JP2006048075A - Solvent for removing liquid immersion exposure process-use resist protection film and method for forming resist pattern by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solvent for removing a liquid immersion exposure process-use resist protection film, the solvent containing a fluorine-based solvent and to be used to remove a protection film forming material which is suitably used for a liquid immersion exposure process, in particular, a liquid immersion exposure process of exposing a resist film in such a state that a liquid of predetermined thickness having a refractive index higher than that of air and lower than that of the resist film is made present in the passage of the lithographic exposure light reaching the resist film and at least on the resist film to improve the resolution of the resist pattern, and to form a resist pattern with high resolution by liquid immersion exposure by using the above solvent. <P>SOLUTION: The solvent for removing a protection film is to be used to remove a resist protection film forming material which is suitably used for a liquid immersion exposure process. The protection film is removed by using the solvent containing a fluorine-based solvent for removing a liquid immersion exposure process-use resist protection film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid immersion lithography process, in particular, a refractive index higher than air and lower than the resist film on at least the resist film in a path through which lithography exposure light reaches the resist film. Protective film removing solvent for removing a resist protective film suitable for use in an immersion exposure process configured to improve the resolution of a resist pattern by exposing the resist film with a liquid having a predetermined thickness interposed therebetween And a resist pattern forming method using the same.

  Lithography is often used to manufacture fine structures in various electronic devices such as semiconductor devices and liquid crystal devices. However, with the miniaturization of device structures, it is required to make finer resist patterns in the lithography process.

  At present, it is possible to form a fine resist pattern having a line width of about 90 nm by the lithography method, for example, in the most advanced region. However, further fine pattern formation is required in the future.

In order to achieve such fine pattern formation of less than 90 nm, the development of an exposure apparatus and a corresponding resist is the first point. Development points for exposure equipment include shortening the wavelength of light sources such as F ₂ excimer laser, EUV (extreme ultraviolet light), electron beam, X-ray, soft X-ray, and increasing the numerical aperture (NA) of the lens. It is common.

  However, shortening the wavelength of the light source requires a new expensive exposure apparatus, and in increasing the NA, there is a trade-off between the resolution and the depth of focus. There is a problem that decreases.

  Recently, as a lithography technique capable of solving such a problem, a method called an immersion exposure (liquid immersion lithography) method has been reported (for example, Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3). In this method, an immersion exposure liquid such as pure water or a fluorine-based inert liquid having a predetermined thickness is interposed between at least the resist film between the lens and the resist film on the substrate during exposure. . In this method, a light source having the same exposure wavelength can be used by replacing the exposure optical path space, which has conventionally been an inert gas such as air or nitrogen, with a liquid having a higher refractive index (n), such as pure water. Similar to the case of using a light source having a shorter wavelength or the case of using a high NA lens, high resolution is achieved and at the same time, there is no reduction in the depth of focus.

  By using such immersion exposure, it is possible to realize the formation of a resist pattern that is low in cost, excellent in high resolution, and excellent in depth of focus, using a lens mounted on an existing apparatus. It is attracting a lot of attention.

Journal of Vacuum Science & Technology B (Journal of Vacuum Science Technology) (J. Vac. Sci. Technol. B) ((Issue Country) USA), 1999, Vol. 17, No. 6, pages 3306-3309. Journal of Vacuum Science & Technology B (Journal of Vacuum Science Technology) (J. Vac. Sci. Technol. B) ((Publishing Country) USA), 2001, Vol. 19, No. 6, pp. 2353-2356. Proceedings of SPIE Vol.4691 (Proceedings of SPAI ((Issuing country) USA) 2002, 4691, pp. 459-465.

  However, in the immersion exposure process as described above, the resist film is directly in contact with the immersion exposure liquid during exposure, so that the resist film is invaded by the immersion exposure liquid. Therefore, it is necessary to verify whether or not a conventionally used resist composition can be applied as it is.

  Currently used resist compositions are compositions that have already been extensively studied and established from the most important characteristic of having transparency to exposure light. The inventors of the presently proposed resist compositions cannot obtain a resist composition having the characteristics suitable for immersion exposure by using the composition as it is or by slightly adjusting the composition. This was experimentally examined. As a result, it was found that there is a resist composition that can be expected in practical use. On the other hand, in immersion exposure, even resist compositions that cannot be obtained with sufficient pattern resolution due to alteration due to immersion exposure liquid are fine and high resolution in lithography by exposure through a normal air layer. It was also confirmed that there are many things that show sex. Such a resist composition is a composition established by spending many development resources, and is a composition excellent in various resist properties such as transparency to exposure light, developability, and storage stability. There are many resist compositions that have only poor resistance to immersion exposure liquids. Some examples of compositions that are not suitable for such immersion exposure but exhibit high resolution in air layer lithography will be shown in the comparative examples of the present invention described below.

  In addition, even when the resist film suitable for the above-mentioned immersion exposure is used, when immersion exposure is performed, it is confirmed that the quality and yield of non-defective products are somewhat lowered compared to exposure through an air layer. Has been.

  The suitability of the above-described conventional resist film for immersion exposure was evaluated based on the following analysis with respect to the immersion exposure method.

  That is, to evaluate the resist pattern formation performance by immersion exposure, (i) the performance of the optical system by the immersion exposure method, (ii) the influence of the resist film on the immersion exposure liquid, and (iii) immersion exposure If the three points of alteration of the resist film by the working liquid can be confirmed, it is judged that it is necessary and sufficient.

  As for the performance of the optical system (i), for example, it is clear that the surface water-resistant photographic photosensitive plate is submerged in water and the surface is irradiated with pattern light. In principle, there is no doubt that there will be no problem if there is no light propagation loss such as reflection at the interface between the substrate and the photosensitive plate surface. The light propagation loss in this case can be easily solved by optimizing the incident angle of the exposure light. Therefore, whether the object to be exposed is a resist film, a photographic photosensitive plate, or an imaging screen, if they are inert to the immersion exposure liquid, that is, If the liquid is not affected by the immersion exposure liquid and does not affect the immersion exposure liquid, it can be considered that there is no change in the performance of the optical system. Therefore, this point is not necessary for a new confirmation experiment.

  Specifically, the influence of the resist film on the immersion exposure liquid (ii) is that the components of the resist film dissolve into the liquid and change the refractive index of the liquid. If the refractive index of the liquid for immersion exposure changes, the optical resolution of the pattern exposure is surely changed from the theory without being experimented. In this regard, simply immersing the resist film in the immersion exposure liquid indicates that the components have dissolved and that the composition of the immersion exposure liquid has changed or the refractive index has changed. If it can be confirmed, it is sufficient, and it is not necessary to actually irradiate pattern light and develop it to confirm the resolution.

  On the other hand, when the resist film in the immersion exposure liquid is irradiated with pattern light and developed to confirm the resolution, the quality of the resolution can be confirmed. It is impossible to distinguish whether the influence is on the resolution due to the alteration, the influence on the resolution due to the alteration of the resist material, or both.

(Iii) Regarding the point that the resolution deteriorates due to the alteration of the resist film due to the immersion exposure liquid, “After the exposure, the immersion exposure liquid is showered on the resist film and then developed. An evaluation test “inspecting the resolution of the resist pattern formed” is sufficient. Moreover, in this evaluation method, the immersion exposure liquid is sprinkled directly on the resist film, and the immersion conditions become more severe. Regarding this point as well, in the case of a test in which exposure is performed in a completely immersed state, it may be caused by the alteration of the immersion exposure liquid, the alteration of the resist composition by the immersion exposure liquid, or both. It is not clear whether the resolution has changed due to the influence.
The phenomena (ii) and (iii) are phenomena that are integrated with each other, and can be grasped by confirming the degree of deterioration of the resist film due to the liquid.

  Based on such analysis, the above-described resist exposure suitability of the currently proposed resist film was obtained by performing a process of applying a shower of immersion exposure liquid to the resist film after exposure, and then developing the resist film. This was confirmed by an evaluation test “inspecting the resolution of the resist pattern”. In addition, it is possible to evaluate by simulating the actual manufacturing process using the “two-beam interference exposure method” in which the exposure pattern light is substituted with interference light from the prism, and the sample is placed in an immersion state and exposed. It is.

  As described above, in order to newly produce a resist film suitable for immersion exposure, it is certain that a lot of development resources are required. On the other hand, among currently proposed resist compositions, Although there is some degradation in quality due to the composition or slight adjustment to the composition, there is a resist composition having characteristics suitable for immersion exposure, while in immersion exposure, Even resist films that do not have sufficient pattern resolution due to alteration due to immersion exposure liquid, there are many that exhibit fine and high resolution in lithography by exposure through a normal air layer. confirmed.

  The present invention has been made in view of the problems of the prior art, and provides a technique in which a resist film obtained from a conventional resist composition established by spending many development resources can be applied to immersion exposure. More specifically, by temporarily forming a specific protective film on the surface of a conventional resist film, the resist film during the immersion exposure and the liquid used are simultaneously modified. It is an object of the present invention to prevent and remove the protective film by using a specific removal solvent and to form a high-resolution resist pattern using immersion exposure.

  According to the present invention, no matter what conventional resist composition is used, the resist pattern has a rough surface such as a T-top shape in the immersion exposure process, and the sensitivity is high. Therefore, it is possible to obtain a resist pattern with high accuracy, excellent resist pattern profile shape, good depth of focus, exposure margin, and good stability over time. Therefore, when the solvent for removing a protective film of the present invention is used, it is possible to effectively form a resist pattern using an immersion exposure process.

  In order to solve the above-mentioned problems, the resist protective film removing solvent for immersion exposure process according to the present invention includes a fluorine-based solvent.

  Further, the resist pattern forming method according to the present invention is a resist pattern forming method using an immersion exposure process, wherein a photoresist film is formed on a substrate, and the resist protection for the immersion exposure process is formed on the resist film. Using a film-forming material, a protective film is formed that is transparent to exposure light, has no substantial compatibility with liquids for immersion exposure, and does not cause mixing with the resist film. Then, the immersion exposure liquid having a predetermined thickness is disposed directly on at least the protection film of the substrate on which the resist film and the protection film are laminated, and the immersion exposure liquid and the protection film are interposed therebetween. The resist film was selectively irradiated with light, heat-treated as necessary, the protective film was removed from the resist film after the irradiation using the protective film removing solvent, and the protective film was removed. Les Developing the strike layer, characterized in that to obtain a resist pattern.

