JPH0529319A - Manufacture of thin-film integrated circuit - Google Patents

Abstract

PURPOSE:To set a substrate temperature at a low temperature and to eliminate an outward-appearance defect and a characteristic defect by a method wherein, after a tantalum film has been formed, via an oxide film, on a silicon substrate, a first aluminum film is formed by a DC sputtering method and a second aluminum film is formed by a high-frequency sputtering method. CONSTITUTION:An SiO2 film 2 is formed on a silicon substrate 1; after that, a Ta2N film 3 is formed by a magnetron sputtering method. Then, an Al-Si film 4 as a conductor film is formed by a DC magnetron sputtering method; after that, an Al film 5 is formed continuously on its upper part by a high-frequency magnetron sputtering method. The substrate temperature in the sputtering operation of the conductor film is set at about 100 deg.C. Since the Al-Si film 4 and the Al film 5 are formed respectively by the DC sputtering method and the high-frequency sputtering method in this manner, the irregularity in the bonding strength of the Al film can be suppressed and the substrate temperature can be lowered. As a result, a thin-film resistance element in which Si residue is small can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film integrated circuit, and more particularly to a method for forming an aluminum film for wiring and bonding pads formed on a tantalum film.

[0002]

2. Description of the Related Art A conventional method of forming a thin film resistance element of a thin film integrated circuit has been performed as follows. First, a SiO ₂ film is formed on a silicon substrate by thermal oxidation, a nitrogen-doped tantalum (Ta ₂ N) film is formed thereon, and an aluminum (Al—Si) film containing silicon and a pure aluminum (Al) film are formed on the SiO ₂ film. A conductive film made of a film is sequentially deposited by the DC sputtering method. When sputtering this conductor film, in order to obtain sufficient adhesiveness such as resist adhesion during pattern formation and wire bonding during assembly,
A desired conductor film was obtained by selecting the temperature during sputtering and the sputtering rate. In general, the conductor film is sputtered by a direct current sputter method, which provides a more stable film thickness distribution than the high frequency sputter method, and the substrate temperature is generally kept constant during the sputter.

Thereafter, the Ta ₂ N film and the conductor film are patterned to form a thin film low antibody made of the Ta ₂ N film and wirings and pads made of the conductor film. Next, in order to obtain stability over time of the thin film resistance element and adhesion strength between the thin film low antibody and the pad, heat treatment is performed at about 250 to 450 ° C. in the atmosphere.

As described above, the conductor film for wiring and pad in the conventional thin film resistance element has a two-layer structure of an Al-Si film and an Al film. This Al film constitutes the uppermost part of the conductor layer and is provided to enhance the bonding strength. In addition, the Al-Si film on the Ta ₂ N film is
-By mutual diffusion of Si and Ta in the Si film, Ta ₂
The N film and the Al-Si film and the Al film are alternately adhered to each other to form an Al film.
It is provided to prevent electromigration such as voids and whiskers in the wiring.

[0005]

However, in the conductor film on the Ta ₂ N film constituting the above-mentioned conventional thin film resistance element or the like, the interdiffusion between Si and Ta in the Al-Si film is caused by Al- Since the temperature tends to depend on the substrate temperature at the time of forming the conductor film made of the Si film and the Al film, the amount of Si diffused into the Ta ₂ N film increases as the substrate temperature at this time increases. Therefore, when the resistance pattern and the conductor pattern are formed, Si cannot be removed from the surface of the Ta ₂ N film, so that there is a drawback that a defective appearance and a defective characteristic occur.

On the other hand, in order to avoid this problem, conventionally, A
Since the substrate temperature at the time of sputtering the l-Si film and the Al film is set to a lower temperature than usual, the uppermost A
There is a problem that the surface of the l-film becomes hard and the variation in bonding strength becomes large.

[0007]

According to a method of manufacturing a thin film integrated circuit of the present invention, a tantalum film is formed on a silicon substrate via an oxide film, and then impurities for wiring and bonding pads are contained on the tantalum film. In a method of manufacturing a thin film integrated circuit in which a first aluminum film and a second aluminum film containing no impurities are sequentially formed, the first aluminum film is formed by a DC sputtering method, and the second aluminum film is formed by a high frequency sputtering method. It is formed by.

