JPH06104227A - Dry etching method - Google Patents

Abstract

PURPOSE:To effectively remove a residue produced in the anisotropic etching operation of an interconnection which is composed mainly of Al and which contains Cu by a method wherein an etching gas containing chlorine or bromine is supplied and a discharge plasma is generated. CONSTITUTION:A silicon oxide film 32 to be used as an interlayer insulating film is deposited on a silicon substrate 31. TiN 33 and Ti 34 as a bimetal are applied onto it. An interconnection layer 35 whose main component is Al and which contains Si and Cu is applied onto it. A photoresist is coated, exposed to light and developed, and a resist pattern 36 provided with lines and spaces is formed. Then, Cl2 gas and BCl3 gas are applied to this object to be treated, and the Al interconnection layer 35, the Ti 34 and the TiN 33 are anisotropically etched by making use of the resist pattern 36 as a mask. Then, the resist pattern 36 is stripped by an oxygen plasma ashing operation. Thereby, a residue produced by the anisotropic etching operation can be removed effectively.

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 etching residues 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 the semiconductor substrate. Next, a predetermined photoresist pattern is formed on the wiring metal layer. This substrate is placed in a vacuum container, an etching gas containing chlorine or bromine is introduced into the vacuum container, discharge plasma is generated, and a 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 forming the wiring, for example, AlSiCu containing Al as a main component is used. However, when such a wiring material is used, the 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. Further, the deposited film adheres to the side wall of the wiring pattern, and after removing the resist pattern, a residual film called a fence remains.

Conventionally, as a post-treatment after etching a wiring metal containing Al as a main component, for example, a method of adding 2-propanol and ashing (Semiconduc) is used.
Tor World, 11 (1991)), a method of adding an H component such as alcohol or acetone and performing ashing (JP-A-3-83337) and the like are known. However, these methods are intended to reduce chlorine remaining after etching to prevent after-corrosion, and the etching residue itself, especially 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, the etching is performed under conditions such that the pressure of the etching gas is lowered and the high frequency output is raised so that no residue is generated. 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 stepped.

Further, the etching products adhere not only to the surface of the substrate but also to the wall surface of the vacuum container and the electrodes. This product reduces the reproducibility of etching characteristics and causes metal contamination of the wafer. Moreover, at present, in order to remove this product, the vacuum container is regularly cleaned in the atmosphere, and there are problems in terms of operation efficiency, work efficiency, and safety of the apparatus.

Further, in future semiconductor devices, it is important that the wiring material mainly contains Cu. But,
At present, in order to etch a Cu film using halogen plasma, it is necessary to heat it to 250 ° C. or higher.
Therefore, a problem arises in the heat resistance of the resist, and anisotropic etching of the Cu film is extremely difficult.

[0008]

The object of the present invention is to provide Al
The residue generated by anisotropically etching the wiring layer containing Cu as a main component and containing Cu can be effectively removed.
Another object of the present invention is to provide a dry etching method capable of realizing dry etching of a wiring layer containing as a main component.

[0009]

According to a first dry etching method of the present invention, 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, and the substrate is formed. Is placed in a vacuum container, and a discharge plasma is generated while introducing an etching gas containing chlorine or bromine into the vacuum container, and the step of anisotropically etching the thin film layer, alcohol in the vacuum container, A processing gas containing at least one gas selected from the group consisting of ketone and alkylphosphine is introduced, or the processing gas is introduced and discharge plasma is generated to remove etching residues existing on the surface of the substrate. And a step of removing it.

The second dry etching method of the present invention is
A thin film layer containing copper as a main component of aluminum and a mask layer having a predetermined pattern are formed on the substrate,
Placing the substrate in a vacuum container, introducing an etching gas containing chlorine or bromine into the vacuum container and generating discharge plasma, and anisotropically etching the thin film layer; and Introduce reducing gas,
Or a step of introducing a reducing gas and generating discharge plasma to reduce the surface of the etching residue existing on the surface of the substrate; and at least one selected from the group consisting of alcohol, ketone and alkylphosphine in the vacuum container. A step of introducing a processing gas containing one kind of gas, or introducing the processing gas and generating discharge plasma to remove etching residues existing on the surface of the substrate. To do.

