Method for etching silicon-containing film and method for manufacturing semiconductor device including the same

Abstract

The method for etching a silicon-containing film according to the present invention includes the steps of: introducing a substrate including a first silicon-containing film and a second silicon-containing film into a process chamber of an etching apparatus; supplying at least one etching gas including FNO into the process chamber; applying a predetermined power to the process chamber maintained at a predetermined pressure to generate direct plasma in the process chamber; and etching the first silicon-containing film on the substrate with radicals of an etching gas activated by the direct plasma, wherein the predetermined pressure is set within a predetermined range in which a slope of an etch rate of the first silicon-containing film with respect to pressure has a different sign from a slope of an etch rate of the second silicon-containing film with respect to pressure.

Description

[Technical Field]

[0001] The present invention relates to a method for etching a silicon-containing film and a method for manufacturing a semiconductor device including the same, and more particularly to an etching method for etching a silicon-containing film by direct plasma using an etching gas containing FNO, and a method for manufacturing a semiconductor device including the etching method. [Background technology]

[0002] Typically, a series of processes such as deposition, etching, and cleaning are performed on a substrate to manufacture a semiconductor device. These processes are performed in a deposition apparatus (e.g., a CVD apparatus), an etching apparatus, or a cleaning apparatus equipped with a process chamber. Among these processes, the etching process is a process for forming an ultrafine structure of a desired shape by selectively removing a portion of a thin film formed on a substrate by a deposition process or the like.

[0003] In an etching process, particularly a dry etching process, a gaseous etching gas reacts with a thin film to be etched, e.g., a silicon-containing film, to form highly volatile reaction by-products, thereby removing a portion of the thin film. Plasma etching, which utilizes plasma, is commonly used to further enhance the reactivity between the etching gas and the thin film to be etched. Plasma converts the etching gas into highly reactive activated species or radicals, thereby increasing the reactivity with the thin film.

[0004] Plasma-based dry etching employs direct plasma technology, which is realized by capacitively coupled plasma (CCP) technology or inductively coupled plasma (ICP) technology. Here, direct plasma technology or direct plasma refers to the technology of directly generating plasma in the process chamber, which is the substrate processing space, or the plasma generated in that chamber. CCP is primarily used in plasma etching (PE) or PECVD (Plasma Enhanced Chemical Vapor Deposition) methods, reactive ion etching (RIE) or reactive ion chemical vapor deposition (Reactive Ion Etching), while ICP is used to generate remote plasma (RP) and direct ICP plasma (using helical, TCP, ECR, or helicone plasma sources).

[0005] In an etching process, it is preferable to have a high etch rate for the film quality to be etched and a low etch rate for the film quality that is not desired to be etched. However, in the past, when etching using direct plasma, there was a limit to the improvement of the etching selectivity.

[0006] Furthermore, the etching gas used in the etching process is required to have as little impact as possible on the global environment by not emitting harmful gases after the etching process.

[0007] Conventionally, large amounts of perfluorochemical gases such as CF4, C2F6, SF6, and NF3 have been used as etching gases. However, conventional perfluorochemical etching gases are difficult to treat the waste gases emitted after the etching process, which requires significant treatment costs to reduce the gas to an acceptable level before being released into the atmosphere. Furthermore, conventional perfluorochemical etching gases are stable compounds with long lifetimes in the atmosphere, and have a very high global warming potential, making them a major cause of global warming.

[0008] For this reason, there is a demand for alternative etching gases that have a low global warming potential and excellent etching performance for silicon-containing films, and F3NO, described in Patent Document 1, is known as one of such alternative etching gases. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Korean Patent 10-2010466 B1 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made to solve the problems of the conventional art, and aims to provide a method for etching a silicon-containing film with high selectivity by activating an etching gas containing FNO, which has a relatively low global warming potential and is eco-friendly, using direct plasma, and a method for manufacturing a semiconductor device including the same. [Means for solving the problem]

[0011] According to one aspect of the present invention, there is provided a method for etching a silicon-containing film, comprising the steps of: introducing a substrate including a first silicon-containing film and a second silicon-containing film into a process chamber of an etching apparatus; supplying at least one etching gas including FNO into the process chamber; applying a predetermined power to the process chamber, which is maintained at a predetermined pressure, to generate direct plasma in the process chamber; and etching the first silicon-containing film on the substrate with activated species of the etching gas activated by the direct plasma, wherein the predetermined pressure is set within a predetermined range in which a slope of an etch rate of the first silicon-containing film with respect to pressure differs in sign from a slope of an etch rate of the second silicon-containing film with respect to pressure.

