Etching Method

Abstract

To provide an etching method and a semiconductor device that enables patterning of h-BN film to a desired shape, thereby obtaining a semiconductor device that can demonstrate the effect of h-BN film.SOLUTION: An etching method includes the steps of depositing a mask film 112 for etching and patterning the h-BN film 111 deposited on the substrate 110 to a predetermined shape, and reactive ion etching by introducing a gas containing F2 gas as the etching gas to etch the h-BN film 111.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an etching method used when manufacturing a semiconductor device including h-BN (hexagonal boron nitride). By law It relates thereto.

Background Art

[0002] h-BN not only has excellent thermal conductivity, but also, for example, Non-Patent Document 1 describes it as a fundamental and technically important material system due to its unique physical properties such as a wide energy bandgap, large light absorption, and neutron capture cross-section. This Non-Patent Document 1 describes a dry etching technique for active devices based on an h-BN epitaxial layer using inductively coupled plasma (ICP) in order to establish a device processing technology for realizing an active device based on h-BN. And Non-Patent Document 1 describes that SF6 is very suitable for etching an h-BN epitaxial layer in an RF plasma environment and shows that it is useful as a guide for future h-BN device processing.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the inventors' experiments have revealed that although SF6 has a fast etching rate for h-BN films, it is not suitable for forming patterns. 1(A), which serves as an etching model, has an h-BN film 102 formed on a Si substrate 101, an aluminum mask film 103 with a thickness of 200 nm patterned to a predetermined shape formed on it, and a resist film 104 for shaping the mask film 103 into the predetermined shape formed on the mask film 103. This model was subjected to dry etching by RIE (Reactive Ion Etching) using SF gas as the etching gas.

[0005] As a result, as shown in FIG. 1(B), the strong isotropy of the SF gas causes etching of the h-BN film 102 to proceed from the sides, ultimately lifting the mask film 103 and causing it to peel off, as shown in FIG. 1(C).

[0006] Thus, when SF6 is used as the etching gas, even if the h-BN film can be removed by etching, it is difficult to achieve the desired patterning. Similarly, when CHF3 is used as the etching gas, even if the h-BN film can be removed by etching, the etching performance is insufficient, and some portions of the h-BN film remain unetched.

[0007] Therefore, an object of the present invention is to provide an etching method and a semiconductor device that can pattern an h-BN film into a desired shape, thereby obtaining a semiconductor device that can utilize the effects of the h-BN film. [Means for solving the problem]

[0008] The etching method of the present invention is an etching method for etching an h-BN film, and is characterized by including a step of introducing a gas containing F2 gas as an etching gas for etching the h-BN film and performing reactive ion etching.

[0009] According to the etching method of the present invention, F gas as an etching gas can etch h-BN films in the same way as SF gas. However, unlike SF gas, F gas has perpendicular anisotropy, and therefore can etch h-BN films without changing the pattern shape.

[0010] The method may include forming a mask film for etching and patterning the h-BN film into a predetermined shape, thereby allowing the h-BN film to be patterned into a predetermined shape.

[0011] The method may include a step of forming a mask film of a predetermined shape in addition to the h-BN film, so that only the h-BN film can be etched and removed.

[0012] The etching gas can be a mixture of F gas and a rare gas, which can reduce the influence of the rare gas on the h-BN film and the substrate while etching with F gas.

[0013] The mixture ratio of the mixed gas may be such that the rare gas is higher than the F2 gas. The rare gas may be He gas. By using He gas, which has a weaker physical etching property than Ar gas, the effect of F2 gas can be more accurately understood.

[0014] The present invention provides a semiconductor device comprising: a substrate; an insulating film provided on the substrate; and a plurality of semiconductor elements formed from a laminate including an h-BN film stacked on the insulating film and a graphene film provided on the h-BN film, the laminate being patterned to form gaps that divide the laminate.

[0015] According to the semiconductor device of the present invention, a plurality of semiconductor elements are formed on an insulating film provided on a substrate by patterning a laminate including an h-BN film and a graphene film to form gaps that divide the laminate. Therefore, a plurality of semiconductor elements that increase the mobility in the graphene film can be formed on the substrate, thereby increasing the degree of integration.

