Dry etching method, dry etching agent, and storage container thereof

Abstract

A dry etching method according to an embodiment of the present disclosure includes a step of generating plasma from a dry etching agent, and a step of etching silicon oxide or silicon nitride using the plasma gas, wherein the dry etching agent contains CF3I and a fluorine-containing linear nitrile compound having 2 or 3 carbon atoms, and the concentration of the fluorine-containing linear nitrile compound relative to CF3I is 1 volume ppm or more and 1 volume % or less.

Description

[Technology Field]

[0001] This disclosure relates to a method for plasma etching silicon-based materials, a dry etching agent used therein, and a storage container for the same.

[0002] In recent years, advancements in semiconductor processing have focused on miniaturization, resulting in thinner processing lines and a dramatic increase in the aspect ratio, which is the ratio of the processing line width to the depth of the trench or hole. Along with these advancements in semiconductor processing technology, development of etching agents used in the etching process is also progressing.

[0003] In this etching process, plasma etching equipment is widely used, and the processing gas is required to highly selectively etch only SiO2 or SiN films from PR films and aC films, for example with a selectivity ratio of 3.0 or higher, and at high speed, for example, with an SiO2 etching rate of 50 nm / min or higher.

[0004] Conventionally, fluorine-containing saturated hydrocarbons such as CF4 gas, c-C4F8 gas, and C4F6 gas, or fluorine-containing unsaturated hydrocarbons, have been known as such etching gases. However, with conventional gases, the selectivity ratio is insufficient, resulting in problems such as the inability to maintain linearity in the etched shape during processing and the inability to obtain a sufficient etching rate, making it difficult to cope with recent miniaturization technologies.

[0005] Furthermore, these fluorine-containing saturated hydrocarbons are substances with long atmospheric lifetimes and high global warming potential (GWP), making them regulated emissions under the Kyoto Protocol (COP3). The semiconductor industry has sought low-GWP alternatives that are economically viable and allow for miniaturization.

[0006] As a gas that satisfies these requirements, for example, Patent Document 1 discloses an etching method using CF3I as a method for generating a desired amount of desired radical ions when performing high aspect ratio etching. Furthermore, Patent Document 2 discloses that CF3I has a higher etching selectivity ratio between the resist layer and the silicon-containing layer (organosilicon oxide layer, etc.) compared to CF4.

[0007] Furthermore, Patent Document 3 discloses a method for producing CF3I, characterized by reacting a predetermined iodine source with a reactant of formula CF3R in the presence of a metal salt catalyst. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 11-340211 [Patent Document 2] Japanese Patent Publication No. 2009-123866 [Patent Document 3] Japanese Patent Publication No. 2008-523089 (International Publication No. 2006 / 063184) [Overview of the project]

[0009] Typically, when storing liquefied high-pressure gases such as CF3I, metal containers and metal valves are commonly used. CF3I is known as a stable compound, and in many cases, materials such as stainless steel, carbon steel, brass, and manganese steel are used for containers and valves due to their cost advantages. However, when the inventors filled manganese steel cylinders with high-purity CF3I, which had been purified to over 99.99% by volume, and actually used it as an etching gas, they obtained the expected results regarding etching rate and etching shape, but found that metal contamination occurred on the wafer.

[0010] In the development of etching gases, in addition to improving the etching shape and selectivity with the mask, it is necessary to minimize the amount of metal contamination generated on the wafer, even if it is not possible to eliminate it completely in the semiconductor manufacturing process, as it affects semiconductor properties. On the other hand, Patent Documents 1 to 3 do not contain any descriptions regarding the purity or impurities of CF3I or metal contamination on the wafer.

[0011] Given this background, there was a need for a method to reduce metal contamination during etching using CF3I without affecting the etching characteristics.

