Atomic layer etching process of metal oxide layer

Abstract

An atomic layer etching method according to an embodiment may include: a step of preparing a substrate on which a metal oxide film is formed; a step of generating a radical-containing reforming gas by supplying a halogen-containing gas and an oxygen-containing gas at a flow rate ratio of 1:0.1 to 1:5, respectively, and supplying the generated radical-containing reforming gas onto the metal oxide film to reform the surface of the metal oxide film; and a step of removing the metal oxide film with the reformed surface.

Description

Technology Field

[0001] The present invention relates to a method for etching a metal oxide film using an atomic layer etching method. Background Technology

[0002] Due to the demand for high performance and low power consumption, the pattern size of semiconductor devices is becoming finer, and innovation is required to move beyond three-dimensional stacked structures to multidimensional stacked structures in the future. Accordingly, there is a need to develop atomic layer etching process technology that can selectively remove desired materials with high precision at the atomic level, going beyond existing wet and dry etching technologies.

[0003] The above atomic layer etching process is utilized to etch various thin films, such as metal oxide films, to form fine patterns by sequentially exposing the etching target layer of a substrate placed in a process chamber to a modifying gas and a reaction gas, thereby enabling the etching target layer to be etched at the atomic layer level.

[0004] Conventionally, in order to etch a metal oxide film using an atomic layer etching process, the surface of the metal oxide film is modified using a halogen-containing gas such as hydrofluoric acid (HF) or nitrogen fluoride (NF3), and the metal oxide film is etched by removing the surface-modified portion.

[0005] Figure 1 is a conceptual diagram showing an atomic layer etching process for metal oxide films currently in use.

[0006] Specifically, in order to etch the metal oxide film (20) formed on the upper surface of the substrate (10), a halogen-containing gas is supplied onto the metal oxide film (20) to modify the surface of the metal oxide film (20). At this time, the halogen-containing gas may be a gas containing radicals generated after being supplied to a remote plasma generator. Then, once the surface modification is complete, a metal oxide precursor gas is supplied onto the metal oxide film (20) to remove and etch the metal oxide film (21) with the modified surface. When the metal oxide film (20) is etched using a halogen-containing gas as described above, damage occurs on the surface of the metal oxide film (20) due to halogen radicals. The atomic layer etching process is repeated multiple times to etch the metal oxide film to a target thickness, and during the process of repeating the process as described above, damage caused by halogen radicals accumulates, causing defects such as pinholes on the surface of the metal oxide film (20). In addition, an oxygen vacancy area in which oxygen is absent may be formed within the metal oxide film (20), and the halogen radical can penetrate into the oxygen vacancy area and significantly degrade the electrical properties of the metal oxide film (20).

[0007] In particular, when metal oxide films are formed on high aspect ratio patterns, there is a problem in that it is difficult to apply atomic layer etching processes due to step coverage and the loading effect, where etching proceeds more smoothly in lower areas; therefore, research is needed on methods to compensate for this. The problem to be solved

[0008] According to one embodiment, the present invention aims to provide technical details regarding an atomic layer etching method that prevents the formation of pinholes caused by halogen elements in an atomic layer etching process for etching a metal oxide film using a halogen-containing gas, prevents the degradation of electrical properties of the metal oxide film by providing a curing effect that fills oxygen vacancy areas within the metal oxide film, and controls the etching rate per unit cycle. means of solving the problem

[0009] An atomic layer etching method according to an embodiment may include: a step of preparing a substrate on which a metal oxide film is formed; a step of generating a radical-containing reforming gas by supplying a halogen-containing gas and an oxygen-containing gas at a flow rate ratio of 1:0.1 to 1:5, respectively, and supplying the generated radical-containing reforming gas onto the metal oxide film to reform the surface of the metal oxide film; and a step of removing the metal oxide film with the reformed surface.

[0010] According to one embodiment, the metal oxide film may have a structure formed on the upper surface of a substrate in which a stepped structure pattern is formed by being embedded to a certain depth from the surface.

[0011] According to one embodiment, the radical-containing reforming gas can be formed by supplying the halogen-containing gas and the oxygen-containing gas to a remote plasma generator.

[0012] According to one embodiment, the metal oxide film may be any one of zirconium oxide (ZrO2), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2), and tantalum oxide (Ta2O5).

