JPH05291204A - Formation method of aluminum-based pattern - Google Patents

Abstract

PURPOSE:To enhance the selectivity in a dry etching operation of an Al-based material layer. CONSTITUTION:An Al-based multilayer film 7 is etched by using a mixed gas of COCl2 (carbonyl chloride) and Cl2. A carbon-based polymer CClx formed as originated from the decomposition product of a resist mask 8 is endowed with a strong chemical bond and a strong electrostatic attraction force due to the introduction of a carbonyl group (>C=O); its etching-resistant property is enhanced. Consequently, it is possible to reduce the energy of impinging ions required for an anisotropic working operation and the decomposition amount of the carbonbased polymer; it is possible to enhance the selectivity of a resist and the selectivity of a substratum; in addition, it is possible to restrain a particle contamination and an aftercorrosion. When a mixed gas of COCl2 and S2Cl2 is used S (sulfur) is added to the constituent component of a sidewall protective film 9, and it is possible to realize higher selectivity, lower contamination, lower damage and higher aftercorrosion-resistantance of the title formation method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an aluminum (Al) -based pattern which is applied in the field of semiconductor device manufacturing, etc., and particularly in dry etching of an Al-based material layer, improved resist selectivity and reduced particle contamination. , A method for suppressing after-corrosion.

[0002]

2. Description of the Related Art A material for electrode wiring of semiconductor devices is A
l, or an Al-Si alloy added with 1 to 2% of silicon (Si), and Al added with 0.5 to 1% of copper (Cu) as a measure against stress migration.
Al-based materials such as —Si—Cu alloys are widely 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.
It is l ^* (chlorine radical), and promotes spontaneous and extremely rapid etching reaction. However, since etching proceeds isotropically only with Cl ^* , the ion-assisted reaction usually proceeds under conditions where the incident ion energy is increased to some extent, and the decomposition formation of the resist mask sputtered by the incident ions is generated. High selectivity is achieved by using the material as a sidewall protective film. BCl ₃ is Al
Is a compound added to reduce the natural oxide film on the surface of the system material layer, BCl _x as the incident ions
^It also plays an important role of supplying ⁺ .

[0004]

By the way, as described above, in order to secure the anisotropy, the incident ion
In the process of using energy to sputter a resist mask, a reduction in resist selectivity is necessarily a problem. The resist selectivity in a typical process is only about 2. Such low selectivity causes a dimensional conversion difference from the resist mask in the processing of a fine wiring pattern, and deteriorates the anisotropic shape.

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

In order to deal with this problem, a method of depositing a reaction product on the surface of a resist mask has been conventionally proposed. For example, the proceedings of the 33rd integrated circuit symposium lecture (1987), p. 114, a process using SiCl ₄ as an etching gas is reported. This aims to increase the etching resistance of the resist mask by coating the surface of the resist mask with Si.

[0007] Further, Proceedings of t
he 11th Symposium on Dry
Process, p. 45, II-2 (1989),
Processes using BBr ₃ have been reported. this is,
By coating the surface of the resist mask with CBr _x having a low vapor pressure, the etching resistance of the resist mask is further enhanced. For the protection mechanism of the resist mask by CBr _x, etc., see the monthly semiconductor world December 1990 issue, p10.
3 to 107 (published by Press Journal), a value of about 5 is reported as the resist selection ratio.

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

[0009]

The method of forming an Al-based pattern of the present invention is proposed to achieve the above-mentioned object, and contains a halogen compound having a carbonyl group and a halogen atom in the molecule. It is characterized in that the Al-based material layer on the substrate is etched by using an etching gas.

The invention is also characterized in that the etching gas further comprises a sulfur-based compound capable of releasing sulfur into the plasma under discharge dissociation conditions.

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

[0012]

The point of the present invention is that by strengthening the film quality of the carbon-based polymer itself, a sufficiently high resist selectivity can be achieved even if the deposition amount is reduced. In the present invention, a halogen compound having a carbonyl group (> C = O) and a halogen atom is used as a method for enhancing the film quality of the carbon-based polymer itself.