  In the above-described configuration, the immersion exposure process has a refractive index higher than that of air and lower than that of the resist film on at least the resist film in the path until the lithography exposure light reaches the resist film. A configuration in which the resolution of the resist pattern is improved by performing exposure while the liquid for immersion exposure having a predetermined thickness is interposed is preferable.

  In the present invention configured as described above, as the immersion exposure liquid, water substantially composed of pure water or deionized water, or a fluorine-based inert liquid can be preferably used. In consideration of easiness and the like, water is more preferable.

  As the resist film that can be used in the present invention, any resist film obtained using a conventionally used resist composition can be used, and there is no need to use it in a particularly limited manner.

  In addition, the protective film that can be used in the present invention is transparent to exposure light, has no substantial compatibility with the liquid for immersion exposure, and causes mixing with the resist film. As a protective film material capable of forming a protective film having such properties, a specific fluorine-based resin is used. A composition formed by dissolving in a fluorinated solvent is used.

  Examples of the fluororesin include chain perfluoroalkyl polyether, cyclic perfluoroalkyl polyether, polychlorotrifluoroethylene, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, tetrafluoroethylene- A hexafluoropropylene copolymer or the like can be used.

  Practically, among commercially available chains, demnum S-20, demnam S-65, demnam S-100, demnam S-200 (above, manufactured by Daikin Industries), which are chain perfluoroalkyl polyethers, rings Cytop series (manufactured by Asahi Glass Co., Ltd.), Teflon (R) -AF1600, Teflon (R) -AF2400 (manufactured by DuPont) and the like which are perfluoroalkyl polyethers can be used.

  Among the fluororesins, a mixed resin composed of a chain perfluoroalkyl polyether and a cyclic perfluoroalkyl polyether is preferable.

  The fluorinated solvent is not particularly limited as long as it can dissolve the fluorinated resin. For example, perfluoroalkane such as perfluorohexane and perfluoroheptane, or perfluorocycloalkane, one of these. Perfluoroalkene with a double bond remaining in the part, and further perfluorocyclic ethers such as perfluorotetrahydrofuran and perfluoro (2-butyl) tetrahydrofuran, perfluorotributylamine, perfluorotetrapentylamine, perfluorotetrahexylamine, etc. The fluorinated solvent can be used. In addition, other organic solvents having compatibility with these fluorine-based solvents, surfactants, and the like can be appropriately mixed and used.

  The fluorine-based resin concentration is not particularly limited as long as it can form a film, but it is preferably about 0.1 to 30 wt% in consideration of applicability and the like.

  As a preferable protective film material, it is preferable that a mixed resin composed of a chain perfluoroalkyl polyether and a cyclic perfluoroalkyl polyether is dissolved in perfluorotributylamine.

  Furthermore, the solvent for removing the protective film of the present invention may be a fluorine-based solvent that dissolves the fluororesin. Among such protective film removing solvents, it is preferable to use a solvent having a boiling point of about 150 ° C. or lower from the viewpoint of drying after washing. From this viewpoint, perfluoro (2-butyl) tetrahydrofuran (boiling point: 102 ° C.) is most preferable.

  As described above, as the resist film material used in the immersion exposure process of the present invention, a conventional positive resist or negative photoresist can be used. Specific examples of these are exemplified below.

  First, acrylic resins, cycloolefin resins, silsesquioxane resins, and the like are used as resin components used for positive photoresists.

  Examples of the acrylic resin include a structural unit (a1) derived from a (meth) acrylic acid ester having an acid dissociable, dissolution inhibiting group, and other (meth) acrylic other than the structural unit (a1). A resin containing 80 mol% or more, preferably 90 mol% (100 mol% is most preferable) of a structural unit derived from a (meth) acrylic acid ester including a structural unit derived from an acid ester is preferable.

  The resin component is a monomer unit having a plurality of different functions other than the unit (a1) in order to satisfy resolution, dry etching resistance, and a fine pattern shape. Consists of a combination of units.

  That is, from a structural unit derived from a (meth) acrylic acid ester having a lactone unit (hereinafter referred to as (a2) or (a2) unit), a (meth) acrylic acid ester having an alcoholic hydroxyl group-containing polycyclic group. A derived structural unit (hereinafter referred to as (a3) or (a3) unit), an acid dissociable, dissolution inhibiting group of the (a1) unit, a lactone unit of the (a2) unit, and an alcohol of the (a3) unit A structural unit (hereinafter referred to as (a4) or (a4) unit) containing a polycyclic group different from any of the functional hydroxyl group-containing polycyclic groups.

  These (a2), (a3) and / or (a4) can be appropriately combined depending on required characteristics and the like. Preferably, by containing at least one unit selected from (a1) and (a2), (a3) and (a4), the resolution and the resist pattern shape are improved. Of the units (a1) to (a4), a plurality of different units may be used in combination.

  And the structural unit derived from the methacrylic acid ester and the structural unit derived from the acrylate ester are the total number of moles of the structural unit derived from the methacrylic acid ester and the structural unit derived from the acrylate ester. On the other hand, the structural unit derived from the methacrylic acid ester is 10 to 85 mol%, preferably 20 to 80 mol%, and the structural unit derived from the acrylate ester is 15 to 90 mol%, preferably 20 to 80 mol%. % Is preferably used.

  Next, the units (a1) to (a4) will be described in detail. The unit (a1) is a structural unit derived from a (meth) acrylic acid ester having an acid dissociable, dissolution inhibiting group. The acid dissociable, dissolution inhibiting group in (a1) has an alkali dissolution inhibiting property that renders the entire resin component insoluble in alkali before exposure, and is dissociated by the action of the generated acid after exposure. It can be used without particular limitation as long as it is changed to be soluble. In general, a group that forms a cyclic or chain tertiary alkyl ester, a tertiary alkoxycarbonyl group, or a chain alkoxyalkyl group is widely known with a carboxyl group of (meth) acrylic acid. .

  As the acid dissociable, dissolution inhibiting group in (a1), for example, an acid dissociable, dissolution inhibiting group containing an aliphatic polycyclic group can be suitably used. As the polycyclic group, one hydrogen element is removed from bicycloalkane, tricycloalkane, teracycloalkane, etc., which may or may not be substituted with a fluorine atom or a fluorinated alkyl group. Examples include groups. Specific examples include groups in which one hydrogen atom has been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. Such a polycyclic group can be appropriately selected and used from among many proposed ArF resists. Of these, an adamantyl group, a norbornyl group, and a tetracyclododecanyl group are industrially preferable.

Monomer units suitable as the (a1) are shown in the following general formulas (1) to (7). In these general formulas (1) to (7), R is a hydrogen atom or a methyl group, R ₁ is a lower alkyl group, R ₂ and R ₃ are each independently a lower alkyl group, and R ₄ is a tertiary alkyl group. Group, R ₅ is a methyl group, R ₆ is a lower alkyl group, and R ₇ is a lower alkyl group. Each of R _{1 to} R ₃ and R _{6 to} R ₇ is preferably a lower linear or branched alkyl group having 1 to 5 carbon atoms, and includes a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, Examples include isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like. Industrially, a methyl group or an ethyl group is preferable. R ₄ is a tertiary alkyl group such as a tert-butyl group or a tert-amyl group, and the case where it is a tert-butyl group is industrially preferable.

  Among the units listed above as the (a1) unit, in particular, the structural units represented by the general formulas (1), (2), and (3) have high transparency, high resolution, and excellent dry etching resistance. Since a pattern can be formed, it is more preferable.

  Since the unit (a2) has a lactone unit, it is effective for enhancing hydrophilicity with the developer. Such a unit (a2) has only to have a lactone unit and can be copolymerized with other structural units of the resin component. For example, examples of the monocyclic lactone unit include a group in which one hydrogen atom has been removed from γ-butyrolactone. Examples of the polycyclic lactone unit include a group obtained by removing one hydrogen atom from a lactone-containing polycycloalkane.

  Monomer units suitable as the above (a2) are shown in the following general formulas (10) to (12). In these general formulas, R is a hydrogen atom or a methyl group.

  The γ-butyrolactone ester of (meth) acrylic acid having an ester bond at the α carbon as shown in the general formula (12) and the norbornane lactone ester as shown in the general formulas (10) and (11) are particularly industrial. It is easy to obtain and preferable.

  The unit (a3) is a structural unit derived from a (meth) acrylic acid ester having an alcoholic hydroxyl group-containing polycyclic group. Since the hydroxyl group in the alcoholic hydroxyl group-containing polycyclic group is a polar group, the use of this increases the hydrophilicity of the entire resin component with the developer and improves the alkali solubility in the exposed area. Therefore, it is preferable that the resin component has (a3) because the resolution is improved. And as a polycyclic group in (a3), it can select from the aliphatic polycyclic group similar to what was illustrated in description of the said (a1) suitably, and can be used.

  The alcoholic hydroxyl group-containing polycyclic group in (a3) is not particularly limited, and for example, a hydroxyl group-containing adamantyl group is preferably used. Furthermore, it is preferable that this hydroxyl group-containing adamantyl group is represented by the following general formula (13) because it has the effect of increasing dry etching resistance and increasing the perpendicularity of the pattern cross-sectional shape. In the general formula, l is an integer of 1 to 3.

  The unit (a3) may be any unit as long as it has an alcoholic hydroxyl group-containing polycyclic group as described above and can be copolymerized with other structural units of the resin component. Specifically, a structural unit represented by the following general formula (14) is preferable. In general formula (14), R represents a hydrogen atom or a methyl group.

  In the unit (a4), the polycyclic group “different from any of the acid dissociable, dissolution inhibiting group, the lactone unit, and the alcoholic hydroxyl group-containing polycyclic group” means that in the resin component, the unit (a4) A polycyclic group in which the (a1) unit acid dissociable, dissolution inhibiting group, the (a2) unit lactone unit, and the (a3) unit alcoholic hydroxyl group-containing polycyclic group do not overlap with each other. (A4) is an acid dissociable, dissolution inhibiting group of unit (a1), a lactone unit of unit (a2), and an alcoholic hydroxyl group-containing polycycle of unit (a3) constituting the resin component This means that none of the formula groups are retained.