[0012] Against this backdrop, the inventors investigated the cause of metal contamination and found that the storage container in which CF3I was filled after high-purity processing was the culprit. It was discovered that contact with manganese steel and stainless steel caused trace amounts of metal components to be mixed into CF3I as fluoride or iodide. As a result of diligent research, the inventors found that by adding a predetermined amount of a fluorine-containing linear nitrile compound with 2 or 3 carbon atoms having a C≡N bond to CF3I, metal contamination from the storage container into CF3I could be suppressed. Furthermore, etching using this mixed gas also exhibited sufficient selectivity between PR and SiO2, resulting in a good etching shape. This led to the completion of this disclosure.

[0013] In other words, the present disclosure provides a dry etching method comprising the steps of plasmaizing a dry etching agent and etching a silicon oxide or silicon nitride using the plasmaized dry etching agent, wherein the dry etching agent contains CF3I and a fluorine-containing linear nitrile compound having 2 or 3 carbon atoms, with the concentration of the fluorine-containing linear nitrile compound relative to CF3I being 1 volume ppm or more and 1 volume percent or less. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram of the storage test container 10 used in the examples and comparative examples. [Figure 2] This is a schematic diagram of the reaction apparatus 20 used in the examples and comparative examples. [Modes for carrying out the invention]

[0015] The embodiments of this disclosure are described below. However, the scope of this disclosure is not limited to these descriptions, and other embodiments may be modified and implemented as appropriate, provided that the intent of this disclosure is not impaired, in addition to the examples given below.

[0016] The dry etching method according to this embodiment comprises the steps of: plasma-forming a dry etching agent; and etching a silicon oxide or silicon nitride using the plasma-formed dry etching agent. The dry etching agent contains at least CF3I and a fluorine-containing linear nitrile compound having 2 or 3 carbon atoms and a C≡N bond.

[0017] The CF3I used in this embodiment is also called trifluoroiodomethane or trifluoroiodide methyl and can be produced by conventionally known methods. For example, according to Patent Document 4, it can be obtained by reacting an iodine source selected from the group consisting of hydrogen iodide, iodine, and iodine monochloride with a reactant selected from the group consisting of reactants of formula: CF3R [wherein R is selected from the group consisting of -SH, -SS-CF3, -S-phenyl, and -SS-(CH3)3] in the presence of a metal salt catalyst.

[0018] Examples of fluorine-containing linear nitrile compounds with 2 or 3 carbon atoms used in this embodiment include CH2FC≡N, CHF2C≡N, CF3C≡N, CH2FCF2C≡N, CHF2CF2C≡N, and CF3CF2C≡N. Among these, CF3C≡N and CF3CF2C≡N are preferred. When the amount added is 1 volume ppm or more relative to CF3I, a sufficient effect in suppressing the occurrence of metal contamination was observed.

[0019] On the other hand, when paying attention to the influence on etching characteristics, in the description of Patent Document 1, although it is suggested that trace impurities in CF3I may affect as a source of radical species other than the target, it is found that they do not have a significant impact on etching characteristics. However, since too many impurities affect the etching performance of CF3I, it is preferably within 1% by volume (10,000 ppm by volume), and more preferably 0.1% by volume (1,000 ppm by volume) or less. As another form of the present disclosure, it is assumed that a fluorine-containing linear nitrile compound having 2 or 3 carbon atoms is enclosed in a container in advance, and passivation treatment is performed on the inner surface of the container.

[0020] Silicon oxide is SiO x (where x is 1 or more and 2 or less), and is usually SiO2. Also, silicon nitride is SiN x (where x is 0.3 or more and 9 or less), and is usually Si3N4.

[0021] As a storage container for CF3I, as long as it is a sealed container that can enclose a gas-liquid mixture at atmospheric pressure or higher, it does not require a special structure and constituent material, and can have a wide range of forms and functions. The present disclosure can be applied when using cylinders made of manganese steel or stainless steel, which are common storage containers for high-pressure gases.

[0022] Manganese steel preferably contains 97% by mass or more of iron and 1% by mass or more and 2% by mass or less of manganese. Even when nickel or chromium is inevitably mixed into manganese steel, the nickel content is preferably 0.25% by mass or less, and the chromium content is preferably 0.35% by mass or less. As manganese steel, for example, SMn420, SMn433, SMn438, SMn443 defined in JIS G 4053:2016, STH11, STH12 defined in JIS G 3429:2013, etc. can be used.

