JP5131436B2 - Etching method - Google Patents

Description

  The present invention relates to an etching method, and more particularly to an etching method using a processing gas for a laminated film including a silicon oxide film layer and a silicon nitride film layer.

  When etching a laminated film including a silicon oxide film layer and a silicon nitride film layer, patterning is performed on the photoresist layer in advance, and the silicon nitride film layer and the photoresist layer are first selected by anisotropic plasma etching. A first step is performed in which only the silicon oxide film layer is etched using a reactive first reactive gas to form holes. Next, a second step of removing foreign matter deposited on the silicon nitride film layer in the first step with an inert gas or the like is performed, and a second reactive gas capable of etching the silicon nitride film layer is further added. A third step is used to etch the silicon nitride layer. Thereafter, there is a method of forming holes by a fourth step of etching the silicon oxide film layer using, for example, the same kind of reactive gas as in the first step, which is selective to the Si substrate.

  Further, as a method of etching a laminated film including a silicon oxide film layer and a silicon nitride film layer by a continuous process, as disclosed in Patent Document 1, a mixed gas containing a CF-based gas and an inert gas is used. There is a method of etching a silicon oxide film layer and then adding a predetermined amount of hydrogen gas to etch the silicon nitride film layer and the underlying silicon oxide film layer.

  Further, as a method of etching a laminated film including a silicon oxide film layer and a silicon nitride film layer by a continuous process, as disclosed in Patent Document 2, a mixed gas containing a CF-based gas and a CHF-based gas is used. There is a method of etching a silicon oxide film layer and a silicon nitride film layer using a mixed gas containing oxygen gas and an inert gas.

JP-A-9-129595 JP-A-15-86568

  However, in the method that requires multiple steps as described above, the complicated etching conditions such as the gas flow rate and the voltage between the electrodes of the etching apparatus must be changed as the reactive gas is changed. There has been a problem that quality stability and production efficiency are lowered.

  Further, in Patent Document 1, there is a risk of explosion due to the introduction of hydrogen gas, and there is a problem in production management such that the flow rate and leakage must be strictly controlled.

  Further, in Patent Document 2, it is necessary to use at least two kinds of gases, so that there are many processes, or complicated etching conditions such as gas flow rate and voltage between electrodes of an etching apparatus must be changed, and product quality is increased. There has been a problem that the stability and production efficiency of the product are reduced.

  The present invention has been made in view of the above-described problems of conventional etching methods, and an object of the present invention is a laminate including a silicon oxide film layer and a silicon nitride film layer using a safe single processing gas. It is to provide a new and improved etching method capable of etching a film.

  In order to solve the above-mentioned problems, the present inventors have arranged a laminated film including at least one silicon oxide film layer and at least one silicon nitride film layer in a processing chamber, and introduced a processing gas into the processing chamber. In the method for etching both the silicon oxide film layer and the silicon nitride film layer of the laminated film, it is possible to etch the laminated film with a single processing gas by using a specific processing gas. It has been found that the problem can be solved, and the present invention has been completed.

That is, the present invention
(1) An object to be processed having a laminated film including at least one silicon oxide film layer and at least one silicon nitride film layer is placed in a processing chamber, and a processing gas is introduced to form the silicon oxide film of the laminated film. In the method for etching both the silicon nitride film layer and the silicon nitride film layer, the processing gas contains C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10). Etching method.
(2) The etching method as described above, wherein the processing gas further contains oxygen gas.
(3) The etching method as described above, wherein the processing gas further contains one or more group 0 gases selected from helium, argon, neon, krypton, and xenon.
(4) The etching method as described above, wherein the laminated film is etched using a resist provided thereon as a mask.
(5) The etching method described above, wherein the C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10) is a compound having an unsaturated bond.
(6) The compound in which the C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10) has one hydrogen atom bonded to at least one carbon atom of an unsaturated bond. The etching method as described above.
It is.

  According to the method of the present invention, even when the resist film serving as a mask is thin, it is possible to etch a fine pattern that has high selectivity with respect to a semiconductor material and has a rectangular shape. In addition, the silicon oxide film and the silicon nitride film can be etched at the same time, and the number of types of gas used is smaller than in the prior art, so that facilities such as piping can be simplified.

