Al WIRING MATERIAL

Abstract

To provide an Al wiring material which suppresses chip cracking and achieves thermal shock resistance while suppressing lowering of yield during manufacture.SOLUTION: Provided is an Al wiring material which suppresses chip cracking and achieves thermal shock resistance while suppressing lowering of yield during manufacture. The Al wiring material contains at least Sc and Zr, and when the content of Sc is x1 [wt.%] and the content of Zr is x2 [wt.%], the conditions 0.01≤x1≤0.5 and 0.01≤x2≤0.3 are satisfied, with the balance comprising Al.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an Al wiring material. Furthermore, it relates to a semiconductor device including the Al wiring material.

Background Art

[0002] In a semiconductor device, the electrodes formed on a semiconductor chip are connected to the electrodes on a lead frame or a substrate by bonding wires or bonding ribbons (collectively also referred to as "wiring materials"). In a power semiconductor device, a wiring material mainly made of aluminum (Al) (hereinafter also simply referred to as "Al wiring material") is used. For example, Patent Document 1 shows an example of using a 300 μmφ Al bonding wire in a power semiconductor module. Also, in a power semiconductor device using an Al wiring material, as a bonding method, wedge bonding is used for both the first connection to the electrode on the semiconductor chip and the second connection to the electrode on the lead frame or the substrate.

[0003] A power semiconductor device using an Al wiring material is often used as a high-power device such as an air conditioner or a solar power generation system, or an in-vehicle semiconductor device. In these semiconductor devices, during device operation, the joint of the wiring material may be exposed to a high temperature of 150°C or higher. When a material made only of high-purity Al is used as the wiring material, softening of the wiring material tends to progress in the temperature environment during device operation, so it has been difficult to use in a high-temperature environment.

[0004] Al wiring materials made of materials with specific elements added to Al have been proposed. For example, Patent Document 2 discloses an Al bonding wire with improved mechanical strength by adding 0.05 to 1 wt% of scandium (Sc) to Al and causing precipitation hardening. Patent Document 3 discloses that an Al wiring material containing 800 ppm by weight or less in total of one or more of nickel (Ni), silicon (Si), and phosphorus (P) exhibits good bonding strength and weather resistance. Patent Document 4 discloses an Al bonding wire containing 0.01 to 0.2 wt% of iron (Fe) and 1 to 20 ppm by weight of Si, with the solid solution amount of Fe being 0.01 to 0.06 wt%, the precipitation amount of Fe being 7 times or less the solid solution amount, and the average crystal grain size being 6 to 12 μm, and it is described that the wire exhibits good bonding reliability.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a power semiconductor device with a significant temperature change accompanying the operating cycle of the device, an impact thermal stress accompanying the temperature change occurs (hereinafter, such a phenomenon is also referred to as "thermal shock"), and the connection part between the Al wiring material and the connected member may be damaged. Specifically, cracks may occur at the connection interface due to the difference in thermal expansion coefficients between the Al wiring material and the connected member accompanying the temperature change during the operating cycle (hereinafter, such a phenomenon is also referred to as "bond crack"). In a power semiconductor device, cracks may also occur at the loop rising part near the connection part due to the bending stress caused by the expansion and contraction of the Al wiring material itself (hereinafter, such a phenomenon is also referred to as "heel crack"). Due to corrosion in the environment during device operation, these bond cracks and heel cracks progress, and ultimately the bonding reliability may be impaired, such as the Al wiring material peeling off from the connected member.

[0007] On the other hand, as a method for suppressing the softening of the Al wiring material in a high-temperature environment, a method of adding other elements to the Al wiring material to suppress the coarsening of crystal grains and strengthen the Al wiring material is conceivable. For the Al wiring material, it is effective to add elements such as Sc, Ni, and Fe to suppress the coarsening of crystal grains. However, as the content of these elements increases, disconnection or scratches may occur during the manufacture of the Al wiring material, resulting in a decrease in yield, or the connected member may be damaged when the Al wiring material is connected to the connected member (hereinafter, such a phenomenon is also referred to as "chip crack"). In addition, when the intermetallic compounds formed between these additive elements and Al aggregate and coarsen, it may have an adverse effect on the occurrence and progress of bond cracks and heel cracks (that is, accelerate the occurrence and progress of cracks).