[0023] In this embodiment, it is preferable that the CF3I used is highly purified to 99.95% by volume or more. For the fluorine-containing straight-chain nitrile compound having 2 or 3 carbon atoms, since a predetermined amount may be contained, there is no problem as long as the purity is 90% by volume or more.

[0024] Next, an etching method using the dry etching agent in this embodiment will be described.

[0025] The preferable composition ratios of the mixed gas of CF3I and the fluorine-containing straight-chain nitrile compound, or the dry etching agent obtained by adding an additive gas and / or an inert gas to this mixed gas are shown below. The total of the volume % of various gases is 100% by volume.

[0026] It is also possible to use only the mixed gas of CF3I and the fluorine-containing straight-chain nitrile compound as the dry etching agent, but usually, from the viewpoints of cost effectiveness and plasma stability, it is used in combination with an additive gas and / or an inert gas. For example, the concentration of the mixed gas of CF3I and the fluorine-containing straight-chain nitrile compound with respect to the total of the mixed gas, the additive gas, and the inert gas is preferably 1 to 90% by volume, more preferably 5 to 80% by volume, and still more preferably 10 to 60% by volume.

[0027] Also, the concentration of the additive gas with respect to the total of the mixed gas, the additive gas, and the inert gas is preferably 0 to 50% by volume, more preferably 0 to 10% by volume.

[0028] Also, the concentration of the inert gas with respect to the total of the mixed gas, the additive gas, and the inert gas is preferably 0 to 98% by volume, more preferably 5 to 80% by volume, and still more preferably 30 to 50% by volume.

[0029] The etching method of this embodiment can be carried out under various dry etching conditions. Furthermore, various additives and inert gases can be added, for example, by mixing them with additive gases and inert gases to achieve the desired etching rate, etching selectivity ratio, and etching shape. Examples of additive gases include O2, O3, CO, CO2, COCl2, COF2, CF2(OF)2, CF3OF, NO2, NO, F2, NF3, Cl2, Br2, and I. 2、 and YF n At least one gas selected from the group consisting of (wherein Y is Cl, Br, or I, and n is an integer, 1 ≤ n ≤ 7) can be used. In addition, to obtain the desired etching shape and etching rate, one or more reducing gases, fluorocarbons, hydrofluorocarbons, and halogen-containing compounds (e.g., H2, HF, HI, HBr, HCl, NH3, CF4, CF3H, CF2H2, CFH3, C2F6, C2F4H2, C2F5H, C3F8, C3F7H, C3F6H2, C3F5H3, C3F4H4, C3F3H5, C3F5H, C3F3H, C3ClF3H, C4F8, C4F6, C5F8, C5F 10 Etching may be performed by adding at least one gas selected from the group consisting of C3F6, C3HF5, C3H2F4, and C3H3F3 as an additive gas. Examples of inert gases include N2, He, Ar, Ne, Kr, and Xe.

[0030] The etching method of this embodiment is not limited to various etching methods such as capacitively coupled plasma (CCP) etching, reactive ion etching (RIE), inductively coupled plasma (ICP) etching, electron cyclotron resonance (ECR) plasma etching, and microwave etching, and can be performed in any manner.

[0031] The gas components contained in the dry etching agent may be introduced into the chamber independently, or they may be prepared as a mixed gas beforehand downstream of the storage container before being introduced into the chamber. The total flow rate of the dry etching agent introduced into the reaction chamber can be appropriately selected considering the concentration and pressure conditions, based on the volume of the reaction chamber and the exhaust capacity of the exhaust section.

[0032] The pressure used during etching is preferably 5 Pa or less, and particularly preferably 1 Pa or less, in order to obtain a stable plasma and to suppress side etching by increasing the straightness of ions. On the other hand, if the pressure inside the chamber is too low, the number of ionized ions will decrease and a sufficient plasma density cannot be obtained, so it is preferable that the pressure be 0.05 Pa or higher.

