JP4687334B2 - Immersion exposure liquid and immersion exposure method - Google Patents

Description

  The present invention relates to a liquid for immersion exposure and an immersion exposure method.

Stepper-type or step-and-scan projection exposure that transfers a reticle pattern as a photomask to each shot area on a photoresist-coated wafer via a projection optical system when manufacturing semiconductor elements, etc. The device is in use.
The theoretical limit value of the resolution of the projection optical system provided in the projection exposure apparatus becomes higher as the exposure wavelength used is shorter and the numerical aperture of the projection optical system is larger. For this reason, with the miniaturization of integrated circuits, the exposure wavelength, which is the wavelength of radiation used in the projection exposure apparatus, has become shorter year by year, and the numerical aperture of the projection optical system has also increased.
Further, when performing exposure, the depth of focus is important as well as the resolution. The theoretical limit values of the resolution R and the depth of focus δ are respectively expressed by the following mathematical formulas.

R = k1 · λ / NA (i)
δ = k2 · λ / NA ² (ii)

Where λ is the exposure wavelength, k1 and k2 are process coefficients, NA is the numerical aperture of the projection optical system, and the refractive index of air is 1, and is defined by the following equation (ii ′). That is, when the same resolution R is obtained, a greater depth of focus δ can be obtained by using radiation having a short wavelength.

NA = sin θ (θ = maximum incident angle of exposure light on resist surface) (ii ′)

As described above, so far, the demand for miniaturization of integrated circuits has been met by shortening the wavelength of the exposure light source and increasing the numerical aperture, and now an ArF excimer laser (wavelength: 193 nm) is used as the exposure light source. Mass production of 1L1S (1: 1 line and space) half pitch 90 nm nodes is under study. However, it is said that it is difficult to achieve the next generation half pitch 65 nm node or 45 nm node, which is further miniaturized, only by using an ArF excimer laser. Thus, for these next-generation technologies, the use of short-wavelength light sources such as F ₂ excimer laser (wavelength 157 nm), EUV (wavelength 13 nm), etc. is being studied. However, the use of these light sources is technically difficult and is still difficult to use.

In the above exposure technique, a photoresist film is formed on the exposed wafer surface, and a pattern is transferred to the photoresist film. In a conventional projection exposure apparatus, a space in which a wafer is placed is filled with air or nitrogen having a refractive index of 1. At this time, when the space between the wafer and the lens of the projection exposure apparatus is filled with a medium having a refractive index n, it is reported that the theoretical limit values of the resolution R and the depth of focus δ are expressed by the following formulas. Yes.

R = k1 · (λ / n) / NA (iii)
δ = k2 · nλ / NA ² (iv)

Here, NA is not the actual numerical aperture of the projection optical system, but means a constant defined by the above formula (ii ′) (exactly, the numerical aperture NA ′ of the projection optical system is NA ′ = n sin θ (n is (Same definition as above))
The above formula fills the liquid of refractive index n between the lens of the projection exposure apparatus and the wafer, and sets an appropriate optical system, thereby reducing the resolution limit value and the depth of focus to 1 / n and n times, respectively. It means that it is theoretically possible to do. For example, when water is used as the medium in the ArF process, since the refractive index n of light having a wavelength of 193 nm in water is n = 1.44, the resolution R is compared with that in exposure using air or nitrogen as a medium. It is theoretically possible to design an optical system with 69.4% (R = k1 · (λ / 1.44) / NA) and a focal depth of 144% (δ = k2 · 1.44λ / NA ² ).
A projection exposure method that can reduce the effective wavelength of radiation for exposure in this way and transfer a finer pattern is called immersion exposure, and in future lithography miniaturization, especially lithography in units of several tens of nm, It is considered an essential technique, and its projection exposure apparatus is also known (see Patent Document 1).

Conventionally, in the immersion exposure method, the liquid filled between the lens of the projection optical system and the substrate is pure water in the ArF excimer laser and fluorine because of high transparency at 157 nm in the F ₂ excimer laser. The use of system inert liquids has been studied.
Pure water is easy to obtain in semiconductor manufacturing factories and has no environmental problems. In addition, it is used as an immersion liquid for ArF (see Patent Document 2) because it can easily adjust the temperature and prevent thermal expansion of the substrate due to heat generated during exposure (see Patent Document 2). Adoption to mass production is certain.
On the other hand, a liquid to which methyl alcohol or the like is added as an additive for reducing the surface tension of pure water and increasing the surface activity is also known (see Patent Document 3).
However, when pure water is used, water may penetrate into the photoresist film, resulting in a shape deterioration in which the cross-sectional shape of the photoresist pattern becomes a T-top shape, and resolution may be reduced. In addition, water-soluble components such as photoacid generators, basic additives, and acids generated by exposure to the photo-resist elute into water, resulting in shape deterioration such as T-top shape, resolution, depth of focus, etc. Reduction, bridging defects, defects in patterns after development, and lens surfaces may be contaminated. In addition, elution of these components into the liquid causes liquid contamination at the same time, making it difficult to reuse the liquid. For this reason, a complicated purification process is frequently required.
For this reason, there is a method of forming an upper layer film on the photoresist film for the purpose of blocking the photoresist film and water, but there are cases where sufficient transparency to exposure and intermixing with the photoresist film are not sufficient. There is also a problem that man-hours become complicated. Furthermore, it has been reported that CaF ₂ conventionally used as a lens material is eroded by water (Non-Patent Document 1), and thus a problem arises that a coating material for coating the lens surface is required. Yes.
On the other hand, since the resolution limit is about 1.44 times that of ArF dry exposure as shown in the above formula (iii), its use is particularly advanced in the next generation technology where the half pitch is 45 nm or less. It is expected to be difficult.

As described above, in the next-generation immersion exposure method in which miniaturization is progressing, a liquid having a refractive index larger than that of pure water at an exposure wavelength (for example, a wavelength of 193 nm) and having a high transmittance with respect to light of these wavelengths is required. It has been. At the same time, the liquid is required to be a liquid that does not adversely affect the photoresist film, such as elution of additives from the photoresist film, dissolution of the resist film, and pattern deterioration, and does not erode the lens. At the same time, with the increase in NA due to the introduction of immersion exposure, the introduction of polarized light as exposure light is being studied, and the liquid is a liquid that does not bend the direction of polarized light due to properties such as optical rotation other than the above requirements. Is expected.
As a method for achieving this object, for example, attempts have been made to increase the refractive index by dissolving various salts in water (Non-Patent Document 2). However, this approach is difficult to control the concentration of salt, and also has problems such as development defects due to elution of water-soluble components as well as water, lens contamination, and the like.
On the other hand, fluorine-based inert liquids such as perfluoropolyether that are being studied for F ₂ exposure are difficult to use at this wavelength because of their low refractive index at, for example, 193 nm. In addition, organic bromides and iodides, which are conventionally known as immersion exposure liquids for microscopes because of their high refractive index at a wavelength of 589 nm, have poor transparency at, for example, 193 nm and are stable against photoresist films. Inferior.
Japanese Patent Laid-Open No. 11-176727 International Publication No. WO99 / 49504 JP-A-10-303114 NIKKEI MICRODEVICE April, 2004 issue p77 Proc. SPIE Vol. 5377 (2004) p. 273

  The present invention has been made to cope with such a problem. In the immersion exposure method, the refractive index is higher than that of pure water, and has excellent transparency at the immersion exposure wavelength. Its upper layer components (especially hydrophilic components) can be prevented from elution and dissolution, and it can suppress defects during resist pattern generation without eroding the lens. An object of the present invention is to provide a liquid for immersion exposure that can suppress, form a pattern with better resolution and depth of focus, and can easily reuse and purify the liquid, and an immersion exposure method using the liquid.

