JPH07122567A - Fabrication of semiconductor device - Google Patents

Abstract

PURPOSE:To enhance the reliability of a semiconductor device by preventing generation of void in the interlayer film between Al alloy wirings. CONSTITUTION:A Ti film 103, a TiN film 104, an Al-Si-Cu film 105, a TiN film 106, and a photoresist 107 are deposited sequentially on a silicon substrate 101. The TiN film 106 is then subjected to side etching using a dry etching system followed by etching of the Af-Si-Cu film 105. Since the width of the TiN film 106 is substantially equalized to that of the Al-Si-Cu film 105, an interlayer film can be interposed between wirings 105, 106 with no gap. This method prevents generation of void in the interlayer film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device,
More particularly, it relates to a method for manufacturing a semiconductor device in dry etching an aluminum alloy film on a semiconductor wafer.

[0002]

2. Description of the Related Art An aluminum alloy film is generally used for wiring used in semiconductor devices such as IC and LSI. However, as the integration degree of LSIs, ICs, and the like has been improved, wiring patterns have become finer, so that electromigration and stress migration have become problems. In order to avoid such a problem, it is known that it is effective to form a heat resistant metal film such as TiN on the upper and lower parts of the aluminum alloy film. Therefore, conventionally, in a method of manufacturing a semiconductor device, a heat-resistant metal film such as TiN is formed on the upper and lower portions of the aluminum alloy film. Hereinafter, a conventional method for a semiconductor device will be described with reference to FIGS. 7 and 8.

First, as shown in FIG. 7A, a silicon oxide film 702 is grown on a silicon substrate 701, and a Ti film 703, a TiN film 704, and an Al-Si-C film are formed thereon.
The u film 705 and the TiN film 706 are formed in this order by a sputtering technique. Then, the photoresist 70 is further added.
7 is applied and a desired pattern is formed by an exposure technique.

Subsequently, the Ti films 703, T shown in FIG.
iN film 704, Al-Si-Cu film 705, TiN film 7
Etching of 06 is performed. The etching is performed using, for example, the dry etching apparatus shown in FIG. This dry etching apparatus includes a chamber 801, a gas supply mechanism 806 for supplying Cl ₂ / BCl ₃ gas into the chamber 801, an upper electrode 802 and a lower electrode 803, a matching box 804, an RF power source 805 (RF frequency 13 .56 MHz) and the like. Dry etching is performed by placing the silicon substrate 701 of FIG. 7A on the lower electrode 803. As a result, as shown in FIG. 7B, TiN films 704, 7
06, a desired wiring pattern made of the Al-Si-Cu film 705 is formed.

[0005]

However, Cl ₂
When the aluminum alloy film having the heat-resistant metal film is etched using / BCl ₃ as an etching gas, the isotropic etching is performed in which the etching proceeds not only in the vertical direction of the silicon substrate 701 but also in the horizontal direction. I will end up. This is because the etching of the aluminum alloy film using Cl ₂ / BCl ₃ is due to a chemical reaction. On the other hand, a refractory metal film such as TiN generally has a low vapor pressure of reaction products, and therefore has no sputtering effect by ions and is difficult to be etched. For this reason, the etching of the refractory metal film becomes difficult to proceed even in the horizontal direction of the silicon substrate 701, and the side wall of the TiN film 706, which is the refractory metal film, is made of the aluminum alloy film as shown in FIG. The side wall of a certain Al-Si-Cu film 705 has a concave shape. That is, the aluminum alloy film has a shape such that side etching occurs.

Other causes of side etching of the aluminum alloy film include the following reasons. Cl ₂
When the aluminum film is etched with / BCl ₃ , a reaction product is formed on the side wall of the aluminum film after etching, and this reaction product causes particles. Therefore, conventionally, after ashing the photoresist with O ₂ plasma or the like and taking measures against corrosion with H ₂ O plasma, alkali treatment with tetramethylammonium hydroxide N (CH ₃ ) ₄ OH is performed. Since tetramethylammonium hydroxide is alkaline, it will etch the aluminum alloy film. As a result, the Al-Si-Cu film 705 is further etched in the horizontal direction of the silicon substrate as compared with the TiN film 706.

