Film formation method
A film formation method using ultrasound and polymerization reduces the environmental impact and steps required for dense film deposition on substrates with irregularities, achieving efficient and high-quality film formation.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOKYO ELECTRON LTD
- Filing Date
- 2023-04-12
- Publication Date
- 2026-06-17
AI Technical Summary
The atomic layer deposition method (ALD) for forming dense films on substrates with irregularities is inefficient due to its high number of steps and environmental load.
A film formation method involving immersion in a polymerization initiator solution, application of ultrasound to bond initiators, and polymerization of monomers on the substrate surface to grow a polymer film without a reduced-pressure environment.
Reduces environmental burden and forms dense films with fewer steps, enabling high-quality film formation on substrates with irregularities.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a film forming method.
Background Art
[0002] Patent Document 1 discloses a technique for selectively preparing a self-assembled monolayer (SAM) on a part of a substrate surface by using a compound containing a hydrogen bonding group and a polymerizable diacetylene group. Further, Patent Document 2 discloses a technique for recess etching a SiN film of an ONON laminated structure portion.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Patent Document 2
Summary of the Invention
Problems to be Solved by the Invention
[0004] In semiconductor manufacturing, when forming a dense film on a substrate surface with irregularities, the atomic layer deposition method (ALD: Atomic Layer Deposition) is adopted. However, since this atomic layer deposition method is a process performed by alternately introducing a plurality of source gases in a reduced-pressure environment, the number of steps is large and the environmental load is high.
[0005] The present disclosure provides a film forming method capable of reducing the environmental load when forming a dense film.
Means for Solving the Problems
[0006] A pattern formation method according to one aspect of the present disclosure is a film formation method for forming a polymer film on the surface of a substrate in a solution, comprising the steps of: immersing the substrate in a first solution containing a polymerization initiator; applying ultrasound to the first solution to bond polymerization initiators to the surface of the substrate; immersing the substrate, on which the polymerization initiators are bonded, in a second solution containing a polymerizable monomer; and growing the polymer on the surface of the substrate by a polymerization reaction of the polymerizable monomer starting from the polymerization initiators. [Effects of the Invention]
[0007] According to one aspect of this disclosure, the environmental burden when forming a dense film can be reduced. [Brief explanation of the drawing]
[0008] [Figure 1] A diagram showing one step (first immersion step) of the film formation method. [Figure 2] A diagram showing one step in the film deposition method (ultrasonic application step). [Figure 3] A diagram showing one step (the second immersion step) of the film formation method. [Figure 4] A diagram showing one step (polymerization step) of the film formation method. [Figure 5] SEM image showing a thin film formed on a substrate. [Figure 6] SEM image showing a substrate with two layers of thin films stacked on it. [Figure 7] An illustrative diagram of a layered structure in which two types of thin films are stacked horizontally. [Figure 8] An illustrative diagram showing the layered structure of one of the thin films in Figure 7 removed. [Modes for carrying out the invention]
[0009] Embodiments of this disclosure will be described below with reference to the drawings. Note that parts common to each drawing may be denoted by the same or corresponding reference numerals, and their descriptions may be omitted.
[0010] <Substrate Processing Method> The film deposition method described herein is a method for forming a polymer film on the surface of a substrate in a solution.
[0011] The substrate material is not particularly limited. Examples of substrate materials include silicon (Si), silicon dioxide (SiO2), silicon nitride (Si3N4), and glass epoxy.
[0012] The form of the substrate is not particularly limited. Examples of substrate forms include a wafer made of single-crystal silicon (Si) processed in a semiconductor device manufacturing process, a substrate on which an insulating layer such as a silicon oxide film (silicon oxide) or silicon nitride film (silicon nitride) is formed, and a glass epoxy substrate (glass substrate) for manufacturing flat panel displays.
[0013] Furthermore, the substrate may be in the form of a substrate on which an SOC film (Silicon-on-Carbon) is formed, or a substrate on which an SOG film (Silicon-on-Glass) is further formed on an SOC film formed on the substrate.