[0033] Furthermore, the substrate temperature during etching is preferably 100°C or lower, and in particular, for anisotropic etching, it is desirable to keep it below 50°C, and especially preferably below 20°C. At temperatures exceeding 100°C, fluorocarbon-derived CF may be produced on mask materials such as PR or aC. n The protective film, which is mainly composed of [unspecified material], may not form sufficiently, resulting in reduced selectivity. Furthermore, at high temperatures, the protective film on the sidewalls may not form sufficiently, leading to a shape anomaly known as bowing, where the etched shape becomes rounded.

[0034] Furthermore, the negative DC self-bias voltage generated between electrodes during etching should be selected according to the desired etching shape. For example, when performing anisotropic etching, it is desirable to generate an electrode voltage of approximately 500V to 10000V in absolute value to increase the energy of the ions. If the absolute value of the negative DC self-bias voltage is too large, it can amplify the energy of the ions and lead to a decrease in selectivity.

[0035] The etching time is preferably within 200 minutes, taking into account the efficiency of the device manufacturing process. Here, etching time refers to the time during which plasma is generated in the chamber and the dry etching agent reacts with the sample. [Examples]

[0036] Examples of the present disclosure are listed below, along with comparative examples, but the present disclosure is not limited to these examples.

[0037] [Example 1] (Store in a storage container) Figure 1 is a schematic diagram of the 10 storage containers used in the examples and comparative examples to temporarily store purified CF3I. A manganese steel pressure vessel 10 with an internal volume of 10 L was prepared as the storage container. 1000 g of CF3I, which had been pre-purified to a high purity of 99.99% or more by volume, was sealed inside. Next, CF3C≡N was added to the CF3I at a concentration of 2 volumes ppm.

[0038] (Etching test) To investigate the effect of additives on etching characteristics, etching tests were conducted using a mixed gas of CF3I and CF3C≡N. Figure 2 is a schematic diagram of the reaction apparatus 20 used in the examples and comparative examples. Inside the chamber 21 are a lower electrode 24 that holds the wafer and also functions as a stage, an upper electrode 25, and a pressure gauge 22. A gas inlet 26 is connected to the top of the chamber 21. The pressure inside the chamber 21 can be adjusted, and the dry etching agent can be excited by a high-frequency power supply (13.56 MHz) 23. This allows the excited dry etching agent to come into contact with the sample 28 placed on the lower electrode 24, and the sample 28 can be etched. When high-frequency power is applied from the high-frequency power supply 23 with the dry etching agent introduced, a DC voltage called a self-bias voltage can be generated between the upper electrode 25 and the lower electrode 24 due to the difference in the migration speed of ions and electrons in the plasma. The gas inside the chamber 21 is discharged via the gas discharge line 27.

[0039] As samples 28, a silicon wafer A having a SiO2 film, a silicon wafer B having a SiN (Si3N4) film, and a silicon wafer C having a PR (photoresist) film were placed on a stage cooled to 15°C. The SiO2 film and the SiN film were fabricated by the CVD method. Also, the PR film was fabricated by coating. Here, as an etching agent, a mixture of CF3I and CF3C≡N, O2, and Ar were set at 25 sccm, 25 sccm, and 500 sccm, respectively, and these gases were sufficiently mixed and circulated in the chamber, and high-frequency power was applied at 400 W to plasmaize the etching agent, thereby performing etching.

[0040] After etching, the etching rate was determined from the change in thickness of the SiO2 film of silicon wafer A, the SiN film of silicon wafer B, and the PR film of silicon wafer C before and after etching. Further, the value obtained by dividing the etching rate of SiO2 and SiN by the etching rate of PR was determined as the etching selectivity for each.

