Dry etching method for carbon atom-containing film

Abstract

To provide a dry etching method for a carbon atom-containing film, with which a carbon atom-containing film can be etched easily at a high etching rate.SOLUTION: A dry etching method for a carbon atom-containing film includes: a mixed gas introduction step of introducing a mixed gas containing oxygen and a sulfur compound into an etching chamber in which a structure provided with a carbon atom-containing film is disposed; and an etching step of turning the mixed gas into plasma within the etching chamber and using the plasma gas as an etching gas to etch the carbon atom-containing film of the structure. In the etching step, the plasma gas is generated such that the analysis result from emission spectral analysis of the plasma gas satisfies at least one of the following requirements (A), (B) and (C). (A) A maximum intensity ratio R1 is 0.52 or higher. (B) A maximum intensity ratio R2 is 0.12 or higher. (C) A maximum intensity ratio R3 is 0.48 or higher.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for dry etching a carbon atom-containing film. [Background technology]

[0002] In semiconductor integrated circuits, elements are becoming increasingly miniaturized and stacked. In the manufacture of semiconductor integrated circuits, there is a demand for technology that uses masks such as photoresist to pattern carbon-containing films to be etched, allowing for the high-precision, high-speed processing of deep holes and trenches with small openings and large aspect ratios in the films to be etched. As a technique for this purpose, for example, Patent Document 1 discloses a method of etching a carbonaceous layer with plasma of an etchant gas mixture containing oxygen and a gas containing a carbon-sulfur terminal ligand. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-200459 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the method described in Patent Document 1 has the following problems. That is, in the above method, it is necessary to repeatedly carry out etching and observe using an electron microscope (SEM) in order to set etching conditions at a high etching rate, and there is room for improvement in terms of easily carrying out etching at a high etching rate.

[0005] The present disclosure has been made in view of the above-mentioned problems, and has an object to provide a dry etching method for a carbon-atom-containing film that can easily etch the carbon-atom-containing film at a high etching rate. [Means for solving the problem]

[0006] The inventors of the present disclosure conducted extensive research to solve the above-mentioned problems. First, the inventors of the present disclosure considered that, in a plasma gas used as an etching gas, ions or radicals derived from oxygen atoms accelerate etching, while ions or radicals derived from S atoms and C atoms slow etching, i.e., promote the deposition of S atoms and C atoms. Therefore, in order to increase the etching rate of a carbon-containing film, it was thought that the ratio of ions or radicals derived from oxygen atoms to ions or radicals derived from S atoms and C atoms could be increased to a certain value or greater. Therefore, the inventors of the present disclosure first focused on the analysis results (optical emission spectroscopy (OES) charts) obtained by performing optical emission spectroscopy on a plasma gas containing a mixture of oxygen and carbonyl sulfide or sulfur dioxide (see FIG. 1). In FIG. 1, the upper optical emission spectroscopy chart is a chart obtained when the concentration of SO in the mixed gas is 30% by volume, and the lower optical emission spectroscopy chart is a chart obtained when the concentration of COS in the mixed gas is 30% by volume. These emission spectroscopy charts show a sharp emission peak near a wavelength of 257 nm, two broad emission peaks near 300 nm and 500 nm, and an emission peak derived from oxygen atoms near 777 nm. Based on these wavelengths, the emission peak near 257 nm is thought to correspond to CS and S, the emission peak near 300 nm to SO, and the peak near 500 nm to CO and S2. Furthermore, it was found that although the absolute values ​​of these emission peak intensities depend on the observation conditions, the intensity ratio between the emission peak intensities is less dependent on the observation conditions. As a result of further intensive research, the inventors of the present disclosure have found that the etching rate increases when the emission peak intensity at 777 nm, derived from oxygen atoms, is equal to or greater than a certain value relative to the emission peak intensities at 257 nm, 300 nm, and 500 nm, respectively, and decreases when these values ​​are lower. In other words, it has been found that the conditions for increasing the etching rate can be easily found by simply observing the results of emission spectroscopy of the plasma gas, without the need to use a sample wafer for observation using a scanning electron microscope (SEM), etc. Furthermore, since each emission peak has a width, it was considered appropriate to specify the position of the emission peak around 257 nm in the wavelength range of 250-260 nm, the position of the emission peak around 300 nm in the wavelength range of 280-350 nm, the position of the emission peak around 500 nm in the wavelength range of 470-600 nm, and the position of the emission peak around 777 nm in the wavelength range of 770-780 nm. Thus, the inventors of the present disclosure have found that the above-mentioned problems can be solved by the present disclosure below.

