Etching method

Abstract

Provided is an etching method wherein an etching object can be selectively etched in comparison to a non-etching object. This etching method comprises an etching step in which etching is performed by bringing an etching gas into contact with a member for etching in the presence of a plasma, said etching gas including an acid fluoride and a saturated fluorocarbon, and said member for etching having an etching object, which is the object of etching by the etching gas, and a non-etching object, which is not the object of etching by the etching gas, and the etching object is selectively etched in comparison to the non-etching object. The etching object has a silicon-containing material, and the non-etching object has a carbon-containing material.

Description

Etching Method

[0001] The present disclosure relates to etching methods.

[0002] Semiconductor manufacturing processes include a process of etching an etching target, which is a target for etching with an etching gas, by plasma etching using an etching gas to micromachine the etching target into a desired shape. In this etching, it is important to be able to selectively etch etching targets such as silicon-containing materials (i.e., etching selectivity) compared to non-etching targets such as carbon-containing materials (e.g., photoresist, carbon masks) that are not targets for etching with the etching gas. For example, Patent Document 1 discloses a technique for etching silicon-containing materials using an etching gas containing carbonyl fluoride.

[0003] Japanese Patent Publication No. 6546889

[0004] However, the technique disclosed in Patent Document 1 sometimes fails to etch silicon-containing materials with excellent etching selectivity. An object of the present disclosure is to provide an etching method that can selectively etch an etching target having a silicon-containing material compared to an etching target having a carbon-containing material.

[0005] In order to solve the above problems, one aspect of the present disclosure is as follows: [1] to [6]: [1] An etching method comprising an etching step of bringing an etching gas containing an acid fluoride and a saturated fluorocarbon into contact with a member to be etched, the member having an etching target that is to be etched by the etching gas and a non-etching target that is not to be etched by the etching gas, in the presence of plasma, to selectively etch the etching target compared to the non-etching target, wherein the etching target comprises a silicon-containing material and the non-etching target comprises a carbon-containing material.

[0006] [2] The etching method according to [1], wherein the carbon-containing material contains 20 mass % or more and 100 mass % or less of carbon. [3] The etching method according to [1] or [2], wherein the silicon-containing material contains silicon and germanium, and the total content of the silicon and the germanium contained in the silicon-containing material is 30 mol % or more.

[0007] [4] The etching method according to [1] or [2], wherein the silicon-containing material is at least one of silicon oxide, silicon nitride, polysilicon, and silicon germanium. [5] The etching method according to any one of [1] to [4], wherein an etching selectivity, which is the ratio of the etching rate of the silicon-containing material to the etching rate of the carbon-containing material, is 5 or more. [6] The etching method according to any one of [1] to [5], wherein the acid fluoride is at least one of carbonyl fluoride, oxalyl fluoride, and trifluoroacetyl fluoride.

[0008] According to the etching method of the present disclosure, an etching target having a silicon-containing material can be selectively etched compared to an etching target having a carbon-containing material.

[0009] 1 is a schematic diagram of an example of a plasma etching apparatus for explaining an embodiment of an etching method according to the present disclosure.

[0010] An embodiment of the present disclosure will be described below. Note that this embodiment shows an example of the present disclosure, and the present disclosure is not limited to this embodiment. Furthermore, various modifications or improvements can be made to this embodiment, and such modifications or improvements may also be included in the present disclosure.

[0011] The etching method according to this embodiment includes an etching step in which an etching gas containing an acid fluoride and a saturated fluorocarbon is brought into contact with an etched 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 to selectively etch the etching object compared to the non-etching object, wherein the etching object comprises a silicon-containing material and the non-etching object comprises a carbon-containing material.

[0012] When the etching gas is brought into contact with a material to be etched, the acid fluoride in the etching gas reacts with the silicon in the material to be etched, thereby progressing the etching of the material to be etched. On the other hand, the material to be etched reacts with oxygen atoms and oxygen-containing compounds (active oxygen molecules, ozone, etc.) produced by the decomposition of the acid fluoride, thereby progressing the etching of the material to be etched.