[0008] Although several reports have been made on Al wiring materials with other elements added to Al to enhance their strength, there is still room for improvement in achieving both suppression of chip crack and resistance to thermal shock (hereinafter, simply referred to as "thermal shock resistance") accompanying the operating cycle of the device while suppressing the decrease in yield during manufacture.

[0009] An object of the present invention is to provide an Al wiring material that suppresses a decrease in yield during manufacturing, achieves both suppression of chip cracking and thermal shock resistance.

Means for Solving the Problems

[0010] As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by an Al wiring material having the following configuration, and have completed the present invention by further studies based on such findings. That is, the present invention includes the following content. [1] Containing at least Sc and Zr, when the content of Sc is x1 [wt%] and the content of Zr is x2 [wt%], 0.01 ≦ x1 ≦ 0.5, and 0.01 ≦ x2 ≦ 0.3 An Al wiring material satisfying the above and having the balance being Al. [2] Further containing Ni, when the content thereof is x3 [wt ppm], the Al wiring material according to [1], satisfying 10 ≦ x3 ≦ 500. [3] The Al wiring material according to [1] or [2], wherein x1 and x2 satisfy the relationship of x2 / x1 > 0.5. [4] The Al wiring material according to any one of [1] to [3], wherein the Vickers hardness of the longitudinal axis portion of the Al wiring material is 40 Hv or less. [5] The Al wiring material according to any one of [1] to [4], which is subjected to a temper heat treatment at 580 to 640 °C for 30 seconds or less. [6] The Al wiring material according to any one of [1] to [5], which does not have a coating mainly composed of a metal other than Al. [7] The Al wiring material according to any one of [1] to [6], which is a bonding wire. [8] The Al wiring material according to any one of [1] to [7], which is subjected to an aging heat treatment at 250 to 400 °C for 30 to 60 minutes after connection to a member to be connected. [9] A semiconductor device including the Al wiring material according to any one of [1] to [8].

Advantages of the Invention

[0011] According to the present invention, it is possible to provide an Al wiring material that achieves both suppression of chip cracking and thermal shock resistance while suppressing a decrease in yield during manufacturing.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in detail with reference to its preferred embodiments.

[0013] [Al Wiring Material] The Al wiring material of the present invention contains at least scandium (Sc) and zirconium (Zr), and when the content of Sc is x1 [wt%] and the content of Zr is x2 [wt%], it is characterized by satisfying 0.01 ≦ x1 ≦ 0.5 and 0.01 ≦ x2 ≦ 0.3.

[0014] Sc raises the recrystallization temperature of the Al wiring material and contributes to suppressing the coarsening of crystal grains and maintaining the strength of the Al wiring material even when the semiconductor device is continuously used in a high-temperature environment. The larger the addition amount of Sc, the more the coarsening of crystal grains is suppressed under a high-temperature environment. However, as described above, when the addition amount of Sc increases, disconnection or scratches may occur during the manufacture of the Al wiring material, resulting in a decrease in yield, or chip cracks may occur when connecting the Al wiring material to a member to be connected. In addition, when the intermetallic compound formed between Sc and Al aggregates and coarsens, it may have an adverse effect on the generation and progression of bond cracks and heel cracks (that is, accelerate the generation and progression of cracks). On the other hand, the Al wiring material of the present invention containing Sc in the range of 0.01 to 0.5% by weight and Zr in the range of 0.01 to 0.3% by weight can suppress the coarsening of crystal grains under a high-temperature environment while maintaining the effect of Sc. Before the connection of the Al wiring material, it exhibits appropriate strength and hardness and can suppress the decrease in yield during manufacture and the occurrence of chip cracks during connection. In addition, when used in a power semiconductor device with a significant temperature change accompanying the operation cycle of the device, the Al wiring material of the present invention can suppress the aggregation and coarsening of the intermetallic compound between Al and Sc and significantly suppress the generation and progression of bond cracks and heel cracks. Thus, the Al wiring material of the present invention can achieve both suppression of chip cracks and thermal shock resistance while suppressing the decrease in yield during manufacture, and significantly contributes to improving the long-term operation reliability of a semiconductor device with a significant temperature change accompanying the operation cycle of the device.

[0015] -Sc (the first element)- The Al wiring material of the present invention contains Sc as the first element in the range of 0.01 to 0.5% by weight. That is, when the content of Sc in the Al wiring material is x1 [% by weight], 0.01 ≤ x1 ≤ 0.5 is satisfied.

