JPH05275395A - Dry etching method - Google Patents

Abstract

PURPOSE:To prevent generation of residue caused by Cu, relating to dry etching of an Al-Si-Cu alloy. CONSTITUTION:By just-etching an Al group multi-layer film 5 containing an Al-1% Si-0.5% Cu layer 3 with ordinal chlorine group gas such as Cl2/BCl2 mixture gas, etc., an Al group wiring pattern 5a having anisotropic shape is formed. At the same time, a Cu2Cl2 with low steam pressure is formed through the reaction between Cu and Cl*. This acts as a micro mask 7 to easily generate a great amount of needle-like residue 5b. So, using Cl2/HI mixture gas, over- etching is performed while a wafer is heated. As a result, not only the residue 5b but the Cu contained in the micro mask 7 are removed in the form of Cu2I2 whose steam pressure is relatively high, leaving no particle contamination. Further, residue chlorine is removed thanks to wafer heating, resulting in improved after-corrosion resistance.

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 applied in the manufacture of semiconductor devices, and more particularly to Al etching method.
The present invention relates to a method of preventing the occurrence of a residue caused by Cu and suppressing after-corrosion when etching an aluminum (Al) -based material layer containing copper (Cu) such as a —Si—Cu alloy.

[0002]

2. Description of the Related Art Aluminum (Al) -based materials are most widely used as wiring materials for semiconductor devices. This Al-based material can prevent the pn junction from being destroyed or deteriorated due to an alloying reaction with the underlying silicon substrate, or can be used as a contact or
In order to prevent silicon from depositing inside the holes and causing conduction failure, it is general to add 1 to 2% of Si. Furthermore, in recent years, in order to improve electromigration resistance and stress migration resistance, Al-containing 0.5 to 1% of Cu is further added.
Si-Cu alloys are also used.

Dry etching of the Al-based material layer is generally performed using a chlorine-based gas. For example, BCl ₃ / Cl disclosed in JP-B-59-22374.
_A mixed gas is a typical example. The chemical species contributing as the main etching species in the etching of the Al-based material layer is C.
l ^* , which promotes spontaneous and extremely rapid etching reaction. However, since the etching proceeds isotropically only with Cl ^* , the ion-assisted reaction normally proceeds under the condition that the incident ion energy is increased to achieve high anisotropy.

[0004]

However, when Cu is contained in the Al-based material layer, the use of the above chlorine-based gas for etching causes a low vapor pressure of the reaction product. It has been pointed out that the residue frequently occurs. This problem will be described with reference to FIG.

For example, as shown in FIG. 2 (a), S
Consider a wafer in which an Al-based multi-layered film 15 is formed on the iO ₂ interlayer insulating film 11 and a resist mask 16 patterned into a predetermined shape is further formed thereon. Here, the Al-based multilayer film 15 includes the TiN barrier metal 12 and Al-1% Si-0.5 from the lower layer side to the upper layer side.
% Cu layer 13 and TiON antireflection film 14 are sequentially laminated.

Next, FIG. 2B shows the state of the wafer when the Al-based multilayer film 15 is etched through the resist mask 16 with a conventional general chlorine-based gas. Here, each material layer after etching is represented by adding the subscript a or the subscript b to the original code. By this etching, the Al-based wiring pattern 15a having an anisotropic shape is formed in the masked portion of the resist mask 16, but the needle-shaped residue 15b is formed in the unmasked portion.
Is occurring in large numbers. This is Al-1% Si-0.
Cu contained in the 5% Cu layer 13 reacts with etching reactive Cl ^* to generate Cu ₂ Cl ₂ having a low vapor pressure,
This functions as a fine etching mask called a micro mask 17, and as a result, Al-1% Si-0.5% Cu is formed in the region shielded by the micromask 17.
Residue 13b of layer 13 and residue 1 of TiN barrier metal 12
This is because 2b remains. This is an unavoidable phenomenon because achievement of anisotropy in the etching of the Al-based material layer depends on high incident ion energy.