[0013] However, when an acid fluoride and a saturated fluorocarbon coexist in an etching gas, carbon is supplied from the saturated fluorocarbon, which captures the oxygen-containing compound and suppresses the etching of the carbon-containing material, so that etching of the non-etching object hardly progresses. Therefore, according to the etching method of this embodiment, it is possible to selectively etch an etching object having a silicon-containing material compared to a non-etching object having a carbon-containing material.

[0014] For example, etching can be performed so that the etching selectivity, which is the ratio of the etching rate of the silicon-containing material to the etching rate of the carbon-containing material ([etching rate of silicon-containing material] / [etching rate of carbon-containing material]), is 5 or more. Furthermore, from the viewpoint of more stable control of etching, etching can be performed so that the etching selectivity is 10 or more depending on the etching conditions.

[0015] In this disclosure, etching means removing part or all of the etching target material of the etched member to process the etched member into a predetermined shape (e.g., a three-dimensional shape) (e.g., processing a film-like etching target material made of a silicon-containing material of the etched member to a predetermined film thickness), and also means removing residues and deposits made of the etching target material from the etched member to clean it.

[0016] The 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 etching method according to the present embodiment, in which the member to be etched is a semiconductor substrate having an etching target and a non-etching target, and the method includes removing at least a part of the etching target from the semiconductor substrate by etching.

[0017] Therefore, by applying the etching method according to this embodiment to the manufacturing process of a semiconductor device, it becomes possible to, for example, transfer a pattern formed in a photoresist to a film made of a silicon-containing material, or to remove a film or residue made of a silicon-containing material present on a film of an object not to be etched.

[0018] The etching method according to this embodiment will be described in further detail below. The etching in the etching method according to this embodiment is plasma etching. The type of plasma source used in plasma etching is not particularly limited, and a commercially available device may be used. Examples of plasma sources include 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).

[0019] [Etching Gas] The etching gas used in the etching method according to this embodiment contains an acid fluoride and a saturated fluorocarbon, but may contain components other than the acid fluoride and the saturated fluorocarbon, and may further contain at least one of a rare gas and an additive gas.

[0020] Examples of rare gases include helium (He), neon (Ne), argon (Ar), xenon (Xe), and krypton (Kr). Examples of additive gases include nitrogen gas (N), hydrogen gas (H), oxygen gas (O), and halogenated hydrocarbon gas (C). m H n X o , X is any of Cl, Br, and I, and m, n, and o are coefficients, provided that n+o≦2m+2), hydrogen fluoride (HF), hydrogen chloride (HCl), and hydrogen bromide (HBr).

[0021] The molar ratio of acid fluoride to saturated fluorocarbon in the etching gas ([molar amount of acid fluoride] / [molar amount of saturated fluorocarbon]) is preferably 0.01 or more and 4 or less. The lower limit of this numerical range is more preferably 0.05, and even more preferably 0.1. The upper limit of this numerical range is more preferably 3, and even more preferably 2. When the molar ratio of acid fluoride to saturated fluorocarbon in the etching gas is within the above numerical range, the etching target can be etched more selectively than the non-etching target.

[0022] The preferred range of the molar ratio of acid fluoride to saturated fluorocarbon in the etching gas may be any combination of the above upper and lower limits. For example, the molar ratio of acid fluoride to saturated fluorocarbon in the etching gas is preferably 0.05 to 3, more preferably 0.1 to 2.

[0023] [Rare Gas Concentration] When a rare gas is contained in the etching gas, plasma may be easily generated. The concentration of the rare gas in the etching gas is preferably more than 0 vol% and not more than 99 vol%, more preferably 5 vol% to 90 vol%, and even more preferably 10 vol% to 85 vol%. If the concentration of the rare gas contained in the etching gas is within the above range, uniform plasma can be easily generated stably, making it easier to uniformly etch the object to be etched.

[0024] [Concentration of Additive Gas] Adding an additive gas to the etching gas can have various effects, depending on the type of additive gas, such as increasing the etching rate of the material to be etched, suppressing the etching rate of the material not to be etched, forming a protective film derived from the etching gas on the material to be etched, and removing deposits formed on the material to be etched.