  The polycyclic group in the unit (a4) is not particularly limited as long as it is selected so as not to overlap with the structural units used as the units (a1) to (a3) in one resin component. is not. For example, as the polycyclic group in the (a4) unit, the same aliphatic polycyclic groups as those exemplified as the (a1) unit can be used, and a number of hitherto known ArF positive resist materials are available. Things can be used. In particular, at least one selected from a tricyclodecanyl group, an adamantyl group, and a tetracyclododecanyl group is preferable in terms of industrial availability. As the unit (a4), any unit may be used as long as it has a polycyclic group as described above and can be copolymerized with other structural units of the resin component.

  Preferred examples of the above (a4) are shown in the following general formulas (15) to (17). In these general formulas, R is a hydrogen atom or a methyl group.

  The composition of the acrylic resin component is excellent in resolution when the (a1) unit is 20 to 60 mol%, preferably 30 to 50 mol%, with respect to the total of structural units constituting the resin component. ,preferable. Moreover, it is excellent in the resolution and it is preferable that (a2) unit is 20-60 mol% with respect to the sum total of the structural unit which comprises a resin component, Preferably it is 30-50 mol%. Further, when the unit (a3) is used, the resist pattern shape is excellent and preferably 5 to 50 mol%, preferably 10 to 40 mol%, based on the total of the constituent units constituting the resin component. When the unit (a4) is used, the resolution from the isolated pattern to the semi-dense pattern is excellent when it is 1 to 30 mol%, preferably 5 to 20 mol%, based on the total of the structural units constituting the resin component. preferable.

  The unit (a1) and at least one unit selected from the units (a2), (a3) and (a4) can be appropriately combined depending on the purpose, but the units (a1) and (a2) and (a3) A ternary polymer is preferable because it is excellent in resist pattern shape, exposure margin, heat resistance, and resolution. The contents of the structural units (a1) to (a3) at that time are as follows: (a1) is 20 to 60 mol%, (a2) is 20 to 60 mol%, and (a3) is 5 to 50 mol% % Is preferred.

  Moreover, the mass average molecular weight (in terms of polystyrene, hereinafter the same) of the resin component resin in the present invention is not particularly limited, but is 5000 to 30000, more preferably 8000 to 20000. If it is larger than this range, the solubility in a resist solvent is deteriorated, and if it is smaller, the dry etching resistance and the resist pattern cross-sectional shape may be deteriorated.

  Moreover, as said cycloolefin type resin, resin which copolymerized the structural unit (a5) shown to following General formula (18), and the structural unit obtained from said (a1) as needed is preferable.

（式中、Ｒ_８は前記（ａ１）単位において酸解離性溶解抑制基として例示した置換基であり、ｍは０〜３の整数である）なお、前記（ａ５）単位においてｍが０の場合は、（ａ１）単位を有する共重合体として用いることが好ましい。

(In the formula, R ₈ is a substituent exemplified as an acid dissociable, dissolution inhibiting group in the unit (a1), and m is an integer of 0 to 3). When m is 0 in the unit (a5) Is preferably used as a copolymer having (a1) units.

  Further, examples of the silsesquioxane-based resin include those having a structural unit (a6) represented by the following general formula (19) and a structural unit (a7) represented by the following general formula (20). .

（式中、Ｒ_９は脂肪族の単環または多環式基を含有する炭化水素基からなる酸解離性溶解抑制基であり、Ｒ_１０は直鎖状、分岐状または環状の飽和脂肪族炭化水素基であり、Ｘは少なくとも１つの水素原子がフッ素原子で置換された炭素原子数１〜８のアルキル基であり、ｍは１〜３の整数である）

(In the formula, R ₉ is an acid dissociable, dissolution inhibiting group composed of a hydrocarbon group containing an aliphatic monocyclic or polycyclic group, and R ₁₀ is a linear, branched or cyclic saturated aliphatic carbonization. A hydrogen group, X is an alkyl group having 1 to 8 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, and m is an integer of 1 to 3)

（式中、Ｒ_１１は水素原子もしくは直鎖状、分岐状または環状のアルキル基であり、Ｒ_１２は直鎖状、分岐状または環状の飽和脂肪族炭化水素基であり、Ｘは少なくとも１つの水素原子がフッ素原子で置換された炭素原子数１〜８のアルキル基である）

Wherein R ₁₁ is a hydrogen atom or a linear, branched or cyclic alkyl group, R ₁₂ is a linear, branched or cyclic saturated aliphatic hydrocarbon group, and X is at least one A hydrogen atom is an alkyl group having 1 to 8 carbon atoms substituted with a fluorine atom)

In the above (a6) and (a7), the acid dissociable, dissolution inhibiting group of R ₉ has an alkali dissolution inhibiting property that renders the entire silsesquioxane resin unexposed to alkali insoluble, and at the same time from an acid generator after exposure. It is a group that dissociates by the action of the generated acid and changes the entire silsesquioxane resin to alkali-soluble. As such, for example, acid dissociable, dissolution inhibiting groups composed of a hydrocarbon group containing a bulky aliphatic monocyclic or polycyclic group, such as the following general formulas (21) to (25): Can be mentioned. By using such an acid dissociable, dissolution inhibiting group, the dissolution inhibiting group after dissociation is hardly gasified, and the degassing phenomenon is prevented.

The carbon number of R ₉ is preferably 7 to 15 and more preferably 9 to 13 because it is difficult to gasify when dissociated, and at the same time, is soluble in an appropriate resist solvent and soluble in a developer.

  As the acid dissociable, dissolution inhibiting group, as long as it is an acid dissociable, dissolution inhibiting group composed of a hydrocarbon group containing an aliphatic monocyclic or polycyclic group, depending on the light source used, for example, ArF excimer laser In the resin for resist compositions, it can be used by appropriately selecting from many proposed ones. In general, those forming a cyclic tertiary alkyl ester with a carboxyl group of (meth) acrylic acid are widely known.

  In particular, an acid dissociable, dissolution inhibiting group containing an aliphatic polycyclic group is preferable. As the aliphatic polycyclic group, an ArF resist can be appropriately selected from those proposed in the ArF resist. For example, examples of the aliphatic polycyclic group include groups in which one hydrogen atom has been removed from a bicycloalkane, tricycloalkane, teracycloalkane, etc., and more specifically, adamantane, norbornane, isobornane, And a group obtained by removing one hydrogen atom from a polycycloalkane such as tricyclodecane or tetracyclododecane.

  Among the above general formulas, a silsesquioxane resin having a 2-methyl-2-adamantyl group represented by the general formula (23) and / or a 2-ethyl-2-adamantyl group represented by the general formula (24) Is preferable because it is less likely to degas and is excellent in resist characteristics such as resolution and heat resistance.

The carbon number in R ₁₀ and R ₁₁ is preferably 1-20, more preferably 5-12, from the viewpoints of solubility in a resist solvent and control of the molecular size. In particular, the cyclic saturated aliphatic hydrocarbon group has high transparency to the high-energy light of the resulting silsesquioxane resin, increases the glass transition point (Tg), and generates acid during PEB (post-exposure heating). It is preferable because it has advantages such as easy control of acid generation from the agent.

  The cyclic saturated aliphatic hydrocarbon group may be a monocyclic group or a polycyclic group. Examples of the polycyclic group include groups in which two hydrogen atoms are removed from bicycloalkane, tricycloalkane, tetracycloalkane and the like, and more specifically, adamantane, norbornane, isobornane, tricyclodecane, And a group obtained by removing two hydrogen atoms from a polycycloalkane such as tetracyclododecane.

More specifically, examples of R ₁₀ and R ₁₂ include groups in which two hydrogen atoms have been removed from the alicyclic compounds represented by the following general formulas (26) to (31) or derivatives thereof. .

  The derivative means that in the alicyclic compounds represented by the chemical formulas (26) to (31), at least one hydrogen atom is a lower alkyl group such as a methyl group or an ethyl group, an oxygen atom, a halogen such as fluorine, chlorine or bromine. It means one substituted with a group such as an atom. Among them, a group obtained by removing two hydrogen atoms from an alicyclic compound selected from the group consisting of chemical formulas (26) to (31) is preferable because of high transparency and industrial availability.

Furthermore, R ₁₁ is preferably a lower alkyl group of 1 to 10, more preferably 1 to 4, in view of solubility in a resist solvent. More specifically, as this alkyl group, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, cyclopentyl group, cyclohexyl group, 2-ethylhexyl group, An n-octyl group etc. can be illustrated.

R ₁₁ is appropriately selected from the candidates according to the desired alkali solubility of the silsesquioxane resin. Alkali solubility is highest when R ₁₁ is a hydrogen atom. When the alkali solubility is increased, there is an advantage that the sensitivity can be increased.

  On the other hand, the larger the number of carbon atoms in the alkyl group and the higher the bulk, the lower the alkali solubility of the silsesquioxane resin. When the alkali solubility is lowered, resistance to an alkali developer is improved, so that an exposure margin when a resist pattern is formed using the silsesquioxane resin is improved, and a dimensional variation accompanying exposure is reduced. Further, since uneven development is eliminated, the roughness of the edge portion of the formed resist pattern is also improved.

  As for X in the general formulas (8) and (9), a linear alkyl group is particularly preferable. The carbon number of the alkyl group is a lower alkyl group of 1 to 8, preferably 1 to 4, from the glass transition (Tg) point of the silsesquioxane resin and the solubility in a resist solvent. Further, the greater the number of hydrogen atoms substituted with fluorine atoms, the better the transparency to high energy light of 200 nm or less and the electron beam, and most preferably, all the hydrogen atoms are substituted with fluorine atoms. Perfluoroalkyl group. Each X may be the same or different. In addition, m in General formula (8) is an integer of 1-3, Preferably it is 1 because it makes it easy to dissociate an acid dissociable dissolution inhibiting group.

  More specifically, examples of the silsesquioxane resin include those represented by the following general formulas (32) and (33).

