JPH08203911A - Plasma etching method of al metallic layer - Google Patents

Abstract

PURPOSE: To provide the process of a large selection ratio with an etching mask, excellent anisotropy, the least particle contamination and after-corrosion. CONSTITUTION: An Al metallic layer 3 is plasma etched away using an inorganic base material layer 4 containing fluorine such as SiOF, etc., as an etching mask. Thus, the etching mask made of the inorganic base material layer 4 containing fluorine is sputtered so as to form an AlFx base sidewall protective film 6 on the side faces of the Al base metallic layer 3 in the patterning step by the active fluorine fed by the sputtering step. Accordingly, the Al base metallic layer 3 is anisotropically patterned while the sidewall protecting film 6 not containing Cl at all has no possibility of causing after-corrosion. Furthermore, the complete effect can be given by using the sidewall protective film made of sulfuric base material together with the S sidewall protective film 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching method for an Al-based metal layer used for electrodes and wirings of semiconductor devices, and more particularly, to an Al-based metal wiring using an inorganic material containing F as an etching mask. The present invention relates to a novel plasma etching method.

[0002]

2. Description of the Related Art Pure Al, an Al-Si alloy in which 1 to 2% of Si is added to Al in order to improve resistance to various migrations, as an internal wiring or electrode material of a semiconductor device such as an LSI, and 0.5 to 1 % Cu-added Al-Si-C
Al-based metals such as u alloys are widely used. Also Al
A Ti-based material layer such as a Ti layer or a TiN layer for improving the adhesion and barrier properties to the underlying layer, or a TiON layer for preventing the reflection of exposure light is stacked on the upper and lower layers of the metal-based metal layer. The structure is heavily used.

Patterning of the Al-based metal layer is generally performed by plasma etching with a Cl-based gas in order to form an AlCl _x -based reaction product having a high vapor pressure. For example, US Pat. No. 4,256,534 discloses a patterning method using a BCl ₃ / Cl ₂ mixed gas.

In plasma etching of the Al-based metal layer, the main etchant is Cl ^* (Cl radical), and spontaneous and rapid etching reaction proceeds.
Therefore, Cl ^* alone causes strong isotropic etching and side etching occurs. Therefore, normally, by adopting plasma etching conditions in which the energy of vertically incident ions on the substrate to be processed is increased to some extent, the ion assist reaction is also used, and the decomposition product of the resist mask sputtered by the incident ions is used as a sidewall protective film. By doing so, anisotropic etching is achieved. The combined use of ion-assisted reactions is the use of alloy components such as Si and Cu, and Ti.
It is also necessary to suppress the generation of a residue by sputtering and removing a compound having a low vapor pressure of a reaction product such as a laminated structure component. BCl ₃ in the mixed gas is a reducing agent used for breakthrough of the natural oxide film existing on the surface of the Al-based metal layer, and also BCl ₃ as incident ions.
_It plays an important role of supplying _x ⁺ .

By the way, in the ion mode anisotropic etching in which the decomposition products of the resist mask sputtered are positively used as the side wall protection film as described above, the selection ratio with respect to the resist mask and the underlying interlayer insulating film is inevitable. Is reduced. Typical Al with BCl ₃ / Cl ₂ mixed gas
In the patterning of the system metal layer, the selectivity ratio to the resist mask is as low as about 2, which is an essential problem due to the use of Cl system gas as the etching gas.
In particular, with the adoption of multi-layered wiring, patterning on a base substrate having a high level difference and adoption of the barrier metal layer and the antireflection film structure described above make the problem even more difficult.

That is, as a means for covering a low selection ratio with respect to the resist mask, thickening the resist mask is considered, but there is a problem of defocusing (DOF) of exposure light at the time of lithography in a high step portion. Also, in the high step portion, the coating thickness becomes thin during spin coating of the resist mask, and the desired film thickness cannot be obtained. In reality, it is not possible to expect sufficient effects simply by increasing the resist coating conditions. .

In the case of an Al-based metal wiring that employs a barrier metal layer or an antireflection film structure, C is used for patterning the laminated structure including these difficult-to-etch material layers.
Since an etching condition of strong ion mode is adopted by using the l-based gas, the etching rate is lowered, and thus the prolonged etching also causes a reduction in resist mask selectivity.

