Hybrid photoresist composition for extreme ultraviolet photolithography applications

Abstract

A resist composition for use in the manufacture of integrated circuits, uses of the resist composition and a lithography method using the resist composition, wherein the resist composition comprises an alkyltin oxocage having a counterion selected from tetrakis(pentafluorophenyl)borate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis[3,5-bis(tert-butyl)phenyl]borate and tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate. A lithography method comprising the steps of: a) providing a resist composition comprising an alkyltin oxocage having a counterion selected from the above borate group; b) exposing the resist composition to a patterned radiation beam or electron beam to form a pattern in the resist composition; and c) developing the resist to form a circuit pattern.

Description

[Technical Field]

[0001] Cross-reference of related applications

[0001] This application claims priority to European / U.S. Patent Application Publication No. 21176454.3, filed on 28 May 2021, which is incorporated herein by reference in its entirety.

[0002]

[0002] The present invention relates to resist compositions for use in lithography, particularly in the manufacture of integrated circuits, the use of alkyltin oxocage cations having large non-nucleophilic pairing ions, a substrate comprising at least one surface coated with a composition comprising alkyltin oxocage cations having large non-nucleophilic pairing ions, and a method for manufacturing semiconductors using such resist compositions. In particular, the present invention relates to resist compositions for use in EUV lithography. Large non-nucleophilic pairing ions include tetrakis(pentafluorophenyl)borate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis[3,5-bis(tert-butyl)phenyl]borate, and tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate. [Background technology]

[0003]

[0003] A lithography apparatus is a machine built to apply a desired pattern onto a substrate. A lithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithography apparatus can project a pattern onto a layer of radiation-sensitive material (resist) provided onto a substrate from a patterning device (e.g., a mask).

[0004]

[0004] The wavelength of radiation used by the lithography apparatus to project a pattern onto a substrate determines the minimum size of the feature that can be formed on the substrate. A lithography apparatus using EUV radiation, which is electromagnetic radiation with a wavelength in the range of 4 to 20 nm, can be used to form smaller features on a substrate than a conventional lithography apparatus (for example, one that can use electromagnetic radiation with a wavelength of 193 nm).

[0005]

[0005] Known resists suitable for use in lithography are called chemically amplified resists (CARs) and are polymer-based. When exposed to electromagnetic waves or electron beams, the polymer in the CAR absorbs photons or interacts with electrons to generate secondary electrons. Due to the generation of secondary electrons, high-energy photons or electrons lose most of their energy. The secondary electrons in the resist may diffuse and generate even lower-energy secondary electrons until the energy of the secondary electrons is lower than the energy required to break bonds or cause ionization within the CAR. The generated electrons excite photoacid generators (PAGs), which can then decompose to catalyze deblocking reactions and change the solubility of the CAR.

[0006]

[0006] Alternative resist systems containing metal oxide nanoclusters for use in lithography, particularly EUV lithography, have been studied to address the problems of CAR. These alternative resist systems contain metal oxide nanoparticles or nanoclusters whose clustering is prevented by a ligand shell. During EUV exposure, photons are absorbed by the nanoparticles or nanoclusters, which leads to the generation of secondary electrons. The electrons break the bond between the ligand and the nanoparticles or nanoclusters. This causes the nanoparticles or nanoclusters to cluster together, changing the solubility of the resist. Because metal oxide nanoparticles have a larger EUV absorption cross-section than the carbon atoms in CAR, they are more likely to absorb EUV photons. Therefore, it is necessary to obtain a lower intensity beam with less power or to shorten the exposure time to EUV photons. Furthermore, the different conversion mechanism has potentially lower chemical noise than CAR resist systems. As described in Cardineau, B et al, Photolithographic properties of tin-oxo clusters using extreme ultraviolet light (13.5 nm), Microelectronic Engineering 127 (2014), pp. 44-50 and Haitjema. J., et al, Extreme ultraviolet patterning of tin-oxo cages, Journal of Micro / Nanolithography, MEMS, and MOEMS, 16(3), 033510 (2017), doi: 10.1117 / 1.JMM.16.3.033510, tin-oxo cage materials have been studied for use as photoresists for EUV lithography. Because tin-oxo cage materials become insoluble upon EUV irradiation, they function as negative-type resists.

