JP3195066B2 - Dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method, and more particularly to a method for removing an etching residue after anisotropically etching a wiring layer of a semiconductor device.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a wiring pattern is formed as follows. First,
An insulating layer and a wiring metal layer are sequentially formed on a semiconductor substrate. Next, a predetermined photoresist pattern is formed on the wiring metal layer. This substrate is placed in a vacuum vessel, an etching gas containing chlorine or bromine is introduced into the vacuum vessel, discharge plasma is generated, and the wiring metal layer is selectively etched by a reactive ion etching (RIE) method. Finally, the resist pattern is removed to form a wiring having a predetermined pattern.

As a metal constituting this wiring, for example, AlSiCu containing Al as a main component is used. However, when such a wiring material is used, a reaction product of the etching gas and Al or Cu having a low vapor pressure adheres to the surface of the insulating layer as an etching residue. In addition, there is also a problem that the deposited film adheres to the side wall of the wiring pattern, and a residue film called a fence remains after the resist pattern is removed.

Conventionally, as a post-treatment after etching of a wiring metal mainly composed of Al, for example, a method of adding 2-propanol and performing ashing (Semiconduc) is used.
to World, 11 (1991)), and a method of adding an H component such as alcohol or acetone to perform ashing (JP-A-3-83337). However, these methods are intended to reduce chlorine remaining after etching to prevent after-corrosion, and the etching residue itself, particularly C
The reaction product of u cannot be removed.

As described above, there is currently no method for removing the etching residue itself. For this reason, etching is performed under conditions that do not produce residues, such as lowering the pressure of the etching gas or increasing the high-frequency output. However, if etching is performed under such conditions, the etching selectivity between the resist and the wiring metal cannot be sufficiently obtained, and the wiring pattern may be thinned or disconnected.

[0006] In addition, the etching product adheres not only to the surface of the substrate but also to the walls and electrodes of the vacuum vessel. This product reduces the reproducibility of etching characteristics and causes metal contamination on the wafer. In addition, in order to remove this product, the vacuum vessel is periodically cleaned in the atmosphere at present, and there are problems in terms of operation efficiency, work efficiency, and safety of the apparatus.

Further, in the future semiconductor devices, those having Cu as a main component as a wiring material will be important. But,
At present, to etch a Cu film using halogen plasma, it is necessary to heat the film to 250 ° C. or higher.
For this reason, a problem arises with respect to the heat resistance of the resist, and it is extremely difficult to anisotropically etch the Cu film.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is
Can be effectively removed by anisotropically etching a wiring layer containing Cu as a main component and containing Cu.
It is an object of the present invention to provide a dry etching method which can also realize dry etching of a wiring layer mainly composed of.

[0009]

According to a first dry etching method of the present invention, a thin film layer mainly containing aluminum and containing copper and a mask layer having a predetermined pattern are formed on a substrate, Is placed in a vacuum vessel, a discharge plasma is generated while introducing an etching gas containing chlorine into the vacuum vessel, and a step of anisotropically etching the thin film layer; ,
Introducing a processing gas containing at least one gas selected from the group consisting of alcohols, ketones and alkyl phosphines into the vacuum vessel, or introducing the processing gas and generating discharge plasma to generate a discharge plasma Removing the etching residue present on the surface.

[0010] The second dry etching method of the present invention comprises:
Forming a thin film layer containing copper as a main component on the substrate and a mask layer having a predetermined pattern thereon,
Installing the substrate in a vacuum vessel, introducing an etching gas containing chlorine into the vacuum vessel and generating discharge plasma, and anisotropically etching the thin film layer;
Subsequent to the anisotropic etching step, a reducing gas is introduced into the vacuum vessel, or a reducing gas is introduced and a discharge plasma is generated to reduce the surface of the etching residue present on the surface of the substrate. And, after the reduction step, introducing a processing gas containing at least one gas selected from the group consisting of alcohol, ketone and alkylphosphine into the vacuum vessel,
Or a step of introducing the processing gas and generating discharge plasma to remove etching residues present on the surface of the substrate.

[0011] The third dry etching method of the present invention comprises:
Forming a wiring layer on a substrate, an insulating layer and a mask layer having a predetermined pattern thereon, installing the substrate in a vacuum vessel, introducing an etching gas containing fluorine into the vacuum vessel, and discharging a discharge plasma. Generating an anisotropic etching of the insulating layer, introducing an etching gas containing chlorine into the vacuum vessel, and generating discharge plasma to convert fluorine of the fluoride layer present on the substrate surface into chlorine. And introducing a processing gas containing at least one gas selected from the group consisting of alcohol, ketone and alkylphosphine into the vacuum vessel, or introducing the processing gas and discharging plasma. it is generated and is characterized by comprising a step of removing the substance layer substituted by chlorine present in the surface of the substrate

[0012] A fourth dry etching method of the present invention comprises:
Forming a thin film layer mainly composed of copper on a substrate surface and a mask layer having a predetermined pattern thereon, setting the substrate in a vacuum container, and introducing an etching gas containing halogen into the vacuum container. Or generating a discharge plasma while introducing the etching gas, and forming a copper halide layer on the surface of the thin film layer, or introducing a processing gas containing alkylphosphine into the vacuum vessel, Or a step of introducing the processing gas and generating discharge plasma to remove the copper halide layer.

