JP2007148167A - Material for protective film formation for liquid immersion exposure process, and method for photoresist pattern formation using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material for protective film formation for a liquid immersion exposure process and a method for photoresist pattern formation using the material by which a protective film can be peeled off with a small amount of a removing liquid for a protective film in a step of removing the protective film after a step of liquid immersion exposure in a liquid immersion exposure process, and thereby, the production cost is reduced and the throughput of products is improved. <P>SOLUTION: The material for protective film formation for a liquid immersion process is a material to form a protective film layered on a photoresist film in a liquid immersion exposure process and contains a cyclic fluoroalkyl polyether having a mass average molecular weight (Mw) of 5,000 to 200,000 and a fluoro organic solvent. The method for forming a photoresist pattern is carried out by using the above material for forming a protective film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a protective film forming material applied to a liquid immersion lithography process and a photoresist pattern forming method using the same. In particular, the present invention provides immersion exposure by reducing the amount of the protective film removal liquid used to remove the protective film from the photoresist film after the immersion exposure process, thereby reducing manufacturing costs and improving product throughput. The present invention relates to a process protective film forming material and a photoresist pattern forming method using the same.

  Photolithographic methods are frequently used to manufacture fine structures in various electronic devices such as semiconductor devices and liquid crystal devices. In recent years, the progress of high integration and miniaturization of semiconductor devices has been remarkable, and further miniaturization is required in forming a photoresist pattern in a photolithography process.

  At present, it is possible to form a fine photoresist pattern having a line width of about 90 nm in, for example, the most advanced region by photolithography, but further research and development of finer pattern formation with a line width of 65 nm has been made. Has been done.

In order to achieve such a finer pattern formation, generally, countermeasures using an exposure apparatus or a photoresist material can be considered. Countermeasures by exposure equipment include shortening the wavelength of light sources such as F ₂ excimer laser, EUV (extreme ultraviolet light), electron beam, X-ray, soft X-ray, and increasing the numerical aperture (NA) of the lens. Measures are listed. Measures using a photoresist material include a method of developing a new material corresponding to the shortening of the exposure light wavelength.

  However, shortening the wavelength of the light source requires an expensive new exposure apparatus. In addition, when the NA is increased, the resolution and the depth of focus are in a trade-off relationship. Therefore, there is a problem that the depth of focus decreases even if the resolution is increased. In addition, the development of a new photoresist material corresponding to the shortening of the wavelength is costly.

  Recently, as a photolithography technique capable of solving such a problem, a liquid immersion lithography method has been reported (for example, see Non-Patent Documents 1 to 3). In this method, during exposure, the photoresist film is exposed by interposing an immersion medium having a predetermined thickness on at least the photoresist film in an exposure optical path between the exposure apparatus (lens) and the photoresist film on the substrate. A photoresist pattern is formed. In this immersion exposure method, an exposure optical path space, which has conventionally been an inert gas such as air or nitrogen, has a refractive index that is larger than the refractive index of these spaces (gas) and smaller than the refractive index of the photoresist film ( n) by substituting with an immersion medium (for example, pure water, fluorine-based inert liquid, etc.), even if a light source having the same exposure wavelength is used, exposure light with a shorter wavelength or high NA lens is used. Similar to the case where it is used, there is an advantage that high resolution is achieved and the depth of focus does not decrease. In addition, currently used photoresist materials can be used.

  By using such an immersion exposure process, a photoresist pattern of a lens that is mounted on an existing exposure apparatus, an exposure light wavelength, a low-cost, higher resolution, and excellent depth of focus. Because it can be formed, it has attracted much attention.

  However, in the immersion exposure process, since exposure is performed with an immersion medium interposed between the exposure lens and the photoresist film, it is natural that the photoresist film is altered by the immersion medium, from the photoresist film. There is a concern about the refractive index fluctuation accompanying the alteration of the immersion medium itself due to the elution component.

  Therefore, in order to cope with this, by forming a protective film on the photoresist film and interposing an immersion medium on this protective film, the refractive index associated with the alteration of the immersion film to the photoresist film and the alteration of the immersion medium. A technique aimed at simultaneously preventing fluctuations has been proposed (see, for example, Patent Document 1).

