JP3353443B2 - Dry etching method for laminated wiring - 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 dry etching a laminated wiring used for a semiconductor device or the like, and more particularly to a method for dry etching a laminated wiring having a structure in which an Al-based metal layer is formed on a high melting point metal layer. .

[0002]

2. Description of the Related Art The degree of integration of semiconductor devices such as LSIs has increased.
As the design rules are refined from sub-half micron to quarter micron, the pattern width of the internal wiring is also being reduced. Conventionally, low-resistance Al and Al-based alloys have been widely used as internal wiring materials. However, such a reduction in the wiring width causes disconnection due to electromigration or stress migration, which is a major problem in device reliability. Is coming.

[0003] As one of measures against such various migrations, as in Al-Cu and Al-Si-Cu,
Methods such as alloying with a low-resistance metal such as Cu and lamination with a barrier metal such as TiN have been adopted. In recent years, as a more effective wiring structure, a high-melting-point metal such as W, Mo or Ta, an alloy thereof, a compound, etc., which can secure a certain degree of conductivity and a high-rigidity wiring layer is formed below the Al-based metal layer. The formed laminated wiring is being studied. High melting point metals such as W have remarkably higher electromigration resistance than Al-based metals. For example, the 35th Federation of Applied Physics-related lectures (Spring 1988) p642, lecture number 29p-V-9 And is widely known. However, since W has a higher electrical resistance than Al and is difficult to use in a single layer, it is difficult to use both layers. Even if the low-resistance Al-based metal layer is broken, the presence of the underlying high-melting metal layer makes it redundant. It is based on the idea that disconnection can be avoided in the entire wiring layer by utilizing the effect.
Among them, when W is used, it is a material having a relatively low resistance among the refractory metals, and a film formation method by blanket CVD has been established. Therefore, it is expected to be used as a highly reliable laminated wiring structure in the future. .

[0004]

However, in the patterning of a laminated wiring including a structure in which an Al-based metal layer is formed on a high melting point metal layer such as W, anisotropic processing is performed on a plurality of different material layers. The need has brought new difficulties to the dry etching process. That is, the Al-based metal layer is switched to a Cl-based gas and the W layer is switched to an F-based gas for patterning due to a difference in vapor pressure of a halide as an etching reaction product. Figure 3 shows the process problems
This will be described with reference to (a) to (d).

First, as shown in FIG. 3A, a Ti adhesion layer 2, a TiN barrier metal layer 3, a refractory metal layer 4 such as W, an Al-based metal layer 4 are formed on an insulating layer 1 on a semiconductor substrate (not shown). A metal layer 5 and an antireflection layer 6 are applied in this order, and a resist mask 7 for patterning is formed. The anti-reflection layer 6 is used for patterning a resist mask on the Al-based metal layer 5 having high reflectivity to prevent irregular reflection of exposure light and perform exposure with good controllability. This is necessary when there is a step on the surface of the Al-based metal layer 5. Next, when the anti-reflection layer 6 and the Al-based metal layer 5 are etched with a Cl-based etching gas, as shown in FIG. 3B, the AlCl _x -based reaction product is removed together with CCl _x which is a decomposition product of the resist. The resist film 7 adheres to the side surfaces of the patterned antireflection layer 6 and the Al-based metal layer 5 as a sidewall adhesion film 8. Next, the etching gas is switched to an F-based gas, and the refractory metal layer 4, the barrier metal layer 3, and the adhesion layer 2 are etched. At this time, the AlCl _x -based side wall adhered film 8 is exposed to the fluorine plasma to cause replacement of halogen atoms, and is converted to an AlF _x -based side wall altered film 9 as shown in FIG. The side wall altered film 9 is a substance containing AlF ₃ as a main component. This AlF ₃ has a sublimation temperature of 1294 ° C. under the atmospheric pressure, an extremely low vapor pressure, and an acid,
Since it has low solubility in alkalis, water and organic solvents, it cannot be removed with a resist stripper. Also, when resist ashing is performed with O ₂ or O ₃ , the side wall altered film 9 further has Al ₂ O ₃
Since it is converted into a system material and covers the resist mask 7, it interferes with resist ashing, or remains as a fence-like residue after resist ashing as shown in FIG. Particularly in the latter case, it may be called a rabbit ear because of its shape.

[0006] Thus, once the side walls alteration film 9 of AlF _x system is formed, its removal is difficult, deteriorating the step coverage such as an interlayer insulating film formed on the laminated wiring, device failure Cause. Further, the fence-like residue that has been partially peeled off results in particle contamination of the substrate to be etched and the etching apparatus. In order to remove by force, a wet process using a strong mechanical / physical external force such as spin cleaning or scrub cleaning is required, which may cause damage to the device, complicate the process, and decrease the throughput. There is.