The organic compound used as the processing gas in the present invention will be described. Alcohol is ROH
(R is an alkyl group), specifically, ethanol (C ₂ H ₅ OH), propanol (C ₃ H ₇ OH), isopropyl alcohol (i-C ₃ H ₇ OH) and the like. Ketone is a compound having a ketone group (> C = O), specifically, acetone (CH ₃ COCH ₃ ),
Acetylacetone (CH ₃ COCH ₂ COCH ₃ ) and the like can be mentioned. Alkyl phosphine is an alkyl group bonded to phosphorus, and specifically, trimethyl phosphine (P (CH ₃ ) ₃ ), triethyl phosphine (P (C ₂
H _{5) 3),} tripropyl phosphine (P (C ₃ H _7)
3 ) and the like. Further, the alkyl group bonded to phosphorus may be a plurality of different alkyl groups. These gases may be used alone or as a mixture of two or more. Further, these gases may be mixed with a halogen gas or the like.

In the first and second methods of the present invention,
Specifically, the thin film layer containing aluminum as a main component and containing copper has an Al content of 96 wt% or more and a Cu content of 0.1 wt% or more.
01 to 4 wt%. In the second method of the present invention, examples of the reducing gas include CO, H ₂ , and BCl ₃ . In the first, second, third, and fourth methods of the present invention, each step may be repeatedly performed.

[0015]

The present inventors have investigated the composition of etching residues generated when reactive ion etching is performed on a wiring layer containing aluminum as a main component and containing copper, and to find a compound capable of removing the etching residues as follows. Experiment was performed.

First, using a photoresist pattern as an etching mask, AlSiCu (Si: 1 wt%, C
u: 2 wt%) was subjected to reactive ion etching using a mixed gas of Cl ₂ / BCl ₃ under the condition that many residues were generated. AES analysis of the residue revealed that the metal components in the main component were Al and Cu.

Accordingly, Al, Al ₂
Assuming Cu or Cu, the reactivity of these metals with acetylacetone, isopropyl alcohol, trimethylphosphine, or a gas to which a small amount of Cl ₂ was added was studied.

At this time, the apparatus shown in FIG. 1 was used. In FIG. 1, an object 1 is placed in a reaction vessel 11 made of quartz glass. A reaction gas is introduced from a gas introduction port 12 provided at one end of the reaction vessel 11, and exhausted from the other end.
The object 1 is heated by the heater 13, and the reaction temperature is monitored by the thermocouple 14. A measurement window 15 made of KBr is attached to the exhaust port side of the reaction vessel 11 so that an infrared absorption spectrum of the attached reaction product can be measured.

First, the reactivity with each organic compound gas was examined while increasing the temperature of Al, Al ₂ Cu or Cu as the object to be processed. However, the temperature of the object to be processed is 160 ° C.
No reaction was observed. From this,
It turns out that the metal itself does not react with these organic compounds.

Next, the reactivity was examined using a gas obtained by adding a small amount of Cl ₂ to acetylacetone, isopropyl alcohol or trimethylphosphine. The reason for adding Cl ₂ is to create conditions similar to those in which chloride of wiring metal is generated by actual reactive ion etching. As a result, it was found that each metal of Al, Al ₂ Cu or Cu can be etched at a rate of several thousand angstroms / min. The reactivity of each gas was as follows.

For Al, the etching rate was highest when an isopropyl alcohol-based gas was used, and the etching rates were the same when a trimethylphosphine-based gas and an acetylacetone-based gas were used.

For Cu, the etching rate is highest when a trimethylphosphine-based gas is used, followed by the etching rate when an acetylacetone-based gas is used, and the etching rate when an isopropyl alcohol-based gas is used. Was.

Regarding Al ₂ Cu, the same etching rate was obtained with any of trimethylphosphine-based, acetylacetone-based and isopropyl alcohol-based gases. However, it was found that Al was removed when an acetylacetone-based gas or trimethylphosphine-based gas was used, and Cu was removed when an isopropyl alcohol-based gas was used, although a small amount remained although it could be removed. Therefore,
Acetylacetone-based gas or a mixed gas of trimethylphosphine or both and isopropyl alcohol,
Alternatively, etching was performed using a gas to which a small amount of Cl ₂ was added, and it was found that neither Al nor Cu remained. Removal effect was greater that the addition of Cl _2.

When the infrared absorption spectrum of the reaction product attached to the measurement window was measured, Al alcoholate,
The spectra of copper acetylacetone and copper trimethylphosphine were observed.

From the above results, it is inferred that the above-mentioned reaction occurs by the following mechanism. That is,
The surfaces of Al, Al ₂ Cu and Cu are chlorinated to form a chloride layer. The chloride layer reacts with isopropyl alcohol, acetylacetone, and trimethylphosphine to produce alcoholate, acetylacetonate, and trimethylphosphine. As shown in FIG. 2, these reaction products have a sufficiently high vapor pressure in consideration of the pressure and temperature during processing. As a result, etching residues can be removed.

FIG. 2 also shows the vapor pressures of Al chloride and Cu chloride. It can be seen that the vapor pressure of Al chloride is sufficiently high. Actually, Cu-free Al
Even if the wiring layer is anisotropically etched using chlorine gas, no residue remains. On the other hand, since the vapor pressure of Cu chloride is low,
It tends to remain as a residue when anisotropically etching using chlorine gas. In the method of the present invention, from Cu chloride,
Since acetylacetonated copper and trimethylphosphinated copper having a high vapor pressure can be generated and removed, it is particularly effective for removing Cu-based residues.

