JPH0328058B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to an electrode made of multilayer metal.

[Prior art]

In recent years, it has been desired to make semiconductor integrated circuit devices mounted on devices such as IC cards thinner. Conventionally, there is a method of forming electrodes as shown in FIG. 2 as an example of reducing the thickness of an integrated circuit device.

As shown in FIG. 2a, an aluminum electrode pad 2 is provided on a semiconductor substrate 1 on which circuit elements are formed, and a silicon nitride film 3 is applied as a passivation film to cover the peripheral area of the aluminum electrode pad 2 and the surface of the semiconductor substrate 1. Form.

Next, titanium, nickel, and palladium are sequentially vacuum-deposited to form a titanium layer 4, a nickel layer 5, and a palladium layer 6.
6. Heat treatment is performed to reduce the internal stress.
Resist is coated on these base metals 4, 5, and 6, and a photolithography process is performed to form holes on the aluminum electrode pads 2. (Fig. 2b) Subsequently, gold is coated and a photolithography process is applied to form a titanium layer 4, a nickel layer 5, on the aluminum electrode 2.
Gold bumps 8 are formed through palladium layer 6.
This gold bump 8 is used for connection with the outside, and is directly mounted on an IC card or the like via this gold bump. Next, the resist 7 used in the photolithography process is removed, and the underlying metals 4, 5, 6, which are the titanium layer 4, the nickel layer 5, and the palladium layer 6, are etched away using the gold bumps 8 as a mask.
After these steps, titanium 4, nickel 5,
An electrode having a structure including a base metal layer made of palladium 6 and gold bumps 8 was formed.

[Problem that the invention seeks to solve]

In electrodes manufactured using conventional manufacturing methods,
During the thermal process, palladium diffuses into the nickel layer, making control of the interface unstable, and the compounds generated by diffusion between the two metals during the thermal process have low strength and change electrical properties. This can lead to destruction of semiconductor devices. Further, after forming the base metal layer, heat treatment is performed to reduce internal stress, but this heat treatment cannot be carried out for a long time because it promotes intermetallic diffusion. Therefore, sufficient relaxation of internal stress is not achieved.

Distortion between metals due to this internal stress causes cracks in the passivation film. Furthermore, due to metal etching in the photolithography process, pinholes are generated at the stepped portions on the periphery of the electrode pads. Etching liquid and the like enter through these cracks and pinholes, corroding the aluminum electrode pads and wiring.

An object of the present invention is to manufacture an electrode having a structure with high strength and corrosion resistance.

[Means to solve the problem]

In the present invention, a multimetal layer containing a metal that forms an amorphous alloy by low-temperature solid phase reaction is formed on the electrode pad, and gold bumps for wiring are selectively formed on these underlying metal layers. Here, low-temperature heat treatment is performed to form an amorphous alloy at the interface between the base metals, and then the base metals are removed using the gold bumps as a mask.

In this way, an electrode of a semiconductor device is formed, which is characterized in that the polymetal layer underlying the gold bumps includes an amorphous layer.

[Effect]

According to the present invention, a plurality of metal layers including a metal forming an amorphous alloy are provided on an electrode pad and an insulating film formed on a substrate. These are subjected to heat treatment at a low temperature that does not destroy the circuit elements within the substrate, causing a low-temperature solid phase reaction between the metal layers. This low-temperature solid phase reaction forms an amorphous alloy layer.

Furthermore, this low-temperature heat treatment can simultaneously relieve internal stress between metal layers.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG. Aluminum electrode pads 12 are selectively formed on a semiconductor substrate 11 on which elements such as transistors and diodes are formed. The entire surface of the semiconductor substrate 11 including the aluminum electrode pad 12 is covered with an insulating film 13 made of silicon nitride, and contact holes are formed using photolithography. This silicon nitride film 13 acts as a passivation film for circuit elements formed on the semiconductor substrate 11. Note that this passivation film is not limited to silicon nitride. Subsequently, titanium, nickel, hafnium, and palladium are sequentially vacuum-deposited over the entire surface including the contact hole to form a titanium layer 14 of 2000 Å, a nickel layer 15 of 5000 Å, a hafnium layer 16 of 3000 Å, and a palladium layer 17 of 500 Å.

(FIG. 1a) Subsequently, the entire surface is covered with resist 18, and the portion where the electrode will be formed is removed by etching. After this, a gold bump 19 as shown in FIG.
is formed by plating. Next, the resist 18 is removed and heat treatment is performed at 380°C. By this low-temperature heat treatment, a low-temperature solid phase reaction occurs at the interface between the nickel layer 15 and the hafnium layer 16, and an amorphous layer 20 is formed. (Figure 1c) Next, nitric acid, hydrochloric acid,
The unreacted hafnium layer 16 and palladium layer 17 are etched away using a mixture of acetic acid and the gold bumps 19 as a mask. (FIG. 1d) Subsequently, the amorphous metal layer 20, the nickel layer 15, and the titanium layer 14 are etched away to the extent that they remain at least on the aluminum electrode pad, thereby forming an electrode. (FIG. 1e) In the electrode thus formed, the amorphous layer 20 is formed by low-temperature heat treatment, and at the same time, the internal stress between the metals is relaxed. The formed amorphous alloy 20 has excellent corrosion resistance, and the nickel layer 1
5 prevents oxidation of the titanium layer 14, and since the titanium layer 14 protects the passivation film 13, corrosion of the aluminum electrode 12 and wiring can be prevented. Furthermore, from this, the aluminum electrode pad 12 and the base metal 14,1
5, 20, 16, and 17 is improved, and variations in contact resistance can also be suppressed. In addition, the amorphous alloy 20 has excellent tensile strength and does not require heat treatment to relieve internal stress, so it suppresses the formation of metal compounds due to diffusion of palladium into the titanium layer 14 and the nickel layer 15. Strength is improved because it can be bent.

In the embodiment shown in FIG. 1, nickel and haunium are used as the metals forming the amorphous alloy, but gold and lanthanum, yttrium and gold, nickel and zirconium, nickel and niobium, etc. can also be used. In this case, heat treatment is performed at a suitable temperature in the range of 100°C to 400°C to form amorphous gold. In this case, the temperature of the heat treatment needs to be a temperature that does not affect the circuit elements formed on the semiconductor substrate.

[Effects of the Invention] As explained above, the thermal process at a low temperature that does not destroy semiconductor circuit elements suppresses the formation of metal compounds, improves strength, and sufficiently relieves internal stress. Corrosion of the electrode pads caused by corrosion can be suppressed. In this way, an electrode with excellent strength and corrosion resistance can be formed.

[Brief explanation of drawings]

FIG. 1 shows a manufacturing method according to an embodiment of the present invention;
The figure shows a conventional example. 11... Semiconductor substrate, 12... Electrode pad, 1
3...passivation, 14, 15, 16, 1
7... Base metal layer, 19... Gold bump, 20...
Amorphous metal.

Claims (1)

[Claims] 1. A semiconductor substrate on which circuit elements are formed, electrode pads selectively provided on this semiconductor substrate,
A first metal layer provided on the electrode pad, an amorphous metal layer provided on the first metal layer, a second metal layer provided on the amorphous metal layer, and a second metal layer provided on the amorphous metal layer. A semiconductor device consisting of two metal layers and metal bumps provided on the metal layer.