On the other hand, under the highly integrated fine design rule in the sub-half micron class, it is required to reduce the resist coating thickness in order to improve the resolution at the time of exposure in photolithography. Moreover,
Excimer laser lithography such as KrF is being adopted along with the shortening of the exposure wavelength, but these chemically amplified resists compatible with excimer laser lithography do not necessarily have sufficient ion incidence resistance. Therefore, there is a trade-off relationship between ensuring the fine workability by reducing the resist coating thickness and ensuring the selection ratio with respect to the resist mask. In particular, in patterning the Al-based metal layer on the step underlying, the residue of the step is removed. In the etching process, the problem of pattern conversion difference due to the film reduction of the resist mask is at a level that cannot be ignored.

In order to deal with such a problem, conventionally, as a measure for reinforcing the resist mask, an attempt has been made to form a material having high ion bombardment resistance on the surface of the resist mask. For example, a method of coating the surface of a resist mask with Si using SiCl ₄ as an etching gas is a third method.
Proceedings of the 3rd integrated circuit symposium lecture (1987),
p. 114, but the increase in the particle level due to the deposition of Si on the substrate to be etched is still unsolved.

A process using a Br-based gas such as BBr ₃ is a Proceedings of the 11t.
h. Symposium on Dry Procedures
s, II-2, p. 45, or Japanese Patent Laid-Open No. 1-3022
No. 7 report. In this process, the reaction product C having a small vapor pressure is applied to the surface of the resist mask.
It is coated with Br _x to enhance etching resistance.
The mechanism of resist mask protection by CBr _x is described in the monthly semiconductor world magazine (published by Press Journal) December 1990 issue, p. 103-107
And a value of 5 is reported as the selectivity ratio to the resist mask. However, in order to achieve such a level of selection ratio, it is necessary to deposit a large amount of CBr _x, which causes problems such as a difference in pattern conversion of Al-based metal wiring and an excessively tapered cross section. There is a high possibility that the particle level inside the plasma etching apparatus will be deteriorated. Further, in the patterning of the Al-based metal layer on the underlying insulating film having a step, a stringer residue extending to the lower part of the step side surface is generated due to excessive deposition of the side wall protective film, which may cause a short circuit between wirings. There is. Further, as an essential problem, a sufficient side wall protection effect cannot be exhibited under high ion energy conditions for patterning a barrier metal layer or an Al-based metal layer having an antireflection film structure. This is C when compared with the binding energy between two atoms.
-Br is 67 ± 5 kcal / mol, 95 ± 7 kcal / mol for C-Cl and 145 ± 5 kca for C-C.
It is also clear from the fact that it is smaller than 1 / mol.
Note that the bond energy between the two atoms is CRC Handbo
ok of Chemistry and Physi
cs, 71st. Edition, 1990-1991
(CRC Press).

Separately from this, an example in which methanol, which is a compound containing C, H and O, which is a constituent element of the resist mask, is added, and the Al-based metal layer is plasma-etched by a Cl ₂ / CH ₃ OH mixed gas is a special case. Kaihei 4-14762
It is disclosed in Japanese Patent Publication No. This utilizes the fact that the decomposition of the resist mask is relatively reduced by the addition of CH ₃ OH, and the selection ratio of 3.5 to 4 is achieved. However, it is difficult to expect the sputtering effect of ion species having a large mass of BCl _x ^+, and it is difficult to remove the natural oxide film.
Therefore, the inducti before the etching actually starts
There is a problem in that the on time (dead time) is prolonged and the patterning uniformity is poor.

On the other hand, as a phenomenon peculiar to the patterning of Al-based metal wiring, there is a problem of after-corrosion.
The mechanism of occurrence of after-corrosion is described in, for example, Monthly Semiconductor World magazine (Press Journal, Inc.), April 1989 issue, p. 101-106, the outline of which is as follows.

