JPH07335622A - Dry etching method - Google Patents

Abstract

PURPOSE:To realize an anisotropic etching process by a method wherein an etched is set to a specific temperature of below control, depositing sulfur on the etched substrate and using etching gas which contains sulfur fluoride com pound that emits free sulfur in plasma under conditions that ionization and discharge take place. CONSTITUTION:For instance, an insulating layer 2 of SiO2, is formed on a semiconductor substrate 1 of an Si wafer or the like by thermal oxidization, and an RuO2 lawyer 3 is formed on the layer 2, as thick as 300nm. The substrate 1 is kept at a temperature of 90 deg. or below, and the RuO2 layer 3 is etched with etching gas of S2F2. With an advance in etching, a side wall protective film 5 of sulfur is formed on the side walls of the patterned RuO2, layer 3 and a resist mask 4, so that the patterned RuO2 layer 3 is protected against side etching, and then an RuO2 layer 3a is formed. By this setup, an RuO2 layer can be anisotropically dry-etched at a practical etching rate.

Description

Detailed Description of the Invention

[0001]

The present invention relates to ruthenium oxide (RuO).
₂ ) Regarding the dry etching method for the layer,
The present invention relates to an anisotropic dry etching method for ruthenium oxide layers, which is a conductive ceramic used for electrode wiring of semiconductor devices and the like.

[0002]

2. Description of the Related Art Recently, DRAMs of 64 Mbits or later,
As a dielectric material for next-generation LSI, lead titanate [PbTiO ₃ ] or PZT [Pb (Zr, Ti)
O ₃ ], PLZT [(Pb, La) (Zr, Ti)
There is a trend to utilize PZT type ferroelectric thin films such as O ₃ ]. Utilizing the ferroelectricity of these materials, it is considered to be used as a capacitor insulating film of DRAM, as an MFS transistor used as an insulating film of MIS transistor, and as an infrared sensor utilizing pyroelectricity. Among them, the FRAM, which is a large-capacity non-volatile memory utilizing the polarization inversion characteristic, is highly expected as a next-generation device expected in the future as a solid-state memory capable of recording moving images on one chip. However, in order to put these ferroelectric devices into practical use, there is much room for studying not only the method for forming a ferroelectric thin film having excellent characteristics but also the method for patterning electrodes on the ferroelectric thin film.

Conventionally, Pt metal is generally used as an electrode material for a ferroelectric thin film such as a PZT system because of its stable characteristics. The patterning of the Pt metal layer is mainly wet etching using aqua regia or ion milling using a rare gas such as Ar.

However, wet etching has a problem of resist adhesion and side etching, and further has a problem of compatibility with other dry processes. Further, in the ion milling, there are problems to be solved, such as damage to the underlying ferroelectric thin film, and spatter redeposition film on the patterned Pt electrode wiring and resist sidewall. As a countermeasure against the latter redeposition, Japanese Patent Laid-Open No. 5-109668 discloses a method of performing multi-step etching by changing the incident angle of Ar ion beam. According to this method, redeposition of Pt can be prevented, but an anisotropic shape cannot be obtained. Further, JP-A-5-21405 discloses a method of physically removing the deposited Pt side wall film with high pressure jet water such as a jet scrubber and a cotton-like roller brush. According to this method, patterning while maintaining the anisotropic shape is possible. However, from a micro perspective, P
The fractured surface of the redeposited side wall film of t is newly formed, there is a concern that the pattern shape may be deteriorated, and the wet process is also used although it is a post-treatment, so that the compatibility with the dry process is also poor. The problem of damage and particle contamination due to the cotton-like roller is still unsolved.

On the other hand, an attempt of anisotropic dry etching using a side wall protective film has also been proposed. For example, 199
Proceedings of the 30th Joint Lecture Meeting on Applied Physics in 3rd Spring Lecture No. 30a-ZE-3 is a report of a process using magnetron RIE with a HBr / CH ₄ mixed gas system. An example of using an ECR plasma etching system with the same gas system is published in Micro Process Conference Proceedings B-7-5, 146 (1993). In both cases, to ensure the resist mask selectivity and anisotropic shape,
Since CH ₄ gas that deposits the carbon-based polymer is added, there is a risk of particle contamination and deterioration of reproducibility. Moreover, the etching rate is as small as about 20 nm / min.