[0007]

[0007] It is desirable to provide a resist composition that achieves acceptable resolution, acceptable line edge roughness, and acceptable sensitivity. CAR does not provide the best resolution because it is inherently probabilistic. Resists containing metal atoms are negative materials with only moderate sensitivity.

[0008]

[0008] One of the objects of the present invention is to address or overcome the shortcomings of existing resist compositions and to provide alternative resist compositions.

[0009]

[0009] Although this application generally refers to EUV lithography throughout, the present invention is not limited to EUV lithography, and it is understood that the subject matter of the present invention may be used in photolithography using electromagnetic waves with frequencies above or below EUV frequencies, or in other types of lithography such as electron beam lithography. [Overview of the project]

[0010]

[0010] According to a first aspect of the present invention, a resist composition for use in the manufacture of an integrated circuit is provided, the resist composition comprising an alkyltin oxocage having a counterion selected from tetrakis(pentafluorophenyl)borate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis[3,5-bis(tert-butyl)phenyl]borate and tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate.

[0011]

[0011] Accordingly, the composition contains an alkyltin oxocage cation having a tetrakis(pentafluorophenyl)borate counterion, a tetrakis[3,5-bis(trifluoromethyl)phenyl]borate counterion, a tetrakis[3,5-bis(tert-butyl)phenyl]borate counterion, or a tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate counterion.

[0012]

[0012] Thus, the composition may include an alkyltin oxo cage having a counter ion (anion) selected from one of the following. i) B(C6F5)4; ii)

Chem.

Chem.

Chem.

[0013]

[0013] Large non-nucleophilic counter ions such as tetrakis(pentafluorophenyl)borate counter ions have been found to make the resist composition function as a positive resist. Such resist compositions have also been found to be highly sensitive. When other counter ions such as hydroxide ions are present, this material acts as a negative resist. In particular, while the presence of large non-nucleophilic counter ions such as tetrakis(pentafluorophenyl)borate counter ions results in a positive resist, the mechanism of action regarding why other resist compositions containing an alkyltin oxo cage cation are negative resists remains unclear, and it is not desired to be bound by any scientific theory. The volume fraction of tin in the film formed from the compound of the present invention is lower than that in the film formed from a compound having a simple anion such as hydroxide ion, but due to the presence of fluorine atoms with high EUV absorbance, it is considered that the overall EUV cross-sectional area does not substantially decrease. Therefore, due to the high EUV absorbance brought about by fluorine atoms, the resist has high sensitivity. Furthermore, having a large group in the borate counter ion can also improve the sensitivity.

[0014]

[0014] The alkyltin oxocage cation is of the formula [(BuSn) 12 O 14 (OH)6] 2+ It may have. Therefore, the resist composition may contain two of the anionic counterions described herein.

[0015]

[0015] The resist composition may be a positive-type resist.

[0016]

[0016] The resist composition may contain a solvent. The solvent may be an alcohol or a fluorinated alkane. For example, the solvent may be butan-1-ol or fluorobenzene.

[0017]

[0017] According to a second aspect of the present invention, the use of an alkyltin oxocage, preferably an n-butyltin oxocage, having a counterion selected from the group consisting of tetrakis(pentafluorophenyl)borate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis[3,5-bis(tert-butyl)phenyl]borate, and tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate, in a resist composition is provided.

[0018]

[0018] The n-butyltin oxocage cation is of the formula [(BuSn) 12 O 14 (OH)6] 2+ It may have.

[0019]

[0019] It may be used as a positive type resist.

[0020]

[0020] Conventional metal-based EUV photoresists were negative-type resists. The present invention provides a CAR alternative which has the additional advantage of a larger absorption cross-section. Unexpectedly, the presence of one of the anions described herein provides positive-type functionality to the resist composition.