AlCl ₃ which is a reaction product of etching and a decomposition product of the etching gas itself remain in the vicinity of the Al-based metal wiring pattern after the Al-based metal layer is patterned with the Cl-based gas. These not only adsorb onto the substrate to be etched, but also penetrate into the inside of the resist mask. When AlCl ₃ or a decomposition product of etching gas comes into contact with the atmosphere, it absorbs water to form water droplets containing Cl ⁻ as an electrolyte, and Al is dissolved in this aqueous solution to cause corrosion. Further, CCl _x , which is a reaction product of the resist and the Cl-based gas, is important for securing the anisotropy of etching as a side wall protective film, but Cl in this side wall protective film also becomes harmful residual chlorine after the etching is completed. Become.

In particular, recently, the addition of Cu to Al-based metal wiring has become common, and the problem of after-corrosion tends to become apparent. This is due to the low vapor pressure of the reaction product CuCl _x , which is supposed to be removed by etching.
This is because if the water remains on the pattern of the 1-based metal wiring and water is supplied thereto, a local battery having Cl ⁻ as an electrolyte and Al and Cu as both electrodes is formed and corrosion is accelerated.
This mechanism is the same as in the case of adopting a laminated structure with a different material layer such as a barrier metal layer containing Ti and an antireflection layer. Therefore, more thorough measures against after-corrosion than ever before are desired.

Further, the residual chlorine contained in the side wall protective film due to the decomposition product of the resist mask causes a strong Al ₂ O ₃ system when the substrate to be processed comes into contact with oxygen in the atmosphere or when O ₂ plasma ashing is performed. It becomes a residue and remains like a fence on the side surface of the patterned Al-based metal wiring to reduce the step coverage of the interlayer insulating film formed in the upper layer.
Further, when peeled off, the particle level on the substrate to be processed deteriorates. For this reason also, it is not preferable to form an excessive side wall protective film.

[0016]

SUMMARY OF THE INVENTION The present invention is directed to solving these problems based on the above technical background. That is, an object of the present invention is to provide an Al-based metal layer having a large etching mask selection ratio, excellent anisotropy, and no particle contamination or dimensional conversion difference due to excessive deposition of a sidewall protective film, or a stringer residue at an underlying step. To provide a plasma etching method.

Another object of the present invention is to provide an Al-based metal layer containing a difficult-to-etch element such as Cu, or a laminated structure of different materials such as a Ti-based material layer without etching residue or after-corrosion. A plasma etching method for a base metal layer is provided.

[0018]

A method of patterning an Al-based metal layer of the present invention is proposed to solve the above-mentioned problems, and an Al-based metal layer containing F is used as an etching mask. It is characterized in that the layer is patterned.

As the inorganic material layer containing F, SiOF is used.
And SiONF can be exemplified. These are SiO _x F
It is a compound to be represented in the form of _y and SiO _x N _y F _z , and does not necessarily have a stoichiometric composition. That is, SiO, which is a normal inorganic dielectric material
_It should be regarded as a structure in which F is contained in ₂ or SiON. Such an inorganic material layer containing F has recently been proposed as an insulating film material having a low dielectric constant for increasing the speed of semiconductor devices, high frequency devices, and the like. As an example, Extend
ed Abstracts of the 1993
International Conference o
n Solid State Devices and
Materisls, Makuhari, 1993,
pp. 161-163, the physical properties of SiOF and the film forming method are reported, and this material is used as an etching mask.

As the etching gas, a gas containing boron halide such as BCl ₃ or a gas containing sulfur halide gas such as S ₂ Cl ₂ which can release free sulfur into plasma under discharge dissociation conditions is adopted. To do.

The Al-based metal layer which is the etching object of the present invention is mainly pure Al, Al--Si alloy, Al.
It is a material layer of any one of -Si-Cu alloys.

Al, which is the etching object of the present invention,
An adhesion layer made of a Ti-based material layer and a barrier metal layer are provided below the system-based metal layer, and the Ti-based material layer is continuously patterned after the patterning of the Al-based metal layer.

Alternatively, an antireflection film made of a Ti-based material layer is provided on the Al-based metal layer, and the Al-based metal layer is continuously patterned after the patterning of the Ti-based material layer. . Of course, a Ti-based material layer may be provided on both the upper and lower layers of the Al-based metal layer.

Further, a W layer is provided under the Al-based metal layer, and the W-layer is continuously patterned after the patterning of the Al-based metal layer. In this case, the W layer plays a role as a redundant layer for ensuring the minimum conduction even when the Al-based metal wiring is disconnected due to stress migration or electromigration, and provides a highly reliable semiconductor device. Is.