[0016] From the perspective of suppressing the coarsening of crystal grains in a high-temperature environment and maintaining the strength of the Al wiring material, the content of Sc in the Al wiring material, that is, x1, is 0.01% by weight or more, preferably 0.02% by weight or more, 0.03% by weight or more, 0.04% by weight or more, or 0.05% by weight or more.

[0017] The upper limit of the content x1 of Sc is 0.5% by weight or less, preferably 0.48% by weight or less, 0.46% by weight or less, 0.45% by weight or less, 0.44% by weight or less, 0.42% by weight or less, or 0.4% by weight or less, from the perspective of suppressing the reduction in yield during manufacturing and chip cracking during connection.

[0018] -Zr (second element)- The Al wiring material of the present invention contains Zr in the range of 0.01 to 0.3% by weight as the second element. That is, when the content of Zr in the Al wiring material is x2 [% by weight], 0.01 ≤ x2 ≤ 0.3 is satisfied.

[0019] By containing Zr in combination with Sc, the Al wiring material of the present invention can achieve both suppression of chip cracking and thermal shock resistance while suppressing the reduction in yield during manufacturing. Here, if only the improvement of the strength of the Al wiring material is focused on, it can be achieved to a certain extent even when Sc is contained alone or Zr is contained alone, but the coexistence of suppression of chip cracking and thermal shock resistance is specifically achieved at a particularly high level when Sc and Zr are contained in combination.

[0020] From the perspective of realizing particularly excellent thermal shock resistance in combination with Sc, the content of Zr in the Al wiring material, that is, x2, is 0.01% by weight or more, preferably 0.02% by weight or more, 0.03% by weight or more, 0.04% by weight or more, or 0.05% by weight or more.

[0021] The upper limit of the content x2 of Zr is 0.3% by weight or less, preferably 0.28% by weight or less, 0.26% by weight or less, 0.25% by weight or less, 0.24% by weight or less, 0.22% by weight or less, or 0.2% by weight or less, from the viewpoint of suppressing the reduction in yield during manufacturing and chip cracking during connection.

[0022] The ratio x2 / x1 of the content x1 [% by weight] of Sc to the content x2 [% by weight] of Zr is not particularly limited as long as each of x1 and x2 is within the above preferred range, and can be, for example, 0.05 or more, 0.1 or more, 0.2 or more, etc. Particularly from the viewpoint of realizing an Al wiring material exhibiting excellent thermal shock resistance over a long period, it is preferable that x1 and x2 satisfy the relationship x2 / x1 > 0.5, more preferably x2 / x1 ≥ 0.55, x2 / x1 ≥ 0.6, x2 / x1 ≥ 0.65, x2 / x1 ≥ 0.7, x2 / x1 ≥ 0.75, or x2 / x1 ≥ 0.8. The upper limit of such an x2 / x1 ratio is not particularly limited as long as each of x1 and x2 is within the above preferred range, but from the viewpoint of easily realizing an Al wiring material exhibiting the desired strength under a high-temperature environment, it can be preferably 10 or less (i.e., 10 ≥ x2 / x1), 8 or less, 6 or less, or 5 or less. When the x2 / x1 ratio is within the above preferred range, particularly when 0.15 ≤ x1, the benefits of the above effects can be more enjoyed.

[0023] -Ni (third element)- The Al wiring material of the present invention may further contain Ni. By containing Ni in addition to Sc and Zr, the corrosion resistance can be improved, and the coarsening of crystal grains under a high-temperature environment can be further suppressed, and the strength of the Al wiring material can be maintained at a high level.

[0024] The content of Ni in the Al wiring material may be in the range of 10 to 500 weight ppm. That is, when the content of Ni in the Al wiring material is x3 [weight ppm], 10 ≤ x3 ≤ 500 may be satisfied.

[0025] From the viewpoint of achieving excellent corrosion resistance, suppressing the coarsening of crystal grains in a high-temperature environment, and maintaining the strength of the Al wiring material, the content of Ni in the Al wiring material, that is, x3, is preferably 10 ppm by weight or more, more preferably 15 ppm by weight or more, 20 ppm by weight or more, 25 ppm by weight or more, or 30 ppm by weight or more.

[0026] The upper limit of the content x3 of Ni is preferably 500 ppm by weight or less, more preferably 450 ppm by weight or less, 400 ppm by weight or less, 350 ppm by weight or less, 300 ppm by weight or less, 250 ppm by weight or less, 200 ppm by weight or less, 150 ppm by weight or less, or 100 ppm by weight or less, from the viewpoint of suppressing the reduction in yield during manufacturing and suppressing chip cracks during connection.