（式中、Ｒ_５，Ｒ_１０，Ｒ_１２，およびｎは前出と同様である）

(Wherein R ₅ , R ₁₀ , R ₁₂ and n are the same as above)

  In all the structural units constituting the silsesquioxane resin of the present invention, the proportion of the structural units represented by (a6) and (a7) is 30 to 100 mol%, preferably 70 to 100%, more preferably 100. Mol%.

  The ratio of the structural unit represented by (a6) to the total of the structural units represented by (a6) and (a7) is preferably 5 to 70 mol%, more preferably 10 to 40 mol%. is there. The proportion of the structural unit represented by (a7) is preferably 30 to 95 mol%, more preferably 60 to 90 mol%.

  By setting the proportion of the structural unit represented by (a6) within the above range, the proportion of the acid dissociable, dissolution inhibiting group is naturally determined, and the change in alkali solubility before and after the exposure of the silsesquioxane resin is positive. This is suitable as a base resin for the resist composition.

  The silsesquioxane resin may have structural units other than the structural units represented by (a6) and (a7) as long as the effects of the present invention are not impaired. For example, those used in silsesquioxane resins for ArF excimer laser resist compositions, for example, alkyl groups such as methyl, ethyl, propyl, and butyl groups represented by the following general formula (34) Examples thereof include alkylsilsesquioxane units having (R ′).

  The mass average molecular weight (Mw) of the silsesquioxane resin (polystyrene conversion by gel permeation chromatography) is not particularly limited, but is preferably 2000 to 15000, and more preferably 3000 to 8000. If it is larger than this range, the solubility in the resist solvent is deteriorated, and if it is smaller, the resist pattern cross-sectional shape may be deteriorated.

  The mass average molecular weight (Mw) / number average molecular weight (Mn), that is, the degree of polymer dispersion is not particularly limited, but is preferably 1.0 to 6.0, more preferably 1.5 to 2.5. It is. If it is larger than this range, the resolution and pattern shape may deteriorate.

  Moreover, since the silsesquioxane resin of the present invention is a polymer having a silsesquioxane having a basic skeleton constituted by the structural units represented by (a6) and (a7), high-energy light of 200 nm or less And high transparency to electron beams. Therefore, the positive resist composition containing the silsesquioxane resin of the present invention is useful, for example, in lithography using a light source having a wavelength shorter than that of an ArF excimer laser. Furthermore, a fine resist pattern of 120 nm or less can be formed. Moreover, it is useful also for the process of forming a fine resist pattern of 120 nm or less, further 100 nm or less by using with the upper layer of a two-layer resist laminated body.

  Furthermore, the resin component used in the negative resist composition is not limited as long as it is commonly used, but specifically, the following are preferable.

  Such a resin component is a resin component that becomes alkali-insoluble with an acid, and has two functional groups in the molecule that can react with each other to form an ester, which is added simultaneously to the resist material. A resin (a8) that becomes alkali-insoluble by dehydration to form an ester by the action of an acid generated from the acid generator is preferably used. The two kinds of functional groups capable of reacting with each other to form an ester here mean, for example, a hydroxyl group and a carboxyl group or a carboxylate ester for forming a carboxylate ester. In other words, two functional groups for forming an ester. As such a resin, for example, a resin having a hydroxyalkyl group and at least one of a carboxyl group and a carboxylate group in the side chain of the resin main skeleton is preferable. Furthermore, as the resin component, a resin component (a9) composed of a polymer having a dicarboxylic acid monoester unit is also preferable.

（式中、Ｒ_１３は水素原子、Ｃ１〜Ｃ６のアルキル基、もしくはボルニル基、アダマンチル基、テトラシクロドデシル基、トリシクロデシル基等の多環式環骨格を有するアルキル基である。） In other words, the (a8) is a resin component having at least a structural unit represented by the following general formula (35).

(Wherein R ₁₃ is a hydrogen atom, a C1-C6 alkyl group, or an alkyl group having a polycyclic ring skeleton such as a bornyl group, an adamantyl group, a tetracyclododecyl group, or a tricyclodecyl group.)

  Examples of such resins include polymers (homopolymers or copolymers) of at least one monomer selected from α- (hydroxyalkyl) acrylic acid and α- (hydroxyalkyl) acrylic acid alkyl ester. (A8-1), and at least one monomer selected from α- (hydroxyalkyl) acrylic acid and α- (hydroxyalkyl) acrylic acid alkyl ester, other ethylenically unsaturated carboxylic acid and ethylenically unsaturated monomer Preferred examples include a copolymer (a8-2) with at least one monomer selected from saturated carboxylic acid esters.

  As the polymer (a8-1), a copolymer of α- (hydroxyalkyl) acrylic acid and α- (hydroxyalkyl) acrylic acid alkyl ester is preferable, and as the copolymer (a8-2), As the other ethylenically unsaturated carboxylic acid and ethylenically unsaturated carboxylic acid ester, those using at least one selected from acrylic acid, methacrylic acid, acrylic acid alkyl ester and methacrylic acid alkyl ester are preferable.

  Examples of the hydroxyalkyl group in the α- (hydroxyalkyl) acrylic acid and α- (hydroxyalkyl) acrylic acid alkyl ester include lower hydroxyalkyl groups such as hydroxymethyl group, hydroxyethyl group, hydroxypropyl group, hydroxybutyl group, etc. Is mentioned. Among these, a hydroxyethyl group or a hydroxymethyl group is preferable because of the ease of forming an ester.

Examples of the alkyl group in the alkyl ester portion of the α- (hydroxyalkyl) acrylic acid alkyl ester include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group. Lower alkyl group such as amyl group, bicyclo [2.2.1] heptyl group, bornyl group, adamantyl group, tetracyclo [4.4.0.1 ^2.5 . And a bridged polycyclic cyclic hydrocarbon group such as 1 ^7.10 ] dodecyl group and tricyclo [5.2.1.0 ^2.6 ] decyl group. Those in which the alkyl group of the ester moiety is a polycyclic hydrocarbon group is effective for improving the dry etching resistance. Among these alkyl groups, lower alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group are preferred because alcohol components that form esters can be easily obtained at low cost.

  In the case of a lower alkyl ester, esterification with a hydroxyalkyl group occurs like a carboxyl group, but in the case of an ester with a bridged polycyclic hydrocarbon, such esterification hardly occurs. Therefore, when an ester with a bridged polycyclic hydrocarbon is introduced into the resin, it is preferable that a carboxyl group is present in the resin side chain.

On the other hand, examples of other ethylenically unsaturated carboxylic acid and ethylenically unsaturated carboxylic acid ester in (a8-2) include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and the like. Examples thereof include alkyl esters such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, n-hexyl and octyl esters of unsaturated carboxylic acids. Moreover, as an alkyl group of an ester part, bicyclo [2.2.1] heptyl group, bornyl group, adamantyl group, tetracyclo [4.4.0.1 ^2.5 . An ester of acrylic acid or methacrylic acid having a bridged polycyclic hydrocarbon group such as 1 ^7.10 ] dodecyl group or tricyclo [5.2.1.0 ^2.6 ] decyl group can also be used. Among these, acrylic acid and methacrylic acid, or lower alkyl esters such as methyl, ethyl, propyl, and n-butyl esters are preferable because they are inexpensive and easily available.

  In the resin of the resin component (a8-2), at least one monomer unit selected from α- (hydroxyalkyl) acrylic acid and α- (hydroxyalkyl) acrylic acid alkyl ester and other ethylenic unsaturation The ratio of the carboxylic acid and the at least one monomer unit selected from the ethylenically unsaturated carboxylic acid ester is in the range of 20:80 to 95: 5, particularly in the range of 50:50 to 90:10. preferable. If the ratio of both units is in the above range, an ester can be easily formed within a molecule or between molecules, and a good resist pattern can be obtained.

（式中、Ｒ_１４およびＲ_１５は炭素数０〜８のアルキル鎖を表し、Ｒ_１６は少なくとも２以上の脂環式構造を有する置換基を表し、Ｒ_１７およびＲ_１８は水素原子、または炭素数１〜８のアルキル基を表す） The resin component (a9) is a resin component having at least a structural unit represented by the following general formula (36) or (37).

(Wherein R ₁₄ and R ₁₅ represent an alkyl chain having 0 to 8 carbon atoms, R ₁₆ represents a substituent having at least two alicyclic structures, and R ₁₇ and R ₁₈ represent a hydrogen atom or carbon. (Represents an alkyl group of 1 to 8)

  A negative resist composition using such a resin component having a dicarboxylic acid monoester monomer unit is preferable in that the resolution is high and the line edge roughness is reduced. Further, the swelling resistance is high, which is more preferable in the immersion exposure process. Examples of such dicarboxylic acid monoester compounds include fumaric acid, itaconic acid, mesaconic acid, glutaconic acid, and traumatic acid.

  Further, the resin having the dicarboxylic acid monoester unit includes a polymer or copolymer (a9-1) of a dicarboxylic acid monoester monomer, a dicarboxylic acid monoester monomer, and the α- (hydroxyalkyl) acrylic acid described above. , Copolymers (a9-2) with at least one monomer selected from α- (hydroxyalkyl) acrylic acid alkyl esters, other ethylenically unsaturated carboxylic acids and ethylenically unsaturated carboxylic acid esters, and the like Preferably mentioned. The resin component used for the said negative resist may be used independently, and may be used in combination of 2 or more type. The weight average molecular weight of the resin component is 1000 to 50000, preferably 2000 to 30000.

  Among the resins described above, positive resists using acrylic resins ((a1) to (a4)) are positive resists containing resins that are relatively resistant to water immersion, but are limited in immersion exposure. The closer to the resolution dimension, the more easily the resolution of the pattern deteriorates. There is no single factor that promotes the degradation of resolution, and in order to remove such a factor, it is extremely effective to form the protective film of the present invention and completely separate the immersion liquid and the resist film.

  For the positive resist using the silsesquioxane resin ((a6) and (a7)) or the negative resist using the specific resin (a8) and / or (a9), the acrylic resin is used. It is considered that the immersion resistance is lower than that of a positive type resist using, and the suitability for immersion exposure can be improved by using the protective film of the present invention.

  Furthermore, when a cycloolefin resin is used, it is known that the immersion exposure resistance is very low as in the comparative example of the present application, and pattern formation itself is impossible. Even when a positive resist containing such a resin is used, it can be applied to immersion exposure by using the protective film of the present invention.

