Etching method and semiconductor device manufacturing method

Abstract

Provided is an etching method capable of selectively etching an object to be etched over an object not to be etched. This etching method comprises an etching step in which an etching gas that contains nitrosyl fluoride is brought into contact with a member (12) to be etched, wherein the member (12) has an object to be etched with the etching gas and an object not to be etched with the etching gas, and in which without use of plasma, the object to be etched is selectively etched over the object not to be etched. Further, the object to be etched contains a silicon germanium and / or silicon which is represented by the chemical formula Si1-xGex, and the object not to be etched contains a silicon germanium and / or germanium which is represented by the chemical formula Si1-yGey. In the chemical formulae, x is not less than 0 but less than 1, y is more than 0 but not more than 1, and x is smaller than y.

Description

[Technical Field]

[0001] This invention relates to an etching method and a method for manufacturing semiconductor devices. [Background technology]

[0002] To improve the performance of semiconductor devices, silicon (Si) and silicon germanium (Si) 1-x Ge x An etching target consisting of at least one of germanium (Ge) and silicon germanium (Si 1-y Ge y A technique is needed to selectively etch a non-etchable object, which consists of at least one of the two chemical formulas. Here, x in both chemical formulas is between 0 and 1, y is greater than 0 and less than or equal to 1, and x is smaller than y.

[0003] One method for etching silicon-containing materials is a dry etching method that uses an etching gas containing nitrosyl fluoride (NOF) and does not use plasma. For example, Patent Document 1 discloses a method for selectively etching polysilicon compared to silicon nitride by generating nitrosyl fluoride by mixing nitric oxide (NO) and fluorine gas (F2). Patent Document 2 also discloses a method for selectively etching polysilicon compared to silicon nitride by generating nitrosyl fluoride by mixing monofluorointerhalogen gas and nitric oxide. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 236055 of 2014 [Patent Document 2] International Publication No. 2018 / 181104 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, a technique for selectively etching an object to be etched containing silicon compared to an object not to be etched containing germanium is not known. The present invention aims to provide an etching method capable of selectively etching an object to be etched containing at least one of silicon and silicon germanium represented by the chemical formula Si 1-x Ge x compared to an object not to be etched containing at least one of germanium and silicon germanium represented by the chemical formula Si 1-y Ge y In both of the above chemical formulas, x is 0 or more and less than 1, y is more than 0 and 1 or less, and x is smaller than y. And a method for manufacturing a semiconductor device.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the present invention is as follows [1] to [8]. [1] An etching gas containing nitrosyl fluoride is brought into contact with an etched member having an object to be etched that is an object of etching by the etching gas and an object not to be etched that is not an object of etching by the etching gas, and without using plasma, An etching step of selectively etching the object to be etched compared to the object not to be etched is provided, The object to be etched contains at least one of silicon and silicon germanium represented by the chemical formula Si 1-x Ge x The object not to be etched contains at least one of germanium and silicon germanium represented by the chemical formula Si 1-y Ge y And in both of the above chemical formulas, x is 0 or more and less than 1, y is more than 0 and 1 or less, and x is smaller than y. An etching method.

[0007] [2] The etching method according to [1], wherein x in the chemical formula is 0 or more and 0.1 or less. [3] The etching method according to [1] or [2], wherein y in the chemical formula is more than 0.1 and 1 or less. [4] The etching method according to [1], wherein y in the chemical formula is 0.2 or more and 1 or less.

[0008] [5] The etching method according to any one of [1] to [4], wherein the temperature condition of the etching step is -50°C or more and 40°C or less. [6] The etching method according to any one of [1] to [5], wherein the etching gas is a gas consisting only of nitrosyl fluoride or a mixed gas containing nitrosyl fluoride and a dilution gas. [7] The etching method according to [6], wherein the dilution gas is at least one selected from nitrogen gas, helium, argon, neon, krypton, and xenon.