[0025] For example, adding a halogenated hydrocarbon to an etching gas may suppress etching of non-etched objects. Also, adding a hydrogen halide to an etching gas may improve the etching selectivity. Furthermore, adding oxygen gas or nitrogen gas may facilitate the removal of deposits formed on the etched material. The optimum concentration of the additive gas in the etching gas varies depending on the desired effect, but is preferably, for example, more than 0% by volume and not more than 99% by volume, more preferably 2% by volume or more and not more than 60% by volume, and even more preferably 5% by volume or more and not more than 50% by volume.

[0026] [Acid Fluoride] An acid fluoride is a compound having a functional group *-C(=O)F in the molecule. Here, "*" means any atom or atomic group. The number of carbon atoms in the acid fluoride is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less.

[0027] Examples of acid fluorides include carbonyl fluoride (COF), oxalyl fluoride (COF), trifluoroacetyl fluoride (CFCOF), formyl fluoride, carbonyl chloride fluoride, acetyl fluoride, 2,2,3,3,3-pentafluoropropanoyl fluoride, 2,2,3,3,4,4,4-heptafluorobutanoyl fluoride, 2,2,3,3,4,4,5,5,5-nonafluoropentanoyl fluoride, 2,2,3,4,4,4-hexafluoro-3-(trifluoromethyl)butanoyl fluoride, and 3,3,3-trifluoro-2,2-bis(trifluoromethyl)propanoyl fluoride. Use of any of these acid fluorides allows for more selective etching of an etched object compared to a non-etched object.

[0028] Among these acid fluorides, carbonyl fluoride, oxalyl fluoride, and trifluoroacetyl fluoride are preferred from the viewpoint of easy availability, and carbonyl fluoride is more preferred. The acid fluorides may be used alone or in combination of two or more. That is, the acid fluoride contained in the etching gas may be at least one of carbonyl fluoride, oxalyl fluoride, and trifluoroacetyl fluoride.

[0029] [Saturated Fluorocarbon] A fluorocarbon is a compound having a fluorine atom and a carbon atom in the molecule (except for acid fluorides). In particular, the fluorocarbon used in the etching gas must be a saturated fluorocarbon having no double or triple bonds.

[0030] From the viewpoint of having a low boiling point and being easy to handle as a gas, the saturated fluorocarbon preferably has a high vapor pressure, for example, a saturated fluorocarbon having a boiling point of 45° C. or less at atmospheric pressure is preferred, and a saturated fluorocarbon having a boiling point of 30° C. or less at atmospheric pressure is more preferred. Furthermore, the saturated fluorocarbon may contain elements other than fluorine atoms (F) and carbon atoms (C), such as bromine atoms (Br), iodine atoms (I), hydrogen atoms (H), nitrogen atoms (N), oxygen atoms (O), silicon atoms (Si), sulfur atoms (S), phosphorus atoms (P), etc.

[0031] Examples of saturated fluorocarbons include tetrafluoromethane (CF), trifluoromethane (CHF), difluoromethane (CHF), fluoromethane (CHF), dibromodifluoromethane (CBrF), trifluoroiodomethane (CFI), hexafluoroethane (CF), octafluoropropane (CF), hexafluorocyclopropane (CF), octafluorocyclobutane (CF), and decafluoro-n-butane (CF 10 ), decafluoroisobutane (i-CF 10 ), tris(trifluoromethyl)amine ((F3C)3N), trifluoro(trifluoromethyl)silane ((F3C)SiF3), trifluoromethylsulfurpentafluoride ((F3C)SF5), p-trifluoromethylphosphorus difluoride ((F3C)PF2), etc. Use of any of these saturated fluorocarbons allows for more selective etching of the object to be etched compared to the object not to be etched.

[0032] [Etching Pressure Conditions] The etching pressure conditions in the etching method according to this embodiment are not particularly limited, but are preferably from 0.1 Pa to 3 kPa, more preferably from 0.5 Pa to 30 Pa, and even more preferably from 1 Pa to 10 Pa. If the pressure conditions are within the above ranges, it is easy to generate plasma stably.