[0012] According to a preferred embodiment of the present invention, the first silicon-containing film is a silicon nitride film, and the second silicon-containing film is a silicon oxide film.

[0013] According to another preferred embodiment of the present invention, the predetermined pressure is set to a value greater than the median value in a range in which the slope of the etch rate of the silicon nitride film with respect to the pressure is positive and the slope of the etch rate of the silicon oxide film with respect to the pressure is negative.

[0014] According to yet another preferred embodiment of the present invention, the predetermined pressure is in the range of 1 mTorr to 10 Torr, and more preferably, in the range of 200 mTorr to 270 mTorr.

[0015] According to yet another preferred embodiment of the present invention, the predetermined power is in the range of 10 W or more and 50,000 W or less, and more preferably in the range of 240 W or more and 320 W or less.

[0016] A semiconductor device manufacturing method according to another aspect of the present invention includes a deposition step of forming a silicon-containing film, including a first silicon-containing film and a second silicon-containing film, on a substrate, and an etching step of etching the silicon-containing film using the etching method according to one aspect of the present invention. [Effects of the Invention]

[0017] According to the present invention, while using an etching gas containing environmentally friendly FNO, it is possible to etch silicon-containing films such as silicon nitride films with high selectivity by adjusting the pressure and applied power during direct plasma generation. [Brief explanation of the drawings]

[0018] [Figure 1A] 1 is a schematic diagram of an etching apparatus for performing an etching method according to one embodiment of the present invention. [Figure 1B] 1 is a schematic diagram of an etching apparatus for performing an etching method according to one embodiment of the present invention. [Figure 2] 1 is a flowchart of an etching method according to an embodiment of the present invention. [Figure 3] 1 is a graph showing the relationship between pressure and applied power and the etching rate of a silicon oxide film. [Figure 4] 1 is a graph showing the relationship between pressure and applied power and the etch rate of a silicon nitride film. [Figure 5] 1 is a graph showing the relationship between pressure and applied power and the etching selectivity of a silicon nitride film relative to a silicon oxide film. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals are used to designate the same components in the drawings, and redundant descriptions thereof will be omitted.

[0020] 1A and 1B show an etching apparatus 1 for carrying out an etching method according to one embodiment of the present invention.

[0021] The etching apparatus 1 is a capacitively coupled plasma apparatus capable of generating direct plasma, and plasma P is directly generated in a process chamber 10 of the etching apparatus 1 by plasma discharge.

[0022] For this purpose, the etching apparatus 1 includes a shower head 20 that also serves as an electrode and an RF power supply connected to the shower head 20. The RF power supply includes an RF generator 30 and an impedance matching network (IMN) 40.

[0023] The shower head 20 of the etching apparatus 1 is disposed at the upper part of the interior of the process chamber 10 and supplies the etching gas and the control gas into the process chamber 10 .

[0024] The RF generator 30 generates the RF power, and the impedance matching network 40 adjusts the impedance to stabilize the plasma.

[0025] As shown in FIGS. 1A and 1B, the etching apparatus 1 includes a stage 50 at the bottom of a process chamber 10, which holds a substrate S as a processing target. The stage 50 of the etching apparatus 1 is grounded and functions as a ground electrode. A hot wire 510 or a heater electrode is provided inside the stage 50, which can adjust the temperature of the substrate S. Although not shown in FIGS. 1A and 1B, the stage 50 may include a fixing means (e.g., an electrostatic chuck) that can fix the substrate S during the etching process.

[0026] When a predetermined amount of RF power is applied to the showerhead 20 while the stage 50 is grounded, a strong alternating electric field is generated between the showerhead 20 and the stage 50, generating plasma P. In the case of a direct CCP type etching apparatus, increasing the power of the RF power supply increases the concentration of activated species, resulting in a higher etch rate.

[0027] When plasma P is generated, radicals R, ions, electrons, ultraviolet rays, etc. may be generated from the etching gas. At least one of these radicals R, ions, electrons, ultraviolet rays, etc. is used in the etching process. Basically, radicals R are electrically neutral, while ions have electrical polarity. Therefore, when plasma P is used in the etching process, radicals R are used to etch the etching target isotropically, and ions are used to etch the etching target anisotropically.