  The above-mentioned patent document 1 is a technique proposed by the present applicant and protects a protective film using a fluorine-containing resin, specifically, a mixed resin of a cyclic perfluoroalkyl polyether and a chain perfluoroalkyl polyether. A film was formed, and it was confirmed that this protective film produced a photoresist profile with a good profile having a rectangular cross-sectional shape in immersion exposure.

"Journal of Vacuum Science & Technology B" (USA), 1999, Vol. 17, No. 6, pages 3306-3309 "Journal of Vacuum Science & Technology B" (USA), 2001, Vol. 19, No. 6, pp. 2353-2356 "Proceedings of SPIE", (USA), 2002, 4691, pp. 459-465. International Publication No. 2004/074937 Pamphlet

  The protective film described in Patent Document 1 uses a pseudo immersion exposure experiment in a state in which the protective film is formed on a photoresist film and then immersed in an immersion medium after exposure, or a prism. The evaluation was performed by immersion exposure using a simple method, and in the evaluation of such an immersion exposure process, the effect could be sufficiently exhibited. However, in an actual mass production process, a local immersion exposure method in which an immersion medium is filled only between an exposure lens that scans at a predetermined speed or more and a substrate has come to be adopted.

  In the local immersion exposure method, for example, a substrate provided with a protective film / photoresist layer is placed on a wafer stage, an exposure lens is arranged above the protective film at a predetermined interval, and the wafer stage is scanned at high speed. While being moved, the immersion medium is continuously dropped onto the protective film from one nozzle, and at the same time, the liquid is exposed while being sucked from the other nozzle.

  In such a local liquid immersion exposure method, water that continues to drip remains as fine water droplets on the surface of the protective film. As the water droplet diameter decreases, the water droplet internal pressure increases exponentially, and the water pressure applied to the protective film becomes larger than the order that has been regarded as a problem in the conventional evaluation methods. If there is a non-uniform portion of the surface of the protective film where microdroplets with extremely high internal pressure remain in this way, droplets penetrate into the protective film through this portion, and this causes pattern defects ( “Watermark defects”). In Patent Document 1, the above-described conventional evaluation method is used, and with such an immersion exposure method, a photoresist pattern having a good profile can be obtained and has an excellent effect, but at a predetermined speed or more in actual mass production. The above point in the local immersion exposure using a scanning lens has not been studied.

  In order to cope with this, the applicant has previously used a cyclic fluoroalkyl polyether as a protective film forming material to further uniform the surface of the protective film and improve the water repellency of the protective film. A technique for solving the above problem has been proposed (Japanese Patent Application No. 2005-144270). The polymer used in this application was a polymer having a mass average molecular weight (Mw) of about 250,000.

  The cyclic fluoroalkyl polyether used in the above-mentioned application can use commercially available products and has the advantage of versatility, but these commercially available products are polymer bodies as described above. In order to remove the protective film using such a high molecular weight polymer from the photoresist film after the immersion exposure process with a protective film removing liquid such as a fluorine-based organic solvent, a corresponding peeling time is required. Furthermore, since the fluorine-based organic solvent (the protective film removing liquid) is expensive, it has been desired to reduce the production cost by reducing the amount of the protective film removing liquid used.

  The inventors of the present invention have used a cyclic fluoroalkyl polyether having a mass average molecular weight (Mw) of a low molecular weight within a specific range, so that the protective film using the low molecular weight polymer is a fluorine-based organic material. Since it exhibits extremely high solubility in the protective film removal liquid consisting of a solvent, the protective film can be removed in a short time with a small amount of the protective film removal liquid, and the characteristics of the protective film may be impaired. I found that there was no, and completed this application.

  That is, the present invention is a material for forming a protective film laminated on a photoresist film in an immersion exposure process, and a cyclic fluoroalkyl polyether having a mass average molecular weight (Mw) of 5,000 to 200,000 And a protective film forming material for an immersion exposure process, comprising a fluorine-based organic solvent.

