JP2009088135A - Resist pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel pattern forming method capable of decreasing the number of steps of a double patterning method. <P>SOLUTION: A resist pattern forming method includes: forming a fist resist film by coating a base with a first positive type resist composition; forming a second resist film by coating the first resist film with a second positive resist composition; selectively exposing the second resist film with a light exposure (Dose<SB>2</SB>) smaller than the smallest light exposure (Eth<SB>1</SB>) of the first resist film and larger than the smallest light exposure (Eth<SB>2</SB>) of the second resist film; forming a rough pattern of the second resist film through development; exposing the first resist film through the rough pattern with a light exposure (Dose<SB>1</SB>) larger than the smallest light exposure (Eth<SB>1</SB>) of the first resist film; and performing development and removing the rough pattern to form a close pattern of the first resist film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a resist pattern forming method.

A technology (pattern formation technology) that forms a fine pattern on a substrate and processes the lower layer of the pattern by etching using this as a mask has been widely adopted for IC creation in the semiconductor industry, and has received great attention. ing.
The fine pattern is usually made of an organic material, and is formed by a technique such as a lithography method or a nanoimprint method. For example, in the lithography method, a resist film made of a resist composition containing a base material component such as a resin is formed on a support such as a substrate, and a photomask in which a predetermined pattern is formed on the resist film ( A step of forming a resist pattern of a predetermined shape on the resist film is performed by performing selective exposure with radiation such as light and electron beam through a mask pattern) and performing development processing. A resist composition in which the exposed portion changes to a property that dissolves in the developer is referred to as a positive type, and a resist composition that changes to a property in which the exposed portion does not dissolve in the developer is referred to as a negative type.
And a semiconductor element etc. are manufactured through the process of processing a board | substrate by an etching using the said resist pattern as a mask.

In recent years, pattern miniaturization is rapidly progressing due to the advancement of lithography technology. As a technique for miniaturization, the wavelength of an exposure light source is generally shortened. Specifically, conventionally, ultraviolet rays typified by g-line and i-line have been used, but now mass production of semiconductor elements using a KrF excimer laser or an ArF excimer laser has started. Lithography using an ArF excimer laser enables pattern formation with a resolution of 45 nm. In addition, in order to further improve the resolution, studies have been made on F ₂ excimer lasers, electron beams, EUV (extreme ultraviolet rays), X-rays, and the like having shorter wavelengths than these excimer lasers.
The resist composition is required to have lithography characteristics such as sensitivity to these exposure light sources and resolution capable of reproducing a pattern with fine dimensions. As a resist composition satisfying such requirements, a chemically amplified resist composition containing a base material component whose solubility in an alkaline developer is changed by the action of an acid and an acid generator that generates an acid upon exposure is used. (See, for example, Patent Document 1). For example, a positive chemically amplified resist usually contains, as a base material component, a resin whose solubility in an alkaline developer is increased by the action of an acid. When a resist pattern is formed, an acid is generated from an acid generator by exposure. When it occurs, the exposed part becomes soluble in the alkaline developer.

As one of the techniques for further improving the resolution, exposure (immersion exposure) is performed by interposing a liquid (immersion medium) having a higher refractive index than air between the objective lens of the exposure machine and the sample. A so-called liquid immersion lithography (hereinafter sometimes referred to as liquid immersion exposure) is known (for example, see Non-Patent Document 1).
According to immersion exposure, even when a light source having the same exposure wavelength is used, the same high resolution as when using a light source with a shorter wavelength or using a high NA lens can be achieved, and the depth of focus can be reduced. It is said that there is no decline. In addition, immersion exposure can be performed by applying an existing exposure apparatus. For this reason, immersion exposure is expected to be able to form resist patterns with low cost, high resolution, and excellent depth of focus. In particular, in terms of lithography characteristics such as resolution, the semiconductor industry is attracting a great deal of attention.
Immersion exposure is effective in forming all pattern shapes, and can be combined with super-resolution techniques such as the phase shift method and the modified illumination method that are currently being studied. Currently, as an immersion exposure technique, a technique mainly using an ArF excimer laser as a light source is being actively researched. Currently, water is mainly studied as an immersion medium.

