JP2008098334A - Liquid for liquid immersion exposure and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid for a liquid immersion having a high transmission factor at 193.4 nm, hard to deteriorate due to an exposure, and excellent in the reusability of the liquid. <P>SOLUTION: The liquid for the liquid immersion exposure is used for a device and a method of liquid immersion exposure for exposure through the liquid filled between a projection optical system and a lens substrate. The liquid comprises a trans-decahydronaphthalene with a content of a cis-decahydronaphthalene less than 0.05 mass%. The trans-decahydronaphthalene is the liquid refined by a precision refining, and further refined by a concentrated sulfric acid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid for immersion exposure and a method for producing the same.

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.

By the way, in the above exposure technique, a photoresist film is formed on the surface of the wafer to be exposed, 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 The 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).

At present, immersion exposure with water is in the stage of mass production examination, and it is considered possible to produce a device of 45 nm half pitch node with NA = 1.35 exposure machine by immersion in water. For the 45 nm half pitch node or less, there is a possibility that it may be realized by an immersion liquid having a higher refractive index than water, and such a high refractive index liquid has been developed. For example, the inventors have developed a liquid composed of a saturated hydrocarbon having an alicyclic skeleton such as trans-decahydronaphthalene and has already filed a patent application (see Patent Document 2).
However, these compounds have problems that the transmittance at the exposure wavelength (193.4 nm) is insufficient due to absorption that is considered to be derived from impurities, and that the transmittance is liable to decrease due to exposure.
Japanese Patent Laid-Open No. 11-176727 International Publication WO2005 / 114711

  The present invention has been made to cope with such problems, and provides an immersion exposure liquid having a high transmittance at 193.4 nm, being hardly deteriorated by exposure, and having excellent liquid reusability. With the goal.

  The inventors purified the trans-decahydronaphthalene, which is a liquid raw material compound, by high-precision distillation, removed impurities that cause absorption, and then obtained a liquid for purification including, for example, concentrated sulfuric acid washing, It has been found that a liquid for immersion exposure having a high transmittance at 193.4 nm, being hardly deteriorated by exposure, and having excellent liquid reusability, has been completed.

The immersion exposure liquid of the present invention is an immersion exposure liquid used in an immersion exposure apparatus or an immersion exposure method for exposing via a liquid filled between a projection optical system and a lens substrate, The liquid is characterized by comprising trans-decahydronaphthalene having a cis-decahydronaphthalene content of less than 0.05% by mass.
The trans-decahydronaphthalene having a cis-decahydronaphthalene content of less than 0.05% by mass is a liquid purified by precision distillation.
The immersion exposure liquid is obtained by purifying trans-decahydronaphthalene having a cis-decahydronaphthalene content of less than 0.05 mass% by concentrated sulfuric acid treatment (hereinafter also referred to as “concentrated sulfuric acid cleaning treatment”). It is a liquid.
The method for producing an immersion exposure liquid according to the present invention includes a cis-decahydronaphthalene used in an immersion exposure apparatus or an immersion exposure method in which exposure is performed via a liquid filled between a projection optical system and a lens substrate. A method for producing a liquid for immersion exposure comprising trans-decahydronaphthalene having a content of less than 0.05% by mass, using trans-decahydronaphthalene having a purity of 99.9% by mass or more as a starting raw material It has the process. Further, it is characterized in that a concentrated sulfuric acid treatment step is further provided after the precision distillation step.

  The liquid for immersion exposure according to the present invention is highly purified by precision distillation of the raw material trans-decahydronaphthalene, and after removing impurities that cause absorption, purification including, for example, concentrated sulfuric acid washing is performed. -Decahydronaphthalene content can be less than 0.05 mass%. As a result, it is an immersion exposure liquid that has a high radiation transmittance at 193.4 nm, hardly undergoes exposure deterioration, and has excellent reusability. By using this liquid, it is possible to form a pattern having an excellent pattern shape with a large depth of focus.

