Etching method and method for manufacturing semiconductor element

Abstract

Provided is an etching method capable of selectively etching an etching target with respect to a specific non-etching target without using plasma, the etching target containing a silicon compound having at least one of a nitrogen atom and an oxygen atom and a silicon atom. An etching method includes an etching step of bringing an etching gas containing fluorine gas into contact with an etched member having an etching target and a non-etching target in the absence of plasma, to selectively etch the etching target with respect to the non-etching target. The etching target contains a silicon compound having at least one of a nitrogen atom and an oxygen atom and a silicon atom. The non-etching target has at least one selected from the group consisting of tantalum, cobalt, copper, titanium nitride, nickel, and amorphous carbon. The etching step is performed at a temperature of 40°C or higher and lower than 350°C.

Description

Technical Field

[0001] This invention relates to etching methods and methods for manufacturing semiconductor devices. Background Technology

[0002] In semiconductor manufacturing processes, etching is used for patterning and removing silicon compounds such as silicon oxide and silicon nitride. For example, Patent Document 1 discloses a method for etching silicon oxide using an etching gas containing fluorine gas (F2) in the absence of plasma. Patent Document 2 discloses a cleaning method for removing silicon nitride using fluorine gas in the absence of plasma. Hereinafter, etching methods that do not use plasma will sometimes be referred to as "plasma-free etching".

[0003] Prior art literature

[0004] Patent Document 1: Japanese Patent Publication No. 533853, 2009

[0005] Patent Document 2: Japanese Patent Publication No. 5571770 Summary of the Invention

[0006] However, in the methods disclosed in Patent Documents 1 and 2, the etching of silicon compounds such as silicon oxide and silicon nitride requires a high temperature of over 350°C. Therefore, etching requires a large amount of energy, resulting in the problem that not only the object to be etched, but also non-objects to be etched are etched.

[0007] The objective of this invention is to provide an etching method and a method for manufacturing a semiconductor device, which enables selective etching of an etchable object relative to a specific non-etchable object without the use of plasma, the etchable object containing a silicon compound having at least one of nitrogen atoms and oxygen atoms as well as silicon atoms.

[0008] To address the aforementioned problem, one aspect of the present invention is shown in [1] to

[10] .

[0009] [1] An etching method comprising an etching step, wherein, in the absence of plasma, an etching gas containing fluorine gas is brought into contact with a component having an object to be etched and a non-object to be etched, wherein the object to be etched is selectively etched relative to the non-object to be etched, the object to be etched being an object etched by the etching gas, and the non-object to be etched being an object not etched by the etching gas.

[0010] The etched object contains a silicon compound having at least one of nitrogen and oxygen atoms, as well as silicon atoms.

[0011] The non-etched object has at least one selected from tantalum, cobalt, copper, titanium nitride, nickel, and amorphous carbon.

[0012] The etching process is carried out at a temperature above 40°C and below 350°C.

[0013] [2] According to the etching method described in [1], the silicon compound is at least one of silicon oxide and silicon nitride.

[0014] [3] The etching process is carried out under pressure conditions of 1 Pa or more and 100 kPa or less according to the etching method described in [1] or [2].

[0015] [4] The etching process is carried out at a temperature of 70°C or higher and 330°C or lower according to any one of [1] to [3].

[0016] [5] In any one of the etching methods described in [1] to [4], the etching gas is a gas consisting only of fluorine gas or a mixture of fluorine gas and inert gas.

[0017] [6] According to the etching method described in [5], the inert gas is at least one selected from nitrogen, helium, argon, neon, krypton and xenon.

[0018] [7] In any one of the etching methods of [1] to [6], the fluorine content in the etching gas is 0.5% by volume or more and 70% by volume or less.

[0019] [8] In any one of the etching methods [1] to [7], the non-etched object is used as a resist in the etching of the etched object by the etching gas.

[0020] [9] According to any one of [1] to [8], the etching rate of the object to be etched is 3 or more relative to the etching rate of the object not to be etched.

[0021]

[10] A method for manufacturing a semiconductor element, wherein the semiconductor element is manufactured using any one of the etching methods described in [1] to [9],

[0022] The etched component is a semiconductor substrate having the etched object and the non-etched object.

[0023] The manufacturing method includes a processing step in which at least a portion of the object to be etched is removed from the semiconductor substrate by etching.

[0024] According to the present invention, it is possible to selectively etch an object containing a silicon compound, having at least one of nitrogen atoms and oxygen atoms as well as silicon atoms, without using plasma. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating an example of an etching apparatus for one embodiment of the etching method of the present invention.

[0026] Figure 2 This is a diagram illustrating the etched component used in Embodiment 1, etc.

