JPH0431182B2 - - Google Patents

Abstract

PURPOSE:To secure a good bonding property of the fine metal wires to the leads by a method wherein the bonding areas of each lead are locally softened by applying ultrasonic vibrations to the bonding areas from the side of the back surface of the lead during the process of bonding of the fine metal wires and the leads. CONSTITUTION:Ultrasonic vibrations in the direction parallel to the back surface of a copper alloy lead 4 are applied to the bonding areas of the copper alloy lead 4 from the side of the back surface during the bonding process. The copper alloy lead 4 is already subjected to a work hardening hysteresis in addition to that a metal element is already added to the composition of the copper alloy led in order to secure the mechanical strength thereof, the hardness thereof is relatively higher than that of a copper wire 1 and the copper alloy lead 14 is hard to be plastically deformed at the time of bonding in the state intact. Thereof, by applying the ultrasonic vibrations to the bonding areas of the copper alloy lead 4 from the back surface of the lead 4, the bonding areas only are locally softened while the mechanical strength is sufficiently kept as the lead 4. By this way, the bonding property of the copper wire 1 to the copper alloy lead, whereto a silver plating is omitted, can be significantly improved and a significant reduction in the amount used of noble metal materials, such as gold and silver, can be attained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, particularly in the manufacturing process of an IC, a transistor, etc.
The present invention relates to a wire bonding method for connecting electrodes on a semiconductor chip and lead terminals using thin metal wires.

[Prior Art] Conventionally, in this type of semiconductor device, gold has been used as the wire material, and the lead surface has been subjected to surface treatment such as silver plating. FIG. 4 shows a schematic external view of a semiconductor device configured in a conventional manner. In the figure, 1 is a metal wire, 2 is a semiconductor chip, 3 is an aluminum electrode formed on the surface of the semiconductor chip 2, 4 is a copper alloy lead, 5 is a silver plating layer formed on the surface of the lead 4, The above wire 1 is attached to the electrode 3 mainly by thermo-compression bonding method combined with ultrasonic waves.
and is joined to the lead 4.

[Problem that the invention seeks to solve]

Here, from the viewpoint of reducing material cost and improving long-term reliability of the device, the wire 1 material is replaced with copper from gold, the silver plating layer 5 on the surface of the lead material is omitted, and the copper wire 1 is bonded directly onto the lead 4. It is possible to do so.

In addition, in ultrasonic thermocompression bonding,
In order to obtain a good bonding condition, it is necessary to sufficiently destroy and remove adsorbed substances such as oxide films on the material surfaces, and to expand the contact area between the new surfaces after the oxide film is destroyed by plastic deformation of the materials at the bonding interface. It is extremely important to do so.

However, when the silver plating layer 5 is omitted and bonding is performed directly to the copper alloy lead 4, the above 2.
Compared with conventional silver-plated leads, it is extremely difficult to obtain good results in terms of both the removal of the oxide film and the plastic deformation at the bonding interface.
Therefore, when bonding to the lead 4, a bonding failure occurs, that is, insufficient bonding strength, and in extreme cases, peeling occurs during bonding.

As a method to solve these problems, in the bonding process mentioned above, the output of ultrasonic waves,
In other words, it is conceivable to set the vibration amplitude larger than in the case of conventional gold, but with this method, if you try to obtain sufficient bonding strength, the copper wire will deform too much during bonding, and the copper wire itself will be deformed. There is a risk that the strength will decrease.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing a semiconductor device that can ensure good bonding between a thin metal wire and a lead.

[Means for solving problems]

A method for manufacturing a semiconductor device according to the present invention is such that during the bonding process between a thin metal wire and a lead, the bonding area of the lead is locally softened by applying ultrasonic waves from the back side of the lead.

[Effect]

In this invention, since the bonding area of the lead is locally softened, the plastic deformability of the bonding area of the lead is improved while maintaining sufficient mechanical strength of the lead. They are joined in a state where they are in contact even in terms of area.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 schematically show a method for manufacturing a semiconductor device according to an embodiment of the present invention. In the figure, 6 is a capillary chip which is a bonding tool, 7 is an ultrasonic vibrator, and 8 is a vibrator.

In the method of this embodiment, the electrode 3 of the semiconductor chip 2 and the bonding area of the copper alloy lead 4 are connected by the copper wire 1 using, for example, an ultrasonic thermocompression bonding method, as in the conventional method. During the process, ultrasonic vibrations are applied to the bonding area of the copper alloy lead 4 from its back surface in a direction parallel to the back surface.

Copper alloy lead 4 has metal elements added to ensure its mechanical strength, and has undergone work hardening history, so it has a relatively high hardness compared to copper wire 1, and is hard to maintain as it is. Resistant to plastic deformation during joining. Therefore, by applying ultrasonic waves to the bonding area of the copper alloy lead 4 from the back side thereof, only the bonding area is locally softened while maintaining sufficient mechanical strength of the lead 4.

Figure 2 shows the relationship between lead hardness and bonding strength obtained through experiments, and it was found that bonding performance was significantly improved by setting the lead hardness to 50 to 100 Hv in terms of Vickers hardness. Ru. Note that in the figure, a indicates the acceptable strength, that is, the required bonding strength.

In the method of this embodiment as described above, since the hardness of the lead bonding area is locally reduced, the bondability of the copper wire to the copper alloy lead without silver plating can be greatly improved, and the , it is possible to achieve a significant reduction in the amount of precious metal materials such as silver used.

FIG. 3 schematically shows another embodiment of the present invention. In this embodiment, ultrasonic vibration is applied to the bonding area of the copper alloy lead 4 from the back surface side in a direction perpendicular to the back surface. That's what I do.

In the above embodiment, an example of application to a copper alloy lead is shown, but similar effects can be obtained when applied to an iron-based lead or the like. Further, the metal thin wire may be a copper alloy thin wire instead of a copper wire.

〔Effect of the invention〕

As described above, according to the method for manufacturing a semiconductor device according to the present invention, during the bonding process between the thin metal wire and the lead, the bonding area of the lead is locally softened by applying ultrasonic waves from the back side. Therefore, it is possible to ensure good bonding between the lead and the thin metal wire, and it is possible to significantly reduce the amount of precious metal material used.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a method for manufacturing a semiconductor device according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between lead hardness and bonding strength, and FIG. 3 is a diagram showing another embodiment of the present invention. FIG. 4 is a schematic diagram for explaining the conventional method. 1... Copper wire, 2... Semiconductor chip, 3... Electrode, 4...
Copper alloy lead. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. In a method for manufacturing a semiconductor device in which electrodes on a semiconductor chip and leads are connected using thin metal wires, ultrasonic waves are applied to the bonding area of the lead from the back side during the wire bonding process. 1. A method of manufacturing a semiconductor device, comprising locally softening the device by softening the semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the lead is made of a copper alloy or an iron alloy. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the thin metal wire is made of copper or a copper alloy. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the hardness of the bonding area of the lead is locally tempered to a range of 50 to 100 in terms of micro-Vickers hardness.