Al wiring material

Abstract

Provided is an Al wiring material that suppresses both a decrease in yield during manufacturing and chip cracking, as well as heat shock resistance. The Al wiring material contains at least Sc and Zr, and when the content of Sc is set to x1 [wt%], the content of Zr is set to x2 [wt%], 0.01≦x1≦0.5, and 0.01≦x2≦0.3 are satisfied, and the remainder contains Al.

Description

[0001] This application is a divisional application of the invention patent application filed on September 17, 2020, with application number 202080069219.0 and invention title "AI Wiring Material". Technical Field

[0002] This invention relates to Al wiring materials. Furthermore, it relates to semiconductor devices incorporating the Al wiring material. Background Technology

[0003] In semiconductor devices, electrodes formed on a semiconductor chip are connected to electrodes on a lead frame or substrate via bonding wires or bonding strips (collectively referred to as "wiring materials"). Power semiconductor devices employ wiring materials primarily made of aluminum (Al) (hereinafter simply referred to as "Al wiring materials"). For example, Patent Document 1 shows an example of using 300 μm φ Al bonding wires in a power semiconductor module. Furthermore, in power semiconductor devices using Al wiring materials, wedge bonding is used as a bonding method for both the first connection to the electrodes on the semiconductor chip and the second connection to the electrodes on the lead frame or substrate.

[0004] Power semiconductor devices using Al wiring materials are widely used in high-power equipment such as air conditioners or solar power systems, as well as automotive semiconductor devices. In these semiconductor devices, the junctions of the wiring components can sometimes reach temperatures exceeding 150°C during operation. When using materials composed solely of high-purity Al as wiring material, the softening of the wiring material is easily accelerated under the operating temperature conditions, making it difficult to use in high-temperature environments.

[0005] A scheme for Al wiring materials has been proposed, which are formed by adding specific elements to Al. For example, Patent Document 2 discloses an Al bonding wire that improves mechanical strength by adding 0.05 to 1 wt% scandium (Sc) to Al and allowing it to precipitate and harden. Patent Document 3 discloses an Al wiring material containing one or more of nickel (Ni), silicon (Si), and phosphorus (P) in a total of less than 800 wt ppm, exhibiting good bonding strength and weather resistance. Patent Document 4 discloses an Al bonding wire containing 0.01 to 0.2 wt% iron (Fe) and 1 to 20 wt ppm Si, with a Fe solid solution content of 0.01 to 0.06 wt%, and a Fe precipitation amount less than 7 times the solid solution content, and an average crystal grain size of 6 to 12 μm. It also describes that the wire exhibits good bonding reliability.

[0006] [Existing technical documents]

[0007] [Patent Literature]

[0008] Patent Document 1: Japanese Patent Application Publication No. 2002-314038

[0009] Patent Document 2: Japanese Patent Publication No. 2016-511529

[0010] Patent Document 3: Japanese Patent Application Publication No. 2016-152316

[0011] Patent Document 4: Japanese Patent Application Publication No. 2014-129578 Summary of the Invention

[0012] [The technical problem the invention aims to solve]

[0013] In power semiconductor devices where temperatures fluctuate significantly during operating cycles, the resulting impactful thermal stress (hereinafter referred to as "thermal shock") can sometimes damage the connection between the Al wiring material and the connected components. Specifically, the difference in thermal expansion coefficients between the Al wiring material and the connected components due to temperature changes during operating cycles can sometimes lead to cracks at the connection interface (hereinafter referred to as "joint cracks"). In power semiconductor devices, the bending stress caused by the expansion and contraction of the Al wiring material itself can sometimes cause cracks at the arc rise near the connection (hereinafter referred to as "heel cracks"). These joint cracks or heel cracks are exacerbated by corrosion in the operating environment, eventually causing the Al wiring material to peel off from the connected components, sometimes compromising connection reliability.