[0016] The semiconductor element can include a gate film provided on the insulating film, a gate insulating film made of an insulating film and an h-BN film or made of an h-BN film provided on the gate film, the graphene film patterned to correspond to the gate insulating film, a gate electrode provided on the gate film, and a pair of electrodes provided on the graphene film and functioning as a source electrode and a drain electrode. By configuring in this way, it is possible to form a large number of semiconductor elements that function as FETs on the substrate. [Effects of the Invention]

[0017] The present invention makes it possible to pattern the h-BN film into a desired shape, thereby obtaining a semiconductor device that can fully utilize the effects of the h-BN film. [Brief explanation of the drawings]

[0018] [Figure 1] These are diagrams for explaining conventional etching methods. (A) shows a state in which a mask and resist are formed on an h-BN film on a substrate and the substrate is etched using SF6. (B) shows a state in which etching using SF6 has progressed and the substrate has been eroded. (C) shows a state in which etching has progressed further, removing the mask and h-BN film and further eroding the substrate. [Figure 2] FIG. 1 is a diagram illustrating an example of an etching apparatus for performing etching. [Figure 3]1A and 1B are diagrams showing the steps of an etching method according to an embodiment of the present invention, in which (A) is a diagram showing a state in which an h-BN film is formed on a substrate, (B) is a diagram showing a state in which a mask film is formed on the h-BN film, (C) is a diagram showing a state in which a resist film is formed on the mask film, and (D) is a diagram showing a state in which the mask film has been patterned and etched. [Figure 4] 4A to 4D are diagrams showing the steps of the etching method according to the present embodiment, continuing from FIG. 3, in which (A) shows the state in which the h-BN film is etched using a mask film, (B) shows the state in which the h-BN film has been etched, (C) shows the state in which the etching of the h-BN film has been completed, and (D) shows the state in which the mask film remaining on the h-BN film has been removed. [Figure 5] 1A and 1B are diagrams showing the state of etching by the etching method according to the present embodiment, in which (A) is a diagram for explaining the state of etching, (B) is a scanning electron microscope photograph of (A), (C) is a scanning electron microscope photograph of (B) enlarged, and (D) is an electron microscope photograph of (C) further enlarged. [Figure 6] 1A and 1B are diagrams for explaining a conventional semiconductor device, in which (A) is a side view and (B) is a plan view. [Figure 7] 1A and 1B are diagrams showing a semiconductor device according to an embodiment of the present invention, in which (A) is a plan view, (B) is a cross-sectional view taken along line AA in (A), and (C) is a cross-sectional view taken along line BB in (A). [Figure 8] (A) is a diagram showing the state in which a gate film, an insulating film, an h-BN film, a graphene film, a mask film, and a resist film are formed on a substrate on which an insulating film has been formed, and (B) is a diagram showing the state in which the gate film, the insulating film, the h-BN film, and the graphene film from Figure 8 have been etched. [Figure 9] 8. (A) is a diagram showing a state in which an insulating film made of an Al2O3 film has been formed on the state shown in FIG. 8, and (B) is a diagram showing a state in which a groove has been formed in the gate electrode formation region. DETAILED DESCRIPTION OF THE INVENTION

[0019] (Embodiment) An etching method for a semiconductor device according to an embodiment of the present invention will be described with reference to the drawings. First, the configuration of an etching apparatus for performing etching by the etching method according to the embodiment of the present invention will be described with reference to the drawings.

[0020] (Explanation of etching equipment) The etching apparatus 10 shown in Fig. 2 includes a reaction chamber 11 in which plasma etching is performed. The reaction chamber 11 is formed with an inlet 12 for introducing an introduction gas (etching gas) that is a processing gas. The reaction chamber 11 also has an exhaust port 13 for evacuating the interior of the chamber. A pump 14 for suctioning the interior of the reaction chamber 11 is connected to the exhaust port 13.

[0021] An anode 15 and a cathode 16 are arranged at the top and bottom of the reaction chamber 11, sandwiching a target (sample) therebetween. The anode 15 is earthed, and a high-frequency power supply 17 is connected to the cathode 16. In addition, the reaction chamber 11 is provided with an electrode and a power supply (not shown) that convert the introduced gas into plasma by irradiating it with electromagnetic waves such as microwaves.

