Plasma etching method and semiconductor device manufacturing method

Abstract

Provided is a plasma etching method capable of selectively etching an etching object containing an oxide of at least one among tin and indium, compared to a non-etching object. The plasma etching method comprises an etching step in which an etching gas containing an unsaturated compound having a fluorine atom and a bromine atom in the molecule is brought into contact with, in the presence of plasma, a member to be etched having an etching object to be etched by the etching gas and a non-etching object not to be etched by the etching gas, etching is performed while applying bias power greater than 0 W to a lower electrode supporting the member to be etched, and the etching object is selectively etched compared to the non-etching object. The etching object contains an oxide of at least one among tin and indium, and the non-etching object contains at least one among a silicon-containing compound and a photoresist.

Description

[Technical field]

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

[0002] Metal oxides such as tin oxide and indium oxide are used as spacers in the patterning of metal interconnects and in the patterning of fins in FinFETs, and indium tin oxide (ITO), a mixture of tin oxide and indium oxide, is often used to make transparent electrodes. In the above-mentioned semiconductor manufacturing process, when a metal oxide is microfabricated into a desired shape, there is a step of etching the metal oxide by plasma etching using an etching gas. In the etching process of this semiconductor manufacturing process, it is important to be able to selectively etch the etching target (metal oxide) that is the target of etching with the etching gas, compared with non-etching targets such as masks that are not the target of etching with the etching gas (i.e., etching selectivity). For example, Patent Documents 1 and 2 disclose techniques for etching metal oxides by plasma etching using an etching gas containing hydrogen bromide or hydrogen iodide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 506572, 2002 [Patent Document 2] Japanese Patent Publication No. 151375, 1994 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the techniques disclosed in Patent Documents 1 and 2 were sometimes unable to etch metal oxides with excellent etching selectivity. An object of the present invention is to provide a plasma etching method and a method for manufacturing a semiconductor device, which are capable of selectively etching an etching object containing at least one of an oxide of tin and indium compared to an etching object that is not to be etched. [Means for solving the problem]

[0005] In order to solve the above problems, one aspect of the present invention is as follows [1] to [9]. [1] An etching process comprising: contacting an etching gas containing an unsaturated compound having a fluorine atom and a bromine atom in a molecule with a member to be etched, the member having an etching object that is to be etched by the etching gas and a non-etching object that is not to be etched by the etching gas, in the presence of plasma; and performing etching while applying a bias power exceeding 0 W to a lower electrode supporting the member to be etched, thereby selectively etching the etching object compared to the non-etching object; The plasma etching method, wherein the object to be etched contains at least one of an oxide of tin and indium, and the object not to be etched contains at least one of a silicon-containing compound and a photoresist.

[0006] [2] The plasma etching method according to [1], wherein the etching gas is a mixed gas containing the unsaturated compound and an inert gas. [3] The plasma etching method according to [2], wherein the concentration of the unsaturated compound in the mixed gas is 1 volume % or more and 50 volume % or less. [4] The plasma etching method according to any one of [1] to [3], wherein the unsaturated compound is bromofluoroethylene.

[0007] [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.

[0008] [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. [7] The plasma etching method according to any one of [1] to [6], wherein the etching is carried out under a process pressure of 1 Pa or more and 10 Pa or less. [8] The plasma etching method according to any one of [1] to [7], wherein the etching is carried out while applying a bias power of 10 W or more and 1200 W or less to a lower electrode supporting the member to be etched.

[0009] [9] A method for manufacturing a semiconductor device, comprising the steps of: manufacturing a semiconductor device by using the plasma etching method according to any one of [1] to [8], the member to be etched is a semiconductor substrate having the etching object and the non-etching object, A method for manufacturing a semiconductor device, comprising the step of removing at least a portion of the etching object from the semiconductor substrate by etching. Effect of the Invention

[0010] According to the present invention, an object to be etched that contains an oxide of at least one of tin and indium can be selectively etched compared to an object not to be etched. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of an example of a plasma etching apparatus for explaining an embodiment of a plasma etching method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of the present invention will be described below. Note that this embodiment is merely an example of the present invention, and the present invention is not limited to this embodiment. In addition, various modifications and improvements can be made to this embodiment, and such modifications and improvements can also be included in the present invention.