  Further, as the acid generator used in combination with the resin component for the positive or negative resist, any one of known acid generators in conventional chemically amplified resists can be appropriately selected and used. .

  Specific examples of the acid generator include diphenyliodonium trifluoromethanesulfonate, (4-methoxyphenyl) phenyliodonium trifluoromethanesulfonate, bis (p-tert-butylphenyl) iodonium trifluoromethanesulfonate, triphenylsulfonium trifluoromethanesulfonate, ( 4-methoxyphenyl) diphenylsulfonium trifluoromethanesulfonate, (4-methylphenyl) diphenylsulfonium trifluoromethanesulfonate, (4-methylphenyl) diphenylsulfonium nonafluorobutanesulfonate, (p-tert-butylphenyl) diphenylsulfonium trifluoromethanesulfonate, Diphenyliodonium nonafluorobutanesulfonate, (P-tert-butylphenyl) iodonium nonafluorobutanesulfonate, triphenylsulfonium nonafluorobutanesulfonate, (4-trifluoromethylphenyl) diphenylsulfonium trifluoromethanesulfonate, (4-trifluoromethylphenyl) diphenylsulfonium nonafluorobutane Examples thereof include sulfonates and onium salts such as tri (p-tert-butylphenyl) sulfonium trifluoromethanesulfonate.

  Among onium salts, triphenylsulfonium salt is preferably used because it is difficult to decompose and hardly generates organic gas. The blending amount of the triphenylsulfonium salt is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, and most preferably 100 mol%, based on the total amount of the acid generator.

（式中、Ｒ_１９、Ｒ_２０、Ｒ_２１は、それぞれ独立に、水素原子、炭素数１〜８、好ましくは１〜４の低級アルキル基、または塩素、フッ素、臭素等のハロゲン原子であり；ｐは１〜１２、好ましくは１〜８、より好ましくは１〜４の整数である。） Of the triphenylsulfonium salts, a triphenylsulfonium salt represented by the following general formula (38) having a perfluoroalkylsulfonic acid ion as an anion can be preferably used because it can increase the sensitivity.

Wherein R ₁₉ , R ₂₀ and R ₂₁ are each independently a hydrogen atom, a lower alkyl group having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, or a halogen atom such as chlorine, fluorine or bromine; p is an integer of 1 to 12, preferably 1 to 8, more preferably 1 to 4.)

The above acid generators may be used alone or in combination of two or more.
The compounding quantity is 0.5 mass part with respect to 100 mass parts of above-mentioned resin components, Preferably it is 1-10 mass parts. If the amount is less than 0.5 parts by mass, pattern formation is not sufficiently performed. If the amount exceeds 30 parts by mass, a uniform solution is difficult to obtain, which may cause a decrease in storage stability.

  The positive or negative resist composition of the present invention is produced by dissolving the resin component, the acid generator, and any components described later, preferably in an organic solvent.

  Any organic solvent may be used as long as it can dissolve the resin component and the acid generator to form a uniform solution, and any one of known solvents for conventional chemically amplified resists may be used. Two or more types can be appropriately selected and used.

  For example, ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate, dipropylene glycol, or dipropylene Polyols and their derivatives such as monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether of glycol monoacetate, cyclic ethers such as dioxane, methyl lactate, ethyl lactate, methyl acetate , Ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, ethoxy Esters such as propionic acid ethyl and the like. These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.

  Further, in such a positive type or negative type resist, in order to improve the resist pattern shape, stability with time, etc., a known amine is preferably used as a quencher, preferably a secondary lower aliphatic amine or a third type. An organic acid such as a class lower aliphatic amine, an organic carboxylic acid or a phosphorus oxo acid can be contained.

  The lower aliphatic amine refers to an alkyl or alkyl alcohol amine having 5 or less carbon atoms. Examples of the secondary and tertiary amines include trimethylamine, diethylamine, triethylamine, di-n-propylamine, triamine. Examples include -n-propylamine, triventylamine, diethanolamine, triethanolamine and the like, and alkanolamines such as triethanolamine are particularly preferable. These may be used alone or in combination of two or more. These amines are usually used in the range of 0.01 to 2.0% by mass with respect to the resin component.

  Suitable examples of the organic carboxylic acid include malonic acid, citric acid, malic acid, succinic acid, benzoic acid, and salicylic acid.

  Examples of phosphorous oxo acids or derivatives thereof include phosphoric acid, phosphoric acid di-n-butyl ester, phosphoric acid diphenyl ester, and other phosphoric acid or derivatives thereof such as phosphonic acid, phosphonic acid dimethyl ester, and phosphonic acid. Of phosphonic acids such as di-n-butyl ester, phenylphosphonic acid, phosphonic acid diphenyl ester, phosphonic acid dibenzyl ester and their esters, phosphinic acids such as phosphinic acid, phenylphosphinic acid and their esters Among these, phosphonic acid is particularly preferable.

  The organic acid is used in a proportion of 0.01 to 5.0 parts by mass per 100 parts by mass of the resin component. These may be used alone or in combination of two or more. These organic acids are preferably used in an equimolar range or less with the amine.

  The positive resist composition of the present invention further contains miscible additives as desired, for example, additional resins for improving the performance of the resist film, surfactants for improving coating properties, dissolution inhibitors, Plasticizers, stabilizers, colorants, antihalation agents and the like can be added and contained.

  Furthermore, in the negative resist composition of the present invention, a crosslinking agent may be blended as necessary for the purpose of further improving the crosslinking density and improving the resist pattern shape, resolution and dry etching resistance. good.

  The crosslinking agent is not particularly limited, and any known crosslinking agent conventionally used in chemically amplified negative resists can be appropriately selected and used. Examples of this cross-linking agent include 2,3-dihydroxy-5-hydroxymethylnorbornane, 2-hydroxy-5,6-bis (hydroxymethyl) norbornane, cyclohexanedimethanol, 3,4,8 (or 9) -trimethyl. Aliphatic having hydroxyl group or hydroxyalkyl group or both such as hydroxytricyclodecane, 2-methyl-2-adamantanol, 1,4-dioxane-2,3-diol, 1,3,5-trihydroxycyclohexane A cyclic hydrocarbon or its oxygen-containing derivative and an amino group-containing compound such as melamine, acetoguanamine, benzoguanamine, urea, ethylene urea, glycoluril, etc. are reacted with formaldehyde or formaldehyde and a lower alcohol, and the hydrogen atom of the amino group is converted to hydroxymethyl. Or a compound substituted with a lower alkoxymethyl group, specifically, hexamethoxymethylmelamine, bismethoxymethylurea, bismethoxymethylbismethoxyethyleneurea, tetramethoxymethylglycoluril, tetrabutoxymethylglycoluril and the like. Particularly preferred is tetrabutoxymethylglycoluril. These crosslinking agents may be used alone or in combination of two or more.

  Next, a resist pattern forming method by an immersion exposure method using the protective film of the present invention will be described. First, a conventional resist composition is applied onto a substrate such as a silicon wafer with a spinner or the like, and then pre-baked (PAB treatment). Note that a two-layer laminate in which an organic or inorganic antireflection film is provided between the substrate and the coating layer of the resist composition may be used.

  The steps so far can be performed using a known method. The operating conditions and the like are preferably set as appropriate according to the composition and characteristics of the resist composition to be used.

  Next, on the surface of the resist film (single layer, multiple layers) cured as described above, for example, “a mixed resin composed of a chain perfluoroalkyl polyether and a cyclic perfluoroalkyl polyether is added. A protective film-forming material composition such as “a composition dissolved in butylamine” is uniformly applied and then cured to form a resist protective film.

  Thus, the board | substrate with which the resist film covered with the protective film was formed is immersed in the liquid for immersion exposure.

  The resist film on the immersed substrate is selectively exposed through a desired mask pattern. Accordingly, at this time, the exposure light passes through the immersion exposure liquid and the protective film and reaches the resist film.

  At this time, the resist film is completely shielded from the liquid for immersion exposure by the protective film, and may be affected by the invasion of the liquid for immersion exposure, such as swelling. Thus, the components are not eluted to alter the optical characteristics such as the refractive index of the immersion exposure liquid.

The wavelength used for exposure in this case is not particularly limited, and ArF excimer laser, KrF excimer laser, F ₂ excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), electron beam, X-ray, soft X-ray, etc. Can be done using radiation. This is mainly determined by the characteristics of the resist film.

As described above, in the resist pattern forming method of the present invention, at the time of exposure, the resist film has a refractive index that is larger than the refractive index of air and smaller than the refractive index of the resist film to be used. Intervene liquid. Examples of such immersion exposure liquid include water or a fluorine-based inert liquid. Specific examples of the fluorine-based inert liquid include fluorine-based compounds such as C ₃ HCl ₂ F ₅ , C ₄ F ₉ OCH ₃ , C ₄ F ₉ OC ₂ H ₅ , and C ₅ H ₃ F ₇ as a main component. Liquid to be used. Among these, it is preferable to use water from the viewpoints of cost, safety, environmental problems, and versatility.

  Further, the refractive index of the immersion exposure liquid to be used is not particularly limited as long as it is within the range of “greater than the refractive index of air and smaller than the refractive index of the resist composition to be used”.

  When the exposure process in the immersion state is completed, the substrate is taken out from the immersion exposure liquid, the liquid is removed from the substrate, and then the protective film is peeled off. The protective film removing solvent of the present invention can be used for peeling off the protective film, and a fluorine-based solvent that dissolves the fluororesin can be used as it is. However, from the viewpoint of drying properties after washing, it is preferable to use a solvent having a boiling point of about 150 ° C. or less, and perfluoro (2-butyl) tetrahydrofuran (boiling point: 102 ° C.) is preferable from this viewpoint.

  Next, PEB (post-exposure heating) is performed on the exposed resist film, followed by development using an alkaline developer composed of an alkaline aqueous solution. However, PEB here may be performed before the protective film peeling step. Further, post-baking may be performed following the development processing. And it rinses preferably using a pure water. In this water rinsing, for example, water is dropped or sprayed on the surface of the substrate while rotating the substrate to wash away the developer on the substrate and the resist composition dissolved by the developer. And by drying, the resist pattern by which the resist film was patterned in the shape according to the mask pattern is obtained.