[0007] Here, Al-
An attempt is made to fill the interlayer film between the wirings of the Si-Cu film 705. However, since the TiN film 706 is projected in the horizontal direction with respect to the Al-Si-Cu film 705, Al
The interlayer film cannot be completely filled between the wirings of the —Si—Cu film 705, and a cavity 708 is generated in the interlayer film. Moisture or the like easily remains in the cavity 708, and this moisture or the like also causes a failure of the semiconductor device. Therefore, the conventional method of manufacturing a semiconductor device has a serious problem that the reliability of the semiconductor device is significantly reduced.

[0008]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to prevent the formation of voids in an interlayer film between aluminum alloy wirings and improve the reliability of a semiconductor device in a method of manufacturing a semiconductor device.

[0009]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, which comprises a step of sequentially forming a heat-resistant metal film and a photoresist on a surface of an aluminum alloy film on a semiconductor wafer, and a gas containing fluorine. A step of side etching the heat resistant metal film in plasma,
The method is characterized by including a step of etching the aluminum alloy film to form a desired metal wiring, and a step of filling an interlayer film between the metal wirings.

In a method of manufacturing a semiconductor device according to a second aspect of the present invention, in the step of side etching the refractory metal film, the semiconductor wafer is brought into contact with one of a pair of electrodes in a gas plasma containing fluorine, 2. The method of manufacturing a semiconductor device according to claim 1, further comprising the step of applying a high frequency voltage between both electrodes.

According to a third aspect of the present invention, in the method of manufacturing a semiconductor device, the step of side-etching the refractory metal film is performed by applying a microwave and a magnetic field to the semiconductor wafer in a gas plasma containing fluorine. The method of manufacturing a semiconductor device according to claim 1, wherein

[0012]

In the method of manufacturing a semiconductor device according to the first aspect of the present invention, first, a refractory metal film (TiN or the like) and a photoresist are sequentially formed on the surface of an aluminum alloy film on a semiconductor wafer. Then, the heat-resistant metal film is side-etched in a gas plasma containing fluorine, and then the aluminum alloy film is etched to form a metal wiring having a desired pattern. Since the refractory metal film is side-etched (undercut), the refractory metal and the metal wiring have substantially the same line width. As a result, the interlayer film can be filled without gaps between the metal wirings, and a void can be prevented from being formed in the interlayer film. Therefore, it becomes possible to avoid a failure of the semiconductor device due to water remaining in the cavity.

In a method of manufacturing a semiconductor device according to a second aspect of the present invention, the semiconductor wafer is brought into contact with one of a pair of electrodes in a gas plasma containing fluorine, and a high frequency voltage is applied between the electrodes. As a result, the heat resistant metal film is side-etched.

In the method of manufacturing a semiconductor device according to the third aspect of the present invention, the heat-resistant metal film is side-etched by applying a microwave and a magnetic field to the semiconductor wafer in the gas plasma containing fluorine. ing.
Thereby, high-density plasma can be generated, and the heat resistant metal film can be etched at high speed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a method of manufacturing a semiconductor device according to a first embodiment of the present invention. First, as shown in FIG. 1A, a silicon oxide film 1 is formed on a silicon substrate 101.
02 was grown, and then Ti was sputtered.
Film 103, TiN film 104, Al-Si-Cu film 10
5, the TiN film 106 is sequentially formed. Then, after applying a photoresist 107 on this, a pattern is formed by an exposure technique.

This silicon substrate 101 is etched using the dry etching apparatus shown in FIG. This dry etching apparatus includes a chamber 201 and a chamber 2
Gas supply mechanism 2 for supplying Cl ₂ / BCl ₃ gas into 01
06, an upper electrode 202 and a lower electrode 203 which are vertically opposed to each other, a matching box 204, an RF power source 205 (RF frequency 13.56 MHz), and the like. The RF power source 205 includes an upper electrode 202 and a lower electrode 2.
It is possible to selectively supply a voltage to any one of the above. The silicon substrate 101 is placed on the lower electrode 203.