[0022] (Explanation of etching method) Next, a method for etching a semiconductor device using such an etching apparatus 10 will be described with reference to the drawings. 3(A), a substrate 110 is prepared onto which an h-BN film 111 is transferred. The substrate 110 can be a Si substrate. Next, as shown in FIG. 3(B), a mask film 112 is formed on the h-BN film 111 by a predetermined procedure. This mask film 112 may be a metal film such as Al, Ni, or Cr, or may be a nitride film made of SiN or an oxide film made of alumina (Al2O3), etc. The mask film 112 may be a single layer, or may be formed by laminating metal films made of different metal materials, or by laminating a metal film and an oxide film.

[0023] Next, as shown in FIG. 3(C), a resist film 113 is formed on the mask film 112. Next, as shown in FIG. 3(D), the resist film 113 is patterned into a predetermined shape, and then the mask film 112 is etched into the shape of the resist film 113.

[0024] Next, as shown in FIG. 4(A), the sample (target) is placed in an etching apparatus 10 (see FIG. 2) and reactive ion etching is performed. The etching gas contains F2 gas. In this embodiment, this gas can be mixed with a rare gas. This rare gas can be helium gas (He), neon gas (Ne), argon gas (Ar), krypton gas (Kr), xenon gas (Xe), radon gas (Rn), or a mixture of two or more of these rare gases. In this embodiment, He gas, the lightest of the rare gases, is used.

[0025] For example, Ar gas can be used as the rare gas. However, since Ar gas has a strong physical etching property, He gas was used to accurately grasp the effect of F2 gas. This allows us to confirm that accurate etching is possible by understanding the etching effect of F2 gas while controlling the mixed gas of F2 gas and He gas at the prototype stage, which allows us to move smoothly to the mass production stage.

[0026] Furthermore, if the mixture ratio of the mixed gas is higher than that of the F2 gas, the F2 gas can be diluted while diffusing. In this embodiment, the mixture ratio of F2 gas + He gas can be 1:9. F2 gas is a special gas, and cannot be supplied from a cylinder at 100%. Therefore, by setting the ratio to 1:9, it becomes possible to supply from a cylinder, making procurement easier. Note that, basically, it is considered that the F2 gas + He gas (rare gas) mixture ratio can be improved in procurement by increasing the ratio of the rare gas, and the mixture ratio of F2 gas + He gas may be 4:6 to 1:9, or even 0.5:9.5.

[0027] By performing reactive ion etching in this manner, the h-BN film 111 is etched into the shape of the mask film 112, as shown in FIG. 4(B). This is because the F gas used as the etching gas has perpendicular anisotropy, and compared with CHF gas, which also has perpendicular anisotropy, the F gas + He gas etch rate is faster for the h-BN film 111 but slower for the Si substrate 110. Therefore, after etching the h-BN film 111 exposed from the mask film 112, excessive etching of the substrate 110 can be prevented.

[0028] Furthermore, with SF gas, the substrate 101 is largely etched from the sides due to its strong isotropy, as shown in FIGS. 1(B) and 1(C). However, by using F gas, the h-BN film 111 exposed from the mask film 112 is etched before the substrate 110 is largely etched, as shown in FIG. 4(C). Therefore, the h-BN film 111 on the substrate 110 can be patterned into a desired shape. Therefore, the etching method according to this embodiment can manufacture a semiconductor device that can fully utilize the effects of h-BN.

[0029] Once the h-BN film 111 has been patterned, the mask film 112 remaining on the h-BN film 111 is then removed by a conventional method, leaving the patterned h-BN film 111 on the substrate 110, as shown in FIG. 4(D).

[0030] In this embodiment, a technique such as forming a resist film 113 on the mask film 112 is used to shape the h-BN film 111 into a predetermined shape. However, a mask pattern with holes in a thin substrate may be used instead of the mask film 112 or the resist film 113. Furthermore, when the h-BN film 111 is not to be processed into a predetermined shape but simply to be processed to a predetermined thickness, it is possible to etch the h-BN film 111 formed on the entire surface of the substrate by the above-mentioned method (method using F gas and He gas) without providing the mask film 112 or the resist film 113. Furthermore, the h-BN film 111 processed to a predetermined thickness in this manner may be further processed into a predetermined pattern using the mask film 112 or the resist film 113.

[0031] Furthermore, in the above description, the mask film 112 and resist film 113 of a predetermined shape are formed on the h-BN film 111 to form the h-BN film 111 into a predetermined shape. However, since the h-BN film 111 can be etched and removed using F gas, a mask film may be formed on top of the h-BN film and then the h-BN film 111 may be etched and removed.

