Plasma etching method and method for manufacturing semiconductor element

Abstract

The present application provides a plasma etching method that selectively etches an etching target containing an oxide of at least one of tin and indium, compared to a non-etching target. A plasma etching method includes the following etching step: an etching gas containing an unsaturated compound having a fluorine atom and a bromine atom in a molecule is brought into contact with an etched member of an etching target having an etching object as an etching gas and a non-etching target not having an etching object of the etching gas, in the presence of plasma, while applying a bias power exceeding 0 W to a lower electrode supporting the etched member, and etching is performed while selectively etching the etching target compared to the non-etching target, the etching target containing an oxide of at least one of tin and indium, and the non-etching target containing at least one of a silicon-containing compound and a photoresist.

Description

TECHNICAL FIELD

[0001] The present application relates to a plasma etching method and a manufacturing method of a semiconductor element. BACKGROUND

[0002] Metal oxides such as tin oxide or indium oxide are used as spacers when forming a pattern of a metal wiring or a fin pattern in a fin field effect transistor (FinFET). In addition, indium tin oxide (ITO), which is a mixture of tin oxide and indium oxide, is often used for manufacturing a transparent electrode.

[0003] In the above-described semiconductor process, when the metal oxide is finely processed into a desired shape, there is a step of etching the metal oxide by plasma etching using an etching gas. In the etching of the semiconductor process, it is important to selectively etch an etching target of the etching gas, i.e., an etching target (metal oxide), compared to a non-etching target such as a mask that is a non-etching target of the etching gas (i.e., etching selectivity).

[0004] For example, in Patent Literature 1 and Patent Literature 2, a technique of etching a metal oxide by plasma etching using an etching gas containing hydrogen bromide or hydrogen iodide is disclosed.

[0005] [Patent Literature]

[0006] [Patent Literature]

[0007] [Patent Literature 1] Japanese Patent Laid-Open Publication No. 506572 / 2002

[0008] [Patent Literature 2] Japanese Patent Laid-Open Publication No. 151375 / 1994 SUMMARY

[0009] [Problems to be Solved by the Invention]

[0010] However, the techniques disclosed in Patent Literature 1 and Patent Literature 2 have a case where a metal oxide cannot be etched with excellent etching selectivity.

[0011] The present application relates to a plasma etching method and a manufacturing method of a semiconductor element.

[0012] [Means for Solving the Problems]

[0013] To solve the aforementioned problems, one aspect of the present application is as follows [1] to [9].

[0014] [1] A plasma etching method comprising the following etching step:

[0015] An etching gas containing an unsaturated compound having a fluorine atom and a bromine atom in a molecule is caused to contact, in the presence of plasma, an etched member having an etching object which is the etching gas and a non-etching object which is not the etching gas, while a bias power exceeding 0 W is applied to a lower electrode supporting the etched member, to selectively etch the etching object compared to the non-etching object,

[0016] The etching object contains an oxide of at least one of tin and indium, and the non-etching object contains at least one of a silicon-containing compound and a photoresist.

[0017] [2]. The plasma etching method according to [1], wherein the etching gas is a mixed gas containing the unsaturated compound and an inactive gas.

[0018] [3]. The plasma etching method according to [2], wherein the concentration of the unsaturated compound in the mixed gas is 1 vol% or more and 50 vol% or less.

[0019] [4]. The plasma etching method according to any one of [1] to [3], wherein the unsaturated compound is bromofluoroethylene.

[0020] [5]. The plasma etching method according to [4], wherein the bromofluoroethylene is at least one of bromotrifluoroethylene, 1-bromo-2,2-difluoroethylene, (E)-1-bromo-1,2-difluoroethylene, (Z)-1-bromo-1,2-difluoroethylene, 1-bromo-1-fluoroethylene, (E)-1-bromo-2-fluoroethylene, (Z)-1-bromo-2-fluoroethylene, 1,1-dibromo-2-fluoroethylene, (E)-1,2-dibromo-2-fluoroethylene, (Z)-1,2-dibromo-2-fluoroethylene, and tribromofluoroethylene.

[0021] [6]. The plasma etching method according to any one of [1] to [5], wherein the silicon-containing compound is a compound having at least one of an oxygen atom and a nitrogen atom and a silicon atom, or amorphous silicon.

[0022] [7]. The plasma etching method according to any one of [1] to [6], wherein the etching is performed at a processing pressure of 1 Pa or more and 10 Pa or less.

