Thin film etching method

Abstract

A method for etching a thin film according to one aspect of the present invention includes the steps of: preparing a substrate on which a pattern including a nitride film is formed; a surface treatment step of treating a surface of the nitride film with an oxygen-containing gas to at least partially oxidize the surface; and an etching step of supplying an etching gas onto the oxide layer to remove at least a portion of an oxide layer on the surface of the nitride film oxidized in the surface treatment step, wherein the surface treatment step and the etching step are repeated in a cycle.

Description

[Technical Field]

[0001] The present invention relates to semiconductor manufacturing, and more particularly to methods for etching thin films. [Background technology]

[0002] In order to manufacture semiconductor devices, various processes are performed in a substrate processing apparatus under a vacuum atmosphere. For example, a substrate is loaded into a process chamber, and processes such as depositing a thin film on the substrate or etching the thin film may be performed. Here, the substrate is supported by a substrate support installed in the process chamber, and processing gases are injected onto the substrate through a gas injection unit installed above the substrate support.

[0003] Meanwhile, when one or more thin film patterns are formed on a substrate, a number of thin films may be exposed on the substrate. For example, insulating films such as oxide films and nitride films may be exposed on the substrate. Subsequently, a process of selectively etching one of these insulating films may be added. Recently, with the increasing integration of semiconductor devices, the thickness of these insulating films has become thinner, which can lead to a problem of etching unwanted insulating films due to insufficient selectivity in the etching step of these insulating films.

[0004] Furthermore, as the thickness of the insulating film becomes thinner, it becomes difficult for the etchant to penetrate, limiting the use of conventional wet etching. Dry etching using halide-based etching gases has been studied, but the etching selectivity is not high enough. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made to solve various problems, including those mentioned above, and aims to provide a method for etching a thin film using dry etching with a high etching selectivity when manufacturing a highly integrated semiconductor device. However, these problems are merely examples, and the scope of the present invention is not limited thereto. [Means for solving the problem]

[0006] In order to solve the above problems, according to one aspect of the present invention, a method for etching a thin film includes the steps of: preparing a substrate on which a pattern including a nitride film is formed; a surface treatment step of treating a surface of the nitride film with an oxygen-containing gas so as to oxidize at least a portion of the surface; and an etching step of supplying an etching gas onto the oxide layer to remove at least a portion of an oxide layer on the surface of the nitride film oxidized in the surface treatment step, wherein the surface treatment step and the etching step are repeated in a cycle.

[0007] According to another aspect of the present invention, there is provided a method for etching a thin film, comprising the steps of: preparing a substrate having a pattern including an oxide film and a nitride film formed thereon; a surface treatment step of treating the surfaces of the oxide film and the nitride film with an oxygen-containing gas so as to at least partially oxidize the surfaces; and an etching step of supplying an etching gas onto the oxide layer to remove at least a portion of an oxide layer on the surface of the nitride film oxidized in the surface treatment step, wherein the surface treatment step and the etching step are repeated in a cycle.

[0008] The oxide layer formed on the oxide film in the surface treatment step of the thin film etching method may have different physical properties from the oxide layer formed on the nitride film.

[0009] In the etching step of the thin film etching method, an etching ratio of the oxide layer formed on the oxide film and an etching ratio of the oxide layer formed on the nitride film may be different from each other.

[0010] In the thin film etching method, an etching rate of an oxide layer formed on the nitride film may be higher than an etching rate of an oxide layer formed on the oxide film.

[0011] In the thin film etching method, the oxygen-containing gas may include at least one of O2, O3, H2O, H2O2, and N2O.

[0012] In the thin film etching method, the etching gas may be a mixed gas of NH3 and NF3, or a halide gas.

[0013] In the thin film etching method, the surface treatment step may be performed in a plasma atmosphere. [Effects of the Invention]

