JP3211312B2 - Dry etching method - Google Patents

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 to the manufacture of semiconductor devices and the like, and more particularly to a method of etching an aluminum (Al) -based material layer with high accuracy while effectively preventing after-corrosion. .

[0002]

2. Description of the Related Art As an electrode wiring material of a semiconductor device, aluminum (Al) or an Al-Si alloy to which 1-2% silicon (Si) is added, and 0.5 to 1 as a measure against stress migration. % Copper (C
Al-based materials such as an Al-Si-Cu alloy to which u) is added are widely used.

[0003] In the processing of an Al-based material layer, after-corrosion and a decrease in the selectivity with respect to the resist have conventionally been a major problem. The mechanism of occurrence of after-corrosion is described in, for example, Monthly Semiconductor World, April 1989, p. 101-106
(Published by the Press Journal), which is summarized below.

[0004] Dry etching of an Al-based material layer is generally performed using a chlorine-based gas. For example, BCl ₃ / Cl ₂ disclosed in JP-B-59-22374 is disclosed.
A mixed gas is a typical example. As a result, AlCl _x as a reaction product, a decomposition product of an etching gas, and the like inevitably remain near the etched pattern. These not only adsorb to the wafer surface, but also resist and
It is also absorbed inside the mask. When these chlorine-based reaction products and decomposition products of the etching gas absorb water in the air to form electrolyte droplets, Al is eluted in the droplets and corrosion occurs. Furthermore, the carbon-based polymer CCl _x formed by the reaction between the resist mask and the chlorine-based active species plays an important role in ensuring anisotropy as a sidewall protective film, but Cl in this carbon-based polymer is also harmful. Will result in residual chlorine.

[0005] The after-corrosion has become more serious since Cu has been added to Al-based wiring materials. It is the etching reaction product CuC
This is because l remains in the vicinity of the pattern even after etching due to its low vapor pressure, and when moisture is supplied thereto, a local battery having Cl ⁻ as an electrolyte and Al and Cu as both electrodes is formed. .

In addition, the use of an Al-based material layer alone as a wiring material layer with the recent miniaturization of design rules is also disadvantageous from the viewpoint of preventing after-corrosion. Is a factor. For example, a barrier metal is laminated between the Al-based material layer and the silicon substrate, and an antireflection film for improving the accuracy of photolithography is laminated on the surface of the Al-based material layer. In these cases, since the dissimilar material layer is exposed in a state of being in contact with the etched cross section, the elution of Al is easily promoted by the local battery effect. Further, micro gaps at the interface between the different material layers are also places where chlorine and chlorine compounds remain.

[0007] The above-mentioned after-corrosion generation mechanism is almost the same for residual bromine to some extent. Therefore, unless otherwise specified in this specification,
Excluding fluorine, chlorine and bromine are collectively referred to as halogen. As countermeasures against after-corrosion, removal of residual halogen by plasma cleaning or rinsing using a fluorine-based gas, or so-called polymer passivation, in which an Al-based material layer after patterning is immediately coated with a polymer, are being studied. However, none of these are decisive measures.

On the other hand, a decrease in selectivity to resist is a problem related to the essence of etching of the Al-based material layer. The reactivity of the Al-based material layer with respect to the chlorine-based gas is so high that the isotropic etching proceeds spontaneously only by flowing the Cl ₂ gas, for example. Therefore, in order to perform anisotropic processing, it is inevitable to increase the incident ion energy, thereby decreasing the selectivity to resist.

As a countermeasure for improving the selectivity with respect to resist, a method of depositing a reaction product on the surface of a resist mask has been conventionally proposed. For example, see the 33rd Integrated Circuit Symposium Proceedings (1987), p. 1
14 is a process using SiCl ₄ as an etching gas, and Processes of the
11th Symposium on Dry Pro
cess, p. 45 (1989) each report a process using BBr ₃ . However, these methods have the problem of reducing the particle level and resist strippability while improving the selectivity to resist.

