JPH07230984A - Method of dry-etching laminated wiring - Google Patents

Abstract

PURPOSE:To enable a laminated wiring which is composed of a W layer and an Al metal layer formed on it and excellent in migration resistance to be anisotropically etched without leaving residues and generating contaminants. CONSTITUTION:An Al metal layer 5 formed on a high-melting point metal layer 4 of W or the like is patterned, a sulfur layer or a polythyazyl layer 9 is formed as a protective film, and then the high-melting point metal layer 4 is patterned. Therefore, an AlClx side wall-deposited film 8 formed on the side face of a resist mask 7 as deposited to it is hardly converted into an AlFx side wall modified film when it is exposed to F plasma, wherein an AlFx side wall modified film is hard to remove. Therefore, a resist mask is smoothly ashed or separated, so that particle contamination can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method for internal wiring used in semiconductor devices and the like, and more particularly to a dry etching method for laminated wiring including a structure in which an Al-based metal layer is formed on a refractory metal layer. .

[0002]

2. Description of the Related Art As the design rules of semiconductor devices such as LSI are miniaturized from half micron to quarter micron, the pattern width of internal wiring is being reduced. As a conventional internal wiring material, low resistance Al or Al
Although many alloys have been used, a decrease in the wiring width causes disconnection due to electromigration or stress migration, which is a serious problem in device reliability.

As a countermeasure against such various migrations, a conductive and highly rigid wiring layer of a refractory metal such as W, Mo, Ta, etc., its alloys, compounds, etc. is formed under the Al-based metal layer. Wiring is being considered. this is,
Even if the Al-based metal layer is broken, the underlying high-melting-point metal layer still exists, so that the wiring layer as a whole can avoid the breakage due to its redundancy effect. In particular, when W is used, it is a material having a relatively low resistance, and since a film formation method by blanket CVD has been established, it can be expected as a highly reliable laminated wiring structure in the future.

[0004]

However, in patterning a laminated wiring including a structure in which an Al-based metal layer is formed on a refractory metal layer such as W, anisotropic processing is performed on a plurality of different material layers. The need brought new challenges to the dry etching process. That is, the Al-based metal layer is switched to the Cl-based gas and the W layer is switched to the F-based gas for patterning due to the difference in vapor pressure of the halide, which is an etching reaction product. Fig. 2 shows the problems in the process based on this etching gas switching.
This will be described with reference to (a) to (c).

First, as shown in FIG. 2A, a semiconductor substrate
On the insulating film 2 on 1 such as adhesion layer and barrier metal layer 3, W
The refractory metal layer 4, the Al-based metal layer 5, and the antireflection layer 6 are
Deposit in order and form a resist mask 7 for patterning
To do. Next, the antireflection layer 6 is formed with a Cl-based etching gas.
And the Al-based metal layer 5 are etched, as shown in FIG.
AlCl_xThe reaction product of the system is the resist mask 7
A side wall adhesion film 8 remains on the side surface of the. Etch here
Switching the fusing gas to F-based gas and adhering to the refractory metal layer 4
The layer / barrier metal layer 3 is etched. At this time,
As shown in (c), AlCl_xThe side wall adhesion film 8 of the system is
Substitution of halogen atoms by exposure to elementary plasma
Happens, AlF_xIt is converted to the side wall altered film 10 of the system. ~ side
Wall alteration film 10 is AlF₃Is a substance whose main component is
This AlF₃Has a very low vapor pressure and is
Since it has low solubility in water, water, and organic solvents, resist removal
It cannot be removed by syneresis. Again O₂And O₃Register at
If you sing, you will get more Al ₂O₃Converted to the substance of the system
As it covers the resist mask, it hinders resist ashing.
Or even after resist ashing
It remains as a soot-like residue. Especially in the latter case,
It is sometimes called Rabbit Ear due to its shape.