Recently, as one of newly proposed lithography techniques, there is a double patterning method in which patterning is performed twice or more (see, for example, Non-Patent Documents 2 to 3). According to this double patterning method, it is supposed that a pattern finer than a pattern formed by one patterning can be formed. For example, Non-Patent Document 2 describes a method as shown in FIG.
That is, first, as shown in FIG. 2A, a laminate in which a substrate 101, a lower layer film 102, and a hard mask 103 are laminated is prepared. Next, a resist film is provided on the hard mask 103, and the resist film is selectively exposed through the mask 105 and developed as shown in FIG. A resist pattern 104 having a plurality of trench patterns arranged at a pitch is formed. Next, after the hard mask 103 is etched using the resist pattern 104 as a mask, the remaining resist pattern 104 is removed. As a result, as shown in FIG. 2C, a hard mask 103 ′ to which the resist pattern is transferred is obtained. Next, as shown in FIG. 2D, the position of the mask 105 is shifted, and a resist material is applied onto the hard mask 103 ′ to fill the voids in the hard mask 103 ′. A resist film having a thickness greater than that of 103 ′ is formed. Then, the resist film is selectively exposed through the shifted mask 105 and developed to form a resist pattern 106. Next, after etching the hard mask 103 ′ using the resist pattern 106 as a mask, the remaining resist pattern 106 is removed. As a result, as shown in FIG. 2E, a hard mask 103 ″ to which a pattern in which a plurality of trench patterns having a space width d / 4 are arranged at a pitch d / 2 is transferred is obtained. By etching using “as a mask, the pattern of the hard mask 103” is transferred to the lower layer film 102, and a pattern 102 ′ having a half pitch of the used mask 105 is formed.
As described above, according to the double patterning method, it is possible to form a resist pattern with higher resolution even when using a light source having the same exposure wavelength or using the same resist composition. The double patterning method can be performed using an existing exposure apparatus.
JP 2003-241385 A Proceedings of SPIE, 5754, 119-128 (2005). Proceedings of SPIE, 5256, 985-994 (2003). Proceedings of SPIE, 6153, 615301-1-19 (2006).

However, in the conventional double patterning method, it is usually necessary to provide a lower layer film on the substrate, and in order to form a pattern on the substrate, the resist film is patterned at least twice, and the hard mask in the lower layer is formed. This etching must be performed at least twice.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a novel pattern forming method capable of reducing the number of steps in a conventional double patterning method.

In order to achieve the above object, the present invention employs the following configuration.
That is, the present invention forms a first resist film by applying a first positive resist composition on a support,
A second positive resist composition is applied onto the first resist film, and the second resist composition has a minimum exposure (Eth ₂ ) smaller than the minimum exposure (Eth ₁ ) of the first resist film. Forming a resist film,
Minimum exposure amount of said first resist film (Eth ₁₎ minimum exposure amount of small and said second resist film than larger exposure amount than _{(Eth 2) (Dose 2)} , the said second resist film Selectively exposed and developed to form a rough pattern of the second resist film,
The first resist film is exposed through the rough pattern with an exposure amount (Dose ₁ ) greater than the minimum exposure amount (Eth ₁ ) of the first resist film, and developed, and the rough pattern And a dense pattern made of the first resist film is formed.