In view of such circumstances, the applicant of the present application has proposed that sulfur (S) which does not become a residual chlorine source instead of conventional CCl _x.
A method for fundamentally solving the after-corrosion by using as a side wall protective material is disclosed in Japanese Patent Application No. Hei 3-21051.
No. 6 proposes this. As the etching gas in this case, a gas mainly containing sulfur halide having a high S / X ratio [ratio of the number of S atoms in the molecule to the number of halogen (X) atoms] is used. For example, when S ₂ Cl ₂ is used as the halogenated sulfur and the etching is performed while controlling the temperature of the wafer to approximately room temperature or less, Cl ^* generated in the plasma under the discharge dissociation condition is an Al-based material layer. It contributes as an etching species. On the other hand, S ₂ C
The free S generated from l ₂ is deposited on the side wall of the pattern where the normal incidence of ions does not occur in principle, and forms a side wall protective film. Since this sidewall protective film does not contain chlorine as a constituent element, it does not become a factor promoting after-corrosion. In addition, since deposits are generated from the gas phase,
The incident ion energy required for anisotropic processing can be reduced, which is advantageous for improving selectivity. Moreover, the deposited S causes the wafer to reach approximately 90 to
Sublimation can be easily removed by heating to about 150 ° C.
There is no concern about particle contamination.

[0011]

The side wall protection by S is as follows.
This is an epoch-making technology having many advantages as described above. However, the surface level of the wafer will increase further in the future,
If significant over-etching of the Al-based material layer is performed along with this, it is expected that the deterioration of the anisotropic shape at the time of over-etching and the decrease in selectivity to resist become serious.

This is related to the fact that the etching of the Al-based material layer is generally performed using an insulating film made of SiO ₂ or the like as a base. That is, when the surface of the insulating film exposed at the time of over-etching is sputtered ion O (oxygen) is released, the side wall protective film which is much trouble formed is removed in the form of such SO _x, sidewall protection effect is reduced This is because there is a fear. Also, when over-etching, halogen radicals are relatively excessive during over-etching, and such a decrease in the side wall protection effect causes deterioration of the anisotropic shape of the Al-based material pattern. Also, the O released from the insulating film
May also cause the resist mask to be removed in the form of _COx or the like, degrading resist selectivity.

In view of this point, the applicant of the present application has proposed H ₂ , H ₂
There is also proposed a technique of adding a compound capable of trapping an excessive halogen / radical, such as S or a silane-based compound, to an etching gas. However, in order to promote the practical use of the process utilizing S deposition in the future, it is necessary to conduct research with a policy of searching for an optimal process according to the content of etching from as many options as possible.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for controlling the S / X ratio, which is different from the method of changing the composition of the etching gas, and to provide a method which enables highly accurate etching of the Al-based material layer. And

[0015]

SUMMARY OF THE INVENTION To achieve the above object, the present invention proposes a processing chamber in which at least a part of an inner wall is covered with a sulfur-based material layer; In a dry etching method for etching an aluminum-based material layer using a plasma device having a shutter member that varies a contact area with the plasma, the contact area between the sulfur-based material layer and the plasma is controlled by operating the shutter member. Adjusting, and then introducing an etching gas containing at least one of a chlorine-based compound and a bromine-based compound into the plasma apparatus, and supplying sulfur and / or from the sulfur-based material layer according to the adjusted contact area. Etching of aluminum-based material layer while depositing sulfur-based material on the surface of substrate to be etched Those were.

[0016]

The present inventor has recognized that in order to control the S / X ratio without changing the composition of the etching gas, it is indispensable to devise the structure and use of the plasma apparatus. Examination proceeded. The configuration of the plasma apparatus according to the present invention includes a shutter member for arranging an S-based material layer on at least a part of the inner wall surface of the processing chamber and changing a contact area between the S-based material layer and the plasma. Is provided. In addition, the idea of the method of use is to set an S / X ratio optimal for a desired process by operating the shutter member, and to change the S / X ratio during the process as needed. is there.