First, T on the Al--Si--Cu film 105
The iN film 106 is etched. Applying an RF power source 205 to the upper electrode 202, CF _4: 100sccm, Pressure: 60
Etching was performed under the conditions of 0 mTorr and RF power density: 5.50 W / cm ² , and TiN was formed as shown in FIG.
Side etching of the side wall of the film 106 proceeds. As a result, the sidewall of the TiN film 106 has a shape that is recessed (side etching has occurred) with respect to the sidewall of the photoresist 107.

Then, the Al-Si-Cu film 105 is etched. RF power source 205 is applied to the lower electrode 203, Cl ₂ : 30 sccm, BCl ₃ : 60 sccm, pressure: 25
Etching is performed under the conditions of 0 mTorr and RF power density: 2.75 W / cm ² . Finally, TiN film 104 and Ti
The film 103 is etched. RF power source 205 is applied to the lower electrode 203, and Cl ₂ : 25sccm, BCl ₃ : 45sc.
cm, pressure: 20 mTorr, RF power density: 1.1 W / c
Etching is performed under the etching condition of m ² .

After the etching is completed, the photoresist 10
7), H ₂ O treatment, etc. as a countermeasure against corrosion of the Al—Si—Cu film, and alkali treatment with tetramethylammonium hydroxide or the like to remove reaction products attached to the side walls of the Al—Si—Cu film. To do. As a result, as shown in FIG. 1C, the TiN film 106 and the Al-Si-C film are formed.
The wiring widths of the u film 105 are substantially equal, and it becomes possible to fill the interlayer film between the wirings without a gap. This can prevent the formation of voids in the interlayer film.

Next, the control of the side etching amount of the TiN film (the undercut amount of the TiN film side wall with respect to the photoresist side wall) will be described. FIG. 3 shows Al-Si-
In the etching of the TiN film 106 formed on the Cu film 105, the side etching amount (circles in the figure) when only the pressure condition is changed, and when the cathode drop voltage in the dry etching apparatus is changed Shows the amount of side etching (triangle mark in the figure). The etching time is 6 minutes. The amount of side etching generated by the etching of the aluminum alloy film and the alkali treatment for removing reaction products after the etching is about 0.1 μm on one side of the wiring. Therefore, in order to improve the formation of the interlayer film, the TiN film 10
It is desirable that the etching amount of No. 6 is equal to the side etching amount of the Al-Si-Cu film 105. Therefore, the side etching amount of the TiN film 106 is set to 0.1 μm.
From FIG. 3, it is required that the pressure is 600 mTorr or more and the cathode drop voltage is −50 V or less.

The side etching amount of the TiN film 106 can be set to a desired value by changing the etching time. 4, CF _4: 100s
ccm, pressure: 600 mTorr, RF power density: 5.5 W /
The relationship between the etching time and the side etching amount in cm ² is shown. It can be confirmed from this figure that the side etching amount of the TiN film 106 becomes 0.1 μm or more by setting the etching time to 6 minutes or more.

From the results of FIGS. 3 and 4, it is possible to control the cathode drop voltage to −50 V or less and change the etching time to control the side etching amount of the TiN film 106 to a desired value. It is a thing. Although CF ₄ is used as the gas plasma containing fluorine in the present embodiment, the same effect can be obtained by using other gas containing fluorine, such as SF ₆ and C ₂ F _6. Is.

Next, a method of manufacturing a semiconductor device according to the second embodiment of the present invention will be described. FIG. 5 is a diagram showing the method for manufacturing the semiconductor device according to the present embodiment.

First, as shown in FIG. 5A, a silicon oxide film 502 is formed on a silicon substrate 501, and subsequently a Ti film 503, a TiN film 504, an Al--Si--Cu film 505, and a TiN film 506. Are sequentially formed by a sputtering technique, a photoresist 507 is applied, and then a pattern is formed by an exposure technique.