  The present invention is also a method for forming a photoresist pattern using an immersion exposure process, wherein a photoresist film is provided on a substrate, and a protective film is formed on the photoresist film using the protective film-forming material. An immersion medium is disposed on at least the protective film of the substrate, and the photoresist film is selectively exposed by an exposure device through the immersion medium and the protective film, and then the protective film is removed from the protective film. There is provided a method for forming a photoresist pattern, wherein the photoresist film is peeled from the photoresist film and then developed, and then the photoresist film is developed to obtain a photoresist pattern.

  According to the present invention, after the immersion exposure process, an immersion exposure process that reduces the use amount of the protective film removal liquid used for peeling the protective film from the photoresist film, reduces the manufacturing cost, and improves the product throughput. A protective film forming material and a photoresist pattern forming method using the same are provided.

  The material for forming a protective film of the present invention can further homogenize the surface of the protective film, and can improve the water repellency characteristics between the minute water droplets and the protective film. Generation of photoresist pattern defects (“water mark defects”) that are likely to occur in the immersion exposure process can be suppressed.

  In addition, the present invention is widely applicable to photoresists currently on the market and is versatile. In addition to this, it is a basic characteristic required as a protective film, which is highly resistant to an immersion medium, and is provided in a lower layer. Low compatibility with the photoresist film, prevention of elution of components from the immersion medium to the photoresist film, prevention of elution of components from the photoresist film to the immersion medium, suppression of gas permeation of the protective film, etc. A material for forming a protective film is also provided. By applying the protective film forming material of the present invention to the immersion exposure process, it becomes possible to form a very fine photoresist pattern exceeding the resolution when lithography is performed using a conventional photoresist material and exposure apparatus. .

  Hereinafter, the present invention will be described in detail.

  The protective film-forming material according to the present invention contains a cyclic fluoroalkyl polyether having a mass average molecular weight (Mw) of 5,000 to 200,000 and a fluorine-based organic solvent. In the present invention, no chain fluoroalkyl polyether is contained.

  As the cyclic fluoroalkyl polyether, a polymer represented by the following formula (I) is preferably used.

In the above formula (I), Rf ₁ is a fluorine atom, a fluoroalkyl group having 1 to 5 carbon atoms or a fluoroalkyl ether group, and Rf ₂ may or may not be present. Is a fluoroalkyl group having 1 to 5 carbon atoms or a fluoroalkyl ether group, and X is —O— or — (CF ₂ ) _q — (where q represents the number of 0 or 1). Y is —O— or — (CF ₂ ) _v — (wherein v is a number of 1 or more), Z is — (O) _s — (wherein s is a number of 0 or 1). P, t and u each represent a number of 0 to 3, and m represents a repeating unit (provided that the polymer Mw satisfies 5,000 to 200,000).

  The polymer of the present invention has a mass average molecular weight of 5,000 to 200,000, preferably 10,000 to 100,000. By using a low molecular weight substance having a molecular weight in the above range, it is possible to efficiently remove the protective film even if the amount of the protective film removal solution used is small, thereby reducing manufacturing costs and improving product throughput. Can be planned.

  Among these, polymers having structural units represented by the following formulas (II) and (III) are preferable.

  In formula (II), p, t and u each represent a number of 0 to 3, r represents a number of 1 to 3, m represents a repeating unit (provided that Mw of the polymer satisfies 5,000 to 200,000) Within the range to be).

  As the polymer having the structural unit represented by the formula (II), a product obtained by reducing the molecular weight of a product marketed as “CYTOP” series (Asahi Glass Co., Ltd.) can be used. It is not limited.

In the formula (III), Rf ₁ is a fluorine atom, a fluoroalkyl group having 1 to 5 carbon atoms or a fluoroalkyl ether group, and Rf ₂ may or may not be present. Is a fluoroalkyl group or fluoroalkyl ether group having 1 to 5 carbon atoms, t is a number from 0 to 3, m is a repeating unit (however, the polymer Mw is 5,000 to 200, 000).

  As the polymer having the structural unit represented by the formula (III), a product obtained by reducing the molecular weight of a product marketed as “Teflon AF1600”, “Teflon AF2400” (all of which are manufactured by DuPont) or the like is used. However, it is not limited to this.

