Etching method and method for manufacturing a semiconductor device

Abstract

Provided is an etching method by which an etching object having silicon nitride can be selectively etched compared to a non-etching object. This etching method comprises an etching step in which an etching gas, which contains a fluorine compound having at most 3 carbon atoms and having, in a molecule, at least one bond among a carbon-oxygen double bond and an ether bond, is brought into contact with a member to be etched having an etching object and a non-etching object in the presence of plasma, and the etching object is selectively etched compared to the non-etching object. The concentration of the fluorine compound in the etching gas is 0.5-40 vol%, and the etching object has silicon nitride.

Description

Technical Field

[0001] The present invention relates to an etching method and a method for manufacturing a semiconductor device.

Background Art

[0002] In the manufacturing process of semiconductors, gases of perfluorinated compounds such as carbon tetrafluoride (CF4) and sulfur hexafluoride (SF6) have been used as etching gases for dry etching apparatuses and chamber cleaning gases for chemical vapor deposition apparatuses (CVD apparatuses). Since these perfluorinated compounds are stable compounds and have a large impact on global warming (due to their high global warming potential), there are concerns about their adverse effects on the environment when released into the atmosphere. Therefore, the development of alternative gases with a low global warming potential is desired. For example, Patent Documents 1 and 2 propose gases of fluorocarbons having at least one unsaturated bond as gases with a relatively low global warming potential.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although the use of the fluorocarbon gases disclosed in Patent Documents 1 and 2 enables the etching of silicon-containing films such as silicon films, silicon dioxide films, silicon nitride films, and metal silicides, Patent Documents 1 and 2 do not mention whether the silicon nitride film can be selectively etched. An object of the present invention is to provide an etching method and a method for manufacturing a semiconductor device that can selectively etch an object to be etched having silicon nitride compared to an object not to be etched.

Means for Solving the Problems

[0005] To solve the above problems, one aspect of the present invention is as follows [1] to

[11] . [1] An etching gas containing a fluorine compound having 3 or less carbon atoms and having at least one of a carbon-oxygen double bond and an ether bond in the molecule is brought into contact with an etched member having an object to be etched, which is an object to be etched by the etching gas, and an object not to be etched, which is not an object to be etched by the etching gas, in the presence of plasma, and an etching step of selectively etching the object to be etched compared to the object not to be etched is provided. An etching method in which the concentration of the fluorine compound in the etching gas is 0.5% by volume or more and 40% by volume or less, and the object to be etched has silicon nitride.

[0006] [2] The etching method according to [1], wherein the object not to be etched has at least one selected from silicon oxide, photoresist, and amorphous carbon. [3] The etching method according to [1] or [2], wherein the etching step is performed under a pressure condition of 1 Pa or more and 3 kPa or less.

[0007] [4] The etching method according to any one of [1] to [3], wherein the etching step is performed under a temperature condition of 0°C or more and 200°C or less. [5] The etching method according to any one of [1] to [4], wherein the concentration of the fluorine compound in the etching gas is 1% by volume or more and 30% by volume or less.

[0008] [6] The etching method according to any one of [1] to [5], wherein the etching gas is a mixed gas containing the fluorine compound and a dilution gas. [7] The etching method according to [6], wherein the dilution gas is at least one selected from nitrogen gas, helium, argon, neon, krypton, and xenon. [8] The etching method according to any one of [1] to [5], wherein the etching gas is a mixed gas containing the fluorine compound, a rare gas, and nitrogen gas, and the concentration of the nitrogen gas in the etching gas is 10% by volume or less.

[0009] [9] The etching method according to [8], wherein the etching gas is a mixed gas containing, in addition to the fluorine compound, a rare gas, and nitrogen gas, an oxygen-containing gas other than the fluorine compound.

[10] The etching method according to any one of [1] to [9], wherein the fluorine compound is at least one selected from carbonyl fluoride, oxalyl fluoride, and hexafluoropropylene oxide.

[0010]

[11] A method for manufacturing a semiconductor device, which uses the etching method according to any one of [1] to

[10] , and the member to be etched is a semiconductor substrate having the object to be etched and the non-etched object, and the method for manufacturing a semiconductor device includes a processing step of removing at least a part of the object to be etched from the semiconductor substrate by the etching. [Effect of the Invention]

[0011] According to the present invention, an object to be etched having silicon nitride can be selectively etched compared to a non-etched object. [Brief Description of the Drawings]

[0012]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0013] An embodiment of the present invention will be described below. Note that this embodiment shows an example of the present invention, and the present invention is not limited to this embodiment. Further, various changes or improvements can be made to this embodiment, and forms with such changes or improvements can also be included in the present invention.

[0014] The etching method according to this embodiment includes an etching step of bringing an etching gas containing a fluorine compound into contact with an etched member having an object to be etched, which is an object of etching by the etching gas, and a non-etching object, which is not an object of etching by the etching gas, in the presence of plasma, and selectively etching the object to be etched as compared with the non-etching object.

[0015] The fluorine compound is a fluorine compound having 3 or less carbon atoms and having at least one of a carbon-oxygen double bond (carbonyl group) and an ether bond in the molecule. Further, the concentration of the fluorine compound in the etching gas is 0.5% by volume or more and 40% by volume or less. Furthermore, the object to be etched has silicon nitride.

[0016] When the etching gas is brought into contact with the etched member, the fluorine compound in the etching gas reacts with the silicon nitride in the object to be etched, so the etching of the object to be etched proceeds. On the other hand, since the non-etching object hardly reacts with the fluorine compound, the etching of the non-etching object hardly proceeds. Therefore, according to the etching method according to this embodiment, the object to be etched can be selectively etched as compared with the non-etching object.