Based on the above results, AlSi
A residue generated by reactive ion etching of Cu was etched using acetylacetone, isopropyl alcohol, or a gas obtained by adding a small amount of Cl ₂ to trimethylphosphine, and it was found that the residue could be removed.

Even when a similar experiment was carried out by using a parallel plate type plasma etching apparatus and generating plasma of the above organic compound, it was possible to remove the residue.

In the treatment with the above-mentioned organic compound gas, the residue can be more effectively removed as the temperature of the object to be treated is increased. The temperature of the object to be processed is preferably set to 150 ° C. or higher.

By repeatedly performing the reactive ion etching with the chlorine-based gas and the treatment with the above-mentioned organic compound gas on the wiring layer containing Al as the main component and Cu, the residue can be removed and the anisotropic shape can be obtained. A good wiring pattern can be formed.

Further, as a result of examining the residue in more detail, it is presumed that the residue has a structure in which Cu is deposited on Al and the surface of the residue is chloride, and an oxide is present on these surfaces. Was done. Therefore, particularly when a thick Cu-based chloride is formed on the surface of the residue by etching of the wiring layer having a high Cu content, first use acetylacetone, trimethylphosphine, or the like which is effective in removing the Cu-based chloride. It is preferable to carry out the treatment, and then carry out the treatment using isopropyl alcohol or the like which is effective in removing the Al-based chloride, or the treatment using these at the same time.

As described above, it is presumed that an oxide is present on the surface of the residue. Therefore, as in the second method of the present invention, the wiring layer is anisotropically etched and then treated with a reducing gas. If the oxide layer is removed by performing the treatment with the gas of the organic compound, the residue can be more effectively removed. That is, the processing temperature and the processing time can be reduced as compared with the case where no reducing gas is used. In addition, the residue can be more effectively removed by repeating the anisotropic etching, the reducing gas treatment, and the treatment with the organic compound gas.

The method of the present invention can be applied not only to the removal of residues remaining on the surface of the object to be processed, but also to the removal of contaminant deposits adhering to the inner wall of the vacuum vessel. In this case, there is an advantage that the cleaning can be performed without releasing the vacuum container to the atmosphere.

When the insulating layer formed on the wiring layer is anisotropically etched using a fluorine-based gas, fluorides such as AlF _x and CuF _x adhere to the wiring layer. This fluoride layer causes a problem of increasing the contact resistance when forming the second wiring layer on the wiring layer. Therefore, the third chlorine or boric fluorine in the fluoride by plasma treatment of chlorine or boron as in the method of the present invention
By performing treatment using an alcohol, a ketone, or an alkylphosphine after the substitution with the element , the material layer on the surface that has been substituted with the chlorine or boron can be removed.

Further, as in the fourth method of the present invention, after a copper halide layer is formed on the surface of a thin film layer containing copper as a main component, a treatment using a ketone and an alkylphosphine is performed. Since the copper halide layer can be removed in the same manner as described above, anisotropic etching of copper can be achieved by repeating these steps.

[0036]

Embodiments of the present invention will be described below. In the following examples, various wiring metals were etched using the apparatus shown in FIG. 3 or FIG.

In FIG. 3, an electrode 22 for mounting the object 1 is provided in a vacuum vessel 21. The electrode 22 has a built-in heater 23 for controlling the temperature of the processing target 1. This electrode 22 is connected to a high frequency power supply 25 via a blocking capacitor 24. The vacuum vessel 21 also serving as a counter electrode is grounded. A high frequency power supply 2 is provided between the electrode 22 and the vacuum vessel 21.
High frequency power of 5 to 13.56 MHz is applied. Further, the vacuum vessel 21 has gas supply lines 26a, 26b
From the valves 27a, 27b and the flow regulator 28a,
The processing gas is supplied at a predetermined flow rate and pressure through 28b. Further, a measurement window 29 made of a KBr single crystal is provided on two opposing side walls of the vacuum vessel 21 so that an infrared absorption spectrum of a reaction product attached to the measurement window 29 can be measured. ing.

On the other hand, the apparatus shown in FIG. 4 has the same configuration as the apparatus shown in FIG. 3 except that a quartz oscillator 30 is provided instead of the measurement window 29. By examining the change in the oscillation frequency of the crystal oscillator 30, the thickness of the reaction product adhered to the crystal oscillator 30 can be measured.

(Example 1) An example in which a wiring layer mainly composed of Al is anisotropically etched and residues are removed by isopropyl alcohol treatment will be described.

First, an object to be processed shown in FIG. 5 was manufactured. A silicon oxide film 32 serving as an interlayer insulating film was deposited on the silicon substrate 31 to a thickness of 100 nm by a low pressure CVD method. On top of this, 70 nm thick TiN33 and 20 nm thick TN33 are used as barrier metals by sputtering.
i34 was applied. Further, 1.0 wt% of Si and 0.5 wt.
A wiring layer 35 containing wt% of Cu was deposited. Apply photoresist and expose using normal lithography technology,
Development was performed to form a resist pattern 36 having a line and space of 0.5 μm width.