[0025]

The point of the present invention is to employ an inorganic material layer containing F as an etching mask, and the side wall protective film required for anisotropic processing is AlF which is a reaction product of Al-based metal and F.
_{It is defined as x,} and the source of this F is determined as an etching mask.

An inorganic material mask containing F such as SiOF and SiONF is gradually sputtered out during plasma etching accompanied by an ion assist reaction, and F is released into plasma as an active species. F as an active species reacts with the exposed side wall of the Al-based metal wiring that is being patterned to form an AlF _x film, and prevents side etching due to attack of the Al-based metal wiring by Cl ^* . This is 158.6 ± 1.5 kcal / mo when Al-F is compared with the binding energy between two atoms according to the above-mentioned source.
1, while the distance between Al and Cl is 122.2 ± 0.2.
It is also clear from the fact that it is kcal / mol.

Usually, in plasma etching using an inorganic material as an etching mask, it is impossible to find the side wall protective film for achieving anisotropic processing as a decomposition product of the resist mask. Therefore, it is important to form the sidewall protective film by some means, and for example, an example of using a deposition gas has been reported. However, as described above, the use of ordinary deposition gas is not practical in terms of increasing the particle level.

In the present invention, since the side wall protective film required for anisotropic processing is formed by fluorinating the side surface itself of the layer to be etched, which is being patterned, a deposition gas is used as the etching gas, Alternatively, it is not necessary to add it separately. The AlF _x formed on the side surface of the layer to be etched is formed as an extremely thin film only on the surface of the Al-based metal wiring, and the fluorination reaction does not proceed inside the Al-based metal wiring.

In the present invention, S ₂ C is used as the deposition gas.
There is a mode in which a halogenated sulfur-based gas that can release free sulfur into plasma under discharge dissociation conditions such as l ₂ is adopted, but since sulfur-based deposits are sublimable, particle contamination may occur. There is no. That is, pure sulfur or polythiazil can be adopted as the sulfur-based deposit, but the sublimation temperature of each in a reduced pressure atmosphere is about 90 ° C. or higher and about 150 ° C. or higher. Conversely, pure sulfur or polythiazyl can be deposited on the substrate to be etched if the substrate to be etched is less than about 90 ° C. and less than about 150 ° C., and can be used as a side wall protective film.

SiOF or SiO used in the present invention
Although the inorganic material mask such as NF contains F,
Originally, since it is a SiO ₂ or SiON based material, it is possible to secure a sufficient selection ratio to the etching mask in plasma etching of the Al based metal layer.

Furthermore, since the AlF _x type thin film formed on the side wall surface of the patterned Al type metal wiring is a dense fluoride and does not contain Cl inside,
The effect of preventing after-corrosion can also be achieved.

In order to form the AlF _x type sidewall protective film, it is conceivable to add an F type gas to the etching gas separately. However, this method, AlF _x based material is formed in the entire etching reaction system, there is a possibility that a new particle contamination source. Therefore, in the present invention has a structure that supplies a topically active F from the etching mask existing in close proximity of the layer to be etched, to prevent the formation of undesired AlF _x based material other than the formation of the sidewall protection film Of.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings. Each of the following examples is an example in which a substrate bias application type helicon wave plasma etching device is used as an etching device.

Example 1 In this example, SiOF was used as an etching mask, and BCl ₃ was used as a boron halide to form an Al film.
This is an example of patterning the base metal layer, which is shown in FIG.
This will be described with reference to (a) to (d).