[0014] According to the thin film etching method according to some embodiments of the present invention, a thin film etching method using dry etching with high etching selectivity can be realized when manufacturing highly integrated semiconductor devices, although the scope of the present invention is not limited by such effects. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a flowchart illustrating a thin film etching method according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating a method for etching a thin film according to an embodiment of the present invention; [Figure 3] 1 is a graph showing the thickness of an oxide layer on the surface of a nitride film oxidized through a surface treatment step and the thickness of the nitride film measured while repeating a unit cycle including a surface treatment step and an etching step in a thin film etching method according to an embodiment of the present invention. [Figure 4] 1A to 1C are schematic cross-sectional views of a substrate illustrating a method for etching a thin film according to some embodiments of the present invention. [Figure 5] 1A to 1C are schematic cross-sectional views of a substrate illustrating a method for etching a thin film according to some embodiments of the present invention. [Figure 6] 10A and 10B are diagrams showing the results of measuring line widths in a laminated structure to which a thin film etching method according to some embodiments of the present invention is applied. [Figure 7] 10A and 10B are diagrams showing the results of measuring line widths in a laminated structure to which a thin film etching method according to some embodiments of the present invention is applied. [Figure 8] 8 is a graph showing the measurement results of FIGS. 6 and 7 together. [Figure 9] 1 is a graph showing in-situ monitoring of etched thickness according to etching time when a thin film etching method according to an embodiment of the present invention is applied; [Figure 10] 1 is a graph showing the results of calculating the amount of fluorine (F) atoms adsorbed on the surface of a thin film during the thin film etching method according to an embodiment of the present invention. [Figure 11] 1 is a graph comparing the etched thickness of a silicon oxide film (SiO2) and a silicon nitride film (SiN) according to process temperature. [Figure 12] 1 is a graph showing RGA intensity obtained by analyzing components of an etchant in a thin film etching method according to an embodiment of the present invention. [Figure 13] 1 is a schematic view showing a substrate processing apparatus for explaining a thin film etching method according to some embodiments of the present invention; [Figure 14] 2 is a schematic diagram showing that fluorine anions form fluorine compounds in the thin film etching method according to the embodiment of the present invention; FIG. [Figure 15] 4 is a graph showing the etching rate and etching selectivity as a function of the flow rate of Ar in the thin film etching method according to the embodiment of the present invention. [Figure 16] 10 is a graph showing the etching rate as a function of the flow rate of Ar in a thin film etching method according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0016] Various preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0017] The examples of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following examples can be modified into various other forms, and the scope of the present invention is not limited to the following examples. Rather, these examples are provided to make the present disclosure more complete and complete, and to fully convey the concept of the present invention to those skilled in the art. In addition, the thickness and size of each layer in the drawings are exaggerated for convenience and clarity of explanation.

[0018] FIG. 1 is a flow chart showing a method for etching a thin film according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a method for etching a thin film according to an embodiment of the present invention.

[0019] 1 and 2, a method for etching a thin film according to an embodiment of the present invention includes a step (S10) of preparing a substrate on which a pattern including a nitride film 55 is formed, a surface treatment step (S20) of treating the exposed surface of the nitride film 55 with an oxygen-containing gas to oxidize at least a portion of the surface, and an etching step (S30) of supplying an etching gas onto the oxide layer 51 to remove at least a portion of the oxide layer 51 on the surface of the nitride film oxidized through the surface treatment step, and is characterized in that the surface treatment step (S20) and the etching step (S30) are repeated at least once as a cycle.

[0020] In the surface treatment step (S20), the oxygen-containing gas may include at least one of O2, O3, H2O, H2O2, and N2O, and the surface treatment step may be performed in a plasma atmosphere or a thermal atmosphere.

[0021] In the etching step (S30), the etching gas may be a mixed gas of NH3 and NF3, or a halide gas.

[0022] 3 is a graph showing the thickness of the oxidation layer 51 (●) on the surface of the nitride film oxidized through the surface treatment step and the thickness of the nitride film (SiN) (◯) measured while repeating a unit cycle consisting of a surface treatment step (S20) and an etching step (S30) in a thin film etching method according to one embodiment of the present invention. Here, the thickness of the nitride film (SiN) (◯) can be understood as a thickness taking into account both the thickness of the pure silicon nitride film 55 and the thickness of the oxidation layer 51 on the surface of the nitride film. Among the steps shown in FIG. 3, the step labeled 'Oxidation' corresponds to the surface treatment step (S20) described above, and the step labeled 'Etch' corresponds to the etching step (S30) described above.

[0023] 1 to 3, during one unit cycle, the thickness of the oxidation layer 51 on the surface of the nitride film oxidized through the surface treatment step gradually increases from an initial thickness of 0 Å to approximately 6.6 Å, and during the etching step, the thickness of the oxidation layer 51 gradually decreases by approximately 6.6 Å. Reflecting this, as the oxidation layer 51 on the surface of the nitride film is etched through the etching step, the thickness of the nitride film gradually decreases by approximately 6.6 Å. By repeating this unit cycle approximately eight times, the thickness of the nitride film gradually decreases from approximately 4775 Å to approximately 4722 Å.

[0024] According to the thin film etching method, the surface of the nitride film 55 is oxidized to a certain extent, and the oxidized unstable oxide layer 51 can be removed using an atomic layer removal (ALR) process. This has the advantage of being applicable to a self-limiting process, and is advantageous in that it can use dry source materials that are commonly used in semiconductor mass production processes, making it suitable for mass production.

[0025] On the other hand, when the above-described thin film etching method is applied to a substrate on which a pattern including an oxide film and a nitride film is formed, the etching selectivity of the oxide film and the nitride film is significantly increased, and therefore, it is expected to be highly useful. The process of applying the above-described thin film etching method to a substrate on which a pattern including an oxide film and a nitride film is formed will be described below.