The object to be processed was etched using the apparatus shown in FIG. 3 under the following conditions. The temperature of the object to be processed is set to 25 ° C. or 70 ° C., Cl ₂ gas is 30 SCCM, BC
l ₃ gas was supplied at a flow rate of 38 SCCM to increase the pressure to 2.5.
The Al wiring layer / Ti / TiN was anisotropically etched using the resist pattern 36 as a mask under the conditions of Pa and RF output 150W. Next, the resist pattern 36 was removed by oxygen plasma ashing.

The cross section and the surface of the object to be processed after the etching were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, a sidewall protective film was observed on the side wall of the Al wiring, and a residue was observed on the exposed silicon oxide film. When the side wall protective film and the residue were analyzed by AES, it was found that the main components were Al and Cu.

Further, after the object to be processed shown in FIG. 5 is anisotropically etched under the same conditions as described above, the vacuum vessel is once evacuated, the wafer temperature is set to 70 ° C., and isopropyl alcohol is supplied at a flow rate of 50 SCCM. Pressure 3Pa
And treated for 40 seconds. Next, the resist pattern was removed by oxygen plasma ashing.

In the same manner as described above, the cross section and the surface of the processed object were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, it was found that the residue was completely removed on the side wall protective film on the side wall of the Al wiring and the silicon oxide film.

During the isopropyl alcohol treatment, the IR spectrum of the reaction product attached to the measurement window was measured. FIG. 6 shows the result. The IR spectrum in FIG. 6 was almost the same as the IR spectrum of isopropyl alcohol alone except for strong absorption at 800 cm ⁻¹ or less, and was identified as an alcoholate.

As described above, Al using chlorine-based gas
The sidewall protective film and the residue generated by the anisotropic etching of the wiring metal whose main component is considered to be chlorides of Al and Cu. It is considered that by treating with isopropyl alcohol, these chlorides react with isopropyl alcohol to generate an alcoholate, and since the alcoholate has a high vapor pressure, residues and the like have been removed.

In the above description, the treatment using isopropyl alcohol alone was performed after the anisotropic etching using the chlorine-based gas. However, the same effect was obtained by the isopropyl alcohol plasma treatment.

When the Al wiring containing no Cu was etched under the same conditions as above, no residue was found. Therefore, it can be said that the method of the present invention is effective when dry-etching a wiring metal containing Al as a main component and containing Cu.

(Embodiment 2) An embodiment in which residues are removed by a multi-step method in which anisotropic etching of a wiring layer containing Al as a main component and treatment with isopropyl alcohol are repeated a predetermined number of times will be described.

An object to be processed shown in FIG. 5 was produced in the same manner as in Example 1. Using the apparatus shown in FIG. 3, the Al wiring layer was anisotropically etched with Cl ₂ and BCl ₃ gas under the same conditions as in Example 1 for 40 seconds. The vacuum vessel was once evacuated once, the wafer temperature was set to 70 ° C., isopropyl alcohol was supplied at a flow rate of 50 SCCM, the pressure was maintained at 3 Pa, and the treatment was performed for 20 seconds. Further, exhaustion of the vacuum vessel, anisotropic etching with a chlorine-based gas, exhaustion of the vacuum vessel, and treatment with isopropyl alcohol were repeated. The emission monitor confirmed that the etching of the Al wiring layer was completed when the processing was repeated six times. afterwards,
Cl ₂ and BCl ₃ gases allow Ti /
TiN was anisotropically etched, and the resist pattern was peeled off by oxygen plasma ashing.

In the same manner as described above, the cross section and the surface of the processed object were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, it was found that the residue was completely removed on the side wall protective film and the silicon oxide film on the Al wiring side wall, and the shape of the wiring pattern was almost vertical. In the method of this embodiment, the generation of chloride by etching the wiring layer and the removal of chloride by isopropyl alcohol treatment are repeated, so that chloride, which is a nucleus of the residue, is effectively removed. It is considered that the shape is also good.

In the above description, the treatment with isopropyl alcohol alone was performed after the anisotropic etching using the chlorine-based gas. However, the same effect was obtained by the isopropyl alcohol plasma treatment.

(Embodiment 3) An embodiment in which a wiring layer mainly containing Al is anisotropically etched, and then a treatment with a reducing gas and a treatment with isopropyl alcohol are sequentially performed to remove the residue will be described.

An object to be processed shown in FIG. 5 was produced in the same manner as in Example 1. Using the apparatus shown in FIG. 3, an Al wiring layer / Ti / Ti was produced under the same conditions as in Example 1 using Cl ₂ and BCl ₃ gases.
N was anisotropically etched. The vacuum vessel was once evacuated once, the wafer temperature was set to 70 ° C., and BCl ₃ was supplied as a reducing gas at a flow rate of 50 SCCM to reduce the pressure to 3C.
The pressure was maintained at Pa, and plasma processing was performed at an RF output of 150 W.
Evacuate the vacuum container again, set the wafer temperature to 70 ° C,
Isopropyl alcohol was supplied at a flow rate of 50 SCCM to maintain the pressure at 3 Pa. Thereafter, the resist pattern was stripped by oxygen plasma ashing.