[0013] The plasma etching method according to the present embodiment includes an etching step of contacting an etching gas containing an unsaturated compound having fluorine and bromine atoms in the molecule with an etched member having an etched object that is an object to be etched by the etching gas and a non-etched object that is not an object to be etched by the etching gas in the presence of plasma, and etching is performed while applying a bias power exceeding 0 W to a lower electrode supporting the etched member, thereby selectively etching the etched object compared to the non-etched object. The etched object contains at least one oxide of tin (Sn) and indium (In), and the non-etched object contains at least one of a silicon-containing compound and a photoresist.

[0014] When the etching gas is brought into contact with the member to be etched, the unsaturated compounds in the etching gas react with the oxides in the material to be etched, and the etching of the material to be etched proceeds. On the other hand, the material to be etched does not react with the unsaturated compounds, and therefore the etching of the material to be etched proceeds little. Therefore, according to the plasma etching method of this embodiment, the material to be etched can be selectively etched compared to the material to be etched.

[0015] For example, etching can be performed so that the ratio of the etching rate of the object to be etched to the etching rate of the object not to be etched is 2 or more, and from the viewpoint of controlling the etching more stably, etching can be performed so that the ratio of the etching rates is 4 or more.

[0016] In the present invention, etching means removing a part or all of the etching object of the etched member to process the etched member into a predetermined shape (e.g., a three-dimensional shape) (e.g., processing the film-like etching object made of the oxide of the etched member to a predetermined film thickness), and also means removing residues and deposits made of the etching object from the etched member to clean it.

[0017] The plasma etching method according to the present embodiment can be used in the manufacture of semiconductor devices. That is, the method for manufacturing a semiconductor device according to the present embodiment is a method for manufacturing a semiconductor device using the plasma etching method according to the present embodiment, in which the member to be etched is a semiconductor substrate having an object to be etched and an object not to be etched, and the method includes a process for removing at least a part of the object to be etched from the semiconductor substrate by etching.

[0018] Therefore, by applying the plasma etching method according to this embodiment to a manufacturing process for semiconductor devices, it becomes possible, for example, to transfer a pattern formed in a photoresist onto a metal oxide film, or to remove a metal oxide film or residue present on a film of an object not to be etched.

[0019] The plasma etching method and the semiconductor device manufacturing method according to the present embodiment will be described in further detail below. The etching of this 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 may be used. For example, high-frequency discharge plasma such as inductively coupled plasma (ICP) and capacitively coupled plasma (CCP), and microwave discharge plasma such as electron cyclotron resonance plasma (ECRP) may be used.

[0020] The plasma etching apparatus shown in FIG. 1, which will be described in detail later, uses an ICP as a plasma source. In the plasma etching method according to the present embodiment, the plasma generation chamber may be separated from the chamber in which the member to be etched is placed, and plasma may be generated in the plasma generation chamber (that is, remote plasma may be used).

[0021] [Etching gas] The etching gas used in the plasma etching method according to the present embodiment is a gas containing an unsaturated compound having fluorine and bromine atoms in the molecule. The type of the unsaturated compound is not particularly limited as long as it has fluorine and bromine atoms in the molecule, but bromofluoroethylene is preferred because it is easily available and easy to handle.

[0022] Specific examples of bromofluoroethylene include 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.

[0023] Among these, bromofluoroethylene having one bromine atom is more preferable from the viewpoint of easy vaporization at normal temperature and normal pressure. Examples of bromofluoroethylene having one bromine atom include 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, and (Z)-1-bromo-2-fluoroethylene. The unsaturated compounds such as bromofluoroethylene may be used alone or in combination of two or more kinds.

[0024] The etching gas may be a gas formed only of an unsaturated compound such as bromofluoroethylene, or may be a mixed gas containing an unsaturated compound such as bromofluoroethylene and an inert gas, or may be a mixed gas containing an unsaturated compound such as bromofluoroethylene, an oxygen atom-containing gas, and an inert gas. The type of inert gas is not particularly limited, but examples thereof include nitrogen gas (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe). These inert gases may be used alone or in combination of two or more.

