JPS621000B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plating method, particularly a bump plating method for semiconductors.

Conventionally, as shown in Fig. 1, the immersion electroplating method as shown in Fig. 2 has been used to form the Ag bump 1 of a silicon diode, and in this method, as shown in Fig. 3, The top of the bump has an uneven shape, which tends to cause poor contact when the lead wire is crimped after that. Therefore, the bump top was polished with a spatula or the like to flatten it to reduce the chance of poor contact. Moreover, this planarization work may break the wafer or scratch the tops of the bumps. In addition, as shown in Fig. 2, there are many incidental operations such as adhering the wafer 2 to the glass plate 3 with wax 4, dissolving the wax and peeling it off, and cleaning afterward, which is also difficult due to the principle of the immersion electroplating method. The drawback is that current cannot flow, and it takes a long time with a small current. The objects of the present invention are to improve the above-mentioned drawbacks, to obtain a trapezoidal shape with a flat bump top and a large contact area as shown in FIG. The purpose is to save time.

In order to achieve the above object, the present invention, as shown in FIG. The feature is that the bumps are grown by applying a large current to the electrodes 12, which are held facing each other and are rubbed against each other, and which can be held by vacuum suction while blocking the penetration of the dipping plating liquid.

Hereinafter, the present invention will be explained in detail with reference to an embodiment shown in FIG. 6. In FIG. 6, 2 is a wafer. First, the wafer is vacuum-adsorbed 14 to an electrode 13 that can be electrically conductive.
The wafer suction surface of the electrode and the wafer contact surface of the guide 17 are
To prevent wafer deformation, it is necessary to make them flush. In addition, in order to leak the air accumulated in the air chamber, the wafer contact surface of the guide is
Insert fine grooves 18. 10 is a porous cloth, but in order to have elasticity, a conductive sponge 1 is used.
Put 9 below. This is set on a carbon disc 11 to increase conductivity. Here, a rim 20 is provided around the disk to collect the plating liquid. Next, the electrodes on which the wafer is set are placed in opposing contact with this disk, and while the disk is rotated 16, a current is applied to both electrodes to grow bumps. With such an apparatus, very good bumps as described above can be formed in a short time.

As explained above, according to the present invention, since a trapezoidal bump with a flat top and a large contact area can be formed, the conventional work of flattening the top of the bump is no longer necessary, and contact failures are greatly reduced. can. In addition, since the wafer can be easily held and removed, there is no need for the conventional work associated with bonding and peeling off wafers, greatly reducing the number of man-hours.Furthermore, by increasing the Ag ion concentration of the plating solution, a large current can be applied. Since high-speed plating can be performed, the plating time can be reduced from about 60 minutes/sheet to about 15 minutes/sheet.

In particular, in the present invention, since the plating liquid device 20 is configured to collect the plating liquid, the entire porous cloth 10 is always impregnated with the plating liquid. Therefore, the plating solution is sufficiently supplied. In addition, since the air 15 is blown around the back surface of the wafer at this time, the plating liquid is prevented from entering between the vacuum-sucked electrode 13 and the back surface of the wafer 2, thereby reducing the plating current. Since the plating liquid flows uniformly from the plating liquid to the electrode 13 across the entire surface of the semiconductor wafer, there is little variation in bump height and size, and a trapezoidal bump shape as shown in FIG. 4 can be obtained.

In the above embodiment, relative rotational motion was performed, but the motion type is not limited to rotation only, and linear motion is also possible.

Further, in the above embodiments, the formation of Ag bumps for silicon diodes has been described, but this plating device can be similarly applied to other shapes such as Au bumps for ICs and LSIs.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a main part of a semiconductor element on which bumps are formed, Fig. 2 is a perspective view of an apparatus for explaining the immersion electroplating method, and Fig. 3 is a sectional view of a semiconductor element obtained by the immersion electroplating method. FIG. 4 is a cross-sectional view of the main part of a semiconductor device having bumps obtained by the present invention, and FIG. 5 is a main part of a plating device for explaining the plating method according to the present invention. FIG. 6 is a sectional view of a main part of a plating device according to an embodiment of the present invention. 2... Wafer, 5... Insulating tape, 6... Aluminum foil, 7... Ag electrode, 8... Plating liquid, 9... Plating tank, 13... Electrode, 17... Guide, 18... Air leak groove, 19... Conductive sponge.

Claims (1)

[Claims] 1. In a plating liquid device that stores plating liquid, place one plating electrode impregnated with the plating liquid and having a surface formed of an elastic material, and on the other hand, bump plating is applied to the surface. The back surface of the semiconductor wafer to be removed is fixed by vacuum suction to the other plating electrode surface, and the plating liquid is prevented from entering between the vacuum suctioned back surface of the semiconductor wafer and the other plating electrode surface. In order to prevent this, the surface of the semiconductor wafer and the surface of the one plating electrode are brought into opposing contact with each other while a gas is blown around the vacuum suction section on the back surface of the semiconductor wafer, and the semiconductor wafer is removed while applying relative motion. A plating method characterized by forming bumps on the wafer surface.