JPH09298188A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the post-treatment process of a dry-etching process and avoid the corrosion and roughing of an Al alloy wiring securely. SOLUTION: An Al alloy film is formed on a silicon substrate 11 with an insulating film 12 therebetween, a resist mask 14 is formed on it and patterned and the Al alloy film is etched by dry-etching to form a wiring layer 13. After that, the resist mask 14 is removed by ashing and then a passivation film 17 is formed on the substrate by using F-based gas plasma and removed by ashing to remove Cl remnants. After that, washing with pure water, drying, washing with alkaline solution and washing with pure water are successively performed to remove the resist remnants 16 and a plasma-polymerized film 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to improvement of a post-treatment process when a wiring using an Al alloy film and a connection hole for the wiring are formed by dry etching.

[0002]

2. Description of the Related Art Conventionally, A has been used for wiring of semiconductor integrated circuits and the like.
An Al alloy film such as 1Si or AlSiCu is used, and dry etching using a resist mask by lithography is generally used for patterning this Al alloy film. Plasma of chlorine (Cl) -based gas is used for dry etching of the Al alloy film. After dry etching, the resist mask is removed by ashing (ashing) using O ₂ plasma or the like, but it is difficult to completely remove the resist exposed to the dry etching plasma only by ashing with O ₂ plasma. The residue remains.

As a method of removing this resist residue,
Conventionally, the following methods have been proposed. After the ashing treatment, a method of washing with an alkaline aqueous solution and then with pure water (see Japanese Patent Laid-Open No. 64-2325). After overashing, or after ashing,
A method of performing an inorganic cleaning by spraying N ₂ gas or the like (see Japanese Patent Laid-Open No. 4-336417).

Further, when the Al alloy film is etched by dry etching using a Cl-based gas, corrosion of the Al alloy wiring (after-corrosion) due to the Cl residue left on the wafer becomes a problem. This is a phenomenon in which when Cl residue is present, HCl is generated during a water washing process or the like, and Al is dissolved by an electrochemical reaction. In particular, it is known that a large amount of HCl is generated if pure water is washed immediately after etching the Al alloy film. Therefore, the following ashing method has been proposed for the purpose of removing resist residues and preventing after-corrosion. After the first ashing treatment, a method of rinsing with an organic solvent and oxidizing the surface of the Al alloy film by the second ashing (Japanese Patent Laid-Open No. Hei 4)
-261016 gazette).

[0005]

However, the previously proposed ashing method is not certain to prevent after-corrosion. One of the reasons is that the plasma polymerized film is formed on the side wall of the Al alloy film wiring by the reaction of the resist and the etching gas in the dry etching process, which repels the alkaline aqueous solution and the organic solvent. The plasma polymerized film is formed on the side wall of the Al alloy film to be etched, and its side wall protection effect brings etching anisotropy. However, due to its water repellency, it is often attached to the wiring side wall together with the plasma polymerized film. It is not possible to reliably remove the remaining Cl residue.

It is considered that covering the surface of the Al alloy film with a passivation film so that it does not come into contact with moisture is effective for suppressing after-corrosion. However, simply covering the surface with a passivation film can remove Cl residues. If not removed, long-term reliability issues remain. Further, even if the gas is switched after etching the Al alloy film to form the passivation film by CHF ₃ -based gas plasma or the like, the occurrence of corrosion still cannot be avoided depending on the subsequent ashing conditions of the resist and the passivation film.

The same problem exists not only in the wiring patterning step but also in the post-treatment of the dry etching step of forming a contact hole in the interlayer insulating film. The interlayer insulating film is Pl-SiO,
In the case of a silicon oxide film such as Pl-TEOS, since fluorine (F) -based gas plasma is used for dry etching, after-corrosion does not become a problem, but a plasma polymerized film is still formed on the side wall of the connection hole. It cannot be removed by the conventional ashing method. Further, when an alkaline aqueous solution is used for removing the resist residue, there is a problem that the surface of the Al alloy wiring exposed in the connection hole becomes rough.

The present invention has been made in consideration of the above circumstances, and is a method of manufacturing a semiconductor device in which the post-treatment process of the dry etching process is improved so that the corrosion and roughness of the Al alloy wiring can be reliably prevented. Is intended to provide.