[0027] Figure 3 This is a diagram illustrating the etched component used in Embodiment 20, etc. Detailed Implementation

[0028] The following describes one embodiment of the present invention. Furthermore, this embodiment illustrates one example of the present invention, and the present invention is not limited to this embodiment. In addition, various modifications or improvements can be made to this embodiment, and such modified or improved methods are also included in the present invention.

[0029] The etching method of this embodiment includes an etching step in which an etching gas containing fluorine gas (F2) is brought into contact with a component to be etched, which has an object to be etched and a non-object to be etched, in the absence of plasma. The object to be etched is selectively etched compared to the non-object to be etched, which is an object etched by the etching gas and the non-object to be etched is not an object etched by the etching gas.

[0030] The object to be etched contains a silicon compound having at least one of nitrogen (N) and oxygen (O) atoms, as well as silicon (Si) atoms. Additionally, the object not to be etched contains at least one selected from tantalum (Ta), cobalt (Co), copper (Cu), titanium nitride (TiN), nickel (Ni), and amorphous carbon (C). Furthermore, in the etching method of this embodiment, the etching process is performed at a temperature of 40°C or higher and below 350°C.

[0031] When the etching gas comes into contact with the component to be etched, the fluorine gas in the etching gas reacts with the silicon compound in the component, thus advancing the etching of the component. In contrast, since the non-etched component hardly reacts with the fluorine gas, the etching of the non-etched component hardly advances. Therefore, the etching method according to this embodiment can selectively etch the component relative to the non-etched component without using plasma.

[0032] Since etching can be performed without using plasma, there is no need to use expensive plasma generators. Therefore, etching of components can be performed at a low cost. In addition, since plasma is not used, corrosion is less likely to occur on components constituting the etching apparatus (e.g., chambers), piping connected to the etching apparatus, components constituting the semiconductor element manufacturing apparatus (e.g., chambers), and piping connected to the semiconductor element manufacturing apparatus described later.

[0033] Furthermore, etching in this invention refers to removing part or all of the etched object from the etched component, processing the etched component into a predetermined shape (e.g., a three-dimensional shape) (e.g., processing the film-like etched object made of the silicon compound into a predetermined film thickness), and also refers to removing residues and deposits made of the etched object from the etched component and cleaning it.

[0034] The etching method of this embodiment can be used to manufacture semiconductor devices. That is, the semiconductor device manufacturing method of this embodiment is a semiconductor device manufacturing method that uses the etching method of this embodiment to manufacture semiconductor devices. The etched component is a semiconductor substrate having an etchable object and a non-etchable object. The manufacturing method includes a processing step in which at least a portion of the etchable object is removed from the semiconductor substrate by etching.

[0035] For example, in the etching method of this embodiment, silicon nitride (e.g., Si3N4) is etched more rapidly than silicon oxide (e.g., SiO2). By utilizing this characteristic, the etching method of this embodiment can be used to manufacture semiconductor devices such as 3D-NAND flash memory and logic devices.

[0036] For example, a structure in which through-holes extending along the stacking direction and penetrating the stack are formed in a laminate of alternating layers of silicon oxide and silicon nitride (see reference). Figure 3 By applying the etching method of this embodiment, the silicon nitride film exposed on the inner surface of the through-hole is selectively and isotropically etched, thereby forming a structure in which the end of the silicon oxide film protrudes within the through-hole. The process of forming a structure having this structure enables the structure to be used as a structure for semiconductor devices, and therefore it is used in the manufacture of semiconductor devices such as 3D-NAND flash memory and logic devices.

[0037] The process of forming the above-mentioned structure by etching has conventionally been carried out using reagent solutions containing phosphoric acid, etc. However, compared with etching using reagent solutions, etching using etching gases offers superior micromachinability. Therefore, the etching method of this embodiment can be expected to contribute to further miniaturization and high integration of semiconductor devices.

[0038] Similarly, when using the non-etched object itself as the structure of the semiconductor element, the non-etched object is a material that is substantially non-reactive with fluorine gas or a material that reacts very slowly with fluorine gas. Specifically, for example, at least one material selected from tantalum, cobalt, copper, titanium nitride, nickel, and amorphous carbon can be used.

[0039] Furthermore, as mentioned above, the etching method of this embodiment can also be used for cleaning. For example, after performing a process of forming a film made of a material containing the silicon compound on a substrate within a cavity, and / or etching the film containing the silicon compound formed on the substrate, the etching method of this embodiment can be used to remove and clean the deposits containing the silicon compound adhering to the inner surface of the cavity. Moreover, in such cleaning, the cavity corresponds to the etched component, which is a constituent element of the present invention, and the deposits correspond to the etched object, which is a constituent element of the present invention.

[0040] The etching method and the semiconductor device manufacturing method of this embodiment will be described in more detail below.

