Al connecting material

Abstract

Provided is an Al connecting material which can suppress the occurrence of internal cracks during production and which exhibits excellent temperature cycle reliability. Provided is an Al connecting material containing 3.0 mass% to 12.0 mass% (inclusive) of Si, and containing 5 mass ppm to 800 mass ppm (inclusive) of at least one of Sr, Na, Eu, and Ca in total.

Description

Technical Field

[0001] The present invention relates to an Al connection material. Background Art

[0002] In a semiconductor device, electrodes formed on a semiconductor chip and electrodes on a lead frame or a substrate are connected by bonding wires (wire materials) or bonding tapes (strip materials). In a power semiconductor device, bonding wires or bonding tapes mainly made of aluminum (Al) are adopted. The wire diameter of the Al bonding wire is mainly in the range of 100 μm to 600 μm, and the width of the Al bonding tape is mainly in the range of 100 μm to 3000 μm, and the thickness is in the range of 50 μm to 600 μm. Herein, the Al bonding wire or the Al bonding tape is collectively referred to as an Al connection material.

[0003] In a power semiconductor device, silicon (Si) is mostly used as a material for the semiconductor chip, and an Al—Si alloy or an Al—Cu alloy is mostly used as a material for the electrodes formed on the semiconductor chip. In addition, power semiconductor devices using Al connection materials are mostly used in high-power equipment such as air conditioners or solar power generation systems, and semiconductor devices for vehicles.

[0004] Regarding the bonding method of the Al connection material, both the first bonding to the electrodes on the semiconductor chip and the second bonding to the electrodes on the lead frame or the substrate are performed by wedge bonding. The so-called wedge bonding is a method of applying ultrasonic vibration and load to the Al connection material via a metal fixture (implement), breaking the surface oxide film of the Al connection material and the electrode material to expose a newly generated surface, and performing solid-phase diffusion bonding. This connection method is characterized by connecting in a solid state without melting the connection material, and is a bonding technique different from the welding technique of melting the connection material.

[0005] Compared with general power semiconductor devices, in next-generation power semiconductor devices, long-term stable operation is required. The power semiconductor device repeats the on and off of the current and operates. When current is supplied to an Si-based semiconductor chip through the Al connection material, the temperature of the first bonding portion rises. On the other hand, when the supply of current is stopped, the temperature of the first bonding portion decreases. In this way, when the power semiconductor operates, the temperature of the first bonding portion repeatedly rises and falls. Thus, in the first bonding portion, the thermal stress caused by the thermal expansion difference between the Al connection material and the semiconductor chip is repeatedly applied. In the case of using a connection material composed only of high-purity Al, the thermal stress causes the Al connection material to break in a relatively short time, and it is difficult to meet the performance requirements of next-generation power semiconductor devices. Therefore, in next-generation power semiconductors, it is required to improve the joint life (hereinafter, referred to as "temperature cycle reliability") accompanying the temperature rise and fall of the first bonding portion.

[0006] Regarding the requirements for temperature cycle reliability, an Al bonding material mainly aimed at improving mechanical strength has been proposed. As a method for improving the mechanical properties of the Al bonding material, 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 that contains 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. In this patent document, it is disclosed that the reduction in the bonding strength of the first joint portion in a cold temperature cycle test in the temperature range of 70°C to 120°C is delayed by the effect of high strength improvement based on solid solution strengthening of Mg or Si or the effect of suppressing cracks based on precipitated magnesium silicide (Mg2Si).

[0008] Patent Document 2 discloses a bonding wire characterized by containing 0.01 to 0.2 mass% of iron (Fe), containing 1 to 20 mass ppm of silicon (Si), and the remaining part being composed of an alloy of Al with a purity of 99.997 mass% or more, having a solid solution amount of Fe of 0.01 to 0.06%, a precipitation amount of Fe being 7 times or less the solid solution amount of Fe, and a fine structure with an average crystal grain size of 6 to 12 μm. In this patent document, it is disclosed that the mechanical strength of the matrix is improved by uniformly dispersing intermetallic compound particles of Fe and Al in Al, and further refining the recrystallized grains, thereby suppressing the reduction in the bonding strength of the first joint portion in a thermal shock test in the temperature range of -50°C to 200°C.

[0009] Patent Document 3 discloses a bonding wire formed by melting an Al - Si alloy containing 0.1 to 5 mass% of silicon (Si) and the remaining part being composed of Al and impurities, and ejecting and rapidly cooling it to form a fine wire. In this patent document, it is disclosed that the molten Al - Si alloy is rapidly cooled to make Si finely and uniformly dispersed, thereby improving the mechanical strength.

[0010] Prior art documents

[0011] Patent documents

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

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

[0014] Patent Document 3: Japanese Patent Application Laid - Open No. 59 - 57440 Summary of the invention

[0015] Technical problem to be solved by the invention

[0016] As described above, compared with general power semiconductor devices, next-generation power semiconductor devices are required to be able to withstand longer usage. When the power semiconductor device operates, the temperature of the first joint repeatedly rises and falls. As a result, since the Al bonding material has a larger coefficient of linear expansion than the semiconductor chip, thermal stress caused by the difference in the coefficient of linear expansion between the two occurs at the first joint, and there is a case where the Al bonding material is finally fatigued and damaged. As one of the tests for accelerating the evaluation of the life (temperature cycle reliability) of the joint accompanying the temperature rise and fall of the first joint, there is a temperature cycle test. The Al bonding material used in next-generation power semiconductors is required to exhibit excellent temperature cycle reliability in the temperature cycle test. However, in the case of an Al bonding material strengthened by adding Si or the like as disclosed in Patent Documents 1 to 3, in the temperature cycle test assumed for use in next-generation power semiconductor devices, the following technical problems have been confirmed: Cracks develop relatively rapidly in the Al alloy electrode having a lower strength than the Al bonding material, and it is difficult to stably obtain good temperature cycle reliability.

[0017] In addition, regarding Al alloys containing a high concentration of alloy elements, due to hardening, workability is reduced, manufacturing yield is deteriorated, quality is reduced, etc., which become obstacles to practical application. It has also been found that in the Al bonding material strengthened by adding Si or the like, cracks (hereinafter referred to as "internal cracks") are generated in the Al bonding material during wire drawing. The reason is considered to be the formation of coarse Si precipitates, non-uniform plastic deformation of the Al phase, etc. The presence of internal cracks can induce adverse conditions such as a decrease in temperature cycle reliability and melting fracture when a large current is applied, so it is required to suppress the occurrence of internal cracks.

[0018] An object of the present invention is to provide an Al bonding material that can suppress the occurrence of internal cracks during manufacturing and exhibits excellent temperature cycle reliability.

[0019] Technical means for solving the technical problems

[0020] The inventors of the present invention conducted in-depth research on the above technical problems and finally found that an Al bonding material containing 3.0 mass% or more and 12.0 mass% or less of Si and containing any one or more of Sr, Na, Eu, and Ca in a total amount of 5 mass ppm or more and 800 mass ppm or less can solve the above technical problems. Based on the relevant insights, further repeated research was conducted, and finally the present invention was completed.

[0021] That is, the present invention includes the following content.

[0022] <1>

[0023] An Al bonding material,

[0024] Containing 3.0% by mass or more and 12.0% by mass or less of Si, and

[0025] containing any one or more of Sr, Na, Eu, and Ca in a total amount of 5 mass ppm or more and 800 mass ppm or less.

