JP5507601B2 - Resist pattern forming method - Google Patents

Description

  The present invention relates to a liquid immersion lithography process, and in particular, a refractive index higher than air at least on the resist film in a path through which lithography exposure light reaches the resist film and a refractive index lower than that of the resist film. The present invention relates to a resist pattern forming method using an immersion exposure process in which the resolution of a resist pattern is improved by exposing the resist film in a state where a liquid having a thickness is interposed.

  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, and 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, a liquid refractive index medium (refractive index liquid, immersion liquid) such as pure water or a fluorine-based inert liquid having a predetermined thickness is formed on at least the resist film between the lens and the resist film on the substrate during exposure. Is to intervene. 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) ((Issuing 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 above-described immersion exposure process, the resist film is directly in contact with the refractive index liquid (immersion liquid) at the time of exposure, so that the resist film is subjected to invasion by the 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 composition can obtain a resist composition having the characteristics suitable for immersion exposure by using the composition as it is or by slightly adjusting the composition. The experiment was examined. As a result, it was found that there is a resist composition that can be expected in practical use. On the other hand, even if the resist composition does not have sufficient pattern resolution due to alteration by liquid in immersion exposure, it shows fine and high resolution in lithography by exposure through a normal air layer. It was also confirmed that there are many. 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 liquid. Some examples of compositions that are not suitable for such immersion exposure but exhibit high resolution in lithography with an air layer will be shown in the examples and comparative examples of the present invention described later.

  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 liquid, (iii) the resist film by the immersion liquid If the three points of alteration 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 liquid, that is, from the immersion liquid. If it is not affected and does not affect the immersion 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 liquid of (ii) is that the components of the resist film are dissolved in the liquid and the refractive index of the liquid is changed. If the refractive index of the liquid is changed, the optical resolution of the pattern exposure is surely changed from the theory without undergoing experimentation. In this regard, if the resist film is simply immersed in the liquid, it is sufficient if the components are dissolved and the composition of the immersion liquid is changed or the refractive index is changed. There is no need to actually irradiate the pattern light and develop it to confirm the resolution.

  On the contrary, when the resist film in the liquid is irradiated with pattern light and developed and the resolution is confirmed, the quality of the resolution can be confirmed by the alteration of the immersion liquid, even though the resolution can be confirmed. It is impossible to distinguish between the influence, the influence of resolution due to the alteration of the resist material, or both.

  Regarding the point that the resolution is deteriorated due to the change of the resist film by the immersion liquid in (iii), “the treatment of applying a shower of immersion liquid to the resist film after exposure is performed, and then development is performed. An evaluation test “inspecting image quality” is sufficient. In addition, in this evaluation method, the liquid is sprinkled directly on the resist film, and the immersion condition becomes more severe. With regard to this point as well, in the case of a test in which exposure is performed in a completely immersed state, the resolution may be affected by the change of the immersion liquid, the deterioration of the resist composition by the immersion liquid, or both effects. I don't know if it has changed.

  The phenomena (ii) and (iii) are front and back integrated phenomena 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 is expressed as follows: “After the exposure, the resist film is subjected to a treatment by applying a shower of immersion liquid to the resist film, and then developed. This was confirmed by an evaluation test “inspecting resolution”. 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, It has also been confirmed that there are many resist films that do not exhibit sufficient pattern resolution due to alteration due to immersion liquid, and that show fine and high resolution in lithography by exposure through a normal air layer. .

  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. Specifically, by forming a specific protective film on the surface of the conventional resist film, the resist film during the immersion exposure and the use liquid are prevented at the same time, It is an object of the present invention to enable formation of a high-resolution resist pattern using immersion exposure.

  In order to solve the above-described problems, the material for forming a resist protective film for an immersion exposure process according to the present invention forms a resist protective film that is provided on a resist film and protects the resist film used for the immersion exposure process. The material is characterized in that it has no substantial compatibility with water and is soluble in alkali.

  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 protective film forming material is formed on the resist film. And forming a protective film having characteristics that are substantially compatible with water and capable of being alkaline, and at least on the protective film of the substrate on which the resist film and the protective film are laminated The immersion exposure liquid having a predetermined thickness is directly disposed on the resist film, and the resist film is irradiated with a predetermined pattern light through the immersion exposure liquid and the protective film, and heat treatment is performed as necessary. The method includes removing the protective film by washing the protective film and the resist film using a developer, and simultaneously developing the resist film 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.

  Furthermore, in the present invention, when forming a resist protective film, it is preferable to add a specific fluorine-containing compound described later as a component thereof.

  The material for forming a protective film of the present invention can be directly formed on a resist film, does not hinder pattern exposure, and the material for forming a protective film of the present invention is insoluble in water. Immersion exposure of water (pure water or deionized water) that is regarded as the most promising immersion liquid for immersion exposure because it does not have optical requirements, ease of handling, and environmental pollution. It can be used as a soaking solution. In other words, even if water that is easy to handle, has good refractive index characteristics, and has no environmental pollution property is used as an immersion liquid for immersion exposure, while resist films having various compositions are used in the immersion exposure process. It is possible to obtain a resist pattern with sufficient protection and good characteristics. In addition, when an exposure wavelength of 157 nm is used as the immersion liquid for immersion exposure, fluorine-based media are considered to be dominant from the viewpoint of absorption of exposure light, and this is the case when such a fluorine-based solvent is used. However, like the above-described water, it is possible to sufficiently protect the resist film during the immersion exposure process and to obtain a resist pattern with good characteristics. Furthermore, since the protective film-forming material of the present invention is soluble in alkali, it is necessary to remove the formed protective film from the resist film before the development process even when the exposure is completed and the development process is performed. Absent. That is, since the protective film obtained using the protective film-forming material of the present invention is soluble in alkali, it is not necessary to provide a protective film removal step before the development step after exposure, and an alkaline developer for resist film The developing process can be performed while leaving the protective film, whereby the removal of the protective film and the development of the resist film can be realized simultaneously. Therefore, the pattern forming method performed using the protective film forming material of the present invention can efficiently form a resist film with good pattern characteristics with extremely low environmental pollution and a reduced number of steps. it can.