[0041] [Etching Gas]

[0042] The etching gas is a gas containing fluorine. The etching gas can be a gas composed solely of fluorine, or it can be a mixture containing fluorine and other gases. When the etching gas is a mixture containing fluorine and other gases, the fluorine content in the etching gas is preferably 0.5% by volume or more and 70% by volume or less, more preferably 1% by volume or more and 60% by volume or less, and even more preferably 5% by volume or more and 50% by volume or less.

[0043] When the etching gas is a mixture containing fluorine and other gases, an inert gas can be used as one of the other gases. That is, the etching gas can be a mixture of fluorine and an inert gas. As the inert gas, at least one selected from nitrogen (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) can be used. The content of the inert gas in the etching gas is not particularly limited and can exceed 0% by volume but be less than 99% by volume.

[0044] [Pressure conditions for the etching process]

[0045] The pressure conditions of the etching process in the etching method of this embodiment are not particularly limited, but are preferably 1 Pa or more and 100 kPa or less, more preferably 100 Pa or more and 80 kPa or less, and even more preferably 1 kPa or more and 60 kPa or less.

[0046] For example, the component to be etched can be placed in the chamber, and etching can be performed while etching gas flows through the chamber. The pressure inside the chamber when the etching gas flows can be above 1 Pa and below 100 kPa. The flow rate of the etching gas is appropriately set according to the size of the chamber and the capacity of the exhaust equipment for depressurizing the chamber, so that the pressure inside the chamber is kept constant.

[0047] Temperature conditions for the etching process

[0048] The etching process in this embodiment requires a temperature condition of 40°C or higher and 350°C or lower, preferably 70°C or higher and 330°C or lower, and more preferably 130°C or higher and 300°C or lower. Here, the temperature condition refers to the temperature of the component being etched, but the temperature of the stage that supports the component being etched and is located within the etching apparatus can also be used.

[0049] If the temperature is above 40°C, the etching rate of the silicon compound being etched tends to be higher. On the other hand, if the temperature is below 350°C, it has advantages such as being able to perform etching without excessive time and energy, placing less load on the etching apparatus and the semiconductor manufacturing apparatus, and suppressing the etching of parts that should not be etched (e.g., non-etchable objects).

[0050] Fluorine gas exhibits almost no reaction with non-etchable materials such as tantalum, cobalt, copper, titanium nitride, nickel, and amorphous carbon under conditions of absence of plasma and temperatures below 350°C. Therefore, by employing the etching method of this embodiment, the etchable material can be selectively etched without significantly etching the non-etchable material. Consequently, the etching method of this embodiment can be used for methods such as using patterned non-etchable materials as resists or masks, and for processing etchable materials into predetermined shapes.

[0051] Furthermore, if the temperature of the object to be etched and the non-object to be etched is below 350°C, the etching selectivity tends to be higher. For example, the ratio of the etching rate of the object to be etched to the etching rate of the non-object to be etched, i.e., the etching selectivity, tends to be 3 or higher. The etching selectivity is preferably 3 or higher, more preferably 5 or higher, and even more preferably 10 or higher.

[0052] [Etched component]

[0053] The etched component using the etching method of this embodiment has an etchable object and a non-etchable object. It can be a component having portions formed of the etchable object and portions formed of the non-etchable object, or it can be a component formed of a mixture of the etchable object and the non-etchable object. Furthermore, the etched component may have portions other than the etchable object and the non-etchable object.

[0054] Furthermore, the shape of the etched component is not particularly limited; for example, it can be plate-shaped, foil-shaped, film-shaped, powder-shaped, or block-shaped. As an example of the etched component, the aforementioned semiconductor substrate can be cited.

[0055] [Etched object]

[0056] The object to be etched contains a silicon compound having at least one of nitrogen and oxygen atoms and silicon atoms. The object to be etched can be composed of the silicon compound or a mixture containing the silicon compound. Alternatively, the silicon compound can be at least one of silicon oxide and silicon nitride.

[0057] Silicon nitride refers to a compound containing silicon and nitrogen in any proportion, such as Si3N4. The purity of silicon nitride is not particularly limited, but is preferably 30% by mass or more, more preferably 60% by mass or more, and even more preferably 90% by mass or more.

[0058] Silicon oxide refers to a compound containing silicon and oxygen in any proportion, such as SiO2. The purity of silicon oxide is not particularly limited, but is preferably 30% by mass or more, more preferably 60% by mass or more, and even more preferably 90% by mass or more.

[0059] In addition, there are no particular limitations on the shape of the object being etched; for example, it can be plate-shaped, foil-shaped, film-shaped, powder-shaped, or block-shaped.