[0021] According to a third aspect of the present invention, there is provided a substrate comprising at least one surface coated with a composition comprising an alkyltin oxo cage having a counter ion selected from the group consisting of tetrakis(pentafluorophenyl)borate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis[3,5-bis(tert-butyl)phenyl]borate, and tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate.

[0022] Thus, the composition comprises an alkyltin oxo cage cation having a tetrakis(pentafluorophenyl)borate counter ion, a tetrakis[3,5-bis(trifluoromethyl)phenyl]borate counter ion, a tetrakis[3,5-bis(tert-butyl)phenyl]borate counter ion, or a tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate counter ion.

[0023]

[0023] The alkyltin oxo cage cation may preferably be an n-butyltin oxo cage dication having the formula [(BuSn) 12 O 14 (OH)6] 2+

[0024]

[0024] The substrate can be any substrate masked with a resist in a lithography process. For example, the substrate can contain silicon. The substrate can be a silicon wafer.

[0025]

[0025] According to a fourth aspect of the present invention, a lithography method is provided, comprising the steps of: a) providing a resist composition comprising an alkyltin oxocage having a counterion selected from the group consisting of tetrakis(pentafluorophenyl)borate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis[3,5-bis(tert-butyl)phenyl]borate and tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate; b) exposing the resist composition to a patterned radiation beam or electron beam to form a pattern on the resist composition; and c) developing the resist to form a circuit pattern.

[0026]

[0026] The alkyltin oxocage is preferably of the formula [(BuSn) 12 O 14 (OH)6] 2+ It may be an n-butyltin oxocage dication having . The resist can be developed in a solvent. The solvent may include alkylbenzene. The alkylbenzene may be selected from ethylbenzene, methylbenzene and xylene. The solvent may be a non-aromatic hydrocarbon solvent, such as petroleum ether (boiling point 40-60°C), or a low molecular weight aliphatic hydrocarbon such as n-alkane or isoalkane.

[0027]

[0027] The resist composition contains approximately 8 to approximately 100 mJ cm -2 Preferably about 10 to about 60 mJ cm -2 At doses of this magnitude, exposure can be directed to a patterned radiation beam or electron beam. The dose is up to approximately 50 mJ cm⁻¹. -2 , 40 mJ cm -2 up to approximately 30 mJ cm -2 Or up to approximately 25 mJ cm -2 This is possible. Because the compounds described herein have high absorption cross-sections and high sensitivity, the resist compositions can be patterned with relatively low doses. This is advantageous for the throughput of the lithography equipment.

[0028]

[0028] The resist composition may be provided by spin coating. With spin coating, the thickness of the resist layer can be carefully controlled.

[0029]

[0029] The patterned radiation beam may be an EUV radiation beam. This allows for the formation of very small patterns within the resist material, which is advantageous in the manufacture of integrated circuits. The patterned radiation beam may include radiation with wavelengths shorter than EUV.

[0030]

[0030] In chemically amplified resists (CARs), there is considerable chemical noise due to the mechanism of action of the CAR, mainly from the noise of the acid and quencher. Chemical noise causes roughness and limits the size of the features that can be realized. In particular, the noise is inherent in the mechanism of action of the CAR, as it is based on the diffusion of acid groups generated from the PAG into the resist before they can react. Acid groups generated from the photoacid generator (PAG) of chemically amplified resists diffuse from inside the resist to the outside of the portion of the resist exposed to electromagnetic waves, which contributes to contour blurring. Therefore, the location where the reaction that changes the solubility of the resist in the developer ultimately occurs is not limited to the region where EUV photons (or any other electromagnetic waves used) are incident on the resist. Furthermore, the acid and quencher of the resist are randomly dispersed. For small features, Poisson noise occurs because the absolute number of acid and quencher is limited. Furthermore, in CAR systems, pattern collapse becomes a problem at low critical dimensions as a result of contour blurring caused by the nature of the CAR system. Furthermore, the decreasing size of the features to be manufactured necessitates alternative resist platforms. When high doses are required, the resist needs to be exposed to an electromagnetic radiation source for extended periods. This reduces the number of chips that can be produced by a single machine within a given time. Tetrakis(pentafluorophenyl)borate counterions, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate counterions, tetrakis[3,5-bis(tert-butyl)phenyl]borate counterions, or tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate counterions, particularly (BuSn) 12 O 14 (OH)6(B(C6F5)4)2, (BuSn) 12 O 14 (OH)6(B((Ph(CF3)2)4)2, (BuSn) 12 O 14 (OH)6(B(Ph(tert-Bu)2)4)2 and (BuSn) 12 O 14By using alkyltin oxocages with (OH)6(B(Ph(C(CF3)2(OMe))2)4)2, at least some of the problems with existing resists can be addressed.

