JPS5915180B2 - Manufacturing method of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a more effective method for manufacturing a semiconductor device having metal bumps, and aims to provide a method for manufacturing a semiconductor device that does not use strong acids or strong alkalis.

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, S formed on a semiconductor substrate 1 such as silicon
An aluminum film for electrode formation is formed on the first insulating layer 2 made of iO2, etc. by means of an electron beam, resistance heating, etc.
00λ coating, leaving the electrode part 3 and removing the rest,
After that, SiO2 (hereinafter referred to as CVDS) was formed by CVD method.
A film 4 (abbreviated as iO2) is deposited for 50,000 to 10,000 A, and a part of the electrode part 3 is left, and the other part is removed. This is shown in Figure 1a. Next, a metal film 5 consisting of multiple layers is formed on the entire surface by a vapor deposition method, and the metal film 5 is made of Cr-
Cu, Ni-Ql, Cr-Ni-0] or Cr-
0]-Au, NiO]-Au, Cr-Ni-0J, etc., are deposited in sequence without stopping the vacuum during the same deposition.

Cr or Ni is aluminum electrode part 3 or CV
This is a film for increasing the adhesion with the DSiO2 film 4, and α
Alternatively, the α layer is a film for facilitating the formation of bumps by plating, and each of Cr and Ni has a thickness of about 1000λ, and the thickness of Cu has a thickness of 1000 to 5000λ. Furthermore, a photosensitive resin 6 for a plating mask is provided on the metal film 5 near the electrode portion to form an opening 7. 1D. Then, using the metal film 5 as one common electrode, a film or 01, solder, etc. is electrodeposited to form metal bumps 8.FIG. 1D.
After forming the photosensitive resin 6 and the unnecessary portions of the metal film 5 by etching, the structure shown in FIG. 1e was obtained. In such a conventional manufacturing method, after the metal bumps 8 are formed, a plurality of layers of the metal film 5 are formed.
In order to remove the metal film, for example, in the case of Cr, a mixed solution of potassium ferricyanide and caustic soda Vα must be used as a strong acid.

For this reason, the metal bumps 8 may also be etched and lose their desired shape, or the etching solution may penetrate into part A (e(7) in Figure 1) due to long-term etching, causing the metal bumps 8 to come into contact with each other. This reduces the area and reduces the adhesion strength, and furthermore, if pinholes exist in the CVDSiO2 film 4, the etching solution damages or contaminates the electrode wiring or circuit elements, significantly reducing reliability. The present invention was made in view of the above-mentioned drawbacks of the conventional method.

An example of the structure of the present invention will be described in detail with reference to FIG. 2 when it is formed of a metal pump.

Desired circuit elements are formed on the semiconductor substrate 11 using a thermal oxide film SlO2L2 as a mask, and there are aluminum wirings for connecting the circuit elements, and the aluminum wirings are connected to pads 1 for connecting to external electrodes. Connected to pole 13.

Furthermore, a first photosensitive resin film (not shown) is deposited on the entire surface of the semiconductor substrate 11 including the aluminum wiring and the patch electrodes 13 (CVDSiO2L4 is used as a protective film). and forming a mask pattern with holes only in the vicinity of the butt electrode 13 to expose the CVDSiO2l4,
The exposed CVDSi is immersed in an HF-based corrosive solution.
O2l4 can be removed.

Then, by removing the unnecessary first photosensitive resin film, the structure shown in FIG. 2a is obtained. After leaving the state shown in Fig. 2a, the CV is removed by vacuum evaporation, sputtering method, electron beam method, etc.
FIG. 2B shows an aluminum film 15 deposited on the surface patterned with DSiO2l4.

Furthermore, a second photosensitive resin film 16 is coated on the aluminum film 15 (a second photosensitive resin film 16 is formed, and a pattern is formed in which holes are opened only in the vicinity of the pad electrode 13, and the exposed aluminum film 1
5, only the open pores are removed using, for example, a H3PO4-based corrosive solution.

