Etching Method

Abstract

Provided is an etching method with which it is possible to selectively etch an oxide. The etching method comprises an etching step in which an etching object (12) having an oxide is placed in a chamber (10), and an etching gas that contains a fluorine-containing compound having a functional group indicated in the chemical formula is used to perform etching of the oxide of the etching object (12) in the chamber (10). The oxide is a metal oxide and / or a semi-metallic oxide. During the etching step, etching is performed without generating plasma of the etching gas inside the chamber (10).

Description

[Technical field]

[0001] The present invention relates to an etching method. [Background technology]

[0002] Metal oxides such as tantalum oxide (Ta2O5) and semi-metal oxides such as silicon dioxide (SiO2) are often used as low- or high-dielectric materials in the manufacture of semiconductor devices. When microfabricating metal oxides or semi-metal oxides into desired shapes, etching is performed using an etching gas. When etching, the etching selectivity between the metal oxide or semi-metal oxide film to be processed and the non-processed film present on the same substrate is important.

[0003] For example, Patent Document 1 discloses a method for etching a metal oxide by performing plasma etching using a fluorine-containing gas such as nitrogen trifluoride (NF3) or carbonyl fluoride (COF2) as an etching gas. In the method disclosed in Patent Document 1, the metal oxide is fluorinated with the fluorine-containing gas to form a metal fluoride, and then the metal fluoride is reacted with an organic substance to form a volatile metal compound, which is then volatilized, thereby etching the metal oxide. Moreover, Patent Document 2 discloses a method of etching a silicon oxide film by plasma etching using a mixed gas of a fluorocarbon such as hexafluoro-1,3-butadiene and carbonyl fluoride. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2012 / 052858 [Patent Document 2] Japan Patent Publication No. 51777, 2016 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method disclosed in Patent Document 1 has a problem that the process is complicated because it requires two steps, namely, a step of forming a metal fluoride by reacting the metal oxide with a fluorine-containing gas, and a step of forming a volatile metal compound by reacting the metal fluoride with an organic substance, in order to etch the metal oxide. Furthermore, the method disclosed in Patent Document 1 uses plasma, so that selective etching as described above is difficult. Furthermore, the method disclosed in Patent Document 2 has a problem in that materials that are not the target of processing (polysilicon, silicon nitride, etc.) are also etched together with the silicon oxide film that is the target of processing. An object of the present invention is to provide an etching method capable of selectively etching metal oxides and semi-metal oxides. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the present invention is as follows [1] to [8]. [1] An etching process comprising placing an object to be etched having an oxide in a chamber, and etching the oxide of the object to be etched in the chamber using an etching gas containing a fluorine-containing compound having a functional group represented by the following chemical formula: The oxide is at least one of a metal oxide and a semi-metal oxide, The etching method according to claim 1, wherein the etching step is performed without generating plasma of the etching gas in the chamber. In the following chemical formulas, * indicates a bonding point with another atom or atomic group.

[0007] [ka]

[0008] [2] The etching method according to [1], wherein in the etching step, the etching is performed by the etching gas without using plasma of the etching gas. [3] The etching method according to [1], wherein a plasma generating source is disposed at a position away from the chamber, and in the etching step, the etching is performed within the chamber using plasma of the etching gas generated outside the chamber by the plasma generating source.

[0009] [4] The etching method according to any one of [1] to [3], wherein the fluorine-containing compound has 1 or more and 5 or less carbon atoms. [5] The etching method according to any one of [1] to [3], wherein the fluorine-containing compound has 1 or more and 3 or less carbon atoms. [6] The etching method according to any one of [1] to [3], wherein the fluorine-containing compound is at least one of carbonyl fluoride and oxalyl fluoride.

[0010] [7] The etching method according to any one of [1] to [6], wherein the metal of the metal oxide contains at least one selected from the group consisting of tungsten, titanium, tantalum, ruthenium, iridium, and rhodium. [8] The etching method according to any one of [1] to [7], wherein the metalloid of the metalloid oxide contains silicon. Effect of the Invention

[0011] According to the present invention, it is possible to selectively etch metal oxides and semi-metal oxides. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of an example of an etching apparatus for explaining a first embodiment of an etching method according to the present invention. FIG. [Diagram 2] FIG. 4 is a schematic diagram of an example of an etching apparatus for explaining a second embodiment of an etching method according to the present invention. [Diagram 3]FIG. 2 is a diagram illustrating an etching target used in the examples, comparative examples, and reference examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An embodiment of the present invention will be described below. Note that this embodiment is merely an example of the present invention, and the present invention is not limited to this embodiment. In addition, various modifications and improvements can be made to this embodiment, and such modifications and improvements can also be included in the present invention.