  By forming a resist pattern in this manner, a resist pattern with a fine line width, particularly a line and space pattern with a small pitch can be manufactured with good resolution. Here, the pitch in the line and space pattern refers to the total distance of the resist pattern width and the space width in the line width direction of the pattern.

  Examples of the present invention will be described below. However, these examples are merely examples for explaining the present invention, and do not limit the present invention. In the following description, comparative examples are also described together with examples.

Example 1
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare a positive resist composition 1. As the resin component, 100 parts by mass of a methacrylic acid ester / acrylic acid ester copolymer composed of three kinds of structural units represented by the following chemical formulas (39a), (39b) and (39c) was used. The ratio of each structural unit p, q, r used for the preparation of the resin component was p = 50 mol%, q = 30 mol%, and r = 20 mol%. The prepared resin component had a mass average molecular weight of 10,000.

  As the acid generator, 3.5 parts by mass of triphenylsulfonium nonafluorobutanesulfonate and 1.0 part by mass of (4-methylphenyl) diphenylsulfonium trifluoromethanesulfonate were used. As the organic solvent, a mixed solvent (mass ratio 6: 4) of 1900 parts by mass of a mixed solvent of propylene glycol monomethyl ether acetate and ethyl lactate was used. Further, 0.3 parts by mass of triethanolamine was used as the nitrogen-containing organic compound.

  A resist pattern was formed using the positive resist composition 1 produced as described above. First, an organic antireflection film composition “AR-19” (trade name, manufactured by Shipley) was applied onto a silicon wafer using a spinner, and baked and dried on a hot plate at 215 ° C. for 60 seconds. An organic antireflection film having a thickness of 82 nm was formed. Then, the positive resist composition 1 is applied onto the antireflection film using a spinner, prebaked on a hot plate at 115 ° C. for 90 seconds, and dried to have a film thickness of 150 nm on the antireflection film. The resist film was formed.

  On the resist film, a fluororesin mainly composed of a cyclic perfluoroalkyl polyether {DEMNUM S-20 (manufactured by Daikin Industries) and Cytop (cyclic perfluoroalkyl polyether manufactured by Asahi Glass Co., Ltd.) (mixed weight) Ratio = 1: 5) is dissolved in perfluorotributylamine, and a protective film material having a resin concentration of 2.5 mass% is spin-coated, heated at 90 ° C. for 60 seconds, and a film thickness of 37 nm. A protective film was formed.

  Next, using an ArF excimer laser (wavelength: 193 nm) with an exposure apparatus NSR-S302B (manufactured by Nikon Corporation, NA (numerical aperture) = 0.60, σ = 0.75) through the mask pattern, Was irradiated (exposure). Then, as an immersion exposure process, pure water was continuously dropped on the resist film at 23 ° C. for 5 minutes while rotating the silicon wafer provided with the resist film after the exposure. The process of this part is a process of exposing in a completely immersed state in an actual manufacturing process, but it is theoretically that the exposure itself in the optical system is completely performed based on the analysis with respect to the previous immersion exposure method. Since the resist film is exposed first, the resist film is loaded with pure water, which is a liquid for immersion exposure, after exposure so that only the influence of the immersion liquid on the resist film can be evaluated. This is a simple configuration.

  After the dropping step of pure water, PEB treatment was performed at 115 ° C. for 90 seconds, and then the protective film was removed using perfluoro (2-butyl) tetrahydrofuran. Thereafter, development was further performed at 23 ° C. with an alkali developer for 60 seconds. As the alkaline developer, an aqueous 2.38 mass% tetramethylammonium hydroxide solution was used.

  When the thus obtained resist pattern with a 130 nm line and space of 1: 1 was observed with a scanning electron microscope (SEM), this pattern profile was good and no fluctuations were observed. .

(Example 2)
In the same procedure as in Example 1, an antireflection film, an ArF positive resist, and a protective film were formed on the substrate. The substrate on which the protective film was formed was subjected to immersion exposure using an experimental apparatus manufactured by Nikon Corporation using a prism, a liquid, and a two-beam interference exposure with a wavelength of 193 nm. It was in contact with the protective film). PEB treatment was performed in the same manner as in Example 1, and the protective film was removed using perfluoro (2-butyl) tetrahydrofuran. Thereafter, the resist film was developed under the same conditions as in Example 1.

  When the resist pattern with the 65 nm line and space obtained in this way having a 1: 1 ratio was observed with a scanning electron microscope (SEM), this pattern profile was good and no fluctuations were observed. It was. Furthermore, when the cross-sectional shape of the obtained pattern was observed with a focused ion beam SEM (Altura 835 manufactured by FEI), it was found that the cross-sectional shape was a good rectangular shape.

(Comparative Example 1)
A similar resist pattern was formed by the same operation as in Example 2 except that the protective film was not provided. As a result, although fluctuations in sensitivity were not observed, some fluctuations (partial narrowing of lines) were observed in the pattern profile. Furthermore, when the cross-sectional shape of the obtained pattern was observed with a focused ion beam SEM (Altura 835 manufactured by FEI), a slight T-top shape was observed.

(Comparative Example 2)
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare a positive resist composition 2.

  As the resin component, 100 parts by mass of a polymer composed of a structural unit represented by the following chemical formula (40) was used. The prepared resin component had a mass average molecular weight of 10,000.

  As the acid generator, 3.5 parts by mass of triphenylsulfonium nonafluorobutanesulfonate and 1.0 part by mass of (4-methylphenyl) diphenylsulfonium trifluoromethanesulfonate were used. As the organic solvent, a mixed solvent (mass ratio 6: 4) of 1900 parts by mass of a mixed solvent of propylene glycol monomethyl ether acetate and ethyl lactate was used. Further, 0.3 parts by mass of triethanolamine was used as the nitrogen-containing organic compound.

  A resist pattern was formed using the positive resist composition 2 produced as described above. First, an organic antireflection film composition “AR-19” (trade name, manufactured by Shipley) was applied onto a silicon wafer using a spinner, and baked and dried on a hot plate at 215 ° C. for 60 seconds. An organic antireflection film having a thickness of 82 nm was formed. Then, the positive resist composition 1 is applied onto the antireflection film using a spinner, prebaked on a hot plate at 115 ° C. for 90 seconds, and dried to have a film thickness of 150 nm on the antireflection film. The resist film was formed. Next, using an ArF excimer laser (wavelength: 193 nm) with an exposure apparatus NSR-S302B (manufactured by Nikon Corporation, NA (numerical aperture) = 0.60, σ = 0.75) through the mask pattern, Was irradiated (exposure). Then, as an immersion exposure process, pure water was continuously dropped on the resist film at 23 ° C. for 5 minutes while rotating the silicon wafer provided with the resist film after the exposure. The process of this part is a process of exposing in a completely immersed state in an actual manufacturing process, but it is theoretically that the exposure itself in the optical system is completely performed based on the analysis with respect to the previous immersion exposure method. In order to be able to evaluate only the influence of the immersion exposure liquid on the resist film, the resist film is subjected to immersion exposure liquid after exposure so that the resist film is exposed first. It is set as the simple structure of making it load. Next, PEB treatment was performed at 115 ° C. for 90 seconds, and further developed at 23 ° C. with an alkali developer for 60 seconds. As the alkaline developer, an aqueous 2.38 mass% tetramethylammonium hydroxide solution was used.

The thus obtained resist pattern with a 130 nm line and space of 1: 1 was observed with a scanning electron microscope (SEM), and the sensitivity (Eth) at that time was determined. As a result, the measurement sensitivity was 9.1 mJ / cm ² , and it was found that the sensitivity deterioration was large as compared with the following.

On the other hand, when the resist composition 2 of Comparative Example 2 was used, a resist pattern was formed by a conventional formation method by exposure through an air layer without performing the immersion exposure process. Was 8.4 mJ / cm ² . When the ratio of the sensitivity of the immersion exposure processing to the sensitivity of normal exposure was determined, it was (9.1 / 8.4 =) 108.3.

(Comparative Example 3)
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare a positive resist composition 3. As the resin component, 100 parts by mass of a copolymer composed of 63 mol% hydroxystyrene units, 24 mol% styrene units and 13 mol% tert-butyl acrylate units was used. The prepared resin component had a mass average molecular weight of 12,000. As an acid generator, 2.8 parts by mass of bis (tert-butylphenyliodonium trifluoromethanesulfonate) and 1.0 part by mass of dimethylmonophenylsulfonium trifluoromethanesulfonate were used. As an organic solvent, 600 parts by mass of ethyl lactate was used. As the nitrogen-containing organic compound, 0.26 part by mass of triethanolamine was used, and 0.28 part by mass of phenylphosphonic acid was used as the other component.

  A resist pattern was formed using the positive resist composition 3 produced as described above. First, an organic antireflection film composition “AR-3” (trade name, manufactured by Shipley) was applied onto a silicon wafer using a spinner, and baked on a hot plate at 220 ° C. for 60 seconds to dry. An organic antireflection film having a thickness of 62 nm was formed. Then, the positive resist composition 3 obtained above is applied on the antireflection film using a spinner, prebaked on a hot plate at 110 ° C. for 90 seconds, and dried to form a film on the antireflection film. A resist film having a thickness of 280 nm was formed. Next, using a KrF excimer laser (wavelength 248 nm) with an exposure apparatus NSR-S203 (manufactured by Nikon Corporation, NA (numerical aperture) = 0.60, σ = 0.75) through the mask pattern, pattern light is used. Was irradiated (exposure). Then, as immersion exposure processing, pure water was continuously dropped on the resist film at 23 ° C. for 5 minutes while rotating the silicon wafer provided with the resist film after the exposure. The process of this part is a process in which exposure is performed in a completely immersed state in an actual manufacturing process, but it is theoretically that the exposure of the optical system itself is completely performed based on the analysis for the previous immersion exposure method. In order to be able to evaluate only the influence of the immersion exposure liquid on the resist film, the resist film is subjected to immersion exposure liquid after exposure so that the resist film is exposed first. It is set as the simple structure of making it load. Next, PEB treatment was performed at 110 ° C. for 90 seconds, and further developed at 23 ° C. with an alkali developer for 60 seconds. As the alkali developer, an aqueous 2.38 mass% tetramethylammonium hydroxide solution was used.

