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

Abstract

An object of the present invention is to provide an etching method, a manufacturing method of a semiconductor device, an etching apparatus, and an etching gas composition, which are excellent in etching speed of silicon. The present invention relates to an etching method of etching silicon using a plasma gas obtained by plasma-izing an etching gas composition containing fluorine gas.

Description

Technical Field

[0001] This invention relates to etching methods, methods for manufacturing semiconductor devices, etching apparatus, and etching gas compositions.

[0002] Prior Technology

[0003] In the manufacture of semiconductor devices, TSV (Through Si Via) technology is sometimes performed, which involves creating a through-hole (opening) that extends from one side of a semiconductor substrate to the other, and forming a conductive material inside the through-hole as a wiring, thereby electrically connecting the conductors on each main surface.

[0004] A representative process for anisotropic dry etching of silicon with high aspect ratio and deep holes, such as vias, is the so-called Bosch process, which involves alternating etching and protective layer formation processes under plasma (Patent Document 1). In the etching process, sulfur hexafluoride (SF6) is primarily used as the etching gas. Furthermore, in the protective layer formation process, fluorinated carbon (especially C4F8), which forms organic deposition films, is primarily used as the protective layer forming gas.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-206991 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] Since sulfur hexafluoride (SF6) has been used as the base gas for supporting anisotropic dry etching technology of silicon, it is not easy to find a substitute gas, but providing a superior substitute gas would be very beneficial.

[0010] The purpose of this invention is to provide an etching method with excellent etching speed for silicon, a method for manufacturing a semiconductor device, an etching apparatus, and an etching gas composition.

[0011] Solution to the problem

[0012] Through diligent research, the inventors discovered that a good etching rate for silicon can be obtained by using plasma gas to etch silicon. The plasma gas is obtained by plasmaizing an etching gas composition containing fluorine gas, thus completing the present invention.

[0013] The present invention (1) relates to an etching method that uses plasma gas to etch silicon, said plasma gas being obtained by plasmaizing an etching gas composition containing fluorine gas.

[0014] The present invention (2) is an etching method according to the present invention (1), characterized in that the etching gas composition further comprises an iodine-containing compound gas.

[0015] The present invention (3) is an etching method according to the present invention (1) or (2) that selectively etches silicon.

[0016] The present invention (4) is an etching method according to the present invention (2) or (3), wherein the iodine-containing compound gas is selected from HI, C x F y I z (where x, y, z are integers greater than or equal to 1) and at least one gas in the group consisting of I2.

[0017] The present invention (5) is an etching method according to the present invention (2) or (3), wherein the iodine-containing compound gas is at least one gas selected from the group consisting of HI and CF3I.

[0018] The present invention (6) is an etching method according to the present invention (2) or (3), wherein the iodine-containing compound gas is HI gas.

[0019] The present invention (7) is an etching method according to any one of (1) to (6) of the present invention, wherein the etching gas composition further comprises an inert gas.

[0020] The present invention (8) is an etching method according to any one of (2) to (7) of the present invention, wherein the volume ratio of fluorine gas to iodine compound gas contained in the etching gas composition is the value obtained by dividing the volume of iodine compound gas by the volume of fluorine gas, and is 0.01 to 100.

[0021] The present invention (9) is an etching method according to any one of (1) to (8) of the present invention, wherein the silicon is any one of a polycrystalline silicon film formed on a substrate, an amorphous silicon film formed on a substrate, an epitaxial growth film of silicon formed on a substrate, or a single crystal silicon substrate.

[0022] The present invention (10) relates to a method for manufacturing a semiconductor device, comprising the following steps: applying the etching method of any one of the present invention (1) to (9) to an etching substrate having silicon to etch the silicon.

[0023] The present invention (11) relates to a method for manufacturing a semiconductor device, which repeatedly performs the following steps: etching a silicon substrate by applying the etching method of any one of the present invention (1) to (9) to the silicon substrate; and forming a protective layer on the surface of the silicon etched by the step.

[0024] The present invention (12) is a method for manufacturing a semiconductor device according to the present invention (10) or (11), wherein the substrate having silicon is any one of a substrate having a polycrystalline silicon film, a substrate having an amorphous silicon film, a substrate having an epitaxial growth film of silicon, or a single crystal silicon substrate.

[0025] The present invention (13) relates to an etching apparatus comprising:

[0026] electrode;

[0027] A stage on which a substrate is placed;

[0028] A fluorine gas supply unit supplies fluorine gas to the substrate; and

[0029] An iodine-containing compound gas supply unit supplies iodine-containing compound gas to the substrate.

