WO2006123643A1

WO2006123643A1 - Material for protective film formation for liquid immersion exposure process, and method for photoresist pattern formation using the same

Info

Publication number: WO2006123643A1
Application number: PCT/JP2006/309718
Authority: WO
Inventors: Masaaki Yoshida; Keita Ishiduka; Tomoyuki Hirano; Tomoyuki Ando
Original assignee: Tokyo Ohka Kogyo Co., Ltd.
Priority date: 2005-05-17
Filing date: 2006-05-16
Publication date: 2006-11-23
Also published as: TW200710581A

Abstract

This invention provides a material for protective film formation for a liquid immersion exposure process, suitable for use in a liquid immersion exposure process, particularly a local exposure liquid immersion process for filling a liquid immersion medium into only between an exposure lens and a substrate comprising a protective film provided on a photoresist layer, the material for protective film formation being formed on a photoresist film, wherein the material for protective film formation comprises a cyclic fluoroalkyl polyether and a fluoro organic solvent, and a method for photoresist pattern formation using the material for protective film formation.

Description

Specification

Material for forming protective film for immersion exposure process and method for forming photoresist pattern using the same

Technical field

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 is suitably applied to a local exposure liquid immersion process in which only a space between a lens of an exposure apparatus and a substrate having a protective film formed on a photoresist layer is filled with an immersion medium.

Background art

[0002] Photolithography is frequently used for the production of fine structures in various electronic devices such as semiconductor devices and liquid crystal devices. In recent years, further miniaturization has been required in the formation of photoresist patterns in the photolithography process where the progress of high integration and miniaturization of semiconductor devices is remarkable.

[0003] Currently, by photolithography, for example, in the state-of-the-art region, the ability to form a fine photoresist pattern with a line width of about 90 nm, and further research into finer pattern formation with a line width of 65 nm. Development is underway.

[0004] In order to achieve such finer pattern formation, generally, a countermeasure using an exposure apparatus or a photoresist material can be considered. As countermeasures by exposure equipment, F

2 Excimer Laser, EUV (extreme ultraviolet light), electron beam, X-ray, soft X-ray, etc. Measures such as shortening the wavelength of the light source and increasing the numerical aperture (NA) of the lens. Measures using photoresist materials include measures to develop new materials that can cope with shorter exposure light wavelengths.

However, in order to shorten the wavelength of the light source, an expensive new exposure apparatus is required. Also, with high NA, there is a trade-off relationship between resolution and depth of focus, so there is a problem that the depth of focus decreases even if the resolution is increased. In addition, the development of new photoresist materials that can cope with shorter wavelengths is costly.

[0006] Recently, immersion lithography (Liquid) has been developed as a photolithography technology that can solve such problems.

Immersion Lithography) method has been reported (for example, see Non-Patent Documents 1 to 3). this According to the method, at the time of exposure, an exposure optical path between an exposure apparatus (lens) and a photoresist film on a substrate exposes the photoresist film by interposing an immersion medium having a predetermined thickness on at least the photoresist film. A 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 ( By substituting with an immersion medium with n) (e.g. pure water, fluorinated inert liquid, etc.), even if a light source with the same exposure wavelength is used, exposure light with a shorter wavelength or high NA lenses are used. As in the case of using, there is an advantage that high resolution is achieved and no reduction in the depth of focus occurs. In addition, currently widely used photoresist materials can be used.

[0007] If such an immersion exposure process is used, a lens mounted on an existing exposure apparatus and an exposure light wavelength are used, and the cost is lower, the resolution is higher, and the depth of focus is also excellent. It has attracted a great deal of attention because it can form a photoresist pattern.

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. There is a concern that the refractive index changes due to alteration of the immersion medium itself due to the elution components from the photoresist film.

Therefore, a protective film is formed on the photoresist film to cope with this, and an immersion medium is interposed on the protective film, so that the immersion medium is transformed into the photoresist film, and the immersion medium itself is removed. There has been proposed a technique aimed at simultaneously preventing refractive index fluctuations accompanying alteration (see, for example, Patent Document 1).

[0010] The above Patent Document 1 is a technique proposed by the applicant of the present application. The protective film includes a fluorine-containing resin, specifically, a cyclic perfluoroalkyl polyether and a chain perfluoroalkyl polyether. A protective film was formed using a mixture of a mixture of grease, and it was confirmed that a good profile photoresist pattern with a rectangular cross-section was obtained by this protective film.

