JP3198599B2 - Method of forming aluminum-based pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an aluminum (Al) -based pattern applied in the field of manufacturing semiconductor devices and the like, and more particularly to improvement of resist selectivity and reduction of particle contamination in dry etching of an Al-based material layer. And methods for suppressing after-corrosion.

[0002]

2. Description of the Related Art As an electrode wiring material of a semiconductor device, A
or an Al-Si alloy to which 1-2% silicon (Si) is added, and an Al to which 0.5-1% copper (Cu) is added as a measure against stress migration
Al-based materials such as -Si-Cu alloys are widely used.

[0003] Dry etching of an Al-based material layer is generally performed using a chlorine-based gas. For example, BCl ₃ / Cl disclosed in JP-B-59-22374 is disclosed.
_Two- mixed gas is a typical example. The chemical species that contributes as the main etching species in the etching of the Al-based material layer is C
l ^* (chlorine radical), which promotes spontaneous and extremely rapid etching reaction. However, since etching proceeds isotropically with Cl ^* alone, the ion assist reaction usually proceeds under conditions where the incident ion energy is increased to some extent, and the decomposition and generation of the resist mask sputtered by the incident ions. High selectivity is achieved by using the material as a sidewall protective film. BCl ₃ is Al
Is a compound added to reduce the natural oxide film on the surface of the system material layer, BCl _x as the incident ions
^It also plays an important role in supplying ⁺ .

[0004]

By the way, as described above, a certain amount of incident ions and
In the process of sputtering a resist mask using energy, there is inevitably a problem of reduced resist selectivity. The resist selectivity in a typical process is only on the order of two. Such low selectivity causes a dimensional conversion difference from a resist mask in processing of a fine wiring pattern, or causes deterioration of an anisotropic shape.

On the other hand, under the design rules of highly miniaturized semiconductor devices, it is required to reduce the thickness of a resist coating film from the viewpoint of improving resolution in photolithography. Therefore, it is becoming difficult to achieve both high resolution based on a thin resist coating and high-precision etching through a resist mask formed from the resist coating.

To cope with this problem, a method of depositing a reaction product on the surface of a resist mask has been conventionally proposed. For example, see the 33rd Integrated Circuit Symposium Proceedings (1987), p. No. 114 reports a process using SiCl ₄ as an etching gas. This is to improve the etching resistance of the resist mask by coating the surface of the resist mask with Si.

[0007] Also, Proceedings of
he 11th Symposium on Dry
Process, p. 45, II-2, (1989) has been reported process using BBr _3. This is intended to further enhance the etching resistance of the resist mask by coating the surface of the resist mask with CBr _x . Regarding the protection mechanism of the resist mask by CBr _x, etc., see the monthly Semiconductor World, December 1990 issue, p.
7 (published by Press Journal), and a value of about 5 is reported as a resist selectivity.

However, in order to achieve the resist selectivity at the above-described level, it is necessary to deposit Si and CBr _x in a considerably large amount, and there is a great possibility that the particle level will be deteriorated in an actual production line. Therefore, an object of the present invention is to solve the above-mentioned problems and to provide an Al-based pattern forming method capable of achieving high resist selectivity while suppressing particle contamination.

[0009]

According to the method of forming an Al-based pattern of the present invention, an aluminum-based material layer on a substrate is formed by using a halogen-based compound selected from chlorine gas and sulfur chloride gas as an etching gas, Is characterized in that etching is performed while the film quality of the carbon-based polymer is enhanced by the addition of.

According to the present invention, a halogen-based compound is used as an etching gas in an aluminum-based material layer on a substrate, and a sulfur-based compound capable of releasing sulfur into plasma under discharge dissociation conditions and carbonyl sulfide are added. Thus, the etching is performed while enhancing the deposition of S and enhancing the film quality of the carbon-based polymer.

The present invention is further characterized in that after the etching of the Al-based material layer is completed, a plasma process is performed using a processing gas containing a fluorine-based compound while heating the substrate.

[0012]

In the present invention, a mixed system containing at least carbonyl sulfide (COS) and a halogen-based compound is used as an etching gas for the Al-based material layer. Here, the halogen-based compound is added to provide a halogen-based chemical species which is a main etching species of the Al-based material layer.