[0007] That is, one aspect of the present disclosure provides a dry etching method for a carbon-atom-containing film, in which the carbon-atom-containing film containing carbon atoms is etched with an etching gas, the method including: a mixed gas introduction step of introducing a mixed gas containing at least oxygen and a sulfur compound into an etching chamber in which a structure including the carbon-atom-containing film is disposed; and an etching step of converting the mixed gas into plasma in the etching chamber to generate a plasma gas, and etching the carbon-atom-containing film of the structure using the plasma gas as the etching gas, wherein in the etching step, the plasma gas is generated so that an analysis result of the plasma gas by optical emission spectroscopy satisfies at least one of the following requirements (A), (B), and (C): (A) The maximum intensity ratio R1 of the maximum emission intensity in the wavelength range of 770-780 nm to the maximum emission intensity in the wavelength range of 250-260 nm is 0.52 or more. (B) The maximum intensity ratio R2 of the maximum emission intensity in the wavelength range of 770-780 nm to the maximum emission intensity in the wavelength range of 280-350 nm is 0.12 or more. (C) The maximum intensity ratio R3 of the maximum emission intensity in the wavelength range of 770-780 nm to the maximum emission intensity in the wavelength range of 470-600 nm is 0.48 or more.

[0008] According to the above-described dry etching method for a carbon atom-containing film, etching of the carbon atom-containing film can be easily carried out at a high etching rate.

[0009] In the etching step, the plasma gas may be generated so that the analysis result of the plasma gas by optical emission spectroscopy satisfies at least two of the requirements (A), (B) and (C) above.

[0010] In the etching step, the plasma gas may be generated so that the analysis result of the plasma gas by optical emission spectroscopy satisfies all of the requirements (A), (B), and (C) above.

[0011] The sulfur compound may be sulfur dioxide or carbonyl sulfide. [Effects of the Invention]

[0012] According to the present disclosure, there is provided a dry etching method for a carbon-atom-containing film, which can easily etch a carbon-atom-containing film at a high etching rate. [Brief explanation of the drawings]

[0013] [Figure 1] 1 shows an optical emission spectroscopic analysis chart obtained by performing optical emission spectroscopic analysis on a plasma gas mixture of oxygen and either carbonyl sulfide or sulfur dioxide (concentration of carbonyl sulfide or sulfur dioxide: 30% by volume). [Figure 2] FIG. 1 is a cross-sectional view showing an example of a structure before an etching step in the dry etching method for a carbon-atom-containing film disclosed herein. [Figure 3] FIG. 1 is a cross-sectional view showing an example of a structure after an etching step in the dry etching method for a carbon-atom-containing film disclosed herein. [Figure 4] FIG. 4 is a partial enlarged view of the mask and the carbon atom-containing film in FIG. 3. [Figure 5] 1 is a graph showing the relationship between the maximum intensity ratio R1 and the etching rate (ER) in Examples 1 to 7 and Comparative Examples 1 to 6. [Figure 6] 1 is a graph showing the relationship between the maximum intensity ratio R2 and the etching rate (ER) in Examples 1 to 7 and Comparative Examples 1 to 6. [Figure 7] 1 is a graph showing the relationship between the maximum intensity ratio R3 and the etching rate (ER) in Examples 1 to 7 and Comparative Examples 1 to 6. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the method for dry etching a carbon-atom-containing film according to the present disclosure will be described in detail with reference to Figures 2 to 4. However, the present disclosure is not limited to the following embodiments.

[0015] FIG. 2 is a cross-sectional view showing an example of a structure before the etching step in the dry etching method for a carbon-atom-containing film according to the present disclosure, FIG. 3 is a cross-sectional view showing an example of a structure after the etching step in the dry etching method for a carbon-atom-containing film according to the present disclosure, and FIG. 4 is a partially enlarged view of the mask and the carbon-atom-containing film in FIG. 3 .