[0014] The etching method according to the present embodiment includes an etching step in which an object to be etched having an oxide is placed in a chamber, and the oxide of the object to be etched is etched in the chamber using an etching gas containing a fluorine-containing compound having a functional group represented by the above chemical formula. The oxide is at least one of a metal oxide and a semi-metal oxide. In the etching step, the etching is performed without generating plasma of the etching gas in the chamber.

[0015] When the fluorine-containing compound having the functional group shown in the above chemical formula is brought into contact with the above oxide, the carbonyl group in the fluorine-containing compound reacts with the oxygen atom in the above oxide to release carbon dioxide, and the fluorine atom in the fluorine-containing compound reacts with a metal or metalloid to generate a volatile metal fluoride or metalloid fluoride, thereby proceeding with etching of the above oxide. As an example, the reaction between carbonyl fluoride and silicon dioxide is shown in the following reaction formula. 2COF2+ SiO2 → SiF4+ 2CO2

[0016] On the other hand, the fluorine-containing compound having the functional group shown in the above chemical formula hardly reacts with materials other than the above oxide (e.g., silicon nitride, polysilicon, amorphous carbon, simple metal, simple metalloid, metal nitride, semimetal nitride, organic matter, photoresist). Therefore, if the etching method according to this embodiment is applied to an etching target having both the above oxide and a material other than the above oxide, it is possible to selectively etch the above oxide without substantially etching materials that do not need to be etched (e.g., silicon nitride, polysilicon, amorphous carbon, simple metal, simple metalloid, metal nitride, semimetal nitride, organic matter, photoresist). Therefore, the etching method according to this embodiment can be suitably used for manufacturing semiconductor elements.

[0017] Photoresist materials refer to photosensitive compositions whose physical properties, such as solubility, change when exposed to light, electron beams, or the like. Examples of photoresist materials include photoresist materials for g-rays, h-rays, i-rays, KrF, ArF, F2, EUV, and the like. The composition of the photoresist material is not particularly limited as long as it is generally used in the semiconductor device manufacturing process, but examples of the photoresist material include polymers obtained by polymerizing compounds having functional groups that contribute to polymerization, such as vinyl groups, (meth)acryloyl groups, glycidyl groups, amino groups, and hydroxyl groups. Examples of the photoresist material include compositions containing polymers prepared from at least one monomer selected from linear olefins, cyclic olefins, styrene, vinylphenol, (meth)acrylic acid, (meth)acrylate, epoxy, melamine, and glycol. Note that (meth)acrylic acid means one or both of acrylic acid and methacrylic acid, and (meth)acrylate means one or both of acrylate and methacrylate.

[0018] In addition, since the etching of the oxide is performed without generating plasma of an etching gas in the chamber, corrosion of the chamber and the piping connected to the chamber is unlikely to occur. Furthermore, since the etching can be performed in a one-step process, the etching of the oxide can be performed easily and at low cost.

[0019] In the present invention, etching means removing part or all of the oxide contained in the etching object to process the etching object into a predetermined shape (e.g., a three-dimensional shape) (e.g., processing the oxide film contained in the etching object to a predetermined film thickness to form wiring), and also means removing residues and deposits consisting of the oxide from the etching object to clean it (e.g., removing oxide deposits accumulated on a semiconductor element without damaging the semiconductor element).

[0020] The etching method according to this embodiment will be described in further detail below by giving two examples, a first embodiment and a second embodiment. First Embodiment The etching method according to the first embodiment is an etching method in which etching is performed by an etching gas without using plasma of the etching gas (plasma gas obtained by converting an etching gas into plasma) in the above-mentioned etching step (hereinafter, this may be referred to as "plasmaless etching").

[0021] The etching method according to the first embodiment can be carried out by performing etching using an etching apparatus that does not have a plasma generation source, or by performing etching using an etching apparatus that has a plasma generation source installed inside or outside a chamber, without operating the plasma generation source.

[0022] The etching method according to the first embodiment will be described in further detail. [Etching gas] The etching gas used is a gas containing a fluorine-containing compound having a functional group shown in the above chemical formula. The type of fluorine-containing compound is not particularly limited as long as it has a functional group shown in the above chemical formula, but from the viewpoint of high volatility and easy handling as a gas, it is preferable that the carbon number is 1 to 5, more preferably 1 to 3, and most preferably 1 or 2.

