Mask pattern formation method and substrate processing method
Patent Information
- Application Number
- JP2025506720
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2025-01-10
- Publication Date
- 2026-02-19
AI Technical Summary
In semiconductor manufacturing, conventional lithography processes face challenges in reducing line edge roughness (LER) and line width roughness (LWR) due to uneven distribution of photoacid generators and quenchers in chemically amplified resists, especially when using extreme ultraviolet (EUV) exposure, which increases variation in photon density and results in increased LER.
A mask pattern forming method involving a coating step with a polymerizable ionic liquid, followed by a polymerization step to generate a polymeric ionic liquid, and a mask pattern forming step using the polymeric ionic liquid, which reduces roughness through self-healing properties, allowing for the formation of smooth mask patterns even under EUV exposure.
The method effectively reduces the roughness of mask patterns and transferred patterns, maintaining low line edge roughness even after EUV exposure, thereby improving the precision of semiconductor devices.
Smart Images
Figure 2024190480000001
Abstract
Description
Mask pattern forming method and substrate processing method
[0001] The present disclosure relates to a mask patterning method and a substrate processing method.
[0002] Patent Document 1 listed below discloses "a resist composition that generates an acid upon exposure and whose solubility in a developer changes due to the action of the acid, the resist composition having a solids concentration of 25 mass % or more, which contains a base component (A) whose solubility in a developer changes due to the action of the acid, and an ionic liquid (Z)" and "a method of forming a resist pattern, which includes the steps of forming a resist film on a support using the resist composition, exposing the resist film, and developing the exposed resist film to form a resist pattern."
[0003] The following Non-Patent Document 1 discloses that "a new method for producing micro- and nano-sized polymer structures from room temperature ionic liquid (RTIL) on Si substrates has been developed by patterned irradiation with electron beam (EB)," that "the extremely low vapor pressure of RTIL, 1-allyl-3-ethylimidazolium bis(trifluoromethane)sulfonylamide, allows it to be introduced into the high-vacuum chamber of an electron beam instrument to carry out radiation-induced polymerization in the nano-region," and that "we have prepared a variety of three-dimensional (3D) micro / nano polymer structures with aspect ratios up to 5 with sub-100 nm resolution."
[0004] Japanese Patent Application Laid-Open No. 2021-092759
[0005] H. Minamimoto, et al., “Polymerization of Room-Temperature Ionic Liquid Monomers by Electron Beam Irradiation with the Aim of Fabricating Three-Dimensional Micropolymer / Nanopolymer Structures”, Langmuir 2015, 31, 4281-4289
[0006] The present disclosure provides a technique that can reduce the roughness of a mask pattern.
[0007] A mask pattern forming method according to one aspect of the present disclosure includes a coating step, a polymerization step, and a mask pattern forming step. The coating step involves coating a substrate with a substance containing a polymerizable ionic liquid. The polymerization step involves inducing a polymerization reaction of the polymerizable ionic liquid in at least a portion of the substance containing the polymerizable ionic liquid, thereby producing a substance containing a polymeric ionic liquid on the substrate. The mask pattern forming step involves forming a mask pattern of the substance containing a polymeric ionic liquid on the substrate using the substance containing a polymeric ionic liquid.
[0008] According to the present disclosure, the roughness of the mask pattern can be reduced.
[0009] FIG. 1 is a flowchart outlining an example of a substrate processing method according to an embodiment. FIG. 2 is a flowchart outlining a first example of a substrate processing method according to an embodiment. FIG. 3A is a schematic diagram outlining the first example of a substrate processing method according to an embodiment. FIG. 3B is a schematic diagram outlining the first example of a substrate processing method according to an embodiment. FIG. 4 is a flowchart outlining a second example of a substrate processing method according to an embodiment. FIG. 5A is a schematic diagram outlining the second example of a substrate processing method according to an embodiment. FIG. 5B is a schematic diagram outlining the second example of a substrate processing method according to an embodiment. FIG. 6 is a flowchart outlining a third example of a substrate processing method according to an embodiment. FIG. 7A is a schematic diagram outlining the third example of a substrate processing method according to an embodiment. FIG. 7B is a schematic diagram outlining the third example of a substrate processing method according to an embodiment. FIG. 8 is a diagram outlining an example of a substrate processing system for carrying out a substrate processing method according to an embodiment. FIG. 9 is a diagram outlining an example of a mask pattern for a polymeric ionic liquid according to an example. FIG. 10 is a diagram outlining an example of a mask pattern for a polymeric ionic liquid according to an example. FIG. 11 is a diagram outlining an example of a mask pattern for a polymeric ionic liquid according to an example. FIG. 12 is a diagram outlining an example of a mask pattern for a polymeric ionic liquid according to an example. 13 is a diagram showing an example of LER of a mask pattern according to an example and a mask pattern according to a comparative example. FIG. 14 is a diagram showing an example of a hardware configuration of a computer constituting a control unit included in a substrate processing system.
[0010] Hereinafter, modes for carrying out a mask pattern forming method and a substrate processing method according to the present disclosure (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. Note that the present disclosure is not limited to these embodiments. Furthermore, the respective embodiments can be appropriately combined within the scope of not causing any contradiction in the processing content. Furthermore, the same components in the following embodiments will be assigned the same reference numerals, and redundant explanations will be omitted.
[0011] When manufacturing semiconductor devices having fine structures, it is necessary to reduce the roughness of the sidewalls of the patterns that occurs in the lithography process in order to reduce dimensional errors of the semiconductor devices. The roughness of the sidewalls of the patterns is measured using line edge roughness (LER), line width roughness (LWR), etc. For example, when the critical dimension (CD) in semiconductor device manufacturing is several tens of nanometers, the LER is several nanometers.
[0012] For example, shortening the wavelength of the resist exposure light source used in the lithography process can improve the exposure resolution and contrast in the resist, thereby reducing LER. However, if the wavelength of the exposure light source is shortened without increasing the exposure light source dose to avoid increasing exposure costs, the number of photons per unit area on the irradiated resist surface will decrease. As a result, the variation in the number of photons on the resist surface will increase, resulting in an increase in LER. In particular, when extreme ultraviolet (EUV) exposure is performed, it is not easy to reduce LER.