[0026] <2>

[0027] The Al joining material as described in <1>,

[0028] when measuring the crystal orientation of the Si phase in the L cross-section (the cross-section in the central axis direction including the central axis) of the Al joining material, the total of the orientation ratios of the <111> crystal orientation and the <110> crystal orientation with an angular difference of 15° or less with respect to the central axis direction is 20% or more and 70% or less.

[0029] <3>

[0030] The Al joining material as described in <1> or <2>,

[0031] The average diameter of the Si phase in the L cross-section is 0.8 μm or more and 4 μm or less.

[0032] <4>

[0033] The Al joining material as described in any one of <1> to <3>,

[0034] further contains any one or more of Ti, B, and Zr in a total amount of 10 mass ppm or more and 500 mass ppm or less.

[0035] <5>

[0036] The Al joining material as described in any one of <1> to <4>,

[0037] further contains any one or more of Ni, Y, Yb, and Sc in a total amount of 5 mass ppm or more and 500 mass ppm or less.

[0038] Advantages of the Invention

[0039] According to the present invention, an Al joining material can be provided, which can suppress the generation of internal cracks during manufacturing and exhibits excellent temperature cycle reliability. Description of the Drawings

[0040] Figure 1 is a schematic diagram for explaining the measurement object surface (inspection surface) when measuring the crystal orientation and average particle size of the Si phase for the Al joining material. The measurement object surface is the cross-section (L cross-section) in the central axis direction including the central axis of the Al joining material.

[0041] Figure 2 is a schematic diagram for explaining the intermediate omission defect of the first joint part.

[0042] Figure 3 It is an example of an internal crack of an Al bonding material observed through a soft X-ray transmission device. Detailed implementation mode

[0043] Hereinafter, the present invention will be described in detail in conjunction with its preferred implementation modes. Sometimes, the drawings will be referred to in the description. However, each drawing only schematically shows the shape, size, and configuration of the components to the extent that the invention can be understood. The present invention is not limited to the following implementation modes and illustrative examples, and can be arbitrarily changed and implemented without departing from the protection scope of the present invention and its equivalent scope.

[0044] [Al bonding material]

[0045] The Al bonding material of the present invention is characterized in that it contains 3.0% by mass or more and 12.0% by mass or less of Si, and contains one or more of Sr, Na, Eu, and Ca in a total amount of 5 mass ppm or more and 800 mass ppm or less.

[0046] As described above, in the temperature cycle test (TCT), when using a bonding material composed only of high-purity Al, cracks progress relatively quickly inside the bonding material, and it is difficult to obtain good temperature cycle reliability. On the other hand, it has also been confirmed that when using an Al bonding material strengthened by adding Si or the like, since cracks progress inside the Al alloy electrode with relatively low strength, it is difficult to obtain the temperature cycle reliability required for next-generation power semiconductor devices. Furthermore, regarding the Al bonding material strengthened by adding Si or the like, internal cracks may occur during its manufacture.

[0047] The inventors of the present invention have conducted in-depth research to solve the above technical problems and finally found that: according to the Al bonding material containing 3.0% by mass or more and 12.0% by mass or less of Si, and containing one or more of Sr, Na, Eu, and Ca in a total amount of 5 mass ppm or more and 800 mass ppm or less, the occurrence of internal cracks can be suppressed during its manufacture, and excellent temperature cycle reliability is also brought. The Al bonding material of the present invention involved significantly contributes to achieving the temperature cycle reliability required for next-generation power semiconductor devices.

[0048] The Al bonding material of the present invention contains 3.0 mass% or more and 12.0 mass% or less of Si, and is composed of an Al phase in which Si is dissolved in Al and an Si phase formed by crystallization or precipitation of Si. Here, in the Al phase, other additive elements may also be dissolved in addition to Si. In addition, the Si phase is a general term for Si crystallized products and Si precipitated products. The so-called Si crystallized products are formed from the solution during solidification and are about 1 to 20 μm in size. In contrast, the so-called Si precipitated products are formed from the solid state and are about 0.1 to several μm in size.

[0049] The Al bonding material of the present invention can suppress the generation of internal cracks during manufacturing and can also bring excellent temperature cycle reliability. The reasons are inferred as follows.

[0050] Regarding the temperature cycle reliability, considering that the linear expansion coefficient of Si is smaller than that of Al, it helps to reduce the difference in the linear expansion coefficients between the Al bonding material and the semiconductor chip, and thus can reduce the generated thermal stress. In addition, the granular Si phase can suppress the growth of cracks generated at the bonding interface into the interior of the Al bonding material.

[0051] In addition, regarding the internal cracks, it is considered that in the surface of the Si phase composed of coarse Si crystallized products, the adhesion to the Al phase is reduced or peeled off from the Al phase, which becomes the starting point of the cracks. It is considered that if a high concentration of Si is contained and any one or more of Sr, Na, Eu, and Ca (hereinafter referred to as "the first element group") are contained in a specified amount, the effect of improving the interfacial adhesion between the Si phase and the Al phase can be obtained, and the occurrence of internal cracks can be suppressed. The reason for this is considered to be that a part of the first element group is concentrated on the surface of the Si phase to improve the adhesion, or by adding the first element group, the shape of the Si phase approaches granular or spherical, and the adhesion is improved, etc.

[0052] As described above, it is inferred that the Al bonding material of the present invention appropriately controls the factors contributing to the suppression of internal cracks and the improvement of temperature cycle reliability, and finally, as described above, it can suppress the generation of internal cracks during manufacturing and can also bring excellent temperature cycle reliability.

[0053] - Si concentration -

[0054] By setting the Si concentration in the range of 3.0 mass% or more and 12.0 mass% or less, it helps to reduce the thermal strain at the joint and improve the temperature cycle characteristics. If it is less than 3.0 mass%, the improvement effect is negligible. If it is higher than 12.0 mass%, there are problems such as low initial joint strength due to hardening and damage to the semiconductor chip. From the viewpoint of obtaining good temperature cycle reliability, the concentration of Si in the Al bonding material of the present invention is 3.0 mass% or more, preferably 3.5 mass% or more, more preferably 3.6 mass% or more, 3.8 mass% or more, 4.0 mass% or more, 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. On the other hand, when the hardness of the Al bonding material is too high, damage to the semiconductor chip is likely to occur during the first bonding under the bonding conditions of ultrasonic vibration and load commonly used. From the viewpoint of obtaining good bonding strength during the first bonding under normal bonding conditions, the Si concentration in the Al bonding material of the present invention is 12.0 mass% or less, preferably 11.5 mass% or less or 11.0 mass% or less, more 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.

[0055] For the concentration analysis of the elements contained in the Al bonding material of the present invention, for example, an ICP (Inductively Coupled Plasma) optical emission spectrometer or an ICP mass spectrometer can be used. When elements such as oxygen or carbon from atmospheric contaminants are adsorbed on the surface of the Al bonding material, it is effective to clean it with acid or alkali according to the adsorbed substances before analysis.

[0056] -Concentration of the first element group-

[0057] From the viewpoint of suppressing the generation of internal cracks during manufacturing and achieving good temperature cycle reliability, the total concentration of the first element group in the Al bonding material of the present invention is 5 mass ppm or more, preferably 10 mass ppm or more, more preferably 20 mass ppm or more, 30 mass ppm or more, 40 mass ppm or more, or 50 mass ppm or more, and further preferably 60 mass ppm or more, 80 mass ppm or more, or 100 mass ppm or more. The upper limit is 800 mass ppm or less, preferably 750 mass ppm or less, or 700 mass ppm or less, more preferably 650 mass ppm or less, or 600 mass ppm or less, and further preferably 580 mass ppm or less, 560 mass ppm or less, or 550 mass ppm or less. When the total concentration of the first element group is within the above preferred range, it is also beneficial from the viewpoints of suppressing damage to the semiconductor chip and easily achieving good first bonding strength.