  Hereinafter, 1) a processing gas and 2) an etching method using the gas will be described in detail.

1) the process gas process gas used in the present _{invention, C a H b F c (} a = 3~5, b = 1~2, characterized in that it comprises a c = 3 to 10). C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10) gas containing two structures of CF gas and CHF gas is a silicon oxide film layer and a silicon nitride film Both layers of the layer can be etched and have a promoting effect. Further, those having an unsaturated bond in the molecule are preferable, and those having one hydrogen atom bonded to at least one carbon atom of the unsaturated bond are more preferable.

As _a mechanism of a phenomenon that can be etched with a single processing gas by using C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10), the present inventors Consider the following process. That is, when C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10) is decomposed in plasma, CF radicals derived from fluorocarbons increase in the gas phase. Radicals can enter shallow holes due to their adsorption properties, but are difficult to penetrate deep. That is, CF radicals can etch the silicon oxide film, but cannot etch the silicon nitride film. On the other hand, since the CH radicals derived from hydrocarbons are small in the size of their molecules, they enter deep holes and etch the silicon nitride film. For this reason, the bottom surface of the contact hole is etched with CH radicals derived from hydrocarbons, and the reverse microloading effect of CF radicals (the effect that the shallow part is not etched and the deep part is etched) is the side wall and shoulder of the contact hole. Is protected. Thereby, it is considered that only the silicon nitride film on the bottom surface of the hole is selectively etched, and the resist is not etched and the selection ratio is secured.

Specific examples of C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10), which is the processing gas of the present invention, include 1,3,3-trifluorocyclopropene, 1 , 3,3,4,4-pentafluorocyclobutene, 3,3,4,4-tetrafluorocyclobutene, 1,3,3,4,4,5,5-heptafluorocyclopentene, 1,3,4 , 4,5,5-heptafluorocyclopentene, 1,2,3,4,4,5,5-heptafluorocyclopentene, 3,3,4,4,5,5-hexafluorocyclopentene and the like cycloalkenes;
1,2,3,3,3-pentafluoropropene, 1,1,3,3,3-pentafluoropropene, 1,2,3,3,4,4,4-heptafluoro-1-butene, 1,1,3,4,4,4-heptafluoro-1-butene, 1,1,1,3,4,4,4-heptafluoro-2-butene, 1,1,1,2,4 , 4,4-heptafluoro-2-butene, 1,2,3,3,4,4,5,5,5-nonafluoro-1-pentene, 1,1,3,3,4,4,5 5,5-nonafluoro-1-pentene, 1,1,1,3,4,4,5,5,5-nonafluoro-2-pentene, 1,1,1,2,4,4,5,5,5 Linear alkenes such as 5-nonafluoro-2-pentene and 1,1,1,4,4,5,5,5-octafluoro-2-pentene;
3,3,3-trifluoro-1-propyne, 3,3,4,4,4-pentafluoro-1-butyne, 3-trifluoromethyl-tetrafluoro-1-butyne, 3,3,4,4 Alkynes such as 5,5,5-heptafluoro-1-pentyne;
1,3,3-trifluoropropadiene, 1,3,4,4,4-pentafluoro-1,2-butadiene, 1,1,1,4,4-pentafluoro-2,3-butadiene, 1 , 2,3,4,4-pentafluoro-1,3-butadiene, 1,1,3,4,4-pentafluoro-1,3-butadiene, 1,3,4,4,5,5,5 -Heptafluoro-1,2-pentadiene, 1,1,4,4,5,5,5-heptafluoro-1,2-pentadiene, 1,2,3,4,5,5,5-heptafluoro- 1,3-pentadiene, 1,1,3,4,5,5,5-heptafluoro-1,3-pentadiene, 1,1,2,4,5,5,5-heptafluoro-1,3- Pentadiene, 1,1,1,3,4,5,5-heptafluoro-2,4-pentadiene, 1,2, , 3,4,5,5-heptafluoro-1,4-pentadiene, 1,1,3,3,4,5,5-heptafluoro-1,4-pentadiene, 1,1,1,4,5 Dienes such as 1,5,5-heptafluoro-2,3-pentadiene;
1,2,2,3,3,4,4-heptafluorocyclobutane, 1,2,3,3,4,4-hexafluorocyclobutane, 2,2,3,3,4,4-hexafluorocyclobutane, 1,1,1,2,3,4,4,4-hexafluorobutane, 1,1,1,3,3,4,4,4-hexafluorobutane, 1,2,2,3,3 4,4,5,5-nonafluorocyclopentane, 1,2,3,3,4,4,5,5-octafluorocyclopentane, 2,2,3,3,4,4,5,5- Octafluorocyclopentane, 1,1,1,2,3,4,4,5,5-decafluoropentane, 1,1,1,3,3,4,4,5,5,5-decafluoropentane And saturated hydrocarbons. Among these, 1,3,4,4,5,5-heptafluorocyclopentene, 1,1,4,4,5,5-heptafluorocyclopentene, which can form a strong deposition film in plasma, has an unsaturated bond, and has an appropriate boiling point, 1,3,4,4,5,5,5-nonafluoro-2-pentene and 1,1,1,2,4,4,5,5,5-nonafluoro-2-pentene are more preferred. Although it is a feature of the present invention that these gases can be used as a single gas, it is of course possible to use a mixture of several of the gases described above.

