JP2007081099A - Immersion exposure liquid and immersion exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid for immersion exposures and an immersion exposure method using the liquid wherein its refractive index is large, and the precise reproducibility of the refractive index is obtained, and further, the elution and dissolution of the components of a photoresist film and the upper-layer film thereof are prevented, and moreover, the defects at the time when generating a resist pattern can be suppressed, with respect to the immersing exposure method. <P>SOLUTION: The liquid for immersion exposures is used in an immersion exposure apparatus or an immersion exposure method wherein an exposure is performed via a liquid having a predetermined refractive index and interposed in a filling way between the lens and substrate of a projection optical system. Hereupon, the predetermined refractive index of the liquid is obtained by mixing with each other a plurality of stereoscopic isomers having different refractive indexes from each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 capable of shortening the effective wavelength of radiation for exposure and transferring a finer pattern is referred to as immersion exposure, and for future miniaturization of lithography, particularly 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.
It has been reported that the above refractive index reproducibility needs to be very high precision in order to form a fine pattern with a sufficient process margin in immersion lithography (Non-patent Document 3). In general, it has been reported that in order to form a pattern of 100 nm or less with a sufficient process margin, it is necessary to control the refractive index with an accuracy of ± (1 × 10 ⁻⁶ ). As described above, it is difficult to meet this requirement with a liquid in which salt or nanoparticles are mixed with water. In addition, even when a liquid composed of a single solvent such as perfluoropolyether and diiodomethane described here is used, the refractive index is strongly influenced by a small amount of impurities, so that it is difficult to satisfy the above requirements. there were.
As an immersion exposure liquid that solves the above problems, the inventors have proposed an immersion exposure liquid containing an alicyclic hydrocarbon or silicon and having a cyclic hydrocarbon (Japanese Patent Application No. 2005-049468). . Furthermore, a method for producing a liquid for immersion exposure, which includes a concentrated sulfuric acid washing step for an alicyclic hydrocarbon compound, has been proposed (Japanese Patent Application No. 2005-019103).
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 Proc. SPIE Vol. 5754 (2005) p. 701

  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 high-precision reproducibility of the refractive index is obtained. It has excellent transparency at the wavelength of, prevents elution and dissolution of the photoresist film or its upper layer film component (especially hydrophilic component), can suppress defects at the time of resist pattern generation without eroding the lens, When used as an immersion liquid, it is possible to form a pattern with superior resolution and depth of focus while suppressing deterioration of the pattern shape, and an immersion liquid that can be easily reused and purified, and a liquid using the liquid An object is to provide an immersion exposure method.

As described above, as an immersion exposure liquid that solves the above-described problems, the inventors have disclosed a compound containing an alicyclic hydrocarbon or silicon and having a cyclic hydrocarbon, and an alicyclic hydrocarbon compound containing concentrated sulfuric acid. We propose a manufacturing method to clean, and when these immersion exposure liquids have both transparency and refractive index and are used as immersion liquids, elution and dissolution of the photoresist film or its upper layer components (especially hydrophilic components) In addition, it has been found that a pattern with better resolution and depth of focus can be formed by solving problems such as defects at the time of generating a resist pattern and lens erosion.
As a result of further intensive studies, the inventors have found that it is possible to produce a liquid excellent in reproducibility of various physical properties of the liquid such as refractive index, transmittance and viscosity, and have completed the present invention.
That is, the immersion exposure liquid of the present invention is used in an immersion exposure apparatus or an immersion exposure method in which exposure is performed through a liquid having a predetermined refractive index filled between a lens of a projection optical system and a substrate. The liquid is characterized in that the liquid has a predetermined refractive index by mixing a plurality of isomers having different refractive indexes, preferably a stereoisomer.
The predetermined refractive index obtained by mixing a plurality of isomers having different refractive indexes, preferably stereoisomers, is characterized in that the fluctuation range is controlled to ± (1 × 10 ⁻³ ). To do.
In particular, the mixture of stereoisomers having different refractive indices is a mixture of cis-decahydronaphthalene and trans-decahydronaphthalene, or a mixture of exo-tetrahydrodicyclopentadiene and endo-tetrahydrodicyclopentadiene. It is characterized by being.
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 liquid for immersion exposure according to the present invention can be obtained by mixing a plurality of stereoisomers having different refractive indexes to have a predetermined refractive index suitable for liquid immersion exposure. As a result, the refractive index is higher than that of pure water, and high-precision reproducibility of the refractive index is obtained.It has excellent transparency at the wavelength during immersion exposure, and the photoresist film or its upper layer film component (especially It is possible to prevent elution and dissolution of the hydrophilic component), and to suppress defects during formation of the resist pattern without eroding the lens. Further, it is possible to form a pattern with better resolution and depth of focus by suppressing the deterioration of the pattern shape, and it is easy to reuse and purify the liquid.

