Etching method
By using etching gases of acyl fluoride and saturated fluorocarbon compounds to selectively etch silicon-containing materials under plasma, the problem of insufficient etching selectivity in existing technologies is solved, and a highly selective etching effect is achieved.
Patent Information
- Application Number
- CN202480028758.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-12-12
- Filing Date
- 2024-12-03
- Publication Date
- 2025-11-25
AI Technical Summary
Existing techniques cannot etch silicon-containing materials with excellent etching selectivity, especially when compared to non-etchable objects containing carbon materials.
In the presence of plasma, etching gases containing acyl fluoride and saturated fluorocarbon compounds are used to contact the objects to be etched and the objects not to be etched. By reacting the acyl fluoride with the silicon-containing materials, the etching of the objects not to be etched is suppressed, thus achieving selective etching.
It achieves highly selective etching of silicon-containing materials, with an etching selectivity of over 5, and stably controls the etching process to avoid over-etching of non-etchable objects.
Smart Images
Figure CN121014100A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to etching methods. Background Technology
[0002] Semiconductor manufacturing processes include the following steps: etching an object to be etched using plasma etching with an etching gas, thereby micro-processing the object into a desired shape. In this etching process, it is important to selectively etch objects such as silicon-containing materials (i.e., etching selectivity) compared to non-etchable objects such as carbon-containing materials (e.g., photoresist, carbon masks) that are not etchable gases. For example, Patent Document 1 discloses a technique for etching silicon-containing materials using an etching gas containing carbonyl fluorine.
[0003] Existing technical documents
[0004] Patent documents
[0005] Patent Document 1: Japanese Patent Publication No. 6546889 Summary of the Invention
[0006] The technical problem that the invention aims to solve
[0007] However, the technology disclosed in Patent Document 1 has the limitation of being unable to etch silicon-containing materials with excellent etching selectivity.
[0008] The subject of this disclosure is to provide an etching method that can selectively etch an etchable object containing silicon material compared to a non-etchable object containing carbon material.
[0009] Technical solutions for solving the problem
[0010] In order to solve the aforementioned problem, one aspect of this disclosure is as described in [1] to [6] below.
[0011] [1] An etching method comprising an etching step in which an etching gas containing an acyl fluoride and a saturated fluorocarbon compound is brought into contact with a part to be etched having an etch target and a non-etch target in the presence of a plasma, thereby etching the etch target selectively relative to the non-etch target, wherein the etch target is the object to be etched by the etching gas and the non-etch target is not the object to be etched by the etching gas.
[0012] The object to be etched has a silicon-containing material, and the object not to be etched has a carbon-containing material.
[0013] [2] According to the etching method described in [1], the carbon-containing material contains more than 20% by mass and less than 100% by mass of carbon.
[0014] [3] According to the etching method described in [1] or [2], the silicon-containing material contains silicon and germanium, and the total content of the silicon and germanium in the silicon-containing material is 30 mol% or more.
[0015] [4] According to the etching method described in [1] or [2], the silicon-containing material is at least one of silicon oxide, silicon nitride, polycrystalline silicon and silicon germanium.
[0016] [5] In any one of the etching methods described in [1] to [4], the etching selection ratio, 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.
[0017] [6] In any one of the etching methods described in [1] to [5], the acyl fluoride is at least one of carbonyl fluoride, oxalyl fluoride and trifluoroacetyl fluoride.
[0018] Invention Effects
[0019] According to the etching method disclosed herein, it is possible to selectively etch objects containing silicon materials compared to non-etchable objects containing carbon materials. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of an example of a plasma etching apparatus illustrating one embodiment of the etching method disclosed herein. Detailed Implementation
[0021] The following describes one embodiment of this disclosure. Furthermore, this embodiment represents only one example of this disclosure, and this disclosure is not limited to this embodiment. In addition, various modifications or improvements can be made to this embodiment, and solutions obtained by implementing such modifications or improvements may also be included in this disclosure.
[0022] The etching method described in this embodiment includes an etching step in which an etching gas containing an acyl fluoride and a saturated fluorocarbon is brought into contact with a component to be etched, which has an etch target and a non-etch target, in the presence of a plasma to perform etching. The etch target is selectively etched relative to the non-etch target. The etch target is the object to be etched by the etching gas, while the non-etch target is not the object to be etched by the etching gas. The etch target has a silicon-containing material, while the non-etch target has a carbon-containing material.