[0025] The oxygen atom-containing gas is not particularly limited as long as it is a compound that has an oxygen atom in its molecule and is a gas under standard conditions, and examples thereof include oxygen gas (O2), ozone (O3), nitrous oxide (N2O), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), sulfur trioxide (SO3), etc. By adding an oxygen atom-containing gas, it may be possible to control the film thickness of the polymer deposited on the non-etching object to any thickness.

[0026] The concentration of the unsaturated compound in the mixed gas is not particularly limited and can be more than 0 volume % and less than 100 volume %, but may be adjusted in consideration of the ignitability of the plasma, etc. In order to make the ignitability of the plasma more sufficient, the concentration of the unsaturated compound in the mixed gas is preferably 1 volume % or more and 50 volume % or less, more preferably 1 volume % or more and 40 volume % or less, even more preferably 3 volume % or more and 30 volume % or less, and particularly preferably 5 volume % or more and 30 volume % or less.

[0027] In addition, if the concentration of the unsaturated compound in the mixed gas is within the above-mentioned numerical range, a high etching selectivity is easily achieved, for example, the etching selectivity is easily set to 3 or more. Here, the etching selectivity is a value calculated by dividing the etching rate of the object to be etched by the etching rate of the object not to be etched.

[0028] The amount of etching gas used in the plasma etching method according to this embodiment, for example the total flow rate of the etching gas into a chamber in which plasma etching is performed in a plasma etching apparatus, may be adjusted according to the internal volume, exhaust capacity, process pressure, etc. of the chamber.

[0029] [Etching process conditions] Although the pressure conditions for the etching step in the plasma etching method according to this embodiment are not particularly limited, the plasma etching is preferably performed under a process pressure of 0.2 Pa to 30 Pa, more preferably under a process pressure of 1 Pa to 15 Pa, even more preferably under a process pressure of 1 Pa to 10 Pa, and particularly preferably under a process pressure of 2 Pa to 8 Pa. Within the above pressure range, the composition of the plasma is stable, making it easy to improve the reproducibility of the etching.

[0030] In a plasma etching apparatus, for example, a high-frequency source power is applied to an RF (radio frequency) coil to form an electric field and a magnetic field, thereby converting an etching gas into plasma and generating plasma. The magnitude of the source power is not particularly limited, but is preferably more than 0 W and not more than 3000 W, more preferably 100 W or more and not more than 1500 W, and even more preferably 200 W or more and not more than 1000 W. If the magnitude of the source power is within the above numerical range, the etching rate of the object to be etched is sufficiently high, and the etching selectivity ratio is sufficiently high.

[0031] The temperature conditions of the etching process in the plasma etching method according to the present embodiment are not particularly limited, but the temperature of the member to be etched (e.g., a semiconductor substrate) during plasma etching is preferably -20°C or more and 250°C or less, more preferably 0°C or more and 100°C or less, and even more preferably 20°C or more and 70°C or less. If the temperature of the member to be etched during plasma etching is within the above numerical range, for example, the deterioration of the resist film formed on the semiconductor substrate, deformation due to sublimation, etc. is suppressed, so that plasma etching can be performed with high patterning accuracy. Here, the temperature in the above temperature conditions is the temperature of the member to be etched, but the temperature of a stage supporting the member to be etched installed in the chamber of the plasma etching device can also be used.

[0032] During plasma etching, it is necessary to apply a bias power exceeding 0 W to the lower electrode supporting the member to be etched. In order to sufficiently increase the etching selectivity ratio of the object to be etched to the object not to be etched, the bias power applied to the lower electrode is preferably 10 W or more and 1200 W or less, more preferably 20 W or more and 800 W or less, even more preferably 20 W or more and 500 W or less, and particularly preferably 30 W or more and 300 W or less.

[0033] [Material to be etched] The member to be etched by the plasma etching method according to the present embodiment has an object to be etched and an object not to be etched, but may have a portion formed of an object to be etched and a portion formed of an object not to be etched, or may be a member 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.

[0034] [Object to be etched] The object to be etched contains at least one oxide of tin and indium, i.e., tin oxide, indium oxide, or indium tin oxide. Examples of tin oxide include SnO and SnO2, and examples of indium oxide include In2O3. The object to be etched may be formed only of the oxide, may have a portion formed only of the oxide and a portion formed of another material, or may be formed of a mixture of the oxide and another material.