[0033] For example, the member to be etched can be placed in a chamber and etched while passing an etching gas through the chamber, and the pressure inside the chamber during the passage of the etching gas can be set to 0.1 Pa or more and 3 kPa or less. The flow rate of the etching gas can be set appropriately so that the pressure inside the chamber is kept constant, depending on the size of the chamber and the capacity of the exhaust equipment for reducing the pressure inside the chamber.

[0034] [Temperature Conditions for Etching] The temperature conditions for etching in the etching method according to this embodiment are not particularly limited, but are 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.

[0035] If the temperature condition is within the above range, the acid fluoride can exist in a gaseous state and the etching rate of the silicon-containing material is likely to be higher. Here, the temperature in the temperature condition refers to the temperature of the member to be etched, but the temperature of a stage that supports the member to be etched and is installed in the chamber of the etching apparatus can also be used.

[0036] At temperatures of 150° C. or less, acid fluoride does not react much with non-etching targets having carbon-containing materials such as photoresist, spin-on carbon, and amorphous carbon, whether or not plasma is being generated. Therefore, when a member to be etched is etched by the etching method according to this embodiment, it is possible to selectively etch targets having silicon-containing materials such as polysilicon, silicon oxide, silicon nitride, and silicon germanium, without substantially etching the non-etching targets.

[0037] Therefore, the etching method according to this embodiment can be used in a method of processing an etching object having a silicon-containing material such as polysilicon, silicon oxide, silicon nitride, or silicon germanium into a predetermined shape by using a patterned non-etching object as a resist or a mask.

[0038] [Subject to be etched] The subject to be etched has a silicon-containing material containing silicon (Si), but may be formed only from the silicon-containing material, may have a portion formed only from the silicon-containing material and a portion formed from another material, or may be formed from a mixture of the silicon-containing material and another material.

[0039] The silicon-containing material refers to a compound consisting of only silicon and containing no other elements, or a compound containing silicon and other elements. Examples of silicon-containing materials include polysilicon (Poly-Si), silicon oxide (SiO x , x is an arbitrary coefficient, for example, SiO2), silicon nitride (Si c N d , c and d are arbitrary coefficients, for example, Si3N4), silicon oxynitride (SiO a N b , a and b are arbitrary coefficients), silicon germanium (Si y Ge 100-y and y is any number greater than 0 and less than 100). The silicon-containing material is preferably at least one of silicon oxide, silicon nitride, polysilicon, and silicon germanium. The silicon-containing material may be used alone or in combination of two or more.

[0040] The silicon content of the silicon-containing material 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. When the silicon-containing material contains silicon and germanium, the total content of silicon and germanium contained in the silicon-containing material is preferably 30 mol% or more. In addition, the shape of the object to be etched is not particularly limited, and may be, for example, a plate, foil, film, powder, or lump.

[0041] [Object to be etched] The object to be etched has a carbon-containing material containing carbon (C), but may be formed only from the carbon-containing material, may have a portion formed only from the carbon-containing material and a portion formed from another material, or may be formed from a mixture of the carbon-containing material and another material.

[0042] The carbon-containing material refers to a compound consisting of only carbon and containing no other elements, or a compound containing carbon and other elements. Examples of the carbon-containing material include amorphous carbon, spin-on carbon, carbon-doped silicon oxide (SiOC), photoresist, etc. One type of carbon-containing material may be used alone, or two or more types may be used in combination.

[0043] The carbon-doped silicon oxide is a compound containing carbon, oxygen, and silicon atoms, but may further contain atoms other than the carbon, oxygen, and silicon atoms, such as hydrogen atoms.

[0044] The carbon content of the carbon-containing material is not particularly limited, but is preferably 20% by mass or more and 100% by mass or less, more preferably 40% by mass or more and less than 100% by mass, and even more preferably 50% by mass or more and 95% by mass or less. That is, in the etching method according to this embodiment, the carbon-containing material preferably contains carbon at 20% by mass or more and 100% by mass or less.