In order to control the formation of the AlF _x -based deteriorated film 9, an inorganic material such as SiO ₂ is used as a mask.
It is effective to reduce the thickness of the mask material. But A
When an inorganic material such as SiO ₂ is formed on the Al-based metal layer 5 such as 1-1% Si by plasma CVD or the like, a process temperature of about 400 ° C. is required to form a dense film having high etching resistance. Since it is necessary, the problem that Si nodules and precipitates at the interface between the Al-based metal layer and the lower refractory metal layer newly occurs. Si nodules scatter ions that are perpendicularly incident on the substrate to be etched due to anisotropic processing, and have a problem of causing a reduction in anisotropic shape and undercut.

When the overmelting is continued after the refractory metal layer 4, the barrier metal layer 3, and the adhesion layer 2 are patterned by switching to the F-based gas, excessive F radicals (F ^* ) are generated due to excessive F radicals (F ^* ). There is a problem in that the melting point metal layer 4 is side-etched and the anisotropic shape is impaired.

These undercuts and side etchings cause problems such as an increase in wiring resistance, a decrease in operation speed, and a decrease in stress migration resistance in a semiconductor device using sub-half micron-class fine wiring, and are not acceptable. Absent.

Accordingly, an object of the present invention is to provide an anisotropic film that does not generate undercut or side etching in patterning a fine-width laminated wiring including a structure in which an Al-based metal layer is formed on a high-melting metal layer. It is to provide a new excellent dry etching method.

Another object of the present invention is to provide a high melting point metal layer with an A
A clean anisotropic process that prevents the generation of fence-like residues in the patterning of fine-width laminated wiring including a structure with an l-based metal layer formed, without the risk of particle contamination on the substrate to be processed or dry etching equipment It is to provide a simple dry etching method.

It is a further object of the present invention to provide anisotropic processing having an excellent shape without deteriorating the step coverage of an interlayer insulating film formed on a laminated wiring due to a deteriorated film remaining on a side wall. It is to provide a dry etching method which enables the following.

Still another object of the present invention is to achieve the above object by using a resist mask which can be formed at a low temperature without concern about generation of Si nodules. Problems other than the above of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0014]

SUMMARY OF THE INVENTION A dry etching method for a laminated wiring according to the present invention has been proposed in order to solve the above-mentioned problems, and comprises a barrier metal layer and a barrier metal layer.
The refractory metal layer formed on the
In a dry etching method for a laminated wiring having a patterned Al-based metal layer, the Al-based metal layer is etched with a Cl-based gas, nitriding is performed on the Al-based metal layer pattern side wall, and then a lower refractory metal layer is formed. The etching is performed by switching the barrier metal layer to a mixed gas containing a Cl-based gas and an O-based gas.

Further, the dry etching method for a multilayer wiring according to the present invention is a dry etching method for a multilayer wiring including a structure in which an Al-based metal layer is formed on a high melting point metal layer.
After etching the l-based metal layer with a Cl-based gas, carbonization treatment is performed on the side wall of the Al-based metal layer pattern, and then the lower refractory metal layer is switched to a mixed gas of a Cl-based gas and an O-based gas for etching. is there.

The refractory metal layer of the present invention is an aluminum-based metal layer.
Lectro migration and stress migration
Redundant layer for countermeasures against
Ta, Mo and their alloys, tungsten silicide
, Tantalum silicide, molybdenum silicide
can do. The Cl-based gas used in the present invention is Cl-based gas.
₂ , BCl ₃ , CCl ₄ , SiCl ₄ , S ₂ Cl ₂ , S ₃ Cl ₂
And SCl ₂ .

The nitriding treatment of the present invention is desirably plasma nitridation using an N-based gas which can be treated at a low temperature. Examples of the N-based gas include N ₂ , NH ₃ , N ₂ H _{4 and the} like.

In the carbonization treatment of the present invention, it is desirable to perform plasma nitridation using a C-based gas which can also be treated at a low temperature.
As the C-based gas, CH ₄ , C ₂ H ₆ , C ₂ H ₄ , C ₃
A hydrocarbon gas such as H ₈ can be exemplified.

