JPH08102472A - Palladium alloy thin wire for semiconductor device - Google Patents

Abstract

PURPOSE: To obtain reliability in bonding with a long loop and short distance between wires, by constituting a thin wire which contains one or two or more kinds of a specific amount of rare earth elements, and Ag and Ca, and one or two or more kinds of Be, Ge, Si, In and Ir, with the residual part composed of Pd and inevitable impurities. CONSTITUTION: This thin wire contains the following: One or two or more kinds of rare earth element: 0.2-100wt.ppm Ag;1-500wt.ppm, Ca; 0.2-100wt.ppm; and one or two or more kinds of Be, Ge, Si; In and Ir: 0.2-100wt.ppm. The residual part is composed of Pd and inevitable impurities. The rare earth elements improve high temperature strength, and the amount is preferably 1-50wt.ppm. Ag and Ca improve the sphericity of a ball, and the amounts of Ag and Ca are preferably 10-500wt.ppm and 1-50wt.ppm, respectively. Be, Ge, Si, In and Ir improve the loop stability, and the amount is preferably 1-50wt.ppm. Thereby bonding is enabled with reliability higher than the conventional case.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a palladium alloy thin wire used as a bonding wire for a semiconductor device.

[0002]

2. Description of the Related Art Generally, one or more rare earth elements: 0.0005 to 2.0 wt% are contained as a palladium alloy bonding wire for semiconductor devices, and if necessary, one of Ca, Be and Ge. Or two or more kinds: 0.0005 to 0.5 wt% is contained, and the rest is Pd
Also known is a palladium alloy thin wire for semiconductor devices, which is characterized by having a composition comprising unavoidable impurities (see Japanese Patent Publication No. 61-12011), and further, Pd.
Alternatively, a low boiling point element having a boiling point lower than that of Pd or Pd alloy in Pd alloy and having a solid solution with Pd: 25 to 10,000 atp
One or more of pm, Zr, Y, rare earth elements, Ca, Sr, and Hf: 10 to 200 atppm is contained, and the remainder is a palladium alloy thin wire for a semiconductor device having a composition of Pd and inevitable impurities. (JP-A-5
It is also known that all of these palladium alloy thin wires have excellent high temperature strength.

[0003]

However, in recent semiconductor devices, there has been a demand for bonding that forms a long loop with a junction interval of more than 4 mm and further reduces the distance between wires. However, with respect to this requirement, sufficiently reliable bonding cannot be obtained with the above-mentioned conventional palladium alloy fine wire having high high-temperature strength.

[0004]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of research to obtain a palladium alloy thin wire that can be bonded more reliably than before, it is obvious that a palladium alloy thin wire that can be bonded more reliably has excellent high-temperature strength. It is necessary that the ball has excellent sphericalness, loop stability, resin flow resistance, and bondability, and the palladium alloy thin wire satisfying these characteristics is one or more rare earth elements: 0 2-100 wt. ppm, A
g: 1 to 5000 wt. ppm, Ca: 0.2-100
wt. ppm, Be, Ge, Si, In, Ir, or two or more: 0.2 to 100 wt. It has been found that the composition has a content of ppm and the rest is Pd and inevitable impurities.

The present invention has been made on the basis of such findings, and one or more rare earth elements:
0.2-100 wt. ppm, Ag: 1 to 5000 w
t. ppm, Ca: 0.2-100 wt. ppm, B
One or more of e, Ge, Si, In, Ir:
0.2-100 wt. It is characterized by a palladium alloy thin wire for a semiconductor device, which has a composition containing Pd and the balance Pd and unavoidable impurities.

In the palladium alloy fine wire for a semiconductor device of the present invention, the component composition contained is limited as described above for the following reason.

(A) Rare Earth Element A rare earth element is a component that improves the high temperature strength of a palladium alloy thin wire, but its content is 0.2 wt. If it is less than ppm, the desired effect cannot be obtained.
wt. This is because if the content is more than ppm, the sphericity of the ball formed during bonding deteriorates, which is not preferable. A more preferable range of the rare earth element content is 1 to 50 wt. It is ppm.

(B) Ag Ag is a component that improves the sphericity of balls formed during the bonding of fine palladium alloy wires, but its content is 1 wt. If it is less than ppm, the desired effect is not obtained, while Ag is 5000 wt. This is because if it is contained in excess of ppm, wire drawing workability is deteriorated, which is not preferable. A more preferable range of the Ag content is 10
~ 500 wt. It is ppm.