  As described above, in the present invention, it is preferable to add a specific fluorine-containing compound described later when forming the protective film. By adding this specific fluorine-containing compound, the coating property when the resist protective film forming material is applied as a coating liquid on the resist film is improved. More importantly, when a protective film to which this specific fluorine-containing compound is added is used, it is possible to improve the resistance to holding in a trace amine-containing atmosphere after pattern exposure of the resist film.

  The following is a brief description of this resistance to holding. That is, a trace amount of amine in the order of ppb is contained in the atmosphere of normal resist exposure and development processes. It is known that when this amine comes into contact with the resist film after the exposure step, the pattern size obtained by subsequent development is distorted. If the resist is subsequently exposed to a trace amount of amine-containing atmosphere after exposure and the resist pattern dimensions obtained by the subsequent development do not greatly disturb, it means that the holding resistance is high.

  In the present invention, one major characteristic is that the protective film has a characteristic of protecting the resist film after exposure from the action of amine by adding a specific fluorine-containing compound described later to the protective film. .

  In the present invention having the above-described configuration, the immersion exposure can be performed by using water or a fluorine-based inert liquid which is substantially pure water or deionized water as the immersion exposure liquid. As described above, in consideration of cost, ease of post-processing, low environmental pollution, etc., water is a more suitable immersion exposure liquid, but when 157 nm exposure light is used. For this, it is preferable to use a fluorine-based solvent that absorbs less exposure light.

  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. This is also the greatest feature of the present invention.

  In addition, as described above, the essential property as the protective film of the present invention is that it has no substantial compatibility with water and is soluble in alkali, and further transparent to exposure light. Thus, no protective film material that can form a protective film having such characteristics is that it does not cause mixing with the resist film, has good adhesion to the resist film, and has good solubility in a developer. As, a composition obtained by dissolving a specific fluoropolymer in a solvent that is not compatible with the resist film and can dissolve the fluoropolymer is used.

  The fluoropolymer which is the base polymer of the protective film of the present invention contains (X-1) an aliphatic cyclic group having both a fluorine atom or a fluorinated alkyl group and (X-2) an alcoholic hydroxyl group or an oxyalkyl group. What has the following structural units contained in the concept of the polymer which comprises water-soluble and alkali-soluble structural unit (X) is suitable.

  That is, in the structural unit (X), (X-1) a fluorine atom or a fluorinated alkyl group and (X-2) an alcoholic hydroxyl group or an alkyloxy group are bonded to an aliphatic cyclic group, respectively. It constitutes the main chain. Examples of the (X-1) fluorine atom or fluorinated alkyl group include those in which part or all of the hydrogen atoms of the fluorine atom or lower alkyl group are substituted with fluorine atoms. Specific examples include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, and a nonafluorobutyl group, and industrially preferred are a fluorine atom and a trifluoromethyl group. The (X-2) alcoholic hydroxyl group or alkyloxy group is simply a hydroxyl group, and the alkyloxy group is a chain, branched or cyclic alkyloxyalkyl group having 1 to 15 carbon atoms, or an alkyl group. It is an oxy group.

The polymer having such a unit (the base polymer of the protective film of the present invention) is formed by cyclopolymerization of a diene compound having a hydroxyl group and a fluorine atom. As the diene compound, heptadiene that easily forms a polymer having a 5-membered ring or a 6-membered ring excellent in transparency and dry etching resistance is preferable. Further, 1,1,2,3,3-pentafluoro- A polymer formed by cyclopolymerization of 4-trifluoromethyl-4-hydroxy-1,6-heptadiene (CF ₂ ═CFCF ₂ C (CF ₃ ) (OH) CH ₂ CH═CH ₂ ) is the most industrially available. preferable.

The general formula (100) representing the polymer is shown below.

In general formula (100), R ⁵ is a hydrogen atom or a chain, branched, or cyclic C1-C15 alkyloxy group or alkyloxyalkyl group, and x and y are each 10 to 90 mol%. .

  Such a polymer can be synthesized by a known method. Moreover, although the polystyrene conversion mass mean molecular weight by GPC of resin of this polymer component is not specifically limited, It is 5000-80000, More preferably, it is 8000-50000.

  As the solvent for dissolving the fluoropolymer, any solvent can be used as long as it is not compatible with the resist film and can dissolve the fluoropolymer. Examples of such solvents include alcohol solvents, paraffin solvents, and fluorine solvents. As the alcohol solvent, a conventional alcohol solvent such as isopropyl alcohol, 1-hexanol, 2-methyl-1-propanol, 4-methyl-2-pentanol can be used, and in particular, 2-methyl-1-propanol. 4-methyl-2-pentanol is preferred. It has been confirmed that n-heptane can be used as a paraffin solvent and perfluoro-2-butyltetrahydrofuran can be used as a fluorine solvent. Of these, alcohol solvents are preferred from the viewpoint of alkali solubility during development.

As described above, it is desirable to add a fluorocarbon compound to the protective film forming material of the present invention. Even if the resist film is left in an atmosphere containing a trace amount of amine after development after immersion exposure, the adverse effect of the amine can be suppressed by the intervention of the protective film. This is because there is no great deviation in dimensions in the resist pattern.
Such fluorocarbon compounds are shown below, but these fluorocarbon compounds are not subject to important new usage rules (SNUR) and can be used.

