Dry etching method for carbon atom-containing film

Abstract

To provide a dry etching method for a carbon atom-containing film, with which an etching rate for a carbon atom-containing film can be improved.SOLUTION: There is provided a dry etching method for a carbon atom-containing film with which a carbon atom-containing film that contains carbon atoms is etched using an etching gas. The dry etching method includes: a mixed gas introduction step of introducing a mixed gas containing at least oxygen and sulfur dioxide into an etching chamber in which a structure is disposed, the structure including the carbon atom-containing film and a mask having a first opening; and an etching step of turning the mixed gas into plasma within the etching chamber to produce a plasma gas, and using the plasma gas as the etching gas to etch the carbon atom-containing film of the structure, thereby forming a second opening. In the etching step, the second opening is formed so that an aspect ratio of 1-40 is achieved.SELECTED DRAWING: Figure 1

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, and the manufacture of semiconductor integrated circuits requires technology that uses masks such as photoresist to pattern the film 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 film to be etched. Known as such a technique is, for example, the method described in Patent Document 1. This publication reports that processing accuracy can be improved by using a plasma gas, which is a mixed gas of oxygen and carbonyl sulfide added, as an etching gas for a carbonaceous layer containing carbon. [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 room for improvement in terms of increasing the etching rate of the carbonaceous layer.

[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 improve the etching rate for the carbon-atom-containing film. [Means for solving the problem]

[0006] The present inventors have unexpectedly found that the above-mentioned problems can be solved by changing the gas added to oxygen during etching of the carbon-atom-containing film from carbonyl sulfide to sulfur dioxide while controlling the anisotropy (aspect ratio) of the openings in the carbon-atom-containing film after etching, and have come to disclose the present invention.

[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 sulfur dioxide into an etching chamber in which a structure including the carbon-atom-containing film and a mask having a first opening is placed; 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 to form a second opening, wherein in the etching step, the second opening is formed so that the aspect ratio defined by the following formula (1) is 1 to 40. Aspect ratio = L2 / L1 (1) (In the formula (1), L1 represents the design width of the first opening, and L2 represents the depth of the second opening.)

[0008] According to the above-described method for dry etching a carbon-atom-containing film, by etching the carbon-atom-containing film with a plasma gas of a mixed gas containing oxygen and sulfur dioxide while controlling the aspect ratio during etching within the above-described range, it is possible to improve the etching rate for the carbon-atom-containing film compared to when etching the carbon-atom-containing film with a plasma gas of a mixed gas containing oxygen and carbonyl sulfide.

[0009] The aspect ratio may be 4-40.

[0010] The first opening may be in the shape of a trench or a hole.

[0011] The carbon atom-containing film may contain amorphous carbon.

[0012] The mask may include an oxygen-containing material.

[0013] The oxygen-containing material may be silicon dioxide.

[0014] In the mixed gas, the content of sulfur dioxide in the total volume of the sulfur dioxide and oxygen may be 20 to 40% by volume. [Effects of the Invention]

[0015] According to the present disclosure, a dry etching method for a carbon-atom-containing film is provided that can improve the etching rate for the carbon-atom-containing film. [Brief explanation of the drawings]

[0016] [Figure 1] 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 2] FIG. 1 is a cross-sectional view showing an example of a structure after an etching step of the dry etching method for a carbon-atom-containing film disclosed herein. [Figure 3] FIG. 3 is a partial enlarged view of the mask and the carbon-atom-containing film in FIG. 2. [Figure 4] 10 is a graph showing the results of plotting the etching rate versus the aspect ratio of the second opening of the carbon-atom-containing film in Examples 1 to 3 and Comparative Examples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0017] 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 1 to 3. However, the present disclosure is not limited to the following embodiments.

[0018] FIG. 1 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. 2 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. 3 is a partially enlarged view of the carbon-atom-containing film of FIG. 2. The dry etching method for a carbon-atom-containing film according to the present disclosure is a method for etching a carbon-atom-containing film 20 containing carbon atoms with an etching gas, and includes a mixed gas introduction step of introducing a mixed gas containing at least oxygen and sulfur dioxide into an etching chamber in which a carbon-atom-containing film 20 and a structure 100 including a mask 30 having a first opening 31 are placed, and an etching step of converting the mixed gas into plasma in the etching chamber to generate a plasma gas, and using this plasma gas to etch the carbon-atom-containing film 20 of the structure 100 to form a second opening 21 (see FIGS. 1 and 2). Then, in the etching step, the second opening 21 is formed so that the aspect ratio defined by the following formula (1) is 1 to 40. Aspect ratio = L2 / L1 (1) (In the above formula (1), L1 represents the design width of first opening 31, and L2 represents the depth of second opening 32.)