  In the present invention, it is preferable to subject the terminal of the polymer having the structural units represented by the above formulas (I), (II) and (III) to fluoromethylation. By performing such terminal fluoromethylation treatment, the solubility of the protective film in the protective film removing solvent is dramatically improved.

  Any fluorine-based organic solvent may be used as long as it can dissolve the cyclic fluoroalkyl polyether used in the present invention. Specifically, perfluoroalkanes or perfluorocycloalkanes such as perfluorohexane and perfluoroheptane, perfluoroalkenes in which some of the double bonds remain, perfluorotetrahydrofuran, perfluoro (2-butyl) And fluorinated organic solvents such as perfluoro cyclic ether such as tetrahydrofuran), perfluorotributylamine, perfluorotetrapentylamine, and perfluorotetrahexylamine. These may be used singly or in combination of two or more. Further, other organic solvents having compatibility and surfactants may be added as additives to improve the solubility.

  When the above polymer is dissolved in the fluorine-based organic solvent, it is preferable to dissolve the polymer so that its concentration is about 0.1 to 30% by mass, particularly 0.5 to 10% by mass, from the viewpoint of applicability and the like. .

  Furthermore, in the present invention, it is preferable to use only one kind of polymer as the cyclic fluoroalkyl polyether. In this way, if a protective film using a single kind of cyclic fluoroalkyl polyether, the surface of the protective film becomes more uniform, and the penetration of droplets into the protective film can be more effectively suppressed. Water mark defects occurring in the photoresist pattern can be more effectively suppressed.

  The protective film-forming material in which the cyclic fluoroalkyl polyether is dissolved in a fluorine-based organic solvent has various additives such as preservatives, stabilizers, and surfactants, as long as the effects of the present invention are not impaired. May be blended.

  Production of the material for forming a protective film of the present invention can be carried out by a conventional method.

  The material for forming a protective film of the present invention is used in an immersion exposure process, but is particularly suitable for local immersion exposure. In the immersion exposure process, the refractive index of the photoresist film provided on the substrate is larger than the refractive index of air and smaller than the refractive index of the photoresist film on at least the photoresist film in the path through which the exposure light reaches the photoresist film. A method for improving the resolution of a photoresist pattern by exposing a photoresist film in a state where a liquid (immersion medium) having a predetermined thickness is interposed.

  As the immersion medium, water (pure water, deionized water, etc.), a fluorinated solvent, or the like is preferably used. Among these, water is regarded as the most preferable material from the viewpoints of optical requirements for immersion exposure (eg, good refractive index characteristics), ease of handling, and lack of environmental pollution.

The material for forming a protective film according to the present invention can be directly formed on a photoresist film and does not hinder pattern exposure. In addition, since it is insoluble in water, it is possible to obtain a photoresist pattern with good characteristics by using water as an immersion medium and sufficiently protecting photoresist films of various compositions during the immersion exposure process. . On the other hand, when exposure light having a wavelength of 157 nm (F ₂ excimer laser or the like) is used, a fluorine-based medium is considered to be promising as an immersion medium from the viewpoint of reducing the absorption of exposure light into the immersion medium. Even when such a fluorinated solvent is used, as in the case of the above-described water, the photoresist film can be sufficiently protected while being subjected to the immersion exposure process, and a photoresist pattern with good characteristics can be obtained. .

  The liquid immersion exposure method using the protective film forming material of the present invention, in particular, the photoresist pattern forming method by the local liquid immersion exposure method is performed as follows, for example.

  First, a conventional photoresist composition is applied onto a substrate such as a silicon wafer with a spinner or the like and then pre-baked (PAB treatment) to form a photoresist film. Note that a photoresist film may be formed after an organic or inorganic antireflection film (lower antireflection film) is provided on the substrate.

  The photoresist composition is not particularly limited, and any photoresist that can be developed with an alkaline aqueous solution, including negative and positive photoresists, can be used. Such photoresists include (i) a positive photoresist containing a naphthoquinonediazide compound and a novolak resin, (ii) a compound that generates an acid upon exposure, a compound that decomposes by an acid and increases its solubility in an aqueous alkali solution, and an alkali-soluble compound. A positive photoresist containing a resin, (iii) a compound that generates an acid upon exposure, a positive photoresist containing an alkali-soluble resin having a group that decomposes with acid and increases solubility in an alkaline aqueous solution, and (iv) by light Examples thereof include, but are not limited to, a negative photoresist containing a compound that generates an acid or a radical, a crosslinking agent, and an alkali-soluble resin.

