Etching gas composition comprising hexafluorobenzene and plasma etching method using same

Abstract

Disclosed are an etching gas composition and a plasma etching method using same. The etching gas composition is supplied to an etching chamber so as to generate plasma, and comprises: a fluorocarbon gas containing hexafluorobenzene (C6F6); a reactive gas; and an inert gas.

Description

Etching gas composition containing hexafluorobenzene and plasma etching method using the same

[0001] The present invention relates to an etching gas composition containing hexafluorobenzene and a plasma etching method using the same.

[0002] Perfluorocarbons (PFCs) are primarily used for silicon oxide etching. PFCs are suitable for etching high-aspect-ratio silicon oxide features because they exhibit high etch rates for silicon oxide, have high selectivity for mask and underlying layer materials, and suppress isotropic etching. However, PFCs persist in the atmosphere for a long time and have a high global warming potential (GWP), making them a designated greenhouse gas along with CO2, N2O, CH4, SF6, and HFCs. Therefore, reducing PFC emissions is essential to addressing global warming. However, according to the World Semiconductor Council (WSC), the amount of PFCs emitted by the global semiconductor industry has continued to increase since 2012. Furthermore, according to the National Greenhouse Gas Inventory Report, the amount of PFCs consumed in semiconductor and display manufacturing processes in Korea has continued to increase since 2000, with most of them being emitted into the atmosphere without being decomposed. With South Korea aiming for carbon neutrality by 2050, the development of etching process technology using alternatives to PFCs is urgently needed to reduce greenhouse gas emissions. Among these substances, hexafluorobenzene (C6F6), a cyclic fluorocarbon, has a significantly lower global warming potential than PFCs, making it a potential PFC replacement.

[0003] One object of the present invention is to provide an etching gas composition comprising hexafluorobenzene that can replace PFC.

[0004] Another object of the present invention is to provide a plasma etching method using the above etching gas composition.

[0005] 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, the etching gas composition comprising a fluorocarbon gas containing hexafluorobenzene (C6F6); a reactive gas; and an inert gas.

[0006] 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 hexafluorobenzene, an inert gas, and a reactive gas to a plasma chamber in which an etching target is placed.

[0007] 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.

[0008] In addition, the plasma etching method of the present invention can provide optimal conditions for the etching selectivity with respect to silicon oxide and a mask.

[0009] 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.

[0010] Figure 2 shows the results of the etching rate of SiO2 according to the C6F6 / O2 ratio in the plasma of C6F6 / O2 / Ar etching gas.

[0011] Figure 3 shows the results of the etching rate of SiO2 according to the Ar ratio in the plasma of C6F6 / O2 / Ar etching gas.

[0012] Figure 4 shows the results of the etching rate of SiO2 according to the Ar fraction in the plasma of C6F6 / O2 / Ar etching gas.

[0013] Figure 5 shows the results of the etching rate of SiO2 according to the source power in the etching device in the plasma of C6F6 / O2 / Ar etching gas.

[0014] Fig. 6 is a graph showing the SiO2 / ACL and SiO2 / PR etching selectivity according to the results of Fig. 5.

[0015] Figure 7 shows the results of the etching rate of SiO2 according to the bias voltage in the etching device in the plasma of C6F6 / O2 / Ar etching gas.

[0016] Fig. 8 is a graph showing the SiO2 / ACL and SiO2 / PR etching selectivity according to the results of Fig. 7.

[0017] 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.

[0018] 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."

[0019] 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.

[0020] 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.

[0021]

[0022] The etching gas composition of the present invention is an etching gas composition that is supplied to an etching chamber to generate plasma, and may include a fluorocarbon gas containing hexafluorobenzene (C6F6); a reactive gas; and an inert gas.

[0023] In one embodiment, the reactive gas may be oxygen (O2) and the inert gas may be argon (Ar), but is not limited thereto. The reactive gas and the inert gas may be gases typically used in plasma etching.

[0024] In one embodiment, the ratio of the fluorocarbon gas and the reactive gas may be about 2 to 5.5: 4.5 to 8. If the ratio of the fluorocarbon gas is less than the above range, the etching speed of the silicon oxide may be slow, thereby increasing the process time. If the ratio of the fluorocarbon gas is greater than the above range, fluorocarbon may be deposited on one surface of the mask layer.

