JPH098043A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To prevent the formation of pits when performing fuming nitric acid cleaning and water cleaning after forming an aluminum alloy film. SOLUTION: A step of forming an aluminum alloy film 3 containing copper on a surface of a silicon substrate 1 on which an oxide film 2 is formed, and a plasma treatment is performed on the aluminum alloy film 3 to form a surface on the surface of the aluminum alloy film 3. After the uniform passivation layer 5 is formed, the silicon substrate 1 is washed with a chemical solution, and after the washing step, a resist pattern is formed on the aluminum alloy film 3 and dry etching is performed using the resist pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device for suppressing corrosion of metal wiring used in VLSI.

[0002]

2. Description of the Related Art FIG. 5 is a manufacturing process diagram of a semiconductor device by a conventional method. In FIG. 5A, after forming a desired semiconductor device in the silicon substrate 1, the oxide film 2 is formed on the silicon substrate 1. In FIG. 5 (b), a few% is formed on the oxide film 2.
The aluminum alloy film 3 containing silicon and copper is deposited. When the aluminum alloy film 3 is deposited, a thin non-uniform oxide film (passive layer) 4 is formed on the surface. Then, it is washed with fuming nitric acid, washed with water and dried. In FIG. 5C, thereafter, the wiring pattern 6 is formed on the aluminum alloy film 3 by using the photolithography technique, and the aluminum alloy film 3 is dry-etched to form the aluminum wiring 3a. In FIG. 5D, the resist 6 remaining on the aluminum wiring 3a is ashed by using oxygen plasma, and the organic residue is removed by using fuming nitric acid.

[0003]

However, according to the conventional method, when an aluminum alloy film is deposited, a thin oxide film (passivation) is formed on the surface, but since it is formed nonuniformly,
In the subsequent cleaning using fuming nitric acid, small holes (pits) are formed due to the corrosion in the arrow A in FIG. 5A and the arrow B in FIG. 5D. In addition, studies by the present inventors have revealed that pits do not occur in fuming nitric acid but occur during subsequent washing with water. The aluminum-based alloy film containing different metals is apt to be corroded during cleaning due to the battery effect between different metals, leading to the loss of aluminum-based alloy wiring.

In view of the above points, an object of the present invention is to provide a method of manufacturing a semiconductor device for modifying the surface of an aluminum-based alloy film to suppress the occurrence of corrosion due to cleaning.

[0005]

SUMMARY OF THE INVENTION The present invention is a method of manufacturing a semiconductor device in which a surface treatment of an aluminum-based alloy film by plasma of oxygen gas is performed after the aluminum-based alloy wiring film containing a dissimilar metal is formed and before cleaning. . Further, in the present invention, a gas species containing oxygen and at least nitrogen is used as the plasma generating gas. Furthermore, the present invention performs the surface treatment of plasma at a substrate temperature of 10
Perform at 0 ° C to 300 ° C.

According to the present invention, by the above structure, the surface of the oxide film is forcibly oxidized (passivated) by using the plasma of the oxygen-based gas, so that the defects of the oxide film formed during the formation of the aluminum-based alloy wiring film are eliminated. Can be reduced and resistant to corrosion. Further, although the physical reason for the effects of nitrogen and substrate temperature is unknown, the corrosion resistance of the surface can be improved.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is a manufacturing process diagram of a semiconductor device used in the present embodiment. In FIG. 1A, after a desired semiconductor device, for example, a MOS transistor is formed in the silicon substrate 1, the silicon oxide film 2 is formed on the silicon substrate 1 by 7
It is formed to a thickness of 00 nm. In FIG. 1 (b), a few% is deposited on the oxide film 2.
The aluminum alloy film 3 containing silicon and copper is deposited to 800 nm by magnetron sputtering. Aluminum alloy film 3
Thin non-uniform oxide film (passive layer) on the surface when deposited
Is formed.

In FIG. 1 (c), plasma treatment with an oxygen-based gas was performed using a downstream type apparatus.
Plasma treatment with an oxygen-based gas is performed at a substrate temperature of 200 ° C.
Oxygen and N2O are mixed at a ratio of 12: 1 and the pressure is 532P.
a) for 100 seconds. By this treatment, the non-uniform passivation layer 4 was replaced with the uniform passivation layer 5. This uniform passivation layer 5 is resistant to corrosion during cleaning. After that, the film was dipped in a fuming nitric acid solution having a concentration of 98% as a chemical solution for 10 minutes to remove organic substances, and then QDR (quic) for 20 minutes.
Washing with water. QDR rinsing is a rinsing method in which pure water is allowed to overflow for a certain period of time, and then the valve attached to the rinsing tank is opened to drain the water inside at once. Can be made. Then it is dried. Corrosion of the aluminum alloy film 3 does not occur during this cleaning.

In FIG. 1D, a wiring pattern 6 is formed on the aluminum alloy film 3 using a photolithography technique, and the aluminum alloy film 3 is dry-etched using a chlorine-based gas to form an aluminum wiring 3a. . At this time, since the organic material is removed by the chemical liquid on the surface on which the resist is formed, the resist can be uniformly formed. FIG.
In (e), the resist 6 remaining on the aluminum wiring 3a is ashed with oxygen plasma, and plasma processing with an oxygen-based gas is performed again under the same conditions using a downstream type apparatus to remove the side surface of the aluminum wiring 3a. A uniform passivation film 7 was formed on the surface. After that, the organic residue is removed using fuming nitric acid as a chemical solution. Corrosion of the aluminum wiring 3a does not occur even during this cleaning.