[0023] When the etching gas comes into contact with the part to be etched, the acyl fluoride in the etching gas reacts with the silicon in the part to be etched, thus initiating the etching of the part to be etched. On the other hand, the non-parts to be etched react with oxygen atoms and oxygen-containing compounds (active oxygen molecules, ozone, etc.) generated by the decomposition of acyl fluoride, thus initiating the etching process.
[0024] However, when acyl fluoride and saturated fluorocarbons coexist in the etching gas, the supply of carbon from the saturated fluorocarbons suppresses the etching of carbon-containing materials by supplementing oxygen-containing compounds, thus almost completely preventing the etching of non-etchable objects. Therefore, according to the etching method of this embodiment, it is possible to selectively etch objects containing silicon materials compared to non-etchable objects containing carbon materials.
[0025] For example, etching can be performed with an etching selectivity ratio ([etching rate of silicon material] / [etching rate of carbon material]) of 5 or higher, which is the ratio of the etching rate of silicon-containing material to the etching rate of carbon-containing material. Furthermore, from the viewpoint of more stable etching control, etching can be performed with an etching selectivity ratio of 10 or higher, depending on the etching conditions.
[0026] Furthermore, etching in this disclosure means removing part or all of the etched object from the etched part to process the etched part into a predetermined shape (e.g., a three-dimensional shape) (e.g., processing the etched part into a film-like etched object formed of silicon-containing material into a predetermined film thickness), and means removing residues or deposits formed by the etched object from the etched part for cleaning, etc.
[0027] The etching method described in this embodiment can be used in the manufacture of semiconductor devices. Specifically, the semiconductor device manufacturing method described in this embodiment is a method for manufacturing semiconductor devices using the etching method described in this embodiment. The etched component is a semiconductor substrate having an etchable object and a non-etchable object. The manufacturing method includes removing at least a portion of the etchable object from the semiconductor substrate by etching.
[0028] Therefore, if the etching method described in this embodiment is applied to the manufacturing process of semiconductor devices, it is possible, for example, to transfer a pattern formed on a photoresist to a film formed of a silicon-containing material, or to remove a film or residue formed of a silicon-containing material present on a film that is not the object to be etched.
[0029] The etching method described in this embodiment will now be explained in more detail.
[0030] The etching method described in this embodiment is plasma etching. The type of plasma source used in plasma etching is not particularly limited; commercially available equipment can be used. Examples 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).
[0031] [Etching Gas]
[0032] The etching gas used in the etching method of this embodiment contains acyl fluoride and saturated fluorocarbon compound, but may also contain components other than acyl fluoride and saturated fluorocarbon compound, and may also contain at least one of rare gas and additive gas.
[0033] Examples of rare gases include helium (He), neon (Ne), argon (Ar), xenon (Xe), and krypton (Kr).
[0034] In addition, examples of additive gases include nitrogen (N2), hydrogen (H2), oxygen (O2), and halogenated hydrocarbon gases (C). m H n X o X is any one of Cl, Br, I, m, n, o are coefficients, where n+o≤2m+2), hydrogen fluoride (HF), hydrogen chloride (HCl), and hydrogen bromide (HBr).
[0035] The molar ratio of acyl fluoride to saturated fluorocarbon in the etching gas ([molar amount of acyl fluoride] / [molar amount of saturated fluorocarbon]) is preferably 0.01 or more and 4 or less. The lower limit of this range is preferably 0.05, more preferably 0.1. Furthermore, the upper limit of this range is more preferably 3, and even more preferably 2. As long as the molar ratio of acyl fluoride to saturated fluorocarbon in the etching gas is within the above-mentioned range, the target object can be selectively etched compared to the non-etchable object.
[0036] As long as the preferred range of the molar ratio of acyl fluoride to saturated fluorocarbon in the etching gas is a combination of the aforementioned upper and lower limits, the specific combination is irrelevant. For example, the molar ratio of acyl fluoride to saturated fluorocarbon in the etching gas is preferably 0.05 or more and 3 or less, more preferably 0.1 or more and 2 or less.
[0037] [Concentration of rare gases]
[0038] When the etching gas contains rare gases, plasma can be easily generated. The concentration of rare gases in the etching gas is preferably greater than 0% by volume and less than 99% by volume, more preferably more than 5% by volume and less than 90% by volume, and even more preferably more than 10% by volume and less than 85% by volume. As long as the concentration of rare gases in the etching gas is within the above range, a stable and uniform plasma can be easily generated, thus allowing for easy and uniform etching of the target object.
