Etching method, method for manufacturing semiconductor device, and etching apparatus

Abstract

Provided are an etching method, a method for manufacturing a semiconductor device, and an etching apparatus, which are capable of improving the etching rate for a nitrogen-containing silicon compound film. The present invention relates to a method for etching a nitrogen-containing silicon compound film at 0°C or lower, using a plasma gas obtained by generating a plasma from an etching gas composition containing a hydrofluorocarbon having 5 or fewer carbon atoms.

Description

Etching Method, Method of Manufacturing Semiconductor Device, and Etching Apparatus

[0001] The present disclosure relates to an etching method, a method of manufacturing a semiconductor device, and an etching apparatus.

[0002] In the manufacture of semiconductors, there is a process of selectively etching a nitrogen-containing silicon compound film such as a SiN film with respect to a silicon film (crystalline silicon: epi-Si, c-Si, polycrystalline silicon: p-Si), a silicon oxide film (SiO ２ , SiO ｘ ), and an organic film (PR, a-C, BARC).

[0003] In non-plasma etching as described in Patent Document 1, in order to improve the etching rate, it is necessary to perform the process under high-pressure conditions. Under high-pressure conditions, hydrogen fluoride or alcohol may cause capillary condensation in recent fine patterns, resulting in a completely different result from that of a blanket film.

[0004] On the other hand, plasma etching can be performed under low-pressure conditions, so it is applicable even in fine patterns. As a technique related to plasma etching, Patent Document 2 shows that a SiN film can be selectively etched by performing plasma etching using a specific hydrofluorocarbon.

[0005] Japanese Patent Application Laid-Open No. 2016-25195 International Publication No. 2018 / 186364

[0006] As a result of intensive studies by the present inventors, it has been newly found that there is room for improvement in the etching rate of the SiN film in the technique described in Patent Document 2.

[0007] The present disclosure solves the newly found problems by the present inventors, and an object thereof is to provide an etching method, a method of manufacturing a semiconductor device, and an etching apparatus capable of improving the etching rate for a nitrogen-containing silicon compound film. [[ID=二十七]]

[0008] As a result of intensive studies, the present inventors have found that by lowering the temperature, the etching rate of a nitrogen-containing silicon compound film by a hydrofluorocarbon is improved, and thus the present disclosure has been completed.

[0009] The present disclosure (1) relates to an etching method for etching a nitrogen-containing silicon compound film at 0 °C or lower using a plasma gas obtained by plasmaizing an etching gas composition containing a hydrofluorocarbon having 5 or less carbon atoms.

[0010] The present disclosure (2) relates to the etching method according to the present disclosure (1), in which the nitrogen-containing silicon compound film is etched at −30 °C or lower.

[0011] The present disclosure (3) relates to the etching method according to the present disclosure (1), in which the nitrogen-containing silicon compound film is etched at −60 °C or lower.

[0012] The present disclosure (4) relates to the etching method according to the present disclosure (1), in which the nitrogen-containing silicon compound film is etched at −80 °C or lower.

[0013] The present disclosure (5) relates to the etching method according to any one of the present disclosures (1) to (4), in which the nitrogen-containing silicon compound film is a silicon nitride film.

[0014] The present disclosure (6) relates to the etching method according to any one of the present disclosures (1) to (5), in which the hydrofluorocarbon has 2 to 4 carbon atoms.

[0015] The present disclosure (7) relates to the etching method according to any one of the present disclosures (1) to (6), in which the hydrofluorocarbon has an unsaturated bond.

[0016] The present disclosure (8) relates to the etching method according to any one of the present disclosures (1) to (6), in which the hydrofluorocarbon has no unsaturated bond.

[0017] The present disclosure (9) relates to the hydrofluorocarbon being 3,3,3-trifluoropropyne (TFPy), trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)(1234E)), 1,1,1,2,3,3,3-heptafluoropropane (C ３ HF ７), related to the etching method according to any one of (1) to (5) of the present disclosure, characterized in that it is one or more selected from the group consisting of cis-1,3,3,3-tetrafluoropropene (HFO-1234ze(Z)), and monofluoromethane.

[0018] The present disclosure (10) relates to the etching method according to any one of (1) to (9) of the present disclosure, wherein the etching gas composition further contains an oxidizing gas.

[0019] The present disclosure (11) is such that the oxidizing gas is O ２ , F ２ , Br ２ , O ３ , CO, CO ２ , COCl ２ , COF ２ , NO, NO ２ , SO ２ and SO ３ , related to the etching method according to (10) of the present disclosure, which is at least one selected from the group consisting of.

[0020] The present disclosure (12) relates to the etching method according to any one of (1) to (11) of the present disclosure, wherein the etching gas composition further contains an inert gas. <00001l9>

[0021] The present disclosure (13) relates to the etching method according to any one of (1) to (12) of the present disclosure, wherein in 100% by volume of the etching gas composition, the total content of the hydrofluorocarbon, oxidizing gas and inert gas is 100% by volume. <000012l>

[0022] [[ID=​​​​​This disclosure (16) relates to a method for manufacturing a semiconductor device, which includes a step of etching the nitrogen-containing silicon compound film on a substrate having the nitrogen-containing silicon compound film by applying the etching method described in any one of these disclosures (1) to (15).

[0025] This disclosure (17) relates to an etching apparatus for etching a nitrogen-containing silicon compound film at 0°C or below, comprising: an electrode; a temperature control unit for adjusting the temperature of the electrode to 0°C or below; a mounting stage for placing a substrate having a nitrogen-containing silicon compound film; and an etching gas supply unit for supplying hydrofluorocarbon with 5 or fewer carbon atoms to the substrate.

[0026] According to this disclosure, the etching method involves using a plasma gas obtained by plasma-forming an etching gas composition containing a hydrofluorocarbon with 5 or fewer carbon atoms to etch a nitrogen-containing silicon compound film at 0°C or below, thereby improving the etching rate for the nitrogen-containing silicon compound film.

