Al bonding wire

Abstract

Provided is an Al wire bond, which is capable of sufficiently obtaining the bonding reliability of a bonding portion of the wire bond in a high-temperature state in which a semiconductor device using the Al wire bond is operated. The Al wire bond contains 0.01 to 1% of Sc and also contains at least one or more of Y, La, Ce, Pr, and Nd in a total amount of 0.01 to 0.1%. Thus, the recrystallization temperature of the wire is increased, recrystallization of the wire bond is suppressed even when the semiconductor device is continuously used in a high-temperature environment, and the strength of the wire is prevented from decreasing, so that the reliability of the bonding portion after a high-temperature long-time test can be sufficiently ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to an Al bonding wire. BACKGROUND

[0002] In a semiconductor device, an electrode formed on a semiconductor element is connected to an electrode on a lead frame or a substrate through a bonding wire. As a material used for the bonding wire, gold (Au) or copper (Cu) is used in an integrated circuit semiconductor device such as an ultra LSI, and on the other hand, aluminum (Al) is mainly used in a power semiconductor device. For example, in Patent Literature 1, an example in which an aluminum bonding wire (hereinafter referred to as "Al bonding wire") is used in a power semiconductor module is shown. Further, in a power semiconductor device using an Al bonding wire, as a bonding method, wedge bonding is used for both connection to an electrode on a semiconductor element and connection to an electrode on a lead frame or a substrate.

[0003] A power semiconductor device using an Al bonding wire is used in many cases as a large power device such as an air conditioner or a solar power generation system, or a semiconductor device for a vehicle. In these semiconductor devices, a bonding portion of the Al bonding wire is further exposed to a high temperature of 100 to 300°C. In a case where a material composed only of high-purity Al is used as the Al bonding wire, in such a temperature environment, the lead is easily softened, and thus it is difficult to use in a high temperature environment.

[0004] In a case where an alloy containing scandium (Sc) (hereinafter referred to as "Sc") in Al is used, and the Sc is precipitated as Al3Sc, it is possible to increase the strength of the Al bonding wire. In Patent Literature 2, a bonding wire containing Al as a main component, and containing 0.05 to 1.0% of Sc is disclosed. By precipitating Al3Sc in the bonding wire, a most appropriate combination of electrical properties and mechanical properties is obtained.

[0005] However, in a case where the bonding wire in which Al3Sc is precipitated is used to be bonded to an electrode of a semiconductor element, since the mechanical strength of the lead is high, chip cracking of the semiconductor element occurs, and practical use is not possible. In view of this, in Patent Literature 3, an invention is disclosed in which Sc is contained in an Al bonding wire, and Al3Sc is not precipitated in the bonding wire in a stage before bonding by a preliminary melting treatment, and Al3Sc is precipitated by an aging heat treatment after bonding. In the stage of bonding, Al3Sc is not precipitated, and thus the lead is softened, and chip cracking does not occur at the time of bonding. On the other hand, the aging heat treatment after bonding precipitates Al3Sc, and thus the strength of the lead is increased, and even if the semiconductor device is used in a high temperature environment, the lead is able to maintain sufficient strength.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE​

[0008] Patent Literature 1: Japanese Patent Application Laid-Open No. 2002-314038

[0009] Patent Literature 2: Japanese Patent Application Laid-Open No. 2016-511529

[0010] Patent Literature 3: Japanese Patent Application Laid-Open No. 2014-47417 SUMMARY

[0011] PROBLEMS TO BE SOLVED BY THE INVENTION

[0012] Even the semiconductor device using the Al wire containing Sc described in Patent Literature 3, in a high temperature state in which the semiconductor device is operated, sometimes cannot sufficiently obtain the joining reliability of the joining portion of the wire.

[0013] The object of the present application is to provide an Al wire in which the joining reliability of the joining portion of the wire is sufficiently obtained in a high temperature state in which a semiconductor device using the Al wire is operated.