[0016] The dry etching method for a carbon-atom-containing film of the present disclosure is a dry etching method for a carbon-atom-containing film in which carbon-atom-containing film 20 containing carbon atoms is etched with an etching gas, and includes a mixed gas introduction step of introducing a mixed gas containing at least oxygen and a sulfur compound into an etching chamber in which carbon-atom-containing film 20 and structure 100 including mask 30 having first opening 31 are placed, and an etching step of converting the mixed gas into plasma in the etching chamber to generate plasma gas, and using this plasma gas to etch the carbon-atom-containing film of structure 100 to form second opening 21 (see FIGS. 2 and 3 ).

[0017] In the etching step, a plasma gas is generated so that the analysis result of the plasma gas by optical emission spectroscopy satisfies at least one of the following requirements (A), (B), and (C): (A) The maximum intensity ratio R1 of the maximum emission intensity in the wavelength range of 770-780 nm to the maximum emission intensity in the wavelength range of 250-260 nm is 0.52 or more. (B) The maximum intensity ratio R2 of the maximum emission intensity in the wavelength range of 770-780 nm to the maximum emission intensity in the wavelength range of 280-350 nm is 0.12 or more. (C) The maximum intensity ratio R3 of the maximum emission intensity in the wavelength range of 770-780 nm to the maximum emission intensity in the wavelength range of 470-600 nm is 0.48 or more.

[0018] According to the above-described dry etching method for a carbon atom-containing film, etching of the carbon atom-containing film can be easily carried out at a high etching rate.

[0019] The mixed gas introduction step and the etching step will be described in detail below.

[0020] <Mixed gas introduction process> The structure 100 includes a carbon-atom-containing film 20 that contains carbon atoms, and a mask 30 having a first opening 31. As shown in FIG. 2 , the structure 100 may further include a support 10 that supports the carbon-atom-containing film 20. In this case, the carbon-atom-containing film 20 is disposed between the mask 30 and the support 10. The structure 100 may further include an intermediate film (not shown) between the support 10 and the carbon-atom-containing film 20. Note that the structure 100 does not necessarily have to include the mask 30.

[0021] (Support) The support 10 is not particularly limited as long as it is a member that supports the carbon-atom-containing film 20, but examples of materials that constitute the support 10 include silicon and germanium. Among these, silicon is preferable. In this case, silicon has a wide band gap, which further improves durability under high pressure.

[0022] The thickness of the support 10 is not particularly limited, but may be 254 μm or more, or may be 520 μm or more. When the thickness of the support 10 is 254 μm or more, the mechanical strength is further improved. Furthermore, the thickness of the support 10 may be 795 μm or less, or may be 725 μm or less. When the thickness of the support 10 is 795 μm or less, it becomes easier to cut the structure 100 to a predetermined wafer size.

[0023] (interlayer film) Examples of intermediate layers include silica (SiO2), silicon nitride (Si3N4), amorphous silicon (a:Si), and polycrystalline silicon (poly:Si).

[0024] (carbon atom-containing film) The carbon-atom-containing film 20 is not particularly limited as long as it is a film containing carbon atoms. The carbon-atom-containing film 20 may be an inorganic carbon film such as amorphous carbon, or may be an organic polymer film such as a resist film or a polyimide film. When the carbon-atom-containing film 20 is amorphous carbon, the etching selectivity (i.e., the ratio of the etching rate Vc of the carbon-atom-containing film 20 to the etching rate Vm of the mask) can be increased when transferring a pattern to the carbon-atom-containing film 20. The amorphous carbon can be formed, for example, by a plasma CVD method or a method of applying and drying a coating liquid containing carbon.

[0025] The thickness of the carbon-atom-containing film 20 is not particularly limited, but may be 0.1 μm or more, or may be 0.5 μm or more. If the thickness of the carbon-atom-containing film 20 is 0.1 μm or more, when an insulating film is stacked as a layer to be etched below the carbon-atom-containing film 20, the carbon-atom-containing film 20 can function as a mask for the layer to be etched. Furthermore, the thickness of the carbon-atom-containing film 20 may be 10.0 μm or less, or may be 5.0 μm or less. If the thickness of the carbon-atom-containing film 20 is 10.0 μm or less, the carbon-atom-containing film 20 is less likely to collapse after etching.

