction, it is effective to subject the ingot to two-stage heat treatment (solution treatment and homogenization treatment) and to control the area reduction rate during wire drawing.

[0097] It is effective to set the solution treatment temperature range to 450°C or higher and lower than 550°C for 1 hour or higher and lower than 6 hours. After this solution treatment, it is effective to perform homogenization treatment at 250°C or higher and lower than 350°C for 2 hours or higher and lower than 6 hours. This can promote the separation and growth of the Si phase that crystallizes during the solidification process, and can adjust the orientation of the <100> crystal orientation and the <111> crystal orientation for the Si phase in the ND direction.

[0098] It is also effective to incorporate wiredrawing in which the die area reduction rate is a high rate, in the range of more than 20% but less than 30%, into the wiredrawing process to increase the processing strain and control the orientation of the crystal orientation of the Si phase. When two or more wiredrawing processes are performed, the die area reduction rate should be more than 20% but less than 30% in at least one wiredrawing process. By adjusting the wire area reduction rate within the above range, the entire Al bonding wire or Al bonding ribbon can be significantly deformed during die processing, thereby increasing the processing strain even within the Al bonding wire or Al bonding ribbon. The Si phase is then aligned in the central axis direction of the Al bonding wire or Al bonding ribbon, and the processing strain within the Si phase is adjusted. Even if it is not easy to adjust the crystal orientation of the Si phase using only the above-mentioned two-stage heat treatment (solution treatment and homogenization treatment) of the ingot, incorporating adjustment of the die area reduction rate within the above range makes it possible to adjust the orientation ratio of the <100> crystal orientation and the <111> crystal orientation of the Si phase in the ND direction.

[0099] As mentioned above, the above is an example of the manufacture of Al bonding wire, which is a wire material, as a representative example of Al bonding wire or Al bonding ribbon. The same procedure can also be used to manufacture Al bonding ribbon, which is a strip material. The temperature and time of the heat treatment can be approximately the same as those described above. Furthermore, when manufacturing Al bonding ribbon by rolling, the die area reduction rate can be adjusted by replacing it with the rolling reduction rate.

[0100] [Semiconductor Device] A semiconductor device can be manufactured by connecting electrodes on a semiconductor chip to external electrodes on a lead frame or substrate using the Al bonding wire or Al bonding ribbon of the present invention. That is, the semiconductor device of the present invention includes the Al bonding wire or Al bonding ribbon of the present invention. As mentioned above, wedge bonding is used for both the first bonding with the electrode on the semiconductor chip and the second bonding with the electrode on the lead frame or substrate.

[0101] In one embodiment, the semiconductor device of the present invention comprises a circuit board, a semiconductor chip, and an Al bonding wire or Al bonding ribbon for electrically connecting the circuit board and the semiconductor chip, and is characterized in that the Al bonding wire or Al bonding ribbon is the Al bonding wire or Al bonding ribbon of the present invention.

[0102] In the semiconductor device of the present invention, the circuit board and semiconductor chip are not particularly limited, and known circuit boards and semiconductor chips that can be used to configure a semiconductor device may be used. Alternatively, a lead frame may be used instead of the circuit board. For example, a semiconductor device may be configured including a lead frame and a semiconductor chip mounted on the lead frame, as in the semiconductor device described in JP 2020-150116 A.

[0103] Examples of the semiconductor device include various semiconductor devices used in electrical appliances (e.g., computers, mobile phones, digital cameras, televisions, air conditioners, solar power generation systems, etc.) and vehicles (e.g., motorcycles, automobiles, trains, ships, aircraft, etc.), and among these, power semiconductor devices are preferred.

[0104] The present invention will be specifically described below with reference to examples, although the present invention is not limited to the examples shown below.

[0105] (Sample) The sample preparation method will be described. The raw material Al had a purity of 4N (99.99% by mass or more), with the remainder consisting of inevitable impurities. The alloying elements Si, the first element group (Sr, Na, Fe, P), the second element group (Ti, Ni, Mg, Cu), and other elements (Mn, Zn) had a purity of 99.99% by mass or more, with the remainder consisting of inevitable impurities. The Al alloy used for the Al bonding wire or Al bonding ribbon was produced by loading the Al raw material and the alloying element raw materials into an alumina crucible and melting them using a high-frequency heating furnace. The atmosphere in the furnace during melting was an Ar atmosphere, and the maximum temperature of the molten metal during melting was 800°C or higher but lower than 1050°C. The cooling method after melting was air cooling (cooling in the air) or water cooling (cooling in water).