In order to solve the above-mentioned problems, it has been an essential condition required for an immersion exposure liquid to have a high transmittance at the exposure wavelength and a sufficiently high refractive index as compared with water. On the other hand, it is generally known that the refractive index in the ultraviolet region of a liquid depends on the polarizability of molecules constituting the liquid. As a method for increasing the polarizability, for example, an element having a mobile n-electron such as sulfur, bromine or iodine is introduced into the molecule, and a carbon-carbon double bond or a carbon-carbon triple bond having a relatively mobile π-electron. In particular, it is generally effective to introduce an aromatic ring. However, compounds containing these elements and molecular structures generally have strong absorption in the far ultraviolet region such as 193 nm and cannot be used for this purpose. On the other hand, examples of the compound having small absorption in the far ultraviolet region include unsubstituted hydrocarbon compounds, cyanated hydrocarbon compounds, fluorinated hydrocarbon compounds, sulfonate ester compounds, some alcohols, and the like. In general, the refractive index is higher than that of water, but the refractive index is not significantly different from that of current water.
On the other hand, the following formula (Lorentz-Lorenz formula) has been proposed as a more accurate theoretical formula for the refractive index of liquid, and the result that the refractive index n of benzene can be accurately predicted using the following formula has been reported. (J. Phys. Chem. A., Vol. 103, No. 42, 1999 p8447).

n = (1 + 4πNα ^eff ) ^0.5

In the above formula, N represents the number of molecules in a unit volume, and the larger the partial molar volume, the larger the value.
From the above formula, it is predicted that the refractive index can be increased by increasing N even when α cannot be increased by introduction of a highly absorbing functional group. As a result of various studies on the molecular structure of the liquid with reference to the above, the alicyclic hydrocarbon liquid of the present invention, which has a high density because it has a compact structure, has both transparency and refractive index, and is a liquid for immersion exposure. When used as a photo resist film or its upper layer film component (especially hydrophilic component) is prevented from elution and dissolution, and further, it solves problems such as defects at the time of resist pattern generation and lens erosion, and more resolution and depth of focus. As a result, the present invention was completed.
As a result of further intensive studies, the inventors have found that the liquid mixture of claim 1 is particularly excellent in pattern formation ability, liquid reuse and manufacturing reproducibility, and has completed the present invention.
That is, the immersion exposure liquid according to the present invention is a liquid used in an immersion exposure apparatus or an immersion exposure method in which exposure is performed through a liquid filled between a lens of a projection optical system and a substrate, The liquid contains 90% by weight or more of a mixed liquid of cis-decahydronaphthalene and trans-decahydronaphthalene, and the value of [cis-decahydronaphthalene / trans-decahydronaphthalene] which is the mixed weight ratio of the mixed liquid is [ 50/50 to 0.001 / 99.999].
In particular, the liquid for immersion exposure of the present invention is a liquid washed with concentrated sulfuric acid, containing 90% or more of radiation transmittance at a wavelength of 193 nm in terms of 1 mm optical path length, 2 ppm or less of dissolved oxygen, and analyzed by ICP-MS. The total amount of metal is 10 ppm or less.
The immersion exposure method of the present invention is an immersion exposure method in which a mask is illuminated with an exposure beam, and the substrate is exposed with the exposure beam through a liquid filled between the lens of the projection optical system and the substrate, The liquid is the liquid for immersion exposure described above.

  The immersion exposure method of the present invention is a liquid mixture for immersion exposure that has a high hydrophobicity and a high refractive index at the exposure wavelength, and each of cis-decahydronaphthalene and trans-decahydronaphthalene at a predetermined ratio. Since a mixed liquid containing 90% by weight or more is used, it is possible to prevent elution and dissolution of the photoresist film or its upper layer film component, particularly a hydrophilic component, and to solve the problem of defects at the time of generating a resist pattern and lens erosion, Further, when used as a liquid for immersion exposure, it is possible to suppress the deterioration of the pattern shape and improve the resolution and the depth of focus. Further, the immersion exposure liquid of the present invention is excellent in reuse and production reproducibility.

The liquid for immersion exposure of the present invention is a mixed liquid containing 90% by weight or more of a mixed liquid of cis-decahydronaphthalene and trans-decahydronaphthalene.
In particular, the value of [cis-decahydronaphthalene / trans-decahydronaphthalene], which is the mixing weight ratio of the mixed liquid, is [50/50 to 0.001 / 99.999], preferably [20/80 to 0.001 / 99.999].
When the value of [cis-decahydronaphthalene / trans-decahydronaphthalene] exceeds 50/50 , that is, when cis-decahydronaphthalene exceeds 50 % by weight in the mixed liquid, the transmittance at 193 nm and the used liquid are changed. Recyclability, which is a property that can be used after repurification, tends to deteriorate.

As a result of studying each property required for the immersion exposure liquid and its characteristic values, it is desired that the chemical interaction with the lens and resist material of the projection optical system is small, and the following properties and characteristic values are as follows. Can be mentioned. Since the liquid for immersion exposure of the present invention is a mixed liquid containing 90% by weight or more of a mixed liquid of cis-decahydronaphthalene and trans-decahydronaphthalene, it satisfies the preferable conditions of each characteristic described below.
(1) Refractive index The refractive index of the immersion exposure liquid is preferably higher than that of pure water because of the above-described formulas (iii) and (iv).
Specifically, the refractive index is a value between water and the resist film before exposure (or an upper film for immersion), and preferably higher than water, at 25 ° C. The refractive index at a wavelength of 193 nm is 1.45 to 1.8, preferably 1.6 to 1.8. In addition, since a change in refractive index due to a change in use environment causes defocusing, it is preferable that the refractive index of the immersion exposure liquid is not easily affected by temperature, pressure, or the like. In particular, since the temperature is assumed to change during use due to heat generated by light absorption of the lens and resist material, it is preferable that the temperature dependence of the refractive index is low. Specifically, the absolute value of the rate of change dn / dT depending on the temperature (T) of the refractive index (n) is preferably 5.0 × 10 ⁻³ (° C. ⁻¹ ), more preferably 7.0 × 10 ^−. Within ⁴ (℃ ^-1 ).
From this viewpoint, the specific heat of the present compound is preferably a large value. Specifically, the specific heat value is preferably 0.1 cal / g · ° C. or more, more preferably 0.30 cal / g · It is above ℃.
The immersion exposure liquid preferably has a refractive index that is not easily affected by chromatic aberration, and preferably has a small wavelength dependency of the refractive index around the exposure wavelength.
(2) Radiation transmittance The radiation transmittance at 193 nm is preferably 70% or more, particularly preferably 90% or more, and more preferably 95% or more, at 25 ° C., with an optical path length of 1 mm. . In this case, if the transmittance is less than 70%, heat generation due to thermal energy caused by light absorption of the liquid is likely to occur, and defocusing and distortion of the optical image due to refractive index variation due to temperature rise are likely to occur. In addition, the amount of light reaching the resist film is reduced due to the absorption of the liquid, which causes a significant decrease in throughput.