[0013] Furthermore, for example, when a conventional chemically amplified resist is used, the distribution of components contained in the chemically amplified resist, such as a photoacid generator and a quencher, tends to become locally non-uniform, which tends to accentuate the variation in the number of photons per unit area on the resist surface, and as a result, the LER tends to increase.
[0014] Therefore, the present disclosure provides a technique that can reduce mask pattern roughness such as LER.
[0015] (Substrate Processing Method) Fig. 1 is a flowchart that outlines an example of a substrate processing method according to an embodiment. In the substrate processing method according to an embodiment, first, in step S101 shown in Fig. 1, a substance containing a polymerizable ionic liquid is applied to a substrate.
[0016] The substrate may be provided with a film to be etched. When the substrate is provided with a film to be etched, a substance containing a polymerizable ionic liquid is applied to the film to be etched. For example, the substrate may be a silicon (Si) wafer. Alternatively, the film to be etched may be made of silicon oxide (SiO ) to provide an insulating film. ２ ) membrane may also be used.
[0017] A polymerizable ionic liquid is a liquid salt composed of ions consisting of cations and anions, one of which is a monomer. For example, when the cation is a monomer, examples of the cation and anion include the cation components and anion components disclosed in JP 2007-042531 A. Further, examples of polymerizable ionic liquids include ionic liquid monomers represented by general formula (A) disclosed in JP 2021-042150 A.
[0018] The substance containing a polymerizable ionic liquid may, for example, consist of a polymerizable ionic liquid. Alternatively, the substance containing a polymerizable ionic liquid may, for example, contain a polymerizable ionic liquid and a solvent for the polymerizable ionic liquid. The solvent is not particularly limited as long as it can dissolve the polymerizable ionic liquid.
[0019] Examples of methods for applying the substance containing a polymerizable ionic liquid to a substrate include spin coating, etc. When the substance containing a polymerizable ionic liquid is applied to a substrate by spin coating, the substance containing a polymerizable ionic liquid can be applied more uniformly to the substrate.
[0020] Next, in step S102 shown in Fig. 1, a polymerizable ionic liquid-containing substance is produced on the substrate by inducing a polymerization reaction of the polymerizable ionic liquid in at least a portion of the substance containing the polymerizable ionic liquid. Inducing a polymerization reaction of the polymerizable ionic liquid in at least a portion of the substance containing the polymerizable ionic liquid means that a monomer contained in the polymerizable ionic liquid undergoes a polymerization reaction in all or part of the substance containing the polymerizable ionic liquid. This produces a polymeric ionic liquid.
[0021] A polymeric ionic liquid is an ionic liquid composed of ions contained in a polymer produced by polymerization of a monomer contained in the polymerizable ionic liquid and non-polymerizable ions. For example, when the monomer contained in the polymerizable ionic liquid is a cation, the ionic liquid may be composed of a polymer containing a cationic divalent group as a repeating unit and an anion contained in the polymerizable ionic liquid.
[0022] The monomer may be incorporated into the main chain of the polymer by a polymerization reaction. Alternatively, the monomer may be incorporated into the side chain of the polymer by a polymerization reaction. For example, when a polymerization reaction is induced on an ionic liquid monomer represented by general formula (A) disclosed in JP 2021-042150 A, the cationic component contained in general formula (A) is incorporated into the main chain of the polymer. For example, when a polymerization reaction is induced on a cationic component disclosed in JP 2007-042531 A, the cationic component is incorporated into the side chain of the polymer.
[0023] When the substance containing a polymerizable ionic liquid consists of a polymerizable ionic liquid, the substance containing a polymeric ionic liquid may consist of a polymeric ionic liquid. When the substance containing a polymerizable ionic liquid contains a polymerizable ionic liquid and a solvent for the polymerizable ionic liquid, the substance containing a polymeric ionic liquid may contain a polymeric ionic liquid and the solvent described above. When the substance containing a polymeric ionic liquid contains the solvent described above, the substance containing a polymeric ionic liquid may be a gel-like substance.
[0024] Methods for inducing a polymerization reaction of the polymerizable ionic liquid in a substance containing the polymerizable ionic liquid include heating the substance containing the polymerizable ionic liquid, irradiating the substance containing the polymerizable ionic liquid with light, and irradiating the substance containing the polymerizable ionic liquid with an electron beam. When the substance containing the polymerizable ionic liquid is irradiated with light or an electron beam, the polymerization reaction of the polymerizable ionic liquid can be more easily induced in selective regions of the substance containing the polymerizable ionic liquid. In other words, a substance containing a polymeric ionic liquid can be more easily produced in selective regions of the substance containing the polymerizable ionic liquid.
[0025] Next, in step S103 shown in Fig. 1, a mask pattern of a material containing a polymeric ionic liquid is formed on a substrate using a material containing a polymeric ionic liquid. Because polymeric ionic liquids are nonvolatile and heat-resistant, the material containing a polymeric ionic liquid can be used to form the mask pattern. Specific examples of methods for forming a mask pattern of a material containing a polymeric ionic liquid on a substrate using a material containing a polymeric ionic liquid will be described later.
[0026] Since a mask pattern of a material containing a polymeric ionic liquid is formed using a material containing a polymeric ionic liquid, roughness of the mask pattern, such as LER, can be reduced. When forming a mask pattern of a material containing a polymeric ionic liquid, damage or irregularities may occur on the surface of the mask pattern. Here, the polymeric ionic liquid has a self-repairing property such that broken polymer chains are repaired by reformation of ionic bonds between ions contained in the polymer and ions not contained in the polymer. It is believed that the self-repairing property of such a polymeric ionic liquid repairs polymer chains near damage or irregularities on the surface of the mask pattern, thereby reducing damage or irregularities on the surface of the mask pattern of the material containing the polymeric ionic liquid. As a result, it is believed that the roughness of the mask pattern is reduced.
[0027] As described above, the substrate processing method according to the embodiment includes a mask pattern forming method including steps S101, S102, and S103 as shown in FIG.
