ORGANICALLY MODIFIED METAL OXIDE NANOPARTICLE, METHOD FOR PRODUCING THE SAME, EUV PHOTORESIST MATERIAL, AND METHOD FOR PRODUCING ETCHING MASK

Abstract

An organically modified metal oxide nanoparticles that can be produced by a simple method and can increase the sensitivity and resolution of a resist material. The EUV photoresist material contains organically modified metal oxide nanoparticles and a solvent. The organically modified metal oxide nanoparticles include a core, a first modification group, and a second modification group. The core includes a plurality of metal atoms and a plurality of oxygen atoms bonded to the plurality of metal atoms. The first modification group is a carboxylic acid carboxylate ligand coordinated to the core. The second modification group is a carboxylic acid carboxylate ligand coordinated to the core and having a smaller molecular weight than the first modification group and/or an inorganic anion smaller in size than the first modification group.

Claims

1. An organically modified metal oxide nanoparticles comprising: a core including a plurality of metal atoms and a plurality of oxygen atoms bonded to the plurality of metal atoms; a first modification group which is a carboxylic acid carboxylate ligand coordinated to the core; and a second modification group which is a carboxylic acid carboxylate ligand coordinated to the core and having a smaller molecular weight than the first modification group and/or an inorganic anion smaller in size than the first modification group.

2. The organically modified metal oxide nanoparticles according to claim 1, wherein the first modification group is a methacrylic acid carboxylate ligand and the second modification group is an acetic acid carboxylate ligand and/or nitrate ion.

3. The organically modified metal oxide nanoparticles according to claim 1, wherein the nanoparticles are represented by General formula M.sub.6O.sub.4(OH).sub.4XnY.sub.12−n, provided that M is the metal atom and is one or more selected from the group consisting of Zr, Hf, and Ti, X is the first modification group, Y is the second modification group, and 1≤n≤11 is satisfied.

4. The organically modified metal oxide nanoparticles according to claim 1, wherein the metal is Zr.

5. An EUV photoresist material comprising: the organically modified metal oxide nanoparticles according to claim 1; and a solvent.

6. A method for producing organically modified metal oxide nanoparticles, the method comprising a reaction step of reacting a metal oxynitrate (an oxo-metal nitrate) and/or a metal oxyacetate an oxo-metal acetate) with methacrylic acid in a hydrophilic liquid.

7. The method for producing organically modified metal oxide nanoparticles according to claim 6, wherein the reaction step is carried out in an air atmosphere.

8. The method for producing organically modified metal oxide nanoparticles according to claim 6, wherein the metal oxynitrate (oxo-metal nitrate) is zirconium oxynitrate (oxo-zirconium nitrate) and the metal oxyacetate (oxo-metal acetate) is zirconium oxyacetate (oxo-zirconium acetate).

9. A method for producing an etching mask, comprising: a film forming step of applying the EUV photoresist material according to claim 5 onto a layer to be etched and drying the EUV photoresist material to obtain a resist film; an exposure step of irradiating the resist film with EUV in a predetermined pattern; and a developing step of removing a portion not irradiated with EUV in the exposure step to form an etching opening.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0020] FIG. 1 is an SEM image of a silicon wafer obtained in Example 1.

[0021] FIG. 2 is an SEM image of a silicon wafer obtained in Example 2.

[0022] FIG. 3 is an SEM image of a silicon wafer obtained in Comparative Example 1.

DESCRIPTION OF EMBODIMENTS

[0023] Organically modified metal oxide nanoparticles according to an embodiment of the present invention include a core, a first modification group, and a second modification group. The core includes a plurality of metal atoms and a plurality of oxygen atoms bonded to the plurality of metal atoms. The first modification group is a carboxylic acid carboxylate ligand coordinated to the core. The second modification group is a carboxylic acid carboxylate ligand coordinated to the core and having a smaller molecular weight than the first modification group and/or an inorganic anion smaller in size than the first modification group.