[0026] (mask) The mask 30 has a first opening 31 that allows the etching gas to pass through and guide it to the carbon-atom-containing film 20. The first opening 31 may be a trench or a hole. The mask 30 is preferably etched by the etching gas at a slower rate than the carbon-atom-containing film 20, and such a mask 30 preferably contains an oxygen-containing material. In this case, the etching rate by the etching gas is lower. Examples of oxygen-containing materials include silicon dioxide and silicon oxynitride. Among these, silicon dioxide is preferred from the viewpoint of economy.

[0027] The thickness of the mask 30 is not particularly limited, and may be 0.01 times or more, or 0.05 times or more, that of the carbon-atom-containing film 20. When the thickness of the mask 30 is 0.01 times or more that of the carbon-atom-containing film 20, anisotropic etching of the carbon-atom-containing film 20 becomes possible. Furthermore, the thickness of the mask 30 may be 0.5 times or less, or 0.2 times or less that of the carbon-atom-containing film 20. When the thickness of the mask 30 is 0.5 times or less that of the carbon-atom-containing film 20, the carbon-atom-containing film 20 is less likely to collapse after etching.

[0028] (etching equipment) The etching device includes an etching chamber. The etching chamber is a container in which the carbon-atom-containing film 20 is etched with a plasma gas obtained by plasmatizing a mixed gas containing oxygen and a sulfur compound. Examples of etching devices include microwave ECR plasma etching devices, capacitively coupled plasma (CCP) etching devices, and inductively coupled plasma (ICP) etching devices, but the etching devices are not limited to these. The etching apparatus is equipped with a plasma gas emission spectrometer capable of analyzing the light emission of the plasma gas of the mixed gas generated in the etching chamber. A plasma gas emission spectrometer comprises, for example, a lens that focuses light that passes through a window installed at a location in an etching chamber where plasma emission (light in the ultraviolet and visible wavelength ranges) can be observed, an optical fiber that guides the light focused by the lens, a spectroscope that separates the light guided by the optical fiber, and a detector that detects the separated light.

[0029] (mixed gas) The mixed gas contains oxygen and a sulfur compound. Examples of sulfur compounds include carbonyl sulfide, sulfur dioxide, hydrogen sulfide, carbon disulfide, and methyl mercaptan. These compounds can be used alone or in combination of two or more. Among these, sulfur dioxide is preferred as the sulfur compound. In this case, a high etching rate can be maintained over a wide concentration range. That is, it is easy to adjust the concentration of the sulfur compound in the mixed gas in order to maintain a high etching rate.

[0030] In addition to oxygen and sulfur compounds, the mixed gas may further contain a gas containing carbon, as necessary, in order to adjust the intensity of the emission peak originating from CO and the like in the wavelength range of 470-600 nm (e.g., around 500 nm) and the intensity of the emission peak originating from CS and the like located in the wavelength range of 250-260 nm (e.g., around 257 nm).

[0031] The content of sulfur compounds in the total volume of oxygen and sulfur compounds is not particularly limited as long as it is greater than 0% by volume, but may be 20 to 40% by volume, or 25 to 35% by volume. When the content of the sulfur compound in the total volume of oxygen and the sulfur compound is in the range of 20 to 40% by volume, the etching rate for the carbon-atom-containing film 20 can be improved more effectively.

[0032] The flow rate of the mixed gas when introduced into the etching chamber may be 0.1 mL / min or more, 1 mL / min or more, or 10 mL / min or more. When the flow rate of the mixed gas is 1 mL / min or more, it is possible to efficiently generate ions and radicals necessary for etching the carbon-atom-containing film 20. The flow rate of the mixed gas when introduced into the etching chamber may be 10,000 mL / min or less, 1,000 mL / min or less, or 100 mL / min or less. When the flow rate of the mixed gas is 10,000 mL / min or less, it becomes easier to maintain the degree of vacuum of the etching apparatus at a low pressure.

[0033] <Etching process> The etching step is a step of generating plasma gas by converting a mixed gas into plasma in an etching chamber, and etching the carbon-atom-containing film 20 of the structure 100 using this plasma gas to form the second opening 21. The structure 100 becomes the structure 200 through the etching step.