  The liquid for immersion exposure of the present invention uses trans-decahydronaphthalene having a purity of 99.9% by mass or more measured by gas chromatography (hereinafter also referred to as GC) as a starting material. Examples of trans-decahydronaphthalene having a GC purity of 99.9% by mass or more include trans-decahydronaphthalene obtained by purifying decahydronaphthalene that is commercially available or synthesized by a known synthesis method by an appropriate method. Examples of the purification method for obtaining trans-decahydronaphthalene having a GC purity of 99.9% by mass or more include methods such as precision distillation and column chromatography using various fillers. Of these, precision distillation is preferred. The number of theoretical plates in the precision distillation is preferably 10 or more. Preferably it is 30 steps or more, more preferably 50 steps or more.

  The immersion exposure liquid of the present invention is trans-decahydronaphthalene containing 99.9% by mass or more of trans-decahydronaphthalene and having a cis-decahydronaphthalene content of less than 0.05% by mass. Preferably, the liquid does not contain components other than trans-decahydronaphthalene and cis-decahydronaphthalene. The content of cis-decahydronaphthalene is preferably less than 0.01% by mass. When the content of cis-decahydronaphthalene is 0.05% by mass or more, the transmittance at 193.4 nm is deteriorated.

In particular, at an exposure wavelength such as 193 nm, a compound containing an olefin having a large absorbance, a compound containing an aromatic ring, sulfur (sulfide, sulfoxide, sulfone structure), a compound containing a halogen, a carbonyl group, an ether group, etc. The proportion is preferably less than 0.01% by mass, particularly preferably less than 0.001% by mass.
In addition, since the liquid comprising the present compound is used in a semiconductor integrated circuit manufacturing process, the metal or metal salt content is preferably low, specifically, the metal content is 100 ppb or less, preferably 10 ppb or less, More preferably, it is 1.0 ppb or less. If the metal content exceeds 100 ppb, the metal ions or metal components may adversely affect the resist film and contaminate the wafer.
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 atomic absorption method.
The oxygen concentration in the liquid 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.

  The liquid for immersion exposure of the present invention can be obtained as a commercially available compound, or can be produced from available raw materials by various existing synthesis methods. For example, it can be synthesized by catalytic hydrogenation of commercially available naphthalene using an appropriate catalyst.

As a catalyst for catalytic hydrogenation, sulfides such as cobalt-molybdenum, nickel-molybdenum, nickel-tungsten can be used in addition to noble metal-based catalysts such as nickel, platinum, rhodium, ruthenium, iridium and palladium. 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 mass relative to the raw material, a hydrogen pressure of 5 to 15 MPa, and a reaction temperature of about 100 ° C to 400 ° C.

Table 1 shows the preferred purity and physical properties of the immersion exposure liquid of the present invention.

The liquid for immersion exposure according to the present invention uses trans-decahydronaphthalene having a GC purity of 99.9% by mass or more, and thus has a low absorbance at 193 nm. However, the absorbance in the wavelength region 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 the method described above.
In addition to the above-described precision distillation and concentrated sulfuric acid washing treatment, for example, water washing, alkali washing, silica gel column purification, permanganate treatment under alkaline conditions, and combinations thereof can be employed.
Specifically, it can be suitably purified by performing precision distillation or further performing concentrated sulfuric acid washing treatment.

Among the above purification operations, concentrated sulfuric acid washing treatment is effective in removing aromatic compounds having a large absorption at 193 nm and compounds having a carbon-carbon unsaturated bond, and is also effective in removing trace basic compounds. is there. 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.
Concentrated sulfuric acid washing is performed after precision distillation, so that impurities that cause absorption can be more efficiently removed.

The precision distillation is preferably performed in a distillation column having a theoretical plate number equal to or greater than the theoretical plate number required for the separation according to the difference in boiling point between the impurity to be removed and the liquid of the present invention. In the present invention, the number of theoretical plates in precision distillation is preferably 10 or more. Preferably it is 30 steps or more, more preferably 50 steps or more.
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.