[0028] Although the etching apparatus 1 of FIG. 1A has a configuration in which an RF power source is connected to the showerhead 20, the etching apparatus 1 is not limited thereto. As shown in FIG. 1B, an RF power source may be additionally connected to the stage 50 in order to perform etching by physical collision of ions in the plasma as well as chemical etching by radicals R.

[0029] The etching apparatus 1 of this embodiment may further include an ICP device. In this case, a coil antenna may be provided in the etching apparatus 1, and an RF power source may be connected to the coil antenna. The etching apparatus 1 of this embodiment may also include a remote plasma device.

[0030] FIG. 2 is a flowchart of the etching method using direct plasma according to this embodiment.

[0031] 2, in the etching method using direct plasma according to this embodiment, first, a substrate S on which a silicon-containing film is formed is carried into a process chamber 10 of an etching apparatus 1 through a gate valve (not shown), and the substrate S is placed on a stage 50 in the etching apparatus 1 (S01). Here, the silicon-containing film formed on the substrate S includes at least a silicon nitride film (SiNx, a first silicon-containing film) and a silicon oxide film (SiO2, a second silicon-containing film). However, the etching method of the present invention is not limited thereto, and may include other silicon-containing films (e.g., polysilicon, a silicide film, etc.).

[0032] Next, an etching gas containing FNO is supplied into the process chamber 10 through the showerhead 20 (S02). In this case, a control gas (e.g., HO, H, HBr, etc.) may be additionally supplied in addition to FNO. Adding a control gas containing hydrogen atoms can adjust the concentration of activated species generated in the FNO direct plasma, thereby controlling the etching selectivity of the silicon-containing film being etched. Furthermore, when physical collision etching (e.g., reactive ion etching) is also performed, an inert gas such as Ar may be additionally supplied. Adding Ar increases ion collisions, improving the etching rate and anisotropy of physical etching. The Ar+ ion beam breaks the bonds between silicon atoms in the silicon-containing film, lowering the activation energy for reaction with the activated species in the etching gas, thereby improving the chemical etching rate using activated species. Conventional perfluoroetching gases such as CF4 and NF3 are sometimes mixed with O2 to increase the concentration of activated F species and increase the etching rate. However, in the etching method of the present invention, FNO is used as the main etching gas, so the etching rate can be sufficiently increased without adding O2.

[0033] Next, a direct plasma is generated in the process chamber 10 by applying an appropriate power to the RF generator 30 of the etching apparatus 1 under appropriate pressure and temperature conditions (S03). As will be described below with reference to Figures 3-5, in an etching method according to an embodiment of the present invention, the etching selectivity of a silicon nitride film relative to a silicon oxide film can be maximized by adjusting the pressure and applied power during direct plasma generation of an etching gas containing F3NO. In this embodiment of the present invention, F3NO is used as the etching gas, and therefore activated species such as F, F2, FNO, and NO are generated in the direct plasma generated in the process chamber 10.

[0034] The activated species in the direct plasma generated in the process chamber 10 react with the silicon-containing film on the substrate S placed on the stage 50 to selectively etch the silicon-containing film (S04). According to the etching method of the embodiment of the present invention, the silicon nitride film can be etched with a high selectivity relative to the silicon oxide film.

[0035] After the etching process is completed, the substrate S is unloaded from the process chamber 10 and transported to the next process.

[0036] Hereinafter, with reference to FIGS. 3 to 5, the relationship between the pressure and applied power during direct plasma generation of an etching gas containing F3NO, and the etch rate and etching selectivity of a silicon-containing film will be described.

[0037] FIG. 3 is a graph showing the relationship between the pressure, applied power, and the etch rate of a silicon oxide film (SiO2) when direct plasma is generated in the direct plasma generation step S03 while flowing F3NO having a purity of 99.99% at a flow rate of 120 sccm into the etching apparatus 1. FIG. 4 is a graph showing the relationship between the pressure, applied power, and the etch rate of a silicon nitride film (SiNx) when direct plasma is generated in the direct plasma generation step S03 under the same conditions as in FIG. 3.

[0038] FIG. 5 shows the relationship between the pressure and applied power in the direct plasma generation step S03 and the etching selectivity of a silicon nitride film to a silicon oxide film.

