JPS5915179B2 - Manufacturing method of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a more effective manufacturing method for semiconductor devices having metal bumps, which actively prevents contamination and corrosion near the bumps that occur when removing a metal film. In the structure of the present invention, an oxide layer is formed in the vicinity of the pad electrode, thereby providing a manufacturing method that provides 15 corrosion resistance to the metal film removal solution. It is.

Conventionally, a manufacturing method as shown in FIG. 1 has been proposed as a method for forming metal bumps on a semiconductor substrate on which circuit elements are formed.

That is, an aluminum film for electrode formation is formed on a first insulating layer 2 made of SiO2 or the like formed on a semiconductor substrate 1 made of 20-100% silicon or the like using an electron beam, resistance heating, or the like.
0,000 Λ was deposited, the rest was removed leaving only the electrode part 3, and then the S10225 (hereinafter abbreviated as CVDSi02) film 4 formed by the CVD method was coated with 5,000 to 1()0
00X deposition, leaving part of the electrode part 3 and removing the rest. This is shown in Figure 1a. Next, a metal film 5 consisting of multiple layers of C is formed on the entire surface by a vapor deposition method.
is Cr■Cu, N30Cu, Cr-Nf-Cu or Cr■-C AU, Ni-CIF-Au, Cr-Ni
- Multiple layers of Cu, etc. are deposited one after another without stopping the vacuum during the same deposition. Cr or Ni is a film of 35 to increase adhesion with the aluminum electrode portion 3 or CVDSi02 film 4, and Cu or Cu-A
u is a film to facilitate the formation of bumps by plating, and the thickness of each of Cr and Ni is approximately 10
00Λ, Cu has a film thickness of 1000 to 5000λ.
Also, a Ti film may be used instead of Cr or Ni (FIG. 1b). Furthermore, a photosensitive resin 6 for a plating mask is provided on the metal film 5 near the electrode portion, and an opening portion 7 is formed (
Figure 1 c).

After that, using the metal film 5 as one common electrode,
U or Cu, solder, etc. are electrodeposited to form metal bumps 8 (FIG. 1d).

The height of the metal bump is usually 5 to 20 μm, and when finished, the photosensitive resin 6 and the metal film 5 are etched and removed to obtain the structure shown in FIG. 1e. . In such a conventional manufacturing method, in order to remove the multiple layers of metal films 5 after forming the metal bumps 8, a metal film removal solution (etching solution), for example, in the case of Cr, a mixture of potassium ferricyanide and caustic soda is used. If the liquid is Cu, a strong acid must be used. As a result, the metal bumps 8 may also be etched and lose their desired shape, or the etching solution may penetrate into the area A in Figure 1 e due to long-term etching, reducing the contact area of the metal bumps 8. If there are pinholes in the CVDSiO2 film 4, the etching solution may
This would damage or contaminate the electrode wiring or circuit elements, significantly reducing reliability. The present invention has been made in view of the above-mentioned drawbacks of the prior art.

A configuration example of the present invention in which Au bumps are formed as metal bumps will be described in detail with reference to FIG.

An aluminum film 13 is deposited as a first metal film on a circuit element (not shown) formed on a semiconductor substrate 11 having a SiO2 film 12 formed by a thermal oxidation method to a thickness of 5000λ to 10000λ by a vacuum evaporation method. be coated on. Next, a first insulating layer 14 is deposited on the entire surface of the aluminum film 13. The first insulating layer may be a photosensitive resin film, or may be a CVDSiO2 film formed at a low temperature. A pattern is formed using the first insulating layer 14 in which only a portion corresponding to one pole of the pad remains, and the surface of the aluminum film 13 is anodized using, for example, a photosensitive resin film pattern to form the Al2O3 film 13'. form. CVDSiO2 instead of the photosensitive resin film pattern
If a film is used, Al2O3 can be easily removed by exposing it to an oxygen atmosphere at 500°C or an oxygen plasma atmosphere.
A film 13' can be formed. The M2O3 film 13' is not formed on the lower surface of the first insulating layer 14. Then the first
In order to remove the insulator layer 14 and leave the single pole part of the pad and the wiring part connecting between the formed circuit elements,
A photosensitive resin film is applied as the second insulating layer 15 and patterned. Since the portion not covered with the second insulating layer 15 is exposed to the Al2O3 film 13//>S, H2O:H3PO4:CrO3=100cc:3.
5cc: 160λ/60 if immersed in 29 80℃ solution
In seconds the Al2O3 film 13/ is removed and then the H3PO4
If the aluminum film 13 is immersed in the system liquid, the aluminum film 13 will also be removed, as shown in Fig. 2b.
obtain the structure of