[0024] The first modification group is preferably a methacrylic acid carboxylate ligand because the organically modified metal oxide nanoparticles are easily soluble in propylene glycol 1-monomethyl ether 2-acetate, (PGMEA) which is a general-purpose resist solvent, and the reactivity of the organically modified metal oxide nanoparticles upon irradiation with EUV is improved. The metal is preferably one or more selected from the group consisting of Zr (zirconium), Hf (hafnium), and Ti (titanium), and more preferably Zr. The second modification group is preferably at least one of the group consisting of an acetic acid carboxylate ligand and a nitrate ion.

[0025] The organically modified metal oxide nanoparticles of the present embodiment are preferably represented by General formula M.sub.6O.sub.4(OH).sub.4X.sub.nYt.sub.2−n. Here, M is a metal and is one or more selected from the group consisting of Zr, Hf, and Ti, X is the first modification group, Y is the second modification group, and 1≤n≤11 is satisfied. Further, Z defined by X/(X+Y)×100, which represents the ratio of X and Y, preferably satisfies the relationship of 5 mol %≤Z≤95 mol %.

[0026] The size of the carboxylic acid carboxylate ligand which is the first modification group is, for example, 0.52 nm, and the size of the inorganic anion which is the second modification group is, for example, 0.33 nm. By comparing the above values, it can be confirmed that the size of the inorganic anion which is the second modification group is smaller than the size of the carboxylic acid carboxylate ligand which is the first modification group.

[0027] An EUV photoresist material according to an embodiment of the present invention contains the organically modified metal oxide nanoparticles of the present embodiment and a solvent. Examples of the solvent include butyl acetate, PGMEA, methanol, ethanol, and propanol. The EUV photoresist material of the present embodiment may further contain a dispersant such as a carboxylic acid, a stabilizer, and a photoresponsive agent such as a photoacid generator.

[0028] A method for producing organically modified metal oxide nanoparticles according to an embodiment of the present invention includes a reaction step of reacting at least one of a metal oxynitrate and a metal oxyacetate with methacrylic acid in a hydrophilic liquid. Examples of the hydrophilic liquid include water, methanol, ethanol, propanol, and acetone. The reaction step may be carried out in an air atmosphere. Therefore, no equipment is required to realize an extremely low humidity environment.

[0029] An example of a method for producing organically modified metal oxide nanoparticles using metal oxynitrate will be described. Methacrylic acid is added to an aqueous solution of metal oxynitrate, and if necessary, the mixture is stirred, and the obtained precipitate is collected by filtration and dried. In this way, the organically modified metal oxide nanoparticles of the present embodiment can be obtained by a simple method. When X is methacrylic acid carboxylate and Y is nitrate ion, the organically modified metal oxide nanoparticles preferably satisfy the relationship of 50 mol %<Z<84 mol %. Further, the metal oxynitrate is preferably zirconium oxynitrate.

[0030] In addition, an example of a method for producing organically modified metal oxide nanoparticles using metal oxyacetate will be described. Methacrylic acid is added to an aqueous solution of metal oxyacetate, and if necessary, the mixture is stirred, and the obtained precipitate is collected by filtration and dried. In this way, the organically modified metal oxide nanoparticles of the present embodiment can be obtained by a simple method. When X is methacrylic acid carboxylate and Y is acetic acid carboxylate, the organically modified metal oxide nanoparticles preferably satisfy the relationship of 58 mol % <Z <92 mol %. Further, the metal oxyacetate is preferably zirconium oxyacetate.

[0031] A method for producing an etching mask according to an embodiment of the present invention includes a film forming step, an exposure step, and a developing step. In the film forming step, the EUV photoresist material of the present embodiment is applied onto a layer to be etched and dried to obtain a resist film. The type of the layer to be etched is not particularly limited. Examples of the layer to be etched includes a silicon layer, a silicon oxide layer, or a silicon nitride layer.