[0009] [8] A method for manufacturing a semiconductor device, which manufactures a semiconductor device using the etching method according to any one of [1] to [7], wherein the member to be etched is a semiconductor substrate having the object to be etched and the object not to be etched, and the method for manufacturing a semiconductor device includes a processing step of removing at least a part of the object to be etched from the semiconductor substrate by the etching. [Advantages of the Invention]

[0010] According to the present invention, an object to be etched containing at least one of silicon and silicon germanium represented by the chemical formula Si 1-x Ge x can be selectively etched compared to an object not to be etched containing at least one of germanium and silicon germanium represented by the chemical formula Si 1-y Ge y . In both of the above chemical formulas, x is 0 or more and less than 1, y is more than 0 and 1 or less, and x is smaller than y. [Brief Description of the Drawings]

[0011] [Figure 1] This is a schematic diagram of an example of an etching apparatus illustrating one embodiment of the etching method according to the present invention. [Modes for carrying out the invention]

[0012] One embodiment of the present invention is described below. This embodiment is merely an example of the present invention, and the present invention is not limited to this embodiment. Furthermore, various modifications or improvements can be made to this embodiment, and such modified or improved forms may also be included in the present invention.

[0013] The etching method according to this embodiment includes an etching step in which an etching gas containing nitrosyl fluoride (NOF) is brought into contact with a member to be etched, which has both an object to be etched by the etching gas and a non-etchable object that is not to be etched by the etching gas, and selectively etches the object to be etched compared to the non-etchable object without using plasma.

[0014] Furthermore, in the etching method according to this embodiment, the object to be etched is the chemical formula Si 1-x Ge x It contains at least one of silicon and silicon germanium represented by the chemical formula Si 1-y Ge y It contains at least one of germanium and silicon germanium represented by . In both chemical formulas, x is between 0 and 1, y is greater than 0 and less than or equal to 1, and x is less than y.

[0015] When etching gas is brought into contact with the material to be etched, the material to be etched reacts with nitrosyl fluoride in the etching gas, causing the etching of the material to be etched to proceed. In contrast, non-etchable materials do not react as readily with nitrosyl fluoride as etchable materials, so etching of non-etchable materials is less likely to proceed. Therefore, according to the etching method of this embodiment, etchable materials can be selectively etched compared to non-etchable materials (i.e., high etching selectivity can be obtained).

[0016] For example, the etching selectivity ratio, which is the ratio of the etching rate of the material to be etched to the etching rate of the non-etched material, can be set to 10 or more. Preferably, the etching selectivity ratio is 30 or more, and more preferably 50 or more. Furthermore, if both the etched object and the non-etched object contain silicon germanium, the chemical formula Si 1-x Ge x x inside and the chemical formula Si 1-y Ge y The difference yx from the internal y is preferably 0.05 or greater, more preferably 0.1 or greater, even more preferably 0.2 or greater, and particularly preferably 0.3 or greater. If the value of yx is within the above range, it is easy to set the etching selectivity to the above value.

[0017] Furthermore, according to the etching method of this embodiment, the object to be etched can be etched without using plasma, eliminating the need to perform etching using expensive plasma generators. Therefore, etching of the component to be etched can be performed at a low cost.

[0018] The etching method according to this embodiment described above can be used in the manufacture of semiconductor devices. That is, the method for manufacturing a semiconductor device according to this embodiment is a method for manufacturing a semiconductor device using the etching method according to this embodiment, wherein the member to be etched is a semiconductor substrate having an object to be etched and an object not to be etched, and the method comprises a processing step of removing at least a portion of the object to be etched from the semiconductor substrate by etching.

[0019] The etching method according to this embodiment can be used, for example, for the manufacture of semiconductor devices such as field-effect transistors. For example, by applying the etching method according to this embodiment to a laminate in which polysilicon films and silicon germanium films are alternately stacked and grooves are formed that extend along the stacking direction and penetrate the laminate, the polysilicon films exposed on the inner surface of the grooves are selectively and isotropically etched, thereby forming a structure in which the edges of the silicon germanium films protrude into the grooves. Since the structure having such a structure can be used as the structure of a semiconductor device, the process can be used in the manufacture of semiconductor devices such as field-effect transistors.

[0020] The process of forming the above structure by etching has conventionally been carried out using a wet etching method with chemical solutions. However, it is generally known that etching using etching gases offers superior microfabrication capabilities compared to etching using chemical solutions. Therefore, the etching method according to this embodiment is expected to contribute to further miniaturization and high integration of semiconductor devices.

[0021] Furthermore, since etching can be performed at low temperatures in the etching method according to this embodiment, it can be used, for example, for the manufacture of semiconductor devices having heat-sensitive circuits. For example, complementary metal oxide semiconductors (CMOS) and the like are susceptible to circuit damage when exposed to high temperatures during etching, but by employing etching according to this embodiment, circuit damage due to heat is less likely to occur.