[0023] Specific examples of the fluorine-containing compound include formyl fluoride, carbonyl fluoride, oxalyl fluoride, 2,2,2-trifluoroacetyl fluoride, 2,2-difluoroacetyl fluoride, 2-fluoroacetyl fluoride, acetyl fluoride, 2,2,3,3,3-pentafluoropropanoyl fluoride, 2,2,3,3-tetrafluoropropanoyl fluoride, 2,3,3,3-tetrafluoropropanoyl fluoride, 3,3,3-trifluoropropanoyl fluoride, and 2,3,3-trifluoropropanoyl fluoride. yl fluoride, 2,2,3-trifluoropropanoyl fluoride, 2,2-difluoropropanoyl fluoride, 2,3-difluoropropanoyl fluoride, 3,3-difluoropropanoyl fluoride, 2-fluoropropanoyl fluoride, 3-fluoropropanoyl fluoride, propionyl fluoride, 2,3,3,3-tetrafluoro-2-(trifluoromethyl)propanoyl fluoride, 3,3,3-trifluoro-2,2-bis(trifluoromethyl)propanoyl fluoride, and the like.

[0024] Among these fluorine-containing compounds, carbonyl fluoride (COF2) and oxalyl fluoride ((COF)2) are particularly preferred, and it is particularly preferred to use at least one of carbonyl fluoride and oxalyl fluoride as the fluorine-containing compound. These fluorine-containing compounds may be used alone or in combination of two or more.

[0025] The etching gas may be a gas consisting of only a fluorine-containing compound, or may be a mixed gas containing a fluorine-containing compound and other gases. When the etching gas is a mixed gas containing a fluorine-containing compound and other gases, the content of the fluorine-containing compound contained in the etching gas is preferably 1% by volume or more, more preferably 5% by volume or more, and even more preferably 10% by volume or more.

[0026] When the etching gas is a mixed gas containing a fluorine-containing compound and other gases, an inert gas can be used as the other gas. That is, the etching gas may be a mixed gas consisting of a fluorine-containing compound and an inert gas. As the inert gas, at least one selected from nitrogen gas (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) can be used. The content of the inert gas contained in the etching gas is not particularly limited, but can be more than 0 volume % and 99 volume % or less, and more preferably more than 50 volume % and 90 volume % or less.

[0027] [Pressure during etching] In the etching step of the etching method according to the first embodiment, an object to be etched is placed in a chamber, an etching gas is supplied into the chamber, and the oxide contained in the object to be etched is etched by the etching gas without using plasma of the etching gas. At this time, the pressure in the chamber is not particularly limited, but may be 1 Pa or more and 101.3 kPa or less.

[0028] For example, an object to be etched can be placed in a chamber and etched while passing an etching gas through the chamber, and the pressure in the chamber during the passage of the etching gas may be 1 Pa or more and 101.3 kPa or less. The flow rate of the etching gas may be appropriately set so that the pressure in the chamber is kept constant depending on the size of the chamber and the capacity of the exhaust equipment for reducing the pressure in the chamber.

[0029] [Object to be etched] The etching target to be etched by the etching method according to the first embodiment contains the oxide. That is, the etching target may be a member made of only the oxide, a member having a portion made of only the oxide and a portion made of another material, or a member made of a mixture of the oxide and another material. The shape of the entire etching target and the shape of the portion of the etching target made of only the oxide are not particularly limited, and may be, for example, a foil, film, powder, or lump.

[0030] The oxide refers to a compound containing a metal or metalloid and oxygen atoms as the main components, such as a compound used as a natural oxide film formed on the surface of a wiring material (simple metal, simple metalloid, or an alloy thereof), a compound used as a deposit formed on the surface of a wiring material (simple metal, simple metalloid, or an alloy thereof), a compound used as an insulating film of a semiconductor element, a compound used as a high-dielectric material or low-dielectric material of a semiconductor element, etc. The oxide may contain elements other than metals, metalloids, and oxygen, such as nitrogen, carbon, fluorine, chlorine, bromine, and iodine.

[0031] The type of metal in the metal oxide is not particularly limited as long as it generates a volatile metal compound (e.g., metal fluoride, metal carbonyl) as an etching product, and specific examples include tungsten (W), titanium (Ti), tantalum (Ta), ruthenium (Ru), iridium (Ir), rhodium (Rh), copper (Cu), tin (Sn), hafnium (Hf), nickel (Ni), cobalt (Co), iron (Fe), or an alloy of two or more of these metals. Similarly, the type of metal in the semi-metal oxide is not particularly limited as in the case of the metal in the metal oxide, and a specific example includes silicon (Si).

[0032] When the etching target has the oxide and a non-etching target that is made of a material other than the oxide and is not a target for etching, the oxide can be selectively etched with respect to the non-etching target by the etching method according to the first embodiment. An example of such an etching target is a substrate having a film of the oxide and a film of the non-etching target.

[0033] The film of the non-etching object may be at least one film selected from a metal film, a silicon film, a silicon nitride film, and an organic film. The silicon nitride film may be a film of a silicon compound having silicon atoms and nitrogen atoms, such as Si3N4(SiN) or SiCN. The silicon film may be a film of polysilicon or amorphous silicon. The organic film may be a film of a carbon material such as photoresist or amorphous carbon. The metal film may be a film made of the above-mentioned metal element or its nitride, carbide, silicide, or the like.