[0026] 4 and 5 are schematic cross-sectional views of a substrate illustrating a method for etching a thin film according to some embodiments of the present invention. Fig. 4 illustrates a state before at least the etching step (S30) is performed in the method for etching a thin film according to some embodiments of the present invention, and Fig. 5 illustrates a state after the etching step (S30) is performed.

[0027] 1 to 5, a method for etching a thin film according to some embodiments of the present invention includes a step (S10) of preparing a substrate S on which a pattern 56 including an oxide film 54 and a nitride film 55 is formed, a surface treatment step (S20) of treating the surfaces of the oxide film 54 and the nitride film 55 exposed in the pattern 56 with an oxygen-containing gas so as to oxidize at least a portion of the surface, and an etching step (S30) of supplying an etching gas onto the oxide layer 51 to remove at least a portion of the oxide layer 51 on the surface of the nitride film oxidized in the surface treatment step, and is characterized in that the surface treatment step (S20) and the etching step (S30) are repeated at least once as a cycle.

[0028] In the surface treatment step (S20), the oxygen-containing gas may include at least one of O2, O3, H2O, H2O2, and N2O, and the surface treatment step may be performed in a plasma atmosphere.

[0029] In the etching step (S30), the etching gas may be a mixed gas of NH3 and NF3, or a halide gas.

[0030] The physical properties of the oxide layer formed on the oxide film 54 in the surface treatment step (S20) may be different from those of the oxide layer formed on the nitride film 55. Therefore, in the etching step (S30), the etching rates of the oxide layer formed on the oxide film 54 and the oxide layer formed on the nitride film 55 may be different from each other. For example, the etching rate of the oxide layer formed on the nitride film 55 may be higher than the etching rate of the oxide layer formed on the oxide film 54. This is because the oxide layer 51 formed on the surface of the nitride film 55 in the surface treatment step (S20) contains both oxygen and nitrogen groups, which makes it easier for the oxide layer 51 to react with fluorine (F) in the subsequent etching step (S30).

[0031] Furthermore, the physical properties of the oxide layer formed on the nitride film 55 in the surface treatment step (S20) may differ from those of the oxide film 54. For example, the oxide film 54 is deposited at a process temperature of about 500 to 600°C, whereas the oxide layer formed on the nitride film 55 in the surface treatment step (S20) is formed at a low temperature of about 150 to 250°C, which may result in a significant difference in film quality.

[0032] As shown in FIG. 5, when the above-described thin film etching method is applied to a stack pattern 56 in which an oxide film 54 and a nitride film 55 are stacked, the oxide film 54 is hardly etched, but the nitride film 55 may be etched relatively more than the oxide film 54.

[0033] 6 and 7 are diagrams showing the results of measuring line widths in a laminated structure to which a thin film etching method according to some embodiments of the present invention is applied, and FIG. 8 is a graph summarizing the measurement results of FIGS. 6 and 7.

[0034] Specifically, Fig. 6 shows the results before applying the etching step (S30) in the thin film etching method according to some embodiments of the present invention, and Fig. 7 shows the results after applying the etching step (S30) in the thin film etching method according to some embodiments of the present invention. The numbers on the horizontal axis of Fig. 8 indicate the numbers of ordered pairs of silicon oxide films (SiO2) and silicon nitride films (SiN) from the top in a thin film structure in which silicon nitride films (SiN) and silicon oxide films (SiO2) are alternately stacked.

[0035] 6 and 7, the separation distance between each unit layer in a thin film structure in which silicon nitride (SiN) and silicon oxide (SiO2) layers are alternately stacked was measured. The trench space having the separation distance can be formed as a word line by being filled with, for example, a conductive material.

[0036] In FIG. 8, the "Pristine SiN" item indicates the separation distance (word line width) between silicon nitride films (SiN) measured in the structure of FIG. 6, and the "ALE SiN" item indicates the separation distance (word line width) between silicon nitride films (SiN) measured in the structure of FIG. 7. Similarly, the "Pristine SiO2" item indicates the separation distance (word line width) between silicon oxide films (SiO2) measured in the structure of FIG. 6, and the "ALE SiO2" item indicates the separation distance (word line width) between silicon oxide films (SiO2) measured in the structure of FIG. 7. In this experimental example, a unit cycle consisting of the surface treatment step (S20) and the etching step (S30) was repeated 10 times.

[0037] Referring to Figures 6 to 8, in a thin film structure in which silicon nitride films (SiN) and silicon oxide films (SiO2) are alternately stacked, the separation distance between the topmost silicon nitride films (SiN) increased by 6.2 nm from 121.1 nm before the unit cycle was applied to 127.3 nm after the unit cycle was repeated 10 times, while the separation distance between the silicon oxide films (SiO2) decreased by approximately 0.4 nm from 115.2 nm before the unit cycle was applied to 114.8 nm after the unit cycle was repeated 10 times.

