JPH0582576A - Bonding wire for semiconductor device and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Structure] The bonding wire for a semiconductor device of the present application is
The average crystal grain size within 50 μm from directly above the neck formed by sparking fine wires of gold or gold alloy is 10
It is characterized in that it is less than μm. Further, the breaking strength at 25 ° C. is 500 kg / cm ² or more, the breaking strength at 250 ° C. is 400 kg / cm ² or more, and the breaking elongation at 25 ° C. is 7% or more and 10% or less. Further, the manufacturing method is characterized in that wire drawing is performed in a water bath at 10 ° C or lower. [Effect] It is possible to prevent the breakage of the heat-affected zone of the bonding wire and improve the followability to the high-speed bonder. In addition, the wire flow does not occur at the time of resin sealing, and the occurrence of short circuit or the like is eliminated. It is possible to significantly reduce the incidence of bending and sagging in the thin wire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding wire for a semiconductor device used for connecting a chip electrode of a semiconductor element such as an IC and an LSI to an external lead and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in the process of assembling a semiconductor device in which semiconductor elements (chips) such as IC and LSI are incorporated,
When connecting a semiconductor element and an external lead, a method of bonding a thin metal wire (bonding wire) to the semiconductor element and the external lead is generally used.

As the above-mentioned bonding wire, usually, a fine wire such as a gold wire, a gold alloy wire or an aluminum wire is preferably used, and a copper fine wire may be used although it is a part.

In particular, a bonding wire made of a gold thin wire or a gold alloy thin wire is not so high in hardness when bonding, and the ball formed at the tip of the bonding wire is easily made into a spherical shape. Therefore, the semiconductor element and the chip electrode on this element can be securely connected without being damaged, and there is no risk of migration, and the corrosion resistance and stability are extremely excellent, so reliability is extremely high. It is extremely high and accounts for most of the amount of bonding wire used for semiconductor devices.

In the above-mentioned bonding wire, since the strength of the heat-affected zone, which is the neck portion just above the ball at the tip portion, is not sufficient, it is easy to break when bonding with an automatic bonder device, and when the wire is not broken. However, there are problems such as disconnection during resin sealing or short circuit due to wire flow, etc. Bonding with improved breaking strength, breaking elongation, heat resistance, etc. by adding a trace amount of elements to the gold thin wire or gold alloy thin wire A wire has been proposed and put into practical use.

[0006] For example, the breaking elongation is 2 to 5 in the case of gold or gold alloy fine wire used as a bonding wire.
The range of 10% is general. With this bonding wire, the strength of the heat-affected zone can be secured, and problems such as disconnection can be reduced.

[0007]

However, even the above-mentioned bonding wire is not sufficient to follow the current advances in semiconductor integration, pin count, and pitch reduction.

For example, the bending of the bonding wire, which has been allowed up to about 100 μm in the past, has recently become 50.
Although it is required to suppress the thickness to less than μm, simply adding a trace amount of element to the gold fine wire or gold alloy fine wire has a poor followability to the recent high-speed bonder, and the bonding wire may sag or bend during bonding. Will occur, which will eventually contribute to poor connection with the semiconductor element and the lead frame. Further, there is also a problem due to contact between bonding wires, which has been a main factor of reducing the yield of semiconductor devices.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a bonding wire for a semiconductor device and a method for manufacturing the same, which can effectively solve the above problems.

[0010]

In order to solve the above-mentioned problems, the present invention adopts the following bonding wire for semiconductor device and its manufacturing method.

That is, the bonding wire for a semiconductor device according to claim 1 is 50 μm from directly above the neck when a fine wire made of gold or a gold alloy is sparked to form a ball.
It is characterized in that the average crystal grain size within m is 10 μm or less.

According to a second aspect of the present invention, there is provided a method of manufacturing a bonding wire for a semiconductor device, in which a raw material of a gold thin wire or a gold alloy thin wire is melted and cast, and then rolled, drawn and annealed. In the method
The wire drawing process is characterized by being performed in a water bath at 10 ° C or lower.

Further, in the semiconductor device bonding wire according to the present invention, the average crystal grain size within 50 μm from directly above the neck is 10 μm or less when a fine wire made of gold or a gold alloy is sparked to form a ball. Yes, the breaking strength of the thin wire at 25 ° C. is 500 kg / cm ² or more, and the breaking strength at 250 ° C. is 400 kg / c.
m ² or more, and the breaking elongation of the thin wire at 25 ° C. is 7% or more and 10% or less.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a bonding wire for a semiconductor device, in which a raw material of a gold thin wire or a gold alloy thin wire is melted and cast, and then rolled, drawn and annealed. In the method
The wire drawing is performed in a water bath at 10 ° C. or less, and the annealing is characterized by continuous annealing.

[0015]

The inventors of the present invention have earnestly studied the various characteristics of the bonding wire made of a gold thin wire or a gold alloy thin wire in order to solve the above-mentioned problems, and as a result, have obtained the following findings.