[0039] [Concentration of added gas]
[0040] By adding a gas to the etching gas, depending on the type of gas added, effects such as increasing the etching rate of the object being etched, suppressing the etching rate of non-objects being etched, forming a protective film derived from the etching gas on the etched part, and removing deposits formed on the etched part can be achieved.
[0041] For example, adding haloalkanes to the etching gas can sometimes suppress the etching of non-etchable objects. Additionally, adding hydrogen halides to the etching gas can sometimes improve the etching selectivity. Furthermore, the addition of oxygen or nitrogen can sometimes facilitate the removal of deposits formed on the etched parts.
[0042] The optimal concentration of the added gas in the etching gas varies depending on the desired effect, but is preferably greater than 0 vol% and less than 99 vol%, more preferably more than 2 vol% and less than 60 vol%, and even more preferably more than 5 vol% and less than 50 vol%.
[0043] Acyl fluoride
[0044] Acyl fluoride refers to a compound having the functional group *-C(=O)F within its molecule. Furthermore, "*" signifies any atom or group of atoms. The number of carbon atoms in the acyl fluoride is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less.
[0045] Examples of acyl fluorides include carbonyl fluoride (COF2), oxalyl fluoride (C2O2F2), trifluoroacetyl fluoride (CF3COF), formyl fluoride, carbonyl chloride fluoride, acetyl fluoride, 2,2,3,3,3-pentafluoropropionyl fluoride, 2,2,3,3,4,4,4-heptafluorobutyryl fluoride, 2,2,3,3,4,4,5,5,5,-nonafluoropentanoyl fluoride, 2,2,3,3,4,4,4-hexafluoro-3-(trifluoromethyl)butyryl fluoride, and 3,3,3-trifluoro-2,2-bis(trifluoromethyl)propionyl fluoride. Using any one of these acyl fluorides allows for more selective etching of the target object compared to the non-etchable object.
[0046] Among these acyl fluorides, from the viewpoint of ease of acquisition, carbonyl fluoride, oxalyl fluoride, and trifluoroacetyl fluoride are preferred, with carbonyl fluoride being more preferred. Acyl fluorides can be used alone or in combination with two or more.
[0047] That is, the acyl fluoride contained in the etching gas can also be at least one of carbonyl fluoride, oxalyl fluoride and trifluoroacetyl fluoride.
[0048] [Saturated fluorocarbons]
[0049] Fluorocarbons are compounds that contain both fluorine and carbon atoms within their molecules (except for acyl fluorides). In particular, fluorocarbons used for etching gases need to be saturated fluorocarbons without double or triple bonds.
[0050] From the perspective of low boiling point and ease of handling as a gas, it is preferable for saturated fluorocarbons to have high vapor pressure. For example, saturated fluorocarbons with a boiling point of 45°C or less at atmospheric pressure are preferred, and saturated fluorocarbons with a boiling point of 30°C or less at atmospheric pressure are even more preferred.
[0051] In addition, saturated fluorocarbons can also contain elements other than fluorine (F) and carbon (C), such as bromine (Br), iodine (I), hydrogen (H), nitrogen (N), oxygen (O), silicon (Si), sulfur (S), and phosphorus (P).
[0052] Examples of saturated fluorocarbons include tetrafluoromethane (CF4), trifluoromethane (CHF3), difluoromethane (CH2F2), fluoromethane (CH3F), dibromodifluoromethane (CBr2F2), trifluoroiodomethane (CF3I), hexafluoroethane (C2F6), octafluoropropane (C3F8), hexafluorocyclopropane (C3F6), octafluorocyclobutane (C4F8), and decafluorobutane (C4F6). 10 ), decafluoroisobutane (i-C4F) 10These include tris(trifluoromethyl)amine ((F3C)3N), trifluoro(trifluoromethyl)silane ((F3C)SiF3), trifluoromethyl sulfur pentafluoride ((F3C)SF5), and p-trifluoromethyl phosphorus difluoride ((F3C)PF2). By using any one of these saturated fluorocarbon compounds, etching of the target object can be performed more selectively compared to non-etchable objects.
