JPH08316262A - Gold wire for bonding - Google Patents

Abstract

PURPOSE: To provide a gold wire, for IC-chip bonding, which is hard to disconnect even when a thermocompression bonding operation is performed jointly by using ultrasonic waves with an increased ultrasonic output and even when a loop is formed by a reverse deformation operation which extremely bends and deforms a ball neck part. CONSTITUTION: Gold of 99.999wt.% or higher purity contains 0.0001 to 0.005wt.% Pt, 0.0001 to 0.005wt.% Ag and 0.00005 to 0.005wt.% Yb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding gold wire used for connecting an electrode of an IC chip and an external lead portion, and more specifically, when assembling a semiconductor device.
The present invention relates to a gold wire for IC chip bonding, which can significantly reduce the extent to which the neck portion of the bonding wire is damaged due to an increase in ultrasonic output.

[0002]

2. Description of the Related Art Conventionally, as a technique for connecting an electrode on an IC chip and an external lead portion, an ultrasonic combined thermocompression bonding method using a gold wire has been mainly used. Further, as the number of electrodes and external lead portions has increased with the recent demand for higher speed and higher functionality of semiconductor devices, the wiring distance from the electrodes to the external lead portions has become longer. On the other hand, in order to make the semiconductor device small and thin, the wiring distance between the electrode and the external lead portion is extremely shortened. For this reason, it is required to perform short wiring while using a large number of lead wires, and in order to cope with this, in the process of forming a loop using a bonding device, the ball neck portion is severed in the opposite direction to the loop formation. Attempts have been made to stabilize the loop height and loop shape by performing so-called reverse deformation in which the loop is stretched after being bent and deformed.

However, the loop formed by performing the reverse deformation as described above, when exposed to the thermal cycle environment associated with the heat generation of the semiconductor in the operation stage of the semiconductor device, has a disconnection defect in the ball neck portion. There was a problem of doing. In order to prevent such disconnection failure during semiconductor operation, when a ball neck is severely bent and deformed to form a loop, a gold wire that is less likely to be disconnected in the subsequent severe thermal cycle test is required. Has been done.

On the other hand, in the related art, for the purpose of improving the problem that the neck portion just above the gold ball is broken by vibration, there is a material containing a predetermined amount of Eu, Ca, Ge, and Be (Japanese Patent Laid-Open No. Hei. 9624). However, the above-mentioned conventional proposal is such that even if the bonding wire is exposed to a severe thermal cycle environment after being bent and deformed severely at the ball neck portion to form a loop, the gold wire is less likely to be broken at the ball neck portion. It is in a state where it cannot be said that it is enough.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and an object of the present invention is to perform ultrasonic thermocompression bonding with an increased ultrasonic output. Also, the gold wire for IC chip bonding is less likely to be broken even if exposed to a harsh thermal cycle environment after forming a loop by performing so-called reverse deformation in which the ball neck is severely bent and deformed to form a loop. Is to provide.

[0006]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors, 99.999% by weight or more of high-purity gold was mixed with platinum (Pt), silver (Ag), and ytterbium (Yb). It has been found that the above-mentioned objects can be achieved by the synergistic effect of each of these elements by containing in a fixed amount, and the present invention has been completed. That is, the first invention of the present application is
9.999% by weight or more of high-purity gold, platinum (Pt):
0.0001 to 0.005% by weight, silver (Ag): 0.0
001 to 0.005% by weight and ytterbium (Y
b): A gold wire for IC chip bonding, containing 0.00005 to 0.005% by weight.

The second invention of the present application is the same as the first invention, except that beryllium (Be): 0.00002 to 0.001% by weight, calcium (Ca): 0.00005 to 0.01% by weight, germanium (Ge). : 0.0001 to 0.01
It is a gold wire for IC chip bonding, which further contains at least one of weight%.

Furthermore, a third invention of the present application is the same as the first or second invention, except that europium (Eu), yttrium (Y), lanthanum (La), lead (Pb), erbium (Er), cadolinium (Gd), Cerium (Ce),
At least one of praseodymium (Pr), neodymium (Nd), and samarium (Sm) is 0.0001 to 0.02.
The gold wire for IC chip bonding is characterized by further containing wt%.