The third dry etching method of the present invention is
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 container, an etching gas containing fluorine is introduced into the vacuum container, and discharge plasma is generated. And a step of anisotropically etching the insulating layer, and introducing an etching gas containing chlorine or bromine into the vacuum container and generating discharge plasma to generate fluorine in the fluoride layer existing on the substrate surface. With chlorine or bromine, and introducing into the vacuum vessel a processing gas containing at least one gas selected from the group consisting of alcohol, ketone and alkylphosphine, or introducing the processing gas. Together with the step of generating discharge plasma to remove etching residues existing on the surface of the substrate. It is intended.

The fourth dry etching method of the present invention is
Whether a thin film layer containing copper as a main component and a mask layer having a predetermined pattern on the surface of the substrate are formed, the substrate is placed in a vacuum container, and an etching gas containing halogen is introduced into the vacuum container. Or a step of introducing discharge gas together with introducing the processing gas to form a copper halide layer on the surface of the thin film layer, and at least selected from the group consisting of ketone and alkylphosphine in the vacuum container. And a step of introducing a processing gas containing one kind of gas or 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), and specific examples thereof include ethanol (C ₂ H ₅ OH), propanol (C ₃ H ₇ OH), and isopropyl alcohol (i-C ₃ H ₇ OH). Ketone is a compound having a ketone group (> C = O), in particular acetone (CH ₃ COCH _3),
Acetylacetone (CH ₃ COCH ₂ COCH ₃₎ and the like. The alkylphosphine is a phosphorus having an alkyl group bonded thereto, and specifically, trimethylphosphine (P (CH ₃ ) ₃ ) and triethylphosphine (P (C ₂
H _{5) 3),} tripropyl phosphine (P (C ₃ H _7)
3 ) and so on. Further, the alkyl group bonded to phosphorus may be a plurality of different alkyl groups. These gases may be used alone or in combination of two or more. Further, these gases may be mixed with 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.
01 to 4 wt%. In the second method of the present invention, the reducing gas may be CO, H ₂ , BCl _3, or the like. In the first, second, third and fourth methods of the present invention, each step may be repeated.

[0015]

The present inventors have investigated the composition of the etching residue generated when the wiring layer containing aluminum as a main component and containing copper is subjected to the reactive ion etching and found the compound capable of removing the etching residue as follows. Experiments were conducted.

First, using the 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 a large number of residues were generated. AES analysis of this residue revealed that the metal components in the main component were Al and Cu.

Therefore, Al and Al _{2 are used} as a model of the residue.
Assuming Cu or Cu, the reactivity of these metals with acetylacetone, isopropyl alcohol, trimethylphosphine, or a gas obtained by adding a small amount of Cl ₂ to them was investigated.

At this time, the apparatus shown in FIG. 1 was used. In FIG. 1, an object 1 to be processed is installed 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 container 11 and exhausted from the other end.
The object 1 to be processed 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 container 11 so that the infrared absorption spectrum of the attached reaction product can be measured.

First, the reactivity of Al, Al ₂ Cu or Cu, which is the object to be treated, with each organic compound gas was examined while raising the temperature. However, the temperature of the object to be processed is 160 ° C.
However, no reaction was observed. From this,
It can be seen that the metal itself does not react with these organic compounds.

Next, the reactivity was investigated 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 the same condition as that in which chloride of the wiring metal is generated by the actual reactive ion etching. As a result, it was found that Al, Al ₂ Cu or each metal of Cu can be etched at a rate of several thousand angstroms / min. The reactivity of each gas was as follows.