[0014] A polymer film refers to a thin film composed of a polymer of monomers. The polymer film may be a single layer or a laminate of two or more layers. In this specification, a thin film refers to a film with a single layer thickness of 1 μm or less.
[0015] The film-forming method of this disclosure includes a step of immersing a substrate in a first solution containing a polymerization initiator (hereinafter referred to as the first immersion step). In the first immersion step, as shown in Figure 1, the substrate 3 is immersed in a solution 2 obtained by dissolving a polymerization initiator 4 in an organic solvent in a reaction vessel 1. Here, the solution 2 obtained by dissolving the polymerization initiator 4 is an example of the first solution.
[0016] The polymerization initiator is not particularly limited. For example, an organic compound having a chlorine-substituted alkyl group or a bromine-substituted alkyl group at one end and a polymerization initiation group at the other end can be used. As such an organic compound, it is preferable to use a sulfonyl chloride compound having a chlorine-substituted alkyl group or a bromine-substituted alkyl group at the end. In the sulfonyl chloride compound, the polymerization initiation group is a chlorosulfonyl group represented by -SO2Cl.
[0017] When the polymerization initiator is a sulfonyl chloride compound, the number of chlorine or bromine substituted on the alkyl group may be one or more. Also, between the chlorine-substituted alkyl group or bromine-substituted alkyl group and the chlorosulfonyl group, a cyclic organic compound such as an aromatic hydrocarbon or an alicyclic hydrocarbon or an arbitrary organic group such as an alkyl group or an amino group may be present.
[0018] Examples of such sulfonyl chloride compounds include sulfonyl chloride compounds such as trichloromethanesulfonyl chloride, tribromomethanesulfonyl chloride, and trichloromethylphenylsulfonyl chloride. Among these, it is preferable to use trichloromethanesulfonyl chloride. These may be used alone or in combination of two or more.
[0019] The first solution is a solution in which a polymerization initiator is dissolved in an organic solvent. The organic solvent is not particularly limited, but from the viewpoint of deactivating radical species generated when irradiated with ultrasonic waves described later, it is preferably an aprotic organic solvent. Examples of such aprotic organic solvents include tetrahydrofuran, dioxane, xylene, toluene, benzene, and the like. Among these, it is preferable to use tetrahydrofuran.
[0020] The concentration of the polymerization initiator in the first solution is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and even more preferably 1% by mass or more and 5% by mass or less with respect to the organic solvent.
[0021] In the film deposition method of this disclosure, if the substrate is silicon or silicon oxide, the substrate may be pre-treated with ozone before immersing it in the first solution.
[0022] Specifically, if the substrate 3 is made of silicon or silicon dioxide, the substrate 3 is exposed to an ozone atmosphere as a pretreatment before being immersed in solution 2 in the first immersion step. This causes polar groups such as hydroxyl groups to bond to the surface of the substrate 3, and when the first immersion step is performed in this state, polymerization initiators 4 such as chlorosulfonyl groups can easily bond to the surface of the substrate 3 to which polar groups such as hydroxyl groups are bonded.
[0023] The film formation method of this disclosure includes a step of applying ultrasound to a first solution to bond polymerization initiator groups to the surface of the substrate (hereinafter referred to as the ultrasound application step). In the ultrasound application step, as shown in Figure 2, when the substrate 3 is immersed in a solution 2 in which a polymerization initiator is dissolved in a reaction vessel 1, and ultrasound 5 is irradiated onto the solution 2, polymerization initiator groups 4 are bonded to the surface of the substrate 3.
[0024] In this specification, ultrasound refers to sound waves with frequencies beyond the audible range (16 kHz to 3000 kHz). Furthermore, ultrasound has high directivity and does not spread easily, so it does not attenuate easily in liquids. In addition, ultrasound has the property of creating localized high-temperature, high-pressure fields in liquids through cavitation (bubble formation and collapse in liquids), thereby generating microfluidism.