[0009]

As described above, according to the present invention, the first group in which a predetermined amount of Pt, Ag, and Yb are essential and a predetermined amount of Be, Ca, and G are used.
a second group consisting of at least one of e, Eu, Y, L
It has a composition containing a third group of components in a predetermined amount of at least one of a, Pb, Er, Gd, Ce, Pr, Nd and Sm. The detailed configuration of the present invention and its operation will be described below. The starting material used in the present invention contains gold with a purity of 99.999% by weight or more, and the balance is inevitable impurities. Pt, Ag,
By using a composition containing Yb so as to have the above-mentioned constitution, the combined use of ultrasonic waves makes it possible to perform thermocompression bonding with ultrasonic waves by increasing the ultrasonic output.
In addition, it is possible to obtain a gold alloy wire having excellent fatigue characteristics in terms of reliability of the neck portion of the bonding wire that has undergone reverse deformation when forming a loop and excellent breaking performance when exposed to a heat cycle environment. Next, the reason why the composition of the gold alloy wire of the present invention is limited as described above will be explained.

[First group; Pt] Pt exhibits an excellent effect of improving the reliability of the ball neck portion in the coexistence with Ag and Yb. When the Pt content is 0.0001% by weight or more, the reliability of the ball neck portion becomes large as compared with less than 0.0001% by weight, and when it exceeds 0.005% by weight, good ball formation cannot be achieved. Therefore, the Pt content is set to 0.0001 to 0.005% by weight. Compared with the case where any one of Ag and Yb is not contained even if the above specified amount of Pt is contained, the reliability of the ball neck portion is improved in the coexistence with Ag and Yb.
Coexistence with g and Yb is required. A more preferable composition is to contain at least one kind of Be, Ca and Ge in a predetermined amount, and this composition exhibits a further excellent effect in improving the reliability of the ball neck portion.

[First group; Ag] Ag, in the coexistence with Pt and Yb, exhibits an excellent effect of improving the reliability of the ball neck portion. When the Ag content is 0.0001% by weight or more, the reliability of the ball neck portion becomes large as compared with less than 0.0001% by weight, and when it exceeds 0.005% by weight, good ball formation cannot be achieved. Therefore, the Ag content is set to 0.0001 to 0.005% by weight. In comparison with the case where any one of Pt and Yb is not contained even if the specified amount of Ag is contained, the reliability of the ball neck portion is improved in the coexistence with Pt and Yb, so that Ag is P
Coexistence with t and Yb is required. A more preferable composition is to contain at least one kind of Be, Ca and Ge in a predetermined amount, and this composition exhibits a further excellent effect in improving the reliability of the ball neck portion.

[First group; Yb] Yb exhibits an excellent effect of improving the reliability of the ball neck portion in the coexistence with Pt and Ag. When the Yb content is 0.00005% by weight or more, the reliability of the ball neck portion becomes large as compared with less than 0.00005% by weight, and when the Yb content is 0.0001% by weight or more, the reliability is further increased. Yb content is 0.0
If it exceeds 05% by weight, good ball formation cannot be achieved and the chip electrode is cracked during bonding. Therefore, the Yb content is 0.00005 to 0.
It was determined to be 005% by weight. Even if Yb is included in the specified amount, P
In comparison with the case where any one of t and Ag is not contained, Yb needs to coexist with Pt and Ag because the reliability of the ball neck portion is improved in coexistence with Pt and Ag. A more preferable composition is a predetermined amount of Be, Ca, G
In this composition, at least one kind of e is added, and a more excellent effect in improving the reliability of the ball neck portion is exhibited.

[Second group; Be, Ca, Ge] Be content is 0.00002 to 0.001% by weight, Ca content is 0.00005 to 0.01% by weight, and Ge content is 0.0.
001 to 0.01% by weight of at least one component,
Coexistence with Pt, Ag and Yb exhibits a more excellent effect in improving the reliability of the ball neck portion, and is therefore preferably used. When the Be content is less than 0.00002% by weight, the Ca content is less than 0.00005% by weight, and the Ge content is less than 0.0001% by weight, the above-mentioned more excellent effects cannot be obtained. Be content is 0.001
If it exceeds the weight%, good ball formation cannot be achieved. If the Ca content exceeds 0.01% by weight, good ball formation cannot be achieved. If the Ge content exceeds 0.01% by weight, electrode cracking during bonding tends to occur. Therefore, preferably used Be content is 0.00002 to 0.001% by weight, Ca content is 0.00005 to 0.01% by weight, and Ge content is 0.
It was determined to be 0001 to 0.01% by weight.

[Third group; Eu, Y, La, Pb, Er,
Gd, Ce, Pr, Nd, Sm] The third group is added to the first group of components.
Group components, namely Eu, Y, La, Pb, Er, Gd,
When 0.0001 to 0.02 wt% of at least one of Ce, Pr, Nd, and Sm is contained, the reliability of the ball neck portion is the same as that of the composition containing only the first group. Have an effect. In this case, even if the third group component is contained, if one of Pt, Ag, and Yb which is the first group component is not contained, an excellent effect on the reliability of the ball neck portion cannot be obtained. .