As described above, once the AlF _x- based side wall altered film 10 is formed, it is difficult to remove it, and the step coverage of the interlayer insulating film formed on the laminated wiring is deteriorated, causing a device failure. Becomes Further, this also results in particle contamination of the substrate to be etched and the etching apparatus. In addition, a wet process using a mechanical external force such as spin cleaning or scrub cleaning is required for strong removal, which may result in complication of the process and reduction in throughput.

Therefore, an object of the present invention is to provide a laminated wiring excellent in anisotropy which is free from shape deterioration such as side etching in dry etching of a laminated wiring including a structure in which an Al-based metal layer is formed on a refractory metal layer. It is to provide a dry etching method that can be formed.

Another object of the present invention is to provide a clean dry etching method which does not cause deterioration of step coverage of an interlayer insulating film due to a side wall altered film or the like and generation of particle contamination due to residues, and also to improve the throughput of the entire process. It is also to provide dry etching without degradation. Other problems of the present invention will be made clear by the description of the present specification and the accompanying drawings.

[0009]

The dry etching method of the present invention was devised to solve the above-mentioned problems, and dry etching a laminated wiring in which an Al-based metal layer is formed on a refractory metal layer. In the method, first, after patterning an Al-based metal layer, a sulfur layer is formed on at least a side surface of a resist mask which is an etching mask, and then the refractory metal layer is patterned.

The sulfur layer is formed from the gas phase by using a specific gas capable of forming free sulfur under discharge dissociation conditions. Examples of this particular gas are S ₂ Cl ₂ , S ₃ C
L ₂ , SCl ₂ , S ₂ Br ₂ , S ₃ Br ₂ , SBr ₂ and H ₂ S can be mentioned.

In the dry etching method of the present invention, first, after patterning the Al-based metal layer, a polythiazyl layer is formed on at least the side surface of the resist mask which is an etching mask, and then the refractory metal layer is patterned.

The polythiazyl layer is formed from the gas phase by using a specific gas capable of producing free sulfur under discharge dissociation conditions and an N-based gas. Examples of this particular gas also include S ₂ Cl ₂ , S ₃ Cl ₂ , SCl ₂ and S ₂ B.
Mention may be made of r ₂ , S ₃ Br ₂ , SBr ₂ and H ₂ S.

[0013]

The point of the present invention is that the sulfur layer or the polythiazyl layer is formed on at least the side surface of the resist mask in advance before the etching gas is switched to perform the etching of the refractory metal layer after the etching of the Al-based metal layer. It is in. That is, the AlCl formed on the side surface of the resist mask when the etching of the Al-based metal layer is completed.
_A sulfur layer or a polythiazyl layer is used as a protective film for preventing contact between the _x- based side wall adhesion film and fluorine plasma.

Therefore, when the etching gas is switched to the F-based gas for etching the refractory metal layer and the F-based plasma atmosphere is established, the side surface of the resist mask is covered with the protective film of the sulfur layer or the polythiazyl layer. Therefore, the AlCl _x system side wall adhesion film formed on the side surface of the resist mask is not converted into an AlF _x system alteration film.

The sulfur or polythiazyl layer formed on the side surface of the resist mask serves as a protective film during the patterning of the refractory metal layer, and after the refractory metal layer patterning is completed, the substrate to be etched is depressurized by the same etching apparatus. Sublimation can be removed by heating in an atmosphere. The heating temperature can be sublimated at about 90 ° C. or higher for the sulfur layer and about 130 ° C. or higher for the polythiazyl layer. Alternatively, when the resist mask is ashed after the etching is completed, both the sulfur layer and the polythiazyl layer can be removed by ashing at the same time as the resist. In this case, the chlorine component in the sidewall adhering film AlCl _x can also be removed at the same time. In either case, the sulfur layer or polythiazyl layer is unlikely to become a new source of particle contamination.