[0023] [8]. The plasma etching method according to any one of [1] to [7], wherein the etching is performed while a bias power of 10 W or more and 1200 W or less is applied to a lower electrode supporting the etched member.

[0024] [9] A method for manufacturing a semiconductor element, wherein the plasma etching method described in any one of [1] to [8] is used to manufacture a semiconductor element, the etched member being a semiconductor substrate having the etching target and the non-etching target,

[0025] The manufacturing method includes a processing step of removing at least a part of the etching target from the semiconductor substrate by the etching.

[0026] Effects of Invention

[0027] According to the present invention, the etching target containing an oxide of at least one of tin and indium is selectively etched compared to the non-etching target. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a schematic diagram of an example of a plasma etching apparatus used to explain an embodiment of the plasma etching method of the present invention. DETAILED DESCRIPTION

[0029] An embodiment of the present invention will be described below. Furthermore, the present embodiment is merely an example of the present invention, and the present invention is not limited by the present embodiment. In addition, various changes or modifications can be made to the present embodiment, and such changed or modified forms can also be included in the present invention.

[0030] The plasma etching method of the present embodiment includes an etching step of contacting an etching gas containing an unsaturated compound having a fluorine atom and a bromine atom in a molecule with an etched member having an etching target as the etching gas and a non-etching target as the non-etching target of the etching gas in the presence of plasma while applying a bias power exceeding 0 W to a lower electrode supporting the etched member, and selectively etching the etching target compared to the non-etching target. The etching target contains an oxide of at least one of tin (Sn) and indium (In), and the non-etching target contains at least one of a silicon-containing compound and a photoresist.

[0031] If the etching gas is contacted with the etched member, the above-described unsaturated compound in the etching gas reacts with the above-described oxide in the etching target, and thus etching of the etching target proceeds. In contrast, the non-etching target hardly reacts with the above-described unsaturated compound, and thus etching of the non-etching target hardly proceeds. Therefore, according to the plasma etching method of the present embodiment, the etching target can be selectively etched compared to the non-etching target.

[0032] For example, the etching can be performed in a manner such that the etching rate of the object is 2 or more times the etching rate of the non-object. Alternatively, from the viewpoint of more stably controlling the etching, the etching can be performed in a manner such that the etching rate of the object is 4 or more times the etching rate of the non-object.

[0033] Further, the etching in the present application refers to removing a part or all of the object to be etched possessed by the member to be etched to process the member to be etched into a specific shape (for example, a three-dimensional shape) (for example, processing a film-shaped object to be etched composed of the oxide described above into a specific film thickness), and also refers to removing and cleaning a residue or a deposit composed of the object to be etched from the member to be etched, and the like.

[0034] The plasma etching method of the present embodiment can be used in the production of a semiconductor element. That is, the production method of a semiconductor element of the present embodiment is a production method of a semiconductor element in which the plasma etching method of the present embodiment is used to produce a semiconductor element, the member to be etched is a semiconductor substrate having an object to be etched and a non-object to be etched, and the production method includes a process step of removing at least a part of the object to be etched from the semiconductor substrate by etching.

[0035] Therefore, if the plasma etching method of the present embodiment is applied to the process of a semiconductor element, for example, a pattern formed in a photoresist can be transferred to a film of a metal oxide, or a film or a residue of a metal oxide present on a film of a non-object to be etched can be removed.

[0036] Hereinafter, the plasma etching method and the production method of a semiconductor element of the present embodiment will be described in more detail.

[0037] The etching of the present embodiment can be achieved by plasma etching. The type of plasma source in the plasma etching is not particularly limited, and a commercially available device can be used. For example, a high-frequency discharge plasma such as an inductively coupled plasma (ICP), a capacitively coupled plasma (CCP), or a microwave discharge plasma such as an electron cyclotron resonance plasma (ECRP) can be used.

[0038] Further, the plasma etching device of Figure 1 described in detail later is a plasma etching device in which ICP is used as a plasma source.

[0039] Further, in the plasma etching method of the present embodiment, the plasma generation chamber and the chamber in which the etching target member is provided can be separated, and the plasma can be generated in the plasma generation chamber (i.e., a remote plasma can be used).

[0040] [etching gas]

[0041] The etching gas used in the plasma etching method of the present embodiment is a gas containing an unsaturated compound having a fluorine atom and a bromine atom in the molecule. The type of the unsaturated compound is not particularly limited as long as it has a fluorine atom and a bromine atom in the molecule, but a bromofluoroethylene is preferable because it is easily available and easy to handle.

