Etching method, semiconductor device manufacturing method, etching apparatus, and etching gas composition

Abstract

The purpose of the present invention is to provide: an etching method exhibiting an excellent etching rate with respect to silicon; a method for manufacturing a semiconductor device; an etching apparatus; and an etching gas composition. The present invention pertains to an etching method for etching silicon by using a plasma gas obtained by converting an etching gas composition containing fluorine gas into plasma.

Description

Etching method, semiconductor device manufacturing method, etching apparatus, and etching gas composition

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

[0002] In the manufacture of semiconductor devices, a TSV (Through Silicon Via) technology is sometimes used in which a via hole (opening) is provided that penetrates from one surface of a semiconductor substrate to the other, and a conductive material that serves as wiring is formed in the via hole, thereby electrically connecting conductors provided on each main surface.

[0003] A typical process for anisotropic dry etching of silicon to form deep holes with high aspect ratios, such as via holes, is the so-called Bosch process, in which an etching step and a protective layer formation step are alternately repeated under plasma (see Patent Document 1). In the etching step of this process, sulfur hexafluoride (SF) is mainly used as an etching gas. ６ In the protective layer forming step of this process, a protective layer forming gas is mainly a fluorocarbon (especially C ４ F ８ ) has been used.

[0004] JP 2013-206991 A

[0005] Sulfur hexafluoride (SF ６ ) has been used as a key gas supporting anisotropic dry etching technology for silicon, so it is not easy to find an alternative gas, but providing an excellent alternative gas would be very beneficial. The present disclosure aims to provide an etching method, a semiconductor device manufacturing method, an etching apparatus, and an etching gas composition that are excellent in etching rate for silicon.

[0006] As a result of extensive research, the present inventors have found that a good etching rate for silicon can be obtained by etching silicon with a plasma gas obtained by converting an etching gas composition containing fluorine gas into plasma, and have thus completed the present disclosure.

[0007] The present disclosure (1) relates to an etching method for etching silicon using a plasma gas obtained by converting an etching gas composition containing fluorine gas into plasma.

[0008] The present disclosure (2) relates to the etching method according to the present disclosure (1), wherein the etching gas composition further contains an iodine-containing compound gas.

[0009] The present disclosure (3) relates to the etching method according to the present disclosure (1) or (2), which selectively etches silicon.

[0010] The present disclosure (4) is a method for manufacturing a gas containing iodine, the gas containing iodine being selected from the group consisting of HI, C ｘ F ｙ I ｚ (where x, y, and z are integers equal to or greater than 1), and I ２ The present invention relates to an etching method according to the present disclosure (2) or (3), wherein the gas is at least one selected from the group consisting of:

[0011] The present disclosure (5) is a method for manufacturing a gas mixture of iodine-containing compounds, comprising: ３ and (3) at least one gas selected from the group consisting of I.

[0012] The present disclosure (6) relates to the etching method according to the present disclosure (2) or (3), in which the iodine-containing compound gas is HI gas.

[0013] The present disclosure (7) relates to the etching method according to any one of the present disclosures (1) to (6), wherein the etching gas composition further contains an inert gas.

[0014] The present disclosure (8) relates to the etching method according to any one of the present disclosures (2) to (7), wherein the volume ratio of the fluorine gas to the iodine-containing compound gas contained in the etching gas composition is 0.01 to 100, as a value obtained by dividing the volume of the iodine-containing compound gas by the volume of the fluorine gas.

[0015] The present disclosure (9) relates to the etching method according to any one of the present disclosures (1) to (8), wherein the silicon is any one of a polysilicon film formed on a substrate, an amorphous silicon film formed on a substrate, an epitaxially grown silicon film formed on a substrate, and a single-crystal silicon substrate.

[0016] The present disclosure (10) relates to a method for manufacturing a semiconductor device, including a step of applying the etching method according to any one of the present disclosures (1) to (9) to a substrate having silicon, thereby etching the silicon.

[0017] The present disclosure (11) relates to a method for manufacturing a semiconductor device, which applies the etching method according to any one of the present disclosures (1) to (9) to a substrate having silicon, and repeatedly performs a step of etching the silicon and a step of forming a protective layer on the surface of the silicon etched by the above step.

[0018] The present disclosure (12) relates to the method for manufacturing a semiconductor device according to the present disclosure (10) or (11), wherein the silicon-containing substrate is any one of a substrate having a polysilicon film, a substrate having an amorphous silicon film, a substrate having an epitaxially grown silicon film, and a single-crystal silicon substrate.

