JP3312348B2 - Gold alloy wire for bonding - Google Patents

Abstract

PURPOSE:To produce an alloy wire for bonding in which wire cutting in time neck part of a bonding wire can remarkably be reduced even being exposed to a severe heat cycle environment after being subjected to reverse deformation at the time of assembling a semiconductor device. CONSTITUTION:In a master alloy in which a gold matrix of 99.999wt.% is incorporated with, by weight, 0.0001 to 0.01% Y, 0.0002 to 0.2% Pt, 0.0001 to 0.01% La, at least one kind of Ag and Pd by 0.0002 to 0.2%, at least one kind of 0.0001 to 0.002% Be and 0.0001 to 0.01% Ca is melted in a vacuum melting furnace, the master alloy is cast, is repeatedly subjected to cold working using a groove roll and a wire drawing machine and heat treatment and is finished into a fine wire having 30mum final wire diameter and 4% elongation percentage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding gold alloy wire used for connecting an electrode of a semiconductor element to an external lead portion, and more particularly, to a method of assembling a semiconductor device which is subjected to severe deformation after being subjected to reverse deformation during assembly. The present invention relates to a gold alloy wire for bonding that can significantly reduce disconnection at a neck portion of a bonding wire even when exposed to a severe thermal cycle environment.

[0002]

2. Description of the Related Art Conventionally, as a technique for connecting an electrode on a semiconductor element to an external lead, an ultrasonic combined thermo-compression bonding method using a gold alloy wire is mainly used. Further, as the number of electrodes and external leads has increased in accordance with recent demands for higher speed and higher functionality of semiconductor devices, the wiring distance from the electrodes to the external leads has become longer. On the other hand, in order to reduce the size and thickness of the semiconductor device, measures are taken by extremely shortening the wiring distance between the electrode and the external lead. For this reason, it is required to perform wiring in a short time while using a large number of lead wires.
In the process of forming a loop using a bonding device, the ball neck is severely bent and deformed in the opposite direction to the loop formation, and then the loop is stretched. Attempts have been made to transform it. However, the loop formed by performing the reverse deformation as described above has a problem that when the semiconductor device is exposed to a heat cycle environment accompanying the heat generation of the semiconductor in the operation stage of the semiconductor device, a disconnection defect occurs in the ball neck portion. Had occurred. In order to prevent such disconnection failure during semiconductor operation, if the ball neck is severely bent and deformed to form a loop, a gold alloy wire that is less likely to be disconnected in a severe thermal cycle test thereafter will be used. Has been requested.

On the other hand, conventionally, the following proposals have been made to prevent disconnection of a bonding gold alloy wire. SUMMARY OF THE INVENTION In order to reduce the disconnection at the time of bonding, In is set to 1 to less.
60 ppm, at least one of Be, Ca, and Ge is contained at 2 to 35 ppm, and Ag, Pd,
Pt, Y and at least one other element are contained in an amount of 1 to 10 ppm. SUMMARY OF THE INVENTION For the purpose of reducing the disconnection when the temperature is maintained at 250 ° C. after bonding, La is contained in an amount of 0.2 to 50 ppm, at least one of Si and Ag is contained in an amount of 1 to 100 ppm, and Be is further contained. , In, Ge, and Ca in an amount of 1 to 30 ppm. In order to reduce the vibration rupture rate after bonding,
e: 1 to 10 ppm, Ca: 1 to 50 ppm, Y: 3 to
100 ppm, Ag: 5 to 100 ppm, respectively. SUMMARY OF THE INVENTION In order to reduce the vibration rupture rate after bonding, A
l: 3 to 50 ppm and Ca: 3 to 30 ppm, respectively, and at least one of Y, La, Be, and at least one other is contained by 3 to 30 ppm. SUMMARY OF THE INVENTION In order to reduce the vibration rupture rate after bonding, G
a: 3 to 50 ppm and Ca: 3 to 30 ppm, respectively, and at least one of Y, La, Be, and at least 3 to 30 ppm.

[0004] However, these conventional proposals have disclosed that even when the bonding wire is severely bent and deformed at the ball neck portion to form a loop, and then exposed to a severe thermal cycle environment, the disconnection at the ball neck portion is prevented. It is in a state where it cannot be said that it is enough as a small amount of gold alloy wire.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a gold alloy wire for bonding that can simultaneously achieve the following objects (1) to (3). (1) A gold alloy wire that is hardly broken even when exposed to a severe thermal cycle environment when a loop is formed by performing a so-called reverse deformation by bending and deforming a ball neck portion severely to form a loop. thing. (2) With the demand for an increase in the number of electrodes, it is required to reduce the dimensions of the electrodes in order to arrange more electrodes, so that a small ball can be formed into a true sphere, and Gold alloy wire with high bonding strength. (3) A gold alloy wire having high high-temperature strength to enable stable loop formation.

