JPS628031B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and a method for forming metal protrusions on a semiconductor substrate, which method includes forming an electrode wiring for taking out an electrode of a semiconductor element formed on a semiconductor substrate using the metal protrusions. At the same time, the present invention flattens the substrate surface, removes the stepped portion, and forms a wiring film and an insulating film to protect it. The present invention aims to provide a highly reliable semiconductor device that does not require a protective film, simplifies the process, and has improved corrosion resistance.

Wire bonding is a method for electrically connecting the electrode pads of semiconductor chips such as LSIs and ICs on which semiconductor elements are formed to external terminals, in which thin metal wires are used to connect each electrode pad by ultrasonic vibration or thermocompression bonding. There is also a wireless bonding method that performs bonding all at once without using thin metal wires.

As one of the wireless bonding methods, an electrode of a metal protrusion is formed on the electrode pad, and the electrode lead formed on a long film is alloyed with the metal protrusion to form a lead on the metal protrusion. There is a so-called film carrier method.

The present invention relates to a semiconductor device in which metal protrusions are formed on electrode pads on a semiconductor substrate.

First, a conventional semiconductor device in which metal protrusions are formed will be described with reference to FIG.

A diffusion layer 2 is formed on a semiconductor substrate 1 made of Si or the like, and a portion of the diffusion layer 2 is provided with a hole in the SiO ₂ film 3 to provide an electrode extraction window. The electrode extraction window is provided with an Al film 4 for connection to an external terminal, and is continuously guided onto the insulating film 3. moreover
In order to protect the Al film 4 from mechanical damage or corrosion, a CVDSiO ₂ film 7 is deposited on the entire surface, and holes are drilled only at the positions where metal protrusions are to be formed.
Then, a metal film 5 consisting of multiple layers called barrier metal is formed by vapor deposition.

Here, for example, the first layer of the barrier metal 5 is
A metal film 5' such as Cr or Ti is formed to a thickness of about 1000 Å to increase the adhesion strength with the Al film 4, and the second layer is a metal film 5'' such as Cu, Ni, Ag, etc. that has good adhesion to the metal protrusions. is formed to a thickness of 3000 to 6000 Å.

Next, the structure shown in FIG. 1 is obtained by forming metal protrusions 6 of Au, Ag, etc. to a height of about 15 μm by electroplating on the metal film 5 where the Al film 4 is exposed.

This conventional structure has the following problems. The aforementioned CVDSiO ₂ film 7 is a protective film for protecting the Al film 4, but the step A in the insulating film 3 or the Al
A step B occurs in the film 4. In this step A and B
If the thickness of the CVDSiO ₂ film 7 becomes thinner, the CVDSiO ₂
Pinholes may occur in the film, or cracks may occur due to strain. For this reason, the etching solution for the metal film 5 penetrates through the pinholes and cracks in the CVDSiO ₂ film 7 and corrodes the Al film 4, causing the diffusion layer 2 and the metal protrusions 6 to become electrically open. If the Al film under the metal protrusion 6 is corroded, the metal protrusion 6 is completely peeled off from the insulating film 3, and the initial purpose cannot be achieved.

In addition, cracks occurring in the CVDSiO ₂ film 7 are
When alloying and connecting the film carrier lead (not shown) and the metal protrusion 6 while applying temperature and pressure, thermal strain and mechanical pressure can easily occur, causing the above-mentioned corrosion of the Al film. cause it to occur. Furthermore, even if the corrosion is temporarily slight and the adhesion strength of electrical defects or metal protrusions does not decrease, the corrosion gradually increases during the use of the semiconductor substrate, resulting in significant damage. This reduced reliability.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and its purpose is to eliminate this problem when etching a barrier metal (multilayer metal layer) during the manufacturing stage of a semiconductor device having metal protrusions. This is intended to improve reliability by preventing corrosion of metal wiring formed on a semiconductor device due to an etchant, or corrosion of metal wiring due to an etchant entering from the outside when a completed semiconductor device is used. Another purpose is to planarize and reduce the contact resistance between the barrier metal and the metal wiring in the manufacture of a completed semiconductor device with the metal protrusions formed thereon.
Furthermore, the purpose is to further simplify the manufacturing process.

Embodiments of the semiconductor device of the present invention will be described below with reference to the drawings.

FIG. 2 shows a semiconductor device manufactured by the method of one embodiment of the present invention. In the figure, a thermal oxide film 22 is formed on a semiconductor substrate 21, and an opening 23 is formed in this thermal oxide film 22. A diffusion layer 24 is formed directly below this opening 23 . A metal wiring pattern 26 made of, for example, an aluminum film extends from the opening 23 on the diffusion layer 24 to the electrode extraction position 25. In addition, the multilayer metal layer 28 (barrier metal: e.g.
Cr-Cu, Ti-Pd, etc.) is the metal wiring pattern 2.
6, and is in a state of covering and protecting the entire area of the metal wiring pattern 26.
The structure is such that metal protrusions such as Au, Cu, etc. are formed on the barrier metal (multilayer metal layer) 28 extending from above the diffusion layer 24 and reaching the electrode extraction position 25.