[0011] Non-Patent Document 1: “Journal of Vacuum Science & Technology B” J, (USA), 1999, Vol. 17, No. 6, 330 6 — Page 3309 Non-Patent Document 2: “Journal of Vacuum Science & Technology B” J, (USA), 2001, Vol. 19, No. 6, pp. 235 3-2356

Non-Patent Document 3: “Proceedings of SPIE”,

(USA), 2002, 4691, 459-465

Patent Document 1: International Publication No. 2004Z074937 Pamphlet

Disclosure of the invention

Problems to be solved by the invention

[0012] The protective film described in Patent Document 1 described above is a simulated immersion exposure dew experiment in a state where a substrate having a protective film formed on a photoresist film is exposed and then immersed in an immersion medium. The evaluation was performed by immersion exposure using a simple method using a prism, and the evaluation of such an immersion exposure process was sufficiently effective. However, in an actual mass production process, a local immersion exposure method has been adopted in which only the space between the exposure lens that scans at a predetermined speed or more and the substrate is filled with an immersion medium.

[0013] In the local immersion exposure method, for example, a substrate provided with a protective film Z photoresist layer is placed on a wafer stage, an exposure lens is arranged above the protective film at a predetermined interval, and a wafer stage. The immersion medium is continuously dropped onto one nozzle force protective film while being moved at a high speed, and exposure is performed while suctioning from the other nozzle.

[0014] 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 increases, the internal pressure of the water droplet increases exponentially, and the water pressure applied to the protective film is not comparable to the order of problems that have been regarded as a problem in previous evaluation methods. It gets bigger. In this way, if there is a non-uniform part of the surface of the protective film where microdroplets with extremely high internal pressure remain, droplets penetrate into the inside of the protective film through this part, which causes pattern defects when forming a photoresist pattern. ("Water'mark defect"). In Patent Document 1, the above-described conventional evaluation method is used, and such a conventional immersion exposure method can provide a photoresist pattern with a good profile and has an excellent effect. However, in actual mass production, Predetermined speed The above points in the local immersion exposure using the scanning lens have not been studied.

[0015] Accordingly, one object of the present invention is to solve the above-mentioned new problems, and in particular to suppress the occurrence of photoresist pattern defects ("water one 'mark defects") due to local immersion, etc. A material for forming a protective film that is widely applicable to commercially available photoresists, has excellent versatility, and has the basic characteristics required for a protective film used in an immersion exposure process. The object is to provide a method for forming a photoresist pattern.

In addition to the above-described effects, another object of the present invention is to provide a protective film forming material that further reduces manufacturing costs and improves product throughput, and a photoresist pattern forming method using the same. Is to provide.

Means for solving the problem

[0017] In the local immersion exposure, the present inventors have made the surface of the protective film more uniform, reduced the contact angle between the water droplet and the protective film, and improved the water repellency of the protective film. As a result of the improvement, the inventors have obtained knowledge that the above problems can be solved, thereby completing the present invention. Furthermore, by using a protective film containing a specific low molecular weight polymer, it is highly soluble in a protective film removal liquid such as a fluorine-based organic solvent that does not impair the characteristics of the protective film. The inventor has obtained the knowledge that the cost can be reduced and the product throughput can be improved, thereby completing the present invention.

That is, the present invention is a material for forming a protective film that is used in an immersion exposure process and is stacked on a photoresist film on a substrate, and includes a cyclic fluoroalkyl polyether and a fluorine-based material. Provided is a material for forming a protective film for an immersion exposure process containing an organic solvent.

Further, the present invention is 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. Thereafter, an immersion medium is disposed on at least the protective film of the substrate, and the photoresist film is selectively exposed by an exposure apparatus through the immersion medium and the protective film, and then the protective film is removed from the photoresist film. Then, the photoresist film is developed, and a photoresist pattern is obtained by developing the photoresist film. [0020] In the method for forming the protective film forming material and the photoresist pattern, the immersion exposure process uses an immersion medium only between the lens of the exposure apparatus and the substrate on which the protective film is formed on the photoresist layer. It is preferably applied to the local immersion exposure process to be filled.

The invention's effect

[0021] The material for forming a protective film of the present invention can achieve further uniformization of the surface of the protective film, and can improve water repellency characteristics between the fine water droplets and the protective film. In particular, it is possible to suppress the occurrence of photoresist pattern defects (“water mark defects”) that are likely to occur in the local immersion exposure process.