[0038] By averaging these measurement results, it was confirmed that the etching amount per cycle (EPC) of the silicon nitride film (SiN) was approximately 6.6 Å / cycle, while the etching amount per cycle (EPC) of the silicon oxide film (SiO2) was approximately 0 Å / cycle. This shows that when the above-mentioned thin film etching method is applied to a substrate on which a pattern including an oxide film and a nitride film is formed, there is a significant difference in the etching selectivity between the oxide film and the nitride film.

[0039] These experimental results confirm that the etching rates per unit cycle (EPC) of silicon nitride (SiN) and silicon oxide (SiO2) are different in the etching step (S30), the etching ratios of the oxide layer formed on the silicon oxide (SiO2) and the oxide layer formed on the silicon nitride (SiN) are different, and the etching rate of the oxide layer formed on the silicon nitride (SiN) is higher than the etching rate of the oxide layer formed on the silicon oxide (SiO2). From these differences, it can be understood that the physical properties of the oxide layer formed on the silicon oxide (SiO2) and the oxide layer formed on the silicon nitride (SiN) are different in the surface treatment step (S20).

[0040] FIG. 9 is a graph showing in-situ monitoring of etched thickness as a function of etching time when a thin film etching method according to an embodiment of the present invention is applied to a structure in which silicon nitride (SiN) and silicon oxide (SiO) films are alternately deposited. FIG. 10 is a graph showing the results of calculating the amount of fluorine (F) atoms adsorbed on the surface of a thin film during the thin film etching method according to an embodiment of the present invention.

[0041] 9 and 10, it can be seen that fluorine (F) atoms are adsorbed onto the surface of a silicon oxide (SiO2) film and require a certain incubation time. That is, it takes a considerable amount of time for a halide-based material to be adsorbed onto the surface of a silicon oxide (SiO2) film and then formed into a SiFx material and then etched. In contrast, silicon nitride (SiN) film has hydrogen groups on its surface compared to silicon oxide (SiO2), so it takes a relatively short time for a halide-based material to be adsorbed onto the surface of a silicon nitride (SiN) film and then formed into a SiFx material and then etched.

[0042] 6 and 7, it can be seen that the thickness of the silicon oxide (SiO2) film increases slightly as a result of applying the thin film etching method according to one embodiment of the present invention. For example, when the separation distance between the topmost silicon oxide (SiO2) films in the stacked pattern decreases slightly from 115.2 nm to 114.8 nm, it can be inferred that a small amount of halide material is adsorbed onto the surface of the silicon oxide (SiO2). From this, it can be seen that fluorine (F) atoms are adsorbed onto the surface of the silicon oxide (SiO2) film and require a certain incubation time, and that after the halide-based material is adsorbed onto the surface of the silicon oxide (SiO2), it takes a considerable amount of time for it to be formed as a SiFx material and etched, resulting in a difference in etching rate between the silicon nitride (SiN) film and the silicon oxide (SiO2) film.

[0043] The rate at which volatile SiF4 material is formed when silicon oxide (SiO2) comes into contact with fluorine (F) is slower than the rate at which volatile SiF4 material is formed when silicon nitride (SiN) comes into contact with fluorine (F). Silicon nitride (SiN) contains a large amount of H inside the silicon nitride because it is deposited using SiH4 and NH3. As the H content in silicon nitride (SiN) increases, the density of the silicon nitride decreases, the compressive stress increases, and the reactivity to etchants increases, resulting in a faster etch rate. In contrast, silicon oxide (SiO2) does not contain H, so the rate at which it changes into volatile SiF4 material is slower than SiN:H. In other words, the difference in etch rate between these films is thought to be due to the difference in density caused by the H content.

[0044] 11 is a graph comparing the etched thickness of a silicon oxide (SiO2) film and a silicon nitride (SiN) film as a function of process temperature. In FIG. 11, the horizontal axis represents the process temperature, which corresponds to the temperature of a heater on which a substrate having a silicon oxide (SiO2) film and / or a silicon nitride (SiN) film formed thereon is mounted in an etching apparatus in which a thin film etching method is performed. The thin film etching method according to an embodiment of the present invention may be performed at a low process temperature range relatively lower than 70°C.

[0045] Referring to FIG. 11, it can be seen that as the process temperature increases, the etching rate of the silicon nitride film (SiN) becomes higher than that of the silicon oxide film (SiO2), and as the process temperature decreases, the etching rate of the silicon oxide film (SiO2) becomes higher than that of the silicon nitride film (SiN).