(3) Viscosity (viscosity)
The viscosity at 20 ° C. is 0.5 Pa · s or less, particularly when used in an environment where the gap between the wafer and the lens material is 1 mm or less, preferably 0.01 Pa · s or less, particularly preferably 0.005 Pa · s. It is as follows. When the viscosity exceeds 0.5 Pa · s, it is difficult for liquid to enter the gap between the resist film (or the upper film for immersion) and the lens material, or as a liquid supply method for immersion, a local immersion method, By using a step-and-scan method that exposes the entire wafer surface by moving the stage on which the wafer is placed as an exposure method, sufficient scanning speed cannot be obtained, resulting in a significant decrease in throughput and a temperature increase due to friction. It tends to be easy to be affected by changes in optical properties due to temperature changes. In particular, when the gap between the wafer and the lens material is 1 mm or less, the viscosity is preferably 0.01 Pa · s or less for the former reason. In this case, the gap distance (liquid film thickness) is set to By reducing it, it is possible to increase the liquid transmittance and make it less susceptible to the absorption of the liquid.
Further, when the viscosity increases, bubbles in the liquid (nanobubbles, microbubbles) are likely to be generated, and the lifetime of the bubbles is prolonged, which is not preferable.
(4) Gas Solubility The gas solubility is preferably 0.5 × 10 5 expressed by the molar fraction of gas in the liquid when oxygen and nitrogen are at 25 ° C. and the partial pressure is 1 atm (atm). ⁻⁴ to 70 × 10 ⁻⁴ , more preferably 2.5 × 10 ⁻⁴ to 50 × 10 ⁻⁴ , and when these gases have a solubility of 0.5 × 10 ⁻⁴ or less, they are generated from a resist or the like. Since nanobubbles are difficult to disappear, light scattering by the bubbles tends to cause resist defects during patterning. Further, if it is 70 × 10 ⁻⁴ or more, ambient gas is absorbed during exposure, so that it is easily affected by changes in optical characteristics due to gas absorption.

(5) Surface tension When used in a step-and-scan type exposure apparatus with immersion by the local immersion method, which is the same as that currently used in immersion exposure of water, scattering of the liquid during scanning is a problem. Therefore, the immersion exposure liquid preferably has a high surface tension. Specifically, the surface tension at 20 ° C. is preferably 5 dyn / cm to 90 dyn / cm, more preferably 20 dyn / cm to 80 dyn / cm.
(6) Handling and environmental characteristics The immersion exposure liquid is preferably a compound that has a low risk of explosion, ignition, ignition, etc. in the usage environment. Specifically, the flash point is preferably 25 ° C or higher, more preferably 50 ° C or higher, and the ignition point is preferably 180 ° C or higher, more preferably 230 ° C or higher. The vapor pressure at 25 ° C. is preferably 50 mmHg or less, more preferably 5 mmHg or less.
Further, it is preferable that the harmfulness to the human body and the environment is low. Specifically, regarding the harmfulness to the human body, a compound having low acute toxicity and having no carcinogenicity, mutagenicity, teratogenicity, reproductive toxicity and the like is preferable. Specifically, for example, a liquid having an allowable concentration of preferably 30 ppm or more, more preferably 70 ppm or more and a negative result of the Ames test is preferable. Regarding the harmfulness to the environment, a compound having no persistence and bioaccumulation is preferable.

(7) Contact angle The contact angle between the immersion exposure liquid and the resist (or the upper film for immersion) is preferably 20 ° to 90 °, more preferably 50 ° to 80 °, and quartz glass. The contact angle with a lens material such as CaF ₂ is preferably 90 ° or less, and preferably 80 ° or less. If the contact angle between the immersion exposure liquid and the resist before exposure (or the immersion upper layer film) is 20 ° or less, the liquid is less likely to enter the gap. When the combination of the step and scan method is used, the liquid is easily scattered in the film. On the other hand, when the contact angle between the liquid of the present invention and the resist before exposure (or the liquid immersion upper film) is 90 ° or more, it becomes easier for gas to be taken in at the uneven resist (or upper film) interface and bubbles are generated. It becomes easy. Such a phenomenon is described in Immersion Lithography Modeling 2003 Year-End Report (International SEMATECH).
Further, when the contact angle between the immersion exposure liquid and the lens material exceeds 90 °, bubbles tend to be generated between the lens surface and the liquid.

In the immersion exposure liquid of the present invention, the total amount of cis-decahydronaphthalene and trans-decahydronaphthalene as measured by gas chromatography is preferably 90% by weight or more. The total amount is particularly preferably 99.0% by weight or more, more preferably 99.9% by weight or more.
The value of [cis-decahydronaphthalene / trans-decahydronaphthalene] can also be measured by gas chromatography.
In particular, at an exposure wavelength such as 193 nm, the ratio of a compound containing an olefin having a large absorbance, a compound containing an aromatic ring, sulfur (sulfide, sulfoxide, sulfone structure), halogen, carbonyl group, ether group, etc. It is preferably less than 0.01% by weight, particularly preferably less than 0.001% by weight.
In addition, since the liquid of the present invention is used in a semiconductor integrated circuit manufacturing process, the metal or metal salt content is preferably low. Specifically, the total amount of contained metals analyzed by ICP-MS is 10 ppm. Below, it is preferably 0.1 ppm or less, more preferably 0.001 ppm or less. If the metal content exceeds 10 ppm, the resist film may be adversely affected by metal ions or metal components, or the wafer may be contaminated.
Examples of the metal include at least one metal selected from Li, Na, K, Mg, Cu, Ca, Al, Fe, Zn, and Ni. These metals can be measured by ICP-MS method.

  The oxygen concentration in the liquid of the present invention is 100 ppm (100 μg / ml) or less, preferably 10 ppm or less, more preferably 2 ppm or less. In particular, the exposure is preferably within 1 ppm, more preferably within 10 ppb. If the oxygen concentration exceeds 100 ppm, the transmittance tends to decrease due to oxidation reaction by dissolved oxygen or the like. Also, even if oxidation reaction does not occur, if oxygen is dissolved, for example, as shown in the examples, dissolved oxygen and ozone generated when radiation is applied to oxygen, depending on the dissolved oxygen concentration The absorbance of the liquid decreases. In addition, when the liquid is exposed in the presence of oxygen, the generated ozone oxidizes the liquid and the deterioration of the liquid stops.

Cis-decahydronaphthalene raw material, trans-decahydronaphthalene raw material, or cis-decahydronaphthalene and trans-decahydronaphthalene mixed raw material (hereinafter, the three raw materials are collectively referred to as this compound) can be obtained as commercially available compounds. Alternatively, it can be produced from available raw materials by various existing synthesis methods. Hereinafter, a specific example is given and demonstrated about the manufacturing method of this compound.
For example, for this compound, naphthalene or naphthalene contained in dry distillation oil from coal coke ovens, petroleum-based catalytic reforming oil and fluid catalytic cracking oil, and naphtha cracking oil as a by-product of ethylene production The derivative can be produced by nuclear hydrogenation by catalytic hydrogenation using a suitable catalyst.
In addition to naphthalene, alkylnaphthalene, benzene, alkylbenzene, phenanthrene, anthracene, other polycyclic aromatics and their derivatives, benzothiophene and their derivatives, etc. Nitrogen-containing compounds such as a containing compound, pyridine and derivatives thereof are contained, and naphthalene and naphthalene derivatives as raw materials can be obtained by separating and purifying from these mixtures.