[0032] In the exposure step, the resist film is irradiated with EUV in a predetermined pattern. In the developing step, the portion not irradiated with EUV in the exposure step is removed to form an etching opening. In the developing step, for example, the resist film is immersed in a developer such as butyl acetate, and the portion not irradiated with EUV is dissolved in the developer and removed. By using the EUV photoresist material of the present embodiment, the width of the etching mask can be reduced to 20 nm or less. Therefore, the layer to be etched can be finely etched.

EXAMPLES

Example 1

[0033] An aqueous solution of zirconium oxynitrate was prepared by dissolving 1.2 g of zirconium oxynitrate in 3 mL of a 5.0 M aqueous nitric acid solution. Into 1 mL of the zirconium oxynitrate aqueous solution, 1 mL of methacrylic acid was added, and the mixture was stirred for 5 minutes and then allowed to stand at room temperature for 5 days. The obtained precipitate was collected by filtration under decompression and vacuum dried at room temperature for 1 day to obtain a white powder. As a result of elemental analysis of the white powder, the carbon and nitrogen contents were found to be 20.5 wt % and 3.8 wt %, respectively. The ratio of amount of substance (so-called mol ratio) was methacrylic acid: nitric acid=61: 39=7.3:4.7. As a result of thermogravimetric analysis of the white powder, the weight loss rate was found to be 54%. Further, the size of methacrylic acid was about 0.52 nm, and the size of nitrate ion was about 0.33 nm.

[0034] As a result of IR analysis of the white powder, an absorption peak derived from the carboxy group (1558 cm.sup.−1) and an absorption peak of the stretching vibration band of C═C (1647 cm.sup.−1) of methacrylic acid, and an absorption peak of the out-of-plane bending vibration band of the vinyl group CH (827 cm.sup.−1) were confirmed. In addition, as a result of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) of the white powder, peaks were found at m/z 1456, 1588, 1611, and 1719, which are almost equal to the molecular weight of zirconia hexamer with some missing methacrylic acid ligands. From the above, it is considered that the obtained white powder is Zr.sub.6O.sub.4(OH).sub.4(MAA).sub.7.3(NO.sub.3).sub.4.7.

[0035] In 5.0 g of PGMEA, 0.2 g of the white powder was dissolved. The undissolved white powder was removed using centrifugation and a filter with a pore size of 0.45 μm. As a result of dynamic light scattering analysis of the solution after the removal, the volume-based average particle size of the white powder was found to be about 2 nm. From this result, it can be considered that the obtained white powder is organically modified metal oxide nanoparticles in which methacrylic acid and nitric acid are coordinated with respect to the core constituted by zirconium and oxygen.

[0036] PGMEA was further added to the solution and diluted twice to obtain a solution A for EUV exposure. The solution A for EUV exposure was dropped onto a silicon wafer and rotated at 1500 rpm for 60 seconds to form a film, and then heated at 80° C. for 60 seconds to obtain a resist film A. The film thickness of the resist film A was measured with a spectroscopic ellipsometer and found to be 20 nm. The resist film A was exposed to EUV with an irradiation amount of 12 to 76 mi/cm.sup.2 through a predetermined pattern, and then immersed in butyl acetate for 30 seconds for development to remove the EUV non-irradiated portion of the resist film A.

[0037] The silicon wafer after development was observed by SEM. FIG. 1 shows an SEM image of the developed silicon wafer when EUV exposure was performed at an irradiation amount of 52 mi/cm.sup.2. As shown in FIG. 1, the line width of the insolubilized resist film A (light-colored portion), which is an etching mask remaining on the silicon wafer (dark-colored portion), was 18 nm, which is narrower than that in Comparative Example 1 described later, formation of nano-patterning with high resolution was confirmed.