[0013] According to one embodiment, the halogen-containing gas may include at least one of nitrogen trifluoride (NF3) gas, fluorine (F2) gas, chlorine trifluoride (ClF3) gas, carbon tetrafluoride (CF4) gas, hydrofluoric acid (HF) gas, dicarbon hexafluoride (C2F6) gas, tricarbon octafluoride (C3F8) gas, tetracarbon hexafluoride (C4F6) gas, sulfur hexafluoride (SF6) gas, carbonyl fluoride (COF3) gas, chlorine (Cl2) gas, hydrogen chloride (HCl) gas, silicon tetrachloride (SiCl4) gas, hydrogen bromide (HBr) gas, boron tribromide (BBr3) gas, silicon tetrabromide (SiBr4) gas, and bromine (Br2) gas.

[0014] According to one embodiment, the oxygen-containing gas may include at least one of oxygen (O2) gas, ozone (O3) gas, nitrous oxide (N2O) gas, nitrogen dioxide (NO2) gas, nitric oxide (NO) gas, and water vapor (H2O).

[0015] According to one embodiment, a unit cycle including the step of modifying the metal oxide film; and the step of heat-treating and etching the metal oxide film can be performed at least 10 times.

[0016] Meanwhile, the recording medium according to the embodiment has a computer-readable structure on which a program for performing the atomic layer etching method described above is recorded. Effects of the invention

[0017] The atomic layer etching method according to the embodiment supplies a specific ratio of oxygen-containing gas along with a halogen-containing gas as a radical-containing modification gas to modify the surface of a metal oxide film, thereby preventing thin film damage caused by halogen radicals during the atomic layer etching process and preventing degradation of the electrical properties of the metal oxide film by providing a curing effect that fills oxygen-deficient regions within the metal oxide film, and can control the etching rate per unit cycle during the atomic layer etching process of the metal oxide film. Brief explanation of the drawing

[0018] Figure 1 is a conceptual diagram showing an atomic layer etching process for metal oxide films currently in use. Figure 2 is a conceptual diagram showing an atomic layer etching process of a metal oxide film according to an embodiment. Figure 3 is a flowchart showing an atomic layer etching process of a metal oxide film according to an embodiment. FIG. 4 is a schematic diagram showing a substrate processing apparatus for performing an atomic layer etching process of a metal oxide film according to an embodiment. Specific details for implementing the invention

[0019] FIG. 2 is a conceptual diagram showing an atomic layer etching process of a metal oxide film according to an embodiment. FIG. 3 is a flowchart showing an atomic layer etching process of a metal oxide film according to an embodiment.

[0020] Referring to FIGS. 2 and FIGS. 3, the atomic layer etching method according to the embodiment includes the steps of: preparing a substrate (10) (S100); modifying the surface of a metal oxide film (20) (S200); and removing the metal oxide film (S400).

[0021] First, in the step (S100) of preparing a substrate (10), a substrate (10) having a metal oxide film (20) formed thereon is prepared, and the metal oxide film (20) is a target layer for etching in an atomic layer etching process.

[0022] The metal oxide film (20) may have various compositions commonly used for manufacturing semiconductor devices. In particular, the metal oxide film (20) may be a high-dielectric thin film comprising a high-k dielectric material having a high dielectric constant.

[0023] Specifically, the metal oxide film (20) can be exemplified by high dielectric thin films such as zirconium oxide (ZrO2), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2), and tantalum oxide (Ta2O5).

[0024] In addition, the metal oxide film (20) may be formed on the upper surface of the substrate (10) and may have a structure formed on the upper surface of the substrate (10) such that a stepped structure pattern is formed by being embedded to a certain depth from the surface. When the metal oxide film (20) is etched through the atomic layer etching method according to the embodiment on the substrate (10) having the structure as described above, it may be applied as an etching process to prevent the occurrence of pinholes and to secure a capacitance value and a space between the sidewalls of the metal oxide film (20).

[0025] The substrate (10) on which the atomic layer etching method according to the embodiment is performed may be any substrate (10) used in a manufacturing process including an etching process. For example, the substrate (10) may be various substrates, such as a wafer for manufacturing semiconductor devices such as DRAM, NAND flash memory, CPU, mobile CPU, etc., or a glass substrate (10) for manufacturing display panels such as LCD panels, OLED panels, etc.