[0017] In addition, according to the etching method of the present embodiment, it is possible to selectively etch an object to be etched having silicon nitride without using gases of perfluorinated compounds such as carbon tetrafluoride and sulfur hexafluoride with a high global warming potential. Therefore, the etching method according to the present embodiment can reduce the environmental load caused by the use of etching gas and suppress the adverse effects on global warming.

[0018] Note that the etching in the present invention means removing part or all of the object to be etched of the member to be etched to process the member to be etched into a predetermined shape (for example, a three-dimensional shape) (for example, processing a film-shaped object to be etched made of silicon nitride of the member to be etched to a predetermined film thickness), and also means removing residues and deposits made of the object to be etched from the member to be etched for cleaning.

[0019] The etching method according to the present embodiment can be used in the manufacture of semiconductor elements. That is, the method for manufacturing a semiconductor element according to the present embodiment is a method for manufacturing a semiconductor element that manufactures a semiconductor element using the etching method according to the present embodiment, wherein the member to be etched is a semiconductor substrate having an object to be etched and a non-object to be etched, and includes a processing step of removing at least a part of the object to be etched from the semiconductor substrate by etching.

[0020] For example, in the etching method according to the present embodiment, etching proceeds more rapidly for silicon nitride (for example, Si3N4) than for silicon oxide (for example, SiO2). By utilizing this characteristic, the etching method according to the present embodiment can be used for the manufacture of semiconductor elements such as 3D-NAND type flash memories and logic devices.

[0021] For example, with respect to a laminate in which a silicon oxide film and a silicon nitride film are alternately laminated and a through-hole extending along the lamination direction and penetrating the laminate is formed (see FIG. 3), by applying the etching method according to this embodiment, the silicon nitride film exposed on the inner surface of the through-hole is selectively and isotropically etched, so that a structure in which the end of the silicon oxide film protrudes into the through-hole can be formed. The process of forming a structure having such a structure can be used for the structure of a semiconductor element, so it is used in the manufacture of semiconductor elements such as 3D-NAND type flash memories and logic devices.

[0022] The process of forming the above structure by etching has conventionally been performed using a chemical solution containing phosphoric acid or the like, but etching using an etching gas is superior in microfabrication to etching using a chemical solution. Therefore, the etching method according to this embodiment can be expected to contribute to further miniaturization and high integration of semiconductor elements.

[0023] Also, similarly, when the non-etching object itself is used as the structure of a semiconductor element, as the non-etching object, a material that does not substantially react with a fluorine compound or a material whose reaction with a fluorine compound is extremely slow is used. Specifically, for example, at least one material selected from silicon oxide (e.g., SiO2), photoresist, and amorphous carbon (C) can be used.

[0024] Furthermore, as described above, the etching method according to this embodiment can also be used for cleaning. For example, after performing in a chamber a step of forming a film made of a material containing silicon nitride on a substrate and a step of etching a film of a material containing silicon nitride formed on the substrate, the deposit containing silicon nitride attached to the inner surface of the chamber can be removed and cleaned by the etching method according to this embodiment. In such cleaning, the chamber corresponds to the etched member which is a constituent requirement of the present invention, and the deposit corresponds to the etching object which is a constituent requirement of the present invention.

[0025] Hereinafter, the etching method and the semiconductor device manufacturing method according to the present embodiment will be described in more detail. The etching in this embodiment can be achieved by plasma etching. The type of plasma source in plasma etching is not particularly limited, and a commercially available device may be used. For example, high-frequency discharge plasmas such as inductively coupled plasma (ICP) and capacitively coupled plasma (CCP), and microwave discharge plasmas such as electron cyclotron resonance plasma (ECRP) can be mentioned.

[0026] Also, the plasma may be generated in a plasma generation chamber separated from the chamber in which the member to be etched is installed (that is, remote plasma may be used). By etching using remote plasma, an object to be etched having silicon nitride may be etched with high selectivity. Note that an etching method in which etching is performed in the chamber by the plasma of the etching gas generated outside the chamber by the plasma generation source may be referred to as "remote plasma etching".

[0027] 〔Etching Gas〕 The etching gas is a gas containing a fluorine compound having 3 or less carbon atoms and having at least one of a carbon-oxygen double bond and an ether bond in the molecule. Examples of the functional group having a carbon-oxygen double bond include a carbonyl group (-(C=O)-) and a formyl group (-(C=O)H). The ether bond (-O-) may be a cyclic ether bond. The type of the fluorine compound is not particularly limited as long as the above requirements are satisfied. For example, 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, 2,3,3-trifluoropropanoyl fluoride, 2,2,3-trifluoropropanoyl fluoride, 2,2-difluoropropanoyl fluoride, 2,3-difluoropropanoyl fluoride, 3,3-difluoropropanoyl fluoride, 2-fluoropropanoyl fluoride, 3-fluoropropanoyl fluoride, propanoyl fluoride, perfluoroisopropanoyl fluoride, hexafluoroacetone, hexafluoropropylene oxide, tetrafluoroethylene oxide, trifluoromethyl ether and the like can be mentioned. These fluorine compounds may be used alone or in combination of two or more. Among these fluorine compounds, from the viewpoints of handleability and availability, at least one selected from carbonyl fluoride (COF2), oxalyl fluoride ((COF)2), and hexafluoropropylene oxide (C3F6O) is more preferable. Many fluorine compounds having 4 or more carbon atoms and having at least one of a carbon-oxygen double bond and an ether bond in the molecule are not preferable because they have low volatility and are difficult to handle as an etching gas.

[0028] The etching gas is a mixed gas containing a fluorine compound gas and another type of gas. However, the concentration of the fluorine compound in the etching gas needs to be 0.5% by volume or more and 40% by volume or less, preferably 1% by volume or more and 30% by volume or less, and more preferably 2% by volume or more and 30% by volume or less.