[0106] A cylindrical ingot with a diameter of 6 mm was obtained by melting, and the ingot was subjected to solution treatment and homogenization treatment. After that, a wire drawing process using a die and intermediate heat treatment were performed to produce an Al bonding wire with a diameter of 300 μm. Furthermore, using the Al bonding wire with a diameter of 300 μm as the starting material, an Al bonding ribbon with a thickness of 100 μm and a width of 600 μm was produced by two-stage rolling. The temperature range of the solution treatment was 500 ° C or higher and lower than 550 ° C, and the time was 2 hours or higher and lower than 4 hours. After the solution treatment, a homogenization treatment was performed continuously during cooling. The temperature range of the homogenization treatment was 250 ° C or higher and lower than 350 ° C, and the time was 2 hours or higher and lower than 5 hours. The cooling method after the homogenization treatment was air cooling in the atmosphere.

[0107] The number of intermediate heat treatments was between three and four. The wire diameter after intermediate heat treatment relative to the final wire diameter was 6.5 to 7.0 times for the first intermediate annealing, 4.0 to 5.0 times for the second intermediate annealing, and 2.0 to 3.0 times for the third intermediate annealing. When intermediate annealing was performed four times, the wire diameter was 7.5 to 8.5 times the final wire diameter. The temperature range of the intermediate heat treatments was adjusted to 300°C or higher and lower than 370°C for 1 hour or longer and less than 3 hours for the first and second intermediate annealings, and 250°C or higher and lower than 400°C for 2 hours or longer and less than 40 hours for the third and fourth intermediate annealings.

[0108] A commercially available lubricant was used during wire drawing, and the wire area reduction rate per die during wire drawing was 10.0% or more and less than 30.0%. The wire area reduction rate was adjusted according to the wire diameter of the die. The temperature range of the final heat treatment was 200°C or more and less than 350°C, and the time of the final heat treatment was 2 hours or more and less than 20 hours. The temperature of the final heat treatment (Tc) was selected within a temperature range 50 to 100°C lower than the temperature (Tm) of the third or fourth intermediate annealing described above.

[0109] In some examples, the wire was drawn using a die with a die angle of 14° or more and less than 18°.

[0110] (Method for measuring element content) The concentration analysis of elements contained in the Al bonding wire or Al bonding ribbon was performed using an ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer) (manufactured by Hitachi High-Tech Science Corporation, "PS3520UVDDII") or an ICP-MS (Inductively Coupled Plasma-Mass Spectrometer) (manufactured by Agilent Technologies, Inc., "Agilent 7700x ICP-MS") as an analytical device.

[0111] (Method for measuring the orientation ratio of the crystal orientation of the Al phase and the Si phase) The L cross section (cross section in the central axis direction including the central axis) of the Al bonding wire or Al bonding ribbon was used as the inspection surface, and the crystal orientation of the Al phase and the Si phase was measured.

[0112] For the measurements, an FE-SEM (SU-70 manufactured by Hitachi High-Technologies Corporation) was used, and the analysis software used was APEX (for data collection), OIM Data Collection (for ChiScan), and OIM Analysis (for data analysis) manufactured by TSL Solutions. Three measurement areas were randomly selected at intervals of 50 cm or more relative to the central axis of the Al bonding wire or Al bonding ribbon, and measurements were performed on the three areas. The measurement area was determined so that it was 300 μm or more and less than 800 μm in the central axis direction of the Al bonding wire or Al bonding ribbon, and the entire Al bonding wire or Al bonding ribbon was included in the direction perpendicular to the central axis. The main conditions for the EDS and EBSD measurements were an acceleration voltage of 15 kV, a measurement magnification of 350x, a scan speed of 30 to 120 points / second, and a measurement interval in the range of 0.1 to 0.3 μm. Here, if the scanning speed is fast, the measurement time can be shortened, but there is a concern that the measurement accuracy of the EDS may decrease. It is desirable to select an appropriate scanning speed within the above range.