  Although the manufacturing method of the process gas of this invention is not specifically limited, It can manufacture as follows. That is, as a method for producing 1,3,3,4,4,5,5-heptafluorocyclopentene, for example, Journal of American Chemical Society, 1964, Vol. 86, 5361. A purified gas obtained by purifying a crude product of 1,3,3,4,4,5,5-heptafluorocyclopentene obtained according to the production method can be used as the treatment gas of the present invention. In addition, as a method for producing 1,1,1,3,4,4,5,5,5-nonafluoro-2-pentene, Journal of Fluorine Chemistry, Vol. 123, 227 (2003). The purified gas obtained by purifying the crude product of 1,1,1,3,4,4,5,5,5-nonafluoro-2-pentene obtained according to the production method is used as the treatment gas of the present invention. Can be used.

If desired, the processing gas of the present invention is filled in an arbitrary container, for example, a cylinder or the like in the same manner as a conventional semiconductor gas, and is subjected to etching. In that case, the content (corresponding to the purity) of C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10) of the processing gas of the present invention is From the viewpoint of expressing the effect satisfactorily, it is preferably 99% by volume or more, more preferably 99.9% by volume or more. The upper limit of the content is usually about 99.999% by volume. Further, when the concentration of the processing gas is low, there may be a deviation in gas purity in a container filled with the processing gas. Specifically, the performance when using each gas in the initial stage and in the stage where the remaining amount is low is greatly biased, which may lead to a decrease in yield in the production line of the factory where etching is performed. Therefore, by improving the processing gas purity in the filling container, there is no bias in the gas purity in the container, so there is no difference in performance when using gas between the initial use and the stage when the remaining amount of gas is low Gas can be used without waste. The content of C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10) is a gas chromatograph using a hydrogen ionization detector (FID) according to the examples described later. Can be measured graphically.

In the processing gas of the present invention, C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10), organic trace compounds derived from the raw material of the gas, nitrogen gas Impurities such as oxygen gas and moisture may be included. The content of these impurities is preferably as low as possible. The first reason is that impurities are dissociated in the processing chamber and various free radicals (etching species) are generated, which affects the plasma reaction. The second reason is that the processing gas is filled in the filled container. This is because the gas purity greatly fluctuates with time due to the presence of impurities when it is taken out from the furnace, making it difficult to perform the plasma reaction stably under a certain condition.

2) Etching Method “Etching” using the method of the present invention refers to a technique for etching a very highly integrated fine pattern on a target object used in a manufacturing process of a semiconductor manufacturing apparatus. The object to be processed in the present invention has a laminated film including at least one silicon oxide film layer and at least one silicon nitride film layer.