[0019]

The point of the present invention is that after etching an Al-based metal layer with a Cl-based gas, nitriding or carbonizing the side surface of the Al-based metal layer pattern, the lower refractory metal layer such as W is formed on the Al-based metal layer. The point is that etching is performed using a mixed gas of a system gas and an O system gas. As described above, WCl ₆ , a chloride of W, has a low vapor pressure, and its boiling point at 1 atm is 3
Since the temperature is as high as 46.7 ° C., it is difficult to perform etching using only Cl-based gas. However, the vapor pressure of W oxychloride WO _x C _y is much higher, and the boiling point of WOCl ₄ , which is a typical oxy chloride, is 227.5 ° C. Although it does not reach 17.5 ° C., which is the boiling point of WF _6, the refractory metal layer such as W can be sufficiently etched by a mixed gas of a Cl-based gas and an O-based gas. The boiling point data is CRC Ha
ndbook of Chemistry and P
histics 71st. Edition (1990,
According to CRC Press).

However, when compared with the vapor pressure of WF ₆ which is a reaction product when W is etched with an F-based gas, W
It is also true that the vapor pressure of OCl ₄ is quite low. For this reason, when a high melting point metal layer such as W is etched by a mixed gas of a Cl-based gas and an O-based gas, the etching proceeds only on the ion irradiation surface in the form of an ion-assisted reaction. That is, isotropic etching by Cl ^* does not occur, and the problem of side etching is solved. This is significantly different from the fact that in the case of etching W with an F-based gas, an isotropic reaction due to poor directivity of F ^* proceeds and side etching easily occurs.

Furthermore, since the F-based gas is not used after the etching of the upper Al-based metal layer, the AlCl _x -based side wall adhered film is not converted into an AlF _x -based side wall altered film. For this reason, a fence-shaped residue that is difficult to remove does not remain, and the problem of particle contamination in the substrate to be etched and the etching apparatus can be solved. At the same time, the step coverage of the interlayer insulating film to be formed later is not reduced.

Although the present invention is based on the above basic concept, in the actual process, the Al-based metal layer pattern which has been already patterned is exposed to Cl-based plasma for a long time while the lower refractory metal layer is being etched. Will be done. That is, a state in which excessive overetching is substantially applied is caused, and a new problem that side etching enters the anisotropically processed Al-based metal layer pattern newly occurs.

In order to avoid this problem, a high-melting-point metal layer may be etched after forming a strong protective film capable of shielding Cl-based plasma on the side surface of the patterned Al-based metal layer. Specifically, plasma nitridation or plasma carbonization that can be processed at a low temperature is most effective. An AlN-based nitride film is formed by plasma nitridation, and an AlC-based carbonized film is formed on the side surface of the Al-based metal layer pattern by plasma carbonization. These Al-based inorganic compounds are much more excellent in plasma resistance to Cl ^* than Al-based metal. . For this reason, there is no fear that side etching may occur in the Al-based metal layer pattern during the etching of the refractory metal layer.

The formation of an AlO _x -based oxide film by plasma oxidation also shows resistance to Cl ^* attack. However, in this case, the resist mask is also exposed to the O-based plasma, and the surface of the resist mask is subjected to a process similar to ashing even for a short time. For this reason, the resist mask is thinned or receded, and as a result, there is a concern about a processing conversion difference in the lamination wiring width. This is desired to be avoided in a semiconductor device based on fine design rules. Therefore, in the present invention, the process is limited to the nitriding process and the carbonizing process in which there is no possibility of the resist mask receding.

A formed on the side surface of the Al-based metal layer pattern
The 1N-based nitride film or AlC-based carbide film is formed by a short-time process at a low temperature near room temperature. Therefore, the thickness of the AlN-based nitride film or the AlC-based carbide film is several nm, and the increase in the number of wiring layers is not at a practically problematic level. The presence of the nitride film or the carbide film also has a secondary effect of preventing after-corrosion of the Al-based metal layer pattern.

When a sulfur-based gas such as S ₂ Cl ₂ , S ₃ Cl ₂ and SCl ₂ among the Cl-based gases used in the present invention is used, free sulfur generated in the plasma is deposited on the substrate to be etched. Then, a sulfur side wall protective film is formed on the pattern side wall parallel to the incident ions. Further, if an N-based gas such as N ₂ is further added to these sulfur chloride-based gases, thiazyl (SN) is formed in the plasma, and this is immediately polymerized, so that the side wall protective film of polythiazyl (SN) _n can be used. is there. These sulfur-based side wall protective films protect the pattern side walls from Cl ^* attack and contribute to further anisotropic processing. In addition, since these sulfur-based side wall protective films can be easily removed by sublimation by heating the substrate to be etched under reduced pressure after etching, there is no fear of substrate contamination or reduction in particle level. Sublimation temperature is about 9 with sulfur
0 ° C. or higher, about 130 ° C. or higher for polythiazyl.