The halogen atom in the above halogen compound is
It contributes as a main etching species of the Al-based material layer. Also,
The important action of the halogen compound in the etching reaction system of the present invention is that the carbonyl group can have a structure in which the C atom is positively charged and the O atom is negatively charged, and has a high polymerization promoting activity. is there. That is, the presence of such a carbonyl group or an atomic group containing the carbonyl group in the plasma increases the degree of polymerization of the carbon-based polymer, and can enhance resistance to ion injection and radical attack. In addition, when the above-mentioned functional group is introduced into the carbon-based polymer, the chemical and physical stability of the carbon-based polymer is higher than that of the conventional carbon-based polymer which is simply composed of a repeating structure of —CX ₂ — (X represents a halogen atom). It is also clear from recent studies that the number will increase. This is because when comparing the binding energies between two atoms, the C—O bond (1077 kJ / m
ol) is much larger than the C—C bond (607 kJ / mol), which is also intuitively understood. Further, the introduction of the carbonyl group increases the polarity of the carbon-based polymer, and the electrostatic attraction force to the wafer that is negatively charged during etching is also increased, so that the surface protection effect of the carbon-based polymer is improved. ..

By thus strengthening the film quality of the carbon-based polymer itself, the incident ion energy required for anisotropic processing can be reduced and the resist selectivity can be improved. This makes it possible to form an etching mask that can withstand practical use even from a relatively thin photoresist coating, and prevent the occurrence of processing size conversion differences, but without sacrificing the high resolution in photolithography. .. In addition, since the amount of carbon-based polymer required to achieve high anisotropy and high selectivity can be reduced, particle contamination can be reduced as compared with the prior art. In addition, the residual chlorine existing in the form of being incorporated in the carbon-based polymer is also reduced, so that the after-corrosion resistance is also improved.

Further, the reduction of the incident ion energy naturally leads to the improvement of the underlayer selectivity.
The sputtering of the interlayer insulating film underlying the l-based material layer is reduced,
It is possible to suppress redeposition and the like on the pattern side wall portion. Therefore, the residual chlorine existing in the form of being incorporated in the redeposited material is also reduced, which also makes it possible to effectively suppress the after-corrosion.

The present invention is based on the above idea, but proposes a method aiming at further reduction of pollution and damage. The method is the above-mentioned etching
A sulfur-based compound capable of releasing sulfur (S) into plasma under discharge dissociation conditions is added to the gas. In this case, in addition to the carbon-based polymer which is the etching reaction product, S can also be used for sidewall protection. S
Will depend on the conditions, but will be deposited on the surface of the wafer if the temperature of the wafer is controlled below room temperature. Therefore, the incident ion energy can be further reduced, and the damage can be thoroughly reduced. In addition, the amount of carbon-based polymer deposited can be relatively reduced, and particle contamination and after-corrosion can be more effectively reduced. Moreover, S easily sublimes when the wafer is heated to approximately 90 ° C. or higher, so that S itself does not become a source of particle contamination.

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

[0018]

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

EXAMPLE 1 In this example, an Al-based multilayer film in which a barrier metal, an Al-1% Si layer, and an antireflection film were sequentially laminated was used as COCl ₂
This is an example of etching using a (carbonyl chloride) / Cl ₂ mixed gas. This process is shown in FIG.
A description will be given with reference to (b) and (d).

First, as an example, as shown in FIG. 1A, a barrier metal 4 having a thickness of about 0.13 μm and an Al-1% Si layer 5 having a thickness of about 0.3 μm are formed on the SiO ₂ interlayer insulating film 1. A Ti-based antireflection film 6 having a thickness of about 0.1 μm was sequentially laminated to form an Al-based multilayer film 7, and a resist mask 8 was further formed on the Al-based multilayer film 7 to prepare a wafer.
Here, the barrier metal 4 is composed of a Ti layer 2 having a thickness of about 0.03 μm and a TiO layer having a thickness of about 0.1 μm in order from the lower layer side.
The N layer 3 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 7 was etched under the following conditions. COCl ₂ flow rate 30 SCCM Cl ₂ flow rate 90 SCCM Gas pressure 2 Pa (= 15 mTorr
r) Microwave power 900 W (2.45 GHz) RF bias power 30 W (13.56 MHz) Wafer temperature Normal temperature Here, since COCl ₂ has halogen atoms which are the main etching species of the Al-based multilayer film 7 in the molecule, Although it is not impossible to form the etching gas by itself, it is used together with Cl ₂ in order to achieve a practical etching rate.