In the same manner as described above, the cross section and the surface of the processed object were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, it was found that the residue was completely removed on the side wall protective film on the side wall of the Al wiring and the silicon oxide film. In this embodiment, since the plasma treatment with BCl ₃ was performed, the treatment time with isopropyl alcohol required for removing the side wall protective film and the residue was only 16 seconds, which was significantly reduced as compared with the first embodiment. .

Instead of BCl ₃ as the reducing gas, C
Similar effects were obtained when O or H ₂ was used.

This is considered to be due to the following reasons. That is, the surface of the residue is oxidized by residual moisture or residual oxygen at the time of etching, oxygen released from the resist at the time of etching, oxygen originating from the underlying insulating film, or the like. This is supported by the fact that the O ₂ peak was reduced as a result of AES analysis after the residue was subjected to H ₂ plasma treatment. Therefore, it is considered that, by treating the residue with a plasma of a reducing gas, the oxide on the surface of the residue is reduced to expose the surface of the chloride of Al or Cu, and the reaction with isopropyl alcohol easily occurs.

In the above description, the treatment with a reducing gas such as BCl ₃ and the treatment with isopropyl alcohol are performed separately. However, a plasma treatment with a mixed gas of a reducing gas such as BCl ₃ and isopropyl alcohol is performed. Had the same effect.

(Example 4) An example in which residues were removed by a multi-step method in which anisotropic etching of a wiring layer containing Al as a main component, treatment with a reducing gas, and treatment with isopropyl alcohol were repeated a predetermined number of times. explain.

An object to be processed shown in FIG. 5 was produced in the same manner as in Example 1. Using the apparatus shown in FIG. 3, the Al wiring layer was anisotropically etched with Cl ₂ and BCl ₃ gas under the same conditions as in Example 1 for 60 seconds. The vacuum vessel is once evacuated once, the wafer temperature is set to 70 ° C., and B is used as a reducing gas.
Cl ₃ was supplied at a flow rate of 50 SCCM, the pressure was maintained at 3 Pa, and plasma treatment was performed at an RF output of 150 W for 10 seconds. The vacuum vessel was evacuated again, the wafer temperature was set to 70 ° C., isopropyl alcohol was supplied at a flow rate of 50 SCCM, and the pressure was maintained at 3 Pa for 10 seconds. Further, exhaustion of the vacuum vessel, anisotropic etching with a chlorine-based gas, exhaustion of the vacuum vessel, plasma treatment with BCl ₃ , exhaustion of the vacuum vessel, and treatment with isopropyl alcohol were repeated. The emission monitor confirmed that the etching of the Al wiring layer was completed at the time when the processing was repeated four times. After that, Ti _{2 is} added by Cl ₂ and BCl ₃ gas.
/ TiN was anisotropically etched, and the resist pattern was peeled off by oxygen plasma ashing.

In the same manner as described above, the cross section and the surface of the processed object were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, it was found that the residue was completely removed on the side wall protective film on the side wall of the Al wiring and the silicon oxide film.

In the above description, the treatment with a reducing gas such as BCl ₃ and the treatment with isopropyl alcohol are performed separately. However, a plasma treatment with a mixed gas of a reducing gas such as BCl ₃ and isopropyl alcohol is performed. Had the same effect.

Further, in the above Examples 1 to 4, similar effects were obtained also when ethanol, acetylacetone, trimethylphosphine, and triethylphosphine were used instead of isopropyl alcohol.

(Example 5) An example in which wiring layers containing Al as a main component and having different Cu contents are formed and etching residues are removed will be described.

An object to be processed shown in FIG. 5 was produced in the same manner as in Example 1. At this time, three types of wiring layers having a Cu content of 0.1 wt%, 0.5 wt%, and 1 wt% were formed as the Al wiring layers 35.

Using an apparatus shown in FIG. 3, the Al wiring layer / Ti / TiN was anisotropically etched with Cl ₂ and BCl ₃ gas under the same conditions as in Example 1. Next, the resist pattern was removed by oxygen plasma ashing. The cross section and the surface of the object after etching were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, a sidewall protective film was observed on the side wall of the Al wiring, and a residue was observed on the exposed silicon oxide film.
These side wall protective films and residues were analyzed by AES. The sidewall protective film and the residue are mainly composed of Al when the Cu concentration is 0.1 wt%, Al and Cu when the Cu concentration is 0.5 wt%, and Cu when the Cu concentration is 1 wt%. It turned out to be a component.

First, after the object to be processed is anisotropically etched under the same conditions as in Example 1, the vacuum vessel is once evacuated, the wafer temperature is set to 100 ° C., and acetylacetone is supplied at a flow rate of 50 SCCM. The pressure was maintained at 3 Pa and the treatment was performed for 40 seconds. Next, the resist pattern was removed by oxygen plasma ashing.

The cross section and the surface of the processed object were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, the Cu concentration was 0.1 wt%, 0.5 wt%
% And 1 wt%, the removal of the residue progressed, but the residue remained slightly within the treatment time under the above conditions. As a result of analysis by AES, it was found that the main component of this residue was Al.

After the object to be processed was anisotropically etched under the same conditions as in Example 1, the vacuum vessel was once evacuated,
The wafer temperature was set to 70 ° C., isopropyl alcohol was supplied at a flow rate of 50 SCCM, the pressure was maintained at 3 Pa, and the processing was performed for 40 seconds. Next, the resist pattern was removed by oxygen plasma ashing.