Example 2

[0038] After adding 2 mL of methacrylic acid to 1 mL of a 20 wt % zirconium oxyacetate aqueous solution, the mixture was stirred at room temperature for 1 hour. The obtained precipitate was collected by filtration under decompression and vacuum dried at room temperature for 1 day to obtain a white powder. As a result of elemental analysis of the white powder, the carbon content was found to be 29 wt %. In addition, as a result of thermogravimetric analysis of the white powder, the weight loss rate was found to be 52%. Furthermore, as a result of IR analysis of the white powder, an absorption peak derived from the carboxy group and an absorption peak of the stretching vibration band of C═C (1647 cm.sup.−I) of methacrylic acid (1558 cm.sup.−1), and an absorption peak of the out-of-plane bending vibration band of the vinyl group CH (827 cm.sup.−1) were confirmed.

[0039] As a result of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) of the white powder, peaks were found at m/z 1595 and 1704, which are almost equal to the molecular weight of zirconia hexamer with a methacrylic acid ligand and an acetic acid ligand, and the molecular weight of the zirconia hexamer with some missing ligands thereof. As a result of .sup.1H-NMR analysis of the white powder dissolved in the solvent, the ratio of amount of the substance was found to be methacrylic acid: acetic acid=87:13=10.4:1.6. From the above, it is considered that the obtained white powder is Zr.sub.6O.sub.4(OH).sub.4(MAA).sub.10.4Ac.sub.1.6 on average.

[0040] In 2.0 g of PGMEA, 0.06 g of the white powder was dissolved. The undissolved white powder was removed using centrifugation and a filter with a pore size of 0.45 μm. As a result of dynamic light scattering analysis of the solution after the removal, the volume-based average particle size of the white powder was found to be about 2 nm. From this result, it can be considered that the obtained white powder is organically modified metal oxide nanoparticles in which methacrylic acid and acetic acid are coordinated with respect to the core constituted by zirconium and oxygen.

[0041] PGMEA was further added to the solution and diluted twice to obtain a solution B for EUV exposure. The solution B for EUV exposure was dropped onto a silicon wafer and rotated at 1500 rpm for 60 seconds to form a film, and then heated at 80° C. for 60 seconds to obtain a resist film B. The film thickness of the resist film B was measured with a spectroscopic ellipsometer and found to be 20 nm. The resist film B was exposed to EUV with an irradiation amount of 7 to 39 mJ/cm.sup.2 through a predetermined pattern, and then immersed in butyl acetate for 30 seconds for development to remove the EUV non-irradiated portion of the resist film B.

[0042] The silicon wafer after development was observed by SEM. FIG. 2 shows an SEM image of a silicon wafer after development when EUV exposure was performed at a low irradiation amount of 22 mJ/cm.sup.2, that is, under the condition that high sensitivity is required for the resist film. As shown in FIG. 2, the line width of the insolubilized resist film B (light-colored portion), which is an etching mask remaining on the silicon wafer (dark-colored portion), was 23 nm, formation of nano-patterning with high sensitivity at an irradiation amount lower than that in Comparative Example 1 described later was confirmed.

Example 3

[0043] A beaker A containing 5 mL of a 20 wt % zirconium oxyacetate aqueous solution and a beaker B containing 10 mL of methacrylic acid were placed in a closed container and left at room temperature for 7 days. The vapor of methacrylic acid was gradually dissolved in the zirconium oxyacetate aqueous solution to obtain a precipitate in the beaker A. The precipitate was collected by filtration under decompression and vacuum dried at room temperature for 1 day to obtain a white powder. As a result of IR analysis of the white powder, an absorption peak derived from the carboxy group (1558 cm.sup.−1) and an absorption peak of the stretching vibration band of C═C (1647 cm.sup.1) of methacrylic acid, and an absorption peak of the out-of-plane bending vibration band of the vinyl group CH (827 cm.sup.−1) were confirmed.

[0044] As a result of .sup.1H-NMR analysis of the white powder dissolved in the solvent, the ratio of the amount of substance was found to be methacrylic acid: acetic acid=34:66=4.1:7.9. From the above, it is considered that the obtained white powder is Zr.sub.6O.sub.4(OH).sub.4(MAA).sub.4.1Ac.sub.7.9 on average.