[0060] [Non-etched objects]

[0061] The non-etched object has at least one selected from tantalum, cobalt, copper, titanium nitride, nickel and amorphous carbon. Since they do not react substantially with fluorine gas or react with fluorine gas very slowly, they are hardly etched even when etched using the etching method of this embodiment.

[0062] Furthermore, the non-etched object can be used as a resist to suppress the etching of the etched object by the etching gas. Therefore, the etching method of this embodiment can utilize methods such as using the patterned non-etched object as a resist or mask, and processing the etched object into a predetermined shape (e.g., processing the film-like etched object of the etched component into a predetermined film thickness), thus making it suitable for the manufacture of semiconductor devices. In addition, since the non-etched object is hardly etched, it is possible to suppress the etching of parts of the semiconductor device that should not be etched, and to prevent the loss of semiconductor device characteristics due to etching.

[0063] Furthermore, any non-etched objects remaining after patterning can be removed using removal methods commonly employed in semiconductor device manufacturing processes. For example, ashing with oxidizing gases such as oxygen plasma or ozone, or dissolution with reagents such as APM (a mixture of ammonia and hydrogen peroxide), SPM (a mixture of sulfuric acid and hydrogen peroxide), or organic solvents can be used.

[0064] Next, refer to Figure 1 This section describes an example of the structure of an etching apparatus capable of implementing the etching method of this embodiment, and an example of an etching method using the etching apparatus. Figure 1 The etching apparatus is a plasma-free etching apparatus that does not use plasma. First, for Figure 1 The etching apparatus will be described.

[0065] Figure 1 The etching apparatus includes a chamber 10, a stage 11, a thermometer 14, an exhaust pipe 13, a vacuum pump 15, and a pressure gauge 16. The etching is performed inside the chamber 10. The stage 11 supports the etched component 12 inside the chamber 10. The thermometer 14 measures the temperature of the etched component 12. The exhaust pipe 13 is used to exhaust the gas inside the chamber 10. The vacuum pump 15 is located in the exhaust pipe 13 and reduces the pressure inside the chamber 10. The pressure gauge 16 measures the pressure inside the chamber 10.

[0066] in addition, Figure 1 The etching apparatus includes an etching gas supply unit that supplies etching gas to the interior of the chamber 10. The etching gas supply unit includes a fluorine gas supply unit 1, an inert gas supply unit 2, a fluorine gas supply pipe 5, and an inert gas supply pipe 6. The fluorine gas supply unit 1 supplies fluorine gas, the inert gas supply unit 2 supplies inert gas, the fluorine gas supply pipe 5 connects the fluorine gas supply unit 1 to the chamber 10, and the inert gas supply pipe 6 connects to the inert gas supply unit 2 at the middle of the fluorine gas supply pipe 5.

[0067] Furthermore, the fluorine gas supply pipe 5 is equipped with a fluorine gas pressure control device 7 for controlling the fluorine gas pressure and a fluorine gas flow control device 3 for controlling the fluorine gas flow rate. In addition, the inert gas supply pipe 6 is equipped with an inert gas pressure control device 8 for controlling the inert gas pressure and an inert gas flow control device 4 for controlling the inert gas flow rate.

[0068] Furthermore, when fluorine gas is supplied to the chamber 10 as an etching gas, fluorine gas is supplied to the chamber 10 via the fluorine gas supply pipe 5 by sending fluorine gas from the fluorine gas supply section 1 to the fluorine gas supply pipe 5.

[0069] Furthermore, when a mixture of fluorine and inert gas is supplied as the etching gas, fluorine gas is supplied from the fluorine gas supply unit 1 to the fluorine gas supply pipe 5, and inert gas is supplied from the inert gas supply unit 2 to the fluorine gas supply pipe 5 via the inert gas supply pipe 6. Thus, the fluorine gas and inert gas mix in the middle of the fluorine gas supply pipe 5 to form a mixed gas, which is then supplied to the chamber 10 via the fluorine gas supply pipe 5.

[0070] Furthermore, the structures of the fluorine gas supply unit 1 and the inert gas supply unit 2 are not particularly limited; for example, they can also be gas cylinders or gas storage cylinders. Additionally, the fluorine gas flow control device 3 and the inert gas flow control device 4 can be, for example, mass flow controllers or flow meters.

[0071] When supplying etching gas to chamber 10, it is preferable to supply the etching gas at a pressure that is (i.e., the pressure of the etching gas supply) Figure 1 The etching gas is supplied while maintaining the value of the fluorine gas pressure control device 7 at a predetermined value. That is, the supply pressure of the etching gas is preferably 1 kPa or more and 1.0 MPa or less, more preferably 5 kPa or more and 0.7 MPa or less, and even more preferably 10 kPa or more and 0.5 MPa or less. If the supply pressure of the etching gas is within the above range, the supply of etching gas to the chamber 10 proceeds smoothly, and... Figure 1 The components of the etching apparatus (e.g., the various devices or the piping) have low loads.