[0041] (Measurement of the amount of metal on the wafer) Next, the amount of metal adhering to a silicon wafer A having a SiO2 film was measured. In the measurement, the method specified in JIS K0160:2009 was used. That is, hydrofluoric acid was placed in a plastic beaker and placed in a container made of PFA (perfluoroalkoxy fluororesin) called a VPD (vapor phase decomposition) container, and the SiO2 film-formed wafer after etching was placed on a wafer stand installed in the VPD container. Next, the VPD container was closed, and the oxide film on the wafer was decomposed with hydrofluoric acid vapor for 10 minutes. 100 μL of a scanning solution (ultrapure water) was dropped onto the surface of the wafer after decomposing the oxide, and the entire surface of the wafer was scanned. After scanning, the entire scanned droplet was dried, dissolved again in ultrapure water, and then analyzed by ICP-MS (inductively coupled plasma mass spectrometer). The obtained analytical value was converted to the number of metal atoms per 1 cm of the wafer from the volume of the dissolution solution and the surface area of the wafer. As a result, the analytical value of iron was 6.5×10 2 atms / cm 11 atms / cm 2 and that was the result.

[0042] (Etching shape evaluation) After performing the etching tests described above, wafers A to C were removed, and wafer D, for etching shape evaluation, was placed on the stage. Wafer D was obtained by depositing a 200 nm thick SiO2 film on a silicon wafer, followed by coating it with a 300 nm thick photoresist film having circular, hole-like openings with a diameter of 100 nm. After etching for 5 minutes using the method described in the etching test section, a cross-sectional SEM image was taken, and the etching shape was observed. As a result, it was confirmed that etching was performed without etching shape abnormalities such as shoulder drop or bowing.

[0043] [Example 2] A storage test sample was prepared under the same conditions as in Example 1, except that CF3I with a CF3C≡N content of 25 volume ppm, obtained by adding CF3C≡N to CF3I, was used. The etching test was also performed in the same manner as in Example 1. The etching shape was also evaluated in the same manner as in Example 1, and it was confirmed that etching was performed without etching shape abnormalities such as shoulder drop or bowing.

[0044] [Example 3] A storage test sample was prepared under the same conditions as in Example 1, except that CF3I with a CF3C≡N content of 129 volume ppm, obtained by adding CF3C≡N to CF3I, was used. The etching test was also performed in the same manner as in Example 1. The etching shape was also evaluated in the same manner as in Example 1, and it was confirmed that etching was performed without etching shape abnormalities such as shoulder drop or bowing.

[0045] [Example 4] A storage test sample was prepared under the same conditions as in Example 1, except that CF3I with a CF3C≡N content of 1231 volume ppm (approximately 0.1 volume%), obtained by adding CF3C≡N to CF3I, was used. The etching test was also performed in the same manner as in Example 1. The etching shape was also evaluated in the same manner as in Example 1, and it was confirmed that etching was performed without etching shape abnormalities such as shoulder drop or bowing.

[0046] [Example 5] A storage test sample was prepared under the same conditions as in Example 1, except that CF3I with a CF3C≡N content of 7927 volume ppm (approximately 0.8 volume%), obtained by adding CF3C≡N to CF3I, was used. The etching test was also performed in the same manner as in Example 1. The etching shape was also evaluated in the same manner as in Example 1, and it was confirmed that etching was performed without etching shape abnormalities such as shoulder drop or bowing.

[0047] [Example 6] A storage test sample was prepared under the same conditions as in Example 1, except that CF3I with a CF3C≡N content of 9328 volume ppm (approximately 0.9 volume%), obtained by adding CF3C≡N to CF3I, was used. The etching test was also performed in the same manner as in Example 1. The etching shape was also evaluated in the same manner as in Example 1, and it was confirmed that etching was performed without etching shape abnormalities such as shoulder drop or bowing.

[0048] [Example 7] A storage test sample was prepared under the same conditions as in Example 1, except that CF3I with a CF3CF2C≡N content of 235 volume ppm, obtained by adding CF3CF2C≡N to CF3I, was used. The etching test was also performed in the same manner as in Example 1. The etching shape was also evaluated in the same manner as in Example 1, and it was confirmed that etching was performed without etching shape abnormalities such as shoulder drop or bowing.

[0049] [Comparative Example 1] Storage test samples were prepared under the same conditions as in Example 1, except that CF3I with a CF3C≡N content of less than 0.1 volume ppm, obtained by purification, was used. The etching test was also performed in the same manner as in Example 1. The etching shape was also evaluated in the same manner as in Example 1, and it was confirmed that etching was performed without etching shape abnormalities such as shoulder drop or bowing.

