JP2861785B2 - Method for forming wiring of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a wiring of a semiconductor device, and more particularly to a method of forming a wiring of a semiconductor device for forming a wiring pattern composed of a metal film mainly composed of aluminum or an aluminum alloy. .

[0002]

2. Description of the Related Art With the increase in the degree of integration of semiconductor devices, metal wiring (hereinafter referred to as Al wiring) having an aluminum or aluminum alloy film (hereinafter, also collectively simply referred to as an Al film) as a main conductive layer for connecting each element. ) Are also required to be further miniaturized and multilayered. Such advances in miniaturization and multilayering increase the unevenness of the surface of a semiconductor device, and make the patterning of an Al wiring formed thereon more difficult. As a method of forming a fine Al wiring on such a large step, a method of forming a metal wiring by dry etching using an oxide film formed on the Al film as a mask has been reported (Jpn.J. Appl. Phys. Vol. .31 (1
992) pp. 4376-4380).

FIGS. 6 (a) and 6 (b) are cross-sectional views of a semiconductor device at each process step, showing a method of forming the above-mentioned metal wiring. Silicon oxide film 20 on silicon substrate 201
2 and then about 500 Å thick T
A TiN / Ti layer 203 made of i and TiN having a thickness of about 1000 angstroms is formed by a sputtering method. Subsequently, an AlCu alloy film 204 having a thickness of about 5000 angstroms is formed by a sputtering method.
An iN film 205 is formed. Thus, a metal film mainly composed of aluminum or an aluminum alloy is formed on silicon oxide film 202. Next, a plasma oxide film having a thickness of about 2000 angstroms is formed by a plasma CVD method.

Next, a resist pattern (not shown) is formed by using a known photolithography technique, and CF ₄ / CHF ₃ / A is formed using the resist pattern as a mask.
_The plasma oxide film is dry-etched by RIE (reactive ion etching) using mixed gas plasma of _r , and a mask oxide film pattern 206 is formed from this (FIG. 6A).

Subsequently, using the mask oxide film pattern 206 as a mask, RIE using a mixed gas plasma of Cl ₂ and N ₂ is performed to dry-etch the metal films 203 to 205 made of the laminated film of TiN / AlCu / TiN / Ti. Thus, the structure shown in FIG. 6B is obtained. As shown in the figure, the etched mask oxide film pattern adheres to the side wall of the Al wiring pattern to form a side wall protective film 207 of the Al wiring pattern. Therefore, during the etching, side etching of the metal film is suppressed, and a favorable anisotropic shape can be obtained for the obtained wiring pattern.

[0006]

In the above-described conventional method for forming a wiring of a semiconductor device, the etched mask oxide film adheres to the side wall of the Al film pattern when the Al film is etched, and the side wall is protected. Acting as a membrane,
A good anisotropic shape can be obtained for the obtained Al wiring pattern.

However, in the Al wiring obtained by the above method, chlorine used as an etching gas is contained in the sidewall protective film, and after-corrosion occurs in the Al wiring pattern due to the presence of the chlorine. Therefore, there is a disadvantage that the long-term reliability of the Al wiring of the semiconductor device is impaired.

In view of the above, the present invention provides a semiconductor device capable of forming a multi-layer fine Al wiring pattern having a long-term reliability with a good anisotropic shape when forming an Al wiring on a substrate. An object of the present invention is to provide a method for forming wiring of a device.

[0009]

In order to achieve the above object, a method for forming a wiring of a semiconductor device according to the present invention comprises a step of forming a metal film mainly composed of aluminum or an aluminum alloy on a main surface of a substrate. Forming an oxide film on the metal film, anisotropically etching the oxide film to form an oxide film pattern, and a gas mixture of Cl2 and N2.
Anisotropically etching the metal film using the oxide film pattern as a mask by RIE using a plasma to form a metal film pattern.
Forming a metal plasma pattern , exposing the metal film pattern to a gas plasma containing boron trichloride as a main component without exposing the metal film pattern to the atmosphere following the anisotropic etching of the metal film.
And exposing step. In addition, the trisalt
Change to gas plasma containing boron
Gas plasma mainly composed of urine can be adopted
You. Further, the metal film pattern is exposed to the gas plasma.
A step of forming Al on a sidewall of the metal film pattern;
Removing the sidewall film containing O, N, Si and Cl.
It is characterized by that.