  Among the naphthalene and naphthalene derivatives used in the production of the present compound, those having a low content of sulfur-containing compounds are preferred. In this case, the content of the sulfur-containing compound is preferably 100 ppm or less, more preferably 50 ppm or less. If the content of the sulfur-containing compound exceeds 100 ppm, the sulfur-containing compound becomes a catalyst poison during catalytic hydrogenation and causes the progress of the nuclear hydrogenation reaction. In addition, sulfur derived from the sulfur-containing compound in this compound If the contained impurities are mixed and cannot be removed by purification, the transmittance of the liquid of the present invention at an exposure wavelength such as 193 nm is reduced.

  Moreover, when manufacturing this compound, it is preferable that the purity of the naphthalene used as a raw material is high, and the preferable purity of naphthalene is 99.0% or more, The especially preferable purity of naphthalene is 99.9% or more. In this case, if the content of sulfur compounds, etc. as impurities is high, the above problem will occur, and if other naphthalene derivatives, aromatic compounds and their derivatives are included as impurities, these impurities are hydrogenated and difficult to separate. This makes it difficult to control the purity of decahydronaphthalene.

In addition to the noble metal catalysts such as nickel, platinum, rhodium, ruthenium, iridium and palladium, sulfides such as cobalt / molybdenum, nickel / molybdenum, nickel / tungsten can be used as catalytic hydrogenation catalysts. . Among these, a nickel-based catalyst is preferable from the viewpoint of its catalytic activity and cost.
These metal catalysts are preferably used by being supported on a suitable carrier. In this case, the catalyst is highly dispersed on the carrier to increase the hydrogenation reaction rate. In addition, the active point deterioration in the catalyst is prevented, and the resistance to the catalyst poison is improved.
As the carrier, SiO ₂ , γ-Al ₂ O ₃ , Cr ₂ O ₃ , TiO ₂ , ZrO ₂ , MgO, ThO ₂ , diatomaceous earth, activated carbon and the like can be preferably used.
In addition, as the catalytic hydrogenation method, a gas phase method without using a solvent and a liquid phase method in which a raw material is dissolved and reacted in an appropriate solvent can be used. Among these, the gas phase method is preferable because of its excellent cost and reaction rate.
When using the gas phase method, the catalyst is preferably nickel, platinum or the like. The larger the amount of catalyst used, the higher the reaction rate, but this is not preferable from the viewpoint of cost. Therefore, in order to increase the reaction rate and complete the reaction, it is preferable to reduce the amount of catalyst and to perform the reaction under conditions of high temperature and hydrogen pressure. Specifically, the reaction is preferably carried out at a catalyst amount of 0.01 to 10 parts by weight relative to the raw material naphthalene (naphthalene derivative), a hydrogen pressure of 5 to 15 MPa, and a reaction temperature of about 100 ° C to 400 ° C.
In addition, for example, a target product can be obtained under mild conditions by a method of removing naphthalene from tetralin as an intermediate using nickel, platinum, or a palladium-based catalyst by a method described in a patent document (Japanese Patent Laid-Open No. 2003-160515). it can.

In the above reaction, the reaction conversion rate is preferably 90% or more, more preferably 99% or more.
After the reaction, it is preferable to remove impurities such as unreacted raw materials and catalysts by performing appropriate purification.
As the purification method, purification methods such as precision distillation, water washing, concentrated sulfuric acid washing, filtration and crystallization, and combinations thereof can be used. Among these, precision distillation is preferable because it is effective for removing both metals and other metals derived from a nonvolatile catalyst and components derived from raw materials. Further, it is preferable to perform a metal removal treatment according to the catalyst in order to remove the metal derived from the catalyst.

The liquid for immersion exposure of the present invention contains 90% by weight or more of a mixed liquid of cis-decahydronaphthalene and trans-decahydronaphthalene at a predetermined ratio, and therefore, it has a low absorbance at, for example, 193 nm. Absorbance is easily affected by trace impurities. Further, when a base component is present in these liquids, even a very small amount has a great influence on the resist profile. These impurities can be removed by purifying the liquid by an appropriate method. For example, it can be purified by concentrated sulfuric acid washing, water washing, alkali washing, silica gel column purification, precision distillation, permanganate treatment under alkaline conditions and combinations thereof.
Specifically, for example, concentrated sulfuric acid washing is repeated until the concentrated sulfuric acid is no longer colored, and then the concentrated sulfuric acid is removed by washing with water and alkali washing, followed by washing with water and drying, followed by precision distillation. it can.
Moreover, impurities can be more efficiently removed by treating with permanganate under alkaline conditions before the treatment.

Among the above purification operations, concentrated sulfuric acid washing is a preferable purification method that is effective for removing aromatic compounds having a large absorption at 193 nm and compounds having a carbon-carbon unsaturated bond, and is effective for removing trace basic compounds. . The treatment is preferably carried out by selecting an optimum stirring method, temperature range, treatment time and number of treatments depending on the compound to be purified.
Specifically, with regard to the temperature, the higher the efficiency of impurity removal, the higher the temperature, but at the same time, it tends to easily generate impurities that cause absorption due to side reactions. A preferred treatment temperature is −20 ° C. to 40 ° C., and a particularly preferred treatment temperature is −10 ° C. to 20 ° C.
As the treatment time is longer, the reaction with the aromatic compound and the impurity having a carbon-carbon unsaturated bond proceeds and the removal efficiency of the impurity increases, but the amount of impurities that cause absorption due to side reactions tends to increase. It is in.
When purifying by the concentrated sulfuric acid treatment, acidic impurities derived from concentrated sulfuric acid remaining in the liquid of the present invention after the treatment. In order to completely remove the sulfonic acid component generated by the concentrated sulfuric acid treatment, it is preferable to perform alkali washing, pure water washing and drying treatment for moisture removal.
Further, by performing precision distillation after washing with concentrated sulfuric acid, impurities that cause absorption can be more efficiently removed.

The precision distillation is preferably carried out in a distillation column having a theoretical plate number equal to or higher than the theoretical plate number required for separation according to the boiling point difference between the impurity to be removed and the liquid of the present invention. From the viewpoint of removing impurities, the preferred number of theoretical plates is 10 to 100. However, when the number of theoretical plates is increased, equipment and manufacturing costs increase. Therefore, purification with a lower number of plates can be achieved by combining with other purification methods. Is possible. The number of theoretical plates is particularly preferably 30 to 100.
The precision distillation is preferably performed under an appropriate temperature condition. When the distillation temperature increases, the effect of reducing absorption tends to decrease due to the oxidation reaction of the compound. A preferable distillation temperature is 30 ° C to 120 ° C, and a particularly preferable distillation temperature is 30 ° C to 80 ° C.
In order to perform distillation in the above temperature range, the precision distillation is preferably performed under reduced pressure as necessary.
The purification treatment is preferably performed in an inert gas atmosphere such as nitrogen or argon. In this case, the oxygen concentration and the organic component concentration in the inert gas are preferably low. A preferable oxygen concentration is 1000 ppm or less, more preferably 10 ppm or less, and particularly preferably 1 ppm or less.
Of the above treatments, the treatment with permanganate is particularly effective for removing non-aromatic carbon-carbon unsaturated bond-containing compounds, but tertiary carbon oxidation reaction occurs for compounds with tertiary carbon. Since it is easy, it is suitable for purification of a compound having no tertiary carbon.
Moreover, it is preferable to perform this process at the low temperature below room temperature from a viewpoint of preventing a side reaction.

