Al WIRING MATERIAL

Abstract

There is provided a novel Al wiring material that achieves a favorable high-temperature reliability as well as a favorable workability and bondability during installation and connection to a device. The Al wiring material contains Mg and Si so as to satisfy 0.05≤x1a≤2.5, 0.02≤x1b≤1, and 0.1≤(x1a+x1b)≤3 where x1a is a content of Mg [% by mass] and x1b is a content of Si [% by mass], and contains one or more selected from the group consisting of Sc, Er, Yb, Gd, Ce and Y so as to satisfy 0.001≤x2≤0.5 where x2 is a total content thereof [% by mass], with the balance comprising Al.

Claims

1. An Al wiring material containing Mg and Si so as to satisfy
0.05≤x1a≤2.5,
0.02≤x1b≤1, and
0.1≤(x1a+x1b)≤3 where x1a is a content of Mg [% by mass] and x1b is a content of Si [% by mass], and containing one or more selected from the group consisting of Sc, Er, Yb, Gd, Ce and Y so as to satisfy
0.001≤x2≤0.5 where x2 is a total content thereof [% by mass], with the balance comprising Al.

2. The Al wiring material according to claim 1, further containing one or more selected from the group consisting of Zr, Fe, Ni, Mn, Cu and Zn so as to satisfy
0.01≤x3≤0.5 where x3 is a total content thereof [% by mass].

3. The Al wiring material according to claim 1, wherein the Al wiring material is a bonding wire.

4. A semiconductor device comprising the Al wiring material according to claim 1.

Description

EXAMPLES

[0084] Hereinafter, the present invention will be described in detail with reference to Examples. However, the present invention is not limited to the following Examples.

[0085] (Sample)

[0086] A method for producing a sample will be described. Al having a purity of 5 N (99.999% by mass or more), and Mg, Si, Sc, Er, Yb, Gd, Ce, Y, Zr, Fe, Ni, Mn, Cu and Zn having a purity of 99.9% by mass or more were molten as raw materials, and an Al ingot having each composition indicated in Tables 1 and 2 was prepared. Subsequently, the ingot was subjected to a solid solution heat treatment at a range of 550 to 640° C. for 5 hours, and quenched (water-cooled). The ingot was then subjected to an extrusion process, a swaging process, followed by a wire drawing process. Some of the samples were subjected to a precipitation heat treatment at a range of 300 to 500° C. for 1 to 30 minutes at a stage where the wire diameter was 2 mm. Next, the samples were each wire drawn with dies such that the final wire diameter was 300 μm. Thereafter, a wire-drawing process using dies was performed to achieve a final wire diameter of 300 μm. After the wire-drawing processing ended, thermal refining heat treatment was performed in a heat treatment time of 2 seconds, and thus obtaining the Al wiring material.

[0087] [Measurement of Element Content]

[0088] The content of additive elements in the Al wiring material was measured by using ICP-OES (“PS3520r.NDDII” manufactured by Hitachi High-Tech Corporation) or ICP-MS (“Agilent 7700×ICP-MS” manufactured by Agilent Technologies, Inc.) as an analysis device.

[0089] <Connection>

[0090] In the semiconductor device, the electrode on the semiconductor chip was an Al—Cu pad (thickness: 2 μm), and an Ni-coated Cu lead frame was used for an external terminal. A first connection part between the electrode on the semiconductor chip and the Al wiring material, and a second connection part between the external terminal and the Al wiring material were both wedge-bonded. In each Examples, a post-bonding heat treatment was performed under the condition of (1) at 200° C. for 30 minutes or (2) at 175° C. for 30 minutes.

[0091] <Evaluation of Bondability>

[0092] —Bonding Strength—

[0093] As for the bonding strength of the Al wiring material in the semiconductor device, the initial shear force S1 of the first connection part (before the power cycle test) was measured (the number of evaluations N=20). In the “Bonding strength” column of Tables 1 and 2, a case in which the value Si was 9 N or more was marked with a symbol of “circle” since the bonding strength was good, a case in which it was 7 N or more and less than 9 N was marked with a symbol of “triangle” since the bonding strength had no problem for normal use, but it was necessary to pay attention, and a case in which it was less than 7 N was marked with a symbol of “cross” since the bondability was inferior.

