JP3010699B2 - Method for etching Al-based material film - Google Patents

Description

The present invention relates to a method for etching an Al (aluminum) -based material film. INDUSTRIAL APPLICABILITY The present invention can be widely used in various fields for etching an Al-based material film. For example, in a process of forming an electronic material (semiconductor device or the like), a wiring structure is formed by dry-etching an aluminum-based material film used as a wiring material or the like. It can be applied to the case where it does.

[Summary of the Invention]

The present invention provides an etching method for an Al-based material film in the case of forming a multilayer structure in which an Al-based material film is sandwiched between an upper layer film and a lower layer film, and includes hydrogen as a constituent element in the molecule and has no deposition property. By performing etching using a mixed gas containing 20 to 99% of a gas and containing a gas to be an etchant of a material to be etched, an etching capable of obtaining a good shape is realized.

[Conventional technology]

The etching technique of the Al-based material film is used for forming an Al wiring in a manufacturing process of a semiconductor device, for example. By the way, Al and Al alloy films used as wiring of semiconductor devices, especially semiconductor integrated circuits,
Recently, an Al multilayer structure laminated with a barrier metal has been used. That is, from the viewpoint of migration resistance and reliability of contact resistance, for example, TION / Ti, T
It is being used in iW and barrier metal structures formed with TiW / Ti layers. Further, since reflection on the Al surface may adversely affect lithography patterning, an antireflection film (for example, an inorganic antireflection film as an inorganic antireflection film)
Structures such as a TiON layer have been used.

From such a background, for example, a laminated film having a structure as shown in FIG. 3 has been used. In FIG.
Reference numeral 1 denotes an aluminum-based material film, for example, Al-Si (for example, Si
(Alloy) film containing about 1% by weight of Reference numeral 2 denotes a barrier metal layer, which is a titanium layer 21 and a Ti layer from the side in contact with the Al-based material film 1.
It consists of 22. Reference numeral 3 denotes an antireflection film formed on the surface of the Al-based material film 1, which is a TiON layer here.

However, in order to etch a film having such a multi-layer structure, good etching cannot be achieved even if a conventional condition for etching a single layer of only an Al—Si film with good anisotropy is applied as it is. That is, the third
In the case where the structure shown in the figure is etched with a normal resist mask 4, as shown in FIG.
And the presence of TION, which is the anti-reflection film 3, between the Al-based material film 1 and the TION / Ti, which is the barrier metal layer 2,
Therefore, good processing cannot always be performed under the conventionally known etching conditions.

That is, in this case, it is preferable that the aluminum-based material film 1 and the barrier metal layer 2 are continuously etched, but in this case, the aluminum-based material film 1 is over-etched under the condition that the barrier metal layer 2 is etched. Will be done.

This situation is shown in FIG. FIG. 2 shows a case where the structure shown in FIG. 3 is etched by an ECR etching apparatus under the etching conditions of gas used: BCl ₃ / Cl ₂ = 60/90 SCCM Pressure: 16 mTorr Microwave: 300 mA RF bias: 40 W As shown, whether the barrier metal layer 2 is satisfactorily etched as shown in FIG.
The aluminum-based material film 1 does not have good anisotropy, and the etching proceeds excessively, resulting in undercut.

In order to prevent the occurrence of undercut, if the incident ion energy is increased, the supply amount of the resist decomposition product is increased, and the side wall is protected by a deposit (deposit), an anisotropic shape is obtained. However, since the incident energy of the ions is large, the following problem occurs.

The selectivity for resist and base 5 (such as SiO ₂ ) decreases.

At the time of overetching, O (oxygen atoms) is generated by etching the underlayer 5, the etching rate of the resist increases, and the selectivity to resist further decreases.

Regarding the improvement of the problem of shape deterioration due to the undercut described above, a technique has been proposed in which a deposition (depositing) gas such as SiCl ₄ or CHCl ₃ is positively added to the gas system used to protect the side walls with a deposit. However, in this conventional method, since the gas itself has a deposition property, a deposit (deposition) is generated not only on the material to be etched, for example, on the wafer, but also on the entire etching chamber, and as a result, particles are generated. It is inevitable and does not provide a radical solution.

[Object of the invention]

The present invention seeks to solve the above-mentioned problems. That is, the present invention provides an Al-based material having a good shape even when the structure to be etched is a multilayer film of an Al-based material film and a barrier metal and / or an antireflection film when etching the Al-based material film. The film can be etched, and at the same time, the anisotropy can be improved without increasing ion energy and without adding a deposition gas, and in that case, the resist film is reduced during overetching. It is an object of the present invention to provide an etching technique capable of reducing the amount and further suppressing the generation of particles.

[Means for solving the problem]

In order to achieve the above object, the present invention provides an Al film having a multilayer structure in which an Al-based material film is sandwiched between an upper film and a lower film.
In a method of etching a base material film, a gas containing hydrogen as a constituent element and having no
A configuration is used in which a mixed gas containing 99% and containing a gas serving as an etchant for the material to be etched is used.

In the present invention, the aluminum-based material film refers to a film made of aluminum, an aluminum alloy, an aluminum compound, or a material containing these as components.