[0019] The present disclosure (13) relates to an etching apparatus including: an electrode; a mounting table for mounting a substrate; a fluorine gas supply unit for supplying fluorine gas to the substrate; and an iodine-containing compound gas supply unit for supplying iodine-containing compound gas to the substrate.

[0020] The present disclosure (14) relates to an etching gas composition containing fluorine gas and an iodine-containing compound gas.

[0021] According to the present disclosure, the etching method uses a plasma gas obtained by plasmatizing an etching gas composition containing fluorine gas to etch silicon, and therefore has an excellent etching rate for silicon.

[0022] According to the present disclosure, the method for manufacturing a semiconductor device includes a step of applying the etching method of the present disclosure to a substrate having silicon to etch the silicon, and therefore has an excellent etching rate for silicon, allowing semiconductor devices to be manufactured with high productivity.

[0023] According to the present disclosure, the etching apparatus is provided with an electrode, a mounting table for placing a substrate thereon, a fluorine gas supply unit for supplying fluorine gas to the substrate, and an iodine-containing compound gas supply unit for supplying iodine-containing compound gas to the substrate, and therefore has an excellent etching rate for silicon.

[0024] According to the present disclosure, the etching gas composition contains fluorine gas and an iodine-containing compound gas, and therefore has an excellent etching rate for silicon.

[0025]

[0013] Fig. 1 is a schematic diagram illustrating an example of an etching apparatus according to an embodiment of the present disclosure. Fig. 2 is a schematic diagram illustrating an overview of the Bosch process.

[0026] The present disclosure will be described in detail below, but the following description of the constituent elements is an example of an embodiment of the present disclosure, and the present disclosure is not limited to these specific details. Various modifications can be made within the scope of the gist of the present disclosure.

[0027] In this specification, unless otherwise specified, the expression "X to Y" in the description of a numerical range means at least X and at most Y. For example, "1 to 5% by mass" means "at least 1% by mass and at most 5% by mass."

[0028] <Etching Method> The etching method of the present disclosure is an etching method for etching silicon using a plasma gas obtained by plasmatizing an etching gas composition containing fluorine gas and, optionally, an iodine-containing compound gas, which has an excellent etching rate for silicon.

[0029] The reason why the above-mentioned effect is obtained is not entirely clear, but it is presumed to be due to the following mechanism: Fluorine gas becomes fluorine radicals by the plasma, and these fluorine radicals react with iodine in the iodine-containing compound to produce IF ５ , IF３ The resulting iodine fluoride compounds are highly reactive, particularly with silicon, and therefore have a high etching rate for silicon. In addition, since the atomic weight of iodine itself is large, it is believed that the ion-assisted etching effect is also excellent.

[0030] Examples of silicon include polycrystalline silicon (p-Si), amorphous silicon, and single crystal silicon. Examples include silicon films such as polysilicon films, amorphous silicon films, and epitaxially grown silicon films formed on a substrate, as well as single crystal silicon substrates. The epitaxial growth may be homoepitaxial growth when the substrate is a silicon substrate, or heteroepitaxial growth when the substrate is a substrate other than a silicon substrate. An epitaxially grown silicon film is typically a single crystal silicon film made of single crystal silicon. In this specification, the term "single crystal silicon" includes both epitaxially grown silicon films and single crystal silicon substrates, unless otherwise specified and unless there is a technical contradiction.

[0031] In the etching method of the present disclosure, etching of silicon, particularly polysilicon films, is preferably carried out at a rate of 15 nm / min or more, more preferably 20 nm / min or more, even more preferably 24.5 nm / min or more, and particularly preferably 30.0 nm / min or more, with no particular upper limit, for example, 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 electrodes (the time during which plasma gas is generated) by measuring the film thickness before and after the etching process using a spectroscopic ellipsometer.

[0032] The etching method of the present disclosure is suitable for selectively etching silicon, particularly polysilicon films. In this specification, "selectively etching silicon" means that the ratio of the etching rates of silicon to a material other than silicon (silicon / material other than silicon) is 1.1 or more. The etching rate ratio is preferably 1.5 or more, more preferably 2 or more, and even more preferably 8 or more. In particular, the etching method of the present disclosure is suitable for selectively etching polysilicon films relative to films other than polysilicon films.

[0033] Examples of films other than polysilicon films include films containing at least Si and O (preferably, films containing at least Si and O and not containing N), films containing at least Si and N, amorphous carbon films, and films containing at least Ti and N. These may be used alone or in combination of two or more. Among these, films containing at least Si and O (preferably, films containing at least Si and O and not containing N) and films containing at least Ti and N are preferred.