As such a fluorocarbon compound,
The following general formula (201)
(C _n F _{2n + 1} SO ₂ ) ₂ NH (201)
(In the formula, n is an integer of 1 to 5.)
A fluorocarbon compound represented by
The following general formula (202)
C _m F _{2m + 1} COOH (202)
(In the formula, m is an integer of 10 to 15.)
A fluorocarbon compound represented by
The following general formula (203)

（式中、ｏは、２〜３の整数である。）
で示される炭化フッ素化合物と、
下記一般式（２０４）

(In the formula, o is an integer of 2 to 3.)
A fluorocarbon compound represented by
The following general formula (204)

（式中、ｐは、２〜３の整数であり、Ｒｆは１部もしくは全部がフッ素原子により置換されているアルキル基であり、水酸基、アルコキシ基、カルボキシル基、アミノ基により置換されていてもよい。）
で示される炭化フッ素化合物とが、好適である。

(In the formula, p is an integer of 2 to 3, and Rf is an alkyl group partially or entirely substituted with a fluorine atom, and may be substituted with a hydroxyl group, an alkoxy group, a carboxyl group, or an amino group. Good.)
And a fluorine-containing compound represented by the formula:

Specific examples of the fluorocarbon compound represented by the general formula (201) include the following chemical formula (205)
(C ₄ F ₉ SO ₂ ) ₂ NH (205)
Or a compound represented by the following chemical formula (206)
(C ₃ F ₇ SO ₂ ) ₂ NH (206)
The fluorine-containing compound represented by these is suitable.

Further, as the fluorocarbon compound represented by the general formula (202), specifically, the following chemical formula (207)
C ₁₀ F ₂₁ COOH (207)
The fluorine-containing compound represented by these is suitable.

  Further, as the fluorocarbon compound represented by the general formula (203), specifically, the following chemical formula (208)

で表される炭化フッ素化合物が好適である。

The fluorine-containing compound represented by these is suitable.

  Specific examples of the fluorine-containing compound represented by the general formula (204) include the following chemical formula (209).

で表される炭化フッ素化合物が好適である。

The fluorine-containing compound represented by these is suitable.

  Since the protective film of the present invention is water-insoluble and highly resistant to other immersion liquids, it can be applied to resist films of any composition including resist films with low resistance to immersion liquids. Accordingly, as the resist film material of the present invention, any known resist can be used, and a conventional positive resist or negative photoresist can be used. Specific examples of these are exemplified below.

  First, as a resin component used for a positive photoresist, a fluorine resin, an acrylic resin, a cycloolefin resin, a silsesquioxane resin, or the like is used.

  Examples of the fluororesin include (A) (i) a fluorine atom or a fluorinated alkyl group and (ii) an alkali-soluble structural unit containing an aliphatic cyclic group having both an alcoholic hydroxyl group or an alkyloxy group (a0-1 And a polymer whose alkali solubility is changed by the action of an acid is preferred.

  The above-mentioned “alkaline solubility changes by the action of an acid” means a change in the polymer in the exposed area. If the alkali solubility increases in the exposed area, the exposed area becomes alkali-soluble. On the other hand, if the alkali solubility in the exposed area decreases, the exposed area becomes insoluble in alkali, and can be used as a negative resist.

  The alkali-soluble structural unit (a0-1) containing an aliphatic cyclic group having both (i) a fluorine atom or a fluorinated alkyl group and (ii) an alcoholic hydroxyl group or an alkyloxy group includes the above (i) and What is necessary is just to have the organic group which has both (ii) couple | bonded with the aliphatic cyclic group, and to have this cyclic group in a structural unit.

  Examples of the aliphatic cyclic group include groups in which one or more hydrogen atoms have been removed from a monocyclic or polycyclic hydrocarbon such as cyclopentane, cyclohexane, bicycloalkane, tricycloalkane, and teracycloalkane. it can. More specifically, examples of the polycyclic hydrocarbon include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. Of these, groups derived from cyclopentane, cyclohexane and norbornane by removing a hydrogen atom are preferred industrially.

  Examples of the (i) fluorine atom or fluorinated alkyl group include those in which part or all of the hydrogen atoms of the fluorine atom or lower alkyl group are substituted with fluorine atoms. Specific examples include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, and a nonafluorobutyl group, and industrially preferred are a fluorine atom and a trifluoromethyl group.

  The (ii) alcoholic hydroxyl group or alkyloxy group may be simply a hydroxyl group, an alkyloxy group having a hydroxy group, an alkyloxy group having an alcoholic hydroxyl group such as an alkyloxyalkyl group or an alkyl group, Examples include an alcoholic hydroxyl group-containing alkyloxyalkyl group and an alcoholic hydroxyl group-containing alkyl group. Examples of the alkyloxy group, the alkyloxyalkyl group or the alkyl group include a lower alkyloxy group, a lower alkyloxy lower alkyl group and a lower alkyl group.

  Specific examples of the lower alkyloxy group include a methyloxy group, an ethyloxy group, a propyloxy group, a butyloxy group, and the like. Specific examples of the lower alkyloxy lower alkyl group include a methyloxymethyl group, Examples thereof include an ethyloxymethyl group, a propyloxymethyl group, and a butyloxymethyl group. Specific examples of the lower alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group.

  In addition, in the (ii) alcoholic hydroxyl group-containing alkyloxy group, alcoholic hydroxyl group-containing alkyloxyalkyl group, or alcoholic hydroxyl group-containing alkyl group, the alkyloxy group, the alkyloxyalkyl group, or one of hydrogen atoms of the alkyl group. Some or all of them may be substituted with fluorine atoms. Preferably, in the alcoholic hydroxyl group-containing alkyloxy group or the alcoholic hydroxyl group-containing alkyloxyalkyl group, a part of the hydrogen atoms in the alkyloxy part thereof is substituted with a fluorine atom, in the alcoholic hydroxyl group-containing alkyl group, Examples thereof include those in which part of the hydrogen atoms of the alkyl group is substituted with fluorine atoms, that is, alcoholic hydroxyl group-containing fluoroalkyloxy groups, alcoholic hydroxyl group-containing fluoroalkyloxyalkyl groups, or alcoholic hydroxyl group-containing fluoroalkyl groups.