（式（１−１）において、Ｒ¹は炭素数１〜１０の脂肪族炭化水素基、炭素数３〜１４の脂環式炭化水素基、シアノ基、水酸基、フッ素原子、炭素数１〜１０のフッ素置換炭化水素基、−Ｓｉ(Ｒ³)₃基、または−ＳＯ₃Ｒ⁴基を表し、ｎ１、ｎ２はそれぞれ独立に１〜３の整数を表し、ａは０〜１０の整数を表し、Ｒ¹が複数存在する場合、そのＲ¹は同一でも異なっていてもよく、２つ以上のＲ¹が相互に結合して環構造を形成してもよく、Ｒ³およびＲ⁴は、炭素数１〜１０のアルキル基を表す。）

（式（１−２)における（ａ）、（ｂ）、（ｃ）において、Ｂはメチレン基またはエチレン基を表し、Ｒ²は炭素数１〜１０の脂肪族炭化水素基、炭素数３〜１４の脂環式炭化水素基、シアノ基、水酸基、フッ素原子、炭素数１〜１０のフッ素置換炭化水素基、−Ｓｉ(Ｒ³)₃基、または−ＳＯ₃Ｒ⁴基を表し、ｂは０〜１０の整数を表し、ｎ３は１〜３の整数を表し、Ｒ²が複数存在する場合、そのＲ²は同一でも異なっていてもよく、２つ以上のＲ²が相互に結合して環構造を形成してもよく、Ｒ³およびＲ⁴は、炭素数１〜１０のアルキル基を表す。） The liquid for immersion exposure of the present invention can have a refractive index of a desired value by mixing a plurality of stereoisomers having different refractive indices, preferably two kinds of stereoisomers in a predetermined ratio. Here, the plurality of stereoisomers refer to isomer groups having the same arrangement order of atoms but different steric arrangements.
Hereinafter, examples of compounds that can be used as isomers in the immersion exposure liquid of the present invention will be described.
As a structure of the compound which produces | generates an isomer group, the compound represented, for example by a following formula (1-1) or a formula (1-2) is mentioned.

(In Formula (1-1), R ¹ is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 14 carbon atoms, a cyano group, a hydroxyl group, a fluorine atom, or 1 to 10 carbon atoms. Represents a fluorine-substituted hydrocarbon group, —Si (R ³ ) ₃ group, or —SO ₃ R ⁴ group, n1 and n2 each independently represent an integer of 1 to 3, and a represents an integer of 0 to 10 , if R ¹ is more present, the R ¹ may be the same or different, two or more R ¹ is may be bonded to form a ring structure with each other, R ³ and R ^4, carbon Represents an alkyl group of formula 1-10.)

(In (a), (b) and (c) in Formula (1-2), B represents a methylene group or an ethylene group, R ² represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, 3 to 3 carbon atoms, 14 represents an alicyclic hydrocarbon group, a cyano group, a hydroxyl group, a fluorine atom, a fluorine-substituted hydrocarbon group having 1 to 10 carbon atoms, a —Si (R ³ ) ₃ group, or a —SO ₃ R ⁴ group, Represents an integer of 0 to 10, n3 represents an integer of 1 to 3, and when a plurality of R ² are present, the R ² may be the same or different, and two or more R ² may be bonded to each other; A ring structure may be formed, and R ³ and R ⁴ represent an alkyl group having 1 to 10 carbon atoms.)

The compound represented by Formula (1-1) will be described.
Examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms in R ¹ include a methyl group, an ethyl group, and an n-propyl group. Examples of two or more R ^{1 s} bonded to each other to form a ring structure include a cyclopentyl group, a cyclohexyl group, and the like. Examples of the alicyclic hydrocarbon group having 3 to 14 carbon atoms include a cyclohexyl group and a norbornyl group. Examples of the fluorine-substituted hydrocarbon group having 1 to 10 carbon atoms include a trifluoromethyl group and a pentafluoroethyl group. The R ⁴ constituting the R ^3, and -SO ₃ R ⁴ groups constituting the -Si (R ^{₃₎ 3} group, an alkyl group having 1 to 10 carbon atoms, as the alkyl group, methyl group, ethyl Groups and the like.
In the formula (1-1), the substituent for R ¹ is an aliphatic saturated hydrocarbon group having 1 to 10 carbon atoms or an alicyclic group having 3 to 14 carbon atoms from the viewpoint of excellent radiation transmittance of 193 nm. Saturated hydrocarbon groups, cyano groups, fluorine atoms, and fluorine-substituted saturated hydrocarbon groups having 1 to 10 carbon atoms are preferred.
Among the above substituents, an aliphatic saturated hydrocarbon group having 1 to 10 carbon atoms and an alicyclic saturated hydrocarbon group having 3 to 14 carbon atoms have a higher refractive index and less interaction with the resist. It is particularly preferable because defects due to elution of water-soluble components in the resist and erosion to the lens material hardly occur.
Moreover, preferable n1 and n2 are 1-3, Especially preferable n1 and n2 are 1 or 2, and preferable a is 0, 1 or 2. When a is particularly 0, for example, the refractive index at 193 nm is particularly preferable.