[0030] The present invention (14) relates to an etching gas composition comprising fluorine gas and iodine-containing compound gas.

[0031] The effects of the invention

[0032] According to the present invention, the etching method uses plasma gas obtained by plasma-infusing an etching gas composition containing fluorine gas to etch silicon, thus achieving excellent etching speed for silicon.

[0033] According to the present invention, a method for manufacturing a semiconductor device includes a step of etching silicon by applying the etching method of the present invention to a substrate having silicon, thereby etching silicon. Therefore, the etching speed of silicon is excellent, and semiconductor devices can be manufactured with good productivity.

[0034] According to the present invention, the etching apparatus includes electrodes, a mounting stage for placing 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, thus achieving excellent etching speed for silicon.

[0035] According to the present invention, the etching gas composition contains fluorine gas and iodine-containing compound gas, thus exhibiting excellent etching speed for silicon. Attached Figure Description

[0036] Figure 1 This is a schematic diagram illustrating an example of an etching apparatus according to one embodiment of the present invention.

[0037] Figure 2(a) to (c) are schematic diagrams representing the outline of the Bosch process. Detailed Implementation

[0038] The present invention will now be described in detail, but the description of the constituent elements described below is merely one example of an embodiment of the present invention and is not limited to its specific contents. Various changes can be made within the scope of its gist.

[0039] In this specification, the expression "X to Y" in the description of numerical ranges means above X and below Y unless otherwise stated. For example, "1 to 5% by mass" means "more than 1% by mass and less than 5% by mass".

[0040] <Etching Method>

[0041] The etching method of the present invention is an etching method that uses plasma gas to etch silicon. The plasma gas is obtained by plasma-entraining an etching gas composition containing fluorine gas and, optionally, an iodine-containing compound gas. Therefore, the etching rate of silicon is excellent.

[0042] Although the reasons for achieving the above effects may not be clear, the mechanism is speculated to be as follows.

[0043] Fluorine gas is converted into fluorine radicals through plasma. These fluorine radicals react with iodine in iodine-containing compounds to generate iodine fluoride compounds such as IF5 and IF3. The generated iodine fluoride compounds are highly reactive, especially to silicon, resulting in excellent etching speeds for silicon. Furthermore, it can be argued that due to the relatively large atomic weight of iodine itself, ion-assisted etching also yields excellent results.

[0044] Examples of silicon include: polycrystalline silicon (p-Si), amorphous silicon, and monocrystalline silicon. Examples include: polycrystalline silicon films, amorphous silicon films, and epitaxial growth films of silicon formed on a substrate; and monocrystalline silicon substrates. It should be noted that epitaxial growth can be homoepitaxial growth when the substrate is a silicon substrate, or heteroepitaxial growth when the substrate is a substrate other than a silicon substrate. Silicon epitaxial growth films are typically monocrystalline silicon films containing monocrystalline silicon. In this specification, when referred to as monocrystalline silicon, unless otherwise stated, the term includes both silicon epitaxial growth films and monocrystalline silicon substrates to the extent that there is no technical inconsistency.

[0045] In the etching method of the present invention, the etching of silicon, especially polycrystalline silicon film, is preferably performed at a speed of 15 nm / min or more, more preferably 20 nm / min or more, even more preferably 24.5 nm / min or more, particularly preferably 30.0 nm / min or more, and there is no particular upper limit, for example, 100 μm / min or less or 1 mm / min or less.

[0046] In this specification, the etching rate is a value calculated based on the film thickness before and after etching, measured using a spectroscopic ellipsometry, and thus on the time during which an electric current is applied to the electrode (the time for plasma gas to be generated).

[0047] The etching method of the present invention is suitable for selective etching of silicon, especially polycrystalline silicon films.

[0048] In this specification, "selectively etching silicon" means that the ratio of the etching rate of silicon to that of other materials (silicon / other materials) is 1.1 or higher. The aforementioned etching rate ratio is preferably 1.5 or higher, more preferably 2 or higher, and even more preferably 8 or higher.

[0049] The etching method of the present invention is particularly suitable for selective etching of polycrystalline silicon films relative to films other than polycrystalline silicon films.

[0050] Examples of films other than polycrystalline silicon films include: films containing at least Si and O (preferably films containing at least Si and O but no N), films containing at least Si and N, amorphous carbon films, and films containing at least Ti and N. These can be used individually or in combination of two or more. Among these, films containing at least Si and O (preferably films containing at least Si and O but no N) and films containing at least Ti and N are preferred.