[0046] The phenomenon that the etching rate of silicon oxide (SiO2) is higher than that of silicon nitride (SiN) at low temperatures (e.g., 50°C) can be explained as follows. The etchant formed by injecting reactive gases NH3 and NF3 can be understood as NH3(HF)3 material. The reaction between silicon oxide (SiO2) and etchant NH3(HF)3 at low temperatures to form salt (NH4)2SiF6 material is as follows:

[0047] NH3(HF)3+HF+SiO2→(NH4)2SiF6+H2O

[0048] Meanwhile, hydrofluoric acid can be formed by the reaction of the H2O with the HF.

[0049] The thin film etching method according to an embodiment of the present invention employs a process of forming salt at low temperatures to remove silicon dioxide (SiO2) and can be understood as an example of atomic layer etching (ALE). This method is applicable because (NH4)2SiF6, a salt that easily decomposes / sublimes at low temperatures, is often formed. When etching silicon dioxide (SiO2) and silicon nitride (SiN), hydrofluoric acid containing -OH has a high etch rate. At low temperatures, F adsorbed on the surface of silicon dioxide (SiO2) and H released from NH3 can combine to form hydrofluoric acid, resulting in a much higher etch rate for silicon dioxide (SiO2) than for silicon nitride (SiN).

[0050] On the other hand, when the temperature is high (e.g., 130°C), the salt (NH4)2SiF6 sublimes the moment it touches the surface of the thin film, forming more hydrogen fluoride than hydrofluoric acid, resulting in a relatively higher etching rate of the silicon nitride (SiN) film.

[0051] However, as described with reference to FIGS. 3 to 8, it was confirmed that the thin film etching method according to the embodiment of the present invention etches the silicon nitride film (SiN) but not the silicon oxide film (SiO2), even at a relatively low process temperature (e.g., a temperature lower than 70°C). This is because, although the surface treatment step (S20) and the etching step (S30) are performed sequentially, the physical properties of the oxide layer formed on the silicon oxide film (SiO2) and the oxide layer formed on the silicon nitride film (SiN) in the surface treatment step (S20) are different, and the etching rate of the oxide layer formed on the silicon nitride film (SiN) in the etching step (S30) is adjusted to be higher than the etching rate of the oxide layer formed on the silicon oxide film (SiO2). When the thin film etching method according to the embodiment of the present invention is implemented at a relatively low process temperature, the degree to which fluorine (F) originating from the etching gas is adsorbed onto the thin film can be reduced, thereby reducing damage to the thin film and providing the advantage of being easily applicable to a self-limiting process.

[0052] FIG. 12 is a graph showing the intensity of RGA obtained by analyzing the components of an etchant in a thin film etching method according to an embodiment of the present invention.

[0053] 12, the NH-F etchant on the right is a relatively heavy polymer that reacts when the etching temperature is 110° C. or higher. In a thin film etching method according to an embodiment of the present invention, in which the etching temperature is 70° C. or lower, the main etchant is the HF material shown on the left. Furthermore, when O2 is added to a mixed gas of NH3 and NF3 or a halide gas as the etching gas, H2O material is generated, which can remove some of the fluorine (F) material adsorbed on the surface and reduce the etching rate.

[0054] As described above, a remote plasma process can be performed to perform the thin film etching method according to one embodiment of the present invention at a low temperature. The following description will be given in conjunction with a substrate processing apparatus that performs the thin film etching method according to some embodiments of the present invention. For example, the surface treatment step (S20) and / or the etching step (S30) can be performed using the substrate processing apparatus.

[0055] FIG. 13 is a schematic diagram showing a substrate processing apparatus 100 for explaining a thin film etching method according to some embodiments of the present invention.

[0056] Referring to FIG. 13, a substrate processing apparatus 100 may include a process chamber 110, a gas injection unit 120, a substrate support unit 130, and a remote plasma reactor 150.

[0057] More specifically, a reaction space 112 in which a substrate S can be processed may be formed in the process chamber 110. The process chamber 110 may be connected to a vacuum pump (not shown) via an exhaust pipe 114 to form a vacuum atmosphere. Furthermore, the process chamber 110 may include an entrance / exit for loading and unloading the substrate S into and from the reaction space 112, and a gate structure (not shown) for opening and closing the entrance / exit. The process chamber 110 may have various shapes, and may include, for example, sidewalls that define the reaction space 112 and a lid, such as a top lid, located at the top end of the sidewalls.

[0058] The gas injector 120 may be coupled to the process chamber 110 to supply a process gas supplied from outside the process chamber 110 to the reaction space 112. More specifically, the gas injector 120 may be coupled to the process chamber 110 to face the substrate support 130. For example, the gas injector 120 may be installed at an upper portion of the process chamber 110 to inject the process gas onto the substrate S placed on the substrate support 130.