[0014] On the other hand, as a method to suppress the softening of Al wiring materials under high-temperature environments, one approach is to add other elements to the Al wiring material to suppress grain coarsening and increase its strength. Adding elements such as Sc, Ni, or Fe is effective in suppressing grain coarsening in Al wiring materials. However, as the content of these elements increases, wire breakage or damage may occur during the manufacturing of Al wiring materials, reducing yield, or damage to the connected components when connecting the Al wiring material (hereinafter, this phenomenon will be referred to as "chip cracking"). Furthermore, if the intermetallic compounds formed between these added elements and Al aggregate and coarsen, they may adversely affect the occurrence and development of bonding cracks or root cracks (i.e., accelerate crack initiation and development).

[0015] There are some reports on Al wiring materials that increase strength by adding other elements to Al, but there is still room for improvement in terms of suppressing chip cracking while reducing yield during manufacturing, and in terms of resistance to thermal shock during device operation cycles (hereinafter referred to as "thermal shock resistance").

[0016] The technical problem of this invention is to provide an Al wiring material that simultaneously suppresses chip cracking and thermal shock resistance while inhibiting the reduction of yield during manufacturing.

[0017] [Technical means used to solve technical problems]

[0018] The inventors of this invention conducted in-depth research on the above-mentioned issues and ultimately discovered that the above-mentioned technical problems could be solved by using an Al wiring material with the following structure. Based on this insight, they conducted further and repeated research and completed this invention.

[0019] That is, the present invention includes the following contents.

[0020] [1] An Al wiring material,

[0021] It contains at least Sc and Zr. When the content of Sc is set as x1 [weight %] and the content of Zr is set as x2 [weight %], it satisfies the following conditions:

[0022] 0.01≦x1≦0.5, and

[0023] 0.01 ≤ x2 ≤ 0.3

[0024] The remaining portion contains Al.

[0025] [2] As described in [1], the Al wiring material,

[0026] When it further contains Ni, and its content is set to x3 [wt ppm], it satisfies 10≦x3≦500.

[0027] [3] Al wiring materials as described in [1] or [2],

[0028] x1 and x2 satisfy the relationship x2 / x1>0.5.

[0029] [4] The Al wiring material as described in any one of [1] to [3],

[0030] The Vickers hardness of the longitudinal axis portion of the Al wiring material is below 40 Hv.

[0031] [5] The Al wiring material as described in any one of [1] to [4],

[0032] A tempering heat treatment was performed at 580–640°C for less than 30 seconds.

[0033] [6] The A1 wiring material as described in any one of [1] to [5],

[0034] It does not have a coating with metals other than Al as the main component.

[0035] [7] The Al wiring material as described in any one of [1] to [6],

[0036] It is a joining line.

[0037] [8] The Al wiring material as described in any one of [1] to [7],

[0038] After being connected to the component, it undergoes an aging heat treatment at 250–400°C for 30–60 minutes.

[0039] [9] A semiconductor device comprising an Al wiring material as described in any one of [1] to [8].

[0040] [Invention Effects]

[0041] According to the present invention, an Al wiring material can be provided that simultaneously suppresses chip cracking and thermal shock resistance while suppressing yield reduction during manufacturing. Detailed Implementation

[0042] The present invention will now be described in detail based on preferred embodiments.

[0043] [AI wiring materials]

[0044] The Al wiring material of the present invention is characterized in that it contains at least scandium (Sc) and zirconium (Zr), wherein when the content of Sc is set as x1 [weight%] and the content of Zr is set as x2 [weight%], it satisfies 0.01≦x1≦0.5 and 0.01≦x2≦0.3.

[0045] Sc raises the recrystallization temperature of Al wiring materials, helping to suppress grain coarsening and maintain the strength of Al wiring materials even when semiconductor devices are used continuously at high temperatures. The higher the amount of Sc added, the more likely grain coarsening at high temperatures is suppressed. However, as mentioned earlier, if the amount of Sc added increases, wire breakage or damage may occur during the manufacture of Al wiring materials, resulting in a lower yield, or chip cracking may occur when connecting the Al wiring materials to the connected components. Furthermore, if the intermetallic compound formed between Sc and Al agglomerates and coarsens, it may adversely affect the occurrence and development of bonding cracks or root cracks (i.e., accelerate the occurrence and development of cracks). In response, the Al wiring material of the present invention contains 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. In the Al wiring material of the present invention, the effect of Sc suppressing grain coarsening at high temperatures is maintained, resulting in appropriate strength and hardness before the Al wiring material is connected, thus suppressing a decrease in yield during manufacturing or chip cracking during connection. Furthermore, when the Al wiring material of the present invention is used in power semiconductor devices where the temperature changes significantly with device operating cycles, it can also suppress the aggregation and coarsening of intermetallic compounds of Al and Sc, significantly suppressing the occurrence and propagation of bonding cracks or root cracks. Thus, the Al wiring material of the present invention combines the suppression of reduced yield during manufacturing with the suppression of chip cracks and thermal shock resistance, significantly contributing to improving the long-term operational reliability of semiconductor devices where the temperature changes significantly with device operating cycles.