  Next, after the protective film forming material according to the present invention is uniformly applied to the surface of the photoresist film, the protective film is formed by curing by heating or the like.

  The substrate on which the photoresist film and the protective film are laminated is placed on the local immersion exposure wafer stage.

  An exposure apparatus (lens) is arranged above the protective film with a predetermined distance from the protective film.

  Next, the photoresist layer is selectively exposed through the protective film while continuously dropping the immersion medium onto the protective film from the nozzle while moving the wafer stage at a high speed.

  In this local liquid immersion exposure, the immersion medium is dropped on the protective film and moves at a predetermined speed or more, so that extremely fine water droplets remain on the surface of the protective film.

  In the present invention, since the cyclic fluoroalkyl polyether is used alone as the protective film, the surface of the protective film is more uniform (such as water repellency uniformity) than in the case of a mixed resin with a chain perfluoroalkyl polyether. In addition, the water repellency of the protective film could be improved.

  Next, the protective film / photoresist film on the substrate in the continuous dropping state is selectively exposed through a mask pattern. Therefore, at this time, the exposure light passes through the immersion medium and the protective film and reaches the photoresist film.

  At this time, the photoresist film is shielded from the immersion medium by the protective film, and is subjected to alteration such as swelling due to the invasion of the immersion medium, or conversely, the components are eluted into the immersion medium to be immersed in the immersion medium. It is possible to prevent alteration of optical characteristics such as the refractive index of the medium itself. Further, since the protective film maintains uniformity as described above and has high water repellency, the fine droplets do not remain on the upper surface of the protective film.

  The exposure light is not particularly limited, and can be performed using radiation that is widely used in the current photolithographic field, such as ArF excimer laser, KrF excimer laser, and VUV (vacuum ultraviolet).

The immersion medium is not particularly limited as long as it is a liquid having a refractive index larger than that of air and smaller than that of the photoresist film used. Examples of such an immersion medium include water (pure water, deionized water), a fluorine-based inert liquid, and the like, but an immersion medium having a high refractive index characteristic that is expected to be developed in the near future can also be used. is there. Specific examples of the fluorinated inert liquid include fluorinated 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 main components. Liquid. Among these, from the viewpoint of cost, safety, environmental problems and versatility, it is preferable to use water (pure water, deionized water), but exposure light having a wavelength of 157 nm (for example, F ₂ excimer laser) is used. When used, it is preferable to use a fluorinated solvent from the viewpoint of low exposure light absorption.

  When the immersion exposure process by the dropping is completed, the substrate is taken out of the exposure stage, the liquid is removed from the substrate, and then the protective film is brought into contact with the protective film removing liquid and peeled off.

  As the protective film removal solution, a fluorine-based organic solvent in which the cyclic fluoroalkyl polyether is dissolved can be used as it is. However, from the viewpoint of drying properties after washing, it is preferable to use a solvent having a boiling point of about 150 ° C. or less. From this viewpoint, perfluoro (2-butyltetrahydrofuran) (boiling point: 102 ° C.) is preferable. In the present invention, as the cyclic fluoroalkyl polyether having a specific low molecular weight range is used, the dissolution rate of the protective film can be greatly improved as shown in the examples described later. The contact time with the liquid can be greatly reduced, and the throughput of the product can be greatly improved without affecting the pattern forming ability.

  Next, PEB (post-exposure heating) is performed on the exposed photoresist film, followed by development using an alkali developer. As the alkali developer, a conventional one can be arbitrarily used. For example, an aqueous solution of tetramethylammonium hydroxide (TMAH) is preferably used, but is not limited thereto. Subsequently, rinsing is performed using pure water or the like. In this water rinse, for example, water is dropped or sprayed on the surface of the substrate while rotating the substrate to wash away the developer on the substrate and the photoresist composition dissolved by the developer. Then, by performing drying, a photoresist pattern in which the photoresist film is patterned into a shape corresponding to the mask pattern is obtained.