[0026] Next, in the step (S200) of modifying the surface of the metal oxide film (20), a radical-containing modification gas is generated, and the generated radical-containing modification gas is supplied onto the metal oxide film (20) to modify the surface of the metal oxide film (20).

[0027] The radical-containing reforming gas may include a halogen-containing gas and an oxygen-containing gas. The radical-containing reforming gas may be formed by supplying the halogen-containing gas and the oxygen-containing gas to a remote plasma generator (RPG). The radical-containing reforming gas can modify the surface of the metal oxide film (20) under relatively low temperature conditions, thereby preventing thermal problems caused by high-temperature heating.

[0028] The remote plasma generator may utilize various conventional structures used to generate radicals and supply them onto a substrate (10). The remote plasma generator may be operated in any one of the following ways: a capacitor coupled plasma (CCP) method, an inductively coupled plasma (ICP) method, or a microwave method.

[0029] The above halogen-containing gas can be used as a reforming gas to surface-modify the surface of the metal oxide film (20) to a certain thickness.

[0030] The above halogen-containing gas may include at least one of nitrogen trifluoride (NF3) gas, fluorine (F2) gas, chlorine trifluoride (ClF3) gas, carbon tetrafluoride (CF4) gas, hydrofluoric acid (HF) gas, dicarbon hexafluoride (C2F6) gas, tricarbon octafluoride (C3F8) gas, tetracarbon hexafluoride (C4F6) gas, sulfur hexafluoride (SF6) gas, carbonyl fluoride (COF3) gas, chlorine (Cl2) gas, hydrogen chloride (HCl) gas, silicon tetrachloride (SiCl4) gas, hydrogen bromide (HBr) gas, boron tribromide (BBr3) gas, silicon tetrabromide (SiBr4) gas, and bromine (Br2) gas. In particular, the above halogen-containing gas may be nitrogen trifluoride (NF3) gas.

[0031] The oxygen-containing gas is supplied together with the halogen-containing gas to generate a radical-containing reforming gas. The oxygen-containing gas enables the control of the concentration of halogen radicals that would occur if only the halogen-containing gas were supplied during the process of reforming the surface of the metal oxide film (20) by forming halogen-oxygen radicals. Accordingly, the oxygen-containing gas allows the etching rate per cycle (Å / cycle, EPC) to be selectively controlled as needed.

[0032] In addition, the oxygen-containing gas can induce a curing effect by filling the oxygen vacancy area (25) present in the metal oxide film (20) with oxygen radicals, thereby suppressing the diffusion of halogen ions into the oxygen vacancy area. Accordingly, the occurrence of defects induced by halogen can be reduced, and the occurrence of pinholes can be prevented.

[0033] The oxygen-containing gas may include at least one of oxygen (O2) gas, ozone (O3) gas, nitrous oxide (N2O) gas, nitrogen dioxide (NO2) gas, nitric oxide (NO) gas, hydrogen peroxide (H2O2) gas, and water vapor (H2O). In particular, the oxygen-containing gas may be oxygen (O2) gas.

[0034] In this step, the halogen-containing gas and the oxygen-containing gas are supplied at a flow rate ratio of 1:0.1 to 1:5, respectively, to generate the radical-containing reforming gas. If the flow rate ratio of the oxygen content in the radical-containing reforming gas deviates from the above range, there is a risk of problems such as the collapse of the etching profile of the metal oxide film (20), the occurrence of pinholes, and a decrease in the etching rate per cycle. In particular, the radical-containing reforming gas can be generated by supplying the halogen-containing gas and the oxygen-containing gas at a flow rate ratio of 1:1.12 to 1:3, respectively.

[0035] The above halogen-containing gas can be supplied at a flow rate of 10 to 300 sccm, and the above oxygen-containing gas can be supplied at a flow rate of 1 to 1500 sccm to produce the above radical-containing reforming gas.

[0036] Specifically, the halogen-containing gas can be supplied at a flow rate of 50 to 100 sccm, and the oxygen-containing gas can be supplied at a flow rate of 100 to 300 sccm to produce the radical-containing reforming gas.

[0037] For example, the above flow rate ratio means that when the halogen-containing gas is supplied at a flow rate of 100 sccm, the oxygen-containing gas can be supplied at a flow rate of 10 sccm to 500 sccm. More specifically, when the halogen-containing gas and the oxygen-containing gas are supplied at a flow rate ratio of 1:3, the halogen-containing gas can be supplied at 50 sccm and the oxygen-containing gas can be supplied at a flow rate of 150 sccm. At this time, the flow rates of the halogen-containing gas and the oxygen-containing gas can be selectively adjusted as needed.