[0027] According to this disclosure, the method for manufacturing a semiconductor device includes a step of etching a nitrogen-containing silicon compound film on a substrate having a nitrogen-containing silicon compound film by applying the etching method of this disclosure. Therefore, it is possible to manufacture semiconductor devices with excellent etching speed for the nitrogen-containing silicon compound film and with high productivity.

[0028] According to this disclosure, the etching apparatus comprises an electrode, a temperature control unit for adjusting the electrode temperature to 0°C or below, a mounting table for placing a substrate having a nitrogen-containing silicon compound film, and an etching gas supply unit for supplying hydrofluorocarbon with 5 or fewer carbon atoms to the substrate, and since it etches the nitrogen-containing silicon compound film at 0°C or below, it has excellent etching speed for the nitrogen-containing silicon compound film.

[0029] Figure 1 is a schematic diagram illustrating an etching apparatus according to one embodiment of the present disclosure.

[0030] The present disclosure will be described in detail below, but the description of the constituent elements described below is an example of an embodiment of the present disclosure and is not limited to these specific contents. It can be implemented in various ways within the scope of its gist.

[0031] In this specification, the notation "X to Y" in descriptions of numerical ranges means "X or greater and Y or less" unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% or greater and 5 mass% or less".

[0032] <Etching Method> The etching method of this disclosure is an etching method that uses a plasma gas obtained by plasma-forming an etching gas composition containing a hydrofluorocarbon with 5 or fewer carbon atoms to etch a nitrogen-containing silicon compound film at 0°C or below. This improves the etching rate for the nitrogen-containing silicon compound film. In this specification, hydrofluorocarbon means an organic compound containing a fluorine atom and a hydrogen atom, that is, a compound containing a fluorine atom, a hydrogen atom, and a carbon atom, preferably a compound composed of a fluorine atom, a hydrogen atom, and a carbon atom. Hydrofluorocarbon may also contain atoms other than fluorine atoms, hydrogen atoms, and carbon atoms, such as nitrogen atoms and oxygen atoms.

[0033] The reason why the above effects are obtained is not entirely clear, but it is presumed to be due to the following mechanism: Hydrofluorocarbons have hydrogen atoms, and by lowering the temperature, the adsorption of hydrogen atoms onto the nitrogen-containing silicon compound film is promoted, and the nitrogen atoms in the nitrogen-containing silicon compound film become NH ３ Because it becomes easier to remove as HCN, etc., the etching rate of nitrogen-containing silicon compound films is improved. On the other hand, CF ４ Fluorocarbons that do not contain hydrogen atoms, such as those mentioned above, do not exhibit the above-mentioned functional properties even at low temperatures, and therefore the etching rate against nitrogen-containing silicon compound films hardly improves.

[0034] Furthermore, in conventional techniques using hydrofluorocarbons with 5 or fewer carbon atoms, there was a trade-off: prioritizing the etching rate for nitrogen-containing silicon compound films reduced selectivity for the nitrogen-containing silicon compound films, and prioritizing selectivity for nitrogen-containing silicon compound films reduced the etching rate for the nitrogen-containing silicon compound films. On the other hand, in the etching method of this disclosure, by using a plasma gas obtained by plasma-forming an etching gas composition containing hydrofluorocarbons with 5 or fewer carbon atoms, and etching the nitrogen-containing silicon compound film at a low temperature, it is possible to selectively etch the nitrogen-containing silicon compound film while improving the etching rate for the nitrogen-containing silicon compound film. Thus, in this disclosure, it is possible to achieve both the etching rate for nitrogen-containing silicon compound films and selectivity for nitrogen-containing silicon compound films. The reason for obtaining this effect is not entirely clear, but it is presumed to be due to a mechanism similar to that described above.

[0035] A nitrogen-containing silicon compound film can be any film containing at least Si and N, for example, silicon nitride (SiN, where SiN does not indicate the stoichiometric ratio of each element, but refers to a film containing silicon atoms and nitrogen atoms. For example, SiN ｘ (x is between 0.3 and 9) or Si ３ N ４ ) film, silicon carbide nitride (SiOCN, where SiOCN does not indicate the stoichiometric ratio of each element and refers to a film containing silicon atoms, oxygen atoms, carbon atoms, and nitrogen atoms.) film, silicon oxynitride (SiON, where SiON does not indicate the stoichiometric ratio of each element and refers to a film containing silicon atoms, oxygen atoms, and nitrogen atoms. For example, Si ４ O ｘ N ｙ (x is between 3 and 6, y is between 2 and 4) or Si ４ O ５ N ３Examples include silicon nitride (SiCN) films and silicon carbide nitride (SiCN) films. These may be used individually or in combination of two or more. Among these, silicon nitride films and silicon carbide nitride films are preferred, with silicon nitride films being more preferred.

[0036] In the etching method of this disclosure, etching of a nitrogen-containing silicon compound film, particularly a silicon nitride film, is preferably carried out at a rate of 70 nm / min or higher, more preferably 100 nm / min or higher, even more preferably 180 nm / min or higher, particularly preferably 250 nm / min or higher, and most preferably 280 nm / min or higher. The upper limit is not particularly limited, but for example, it may be 100 μm / min or less or 1 mm / min or less. In this specification, the etching rate is a value calculated based on the time during which power is applied to the electrode (the time during which plasma gas is generated) by measuring the film thickness before and after the etching process using a spectroscopic ellipsometer.

[0037] The etching method of this disclosure is suitable for selectively etching nitrogen-containing silicon compound films, particularly silicon nitride films. In this specification, "selectively etching nitrogen-containing silicon compound films" means that the ratio of the etching rates of the nitrogen-containing silicon compound film to that of materials other than the nitrogen-containing silicon compound film (nitrogen-containing silicon compound film / materials other than the nitrogen-containing silicon compound film) is 1.1 or higher. The above etching rate ratio is preferably 1.5 or higher, more preferably 2 or higher, and even more preferably 5 or higher. There is no particular upper limit, but for example, it is 10,000 or less. In particular, the etching method of this disclosure is suitable for selectively etching nitrogen-containing silicon compound films against films other than nitrogen-containing silicon compound films.