[0050] [Comparative Example 2] Storage test samples were prepared under the same conditions as in Example 1, except that CF3I with a CF3C≡N content of 25936 volume ppm (approximately 2.6 volume%), obtained by adding CF3C≡N to CF3I, was used. The etching test was also performed in the same manner as in Example 1. The etching shape was evaluated in the same manner as in Example 1, and there were no etching shape abnormalities such as shoulder drop or bowing, but the amount of photoresist etched was greater than in Examples 1 to 6 due to the decrease in the SiO2 / PR selectivity ratio.

[0051] [Comparative Example 3] Storage test samples were prepared under the same conditions as in Example 1, except that CF3I with a CF3C≡N content of 111608 volume ppm (approximately 11 volume%), obtained by adding CF3C≡N to CF3I, was used. Etching tests were also performed in the same manner as in Example 1. When the etching shape was evaluated in the same manner as in Example 1, there was no bowing, but as the SiO2 / PR selectivity ratio decreased, the amount of photoresist etched increased significantly compared to Examples 1 to 6, and shoulder drop was observed in some patterns.

[0052] [Comparative Example 4] The test was conducted under the same conditions as in Example 1, except that CF3I containing 28 volume ppm of CF3C≡CH was used instead of CF3C≡N. The etching test was also performed in the same manner as in Example 1. The etching shape was also evaluated in the same manner as in Example 1, and it was confirmed that etching was performed without any etching shape abnormalities such as shoulder drop or bowing.

[0053] [Comparative Example 5] The test was conducted under the same conditions as in Example 1, except that CF3I containing 8523 volume ppm of fluorine-free CH3C≡N was used instead of CF3C≡N. The etching test was also performed in the same manner as in Example 1. The etching shape was evaluated in the same manner as in Example 1, and there were no etching shape abnormalities such as shoulder drop or bowing, but the amount of photoresist etched was greater than in Examples 1 to 6 due to the decrease in the SiO2 / PR selectivity ratio.

[0054] The results above are summarized in Table 1. [Table 1]

[0055] In Comparative Examples 1 and 4, although the etching characteristics were good, iron components were detected on the wafer. This is thought to be because the contamination of the wafer by iron components by the fluorine-containing linear nitrile compound with 2 or 3 carbon atoms was not suppressed. On the other hand, as shown in the results of Examples 1 to 7, CF3I containing CF3C≡N or CF3CF2C≡N showed very little iron contamination. Although there are some unclear points regarding the process by which corrosion of the storage container was suppressed, possible explanations include the fluorine-containing linear nitrile compound forming a passivation film on the inner surface of the storage container to prevent the elution of iron components from the storage container, the fluorine-containing linear nitrile compound significantly lowering the vapor pressure of substances that are sources of iron contamination contained in CF3I, and the fluorine-containing linear nitrile compound suppressing the adhesion of iron components to the wafer.

[0056] However, when a fluorine-containing linear nitrile compound was added to CF3I, the etching selectivity ratio of SiO2 to SiN relative to PR changed depending on the content. In each example, the selectivity ratio of PR to SiO2 (SiO2 / PR) was sufficient, and in particular, Examples 1 to 7, in which the content of the fluorine-containing linear nitrile compound was 10,000 volume ppm (1 volume%) or less, showed a good SiO2 / PR etching selectivity ratio of over 3. Furthermore, no abnormalities in the etching shape occurred during hole pattern etching. Therefore, it can be said that good etching characteristics were obtained when using CF3I containing a fluorine-containing linear nitrile compound in an amount of 1 volume ppm to 10,000 volume ppm.

[0057] On the other hand, as shown in Comparative Examples 2 and 3, when CF3C≡N was included in concentrations exceeding 10,000 ppm by volume, a significant decrease in the etching selectivity ratio of SiO2 / PR was observed. In pattern etching, the amount of etching in the resist portion increased noticeably, and in Comparative Example 3, the surface of the SiO2 film was even etched, resulting in a significant deterioration in the performance as an etching gas.