[0072] Furthermore, from the viewpoint of uniformly etching the surface of the etched component 12, the pressure of the etching gas supplied to the chamber 10 is preferably 1 Pa or more and 100 kPa or less, more preferably 100 Pa or more and 80 kPa or less, and even more preferably 1 kPa or more and 60 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 can easily become higher.

[0073] The pressure within chamber 10 before the etching gas is supplied is not particularly limited, as long as it is below or lower than the supply pressure of the etching gas; for example, it is preferably 10. -5 Pa or higher and lower than 10 kPa, more preferably 1 Pa or higher and lower than 2 kPa.

[0074] The pressure difference between the supply pressure of the etching gas and the pressure inside the chamber 10 before the etching gas is supplied is preferably 1.0 MPa or less, more preferably 0.5 MPa or less, and even more preferably 0.3 MPa or less. If the differential pressure is within the above range, the etching gas can be supplied to the chamber 10 smoothly and easily.

[0075] When supplying etching gas to 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 above 0°C and below 150°C.

[0076] The temperature of the etched component 12 during etching must be above 40°C and below 350°C, preferably above 70°C and below 330°C, and more preferably above 130°C and below 300°C. Within this temperature range, the etching of the etched object (especially silicon nitride) on the etched component 12 proceeds smoothly, the load on the etching apparatus is small, and the lifespan of the etching apparatus is easily extended.

[0077] The etching processing time (hereinafter sometimes referred to as "etching time") can be arbitrarily set according to the desired degree of etching of the etched object on the etched component 12, but considering the production efficiency of semiconductor device manufacturing processes, it is preferably within 60 minutes, more preferably within 40 minutes, and even more preferably within 30 minutes. Furthermore, the etching processing time refers to the time from the introduction of etching gas into the cavity 10 to the discharge of etching gas from the cavity 10 to complete the etching process.

[0078] The etching method of this embodiment can be used as follows: Figure 1 The etching process is carried out using a general plasma-free etching apparatus, similar to the etching apparatus used in semiconductor device manufacturing. There are no particular limitations on the structure of the etching apparatus that can be used.

[0079] For example, the positional relationship between the fluorine gas supply pipe 5 and the etched component 12 is not particularly limited as long as the etching gas can contact the etched component 12. In addition, the structure of the temperature control mechanism of the chamber 10 is not particularly limited as long as the temperature of the etched component 12 can be adjusted to any temperature. Therefore, the temperature control mechanism can be directly provided on the stage 11, or the chamber 10 can be heated or cooled from the outside of the chamber 10 by an external temperature controller.

[0080] in addition, Figure 1 The material of the etching apparatus is not particularly limited, as long as it is resistant to fluorine gas and can be depressurized to a predetermined pressure. For example, the parts in contact with the etching gas can be made of metals such as nickel, nickel-based alloys, aluminum, stainless steel, platinum, copper, and cobalt, ceramics such as alumina, fluoropolymers, etc.

[0081] Specific examples of nickel-based alloys include Inconel (registered trademark), HASTELLOY (registered trademark), and Monel (registered trademark). Additionally, examples of fluoropolymers include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyvinylidene fluoride (PVDF), Teflon (registered trademark), VITON (registered trademark), and Kalrez (registered trademark).

[0082] Example

[0083] The present invention will be described in more detail below with examples, comparative examples and reference examples shown.

[0084] (Example 1)

[0085] Using structure and Figure 1 The etching apparatus is largely the same as the etching apparatus used to etch the component being etched. (Refer to...) Figure 2 The etched component used in Example 1 will be described.

[0086] A component (manufactured by KSTWorld Co., Ltd.) is prepared by forming a 3μm thick silicon nitride film 22 on a square silicon substrate 21 with a side length of 2 inches. A rectangular nickel substrate 23 with dimensions of 1 inch × 2 inches is then bonded to the silicon nitride film 22 using grease (DEMNUMGREASE L-200 manufactured by Daikin Industries, Ltd.). This laminate is then used as the component to be etched. Figure 2 As shown, the nickel substrate 24 is bonded to cover approximately half of the silicon nitride film 22. Furthermore, the silicon nitride film 22 is the object to be etched, while the non-etched object, the nickel substrate 23, is used as a resist.

[0087] In addition, in the aforementioned etched components, comparative laminates were fabricated in which the etched object, namely the silicon nitride film 22, was replaced with a non-etched object, namely any one of the following films: tantalum, cobalt, copper, titanium nitride, nickel, and amorphous carbon.

[0088] The etched component and the six comparative laminates are placed side by side on the stage inside the chamber of the etching apparatus, and the temperature of the stage is raised to 150°C.