Examples of the alcoholic hydroxyl group-containing fluoroalkyloxy group include (HO) C (CF ₃ ) ₂ CH ₂ O— group (2-bis (hexafluoromethyl) -2-hydroxy-ethyloxy group, (HO) C (CF ₃ ) ₂ CH ₂ CH ₂ O— group (3-bis (hexafluoromethyl) -3-hydroxy-propyloxy group and the like, and examples of the alcoholic hydroxyl group-containing fluoroalkyloxyalkyl group include (HO) C (CF ₃ ) ₂ CH ₂ O—CH ₂ — group, (HO) C (CF ₃ ) ₂ CH ₂ CH ₂ O—CH ₂ — group, etc., and the alcoholic hydroxyl group-containing fluoroalkyl group includes (HO) C ( CF _{3) 2} CH ₂ - group (2-bis (hexafluoro-methyl) -2-hydroxy - _{ethyl, (HO) C (CF 3} ) 2 CH 2 CH 2 - group (3-bis (hexafluoromethyl) -3-hydroxy-propyl group, etc.).

  These groups (i) and (ii) may be bonded directly to the aliphatic cyclic group. In particular, the structural unit (a0-1) has an alcoholic hydroxyl group-containing fluoroalkyloxy group, an alcoholic hydroxyl group-containing fluoroalkyloxyalkyl group, or an alcoholic hydroxyl group-containing fluoroalkyl group bonded to a norbornene ring, and a double of the norbornene ring A unit represented by the following general formula (56) formed by cleaving the bond is preferable because it is excellent in transparency, alkali solubility and dry etching resistance, and easily available industrially.

In General Formula (56), Z is an oxygen atom, an oxymethylene group (—O (CH ₂ ) —), or a single bond, and n ′ and m ′ are each independently an integer of 1 to 5.

  And the polymer unit used in combination with such (a0-1) unit will not be limited if it is a conventionally well-known thing. When used as the polymer (A-1) whose alkali solubility is increased by the action of a positive acid, the structural unit (a0-2) derived from a (meth) acrylic ester having a known acid dissociable, dissolution inhibiting group Since it is excellent in resolution, it is preferable.

  Examples of the structural unit (a0-2) include structural units derived from tertiary alkyl esters of (meth) acrylic acid such as tert-butyl (meth) acrylate and tert-amyl (meth) acrylate. .

  And a polymer (A) is a polymer (A-2) which further comprises alkalinity solubility by the effect | action of an acid which comprises the fluorinated alkylene structural unit (a0-3) which improves the transparency of a polymer. There may be. By including such a structural unit (a0-3), the transparency is further improved. The structural unit (a0-3) is preferably a unit derived from tetrafluoroethylene.

  The general formulas (57) and (58) representing the polymer (A-1) and the polymer (A-2) are shown below.

In the general formula (57), Z, n ′ and m ′ are the same as those in the general formula (56), R ³ is a hydrogen atom or a methyl group, and R ⁴ is an acid dissociable, dissolution inhibiting group. .

In the general formula (58), Z, n ′, m ′, R ³ and R ⁴ are the same as those in the general formula (57).

  Further, the polymer (A-1) containing the general formula (56) and the polymer (A-2) have different structural formulas, but (i) a fluorine atom or a fluorinated alkyl group and (ii) The following are included in the concept of a polymer comprising an alkali-soluble structural unit (a0-1) containing an aliphatic cyclic group having both alcoholic hydroxyl groups and whose alkali solubility is changed by the action of an acid: It may have a structural unit.

  That is, in the structural unit (a0-1), (i) a fluorine atom or a fluorinated alkyl group and (ii) an alcoholic hydroxyl group are bonded to each other on an aliphatic cyclic group, and the cyclic group constitutes the main chain. It is what. Examples of the (i) fluorine atom or fluorinated alkyl group include the same ones as described above. In addition, (ii) the alcoholic hydroxyl group is simply a hydroxyl group.

The polymer (A) having such a unit is formed by cyclopolymerization of a diene compound having a hydroxyl group and a fluorine atom. As the diene compound, heptadiene that easily forms a polymer having a 5-membered ring or a 6-membered ring excellent in transparency and dry etching resistance is preferable. Further, 1,1,2,3,3-pentafluoro- A polymer formed by cyclopolymerization of 4-trifluoromethyl-4-hydroxy-1,6-heptadiene (CF ₂ ═CFCF ₂ C (CF ₃ ) (OH) CH ₂ CH═CH ₂ ) is the most industrially available. preferable.

  When used as a polymer (A-3) whose alkali solubility is increased by the action of a positive acid, it contains a structural unit (a0-4) in which the hydrogen atom of the alcoholic hydroxyl group is substituted with an acid dissociable, dissolution inhibiting group. A polymer consisting of As the acid dissociable, dissolution inhibiting group, a chain, branched or cyclic alkyloxymethyl group having 1 to 15 carbon atoms is preferred from the viewpoint of acid dissociation, and in particular, a lower alkoxymethyl group such as a methoxymethyl group. It is excellent in resolution and pattern shape. The acid dissociable, dissolution inhibiting group is preferably in the range of 10 to 40%, preferably 15 to 30%, with respect to the total hydroxyl groups, and is excellent in pattern forming ability.

The general formula (59) representing the polymer (A-3) is shown below.

In the general formula (59), ^{R 5} is alkyloxy methyl group hydrogen atom or a C1 to C15, x, y is 10 to 90 mol%, respectively.

  Such a polymer (A) can be synthesized by a known method. Moreover, the polystyrene conversion mass average molecular weight by GPC of resin of this (A) component is although it does not specifically limit, It is 5000-80000, More preferably, it is 8000-50000.

  In addition, the polymer (A) can be composed of one or more kinds of resins, for example, some selected from the above (A-1), (A-2), and (A-3). Two or more kinds of these may be mixed and used, and other well-known resins for photoresist compositions may be mixed and used.

  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 resistance to dry etching. Since an excellent 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 is 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 such as 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。

(Wherein 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).
In addition, when m is 0 in the (a5) unit, it is preferably used as a copolymer having the (a1) unit.

  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. When R ₁₁ is a hydrogen atom, the alkali solubility is highest. 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.