[0051] The ratio of the etching rate of the polycrystalline silicon film to that of the film containing at least Si and O (polycrystalline silicon 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.

[0052] As a film containing at least Si and O (preferably a film containing at least Si and O but no N), silicon oxide (SiO₂, where SiO does not refer to the stoichiometry of the elements, but rather to a film containing silicon atoms and oxygen atoms) can be cited as an example. x (x is 1 or more and 2 or less), SiO2 film.

[0053] In this specification, a membrane containing at least Si and O but no N means that the N content in 100% by mass of the membrane 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.

[0054] The ratio of the etching rate of the polycrystalline silicon film to that of the film containing at least Si and N (polycrystalline silicon 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.

[0055] As a film containing at least Si and N, an example is silicon nitride (SiN). Here, SiN does not refer to the stoichiometry of the elements, but rather to a film containing both silicon and nitrogen atoms. For example, SiN... x (x is 0.3 or higher and 9 or lower), Si3N4 film, silicon oxynitride (SiOCN, where SiOCN does not refer to the stoichiometry of the elements, but refers to a film containing silicon, oxygen, carbon, and nitrogen atoms), silicon oxynitride (SiON, where SiON does not refer to the stoichiometry of the elements, but refers to a film containing silicon, oxygen, and nitrogen atoms. For example, Si4O x N y (x is 3 or more and less than 6, y is 2 or more and less than 4), Si4O5N3 film, silicon carbide (SiCN, where SiCN does not represent the stoichiometry of the elements, but refers to a film containing silicon atoms, carbon atoms and nitrogen atoms. For example, materials containing 20-50 atomic% silicon, 5-30 atomic% carbon and 10-30 atomic% nitrogen) film.

[0056] The etching rate ratio of polycrystalline silicon film to amorphous carbon film (polycrystalline silicon film / amorphous carbon film) is preferably 1.2 or higher, more preferably 1.5 or higher, and even more preferably 2 or higher.

[0057] As an amorphous carbon film, an example of an amorphous carbon film that does not have a crystalline structure can be cited.

[0058] The ratio of the etching rate of the polycrystalline silicon film to that of the film containing at least Ti and N (polycrystalline silicon 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.

[0059] As a film containing at least Ti and N, an example is titanium nitride (TiN, where TiN does not represent the stoichiometry of the elements, but refers to a film containing titanium atoms and nitrogen atoms. For example, TiN...) x (x is 0.3 or higher and 9 or lower), Ti3N4 film, titanium oxide (TiOCN, where TiOCN does not represent the stoichiometry of the elements, but refers to a film containing titanium atoms, oxygen atoms, carbon atoms, and nitrogen atoms), titanium oxide (TiON, where TiON does not represent the stoichiometry of the elements, but refers to a film containing titanium atoms, oxygen atoms, and nitrogen atoms. For example, Ti4O x N y (x is 3 or more and less than 6, y is 2 or more and less than 4), Ti4O5N3 film, titanium nitride carbide (TiCN, where TiCN does not represent the stoichiometry of the elements, 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 listed) film.

[0060] In the etching method of the present invention, the silicon film is preferably formed on a substrate.

[0061] The substrate is not particularly limited as long as a silicon film is formed on it; a semiconductor device substrate is preferred, and examples include silicon substrates, compound semiconductor substrates, quartz substrates, and glass substrates. In addition to the silicon film, other films besides the silicon film, as well as films containing metal nitrides, metal wiring films, etc., may be formed on the surface of the substrate. The films other than the silicon film are adjacent to the silicon film, and the exposed state of the silicon film and the films other than the silicon film is suitable for the etching method of the present invention.

[0062] There are no particular limitations on the method for forming the film on the substrate surface; examples include chemical vapor deposition (CVD) and sputtering. Furthermore, there are no particular limitations on the thickness of the silicon film; for example, it can be set to a thickness of 0.1 nm to 1 μm.

[0063] The etching method of the present invention preferably involves placing the substrate within a cavity and performing the etching. The etching method of the present invention preferably includes the steps of applying a reduced pressure to the cavity and / or purging the cavity with an inert gas. The etching method of the present invention further preferably includes the steps of etching silicon within the cavity using a plasma gas obtained by plasma-entraining the etching gas composition of the present invention, followed by applying a reduced pressure to the cavity and / or purging the cavity with an inert gas. This is because byproducts generated during etching can be removed.

[0064] The depressurization state refers to a pressure state in which the pressure inside the chamber is lower than the pressure during etching (process pressure), which is approximately below 0.133 kPa.