  Since the immersion exposure liquid of the present invention is a low-polarity compound, the solubility of gases such as oxygen and nitrogen is high. For this reason, it is easily affected by dissolution of these gases. For example, when left in an air atmosphere, absorption of dissolved oxygen or absorption of ozone generated when dissolved oxygen is excited by light, or oxidation reaction involving dissolved oxygen, etc. For example, there is a tendency that the transmittance of 193 nm decreases. For this reason, these compounds are preferably degassed and stored in an inert gas with little absorption such as nitrogen and argon. Specifically, the oxygen concentration in the preservation liquid is preferably 100 ppm or less, and more preferably 10 ppm or less. In addition, when deoxygenation cannot be performed before exposure, 1 ppm or less is particularly preferable, and 10 ppb or less is more preferable.

The immersion exposure method using the immersion exposure liquid of the present invention will be described below.
As described above, the immersion exposure liquid of the present invention is preferably stored in an inert gas. As the container at that time, the container component or the component of the container lid (for example, blended in plastic) is used. It is preferable to store in a container that does not dissolve the plasticizer or the like. Examples of preferred containers include, for example, glass, metal (eg, SUS), earthenware, PTFE (polytetrafluoroethylene), PFEP (perfluoroethylene propene copolymer), ECTFE (ethylene-chlorotrifluoroethylene copolymer), PTFE / PDD (polytetrafluoroethylene-perfluorodioxole copolymer), PFA (perfluoroalkoxyalkane), ETFE (ethylene-tetrafluoroethylene copolymer), PVDF (polyvinylidene fluoride), PVF (polyvinyl fluoride), PCTFE ( A container made of a fluororesin such as polychlorotrifluoroethylene is preferable, and a container made of glass or fluororesin is particularly preferable.
Examples of preferable container lids include, for example, a lid made of polyethylene and containing no plasticizer, a material made of glass, metal (eg, SUS), earthenware, PTFE (polytetrafluoroethylene), PFEP (perfluoroethylene). Propene copolymer), ECTFE (ethylene-chlorotrifluoroethylene copolymer), PTFE / PDD (polytetrafluoroethylene-perfluorodioxole copolymer), PFA (perfluoroalkoxyalkane), ETFE (ethylene-tetrafluoroethylene copolymer), Examples of the lid include a fluorine resin such as PVDF (polyvinylidene fluoride), PVF (polyvinyl fluoride), and PCTFE (polychlorotrifluoroethylene).
Further, the pipe used for liquid feeding from the container to the exposure machine is preferably a pipe that does not cause elution as described above, and preferable materials for the pipe include glass, metal, ceramics, and the like.

When the immersion exposure liquid of the present invention is used for immersion exposure, fine particles and bubbles (microbubbles) cause pattern defects and the like, and thus exposure to removal of dissolved gases causing fine particles and bubbles is exposed. It is preferable to make it before.
Examples of the method for removing the fine particles include a method of filtering using a suitable filter. As the filter, a filter using a material that has good removal efficiency of fine particles and does not change in absorption at the exposure wavelength due to elution during filtration is preferable. Preferred filter materials include, for example, glass, metal (for example, SUS, silver), and metal oxides, PTFE (polytetrafluoroethylene), PFEP (perfluoroethylene propene copolymer), ECTFE (ethylene-chlorotrifluoroethylene copolymer). PTFE / PDD (polytetrafluoroethylene-perfluorodioxole copolymer), PFA (perfluoroalkoxyalkane), ETFE (ethylene-tetrafluoroethylene copolymer), PVDF (polyvinylidene fluoride), PVF (polyvinyl fluoride) And fluororesins such as PCTFE (polychlorotrifluoroethylene). Moreover, it is preferable that the material of peripheral parts, such as a filter housing, a core, a support, and a plug, is also a material selected from the preferable materials for the filter.
Examples of the method for removing dissolved gas include a vacuum degassing method, an ultrasonic degassing method, a degassing method using a gas permeable membrane, and a degassing method using various degassers.

  Since the immersion exposure liquid of the present invention becomes a part of the optical system during exposure, it is preferably used in an environment free from the influence of changes in optical properties such as the refractive index of the liquid. For example, it is preferably used in an environment where the temperature, pressure, etc. that affect the optical characteristics of the liquid are constant. For example, the temperature is preferably controlled within a range of ± 0.1 ° C., more preferably ± 0.01 ° C.

In addition, immersion exposure using the liquid of the present invention can be performed in the atmosphere, but as described above, the solubility of oxygen in the liquid of the present invention is high, which affects the absorption characteristics at the exposure wavelength. In some cases, the exposure is preferably performed in an inert gas that has little absorption at the exposure wavelength and does not cause a chemical reaction with the liquid. Preferred examples of the inert gas include nitrogen and argon.
Moreover, it is preferable to manage the organic component density | concentration in use atmosphere below a fixed level from a viewpoint of preventing the change of the absorption characteristic in the exposure wavelength of the liquid by the contamination by the organic component in air. Examples of the management method of the organic component concentration include a method using a filter for adsorbing an organic component, various gas purification pipes (apparatus), etc. in addition to using a high-purity inert gas atmosphere. For concentration management, it is preferable to periodically analyze the ambient atmosphere. For this purpose, for example, various analysis methods using gas chromatography can be used.

As a liquid supply method for immersion liquid in the exposure region, a moving pool method, a semming stage method, and a local fill method (local immersion method) are known (special seminar immersion exposure technology (held on May 27, 2004). ) Refer to seminar text), and the local immersion method is preferable because the amount of immersion exposure liquid used is small.
As the final (objective) lens material for immersion exposure using this liquid, the current CaF ₂ or fused silica is preferable from the viewpoint of its optical characteristics. Other preferable lens materials include, for example, fluorine salts of high-period alkaline earth metals M, salts represented by the general formula Ca _x M _1-x F ₂ , oxides of alkaline earth metals such as CaO, SrO, BaO, etc. When the material is used, the refractive index of the lens is higher than that of CaF ₂ (n @ 193 nm = 1.50) and fused silica (n @ 193 nm = 1.56). This is preferable when designing and processing a lens with a high NA exceeding 1.5.
The liquid of the present invention can be reused after use because the extraction of the resist component is extremely small. When resist (or resist upper layer film) in which the influence of elution from the resist film at the time of exposure is negligible is used, the liquid of the present invention can be reused without purification. In that case, degassing, filtration, etc. It is preferable to reuse after processing. These treatments are preferably performed inline from the viewpoint of simplifying the process.
In addition, even if elution from the resist film is negligible in one use during use, if the number of use exceeds a certain number, the physical properties of the liquid change due to the effect of accumulated impurities. Therefore, it is preferable to recover and purify after a certain number of uses.
Examples of the purification method include water washing treatment, acid washing, alkali washing, precision distillation, purification using an appropriate filter (packed column), filtration and the like, and the liquid purification method of the present invention described above, or A method based on a combination of these purification methods may be mentioned. Among these, it is preferable to carry out purification by water washing treatment, alkali washing, acid washing, precision distillation or a combination of these purification methods.
The alkali cleaning is removal of acid generated by exposure eluted in the liquid of the present invention, the acid cleaning is removal of basic components in the resist eluted in the liquid of the present invention, and the water washing treatment is a resist film eluted in the liquid of the present invention. It is effective for removal of eluate such as photo acid generator, basic additive and acid generated during exposure.
The precision distillation is effective for removing low-volatile compounds among the above-mentioned additives and is effective for removing hydrophobic components generated by the decomposition of protecting groups in the resist during exposure.

