Dry etching gas composition containing sulfur-containing fluorocarbon and dry etching method using the same

Abstract

Provided is a novel etching gas composition comprising a sulfur-containing compound, which can selectively etch SiO2 relative to low dielectric constant materials (low-k materials (SiON, SiCN, SiOCN, SiOC)). A dry etching gas composition comprising a saturated and cyclic sulfur-containing fluorocarbon compound represented by the general formula (1): CxFySz (wherein x, y and z are 2≤x≤5, y≤2x, 1≤z≤2).

Description

Technical Field

[0001] The present invention relates to a dry etching gas composition containing a sulfur-containing fluorocarbon and a dry etching method using the same. Background Art

[0002] As semiconductor devices become more miniaturized and 3D-ized, the requirements for etching processes become more stringent year by year. It is required to develop new etching technologies that can meet such stringent requirements. In recent years, in order to reduce the parasitic capacitance that increases with the miniaturization of semiconductor devices, low dielectric constant materials represented by SiOC are used as silicon-based films containing carbon. However, it is difficult to selectively etch silicon oxide films and silicon nitride films relative to low dielectric constant materials in existing FC gases and HFC gases. In the manufacture of actual devices, damage to low dielectric constant films during dry etching (due to the invasion of ions and ultraviolet light generated by plasma, the composition and structure of the film, the changes in electrical properties such as dielectric constant) becomes a problem.

[0003] As a solution to the above-mentioned problems, the present applicant has proposed that an etching gas composition containing a specific hydrofluorocarbon (1,1,4,4-tetrafluoro-1,3-butadiene) is effective (Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-149451 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] Therefore, the object of the present invention is to provide a novel etching gas composition containing a sulfur-containing compound that can selectively etch SiO2 relative to low dielectric constant materials (low-k materials (SiON, SiCN, SiOCN, SiOC)).

[0009] Solutions for solving problems

[0010] According to the present invention, the following solutions are provided. [1]

[0012] A dry etching gas composition comprises a saturated and cyclic sulfur-containing fluorocarbon compound represented by the general formula (1): CxFySz (wherein x, y and z are 2≤x≤5, y≤2x, 1≤z≤2). [2]

[0014] The dry etching gas composition according to [1], wherein the sulfur-containing fluorocarbon compound is 2,2,3,3,4,4,5,5-octafluorotetrahydrothiophene (C4F8S). [3]

[0016] The dry etching gas composition according to [1] or [2], wherein the sulfur-containing fluorocarbon is contained in an amount of 1 to 100 vol%. [4]

[0018] The dry etching gas composition according to any one of [1] to [3], further comprising, in addition to the sulfur-containing fluorocarbon, at least one oxygen-containing compound selected from the group consisting of O2, O3, CO, CO2, NO, NO2, SO2 and SO3. [5]

[0020] The dry etching gas composition according to any one of [1] to [4], further comprising, in addition to the sulfur-containing fluorocarbon, at least one inert gas selected from the group consisting of N 2 , He, Ar, Ne and Xe. [6]

[0022] A dry etching method comprising the following steps: using the dry etching gas composition described in any one of [1] to [5], plasma etching is performed on a stacked structure comprising at least two or more selected from the group consisting of (a1) a silicon-based film containing carbon, (a2) a crystalline silicon film, (a3) ​​an amorphous silicon film, (a4) a polycrystalline silicon film (polysilicon film), (a5) a silicon oxynitride film, (a6) an amorphous carbon film, (a7) a photoresist film, (a8) a silicon oxide film and (a9) a silicon nitride film, and selectively etching the films other than the (a6) amorphous carbon film and the (a7) photoresist film, either individually or simultaneously. [7]

[0024] A dry etching method comprising the following steps: using the dry etching gas composition described in any one of [1] to [5], plasma etching is performed on a stacked structure comprising at least two or more selected from the group consisting of (a1) a silicon-based film containing carbon, (a2) a crystalline silicon film, (a3) ​​an amorphous silicon film, (a4) a polysilicon film, (a5) a silicon oxynitride film, (a6) an amorphous carbon film, (a7) a photoresist film and (a8) a silicon oxide film, and only the (a8) silicon oxide film is selectively etched. [8]

[0026] The dry etching method according to [6] or [7], wherein the etching gas composition according to any one of [1] to [5] is converted into plasma so as to generate ions or active species containing S, and etching is performed. [9]

[0028] The dry etching method according to any one of [6] to [8], wherein etching is performed using the dry etching gas composition according to any one of [1] to [5] under plasma conditions capable of simultaneously etching the (b1) silicon oxide film and the (b2) silicon nitride film.