[0034] The etching rate ratio between a polysilicon film and a film containing at least Si and O (polysilicon film / film containing at least Si and O) is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more. Examples of films containing at least Si and O (preferably films containing at least Si and O and not containing N) include silicon oxide (SiO, where SiO does not indicate the stoichiometric ratio of each element but refers to a film containing silicon atoms and oxygen atoms. For example, SiO ｘ (x is 1 or more and 2 or less) and SiO ２ In this specification, a film containing at least Si and O but not N means that the N content in 100% by mass of the film is 1% by mass or less, preferably 0.1% by mass or less, more preferably 0.01% by mass or less, and even more preferably 0% by mass.

[0035] The etching rate ratio between the polysilicon film and the film containing at least Si and N (polysilicon film / film containing at least Si and N) is preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 2 or more. The film containing at least Si and N includes 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 0.3 or more and 9 or less) and Si ３ N ４ ) film, silicon oxide carbonitride (SiOCN, where SiOCN does not indicate the stoichiometric ratio of each element, but 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, but refers to a film containing silicon atoms, oxygen atoms, and nitrogen atoms. For example, Si ４ O ｘ N ｙ (x is 3 or more and 6 or less, y is 2 or more and 4 or less) or Si ４ O ５ N ３ ) film, and silicon carbide nitride (SiCN; here, SiCN does not indicate the stoichiometric ratio of each element, but refers to a film containing silicon atoms, carbon atoms, and nitrogen atoms. For example, a material containing 20 to 50 atomic % of silicon, 5 to 30 atomic % of carbon, and 10 to 30 atomic % of nitrogen) film.

[0036] The etching rate ratio of the polysilicon film to the amorphous carbon film (polysilicon film / amorphous carbon film) is preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 2 or more. Examples of amorphous carbon films include amorphous carbon films that do not have a crystalline structure.

[0037] The etching rate ratio between the polysilicon film and the film containing at least Ti and N (polysilicon film / film containing at least Ti and N) is preferably 2 or more, more preferably 4 or more, and even more preferably 8 or more. The film containing at least Ti and N includes 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 0.3 or more and 9 or less) and Ti ３ N４ ) film, titanium oxycarbonitride (TiOCN, where TiOCN does not indicate the stoichiometric ratio of each element, but 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, but refers to a film containing titanium atoms, oxygen atoms, and nitrogen atoms. For example, Ti ４ O ｘ N ｙ (x is 3 or more and 6 or less, y is 2 or more and 4 or less) or Ti ４ O ５ N ３ ) film, and titanium carbide nitride (TiCN; here, 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, a material containing 20 to 50 atomic % of titanium, 5 to 30 atomic % of carbon, and 10 to 30 atomic % of nitrogen) film.

[0038] In the etching method of the present disclosure, the silicon film is preferably formed on a substrate. The substrate is not particularly limited as long as the silicon film is formed on the substrate, but is preferably a semiconductor device substrate, and examples thereof include a silicon substrate, a compound semiconductor substrate, a quartz substrate, and a glass substrate. In addition to the silicon film, a film containing a metal nitride, a metal wiring film, etc. may be formed on the surface of the substrate, in addition to the above-mentioned film other than the silicon film. A mode in which the film other than the silicon film is adjacent to the silicon film and the silicon film and the film other than the silicon film are exposed is suitable for the etching method of the present disclosure.

[0039] The method for forming the film on the substrate surface is not particularly limited, but examples thereof include chemical vapor deposition (CVD) and sputtering. The thickness of the silicon film is also not particularly limited, but can be, for example, 0.1 nm to 1 μm.

[0040] In the etching method of the present disclosure, the substrate is preferably placed in a chamber and the etching is performed. The etching method of the present disclosure preferably includes a step of reducing the pressure inside the chamber and / or a step of replacing the atmosphere inside the chamber with an inert gas. The etching method of the present disclosure more preferably includes a step of etching silicon using a plasma gas obtained by plasmatizing the etching gas composition of the present disclosure in the chamber, and then reducing the pressure inside the chamber and / or replacing the atmosphere inside the chamber with an inert gas. This is because by-products generated during etching can be removed. A reduced pressure state refers to a state in which the pressure inside the chamber is lower than the pressure (process pressure) during etching, and generally means 0.133 kPa or less.

[0041] In the etching method of the present disclosure, after the step of subjecting the inside of the chamber to a reduced pressure state, a step of replacing the inside of the chamber with an inert gas may be carried out.

[0042] <<Etching Gas Composition>> The etching gas composition of the present disclosure contains fluorine (F ２ ) gas and iodine-containing compound gas.

[0043] The iodine-containing compound gas is not particularly limited as long as it is a compound gas containing iodine, and examples thereof include HI, C ｘ F ｙ I ｚ (where x, y, and z are integers of 1 or greater), I ２ These may be used alone or in combination of two or more. Among them, HI, C ｘ F ｙ I ｚ is preferred.