[0027] The balance of the Al wiring material of the present invention contains Al. As the aluminum raw material for manufacturing the Al wiring material, it is preferable to use aluminum with a purity of 5N (Al: 99.999% by weight or more) or more. The balance of the Al wiring material of the present invention may contain elements other than Al as long as the effects of the present invention are not inhibited. The content of Al in the balance of the Al wiring material of the present invention is not particularly limited as long as the effects of the present invention are not inhibited, but is preferably 98% by weight or more, 98.5% by weight or more, 99% by weight or more, 99.5% by weight or more, 99.6% by weight or more, 99.7% by weight or more, 99.8% by weight or more, or 99.9% by weight or more. In a preferred embodiment, the balance of the Al wiring material of the present invention consists of Al and inevitable impurities.

[0028] The following shows a particularly preferred embodiment as an Al wiring material that can achieve both suppression of chip cracks and high-level thermal shock resistance while suppressing the reduction in yield during manufacturing.

[0029] In a particularly preferred embodiment, the Al wiring material of the present invention contains Sc and Zr. When the content of Sc is x1 [wt%] and the content of Zr is x2 [wt%], it satisfies 0.01 ≦ x1 < 0.15 and 0.01 ≦ x2 ≦ 0.3, and the balance consists of Al and inevitable impurities. Hereinafter, such an embodiment is also referred to as the "first embodiment".

[0030] In another particularly preferred embodiment, the Al wiring material of the present invention contains Sc, Zr, and Ni. When the content of Sc is x1 [wt%], the content of Zr is x2 [wt%], and the content of Ni is x3 [wt ppm], it satisfies 0.01 ≦ x1 < 0.15, 0.01 ≦ x2 ≦ 0.3, and 10 ≦ x3 ≦ 500, and the balance consists of Al and unavoidable impurities. Hereinafter, such an embodiment is also referred to as the "second embodiment".

[0031] In another particularly preferred embodiment, the Al wiring material of the present invention contains Sc and Zr. When the content of Sc is x1 [wt%] and the content of Zr is x2 [wt%], it satisfies 0.15 ≦ x1 ≦ 0.5 and 0.01 ≦ x2 ≦ 0.3, and the balance consists of Al and unavoidable impurities. Hereinafter, such an embodiment is also referred to as the "third embodiment".

[0032] In another particularly preferred embodiment, the Al wiring material of the present invention contains Sc, Zr, and Ni. When the content of Sc is x1 [wt%], the content of Zr is x2 [wt%], and the content of Ni is x3 [wt ppm], it satisfies 0.15 ≦ x1 ≦ 0.5, 0.01 ≦ x2 ≦ 0.3, and 10 ≦ x3 ≦ 500, and the balance consists of Al and unavoidable impurities. Hereinafter, such an embodiment is also referred to as the "fourth embodiment".

[0033] From the viewpoint of being able to realize an Al wiring material having particularly excellent long-term thermal shock resistance, in the above-described third and fourth embodiments, particularly in the third embodiment, it is preferable that the content x1 [wt%] of Sc and the content x2 of Zr satisfy the relationship of x2 / x1 > 0.5. The preferred range of such a ratio x2 / x1 is as described above.

[0034] The contents of Sc, Zr, Ni, etc. in the Al wiring material can be measured by the method described in [Measurement of Element Contents] described later.

[0035] The Al wiring material of the present invention may or may not have a coating mainly composed of a metal other than Al on the outer periphery of the Al wiring material. In a preferred embodiment, the Al wiring 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 wiring material. Here, the "coating mainly composed of a metal other than Al" refers to a coating in which the content of the metal other than Al is 50% by weight or more.

[0036] The Al wiring material of the present invention may be an Al bonding wire or an Al bonding ribbon. When the Al wiring material of the present invention is an Al bonding wire, its wire diameter is not particularly limited and may be, for example, 50 to 600 μm. When the Al wiring material of the present invention is an Al bonding ribbon, the dimensions (w × t) of its rectangular or substantially rectangular cross-section are not particularly limited and may be, for example, w may be 100 to 3000 μm and t may be 50 to 600 μm.