[0113] -Crystal orientation of Al phase- To measure the orientation ratio of the crystal orientation of the Al phase in the L-section of the Al bonding wire or Al bonding ribbon, an SEM-EDS-EBSD device was used, and a method was used in which the Al concentration and Si concentration information obtained by SEM-EDS was combined with the crystal orientation information obtained by EBSD. Specifically, the measurement was performed according to the following procedures (1) to (3). (1) In the measurement area where the L-section of the Al bonding wire or Al bonding ribbon was used as the inspection surface, Al and Si concentration measurements were performed using EDS and crystal orientation measurements were performed using EBSD simultaneously. (2) Al and Si were separated and extracted using the Chi Scan function, a function of the EBSD analysis software. Specifically, Al and Si were separated and identified from the EDS measurement results of Si by setting a tolerance equivalent to the Si threshold. The Al and Si crystal information in the material file was used for crystal orientation analysis. Here, the tolerance condition was mainly set to 30% and adjusted as necessary. (3) For the region identified as Al phase, the crystal orientation was analyzed, and the orientation ratio of the <100> crystal orientation of the Al phase in the RD direction was calculated. As the crystal orientations to be investigated, at least three types of typical crystal orientations of Al metal, <111>, <110>, and <100>, were selected, and, if necessary, a crystal orientation with a high ratio was also selected. Here, the orientation ratio of the crystal orientations was calculated using the partial ratio.

[0114] The orientation ratio of the <100> crystal orientation of the Al phase in the RD direction was determined as the average value (arithmetic mean) of the values ​​obtained for the three measurement regions by the above steps (1) to (3).

[0115] -Crystal orientation of Si phase- To measure the orientation ratio of the crystal orientation of the Si phase in the L cross section of the Al bonding wire or Al bonding ribbon, a SEM-EDS-EBSD device was used, similar to the measurement of the orientation ratio of the crystal orientation of the Al phase, and a method was used in which the information on the Al concentration and Si concentration obtained by SEM-EDS was combined with the information on the crystal orientation obtained by EBSD. In detail, after performing the above procedures (1) and (2), the measurement was performed according to the following procedure (3). (3) The crystal orientation of the region identified as the Si phase was analyzed, and the orientation ratio of the <100> crystal orientation and the orientation ratio of the <111> crystal orientation of the Si phase in the ND direction were calculated. The partial ratio was used for the orientation ratio of the crystal orientation.

[0116] The orientation ratio of the <100> crystal orientation and the orientation ratio of the <111> crystal orientation of the Si phase in the ND direction were calculated as the average value (arithmetic mean) of the values ​​obtained for the three measurement regions by the above steps (1) to (3).

[0117] (Small diameter ratio of Si phase [Ns / Nc × 100 (%)]) To measure the small diameter ratio of Si phase [Ns / Nc × 100 (%)] in the L cross section, a SEM-EDS-EBSD device was used, similar to the measurement of the orientation ratio of the crystal orientation of the Al phase. The method combined the information on the Al concentration and Si concentration obtained by SEM-EDS with the information on the crystal orientation obtained by EBSD. Specifically, after performing the above procedures (1) and (2), the measurement was performed according to the following procedure (3). (3) For the region identified as the Si phase, the crystal orientation was analyzed, and if the orientation difference between the measurement points was 15° or more, it was determined to be a grain boundary, and the circle-equivalent diameter of each crystal grain was calculated. The number of crystal grains identified as the Si phase was tallied to determine the total number of Si phase particles Nc. Here, Si phases with a circle-equivalent diameter of 0.5 μm or more were targeted. Taking into account the analytical accuracy of current EDS and EBSD analysis devices, fine particles less than 0.5 μm were excluded. Next, the number Ns of Si phases having a circle equivalent diameter in the range of 0.5 μm to 0.8 μm was counted, and the ratio of Ns to Nc [Ns / Nc×100(%)] (small diameter ratio of Si phases) was calculated.

[0118] The small diameter ratio of the Si phase was determined as the average (arithmetic mean) of the values ​​obtained for the three measurement regions by the above procedures (1) to (3).