  Further, since the 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 the 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. Further, 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 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. For this purpose, for example, various analysis methods using 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 those 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 in-line 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 the removal of eluents 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 liquid for immersion exposure of the present invention can be used alone or as a mixture. A preferred example is when used alone. By using it alone, it becomes easy to set immersion exposure conditions.
Further, the liquid of the present invention can be used by mixing with liquids other than the present invention as required, 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 a chemical structure similar to decahydronaphthalene, they are excellent in 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 concentration of, for example, 0.1 to 20% by mass, 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.
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.

化合物（Ｓ１−１）５３．９２ｇ（５０モル％）、化合物（Ｓ１−２）１０．６９ｇ（１０モル％）、化合物（Ｓ１−３）３５．３８ｇ（４０モル％）を２−ブタノン１８７ｇに溶解した単量体溶液（１）、ジメチル２，２'−アゾビス（２−メチルプロピオネート）３．３７ｇを２−ブタノン６４ｇに溶解した溶液（２）を準備し、更に２−ブタノンを１５ｇ投入した１０００ｍｌの三つ口フラスコに前に準備した単量体溶液（１）２８．７７ｇ、溶液（２）４．２３ｇを投入し、その後減圧置換法にて窒素パージする。窒素パージの後、反応釜を攪拌しながら８０℃に加熱し、１５分後、単量体溶液（１）２５８．９８ｇ、溶液（２）２４．６４ｇを送液ポンプを用いて３時間かけて滴下した。滴下終了後更に４時間攪拌した。重合終了後、重合溶液は放冷することにより３０℃以下に冷却した。反応終了後、溶液は放冷し３０℃以下に冷却し、４０００ｇのイソプロピルアルコールへ投入し、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２０００ｇのイソプロピルアルコールにてスラリー上で洗浄した後、ろ別し、６０℃にて１７時間乾燥し、白色粉末の重合体を得た（８５ｇ、収率８５質量％）。この重合体はＭｗが７，６００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５３．１：８．５：３８．４（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 evaluation resist film, the characteristics (elution test, film solubility test, patterning evaluation) 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) 53.92 g (50 mol%), compound (S1-2) 10.69 g (10 mol%), compound (S1-3) 35.38 g (40 mol%) into 2-butanone 187 g A dissolved monomer solution (1) and a solution (2) in which 3.37 g of dimethyl 2,2′-azobis (2-methylpropionate) was dissolved in 64 g of 2-butanone were prepared, and further 15 g of 2-butanone was prepared. The previously prepared monomer solution (1) 28.77 g and solution (2) 4.23 g are charged into the charged 1000 ml three-necked flask, and then purged with nitrogen by the vacuum replacement method. After purging with nitrogen, the reaction kettle was heated to 80 ° C. with stirring. After 15 minutes, 258.98 g of monomer solution (1) and 24.64 g of solution (2) were added over 3 hours using a liquid feed pump. It was dripped. After completion of the dropwise addition, the mixture was further stirred for 4 hours. After completion of the polymerization, the polymerization solution was allowed to cool and then cooled to 30 ° C. or lower. After completion of the reaction, the solution is allowed to cool, cooled to 30 ° C. or lower, poured into 4000 g of isopropyl alcohol, and the precipitated white powder is filtered off. The filtered white powder was washed twice with 2000 g of isopropyl alcohol on the slurry, filtered, and dried at 60 ° C. for 17 hours to obtain a white powder polymer (85 g, yield 85 mass). %). This polymer has Mw of 7,600, and as a result of ¹³ C-NMR analysis, the repeating unit represented by compound (S1-1), compound (S1-2), compound (S1-3), and each repeating unit Was a copolymer having a content ratio of 53.1: 8.5: 38.4 (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質量％）。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, yield 89 mass%). Resin (E-1) had Mw of 7,300.