[0038] In particular, the above flow rate ratio can be selectively adjusted according to the flow rate of the halogen-containing gas.

[0039] More specifically, when the halogen-containing gas is supplied at a rate of less than 100 sccm, the halogen-containing gas and the oxygen-containing gas can be supplied at a flow rate ratio of 1:2 to 1:4.

[0040] In addition, when the halogen-containing gas is supplied at a rate of 100 sccm or more, the halogen-containing gas and the oxygen-containing gas can be supplied at a flow rate ratio of 1:1.4 to 1:3.

[0041] In this step (S200), the radical-containing modified gas can be supplied to the upper surface of the metal oxide film (20) and reacted for a time of 0.5 to 60 seconds to modify the surface of the metal oxide film (20).

[0042] Additionally, this step (S200) may be configured to include a first purge step (S300) in which a radical-containing reforming gas is supplied to reform the surface of the metal oxide film (20), and then a purge gas is supplied to remove the reforming gas remaining on the metal oxide film (20) and the substrate (10). The purge gas may be an inert gas such as argon gas or nitrogen gas.

[0043] Next, in the step (S400) of removing the metal oxide film (20), atomic layer etching can be performed by removing the surface-modified portion of the metal oxide film (20).

[0044] In this step, the metal oxide film (21) with a modified surface can be removed using various conventional methods used to remove the metal oxide film (20) after surface modification in an atomic layer etching process.

[0045] For example, in this step, the metal oxide film (20) with the surface modified can be removed by supplying a metal organic precursor gas to the upper surface of the metal oxide film (21) with the surface modified.

[0046] The above metal-organic precursor gas may include at least one of trimethylaluminum (TMA), bisacetylacetonatetin (Sn(acac)2), dimethylammonium iodide (DMAI), tetraethoxygermanium (Ge(OEt)4), tetramethyltin (Sn(Me)4), tetraethyltin (Sn(Et)4), diethylaluminium chloride (DMAC), and titanium tetrachloride (TiCl4).

[0047] As described above, when a metal-organic precursor gas is supplied to a metal oxide film (21) with a modified surface, the portion of the metal oxide film (20) with a modified surface can be removed by the metal-organic precursor gas.

[0048] Next, the process may be configured to include a second purging step (S500) in which a metal-organic precursor gas is supplied as described above to remove the surface-modified metal oxide film (21), and then a purging gas is supplied to remove all residual gas and components of the removed metal oxide film (20). To this end, the first and second purging processes (S300, S500) as described above can be performed by exhausting the interior of the process chamber (110).

[0049] In an atomic layer etching method according to one embodiment, an atomic layer etching process can be performed by performing a unit cycle n times, which includes the surface modification treatment (S200), the first purging treatment (S300), the removal of the metal oxide film (20) (S400), and the second purging treatment (S500) (where n is a natural number greater than or equal to 1). When the unit cycle is performed once, one layer of atoms can be removed from the metal oxide film (20). Therefore, the etching thickness of the metal oxide film (20) can be controlled by controlling the number of cycles.

[0050] The atomic layer etching method according to the above-described embodiment supplies a specific ratio of oxygen-containing gas along with a halogen-containing gas as a radical-containing modification gas to modify the surface of the metal oxide film (20), thereby preventing thin film damage caused by halogen elements during the atomic layer etching process, and provides a curing effect that fills the oxygen-free region within the metal oxide film (20), thereby preventing degradation of the electrical properties of the metal oxide film (20), and can control the etching rate per unit cycle during the atomic layer etching process of the metal oxide film (20).

[0051] The atomic layer etching method according to the embodiment described above can be performed using various types of conventional substrate processing devices utilized for performing an atomic layer etching process.

[0052] For example, FIG. 4 is a schematic diagram showing a substrate processing apparatus for performing an atomic layer etching process of a metal oxide film according to an embodiment.

[0053] Referring to FIG. 4, a substrate processing device (100) according to one embodiment can be performed using a substrate processing device having a structure including a process chamber (110), a gas injection unit (120), a substrate mounting unit (130), and a remote plasma generation unit (150).

[0054] The above process chamber (110) can form a hermetic processing space (111) inside so as to perform a substrate processing process such as an atomic layer etching process.