Next, with the second photosensitive resin film 16 provided, a metal film 17 consisting of a plurality of layers is deposited by a vapor deposition method, a sputtering method, or the like.

Here, when the metal film 17 consisting of multiple layers is composed of metal bump cancer, it has a j structure of Cr and cLl.
The state in which the metal film 17 is deposited is shown in FIG. 2c.

As shown in the figure, the metal film 17 is an aluminum film 1
5 and the pattern of the second photosensitive resin film 16, the metal film 17' remains on the pad electrode. In this state, the metal film 17' and the aluminum film 15 come into contact with each other at a stepped portion, and electrical continuity can be obtained. Next, the second photosensitive resin film 1
6 and the metal film 17 on the second photosensitive resin film 16 are removed.

For removal, by dissolving the second photosensitive resin film 16 with a solvent, the metal film 17 is also removed, leaving only the metal film 171 on the pad electrode. Next, a mask for forming metal bumps is formed using the third photosensitive resin 18, and holes are opened only in the desired portions of the pad electrode.After that, as shown in FIG.
Gold plating is performed, but the surface to be plated is 0.
If it is one surface, that surface will be contaminated or an oxide film will be formed during the formation of the second and third photosensitive resin films 18, which will significantly hinder the plating process.

Therefore, in order to remove the contaminants and oxides formed on the surface of the 01, it is thoroughly washed and the oxides are removed using a 1 to 10% HCI solution. To remove oxides using HCI as described above, for example, by immersing the surface in a 5% HCI solution for 5 seconds, about 100 to 200 λ of the α surface can be removed and a clean surface can be obtained. Furthermore, when performing Au plating, the portions on the semiconductor substrate to be plated, ie, the pad electrode portions, must all be the same.

Regarding the common electrode for plating described above, the aluminum film 15 obtained in the process shown in FIG. 2c, which is a feature of the present invention, is brought into contact with the metal film 17' to form a common electrode.

Therefore, at the end of the semiconductor substrate, a connection with an external electrode is obtained by using a conductive paste, or a part of the third photosensitive resin film 18 is removed to obtain a connection with an external electrode. I can do it. In addition, when the Kingyo bump is formed of Au, the plating bath may be a cyanide bath, a neutral phosphate bath,
Acidic phosphorus? A salt bath, an acidic citric acid bath, etc. are used, but the acidic citric acid bath, which has few pinholes and relatively low hardness, is suitable for forming bumps on a semiconductor substrate as in the present invention.

If the plating bath is treated with the semiconductor substrate as a negative pole and the Pt plate as a positive pole at a current density of about 0.4 A/Md, a 10-15 μm thick bump 19 will be formed in 40-90 minutes.

This state is shown in FIG. 2e. Then the third part which became unnecessary.
If the photosensitive resin film 18 is removed with a solvent and the aluminum film 15 is also immersed in a H3PO4-based or NaOH corrosive solution, the film 719 can be removed without using strong acid or strong alkali.
FIG. 2 FO can be easily removed without corrosion. Next, another example of the structure of the present invention will be explained with reference to FIG. 3.

The sections up to FIG. 2c of the above-mentioned configuration example are almost the same, and will therefore be omitted. After removing the second photosensitive resin film 16 and metal film 17, which are no longer needed as shown in FIG. After that, a round plating process is performed to form a bump 20 as shown in FIG. 3 e'. In this step, since everything except the metal film 177 is covered with the Al2O3 film 15', the Au bumps are formed only on the metal film 17'. A
After the formation of the u-bumps is completed, the Al2O3 film 15/ can be easily removed by dipping it in a mixed solution of H3PO3 and CrO3, and the aluminum film 15 can be easily removed by raising the temperature of the H3PO4 solution, resulting in the structure shown in FIG. 3f'. This configuration example does not require a photosensitive resin film for plating. Once the desired metal bumps have been formed, heat the bumps at 4000C or more in an inert gas atmosphere to improve the electrical condition between each metal film.
Heat treatment at 550° C. for 20 to 60 minutes is sufficient. Through this heat treatment, the metal film is formed more minutely, and at the same time, a compound is formed between the metal films, which not only maintains a good electrical state but also has mutual adhesion (adhesive force). ) will also increase. Although the configuration example of the present invention has been described in detail with respect to the case where gold bumps are formed, it goes without saying that the present invention can also be applied to the formation of other bumps, such as solder bumps, Cu bumps, or a combination thereof.

