JPS61166939A - Aluminum wire rod for semiconductor device bonding - Google Patents

Abstract

PURPOSE:To obtain the titled Al wire rod satisfying the various properties required of a bonding wire rod at low cost by incorporating prescribed amounts of Ni, Mg, Si, Fe, Cu, etc., to Al. CONSTITUTION:The Al wire rod for semiconductor device bonding consists of, by weight, 0.05-2.0% Ni, 0.2-4.0% Mg, <=0.02% Si, <=0.02% Fe, <=0.03% Cu, if necessary <=0.5% Ti and <=0.1% B, further <=1.0% of >=1 kind among Zr, Mn, and rare earth elements, and the balance Al. This wire rod has excellent characteristics as follows: high tensile strength; superior corrosion resistance; a nearly perfectly spherical shape of the ball (in case of ball bonding) and rare occurrence of variance in its size; superior heat resistance; no occurrence of constriction between the wire rod and the ball (in case of ball bonding); high strength after bonding; and such superior wire drawing workability that enables the wire drawing into an extra fine wire.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an aluminum wire for bonding used for connecting semiconductor chip electrodes and external lead parts, and in particular improves pole bonding properties and bonding strength, and improves wedge bonding by ultrasonic pressure welding. The present invention provides an aluminum wire material that can be used not only for bonding but also for ball bonding by thermocompression bonding.

[Conventional technology]

Generally, wedge bonding using ultrasonic bonding and pole bonding using thermocompression bonding are used to connect semiconductor chip electrodes and external lead portions using bonding wires. Wedge bonding is a process in which the sides of both ends of a bonding wire are crushed using ultrasonic energy to connect semiconductor chip electrodes and external leads. Compared to pole bonding, the connection time is two to three times longer and the bonding time is longer. It has directional properties, and the wiring direction is limited to in-plane directions, making it difficult to use for connecting semiconductor elements arranged radially. On the other hand, in pole bonding, one end of the bonding wire is melted electrically or with an oxygen-hydrogen flame, and the ball formed at that time is crushed while applying ultrasonic waves and heated to a temperature of 250 to 400 degrees Celsius to form a semiconductor chip electrode. and the other end is connected to the external lead part by ultrasonic connection.

Such bonding wires are required to have the following characteristics.

(1) High tensile strength.

(2) Excellent corrosion resistance.

(3) Ball shape is a true sphere (in case of pole bonding)
, with little variation in size.

(4) It has high heat resistance (in the case of pole bonding) and no constriction occurs between the wire and the ball.

(5) High strength after bonding.

(6) Good wire drawability up to ultra-fine wires of 60 μm or less.

Conventional bonding wires include Au wire, Au alloy wire, and A
J! -Si alloy wire, A, e-Nt alloy wire.

8λ-M (1 alloy wire etc. are used.

[Problem that the invention seeks to solve]

All wires and Al1 alloy wires are expensive, while most semiconductor chip electrodes are made of A (or A) alloy. It has the disadvantage of forming intermetallic compounds and becoming brittle, making it inferior to the case of using A!2 alloy wire in terms of reliability.
2).

It was inferior in terms of (3), (4), and (5) and could not be used for thermocompression bonding. Furthermore, the Al-N1 alloy wire has the above-mentioned (1
) and (5), AJ! -M(1 alloy wire is inferior in terms of (3) and (4) above.

Means for Solving Problem C] In view of this, the present invention has been developed as a result of various studies to provide a semiconductor element bonding device that satisfies the above characteristics and can be used not only for wedge bonding by ultrasonic bonding but also for pole bonding by thermocompression bonding. It is a product developed from aluminum wire.

That is, one of the wire rods of the present invention has a N i of 0.05 to 2.0w.
t% (hereinafter wt% is simply abbreviated as %), Mg0.2-4
．． 0%, 3i 0.02% or less, Fed 0.02% or less, Cu 0003% or less, and the balance is A.

Moreover, another one of the wire rods of the present invention has a Ni of 0.05 to 2.
0%, Mg0.2-4.0%, 3i 0.02% or less, 1:eo, 02% or less, CIJ 0103% or less, T
It is characterized in that it contains 0.5% or less of i, 8001% or less, and the remainder consists of Al.