In this process, a radical reaction using Cl ^*, which is dissociated and produced from Cl ₂ and COCl ₂ by ECR discharge, as a main etching species, causes Cl _x ⁺ , C ⁺ , CO ⁺ , and COC.
Etching progressed by a mechanism assisted by ions such as l ⁺ , and the Al-based multilayer film 7 was removed in the form of AlCl _x , TiCl _x or the like. At the same time, the resist mask 8
CCl _x was generated due to the decomposition product of, and further a carbonyl group was incorporated into the structure to generate a strong carbon-based polymer. Since the carbon-based polymer has a low RF bias power and is not produced in a large amount as compared with the conventional process, it is deposited on the side wall of the pattern to form the side wall protective film 9 as shown in FIG. Even with a small amount, it exhibited high etching resistance and contributed to anisotropic processing. As a result, the Al-based wiring pattern 7a having a good anisotropic shape was formed. However, in the figure, each material layer after patterning is
The reference numeral of the corresponding original material layer is shown with a suffix a.

Further, with the RF bias power of the above level, the underlying SiO ₂ interlayer insulating film 1 was not sputtered and redeposited on the pattern side wall portion, and the early generation of after-corrosion was suppressed. The etching rate of the Al-based multilayer film 7 in this embodiment is about 950 nm /
The selection ratio to the resist was about 5.

After completion of etching, the wafer was transferred to a plasma ashing apparatus attached to the above etching apparatus, and O ₂ plasma ashing was performed under normal conditions.
As a result, as shown in FIG. 1D, the resist mask 8 and the side wall protective film 9 were burned and removed. In the process of this example, since the amount of carbon-based polymer produced was small, the particle level did not deteriorate even if the number of wafers processed was increased.

Example 2 In this example, the same Al-based multilayer film was etched using a COBr ₂ (carbonyl bromide) / Cl ₂ mixed gas. The etching conditions in this embodiment are COCl.
_The procedure is the same as in Example 1 except that COBr ₂ is used instead of ₂ . However, since COBr ₂ is a liquid substance at room temperature, it was introduced into the etching chamber after being vaporized by He gas bubbling.

In this etching process, CCl _x , CB
r _x and a carbon-based polymer in which a carbonyl group was incorporated were generated, and the sidewall protective film 9 was formed by these deposits. Particularly, in this embodiment, B is used as halogen.
Since r is involved, the surface of the resist mask 8 is protected by CBr _x, so that the resist selectivity is about 6 which is higher than that of the first embodiment. Also, Br is S
Since the reactivity with respect to i is low, the selectivity with respect to the underlying SiO ₂ interlayer insulating film 1 is improved as compared with the first embodiment.

Example 3 In this example, the same Al-based multilayer film was used as C₂O₂Cl₂(salt
Oxalyl chloride / Cl ₂Example of etching using
It A magnetic field microphone is used for the wafer shown in FIG.
Set it on a microwave plasma etching device, and as an example
The Al-based multilayer film 7 was etched under the following conditions.

C ₂ O ₂ Cl ₂ flow rate 30 SCCM Cl ₂ flow rate 90 SCCM Gas pressure 2 Pa (= 15 mTorr)
r) Microwave power 900 W (2.45 GHz) RF bias power 25 W (13.56 MHz) Wafer temperature Normal temperature C ₂ O ₂ Cl ₂ was vaporized by He gas bubbling and then introduced into the etching chamber.

