JP2776727B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device,
More specifically, the present invention relates to a method for manufacturing a semiconductor device in dry etching of an aluminum alloy film on a semiconductor wafer.

[0002]

2. Description of the Related Art Aluminum alloy films are generally used for wiring used in semiconductor devices such as ICs and LSIs. However, with the improvement in the degree of integration of LSIs, ICs, and the like, the 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 portions of the aluminum alloy film. Therefore, conventionally, in a method of manufacturing a semiconductor device, a heat-resistant metal film such as TiN has been formed above and below an aluminum alloy film. Hereinafter, a conventional method for a semiconductor device will be described with reference to FIGS.

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, an Al--Si--C
The u film 705 and the TiN film 706 are formed in this order by using a sputtering technique. Then, the photoresist 70
7 is applied, and a desired pattern is formed by an exposure technique.

Subsequently, the Ti film 703, T
iN film 704, Al-Si-Cu film 705, TiN film 7
06 is performed. The etching is performed using, for example, a 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 supply 805 (RF frequency 13 .56 MHz). By placing the silicon substrate 701 of FIG. 7A on the lower electrode 803, dry etching is performed. As a result, as shown in FIG. 7B, the TiN films 704, 7
06, a desired wiring pattern composed of the Al-Si-Cu film 705 is formed.

[0005]

However, Cl ₂
When an aluminum alloy film having a heat-resistant metal film is etched using / BCl ₃ as an etching gas, the etching proceeds in the vertical direction of the silicon substrate 701 and isotropic etching in which the etching also proceeds in the horizontal direction. I will. This is because the etching of the aluminum alloy film using Cl ₂ / BCl ₃ is caused by a chemical reaction. On the other hand, a heat-resistant metal film such as TiN generally has a low vapor pressure of a reaction product and thus has no sputtering effect due to ions, and is hardly etched. Therefore, the etching of the heat-resistant metal film hardly proceeds even in the horizontal direction of the silicon substrate 701, and the aluminum alloy film is applied to the side wall of the TiN film 706, which is the heat-resistant metal film, as shown in FIG. The Al-Si-Cu film 705 has a shape in which the side wall is depressed. That is, the aluminum alloy film has a shape in which side etching occurs.

Further, the following reasons are listed as other causes of the side etching of the aluminum alloy film. Cl ₂
When the aluminum film is etched with / BCl ₃ , a reaction product is formed on the side wall of the etched aluminum film, and the reaction product causes particles. Therefore, conventionally, after ashing of the photoresist with O ₂ plasma or the like and countermeasures against corrosion by H ₂ O plasma, alkali treatment with tetramethylammonium hydroxide N (CH ₃ ) ₄ OH has been 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, the Al-
It is assumed that an interlayer film is to be filled between the wirings of the Si-Cu film 705. However, since the TiN film 706 protrudes in the horizontal direction with respect to the Al-Si-Cu film 705,
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. Water and the like easily remain in the cavity 708, and the water and the like may cause a failure of the semiconductor device. Therefore, in the conventional method for manufacturing a semiconductor device, there has been a serious problem that the reliability of the semiconductor device is greatly reduced.

[0008]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method of manufacturing a semiconductor device, which prevents the occurrence of voids in an interlayer film between aluminum alloy wirings and improves the reliability of a semiconductor device.

[0009]

The method of manufacturing a semiconductor device of the present invention SUMMARY OF] includes a step of forming a refractory metal film and the mask in order to metal <br/> membrane surface containing aluminum on a semiconductor wafer, a fluorine gas and performing side etching of the previous SL refractory metal film in the plasma, and forming a metal interconnection continues etching the metal film containing pre SL aluminum, a step of filling the interlayer insulating film between before Symbol metal wires It is characterized by including .

According to a second aspect of the present invention, in the method of manufacturing a semiconductor device, the step of performing side etching of the heat-resistant metal film includes contacting the semiconductor wafer with one of a pair of electrodes in a gas plasma containing fluorine. 2. The method for manufacturing a semiconductor device according to claim 1, comprising a process 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 performing the side etching of the heat-resistant metal film is performed by applying a microwave and a magnetic field to the semiconductor wafer in a gas plasma containing fluorine. 2. 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 heat-resistant 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, after performing the side etching of the heat-resistant metal film in a gas plasma containing fluorine, the aluminum alloy film is etched to form a metal wiring having a desired pattern. Since the heat-resistant metal film is side-etched (undercut), the line widths of the heat-resistant metal and the metal wiring are substantially equal. As a result, the interlayer film can be filled without gaps between the metal wirings, and the formation of a cavity in the interlayer film can be prevented. Therefore, it is possible to avoid a failure of the semiconductor device due to, for example, moisture remaining in the cavity.

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 two electrodes. Thus, the side etching of the heat-resistant metal film is performed.

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

[0015]

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

FIG. 1 is a view 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, followed by a sputtering technique for Ti
Film 103, TiN film 104, Al-Si-Cu film 10
5. A TiN film 106 is formed in order. Then, after a photoresist 107 is applied thereon, a pattern is formed by an exposure technique.

The silicon substrate 101 is etched using a 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 supply 205 (RF frequency 13.56 MHz), and the like. The RF power source 205 includes the upper electrode 202 and the lower electrode 2
03 can be selectively supplied with a voltage. The silicon substrate 101 is mounted on the lower electrode 203.

First, T on the Al-Si-Cu film 105
The iN film 106 is etched. An RF power source 205 is applied to the upper electrode 202, CF ₄ : 100 sccm, pressure: 60
Etching was performed under the conditions of 0 mTorr and RF power density: 5.50 W / cm ² , and as shown in FIG.
The side etching of the side wall of the film 106 proceeds. As a result, the sidewall of the TiN film 106 has a shape recessed (side etching has occurred) with respect to the sidewall of the photoresist 107.

