JPH0574742A - Method for preventing al alloy from corroding after dry etching - Google Patents

Abstract

PURPOSE:To prevent the generation of corrosion subsequent dry etching of an aluminium alloy, which is used as a wiring, by a method wherein after an Al alloy film is subjected to etching treatment, it is rapidly dipped in a solution, which contains one kind of a surface-active agent having a polar group and a non-polar group and does not contain water content. CONSTITUTION:A substrate 2 is etched with Cl2 or Cl-containing gas in a load lock chamber 1. The etched substrate 2 is transferred to a solution treating chamber 6 via a load lock chamber 4 and a transfer unit 5. The substrate 2 is dipped in a solution, which contains alkoxy ethanolamine, desirably 30 to 70wt.% of alkoxy ethanolamine, and a polar solvent and does not contain water and after a necessary time elapses, the substrate 2 is rinsed with pure water. After that, the pure water is immediately shaken off, the substrate is dried or is heated in a drying unit 7 or a surface treatment is performed using O2 or O3. Thereby, the generation of corrosion subsequent to an etching of an Al alloy is prevented, a change in a wiring due to a corrosion preventive treatment is also prevented from being generated and the improvement of the product characteristics of the Al alloy and the yield of the Al is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of preventing corrosion after dry etching of an aluminum alloy used as wiring in manufacturing a semiconductor integrated circuit device.

[0002]

2. Description of the Related Art Conventionally, aluminum alloy (Al-Si, A
1-Si-Cu) is widely used, and a general method is a method of patterning a resist by a photolithography method and then performing dry etching using this resist as a mask.

This dry etching includes chlorine (Cl) as typified by reactive ion etching (RIE).
₂ ) or a gas containing Cl is turned into plasma and processed faithfully to the mask pattern. A large amount of Cl-based residues, mainly Al and Cu chlorides, are attached to the surface of the substrate etched with Cl ₂ or a gas containing Cl. Corrosion occurs.

Such corrosion causes serious problems such as a short circuit between wirings, an increase in wiring resistance, and a decrease in reliability of wirings. Particularly, in the Al alloy containing Cu, the above problem of corrosion is remarkable.

Many methods have been proposed to prevent the above corrosion, and the following methods are being put into practical use.

A gas containing Cl ₂ or Cl
After etching the 1-alloy, it is a mask material by a method of substituting Cl ions with F ions by a gas plasma containing fluorine (F) without exposing to the atmosphere, or by a gas plasma mainly containing oxygen (O ₂ ). By ashing (removing) the resist, removing Cl together with the resist, and oxidizing the Al alloy surface to chemically stabilize it, or by a mixed gas plasma of the gas containing F and O ₂ described above, How to get the effect of two methods.

A gas containing Cl ₂ or Cl
A method of evaporating Cl by heating the substrate after depressurizing or returning to the atmosphere after etching the 1-alloy, or a method of blowing nitrogen (N ₂ ) gas during heating.

A gas containing Cl ₂ or Cl
After etching the 1-alloy, it is returned to the atmosphere and then immediately washed with water to remove residual Cl ions.

A gas containing Cl ₂ or Cl
After etching the 1-alloy, or after adding the method for reducing Cl as described above or above, it is washed with water or immersed in nitric acid, or disclosed in JP-A-62-
No. 281332 or a derivative thereof, or a solution containing a metal, as disclosed in JP-A No. 2-5418, to further enhance the effect of removing residual Cl, and an Al alloy. A method of chemically stabilizing the surface.

It is presumed from these methods that in order to prevent the corrosion of the Al alloy, it is necessary to reduce the residue of Cl ions from the etching of the Al alloy to the standing in the atmosphere, and the An important issue is how to remove residual F by Cl substitution with F remaining after the Cl ion reducing means so as not to cause abnormalities in the wiring.

These wiring irregularities mean that HCl and HF are formed by the residue of Cl and F, which causes corrosion defects in a part of the Al alloy. The Al alloy containing Cu is partially contained in the presence of nitric acid. This means that holes are formed on the surface of the Al alloy to be etched after being melted, and that the Al alloy is melted by being immersed in choline or its derivative, and the wiring width is narrowed.