[0045] Photoresist refers to a photosensitive composition whose physical properties, including solubility, change when exposed to light, an electron beam, or the like. Examples 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 commonly used in semiconductor manufacturing processes, but examples include compositions containing a polymer synthesized from at least one monomer selected from chain olefin, cyclic olefin, styrene, vinylphenol, acrylic acid, methacrylate, epoxy, melamine, and glycol.

[0046] Furthermore, the non-etching object can be used as a resist or mask to suppress etching of the etching object by the etching gas. Therefore, the etching method according to the present embodiment can be used in a method of processing the etching object into a predetermined shape (e.g., processing a film-like etching object of a member to be etched to a predetermined film thickness) by using the patterned non-etching object as a resist or mask, and is therefore suitable for use in the manufacture of semiconductor devices. Furthermore, since the non-etching object is hardly etched, etching of portions of the semiconductor device that should not be etched can be suppressed, and the loss of properties of the semiconductor device due to etching can be prevented.

[0047] The non-etched material remaining after patterning can be removed by a removal method commonly used in semiconductor device manufacturing processes, such as ashing using an oxidizing gas such as oxygen plasma or ozone, or dissolving and removing using chemicals such as APM (a mixture of aqueous ammonia and hydrogen peroxide), SPM (a mixture of sulfuric acid and hydrogen peroxide), or organic solvents.

[0048] The following describes an example of plasma etching of a polysilicon film, a silicon oxide film, a silicon nitride film, a silicon germanium film, a photoresist film, and a spin-on carbon film formed on the surface of a substrate (corresponding to a member to be etched) using a plasma etching apparatus. The etching apparatus shown in Figure 1 is a plasma etching apparatus that uses an ICP as a plasma source.

[0049] 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 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 to convert an etching gas into plasma, a source power supply (not shown) that applies high-frequency source power to the RF coil 15, a vacuum pump 21 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 emission generated as plasma is generated, and a spectroscope 17 that disperses the plasma emission captured by the sensor 16 to monitor changes in the plasma emission over time.

[0050] Substrate 20 has a surface on which a polysilicon film, a silicon oxide film, a silicon nitride film, a silicon germanium film, a photoresist film, and a spin-on carbon film are formed. A charge-coupled device (CCD) image sensor, for example, can be used as sensor 16. However, instead of providing sensor 16 and spectroscope 17, a viewing window may be provided in chamber 1, and the interior of chamber 1 may be visually observed through the viewing window to confirm the change in plasma light emission over time.

[0051] The chamber 1 also includes an etching gas supply unit that supplies an etching gas to the interior of the chamber 1. The etching gas supply unit includes an acid fluoride gas supply unit 3 that supplies an acid fluoride gas, an inert gas supply unit 4 that supplies an inert gas, a saturated fluorocarbon supply unit 5 that supplies a saturated fluorocarbon, an etching gas supply pipe 11 that connects the acid fluoride gas supply unit 3 to the chamber 1, 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, and a saturated fluorocarbon supply pipe 13 that connects the saturated fluorocarbon supply unit 5 to an intermediate portion of the etching gas supply pipe 11.

[0052] When acid fluoride gas and saturated fluorocarbon are supplied to the chamber 1 as etching gases, acid fluoride gas is fed from the acid fluoride gas supply unit 3 to the etching gas supply pipe 11, and saturated fluorocarbon is fed from the saturated fluorocarbon supply unit 5 to the etching gas supply pipe 11 via the saturated fluorocarbon supply pipe 13. As a result, the acid fluoride gas and saturated fluorocarbon are mixed in the middle of the etching gas supply pipe 11 to form a mixed gas, and this mixed gas is supplied to the chamber 1 via the etching gas supply pipe 11.