In addition to the components of the first group and the components of the second group, the components of the third group, namely Eu, Y, La, Pb, Er, G.
When at least one of d, Ce, Pr, Nd, and Sm is contained in an amount of 0.0001 to 0.02% by weight, the reliability of the ball neck portion is such that the first group of components and the second group of components are It has an even more excellent effect equivalent to that of the composition contained at the same time. In this case, even if the components of the second group and the third group are contained but any one of Pt, Ag and Yb which is the component of the first group is not contained, an excellent effect on the reliability of the ball neck portion is obtained. Can't get

[0016]

EXAMPLES Examples and comparative examples shown in Tables 1 to 10 will be described below. (Example 1) 99.999 so that the composition shown in the table is obtained.
A master alloy containing weight% of gold and each element is melted in a vacuum melting furnace and then cast, and cold working and heat treatment using a groove roll and a wire drawing machine are repeated to obtain a final wire diameter of 30 μm and an elongation of 4%. Finished to be a fine line. Using this thin wire as a bonding wire, ultrasonic thermocompression bonding was performed on the IC chip electrode using a high-speed automatic bonder. Set the ultrasonic output to 0.
After making the first ball joint with 5W, temporarily move the capillary in the direction opposite to the loop formation and set the reverse angle to 60 degrees with respect to the vertical direction, and severely bend and deform the ball neck, and then normal Loops were formed.
First, a ball shape and vibration test were performed using a thin wire, and further bonding was performed on the IC chip electrode, followed by electrode cracking at the time of bonding and a thermal cycle test. The measurement results are shown in Table 2.

(Examples 2 to 124 / Comparative Examples 1 to 13) Fine wires were finished and tested in the same manner as in Example 1 except that the compositions shown in the table were used. The results are shown in Table 2, Table 4, Table 7,
It shows in Table 10.

The measuring method is as follows. [Ball Shape] Gold balls were produced using an electric torch incorporated in a high-speed automatic bonder, and the size, sphericity, and surface condition of the gold balls were observed using a scanning electron microscope. The size of the gold ball is 2.5 times the wire diameter, that is, 75 μm
Based on φ, the sphericity and surface condition were measured by comparison with a comparative sample. When 10 pieces are measured and all are good, "good", 1
When there is a defect even in individual pieces, it is displayed as "defective".

[Electrode cracking at the time of bonding] 100 bonding tests were performed using a high-speed automatic bonder, and those with no electrode cracking failure were evaluated as “good”, and those with even one cracking failure were evaluated as “failed”. Was displayed. "

[Thermal Cycle Test] After forming a loop, it was sealed with an epoxy resin, -10 ° C. × 30 minutes and 150 ° C. ×
A 30-minute heat cycle test was performed 2000 times. 100 samples were subjected to measurement, and the presence or absence of disconnection was confirmed by a continuity test. The number of broken wires was expressed as a breakage rate (%).

[Vibration Test] Bonding was performed in the same manner as in Example 1 except that a silver-plated lead frame 1 was prepared as a substrate material instead of the IC chip electrode.
Used as a material for vibration test. Using the vibration tester 2 shown in FIG. 1, the wire 3 having the tip bonded to the lead frame 1 is held by the clamp 4, and a vibration test in which the wire 5 is oscillated to the left and right sides about the shaft 5 is performed under the following conditions, and the rupture occurs. The number of vibrations until reaching was measured. Span distance (L ₁ ): 150 μm Bilateral amplitude (L ₂ ): 26 μm Vibration frequency: 40 Hz (40 times per second) The same test was repeated 3 times, and the obtained average value was displayed.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

[Table 4]

[0026]

[Table 5]

[0027]

[Table 6]

[0028]

[Table 7]

[0029]

[Table 8]

[0030]

[Table 9]

[0031]

[Table 10]

As is clear from the above measurement results, Examples 1 to 10 containing a predetermined amount of Pt, Ag, and Yb of the first group of components had a good ball shape and cracked electrodes during bonding. In addition to having no defects, the fracture rate after the heat cycle test was 1%, and the number of vibrations until the fracture in the vibration test was 11,000 times or more, which was excellent in improving the reliability of the ball neck part. It was Among these, Y
Examples in which the content of b is 0.0001% by weight or more,
Number of vibrations up to breakage in vibration test is 12,000
Over the times, it showed an excellent effect by improving the reliability of the ball neck portion.