The cross section and the surface of the processed object were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, the Cu concentration was 0.1 wt% and 0.5 w%.
In the case of t%, the residue was completely removed on the side wall protective film of the Al wiring side wall and the silicon oxide film. Also, C
When the u concentration was 1 wt%, the removal of the residue proceeded, but some residue remained within the treatment time under the above conditions. As a result of AES analysis, the main component of this residue was C
u.

Further, the wafer was set at a temperature of 100 ° C., acetylacetone was supplied at a flow rate of 50 SCCM, the pressure was maintained at 3 Pa, and the processing was performed for 40 seconds. Subsequently, the object was processed for 40 seconds at a wafer temperature of 70 ° C. in a vacuum vessel, isopropyl alcohol was supplied at a flow rate of 50 SCCM, and the pressure was maintained at 3 Pa. Next, the resist pattern was removed by oxygen plasma ashing.

The cross section and the surface of the processed object were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, the Cu concentration was 0.1 wt%, 0.5 wt%
% And 1 wt%, the residue was completely removed on the side wall protective film of the Al wiring side wall and the silicon oxide film. As described above, the method of this embodiment is also effective for an Al wiring layer having a high Cu content.

The results can be interpreted as follows. As described above, it is considered that the residue after the etching of the Al wiring metal containing Cu has a structure in which Cu is deposited on Al and the surface thereof is chloride. Therefore, the treatment with acetylacetone converts and removes the Cu-based chloride into copper acetylacetone having a high vapor pressure, and the treatment with isopropyl alcohol converts the Al-based chloride into Al alcoholate having a high vapor pressure. Removed. Actually, when the IR spectrum was measured in the measurement window during the above treatment, copper acetylacetone and Al alcoholate were detected.

In the case of the Al wiring layer having a low Cu concentration, the same effect as described above was obtained by using ethanol instead of isopropyl alcohol. On the other hand, in the case of an Al wiring layer having a high Cu concentration, instead of acetylacetone,
Even when trimethylphosphine and triethylphosphine were used, the same effect as described above was obtained.

In the above description, the acetylacetone treatment and the isopropyl alcohol treatment are performed after the anisotropic etching using the chlorine-based gas. However, the same effect can be obtained by the acetylacetone plasma treatment and the isopropyl alcohol plasma treatment. Was. Furthermore, the treatment can be performed using acetylacetone and isopropyl alcohol simultaneously.

(Embodiment 6) An embodiment in which the inner wall of a vacuum vessel is dry-cleaned using isopropyl alcohol will be described.

A sample in which a large amount of metal film containing Al as a main component and containing 1.0% by weight of Si and 0.5% by weight of Cu was placed in a vacuum vessel, and Cl ₂ gas was supplied to 76SCC.
M and BCl ₃ gas were supplied at a flow rate of 60 SCCM, the pressure was maintained at 3 Pa, and the metal film was etched at an RF output of 150 W. The sample was etched again in this vacuum container, and the number of particles having a size of 0.5 μm or less was measured. The result was 1328 particles / wafer, indicating that the contamination of the inner wall of the vacuum container was considerably advanced.

The vacuum vessel is evacuated once, the wafer is not put in, the temperature of the inner wall of the vacuum vessel and the electrode are set to 70 ° C., and isopropyl alcohol is introduced so that the pressure in the vacuum vessel becomes 3 Pa. Plasma was generated under the condition of 150 W and left for a certain time. During this time, the emission of Al was observed by emission analysis in the vacuum vessel.
The light emission of 1 gradually weakened and disappeared after 260 seconds. When the IR spectrum was measured in the measurement window, Al alcoholate was detected. The vacuum container was evacuated again, the sample was etched, and the number of particles having a size of 0.5 μm or less was measured. This is considered to be mainly due to the fact that the inner wall of the vacuum vessel was significantly cleaned.

An experiment similar to the above was performed using an apparatus having a crystal oscillator 30 shown in FIG. As a result, after intentionally contaminating the inside of the vacuum vessel, the film thickness of the contaminated deposits attached to the quartz oscillator 30 was 1.86 μm. On the other hand, after the isopropyl alcohol treatment, the film thickness of the contaminant deposits attached to the quartz oscillator 30 was below the detection limit.

By performing the isopropyl alcohol treatment on the inner wall of the vacuum vessel contaminated as described above, dry cleaning can be performed. Further, by monitoring the film thickness of the contaminated deposits, the cleaning time of the vacuum container can be accurately grasped, and the particles can be prevented from adhering to the object to be processed.

The same effect as described above was obtained when ethanol, acetylacetone, trimethylphosphine, or triethylphosphine was used instead of isopropyl alcohol.

(Embodiment 7) An effective method for forming a contact hole by anisotropically etching an insulating layer on a wiring layer will be described.

First, as shown in FIG. 7A, a silicon oxide film 32 serving as an interlayer insulating film was deposited on a silicon substrate 31 to a thickness of 100 nm by a low pressure CVD method. On top of this, 70 nm thick TiN33 and 20 nm thick Ti34 were deposited as barrier metals by sputtering. A wiring layer 35 composed mainly of Al and containing 1.0 wt% of Si and 0.5 wt% of Cu was deposited thereon by sputtering. A photoresist was applied, exposed and developed using a normal lithography technique, to form a resist pattern 36 having a 0.5 μm width line and space.