[0034] (plasma gas) As described above, in the etching step, the plasma gas is generated so that the analysis result of the plasma gas by optical emission spectroscopy satisfies at least one of the above requirements (A), (B), and (C). In this case, etching of the carbon-atom-containing film can be easily improved at a higher etching rate compared to when R1 is less than 0.52, R2 is less than 0.12, or R3 is less than 0.48.

[0035] Here, from the viewpoint of further improving the etching rate for the carbon atom-containing film, it is preferable to generate a plasma gas so that the analysis result of the plasma gas by optical emission spectroscopy satisfies at least two of the above requirements (A), (B), and (C), and it is particularly preferable to generate a plasma gas so that the analysis result of the plasma gas by optical emission spectroscopy satisfies all of the above requirements (A), (B), and (C).

[0036] R1 may be 0.25 or more, 0.35 or more, or 0.45 or more, and may be 100 or less, 50 or less, or 10 or less.

[0037] R2 may be 0.08 or more, 0.09 or more, or 0.10 or more. R2 may be 50 or less, 10 or less, or 5 or less.

[0038] R3 may be 0.38 or more, 0.42 or more, or 0.46 or more, and may be 100 or less, 50 or less, or 10 or less.

[0039] (Pressure inside the etching chamber) The pressure in the etching chamber when dry etching is performed may be 0.1 mTorr to 100 mTorr, or may be 0.1 mTorr to 100 mTorr. When the pressure in the etching chamber is 0.1 mTorr to 100 mTorr, the pressure is low, and therefore excellent shape control can be achieved for second opening 21.

[0040] (antenna power) When an inductively coupled plasma (ICP) etching device is used as the etching device, the antenna power is not particularly limited, and may be 50 to 1000 W, 100 to 800 W, or 200 to 600 W. By setting the antenna power to 50 to 1000 W, the carbon-atom-containing film 20 can be etched anisotropically at high speed.

[0041] (bias power) When an inductively coupled plasma (ICP) etching device is used as the etching device, the bias power is not particularly limited, but may be 10 W or more, 25 W or more, or 50 W or more. By setting the bias power to 10 W or more, it becomes easier to increase the aspect ratio. The bias power may be equal to or less than 500 W, equal to or less than 300 W, or equal to or less than 200 W. By setting the bias power to equal to or less than 500 W, it becomes easier to appropriately control the dry etching.

[0042] (Second opening) The shape of the second opening 21 in the carbon-atom-containing film 20 after etching is the same as the shape of the first opening 31. That is, when the first opening 31 is a trench, the second opening 21 is also a trench, and when the first opening 31 is a hole, the second opening 21 is also a hole.

[0043] The aspect ratio after etching is not particularly limited, but may be 0.1-60, 1-40, 4-40, 5-40, or 5-25. When the aspect ratio is 60 or less, the etching rate of the carbon-atom-containing film 20 can be improved compared to when the carbon-atom-containing film 20 is etched with a plasma gas of a mixed gas containing oxygen and carbonyl sulfide. When a layer (underlayer) is provided on the opposite side of the carbon-atom-containing film 20 from the mask 30, when the aspect ratio is 0.1 or more, the carbon-atom-containing film 20 becomes more effective as a mask when etching the underlayer. Examples of the underlayer include silica (SiO2), silicon nitride (Si3N4), amorphous silicon (a:Si), and polycrystalline silicon (poly:Si).

[0044] Here, the aspect ratio is expressed by the above formula (1). That is, the aspect ratio refers to the ratio (L2 / L1) of the depth (L2) of the second opening 21 to the design width (L1) of the first opening 31 (see FIG. 4). The design width of the first opening 31 refers to the length of the first opening 31 along the interface between the carbon-atom-containing film 20 and the mask 30 in the cross section of the mask 30. Here, when the first opening 31 in the mask 30 has a trench pattern, the cross section of the mask 30 refers to the cross section along a plane perpendicular to the longitudinal direction of the trench and along the thickness direction of the mask 30. The depth of the second opening 21 refers to the length from the interface between the carbon-atom-containing film 20 and the mask 30 to the bottom surface of the second opening 21 in the cross section of the carbon-atom-containing film 20, which is the length along the thickness direction of the carbon-atom-containing film 20.

[0045] Examples of analytical instruments for checking the etching performance include a scanning electron microscope (SEM), a transmission electron microscope (TEM), and a spectroscopic ellipsometer, but the analytical instrument is not particularly limited as long as it is a device that can check the etching rate and the occurrence of bowing.