When the processing gas of the present invention is used as an etching gas, it consists of helium, argon, neon, krypton, and xenon in order to control the concentration of etching species generated in plasma, control of ion energy, and suitability of the hole shape. At least one group 0 gas selected from the group may be added and used as a plasma reaction mixed gas. The added amount of the group 0 gas is such that the total amount of the group 0 gas with respect to C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10) is a volume ratio [inert gas / C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10)] is preferably 2 to 200, and more preferably 5 to 150. Further, the group 0 gas may be used as a mixture of two or three kinds as required.

Further, O ₂ and / or O ₃ may be added and used for relaxing the etching stop. The amount of O ₂ and O ₃ added is determined by the total amount of O ₂ and O ₃ with respect to C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10). ₂ and / or O ₃ ) / C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10)], preferably 0.1 to 50, 0.5 to 30 is more preferable.

In the method of the present invention, the laminated film is preferably etched using a resist provided thereon as a mask. That is, since a C _a H _b F _c (a = 3 to 5, b = 1 to 2, c = 3 to 10) -based gas containing CF and CHF groups as constituent elements is used, the etching of the laminated film against resist etching is selected. The ratio can be improved.
In this specification, the resist refers to a pattern formed of a photosensitive resist composition, and the resist is formed, for example, by irradiating the photosensitive resist composition with radiation of 195 nm or less.

  Here, the selection ratio of the laminated film to the resist refers to (average etching rate of laminated film) / (average etching rate of resist). The high etching selectivity to resist is also referred to as having etching selectivity with respect to the resist. With this etching selectivity, the laminated film can be etched without destroying the resist.

  Etching is performed until the underlying layer is exposed if the underlying layer of the laminated film is a material having a sufficient etching selectivity by the processing gas. In addition, if the etching selectivity is not sufficient, the etching can be finished at the upper layer of the laminated film.

In the etching method of the present invention, the plasma density at the time of etching is not particularly limited, but from the viewpoint of better expressing the effects of the present invention, the plasma density is preferably 10 ¹² ions / cm ³ or more, more preferably It is desirable to perform etching in a high-density plasma atmosphere of 10 ¹² to 10 ¹³ ions / cm ³ . A phenomenon that the selectivity is lowered in the conventional fluorine-containing compound by setting the plasma density to 10 ¹² ions / cm ³ or more has been observed. However, C _a H _b F _c (a = 3-5, b = 1-2, c = 3-10), such a phenomenon is unlikely to occur, etching can be performed at a high etching rate while ensuring high selectivity, and a fine pattern can be formed. It can be formed efficiently.

  Examples of plasma generators include helicon wave system, high frequency induction system, parallel plate type, magnetron system and microwave system. However, since plasma generation in a high density region is easy, helicon wave system, high frequency induction. The apparatus of a system and a microwave system is used suitably.

  The pressure at the time of etching is not particularly limited, and the plasma reaction gas of the present invention is usually contained in the etching chamber together with other gas components if desired, in a processing chamber (etching chamber) deaerated to a vacuum. Preferably it introduce | transduces so that it may become 0.0001-1300Pa, More preferably, it is 0.13-1.3Pa.

  Although the ultimate temperature of the to-be-etched substrate at the time of etching is not particularly limited, it is preferably in the range of 0 to 300 ° C, more preferably 60 to 250 ° C, and further preferably 80 to 200 ° C. The substrate temperature may or may not be controlled by cooling or the like. Although the etching time is generally 5 to 10 minutes, the plasma reaction gas of the present invention can be etched at a high speed, so that productivity can be improved in 2 to 5 minutes.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Unless otherwise specified, “parts” in the examples means “parts by weight”.

The content of C _a H _b F _c (a = 3 to 5, b = 1, c = 3 to 10) in the processing gas (plasma reaction gas) was determined by a gas chromatography (GC) method.