The sulfur layer is composed of S ₂ Cl ₂ , S ₃ Cl ₂ , S
Cl ₂ , S ₂ Br ₂ , S ₃ Br ₂ , SBr ₂ and H ₂
Sulfur radicals (S ^* ) and halogen radicals are generated when a single gas or a mixed gas selected from S is discharged and dissociated, and of these, S ^* is deposited as free sulfur on the substrate to be etched. As described above, sulfur can be deposited when the substrate temperature to be processed is 90 ° C. or lower. The deposited sulfur layer has a dense film quality and has a sufficient barrier property as a protective film.

The polythiazyl layer is S₂Cl₂, S₃
Cl₂, SCl₂, S₂Br₂, S ₃Br₂, SBr₂
And H₂Gas selected from S and N₂, NF₃, N₂
H_FourDischarge dissociation of mixed gas with N-based gas such as
S to generate^*And N^*Reacts first and then thiazyl (SN)
Are formed, and these are polymerized (SN)_nIn the form of
Deposited on the substrate. Polythiazil I mentioned earlier
As described above, when the temperature of the substrate to be processed is 130 ° C. or lower, it is deposited.
be able to. The quality of the deposited polythiazyl layer is also extremely high
It is dense and serves as a protective film from F-based plasma.
Has a sufficient barrier property.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

Example 1 This example is an example in which a sulfur layer is formed as a protective film on the side surface of a resist mask, and this process is shown in FIG.
This will be described with reference to (d). In FIG. 1, the same parts as those in FIG. 2 used for explaining the conventional example are designated by the same reference numerals.

[0020] First, as shown in FIG. 1 (a), an insulating film 2 of SiO ₂ or the like on a semiconductor substrate 1 such as Si, Ti and Ti
An adhesion layer / barrier metal layer 3 made of a laminated film of N, a refractory metal layer 4 made of W formed by blanket CVD, an Al-based metal layer 5 made of Al-1% Si, and an antireflection layer made of TiON as an example. 6 are sequentially formed in this order. The semiconductor substrate 1 and the upper adhesion layer / barrier metal layer 3, refractory metal layer 4, and Al-based metal layer 5 may be connected to each other by a connection hole (not shown) formed in the insulating film 2. Of course, the semiconductor substrate 1 may be a lower wiring layer made of polycrystalline Si or the like. The thickness of each layer is, for example, 70 nm for the adhesion layer / barrier metal layer 3 in total and 200 nm for the refractory metal layer 4.
nm, the Al-based metal layer 5 is 500 nm, and the antireflection layer 6 is 5 nm.
It is 0 nm.

Next, as an example, a negative-type three-component system chemically amplified photoresist SAL-60 manufactured by Shipley Co., Ltd.
1 and 0.3 by KrF excimer laser lithography
A resist mask 7 having a width of 5 μm is formed. The sample formed up to this point will be referred to as a substrate to be etched.

The substrate to be etched is first subjected to etching of the antireflection layer 6 and the Al-based metal layer 5 under the following etching conditions by a substrate bias application type ECR plasma etching apparatus. BCl ₃ 60 sccm Cl ₂ 90 sccm Gas pressure 1.3 Pa Microwave power 1200 W (2.45 GHz) RF bias power 60 W (2 MHz) Substrate temperature Room temperature In this etching process, the Al-based metal layer 5 has a large vapor pressure. The reaction product, AlCl ₃ , is removed and is shown in FIG.
As shown in (b), a part thereof becomes the side wall adhesion film 8 and adheres to the side surface of the resist mask 5. The side wall adhesion film adheres also to the side surfaces of the patterned antireflection layer 6 and the Al-based metal layer 5, but FIG. 1B shows only the side wall adhesion film 9 on the side surface of the resist mask.