[0094] —Effective Bond Area Ratio—

[0095] For the effective bond area ratio (R) of the Al wiring material in the semiconductor device, the fractured bonded part in the first connection part in which the shear strength S1 had been measured was observed with an optical microscope or a SEM. By image analysis, a bond area M1 and an unbonded area M3 which was determined that the electrode was deformed at the time of bonding but a metal junction was not achieved were determined, and an achieved metal junction M2 (=M1−M3) was calculated. The value R was calculated as the ratio (M2/M1) of M2 to M1. In a column “Effective bond area ratio” column of Tables 1 and 2, a case in which the R value was 0.9 or more was marked with a symbol of “circle” since the bondability was favorable, a case in which it was 0.7 or more and less than 0.9 was marked with a symbol of “triangle” since the bondability had no problem for normal use, but it was necessary to pay attention, and a case in which it was less than 0.7 was marked with a symbol of “cross” since the bondability was inferior.

[0096] —Chip Damage—

[0097] A chip damage in the semiconductor device was evaluated by dissolving metal on a pad surface by acid, and observing a part under the pad by a microscope (the number of evaluations N=50). In the “chip damage” column of Tables 1 and 2, a case in which a crack, traces of bonding and the like were not found was determined to be favorable to be marked with a symbol of “circle”, a case in which there was no crack but traces of bonding were found at some spots (three spots or less of the number of evaluations 50) was marked with a symbol of “triangle”, and other cases were marked with a symbol of “cross”.

[0098] <Evaluation of High-Temperature Reliability>

[0099] The high-temperature reliability was evaluated by a power cycle test. In the power cycle test, heating and cooling were alternately and repeatedly performed for the semiconductor device in which the Al wiring material was connected. The heating was performed for 2 seconds until the maximum temperature reached about 140° C., and the cooling was performed for 25 seconds until the temperature of the connection part reached 30° C. thereafter. This heating-cooling cycle was repeated. The semiconductor device that had been subjected to the post-bonding heat treatment at 200° C. for 30 minutes was subjected to the above described cycle of 50,000 times and 100,000 times, and evaluated. The semiconductor device that had been subjected to the post-bonding heat treatment at 175° C. for 30 minutes was subjected to the above described cycle of 50,000 times, and evaluated.

[0100] The high-temperature reliability of the connection part was evaluated by measuring the bond shear force of the first connection part after the power cycle test. The high-temperature reliability was evaluated by a ratio S2/S1 where the initial shear force of the connection part was S1 and the shear force after the power cycle test was S2. In the “High-temperature reliability of connection part” column of Tables 1 and 2, a case in which the ratio S2/S1 was 0.9 or more was marked with a symbol of “double circle” since the reliability was excellent, a case in which the ratio S2/S1 was 0.8 or more and less than 0.9 was marked with a symbol of “circle” since the reliability was favorable, a case in which the ratio S2/S1 was 0.6 or more and less than 0.8 was marked with a symbol of “triangle” since the reliability had no problem for normal use, but it was necessary to pay attention, and a case in which the ratio S2/S1 was less than 0.6 was marked with a symbol of “cross” since the high-temperature reliability was inferior.

[0101] The production conditions of the Al wiring materials and the evaluation results are shown in Tables 1 and 2.