[0042] As specific examples of the bromofluoroethylene, bromotrifluoroethylene, 1-bromo-2,2-difluoroethylene, (E)-1-bromo-1,2-difluoroethylene, (Z)-1-bromo-1,2-difluoroethylene, 1-bromo-1-fluoroethylene, (E)-1-bromo-2-fluoroethylene, (Z)-1-bromo-2-fluoroethylene, 1,1-dibromo-2-fluoroethylene, (E)-1,2-dibromo-2-fluoroethylene, (Z)-1,2-dibromo-2-fluoroethylene, and tribromofluoroethylene can be listed.

[0043] Among these, from the viewpoint of being easily vaporized at normal temperature and pressure, a bromofluoroethylene having one bromine atom is more preferable. As examples of the bromofluoroethylene having one bromine atom, bromotrifluoroethylene, 1-bromo-2,2-difluoroethylene, (E)-1-bromo-1,2-difluoroethylene, (Z)-1-bromo-1,2-difluoroethylene, 1-bromo-1-fluoroethylene, (E)-1-bromo-2-fluoroethylene, (Z)-1-bromo-2-fluoroethylene can be listed.

[0044] Further, the unsaturated compound such as the bromofluoroethylene can be used alone or two or more kinds thereof can be used in combination.

[0045] The etching gas can be a gas formed only of the unsaturated compound such as the bromofluoroethylene, a mixed gas containing the unsaturated compound such as the bromofluoroethylene and a non-reactive gas, or a mixed gas containing the unsaturated compound such as the bromofluoroethylene, a gas containing an oxygen atom, and a non-reactive gas.

[0046] The type of the non-reactive gas is not particularly limited, but for example, nitrogen (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) can be listed. These non-reactive gases can be used alone or two or more kinds thereof can be used in combination.

[0047] As the gas containing an oxygen atom, there is no particular limitation as long as it is a compound having an oxygen atom in the molecule and being a gas in the standard state, but for example, oxygen (O2), ozone (O3), nitrous oxide (N2O), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), sulfur trioxide (SO3), and the like can be exemplified. By adding the gas containing an oxygen atom, it is possible to control the film thickness of the polymer deposited on the non-etching object to an arbitrary thickness.

[0048] The concentration of the unsaturated compound in the mixed gas is not particularly limited, and can be set to more than 0 vol% and less than 100 vol%, and can be adjusted in consideration of ignition property of the plasma and the like. In order to make the ignition property of the plasma more sufficient, the concentration of the unsaturated compound in the mixed gas is preferably set to 1 vol% or more and 50 vol% or less, more preferably 1 vol% or more and 40 vol% or less, particularly preferably 3 vol% or more and 30 vol% or less, and particularly preferably 5 vol% or more and 30 vol% or less.

[0049] Further, as long as the concentration of the unsaturated compound in the mixed gas is within the above numerical range, a high etching selectivity is easily achieved, and for example, the etching selectivity easily becomes 3 or more. Here, the etching selectivity is a value calculated by dividing the etching rate of the etching object by the etching rate of the non-etching object.

[0050] Further, the amount of use of the etching gas in the plasma etching method of the present embodiment, for example, the total flow rate of the etching gas to the chamber in which plasma etching is performed in the plasma etching apparatus, is preferably adjusted in accordance with the inner volume of the chamber, the exhaust capacity, the processing pressure, and the like.

[0051] [Conditions of the etching step]

[0052] The pressure condition of the etching step in the plasma etching method of the present embodiment is not particularly limited, but the plasma etching is preferably performed at a processing pressure of 0.2 Pa or more and 30 Pa or less, more preferably at a processing pressure of 1 Pa or more and 15 Pa or less, further preferably at a processing pressure of 1 Pa or more and 10 Pa or less, and particularly preferably at a processing pressure of 2 Pa or more and 8 Pa or less. If it is within the above pressure range, the composition of the plasma is stable, and thus the reproducibility of etching is easily improved.

[0053] In the plasma etching apparatus, the etching gas is plasma-ized to generate plasma by forming an electric field and a magnetic field, for example, by applying a high-frequency source power to an RF (radio frequency) coil. The magnitude of the source power is not particularly limited, but is preferably set to more than 0 W and 3000 W or less, more preferably to 100 W or more and 1500 W or less, and particularly preferably to 200 W or more and 1000 W or less. If the magnitude of the source power is within the above numerical range, the etching speed of the etching target is sufficiently large, and at the same time, the etching selectivity is sufficiently high.