Specific examples of preferred alicyclic saturated hydrocarbon compounds represented by formula (1-1) are listed below. In the present specification, the description of the hydrogen atom bonded to the carbon atom forming the ring in the alicyclic saturated hydrocarbon compound is omitted. Moreover, it represents with the chemical structural formula containing each stereoisomer group.

式（１−１）で表される好ましいフッ素原子含有化合物の具体例を以下に列挙する。

式（１−１）で表される好ましいフッ素置換飽和炭化水素化合物の具体例を以下に列挙する。

Specific examples of preferred cyano group-containing compounds represented by formula (1-1) are listed below.

Specific examples of preferred fluorine atom-containing compounds represented by formula (1-1) are listed below.

Specific examples of preferred fluorine-substituted saturated hydrocarbon compounds represented by formula (1-1) are listed below.

式（２−１）において、Ｒ¹およびａは、式（１−１）のＲ¹およびａと同一である。
式（２−１）における具体例としては、上記（１−１−１６）、（１−１−１８）、（１−１−１９）、（１−１−２０）、（１−１−３３）、（１−１−３４）、（１−１−３５）、（１−１−３６）、（１−１−３７）、（１−１−３８）で挙げた化合物が挙げられる。
この中で、置換機を有さない化合物が例えば１９３ｎｍにおける屈折率が高くなるため好ましく、式（２−１）における特に好ましい例としては、デカヒドロナフタレンが挙げられ、屈折率の異なる立体異性体としては、ｃｉｓ‐デカヒドロナフタレンおよびｔｒａｎｓ‐デカヒドロナフタレンが挙げられる。 Among the preferred compounds represented by the formula (1-1), alicyclic saturated hydrocarbon compounds are preferred, and among them, particularly preferred compounds include compounds represented by the following formula (2-1).

In Formula (2-1), R ¹ and a are the same as R ¹ and a in Formula (1-1).
Specific examples of formula (2-1) include the above (1-1-16), (1-1-18), (1-1-19), (1-1-20), (1-1-1- 33), (1-1-34), (1-1-35), (1-1-36), (1-1-37), and (1-1-38).
Among these, a compound having no substitution machine is preferable because, for example, the refractive index at 193 nm is high, and a particularly preferable example in the formula (2-1) is decahydronaphthalene, and stereoisomers having different refractive indexes. As cis-decahydronaphthalene and trans-decahydronaphthalene.

The compound represented by Formula (1-2) will be described.
R ² is the same as R ¹ in formula (1-1).
In formula (1-2), the substituent of R ² is an aliphatic saturated hydrocarbon group having 1 to 10 carbon atoms or alicyclic saturation having 3 to 14 carbon atoms from the viewpoint of excellent radiation transmittance at 193 nm. A hydrocarbon group, a cyano group, a fluorine atom, and a fluorine-substituted saturated hydrocarbon group having 1 to 10 carbon atoms are preferred.
Among the above substituents, an aliphatic saturated hydrocarbon group having 1 to 10 carbon atoms and an alicyclic saturated hydrocarbon group having 3 to 14 carbon atoms are preferable for the same reason as R ^{1 in} (1-1).
Preferred b is 0, 1 or 2, and n3 is 1 to 3, particularly preferably 1 or 2. In particular, b is preferably 0 because the refractive index at 193 nm is increased.
Examples of preferred compound (1-2) are shown below.

式（２−２）、（２−２'）において、Ｒ²は式（１−２）におけるＲ²と同一であり、好ましいｉは０、１または２である。ｉが０であることが（１−１）におけるａと同様の理由で特に好ましい。
好ましい化合物（２−２）、（２−２'）の具体例としては上記（１−２−１）〜（１−２−６）の化合物が挙げられる。
特に好ましい具体例としては、テトラヒドロジシクロペンタジエンが挙げられ、屈折率の異なる立体異性体としては、ｅｎｄｏ‐テトラヒドロジシクロペンタジエンおよびｅｘｏ−テトラヒドロジシクロペンタジエンが挙げられる。 Preferred compounds in formula (1-2) are represented by formula (2-2) and formula (2-2 ′).

Equation (2-2), in (2-2 '), R ² is the same as R ² in the formula (1-2), preferably i is 0, 1 or 2. It is particularly preferable that i is 0 for the same reason as a in (1-1).
Specific examples of preferred compounds (2-2) and (2-2 ′) include the compounds (1-2-1) to (1-2-6) described above.
Particularly preferred specific examples include tetrahydrodicyclopentadiene, and stereoisomers having different refractive indices include endo-tetrahydrodicyclopentadiene and exo-tetrahydrodicyclopentadiene.