  As described above, in the present invention, the polymer used for the protective film is a specific low molecular region cyclic fluoroalkyl polyether, so that the protective film can be removed in a short time, thereby reducing the manufacturing cost and the product. Throughput can be increased. In addition, since the protective film was uniform and improved water repellency, the immersion medium did not bleed into the protective film even during local exposure immersion, resulting in the occurrence of water mark defects and the origin of this. It is possible to prevent pattern defects that occur. Note that the protective film formed of the protective film forming material of the present invention is excellent in water repellency, so that the immersion medium is well separated after the exposure is completed, and the adhesion amount of the immersion medium is reduced.

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

  According to the present invention, it is widely applicable to currently marketed photoresists (especially, ArF photoresists), is excellent in versatility, and has high resistance to immersion media, which is a basic characteristic required as a protective film. Low compatibility with the photoresist film provided in the lower layer, prevention of elution of components from the immersion medium to the photoresist film, prevention of elution of components from the photoresist film to the immersion medium, suppression of gas permeation of the protective film, A material for forming a protective film having the above characteristics was obtained.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
<Material for protective film formation>
A solution comprising a cyclic fluoroalkyl polyether having a structural formula represented by the following formula (II-a) and having different mass average molecular weights (Mw) as shown in the following Table 1 and dissolved in perfluorotributylamine (Solid content concentration of 1.0% by mass) was used as Samples 1 to 5 and Comparative Sample 1.

Example 1
[Protection film dissolution rate]
Samples 1 to 5 and Comparative Sample 1 shown in Table 1 below were each applied onto a substrate by a spinner and then soft baked at 90 ° C. for 60 seconds to form a 28 nm thick protective film.

  Next, perfluoro (2-butyltetrahydrofuran) was dropped as a protective film removal solution on this protective film, and the rate at which the protective film was dissolved was measured. Further, the protective film removal property was evaluated from the viewpoint of throughput from the dissolution rate of the protective film. The results are shown in Table 1. In Table 1, in the “Protective film removal” evaluation column, “◯” indicates that the protective film dissolution rate is excellent and the protective film removal effect is sufficiently excellent from the viewpoint of throughput, and “Δ” indicates that from the viewpoint of throughput. The effect of removing the protective film is improved as compared with the conventional product, and “x” indicates the level that is required to improve the throughput as in the conventional product.

(Example 2)
The water repellency and scan followability of Samples 1 to 5 and Comparative Sample 1 shown in Table 1 below were evaluated by measuring the falling angle and contact angle.

[Falling angle]
After 50 μL of each of Samples 1 to 5 and Comparative Sample 1 shown in Table 1 below was dropped on the substrate, the substrate was ramped at a rate of 1 ′ per second, and the droplets on the substrate dropped. The inclination angle (falling angle) of the substrate at the time of starting to move was measured. The drop angle was measured using a drop angle meter “Drop Master 700” (manufactured by Kyowa Interface Science Co., Ltd.). The results are shown in Table 1.

[Contact angle]
2 μL of each of Samples 1 to 5 and Comparative Sample 1 shown in Table 1 below were dropped on the substrate, and the contact angle between the droplet and the substrate was measured. The results are shown in Table 1.

  As is clear from the results in Table 1, the protective film containing the polymer used in the present invention has a high dissolution rate and excellent solubility in the removal solution. That is, it is possible to dissolve and remove the protective film with a smaller amount of removal solution than in the prior art, thereby reducing the manufacturing cost and improving the throughput. In addition, it is excellent in water repellency and scan followability, and is suitable for a local liquid immersion exposure process.

(Example 3)
[Pseudo immersion exposure evaluation using ArF dry exposure machine (= non-immersion exposure machine)]
An organic antireflective coating composition “ARC29” (manufactured by Brewer) is applied onto a silicon wafer using a spinner, baked on a hot plate at 225 ° C. for 60 seconds, and dried to prevent reflection of 77 nm in thickness. A film was formed. Then, a positive photoresist for ArF (“TARF-P6111ME”; manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied on the antireflection film, prebaked on a hot plate at 130 ° C. for 90 seconds, and dried. As a result, a photoresist film having a film thickness of 225 nm was formed on the antireflection film.