[0059] In some embodiments, the gas injection unit 120 may include an inlet 122 through which the process gas is drawn in, and a distribution plate 124 for injecting the process gas that has entered through the inlet 122 and been dispersed therein into the reaction space 112. The gas injection unit 120 may further include a blocker plate for dispersing the process gas that has passed through the inlet 122. For example, the inlet 122 may be provided with a connection pipe 152 that connects the remote plasma reactor 150 and the gas injection unit 120, and the process gas may be supplied into the gas injection unit 120 through one side of the connection pipe 152.

[0060] In some embodiments, the gas injector 120 may have various shapes such as a shower head shape, a nozzle shape, etc. When the gas injector 120 has a shower head shape, the gas injector 120 may be coupled to the process chamber 110 in a form that partially covers the top of the process chamber 110. For example, the gas injector 120 may be coupled to a cover or a top lid of the process chamber 110.

[0061] The substrate support 130 may be coupled to the process chamber 110 to support the substrate S in the reaction space 112. For example, the substrate support 130 may be installed in the process chamber 110 to face the gas injection unit 120. Furthermore, the substrate support 130 may be provided with a heater 182 for heating the substrate S. For example, the heater 182 may be provided within the substrate support 130. The heater power supply 180 is connected to the heater 182 to apply power to the heater 182, and an AC filter 185 may additionally be interposed between the heater 182 and the heater power supply 180.

[0062] The shape of the upper plate of the substrate support 130 generally corresponds to the shape of the substrate S, but is not limited thereto, and may be provided in various shapes larger than the substrate S so that the substrate S can be stably placed thereon. For example, the shaft of the substrate support 130 may be connected to an external motor (not shown) to enable lifting and lowering, and in this case, a bellows tube (not shown) may be connected to maintain airtightness. Furthermore, since the substrate support 130 is configured to place the substrate S thereon, it may also be called a substrate placement unit, a susceptor, etc.

[0063] In some embodiments, the substrate support 130 may further include an electrostatic electrode to apply an electrostatic force to fix the substrate S thereon. In this case, the electrostatic electrode may be supplied with DC power from an electrostatic force power supply (not shown).

[0064] The remote plasma reactor 150 may be disposed outside the process chamber 110 so as to be connected to the gas injection unit 120. The remote plasma reactor 150 may be connected to the gas injection unit 120 via a connection pipe 152. Furthermore, a process gas may be introduced into the remote plasma reactor 150 via an inlet pipe 154. The remote plasma reactor 150 may also be referred to as a remote plasma generator.

[0065] Furthermore, a plasma power supply unit 140 for applying power may be connected to the remote plasma reactor 150. For example, the plasma power supply unit 140 may include at least one RF (radio frequency) power supply to apply at least one RF power to the process chamber 110. The remote plasma reactor 150 may form a plasma atmosphere using an inductively coupled plasma (ICP) method, a capacitively coupled plasma (CCP) method, a toroidal plasma method, a microwave (MW) method, or the like.

[0066] The remote plasma reactor 150 may receive at least one process gas via an inlet pipe 154, and may generate an etchant by activating the process gas through application of plasma power to form a plasma atmosphere therein. For example, the etchant may contain radicals, which may be supplied to the gas injection unit 120 via a connection pipe 152 and injected onto the substrate S via the gas injection unit 120. Optionally, the connection pipe 152 may be heated to prevent the generation or adsorption of by-products. For example, the connection pipe 152 may be wrapped with a heater jacket or heating tape.

[0067] In some embodiments, the gas injection unit 120 may be supplied with an additional process gas via a side pipe 153 connected to the middle of the connecting pipe 152, without passing through the remote plasma reactor 150. The process gas supplied via the side pipe 153 and the process gas or radicals supplied via the remote plasma reactor 150 may be mixed or react with each other in the connecting pipe 152.

[0068] In some embodiments, the substrate processing apparatus 100 may be used as an etching apparatus or a surface processing apparatus for surface processing or etching a thin film on a substrate S.

[0069] 4, 5, and 13, a composite film pattern 56 may be formed on a substrate S. For example, the substrate S may include a semiconductor wafer 52, and a structure for forming a semiconductor device may be formed on the semiconductor wafer 52. More specifically, the composite film pattern 56 may be formed on the semiconductor wafer 52. The semiconductor wafer 52 may include a single crystal structure of a semiconductor material, such as silicon, germanium, silicon-germanium, etc., and may further include a semiconductor epitaxial layer, etc.

[0070] The composite film pattern 56 may include a pattern structure in which a plurality of first insulating layers 54 and a plurality of second insulating layers 55 are alternately stacked. After the first insulating layers 54 and the second insulating layers 55 are alternately stacked, they may be patterned using photolithography and etching techniques to form a plurality of trenches 57. For example, the first insulating layer 54 may include a silicon oxide film, and the second insulating layer 55 may include a silicon nitride film.