Reference example 3
A radiation sensitive resin composition was obtained by the following method.
A resin, acid generator, acid diffusion controller, and solvent shown in Table 2 were mixed to obtain a uniform solution, and then filtered through a membrane filter having a pore size of 200 nm to prepare a radiation sensitive resin composition (F-1). . In Table 2, the part is based on mass.
The acid generator (B), acid diffusion controller (C), and solvent (D) used are shown below.
Acid generator (B)
B-1: Triphenylsulfonium nonafluorobutanesulfonate acid diffusion controller (C)
C-1: 2-Phenylbenzimidazole solvent (D)
D-1: Propylene glycol monomethyl ether acetate

Reference example 4
An upper layer film composition for immersion was obtained by the following method.
A resin and a solvent shown in Table 3 were mixed to obtain a uniform solution, and then filtered through a membrane filter having a pore size of 200 nm to prepare an upper layer film composition (G1) for immersion. In Table 3, n-BuOH represents normal butanol, and the parts are based on mass.

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 shown in Table 4 (H-1).
Moreover, after forming a resist film (film thickness of 205 nm) using the radiation-sensitive resin composition by the same method as described above, an upper layer film composition for immersion shown in Table 4 is spin-coated on this resist film, An upper film of 32 nm thickness was formed by PB (130 ° C., 90 seconds) (H-2).

Example 1
By subjecting 3000 g of commercially available decahydronaphthalene (manufactured by Nippon Steel Chemical Co., Ltd.) to a precision distillation in a distillation column having 40 theoretical plates, 600 g of a fraction having a GC purity of trans-decahydronaphthalene of 100% by mass was obtained. The GC purity was 99.96% by mass of trans-decahydronaphthalene and 0.04% by mass of cis-decahydronaphthalene. The flask containing the obtained fraction was reduced in pressure and returned to normal pressure with nitrogen three times to replace the dissolved air with nitrogen. This liquid is designated as EK-1.
The transmittance of the obtained EK-1 was measured. As a measuring method, absorbance was measured using two types of cells having optical path lengths of 2 cm and 1 cm using V7100 manufactured by JASCO, and the difference between the two was defined as absorbance per 1 cm. Based on this value, the transmittance per mm was calculated according to Lambert Beer's law. The transmittance of EK-1 measured by this method at 193.4 nm was 99.0% / mm.

Example 2
200 g of EK-1 obtained in Example 1 was put into an eggplant flask purged with nitrogen, 30 g of concentrated sulfuric acid was added, and the mixture was vigorously stirred with a magnetic stirrer. Thereafter, concentrated sulfuric acid was removed by decantation, and the same concentrated sulfuric acid washing operation was performed twice. Thereafter, the organic layer was washed with 30 g of water and distilled under reduced pressure. The GC purity was 99.97% by mass of trans-decahydronaphthalene and 0.03% by mass of cis-decahydronaphthalene. The operation of depressurizing the flask containing the obtained fraction and returning to normal pressure with nitrogen was performed three times to replace the dissolved air with nitrogen. This liquid is designated as EK-2. The transmittance at 193.4 nm of EK-2 measured by the same method as in Example 1 was 99.4% / mm.

Comparative Example 1
100 g of commercially available decahydronaphthalene (manufactured by Nippon Steel Chemical Co., Ltd.) was washed with concentrated sulfuric acid and simply distilled in the same manner as in Example 2 to obtain EKH-1. The GC purity was 99.94% by mass of trans-decahydronaphthalene and 0.06% by mass of cis-decahydronaphthalene. The transmittance at 193.4 nm of EKH-1 measured by the same method as in Example 1 was 84.3% / mm.

Example 3
AK-1, EK-2, and EKH-1 were irradiated with 2000 mJ of ArF laser, and the transmittance at 193.4 nm was measured. Further, the sample after irradiation was subjected to concentrated sulfuric acid washing and simple distillation in the same manner as in Example 2, and the transmittance at 193.4 nm was measured. The results are shown in Table 5.