That is, when the contact area between the S-based material layer and the plasma is increased by operating the shutter member, the supply amount of S from the S-based material layer increases, and the apparent appearance of the etching reaction system is increased. The S / X ratio increases. Strictly speaking, depending on the type of the S-based material layer, there is a possibility that a compound containing S as a constituent element may be sputtered as it is or in the form of a fragment in addition to S alone, In order to simplify the description, only a single S will be handled. Conversely, when the contact area is reduced, the supply amount of S decreases, and the S / X ratio decreases.

According to this method, the S / X ratio can be easily changed only by mechanically operating the shutter member, and other parameters such as the wafer temperature and the composition ratio of the etching gas are changed. No need. Therefore, the time required for stabilizing the discharge state can be shortened, the throughput can be improved, and the reproducibility of the process can be improved. Further, since S deposited on the wafer is supplied from the S-based material layer in order to achieve high anisotropy and high selectivity, the compound serving as the main component of the etching gas is not necessarily released into the molecule. It is not necessary to have atoms as constituent elements. Therefore, a stable, highly versatile and inexpensive compound such as Cl ₂ can be used.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

Embodiment 1 In this embodiment, the present invention is applied to the etching of an Al-based multilayer film using Cl ₂ and the S / Cl ratio is changed between just etching and over etching. It is.

Before describing the actual etching process, FIG. 3 shows an example of the configuration of an RF bias applied type magnetic field microwave plasma etching apparatus used in carrying out the present invention. I will explain while. The basic components are a magnetron 11 that generates a microwave of 2.45 GHz, a rectangular waveguide 12 and a circular waveguide 13 that guide the microwave, and an ECR (Electron Cyclotron Resonance) discharge using the microwave. A quartz bell jar 14 for generating ECR plasma P therein, the circular waveguide 13 and the bell jar 1
4.75 x 10 ^-2 T (87
5 Gauss), a sample coil 16 connected to the bell jar 14 and evacuated to a high vacuum in the direction of arrow A, and a gas required for processing is supplied to the sample chamber 16 and the bell jar 14 by arrows. Gas introduction pipe 17 supplied from B ₁ and B ₂ directions, wafer 1
A wafer mounting electrode 19 for mounting the wafer 8, a coolant buried in the wafer mounting electrode 19 and supplied from a cooling facility such as a chiller is circulated in the directions of arrows C ₁ and C ₂ , and the wafer 18 is cooled.
And a RF power supply 22 connected through a blocking capacitor 21 for applying an RF bias to the wafer mounting electrode 19.

Here, an S-based material layer 23 is provided on the inner wall surface of the bell jar 14 near the wafer 18. The S-based material layer 23 does not necessarily have to continuously circumnavigate the inner wall surface of the bell jar 14; for example, even if a block-shaped or plate-shaped solid is discontinuously arranged on the inner wall surface. good. Specific constituent materials of the S-based material layer 23 include sulfur (S), silicon sulfide (SiS or SiS ₂ ), polythiazyl [(SN) _x ], and the like. As the method for forming the S-based material layer 23, a plate-like body cut out from a film or block formed by an appropriate method is adhered, or electron beam evaporation or E-beam evaporation is performed.
A method of forming a film directly on the inner wall surface by CR sputtering may be considered. In this embodiment and each embodiment described later,
A SiS ₂ layer formed by electron beam evaporation was used.

Further, on the inner peripheral side of the S-based material layer 23, a cylindrical elevating shutter 24 which can be raised and lowered in the direction of arrow D by a driving means (not shown) is provided. Here, FIG. 3A shows a state in which the S-based material layer 23 is almost completely shielded from the ECR plasma P by the elevating shutter 24 (shutter opening degree 0%), and FIG. This shows a state where the entire surface of the S-based material layer 23 is exposed by lowering the shutter 14 (shutter opening degree 100%).

FIG. 4 is a perspective view showing the inside of the bell jar 14 partially cut away to more clearly show the arrangement of the elevating shutter 24. As shown in FIG. The side wall surface of the bell jar 14, the elevating shutter 24, and the wafer mounting electrode 19 are all arranged concentrically. The contact area between the S-based material layer 23 and the ECR plasma P can be arbitrarily adjusted by changing the vertical distance of the vertical shutter 24 in the direction of arrow D.