In addition to the above effects, the material for forming a protective film of the present invention further reduces the amount of the protective film removal liquid used for removing the protective film from the photoresist film after the immersion exposure step. In addition, the manufacturing cost can be reduced and the product throughput can be improved.

[0023] The present invention is widely applicable to photoresists currently on the market and is versatile. In addition, the present invention is a basic property required as a protective film, and has high resistance to an immersion medium. Low compatibility with the photoresist film provided in the lower layer, immersion medium force Prevention of elution of components into the photoresist film, prevention of elution of components from the photoresist film into the immersion medium, inhibition of gas permeation of the protective film A material for forming a protective film having the above characteristics is provided. By applying the protective film-forming material of the present invention to the immersion exposure process, it is possible to form a very fine photoresist pattern that exceeds the resolution of lithography using conventional photoresist materials and exposure equipment. Become.

BEST MODE FOR CARRYING OUT THE INVENTION

[0024] Hereinafter, the present invention will be described in detail.

In the present specification, the “fluoroalkyl group” refers to a group in which part to all of the hydrogen atoms of the alkyl group are substituted with fluorine atoms. A group in which all of the hydrogen atoms of the alkyl group are substituted with fluorine atoms is also referred to as a perfluoroalkyl group.

[0026] The "fluoroalkyl ether group" refers to a group in which part to all of the hydrogen atoms of the alkyl ether group are substituted with fluorine atoms. A group in which all of the hydrogen atoms of the alkyl ether group are substituted with fluorine atoms is also referred to as a perfluoroalkyl ether group. The material for forming a protective film according to the present invention contains a cyclic fluoroalkyl polyether and a fluorine-based organic solvent. In the present invention, a chain-type fluoroalkyl polyether is not contained.

[0028] As the cyclic fluoroalkyl polyether, a polymer having a structural unit represented by the following formula (I) is preferably used.

(I)

[0030] In the above formula (I), Rf represents a fluorine atom, a fluoroalkyl group having 1 to 5 carbon atoms, or

1

A fluoroalkyl ether group, Rf may or may not be present

2

(May be present in plural) is a fluoroalkyl group or a fluoroalkyl ether group having 1 to 5 carbon atoms, and X is —o— or — (CF) — (where q is a number of 0 or 1)

2 q

Y is — O— or — (CF) − (where V represents a number of 1 or more), and Z

2

Is — (O) — (where s represents the number 0 or 1), p, t and u each represent a number from 0 to 3, and m represents a repeating unit.

[0031] Among them, a polymer having a structural unit represented by the following formulas (Π) and (III) is preferable.

(II)

[0033] In the formula (II), p, t, and u each represent a number from 0 to 3, r represents a number from 1 to 3, and m represents a repeating unit.

[0034] The polymer having the structural unit represented by the formula (II) is a Cytop series (Asahi Glass Co., Ltd.). _C which is commercially available as Ltd.) and the like, can be suitably used

[0036] In the formula (III), Rf represents a fluorine atom, a fluoroalkyl group having 1 to 5 carbon atoms or a fluorine atom.

1

Fluoroalkyl ether group, Rf may or may not be present

2

The case (which may be present in plural) is a fluoroalkyl group or a fluoroalkyl ether group having 1 to 5 carbon atoms, t is a number from 0 to 3, and m is a repeating unit.

[0037] The polymer having the structural unit represented by the formula (III) is commercially available as "Teflon AF1600", "Teflon A F2400J (all of which are manufactured by DuPont)" and can be suitably used.

[0038] In the present invention, commercially available products can be used as cyclic fluoroalkyl polyethers as described above, and there is an advantage that they are versatile. However, these commercially available products have a mass average molecular weight of several tens of polymers. It is a polymer of about 10,000 (for example, about 250,000). After removing the protective film using a high molecular weight polymer from the photoresist film by the protective film removing liquid such as a fluorine-based organic solvent after the immersion exposure process, it takes a corresponding peeling time.