[0025] Furthermore, the surface of the substrate 3 may have a complex uneven pattern. Even in this case, the ultrasonic waves travel through the solution 2 to reach the uneven areas and cause cavitation. As a result, even if the surface of the substrate 3 has irregularities, a uniform film can be deposited in the areas with irregularities.
[0026] The conditions for irradiating with ultrasound are not particularly limited, but for example, it is preferable to irradiate with ultrasound having a frequency of 16 to 3000 kHz and an output of 50 to 600 W for 10 to 90 minutes.
[0027] The polymerization initiator is a polymerization initiator derived from the polymerization initiator. For example, if the polymerization initiator is a sulfonyl chloride compound, the polymerization initiator is the chlorosulfonyl group mentioned above.
[0028] It is preferable that the polymerization initiator is selectively bonded to the surface of a substrate having a predetermined polar group. For example, by pre-forming regions on the substrate surface that have polar groups such as hydroxyl groups (polar regions) and regions that do not have polar groups (non-polar regions), the polymerization initiator can be bonded only to the polar regions on the substrate surface.
[0029] When the polymerization initiator is a sulfonyl chloride compound, the chlorosulfonyl group, which is the polymerization initiator, is highly reactive with hydroxyl groups, and therefore can be selectively bonded to the surface of the substrate to which the hydroxyl group is attached.
[0030] The film-forming method of this disclosure includes a step of immersing a substrate on which polymerization initiator groups are bonded to its surface in a second solution containing a polymerizable monomer (hereinafter referred to as the second immersion step). In the second immersion step, as shown in Figure 3, with polymerization initiator groups 4 bonded to the surface of the substrate 3, the substrate 3 is immersed in a solution 2 obtained by dissolving a polymerizable monomer 8 in an organic solvent in a reaction vessel 1. Here, the solution 2 in which the polymerizable monomer 8 is dissolved is an example of the second solution.
[0031] The second solution may be prepared in reaction vessel 1 after the ultrasonic treatment step, and the substrate 3 may be immersed in the second solution in reaction vessel 1 after the ultrasonic treatment step, or the second solution may be prepared in a reaction vessel separate from reaction vessel 1, and the substrate 3 after the ultrasonic treatment step may be immersed in the second solution in the separate reaction vessel.
[0032] The polymerizable monomer is not particularly limited, but for example, radical polymerizable monomers such as crosslinkable monomers having two or more unsaturated double bonds in one molecule can be used.
[0033] The crosslinkable monomer having two or more unsaturated double bonds in one molecule is not particularly limited, but examples include dicyclopentadiene dimethacrylate, dicyclopentadiene diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, glycerin dimethacrylate, glycerin diacrylate, pentaerythritol triacrylate, and methacrylic anhydride. Among these, ethylene glycol dimethacrylate is preferred.
[0034] The concentration of polymerizable monomer in the second solution is preferably 0.1% to 40% by volume relative to the organic solvent, more preferably 0.5% to 20% by volume, and even more preferably 1% to 10% by mass.
[0035] Furthermore, in the second immersion step, radical active species may be generated on the surface of the substrate to which the polymerization initiator group is bound. Specifically, as shown in Figure 3, when the substrate 3 is immersed in a solution 2 in which polymerizable monomer 8 is dissolved in a reaction vessel 1, UV light or the like is irradiated onto the substrate 3, radicals 7 are generated on the surface of the substrate 3 to which the polymerization initiator group 4 is bound, and the polymerization initiator group 4 becomes a radical active species.
[0036] The film-forming method of this disclosure includes a step (polymerization step) in which a polymer is grown on the surface of a substrate by a polymerization reaction of polymerizable monomers starting from polymerization initiator groups. In the polymerization step, as shown in Figure 4, a substrate 3 on which polymerization initiator groups 4 are bonded to the surface is immersed in a solution 2 in which polymerizable monomers are dissolved in a reaction vessel 1, and a polymerization reaction of polymerizable monomers occurs, and a polymer (polymer of polymerizable monomer 8) grows on the substrate 3 starting from the polymerization initiator groups 4.