[0038] Examples of films other than nitrogen-containing silicon compound films include polysilicon films, films containing at least Si and O but not N, amorphous carbon films, photoresist films (PR films), and films containing at least Ti and N. These may be used individually or in combination of two or more. Among these, polysilicon films, films containing at least Si and O but not N, amorphous carbon films, and photoresist films (PR films) are preferred.

[0039] Examples of polysilicon films include polycrystalline silicon (p-Si), amorphous silicon, and single-crystal silicon films. Examples include silicon films such as polysilicon films and amorphous silicon films formed on a substrate, or silicon films grown using epitaxial growth, and single-crystal silicon substrates. Epitaxial growth can be homoepitaxial growth when the substrate is a silicon substrate, or heteroepitaxial growth when the substrate is a non-silicon substrate. Epitaxially grown silicon films are typically single-crystal silicon films composed of single-crystal silicon.

[0040] A film containing at least Si and O but not N is silicon oxide (SiO, where SiO does not represent the stoichiometric ratio of each element, but refers to a film containing silicon atoms and oxygen atoms. For example, SiO ｘ (x is between 1 and 2) or SiO ２ Examples include films. In this specification, a film containing at least Si and O but not N means that the N content is 0% by mass in 100% by mass of the film.

[0041] Examples of amorphous carbon films include amorphous carbon films that do not have a crystalline structure.

[0042] The photoresist film (PR film) is not particularly limited to negative or positive types, but examples include films made of organic polymers. One example is a film obtained by coating a photoresist containing a solvent, a photoresist resin, and a photoacid generator, and curing it as needed. Examples of base polymers for the photoresist resin include acrylates, novolac resins, polymethyl methacrylate, and polyolefin sulfonates.

[0043] As a film containing at least Ti and N, titanium nitride (TiN, where TiN does not indicate the stoichiometric ratio of each element, but refers to a film containing titanium atoms and nitrogen atoms. For example, TiN ｘ (x is between 0.3 and 9) or Ti ３ N ４ ) film, titanium carbide nitride (TiOCN, where TiOCN does not indicate the stoichiometric ratio of each element, and refers to a film containing titanium atoms, oxygen atoms, carbon atoms, and nitrogen atoms.) film, titanium oxynitride (TiON, where TiON does not indicate the stoichiometric ratio of each element, and refers to a film containing titanium atoms, oxygen atoms, and nitrogen atoms. For example, Ti ４ O ｘ N ｙ (x is between 3 and 6, y is between 2 and 4) and Ti ４ O ５ N ３ Examples include ) films and titanium carbide nitride (TiCN, where TiCN does not indicate the stoichiometric ratio of each element, but refers to a film containing titanium atoms, carbon atoms, and nitrogen atoms. For example, materials containing 20-50 atomic% titanium, 5-30 atomic% carbon, and 10-30 atomic% nitrogen can be used.) films.

[0044] In the etching method of this disclosure, the nitrogen-containing silicon compound film is preferably formed on a substrate. The substrate is not particularly limited as long as the nitrogen-containing silicon compound film is formed on it, but it is preferably a semiconductor device substrate, and examples include silicon substrates, compound semiconductor substrates, quartz substrates, glass substrates, etc. In addition to the nitrogen-containing silicon compound film, other films besides the nitrogen-containing silicon compound film may be formed on the surface of the substrate, as well as films containing metal nitrides, metal wiring films, etc. An embodiment in which the films other than the nitrogen-containing silicon compound film are adjacent to the nitrogen-containing silicon compound film, and both the nitrogen-containing silicon compound film and the films other than the nitrogen-containing silicon compound film are exposed, is preferred for the etching method of this disclosure.

[0045] The method for forming the film on the substrate surface is not particularly limited, but examples include chemical vapor deposition (CVD) and sputtering. The thickness of the nitrogen-containing silicon compound film is also not particularly limited, but can be, for example, 0.1 nm to 1 μm.

[0046] The etching method of this disclosure preferably involves placing the substrate in a chamber and performing the etching. The etching method of this disclosure preferably includes a step of reducing the pressure inside the chamber and / or replacing the pressure inside the chamber with an inert gas. The etching method of this disclosure more preferably includes a step of reducing the pressure inside the chamber and / or replacing the pressure inside the chamber with an inert gas after etching a nitrogen-containing silicon compound film using a plasma gas obtained by plasma-generating the etching gas composition of this disclosure in a chamber. This is because it is possible to remove by-products generated during etching. Reduced pressure means a state in which the pressure inside the chamber is lower than the etching pressure (process pressure), and generally means less than 1 Pa.

[0047] The etching method of this disclosure may include a step of subjecting the chamber to a reduced pressure state, followed by a step of replacing the chamber with an inert gas.

[0048] <<Etching Gas Composition>> The etching gas composition of this disclosure contains a hydrofluorocarbon having 5 or fewer carbon atoms. The hydrofluorocarbon having 5 or fewer carbon atoms may be used alone, or two or more may be used in combination.

[0049] The number of carbon atoms in the hydrofluorocarbon is 5 or less, preferably 4 or less. On the other hand, the lower limit of the number of carbon atoms in the hydrofluorocarbon may be 1 or more, but it is preferably 2 or more, more preferably 3 or more, because it is easier to obtain a high etching rate.

[0050] The number of hydrogen atoms in the hydrofluorocarbon is preferably 1 to 5, more preferably 1 to 4, and even more preferably 1 to 2.

[0051] The number of fluorine atoms in the hydrofluorocarbon is usually determined by the number of carbon atoms and hydrogen atoms in the hydrofluorocarbon, and each carbon atom has as many fluorine atoms as there are bonds that are not bonded to a hydrogen atom or another carbon atom, preferably 1 to 10, more preferably 1 to 8, and even more preferably 1 to 4.

[0052] The hydrofluorocarbon may or may not have unsaturated bonds, but it is preferable that it has unsaturated bonds. The unsaturated bonds may be double bonds or triple bonds.