[0034] [Etching Equipment] Next, an example of the configuration of an etching apparatus that can be used in the etching method according to the first embodiment and an example of an etching method for the oxide using the etching apparatus will be described with reference to Fig. 1. The etching apparatus in Fig. 1 is a general etching apparatus used in the semiconductor device manufacturing process, and is a plasmaless etching apparatus that performs plasmaless etching. First, the configuration of the etching apparatus in Fig. 1 will be described.

[0035] The etching apparatus of FIG. 1 comprises a chamber 10 in which etching is performed, a stage 11 that supports an object 12 to be etched inside the chamber 10, a thermometer 14 that measures the temperature of the object 12 to be etched, an exhaust pipe 13 that exhausts gas from inside the chamber 10, a vacuum pump 15 that is connected to the exhaust pipe 13 and reduces the pressure inside the chamber 10, and a pressure gauge 16 that measures the pressure inside the chamber 10.

[0036] 1 is equipped with an etching gas supply unit that supplies an etching gas into the chamber 10. This etching gas supply unit has a fluorine-containing compound gas supply unit 1 that supplies a gas of a fluorine-containing compound having a functional group represented by the above chemical formula, an inert gas supply unit 2 that supplies an inert gas, a fluorine-containing compound gas supply pipe 5 that connects the fluorine-containing compound gas supply unit 1 and the chamber 10, and an inert gas supply pipe 6 that connects the inert gas supply unit 2 to an intermediate portion of the fluorine-containing compound gas supply pipe 5.

[0037] Furthermore, the fluorine-containing compound gas supply pipe 5 is provided with a pressure gauge 7 for measuring the pressure of the fluorine-containing compound gas, and a fluorine-containing compound gas flow rate control device 3 for controlling the flow rate of the fluorine-containing compound gas. Furthermore, the inert gas supply pipe 6 is provided with an inert gas pressure control device 8 for controlling the pressure of the inert gas, and an inert gas flow rate control device 4 for controlling the flow rate of the inert gas.

[0038] When a fluorine-containing compound gas is supplied to the chamber 10 as an etching gas, the fluorine-containing compound gas is sent from the fluorine-containing compound gas supply section 1 to the fluorine-containing compound gas supply piping 5, whereby the fluorine-containing compound gas is supplied to the chamber 10 via the fluorine-containing compound gas supply piping 5.

[0039] When a mixed gas of a fluorine-containing compound gas and an inert gas is supplied as the etching gas, a fluorine-containing compound gas is sent from the fluorine-containing compound gas supply unit 1 to the fluorine-containing compound gas supply pipe 5, and an inert gas is sent from the inert gas supply unit 2 to the fluorine-containing compound gas supply pipe 5 via the inert gas supply pipe 6. As a result, the fluorine-containing compound gas and the inert gas are mixed in the middle part of the fluorine-containing compound gas supply pipe 5 to form a mixed gas, and this mixed gas is supplied to the chamber 10 via the fluorine-containing compound gas supply pipe 5.

[0040] The configurations of the fluorine-containing compound gas supply unit 1 and the inert gas supply unit 2 are not particularly limited, and may be, for example, a gas bottle or a cylinder. As the fluorine-containing compound gas flow rate control device 3 and the inert gas flow rate control device 4, for example, a mass flow controller or a flow meter can be used.

[0041] When the etching gas is supplied to the chamber 10, it is preferable to supply the etching gas while maintaining the supply pressure of the etching gas (i.e., the value of the pressure gauge 7 in FIG. 1) at a predetermined value. That is, the supply pressure of the etching gas is preferably 2 Pa or more and 1 MPa or less, more preferably 10 Pa or more and 0.5 MPa or less, and further preferably 50 Pa or more and 0.3 MPa or less. When the supply pressure of the etching gas is within the above range, the etching gas is smoothly supplied to the chamber 10, and the load on the parts of the etching apparatus in FIG. 1 (e.g., the various devices and the piping) is small.

[0042] From the viewpoint of uniformly etching the surface of the etching object 12, the pressure of the etching gas supplied into the chamber 10 is preferably 0.1 Pa or more and 101.3 kPa or less, and more preferably 1 Pa or more and 70 kPa or less. If the pressure of the etching gas in the chamber 10 is within the above range, a sufficient etching rate can be obtained, and it becomes easy to selectively etch the oxide with respect to the object not to be etched (the etching selectivity tends to be high).

