JPS61141158A - Formation of bump electrode - Google Patents

Abstract

PURPOSE:To improve the reliability while preventing metals from corroding producing no stain on the surface of bump electrodes by a method wherein bump electrode forming regions are coated with photoresist film as the mask in case of selective plating of bump electrodes while the overall periphery is coated with resist film with different chemical property. CONSTITUTION:An oxide film 2, an Al wiring 3, a nitride film 4 are laminated on the surface of a silicon wafer 1 and then a Ti film 5 of bond metal coming into contact with the Al wiring 3 within an opening of the nitride film 4 and a Cu film 6 of barrier metal are successively evaporated further patterning the Cu film 6 by photoetching process. Next openings are formed to form selective plating mask by means of coating upper part and near part of Ti film 5 and Al film 3 with negative type resist films 8 and the overall peripheral parts thereof with resist films 9 and then irradiating the parts excluding the central part with light for development. Successively the negative resist films 8 are left by means of forming bump electrodes 7 by electroplating process of metal and the removing the positive resist films 9 by organic solvent such as acetone etc. Finally the bump electrodes 7 may be finished by removing the Ti film 5 using etchant such as HF etc. utilizing the negative resist films 8 as masks.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a method for forming bump electrodes provided on a semiconductor wafer with a base metal layer interposed therebetween.

[Prior art and its problems]

The bump electrode has a structure as shown in FIG. 2, and has an opening in a protective film 4 such as a nitride film, which is further provided by plasma CVD or the like on an aluminum wiring 3 which is in contact with an opening in an oxide film 2 of a semiconductor wafer 1. A buffer amide pole 7 is formed on a base metal layer consisting of a laminated layer of an adhesive metal film 5 and a barrier metal film 6 which are in contact with each other by, for example, electroplating using a photoresist layer as a mask. After forming such a bump electrode, the barrier metal film 6 and the adhesive metal film 5 other than directly under the puffer electrode 7 are sequentially removed by etching.
In this case, it is difficult to form a perfect etching mask for the base metal layer directly under the bump electrode 7, and for example, the T
G of the barrier metal directly under the bump electrode during etching of I film 6
The gold corrodes and adheres as dirt on the surface of the bump electrode 7 made of gold, intervening on the contact surface of the bump electrode with other conductors and causing poor contact.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a bump electrode in which corrosion of metals directly under the bump electrode other than the desired metal is prevented during etching of the underlying metal layer after the bump electrode is formed. 1

[Key points of the invention]

According to the present invention, after depositing the base metal layer, substantially the area where the bump electrode is to be formed is covered with a photoresist film, and the entire surrounding area is covered with another type of resist film having chemical properties different from that of the photoresist. , after forming an opening in the photoresist film by corresponding photoetching, forming a bump electrode in contact with the underlying metal layer at the opening by plating, and then removing the other types of resist films mentioned above and removing the exposed underlying metal. The above objective is achieved by etching away the layer.

[Embodiments of the invention]

1(al to e) show the steps of an embodiment of the present invention, and the same parts as in FIG. 2 are given the same reference numerals. An oxide film 2, an AI After laminating the wiring 3 and the nitride film 4, a T1 film 5 of an adhesive metal that contacts the AI wiring 3 at the opening of the nitride film 4. A C film 6 of barrier metal □ is sequentially deposited.Then, Cu is deposited by photo-etching.
This state in which the film 6 is patterned is shown in Figure 1+a+.
It is. Next, a negative type resist film 8 is applied above and in the vicinity of the contact area between the Ti film 5 and the ^l film 3, and a positive type resist film 9 is applied all over the surrounding area, and then light is irradiated to areas other than the central part. By developing with a negative resist developer, openings are formed and a mask for selective plating is completed. Although the positive resist film 9 is irradiated with light, it remains as it is because it is not dissolved by the negative resist developer. This state is shown in Figure 1 (Fig. 1).Next, bump electrodes 7 are formed by gold electroplating (Fig. 0). Next, if only the positive resist film 9 is removed using an organic solvent such as acetone, the negative resist film 8 remains (Fig. d). Using this negative resist film 8 as a mask, the TI film 5 is removed with an encinder solution such as HF (Fig. e), thereby completing a bump electrode. In this case, since the C11 film 6 is completely covered with the negative resist film 8, it will not be corroded and the surface of the bump electrode 7 will not be contaminated. In the above example, the Cu film was patterned in advance, but the negative resist film 8 was formed after forming the bump electrodes without patterning.
Even if you select and etch as a mask, 1 well,
Even during etching of the τl film, since the surface is covered with a negative resist film, the elution of Cu is minimal. Alternatively, the resist types in the above embodiment may be reversed, and a positive resist may be used near the bump electrode formation area and a negative resist may be used around the bump electrode formation area. However, in addition, the resist film used around the bump electrode formation area may not develop photosensitivity. It is also possible to use an acid-resistant film that does not dissolve during development of the photoresist in the center.

【Effect of the invention】

In the present invention, the bump electrode formation area is covered with a photoresist film as a mask during selective plating of the bump electrode, and the entire surrounding area is covered with a resist film with different chemical properties.
When etching the base metal layer, the photoresist film can be left behind and used as a mask, preventing undesirable metal corrosion during etching the base metal layer, preventing contamination on the surface of the bump electrode, and creating a highly reliable semiconductor. It is extremely effective in manufacturing devices.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part sequentially showing the steps of an embodiment of the present invention, and FIG. 2 is a sectional view of a main part showing the structure of a general bump electrode. l: Silicon wafer, 3+AI wiring,! : Tl film, 6+
Cu film, 7: bump electrode, 8: negative resist film, 9: positive resist film. (a) (b) (C) (d) (e) Figure 2

Claims (1)

[Claims] 1) After depositing the base metal layer on the semiconductor substrate, cover almost the area where the bump electrodes are to be formed with a photoresist film, and cover the entire surrounding area with another type of resist film having chemical properties different from the photoresist. After forming an opening in the photoresist film by corresponding photoetching, forming a bump electrode that contacts the base metal layer at the opening by plating, and then removing the other type of resist film and exposing it. A bump electrode forming method characterized by removing a base metal layer formed by etching.