As described above, the Pt electrode has a problem in workability despite the stability of its characteristics.
Recently, there is a trend to consider the use of conductive ceramics such as ITO and RuO ₂ as other electrode materials. Above all, Ru
It has been reported that O ₂ has less mutual diffusion with a ferroelectric thin film than ITO, exhibits excellent ohmic properties even compared with Pt, and exhibits time dependence (TDDB) of breakdown characteristics (J .Electrochem.Soc., 140- 9,2640 (199
3)).

RuO ₂ is also a material which is difficult to dry-etch due to the small vapor pressure of Ru halide, but its fluoride RuF ₅ has a boiling point of 250 ° C., so if the substrate to be etched is heated. Etching under reduced pressure with a F-based gas is possible. For example, J. Elec
trochem.Soc., 140- 9, 2635 (1993) has CCl ₂ F.
An example of RIE using ₂ (CFC12) has been reported. However, in this etching method, the etching rate is as low as several nm to several tens of nm / min at most, and not only the CFC 12 but the specific CFC is being regulated from the viewpoint of global environmental protection under the present circumstances.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an anisotropic dry etching method of RuO _{2 which} is promising as an electrode material for a PZT-based ferroelectric thin film or the like.

Another object of the present invention is to provide the above dry etching method by a clean dechlorofluorocarbon process while ensuring a practical etching rate.
Other problems of the present invention will be made clear by the description in the present specification.

[0010]

The dry etching method of RuO _{2 according to} the present invention is proposed to solve the above-mentioned problems, and the substrate to be etched is controlled to 90 ° C. or lower, and Etching is performed by using an etching gas containing a fluorinated sulfur compound capable of releasing free sulfur into plasma under discharge ionization conditions while depositing sulfur on the substrate.

Further, according to the dry etching method of RuO ₂ of the present invention, the substrate to be etched is controlled at 150 ° C. or lower, and the sulfur nitride compound is deposited on the substrate to be etched, while it is exposed to the plasma under discharge ionization conditions. Etching is performed using an etching gas containing a fluorinated sulfur compound capable of releasing free sulfur and an etching gas containing a nitrogen gas.

Further, according to the dry etching method of RuO ₂ of the present invention, the substrate to be etched is controlled to 400 ° C. or lower, and the ammonium sulfide compound is deposited on the substrate to be etched while plasma is formed under discharge ionization conditions. A fluorinated sulfur compound capable of releasing free sulfur to
Etching is performed with an etching gas containing NH ₃ .

The fluorinated sulfur compounds capable of releasing free sulfur into plasma under the conditions of discharge ionization used in the present invention are S ₂ F ₂ , SF ₂ , SF ₄ and S ₂ F ₁₀
Can be used alone or in combination. SF ₆ gas, which is well known as a fluorinated sulfur compound, has an F / S ratio of 6, does not release free sulfur into plasma under discharge ionization conditions, and is suitable for the purpose of the present invention. do not do.

As the nitrogen-based gas used in the present invention, N ₂ , NF ₃ and N ₂ H ₄ can be used alone or in combination.

[0015]

The point of the present invention is to use a specific sulfur fluoride compound capable of releasing free sulfur into plasma under discharge ionization conditions and to control a specific temperature of the substrate to be etched. That is, Ru fluoride is formed as a volatile product or a sublimable product in the form of reactive etching, and etching is performed while removing this fluoride out of the reaction system. As described above, since RuF ₅ of Ru fluoride has an mp of 250 ° C., if the substrate to be etched is heated under reduced pressure, patterning at a practical etching rate becomes possible. The above RuF
₅ Melting point data published by CRC Press
Handbook of Chemistry and Physics, 71st.Edition
(1990-1991), but there is also a document that the temperature is 227 ° C.

