JPH09321075A - Bonding wire - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a bonding wire which has high strength but little damage during wire bonding and which is unlikely to cause disconnection during semiconductor assembly. SOLUTION: Ca is 0.0003 to 0.003% by weight.
Containing 0.0005 to 0.01% by weight of Mg, and further containing one or more of Pt, Pd, and Cu in a total amount of 0.01 to
A bonding wire containing 2.0% by weight and the balance of Au and inevitable impurities, and 0.0003 to Ca.
Includes 0.003% by weight, 0.0005 to 0.01 Mg
0.01 wt% to 2.0 wt% of Pt, Pd, and Cu in total, and 0.0001 to 0.002 wt% of Be and Ge in total. %, And the rest is a bonding wire consisting of Au and unavoidable impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding wire used for connecting an electrode on a semiconductor element and an external lead, and more specifically, it is made of a specific gold alloy which is unlikely to break during wire assembly of a semiconductor device. Regarding bonding wire.

[0002]

2. Description of the Related Art Bonding wires having a diameter in the range of 0.02 to 0.1 mm are used for connecting electrodes of semiconductor elements such as IC and LSI to external leads. Since this bonding wire is required to have good conductivity, good bondability with a semiconductor element or an external lead, and good environmental resistance in an atmosphere of use, the bonding wire is mainly made of gold (Au) or Alloys are used. 2. Description of the Related Art In recent years, there has been an increasing need to use wires with a smaller wire diameter due to the demand for higher pin counts and lower costs for semiconductor devices. Such thinning of the wire causes disconnection of the wire due to vibration or the like during the assembly of the semiconductor device, and the disconnection of the wire has been a serious problem in assembling the semiconductor device. For this reason, recently, a wire having a high strength is generally used.

On the other hand, in recent wire bonding, since it is necessary to control the wire shape at the time of bonding more precisely, it is common to use a wire shape control method called a reverse mode which applies a large load to the neck portion of the wire. Has become. The use of this reverse mode has a drawback that the neck portion of the wire tends to be damaged, which easily breaks the wire. Generally, damages caused by the reverse mode tend to occur more easily in high-strength wires, so it is not enough to simply use high-strength wires as a measure for preventing disconnection.

[0004]

SUMMARY OF THE INVENTION In view of the above situation, it is an object of the present invention to provide a bonding wire which has high strength but little damage during wire bonding and which is unlikely to cause disconnection during semiconductor assembly.

[0005]

A bonding wire of the present invention for solving the above-mentioned object contains Ca in an amount of 0.0003.
~ 0.003 wt%, Mg 0.0005-0.0
It is characterized by containing 1% by weight, 0.01 to 2.0% by weight in total of one or more of Pt, Pd, and Cu, with the balance being Au and inevitable impurities.

Another bonding wire of the present invention contains 0.0003 to 0.003% by weight of Ca and Mg
Containing 0.0005 to 0.01% by weight, Pt, Pd, C
0.01 to 2.0 wt% in total of one or more of u, and 0.00 in total of one or more of Be and Ge.
It is characterized by containing 01 to 0.002% by weight, and the balance being Au and inevitable impurities.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, Ca is an additive element that brings the strength and heat resistance required for a bonding wire. Addition amount of Ca is 0.0003 to 0.003% by weight
The reason is that if it is less than 0.0003% by weight, the desired strength and heat resistance cannot be obtained, and conversely, if it exceeds 0.003%, the effect of addition is saturated.

Mg is an additive element that lengthens the length of the recrystallized portion immediately above the ball during ball formation. The addition amount of Mg was set to 0.
The reason why the content is set to 0005 to 0.01% by weight is that the desired recrystallization length cannot be obtained if it is less than 0.0005% by weight, and conversely, if it exceeds 0.01%, the effect of addition is saturated. .

Pt, Pd, and Cu are additive elements for improving the wire strength.
The content of 01 to 2.0% by weight is that the effect of improving the strength is insufficient if it is less than 0.01%, and conversely if it exceeds 2.0% by weight, the ball formed during ball bonding is not a true sphere. Therefore, it becomes difficult to obtain good bondability.