[0046] -Sc (first element)-

[0047] The Al wiring material of the present invention contains Sc as a 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 set as x1 [% by weight], it satisfies 0.01 ≤ x1 ≤ 0.5.

[0048] From the viewpoint of suppressing grain coarsening under high temperature conditions and maintaining the strength of Al wiring materials, the content of Sc in Al wiring materials, i.e., 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.

[0049] From the viewpoint of suppressing the decrease in yield during manufacturing and the chip cracking during connection, the upper limit of the Sc content x1 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.

[0050] -Zr (second element)-

[0051] The Al wiring material of the present invention contains Zr as a second element in the range of 0.01 to 0.3% by weight. That is, when the Zr content in the Al wiring material is set to x2 [% by weight], it satisfies 0.01 ≤ x2 ≤ 0.3.

[0052] By incorporating Zr and Sc in combination, the Al wiring material of the present invention can simultaneously suppress chip cracking and improve thermal shock resistance while minimizing yield reduction during manufacturing. While improving the strength of the Al wiring material can be achieved to some extent even with only Sc or only Zr, the combination of Sc and Zr achieves a particularly high level of both chip crack suppression and thermal shock resistance.

[0053] From the viewpoint of achieving particularly excellent thermal shock resistance in combination with Sc, the content of Zr in Al wiring material, i.e., 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.

[0054] From the viewpoint of suppressing the reduction of yield during manufacturing and the chip cracking during connection, the upper limit of Zr content x2 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.

[0055] As long as x1 and x2 are each within the above-mentioned preferred range, the ratio x2 / x1 of the Sc content x1 [weight%] to the Zr content x2 [weight%] is not particularly limited, for example, it can be set to 0.05 or more, 0.1 or more, 0.2 or more, etc. In particular, from the viewpoint of achieving Al wiring materials that exhibit excellent thermal shock resistance over a long period of time, x1 and x2 preferably satisfy the relationship x2 / x1 > 0.5, and more preferably satisfy the relationship 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. As long as x1 and x2 are each within the above-mentioned preferred range, the upper limit of the x2 / x1 ratio is not particularly limited. However, from the viewpoint of easily achieving Al wiring materials that exhibit the desired strength in high-temperature environments, it is preferable to set it to 10 or less (i.e., 10 ≥ x2 / x1), 8 or less, 6 or less, or 5 or less. If the x2 / x1 ratio is within the above-mentioned preferred range, especially when it is 0.15 ≤ x1, the benefits of the above-mentioned effects can be further enjoyed.

[0056] -Ni (the third element)-

[0057] The Al wiring material of the present invention may also contain Ni. In addition to Sc and Zr, the presence of Ni can improve corrosion resistance and further suppress grain coarsening under high temperature conditions, thereby maintaining the strength of the Al wiring material at a high level.

[0058] The Ni content in Al wiring materials can be set to a range of 10 to 500 ppm by weight. That is, when the Ni content in Al wiring materials is set to x3 [ppm by weight], the condition 10 ≤ x3 ≤ 500 can be met.

[0059] From the viewpoint of achieving excellent corrosion resistance and suppressing grain coarsening under high temperature conditions to maintain the strength of Al wiring materials, the Ni content in Al wiring materials, i.e., 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.

[0060] From the viewpoint of suppressing the reduction of yield during manufacturing and the chip cracking during connection, the upper limit of Ni content x3 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.