[0031]

[0031] Features described in relation to one aspect of the present invention are applicable to other aspects of the present invention, and features of each aspect of the present invention can be combined with features described in relation to other aspects of the present invention. All such combinations of subject matter are explicitly considered and disclosed.

[0032]

[0032] Hereinafter, embodiments of the present invention will be described as merely illustrative examples with reference to the attached schematic diagram. [Brief explanation of the drawing]

[0033] [Figure 1] This document describes a lithography system including a lithography apparatus and a radiation source that may be used to irradiate the resist composition of the present invention. [Figure 2a] This graph shows the residual thickness of a resist containing the resist composition according to the present invention as a function of dose. [Figure 2b] This is a schematic description of the structure of an exemplary bis(tetrakis(pentafluorophenyl)borate)alkyltin oxocage. [Figure 3a] This graph shows the remaining thickness of resists containing prior art resist compositions. [Figure 3b] This is a schematic description of the structure of existing alkyltin oxocages containing hydroxide counterions. [Figure 4] This graph shows the mass spectrum of [(BuSn)12O14(OH)6]2+ accompanied by a tetrakis(pentafluorophenyl)borate counterion. [Figure 5a] This graph shows the 1H NMR spectrum of [(BuSn)12O14(OH)6]2+ accompanied by OH- and tetrakis(pentafluorophenyl)borate counterions. [Figure 5b]This graph shows the 1H NMR spectrum of [(BuSn)12O14(OH)6]2+ accompanied by OH- and tetrakis(pentafluorophenyl)borate counterions. [Modes for carrying out the invention]

[0034]

[0033] Figure 1 shows a lithography system that may be used to irradiate the resist composition of the present invention. The lithography system includes a radiation source SO and a lithography apparatus LA. The radiation source SO is configured to generate an extreme ultraviolet (EUV) radiation beam B. The lithography apparatus LA includes an illumination system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS, and a substrate table WT configured to support a substrate W. A layer of the resist composition according to an embodiment of the present invention is provided on the substrate W. The illumination system IL is configured to adjust the radiation beam B before it is incident on the patterning device MA. The projection system is configured to project the radiation beam B (which is patterned here by the mask MA) onto the substrate W. The substrate W may include a previously formed pattern. If the substrate W includes a previously formed pattern, the lithography apparatus aligns the patterned radiation beam B with the previously formed pattern on the substrate W.

[0035]

[0034] The radiation source SO, the illumination system IL, and the projection system PS can all be constructed and arranged to be isolated from the external environment. The radiation source SO can be supplied with a gas (e.g., hydrogen) at a pressure below atmospheric pressure. The illumination system IL and / or the projection system PS can be supplied with a vacuum. The illumination system IL and / or the projection system PS can be supplied with a small amount of gas (e.g., hydrogen) at a pressure far below atmospheric pressure.