[0058] If a large amount of CF3C≡N is mixed in, the aforementioned CF n In the formation of a protective film mainly composed of CF, the nitrogen in the molecule is CF n It acts as an inhibitor of film polymerization, resulting in insufficient protective film formation. Therefore, it is thought that CF3C≡N promotes etching of the mask, leading to a decrease in selectivity. This phenomenon is thought to occur similarly when other fluorine-containing linear nitrile compounds are used.

[0059] On the other hand, in Comparative Example 4, the effects of additives other than CF3C≡N were investigated. As a result, CF3C≡CH did not exhibit the effect of preventing iron contamination that was observed with CF3C≡N.

[0060] On the other hand, in Comparative Example 5, the effect of fluorine-free additives other than CF3C≡N was investigated. As a result, in CH3C≡N, the absence of fluorine resulted in CF n The etching selectivity ratio of SiO2 / PR deteriorated, possibly due to insufficient formation of a protective film primarily composed of film. Furthermore, its effectiveness in preventing iron contamination was also smaller compared to CF3C≡N.

[0061] As described above, according to this disclosure, it is possible to reduce the amount of metal contamination in etching using CF3I without affecting the etching characteristics. [Explanation of symbols]

[0062] 10: Storage test container 11: Test piece 12: Valve 13: Lid 14: Pressure vessel 20: Reactor 21: Chamber 22: Pressure gauge 23: High frequency power supply 24: Lower electrode 25: Upper electrode 26: Gas inlet 27: Gas discharge line 28: Sample

Claims

1. a step of generating plasma from the dry etching agent; and etching silicon oxide or silicon nitride using a plasma-converted dry etching agent, A dry etching method, wherein the dry etching agent contains CF3I and a fluorine-containing straight-chain nitrile compound having 2 or 3 carbon atoms, the concentration of the fluorine-containing straight-chain nitrile compound relative to CF3I being 1 volume ppm or more and 1 volume % or less.

2. 2. The dry etching method according to claim 1, wherein the fluorine-containing linear nitrile compound having 2 or 3 carbon atoms is CF3C≡N or CF3CF2C≡N.

3. the etchant includes an additive gas; The additive gas is O2, O3, CO, CO2, COCl2, COF2, CF2(OF)2, CF3OF, NO2, NO, F2, NF3, Cl2, Br2, I2, and YF n 3. The dry etching method according to claim 1, wherein the gas is at least one gas selected from the group consisting of (wherein Y represents Cl, Br, or I, and n represents an integer, 1≦n≦7).

4. the etchant includes an additive gas; The additive gas is H2, HF, HI, HBr, HCl, NH3, CF4, CF3H, CF2H2, CFH3, C2F6, C2F4H2, C2F5H, C3F8, C3F7H, C3F6H2, C3F5H3, C3F4H4, C3F3H5, C3F5H, C3F3H, C3ClF3H, C4F8, C4F6, C5F8, C5F 10 4. The dry etching method according to claim 1, wherein the gas is at least one selected from the group consisting of C3F6, C3HF5, C3H2F4, and C3H3F3.

5. Furthermore, the dry etching agent contains an inert gas, 5. The dry etching method according to claim 1, wherein the inert gas is selected from the group consisting of N2, He, Ar, Ne, Kr, and Xe.

6. A dry etching agent comprising CF3I and a fluorine-containing, straight-chain nitrile compound having 2 or 3 carbon atoms, the concentration of the fluorine-containing, straight-chain nitrile compound relative to CF3I being 1 ppm by volume or more and 1% by volume or less.

7. A storage container filled with the dry etching agent according to claim 6 and sealed.

8. A storage container filled with and sealed with a mixture containing CF3I and a fluorine-containing linear nitrile compound having 2 or 3 carbon atoms, the concentration of the fluorine-containing linear nitrile compound relative to CF3I being 1 volume ppm or more and 1 volume % or less.

9. 9. The storage container according to claim 7, wherein the storage container is made of manganese steel or stainless steel.

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