Al WIRING MATERIAL

Abstract

There is provided a novel Al wiring material that suppresses an increase in cold strength and exhibits a favorable high-temperature reliability. The Al wiring material contains one or more selected from the group consisting of Er, Yb and Gd so as to satisfy 0.001≤x1≤0.6 where x1 is a total content thereof [% by mass], with the balance comprising Al.

Claims

1. An Al wiring material containing one or more selected from the group consisting of Er, Yb and Gd so as to satisfy
0.001≤x1≤0.6 where x1 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 Sc and Zr so as to satisfy
0.005≤x2≤0.6 where x2 is a total content thereof [% by mass].

3. The Al wiring material according to claim 1, further containing one or more selected from the group consisting of Si, Fe, Ni, Ce, Y and Zn so as to satisfy
0.001≤x3≤1 where x3 is a total content thereof [% by mass].

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

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

Description

EXAMPLES

[0087] Hereinafter, the present invention will be described in detail with reference to Examples. However, the present invention is not limited to the following Examples.

[0088] (Sample)

[0089] A method for producing a sample will be described. Al having a purity of 5 N (99.999% by mass or more), and Er, Yb, Gd, Sc, Zr, Si, Fe, Ni, Ce, Y 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 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 350 to 600° C. for 1 to 60 minutes at a stage where the wire diameter was 2 mm. 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.

[0090] [Measurement of Element Content]

[0091] The content of additive elements in the Al wiring material was measured by using ICP-OES (“PS3520UVDDII” manufactured by Hitachi High-Tech Corporation) or ICP-MS (“Agilent 7700x ICP-MS” manufactured by Agilent Technologies, Inc.) as an analysis device.

[0092] [Mechanical Properties of Wire]

[0093] —Change in Strength after Heating—

[0094] Before and after a heat treatment, a tensile test was performed, and a change in strength after heating a wire was evaluated as a change in breaking strength of the wire. For measurement of the breaking strength, the tensile test was performed with a tensile tester manufactured by Instron under conditions of a distance between gauge points of 100 mm, a tensile speed of 10 mm/min, and a load cell rating load of 1 kN. An average value obtained in five measurements was used. The heat treatment of the wire was performed in a nitrogen atmosphere at 350° C. for 4 hours or at 400° C. for 1 hour. The change in strength after heating was evaluated by a ratio F2/F1 where the wire strength before the heat treatment was F1 and the wire strength after the heat treatment was F2. In the “Change in strength after heating” column of Tables 1 and 2, a case in which the ratio F2/F1 was 1.2 or more was marked with a symbol of “double circle” since an improvement in the high-temperature reliability of the wire was significant, a case in which the ratio F2/F1 was 1.0 or more and less than 1.2 was marked with a symbol of “circle” since the strength was favorable in a general high-temperature environment, a case in which the ratio F2/F1 was 0.7 or more and less than 1.0 was marked with a symbol of “triangle” since the strength had no problem for normal use, but it was necessary to pay attention for use in a high-temperature environment, and a case in which the ratio F2/F1 was less than 0.7 was marked with a symbol of “cross” since the high-temperature reliability was inferior.

[0095] —Measurement of Hardness—

[0096] The Vickers hardness Hv of the longitudinal axis part of the Al wiring material was measured by using a micro Vickers hardness tester. The measurement target area was set to a cross section (L cross section) parallel with the longitudinal direction including the longitudinal axis of the Al wiring material, and hardness at the longitudinal axis part (that is, the center position of the Al wiring material) was measured. An average of measurement values at five points was employed as the Vickers hardness of the sample. In the “Hardness Hv” column of Tables 1 and 2, a case in which the Vickers hardness Hv was within the range of 20 or more and less than 35 was marked with a symbol of “circle” since the Al wiring material was soft, a case in which it was within the range of 35 or more and less than 45 was marked with a symbol of “triangle”, and a case in which it was within the range of 45 or more was marked with a symbol of “cross” since the Al wiring material was hard and had a concern of inferior deformability.

[0097] <Connection>

[0098] 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 some Examples and Comparative Examples, a post-bonding heat treatment (aging heat treatment) was performed at 300° C. for 30 minutes after the connection.

[0099] <Evaluation of Chip Damage>

[0100] 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”.