[0009]

A method of manufacturing a semiconductor device according to the present invention comprises a step of forming an Al alloy film on a semiconductor substrate via an insulating film, and a resist mask formed on the Al alloy film by patterning. , A by dry etching
l forming an interconnection layer by etching the alloy film, removing the resist mask by ashing, forming a passivation film on the substrate by using a fluorine-based gas plasma, and removing the passivation film by ashing. The method is characterized by including a step of removing the impurities, a step of washing the substrate with pure water and then drying, and a step of washing the substrate with an alkaline aqueous solution and then again with pure water.

A method of manufacturing a semiconductor device according to the present invention is
A step of forming a first wiring layer of an Al alloy film on the semiconductor substrate via a first insulating film, and forming a second insulating film covering the first wiring layer; Patterning a resist mask on the insulating film, and forming a connection hole for the first wiring layer by dry etching the second insulating film; and removing the resist mask by ashing. A step of cleaning the substrate with pure water and then drying, a step of cleaning the substrate with an alkaline aqueous solution, and a second cleaning with pure water, and the first insulating film on the second insulating film through the connection hole. And the step of forming a second wiring layer connected to the wiring layer.

In the present invention, an aqueous solution containing tetramethylammonium hydroxide is preferably used as the alkaline aqueous solution. In the present invention, preferably,
The time for washing with pure water before washing with the alkaline aqueous solution is set to 8 to 12 minutes.

According to the method for forming an Al alloy film wiring according to the present invention, most of the Cl residue is removed by forming a passivation film following the ashing step of the resist mask after etching the Al alloy film and removing the ashing. Corrosion can be prevented. Further, by making the plasma polymerized film hydrophilic by washing with pure water after the passivation film ashing, the resist residue and the plasma polymerized film can be surely removed by subsequent washing with an alkaline aqueous solution.

According to the method of forming the connection hole for the Al alloy film wiring according to the present invention, the plasma polymerized film is made hydrophilic by the pure water cleaning after the resist mask ashing step, and the resist residue is cleaned by the subsequent alkaline aqueous solution cleaning. And the plasma polymerized film can be reliably removed. Further, the Al exposed in the connection hole by the pure water cleaning
Since the surface of the alloy film wiring is oxidized, the surface of the wiring is not roughened by the subsequent cleaning treatment with the alkaline aqueous solution.

In the present invention, the time of washing with pure water prior to the washing with the alkaline aqueous solution is important. If the time for cleaning with pure water is as short as about 5 minutes or less, the plasma polymerized film and the resist residue cannot be reliably removed by the subsequent treatment with the alkaline aqueous solution. On the other hand, if pure water cleaning is performed for a sufficient time of about 15 minutes or more, the plasma polymerized film and the resist residue can be reliably removed, but after-corrosion occurs. It is considered that this is because the battery effect by washing with pure water for a long time becomes remarkable. According to the experiment, by setting the cleaning time of pure water to 8 to 12 minutes, it is possible to reliably remove the plasma polymerized film and the resist residue and prevent corrosion. Furthermore, it is also important to immediately perform drying after washing with pure water prior to washing with an alkaline aqueous solution in order to suppress the occurrence of after-corrosion.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a wiring forming process of a semiconductor device according to an embodiment of the present invention. In FIG. 1A, an Al alloy film is formed on a silicon substrate 11 via an insulating film 12 such as a silicon oxide film, a resist mask 14 is patterned thereon, and the Al alloy film is etched by dry etching. This is a state in which the wiring layer 13 is formed. A
The l alloy film is formed by sputtering, and if necessary, a barrier metal such as a TiN film is formed on the surface thereof.

For dry etching of the Al alloy film, as shown in FIG.
The asher integrated microwave plasma etching apparatus as shown in FIG. That is, the wafer 34 on which the resist mask is patterned is put in the etching chamber 31, and B
The Al alloy film is etched by plasma of Cl ₃ + Cl ₂ gas. At this time, as shown in FIG.
A plasma polymerized film 15 is formed on the side wall of 3 in a crown shape.