The above compound is preferably a liquid at a temperature at which the immersion exposure apparatus operates, and the refractive index is higher than that of pure water for the reasons of the above formulas (iii) and (iv).
Specifically, it is preferable that the refractive index is a value between water and the resist film before exposure (or an upper film for immersion), and a higher value than water, and the refractive index is 193 nm. The refractive index is 1.45 to 1.8, preferably 1.6 to 1.8, and the refractive index at a wavelength of 248 nm is 1.42 to 1.65, preferably 1.5 to 1.65. Moreover, at 25 degreeC, the refractive index in D line | wire (wavelength 589nm) is 1.4 or more, Preferably it is 1.4-2.0, More preferably, it is the range of 1.40-1.65.
Within the preferable refractive index range, the fluctuation range of the predetermined refractive index of the immersion exposure liquid obtained by mixing the stereoisomers is controlled to ± (1 × 10 ⁻³ ), preferably ± (1 × 10 ⁻⁴ ), more preferably ± (1 × 10 ⁻⁶ ). In particular, by setting the fluctuation range to a predetermined refractive index ± (1 × 10 ⁻⁶ ), a pattern of 100 nm or less can be formed with a sufficient process margin.

In addition, since the refractive index change due to the change in the use environment causes defocusing, the present compound is preferably a compound whose refractive index is hardly affected by temperature, pressure and 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 ℃.
Moreover, it is preferable that the refractive index of the compound is not easily affected by chromatic aberration, and it is preferable that the wavelength dependence of the refractive index around the exposure wavelength is small.

The liquid for immersion exposure according to the present invention is preferably mixed with a compound having a structure represented by the above formulas (1-1) and (1-2), and thus has a small absorbance at 193 nm, for example. Is susceptible to 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, each stereoisomer of the compound having the structure of (1-1) and (1-2) is concentrated sulfuric acid washing, water washing, alkali washing, silica gel column purification, precision distillation, permanganate treatment under alkaline conditions. And a combination 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.
Further, depending on the compound, impurities can be more efficiently removed by treatment with permanganate under alkaline conditions before the previous 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, the higher the temperature, the higher the efficiency of impurity removal, but at the same time, it tends to 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.

The isomer compound of the above raw material can be obtained as a commercial product or synthesized by a known method, or can be obtained by separating an isomer mixture obtained by a similar method by an appropriate method.
For example, trans-decahydronaphthalene / cis-decahydronaphthalene raw material isomer compound among isomers suitable as the immersion exposure liquid of the present invention can be produced by the following method.
Using appropriate catalyst for naphthalene or naphthalene derivatives contained in dry distillation oil from coal coke oven, petroleum-based catalytic reforming oil and fluid catalytic cracking oil, and naphtha cracking oil of ethylene production by-product And can be produced by nuclear hydrogenation by catalytic hydrogenation.
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, 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, which prevents the progress of the nuclear hydrogenation reaction, and contains sulfur-containing impurities derived from the sulfur-containing compound. However, if it cannot be removed by purification, the transmittance of the liquid of the present invention at an exposure wavelength such as 193 nm will be reduced.

  In addition, when producing cis-decahydronaphthalene or trans-decahydronaphthalene and a mixture thereof, the purity of naphthalene as a raw material is preferably high, and the preferable purity of naphthalene is 99.0% or more, and particularly 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, washing with water, washing with concentrated sulfuric acid, filtration and crystallization, and combinations thereof can be used. Among these, precision distillation is preferable because it is effective for removing both non-volatile catalyst-derived metals and other metals 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.

In addition, the isomer compound of exo-tetrahydrodicyclopentadiene / endo-tetrahydrodicyclopentadiene among other suitable isomers as the immersion exposure liquid of the present invention can be produced by the following method.
Tetrahydrodicyclopentadiene is hydrogenated under appropriate conditions, dicyclopentadiene (exo, endo mixture) or endo dicyclopentadiene, which is known to be useful as a raw material monomer for optical lenses and optical film resins, The obtained tetrahydrodicyclopentadiene can be obtained by purification by a method such as distillation. In addition, when it is desired to selectively obtain the exo isomer from dicyclopentadiene, an exo isomer is selectively obtained by isomerizing a mixture of dicyclopentadiene using an appropriate catalyst, and the above hydrogenation reaction is performed. Or exo tetrahydrodicyclopentadiene is selected by isomerizing endo (endo, exo mixed) tetrahydrodicyclopentadiene obtained by hydrogenation of endo (endo, exo mixed) dicyclopentadiene with an appropriate catalyst. Can be obtained.
Dicyclopentadiene is prepared by the general to dimerization of cyclopentadiene contained in a large amount in a so-called C ₅ fraction of the pyrolysis product of naphtha.
This dicyclopentadiene contains, for example, a hydrocarbon component derived from a C ₅ fraction such as 5-isopropenyl norbornene as an impurity. When these compounds are contained, these compounds are hydrogenated and isomerized after the isomerization. Impurity-derived hydrocarbon products remain, making purification of the final product tetrahydrodicyclopentadiene difficult. Therefore, it is preferable to use the one purified in advance by a method such as purification. The purity in this case is preferably 95% or more, more preferably 97% or more.
In addition, dicyclopentadiene preferably has a low content of sulfur-containing components that are catalyst poisons of hydrogenation reactions, for example. Specifically, the sulfur-containing components present in dicyclopentadiene are preferably 500 ppb or less, Preferably it is 50 ppb or less. When the amount of the sulfur-containing component is 500 ppb, the hydrogenation reaction in the subsequent step is likely to be inhibited.
Here, the sulfur-containing component means the total amount of sulfur elements present in the form of inorganic or organic compounds such as free sulfur, elemental sulfur, hydrogen sulfide, mercaptans, disulfides, and thiophene, and sulfur chemiluminescence The analysis can be performed by gas chromatography equipped with a detector (SCD). The sulfur fraction can be removed by, for example, the method of JP-A No. 2001-181217. Hydrogenation of the dicyclopentadiene can be carried out using a known hydrogenation catalyst of carbon-carbon double bond. The hydrogenation can be carried out by the methods disclosed in, for example, JP-A-60-209536 and JP-A-2004-123762. Tetrahydrodicyclopentadiene can be obtained by distillation after the above hydrogenation. For example, a method of isomerization using various Lewis acids is known to selectively obtain an exo form. This isomerization can be carried out, for example, by a method using aluminum halide, sulfuric acid or the like as a Lewis acid (Japanese Patent Laid-Open No. 2002-255866). In this reaction, it is known that adamantane is produced as a by-product. However, when a large amount of adamantane is present, the transmittance at 193 nm decreases, so the amount of adamantane coexisting in the final liquid is 0.5 wt. % Or less, preferably 0.1% by weight, more preferably 0.05% by weight or less. The adamantane can be removed by appropriately setting the conditions for the isomerization reaction or by various known purification methods.