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

Regarding Cu, the etching rate is highest when using a trimethylphosphine-based gas, followed by the etching rate when using an acetylacetone-based gas and the etching rate when using an isopropyl alcohol-based gas. It was

With respect to Al ₂ Cu, the same etching rate was obtained with any of trimethylphosphine-based gas, acetylacetone-based gas and isopropyl alcohol-based gas. However, it was found that when acetylacetone-based gas or trimethylphosphine-based gas was used, Al was removed, and when isopropyl alcohol-based gas was used, Cu was removed but remained in a small amount. Therefore,
Acetylacetone-based gas or mixed gas of trimethylphosphine or both and isopropyl alcohol,
Alternatively, when etching was performed using a gas to which a small amount of Cl ₂ was added, it was found that Al and Cu did not remain. The removal effect was greater with the addition of Cl ₂ .

Further, when the infrared absorption spectrum of the reaction product attached to the measurement window was measured, Al alcoholate,
Spectra of copper acetylacetone and copper trimethylphosphine were observed.

From the above results, it is presumed that the above reaction is caused by the following mechanism. That is,
The surface of Al, Al ₂ Cu, Cu is chlorinated to form a chloride layer. This chloride layer reacts with isopropyl alcohol, acetylacetone, and trimethylphosphine to produce alcoholate, acetylacetone compound, and trimethylphosphine compound. As shown in FIG. 2, these reaction products have a sufficiently high vapor pressure in view of the pressure and temperature during processing. As a result, the etching residue can be removed.

Note that FIG. 2 also shows vapor pressures of Al chloride and Cu chloride. It can be seen that the vapor pressure of Al chloride is sufficiently high. Actually, Al that does not contain Cu
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 etched using chlorine gas. In the method of the present invention, from Cu chloride,
Since acetylacetonide 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, the actual AlSi
When the residue produced by reactive ion etching of Cu was etched using a gas obtained by adding a small amount of Cl ₂ to acetylacetone, isopropyl alcohol or trimethylphosphine, it was found that the residue could be removed.

It was possible to remove the residue even when the same experiment was performed by using the parallel plate type plasma etching apparatus to generate the plasma of the organic compound.

When the above-mentioned gas treatment of the organic compound is carried out, the residue can be removed more effectively by raising the temperature of the object to be treated. The temperature of the object to be processed is preferably 150 ° C. or higher.

If the wiring layer containing Al as a main component and Cu is repeatedly subjected to the reactive ion etching with a chlorine-based gas and the treatment with the gas of the above-mentioned organic compound, the residue can be removed and the anisotropic shape can be obtained. It is possible to form a good wiring pattern.

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, the surface of which is a chloride, and further an oxide is present on these surfaces. Was done. Therefore, when a thick Cu-based chloride is formed on the surface of the residue especially by etching 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 that the treatment is performed, and then the treatment is performed using isopropyl alcohol or the like, which is effective in removing the Al-based chloride, or the treatment is performed simultaneously using these.

As described above, since it is presumed that oxides are present on the surface of the residue, as in the second method of the present invention, the wiring layer is anisotropically etched and then treated with a reducing gas. The residue can be removed more effectively by removing the oxide layer by using the organic compound gas and then treating the organic compound with the gas. That is, as compared with the case where no reducing gas is used, the processing temperature can be lowered and the processing time can be shortened. Further, the residue can be removed more effectively 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 the residue remaining on the surface of the object to be processed but also to the removal of the contaminated deposit adhering to the inner wall of the vacuum container. In this case, there is an advantage that the vacuum container can be cleaned without being exposed 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 contact resistance when forming the second wiring layer on the wiring layer. Therefore, if chlorine in the fluoride is replaced with chlorine or bromine by plasma treatment with chlorine or bromine as in the third method of the present invention, and then treatment with alcohol, ketone, or alkylphosphine is performed, chlorine on the surface is removed. Alternatively, the material layer replaced with bromine can be removed.

Further, as in the fourth method of the present invention, if a copper halide layer is formed on the surface of a thin film layer containing copper as a main component and then a treatment with a ketone or an alkylphosphine is carried out, Since the copper halide layer can be removed in the same manner as, the anisotropic etching of copper can be achieved by repeating these steps.

[0036]

EXAMPLES Examples 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 4.

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

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

Example 1 An example will be described in which a wiring layer containing Al as a main component is anisotropically etched and then the residue is removed by isopropyl alcohol treatment.