  With respect to X in the general formulas (19) and (20), 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 (19) is an integer of 1-3 for the reason of making it easy to dissociate an acid dissociable dissolution inhibiting group, Preferably it is 1.

  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。）

(In the formula, R ₅ , R ₁₀ , R ₁₂ , and n are the same as described 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.

  In other words, the (a8) is a resin component having at least a structural unit represented by the following general formula (35).

（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。）

(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.)

  As an example of such a resin, a polymer (homopolymer or copolymer) 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, and 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 the α- (hydroxyalkyl) acrylic acid alkyl ester include lower hydroxyalkyl groups such as a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, and a hydroxybutyl group. 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.

  The resin component (a9) is a resin component having at least a structural unit represented by the following general formula (36) or (37).

（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。）

(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 formula 1-8.)

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.

Furthermore, as the resin having the dicarboxylic acid monoester unit, the polymer or copolymer (a9-1) of the dicarboxylic acid monoester monomer, the dicarboxylic acid monoester monomer, and the α- (hydroxyalkyl) acrylic acid described above are used. , A copolymer (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 above-mentioned resins, positive resists using fluororesins and acrylic resins ((a1) to (a4)) are resists that contain a resin that is relatively resistant to immersion. The closer to the limit resolution dimension, the easier the pattern resolution degrades. There is not only one factor that promotes the degradation of resolution, and in order to remove such various factors, 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.

  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.

（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。）

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. -N-propylamine, tripentylamine, diethanolamine, triethanolamine and the like can be mentioned, 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 cyclic fluoroalcohol polymer represented by the following chemical formula (100) is converted into 2-methyl-1-propyl alcohol. After a protective film forming material composition according to the present invention such as “dissolved composition” is uniformly applied, it is cured to form a resist protective film.

  In this way, the substrate on which the resist film covered with the protective film is formed is applied to a refractive index liquid (a liquid having a refractive index larger than the refractive index of air and smaller than the refractive index of the resist film: specialized in the present invention. In this case, it is immersed in pure water, deionized water, or a fluorinated solvent).

  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 refractive index liquid and the protective film and reaches the resist film.

  At this time, the resist film is completely shielded from the refractive index liquid such as pure water by the protective film, and the resist film may be subjected to alteration such as swelling under the invasion of the refractive index liquid. In addition, the components are not eluted in deionized water or a fluorine-based solvent, and optical properties such as the refractive index of the refractive index liquid are not altered.

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, the refractive index is larger than the refractive index of air and smaller than the refractive index of the resist film to be used on the resist film through the protective film during exposure. A liquid having a refractive index (refractive index liquid) is interposed. Examples of such a refractive index liquid include water (pure water, deionized water), a fluorine-based inert liquid, and the like. 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, from the viewpoint of cost, safety, environmental problems and versatility, it is preferable to use water (pure water or deionized water). However, when exposure light having a wavelength of 157 nm is used, the exposure light From the viewpoint of low absorption, it is preferable to use a fluorinated solvent.

  Further, the refractive index of the refractive index 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 liquid immersion state is completed, the substrate is taken out of the refractive index liquid, and the liquid is removed from the substrate.

  Next, PEB (post-exposure heating) is performed on the resist film with a protective film on the exposed resist film, followed by development using an alkaline developer composed of an alkaline aqueous solution. Since the developing solution used in this development processing is alkaline, the protective film is first dissolved and flowed, and then the soluble portion of the resist film is dissolved and flowed. In addition, you may post-bake following a development process. 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, the protective film component dissolved by the developer, and the resist composition. And by drying, the resist pattern by which the resist film was patterned in the shape according to the mask pattern is obtained. As described above, in the present invention, the removal of the protective film and the development of the resist film are realized simultaneously by a single development process.

  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 suitably explaining the present invention, and do not limit the present invention. In the following description, comparative examples are also described together with examples.

( Reference Example 1)
In the present embodiment, by using the coercive Mamorumaku forming material to form a protective film on the substrate was evaluated solubility water resistance and alkaline developer of the protective film.
As a base polymer, a copolymer composed of structural units of cyclic fluoroalcohol represented by the general formula (100) (molecular weight 13800, R ⁵ is all hydrogen atoms, x: y = 50: 50 (moles) %)) Was used. As the solvent, two kinds of 2-methyl-1-propanol and 4-methyl-2-pentanol were used to prepare respective 2% by mass solutions, which were used as protective film-forming compositions.

  The two types of protective film forming compositions were applied onto a semiconductor substrate using a spin coater under a coating condition of 1500 rpm. After the application, the coating was cured by heating at 90 ° C. for 90 seconds to obtain two types of protective films for evaluation. The film thickness of the protective film (film 1) using 2-methyl-1-propanol as a solvent is 50.3 nm, and the film thickness of the protective film using 4-methyl-2-pentanol as a solvent is 28. 0.5 nm.

Evaluation of the protective film is (i) confirmation of surface condition by visual observation, (ii) film loss after rinsing with pure water simulating immersion in liquid (pure water) in immersion exposure process. (Iii) Three items of dissolution rate (film thickness conversion: nm / second) when immersed in an alkali developer (2.38% concentration TMAH) were carried out.
As a result, the surface condition by visual observation was good in both the film 1 and the film 2, the film thickness of the film 1 after water rinsing was 50.8 nm, and the film thickness of the film 2 was 28.8 nm. Remained good. Further, the dissolution rate by the developer was 3 nm / second for the film 1 and 2 nm / second for the film 2.
It was judged that neither the film 1 nor the film 2 was rinsed with pure water for 90 seconds, the surface state was changed, and the film thickness was not affected by water.

( Reference Example 2)
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare Resist Composition 1.
As the resin component, 100 parts by mass of a copolymer composed of structural units represented by the following general formula (102) was used. The ratio of each structural unit 1 and m used for the preparation of the resin component was 1 = 50 mol% and m = 50 mol%.

As the acid generator, 5.0 parts by mass of triphenylsulfonium nonafluorobutanesulfonate was used.
As the organic solvent, a 5.5% strength aqueous solution of ethyl lactate was used.
Further, 0.5 parts by mass of tri-n-octylamine was used as the nitrogen-containing organic compound.