[0053] [Etching pressure conditions]
[0054] The etching pressure conditions in the etching method described in this embodiment are not particularly limited, but are preferably set to 0.1 Pa or more and 3 kPa or less, more preferably 0.5 Pa or more and 30 Pa or less, and even more preferably 1 Pa or more and 10 Pa or less. As long as the pressure conditions are within the above range, plasma can be easily and stably generated.
[0055] For example, the part to be etched can be placed in the chamber, and etching can be performed while etching gas flows through the chamber. However, the pressure in the chamber during etching gas flow can be set to be above 0.1 Pa and below 3 kPa. The flow rate of the etching gas is appropriately set according to the size of the chamber and the capacity of the exhaust equipment for depressurizing the chamber, so that the pressure in the chamber is maintained at a constant level.
[0056] [Temperature conditions for etching]
[0057] The etching temperature conditions in the etching method described in this embodiment are not particularly limited, but are preferably set to 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.
[0058] As long as the temperature conditions are within the aforementioned range, acyl fluorides can exist in a gaseous state, and the etching rate of silicon-containing materials can easily become higher. Here, the temperature conditions refer to the temperature of the part being etched, but the temperature of the stage that supports the part being etched and is located within the etching apparatus can also be used.
[0059] Acyl fluorides are unlikely to react with non-etchable materials such as photoresist, spin-coated carbon, and amorphous carbon at temperatures below 150°C, whether or not plasma is generated. Therefore, by etching the part to be etched using the etching method described in this embodiment, it is possible to selectively etch objects containing silicon materials such as polycrystalline silicon, silicon oxide, silicon nitride, and silicon germanium with almost no etching of non-etchable materials.
[0060] Therefore, the etching method according to this embodiment can be used as a patterned non-etched object as a resist or mask and to process an etched object having silicon-containing materials such as polysilicon, silicon oxide, silicon nitride, and silicon germanium into a predetermined shape.
[0061] [Object to be etched]
[0062] The object to be etched has a silicon-containing material containing silicon (Si), but it can be an etched object formed only of silicon-containing material, or an etched object having parts formed only of silicon-containing material and parts formed of other materials, or an etched object formed of a mixture of silicon-containing material and other materials.
[0063] Silicon-containing materials refer to compounds formed solely of silicon without containing other elements, or compounds containing both silicon and other elements. Examples of silicon-containing materials include polycrystalline silicon (Poly-Si) and silicon oxide (SiO₂). x x is an arbitrary coefficient, such as SiO2, silicon nitride (SiO2), etc. c N d c and d are arbitrary coefficients, such as Si3N4 and silicon oxynitride (SiO2). a N b (where a and b are arbitrary coefficients), silicon-germanium (Si) y Ge 100-y (where y is any number greater than 0 and less than 100), etc. The silicon-containing material is preferably at least one of silicon oxide, silicon nitride, polycrystalline silicon, and silicon-germanium. A single silicon-containing material can be used alone, or in combination of two or more.
[0064] The silicon content in 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 both silicon and germanium, it is preferable that the combined content of silicon and germanium in the silicon-containing material is 30 mol% or more.
[0065] In addition, the shape of the object being etched is not particularly limited; for example, it can be plate-shaped, foil-shaped, film-shaped, powder-shaped, or block-shaped.
[0066] [Non-etched objects]
[0067] The non-etched object has carbon-containing material containing carbon (C), but it can be a non-etched object formed only of carbon-containing material, or a non-etched object having parts formed only of carbon-containing material and parts formed of other materials, or a non-etched object formed of a mixture of carbon-containing material and other materials.
[0068] Carbon-containing materials refer to compounds formed solely of carbon without containing other elements, or compounds containing both carbon and other elements. Examples of carbon-containing materials include amorphous carbon, spin-coated carbon, carbon-doped silicon oxide (SiOC), and photoresists. Carbon-containing materials can be used alone or in combination of two or more.
[0069] Furthermore, carbon-doped silicon oxide refers to a compound containing carbon atoms, oxygen atoms, and silicon atoms. However, carbon-doped silicon oxide may also contain atoms other than these, such as hydrogen atoms, in addition to carbon atoms, oxygen atoms, and silicon atoms.
[0070] 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 20% by mass or more and 100% by mass or less of carbon.
[0071] Photoresist refers to a composition whose physical properties, such as solubility, change with light and electron beams, resulting in photosensitivity. 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 a composition commonly used in semiconductor manufacturing processes; however, examples include 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.