[0119] (Method for Measuring the Average Diameter of Si Phase) To measure the average diameter of the Si phase in the L-section of an Al bonding wire or Al bonding ribbon, a SEM-EDS-EBSD device was used, similar to the measurement of the crystal orientation of the Al phase. The method combined the information on the Al concentration and Si concentration obtained by SEM-EDS with the information on the crystal orientation obtained by EBSD. Specifically, after performing the above procedures (1) and (2), the measurement was performed according to the following procedure (3). (3) For the region identified as the Si phase, the crystal orientation was analyzed, and if the orientation difference between the measurement points was 15° or more, it was determined to be a grain boundary, and the circle-equivalent diameter of each crystal grain was calculated. The circle-equivalent diameters of each crystal grain were then averaged to calculate the average diameter of the Si phase. Here, the average value obtained by area average (area-weighted average) was used in the average calculation. Furthermore, when calculating the average diameter of the Si phase in the L-section, only Si phases with a diameter (circle-equivalent diameter) of 0.5 μm or more were considered.

[0120] The average diameter of the Si phase was determined as the average (arithmetic mean) of the values ​​obtained for the three measurement regions according to the above procedures (1) to (3).

[0121] (Method for Measuring the Shape of Si Phase) To measure the shape ratio (e / f) of the Si phase in the L cross section of an Al bonding wire or Al bonding ribbon, a SEM-EDS-EBSD device was used, similar to the measurement of the orientation ratio of the crystal orientation of the Al phase. A method was used in which the information on the Al concentration and Si concentration obtained by SEM-EDS was combined with the information on the crystal orientation obtained by EBSD. Specifically, after performing the above procedures (1) and (2), the measurement was performed according to the following procedure (3). (3) For the region identified as the Si phase, the crystal orientation was analyzed, and if the orientation difference between the measurement points was 15° or more, it was determined to be a grain boundary, and the shape ratio (e / f) of each crystal grain was calculated. The shape ratios (e / f) of each crystal grain were then averaged to calculate the average value of the shape ratio (e / f) of the Si phase. Here, the average value of the shape ratio (e / f) of the Si phase was calculated using the numerical value of the Grain Shape Aspect Ratio ("Grain Shape Aspect Ratio") of the analysis software. Regarding the calculation method of the grain shape aspect ratio, the ratio (e / f) of the short side length (e) (Grain Shape Minor Axis) and the long side length (f) (Grain Shape Major Axis) of one crystal grain is automatically calculated by the software. Here, for the average calculation, the average value obtained by area average (area weighted average) was used.

[0122] The shape ratio (e / f) of the Si phase was determined as the average value (arithmetic mean) of the values ​​obtained for the three measurement regions by the above procedures (1) to (3).

[0123] (Method for evaluating Al bonding wire or Al bonding ribbon) The evaluation method for Al bonding wire will be described. The wire diameter of the Al bonding wire used for evaluation was Φ300 μm. The semiconductor chip used was made of Si, and the electrodes on the semiconductor chip were made of a 4 μm thick film of an alloy with a composition of Al-0.5% Cu. The substrate used was an Al alloy with a 5 μm thick film of Ni. A commercially available wire bonder (manufactured by Ultrasonic Industries Co., Ltd.) was used to bond the Al bonding wire, and wedge bonding was used for both the first bonding (bonding to the electrode on the semiconductor chip) and the second bonding (bonding to the substrate). The Al bonding ribbon was bonded using a Hesse fully automatic bonder "BJ955" equipped with a ribbon bond head.

[0124] (Method for Evaluating High-Speed ​​Temperature Cycle Reliability) A commercially available high-speed thermal shock tester was used for the high-speed temperature cycle test (high-speed TCT). In high-speed TCT, hot air is blown onto the sample to rapidly heat it. The sample used for high-speed TCT had a structure in which a semiconductor chip was mounted on a substrate, and electrodes on the semiconductor chip and electrodes on the substrate were connected with Al bonding wire or Al bonding ribbon. The sample placed in the sample chamber of the high-speed thermal shock tester was repeatedly subjected to thermal loads, with heating and cooling cycles consisting of one cycle. The minimum temperature during cooling was -50°C, and the maximum temperature during heating was 175°C. The heating time, including the temperature rise time, was 20 seconds, and the cooling time, including the temperature drop time, was 40 seconds. After the start of the test, the sample was removed after 20,000 cycles and a shear strength test of the first bonded joint was performed. The shear strength (shear strength) value of the first bonded joint used to evaluate the high-speed temperature cycle reliability was the average shear strength of 10 randomly selected first bonded joints. The ratio (percentage) of the average shear strength after high-speed TCT to the average shear strength before the test was taken as the strength retention rate. The higher this strength retention rate, the better the reliability of the joint. A strength retention rate of 85% or more was judged to be excellent and given a rating of "3," 75% or more but less than 85% was judged to be excellent and given a rating of "2," 70% or more but less than 75% was judged to require improvement and given a rating of "1," and less than 70% was judged to be problematic in practical use and given a rating of "0." "3" and "2" were judged to be pass, while "1" and "0" were judged to be fail. The evaluation results are shown in the "High-speed temperature cycle reliability" column in the table. The high-speed temperature cycle reliability required for next-generation SiC semiconductors corresponds to 20,000 cycles.