[0032] (Example) The etching method according to the present embodiment shown in FIGS. 3 and 4 was carried out. First, the substrate 110 to which the h-BN film 111 shown in FIG. 3(A) had been transferred was cleaned. This cleaning was performed using an organic draft chamber, HSS-200 manufactured by UNION Co., Ltd. Cleaning was performed for 1 minute using pure water to which ultrasonic waves were applied. 3(B), an aluminum film was formed as a mask film 112. This aluminum film was formed to a thickness of 200 nm using a sputtering apparatus E-200S manufactured by Canon Anelva Corporation.

[0033] Next, the formed mask film 112 was washed. For this washing, HSS-200 manufactured by UNION was used. The washing was performed with acetone to which ultrasonic waves were applied for 1 minute, and with ethanol to which ultrasonic waves were applied for 1 minute.

[0034] Next, as shown in FIG. 3(D), the formed resist film 113 is patterned by a maskless exposure device. In the resist coating process, a Tokyo Ohka Kogyo Co., Ltd. OFPR-8600 photosensitive resin solution was used to form the resist film. The pre-baking process involved heating at 90°C for 90 seconds. The maskless exposure device used for the exposure process was a Heidelberg Instruments MLA100. The exposure dose was 1500 mJ / cm. 2 The development process was performed with Deforce 0. Tokyo Ohka Kogyo Co., Ltd.'s NMD-W was used as the TMAH alkaline developer. The rinse process involved washing with pure water in an overflowing state. The post-bake process involved heating at 130°C for 5 minutes.

[0035] Next, the mask film 112, which is an aluminum film exposed from the resist film 113, is etched. The aluminum was etched using an HSS-2000HS manufactured by Dan Industries. The etching solution used was a mixed acid Al etching solution, and the processing time was 6 minutes, with 1 minute after discoloration. The rinse process involved cleaning with pure water in an overflowing state.

[0036] Next, the h-BN film 111 exposed from the mask film 112 is etched. For the etching process, an RIE-101iPH, which is an ICP-RIE (Inductive Coupled Plasma-RIE: Inductively Coupled Reactive Ion Etching) manufactured by Samco, was used. The etching conditions were as follows: a mixed gas of F2 gas and He gas in a ratio of 1:9 was used as the etching gas, the ICP power was 300 W, the bias power was 100 W, the gas flow rate was 20 sccm, the process pressure was 1 Pa, and the etching time was 10 minutes.

[0037] Next, the remaining resist film 113 was removed by using HSS-200 manufactured by UNION Co., Ltd., and was performed using acetone with ultrasonic waves applied for 1 minute and ethanol with ultrasonic waves applied for 1 minute. Then, the mask film 112 was removed to expose the h-BN film 111. The mask film 112 was removed using an HSS-2000HS manufactured by Dan Industries Co., Ltd. with an Al mixed acid etching solution for 6 minutes. The rinsing process involved cleaning with pure water in an overflowing state.

[0038] The h-BN film etched in this manner was observed using a JEOL JIB-4600F scanning electron microscope (combined beam processing and observation system). As shown in Figures 5(A) to 5(D), it can be seen that a patterned h-BN film is microfabricated on a Si substrate.

[0039] In this way, the h-BN film can be patterned, and a semiconductor device using the h-BN film can be fabricated. In this embodiment, a semiconductor device will be described in which an h-BN film is combined with graphene, which is a sheet-like substance in which one carbon atom is arranged in a hexagonal lattice pattern.

[0040] (Description of a conventional semiconductor device) First, a conventional semiconductor device that combines an h-BN film and graphene will be described with reference to FIG. In a conventional semiconductor device 120 shown in FIGS. 6(A) and 6(B), an insulating film 122 made of an oxide film, for example, SiO 2 is provided on a substrate 121 (semiconductor substrate) made of Si. An h-BN film 123 is provided by transfer on the insulating film 122. Furthermore, a graphene film 124 is provided by transfer on the h-BN film 123. A pair of electrodes 125 is formed on the graphene film 124.

[0041] In this way, conventional semiconductor device 120 is constructed, and graphene film 124 is formed on h-BN film 123, thereby achieving electronic characteristics with mobility 10 times or more higher than that of a graphene film provided on a Si substrate.