Immersion exposure is performed using the liquid for immersion exposure.
A photoresist film is formed by applying a photoresist on the substrate. As the substrate, for example, a silicon wafer, a wafer coated with aluminum, or the like can be used. In order to maximize the potential of the resist film, an organic or inorganic antireflection film is formed on the substrate to be used, as disclosed in, for example, Japanese Patent Publication No. 6-12452. I can leave.
The photoresist used is not particularly limited, and can be selected in a timely manner according to the purpose of use of the resist. Examples of the resin component of the photoresist include a polymer containing an acid dissociable group. The acid-dissociable group is preferably not decomposed by exposure, and in particular, the product after decomposition is preferably volatilized under the exposure conditions and does not elute into the liquid of the present invention. Examples of these polymers include resins containing alicyclic groups, lactone groups and derivatives thereof in the polymer side chain, resins containing hydroxystyrene derivatives, and the like.
In particular, a photoresist using a resin containing an alicyclic group, a lactone group and derivatives thereof in the polymer side chain is preferable. Since these photoresists contain a chemical structure similar to an alicyclic hydrocarbon compound or a cyclic hydrocarbon compound containing a silicon atom in the ring structure, they have excellent affinity with the immersion exposure liquid of the present invention. Also, the photoresist film is not eluted or dissolved.

Examples of the photoresist include a chemically amplified positive or negative resist containing a polymer containing an acid dissociable group as a resin component, an acid generator, and an additive such as an acid diffusion controller. Can do.
When the immersion exposure liquid of the present invention is used, a positive resist is particularly preferable. In a chemically amplified positive resist, an acid-dissociable organic group in the polymer is dissociated by the action of an acid generated from an acid generator by exposure to generate, for example, a carboxyl group. The solubility in an alkali developer is increased, and the exposed portion is dissolved and removed by the alkali developer to obtain a positive resist pattern.

The photoresist film is prepared by dissolving a resin composition for forming a photoresist film in a suitable solvent at a solid content concentration of, for example, 0.1 to 20% by weight, and then filtering with a filter having a pore diameter of, for example, about 30 nm. A solution is prepared, and this resist solution is applied onto a substrate by an appropriate application method such as spin coating, cast coating, roll coating, and the like, and pre-baked (hereinafter referred to as “PB”) to volatilize the solvent. To form. In this case, a commercially available resist solution can be used as it is. The photoresist film preferably has a higher refractive index than the liquid immersion upper layer film and the liquid for immersion exposure. Specifically, the refractive index n _{RES of the} photoresist film is in the range of 1.65 or more. Is preferred. In particular, when NA is 1.3 or more, n _RES is preferably larger than 1.75. In this case, it is possible to prevent a decrease in contrast of exposure light accompanying an increase in NA.
In the immersion exposure method, an upper layer film for immersion can be further formed on the photoresist film.

As the upper layer film for immersion, a protective film can be formed on the photoresist film without causing sufficient transparency with respect to the wavelength of the exposure light and intermixing with the photoresist film. Any film can be used as long as it can maintain a stable film without eluting into a liquid and can be peeled off before development. In this case, it is preferable that the upper layer film is a film that is easily dissolved in an alkaline solution as a developer because it is peeled off during development.
The substituent for imparting alkali solubility is preferably a resin having at least one of a hexafluorocarbinol group and a carboxyl group in the side chain.
The upper layer film for immersion preferably has a function of preventing multiple interference at the same time. In this case, the refractive index n _OC of the upper layer film for immersion is preferably a mathematical formula shown below.

n _OC = (n _lq × n _RES ) ^0.5

Here, n _lq represents the refractive index of the immersion exposure liquid, and n _RES represents the refractive index of the resist film.
Specifically, n _OC is preferably in the range of 1.6 to 1.9.
The immersion upper film is formed by dissolving the resin composition for an immersion upper film on a resist film in a solvent that does not intermix with the resist film at a solid concentration of 0.01 to 10%, and then at the time of forming the photoresist film. It can be formed by applying and pre-baking in the same manner.

  The contact angle between the immersion exposure liquid and the resist (or the upper layer film for immersion) is preferably 20 ° to 90 °, and the molecular design of the resist (or the upper layer film for immersion) is performed. Thus, a suitable contact angle can be obtained. Examples of the molecular structure of the resist (or the upper film for immersion) with a preferable contact angle include hydrophilic structures such as a lactone structure, a hexafluorocarbinol structure, and a carboxyl group.

The photoresist film or the photoresist film on which the immersion upper layer film is formed is irradiated with radiation through a mask having a predetermined pattern, using the immersion exposure liquid of the present invention as a medium, and then developed, whereby a resist is obtained. Form a pattern. In this step, immersion exposure is performed, baking is performed at a predetermined temperature, and development is performed.
The radiation used for immersion exposure depends on the photoresist film used and the combination of the photoresist film and the upper layer film for immersion, for example, visible rays; ultraviolet rays such as g rays and i rays; Various types of radiation such as ultraviolet rays; X-rays such as synchrotron radiation; and charged particle beams such as electron beams can be selectively used. In particular, an ArF excimer laser (wavelength 193 nm) is preferable.
In order to improve the resolution, pattern shape, developability, etc. of the resist film, it is preferable to perform baking (hereinafter referred to as “PEB”) after exposure. The baking temperature is appropriately adjusted depending on the resist used and the like, but is usually about 30 to 200 ° C., preferably 50 to 150 ° C.
Next, the photoresist film is developed with a developer and washed to form a desired resist pattern.

化合物（Ｓ１−１）３９．８５ｇ（４０モル％）、化合物（Ｓ１−２）２７．４７ｇ（２０モル％）、化合物（Ｓ１−３）３２．６８ｇ（４０モル％）を２−ブタノン２００ｇに溶解し、更にアゾビスイソ吉草酸メチル４．１３ｇを投入したモノマー溶液を準備し、１００ｇの２−ブタノンを投入した１０００ｍｌの三口フラスコを３０分窒素パージする。窒素パージの後、反応釜を攪拌しながら８０℃に加熱し、事前に準備した上記モノマー溶液を滴下漏斗を用いて３時間かけて滴下した。滴下開始を重合開始時間とし、重合反応を５時間実施した。重合終了後、重合溶液は水冷することにより３０℃以下に冷却し、２０００ｇのメタノールへ投入し、析出した白色粉末をろ別する。ろ別された白色粉末を２度４００ｇのメタノールにてスラリー上で洗浄した後、ろ別し、５０℃にて１７時間乾燥し、白色粉末の重合体を得た（７５ｇ、収率７５重量％）。この重合体は分子量が１０，３００であり、¹³Ｃ−ＮＭＲ分析の結果、化合物（Ｓ１−１）、化合物（Ｓ１−２）、化合物（Ｓ１−３）で表される繰り返し単位、各繰り返し単位の含有率が４２．３：２０．３：３７．４（モル％）の共重合体であった。この重合体を樹脂（Ａ−１）とする。 In order to evaluate the immersion exposure liquid of the present invention, a resist film was formed using the radiation sensitive resin composition shown below. Moreover, the upper layer film for immersion shown below was formed in a part thereof. Using this resist film for evaluation, characteristics (patterning evaluation, recyclability, variation between production lots) as an immersion exposure liquid were measured.
Reference example 1
Resin used for a radiation sensitive resin composition was obtained by the following method.