[0027]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 In this embodiment, in the etching of a laminated structure in which an Al-1% Si alloy layer is formed on a W layer, the Al-1% Si alloy layer is patterned and then subjected to a nitriding treatment. is there. This will be described with reference to FIGS. The same parts as those in FIG. 3 used for the description of the conventional example are given the same reference numerals.

First, as shown in FIG. 1A, an insulating film 1 such as SiO ₂ is formed on a semiconductor substrate (not shown) such as Si. Next, an adhesion layer 2 made of Ti, a barrier metal layer 3 made of TiN, a refractory metal layer 4 made of W by blanket CVD, an Al-based metal layer 5 made of Al-1% Si by sputtering, and an antireflection layer made of TiON 6
Are formed in this order. After forming the barrier metal layer, RTA is performed at 650 ° C. for about 60 seconds in an inert atmosphere,
The barrier properties may be improved. Although not shown, the insulating film 2 may have a multi-layer wiring structure in which a connection hole is opened to make contact with an impurity diffusion region formed in the semiconductor substrate. Semiconductor substrates such as Si are made of Al alloy or polycrystalline Si.
A lower wiring layer made of the same may be used. The thickness of each layer is
As an example, the adhesion layer 2 is 30 nm, and the barrier metal layer 3 is 7 nm.
0 nm, refractory metal layer 4 is 200 nm, Al-based metal layer 5
Is 500 nm and the antireflection layer 6 is 35 nm.

Next, as an example, a negative three-component chemically amplified photoresist, SAL-601 manufactured by Shipley Co., Ltd.
0.35 by KrF excimer laser lithography
A resist mask having a width of μm is formed. The sample formed so far is used as a substrate to be etched.

First, the antireflection layer 6 made of TiON and the Al-based metal layer 5 are etched from the substrate to be etched by a substrate bias application type ECR plasma etching apparatus under the following etching conditions. BCl ₃ 90 sccm Cl ₂ 60 sccm Gas pressure 2.0 Pa Microwave power 900 W (2.45 GHz) RF bias power 40 W (13.56 MH)
z) Substrate temperature 25 ° C. In this etching process, the radical reaction due to Cl ^* is C
The etching proceeds anisotropically in a form assisted by ions such as l ⁺ and BCl _x ⁺ . At the same time, as shown in FIG. 1B, a side wall adhesion film 8 mainly composed of AlCl _X is formed on the side surfaces of the resist mask, the patterned antireflection layer 6 and the Al-based metal layer 5. The sidewall adhesion film 8 also contains the decomposition product CCl _x of the resist. When the surface of the refractory metal layer 4 is exposed, the etching stops at this surface. This is because the vapor pressure of WCl ₆ is low and the etching rate is extremely low as described above.

After the anti-reflection layer 6 and the Al-based metal layer 5 are etched, N ₂ plasma treatment is performed for 15 seconds in the same substrate bias applying type ECR plasma etching apparatus under the following conditions as an example. N ₂ 90 sccm Ar 60 sccm Gas pressure 2.0 Pa Microwave power 900 W (2.45 GHz) RF bias power 0 W Substrate temperature 25 ° C. Substrate heating at about 250 ° C. before N ₂ plasma treatment, AlCl _x The side wall film 8 of the system may be removed. In this case, the substrate may be transferred to a substrate heating chamber via a gate valve and subjected to lamp annealing or the like. By the short-time N ₂ discharge, an AlN-based sidewall nitride film 10 is formed on the side surface of the pattern of the Al-based metal layer 5. This is shown in FIG. The figure shows a state in which the sidewall adhesion film 8 has been removed. In FIG. 2, the thickness of the sidewall nitride film 10 is exaggerated for the sake of explanation.

Next, switching to a mixed gas of Cl-based and O-based,
As an example, the lower refractory metal layer 4, barrier metal layer 3, and adhesion layer 2 are patterned under the following etching conditions. Cl ₂ 90 sccm O ₂ 20 sccm Gas pressure 2.0 Pa Microwave power 900 W (2.45 GHz) RF bias power 40 W (13.56 MH)
The z) substrate temperature 25 ° C. This etching process, the refractory metal layer 4 such as W is Cl ^*
Etching proceeds anisotropically in such a manner that a radical reaction caused by Cl ⁺ and O ⁺ is assisted by the incidence of ions such as Cl ⁺ and O ⁺ . This is because the desorbed reaction product is an oxychloride of W such as WOCl ₄ and the vapor pressure is relatively low, so that only the incident surface of ions that are incident perpendicular to the substrate is etched. Therefore, side etching does not occur in the refractory metal layer pattern even in the over-etching step. The lower barrier metal layer 3 and the adhesion layer 2 are mainly removed as chlorides of Ti. As a result, as shown in FIG. 1D, the refractory metal layer 4, the barrier metal layer 3, and the adhesion layer 2 are all patterned with good anisotropy.