[0035] Furthermore, the object to be etched may not only be a material consisting essentially of a specific metal (tin, indium) or its compound, but may also be a material containing 10 mol % or more of a specific metal or its compound, more preferably 20 mol % or more, and even more preferably 30 mol % or more. For example, the plasma etching method according to this embodiment can be applied to alloys with other metals, materials containing impurities, oxides, nitrides, oxynitrides, oxyfluorides, etc.

[0036] The oxide here refers to a compound containing a metal and oxygen. The oxide is, for example, M x O y(M is tin or indium, and x and y are any natural numbers), and is a compound containing at least 10 mol % or more of a metal, more preferably 15 mol % or more, and further preferably 20 mol % or more. Specific examples include compounds represented by MO, M2O3, MO2, MO3, M3O4, and M2O5.

[0037] The term "nitride" as used herein refers to a compound containing a metal and nitrogen. a N b (M is tin or indium, a and b are any natural numbers), and is a compound containing at least 10 mol % or more of metal, more preferably 15 mol % or more, and further preferably 20 mol % or more. 16 Examples include compounds represented by N2.

[0038] Furthermore, the term "oxynitride" as used herein refers to a compound having a metal, oxygen, and nitrogen. The oxynitride is, for example, M c N d O e (M is tin or indium, and c, d, and e are any natural numbers), and the compound contains at least 10 mol % or more of a metal, more preferably 15 mol % or more, and further preferably 20 mol % or more.

[0039] Furthermore, the term "acid fluoride" as used herein refers to a compound having a metal, oxygen, and fluorine. The acid fluoride is, for example, M f F g O h (M is tin or indium, and f, g, and h are any natural numbers), and is a compound containing at least 10 mol % or more of a metal, more preferably 15 mol % or more, and even more preferably 20 mol % or more. The shape of the material containing the specific metal is not particularly limited, and may be in the form of particles, lumps, film, foil, or powder.

[0040] [Non-etching objects] 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 unsaturated compound, or reacts very slowly with the unsaturated compound, so that etching hardly progresses even when the non-etching object is etched by the plasma etching method according to the present embodiment. Alternatively, the vapor pressure of the reaction product between the unsaturated compound and the non-etching object is low, so that etching hardly progresses.

[0041] The type of silicon-containing compound is not particularly limited as long as it is a compound having a silicon atom, and examples thereof include compounds having at least one of an oxygen atom and a nitrogen atom and a silicon atom, polysilicon, and amorphous silicon (Si). Examples of compounds having at least one of an oxygen atom and a nitrogen atom and a silicon atom include silicon oxide, silicon nitride, and silicon oxynitride.

[0042] Silicon oxide refers to a compound having silicon and oxygen in any ratio, and an example thereof is silicon dioxide (SiO2). The purity of silicon oxide 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.

[0043] 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. Silicon oxynitride refers to a compound having silicon, oxygen, and nitrogen in any ratio, and an example thereof is Si2N2O.

[0044] Photoresist refers to a photosensitive composition whose physical properties, including solubility, change when exposed to light or an electron beam. Examples of photoresists include photoresists for g-line, h-line, i-line, KrF, ArF, F2, and EUV. The composition of the photoresist is not particularly limited as long as it is one that is generally used in the semiconductor manufacturing process, and examples of the composition include a composition containing a polymer synthesized from at least one monomer selected from linear olefin, cyclic olefin, styrene, vinylphenol, acrylic acid, methacrylate, epoxy, melamine, and glycol.

[0045] In addition, the non-etching object can be used as a resist or mask for suppressing etching of the etching object by the etching gas. Therefore, the plasma etching method according to the present embodiment can be used in a method of processing the etching object into a predetermined shape (for example, processing a film-like etching object of a member to be etched into a predetermined film thickness) by using the patterned non-etching object as a resist or mask, and can be suitably used for manufacturing semiconductor elements. In addition, since the non-etching object is hardly etched, it is possible to suppress etching of the parts of the semiconductor element that should not be etched, and it is possible to prevent the characteristics of the semiconductor element from being lost due to etching.