On the other hand, COS is added to enhance the film quality of the carbon-based polymer. The greatest point of the present invention is that a sufficiently high resist selectivity is achieved by reducing the deposition amount by strengthening the carbon-based polymer. COS has a linear molecular structure of O = C = S, and the carbonyl group in the molecule has a high polymerization promoting activity, thereby increasing the degree of polymerization of the carbon-based polymer.
Increases resistance to ion incidence and radical attack. Further, when a carbonyl group is introduced into a carbon-based polymer, chemical and physical stability is increased as compared with a conventional carbon-based polymer having a repeating structure of -CX _2- (X represents a halogen atom). Has also been clarified by recent studies. This is intuitively understood from the comparison of the bond energy between two atoms that the C—O bond (1077 kJ / mol) is much larger than the C—C bond (607 kJ / mol). Furthermore, the introduction of the carbonyl group increases the polarity of the carbon-based polymer, and increases the electrostatic attraction force of the negatively charged wafer during etching, thereby improving the surface protection effect of the carbon-based polymer. .

Further, carbonyl sulfide can release S (sulfur) under discharge dissociation conditions. This S is deposited on the surface of the wafer if the temperature is controlled to be approximately equal to or lower than room temperature, depending on conditions, and contributes to the protection of the side wall or the surface of the base. In addition, if the wafer is heated to about 90 ° C. or higher, it easily sublimates, and S itself does not become a source of particle contamination.

[0015] As described above, the film quality of the carbon-based polymer itself is enhanced, and the deposition of S can be expected.
Energy can be reduced and resist selectivity can be improved. This makes it possible to etch practically even from relatively thin photoresist coatings.
A mask can be formed, and a difference in processing size conversion can be prevented, but high resolution in photolithography is not sacrificed. In addition, the amount of carbon-based polymer deposited for achieving high anisotropy and high selectivity can be reduced, so that particle contamination can be reduced as compared with the prior art. In addition, the residual chlorine existing in the form of being incorporated into the carbon-based polymer is also reduced, so that the after-corrosion resistance is also improved.

Further, the reduction of the incident ion energy naturally leads to an improvement in the underlayer selectivity.
reduce the sputter of the interlayer insulating film underlying the l-type material layer,
The re-adhesion to the pattern side wall and the like can be suppressed. Therefore, the residual chlorine present in the form of being incorporated into the reattachment is also reduced, and this also makes it possible to effectively suppress after-corrosion.

The present invention is based on the above concept, but also proposes a method for further reducing pollution and damage. The method is the above-mentioned etching and
This is to add a sulfur-based compound capable of releasing sulfur (S) into plasma under discharge dissociation conditions to the gas. In this case, since the deposition of S is enhanced, the incident ions
Energy can be further reduced, and high selection, low pollution, and low damage can be thoroughly achieved. Further, the amount of carbon-based polymer deposited can be relatively reduced, and particle contamination and after-corrosion can be more effectively reduced.

The present invention further proposes a method for thoroughly taking measures against after-corrosion. That is, after the etching of the Al-based material layer is completed, plasma processing is performed using a processing gas containing a fluorine-based compound while heating the substrate (wafer). As a result, the residual chlorine remaining in the vicinity of the pattern is replaced with fluorine, and the vapor pressure of the side wall protective material that binds or occludes the residual chlorine is increased by plasma radiant heat or direct heating of the wafer, etc., thereby facilitating desorption. . Therefore, even if moisture is adsorbed on the etched wafer, a local battery using residual chlorine as an electrolyte is less likely to be formed, and corrosion of the Al-based pattern can be suppressed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

Embodiment 1 In this embodiment, an Al-based multilayer film in which a barrier metal, an Al-1% Si layer, and an antireflection film are sequentially laminated is formed by using a COS / C
This is an example in which etching is performed using a l ₂ mixed gas. This process will be described with reference to FIGS. 1 (a), 1 (b) and 1 (d). First, as an example, as shown in FIG. 1A, a barrier metal 4 having a thickness of about 0.13 μm, an Al-1% Si layer 5 having a thickness of about 0.3 μm, and a thickness 5 are formed on the SiO ₂ interlayer insulating film 1. A wafer having an Al-based multilayer film 7 formed by sequentially laminating a TiON anti-reflection film 6 of about 0.1 μm and a resist mask 8 formed thereon was prepared.
Here, the barrier metal 4 includes a Ti layer 2 having a thickness of about 0.03 μm and a TiO layer having a thickness of about 0.1 μm in this order from the lower layer side.
The N layers 3 are sequentially laminated.