数（１)において、Ｒｍは混合物のモル屈折率を、Ｒ₁は異性体１のモル屈折率を、Ｒ₂は異性体２のモル屈折率をそれぞれ表す。
また、各異性体のモル屈折率をＲｉで表すと、Ｒ_ｉは数（２)で表される。

数（２)において、ｎ_ｉは各異性体の屈折率を、ρ_ｉは密度を、Ｍ_ｉは分子量をそれぞれ表す。
また、χ₁、χ₂等はそれぞれ異性体１および異性体２のモル分率であり、

である。
本発明において立体異性体を混合する場合、成分の分子量が同じであるため、数（１）および数（２）から複数の異性体の混合物の屈折率ｎ_ｍは数（４）で表される。

ここでｎ_ｉ、ρ_ｉ、χ_ｉの定義は数（１）と同じである。
本式から導き出されるモル分率χ_ｉにしたがって複数の異性体ｉの混合比を決め、その比にしたがって各異性体を混合することにより望まれる所定の屈折率を達成することができる。
屈折率の精度を保つためには、混合比の精度を必要に応じて決めて、該精度で異性体を混合すればよい。混合比の精度は数（３）および数（４）より決まり、要求される屈折率の精度および混合する成分の屈折率の差により決まる。
数（３）および数（４）より、要求される混合比の精度は屈折率の差に反比例するため、屈折率の近い成分を混合した場合の方が高い屈折率精度を得やすい。本発明では屈折率の差が極めて小さい立体異性体を混合するため、高い屈折率精度を容易に得ることができる。 The liquid for immersion exposure of the present invention can be obtained by mixing the above-mentioned plurality of isomers, preferably stereoisomers, at a ratio such that the refractive index becomes a predetermined value. Here, the predetermined value means a value of a refractive index required at the time of immersion exposure.
The mixing ratio for obtaining a predetermined refractive index can be obtained from, for example, an equation of molar refractive index of the mixture. That is, when a plurality of isomers are mixed, the molar refractive index Rm of the mixture is expressed by the number (1).

In number (1), Rm represents the molar refractive index of the mixture, R ₁ represents the molar refractive index of isomer 1, and R ₂ represents the molar refractive index of isomer 2.
Also, to represent the molar refraction index of each isomer in Ri, R _i is represented by the number (2).

In the number (2), n _i represents the refractive index of each isomer, ρ _i represents the density, and M _i represents the molecular weight.
Χ ₁ , χ ₂ etc. are the mole fractions of isomer 1 and isomer 2, respectively.

It is.
When mixing stereoisomers in the present invention, represented by the molecular weight of the components are the same, the number (1) and the number refractive index of mixture of isomers from (2) n _m is a number (4) .

Here, the definitions of n _i , ρ _i , and χ _i are the same as the number (1).
A predetermined refractive index desired can be achieved by determining a mixing ratio of a plurality of isomers _i according to the molar fraction χ _i derived from this formula and mixing each isomer according to the ratio.
In order to maintain the accuracy of the refractive index, the accuracy of the mixing ratio may be determined as necessary, and the isomers may be mixed with the accuracy. The accuracy of the mixing ratio is determined by the numbers (3) and (4), and is determined by the required accuracy of the refractive index and the difference in the refractive indexes of the components to be mixed.
From the numbers (3) and (4), the required accuracy of the mixing ratio is inversely proportional to the difference in refractive index, and therefore it is easier to obtain higher refractive index accuracy when components having similar refractive indexes are mixed. In the present invention, since stereoisomers having a very small difference in refractive index are mixed, high refractive index accuracy can be easily obtained.