[0010] method for forming the wiring, furthermore, following the step of exposing the metal layer pattern to said gas plasma, without metal film pattern, without exposure to the atmosphere, a halogen element essentially comprises oxygen and hydrogen Gas down
Preferably, the method includes a step of exposing to flow plasma . The step of exposing the metal film pattern to the downflow plasma is particularly preferably performed at a substrate temperature of 240 ° C. or higher.

[0011]

Immediately after the metal film mainly composed of aluminum or aluminum alloy is anisotropically etched by gas plasma containing chlorine using the oxide film as a mask, the obtained Al
A protective film containing Al, O, Si, and Cl is formed on the side wall of the wiring pattern. In order to remove this protective film,
It is necessary to have a process capable of simultaneously removing Al, Al ₂ O ₃ , Si, and SiO ₂ by etching.

In the method for forming a wiring of a semiconductor device according to the present invention, subsequent to the anisotropic etching of the metal film, the metal film is exposed to a gas plasma containing at least one of BCl ₃ and BBr ₃ without exposing the metal film to the atmosphere. By exposing the metal film, plasma treatment of the metal film is performed to remove the side wall protective film containing Al, O, Si, and Cl, thereby preventing after-corrosion of the metal film due to the presence of Cl.

The method for forming a wiring of a semiconductor device according to the present invention comprises:
Following the step of exposing the metal film to a gas plasma containing at least one of BCl ₃ and BBr ₃ , exposing the metal film to a gas plasma containing oxygen and hydrogen and containing no halogen element without exposing the metal film to the atmosphere Is included, residual chlorine can be substantially completely removed, and after-corrosion of the metal film due to chlorine can be further prevented.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. FIGS. 1A to 1C are cross-sectional views of a semiconductor integrated circuit in each process step, each showing a method for forming a wiring of a semiconductor device according to an embodiment of the present invention.

In the method of this embodiment, first, the silicon substrate 1
01, a silicon oxide film 102 is formed,
A TiN / Ti layer 103 consisting of 00 Å thick Ti and about 1000 Å thick TiN;
It is formed by a sputtering method. Subsequently, the AlCu alloy film 10 having a thickness of about 5000 Å is formed by sputtering.
Next, a TiN film 105 having a thickness of about 500 Å is continuously formed without being taken out to the atmosphere. Thereby, a metal film mainly composed of an aluminum alloy is formed on silicon oxide film 102. Next, a plasma oxide film having a thickness of about 2000 angstroms is formed by a plasma CVD method.

Next, a resist pattern (not shown) is formed by using a known photolithography technique, and CF ₄ / CHF ₃ / A is formed using the resist pattern as a mask.
_The plasma oxide film is dry-etched by RIE (reactive ion etching) using a mixed gas plasma of _r , and a mask oxide film pattern 106 is formed from this (FIG. 1A).

Subsequently, using the mask oxide film pattern 106 as a mask, RIE using a mixed gas plasma of Cl ₂ and N ₂ is performed to dry-etch the metal films 103 to 105 made of the laminated film of TiN / AlCu / TiN / Ti. Thus, the structure shown in FIG. 1B is obtained. The etching conditions at this time are, for example, Cl ₂ : N ₂ =
63:13 (sccm ratio) as a pressure of 5 mTorr
And 500 W as RF power.

Immediately after the plasma etching of the metal film, the side wall protective film 107 is formed on the side wall of the obtained Al wiring pattern.
Are formed. The composition of the sidewall protective film 107 is represented by A
The side of the lCu alloy film 104 was analyzed by micro Auger analysis (μ-AES). Figure 2 shows the result.
(A). In this figure, the horizontal axis represents the SiO the A _r sputtering amount
_The value is expressed in terms of ₂ (angstrom), and the vertical axis is the measured atomic concentration (%) of each element. The sidewall protective film 107 contains Al, O, N, Si, Cl, and Si.
The film has a thickness of 400 to 500 angstroms in terms of O ₂ .

As can be understood from FIG. 2A, Cl is trapped at the interface between the side wall protective film 107 and the AlCu alloy film 104. When the substrate is taken out into the atmosphere with the Cl-containing side wall film adhered, after-corrosion due to Cl occurs in the Al film, and a fatal defect may occur in the Al wiring. . Further, the Al wiring to which such a sidewall film adheres has a problem in long-term reliability.