[0046] The non-etched objects remaining after patterning can be removed by removal methods commonly used in semiconductor device manufacturing processes, such as ashing using oxidizing gases such as oxygen plasma or ozone, or dissolving and removing using chemicals such as APM (a mixture of ammonia water and hydrogen peroxide), SPM (a mixture of sulfuric acid and hydrogen peroxide), or organic solvents.

[0047] Hereinafter, an example of plasma etching of a tin oxide film, an amorphous silicon film, a silicon oxide film, a silicon nitride film, and a photoresist film formed on the surface of a substrate (corresponding to a member to be etched) using the plasma etching apparatus shown in Fig. 1 will be described. The plasma etching apparatus in Fig. 1 uses an ICP as a plasma source. First, the plasma etching apparatus in Fig. 1 will be described.

[0048] The plasma etching apparatus of FIG. 1 includes a chamber 1 in which plasma etching is performed, a lower electrode 2 that supports a substrate 20 to be plasma etched inside the chamber 1, a bias power power supply (not shown) that applies bias power to the lower electrode 2, an RF coil 15 that forms an electric field and a magnetic field inside the chamber 1 for turning an etching gas into plasma, a source power power supply (not shown) that applies high-frequency source power 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 captures plasma light emission generated as plasma is generated, and a spectrometer 17 that disperses the plasma light emission captured by the sensor 16 to monitor changes in the plasma light emission over time.

[0049] The substrate 20 has a surface on which a tin oxide film, an amorphous silicon film, a silicon oxide film, a silicon nitride film, and a photoresist film are formed. For example, a CCD (Charge-Coupled Device) image sensor can be used as the sensor 16. However, instead of providing the sensor 16 and the spectroscope 17, a sight hole may be provided in the chamber 1, and the inside of the chamber 1 may be visually observed through the sight hole to confirm the change in plasma emission over time.

[0050] The chamber 1 also includes an etching gas supply unit that supplies an etching gas to the inside of the chamber 1. The etching gas supply unit includes an unsaturated compound gas supply unit 3 that supplies an unsaturated compound gas, an inert gas supply unit 4 that supplies an inert gas, an etching gas supply pipe 11 that connects the unsaturated compound gas supply unit 3 and the chamber 1, and an inert gas supply pipe 12 that connects the inert gas supply unit 4 to an intermediate portion of the etching gas supply pipe 11.

[0051] When an unsaturated compound gas is supplied to the chamber 1 as an etching gas, the unsaturated compound gas is sent from the unsaturated compound gas supply section 3 to the etching gas supply pipe 11, so that the unsaturated compound gas is supplied to the chamber 1 via the etching gas supply pipe 11.

[0052] 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. For example, -5 The pressure is preferably from 1 Pa to less than 100 kPa, more preferably from 1 Pa to 50 kPa, and even more preferably from 1 Pa to 20 kPa.

[0053] When a mixed gas of an unsaturated compound gas and an inert gas is supplied as the etching gas, the unsaturated compound gas is fed from the unsaturated compound gas supply unit 3 to the etching gas supply pipe 11, and the inert gas is fed from the inert gas supply unit 4 to the etching gas supply pipe 11 via the inert gas supply pipe 12. As a result, the unsaturated compound gas and the inert gas are mixed in the middle of the etching gas supply pipe 11 to become a mixed gas, and this mixed gas is supplied to the chamber 1 via the etching gas supply pipe 11.

[0054] When plasma etching is performed using such a plasma etching apparatus, a substrate 20 is placed on the lower electrode 2 disposed inside the chamber 1, and the pressure inside the chamber 1 is reduced to, for example, 1 Pa or more and 10 Pa or less by the vacuum pump 13, and then an etching gas is supplied into the chamber 1 by the etching gas supply unit. When a high-frequency (e.g., 13.56 MHz) source power is applied to the RF coil 15, an electric field and a magnetic field are formed inside the chamber 1, accelerating electrons, and these accelerated electrons collide with unsaturated compound molecules in the etching gas to generate new ions and electrons, which results in a discharge and the formation of plasma. The generation of plasma can be confirmed using a sensor 16 and a spectrometer 17.

[0055] When the plasma is generated, the tin oxide film formed on the surface of the substrate 20 is etched. The amount of the etching gas supplied to the chamber 1 and 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 inert gas with mass flow controllers (not shown) installed in the etching gas supply pipe 11 and the inert gas supply pipe 12, respectively.