[0028] Next, in step S104 shown in Fig. 1, the substrate is etched using a mask pattern of a substance containing a polymeric ionic liquid as a mask. If the substrate has a film to be etched, the film to be etched on the substrate is etched. If the substrate does not have a film to be etched, the substrate is etched. A specific example of a method for etching a substrate using a mask pattern of a substance containing a polymeric ionic liquid as a mask will be described later. Note that it is also possible to perform only steps S101, S102, and S103 without performing step S104.
[0029] (First Example of Substrate Processing Method) Fig. 2 is a flowchart showing a first example of a substrate processing method according to an embodiment. Figs. 3A and 3B are schematic views for explaining the first example of a substrate processing method according to an embodiment. Fig. 3A shows the state of a substrate viewed from a direction along the surface of the substrate in the first example of the substrate processing method. Fig. 3B shows the state of a substrate viewed from a direction normal to the surface of the substrate in the first example of the substrate processing method.
[0030] First, in step S201 shown in FIG. 2, a substrate 10 having an etching target film 20 formed thereon is prepared as shown in (a) of FIG. 3A and (a) of FIG. 3B. Here, the etching target film 20 is, for example, a silicon oxide film, and the substrate 10 is, for example, a silicon wafer. For example, a chemical vapor deposition (CVD) method is used to deposit, on the silicon wafer, a film containing, for example, tetraethoxysilane (TEOS) and oxygen (O ２ ) gas, a silicon oxide film can be formed on a silicon wafer.
[0031] 2, as shown in (b) of Figure 3A and (b) of Figure 3B, a substance 30 containing a polymerizable ionic liquid is applied to the etching target film 20 provided on the substrate 10 by, for example, spin coating. This forms a layer of the substance 30 containing a polymerizable ionic liquid on the etching target film 20 provided on the substrate 10. Note that the process in step S202 shown in Figure 2 corresponds to the process in step S101 shown in Figure 1.
[0032] Next, in step S203 shown in Figure 2, for example, an electron beam is irradiated onto the entire layer of substance 30 containing the polymerizable ionic liquid, as shown in (c) of Figure 3A and (c) of Figure 3B. This causes a polymerization reaction of the polymerizable ionic liquid throughout the entire substance 30 containing the polymerizable ionic liquid. In this way, a layer of substance 40 containing a polymeric ionic liquid is produced on the etching target film 20 provided on the substrate 10. Note that the process in step S203 shown in Figure 2 corresponds to the process in step S102 shown in Figure 1.
[0033] 2, a photoresist 50 is applied to the layer of the substance 40 containing the polymeric ionic liquid, as shown in (d) of Figure 3A and (d) of Figure 3B. The photoresist 50 is not particularly limited, but may be, for example, a chemically amplified resist.
[0034] 2, selective regions of the photoresist 50 are exposed to light through the photomask M, as shown in (e) of FIG. 3A and (e) of FIG. 3B. This transfers the pattern of the photomask M to the photoresist 50 as a resist pattern 60. Examples of the exposure method include the use of KrF excimer laser light, EUV light, etc.
[0035] Next, in step S206 shown in FIG. 2, the photoresist 50 is developed as shown in (f) of FIG. 3A and (f) of FIG. 3B. That is, the photoresist 50 in the unexposed areas other than the selective areas is removed. Examples of the development method include dip development. Note that post-baking may be performed after the photoresist 50 is developed. In this way, a resist pattern 60 is formed in the layer of the substance 40 containing the polymeric ionic liquid.
[0036] 3B(f), the roughness of the resist pattern 60 may be relatively large. In particular, when the photoresist 50 is exposed to EUV light in step S205, the roughness of the resist pattern 60 tends to be large.
[0037] Next, in step S207 shown in FIG. 2, as shown in (g) of FIG. 3A and (g) of FIG. 3B, the resist pattern 60 is used as a mask to etch a portion of the layer of the polymeric ionic liquid-containing substance 40. Examples of etching methods include dry etching using plasma of an oxygen-containing gas. This forms a mask pattern of the polymeric ionic liquid-containing substance 40 on the etching target film 20 provided on the substrate 10. Note that the processes in steps S204, S205, S206, and S207 shown in FIG. 2 correspond to the process in step S103 shown in FIG. 1.
[0038] Here, as shown in (g) of FIG. 3B , the roughness of the mask pattern of the polymeric ionic liquid-containing material 40 is relatively small due to the self-healing properties of the polymeric ionic liquid. More specifically, when etching a portion of the layer of the polymeric ionic liquid-containing material 40, the relatively large roughness of the resist pattern 60 may be transferred to the mask pattern of the polymeric ionic liquid-containing material 40. However, the self-healing properties of the polymeric ionic liquid repair polymer chains near damage or irregularities on the surface of the mask pattern of the polymeric ionic liquid-containing material 40. Accordingly, the surface irregularities of the mask pattern of the polymeric ionic liquid-containing material 40 are reduced. This is believed to result in reduced roughness of the mask pattern. That is, a mask pattern of the polymeric ionic liquid-containing material 40 having a roughness smaller than that of the resist pattern 60 can be formed on the etching target film 20 provided on the substrate 10. In this way, the roughness of the mask pattern can be reduced. In particular, the roughness of the mask pattern can be reduced even when the photoresist 50 is exposed to EUV light in step S205.
[0039] 2, the etching target film 20 provided on the substrate 10 is etched using a mask pattern of the substance 40 containing the polymeric ionic liquid as a mask, as shown in (h) of FIG. 3A and (h) of FIG. 3B. Examples of the etching method include wet etching using hydrofluoric acid and dry etching using plasma of a gas containing fluorine, when the etching target film 20 is a silicon oxide film. The process in step S208 shown in FIG. 2 corresponds to the process in step S104 shown in FIG. 1.
[0040] 3B (g), the roughness of the etched film 20 to be etched is comparable to the roughness of the mask pattern of the material 40 containing the polymeric ionic liquid. That is, a mask pattern of the material 40 containing the polymeric ionic liquid, which has a roughness smaller than that of the resist pattern 60, can be transferred to the film 20 to be etched provided on the substrate 10. In this way, the roughness of the pattern transferred to the film 20 to be etched can be reduced. In particular, even when the photoresist 50 is exposed to EUV light in step S205, the roughness of the pattern transferred to the film 20 to be etched can be reduced.