[0089] Next, fluorine gas at a flow rate of 50 mL / min and argon gas at a flow rate of 450 mL / min are mixed to form a mixed gas, which is used as the etching gas. Then, the etching gas is supplied to the chamber at a flow rate of 500 mL / min and allowed to circulate for 3 minutes to perform etching. As a result, the exposed portions of the silicon nitride film 22 of the etched component not covered by the nickel substrate 23 are etched. The pressure inside the chamber during the etching gas flow is 10 kPa, and the partial pressure of the fluorine gas is 1 kPa. After the etching gas flow is complete, the heating of the stage is stopped, and the interior of the chamber is purged with argon gas.

[0090] After etching, the chamber was opened, the etched component was removed, and the nickel substrate 23 was removed from the etched component. The bonding surface was cleaned with ethanol to remove the grease. Then, using an atomic force microscope VN-8010 manufactured by Keyence Corporation, the size of the step on the covered surface 22a of the silicon nitride film 22 covered by the nickel substrate 23 and thus not etched, and the etched surface 22b of the silicon nitride film 22 not covered by the nickel substrate 23 and thus etched, were measured. The etching rate of silicon nitride (nm / min) was calculated by dividing the measured step size (nm) by the etching time (min). The results are shown in Table 1.

[0091] In addition, the same operation was performed on the six comparative laminates as on the etched components, and the etching rates (nm / min) for elemental tantalum, cobalt, copper, titanium nitride, nickel, and amorphous carbon were calculated by dividing the step size (nm) by the etching time (min). The results are shown in Table 1.

[0092] Furthermore, the conditions for determining the step size obtained by atomic force microscopy are as follows.

[0093] Measurement pressure: Atmospheric pressure (101.3 kPa)

[0094] Measurement temperature: 28℃

[0095] Atmosphere measurement: In the atmosphere

[0096] Scanning range: width 80.0 μm, height 20.0 μm, angle 0°

[0097] Table 1

[0098]

[0099] *) The volume ratio of fluorine gas to inert gas, for example, when fluorine gas:inert gas = 10:90, is recorded as 10 / 90.

[0100] (Examples 2-18)

[0101] As shown in Tables 1-3, the etched object was set as a silicon oxide film or a silicon nitride film, and the etching conditions (composition of etching gas, stage temperature, chamber pressure, and etching time) were set as shown in Tables 1-3. Etching was performed in the same manner as in Example 1, and the etching rates for the etched object, tantalum, cobalt, copper, titanium nitride, nickel, and amorphous carbon were calculated respectively. The results are shown in Tables 1-3.

[0102] Table 2

[0103]

[0104] *) The volume ratio of fluorine gas to inert gas, for example, when fluorine gas:inert gas = 10:90, is recorded as 10 / 90.

[0105] Table 3

[0106]

[0107] *1) The volume ratio of fluorine gas to inert gas, for example, when fluorine gas:inert gas = 10:90, it is recorded as 10 / 90.

[0108] *2) Regarding Example 19 and Comparative Examples 3 and 4, the etch selectivity when the etched object is silicon nitride is recorded to the left of " / ", and the etch selectivity when the etched object is silicon oxide is recorded to the right of " / ".

[0109] (Example 19)

[0110] The etched component with a silicon oxide film, the etched component with a silicon nitride film, and the above-mentioned six comparative laminates were placed side by side on a stage inside the chamber of the etching apparatus, and etched in the same manner as in Example 1. The etching rates for each were calculated. The results are shown in Table 3.

[0111] (Compare Examples 1 and 2)

[0112] The stage temperature was set to 30°C, and etching was performed in the same manner as in Examples 1 and 2. The results are shown in Table 3.

[0113] (Comparative Example 3)

[0114] The stage temperature was set to 400°C, the etching time to 1 minute, and the non-etched object of the comparison stack was set to be only titanium nitride. Otherwise, the etching was performed in the same manner as in Example 19. The results are shown in Table 3.

[0115] (Comparative Example 4)

[0116] The etching gas was replaced with iodine heptafluoride (IF7) gas, and the etching was performed in the same manner as in Example 1. The results are shown in Table 3.

[0117] (Example for reference)

[0118] Components (manufactured by KST World Co., Ltd.) are prepared, each having a 100nm thick film of a non-etched material (tantalum, cobalt, copper, titanium nitride, nickel, or amorphous carbon) formed on a square silicon substrate with sides of 2 inches. A rectangular nickel substrate measuring 1 inch × 2 inches is bonded to this non-etched material film using grease (DEMNUM GREASE L-200 manufactured by Daikin Industries, Ltd.). Six such laminates are used as reference examples. The nickel substrate is bonded such that it covers approximately half of the non-etched material film.