[0058] - Crystal orientation of Si phase in the L cross-section -

[0059] From the viewpoints of obtaining better temperature cycle reliability and reducing the frequency of wire breakage during wire drawing processing, when measuring the crystal orientation of the Si phase in the L cross-section of the Al bonding material, the total ratio of the <111> crystal orientation and the <110> crystal orientation with an angular difference of 15° or less with respect to the central axis direction (hereinafter also referred to as the "<111> + <110> total ratio of the Si phase") is preferably in the range of 20% or more and 70% or less. In the present invention, the L cross-section of the Al bonding material, that is, the cross-section in the central axis direction including the central axis of the Al bonding material, is as described in the column of "(Method for measuring the crystal orientation of the Si phase)" below Figure 1 as described.

[0060] In addition to the control of the Al alloy components described above, when the total ratio of <111> + <110> of the Si phase is within the above range, the following effects can be obtained: the number of test cycles until the occurrence of a decrease in joint strength is extended, the temperature difference in the temperature cycle test is increased, etc., and better temperature cycle reliability can be achieved. The reason is considered to be that, by the alignment of the <111> crystal orientation and the <110> crystal orientation of the Si phase, effects such as the improvement of the adhesion at the interface between the Si phase and the Al phase and the reduction of the deformation in the central axis direction of the Al connection material are exhibited, and thus the occurrence of defects such as the progress of cracks at the joint caused by thermal strain in the temperature cycle test is suppressed. In addition, for an Al alloy containing Si at a high concentration of 3.0 mass% or more and 12.0 mass% or less, the frequency of wire breakage tends to increase in the wire drawing process. It is considered that one of the reasons is that the particles of the Si phase precipitated during solidification cause stress concentration during wire drawing and induce wire breakage. Regarding this point, it is inferred that when the first element group is contained in a specified amount and the total ratio of <111> + <110> of the Si phase is adjusted to the above preferred range, the occurrence of wire breakage can be reduced by the effect of alleviating stress concentration during wire drawing. From the viewpoint of obtaining more excellent temperature cycle reliability and reducing the occurrence frequency of wire breakage in wire drawing, the total ratio of <111> + <110> of the Si phase is preferably 25% or more, more preferably 26% or more, 28% or more, or 30% or more, and the upper limit is preferably 65% or less, more preferably 60% or less, 58% or less, 56% or less, 55% or less, 54% or less, 52% or less, or 50% or less.

[0061] For the determination of the total ratio of <111> + <110> of the Si phase in the L-section of the Al bonding material, a method that combines the information of the Al concentration and Si concentration obtained by SEM-EDS with the information of the crystal orientation obtained by electron backscatter electron diffraction method (EBSD) can be used. Specifically, in the measurement region where the L-section of the Al bonding material is used as the inspection surface, the concentration measurement of Al and Si by EDS and the crystal orientation analysis by EBSD are carried out simultaneously. Then, using the analysis software attached to the device, the Al phase and the Si phase are separated and extracted from the measurement results of EDS. Specifically, it is preferable to use the function of Chi Scan (chemical-assisted scanning) of the analysis software OIM Data Collection or OIM Anaysis (both manufactured by TSL Solutions) attached to the FE-SEM device. Then, for the region determined to be the Si phase, the orientation ratio of the <111> crystal orientation and the <110> crystal orientation of the Si phase can be calculated by using the analysis software attached to the device. When calculating this orientation ratio, the partial ratio calculated by taking only the area of the crystal orientation identified based on a certain reliability as the population in the measurement region is adopted. Therefore, in one embodiment, the orientation ratio of the crystal orientation of the Si phase in the L-section of the Al bonding material of the present invention is calculated by the following steps (1) to (3).

[0062] (1) In the measurement region where the L-section of the Al bonding material is used as the inspection surface, the concentration measurement of Al and Si by EDS and the crystal orientation measurement by EBSD are carried out simultaneously.

[0063] (2) Using the Chi Scan function, Al and Si are separated and extracted. Specifically, according to the EDS measurement result of Si, a tolerance equivalent to the threshold value of Si is set, so that Al and Si can be separated and identified. Using the crystal information of Al and Si from the material file, the crystal orientation can be analyzed.

[0064] (3) For the region determined to be the Si phase, the crystal orientation is analyzed, and the orientation ratio of the <111> crystal orientation and the <110> crystal orientation of the Si phase is calculated.

[0065] In the step (2) above, the setting of the tolerance (%) can be selected in the range of 20 - 40%, and in the standard analysis of the L-section of the Al bonding material, it is preferably compared at about 30%. A supplementary explanation for this step of adjusting the tolerance is given. Comparing with the shape and size of the Si phase identified from the EDS map showing the Si element concentration in two-dimensional display by EDS, it is preferable to select or confirm the value of the tolerance in the same way as the shape and size of the Si phase extracted and identified in the ChiScan function.

[0066] In the present invention, the orientation ratio of the <111> crystal orientation to the orientation ratio of the <110> crystal orientation of the Si phase in the L cross-section is set to the average value of each value obtained by measuring at three or more locations. When selecting the measurement region, from the viewpoint of ensuring the objectivity of the measurement data, it is preferable to obtain a measurement sample from the Al bonding material to be measured at intervals of 50 cm or more in the central axis direction of the Al bonding material for measurement. In addition, in the present invention, regarding the measurement region of the crystal orientation based on the EBSD method, it is expected that the length in the central axis direction of the Al bonding material is 300 μm or more and less than 800 μm, and the entire Al bonding material enters in the direction perpendicular to the central axis of the Al bonding material. However, in the case of a large size and difficulty in measuring the whole, it can be adjusted within a range of less than 600 μm.

[0067] -Average diameter of Si phase in L cross-section-

[0068] The Al bonding material of the present invention preferably has an average diameter of the Si phase in its L cross-section of 0.8 μm or more and 4 μm or less.

[0069] Regarding the Al bonding material strengthened by adding Si or the like, it is likely to damage the semiconductor chip during the first bonding. When adjusting the ultrasonic vibration or load to reduce such damage, there may be a phenomenon (hereinafter also referred to as "intermediate leakage") in which a portion with insufficient metal bonding is formed near the center of the bonding region between the Al bonding material and the electrode. Since the portion where intermediate leakage occurs has insufficient metal bonding, the bonding strength is low, which becomes the starting point of defects in the temperature cycle test.

[0070] When the average diameter of the Si phase in the L cross-section is in the range of 0.8 μm or more and 4 μm or less, the intermediate leakage of the first bonding portion can be suppressed. It is considered that by controlling the average diameter of the Si phase, effects such as promoting the deformation of the Al phase contributing to bonding or improving the transmission efficiency of ultrasonic vibration to the central portion of the bonding region can be obtained, and intermediate leakage can be suppressed.

[0071] From the viewpoint of further suppressing the intermediate leakage of the first bonding portion, the average diameter of the Si phase in the L cross-section of the Al bonding material of the present invention is more preferably 3.5 μm or less, even more preferably 3.4 μm or less, 3.2 μm or less, or 3 μm or less, and its lower limit is more preferably 1 μm or more, even more preferably 1.2 μm or more.