[0014] MEANS OF SOLVING THE PROBLEMS

[0015] In the Al wire containing Sc, by the aging heat treatment after joining, Al3Sc is precipitated, whereby, as described in Patent Literature 3, the strength of the wire can be increased. On the other hand, it was ascertained that, when the semiconductor device is continuously used in a high temperature environment, the recrystallization of the Al wire further proceeds, as a result, the strength of the lead wire decreases.

[0016] In this regard, it was ascertained that, in the Al wire containing Sc of 0.01 to 1%, in addition to Sc, at least one or more of yttrium, lanthanum, cerium, praseodymium, neodymium (hereinafter referred to as "Y, La, Ce, Pr, Nd") is contained in total of 0.01 to 0.1%, whereby the recrystallization temperature of the lead wire is increased, even when the semiconductor device is continuously used in a high temperature environment, the recrystallization of the wire can be suppressed, and the decrease in the strength of the lead wire can be prevented.

[0017] The present application is obtained based on the above insight, and the gist thereof is as follows.

[0018] [1] An Al wire characterized by containing, in mass%, 0.01 to 1% of Sc, and containing at least one or more of Y, La, Ce, Pr, Nd in total of 0.01 to 0.1%, the remainder being composed of Al and unavoidable impurities.

[0019] [2] The Al wire described in the above [1], characterized in that,

[0020] [2] The Al wire described in the above [1], characterized in that,

[0021] The average crystal grain size in a cross section perpendicular to the length direction of the lead (hereinafter, referred to as "C cross section") is 0.1 to 50 μm.

[0022] [3] The Al bonding wire according to any one of the above [1] or [2], characterized in that,

[0023] In the C cross section, the area ratio of the crystal whose angle difference between the crystal <111> orientation and the length direction of the lead is within 15° is 30 to 90%.

[0024] [4] The Al bonding wire according to any one of the above [1] to [3], characterized in that,

[0025] The Vickers hardness is in the range of Hv20 to 40.

[0026] [5] The Al bonding wire according to any one of the above [1] to [4], characterized in that,

[0027] The lead diameter is 50 to 600 μm.

[0028] Effects of the Invention

[0029] The present application can sufficiently ensure the reliability of the bonding portion after a high-temperature long-time service by containing 0.01 to 1% of Sc in the Al bonding wire and containing at least one or more of Y, La, Ce, Pr, and Nd in total of 0.01 to 0.1%, thereby increasing the recrystallization temperature of the lead and inhibiting the recrystallization of the bonding wire even when the semiconductor device is continuously used in a high-temperature environment, and preventing the strength of the lead from decreasing. DETAILED DESCRIPTION

[0030] In the bonding wire containing Sc in the Al bonding wire, as described in Patent Literature 3, Sc is forcibly dissolved by a preliminary melting treatment without precipitating Al3Sc, so that the lead is softened at the bonding stage and the chip cracking does not occur at the time of bonding. Further, Al3Sc is precipitated by the aging heat treatment after the bonding, as a result, the strength of the lead is increased and the recrystallization temperature is increased, the recrystallization at the time of use in a high temperature is prevented, and the strength of the lead can be maintained.

[0031] However, as described above, even the semiconductor device having the Al bonding wire in which Sc is precipitated, if the semiconductor device is operated for a long time in a high-temperature state, the phenomenon that the bonding strength of the bonding portion of the bonding wire decreases occurs, that is, it is found that the bonding reliability cannot be sufficiently obtained. If the cross section of the bonding wire of the semiconductor device after a high-temperature long-time operation is observed, the crystal grain size of the lead is increased compared with that at the time of bonding, and it is inferred that the recrystallization of the lead is further progressed due to the high-temperature long-time operation, thereby the strength of the lead is decreased and the reliability of the bonding portion is decreased.

[0032] To this end, the present application contains 0.01 to 1% of Sc in the Al wire, and further contains at least one or more of Y, La, Ce, Pr, Nd (hereinafter, referred to as "Y, La, etc." in total of 0.01 to 0.1% in addition to Sc. Thereby, the recrystallization temperature of the lead is increased, and even when the semiconductor device is used for a long time in a high temperature environment, the recrystallization of the wire can be sufficiently suppressed, and the strength of the lead can be prevented from being reduced. Hereinafter, it will be described in detail.