[0054] The temperature condition for the etching step in the plasma etching method of the present embodiment is not particularly limited, but the temperature of the etched member (for example, a semiconductor substrate) at the time of plasma etching is preferably set to -20°C or more and 250°C or less, more preferably to 0°C or more and 100°C or less, and particularly preferably to 20°C or more and 70°C or less. If the temperature of the etched member at the time of plasma etching is within the above numerical range, for example, deformation of a resist film formed on a semiconductor substrate due to deterioration, sublimation, or the like can be suppressed, and thus plasma etching can be performed with high patterning accuracy. Here, the temperature of the above temperature condition is the temperature of the etched member, and the temperature of a stage that supports the etched member in a chamber of a plasma etching apparatus can also be used.

[0055] At the time of plasma etching, a bias power of more than 0 W must be applied to a lower electrode that supports the etched member. In order to sufficiently increase the etching selectivity of the etching target with respect to the non-etching target, the bias power applied to the lower electrode is preferably set to 10 W or more and 1200 W or less, more preferably to 20 W or more and 800 W or less, further preferably to 20 W or more and 500 W or less, and particularly preferably to 30 W or more and 300 W or less.

[0056] [Etched Member]

[0057] The etched member etched by the plasma etching method of the present embodiment has an etching target and a non-etching target, but can also be a member having a portion formed of the etching target and a portion formed of the non-etching target, or a member formed of a mixture of the etching target and the non-etching target. In addition, the etched member can have a portion other than the etching target and the non-etching target.

[0058] In addition, the shape of the etched member is not particularly limited, and for example, can be a plate shape, a foil shape, a film shape, a powder shape, or a block shape. As an example of the etched member, the aforementioned semiconductor substrate can be given.

[0059] [Etching Target]

[0060] The etching target contains an oxide of at least one of tin and indium, i.e., tin oxide, indium oxide, or indium tin oxide. As examples of tin oxide, SnO, SnO2may be given, and as examples of indium oxide, In2O3may be given. The etching target can be formed of only the above oxide, can have a portion formed of only the above oxide and a portion formed of another material, or can be formed of a mixture of the above oxide and another material.

[0061] Further, the etching target can be not only a material formed of only a single substance of a specific metal (tin, indium) or a compound thereof, but also a material containing 10 mol% or more of a single substance of a specific metal or a compound thereof, more preferably a material containing 20 mol% or more, and further preferably a material containing 30 mol% or more, such as an alloy formed of another metal or a material containing an impurity, an oxide, a nitride, an oxynitride, an oxyfluoride, or the like, and the plasma etching method of the present embodiment can be applied thereto.

[0062] Here, the oxide means a compound having a metal and oxygen. The oxide is, for example, a compound represented by MxOy x O y (M is tin or indium, and x and y are arbitrary natural numbers), and is a compound containing at least 10 mol% or more, preferably 15 mol% or more, and more preferably 20 mol% or more of a metal. Specifically, a compound represented by MO, M2O3, MO2, MO3, M3O4, M2O5, or the like can be given.

[0063] Further, the nitride means a compound having a metal and nitrogen. The nitride is, for example, a compound represented by M a N b (M is tin or indium, and a and b are arbitrary natural numbers), and is a compound containing at least 10 mol% or more, preferably 15 mol% or more, and more preferably 20 mol% or more of a metal. Specifically, a compound represented by MN, M2N, M3N2, M3N4, M4N, M7N3, M 16 N2, or the like can be given.

[0064] Further, the oxynitride means a compound having a metal, oxygen, and nitrogen. The oxynitride is, for example, a compound represented by M c N d O e (M is tin or indium, and c, d, e are arbitrary natural numbers), and is a compound containing at least 10 mol% or more, preferably 15 mol% or more, and more preferably 20 mol% or more of a metal.

[0065] Further, the oxyfluoride means a compound having a metal, oxygen, and fluorine. The oxyfluoride is, for example, a compound represented by M f Fg O h (M is tin or indium, and f, g, h are arbitrary natural numbers) and is a compound containing at least 10 mol% or more, preferably 15 mol% or more, and more preferably 20 mol% or more of metal.

[0066] The shape of the material containing the specific metal is not particularly limited and can be granular, massive, film-like, foil-like, or powdery.