Next, a protective film made of the sulfur layer 8 is formed on the side surface of the resist mask. As an example, the sulfur layer 9 is formed by processing for 20 seconds under the following conditions. S ₂ Cl ₂ 20 sccm H ₂ 20 sccm Gas pressure 1.3 Pa Microwave power 1200 W (2.45 GHz) Substrate temperature Room temperature In this process, S ^* generated in plasma becomes free sulfur and is etched. A thickness of about 10 nm is deposited on the entire surface of the substrate. The addition of H ₂ gas has the effect of consuming Cl ^* and promoting the deposition of sulfur, but it is not necessary to add it. Other H-based gas such as SiH ₄ may be used as the gas having the effect of consuming the halogen radicals. The sulfur layer 9 may be applied so as to protect only the side wall adhesion film 8 on the side surface of the resist mask 7, but in practice, as shown in FIG.
The side wall adhering film 8 on the side surface, the patterned antireflection layer 6, and the side surface of the Al-based metal layer 5 are covered and are densely formed with a uniform film thickness. Sulfur is also deposited on the upper surface of the resist mask 7 and the exposed surface of the refractory metal layer 4, but the deposited film on the refractory metal layer 4 is omitted in FIG. 1C.

Subsequently, the refractory metal layer 4 and the adhesion layer / barrier metal layer 3 are continuously patterned under the following etching conditions. S ₂ F ₂ 50 sccm Cl ₂ 50 sccm Gas pressure 1.3 Pa Microwave power 1200 W (2.45 GHz) RF bias power 60 W (2 MHz) Substrate temperature Room temperature In the etching process, the refractory metal layer 4 is S. ₂ F
Radical reaction by F ^* produced by _second discharge dissociation, also S S ⁺ that dissociated from ₂ F _2, the etching proceeds in mechanism is assisted on the incident energy of ions of SF ⁺ like. In addition, the adhesion layer / barrier metal layer 3 is the added C
Etched with l ₂ gas. On the other hand, S ^* generated by dissociation from S ₂ F ₂ becomes free sulfur and is deposited on the pattern side wall portion of the refractory metal layer 4 and the adhesion layer / barrier metal layer 3 where the ion incidence is small, and is subjected to anisotropic etching. Contribute.

During the above etching process, the resist mask side
Side wall adhesion film 8 is a protective film consisting of sulfur layer 9 to the end
Is separated from the F-based plasma by the
IF _xWill never be converted to. After etching is completed,
The etching substrate is heated to 90 ° C. or higher in a reduced pressure atmosphere.
And sulfur was removed by sublimation, and as a result, it is shown in FIG. 1 (d).
Antireflection layer 6, Al-based metal layer 5, refractory metal layer
4. Laminated wiring consisting of adhesion layer and barrier metal layer 3
Strokes with a width of 0.35 μm, which is highly anisotropic
Was done. On the side surface of the resist mask, AlCl_xSystem side wall
A part of the adhered film remains, but the illustration is omitted in FIG.
It

After that, the resist mask 7 is removed by ashing or a stripping solution. Because the resist mask side AlF _x system no residual sidewall alteration film, the resist mask 7 by any removal method can be completely eliminated, the occurrence of particle contamination are not.

Example 2 This example is an example in which the process for forming the sulfur layer 9 was carried out with H ₂ S, and the etching process before and after that was the same as that in Example 1, so refer again to FIG. Only the process of forming layer 9 will be described. The protective film composed of the sulfur layer 9 is formed by, for example, treating the material for 20 seconds under the following conditions. H ₂ S 50 sccm Gas pressure 1.3 Pa Microwave power 1200 W (2.45 GHz) Substrate temperature Room temperature During this treatment process, S ^* generated in plasma by discharge dissociation of H ₂ S becomes free sulfur. A thickness of about 10 nm is deposited on the entire surface of the substrate to be etched. The sulfur layer 9 is
The side wall adhesion film 8 on the side surface of the resist mask 7, the patterned antireflection layer 6, and the side surface of the Al-based metal layer 5 are formed. Since the substrate bias is not applied under the above processing conditions, sulfur is also deposited on the upper surface of the resist mask 9 and the exposed surface of the refractory metal layer 4. However, in FIG. Illustration is omitted.