[0119] The etching time was set to 30 minutes. Otherwise, the etching of six reference laminates was performed in the same manner as in Example 1, and the etching rate of the film on the non-etched object was calculated. The results are shown in Table 3.

[0120] (Example 20)

[0121] Reference Figure 3 The etched component used in Example 20 will be described. Figure 3 The etched component has a structure obtained by alternately stacking 30 layers of silicon nitride film 32 with a thickness of 35 nm and silicon oxide film 33 with a thickness of 35 nm on a silicon substrate 31. Figure 3 (For convenience, a structure with five alternating layers is shown in the image.) Additionally, Figure 3 The etched component has a structure in which an amorphous carbon film 35 with a thickness of 1 μm is stacked on top of the uppermost silicon oxide film 33. Here, the silicon nitride film 32 and the silicon oxide film 33 are the objects to be etched, while the amorphous carbon film 35 is not. Furthermore, Figure 3 The etched component has a through hole 34 with a diameter of 100 nm that penetrates 30 layers of silicon nitride film 32, 30 layers of silicon oxide film 33 and 1 layer of amorphous carbon film 35 in the stacking direction.

[0122] The etched component is placed on the structure and Figure 1 On the stage of an etching apparatus largely similar to that used elsewhere, the stage temperature was raised to 150°C. Next, fluorine gas at a flow rate of 10 mL / min and argon gas at a flow rate of 90 mL / min were mixed to form a mixed gas, which was then used as the etching gas. This etching gas was then supplied to the chamber and allowed to circulate for 1 minute for etching. The pressure inside the chamber during etching gas circulation was 10 kPa. After the etching gas circulation was complete, the heating of the stage was stopped, and the chamber was purged with argon gas.

[0123] Open the chamber and remove the etched component. In the etched component, the portion of the silicon nitride film 32 exposed on the inner surface of the through hole 34 is etched. In particular, compared with the silicon oxide film 33, the silicon nitride film 32 is preferentially etched, so a portion of the inner surface of the through hole 34 extends radially outward.

[0124] The portion of the silicon oxide film 33 exposed on the inner surface of the through hole 34 is more difficult to etch than the silicon nitride film 32, and the amorphous carbon film 35 is hardly etched. Therefore, the ends of the silicon oxide film 33 and the amorphous carbon film 35 protrude into the through hole 34.

[0125] The etched component was cut off and the cross-sections of the 30-layer silicon nitride film 32 and the 30-layer silicon oxide film 33 were analyzed using a scanning electron microscope. Specifically, for the 30-layer silicon nitride film 32, the radial distances between the portions of the silicon nitride film 32 exposed on the inner surface of the through-hole 34 and the portions of the amorphous carbon film 35 exposed on the inner surface of the through-hole 34 were measured. Similarly, for the 30-layer silicon oxide film 33, the radial distances between the portions of the silicon oxide film 33 exposed on the inner surface of the through-hole 34 and the portions of the amorphous carbon film 35 exposed on the inner surface of the through-hole 34 were measured.

[0126] That is, the inner surface of the through-hole 34 was expanded radially outward by etching, increasing the radius of the through-hole 34, and the difference in radius was measured. Then, the relative etching rates of silicon nitride and silicon oxide relative to amorphous carbon were calculated by dividing this difference by the etching time. Furthermore, the etching rate of amorphous carbon was calculated by comparing the diameter of the through-hole 34 before and after etching, and the change in diameter was almost imperceptible.

[0127] Then, the average and standard deviation of the etching rates of the 30-layer silicon nitride film 32 and silicon oxide film 33 were calculated, and the variation of the relative etching rate in the in-plane direction (parallel to the film surface) with respect to the stacking direction of the films and the uniformity of the relative etching rate were evaluated. The results are shown in Table 4.

[0128]

[0129] (Examples 21-27)

[0130] The etching conditions (composition of etching gas, stage temperature, chamber pressure, and etching time) were as shown in Table 4. Etching was performed in the same manner as in Example 20, and the relative etching rates of silicon nitride and silicon oxide relative to amorphous carbon were calculated. The results are shown in Table 4.

[0131] The results of Examples 1-6 show that as the temperature of the stage increases, the etching rate of silicon nitride and silicon oxide increases.

[0132] As can be seen from the results of Examples 7 to 10, the smaller the proportion of inert gas in the etching gas, the faster the etching rate of silicon nitride and silicon oxide.

[0133] The results of Examples 15-18 show that the same results can be obtained even when nitrogen or helium is used instead of argon as the inert gas.