[0037] The manufacturing method of the Al wiring material of the present invention is not particularly limited, and it may be manufactured using known processing methods such as extrusion processing, swaging processing, wire drawing processing, and rolling processing. For example, when containing Sc, Zr, etc., after weighing an aluminum raw material and a raw material such as Ni so that the content of Ni etc. is within the above specific range as starting materials, an ingot is obtained by melting and mixing them. Alternatively, as raw materials for Sc, Zr, Ni, etc., master alloys containing these elements may be used. This ingot can be processed to the final dimensions to form an Al wiring material. In the Al wiring material of the present invention containing Sc, Zr, etc. and having the content of Ni etc. within the above specific range, it can be manufactured (processed) while suppressing the occurrence of wire breakage and scratches to a level that causes no problem in mass production.

[0038] During processing or after processing is completed, it is preferable to perform solution heat treatment to dissolve Sc, Zr, and Ni etc. when contained. The conditions for solution heat treatment may be, for example, 570 to 640 °C for 30 minutes to 3 hours. In the above-described first and second embodiments, when x2 satisfies 0.01 ≦ x2 ≦ 0.15, since all of Sc, Zr, etc. can be dissolved during ingot production, solution heat treatment may not particularly be carried out.

[0039] The following further explains in accordance with the production of Al bonding wire. After processing is completed and when the above solution heat treatment has been carried out, a temper heat treatment for softening the wire is performed at a subsequent stage. A temper heat treatment may also be added during processing. By the temper heat treatment, the crystal structure of the wire is changed from a worked structure to a recrystallized structure. Thereby, since the crystal structure becomes a recrystallized structure, softening of the wire can be realized. As the temperature conditions for the temper heat treatment, for example, the tensile strength of the wire tempered by changing only the furnace temperature at a constant wire feeding speed may be confirmed, and the heat treatment temperature may be determined so that the tensile strength is in the range of 60 to 140 MPa. The heat treatment temperature may be, for example, in the range of 580 to 640 °C. In a preferred embodiment, the time for the temper heat treatment is 30 seconds or less (more preferably 25 seconds or less or 20 seconds or less). By performing such a short-time temper heat treatment, even when the Sc content is relatively high as in the above-described third and fourth embodiments, the crystal structure can be changed to a recrystallized structure without precipitation of intermetallic compounds.

[0040] In the Al wiring material of the present invention, preferably, by performing a solution treatment in the manufacturing process, when Sc and Zr are contained, Ni or the like and their intermetallic compounds do not precipitate. Therefore, in the Al wiring material according to a preferred embodiment, when the total content of Sc and Zr in the Al wiring material is 100% by weight, the total amount of Sc and Zr present in the phase separated from Al as the intermetallic compound phase is preferably 5% by weight or less, more preferably 4% by weight or less, 3% by weight or less, 2% by weight or less, or 1% by weight or less. The total amount of Sc and Zr present in the intermetallic compound phase in the Al wiring material can be measured by chemical analysis of the electrolytic extraction residue of the Al wiring material.

[0041] When Sc and Zr are dissolved and the crystal structure is a recrystallized structure, the Al wiring material exhibits appropriate hardness. In the Al wiring material of the present invention, the Vickers hardness of the longitudinal axis portion (the axis portion in the longitudinal direction; that is, the central portion of the Al wiring material) is 40 Hv or less. Here, the longitudinal axis of the Al wiring material means the central axis when the Al wiring material is an Al bonding wire, and the central axis that satisfies the center of w and the center of t when the Al wiring material is an Al bonding ribbon having a rectangular or substantially rectangular cross section (w×t). Since the Al wiring material of the present invention has appropriate hardness at the time of connection to the member to be connected, the occurrence of chip cracks can be suppressed. The Vickers hardness of the Al wiring material can be measured by the method described in [Measurement of Vickers hardness] below.

[0042] In the Al wiring material of the present invention, the average crystal grain size in a cross-section (C cross-section) perpendicular to the wire longitudinal direction is preferably 1 to 50 μm. If the average crystal grain size is 1 μm or more, recrystallization due to the temper heat treatment during processing proceeds moderately. Combined with the solution heat treatment performed during the manufacturing process of the Al wiring material to forcibly dissolve the contained components, the Al wiring material softens, preventing the occurrence of chip cracks during bonding and the deterioration of the bonding property at the joint. On the other hand, if the average crystal grain size exceeds 50 μm, it indicates that the recrystallization of the Al wiring material has progressed too far, and there is a risk of a decrease in the reliability of the joint. By performing the temper heat treatment during the processing, it is easy to make the average crystal grain size in the C cross-section of the Al wiring material 1 to 50 μm. The average crystal grain size is obtained by using a measurement method such as EBSD (Electron Back Scatter Diffraction Patterns) to determine the area of each crystal grain, and is the average of the diameters when the area of each crystal grain is regarded as a circle. The average crystal grain size of the C cross-section of the Al wiring material can be measured by the method described in [Measurement of the average crystal grain size of the C cross-section] described later.