[0033] The Al wire of the present application contains 0.01 to 1% of Sc in terms of mass%, and contains at least one or more of Y, La, Ce, Pr, Nd in total of 0.01 to 0.1%, and the remaining portion is composed of Al and inevitable impurities. The material having such a composition is subjected to wire drawing processing to produce a wire having a prescribed diameter. In order to forcibly melt Sc and Y, La, etc., it is preferable to perform a melting heat treatment before the wire drawing processing, during the wire drawing processing, or after the wire drawing processing is completed. As the melting heat treatment conditions, it is preferable to perform at 570 to 640°C for 1 to 3 hours.

[0034] In the case where the above melting heat treatment is performed after the wire drawing processing is completed, a tempering heat treatment for softening the lead is performed at a later stage. The tempering heat treatment can also be additionally performed during the wire drawing. By the tempering heat treatment, the crystal structure of the lead is changed from a processed structure to a recrystallized structure. Thereby, the crystal structure becomes a recrystallized structure, and thus the softening of the lead can be achieved. As the tempering heat treatment conditions, it is preferable to perform at 250 to 300°C for 5 to 15 seconds. Thereby, Sc and Y, La, etc. which are solid-solved are not precipitated, and the crystal structure is set to a recrystallized structure.

[0035] In the present application, it is preferable that Sc and Y, La, etc. are not precipitated in the lead by performing the melting treatment during the lead manufacturing as described above. In the case where the melting heat treatment is not performed, the precipitates of Sc and Y, La, etc. are precipitated in the lead, and thus the Vickers hardness of the lead exceeds Hv40. To this end, as a result of performing the melting heat treatment and the tempering heat treatment, Sc and Y, La, etc. are forcibly solid-solved, and in addition, the crystal structure is set to a recrystallized structure, and thereby the Vickers hardness of the lead is Hv40 or less, and the softening is performed. By joining the semiconductor electrode using the Al wire of the present application which is thus softened, the chip cracking of the semiconductor electrode does not occur.

[0036] After the bonding is completed, in order to cause Sc and Y, La, etc. in the bonding wire to precipitate, the semiconductor device including the bonding wire is subjected to aging heat treatment. As a result of the aging heat treatment, Sc and Y, La, etc. in the bonding wire precipitate. Sc precipitates as Al3Sc, Y precipitates as Al3Y, and La precipitates as Al 11 La3, Ce precipitates as Al 11 Ce3, Pr precipitates as Al 11 Pr3, Nd precipitates as Al 11 Nd3. As a result of the formation of these precipitates in the lead wire, the lead wire is precipitation-strengthened, and the strength of the lead wire increases. As the aging heat treatment conditions, it is preferable to set to 250 to 400°C, 30 to 60 minutes.

[0037] After the aging heat treatment, and after a high-temperature, long-time experience under not-so-severe conditions, both the Al bonding wire containing only Sc and the Al bonding wire containing Sc and Y, La, etc. are subject to precipitation hardening by the precipitates, while not causing excessive recrystallization, and thus the mechanical strength can be maintained, and the reliability of the bonding portion of the bonding wire and the electrode of the semiconductor device is sufficiently ensured. However, it was ascertained that in a more severe environment, that is, in an environment maintained at a higher temperature and for a longer time, if it is an Al bonding wire containing only Sc, the reliability of the bonding portion decreases. In this regard, if it is the Al bonding wire of the present application containing Y, La, etc. in addition to Sc, it is known that even after being exposed to such a more severe environment, the reliability of the bonding portion is ensured.

[0038] An evaluation test for the reliability of the bonding portion after a high-temperature, long-time experience will be described.

[0039] The composition of the bonding wire used was an Al bonding wire of a comparative example containing only Sc at 0.5 mass%, and an Al bonding wire of the present application containing 0.5% of Sc and 0.1% of Y. The lead wire after drawing had a wire diameter of 200 μm. A melting heat treatment was performed during the drawing process to forcibly solid-solve Sc and Y, and a tempering heat treatment was performed on the lead wire after drawing to adjust the Vickers hardness of the bonding wire to Hv40 or less.