[0029] If plasma etching is performed with the concentration of the fluorine compound in the etching gas within the above range, an object to be etched having silicon nitride can be selectively etched compared to an object not to be etched. For example, the etching selectivity, which is the ratio of the etching rate of the object to be etched to the etching rate of the object not to be etched, is likely to be 5 or more. The etching selectivity is preferably 5 or more, more preferably 7 or more, and even more preferably 10 or more.

[0030] As the other type of gas constituting the etching gas together with the fluorine compound gas, an inert dilution gas can be used. That is, the etching gas can be a mixed gas containing a fluorine compound and a dilution gas. As the dilution gas, at least one selected from nitrogen gas (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) can be used.

[0031] In particular, when the etching gas contains a small amount of nitrogen gas, that is, when the etching gas is a mixed gas containing a fluorine compound, a dilution gas, and nitrogen gas, the etching rate of silicon nitride may increase. The concentration of nitrogen gas in the etching gas is preferably 10% by volume or less, more preferably 5% by volume or less, and even more preferably 3% by volume or less. Note that the dilution gas is at least one selected from helium, neon, argon, krypton, and xenon.

[0032] In addition, when the etching gas contains a noble gas and a small amount of nitrogen gas, further adding an oxygen-containing gas may improve the etching rate of silicon nitride and the etching selectivity. Here, the oxygen-containing gas is a compound that is a gas under standard conditions and, other than the above fluorine compound, has an oxygen atom in the molecule. Examples of the oxygen-containing gas include oxygen gas (O2), ozone (O3), nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O), sulfur dioxide (SO2), sulfur trioxide (SO3), carbon monoxide (CO), carbon dioxide (CO2), and the like. In particular, from the viewpoint of ease of handling, oxygen gas, nitric oxide, nitrogen dioxide, nitrous oxide, sulfur dioxide, and carbon dioxide are preferable, and oxygen, nitric oxide, and nitrous oxide are more preferable.

[0033] The volume ratio of the oxygen-containing gas to the nitrogen gas in the etching gas (oxygen-containing gas / nitrogen gas) is preferably 0.1 or more and 2 or less, more preferably 0.15 or more and 1 or less, and even more preferably 0.2 or more and 0.6 or less. If the volume ratio of the nitrogen gas to the oxygen-containing gas is within the above range, the effect of improving the etching rate of silicon nitride and the effect of improving the etching selectivity are easily obtained.

[0034] 〔Pressure conditions of the etching process〕 The pressure conditions of the etching process in the etching method according to this embodiment are not particularly limited, but are preferably 1 Pa or more and 3 kPa or less, more preferably 3 Pa or more and 2 kPa or less, and even more preferably 10 Pa or more and 1.5 kPa or less. If the pressure conditions are within the above range, it is easy to stably generate plasma.

[0035] For example, an etching member can be arranged in the chamber and etching can be performed while flowing the etching gas through the chamber. However, the pressure in the chamber during the flow of the etching gas can be 1 Pa or more and 3 kPa or less. The flow rate of the etching gas can be appropriately set according to the size of the chamber and the capacity of the exhaust equipment for reducing the pressure in the chamber so that the pressure in the chamber is kept constant.

[0036] 〔Temperature Conditions of the Etching Process〕 The temperature conditions of the etching process in the etching method according to this embodiment are not particularly limited, but it is preferably 0°C or higher and 200°C or lower, more preferably 5°C or higher and 170°C or lower, and even more preferably 20°C or higher and 150°C or lower. If the temperature conditions are within the above range, the fluorine compound can exist in a gaseous state, and the etching rate of silicon nitride is more likely to be higher. Here, the temperature of the temperature conditions is the temperature of the member to be etched, but the temperature of the stage that supports the member to be etched and is installed in the chamber of the etching apparatus can also be used.

[0037] The fluorine compound hardly reacts with non-etching targets such as silicon oxide, photoresist, and amorphous carbon at temperatures of 200°C or lower. Therefore, if the member to be etched is etched by the etching method according to this embodiment, the object to be etched having silicon nitride can be selectively etched with hardly any etching of the non-etching target. Thus, the etching method according to this embodiment can be used for a method of processing an object to be etched having silicon nitride into a predetermined shape by using the patterned non-etching target as a resist or a mask.

[0038] Furthermore, if the temperatures of the object to be etched and the non-etching target are 200°C or lower, the etching selectivity is likely to be high. For example, the etching selectivity ratio, which is the ratio of the etching rate of the object to be etched having silicon nitride to the etching rate of the non-etching target, is likely to be 5 or more.

[0039] 〔Member to be Etched〕 The member to be etched by the etching method according to the present embodiment has an object to be etched and an object not to be etched, but may have a part formed of an object to be etched and a part formed of an object not to be etched, or may be a part formed of a mixture of an object to be etched and an object not to be etched. The member to be etched may also have something other than an object to be etched and an object not to be etched. The shape of the member to be etched is not particularly limited, and may be, for example, a plate, a foil, a film, a powder, a lump, etc. An example of the member to be etched is the above-mentioned semiconductor substrate.

[0040] [Object to be etched] The object to be etched has silicon nitride, but may be made of silicon nitride alone, may have a portion made of silicon nitride alone and a portion made of another material, or may be made of a mixture of silicon nitride and another material.

[0041] Silicon nitride refers to a compound containing silicon and nitrogen in any ratio, and an example thereof is Si3N4. The purity of silicon nitride is not particularly limited, but is preferably 30% by mass or more, more preferably 60% by mass or more, and even more preferably 90% by mass or more. Furthermore, the shape of the object to be etched is not particularly limited, and may be, for example, a plate, foil, film, powder, or lump.