[0046] The gist of the present disclosure is as follows. [1] A dry etching method for a carbon-atom-containing film, in which the carbon-atom-containing film containing carbon atoms is etched with an etching gas, the method comprising: a mixed gas introducing step of introducing a mixed gas containing at least oxygen and a sulfur compound into an etching chamber in which a structure having the carbon-atom-containing film is disposed; and an etching step of converting the mixed gas into plasma in the etching chamber to generate a plasma gas, and etching the carbon-atom-containing film of the structure using the plasma gas as the etching gas, wherein in the etching step, the plasma gas is generated so that an analysis result of the plasma gas by optical emission spectroscopy satisfies at least one of the following requirements (A), (B), and (C): (A) The maximum intensity ratio R1 of the maximum emission intensity in the wavelength range of 770-780 nm to the maximum emission intensity in the wavelength range of 250-260 nm is 0.52 or more. (B) The maximum intensity ratio R2 of the maximum emission intensity in the wavelength range of 770-780 nm to the maximum emission intensity in the wavelength range of 280-350 nm is 0.12 or more. (C) The maximum intensity ratio R3 of the maximum emission intensity in the wavelength range of 770-780 nm to the maximum emission intensity in the wavelength range of 470-600 nm is 0.48 or more. [2] The dry etching method for a carbon-atom-containing film according to [1], wherein in the etching step, the plasma gas is generated so that an analysis result of the plasma gas by optical emission spectroscopy satisfies at least two of the requirements (A), (B), and (C). [3] The dry etching method for a carbon-atom-containing film according to [2], wherein in the etching step, the plasma gas is generated so that an analysis result of the plasma gas by optical emission spectroscopy satisfies all of the requirements (A), (B), and (C). [4] The method for dry etching a carbon-atom-containing film according to any one of [1] to [3], wherein sulfur dioxide or carbonyl sulfide is used as the sulfur compound. [Example]

[0047] The present disclosure will be described in more detail below with reference to examples and comparative examples, although the present disclosure is not limited to the following examples.

[0048] Example 1 First, a 150mm diameter wafer was placed on the processing stage inside the etching chamber of the etching equipment. The etching equipment used was an inductively coupled plasma (ICP) etching equipment (product name "NLD6000", manufactured by ULVAC). This etching equipment was equipped with a plasma optical emission spectrometer capable of analyzing the light emitted from the plasma gas. The plasma optical emission spectrometer analyzes the plasma light by collecting light that passes through a window installed in a location where the plasma light can be observed using a lens and directing it into an optical fiber, which then detects the light using a spectrometer and detector capable of detecting light in the ultraviolet and visible regions.

[0049] The vacuum pressure in the etching chamber was set to 7.5 mTorr, the antenna power to 200 W, and the bias power to 50 W. The mixed gas was introduced into the etching chamber at a flow rate of 50 mL / min to generate plasma gas as the etching gas. In this case, the mixed gas consisted of a mixed gas of oxygen and carbonyl sulfide (COS), the etching time was 5 minutes, and the content of COS in the total volume of oxygen and COS was 30% by volume (the content of oxygen was 70% by volume).

[0050] At this time, the plasma gas was subjected to optical emission spectroscopy using a plasma optical emission spectrometer. The results of the optical emission spectroscopy of the plasma gas are shown in Table 1. As shown in Table 1, the maximum emission intensity in the wavelength range of 770-780 nm was determined as S 770-780 , the maximum emission intensity in the wavelength range of 250-260 nm is S 250-260 , the maximum emission intensity in the wavelength range of 280-350 nm is S 280-350 , the maximum emission intensity in the wavelength range of 470-600 nm is S 470-600 When R1(=S 770-780 / S 250-260 ) is 0.52, R2(=S 770-780 / S 280-350 ) is 0.13, R3(=S 770-780 / S 470-600 ) was 0.48. Next, a laminate consisting of a Si substrate (thickness: 625 μm) as a support and an amorphous carbon film (thickness: 700 nm) as a carbon-containing film was prepared. A silicon dioxide film (thickness: 50 nm) with a mask pattern for the first opening formed by lithography was placed on the amorphous carbon film of this laminate to prepare a 20 mm square structure (see Figure 2). The mask pattern was a trench pattern, with a trench design width (design width of the first opening) of 80 nm and a mask width (width between adjacent trench patterns) of 80 nm. The structure obtained as described above was attached to a 150 mm diameter wafer and placed on a processing stage in the etching chamber of an etching system. An inductively coupled plasma (ICP) etching system (product name "NLD6000" manufactured by ULVAC, Inc.) was used as the etching system.