[0029] Effects of the Invention

[0030] According to the present invention, a novel etching gas composition containing a sulfur-containing compound and capable of selectively etching SiO2 relative to low dielectric constant materials (low-k materials (SiON, SiCN, SiOCN, SiOC)) can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a figure which shows the result of an etching test.

[0032] Figure 2 Graph showing SiO2 selectivity of the etching composition of the present invention.

[0033] Figure 3 This is a diagram showing the results of the etching test in the form of a bar graph based on the etching rate of ACL. DETAILED DESCRIPTION

[0034] The dry etching gas composition in the present invention includes a mixed gas containing a saturated and cyclic sulfur-containing fluorocarbon represented by the following general formula (1), or a single gas.

[0035] General formula (1): CxFySz

[0036] (where x, y and z are 2≤x≤5, y≤2x+2, 1≤z≤2)

[0037] In general formula (1), from the viewpoint of easy handling of dry etching gas, it is preferred to use a compound satisfying x=2 to 5, y=4 to 10, and z=1. Examples of suitable compounds include:

[0038]

[0039] Tetrafluorothiirane (C2F4S),

[0040]

[0041] 2,2,3,3,4,4-Hexafluorothietane (C3F6S),

[0042]

[0043] 2,2,3-Trifluoro-3-(trifluoromethyl)-thiirane (C3F6S),

[0044]

[0045] 2,2,3,3,4,4,5,5-octafluorotetrahydrothiophene (C4F8S),

[0046]

[0047] 2,3-Difluoro-2,3-bis(trifluoromethyl)-thiirane (C4F8S),

[0048]

[0049] 2,2-Difluoro-3,3-bis(trifluoromethyl)-thiirane (C4F8S),

[0050]

[0051] 2,2,3,3,4,4,5,5,6,6-Decafluorotetrahydro-2H-thiopyran (C5F 10 S) etc.

[0052] In the dry etching gas composition of the present invention, it is preferred to use a sulfur-containing fluorocarbon represented by the general formula (1) with a purity of 95.0 vol% to 100.0 vol%. It is more preferred to use a purity of 99 vol% or more, and it is further preferred to use a purity of 99.9 vol% or more. As impurity components contained, N2, O2, CO2, H2O, HF, HCl, SO2, CH4, etc. can be cited, but among these impurity components, H2O, HF, HCl, SO2, etc. are highly likely to corrode the passages through which the gas flows, and therefore, it is preferred to remove them as much as possible through purification.

[0053] In the dry etching gas composition of the present invention, the sulfur-containing fluorocarbon compound represented by the general formula (1) is mixed with other fluorocarbon (FC) gas and hydrofluorocarbon (HFC) gas, so that the selectivity of the etching target material to the non-etching target material can be further improved compared with the case where the compound represented by the general formula (1) is not mixed. In addition, when etching a structure patterned with the non-etching target material, the vertical processing accuracy is also improved.

[0054] In the above-mentioned structure patterned by the non-etching object material, when the etching object material is a Si-based material containing oxygen such as SiO2, the compound represented by the general formula (1) is preferably used in a mixture with an etching gas such as CF4, CHF3, C2F6, C3F8, C4F8, C4F6, C5F8, etc., in terms of selective etching and etching with good vertical processing accuracy. In particular, when high selectivity is required, it is preferably mixed with C4F8, C4F6, and C5F8 having a large amount of C.

[0055] In a structure patterned by a non-etching target material, when the etching target material is a Si-based material containing nitrogen such as SiN, mixing the gas compound represented by the general formula (1) with an HFC gas such as CHF3, CH2F2, or CH3F for plasma etching is preferred in terms of selective etching and etching with good vertical processing accuracy. In particular, when high selectivity is required, it is also effective to use an HFC gas with a C number of 2 or more.

[0056] In the dry etching gas composition of the present invention, for a composition containing a compound represented by general formula (1), at least one oxygen-containing compound selected from the group consisting of O2, O3, CO, CO2, NO, NO2, SO2 and SO3 is added, thereby achieving effects such as suppressing excess deposits, improving the etching rate of the etching object, and improving the selectivity of the etching object to non-etching materials.

[0057] In the dry etching gas composition of the present invention, at least one inert gas selected from the group consisting of N2, He, Ar, Ne and Xe may be added to the composition containing the compound represented by the general formula (1). Among them, He, Ar and Xe are preferably used.