[0044] C ｘ F ｙ I ｚ (where x, y, and z are integers of 1 or more) is not particularly limited, and examples thereof include CF ３ I, CF ２ I ２ , CFI ３ , C ２ F ５ I, C ２ F ４I ２ , C ２ F ３ I ３ , C ２ F ２ I ４ , C ２ FI ５ , C ３ F ７ I, C ３ F ６ I ２ , C ３ F ５ I ３ , C ３ F ４ I ４ , C ３ F ３ I ５ , C ３ F ２ I ６ , C ３ FI ７ These may be used alone or in combination of two or more. ３ I is preferred.

[0045] The iodine-containing compound gases are HI and CF ３ Preferably, the gas is at least one selected from the group consisting of 1 and 2, and more preferably, 1H 2 gas.

[0046] As mentioned above, in the etching step of the Bosch process, the etching gas is mainly SF ６ However, SF ６ However, there is a problem in that the so-called global warming potential (GWP) is very high at 25,200. On the other hand, the fluorine gas used in the present disclosure has a GWP of 0, and therefore the present disclosure is also superior in that a gas with a low GWP is used. Furthermore, as the iodine-containing compound gas, HI (GWP 0), CF ３ By using I (GWP 0.4), the present disclosure is superior in that it uses a gas with a low GWP.

[0047] The volume ratio of fluorine gas to iodine-containing compound gas contained in the etching gas composition of the present disclosure, calculated by dividing the volume of the iodine-containing compound gas by the volume of the fluorine gas, is preferably 0.01 to 100, more preferably 0.1 to 10, and even more preferably 0.2 to 5. This tends to result in a superior etching rate for silicon.

[0048] The etching gas composition of the present disclosure is not particularly limited as long as it contains fluorine gas and, if necessary, an iodine-containing compound gas. 100% by volume of the etching gas composition may contain 100% by volume of fluorine gas and iodine-containing compound gas in total, but the etching gas composition may further contain an inert gas.

[0049] Examples of inert gases include Ar and N ２ , He, Ne, Kr, etc. These may be used alone or in combination of two or more. Among these, Ar is preferred because it is stable and inexpensive.

[0050] The content of fluorine gas or the total content of fluorine gas and iodine-containing compound gas in a 100% by volume etching gas composition of the present disclosure 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 16 to 40% by volume. When the content of fluorine gas or the total content of fluorine gas and iodine-containing compound gas is within the above range, the etching rate for silicon tends to be excellent while reducing costs. The content of inert gas in a 100% by volume etching gas composition of the present disclosure 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 84% by volume. When the content of inert gas is within the above range, the etching rate for silicon tends to be excellent while reducing costs and taking safety into consideration. In this specification, the content of each gas component in the gas composition is measured, for example, by infrared spectroscopy.

[0051] In the etching gas composition of the present disclosure, the total content of the fluorine gas, the iodine-containing compound gas, and the inert gas is preferably 80% by volume or more, more preferably 90% by volume or more, even more preferably 95% by volume or more, particularly preferably 98% by volume or more, and may be 100% by volume. When the gas composition of the etching gas composition is within the above range, the etching rate for silicon tends to be superior.

[0052] The etching gas composition of the present disclosure may contain an oxidizing gas, but is advantageous in that it does not need to contain an oxidizing gas, or even if it does contain an oxidizing gas, it can be contained in a small amount. The oxidizing gas is blended for the purpose of removing substances generated during etching, but in the present disclosure, which uses fluorine gas and an iodine-containing compound gas in combination, the generation of unnecessary products can be suppressed, so the amount of oxidizing gas used can be reduced. The oxidizing gas can be O ２ , O ３ , CO, CO ２ , COCl ２ , COF ２ , NO ２ and the like. These may be used alone or in combination of two or more. When the etching gas composition of the present disclosure contains an oxidizing gas, the content of the oxidizing gas in 100 volume% of the etching gas composition of the present disclosure is 1 volume% or more and 50 volume% or less, 2 volume% or more and 30 volume% or less, or 5 volume% or more and 20 volume% or less. When the etching gas composition of the present disclosure does not contain an oxidizing gas or contains only a small amount of an oxidizing gas, the content of the oxidizing gas in 100 volume% of the etching gas composition of the present disclosure is preferably 1 volume% or less, more preferably 0.5 volume% or less, even more preferably 0.1 volume% or less, particularly preferably 0.01 volume% or less, and may even be 0.00 volume%.