[0043] The specific resistance of the Al wiring material of the present invention is preferably 3.6 μΩ·cm or less. Further, when the Al wiring material of the present invention is subjected to a heat treatment at 300 °C for 30 minutes, its specific resistance is preferably 3.0 μΩ·cm or less. Since the Al wiring material of the present invention has such a low specific resistance, the heat generation amount during device operation can be reduced, and (1) recrystallization and softening of the Al wiring material, and (2) the occurrence and progression of cracks can be suppressed, ensuring the bonding reliability even during the long-term operation of the semiconductor device. The specific resistance of the Al wiring material can be measured by the DC four-terminal measurement method. For example, using RM3544-01 manufactured by Hioki Electric Co., Ltd. as a resistance meter, it can be measured under the conditions of a sample length of 400 mm and a measurement current of 1 mA. The number of measurements is 5 times, and the arithmetic mean value can be obtained as the specific resistance value of each sample.

[0044] The Al wiring material of the present invention contains Sc, Zr, and when containing Ni, etc. in the above-specified amounts, and exhibits appropriate strength by the action of solid solution strengthening and microstructure control by heat treatment in the process of manufacturing the wiring material. For example, the Al wiring material of the present invention can exhibit a fracture strength of 50 to 130 MPa. The fracture strength of the Al wiring material can be measured by the method described in [Measurement of Mechanical Properties] below.

[0045] The connection between the Al wiring material of the present invention and the member to be connected is carried out by wedge bonding for both the first connection with the electrode on the semiconductor chip and the second connection with the electrode on the lead frame or circuit board (also simply referred to as "substrate"). After the connection with the member to be connected, it is preferable to perform aging heat treatment on the semiconductor device including the Al wiring material. As a result of the aging heat treatment, Sc and Zr in the Al wiring material form an intermetallic compound Al3(Sc x ,Zr 1-x )(wherein x satisfies 0 < x < 1. The same applies hereinafter), and fine phases of the intermetallic compound precipitate. As a result of forming such fine phases in the Al wiring material, the Al wiring material is precipitation-strengthened and its strength increases. The aging heat treatment conditions are not particularly limited as long as fine phases of the intermetallic compound Al3(Sc x ,Zr 1-x ) can be formed. For example, 250 to 400 °C for 30 to 60 minutes is preferable. When Sc and Zr are added to the Al wiring material individually, Al3Sc and Al3Zr are formed as intermetallic compounds respectively. Although the fine phases of these Al3Sc and Al3Zr also have the effect of increasing the strength of the Al wiring material by precipitation strengthening, the present inventors have found that compared with the fine phases of these Al3Sc and Al3Zr, the fine phase of Al3(Sc x ,Zr 1-x ) has a significantly lower rate of aggregation and coarsening, and moreover, the coarsening of the crystal grains of Al (matrix phase) can be significantly suppressed, so that particularly excellent thermal shock resistance can be realized over a long period.

[0046] Therefore, the present invention also provides a method for manufacturing a semiconductor device. In a preferred embodiment, the method for manufacturing a semiconductor device of the present invention is (A) A step of connecting an electrode on a semiconductor chip and an electrode on a lead frame or a substrate with the Al wiring material of the present invention, and (B) A step of performing aging heat treatment after connection with the Al wiring material are included.

[0047] The semiconductor chip, lead frame or substrate used in step (A) may be a known one that can be used to construct a semiconductor device, as described later. Also, the details and preferred embodiments of the Al wiring material of the present invention used in step (A) are as described above. In step (A), both the first connection with the electrode on the semiconductor chip and the second connection with the electrode on the lead frame or substrate are carried out by wedge bonding.

[0048] In step (B), Sc and Zr in the Al wiring material form an intermetallic compound Al3(Sc x ,Zr 1-x ) with Al, and fine phases of the intermetallic compound precipitate.

[0049] [Semiconductor device] A semiconductor device can be manufactured by connecting an electrode on a semiconductor chip and an electrode on a lead frame or a circuit board using the Al wiring material of the present invention.