[0039] Therefore, in another embodiment of the present invention, a cyclic fluoroalkyl polyether having a mass average molecular weight (MW) of a low molecular weight in the range of 5,000 to 200,000 is used. And Since the protective film using the low molecular weight polymer exhibits extremely high solubility in the protective film removing liquid such as a fluorine-based organic solvent, a small amount of the protective film removing liquid is used and the thickness of the protective film is short. The protective film can be removed in time, and the protective film characteristics are not impaired at all, thereby reducing the manufacturing cost and improving the product throughput. Since the fluorine-based organic solvent (the protective film removing liquid) is expensive, the amount of the protective film removing liquid can be reduced to reduce the manufacturing cost. [0040] When such a low molecular weight polymer is used, in the above formulas (I), (II), and (III), m is within the range where Mw of the polymer satisfies 5,000-200,000. Means repeating unit

[0041] Such a low molecular weight polymer is commercially available as “Cytop” series (manufactured by Asahi Glass Co., Ltd.) as a polymer having a structural unit represented by the above formula (II)! This is not limited to the force that can be used for a low molecular weight product. Examples of the polymer having the structural unit represented by the above formula (II I) include low molecular weight polymers such as “Teflon AF1600”, “Teflon AF 2400” (all of which are manufactured by DuPont).力 The power that can be used is not limited to this.

[0042] When a low molecular weight polymer is used, it is preferable to treat the terminal of the polymer having the structural units represented by the above formulas (I), (II), and (III) with fluoromethyli. By performing such a terminal fluoromethylation treatment, the solubility of the protective film in the protective film removing solvent is dramatically improved.

[0043] In the present invention, it is preferable to use only one type of polymer as the cyclic fluoroalkyl polyether, even though the above! In this way, with a protective film using a single kind of cyclic fluoroalkyl polyether, the surface of the protective film becomes even more uniform, and the penetration of droplets into the protective film is more effectively suppressed. As a result, water mark defects generated in the photoresist pattern can be more effectively suppressed.

[0044] The fluorinated organic solvent is not particularly limited as long as it can dissolve the cyclic fluoroalkylpolyether used in the present invention. Specifically, perfluoroalkanes such as perfluorinated hexane and perfluoroheptane or perfluorocycloalkanes, perfluoroalkenes in which some of the double bonds remain, and perfluoroalkanes. Examples thereof include perfluoro cyclic ethers such as tetrahydrofuran and perfluoro (2-butyltetrahydrofuran), and fluorine-based organic solvents such as perfluorotributylamine, perfluorotetrapentylamine, and perfluorotetrahexylamine. These may be used alone or in admixture of two or more. It is also possible to improve solubility by adding other compatible organic solvents or surfactants as additives. [0045] When the above polymer is dissolved in a fluorinated 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.

[0046] The protective film-forming material in which the cyclic fluoroalkyl polyether is dissolved in a fluorine-based organic solvent includes a preservative, a stabilizer, and a surfactant as long as the effects of the present invention are not impaired. You may mix various additives such as ヽ.

[0047] The protective film-forming material of the present invention can be produced by a conventional method.

[0048] The material for forming a protective film of the present invention is used in an immersion exposure process, and is particularly preferably used 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 having a refractive index is interposed.

[0049] As the immersion medium, water (pure water, deionized water, etc.), a fluorinated solvent, or the like is preferably used. Above all, water is regarded as the most preferable because of optical requirements for immersion exposure (good refractive index characteristics, etc.), ease of handling, and lack of environmental pollution.

[0050] The protective film-forming material according to the present invention can be directly formed on the photoresist film, and does not hinder non-turn 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. it can. On the other hand, if exposure light with a wavelength of 157 nm (such as F excimer laser) is used, the absorption of exposure light into the immersion medium is reduced.

2

From this point of view, fluorinated media are considered to be promising as immersion media, but even when such a fluorinated solvent is used, a photoresist film is used in the immersion exposure process as in the case of the water described above. While being provided, it is possible to obtain a photoresist pattern with sufficient protection and good characteristics.

[0051] An immersion exposure method using the material for forming a protective film of the present invention, in particular, a photoresist pattern formation method by a local immersion exposure method is performed as follows, for example. [0052] First, a conventional photoresist composition is applied onto a substrate such as a silicon wafer with a spinner or the like, and then pre-beta (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.

[0053] The photoresist composition is not particularly limited, and any photoresist that can be developed with an aqueous alkaline solution, including negative and positive photoresists, can be used. Such photoresists include: (i) a positive photoresist containing naphthoquinone diazide compound and novolac resin; (ii) a compound that generates an acid upon exposure; (Iii) A compound that generates an acid upon exposure, an alkali-soluble resin having a group that decomposes with an acid and increases the solubility in an alkaline aqueous solution. And (iv) a force that includes a compound that generates an acid or radical by light, a negative photoresist that contains a crosslinking agent and an alkali-soluble resin, and the like.

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 a wafer stage for local immersion exposure.

An exposure apparatus (lens) is disposed 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 nozzle force protective film while moving the wafer stage at a high speed.