[0043] The pressure in the chamber 10 before the etching gas is supplied is not particularly limited as long as it is equal to or lower than the supply pressure of the etching gas. For example, -5 The pressure is preferably from 1 Pa to less than 30 kPa, and more preferably from 1 Pa to 10 kPa.

[0044] The differential pressure between the supply pressure of the etching gas and the pressure in the chamber 10 before the etching gas is supplied is preferably 0.5 MPa or less, more preferably 0.3 MPa or less, and even more preferably 0.1 MPa or less. If the differential pressure is within the above range, the etching gas is easily supplied to the chamber 10 smoothly.

[0045] It is preferable that the etching gas be supplied while maintaining the temperature of the etching gas at a predetermined value when it is supplied to the chamber 10. That is, the supply temperature of the etching gas is preferably 10° C. or more and 100° C. or less. The temperature of the etching object 12 during etching is preferably 105° C. to 500° C., more preferably 110° C. to 450° C., and even more preferably 120° C. to 400° C. Within this temperature range, etching of the oxide proceeds smoothly, the load on the etching device is small, and the life of the etching device is likely to be long.

[0046] The etching process time (hereinafter sometimes referred to as "etching time") can be set arbitrarily depending on the degree to which the oxide is desired to be etched, but considering the production efficiency of the semiconductor device manufacturing process, it is preferably within 60 minutes, more preferably within 40 minutes, and even more preferably within 30 minutes. Note that the etching process time refers to the time from when the etching gas is introduced into the chamber 10 to when the etching gas inside the chamber 10 is exhausted to finish the etching.

[0047] The etching method according to the first embodiment can be performed using a general plasmaless etching apparatus used in the semiconductor device manufacturing process, such as the etching apparatus shown in FIG. 1, and the configuration of the usable etching apparatus is not particularly limited. For example, the positional relationship between the fluorine-containing compound gas supply pipe 5 and the etching subject 12 is not particularly limited as long as the etching gas can be brought into contact with the etching subject 12. In addition, as for the configuration of the temperature control mechanism of the chamber 10, since it is only necessary to adjust the temperature of the etching subject 12 to an arbitrary temperature, the temperature control mechanism may be directly provided on the stage 11, or the chamber 10 may be heated or cooled from outside the chamber 10 by an external temperature controller.

[0048] The material of the etching apparatus in FIG. 1 is not particularly limited as long as it has corrosion resistance against the fluorine-containing compound used and can be decompressed to a predetermined pressure. For example, metals such as nickel, nickel-based alloys, aluminum, stainless steel, and platinum, ceramics such as alumina, and fluororesins can be used for the parts that come into contact with the etching gas. Specific examples of nickel-based alloys include Inconel (registered trademark), Hastelloy (registered trademark), and Monel (registered trademark). Examples of fluororesins include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyvinylidene fluoride (PVDF), Teflon (registered trademark), Viton (registered trademark), and Kalrez (registered trademark).

[0049] Second Embodiment The etching method according to the second embodiment is an etching method in which a plasma generation source is disposed at a position remote from the chamber, and in the above-mentioned etching step, etching is performed within the chamber using plasma of an etching gas generated outside the chamber by the plasma generation source (hereinafter, this may be referred to as "remote plasma etching").

[0050] The etching method according to the second embodiment can be carried out by supplying plasma of an etching gas generated by a plasma source disposed at a position away from the chamber into a chamber in which an object to be etched is placed, and etching the oxide of the object to be etched with the plasma of the etching gas. By using the etching method according to the second embodiment, the oxide of the object to be etched can be etched at a mild temperature in some cases.

[0051] An example of the configuration of an etching apparatus that can be used in the etching method according to the second embodiment and an example of an etching method for the above-mentioned oxide using the etching apparatus will be described with reference to Fig. 2. However, since the etching method according to the second embodiment is almost similar to the etching method according to the first embodiment except that it has a plasma generation source and that etching is performed with plasma of an etching gas, a description of the same parts as in the etching method according to the first embodiment will be omitted and only the different parts will be described.

[0052] The etching apparatus in Fig. 2 is a remote plasma etching apparatus that performs remote plasma etching, and has a remote plasma generator 17, which is a plasma generation source, outside the chamber 10. More specifically, the etching apparatus in Fig. 2 has the remote plasma generator 17 at a position between the chamber 10 and the connection part of the fluorine-containing compound gas supply pipe 5 with the inert gas supply pipe 6.

[0053] An etching gas is supplied to a remote plasma generator 17 via a fluorine-containing compound gas supply pipe 5, and the remote plasma generator 17 converts the etching gas into plasma. The plasma of the etching gas generated by the remote plasma generator 17 is supplied to the chamber 10 via the fluorine-containing compound gas supply pipe 5, and is used to etch the oxides contained in the object to be etched. There is no particular limitation on the plasma source that can be used as the remote plasma generator 17, and a commercially available device can be used. For example, an intelligent remote plasma source ASTRON Paragon (registered trademark) manufactured by Nippon MKS Co., Ltd. can be used. EXAMPLES

[0054] The present invention will be described in more detail below with reference to examples, comparative examples and reference examples. (Example 1-1) An etching apparatus having substantially the same configuration as the etching apparatus of FIG. 1 was used to perform plasmaless etching of an object to be etched.