[0055] The above process chamber (110) may have a structure in which an exhaust section (not shown) is connected to discharge process gas, radical-containing reforming gas, metal-organic precursor gas, purge gas, etc., within the processing space (111).

[0056] The process chamber (110) can be implemented in various shapes. For example, the process chamber (110) may have a structure including a chamber body (113) that defines a processing space (111) and a chamber lid (115) located at the top of the chamber body (113). Additionally, the process chamber (110) may include a gate (117) installed on the side wall of the chamber body (113) to form a space through which the substrate (10) flows in and out.

[0057] The above gas injection unit (120) may be installed in the process chamber (110) to supply radical-containing reforming gas, metal-organic precursor gas, and purge gas to the processing space (111), respectively. The radical-containing reforming gas, metal-organic precursor gas, purge gas, etc., may be supplied by connecting to a gas supply unit (not shown), such as a gas storage tank, installed outside the process chamber (110). Additionally, the above gas injection unit (120) may be connected to a remote plasma generator (150) to receive halogen-containing gas and oxygen-containing gas, respectively, to generate radical-containing reforming gas, and to inject the generated radical-containing reforming gas into the process chamber (110).

[0058] The above gas injection unit (120) may be installed above the process chamber (110) opposite the substrate mounting unit (130) to inject various gases onto the substrate mounted on the substrate mounting unit (130).

[0059] The above gas injection unit (120) may have various shapes, such as a shower head or a nozzle. In particular, when the gas injection unit (120) is in the form of a shower head, the gas injection unit (120) may form a structure that is coupled to the process chamber (110) together with the chamber lid (115) in a manner that covers the upper part of the process chamber (110).

[0060] The substrate mounting portion (130) is installed in the process chamber (110) opposite to the gas injection portion (120), and a substrate can be mounted thereon. The substrate mounting portion (130) may be larger than the substrate (10) and have various shapes so as to stably mount the substrate (10) on which a metal oxide film (20) is formed. The substrate mounting portion (130) may have a structure that is connected separately from an external driving unit and capable of moving up and down.

[0061] The above substrate mounting portion (130) can be implemented using various conventional chuck structures such as electrostatic chucks, vacuum chucks, etc.

[0062] The remote plasma generator (150) receives a halogen-containing gas and an oxygen-containing gas, respectively, and generates and supplies a radical-containing reforming gas. The remote plasma generator (150) can be implemented using various types of conventional remote plasma generators that are utilized to generate a gas containing radicals or active species by receiving the gas. The remote plasma generator (150) may include an inductively coupled plasma (ICP) type remote plasma generator.

[0063] The above remote plasma generation unit (150) is connected to the gas injection unit (120) via a waveguide (WG) and can supply a radical-containing reforming gas to the gas injection unit (120). A substrate processing device such as the above can perform an atomic layer etching process on a metal oxide film formed on the upper surface of a substrate and can perform a purge process by supplying a purge gas.

[0064] Meanwhile, the atomic layer etching method according to the embodiment described above may be implemented as an application or in the form of program instructions that can be executed through various computer components and recorded on a computer-readable recording medium. The computer-readable recording medium may include program instructions, data files, data structures, etc., either individually or in combination.

[0065] The program instructions recorded on the computer-readable recording medium may be those specifically designed and configured for the present invention, or they may be those known and available to those skilled in the art of computer software. Examples of the computer-readable recording medium may include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs and DVDs; magneto-optical media such as floptical disks; and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory.

[0066] Examples of the above program instructions may include not only machine code, such as that generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter, etc. The above hardware device may be configured to operate as one or more software modules to perform processing according to the embodiment, and vice versa.

[0067] The above recording medium may be implemented as a control unit of the substrate processing device to perform the atomic layer etching method according to the embodiment. The substrate processing device may be controlled according to a program recorded on the recording medium and driven to perform the atomic layer etching method according to the embodiment.

[0068] The present invention will be explained in more detail below with reference to examples.

[0069] The presented embodiments are merely specific examples of the invention and are not intended to limit the technical scope of the invention.

[0070] <Example>

[0071] A substrate having a zirconium oxide film with a thickness of 100 Å formed on its upper surface was prepared. The prepared substrate was placed in a process chamber, and an atomic layer etching process was performed to etch the zirconium oxide film.