[0058] In this local immersion exposure, the immersion medium is dropped on the protective film and moves at a predetermined speed or higher, so that very fine water droplets are scattered on the surface of the protective film.

[0059] 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 than in the case of the mixed resin with the chain fluoroalkyl polyether. (Uniformity of water repellency, etc.) could be achieved, and the contact angle between the protective film and the droplet could be reduced. [0060] This will be described below.

[0061] As shown in Equation 1 below, it is known that the stress (difference between internal pressure and external pressure) applied to a microdroplet is proportional to the surface tension of the droplet and inversely proportional to its sphere radius! / Speak.

[0062] (P -P) = 2 y / r (Formula 1)

[In Equation 1, P represents the internal pressure of the droplet (unit: Pa), P represents the external pressure of the droplet (unit: Pa), y represents the surface tension of the droplet (unit: NZm ² ), r Indicates the sphere radius (unit: m). ]

[0063] Since the surface tension of water is constant at room temperature, it can be seen that the internal pressure (P) of the droplet increases in inverse proportion to the sphere radius (r).

[0064] Further, the spherical radius (r) of the droplet is determined by the amount of the droplet and the contact angle with the material (protective film) that comes into contact with the liquid. When the contact angle is high, the internal pressure (P) of the droplet increases. Therefore, in order to reduce the internal pressure, it is required to reduce the contact angle.

[0065] In addition to the above, if there is a non-uniform surface (such as a non-uniform water repellency) on the surface of the protective film to which the microdroplet falls and comes into contact, the droplets penetrate into the protective film through this site. For this reason, a more uniform film quality of the protective film is required.

[0066] By forming a protective film using the protective film-forming material of the present invention, the above-mentioned problems could be solved, as confirmed in the examples described later.

Next, the protective film Z 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.

[0068] 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 in the immersion medium. Thus, alteration of optical characteristics such as the refractive index of the immersion medium itself is prevented. In addition, the protective film maintains uniformity as described above, and also has a low contact angle and high water repellency, so that the dropped microdroplet does not remain on the upper surface of the protective film. Also, it does not penetrate inward from the interface with the photoresist on the periphery.

[0069] The exposure light is not particularly limited, and can be performed using radiation generally used in the field of photolithography, 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 to be 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 fluorinated inert liquids include C HC1 F

3 2 5, C F OCH

4 9 3, C F OC H

4 9 2 5, C H F, etc.

Examples thereof include liquids mainly composed of 5 3 7 fluorine-based compounds. Of these, water (pure water, deionized water) is preferably used from the viewpoints of cost, safety, environmental problems, and versatility.

1S Exposure light with a wavelength of 157 nm (eg F excimer laser)

2

From the viewpoint of low light absorption, it is preferable to use a fluorinated solvent.

[0071] When the immersion exposure process by dripping is completed, the substrate is taken out of the exposure stage, the substrate force liquid is removed, and then the protective film is brought into contact with the protective film removing liquid to be peeled off.

[0072] As the protective film removal solution, a fluorine-based solvent that dissolves the cyclic fluoroalkyl polyether 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 lower. Perfluoro (2-propyltetrahydrofuran) (boiling point 102 ° C) is preferable. In the case where the above-mentioned cyclic fluoroalkyl polyester in the specific low molecular weight range is used in the protective film, the dissolution rate of the protective film can be greatly improved as shown in the following examples. In addition, the contact time to the protective film (protective film peeling time) can be greatly shortened, and the throughput of the product that does not affect the pattern forming ability can be greatly improved.

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, a force for suitably using an aqueous solution of tetramethylammonium hydroxide (TMAH) or the like is not limited thereto. A post-beta may be performed following the development process. 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, the photoresist pattern is patterned into a shape corresponding to the mask pattern. Can be obtained.

[0074] Thus, in the present invention, the protective film is uniform and the contact angle can be reduced, so that the immersion medium does not penetrate into the protective film even in local exposure immersion, Generation of water mark defects and pattern defects derived therefrom can be prevented in advance. In addition, since the protective film formed of the protective film forming material of the present invention is excellent in water repellency, the amount of the immersion medium that adheres easily after the completion of the exposure is reduced.

By forming a photoresist pattern in this way, 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 means the total distance of the photoresist pattern width and the space width in the line width direction of the pattern.