[0055] The etching object used in Example 1-1 will be described with reference to FIG. 3. A silicon dioxide (SiO2) film 22 with a thickness of 1004 nm was formed on a square silicon substrate 21 with sides of 2 cm. A rectangular alumina substrate 23 with dimensions of 1 cm×2 cm (thickness of 1 mm) was bonded to the silicon dioxide film 22 using grease (Daimnum Grease L-200 manufactured by Daikin Industries, Ltd.), and this was used as the etching object. The silicon substrate 21 with the silicon dioxide film 22 was manufactured by forming a silicon dioxide film with a thickness of 1004 nm on a circular silicon substrate with a radius of 10 cm, and then cutting it into a square shape with sides of 2 cm, and was manufactured by KST World Corporation.

[0056] The object to be etched was placed on a stage inside the chamber of the etching device, and the temperature of the stage was raised to 150°C. Next, carbonyl fluoride gas at a flow rate of 200 mL / min was mixed with argon at a flow rate of 800 mL / min to form a mixed gas, which was used as an etching gas. Then, this etching gas was supplied into the chamber at a flow rate of 1000 mL / min and circulated for 10 minutes to perform etching. The pressure inside the chamber during the flow of the etching gas was set to 10 kPa. When the flow of the etching gas was completed, the heating of the stage was stopped, and the inside of the chamber was replaced with argon.

[0057] The chamber was opened, the object to be etched was removed, the alumina substrate 23 was removed from the object to be etched, and the adhesive surface was washed with ethanol to remove the grease. Then, using an atomic force microscope VN-8010 manufactured by Keyence Corporation, the size of the step between the cover surface 22a of the silicon dioxide film 22 that is covered by the alumina substrate 23 and not etched, and the etched surface 22b of the silicon dioxide film 22 that is not covered by the alumina substrate 23 and is etched, was measured. The measurement conditions for the size of the step were as follows.

[0058] Measurement pressure: atmospheric pressure (101.3 kPa) Measurement temperature: 28℃ Measurement atmosphere: Air Scanning range: width 80.0 μm, height 20.0 μm, angle 0° The etching rate of silicon dioxide (unit: nm / min) was calculated by dividing the measurement result of the step size (unit: nm) by the etching time (unit: min). The results are shown in Table 1.

[0059] [Table 1]

[0060] (Example 1-2) The etching target was etched in the same manner as in Example 1-1, except that the flow rate of the carbonyl fluoride gas was 500 mL / min and the flow rate of the argon gas was 500 mL / min, and the etching rate of the silicon dioxide was calculated. The results are shown in Table 1. (Examples 1-3) The etching target was etched in the same manner as in Example 1-1, except that the pressure inside the chamber was set to 50 kPa, and the etching rate of silicon dioxide was calculated. The results are shown in Table 1.

[0061] (Examples 1 to 4) The etching target was etched in the same manner as in Example 1-1, except that the stage temperature was set to 300° C., and the etching rate of silicon dioxide was calculated. The results are shown in Table 1. (Examples 1 to 5) The etching target was etched in the same manner as in Example 1-1, except that helium was used as the inert gas instead of argon, and the etching rate of silicon dioxide was calculated. The results are shown in Table 1.

[0062] (Examples 1 to 6) The etching target was etched in the same manner as in Example 1-1, except that oxalyl fluoride gas was used as the fluorine-containing compound gas instead of carbonyl fluoride gas, and the etching rate of silicon dioxide was calculated. The results are shown in Table 1. (Examples 1 to 7) The etching target was etched in the same manner as in Example 1-1, except that the etching target had a tungsten oxide (WO3) film instead of a silicon dioxide film, and the etching rate of the tungsten oxide was calculated. The results are shown in Table 1.

[0063] (Examples 1 to 8) The etching target was etched in the same manner as in Example 1-1, except that the etching target had a tantalum oxide (Ta2O5) film instead of a silicon dioxide film, and the etching rate of tantalum oxide was calculated. The results are shown in Table 1. (Examples 1 to 9) The etching object was etched in the same manner as in Example 1-1, except that the etching object was etched with a titanium oxide (TiO2) film instead of a silicon dioxide film, and the etching rate of titanium oxide was calculated. The results are shown in Table 1.