Therefore, as a method of removing the residue 15b, for example, the 37th Applied Physics Association Lecture (1
990 Spring Annual Meeting) Proceedings, p. 456, Lecture No. 28a-ZF-1 reports a method of chemically removing the residue. Specifically, the needle-like residue 15b is eroded from the lateral direction and is removed by performing overetching under isotropic conditions where the radical reaction is the main component. However, although this method is effective for removing the residue 15b, the micro mask 17 itself cannot be decomposed and removed. Therefore, as shown in FIG. 2C, the micro mask 17 itself is regarded as a particle contamination source. There is a great risk of becoming.

Further, as a problem when Cu is contained in the Al-based material layer, reduction in after-corrosion resistance is pointed out. This is due to the low vapor pressure of Cu ₂ Cl
_If water is supplied to the portion where ₂ remains near the wiring pattern, a local battery having Cl ⁻ as an electrolyte and Al and Cu as both electrodes is formed, and corrosion of the wiring pattern is promoted. is there.

Therefore, it is an object of the present invention to provide a method for suppressing the occurrence of residues due to Cu and improving the after-corrosion resistance when dry-etching an Al-based material layer containing Cu.

[0010]

A dry etching method according to the present invention is proposed to achieve the above-mentioned object, and contains at least one of a chlorine compound or a bromine compound and an iodine compound. It is characterized in that the Al-based material layer containing Cu is etched while the substrate to be etched is heated using an etching gas.

The present invention also provides a just etching step of etching an Al-based material layer containing Cu substantially by the thickness thereof by using an etching gas containing at least one of a chlorine-based compound and a bromine-based compound, An overetching step of etching the remaining portion of the Cu-containing Al-based material layer while heating the substrate to be etched using an etching gas containing at least one of a chlorine-based compound or a bromine-based compound and an iodine-based compound. It is characterized by having.

Further, the present invention uses an etching gas capable of producing at least one of a chlorine-based chemical species or a bromine-based chemical species and a sulfur-based chemical species in plasma under discharge dissociation conditions, and uses an Al-based gas containing Cu. Using the just etching step of etching the material layer substantially by the thickness of the material layer and the etching gas containing at least one of a chlorine-based compound or a bromine-based compound and an iodine-based compound, while heating the substrate to be etched, the Cu And an over-etching step of etching the remaining portion of the Al-based material layer containing.

[0013]

The present inventor considered that a chemical species that gives a Cu compound having a vapor pressure as high as possible is necessary as an etching reaction product in order to prevent generation of a residue due to Cu, and paid attention to iodine. CRC Handbook o
f Chemistry and Physics, 7
1st Edition, 6-51 (CRC Pres
s Inc. ), Or the same 53rd Edition
n, D-172, the data of the vapor pressure of the inorganic compound is 1 to 760 mmHg (= 1.33 × 1
It is clear that the temperature at which the vapor pressure is 0 ^{2 to} 1.01 × 10 ⁵ Pa) is lower in Cu ₂ I ₂ than in both Cu ₂ Cl ₂ and Cu ₂ Br ₂ . This is, in other words, the vapor pressure of Cu ₂ I ₂ at the same temperature, Cu ₂
That is, it is higher than the vapor pressure of either Cl ₂ or Cu ₂ Br ₂ . The gas pressure of the etching reaction system in which normal dry etching is performed belongs to a region much lower than the above pressure range, but the same tendency is maintained even under such a low pressure.

Therefore, if Cu ₂ I ₂ is produced in an etching reaction system containing iodine, it is Cu ₂ C _2.
It can be desorbed at a wafer temperature lower than l ₂ or the like.

In the present invention, the iodine compound for supplying iodine to the etching reaction system is added to at least one of the chlorine compound and the bromine compound. Removal of Al occupying most of the Al-based material layer and Si added in a small amount in the form of chloride or bromide by chlorine-based and bromine-based chemicals generated from chlorine-based and bromine-based compounds. You can Moreover, since the etching at this time is performed while heating the substrate to be etched (wafer), Cu, which is also added in a small amount, is removed in the form of Cu ₂ I ₂ . Therefore, there is no risk that any residue will remain on the wafer. Furthermore, since the chlorine remaining in the form of AlCl _x or the like in the vicinity of the pattern can be reduced by the above-mentioned wafer heating, the after-corrosion resistance can also be improved.