[0072] Furthermore, the non-etched object can be used as a resist or mask to suppress the etching of the etched object by the etching gas. Therefore, the etching method according to this embodiment can utilize methods such as using the patterned non-etched object as a resist or mask and processing the etched object into a predetermined shape (e.g., processing the film-like etched object having the etched part into a predetermined film thickness), thus making it suitable for the manufacture of semiconductor devices. In addition, since the non-etched object is hardly etched, it is possible to suppress the etching of portions of the semiconductor device that should not be etched, preventing the loss of semiconductor device characteristics due to etching.
[0073] Furthermore, non-etched objects remaining after patterning can be removed using removal methods commonly used in semiconductor device manufacturing processes. Examples include ashing using oxidizing gases such as oxygen plasma and ozone, dissolution using liquid chemical reagents such as APM (a mixture of ammonia and hydrogen peroxide), SPM (a mixture of sulfuric acid and hydrogen peroxide), and organic solvents.
[0074] The following describes examples of plasma etching of polysilicon films, silicon oxide films, silicon nitride films, silicon germanium films, photoresist films, and spin-coated carbon films formed on the surface of a substrate (equivalent to the etched part) using a plasma etching apparatus. Figure 1 The etching apparatus is a plasma etching apparatus that uses ICP as the plasma source.
[0075] Figure 1 The plasma etching apparatus comprises: a chamber 1, in which plasma etching is performed; a lower electrode 2, which supports a substrate 20 to be plasma etched inside the chamber 1; a bias power supply (not shown), which applies bias power to the lower electrode 2; an RF coil 15, which forms an electric field and a magnetic field inside the chamber 1 for plasmaifying the etching gas; a source power supply (not shown), which applies high-frequency source power to the RF coil 15; a vacuum pump 21, which depressurizes the interior of the chamber 1; a pressure gauge 14, which measures the pressure inside the chamber 1; a sensor 16, which captures the plasma emission that occurs along with the generation of plasma; and a spectrometer 17, which splits the plasma emission captured by the sensor 16 and monitors the temporal changes in the plasma emission.
[0076] The substrate 20 has a polycrystalline silicon film, a silicon oxide film, a silicon nitride film, a silicon-germanium film, a photoresist film, and a spin-coated carbon film formed on its surface. The sensor 16 can be, for example, a CCD (Charge-Coupled Device) image sensor. However, instead of providing the sensor 16 and the beam splitter 17, an observation window can be provided in the chamber 1 to visually observe the interior of the chamber 1 and confirm the temporal changes in plasma emission.
[0077] Additionally, chamber 1 includes an etching gas supply unit for supplying etching gas to the interior of chamber 1. The etching gas supply unit includes: an acyl fluoride gas supply unit 3 for supplying acyl fluoride gas; an inert gas supply unit 4 for supplying inert gas; a saturated fluorocarbon compound supply unit 5 for supplying saturated fluorocarbon compound; an etching gas supply pipe 11 connecting the acyl fluoride gas supply unit 3 and chamber 1; an inert gas supply pipe 12 connecting the inert gas supply unit 4 at the middle of the etching gas supply pipe 11; and a saturated fluorocarbon compound supply pipe 13 connecting the saturated fluorocarbon compound supply unit 5 at the middle of the etching gas supply pipe 11.
[0078] Furthermore, when supplying acyl fluoride gas and saturated fluorocarbon compound as etching gas to chamber 1, acyl fluoride gas is supplied from acyl fluoride gas supply unit 3 to etching gas supply pipe 11, and saturated fluorocarbon compound is supplied from saturated fluorocarbon compound supply unit 5 to etching gas supply pipe 11 via saturated fluorocarbon compound supply pipe 13. Thus, at the middle section of etching gas supply pipe 11, acyl fluoride gas and saturated fluorocarbon compound are mixed to form a mixed gas, which is then supplied to chamber 1 via etching gas supply pipe 11.
[0079] Furthermore, when a mixture of acyl fluoride gas, saturated fluorocarbon compound, and inert gas is supplied as the etching gas, acyl fluoride gas is supplied from the acyl fluoride gas supply unit 3 to the etching gas supply pipe 11, and saturated fluorocarbon compound is supplied from the saturated fluorocarbon compound supply unit 5 to the etching gas supply pipe 11 via the saturated fluorocarbon compound supply pipe 13. Inert gas is further supplied from the inert gas supply unit 4 to the etching gas supply pipe 11 via the inert gas supply pipe 12. Thus, at the middle section of the etching gas supply pipe 11, the acyl fluoride gas, saturated fluorocarbon compound, and inert gas are mixed to form a mixed gas, which is then supplied to the chamber 1 via the etching gas supply pipe 11.