The elevating shutter 24 can be formed by appropriately selecting a material that does not consume radicals and does not cause unnecessary contamination in the etching reaction system. Examples of such a material include stainless steel and alumina. Can be used. In this embodiment and each of the embodiments described later, the elevating shutter 24 made of stainless steel is employed.

Next, the above-described microwave magnetic plasma having a magnetic field
The Al-based multilayer film was actually etched using an etching apparatus. This process will be described with reference to FIG. Wafer 18 used as a sample in this embodiment
As shown in FIG. 1 (a), an Al-based multilayer film 2 is laminated on an SiO ₂ interlayer insulating film 1, and a resist mask 3 patterned in a predetermined shape is formed thereon. It is.

Although the Al-based multilayer film 2 is depicted as a single-layer film in the drawings, in practice, the layer thickness Ti
An Al-1% Si layer (0.4 μm) and a TiON antireflection film (0.03 μm) on a two-layer barrier metal consisting of a layer (0.03 μm) and a TiON layer (0.07 μm)
Are sequentially laminated. In addition, the resist
The mask 3 is formed to have a pattern width of about 0.5 μm using, for example, a novolak positive photoresist (trade name: TSMR-V3, manufactured by Tokyo Ohka Kogyo Co., Ltd.) and a g-line stepper.

This wafer 18 was set on the wafer mounting electrode 19 of the above-described apparatus, and an ethanol refrigerant was circulated through the cooling pipe 20. In this state, as an example, the Al-based multilayer film 2 was etched to a just-etched state under the following conditions. Cl ₂ flow rate 50 SCCM Gas pressure 1.3 Pa (10 mTorr) Microwave power 850 W RF bias power 30 W (2 MHz) Wafer temperature 20 ° C. Shutter opening 80% In this process, even if the RF bias power is relatively low, Regardless, as shown in FIG.
An Al-based wiring pattern 2a having an excellent anisotropic shape was formed. This is because S supplied from the S-based material layer 23 accumulates on the pattern side wall to form the side wall protective film 4. Since such a low bias conditions, sputtering of the resist mask 3 due to the incident ion is small, CCl _x
The proportion of chlorine-containing reaction products, such as, for example, which contributes to side wall protection is much smaller than in conventional general processes. As described above, the process utilizing the deposition of S is extremely advantageous from the viewpoint of preventing after-corrosion.

Next, by operating the lifting / lowering type shutter 24, only the opening of the shutter among the above-mentioned etching conditions was increased to 100%, and over-etching was performed.
In this over-etching step, since the underlying SiO ₂ interlayer insulating film 1 is exposed on at least a part of the wafer surface, O is released into the etching reaction system by ion sputtering. This O may remove the side wall protective film 4 and the resist mask 3 in the form of SO _x , CO _x, etc., but in this embodiment, the O-based material layer 23 is removed by increasing the shutter opening. Is promoted, and the S / Cl ratio of the etching reaction system is increased. Therefore,
The selectivity with respect to the resist and the side wall protection effect did not decrease at all, and a favorable anisotropic shape of the Al-based wiring pattern 2a could be maintained even after overetching.

Finally, the wafer 18 was transferred to a plasma ashing apparatus and subjected to resist ashing using O ₂ plasma under ordinary conditions. As a result,
As shown in FIG. 1C, at the same time as the resist mask 3 is removed by burning, the sidewall protective film 4 is also removed by burning or sublimation, so that no particle contamination occurs on the wafer. Did not. Also, at this time,
Residual chlorine occluded in the mask 3 and the side wall protective film 4 was also removed. After the resist ashing, the wafer 18 was allowed to stand in the air on a test basis, and no after-corrosion was observed even after 72 hours.

Since the sidewall protective film 4 can be removed by sublimation only by heating the wafer 18 after etching to approximately 90 to 150 ° C., it may be removed alone before resist ashing is performed.

Embodiment 2 This embodiment is also an example of etching an Al-based multilayer film using Cl ₂ , but unlike the first embodiment, a magnetic field microwave plasma etching apparatus having a rotary shutter is used.
As the etching mask, a mask formed by a three-layer resist process was used.