The liquid for immersion exposure according to the present invention can be obtained, for example, by mixing two kinds of isomers, preferably stereoisomers, according to the above formula so as to have a target refractive index. By mixing stereoisomers having the same atomic arrangement order but different steric arrangement, a mixture of stereoisomers having a very small difference in refractive index is obtained. Therefore, high refractive index accuracy, for example, the fluctuation range of the refractive index can be controlled within ± (1 × 10 ⁻³ ).
Among the liquids for immersion exposure according to the present invention, a preferable liquid is a mixture of stereoisomers of the compound represented by the above formula (1-1) or the stereoisomer of the compound represented by the above formula (1-2). A mixture of bodies. A particularly preferred liquid is a mixture of cis-decahydronaphthalene and trans-decahydronaphthalene, or a mixture of exo-tetrahydrodicyclopentadiene and endo-tetrahydrodicyclopentadiene.

The liquid for immersion exposure according to the present invention has less chemical interaction with the lens and resist material of the projection optical system, and satisfies the preferable conditions of the following properties and characteristic values.
(1) Refractive index, etc. The refractive index of the immersion exposure liquid of the present invention, the temperature dependency of the refractive index, the specific heat, etc. are the same as the properties and characteristic values required for each compound constituting the above-mentioned mixture. .
Specifically, at 25 ° C., the refractive index at a wavelength of 193 nm is in the range of 1.45 to 1.8, preferably 1.6 to 1.8, and the temperature dependency of the refractive index is 5.0 ×. It is within 10 ⁻³ (° C. ⁻¹ ), preferably within 7.0 × 10 ⁻⁴ (° C. ⁻¹ ), and the specific heat is 0.1 cal / g · ° C. or higher. Further, the required fluctuation range of the refractive index is within ± (1 × 10 ⁻³ ), preferably within ± (1 × 10 ⁻⁴ ), and more preferably within ± (1 × 10 ⁻⁶ ).
(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 Ames test result 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.

(8) Impurities etc. The immersion exposure liquid of the present invention can measure the purity of mixed components and impurities by gas chromatography.
Impurities include compounds containing olefins with large absorbance, compounds containing aromatic rings, sulfur (sulfide, sulfoxide, sulfone structures), halogen, carbonyl groups, ether groups, etc., particularly at exposure wavelengths such as 193 nm Is mentioned. The proportion 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.

(9) Oxygen concentration 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. When the oxygen concentration exceeds 100 ppm, the transmittance tends to decrease due to oxidation reaction by dissolved oxygen. Also, even when 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.

The immersion exposure method using the immersion exposure liquid of the present invention will be described below.
The immersion exposure liquid of the present invention is preferably stored in an inert gas, but as a container at that time, a container component or a component of a container lid (for example, a plasticizer blended in a plastic) is used. It is preferable to store in a container without elution. 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 at the time of 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 the 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, but for this purpose, various analysis methods using, for example, gas chromatography can be used.

As a liquid supply method for immersion area exposure, 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 preferred 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.

The immersion exposure liquid represented by the formula (1-1) and the formula (1-2) is used by mixing stereoisomers.
Further, the liquid of the present invention can be used by mixing with liquids other than the present invention as necessary, and by doing so, for example, optical property values such as refractive index and transmittance, contact angle, specific heat, viscosity, A physical property value such as an expansion coefficient can be set to a desired value.
As the liquid other than the present invention used for this purpose, other defoamable solvents, various antifoaming agents, surfactants, and the like can be used. Reduction of bubbles and control of surface tension It is effective for.

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 chemical structures similar to the formulas (1-1) and (1-2), 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 immersion upper layer film and the immersion liquid, and specifically, the refractive index n _{RES of the} photoresist film is preferably in the range of 1.65 or more. . 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 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 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) or a KrF excimer laser (wavelength 248 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.
A lower antireflection film ARC29 (manufactured by Bruwa Science) was applied on an 8-inch silicon wafer by spin coating and PB (90 ° C., 60 seconds) to form a 29 nm-thick coating film under the same conditions. A resist film (film thickness 60 nm) was formed using the radiation sensitive resin composition (F-1) (H-1).
Moreover, after forming a resist film (film thickness of 60 nm) using the radiation sensitive resin composition (F-1) by the same method 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).

Production 1 of purified liquid used in Examples 1-3
Commercially available trans-decahydronaphthalene was purified by the following method.
In a nitrogen-substituted glove box, 200 ml eggplant type containing a stirrer chip coated with 100 ml of commercially available trans-decahydronaphthalene (manufactured by Tokyo Kasei Co., Ltd .; transmittance of 193.39 nm in terms of optical path length 1 mm is 10% or less) The flask was put in 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 separated organic layer was washed once with 50 ml of deionized water and three times with a saturated aqueous solution of sodium bicarbonate. Thereafter, the organic layer was washed with pure water three times. Thereafter, the organic layer was washed twice with 20 ml of a saturated aqueous sodium hydrogen carbonate solution and 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 inside of the system was depressurized with a vacuum pump and returned to normal pressure with nitrogen three times to replace the nitrogen, and purified trans-decahydronaphthalene (1) Got.