[0080] The pressure inside chamber 1 before the etching gas is supplied is not particularly limited, as long as it is below or lower than the supply pressure of the etching gas; for example, 10 is preferred. -5 Pa or more and less than 100 kPa, more preferably 0.1 Pa or more and less than 50 kPa, even more preferably 0.3 Pa or more and less than 15 Pa, and particularly preferably 1 Pa or more and less than 10 Pa.
[0081] When performing plasma etching using such a plasma etching apparatus, a substrate 20 is placed on the lower electrode 2 disposed inside the chamber 1. After the pressure inside the chamber 1 is reduced to, for example, 1 Pa or more and 10 Pa or less by a vacuum pump 21, etching gas is supplied to the inside of the chamber 1 through an etching gas supply unit. Furthermore, 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, causing electrons to be accelerated. These accelerated electrons collide with unsaturated compound molecules in the etching gas to generate new ions and electrons, resulting in a discharge and the formation of plasma. The generation of plasma can be confirmed using a sensor 16 and a spectrometer 17.
[0082] When plasma is generated, the object to be etched on the surface of the substrate 20 is etched. The amount of etching gas supplied to the chamber 1 and the concentration of acyl fluoride in the etching gas (mixed gas) can be adjusted by controlling the flow rates of acyl fluoride, inert gas, and saturated fluorocarbon by means of mass flow controllers (not shown) respectively provided in the etching gas supply pipe 11, the inert gas supply pipe 12, and the saturated fluorocarbon supply pipe 13.
[0083] Example
[0084] The present disclosure will now be described in more detail through examples and comparative examples.
[0085] (Example 1)
[0086] Seven types of substrates were prepared. The first substrate was a polycrystalline silicon film with a thickness of 600 nm deposited on a square silicon substrate with one side of 1 cm (manufactured by SEIREN KST Co., Ltd.). In addition, in Table 2 described later, polycrystalline silicon is sometimes referred to as "PSi".
[0087] The second substrate is a silicon substrate with a side square of 1 cm on which a silicon oxide (SiO2) film with a thickness of 800 nm has been formed (manufactured by SEIREN KST Co., Ltd.).
[0088] The third substrate is a silicon nitride (Si3N4) film with a thickness of 800nm formed on a square silicon substrate with one side of 1cm (manufactured by SEIREN KST Co., Ltd.).
[0089] The fourth substrate is a silicon-germanium film with a thickness of 80 nm deposited on a square silicon substrate with one side of 1 cm (manufactured by SEIREN KST Co., Ltd.). The molar ratio of silicon to germanium ([molar amount of Si]:[molar amount of Ge]) of this silicon-germanium substrate is 20:80. Furthermore, in Table 2 described later, the polycrystalline silicon of the fourth substrate is referred to as "Si20Ge80".
[0090] The fifth substrate is a silicon-germanium film with a thickness of 80 nm deposited on a square silicon substrate with one side of 1 cm (manufactured by SEIREN KST Co., Ltd.). The molar ratio of silicon to germanium ([molar amount of Si]:[molar amount of Ge]) of this silicon-germanium substrate is 95:5. Furthermore, in Table 2 described later, the polycrystalline silicon of the fifth substrate is referred to as "Si95Ge5".
[0091] The sixth substrate is a silicon substrate with a square side measuring 1 cm, on which a photoresist film with a thickness of 600 nm has been deposited. This photoresist film is formed by coating an i-line photoresist TSCR (trade name) manufactured by Tokyo Ohka Kogyo Co., Ltd. onto the silicon substrate and then curing it by exposure. Furthermore, the i-line photoresist TSCR (trade name) contains 67% carbon by mass. Additionally, in Table 2 described later, the photoresist is sometimes referred to as "PR".
[0092] The seventh substrate is a silicon substrate (manufactured by SEIREN KST Co., Ltd.) on which a spin-coated carbon film with a thickness of 600 nm has been deposited. This spin-coated carbon film was obtained by depositing spin-coated carbon ODL-50 manufactured by Shin-Etsu Chemical Co., Ltd. on the silicon substrate. Furthermore, the spin-coated carbon ODL-50 contains 80% carbon by mass. Additionally, in Table 2 described later, the spin-coated carbon is sometimes referred to as "SOC".