(C) Ca Ca is a component that coexists with Ag to improve the sphericity of the ball formed during the bonding of the palladium alloy thin wire, but its content is 0.2 wt. If it is less than ppm, the desired effect cannot be obtained, while Ca is 100 wt. This is because if it is contained in excess of ppm, wire drawing workability is deteriorated, which is not preferable. A more preferable range of the Ca content is 1 to 50 wt. It is ppm.

(D) Be, Ge, Si, In, Ir These components coexist with Ag and Ca to improve the loop stability of the palladium alloy thin wire, but their content is 0.2 wt. If it is less than ppm, the desired effect cannot be obtained, while if it is 100 wt. This is because it is not preferable because if the content exceeds 0.0 ppm, the bondability deteriorates. A more preferable range of the content of Be, Ge, Si, In, Ir is 1 to 50 wt. It is ppm.

[0011]

EXAMPLES Pd obtained by melting Pd alloys adjusted to the component compositions shown in Tables 1 to 7 in a normal vacuum melting furnace
Cast d alloy molten metal, diameter: 55mm, length: 150m
m billets were produced. These billets were reduced to a diameter of 8 mm with a groove roll and a single head wire drawing machine, and then
An ultrafine wire having a diameter of 25 μm was formed by a continuous wire drawing machine. Further, as a final treatment, in a ring furnace, after adjusting the temperature and speed, annealing was carried out by a tensile rupture tester so that the elongation was 4%. Was produced.

The Pd alloy fine wires 1 to 51 of the present invention and the conventional Pd alloy fine wires 1 to 9 were subjected to the following tests to evaluate various characteristics, and the results are shown in Table 1.
~ Shown in Table 7.

High temperature strength test The Pd alloy fine wires 1 to 51 of the present invention and the conventional Pd alloy fine wires 1 to 9 were subjected to a tensile test at 250 ° C to measure the cutting strength.

Ball Sphericality Test Pd Alloy Fine Wires 1 to 51 of the Present Invention and Conventional Pd Alloy Fine Wire 1
One end of ˜9 was heated and the ball was raised as shown in FIG. 1, the sizes of the long axis and the short axis of the ball were measured, and the difference was determined as an absolute value.

Bondability test Pd alloy fine wires 1 to 51 of the present invention and conventional Pd alloy fine wires 1
Balls 9 to 9 in the air, are bonded to the first bonding point on Al of the Si substrate at 200 ° C., and are then bonded to the second bonding point 4 mm apart to form a loop.
In the examples, the case where even one piece was not joined was indicated by x, and the case where all were joined was indicated by o.

Loop stability test Pd alloy fine wires 1 to 51 of the present invention and conventional Pd alloy fine wires 1
9 to 9 are bonded to the first bonding point A and then to the second bonding point B 4 mm apart to form a loop, and the first bonding point A and the second bonding point B are connected as shown in FIG. The maximum value of the bending amount (μm) from the center line was measured.

Resin flow resistance test Pd alloy fine wires 1 to 51 of the present invention and conventional Pd alloy fine wires 1
A 9 mm loop stability test of 4 mm was molded at 170 ° C., and as shown in FIG. 2, resin flow from the center line connecting the first joining point A and the second joining point B The maximum value of the bending amount (μm) was measured.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

[0022]

[Table 5]

[0023]

[Table 6]

[0024]

[Table 7]

[0025]

From the results shown in Tables 1 to 7, the Pd alloy fine wires 1 to 51 of the present invention have substantially the same high temperature strength as the conventional Pd alloy fine wires 1 to 9, but the true ball It can be seen that the spherical property is excellent, and further, the bonding property, the stability of the loop, and the resin flow resistance are also excellent. As described above, the palladium alloy thin wire of the present invention can perform more reliable bonding than before, and can greatly contribute to the development of the semiconductor device industry.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a major axis and a minor axis of a ball that has been ball-up in a ball sphericity test.

FIG. 2 is an explanatory diagram of a bending amount measured in a loop stability test and a resin flow resistance test.

Claims (1)

[Claims] 1. One or more rare earth elements: 0.
2-100 wt. ppm, Ag: 1 to 5000 wt. ppm, Ca: 0.2-100 wt. One or more of ppm, Be, Ge, Si, In, Ir:
0.2-100 wt. A palladium alloy thin wire for a semiconductor device, which has a composition containing ppm, and the remainder being Pd and inevitable impurities.