First, the object to be processed shown in FIG. 5 was produced. 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 that, TiN 33 with a thickness of 70 nm and T with a thickness of 20 nm are used as a barrier metal by a sputtering method.
i34 was deposited. On top of that, 1.0 wt% Si and 0.5
A wiring layer 35 containing wt% Cu was deposited. Apply photoresist and expose using normal lithographic techniques,
Development was performed to form a resist pattern 36 having a line and space width of 0.5 μm.

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

With respect to the object to be processed after etching, the cross section and the surface were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, a side wall 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 protection film and the residue were analyzed by AES, it was found that the main components were Al and Cu.

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

Similarly to the above, the cross-section and the surface of the object to be treated after the treatment 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 protection film on the side wall of the Al wiring and the silicon oxide film.

Also, the IR spectrum of the reaction product adhering to the measurement window was measured during the isopropyl alcohol treatment. The result is shown in FIG. The IR spectrum of 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 gas is used.
The side wall protective film and the residue generated by anisotropic etching of the wiring metal containing as a main component are considered to be chlorides of Al and Cu. It is considered that by treating with isopropyl alcohol, these chlorides and isopropyl alcohol react with each other to form an alcoholate, and the vapor pressure of this alcoholate is high, so that the residue and the like are removed.

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

When an 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.

(Example 2) An example in which the residue is 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.

The object to be processed shown in FIG. 5 was prepared in the same manner as in Example 1. Using the apparatus of FIG. 3, the Al wiring layer was anisotropically etched for 40 seconds with Cl ₂ and BCl ₃ gas under the same conditions as in Example 1. The vacuum vessel was once evacuated as it was, the wafer temperature was set to 70 ° C., isopropyl alcohol was supplied at a flow rate of 50 SCCM to maintain the pressure at 3 Pa, and processing was performed for 20 seconds. Further, evacuation of the vacuum container, anisotropic etching with a chlorine-based gas, evacuation of the vacuum container, and treatment with isopropyl alcohol were repeated. The emission monitor confirmed that the etching of the Al wiring layer was completed when the treatment was repeated 6 times. afterwards,
Ti / of the barrier metal by Cl ₂ and BCl ₃ gas
TiN was anisotropically etched, and the resist pattern was removed by oxygen plasma ashing.

Similarly to the above, the cross-section and the surface of the object to be treated after the treatment 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 protection film on the side wall of the Al wiring and the silicon oxide film, and the shape of the wiring pattern was almost vertical. In the method of the present embodiment, the chloride that forms the core of the residue is effectively removed as a result of repeated generation of chloride by etching the wiring layer and removal of chloride by isopropyl alcohol treatment. It is thought that the shape will be good.

Further, in the above description, the treatment with isopropyl alcohol alone was performed after the anisotropic etching using the chlorine gas, but the same effect was obtained with the isopropyl alcohol plasma treatment.

(Embodiment 3) An embodiment in which the residue is removed by anisotropically etching a wiring layer containing Al as a main component, and then sequentially performing a treatment with a reducing gas and a treatment with isopropyl alcohol will be described.

The object to be processed shown in FIG. 5 was prepared in the same manner as in Example 1. Using the apparatus of FIG. 3 and using Cl ₂ and BCl ₃ gas under the same conditions as in Example 1, Al wiring layer / Ti / Ti
N was anisotropically etched. Evacuate the vacuum vessel as it is, set the wafer temperature to 70 ° C., supply BCl ₃ as a reducing gas at a flow rate of 50 SCCM, and set the pressure to 3
It was maintained at Pa and plasma-treated at an RF output of 150 W.
Evacuate the vacuum vessel again and 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 for processing. Then, the resist pattern was removed by oxygen plasma ashing.

Similarly to the 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 protection film on the side wall of the Al wiring and the silicon oxide film. In this example, since the plasma treatment with BCl ₃ was performed, the treatment time with isopropyl alcohol required to remove the sidewall protective film and the residue was 16 seconds, which was significantly shorter than that in Example 1. .