[0072] A method for measuring the average diameter of Si phases in the L-section of an Al bonding material will be described. For the measurement of the average diameter of Si phases in the L-section, similar to the measurement of the total ratio of <111> + <110> of the above Si phases, a method of combining the information on Al concentration and Si concentration obtained by SEM-EDS with the information on crystal orientation obtained by EBSD can be adopted. The detailed steps can be the same as those described above in connection with the measurement of the total ratio of <111> + <110> of the Si phase, that is, for the region determined to be the Si phase, the crystal orientation can be analyzed by using the analysis software attached to the device. When the orientation difference between measurement points is 15° or more, it is judged as a grain boundary, and the equivalent circle diameter is calculated. The average value of the equivalent circle diameters of each Si phase is defined as the average diameter of the Si phase. In the process of obtaining the average diameter of the Si phase, the parts where the crystal orientation cannot be measured or the parts where the reliability of orientation analysis is low although it can be measured are excluded from the calculation. Therefore, in one embodiment, the average diameter of the Si phase in the L-section of the Al bonding material of the present invention is calculated by the following steps (1) to (3).

[0073] (1) Take the L-section of the Al bonding material as the inspection surface, and simultaneously perform the concentration measurement of Al and Si using EDS and the crystal orientation measurement using EBSD.

[0074] (2) Use the Chi Scan function to separate and extract Al and Si. Specifically, according to the measurement result of EDS of Si, set the tolerance equivalent to the threshold value of Si, so that Al and Si can be separated and identified. Using the crystal information of Al and Si from the material file, the crystal orientation can be analyzed.

[0075] (3) For the region determined to be the Si phase, analyze the crystal orientation. When the orientation difference between measurement points is 15° or more, it is judged as a grain boundary, and the equivalent circle diameter of each grain is obtained. Then, the equivalent circle diameters of each grain are averaged to calculate the average diameter of the Si phase. Here, for the average calculation, the average value obtained by area averaging of the region that can be selected by the software attached to the device is used. By using the average value obtained by area averaging, it is possible to accurately measure and determine whether the conditions related to the average diameter of the Si phase, which is preferable for suppressing the intermediate void in the first joint portion, are satisfied. In the calculation of area averaging, it is calculated based on the average of the values obtained by multiplying the proportion of the area of each particle in the total area of all particles by the area value of each particle, and the software automatically performs the calculation.

[0076] In the present invention, when calculating the average diameter of the Si phase in the L-section, only the Si phases with a diameter (equivalent circle diameter) of 0.5 μm or more are targeted. Thereby, it is possible to accurately determine whether the requirements related to the average diameter of the Si phase in the L-section, which is preferable for suppressing the intermediate void in the first joint portion, are satisfied.

[0077] When measuring the average diameter of the Si phase in the L cross-section, the setting range of the tolerance in the step of (2) above, the method for obtaining the sample for measurement, or the measurement region of the crystal orientation based on the EBSD method, such as the measurement of the total ratio of <111> + <110> for the Si phase, is as described above.

[0078] It should be noted that, among the methods for measuring the average diameter of the Si phase, in addition to the above, there are several methods including binarization processing from the observation image of the L cross-section. However, in the present invention, due to having multiple measurement functions, obtaining the total ratio of <111> + <110> of the above Si phase, the average diameter of the Si phase, and other multiple characteristics in one measurement, being able to automatically analyze, being a popular device and analysis technique, and being easy to measure, etc., for the reasons described above, a method of combining the information of the Al concentration and Si concentration obtained by SEM-EDS with the information of the crystal orientation obtained by EBSD is adopted.

[0079] -Average diameter of the Al phase in the L cross-section-

[0080] The Al bonding material of the present invention preferably has an average diameter of the Al phase in its L cross-section of 5 μm or more and 40 μm or less.

[0081] By the range where the average diameter of the Al phase in the L cross-section is 5 μm or more and 40 μm or less, a good effect of being able to reduce the deviation of the bonding strength in the second bonding can be obtained. That is, it is considered that the reason is that the effect of promoting the deformation of the Al bonding material brought about by ultrasonic vibration by containing Si at a specified concentration and containing any one or more of Sr, Na, Eu, and Ca as the first element group in a specified amount, and the effect of making the deformation of the Al bonding material uniform in two directions parallel or perpendicular to the central axis of the Al bonding material by setting the average diameter of the Al phase to 5 μm or more and 40 μm or less act synergistically.

[0082] For the measurement of the average diameter of the Al phase in the L cross-section of the Al bonding material, similar to the measurement of the average diameter of the Si phase, a method of combining the information of the Al concentration and Si concentration obtained by SEM-EDS with the information of the crystal orientation obtained by EBSD can be adopted. Therefore, in one embodiment, after performing the steps of (1) and (2) above for the L cross-section of the Al bonding material of the present invention, the average diameter of the Al phase is calculated according to the following step (3).

[0083] (3) For the regions determined to be the Al phase, the crystal orientation is analyzed. When the orientation difference between points is 15° or more, it is judged as a grain boundary, and the equivalent circle diameter of each grain is obtained. Then, the equivalent circle diameters of each grain are averaged to calculate the average diameter of the Al phase. Regarding the average calculation, similar to the measurement of the average diameter of the Si phase, the average value obtained by area averaging that can be selected by the software attached to the device is used.

[0084] When calculating the average diameter of the Al phase in the L cross-section, only the Al phase with a diameter (equivalent circle diameter) of 0.5 μm or more is targeted. In addition, when measuring the average diameter of the Al phase in the L cross-section, the setting range of the tolerance in the steps of (2) above, the method of obtaining the measurement sample, or the measurement region of the crystal orientation based on the EBSD method is the same as described above for the sum ratio of <111> + <110> of the Si phase.

[0085] -Addition of Ti, B, Zr-

[0086] The Al bonding material of the present invention may further contain one or more of Ti, B, Zr in a total amount of 10 mass ppm or more and 500 mass ppm or less (hereinafter also referred to as the "second element group").

[0087] When joining the Al bonding material by applying ultrasonic vibration and load, it is very important to manage the joining shape. When performing the shear strength test of the joint part, in the indentation of the fracture part, the joining shape of the Al bonding material is evaluated based on the indentation length in the central axis direction of the Al bonding material (hereinafter referred to as the "joining length"). Reducing the deviation of this joining length and stabilizing it further contribute to the improvement of the temperature cycle reliability. In this regard, in the Al bonding material strengthened by adding Si or the like, in order to improve the joinability, it is effective to perform the joining under the condition of a large ultrasonic output at the initial stage of the joining time. However, under such joining conditions, since strong ultrasonic vibration is applied in the initial stage of deformation, the sliding between the joining tool and the Al bonding material becomes unstable, and there is a concern that the deviation of the joining length may increase.

[0088] The inventors of the present invention, in the process of studying the Al bonding material containing 3.0 mass% or more and 12.0 mass% or less of Si and containing the first element group in a specified amount, found that by further containing the second element group in a total amount of 10 mass ppm or more and 500 mass ppm or less, when joining the Al bonding material by applying ultrasonic vibration and load, the deviation of the joining length of the Al bonding material can be reduced. It is considered that the second element group is concentrated on the surface of the Al bonding material or affects the oxide film on the surface of the Al bonding material, thereby playing a role in controlling the friction, crystal structure, hardness, etc. of the surface of the Al bonding material.