After this, the wafer 34 is transferred to the ashing chamber 32 via the transfer section 33, and resist ashing is performed first. In this resist ashing, the temperature of the stage 35 is set to 24 ° C. and the plasma of O ₂ + CHF ₃ gas is used.
Here, a part of Cl in the Cl residue can be replaced with F by introducing a part of CHF ₃ gas into the O ₂ gas. Then, in the same ashing chamber 32, the gas is replaced with C
By switching to only HF ₃ , the passivation film 17 is formed as shown in FIG. FIG. 1B shows a state in which a resist residue 16 that cannot be completely removed by resist ashing remains on the wiring layer 13.

Subsequently, the wafer is taken out from the apparatus of FIG. 3 and the passivation film 17 is ashed by irradiation of O ₃ gas and ultraviolet light in another ashing apparatus. At this time, the temperature of the stage is about 210 ° C., and the ashing processing time is 1 to 2 minutes. By this ashing process, the passivation film 17 is removed as shown in FIG. 1C, and at the same time, the Cl residue in the Al alloy film etching step is removed. As described above, the series of steps from the etching of the Al alloy film to the removal of the ashing of the resist mask and the formation of the passivation film are carried out by using the etching apparatus integrated with the asher without exposing the wafer 34 to the atmosphere. .

After that, the wafer is taken out of the ashing device and first washed with pure water at room temperature for about 10 minutes. For this pure water cleaning, for example, a batch processing cleaning device with a bubbler is used. Immediately after cleaning, the product is dried with a spin dryer, and then alkaline cleaning is performed by spraying an alkaline aqueous solution and holding for 10 seconds. As the alkaline aqueous solution, tetramethylammonium hydroxide TMAH (= (CH ₃ ) ₄ N.
An aqueous solution containing a few% of (OH) is used. Then, again, after cleaning with pure water, a baking process is performed. From the alkaline aqueous solution treatment to the pure water washing treatment and the baking treatment, it is possible to carry out as a continuous treatment by the developer of the batch treatment system. Through the above processing, as shown in FIG. 1D, the plasma polymerized film 15 and the resist residue 16 are reliably removed.

In this example, the effect of removing the plasma-polymerized film and the corrosion resistance (corrosion suppressing effect) when the time of the pure water cleaning treatment prior to the cleaning treatment with the alkaline aqueous solution was variously changed. The results determined by the subsequent observation of the surface condition are summarized in Table 1 below. ◯ is good, Δ is slightly bad, and x is bad.

[0021]

[Table 1]

In the pure water washing treatment for 5 minutes, a small amount of the plasma polymerized film was observed even after the treatment with the alkaline aqueous solution. It is considered that this is because the plasma polymerized film is not sufficiently hydrophilic. By the cleaning treatment for 15 minutes, both the plasma polymerized film and the resist residue were completely removed, but a slight amount of corrosion was observed. An extremely good result has been obtained by washing with pure water for 10 minutes. According to the results of experiments conducted in smaller time increments, it was confirmed that a pure water cleaning treatment for 8 to 12 minutes provided a practically effective effect.

Next, another embodiment of the present invention will be described with reference to FIG. As shown in FIG. 2A, the first insulating film 22 is formed on the silicon substrate 21 with the first Al alloy film interposed therebetween.
The wiring layer 23 is formed. Up to this point, the steps of the previous example are followed. Then, the first wiring layer 23 is covered and the Pl-S
forming a second insulating film 24 such as iO or Pl-TEOS,
A resist mask 25 is patterned thereon, and a connection hole 26 is formed by dry etching. For dry etching of the second insulating film 24, for example, CHF ₃ + CF _{4 is used.}
Gas plasma is used. At this time, a plasma polymerized film 27 is formed on the inner wall of the connection hole 26 as shown in the figure.

After that, as shown in FIG. 2B, the resist mask 25 is removed by ashing with O ₂ gas plasma. As shown, the resist residue 28 remains on the second insulating film 24, and the plasma polymerized film 27 in the connection hole 26 also remains without being removed.