Two lots of commercial trans-decahydronaphthalene having different production lots were prepared, and the above operation was repeated for each lot to obtain purified trans-decahydronaphthalene (2) and purified trans-decahydronaphthalene (3). Moreover, commercial cis-decahydronaphthalene was prepared, and the same purification operation as that of trans-decahydronaphthalene was repeated to obtain purified cis-decahydronaphthalene.
Using the obtained purified trans-decahydronaphthalene and the refractive index at 193.39 nm of purified cis-decahydronaphthalene as a measuring device, a goniometer spectrometer type 1 UV-VIS-IR manufactured by MOLELER-WEDEL was used. It was measured at a measurement temperature of 25 ° C. by the angle method.
The refractive index of purified trans-decahydronaphthalene and purified cis-decahydronaphthalene at a wavelength of 193.39 nm was as follows.
Purified trans-decahydronaphthalene (1): 1.634452
Purified trans-decahydronaphthalene (2): 1.634457
Purified trans-decahydronaphthalene (3): 1.634450
Purified cis-decahydronaphthalene: 1.641536
Further, when the dissolved oxygen and dissolved nitrogen concentrations of each of the liquids were analyzed by gas chromatography (detector TCD), the dissolved oxygen concentration was less than 1 ppm (below the detection limit), and the dissolved nitrogen concentration was 119 ppm. In addition, when the metal content of Li, Na, K, Mg, Cu, Ca, Al, Fe, Mn, Sn, Zn, and Ni of this liquid was measured by atomic absorption spectrometry, Ca was 1 ppb, Zn was 6 ppb, and other metals. Was less than 1 ppb (less than the detection limit).

Examples 1 to 3
Purified trans-decahydronaphthalene (1) and purified cis-decahydronaphthalene were mixed at the following ratio to obtain an immersion exposure liquid (EKS-1). Similarly, liquids for immersion exposure (EKS-2) and (EKS-3) were obtained. In the examples, the mixing ratio is based on weight.
EKS-1: purified cis-decahydronaphthalene / purified trans-decahydronaphthalene (1) = 0.68 / 99.32
EKS-2: Purified cis-decahydronaphthalene / purified trans-decahydronaphthalene (2) = 0.61 / 99.39
EKS-3: purified cis-decahydronaphthalene / purified trans-decahydronaphthalene (3) = 0.71 / 99: 29
The obtained immersion exposure liquids (EKS-1 to EKS-3) were measured for refractive index and transmittance at a wavelength of 193.39 nm, and viscosity (viscosity). The results are shown in Table 2.
The refractive index at a wavelength of 193.39 nm was measured at a measurement temperature of 25 ° C. by the minimum deviation method using the above-described goniometer spectrometer type 1 UV-VIS-IR manufactured by MOLLER-WEDEL.
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.
The viscosity (viscosity) was measured by the vibration disk method.

Production of purified liquid used in Examples 4-6 2
Commercially available exo-tetrahydrodicyclopentadiene was purified by the following method.
In a nitrogen-substituted glove box, commercially available exo-tetrahydrodicyclopentadiene (product name: exo-Tetrahydrocyclopentadiene (special grade) (GC measurement result endo-tetrahydrodicyclopentadiene: 1.5%, exo-tetrahydrodicyclopentadiene: 97 0.5%, 1.0% of other components))) 100 ml was put into a 200 ml eggplant flask containing a glass-coated stirrer chip 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 separated organic layer was washed once with 50 ml of deionized water and three times with a saturated aqueous solution of sodium bicarbonate. Thereafter, the organic layer was washed with pure water three times. Thereafter, the organic layer was washed twice with 20 ml of a saturated aqueous sodium hydrogen carbonate solution and 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 fitted with a three-way cock, and the operation of reducing the pressure inside the system with a vacuum pump and returning to normal pressure with nitrogen was repeated three times to purify exo-tetrahydrodicyclopentadiene (1 )

