JPH0254667B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrafine aluminum alloy wire used as a lead wire for semiconductor devices.

Conventionally, aluminum alloy wires are used as well as gold wires as bonding wires that electrically connect semiconductors and external terminals. In this case, aluminum alloy wires include Al-1%Si alloy, Al-1%Si alloy, etc. Mn alloy etc. are often used. Bonding wires made of these alloy wires are usually bonded to silicon chips, lead posts, etc. by thermocompression bonding, ultrasonic bonding,
Or a combination of both is used.

In this case, when thermocompression bonding is used, the wire rod is naturally softened by heating, and the strength of the joint portion is reduced. Even in the case of ultrasonic bonding, although the work is performed at room temperature, the ultrasonic energy is converted into heat when ultrasonic waves are applied, and this softens the wire and the bonded portion thereof.

If the joint becomes soft and its strength decreases in this way, it will cause frequent troubles such as wire breakage and abnormal deformation during subsequent assembly of semiconductor elements, and even if trouble does not occur,
Deterioration in reliability as a semiconductor device is inevitable.

In recent years, there has been a growing demand for improvements in the performance and reliability of semiconductor devices, and for bonding wires, in addition to ensuring the above-mentioned strength, further improvements in corrosion resistance and ductility are desired.

On the other hand, it is known that increasing the strength tends to lead to a decrease in ductility, and if the ductility decreases, it not only becomes difficult to expand and contract into ultra-fine wires, but also improves the wiring properties during device assembly and the wiring area after assembly. Also, from this point of view, it is essential to improve ductility along with an increase in strength.

The present invention has been made in view of the above-mentioned circumstances, and aims to provide an innovative ultrafine aluminum alloy wire for semiconductor devices that has high strength, high toughness, and excellent corrosion resistance. It is.

There are various ways to modify alloys to obtain desired properties. However, considering the purpose of use of the present invention, it is likely that the material will be subjected to a considerable heat load during use, and so-called work hardening or heat treatment hardening cannot be expected.

Therefore, it is effective to rely on so-called structure control, such as strengthening of the base material through alloying, crystal grain size through alloying, and size and dispersion state of second phase or precipitates.

The present invention was made based on this knowledge, and was based on an Al-Mg alloy, various additive elements were added thereto, various effects of these elements on performance were studied, and a predetermined satisfactory result was obtained. This was a successful achievement in achieving an alloy composition with high performance.

In the present invention, from the standpoint of improving strength and maintaining ductility, Mg is used as a basic additive element. Thus, its addition range is 2-5% by weight. If it is less than 2%, the strength will be insufficient, and if it is less than 5%, the stretchability into ultra-fine wire will be reduced.

However, Mn0.05~0.5% is added to the above basic alloy.
Either or both of 0.05 to 0.35% Cr is added. These are aimed at preventing stress corrosion cracking, suppressing recrystallization and improving heat resistance based on this, or improving ductility based on refinement of crystal grains.

If Mn is 0.05% or less and Cr is 0.05% or less, stress corrosion cracking resistance will not be exhibited, and the grain refinement effect will be reduced. In addition, if Mn is 0.5% or more and Cr is 0.35% or more, coarse Mn-containing and Cr-containing compounds will precipitate, resulting in decreased workability and corrosion resistance, so they are excluded.

Furthermore, Zr may be added instead of Cr in the above. Zr similarly prevents recrystallization and improves heat resistance, and also contributes to grain refinement and improves ductility. However, in this case, if it is less than 0.05%, there is no effect, and if it is more than 0.4%, coarse precipitates are formed and workability is deteriorated.

Further, depending on the case, B may be added in addition to the above composition. The addition of B improves ductility by refining the grains, and exhibits a remarkable effect especially when coexisting with Cr and Zr. However, in this case as well, there is no effect below 0.005%;
If it exceeds 0.05%, the grain refining effect will be saturated to a certain level and coarse precipitates will be formed, which will reduce workability, so it is excluded.