[0036]

[0035] The radiation source SO shown in Figure 1 is of a type that can be called a laser-generated plasma (LPP) source. Laser 1 (which may be, for example, a CO2 laser) is positioned to impart energy to a fuel, such as tin (Sn), provided from a fuel ejector 3, via a laser beam 2. Although tin is mentioned in the following description, any suitable fuel can be used. The fuel may be, for example, in liquid form, and may be, for example, a metal or an alloy. The fuel ejector 3 may include a nozzle configured to guide the tin (for example, in the form of a droplet) along a trajectory toward the plasma-forming region 4. Laser beam 2 is incident on the tin in the plasma-forming region 4. The imparting of laser energy to the tin results in plasma 7 in the plasma-forming region 4. Radiation, including EUV radiation, is emitted from the plasma 7 during the de-excitation and recombination of ions in the plasma.

[0037]

[0036] EUV radiation is collected and focused by a near-normal incident radiation concentrator 5 (sometimes more commonly called a normal incident radiation concentrator). The concentrator 5 may have a multilayer structure arranged to reflect EUV radiation (e.g., EUV radiation having a desired wavelength such as 13.5 nm). The concentrator 5 may have an elliptical configuration with two elliptical foci. As will be discussed below, the first focal point may be in the plasma-forming region 4, and the second focal point may be at an intermediate focal point 6.

[0038]

[0037] Laser 1 can be separated from the radiation source SO. If laser 1 is separated from the radiation source SO, the laser beam 2 can be sent from laser 1 to the radiation source SO using a beam delivery system (not shown) including, for example, a suitable guide mirror and / or beam expander and / or other optical systems. Laser 1 and the radiation source SO together can be considered as a radiation system.

[0039]

[0038] The radiation reflected by the light concentrator 5 forms a radiation beam B. The radiation beam B is focused at point 6 to form an image of the plasma-forming region 4 and serves as a virtual radiation source for the illumination system IL. Point 6, where the radiation beam B is focused, can be called an intermediate focus. The radiation source SO is positioned such that the intermediate focus 6 is located at or near the aperture 8 of the closed structure 9 of the radiation source.

[0040]

[0039] The radiation beam B is sent from the radiation source SO to the illumination system IL, which is configured to adjust the radiation beam. The illumination system IL may include a field facet mirror device 10 and a pupil facet mirror device 11. Together, the field facet mirror device 10 and the pupil facet mirror device 11 provide a radiation beam B having a desired cross-sectional shape and a desired angular distribution. The radiation beam B is sent from the illumination system IL and incident on a patterning device MA held by a support structure MT. The patterning device MA reflects and patterns the radiation beam B. The illumination system IL may include other mirrors or devices in addition to or instead of the field facet mirror device 10 and the pupil facet mirror device 11.

[0041]

[0040] Following reflection from the patterning device MA, the patterned radiant beam B enters the projection system PS. The projection system includes a plurality of mirrors, which are configured to project the radiant beam B onto a substrate W held by a substrate table WT. The projection system PS can apply a reduction factor to the radiant beam to form an image with features smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 can be applied. In Figure 1, the projection system PS has two mirrors, but the projection system can include any number of mirrors (e.g., six mirrors).

[0042]

[0041] The radiation source SO shown in Figure 1 may include components not shown. For example, a spectral filter may be provided to the radiation source. The spectral filter may substantially transmit EUV radiation but substantially block radiation of other wavelengths, such as infrared radiation.

[0043]

[0042] The term "EUV radiation" can be considered to encompass electromagnetic radiation having wavelengths in the range of 4 to 20 nm (for example, in the range of 13 to 14 nm). EUV radiation may have wavelengths less than 10 nm (for example, 6.7 nm or 6.8 nm in the range of 4 to 10 nm).

[0044]

[0043] Figure 1 depicts the radiation source SO as a laser-generated plasma (LPP) source, but any radiation source suitable for generating EUV radiation can be used. For example, EUV-emitting plasma can be generated by using an electrical discharge to convert a fuel (e.g., tin) into a plasma state. This type of radiation source can be called a discharge-generated plasma (DPP) source. The discharge can be generated by a power source, which may form part of the radiation source or may be a separate entity connected to the radiation source SO via an electrical connection.