[0076] According to the present invention, an immersion medium that is widely applicable to currently marketed photoresists (especially, ArF photoresists), has excellent versatility, and is a basic characteristic required as a protective film. High resistance, low compatibility with the underlying 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, protective film Thus, a material for forming a protective film having characteristics such as inhibition of gas permeation was obtained.

Example

Next, the ability to explain the present invention in more detail by way of examples The present invention is not limited to these examples.

[0078] (Example 1)

“TARF-P6111” (manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a positive photoresist composition, is applied on a silicon wafer by a spinner method and dried on a hot plate at 130 ° C. for 90 seconds. A 200 nm thick photoresist layer was formed.

[0079] On the photoresist layer, "CYTOP CTX-809SP2" (manufactured by Asahi Glass Co., Ltd.) was dissolved in perfluorotributylamine to form a protective film material having a concentration of 1% by mass by the spinner method. After coating, soft beta was performed at 90 ° C for 60 seconds to form a protective film with a thickness of 33 nm.

Next, droplets (pure water, droplet size 1.9 L) were dropped on this protective film and air-dried. This At that time, the contact angle between the protective film and the droplet (that is, the angle formed by the horizontal line on the upper surface of the protective film and the tangent at the edge of the droplet) was measured over time and graphed. The results are shown in Figure 1. Figure 2 shows a photomicrograph of the air-dried droplets over time (photo taken from above). In the figure, the descriptions of Os, 500s, and 1000s indicate the elapsed time after dropping a droplet, 0 seconds (= immediately after dropping), 500 seconds, and 1000 seconds, respectively. A white broken line in the figure indicates a dropping center line.

[0081] (Comparative Example 1)

“TARF-P6111” (manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a positive photoresist composition, is applied onto a silicon wafer by a spinner method, and is pre-betaned at 130 ° C. for 90 seconds on a hot plate. A photoresist layer having a thickness of 200 nm was formed by drying.

[0082] On the photoresist layer, "DEMNUM S-20" (Daikin Co., Ltd.) and "CYTOP C TX-809SP2" (mixing mass ratio = 1: 5) After a protective film material dissolved in rotributylamine and having a concentration of 1.2% by mass was applied by a spinner method, soft beta was performed at 90 ° C. for 60 seconds to form a protective film having a thickness of 33 nm.

Next, droplets (pure water, droplet size 1.9 L) were dropped on this protective film and air-dried. At this time, the contact angle between the protective film and the droplet (that is, the angle formed between the horizontal line on the upper surface of the protective film and the tangent line at the edge of the droplet) was measured over time and graphed. The results are shown in Figure 3. Figure 4 shows a photomicrograph (taken from above) showing the time course of air-dried droplets. In the figure, the descriptions of 0 s, 500 s, and 1 000 s indicate the elapsed time after dropping the droplet, 0 seconds (= immediately after dropping), 500 seconds, and 1000 seconds, respectively. A white broken line in the figure indicates a dropping center line.

[0084] <Evaluation>

As is clear from the comparison force between Fig. 1 and Fig. 3, the protective film of Fig. 1 (Example 1) has an initial contact angle of 114.7 °, whereas the protective film of Fig. 3 (Comparative Example 1) The initial contact angle was 118. 0 °. That is, by using the protective film forming material of the present invention, the initial contact angle can be reduced by 3.3 °, the assumed radius of the same volume droplet can be increased, and the internal pressure of the droplet can be reduced, As a result, the droplets seem to have penetrated into the protective film.

[0085] In Fig. 3, the measurement after 1000 seconds could not be performed. As shown in Fig. 4 (described later), it seems that measurement was not possible because the center of the droplet was shifted. [0086] Further, when the time required from the initial droplet size of 1.8 μL to drying and disappearing was measured, it took 1482 seconds under the conditions using the protective film of Example 1. On the other hand, when the protective film of Comparative Example 1 was used, it took 1252 seconds, and using the protective film of Example 1 required a longer time to dry the droplets. It seems that the risk of water's mark that the speed of soaking is slow has decreased.

In addition, as is clear from the comparison between FIG. 2 and FIG. 4, in FIG. 2 (Example 1), the dropped droplet shows almost no deviation of the center line force over time, whereas FIG. In 4 (Comparative Example 1), the drop force of the dropped liquid has already shown a considerable shift of the center line force (shift to the left in the figure) after 500 seconds have elapsed, and after 1000 seconds have passed, as described above. The displacement to the left was so strong that the contact angle could not be measured. This is probably because the surface of the protective film of Comparative Example 1 lacks uniformity. That is, it was proved that the protective film used in Example 1 had higher surface uniformity than the protective film used in Comparative Example 1.