[0067] [Non-etching object]

[0068] The non-etching object contains at least one of a silicon-containing compound and a photoresist. The non-etching object does not substantially react with the above-mentioned unsaturated compound, or reacts extremely slowly with the above-mentioned unsaturated compound, and thus etching hardly proceeds even if etching is performed by the plasma etching method of the present embodiment. Alternatively, since the vapor pressure of the reaction product of the above-mentioned unsaturated compound and the non-etching object is low, etching hardly proceeds.

[0069] The type of the silicon-containing compound is not particularly limited as long as it is a compound having a silicon atom, but as examples, a compound having at least one of an oxygen atom and a nitrogen atom and a silicon atom, or polycrystalline silicon, amorphous silicon (Si) can be listed. As the compound having at least one of an oxygen atom and a nitrogen atom and a silicon atom, for example, silicon oxide, silicon nitride, and silicon oxynitride can be listed.

[0070] The silicon oxide refers to a compound having silicon and oxygen in any ratio, and as an example, silicon dioxide (SiO2) can be listed. The purity of the silicon oxide is not particularly limited, but it is preferably 30% by mass or more, more preferably 60% by mass or more, and further preferably 90% by mass or more.

[0071] The silicon nitride refers to a compound having silicon and nitrogen in any ratio, and as an example, Si3N4 can be listed. The purity of the silicon nitride is not particularly limited, but it is preferably 30% by mass or more, more preferably 60% by mass or more, and further preferably 90% by mass or more.

[0072] The silicon oxynitride refers to a compound having silicon, oxygen, and nitrogen in any ratio, and as an example, Si2N2O can be listed.

[0073] Photoresist refers to a photosensitive composition whose physical properties, primarily solubility, change due to light or electron beams. Examples include photoresists for g-lines, h-lines, i-lines, KrF, ArF, F2, and EUV. The composition of photoresist is not particularly limited as long as it is commonly used in semiconductor processes; for example, compositions containing polymers synthesized from at least one monomer selected from linear olefins, cyclic olefins, styrene, vinylphenol, acrylic acid, methacrylates, epoxy compounds, melamine, and glycols can be included.

[0074] Furthermore, the non-etched object can be used as a resist or mask to suppress etching of the etched object caused by etching gases. Therefore, the plasma etching method of this embodiment can be used in methods such as using a patterned non-etched object as a resist or mask to process the etched object into a specific shape (e.g., processing the film-like etched object of the etched component into a specific film thickness), and is therefore suitable for the manufacture of semiconductor devices. In addition, since the non-etched object is hardly etched, the etching of parts of the semiconductor device that should not be etched can be suppressed, and the loss of semiconductor device characteristics due to etching can be prevented.

[0075] Furthermore, any non-etched objects remaining after patterning can be removed using methods commonly used in semiconductor device manufacturing processes. Examples include ashing by oxidizing gases such as oxygen plasma or ozone, or dissolution using solutions such as APM (a mixture of ammonia and hydrogen peroxide), SPM (a mixture of sulfuric acid and hydrogen peroxide), or organic solvents.

[0076] The following uses Figure 1 The plasma etching apparatus shown illustrates an example of plasma etching of tin oxide film, amorphous silicon film, silicon oxide film, silicon nitride film, and photoresist film formed on the surface of a substrate (equivalent to the etched component). Figure 1 The plasma etching apparatus is a plasma etching apparatus that uses ICP as the plasma source. First, let me explain... Figure 1 Plasma etching apparatus.

[0077] Figure 1A plasma etching apparatus of the present application includes a chamber 1 in which plasma etching is performed, a lower electrode 2 that supports a substrate 20 on which plasma etching is performed inside the chamber 1, a bias power source (not shown) that applies a bias power to the lower electrode 2, an RF coil 15 that forms an electric field and a magnetic field for plasma-izing an etching gas inside the chamber 1, a source power source (not shown) that applies a source power of a high frequency to the RF coil 15, a vacuum pump 13 that reduces the pressure inside the chamber 1, a pressure gauge 14 that measures the pressure inside the chamber 1, a sensor 16 that inputs plasma light generated with plasma generation, and a light splitter 17 that monitors a temporal change in the plasma light by splitting the plasma light input from the sensor 16.

[0078] The substrate 20 has a tin oxide film, an amorphous silicon film, a silicon oxide film, a silicon nitride film, and a photoresist film formed on a surface thereof. As the sensor 16, a CCD (Charge-Coupled Device) image sensor can be used, for example. However, instead of providing the sensor 16 and the light splitter 17, a peephole can be provided in the chamber 1, and the temporal change in the plasma light can be confirmed by visually observing the inside of the chamber 1 from the peephole.