[0022] Furthermore, when the non-etching target itself is used as a structure for a semiconductor device, the non-etching target is a material that does not substantially react with nitrosyl fluoride or a material that reacts with nitrosyl fluoride very slowly. That is, the non-etching target is a material with the chemical formula Si 1-x Ge x At least one of germanium represented by the formula and silicon germanium can be used. However, in the above chemical formula, y is greater than 0 and less than or equal to 1.

[0023] Furthermore, the etching method according to this embodiment can also be used for cleaning. For example, after performing a step of forming a film made of a silicon-containing material on a substrate, or a step of etching a film of a silicon-containing material formed on a substrate, in a chamber, the silicon-containing deposits adhering to the inner surface of the chamber can be removed and cleaned using the etching method according to this embodiment. In such cleaning, the chamber corresponds to the member to be etched, which is a constituent element of the present invention, and the deposits correspond to the object to be etched, which is a constituent element of the present invention.

[0024] The etching method according to this embodiment will be described in more detail below. [Etching gas] The etching gas is a gas containing nitrosyl fluoride, but it may be a gas consisting only of nitrosyl fluoride, or a mixed gas containing nitrosyl fluoride and other gases. When the etching gas is a mixed gas containing nitrosyl fluoride and other gases, the content of nitrosyl fluoride in the etching gas is preferably 1% by volume or more, more preferably 5% by volume or more and 80% by volume or less, even more preferably 10% by volume or more and 70% by volume or less, and particularly preferably 20% by volume or more and 60% by volume or less.

[0025] By performing etching with the nitrosyl fluoride content in the etching gas within the above range, the etching target can be etched more selectively than the non-etched target. For example, the etching selectivity ratio, which is the ratio of the etching rate of the etching target to the etching rate of the non-etched target, can be set to 10 or higher.

[0026] Dilution gases and additive gases can be used as other gases that make up the etching gas along with nitrosyl fluoride gas. That is, the etching gas can be a mixed gas containing nitrosyl fluoride and at least one of the dilution gas and the additive gas. Here, the additive gas is the gas remaining after removing nitrosyl fluoride and the dilution gas.

[0027] As the diluent gas, an inert gas is preferred, specifically, at least one selected from nitrogen gas (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe). The amount of diluent gas contained in the etching gas is not particularly limited, but it can be greater than 0 volume% and less than or equal to 99 volume%.

[0028] Examples of additive gases include nitrogen oxides such as nitric oxide (NO) and nitrous oxide (N2O). Using a mixed gas containing these additive gases as the etching gas can sometimes increase the etching selectivity. The amount of additive gas contained in the etching gas is not particularly limited, but it is preferably 0% to 50% by volume, more preferably more than 0% to 10% by volume, and even more preferably 1% to 7% by volume.

[0029] Furthermore, if the etching gas contains metallic components, it may cause contamination of the material to be etched. For this reason, it is preferable that the etching gas does not contain metallic components, and for example, it is preferable that the metallic component content be 1 ppm by mass or less. Examples of metallic components include chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), nickel (Ni), tungsten (W), aluminum (Al), copper (Cu), manganese (Mn), etc.

[0030] These metallic components can be removed from the etching gas by distillation or by contacting the etching gas with an adsorbent. Examples of adsorbents include fluorides of metals belonging to Group 1 or Group 2 of the periodic table. Through such treatment, it is possible to reduce the content of metallic components in the etching gas to 1 ppm by mass or less.

[0031] [Pressure conditions for the etching process] The pressure conditions for the etching process in the etching method according to this embodiment are not particularly limited as long as the object to be etched is selectively etched compared to the object not to be etched, but it is preferably 1 Pa to 80 kPa, more preferably 100 Pa to 55 kPa, even more preferably 1 kPa to 40 kPa, and particularly preferably 5 kPa to 20 kPa.

[0032] For example, etching can be performed by placing the workpiece to be etched inside a chamber and circulating etching gas through the chamber. The pressure inside the chamber during the circulation of the etching gas can be set to between 1 Pa and 80 kPa. The flow rate of the etching gas should be appropriately set according to the size of the chamber and the capacity of the exhaust system that reduces the pressure inside the chamber, so as to maintain a constant pressure.