[0089] From the perspective of reducing the deviation of the bonding length during bonding and better achieving the temperature cycle reliability required for next-generation power semiconductor devices, the total concentration of the second element group in the Al bonding material of the present invention is preferably 20 mass ppm or more, more preferably 30 mass ppm or more, 40 mass ppm or more, or 50 mass ppm or more. From the perspective of suppressing damage to the semiconductor chip and easily achieving good first bonding strength, its upper limit is preferably 450 mass ppm or less, more preferably 440 mass ppm or less, 420 mass ppm or less, or 400 mass ppm or less.

[0090] - Addition of Ni, Y, Yb, Sc -

[0091] The Al bonding material of the present invention further contains any one or more of Ni, Y, Yb, and Sc with a total of 5 mass ppm or more and 500 mass ppm or less (hereinafter, also referred to as "the third element group").

[0092] By further containing any one or more of Ni, Y, Yb, and Sc with a total of 5 mass ppm or more and 500 mass ppm or less, it is possible to suppress the occurrence of damage and scraping on the surface of the Al bonding material and form a smooth surface. There is a case where an Al alloy containing Si at a high concentration of 3.0 mass% or more and 12.0 mass% or less: due to surface hardening, exfoliation of Si phases and Al oxides present on the surface, etc., damage and scraping occur on the surface during wire drawing processing, belonging to an Al bonding material with large surface irregularities. It is inferred that by adding the third element group, the stabilization of Al oxides on the surface of the Al bonding material, the reduction of friction between the Al bonding material and the die, etc. are promoted, and thus the damage and scraping during wire drawing processing can be reduced. It is considered that by adding the third element group in combination with the first element group, the occurrence of damage and scraping on the surface of the Al bonding material can be suppressed, and the effect of forming a smooth surface can be improved.

[0093] From the perspective of forming an Al bonding material with a smooth surface by suppressing the occurrence of surface damage and scraping, the total concentration of the third element group in the Al bonding material of the present invention is preferably 10 mass ppm or more, more preferably 20 mass ppm or more, 30 mass ppm or more, 40 mass ppm or more, or 50 mass ppm or more. From the perspective of suppressing damage to the semiconductor chip and easily achieving good first bonding strength, its upper limit is preferably 450 mass ppm or less, more preferably 440 mass ppm or less, 420 mass ppm or less, or 400 mass ppm or less.

[0094] As the aluminum raw material for manufacturing the Al connection material of the present invention, Al with a purity of 4N (Al: 99.99% by mass or more) is preferably used, and Al of 5N (Al: 99.999% by mass or more) or more with fewer impurities is more preferably used.

[0095] In the range that does not hinder the effects of the present invention, the Al connection material of the present invention may further contain elements other than Al, Si, the first element group, the second element group, and the third element group (hereinafter also referred to as "other elements"). The total concentration of other elements in the Al connection material is not particularly limited as long as the effects of the present invention are not hindered. The total concentration of such 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 other elements is not particularly limited and may be 0% by mass.

[0096] In one embodiment, the remainder of the Al connection material of the present invention consists of Al and inevitable impurities. Therefore, in a preferred embodiment, the Al connection material of the present invention consists of Al, Si, any one or more of the first element group, and inevitable impurities. In another preferred embodiment, the Al connection material of the present invention consists of Al, Si, any one or more of the first element group, any one or more of the second element group, and inevitable impurities. And in yet another preferred embodiment, the Al connection material of the present invention consists of Al, Si, any one or more of the first element group, any one or more of the third element group, and inevitable impurities. And in another preferred embodiment, the Al connection material of the present invention consists of Al, Si, any one or more of the first element group, any one or more of the second element group, any one or more of the third element group, and inevitable impurities.

[0097] In a preferred embodiment, the Al connection material of the present invention does not have a coating mainly composed of a metal other than Al on the outer periphery of the Al connection material. Here, the "coating mainly composed of a metal other than Al" means a coating in which the content of a metal other than Al is 50% by mass or more.

[0098] The Al connection material of the present invention can be an Al bonding wire or an Al bonding tape. When the Al connection material of the present invention is an Al bonding wire, its wire diameter is not particularly limited, and for example, it can be in the range of 100 to 600 μm. When the Al connection material of the present invention is an Al bonding tape, the dimensions (W×T) of its rectangular or substantially rectangular cross-section are not particularly limited. For example, W can be 100 to 3000 μm, and T can also be 50 to 600 μm.

[0099] During the manufacturing of the Al connection material of the present invention, the occurrence of internal cracks can be suppressed, and excellent temperature cycle reliability can be achieved. Therefore, the Al connection material of the present invention can be preferably used as an Al connection material for semiconductor devices, especially as an Al connection material for power semiconductor devices.

[0100] - Manufacturing method of Al connection material -

[0101] An example of the manufacturing method of the Al connection material of the present invention will be described. Hereinafter, an example of the manufacturing of an Al bonding wire with a wire diameter of 200 to 400 μm will be described.

[0102] Preferably, the Al and alloy elements used as raw materials have high purity. The Al preferably consists of 99.99% by mass or more in purity, and the remaining part consists of inevitable impurities. The Si, the first element group, the second element group, and the third element group used as alloy elements preferably have a purity of 99.9% by mass or more, and the remaining part consists of inevitable impurities. It is possible to load the raw materials of Al and alloy elements into a graphite or alumina crucible processed in such a way as to obtain a cylindrical ingot, and melt them using an electric furnace or a high-frequency heating furnace to manufacture the Al alloy used in the bonding wire. Considering the workability in the subsequent processing steps, the diameter of the cylindrical ingot is preferably set to be Φ6 mm or more and less than 8 mm. In order to prevent excessive oxidation of the Al or other elements constituting the wire, the atmosphere in the furnace during melting is preferably set to an inert atmosphere or a reducing atmosphere. Considering that while ensuring the fluidity of the melt, it is easy to control the shape, size, etc. of the Si phase during solidification, the maximum temperature reached by the melt during melting is preferably in the range of 800 °C or more and less than 1050 °C. The cooling method after melting can adopt water cooling, furnace cooling, air cooling, etc.

[0103] After performing a solution treatment by heating the obtained cylindrical ingot at a high temperature, the wire of the target wire diameter can be manufactured by repeatedly performing wire drawing using a die. The wire after wire drawing can be used as an Al alloy bonding wire by performing a final heat treatment using an electric furnace.

[0104] In order to control the crystal orientation and particle size 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 wire drawing processing conditions. When performing wire drawing processing, it is effective to use a lubricating fluid in order to ensure the lubricity at the contact interface between the wire and the die.

[0105] Regarding the Al connection material of the present invention containing the first element group (Sr, Na, Eu, Ca), it tends to be easy to control the particle size of the Si phase. Since the first element group affects the morphology of the Si phase, there are cases where the appropriate range of manufacturing conditions varies depending on the type or concentration of the first element group.

[0106] An example of the manufacturing conditions for controlling the total ratio of <111> + <110> in the Si phase in the L cross-section to be in the range of 20% or more and 70% or less is shown below.

[0107] In order to adjust the crystal orientation of the Si phase, it is effective to perform a two-stage heat treatment on the ingot and control the area reduction rate of wire drawing processing.

[0108] It is effective to set the temperature range of the solution treatment to be 400 °C or more and less than 550 °C, and the time to be 1 hour or more and less than 6 hours. After this solution treatment, it is effective to perform the homogenization treatment in the range of 250 °C or more and less than 350 °C, and the time to be 2 hours or more and less than 10 hours. Thereby, by promoting the fracture and growth of the Si phase crystallized during solidification, the orientations of <111> and <110> can be promoted for the crystal orientation of the Si phase.