[0088] (Example 2)

Apply an organic antireflective coating composition “ARC-29Α” (Nissan Chemical Industry Co., Ltd.) onto a silicon wafer by the spinner method, and baked on a hot plate at 210 ° C for 60 seconds to dry. An organic liquid antireflection film with a film thickness of 77 nm was formed from Tsuji. A positive photoresist composition “TARF-P6111” (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied onto the antireflection film by a spinner method, and pre-beta was applied on a hot plate at 130 ° C for 90 seconds. Then, a photoresist layer having a film thickness of 200 nm was formed on the antireflection film.

[0089] On the photoresist layer, "CYTOP CTX-809SP2" (manufactured by Asahi Glass Co., Ltd.) was dissolved in perfluorotributylamine to form a protective film material having a concentration of 1% by mass by the spinner method. After coating, soft beta was performed at 90 ° C for 60 seconds to form a protective film with a thickness of 33 nm.

[0090] The substrate on which this protective film was formed was subjected to immersion exposure using an experimental apparatus manufactured by Nikon Corporation using a prism, liquid, and two-beam interference exposure with a wavelength of 193 nm (the bottom surface of this prism is Contact with the protective film via water!

[0091] Subsequently, PEB treatment was performed at 115 ° C for 90 seconds, and then the protective film was removed using perfluoro (2-butyltetrahydrofuran). Thereafter, it was further developed with an alkaline developer at 23 ° C for 60 seconds. As the alkali developer, 2.38 mass ^_0/0 tetramethylammonium - © beam An aqueous hydroxide solution was used.

[0092] When a 65 nm line-and-space photoresist pattern obtained in this way was observed with a scanning electron microscope (SEM), the photoresist pattern profile was satisfactory, and fluctuations, etc. It was a force not observed at all.

[0093] (Example 3)

Cyclic fluoroalkyl polyethers having a structural formula represented by the following formula (Il-a) and having different mass average molecular weights (Mw) as shown in Table 1 below are converted into perfluorotributylamine. The dissolved solution (solid content concentration 1.0 mass%) was used as Samples 1-6.

[0094]

[0095] [Protection film dissolution rate]

Samples 1 to 6 shown in Table 1 below were each applied onto a substrate by a spinner, and then soft beta at 90 ° C. for 60 seconds to form a protective film having a thickness of 28 nm.

Next, perfluoro (2-ptyltetrahydrofuran) was dropped as a protective film removal solution on the protective film, and the rate at which the protective film was dissolved was measured. In addition, from the rate of dissolution of the protective film, the point-of-thickness protective film removability of the throughput was evaluated. The results are shown in Table 1. In Table 1, in the “Protective film removability” evaluation column, “A” indicates that the protective film dissolution rate is excellent, and the throughput of the throughput is sufficiently excellent, and “B” indicates the throughput. Point Indicates that the protective film removal effect has been improved compared to the conventional product, and “C” indicates that it is the same level as the conventional product and requires improved throughput.

[Example 4]

The water repellency and scan followability of Samples 1 to 6 shown in Table 1 below were evaluated by measuring the falling angle and contact angle. [0098] [Falling angle]

After dropping 50 L of each sample 16 shown in Table 1 onto the substrate, the substrate was ramped up at a rate of inclination rate of ^ per second, and the droplet on the substrate started to move. The substrate tilt angle (rolling angle) 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.

[0099] [Contact angle]

2 L of each sample 16 shown in Table 1 below was dropped on the substrate, and the contact angle between the droplet and the substrate was measured. The results are shown in Table 1.

[0100] [Table 1]

[0101] As is clear from the results in Table 1, a protective film containing a cyclic fluoroalkyl polyether (sample 26) with a low molecular weight of 5,000 200,000 (Mw) 5,000 When is used, it is superior in solubility in the removal solution with a faster dissolution rate than Sample 1 with a mass average molecular weight (Mw) of 250,000. That is, it is possible to dissolve and remove the protective film with a smaller amount of removal solution than in the prior art, and there is an excellent effect that the manufacturing cost can be reduced and the throughput can be improved. Both Sample 1 and Sample 26 have excellent water repellency and excellent scan followability, and are suitable for the local liquid immersion exposure process.