[0033] [Temperature conditions for the etching process] The temperature conditions for the etching process in the etching method according to this embodiment are not particularly limited, but are preferably -100°C or higher and 100°C or lower, more preferably -80°C or higher and 80°C or lower, even more preferably -60°C or higher and 50°C or lower, and particularly preferably -50°C or higher and 40°C or lower.

[0034] If the temperature conditions are within the above range, the etchable object can be etched more selectively than the non-etchable object, and the etching selectivity ratio, which is the ratio of the etching rate of the etchable object to the etching rate of the non-etchable object, can be increased. Here, the temperature in the temperature conditions refers to the temperature of the material to be etched, but the temperature of the stage that supports the material to be etched, which is installed in the chamber of the etching apparatus, can also be used.

[0035] Under conditions where plasma is not generated and at a predetermined temperature (e.g., below 50°C), nitrosyl fluoride reacts more slowly with non-etchable materials such as germanium, silicon germanium, silicon oxide, silicon nitride, photoresist, and amorphous carbon than with etchable materials. Therefore, when the component to be etched has both etchable and non-etchable materials, the etching method according to this embodiment allows for selective etching of the etchable materials with minimal etching of the non-etchable materials.

[0036] Therefore, the etching method according to this embodiment can be used for methods such as processing an object to be etched into a predetermined shape by using a patterned non-etchable object as a mask, or for removing an object to be etched from a structure having both an object to be etched and a non-etchable object.

[0037] [Material to be etched] The member to be etched by the etching method according to this embodiment has both an etchable object and a non-etchable object. However, it may also be a member having a portion formed by the etchable object and a portion formed by the non-etchable object, or a member formed by a mixture of the etchable object and the non-etchable object. Furthermore, the member to be etched may also have components other than the etchable object and the non-etchable object. Furthermore, the shape of the material to be etched is not particularly limited and may be, for example, plate-shaped, foil-shaped, film-shaped, powder-shaped, or lump-shaped. An example of the material to be etched is the semiconductor substrate mentioned above.

[0038] [Object to be etched] The etchable object contains at least one of silicon and silicon germanium, but may be formed of at least one of silicon and silicon germanium alone, or may have a portion formed of at least one of silicon and silicon germanium alone and a portion formed of another material, or may be formed of a mixture of at least one of silicon and silicon germanium and another material.

[0039] Here, silicon is a compound composed of silicon atoms (chemical formula Si 1-x Ge x A compound represented by the above chemical formula where x is 0, examples include single-crystal silicon, polysilicon, and amorphous silicon. Silicon germanium is a compound composed of silicon and germanium, with the chemical formula Si 1-x Ge xIt is represented as follows. In the above chemical formula, x is greater than 0 but less than 1, preferably greater than 0 but 0.1 or less, more preferably greater than 0 but 0.07 or less, and even more preferably greater than 0 but 0.05 or less. Note that if both the etched object and the non-etched object contain silicon germanium, then x in both chemical formulas representing silicon germanium is smaller than y.

[0040] The proportion of silicon atoms among all atoms constituting the etched material is preferably 95% by mass or more, more preferably 97% by mass or more, and even more preferably 99% by mass or more. Furthermore, the etching target may contain atoms other than silicon and germanium, as long as it does not affect the effects of the present invention. For example, even if hydrogen atoms derived from the raw materials of the polysilicon film are contained in the polysilicon film, the effects of the present invention can be obtained without any problems. Furthermore, the shape of the object to be etched is not particularly limited and may be, for example, plate-shaped, foil-shaped, film-shaped, powder-shaped, or lump-shaped.

[0041] [Non-etchable objects] Non-etchable objects either do not react substantially with nitrosyl fluoride, or react with nitrosyl fluoride very slowly, so even if etching is performed by the etching method according to this embodiment, etching hardly progresses. Non-etchable objects contain at least one of germanium and silicon germanium, but may be formed of at least one of germanium and silicon germanium alone, or may have a portion formed of at least one of germanium and silicon germanium and a portion formed of another material, or may be formed of a mixture of at least one of germanium and silicon germanium and another material.