[0109] Regarding the wire drawing processing conditions, it is effective to set the area reduction rate of the wire for each die used during wire drawing to be in the range of 10% or more and less than 30%. Here, when the area reduction rate of each die is set to P1, P1 is expressed by the following formula.

[0110] P1 = {(R2 2 - R1 2 ) / R2 2} × 100

[0111] In the formula, R2 represents the diameter (mm) of the wire before processing, and R1 represents the diameter (mm) of the wire after processing.

[0112] Compared with the normal wire drawing processing conditions, by adjusting the area reduction rate of the wire in the above high range (high area reduction rate), the wire as a whole is deformed to a large extent during die processing, and the processing strain increases to the inside of the wire. The Si phase is arranged in the central axis direction of the wire, and at the same time, the processing strain within the Si phase is adjusted. By performing the subsequent heat treatment from such a state of wire drawing processing, it is possible to increase the orientation ratio of the <111> crystal orientation and the <110> crystal orientation with high atomic density.

[0113] In order to adjust the average diameter of the Si phase in the L cross-section to a range of 0.8 μm or more and 4 μm or less, it is effective to set the temperature during melting to 800°C or more and less than 1000°C, adjust the casting temperature in the range of 700°C or more and less than 780°C, and control the solution treatment temperature in the range of 400°C or more and less than 550°C and the time in the range of 1 hour or more and less than 6 hours. The casting temperature refers to the temperature when the molten liquid is cast into a mold or the like, which is equivalent to the solidification start temperature. When the casting temperature is high, the Si phase crystallized during solidification tends to coarsen and columnarize, and the average diameter of the Si phase tends to increase. When the solution treatment temperature is high, the columnar Si phase breaks and granulates, so the average diameter of the Si phase tends to decrease. In order to further reduce the average diameter of the Si phase, it is effective to increase the cooling rate during solidification. For example, water cooling is also effective.

[0114] In order to control the average diameter of the Al phase in the L cross-section within the range of 5 μm or more and 40 μm or less, it is effective to adjust the temperature and time of the heat treatment at the final wire diameter and control the grain growth caused by the recrystallization of the Al phase.

[0115] As described above, as a representative example of the Al connection material in the above text, an example of the manufacture of an Al bonding wire as a wire has been described. The Al bonding tape as a strip material can also be manufactured basically by the same steps. The temperature and time of the heat treatment can use conditions substantially the same as those described above. In addition, in the case of manufacturing the Al bonding tape by rolling process, it is only necessary to adjust by replacing the area reduction rate of the mold with the reduction rate.

[0116] [Semiconductor device]

[0117] By using the Al connection material of the present invention, a semiconductor device can be manufactured by connecting the electrodes on the semiconductor chip to the external electrodes on the lead frame or substrate. As described above, both the first bonding to the electrodes on the semiconductor chip and the second bonding to the electrodes on the lead frame or substrate are performed by wedge bonding.

[0118] In one embodiment, the semiconductor device of the present invention includes a circuit board, a semiconductor chip, and an Al connection material for conducting the circuit board and the semiconductor chip, and the Al connection material is characterized in that it is the Al connection material of the present invention.

[0119] In the semiconductor device of the present invention, the circuit board and the semiconductor chip are not particularly limited, and known circuit boards and semiconductor chips that can be used to constitute the semiconductor device may be employed. Alternatively, in addition, a lead frame may be used instead of the circuit board. For example, like the semiconductor device described in Japanese Unexamined Patent Application Publication No. 2020-150116, it may be configured as a semiconductor device including a lead frame and a semiconductor chip mounted on the lead frame.

[0120] Examples of the semiconductor device include various semiconductor devices used in electrical products (such as computers, mobile phones, digital cameras, televisions, air conditioners, solar power generation systems, etc.) and transportation means (such as motorcycles, automobiles, trains, ships, and airplanes, etc.). Among them, power semiconductor devices (power semiconductor devices) are preferred.

[0121] Examples

[0122] Hereinafter, specific examples of the present invention will be shown and described in detail. It should be noted that the present invention is not limited to the examples shown below.

[0123] (Specimen)

[0124] The method for manufacturing the specimen will be described. Al used as the raw material is a material with a purity of 4N (99.99 mass% or more), and the remaining part is composed of inevitable impurities. Si, the first element group (Sr, Na, Eu, Ca), the second element group (Ti, B, Zr), and the third element group (Ni, Y, Yb, Sc) used as alloying elements are materials with a purity of 99.99 mass% or more, and the remaining part is composed of inevitable impurities. The Al alloy used in the Al connection material is manufactured by charging the raw materials of Al and alloying elements into an alumina crucible and melting them using a high-frequency heating furnace. The atmosphere in the furnace during melting is set to an Ar atmosphere, the maximum temperature reached by the molten liquid during melting is set to 800 °C or higher and less than 1000 °C, and the casting temperature is set to 700 °C or higher and less than 780 °C. The cooling method after melting is set to air cooling by cooling in the atmosphere or water cooling by cooling in water.

[0125] A cylindrical ingot with a diameter of Φ6 mm is obtained by melting. After solution treatment and homogenization treatment of the ingot, wire drawing using a die and intermediate heat treatment are performed to produce an Al connection material (Al bonding wire) with a diameter of Φ300 μm. The temperature range of the solution treatment is set to 400 °C or higher and less than 550 °C, and the time is set to 1 hour or longer and less than 4 hours. After the solution treatment is completed, the homogenization treatment is continuously performed during the cooling process. The temperature range of the homogenization treatment is set to 250 °C or higher and less than 350 °C, and the time is set to 4 hours or longer and less than 10 hours. The cooling method after the homogenization treatment is set to air cooling by cooling in the atmosphere.

[0126] During wire drawing, a commercially available lubricant is used, and the wire area reduction rate for each die during wire drawing is set to be 14% or more and less than 30%. The temperature range of the final heat treatment is set to be 250°C or more and less than 350°C, and the time of the final heat treatment is set to be 4 hours or more and less than 18 hours.

[0127] (Method for measuring element content)

[0128] Regarding the concentration analysis of the elements contained in the Al bonding material, as an analytical device, ICP-OES ("PS3520UVDDII" manufactured by Hitachi High-Tech Science Co., Ltd.) or ICP-MS ("Agilent 7700x ICP-MS" manufactured by Agilent Technologies Co., Ltd.) is used for measurement.

[0129] (Method for measuring crystal orientation of Si phase)

[0130] Taking the L cross-section (the cross-section in the central axis direction including the central axis) of the Al bonding material as the inspection surface, the crystal orientation of the Si phase is measured. In the present invention, the central axis of the Al bonding material and the cross-section in the central axis direction including the central axis (L cross-section) are as Figure 1 shown. Figure 1 shows the case where the Al bonding material is an Al bonding wire having a circular cross-sectional shape. However, when the Al bonding material is an Al bonding tape having a rectangular or substantially rectangular cross-sectional shape with a width W and a thickness T, the central axis refers to the center of the width W and the axis passing through the center of the thickness T, or the L cross-section is the cross-section in the central axis direction including the central axis and the cross-section in the direction of the thickness T. When performing cross-section processing to expose the L cross-section of the Al bonding material, it may deviate from the central axis of the Al bonding material. At this time, if the length in the direction perpendicular to the central axis of the L cross-section is 90% or more of the wire diameter (thickness T in the case of a tape) of the Al bonding material, it can be regarded as a cross-section including the central axis.