[0071] In some embodiments, the substrate S may be processed using the substrate processing apparatus 100. For example, the substrate S may be processed while being placed on the substrate support 130 in the process chamber 110. More specifically, a step of drawing the substrate S into the process chamber 110 and placing it on the substrate support 130 may be performed.

[0072] To perform the surface treatment step (S20) of the thin film etching method according to some embodiments, an oxygen-containing gas containing at least one of O2, O3, HO, HO, and NO is supplied to and activated by the remote plasma reactor 150, and the activated oxygen-containing gas is then exhausted from the remote plasma reactor 150 and reaches the composite film pattern 56 on the substrate S. In a modified embodiment of the present invention, the surface treatment step (S20) of the thin film etching method may be performed in a thermal atmosphere using a heater or the like, rather than in a plasma atmosphere using the remote plasma reactor 150.

[0073] Meanwhile, to perform the etching step (S30) of the thin film etching method according to some embodiments, the method may include an etchant supply step of activating a first gas G1 containing at least one of a halogen-containing gas and a hydrogen-containing gas in a remote plasma reactor 150 to generate an etchant ET and discharging the etchant ET in the direction of the gas injection unit 120; a second gas supply step of supplying a second gas G2 containing an inert gas to the etchant ET after the etchant ET is discharged from the remote plasma reactor 150 and before the etchant ET reaches the composite film pattern 56 on the substrate S; and an etching step of at least partially etching the second insulating layer 55 relative to the first insulating layer 54 using at least the etchant ET or a reactant of the etchant.

[0074] For example, the first gas G1 may be supplied into the remote plasma reactor 150 through the inlet pipe 154, and the second gas G2 may be supplied into the connection pipe 152 through one side of the connection pipe 152. More specifically, the second gas G2 may be supplied into the connection pipe 152 through a side pipe 153 connected to one side of the connection pipe 152.

[0075] The first gas G1 and the second gas G2 can be combined in various ways to generate the etchant ET or a reactant of the etchant. Four exemplary combinations of the first gas G1 and the second gas G2 will be described below.

[0076] In the first case, the first gas G1 may include a halogen-containing gas, and the second gas G2 may include an inert gas, a hydrogen-containing gas, and an oxygen-containing gas. In this case, the etchant ET may be formed by activating the halogen-containing gas, and the reactant of the etchant ET may be generated by reacting at least a portion of the etchant ET with the hydrogen-containing gas and the oxygen-containing gas.

[0077] In a second case, the first gas G1 may include a halogen-containing gas and a hydrogen-containing gas, and the second gas G2 may include an inert gas and an oxygen-containing gas. In this case, the etchant ET may be formed by activating or partially reacting the halogen-containing gas and the hydrogen-containing gas with each other, and the reactant of the etchant ET may be generated by reacting at least a portion of the etchant ET with the oxygen-containing gas.

[0078] In a third case, the first gas G1 may include a halogen-containing gas, a hydrogen-containing gas, and an oxygen-containing gas, and the second gas G2 may include an inert gas, in which case the etchant ET may be formed by activating or partially reacting the halogen-containing gas, the hydrogen-containing gas, and the oxygen-containing gas with each other.

[0079] In a fourth case, the first gas G1 may include a hydrogen-containing gas, and the second gas G2 may include an inert gas, a halogen-containing gas, and an oxygen-containing gas. In this case, the etchant ET may be formed by activating the hydrogen-containing gas, and the reactant of the etchant ET may be generated by reacting at least a portion of the etchant ET, the halogen-containing gas, and the oxygen-containing gas.

[0080] In the above case, the first gas G1 may further include an inert gas, for example, Ar gas, to generate plasma in the remote plasma reactor 150.

[0081] The halogen-containing gas may serve as a source gas for generating the etchant ET and may include, for example, a halogen-based gas such as fluorine (F) or chlorine (Cl). The inert gas in the second gas G2 may serve to increase the reactivity of the etchant ET and may be supplied to the etchant ET along the flow path of the etchant ET between the remote plasma reactor 150 and the substrate S on the substrate support 130. The inert gas in the second gas G2 is supplied after the exhaust end of the remote plasma reactor 150 and may therefore be distinguished from the inert gas in the first gas G1 supplied to the remote plasma reactor 150.

[0082] In some embodiments, in the etchant supply step, the etchant ET is supplied to the gas injection section 120 through a connecting pipe 152 connecting the remote plasma reactor 150 and the gas injection section 120, and in the second gas supply step, an inert gas can be supplied to the etchant ET flowing within the connecting pipe 152 through a side pipe 153 connected to the middle of the connecting pipe 152.