[0061] The remaining portion of the Al wiring material of the present invention comprises Al. As the aluminum raw material used in manufacturing the Al wiring material, aluminum with a purity of 5N (Al: 99.999% by weight or more) is preferably used. Without impairing the effects of the present invention, the remaining portion of the Al wiring material of the present invention may contain elements other than Al. The Al content in the remaining portion of the Al wiring material of the present invention is not particularly limited without hindering the effects of the present invention, 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 remaining portion of the Al wiring material of the present invention consists of Al and unavoidable impurities.

[0062] As an Al wiring material that can achieve a high level of both suppressing the reduction of yield during manufacturing and suppressing chip cracks, as well as thermal shock resistance, a particularly preferred embodiment is shown below.

[0063] In a particularly preferred embodiment, the Al wiring material of the present invention is characterized by containing Sc and Zr, wherein when the content of Sc is set to x1 [weight%] and the content of Zr is set to x2 [weight%], the conditions 0.01 ≤ x1 < 0.15 and 0.01 ≤ x2 ≤ 0.3 are met, and the remainder consists of Al and unavoidable impurities. Hereinafter, this embodiment will be referred to as the "first embodiment".

[0064] In another particularly preferred embodiment, the Al wiring material of the present invention is characterized by containing Sc, Zr, and Ni, wherein when the content of Sc is set to x1 [weight %], the content of Zr is set to x2 [weight %], and the content of Ni is set to x3 [weight ppm], the following conditions are met: 0.01 ≤ x1 < 0.15, 0.01 ≤ x2 ≤ 0.3, 10 ≤ x3 ≤ 500, and the remainder consists of Al and unavoidable impurities. This embodiment will be referred to hereafter as the "Second Embodiment".

[0065] In another particularly preferred embodiment, the Al wiring material of the present invention is characterized by containing Sc and Zr, wherein when the content of Sc is set to x1 [weight%] and the content of Zr is set to x2 [weight%], the following conditions are met: 0.15 ≤ x1 ≤ 0.5 and 0.01 ≤ x2 ≤ 0.3, and the remainder consists of Al and unavoidable impurities. Hereinafter, this embodiment will be referred to as the "Third Embodiment".

[0066] In another particularly preferred embodiment, the Al wiring material of the present invention is characterized by containing Sc, Zr, and Ni, wherein when the content of Sc is set to x1 [weight %], the content of Zr is set to x2 [weight %], and the content of Ni is set to x3 [weight ppm], the following conditions are met: 0.15 ≤ x1 ≤ 0.5, 0.01 ≤ x2 ≤ 0.3, and 10 ≤ x3 ≤ 500, with the remainder consisting of Al and unavoidable impurities. Hereinafter, this embodiment will be referred to as the "Fourth Embodiment".

[0067] In particular, from the viewpoint of achieving Al wiring materials with especially long-term excellent thermal shock resistance, in the third and fourth embodiments described above, especially the third embodiment, it is preferable that the content of Sc x1 [weight%] and the content of Zr x2 satisfy the relationship x2 / x1 > 0.5. The preferred range of this ratio x2 / x1 is as described above.

[0068] The contents of Sc, Zr, Ni, etc. in Al wiring materials can be determined by the method described later in the section on "Determination of Element Content".

[0069] The Al wiring material of the present invention may have a coating with a metal other than Al as the main component on its outer periphery, or it may not have such a coating. In a preferred embodiment, the Al wiring material of the present invention does not have a coating with a metal other than Al as the main component on its outer periphery. Here, "a coating with a metal other than Al as the main component" means a coating with a content of 50% by weight or more of the metal other than Al.

[0070] The Al wiring material of the present invention can be either Al bonding wire or Al bonding tape. When the Al wiring material of the present invention is an Al bonding wire, its wire diameter is not particularly limited, for example, it can be 50 to 600 μm. When the Al wiring 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 be 50 to 600 μm.