[0040] In the semiconductor device, both the first bonding portion between the semiconductor chip and the bonding wire, and the second bonding portion between the external terminal and the bonding wire were wedge bonding.

[0041] The high-temperature, long-time experience was performed by a power cycle test. The power cycle test is a test in which a semiconductor device to which an Al bonding wire is bonded is repeatedly subjected to heating and cooling. The heating is heating for two seconds until the temperature of the bonding portion of the bonding wire in the semiconductor device reaches 140°C, and thereafter, the temperature is cooled for five seconds until the temperature of the bonding portion reaches 30°C. This cycle of heating and cooling is repeated 200,000 times.

[0042] After the above high-temperature long-time experience, the joining shear strength of the first joining portion was measured, and the joining portion reliability was evaluated. As a result, for the Al joining wire containing only Sc at 0.5 mass%, the joining portion shear strength was less than 50% compared to the initial, and the reliability of the joining portion was insufficient. In contrast, for the Al joining wire of the present application containing 0.5% of Sc and 0.1% of Y, the joining portion shear strength was 90% or more compared to the initial, and the reliability of the joining portion could be sufficiently ensured.

[0043] The composition of the joining wire of the present application is described. % indicates mass%.

[0044] "0.01 to 1% of Sc"

[0045] By containing 0.01% or more of Sc in the Al joining wire, the precipitation strengthening effect of the lead wire and the effect of preventing recrystallization development in the high-temperature long-time use of the semiconductor device can be exerted in combination with the composite addition effect of Y, La, etc. described above. Sc is more preferably 0.1% or more, even more preferably 0.3% or more, and further preferably 0.5% or more. On the other hand, if the Sc content exceeds 1%, the hardness of the lead wire is too high, which can cause the occurrence of chip cracks, deterioration of the joining property, reduction of the joining portion reliability, and the like, so the upper limit is set to 1%. Sc is even more preferably 0.8% or less.

[0046] "At least one or more of Y, La, Ce, Pr, and Nd totaling 0.01 to 0.1%"

[0047] By containing at least one or more of Y, La, Ce, Pr, and Nd (Y, La, etc.) totaling 0.01% or more, the precipitation strengthening effect of the lead wire and the effect of preventing recrystallization development in the high-temperature long-time use of the semiconductor device can be exerted in combination with the composite addition effect of Sc described above. Any one of Y, La, Ce, Pr, and Nd exerts the effect in the same manner. The total content of Y, La, etc. is more preferably 0.03% or more. It is even more preferably 0.05% or more. On the other hand, if the total content of Y, La, etc. exceeds 0.1%, the hardness of the lead wire is too high, which can cause the occurrence of chip cracks, deterioration of the joining property, reduction of the joining portion reliability, and the like, so the upper limit is set to 0.1%. The total content of Y, La, etc. is even more preferably 0.08% or less.

[0048] For the concentration analysis of Sc, Y, or La, etc. in the joining wire, an ICP emission spectrophotometer or an ICP mass spectrometer can be used. The content of Sc, Y, or La, etc. shown in the present application is based on the concentration measured by ICP emission spectrophotometry or ICP mass spectrometry.

[0049] The remaining portion of the bonding wire consists of Al and unavoidable impurities. Examples of unavoidable impurity elements include Si, Fe, and Cu. The lower the total content of unavoidable impurities, the smaller the deviation in material properties can be suppressed, which is preferable. As the aluminum raw material for manufacturing the lead wire, using aluminum with a purity of 4N (Al: 99.99% or higher) yields preferred results.

[0050] Average crystal grain size of the lead

[0051] In this invention, preferably, the average crystal grain size in the cross-section (C-section) perpendicular to the lead length direction of the bonding wire is 0.1 to 50 μm. As a method for determining the average crystal grain size, the area of ​​each crystal grain is obtained using methods such as EBSD (Electron Back Scatter Diffraction Patterns), and the area of ​​each grain is taken as the average of the diameters when considered as circles. If the average crystal grain size is 0.1 μm or more, recrystallization caused by the tempering heat treatment during wire drawing is moderately achieved. Combined with the forced solid solution treatment of the lead components during lead manufacturing, the lead is softened, preventing chip cracking during bonding and reduced bonding strength. On the other hand, if the average crystal grain size is higher than 50 μm, it indicates excessive recrystallization of the lead. Even if precipitates form during aging heat treatment, sufficient strength may not be obtained, potentially reducing the reliability of the bonding. By performing tempering heat treatment during lead drawing, the average crystal grain size of the lead's C-section can be set to 0.1 to 50 μm.