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

After completion of the etching, the photoresist 10
7 removal, corrosion protection of Al-Si-Cu film by H ₂ O processing and the like, an alkali treatment by tetramethylammonium hydroxide for removal of the reaction products adhering to the side walls of the Al-Si-Cu film, etc. Do. As a result, as shown in FIG. 1C, the TiN film 106 and the Al-Si-C
The wiring width of the u film 105 becomes substantially equal, and the interlayer film can be filled between the wirings without any gap. This can prevent a cavity from being formed in the interlayer film.

Next, control of the amount of side etching of the TiN film (the amount of undercut of the side wall of the TiN film with respect to the side wall of the photoresist) will be described. FIG. 3 shows Al-S
In the etching of the TiN film 106 formed on the i-Cu film 105, the side etching amount (circled in the figure) when only the pressure condition is changed, and the cathode drop voltage
( Indicated by a triangle in the figure) . The etching time is 6 minutes. In addition, the amount of side etching caused by the etching of the aluminum alloy film and the alkali treatment for removing the 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, it is desirable that the etching amount of the TiN film 106 is equal to the side etching amount of the Al—Si—Cu film 105. Therefore, Ti
It is found from FIG. 3 that in order to set the side etching amount of the N film 106 to 0.1 μm, the pressure may be set to 600 mTorr or more and the cathode drop voltage may be set to −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. FIG. 4 shows 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. From this figure, it can be confirmed 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.

According to the results shown in FIGS. 3 and 4, the amount of side etching of the TiN film 106 can be controlled to a desired value by setting the cathode drop voltage to -50 V or less and changing the etching time. Things. In the present embodiment, the description has been made using CF ₄ as the gas plasma containing fluorine. However, the same effect can be obtained by using other gas containing fluorine, for example, SF ₆ , C ₂ F ₆ or the like. It is.

Next, a method of manufacturing a semiconductor device according to a second embodiment of the present invention will be described. FIG. 5 is a diagram illustrating the method of 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, followed by 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. Further, after a photoresist 507 is applied, a pattern is formed by an exposure technique.

The silicon substrate 501 is etched using a plasma etching apparatus shown in FIG. This plasma etching apparatus includes a waveguide 604 for propagating a microwave, a solenoid coil 605 for generating a magnetic field in the waveguide 604, a quartz bell 606, and an RF power supply 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 condition at this time is CF4:
100 sccm, pressure: 10 mTorr, microwave current: 300 mA, RF power density: 0 W / cm 2 (sun
That is, the RF power supply 603 is not used) . This allows
As shown in FIG. 5B, side etching occurs in the TiN film 506 with respect to the photoresist 507.

Subsequently, an Al-Si-Cu film 505, Ti
The N film 504 and the Ti film 503 are etched. The etching conditions are as follows: Cl ₂ : 70 sccm, BCl ₃ : 30 sccm, pressure: 8 mTorr, microwave current: 300 mA, RF power density: 0.28 W / cm ² . After the etching process is completed, the photoresist is removed, the corrosion of the Al—Si—Cu film is prevented by H ₂ O treatment, etc., and the Al—Si—
An alkali treatment with tetramethylammonium hydroxide or the like for removing a reaction product attached to the side wall of the Cu film is performed. As a result, the TiN film 506 and the Al-Si-C
The wiring width of the u film 505 becomes substantially equal (FIG. 5C),
It is possible to fill the interlayer film between the wirings without any gap.
Thereby, it is possible to prevent a cavity from being formed in the interlayer film.

According to the method of manufacturing a semiconductor device according to the present embodiment, since a microwave (frequency 2.45 GHz) plasma etching apparatus is used, the parallel plate type dry etching apparatus (frequency 13.56
MHz) can be obtained. Therefore, according to the present embodiment, high-speed etching of the TiN film 506 can be performed. Further, since the RF electrode is connected to the lower electrode on which the wafer is mounted, 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 heat-resistant metal film such as TiN is etched to form the wiring width of the heat-resistant 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, a cavity can be prevented from being formed in the interlayer film, and a failure of the semiconductor device due to moisture or the like remaining in the cavity can be avoided.

[Brief description of the drawings]

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

FIG. 2 is a 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 graph 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 the etching characteristics of the method for manufacturing a semiconductor device according to the first embodiment of the present invention.

FIG. 5 is a view illustrating a method for manufacturing a semiconductor device according to a second example of the present 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 of manufacturing a semiconductor device.

FIG. 8 is a 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)

(57) [Claims] 1. Including aluminum on a semiconductor wafer
Forming a refractory metal film and the mask in sequence the surface of the metal film, by etching and performing side etching of the previous SL refractory metal film, subsequently the metal film containing pre SL aluminum in a gas plasma containing fluorine metal wires process and method of manufacturing a semiconductor device which comprises a step of filling the interlayer insulating film between before Symbol metal wire to form a. 2. The method according to claim 1 , wherein the step of forming the metal wiring and the step of forming the metal wiring are performed.
Removing the mask between the step of filling the insulating film;
Process and corrosion prevention treatment of aluminum-containing metal film.
2. The method according to claim 1 , further comprising the step of: removing a reaction product . 3. A pre-Symbol step of performing side etching of the refractory metal film, contact the semiconductor wafer on one of the pair of electrodes
Applying a high frequency between the electrodes in the state of touching,
Or / and a manufacturing method for half <br/> conductor device according to claim 1, characterized in that prior SL by applying a microwave and a magnetic field to the semiconductor wafer.