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

It is considered that this is due to the following reasons. That is, the surface of the residue is oxidized by residual water and residual oxygen during etching, oxygen released from the resist during 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 treated with H ₂ plasma. Therefore, it is considered that by treating the residue with 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, but the mixed gas plasma treatment with a reducing gas such as BCl ₃ and isopropyl alcohol is performed. Also obtained similar effects.

(Example 4) Example in which the residue was 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.

The object to be processed shown in FIG. 5 was prepared in the same manner as in Example 1. Using the apparatus of FIG. 3, the Al wiring layer was anisotropically etched for 60 seconds with Cl ₂ and BCl ₃ gas under the same conditions as in Example 1. Evacuate the vacuum container as it is, set the wafer temperature to 70 ° C., and use B as a reducing gas.
Cl ₃ was supplied at a flow rate of 50 SCCM to maintain the pressure 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, the evacuation of the vacuum container, anisotropic etching with a chlorine-based gas, evacuation of the vacuum container, plasma treatment with BCl ₃ , evacuation of the vacuum container, and treatment with isopropyl alcohol were repeated. The emission monitor confirmed that the etching of the Al wiring layer was completed when the treatment was repeated four times. After that, Ti was added by Cl ₂ and BCl ₃ gas.
/ TiN was anisotropically etched, and the resist pattern was removed by oxygen plasma ashing.

Similarly to the above, the cross section and the surface of the object to be treated after the treatment 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 protection 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 were performed separately, but a mixed gas plasma treatment with a reducing gas such as BCl ₃ and isopropyl alcohol was performed. Also obtained similar effects.

Further, similar effects were obtained when ethanol, acetylacetone, trimethylphosphine or triethylphosphine was used in place of isopropyl alcohol in Examples 1 to 4 above.

(Embodiment 5) An embodiment 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.

The object to be processed shown in FIG. 5 was prepared in the same manner as in Example 1. At this time, as the Al wiring layer 35, three kinds of wiring layers having Cu contents of 0.1 wt%, 0.5 wt%, and 1 wt% were formed.

Using the apparatus shown in FIG. 3 for these objects to be processed, the Al wiring layer / Ti / TiN was anisotropically etched under the same conditions as in Example 1 using Cl ₂ and BCl ₃ gas. Next, the resist pattern was removed by oxygen plasma ashing. Regarding the object to be processed after etching, the cross section and the surface were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, a side wall 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 side wall 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 an ingredient.

Therefore, first, 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 100 ° C., and acetylacetone was 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.

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

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

With respect to the object to be treated after the treatment, the cross section and the surface were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, Cu concentration is 0.1 wt% and 0.5 w
In the case of t%, the residue was completely removed on the side wall protection film on the side wall of the Al wiring and the silicon oxide film. Also, C
When the u concentration was 1 wt%, removal of the residue proceeded, but some residue remained within the processing time under the above conditions. As a result of analysis by AES, the main component of this residue is C
It turned out to be u.

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

With respect to the object to be treated after the treatment, the cross section and the surface were observed with an electron microscope, and the surface was observed with an optical microscope. As a result, the Cu concentration is 0.1 wt%, 0.5 wt
%, The residue was completely removed on the sidewall protection film on the sidewall of the Al wiring 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.

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

In the case of an Al wiring layer having a low Cu concentration, the same effect as above was obtained even when ethanol was used 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 or triethylphosphine was used, the same effect as above was obtained.

Further, in the above description, the acetylacetone treatment and the isopropyl alcohol treatment were performed after the anisotropic etching using the chlorine gas, but the same effect can be obtained by performing the acetylacetone plasma treatment and the isopropyl alcohol plasma treatment. It was Further, the treatment can be performed by simultaneously using acetylacetone and isopropyl alcohol.

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

A sample on which a large amount of a metal film containing Al as a main component and 1.0 wt% Si and 0.5 wt% Cu was formed was placed in a vacuum container, and Cl ₂ gas was added to 76 SCC.
M and BCl ₃ gas were supplied at a flow rate of 60 SCCM to maintain the pressure at 3 Pa, and the metal film was etched at an RF output of 150 W. When the sample was etched again in this vacuum container and the number of particles of 0.5 μm or less was measured, it was 1328 particles / wafer, and it was found that the inner wall of the vacuum container was considerably contaminated.