GC measurement condition device: HP6890 manufactured by Hewlett-Packard Company
Column: NEUTRA BOND-1, Length 60 m / ID 250 μm / film 1.50 μm
Injection temperature: 150 ° C
Detector temperature: 250 ° C
Carrier gas: Nitrogen (23.2 mL / min)
Make-up gas: nitrogen (30 ml / min), hydrogen (50 mL / min), air (400 mL / min)
Split ratio: 137/1
Temperature rising program: (1) Holding at 40 ° C. for 20 min (2) Temperature rising at 40 ° C./min (3) Holding at 250 ° C. for 14.75 min Holding detector: FID

[Production Example 1] Production of 1,3,3,4,4,5,5-heptafluorocyclopentene 1,3,3,4,4,5,5-heptafluorocyclopentene was obtained from Journal of American Chemical Society, 1964. , Vol. 86,5361, and a purified product of the compound was obtained.
In a glass four-necked reactor equipped with a stirrer and a dropping funnel, 700 parts of anhydrous triethylene glycol dimethyl ether (manufactured by Aldrich) and 300 parts of octafluorocyclopentene (manufactured by Shinquest) are charged and placed in an acetone / dry ice bath. Soaked and cooled to -30 ° C. Here, 62 parts of a triethylene glycol dimethyl ether solution (concentration 2 mol / L) of sodium borohydride was dropped from a dropping funnel. After completion of the dropwise addition, the whole volume was stirred for 2 hours at a temperature of -30 to -20 ° C, and further stirred for 6 hours while raising the temperature to room temperature.

  After completion of the reaction, 1500 parts of water was added little by little to the reaction solution, and the two layers were separated. The lower layer was taken out, washed with saturated aqueous sodium hydrogen carbonate, and dried over anhydrous magnesium sulfate. Magnesium sulfate was removed by filtration, and the obtained filtrate was purified using a KS distillation column (manufactured by Toshin Seiki Co., Ltd., 30 plates). The desired product 1,3,3,4,4,4 178 parts of 5,5-heptafluorocyclopentene were obtained.

[Production Example 2] Production of 1,1,1,3,4,4,5,5,5-nonafluoro-2-pentene 1,1,1,3,4,4,5,5,5-Nonafluoro- 2-Pentene is described in Journal of Fluorine Chemistry, Vol. 123, 227 (2003). A glass reactor was charged with 119 parts of hexafluoropropene dimer (perfluoro (2-methyl-2-pentene)), 65 parts of t-butanol and 50 parts of triethylamine, and stirred at a temperature of 60 ° C. overnight. After cooling to room temperature, 90 parts of water was added to the mixed solution to separate into two layers. The lower layer was washed with 5% HCl aqueous solution and then with saturated brine, and then dried over magnesium sulfate to obtain a crude product. Next, a crude product and 5 parts of p-toluenesulfonic acid were charged in a glass reactor equipped with a condenser and heated at a temperature of 120 ° C. for 5 hours. After cooling to room temperature, water was added and stirred, and 75 parts of triethylamine was further added from the dropping funnel. A trap immersed in a dry ice / acetone bath was attached to the outlet of the condenser via a tube to collect the distillate components. The contents collected in the trap were washed with a 5% aqueous hydrochloric acid solution and then with a saturated saline solution and then dried over magnesium sulfate. When the obtained crude product was purified using a KS distillation column (manufactured by Toshin Seiki Co., Ltd., 30 theoretical plates), the desired product 1,1,1,3,4,4,5,5, 52 parts of 5-nonafluoro-2-pentene were obtained.

  A newly prepared cylinder made of SUS316 having a capacity of 150 mL was dried under reduced pressure, and 1,3,3,4,4,5,5-heptafluorocyclopentene obtained in Examples 1 and 2 and 1,1, The purified products of 1,3,4,4,5,5,5-nonafluoro-2-pentene were each filled through a filter. These cylinders were immersed in a refrigerant kept at -196 ° C, and the valve-out was connected to a vacuum line. The valve was opened for 5 seconds to remove nitrogen and oxygen inside the cylinder, the cylinder was once returned to room temperature, and immersed in a refrigerant kept at −196 ° C. to remove nitrogen and oxygen five times. By the above operation, a plasma reaction gas was obtained in a form filled in a cylinder. Separately, 1,3,3,4,4,5,5-heptafluorocyclopentene and 1,1,1,3,4,4,5,5,5-nonafluoro-2-pentene in the plasma reaction gas The contents were determined by gas chromatography analysis and found to be 99.2% by volume and 99.8% by volume, respectively.