In the present specification and claims, “exposure” is a concept including general irradiation of radiation.
“Minimum exposure amount (Eth ₁ ) of the first resist film” means that a first positive resist composition is applied on a support to form a first resist film, and the first resist film is coated on the first resist film. On the other hand, when selectively exposed, the minimum exposure amount at which the support is exposed by development in the exposed portion.
The “minimum exposure amount (Eth ₂ ) of the second resist film” means that the first resist film is formed by applying the first positive resist composition on the support, When a second positive resist composition is applied to form a second resist film, and the second resist film is selectively exposed, the first resist film is developed by development in the exposed portion. This is the minimum exposure amount at which exposure occurs.
“Optimum exposure amount (Eop ₂ ) of the second resist film” means that the first resist film is formed by coating the first positive resist composition on the support, The second positive resist composition is applied to form a second resist film, and when the second resist film is selectively exposed and developed, a pattern of the second resist film is formed. Is the optimum exposure amount that can be faithfully reproduced according to the design pattern dimensions.
In the present specification, unless otherwise specified, the “alkyl group” includes linear, branched and cyclic monovalent saturated hydrocarbon groups.
The “lower alkyl group” is an alkyl group having 1 to 5 carbon atoms.
“Aliphatic” means that the group or compound does not have aromatic character.
“Aliphatic cyclic group” means a monocyclic group or a polycyclic group having no aromaticity.

  The present invention can provide a novel pattern forming method capable of reducing the number of steps in the double patterning method.

≪Resist pattern formation method≫
The resist pattern forming method of the present invention includes a step of applying a first positive resist composition on a support to form a first resist film (hereinafter referred to as a first resist film forming step), and the step. A second resist having a minimum exposure (Eth ₂ ) smaller than the minimum exposure (Eth ₁ ) of the first resist film by applying a second positive resist composition on the first resist film A step of forming a film (hereinafter referred to as a second resist film forming step), and a minimum exposure amount (Eth) of the second resist film that is smaller than the minimum exposure amount (Eth ₁ ) of the _first resist film. ₂ ) a step of selectively exposing and developing the second resist film with an exposure amount (Dose ₂ ) larger than (Dose ₂ ) to form a coarse pattern made of the second resist film (hereinafter referred to as a coarse pattern). Forming process) and the first. The first resist film is exposed through the rough pattern with an exposure amount (Dose ₁ ) larger than the minimum exposure amount (Eth ₁ ) of the resist film, and developed to remove the rough pattern. And a step of forming a dense pattern made of the first resist film (hereinafter referred to as a dense pattern forming step).

Hereinafter, a preferred embodiment of the resist pattern forming method of the present invention will be described with reference to FIG.
In the present embodiment, first, as shown in FIG. 1A, a first positive resist composition is applied on a support 10 to form a first resist film 1 (first resist film). Forming step). Subsequently, as shown in FIG. 1B, a second positive resist composition is applied onto the first resist film ₁ and is smaller than the minimum exposure amount (Eth ₁ ) of the first resist film. A second resist film 2 having a minimum exposure amount (Eth ₂ ) is formed (second resist film forming step). Next, the second resist is exposed at an exposure amount (Dose ₂ ) that is smaller than the minimum exposure amount (Eth ₁ ) of the first resist film 1 and larger than the minimum exposure amount (Eth ₂ ) of the second resist film 2. The film 2 is selectively exposed through a photomask.
In the present invention, the second resist film 2 is formed from a positive resist composition, and a small minimum exposure amount than the lowest exposure of the first resist film 1 (Eth ₁₎ (Eth ₂ )have. Therefore, the exposure amount (Dose ₂ ) when selectively exposing the second resist film 2 is smaller than the minimum exposure amount (Eth ₁ ) of the first resist film 1 and the second resist film 2 By setting it larger than the minimum exposure amount (Eth ₂ ), the exposed portion of the second resist film 2 is exposed, and the first resist film 1 is not exposed regardless of the exposed portion or the unexposed portion.
Thereafter, development is performed to form a rough pattern 2 ′ made of the second resist film 2 as shown in FIG. 1C (coarse pattern forming step). Subsequently, the first resist film 1 is exposed through the coarse pattern 2 ′ with an exposure amount (Dose ₁ ) larger than the minimum exposure amount (Eth ₁ ) of the first resist film 1. By this exposure, an unexposed portion is generated in a portion of the first resist film 1 corresponding to the vicinity of the side wall of the rough pattern 2 ′. In addition, light reaches other than the entire rough pattern 2 ′ and the portion of the first resist film 1 corresponding to the vicinity of the side wall of the rough pattern 2 ′ (that is, these portions correspond to the exposed portion). .
In the present invention, since the first resist film 1 and the second resist film 2 are formed of a positive resist composition, the exposure is performed on the first resist film 1 through the rough pattern 2 ′. When the development is performed after performing the above, the exposed portion of the first resist film 1 other than the portion corresponding to the vicinity of the side wall of the rough pattern 2 ′ and the entire exposed portion of the rough pattern 2 ′ are removed, while the first resist film 1 is removed. The unexposed portion of the film 1 corresponding to the vicinity of the side wall of the coarse pattern 2 ′ remains as it is, and a positive type finer than the coarse pattern 2 ′ is formed on the support 10 as shown in FIG. The resist pattern (dense pattern 1 ′) is formed (dense pattern forming step).
Hereinafter, each process of a 1st resist film formation process, a 2nd resist film formation process, a rough pattern formation process, and a dense pattern formation process is demonstrated in detail.