[0042] [Non-etching objects] The non-etching object either does not substantially react with the fluorine compound or reacts extremely slowly with the fluorine compound. Therefore, even if etching is performed by the etching method according to the present embodiment, the etching hardly progresses. The non-etching object is not particularly limited as long as it has the above properties, and examples thereof include silicon oxide, photoresist, amorphous carbon, titanium nitride, metals such as copper, nickel, and cobalt, and oxides and nitrides of these metals. Among these, silicon oxide, photoresist, and amorphous carbon are more preferable from the viewpoints of handleability and availability.

[0043] Photoresist means a photosensitive composition whose physical properties such as solubility change by light, electron beam, etc. Examples thereof include photoresists for g-line, h-line, i-line, KrF, ArF, F2, EUV, etc. The composition of the photoresist is not particularly limited as long as it is generally used in the semiconductor manufacturing process. For example, a composition containing a polymer synthesized from at least one monomer selected from chain olefins, cyclic olefins, styrene, vinylphenol, acrylic acid, methacrylate, epoxy, melamine, and glycol can be mentioned.

[0044] In addition, the non-etching object can be used as a resist or a mask for suppressing the etching of the etching object by the etching gas. Therefore, the etching method according to the present embodiment can be used in methods such as using the patterned non-etching object as a resist or a mask to process the etching object into a predetermined shape (for example, processing the film-shaped etching object of the member to be etched into a predetermined film thickness), and thus can be suitably used for the manufacture of semiconductor elements. Further, since the non-etching object is hardly etched, it is possible to suppress the etching of the portion that should not be etched in the semiconductor element, and prevent the characteristics of the semiconductor element from being lost due to etching.

[0045] Note that the non-etching target objects remaining after patterning can be removed by a removal method commonly used in the semiconductor device manufacturing process. For example, ashing with an oxidizing gas such as oxygen plasma or ozone, or dissolution and removal using a chemical solution such as APM (a mixed solution of aqueous ammonia and hydrogen peroxide), SPM (a mixed solution of sulfuric acid and hydrogen peroxide), or an organic solvent can be mentioned.

[0046] Next, with reference to FIG. 1, an example of the configuration of an etching apparatus capable of implementing the etching method according to the present embodiment and an example of the etching method using the etching apparatus will be described. The etching apparatus of FIG. 1 is a remote plasma etching apparatus that performs remote plasma etching. First, the etching apparatus of FIG. 1 will be described.

[0047] The etching apparatus of FIG. 1 includes a chamber 10 in which etching is performed, a remote plasma generation apparatus 20 that is a plasma generation source, a stage 11 that supports an etching member 12 to be etched inside the chamber 10, a thermometer 14 that measures the temperature of the etching member 12, an exhaust pipe 13 for discharging the gas inside the chamber 10, a vacuum pump 15 provided in the exhaust pipe 13 for reducing the pressure inside the chamber 10, and a pressure gauge 16 that measures the pressure inside the chamber 10.

[0048] In addition, the etching apparatus of FIG. 1 includes an etching gas supply unit that supplies etching gas into the chamber 10. This etching gas supply unit includes a fluorine compound gas supply unit 1 that supplies a fluorine compound gas, a rare gas supply unit 2 that supplies a rare gas, a nitrogen gas supply unit 3 that supplies nitrogen gas, a fluorine compound gas supply pipe 7 that connects the fluorine compound gas supply unit 1 and the chamber 10, a rare gas supply pipe 8 that connects the rare gas supply unit 2 to an intermediate portion of the fluorine compound gas supply pipe 7, and a nitrogen gas supply pipe 9 that connects the nitrogen gas supply unit 3 to an intermediate portion of the rare gas supply pipe 8.

[0049] Note that the etching apparatus in Fig. 1 has a remote plasma generator 20 outside the chamber 10. More specifically, the etching apparatus in Fig. 1 has a remote plasma generator 20 at a position between the connection part of the fluorine compound gas supply pipe 7 and the rare gas supply pipe 8 and the chamber 10.

[0050] Furthermore, the fluorine compound gas supply pipe 7 is provided with a fluorine compound gas pressure control device 17 for controlling the pressure of the fluorine compound gas and a fluorine compound gas flow control device 4 for controlling the flow rate of the fluorine compound gas. Furthermore, the rare gas supply pipe 8 is provided with a rare gas pressure control device 18 for controlling the pressure of the rare gas and a rare gas flow control device 5 for controlling the flow rate of the rare gas. Furthermore, the nitrogen gas supply pipe 9 is provided with a nitrogen gas pressure control device 19 for controlling the pressure of the nitrogen gas and a nitrogen gas flow control device 6 for controlling the flow rate of the nitrogen gas.

[0051] When supplying a fluorine compound gas as the etching gas to the chamber 10, the fluorine compound gas is sent from the fluorine compound gas supply section 1 to the fluorine compound gas supply pipe 7, and the fluorine compound gas is supplied to the remote plasma generator 20 via the fluorine compound gas supply pipe 7.

[0052] When supplying a mixed gas of a fluorine compound gas, a rare gas, and a nitrogen gas as the etching gas, the fluorine compound gas is sent from the fluorine compound gas supply section 1 to the fluorine compound gas supply pipe 7, and at the same time, the rare gas and the nitrogen gas are respectively sent from the rare gas supply section 2 and the nitrogen gas supply section 3 to the fluorine compound gas supply pipe 7 via the rare gas supply pipe 8 and the nitrogen gas supply pipe 9. Thus, the mixed gas is supplied to the remote plasma generator 20 via the fluorine compound gas supply pipe 7.

[0053] The gas or mixed gas of the fluorine compound is plasma - ized in the remote plasma generator 20 and supplied into the chamber 10. Note that the remote plasma generator 20 and the chamber 10 may be directly connected or connected by piping. The configurations of the fluorine - compound gas supply section 1, the rare - gas supply section 2, and the nitrogen - gas supply section 3 are not particularly limited, and may be, for example, cylinders or gas cylinders. Also, as the fluorine - compound gas flow - rate controller 4, the rare - gas flow - rate controller 5, and the nitrogen - gas flow - rate controller 6, for example, a mass - flow controller or a flowmeter can be used.