[0053] The number of unsaturated bonds in the hydrofluorocarbon is preferably 0 to 2, more preferably 1 to 2.

[0054] When the hydrofluorocarbon does not have unsaturated bonds, it tends to selectively etch polysilicon films, films containing at least Si and O but not N, amorphous carbon films, and especially amorphous carbon films, nitrogen-containing silicon compound films, particularly silicon nitride films.

[0055] When the hydrofluorocarbon has unsaturated bonds, it tends to selectively etch a nitrogen-containing silicon compound film, particularly a silicon nitride film, against a polysilicon film, a film containing at least Si and O but not N.

[0056] Examples of the hydrofluorocarbons include compounds having triple bonds such as 3,3,3-trifluoropropyne (TFPy), 3,3-difluoropropyne, 3-monofluoropropyne, 4,4,4-trifluorobutyne, 4,4-difluorobutyne, 4-monofluorobutyne, 5,5,5-trifluoropentine, 5,5-difluoropentine, 5-monofluoropentine, and 2-monofluoroethine; trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)(1234E)), cis-1,3,3,3-tetrafluoropropene (HFO-1234ze(Z)), cis-1,1,1,4,4,4-hexafluorobuta-2-ene (HFO-1336mzz(Z)), trans-1-chloro-3,3,3-trifluoropropene (HFO-1233zd(E)), 2,3,3,3-tetrafluoropropene (HFO-12 34yf), 1,1,3,3-tetrafluoropropene, trans-1,2,3,3,3-pentafluoropropene (HFO-1225ye(E)), cis-1,2,3,3,3-pentafluoropropene (HFO-1225ye(Z)), 1,1,3,3,3-pentafluoropropene (HFO-1225zc), 1,1,2,3,3-pentafluoropropene (HFO-1225yc), trans-1-chloro-3,3,3-trifluoropropene Lopen (HFO-1233zd(E)), cis-1-chloro-3,3,3-trifluoropropene (HFO-1233zd(Z)), 1-chloro-2,3,3,3-tetrafluoropropene (Z) (HFO-1224yd(Z)), trans-1,3,3,3-tetrafluorobutene, cis-1,3,3,3-tetrafluorobutene, trans-1-chloro-3,3,3-trifluorobutene, 2,3,3,3-tetrafluorobutene, 1,1 ,3,3-tetrafluorobutene, trans-1,2,3,3,3-pentafluorobutene, cis-1,2,3,3,3-pentafluorobutene, 1,1,3,3,3-pentafluorobutene, 1,1,2,3,3-pentafluorobutene, trans-1-chloro-3,3,3-trifluorobutene, cis-1-chloro-3,3,3-trifluorobutene, 1-chloro-2,3,3,3-tetrafluorobutene (Z), trans-1,3,3Compounds having double bonds such as 3-tetrafluoropentene, cis-1,3,3,3-tetrafluoropentene, trans-1-chloro-3,3,3-trifluoropentene, 2,3,3,3-tetrafluoropentene, 1,1,3,3-tetrafluoropentene, trans-1,2,3,3,3-pentafluoropentene, cis-1,2,3,3,3-pentafluoropentene, 1,1,3,3,3-pentafluoropentene, 1,1,2,3,3-pentafluoropentene, trans-1-chloro-3,3,3-trifluoropentene, cis-1-chloro-3,3,3-trifluoropentene, 1-chloro-2,3,3,3-tetrafluoropentene (Z), trans-1,3,3-trifluoroethene, cis-1,3,3-trifluoroethene, trans-1,1,1-trifluoroethene, and cis-1,1,1-trifluoroethene; 1,1,1,2,3,3,3-heptafluoropropane (C, ３ HF ７), 1,1,2,3,3,3-hexafluoropropane, 1,1,1,3,3,3-hexafluoropropane, 1,1,1,2,3,3-hexafluoropropane, 1,2,3,3,3-pentafluoropropane, 1,1,3,3,3-pentafluoropropane, 1,1,1,3,3-pentafluoropropane, 1,1,2,3,3-pentafluoropropane, 2,3,3,3-tetrafluoropropane, 1,3,3,3-tetrafluoropropane, 1,1,1,3-tetrafluoropropane, 1,1,1,2- Tetrafluoropropane, 1,1,2,3-tetrafluoropropane, 1,1,3,3-tetrafluoropropane, 1,1,1,2,3,3,3-heptafluorobutane, 1,1,2,3,3,3-hexafluorobutane, 1,1,1,3,3,3-hexafluorobutane, 1,1,1,2,3,3-hexafluorobutane, 1,2,3,3,3-pentafluorobutane, 1,1,3,3,3-pentafluorobutane, 1,1,1,3,3-pentafluorobutane, 1,1,2,3,3-pentafluorobutane, 2,3,3,3-tetrafluorobutane, 1 ,3,3,3-tetrafluorobutane, 1,1,1,3-tetrafluorobutane, 1,2,3,3-tetrafluorobutane, 1,1,1,2-tetrafluorobutane, 1,1,2,3-tetrafluorobutane, 1,1,3,3-tetrafluorobutane, 1,1,1,2,3,3,3-heptafluoropentane, 1,1,2,3,3,3-hexafluoropentane, 1,1,1,2,3,3-hexafluoropentane, 1,1,1,2,3,3-hexafluoropentane, 1,2,3,3,3-pentafluoropentane, 1,1,3,3,3-pentafluoro Pentane, 1,1,1,3,3-pentafluoropentane, 1,1,2,3,3-pentafluoropentane, 2,3,3,3-tetrafluoropentane, 1,3,3,3-tetrafluoropentane, 1,1,1,3-tetrafluoropentane, 1,2,3,3-tetrafluoropentane, 1,1,1,2-tetrafluoropentane, 1,1,1,2,2-pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,Examples include compounds without unsaturated bonds such as 1,2-trifluoroethane, 1,1,1-trifluoroethane, trifluoromethane, difluoromethane, and monofluoromethane. These may be used alone or in combination of two or more. Among them are 3,3,3-trifluoropropyne (TFPy), trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)(1234E)), and 1,1,1,2,3,3,3-heptafluoropropane (C, ３ HF ７ ), cis-1,3,3,3-tetrafluoropropene (HFO-1234ze(Z)), monofluoromethane is preferred, and 3,3,3-trifluoropropyne (TFPy), trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)(1234E)), 1,1,1,2,3,3,3-heptafluoropropane (C ３ HF ７ ), monofluoromethane is more preferred.