Furthermore, another one of the wire rods of the present invention has Ni0.05 to 2,
0%, Mgo, z ~ 4.0%, Si 0.02% or less, 1
:eo, 02% or less, Cu0.03% or less, 7i0.5
% or less, 30.1% or less, and further zr, Ml'l
, rare earth elements, and the remainder is λ.

[For production]

In the present invention, the purpose of adding N1 is to make the ball shape in pole bonding similar to a pearl, increase heat resistance, make constriction between the wire rod and ball less likely to occur, and increase strength after bonding. .05~2.
The reason why it is limited to 0% is because if it is less than 0.05%, sufficient high-temperature strength cannot be obtained, and constriction is likely to occur between the wire and the ball, and the strength after bonding will decrease, and if it exceeds 2.0%. This is because the corrosion resistance of the wire decreases. The purpose of adding Mill is to improve tensile strength without reducing corrosion resistance, and the reason why the Mg content is limited to 0.2 to 4.0% is that less than 0.2% does not have a sufficient strength improvement effect. If it exceeds 4%, work hardening will be significant and the wire rod will not be able to be stretched or contracted.

In addition, the Si content is 0.02% or less, and the Fe content is 0.0%.
The reason why we limited the Cu content to 0.03% or less is that these are impurities that are inevitably included and are effective in improving strength, but they significantly reduce corrosion resistance. This results in not only insufficient corrosion resistance but also poor ball shape, so it is particularly desirable to keep these contents to 0.01% or less.

Next, the addition of Ti and B to the above A, e-Ni-Mg-8i-Fe-Cu alloy is to refine the crystal grains of the ingot and stabilize the quality of the wire rod by adding them at the same time. , T1 content 0.5% or less, B content go,
The reason why the content is limited to 1% or less is because if the content exceeds this, a coarse second phase will crystallize, making it impossible to form ultra-fine wires by stretching.

Furthermore, the above A, e-Ni-M! ] −8t −Fe −
The reason for adding one or more of Zr, Mn, and rare earth elements to the Cu-Ti-8 alloy is to improve the heat resistance due to the mutual effect with Ni and further increase the strength after bonding. The reason why the total content of one or more of these elements is limited to 1.0% or less is that if the content exceeds this, a second phase will crystallize and the wire will be drawn into an ultra-fine wire. This is because it becomes difficult. The rare earth elements include cerium group (La, C0.Pr.

Nd, Pm, Sm) and yttrium group (S
C.

Y, En, Gd, Tb, Dy, Ho, Er.

Tm, Yb, Lu) and generally la.

It is preferable to use C, e, Sn, Gd, or mitsch metal (a mixture of rare earth elements, hereinafter abbreviated as MM).

The wire rod of the present invention has the above-mentioned alloy composition, and all impurity elements other than the above-mentioned elements contained in the base metal deteriorate corrosion resistance and ball shape, so it is necessary to suppress them to a small amount as much as possible. The total content of 0.01
% or less, preferably 0.005% or less. For this reason, the Al ingot used should be one with a purity of 99.95% or higher and a low amount of impurity elements other than alloying elements, or one with a purity of 99.99% or higher, preferably a purity of 9.
It is preferable to use a high purity Al metal of 9.995% or higher.

〔Example〕

High-purity Ai ingot with a purity of 99.999% is melted, and into this is 8λ with a purity of 99.999% and N with a purity of 99,999%.
i, fvH+ with a purity of 99.99%, Si with a purity of 99,999.

CLI with a purity of 99.999%, Ti with a purity of 99.9%,
B with a purity of 99%, Z r with a purity of 99.6%, 99.
99% Mn.

MM (Ce 40% or more), C0. with a purity of 99.9%. Each master alloy made using La with a purity of 99.9% and Nd with a purity of 99.9% was added to produce an alloy having the composition shown in Table 1. Cast in a mold.

After soaking this ingot at a temperature of 550°C for 48 hours, it was hot groove rolled into a wire rod with a diameter of 5Si, which was then subjected to cold wire drawing and intermediate annealing at 360°C at 29H15 repeatedly. Fi thin wire, 100~3
Final annealing was performed at a temperature of 60° C. for 2 hours to obtain an aluminum wire for bonding.