[0064] (Examples 1 to 10) The etching target was etched in the same manner as in Example 1-1, except that the etching target had a ruthenium oxide (RuO4) film instead of a silicon dioxide film, and the etching rate of ruthenium oxide was calculated. The results are shown in Table 1. (Examples 1 to 11) The etching target was etched in the same manner as in Example 1-1, except that the etching target had an iridium oxide (IrO2) film instead of a silicon dioxide film, and the etching rate of iridium oxide was calculated. The results are shown in Table 1.

[0065] (Examples 1 to 12) The etching target was etched in the same manner as in Example 1-1, except that the etching target had a rhodium oxide (Rh2O3) film instead of a silicon dioxide film, and the etching rate of rhodium oxide was calculated. The results are shown in Table 1. (Reference example 1-1) The etching target was etched in the same manner as in Example 1-1, except that the etching target had a polysilicon (Si) film instead of a silicon dioxide film, and the etching rate of the polysilicon was calculated. The results are shown in Table 1.

[0066] (Reference example 1-2) The etching object was etched in the same manner as in Example 1-1, except that the etching object had a silicon nitride (Si3N4) film instead of a silicon dioxide film, and the etching rate of silicon nitride was calculated. The results are shown in Table 1. (Reference example 1-3) The etching target was etched in the same manner as in Example 1-1, except that the etching target had a silicon carbide (SiC) film instead of a silicon dioxide film, and the etching rate of silicon carbide was calculated. The results are shown in Table 1.

[0067] (Reference example 1-4) The etching object was etched in the same manner as in Example 1-1, except that the etching object was etched with a hardened photoresist film (photoresist TSCR (registered trademark) manufactured by Tokyo Ohka Kogyo Co., Ltd.) instead of a silicon dioxide film, and the etching rate of the photoresist was calculated. The results are shown in Table 1. (Reference example 1-5) The etching target was etched in the same manner as in Example 1-1, except that the etching target had an amorphous carbon film instead of a silicon dioxide film, and the etching rate of the amorphous carbon was calculated. The results are shown in Table 1.

[0068] (Reference example 1-6) The etching target was etched in the same manner as in Example 1-1, except that the etching target had a tungsten film instead of a silicon dioxide film, and the etching rate of tungsten was calculated. The results are shown in Table 1. (Reference example 1-7) The etching target was etched in the same manner as in Example 1-1, except that the etching target had a titanium nitride (TiN) film instead of a silicon dioxide film, and the etching rate of titanium nitride was calculated. The results are shown in Table 1.

[0069] (Reference example 1-8) The etching target was etched in the same manner as in Example 1-1, except that the etching target had a tantalum film instead of a silicon dioxide film, and the etching rate of tantalum was calculated. The results are shown in Table 1. (Reference example 1-9) The etching target was etched in the same manner as in Example 1-1, except that the etching target had a ruthenium film instead of a silicon dioxide film, and the etching rate of ruthenium was calculated. The results are shown in Table 1.

[0070] (Reference example 1-10) The etching target was etched in the same manner as in Example 1-1, except that the etching target had an iridium film instead of a silicon dioxide film, and the etching rate of iridium was calculated. The results are shown in Table 1. (Reference example 1-11) The etching target was etched in the same manner as in Example 1-1, except that the etching target had a rhodium film instead of a silicon dioxide film, and the etching rate of rhodium was calculated. The results are shown in Table 1.

[0071] From the results of Example 1-1, it is clear that by using an etching gas containing a fluorine-containing compound, silicon dioxide can be etched even by plasma-less etching. From the results of Examples 1-2 to 1-4, it is clear that the etching rate of silicon dioxide increases as the ratio of the fluorine-containing compound in the etching gas, the pressure in the chamber, or the temperature of the stage increases.

[0072] From the results of Example 1-5, it is apparent that even when helium is used as the inert gas for diluting the fluorine-containing compound, silicon dioxide can be etched at an etching rate comparable to that of Example 1-1. The results of Example 1-6 show that even when oxalyl fluoride is used as the fluorine-containing compound, silicon dioxide can be etched at an etching rate comparable to that of Example 1-1.

[0073] The results of Examples 1-7 to 1-12 show that by using an etching gas containing a fluorine-containing compound, tungsten oxide, tantalum oxide, titanium oxide, ruthenium oxide, iridium oxide, and rhodium oxide can be etched even by plasma-less etching. On the other hand, the results of Reference Examples 1-1 to 1-11 show that materials other than the above oxides are hardly etched by plasmaless etching. From the above results, it is understood that the above oxides can be selectively etched by plasmaless etching.