[0042] Here, germanium is a compound composed of germanium atoms (chemical formula Si 1-y Ge yThis refers to compounds represented by the above chemical formula where y is 1. Examples include single-crystal germanium such as α-germanium and β-germanium, and amorphous germanium. Silicon germanium is a compound composed of silicon and germanium, with the chemical formula Si 1-y Ge y It is represented as follows. In the above chemical formula, y is greater than 0 and less than 1, but preferably greater than 0.1 and less than 1, more preferably 0.2 or more and less than 1, even more preferably 0.25 or more and less than 1, and particularly preferably 0.3 or more and less than 1. Note that if both the etched object and the non-etched object contain silicon germanium, x in both chemical formulas representing silicon germanium is smaller than y.

[0043] Furthermore, the non-etching target may contain atoms other than silicon and germanium, as long as it does not affect the effects of the present invention. For example, even if hydrogen atoms derived from the raw materials of the silicon germanium film are contained in the silicon germanium film, the effects of the present invention can be obtained without any problems.

[0044] Furthermore, non-etching targets may include, along with germanium and silicon germanium, silicon oxides (e.g., silicon dioxide (SiO2)) composed of silicon (Si) and oxygen (O), amorphous carbon, and photoresist. Furthermore, the shape of the non-etching object is not particularly limited and may be, for example, plate-shaped, foil-shaped, film-shaped, powder-shaped, or lump-shaped.

[0045] Since non-etchable objects are hardly etched by the etching method according to this embodiment, the etching of etchable objects by the etching gas can be suppressed by the non-etchable objects. Therefore, the non-etchable objects can be used as a resist or mask to suppress the etching of etchable objects by the etching gas, or they can be used as a material for forming a structure.

[0046] Therefore, the etching method according to this embodiment can be used to process an object to be etched into a predetermined shape by using a patterned non-etchable object as a resist or mask (for example, processing a film-like object to be etched on the component to be etched to a predetermined film thickness), and is therefore suitably used for the manufacture of semiconductor devices.

[0047] Furthermore, since the non-etched material is hardly etched, the etching of parts of the semiconductor device that should not be etched can be suppressed by the non-etched material, thus preventing the loss of semiconductor device properties due to etching.

[0048] Next, an example of the configuration of an etching apparatus capable of implementing the etching method according to this embodiment, and an example of an etching method using the etching apparatus, will be described with reference to Figure 1. The etching apparatus in Figure 1 is an etching apparatus capable of plasmaless etching without using plasma. First, the etching apparatus in Figure 1 will be described.

[0049] The etching apparatus shown in Figure 1 comprises a chamber 10 in which etching is performed, a stage 11 that supports the workpiece to be etched 12 inside the chamber 10, a thermometer 14 for measuring the temperature of the workpiece to be etched 12, an exhaust pipe 13 for discharging gas from inside the chamber 10, a vacuum pump 15 provided in the exhaust pipe 13 for reducing the pressure inside the chamber 10, and a pressure gauge 16 for measuring the pressure inside the chamber 10.

[0050] Furthermore, the etching apparatus shown in Figure 1 is equipped with an etching gas supply unit that supplies etching gas into the chamber 10. This etching gas supply unit includes a nitrosyl fluoride gas supply unit 1 that supplies nitrosyl fluoride gas, a dilution gas supply unit 2 that supplies dilution gas, a nitrosyl fluoride gas supply pipe 5 that connects the nitrosyl fluoride gas supply unit 1 and the chamber 10, and a dilution gas supply pipe 6 that connects the dilution gas supply unit 2 to the middle of the nitrosyl fluoride gas supply pipe 5.

[0051] Furthermore, the nitrosyl fluoride gas supply piping 5 is equipped with a nitrosyl fluoride gas pressure control device 7 for controlling the pressure of the nitrosyl fluoride gas and a nitrosyl fluoride gas flow rate control device 3 for controlling the flow rate of the nitrosyl fluoride gas. Furthermore, the dilution gas supply piping 6 is equipped with a dilution gas pressure control device 8 for controlling the pressure of the dilution gas and a dilution gas flow rate control device 4 for controlling the flow rate of the dilution gas.

[0052] Furthermore, when supplying nitrosyl fluoride gas to the chamber 10 as an etching gas, the nitrosyl fluoride gas is sent from the nitrosyl fluoride gas supply unit 1 to the nitrosyl fluoride gas supply pipe 5, thereby supplying the nitrosyl fluoride gas to the chamber 10 via the nitrosyl fluoride gas supply pipe 5.