  On the photoresist film, each of the above samples 1 to 5 (adjusted to a solid content concentration of 1.1% by mass) was applied and heated at 90 ° C. for 60 seconds to form a protective film having a thickness of 28 nm.

  Next, it exposed using the exposure machine for ArF ("NSR-S302A"; Nikon Corporation make). After the exposure, pure water was dropped for 1 minute and placed in a simulated immersion environment. Next, after PEB treatment was performed at 130 ° C. for 90 seconds, the protective film was peeled off by contacting with perfluoro (2-butyltetrahydrofuran) for 30 seconds. Thereafter, development was further performed at 23 ° C. for 60 seconds using a 2.38 mass% TMAH aqueous solution.

  The 130 nm line and space pattern (1: 1) thus obtained was observed with a scanning electron microscope (SEM), and a good shape line and space pattern could be formed.

Claims (8)

  Cyclic fluoroalkyl polyether and fluorine-based organic solvent having a mass average molecular weight (Mw) of 5,000 to 200,000 for forming a protective film laminated on a photoresist film in an immersion exposure process A material for forming a protective film for an immersion exposure process, comprising: The material for forming a protective film for an immersion exposure process according to claim 1, wherein the cyclic fluoroalkyl polyether is a polymer having a structural unit represented by the following formula (I).

[In formula (I), when Rf ₁ is a fluorine atom or a fluoroalkyl group or a fluoroalkyl ether group having 1 to 5 carbon atoms, which may or may not have even Rf ₂ are present, it is present ( Is a fluoroalkyl group having 1 to 5 carbon atoms or a fluoroalkyl ether group, and X is —O— or — (CF ₂ ) _q — (where q represents the number of 0 or 1). Y is —O— or — (CF ₂ ) _v — (wherein v is a number of 1 or more), Z is — (O) _s — (wherein s is a number of 0 or 1). P, t and u each represent a number of 0 to 3, and m represents a repeating unit (provided that the polymer Mw satisfies 5,000 to 200,000). ]   The material for forming a protective film for an immersion exposure process according to claim 2, wherein the terminal of the polymer having the structural unit represented by the formula (I) is fluoromethylated. The material for forming a protective film for an immersion exposure process according to any one of claims 1 to 3, wherein the cyclic fluoroalkyl polyether is a polymer having a structural unit represented by the following formula (II).

[In the formula (II), p, t and u each represent a number of 0 to 3, r represents a number of 1 to 3, m represents a repeating unit (provided that Mw of the polymer is 5,000 to 200,000) Within the range of satisfaction). ] The material for forming a protective film for an immersion exposure process according to any one of claims 1 to 3, wherein the cyclic fluoroalkyl polyether is a polymer having a structural unit represented by the following formula (III).

[In Formula (III), Rf ₁ is a fluorine atom, or a fluoroalkyl group or fluoroalkyl ether group having 1 to 5 carbon atoms, and Rf ₂ may or may not be present. A plurality of which may be present) is a fluoroalkyl group or fluoroalkyl ether group having 1 to 5 carbon atoms, t is a number from 0 to 3, m is a repeating unit (however, the polymer Mw is 5,000 to 200). , 000). ]   The material for forming a protective film for an immersion exposure process according to any one of claims 1 to 5, wherein only one kind of polymer is used as the cyclic fluoroalkyl polyether.   A photoresist pattern forming method using an immersion exposure process, wherein a photoresist film is provided on a substrate, and the protective film is formed on the photoresist film using the protective film forming material according to claim 1. After the formation, an immersion medium is disposed on at least the protective film of the substrate, the photoresist film is selectively exposed through the immersion medium and the protective film, and then the protective film is used for the protective film. A method for forming a photoresist pattern, wherein the photoresist film is peeled off by being brought into contact with a removing solution, and then the photoresist film is developed to obtain a photoresist pattern.   The method for forming a photoresist pattern according to claim 7, wherein a fluorine-based organic solvent having a boiling point of 150 ° C. or lower is used as the protective film removing liquid.