[0054] When supplying the etching gas to the chamber 10, it is preferable to supply the etching gas while maintaining the pressure of the etching gas (that is, the value of the fluorine - compound gas pressure controller 17 in FIG. 1) at a predetermined value. That is, the supply pressure of the etching gas is preferably 1 Pa or more and 0.2 MPa or less, more preferably 10 Pa or more and 0.1 MPa or less, and even more preferably 50 Pa or more and 50 kPa or less. If the supply pressure of the etching gas is within the above range, the supply of the etching gas to the chamber 10 is smoothly performed, and the load on the components (for example, the various devices and the piping) of the etching apparatus in FIG. 1 is small.

[0055] Also, from the viewpoint of uniformly etching the surface of the member to be etched 12, the pressure of the etching gas supplied into the chamber 10 is preferably 1 Pa or more and 80 kPa or less, more preferably 10 Pa or more and 50 kPa or less, and even more preferably 100 Pa or more and 20 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 the etching selectivity is likely to be high.

[0056] The pressure in the chamber 10 before supplying the etching gas is not particularly limited as long as it is equal to or lower than the supply pressure of the etching gas, but for example, 10 -5It is preferably more than 1 Pa and less than 10 kPa, and more preferably more than 1 Pa and less than 2 kPa.

[0057] The differential pressure between the supply pressure of the etching gas and the pressure in the chamber 10 before supplying the etching gas 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 supply of the etching gas to the chamber 10 is likely to be performed smoothly.

[0058] When supplying the etching gas to the chamber 10, it is preferable to supply it while maintaining the temperature of the etching gas at a predetermined value. That is, the supply temperature of the etching gas is preferably 0°C or more and 150°C or less. The temperature of the member 12 to be etched during etching is preferably 0°C or more and 200°C or less, more preferably 5°C or more and 170°C or less, and even more preferably 20°C or more and 150°C or less. Within this temperature range, the etching of the object to be etched (particularly silicon nitride) of the member 12 to be etched proceeds smoothly, the load on the etching apparatus is small, and the life of the etching apparatus is likely to be long.

[0059] The etching treatment time (hereinafter, may also be referred to as "etching time") can be arbitrarily set depending on how much the object to be etched of the member 12 to be etched is desired to be etched. However, 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 20 minutes. Note that the etching treatment time refers to the time during which the plasma-etched etching gas is in contact with the member 12 to be etched inside the chamber 10.

[0060] The etching method according to the present embodiment can be performed using a general plasma etching apparatus used in a semiconductor device manufacturing process, such as the etching apparatus of FIG. 1, and the configuration of the usable etching apparatus is not particularly limited. For example, the positional relationship between the pipe 7 for supplying the fluorine compound gas and the member 12 to be etched is not particularly limited as long as the etching gas can be brought into contact with the member 12 to be etched. Also, regarding the configuration of the temperature adjustment mechanism of the chamber 10, it is only necessary to be able to adjust the temperature of the member 12 to be etched to an arbitrary temperature. Thus, a configuration in which the temperature adjustment mechanism is directly provided on the stage 11 may be used, or heating or cooling may be performed on the chamber 10 from the outside of the chamber 10 using an external temperature regulator.

[0061] Also, the material of the etching apparatus in FIG. 1 is not particularly limited as long as it has corrosion resistance against the fluorine compound to be used and can be depressurized to a predetermined pressure. For example, for the portion in contact with the etching gas, metals such as nickel, nickel-based alloys, aluminum, stainless steel, platinum, copper, cobalt, etc., ceramics such as alumina, and fluororesins can be used.

[0062] Specific examples of nickel-based alloys include Inconel (registered trademark), Hastelloy (registered trademark), Monel (registered trademark), etc. Also, examples of fluororesins include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), ethylene tetrafluoride-perfluoroalkoxyethylene copolymer (PFA), polyvinylidene fluoride (PVDF), Teflon (registered trademark), Viton (registered trademark), Kalrez (registered trademark), etc.

Example

[0063] Examples and comparative examples are shown below to explain the present invention in more detail. (Example 1) Using an etching apparatus having substantially the same configuration as the etching apparatus in FIG. 1, the member to be etched was etched. The member to be etched used in Example 1 will be described with reference to FIG. 2.

[0064] A silicon substrate 21 with a square shape of 2 inches on one side and a silicon nitride film 22 with a thickness of 1 μm formed thereon (manufactured by C. S. T. World Co., Ltd.) was prepared. On the silicon nitride film 22, a rectangular silicon dioxide substrate 23 with dimensions of 1 inch × 2 inches was adhered using grease (Demnum Grease L-200 manufactured by Daikin Industries, Ltd.). The laminate thus produced was used as an etched member. As shown in FIG. 2, the silicon dioxide substrate 23 was adhered so as to cover approximately half of the silicon nitride film 22. Note that the silicon nitride film 22 is the object to be etched, and the silicon dioxide substrate 23, which is not the object to be etched, is used as a resist.

[0065] In addition, in the above etched member, a comparative laminate in which the silicon nitride film 22, which is the object to be etched, was replaced with a film of any one of silicon dioxide, photoresist, and amorphous carbon, which are not the objects to be etched, was produced respectively. The above etched member and these three comparative laminates were arranged and placed on a stage inside the chamber of an etching apparatus, and the temperature of the stage was set to 20°C.