[0065] The etching method of the present invention can also perform a process of replacing the chamber with an inert gas after performing a process of applying a depressurization state to the chamber.

[0066] <<Etching Gas Composition>>

[0067] The etching gas composition of the present invention comprises fluorine gas (F2) and iodine-containing compound gas.

[0068] As for gases containing iodine compounds, there are no particular limitations as long as the gas contains iodine compounds; examples include: HI, C. x F y I z (where x, y, and z are integers greater than or equal to 1), I2, etc. These can be used individually or in combination of two or more. Among them, HI and C are preferred. x F y I z .

[0069] As C x Fy I z (Where x, y, and z are integers greater than or equal to 1), there are no particular limitations. Examples include: CF3I, CF2I2, CFI3, C2F5I, C2F4I2, C2F3I3, C2F2I4, C2FI5, C3F7I, C3F6I2, C3F5I3, C3F4I4, C3F3I5, C3F2I6, C3FI7, etc. These can be used individually or in combination of two or more. Among them, CF3I is preferred.

[0070] The iodine-containing compound gas is preferably at least one gas selected from the group consisting of HI and CF3I, and more preferably HI gas.

[0071] As mentioned above, SF6 is mainly used as the etching gas in the Bosch etching process. However, SF6 also has the problem of a very high global warming coefficient (GWP) of 25,200. On the other hand, the fluorine gas used in this invention has a GWP of 0, thus this invention is also superior in terms of using gases with lower GWP. Furthermore, by using HI (GWP 0) and CF3I (GWP 0.4) as iodine-containing compound gases, this invention is superior in terms of using gases with lower GWP.

[0072] The volume ratio of fluorine gas to iodine-containing compound gas in the etching gas composition of the present invention is the value obtained by dividing the volume of iodine-containing compound gas by the volume of fluorine gas, preferably 0.01 to 100, more preferably 0.1 to 10, and even more preferably 0.2 to 5. Therefore, there is a tendency for a more superior etching rate for silicon.

[0073] The etching gas composition of the present invention is not particularly limited as long as it contains fluorine gas and, if desired, iodine-containing compound gas. In 100% by volume of the etching gas composition, it may contain a total of 100% by volume of fluorine gas and iodine-containing compound gas, but the etching gas composition may further contain inert gas.

[0074] Examples of inert gases include Ar, N2, He, Ne, and Kr. These can be used individually or in combination of two or more. Among them, Ar is preferred for its stability and economic efficiency.

[0075] In the etching gas composition of the present invention, the content of fluorine gas, or the total content of fluorine gas and iodine-containing compound gas, can be 100% by volume, 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, there is a tendency to reduce costs and achieve excellent etching speed for silicon.

[0076] In the etching gas composition of the present invention, the content of inert gas 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, there is a tendency to reduce costs, thereby taking into account safety, and to achieve excellent etching speed for silicon.

[0077] In this specification, the content of each gaseous component in the gas composition is determined, for example, by infrared spectroscopy.

[0078] In the etching gas composition of the present invention, the total content of fluorine gas, iodine-containing compound gas and 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 also be 100% by volume. When the gas composition of the etching gas composition is within the above range, there is a tendency for a better etching rate for silicon.

[0079] The etching gas composition of the present invention may contain an oxidizing gas, but it is also excellent in that it does not need to contain an oxidizing gas or only a small amount is required even if an oxidizing gas is included. Oxidizing gases are formulated to remove substances generated during the etching process, but in the present invention, which uses a combination of fluorine gas and iodine-containing compound gas, the amount of oxidizing gas used can be reduced because the formation of unwanted products can be suppressed.

[0080] Examples of oxidizing gases include: O2, O3, CO, CO2, COCl2, COF2, NO2, etc. These can be used individually or in combination of two or more.

[0081] When the etching gas composition of the present invention contains an oxidizing gas, the content of the oxidizing gas in 100 vol% of the etching gas composition of the present invention is 1 vol% or more and 50 vol% or less, 2 vol% or more and 30 vol% or less, or 5 vol% or more and 20 vol% or less.

[0082] When the etching gas composition of the present invention contains no or a small amount of oxidizing gas, the content of oxidizing gas in 100 vol% of the etching gas composition of the present invention is preferably 1 vol% or less, more preferably 0.5 vol% or less, even more preferably 0.1 vol% or less, particularly preferably 0.01 vol% or less, and may also be 0.00 vol%.