[0053] In the etching method of the present disclosure, silicon is etched using a plasma gas obtained by converting the etching gas composition of the present disclosure into plasma. Specifically, for example, fluorine gas is supplied into a chamber, and the etching gas composition of the present disclosure is prepared in the chamber. The etching gas composition of the present disclosure prepared in the chamber is then converted into plasma, and the plasma gas is used to etch silicon on a substrate placed in the chamber.

[0054] In the etching method of the present disclosure, fluorine gas and, if necessary, an iodine-containing compound gas are supplied into the chamber, and they may be supplied independently into the chamber, or may be prepared in advance as a mixed gas and then supplied into the chamber. The total flow rate of the gases supplied into the chamber can be appropriately selected in consideration of the concentration conditions and pressure conditions, depending on the volume of the chamber and the exhaust capacity of the gas exhaust means.

[0055] In the following description, silicon to be etched is also referred to as a “member to be etched.” The etching gas composition used in the etching method of the present disclosure is as described above for the etching gas composition of the present disclosure.

[0056] [Etching Apparatus] The etching method of the present disclosure can be realized, for example, by using the following etching apparatus. Such an etching apparatus also constitutes one aspect of the present disclosure. The etching apparatus of the present disclosure includes an electrode, a mounting table for mounting a substrate, a fluorine gas supply unit that supplies fluorine gas to the substrate, and an iodine-containing compound gas supply unit that supplies iodine-containing compound gas to the substrate. The etching apparatus of the present disclosure may further include an inert gas supply unit that supplies an inert gas into the chamber. Note that if an iodine-containing compound gas is not supplied, the iodine-containing compound gas supply unit may not be provided.

[0057] Fig. 1 is a schematic diagram showing an example of an etching apparatus according to an embodiment of the present disclosure. The etching apparatus 100 shown in Fig. 1 includes a chamber 110 in which a substrate 18 is placed, a fluorine gas supply unit 140 connected to the chamber 110 and supplying fluorine gas, an iodine-containing compound gas supply unit 150 that supplies an iodine-containing compound gas, an inert gas supply unit 130 that supplies 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.

[0058] The etching apparatus 100 further includes a control unit (not shown). This control unit is, for example, a computer, and includes a program, memory, and a CPU. The program incorporates steps for performing a series of operations in the etching method, and in accordance with the program, the temperature of the substrate 18, the opening and closing of the valves of each supply unit, the flow rate of each gas, the pressure inside the chamber 110, and the power applied to the electrodes are adjusted. This program is stored on a computer storage medium, such as a compact disk, a hard disk, a magneto-optical disk, or a memory card, and is installed in the control unit.

[0059] The chamber 110 contains a lower electrode 14, which holds a substrate 18 and also functions as a stage (a support for placing the substrate), and an upper electrode 15. A pipe 121, which serves as a gas inlet, is connected to the top of the chamber 110. The pressure inside the chamber 110 is adjustable, and an etching gas composition can be excited (generated into plasma) by a high-frequency power source (not shown) that outputs high-frequency (e.g., 13.56 MHz, microwave, etc.) power. This allows the excited etching gas composition (plasma gas) to come into contact with the substrate 18 placed on the lower electrode 14, thereby etching the substrate 18. When high-frequency power is applied from the high-frequency power source (not shown) 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 migration speeds of ions and electrons in the plasma. Gas inside the chamber 110 is exhausted via a pipe 122, which serves as a gas exhaust line.

[0060] The chamber 110 is not particularly limited as long as it is resistant to the gas used and can be depressurized to a predetermined pressure, but typically a general chamber provided in a semiconductor etching apparatus is used. Furthermore, the supply pipe for supplying the etching gas and other piping are also not particularly limited as long as they are resistant to the gas used, and general piping can be used.

[0061] The fluorine gas supply unit 140 adjusts the supply amount using valves 143 and 144 and a flow rate adjusting means 142 , and supplies fluorine gas from pipes 141 and 145 to the pipe 121 .

[0062] The iodine-containing compound gas supply unit 150 adjusts the supply amount using valves 153 and 154 and a flow rate adjusting means 152 , and supplies the iodine-containing compound gas from pipes 151 and 155 to the pipe 121 .

[0063] The inert gas supply unit 130 adjusts the supply amount using valves 133 and 134 and a flow rate adjusting means 132 , and supplies the inert gas from pipes 131 and 135 to the pipe 121 .

[0064] A heating means (not shown) for heating the chamber 110 may be disposed outside the chamber 110 .