[0093] In addition, polycrystalline silicon films, silicon oxide films, silicon nitride films, and silicon-germanium films are the objects to be etched, while photoresist films and spin-coated carbon films are not the objects to be etched.
[0094] Use with Figure 1 The plasma etching of the aforementioned seven substrates was performed using the RIE-200iP ICP etching apparatus manufactured by SAMCO Corporation, which has a similar structure to the plasma etching apparatus.
[0095] The chamber volume of the ICP etching apparatus is 46,000 cm³. 3 The etching gas was a mixture of carbonyl fluorine gas, tetrafluoromethane, and argon. The concentration of carbonyl fluorine in the etching gas was adjusted to 9% by volume by setting the flow rate of carbonyl fluorine gas to 5 sccm, the flow rate of tetrafluoromethane to 10 sccm, and the flow rate of argon to 40 sccm. Here, sccm is the volumetric flow rate (cm³) per minute normalized to the conditions of 0°C and 1 atmosphere. 3 ).
[0096] As shown in Table 1, with the process pressure inside the chamber set to 3 Pa, the source power to 300 W, the bias power to 200 W, and the substrate temperature to 20 °C, the flow rates of carbonyl fluorine gas, tetrafluoromethane, and argon, as well as the process pressure, source power, and bias power, were constantly monitored. Plasma etching was performed while confirming that there were no discrepancies between the set values and the actual values. The results are shown in Table 2.
[0097] Table 2 shows the etching rates of each film on the first to seventh substrates. The case where deposits are formed without etching is indicated as "depo".
[0098] Additionally, Table 2 shows the etching selectivity ([etching rate of the etched object] / [etching rate of the non-etched object]) calculated by dividing the etching rate of the etched object (polysilicon film, silicon oxide film, silicon nitride film, silicon-germanium film) by the etching rate of the non-etched object (photoresist film, spin-coated carbon film). The etching selectivity in cases where deposits are formed without etching the non-etched object is indicated by "-".
[0099] [Table 1]
[0100]
[0101] [Table 2]
[0102]
[0103] In addition, the film thickness of etched and non-etched objects other than silicon and germanium was measured using a Filmetrics reflectance spectrophotometer F20. The film thickness measurement conditions are as follows.
[0104] The measurement atmosphere was air, and the measurement temperature was 25℃. The measurement wavelength range was the range with a goodness of fit of 0.9 or higher. Specifically, the following wavelength ranges were used as benchmarks for measurement: 500–1200 nm for polycrystalline silicon, 300–1100 nm for silicon oxide, 500–1500 nm for silicon nitride, 400–1000 nm for photoresist, and 400–1000 nm for spin-coated carbon.
[0105] The thickness of silicon-germanium films was measured using a scanning electron microscope (SU-9000) manufactured by Hitachi High Technology Corporation. The film thickness measurement conditions are as follows.
[0106] Pressure in the sample chamber: 4 × 10 -6 Pa
[0107] Measurement temperature: 25℃
[0108] Accelerating voltage: 10.0kV
[0109] Transmitting current: 15000nA
[0110] Magnification: 400kx
[0111] In addition, the etching rate of both the etched object and the non-etched object is calculated by subtracting the etched film thickness from the film thickness before etching and dividing it by the etching time.
[0112] (Examples 2 to 17)
[0113] Except for the differences in the type of etching gas and etching conditions as shown in Table 1, plasma etching of the seven substrates described above was performed in the same manner as in Example 1. The etching rates of the etched object and the non-etched object were then calculated, and the etching selectivity ratio was determined. The results are presented in Table 2.
[0114] In addition, “C2F4O” in Table 1 is trifluoroacetyl fluoride, “C2F6” is hexafluoroethane, and “C4F8” is octafluorocyclobutane.
[0115] (Comparative Example 1)
[0116] Except that hexafluorobutadiene (C4F6) was used instead of acyl fluoride, plasma etching of the seven substrates described above was performed in the same manner as in Example 1. The etching rates of the etched and unetched substrates were then calculated, and the etching selectivity ratio was determined. The results are presented in Table 2.