[0083] In the etching method of the present invention, silicon is etched using a plasma gas, which is obtained by plasmaizing the etching gas composition of the present invention. Specifically, for example, fluorine gas is supplied to a chamber to prepare the etching gas composition of the present invention within the chamber. Then, the etching gas composition of the present invention prepared in the chamber is plasmaized, and the silicon of a substrate placed in the chamber is etched using this plasma gas.

[0084] In the etching method of the present invention, fluorine gas and, if necessary, iodine-containing compound gas are supplied to the chamber. These can be supplied separately and independently, or they can be prepared as a mixed gas before being supplied to the chamber. The total flow rate of the gas supplied to the chamber can be appropriately selected based on the chamber volume, the exhaust capacity of the gas exhaust mechanism, and considering concentration and pressure conditions.

[0085] In the following description, silicon, which is the object of etching, will also be referred to as the etched component. Furthermore, the etching gas composition used in the etching method of the present invention is as described in the description of the etching gas composition of the present invention.

[0086] [Etching apparatus]

[0087] The etching method of the present invention can be implemented, for example, by using the etching apparatus described below. This etching apparatus is also part of the present invention.

[0088] The etching apparatus of the present invention includes: an electrode; a stage on which a substrate is placed; 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 invention may further include an inert gas supply unit that supplies inert gas into the chamber. It should be noted that if iodine-containing compound gas is not supplied, the iodine-containing compound gas supply unit may be omitted.

[0089] Figure 1 This is a schematic diagram illustrating an example of an etching apparatus according to one embodiment of the present invention.

[0090] Figure 1 The etching apparatus 100 shown includes: a chamber 110 in which a substrate 18 is disposed; a fluorine gas supply unit 140 connected to the chamber 110 and supplying fluorine gas; an iodine-containing compound gas supply unit 150 supplying iodine-containing compound gas; an inert gas supply unit 130 supplying inert gas; an upper electrode 15; and a lower electrode 14. It should be noted that the etching apparatus 100 may also omit the inert gas supply unit 130.

[0091] The etching apparatus 100 further includes a control unit (not shown). This control unit may include, for example, a computer, and includes a program, memory, and CPU. The program is equipped with a set of steps to perform a series of actions in the etching method, and performs adjustments such as adjusting the temperature of the substrate 18, opening and closing valves in each supply unit, adjusting the flow rate of each gas, adjusting the pressure in the chamber 110, and adjusting the power applied to the electrodes according to the program. The program is stored in a computer memory medium, such as an optical disc, hard disk, magneto-optical disk, or memory card, and is installed in the control unit.

[0092] The chamber 110 contains a lower electrode 14, which serves to hold the substrate 18 and also functions as a stage (a platform on which the substrate is placed); and an upper electrode 15. Additionally, a pipe 121 serving as a gas inlet is connected to the upper part of the chamber 110. Pressure can be adjusted within the chamber 110, and the etching gas composition can be excited (plasmized) by a radio frequency power supply (not shown) that outputs high-frequency (e.g., 13.56 MHz, microwave, etc.) power. This allows the excited etching gas composition (plasma gas) to contact the substrate 18 disposed on the lower electrode 14, etching the substrate 18. The configuration is as follows: when high-frequency power is applied from the radio frequency power supply (not shown) while the etching gas composition is introduced, a DC voltage called a self-bias voltage is generated between the upper electrode 15 and the lower electrode 14 due to the difference in the movement speeds of ions and electrons in the plasma. The gas within the chamber 110 is discharged via the pipe 122, which serves as a gas exhaust line.

[0093] The chamber 110 is not particularly limited as long as it is resistant to the gas used and can be depressurized to a specific pressure; common chambers found in semiconductor etching apparatuses are generally applicable. Similarly, the supply pipe or other piping for the etching gas is also not particularly limited as long as it is resistant to the gas used; common materials can be used.

[0094] The refrigerant supply unit 140 uses valves 143 and 144 and flow adjustment mechanism 142 to adjust the supply amount, and supplies refrigerant from piping 141 and 145 to piping 121.

[0095] The iodine-containing compound gas supply unit 150 uses valves 153 and 154 and flow adjustment mechanism 152 to adjust the supply amount, and supplies the iodine-containing compound gas to the piping 121 from piping 151 and 155.

[0096] The inert gas supply unit 130 uses valves 133 and 134 and flow adjustment mechanism 132 to adjust the supply amount, and supplies inert gas from piping 131 and 135 to piping 121.

[0097] A heating mechanism (not shown) may be provided on the outside of the chamber 110 to heat the chamber 110.