[0065] A gas exhaust means for exhausting the gas after the reaction is provided on one side of the chamber 110. A vacuum pump 127 of the gas exhaust means exhausts the gas after the reaction from the chamber 110 via a pipe 122. The gas after the reaction can be recovered by providing a liquid nitrogen trap (not shown) between the pipe 122 and the vacuum pump 127. Valves 125 and 126 are provided on the pipes 121 and 122 to adjust the pressure. In addition, in FIG. 1, PIs 123 and 124 are pressure gauges, and a control unit can control the flow rate adjustment means and the valves based on the indicated values.

[0066] The etching method will be specifically described using the etching apparatus 100 as an example. [Etching Method Using the Etching Apparatus] In the etching method of the present disclosure, silicon such as a polysilicon film is etched by bringing a plasma gas (excited etching gas composition) obtained by converting the etching gas composition of the present disclosure into plasma into silicon, such as a polysilicon film, into contact with the silicon.

[0067] In the etching method of the present disclosure, first, the substrate 18 on which the polysilicon film is formed is placed in the chamber 110. Next, the interior of the chamber 110, the pipes 121 and 122, the pipes 131 and 135, the pipes 141 and 145, and the pipes 151 and 155 are evacuated to a predetermined pressure by the vacuum pump 127. At this time, the temperature inside the chamber may be adjusted to a predetermined temperature by a heating means (not shown). Once the inside of the chamber is stabilized, fluorine gas and iodine-containing compound gas are supplied to the pipe 121 at predetermined flow rates from the fluorine gas supply unit 140 and the iodine-containing compound gas supply unit 150. Note that an inert gas may be supplied to the pipe 121 at a predetermined flow rate from the inert gas supply unit 130.

[0068] When fluorine gas and an iodine-containing compound gas are used in combination, they are mixed to a predetermined composition and supplied to the chamber 110. While the mixed etching gas (the etching gas composition of the present disclosure) is introduced into the chamber 110, the pressure inside the chamber 110 is controlled to a predetermined value. High-frequency power is applied from a high-frequency power source (not shown) for a predetermined time, generating 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 the excited etching gas composition reacts with the material to be etched, thereby performing etching. The flow rate of the etching gas can be appropriately set based on the volume and pressure of the chamber, etc.

[0069] After the etching process is completed, the vacuum pump 127 is stopped, and the atmosphere is replaced with an inert gas to release the vacuum. As described above, the etching method of the present disclosure using the etching apparatus described above can etch silicon, which is the member to be etched.

[0070] (Etching conditions in the etching method of the present disclosure) In the etching method of the present disclosure, the temperature of the member to be etched (electrode) when the plasma gas obtained by plasmatizing the etching gas composition of the present disclosure is brought into contact with the member to be etched is preferably 100°C or less, more preferably 80°C or less, and particularly preferably 50°C or less. It may also be used after cooling, in which case the temperature is preferably 20°C or less, more preferably 15°C or less. At temperatures above 100°C, the reactivity of fluorine gas increases, which may increase the load on the etching apparatus. The temperature of the substrate is the same as the temperature of the electrode, and is essentially equal to the temperature of the member to be etched (film); however, during the etching reaction, the temperature of the substrate or the member to be etched (film) may rise due to the heat of reaction. In the present disclosure, it is sufficient that at least the temperature of the electrode (preferably the lower electrode) is within the above temperature range.

[0071] Furthermore, when the plasma gas is brought into contact with the member to be etched, the pressure in the chamber in which the substrate on which the member 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 increase the linearity of ions and suppress side etching. On the other hand, if the pressure in the chamber is too low, there is a risk that the number of ionized ions will be too low and sufficient plasma density will not be obtained, so the pressure is preferably 0.05 Pa or more.

[0072] When performing plasma etching, it is preferable to generate a negative DC self-bias voltage between the electrodes. The generated negative DC self-bias voltage is preferably 500 V or more in absolute value, more preferably 750 V or more in absolute value, in order to perform highly linear etching in the direction perpendicular to the etched material. The higher the absolute value of the negative DC self-bias voltage, the more likely it is that side etching will be reduced. However, if the absolute value of the negative DC self-bias voltage exceeds 10,000 V, there is a risk of significant damage to the substrate. Therefore, it is preferable that the absolute value of the DC self-bias voltage is 10,000 V or less. Furthermore, the power applied to the electrodes is preferably 100 to 1,000 W, more preferably 150 to 500 W.

[0073] The processing time of the etching step is not particularly limited, but is preferably within 60 minutes in consideration of the efficiency of the semiconductor device manufacturing process. Here, the processing time of the etching step refers to the time during which power is applied to the electrodes (the time during which plasma gas is generated).

[0074] The etching method of the present disclosure can be performed using various etching methods, including, but not limited to, capacitively coupled plasma (CCP) etching, reactive ion etching (RIE), inductively coupled plasma (ICP) etching, electron cyclotron resonance (ECR) plasma etching, and microwave etching.