[0057] The etching gas composition of this disclosure is not particularly limited as long as it contains hydrofluorocarbons having 5 or fewer carbon atoms, and may contain 100% by volume of hydrofluorocarbons having 5 or fewer carbon atoms in 100% by volume of the etching gas composition, but the etching gas composition may further contain an inert gas and / or an oxidizing gas.

[0058] Examples of inert gases include Ar and N. ２ Examples include He, Ne, and Kr. These can be used individually or in combination of two or more. Among these, Ar is preferred for its stability and low cost.

[0059] Since oxidizing gases can remove depositions derived from hydrofluorocarbons, the etching gas composition of this disclosure tends to yield better etching shapes when it contains an oxidizing gas. Therefore, it is preferable that the etching gas composition of this disclosure contains an oxidizing gas. It is especially preferable to use the oxidizing gas when the hydrofluorocarbon has unsaturated bonds. This is presumed to be because depositions derived from the hydrofluorocarbon are more likely to form when the hydrofluorocarbon has unsaturated bonds. Furthermore, when the etching gas composition of this disclosure contains an oxidizing gas, the etching rate for films containing at least Si and O but not N (preferably silicon oxide films) decreases, and nitrogen-containing silicon compound films, particularly silicon nitride films, tend to be etched more selectively against films containing at least Si and O but not N (preferably silicon oxide films).

[0060] The oxidizing gas is not particularly limited as long as it is a gas that can react with and remove the deposition derived from the hydrofluorocarbon, for example, O ２ F ２ , Br ２ , O ３ CO, CO ２ COCl ２ COF ２ No, no ２ SO ２ SO ３ These are some examples. These may be used individually or in combination of two or more. Among them, O ２ F ２ , Br ２ , O ３ CO, CO ２ COCl ２ COF ２ No, no ２ SO ２ SO ３ Preferably, O ２ It is preferable.

[0061] The volume ratio of hydrofluorocarbons having 5 or fewer carbon atoms to oxidizing gases in the etching gas composition of this disclosure is the value obtained by dividing the volume of oxidizing gas by the volume of hydrofluorocarbons having 5 or fewer carbon atoms, and is preferably 0 to 100, more preferably 0.01 to 10, even more preferably 0.1 to 5, and particularly preferably 0.5 to 3. This tends to allow the effects of this disclosure to be more favorably obtained and to yield a better etching shape. Furthermore, it tends to selectively etch nitrogen-containing silicon compound films, particularly silicon nitride films, against films containing at least Si and O but not N (preferably silicon oxide films).

[0062] In 100% by volume of the etching gas composition of this disclosure, the content of hydrofluorocarbons having 5 or fewer carbon atoms, or the total content of hydrofluorocarbons having 5 or fewer carbon atoms and oxidizing gases, may be 100% by volume, but is preferably 1 to 90% by volume, more preferably 5 to 80% by volume, even more preferably 10 to 60% by volume, and particularly preferably 15 to 40% by volume. When the content of hydrofluorocarbons having 5 or fewer carbon atoms, or the total content of hydrofluorocarbons having 5 or fewer carbon atoms and oxidizing gases, is within the above range, the effects of this disclosure tend to be superior while reducing costs. In 100% by volume of the etching gas composition of this disclosure, the content of inert gases is preferably 10 to 99% by volume, more preferably 20 to 95% by volume, even more preferably 40 to 90% by volume, and particularly preferably 60 to 85% by volume. When the content of inert gases is within the above range, the effects of this disclosure tend to be superior while reducing costs and considering safety. In this specification, the content of each gas component in the gas composition is measured, for example, by infrared spectroscopy.

[0063] In 100 volume percent of the etching gas composition of this disclosure, the total content of hydrofluorocarbons having 5 or fewer carbon atoms and inert gases is preferably 80 volume percent or more, more preferably 90 volume percent or more, even more preferably 95 volume percent or more, particularly preferably 98 volume percent or more, and may be 100 volume percent. When the gas composition of the etching gas composition is within the above range, the effects of this disclosure tend to be superior. In 100 volume percent of the etching gas composition of this disclosure, the total content of hydrofluorocarbons having 5 or fewer carbon atoms, oxidizing gases and inert gases is preferably 80 volume percent or more, more preferably 90 volume percent or more, even more preferably 95 volume percent or more, particularly preferably 98 volume percent or more, and may be 100 volume percent. When the gas composition of the etching gas composition is within the above range, the effects of this disclosure tend to be superior.

[0064] In 100% by volume of the etching gas composition of this disclosure, the hydrogen gas content is preferably 1% by volume or less, more preferably 0.1% by volume or less, even more preferably 0.01% by volume or less, and particularly preferably 0.00% by volume. This tends to result in superior effects of the disclosure. In 100% by volume of the etching gas composition of this disclosure, SF ６ The gas content is preferably 1% by volume or less, more preferably 0.1% by volume or less, even more preferably 0.01% by volume or less, and particularly preferably 0.00% by volume. This tends to result in superior effects of the present disclosure. In 100% by volume of the etching gas composition of the present disclosure, NF ３ The gas content is preferably 1% by volume or less, more preferably 0.1% by volume or less, even more preferably 0.01% by volume or less, and particularly preferably 0.00% by volume. This tends to result in superior effects of the present disclosure. In 100% by volume of the etching gas composition of the present disclosure, CF ４ The gas content is preferably 1% by volume or less, more preferably 0.1% by volume or less, even more preferably 0.01% by volume or less, and particularly preferably 0.00% by volume. This tends to result in superior effects of the present disclosure.