In this example, since C ₂ O ₂ Cl ₂ having two carbonyl groups in one molecule was used, the polymerization of the carbon-based polymer and the enhancement of the film quality by the introduction of the carbonyl group were promoted. Therefore, although the incident ion energy was lower than in Example 1, good anisotropic processing could be performed. The etching rate in the above process depends on the acceleration of carbon-based polymer deposition and
A slight decrease due to the reduction in F-bias power, 93
Although it was 0 nm / min, the resist selection ratio was improved to about 7.

Example 4 In this example, the same Al-based multilayer film was used as C₂O₂Br₂(Smell
Oxalyl chloride / Cl ₂Example of etching using
It The etching conditions in this embodiment are C₂O₂Cl
₂To C₂O₂Br₂Example 3 except that it was changed to
Is the same. C₂O₂Br₂Is also a liquid substance at room temperature
Therefore, after evaporating by He gas bubbling, etch
Was introduced into the chamber.

In this process, since Br is involved as a halogen, the selection ratio with respect to the resist mask 8 is improved to about 8 as compared with the third embodiment.

Example 5 In this example, the same Al-based multilayer film was used as COCl ₂ / S ₂ C
This is an example of etching using l ₂ mixed gas. First,
The wafer shown in FIG. 1A was set in a magnetic field microwave plasma etching apparatus, and the Al-based multilayer film 7 was etched under the following conditions as an example.

COCl ₂ flow rate 50 SCCM S ₂ Cl ₂ flow rate 70 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 0 ° C. (using ethanol-based refrigerant) Here, the wafer cooling is the cooling pipe embedded in the wafer mounting electrode. Then, an ethanol-based refrigerant was supplied from a chiller installed outside the apparatus and circulated.

In this etching process, in addition to the carbon-based polymer containing CCl _x and the carbonyl group, S dissociated and produced from S ₂ Cl ₂ also contributed as a constituent component of the sidewall protective film 9. Therefore, as shown in FIG. 1B, even under the condition that the RF bias power is further lowered as compared with the first embodiment,
The Al-based wiring pattern 7a having a good anisotropic shape could be formed. Al-based multilayer film 7 in this embodiment
The etching rate of was slightly lower than that of Example 1 due to wafer cooling and increase in deposits to about 900 nm / min, but the resist selectivity was improved to about 9. As a result, the decrease in the film thickness of the resist mask 8 and the receding of the edge were hardly recognized. In addition, the amount of carbon-based polymer produced can be reduced by the amount that S can be expected to be deposited, and the lower bias improves the underlayer selectivity.
The after-corrosion resistance was also greatly improved due to, for example, suppression of reattachment of the SiO ₂ interlayer insulating film 1 by sputtering.

When O ₂ plasma ashing was performed after the etching was completed, the resist mask 8 and the side wall protective film 9 were promptly removed as shown in FIG. 1 (d). Here, the side wall protective film 9 contains the carbon-based polymer and S, but S is removed by sublimation by plasma radiant heat or reaction heat, and also by combustion reaction by O ^* , and no S is present on the wafer. No particle contamination was left.

Example 6 In this example, the same Al-based multilayer film was used as COBr ₂ / S ₂ C
This is an example of etching using l ₂ mixed gas. The etching conditions in this embodiment are COCl ₂ and COBr ₂
Example 5 is the same as Example 5 except that it was changed to.

In this process, since Br is involved as a halogen, the selection ratio with respect to the resist mask 8 is improved to about 10 as compared with the fifth embodiment.

Example 7 In this example, the same Al-based multilayer film was used as C ₂ O ₂ Cl ₂ / S.
After etching with ₂ Cl ₂ mixed gas, CF ₄ /
This is an example of performing plasma processing using an O ₂ mixed gas.
This process is shown in FIG. 1 (a), (b), (c), (d).
Will be described with reference to.

First, the wafer shown in FIG. 1A was set in a magnetic field microwave plasma etching apparatus, and the Al type multilayer film 7 was etched under the same conditions as in Example 5.

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

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

Subsequently, normal O ₂ plasma ashing was performed to remove the resist mask 8 as shown in FIG. 1 (d). The wafer after resist ashing was opened to the atmosphere on a trial basis, but after-corrosion was not observed even after 72 hours.