[0058] Examples of the etching gas used in the method of the present invention include the following compositions.

[0059] (a) The compound represented by the general formula (1) can be prepared at a purity of 90 vol% or more, preferably at a purity of 99 vol% or more, and particularly preferably at a purity of 99.999 vol% or more.

[0060] (b) In the dry etching composition used for etching, the compound represented by the general formula (1) is preferably contained in an amount of 1 to 100 vol%.

[0061] (c) In the dry etching composition used for etching, in addition to the compound represented by the general formula (1), it is preferred to further contain at least one compound selected from the group of compounds containing oxygen atoms consisting of O2, O3, CO, CO2, NO, NO2, SO2 and SO3, and O2 is particularly preferred. The ratio of the compound containing oxygen atoms is preferably 5 to 50%, particularly preferably 10 to 35%, relative to the total amount of the compound represented by the general formula (1) and the compound containing oxygen atoms.

[0062] (d) The dry etching composition used in etching preferably contains a compound represented by the general formula (1), and contains at least one of the above-mentioned oxygen atom-containing compound group and / or at least one of the inert gas group consisting of a rare gas or N2, and Ar is particularly preferably used. The ratio of the inert gas contained in the etching gas composition is preferably 1 to 80 vol%, and particularly preferably 50 to 75 vol%.

[0063] The dry etching apparatus used in the dry etching of the present invention can utilize any apparatus used in the relevant technical field without particular limitation, and for example, apparatuses of the helicon wave method, high frequency induction method, parallel plate method, magnetron method, and microwave method can be used.

[0064] The dry etching method of the present invention performs vertical processing of patterned wafers of fine Si-based materials, and therefore, the etching device must be equipped with a vacuum container suitable for ion-assisted etching and capable of reproducing low gas pressure conditions. Under low pressure conditions, the straightness of particles in the plasma is improved, and the ions irradiated to the substrate also reach the substrate without interfering with other particles. Therefore, the number of ions vertically incident on the substrate increases, which is beneficial to vertical processing. In the dry etching method of the present invention, the pressure in the vacuum container during etching is preferably adjusted to 100Torr to 0.1mTorr, and more preferably adjusted to 100mTorr to 0.1mTorr.

[0065] In the dry etching method of the present invention, the compound represented by the general formula (1) is preferably introduced as a gas into the vacuum container of the etching device. Therefore, the etching device used in the dry etching method of the present invention preferably has a mechanism for introducing the compound represented by the general formula (1) as a gas and further for adjusting the amount of the introduced compound. In addition, for this mechanism, in addition to the gas compound represented by the general formula (1), it is effective to use a plurality of the aforementioned other gas compounds, such as O2, Ar, etc., according to the purpose in the plasma etching method of the present invention. Therefore, it is preferred that the mechanism for introducing the gas and adjusting the amount of the introduced gas also has 4 or more.

[0066] Example

[0067] In this example (etching test), a parallel plate type capacitively coupled plasma etching apparatus manufactured by SAMCO was used as a plasma etching apparatus. The composition of the deposited film was determined by SEM-EDX (scanning electron microscope / energy dispersive X-ray spectroscopy).

[0068] As a silicon oxide film (SiOm) (m represents a natural number), a SiO2 film of 1000 nm deposited on a silicon wafer by plasma CVD is used. As a silicon nitride film (SiN), a SiN film of 300 nm deposited on a silicon wafer by thermal CVD is used. As an amorphous carbon film (ACL), a ACL of 400 nm deposited on a silicon wafer by plasma CVD is used. As a carbon-containing silicon film (SiOC), BlackDiamond-3 (hereinafter BD-3), which is a registered trademark of Applied Materials, is deposited on a silicon wafer to be 500 nm. As a SiON film, a SiON of 500 nm deposited on a silicon wafer by plasma CVD is used. As a SiCN film, a SiCN of 500 nm deposited on a silicon wafer by plasma CVD is used. As a SiOCN film, a SiOCN of 500 nm deposited on a silicon wafer by plasma CVD is used.

[0069] The sample film thickness during etching was measured using an optical interference film thickness measuring device. The etching conditions are shown in the following Table 1. The etching rate of the gas was calculated using the following formula.

[0070]

[0071] The A / B selection ratio is calculated using the following formula.