[0117] (Comparative Example 2)
[0118] Except for changing the etching gas to a mixture of acyl fluoride and argon (without using saturated fluorocarbons), plasma etching of the seven substrates described above was performed in the same manner as in Example 1. The etching rates of the etched and unetched objects were then calculated, and the etching selectivity ratio was determined. The results are shown in Table 2.
[0119] (Comparative Example 3)
[0120] Except for changing the etching gas to a mixture of acyl fluoride, hexafluorobutadiene, and argon (using unsaturated fluorocarbons instead of saturated fluorocarbons), plasma etching of the seven substrates described above was performed in the same manner as in Example 1. The etching rates of the etched and unetched substrates were then calculated, and the etching selectivity ratio was determined. The results are shown in Table 2.
[0121] Based on the results of Examples 1-6, 8, and 9, it is evident that when carbonyl fluorine is used as the acyl fluoride, even with changes in the type of saturated fluorocarbon compound, the type of rare gas, the source power, the bias power, the pressure within the chamber, and the temperature of the substrate, the non-etchable object is not etched, but rather deposits are formed on the non-etchable object. Based on these results, it can be stated that the etching selectivity of Examples 1-6, 8, and 9 is infinitely large.
[0122] As shown in the results of Example 7, even with a flow ratio of carbonyl fluorine to tetrafluoromethane of 3:1, the object to be etched was etched rapidly, while the non-object to be etched was hardly etched. Based on this result, Example 7 demonstrates that it was able to etch the object to be etched with a high etch selectivity.
[0123] The results of Examples 10 and 11 show that when octafluorocyclobutane is used as the saturated fluorocarbon compound, the etchable object is etched without problems, while the non-etchable object is hardly etched. These results indicate that Examples 10 and 11 were able to etch the etchable object with a high etch selectivity.
[0124] The results of Examples 12-17 show that when oxalyl fluoride or trifluoroacetyl fluoride is used as the fluoride, the object to be etched is etched without problems, while the non-object to be etched is not etched but deposits are formed on the non-object to be etched, or the non-object to be etched is hardly etched. Based on these results, Examples 12-17 are able to etch the object to be etched with a high etch selectivity.
[0125] The results of Comparative Example 1 show that when unsaturated fluorocarbons are used as the etching gas instead of saturated fluorocarbons, the etching rate of the non-etchable object increases, and therefore the etch selectivity decreases. This suggests that unsaturated fluorocarbons are unsuitable as etching gases.
[0126] The results of Comparative Example 2 show that when an etching gas without saturated fluorocarbons is used, the etching rate of the non-etched object increases, and therefore the etch selectivity decreases. This suggests that saturated fluorocarbons are necessary as etching gases.
[0127] According to the results of Comparative Example 3, when an etching gas containing unsaturated fluorocarbons instead of saturated fluorocarbons is used, the etching rate of the non-etchable object increases, thus reducing the selectivity ratio between the etchable and non-etchable objects. In particular, due to the formation of deposits in polysilicon and silicon-germanium, the etching selectivity becomes 0.
[0128] Explanation of reference numerals in the attached figures
[0129] 1 chamber
[0130] 2 Lower electrode
[0131] 3 Acyl fluoride gas supply section
[0132] 5. Saturated Fluorocarbon Supply Department
[0133] 11. Piping for etching gas supply
[0134] 13 Piping for saturated fluorocarbon supply
[0135] 15 RF coils
[0136] 20 substrate
Claims
1. An etching method, The process includes an etching step in which an etching gas containing acyl fluoride and saturated fluorocarbon compounds is brought into contact with a component to be etched, comprising a target object and a non-target object, in the presence of plasma. The target object is selectively etched relative to the non-target object, which is the object to be etched by the etching gas, while the non-target object is not. The object to be etched has a silicon-containing material, and the object not to be etched has a carbon-containing material.
2. The etching method according to claim 1, The carbon-containing material contains more than 20% by mass and less than 100% by mass of carbon.
3. The etching method according to claim 1 or 2, The silicon-containing material contains silicon and germanium, and the total content of silicon and germanium in the silicon-containing material is more than 30 mol%.
4. The etching method according to claim 1 or 2, The silicon-containing material is at least one of silicon oxide, silicon nitride, polycrystalline silicon, and silicon-germanium.
5. The etching method according to claim 1 or 2, The etching selectivity ratio, 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 claim 1 or 2, The acyl fluoride is at least one of carbonyl fluoride, oxalyl fluoride, and trifluoroacetyl fluoride.