Under the above processing conditions, the dense sulfur layer 9
As a result, the same effects as in Example 1 can be obtained, and there is also an economic merit due to the use of inexpensive H ₂ S gas.

Example 3 In this example, the side surface of the resist mask was made of polythiazil.
This is an example of forming a protective film for
The process is the same as in Example 1, so refer also to FIG.
Only the formation process of the polythiazyl layer 9 will be described. Po
The lithiadyl layer 9 is, for example, for 20 seconds under the following conditions.
Formed. S₂Br₂ 20 sccm N₂ 20 sccm Gas pressure 1.3 Pa Microwave power 1200 W (2.45 GHz) Substrate temperature Room temperature In this process, S₂Br₂Dissociated from S^*When
N₂Dissociated from N ^*And react in the plasma
First, it produces thiazil, which polymerizes and forms on the substrate to be processed.
accumulate. The polythiazyl layer 9 is as shown in FIG.
The side wall adhesion film 8 on the side surface of the resist mask 7 and the pattern
To cover the side surfaces of the antireflection layer 6 and the Al-based metal layer 5 that have been coated.
And is formed extremely densely with a uniform film thickness of about 10 nm.
Polythiazyl has a high melting point on the upper surface of the resist mask 7
Although it is also deposited on the surface of the metal layer 4, it has a high melting point in FIG.
The deposited film on the metal layer 4 is not shown.

In the present embodiment, since the film quality of the polythiazyl layer 9 is more dense than that of sulfur, the polythiazyl layer 9 has a high resistance to the incidence of ions and the effect as a protective film is more complete.

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

For forming a sulfur layer or a polythiazyl layer
Is S₂Cl₂, H₂S, S₂Br₂Three types of gas are illustrated
However, other than this S₃Cl₂, SCl₂SCl-based gas such as
Su, S ₃Br₂, SBr₂SBr-based gas such as H and H₂
S can be used. Also mix these gases
You may use.

A mixed gas of S ₂ F ₂ and Cl ₂ was used for etching the refractory metal layer and the adhesion layer / barrier metal layer. A Cl-based gas and an etching gas may be switched and used for the metal layer. The etching of a single-layer high-melting-point metal layer such as W using S ₂ F ₂ or a mixed gas obtained by adding an N-based gas thereto is performed by the etching proposed in Japanese Patent Application No. 4-288885 filed by the present inventor. This is a highly reproducible anisotropic dry etching method using a sulfur-based side wall protective film such as sulfur or polythiazyl. Of course, SF
_The refractory metal layer may be etched with a general-purpose F-based gas such as ₆ .

Although W is exemplified as the refractory metal layer, T
Other refractory metals such as a and Mo may be used. Further, it is obvious that the method can be applied to dry etching of a laminated wiring structure in which a process of etching with an F-based gas such as a refractory metal silicide under an Al-based metal layer is performed. Further, the materials and constitutions of the antireflection layer and the adhesion layer / barrier metal layer adopted in this embodiment, and the presence or absence thereof may be arbitrarily selected.

[0035]

As is apparent from the above description, according to the present invention, a dry etching method for patterning a laminated wiring including a structure in which an Al-based metal layer is formed on a refractory metal layer using a resist mask is used. It is possible to realize a clean process that does not generate a difficult-to-remove residue after completion, does not deteriorate step coverage of the interlayer insulating film, and does not cause particle contamination.

Further, according to the present invention, since a series of steps can be continuously performed only by switching the gas in the same etching apparatus, a wet process is not used and the throughput of the whole process is excellent.