Therefore, in the present embodiment, while the silicon substrate immediately after the dry etching is held in a vacuum chamber, the Al and O are continuously subjected to RIE using a gas plasma containing boron trichloride (BCl ₃ ). ,
The sidewall film containing N, Si, and Cl is removed. By adopting this step, a structure (FIG. 1C) in which the sidewall protective film 107 is removed can be obtained. At this time, the processing conditions using the BCl ₃ plasma include, for example, a flow rate of BCl ₃ of 50 scc.
m, the pressure is 10 mTorr, the RF power is 200 W, and the etching time is 30 seconds.

FIG. 2B shows the result of analyzing the components of the side wall of the Al wiring after the plasma treatment with BCl ₃ , similarly to FIG. 2A. Referring to FIG. 2B, it can be understood that most of the sidewall protection film is removed from the Al wiring by the plasma treatment, since all components other than Al are greatly reduced. It is also shown that the layer containing Cl appears on the outermost surface of the side wall. By removing Cl adhering to the side wall surface, after-corrosion caused by Cl can be substantially completely prevented, and therefore, a highly reliable Al wiring can be formed even in the long term. .

In this embodiment, in order to remove Cl from the side wall surface, the silicon substrate after the BCl ₃ plasma treatment is transferred to another chamber by vacuum transfer, where halogen containing oxygen and hydrogen is substantially contained. The process is performed by a down-flow plasma using a gas plasma that is not included in the gas, for example, CH ₃ OH. By this processing, A
Cl adhered to the side wall surface of the l-wiring can be substantially completely removed, and after-corrosion occurring after the silicon substrate is taken out to the atmosphere can be suppressed.
The conditions in the downflow plasma processing are, for example, C
H ₃ OH flow rate is 100 sccm, pressure is 1.2 Torr,
The microwave power is 1000 W, the wafer stage temperature is 200 ° C., and the processing time is 120 seconds.

FIGS. 3 to 5 are diagrams showing the effects of the above embodiment, in which the above-mentioned BCl ₃ plasma processing conditions and down-flow plasma processing conditions are partially changed, and the changed processing conditions and the results obtained therefrom are shown. It shows the relationship with the number of corrosion of the given wiring. Hereinafter, each of them will be described. In addition, all the plasma conditions not specified below adopt the above-mentioned conditions.

FIG. 3 shows the result of examining the processing time dependency of the number of after-corrosion occurrences under the condition that only the processing time in the BCl ₃ plasma processing is changed and other conditions are as described above. In the same figure, this dependency is shown for the case where the elapsed time left in the air after the downflow plasma treatment is 24 hours (a) and 48 hours (b). As can be understood from the figure, the number of occurrences of corrosion decreases as the duration of the BCl ₃ plasma treatment increases, and if the plasma treatment time is 30 seconds or less, the corrosion occurs when the plasma treatment is left in the air.
When the BCl ₃ plasma processing time of sec or more is adopted, the corrosion can be substantially completely removed.

FIG. 4 shows that in the down flow plasma processing, CH ₃ OH is substantially changed by changing various gas conditions.
Of the number of corrosions occurring after standing for 24 hours after the treatment, the downflow treatment time dependence was determined, when the BCl ₃ plasma treatment was not performed before (c), and the BCl ₃ plasma treatment was performed for 30 seconds. The results obtained by examining each of the cases (d) are shown. From this figure, it can be seen that the effectiveness of the BCl ₃ plasma treatment can be confirmed, and that the after-corrosion can be substantially completely prevented when the flow rate of CH ₃ OH is 100 sccm or more. The greater the hydrogen content in the gas for the downflow plasma treatment, the greater the effect of preventing corrosion.

FIG. 5 shows the case where the BCl ₃ plasma treatment is performed for 15 seconds, and then the down flow plasma treatment with CH ₃ OH is performed for 90 seconds. 24 hours after treatment (e)
And the results obtained by examining each of 48 hours (f). As shown in the figure, in the down-flow plasma treatment, an after-corrosion preventing effect appears at a substrate temperature of 200 ° C. or higher, and a sufficient after-corrosion preventing effect can be obtained at a substrate temperature of 240 ° C. or higher. In this case, the substrate temperature in the down-flow plasma processing is 240 ° C.
With more, reducing the time required for time and BCl ₃ plasma processing required for down-flow plasma processing becomes possible, thereby enabling the overall increased throughput.

In the above embodiment, the side wall film made of the oxide film formed at the time of dry etching of the Al film is removed by BCl ₃ gas plasma treatment, and then downflow plasma treatment by CH ₃ OH gas plasma is performed. By substantially completely removing the remaining Cl, the occurrence of corrosion is effectively suppressed, thereby making it possible to form a highly reliable Al wiring.