[0056] From the viewpoint of uniformly etching the surface of the substrate 20, the pressure of the etching gas supplied into the chamber 1 is preferably from 0.01 Pa to 500 Pa, more preferably from 0.1 Pa to 100 Pa, even more preferably from 1 Pa to 30 Pa, and particularly preferably from 1 Pa to 10 Pa. If the pressure of the etching gas in the chamber 1 is within the above range, the object to be etched is likely to be etched at a sufficient rate, and the ratio of the etching rate to the object not to be etched, i.e., the etching selectivity, is likely to be high. EXAMPLES

[0057] The present invention will be described more specifically below with reference to examples and comparative examples. Example 1 Plasma etching was performed on five types of substrates using an ICP etching apparatus RIE-200iP manufactured by Samco Inc., which has a configuration similar to that of the plasma etching apparatus in Fig. 1. The first substrate was a 2-inch square silicon substrate with a 300-nm-thick tin oxide (SnO2) film formed on it (manufactured by Seiren KST Co., Ltd.). The second substrate was a 2-inch square silicon substrate with an 800-nm-thick amorphous silicon film formed on it (manufactured by Seiren KST Co., Ltd.).

[0058] The third substrate is a 2-inch square silicon substrate with a 600-nm-thick silicon oxide (SiO2) film formed thereon (manufactured by Seiren KST Co., Ltd.). The fourth substrate is a 2-inch square silicon substrate with an 800-nm-thick silicon nitride (Si3N4) film formed thereon (manufactured by Seiren KST Co., Ltd.).

[0059] The fifth substrate is a square silicon substrate with sides of 2 inches on which a photoresist film with a thickness of 600 nm is formed. This photoresist film is formed by applying i-line photoresist TSCR (registered trademark) manufactured by Tokyo Ohka Kogyo Co., Ltd. onto the silicon substrate, exposing it to light, and curing it. The tin oxide film is the object to be etched, and the amorphous silicon film, the silicon oxide film, the silicon nitride film, and the photoresist film are the objects not to be etched.

[0060] The internal volume of the chamber is 46,000 cm 3 The etching gas was a mixture of bromotrifluoroethylene gas and argon gas. The flow rate of bromotrifluoroethylene gas was set to 10 sccm and the flow rate of argon to 90 sccm, so that the concentration of bromotrifluoroethylene in the etching gas was adjusted to 10 volume percent. Here, sccm is the volumetric flow rate (cm) per minute standardized under the conditions of 0°C and 1 atm. 3 ).

[0061] Plasma etching was performed with the process pressure inside the chamber set to 3 Pa, source power set to 600 W, bias power set to 200 W, and substrate temperature set to 20°C, while constantly monitoring the flow rate of bromotrifluoroethylene gas, flow rate of argon gas, process pressure, source power, and bias power, and checking that there was no difference between the set value and the actual value. The results are shown in Table 1.

[0062] Table 1 shows the etching rates of the object to be etched and the object not to be etched, as well as the ratio of the etching rate of the object to be etched to the etching rate of the non-etched object ([etching rate of the object not to be etched] / [etching rate of the object to be etched], hereafter referred to as the "etching selectivity").

[0063] [Table 1]

[0064] The film thickness of the etching target and the non-etching target was measured using a reflectance spectroscopic film thickness meter F20 manufactured by Filmetrics. 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 film thickness measurement conditions were as follows.

[0065] The measurement was performed in air at a temperature of 25°C. The measurement wavelength range was a range where the Goodness of fit was 0.9 or more, and specifically, the following wavelength ranges were used as a guide: tin oxide: 350-700 nm, amorphous silicon: 500-1200 nm, silicon oxide: 300-1100 nm, silicon nitride: 500-1500 nm, and photoresist: 400-1000 nm.

[0066] (Examples 2 to 15) Plasma etching was performed in the same manner as in Example 1, except that the etching conditions were as shown in Tables 1 and 2, and the etching rates and etching selectivity ratios of the objects to be etched and the objects not to be etched were measured. The results are shown in Tables 1 and 2.