[0102] (Example 5)

[Pseudo immersion exposure evaluation using ArF dry exposure machine (= non-immersion exposure machine)] Silicone anti-reflective coating composition “ARC29” (Brewer Co.) using a spinner An antireflection film with a thickness of 77 nm was formed by coating on a wafer, baking on a hot plate at 225 ° C for 60 seconds and drying. On this antireflection film, ArF positive photoresist (“TARF-P6111ME”; manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied, pre-betaed at 130 ° C for 90 seconds on a hot plate, and dried. As a result, a 225 nm thick photoresist film was formed on the antireflection film.

[0103] On the photoresist film, each of the above samples 2 to 6 (however, the solid content concentration was adjusted to 1.1% by mass) was applied and heated at 90 ° C for 60 seconds to protect the film with a thickness of 28 nm. A film was formed.

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

When the 130 nm line “and” space pattern (1: 1) obtained in this way was observed with a scanning electron microscope (SEM), a well-shaped line “and” space pattern could be formed.

Industrial applicability

[0106] The material for forming a protective film of the present invention is extremely excellent in the uniformity of the film surface and can reduce the contact angle with respect to a droplet dropped during the local liquid immersion exposure. In forming a photoresist pattern, a photoresist pattern free from pattern defects can be obtained. Therefore, it is particularly preferably used for local liquid immersion exposure.

Brief Description of Drawings

FIG. 1 is a graph showing a change with time of a contact angle between a protective film and a droplet used in Example 1.

FIG. 2 is a photomicrograph (drawing substitute photo) showing a change with time of a droplet dropped on the protective film used in Example 1.

FIG. 3 is a graph showing the change over time in the contact angle between the protective film and the droplet used in Comparative Example 1.圆 4] A photomicrograph (drawing substitute photo) showing the change over time of the droplet dropped on the protective film used in Comparative Example 1.

Claims

The scope of the claims

[1] A material used in the immersion exposure process to form a protective film laminated on a photoresist film on a substrate, which contains a cyclic fluoroalkyl polyether and a fluorine-based organic solvent A material for forming a protective film for an immersion exposure process.

[2] The material for forming a protective film for an immersion exposure process according to [1], which is a polymer having a constitutional unit represented by the following formula (I):

(I)

[In the formula (I), Rf represents a fluorine atom, a fluoroalkyl group having 1 to 5 carbon atoms or

1

If it is a haloalkyl ether group and Rf is present or absent

2

Is a fluoroalkyl group or a fluoroalkyl ether group having 1 to 5 carbon atoms, and X is o or — (CF) — (where q represents the number of 0 or 1)

2 q

), Y is —O or — (CF) − (where V represents a number of 1 or more), and Z is — (

2

O) (wherein s represents a number of 0 or 1), p, t and u each represent a number of 0 to 3, and m represents a repeating unit. ]

[3] The material for forming a protective film for an immersion exposure process according to claim 1, which is a polymer having a structural unit represented by the following formula (II):

[In formula (II), p, t and u each represent a number from 0 to 3, r represents a number from 1 to 3, and m represents a repetition. Means a unit. ]

2. The material for forming a protective film for an immersion exposure process according to claim 1, which is a polymer having a structural unit represented by the following formula (III):

[In the formula (III), Rf represents a fluorine atom, a fluoroalkyl group having 1 to 5 carbon atoms or

1

Fluoroalkyl ether group, Rf may or may not be present

2

The case (which may be present in plural) is a fluoroalkyl group or a fluoroalkyl ether group having 1 to 5 carbon atoms, t is a number from 0 to 3, and m is a repeating unit. ]

[5] The weight average molecular weight (Mw) of the cyclic fluoroalkyl polyether is 5,000 to 200, 00

The material for forming a protective film according to claim 1, wherein the material is 0.

6. The material for forming a protective film for an immersion exposure process according to claim 1, wherein only one type of polymer is used as the cyclic fluoroalkyl polyether.

[7] 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. Then, 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 protected from the photoresist film. A method for forming a photoresist pattern, wherein the film is removed, and then the photoresist film is developed to obtain a photoresist pattern.

8. The liquid immersion exposure process according to claim 1, wherein the liquid immersion exposure process is a local liquid immersion exposure process in which only a space between the lens of the exposure apparatus and the substrate having a protective film formed on the photoresist layer is filled with the liquid immersion medium. Material for forming a protective film for immersion exposure processes.

[9] The immersion exposure process is based on the lens of the exposure apparatus and a protective film formed on the photoresist layer. 8. The method for forming a photoresist pattern according to claim 7, which is a local immersion exposure process in which only a space between the plates is filled with an immersion medium.