Examples 4 to 5 and Comparative Example 2
Using the resist film for evaluation, the immersion exposure liquid (EK-1) of the present invention was evaluated by an elution test, a film solubility test, and patterning evaluation (immersion patterning evaluation). The results are shown in Table 6.
(1) Dissolution test About 4 ml of liquid was adjusted to a thickness of 2 mm on a wafer coated with a resist film for evaluation and immersed for 180 seconds. Thereafter, the absorbance of the liquid at a wavelength of 193.4 nm was measured. When the change in absorbance before and after the immersion was 0.05 or less, the dissolution test result was “◯”, and when it was larger than 0.05, the dissolution test result was “x”.
(2) Film solubility test After measuring the initial film thickness of the wafer coated with the evaluation resist, about 4 ml of liquid was immersed for 180 seconds so that the thickness of the liquid film was 2 mm, and then the liquid was removed. Then, the film thickness of the liquid immersion site was measured. At this time, if the reduction amount of the film thickness is within 0.5% of the initial film thickness, it is judged that the liquid for immersion exposure does not dissolve the resist film. It was set as “x” because the exposure liquid dissolves the resist film.
(3) Patterning evaluation test A wafer coated with a resist film for evaluation is exposed with an ArF projection exposure apparatus S306C (manufactured by Nikon Corporation) under the optical conditions of NA = 0.78 and σ: 0.85 2/3 Ann. (Exposure amount 30 mJ / cm ² ), PEB (130 ° C., 90 seconds) is then performed on a CLEAN TRACK ACT8 hot plate, and paddle development (developer component 2.38% by mass) is performed on the CLEAN TRACK ACT8 LD nozzle. An aqueous tetramethylammonium hydroxide solution (60 seconds), rinsed with ultrapure water, and then spin-dried for 15 seconds to form a substrate A after development. Then, after immersion of the immersion exposure liquid to a film thickness of 2 mm for 180 seconds on a substrate which has been subjected to exposure in the same manner as the above-described substrate A after development, the liquid is removed by spin drying, and PEB (130 ° C. , 90 seconds), and development was performed to obtain a substrate B after development. After development, the substrates A and B were observed with a scanning electron microscope (manufactured by Hitachi Instrument Co., Ltd.) S-9360, and a pattern corresponding to a mask pattern of 90 nm line and 90 nm space was observed. At this time, a pattern is obtained in a rectangular shape with respect to the substrate B. If the line width difference ΔCD between the line portions of the substrates A and B is 10% or less of the line width, “◯” is obtained. × ”.

  Since the liquid for immersion exposure of the present invention comprises trans-decahydronaphthalene having a cis-decahydronaphthalene content of less than 0.05% by mass, the photoresist film is not dissolved during the immersion exposure, and resolution and development are achieved. It is possible to form a resist pattern having excellent properties and the like, and it can be used very suitably for the manufacture of semiconductor devices that are expected to be further miniaturized in the future.

Claims (5)

  An immersion exposure liquid used for an immersion exposure apparatus or an immersion exposure method for exposing through a liquid filled between a projection optical system and a lens substrate, the liquid containing cis-decahydronaphthalene An immersion exposure liquid comprising trans-decahydronaphthalene in an amount of less than 0.05% by mass.   The liquid for immersion exposure according to claim 1, wherein the trans-decahydronaphthalene having a cis-decahydronaphthalene content of less than 0.05% by mass is a liquid purified by precision distillation.   3. The liquid according to claim 1, wherein the liquid is a liquid obtained by purifying trans-decahydronaphthalene having a cis-decahydronaphthalene content of less than 0.05% by mass by a concentrated sulfuric acid treatment. Liquid for immersion exposure. Trans- with a cis-decahydronaphthalene content of less than 0.05% by weight used in an immersion exposure apparatus or immersion exposure method for exposing via a liquid filled between the projection optical system and the lens substrate A method for producing a liquid for immersion exposure comprising decahydronaphthalene,
A method for producing a liquid for immersion exposure, comprising using trans-decahydronaphthalene having a purity of 99.9% by mass or more as a starting raw material and having a precision distillation step.   5. The method for producing a liquid for immersion exposure according to claim 4, further comprising a concentrated sulfuric acid treatment step after the precision distillation step.