Comparing the surface dark-field image of the aluminum-based alloy film after cleaning prepared by the conventional method with the dark-field image of the film surface cleaned after cleaning in the present embodiment, the conventional method clearly shows pitting. While (white bright spots) are seen, no corrosion is seen by the method of the present embodiment. Corrosion can be reduced by performing a plasma treatment with an oxygen-based gas before the step of cleaning with fuming nitric acid to completely passivate it.

FIG. 2 is a plot of the yield due to a disconnection defect in the wafer, which is formed by forming a wiring pattern of 0.8 μm on an aluminum-based alloy film by using photolithography and dry etching techniques, and plotting the yield. In order to confirm the effect of the plasma treatment with the oxygen-based gas, the wafer was subjected to the plasma treatment with the oxygen-based gas and the fuming nitric acid cleaning three times, and the wafer was subjected to the fuming nitric acid cleaning without the plasma treatment with the oxygen-based gas. In the present embodiment that has been subjected to the oxygen plasma treatment, the initial yield remains the same, but in the conventional example in which the oxygen plasma treatment has not been performed, the yield sharply drops to about 25% at the third time. FIG. 3 is a surface view showing an SEM (electron microscope) photograph of a wafer that has not been plasma-treated with an oxygen-based gas. An aluminum defect 20 in which a part of the wiring was chipped in a V shape due to the fuming nitric acid cleaning was observed, and finally the wiring was broken, which causes a reduction in yield. On the other hand, in the present embodiment, aluminum defects 20 are not observed because of the uniform passivation layers 5 and 7, and the yield is very high at the initial yield. As described above, according to the present embodiment, aluminum deficiency due to cleaning can be prevented by the plasma treatment using the oxygen-based gas.

(Embodiment 2) Processing is performed in the same steps as in FIG. 1. In Embodiment 1, oxygen and N2O are used as processing gases.
However, in this embodiment, the surface treatment is performed only with oxygen. The substrate temperature is 60 ° C. for the plasma treatment with oxygen-based gas
~ 140 ° C, pressure 0.3 Torr ~ 0.7 Torr
r and oxygen gas flow rates were changed in the range of 100 sccm to 600 sccm, and the treatment time was 5 minutes.

FIG. 4 is a list of the treatment conditions of the plasma treatment with an oxygen-based gas and the average number of corrosion holes in an area of 360 μm 2 after cleaning with fuming nitric acid. The number of corrosion holes is the average of three points in the wafer, and since the corrosion is intentionally searched for, it is safe to assume that there is no corrosion where there is one. The higher the substrate temperature, the higher the effect on corrosion, but it hardly depends on the pressure and the flow rate (FIGS. 4A and 4B). However, there is a marked difference as compared with the case where the plasma treatment with the oxygen-based gas is not performed (FIG. 4 (c)).

As described above, according to the present embodiment, by setting the substrate temperature to 100 ° C. or higher, there is an effect against corrosion. Further, when the substrate temperature is high, residual chlorine after dry etching can be removed. Furthermore, the substrate temperature is 300 ° C
However, it was found that hillock-like things were seen, but corrosion could not be seen, and the surface morphology was changed, and it could not be used because a short circuit with the upper layer wiring occurred. That is, it is desirable to perform the plasma surface treatment at a substrate temperature of 100 ° C to 300 ° C.

Although the downstream type plasma generator is used in the present invention, if oxygen plasma can be obtained, the same effect can be obtained in another type of device. Although copper is used as the dissimilar metal in the present embodiment, similar effects can be expected for dissimilar metals such as palladium and titanium and dissimilar metals mixed with them.

[0016]

As described above, according to the present invention,
Wiring can be stably formed without corrosion on the aluminum alloy film containing different metals, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a yield transition diagram of wirings produced by the present invention.

[Fig. 3] Surface view of aluminum wiring defect

FIG. 4 is a diagram showing a list of processing conditions and corrosion numbers according to the second embodiment of the present invention.

FIG. 5 is a manufacturing process diagram of a semiconductor device by a conventional method.

[Explanation of symbols]

 1 Silicon substrate 2 Oxide film 3 Aluminum alloy film containing copper 4 Non-uniform passivation film 5,7 Uniform passivation film

Claims (4)

[Claims] 1. A step of forming an aluminum-based alloy wiring film containing a dissimilar metal on a surface of a substrate, and a plasma treatment of the aluminum-based alloy wiring film to uniformly move the surface of the aluminum-based alloy wiring film. A step of forming a body layer, a step of cleaning the substrate with a chemical solution to remove organic substances, a step of cleaning with a chemical solution and a rinsing with water, and a step of rinsing with water after the aluminum-based alloy wiring film. Forming a resist pattern on the substrate and performing dry etching using the resist pattern. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the organic substance is removed by a cleaning process using a chemical solution. 3. The method of manufacturing a semiconductor device according to claim 1, wherein a gas species containing oxygen and at least nitrogen is used as the plasma generating gas. 4. Plasma surface treatment is performed at a substrate temperature of 100.degree.
The method for manufacturing a semiconductor device according to claim 1, wherein the method is performed at 300 ° C.