The second point of the present invention is to deposit a sulfur compound such as sulfur, a sulfur nitride compound or an ammonium sulfide compound on a substrate to be etched,
That is, the etching is performed by utilizing the competitive reaction between the etching of the RuO ₂ layer and the deposition of the sulfur or the sulfur compound. In this process, the sulfur or sulfur-based compound deposited on the surface of the RuO ₂ layer is rapidly sputtered by the incident ions, so that the RuO ₂ layer is etched. However, a deposited film is formed on the side wall of the resist mask in which ion incidence does not occur in principle and the RuO ₂ layer where etching is progressing, and prevents side etching due to radical reaction.

By the way, in order to deposit the sublimable sulfur or sulfur-based compound on the substrate to be etched, it is necessary to control the temperature of the substrate to be etched. Specifically, sulfur is 90 ° C or lower, and sulfur nitride compounds are 15
It is 0 ° C or lower, and 400 ° C or lower in the case of ammonium sulfide compounds. By controlling the heating temperature of the substrate to be etched, a practical etching rate of the RuO ₂ layer can be realized. The lower limit of the control temperature is not particularly limited, but considering the balance with the etching rate, it is preferable to set the temperature close to the upper control temperature.

Incidentally, polythiazyl represented by the general formula (SN) _x is a typical example of the sulfur nitride compound. As a mechanism of forming polythiazyl, S generated in plasma by discharge dissociation of a sulfur fluoride compound and N generated in plasma by discharge dissociation of nitrogen gas are combined to first form thiazyl (N≡S). To be done. This compound has an unpaired electron in the molecule, so it is easily polymerized to give (SN) ₂ and further (SN) ₂ is 2
Polymerization is repeated even at about 0 ° C (SN) ₄ , (SN) _x
Becomes (SN) _x, that is, polythiazyl is a stable substance and does not decompose up to about 150 ° C. In the present invention, the substrate to be etched is controlled at 150 ° C. or lower (S
N) _x can be used as a side wall protective film.

Another sulfur-based compound, an ammonium sulfide-based compound, is formed by reacting S ₃ and NH ₃ generated in plasma by discharge dissociation of a fluorinated sulfur-based compound with ammonium monosulfide ( NH ₄ ) ₂ S is a typical compound, but polyammonium sulfide (NH ₄ ) ₂ S _{x and the} like are also mixed. Since these ammonium sulfide compounds do not decompose and sublimate up to 400 ° C., they can be used as a side wall protective film.

Another point of the present invention is RuO ₂
After the etching of the layer is completed, the substrate to be etched is heated so that the sulfur or the sulfur-based compound deposited on the substrate to be etched is sublimated or decomposed and sublimated to be removed from the substrate to be etched. The heating temperature may be set to a temperature exceeding the upper limit of the substrate control temperature during etching. Further, when the process of removing the resist mask by ashing is used after the completion of the etching of the RuO ₂ layer, it is possible to remove the sulfur or the sulfur-based compound by ashing or by heating the substrate during the ashing. As a result, a clean process can be realized in which there is no concern of substrate contamination due to deterioration of the particle level.

Utilizing the deposition of sulfur as a side wall protective film,
Proposals for anisotropic etching of polycrystalline silicon layers,
The present inventors, for example, monthly Semiconductor World magazine 1
It was published in the January 993 issue, pages 140-144 (published by Press Journal). The present invention was inspired by the successful application of this process in combination with specific temperature control for etching RuO ₂ layers.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the accompanying drawings. In all of the following Examples 1 to 3, the substrate bias application type ECR plasma etching apparatus was used, but it goes without saying that other etching apparatuses can be used as appropriate.

Example 1 This example is an example in which the RuO ₂ layer on the insulating film was etched with S ₂ F ₂ gas, and this will be described with reference to FIGS. 1 (a) to 1 (c). First, as shown in FIG.
An insulating layer 2 made of, for example, SiO _{2 is} formed on a semiconductor substrate 1 such as a Si wafer by thermal oxidation or the like, and RuO ₂ is formed thereon.
The layer 3 is formed to a thickness of 300 nm. The RuO ₂ layer 3 is formed by reactive sputtering using a Ru metal as a target and using an Ar / O ₂ mixed gas. Next, as an example, a chemically amplified three-component negative resist SAL-601
Then, the resist mask 4 having a width of 0.35 μm is patterned by KrF excimer laser lithography.