[0008]

The present invention will be described below with reference to the drawings. 1A to 1D are cross-sectional views of a semiconductor chip for explaining a first embodiment of the present invention, which is a case where the present invention is applied to a method of manufacturing a thin film resistance element.

First, as shown in FIG. 1A, a SiO ₂ film 2 having a thickness of about 1 μm is formed on a silicon substrate 1, and then a nitrogen-doped tantalum (Ta ₂ N) film 3 is magnetron sputtered. It is formed by the method.

Next, as shown in FIG. 1B, an aluminum (Al--Si) film 4 containing 1% of silicon as a conductor film is formed by a direct current (DC) magnetron sputtering method to a thickness of about 0.
After being formed to a thickness of 8 μm, a pure aluminum (Al) film 5 having a thickness of about 1 μm is continuously formed on the upper portion thereof by a radio frequency (RF) magnetron sputtering method. The substrate temperature during the sputtering of the conductor film was about 100 ° C.

Next, as shown in FIG. 1C, the conductor film is patterned to form an Al-Si film 4 and A having a minimum width of about 40 μm.
A bonding pad composed of the I film 5 is formed. Next, as shown in FIG. 1D, the Ta ₂ N film 3 is patterned to form a thin film resistance element having a minimum width of 10 μm. Then, in order to obtain stability over time of the thin film resistance element, 4
Heat treatment at 50 ° C. was performed.

As described above, in the first embodiment, Al
-By forming the Si film 4 and the Al film 5 by direct current sputtering and high frequency sputtering, respectively, variation in bonding strength of the Al film can be suppressed more than before, and the thin film resistance element with less Si residue due to the low substrate temperature. was gotten.

2 (a) to 2 (d) are sectional views of a semiconductor chip for explaining a second embodiment of the present invention, in which the present invention is applied to a method of manufacturing a thin film capacitor element.

First, as shown in FIG. 2A, after a SiO ₂ film 2 is formed on a silicon substrate 1, α-tantalum (α-T) having a smaller nitrogen doping amount than a nitrogen-doped tantalum film is formed.
a) The film 13 is formed by the magnetron sputtering method.
Next, as shown in FIG. 2B, after patterning the α-Ta film 13, only the portion to be a capacitor is 0.0
Anodization is performed in a 1% citric acid solution to form a tantalum anodic oxide (Ta ₂ O ₅ ) film 16.

Next, as shown in FIG. 1C, the Al--Si film 14 and the Al film 1 as conductor films are formed as in the first embodiment.
5 are continuously formed by the DC sputtering method and the high frequency sputtering method. Next, as shown in FIG. 2D, these conductor films were patterned to form wirings connected to the capacitor element.

As described above, according to the second embodiment, it is possible to prevent the deterioration of the insulation resistance characteristic due to the Si residue and to improve the adhesion strength of the wiring as compared with the conventional case.

Although the aluminum film containing silicon has been described in the above embodiment, the same effect can be obtained in the case of aluminum containing copper.

[0018]

As described above, according to the present invention, the first aluminum film containing impurities and the second aluminum film containing no impurities are sequentially deposited on the tantalum film formed via the silicon oxide film. At this time, the first aluminum film was formed by the DC sputtering method and the second aluminum film was formed by the high frequency sputtering method, so that the substrate temperature during the sputtering of the conductor film was lowered to suppress the Si residue. Even in such a case, the film surface of the uppermost second aluminum film is softened, the adhesion strength of bonding is improved as compared with the conventional case, and the variation in bonding strength is reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor chip for explaining a first embodiment of the present invention.

FIG. 2 is a sectional view of a semiconductor chip for explaining a second embodiment of the present invention.

[Explanation of symbols]

1 Silicon substrate 2 SiO ₂ film 3 Ta ₂ N film 4, 14 Al-Si film 5, 15 Al film 13 α-Ta film 16 Ta ₂ O ₅ film

Claims (2)

[Claims] 1. A tantalum film is formed on a silicon substrate via an oxide film, and a first aluminum film containing impurities for wiring and a bonding pad and a second aluminum film containing no impurities are formed on the tantalum film. A method of manufacturing a thin film integrated circuit, wherein a first aluminum film is formed by a DC sputtering method and a second aluminum film is formed by a high frequency sputtering method. 2. The first aluminum film contains S as an impurity.
The method of manufacturing a thin film integrated circuit according to claim 1, wherein the thin film integrated circuit contains i or Cu.