[0045]

[0044] Figure 2a is a graph showing the thickness of the resist containing the resist composition according to the present invention as a function of dose. Figure 2b shows the structure of bis(tetrakis(pentafluorophenyl)borate)alkyltin oxocagement according to an embodiment of the present invention. The resist was spin-coated from fluorobenzene and developed with toluene. As is clear from the graph, approximately 10-25 mJ cm -2 At dose levels, the thickness of the resist after development was measured to be zero or very close to zero. At lower dose levels, the resist thickness was 15-25 nm. Therefore, the resist composition according to the present invention exhibits unexpected positive properties at such low dose levels. At higher dose levels, the residual thickness is greater than zero, but approximately 10 mJ cm. -2 Lower doses, and even 100 mJ cm²-2 It remains smaller than the thickness observed at the dose up to that point.

[0046]

[0045] Figure 3a is a graph showing the remaining thickness of resists containing prior art resist compositions. In Figure 3a, TinOH refers to a tin oxocage having hydroxide counterions, and TinA refers to a tin oxocage having AcOH counterions. Figure 3b is a schematic depiction of the structure of an existing alkyltin oxocage containing hydroxide counterions. The resists were spin-coated from toluene and developed with isopropanol and water. This comparative example yielded approximately 11-50 mJ cm⁻¹. -2 This shows how this resist composition becomes less soluble and therefore acts as a negative-type resist at a dose of approximately 100 mJ cm⁻¹. -2 This continues even at even higher doses. This occurs when the counterion is a hydroxide ion or an AcOH ion. At high doses, the remaining thickness of the resist begins to decrease, but such doses are extremely high and unsuitable for use in commercial lithography methods.

[0047]

[0046] Figure 4 shows the alkyltin oxocages in CDCl3 at 400 MHz, having hydroxide (black) or tetrakis(pentafluorophenyl)borate (gray) counteranions. 1 [(BuSn)] with tetrakis(pentafluorophenyl)borate counterions, as measured by 1H NMR spectroscopy. 12 O 14 (OH)6] 2+ of 1 This graph shows the 1H NMR spectrum. This graph is [(BuSn) 12 O 14 (OH)6] 2+ This graph shows the difference in the chemical shift of the proton of the butyl group between the case with a tetrakis(pentafluorophenyl)borate counterion and the case with a hydroxide counterion, illustrating the expected changes due to anion exchange. The x-axis represents parts per million (ppm), and the y-axis represents relative intensity (rel).

[0048]

[0047] Figures 5a and 5b are OH - and with tetrakis(pentafluorophenyl)borate counterions [(BuSn) 12 O 14 (OH)6] 2+ These are graphs showing the mass spectra. Figure 5a shows the negative ion electrospray ionization (ESI) mass spectrum of an alkyltin oxocage with a tetrakis(pentafluorophenyl)borate counterion, and Figure 5b shows the positive ion electrospray ionization (ESI) mass spectrum of an alkyltin oxocage with a tetrakis(pentafluorophenyl)borate counterion. These graphs show the atomic mass against charge of the negative ion (5a) and positive ion (5b), demonstrating that the atomic masses of both the anions and cations of the photoresist material are correct. The x-axis is atomic mass against charge (m / z), and the y-axis is intensity in arbitrary units. [Examples]

[0049]

[0048] The compounds described herein can be synthesized by any suitable synthetic route. For example, bis(tetrakis(pentafluorophenyl)borate) tin oxocage can be synthesized from dihydroxy tin oxocage via anion exchange. Dihydroxy tin cage (0.1 mmol; 250 mg) can be sonicated in 4 mL of toluene for 10 minutes. A 10 mL aqueous solution of tetrakis(pentafluorophenyl) hydrogen borate (0.2 mmol; 136 mg) can be added. The resulting mixture can be sonicated for 1 hour and then left at 20°C for 1 hour. The resulting slurry can be filtered (P4 grit) and washed with aliquots of 4 × 10 mL of water to obtain an off-white powder.