[0042] This conventional semiconductor device 120 functions as a FET (Field Effect Transistor) by making the substrate 121 function as a gate and making the pair of electrodes 125 function as a source electrode and a drain electrode.

[0043] However, in the conventional semiconductor device 120, the h-BN film 123 could not be etched into a predetermined shape, and therefore the h-BN film 123 and the graphene film 124 are provided over the entire insulating film 122 formed on the substrate 121, and therefore the semiconductor device has to be constructed for each substrate 121. Therefore, it is difficult to integrate semiconductor devices including the h-BN film 123 and the graphene film 124.

[0044] (Description of the Semiconductor Device According to the Present Embodiment) In the semiconductor device according to the embodiment of the present invention, the etching method shown in FIG. 4 can be used to pattern the h-BN film 123 and other films into a predetermined shape, allowing multiple semiconductor elements to be configured on the substrate.

[0045] (Explanation of the configuration of the semiconductor device) As shown in FIGS. 7A to 7C, a semiconductor device 130 has an insulating film 132 made of SiO 2 provided on a substrate 131 made of Si, similar to the conventional semiconductor device 120 shown in FIG. A plurality of semiconductor elements 140 are provided on the insulating film 132 by forming gaps S that divide the stacked body by patterning.

[0046] The semiconductor element 140 includes a gate film 141 made of Si, an insulating film 142 , an h-BN film 143 , a graphene film 144 , a pair of electrodes 145 , and a gate electrode 146 . In the semiconductor element 140, the insulating film 132, the gate film 141, the insulating film 142, the h-BN film 143, and the graphene film 144 are covered with the insulating film 133, with the pair of electrodes 145 and the gate electrode 146 exposed.

[0047] 7(C), a pair of electrodes 145 is formed on a main body 140A of the semiconductor element 140, which is formed in a T-shape, and is connected to the graphene film 144. Also, as shown in FIG. 7(B), a gate electrode 146 is formed on a protruding portion 140B of the semiconductor element 140, which is formed in a T-shape, and is connected to the gate film 141 through the insulating film 142, the h-BN film 143, and the graphene film 144. Also, the pair of electrodes 145 is insulated from the h-BN film 143 and the graphene film 144 by the insulating film 142.

[0048] (Explanation of the manufacturing method of the semiconductor device) Next, a method for manufacturing the semiconductor device 130 will be described with reference to the drawings. 8(A), first, a conductive film, for example, a high-concentration single-crystal Si film, is formed on an insulating film 132 formed on a substrate 131 to form a gate film 141. This gate film 141 (conductive film) needs to be bonded to the h-BN film 143 by van der Waals forces when the h-BN film 143 is formed, and a flatness of 2 nm or less is required to ensure high mobility of the graphene film, so a single-crystal Si film is optimal.

[0049] Next, for example, a silicon oxide film is formed by thermal oxidation to form the insulating film 142. This thermal oxidation is performed because the insulating film 142 needs to have a flatness of 2 nm or less. As another example, the film can be formed by chemical vapor deposition (CVD), but in this case, the flatness is adjusted to 2 nm or less by chemical mechanical polishing (CMP) after the insulating film is deposited. Note that a silicon oxide film is not necessarily required as the insulating film 142.

[0050] Next, an h-BN film 143 is transferred, followed by a graphene film 144 that will become an active layer. Next, for example, Al2O3 is deposited as an insulating film by ALD (Atomic Layer Deposition) to form a mask film 112 (see FIG. 3C) shown in FIG. 3D. Note that any type of insulating film can be used as long as it is deposited by ALD. Furthermore, as a mask for etching the mask film 112, a film made of a different material from the insulating film deposited by the ALD method, such as a silicon oxide film, is deposited to form a resist film 113 shown in Fig. 3(C). Note that the deposition of a mask is not necessarily required.

[0051] 4(A) to 4(D), the mask film 112 is patterned by the resist film 113 etched into a predetermined shape by photolithography, and then the graphene film 144, the h-BN film 143, the insulating film 142, and the gate film 141 are removed by anisotropic etching, for example, RIE. Thereafter, the resist film 113 and the mask film 112 are removed (see FIG. 8(B)).