[0053] When a mixed gas of acid fluoride gas, saturated fluorocarbon, and inert gas is supplied as the etching gas, acid fluoride gas is fed from the acid fluoride gas supply unit 3 to the etching gas supply pipe 11, saturated fluorocarbon is fed from the saturated fluorocarbon supply unit 5 to the etching gas supply pipe 11 via the saturated fluorocarbon supply pipe 13, and further, 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. In this way, the acid fluoride gas, saturated fluorocarbon, and inert gas are mixed in the middle of the etching gas supply pipe 11 to form a mixed gas, and this mixed gas is supplied to the chamber 1 via the etching gas supply pipe 11.

[0054] 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 0.1 Pa to less than 100 kPa, more preferably from 0.1 Pa to 50 kPa, even more preferably from 0.3 Pa to 15 Pa, and particularly preferably from 1 Pa to 10 Pa.

[0055] 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 by a vacuum pump 21 to, for example, 1 Pa or more and 10 Pa or less, and then an etching gas is supplied into the chamber 1 by an 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. These accelerated electrons collide with unsaturated compound molecules in the etching gas, generating new ions and electrons, resulting in a discharge and forming plasma. The generation of plasma can be confirmed using a sensor 16 and a spectrometer 17.

[0056] When the plasma is generated, the etching target 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 acid fluoride in the etching gas (mixed gas) can be adjusted by controlling the flow rates of the acid fluoride, the inert gas, and the saturated fluorocarbon with mass flow controllers (not shown) installed in the etching gas supply pipe 11, the inert gas supply pipe 12, and the saturated fluorocarbon supply pipe 13, respectively.

[0057] The present disclosure will be described in more detail below with reference to examples and comparative examples. (Example 1) Seven types of substrates were prepared. That is, the first substrate was a square silicon substrate with sides of 1 cm and on which a polysilicon film with a thickness of 600 nm was formed (manufactured by Seiren KST Co., Ltd.). Note that in Table 2 described below, polysilicon may also be referred to as "PSi."

[0058] The second substrate was a 1 cm square silicon substrate with an 800 nm thick silicon oxide (SiO2) film formed thereon (manufactured by Seiren KST Co., Ltd.). The third substrate was a 1 cm square silicon substrate with an 800 nm thick silicon nitride (Si3N4) film formed thereon (manufactured by Seiren KST Co., Ltd.).

[0059] The fourth substrate was a 1 cm square silicon substrate with an 80 nm thick silicon germanium film formed on it (manufactured by Seiren KST Co., Ltd.). The molar ratio of silicon to germanium in this silicon germanium ([Si molar amount]:[Ge molar amount]) was 20:80. In Table 2 described below, the polysilicon of the fourth substrate is referred to as "Si20Ge80."

[0060] The fifth substrate was a 1 cm square silicon substrate with an 80 nm thick silicon germanium film formed on it (manufactured by Seiren KST Co., Ltd.). The molar ratio of silicon to germanium in this silicon germanium ([Si molar amount]:[Ge molar amount]) was 95:5. In Table 2 described below, the polysilicon of the fifth substrate is referred to as "Si95Ge5."

[0061] The sixth substrate was a square silicon substrate with sides measuring 1 cm and on which a photoresist film with a thickness of 600 nm was formed. This photoresist film was formed by applying i-line photoresist TSCR (trade name) manufactured by Tokyo Ohka Kogyo Co., Ltd. to the silicon substrate, exposing it to light, and curing it. The carbon content of the i-line photoresist TSCR (trade name) was 67 mass %. In Table 2 described below, photoresist may also be abbreviated as "PR."

[0062] The seventh substrate was a square silicon substrate with sides of 1 cm and a 600 nm thick spin-on carbon film formed on it (manufactured by Seiren KST Co., Ltd.). This spin-on carbon film was formed by depositing spin-on carbon ODL-50 manufactured by Shin-Etsu Chemical Co., Ltd. on the silicon substrate. The carbon content of the spin-on carbon ODL-50 was 80 mass %. In Table 2 described below, spin-on carbon may also be referred to as "SOC." The polysilicon film, silicon oxide film, silicon nitride film, and silicon germanium film are objects to be etched, while the photoresist film and spin-on carbon film are objects not to be etched.