[0019] According to the above-described dry etching method for a carbon-atom-containing film, by etching the carbon-atom-containing film 20 with a plasma gas of a mixed gas containing oxygen and sulfur dioxide while controlling the aspect ratio during etching to within the above-described range, it is possible to improve the etching rate for the carbon-atom-containing film 20 compared to the case of etching the carbon-atom-containing film 20 with a plasma gas of a mixed gas containing oxygen and carbonyl sulfide.

[0020] The mixed gas introduction step and the etching step will be described in detail below.

[0021] <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. 1 , 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.

[0022] (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.

[0023] 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 into wafers of a predetermined size. (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 to the etching rate Vm of the mask) can be increased when a pattern is transferred to the carbon-atom-containing film 20.

[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 intermediate film is laminated 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 rate lower than that of 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 chamber) The etching chamber is a container in which the carbon-atom-containing film 20 is etched with a plasma gas obtained by converting a mixed gas containing oxygen and sulfur dioxide into plasma, and constitutes a part of the etching apparatus. 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.

[0029] (mixed gas) The mixed gas contains oxygen and sulfur dioxide. The content of sulfur dioxide in the total volume of oxygen and sulfur dioxide 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 sulfur dioxide in the total volume of oxygen and sulfur dioxide is within the range of 20 to 40% by volume, the etching rate for the carbon-atom-containing film 20 can be improved more effectively.

[0030] 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.

[0031] <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.

[0032] (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.

[0033] (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.

[0034] (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.

[0035] (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.

[0036] The aspect ratio after etching is not particularly limited as long as it is 1-40, but may be 4-40, 5-40, or 5-25. When the aspect ratio is 40 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 that is 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 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).

[0037] 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. 3). 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.

[0038] Examples of analytical instruments for checking etching performance include SEM (scanning electron microscope) and TEM (transmission electron microscope), 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.

[0039] 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 sulfur dioxide into an etching chamber in which a structure including the carbon-atom-containing film and a mask having a first opening is placed; and an etching step of converting the mixed gas into plasma in the etching chamber to generate a plasma gas, and using this plasma gas as the etching gas to etch the carbon-atom-containing film of the structure to form a second opening, wherein in the etching step, the second opening is formed so that the aspect ratio is 1 to 40. [2] The method for dry etching a carbon-atom-containing film according to [1], wherein the aspect ratio is 4 to 40. [3] The method for dry etching a carbon-atom-containing film according to [1] or [2], wherein the first opening has a shape of a trench or a hole. [4] The method for dry etching a carbon-atom-containing film according to any one of [1] to [3], wherein the carbon-atom-containing film contains amorphous carbon. [5] The method for dry etching a carbon-atom-containing film according to any one of [1] to [4], wherein the mask contains an oxygen-containing material. [6] The method for dry etching a carbon-atom-containing film according to [5], wherein the oxygen-containing material is silicon dioxide. [7] The method for dry etching a carbon-atom-containing film according to any one of [1] to [6], wherein in the mixed gas, a content of the sulfur dioxide in the total volume of the sulfur dioxide and the oxygen is 20 to 40 volume %. [Example]

[0040] 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.

[0041] [Example 1] First, 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 1). The mask pattern was a trench pattern, and the trench design width (design width of the first opening) L1 was 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. Then, dry etching of the amorphous carbon film was carried out as follows. That is, the vacuum pressure in the etching chamber was set to 3.8 mTorr, the antenna power was set to 400 W, and the bias power was set to 100 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 amorphous carbon film was dry-etched using this plasma gas, and a trench pattern was formed as a second opening in the amorphous carbon film. In this way, dry etching of the carbon-containing film was completed. The mixed gas consisted of oxygen and sulfur dioxide, the etching time was 2 minutes 30 seconds, and the sulfur dioxide content of the total volume of oxygen and sulfur dioxide was 30 volume % (oxygen content was 70 volume %). The second opening was formed so that the etching depth L2 was 600 nm, i.e., the aspect ratio was 7.5. The aspect ratio was calculated using the following formula (1). Aspect ratio = Etching depth L2 (nm) ÷ Trench design width L1 (nm) (1) After etching was completed, the cross section of the amorphous carbon film was observed with an SEM (product name "SU8230", manufactured by Hitachi High-Technologies Corporation) to confirm the etching depth (L2) of the trench pattern formed in the amorphous carbon film. The measured etching depth L2 was 599 nm, and the etching rate was 240 nm / min, as shown in Table 1. The aspect ratio based on the measured etching depth L2 was 7.5. Furthermore, when observing the cross section of the amorphous carbon film with an SEM, the second opening was checked and it was found that the inner wall surface of the second opening was not significantly etched, bowing was suppressed, and highly anisotropic etching was progressing.