[0125] (Method for evaluating the variation in bond strength in high-speed temperature cycle testing) In the above-mentioned high-speed TCT, the shear strength of 20 first bonded sections was measured after 20,000 cycles. When evaluating the variation in bond strength in the high-speed TCT, the unbiased standard deviation (σ) of the shear strength was calculated. Since the unbiased standard deviation of the shear strength of the first bonded section is not significantly affected by the conditions of the first bond, it is useful as an index for appropriately evaluating the characteristics of Al bonding wire or Al bonding ribbon. If σ was less than 30 gf, the variation in bonding strength was judged to be particularly small and the stability was excellent, and the rating was "3." If σ was 30 gf or more but less than 50 gf, the variation in bonding strength was judged to be small and the stability was excellent, and the rating was "2." If σ was 50 gf or more but less than 70 gf, the variation in bonding strength was judged to be within the acceptable range and the stability was good, and the rating was "1." If σ was 70 gf or more, the variation in bonding strength was judged to be large and there was a practical problem, and the rating was "0." The evaluation results are shown in the column "Variation in high-speed TCT bonding strength" in the table.

[0126] (Method for Evaluating First Bond Strength) The method for evaluating the first bond strength will be described. The first bond strength was evaluated by a shear strength test. First bonding was performed at 10 locations under bonding conditions suitable for the reliability test, and the shear strength (shear strength) of the first bonded portion was measured. Under these bonding conditions, the ultrasonic output was set slightly higher to ensure a sufficient bonding area. A commercially available microshear strength tester (Nordson 4000-PLUS) was used to measure the shear strength. The shear rate was 200 μm / sec, and the height of the shear tool was 10 μm from the electrode surface. The shear strength was measured by fixing the substrate to which the Al bonding wire or Al bonding ribbon was bonded using a jig. If the average shear strength of the 10 first joints was 1500 gf or more, it was judged to be excellent and rated as "3", if it was 1300 gf or more but less than 1500 gf, it was judged to have no practical problem and rated as "2", if it was 1000 gf or more but less than 1300 gf, it was judged to need improvement and rated as "1", and if it was less than 1000 gf, it was judged to have a practical problem and rated as "0". The evaluation results are shown in the "1st joint strength" column in the table.

[0127] (Method for Evaluating Wire Breakage During Processing) The method for evaluating wire breakage during processing will be described below. Wire drawing was performed from a wire diameter of 6 mm to a wire diameter of 0.3 mm, and the number of wire breakages was confirmed. The wire drawing conditions, such as the feed rate and area reduction rate, were selected from the conditions described above, and the appropriate manufacturing conditions were adjusted and changed for each wire. The length of the drawn Al bonding wire ranged from 100 to 200 m, and the number of wire breakages was calculated by converting it to per 100 m. If the number of wire breakages was 0, it was judged to be good and rated as "3." If it was 1, it was judged that it could be addressed by improving the manufacturing conditions and rated as "2." If it was 2 to 4, it was judged that there was a decrease in productivity and rated as "1." If it was 5 or more, it was judged that it was difficult to use in practice and rated as "0." The evaluation results are shown in the "Wire Breakage During Processing" column in the table.