The vacuum vessel was once evacuated, the temperature of the inner wall of the vacuum vessel and the electrode was set to 70 ° C. without inserting the wafer, and isopropyl alcohol was introduced so that the pressure in the vacuum vessel became 3 Pa. Plasma was generated under the condition of 150 W and left for a certain period of time. During this time, when the emission of Al was observed by the emission analysis in the vacuum container,
The light emission of 1 gradually weakened and disappeared after 260 seconds. Further, when the IR spectrum was measured through the measurement window, Al alcoholate was detected. The vacuum vessel was evacuated again, the above sample was etched, and the number of particles of 0.5 μm or less was measured. As a result, the number was significantly reduced to 4 particles / wafer. This is probably because the inner wall of the vacuum container was largely cleaned.

An experiment similar to the above was carried out using an apparatus equipped with the crystal oscillator 30 shown in FIG. As a result, after the inside of the vacuum container was intentionally contaminated, the film thickness of the contaminated deposit adhered to the crystal oscillator 30 was 1.86 μm. On the other hand, after the isopropyl alcohol treatment, the film thickness of the contaminated deposit adhered to the crystal oscillator 30 was below the detection limit.

Dry cleaning is possible by treating the inner wall of the vacuum container thus contaminated with isopropyl alcohol. Further, by monitoring the film thickness of the contaminated deposit, it is possible to accurately grasp the cleaning time of the vacuum container and prevent particles from adhering to the object to be processed.

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

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

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

This object was etched using the apparatus shown in FIG. 3 under the following conditions. The temperature of the object to be processed is set to 70 ° C., Cl ₂ gas is 30 SCCM, and BCl ₃ gas is 3
It is supplied at a flow rate of 8 SCCM, the pressure is maintained at 2.5 Pa, and the resist pattern 36 is formed under the condition of RF output of 150 W.
The Al wiring layer / Ti / TiN was anisotropically etched using the as a mask. Next, the resist pattern 36 was removed by oxygen plasma ashing.

Next, as shown in FIG. 7B, the reduced pressure CV
A silicon oxide film 37 was deposited as an interlayer insulating film by the D method. A photoresist was applied, and exposure and development were performed using a normal lithography technique to form a resist pattern 38.

Further, as shown in FIG. 7C, the silicon oxide film 37 was subjected to reactive ion etching with a mixed gas of CHF ₃ / CO using the resist pattern 38 as a mask to form a contact hole. 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. Figure 7
After the step (c), tungsten was embedded in the contact hole by the 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. 7C, the vacuum vessel was once evacuated, BCl ₃ was introduced to set the pressure to 3 Pa, and the exposed Al wiring was exposed to BCl ₃ gas under an RF output of 150 W. Exposed to plasma 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 to be treated is set to 70
The temperature was set to 0 ° C., isopropyl alcohol was introduced into the vacuum container to maintain the pressure at 3 Pa, and the exposed Al wiring was exposed to the isopropyl alcohol atmosphere for 3 minutes. Then
Tungsten was embedded in the contact hole by the low pressure CVD method. When the contact resistance between Al and W was measured,
It was 0.2 Ω / μm ² and was greatly reduced.

These 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 Al wiring surface. Next, when the Al wiring surface is subjected to BCl ₃ gas plasma treatment, F is replaced with Cl, and AlCl _x and AlOCl _x are generated on the Al wiring surface. When the surface of the Al wiring is treated with isopropyl alcohol, AlCl _x and AlOCl _x are converted into alcoholates and are removed. Therefore, the contact resistance between Al and W embedded in the contact hole is significantly reduced as compared with the case where such treatment is not performed.

The present invention is also effective for other than Al wiring, for example, copper wiring. Further, when ethanol, acetylacetone, trimethylphosphine, or triethylphosphine was used instead of isopropyl alcohol, the same effect as above was obtained.