A schematic sectional view of the magnetic field microwave plasma etching apparatus used in this embodiment is the same as that of FIG. 3, but a perspective view of the bell jar 14 partially cut away is shown in FIG. become. That is, the apparatus of the present embodiment includes the cylindrical rotary shutter 25 having the slit-shaped opening 25a, and the S-based material layer 23a is also formed in a strip shape following the opening pattern of the opening 25a. ing. The rotary shutter 25 is rotatable in a direction indicated by an arrow E by driving means (not shown).

Here, the positional relationship between the rotary shutter 25 and the S-based material layer 23a will be described with reference to FIG. 5A is a cross-sectional view taken along the line FF of FIG. 5, wherein FIG. 5A is a state in which the S-based material layer 23 a is shielded by the rotary shutter 25 (shutter opening degree: 0%), and FIG. The state where the entire surface of the layer 23a is exposed through the opening 25a (the shutter opening is 100%) is shown. S-based material layer 23a and EC
The contact area with the R plasma P can be arbitrarily adjusted by changing the rotation angle of the rotary shutter 25.

The Al-based multilayer film was actually etched using the above-mentioned magnetic field microwave plasma etching apparatus. Wafer 1 used as a sample in this embodiment
8 is shown in FIG. This wafer 18 has the structure shown in FIG. 1 up to the portion where the Al-based multilayer film 2 is laminated on the SiO ₂ interlayer insulating film 1.
7A, except that the etching mask is formed by a three-layer resist process, and the lower resist layer 5 and the SOG intermediate film 6 are sequentially laminated. Here, the SOG intermediate film 6 is formed by performing RIE using an upper resist layer (not shown) formed by photolithography and development as a mask. The lower resist layer 5 is formed by etching using the upper resist layer, the SOG intermediate film 6, and a mask. However, since the upper resist layer is a thin layer that emphasizes the resolution, it is removed while the thick lower resist layer 5 is being etched.
Therefore, the layer finally constituting the upper surface of the etching mask in the three-layer resist process becomes the SOG intermediate film 6.

The wafer 18 was set on the wafer mounting electrode 19 of the above-mentioned microwave magnetic plasma etching apparatus having a magnetic field, and as an example, the Al-based multilayer film 2 was etched to the just-etched state under the following conditions. Cl ₂ flow rate 50 SCCM Gas pressure 1.3 Pa (10 mTorr) Microwave power 850 W RF bias power 30 W (2 MHz) Wafer temperature 20 ° C. Shutter opening 90% When using an etching mask by a three-layer resist process, an etching mask Since the upper surface is made of SiO ₂ material (SOG), CCl _{x and the} like derived from the resist material cannot contribute in principle to sidewall protection. However, in this embodiment, since the sidewall protective film is formed by S deposited from the gas phase, anisotropic processing is possible, and the effect of preventing after-corrosion is further improved. Among the above conditions, the shutter opening was set to be 1 compared with the just etching step of the first embodiment.
The reason for increasing the value by 0% is to compensate for the decrease in the side wall protection effect due to the inability to expect the deposition of CCl _x .
As a result, although not shown, an Al-based wiring pattern having an excellent anisotropic shape was formed.

Next, by operating the rotary shutter 25, only the opening degree of the shutter among the above etching conditions was increased to 100%, and over-etching was performed.
In this step, since the supply of S from the S-based material layer 23a is promoted, the resist selectivity and the side wall protection effect are not reduced at all, and the Al-based wiring pattern can maintain a favorable anisotropic shape. Was completed.

The sidewall protective film made of S could be easily removed by sublimation by heating the wafer after completion of the etching.

Although the present invention has been described based on two embodiments, the present invention is not limited to these embodiments. For example, as the chlorine-based compound and the bromine-based compound contained in the etching gas, HCl, B
Cl ₃ , Br ₂ , HBr, BBr ₃ , CBr ₄ , SiB
r ₄ , CH ₃ Br, CH ₂ Br ₂ , CHBr ₃ or the like may be used. Also, a rare gas such as He or Ar may be added to the etching gas to obtain a cooling effect, a sputtering effect, a dilution effect, and the like.