[0079] Further, the chamber 1 includes an etching gas supply portion that supplies an etching gas to the inside of the chamber 1. The etching gas supply portion includes an unsaturated compound gas supply portion 3 that supplies an unsaturated compound gas, a non-active gas supply portion 4 that supplies a non-active gas, an etching gas supply pipe 11 that connects the unsaturated compound gas supply portion 3 to the chamber 1, and a non-active gas supply pipe 12 that connects the non-active gas supply portion 4 to an intermediate portion of the etching gas supply pipe 11.

[0080] Further, as the etching gas, when the unsaturated compound gas is supplied to the chamber 1, the unsaturated compound gas is supplied to the chamber 1 by being sent from the unsaturated compound gas supply portion 3 to the etching gas supply pipe 11 and by being supplied to the chamber 1 through the etching gas supply pipe 11.

[0081] The pressure in the chamber 1 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, but is preferably 10 kPa or higher and lower than 100 kPa, more preferably 1 Pa or higher and 50 kPa or lower, and further preferably 1 Pa or higher and 20 kPa or lower. -5 Pa or higher and lower than 100 kPa, more preferably 1 Pa or higher and 50 kPa or lower, and further preferably 1 Pa or higher and 20 kPa or lower.

[0082] Further, as the etching gas, a mixed gas of the unsaturated compound gas and the inactive gas is supplied, and the unsaturated compound gas is sent out from the unsaturated compound gas supply part 3 to the etching gas supply pipe 11, and the inactive gas is sent out from the inactive gas supply part 4 to the etching gas supply pipe 11 via the inactive gas supply pipe 12. Thus, in the intermediate portion of the etching gas supply pipe 11, the unsaturated compound gas and the inactive gas are mixed to become a mixed gas, and this mixed gas is supplied to the chamber 1 via the etching gas supply pipe 11.

[0083] When plasma etching is performed using the plasma etching apparatus as such, the substrate 20 is placed on the lower electrode 2 arranged in the inside of the chamber 1, and the pressure in the inside of the chamber 1 is reduced to, for example, 1 Pa or more and 10 Pa or less by the vacuum pump 13, and then the etching gas is supplied to the inside of the chamber 1 by the etching gas supply part. Then, if the source power of high frequency (for example, 13.56 MHz) is applied to the RF coil 15, the electric field and the magnetic field are formed in the inside of the chamber 1 to accelerate the electrons, and the accelerated electrons collide with the unsaturated compound molecules in the etching gas to generate new ions and electrons, and as a result, discharge occurs to form the plasma. The generation of the plasma can be confirmed using the sensor 16 and the spectrometer 17.

[0084] If the plasma is generated, the tin oxide film formed on the surface of the substrate 20 can be etched. The supply amount of the etching gas to the chamber 1 or the concentration of the unsaturated compound in the etching gas (mixed gas) can be adjusted by controlling the flow rates of the unsaturated compound gas and the inactive gas respectively by the mass flow controllers (not shown) respectively arranged in the etching gas supply pipe 11 and the inactive gas supply pipe 12.

[0085] The pressure of the etching gas supplied to the inside of the chamber 1 is preferably 0.01 Pa or more and 500 Pa or less, more preferably 0.1 Pa or more and 100 Pa or less, and further preferably 1 Pa or more and 30 Pa or less, and particularly preferably 1 Pa or more and 10 Pa or less from the viewpoint of uniformly etching the surface of the substrate 20. If the pressure of the etching gas in the inside of the chamber 1 is in the above range, the etching of the etching target is easily performed at a sufficient speed, and the ratio of the etching speed of the non-etching target to the etching speed of the etching target, that is, the etching selectivity is easily increased.

[0086] [Examples]

[0087] The following examples and comparative examples will more specifically illustrate the present application.

[0088] (Example 1)

[0089] The unsaturated compound gas used in the above example has a molecular weight of 60 or more and 200 or less, and the inactive gas has a molecular weight of 20 or more and 60 or less. Figure 1Plasma etching apparatuses of the same structure as the ICP etching apparatus of the present application were ICP etching apparatuses RIE-200iP manufactured by SAMCO Inc. Plasma etching of five kinds of substrates was performed using the ICP etching apparatuses. The first substrate was a substrate (manufactured by SEIREN KST Co., Ltd.) on which a 300-nm-thick tin oxide (Sn02) film was formed on a 2-inch square silicon substrate. The second substrate was a substrate (manufactured by SEIREN KST Co., Ltd.) on which an 800-nm-thick amorphous silicon film was formed on a 2-inch square silicon substrate.