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

(Embodiment 8) An embodiment in which the 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 to a thickness of 100 nm on a silicon substrate 31 by a low pressure CVD method. A Cu film 41 having a thickness of 800 nm was deposited thereon by a sputtering method. A photoresist was applied, and exposure and development were performed by using a normal lithography technique to form a resist pattern 42 having a 0.5 μm wide line and space. Place this object in a vacuum container,
Cl ₂ gas is supplied at a pressure of 3 Pa at room temperature, and the resist pattern 42 is used as a mask to expose the exposed Cu film 41 surface to anisotropic chlorination by exposing it 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 plasma treatment described above is not always necessary, and treatment combined 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 this 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 the acetylacetone treatment before peeling the resist pattern 42, the fine processing of the Cu wiring could be realized as shown in FIG. 8C.

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.

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

Although the wafer temperature was set to 100 ° C. during the acetylacetone treatment and 70 ° C. during the isopropyl alcohol treatment in the above Examples 1 to 8, the processing time can be shortened as the wafer temperature increases. Further, regarding the treatment with trimethylphosphine which is not described in the above examples, it is preferable to set the temperature to 40 ° C. or higher. In particular, if the wafer temperature is set to 150 ° C. or higher, the processing time with the above gas can be significantly shortened.

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

[0100]

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

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus used to investigate the reaction of Al, Al ₂ Cu or Cu with 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 example 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 sectional view of a semiconductor device having a wiring metal layer formed in Example 1 of the present invention.

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

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

8A to 8C are cross-sectional views showing a process of forming a metal wiring according to an eighth embodiment of the present invention.

[Explanation of symbols]

21 ... Vacuum container, 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 rate regulator, 29 ... Measurement 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.

Front page continuation (72) Inventor Haruo Okano 1 Komukai Toshiba-cho, Kouki-ku, Kawasaki City, Kanagawa Prefecture

Claims (4)

[Claims] 1. 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 container, and chlorine or chlorine is placed in the vacuum container. Introducing an etching gas containing bromine and generating discharge plasma to anisotropically etch the thin film layer, and at least one selected from the group consisting of alcohol, ketone and alkylphosphine in the vacuum vessel. Introducing a processing gas containing a gas, or introducing the processing gas and generating discharge plasma to remove etching residues existing on the surface of the substrate. . 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 container, and chlorine or chlorine is placed in the vacuum container. Introducing an etching gas containing bromine and generating discharge plasma, anisotropically etching the thin film layer, and introducing a reducing gas into the vacuum container, or introducing a reducing gas and discharging. A step of generating plasma to reduce the surface of the etching residue existing on the surface of the substrate, and a processing gas containing in the vacuum container at least one gas selected from the group consisting of alcohol, ketone and alkylphosphine Of the etching residue present on the surface of the substrate by introducing a treatment gas or generating a discharge plasma with the introduction of the processing gas. And a step of removing the dry etching. 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 container, and an etching gas containing fluorine is introduced into the vacuum container. And discharge plasma is generated to anisotropically etch the insulating layer, and an etching gas containing chlorine or bromine is introduced into the vacuum container and discharge plasma is generated to exist on the substrate surface. Substituting chlorine or bromine for fluorine in the fluoride layer, and introducing into the vacuum vessel a processing gas containing at least one gas selected from the group consisting of alcohols, ketones and alkylphosphines, or A processing gas is introduced and discharge plasma is generated to remove the substance layer substituted with chlorine or bromine existing on the surface of the substrate. A dry etching method comprising the steps of: 4. A thin film layer containing copper as a main component and a mask layer having a predetermined pattern formed on the surface of the substrate,
The substrate is placed in a vacuum container, and an etching gas containing halogen is introduced into the vacuum container, or a discharge plasma is generated together with the introduction of the processing gas to generate a copper halide on the surface of the thin film layer. A step of forming a layer, and introducing a treatment gas containing at least one gas selected from the group consisting of ketone and alkylphosphine into the vacuum vessel, or introducing the treatment gas and generating discharge plasma And a step of removing the copper halide layer.