This wafer was set in an RF bias application type magnetic field microwave plasma etching apparatus, and as an example, the Al-based multilayer film 7 was etched under the following conditions. COS flow rate 30 SCCM Cl ₂ flow rate 90 SCCM Gas pressure 2 Pa (= 15 mTorr)
r) Microwave power 900 W (2.45 GHz) RF bias power 30 W (13.56 MHz) Wafer temperature Room temperature In this process, the radical reaction using Cl ^*, which is dissociated and generated from Cl ₂ by ECR discharge, as a main etching species is Cl
Etching proceeds by a mechanism assisted by ions such as _x ⁺ , S ⁺ , CO ⁺ , COS ⁺ , and the Al-based multilayer film 7
It was removed in the form of Cl _x , TiCl _x, etc. At the same time, CC derived from the decomposition product of the resist mask 8
l _x is generated, strong carbonaceous polymer was formed additionally carbonyl group is incorporated into its structure. The amount of this carbon-based polymer is not as large as that of the conventional process due to low RF bias power. However, the carbon-based polymer is deposited on the pattern side wall to form a side wall protective film 9 as shown in FIG. Even a small amount exhibited high etching resistance and contributed to anisotropic processing. Further, S was released from COS, and this S also constituted the side wall protective film 9 together with the carbon-based polymer.

As a result, as shown in FIG.
An Al-based wiring pattern 7a having a good anisotropic shape was formed. However, in the drawing, each material layer after patterning is represented by adding a suffix a to the code of the corresponding original material layer. Furthermore, with the RF bias power of the above-described level, the underlying SiO ₂ interlayer insulating film 1 was not sputtered and re-adhered to the pattern side wall portion, and early generation of after-corrosion was suppressed. Note that, in the present embodiment, Al
The etching rate of the system multilayer film 7 was about 950 nm / min, and the resist selectivity was about 5.

After completion of the etching, the wafer was transferred to a plasma ashing device attached to the above etching device, and subjected to O ₂ plasma ashing under normal conditions.
As a result, as shown in FIG. 1D, the resist mask 8 and the sidewall protective film 9 were removed by burning. In the process of this example, the amount of carbon-based polymer produced was small, so that even if the number of wafer treatments was increased, the particle level did not deteriorate.

Embodiment 2 This embodiment is an example in which the same Al-based multilayer film is etched using a COS / S ₂ Cl ₂ mixed gas. First, the wafer shown in FIG. 1A was set in a magnetic field microwave plasma etching apparatus, and as an example, the Al-based multilayer film 7 was etched under the following conditions.

COS flow rate 25 SCCM S ₂ Cl ₂ flow rate 95 SCCM Gas pressure 2 Pa (= 15 mTorr)
r) Microwave power 900 W (2.45 GHz) RF bias power 15 W (13.56 MHz) Wafer temperature 0 ° C. (using ethanol-based refrigerant) Here, the above-mentioned wafer cooling is performed by a cooling pipe buried in a wafer mounting electrode. Then, an ethanol-based refrigerant was supplied from a chiller installed outside the apparatus and circulated.

[0026] In this etching process, CCl _x, CCl _x containing a carbonyl group, other S generating dissociated from COS, S to produce dissociated from S ₂ Cl ₂ was also added to the configuration of the sidewall protection film 9. That is, the deposition amount of S is further increased as compared with the first embodiment. Therefore, although the RF bias power is slightly reduced compared to the first embodiment,
As shown in FIG. 1B, an Al-based wiring pattern 7a having a favorable anisotropic shape could be formed. Although the etching rate of the Al-based multilayer film 7 in this embodiment is slightly lower than that in Embodiment 1 to about 900 nm / min due to the cooling of the wafer and the increase of the deposits, the selectivity to resist is improved to about 10. did. As a result, almost no decrease in the thickness of the resist mask 8 or retreat of the edge was recognized. In addition, the amount of carbon-based polymer produced could be reduced by an amount that could be expected to deposit S, and the under bias was improved to improve the underlayer selectivity, and the sputter re-deposition of the SiO ₂ interlayer insulating film 1 was suppressed. For this reason, after-corrosion resistance has also been greatly improved.

When O ₂ plasma ashing was performed after the etching was completed, the resist mask 8 and the side wall protective film 9 were promptly removed as shown in FIG. Here, although the carbon-based polymer and S are contained in the side wall protective film 9, S is removed by sublimation by plasma radiant heat or reaction heat, and also removed by a combustion reaction by O ^*. There was no particle contamination left.

Embodiment 3 This embodiment is an example in which the same Al-based multilayer film is etched using a COS / S ₂ Cl ₂ mixed gas and then subjected to a plasma treatment using a CF ₄ / O ₂ mixed gas. . This process will be described with reference to FIGS. 1 (a), 1 (b), 1 (c) and 1 (d). First, the wafer shown in FIG. 1A is set in a magnetic field microwave plasma etching apparatus,
The Al-based multilayer film 7 was etched under the same conditions as in Example 2.