[0006]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors, yttrium (Y), platinum (Pt), lanthanum (La), yttrium (Y), platinum (Pt),
At least one of silver (Ag) and palladium (Pd),
By containing at least one of beryllium (Be) and calcium (Ca) in a predetermined weight%, the above-mentioned objects (1) to (3) can be achieved by a synergistic effect of these elements.
Were found to be achieved at the same time, and the present invention was completed. That is, the present invention provides yttrium (Y): 0.
0001-0.01% by weight, platinum (Pt): 0.000
2 to 0.2% by weight, lanthanum (La): 0.0001 to
0.01% by weight of silver (Ag) or palladium (Pd)
At least one of 0.0002 to 0.2% by weight, beryllium (Be): 0.0001 to 0.002% by weight or calcium (Ca): 0.0001 to 0.01% by weight, and This is a gold alloy wire for semiconductor element bonding that is used in a reverse deformation and has a composition of 99.999% by weight or more of high-purity gold and unavoidable impurities. Here, the reverse deformation means that in the process of forming a loop using a bonding apparatus, the ball neck portion is severely bent and deformed in a direction opposite to the loop formation. By forming a loop after performing such a reverse deformation, the loop height and the loop shape can be stabilized, but the loop formed by performing the reverse deformation on the conventional bonding gold alloy wire is a semiconductor. If the semiconductor device is exposed to an environment of a heat cycle caused by heat generation of the semiconductor in an operation stage of the apparatus, there is a problem that a disconnection failure occurs in a ball neck portion. According to the present invention, the loop formed by performing the reverse deformation and severely bending and deforming the ball neck portion by using the above-described alloy composition can be disconnected at the ball neck portion even when exposed to a severe thermal cycle environment. And a gold alloy wire for semiconductor element bonding which can be reduced.

[0007]

The detailed configuration of the present invention and its operation will be described below. The starting material used in the present invention has a purity of 99.
It contains 999% by weight or more of gold and the balance is made of unavoidable impurities. When the purity of gold is less than 99.999% by weight, it is not possible to obtain a gold alloy wire with little disconnection under a severe thermal cycle environment due to the impurities contained therein. In the present invention, (1) Y: 0.0001 to 0.01% by weight (2) Pt: 0.0002 to 0.2% by weight (3) La: 0.0001 to 0.01 % By weight (4) At least one of Ag and Pd: 0.0002 to
By making the composition containing 0.2% by weight, the synergistic effect of the metal elements causes the ball neck to be severely bent and deformed, and even after the loop is stretched, the wire breaks in a severe thermal cycle environment. And a small ball can be formed into a true sphere, and a gold alloy wire having higher connection strength can be obtained.

[0008] Even if at least one of Y, Pt, La, and Ag or Pd is contained, if Y is less than 1 ppm, the effect of reducing the disconnection in the heat cycle test cannot be obtained. On the other hand, when Y exceeds 100 ppm, shrinkage cavities occur in the ball, and the bonding strength is reduced. Therefore, the Y content is 1 to 100 ppm
It is necessary to be. More preferable Y content is 1 to
At 30 ppm, the effect of reducing the disconnection in the thermal cycle test is further improved.

Even if at least one of Y, Pt, La, and Ag or Pd is contained, if Pt is less than 2 ppm, the effect of reducing the disconnection in the heat cycle test cannot be obtained, and
The sphericity of a small ball cannot be obtained. Pt is 200
If it exceeds 0 ppm, the ball becomes hard and a problem occurs that the electrode is broken at the time of pressure bonding. For this reason, the Pt content needs to be 2 to 2000 ppm. The more preferable Pt content is 2 to 10 ppm, and in this range, the effect of reducing disconnection in a heat cycle test is further improved.

[0010] Even if at least one of Y, Pt, La, and Ag or Pd is contained, if La is less than 1 ppm, the effect of reducing the disconnection in the heat cycle test cannot be obtained. Also L
If a exceeds 100 ppm, shrinkage cavities occur in the ball, and the bonding strength decreases. Therefore, the La content is 1 to 100.
ppm. The more preferable La content is 1 to 50 ppm, and in this range, the effect of reducing disconnection in a heat cycle test is further improved.