[First resist film forming step]
The support 10 is not particularly limited, and a conventionally known one can be used. For example, a substrate for electronic components, a substrate on which a predetermined wiring pattern is formed, and the like can be exemplified. More specifically, a silicon substrate, a metal substrate such as copper, chromium, iron, and aluminum, a glass substrate, and the like can be given. As a material for the wiring pattern, for example, copper, aluminum, nickel, gold or the like can be used.
Further, the support 10 may be a substrate in which an inorganic and / or organic film is provided on the substrate as described above. An inorganic antireflection film (inorganic BARC) is an example of the inorganic film. Examples of the organic film include an organic antireflection film (organic BARC) and an organic film such as a lower layer film in a multilayer resist method. In particular, it is preferable that a lower layer film is provided because a pattern with a high aspect ratio can be formed on the substrate, which is useful in manufacturing semiconductors.

  Here, the multilayer resist method is a method in which at least one organic film (lower film) and at least one resist film are provided on a substrate, and the lower layer is patterned using the resist pattern formed on the upper resist film as a mask. It is said that a high aspect ratio pattern can be formed. According to the multilayer resist method, by securing a required thickness with the lower layer film, the resist film can be thinned and a fine pattern with a high aspect ratio can be formed.

When the organic film is provided, the organic film is formed by, for example, applying a material for forming an organic film in which a resin component or the like constituting the organic film is dissolved in an organic solvent to the substrate with a spinner or the like, preferably 200 to 300 ° C., preferably 30 It can be formed by baking treatment under heating conditions of ˜300 seconds, more preferably 60 to 180 seconds.
The organic film forming material will be described later in detail.
The thickness of the organic film is preferably 10 to 500 nm, more preferably 50 to 450 nm. By setting it within this range, there are effects that a pattern with a high aspect ratio can be formed and sufficient etching resistance can be ensured during substrate etching.

  A hard mask layer made of a silicon-based material may be further provided between the resist film and the organic film. The hard mask layer can be formed by a conventionally known method using a conventionally known silicon-based material.

There is no restriction | limiting in particular as a 1st positive resist composition, According to the exposure light source to be used, lithography characteristics, etc. from the many resist compositions proposed until now as a positive resist composition suitably Can be used.
Details of the resist composition will be described later.

The first resist film can be formed by applying the first positive resist composition on the support 10. The first positive resist composition can be applied by a conventionally known method using a spinner or the like.
Specifically, for example, the first chemically amplified resist composition is applied onto the support 10 with a spinner or the like, and is baked (pre-baked) at a temperature of 80 to 150 ° C. for 40 to 120 seconds, preferably 60. The first resist film 2 can be formed by applying for 90 seconds and volatilizing the organic solvent.
The thickness of the first resist film 1 is preferably 50 to 500 nm, more preferably 50 to 450 nm. By setting it within this range, the dense pattern 1 ′ can be formed with high resolution, and sufficient resistance to etching can be obtained.