[0075] [Method for manufacturing a semiconductor device] The etching method of the present disclosure described above can be used as a method for etching silicon by applying the etching method to a silicon-containing substrate. By etching silicon on a substrate using the etching method of the present disclosure, semiconductor devices can be manufactured inexpensively. The method for manufacturing a semiconductor device of the present disclosure is characterized by comprising a step of applying the etching method to a silicon-containing substrate to etch silicon. The step of applying the etching method to a silicon-containing substrate to etch silicon can be performed by the etching method of the present disclosure described above. The silicon-containing substrate is not particularly limited as long as it contains a portion made of silicon, and examples include substrates having a silicon film such as a substrate having a polysilicon film, a substrate having an amorphous silicon film, and a substrate having an epitaxially grown silicon film; a single-crystal silicon substrate, and the like.

[0076] The semiconductor device manufacturing method of the present disclosure preferably applies the etching method of the present disclosure to a silicon-containing substrate, alternately repeating an etching step of etching the silicon and a protective layer formation step of forming a protective layer on the surface of the silicon etched by the etching step. That is, the semiconductor device manufacturing method of the present disclosure preferably uses the so-called Bosch process, which is a typical process for anisotropic dry etching of silicon, in which the etching step and the protective layer formation step are alternately repeated. By using the Bosch process for the semiconductor device manufacturing method of the present disclosure, a semiconductor device can be manufactured that includes a substrate having holes with high verticality and good sidewall shape.

[0077] In the etching step of the Bosch process, sulfur hexafluoride (SF ６ ) has been used in the past, but the present disclosure is characterized by using an etching gas composition containing fluorine gas and an iodine-containing compound gas, and the other aspects are the same as those of the conventionally known method.

[0078] 2A and 2B are schematic diagrams showing the outline of the Bosch process. In FIG. 2A, the silicon surface is etched by an etching gas. Next, after FIG. 2A, in FIG. 2B, a protective layer forming gas, C ４ F ８ A protective layer is formed on the silicon surface by this process. After FIG. 2(b), in FIG. 2(c), the silicon surface is etched using an etching gas. At this time, by applying power in a direction perpendicular to the substrate (downward in the plane of the paper), the silicon surface is preferentially etched downward in the plane of the paper while the protective layer on the sidewall is maintained. Then, after FIG. 2(c), FIG. 2(b) is performed again. As described above, by alternately repeating FIG. 2(b) and FIG. 2(c), deep holes with a high aspect ratio (hole depth / hole diameter) can be formed in silicon. Note that PR in FIG. 2 stands for photoresist.

[0079] The step of applying the etching method to a substrate containing silicon to etch silicon can be performed by the etching method of the present disclosure described above.

[0080] The protective layer forming step of forming a protective layer on the surface of the silicon etched in the etching step may be performed according to a known method, for example, by using a protective layer forming gas to form a protective layer on the surface of the silicon.

[0081] The protective layer forming gas (deposition gas) is not particularly limited as long as it can form an organic deposition film, and examples thereof include fluorocarbons and fluorohydrocarbons having double bonds. These may be used alone or in combination of two or more. Examples of the fluorocarbons include C ２ F ２ , C ２ F ４ , C ３ F ４ , C ３ F ６ , C ４ F ２ , C ４ F ４ , C ４ F ６ , C ４ F ８ , C ５ F ４ , C ５ F ６ , C ５ F ８ These may be used alone or in combination of two or more. ４ F ８ is preferred.

[0082] The protective layer forming step may be carried out under known process conditions, for example, the same conditions as those for temperature, pressure, and plasma as those described in the etching method.

[0083] The etching process and the protective layer formation process can also be performed in the same chamber. In this case, the etching process and the protective layer formation process can be switched by switching gases without moving the substrate between chambers, allowing for efficient manufacturing of semiconductor devices.

[0084] 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 processed, a silicon wafer on which a polycrystalline silicon (p-Si) film (polysilicon film) is formed, a thermally oxidized SiO ２ A silicon wafer having a film formed thereon, a silicon wafer having a SiN film formed thereon, a silicon wafer having an amorphous carbon (aC) film formed thereon, and a silicon wafer having a TiN film formed thereon were prepared.

[0085] 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 etching amount was calculated. Furthermore, based on the calculated etching amount, the etching rate and the selectivity (p-Si / SiO ２ The selectivity ratio, p-Si / SiN selectivity ratio, p-Si / aC selectivity ratio, and p-Si / TiN selectivity ratio were calculated.