[0025] In one embodiment, the ratio of the fluorocarbon gas, the reactive gas, and the inert gas may be about 1:0.7 to 1.3:2.5 to 30. If the ratio of the inert gas is outside the above range, the silicon oxide may not be etched.

[0026] In one embodiment, the fraction of the inert gas in the etching gas composition may be about 60 to 98%. When the fraction of the inert gas is less than 60% or greater than 98%, the etching rate may be significantly reduced, and in particular, when the fraction of the inert gas is less than 60%, a fluorocarbon film may be deposited on one surface of the mask layer.

[0027]

[0028] The present invention describes a plasma etching method using the above etching gas composition. The plasma etching method may include a step of plasma etching the etching object by providing a fluorocarbon gas containing hexafluorobenzene, an inert gas, and a reactive gas to a plasma chamber in which an etching object is placed.

[0029] In one embodiment, a fluorocarbon gas containing hexafluorobenzene can be prepared by vaporizing a hexafluorobenzene solution at about 80 to 150°C. For example, the hexafluorobenzene solution can be vaporized at about 135°C.

[0030] In one embodiment, the connecting line supplying the fluorocarbon gas containing hexafluorobenzene to the plasma chamber may be heated to 80 to 170°C. For example, the connecting line supplying the fluorocarbon gas containing hexafluorobenzene to the plasma chamber may be heated to about 155°C. To prevent the droplet from splashing, the connecting line may be set higher than the vaporization temperature of the hexafluorobenzene solution.

[0031] In one embodiment, the source power supplied to the fluorocarbon gas including hexafluorobenzene, the inert gas, and the reactive gas may be about 250 to 500 W. When the source power is less than about 250 W, the silicon oxide may not be etched, and the fluorocarbon film may be deposited.

[0032] In one embodiment, the bias voltage applied to the rear surface of the etching target may be, but is not limited to, -400 to -1000 V.

[0033] In one embodiment, the etching ratio of the silicon oxide to the mask layer may be, but is not limited to, 1 to 15.

[0034]

[0035] 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.

[0036]

[0037] <Examples 1 to 3 and Comparative Examples 1 to 3>

[0038] 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. Hexafluorobenzene (C6F6) has a boiling point of about 80.5°C, which is higher than room temperature, and thus exists in a liquid state at room temperature. In order to introduce C6F6 into an inductively coupled plasma (ICP) system, which is an etching chamber, C6F6 must be heated above its boiling point to vaporize it. To this end, in the schematic diagram of FIG. 1, a canister containing a C6F6 solution and a chamber connection line are heated to vaporize C6F6. The canister is heated to about 135°C, and the chamber connection line is heated to about 155°C. A mass flow controller (MFC) is used to introduce the vaporized C6F6 into the chamber at a desired flow rate.

[0039] In order to confirm the etching characteristics according to the C6F6 and O2 ratio in the plasma of C6F6 / O2 / Ar etching gas, the ratio of C6F6 and O2 was adjusted to the composition shown in Table 1 below. The etching target was a SiO2 thin film formed on a silicon (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.

[0040] C6F6(sccm)O2(sccm)Ar(sccm)Example 12820Example 23720Example 35520Comparative Example 16420Comparative Example 28220Comparative Example 310020

[0041]

[0042] <Examples 4 to 16 and Comparative Examples 4 to 6>

[0043] In order to confirm the etching characteristics according to the Ar flow rate in the plasma of C6F6 / O2 / Ar etching gas, etching was performed in the same manner as in Example 1 except that the Ar ratio was adjusted to the composition shown in Table 2 below.

[0044] C6F6(sccm)O2(sccm)Ar(sccm)Comparative Example 4555Comparative Example 55510Comparative Example 65512Example 45513Example 55515Example 65520Example 75525Example 85530Example 95535Example 105540Example 115545Example 125550Example 135560Example 145575Example 1555100Example 1655125

[0045]

[0046] <Examples 17 to 20 and Comparative Examples 7 to 12>

[0047] In order to confirm the etching characteristics according to the Ar fraction in the plasma of C6F6 / O2 / Ar etching gas, etching was performed in the same manner as in Example 1 except that the ratios of C6F6, O2, and Ar were adjusted to the composition shown in Table 3 below.