The present invention also proposes a method in which just etching is performed using a conventionally known chlorine-based or bromine-based gas, and an iodine-based compound is added to the above-mentioned gas during overetching. During overetching, the wafer is heated. As a result, even if a residue is generated in the just etching step, Al and Si forming the residue are mainly removed in the form of chloride or bromide and Cu in the form of iodide during overetching. Therefore, particle contamination due to Cu can be prevented.

According to this method, since it is not necessary to particularly heat the wafer in the just etching step which occupies most of the etching step, the resist selectivity can be improved.

In the present invention, in order to achieve a more thorough reduction of pollution, at least one of a chlorine-based chemical species or a bromine-based chemical species and a sulfur-based chemical species can be generated in the plasma under discharge dissociation conditions during just etching. Etching gas is used. This is because the Al-based material layer is just-etched with chlorine-based chemical species or bromine-based chemical species as before, while S (sulfur) is used for sidewall protection.

The applicant of the present application has proposed a technique of utilizing S for side wall protection in Japanese Patent Application No. 3-210516. Although depending on the conditions, S is deposited on the surface of the wafer if the temperature of the wafer is controlled below room temperature. Therefore, if S is used for side wall protection,
It is possible to reduce the deposition amount of the carbon-based polymer necessary for anisotropic processing and further the incident ion energy, improve the selectivity, and reduce particle contamination. Further, the carbon-based polymer inevitably incorporates chlorine in its structure, but S does not have such a case.
Is also effective from the viewpoint of improving the after-corrosion resistance. Moreover, S is about 90 ° C for the wafer.
If it is heated above, it is easily sublimated, so that it does not itself become a source of particle contamination. In the present invention, S can be removed by heating the wafer during overetching.

As a technique related to the present invention,
The applicant of the present application has previously proposed, in Japanese Patent Application No. 3-91544, a technique for etching an Al-based material layer using an etching gas containing a chlorine-based compound and HI (hydrogen iodide). This is because HI was selected as a compound capable of efficiently releasing H under discharge dissociation conditions, paying attention to the fact that H is contained in the decomposition product of the resist mask to promote its deposition. That is, since the interatomic bond energy of the HI bond is smaller than that of the H-Cl bond or the H-Br bond, the use of HI promotes the deposition of the carbon-based polymer as compared with the case of using another hydrogen halide. It is. In this prior art, whether or not the Al-based material layer contains Cu has nothing to do with the gist of the invention.

On the other hand, the present invention is based on the premise that the Al-based material layer contains Cu, and the residue generated during just etching due to this Cu will be removed by using HI during overetching. It is what Therefore, the present invention is different in purpose and effect from the prior application of the applicant of the present application.

[0022]

EXAMPLES Specific examples of the present invention will be described below.

Example 1 In this example, TiN barrier metal, Al-1% Si-
This is an example in which an Al-based multilayer film in which a 0.5% Cu layer and a TiON antireflection film are stacked is etched using a Cl ₂ / BCl ₃ / HI mixed gas. This process is illustrated in Figure 1.
A description will be given with reference to (a) and (c).

The wafer used as the etching sample in this embodiment is SiO 2 as shown in FIG.
_The Al-based multilayer film 5 is formed on the _two- layer insulating film 1, and the resist mask 6 patterned into a predetermined shape is further formed on the Al-based multilayer film 5. Here, the Al-based multilayer film 5 has a thickness of about 0.1 μm from the lower layer side to the upper layer side.
m TiN barrier metal 2 with a thickness of about 0.4 μm Al-
1% Si-0.5% Cu layer 3, T about 0.03 μm thick
The iON antireflection film 4 is sequentially laminated.