At the time of over-etching, lowering the power of the RF bias or increasing the RF frequency can achieve better selectivity to the underlayer and lower damage. The S deposited on the surface of the lifting / lowering shutter 24 or the rotary shutter 25 is provided with a heating mechanism in advance to these shutter members, and is operated each time one etching is completed to remove sublimation, or It can be removed by performing plasma cleaning between sheet processing. These measures are effective in preventing an excessive increase in the S / X ratio of the etching reaction system.

Further, the present invention can be appropriately combined with conventionally known countermeasures for preventing after-corrosion such as fluorine substitution and washing with water, so that more excellent effects can be obtained.

[0042]

As is clear from the above description, the present invention provides a process for utilizing the deposition of S for protecting the side wall. First, it is extremely effective as a measure for preventing after-corrosion in dry etching of an Al-based material layer. Are better. In addition, the S / X ratio of the etching reaction system during the process is controlled by mechanically changing the contact area between the plasma and the S-based material layer provided on the inner wall of the processing chamber of the plasma apparatus by using a shutter member. Can be done quickly and easily. Also,
By supplying S for protecting the side wall from the S-based material layer, a general-purpose chlorine-based compound or bromine-based compound can be used stably and inexpensively as an etching gas, which has a great economical advantage.

The present invention is extremely suitable for manufacturing a semiconductor device which is designed based on a fine design rule and has a high degree of integration and high performance.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a process example in which the present invention is applied to the etching of an Al-based multilayer film on a SiO ₂ interlayer insulating film in the order of steps, and FIG. Is formed, (b) is a state in which an Al-based wiring pattern is formed by etching,
(C) shows a state in which the resist mask and the sidewall protective film have been removed, respectively.

FIG. 2 is a schematic cross-sectional view showing a state of a wafer having an etching mask formed by a three-layer resist process on an Al-based multilayer film.

FIG. 3 is a schematic cross-sectional view showing an example of a configuration of an RF bias application type magnetic field microwave plasma etching apparatus used in carrying out the dry etching method of the present invention, and FIG. 0% shutter opening
(B) represents the case where the shutter opening is 100%.

FIG. 4 is a schematic perspective view showing a vertically movable shutter and its peripheral members of the magnetic field microwave plasma etching apparatus shown in FIG.

FIG. 5 is a partial cutaway view of a rotary shutter and its peripheral members in another configuration example of an RF bias application type magnetic field microwave plasma etching apparatus used in carrying out the dry etching method of the present invention. It is a schematic perspective view shown.

6A and 6B are cross-sectional views taken along the line FF of FIG. 5, wherein FIG. 6A illustrates a case where the shutter opening of the rotary shutter is 0%, and FIG. 6B illustrates a case where the shutter opening is 100%.

[Explanation of symbols]

1 ... SiO ₂ interlayer insulating film 2, ... Al-based multilayer film 2a ... Al-based wiring patterns 3 ... resist mask 4 ... side wall protective film 5 ... lower resist layer 6 ... SOG intermediate film 14 ··· Bell jar 16 ··· Sample chamber 18 ··· Wafer 19 ··· Wafer mounting electrode 23 and 23a ··· S-based material layer 24 ··· Lifting type shutter 25 ··· Rotating type Shutter 25a ... opening

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065 C23F 4/00

Claims (1)

(57) [Claims] And wherein 1 inner wall portion of the at least partially coated with a sulfur-based material layer processing chamber, and a shutter member for changing the contact area between the sulfur-based material layer and the plasma
Of an aluminum-based material layer using a plasma
In the dry etching method for performing the etching, the shutter member is operated and the sulfur-based material layer and the
The contact area with plasma is adjusted, and then an etching gas containing at least one of a chlorine-based compound and a bromine-based compound is introduced into the plasma device, and supplied from the sulfur-based material layer according to the adjusted contact area. A dry etching method characterized by etching an aluminum-based material layer while depositing sulfur and / or a sulfur-based material on a surface of a substrate to be etched.