The thus obtained resist pattern with a 140 nm line and space of 1: 1 was observed with a scanning electron microscope (SEM), and the sensitivity (Eth) at that time was determined. As a result, the sensitivity was 22.0 mJ / cm ² . Moreover, the resist pattern became T-top shape and the surface roughness was seen.

On the other hand, when the resist composition 3 of this comparative example was used and a resist pattern was formed by a conventional formation method by exposure through an air layer without performing the immersion exposure process, the sensitivity was It was 20.0 mJ / cm ² . The sensitivity ratio of the immersion exposure process to the sensitivity of this normal exposure was determined to be (22.0 / 20.0 =) 108.8. The resist pattern was not rough and was good.

(Comparative Example 4)
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare a positive resist composition 4. The resin component includes 64 parts by mole of hydroxystyrene units, 70 parts by weight of a copolymer composed of 36 mole% 1-ethoxy-1-ethyloxystyrene units, 67 mole% of hydroxystyrene units, and 33 units of tetrahydropyranyloxystyrene units. A mixed resin of 30 parts by mass of a copolymer composed of mol% structural units was used. The prepared resin component had a mass average molecular weight of 8,000. As the acid generator, 4 parts by mass of bis (cyclohexylsulfonyl) diazomethane and 1 part by mass of tert-butylphenyliodonium trifluoromethanesulfonate were used. As the organic solvent, a mixed solvent (mass ratio 6: 4) of 600 parts by mass of a mixed solvent of propylene glycol monomethyl ether acetate and ethyl lactate was used. As the nitrogen-containing organic compound, 0.52 parts by mass of triisopropanolamine was used, and as the other components, 0.54 parts by mass of dodecanoic acid was used.

  A resist pattern was formed using the positive resist composition 4 produced as described above. First, an organic antireflection film composition “DUV-44” (trade name, manufactured by Brewer Science) is applied onto a silicon wafer using a spinner, and baked on a hot plate at 225 ° C. for 90 seconds to be dried. Thus, an organic antireflection film having a film thickness of 65 nm was formed. Then, the positive resist composition 4 obtained above is applied on the antireflection film using a spinner, prebaked on a hot plate at 90 ° C. for 90 seconds, and dried to form a film on the antireflection film. A resist film having a thickness of 280 nm was formed. Next, using a KrF excimer laser (wavelength 248 nm) with an exposure apparatus NSR-S203 (manufactured by Nikon Corporation, NA (numerical aperture) = 0.60, σ = 0.75) through the mask pattern, pattern light is used. Was irradiated (exposure). Then, as immersion exposure processing, pure water was continuously dropped on the resist film at 23 ° C. for 5 minutes while rotating the silicon wafer provided with the resist film after the exposure. The process of this part is a process in which exposure is performed in a completely immersed state in an actual manufacturing process, but it is theoretically that the exposure of the optical system itself is completely performed based on the analysis for the previous immersion exposure method. In order to be able to evaluate only the influence of the immersion exposure liquid on the resist film, the resist film is subjected to immersion exposure liquid after exposure so that the resist film is exposed first. It is set as the simple structure of making it load. Next, PEB treatment was performed at 110 ° C. for 90 seconds, and further developed at 23 ° C. with an alkali developer for 60 seconds. As the alkali developer, an aqueous 2.38 mass% tetramethylammonium hydroxide solution was used.

The thus obtained resist pattern with a 140 nm line and space of 1: 1 was observed with a scanning electron microscope (SEM), and the sensitivity (Eth) at that time was determined. As a result, the sensitivity was 26.5 mJ / cm ² . Moreover, the resist pattern became T top shape, and the surface roughness was seen.

On the other hand, when the resist composition 4 of this comparative example was used and the resist pattern was formed by a conventional formation method by exposure through an air layer without performing the immersion exposure treatment, the sensitivity was It was 16.5 mJ / cm ² . The sensitivity ratio of the immersion exposure process to the sensitivity of normal exposure was determined to be (26.5 / 16.5 =) 156.6. The resist pattern was good with no surface roughness.

  In the first and second embodiments, a 130 nm line-and-space pattern with a good profile can be obtained even in immersion exposure in which a protective film is formed, without deterioration of characteristics necessary for pattern formation such as sensitivity. It is shown. Further, although the resist film used in the above example was a positive resist film, it is apparent that the resist film can be similarly applied to a negative resist film.

(Example 3)
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare a positive resist. As the resin component, 100 parts by mass of a polymer composed of the structural unit represented by the general formula (40) was used. The mass average molecular weight of the resin component was 10,000. As the acid generator, 3.5 parts by mass of triphenylsulfonium nonafluorobutanesulfonate and 1.0 part by mass of (4-methylphenyl) diphenylsulfonium trifluoromethanesulfonate were used. As the organic solvent, a mixed solvent (mass ratio 6: 4) of 1900 parts by mass of a mixed solvent of propylene glycol monomethyl ether acetate and ethyl lactate was used. Further, 0.3 parts by mass of triethanolamine was used as the nitrogen-containing organic compound.

  An antireflection film, an ArF positive resist and a protective film were formed on the substrate in the same procedure as in Example 1 except that the positive resist composition produced as described above was used (however, the resist film thickness Only 140 nm). The substrate on which the protective film was formed was subjected to immersion exposure processing by the same means as in Example 2. The resist film was removed from the protective film under the same conditions as in Example 1, PEB treated, and then developed.

  When the 90 nm line and space resist pattern obtained in this way was observed with a scanning electron microscope (SEM), this pattern profile was good, fluctuation (pattern narrowing), etc. Was not observed at all.

(Comparative Example 5)
Although the positive photoresist shown in Example 3 above was used and a resist pattern having a 90 nm line and space of 1: 1 was formed in exactly the same manner except that no protective film was formed, the scanning type When observed with an electron microscope (SEM), the pattern was severely fluctuated and swollen, and the pattern could not be observed.

Example 4
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare a positive resist composition. As the resin component, a polymer composed of structural units represented by the following general formulas (41) and (42) (unit 85 parts by mass of formula (41) and unit 15 parts by mass of formula (42)) was used. The mass average molecular weight of the resin component was 10,000. As the acid generator, 3.0 parts by mass of triphenylsulfonium nonafluorobutanesulfonate was used. As the organic solvent, a mixed solvent (mass ratio 6: 4) of 1900 parts by mass of a mixed solvent of propylene glycol monomethyl ether acetate and ethyl lactate was used. Furthermore, 0.25 part by mass of triethanolamine was used as the nitrogen-containing organic compound.

（式（４２）中、ｊ＝５０モル％、ｋ＝３０モル％、ｌ＝２０モル％である）

(In formula (42), j = 50 mol%, k = 30 mol%, and l = 20 mol%)

  An antireflection film, an ArF positive resist, and a protective film were formed on the substrate in the same procedure as in Example 1 except that the positive resist manufactured as described above was used (however, only the resist film thickness was changed) 140 nm). The substrate on which this protective film was formed was subjected to immersion exposure processing by the same means as in Example 2. The resist film was removed from the protective film under the same conditions as in Example 1, PEB treated, and then developed.

  When the 90 nm line and space resist pattern obtained in this way was observed with a scanning electron microscope (SEM), this pattern profile was good, fluctuation (pattern narrowing), etc. Was not observed at all.

(Comparative Example 6)
Although the positive photoresist shown in Example 4 above was used and a resist pattern having a 90 nm line and space of 1: 1 was formed in exactly the same manner except that no protective film was formed, a scanning type Observation with an electron microscope (SEM) revealed slight distortion and swelling of the pattern.

(Example 5)
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare a negative resist composition. As the resin component, a polymer composed of structural units represented by the following general formula (43) was used. A crosslinking agent composed of 10% by mass of tetrabutoxymethylated glycoluril, an acid generator composed of 1% by mass of triphenylsulfonium nonafluorobutanesulfonate, and 0.6% by mass of 4-phenyl based on this resin component. A negative resist material in which an amine component composed of pyridine was dissolved in propylene glycol monomethyl ether and the solid content weight was 8.1% by mass was used.

（式中、ｍ：ｎは８４：１６（モル％）である）

(Wherein m: n is 84:16 (mol%))

  A resist pattern was formed using the negative resist composition produced as described above. First, an organic antireflection film composition “AR-19” (trade name, manufactured by Shipley) was applied onto a silicon wafer using a spinner, and baked and dried on a hot plate at 215 ° C. for 60 seconds. An organic antireflection film having a thickness of 32 nm was formed. Then, the negative resist composition is applied onto the antireflection film using a spinner, pre-baked on a hot plate at 110 ° C. for 60 seconds, and dried to have a film thickness of 300 nm on the antireflection film. A resist film was formed. On the resist film, a mixed resin composed of demnum S-10 (manufactured by Daikin Industries) and CYTOP (manufactured by Asahi Glass) (mixing weight ratio = 1: 5) is dissolved in perfluorotributylamine to give a resin concentration of 2 A protective film material having a thickness of 0.5 wt% was spin-coated and heated at 90 ° C. for 60 seconds to form a protective film having a thickness of 37 nm. The substrate on which the protective film was formed was subjected to an exposure process by the same means as in Example 1, followed by a water dropping process on the resist film (however, the water dropping process was performed for 2 minutes). The resist film was removed from the protective film under the same conditions as in Example 1, PEB treated, and then developed.

  When the resist pattern with 160 nm line and space obtained in this way was observed with a scanning electron microscope (SEM), this pattern profile was good, fluctuation (pattern narrowing), No swelling or the like was observed.

(Comparative Example 7)
Although the negative photoresist shown in Example 5 was used and a resist pattern having a 160 nm line and space of 1: 1 was formed in exactly the same manner except that the protective film was not formed, the scanning type Observation with an electron microscope (SEM) revealed slight distortion and swelling of the pattern.

(Example 6)
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare a positive resist composition. As the resin component, 100 parts by mass of a methacrylic acid ester copolymer composed of three types of structural units represented by the following general formula (44) was used. The ratio of each structural unit s, t, u used for the preparation of the resin component was s = 40 mol%, t = 40 mol%, u = 20 mol%. The prepared resin component had a mass average molecular weight of 10,000.