Next, the wafer was transferred to a post-processing chamber attached to the etching apparatus, and subjected to a plasma process under the following conditions as an example. CF ₄ flow rate 100 SCCM O ₂ flow rate 50 SCCM Gas pressure 10 Pa (= 75 mTorr)
r) Microwave power 900 W (2.45 GHz) RF bias power 0 W (13.56 MHz) Wafer temperature 100 ° C. By this plasma treatment, as shown in FIG. 1C, the sidewall protective film 9 is quickly removed. Was. The mechanism of this removal is, for carbon-based polymers, combustion by O ^* , increase in vapor pressure by fluorine substitution, etc., and for S, sublimation by wafer heating, combustion by O ^* , and SF _x by F ^*.
And the like.

By this plasma treatment, Cl absorbed or bonded to the resist mask 8 was also replaced by F.

Subsequently, ordinary O ₂ plasma ashing was performed to remove the resist mask 8 as shown in FIG. The wafer after the resist ashing was experimentally opened to the atmosphere, but no after-corrosion was observed even after 96 hours.

Although the present invention has been described based on the three embodiments, the present invention is not limited to these embodiments. For example, as the sulfur-based compound capable of releasing sulfur into plasma under discharge dissociation conditions, in addition to the above-mentioned S ₂ Cl ₂ , sulfur chloride such as S ₃ Cl ₂ and SCl ₂ , S ₃ Br ₂ , S ₂ Br ₂ , sulfur bromide such as SBr ₂ , H ₂ S or the like can be used. S ₂ F ₂ , SF
Sulfur fluorides such as ₂ , SF ₄ and S ₂ F ₁₀ can also release S, but the F ^* generated from these compounds is A
Since it combines with 1 and Ti to generate AlF _x , TiF _x, etc. having a low vapor pressure, it is highly possible to lower the etching rate or deteriorate the particle level, so that the heat resistance of the resist mask is not deteriorated. It is necessary to consider, for example, heating the wafer in the range.

The etching gas used in the present invention includes:
A rare gas such as Ar or He may be appropriately added in the sense of expecting a sputtering effect, a dilution effect, a cooling effect, and the like. As the gas used for the plasma processing, the above-mentioned CF
_{In addition to the 4} / O ₂ mixed gas, an NF ₃ / O ₂ mixed gas or the like can be used.

Further, it goes without saying that the configuration of the sample wafer, the etching apparatus to be used, the etching conditions, and the like can be appropriately changed.

[0035]

As is apparent from the above description, in the present invention, in etching an Al-based material layer, a carbon-based etching gas in which COS is added to a halogen compound that supplies a main etching species is used. High anisotropy and high selectivity can be achieved even when the film quality of the polymer is enhanced and the amount of the polymer deposited is reduced. Therefore, it is possible to prevent the occurrence of the processing size conversion difference, and to greatly improve the after-corrosion resistance. Further, if a sulfur-based compound capable of releasing S under discharge dissociation conditions is added to the etching gas, higher selection, lower contamination, lower damage, and the like can be achieved. In addition, S that has contributed to side wall protection can be easily removed by sublimation and does not cause particle contamination.

Therefore, the present invention is designed based on a fine design rule, and is extremely effective for manufacturing a semiconductor device which requires high integration, high performance and high reliability.

[Brief description of the drawings]

FIGS. 1A and 1B are schematic cross-sectional views showing a process example to which the present invention is applied in the order of steps, wherein FIG. 1A shows a state in which a resist mask is formed on an Al-based multilayer film, and FIG. A state in which an Al-based wiring pattern having an anisotropic shape is formed while being formed, (c) shows a state in which a sidewall protective film is removed, and (d) shows a state in which a resist mask is removed by ashing.

[Explanation of symbols]

1 ... SiO ₂ interlayer insulating film 2 ... Ti layer 3 ... TiON layer 4 ... barrier metal 5 ··· Al-1% Si layer 6 ... TiON antireflection film 7 ... Al system Multilayer film 7a: Al-based wiring pattern 8: Resist mask 9: Side wall protective film

Claims (3)

(57) [Claims] An aluminum-based material layer on a substrate is made of chlorine.
A method for forming an aluminum-based pattern, characterized in that a halogen-based compound selected from a gas and a sulfur chloride gas is used as an etching gas , and etching is performed by adding carbonyl sulfide while enhancing the film quality of a carbon-based polymer. 2. An aluminum-based material layer on a substrate is formed by adding a sulfur-based compound capable of releasing sulfur into plasma under discharge dissociation conditions and carbonyl sulfide while using a halogen-based compound as an etching gas.
A method of forming an aluminum-based pattern, characterized in that etching is performed while enhancing deposition of carbon and enhancing the film quality of a carbon-based polymer. 3. After the etching of the aluminum-based material layer according to claim 1 or 2, plasma processing is performed using a processing gas containing a fluorine-based compound while heating the substrate. Method for forming an aluminum-based pattern.