[0090] The third substrate was a substrate (manufactured by SEIREN KST Co., Ltd.) on which a 600-nm-thick silicon oxide (Si02) film was formed on a 2-inch square silicon substrate. The fourth substrate was a substrate (manufactured by SEIREN KST Co., Ltd.) on which an 800-nm-thick silicon nitride (Si3N4) film was formed on a 2-inch square silicon substrate.

[0091] The fifth substrate was a substrate on which a 600-nm-thick photoresist film was formed on a 2-inch square silicon substrate. The photoresist film was formed by applying an i-line photoresist TSCR (registered trademark) manufactured by Tokyo Ohka Kogyo Co., Ltd. to the silicon substrate, performing exposure, and hardening the photoresist.

[0092] The tin oxide film was an etching target, and the amorphous silicon film, the silicon oxide film, the silicon nitride film, and the photoresist film were non-etching targets.

[0093] In addition, the volume of the inside of the chamber was 46000 cm3, and the etching gas was a mixed gas of bromotrifluoroethylene gas and argon. The concentration of bromotrifluoroethylene in the etching gas was adjusted to 10 vol% by setting the flow rate of the bromotrifluoroethylene gas to 10 seem and the flow rate of the argon to 90 seem. Here, seem is the volume flow rate per 1 minute (cm3 / min) normalized under the conditions of 0°C and 1 atm. 3 3

[0094] After the processing pressure of the inside of the chamber was set to 3 Pa, the source power was set to 600 W, the bias power was set to 200 W, and the temperature of the substrate was set to 20°C, the flow rate of the bromotrifluoroethylene gas, the flow rate of the argon, the processing pressure, the source power, and the bias power were monitored in real time, and plasma etching was performed while confirming that there was no difference between the set values and the executed values. The results are shown in Table 1.

[0095] The etching speed of each of the etching target and the non-etching target, and the ratio of the etching speed of the etching target to the etching speed of the non-etching target ([etching speed of non-etching target] / [etching speed of etching target], hereinafter referred to as "etching selectivity ratio") are shown in Table 1. ​​

[0096] Table 1

[0097]

[0098] Further, the film thickness of the etching target and the non-etching target was measured using a reflectance spectrophotometer film thickness meter F20 manufactured by FILMETRICS, Inc. Furthermore, the etching rate of the etching target and the non-etching target was calculated by subtracting the film thickness after etching from the film thickness before etching, and dividing the result by the etching time. The measurement conditions of the film thickness were as follows.

[0099] The measurement environment was air, and the measurement temperature was 25°C. The measurement wavelength range was a wavelength range in which the Goodness of fit was 0.9 or more, and specifically, the following wavelength ranges were measured as a reference. That is, the wavelength range of tin oxide was 350 to 700 nm, the wavelength range of amorphous silicon was 500 to 1200 nm, the wavelength range of silicon oxide was 300 to 1100 nm, the wavelength range of silicon nitride was 500 to 1500 nm, and the wavelength range of photoresist was 400 to 1000 nm.

[0100] (Examples 2 to 15)

[0101] Plasma etching was performed in the same manner as in Example 1 except that the etching conditions were as described in Tables 1 and 2, and the etching rate and the etching selectivity of the etching target and the non-etching target were measured. The results are shown in Tables 1 and 2.

[0102] Table 2

[0103]

[0104] (Comparative Examples 1 to 3)

[0105] Plasma etching was performed in the same manner as in Example 1 except that the bromotrifluoroethylene in the etching gas was changed to sulfur hexafluoride (SF6) gas, hexafluorobutadiene (C4F6) gas, and hydrogen bromide (HBr) gas, respectively, and the etching rate and the etching selectivity of the etching target and the non-etching target were measured. The results are shown in Table 2.

[0106] (Comparative Example 4)

[0107] Plasma etching was performed in the same manner as in Example 1 except that the bias power was set to 0 W, and the etching rate and the etching selectivity of the etching target and the non-etching target were measured. The results are shown in Table 2.

[0108] As is clear from the results of Examples 1 to 3, by using bromotrifluoroethylene as the etching gas, tin oxide, indium oxide, and indium tin oxide can be selectively etched with respect to the non-etching target.

[0109] From the results of Examples 1, 4, 5, the higher the temperature of the stage, the higher the etching rate of tin oxide. On the other hand, the lower the temperature of the stage, the more the etching of the non-etching object is suppressed, and thus the etching selectivity becomes higher.