Compound (S1-1) 39.85 g (40 mol%), compound (S1-2) 27.47 g (20 mol%), compound (S1-3) 32.68 g (40 mol%) into 2-butanone 200 g Dissolve and prepare a monomer solution charged with 4.13 g of methyl azobisisovalerate, and purify a 1000 ml three-necked flask charged with 100 g of 2-butanone with nitrogen for 30 minutes. After purging with nitrogen, the reaction kettle was heated to 80 ° C. with stirring, and the monomer solution prepared in advance was added dropwise using a dropping funnel over 3 hours. The dripping start was set as the polymerization start time, and the polymerization reaction was carried out for 5 hours. After completion of the polymerization, the polymerization solution is cooled with water to 30 ° C. or less, put into 2000 g of methanol, and the precipitated white powder is filtered off. The filtered white powder was washed twice with 400 g of methanol on the slurry, filtered, and dried at 50 ° C. for 17 hours to obtain a white powder polymer (75 g, yield 75% by weight). ). This polymer has a molecular weight of 10,300. As a result of ¹³ C-NMR analysis, the polymer (S1-1), the compound (S1-2), the repeating unit represented by the compound (S1-3), and each repeating unit. Was a copolymer having a content of 42.3: 20.3: 37.4 (mol%). This polymer is referred to as “resin (A-1)”.

化合物（Ｓ２−１）５０ｇ、化合物（Ｓ２−２）５ｇ、化合物（Ｓ２−３）２５ｇ、化合物（Ｓ２−４）２０ｇ、およびアゾビスイソ吉草酸メチル６．００ｇをメチルエチルケトン２００ｇに溶解し、均一溶液としたモノマー溶液を準備した。そして、メチルエチルケトン１００ｇを投入した１０００ｍｌの三口フラスコを３０分窒素パージした。窒素パージ後、フラスコ内を攪拌しながら８０℃に加熱し、事前に調製した上記モノマー溶液を滴下漏斗を用いて、１０ｍｌ／５分の速度で滴下した。滴下開始時を重合開始時点として、重合を５時間実施した。重合終了後、反応溶液を３０℃以下に冷却し、次いで該反応溶液をヘプタン２０００ｇ中へ投入し、析出した白色粉末をろ別した。ろ別した白色粉末をヘプタン４００ｇと混合してスラリーとして攪拌する操作を２回繰り返して洗浄した後、ろ別し、５０℃にて１７時間乾燥して、白色粉末の樹脂（Ｅ−１）を得た（８９ｇ、収率８９重量％）。樹脂（Ｅ−１）は、Ｍｗが７，３００であった。 Reference example 2
A resin for forming an upper film for immersion was obtained by the following method.

50 g of compound (S2-1), 5 g of compound (S2-2), 25 g of compound (S2-3), 20 g of compound (S2-4) and 6.00 g of methyl azobisisovalerate are dissolved in 200 g of methyl ethyl ketone, A monomer solution was prepared. Then, a 1000 ml three-necked flask charged with 100 g of methyl ethyl ketone was purged with nitrogen for 30 minutes. After purging with nitrogen, the inside of the flask was heated to 80 ° C. with stirring, and the monomer solution prepared in advance was added dropwise at a rate of 10 ml / 5 minutes using a dropping funnel. The polymerization was carried out for 5 hours with the start of dropping as the start of polymerization. After completion of the polymerization, the reaction solution was cooled to 30 ° C. or lower, and then the reaction solution was put into 2000 g of heptane, and the precipitated white powder was filtered off. The operation of mixing the filtered white powder with 400 g of heptane and stirring as a slurry was repeated twice, washed, filtered and dried at 50 ° C. for 17 hours to obtain a white powder resin (E-1). Obtained (89 g, 89 wt% yield). Resin (E-1) had Mw of 7,300.

Reference example 3
A radiation sensitive resin composition (F-1) was obtained by the following method.
Resin (A-1) 100 parts by weight, 4-nonafluoro-n-butylsulfonyloxyphenyl diphenylsulfonium nonafluoro-n-butanesulfonate as an acid generator 2.5 parts by weight, 2-phenyl as an acid diffusion controller 0.2 parts by weight of benzimidazole and 750 parts by weight of propylene glycol monomethyl ether acetate as a solvent were weighed, mixed, and made into a uniform solution, and then filtered through a membrane filter having a pore size of 200 nm to thereby form a radiation sensitive resin composition. (F-1) was prepared.

Reference example 4
The upper layer film composition (G-1) for immersion was obtained by the following method.
1 part by weight of the resin (E-1) and 99 parts by weight of normal butanol as a solvent are respectively weighed, mixed and made into a uniform solution, and then filtered through a membrane filter having a pore size of 200 nm to obtain an upper layer film composition for immersion. (G-1) was prepared.

Reference Example 5
Resist films for evaluation (H-1 and H-2) were obtained by the following method.
On the 8-inch silicon wafer, spin coating, PB (90 ° C., 60 seconds) is applied to the lower antireflection film ARC29 (Bluwa Science Co., Ltd.) to form a 77 nm-thickness coating film, under the same conditions. A resist film (thickness 205 nm) was formed using the radiation sensitive resin composition (F-1) (H-1).
Moreover, after forming a resist film (film thickness of 205 nm) using the radiation sensitive resin composition (F-1) in the same manner as described above, an upper film composition for immersion (G- An upper layer film of 32 nm thickness was formed by spin coating and PB (130 ° C., 90 seconds) (H-2).

Example 1
Trans-decahydronaphthalene (product name: trans-Decahydronaphthalene (special grade) (measurement result of GC) cis-decahydronaphthalene: 0.2%, trans-decahydronaphthalene: 99. 6%, 0.1% of other components)) 100 ml was placed in a 200 ml eggplant-shaped flask containing a magnetic stirrer tip and thoroughly purged with nitrogen. Next, 20 ml of concentrated sulfuric acid (first grade manufactured by Wako Pure Chemical Industries, Ltd.) sufficiently substituted with nitrogen in the same glove box was added and stirred at room temperature for 15 minutes. Then, the liquid mixture was left still, the organic layer and sulfuric acid were fully separated, and the sulfuric acid was removed by decantation. Further, the same sulfuric acid washing operation was repeated 4 times. Thereafter, the organic layer was washed twice with 20 ml of a saturated aqueous sodium hydrogen carbonate solution. Washed twice with 20 ml of ion-exchanged water. Thereafter, the organic layer was distilled under reduced pressure (pressure 2-3 mmHg) to obtain 83 ml of a fraction. This fraction was transferred to an eggplant-shaped flask equipped with a three-way cock, and the operation of depressurizing the system with a vacuum pump and returning to normal pressure with nitrogen was repeated three times to purify decahydronaphthalene (hereinafter referred to as EKS-). 1). As a result of GC measurement of the obtained EKS-1, cis-decahydronaphthalene was 0.3%, trans-decahydronaphthalene was 99.5%, and other components were 0.2%. In addition, GC measurement was measured by GC6850 (column Agilent technology HP-1 (nonpolar type) detector FID) of Agilent technology. The measurement was performed under the conditions of an inlet temperature of 250 ° C., a column temperature of 70 ° C. to 300 ° C. (temperature raising method), and a carrier gas of helium. The purity was determined from the area ratio with the total peak area of FID as 100%.

Transmittance was measured in a JASCO-V-550 manufactured by JASCO Corporation by sampling the liquid in a 10 mm path length cell with a polytetrafluoroethylene lid in a nitrogen atmosphere glove box where the oxygen concentration was controlled to 0.5 ppm or less. Using the above cell, air was measured as a reference. The value converted into the optical path length of 1 mm is a value obtained by correcting the reflection of the cell by calculation. When the transmittance at 193 nm was measured, the transmittance at 193 nm was 97.9% in terms of 1 mm optical path length.
When the metal content (Li, Na, K, Mg, Cu, Ca, Al, Fe, Zn, Ni) of this liquid was measured by the ICP-MS method, all metals were less than the detection limit (1 ppb). The amount of dissolved oxygen was measured by gas chromatography using TCD as a detector. As a result, it was 1.0 ppm or less (detection limit).
The characteristic values of the obtained EKS-1 are shown in Table 2.