[0051] Then, the amorphous carbon film was dry-etched as follows. First, the vacuum pressure in the etching chamber was set to 7.5 mTorr, the antenna power to 200 W, and the bias power to 50 W. A mixed gas was introduced into the etching chamber at a flow rate of 50 mL / min to generate plasma gas as an etching gas. The mixed gas consisted of a mixed gas of oxygen and carbonyl sulfide (COS), the etching time was 5 minutes, and the COS content in the total volume of oxygen and COS was 30% by volume (the oxygen content was 70% by volume). That is, the plasma gas was generated as an etching gas so that the same analytical results as those obtained by the optical emission spectroscopic analysis of the plasma gas could be obtained. Then, the amorphous carbon film was dry-etched with this plasma gas to form a trench pattern as a second opening in the amorphous carbon film, thus completing the dry etching of the carbon-atom-containing film.

[0052] Example 2 During the optical emission spectroscopic analysis of the plasma gas and the dry etching of the amorphous carbon film, a mixed gas having the composition shown in Table 1 (COS=10% by volume, oxygen=90% by volume) was used as the mixed gas, R1, R2, and R3 obtained by the optical emission spectroscopic analysis of the plasma gas were as shown in Table 1, and dry etching of the amorphous carbon was carried out in the same manner as in Example 1, except that a silicon dioxide film (thickness: 50 nm) on which a mask pattern as a first opening was formed by lithography was not placed as a mask on the amorphous carbon film of the laminate.

[0053] Example 3 Dry etching of the amorphous carbon was carried out in the same manner as in Example 1, except that a silicon dioxide film (thickness: 50 nm) on which a mask pattern as the first opening was formed by lithography was not placed as a mask on the amorphous carbon film of the laminate.

[0054] (Comparative Examples 1 to 3) Dry etching of amorphous carbon was carried out in the same manner as in Example 1, except that a mixed gas having the composition shown in Table 1 was used as the mixed gas during the optical emission spectroscopic analysis of the plasma gas and the dry etching of the amorphous carbon film, R1, R2, and R3 determined by the optical emission spectroscopic analysis of the plasma gas were as shown in Table 1, and a silicon dioxide film (thickness: 50 nm) on which a mask pattern serving as a first opening was formed by lithography was not placed as a mask on the amorphous carbon film of the laminate.

[0055] Example 4 Dry etching of amorphous carbon was carried out in the same manner as in Example 1, except that a mixed gas (SO2=30% by volume, oxygen=70% by volume) having the composition shown in Table 2 was used as the mixed gas during the optical emission spectroscopic analysis of the plasma gas and the dry etching of the amorphous carbon film, R1, R2, and R3 determined by the optical emission spectroscopic analysis of the plasma gas were as shown in Table 2, and a pattern was formed on the amorphous carbon film for the etching time shown in Table 2.

[0056] Comparative Example 4 Dry etching of amorphous carbon was carried out in the same manner as in Example 1, except that a mixed gas (SO2=100% by volume, oxygen=0% by volume) having the composition shown in Table 2 was used as the mixed gas during the optical emission spectroscopic analysis of the plasma gas and the dry etching of the amorphous carbon film, R1, R2, and R3 determined by the optical emission spectroscopic analysis of the plasma gas were as shown in Table 2, and a pattern was formed on the amorphous carbon film for the etching time shown in Table 2.

[0057] (Examples 5 to 7) Dry etching of amorphous carbon was carried out in the same manner as in Example 1, except that a mixed gas having the composition shown in Table 2 was used as the mixed gas during the optical emission spectroscopic analysis of the plasma gas and the dry etching of the amorphous carbon film, R1, R2, and R3 determined by the optical emission spectroscopic analysis of the plasma gas were as shown in Table 2, and a silicon dioxide film (thickness: 50 nm) on which a mask pattern serving as a first opening was formed by lithography was not placed as a mask on the amorphous carbon film of the laminate.

