JPH0795553B2 - Bonding wire for connecting semiconductor device and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bonding wire for connecting a semiconductor element such as an IC or a transistor, and a manufacturing method thereof.

[Prior Art] A bonding wire for connecting a semiconductor element is required to have a small wire diameter, high quality, and high reliability. Conventionally,
As this type of bonding wire, a thin wire made of gold, aluminum, or copper has been put into practical use or is being studied for practical use. In the case of a thin wire made of gold, its connection characteristics are good, but there is a problem in that it is expensive.
Therefore, in recent years, a bonding wire made of aluminum, an aluminum alloy, copper or a copper alloy has been attracting attention and is being put to practical use in order to reduce the cost by removing the noble metal.

[Problems to be Solved by the Invention] In the case of a bonding wire used for an application requiring connection, foreign matter is disliked in order to maintain good connection characteristics. That is, it is said that it is preferable to make a bonding wire using a high-purity metal.

However, high-purity metal is expensive in itself. In addition, wire drawing workability is poor due to insufficient strength. For example, in the case of a bonding wire made of high-purity aluminum, its recrystallization temperature is low, so that it is recrystallized and becomes soft due to frictional heat during wire drawing.

Furthermore, if the material ingot for a bonding wire made of a high-purity metal is remelted or cast, foreign matter or the like may be mixed during the process and high purity cannot be maintained.

Therefore, an object of the present invention is to provide a bonding wire for connecting a semiconductor element, which is excellent in wire drawing workability at low cost and can maintain good connection characteristics, and a manufacturing method thereof.

[Means for Solving the Problems] and [Operation and Effect] The bonding wire for connecting a semiconductor element according to the present invention has a metal fine wire made of copper or gold on which the same kind of metal having higher purity is applied. It is covered.

Since the coating metal has a high purity, the bonding wire exhibits good connection characteristics. Further, in contrast to a bonding wire made of only high-purity metal, the bonding wire of the present invention has a high-purity metal only on the surface thereof, and thus is low in cost and excellent in wire drawing workability. That is, the metal having a relatively low purity contributes to the cost reduction and the strength improvement.

In addition, "copper" and "gold" used in this specification
Are the same as the alloys, respectively, and
Includes not only combinations of the same metals, but also combinations such as copper alloys and copper. By using the same kind of metal as the inner metal as the coating metal, the obtained wire becomes electrochemically stable, and the risk of corrosion from the end face can be reduced. Also, the adhesion between the metal inside and the adherent coating material is improved.

Although the coating metal having a relatively high purity contributes to improving the connection characteristics of the bonding wire, the purity of the coating metal is preferably 99.999% or more in order to exhibit good connection characteristics.

The coating of a metal having a relatively high purity is realized by a vapor phase method, a hot dip plating method, a wire drawing process or the like.

A method for manufacturing a bonding wire for connecting a semiconductor element according to the present invention is characterized in that the surface of a metal thin wire made of copper or gold is coated with the same kind of metal having a higher purity than the metal thin wire by a vapor phase method. To do.

Compared with other coating methods, the coating by the vapor phase method is easier to manage for high purification and cleaning. Therefore, if a wire whose surface is coated with a clean metal that does not contain foreign matter is drawn to a fine wire of a predetermined size by plastic working, it is possible to obtain a high-purity and high-quality thin metal wire with less breakage. be able to.

The coating process by the vapor phase method and the other wire drawing process may be alternately performed a plurality of times. In this case, foreign substances are less likely to be mixed in during processing, and moreover, disconnection is less likely to occur.

According to the vapor phase method, the thickness of the coating layer can be reduced. Therefore, if a thin metal wire having a particularly small wire diameter is prepared, and a metal is attached to the surface thereof by the vapor phase method and then the metal is plastically worked, the number of steps of the plastic working can be reduced. In addition, the wire drawing work is reasonably easy and the production efficiency is improved.

As a coating method by a vapor phase method, physical vapor deposition such as a sputtering method or chemical vapor deposition such as plasma CVD can be adopted. If the coating is performed by the sputtering method, a wide range of materials can be attached to the fine wire with a strong adhesive force. Further, the coating by the chemical vapor deposition method uses a gas that is easily generated, and enables high-purity and high-quality deposition.

As a wire drawing process after metal coating by the vapor phase method, industrially, it is convenient to use a drawing die in a cold state. If a drawing die is used, plastic working can be performed while improving the adhesion between the core material and the adherent coating material.

As described above, according to the present invention, it is possible to obtain a bonding wire that is low in cost, excellent in wire drawing workability, and capable of maintaining good connection characteristics. Further, according to the method according to the present invention, it is possible to obtain a high-purity and high-quality bonding wire with less contamination of foreign substances during the manufacturing process.

[Example] Example 1 99.9% pure copper wire having a wire diameter of 90 μm φ, with a purity of 99.9
998% copper is coated by the sputtering method and the wire diameter is 100
μmφ. This was wire-drawn to a wire diameter of 25 μmφ to obtain a bonding wire.

Using this bonding wire, a ball was produced by an arc discharge method in an Ar atmosphere and was bonded to the Al vapor deposition electrode part by the ball bonding method.
The bonding property was also excellent in the wedge bonding part with the plated lead frame part.

Claims (6)

[Claims] 1. A bonding wire for connecting a semiconductor element, wherein the surface of a fine metal wire made of copper or gold is coated with the same kind of metal having a higher purity than that. 2. The bonding wire for connecting a semiconductor element according to claim 1, wherein the purity of the coating metal is 99.999% or more. 3. A method of manufacturing a bonding wire for connecting a semiconductor element, characterized in that the surface of a metal thin wire made of copper or gold is coated with the same kind of metal having a higher purity than the metal thin wire by a vapor phase method. . 4. The method of manufacturing a bonding wire for connecting a semiconductor element according to claim 3, wherein the vapor phase coating is performed by a sputtering method. 5. The method for manufacturing a bonding wire for connecting a semiconductor element according to claim 3, wherein the vapor phase coating is performed by a chemical vapor deposition method. 6. The method of manufacturing a bonding wire for connecting a semiconductor element according to claim 3, wherein a wire drawing process is performed after the covering step.