[0037] The conditions for the polymerization reaction are not particularly limited, but the polymerization time is, for example, 3 minutes to 5 hours, preferably 10 minutes to 3 hours, and more preferably 30 minutes to 2 hours. The temperature is also 3°C to 80°C, preferably 5°C to 60°C, and more preferably 10°C to 40°C. During the polymerization reaction, the second solution may be stirred, or the ultrasonic waves described above may be irradiated.
[0038] The type of polymerization reaction is not particularly limited, but a living radical polymerization reaction is preferred. A living radical polymerization reaction is a reaction that does not involve side reactions that deactivate the ends of the polymer, such as chain transfer reactions or termination reactions. When the polymerization reaction is a living radical polymerization reaction, polymers of uniform length are obtained, and it is possible to modify the ends of the polymer again, resulting in a sharp molecular weight distribution that is easy to control in terms of the degree of polymerization.
[0039] In the polymerization process, to carry out a living radical polymerization reaction, it is preferable to make the polymerization initiator group 4 a radical active species in the second immersion step, as described above. Furthermore, in the polymerization process, the living radical polymerization reaction can be carried out by irradiating the substrate 3 with UV light or the like.
[0040] As described above, the film deposition method of this disclosure provides a low-energy, low-step semiconductor manufacturing process by growing a polymer on the surface of a substrate to which polymerization initiators have been bonded by applying ultrasound to the first solution, through a polymerization reaction of polymerizable monomers. Therefore, the film deposition method of this disclosure can be carried out even without a reduced-pressure environment such as ALD, and can form a dense film with a small number of steps, thus contributing to a reduction in environmental impact.
[0041] Furthermore, even if the polymerizable monomer is a low molecular weight monomer, film formation is possible within the fine pattern. Moreover, by polymerizing low molecular weight monomers, an isotropic and dense film can be formed, enabling high-quality film formation.
[0042] Specifically, the ultrasonic application process allows polymerization initiation groups 4 to be bonded to the side surface 9 of the substrate 3, and the polymerization process allows a film of polymerizable monomers 8 (different polymers 81 and 82) to be formed horizontally starting from the polymerization initiation groups 4 (Figure 7). Furthermore, both films of the different polymers 81 and 82 become nanoscale thin films.
[0043] Furthermore, by selecting polymerizable monomers such that polymer 81 is decomposed by plasma (e.g., oxygen plasma) and polymer 82 is not decomposed by plasma, when plasma is irradiated onto the substrate 3, the polymer 81 film is removed and the polymer 82 film remains (Figure 8). This makes it possible to form a thin film on the substrate 3 with a nanoscale microspace between the side surface 9 and the remaining polymer 82. [Examples]
[0044] The film deposition method of this disclosure will be further explained below with reference to examples.
[0045] [Example 1] In a 50 mL vial, approximately 40 mL of tetrahydrofuran (THF) as an organic solvent and 1 g of trichloromethanesulfonyl chloride as a polymerization initiator were added and stirred to prepare a solution in which the polymerization initiator was dissolved in the organic solvent (first solution).
[0046] A silicon (Si) substrate was placed in a vial, and the vial was set in an ultrasonic irradiation device containing 1.5 L of water. The vial was then irradiated with ultrasound under a nitrogen atmosphere at a frequency of 430 kHz, an output of 80 W, and an irradiation time of 30 minutes.
[0047] After ultrasonic irradiation, 2 mL of ethylene glycol dimethacrylate was added to the vial as a polymerizable monomer (second solution), and after standing for 45 minutes (polymerization reaction), the substrate was removed from the vial, washed with THF, and dried.
[0048] The cross-section of the substrate after drying was observed using a scanning electron microscope (SEM). As a result, it was confirmed that a dense thin film was formed on the substrate surface in Example 1.
[0049] [Example 2] The procedure was the same as in Example 1, except that the silicon (Si) substrate was replaced with a silicon oxide (SiO2) substrate, and observations were made. As a result, it was confirmed that a dense thin film was formed on the substrate surface in Example 2.