Since no F-based gas is used, AlCl
_{The x-} based side wall film 8 is not converted into an AlF _x -based altered film. Therefore, the sidewall adhesion film 8 can be easily removed by heating the substrate at about 250 ° C. after the completion of the etching. As described above, when the substrate is heated and transferred to a vacuum preparatory chamber connected to an etching apparatus and subjected to lamp annealing, a decrease in throughput can be suppressed. Thereafter, when resist ashing is performed and the resist mask 8 is removed, the laminated wiring pattern shown in FIG. 1E is completed. When the resist mask 7 is removed with a resist stripper, the sidewall adhesion film 8 can be simultaneously wet-removed by the stripper treatment and the subsequent pure water cleaning, and there is no possibility of leaving any residue.

According to the present embodiment, the effect of the AlC-based side wall nitride film 10 makes it possible to pattern a laminated wiring having an anisotropic shape without side etching without generating a fence-like residue.

Embodiment 2 In this embodiment, in etching a laminated structure in which an Al-1% Si alloy layer is formed on a W layer, the Al-1% Si alloy layer is subjected to a Cl-based gas, and then carbonized on the side surface of the pattern. This is an example in which processing has been performed. This will be described again with reference to FIGS.

The substrate to be etched used in this embodiment is the same as that used in the first embodiment, and a duplicate description will be omitted. The anti-reflection layer 6 made of TiON and the Al-based metal layer 5 are first etched from the substrate to be etched shown in FIG. 1A by a substrate bias application type ECR plasma etching apparatus under the following etching conditions as an example. BBr ₃ 30 sccm Cl ₂ 90 sccm Gas pressure 2.0 Pa Microwave power 900 W (2.45 GHz) RF bias power 40 W (13.56 MH)
z) Substrate temperature: 25 ° C. In this etching process, the etching proceeds anisotropically in such a manner that a radical reaction using Cl ^* as a main etchant is assisted by ions such as Cl ⁺ and BBr _x ⁺ . At the same time,
Resist mask and patterned antireflection layer 6, A
As shown in FIG. 1B, AlC
sidewall deposition film 8 including AlBr _X or the like as a main component l _X is formed. When the surface of the refractory metal layer 4 is exposed, the etching stops at this surface. This is, as mentioned earlier, W
This is because the vapor pressure of Cl ₆ is low and the etching rate is extremely low.

After the anti-reflection layer 6 and the Al-based metal layer 5 are etched, a C-based plasma treatment is performed for 15 seconds in the same substrate bias applying type ECR plasma etching apparatus as an example under the following conditions. CH ₄ 90 sccm Ar 60 sccm Gas pressure 2.0 Pa Microwave power 900 W (2.45 GHz) RF bias power 0 W Substrate temperature 25 ° C. Substrate heating at about 250 ° C. before CH ₄ plasma treatment, AlCl _x The system side wall adhesion film 8 may be removed. By this short CH ₄ discharge, an AlC-based sidewall nitride film 10 is formed on the side surface of the Al-based metal layer 5 pattern. This is shown in FIG. The figure shows a state where the side wall adhesion film 8 has been removed.

Next, the etching gas is switched to a mixed gas of Cl-based and O-based, and as an example, the lower refractory metal layer 4, barrier metal layer 3, and adhesion layer 2 are patterned under the following etching conditions. HCl 90 sccm O ₂ 20 sccm Gas pressure 2.0 Pa Microwave power 900 W (2.45 GHz) RF bias power 40 W (13.56 MH)
The z) substrate temperature 25 ° C. This etching process, the refractory metal layer 4 such as W is Cl ^*
Etching proceeds anisotropically in such a manner that a radical reaction caused by Cl ⁺ and O ⁺ is assisted by the incidence of ions such as Cl ⁺ and O ⁺ . This is because the desorbed reaction product is an oxychloride of W such as WOCl ₄ and the vapor pressure is relatively low, so that only the incident surface of ions that are incident perpendicular to the substrate is etched. Therefore, side etching does not occur in the refractory metal layer pattern even in the over-etching step. The lower barrier metal layer 3 and the adhesion layer 2 are mainly removed as chlorides of Ti. As a result, as shown in FIG. 1D, the refractory metal layer 4, the barrier metal layer 3, and the adhesion layer 2 are all patterned with good anisotropy.