A resist pattern was formed using the 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 on a hot plate at 215 ° C. for 60 seconds to dry. An organic antireflection film having a thickness of 82 nm was formed. Then, the resist composition 1 is applied onto the antireflection film by using a spinner, prebaked on a hot plate at 115 ° C. for 90 seconds, and dried to thereby form a resist having a thickness of 150 nm on the antireflection film. A film was formed.

On the resist film, a copolymer having a cyclic fluoroalcohol represented by the chemical formula (100) as a structural unit (molecular weight 13800, R ⁵ is all hydrogen atoms, x: y = 50: 50 (mol%) )) Is dissolved in 2-methyl-1-propyl alcohol, and a protective film material having a resin concentration of 2.5 wt% is spin-coated, heated at 90 ° C. for 60 seconds, and a film thickness of 72.1 nm is protected. A film was formed.

  Next, using an ArF excimer laser (wavelength 193 nm) with an exposure apparatus NSR-S302 (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 2 minutes while rotating the silicon wafer provided with the resist film after the exposure. In the actual manufacturing process, the process of this part is an exposure process in a completely immersed state, but it is theoretically that the exposure itself in the optical system is completely performed based on the analysis for the previous immersion exposure method. In order to be able to evaluate only the effect of the immersion liquid on the resist film, the resist film is loaded with pure water, which is a refractive index liquid (immersion liquid), after exposure. It is set as the simple structure of letting it.

  After the pure water dropping step, PEB treatment was performed at 115 ° C. for 90 seconds, and then developed with an alkali developer at 23 ° C. for 60 seconds with the protective film remaining. As the alkaline developer, an aqueous 2.38 mass% tetramethylammonium hydroxide solution was used. By this development process, the protective film was completely removed, and the development of the resist film could be realized well.

  When the 300 nm line and space resist pattern obtained in this way was observed with a scanning electron microscope (SEM), this pattern profile was good and no fluctuations were observed. .

(Comparative Example 1)
Although the positive photoresist shown in Reference Example 2 above was used to form a resist pattern with a 300 nm line and space of 1: 1 by the same means except that no protective film was formed, a scanning type When observed with an electron microscope (SEM), the pattern was severely fluctuated and swollen, and the pattern could not be observed.

( Reference Example 3)
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare Resist Composition 1.
As the resin component, 100 parts by mass of a copolymer composed of structural units represented by the following chemical formula (103) was used. The ratio of each structural unit l, m, n used for the preparation of the resin component was 1 = 40 mol%, m = 40 mol%, and n = 20 mol%.

As the acid generator, 53.50 parts by mass of triphenylsulfonium nonafluorobutanesulfonate and 0.75 part by mass of triphenylsulfonium-TF were used.
As the organic solvent, a 6.0% aqueous solution of ethyl lactate was used.
Further, 1.20 parts by mass of tri-2- (2-methoxyethoxy) ethylamine was used as the nitrogen-containing organic compound.

A resist pattern was formed using the 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 on a hot plate at 215 ° C. for 60 seconds to dry. An organic antireflection film having a thickness of 82 nm was formed. Then, the resist composition 1 is applied onto the antireflection film by using a spinner, prebaked on a hot plate at 115 ° C. for 90 seconds, and dried to thereby form a resist having a thickness of 150 nm on the antireflection film. A film was formed.

On the resist film, a copolymer having a cyclic fluoroalcohol represented by the chemical formula (100) as a structural unit (molecular weight 13800, R ⁵ is all hydrogen atoms, x: y = 50: 50 (mol%) )) Is dissolved in 2-methyl-1-propyl alcohol, and a protective film material having a resin concentration of 2.5 wt% is spin-coated, heated at 90 ° C. for 60 seconds, and a film thickness of 72.1 nm is protected. A film was formed.

  Next, using an ArF excimer laser (wavelength 193 nm) with an exposure apparatus NSR-S302 (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 2 minutes while rotating the silicon wafer provided with the resist film after the exposure. In the actual manufacturing process, the process of this part is an exposure process in a completely immersed state, but it is theoretically that the exposure itself in the optical system is completely performed based on the analysis for the previous immersion exposure method. In order to be able to evaluate only the effect of the immersion liquid on the resist film, the resist film is loaded with pure water, which is a refractive index liquid (immersion liquid), after exposure. It is set as the simple structure of letting it.

  After the pure water dropping step, PEB treatment was performed at 115 ° C. for 90 seconds, and then developed with an alkali developer at 23 ° C. for 60 seconds with the protective film remaining. As the alkaline developer, an aqueous 2.38 mass% tetramethylammonium hydroxide solution was used. By this development process, the protective film was completely removed, and the development of the resist film could be realized well.

  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 1 )
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare a resist composition.
As the resin component, 100 parts by mass of a copolymer composed of structural units represented by the following chemical formula (104) was used. The ratio of each structural unit l, m, n used for the preparation of the resin component was 1 = 20 mol%, m = 40 mol%, and n = 40 mol%.

  As the acid generator, 2.0 parts by mass of triphenylsulfonium nonafluorobutanesulfonate and 0.8 parts by mass of tri (tertbutylphenyl) sulfonium trifluoromethanesulfonate were used.

  As the organic solvent, a 7.0% aqueous solution of a mixed solvent of propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate (mixing ratio 6: 4) was used. Further, 0.25 parts by mass of triethanolamine was used as the nitrogen-containing organic compound. Furthermore, 25 parts by mass of γ-butyrolactone was added as an additive.

  A resist pattern was formed using the resist composition produced as described above. First, an organic antireflection film composition “ARC29” (trade name, manufactured by Brewer) was applied onto a silicon wafer using a spinner, and baked on a hot plate at 205 ° C. for 60 seconds to dry. An organic antireflection film having a thickness of 77 nm was formed. Then, the 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 thereby form a resist film having a thickness of 225 nm on the antireflection film. Formed.