[0048] C6F6(sccm)O2(sccm)Ar(sccm)Ar Fraction(%)Comparative Example 7151500.0Comparative Example 810101033.3Comparative Example 97.57.51550.0Comparative Example 10771653.3Comparative Example 116.56.51756.7Example 17661860.0Example 6552066.7Example 182.52.52583.3Example 190.50.52996.7Example 200.20.229.698.7Comparative Example 120030100.0

[0049]

[0050] <Examples 21 to 23 and Comparative Example 13>

[0051] In order to determine the etching characteristics of SiO2, ACL (amorphous carbon layer), and PR (photoresist) according to the source power in the plasma of C6F6 / O2 / Ar etching gas, the source power was adjusted as shown in Table 4 below, and etching was performed in the same manner as in Example 6, except that the etching target was a SiO2 thin film, ACL, or PR mask layer formed on a silicon (Si) substrate.

[0052] Source Power (W) Comparison Example 13200 Example 21250 Example 22300 Example 23400

[0053]

[0054] <Examples 24 to 26>

[0055] In order to determine the etching characteristics of SiO2, ACL (amorphous carbon layer), and PR (photoresist) according to the bias voltage in the plasma of C6F6 / O2 / Ar etching gas, etching was performed in the same manner as in Example 21 except that the bias voltage was adjusted as shown in Table 5 below.

[0056] Bias voltage (V) Example 24-400 Example 21-600 Example 25-800 Example 26-1000

[0057]

[0058] Experimental Example 1

[0059] Figure 2 shows the results of the etching rate of SiO2 according to the C6F6 / O2 ratio in the plasma of C6F6 / O2 / Ar etching gases. As the C6F6 / O2 gas ratio increased from about 2 / 8 to 5 / 5, the etching rate of SiO2 increased, and the etching rate reached a maximum when the C6F6 / O2 gas ratio was about 5 / 5. As the C6F6 / O2 ratio increased from about 2 / 8 to 5 / 5, the amount of etchant increased, so the etching rate of SiO2 increased. When the C6F6 / O2 gas ratio became about 6 / 4, SiO2 was not etched and a fluorocarbon film was deposited. This is because the fluorocarbon film was excessively deposited and the amount of O2 to remove it decreased, so SiO2 was not etched and a fluorocarbon film was deposited. As the C6F6 / O2 gas ratio changed from 6 / 4 to 10 / 0, the deposition rate of the fluorocarbon film increased. When the ratio of fluorocarbon increases in a fluorocarbon plasma such as C6F6, the amount of etchant such as F increases, which increases the etching rate of SiO2. However, if the ratio of fluorocarbon increases excessively, a thick fluorocarbon film may be formed, which may hinder etching. Therefore, it is important to secure an appropriate composition ratio of etching gases in order to etch SiO2 with a fluorocarbon plasma.

[0060] Figure 3 shows the results of the etching rate of SiO2 according to the Ar ratio in the plasma of C6F6 / O2 / Ar etching gas. When the Ar flow rate was about 5 to 12 sccm, SiO2 was not etched. When the Ar flow rate was about 5 to 12 sccm, the Ar flow rate was small among the total gas flow rates, so the C6F6 / O2 / Ar plasma was not sufficiently dissociated, and heavy species involved in the deposition of the fluorocarbon film were formed, so that SiO2 was not etched. Thereafter, when the Ar flow rate increased to about 13 sccm or more, SiO2 began to be etched. When the Ar flow rate was about 13 to 50 sccm, the C6F6 / O2 / Ar plasma was sufficiently dissociated, so that SiO2 was etched. Even when the Ar flow rate increased from about 13 to 50 sccm, the etching rate of SiO2 was almost constant. As the Ar flow rate exceeded approximately 50 sccm, the etching rate of SiO2 increased slightly.

[0061] Fig. 4 shows the results of the etching rate of SiO2 according to the Ar fraction in the plasma of C6F6 / O2 / Ar etching gas. In Fig. 4, when Ar / (C6F6+O2+Ar) is about 0 to 56.67%, the amount of Ar is not sufficient to sufficiently separate the C6F6 / O2 / Ar plasma, so that a fluorocarbon film is deposited. As the Ar / (C6F6+O2+Ar) ratio increases from about 0 to 56.67%, the flow rate of C6F6 involved in the fluorocarbon film deposition decreases, so that the fluorocarbon film deposition rate decreases. When the Ar / (C6F6+O2+Ar) ratio is about 60 to 96.67%, the C6F6 / O2 / Ar plasma is sufficiently separated, so that SiO2 is etched. As the Ar / (C6F6+O2+Ar) ratio increased from about 60 to 96.67%, the Ar flow rate increased, which increased the ion density and thus the SiO2 etching rate, but the increase was slight. Afterwards, as the Ar / (C6F6+O2+Ar) ratio increased beyond about 96.67%, the C6F6 flow rate, which provides an etchant such as F, decreased significantly, which decreased the SiO2 etching rate.