[0066] Next, carbonyl fluoride gas with a flow rate of 30 mL / min and argon with a flow rate of 970 mL / min were mixed to form a mixed gas, and this mixed gas 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 3 minutes to perform remote plasma etching. The pressure inside the chamber during the circulation of the etching gas was set to 500 Pa. Also, as a remote plasma generator, an Intelligent Remote Plasma Source ASTRON Paragon (registered trademark) manufactured by MKS Japan Co., Ltd. was used, and the source power was set to 100 W. As a result, the exposed portion of the silicon nitride film 22 of the above etched member that was not covered by the silicon dioxide substrate 23 was etched. After the circulation of the etching gas was completed, the inside of the chamber was replaced with argon.

[0067] When the etching was completed, the chamber was opened, and the etched member was taken out. The silicon dioxide substrate 23 was removed from the taken-out etched member, 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 height difference between the covered surface 22a of the silicon nitride film 22 that was covered by the silicon dioxide substrate 23 and not etched, and the etched surface 22b of the silicon nitride film 22 that was not covered by the silicon dioxide substrate 23 and was etched was measured. By dividing the measured height difference (nm) by the etching time (min), the etching rate (nm / min) of silicon nitride was calculated. The results are shown in Table 1.

[0068] Also, for the three comparative laminates, the same operations as for the etched member were performed. By dividing the height difference (nm) by the etching time (min), the etching rates (nm / min) of silicon dioxide, photoresist, and amorphous carbon were calculated respectively. Furthermore, the ratio of the etching rate of the non-etching target to the etching rate of silicon nitride (etching selectivity) was calculated respectively. The results are shown in Table 1.

[0069] The measurement conditions for the height difference by the atomic force microscope are as follows. Measurement pressure: Atmospheric pressure (101.3 kPa) Measurement temperature: 28 °C Measurement atmosphere: Air Scanning range: Width 80.0 μm, height 20.0 μm, angle 0°

[0070]

Table 1

[0071] (Examples 2 to 15) The object to be etched is a silicon nitride film, and the non-etching objects are silicon dioxide, photoresist, and amorphous carbon. The etching conditions (composition of the etching gas, temperature of the stage, pressure in the chamber, etching time, source power of the remote plasma generator) are as shown in Table 1, and remote plasma etching was performed in the same manner as in Example 1. Then, the etching rates of the object to be etched and the non-etching objects were calculated respectively, and the etching selectivity was calculated from these numerical values. The results are shown in Tables 1 and 2.

[0072]

Table 2

[0073] (Comparative Example 1) Remote plasma etching was performed in the same manner as in Example 1, except that the etching gas was a mixed gas of sulfur hexafluoride gas and argon, the source power of the remote plasma generator was 400 W, and the etching time was 1 minute. Then, the etching rates of the object to be etched and the non-etching objects were calculated respectively, and the etching selectivity was calculated from these numerical values. The results are shown in Table 2.

[0074] (Comparative Example 2) Etching was performed in the same manner as in Example 1, except that the etching gas was a mixed gas of carbonyl fluoride gas with a flow rate of 300 mL / min and argon with a flow rate of 700 mL / min, the stage temperature was 150 °C, the source power of the remote plasma generator was 0 W (i.e., no plasma was generated), and the etching time was 30 minutes. Then, the etching rates of the object to be etched and the non-etching objects were calculated respectively, and the etching selectivity was calculated from these numerical values. The results are shown in Table 2.

[0075] (Comparative Example 3) Except that the etching gas was a mixed gas of carbonyl fluoride gas at a flow rate of 800 mL / min and argon at a flow rate of 200 mL / min, and the source power of the remote plasma generator was 400 W, remote plasma etching was performed in the same manner as in Example 1. Then, the etching rates of the object to be etched and the non-etching object were calculated respectively, and the etching selectivity was calculated from the numerical values. The results are shown in Table 2.

[0076] (Examples 16 to 27) Using the ICP etching apparatus RIE-200iP manufactured by Samco, Inc., plasma of the etching gas was generated in the chamber, and normal plasma etching was performed in which etching was performed in the chamber by the plasma of the etching gas. Except that the etching conditions (composition of the etching gas, temperature of the stage, pressure in the chamber, etching time, source power and bias power of the plasma generator) were as shown in Table 3, etching was performed on the member to be etched and the reference laminate in the same manner as in Example 1. Then, in the same manner as in Example 1, the etching rates of the object to be etched and the non-etching object were calculated respectively, and the etching selectivity was calculated from the numerical values. The results are shown in Table 3.

[0077] [Table 3]

[0078] (Comparative Example 4) Except that the etching gas was a mixed gas of sulfur hexafluoride gas and argon, and the bias power of the plasma generator was 80 W, plasma etching was performed in the same manner as in Example 16. Then, the etching rates of the object to be etched and the non-etching object were calculated respectively, and the etching selectivity was calculated from the numerical values. The results are shown in Table 3.

[0079] (Comparative Example 5) Plasma etching was performed in the same manner as in Example 16, except that the etching gas was a mixed gas of carbonyl fluoride gas at a flow rate of 40 mL / min and argon at a flow rate of 10 mL / min. Then, the etching rates of the object to be etched and the non-etched object were calculated respectively, and the etching selectivity was calculated from these values. The results are shown in Table 3.

[0080] (Example 28) The etched member used in Example 28 will be described with reference to FIG. 3. The etched member in FIG. 3 has a structure in which 30 layers each of a silicon nitride film 32 with a thickness of 35 nm and a silicon oxide film 33 with a thickness of 35 nm are alternately laminated on a silicon substrate 31 (in FIG. 3, for the sake of convenience, a structure in which 5 layers are alternately laminated is shown). Further, the etched member in FIG. 3 has a structure in which an amorphous carbon film 35 with a thickness of 300 nm is further laminated on the uppermost silicon oxide film 33. Here, the silicon nitride film 32 and the silicon oxide film 33 are objects to be etched, and the amorphous carbon film 35 is a non-etched object. Furthermore, the etched member in FIG. 3 has a through hole 34 with a diameter of 100 nm penetrating in the lamination direction through 30 layers of the silicon nitride film 32, 30 layers of the silicon oxide film 33, and 1 layer of the amorphous carbon film 35.