[0041] (Second Example of Substrate Processing Method) Fig. 4 is a flowchart showing a second example of a substrate processing method according to an embodiment. Figs. 5A and 5B are schematic views for explaining the second example of a substrate processing method according to an embodiment. Fig. 5A shows the state of a substrate viewed from a direction along the surface of the substrate in the second example of the substrate processing method. Fig. 5B shows the state of a substrate viewed from a direction normal to the surface of the substrate in the second example of the substrate processing method.
[0042] First, in step S301 shown in Fig. 4, as shown in (a) of Fig. 5A and (a) of Fig. 5B, a substrate 10 provided with an etching target film 20 is prepared in the same manner as in step S201 shown in Fig. 2. Here, the etching target film 20 is, for example, a silicon oxide film, and the substrate 10 is, for example, a silicon wafer.
[0043] 4, a recess is formed in the etching target film 20 provided on the substrate 10, as shown in (b) of FIG. 5A and (b) of FIG. 5B. A method for forming a recess in the etching target film 20 includes etching the etching target film 20. For example, when the etching target film 20 is a silicon oxide film, etching methods include wet etching using hydrofluoric acid and dry etching using plasma of a gas containing fluorine. The shape of the recess is not particularly limited.
[0044] Here, as shown in FIG. 5B(b), the roughness of the recess formed in the etching target film 20 may be relatively large.
[0045] Next, in step S303 shown in Fig. 4, a substance 30 containing a polymerizable ionic liquid is applied to the recesses by, for example, spin coating, as shown in Fig. 5A(c) and Fig. 5B(c). This forms a substance 30 containing a polymerizable ionic liquid embedded in the recesses. Note that the process in step S303 shown in Fig. 4 corresponds to the process in step S101 shown in Fig. 1.
[0046] Next, in step S304 shown in FIG. 4, for example, the entire polymerizable ionic liquid-containing substance 30 is irradiated with an electron beam, as shown in (d) of FIG. 5A and (d) of FIG. 5B. This causes a polymerization reaction of the polymerizable ionic liquid in the polymerizable ionic liquid-containing substance 30. In this way, a polymeric ionic liquid-containing substance 40 is produced, embedded in the recesses. Note that the process in step S304 shown in FIG. 4 corresponds to the process in step S102 shown in FIG. 1.
[0047] Next, in step S305 shown in Figure 4, the etching target film 20 provided on the substrate 10, excluding the polymeric ionic liquid-containing substance 40, is etched, as shown in (e) of Figure 5A and (e) of Figure 5B. Examples of etching methods include wet etching using hydrofluoric acid or dry etching using plasma of a fluorine-containing gas when the etching target film 20 is a silicon oxide film. This forms a mask pattern of the polymeric ionic liquid-containing substance 40 on the substrate 10. The process in step S305 shown in Figure 4 corresponds to the process in step S103 shown in Figure 1.
[0048] Here, as shown in (e) of FIG. 5B , the roughness of the mask pattern of the polymeric ionic liquid-containing material 40 is relatively small due to the self-healing properties of the polymeric ionic liquid. More specifically, when etching the etching target film 20 provided on the substrate 10, the relatively large roughness of the recesses formed in the etching target film 20 may be transferred to the mask pattern of the polymeric ionic liquid-containing material 40. However, due to the self-healing properties of the polymeric ionic liquid, polymer chains near the damaged or uneven surface of the mask pattern of the polymeric ionic liquid-containing material 40 are repaired. Accordingly, the surface unevenness of the mask pattern of the polymeric ionic liquid-containing material 40 is reduced. As a result, the roughness of the mask pattern is thought to be reduced. That is, a mask pattern of the polymeric ionic liquid-containing material 40 can be formed on the substrate 10 with a roughness smaller than the roughness of the recesses formed in the etching target film 20. In this way, the roughness of the mask pattern can be reduced.
[0049] Next, in step S306 shown in FIG. 4, the substrate 10 is etched using a mask pattern of the substance 40 containing the polymeric ionic liquid as a mask, as shown in (f) of FIG. 5A and (f) of FIG. 5B. This forms the substrate 10 with convex portions. Examples of etching methods include, when the substrate 10 is a silicon wafer, wet etching using an aqueous potassium hydroxide (KOH) solution or dry etching using plasma of a gas containing fluorine or chlorine. The process in step S306 shown in FIG. 4 corresponds to the process in step S104 shown in FIG. 1.
[0050] 5B(f), the roughness of the convex portions of the etched substrate 10 is comparable to the roughness of the mask pattern of the polymeric ionic liquid-containing material 40. In other words, it is possible to transfer onto the substrate 10 a mask pattern of the polymeric ionic liquid-containing material 40 having a roughness smaller than the roughness of the concave portions formed in the etching target film 20. In this way, the roughness of the pattern transferred onto the substrate 10 can be reduced.
[0051] (Third Example of Substrate Processing Method) Fig. 6 is a flowchart showing a third example of a substrate processing method according to an embodiment. Figs. 7A and 7B are schematic views for explaining the third example of a substrate processing method according to an embodiment. Fig. 7A shows the state of a substrate viewed from a direction along the surface of the substrate in the third example of the substrate processing method. Fig. 7B shows the state of a substrate viewed from a direction normal to the surface of the substrate in the third example of the substrate processing method.
[0052] First, in step S401 shown in Fig. 6, as shown in (a) of Fig. 7A and (a) of Fig. 7B, a substrate 10 provided with an etching target film 20 is prepared in the same manner as in step S201 shown in Fig. 2 and step S301 shown in Fig. 3. Here, the etching target film 20 is, for example, a silicon oxide film, and the substrate 10 is, for example, a silicon wafer.
[0053] 6, as shown in (b) of Figure 7A and (b) of Figure 7B, a substance 30 containing a polymerizable ionic liquid is applied to the etching target film 20 provided on the substrate 10 by, for example, spin coating. This forms a layer of the substance 30 containing a polymerizable ionic liquid on the substrate 10. Note that the process in step S402 shown in Figure 6 corresponds to the process in step S101 shown in Figure 1.