[0012]

However, in the above-mentioned method, the above-mentioned Al alloy is completely prevented from being corroded, and the Al alloy pattern state is changed during etching with Cl ₂ or a gas containing Cl. It was practically very difficult to stabilize the Al alloy surface after etching without causing it.

In particular, when Al-Si-Cu or Al-Cu is used as the Al alloy and TiW or TiN is used as the barrier metal, it is very difficult to prevent corrosion by any of the above methods.

Further, a method of immersing in the above choline or its derivative (JP-A-62-281332).
In those solutions, 90% by weight or more of water (H
₂ O) is included, and exhibits a strongly basic property under the influence of the water content. Usually, aluminum has a property of being easily dissolved in an acid or a base, and therefore, there is a problem that a part of an aluminum alloy wiring after pattern formation is dissolved and an aluminum alloy wiring hole or a defect is generated.

According to the present invention, the Al alloy described above is replaced by Cl
It is an object of the present invention to provide a method for preventing corrosion after etching with a gas containing ₂ or Cl and maintaining a good Al alloy pattern state during the etching.

[0016]

SUMMARY OF THE INVENTION The present invention relates to an A on a substrate.
l ₂ or Cl _{2 during} the etching treatment of the alloy film
A solution containing a kind of surfactant having a polar group and a non-polar group immediately after etching with a gas containing, and containing no water, more specifically, alkoxy such as monoethanolamine or triethanolamine. It is characterized in that a means for immersing in a solution containing ethanolamine and a polar solvent such as alkylpyrrolidone and dimethylsulfoxide and containing no water is introduced.

As a kind of surfactant solution having the above-mentioned polar group (hydrophilic group) and non-polar group (hydrophobic group) used in the present invention, a mixed solution of alkylpyrrolidone and triethanolamine, dimethyl sulfoxide and There is a mixed solution of monoethanolamine.

It is important that there is no water in the solution, and the content of the alkoxyethanolamine in the solution is preferably in the range of 30 to 70 wt%.

It is considered that the immersion time for the solution treatment is approximately 0.5 to 7 minutes. The treatment solution in this invention is the same as that generally used as a resist stripping agent.

However, if the Al alloy layer is patterned using the resist pattern as a mask by the above-mentioned general dry etching and then taken out into the air and then removed by a stripping agent, corrosion will occur on the surface of the Al alloy, causing a problem. Occurs. That is, it is common to carry out the steps from dry etching to ashing (when using an Al alloy) in a vacuum, but after the ashing, the solvent used as the resist stripping agent is used. The chlorine-based residue can be appropriately removed.

[0021]

In the present invention, since the treatment solution with a kind of surfactant having the polar group and the non-polar group does not contain water, the chloride ion trap does not change to the acid or base side described above. During the treatment, it has an effect of not showing any perforation or corrosion phenomenon to the Al alloy wiring on the element.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of an apparatus for carrying out the present invention. The substrate 2 is transferred from the load lock chamber 1 whose pressure is reduced by the exhaust means P to, for example, the parallel plate RIE processing chamber 3 by a transfer means (not shown). The processing chamber is also depressurized by the vacuum evacuation means P, and a gas containing Cl ₂ or Cl is mainly used as a reaction gas, and the reaction gas can be turned into plasma by high-frequency power to faithfully process the Al alloy on the mask. You can do it.

The above-mentioned processing chamber is not limited to the parallel plate RIE, but the magnetron / R having a higher processing accuracy is used.
IE processing room, electron cyclotron resonance) / (ECR)
It may be a processing chamber according to. The substrate after the etching of the Al alloy is then transferred to the load lock chamber 4 and returned to atmospheric pressure. Here, the single-wafer processing apparatus is shown as a basic example, but the same applies to a batch type processing apparatus having high mass productivity.