[0081] This etched member was placed on the stage of an etching apparatus having substantially the same configuration as the etching apparatus in FIG. 1, and the temperature of the stage was set to 20°C. Next, carbonyl fluoride gas at a flow rate of 30 mL / min and argon at a flow rate of 970 mL / min were mixed to form a mixed gas, and this mixed gas was used as the etching gas. Then, the etching gas plasmaized by remote plasma was supplied into the chamber and circulated for 3 minutes to perform remote plasma etching. The pressure inside the chamber during the circulation of the etching gas was set to 500 Pa. After the circulation of the etching gas was completed, the inside of the chamber was replaced with argon.

[0082] The chamber was opened and the etched member was taken out. In the etched member, the portion of the silicon nitride film 32 exposed on the inner surface of the through hole 34 was etched, and in particular, since the silicon nitride film 32 was preferentially etched compared to the silicon oxide film 33, a part of the inner surface of the through hole 34 had spread radially outward.

[0083] The portion of the silicon oxide film 33 exposed on the inner surface of the through hole 34 was less etched compared to the silicon nitride film 32, and since the amorphous carbon film 35 was hardly etched, a structure was formed in which the ends of the silicon oxide film 33 and the amorphous carbon film 35 protruded into the through hole 34.

[0084] The taken-out etched member was cut, and the cross sections of 30 layers of the silicon nitride film 32 and the cross sections of 30 layers of the silicon oxide film 33 were analyzed by a scanning electron microscope respectively. Specifically, for each of the 30 layers of the silicon nitride film 32, the radial distance between the portion of the silicon nitride film 32 exposed on the inner surface of the through hole 34 and the portion of the amorphous carbon film 35 exposed on the inner surface of the through hole 34 was measured. Also, for each of the 30 layers of the silicon oxide film 33, the radial distance between the portion of the silicon oxide film 33 exposed on the inner surface of the through hole 34 and the portion of the amorphous carbon film 35 exposed on the inner surface of the through hole 34 was measured.

[0085] That is, due to etching, the inner surface of the through hole 34 spreads radially outward and the radius of the through hole 34 increases, and the difference in the radius was measured. Then, by dividing that by the etching time, the relative etching rates of silicon nitride and silicon oxide with respect to amorphous carbon were calculated. The etching rate of the amorphous carbon was calculated by comparing the diameters of the through hole 34 before and after etching, but almost no change in diameter was observed.

[0086] Then, the average value and standard deviation of the etching rates of the 30-layer silicon nitride film 32 and silicon oxide film 33 were calculated to evaluate whether the relative etching rate in the in-plane direction (the direction parallel to the surface of the film) changes depending on the stacking direction position of the film and the uniformity of the relative etching rate. The results are shown in Table 4.

[0087]

Table 4

[0088] (Examples 29 to 31) The etching conditions (composition of the etching gas, temperature of the stage, pressure in the chamber, etching time, source power of the plasma generator) were set as shown in Table 4, and plasma etching was performed in the same manner as in Example 28. Then, in the same manner as in Example 28, the relative etching rates of silicon nitride and silicon oxide with respect to amorphous carbon were calculated, and the average value and standard deviation of each etching rate were calculated. The results are shown in Table 4.

[0089] (Examples 32 to 35) Etching was performed on the same etched member as in Example 28 using an ICP etching apparatus RIE-200iP manufactured by Samco, Inc. The bias power of the plasma generator was set to 0 W, and the other etching conditions (composition of the etching gas, temperature of the stage, pressure in the chamber, etching time, source power of the plasma generator) were as shown in Table 5. Then, in the same manner as in Example 28, the relative etching rates of silicon nitride and silicon oxide with respect to amorphous carbon were calculated, and the average value and standard deviation of each etching rate were calculated. The results are shown in Table 5.

[0090]

Table 5

[0091] From the results of Examples 1 to 3, when the source power was 400 W, the etching rate of silicon nitride was higher than that when the source power was 100 W or 800 W. On the other hand, the etching of the non-etching target hardly proceeded regardless of the source power. From the results of Examples 4 to 6, it was suggested that there was a point at which the etching rate of silicon nitride reached a maximum with respect to the concentration of carbonyl fluoride in the etching gas. On the other hand, the etching of the non-etching target hardly proceeded regardless of the concentration of carbonyl fluoride in the etching gas.

[0092] From the results of Examples 7 and 8, it can be seen that the etching of silicon nitride proceeds without problems even when the pressure in the chamber is 100 Pa or 1500 Pa. On the other hand, the etching of the non-etching target hardly proceeded. From the results of Examples 9 and 15, it can be seen that increasing the temperature of the stage improves the etching rates of silicon nitride, which is the etching target, and silicon oxide, photoresist, and amorphous carbon, which are non-etching targets.

[0093] From the results of Examples 10 and 11, it can be seen that even when oxalyl fluoride or hexafluoropropylene oxide is used as the etching gas, the etching of silicon nitride proceeds, and the etching of the non-etching target hardly proceeds. From the results of Examples 12 and 13, it can be seen that when a mixed gas of carbonyl fluoride, argon, and nitrogen gas is used as the etching gas, the etching rate of silicon nitride is improved. Also, the etching of the non-etching target slightly proceeded. The reason for the improvement in the etching rate of silicon nitride is considered to be that the dissociation of fluorine atoms from carbonyl fluoride was promoted by adding nitrogen gas.