[0054] Next, in step S403 shown in FIG. 6 , as shown in (c) of FIG. 7A and (c) of FIG. 5B , for example, an electron beam is irradiated onto a portion of the layer of the polymerizable ionic liquid-containing substance 30. This causes a polymerization reaction of the polymerizable ionic liquid in a portion of the polymerizable ionic liquid-containing substance 30. For example, by scanning the layer of the polymerizable ionic liquid-containing substance 30 with an electron beam, a polymerization reaction of the polymerizable ionic liquid is caused in selective regions of the layer of the polymerizable ionic liquid-containing substance 30. In this way, a polymeric ionic liquid-containing substance 40 is produced on the etching target film 20 provided on the substrate 10. Note that the process in step S403 shown in FIG. 6 corresponds to the process in step S102 shown in FIG. 1 .
[0055] Next, in step S404 shown in FIG. 6 , the polymerizable ionic liquid-containing material 30 is developed, as shown in (d) of FIG. 7A and (d) of FIG. 7B . That is, the polymerizable ionic liquid-containing material 30, excluding the polymerizable ionic liquid-containing material 40, is removed. Examples of development methods include dip development using a solvent that dissolves the polymerizable ionic liquid. In this manner, a mask pattern of the polymerizable ionic liquid-containing material 40 is formed on the etching target film 20 provided on the substrate 10. Note that the process in step S404 shown in FIG. 6 corresponds to the process in step S103 shown in FIG. 1 .
[0056] Here, as shown in (d) of FIG. 7B , the roughness of the mask pattern of the polymeric ionic liquid-containing material 40 is relatively small due to the self-healing properties of the polymeric ionic liquid. More specifically, when developing the polymerizable ionic liquid-containing material 30, damage or irregularities may occur on the surface of the mask pattern of the polymeric ionic liquid-containing material 40. However, the self-healing properties of the polymeric ionic liquid allow polymer chains in the vicinity of the damage or irregularities on the surface of the mask pattern of the polymeric ionic liquid-containing material 40 to be repaired. Accordingly, the surface irregularities of the mask pattern of the polymeric ionic liquid-containing material 40 are reduced. This is believed to result in reduced roughness of the mask pattern. In other words, a mask pattern of the polymeric ionic liquid-containing material 40 with relatively small roughness can be formed on the substrate 10. In this way, the roughness of the mask pattern can be reduced.
[0057] Next, in step S405 shown in Figure 6, the etching target film 20 provided on the substrate 10 is etched using a mask pattern of the substance 40 containing the polymeric ionic liquid as a mask, as shown in (e) of Figure 7A and (e) of Figure 7B. Examples of the etching method include wet etching using hydrofluoric acid or dry etching using plasma of a gas containing fluorine when the etching target film 20 is a silicon oxide film. The process in step S405 shown in Figure 6 corresponds to the process in step S104 shown in Figure 1.
[0058] 7B(e), the roughness of the etched film 20 to be etched is comparable to the roughness of the mask pattern of the polymeric ionic liquid-containing material 40. That is, a mask pattern of the polymeric ionic liquid-containing material 40 with relatively small roughness can be transferred to the film 20 to be etched provided on the substrate 10. In this way, the roughness of the pattern transferred to the film 20 to be etched can be reduced.
[0059] (Substrate Processing System) Fig. 8 is a diagram illustrating an example of a substrate processing system for carrying out the substrate processing method according to the embodiment. The substrate processing system 100 shown in Fig. 8 includes a CVD apparatus 110, an ionic liquid processing apparatus 120, an etching apparatus 130, a resist coating apparatus 140, an exposure apparatus 150, a developing apparatus 160, a post-bake apparatus 170, a transport mechanism 180, and a control apparatus 200.
[0060] The CVD apparatus 110 is configured to provide a film 20 to be etched on a substrate 10. For example, a silicon wafer is etched with tetraethoxysilane (TEOS) and oxygen (O ２ ) gas to form a silicon oxide film on a silicon wafer. The ionic liquid treatment device 120 includes a spin coater 120a and an electron beam irradiation device 120b. The spin coater 120a is configured to apply a substance 30 containing a polymerizable ionic liquid to a substrate 10 or a film 20 to be etched provided on the substrate 10. The electron beam irradiation device 120b is configured to irradiate an electron beam onto a layer of the substance 30 containing the polymerizable ionic liquid, thereby producing a substance 40 containing a polymeric ionic liquid. The etching device 130 is configured to etch the substrate 10, the film 20 to be etched, the layer of the substance 40 containing the polymeric ionic liquid, etc.
[0061] The resist coating device 140 is configured to coat the photoresist 50. The exposure device 150 is configured to expose the photoresist 50 to KrF excimer laser light, EUV light, or the like through a photomask. The development device 160 is configured to develop the substance 30 containing the polymerizable ionic liquid or the photoresist 50. The post-baking device 170 is configured to bake the photoresist 50 after the photoresist 50 has been developed.
[0062] The transfer mechanism 180 is configured to hold the substrate 10 and to be movable within the substrate processing system 100. The transfer mechanism 180 is also configured to transfer the substrate 10 into and out of each of the CVD apparatus 110, the ionic liquid treatment apparatus 120, the etching apparatus 130, the resist coating apparatus 140, the exposure apparatus 150, the developing apparatus 160, and the post-bake apparatus 170. The control device 200 controls the CVD apparatus 110, the ionic liquid treatment apparatus 120, the etching apparatus 130, the resist coating apparatus 140, the exposure apparatus 150, the developing apparatus 160, the post-bake apparatus 170, and the transfer mechanism 180. In this way, the control device 200 executes the substrate processing method or the mask pattern formation method according to the embodiment. The configuration of the control device 200 will be described later.
[0063] Examples of the present disclosure will be specifically described below, but the present disclosure is not limited to the examples shown below.
[0064] Silicon oxide (SiO ２ A silicon wafer was prepared as a substrate on which a film of the polymerizable ionic liquid was formed. and a cation (1-ethyl-3-vinylimidazolium) which is a monomer represented by the chemical formula A polymerizable ionic liquid containing an anion (bis(trifluoromethanesulfonyl)imide) represented by the formula:
[0065] Next, the polymerizable ionic liquid was applied to the entire surface of the silicon oxide film on the silicon wafer by spin coating, thereby forming a film of the polymerizable ionic liquid on the silicon oxide film.