[0052] <111> Orientation Area Ratio of Leads

[0053] In this invention, preferably, in a cross-section (C-section) perpendicular to the length direction of the bonding wire, the area ratio (hereinafter referred to as "<111> orientation area ratio") of the crystal with an angle difference of less than 15° between the <111> orientation and the lead length direction is 30% to 90%. EBSD can be used to measure the <111> orientation area ratio. By using the cross-section perpendicular to the length direction of the bonding wire as the inspection surface, the <111> orientation area ratio can be calculated using the analysis software attached to the device. In the process of obtaining the <111> orientation area ratio, calculations are performed excluding areas where the crystal orientation cannot be measured, or areas where the reliability of orientation analysis is low even if it can be measured. If the <111> orientation area ratio is less than 90%, recrystallization based on the tempering heat treatment during wire drawing is appropriately performed, combined with the forced solid solution treatment of the lead components during lead manufacturing, thereby softening the lead and preventing chip cracking during bonding and reduced bonding strength of the bonding joint. On the other hand, if the <111> orientation area ratio is less than 30%, it indicates that the recrystallization of the lead wire has been excessive, and even if precipitates are formed during aging heat treatment, it will be difficult to obtain sufficient strength, and the reliability of the joint may be reduced. By performing tempering heat treatment during lead wire drawing, the <111> orientation area ratio in the cross-section perpendicular to the lead wire length direction can be set to 30-90%.

[0054] Vickers Hardness of Lead Wire

[0055] In this invention, preferably, the Vickers hardness in a cross-section (C-section) perpendicular to the lead length direction of the bonding wire is in the range of Hv20 to 40. By setting it to Hv40 or below, chip cracking will not occur during bonding, good bonding performance can be achieved, and wire arcs can be easily formed for wiring of semiconductor devices. On the other hand, if the Vickers hardness decreases to less than Hv20, it indicates that the recrystallization of the lead wire has excessively developed, and even if precipitates are formed during aging heat treatment, it is difficult to obtain sufficient strength, and the reliability of the bonding joint may be reduced. Therefore, the lower limit of the Vickers hardness is preferably set to Hv20. As mentioned above, by performing melt heat treatment during the lead wire manufacturing process to force the lead wire to contain components in solid solution, and further performing tempering heat treatment during wire drawing, the Vickers hardness of the lead wire can be set to the range of Hv20 to 40.

[0056] Lead Diameter

[0057] In this invention, preferably, the diameter of the bonding wire is 50 to 600 μm. In power systems, large currents flow, so wires with a diameter of 50 μm or more are usually used. However, if the diameter is 600 μm or more, it is difficult to process or the wire bonding machine is not compatible. Therefore, wires with a diameter of 600 μm or less are used.

[0058] Example

[0059] Aluminum with a purity of 99.99% by mass (4N) and yttrium, lanthanum, cerium, praseodymium, and neodymium with a purity of 99.9% by mass or higher were melted to obtain an Al alloy with the compositions shown in Tables 1 and 2. This alloy was cast into ingots, which were then subjected to grooved roll rolling and further wire drawing. At a lead diameter of 800 μm, a melt heat treatment was performed at 620°C for 3 hours, followed by rapid cooling in water. Subsequently, the final wire diameter was set to 200 μm, and die drawing was performed. After wire drawing, a tempering heat treatment was conducted at 270°C for 10 seconds.

[0060] Using this lead wire, the average crystal grain size, the area ratio of crystals with an angle difference of less than 15° between the <111> orientation and the lead wire length direction (section C) are measured in a cross section perpendicular to the length direction of the lead wire (section C).