[0098] A gas discharge mechanism for discharging the reacted gas is provided on one side of chamber 110. The reacted gas is discharged from chamber 110 via pipe 122 through a vacuum pump 127, which serves as the gas discharge mechanism. The reacted gas can be recovered by installing a liquid nitrogen cold trap (not shown) between pipe 122 and vacuum pump 127. Valves 125 and 126 can be installed on pipes 121 and 122 to adjust the pressure. Additionally, in Figure 1 In this system, PI123 and 124 are pressure gauges, and the control unit can control each flow adjustment mechanism and each valve based on their indicated values.

[0099] Taking the etching apparatus 100 as an example, the etching method will be explained in detail.

[0100] [Etching method using the above-described etching apparatus]

[0101] In the etching method of the present invention, silicon such as polycrystalline silicon films is etched by contacting a plasma gas (an excited etching gas composition) obtained by plasmaifying the etching gas composition of the present invention with silicon such as polycrystalline silicon films.

[0102] In the etching method of the present invention, firstly, a substrate 18 with a polycrystalline silicon film formed thereon is placed in a chamber 110. Then, a vacuum pump 127 is used to evacuate the interior of chamber 110, pipes 121 and 122, pipes 131 and 135, pipes 141 and 145, and pipes 151 and 155 to a specific pressure. At this time, the temperature inside the chamber can be adjusted to a specific temperature using a heating mechanism (not shown). After stabilization inside the chamber, fluorine gas and iodine-containing compound gas are supplied to pipe 121 at specific flow rates from the fluorine gas supply unit 140 and the iodine-containing compound gas supply unit 150. It should be noted that inert gas can also be supplied to pipe 121 at a specific flow rate from the inert gas supply unit 130.

[0103] When using a combination of fluorine gas and iodine-containing compound gas, they are mixed in a specific composition and supplied to chamber 110. While introducing the mixed etching gas (the etching gas composition of the present invention) into chamber 110, the pressure inside chamber 110 is controlled to a specific level. A DC voltage, called a self-bias voltage, is generated between the upper electrode 15 and the lower electrode 14 for a specific time after high-frequency power is applied from a radio frequency power source (not shown), exciting the etching gas composition. This excited etching gas composition reacts with the component 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.

[0104] After the etching process is completed, the vacuum pump 127 is stopped, and the vacuum is released by purging with inert gas. As described above, the etching method of the present invention using the above-described etching apparatus can etch silicon, which is the component to be etched.

[0105] (Etching conditions in the etching method of the present invention)

[0106] In the etching method of the present invention, the temperature of the etched component (electrode) when the plasma gas obtained by plasmaating the etching gas composition of the present invention comes into contact with the etched component is preferably below 100°C, more preferably below 80°C, and particularly preferably below 50°C. Alternatively, it can be used under cooling, preferably below 20°C, and more preferably below 15°C. At temperatures exceeding 100°C, the reactivity of fluorine gas increases, raising concerns about increasing the load on the etching apparatus. It should be noted that while the temperature of the substrate is the same as the temperature of the electrode, and substantially equal to the temperature of the etched component (film), the temperature of the substrate or the etched component (film) may rise during the etching reaction due to the heat of reaction. In the present invention, it is sufficient that at least the temperature of the electrode (preferably the lower electrode) is within the above-mentioned temperature range.

[0107] Furthermore, in order to obtain a stable plasma and to improve the linearity of ions to suppress side etching, the pressure in the chamber where the substrate on which the etched component is placed is preferably 10 Pa or less, more preferably 5 Pa or less, and even more preferably 1 Pa or less when the plasma gas comes into contact with the component to be etched. On the other hand, if the pressure in the chamber is too low, there is a concern that there will be fewer free ions and insufficient plasma density can not be obtained, so it is preferably 0.05 Pa or more.

[0108] During plasma etching, it is preferable to generate a negative DC self-bias voltage between the electrodes. To achieve highly linear etching relative to the etched component in the vertical direction, the generated negative DC self-bias voltage is preferably 500 V or more in absolute value, and more preferably 750 V or more in absolute value. A higher absolute value of the negative DC self-bias voltage reduces side etching; however, if the absolute value of the negative DC self-bias voltage exceeds 10,000 V, there is a concern about increased damage to the substrate. Therefore, the absolute value of the DC self-bias voltage is preferably 10,000 V or less.

[0109] In addition, the power applied to the electrodes is preferably 100 to 1000 W, and more preferably 150 to 500 W.

[0110] There is no particular limitation on the processing time of the etching process, but considering the efficiency of semiconductor device manufacturing processes, it is preferably within 60 minutes. Here, the processing time of the etching process refers to the time during which electricity is applied to the electrodes (the time for generating plasma gas).