[0101] <Evaluation of High-Temperature Reliability>

[0102] —First Connection Part—

[0103] The high-temperature reliability with respect to the first connection part 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. In the heating, two types of conditions including a middle-temperature condition and a high-temperature condition were used. For the middle-temperature condition, heating was performed for 2 seconds until the maximum temperature of the connection part of the Al wiring material in the semiconductor device reached about 120° C., and cooling was performed for 20 seconds until the temperature of the connection part reached 30° C. thereafter. This heating-cooling cycle was repeated 100,000 times. For the high-temperature condition, heating was performed for 2 seconds until the maximum temperature of the connection part of the Al wiring material in the semiconductor device reached about 140° C., and cooling was performed for 25 seconds until the temperature of the connection part reached 30° C. thereafter. This heating-cooling cycle was repeated 100,000 times.

[0104] —Second Connection Part—

[0105] The high-temperature reliability with respect to the second connection part was evaluated by a temperature cycle test (hereinafter referred to as TCT). TCT was a test in which the semiconductor device in which the Al wiring material was connected was placed in a furnace of a temperature cycle tester and switching between a high temperature and a low temperature was continuously repeated. The high temperature was set to 125° C., and the low temperature was set to −40° C. The cycle of the high temperature and the low temperature was repeated 1,000 times.

[0106] 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 and the bond shear force of the second connection part after the temperature 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 or the temperature cycle test was S2. In the “High-temperature reliability” 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.

[0107] The production conditions of the Al wiring materials and the evaluation results are shown in Tables 1 and 2.

TABLE-US-00001 TABLE 1 Additive elements in Al wiring material Heat treatment condition Second group Solution Precipitation First group element element Third group element heat heat (% by mass) (% by mass) (% by mass) treatment treatment Er Yb Gd Sc Zr Si Fe Ni Ce Y Zn (° C.) (° C.) Working 1 0.002 620 — Example 2 0.01 0.005 0.005 0.006 580 350 3 0.02 0.1 0.1 620 — 4 0.08 0.006 620 520 5 0.1 0.05 620 300 6 0.15 0.05 0.1 620 450 7 0.2 0.05 0.1 0.2 600 350 8 0.2 0.2 0.1 620 — 9 0.2 0.1 0.1 0.003 620 600 10 0.5 0.2 0.2 620 500 11 0.05 580 — 12 0.001 0.005 0.005 580 380 13 0.01 0.004 0.01 620 450 14 0.02 0.001 620 500 15 0.08 0.005 0.1 600 600 16 0.1 0.2 0.002 620 — 17 0.2 0.2 0.1 0.002 610 400 18 0.4 0.1 620 400 19 0.1 0.007 0.1 580 — 20 0.2 0.2 0.2 0.1 600 350 21 0.3 0.2 0.05 0.5 620 300 22 0.1 600 — 23 0.008 0.004 0.005 550 450 24 0.2 0.2 0.4 0.4 580 400 25 0.2 0.6 — 500 26 0.1 0.1 0.1 0.1 0.08 — 300 27 0.4 0.2 0.05 0.1 0.5 550 400 28 0.6 0.05 640 400 Mechanical properties High-temperature reliability Post- Change in strength First connection part Second bonding after heating Hardness Chip Middle High connection heat 350° C. 400° C. Hv damage temp. temp. part treatment Working 1 ◯ Δ ◯ ◯ ◯ Δ Δ No Example 2 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 3 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 4 ⊚ ◯ ◯ ◯ ⊚ ◯ ⊚ Yes 5 ⊚ ◯ ◯ ◯ ⊚ ◯ ⊚ Yes 6 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 7 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ No 8 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 9 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ No 10 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 11 ⊚ ◯ ◯ ◯ ◯ Δ Δ No 12 ◯ ◯ ◯ ◯ ◯ ◯ ⊚ Yes 13 ⊚ ⊚ ◯ ◯ ⊚ ◯ Δ No 14 ◯ Δ ◯ ◯ ◯ Δ Δ Yes 15 ⊚ ◯ ◯ ◯ ⊚ ◯ ⊚ Yes 16 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ◯ Yes 17 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 18 ⊚ ⊚ ◯ ◯ ⊚ ⊚ Δ Yes 19 ⊚ ◯ ◯ ◯ ◯ Δ ⊚ Yes 20 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 21 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 22 ⊚ ◯ ◯ ◯ ◯ Δ Δ No 23 ◯ Δ ◯ ◯ ◯ Δ ⊚ Yes 24 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 25 ⊚ ⊚ ◯ Δ ⊚ ◯ Δ Yes 26 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 27 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 28 ⊚ ◯ ◯ ◯ ⊚ Δ ⊚ No