The aluminum alloy with the above composition has a minimum diameter
It is desirable to use it within the range of 0.02 mm and maximum diameter of 0.06 mm. If it is less than 0.02 mm, it will be difficult to draw the above composition alloy, and if it is more than 0.06 mm, the semiconductor device will be so fine that wiring will be difficult.

Example 1 An aluminum alloy having the composition shown in Table 1 was melted and processed,
Wire rods with a diameter of 0.03 mm were annealed at 350°C for 1 hour, and then mechanical properties and corrosion tests were conducted.

The corrosion test was measured by the degree of decrease in tensile strength when exposed for 300 hours in a constant temperature bath at a temperature of 90°C and a relative humidity of 90%. ◎ indicates almost no difference from the initial value, 〇 indicates 80-95% of the initial value, △ indicates 65-95% of the initial value
Cases in the 80% range are shown.

It is clearly seen that the alloy wire of the present invention has higher strength and elongation than the conventional alloy wire and comparative wire.

In order to maximize the performance of the alloy of the present invention, various measures can be taken in terms of manufacturing conditions, but among them, solidification is as rapid as possible during the production of ingots, and alloying elements in the ingots are It is important to form a solid solution as much as possible, to disperse precipitates as finely and uniformly as possible, and to make crystal grains as fine as possible.

In the case of this example, the solidification rate of the molten metal is 200℃/S
The casting conditions such as mold structure, mold cooling, casting amount, and casting temperature were controlled so that the results were as follows.

The thus obtained 30 mmφ ingot was heated to 450 to 460° C. within the shortest possible time and extruded into a 2 mmφ rough wire, which was drawn to 0.03 mmφ with appropriate intermediate annealing.

Example 2 Using the 0.03 mmφ wire rod of Example 1, wedge bonding was performed using ultrasonic waves to a Fe-41%Ni alloy strip on which Au was deposited, and the bonding strength A and collapse width W were measured. Please refer to the attached drawings for the measurement status of the bonding strength A and the collapse width W. Table 2 shows the measurement results. As is clear from Table 2, it is clearly seen that the alloy of the present invention has excellent connection performance even when actually bonded.

As detailed above, the alloy of the present invention exhibits high strength and ductility even when subjected to heat load while maintaining sufficient corrosion resistance, thereby increasing the strength and reliability of semiconductor device wiring. This not only improves product reliability, but also reduces the frequency of disconnections in wiring parts when using plastic packaging, molding, and resin pouring, and improves moldability, which improves device assembly efficiency and improves assembly steps. This greatly contributes to the improvement of students' performance, and its significance is enormous.

[Brief explanation of drawings]

The figure is an explanatory diagram showing the measurement of the breaking strength of the connection part (neck strength) and the crushing width. 1 is the wire, 2 is the board, the A direction is the tensile direction, B is the fracture location, and W is the crushing width. show.

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Claims (1)

[Claims] 1. Aluminum for semiconductor devices containing 2 to 5% Mg, 0.05 to 0.5% Mn or 0.05 to 0.35% Cr, or both, with the remainder being unavoidable impurities and Al. Alloy ultra-fine wire. 2 Mg2~5%, Mn0.05~0.5% and Zr0.05~
Contains 0.4%, with the remainder being unavoidable impurities and Al.
Ultrafine aluminum alloy wire for semiconductor devices. 3 Contains Mg2-5% and Zr0.05-0.4%,
Ultrafine aluminum alloy wire for semiconductor devices, the remainder of which is unavoidable impurities and Al. 4 Contains 2 to 5% Mg, 0.05 to 0.5% Mn or 0.05 to 0.35% Cr, or both, and 0.005 to 0.05% B, with the remainder being unavoidable impurities and Ultrafine aluminum alloy wire for semiconductor devices made of Al. 5 Mg2~5%, Mn0.05~0.5% and Zr0.05~
An aluminum alloy ultrafine wire for semiconductor devices, which contains 0.4% B, further contains 0.005 to 0.05% B, and the remainder consists of inevitable impurities and Al. 6 Contains Mg2-5% and Zr0.05-0.4%,
An aluminum alloy ultrafine wire for semiconductor devices further containing 0.005 to 0.05% of B, with the remainder consisting of inevitable impurities and Al.