[0053] Furthermore, when supplying a mixed gas of nitrosyl fluoride gas and a diluent gas such as an inert gas as the etching gas, nitrosyl fluoride gas is sent from the nitrosyl fluoride gas supply unit 1 to the nitrosyl fluoride gas supply pipe 5, and diluent gas is sent from the diluent gas supply unit 2 to the nitrosyl fluoride gas supply pipe 5 via the diluent gas supply pipe 6. As a result, the nitrosyl fluoride gas and the diluent gas are mixed in the middle of the nitrosyl fluoride gas supply pipe 5 to form a mixed gas, and this mixed gas is supplied to the chamber 10 via the nitrosyl fluoride gas supply pipe 5. However, the nitrosyl fluoride gas and the diluent gas may be supplied to the chamber 10 separately and mixed within the chamber 10.

[0054] The configuration of the nitrosyl fluoride gas supply unit 1 and the dilution gas supply unit 2 is not particularly limited and may be, for example, a cylinder or a gas cylinder. Furthermore, the nitrosyl fluoride gas flow rate control device 3 and the dilution gas flow rate control device 4 may be, for example, a mass flow controller or a flow meter.

[0055] When supplying etching gas to the chamber 10, it is preferable to maintain the etching gas supply pressure (i.e., the value of the nitrosyl fluoride gas pressure control device 7 in Figure 1) at a predetermined value. Specifically, the etching gas supply pressure is preferably 20 kPa or more and 1500 kPa or less, more preferably 40 kPa or more and 700 kPa or less, and even more preferably 60 kPa or more and 400 kPa or less. If the etching gas supply pressure is within the above range, the etching gas will be supplied to the chamber 10 smoothly, and the load on the components of the etching apparatus in Figure 1 (for example, the various devices and the piping) will be small.

[0056] Furthermore, the pressure of the etching gas supplied into the chamber 10 is preferably 0.1 Pa or more and 80 kPa or less, more preferably 100 Pa or more and 55 kPa or less, and even more preferably 1.3 kPa or more and 40 kPa or less. If the pressure of the etching gas in the chamber 10 is within the above range, a sufficient etching rate can be obtained and the etching selectivity ratio tends to be high.

[0057] The pressure inside the chamber 10 before supplying the etching gas is not particularly limited as long as it is less than or equal to the etching gas supply pressure, or lower than the etching gas supply pressure, but it is preferably 0.1 Pa or more and less than 40 kPa, and more preferably 10 Pa or more and 20 kPa or less.

[0058] The difference between the etching gas supply pressure and the pressure inside chamber 10 before the etching gas is supplied is preferably 1.5 MPa or less, more preferably 0.6 MPa or less, and even more preferably 0.2 MPa or less. If the difference is within the above range, the etching gas can be supplied to chamber 10 smoothly.

[0059] When supplying etching gas to the chamber 10, it is preferable to supply the etching gas while maintaining its temperature at a predetermined value. That is, the supply temperature of the etching gas is preferably between -50°C and 100°C. The temperature of the etched member 12 during etching is preferably -100°C to 100°C, more preferably -80°C to 80°C, even more preferably -60°C to 50°C, and particularly preferably -50°C to 40°C. Within this temperature range, the etching of the etchable object on the etched member 12 proceeds smoothly, the load on the etching apparatus is small, and the lifespan of the etching apparatus tends to be extended.

[0060] The etching process time (hereinafter sometimes referred to as "etching time") can be arbitrarily set depending on how much etching is desired on the material to be etched on the component to be etched 12. However, considering the production efficiency of the semiconductor device manufacturing process, it is preferable that the etching time be within 180 minutes, more preferably within 120 minutes, even more preferably within 60 minutes, and particularly preferably within 40 minutes. The etching process time refers to the time from when the etching gas is introduced into the chamber 10 until the etching gas is exhausted from the chamber 10 to complete the etching.

[0061] The etching method according to this embodiment can be carried out using a general etching apparatus used in semiconductor device manufacturing processes, such as the etching apparatus shown in Figure 1, and the configuration of the usable etching apparatus is not particularly limited. For example, the positional relationship between the nitrosyl fluoride gas supply pipe 5 and the member to be etched 12 is not particularly limited, as long as the etching gas can be brought into contact with the member to be etched 12. Also, regarding the configuration of the temperature control mechanism of the chamber 10, it is sufficient if the temperature of the member to be etched 12 can be adjusted to any desired temperature, so the temperature control mechanism for the member to be etched 12 may be directly mounted on the stage 11, or an external temperature controller may be used to heat or cool the chamber 10 from the outside.