Since no F-based gas is used, AlCl
_{The x-} based side wall film 8 is not converted into an AlF _x -based altered film. For this reason, the sidewall adhesion film can be easily removed by heating the substrate at about 250 ° C. after the completion of the etching. For substrate heating, if the substrate is conveyed to a vacuum preliminary chamber connected to an etching apparatus and subjected to lamp annealing, a decrease in throughput can be suppressed. Thereafter, when resist ashing is performed and the resist mask 8 is removed, the laminated wiring pattern shown in FIG. 1E is completed. When the resist mask 7 is removed with a resist stripper, the sidewall adhesion film 8 can be simultaneously wet-removed by the stripper treatment and the subsequent pure water cleaning, and there is no possibility of leaving any residue.

According to this embodiment, due to the effect of the AlC-based side wall carbon film, patterning of a laminated wiring having an anisotropic shape without side etching can be performed without generating a fence-like residue.

Embodiment 3 This embodiment is an example in which a stacked wiring is etched using S ₂ Cl ₂ as a Cl-based gas. This process is also shown in FIGS. 2 (a) to 2 (d) and FIG. 1 (a). It will be described with reference to FIG.

The substrate to be etched used in the present embodiment is the same as that shown in FIG. 1A used in the first embodiment, and a duplicate description will be omitted. The anti-reflection layer 6 made of TiON is formed on the substrate to be etched by a substrate bias application type ECR plasma etching apparatus under the following conditions as an example.
The l-based metal layer 5 is etched. S ₂ Cl ₂ 150 sccm Gas pressure 2.0 Pa Microwave power 900 W (2.45 GHz) RF bias power 30 W (2 MHz) Substrate temperature 20 ° C. In this etching process, radical reaction due to Cl ^* is C.
Etching proceeds anisotropically in a form assisted by ions such as l ⁺ and SCl _x ⁺ . At the same time, free sulfur generated by discharge dissociation in the plasma is deposited on the substrate to be etched. For this reason, the side surfaces of the resist mask 7, the patterned antireflection layer 6, and the Al-based metal layer 5 are formed as shown in FIG.
As shown in FIG. 3A, a sidewall adhesion film 8 mainly containing sulfur and AlCl _x is formed. When the surface of the refractory metal layer 4 is exposed, the etching stops at this surface.

After the anti-reflection layer 6 and the Al-based metal layer 5 are etched, an N ₂ plasma treatment is performed for 15 seconds in the same substrate bias applying type ECR plasma etching apparatus as an example under the following conditions. N ₂ 90 sccm Ar 60 sccm Gas pressure 2.0 Pa Microwave power 900 W (2.45 GHz) RF bias power 0 W Substrate temperature 25 ° C. Substrate heating at about 250 ° C. prior to N ₂ plasma treatment, sulfur and The sidewall adhesion film 8 mainly composed of AlCl _x may be removed. By this short-time N ₂ discharge, A
AlN-based sidewall nitride film 1 on the side surface of the l-based metal layer 5 pattern
0 is formed. This state is shown in FIG. The figure shows a state where the side wall adhesion film 8 has been removed.

Next, the etching gas is switched to a mixed gas of S ₂ Cl ₂ and O-based, and as an example, the lower refractory metal layer 4, barrier metal layer 3, and adhesion layer 2 are patterned under the following etching conditions. S ₂ Cl ₂ 80 sccm O ₂ 10 sccm Gas pressure 2.0 Pa Microwave power 900 W (2.45 GHz) RF bias power 30 W (2 MHz) Substrate temperature 20 ° C. In this etching process, a high melting point metal layer such as W is used. 4 is Cl ^*
Etching proceeds anisotropically in such a manner that a radical reaction caused by Cl ⁺ , SCl _x ⁺ , O ^{+ and the} like is assisted by the incidence of ions. The reaction product desorbed at this time is an oxychloride of W such as WOCl ₄ , and the etching proceeds only on the incident surface of ions which are incident perpendicularly to the substrate because the vapor pressure is relatively low. Also, as in the previous etching, the sidewall protective film 1 of sulfur is used.
No. 1 also adheres to the side surface of the refractory metal layer pattern, so that side etching does not enter the refractory metal layer pattern even in the over-etching step. Similarly, the lower barrier metal layer 3 and the adhesion layer 2 are also removed as Ti oxychloride. Again, sulfur sidewall protective film 11
Effectively prevents side etching. As a result, FIG.
As shown in (c), the refractory metal layer 4 and the barrier metal layer 3
The adhesive layer 2 is patterned with good anisotropy.