The object to be processed was etched using the apparatus shown in FIG. 3 under the following conditions. The temperature of the object is set to 70 ° C., Cl ₂ gas is 30 SCCM, and BCl ₃ gas is 3
The resist pattern 36 was supplied at a flow rate of 8 SCCM and the pressure was maintained at 2.5 Pa.
Was used as a mask to anisotropically etch the Al wiring layer / Ti / TiN. Next, the resist pattern 36 was removed by oxygen plasma ashing.

Next, as shown in FIG.
A silicon oxide film 37 was deposited as an interlayer insulating film by Method D. A photoresist was applied, and exposed and developed using a normal lithography technique, to form a resist pattern 38.

Further, as shown in FIG. 7C, using the resist pattern 38 as a mask, a contact hole was formed by reactive ion etching of the silicon oxide film 37 with a mixed gas of CHF ₃ / CO. Next, the resist pattern 38 was removed by oxygen plasma ashing.

At this stage, the exposed surface of the Al wiring is
When measured by ES, a large amount of F was detected. FIG.
After the step (c), tungsten was buried in the contact holes by a low pressure CVD method. When the contact resistance between Al and W was measured, it was 0.9 Ω / μm ² .

On the other hand, after the step of FIG. 7 (c), the vacuum vessel was once evacuated, BCl ₃ was introduced, the pressure was set to 3 Pa, and the exposed Al wiring was connected to BCl ₃ gas under the condition of RF output 150W. The plasma was exposed for 2 minutes at room temperature. At this stage, when the surface of the exposed Al wiring was measured by AES, F was hardly detected and Cl was detected. B
After the Cl ₃ gas plasma treatment, the temperature of the object
C., isopropyl alcohol was introduced into the vacuum vessel to maintain the pressure at 3 Pa, and the exposed Al wiring was exposed to an isopropyl alcohol atmosphere for 3 minutes. Then
Tungsten was buried in the contact hole by a low pressure CVD method. When the contact resistance between Al-W was measured,
0.2 Ω / μm ² , which was significantly reduced.

The results can be interpreted as follows. When the silicon oxide film is subjected to reactive ion etching using an F-based gas in the step of FIG. 7C, AlF _x and AlOF _x are generated on the surface of the Al wiring. Next, when the surface of the Al wiring is treated with BCl ₃ gas plasma, F is replaced with Cl, and AlCl _x and AlOCl _x are generated on the surface of the Al wiring. When the surface of the Al wiring is treated with isopropyl alcohol, AlCl _x and AlOCl _x are converted into alcoholates and thus removed. Therefore, the contact resistance between Al and W embedded in the contact hole is significantly reduced as compared with a case where such a treatment is not performed.

Note that the present invention is effective also in the case of copper wiring other than Al wiring. The same effect as described above was obtained also when ethanol, acetylacetone, trimethylphosphine, and triethylphosphine were used instead of isopropyl alcohol.

Further, in Examples 1 to 7, the gas containing chlorine was used as the etching gas for the aluminum film containing copper and the copper film, but a gas containing bromine such as bromine or hydrogen bromide may be used.

(Embodiment 8) An embodiment in which a Cu wiring layer is dry-etched will be described.

First, as shown in FIG. 8A, a silicon oxide film 32 serving as an interlayer insulating film was deposited on a silicon substrate 31 to a thickness of 100 nm by a low pressure CVD method. An 800 nm-thick Cu film 41 was deposited thereon by a sputtering method. A photoresist was applied, exposed and developed using a normal lithography technique, to form a resist pattern 42 having a 0.5 μm-wide line and space. This object is placed in a vacuum vessel,
A Cl ₂ gas is supplied at a pressure of 3 Pa and at room temperature, and the resist pattern 42 is used as a mask to expose the surface of the Cu film 41 by anisotropic chlorination by exposing to Cl ₂ gas plasma at room temperature and RF output of 150 W. A chloride layer 43 having a thickness of 150 Å was formed. Note that the above plasma treatment is not necessarily required, and treatment in combination with heat treatment may be performed.

Next, as shown in FIG. 8B, the inside of the vacuum vessel was once evacuated, acetylacetone was introduced, the pressure was set to 20 Pa, and the temperature was set to 160 ° C. for processing. next,
The resist pattern 42 was removed by oxygen plasma ashing. The cross section and the surface of the object were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, it was found that the chloride layer 43 was removed and anisotropic etching was possible.

Further, by repeating the anisotropic chlorination and acetylacetone treatment before stripping the resist pattern 42, fine processing of the Cu wiring could be realized as shown in FIG. 8 (c).

Similar effects were obtained when trimethylphosphine or triethylphosphine was used instead of acetylacetone. In the above description, the acetylacetone treatment is performed after the anisotropic chlorination, but the same effect can be obtained by performing the acetylacetone plasma treatment.

Further, the surface of the copper film may be halogenated using another gas containing chlorine or a halogen other than chlorine, for example, a gas containing bromine.

In Examples 1 to 8, the wafer temperature was set at 100 ° C. during the acetylacetone treatment and at 70 ° C. during the isopropyl alcohol treatment. However, the higher the wafer temperature, the shorter the processing time. Further, for the treatment with trimethylphosphine which is not described in the above embodiment, the temperature may be set to 40 ° C. or higher. In particular, if the wafer temperature is set to 150 ° C. or higher, the processing time using the above gas can be significantly reduced.