[0083] For example, the halogen-containing gas may include NF3 gas, the hydrogen-containing gas may include NH3 gas, the oxygen-containing gas may include at least one of O2, O3, HO, HO, and NO, and the inert gas may include Ar gas. In the remote plasma reactor 150, the NF3 gas may be decomposed to generate fluorine (F) or fluorine radicals. Alternatively, a mixture of NF3 gas and Ar gas may be supplied to the remote plasma reactor 150 via the inlet pipe 154. Optical emission spectroscopy (OES) analysis performed on the connecting pipe 152 confirmed that a fluorine (F) peak was observed.

[0084] As described above, the Ar gas in the first gas G1 supplied through the inlet pipe 154 can be functionally differentiated from the Ar gas in the second gas G2 supplied through the side pipe 153. The Ar gas in the first gas G1 can perform functions such as regulating plasma ignition, pressure, or concentration in the remote plasma reactor 150. On the other hand, the Ar gas supplied as an inert gas in the second gas G2 can increase the number of adsorbed etchants ET and enhance etching reactivity. For example, when the Ar gas in the second gas G2 is supplied into the connecting pipe 152, the Ar gas is ionized by gas collisions, generating electrons, which can anionize fluorine or fluorine radicals.

[0085] As shown in FIG. 14, anionized fluorine or fluorine radicals can generate fluorine complexes (F complexes), such as 2F. Because the number of bonds that an etchant can adsorb onto a thin film is limited, the adsorption of such fluorine complexes onto the thin film can increase the concentration of fluorine adsorbed onto the thin film compared to when a single fluorine or fluorine radical adsorbs onto the thin film. This increases the concentration of fluorine adsorbed onto the thin film, which can lead to faster formation of volatile compounds, such as SiF, and thus to a higher etching rate. Therefore, the inert gas in the second gas G2 can provide electrons to the etchant ET.

[0086] As shown in FIG. 15, the higher the flow rate of Ar gas in the second gas G2 supplied to the etchant ET, the higher the etch rate of the ALD SiN film, but the ALD SiO2 film is hardly etched. This indicates that the higher the flow rate of Ar gas in the second gas G2, the higher the etch selectivity of the ALD SiN film relative to the ALD SiO2 film. Considering that the Ar gas in the second gas G2 is an inert gas and does not participate in the etching reaction itself, the Ar gas in the second gas G2 can be interpreted as increasing the concentration of halogen elements adsorbed on the thin film and thereby increasing the etch rate. For example, under the conditions of FIG. 15, the temperature of the heater 182 or the substrate support 130 may be 70° C. or less.

[0087] 16, as a comparative example, the etching rate of the SiN film decreases as the flow rate of Ar gas in the first gas G1 supplied into the remote plasma reactor 150 via the inlet pipe 154 increases. Therefore, it can be seen that the Ar gas in the first gas G1 and the Ar gas in the second gas G2 have completely different functions and, in fact, have opposing effects.

[0088] The present invention has been described with reference to the embodiments shown in the drawings, but these are merely illustrative, and those skilled in the art will recognize that various modifications and equivalent embodiments are possible. Therefore, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims.

Claims

1. providing a substrate having a pattern formed thereon, the substrate comprising a nitride film; a surface treatment step of treating the surface of the nitride film with an oxygen-containing gas so that the surface is at least partially oxidized; an etching step of supplying an etching gas onto the oxide layer to remove at least a portion of the oxide layer on the surface of the nitride film oxidized through the surface treatment step; A thin film etching method, characterized in that the surface treatment step and the etching step are repeated as a cycle.

2. providing a substrate having a pattern including an oxide film and a nitride film formed thereon; a surface treatment step of treating the surfaces of the oxide film and the nitride film with an oxygen-containing gas so that the surfaces are at least partially oxidized; an etching step of supplying an etching gas onto the oxide layer to remove at least a portion of the oxide layer on the surface of the nitride film oxidized through the surface treatment step; A thin film etching method, characterized in that the surface treatment step and the etching step are repeated as a cycle.

3. 3. The method of claim 2, wherein the oxide layer formed on the oxide film in the surface treatment step and the oxide layer formed on the nitride film have different physical properties.

4. 4. The method of claim 3, wherein, in the etching step, an etching rate of the oxide layer formed on the oxide film and an etching rate of the oxide layer formed on the nitride film are different from each other.

5. 5. The method for etching a thin film according to claim 4, wherein an etching rate of the oxide layer formed on the nitride film is greater than an etching rate of the oxide layer formed on the oxide film.

6. The oxygen-containing gas is O ２ , O ３ , H ２ O, H ２ O ２ and N ２ 3. The thin film etching method according to claim 1, wherein the etching gas contains at least one of O.

7. The etching gas is NH ３ and NF ３ 3. The thin film etching method according to claim 1, wherein the gas used is a mixed gas of the above or a halide gas.

8. 3. The thin film etching method according to claim 1, wherein the surface treatment step is performed in a plasma atmosphere.

9. 3. The thin film etching method according to claim 1, wherein the surface treatment step is carried out in a thermal atmosphere.

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