[0050] The semiconductor device of the present invention includes the Al wiring material of the present invention. The Al wiring material of the present invention achieves both suppression of chip crack and heat shock resistance while suppressing a decrease in yield during manufacturing. A semiconductor device including the Al wiring material can achieve excellent operating reliability even when the temperature change accompanying the operating cycle of the device is significant.

[0051] In one embodiment, the semiconductor device of the present invention includes a circuit board, a semiconductor chip, and an Al wiring material for electrically connecting the circuit board and the semiconductor chip, and the Al wiring material is the Al wiring material of the present invention. Here, the "Al wiring material of the present invention" referred to in the semiconductor device of the present invention means that when Sc, Zr, and Ni etc. are contained, as long as the content of Ni etc. is within the above-mentioned preferred range, even when Sc, Zr, and at least a part of Ni etc. form an intermetallic compound with Al, it should be noted that this case is also included. In the semiconductor device of the present invention, even when it is operated for a long time in a high-temperature environment, the total amount of Sc and Zr present in the phase separated from Al as the intermetallic compound phase can be maintained within a suitable range, and the intermetallic compound can be maintained in a fine phase.

[0052] 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 form the semiconductor device may be used. Alternatively, a lead frame may be used instead of the circuit board. For example, it may be configured as a semiconductor device including a lead frame and a semiconductor chip mounted on the lead frame, as in the semiconductor device described in Japanese Patent Application Laid-Open No. 2002-246542.

[0053] 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 vehicles (such as motorcycles, automobiles, trains, ships, and airplanes, etc.). Among them, power semiconductor devices (power semiconductor devices) are preferred.

Examples

[0054] Aluminum with a purity of 5N (above 99.999 wt%) and Sc, Zr, and Ni with a purity of 99.9 wt% or more were melted as raw materials to obtain an Al ingot with the composition shown in Table 1. After subjecting the ingot to extrusion processing and swaging processing, it was heat-treated at 580 °C for 2 hours, and further wire drawing was performed. At the stage where the wire diameter reached 1 mm, solution heat treatment was carried out at 580 °C for 1 hour and then rapidly cooled (water-cooled). Thereafter, die wire drawing was performed with the final wire diameter set to 200 μm, and after the wire drawing was completed, temper heat treatment was performed so that the tensile strength would be 120 MPa at a heat treatment time of 15 seconds to obtain an Al wiring material.

[0055] [Measurement of Element Content] The contents of Sc, Zr, Ni, etc. in the Al wiring material were measured using an ICP-OES ("PS3520UVDDII" manufactured by Hitachi High-Tech Science Corporation) or an ICP-MS ("Agilent 7700x ICP-MS" manufactured by Agilent Technologies, Inc.) as an analytical device.

[0056] [Measurement of Vickers Hardness] The Vickers hardness of the longitudinal axis portion of the Al wiring material was measured using a micro Vickers hardness tester ("HM-200" manufactured by Mitutoyo Corporation). The hardness at the longitudinal axis portion (i.e., the center position of the Al wiring material) was measured with a cross-section parallel to the longitudinal direction (L cross-section) including the longitudinal axis of the Al wiring material as the measurement target surface. The average of the measurement values at 5 locations was adopted as the Vickers hardness of the sample.

[0057] [Measurement of Average Crystal Grain Size of C Cross-Section] The measurement of the average crystal grain size of the C cross-section was performed using the EBSD method (EBSD analysis system "AZtec HKL" manufactured by Oxford Instruments Japan Co., Ltd.). Specifically, the area of each crystal grain was determined for the entire C cross-section, the area of each crystal grain was converted into the area of a circle, and the average of its diameter was calculated and adopted as the average crystal grain size. The area of each crystal grain was determined by defining the position where the azimuth difference between adjacent measurement points was 15 degrees or more as the grain boundary.

[0058] [Measurement of Mechanical Properties] The breaking strength of the Al wiring material was measured by pulling it using an Instron tensile testing machine under the conditions of a gauge length of 100 mm, a tensile speed of 10 mm / min, and a load cell rated load of 1 kN. The measurement was carried out 5 times, and the average value was adopted as the breaking strength of the sample.

[0059] <Evaluation of wire breakage rate> The wire breakage rate [times / km] was calculated by the formula: N / L, based on the number of wire breaks (N [times]) when wire drawing was performed from a wire diameter of 1 mm to 200 μm using a die, and the length (L [km]) of the Al wiring material (wire diameter 200 μm) after wire drawing.