The present invention is characterized in that Mg is added at the same time in addition to the strength enhancement of the wire by Ca, Pt, Pd, and Cu. That is, we say that wire breakage due to vibration etc. mainly occurs at the neck part of the first bond, and in order to prevent wire breakage, the wire has a certain level of strength and at the same time corresponds to the neck part of the wire. It has been found that the length of the recrystallized portion just above the ball needs to be longer than a certain length. The present invention is based on this finding, and it is not possible to satisfy the requirements of the above ages only by increasing the strength by Ca, Pt, Pd, Cu or by increasing the length of the recrystallized portion by Mg to obtain the desired characteristics. Is impossible.

B in the invention according to claim 2 of the present invention
e and Ge are additive elements for stabilizing the effect of Ca addition, and 0.001 to 0.002% by weight of one or more of Be and Ge is 0.00
This is because if it is less than 01% by weight, the desired property stabilizing effect cannot be obtained, and conversely if it exceeds 0.002% by weight, the effect of addition is saturated.

In the present invention, a rare earth element,
It is possible to further increase the strength by adding an element such as Sr or Sn, but in that case, it is necessary to take care not to shorten the recrystallization length. For example, in the case of a light rare earth element such as Ce, the addition amount is 10 p
It is necessary to be less than pm.

[0013]

EXAMPLES High-purity gold having a purity of 99.999% by weight, a gold mother alloy containing 1% by weight of a predetermined additive element, and a purity of 99.99.
%, Pt, Pd, and Cu were used to melt-cast a gold alloy having the composition shown in Table 1. The obtained ingot was subjected to groove roll processing and further wire drawing using a Guyamond die to obtain an alloy wire having a diameter of 0.025 mm. The properties were adjusted by subjecting the obtained alloy wire to heat treatment to obtain a sample.

As an evaluation of the sample thus manufactured, a tensile test was used for the wire strength. The length of the recrystallized portion just above the ball was measured by observing the structure of the sample formed with a wire bonder with a metal microscope and SEM after aqua regia etching.
evaluated.

Regarding the wire breakage rate at the time of assembling a semiconductor, a vibration adding device was applied to a sample wire-bonded by ultrasonic thermocompression bonding to a lead frame for a 64-pin QFP package (wire length is 2 to 2.5 mm). Was used as a substitute characteristic by obtaining a wire breakage rate when a vibration having an amplitude of 0.5 mm at 50 Hz was applied for 150 seconds.

Further, for the purpose of confirming the bonding property, that is, the bonding property between the bonding wire and the electrode of the semiconductor element and the external lead, the wire bonded by the same method as described above is hooked and a tensile test is conducted. did. Further, as a confirmation of the bonding bond reliability during storage, a pull test was performed on the sample wire-bonded by the same method as above, after holding at 200 ° C. for 100 hours. In the pull test, the case where the breakage occurred at the wire portion was judged to be good, and the case where the breakage occurred at the joint was judged to be bad.

Table 1 shows the composition of each sample, and Table 2 shows the results of the above evaluations together with the evaluation results of the comparative materials. Table 1, Table 2
As is clear from the above, it can be seen that the bonding wire according to the present invention exhibits a lower value of wire breakage due to vibration than the comparative product, even though the bonding wire according to the present invention has high wire strength. Also, the bonding bondability and the bonding bond reliability are good, and it can be seen that there is no problem in using as a bonding wire.

[0018]

[Table 1]

[Table 2]

[0019]

As is apparent from the above, according to the present invention, it is possible to provide a bonding wire which is less likely to be broken during the assembly of a semiconductor device and in which the assembly yield of the semiconductor device is less likely to decrease.

Claims (2)

[Claims] 1. An amount of Ca of 0.0003 to 0.003% by weight.
Containing 0.0005 to 0.01% by weight of Mg, and further containing one or more of Pt, Pd, and Cu in a total amount of 0.01 to
A bonding wire comprising 2.0% by weight and the balance being Au and inevitable impurities. 2. The amount of Ca is 0.0003 to 0.003% by weight.
Containing, 0.0005-0.01 weight% Mg, P
At least one of t, Pd, and Cu is 0.01 to
2.0% by weight, 0.001 to 0.002% by weight in total of one or more of Be and Ge, and the balance A
A bonding wire comprising u and unavoidable impurities.