[0063] Plasma etching of the seven types of substrates was carried out using an ICP etching apparatus RIE-200iP manufactured by Samco Corporation, which has a configuration similar to that of the plasma etching apparatus shown in Figure 1. The chamber volume of the ICP etching apparatus was 46,000 cm 3 The etching gas was a mixed gas of carbonyl fluoride gas, tetrafluoromethane, and argon. The flow rate of carbonyl fluoride gas was set to 5 sccm, the flow rate of tetrafluoromethane to 10 sccm, and the flow rate of argon to 40 sccm, so that the concentration of carbonyl fluoride in the etching gas was adjusted to 9% by volume. Here, sccm is the volumetric flow rate (cm) per minute normalized under the conditions of 0°C and 1 atmosphere. 3 )

[0064] As shown in Table 1, plasma etching was performed with the process pressure inside the chamber set to 3 Pa, the source power set to 300 W, the bias power set to 200 W, and the substrate temperature set to 20° C., and the flow rates of carbonyl fluoride gas, tetrafluoromethane gas, argon gas, process pressure, source power, and bias power were constantly monitored to confirm that there was no difference between the set values ​​and the actual values. The results are shown in Table 2.

[0065] Table 2 shows the etching rates of each film on the first to seventh substrates. When etching did not progress and deposits formed, this is indicated as "depo." Table 2 also shows the etching selectivity ([etching rate of object to be etched] / [etching rate of object not to be etched]) calculated by dividing the etching rate of the object to be etched (polysilicon film, silicon oxide film, silicon nitride film, silicon germanium film) by the etching rate of the object not to be etched (photoresist film, spin-on carbon film). When etching did not progress and deposits formed on the object not to be etched, this is indicated as "-."

[0066]

[0067]

[0068] The film thickness of etching targets other than silicon germanium and non-etching targets was measured using a Filmetrics Reflectance Spectroscopic Film Thickness Meter F20. The film thickness measurement conditions were as follows: the measurement atmosphere 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 higher, and specifically, measurements were performed using the following wavelength ranges as a guide: polysilicon: 500 to 1200 nm, silicon oxide: 300 to 1100 nm, silicon nitride: 500 to 1500 nm, photoresist: 400 to 1000 nm, and spin-on carbon: 400 to 1000 nm.

[0069] The thickness of the silicon germanium film was measured using a scanning electron microscope (SU-9000) manufactured by Hitachi High-Technologies Corporation. The film thickness measurement conditions were as follows: Pressure in the sample chamber: 4×10 -6 Pa Measurement temperature: 25°C Acceleration voltage: 10.0 kV Emission current: 15,000 nA Measurement magnification: 400 kx Furthermore, the etching rates of the etching object and the non-etching object were calculated by subtracting the film thickness after etching from the film thickness before etching and dividing the result by the etching time.

[0070] (Examples 2 to 17) Plasma etching of the above seven types of substrates was performed in the same manner as in Example 1, except that the type of etching gas and etching conditions were different as shown in Table 1. Then, the etching rates of the etching target and non-etching target were calculated, as well as the etching selectivity ratio. The results are shown in Table 2. Note that in Table 1, "C2F4O" is trifluoroacetyl fluoride, "C2F6" is hexafluoroethane, and "C4F8" is octafluorocyclobutane.

[0071] Comparative Example 1 Plasma etching of the seven types of substrates was carried out in the same manner as in Example 1, except that hexafluorobutadiene (CF) was used instead of acid fluoride. The etching rates of the etching target and non-etching target were calculated, and the etching selectivity ratio was also calculated. The results are shown in Table 2.

[0072] Comparative Example 2 Plasma etching was performed on the seven types of substrates described above in the same manner as in Example 1, except that the etching gas was changed to a mixed gas of acid fluoride and argon (saturated fluorocarbon was not used). The etching rates of the etching target and non-etching target were calculated, and the etching selectivity ratio was also calculated. The results are shown in Table 2.