[0094] From the results of Example 14, it can be seen that when using a mixed gas containing carbonyl fluoride, argon, nitrogen gas, and further oxygen gas as the etching gas, the etching rate and etching selectivity of silicon nitride are further improved. It is considered that the addition of oxygen gas further promoted the dissociation of fluorine atoms from carbonyl fluoride.

[0095] From the results of Comparative Example 1, it can be seen that when using sulfur hexafluoride as the etching gas, both silicon nitride and the object not to be etched are etched. From the results of Comparative Example 2, it can be seen that under the conditions where plasma is not generated, the etching of silicon oxide, photoresist, and amorphous carbon proceeds at the same rate as silicon nitride, so it is difficult to selectively etch silicon nitride. From the results of Comparative Example 3, it can be seen that when the concentration of carbonyl fluoride in the etching gas is too high, the etching of silicon oxide, photoresist, and amorphous carbon also proceeds together with silicon nitride.

[0096] From the results of Examples 16 to 27, it can be seen that even when using an ICP etching apparatus, it is possible to selectively etch silicon nitride compared to the object not to be etched. Also, when the bias power is increased or when using a mixed gas with nitrogen gas added as the etching gas, it can be seen that the etching rate of silicon nitride is improved. Further, when using a mixed gas with nitrogen gas and oxygen gas added as the etching gas, it can be seen that the etching rate of silicon nitride is further improved. On the other hand, when the source power is increased, when the concentration of carbonyl fluoride in the etching gas is decreased, or when using oxalyl fluoride or hexafluoropropylene oxide as the etching gas, no significant effect was observed on the etching rates of silicon nitride and the object not to be etched.

[0097] From the results of Comparative Example 4, it can be seen that when sulfur hexafluoride is used as the etching gas, silicon oxide, photoresist, and amorphous carbon, which are non-etching targets, are etched together with silicon nitride. From the results of Comparative Example 5, it can also be seen that when the concentration of carbonyl fluoride in the etching gas is too high, silicon oxide, photoresist, and amorphous carbon, which are non-etching targets, are etched together with silicon nitride.

[0098] From the results of Examples 28 to 35, it can be seen that when etching is performed on a laminated film of amorphous carbon, silicon nitride, and silicon oxide, the silicon nitride layer can be selectively etched. Since the ratio of the standard deviation of the etching rate to the average value of the etching rate of silicon nitride is approximately 2 to 7%, it was found that the etching of the 30 silicon nitride films 32 proceeded almost uniformly regardless of the stacking direction position of the silicon nitride film 32. On the other hand, the etching rates of silicon oxide and amorphous carbon were smaller than the etching rate of silicon nitride under any conditions. Also, the standard deviation of the etching rate of silicon oxide was 3 or less under any conditions.

Explanation of Reference Numerals

[0099] 1 ··· Fluorine compound gas supply unit 2 ··· Rare gas supply unit 3 ··· Nitrogen gas supply unit 4 ··· Fluorine compound gas flow rate control device 5 ··· Rare gas flow rate control device 6 ··· Nitrogen gas flow rate control device 7 ··· Pipe for supplying fluorine compound gas 8 ··· Pipe for supplying rare gas 9 ··· Pipe for supplying nitrogen gas 10 ··· Chamber 11 ··· Stage 12 ··· Member to be etched 13 ··· Exhaust pipe 14 ··· Thermometer 15 ··· Vacuum pump 16 ··· Pressure gauge 17 ··· Fluorine compound gas pressure control device 18 ··· Noble gas pressure control device 19 ··· Nitrogen gas pressure control device 20 ··· Remote plasma generator 21 ··· Silicon substrate 22 ··· Silicon nitride film 23 ··· Silicon dioxide substrate 31 ··· Silicon substrate 32 ··· Silicon nitride film 33 ··· Silicon oxide film 34 ··· Through-hole 35 ··· Amorphous carbon film

Claims

1. An etching step is provided in which an etching gas containing a fluorine compound having at least one of a carbon-oxygen double bond and an ether bond in the molecule and having 3 or less carbon atoms is brought into contact with an etched member having an object to be etched by the etching gas and a non-etching object that is not an object to be etched by the etching gas in the presence of plasma, and the object to be etched is selectively etched compared to the non-etching object. The etching gas is a mixed gas containing the fluorine compound, a rare gas, and nitrogen gas, and the concentration of the nitrogen gas in the etching gas is 10% by volume or less. The concentration of the fluorine compound in the etching gas is 1% by volume or more and 30% by volume or less, the object to be etched has silicon nitride. The non-etching object has at least one selected from the group consisting of silicon oxide, photoresist, amorphous carbon, titanium nitride, copper, nickel, cobalt, and oxides and nitrides of copper, nickel, and cobalt. An etching method.

2. The etching method according to claim 1, wherein the non-etching object has at least one selected from silicon oxide, photoresist, and amorphous carbon.

3. The etching method according to claim 1 or claim 2, wherein the etching step is performed under a pressure condition of 1 Pa or more and 3 kPa or less.

4. The etching method according to any one of claims 1 to 3, wherein the etching step is performed under a temperature condition of 0 ° C or more and 200 ° C or less.

5. The etching method according to any one of claims 1 to 4, wherein the etching gas is a mixed gas containing, in addition to the fluorine compound, a rare gas, and nitrogen gas, an oxygen-containing gas other than the fluorine compound.

6. The etching method according to any one of claims 1 to 5, wherein the fluorine compound is at least one selected from carbonyl fluoride, oxalyl fluoride, and hexafluoropropylene oxide.

7. A method for manufacturing a semiconductor device, which uses the etching method according to any one of claims 1 to 6, wherein The etched member is a semiconductor substrate having the object to be etched and the non-etching object. A method for manufacturing a semiconductor device, comprising a processing step of removing at least a part of the object to be etched from the semiconductor substrate by the etching.

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