[0111] The etching method of the present invention can be performed using various etching methods, and is 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, etc.

[0112] [Semiconductor Device Manufacturing Method]

[0113] The etching method of the present invention described above can be used in the form of etching silicon onto a silicon substrate by applying the etching method described above. By using the etching method of the present invention to etch silicon on a substrate, semiconductor devices can be manufactured economically.

[0114] The method for manufacturing a semiconductor device according to the present invention is characterized by comprising the following step: applying the above-described etching method to a silicon-containing substrate to etch silicon. The step of applying the above-described etching method to a silicon-containing substrate to etch silicon can be performed by the etching method of the present invention. As for the silicon-containing substrate, there is no particular limitation as long as it contains a silicon portion; examples include substrates with polycrystalline silicon films, substrates with amorphous silicon films, substrates with silicon epitaxial growth films, and monocrystalline silicon substrates.

[0115] The semiconductor device manufacturing method of the present invention preferably involves alternating and repeating the following steps: an etching step, in which the etching method of the present invention is applied to a silicon substrate to etch the silicon; and a protective layer formation step, in which a protective layer is formed on the surface of the silicon etched by the above-described etching step. That is, the semiconductor device manufacturing method of the present invention preferably employs the so-called Böhler process, a representative process of anisotropic dry etching of silicon, alternating and repeating the etching step and the protective layer formation step. By using the Böhler process for manufacturing the semiconductor device of the present invention, it is possible to manufacture a semiconductor device with a substrate having holes having high verticality and good sidewall shape.

[0116] In the etching process of the Bosch process, sulfur hexafluoride (SF6) is mainly used as the etching gas. However, in this invention, the feature is the use of an etching gas composition containing fluorine gas and iodine compound gas, otherwise the same as previously known methods.

[0117] Figure 2 It is a schematic diagram representing the outline of the Bosch process.

[0118] exist Figure 2In (a), the surface of silicon is etched using an etching gas. Then, in Figure 2 After (a), in Figure 2 In (b), a protective layer is formed on the surface of silicon by using C4F8 as a protective layer forming gas. Figure 2 After (b), Figure 2 In step (c), the surface of silicon is etched using an etching gas. At this time, an electric current is applied perpendicularly to the substrate (in the direction below the paper), thereby preferentially etching the surface of silicon in the direction below the paper while maintaining the protective layer of the sidewalls. Then, in Figure 2 After (c), execute again. Figure 2 (b). As described above, through alternating repetition Figure 2 (b) Figure 2 (c) enables the formation of deep holes with high aspect ratios (hole depth / hole diameter) on silicon. It should be noted that... Figure 2 PR in the text refers to photoresist.

[0119] The process of etching silicon onto a silicon substrate using the above-described etching method can be performed using the etching method of the present invention.

[0120] The protective layer formation process, which forms a protective layer on the surface of silicon after etching, can be carried out using known methods. For example, a protective layer forming gas can be used to form the protective layer on the silicon surface during the protective layer formation process.

[0121] The protective layer forming gas (deposition gas) is not particularly limited as long as it can form an organic deposition film; examples include fluorinated carbons or hydrofluorocarbons with double bonds. These can be used alone or in combination of two or more. Examples of fluorinated carbons include C2F2, C2F4, C3F4, C3F6, C4F2, C4F4, C4F6, C4F8, C5F4, C5F6, and C5F8. These can be used alone or in combination of two or more. C4F8 is preferred.

[0122] The process conditions in the protective layer formation process can also be performed according to known methods. For example, the same conditions as those described in the etching method above, such as temperature, pressure, and plasma, can be used.

[0123] Etching and protective layer formation processes can also be performed within the same chamber. In this case, the etching and protective layer formation processes can be switched by changing the gas without moving the substrate between the chambers, thereby enabling the efficient manufacture of semiconductor devices.

[0124] Example

[0125] The present invention will be described in detail below through embodiments, but the present invention is not limited to these embodiments.

[0126] First, as substrates to be processed, silicon wafers with polycrystalline silicon (p-Si) films, silicon wafers with thermally oxidized SiO2 films, silicon wafers with SiN films, silicon wafers with amorphous carbon (aC) films, and silicon wafers with TiN films are prepared respectively.

[0127] For the substrate being processed, the film thickness before and after etching was measured using a spectroscopic ellipsometry (manufactured by SEMILAB Co., Ltd., Japan, product name: SE-2000), and the etching amount was calculated. Then, based on the calculated etching amount, the etching rate and selectivity (p-Si / SiO2 selectivity, p-Si / SiN selectivity, p-Si / aC selectivity, and p-Si / TiN selectivity) were calculated.