[Example 1] Preparation of resist solution Ternary copolymer consisting of 2,2,2-trifluoromethyl methacrylate, 2-ethyladamantyl methacrylate and t-butyl methacrylate [copolymerization ratio: 0.4: 0.35: 0.25 (molar ratio), molecular weight 8700] 10 parts, and 0.15 part of triphenylsulfonium methanesulfonate, which is an acid generator, are dissolved in 70 parts of propylene glycol monomethyl ether acetate and filtered through a filter having a pore size of 100 nm. A solution was prepared. This resist solution is applied by spin coating on an 8-inch silicon substrate on which a silicon nitride film having a thickness of about 2 μm and a silicon oxide film having a thickness of about 2 μm are formed, and prebaked at 120 ° C. on a hot plate. Thus, a resist film having a thickness of 3000 nm was formed. This resist film was exposed through a mask pattern by an X-ray exposure apparatus. Thereafter, post-baking was performed at 130 ° C., and development was performed at 25 ° C. for 60 seconds using a 2.38% tetramethylammonium hydroxide aqueous solution, followed by drying to form a 100 nm contact hole pattern.

Etching with Process Gas After the substrate prepared in Example 1 is set in an etching chamber of a parallel plate plasma etching apparatus and the system is evacuated, the plasma reaction gas produced in Production Example 1 is supplied at a rate of 15 sccm. Further, oxygen and argon were introduced into the etching chamber at a rate of 15 sccm and 400 sccm, respectively. The internal pressure was maintained at 5 mTorr, and dry etching was performed at a plasma density of 10 ¹² ions / cm ³ . Table 1 shows the etching rate and the selectivity to the resist.

[Example 2]
The same experiment as in Example 1 was performed except that the plasma reaction gas produced in Production Example 2 was used instead of the plasma reaction gas produced in Production Example 1. Table 1 shows the etching rate and the selectivity to the resist.

[Comparative Example 1]
Instead of the plasma reaction gas produced in Production Example 1, it was carried out except that hexafluoro-1,3-butadiene (manufactured by Kanto Denka Kogyo Co., Ltd.) was etched at a rate of 15 sccm and difluoromethane was etched at a rate of 30 sccm. The same experiment as in Example 1 was performed. Table 1 shows the etching rate and the selectivity to the resist.

[Comparative Example 2]
The same experiment as in Example 1 was performed except that hexafluoro-1,3-butadiene was used instead of the plasma reaction gas produced in Production Example 1. Table 1 shows the etching rate and the selectivity to the resist.

From the results shown in Table 1, when the dry etching is performed using the processing gas of the present invention (Examples 1 and 2) and when the conventional product is used (Comparative Examples 1 and 2), Examples 1 and 2 are more It can be seen that a pattern having excellent selectivity and a good shape can be formed, and even if the plasma speed is in a high density region, processing can be performed at a high etching speed without significantly reducing the selectivity. Furthermore, since there are few kinds of gas, it can implement | achieve low cost from simplification of piping etc.

Claims (3)

An object to be processed having a laminated film including at least one silicon oxide film layer and at least one silicon nitride film layer is placed in a processing chamber, and a processing gas is introduced so that the silicon oxide film layer and silicon of the laminated film are introduced. In the method of etching both nitride layers, the processing gas is 1,3,3,4,4,5,5-heptafluorocyclopentene, 1,1,1,3,4,4,5,5, Hydrofluorocarbon selected from the group consisting of 5-nonafluoro-2-pentene and 1,1,1,2,4,4,5,5,5-nonafluoro-2-pentene, oxygen gas, helium, argon Etching method, characterized in that it is a processing gas containing a group 0 gas selected from neon, krypton and xenon . The hydrofluorocarbon is 1,3,3,4,4,5,5-heptafluorocyclopentene or 1,1,1,3,4,4,5,5,5-nonafluoro-2-pentene. Item 2. The etching method according to Item 1. The etching method according to claim 1, wherein the stacked film is etched using a resist provided thereon as a mask.