The sample used in this example is Si (not shown).
And the like, an adhesion layer / barrier metal layer 2 formed by stacking a Ti layer and a TiN layer formed on an interlayer insulating film 1 made of SiO ₂ on a semiconductor substrate, an Al-based metal layer 3 made of Al-0.5% Cu, and SiOF. The inorganic material layer 4 and the resist mask 5 are sequentially formed. As an example of the thickness of each layer, the interlayer insulating film 1 has a reduced pressure C of 600 n.
The adhesion layer / barrier metal layer 2 is formed by VD, and the lower Ti layer is 30 nm and the upper TiN layer is 70 nm.
All of 100 nm are formed by sputtering or reactive sputtering. Al
The system metal layer 4 is also deposited by sputtering to a thickness of 500 nm. The inorganic material layer 4 has a thickness of 100 nm by adding SiF ₄ to the plasma generation chamber in addition to the source gas SiH ₄ / N ₂ O mixed gas by an ECR plasma CVD apparatus capable of applying a substrate bias, for example. Formed to a thickness. The resist mask 5 is a mask for patterning the inorganic material layer 4, and is formed selectively by a chemically amplified resist and KrF excimer laser lithography into a pattern having a width of 0.35 μm. A connection hole (not shown) is opened in the interlayer insulating film 1, and an active layer such as a diffusion layer of a semiconductor substrate and an adhesion layer / barrier metal layer 2 (not shown) are also formed.
May form an ohmic contact. In this case, the adhesion layer / barrier metal layer 2 is formed so as to conformally cover the connection hole under a sputtering condition using a collimator or the like having a large vertical incidence component. This state is shown in FIG.

Next, using the resist mask 5 as a mask, the inorganic material layer 4 is patterned using an F-based gas,
The resist mask 5 is removed by ashing. This process is
RIE device, etc. that connects inline ashing device
A known plasma etching apparatus may be used. FIG. 1B shows a state in which an etching mask made of the inorganic material layer 4 is formed, which is a substrate to be etched.

This substrate to be etched is set on the substrate stage of a helicon wave plasma etching apparatus of the substrate bias application type, and the Al-based metal layer is mixed with BCl ₃ / Cl ₂ mixed gas which is a general etching gas for the Al-based metal layer. 3 and the laminated film including the adhesion layer / barrier metal layer 2 were taken as an example and continuously patterned under the following conditions. BCl ₃ flow rate 50 sccm Cl ₂ flow rate 50 sccm Gas pressure 0.13 Pa Helicon wave power source power 2500 W (13.56 MHz) Substrate bias power 100 W (13.56 MHz) Substrate temperature 20 ° C. The substrate temperature was temperature controlled. From the top surface of the substrate stage to the back surface of the substrate to be processed, He as a heat transfer gas was
The flow rate was 0 sccm, and a constant temperature was maintained. The state of the substrate to be etched during plasma etching is shown in FIG. Normally, an inorganic material such as SiO ₂ or SiON is used as an etching mask and a BCl ₃ / Cl ₂ mixed gas is used to
When plasma-etching the 1-based metal layer, there is no supply source of the side wall protective film, and thus the patterned A
The l-based metal layer is largely side-etched. However, in this embodiment, the side surface of the Al-based metal layer being patterned is fluorinated by the active F emitted by sputtering the mask made of the inorganic-based material layer 4 made of SiOF, and the side wall protective film 6 made of AlF _x. As a result, side etching does not occur.

FIG. 1D shows a state in which the adhesion layer / barrier metal layer 2 is patterned under the same plasma etching conditions to complete the laminated wiring including the Al-based metal layer 3. The selection ratio to the etching mask was 8, which was much higher than the selection ratio of about 2 when the resist mask was used. Further, in the conventional plasma etching using the resist mask, the carbon-based polymer containing Cl serves as the side wall protective film, but the AlF _x type side wall protective film 6 in this embodiment does not contain Cl, so that it is caused by residual chlorine. After-corrosion does not occur. 1 (c) and 1 (d), the thickness of the side wall protective film 6 is exaggerated, but it is actually an extremely thin film.

After completion of the plasma etching, the inorganic material 4
The mask may be separately removed with an F-based gas, or may be left as it is and used as a part of an upper interlayer insulating film formed later. Since the sidewall protection film 6 of AlF _x system is a chemically stable substance, no inconvenience at all by residual anyway. According to the present embodiment, it is possible to form an Al-based metal wiring free from side etching, after-corrosion and particle contamination by using an inorganic material made of SiOF as an etching mask. Further, since the thickness of the etching mask can be reduced by improving the selection ratio with respect to the etching mask, highly accurate patterning without pattern conversion difference can be realized. Furthermore, since the carbon-based polymer does not accumulate even if the number of substrates to be etched is increased, the maintenance man-hours for chamber cleaning can be reduced.