On the resist film, a copolymer having a cyclic fluoroalcohol represented by the chemical formula (100) as a structural unit (molecular weight 13800, R ⁵ is all hydrogen atoms, x: y = 50: 50 (mol%) ), And 10 wt% of C ₁₀ F ₂₁ COOH with respect to the copolymer, dissolved in 2-methyl-1-propyl alcohol, and spin-coated with a protective film material having a resin concentration of 2.6% And it heated at 90 degreeC for 60 second, and formed the protective film with a film thickness of 70.0 nm.

  Next, pattern light was irradiated (exposed) using an ArF excimer laser (wavelength: 193 nm) with an exposure apparatus Nikon-S302A (manufactured by Nikon) through the mask pattern. 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. In the actual manufacturing process, the process of this part is an exposure process in a completely immersed state, but it is theoretically that the exposure itself in the optical system is completely performed based on the analysis for the previous immersion exposure method. In order to be able to evaluate only the effect of the immersion liquid on the resist film, the resist film is loaded with pure water, which is a refractive index liquid (immersion liquid), after exposure. It is set as the simple structure of letting it.

  After the pure water dropping step, PEB treatment was performed at 115 ° C. for 90 seconds, and then developed with an alkali developer at 23 ° C. for 60 seconds with the protective film remaining. As the alkaline developer, an aqueous 2.38 mass% tetramethylammonium hydroxide solution was used. By this development process, the protective film was completely removed, and the development of the resist film could be realized well.

  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 a good rectangular shape.

  Moreover, after leaving the substrate on which pure water was dropped after exposure for 60 minutes in an atmosphere having an amine concentration of 2.0 ppb, the same development treatment as described above was performed, and the resist pattern shape was observed in the same manner. There was no significant difference from the pattern profile.

  At this time, the amount of dimensional variation with respect to the post-exposure leaving in an atmosphere with an amine concentration of 2.0 ppb was 0.53 nm / min.

(Example 2 )
A material for forming a protective film is a copolymer having a cyclic fluoroalcohol represented by the chemical formula (100) as a structural unit (molecular weight is 13800, R ⁵ is all hydrogen atoms, and x: y = 50: 50 (moles). And 10 wt% of the compound represented by the following chemical formula (105) with respect to the copolymer, and dissolved in 2-methyl-1-propyl alcohol to make the resin concentration 2.6%. The resist pattern shape was observed in the same manner as in Example 1 above.

  As a result, the resist pattern having a 130 nm line and space of 1: 1 was a good rectangular shape regardless of whether or not it was left for 60 minutes.

(Example 3 )
A material for forming a protective film is a copolymer having a cyclic fluoroalcohol represented by the chemical formula (100) as a structural unit (molecular weight is 13800, R ⁵ is all hydrogen atoms, and x: y = 50: 50 (moles). And 10 wt% of (C ₄ F ₉ SO ₂ ) ₂ NH with respect to the copolymer was dissolved in 2-methyl-1-propyl alcohol to give a resin concentration of 2.6%. Except for the above, the resist pattern shape was observed in the same manner as in Example 1 .

  As a result, the resist pattern having a 130 nm line and space of 1: 1 was a good rectangular shape regardless of whether or not it was left for 60 minutes.

(Example 4 )
A material for forming a protective film is a copolymer having a cyclic fluoroalcohol represented by the chemical formula (100) as a structural unit (molecular weight is 13800, R ⁵ is all hydrogen atoms, and x: y = 50: 50 (moles). And 10 wt% C ₁₀ F ₂₁ COOH with respect to the copolymer, and further 0.1 wt% of the compound represented by the chemical formula (105) with respect to the copolymer, Except for dissolving in methyl-1-propyl alcohol and adjusting the resin concentration to 2.6%, exposure was performed in exactly the same manner as in Example 1 above, and development was performed immediately after dropping pure water. The resist pattern shape was observed. As a result, the resist pattern having a 130 nm line and space of 1: 1 was a good rectangular shape, and no decrease in film thickness was observed.

  Moreover, after leaving the substrate on which pure water was dropped after exposure for 65 minutes in an atmosphere with an amine concentration of 2.0 ppb, the same development treatment as described above was performed, and the resist pattern shape was observed in the same manner. There was no significant difference from the pattern profile.

(Example 5 )
A material for forming a protective film is a copolymer having a cyclic fluoroalcohol represented by the chemical formula (100) as a structural unit (molecular weight is 13800, R ⁵ is all hydrogen atoms, and x: y = 50: 50 (moles). And 10 wt% C ₁₀ F ₂₁ COOH with respect to the copolymer, and 0.4 wt% of the compound represented by the chemical formula (105) with respect to the copolymer, Except for dissolving in methyl-1-propyl alcohol and adjusting the resin concentration to 2.6%, exposure was performed in exactly the same manner as in Example 1 above, and development was performed immediately after dropping pure water. The resist pattern shape was observed. As a result, the resist pattern having a 130 nm line and space of 1: 1 was a good rectangular shape, and no decrease in film thickness was observed.

  Moreover, after leaving the substrate on which pure water was dropped after exposure for 65 minutes in an atmosphere with an amine concentration of 2.0 ppb, the same development treatment as described above was performed, and the resist pattern shape was observed in the same manner. There was no significant difference from the pattern profile.

(Example 6 )
A material for forming a protective film is a copolymer having a cyclic fluoroalcohol represented by the chemical formula (100) as a structural unit (molecular weight is 13800, R ⁵ is all hydrogen atoms, and x: y = 50: 50 (moles). And 10 wt% C ₁₀ F ₂₁ COOH with respect to the copolymer, and 0.8 wt% of the compound represented by the chemical formula (105) with respect to the copolymer, This resist was subjected to development treatment immediately after the exposure and dropping of pure water were performed in exactly the same manner as in Example 1 except that it was dissolved in methyl-1-propyl alcohol and the resin concentration was 2.6%. The pattern shape was observed. As a result, the resist pattern having a 130 nm line and space of 1: 1 was a good rectangular shape, and no decrease in film thickness was observed.