TABLE-US-00001 TABLE 1 First group element Second group element Third group element (% by mass) (% by mass) (% by mass) Mg Si Mg + Si Sc Er Yb Gd Ce Y Zr Fe Ni Mn Cu Zn Working 1 0.1 0.1 0.2 0.005 Example 2 0.2 0.1 0.3 0.001 0.03 0.005 3 0.5 0.5 1.0 0.02 0.03 4 1.2 0.7 1.9 0.3 0.1 5 2.0 1.0 3.0 0.1 6 0.5 0.4 0.9 0.1 0.005 0.3 7 0.6 0.1 0.7 0.05 0.3 8 0.1 0.06 0.16 0.003 0.01 9 0.14 0.2 0.34 0.06 0.05 10 0.6 0.4 1.0 0.3 0.1 0.1 11 1.2 0.7 1.9 0.1 12 0.5 0.5 1.0 0.2 0.1 0.25 13 0.12 0.05 0.17 0.06 14 0.3 0.4 0.7 0.003 0.2 0.3 15 1.2 0.7 1.9 0.2 0.01 16 0.2 0.3 0.5 0.1 0.4 0.1 17 0.1 0.1 0.2 0.03 18 0.4 0.3 0.7 0.1 0.05 19 1.2 0.7 1.9 0.004 0.02 20 1.1 0.5 1.6 0.03 0.04 21 0.5 0.5 1.0 0.1 0.3 0.1 22 0.2 0.2 0.4 0.3 0.2 0.2 23 0.4 0.2 0.6 0.05 0.08 0.3 24 0.4 0.5 0.9 0.1 0.4 25 0.8 0.4 1.2 0.2 0.03 0.1 High-temperature reliability of Heat treament of Al connection part wiring material 50,000 100,000 50,000 Solution Precipitation times times times Bondability heat heat Post-bonding heat Post-bonding Effective treatment treatment treatment heat treatment Bonding bond area Chip (° C.) (° C.) 200° C.-30 min 175° C.-30 min strength ratio damage Working 1 580 300 ⊚ ⊚ ◯ ◯ ◯ ◯ Example 2 620 — ⊚ ◯ ⊚ ◯ ◯ ◯ 3 620 400 ⊚ ⊚ ⊚ ◯ ◯ ◯ 4 620 420 ⊚ ⊚ ⊚ ◯ ◯ ◯ 5 620 450 ⊚ ⊚ ◯ Δ ◯ ◯ 6 600 330 ⊚ ⊚ ⊚ ◯ ◯ ◯ 7 620 300 ⊚ ⊚ ⊚ ◯ ◯ ◯ 8 620 350 ⊚ ◯ ⊚ ◯ ◯ ◯ 9 600 400 ⊚ ⊚ ⊚ ◯ ◯ ◯ 10 — 400 ⊚ ⊚ ⊚ ◯ ◯ ◯ 11 600 400 ⊚ ⊚ ◯ ◯ ◯ ◯ 12 580 400 ⊚ ⊚ ⊚ ◯ ◯ ◯ 13 620 — ⊚ ⊚ ◯ ◯ ◯ ◯ 14 550 450 ⊚ ⊚ ⊚ ◯ ◯ ◯ 15 600 400 ⊚ ⊚ ⊚ ◯ ◯ ◯ 16 600 330 ⊚ ⊚ ⊚ ◯ ◯ ◯ 17 — 500 ⊚ ⊚ ◯ ◯ ◯ ◯ 18 620 400 ⊚ ⊚ ⊚ ◯ ◯ ◯ 19 620 300 ⊚ ◯ ⊚ ◯ ◯ ◯ 20 600 500 ⊚ ⊚ ⊚ ◯ ◯ ◯ 21 600 400 ⊚ ⊚ ⊚ ◯ ◯ ◯ 22 600 300 ⊚ ⊚ ⊚ ◯ ◯ ◯ 23 600 350 ⊚ ⊚ ⊚ ◯ ◯ ◯ 24 600 300 ⊚ ⊚ ⊚ ◯ ◯ ◯ 25 600 300 ⊚ ⊚ ⊚ ◯ ◯ ◯