[0060] In the semiconductor device, the electrodes of the semiconductor chip are Al-Cu pads, and Ag is used for the external terminals. Both the first connection part between the electrode of the semiconductor chip and the Al wiring material and the second connection part between the external terminal and the Al wiring material were wedge-bonded. After the connection, aging heat treatment was performed at 300 °C for 30 minutes.

[0061] <Evaluation of chip damage> Chip cracks in the semiconductor device were evaluated by dissolving the metal on the pad surface with acid and observing under a microscope the area under the pad (the number of evaluations N = 50). When no cracks and no bonding traces were observed, it was rated as "◎"; when there were no cracks but bonding traces were confirmed in some places (3 or fewer out of 50 evaluations), it was rated as "○"; otherwise, it was rated as "×" and described in the "Chip Damage" column of Table 1.

[0062] <Evaluation of thermal shock resistance> The thermal shock resistance was tested by a power cycle test. For the semiconductor device with the Al wiring material connected, heating and cooling were alternately repeated. Heating was applied for 2 seconds until the temperature of the connection part of the Al wiring material in the semiconductor device reached 120 °C, and then cooling was applied for 20 seconds until the temperature of the connection part reached 30 °C. This heating and cooling cycle was repeated 100,000 times.

[0063] After the above power cycle test, the joint share strength of the first connection part was measured, and the reliability of the connection part was evaluated. The share strength measurement was performed as a comparison with the share strength of the initial connection part. The results were described in the "thermal shock test" column of Table 1 as "◎" for 90% or more of the initial connection strength, "○" for 80% or more, "△" for 60% or more, and "×" for less than 60%.

[0064] The manufacturing conditions and manufacturing results are shown in Table 1. In Table 1, the numerical values where the content of the additive element is outside the scope of the present invention are underlined.

[0065]

Table 1

[0066] In all of Invention Examples No. 1 to 53, the contents of Sc and Zr were within the scope of the present invention, and good results were obtained in terms of the wire breakage rate, chip damage, and thermal shock test. Invention Examples No. 1 to 9 correspond to the first embodiment, Invention Examples No. 10 to 22 correspond to the third embodiment, Invention Examples No. 23 to 35 correspond to the second embodiment, and Invention Examples No. 36 to 53 correspond to the fourth embodiment, respectively. It was confirmed that Invention Examples No. 10 to 20 and 22, which correspond to the third embodiment and have a Zr / Sc weight ratio exceeding 0.5, showed extremely good results in the thermal shock test. Note that in Invention Example No. 53, the content of Ni was outside the upper limit of the preferred range, and the value of the wire breakage rate was higher compared to other invention examples.

[0067] In Comparative Examples No. 1 and 2, only one of Sc and Zr was contained, and the thermal shock test was "×". In Comparative Examples No. 3 and 4, the content of Sc or Zr was outside the lower limit of the scope of the present invention, and the thermal shock test was "×". In Comparative Examples No. 5 and 6, the content of Sc or Zr was outside the upper limit of the scope of the present invention, and the chip damage was "×".

Claims

1. When it contains at least Sc, Zr, and Ni, and the Sc content is x1 [weight %], the Zr content is x2 [weight %], and the Ni content is x3 [weight ppm], 0.01 ≤ x1 ≤ 0.5, 0.01 ≤ x² ≤ 0.3, and 25 ≤ x 3 ≤ 500 The condition is met, and the remainder contains Al. Al wiring material having a breaking strength of 50 MPa or more and 130 MPa or less.

2. The Al wiring material according to Claim 1, wherein x1 and x2 satisfy the relationship x2 / x1 > 0.

5.

3. The Al wiring material according to claim 1 or 2, wherein the Vickers hardness of the longitudinal axis portion of the Al wiring material is 40 Hv or less.

4. The Al wiring material according to any one of Claims 1 to 3, which has been subjected to a tempering heat treatment at 580 to 640°C for 30 seconds or less.

5. The Al wiring material according to any one of Claims 1 to 4, which does not have a coating mainly composed of a metal other than Al.

6. The Al wiring material according to any one of claims 1 to 5, which is a bonding wire.

7. The Al wiring material according to any one of claims 1 to 6, which is subjected to aging heat treatment at 250 to 400°C for 30 to 60 minutes after connection to the member to be connected.

8. A semiconductor device comprising the Al wiring material according to any one of Claims 1 to 7.