Furthermore, although the metal film on the pad electrode has been described as having a two-layer structure of Cr-0, other metal films such as Ni-Cu, Ti-Ql, and Cr-0 can also be used.
r-Ni-Cu, Cr-Ti-Cu, Ni-Q M, N
i-α TO ALl, Ti-α Au, C total Ni-α-frame,
A configuration of C 卜Ti-0]-Au may also be used. In the manufacturing method of the present invention, when removing unnecessary metal films, strong acid or strong alkaline solutions are not used as in the conventional methods, so there is no possibility of damaging the semiconductor substrate on which circuit elements are formed or wiring materials, etc. Since there is no risk of contamination or contamination, manufacturing L can also obtain a safe process.

Furthermore, since the metal film is formed using the so-called lift-off method that utilizes the step between the photosensitive resin and the aluminum film, the metal film 1
The metal film 17' can be reliably formed, rather than the method 9 in which the formation of the metal film 7' is extremely easy.

[Brief explanation of drawings]

1A to 1E are cross-sectional views of the structure of a semiconductor device for explaining a conventional method of forming metal bumps, FIGS. FIG. 2 is a structural cross-sectional view of a semiconductor device for explaining a method of forming bumps. 11... Semiconductor substrate, 13... Pad electrode, 14... CVDSiO2 film, 15...
...Aluminum film, 17...Metal film.

Claims (1)

[Claims] 1. Forming a first insulating layer on a semiconductor substrate including a pad electrode wired on the semiconductor substrate, and using a first photosensitive resin film at a desired position on the pad electrode. A step of opening a window for taking out the electrode and removing the first photosensitive resin film, and depositing a first metal film on the first insulating layer in which the window has been opened and on the pad electrode. a step of applying a second photosensitive resin film on the first metal film to form a pattern in which the first metal film is exposed only on the pad electrode; the first metal film and the second photosensitive resin pattern, the second metal film is a step of lifting off leaving only on the pad electrode, a step of forming a third photosensitive resin film with a window in the region including the pad electrode, and using the third photosensitive resin film as a mask, Further, a step of forming a metal bump on the second metal film on the pad electrode using the first metal film as a plating electrode, and removing the third photosensitive resin film and the first metal film. 1. A method for manufacturing a semiconductor device, comprising the steps of: 2. The method of manufacturing a semiconductor device according to claim 1, wherein the first metal film is composed of an Al film. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the second and third photosensitive resin films are positive photosensitive resin films that become soluble in a solvent upon irradiation with light. . 4. Forming a first insulating layer on a semiconductor substrate including pad electrodes wired on the semiconductor substrate, and opening a window for taking out the electrode using a first photosensitive resin film at a desired position on the electrode. and removing the first photosensitive resin film, depositing a first metal film on the window-opened first insulating layer and on the electrode, and removing the first metal film. A second photosensitive resin film is applied on the film, a pattern is formed in which the first metal film is exposed only on the pad electrode, and the first metal film is coated using the second photosensitive resin film as a mask. a step of removing the exposed portion of the film, then a step of covering the entire surface with a second metal film, and a step of removing the second metal film on the second photosensitive resin film and the second metal film on the second photosensitive resin film. a step of removing a metal film; a step of forming an oxide on the surface of the first metal film; and a step of using the first metal film as a plating electrode and using the oxide on the surface of the first metal film for plating. As a mask,
A method for manufacturing a semiconductor device, comprising the steps of: forming a metal bump on the second metal film; and removing oxides on the first metal film and the surface of the metal film. 5. The method of manufacturing a semiconductor device according to claim 4, wherein the first metal film is composed of an Al film.