TABLE-US-00002 TABLE 2 First group element Second group element Third group element (% by mass) (% by mass) (% by mass) Mg + Mg Si Si Sc Er Yb Gd Ce Y Zr Fe Ni Mn Cu Zn Working 26 0.05 0.05 0.1 0.03 0.02 Example 27 0.15 0.02 0.17 0.001 0.001 0.05 28 0.4 0.5 0.9 0.2 0.2 0.4 29 1.0 0.6 1.6 0.2 0.1 0.2 30 2.5 0.5 3.0 0.03 0.02 0.3 31 0.3 0.2 0.5 0.1 0.1 0.2 0.06 32 0.6 0.8 1.2 0.05 0.1 0.3 0.03 0.05 33 0.5 0.5 1.0 0.1 0.2 0.1 0.2 0.2 0.1 Com- 1 0.2 0.2 0.4 parative 2 0.3 0.2 0.5 0.1 Example 3 0.1 0.1 0.2 4 0.06 0.03 0.09 0.03 0.03 5 0.18 0.01 0.19 0.02 6 2.4 0.7 3.1 0.02 0.1 0.1 7 1.0 1.1 2.1 0.08 8 0.4 0.4 0.8 0.0005 0.0004 0.1 9 0.4 0.4 0.8 0.17 0.17 0.18 0.1 0.2 10 0.02 11 0.01 12 0.1 0.02 13 0.05 0.05 0.2 High-temperature reliability of Heat treament of Al connection part wiring material 50,000 100,000 50,000 Solution Precipitation times times times Bondability heat heat Post-bonding heat Post-bonding Effective treatment treatment treatment heat treatment Bonding bond area Chip (° C.) (° C.) 200 ° C.-30 min 175° C.-30 min strength ratio damage Working 26 620 400 ⊚ ◯ ◯ ◯ ◯ ◯ Example 27 620 300 ⊚ ◯ ⊚ ◯ ◯ ◯ 28 640 450 ⊚ ⊚ ⊚ ◯ Δ ◯ 29 640 400 ⊚ ⊚ ◯ ◯ Δ Δ 30 640 400 ⊚ ⊚ ⊚ Δ Δ ◯ 31 620 350 ⊚ ⊚ ⊚ ◯ ◯ ◯ 32 620 400 ⊚ ⊚ ⊚ ◯ ◯ ◯ 33 640 400 ⊚ ⊚ ⊚ ◯ Δ ◯ Comparative 1 640 300 X X X Δ Δ ◯ Example 2 640 400 X X X Δ Δ ◯ 3 640 400 X X X Δ Δ ◯ 4 640 400 X X X Δ Δ ◯ 5 640 400 X X X Δ Δ ◯ 6 640 400 Δ X X X X X 7 640 400 Δ X X ◯ X X 8 640 400 X X X ◯ ◯ ◯ 9 640 400 Δ X X Δ X X 10 640 400 X X X Δ Δ ◯ 11 640 400 X X X Δ Δ ◯ 12 640 400 X X X Δ Δ ◯ 13 640 400 X X X Δ Δ ◯

[0102] For the Al wiring materials in Examples 1 to 33, the contents of Mg and Si and the total contents of Sc, Er, Yb, Gd, Ce and Y was within the range of the present invention, the bondability was favorable regardless of the presence or absence of a heat treatment during production of the wiring materials and after connection as well as the temperature and time thereof. Further, for the Al wiring materials in Examples 1 to 33, the high-temperature reliability (50,000 times) was evaluated to be favorable as marked with a symbol of “double circle”.

[0103] For the Al wiring materials in Examples 2 to 4, 6 to 10, 12, 14 to 16, 18 to 25, 27, 28, and 30 to 33, the contents of Zr, Fe, Ni, Mn, Cu and Zn were also within the preferred range of the present invention, the high-temperature reliability when the heat treatment after connection (post-bonding heat treatment) was performed at a low temperature of 175° C. for 30 minutes was evaluated to be favorable as marked with a symbol of “double circle”.

[0104] For the Al wiring materials in Comparative Examples 1 to 3, and 8, the contents of Sc, Er, Yb, Gd, Ce and Y were out of the lower limit of the range of the present invention, and the results of the high-temperature reliability of the connection part were inferior as marked with a symbol of “cross”. For the Al wiring materials in Comparative Examples 4, 5, and 10 to 13, the contents of Mg and Si (at least one or more of x1a, x1b, and x1a+x1b) were out of the lower limit of the range of the present invention, and the results of the high-temperature reliability of the connection part were inferior as marked with a symbol of “cross”. For the Al wiring materials in Comparative Examples 6 and 7, the contents of Mg and Si (at least one or more of x1a, x1b, and x1a+x1b) were out of the upper limit of the range of the present invention, and the results of chip damage were inferior as marked with a symbol of “cross”. For the Al wiring material in Comparative Example 9, the contents of Sc, Er, Yb, Gd, Ce and Y were out of the upper limit of the range of the present invention, and the result of chip damage was inferior as marked with a symbol of “cross”.

[0105] For the Al wiring materials in Examples 1 to 33, it was confirmed that, even when the post-bonding heat treatment was not performed after connection, favorable effects of the high-temperature reliability and the bondability were achieved as compared to Comparative Examples.