When a bonding wire with a diameter of 25 μm is used, if the breaking strength of the bonding wire at room temperature (25 ° C.) is less than 500 kg / cm ² (less than 10 g in terms of breaking load), the followability to a high-speed bonder is poor. The occurrence rate of disconnection of the bonding wire is increased. Therefore, the breaking strength of the bonding wire at room temperature (25 ° C.) is preferably 500 kg / cm ² or more (10 g or more in terms of breaking load).

Further, the high temperature of the bonding wire (2
If the breaking strength at 50 ° C. is less than 400 kg / cm ² (less than 8 g in terms of breaking load), wire flow will occur during resin encapsulation even if wire breakage does not occur during bonding, and the rate of occurrence of short circuits will increase. Therefore, the breaking strength of the bonding wire at a high temperature (250 ° C.) is 400 kg / cm ² or more (8 g when converted to breaking load).
The above is preferable.

In addition, the room temperature (2
If the breaking elongation at 5 ° C.) is less than 7%, the occurrence of bending cannot be suppressed sufficiently, and if it exceeds 10%, the rate of occurrence of bending and sag is significantly increased. Therefore,
The breaking elongation of the bonding wire at room temperature (25 ° C.) is preferably 7% or more and 10% or less.

When the size of the crystal grains of the bonding wire is 10 μm or more, when the high speed bonding is performed by using the bonding wire, the bonding wire is sparked, so that the neck portion immediately above the ball is formed at the tip. The occurrence rate of wire breakage in a certain heat-affected zone increases. Therefore, it is desirable that the crystal grains of the bonding wire have a size of 10 μm or less.

In the bonding wire for a semiconductor device according to claim 1 of the present invention, when a fine wire made of gold or a gold alloy is sparked to form a ball, 50 μm from just above the neck.
By setting the average crystal grain size within m to 10 μm or less, disconnection of the heat-affected zone of the thin wire is prevented.

In the method of manufacturing a bonding wire for a semiconductor device according to a second aspect of the present invention, a raw material for a gold thin wire or a gold alloy thin wire is melted and cast, and then rolled, drawn and annealed to manufacture a semiconductor device bonding wire. In the method, the wire drawing process is performed in a water bath at 10 ° C. or less to measure the average crystal grain size within 50 μm from directly above the neck when a fine wire made of gold or a gold alloy is sparked to form a ball. Control to 10 μm or less.

According to a third aspect of the bonding wire for a semiconductor device, when a fine wire made of gold or a gold alloy is sparked to form a ball, 50 μm from just above the neck.
The average grain size within 10 μm or less, the breaking strength of the thin wire at 25 ° C. is 500 kg / cm ² or more, and the breaking strength at 250 ° C. is 400 kg / c.
By setting m ² or more, breakage of the heat-affected zone of the thin wire can be prevented, the occurrence rate of breakage of the bonding wire can be reduced, and followability with a high-speed bonder can be improved. In addition, the wire flow does not occur at the time of resin sealing, and the occurrence rate of short circuit is reduced.

When the breaking elongation of the thin wire at 25 ° C. is 7% or more and 10% or less, the occurrence rate of bending and sagging in the thin wire is significantly reduced.

Further, in the method of manufacturing a bonding wire for a semiconductor device according to a fourth aspect of the invention, a bonding wire for a semiconductor device is manufactured by melting and casting a raw material of a gold thin wire or a gold alloy thin wire, and then rolling, drawing and annealing. In the method, the wire drawing process is performed in a water bath at 10 ° C. or less to measure the average crystal grain size within 50 μm from directly above the neck when a fine wire made of gold or a gold alloy is sparked to form a ball. Control to 10 μm or less.

Further, by making the annealing continuous annealing, the breaking elongation of the thin wire at 25 ° C. is 7% or more and 10% or more.
Control below%.

[0026]

EXAMPLE An example of the present invention will be described below.

The bonding wire of this example was manufactured by the following method.

First, a predetermined amount of raw materials for the bonding wire were weighed so as to have the composition shown in Table 1, and these raw materials were melted by a melting method and then cast to obtain an Au alloy.

[0029]

[Table 1]

Next, these Au alloys are rolled, and then, in a water bath at 10 ° C. or lower, a predetermined wire diameter (25 in this case).
(μm). Here, the area reduction rate when drawing a gold alloy fine wire with a wire diameter of 30 μm to a wire diameter of 25 μm is 2
% Or less.

Then, in a predetermined atmosphere (here, in an inert atmosphere), continuous annealing was performed at a predetermined temperature (here, 600 ° C.) to obtain a gold alloy fine wire having a breaking elongation of 7 to 10%. Finally, the annealed gold alloy thin wire was wound around a bonding spool to form a bonding wire.

Table 2 compares the characteristics of the bonding wire of the above embodiment (Example) with the characteristics of a conventional bonding wire (Comparative Example).