Thereafter, as in the previous embodiment, cleaning with pure water is performed, drying is performed, cleaning treatment with an alkaline aqueous solution is performed, cleaning treatment with pure water is performed again, and then baking is performed. As a result, the resist residue 28 and the plasma polymerized film 27 can be removed as shown in FIG. The time for cleaning with pure water before the cleaning with the alkaline aqueous solution is preferably set to be approximately the same as that in the previous embodiment. If pure water cleaning is not performed prior to the cleaning with the alkaline aqueous solution, the resist residue 28 can be removed, but the plasma polymerized film 27 cannot be removed, and the first wiring layer exposed in the connection hole 26 by the alkaline aqueous solution cleaning process. 23 surface roughness was observed. In addition, this cleaning with pure water could prevent the surface of the first wiring layer 23 from becoming rough. This is because the surface of the first wiring layer 23 is protected by the oxide film.

In the case of this embodiment, since the Cl-based gas is not used in the dry etching for forming the connection hole 26, C
l There is no risk of after-corrosion due to residue,
Therefore, it is possible to increase the time for cleaning with pure water, but it is not preferable to increase the cleaning time longer than necessary in terms of productivity. Further, in the case of this example, the cleaning with the alkaline aqueous solution is performed in the dark portion covered with a cover so that light does not enter the treated portion, so that Cl radicals generated by photoexcitation from the developer component cause Al radical It was found that the battery effect of being scraped can be prevented.

After the above-mentioned processing, an Al alloy film is again sputtered as shown in FIG. 2D, and this is patterned to make a second contact with the first wiring layer 23.
The wiring layer 29 is formed. Even after the dry etching step of the second wiring layer 29, the resist residue is removed and the after-corrosion is prevented by performing the same ashing process as in the previous embodiment.

[0028]

As described above, according to the present invention, the post-treatment process after patterning the Al alloy film by dry etching is improved to reliably remove the resist residue and the plasma polymerized film, and the wiring corrosion due to after-corrosion. It is possible to obtain a semiconductor device having a highly reliable Al alloy film wiring in which the occurrence of the noise does not occur. Further, according to the present invention, the post-treatment process after forming the connection hole by dry etching is improved,
By reliably removing the resist residue and the plasma polymerized film, it is possible to obtain a semiconductor device having a highly reliable multilayer wiring structure formed of an Al alloy film.

[Brief description of drawings]

FIG. 1 shows a manufacturing process of a semiconductor device according to an embodiment of the present invention.

FIG. 2 shows a manufacturing process of a semiconductor device according to another embodiment of the present invention.

FIG. 3 shows an asher-integrated dry etching apparatus used in Examples.

[Explanation of symbols]

11 ... Silicon substrate, 12 ... Insulating film, 13 ... Wiring layer, 1
4 ... Resist mask, 15 ... Plasma polymerized film, 16 ... Resist residue, 17 ... Passivation film, 21 ... Silicon substrate, 22 ... First insulating film, 23 ... First wiring layer, 24
... second insulating film, 25 ... resist mask, 26 ... connection hole, 27 ... plasma thick film, 28 ... resist residue, 29
… Second wiring layer.

Claims (4)

[Claims] 1. A step of forming an Al alloy film on a semiconductor substrate via an insulating film, and a resist mask being patterned on the Al alloy film,
A step of etching the Al alloy film by dry etching to form a wiring layer, a step of removing the resist mask by ashing, a step of forming a passivation film on the substrate using a fluorine-based gas plasma, A semiconductor comprising a step of removing the passivation film by ashing, a step of washing the substrate with pure water and then a drying step, and a step of washing the substrate with an alkaline aqueous solution and then again with pure water. Device manufacturing method. 2. A semiconductor substrate having a first insulating film A
a step of forming a first wiring layer of an alloy film and forming a second insulating film covering the first wiring layer; and forming a resist mask on the second insulating film by patterning and dry etching. A step of forming a connection hole for the first wiring layer by etching the second insulating film according to, a step of ashing and removing the resist mask, a step of cleaning the substrate with pure water and then drying the substrate. A step of washing the substrate with an alkaline aqueous solution and then again with pure water, and forming a second wiring layer on the second insulating film, the second wiring layer being connected to the first wiring layer via the connection hole. A method of manufacturing a semiconductor device, comprising: 3. The method of manufacturing a semiconductor device according to claim 1, wherein the alkaline aqueous solution is an aqueous solution containing tetramethylammonium hydroxide. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the cleaning time with pure water before the cleaning with the alkaline aqueous solution is set to 8 minutes to 12 minutes.