This silicon substrate 501 is etched using the plasma etching apparatus shown in FIG. This plasma etching apparatus includes a waveguide 604 that propagates microwaves, a solenoid coil 605 that generates a magnetic field in the waveguide 604, a quartz bell jar 606, and an RF power source 60.
3, a matching box 602, a sample table 601 on which the silicon substrate 501 is placed, and the like. First, the TiN film 506 on the Al-Si-Cu film 505 is etched. The etching conditions at this time are CF ₄ :
100 sccm, pressure: 10 mTorr, microwave current: 30
0 mA, RF power density: 0 W / cm ² . As a result, as shown in FIG.
On the other hand, side etching occurs in the TiN film 506.

Subsequently, the Al-Si-Cu film 505, Ti
The N film 504 and the Ti film 503 are etched. The etching conditions are Cl ₂ : 70 sccm, BCl ₃ : 30 sccm, pressure: 8 mTorr, microwave current: 300 mA, and RF power density: 0.28 W / cm ² . After the etching process is completed, the photoresist is removed, the H ₂ O process or the like is taken as a measure against corrosion of the Al-Si-Cu film, and the Al-Si-
Alkali treatment with tetramethylammonium hydroxide or the like is performed to remove the reaction product attached to the side wall of the Cu film. As a result, the TiN film 506 and the Al-Si-C film are formed.
The wiring widths of the u film 505 are substantially equal ((c) of FIG. 5),
It becomes possible to fill the interlayer film between the wirings without any gap.
This makes it possible to prevent the formation of voids in the interlayer film.

According to the method of manufacturing the semiconductor device of the present embodiment, since the microwave (frequency: 2.45 GHz) plasma etching device is used, the parallel plate type dry etching device (frequency: 13.56
It is possible to obtain a high-density plasma compared with (MHz). Therefore, according to this embodiment, the TiN film 506 can be etched at high speed. Further, since the RF electrode is connected to the lower electrode on which the wafer is placed, the cathode drop voltage can be controlled independently, and the side etching amount of the TiN film can be set to a desired value.

[0029]

As described above, according to the present invention, in the method of manufacturing a semiconductor device, the side width of the refractory metal film such as TiN is caused to cause the wiring width of the refractory metal film and the aluminum alloy film. Can be made substantially equal, and the interlayer film can be filled between the aluminum alloy films without any gap. As a result, it is possible to prevent a cavity from being formed in the interlayer film, and it is possible to avoid a failure of the semiconductor device due to residual moisture or the like in the cavity.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method for manufacturing a semiconductor device according to a first exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of a dry etching apparatus used in the method for manufacturing a semiconductor device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing etching characteristics of the method for manufacturing a semiconductor device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing etching characteristics of the method for manufacturing a semiconductor device according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a manufacturing method of a semiconductor device according to a second embodiment of the invention.

FIG. 6 is a sectional view of a microwave plasma etching apparatus used in a method for manufacturing a semiconductor device according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a conventional method for manufacturing a semiconductor device.

FIG. 8 is a cross-sectional view of a dry etching apparatus used in a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

101, 501 Silicon substrate (semiconductor wafer) 105, 505 Al-Si-Cu film (aluminum alloy film) 106, 506 TiN film (heat resistant metal film) 107, 507 Photoresist

Claims (3)

[Claims] 1. A step of sequentially forming a refractory metal film and a photoresist on a surface of an aluminum alloy film on a semiconductor wafer, a step of side etching the refractory metal film in a gas plasma containing fluorine, and the aluminum alloy film. And a step of forming a desired metal wiring, and a step of filling an interlayer film between the metal wirings. 2. The step of side-etching the refractory metal film comprises a step of bringing the semiconductor wafer into contact with one of a pair of electrodes in a gas plasma containing fluorine and applying a high-frequency voltage between the electrodes. The method for manufacturing a semiconductor device according to claim 1, wherein 3. The semiconductor device according to claim 1, wherein the step of side-etching the refractory metal film comprises a step of applying a microwave and a magnetic field to the semiconductor wafer in a gas plasma containing fluorine. Manufacturing method.