[0033]

[Table 2]

As is clear from Table 2, in the bonding wire of the present invention, the bending of 50 μm or more did not occur at all, and there was no wire breakage during bonding or short-circuiting after resin sealing. It is clear that the properties are significantly improved compared to.

As explained above, according to the bonding wire of the above embodiment, the breaking strength at 25 ° C. is 500.
kg / cm ² or more (10 g or more when converted to breaking load), and breaking strength at 250 ° C. is 400 kg /
Since it is determined to be cm ² or more (8 g or more when converted to breaking load), the breaking of the bonding wire can be eliminated, and the followability with respect to the high-speed bonder is improved.
In addition, the wire flow does not occur at the time of resin sealing, and the occurrence of short circuit or the like is eliminated.

Since the breaking elongation of the bonding wire at 25 ° C. is 7% or more and 10% or less, the rate of occurrence of bending and sag in the bonding wire can be significantly reduced.

Further, since the size of the crystal grains of the bonding wire is 10 μm or less, it is possible to prevent the breakage of the heat-affected zone of the bonding wire.

As described above, it is possible to provide a bonding wire having features such as no defects such as disconnection and short circuit, improved followability to a high-speed bonder, and no defects such as bending and sagging during bonding. Become.

[0039]

As described above, according to the first aspect of the present invention.
According to the bonding wire for a semiconductor device described above, when the fine wire made of gold or gold alloy is sparked to form a ball, the average crystal grain size within 50 μm from directly above the neck is 10 μm or less. It is possible to prevent disconnection of the heat affected zone.

According to the method for manufacturing a bonding wire for a semiconductor device according to the second aspect, a bonding wire for a semiconductor device is prepared by melting and casting a raw material of a gold thin wire or a gold alloy thin wire, and then rolling, drawing and annealing. In the manufacturing method of 1., since the wire drawing process is performed in a water bath at 10 ° C. or less, the average crystal grain size within 50 μm from directly above the neck when the fine wire is sparked to form a ball is 10 μm. The following can be controlled.

According to the bonding wire for a semiconductor device of the third aspect, when a fine wire made of gold or a gold alloy is sparked to form a ball, 50 from just above the neck.
the average crystal grain size within μm is 10 μm or less,
Breaking strength of the thin wire at 25 ° C. is 500 kg / cm
² or more, 400kg breaking strength at 250 ℃
/ Cm ² or more, it is possible to prevent breakage of the heat-affected zone of the thin wire, reduce the occurrence rate of breakage of the bonding wire, and improve followability to a high-speed bonder. Further, wire flow does not occur during resin sealing, and the occurrence rate of short circuits can be reduced.

Further, since the breaking elongation of the thin wire at 25 ° C. is set to 7% or more and 10% or less, the occurrence rate of bending and sagging in the thin wire can be significantly reduced.

According to the method of manufacturing a bonding wire for a semiconductor device according to a fourth aspect, a bonding wire for a semiconductor device in which a raw material of a gold thin wire or a gold alloy thin wire is melted and cast, and then rolled, drawn and annealed. In the manufacturing method of 1., since the wire drawing process is performed in a water bath at 10 ° C. or less, the average crystal grain size within 50 μm from directly above the neck when the fine wire is sparked to form a ball is 10 μm. The following can be controlled. In addition, since the annealing is continuous annealing, the thin wire is 25 ° C.
The elongation at break can be controlled to 7% or more and 10% or less.

As described above, a bonding wire for a semiconductor device and a method for manufacturing the same, which are characterized in that there are no problems such as disconnection and short-circuiting, that the followability to a high-speed bonder is improved, and that there are no problems such as bending and sagging during bonding. It becomes possible to provide.

Claims (4)

[Claims] 1. A bonding wire for a semiconductor device, wherein an average crystal grain size within 50 μm from directly above the neck is 10 μm or less when a fine wire made of gold or a gold alloy is sparked to form a ball. 2. A raw material for a fine gold wire or fine gold alloy wire is melted.
A method for producing a bonding wire for a semiconductor device, which comprises casting, followed by rolling, wire drawing, and annealing, wherein the wire drawing is performed in a water bath at 10 ° C or lower. 3. The average crystal grain size within 50 μm from directly above the neck is 10 μm or less when a fine wire made of gold or a gold alloy is sparked to form a ball, and the breaking strength at 25 ° C. of the fine wire is 500 kg. / Cm ² or more,
Moreover, the breaking strength at 250 ° C. is 400 kg / cm ²
The above is the elongation at break of the fine wire at 25 ° C. of 7%.
A bonding wire for a semiconductor device, which is not less than 10%. 4. A raw material for a gold wire or a gold alloy wire is melted.
In the method for manufacturing a bonding wire for a semiconductor device, which comprises casting, then rolling, wire drawing, and annealing, the wire drawing is performed in a water bath at 10 ° C. or less, and the annealing is continuous annealing. Method for manufacturing bonding wire for device.