This wafer was set in an RF bias application type magnetic field microwave plasma etching apparatus, and as an example, the Al type multilayer film 5 was etched under the following conditions. Cl ₂ flow rate 80 SCCM BCl ₃ flow rate 10 SCCM HI flow rate 30 SCCM Gas pressure 2 Pa (= 15 mTorr)
r) Microwave power 900W (2.45GHz) RF bias power 30W (13.56MHz) Wafer temperature 150 ° C

This gas system is obtained by adding HI to the most general mixed gas used for dry etching of Al-based material layers. In the above etching process, the Al-based multilayer film 5 was etched by a mechanism in which the radical reaction by Cl ^* was assisted by the incident energy of ions such as Cl ⁺ and BCl _x ⁺ . BCl ₃ is Al-1% Si-0.
It also contributes to the rapid progress of etching by reducing the natural oxide film on the surface of the 5% Cu layer 3. Also Cu
Produced Cu ₂ I _{2 and the} like by reacting with I ^* , I ^{+ and the} like produced from HI, which was rapidly desorbed under the wafer heating conditions. In the etching reaction system, the fragments of the resist mask 6 sputtered by the above ions and Cl ^* react with each other to generate CCl _{x and the} like. This CCl _x was deposited on the side wall surface of the pattern to form a side wall protection film (not shown), which contributed to anisotropic processing.

As a result, as shown in FIG. 1 (c),
Immediately below the resist mask 6, an Al-based wiring pattern 5a having an anisotropic shape was formed. In the figure, each material layer after etching is represented by adding the subscript a to the original code. At this time, no residue was generated on the wafer.

After that, the wafer was transferred to a plasma ashing apparatus attached to the etching apparatus, and O ₂ plasma ashing was performed under normal conditions to remove the resist mask 6. Although this wafer was left in the atmosphere for a test, no after-corrosion was observed even after 72 hours.

Example 2 In this example, the same Al-based multilayer film was just-etched using a Cl ₂ / BCl ₃ mixed gas, and then Cl ₂ / HI was used.
In this example, the residue is removed by performing overetching using a mixed gas. This process is illustrated in Figure 1.
A description will be given with reference to (a), (b) and (c).

The wafer used as an etching sample in this example is the same as that shown in FIG. This wafer was set in an RF bias application type magnetic field microwave plasma etching apparatus, and as an example, the Al-based multilayer film 5 was just etched under the following conditions. Cl ₂ flow rate 90 SCCM BCl ₃ flow rate 30 SCCM Gas pressure 2 Pa (= 15 mTorr
r) Microwave power 900W (2.45GHz) RF bias power 30W (13.56MHz) Wafer temperature 25 ° C

This gas system is the most general mixed gas conventionally used for dry etching of Al material layers. In this just etching process, the ion assist mechanism and the side wall protection effect by CCl _{x are used} .
As shown in (b), an Al-based wiring pattern 5a having an anisotropic shape was formed immediately below the resist mask 6. However, in the vicinity of this Al-based wiring pattern 5a,
A large amount of needle-shaped residue 5b was generated. This is the above A
This is because Cu contained in the l-1% Si-0.5% Cu layer 3 reacts with Cl ^* in the gas phase to produce Cu ₂ Cl ₂ having a low vapor pressure, which functions as the micro mask 7. is there.

In the drawings, each material layer after etching is represented by adding the subscript a or the subscript b to the original code.

Then, as an example, Al is formed under the following conditions.
The system multilayer film 5 was over-etched. Cl ₂ flow rate 60 SCCM HI flow rate 60 SCCM Gas pressure 2 Pa (= 15 mTor)
r) Microwave power 900 W (2.45 GHz) RF bias power 15 W (13.56 MHz) Wafer temperature 150 ° C. In this overetching step, the residue 5b was removed as shown in FIG. 1 (c). That is, Al-1%
The residue 3b of the Si-0.5% Cu layer 3 is AlCl _x , Si
Cl _x , Cu ₂ I _2, etc., the residue 2b of the TiN layer 2 is in the form of TiCl _x, etc., and the micro mask 7 is Cu ₂
It was removed in the form of I _2, etc. Therefore, the particle level on the wafer was not deteriorated at all. Further, in this step, the RF bias power is reduced as compared with the case of just etching from the viewpoint of preventing damage to the base, but by efficiently depositing a carbon-based polymer such as CH _x Cl _y , Al-based wiring The anisotropic shape of the pattern 5a was maintained. Further, by heating the wafer, chlorine remaining in the vicinity of the Al-based wiring pattern 5a was almost volatilized and removed.

After that, the wafer was transferred to a plasma ashing apparatus attached to the etching apparatus, and O ₂ plasma ashing was performed under normal conditions to remove the resist mask 6. Although this wafer was left in the atmosphere for a test, no after-corrosion was observed even after 72 hours.