[0066] Next, the linear regions of the polymerizable ionic liquid film were irradiated with an electron beam to induce polymerization of the cations (monomers) in the linear regions of the polymerizable ionic liquid film, thereby producing polymerized cations and anions in the linear regions of the polymerizable ionic liquid film.
[0067] Next, the polymerizable ionic liquid was removed from the non-irradiated areas using propylene glycol monomethyl ether acetate as a solvent. This resulted in the formation of a polymeric ionic liquid mask pattern on the silicon oxide film. The polymeric ionic liquid mask pattern consisted of multiple linear wall portions with varying widths.
[0068] 9A and 9B are diagrams showing an example of a mask pattern of a polymeric ionic liquid according to an embodiment. FIG. 9A shows an example of a mask pattern of a polymeric ionic liquid after application of plasma of a fluorine-containing gas. Here, application of plasma of a fluorine-containing gas was intended to be dry etching using plasma of a fluorine-containing gas. FIG. 9B shows an example of a mask pattern of a polymeric ionic liquid before application of plasma of a fluorine-containing gas. FIG. 9C shows conditions for forming the mask pattern of the polymeric ionic liquid shown in FIG. 9A or 9B.
[0069] As shown in Figure 9(c), first, an electron beam was applied to a polymerizable ionic liquid film in a number of linear regions with widths of 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, and 200 nm. The spacing between the linear regions was 3.6 μm. Next, an electron beam was applied to two linear regions perpendicular to the linear regions. The width and spacing of the two linear regions were 500 nm and 20 μm, respectively. In this manner, the polymeric ionic liquid mask pattern shown in Figure 9(a) or (b) was formed.
[0070] When forming the mask pattern of the polymeric ionic liquid shown in Figure 9(a) or (b), the spin coating speed was set to 4000 rpm. The acceleration voltage, beam current, and dose of the electron beam were 30 kV, 1 nA, and 250 mC / cm, respectively. ２As shown in Figures 9(a) and (b), when a plurality of linear regions having a width of at least 30 nm were irradiated with an electron beam, the formation of a mask pattern of the polymeric ionic liquid consisting of a plurality of linear wall portions was confirmed.
[0071] FIG. 10 shows an example of a mask pattern for a polymeric ionic liquid according to an example. The mask pattern for a polymeric ionic liquid shown in FIG. 10 was formed in the same manner as in the formation of the mask pattern for a polymeric ionic liquid shown in FIG. 9(b). FIG. 10 shows the mask pattern for a polymeric ionic liquid before application of a fluorine-containing gas plasma. FIG. 10(a) shows the mask pattern for a polymeric ionic liquid obtained by irradiating a linear region having a width of 30 nm in a polymerizable ionic liquid film with an electron beam. FIG. 10(b) shows the mask pattern for a polymeric ionic liquid obtained by irradiating a linear region having a width of 40 nm in a polymerizable ionic liquid film with an electron beam. FIG. 10(c) shows the mask pattern for a polymeric ionic liquid obtained by irradiating a linear region having a width of 50 nm in a polymerizable ionic liquid film with an electron beam.
[0072] When forming the mask patterns of the polymeric ionic liquid shown in Figure 10(a), (b), or (c), the spin coating speed was set to 6000 rpm. The acceleration voltage, beam current, and dose of the electron beam were 30 kV, 1 nA, and 550 mC / cm, respectively. ２ As shown in (a), (b), and (c) of Figure 10, when multiple linear regions with widths of 30 nm, 40 nm, and 50 nm were irradiated with an electron beam, the formation of a polymeric ionic liquid mask pattern with multiple linear walls was confirmed. Furthermore, as shown in (a), (b), and (c) of Figure 10, the sidewalls of the polymeric ionic liquid mask pattern with multiple linear walls were smooth. This confirmed that the LER of the sidewalls of the polymeric ionic liquid mask pattern was small before dry etching using fluorine-containing gas plasma was applied. This confirmed that the LER of the sidewalls of the mask pattern can be reduced by using a polymeric ionic liquid.
[0073] FIG. 11 shows an example of a mask pattern for a polymeric ionic liquid according to an example. The mask pattern for a polymeric ionic liquid shown in FIG. 11 was formed in the same manner as in the formation of the mask pattern for a polymeric ionic liquid shown in FIG. 9(a). FIG. 11 shows the mask pattern for the polymeric ionic liquid after application of a plasma of a fluorine-containing gas. FIG. 11(a) shows the mask pattern for the polymeric ionic liquid when a linear region having a width of 30 nm in a polymerizable ionic liquid film is irradiated with an electron beam. FIG. 11(b) shows the mask pattern for the polymeric ionic liquid when a linear region having a width of 40 nm in a polymerizable ionic liquid film is irradiated with an electron beam. FIG. 11(c) shows the mask pattern for the polymeric ionic liquid when a linear region having a width of 50 nm in a polymerizable ionic liquid film is irradiated with an electron beam.
[0074] When forming the mask patterns of the polymeric ionic liquid shown in Figure 11(a), (b), or (c), the spin coating speed was set to 5,000 rpm. The acceleration voltage, beam current, and dose of the electron beam were 30 kV, 1 nA, and 550 mC / cm, respectively. ２ As shown in (a), (b), and (c) of Figure 11, when multiple linear regions with widths of 30 nm, 40 nm, and 50 nm were irradiated with an electron beam, the formation of a polymeric ionic liquid mask pattern with multiple linear walls was confirmed. Furthermore, as shown in (a), (b), and (c) of Figure 11, the sidewalls of the polymeric ionic liquid mask pattern with multiple linear walls were smooth. Therefore, it was confirmed that the LER of the sidewalls of the polymeric ionic liquid mask pattern was small even after dry etching using plasma of a fluorine-containing gas was applied. This confirmed that the LER of the sidewalls of the mask pattern can be reduced by using a polymeric ionic liquid.