Even if at least one of Y, Pt, La, and Ag or Pd is contained, if at least one of Ag or Pd is less than 2 ppm, the effect of reducing the disconnection in the heat cycle test cannot be obtained, The sphericity of a small ball cannot be obtained. Also, at least one of Ag and Pd is 2,000
When the content exceeds ppm, the ball becomes hard and a problem occurs that the electrode is broken at the time of pressure bonding. Therefore, the content of at least one of Ag and Pd needs to be 2 to 2000 ppm. More preferably, the content of at least one of Ag and Pd is 2 to 20 ppm, and in this range, the effect of reducing disconnection in a heat cycle test is further improved.

Further, in the present invention, Be is added to the above composition.
Alternatively, at least one of Ca is contained in a predetermined amount.
e or Ca increases the high-temperature strength, enables stable loop formation, and is effective in improving the bonding strength during bonding. If both Be and Ca are less than 1 ppm, the effect of improving the high-temperature strength is small. On the other hand, if Be exceeds 20 ppm, oxidation of the ball surface proceeds, and the bonding strength decreases. On the other hand, if Ca exceeds 100 ppm, the ball becomes hard and a problem occurs that the electrode is broken at the time of pressure bonding. Therefore, at least one of Be and Ca has Be of 1 to 2
It is necessary that 0 ppm and Ca are 1 to 100 ppm. More preferably, the Be content is 1 to 10 ppm,
When the content of a is 1 to 40 ppm, and in this range, the high temperature strength is further improved.

[0013]

【Example】

(Example 1) 99.999 to obtain the composition shown in Table 1.
In a vacuum melting furnace, a metal alloy containing 10% by weight of metal and each element is melted and cast, and cold working and heat treatment using a groove roll and a wire drawing machine are repeated to obtain a fine wire having a final wire diameter of 30 μm and an elongation of 4%. Finished to be. Bonding strength using this finishing material,
High temperature strength, ball shape, electrode cracking at the time of bonding, and a fracture test of the ball neck after thermal cycling were performed. Table 2 shows the results.

(Examples 2 to 22 / Comparative Examples 1 to 15) Table 1
Except that the composition was as shown in Example 1, and the test was performed in the same manner as in Example 1. Table 2 shows the results.

The measuring method is as follows. [Joining Strength] After bonding was performed using a high-speed automatic bonder, the shear load between the ball crimping portion and the Al electrode portion measured using a bonding strength tester (shear tester) was displayed.

[High temperature strength] Tensile tester (Tensilon UT)
After holding for 20 seconds in an atmosphere of 250 ° C. using M-II), a tensile test was performed as it was, and the maximum load was indicated.

[Ball Shape] A gold ball was prepared using an electric torch incorporated in a high-speed automatic bonder, and the size, sphericity, and surface state of the gold ball were observed using a scanning electron microscope. The size of the gold ball is 2.5 times the wire diameter,
That is, the sphericity and the surface state were measured in comparison with a comparative sample based on 75 μmφ. Ten samples were evaluated as “good” when all were good and “bad” when there was even one defect.

[Electrode cracking at the time of bonding] A 100-piece bonding test was performed using a high-speed automatic bonder. ".

[Break rate of ball neck after thermal cycle] After the first ball bonding with a high-speed automatic bonder,
The capillary was once moved in the direction opposite to the loop formation, the reverse angle was set to 60 degrees with respect to the vertical direction, the ball neck was severely bent and deformed, and then a regular loop was formed. Further, after the ball neck portion was sealed with an epoxy resin, a thermal cycle test was performed 2000 times at -10 ° C for 30 minutes and at 150 ° C for 30 minutes. One hundred samples were subjected to measurement, and the presence or absence of disconnection was confirmed by a continuity test. The number of broken wires was indicated by a breaking rate (%).

[0020]

[Table 1]

[0021]

[Table 2]

As apparent from Tables 1 and 2, Y, P
at least one of t, La, Ag or Pd, Be or C
a of the invention examples 1 to 22 containing at least one of them in the above-mentioned ranges, the bonding strength between the ball crimping portion and the electrode portion is 52.1 g or more, and the high-temperature strength in a tensile test is 15.2 g.
0 g or more, and the gold ball size (small ball molding), sphericity, and ball surface condition are all good, and there is no occurrence of electrode cracking failure during bonding and reverse deformation is performed. It can be seen that the number of disconnections is as good as 1 or less even when exposed to a severe thermal cycle environment after forming a loop.