[0062] Furthermore, the material of the etching apparatus shown in Figure 1 is not particularly limited as long as it has corrosion resistance to nitrosyl fluoride and can be reduced to a predetermined pressure. For example, the part that comes into contact with the etching gas can be made of metals such as yttrium (Y), nickel, nickel-based alloys, aluminum (Al), stainless steel, platinum (Pt), compounds of these metals (e.g., metal fluorides, metal nitrides, metal oxides), ceramics such as alumina, fluororesins, or fluororubber.

[0063] Specific examples of nickel-based alloys include Inconel®, Hastelloy®, and Monel®. Examples of fluororesins include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), and polyvinylidene fluoride (PVDF). Examples of fluororubbers include Viton® and Kalrez®. [Examples]

[0064] The present invention will be described in more detail below with reference to examples and comparative examples. (Example 1) Etching of the samples to be etched was performed using an etching apparatus having substantially the same configuration as the etching apparatus in Figure 1. The samples to be etched used in Example 1 are described below. A 500 nm thick polysilicon film was deposited on the surface of a 100 mm diameter disc-shaped silicon wafer (manufactured by Seiren KST Co., Ltd.), and a 100 nm thick silicon germanium (Si) film was deposited on the surface of a 100 mm diameter disc-shaped silicon wafer. 0.7 Ge 0.3 We prepared samples with the film deposited (manufactured by Seiren KST Co., Ltd.).

[0065] Next, these two types of samples to be etched were placed side by side on a stage inside the chamber of the etching apparatus, and the temperature of the stage was cooled to 20°C. Then, nitrosyl fluoride gas at a flow rate of 10 mL / min and argon at a flow rate of 90 mL / min were mixed to form a mixed gas, which was used as the etching gas. This etching gas was then supplied into the chamber at a flow rate of 100 mL / min and circulated for 1 minute to perform etching. The pressure inside the chamber during the circulation of the etching gas was set to 6.7 kPa, and the partial pressure of the nitrosyl fluoride gas was set to 0.67 kPa.

[0066] This process etched the polysilicon film and silicon germanium film of the two types of samples described above. After the etching gas flow was completed, the stage was cooled, and the inside of the chamber was replaced with argon. After etching was complete, the chamber was opened and the etched sample was removed, and the film thicknesses of the polysilicon film and silicon germanium film were measured. The film thicknesses of the polysilicon film and silicon germanium film were measured using the F20 film thickness measurement system manufactured by Filmetrics Co., Ltd. The measurement conditions for the film thickness were as follows.

[0067] Measured pressure: Atmospheric pressure (101.3 kPa) Measurement temperature: 28℃ Measurement atmosphere: Air Measurement wavelength range: 600~1100nm

[0068] For both the polysilicon film and the silicon germanium film, the etching rates (nm / min) for polysilicon and silicon germanium were calculated by subtracting the film thickness after etching (nm) from the film thickness before etching (nm) and dividing the result by the etching time (min). Then, the ratio of the etching rate of the etched material (polysilicon) to the etching rate of the non-etched material (silicon germanium) (etching selectivity ratio) was calculated. The results are shown in Table 1.

[0069] [Table 1]

[0070] (Examples 2-12 and Comparative Examples 1-4) Except for the flow rates of nitrosyl fluoride gas and argon, the stage temperature, and the pressure inside the chamber being as shown in Table 1, five types of samples to be etched were etched in the same manner as in Example 1, and the etching rates and their ratios for polysilicon, silicon germanium, and germanium were calculated, respectively. The results are shown in Table 1.

[0071] The etched samples used in Examples 5-7 and Example 11 were silicon wafers with a diameter of 100 mm, and a film thickness of 100 nm on the surface. 0.8 Ge 0.2 film, Si 0.2 Ge 0.8 film, Si 0.95 Ge 0.05 film, Si 0.5 Ge 0.5 These are films, or germanium films, both manufactured by Seiren KST Co., Ltd.