[0052] Next, as shown in FIG. 9(A), an Al2O3 film is deposited as an insulating film 133 by the ALD method as a film with good step coverage. Next, a pattern is formed by photolithography in areas other than the gate electrode 146 (see FIGS. 7A and 7B), and then the Al2O3 film, graphene film 144, h-BN film 143, and insulating film 142 in the desired area (gate electrode formation area G (see FIG. 9B)) are etched by RIE according to the procedure shown in FIG. 4 to form a groove for the gate electrode 146. The photoresist is then removed.

[0053] In the state shown in FIG. 9(A), the insulating film 133 (Al2O3 film) has only been deposited and has not been processed. It is also possible to deposit a mask film in the same manner as above after depositing the Al2O3 film, and then process the mask film and then process the Al2O3 film.

[0054] Next, an Al2O3 film is deposited in the gate electrode formation region G by the ALD method, which has excellent step coverage characteristics, and the deposited Al2O3 film 133a on the bottom (flat portion) is removed by RIE, leaving the Al2O3 film 133b only on the sidewalls of the trench.

[0055] Next, a resist film is formed by photolithography in areas other than the areas where the pair of electrodes 145 (see FIG. 7) are to be formed, and the Al2O3 film is removed. Then, Ti is deposited in the areas where the Al2O3 film has been removed to form the pair of electrodes 145, thereby manufacturing the semiconductor device 130 shown in FIG.

[0056] (Explanation of the semiconductor device's functions) In the semiconductor device 130 shown in Figures 7(A) to 7(C) manufactured as described above, the semiconductor elements 140 are arranged at predetermined intervals, so that the gate film 141 of each semiconductor element 140 is in a non-conductive state due to the insulating film 132.

[0057] Therefore, each semiconductor element 140 functions as an independent FET, with a gate film 141 functioning as a gate, an insulating film 142 functioning as a gate insulating film and an h-BN film 143 formed on the insulating film 142, a graphene film 144 formed on the h-BN film 143, a pair of electrodes 145 made of a metal thin film functioning as a source electrode and a drain electrode, and a gate electrode 146 connected to the gate film 141. Therefore, by patterning a large number of semiconductor elements 140 on the substrate 131, a highly integrated semiconductor device 130 can be obtained.

[0058] Furthermore, in the semiconductor device 140, the h-BN film 143 is superimposed on the graphene film 144, and therefore the mobility in the graphene film 144 can be increased.

[0059] In the present embodiment, the semiconductor element 140 has the h-BN film 144 provided on the gate film 141 via the insulating film 143, and the insulating film 143 and the h-BN film 144 function as a gate insulating film. However, as described above, the insulating film 143 may be omitted, and only the h-BN film 144 may function as a gate insulating film. Furthermore, although the semiconductor element 140 functions as a FET, even if it functions as another element, since it is formed on the insulating film 132, the other elements can be operated independently. [Industrial Applicability]

[0060] The present invention is suitable for manufacturing semiconductor devices that include h-BN films. [Explanation of symbols]

[0061] 10 Etching equipment 11 Reaction chamber 12 Introduction 13 Exhaust port 14 Pump 15 anodes 16 cathode 17 High frequency power supply 101 Substrate 102 h-BN membrane 103 Mask membrane 104 Resist film 110 Substrate 111 h-BN membrane 112 Mask membrane 113 Resist film 120 Conventional semiconductor device 121 PCB 122 insulating film 123 h-BN membrane 124 Graphene film 125 electrode 130 Semiconductor devices 131 Circuit Board 132,133 insulating film 133a, 133b Al2O3 140 Semiconductor elements 140A main body 140B Protrusion 141 Gate membrane 142 insulating film 143 h-BN membrane 144 Graphene Film 145 Electrode 146 gate electrode S Gap G Gate electrode formation region

Claims

1. An etching method for etching an h-BN film, comprising the step of introducing a gas containing F2 gas as an etching gas for etching the h-BN film and performing reactive ion etching.

2. 2. The etching method according to claim 1, further comprising the step of forming a mask film for etching and patterning the h-BN film into a predetermined shape.

3. 2. The etching method according to claim 1, further comprising the step of forming a mask film of a predetermined shape in addition to said h-BN film.

4. 4. The etching method according to claim 1, wherein the etching gas is a mixed gas of F2 gas and a rare gas.

5. 5. The etching method according to claim 4, wherein the mixture ratio of the mixed gas is such that the rare gas is higher than the F2 gas.

6. 6. The etching method according to claim 4, wherein the rare gas is He gas.

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