JPS62266851A - Forming method for solder bump electrode - Google Patents

Abstract

PURPOSE:To form solder bump electrodes on a wafer substrate at a relatively narrow pitch interval, by including a patterning process, by which an opening part is provided on an aluminum electrode on a wafer substrate, an electrolytic plating process, by which a solder layer is grown, and a removing process of dry film resist. CONSTITUTION:A barrier metal 4 is formed on an aluminum pad electrode 2 on a wafer substrate 1. Dry film resist 6 is further laminated and developed. Thereafter, with the barrier metal 4 as an electrode, electrolytic plating is performed. As the dry film resist 6, the material having the thickness of about 25mum or more is used. On the aluminum pad electrode 2, a solder pad electrode 5 having the thickness of about 25mum or more is grown. The dry film resist 6 is separated, and the extra barrier metal material is etched away. When fused molding process (wet back) process is performed in accordance with ordinary processes, a semi-spherical solder bump electrode 5 can be obtained. The pitch interval between the bump electrodes can be made very narrow.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a solder bump electrode, and particularly to a method for forming a solder bump electrode for a flip chip.

[Conventional technology]

Conventionally, in a method of forming a solder bump electrode by a solder plating method, a liquid resist has been used as a metal resist.

FIGS. 2(a) to (C1) show a conventional method of forming solder bang electrodes, in which VC is first provided with a barrier metal layer 4 on an aluminum butt electrode 2 on a wafer substrate 1, and then a liquid resist is formed on the aluminum butt electrode 2. After the patterning step 7, the solder bump electrode 5 is formed by electrolytic plating.
As shown in Fig. 2 (bl), after completing the resist stripping and barrier metal etching removal process 8, it is melt-molded and shaped into a hemispherical shape with the desired bump height as shown in Fig. 2 (C). be done.

[Problem that the invention seeks to solve]

However, in this conventional method of forming solder bumps,
Since the liquid resist 7 is used, it is difficult to increase the resist film thickness, and the resist film is normally used with a film thickness of several μm at most. -・Liquid resist is approximately 20μ
It is said that it is possible to coat and pattern a film up to a thickness of m, but in reality it is difficult to form a film with a uniform thickness due to the effects of liquid dripping before gribake, etc.
Furthermore, since the pattern accuracy also decreases, it is usually not possible to form a film with a thickness of 20 μm or more. Therefore, about 3
Considering the case where the coating is applied to a film thickness of ~5 μm, the solder formed by electrolytic plating has the property of growing equally in all directions, so the thickness of the plated solder layer is 30 to 70 μm.
If you try to form it to μm, it will become as shown in A. That is, when it is desired to narrow the pitch interval of the solder bump electrodes, the lateral spread of the solder layer 7 becomes a major obstacle. As a unique property of liquid resist, it is necessary to insert a pre-bake step during the pattern formation process, so as long as liquid resist is used, it is almost impossible to form solder bump electrodes with narrow pitch intervals. Become.

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, an object of the present invention is to provide a method for forming solder bump electrodes that can form solder bump electrodes on a substrate at relatively narrow pitch intervals.

[Means for Solving the Problems] The method for forming bump electrodes of the present invention is based on an aluminum band of a wafer substrate! Dry film resist patterning process with openings at the top;
The process includes an electrolytic plating process in which a solder layer is grown on the aluminum pad' through a resist, and a resist removal process in which the dry film resist is removed from the T-'7 wafer substrate.

That is, according to the present invention, a dry film resist is used in place of the conventional liquid resist for the resist during the soldering electrolytic process.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1(al~(C1) is a process sequence diagram showing one embodiment of the present invention. First, as shown in FIG. 1(al), the barrier metal 4 is entirely formed on the aluminum pad electrode 2 of the wafer l substrate 1. After further laminating and developing a dry film resist 6, electrolytic plating is performed using the barrier metal 4 as an electrode.
Use a film with a thickness of 5 μm or more. However, either the water-soluble form or the ready-to-drink form may be used for the young. Thus the aluminum pad'j1. Approximately 25μ on pole 2
m or more solder pad electrodes 5 are grown.

Etch to remove and further VC melt B according to normal process.
To perform the Z-shaped (waet-back) process, see Figure 1 (C1
A hemispherical solder bank electrode 5 can be obtained.

In the present invention, this last melt-forming step is carried out in the first step.
Since the height of the solder bump electrode 5 left in the process of Fig. BL is at least 25 μm, it is also possible to use the shape shown in Fig. 1 for optical separation.

〔Effect of the invention〕

As explained in detail above, in accordance with the present invention, t''L is achieved by using Citrifilm resist as a resist for solder plating instead of the conventional liquid resist, so that the film thickness of the resist can be made much thicker. Since the solder material can be grown only in the vertical direction and its spread in the lateral direction can be suppressed, it is possible to form the pitch of the bump electrodes to be extremely narrow.

At this time, since the dry film resist 6 can be patterned even if it has a thickness of 50 μm or more, it is also possible to form bump electrodes with a thickness of 50 μm or more by melt molding. It can be used for various purposes.

[Brief explanation of drawings]

FIG. 1 (at to (C)) is a process sequence diagram showing an embodiment of the invention, and FIG. 1... Wafer f substrate, 2... Aluminum pad electrode, 3... Passivation film, 4...
... Barrier metal layer, 5 ... Solder bump electrode, 6 ... Dry film resist, 7
...Liquid resist. (C) 1st session

Claims (1)

[Claims] a dry film resist patterning process for forming openings on the aluminum pad electrodes of the wafer substrate; an electrolytic plating process for growing a solder layer on the aluminum pad electrodes through the dry film resist; - A method for forming a solder bump electrode, comprising a resist removal step of removing a film resist from a wafer substrate.