In addition, in addition to the first group of components, Examples 11 to 77 containing a second group of components consisting of a predetermined amount of at least one of Be, Ca and Ge have good ball shapes. In addition, there is no occurrence of electrode cracking defects during bonding, the breakage rate after the thermal cycle test is 1% or less, and the number of vibrations until breakage in the vibration test is 1100.
An excellent effect was shown with 0 times or more. Among these, Yb
The content of 0.0001% by weight or more is 0, the breaking rate after the heat cycle test is 0%, the number of vibrations up to the breaking in the vibration test is 13,000 times or more, and the ball neck portion It showed a more excellent effect in improving reliability.

In addition to the components of the first group, Eu,
Y, La, Pb, Er, Gd, Ce, Pr, Nd, Sm
Examples 78 to 98 containing at least one predetermined amount of the third group of components showed the same effect as Examples 1 to 10 containing only the first group.

Furthermore, in addition to the components of the first group and the components of the second group, Eu, Y, La, Pb, Er, Gd,
Examples 99 to 124 containing a third group of components consisting of a predetermined amount of at least one of Ce, Pr, Nd and Sm,
Compared with Examples 11 to 77 in which the components of the first group and the components of the second group were contained at the same time, the same excellent effect was exhibited.

On the other hand, the first group and the second group according to the present invention
It can be seen that in Comparative Example 1 which does not contain any of the components of the group 3 and the group 3, the fracture rate after the thermal cycle test is 15% and the number of times until the fracture in the vibration test is about 6,400.
Further, Comparative Examples 2 to 10 not containing any one component of the first group have a fracture rate of 6 to 9 after the thermal cycle test.
%, The number of times until breakage in the vibration test is 8,000 times or more and 10,000 times or less, which is improved as compared with Comparative Example 1, but inferior as compared with the present invention. Furthermore, even if all the components of the first group are contained, the content of any one of them is outside the scope of the present invention.
Shows that the fracture rate after the heat cycle test is 2% and the number of times until the fracture in the vibration test is 11,000 or more, which is close to the present invention, either ball shape or chip electrode cracking is obtained. It is understood that the present invention is inferior to the present invention in respect of.

[0037]

As described above, the IC according to the present invention
Since the gold wire for chip bonding has a composition containing 99.999% by weight or more of high-purity gold and a predetermined amount of Pt, Ag and Yb, ultrasonic combined thermocompression bonding with increased ultrasonic output is performed. Moreover, in the neck portion of the loop formed by applying the reverse deformation, the fatigue property was excellent, and the fracture performance when exposed to the environment of the heat cycle could be significantly improved. Therefore, high reliability can be obtained in assembling a semiconductor device in which a large number of lead wires are used for short wiring, and it is extremely useful for accelerating speeding up, high functionality, miniaturization, and thinning of the semiconductor device.

In the case where the composition is such that 99.999% by weight or more of high-purity gold contains a predetermined amount of Pt, Ag and Yb, and further contains a predetermined amount of at least one of Be, Ca and Ge. Improves fatigue characteristics and rupture performance when exposed to the environment of thermal cycle in the neck part of the loop formed by applying reverse deformation and ultrasonic combined thermocompression bonding with increased ultrasonic output It was possible to make the above-mentioned effect more effective.

[Brief description of drawings]

FIG. 1 is a simplified diagram showing an outline of a vibration test.

[Explanation of symbols]

 1: Lead frame 2: Vibration tester 3: Bonding wire 4: Clamp 5: Amplitude center axis

Claims (3)

[Claims] 1. A high purity gold of 99.999% by weight or more,
Platinum (Pt): 0.0001 to 0.005% by weight, silver (Ag): 0.0001 to 0.005% by weight, and ytterbium (Yb): 0.00005 to 0.005% by weight. Gold wire for IC chip bonding. 2. Beryllium (Be): 0.00002-
0.001% by weight, calcium (Ca): 0.0000
5 to 0.01% by weight, germanium (Ge): 0.00
The gold wire for IC chip bonding according to claim 1, which contains at least one of 01 to 0.01% by weight. 3. Europium (Eu), yttrium (Y), lanthanum (La), lead (Pb), erbium (Er), cadolinium (Gd), cerium (Ce),
At least one of praseodymium (Pr), neodymium (Nd), and samarium (Sm) is 0.0001 to 0.02.
% Or claim 2 characterized in that the content of 1 wt%
Gold wire for IC chip bonding described.