Example 3 In this example, the same Al-based multilayer film was used as BCl ₃ / S ₂ Cl ₂
After just etching using mixed gas, Cl ₂ /
In this example, over-etching is performed using a HI mixed gas to remove the residue. The wafer used as the etching sample in this example is the same as that shown in FIG. This wafer was set in an RF bias application type magnetic field microwave plasma etching apparatus, and as an example, the Al-based multilayer film 5 was just-etched under the following conditions.

BCl ₃ flow rate 30 SCCM S ₂ Cl ₂ flow rate 90 SCCM Gas pressure 2 Pa (= 15 mTorr)
r) Microwave power 900 W (2.45 GHz) RF bias power 25 W (13.56 MHz) Wafer temperature 0 ° C. In this just etching process, Cl ^* serves as a main etching species and etching progresses, while S ₂ Cl ₂ S generated from contributed to sidewall protection. Therefore, as compared with the just etching process of the first embodiment, the RF bias
Good anisotropic processing could be performed despite a slight decrease in power and a decrease in the amount of carbon-based polymer deposited.

Next, over-etching was performed under the same conditions as in the over-etching process of Example 2 described above. By heating the wafer at this time (150 ° C.), S deposited in the just etching step was quickly removed by sublimation. Then, O ₂ plasma ashing is performed to remove the resist
The mask 6 was removed and the wafer was left in the atmosphere for a test, but after-corrosion was not observed even after 96 hours. The after-corrosion resistance was improved as compared with Example 2 because the amount of carbon-based polymer that contributes to sidewall protection during just etching was reduced, and the amount of residual chlorine near the pattern was reduced.

Example 4 In this example, the same Al-based multilayer film was used as Cl ₂ / BCl ₃ / S.
After just etching using ₂ Br ₂ mixed gas,
In this example, the residue is removed by performing overetching using a Cl ₂ / HBr / HI mixed gas. First, Fig. 1
The wafer shown in (a) was set in an RF bias application type magnetic field microwave plasma etching apparatus, and as an example, the Al-based multilayer film 5 was just-etched under the following conditions.

Cl ₂ flow rate 80 SCCM BCl ₃ flow rate 20 SCCM S ₂ Br ₂ flow rate 30 SCCM Gas pressure 2 Pa (= 15 mTor)
r) Microwave power 900 W (2.45 GHz) RF bias power 30 W (13.56 MHz) Wafer temperature 0 ° C. In this just etching process, Cl ^* and Br ^* are the main etching species and the etching progresses, while S ₂
S generated from Br ₂ contributed to the side wall protection. This Br
The presence of contributes to the improvement of resist selectivity. This is because when comparing the saturated vapor pressures of the etching reaction products of the resist mask, CBr ₄
Is lower than that of CCl ₄ ,
This is because the surface of the resist mask is protected by CBr _x . For the improvement of resist selectivity by Br, see, for example, Monthly Semiconductor World, 1990.
December issue, p103-107.

Subsequently, as an example, overetching was performed under the following conditions. Cl ₂ flow rate 30 SCCM HBr flow rate 30 SCCM HI flow rate 60 SCCM Gas pressure 2 Pa (= 15 mTorr)
r) Microwave power 900 W (2.45 GHz) RF bias power 15 W (13.56 MHz) Wafer temperature 150 ° C. In this step, as a matter of course, the residue 5b is removed as shown in FIG. 1 (c). However, the high resist selectivity due to the use of Br was maintained as in the just etching. Further, due to the wafer heating (150 ° C.) at this time, S deposited in the just etching step was quickly sublimated and removed.

After that, O ₂ plasma ashing was performed to remove the resist mask 6 and the wafer was allowed to stand in the atmosphere for a test, but after-corrosion was not observed even after 120 hours. The reason why the after-corrosion resistance was further improved as compared with Example 3 is that the supply amount of the carbon-based polymer was reduced and the residual chlorine amount in the vicinity of the pattern was significantly reduced due to the improvement in the resist selectivity.