[0131] In addition, FE-SEM (SU-70 manufactured by Hitachi High-Tech Corporation) was used in the measurement, and APEX (for data collection), OIM Data Collection (for chemical-assisted scanning), and OIM Analysis (for data analysis) manufactured by TSL Solutions were used in the analysis software. Three measurement regions were randomly selected at intervals of 50 cm or more in the central axis direction of the Al connection material, and measurements were performed on these three regions. The measurement regions were determined such that they were 300 μm or more and less than 800 μm in the central axis direction of the Al connection material, and the entire Al connection material entered in the direction perpendicular to the central axis. In addition, regarding the main conditions for EDS and EBSD measurements, the acceleration voltage was 15 kV, the measurement magnification was 350 times, the scanning speed was 30 to 120 points / second, and the measurement interval was in the range of 0.1 to 0.3 μm. Here, when the scanning speed is fast, the measurement time can be shortened, but it may cause a decrease in the measurement accuracy of EDS. It is expected to select an appropriate scanning speed within the above range.

[0132] In the measurement of the orientation ratio of the crystal orientation of the Si phase in the L cross-section of the Al connection material, a 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 was adopted. Specifically, the measurement was carried out according to the following steps (1) to (3).

[0133] (1) In the measurement region where the L cross-section of the Al connection material is used as the inspection surface, the concentration measurement of Al and Si using EDS and the crystal orientation measurement using EBSD were carried out simultaneously.

[0134] (2) Using the ChiScan function, which is a function of the EBSD analysis software, Al and Si were separated and extracted. Specifically, according to the EDS measurement result of Si, a tolerance equivalent to the threshold value of Si was set, so that Al and Si were separated and identified. The crystal information of Al and Si was used from the material file for the analysis of the crystal orientation. Here, the tolerance condition was mainly set to 30%, and it can be adjusted as needed.

[0135] (3) For the region determined to be the Si phase, the crystal orientation was analyzed, and the orientation ratio of the <111> crystal orientation and the orientation ratio of the <110> crystal orientation of the Si phase were calculated. Regarding the orientation ratio of the crystal orientation, the partial ratio was used.

[0136] The orientation ratio of the <111> crystal orientation and the orientation ratio of the <110> crystal orientation of the Si phase were set as the average values of the respective values obtained through the above steps (1) to (3) for the three measurement regions.

[0137] (Method for measuring average diameter of Si phase)

[0138] For the measurement of the average diameter of the Si phase in the L cross-section of the Al connection material and the measurement of the crystal orientation of the Si phase, a method that combines the information on Al concentration and Si concentration obtained by SEM-EDS with the information on crystal orientation obtained by EBSD is used. Specifically, after performing the steps (1) and (2) above, the measurement is carried out according to the following step (3).

[0139] (3) For the region determined to be the Si phase, analyze the crystal orientation. When the orientation difference between points is 15° or more, it is judged as a grain boundary, and the equivalent circle diameter of each grain is obtained. Then, the equivalent circle diameters of each grain are averaged to calculate the average diameter of the Si phase. Here, in the average calculation, the average value obtained in the regional average is used. In addition, when calculating the average diameter of the Si phase in the L cross-section, only Si phases with a diameter (equivalent circle diameter) of 0.5 μm or more are targeted.

[0140] The average diameter of the Si phase is set as the average value of the values obtained for three measurement regions through the above steps (1) to (3). In addition, through the same steps, the average diameter of the Al phase in the L cross-section of the Al connection material is also measured.

[0141] (Evaluation method for Al connection material)

[0142] The evaluation method for the Al connection material will be described. The wire diameter of the Al connection material (Al bonding wire) used in the evaluation is set to Φ300 μm. The semiconductor chip is a product made of Si, and the electrodes on the semiconductor chip are electrodes formed of an alloy with a composition of Al-0.5% Cu with a thickness of 4 μm. The substrate is a substrate with Ni deposited on the Al alloy with a thickness of 15 μm. The bonding of the Al connection material uses a commercially available wire bonder (manufactured by Ultrasonic Industry Co., Ltd.), and both the first bonding and the second bonding are set as wedge bonding.

[0143] (Evaluation method for temperature cycle reliability)

[0144] The evaluation of the temperature cycle test was carried out using a commercially available thermal shock test device. In the temperature cycle test, the specimen chamber was repeatedly heated and cooled by moving it between a low-temperature bath and a high-temperature bath. The temperature of the low-temperature bath was set at -40°C, and the temperature of the high-temperature bath was set at 175°C. The test started with the specimen chamber in the high-temperature bath, and one cycle was defined as the movement of the specimen chamber to the low-temperature bath and back to the high-temperature bath. The residence times of the specimen chamber in the low-temperature bath and the high-temperature bath were set at 20 minutes each. The specimen for the temperature cycle test had a structure in which a semiconductor chip was mounted on a substrate, and the electrodes on the semiconductor chip and the electrodes on the substrate were connected by an Al bonding material. After the start of the test, the specimen was taken out every 250 cycles and the shear test of the first joint was carried out. For the shear strength value of the first joint used in the evaluation of the temperature cycle reliability, the average value of the shear strengths of five randomly selected first joints was adopted. The number of cycles at the moment when the shear strength decreased to less than 70% of the value before the temperature cycle test was defined as the joint life. When the joint life was less than 500 cycles, it was judged that there was a problem in application and recorded as "0". When the joint life was 500 cycles or more and less than 750 cycles, it was judged that there was no problem in application and recorded as "1". When the joint life was 750 cycles or more and less than 1000 cycles, it was judged to be excellent and recorded as "2". When the joint life was 1000 cycles or more, it was judged to be particularly excellent and recorded as "3". "0" was unqualified, and "1", "2", and "3" were qualified. The evaluation results were recorded in the "Temperature Cycle Reliability" column in the table.

[0145] (Method for evaluating internal cracks)

[0146] The method for evaluating the internal cracks of the Al bonding material will be described. For the manufactured Al bonding material, the evaluation was carried out by observation using a soft X-ray projection inspection device (manufactured by Matsueda Precision, μB2600) (hereinafter referred to as X-ray observation). The measurement conditions of the X-ray observation can be appropriately determined according to the wire diameter of the Al bonding material. However, in the case of the Al bonding material with a wire diameter of 300 μm manufactured in this example, the adjustment was carried out in the range of a voltage of 50 to 80 kV and a current of 60 to 90 μA. Three places were randomly selected at intervals of 1 m or more in the central axis direction of the Al bonding material, and three specimens each about 8 cm long were selected at the three places, and a total of 9 specimens were used as the measurement specimens. Figure 3An example of X-ray observation of an Al connection material with a wire diameter of 300 μm is shown to observe internal cracks. When the length of the internal crack is 0.3 mm or more, it is judged as a defective part with problems and scored "2". When it is 0.1 mm or more and less than 0.3 mm, it is judged as something to be noted and scored "0.5". The sum of the scores at the measurement positions is set as the "crack index". Regarding the crack index of the entire measurement specimen, when it is zero, it is judged as good and evaluated as "3". When it is in the range of 0.1 to 2.0, it is judged that there is no problem in application and evaluated as "2". When it is in the range of 2.0 to 5.0, it is judged that improvement is needed and evaluated as "1". When it is higher than 6.0, it is judged as difficult to apply and evaluated as "0". The evaluation results are recorded in the "Internal Crack" column in the table.