Further, since each layer of the laminated wiring is patterned by the optimum etching gas, wiring having an excellent anisotropic shape can be processed. Further, if a process of forming a side wall protective film of sulfur or polythiazyl is used for patterning the refractory metal layer, the anisotropic shape can be further improved. At the same time, since the sulfur-based side wall protective film is also formed on the side surface of the resist mask, etching with good controllability without film loss of the resist mask is possible. Further, since the protective effect of the resist mask can be expected, the film thickness thereof can be reduced, which further contributes to the improvement of fine workability.

Due to the above effect, the laminated wiring of the refractory metal layer and the Al-based metal layer can be processed with high reliability, and in particular, it has a laminated wiring structure based on a fine design rule of, for example, 0.5 μm or less. It is extremely effective in the manufacturing process of semiconductor devices.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view for explaining Embodiments 1, 2 and 3 to which the present invention is applied in the order of steps, (a) is a cross-sectional view of a substrate to be etched having a resist mask formed thereon,
(B) shows a state in which a sidewall adhesion film is formed on the side surface of the resist mask by patterning an Al-based metal layer, (c) shows a state in which a protective film made of a sulfur layer or a polythiazyl layer is formed,
(D) shows a state in which the laminated wiring structure is completed by etching the refractory metal layer and the adhesion layer / barrier metal layer.

2A and 2B are schematic cross-sectional views illustrating a problem in dry etching of a conventional laminated wiring, FIG. 2A is a cross-sectional view of an etched substrate on which a resist mask is formed, and FIG. 2B is a patterning of an Al-based metal layer. Then, the side wall adhesion film is formed on the side surface of the resist mask, and (c) is the state where the laminated wiring structure is patterned by etching the refractory metal layer and the adhesion layer / barrier metal layer to form the side wall alteration film. .

[Explanation of symbols]

 1 Semiconductor Substrate 2 Insulating Film 3 Adhesion Layer and Barrier Metal Layer 4 Refractory Metal Layer 5 Al-based Metal Layer 6 Antireflection Layer 7 Resist Mask 8 Sidewall Adhesive Film 9 Sulfur or Polythiazyl Layer 10 Sidewall Altered Film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H01L 21/3213 H05H 1/46 A 9014-2G H01L 21/88 RD

Claims (7)

[Claims] 1. A dry etching method for patterning a laminated wiring including a structure in which an Al-based metal layer is formed on a refractory metal layer by using a resist mask, wherein at least the resist mask is formed after the Al-based metal layer is patterned. A dry etching method for laminated wiring, comprising forming a sulfur layer on a side surface and then patterning the refractory metal layer. 2. The dry etching method for laminated wiring according to claim 1, wherein the sulfur layer is formed by using a gas that can generate free sulfur in plasma under discharge dissociation conditions. 3. The sulfur layer comprises S ₂ Cl ₂ , S ₃ Cl ₂ ,
SCl ₂ , S ₂ Br ₂ , S ₃ Br ₂ , SBr ₂ and H
The dry etching method for laminated wiring according to claim 1, wherein the dry etching is performed by discharge dissociation of at least one gas selected from the group consisting of ₂ S. 4. A dry etching method of patterning a laminated wiring including a structure in which an Al-based metal layer is formed on a refractory metal layer by using a resist mask, wherein at least the resist mask is formed after the Al-based metal layer is patterned. A dry etching method for laminated wiring, comprising forming a polythiazyl layer on a side surface and then patterning the refractory metal layer. 5. The dry layered wiring according to claim 4, wherein the polythiazyl layer is formed by using a gas capable of generating free sulfur in plasma under discharge dissociation conditions and an N-based gas. Etching method. 6. The polythiazyl layer comprises S ₂ Cl ₂ , S ₃ C
l ₂ , SCl ₂ , S ₂ Br ₂ , S ₃ Br ₂ , SBr ₂ and H ₂ S and at least one gas selected from the group consisting of an N-based gas and formed by discharge dissociation. Item 4. A dry etching method for laminated wiring according to item 4. 7. The dry etching method for laminated wiring according to claim 1, wherein the pattern width of the laminated wiring is 0.5 μm or less.