Next, the method for manufacturing the semiconductor device of the above embodiment will be described in a third manner.
This will be explained in detail based on Figures a to e. First, a thermal oxide film 22 having an opening 23 is formed on a semiconductor substrate 21, and a diffusion layer 24 is formed through this opening 23. Next, apply an aluminum film of 1 to 2 μm over the entire surface.
The opening part 2 is coated to a thickness of
An aluminum wiring pattern 26 extending from around 3 to the external electrode extraction position 25 is formed (FIG. 3a).

Next, a barrier metal 28 made of a multilayer metal layer is deposited on the entire surface of the semiconductor substrate 21. The barrier metal 28 is formed of a metal film consisting of multiple layers of Cr-Cu, Ti-Pd, Ti-Cu, etc., for example.
Then, the electrode extraction position 2 on the wiring pattern 26
A plating pattern is formed using photosensitive resin 29 exposing barrier metal 28 near 5 (FIG. 3b).

Next, metal protrusions 30 are formed in the openings of the photosensitive resin 29 by electroplating using the barrier metal 28 as a cathode. The metal protrusion 30 is made of metal such as Au or Cu and has a height of 10 to 30 μm (FIG. 3c).

Once the metal protrusions 30 have been formed by the electrolytic method, the photosensitive resin 2 used as the plating pattern is removed.
9 is removed and a photosensitive resin is applied again to form a pattern 31 made of the photosensitive resin that is at least the same as or larger than the aluminum wiring pattern 26 (FIG. 3d). Further, by selectively etching the exposed barrier metal 28 using the pattern 31 as an etching mask and leaving the barrier metal 28' on the wiring pattern 26, the embodiment of the present invention shown in FIG. A semiconductor device can be obtained.

In the structure of the semiconductor device shown in FIG. 3e,
In the selective etching process of the barrier metal 28, since the barrier metal 28' and the photosensitive resin pattern 31 can be etched while remaining on the aluminum wiring pattern 26, the aluminum wiring pattern 26 is not corroded by the etching solution. Also, even when the entire process is completed,
Due to the presence of barrier metal 28', especially acidic,
The aluminum wiring pattern 26 will not be corroded even by a solution that is likely to be corroded by alkaline liquids and may enter from the outside, and a high yield can be expected. Also,
Since the present invention does not require a CVDSiO ₂ or Si ₃ N ₄ film as a protective film, the process of depositing the protective film and the photoetching process for forming a pattern can be omitted, and the process can be simplified. It becomes possible.

Further, in the present invention, the barrier metal 28' is formed directly on the wiring pattern 26, so that the surface including the barrier metal can be flattened, and breakage of the barrier metal can be eliminated. and,
The wiring pattern and the barrier metal can be formed continuously, and the barrier metal can be formed without contaminating the surface of the wiring pattern 26 before forming the barrier metal, and since the barrier metal is formed in contact with the entire area on the wiring pattern, the contact resistance between the barrier metal and the wiring pattern can be reduced. This makes it possible to reduce the size of the wire, making it possible to achieve low-resistance connections, which are important for wiring. Therefore, according to the present invention, manufacturing costs can be reduced and a highly reliable wiring lead-out structure can be realized.

Note that when a heat-resistant photosensitive resin, such as a reduced butadiene resin or a polyimide resin, is used as the photosensitive resin 31' used as an etching mask for the barrier metal 28', the heat resistance temperature of these resins is at least 350°C or higher. Therefore, this photosensitive resin may be left as a protective film for the aluminum wiring pattern 26. In this method, since the aluminum wiring pattern 26 can be coated with the barrier metal 28' and the heat-resistant photosensitive resin, even higher reliability and yield can be expected. In the method described above, it was explained that the barrier metal to be left is left in all layers, but if a single layer is used, for example,
Only Cr and Ti may remain.

As described above, the method for manufacturing a semiconductor device of the present invention leaves a barrier metal (multilayer metal layer) directly on the metal wiring pattern with the same or larger dimensions as the metal wiring pattern made of aluminum or the like. , it is possible to prevent the metal wiring pattern from being corroded by the etching solution generated during etching of the barrier metal, and even after the manufacturing process is finished, the barrier metal can prevent corrosive liquid from entering from the outside; It contributes to the simplification of the circuit, realization of low resistance, and improvement of reliability, and has high industrial utility value.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of a conventional semiconductor device having metal protrusions, FIG. 2 is a front sectional view of a semiconductor device according to an embodiment of the present invention, and FIG. 3 is a front sectional view for explaining a method of manufacturing the semiconductor device. FIG. 21... Semiconductor substrate, 22... Thermal oxide film, 23
...opening, 24...diffusion layer, 25...electrode extraction position, 26...metal wiring pattern, 28...multilayer metal layer (barrier metal).

Claims (1)

[Claims] 1. A step of selectively forming a wiring pattern covering the opening on a semiconductor substrate on which an insulating film having an opening is formed, forming a barrier metal layer on the semiconductor substrate including the wiring pattern, and forming a barrier metal layer on the semiconductor substrate including the wiring pattern. It is characterized by comprising the steps of selectively forming metal protrusions on a barrier metal layer on a pattern, and selectively removing the barrier metal layer to leave the barrier metal layer in contact with the wiring pattern over the entire area above the wiring pattern. A method for manufacturing a semiconductor device.