[0065] In the etching method of this disclosure, a nitrogen-containing silicon compound film is etched using a plasma gas obtained by plasma-generating the etching gas composition of this disclosure. Specifically, for example, a hydrofluorocarbon with 5 or fewer carbon atoms is supplied into a chamber to prepare the etching gas composition of this disclosure in the chamber. Then, the etching gas composition of this disclosure prepared in the chamber is plasma-generated, and the nitrogen-containing silicon compound film on the substrate placed in the chamber is etched with the plasma gas.

[0066] In the etching method of this disclosure, a hydrofluorocarbon having 5 or fewer carbon atoms and, if necessary, an oxidizing gas are supplied into the chamber. These may be supplied to the chamber independently, or they may be prepared as a mixed gas beforehand and then supplied to the chamber. The total flow rate of the gas supplied to the chamber can be appropriately selected considering the concentration and pressure conditions, depending on the volume of the chamber and the exhaust capacity of the gas discharge means.

[0067] In the following description, the nitrogen-containing silicon compound film to be etched is also referred to as the etched component. Furthermore, the etching gas composition used in the etching method of this disclosure is as described in the description of the etching gas composition of this disclosure.

[0068] [Etching apparatus] The etching method of this disclosure can be realized, for example, by using the etching apparatus described below. Such an etching apparatus is also one of the present disclosures. The etching apparatus of this disclosure comprises an electrode, a temperature control unit for adjusting the temperature of the electrode to 0°C or below, a mounting stage for placing a substrate having a nitrogen-containing silicon compound film, and an etching gas supply unit for supplying hydrofluorocarbon with 5 or fewer carbon atoms to the substrate. The etching apparatus of this disclosure may further comprise an oxidizing gas supply unit for supplying an oxidizing gas into the chamber and / or an inert gas supply unit for supplying an inert gas into the chamber. The etching apparatus of this disclosure is an apparatus for etching a nitrogen-containing silicon compound film at 0°C or below.

[0069] Figure 1 is a schematic diagram showing an example of an etching apparatus according to one embodiment of the present disclosure. The etching apparatus 100 shown in Figure 1 includes a chamber 110 in which a substrate 18 is placed, an etching gas supply unit 140 connected to the chamber 110 for supplying hydrofluorocarbon with 5 or fewer carbon atoms, an oxidizing gas supply unit 150 for supplying an oxidizing gas, an inert gas supply unit 130 for supplying an inert gas, an upper electrode 15, and a lower electrode 14. Note that the etching apparatus 100 does not necessarily have to include the inert gas supply unit 130 and / or the oxidizing gas supply unit 150.

[0070] Furthermore, the etching apparatus 100 includes a control unit (not shown). This control unit consists of, for example, a computer and includes a program, memory, and a CPU. The program incorporates a set of steps to perform a series of operations in the etching method, and according to the program, it adjusts the temperature of the substrate 18, opens and closes the valves of each supply unit, adjusts the flow rate of each gas, adjusts the pressure in the chamber 110, adjusts the power applied to the electrodes, and so on. This program is stored on a computer storage medium, such as a compact disk, hard disk, magneto-optical disk, or memory card, and installed in the control unit. The control unit functions as a temperature control unit that adjusts the temperature of the electrodes to 0°C or below.

[0071] Chamber 110 contains a lower electrode 14 that has the function of holding the substrate 18 and also functions as a stage (a mounting platform on which the substrate is placed), and an upper electrode 15. A pipe 121, which is a gas inlet, is connected to the top of the chamber 110. The pressure inside the chamber 110 can be adjusted, and the etching gas composition can be excited (plasma-ified) by a high-frequency power supply (not shown) that outputs high-frequency power (e.g., 13.56 MHz, microwave, etc.). This allows the excited etching gas composition (plasma gas) to come into contact with the substrate 18 placed on the lower electrode 14, and the substrate 18 can be etched. When high-frequency power is applied from the high-frequency power supply with the etching gas composition introduced, a DC voltage called a self-bias voltage can be generated between the upper electrode 15 and the lower electrode 14 due to the difference in the movement speed of ions and electrons in the plasma. The gas inside the chamber 110 is discharged via pipe 122, which is a gas discharge line.

[0072] The chamber 110 is not particularly limited as long as it is resistant to the gas used and can be reduced to a predetermined pressure, but typically a general chamber such as those found in semiconductor etching equipment is used. Similarly, the supply pipes and other piping for supplying the etching gas are not particularly limited as long as they are resistant to the gas used, and general types can be used.

[0073] The etching gas supply unit 140 adjusts the supply amount using valves 143 and 144 and flow rate adjustment means 142 to supply hydrofluorocarbons with 5 or fewer carbon atoms from pipes 141 and 145 to pipe 121.

[0074] The oxidizing gas supply unit 150 adjusts the supply amount using valves 153 and 154 and flow rate adjustment means 152 to supply oxidizing gas from pipes 151 and 155 to pipe 121.

[0075] The inert gas supply unit 130 adjusts the supply amount using valves 133 and 134 and flow rate adjustment means 132 to supply inert gas from pipes 131 and 135 to pipe 121.

[0076] Outside the chamber 110, heating means (not shown) for heating the chamber 110 and cooling means (not shown) for cooling the chamber 110 may be provided.

[0077] One side of the chamber 110 is equipped with a gas discharge means for discharging the reaction gas. The vacuum pump 127 of the gas discharge means discharges the reaction gas from the chamber 110 via the piping 122. The reaction gas can be recovered by installing a liquid nitrogen trap (not shown) between the piping 122 and the vacuum pump 127. Valves 125 and 126 are installed in the piping 121 and 122 to adjust the pressure. In Figure 1, PI 123 and 124 are pressure gauges, and the control unit can control each flow rate adjustment means and each valve based on their readings.

[0078] The etching method will be specifically described using this etching apparatus 100 as an example. [Etching method using the above etching apparatus] In the etching method of this disclosure, the nitrogen-containing silicon compound film, such as a silicon nitride film, is etched by bringing the plasma gas (excited etching gas composition) obtained by plasmaizing the etching gas composition of this disclosure into contact with the film.