Next, as an example, RuO _{2 is used under the following} conditions.
The layer 3 is etched. S ₂ F ₂ flow rate 30 sccm H ₂ flow rate 5 sccm Gas pressure 0.13 Pa Microwave power 1500 W (2.45 GHz) RF bias power 50 W (2 MHz) Substrate temperature 80 ° C. Of the above gases, H ₂ is directly etched However, hydrogen radicals (H ^* ) are generated and S ₂ F ₂
It plays the role of supplementing F ^* generated from the above and removing it in the form of HF outside the etching system. That is, the deposition of sulfur is promoted by reducing the radical property in the reaction system. Of course, the etching may proceed with S ₂ F ₂ alone.

Under the above etching conditions, the RuO ₂ layer 3
Etching progresses. As the etching progresses, a sidewall protecting film 5 of sulfur is adhered and formed on the sidewalls of the patterned RuO ₂ layer 3 and the resist mask 4 to prevent the side etching. As a result, as shown in FIG.
The O ₂ layer pattern 3a is formed. The etching rate was 200 nm / min. After that, when the substrate to be etched was subjected to a heat treatment at a temperature higher than 90 ° C., the side wall protective film 5 sublimated, and no trace of sulfur remained on the substrate to be etched. The resist pattern 4 was removed with a resist stripping solution, and as shown in FIG. 1C, a RuO ₂ layer pattern 3a having a width of 0.35 μm with no dimension conversion difference was formed with good anisotropy. The sulfur side wall protective film 5 can be removed by ashing with O ₂ plasma or the like. In this case, the ashing of the resist mask 4 can also be used.

Example 2 In this example, R on the insulating layer 2 also made of SiO ₂ or the like was used.
This is an example of etching the uO ₂ layer 3a with a mixed gas of S ₂ F ₂ and N ₂ , which will also be described with reference to FIGS. 1 (a) to 1 (c).

The substrate to be etched shown in FIG. 1A is the same as that of the first embodiment, and the description of the processes up to this point will be omitted. Next, the substrate to be etched is etched under the following conditions as an example. S ₂ F ₂ flow rate 40 sccm N ₂ flow rate 20 sccm Gas pressure 1.3 Pa Microwave power 1500 W (2.45 GHz) RF bias power 50 W (2 MHz) Substrate temperature 140 ° C. Of the above gases, N ₂ is directly etched However, it does not contribute to the formation of N ^* and combines with S generated from S ₂ F ₂ to form a sulfur nitride compound such as polythiazyl (SN) _x .

By adopting the above etching conditions, RuO
Etching of the _second layer 3 proceeds. Ru progressing etching
A side wall protective film 5 of a sulfur nitride based compound such as polythiazyl is adhered and formed on the side walls of the O ₂ layer 3 and the resist mask 4 to prevent side etching. As a result, as shown in FIG. _{A two-} layer pattern 3a is formed.
The etching rate was 300 nm / min. afterwards,
When the substrate to be etched was subjected to a heat treatment at above 150 ° C., the side wall protective film 5 sublimated, and no trace of the sulfur nitride compound was left on the substrate to be etched. The resist pattern 4 was removed with a resist stripping solution, and as shown in FIG. 1C, a RuO ₂ layer pattern 3a having a width of 0.35 μm with no dimension conversion difference was formed with good anisotropy.

According to this embodiment, since the temperature of the substrate to be etched is set to 140 ° C., the etching rate is higher than that of the first embodiment, and since strong polythiazil is used as the side wall protective film, it is anisotropic. No slight deterioration was observed in the elastic shape.

Example 3 In this example, RuO ₂ on the insulating layer 2 made of SiO ₂ or the like was used.
This is an example of etching the layer 3 with a mixed gas of S ₂ F ₂ and NH ₃ using an inorganic mask, which is shown in FIGS.
Will be described with reference to.

First, as shown in FIG. 2 (a), sequentially forming an insulating layer 2 and RuO ₂ layer 3 on the substrate 1 such as a Si wafer made of, for _example, SiO _2. The forming method is the same as in the first embodiment. Next, as an example, S with a thickness of 0.2 μm is used.
After forming an iO ₂ film by sputtering, a resist mask (not shown) is used to perform patterning into a desired shape having a width of 0.35 μm to form the inorganic mask 6.