[0128] [Example, Comparative Example]

[0129] use Figure 1 The etching apparatus 100 is shown. First, the substrate to be processed is placed on the lower electrode in the chamber, and the chamber is fully evacuated. Then, the temperature of the lower electrode is set to 15°C. The temperature of the substrate is the same as the temperature of the lower electrode, which is essentially equal to the temperature of the film to be etched. Next, gas is circulated as described in Table 1. The pressure in the chamber is set to 1 Pa at this time. Then, high-frequency power (400 W applied, with an absolute value of 550 V for the negative DC self-bias voltage) is applied to plasmaize the etching gas composition. Etching is performed by the plasma gas. After the etching time described in Table 1, the applied power is stopped, and the gas flow also stops, thus ending the etching process. Finally, the chamber is evacuated and replaced with N2 gas, after which the substrate to be processed is removed. The results are shown in Table 1. Silicon wafers with polycrystalline silicon (p-Si) films, silicon wafers with thermally oxidized SiO2 films, silicon wafers with SiN films, silicon wafers with amorphous carbon (aC) films, and silicon wafers with TiN films are all placed in the same chamber as substrates to be processed, and etching is performed simultaneously.

[0130] [Table 1]

[0131]

[0132] According to Table 1, a plasma gas obtained by plasmaizing an etching gas composition containing fluorine gas was used to etch a polycrystalline silicon film. Furthermore, it was found that in the embodiment where a plasma gas obtained by plasmaizing an etching gas composition containing fluorine gas and an iodine-containing compound gas was used to etch the polycrystalline silicon film, the etching rate was excellent. Additionally, it was found that a synergistic effect was achieved by using fluorine gas and an iodine-containing compound gas in combination. It is believed that amorphous silicon and monocrystalline silicon can also be etched in the same way as polycrystalline silicon.

[0133] Explanation of reference numerals in the attached figures

[0134] 14: Lower electrode

[0135] 15: Upper electrode

[0136] 18:Substrate

[0137] 100: Etching apparatus

[0138] 110: Chamber

[0139] 121, 122:Piping

[0140] 123, 124: PI (piston piezometer)

[0141] 125, 126: Valves

[0142] 127: Vacuum pump

[0143] 130: Inert Gas Supply Department

[0144] 131, 135:Piping

[0145] 132: Flow Adjustment Agency

[0146] 133, 134: Valves

[0147] 140: Fluorine Supply Department

[0148] 141, 145:Piping

[0149] 142: Flow Adjustment Mechanism

[0150] 143, 144: Valves

[0151] 150: Iodine-containing compound gas supply unit

[0152] 151, 155:Piping

[0153] 152: Flow Adjustment Agency

[0154] 153, 154: Valves

Claims

1. An etching method that uses a plasma gas to etch silicon, said plasma gas being obtained by plasmaizing an etching gas composition containing fluorine gas.

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

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

4. The etching method according to claim 2, wherein, The iodine-containing compound gas is selected from HI and C. x F y I z At least one gas in the group consisting of I2 and x, y, z are integers of 1 or more.

5. The etching method according to claim 2, wherein, The iodine-containing compound gas is at least one gas selected from the group consisting of HI and CF3I.

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

7. The etching method according to 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 in the etching gas composition is the value obtained by dividing the volume of iodine-containing compound gas by the volume of fluorine gas, and is between 0.01 and 100.

9. The etching method according to claim 1, wherein, The silicon is any one of the following: a polycrystalline silicon film formed on a substrate, an amorphous silicon film formed on a substrate, an epitaxial growth film of silicon formed on a substrate, or a single-crystal silicon substrate.

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

11. A method for manufacturing a semiconductor device, wherein the following steps are repeated: A process of etching silicon onto a substrate having silicon using the etching method described in any one of claims 1 to 9; and The process of forming a protective layer on the surface of silicon that has been etched through the aforementioned process.

12. The method of manufacturing a semiconductor device according to claim 10, wherein, The silicon substrate is any one of the following: a substrate with a polycrystalline silicon film, a substrate with an amorphous silicon film, a substrate with an epitaxial growth film of silicon, or a monocrystalline silicon substrate.

13. An etching apparatus comprising: electrode; A stage on which a substrate is placed; A fluorine gas supply unit supplies fluorine gas to the substrate; and An iodine-containing compound gas supply unit supplies 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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