Residual Cl on the substrate surface returned to atmospheric pressure
And F-substituted F is attached. Although the description of the F substitution is omitted here, after etching is performed in the processing chamber 3 with Cl ₂ or a gas containing Cl, for example, CF ₄ ,
F substitution may be carried out with CHF ₃ or O ₂ / CF ₄ , O ₂ / CHF ₃ . However, it is usually desirable to install a separate processing chamber for F replacement.

Next, the solution is transferred to the solution processing chamber 6 through the transfer unit 5. In the transfer unit 5, Cl adhering to the substrate reacts with moisture in the atmosphere, and corrosion is most likely to occur. .. Therefore, in the transport unit 5,
It is desirable to transfer the solution to the next solution processing chamber 6 as soon as possible or to provide a means for preventing contact between the atmosphere and the substrate to be processed as N ₂ atmosphere.

Further, it is also preferable to additionally provide means for heating the substrate to be processed and to add a method of positively evaporating Cl or F. In particular, as an Al alloy, Al-Si-C
When TiW is used as a barrier metal for u or Al-Cu, the role of the transport unit 5 is important because corrosion tends to proceed rapidly after being left in the air.

The substrate transferred to the solution unit 6 contains alkoxyethanolamine as a solution, preferably 30
.About.70 wt%, and contains any of polar solvents such as alkylpyrrolidone and dimethylsulfoxide, and does not contain water.

The substrate to be treated is immersed in the solution by a paddle type or a dip type and immediately rinsed with pure water after a required time has elapsed. Immediately after completion of the rinse, the film is shaken off and dried, or heated in the drying unit 7, and if necessary, further surface-treated with O ₂ or O ₃ (ozone).

Next, embodiments of the present invention will be described with reference to specific examples. An insulating film 9 made of a CVD-SiO ₂ film is deposited on the surface of the substrate 8 of FIG.
Was deposited by a sputtering method, and a resist pattern was formed thereon by using ordinary lithography.

Next, as shown in FIG. 2B, dry etching is used to form Al using the resist pattern as a mask.
The alloy layer 10 was patterned. An electron cyclotron resonance type device is used for dry etching, and BCl ₃ 60 [SCCM], Cl ₂ 90 is used as etching gas.
Etching was performed using [SCCM] at a pressure of 10 [mTorr] and a microwave output of 800 [W], the substrate was transported in vacuum, and ashing was performed by a microwave downflow asher. Ashing is O ₂ 200 [SCCM], CF ₄ 1
0 [SCCM], pressure 1 [Torr] microwave output 5
It was conducted under the condition of 00 [W]. In this case, the following Table 1 shows the relationship between the type of gas used for ashing and the time until corrosion occurs when left in the atmosphere.

[Table 1] From this result, it is understood that the mixed gas of O ₂ and CF ₄ is effective in preventing corrosion.

Next, the Al alloy substrate was taken out into the air and immersed in an aqueous solution of choline for 30 seconds, immersed in a mixed solution of monoethanolamine and dimethylsulfoxide for 3 minutes, and immersed in HNO ₃ for 15 minutes. ,
The following experiment was conducted.

First, a substrate treated with each solution was formed,
The open yield of 0.6 μm Al wiring was measured. or,
Al alloy wiring is thin and there is no defect. Scanning electron microscope (SE
M) was used to observe the shape of the Al alloy wiring. The results are shown in Table 2 below.

[0033]

[Table 2]

From the results shown in Table 2 above, it was found that the mixed solution of monoethanolamine + dimethyl sulfoxide was effective in forming the pattern of the Al alloy.

FIG. 3 shows the results of XPS analysis of residual chlorine on the surface of the substrate, which was immersed in a mixed solution of the above monoethanolamine and dimethylsulfoxide and HNO ₃ . According to this figure, it was found that the chlorine concentration on the aluminum alloy surface of the substrate treated with the mixed solution of monoethanolamine + dimethylsulfoxide was extremely low. Comprehensively judging the above results,
It was confirmed that the mixed solution of monoethanolamine and dimethylsulfoxide is very effective in removing residual chlorine and forming an aluminum alloy pattern.