[0067] [Table 2]

[0068] (Comparative Examples 1 to 3) Except for changing the bromotrifluoroethylene in the etching gas to sulfur hexafluoride (SF6) gas, hexafluorobutadiene (C4F6) gas, and hydrogen bromide (HBr) gas, plasma etching was performed in the same manner as in Example 1, and the etching rates and etching selectivities of the objects to be etched and the objects not to be etched were measured. The results are shown in Table 2.

[0069] Comparative Example 4 Plasma etching was carried out in the same manner as in Example 1, except that the bias power was set to 0 W, and the etching rates and etching selectivity ratios of the object to be etched and the object not to be etched were measured. The results are shown in Table 2.

[0070] From the results of Examples 1 to 3, it is clear that by using bromotrifluoroethylene as an etching gas, tin oxide, indium oxide, and indium tin oxide can be selectively etched relative to non-etching objects. From the results of Examples 1, 4, and 5, it can be seen that the higher the stage temperature, the higher the etching rate of tin oxide. On the other hand, it can be seen that the lower the stage temperature, the more the etching of the non-etching object is suppressed, and therefore the etching selectivity becomes higher. From the results of Examples 1, 6, and 7, it can be seen that the etching rate of tin oxide increases as the source power is lowered, suggesting that the higher the source power, the more chemical species that inhibit etching are generated.

[0071] From the results of Examples 1 and 8 and Comparative Example 4, it can be seen that lowering the bias power suppresses the etching of non-etching objects, thereby increasing the etching selectivity. In particular, since polymers generated by polymerization of bromotrifluoroethylene were deposited on the amorphous silicon film and the photoresist film, the etching of the amorphous silicon film and the photoresist film was suppressed. Therefore, it is considered that a particularly high etching selectivity was exhibited for the amorphous silicon and the photoresist with respect to tin oxide.

[0072] From the results of Examples 1 and 9, it can be seen that increasing the pressure in the chamber has little effect on the etching rate of tin oxide, whereas the etching rate of non-etching objects decreases, resulting in an improvement in the etching selectivity. The results of Examples 10 and 11 show that the etching rate of tin oxide increases as the ratio of bromofluoroethylene in the etching gas increases.

[0073] The results of Examples 12 to 15 show that selective etching of tin oxide can be carried out without problems even when 1-bromo-1-fluoroethylene, 1-bromo-2,2-difluoroethylene, (E)-1-bromo-2-fluoroethylene, or (Z)-1-bromo-2-fluoroethylene is used as the etching gas.

[0074] It can be seen from the results of Comparative Examples 1 to 3 that when sulfur hexafluoride, hexafluorobutadiene, or hydrogen bromide is used as the etching gas, the etching rate and etching selectivity of tin oxide tend to decrease. [Explanation of symbols]

[0075] 1. Chamber 2. Bottom electrode 3. Unsaturated compound gas supply section 4. Inert gas supply section 11 Etching gas supply pipe 12 Inert gas supply piping 13 Vacuum pump 14. Pressure gauge 15. RF coil 16. Sensor 17...Spectrometer 20... Substrate

Claims

1. the etching method comprises an etching step of contacting an etching gas containing an unsaturated compound having a fluorine atom and a bromine atom in a molecule with a member to be etched, the member having an etching object that is a target for etching by the etching gas and a non-etching object that is not a target for etching by the etching gas, in the presence of plasma, and performing etching while applying a bias power exceeding 0 W to a lower electrode supporting the member to be etched, thereby selectively etching the etching object compared to the non-etching object; The plasma etching method, wherein the object to be etched contains at least one of an oxide of tin and indium, and the object not to be etched contains at least one of a silicon-containing compound and a photoresist.

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

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

4. 4. The plasma etching method according to claim 1, 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. 6. The plasma etching method according to claim 1, 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 is amorphous silicon.

7. 7. The plasma etching method according to claim 1, wherein the etching is carried out under a process pressure of 1 Pa or more and 10 Pa or less.

8. 8. The plasma etching method according to claim 1, 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 member to be etched.

9. A method for manufacturing a semiconductor device using the plasma etching method according to any one of claims 1 to 8, comprising the steps of: the member to be etched is a semiconductor substrate having the etching object and the non-etching object, A method for manufacturing a semiconductor device, comprising the step of removing at least a portion of the etching object from the semiconductor substrate by etching.

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