Comparative Example 1

[0045] In a glovebox, 1.02 g of methacrylic acid was added to 1.40 g of 85% zirconium butoxide solution in 1-butanol. Then, the mixture was stirred and allowed to stand for about 3 weeks to obtain a single crystal of Zr.sub.6O.sub.4(OH).sub.4(MAA).sub.12. The single crystal was collected by filtration under decompression, vacuum dried at room temperature for 1 day, and pulverized to obtain a white powder. As a result of elemental analysis of the white powder, the carbon content was found to be 36 wt %. As a result of thermogravimetric analysis of the white powder, the weight loss rate was found to be 57%.

[0046] In addition, as a result of IR analysis of the white powder, an absorption peak derived from the carboxy group (1558 cm.sup.−1) and an absorption peak of the stretching vibration band of C═C (1647 cm.sup.−1) of methacrylic acid, and an absorption peak of the out-of-plane bending vibration of the vinyl group CH (827 cm.sup.−1) were confirmed. Furthermore, as a result of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) of the white powder, a peak was found at m/z 1702, which is almost equal to the molecular weight of zirconia hexamer coordinated with methacrylic acid. From the above, it is considered that the obtained white powder is Zr.sub.6O.sub.4(OH).sub.4(MAA).sub.12 on average.

[0047] In 3.0 g of PGMEA, 0.09 g of the white powder was dissolved. The undissolved white powder was removed using centrifugation and a filter with a pore size of 0.45 μm. As a result of dynamic light scattering analysis of the solution after the removal, the volume-based average particle size of the white powder was found to be about 2 nm. From this result, it can be considered that the obtained white powder is organically modified metal oxide nanoparticles in which methacrylic acid is coordinated with respect to the core constituted by zirconium and oxygen. PGMEA was further added to the solution and diluted twice to obtain a solution C for EUV exposure. The solution C for EUV exposure was dropped onto a silicon wafer and rotated at 1500 rpm for 60 seconds to form a film, and then heated at 80° C. for 60 seconds to obtain a resist film C. The film thickness of the resist film C was measured with a spectroscopic ellipsometer and found to be 20 nm.

[0048] The resist film C was exposed to EUV with an irradiation amount of 28 to 60 mJ/cm.sup.2 through a predetermined pattern, and then immersed in butyl acetate for 30 seconds for development to remove the EUV non-irradiated portion of the resist film C. The silicon wafer after development was observed by SEM. FIG. 3 shows an SEM image of the developed silicon wafer when EUV exposure was performed at an irradiation amount of 46 mJ/cm.sup.2. As shown in FIG. 3, the line width of the insolubilized resist film C (light-colored portion), which is an etching mask remaining on the silicon wafer (dark-colored portion), was 21 nm.

Example 4

[0049] In a glovebox, 0.9 mL of methacrylic acid, which is the raw material of the second modification group, and 1.1 mL of isobutyric acid, which is the raw material of the first modification group were added to 1.63 mL of 80% zirconium butoxide solution in 1-butanol. Then, the mixture was stirred for about 7 days to obtain a white precipitate. The white precipitate was collected by filtration under decompression, vacuum dried at room temperature for 1 day, and pulverized to obtain a white powder. As a result of .sup.1H-NMR analysis of the white powder dissolved in the solution, the ratio of amount of substance was found to be methacrylic acid: isobutyric acid=7:3. In 5.0 g of PGMEA, 0.15 g of the white powder was dissolved. As a result of dynamic light scattering analysis of the solution, the volume-based average particle size of the white powder was found to be about 1 nm. From the above, it is considered that the obtained white powder is organically modified metal oxide nanoparticles in which methacrylic acid and isobutyric acid are coordinated with respect to the core constituted by zirconium and oxygen.