[0071] The manufacturing method of the Al wiring material of the present invention is not particularly limited, and known processing methods such as extrusion, forging, wire drawing, and rolling can be used. For example, when containing Sc, Zr, and Ni, aluminum raw materials and raw materials containing Sc, Zr, and Ni are weighed as starting materials and melt-mixed to obtain an ingot, with the content of Ni and the like within the specific range mentioned above. Alternatively, a master alloy containing these elements can be used as the raw materials for Sc, Zr, and Ni. Processing the ingot to the final size can form the Al wiring material. In the Al wiring material of the present invention, when containing Sc, Zr, and Ni, the content of Ni and the like is within the specific range mentioned above, it is possible to manufacture (process) the material while suppressing the occurrence of wire breakage or damage to a level that does not pose a problem for mass production.

[0072] During or after processing, Ni and other materials containing Sc and Zr are dissolved in solid solution; therefore, solution heat treatment is preferred. The conditions for solution heat treatment can be, for example, 570–640°C for 30 minutes to 3 hours. Furthermore, in the aforementioned first and second embodiments, when x2 satisfies 0.01 ≤ x2 ≤ 0.15, Sc and Zr can be completely dissolved during the manufacture of the cast steel ingot, thus solution heat treatment may not be necessary.

[0073] The manufacturing process of the Al bonding wire is further explained below.

[0074] After processing, following the solution heat treatment described above, a tempering heat treatment for softening the wire is performed in a subsequent stage. Tempering heat treatment can also be added during processing. Through tempering heat treatment, the crystalline structure of the wire changes from the processed structure to a recrystallized structure. Thus, the crystalline structure becomes a recrystallized structure, thereby achieving wire softening. As for the temperature conditions for tempering heat treatment, for example, the wire feeding speed is kept constant while only the furnace temperature is varied, thereby confirming the tensile strength of the wire after tempering, and determining the heat treatment temperature so that this tensile strength is in the range of 60 to 140 MPa. The heat treatment temperature can be set, for example, in the range of 580 to 640°C. In a preferred embodiment, the tempering heat treatment time is 30 seconds or less (more preferably 25 seconds or less, or 20 seconds or less). By performing such a short tempering heat treatment, even with a relatively high Sc content as in the third and fourth embodiments described above, intermetallic compounds can be prevented from precipitating, and the crystalline structure can be changed to a recrystallized structure.

[0075] In the Al wiring material of the present invention, preferably, by performing a solid solution treatment during its manufacturing process, Ni and their intermetallic compounds will not precipitate even when Sc and Zr are present. Therefore, in the Al wiring material of a preferred embodiment, when the total content of Sc and Zr in the Al wiring material is set to 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 determined by chemical analysis of the electrolytic extraction residue of the Al wiring material.

[0076] By solid-solution with Sc and Zr, and by causing the crystalline structure to recrystallize, the Al wiring material exhibits appropriate hardness. In the Al wiring material of the present invention, the Vickers hardness of its longitudinal axis portion (the axis portion in the length direction; that is, the center portion of the Al wiring material) is 40 Hv or less. Here, the longitudinal axis of the Al wiring material refers to its central axis when the Al wiring material is an Al bonding line; and when the Al wiring material is a rectangular or approximately rectangular Al bonding band (w×t), it refers to the central axis satisfying the center of w and the center of t. The Al wiring material of the present invention has appropriate hardness when connected to the connected component, thus suppressing the occurrence of chip cracks. The Vickers hardness of the Al wiring material can be measured by the method described later in the section on "Measurement of Vickers Hardness".

[0077] In the Al wiring material of the present invention, the average grain size in the cross section (C-section) perpendicular to the line length direction is preferably 1 to 50 μm. If the average grain size is 1 μm or more, recrystallization will proceed moderately through tempering heat treatment during processing. In addition, the Al wiring material is softened by performing solution heat treatment during manufacturing to force the contained components to solidify, thus preventing chip cracking during bonding and reduced bonding strength of the bonding joint. On the other hand, when the average grain size is higher than 50 μm, excessive recrystallization of the Al wiring material is observed, which may reduce the reliability of the bonding joint. By performing tempering heat treatment during processing, the average grain size in the C-section of the Al wiring material can be easily set to 1 to 50 μm. For the average grain size, the area of ​​each grain is obtained using measurement methods such as EBSD (Electron Back Scatter Diffraction Patterns), and is set as the average of the diameters when the area of ​​each grain is considered as a circle. The average grain size of the C-section of the Al wiring material can be determined by the method described later in the section on "Determination of the Average Grain Size of the C-section".