[0050]

[0049] Hydrogen tetrakis(pentafluorophenyl)borate can be synthesized using ion exchange between sodium tetrakis(pentafluorophenyl)borate and HCl. 20 mL of an aqueous solution of Na-B(C6F5)4 (10% w / w) can be heated to 40°C, and 0.3 mL of HCl (37% w / w) can be added while stirring at 40°C for 30 minutes. The solution is cooled to room temperature, and the product is extracted by adding 20 mL of diethyl ether five times, and then evaporated at 35°C. The crystals can also be recovered by filtration.

[0051]

[0050] The above description is intended to be illustrative and not limiting. It will be apparent to those skilled in the art that modifications to the present invention can be made as described without departing from the scope of the claims.

[0052]

[0051] The present invention relies on providing alkyltin oxocages having a large non-nucleophilic counterion, such as a tetrakis(pentafluorophenyl)borate counterion, which are suitable for low doses, particularly about 10-25 mJ cm⁻¹. -2 Furthermore, it unexpectedly provides positive properties even at higher doses. For this reason, compositions containing such compounds are very suitable for the manufacture of integrated circuits. The present invention provides a useful alternative positive resist composition that is sensitive to low dose radiation.

Claims

1. A resist composition for use in the manufacture of integrated circuits, comprising an alkyltin oxocage having a counterion selected from tetrakis(pentafluorophenyl)borate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis[3,5-bis(tert-butyl)phenyl]borate, and tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate.

2. Alkyltin oxocage cations are given by formula [(BuSn) １２ O １４ (OH) ６ ] ２＋ A resist composition according to claim 1, having the following characteristics.

3. The resist composition according to claim 1 or 2, wherein the resist is a positive-type resist.

4. The resist composition according to claim 1 or 2, further comprising a solvent, wherein the solvent is optionally an alcohol or a fluorinated hydrocarbon.

5. Use in a resist composition of an alkyltin oxocage, preferably an n-butyltin oxocage, having a counterion selected from the group consisting of tetrakis(pentafluorophenyl)borate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis[3,5-bis(tert-butyl)phenyl]borate, and tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate.

6. n-butyltin oxocage cation is given by formula [(BuSn) １２ O １４ (OH) ６ ] ２＋ The use according to claim 5, having the following characteristics.

7. A substrate comprising at least one surface coated with a composition containing an alkyltin oxocage having a counterion selected from the group consisting of tetrakis(pentafluorophenyl)borate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis[3,5-bis(tert-butyl)phenyl]borate, and tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate.

8. The alkyltin oxo cage cation is preferably an n-butyltin oxo cage dication having the formula [(BuSn) １２ O １４ (OH) ６ ２＋ The substrate according to claim 7, which is an n-butyltin oxo cage dication having​

9. Lithography method, a) Providing a resist composition comprising an alkyltin oxocage having a counterion selected from the group consisting of tetrakis(pentafluorophenyl)borate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis[3,5-bis(tert-butyl)phenyl]borate and tetrakis[(3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxypropan-2-yl)phenyl)phenyl]borate, b) The step of exposing the resist composition to a patterned radiation beam or electron beam to form a pattern on the resist composition, c) The step of developing the resist to form a circuit pattern. Lithography methods including [specific feature / method].

10. The alkyltin oxocage is preferably of the formula [(BuSn) １２ O １４ (OH) ６ ] ２＋ The lithography method according to claim 9, wherein the n-butyltin oxocage dication is having

11. The lithography method according to claim 9 or 10, wherein the resist is developed in a solvent, and optionally the solvent comprises an alkylbenzene, and optionally the alkylbenzene is selected from ethylbenzene, methylbenzene, and xylene.

12. The resist composition contains approximately 8 to approximately 100 mJ cm⁻¹ －２ Preferably about 10 to about 60 mJ / cm －２ The lithography method according to claim 9 or 10, wherein exposure is made to a patterned radiation beam or electron beam at a dose of .

13. The lithography method according to claim 9 or 10, wherein the resist composition is provided via spin coating.

14. The lithography method according to claim 9 or 10, wherein the patterned radiation beam is an EUV radiation beam.

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