[0062]

[0063] Experimental Example 2

[0064] Figure 5 shows the results of the etching rate of SiO2 according to the source power in the etching device in the plasma of C6F6 / O2 / Ar etching gas. When the source power was approximately 200 W, none of SiO2, ACL, and PR were etched, and a carbon fluorocarbon film was deposited. As the source power increased to approximately 250 W, all of SiO2, ACL, and PR were etched. Thereafter, as the source power increased, the etching rate of SiO2, ACL, and PR all increased. This is because as the source power increased, the power applied to the plasma increased, which increased the ion density.

[0065] Fig. 6 is a graph showing the SiO2 / ACL and SiO2 / PR etching selectivities according to the results of Fig. 5. In Fig. 6, when the source power was about 200 W, neither SiO2, ACL, nor PR were etched, so the etching selectivities could not be measured. As the source power increased to about 250 W or more, the rate at which the etching rates of ACL and PR increased was greater than the rate at which the etching rate of SiO2 increased, so that both the SiO2 / ACL and SiO2 / PR etching selectivities decreased. In addition, since the etching rate of ACL was slower than that of PR, the SiO2 / ACL etching selectivity was greater than the SiO2 / PR etching selectivity.

[0066] Figure 7 shows the results of the etching rate of SiO2 according to the bias voltage within the etching device in the plasma of C6F6 / O2 / Ar etching gas. As the bias voltage increases, the ion energy increases, so the etching rates of SiO2, ACL, and PR all increase.

[0067] Fig. 8 is a graph showing the SiO2 / ACL and SiO2 / PR etching selectivities according to the results of Fig. 7. As the bias voltage increases, the etching speed of ACL or PR increases more rapidly than that of SiO2, so the SiO2 / ACL and SiO2 / PR etching selectivities decrease.

[0068]

[0069] 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. An etching gas composition that is supplied to an etching chamber to generate plasma, Fluorocarbon gas containing hexafluorobenzene (C6F6); reactive gases; and An etching gas composition comprising an inert gas.

2. In paragraph 1, An etching gas composition in which the ratio of the above fluorocarbon gas and the above reactive gas is 2 to 5.5: 4.5 to 8 3. In paragraph 1, An etching gas composition in which the ratio of the above-mentioned fluorocarbon gas, the above-mentioned reactive gas, and the above-mentioned inert gas is 1:0.7 to 1.3:2.5 to 30.

4. In paragraph 1, An etching gas composition, wherein the fraction of the inert gas in the etching gas composition is 60 to 98%.

5. In paragraph 1, An etching gas composition wherein the reactive gas is oxygen (O2) and the inert gas is argon (Ar).

6. A plasma etching method comprising the step of plasma etching an etching target by providing a fluorocarbon gas containing hexafluorobenzene, an inert gas, and a reactive gas to a plasma chamber in which an etching target is placed.

7. In paragraph 6, A plasma etching method for preparing a fluorocarbon gas containing hexafluorobenzene by vaporizing a hexafluorobenzene solution at 80 to 150°C.

8. In paragraph 6, A plasma etching method, wherein a connecting line supplying fluorocarbon gas containing hexafluorobenzene to the plasma chamber is heated to 80 to 170°C.

9. In paragraph 6, A plasma etching method, wherein the source power supplied to the fluorocarbon gas, inert gas and reactive gas containing the above hexafluorobenzene is 250 to 500 W.

10. In paragraph 6, A plasma etching method, wherein the bias voltage applied to the rear surface of the etching target is -400 to -1000 V.

11. In paragraph 6, A plasma etching method in which the above etching target is silicon oxide having an ACL (Amorphous Carbon Layer) or PR (photoresist) mask layer formed thereon.

12. In paragraph 11, A plasma etching method wherein the etching ratio of the silicon oxide to the mask layer is 1 to 15.

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