Next, FIG. 4 shows A formed by similar processing.
It is the result of examining the product yield of 1-Si-Cu wiring.
It can be seen that the yield can be remarkably improved as compared with washing with water or nitric acid treatment, and at the same time, it can be seen that there is a correlation with the amount of residual Cl by XPS.

FIG. 5 shows the yield of Al-Si-Cu wiring when the time for immersing the substrate to be treated in the same mixed solution of alkylpyrrolidone and triethanolamine was changed. Within 0.5 to 7 minutes, there was no dependency and a good yield was obtained. Furthermore, the formed Al-Si-Cu (0.5
%) When the wiring is observed by SEM, when the wiring is washed with water, nitric acid, or immersed in choline or a derivative thereof, the Al wiring of the present invention and the tripyrrolidone of the present invention are thinned in comparison with the case where a part of the Al wiring is lost or dissolved and becomes thin. It was confirmed that in the mixed solution of ethanolamine, abnormalities did not occur without exception. Here, the solution treatment in the above-mentioned solution unit 6 will be described in detail below. This solution treatment is performed by using a device as shown in FIG. 6 and sequentially performing a step of applying a solution, a step of leaving the solution for a long time, a step of removing by shaking, a step of washing with pure water, and a step of drying. In the step of applying the solution, it is important that the solution 13 is evenly spread on the substrate 8,
In the experiment, the liquid supply amount was 150 cc / min, the liquid supply time was 5 seconds,
The rotation speed was 1000 rpm. Subsequently, a step of soaking the solution 13 on the substrate 8 was performed for about 10 seconds with the same liquid supply amount. In this step, the leaving time after the solution is stored, which has the effect of moving the solution 13 on the substrate 8, may be the time required for peeling the residue, which is significantly different from the immersion in the solution.
It is not necessary to completely dissolve the residue. The standing time must be changed depending on the amount and quality of the residue, but from the experimental results, 15 seconds or more is sufficient. Then, the process which shakes off the adhered substance which peeled was performed. In the experiment without this step, the residue cannot be completely removed,
Corrosion has occurred. Subsequently, a step of washing with pure water was performed for 30 seconds, and finally, a step of shaking off and drying was performed for 30 seconds. FIG. 7 shows the relationship among the supply of solution, the supply of pure water, and the rotation speed of the turntable 12 in each of the above steps. FIG. 7 shows a case of using the apparatus of FIG. 6, which is composed of one processing chamber, but the steps of washing with pure water and shaking off and drying are performed in different processing chambers by connecting the apparatuses having the same structure. By doing so, the processing time is significantly reduced.

With the above method and apparatus, Al
After etching the alloy, it is possible to completely prevent corrosion, and it is possible to prevent a change in wiring due to a treatment for preventing corrosion. The device capable of obtaining such an effect is not limited to the example described above, but is widely used in Al.
Applicable to alloy etching equipment.

[0039]

As described above in detail, according to the present invention, the corrosion of the Al alloy on the semiconductor element after etching is completely prevented, and naturally the change of the wiring due to the treatment for preventing the corrosion is also prevented. In addition, since the product characteristics are improved and the yield is remarkably increased, the industrial effect is very large.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a method implementation device of the present invention.

FIG. 2 is a sectional view of a substrate.

FIG. 3 is a residual chlorine amount comparison chart.

FIG. 4 is a product yield characteristic diagram.

FIG. 5 is a characteristic diagram of immersion time.

FIG. 6 is an apparatus diagram for performing solution processing.

FIG. 7 is an explanatory diagram of solution processing.

[Explanation of symbols]

 8 substrate 9 insulating layer 10 Al alloy film 11 resist

Claims (1)

[Claims] 1. An aluminum alloy film is deposited on a substrate,
In forming a resist pattern thereon, etching the aluminum alloy film using the resist pattern as a mask, removing the resist pattern, and performing a process for preventing corrosion. In manufacturing a semiconductor device, the corrosion preventing process is performed. Is a kind of surfactant having a polar group and a non-polar group, and a means for immersing in a solution containing no water, a water rinse for removing the treatment solution, and a drying means. A method for preventing corrosion after dry etching of an Al alloy.