Further, Y: 0.0001 to 0.003% by weight, Pt: 0.0002 to 0.001% by weight, La:
0.0001 to 0.005% by weight, at least one of Ag and Pd: 0.0002 to 0.002% by weight, Be
0.0001 to 0.001% by weight or Ca 0.0001
Examples 1,2,4,6,8,9,11,12,14-16,1 containing at least one of 0.004% by weight.
8 to 20 and 22, in addition to the above-described effects, even when exposed to a severe thermal cycle environment after performing a reverse deformation to form a loop, the number of disconnections is extremely good at zero.

On the other hand, Comparative Example 1 containing no Y, L
In Comparative Example 5 containing no a, it is found that the number of disconnections is 7 or more when exposed to a severe thermal cycle environment after forming a loop by performing reverse deformation.

In Comparative Example 2 in which the content of Y exceeds 0.01% by weight, Comparative Example 6 in which the content of La exceeds 0.01, and Comparative Example 8 in which the content of Be exceeds 0.002, The joint strength between the ball crimping part and the electrode part is 37.2 g
It can be seen that:

Comparative Example 4 in which the Pt content exceeds 0.2% by weight, Comparative Example 9 in which the Ca content exceeds 0.01% by weight, and Ag or Pd content of 0.2% by weight. In Comparative Examples 11 and 12, which exceed the above, it can be seen that there is an electrode cracking defect during bonding.

Comparative Example 7 containing neither Be nor Ca
It can be seen that the high-temperature strength in the tensile test was 11.3 g.

In addition to containing Ga instead of Pt, Ag
In Comparative Example 13 containing neither Pd nor Pd, the ball shape was found to be defective.

Comparative Example 3 containing no Pt, Ag or Pd
In Comparative Example 10 which does not contain any of the above, the ball shape is poor, and the number of disconnections when exposed to a severe thermal cycle environment after forming a loop by performing reverse deformation may be 6 times or more. I understand.

In Comparative Example 14 containing Al instead of Pt and containing neither Ag nor Pd, the ball shape was poor, and the ball was subjected to a reverse deformation to form a loop and then subjected to a severe heat cycle environment. It can be seen that the number of disconnections when exposed is twelve.

In Comparative Example 15 containing In instead of La, the bonding strength between the ball crimping portion and the electrode portion was 37.
It can be seen that the weight is 4 g and the ball shape is defective.

[0032]

As described above, the present invention provides 99.9
99% by weight or more of high purity gold, at least one of Y, Pt, La, Ag or Pd, and at least one of Be or Ca
Since the gold alloy wire for bonding is characterized by containing a predetermined amount of each species, even if the loop formed by performing reverse deformation is exposed to severe thermal cycle environment, there are few disconnections, so many leads It is possible to perform short wiring using wires, and since a small ball can be formed into a true sphere and the bonding strength at the time of bonding is high, it is possible to arrange more electrodes, and The advantage of being able to form a stable loop because of its excellent high-temperature strength can be achieved at the same time. Therefore, high speed, high performance, miniaturization,
A gold alloy wire for bonding, which is extremely useful for promoting thinning, can be provided.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-112259 (JP, A) JP-A-5-179375 (JP, A) JP-A-4-38840 (JP, A) JP-A-62-162 290836 (JP, A) JP-A-54-98174 (JP, A) JP-A-2-259032 (JP, A) Ed. Koji Nihei, Seio Hayakawa, Fumio Miyashiro, Semiconductor Packaging Technology Handbook, Science Forum Japan, Inc. , September 25, 1986, p. 61-64 (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 5/02 H01L 21/60

Claims (1)

(57) [Claims] 1. Yttrium (Y): 0.0001-
0.01% by weight, platinum (Pt): 0.0002 to 0.2
% By weight, lanthanum (La): 0.0001 to 0.01% by weight , at least silver (Ag) or palladium (Pd)
1 type: 0.0002 to 0.2% by weight, beryllium (B
e): at least one of 0.0001 to 0.002% by weight or calcium (Ca): 0.0001 to 0.01% by weight, and the balance is from 99.999% by weight or more of high-purity gold and inevitable impurities. What is claimed is: 1. A gold alloy wire for bonding a semiconductor element, which is reversely deformed and used.