[0058] (Comparative Examples 5 to 6) Dry etching of amorphous carbon was carried out in the same manner as in Example 1, except that a mixed gas having the composition shown in Table 2 was used as the mixed gas during the optical emission spectroscopic analysis of the plasma gas and the dry etching of the amorphous carbon film, R1, R2, and R3 determined by the optical emission spectroscopic analysis of the plasma gas were as shown in Table 2, and a silicon dioxide film (thickness: 50 nm) on which a mask pattern serving as a first opening was formed by lithography was not placed as a mask on the amorphous carbon film of the laminate.

[0059] For Examples 1 and 4 and Comparative Example 4, the cross section of the amorphous carbon film after etching was completed was observed using an SEM (product name "SU8230", manufactured by Hitachi High-Technologies Corporation), and the etching depth of the trench pattern formed in the amorphous carbon film was determined. The etching rate was also calculated from the etching time and etching depth. The results are shown in Tables 1 and 2. The maximum pattern widths were 76 nm, 86 nm, and 84 nm, and it was confirmed that no bowing abnormality occurred.

[0060] Furthermore, for Examples 2, 3, 5 to 7 and Comparative Examples 1 to 3, 5, and 6, the thickness of the amorphous carbon film before and after etching was measured using a spectroscopic ellipsometer (product name "M-2000U", manufactured by JA Woollam) to determine the etching rate. The results are shown in Tables 1 and 2.

[0061] Furthermore, the relationship between the maximum intensity ratio R1 and the etching rate (ER), the relationship between the maximum intensity ratio R2 and the etching rate (ER), and the relationship between the maximum intensity ratio R3 and the etching rate (ER) are shown in FIGS. 5 to 7, respectively.

[0062] From the results shown in Tables 1 and 2 and FIGS. 5 to 7, it was found that, regardless of the presence or absence of a pattern in the amorphous carbon film as the carbon-atom-containing film, in Examples 1 to 7, a higher etching rate could be obtained simply by adjusting R1, R2, and R3 compared to Comparative Examples 1 to 6.

[0063] [Table 1]

[0064] [Table 2] [Explanation of symbols]

[0065] 10...support, 20...carbon atom-containing film, 21...second opening, 30...mask, 31...first opening, 100...structure, L1...design width of first opening, L2...depth of second opening.

Claims

1. A method for dry etching a carbon-atom-containing film, which includes etching a carbon-atom-containing film containing carbon atoms with an etching gas, comprising: a mixed gas introduction step of introducing a mixed gas containing at least oxygen and a sulfur compound into an etching chamber in which the structure including the carbon atom-containing film is disposed; an etching step of generating a plasma gas by converting the mixed gas into plasma in the etching chamber, and etching the carbon-atom-containing film of the structure by using the plasma gas as the etching gas, a method for dry etching a carbon-atom-containing film, wherein in the etching step, the plasma gas is generated so that an analysis result of the plasma gas by optical emission spectroscopy satisfies at least one of the following requirements (A), (B), and (C): (A) The maximum intensity ratio R1 of the maximum emission intensity in the wavelength range of 770-780 nm to the maximum emission intensity in the wavelength range of 250-260 nm is 0.52 or more. (B) The maximum intensity ratio R2 of the maximum emission intensity in the wavelength range of 770-780 nm to the maximum emission intensity in the wavelength range of 280-350 nm is 0.12 or more. (C) The maximum intensity ratio R3 of the maximum emission intensity in the wavelength range of 770-780 nm to the maximum emission intensity in the wavelength range of 470-600 nm is 0.48 or more.

2. 2. The dry etching method for a carbon-atom-containing film according to claim 1, wherein in the etching step, the plasma gas is generated so that an analysis result of the plasma gas by optical emission spectroscopy satisfies at least two of the requirements (A), (B), and (C).

3. 3. The dry etching method for a carbon-atom-containing film according to claim 2, wherein in the etching step, the plasma gas is generated so that an analysis result of the plasma gas by optical emission spectroscopy satisfies all of the requirements (A), (B), and (C).

4. 4. The method for dry etching a carbon-containing film according to claim 1, wherein sulfur dioxide or carbonyl sulfide is used as the sulfur compound.

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