[0074] (Examples 2-1 to 2-13) A silicon substrate on which an oxide film shown in Table 2 was formed and a silicon substrate on which a film of a non-etching object was formed were placed side by side on a stage in the same chamber, and etching of the etching object was performed in the same manner as in Example 1-1, except that plasmaless etching was performed at the stage temperature and chamber pressure shown in Table 2. The types of oxide and the types of non-etching objects are as shown in Table 2. Then, the etching rates of the oxide film and the film of the non-etching object were calculated, and the etching selectivity was calculated from the numerical values. The results are shown in Table 2. The etching selectivity is (etching rate of oxide film) / (etching rate of film of non-etching object).

[0075] [Table 2]

[0076] (Examples 3-1 to 3-11) The etching object was etched in the same manner as in Example 2-1, except that remote plasma etching was performed using an etching apparatus having a configuration substantially similar to that shown in Fig. 2, that carbonyl fluoride gas with a flow rate of 250 mL / min was used as the etching gas, that the etching time was 30 seconds, that the stage temperature was 30°C, and that the pressure in the chamber was 0.133 kPa. The types of oxides and the types of objects not to be etched are as shown in Table 3.

[0077] Then, the etching rates of the oxide film and the film of the non-etching object were calculated in the same manner as in Example 2-1, and the etching selectivity was calculated from the numerical values. The results are shown in Table 3. The intelligent remote plasma source ASTRON Paragon (registered trademark) manufactured by Nippon MKS Co., Ltd. was used as the plasma generation source, and the source power was set to 7 kW.

[0078] [Table 3]

[0079] (Comparative Examples 1 to 11) The etching object was etched in the same manner as in Example 2-1, except that a plasma of an etching gas was generated in a chamber, and etching was performed in the chamber using the plasma of the etching gas, and the etching conditions were as follows. The types of oxide and the types of objects not to be etched were as shown in Table 3. Then, the etching rates of the oxide film and the film of the object not to be etched were calculated in the same manner as in Example 2-1, and the etching selectivity was calculated from the numerical values. The results are shown in Table 3.

[0080] The etching conditions were as follows. A mixed gas of carbonyl fluoride at a flow rate of 100 mL / min and argon at a flow rate of 900 mL / min was used as the etching gas. The etching time was 30 seconds, the stage temperature was 30°C, and the pressure inside the chamber was 0.001 kPa. The etching device used was a parallel plate type plasma CVD device RIE-800iPC manufactured by Samco Corporation, with a source power of 500 W and a bias power of 100 W.

[0081] From the results of Examples 2-1 to 2-13 and Examples 3-1 to 3-11, it is found that even when the oxide and the non-etching object are simultaneously etched by plasmaless etching and remote plasma etching, it is possible to selectively etch the oxide with respect to the non-etching object. It is also found that the etching rate of the oxide is faster in remote plasma etching than in plasmaless etching, and that the etching selectivity of plasmaless etching is higher than that of remote plasma etching. On the other hand, the results of Comparative Examples 1 to 11 show that when etching is performed under conditions in which plasma is generated in the chamber, the oxide cannot be selectively etched, and that the non-etching target is etched preferentially over the oxide. [Explanation of symbols]

[0082] 1. Fluorine-containing compound gas supply section 2. Inert gas supply section 3. Fluorine-containing compound gas flow rate control device 4. Inert gas flow control device 5. Fluorine-containing gas supply pipe 6. Inert gas supply piping 7, 16 Pressure gauge 10. Chamber 11 Stage 12. Etching object 13 Exhaust piping 14...Thermometer 15 Vacuum pump 17. Remote plasma generator 21 Silicon substrate 22. Silicon dioxide film 23. Alumina substrate

Claims

1. The method includes an etching step of placing an object to be etched having an oxide in a chamber, and etching the oxide of the object to be etched in the chamber using an etching gas containing a fluorine-containing compound having a functional group represented by the following chemical formula: The oxide is a metal oxide, and a metal of the metal oxide contains at least one selected from titanium, ruthenium, iridium, and rhodium; The etching method according to claim 1, wherein the etching step is performed without generating plasma of the etching gas in the chamber. In the following chemical formulas, * indicates a bonding point with another atom or atomic group. 【Chemistry 1】

2. 2. The etching method according to claim 1, wherein in the etching step, the etching is performed by the etching gas without using plasma of the etching gas.

3. 2. The etching method according to claim 1, wherein a plasma generating source is disposed at a position away from the chamber, and in the etching step, the etching is performed in the chamber by plasma of the etching gas generated outside the chamber by the plasma generating source.

4. 4. The etching method according to claim 1, wherein the fluorine-containing compound has 1 or more and 5 or less carbon atoms.

5. 4. The etching method according to claim 1, wherein the fluorine-containing compound has 1 or more and 3 or less carbon atoms.

6. 4. The etching method according to claim 1, wherein the fluorine-containing compound is at least one of carbonyl fluoride and oxalyl fluoride.

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