[0086] [Examples and Comparative Examples] The etching apparatus 100 shown in FIG. 1 was used. First, a substrate to be processed was placed on the lower electrode in the chamber, and the chamber was fully evacuated. The temperature of the lower electrode was then set to 15°C. The temperature of the substrate was the same as that of the lower electrode, and was essentially equal to the temperature of the film to be etched. Next, gas was circulated as shown in Table 1. The pressure in the chamber at this time was set to 1 Pa. Then, high-frequency power was applied (applied power: 400 W, absolute value of negative DC self-bias voltage: 550 V), the etching gas composition was converted into plasma, and etching was performed with the plasma gas. After the etching time shown in Table 1 had elapsed, the application of power was stopped, the flow of gas was also stopped, and etching was completed. Finally, the chamber was evacuated, and N ２ The substrates were removed after the gas was replaced with the gas. The results are shown in Table 1. The substrates were silicon wafers on which polycrystalline silicon (p-Si) films (polysilicon films) were formed, thermally oxidized SiO ２ The silicon wafer with the film formed thereon, the silicon wafer with the SiN film formed thereon, the silicon wafer with the amorphous carbon (aC) film formed thereon, and the silicon wafer with the TiN film formed thereon were all placed in the same chamber and etched simultaneously.

[0087]

[0088] As can be seen from Table 1, a polysilicon film could be etched using a plasma gas obtained by plasmatizing an etching gas composition containing fluorine gas. Furthermore, in an example in which a polysilicon film was etched using a plasma gas obtained by plasmatizing an etching gas composition containing fluorine gas and an iodine-containing compound gas, it was found that the etching rate for the polysilicon film was excellent. Furthermore, it was found that a synergistic effect could be achieved by using fluorine gas and an iodine-containing compound gas in combination. It is believed that amorphous silicon and single-crystal silicon can also be etched in the same way as polysilicon.

[0089] 14 Lower electrode 15 Upper electrode 18 Substrate 100 Etching apparatus 110 Chamber 121, 122 Pipes 123, 124 PI (pressure gauge) 125, 126 Valves 127 Vacuum pump 130 Inert gas supply unit 131, 135 Pipes 132 Flow rate adjustment means 133, 134 Valves 140 Fluorine gas supply unit 141, 145 Pipes 142 Flow rate adjustment means 143, 144 Valves 150 Iodine-containing compound gas supply unit 151, 155 Pipes 152 Flow rate adjustment means 153, 154 Valves

Claims

1. An etching method for etching silicon using a plasma gas obtained by plasmatizing an etching gas composition containing fluorine gas.

2. The etching method according to claim 1, wherein the etching gas composition further contains an iodine-containing compound gas.

3. The etching method according to claim 1, wherein silicon is selectively etched.

4. The iodine-containing compound gas is HI, C ｘ F ｙ I ｚ (where x, y, and z are integers equal to or greater than 1), and I ２ 3. The etching method according to claim 2, wherein the gas is at least one selected from the group consisting of:

5. The iodine-containing compound gas is HI and CF ３ 3. The etching method according to claim 2, wherein the gas is at least one gas selected from the group consisting of I.

6. The etching method according to claim 2, wherein the iodine-containing compound gas is HI gas.

7. The etching method of claim 1, wherein the etching gas composition further comprises an inert gas.

8. The etching method according to claim 2, wherein the volume ratio of fluorine gas to iodine-containing compound gas contained in the etching gas composition is 0.01 to 100, calculated by dividing the volume of the iodine-containing compound gas by the volume of the fluorine gas.

9. The etching method according to claim 1, wherein the silicon is one of a polysilicon film formed on a substrate, an amorphous silicon film formed on a substrate, an epitaxially grown silicon film formed on a substrate, and a single crystal silicon substrate.

10. A method for manufacturing a semiconductor device, comprising the step of applying the etching method according to any one of claims 1 to 9 to a substrate having silicon to etch the silicon.

11. A method for manufacturing a semiconductor device, which comprises repeatedly performing a step of etching silicon by applying the etching method according to any one of claims 1 to 9 to a substrate having silicon, and a step of forming a protective layer on the surface of the silicon etched by the above step.

12. The method for manufacturing a semiconductor device according to claim 10, wherein the silicon-containing substrate is any one of a substrate having a polysilicon film, a substrate having an amorphous silicon film, a substrate having an epitaxially grown silicon film, and a single-crystal silicon substrate.

13. An etching apparatus comprising: an electrode; a mounting table for mounting a substrate thereon; a fluorine gas supply unit for supplying fluorine gas to the substrate; and an iodine-containing compound gas supply unit for supplying iodine-containing compound gas to the substrate.

14. An etching gas composition comprising fluorine gas and an iodine-containing compound gas.

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