Example 2 This example is an example in which SiONF is used as an etching mask and a laminated structure film including a structure in which an Al-based metal layer is formed on a W layer is patterned by two-step etching. As an etching gas, an etching gas containing a halogenated sulfur-based gas capable of releasing free sulfur into plasma under discharge dissociation conditions was used. This is shown in FIG.
This will be described with reference to (d). In the figure, the same components as those in FIGS. 1A to 1D referred to in the previous embodiment are designated by the same reference numerals.

The sample used in this example is Si (not shown).
Adhesion layer / barrier metal layer 2, W layer 7, Al-1% Si-0.5% C formed by stacking a Ti layer and a TiN layer formed on an interlayer insulating film 1 made of SiO ₂ on a semiconductor substrate such as
An Al-based metal layer 3 made of u, an inorganic material 4 made of SiONF, and a resist mask 5 are sequentially formed. As an example, the thickness of each layer is 60 for the interlayer insulating film 1.
The adhesion layer / barrier metal layer 2 was formed by low pressure CVD to a thickness of 0 n, and the lower Ti layer was 30 nm, the upper TiN layer was 70 nm, and a total of 100 nm was formed by sputtering or reactive sputtering. Is. The W layer 7 is formed by blanket CVD to 500 nm, and the Al-based metal layer 4 is formed by sputtering 4 nm.
It is deposited to a thickness of 00 nm. Inorganic material layer 4
As an example, an ECR plasma CVD apparatus capable of applying a substrate bias is used to produce SiH ₄ / N ₂ which is a source gas.
In addition to the O / NH ₃ mixed gas, SiF ₄ was added to the plasma generation chamber to form a film having a thickness of 100 nm. Further, the resist mask 5 is a mask for patterning the inorganic material layer 4, and is 0.35 μm by a chemically amplified resist and KrF excimer laser lithography.
It is formed selectively in a width pattern. A connection hole (not shown) is opened in the interlayer insulating film 1, and an active layer such as a diffusion layer (not shown) of the semiconductor substrate and an adhesion layer / barrier metal layer 2 also form an ohmic contact.
The structure may be such that the W layer 7 formed by blanket CVD is embedded therein. In this case, the adhesion layer / barrier metal layer 2 is formed so as to conformally cover the connection hole under a sputtering condition using a collimator or the like having a large vertical incidence component. This state is shown in FIG.

Next, using the resist mask 5 as a mask, the inorganic material layer 4 is patterned using an F-based gas.
The resist mask 5 is removed by ashing. This process is
RIE device, etc. that connects inline ashing device
A known plasma etching apparatus may be used. FIG. 1 shows a state in which an etching mask made of an inorganic material layer is formed.
Shown in (b), this is the substrate to be etched.

The substrate to be etched was set on the substrate stage of a helicon wave plasma etching apparatus of the substrate bias application type, and first, the Al-based metal layer 3 was patterned under the following conditions as an example. S ₂ Cl ₂ flow rate 20 sccm Cl ₂ flow rate 50 sccm Gas pressure 0.13 Pa Helicon wave power source power 2500 W (13.56 MHz) Substrate bias power 100 W (13.56 MHz) Substrate temperature 20 ° C. Substrate temperature is temperature control He as a heat transfer gas is directed from the upper surface of the processed substrate stage toward the rear surface of the substrate to be processed.
The flow rate was 0 sccm, and a constant temperature was maintained. The state of the substrate to be etched after the patterning of the Al-based metal layer 3 is shown in FIG. In this plasma etching step, the side surface of the Al-based metal layer that is being patterned is fluorinated by the active F emitted by sputtering the mask made of the inorganic-based material layer 4 of SiONF.
A thin film of IF _x is formed. In addition to this, free sulfur generated by dissociation of S ₂ Cl ₂ is deposited on the surface of the AlF _x thin film, and the side wall protective film 6 is formed by AlF _x and sulfur, so that the Al-based metal layer 3 is extremely different. It is patterned with good orientation. The etching mask selection ratio was 9.