Next, as an example, RuO _{2 is used under the following} conditions.
The layer 3 is etched. S ₂ F ₂ flow rate 40 sccm NH ₃ flow rate 20 sccm Gas pressure 0.13 Pa Microwave power 1500 W (2.45 GHz) RF bias power 50 W (2 MHz) Substrate temperature 350 ° C Of the above gases, NH ₃ is directly etched However, it reacts with free sulfur generated from S ₂ F ₂ to form an ammonium sulfide-based compound on the substrate to be etched.

Under the above etching conditions, the RuO ₂ layer 3
Etching progresses. The side wall protective film 5 made of a strong ammonium sulfide-based compound is adhered and formed on the side walls of the RuO ₂ layer 3 and the inorganic mask 5 which are being etched.
Side etching is prevented despite the high temperature etching condition of ℃, and the RuO ₂ layer pattern 3a is formed as shown in FIG. 2 (b). Etching rate is 700 nm
A value of / min or more was obtained. After that, when the substrate to be etched was subjected to a heat treatment at a temperature higher than 400 ° C. under a reduced pressure atmosphere, the side wall protective film 5 sublimated, and no trace of the ammonium sulfide-based compound remained on the substrate to be etched. When the inorganic mask 5 is removed by known wet etching or plasma etching, as shown in FIG. 2C, the Pt-based metal layer pattern 3a having a width of 0.35 μm without pattern shift.
Was formed with good anisotropy.

According to this embodiment, since the temperature of the substrate to be etched is set to 350 ° C., the etching rate is further increased as compared with the previous embodiment 2, and a strong ammonium sulfide compound is used as the side wall protection film. Therefore, no slight deterioration was observed in the anisotropic shape.

Example 4 In this example, RuO ₂ on a ferroelectric layer made of PZT or the like was used.
This is an example in which the layer is etched with a mixed gas of S ₂ F ₂ and N ₂ , which is a step following Examples 1 to 3 above. First,
A configuration example of a helicon wave plasma etching apparatus having a substrate heating mechanism using a halogen lamp adopted in this embodiment will be described with reference to the schematic sectional view shown in FIG.

This etching apparatus has a construction in which a helicon wave plasma generation source and a means for heating a substrate to be etched by a W halogen lamp are provided. The helicon wave plasma generation source is a helicon wave antenna 17 that circulates around a bell jar 16 made of a dielectric material such as quartz or alumina, a helicon wave plasma power source 18, a matching network 1.
9 and a solenoid coil assembly 20 including an inner peripheral coil and an outer peripheral coil. Of these, the inner coil contributes to the propagation of the helicon wave, and the outer coil contributes to the transport of the generated plasma. Substrate to be etched 1
The substrate stage 12 on which 1 is mounted has a built-in substrate stage heating means 13 such as a resistance heater, while the infrared beam generated by the infrared irradiation and heating means 14 including a W halogen lamp and a reflecting mirror is made of quartz glass or the like. The substrate 1 to be etched is heated from the surface through the light irradiation window 15. The infrared irradiation heating means 14 is used for the substrate 11 to be etched.
It is desirable to provide a plurality of, for example, four, axially symmetrically with respect to the central axis. Reference numeral 21 is a multi-pole magnet that controls the divergent magnetic field in the etching chamber 23, and 22 is a substrate bias power supply that controls the ion energy incident on the substrate 11 to be etched. In this figure, details of the apparatus such as the etching gas introduction hole, the vacuum pump, the gate valve, etc. are omitted. According to the etching apparatus of the present invention, plasma etching with high density plasma of the order of 10 ¹³ / cm ³ is possible due to the structural characteristics of the helicon wave antenna.

The present embodiment is an example in which a ferroelectric layer is formed on the RuO ₂ layer pattern 3a formed in Examples 1 to 3, and an upper RuO ₂ layer is further formed on the ferroelectric layer and patterned. This process will be described with reference to FIGS.