[0073] Comparative Example 3 Plasma etching of the seven types of substrates was carried out in the same manner as in Example 1, except that the etching gas was changed to a mixed gas of acid fluoride, hexafluorobutadiene, and argon (unsaturated fluorocarbon was used instead of saturated fluorocarbon). The etching rates of the etching target and non-etching target were calculated, and the etching selectivity was also calculated. The results are shown in Table 2.

[0074] As can be seen from the results of Examples 1 to 6, 8, and 9, when carbonyl fluoride was used as the acid fluoride, the non-etching target was not etched and deposits formed on the non-etching target, even when the type of saturated fluorocarbon, the type of rare gas, the source power, the bias power, the pressure in the chamber, and the temperature of the substrate were changed. From these results, it can be said that the etching selectivity of Examples 1 to 6, 8, and 9 is infinite.

[0075] As can be seen from the results of Example 7, even when the flow ratio of carbonyl fluoride to tetrafluoromethane was 3:1, the target to be etched was quickly etched, whereas the target not to be etched was hardly etched. This result shows that Example 7 can etch the target to be etched with a high etching selectivity.

[0076] As can be seen from the results of Examples 10 and 11, when octafluorocyclobutane was used as the saturated fluorocarbon, the etching target was etched without any problems, whereas the non-etching target was hardly etched. These results show that Examples 10 and 11 were able to etch the etching target with a high etching selectivity.

[0077] As can be seen from the results of Examples 12 to 17, when oxalyl fluoride or trifluoroacetyl fluoride was used as the acid fluoride, the etching target was etched without any problems, whereas the non-etching target was not etched and deposits formed on the non-etching target, or was barely etched. These results show that Examples 12 to 17 were able to etch the etching target with a high etching selectivity.

[0078] As can be seen from the results of Comparative Example 1, when unsaturated fluorocarbon was used as the etching gas instead of saturated fluorocarbon, the etching rate of the non-etching target improved, and therefore the etching selectivity decreased. This suggests that unsaturated fluorocarbon is not suitable as an etching gas.

[0079] As can be seen from the results of Comparative Example 2, when an etching gas not containing saturated fluorocarbon was used, the etching rate of the non-etching target improved, and therefore the etching selectivity decreased. This suggests that saturated fluorocarbon is essential as an etching gas.

[0080] As can be seen from the results of Comparative Example 3, when an etching gas containing an unsaturated fluorocarbon was used instead of a saturated fluorocarbon, the etching rate of the non-etching target increased, and therefore the selectivity between the etching target and the non-etching target decreased. In particular, deposits were formed on polysilicon and silicon germanium, resulting in an etching selectivity of 0.

[0081] REFERENCE SIGNS LIST 1... Chamber 2... Lower electrode 3... Acid fluoride gas supply unit 5... Saturated fluorocarbon supply unit 11... Etching gas supply pipe 13... Saturated fluorocarbon supply pipe 15... RF coil 20... Substrate

Claims

1. An etching method comprising an etching step of contacting an etching gas containing an acid fluoride and a saturated fluorocarbon with an etched member having an etching object that is to be etched with the etching gas and a non-etching object that is not to be etched with the etching gas in the presence of plasma to selectively etch the etching object compared to the non-etching object, wherein the etching object comprises a silicon-containing material and the non-etching object comprises a carbon-containing material.

2. The etching method according to claim 1, wherein the carbon-containing material contains carbon in an amount of 20% by mass or more and 100% by mass or less.

3. An etching method according to claim 1 or 2, wherein the silicon-containing material contains silicon and germanium, and the total content of the silicon and germanium contained in the silicon-containing material is 30 mol % or more.

4. The etching method according to claim 1 or 2, wherein the silicon-containing material is at least one of silicon oxide, silicon nitride, polysilicon, and silicon germanium.

5. The etching method according to claim 1 or 2, wherein an etching selectivity, which is a ratio of an etching rate of said silicon-containing material to an etching rate of said carbon-containing material, is 5 or more.

6. The etching method according to claim 1 or 2, wherein the acid fluoride is at least one of carbonyl fluoride, oxalyl fluoride, and trifluoroacetyl fluoride.

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