[0147] (Evaluation method for wire breakage during processing)

[0148] The evaluation method for wire breakage during processing will be described. From the wire diameter Perform wire drawing processing until the wire diameter Confirm the number of wire breakages. The transfer speed, area reduction rate, etc. as the processing conditions of wire drawing are selected from the above-mentioned conditions, and appropriate manufacturing conditions are adjusted and changed for each wire. The length of the Al connection material for wire drawing is in the range of 100 to 200 m. Converted to per 100 m, calculate the number of wire breakages. When the number of wire breakages is 0 times, it is judged as good and evaluated as "3". When it is 1 time, it is judged that it can be dealt with by improving the manufacturing conditions and evaluated as "2". When it is 2 to 4 times, the low productivity is regarded as a problem and evaluated as "1". When it is 5 times or more, it is judged as difficult to be practical and evaluated as "0". The evaluation results are recorded in the "Wire Breakage during Processing" column in the table.

[0149] (Evaluation method for intermediate omission in the first joint part)

[0150] The evaluation method for the intermediate omission defect in the first joint part will be described. After the shear strength test of the first joint part described above, observe the indentation on the fracture surface of the electrode side with an optical microscope or SEM, and judge the part where no metal joint is obtained in the fracture area as an intermediate omission. The part where the intermediate omission occurs is the part where the electrode does not joint even if it is deformed, and it can be distinguished from the area where it is jointed as a metal joint. The shear strength test is the above-mentioned conditions, and the fracture surfaces of 10 first joint parts are observed. Then, the ratio of the total length (K) in the joint width direction of the intermediate omission area to the joint length (J) in the direction perpendicular to the central axis of the Al connection material (joint width direction) is obtained as the intermediate omission ratio (K / J) ( Figure 2)。The intermediate omission ratio is confirmed among the 10 fracture surfaces, and the maximum value thereof is defined as the "intermediate omission defect rate". When the intermediate omission defect rate is less than 5%, it is judged as good and evaluated as "3". When it is 5% or more and less than 15%, it is judged that there is no problem in application and evaluated as "2". When it is 15% or more and less than 25%, it is judged that improvement is needed and evaluated as "1". When it is higher than 25%, it is judged as an obstacle to mass production and evaluated as "0". The evaluation results are recorded in the column of "intermediate omission of the first joint part" in the table.

[0151] (Evaluation method for the stability of the joint length)

[0152] The evaluation method for the stability of the joint length will be described. After performing the above-mentioned shear strength test of the first joint part, the evaluation is carried out according to the indentation length (joint length) in the indentation of the fracture surface on the electrode side. Specifically, for the indentation of the fracture surface, the joint length (μm) in the central axis direction of the Al connection material is measured, and the population standard deviation (σ) is calculated. When σ is 15 or more, it is judged that there is a problem in practical use and evaluated as "1". When σ is 5 or more and less than 15, it is judged as good and evaluated as "2". When σ is less than 5, it is judged as excellent and evaluated as "3". "1" is unqualified, and "2" and "3" are qualified. The evaluation results are recorded in the column of "stability of the joint length" in the table.

[0153] (Evaluation method for surface damage and scraping)

[0154] Regarding the surface shape of the Al connection material, the evaluation is carried out by paying attention to damage and scraping. The wire diameter of the Al connection material is set to For the Al connection material, three measurement areas are randomly selected at intervals of 1 m or more in the central axis direction. Three lengths of about 2 cm are taken from each of the three areas, and a total of 9 specimens are observed. The surface is observed at a magnification in the range of 50 - 500 times of SEM. Damage with a length of 50 μm or more and scraping with a length of 30 μm or more are judged as defective. The positions of the damage and scraping are counted. When the number is 0, it is judged as good, judged as qualified, and evaluated as "3". When it is 2 or less, it is judged that there is no problem in application and evaluated as "2". When it is 3 - 7, it is judged that the surface property is defective and evaluated as "1". When it is 8 or more, it is judged that it is difficult to apply and evaluated as "0". The evaluation results are recorded in the column of "surface property" of the surface light.

[0155] The evaluation results of the examples and comparative examples are shown in Tables 1 - 3.

[0156] [Table 1]

[0157]

[0158] [Table 2]

[0159]

[0160] [Table 3]

[0161]

[0162] It was confirmed that the Al bonding materials of Examples No. 1 to 47 all contain Si in an amount of 3.0% by mass or more and 12.0% by mass or less, and contain one or more of the first element group (Sr, Na, Eu, Ca) in a total amount of 5 mass ppm or more and 800 mass ppm or less. During manufacturing, the occurrence of internal cracks can be suppressed, and good temperature cycle reliability can be exhibited.

[0163] In addition, it was confirmed that the Al bonding materials of Examples No. 1 to 3, 5 to 24, 26 to 37, 39 to 47, in which the total ratio of <111> + <110> of the Si phase in the L cross section is 20% or more and 70% or less, tend to obtain better temperature cycle reliability and can reduce the occurrence frequency of processing breakage.

[0164] It was confirmed that the Al bonding materials of Examples No. 1 to 11, 13, 14, 16 to 27, 29 to 47, in which the average diameter of the Si phase in the L cross section is 0.8 μm or more and 4 μm or less, can suppress the middle omission of the first joint portion. In addition, it was also confirmed that the Al bonding materials in which the average diameter of the Al phase in the L cross section is 5 μm or more and 40 μm or less tend to belong to better results in the joint strength stability of the second joint portion.

[0165] Furthermore, it was confirmed that the Al bonding materials of Examples No. 20 to 23, 25 to 27, 41 to 47, which contain one or more of the second element group (Ti, B, Zr) in a total amount of 10 mass ppm or more and 500 mass ppm or less, can reduce the deviation of the joint length during joining and stabilize the joint length.

[0166] It was confirmed that the Al bonding materials of Examples No. 29 to 36, 38, 39, 41 to 47, which contain one or more of the third element group (Ni, Y, Yb, Sc) in a total amount of 5 mass ppm or more and 500 mass ppm or less, can suppress the occurrence of surface damage and scraping and have a smooth surface.

[0167] On the other hand, it was confirmed that for the Al bonding materials of Comparative Examples No. 1 to 7, neither the Si concentration nor the concentration of the first element group is within the scope of the present invention, and neither the effect of suppressing the occurrence of internal cracks during manufacturing nor the temperature cycle reliability can be obtained sufficiently.

Claims

1. An Al bonding material, containing Si in an amount of 3.0% by mass or more and 12.0% by mass or less, and containing one or more of Sr, Na, Eu, and Ca in a total amount of 5 mass ppm or more and 800 mass ppm or less.

2. The Al bonding material according to claim 1, when measuring the crystal orientation of the Si phase in the L cross-section of the Al bonding material, i.e., the cross-section in the central axis direction including the central axis, the total of the orientation ratios of the <111> crystal orientation and the <110> crystal orientation with an angular difference of 15° or less with respect to the central axis direction is 20% or more and 70% or less.

3. The Al bonding material according to claim 1 or 2, the average diameter of the Si phase in the L cross-section is 0.8 μm or more and 4 μm or less.

4. The Al bonding material according to any one of claims 1 to 3, further containing one or more of Ti, B, and Zr in a total amount of 10 mass ppm or more and 500 mass ppm or less.

5. The Al bonding material according to any one of claims 1 to 4, further containing one or more of Ni, Y, Yb, and Sc in a total amount of 5 mass ppm or more and 500 mass ppm or less.

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