On the RuO ₂ layer pattern 3a formed in the above embodiment, a ferroelectric layer 7 made of PZT or the like is formed, for example, 2
After being formed by sputtering with a thickness of 00 nm, it is annealed at 500 to 700 ° C. if necessary to form a perovskite structure. On the ferroelectric layer 7, an upper layer Ru that becomes an upper layer electrode is formed.
An O ₂ layer 8 is formed by 300 nm reactive sputtering, and a resist mask 4 having a width of 0.35 nm is formed. This sample shown in FIG. 3A is used as a substrate to be etched.

The substrate 11 to be etched is set on the substrate stage 12 of the helicon wave plasma etching apparatus shown in FIG. 4, and etching is performed under the following conditions as an example. S ₂ F ₂ flow rate 40 sccm N ₂ flow rate 20 sccm Gas pressure 0.13 Pa Helicon wave plasma power source power 1500 W (13.5
6 GHz) Substrate bias power 50 W (2 MHz) Infrared irradiation power source power 500 W Substrate temperature 140 ° C. The infrared irradiation power source power is the total of four W halogen lamps. Of the above gases, N ₂ does not directly contribute to etching, but it forms N ^* and combines with S generated from S ₂ F ₂ to form a sulfur nitride compound such as polythiazyl (SN) _x. .

By adopting the above etching conditions, the upper layer R
Etching of the uO ₂ layer 8 proceeds. The etching mechanism is almost the same as in Example 2, but in this example, an etching rate of 500 nm / min, which is higher than that in Example 2, was obtained due to the effect of heating the substrate from the surface by high-density plasma and infrared irradiation. The state after the etching is shown in FIG. Needless to say, the main component of the side wall protective film 5 in the figure is a sulfur nitride-based compound such as polythiazyl (SN) _x .

After the etching is completed, the side wall protective film 5 and the resist mask 5 are removed in the same manner as in Example 2, and the process shown in FIG.
The structure shown in (c) is obtained. According to this example, due to the effect of the side wall protective film of the sulfur nitride based compound, the upper RuO ₂ pattern having a width of 0.35 μm without pattern shift was formed with good anisotropy.

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

For example, as a sulfur fluoride-based gas, S ₂ F
_{Although 2} is illustrated, SF ₂ , SF ₄ , S ₂ F _10, etc., SF ₆
Other sulfur fluoride-based gases can be used as appropriate. Also, H
_{Since 2} S gas also releases free sulfur in the plasma,
Even with a mixed gas of H ₂ S and a general-purpose fluorine-based gas, the same effects as those of these sulfur fluoride-based gases can be expected by selecting the process conditions.

Although N ₂ was taken as a representative nitrogen-based gas, N ₂ H ₄ and NF ₃ can also be used. As described above, NH ₃ produces an ammonium sulfide-based compound even with the same nitrogen-based gas.

Halogen produced from sulfur fluoride gas
For the purpose of capturing radicals and promoting sulfur deposition,
In Example 1, H₂Was added, but in addition to H₂S, SiH_Four,
Si ₂H₆H-based gas such as H may be added. Of course
Even if it is not added, it does not hinder the progress of etching.

In addition, for the purpose of obtaining the cooling effect of the substrate to be processed, the dilution effect, the stabilization of the discharge, etc., He,
A rare gas such as Ar may be added.

As the etching apparatus, an ECR plasma etching apparatus and a helicon wave plasma etching apparatus were used. This is an IC such as a parallel plate type RIE apparatus having a substrate stage temperature control mechanism, a magnetron RIE apparatus, or the like.
It is also possible to use another type of etching apparatus such as a P (Inductively Coupled Plasma) etching apparatus and a TCP (Transformer Coupled Plasma) etching apparatus.

Although PZT is exemplified as the ferroelectric thin film, various ferroelectric materials such as PLZT and SrTiO ₃ or other high dielectric materials such as Ta ₂ O ₅ can be used. Also, R
It goes without saying that the present invention can be applied to the case where the uO ₂ layer is used as an electrode of a compound semiconductor device, an electrode / wiring of an oxide high temperature superconducting device, or the like.

[0049]

As is apparent from the above description, according to the dry etching method of the present invention, anisotropic dry etching of the RuO ₂ layer can be achieved while ensuring a practical etching rate.