The drawability of these wire rods was compared, the tensile strength and elongation were measured, and one end of the wire was melted using an arc while blowing gas using an ordinary manual ball bonding device. Wire rod (1) as shown in
A ball (2) is formed at one end, and the vacuum degree H is applied to this ball (2).
/D and constriction rate do/d (where H is the diameter of the ball in the longitudinal direction, D is the diameter of the ball in the lateral direction, d is the diameter of the wire,
The ball was then thermocompression bonded to a semiconductor chip electrode, the other end of the wire was ultrasonically welded to the external lead, and the strength of the wire after bonding was measured. Also, during the upper 2 cold wire drawing process, diameter 1.0. A sample was taken from the wire rod, and the sample was subjected to salt water spraying for 4 days based on JIS2371 to examine its corrosion resistance. These results are shown in Table 2.

As is clear from Tables 1 and 2, conventional wire NQ54
Not only does it have poor corrosion resistance, but poles are not formed and thermocompression bonding is impossible. Conventional wire material Na55 shows good corrosion resistance, but has low sphericity, high constriction rate, and poor poleability. The strength after bonding is low, and although the conventional wire NQ56 has good pole bonding properties, its tensile strength is low and its strength against bonding corrosion is low.

On the other hand, it can be seen that the wire rods Nα1 to Nα40 of the present invention all have high strength after bonding, form a pole close to a perfect sphere, have little constriction, and can be pole bonded. It is also seen that although the corrosion resistance is slightly inferior in the wire rods NQ11 to 14 of the present invention, which have a large total content of impurities, the others have good corrosion resistance. In particular, wire rods NQ15 to 24 of the present invention to which T1 and B were added showed improvements in tensile strength, elongation, and strength after bonding, and furthermore, Zr and Mn.

In the wire rods NQ25 to 40 of the present invention to which one or more rare earth elements were added, further improvement was observed in the tensile strength and the strength after bonding.

On the other hand, it can be seen that comparative alloys Nos. 41 to 53, which fall outside the composition range of the wire of the present invention, are inferior in corrosion resistance, strength after bonding, and wire drawability. That is, from the composition range of the wire of the present invention, N1°Si, F0. Comparative wire material Na42. has a higher total content of Cu and impurities. No45~4
7 and NQ53 have poor corrosion resistance, and the comparative wire material NQ41°43, which contains less Ni and Mill, has low strength after bonding, and especially the comparative wire material NQ41, which contains the least amount of Ni, has a large constriction.

It also contains a lot of Ma, T+, s, zr, vn, and rare earth elements.
Comparison wire Nα44. In Nos. 48 to 54, there were many wire breaks during the cold wire drawing process, and it was not possible to process the wires into ultrafine wires of 30 μm.

〔Effect of the invention〕

As described above, the wire rod of the present invention satisfies the above-mentioned characteristics required for bonding wire rods, and can be used not only for wedge bonding but also for pole bonding, and can replace expensive AIJ or AL+alloy wires at a lower cost and at the same level. It exhibits remarkable effects such as exhibiting high performance and no fear of the formation of intermetallic compounds at the bonding surface.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of ball sphericity and constriction rate in pole bonding.

Claims (6)

[Claims] (1) Ni0.05-2.0wt%, Mg0.2-4.
0wt%, Si0.02wt% or less, Fe0.02wt
% or less, including Cu0.03wt% or less, and the balance being Al. (2) The aluminum wire for semiconductor element bonding according to claim 1, wherein the total content of impurity elements other than Ni, Mg, Si, Fe, and Cu is 0.01 wt% or less. (3) Ni0.05-2.0wt%, Mg0.2-4.
0wt%, Si0.02wt% or less, Fe0.02wt
% or less, Cu 0.03 wt % or less, Ti 0.5 wt % or less, B 0.1 wt % or less, and the balance is Al. (4) The aluminum wire for semiconductor device bonding according to claim 3, wherein the total content of impurity elements other than Ni, Mg, Si, Fe, Cu, Ti, and B is 0.01 wt% or less. (5) Ni0.05-2.0wt%, Mg0.2-4.
0wt%, Si0.02wt% or less, Fe0.02wt
% or less, Cu 0.03 wt % or less, Ti 0.5 wt % or less, B 0.1 wt % or less, and a total of 1.0 wt % or less of any one or more of Zr, Mn, and rare earth elements, and the balance is Al. Aluminum wire material for bonding semiconductor devices. (6) Ni, Mg, Si, Fe, Cu, Ti, B, Zr
, Mn, and the total content of impurity elements other than rare earth elements is 0.
．． The aluminum wire for bonding semiconductor elements according to claim 5, wherein the aluminum wire has a content of 0.01 wt% or less.