Etching gas composition comprising heptafluoroisopropyl trifluoromethyl ketone, and plasma etching method using same

Abstract

The present invention provides an etching gas composition, and a plasma etching method using same. The etching gas composition, which is supplied to an etching chamber so as to generate plasma, comprises: a fluorocarbon gas including heptafluoroisopropyl trifluoromethyl ketone (C5F10O); and an inert gas.

Description

Etching gas composition comprising heptafluoroisopropyl trifluoromethyl ketone and plasma etching method using the same

[0001] The present invention relates to an etching gas composition comprising heptafluoroisopropyl trifluoromethyl ketone and a plasma etching method using the same.

[0002] Etching of silicon-based dielectrics, such as SiO2 or Si3N4, primarily uses perfluorocarbons (PFCs) such as CF4, C2F6, and c-C4F8, or hydrofluorocarbons (HFCs) such as CHF3. When etching with PFCs or HFCs, fluorocarbon film deposition, fluorocarbon film etching, and substrate etching occur simultaneously, forming a steady-state fluorocarbon film on the substrate surface. Depending on the target material to be etched, the thickness and degree of crosslinking of the steady-state fluorocarbon film formed on the substrate surface vary, and this can be utilized to implement anisotropic etching profiles. Because of these characteristics, PFCs and HFCs are used in various etching processes such as contact hole etching, self-aligned contact (SAC) etching, 3D-NAND stack etching, and gate spacer etching. However, PFCs and HFCs have a long atmospheric lifetime and high global warming potential (GWP), so they were defined as greenhouse gases along with CO2, N2O, CH4, and SF6 through the Kyoto Protocol in 1997. Each country agreed to reduce greenhouse gas emissions through the Paris Agreement in 2015 and completed detailed implementation rules for greenhouse gas reduction through the Glasgow Agreement in 2021. South Korea declared carbon neutrality by 2050 and set a medium-term goal of reducing greenhouse gas emissions by 40% by 2030 compared to 2018. Therefore, research is actively being conducted in various industrial fields to replace existing greenhouse gases with alternative substances with lower GWP.

[0003] Among the candidates for low GWP alternatives, those with multiple bonds or containing oxygen or hydrogen in their molecular structures are attracting attention because they are easily decomposed by reacting with hydroxyl radicals (-OH) in the atmosphere. For example, heptafluoroisopropyl trifluoromethyl ketone (C5F) 1O O) is attracting attention as an insulating gas for high-voltage devices that can replace SF6, a greenhouse gas, due to its very low GWP of less than 1. Heptafluoroisopropyl trifluoromethyl ketone and its isomers, PPVE (perfluoropropyl vinyl ether) and PIPVE (perfluoroisopropyl vinyl ether), have been reported as substances that can replace existing PFCs in dielectric etching processes. Therefore, it is expected that heptafluoroisopropyl trifluoromethyl ketone, like PPVE and PIPVE, can be used in dielectric etching processes as a replacement for PFCs.

[0004] One object of the present invention is to provide an etching gas composition comprising heptafluoroisopropyl trifluoromethyl ketone capable of etching a dielectric by replacing PFC.

[0005] Another object of the present invention is to provide a plasma etching method using the above etching gas composition.

[0006] In order to achieve the above object, the present invention provides an etching gas composition that is supplied to an etching chamber to generate plasma, wherein heptafluoroisopropyl trifluoromethyl ketone (C5F) 10 Provided is an etching gas composition comprising a fluorocarbon gas containing O) and an inert gas.

[0007] In addition, the present invention provides a plasma etching method including a step of plasma etching an etching target by providing a fluorocarbon gas containing heptafluoroisopropyl trifluoromethyl ketone and an inert gas to a plasma chamber in which an etching target is placed.

[0008] According to the present invention, the etching gas composition of the present invention has a very low global warming potential compared to PFC, thereby reducing greenhouse gas emissions.

[0009] In addition, the plasma etching method of the present invention can provide optimal conditions for the etching selectivity with respect to a mask of silicon nitride and silicon oxide or a Si substrate.

[0010] FIG. 1 is a schematic diagram of an inductively coupled plasma etching chamber that performs a plasma etching method according to an embodiment of the present invention.

[0011] Figure 2 is C5F 10 Ar / (C5F) in O / Ar plasma 10 This is a result showing the SiO2 etching speed according to the O+Ar ratio.

[0012] Figure 3 is C5F 10 The results show the etching rates of SiO2, Si3N4, Si, and ACL according to source power in O / Ar plasma.