[0050] The solution was dropped onto a silicon wafer and rotated at 1500 rpm for 60 seconds to form a film, and then heated at 80° C. for 60 seconds to obtain a resist film. The resist film was exposed to EUV with an irradiation amount of 0 to 25 mJ/cm.sup.2, then immersed in butyl acetate for 30 seconds for development, dried, and then the film thickness was measured with a spectroscopic ellipsometer. As a result, a film insolubilized at an irradiation amount of 15 mJ/cm.sup.2 or more remained, and the film thickness increased with an increase in the irradiation amount, and at 25 mJ/cm.sup.2, the film thickness became about 17 nm, confirming the reactivity with EUV exposure.

Example 5

[0051] In a glovebox, 1 mL of methacrylic acid, which is the raw material of the first modification group, and 1 mL of propionic acid, which is the raw material of the second modification group were added to 1.63 mL of 80% zirconium butoxide solution in 1-butanol. Then, the mixture was stirred for about 5 days to obtain a white precipitate. The white precipitate was collected by filtration under decompression, vacuum dried at room temperature for 1 day, and pulverized to obtain a white powder. As a result of .sup.1H-NMR analysis of the white powder dissolved in the solution, the ratio of amount of substance was found to be methacrylic acid: propionic acid=7: 3. In 5.0 g of PGMEA, 0.15 g of the white powder was dissolved. As a result of dynamic light scattering analysis of the solution, the volume-based average particle size of the white powder was found to be about 2 nm. From the above, it is considered that the obtained white powder is organically modified metal oxide nanoparticles in which methacrylic acid and propionic acid are coordinated with respect to the core constituted by zirconium and oxygen.

[0052] The solution was dropped onto a silicon wafer and rotated at 1500 rpm for 60 seconds to form a film, and then heated at 80° C. for 60 seconds to obtain a resist film. The resist film was exposed to EUV with an irradiation amount of 0 to 25 mJ/cm.sup.2, then immersed in butyl acetate for 30 seconds for development, dried, and then the film thickness was measured with a spectroscopic ellipsometer. As a result, a film insolubilized at an irradiation amount of 5 mJ/cm.sup.2 or more remained, and the film thickness increased with an increase in the irradiation amount, and at 25 mJ/cm.sup.2, the film thickness became about 40 nm, confirming the reactivity with EUV exposure.

Example 6

[0053] In a glovebox, 1 mL of methacrylic acid, which is the raw material of the second modification group, and 1 mL of butyric acid, which is the raw material of the first modification group were added to 1.63 mL of 80% zirconium butoxide solution in 1-butanol. Then, the mixture was stirred for about 5 days to obtain a white precipitate. The white precipitate was collected by filtration under decompression, vacuum dried at room temperature for 1 day, and pulverized to obtain a white powder. As a result of .sup.1H-NMR analysis of the white powder dissolved in the solution, the ratio of amount of substance was found to be methacrylic acid: isobutyric acid=2: 1. In 5.0 g of PGMEA, 0.15 g of the white powder was dissolved. As a result of dynamic light scattering analysis of the solution, the volume-based average particle size of the white powder was found to be about 2 nm. From the above, it is considered that the obtained white powder is organically modified metal oxide nanoparticles in which methacrylic acid and butyric acid are coordinated with respect to the core constituted by zirconium and oxygen.

[0054] The solution was dropped onto a silicon wafer and rotated at 1500 rpm for 60 seconds to form a film, and then heated at 80° C. for 60 seconds to obtain a resist film. The resist film was exposed to EUV with an irradiation amount of 0 to 25 mJ/cm.sup.2, then immersed in butyl acetate for 30 seconds for development, dried, and then the film thickness was measured with a spectroscopic ellipsometer. As a result, a film insolubilized at an irradiation amount of 9 mJ/cm.sup.2 or more remained, and the film thickness increased with an increase in the irradiation amount, and at 25 mJ/cm.sup.2, the film thickness became about 33 nm, confirming the reactivity with EUV exposure.