[0110] From the results of Examples 1, 6, 7, the lower the source power, the higher the etching rate of tin oxide. This suggests that the higher the source power, the more chemical species that hinder etching are generated.

[0111] From the results of Examples 1, 8, and Comparative Example 4, if the bias power is lowered, the etching of the non-etching object is suppressed, and thus the etching selectivity becomes higher. In particular, on the amorphous silicon film and the photoresist film, the etching of the amorphous silicon film and the photoresist film is suppressed due to the accumulation of polymers generated by the polymerization of bromotrifluoroethylene. Thus, with respect to the amorphous silicon and the photoresist, it is considered that a particularly high etching selectivity is exhibited for tin oxide.

[0112] From the results of Examples 1, 9, even if the pressure in the chamber is increased, the etching rate of tin oxide is hardly affected, and the etching rate of the non-etching object is decreased. As a result, the etching selectivity is increased.

[0113] From the results of Examples 10, 11, the higher the proportion of bromofluoroethylene in the etching gas, the higher the etching rate of tin oxide.

[0114] From the results of Examples 12 to 15, even if 1-bromo-1-fluoroethylene, 1-bromo-2,2-difluoroethylene, (E)-1-bromo-2-fluoroethylene, or (Z)-1-bromo-2-fluoroethylene is used for the etching gas, the selective etching of tin oxide can be performed without problems.

[0115] From the results of Comparative Examples 1 to 3, when sulfur hexafluoride, hexafluorobutadiene, or hydrogen bromide is used for the etching gas, there is a tendency for the etching rate and the etching selectivity of tin oxide to be lowered.

[0116] Explanation of Reference Numerals

[0117] 1: chamber

[0118] 2: lower electrode

[0119] 3: unsaturated compound gas supply section

[0120] 4: non-active gas supply section

[0121] 11: etching gas supply pipe

[0122] 12: non-active gas supply pipe

[0123] 13: vacuum pump

[0124] 14: pressure gauge

[0125] 15: RF coil

[0126] 16: sensor

[0127] 17: beamsplitter

[0128] 20: substrate

Claims

1. A plasma etching method comprising the following etching step: an etching gas containing an unsaturated compound having a fluorine atom and a bromine atom in a molecule is brought into contact with an etched member having an etching object which is an etching object of the etching gas and a non-etching object which is not an etching object of the etching gas in the presence of plasma while applying a bias power exceeding 0 W to a lower electrode supporting the etched member, and the etching object is selectively etched compared to the non-etching object, the etching object contains an oxide of at least one of tin and indium, and the non-etching object contains at least one of a silicon-containing compound and a photoresist.

2. The plasma etching method according to claim 1, wherein the etching gas is a mixed gas containing the unsaturated compound and an inactive gas.

3. The plasma etching method according to claim 2, wherein the concentration of the unsaturated compound in the mixed gas is 1 vol% or more and 50 vol% or less.

4. The plasma etching method according to any one of claims 1 to 3, wherein the unsaturated compound is bromofluoroethylene.

5. The plasma etching method according to claim 4, wherein the bromofluoroethylene is at least one of bromotrifluoroethylene, 1-bromo-2,2-difluoroethylene, (E)-1-bromo-1,2-difluoroethylene, (Z)-1-bromo-1,2-difluoroethylene, 1-bromo-1-fluoroethylene, (E)-1-bromo-2-fluoroethylene, (Z)-1-bromo-2-fluoroethylene, 1,1-dibromo-2-fluoroethylene, (E)-1,2-dibromo-2-fluoroethylene, (Z)-1,2-dibromo-2-fluoroethylene, and tribromofluoroethylene.

6. The plasma etching method according to any one of claims 1 to 3, wherein the silicon-containing compound is a compound having at least one of an oxygen atom and a nitrogen atom and a silicon atom, or amorphous silicon.

7. The plasma etching method according to any one of claims 1 to 3, wherein the etching is performed at a processing pressure of 1 Pa or more and 10 Pa or less.

8. The plasma etching method according to any one of claims 1 to 3, wherein the etching is performed while applying a bias power of 10 W or more and 1200 W or less to a lower electrode supporting the etched member.

9. A method for manufacturing a semiconductor element, the method for manufacturing a semiconductor element using the plasma etching method according to any one of claims 1 to 8, the etched member being a semiconductor substrate having the etching object and the non-etching object, the method for manufacturing a semiconductor element comprising a processing step of removing at least a part of the etching object from the semiconductor substrate by the etching.

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