[0050] [Example 3] The silicon (Si) substrate was subjected to the same procedure as in Example 1, except that it was exposed to ozone gas beforehand (ozone treatment) before being placed in the vial, and then observed. As a result, it was confirmed that a dense thin film was formed on the substrate surface in Example 3.
[0051] [Example 4] The silicon dioxide (SiO2) substrate was subjected to ozone gas beforehand (ozone treatment) before being placed in the vial, but otherwise the procedure was the same as in Example 2 and observed. As a result, it was confirmed that a dense thin film was formed on the substrate surface in Example 4 (Figure 5).
[0052] [Example 5] After the polymerization reaction, 2 mL of ethylene glycol dimethacrylate was added as a polymerizable monomer and allowed to stand for 45 minutes (polymerization reaction). The procedure was carried out in the same manner as in Example 4, and observations were made. As a result, it was confirmed that a dense thin film was laminated on the substrate surface in Example 5 (Figure 6).
[0053] Examples 1 to 5 showed that by applying ultrasound to the first solution to bond polymerization initiators to the substrate, a dense thin film can be formed on the substrate surface by growing a polymer through the polymerization reaction of a polymerizable monomer (see Figure 5). Furthermore, in Example 5, it was found that multiple dense thin films can be laminated on the substrate surface by repeating the polymerization reaction of the polymerizable monomer (see Figure 6).
[0054] The embodiments disclosed above include, for example, the following aspects: (Note 1) A method for forming a polymer film on the surface of a substrate in a solution, A step of immersing the substrate in a first solution containing a polymerization initiator, A step of applying ultrasound to the first solution to bond polymerization initiators to the surface of the substrate, The steps include immersing the substrate, on which the polymerization initiator is bonded to the surface, in a second solution containing a polymerizable monomer, The process includes growing the polymer on the surface of the substrate by a polymerization reaction of the polymerizable monomer starting from the polymerization initiator. Film formation method. (Note 2) The polymerization initiation group selectively bonds to the surface of a substrate having a predetermined polar group. The film deposition method described in Appendix 1. (Note 3) The polymerization reaction is a living radical polymerization reaction. The film formation method described in Appendix 1 or 2. (Note 4) A radical active species is generated on the surface of the substrate to which the polymerization initiating group is bonded. The film formation method described in any one of the appendices 1 to 3. (Note 5) The substrate is silicon or silicon oxide. The film formation method according to any one of the appendices 1 to 4, wherein the substrate is treated with ozone before immersing it in the first solution. (Note 6) The film formation method according to any one of Appendix 1 to 5, wherein irregularities are formed on the surface of the substrate.
[0055] While embodiments of this disclosure have been described above, this disclosure is not limited to these embodiments, and various modifications and changes are possible within the scope of the disclosure described in the claims. [Explanation of Symbols]
[0056] 1. Reaction vessel 2 solution 3 circuit boards 4. Polymerization initiators (polymerization initiator groups) 5. Ultrasound 6 UV 7 radicals 8 Polymerizable monomers 81 Polymers 82 Polymers 9 Side view
Claims
1. A method for forming a polymer film on the surface of a substrate in a solution, A step of immersing the substrate in a first solution containing a polymerization initiator, A step of applying ultrasound to the first solution to bond polymerization initiators to the surface of the substrate, The steps include immersing the substrate, on which the polymerization initiator is bonded to the surface, in a second solution containing a polymerizable monomer, The process includes growing the polymer on the surface of the substrate by a polymerization reaction of the polymerizable monomer starting from the polymerization initiator. Film formation method.
2. The polymerization initiation group selectively bonds to the surface of a substrate having a predetermined polar group. The method for forming a film according to claim 1.
3. The polymerization reaction is a living radical polymerization reaction. The method for forming a film according to claim 1.
4. A radical active species is generated on the surface of the substrate to which the polymerization initiating group is bonded. The method for forming a film according to claim 1.
5. The substrate is silicon or silicon oxide. The film-forming method according to claim 1, wherein the substrate is ozone-treated in advance before immersing it in the first solution.
6. The film-forming method according to any one of claims 1 to 5, wherein irregularities are formed on the surface of the substrate.