[0013] Fig. 4 is a graph showing the etching selectivity of SiO2 / Si, SiO2 / ACL, Si3N4 / Si, and Si3N4 / ACL according to the results of Fig. 3.

[0014] Figure 5 shows the results of measuring the spectral density of radicals according to source power.

[0015] Figure 6 is a graph showing the ratio of F radical and CF2 radical densities according to the results of Figure 5.

[0016] Figure 7 is C5F 10This graph illustrates the etching of SiO2, Si3N4, Si, and ACL according to the change in bias voltage in O / Ar plasma.

[0017] Fig. 8 is a graph showing the etching selectivity of SiO2 / Si, SiO2 / ACL, Si3N4 / Si, and Si3N4 / ACL according to the results of Fig. 7.

[0018] Figure 9 shows the results of measuring the spectral density of radicals according to changes in bias voltage.

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention can be modified in various ways and can take various forms, and thus specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention. In describing each drawing, similar reference numerals are used to indicate similar components. In the attached drawings, the dimensions of structures are shown larger than actual size to ensure clarity of the present invention.

[0020] While terms like "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, a first component could be referred to as a "second component," and similarly, a second component could also be referred to as a "first component."

[0021] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0022] Meanwhile, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning within the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0023]

[0024] The etching gas composition of the present invention is an etching gas composition that is supplied to an etching chamber to generate plasma, and comprises heptafluoroisopropyl trifluoromethyl ketone (C5F). 10 O) containing fluorocarbon gas; and may include an inert gas.

[0025] In one embodiment, the inert gas may be, but is not limited to, argon (Ar). The inert gas may be a gas typically used in plasma etching.

[0026] In one embodiment, the fraction of the inert gas in the etching gas composition may be 82.5 to 90%. For example, the fraction of the inert gas may be 85 to 90%. If the fraction of the inert gas is less than 82.5% or greater than 90%, the etching rate may decrease, thereby increasing the etching process time.

[0027]

[0028] The present invention describes a plasma etching method using the above etching gas composition. The plasma etching method comprises: adding heptafluoroisopropyl trifluoromethyl ketone (C5F) to a plasma chamber in which an etching target is placed. 10 It may include a step of plasma etching an etching target by providing a fluorocarbon gas and an inert gas including O).

[0029] In one embodiment, C5F 10 O Vaporize the solution at 25 to 100 ℃ to obtain the C5F 10 Fluorocarbon gas containing O can be prepared. For example, the above C5F 10 O solution can be vaporized at 70 ℃.

[0030] In one embodiment, the C5F in the plasma chamber 10 The connecting line supplying O can be heated to 60 to 100°C. For example, the connecting line can be heated to 80°C. To prevent the droplet from splashing, the connecting line can be set higher than the vaporization temperature of the heptafluoroisopropyl trifluoromethyl ketone solution.

[0031] In one embodiment, C5F 10The source power supplied to the fluorocarbon gas and inert gas containing O may be, but is not limited to, 150 to 550 W. Since the etching rates of SiO2, Si3N4, Si, and ACL increase depending on the source power, the source power can be adjusted to suit the desired etching rate.

[0032] In one embodiment, the bias voltage applied to the rear surface of the etching target may be, but is not limited to, -300 to -1100 V.

[0033] In one embodiment, the etching target may include, but is not limited to, one or more selected from the group consisting of silicon oxide having an ACL (Amorphous Carbon Layer) mask layer formed thereon, silicon nitride having an ACL mask layer formed thereon, silicon oxide having a PR (photoresist) mask layer formed thereon, silicon nitride having a PR mask layer formed thereon, silicon oxide formed on a Si substrate, and silicon nitride formed on a Si substrate. The etching target may include a silicon-based dielectric that is commonly used.

[0034] In one embodiment, the etching ratio of the PR, ACL or Si to the silicon oxide or silicon nitride may be, but is not limited to, 1.5 to 5.

[0035]

[0036] Hereinafter, to aid understanding of the present invention, examples will be given in detail. However, the following examples are intended only to illustrate the scope of the present invention and are not intended to limit its scope. These examples are provided to more fully explain the present invention to those of average skill in the art.

