JPH0691120B2 - Method for manufacturing semiconductor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and in particular, in the manufacturing process of ICs, transistors, etc., electrodes and lead terminals on a semiconductor chip are formed by using thin metal wires. The present invention relates to a wire bonding method for connecting.

[Conventional technology]

Conventionally, in this type of semiconductor device, gold has been used as a wire material, and the surface of the lead has been subjected to surface treatment such as silver plating. FIG. 5 shows a schematic external view of a semiconductor device constructed by a conventional method. In the figure, 11 is a metal wire, 12 is a semiconductor chip, 13 is an aluminum electrode formed on the surface of the semiconductor chip 12, 14 is a copper alloy lead, and 15 is a silver plating layer formed on the surface of the lead 14. The wire 11 is joined to the electrode 13 and the lead 14 mainly by an ultrasonic combined thermocompression bonding method.

[Problems to be solved by the invention]

From the viewpoint of reducing the material cost and improving the long-term reliability of the element, the wire 11 material is changed from gold to copper, the silver plating layer 15 on the surface of the lead material 14 is omitted, and the copper wire 11 is directly bonded onto the lead 14. It is possible to do it.

In thermocompression bonding combined with ultrasonic wave, in order to obtain a good bonding state, the oxide film on the surface of the material should be sufficiently destroyed and removed, and the oxide film should be destroyed by the plastic deformation of the material at the bonding interface. It is extremely important to expand the contact area between the newborns who come later.

However, when the silver plating layer 15 is omitted and the copper alloy lead 14 is directly bonded, both of the above two points, that is, the removal of the oxide film and the plastic deformation at the bonding interface, are better than those of the conventional silver plating lead. It is extremely difficult to obtain such a result. As a result, a bonding failure may occur during bonding to the lead 14, that is, the bonding strength may be insufficient, and in an extreme case, peeling during bonding may occur.

As a method of solving such a problem, it is conceivable to set the output of ultrasonic waves, that is, the vibration amplitude to be larger than that of the conventional gold in the above-mentioned bonding process, but with this method, sufficient bonding strength is obtained. Therefore, the copper wire may be excessively deformed during bonding, and the strength of the copper wire itself may be reduced.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a semiconductor device capable of ensuring good bondability between a metal thin wire and a lead.

[Means for solving problems]

In the method for manufacturing a semiconductor device according to the present invention, prior to the bonding step of the metal thin wire and the lead, a laser beam is irradiated while the irradiation area is shielded from the atmosphere to locally heat and soften the bonding area of the lead. It was done.

[Action]

In this invention, since the lead bonding area is locally heated and softened by laser beam irradiation, the plastic deformability of the lead bonding area is improved while maintaining sufficient mechanical strength of the lead. Since the irradiation area of the beam is shielded from the atmosphere, not only is the oxidation of the bonding area prevented, but heating in a low oxygen partial pressure atmosphere causes the oxide film on the surface of the bonding area to be thermally desorbed, thus increasing the plastic deformability. And a metal wire is bonded to the bonding area of the lead whose surface has been cleaned.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows a method of manufacturing a semiconductor device according to an embodiment of the present invention. In the figure, 1 is a lead, 2 is a laser beam oscillation gun, 3 is a laser beam, 4
Is a container, 4a and 4b are lead-in and-out ports of the container 4, 4c is an exhaust port of the container 4, 4d is a glass transparent window of the container 4, and 5 is a processing station.

In the method of this embodiment, the lead 1 is placed on the processing station 5 before the wire bonding step, the processing station 5 is carried into the container 4 from the carry-in port 4a, and the carry-in port 4a and the discharge port 4b are closed. Then, the air in the container 4 is exhausted from the exhaust port 4c to increase the degree of vacuum in the container 4.
10 ^-1 to 10 ^-4 torr, and the laser beam 3 from the laser oscillating gun 2 is passed through the glass transmission window 4d and the lead 1 on the processing station 5 is cut off from the atmosphere.
The bonding area is irradiated and the bonding area is heated and softened. After softening the bonding area of the lead 1 in this way, the lead 1 is carried out from the container 4, and the lead 1 and the electrode (not shown) of the semiconductor chip are made of copper wire by, for example, an ultrasonic combined thermocompression bonding method. Connect.

In addition to the addition of a metal element for ensuring its mechanical strength, the copper alloy lead 1 has undergone work hardening history, has a relatively high hardness as compared with a copper wire, and is plastically deformed as it is. Hard to do. Therefore, by irradiating the bonding area of the copper alloy lead 1 with the laser beam 3, only the bonding area is locally softened and the irradiation area is shielded from the atmosphere while maintaining sufficient mechanical strength as the lead 1. The irradiation of the laser beam not only prevents the oxide film from increasing when the bonding area is heated, but also removes the oxide film on the surface of the bonding area by heating under a low oxygen partial pressure to clean the surface. Is performed to secure the bondability.