Since no F-based gas is used, AlCl
_{The x-} containing side wall film 8 is not converted into an AlF _x -based altered film. Therefore, by heating the substrate after the etching, the AlCl _x -based side wall adhered film 8 can be easily removed. At the same time, the sidewall protective film 11 of sulfur can be removed by sublimation. Thereafter, the resist mask 8 is removed by resist ashing, thereby completing a laminated wiring as shown in FIG. The removal of the resist mask may be performed by a stripping solution.

According to the present embodiment, S _{2 is used} as the Cl-based gas.
Since Cl ₂ was used and the side wall adhesion film 8 containing sulfur and the side wall protection film 11 for sulfur were also used, the anisotropic shape was somewhat deteriorated even though the substrate bias power was lowered as compared with the first embodiment. Nor. In addition, the selectivity between the base insulating film 1 and the resist mask 7 is improved, and damage to the insulating film 21 is reduced. Further, since there is no reattachment of the base insulating film 1 by sputtering, it contributes to improvement of the particle level.

In this embodiment, S _{2 is used} as the sulfur chloride-based gas.
Although Cl ₂ was used, the same effect can be obtained by using S ₃ Cl ₂ , SCl ₂ or a mixed gas thereof. When an N-based gas is further added to these sulfur chloride-based gases, the thiazyl (SN) generated in the plasma is polymerized in the gas phase to become polythiazyl (SN) _n and deposited on the substrate to be etched. N ₂ , N ₂ H _{4 and the} like can be used as the N-based gas. Since polythiazyl forms the sidewall protective film 11 which is stronger than sulfur, the substrate bias in the etching can be further reduced, and this is effective for ensuring the above effects in the present embodiment. The sublimation removal temperature of polythiazyl is 130 ° C. or higher in a reduced-pressure atmosphere, and there is no possibility of leaving residue or contamination.

In this embodiment, the nitriding treatment is performed on the side surface of the pattern of the Al-based metal layer 5, but the carbonization treatment may be performed as in the second embodiment.

Although the present invention has been described with reference to the three embodiments, the present invention is not limited to these embodiments.

Blanket CVD as high melting point metal layer 4
However, other refractory metals such as Ta and Mo, alloys thereof, and silicide may be used. Although Al-Si is exemplified as the Al-based metal layer 6, Al-Si-Cu
An alloy, an Al-Cu alloy or pure Al may be used.

Although TiON is exemplified as the antireflection layer,
By selecting conditions such as exposure wavelength, a-Si, Si
O ₂ , Si ₃ N ₄ , SiON, SiC or an organic material may be appropriately selected and used. Barrier was also used TiN as a metal layer, TiON, TiW, TiSi _x
Etc. may be used. The barrier metal layer and the adhesion layer may not be used if unnecessary.

The etching gas system is not limited to the examples described in the embodiments. For example, other gases such as CCl ₄ and SiCl ₄ may be used as the Cl-based gas.
Addition of a Br-based gas such as HBr or an I-based gas such as HI is also effective in improving the selectivity with respect to a resist mask or a base material layer. Of course, an inert diluent gas such as Ar or He may be added. As the etching apparatus, a substrate bias applying type ECR plasma etching apparatus was used.
There is no particular limitation on the type of magnetron RIE device, helicon wave plasma etching device, and the like. If a multi-chamber continuous processing system including a load lock chamber, a substrate heating chamber, an assembling chamber, and the like is used, an improvement in throughput can be expected.

[0054]

As is apparent from the above description, according to the present invention, in a method for dry etching a laminated wiring including a structure in which an Al-based metal layer is formed on a high-melting-point metal layer such as W, an etching gas system is used. After removing the F-based gas and etching the Al-based metal layer with a Cl-based gas, nitriding or carbonizing the side surface of the Al-based metal layer pattern, then etching the refractory metal layer with a mixed gas of Cl-based and O-based. By doing so, the following effects are exhibited.

Since the F-based gas such as SF ₆ has been eliminated from the etching gas system, side etching due to excess F ^* during etching or over-etching of the underlying refractory metal layer is eliminated. The fact that the ion-assist mode is used in principle for the etching of the refractory metal layer also contributes to the improvement of the anisotropy.

Further, it is possible to avoid the possibility of particle contamination of the substrate to be etched or the etching apparatus due to the fence-like residue based on the AlF _x -based side wall altered film adhered to the resist mask or the side surface of the wiring pattern. In addition, since there is no need for wet cleaning with strong mechanical and physical external force, which was conventionally performed to remove fence-like residues,
There is no damage to the substrate to be etched.

Since the fence-shaped residue does not remain on the laminated wiring after the etching, the step coverage of the interlayer insulating film formed thereon is improved.