[0037]

[0038] <Examples 1 to 4 and Comparative Examples 1 to 7>

[0039] Figure 1 is a schematic diagram of an inductively coupled plasma etching chamber that performs a plasma etching method according to an embodiment of the present invention. Heptafluoroisopropyl trifluoromethyl ketone (hereinafter referred to as C5F) 10 O) was used. C5F 10 O exists in liquid form at room temperature with a boiling point of 24 ℃. C5F 10 To introduce O into the inductively coupled plasma (ICP) system, which is an etching chamber, the canister and the chamber connection line are heated as shown in Fig. 1 to form C5F 10 O was vaporized and introduced into the chamber. The canister was heated using a heating jacket, and the chamber connection line was heated to a temperature higher than the canister heating temperature to prevent splashing of droplets. C5F 10 The O canister was heated to about 70°C, and the chamber connection line was heated to about 80°C. Vaporized C5F 10 To introduce C5F into the chamber at the desired flow rate, a mass flow controller (MFC) is used. 10 O was adjusted and introduced into the chamber.

[0040] C5F 10 Ar / (C5F) in O / Ar plasma 10 In order to confirm the SiO2 etching characteristics according to the O+Ar ratio, C5F was used with the composition shown in Table 1 below. 10 The ratio of O and Ar was controlled. The etching target was a SiO2 thin film formed on a Si substrate, and the source power was set to approximately 250 W, the bias voltage to approximately -600 V, the gas pressure to approximately 10 mTorr, and the electrode temperature to approximately 15°C.

[0041] C5F 10O(sccm)Ar(sccm)Ar Fraction(%)Comparative Example 13000.0Comparative Example 225516.7Comparative Example 3201033.3Comparative Example 4151550.0Example 1102066.7Example 252583.3Example 342686.7Example 432790.0Comparative Example 522893.3Comparative Example 612996.7Comparative Example 7030100.0

[0042]

[0043] <Examples 5 to 9>

[0044] C5F 10 In order to confirm the etching characteristics according to the source power in O / Ar plasma, the source power was adjusted according to Table 2 below, and etching was performed in the same manner as in Example 4, except that the etching targets were SiO2 thin films, Si3N4 thin films, Si substrates, and ACL mask layers.

[0045] Source Power (W) Example 5200 Example 6250 Example 7300 Example 8400 Example 9500

[0046]

[0047] <Examples 10 to 12>

[0048] C5F 10 In order to confirm the SiO2 etching characteristics according to the bias voltage in O / Ar plasma, the bias voltage was adjusted according to Table 3 below, and etching was performed in the same manner as in Example 6, except that the etching targets were a SiO2 thin film, a Si3N4 thin film, a Si substrate, and an ACL mask layer.

[0049] Bias voltage (V) Example 10-400 Example 6-600 Example 11-800 Example 12-1000

[0050]

[0051] Experimental Example 1

[0052] Figure 2 is C5F 10 Ar / (C5F) in O / Ar plasma 10This is the result showing the SiO2 etching rate according to the ratio of O+Ar. In Fig. 2, Ar / (C5F 10 C5F when the O+Ar) ratio is about 0 to 66.7% 10 It was determined that the plasma density did not change much because O was not sufficiently dissociated, and thus the SiO2 etching rate did not change much. Afterwards, Ar / (C5F 10 As the O+Ar) ratio increases from about 66.7% to 90%, C5F 10 As the separation of O increased, the plasma density increased, and many ions or radicals involved in etching, such as F or CF3, were generated, which increased the SiO2 etching rate. Ar / (C5F 10 When the ratio of O+Ar increases from about 90% to 100%, C5F, which can supply ions or radicals such as F or CF3, 10 As the flow rate of O decreased, the etching rate of SiO2 decreased.

[0053]

[0054] Experimental Example 2

[0055] Figure 3 is C5F 10 The results show the etching rates of SiO2, Si3N4, Si, and ACL according to the source power in an O / Ar plasma. As the source power increased from approximately 200 W to 500 W, the etching rates of SiO2, Si3N4, Si, and ACL all increased. This is because as the source power increased, the power applied to the plasma increased, which in turn increased the plasma density.

[0056] Fig. 4 is a graph showing the etching selectivity of SiO2 / Si, SiO2 / ACL, Si3N4 / Si, and Si3N4 / ACL according to the results of Fig. 3. As the source power increased, the etching selectivity of SiO2 / Si, SiO2 / ACL, Si3N4 / Si, and Si3N4 / ACL all decreased. This is because as the source power increased, the etching rate increase rate of Si and ACL was greater than that of SiO2 and Si3N4.