In the method of the present embodiment as described above, since the hardness of the lead is locally reduced by laser beam irradiation, the bondability of the copper wire to the copper alloy lead without silver plating can be significantly improved. The amount of precious metal materials such as gold, silver and silver can be significantly reduced.

Further, in this method, since the irradiation area of the laser beam is shielded from the atmosphere, the lead surface can be cleaned during the irradiation of the laser beam, and as a result, good bondability can be guaranteed.

Further, FIG. 2 schematically shows a second embodiment of the present invention. In the method of the present embodiment, an inert gas is fed into the container 4 to control the amount of oxygen mixed in the container 4 to 10.000 ppm or less so that the irradiation area of the laser beam 3 is blocked from the atmosphere. There is. In the figure, 4e and 4f are a gas supply port and a gas exhaust port of the container 4.

Further, FIG. 3 schematically shows a third embodiment of the present invention. In the method of this embodiment, the shield cylinder 6 is provided on the bonding area of the lead 4 and the shield cylinder 6 is provided.
The non-corrosive gas 7 other than oxygen is blown to the bonding area by means of, and the oxygen concentration of the atmosphere is controlled to 10.000 ppm or less so that the irradiation area of the laser beam 3 is shielded from the atmosphere.

Further, FIG. 4 schematically shows a fourth embodiment of the present invention. In this embodiment, 0.005 cc to 0.1 cc of water 8 (or alcohol) is applied to the irradiation area of the laser beam 3 immediately before the irradiation of the beam. , Mixed solution of water and alcohol). That is, in the method of the present embodiment, as shown in FIGS. 4A and 4B, when water 8 is dropped on the bonding area of the lead 1 and the laser beam 3 is applied to this bonding area, the laser beam 3 Water 8 evaporates due to heat,
As shown in FIG. 4 (c), a water vapor atmosphere 9 is formed in the bonding area, and the water vapor atmosphere 9 blocks the irradiation region of the laser beam 3 from the atmosphere.
Here, in order to prevent the water vapor 9 from being diffused during the irradiation of the beam 3, as shown in FIG. 4 (d), after dropping water 8 on the bonding area, the shield cylinder 10 is placed on the bonding area and the laser beam is applied. The beam 3 may be emitted.

Although the above-mentioned embodiment shows an example of application to a copper alloy lead, the same effect can be obtained when applied to an iron lead or the like.

〔The invention's effect〕

As described above, according to the method for manufacturing a semiconductor device of the present invention, before the bonding step of the metal fine wire and the lead,
Since the laser beam is irradiated while the irradiation area is shielded from the atmosphere to locally heat the bonding of the leads, the bonding area is softened and the surface is cleaned, and good bonding between the leads and the fine metal wires is achieved. And the amount of precious metal used can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a schematic view showing a method for manufacturing a semiconductor device according to a first embodiment of the present invention, FIG. 2 is a schematic view showing a second embodiment of the present invention, and FIG. 3 is a third view of the present invention. 4 is a schematic view showing an embodiment, FIGS. 4 (a) to 4 (c) are schematic views showing respective situations of the fourth embodiment of the present invention, and FIG. 4 (d) is a modification of the fourth embodiment. FIG. 5 is a schematic diagram for explaining a conventional method. 1 ... Copper alloy lead, 3 ... Laser beam, 4 ... Container, 4d ... Glass transmission window, 6 ... Shield cylinder, 7 ... Non-corrosive gas, 8 ... Water. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (5)

[Claims] 1. A method of manufacturing a semiconductor device, in which electrodes and leads on a semiconductor chip are connected by using a fine metal wire, in which a laser beam is irradiated before the wire bonding step while the irradiation area is shielded from the atmosphere. A method of manufacturing a semiconductor device, comprising locally heating and softening the bonding area of the lead. 2. The semiconductor device according to claim 1, wherein the lead is arranged in a vacuum container of 10 ^-1 to 10 ^-4 torr, and the laser beam is irradiated through a glass transmission window. Manufacturing method. 3. The lead according to claim 1, wherein the lead is arranged in a container in which the amount of oxygen mixed is controlled to 10.000 ppm or less, and the laser beam is irradiated through a glass transmission window. Manufacturing method of semiconductor device. 4. A non-corrosive gas other than oxygen is blown using a shield tube to control the oxygen concentration of the portion corresponding to the laser beam irradiation area on the lead to 10.000 ppm or less. A method of manufacturing a semiconductor device according to claim 1. 5. The laser beam irradiation region is supplied with water, alcohol or a mixed liquid of water and alcohol in a range of 0.005 cc to 0.1 cc immediately before beam irradiation. A method of manufacturing a semiconductor device according to the item.