[0039] 3, in etching a silicon oxide film using direct plasma of an etching gas containing F3NO, the etch rate decreases in inverse proportion to the pressure in the process chamber 10. That is, in FIG. 3, the slope (tangent slope) of the graph of the etch rate versus pressure is negative. Therefore, as the pressure increases, the etch rate of a silicon oxide film using direct plasma of an etching gas containing F3NO decreases.

[0040] For example, when the applied power during direct plasma generation is 240 W, if the pressure during direct plasma generation increases to 200 mTorr, the etch rate of the silicon oxide film decreases by approximately 18% compared to when the pressure condition is 130 mTorr. If the pressure during direct plasma generation is further increased to 270 mTorr, the etch rate of the silicon oxide film decreases even further, but the absolute value of the slope becomes smaller.

[0041] When the applied power during direct plasma generation of an etching gas containing F3NO is increased to 320 W, the concentration of active species generally increases, and the etch rate generally increases compared to when the power is 240 W. However, as the pressure during direct plasma generation increases, the etch rate of the silicon oxide film decreases, and therefore the slope of the graph of the etch rate versus pressure is negative, just like when the power is 240 W.

[0042] On the other hand, as shown in Figure 4, when etching a silicon nitride film using direct plasma of an etching gas containing F3NO, the etch rate of the silicon nitride film generally increases in proportion to the pressure at the time of direct plasma generation, unlike the behavior of the etch rate of a silicon oxide film. That is, the slope (tangent slope) of the graph of the etch rate versus pressure in Figure 4 is positive, unlike the graph in Figure 3. Therefore, as the pressure at the time of direct plasma generation increases, the etch rate of the silicon nitride film using direct plasma of an etching gas containing F3NO increases.

[0043] For example, when the applied power during direct plasma generation is 240 W, if the pressure during direct plasma generation is increased to 200 mTorr, the etch rate of the silicon nitride film increases by approximately 14% compared to when the pressure condition is 130 mTorr. If the pressure condition is further increased to 270 mTorr, the etch rate of the silicon nitride film increases by approximately 15% compared to when the pressure condition is 200 mTorr.

[0044] When the applied power during direct plasma generation is increased to 320 W, unlike the behavior of the silicon oxide film etch rate, the silicon nitride film etch rate itself does not change significantly compared to when the applied power is 240 W. However, as with the 240 W applied power, the silicon nitride film etch rate generally increases as the pressure during direct plasma generation increases, and therefore the slope of the etch rate versus pressure graph is generally positive. However, as the pressure increases from 130 mTorr to 200 mTorr, the silicon nitride film etch rate barely changes, but when the pressure is further increased to 270 mTorr, the etch rate increases dramatically by about 30%.

[0045] In the fabrication of semiconductor devices such as NAND and DRAM, it is sometimes necessary to maximize the etching selectivity of silicon nitride to silicon oxide, which requires that the etch rate of silicon oxide be as low as possible and the etch rate of silicon nitride be as high as possible under the same conditions.

[0046] As shown in Figures 3 and 4, when etching silicon oxide and silicon nitride films using direct plasma with an etching gas containing F3NO, the etch rate behavior of silicon oxide and silicon nitride films with respect to pressure and applied power differs. Therefore, by utilizing this fact and adjusting the pressure and applied power during direct plasma generation with an etching gas containing F3NO, the etching selectivity of silicon nitride to silicon oxide can be significantly improved.

[0047] That is, as shown in FIG. 5, for the same applied power, increasing the pressure during direct plasma generation of an etching gas containing FNO can increase the etching selectivity of a silicon nitride film relative to a silicon oxide film. This is because, as described above, within the pressure range of 130 mTorr to 270 mTorr, the slope of the graph of the etch rate of a silicon oxide film versus pressure is negative, while the slope of the graph of the etch rate of a silicon nitride film versus pressure is positive. Therefore, it is preferable to set the pressure condition to a value greater than the median value of the pressure range (200 mTorr in FIGS. 3 and 5) within the pressure range where the slope of the etch rate of a silicon nitride film versus pressure is positive and the slope of the etch rate of a silicon oxide film versus pressure is negative, thereby increasing the etching selectivity as much as possible.