[0134] The results from Examples 11-14 show that the higher the pressure inside the chamber, the faster the etching rate of silicon nitride and silicon oxide. This is believed to be because the increased partial pressure of fluorine gas inside the chamber increases the frequency of contact between the surfaces of silicon nitride and silicon oxide and the fluorine gas, thus accelerating the etching process.

[0135] As shown in the results of Example 19, even when silicon nitride and silicon oxide are present in the same chamber, their respective etching proceeds without problems. On the other hand, as shown in the results of Examples 1-19 and the Reference Example, the etching of tantalum, cobalt, titanium nitride, copper, nickel, and amorphous carbon is almost non-existent. From the above results, it is clear that by employing the etching method of this embodiment, silicon nitride and silicon oxide can be selectively etched compared to the non-etched object.

[0136] The results of Comparative Examples 1 and 2 show that when the stage temperature is as low as 30°C, the etching of the object to be etched hardly occurs. On the other hand, the results of Comparative Example 3 show that when the stage temperature is too high, reaching 400°C, the etching of the non-etchable object proceeds, and therefore it is not possible to selectively etch the object to be etched compared to the non-etchable object.

[0137] As can be seen from the results of Comparative Example 4, even when iodine heptafluoride is used as the etching gas and etching is performed under the same conditions as the etching method of this embodiment, the etching of the object to be etched is almost non-existent.

[0138] The results from Examples 20-27 show that increasing the stage temperature, increasing the ratio of fluorine gas flow rate to inert gas flow rate, and increasing the pressure within the chamber increases the etching rate of silicon nitride and silicon oxide. On the other hand, even changing the type of inert gas has almost no effect on the etching rate.

[0139] Furthermore, it was found that since the standard deviation of the etching rate is approximately 4–8% of the average etching rate of silicon nitride, the etching of the 30-layer silicon nitride film 32 proceeds roughly uniformly, regardless of the stacking orientation of the silicon nitride film 32. In contrast, the etching rate of silicon oxide is lower than that of silicon nitride under all conditions, and the standard deviation of the etching rate of silicon oxide is less than 0.5 under all conditions.

[0140] Explanation of reference numerals in the attached figures

[0141] 1…Fluorine Supply Department

[0142] 2…Inert gas supply section

[0143] 3…Fluorine gas flow control device

[0144] 4…Inert gas flow control device

[0145] 5… Fluorine gas supply piping

[0146] 6… Piping for inert gas supply

[0147] 7…Fluorine gas pressure control device

[0148] 8…Inert gas pressure control device

[0149] 10…chamber

[0150] 11…Platform

[0151] 12…etched components

[0152] 13…Exhaust piping

[0153] 14…Thermometer

[0154] 15…vacuum pump

[0155] 16… Pressure gauge

[0156] 21…Silicon substrate

[0157] 22…Silicon nitride film

[0158] 23…Nickel substrate

[0159] 31…Silicon substrate

[0160] 32…Silicon nitride film

[0161] 33…Silicon oxide film

[0162] 34… Through hole

[0163] 35…Amorphous carbon film

Claims

1. An etching method comprising an etching step, wherein, in the absence of plasma, an etching gas containing fluorine gas is brought into contact with a component having an object to be etched and a non-object to be etched, wherein the object to be etched is selectively etched relative to the non-object to be etched, the object to be etched being an object etched by the etching gas, and the non-object to be etched being an object not etched by the etching gas. The object to be etched contains at least one of silicon oxide and silicon nitride. The non-etched object has at least one selected from tantalum, cobalt, copper, titanium nitride, nickel, and amorphous carbon. The etching process is performed at a temperature above 40°C and below 350°C. The etching gas is a gas consisting solely of fluorine or a mixture of fluorine and inert gases.

2. The etching method according to claim 1, wherein the etching process is performed under pressure conditions of 1 Pa or more and 100 kPa or less.

3. The etching method according to claim 1 or 2, wherein the etching process is performed at a temperature of 70°C or higher and 330°C or lower.

4. The etching method according to claim 1 or 2, wherein the inert gas is at least one selected from nitrogen, helium, argon, neon, krypton and xenon.

5. The etching method according to claim 1 or 2, wherein the fluorine content in the etching gas is 0.5% by volume or more and 70% by volume or less.

6. The etching method according to claim 1 or 2, wherein the non-etched object is used as a resist in the etching of the etched object by the etching gas.

7. The etching method according to claim 1 or 2, wherein the ratio of the etching rate of the object to be etched to the etching rate of the non-object to be etched, i.e., the etching selectivity ratio, is 3 or more.

8. A method for manufacturing a semiconductor element, comprising manufacturing the semiconductor element using the etching method according to any one of claims 1 to 7. The etched component is a semiconductor substrate having the etched object and the non-etched object. The manufacturing method includes a processing step in which at least a portion of the object to be etched is removed from the semiconductor substrate by etching.

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