Further, a gas containing hydrogen as a constituent element in a molecule (hereinafter, abbreviated as an H-containing gas) refers to a gas which can be decomposed during etching to generate hydrogen atoms (H) from the molecule. Examples include hydrogen halide, hydrogen sulfide, and compounds of hydrogen with other nonmetallic elements. As the H-containing gas, a gas which does not itself have a deposition property is used. That is, a gas containing C or Si in the molecule is not used. As the H-containing gas, at least one selected from the group consisting of HCl, HBr and HF is used.
Preferably, a seed is used.

Further, the mixed gas containing 20 to 99% of the H-containing gas refers to a gas component serving as an etchant for etching the Al-based material film as a material to be etched and the H-containing gas of 20 to 99% in total. % (Volume%, that is, flow rate%). The more preferable content of the H-containing gas is particularly 20 to 50% in consideration of the etch rate.

As a gas to be an etchant, various gases known as etching gases for Al-based materials can be arbitrarily used, and a chlorine-based gas can be preferably used. For example, BCl ₃ , Cl _2, and a mixed gas system thereof are used.
In addition to the gas serving as the etchant and the H-containing gas, other gases may be appropriately added as a diluting gas or the like.

(Operation)

It is considered that the etching method of the present invention exhibits the following operation.

The H-containing gas itself has poor deposition properties, for example, HCl and the like have no deposition properties at all.

During etching, hydrogen generated by the plasma, etc. (H) by reaction of the resist degradation product with (C _z H _y) which is susceptible to deposition of carbon-based material.

Oxygen (O) generated by etching the underlying SiO ₂ or the like at the time of over-etching can be trapped in the form of OH, thereby suppressing an increase in the resist etching rate at the time of over-etching.

According to the present invention, it is considered that the above-described actions work synergistically to bring about an effect. In addition, the best functioning of these effects and the achievement of good etching can be achieved when the H-containing gas is 20 to 99%, preferably 20 to 50%. It was found as a result of examination.

Further, since the added H-containing gas itself does not have a deposition property, there is basically no problem such as an increase in particles. (A technique for improving the shape by adding CHCl ₃ is known. However, this is a problem that when plasma discharge is performed, a deposition atmosphere is formed in all regions in the plasma, and dust is easily generated. There is no danger).

〔Example〕

Hereinafter, embodiments of the present invention will be described. However, needless to say, the present invention is not limited to the embodiments described below.

Example 1 In this example, a barrier metal layer 2 and an antireflection film 3 shown in FIG.
Was used. The Al-based material film 1 is made of Al
-Barrier metal layer 2 consisting of Si alloy (containing 1 wt% of Si)
Is composed of a TiON layer 21 and a Ti layer 22. The anti-reflection film 3 is made of TION
Layer. The underlayer 5 is SiO ₂ .

In the present embodiment, a gas mixture (BCl ₃ / Cl ₂ = 60/90 SCCM) to which a HCl gas was added as an H-containing gas was used for the comparative conventional example (see FIG. 2). Using.
In this embodiment, etching was performed under the following two conditions.

(Etching-) Here, the comparative gas system (BCl ₃ / Cl ₂ = 60 / 90SCCM)
HCl gas, which is an H-containing gas, was added to 40 SCCM. However, in this case, to keep the amount of Cl entering the system constant,
The Cl ₂ flow rate was 70 SCCM. The amount of the H-containing gas is about 23.5.

That is, the etching was performed with an ECR etching apparatus under the following etching conditions.

Gas used: BCl ₃ / Cl ₂ / HCl = 60/70 / 40SCCM Pressure: 16 mTorr Microwave: 300 mA RF bias: 40 W The shape obtained by etching is shown in FIG. The above etching conditions are based on the time required for just etch.
FIG. 1 is a drawing based on a photograph of the case where etching was performed for 78.3 seconds and over-etching was performed for 51.8 seconds. As shown in the figure, the undercut disappeared and the etching was performed with good anisotropy. This is due to the added HC
It is presumed that the gas has enhanced the sidewall protection effect, but details are unknown. However, the just-etching time is only delayed by about 2 seconds, and it is hardly considered to be simply a gas dilution effect.

In the prior art, the process of of H ₂ added 0.5% to 10% is known (JP 57-170537), but the present invention is the action that this is different. That is, in the H ₂ addition of the prior art, with in H ₂ addition, although selectivity to the resist of the etched portion is the direction to decrease, the addition range of the present invention,
There is no reduction in the resist selectivity. For example, under the conditions of this example, an anisotropy was obtained at the time of adding 22% or more, and the effect was recognized.

(Etching-) In order to further observe the above-mentioned effect, the case where the incident ion energy was reduced to 30 W was performed. In this case, 98 SCCM of H-containing HCl is added (about 49.5 H-containing gas).
%) Was effective.

 That is, here, the following conditions were set.

Gas used: BCl ₃ / Cl ₂ / HCl = 60/40 / 98SCCM Pressure: 16 mTorr Microwave: 300 mA RF bias: 30 W The etching results are shown in FIG. FIG. 4 (a)
Is a drawing based on a photograph in which the etching time is 81.8 seconds, which is about 30% overetching, while the just etching time under the above conditions is 62.4 seconds.