In addition, various modifications can be made without departing from the spirit of the present invention.

[0100]

As described above, by using the method of the present invention, the residue generated by anisotropically etching a wiring layer containing Al as a main component and containing Cu can be effectively removed. Similarly, contaminants attached to the inner wall of the vacuum vessel can be efficiently dry-cleaned. Further, by anisotropically etching the insulating layer on the wiring layer, the fluoride adhering to the wiring layer surface can be effectively removed. Further, dry etching of a wiring layer containing Cu as a main component can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus used for examining a reaction between Al, Al ₂ Cu or Cu and isopropyl alcohol, acetylacetone or triphenylphosphine.

FIG. 2 is a characteristic diagram showing a vapor pressure of a reaction product of an etching residue and isopropyl alcohol, acetylacetone, or triphenylphosphine.

FIG. 3 is a configuration diagram of a dry etching apparatus used in an embodiment of the present invention.

FIG. 4 is a configuration diagram of another dry etching apparatus used in the embodiment of the present invention.

FIG. 5 is a cross-sectional view of a semiconductor device having a wiring metal layer formed in Embodiment 1 of the present invention.

FIG. 6 is an infrared absorption spectrum diagram of a reaction product of an etching residue and isopropyl alcohol.

FIGS. 7A to 7C are cross-sectional views illustrating steps of forming a metal wiring according to a seventh embodiment of the present invention.

FIGS. 8A to 8C are cross-sectional views illustrating a process of forming a metal wiring in Example 8 of the present invention.

[Explanation of symbols]

21: vacuum vessel, 22: electrode, 23: heater, 24: blocking capacitor, 25: high-frequency power supply, 26a, 2
6b: gas supply line, 27a, 27b: valve, 28
a, 28b: flow regulator, 29: measuring window, 30: crystal oscillator, 31: silicon substrate, 32: oxide film, 33: Ti
N, 34: Ti, 35: wiring layer, 36: resist pattern, 37: silicon oxide film, 38: resist pattern,
41: Cu film, 42: resist pattern, 43: chloride layer.

Continuation of the front page (72) Inventor Haruo Okano 1 Toshiba-cho, Komukai, Koyuki-ku, Kawasaki-city, Kanagawa Prefecture (56) References JP-A-4-188724 (JP, A) JP-A-55- 91842 (JP, A) JP-A-3-173125 (JP, A) JP-A 1-215986 (JP, A) JP-A-60-86285 (JP, A) JP-A 4-159718 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/3065 C23F 4/00

Claims (4)

(57) [Claims] 1. A thin film layer containing aluminum as a main component and copper and a mask layer having a predetermined pattern are formed on a substrate, the substrate is placed in a vacuum vessel, and chlorine is introduced into the vacuum vessel. A step of introducing an etching gas containing the gas and generating a discharge plasma to anisotropically etch the thin film layer; and following the anisotropic etching step, a group consisting of alcohol, ketone and alkylphosphine in the vacuum vessel. Introducing a processing gas containing at least one type of gas selected from the group consisting of: (a) introducing the processing gas and generating discharge plasma to remove etching residues present on the surface of the substrate; A dry etching method characterized in that: 2. A thin film layer containing aluminum as a main component and containing copper and a mask layer having a predetermined pattern are formed on a substrate, the substrate is placed in a vacuum vessel, and chlorine is introduced into the vacuum vessel. A step of introducing discharge gas containing the gas and generating a discharge plasma to anisotropically etch the thin film layer, and, following the anisotropic etching step, introducing a reducing gas into the vacuum vessel, or A step of introducing a reducing gas and generating discharge plasma to reduce the surface of the etching residue present on the surface of the substrate; and, following the reducing step, alcohol in the vacuum vessel;
Introducing a processing gas containing at least one gas selected from the group consisting of ketones and alkyl phosphines, or generating a discharge plasma while introducing the processing gas to generate an etching residue present on the surface of the substrate And a step of removing. 3. A wiring layer, an insulating layer, and a mask layer having a predetermined pattern are formed on a substrate, the substrate is placed in a vacuum vessel, and an etching gas containing fluorine is introduced into the vacuum vessel. Simultaneously generating a discharge plasma and anisotropically etching the insulating layer; introducing an etching gas containing chlorine into the vacuum vessel and generating a discharge plasma to form a fluoride existing on the surface of the substrate; Replacing fluorine in the layer with chlorine ; and introducing a processing gas containing at least one gas selected from the group consisting of alcohol, ketone and alkylphosphine into the vacuum vessel, or introducing the processing gas. by generating discharge plasma as well as a feature that it has and a step of removing the substance layer substituted by chlorine present in the surface of the substrate Dry etching method that. 4. A thin film layer containing copper as a main component on a substrate surface and a mask layer having a predetermined pattern formed thereon.
The substrate is placed in a vacuum vessel, and an etching gas containing halogen is introduced into the vacuum vessel, or a discharge plasma is generated while introducing the etching gas,
Forming a copper halide layer on the surface of the thin film layer; and introducing a processing gas containing alkyl phosphine into the vacuum vessel, or generating a discharge plasma while introducing the processing gas to form the copper. A step of removing the halide layer.