TABLE-US-00002 TABLE 2 Additive elements in Al wiring material Heat treatment condition Second group Solution Precipitation First group element element Third group element heat heat (% by mass) (% by mass) (% by mass) treatment treatment Er Yb Gd Sc Zr Si Fe Ni Ce Y Zn (° C.) (° C.) Working 29 0.002 0.001 0.01 0.02 0.002 620 400 Example 30 0.01 0.01 0.005 620 450 31 0.03 0.02 0.03 0.01 0.005 640 400 32 0.005 0.01 0.01 620 450 33 0.02 0.005 0.1 0.1 620 — 34 0.2 0.2 0.2 0.4 0.4 0.2 620 400 35 0.2 0.2 0.4 0.3 0.1 600 400 36 0.1 0.3 0.007 0.04 620 400 37 0.3 0.3 0.3 0.5 0.1 640 400 38 0.2 0.1 0.1 0.2 0.2 620 400 39 0.1 0.2 0.1 0.2 0.1 0.1 0.15 630 300 40 0.2 0.1 0.15 0.08 0.05 0.1 0.3 620 350 Comparative 1 0.0005 620 300 Example 2 0.0005 620 400 3 0.0008 620 400 4 0.7 620 400 5 0.3 0.3 0.2 620 400 6 0.2 620 400 7 0.2 0.1 620 400 8 0.1 0.2 620 400 Mechanical properties High-temperature reliability Post- Change in strength First connection part Second bonding after heating Hardness Chip Middle High connection heat 350° C. 400° C. Hv damage temp. temp. part treatment Working 29 ◯ ◯ ◯ ◯ ◯ ◯ ◯ No Example 30 ⊚ ◯ ◯ ◯ ⊚ ◯ ⊚ Yes 31 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 32 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes 33 ⊚ ⊚ ◯ ◯ ⊚ ⊚ Δ Yes 34 ⊚ ⊚ Δ Δ ⊚ ⊚ ⊚ Yes 35 ⊚ ◯ ◯ Δ ⊚ ◯ ⊚ No 36 ⊚ ◯ ◯ ◯ ⊚ ◯ ⊚ Yes 37 ◯ ⊚ ◯ ◯ ◯ ⊚ ⊚ Yes 38 ⊚ ⊚ ◯ ◯ ⊚ ⊚ Δ Yes 39 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ No 40 ⊚ ⊚ ◯ ◯ ⊚ ⊚ ⊚ Yes Comparative 1 X X ◯ ◯ X X X Yes Example 2 X X ◯ ◯ X X X Yes 3 X X ◯ ◯ X X X Yes 4 ⊚ ◯ X X ◯ X ◯ Yes 5 ⊚ ◯ X X ◯ X ◯ Yes 6 X X Δ Δ Δ X X No 7 X X Δ Δ Δ X Δ Yes 8 X X ◯ Δ X X Δ Yes

[0108] For the Al wiring materials in Examples 1 to 40, the total content x1 of Er, Yb and Gd was within the range of the present invention, and the results of the change in strength after heating at 350° C., the chip damage, the hardness, and the high-temperature reliability of the first connection part under the middle-temperature condition were 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.

[0109] For the Al wiring materials in Examples 2, 3, 6 to 10, 12, 13, 15 to 18, 20, 21, 24 to 27, 29, 31, and 33 to 40, the contents of Sc and Zr were also within the preferred ranges of the present invention, the results of the change in strength after heating at 400° C. were favorable as marked with a symbol of “circle” or “double circle”, and the results of the high-temperature reliability of the first connection part under the middle-temperature condition and the high-temperature condition were favorable as marked with a symbol of “circle” or “double circle”.

[0110] For the Al wiring materials in Examples 2 to 10, 12, 14 to 17, 19 to 21, 23, 24, 26 to 32, 34 to 37, 39, and 40, the contents of Si, Fe, Ni, Ce, Y and Zn were also within the preferred ranges of the present invention, and the results of the high-temperature reliability of the second connection part were also favorable.

[0111] For the Al wiring materials in Comparative Examples 1 to 3 and 6 to 8, the contents of Er, Yb and Gd were out of the lower limit of the range of the present invention, and the results of the change in strength after heating at 350° C. were inferior as marked with a symbol of “cross”. For the Al wiring materials in Comparative Examples 4 and 5, the contents of Er, Yb and Gd were out of the upper limit of the range of the present invention, and the results of the chip damage and the hardness were inferior as marked with a symbol of “cross”.