[0079] In the etching method of this disclosure, first, a substrate 18 on which a silicon nitride film is formed is placed in a chamber 110. Next, the chamber 110, pipes 121 and 122, pipes 131 and 135, pipes 141 and 145, and pipes 151 and 155 are evacuated to a predetermined pressure using a vacuum pump 127. At this time, the temperature inside the chamber may be adjusted to a predetermined temperature using heating means (not shown) or cooling means (not shown). Once the inside of the chamber is stable, hydrofluorocarbon with 5 or fewer carbon atoms is supplied to pipe 121 from an etching gas supply unit 140 at a predetermined flow rate. Alternatively, inert gas may be supplied to pipe 121 from an inert gas supply unit 130 at a predetermined flow rate. Similarly, oxidizing gas may be supplied to pipe 121 from an oxidizing gas supply unit 150 at a predetermined flow rate.

[0080] A hydrofluorocarbon with five or fewer carbon atoms and, if necessary, an oxidizing gas are mixed in a predetermined composition and supplied to the chamber 110. The pressure inside the chamber 110 is controlled to a predetermined level while introducing the mixed etching gas (etching gas composition of this disclosure) into the chamber 110 as necessary. High-frequency power is applied from a high-frequency power supply for a predetermined time to generate a DC voltage called a self-bias voltage between the upper electrode 15 and the lower electrode 14 to excite the etching gas composition, and etching is performed by reacting the excited etching gas composition with the material to be etched. The flow rate of the etching gas can be appropriately set based on the volume and pressure of the chamber, etc.

[0081] After the etching process is completed, the vacuum pump 127 is stopped and the vacuum is released by replacing it with an inert gas. As described above, the etching method of this disclosure using the etching apparatus can etch the nitrogen-containing silicon compound film, which is the component to be etched.

[0082] (Etching conditions in the etching method of this disclosure) In the etching method of this disclosure, the temperature of the member to be etched (electrode) when the plasma gas obtained by plasma-forming the etching gas composition of this disclosure is brought into contact with the member to be etched is 0°C or lower, preferably -30°C or lower, more preferably -60°C or lower, and particularly preferably -80°C or lower. The lower limit is not particularly limited, but for example, it is -196°C or higher. The temperature of the substrate is the same as the temperature of the electrode on which the substrate is placed, and is substantially equal to the temperature of the member to be etched (film). However, during the etching reaction, the temperature of the substrate and the temperature of the member to be etched (film) may rise due to the heat of reaction. In this disclosure, it is sufficient that the temperature of at least the electrode (preferably the lower electrode) is within the above temperature range.

[0083] Furthermore, when bringing the plasma gas into contact with the material to be etched, the pressure inside the chamber where the substrate on which the material to be etched is formed is placed is preferably 10 Pa or less, more preferably 5 Pa or less, and even more preferably 1 Pa or less, in order to obtain a stable plasma and to suppress side etching by increasing the straightness of ions. On the other hand, if the pressure inside the chamber is too low, there is a risk that the number of ionized ions will decrease and a sufficient plasma density cannot be obtained, so it is preferable that the pressure be 0.05 Pa or higher.

[0084] When performing plasma etching, it is preferable to generate a negative DC self-bias voltage between the electrodes. The negative DC self-bias voltage to be generated is preferably 500V or more in absolute value, and more preferably 750V or more in absolute value, in order to perform etching with high linearity perpendicular to the material to be etched. The higher the absolute value of the negative DC self-bias voltage, the more it is possible to reduce side etching. On the other hand, if the absolute value of the negative DC self-bias voltage exceeds 10,000V, there is a risk of increased damage to the substrate, so it is preferable that the absolute value of the DC self-bias voltage is 10,000V or less. In addition, the power applied to the electrodes is preferably 100 to 1,000W, more preferably 150 to 500W.

[0085] The processing time for the etching process is not particularly limited, but considering the efficiency of the semiconductor device manufacturing process, it is preferably within 60 minutes. Here, the processing time for the etching process refers to the time during which power is applied to the electrode (the time during which plasma gas is generated).

[0086] The etching method of this disclosure is not particularly limited, but examples include capacitively coupled plasma (CCP) etching, reactive ion etching (RIE), inductively coupled plasma (ICP) etching, electron cyclotron resonance (ECR) plasma etching, and microwave etching. In particular, inductively coupled plasma etching is preferred among the etching methods of this disclosure. Generally, inductively coupled plasma is considered to have a higher electron density than capacitively coupled plasma processing equipment, and a high decomposition rate of etching gas can be expected.

[0087] [Method for Manufacturing Semiconductor Devices] The etching method of the present disclosure described above can be used as a method for etching a nitrogen-containing silicon compound film by applying the etching method to a substrate having a nitrogen-containing silicon compound film. By etching a nitrogen-containing silicon compound film on a substrate using the etching method of the present disclosure, semiconductor devices can be manufactured at low cost. The method for manufacturing semiconductor devices of the present disclosure is characterized by comprising a step of etching a nitrogen-containing silicon compound film by applying the etching method described above to a substrate having a nitrogen-containing silicon compound film. The step of etching a nitrogen-containing silicon compound film by applying the etching method described above to a substrate having a nitrogen-containing silicon compound film can be carried out by the etching method of the present disclosure described above. The substrate having a nitrogen-containing silicon compound film is not particularly limited as long as there is a portion composed of the nitrogen-containing silicon compound film, but examples include a substrate having a silicon nitride film, a substrate having a silicon nitride carbide film, a substrate having a silicon oxynitride film, and a substrate having silicon nitride carbide.

[0088] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to these examples. First, as substrates to be treated, thermally oxidized SiO ２ Silicon wafers with films formed on them, silicon wafers with SiN films formed on them, silicon wafers with polycrystalline silicon (p-Si) films (polysilicon films) formed on them, silicon wafers with organic ArF resist films (PR) formed on them, and silicon wafers with amorphous carbon (a-C) films formed on them were prepared.