[0075] Figure 12 shows an example of a mask pattern for a polymeric ionic liquid according to an example. The mask pattern for a polymeric ionic liquid shown in Figure 12 was formed in the same manner as in the formation of the mask pattern for a polymeric ionic liquid shown in Figure 9(a). Figure 12 shows an example of a mask pattern for a polymeric ionic liquid after dry etching using plasma of a fluorine-containing gas was applied to a silicon oxide film. Note that Figure 12(b) is an enlarged view of the dotted line portion in Figure 12(a), Figure 12(c) is an enlarged view of the dotted line portion in Figure 12(b), and Figure 12(d) is an enlarged view of the dotted line portion in Figure 12(c).
[0076] As shown in Figure 12, not only the sidewalls of the polymeric ionic liquid mask pattern, which consisted of multiple linear walls, but also the sides of the etched silicon oxide film were smooth. This confirmed that the smooth polymeric ionic liquid mask pattern was transferred to the silicon oxide film after dry etching using fluorine-containing gas plasma. This confirmed that the polymeric ionic liquid was able to reduce the LER not only on the sidewalls of the mask pattern but also on the silicon oxide film.
[0077] FIG. 13 shows an example of LER for a mask pattern according to an example and a mask pattern according to a comparative example. In FIG. 13, "molecular weight 3000" indicates a mask pattern according to an example in which the average molecular weight of the polymeric ionic liquid is approximately 3000. "molecular weight 15000" indicates a mask pattern according to an example in which the average molecular weight of the polymeric ionic liquid is approximately 15000. "KrF resist" indicates a conventional resist according to a comparative example. "Before" and "after" refer to before and after dry etching using a plasma of a fluorine-containing gas, respectively. The vertical axis of FIG. 13 indicates the root-mean-square roughness (Sq) value (nm) as the LER of the mask pattern.
[0078] 13, the Sq value of the mask pattern according to the example hardly changed before and after dry etching using plasma of a gas containing fluorine, both for molecular weights of 3000 and 15000. In other words, it was confirmed that the LER of the mask pattern according to the example was maintained even after dry etching using plasma of a gas containing fluorine.
[0079] 13, the Sq value of the mask pattern according to the comparative example increased after dry etching using plasma of a gas containing fluorine compared to before dry etching. That is, it was confirmed that the LER of the mask pattern according to the comparative example increased after dry etching using plasma of a gas containing fluorine.
[0080] (Hardware Configuration of Computer) The control device 200 included in the substrate processing system 100 shown in Fig. 8 is realized by, for example, a computer 300 as shown in Fig. 14. Fig. 14 is a diagram showing an example of the hardware configuration of the computer 300 constituting the control device 200 included in the substrate processing system 100. The computer 300 includes a CPU (Central Processing Unit) 310, a RAM (Random Access Memory) 320, a ROM (Read Only Memory) 330, and an auxiliary storage device 340. The computer 300 also includes a communication interface (I / F) 350, an input / output interface (I / F) 360, and a media interface (I / F) 370.
[0081] The CPU 310 operates and controls each unit based on programs stored in the ROM 330 or the auxiliary storage device 340. The ROM 330 stores a boot program executed by the CPU 310 when the computer 300 starts up, programs that depend on the hardware of the computer 300, and the like.
[0082] The auxiliary storage device 340 is, for example, a hard disk drive (HDD) or a solid state drive (SSD), and stores programs executed by the CPU 310 and data used by the programs. The CPU 310 reads the programs from the auxiliary storage device 340, loads them into the RAM 320, and executes the loaded programs. The communication I / F 350 receives signals and data from the ionic liquid treatment device 120, the etching device 130, etc. via a communication network (NW) such as a local area network (LAN), and sends them to the CPU 310. The communication I / F 350 also transmits signals and data generated by the CPU 310 to the ionic liquid treatment device 120, the etching device 130, etc. via the communication network.
[0083] The CPU 310 controls the input device and the output device via the input / output I / F 360. The CPU 310 acquires a signal input from the input device via the input / output I / F 360 and sends the signal to the CPU 310. The CPU 310 also outputs generated data to the output device via the input / output I / F 360.
[0084] The media I / F 370 reads a program or data stored in the recording medium 380 and stores it in the auxiliary storage device 340. The recording medium 380 is, for example, an optical recording medium such as a DVD (Digital Versatile Disc) or a PD (Phase Change Rewritable Disc), a magneto-optical recording medium such as an MO (Magneto-Optical disk), a tape medium, a magnetic recording medium, or a semiconductor memory.
[0085] The CPU 310 of the computer 300 executes a program loaded onto the RAM 320 to realize each process illustrated in the flowchart of Figure 1, 2, 4, or 6. The CPU 310 of the computer 300 reads the program loaded onto the RAM 320 from the recording medium 380 and stores it in the auxiliary storage device 340. As another example, the CPU 310 of the computer 300 may obtain a program from another device via the communication network and store it in the auxiliary storage device 340.
[0086] It should be noted that the disclosed embodiments are illustrative in all respects and should not be considered limiting. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims.
[0087] Furthermore, the following supplementary notes are disclosed regarding the above-described embodiment.