Example 2
Decahydronaphthalene (Product name: Decahydronaphthalene (cis-and trans-mixture) (first grade) (GC measurement result cis-decahydronaphthalene 35.7%, trans-decahydronaphthalene 65.3%, other components The purified decahydronaphthalene (hereinafter referred to as EKS-2) was obtained by purification and nitrogen substitution in the same manner as in Example 1, using less than 0.1%) as a starting material. As a result of GC measurement of EKS-2, it was 35.6% cis-decahydronaphthalene, 65.4% trans-decahydronaphthalene, and 0.1% of other components, and the measurement described in Example 1 When the transmittance at 193 nm was measured by the method, the transmittance at 193 nm was 1 m for the optical path length. The metal content (Li, Na, K, Mg, Cu, Ca, Al, Fe, Zn, Ni) of this liquid was measured by ICP-MS method, and all metals were detected. It was less than the limit (1 ppb).

Comparative Example 1
Cis-decahydronaphthalene (product name: cis-Decahydronaphthalene (special grade)) manufactured by Tokyo Chemical Industry (GC measurement result cis-decahydronaphthalene 99.2%, trans-decahydronaphthalene 0.7%, other components 0.1% ) Was used as a starting material and purified and nitrogen-substituted in the same manner as in Example 1 to obtain purified decahydronaphthalene (hereinafter referred to as HK-1). As a result of GC measurement of HK-1 by the method of Example 1, cis-decahydronaphthalene was 99.1%, trans-decahydronaphthalene was 0.8%, and other components were 0.1%. Further, when the transmittance at 193 nm was measured by the measurement method described in Example 1, the transmittance at 193 nm was 80.3% in terms of 1 mm optical path length.
In order to improve the transmittance, the purification operation was repeated again in the same manner, but the transmittance at 193 nm after repurification was 79.5% in terms of 1 mm optical path length.

Using the resist film for evaluation described above, the immersion exposure liquid obtained in each of the examples and comparative examples was subjected to sensitivity, patterning evaluation (immersion patterning evaluation, immersion exposure evaluation using a two-speed interference exposure machine), recyclability, Evaluation was based on variation in characteristics between production lots. The results are shown in Table 3 and Table 4.
(1) Exposure experiment using two-beam interference The resist for evaluation made in the same manner as the resist film H-2 except that the film thickness of the lower antireflection film was 29 nm and the resist film thickness was 60 nm (for 35 nm) Two-beam interference type ArF immersion simple exposure device (Nikon Corporation, for 35 nm 1L / 1S, using TE polarized light exposure) between wafer and wafer (gap 0.7 mm) After the purification, the immersion exposure liquid is inserted for exposure, and then the immersion exposure liquid on the wafer is removed by air drying, and the wafer is subjected to PEB (115 ° C., 90 seconds) on a CLEAN TRACK ACT8 hot plate. ), And paddle development (developer component, 2.38 wt% tetrahydroammonium hydroxide aqueous solution) (60 seconds) with the CLEAN TRACKACT8 LD nozzle. Scanning after development board was rinsed with water electron microscope (Hitachi Instruments Co., Ltd.) was observed pattern S-9360. At this time, the case where the cross-sectional shape of the pattern observed with the SEM is rectangular and the dimensional variation such as roughness has a shape of ± 10% or less of the desired dimension is “◯”, and the case where a good pattern is not obtained is “×” " The results are shown in Table 3. Sensitivity represents the exposure amount at which the desired dimensions are obtained.

(2) Recyclability 30 ml of each of EKS-1, EKS-2, and HK-1 was brought into contact with the resist film H1 for 30 minutes so that the thickness of the liquid film was 3 mm. , Called EKS-2 after contact, and HK-1 after contact). Then, EKS-1, EKS-2 after contact, and HK-1 after contact were purified in the same manner as in Example 1 (re-purified EKS-1, re-purified EKS-2, re-purified HK-1 and Call). Thereafter, the radiation transmittance at 193 nm was measured for three types of liquid before contact, after contact purification, and after repurification liquid. The results are shown in Table 3.
(3) Variation among production lots EKS-1, EKS-2 and HK-1 were produced three times by the methods of Examples 1 and 2 and Comparative Example 1, and the difference between lots in refractive index and transmittance at 193 nm was measured. . The results are shown in Table 4.
The refractive index of 193 nm was measured at a measurement temperature of 25 ° C. by a minimum deviation method as a measuring method using a goniometer spectrometer type 1 UV-VIS-IR manufactured by MOLLER-WEDEL as a measuring device.

The immersion exposure liquid of the present invention contains 90% by weight or more of a mixed liquid of cis-decahydronaphthalene and trans-decahydronaphthalene, and has a mixed weight ratio of the mixed liquid [cis-decahydronaphthalene / trans- Since the value of [decahydronaphthalene] is [ 50/50 to 0.001 / 99.999], the photoresist film is not dissolved at the time of immersion exposure, and a resist pattern having excellent resolution and developability is formed. In addition, a liquid for immersion exposure can be obtained which is recyclable and does not vary between production lots. Therefore, it can be used very suitably for the manufacture of semiconductor devices that are expected to be further miniaturized in the future.

Claims (8)

A liquid used in an immersion exposure apparatus or an immersion exposure method in which exposure is performed via a liquid filled between a lens of a projection optical system and a substrate, the liquid being cis-decahydronaphthalene and trans-deca The mixed liquid of hydronaphthalene contains 90% by weight or more, and the value of [cis-decahydronaphthalene / trans-decahydronaphthalene], which is the mixed weight ratio of the mixed liquid, is [ 50/50 to 0.001 / 99.999. A liquid for immersion exposure.   2. The liquid for immersion exposure according to claim 1, wherein the mixed liquid of cis-decahydronaphthalene and trans-decahydronaphthalene contains 99% by weight or more.   The value of [cis-decahydronaphthalene / trans-decahydronaphthalene], which is the mixing weight ratio of the mixed liquid, is [35.6 / 65.4 to 0.3 / 99.5]. Item 3. The liquid for immersion exposure according to item 1 or 2. 4. The liquid for immersion exposure according to claim 1 , wherein the radiation transmittance at a wavelength of 193 nm in terms of an optical path length of 1 mm is 90% or more. Mixed liquid obtained by mixing cis-decahydronaphthalene and trans-decahydronaphthalene raw materials after washing with concentrated sulfuric acid, respectively, or obtained by washing concentrated cis-decahydronaphthalene and trans-decahydronaphthalene mixed raw materials with concentrated sulfuric acid The liquid for immersion exposure according to claim 3 or 4, wherein the liquid is a mixed liquid. Claim 4 or claim 5, wherein the liquid for liquid immersion lithography, wherein the amount of oxygen dissolved in the mixed liquid is 2ppm or less. The liquid for immersion exposure according to claim 4, 5 or 6, wherein the total amount of contained metals analyzed by ICP-MS is 10 ppm or less. An immersion exposure method for illuminating a mask with an exposure beam and exposing the substrate with the exposure beam via a liquid filled between a lens of the projection optical system and the substrate, wherein the liquid is claimed in claim 1. Item 8. A liquid immersion exposure method according to any one of items 7 to 9, wherein the liquid is a liquid for immersion exposure.