[0061] The average crystal grain size is determined as follows: the area of ​​each grain is obtained using the EBSD method, the area of ​​each grain is converted into the area of ​​a circle, and the average of its diameter is used.

[0062] The <111> orientation area ratio was measured in a cross section perpendicular to the length direction of the bonding line, using EBSD-based measurements. The <111> orientation area ratio was calculated using analytical software attached to the device.

[0063] Vickers hardness is measured using a miniature Vickers hardness tester, which measures the hardness at the center of the radial direction in the C-section.

[0064] In semiconductor devices, the semiconductor chip electrodes are Al-Cu, and the external terminals are Ag. Both the first junction between the semiconductor chip electrodes and the bonding wires, and the second junction between the external terminals and the bonding wires, are wedge-joints.

[0065] After joining, the material is subjected to aging heat treatment at 350°C for 45 minutes.

[0066] For the bonding performance of bonding wires in semiconductor devices, a judgment is made based on whether there is bonding failure (non-bonding) in the initial stage of the first bonding part (before long-term exposure to high temperature). Bonded bonding parts are marked as ○, and non-bonded bonding parts are marked as ×, and recorded in the "Bondability" column of Tables 1 and 2.

[0067] For the evaluation of chip cracks in semiconductor devices, the metal on the surface of the pads is dissolved with acid, and the presence of chip cracks under the pads is observed and evaluated using a microscope. Crack-free areas are marked as ○, and cracked areas as ×, and recorded in the "Chip Cracks" column of Tables 1 and 2.

[0068] The high-temperature long-term exposure was conducted through a power cycling test. The power cycling test involved repeatedly heating and cooling a semiconductor device with Al bonding wires. Heating was performed for two seconds until the temperature of the bonding wire junction in the semiconductor device reached 140°C, followed by five seconds of cooling until the junction temperature reached 30°C. This heating and cooling cycle was repeated 200,000 times.

[0069] After prolonged exposure to the aforementioned high temperatures, the shear strength of the first joint was measured to evaluate the reliability of the joint. The shear strength was measured by comparing it with the initial shear strength of the joint. A joint strength of 95% or more was designated as ◎, 90% or more but less than 95% as ○, 50% or more but less than 90% as △, and less than 50% as ×, and these values ​​were recorded in the "Reliability Test" column of Tables 1 and 2.

[0070] The manufacturing conditions and results are shown in Tables 1 and 2. Y, La, Ce, Pr, and Nd (Y, La, etc.) are shown as "secondary components". In Table 2, values ​​whose component content deviates from the scope of this invention, and values ​​whose evaluation results deviate from the preferred scope of this invention, are marked with an underline.

[0071] [Table 1]

[0072]

[0073] [Table 2]

[0074]

[0075] Table 1 lists examples No. 1 to 54 of this invention. The composition of the leads falls within the scope of this invention. Furthermore, the average crystal grain size, <111> orientation area ratio, and Vickers hardness of the leads are all within the preferred range of this invention. The evaluation results for bonding and chip cracking are all "○". This is the result of containing the components specified in this invention, and through melt heat treatment to force the containing elements into solid solution, followed by appropriate recrystallization through tempering heat treatment.

[0076] In the evaluation of the reliability of the joints after prolonged high-temperature exposure in Examples No. 1 to 54 of this invention, all results were marked with "○" or "◎". This is because, as a result of the presence of the components specified in this invention, and the precipitation of Sc, Y, La, etc., during the aging heat treatment after bonding, precipitation strengthening of the lead is achieved, while the recrystallization temperature is increased, preventing the development of recrystallization during prolonged high-temperature exposure. In particular, regarding Examples No. 19 to 36 of this invention, the Sc content is within the preferred range of this invention, and the reliability evaluation results of the joints are all marked with "◎".

[0077] Table 2 lists comparative examples No. 1 to 10.