[0048] However, the present invention is not limited to this. Even if the signs of the slopes of the etch rate versus pressure graphs are the same, if the absolute values ​​of the slopes of the etch rates of a silicon oxide film and a silicon nitride film versus pressure are different, the etching selectivity of a silicon nitride film relative to a silicon oxide film can be increased by adjusting the pressure conditions. For example, even in a pressure range in which the etch rate of a silicon oxide film increases with increasing pressure, if the etch rate of a silicon nitride film increases more steeply as the pressure increases within that pressure range, the etching selectivity can be increased by increasing the pressure as much as possible within that pressure range. Also, if the etch rate of a silicon oxide film remains substantially constant as the pressure increases, but the etch rate of a silicon nitride film increases as the pressure increases within that pressure range, the etching selectivity of a silicon nitride film relative to a silicon oxide film can be similarly increased by appropriately adjusting the pressure within such a pressure range.

[0049] That is, a pressure range in which the change rates of the etch rates of the silicon nitride film and the silicon oxide film according to the pressure are different within a predetermined pressure range can be found, and pressure conditions can be selected so as to maximize the etching selectivity.

[0050] 3-5, the pressure range is exemplified as 130 mTorr to 270 mTorr, and the etching selectivity is maximized by taking into consideration the gradient of the etch rates of the silicon nitride film and the silicon oxide film with respect to the pressure. However, the present invention is not limited to this exemplary pressure range (and the range of applied power), and can be similarly applied to other pressure ranges in which the gradient of the etch rate with respect to the pressure is large. For example, the pressure range may be any range within the range of 1 mTorr to 10 Torr in which the etching selectivity can be increased.

[0051] On the other hand, as the applied power for direct plasma generation increases under the same pressure conditions, the etch rate of a silicon oxide film increases significantly, while the relative increase rate for a silicon nitride film is small. Therefore, as can be seen from FIG. 5, under the same pressure conditions, the lower the applied power for direct plasma generation, the higher the etch selectivity of a silicon nitride film relative to a silicon oxide film. However, since lowering the applied power reduces the etch rate of a silicon nitride film, when adjusting the applied power to increase the etch selectivity, it is preferable to determine the applied power so that the etch rate does not decrease too much. While FIGS. 3 to 5 illustrate examples of applied power in the range of 240 W or more and 320 W or less, the present invention is not limited to this range. For example, the applied power may be any range within the range of 10 W or more and 50,000 W or less that can increase the etch selectivity.

[0052] According to one embodiment of the present invention, a semiconductor device can be manufactured on a substrate using the etching method of the present invention. For example, a method for manufacturing a semiconductor device according to one embodiment of the present invention includes a deposition step of depositing a silicon-containing film including a silicon nitride film (first silicon-containing film) and a silicon oxide film (second silicon-containing film) on a substrate, and a step of etching the silicon nitride film with a high selectivity relative to the silicon oxide film using the etching method of the present invention.

Claims

1. 1. A method for etching a silicon-containing film, comprising: introducing a substrate including a silicon nitride film and a silicon oxide film into a process chamber of an etching apparatus; The process chamber 3 providing at least one etching gas comprising NO; applying a predetermined power to the process chamber maintained at a predetermined pressure to generate a direct plasma in the process chamber; and etching the silicon nitride film on the substrate with radicals of an etching gas activated by the direct plasma, the predetermined pressure is set to a value greater than a median value in a range in which the slope of the etch rate of the silicon nitride film with respect to the pressure is positive and the slope of the etch rate of the silicon oxide film with respect to the pressure is negative; Method for etching silicon-containing films.

2. 2. The method for etching a silicon-containing film according to claim 1, wherein the predetermined pressure is in the range of 1 mTorr to 10 Torr.

3. 3. The method for etching a silicon-containing film according to claim 2, wherein the predetermined pressure is equal to or greater than 200 mTorr and equal to or less than 270 mTorr.

4. 2. The method for etching a silicon-containing film according to claim 1, wherein the predetermined power is in the range of 10 W or more and 50,000 W or less.

5. 4. The method for etching a silicon-containing film according to claim 3, wherein the predetermined power is 240 W or more and 320 W or less.

6. The method for etching a silicon-containing film according to claim 1 , wherein the etching apparatus is a direct CCP apparatus.

7. The method for etching a silicon-containing film according to claim 1 , wherein the etching gas further comprises a control gas containing hydrogen atoms.

8. depositing a silicon-containing film on a substrate, the silicon-containing film including a silicon nitride film and a silicon oxide film; and an etching step of etching a silicon-containing film using the etching method according to any one of claims 1 to 7. A method for manufacturing semiconductor devices.

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