Sulfur or a sulfur-based compound that has contributed to anisotropic etching as a side wall protective film can be easily removed by sublimation by heating after completion of etching, or can be completely removed by ashing. There is no concern.

Since the present invention is basically a dry process, it is excellent in compatibility with the preceding and subsequent steps. Also, from the viewpoint of environmental protection, it is a clean process that does not use specific CFC gas. As described above, according to the dry etching method of the present invention, RuO ₂ as an electrode wiring material for various electronic devices as well as a semiconductor device using a ferroelectric thin film is used.
It is intended to provide a processing method which is extremely useful for practical application of layers.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view for explaining Examples 1 and 2 to which the present invention is applied, in the order of steps, in which (a) shows an insulating layer and a RuO ₂ layer sequentially formed on a semiconductor substrate, and In the state where a resist mask having a desired shape is formed,
(B) is a state in which the etching of the RuO ₂ layer is completed while depositing the sidewall protection film, and (c) is a state in which the sidewall protection film and the resist mask are removed to complete the RuO ₂ layer pattern.

FIG. 2 is a diagram illustrating a third embodiment to which the present invention is applied in the order of steps thereof.
It is a schematic sectional drawing for clarity, (a) is on a semiconductor substrate
Insulating layer and RuO₂Layers are sequentially formed on which the desired shape is formed.
(B) shows the side wall protection.
RuO while depositing a protective film ₂The state that the layer etching is completed
State, (c) is RuO after removing the side wall protective film and the inorganic mask.
₂The layer pattern is in a completed state.

FIG. 3 is a schematic cross-sectional view for explaining Example 4 to which the present invention is applied in the order of steps, in which (a) sequentially forms a ferroelectric layer and an upper RuO ₂ layer on a RuO ₂ pattern, A state where a resist mask having a desired shape is formed thereon, (b) a state in which the upper side RuO ₂ layer has been etched while depositing the side wall protective film, and (c) shows a state in which the side wall protective film and the resist mask are removed. Then, the upper RuO ₂ layer pattern is completed.

FIG. 4 is a schematic sectional view of a helicon wave plasma etching apparatus used in Example 4 to which the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 semiconductor substrate 2 insulating layer 3 RuO ₂ layer 3a RuO ₂ layer pattern 4 resist mask 5 sidewall protective film 6 inorganic mask 7 ferroelectric layer 8 upper layer RuO ₂ layer 8a upper layer RuO ₂ layer pattern 11 etched substrate 14 infrared irradiation heating means 15 Light irradiation window 17 Helicon wave antenna

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/88 D

Claims (5)

[Claims] 1. A fluorinated sulfur compound capable of releasing free sulfur into plasma under discharge ionization conditions while controlling the substrate to be etched to 90 ° C. or lower and depositing sulfur on the substrate to be etched. A method for dry-etching a ruthenium oxide layer, which comprises etching the ruthenium oxide layer using an etching gas containing the same. 2. Fluorine sulfur capable of releasing free sulfur into plasma under discharge ionization conditions while controlling the substrate to be etched to 150 ° C. or lower and depositing a sulfur nitride compound on the substrate to be etched. A method of dry etching a ruthenium oxide layer, which comprises etching the ruthenium oxide layer using an etching gas containing a nitrogen-based compound and an etching gas containing a nitrogen-based gas. 3. Fluorine sulfur capable of releasing free sulfur into plasma under discharge ionization conditions while controlling the substrate to be etched to 400 ° C. or lower and depositing an ammonium sulfide compound on the substrate to be etched. System compounds and N
A method of dry etching a ruthenium oxide layer, which comprises etching the ruthenium oxide layer with an etching gas containing H ₃ . 4. A fluorinated sulfur compound capable of releasing free sulfur into plasma under discharge ionization conditions is S ₂ F ₂ ,
The dry etching method according to claim 1, 2 or 3, wherein the dry etching method is at least one selected from the group consisting of SF ₂ , SF ₄ and S ₂ F ₁₀ . 5. A nitrogen-based gas is N ₂ , NF ₃ or N ₂ .
The dry etching method according to claim 2, wherein the dry etching method is at least one selected from the group consisting of ₂ H ₄ .