The dry etching method of the present invention does not require the use of an inorganic mask and is a process using a resist mask.
No heat history at around 00 ° C is included, and therefore, S
There is no precipitation of i-nodules. For this reason, there is no concern about deterioration of the anisotropic shape due to scattering of ions by Si nodules.

On the side walls of the Al-based metal layer pattern, AlN
Since a thin and strong sidewall protective film such as Al and AlC is formed,
Concerns about after-corrosion are dispelled.

By the above effects, a dry etching method for a low-resistance and highly reliable laminated wiring having low resistance and excellent resistance to various migrations such as electromigration and stress migration is established, and its practical use becomes possible. The dry etching method for laminated wiring according to the present invention is particularly effective when used for internal wiring of a semiconductor device having a fine wiring width of 0.5 μm or less, and the effect of the present invention is extremely large.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing steps in Examples 1 and 2 of a dry etching method for a laminated wiring according to the present invention;
(A) is a state in which an adhesion layer, a barrier metal layer, a refractory metal layer, an Al-based metal layer, an antireflection layer and a resist mask are sequentially formed on a base insulating film, and (b) is an antireflection layer and an Al-based metal layer. Is patterned to form a side wall adhesion film, (c) is a state in which a side wall nitride film or a side wall carbonization film is formed on the side surface of the Al-based metal layer pattern, and (d) is a state in which the refractory metal layer and the adhesion layer are continuously formed. FIG. 4E shows a state in which the barrier metal layer is patterned, and FIG. 4E shows a state in which the resist mask is removed by ashing to complete the laminated wiring.

FIG. 2 is a schematic cross-sectional view showing a step in a dry etching method for a laminated wiring according to a third embodiment of the present invention, in which (a) an antireflection layer and an Al-based metal layer are patterned to form a sidewall adhesion film; (B) a state in which a side wall nitride film or a side wall carbide film is formed, (c) a state in which a high melting point metal layer, an adhesion layer and a barrier metal layer are continuously patterned to form a sulfur-based side wall protective film, (D) shows a state in which the resist mask is removed by ashing to complete the laminated wiring.

FIG. 3 is a schematic cross-sectional view showing a problem in a process of a conventional dry etching method for a laminated wiring, wherein (a) shows an adhesion layer, a barrier metal layer, a high melting point metal layer,
(b) shows a state in which an anti-reflection layer and an Al-based metal layer are patterned to form a sidewall adhesion film, and (c) shows a state in which a high melting point is continuously formed. The state in which the side wall altered film is formed by patterning the metal layer, the adhesion layer, and the barrier metal layer is shown. (D) is the state in which the resist mask is removed by ashing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating film 2 Adhesion layer 3 Barrier metal layer 4 Refractory metal layer 5 Al-based metal layer 6 Antireflection layer 7 Resist mask 8 Side wall adhesion film 9 Side wall alteration film 10 Side wall nitride film or side wall carbon film 11 Side wall protection film

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065 H01L 21/28 301 H01L 21/3213

Claims (6)

(57) [Claims] 1. A barrier metal layer, and said barrier metal layer
A refractory metal layer formed on the refractory metal layer,
In the dry etching method of a multilayer wiring having a formed Al-based metal layer, after etching the Al-based metal layer with a gas containing a Cl-based gas, a nitriding treatment to the Al-based metal layer pattern sidewalls applied,
Thereafter, the refractory metal layer and the barrier metal layer are
A dry etching method for a laminated wiring, characterized by etching with a mixed gas containing a system gas and an O system gas. 2. A dry etching method for a laminated wiring including Al-based metal layer on the refractory metal layer is formed structure, after etching the Al-based metal layer with a gas containing a Cl-based gas, the Al-based metal Carbonization treatment on the layer pattern side wall,
Thereafter, the high melting point metal layer is etched with a mixed gas containing a Cl-based gas and an O-based gas, wherein the dry etching method for a stacked wiring is performed. 3. The method according to claim 1, wherein the refractory metal layer is a redundant layer for preventing electromigration and stress migration of the Al-based metal layer.
Or the dry etching method according to claim 2. Wherein said refractory metal layer is characterized by at least one selected W, Ta, Mo and their alloys, tungsten silicide, tantalum silicide, from the group consisting of molybdenum silicide, claim 1 or The dry etching method according to claim 2. 5. The Cl-based gas comprises Cl ₂ , BCl ₃ , CCl
_4. The dry etching method according to claim 1, wherein the dry etching method is at least one selected from the group consisting of SiCl ₄ , S ₂ Cl ₂ , S ₃ Cl ₂ and SCl ₂ . 6. The dry etching method according to claim 1, wherein the pattern width of the laminated wiring is 0.5 μm or less.