[0072] In the above atomic layer etching process, NF3 gas and O2 gas were first supplied to a remote plasma generator to which a 300 W RF power source was applied to generate a radical-containing modified gas. The generated radical-containing modified gas was supplied onto the zirconium oxide film for 30 seconds to perform a modification treatment on the surface of the zirconium oxide film. At this time, the flow rate ratio of the NF3 gas and O2 gas was adjusted to 1:0.2, 1:0.3, 1:0.4, 1:1.3, 1:1.4, 1:2, and 1:3, respectively, to modify the surface of the zirconium oxide film. Then, a purge gas was supplied into the processing space to perform a purge treatment.

[0073] Next, the surface-modified substrate was heated to a temperature of 300°C to sublimate and remove the surface of the surface-modified zirconium oxide film. Then, a purge gas was supplied into the processing space to perform a purge treatment.

[0074] In addition, the atomic layer etching process was performed by repeating the unit cycle, which includes the modification treatment, purging treatment, surface removal, and purging treatment described above, multiple times.

[0075] <Comparative Example>

[0076] The atomic layer etching process was performed in the same manner as in the example, except that NF3 gas was supplied alone without supplying O2 gas.

[0077] <Experimental Example>

[0078] (1) NF 3 Impact assessment of reforming treatment performed using gas-only supply

[0079] The effect on the physical properties of the thin film when NF3 gas is used alone was evaluated. In this case, the evaluation of the effect when NF3 gas is supplied alone was performed under the same conditions as the comparative example, except for (a) supplying NF3 gas and performing the modification treatment for 15 seconds, (b) supplying RF power at 300 W to generate a radical-containing modification gas and performing the modification treatment, (c) performing the modification treatment under a pressure condition of 1 Torr, and (d) performing the modification treatment under a temperature condition of 30 ℃.

[0080] As a result, when performed under the conditions according to the comparative example (conditions of 30 seconds, 500W RF power, 100 sccm flow rate, 2 Torr, and 50 ℃), the unit area (1.5 μm) 2 It was confirmed that the number of pinholes that occurred was the smallest at less than 20.

[0081] In addition, the formation of pinholes is affected by processing time, RF power, pressure conditions, modification temperature, and gas flow rate, and since the number of pinholes formed varies depending on the conditions, it was confirmed that modification conditions influence pinhole formation.

[0082] In particular, it was confirmed that while using NF3 gas alone can reduce the number of pinholes formed, it is not possible to completely suppress the formation of pinholes or control the number of pinholes per unit area to 10 or fewer, indicating that additional alternatives are needed.

[0083] (2) Evaluation of the effect of flow rate ratio on the atomic layer etching process

[0084] After performing an atomic layer etching process according to the methods of the examples and comparative examples, the change in physical properties was evaluated.

[0085] As a result, it was confirmed that when the atomic layer etching process was performed using the method according to the comparative example, a number of pinholes were formed on the zirconium oxide film after the atomic layer etching process was completed, causing defects in the zirconium oxide film.

[0086] On the other hand, when reforming with oxygen gas supplied together, it was confirmed that the number of pinholes decreased as the oxygen gas flow rate ratio increased. In particular, it was confirmed that no pinholes occurred when NF3 gas was supplied at a flow rate of 100 sccm and O2 gas at a flow rate of 140 sccm, i.e., when the flow rate ratio was 1:1.4, while it was confirmed that pinholes occurred, albeit in small amounts, when the O2 gas flow rate was 130 sccm.

[0087] In addition, it was confirmed that when NF3 gas was supplied at a relatively low flow rate of 50 sccm and O2 gas was supplied at a flow rate of 100 sccm, a small amount of pinholes occurred, and it was confirmed that when NF3 gas was supplied at a flow rate of 50 sccm and O2 gas was supplied at a flow rate of 150 sccm, that is, when supplied at a flow rate ratio of 1:3, no pinholes occurred.

[0088] As described above, the prevention of pinhole formation caused by the addition of O2 gas is achieved by supplying an oxygen-containing gas in a process where a halogen-containing gas is used alone; this fills the oxygen vacancy region in the oxide film with oxygen radicals, inducing a curing effect and suppressing the diffusion of halogen ions into the oxygen vacancy region. Consequently, the occurrence of defects induced by halogens can be reduced, and pinholes can be eliminated.