As understood from the present embodiment, under this low incident ion energy condition in which the applied RF bias power is 30 W, the effect can be recognized by adding about 50% of the H-containing gas.

The result under both of the above-mentioned etching conditions, that is,
When the RF bias is 40 W, the H-containing gas, HCl, is effective by adding about 22% (etching), and the RF bias is 30 W
Considering the result that the H-containing gas HCl is effective (addition of about 50%) at the time of (1), it is considered that the effect can be obtained by increasing the amount of added HCl when the bias is further reduced.

FIG. 4 (b) shows that the material to be etched which has been separately etched in the same manner as described above is covered with the SiN layer 6 after the resist is removed so that the sectional photograph becomes clear. Drawing is based on the obtained SEM photograph.

As described above, when the present invention is carried out, the effect increases as the amount of H-containing gas such as HCl is increased as the conditions of low incident ion energy are set. This is different from the function of a conventionally known additive gas (0.5 to 10%; Japanese Patent Application Laid-Open No. Sho 57-170537).

Further, the present invention can be carried out with the effect of reducing the amount of resist film loss during overetching. At the time of overetching, for example, an SiO ₂ film as the base 5 is sputter-etched, oxygen is generated, and the etching rate of the resist increases. However, containing H such as HCl
By adding the gas, oxygen can be effectively trapped and the etching rate of the resist can be reduced.

FIG. 5 shows the resist etching rate on SiO ₂ . The horizontal axis shows the flow rate of Cl ₂ / HCl, and the vertical axis shows the etching rates of SiO ₂ and resist. According to the graph II in FIG. 5, the incident energy of ions should not be changed because the etch rate of SiO ₂ is not changed, but by adding HCl,
It can be seen that the etch rate of the resist is reduced (see graph I), and that the amount of reduction in the resist film during overetch can be reduced.

As is clear from the above results, in the case of the present invention, the amount (0.5 to 10%) which is conventionally considered to be appropriate as an additive gas
The effect was observed at a much higher level than
%, The effect also has both shape improvement and resist film reduction. In particular, the effect has not been known as an effect of the additive gas at all, and is an effect that cannot be exhibited by the conventional technology.

As described above, by employing the present invention, anisotropic processing can be performed in a low ion incident energy region where anisotropic etching cannot be performed conventionally.

Based on the above-described embodiment, the fact that the operation of the present invention is different from that of the prior art will be further described as follows.

That is, the addition amount of the H-containing gas such as HCl in the present invention needs to be increased as the incident ion energy is reduced, and the effect and properties of the conventionally known addition gas are different.

For example, according to the above embodiment, the RF bias is 40
In the case of W, it is preferable that the amount of HCl added is greater than 24%, and in the case of 30W, it is considered that a favorable effect is obtained if it is greater than 50%. Thus, the RF bias 40
The inventor's finding that addition of 24% or more of HCl at W and addition of 50% or more at 30W is effective, and that at an RF bias of 50W an anisotropic shape can be obtained without necessarily adding HCl. In consideration of the above, it is easy to understand that, under the conditions of the above embodiment, when the RF bias is further reduced to a value lower than 40 W, the effect can be obtained by increasing the amount of HCl added. Let's do it. According to the extrapolation of the graph of the relationship between the RF bias and the amount of HCl added, 20
With the RF bias of W and 10 W, the added amount of HCl is considered to be about 75% and 99%.

In addition, according to the study of the present inventors, the H-containing gas was reduced to 10 to 99%.
It has been clarified that the effects of the present invention can be obtained by etching with the contained mixed gas.

〔The invention's effect〕

As described above, according to the present invention, various Al-based material films can be favorably etched. For example, the structure to be etched is a via metal and / or an anti-reflection film and the like.
Even in the case of a multilayer film with a base material film, an Al-based material film can be etched in a good shape, and at that time, there is no need to increase ion energy, and there is no need to add a deposition gas. Can be improved. Further, the amount of resist film loss during overetch can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of an etched shape obtained in Example-1. FIG. 2 is a sectional view of an etched shape obtained in a conventional example (comparative example). FIG. 3 is a cross-sectional view showing an example of a material to be etched. 4 (a) and 4 (b) are cross-sectional views of different etching shapes obtained in Example-1. FIG. 5 is a graph showing the dependence of the etching rate of resist and SiO _{2 on} the flow rate of H-containing gas (HCl). 1 ... Aluminum-based material film, 2 ... Via metal layer,
3. Antireflection film.

Claims (2)

(57) [Claims] In an etching method for an Al-based material film having a multilayer structure in which an Al-based material film is sandwiched between an upper film and a lower film, hydrogen is contained in a molecule as a constituent element and has a deposition property. A method of etching an Al-based material film, comprising using a mixed gas containing 20 to 99% of a non-existing gas and containing a gas serving as an etchant for a material to be etched. 2. The gas containing hydrogen as a constituent element in a molecule thereof is at least one selected from the group consisting of HCl, HBr, HF, H ₂ , and H ₂ S.
The method for etching an Al-based material film as described above.