  Moreover, after leaving the substrate on which pure water was dropped after exposure for 65 minutes in an atmosphere with an amine concentration of 2.0 ppb, the same development treatment as described above was performed, and the resist pattern shape was observed in the same manner. There was no significant difference from the pattern profile.

(Example 7 )
The following resin component, acid generator, and nitrogen-containing organic compound were uniformly dissolved in an organic solvent to prepare a resist composition.

  As the resin component, 100 parts by mass of a copolymer composed of structural units represented by the following chemical formula (106) was used. The ratio of each structural unit l, m, n used for the preparation of the resin component was 1 = 50 mol%, m = 30 mol%, and n = 20 mol%.

  As the acid generator, 3.5 parts by mass of triphenylsulfonium nonafluorobutanesulfonate and 1.0 part by mass of diphenylmonomethylphenylsulfonium trifluoromethanesulfonate were used. As the organic solvent, a 7.0% aqueous solution of a mixed solvent of ethyl lactate and propylene glycol monomethyl ether acetate (mixing ratio 4: 6) 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 resist composition produced as described above. First, an organic antireflection film composition “ARC29” (trade name, manufactured by Brewer) was applied onto a silicon wafer using a spinner, and baked on a hot plate at 205 ° C. for 60 seconds to dry. An organic antireflection film having a thickness of 77 nm was formed. Then, the 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 thereby form a resist film having a thickness of 225 nm on the antireflection film. Formed. This was designated as evaluation substrate 1.

On the resist film on the substrate for evaluation 1, a copolymer having a cyclic fluoroalcohol represented by the chemical formula (100) as a structural unit (molecular weight is 13800, R5 is all hydrogen atoms, x: y = 50 : 50 (mol%)), and 10 wt% of C ₁₀ F ₂₁ COOH with respect to the copolymer was dissolved in 2-methyl-1-propyl alcohol to give a resin concentration of 2.6% A film material was spin-coated and heated at 90 ° C. for 60 seconds to form a protective film having a thickness of 70.0 nm. This was designated as evaluation substrate 2.

  Next, the evaluation substrates 1 and 2 were irradiated (exposed) with pattern light using an ArF excimer laser (wavelength: 193 nm) by an exposure apparatus Nikon-S302A (manufactured by Nikon) through a mask pattern. Each substrate was extracted with 35 mL of pure water at room temperature for 5 minutes.

  After the extract was concentrated (50-fold concentration), the extracted amine concentration and the extracted cation and anion concentrations that were thought to be due to the generation of acid were quantified by capillary electrophoresis-mass spectrometry. The results are shown in Table 1 below.

（単位：ｎｇ／ｃｍ^２）
（評価基板２における各数値は、結果が本分析法による定量限界以下の数値であったことを示す）

(Unit: ng / cm ² )
(Each numerical value on the evaluation board 2 indicates that the result was a numerical value below the limit of quantification by this analysis method)

  From this result, it was found that, in the immersion exposure process, it is clear that the elution amount of the resist component into the immersion medium can be suppressed by providing the protective film component of the present invention.

  As described above, according to the present invention, any conventional resist composition can be used to form a resist film, and any immersion liquid can be used in the immersion exposure process. Even when using, the resist pattern has a T-top shape and the surface of the resist pattern is not rough, the sensitivity is high, the resist pattern profile shape is excellent, the depth of focus, the exposure margin, and the reserve A highly accurate resist pattern with good temporal stability can be obtained. Therefore, when the protective film of the present invention is used, it is possible to effectively form a resist pattern using an immersion exposure process.

Claims (7)

A resist pattern forming method using an immersion exposure process,
A resist film is formed on the substrate,
A protective film is formed on the resist film using a material for forming a protective film that is transparent to exposure light, has no substantial compatibility with water, and is soluble in alkali. And
An immersion exposure liquid having a predetermined thickness is directly disposed on at least the protective film of the substrate on which the resist film and the protective film are laminated,
The resist film is selectively irradiated with light through the immersion exposure liquid and the protective film, and heat treatment is performed as necessary.
At the same time the protective film is removed by development processing and the resist film and the protective film using an alkaline developer, saw including obtaining a resist pattern,
A method for forming a resist pattern, wherein the protective film-forming material contains a fluorocarbon compound . 2. The resist pattern forming method according to claim 1, wherein the protective film forming material is a composition further containing a fluoropolymer and a solvent. The fluoropolymer has the following general formula (100)

(In the formula, R ⁵ is a hydrogen atom or a chain, branched, or cyclic C1-C15 alkyloxyalkyl group, and x and y are each 10 to 90 mol%.)
The resist pattern forming method according to claim 2, wherein the polymer has a cyclic fluoroalcohol represented by the structural unit as a structural unit. 4. The resist pattern formation according to claim 3, wherein the protective film forming material is a composition in which a polymer having the cyclic fluoroalcohol as a structural unit and the fluorocarbon compound are dissolved in an alcohol solvent. Method. A resist pattern forming method according to claim 1, any one of 4, wherein the fluorocarbon compound is a fluorocarbon compound represented by any one of the following formulas (201) to (204).
(C _n F _{2n + 1} SO ₂ ) ₂ NH (201)
(In the formula, n is an integer of 1 to 5.)
C _m F _{2m + 1} COOH (202)
(In the formula, m is an integer of 10 to 15.)

(In the formula, o is an integer of 2 to 3.)

(In the formula, p is an integer of 2 to 3, Rf is an alkyl group partially or entirely substituted with a fluorine atom, and may be substituted with a hydroxyl group, an alkoxy group, a carboxyl group, or an amino group. Good.) The resist pattern forming method according to any one of claims 1 to 5, characterized in that the immersion exposure liquid is water substantially made of pure or deionized water or fluorinated solvent. The exposure light, the resist pattern forming method according to any one of claims 1 to 6, characterized in that the light of 157nm or 193nm and the main wavelength.