[0078] Comparative Examples No. 1 to 3 all had Sc content below the lower limit of this invention, resulting in a reliability evaluation result of "×". Furthermore, when evaluating the lead internals after prolonged high-temperature exposure, Comparative Examples No. 1 to 3 all had an average crystal grain size higher than 50 μm. This was presumably due to insufficient Sc in the leads, insufficient increase in mechanical strength after aging heat treatment, insufficient increase in recrystallization temperature, and excessive recrystallization during prolonged high-temperature exposure. Comparative Example No. 1 also had a total Y, La, etc. content below the lower limit of this invention. Comparative Example No. 3 still had a total Y, La, etc. content exceeding the upper limit of this invention, resulting in a bonding quality and chip cracking result of "×".

[0079] In Comparative Examples No. 4 and 5, the total content of Y, La, etc., was less than the lower limit of this invention. The reliability evaluation results were both "△". Furthermore, the average crystal grain size of the lead wires after prolonged high-temperature exposure was found to exceed 50 μm. This was presumed to be due to insufficient total content of Y, La, etc., in the lead wires, resulting in insufficient increase in mechanical strength and recrystallization temperature after aging heat treatment, leading to excessive recrystallization during prolonged high-temperature exposure.

[0080] In Comparative Example No. 6, the total content of Y, La, etc., exceeded the upper limit of the present invention. As a result, the Vickers hardness of the lead wire was outside the preferred range. Furthermore, the bonding performance and chip cracking were rated "×", and the reliability evaluation result was "×".

[0081] In Comparative Examples No. 7-9, the Sc content exceeds the upper limit of the present invention. Furthermore, in Comparative Examples No. 7 and 8, the total content of Y, La, etc., is less than the lower limit of the present invention, while in Comparative Example No. 10, the total content of Y, La, etc., exceeds the upper limit of the present invention. Since the Sc content in Comparative Examples No. 7-10 all exceeds the upper limit of the present invention, the Vickers hardness deviates from the preferred upper limit of the present invention. When Sc exceeds the upper limit, even forced solid solution cannot completely dissolve it and will precipitate, thus the Vickers hardness deviates. In Comparative Example No. 10, the total content of Y, La, etc., all exceeds the upper limit, therefore the average crystal grain size is less than the preferred lower limit of the present invention, and the <111> orientation area ratio deviates from the preferred upper limit of the present invention. When Sc and Y, La, etc., deviate from the upper limit, they cannot completely dissolve and will precipitate, thus the grain size becomes smaller and the <111> orientation increases. As a result, Comparative Examples No. 7-10 all have "×" for bonding and chip cracking, and the reliability evaluation result of the bonding after long-term high-temperature exposure is also "×".

Claims

1. An Al bonding wire, characterized by, comprising at least one of Y, La, Ce, Pr, Nd, Sc, and the remainder, containing 0.01 to 1% of Sc in mass%, and containing 0.01 to 0.1% in total of at least one or more of Y, La, Ce, Pr, Nd, and the remainder consisting of Al with a purity of 99.99 mass% or more and inevitable impurities.

2. The Al bonding wire according to claim 1, characterized by, containing 0.3% or more of Sc.

3. The Al bonding wire according to claim 1, characterized by, containing 0.5% or more of Sc.

4. The Al bonding wire according to claim 1, characterized by, containing 0.8% or less of Sc.

5. The Al bonding wire according to claim 1, characterized by, containing 0.03% or more in total of at least one or more of Y, La, Ce, Pr, and Nd.

6. The Al bonding wire according to claim 1, characterized by, containing 0.05% or more in total of at least one or more of Y, La, Ce, Pr, and Nd.

7. The Al bonding wire according to claim 1, characterized by, containing 0.08% or less in total of at least one or more of Y, La, Ce, Pr, and Nd.

8. The Al bonding wire according to claim 1, characterized by, having an average crystal grain size of 0.1 to 50 μm in a cross section perpendicular to the lead length direction of the Al bonding wire.

9. The Al bonding wire according to claim 1, characterized by, having an area ratio of crystals having an angle difference of 15° or less between the crystal <111> orientation and the lead length direction of 30 to 90% in a cross section perpendicular to the lead length direction of the Al bonding wire.

10. The Al bonding wire according to claim 1, characterized by, having a Vickers hardness in the range of Hv20 to 40.

11. The Al bonding wire according to any one of claims 1 to 9, characterized by, having a lead diameter of 50 to 600 μm.

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