[0128] (Method for evaluating surface scratches and abrasions) The surface quality of the Al bonding wire or Al bonding ribbon was evaluated, focusing on scratches and abrasions. The wire diameter of the Al bonding wire was Φ300 μm. The Al bonding ribbon was 100 μm thick and 600 μm wide. Three measurement areas were randomly selected at intervals of 1 m or more along the central axis of the Al bonding wire or Al bonding ribbon, and three pieces of approximately 2 cm length were taken from each of the three locations, for a total of nine samples. Specifically, the surface was observed using an SEM at magnifications ranging from 50 to 500 times. Scratches longer than 50 μm and abrasions longer than 30 μm were judged to be defective. The number of scratches and abrasions was counted, and if there were zero, the sample was judged to be good and passed, giving a rating of "3." If there were one to two locations, the sample was judged to be acceptable for practical use, giving a rating of "2." If there were three to seven locations, the surface quality was judged to be poor, giving a rating of "1." If there were eight or more locations, the sample was judged to be difficult to use, giving a rating of "0." The evaluation results are shown in the "Surface properties" column in the table.

[0129] The evaluation results of the examples and comparative examples are shown in Tables 1 to 4. Examples 1 to 44 and comparative examples 1 to 10 in Tables 1 to 3 are results for Al bonding wires, and Examples B1 to B3 and comparative example B1 in Table 4 are results for Al bonding ribbons.

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[0131]

[0132]

[0133]

[0134] REFERENCE SIGNS LIST 1 Al bonding wire 10 Central axis 11 L-section 2 Al bonding ribbon 20 Central axis 21 L-section 3 Al bonding wire or Al bonding ribbon 31 Si phase 32 Central axis direction of Al bonding wire or Al bonding ribbon

Claims

1. An Al bonding wire or Al bonding ribbon containing 3.0% by mass or more and 20.0% by mass or less of Si, wherein, when the crystal orientation of the Al phase in the L cross section (cross section in the central axis direction including the central axis) of the Al bonding wire or Al bonding ribbon is measured, the orientation ratio of the <100> crystal orientation, which has an angular difference of 15° or less with respect to the direction parallel to the central axis (RD direction), is 15% or more and 50% or less, and when the number of Si phases having a circular equivalent diameter of 0.5 μm or more and 0.8 μm or less in the L cross section is Ns and the number of Si phases having a circular equivalent diameter of 0.5 μm or more in the L cross section is Nc, the ratio of Ns to Nc [Ns / Nc x 100 (%)] is 30% or more and 95% or less.

2. An Al bonding wire or Al bonding ribbon as described in claim 1, wherein the ratio of Ns to Nc [Ns / Nc x 100 (%)] is 40% or more.

3. An Al bonding wire or Al bonding ribbon as described in claim 1 or 2, wherein, when the crystal orientation of the Si phase in the L cross section is measured, the total orientation ratio of the <100> crystal orientation and the <111> crystal orientation, which have an angular difference of 15° or less with respect to the perpendicular direction (ND direction) of the central axis, is 20% or more and 60% or less.

4. An Al bonding wire or Al bonding ribbon described in any one of claims 1 to 3, wherein the average ratio (e / f) of the short side length e to the long side length f of the Si phase in the L cross section is 0.20 or more and 0.70 or less.

5. An Al bonding wire or Al bonding ribbon according to any one of claims 1 to 4, further containing at least one of Sr, Na, Fe, and P in a total amount of 10 ppm by mass or more and 800 ppm by mass or less.

6. An Al bonding wire or Al bonding ribbon according to any one of claims 1 to 5, further containing at least one of Ti, Ni, Mg, and Cu in a total amount of 100 ppm by mass or more and 2000 ppm by mass or less.

7. An Al bonding wire or Al bonding ribbon according to any one of claims 1 to 6, wherein the total concentration of elements other than Al, Si, Sr, Na, Fe, P, Ti, Ni, Mg and Cu in the Al bonding wire or Al bonding ribbon is 0.5 mass% or less.

8. An Al bonding wire or Al bonding ribbon according to any one of claims 1 to 7, wherein the orientation ratio of the crystal orientation, the circle equivalent diameter of the Si phase, and the number thereof are values ​​measured using a SEM-EDS-EBSD device.

9. An Al bonding wire or Al bonding ribbon described in any one of claims 4 to 8, wherein the average value of the ratio (e / f) of the short side length e to the long side length f of the Si phase is a value measured using a SEM-EDS-EBSD device.

10. An Al bonding wire or Al bonding ribbon according to any one of claims 1 to 9, which is for use in a semiconductor device.

11. A semiconductor device comprising an Al bonding wire or an Al bonding ribbon according to any one of claims 1 to 10.

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