When the surface of the W layer 7 is exposed, the etching gas is switched, and as an example, the W layer 7 and the adhesion layer / barrier metal layer 2 are continuously patterned under the following conditions. S ₂ F ₂ flow rate 50 sccm Gas pressure 0.13 Pa Helicon wave power source power 2500 W (13.56 MHz) Substrate bias power 100 W (13.56 MHz) Substrate temperature 20 ° C. Dissociation of S ₂ F _{2 in} this plasma etching process Anisotropic etching proceeds in a form in which the radical reaction by F ^* generated by is assisted by the incident energy of SF ⁺ . Also at this time, free sulfur similarly generated by dissociation of S ₂ F ₂ adheres to the side surface of the W layer 2 which is being patterned and forms a sidewall protective film (not shown) made of sulfur to form anisotropy. Contribute to the improvement of. After the patterning is completed, the substrate to be etched is heated to a temperature of about 90 ° C. or higher in a reduced pressure atmosphere to sublimate and remove the sulfur in the side wall protection film 6 to complete the patterning. This state is shown in FIG. Sulfur in the side wall protection film 6 may be left as it is, and may be removed by sublimation in the next step, for example, immediately before the formation of the upper interlayer insulating film. Sulfur does not become a pollution source for the laminated wiring including the Al-based metal layer 3 and the W layer 7, and in addition to reducing after-corrosion caused by contact between the moisture in the atmosphere and the Al-based metal layer 3, AlF _x It exerts a thorough effect in cooperation with the side wall protective film 6 made of. Although the thickness of the sidewall protection film 6 made of the remaining AlF _x is exaggerated in the figure, it is actually an extremely thin film.

In the conventional plasma etching using the resist mask, the carbon-based polymer containing Cl becomes the side wall protective film. However, since the AlF _x type side wall protective film 6 in this embodiment does not contain Cl, it remains in the residual chlorine. There is no after-corrosion caused. After the plasma etching is completed, the mask made of the inorganic material layer 4 may be separately removed with an F-based gas, or may be left as it is and used as a part of an upper interlayer insulating film formed later. Since the sidewall protection film 6 of AlF _x system is a chemically stable substance, no inconvenience at all by residual anyway.

According to this embodiment, it is possible to form an Al-based laminated metal wiring free from side etching, after-corrosion and particle contamination by using an inorganic material of SiONF as an etching mask. Further, since the thickness of the etching mask can be reduced by improving the selection ratio with respect to the etching mask, highly accurate patterning without pattern conversion difference can be realized. Furthermore, since the carbon-based polymer does not accumulate even if the number of substrates to be etched is increased, the maintenance man-hours for chamber cleaning can be reduced.

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

First, in each of the above-described embodiments, an example of patterning a structure in which an Al-based metal layer and an adhesion layer / barrier metal layer or a W layer as a redundant layer is laminated is shown. A structure in which an antireflection film such as TiON is further formed thereon may be used. Of course, it may be a single Al-based metal layer.

Al-1% Si and Al as an Al-based metal layer
Although -1% Si-0.5% Cu is exemplified, various Al alloys such as pure Al and the like may be used, and the film forming method thereof is not limited.

Although BCl ₃ is used as the boron halide gas, BBr ₃ may be used. In this case, another C
You may use together with 1 type gas. Further, S ₂ Cl ₂ is exemplified as a halogenated sulfur-based gas capable of releasing free sulfur into plasma under discharge dissociation conditions, but S ₃ Cl ₂ , SC
It is possible to use sulfur chloride gases such as l ₂ and sulfur bromide gases such as S ₂ Br ₂ , S ₃ Br ₂ and SBr ₂ . In the case of patterning the W layer, S ₂ F ₂ , SF
Sulfur fluoride gas such as ₂ , SF ₄ and S ₂ F ₁₀ may be used. SF _{6, which} is generally used as a sulfur fluoride gas, is excluded because it is difficult to release free sulfur into plasma under discharge dissociation conditions.

If a halogenated sulfur-based gas capable of releasing free sulfur into plasma under these discharge dissociation conditions is used together with an N-based gas such as N ₂ or N ₂ H ₄ , the free sulfur is immediately released into the plasma. Compound with the active nitrogen of to form thiazyl (SN). This thiazyl is deposited as polythiazil on the substrate to be etched while polymerizing. Polythiazyl can also form a strong sidewall protective film and contribute to anisotropic processing.