Incidentally, the above-mentioned second to fourth embodiments.
In, the wafer temperatures in the just etching process and the over etching process are significantly different. In such a case, in order to prevent the throughput from being lowered due to the time required for raising and lowering the temperature of the wafer, a multi-chamber type etching apparatus in which a plurality of etching chambers with different set temperatures of the wafer mounting electrodes are connected under high vacuum is used. It is particularly preferred to use.

Alternatively, the present inventor first made a Japanese Patent Application No. 3-30.
It is also very effective to use an ECR plasma device equipped with a wafer-placed electrode in which a fixed electrode having a cooling means and a movable electrode having a heating means are combined as proposed in 1279 specification. ..

Although the present invention has been described based on the four examples, the present invention is not limited to these examples. For example, as the chlorine-based compound, HCl or the like may be used in addition to Cl ₂ and BCl ₃ described above. As the bromine-based compound, in addition to the above-mentioned HBr, BBr ₃ or a compound obtained by vaporizing Br ₂ can be used.

The etching gas capable of generating at least one of chlorine-based species or bromine-based species and sulfur-based species in plasma under discharge dissociation conditions is also the above-mentioned BCl.
₃ / S ₂ Cl ₂ mixed gas or Cl ₂ / BCl ₃ / S ₂ Br
It is not limited to ₂ mixed gas. For example, in the above mixed gas, a compound such as S ₂ Cl ₂ or S ₂ Br ₂ that can supply both a sulfur-based species and a halogen-based species from one molecule is used, but only a sulfur-based species is used. H
It may be separately supplied from a molecule such as ₂ S.

The Al-based material layer containing Cu has the above-mentioned A content.
Besides the 1-Si-Cu alloy, an Al-Cu alloy or the like may be used. In addition, it goes without saying that the etching conditions, the etching apparatus to be used, the structure of the sample wafer, etc. can be changed as appropriate.

[0047]

As is clear from the above description, according to the present invention, when etching the Al-containing material layer containing Cu, by adding HI to the gas system during overetching, It is possible to prevent the occurrence of a residue that occurs and improve the after-corrosion resistance. In particular, when S is used for sidewall protection in the just etching step, the after-corrosion resistance can be further improved.

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

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view for explaining a process example to which the present invention is applied in the order of steps, (a) shows a state where a resist mask is formed on an Al-based multilayer film, and (b) shows an Al-based multilayer film. The film is just etched, (c)
Represents the state in which the residue was removed.

FIG. 2 is a schematic cross-sectional view illustrating a conventional process example according to the order of steps in order to explain a conventional problem, FIG. 2A is a state in which a resist mask is formed on an Al-based multilayer film, (b) is a state in which the Al-based multilayer film has been just etched, and (c) is a micro-film as the residue is removed.
Represents the state where particles of the mask are generated.

[Explanation of symbols]

1 · · · SiO ₂ interlayer insulating film 2 · · · TiN barrier metal 3 ··· Al-1% Si- 0.5% Cu layer 4 · · · TiON antireflection film 5 · · · Al-based multilayer film 5a · ·・ Al-based wiring pattern 5b ・ ・ ・ Residue 6 ・ ・ ・ Resist mask 7 ・ ・ ・ Micro mask

Claims (3)

[Claims] 1. An aluminum-based material layer containing copper is etched using an etching gas containing at least one of a chlorine-based compound or a bromine-based compound and an iodine-based compound while heating the substrate to be etched. Dry etching method. 2. A just etching step of etching an aluminum-based material layer containing copper substantially by the thickness of the layer using an etching gas containing at least one of a chlorine-based compound and a bromine-based compound, and a chlorine-based compound Or using an etching gas containing at least one of a bromine-based compound and an iodine-based compound, and having an overetching step of etching the remainder of the copper-containing aluminum-based material layer while heating the substrate to be etched. Characteristic dry etching method. 3. An aluminum-based material layer containing copper is formed by using an etching gas capable of generating at least one of chlorine-based species or bromine-based species and sulfur-based species in plasma under discharge dissociation conditions. The just etching step of etching substantially the thickness of the layer and an etching gas containing at least one of a chlorine-based compound or a bromine-based compound and an iodine-based compound are used to contain the copper while heating the substrate to be etched. And a step of etching the remaining part of the aluminum-based material layer, the dry etching method.