[0072] The results from Examples 1-3, 10, and 12 show that when the etching temperature (stage temperature) is between -20°C and 40°C, polysilicon is selectively etched compared to silicon germanium. Furthermore, as the etching temperature decreases, the etching selectivity ratio, which is the ratio of the etching rate of the etched material to the etching rate of the non-etched material, improves.

[0073] Furthermore, the etching selectivity ratio was particularly high when the etching temperature (stage temperature) was between -20°C and 20°C, while it was slightly lower when the etching temperature was 40°C. Furthermore, using a mixed gas containing nitric oxide as the etching gas increased the etching selectivity ratio.

[0074] The results from Examples 3 to 6 show that if the germanium content in the non-etching target is 20 mol% or more, polysilicon is selectively etched compared to silicon germanium. The results from Example 7 show that even if the silicon germanium material contains 5 mol% germanium, it is selectively etched compared to silicon germanium material containing 30 mol% germanium (non-etchable material).

[0075] The results from Examples 8 and 9 show that polysilicon is selectively etched compared to silicon germanium, even when the proportion of nitrosyl fluoride in the etching gas is 50% by volume or when the pressure inside the chamber during etching is 20 kPa. The results from Example 11 show that even if the etched material contains 50 mol% germanium, it is selectively etched compared to amorphous germanium.

[0076] The results from Comparative Examples 1-3 show that when a mixed gas of nitric oxide, fluorine gas, and argon, or a mixed gas of nitric oxide, chlorine trifluoride (ClF3), and argon, or a mixed gas of nitric oxide, chlorine monofluoride (ClF), and argon is used as the etching gas, silicon germanium is preferentially etched compared to polysilicon. This indicates that even when a mixed gas containing nitric oxide and fluorine-containing atomic gas is used as the etching gas, selective etching, in which polysilicon is selectively etched compared to silicon germanium, cannot be achieved.

[0077] Furthermore, the results from Comparative Example 4 show that when both the etched and non-etched materials are silicon germanium, the etching rate is lower when the germanium ratio is higher, and silicon germanium with a high germanium ratio is not suitable as an etched material. [Explanation of Symbols]

[0078] 1. Nitrosyl Fluoride Gas Supply Unit 2. Dilution gas supply unit 3. Nitrosyl Fluoride Gas Flow Control Device 4. Dilution gas flow control device 5. Piping for supplying nitrosyl fluoride gas. 6. Piping for supplying dilution gas. 7. Nitrosyl Fluoride Gas Pressure Control Device 8. Dilution gas pressure control device 10 chambers 11... Stages 12. Etching material 13. Exhaust piping 14...Thermometer 15. Vacuum pump 16. Pressure gauge

Claims

1. The etching process involves bringing an etching gas containing nitrosyl fluoride into contact with a member to be etched, which has an object to be etched by the etching gas and a non-etchable object that is not to be etched by the etching gas, and selectively etching the object to be etched compared to the non-etchable object without using plasma. The etching target is the chemical formula Si 1-x Ge x It contains at least one of silicon and silicon germanium represented by the chemical formula Si 1-y Ge y It contains at least one of germanium and silicon germanium represented by, An etching method in which x in both chemical formulas is 0 or greater and less than 1, y is greater than 0 and less than or equal to 1, and x is smaller than y.

2. The etching method according to claim 1, wherein x in the chemical formula is 0 or more and 0.1 or less.

3. The etching method according to claim 1, wherein y in the chemical formula is greater than 0.1 and less than or equal to 1.

4. The etching method according to claim 1, wherein y in the chemical formula is 0.2 or more and 1 or less.

5. The etching method according to claim 1, wherein the temperature conditions for the etching step are -50°C or higher and 40°C or lower.

6. The etching method according to claim 1, wherein the etching gas is a gas consisting solely of nitrosyl fluoride, or a mixed gas containing nitrosyl fluoride and a diluent gas.

7. The etching method according to claim 6, wherein the diluent gas is at least one selected from nitrogen gas, helium, argon, neon, krypton, and xenon.

8. A method for manufacturing a semiconductor device using the etching method described in any one of claims 1 to 7, The member to be etched is a semiconductor substrate having the object to be etched and the object not to be etched, A method for manufacturing a semiconductor device, comprising a processing step of removing at least a portion of the object to be etched from the semiconductor substrate by etching.

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