Example 8 In this example, the same Al-based multilayer film was used as C ₂ O ₂ Br ₂ / S.
After etching with ₂ Cl ₂ mixed gas, CF ₄ /
This is an example of performing plasma processing using an O ₂ mixed gas.
In this example, the wafer shown in FIG. 1A was set in a magnetic field microwave plasma etching apparatus, the Al-based multilayer film 7 was etched under the same conditions as in Example 6, and then the same conditions as in Example 7 were used. Plasma treatment was performed.

In this process, since the Br-based chemical species are used for etching with high resist selectivity, the amount of carbon-based polymer deposited is further reduced.
The wafer after resist ashing was opened to the atmosphere on a trial basis, but after-corrosion was not observed even after 96 hours.

As described above, the present invention is based on eight examples.
Although described, the invention is in no way limited to these examples.
Not a thing. For example, the halogen used in the present invention
Compounds that have one carbonyl group in the molecule
As the above-mentioned COCl₂, COBr₂Other than COF
₂(Carbonyl fluoride), COClF (calcium fluoride fluoride)
Bonyl), COBrF (carbonyl bromide fluoride), CO
IF (carbonyl fluoride iodide; liquid at room temperature), etc.
The one having two carbonyl groups in the molecule is
C mentioned above₂O₂Cl₂, C ₂O₂Br₂And C₂O₂F
₂(Oxalyl fluoride) and the like. However, these changes
F produced from compound^*Is combined with Al and Ti
Low AlF_x, TiF_xEtching rate
Lower the particle level or worsen the particle level
Heat resistance of the resist mask is degraded.
It is necessary to consider such as heating the wafer within the range
It

Discharge Sulfur in plasma under discharge dissociation conditions
As the sulfur-based compound capable of releasing sulfur, the above S₂Cl
₂And S₃Cl₂, SCl₂Sulfur chloride such as S₃B
r₂, S₂Br₂, SBr₂Sulfur bromide such as H₂S etc.
Can be used. S ₂F₂, SF₂, SF_Four，
S₂F_TenSulfur fluoride such as can also release S
But both are F^*Is generated, so the above consideration is necessary.
It is important.

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

Further, it goes without saying that the structure of the sample wafer, the etching apparatus used, the etching conditions, etc. can be appropriately changed.

[0049]

As is clear from the above description, in the present invention, the film quality of the carbon-based polymer is enhanced by using the etching gas to which the halogen compound containing the carbonyl group is added in the etching of the Al-based material layer. However, it is possible to achieve high anisotropy and high selectivity even if the deposition amount is reduced. Therefore, it is possible to prevent the occurrence of processing size conversion difference and significantly improve the after-corrosion resistance. When the halogen compound is used in combination with a sulfur-based compound capable of releasing S under discharge dissociation conditions,
Further high selectivity, low pollution, low damage, etc. can be achieved. Moreover, since S that has contributed to the protection of the side wall can be easily sublimated and removed, it does not cause particle contamination.

Therefore, 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 showing an example of a process 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 a side wall protective film. The state in which an Al-based wiring pattern having an anisotropic shape is formed while being formed, (c) shows a state in which the sidewall protective film has been removed, and (d) shows a state in which the resist mask has been removed by ashing.

[Explanation of symbols]

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

Claims (3)

[Claims] 1. A method for forming an aluminum-based pattern, which comprises etching an aluminum-based material layer on a substrate using an etching gas containing a halogen compound having a carbonyl group and a halogen atom in the molecule. 2. An aluminum gas on a substrate using an etching gas containing a halogen compound having a carbonyl group and a halogen atom in the molecule and a sulfur compound capable of releasing sulfur into plasma under discharge dissociation conditions. A method for forming an aluminum-based pattern, which comprises etching a material layer. 3. After the etching of the aluminum-based material layer according to claim 1 or 2, the plasma processing is performed using a processing gas containing a fluorine-based compound while heating the substrate. And a method of forming an aluminum-based pattern.