[0078] The resistivity of the Al wiring material of the present invention is preferably 3.6 μΩ·cm or less. Furthermore, when the Al wiring material of the present invention is subjected to heat treatment at 300°C for 30 minutes, its resistivity is preferably 3.0 μΩ·cm or less. Because of this low resistivity, the Al wiring material of the present invention can reduce heat generation during device operation, suppress (1) recrystallization and softening of the Al wiring material, and (2) the occurrence and propagation of cracks, ensuring bonding reliability even during long-term operation of the semiconductor device. The resistivity of the Al wiring material can be measured using a DC 4-terminal measurement method. For example, using an RM3544-01 manufactured by Hioki Electric Co., Ltd. as a resistance meter, the measurement was performed under conditions of a sample length of 400 mm and a measuring current of 1 mA. The number of measurements was set to 5, and the arithmetic mean was obtained as the resistivity value of each sample.

[0079] The Al wiring material of the present invention, when containing Sc, Zr, and Ni in the aforementioned specific amounts, exhibits appropriate strength through the effect of microstructure control based on solid solution strengthening and heat treatment during the wiring material manufacturing process. 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 later in the section on [Determination of Mechanical Properties].

[0080] In the connection between the Al wiring material of the present invention and the connected component, the first connection with the electrode on the semiconductor chip and the second connection with the electrode on the lead frame or circuit board (hereinafter referred to as the "board") are both implemented by wedge bonding. After connection with the connected component, it is preferable to perform an aging heat treatment on the semiconductor device containing 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) with Al. x Zr 1－x (where x satisfies 0 < x < 1. The same applies below.) This fine phase precipitation of the intermetallic compound. As a result of the formation of this fine phase in the Al wiring material, the Al wiring material is strengthened by precipitation, and its strength increases. As an aging heat treatment condition, if the intermetallic compound Al3(Sc) can be formed... x Zr 1－x The fine phase of Al3(Sc) is not particularly limited, but for example, a temperature of 250–400°C and a time of 30–60 minutes are preferred. Furthermore, when Sc and Zr are added separately to the Al wiring material, Al3Sc and Al3Zr are formed as intermetallic compounds, respectively. Although these fine phases of Al3Sc and Al3Zr also increase the strength of the Al wiring material through precipitation strengthening, the inventors of this invention have found that, compared to these fine phases of Al3Sc and Al3Zr, Al3(Sc) x Zr 1－x The rate of fine phase aggregation and coarsening of Al (parent phase) is significantly reduced. On this basis, the coarsening of Al (parent phase) grains can also be significantly suppressed, thus achieving particularly excellent thermal shock resistance over a long period of time.

[0081] 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 includes:

[0082] (A) The process of connecting electrodes on a semiconductor chip to electrodes on a lead frame or substrate using the Al wiring material of the present invention, and

[0083] (B) The process of performing aging heat treatment after connecting using Al wiring material.

[0084] The semiconductor chip, lead frame, or substrate used in step (A), as described below, can be any known components used to construct a semiconductor device. Furthermore, the detailed and preferred embodiments of the Al wiring material of the present invention used in step (A) are as described above. In step (A), the first connection to the electrodes on the semiconductor chip and the second connection to the electrodes on the lead frame or substrate are both implemented by wedge bonding.

[0085] In process (B), Sc and Zr in the Al wiring material form an intermetallic compound Al3(Sc) with Al. x Zr 1－x ( ), the fine phase precipitation of the intermetallic compound.

[0086] [Semiconductor Devices]

[0087] By using the Al wiring material of the present invention, electrodes on a semiconductor chip and electrodes on a lead frame or circuit board can be connected, thereby enabling the manufacture of semiconductor devices.

[0088] The semiconductor device of the present invention includes the Al wiring material of the present invention. The Al wiring material of the present invention combines the suppression of chip cracking while reducing yield during manufacturing, and thermal shock resistance. The semiconductor device incorporating the Al wiring material can achieve excellent operational reliability even when the temperature changes significantly with the device's operating cycle.