Further, the thickness of the Al2O3 film 13' is preferably about 3000λ. The second insulating layer 15, that is, the photosensitive resin film that is no longer needed is removed, and the third insulating layer 16 is then deposited on the entire surface. The third insulating layer 16 is made of CVDSiO2, and in order to open only the pad electrode, a fourth insulating layer/photosensitive resin film is applied to form a pattern in which only one pad electrode is opened. , Then, by immersing it in an HF-based corrosive solution, the third insulating layer on the pad electrode is corroded,
If the hole is opened and the fourth insulating layer is removed, the result is shown in FIG. 2c.
′ is obtained. In the above process, the size of the hole formed by the fourth insulating layer is between the pattern formed by the first insulating layer 14 and the second insulating layer, and at least the size of the opening is equal to CV.
Al2O3 in the part opened by the DSiO2 film 16
A membrane 13' must be present. Then, Fig. 2c
The second metal film 17 is deposited in this state. In the case of the second metal film, which is a 0-α film in this configuration example, Cr, lOOOOλ, and CrlOOOO to 5000λ are sequentially deposited in the same vacuum vessel. Other configurations of the second metal film include Ni-Cu, Ti-Ql, Cr-M-Cu
, Cr-Ti-01, Ni-01-Au, Ni-0]-
Au, Ti-Q1-Al, O-Ni-α-Au, Cr-
A Ti-α-frame structure may also be used. Further, a photosensitive resin film is applied as a fifth insulating layer on the second metal film 17, and a pattern is formed in which only the portion to be plated near the pad dowel is opened, and the plating process is performed in the next step. However, the second hole opened and exposed by the fifth insulating layer is
The surface of the metal film 17 may be contaminated or have oxides formed during the process, which results in the formation of defective metal bumps after the plating process.

Therefore, the oxides are removed by cleaning with an organic solvent such as acetone or trichlene and immersing in a 1 to 10% HCI solution. For example, if immersed in 5% HCI solution for 5 seconds, Cu
A clean Cu surface can be obtained by removing 100 to 200λ from the surface.

In addition, plating baths for Au plating include cyanide baths, neutral phosphate baths, acidic phosphate baths, and acidic citric acid baths. A citric acid bath is preferred.

When plating, a second metal film is exposed at the end of the semiconductor substrate 11, used as a common electrode for plating, and a negative electric field is applied, while a positive electric field is applied to the Pt plate or the like. , 40~ at current density 0.4mA/M77l
Au bumps 18 with a height of 10 to 15 μm can be formed in the openings of the second metal film 17 in 60 minutes. After the formation of the plating is completed, the fifth insulating layer, that is, the photosensitive resin film is removed, and the second metal film 17 is removed using the Au bumps 18 as a mask.

In this configuration example, since the second metal film is composed of Cr-CuC, the Cu film is removed with, for example, a 10% ferric chloride solution, and the Cr film is removed with a mixed solution of potassium ferricyanide and NaOH. It is something. In this way, the structure shown in FIG. 2e is obtained. In the configuration example of the present invention, the metal bump is A
This was the case of u, but it may also be a solder bump.

In addition, if heat treatment is performed at 300 to 550°C for 20 to 60 minutes in order to increase the adhesion force (adhesive force) between each metal film and reduce electrical contact resistance, the metal film becomes even more dense. Moreover, alloying is promoted and the above-mentioned effects can be obtained. According to the manufacturing method of the present invention, the second
Even if the corrosive liquid permeates during patterning of the metal film and reaches the vicinity of the pad electrode, the surface of the peripheral edge of the pad electrode is a corrosion-resistant Al2O3 film, so there is no risk of damage to the pad electrode as in the past. It does not cause deterioration of electrical characteristics or decrease in metal bump strength.

For reference, FIG. 3B shows a state in which the pad electrode 13 is partially damaged. Furthermore, since a part of the butt electrode is an Al2O3 film, the CVDSiO2 film 16 has good adhesion to this part, which has the effect of preventing contaminants from advancing between the CVDSiO2 and the pad electrode. be.

[Brief explanation of the drawing]

Figures 1 a-e are structural cross-sectional views of a semiconductor device for explaining a conventional method for forming metal bumps, and Figures 2 a-e are for explaining a method for forming metal bumps in an embodiment of the present invention. FIG. 3 is a structural cross-sectional view of a semiconductor device for illustrating an example of the effects of the present invention. 11... Semiconductor substrate, 13... Pad electrode, 13'... Al2O3 film, 16...
...CVDSiO2 film, 17...second metal film, 18...metal bump.

Claims (1)

[Claims] 1. A step of forming a first metal film for wiring on a semiconductor substrate, a step of forming a pattern of a first insulating layer on the first metal film, and a step of forming a first metal film for wiring on the semiconductor substrate. forming an oxide on the exposed surface of the first metal film not covered with an insulating layer; removing the first insulating layer; forming a second insulating layer having a larger pattern so as to cover the unoxidized portion of the first metal film; and using the pattern of the second insulating layer as a mask, oxides on the surfaces of the metal film and the first metal film are removed, and then,
a step of removing the second insulator layer; and a step of forming a pattern of a third insulator layer in which the first metal film surface is exposed so that the oxide is exposed on the peripheral edge surface; A step of depositing a second metal film on the entire surface and forming a pattern in which holes are formed only on the first metal film using a fourth insulating layer; A semiconductor comprising the steps of: forming a metal bump on the exposed second metal film; and removing the fourth insulating layer and the exposed second metal film. Method of manufacturing the device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the first metal film is composed of an aluminum film.