  As the acid generator, 0.8 parts by mass of tri- (4-tert-butylphenyl) sulfonium trifluoromethanesulfonate and 2.0 parts by mass of (4-methylphenyl) diphenylsulfonium nonafluorobutanesulfonate were used. Further, as the organic solvent, a mixed solvent of 1520 parts by mass (mass ratio 6: 4) of propylene glycol monomethyl ether acetate and ethyl lactate and 380 parts by mass of γ-butyrolactone was used. Furthermore, 0.25 part by mass of triethanolamine was used as the nitrogen-containing organic compound.

  A resist pattern was formed using the positive resist composition produced as described above. First, an organic antireflection film composition “AR-19” (trade name, manufactured by Shipley) was applied onto a silicon wafer using a spinner, and baked and dried on a hot plate at 215 ° C. for 60 seconds. An organic antireflection film having a thickness of 82 nm was formed. Then, the positive resist composition is applied onto the antireflection film by using a spinner, prebaked on a hot plate at 130 ° C. for 90 seconds, and dried to have a film thickness of 200 nm on the antireflection film. A resist film was formed.

  On the resist film, a mixed resin consisting of demnum S-20 (manufactured by Daikin Industries) and CYTOP (manufactured by Asahi Glass) (mixing weight ratio = 1: 5) is dissolved in perfluorotributylamine to give a resin concentration of 2 A protective film material having a thickness of 0.5 wt% was spin-coated and heated at 90 ° C. for 60 seconds to form a protective film having a thickness of 37 nm.

  Next, using an ArF excimer laser (wavelength: 193 nm) with an exposure apparatus NSR-S302B (Nikon Corporation, NA (numerical aperture) = 0.60, 2/3 annular illumination) through the mask pattern Irradiated with light (exposure). Then, as an immersion exposure process, pure water was continuously dropped on the resist film at 23 ° C. for 2 minutes while rotating the silicon wafer provided with the resist film after the exposure. The process of this part is a process of exposing in a completely immersed state in an actual manufacturing process, but it is theoretically that the exposure itself in the optical system is completely performed based on the analysis with respect to the previous immersion exposure method. Since the resist film is exposed first, the resist film is loaded with pure water, which is a liquid for immersion exposure, after exposure so that only the influence of the immersion liquid on the resist film can be evaluated. This is a simple configuration.

  After the dropping step of pure water, PEB treatment was performed at 130 ° C. for 90 seconds, and then the protective film was removed using perfluoro (2-butyltetrahydrofuran). Further, development was performed at 23 ° C. with an alkali developer for 60 seconds. As the alkaline developer, an aqueous 2.38 mass% tetramethylammonium hydroxide solution was used.

When the thus obtained resist pattern with a 130 nm line and space of 1: 1 was observed with a scanning electron microscope (SEM), this pattern profile was good and no fluctuations were observed. . In addition, the sensitivity at that time was 17.0 mJ / cm ² and the depth of focus was 1.0 μm. Furthermore, the exposure margin for obtaining a 130 nm line pattern within a range of ± 10% was as good as 13.15%.

(Example 7)
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare a positive resist composition. As a resin component, the polymer which consists of a structural unit shown in the said General formula (41) and the following general formula (45), respectively (the unit 85 mass part of Formula (41), and the unit 15 mass part of Formula (45)) Was used. The mass average molecular weight of the resin component was 10,000. As the acid generator, 2.4 parts by mass of triphenylsulfonium nonafluorobutanesulfonate was used. As the organic solvent, a mixed solvent (mass ratio 6: 4) of 1900 parts by mass of a mixed solvent of propylene glycol monomethyl ether acetate and ethyl lactate was used. Further, 0.27 parts by mass of triethanolamine was used as the nitrogen-containing organic compound. 0.26 mass of salicylic acid was used as the organic carboxylic acid.

（ｘ＝４０モル％、ｙ＝４０モル％、ｚ＝２０モル％である）

(X = 40 mol%, y = 40 mol%, z = 20 mol%)

An antireflection film, the prepared positive resist, and a protective film were formed on the substrate in the same procedure as in Example 1 (however, the resist film thickness was changed to 150 nm and the prebake temperature was 95). 90 ° C. and PEB was changed to 90 ° C. for 90 seconds). The substrate on which this protective film was formed was subjected to immersion exposure processing by the same means as in Example 2. The resist film was subjected to PEB treatment, and then the protective film was removed under the same conditions as in Example 1. The resist film was left for 180 seconds at a location where the amine concentration in the atmosphere was about 5 ppb, and then developed.

When the resist pattern with a 130 nm line and space obtained in this way having a 1: 1 ratio was observed with a scanning electron microscope (SEM), this pattern profile was good, fluctuation (pattern narrowing), etc. Was not observed at all. The sensitivity at that time was 26.0 mJ / cm ² .

(Comparative Example 8)
A resist pattern was formed after leaving for 180 seconds in the same manner as in Example 7 using the resist composition prepared in Example 7 except that the protective film was not used.
When a resist pattern having a 130 nm line and space of 1: 1 was observed with a scanning electron microscope (SEM), the pattern profile was a T-top shape. The sensitivity at that time was 33.0 mJ / cm ² . This is because the acid on the resist film was deactivated by amine in the atmosphere because no protective film was used.

As can be seen from the results of Example 7 and Comparative Example 8, the use of the protective film can eliminate the influence on the amine in the atmosphere. That is, the stability over time (post
exposure delay)

(Example 8)
As component (A), 85 parts by mass of a silsesquioxane resin represented by the following chemical formula (46) and 15 mass parts of a methacrylic acid ester / acrylic acid ester copolymer composed of three types of structural units represented by the following chemical formula (47) Mixed resin was used. The ratio of each structural unit v, w, x of the copolymer of the chemical formula (47) is v = 40 mol%, w = 40 mol%, x = 20 mol%, and its mass average molecular weight was 10,000. It was.

  As component (B), 2.4 parts by mass of triphenylsulfonium nonafluorobutanesulfonate was used. As the component (C), a mixed solvent of 1900 parts by mass (mass ratio 8: 2) of a mixed solvent of ethyl lactate and γ-butyrolactone was used. As component (D), 0.27 parts by mass of triethanolamine was used. As component (E), 0.26 parts by mass of salicylic acid was used.

  Next, an organic antireflection film composition “AR-19” (trade name, manufactured by Shipley) is applied onto a silicon wafer using a spinner, and baked on a hot plate at 215 ° C. for 60 seconds to be dried. As a result, an organic antireflection film having a thickness of 82 nm was formed. A positive resist composition was applied on the antireflection film using a spinner, prebaked at 95 ° C. for 90 seconds on a hot plate, and dried to form a resist layer having a thickness of 150 nm on the antireflection film. . Next, on the resist film, a fluorine-based resin {Demnam S-10 (Daikin Kogyo Co., Ltd.) and Cytop (Asahi Glass Co., Ltd. cyclic perfluoroalkyl polyether) containing cyclic perfluoroalkyl polyether as a main component. (Mixed weight ratio = 1: 5 mixed resin) was dissolved in perfluorotributylamine, and a fluorine-based protective film material having a resin concentration of 2.5 mass% was spin-coated and heated at 90 ° C. for 60 seconds. Then, a protective film having a thickness of 37 nm was formed. As an evaluation test 2, immersion exposure was performed by using an experimental apparatus manufactured by Nikon Corporation and performing an experiment (two-beam interference experiment) using a prism, water, and two beam interferences of 193 nm. A similar method is also disclosed in Non-Patent Document 2 and is known as a method for easily obtaining a line and space pattern at the laboratory level.

In the immersion exposure in Example 8, a water layer was formed as an immersion exposure liquid between the upper surface of the protective film and the lower surface of the prism. In addition, the exposure amount which obtained the line and space pattern stably was selected for the exposure amount. Next, PEB treatment was performed at 90 ° C. for 90 seconds, and the protective film was removed using perfluoro (2-butyl) tetrahydrofuran. Thereafter, development processing was performed in the same manner as in Example 1. As a result, 65 nm line and space (1: 1) was obtained. The pattern shape was highly rectangular.

Claims (7)

  A solvent for removing a resist protective film for an immersion exposure process, which is a solvent for removing a protective film for removing a resist protective film suitable for use in an immersion exposure process, comprising a fluorine-based solvent.   The solvent for removing a resist protective film for an immersion exposure process according to claim 1, wherein the fluorine-based solvent is a fluorine-based solvent having a boiling point of 150 ° C. or lower.   The solvent for removing a resist protective film for an immersion exposure process according to claim 1, wherein the fluorine-based solvent is perfluoro (2-butyl) tetrahydrofuran.   In the immersion exposure process, at least the resist film on the path until the lithography exposure light reaches the resist film, the immersion film having a predetermined thickness that has a refractive index larger than air and smaller than the resist film. 4. The immersion exposure process according to claim 1, wherein the resist pattern resolution is improved by exposing the resist film with an exposure liquid interposed therebetween. 5. Resist protective film removal solvent.   The solvent for removing a resist protective film for an immersion exposure process according to claim 4, wherein the immersion exposure liquid is water substantially composed of pure water or deionized water.   A resist pattern forming method using an immersion exposure process, wherein a photoresist film is formed on a substrate, and a resist protective film forming material for an immersion exposure process is formed on the resist film, and is transparent to exposure light. Forming a protective film that has substantially no compatibility with the liquid for immersion exposure and that does not cause mixing with the resist film, and the resist film and the protective film are laminated. The liquid for immersion exposure having a predetermined thickness is directly disposed on at least the protective film of the substrate, and the resist film is selectively irradiated with light through the liquid for immersion exposure and the protective film, A resist film which is heat-treated as necessary, and removes the protective film from the irradiated resist film using the protective film removing solvent according to any one of claims 1 to 6, and the protective film is removed. Develop A method of forming a resist pattern comprises obtaining a strike pattern. In the immersion exposure process, at least the resist film on the path until the lithography exposure light reaches the resist film, the immersion film having a predetermined thickness that has a refractive index larger than air and smaller than the resist film. 7. The resist pattern forming method according to claim 6, wherein a resist pattern is obtained by exposing the resist film in a state where an exposure liquid is interposed.