[0072] A / B selectivity = etching rate of film A (nm / min) ÷ etching rate of film B (nm / min)

[0073] [Etching test]

[0074] Using different samples with SiO2, SiN, ACL, etc. deposited on silicon wafers, etching tests were performed under the conditions shown in Table 1. As a comparative example, perfluorocyclobutane (1,1,2,2,3,3,4,4-octafluorocyclobutane (C4F8)) containing no sulfur was used for etching gas, and as an embodiment of the present invention, perfluorothiocyclopentane (2,2,3,3,4,4,5,5-octafluorotetrahydrothiophene (C4F8S)) containing sulfur was used as shown in the following formula:

[0075]

[0076] [Table 1]

[0077] Table 1. Etching test conditions

[0078]

[0079] The test results are shown in Figure 1 . Figure 1 In the figure, BD-3 refers to black diamond 3. Ar always flows at 50 sccm, etching gas always flows at 20 sccm, and the amount of oxygen (O2) (sccm) is changed. When the amount of oxygen exceeds 20% of the total (x+y) of etching gas (x) and oxygen (y), etching of ACL is started.

[0080] The etching rate of SiO2 in the etching gas (C4F8S) of the embodiment increases sharply as the O2 ratio increases, and the etching rate of SiO2 reaches the maximum (approximately 80nm / minute) when the O2 ratio is around 25%, but the etching rate of SiO2 in the comparative example (C4F8) also shows the same behavior. In addition, there is no difference in the etching rate values ​​between the etching gas (C4F8S) of the embodiment and the etching gas (C4F8) of the comparative example, but the etching rates of SiN, BD-3, SiON, SiCN, and SiOCN increase slightly as the O2 ratio increases, and when the O2 ratio exceeds 20%, the etching rate shows the same behavior of starting to increase sharply.

[0081] For the results obtained in the examples and comparative examples, the etching rate ratios of SiO2 / BD-3, SiO2 / SiON, SiO2 / SiCN, and SiO2 / SiOCN were calculated and summarized as follows: Figure 2 .Depend on Figure 2 It can be seen that in both the examples and the comparative examples, the etching rate ratio is large when the O2 ratio is 20%, but the etching rate ratio becomes small when the O2 ratio is 33%.

[0082] For the results obtained in the examples and comparative examples, the etching rate ratios of SiO2 / ACL, SiN / ACL, polysilicon (Poly-Si) / ACL, BD-3 / ACL, SiON / ACL, SiCN / ACL, and SiOCN / ACL at an O2 ratio of 33% were calculated and summarized as follows: Figure 3 .Depend on Figure 3 It can be seen that the etching gas of the example has a larger etching rate ratio with respect to ACL for all materials than the etching gas of the comparative example.

[0083] From the above results, it can be seen that there is a significant difference in etching behavior between the embodiment of the present invention using an etching gas containing sulfur and the comparative example using an existing etching gas that does not contain sulfur. That is, it can be considered that the selectivity between SiO2 and low-k materials (SiON, SiCN, SiOCN, SiOC) of the new etching gas of the present invention is as large as that of the existing etching gas, but in the present invention, by using a new compound containing sulfur, the etching rate of ACL does not increase even if the O2 ratio increases, so the etching selectivity between ACL and low-k materials is greater than that of the existing etching gas. In addition, by combining the etching gas of the present invention with the existing etching gas, the difference in etching rate between ACL and low-k materials can be changed, and more precise etching can be performed.

Claims

1. A dry etching method, comprising the following steps: using a dry etching gas composition containing a saturated and cyclic sulfur-containing fluorocarbon represented by the general formula (1): CxFySz, to perform plasma etching on a stacked structure containing SiO2 and at least one selected from SiOC, SiCN, SiOCN, SiON and amorphous carbon, and selectively etching SiO2, wherein x, y and z are 2≤x≤5, y≤2x, 1≤z≤2, in, The sulfur-containing fluorocarbon compound is 2,2,3,3,4,4,5,5-octafluorotetrahydrothiophene, The dry etching gas composition includes an oxygen-containing compound in addition to the sulfur-containing fluorocarbon compound. The oxygen-containing compound is at least one selected from the group consisting of O2, O3, CO, CO2, NO, NO2, SO2 and SO3, The ratio of the oxygen-containing compound to the total amount of the sulfur-containing fluorocarbon compound and the oxygen-containing compound is 20 to 33%.

2. The dry etching method according to claim 1, wherein: The dry etching gas composition is converted into plasma so as to generate ions or active species containing S, and etching is performed.

3. The dry etching method according to claim 1 or 2, wherein: The dry etching gas composition includes, in addition to the sulfur-containing fluorocarbon, at least one inert gas selected from the group consisting of N2, He, Ar, Ne and Xe.

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