[0088] (Supplementary Note 1) A mask pattern forming method comprising: a coating step of coating a substrate with a substance containing a polymerizable ionic liquid; a polymerization step of inducing a polymerization reaction of the polymerizable ionic liquid in at least a portion of the substance containing the polymerizable ionic liquid to produce a substance containing a polymeric ionic liquid on the substrate; and a mask pattern forming step of forming a mask pattern of the substance containing the polymeric ionic liquid on the substrate using the substance containing the polymeric ionic liquid. (Supplementary Note 2) The mask pattern forming method according to Supplementary Note 1, wherein the coating step comprises forming a layer of the substance containing the polymerizable ionic liquid on the substrate by applying the substance containing the polymerizable ionic liquid to the substrate, the polymerization step comprises inducing a polymerization reaction of the polymerizable ionic liquid in the substance containing the polymerizable ionic liquid to produce a layer of the substance containing the polymeric ionic liquid on the substrate, and the mask pattern forming step comprises forming a resist pattern on the layer of the substance containing the polymeric ionic liquid and etching a portion of the layer of the substance containing the polymeric ionic liquid using the resist pattern as a mask to form a mask pattern of the substance containing the polymeric ionic liquid on the substrate. (Supplementary Note 3) The mask pattern forming method according to Supplementary Note 1, further comprising: a recess forming step of forming recesses in the substrate; wherein the applying step comprises applying a substance containing a polymerizable ionic liquid to the recesses to form a substance containing a polymerizable ionic liquid embedded in the recesses; the polymerizing step comprises generating a substance containing a polymeric ionic liquid embedded in the recesses by causing a polymerization reaction of the polymerizable ionic liquid in the substance containing the polymerizable ionic liquid; and the mask pattern forming step comprises etching a part of the substrate excluding the substance containing the polymeric ionic liquid to form a mask pattern of the substance containing the polymeric ionic liquid on the substrate.(Supplementary Note 4) The mask pattern forming method according to Supplementary Note 1, wherein the coating step comprises coating the substrate with a substance containing a polymerizable ionic liquid to form a layer of the substance containing the polymerizable ionic liquid on the substrate, the polymerizing step comprises inducing a polymerization reaction of the polymerizable ionic liquid in a part of the substance containing the polymerizable ionic liquid to produce a substance containing a polymeric ionic liquid on the substrate, and the mask pattern forming step comprises developing the substance containing the polymerizable ionic liquid to form a mask pattern of the substance containing the polymerizable ionic liquid on the substrate. (Supplementary Note 5) The mask pattern forming method according to any one of Supplementary Notes 1 to 4, wherein the substance containing the polymerizable ionic liquid comprises a solvent for the polymerizable ionic liquid, and the substance containing the polymeric ionic liquid comprises the solvent. (Supplementary Note 6) The mask pattern forming method according to any one of Supplementary Notes 1 to 5, wherein the polymerization step comprises irradiating the substance containing the polymerizable ionic liquid with light or an electron beam to induce a polymerization reaction of the polymerizable ionic liquid in the substance containing the polymerizable ionic liquid. (Supplementary Note 7) The mask pattern forming method according to any one of Supplementary Notes 1 to 6, wherein the applying step includes applying the substance containing the polymerizable ionic liquid to the substrate by spin coating. (Supplementary Note 8) A substrate processing method, comprising: the mask pattern forming method according to any one of Supplementary Notes 1 to 7; and a substrate etching step of etching the substrate using a mask pattern of the substance containing the polymeric ionic liquid as a mask.
[0089] 10 Substrate 20 Film to be etched 30 Substance containing polymerizable ionic liquid 40 Substance containing polymeric ionic liquid 50 Photoresist 60 Resist pattern 100 Substrate processing system 110 CVD apparatus 120 Ionic liquid processing apparatus 120a Spin coater 120b Electron beam irradiation apparatus 130 Etching apparatus 140 Resist coating apparatus 150 Exposure apparatus 160 Development apparatus 170 Post-bake apparatus 180 Transport mechanism 200 Control apparatus 300 Computer 310 CPU 320 RAM 330 ROM 340 Auxiliary storage device 350 Communication interface 360 Input / output interface 370 Media interface 380 Recording medium
Claims
1. A mask pattern forming method comprising: a coating step of coating a substrate with a substance containing a polymerizable ionic liquid; a polymerization step of generating a substance containing a polymerizable ionic liquid on the substrate by inducing a polymerization reaction of the polymerizable ionic liquid in at least a portion of the substance containing the polymerizable ionic liquid; and a mask pattern forming step of forming a mask pattern of the substance containing the polymerizable ionic liquid on the substrate using the substance containing the polymerizable ionic liquid.
2. The method for forming a mask pattern according to claim 1, wherein the coating step includes coating the substrate with a substance containing a polymerizable ionic liquid to form a layer of the substance containing the polymerizable ionic liquid on the substrate, the polymerization step includes causing a polymerization reaction of the polymerizable ionic liquid in the substance containing the polymerizable ionic liquid to generate a layer of the substance containing polymeric ionic liquid on the substrate, and the mask pattern formation step includes forming a resist pattern on the layer of the substance containing polymeric ionic liquid, and etching a portion of the layer of the substance containing polymeric ionic liquid using the resist pattern as a mask, to form a mask pattern of the substance containing polymeric ionic liquid on the substrate.
3. The method for forming a mask pattern according to claim 1, further comprising: a recess forming step of forming recesses in the substrate, wherein the applying step comprises applying a substance containing a polymerizable ionic liquid to the recesses to form a substance containing a polymerizable ionic liquid embedded in the recesses, the polymerizing step comprises generating a substance containing a polymerizable ionic liquid embedded in the recesses by inducing a polymerization reaction of the polymerizable ionic liquid in the substance containing the polymerizable ionic liquid, and the mask pattern forming step comprises forming a mask pattern of the substance containing the polymerizable ionic liquid on the substrate by etching a portion of the substrate excluding the substance containing the polymerizable ionic liquid.
4. The mask pattern forming method according to claim 1, wherein the coating step includes forming a layer of the material containing polymerizable ionic liquid on the substrate by coating the substrate with a material containing polymerizable ionic liquid; the polymerization step includes generating a material containing polymeric ionic liquid on the substrate by inducing a polymerization reaction of the polymerizable ionic liquid in a part of the material containing polymerizable ionic liquid; and the mask pattern forming step includes developing the material containing polymerizable ionic liquid to form a mask pattern of the material containing polymeric ionic liquid on the substrate.
5. The method for forming a mask pattern according to claim 1, wherein the substance containing the polymerizable ionic liquid contains a solvent for the polymerizable ionic liquid, and the substance containing the polymeric ionic liquid contains the solvent.
6. The method for forming a mask pattern according to claim 1, wherein the polymerization step includes inducing a polymerization reaction of the polymerizable ionic liquid in a substance containing the polymerizable ionic liquid by irradiating the substance containing the polymerizable ionic liquid with light or an electron beam.
7. The method of forming a mask pattern according to claim 1, wherein the applying step includes applying the substance containing the polymerizable ionic liquid to the substrate by spin coating.
8. A substrate processing method comprising: the mask pattern forming method according to any one of claims 1 to 7; and a substrate etching step of etching the substrate using a mask pattern of a substance containing the polymeric ionic liquid as a mask.