[0089] In one embodiment, the semiconductor device of the present invention is characterized by comprising a circuit board, a semiconductor chip, and an Al wiring material for conducting the circuit board and the semiconductor chip, wherein the Al wiring material is the Al wiring material of the present invention. It should be noted that the term "Al wiring material of the present invention" in the context of the semiconductor device of the present invention refers to a material in which the content of Ni, etc., is within the aforementioned preferred range when Sc, Zr, and Al are present, and also includes cases where at least a portion of Ni, etc., forms an intermetallic compound with Al when Sc, Zr, and Al are present. In the semiconductor device of the present invention, even when operated for extended periods at high temperatures, the total amount of Sc and Zr present in the phase separated from Al can be maintained within a preferred range as an intermetallic compound phase, and the intermetallic compound can be maintained in a fine phase state.

[0090] 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 construct the semiconductor device can be used. Alternatively, a lead frame can be used instead of the circuit board. For example, as described in Japanese Patent Application Publication No. 2002-246542, the semiconductor device can be configured to include a lead frame and a semiconductor chip mounted on the lead frame.

[0091] As semiconductor devices, examples include various semiconductor devices supplied to electrical products (such as computers, mobile phones, digital cameras, televisions, air conditioners, solar power generation systems, etc.) and vehicles (such as motorcycles, automobiles, trams, ships and airplanes, etc.), among which power semiconductor devices (power semiconductor devices) are preferred.

[0092] [Example]

[0093] Aluminum with a purity of 5N (≥99.999 wt%) and Sc, Zr, and Ni with a purity of ≥99.9 wt% were melted to obtain Al ingots with the compositions shown in Table 1. These ingots were then extruded and forged, followed by heat treatment at 580°C for 2 hours and wire drawing. At a wire diameter of 1 mm, a solution heat treatment at 580°C for 1 hour was performed, followed by quenching (water cooling). Subsequently, the final wire diameter was set to 200 μm and wire drawing was performed. After wire drawing, a tempering heat treatment was conducted for 15 seconds to achieve a tensile strength of 120 MPa, yielding the Al wiring material.

[0094] [Determination of elemental content]

[0095] The contents of Sc, Zr and Ni in Al wiring materials were determined using ICP-OES (PS3520UVDDII manufactured by Hitachi High-Tech Science Co., Ltd.) or ICP-MS (Agilent 7700xICP-MS manufactured by Agilent Technologies Co., Ltd.) as analytical instruments.

[0096] [Determination of Vickers hardness]

[0097] The Vickers hardness of the longitudinal axis portion of the Al wiring material was measured using a miniature Vickers hardness tester (Mitutoyo Corporation's "HM-200"). A cross-section (L-section) containing the longitudinal axis of the Al wiring material and parallel to its length was used as the measurement surface, and the hardness of the longitudinal axis portion (i.e., the center position of the Al wiring material) was measured. The average of the five measured values ​​was used as the Vickers hardness of the sample.

[0098] [Determination of the average crystal grain size of section C]

[0099] The average grain size of the C-section was determined using the EBSD method (measurement apparatus manufactured by Oxford Instruments Co., Ltd., EBSD analysis system "Aztec HKL"). Specifically, the area of ​​each grain was calculated for the entire C-section, and the area of ​​each grain was converted into the area of ​​a circle. The average diameter of this circle was then calculated and used as the average grain size. Furthermore, the area of ​​each grain was determined by defining grain boundaries as locations where the orientation difference between adjacent measurement points was 15 degrees or more.

[0100] [Determination of mechanical properties]

[0101] The tensile strength of the Al wiring material was determined using an Instron tensile testing machine under the conditions of 100 mm interval between test points, a tensile speed of 10 mm / min, and a rated load of 1 kN for the load cell. The test was performed five times, and the average value was used as the tensile strength of the specimen.

[0102] <Evaluation of wire breakage rate>

[0103] The breakage rate [times / km] is calculated using the formula N / L, based on the number of breaks (N [times]) during die drawing of wire diameters from 1 mm to 200 μm and the length (L [km]) of the Al wiring material (200 μm wire diameter) after die drawing.