Two lots of commercially available exo-tetrahydrodicyclopentadiene having different production lots were prepared, and the above procedure was repeated for each lot to obtain purified exo-tetrahydrodicyclopentadiene (2) and purified exo-tetrahydrodicyclopentadiene (3). . Also, commercially available tetrahydrodicyclopentadiene (exo / endo = 50/50) is prepared, and the same purification operation as that of exo-tetrahydrodicyclopentadiene is repeated to purify tetrahydrodicyclopentadiene (exo / endo = 50/50). Got.
The obtained purified exo-tetrahydrodicyclopentadiene and purified tetrahydrodicyclopentadiene (exo / endo = 50/50) having a refractive index at 193.39 nm as a measuring device were measured using a goniometer spectrometer type 1 UV manufactured by MOLLER-WEDEL. Measurement was performed at a measurement temperature of 25 ° C. by the minimum deflection angle method using −VIS-IR.
The refractive index of purified trans-decahydronaphthalene and purified cis-decahydronaphthalene at a wavelength of 193.39 nm was as follows.
Purified exo-tetrahydrodicyclopentadiene (1): 1.649070
Purified exo-tetrahydrodicyclopentadiene (2): 1.649080
Purified exo-tetrahydrodicyclopentadiene (3): 1.649073
Purified tetrahydrodicyclopentadiene (exo / endo = 50/50): 1.654338
Further, when the dissolved oxygen and dissolved nitrogen concentrations of each of the liquids were analyzed by gas chromatography (detector TCD), the dissolved oxygen concentration was less than 1 ppm (below the detection limit), and the dissolved nitrogen concentration was 119 ppm. In addition, when the metal content of Li, Na, K, Mg, Cu, Ca, Al, Fe, Mn, Sn, Zn, and Ni of this liquid was measured by atomic absorption spectrometry, Ca was 1 ppb, Zn was 6 ppb, and other metals. Was less than 1 ppb (less than the detection limit).

Example 4 to Example 6
Purified exo-tetrahydrodicyclopentadiene (1) and purified tetrahydrodicyclopentadiene (exo / endo = 50/50) were mixed at the following ratio to obtain a liquid for immersion exposure (EKS-4). Similarly, immersion exposure liquids (EKS-5) and (EKS-6) were obtained.
EKS-4: purified exo-tetrahydrodicyclopentadiene (1) / purified tetrahydrodicyclopentadiene (exo / endo = 50/50) = 99.43: 0.57
EKS-5: purified exo-tetrahydrodicyclopentadiene (2) / purified tetrahydrodicyclopentadiene (exo / endo = 50/50) = 99.62: 0.38
EKS-6: purified exo-tetrahydrodicyclopentadiene (3) / purified tetrahydrodicyclopentadiene (exo / endo = 50/50) = 99.49: 0.51
The refractive index and transmittance at a wavelength of 193.39 nm and the viscosity (viscosity) of the obtained immersion exposure liquids (EKS-4 to EKS-6) were measured in the same manner as in Example 1. The results are shown in Table 3.

Example 7 to Example 12
The immersion exposure liquids obtained in Examples 1 to 6 were evaluated by immersion exposure using a sensitivity two-speed interference exposure machine using the evaluation resist film obtained in Reference Example 5. The results are shown in Table 4.
Evaluation was performed by the following method by immersion exposure using a two-speed interference exposure machine.
Two-beam interference type ArF immersion is applied to a wafer coated with an evaluation resist film made in the same manner as the resist film H-2 except that the thickness of the lower antireflection film is 29 nm and the resist film thickness is 60 nm. Exposure is performed by inserting the purified immersion exposure liquid between the lens and wafer (gap 0.7 mm) of a simple exposure apparatus for use (manufactured by Nikon Corporation, for 35 nm 1 L / 1S, using TE polarized exposure), Thereafter, the immersion exposure liquid on the wafer is removed by air drying, PEB (115 ° C., 90 seconds) is performed on the CLEAN TRACK ACT8 hot plate, and paddle development (development) is performed on the LD nozzle of the CLEAN TRACKACT8. Liquid component, 2.38 wt% tetrahydroammonium hydroxide aqueous solution) (60 seconds), rinsed with ultrapure water, and after development, the substrate was scanned by electron microscope The pattern was observed with a mirror (manufactured by Hitachi Sokki Co., Ltd.) 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 sensitivity represents the exposure amount at which a desired dimension is obtained.

  The liquid for immersion exposure of the present invention can provide a liquid for immersion exposure having a predetermined refractive index suitable for immersion exposure by mixing a plurality of stereoisomers having different refractive indexes. An excellent resist pattern can be formed, and can be used very suitably for the manufacture of semiconductor devices that are expected to be further miniaturized in the future.

Claims (6)

A liquid used in an immersion exposure apparatus or an immersion exposure method for exposing through a liquid having a predetermined refractive index filled between a lens of a projection optical system and a substrate,
A liquid for immersion exposure, wherein the liquid has the predetermined refractive index by mixing a plurality of isomers having different refractive indexes.   2. The immersion exposure liquid according to claim 1, wherein the isomer is a stereoisomer. 3. The immersion exposure liquid according to claim 1, wherein the predetermined refractive index is controlled to have a fluctuation range of ± (1 × 10 ⁻³ ).   4. The immersion exposure liquid according to claim 2, wherein the mixture of stereoisomers is a mixture of cis-decahydronaphthalene and trans-decahydronaphthalene.   4. The immersion exposure liquid according to claim 2, wherein the mixture of stereoisomers is a mixture of exo-tetrahydrodicyclopentadiene and endo-tetrahydrodicyclopentadiene.   An immersion exposure method for illuminating a mask with an exposure beam and exposing the substrate with the exposure beam through a liquid filled between a lens of the projection optical system and the substrate, wherein the liquid is claimed in claim 1. 6. A liquid immersion exposure method according to any one of items 5 to 5.