A rare gas such as Ar or He or a gas such as CO, NO or H ₂ which captures a halogen and controls its concentration may be further added to the etching gas.

A substrate bias application type helicon wave plasma etching apparatus was used as the etching apparatus, but a more general parallel plate type RIE apparatus, an ECR plasma etching apparatus, or a high density plasma treatment is possible.
CP (Inductively Coupled Pl)
asma) etching device, TCP (Transform)
A mer coupled plasma) etching device or the like can be used.

[0054]

As is apparent from the above description, according to the plasma etching method for an Al-based metal layer of the present invention, the selectivity ratio with respect to the etching mask is large, the anisotropy is excellent, and the excessive side wall protective film is provided. It is possible to provide a plasma etching method for an Al-based metal layer that is free of particle contamination and dimensional conversion difference due to the deposition of copper, or a stringer residue at the underlying step.

Further, according to the present invention, in particular, even if it is a laminated structure of different materials such as an Al-based metal layer containing an element that is difficult to etch such as Cu and a Ti-based material layer, Al without etching residue or after-corrosion. It is possible to provide a plasma etching method for a base metal layer. The present invention provides an excellent plasma etching method for Al-based metal wiring, which can sufficiently meet the demand for thinning of an etching mask due to the miniaturization of design rules.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view for explaining a first embodiment to which the present invention is applied in the order of steps, in which (a) shows an adhesion layer / barrier metal layer and an Al-based metal layer formed on an interlayer insulating film. A state where an inorganic material layer and a resist mask are formed, (b) a state where an etching mask is formed by the inorganic material layer,
(C) is a state in which the Al-based metal layer is halfway plasma-etched using the inorganic material layer as a mask, and (d) is the Al
The system metal layer and the adhesion layer / barrier metal layer are plasma-etched to complete wiring by the Al system metal layer.

2A to 2C are schematic cross-sectional views illustrating Example 2 to which the present invention has been applied in the order of steps, in which FIG. 2A shows an adhesion layer / barrier metal layer, a W layer, and an Al-based metal layer formed on an interlayer insulating film. In addition, a state in which an inorganic material layer and a resist mask are further formed, (b) is a state in which an etching mask is formed by the inorganic material layer, and (c) is an Al-based metal layer that is plasma-etched using the inorganic material layer as a mask. The state (d) is a state in which the W layer and the adhesion layer / barrier metal layer are continuously plasma-etched to complete the laminated wiring including the Al-based metal layer and the W layer.

[Explanation of symbols]

 1 Interlayer Insulating Film 2 Adhesion Layer and Barrier Metal Layer 3 Al-based Metal Layer 4 Inorganic Material Layer 5 Resist Mask 6 Sidewall Protection Film 7 W Layer

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Claims (8)

[Claims] 1. A plasma etching method for an Al-based metal layer, wherein the Al-based metal layer is patterned using the inorganic material layer containing F as an etching mask. 2. The plasma etching method for an Al-based metal layer according to claim 1, wherein the inorganic material layer containing F is a layer containing any one of SiOF and SiONF. 3. The plasma etching method for an Al-based metal layer according to claim 1, wherein an etching gas containing boron halide is used. 4. The A according to claim 1, wherein an etching gas containing a halogenated sulfur-based gas capable of releasing free sulfur into plasma under discharge dissociation conditions is used.
Plasma etching method for l-based metal layer. 5. The Al-based metal layer is a material layer of any one of pure Al, an Al—Si alloy, and an Al—Si—Cu alloy. The plasma etching method for an Al-based metal layer according to claim 1. 6. The Ti-based material layer is provided below the Al-based metal layer, and the Ti-based material layer is continuously patterned after the patterning of the Al-based metal layer. 5. The plasma etching method for an Al-based metal layer according to any one of 1, 2, 3 and 4. 7. The Ti-based material layer is provided on the Al-based metal layer, and the Al-based metal layer is continuously patterned following the patterning of the Ti-based material layer. 5. The plasma etching method for an Al-based metal layer according to any one of 1, 2, 3, and 4. 8. The method according to claim 1, wherein a W layer is provided below the Al-based metal layer, and the W-layer is continuously patterned after the patterning of the Al-based metal layer. The plasma etching method for an Al-based metal layer according to any one of 3 and 4.