[0089] The film thickness of the substrate to be treated was measured before and after etching using a spectroscopic ellipsometer (manufactured by Nippon Semilab Co., Ltd., product name: SE-2000), and the amount of etching was calculated. Furthermore, the etching rate (ER) and selectivity ratio were calculated based on the calculated amount of etching.

[0090] [Examples and Comparative Examples] An etching apparatus 100 shown in Figure 1 was used. This etching apparatus is an inductively coupled plasma processing apparatus. First, the substrate to be processed was placed on the lower electrode in the chamber, and after the chamber was sufficiently evacuated, the temperature of the lower electrode was set to the temperatures listed in Tables 1 to 6. The temperature of the substrate was the same as the temperature of the lower electrode and was substantially equal to the temperature of the film to be etched. Next, gas was circulated as described in Tables 1 to 6. The pressure in the chamber at this time was 1 Pa. Then, high-frequency power was applied (applied power was 300 W, and the absolute value of the negative DC self-bias voltage was 550 V), the etching gas composition was plasma-generated, and etching was performed with the plasma gas. After a predetermined time (1 to 3 minutes, etching time as listed in the table) had elapsed, the power application was stopped, the gas circulation was also stopped, and etching was completed. Finally, the chamber was evacuated, and N ２ The substrate was removed after gas replacement. The results are shown in Tables 1 to 6. The substrate to be treated was thermally oxidized SiO ２ Silicon wafers with a film formed on them, silicon wafers with a SiN film formed on them, silicon wafers with a polycrystalline silicon (p-Si) film (polysilicon film) formed on them, silicon wafers with an ArF resist (PR) film formed on them, and silicon wafers with an amorphous carbon (a-C) film formed on them were all placed in the same chamber and etched simultaneously. In the table, an asterisk (*) next to the etching rate (ER in the table) indicates that all of the target films were etched. Also, TFPy in the table refers to 3,3,3-trifluoropropyne (C) ３ HF ３ ), 1234E is trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E), C ３ H ２ F ４ ), C ３ HF ７ This is 1,1,1,2,3,3,3-heptafluoropropane, CH ３ F stands for monofluoromethane.

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097] Tables 1 to 6 show that in the example where a nitrogen-containing silicon compound film is etched at 0°C or below using a plasma gas obtained by plasma-forming an etching gas composition containing a hydrofluorocarbon with 5 or fewer carbon atoms, the etching rate for the nitrogen-containing silicon compound film can be improved. Furthermore, Table 4 shows that when the etching gas composition of this disclosure contains an oxidizing gas, the etching rate for a film containing at least Si and O but not N (preferably a silicon oxide film) decreases, and nitrogen-containing silicon compound films, particularly silicon nitride films, can be etched more selectively from a film containing at least Si and O but not N (preferably a silicon oxide film).

[0098] 14 Lower electrode 15 Upper electrode 18 Substrate 100 Etching apparatus 110 Chamber 121, 122 Piping 123, 124 PI (pressure gauge) 125, 126 Valve 127 Vacuum pump 130 Inert gas supply unit 131, 135 Piping 132 Flow rate adjustment means 133, 134 Valve 140 Etching gas supply unit 141, 145 Piping 142 Flow rate adjustment means 143, 144 Valve 150 Oxidizing gas supply unit 151, 155 Piping 152 Flow rate adjustment means 153, 154 Valve

Claims

An etching method for etching a nitrogen-containing silicon compound film at 0°C or below using a plasma gas obtained by plasma-forming an etching gas composition containing a hydrofluorocarbon with 5 or fewer carbon atoms. The etching method according to claim 1, wherein the nitrogen-containing silicon compound film is etched at -30°C or below. The etching method according to claim 1, wherein the nitrogen-containing silicon compound film is etched at -60°C or below. The etching method according to claim 1, wherein the nitrogen-containing silicon compound film is etched at -80°C or below. The etching method according to claim 1, wherein the nitrogen-containing silicon compound film is a silicon nitride film. The etching method according to claim 1, wherein the number of carbon atoms in the hydrofluorocarbon is 2 to 4. The etching method according to claim 1, wherein the hydrofluorocarbon has unsaturated bonds. The etching method according to claim 1, wherein the hydrofluorocarbon does not have unsaturated bonds. The hydrofluorocarbons are 3,3,3-trifluoropropyne (TFPy), trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)(1234E)), and 1,1,1,2,3,3,3-heptafluoropropane (C ３ HF ７ The etching method according to claim 1, characterized in that it is one or more selected from the group consisting of ), cis-1,3,3,3-tetrafluoropropene (HFO-1234ze(Z)), and monofluoromethane. The etching method according to claim 1, wherein the etching gas composition further comprises an oxidizing gas. wherein the oxidizing gas is O ２ , F ２ , Br ２ , O ３ , CO, CO ２ , COCl ２ , COF ２ , NO, NO ２ , SO ２ and SO ３ ​ The etching method according to claim 1, wherein the etching gas composition further comprises an inert gas. The etching method according to claim 1, wherein the total content of the hydrofluorocarbon, oxidizing gas, and inert gas in the etching gas composition is 100% by volume. The etching method according to claim 1, wherein the nitrogen-containing silicon compound film is selectively etched. The hydrofluorocarbon has 2 to 4 carbon atoms and has unsaturated bonds, The etching method according to claim 1, wherein the etching gas composition further comprises an oxidizing gas. A method for manufacturing a semiconductor device, comprising the step of etching the nitrogen-containing silicon compound film on a substrate having the nitrogen-containing silicon compound film by applying the etching method described in any one of claims 1 to 15. Electrodes and, A temperature control unit that adjusts the electrode temperature to 0°C or below, A mounting platform on which a substrate having a nitrogen-containing silicon compound film is placed, An etching gas supply unit that supplies hydrofluorocarbon with 5 or fewer carbon atoms to the substrate, An etching apparatus equipped with the following features for etching nitrogen-containing silicon compound films at temperatures below 0°C.

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