[0104] In semiconductor devices, the electrodes of the semiconductor chip are Al-Cu pads, and the external terminals use Ag. The first connection between the semiconductor chip electrodes and the Al wiring material, and the second connection between the external terminals and the Al wiring material, are both wedge-jointed. After connection, an aging heat treatment at 300°C for 30 minutes is performed.

[0105] <Evaluation of Chip Damage>

[0106] For chip cracks in semiconductor devices, the metal on the surface of the pads is dissolved with acid, and the pads are evaluated under a microscope (N=50 evaluations). Cases where no cracks or bonding marks are observed are marked "◎", cases where bonding marks are confirmed even though there are no cracks (less than 3 out of 50 evaluations) are marked "○", and all others are marked "×". These are recorded in the "Chip Damage" column of Table 1.

[0107] <Evaluation of thermal shock resistance>

[0108] Thermal shock resistance was assessed through a power cycling test. The power cycling test involved alternating heating and cooling of a semiconductor device with Al interconnects. Heating consisted of raising the temperature of the Al interconnect junction to 120°C within 2 seconds, followed by cooling it to 30°C within 20 seconds. This heating-cooling cycle was repeated 100,000 times.

[0109] Following the aforementioned power cycling test, the joint shear strength of the first connection was measured to evaluate the reliability of the connection. The shear strength was determined by comparing it with the initial shear strength of the connection. A value of 90% or more of the initial connection strength was designated as "◎", 80% or more as "○", 60% or more as "△", and less than 60% as "×", and these values ​​were recorded in Table 1, "Thermal Shock Test".

[0110] Table 1 shows the manufacturing conditions and results. In Table 1, values ​​for the content of added elements that are outside the scope of this invention are underlined.

[0111] [Table 1]

[0112]

[0113] Examples No. 1 to 53 of this invention all have Sc and Zr contents within the range of this invention, and the results of wire breakage rate, chip damage, and thermal shock test are all good. Furthermore, Examples No. 1 to 9 correspond to the first embodiment, Examples No. 10 to 22 correspond to the third embodiment, Examples No. 23 to 35 correspond to the second embodiment, and Examples No. 36 to 53 correspond to the fourth embodiment. Examples No. 10 to 20 and 22, which correspond to the third embodiment and have a Zr / Sc weight ratio higher than 0.5, showed extremely good results in the thermal shock test. Furthermore, in Example No. 53, the Ni content deviates from the upper limit of the preferred range, and the wire breakage rate is higher compared to other examples of this invention.

[0114] Comparative Examples No. 1 and 2, which contain only Sc and Zr, have a thermal shock test result of ×.

[0115] Comparative Examples No. 3 and 4 show Sc or Zr content that deviates from the lower limit of the scope of this invention, and their thermal shock test results are ×.

[0116] In Comparative Examples No. 5 and 6, the content of Sc or Zr deviates from the upper limit of the scope of this invention, and the chip damage is ×.

Claims

1. An Al wiring material, It must contain at least Sc and Zr. Let the content of Sc be x1 [weight %] and the content of Zr be x2 [weight %], then the following condition is met: 0.01≦x1≦0.5, and 0. 01≦x2≦0.3， The remaining portion contains Al.

2. The A1 wiring material according to claim 1, It also contains Ni, and when its content is set to x3 [weight ppm], it satisfies 10≦x3≦500.

3. The A1 wiring material according to claim 1 or 2, x1 and x2 satisfy the relationship x2 / x1>0.

5.

4. The A1 wiring material according to any one of claims 1 to 3, The Vickers hardness of the longitudinal axis portion of the Al wiring material is below 40 Hv.

5. The A1 wiring material according to any one of claims 1 to 4, Perform a tempering heat treatment at 580–640°C for no more than 30 seconds.

6. The A1 wiring material according to any one of claims 1 to 5, It does not have a coating with metals other than Al as the main component.

7. The A1 wiring material according to any one of claims 1 to 6, It is a joining line.

8. The A1 wiring material according to any one of claims 1 to 7, After being connected to the component, it undergoes an aging heat treatment at 250–400°C for 30–60 minutes.

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

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