The configuration of the above embodiment is an exemplification, and the method of forming the wiring of the semiconductor device of the present invention is not limited to the configuration of the above embodiment. For example, in the above embodiment, the example in which the plasma treatment of the BCl ₃ gas is performed has been described, but BBr ₃ (boron tribromide) can be employed instead of BCl ₃ .

[0029]

As described above, the method for forming a wiring of a semiconductor device according to the present invention comprises the steps of forming a metal film mainly composed of aluminum or an aluminum alloy, and forming an acid on the metal film.
Forming oxide film and anisotropically etching oxide film
Forming an oxide film pattern and mixing Cl2 and N2.
Oxide film pattern by RIE using combined gas plasma
Anisotropically etching the metal film as a mask to pattern the metal film
Forming an anisotropic etchant of the metal film.
Do not expose the metal film pattern to the atmosphere
Gas containing boron trichloride or boron tribromide as the main component
By adopting the step of exposing to plasma, Cl present at the interface between the Al wiring and the side wall protective film can be removed. In addition, it is possible to form a highly reliable Al wiring in a long term.

The above-mentioned boron trichloride or boron tribromide
Following the step of exposing the metal layer pattern to a gas plasma containing a metal film pattern, not including without exposing to the atmosphere, a halogen element include oxygen and hydrogen substantially moth
The method further includes a step of exposing the metal film pattern to the side wall surface, thereby removing Cl adhered to the side wall surface of the metal film pattern , thereby more effectively preventing after-corrosion occurring in the Al wiring. .

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views of a semiconductor device at respective process steps, illustrating a method for forming a wiring of a semiconductor device according to an embodiment of the present invention;

FIGS. 2A and 2B are graphs showing the results of micro Auger analysis of components on the side walls of Al wiring before and after BCl ₃ gas plasma treatment, respectively.

FIG. 3 is a graph showing the dependency of the treatment time by BCl ₃ plasma on the after-corrosion prevention effect of the Al wiring.

FIG. 4 is a graph showing the dependency of the after-corrosion prevention effect of Al wiring on the presence or absence of BCl ₃ treatment and the gas conditions of the downflow treatment.

FIG. 5 is a graph showing a substrate temperature dependency in a downflow plasma process with respect to an after-corrosion prevention effect of an Al wiring.

FIGS. 6A and 6B are cross-sectional views of a semiconductor device at respective process stages, showing a conventional method for forming a wiring of a semiconductor device.

DESCRIPTION OF SYMBOLS 101, 201 Silicon substrate 102, 202 Silicon oxide film 103, 203 TiN / Ti layer 104, 204 AlCu alloy film 105, 205 TiN layer 106, 206 Mask oxide film pattern 107, 207 Side wall protective film

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/3205 H01L 21/3213 H01L 21/3065 H01L 21/768

Claims (5)

(57) [Claims] A step of forming a metal film mainly composed of aluminum or an aluminum alloy on a main surface of a substrate, a step of forming an oxide film on the metal film, and anisotropically etching the oxide film. forming the oxide film pattern, Cl2
Forming a metal film pattern by anisotropically etching the metal film using the oxide film pattern as a mask by RIE using a mixed gas plasma of N2 and N2. Following the anisotropic etching of step 3, the metal film pattern is mainly exposed to boron trichloride without being exposed to the air.
A method for forming a wiring of a semiconductor device, comprising a step of exposing to gas plasma as a component . 2. The method according to claim 1, wherein a gas plasma mainly containing boron tribromide is used instead of the gas plasma mainly containing boron trichloride. Wherein exposing the metal layer pattern to said gas plasma, formed in the side wall of the metal film pattern A
3. The method for forming a wiring of a semiconductor device according to claim 1, wherein the method is a step of removing a sidewall film containing 1, O, N, Si and Cl . 4. Following the step of exposing the metal film pattern to the gas plasma, exposing the metal film pattern to a down-flow plasma of a gas containing oxygen and hydrogen and substantially containing no halogen element without exposing the metal film pattern to the atmosphere. 4. The method for forming a wiring of a semiconductor device according to claim 1, further comprising the step of exposing. 5. The method according to claim 4, wherein the step of exposing the metal film pattern to the downflow plasma is performed at a substrate temperature of 240 ° C. or higher .