[0089] Furthermore, it was determined that adding oxygen gas to a halogen-containing gas forms halogen oxides, enabling control of halogen radical concentrations and thus controlling the etching rate per cycle (Å / cycle, EPC).

[0090] In particular, when comparing the EPC using the method according to the comparative example and the method according to the example, it was confirmed that the comparative example was 2.96 Å / cycle, whereas the example was 2.37 Å / cycle, indicating a 20% reduction in EPC.

[0091] (3) Evaluation of the impact on the number of times the atomic layer etching process is performed

[0092] The effect of the composition of the reforming gas on the number of atomic layer etching process cycles was evaluated. As a result, it was confirmed that when using the method according to the comparative example, the etching profile of the zirconium oxide film collapsed after 11 unit cycles, whereas when using the method according to the example, it was confirmed that no change occurred in the etching profile even when the number of atomic layer etching process cycles was increased to 11 or more due to the addition of oxygen gas.

[0093] (4) Evaluation of the impact of oxygen-containing gas flow rate ratio on EPC

[0094] The effect of oxygen-containing gas supply flow rate on EPC was evaluated. To this end, EPC was evaluated when NF3 gas and O2 gas were supplied at flow rate ratios of 1:1.2 and 1:1.3, respectively.

[0095] As a result, it was confirmed that when NF3 gas and O2 gas were supplied at a flow rate ratio of 1:1.2, the EPC was 2.74 Å / cycle, and when NF3 gas and O2 gas were supplied at a flow rate ratio of 1:1.3, the EPC was 2.37 Å / cycle. Based on the above results, it was determined that increasing the flow rate ratio of O2 gas could decrease the EPC, and decreasing the flow rate ratio of O2 gas could increase the EPC. Explanation of the symbols

[0096] 10: Substrate 20: Metal oxide film 21: Surface-modified metal oxide film 100: Substrate processing device 110: Process Chamber 111: Processing space 113: Chamber body 115: Chamber Lid 117: Gate 120: Gas injection unit 130: Substrate mounting area 150: Remote plasma generator

Claims

Claim 1 An atomic layer etching method comprising: a step of preparing a substrate on which a metal oxide film is formed; a step of generating a radical-containing reforming gas by supplying a halogen-containing gas and an oxygen-containing gas at a flow rate ratio of 1:0.1 to 1:5, respectively, and supplying the generated radical-containing reforming gas onto the metal oxide film to reform the surface of the metal oxide film; and a step of removing the metal oxide film with the reformed surface. Claim 2 In claim 1, the metal oxide film is formed by an atomic layer etching method on a substrate having a stepped structure pattern formed by being embedded to a certain depth from the surface. Claim 3 In claim 1, the radical-containing reforming gas is formed by supplying the halogen-containing gas and the oxygen-containing gas to a remote plasma generator for an atomic layer etching method. Claim 4 In claim 1, the metal oxide film is an atomic layer etching method in which any one of zirconium oxide (ZrO2), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2) and tantalum oxide (Ta2O5). Claim 5 The atomic layer etching method according to claim 1, wherein the halogen-containing gas comprises at least one of nitrogen trifluoride (NF3) gas, fluorine (F2) gas, chlorine trifluoride (ClF3) gas, carbon tetrafluoride (CF4) gas, hydrofluoric acid (HF) gas, dicarbon hexafluoride (C2F6) gas, tricarbon octafluoride (C3F8) gas, tetracarbon hexafluoride (C4F6) gas, sulfur hexafluoride (SF6) gas, carbonyl fluoride (COF3) gas, chlorine (Cl2) gas, hydrogen chloride (HCl) gas, silicon tetrachloride (SiCl4) gas, hydrogen bromide (HBr) gas, boron tribromide (BBr3) gas, silicon tetrabromide (SiBr4) gas and bromine (Br2) gas. Claim 6 In claim 1, the oxygen-containing gas comprises at least one of oxygen (O2) gas, ozone (O3) gas, nitrous oxide (N2O) gas, nitrogen dioxide (NO2) gas, nitric oxide (NO) gas and water vapor (H2O). Claim 7 An atomic layer etching method according to claim 1, comprising the step of modifying the metal oxide film; and the step of heat-treating and etching the metal oxide film, wherein the unit cycle is performed at least 10 times. Claim 8 A computer-readable recording medium having a program for performing an atomic layer etching method described in any one of claims 1 to 7.

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