[0057] Figure 5 shows the results of measuring the spectral density of radicals according to the source power. The spectral density of radicals was measured using an optical emission spectrometer (OES). The densities of CF2 (approximately 251.9 nm), CF (approximately 256 nm), F (approximately 703.8 nm), and O (approximately 777 nm) radicals all increased as the source power increased from approximately 200 W to 500 W. As mentioned in the results of Figure 4, the density of these radicals also increased because the power applied to the plasma increased, which increased the plasma density. In addition, as the source power increased, the density of the F radical increased faster than that of the CF2 radical. This is because as the source power increases, the probability of the CF bond of the CF2 radical being broken and the generation of the F radical increases. It was determined that the density of the F radical increased more than that of the CF2 radical.

[0058] Figure 6 is a graph showing the ratio of the density of F radicals and CF2 radicals according to the results of Figure 5. As the source power increases, the intensity of the F radicals increases faster than that of the CF2 radicals, so the F / CF2 ratio also increases. CF2 radicals are mainly involved in deposition, while F radicals are mainly involved in etching. This means that as the F / CF2 ratio increases, the number of radicals involved in etching becomes greater than that of deposition. Therefore, as the source power increases, the amount of radicals involved in etching increases more than that of deposition. Therefore, as shown in Figure 3, as the source power increases, the etching rate increases.

[0059]

[0060] Experimental Example 3

[0061] Figure 7 is C5F 10 This graph illustrates the etching of SiO2, Si3N4, Si, and ACL according to the variation of bias voltage in an O / Ar plasma. In Fig. 7, when the bias voltage increased from approximately -400 V to -1000 V, the etching rates of SiO2, Si3N4, Si, and ACL all increased. This is because the ion energy increases as the bias voltage increases, so the etching rates increased in all thin films.

[0062] Fig. 8 is a graph showing the etching selectivity of SiO2 / Si, SiO2 / ACL, Si3N4 / Si, and Si3N4 / ACL according to the results of Fig. 7. As the bias voltage increased, the etching selectivity of SiO2 / Si, SiO2 / ACL, Si3N4 / Si, and Si3N4 / ACL all decreased. This is because, as in Fig. 4, as the bias voltage increases, the etching rate increase rate of Si or ACL is greater than that of SiO2 or Si3N4.

[0063] Figure 9 shows the results of measuring the spectral density of radicals according to changes in bias voltage. Unlike Figure 5, where the source power was varied, there was no change in intensity of the CF2, CF, F, and O radicals even when the bias voltage increased. The bias voltage is a variable that affects ion energy, and it was determined that the intensity of the CF2, CF, F, and O radicals hardly changed even when the bias voltage increased.

[0064]

[0065] Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. In the etching gas composition that is supplied to the etching chamber to generate plasma, Heptafluoroisopropyl trifluoromethyl ketone (C5F) 10 Fluorocarbon gas containing O); and An etching gas composition comprising an inert gas.

2. In paragraph 1, An etching gas composition wherein the above inert gas is argon (Ar).

3. In paragraph 2, An etching gas composition, wherein the fraction of an inert gas in the above etching gas composition is 82.5 to 90%.

4. In paragraph 2, An etching gas composition, wherein the fraction of an inert gas in the above etching gas composition is 85 to 90%.

5. A plasma etching method comprising the step of plasma etching an etching target by providing a fluorocarbon gas containing heptafluoroisopropyl trifluoromethyl ketone and an inert gas to a plasma chamber in which an etching target is placed.

6. In paragraph 5, A plasma etching method for preparing a fluorocarbon gas containing heptafluoroisopropyl trifluoromethyl ketone by vaporizing a heptafluoroisopropyl trifluoromethyl ketone solution at 25 to 100°C.

7. In paragraph 5, A plasma etching method, wherein a connecting line supplying the heptafluoroisopropyl trifluoromethyl ketone to the plasma chamber is heated to 60 to 100°C.

8. In paragraph 5, A plasma etching method, wherein the source power supplied to the fluorocarbon gas and inert gas containing the heptafluoroisopropyl trifluoromethyl ketone is 150 to 550 W.

9. In paragraph 5, A plasma etching method, wherein the bias voltage applied to the rear surface of the etching target is -300 to -1100 V.

10. In paragraph 5, A plasma etching method, wherein the etching target comprises at least one selected from the group consisting of silicon oxide having an ACL (Amorphous Carbon Layer) mask layer formed thereon, silicon nitride having an ACL mask layer formed thereon, silicon oxide having a PR (photoresist) mask layer formed thereon, silicon nitride having a PR mask layer formed thereon, silicon oxide formed on a Si substrate, and silicon nitride formed on a Si substrate.

11. In paragraph 10, A plasma etching method wherein the etching ratio of the PR, ACL or Si to the silicon oxide or silicon nitride is 1.5 to 5.

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