[0042] [Comparative Example 1] Dry etching of an amorphous carbon film was performed in the same manner as in Example 1, except that the mixed gas, etching time, and aspect ratio were as shown in Table 1. The etching rate was then calculated. The results are shown in Table 1. As shown in Table 1, the etching rate was 170 nm / min.

[0043] [Example 2] Dry etching of the amorphous carbon film was carried out in the same manner as in Example 1, except that the thickness of the amorphous carbon film of the laminate was 2400 nm, the thickness of the silicon dioxide film used as a mask was 350 nm, and the mixed gas, etching time, and aspect ratio were as shown in Table 2. The etching rate was then calculated. The results are shown in Table 2. As shown in Table 2, the etching rate was 154 nm / min.

[0044] Comparative Example 2 Dry etching of the amorphous carbon film was carried out in the same manner as in Example 2, except that the thickness of the amorphous carbon film of the laminate was 2400 nm, the thickness of the silicon dioxide film used as a mask was 350 nm, and the mixed gas, etching time, and aspect ratio were as shown in Table 2. The etching rate was then calculated. The results are shown in Table 2. As shown in Table 2, the etching rate was 107 nm / min.

[0045] [Example 3] Dry etching of the amorphous carbon film was carried out in the same manner as in Example 1, except that the thickness of the amorphous carbon film of the laminate was 2400 nm, the thickness of the silicon dioxide film used as a mask was 350 nm, and the mixed gas, etching time, and aspect ratio were as shown in Table 3. The etching rate was then calculated. The results are shown in Table 3. As shown in Table 3, the etching rate was 123 nm / min.

[0046] Comparative Example 3 Dry etching of the amorphous carbon film was carried out in the same manner as in Example 3, except that the thickness of the amorphous carbon film of the laminate was 2400 nm, the thickness of the silicon dioxide film used as a mask was 350 nm, and the mixed gas, etching time, and aspect ratio were as shown in Table 3. The etching rate was then calculated. The results are shown in Table 3. As shown in Table 3, the etching rate was 88 nm / min. [Table 1] [Table 2] [Table 3]

[0047] Based on the results shown in Tables 1 to 3, the etching rate was plotted against the aspect ratio in Examples 1 to 3 and Comparative Examples 1 to 3, and the results are shown in FIG. The results shown in FIG. 4 show that when dry etching a carbon-containing film with approximately the same aspect ratio, the etching rate is higher when using a mixed gas containing sulfur dioxide than when using a mixed gas containing carbonyl sulfide. [Explanation of symbols]

[0048] 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 dry etching method for a carbon-atom-containing film, which etches 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 sulfur dioxide into an etching chamber in which a structure including the carbon atom-containing film and a mask having a first opening is placed; 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 using the plasma gas as the etching gas to form a second opening, In the etching step, the second opening is formed so that an aspect ratio defined by the following formula (1) is 1 to 40: Aspect ratio=L2 / L1 (1) (In the formula (1), L1 represents the design width of the first opening, and L2 represents the depth of the second opening.)

2. 2. The method for dry etching a carbon-atom-containing film according to claim 1, wherein the aspect ratio is 4 to 40.

3. 2. The method for dry etching a carbon-atom-containing film according to claim 1, wherein the first opening has a shape of a trench or a hole.

4. 2. The method for dry etching a carbon-atom-containing film according to claim 1, wherein the carbon-atom-containing film contains amorphous carbon.

5. The method for dry etching a carbon-atom-containing film according to claim 1 , wherein the mask comprises an oxygen-containing material.

6. 6. The method for dry etching a carbon-atom-containing film according to claim 5, wherein the oxygen-containing material is silicon dioxide.

7. 7. The method for dry etching a carbon-atom-containing film according to claim 1, wherein in the mixed gas, a content of the sulfur dioxide in a total volume of the sulfur dioxide and the oxygen is 20 to 40 volume %.

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