[Second resist film forming step]
As the second positive resist composition, a positive resist capable of forming a second resist film having a minimum exposure amount (Eth ₂ ) smaller than the minimum exposure amount (Eth ₁ ) of the _first resist film. A composition, that is, one having higher sensitivity to the exposure light source than the first positive resist composition, is appropriately selected from a number of resist compositions that have been proposed as positive resist compositions. be able to. Details of the resist composition will be described later.
Although the minimum exposure amount (Eth ₂ ) of the _second resist film needs to be smaller than the minimum exposure amount (Eth ₁ ) of the _first resist film, the optimum exposure amount (Eop) of the second resist film is further required. ₂ ) is preferably smaller than the minimum exposure amount (Eth ₁ ) of the first resist film. Thereby, the range of conditions for forming the coarse pattern is widened, and a coarse pattern having a suitable shape made of the second resist film can be formed under more appropriate conditions.

Minimum exposure amount of the second resist film (Eth ₂₎ is specifically preferably from 10 mJ / cm ² or less, more preferably 8 mJ / cm ² or less, particularly preferably 5 mJ / cm ² or less. Optimum exposure of the second resist film (Eop ₂₎ is specifically preferably from 12 mJ / cm ² or less, more preferably 10 mJ / cm ² or less, particularly preferably 8 mJ / cm ² or less.

In addition, when applying the second resist film on the upper layer side, it is necessary to form the film without affecting the first resist film on the lower layer side. Therefore, the second positive resist composition contains an organic solvent (S ₂ ) that dissolves the base material of the second positive resist composition and does not dissolve the base material of the first positive resist composition. It is preferable to do. Thereby, mixing at the interface between the first resist film on the lower layer side and the second resist film on the upper layer side can be suppressed. Here, mixing refers to a phenomenon in which components of the first resist film are dissolved in the second positive resist composition when the second positive resist composition is applied onto the first resist film. . The organic solvent will be described later in detail.

The second resist film 2 can be formed by applying a second positive resist composition onto the first resist film 1. The application of the second positive resist composition can be performed by a conventionally known method using a spinner or the like.
Specifically, for example, a second positive resist composition is applied onto the first resist film 1 with a spinner or the like, and a baking process (pre-baking) is preferably performed for 40 to 120 seconds under a temperature condition of 80 to 150 ° C. Is applied for 60 to 90 seconds, and the second resist film 2 can be formed by volatilizing the organic solvent.
The thickness of the second resist film 2 is preferably 50 to 500 nm, more preferably 50 to 450 nm. By setting it within this range, light shielding can be effectively obtained for the portion of the first resist film 1 corresponding to the vicinity of the side wall of the coarse pattern 2 ′.

[Rough pattern forming process]
When exposure is performed with an exposure amount (Dose ₂ ) that is smaller than the minimum exposure amount (Eth ₁ ) of the first resist film and larger than the minimum exposure amount (Eth ₂ ) of the second resist film, the second resist on the upper layer side The exposed portion of the film is exposed because the exposure amount (Dose ₂ ) is larger than the minimum exposure amount (Eth ₁ ) of the second resist film, whereas the first resist film on the lower layer side is exposed to the exposure amount (Dose). _{Since 2} ) is smaller than the minimum exposure amount (Eth ₁ ) of the first resist film, it is not exposed to light. As the exposure at this time, for example, the second resist film is selectively exposed through a photomask (mask pattern) on which a predetermined pattern is formed. Then, for example, a baking process (PEB (post-exposure heating)) is performed for 40 to 120 seconds, preferably 60 to 90 seconds under a temperature condition of 80 to 150 ° C. Alkali development with aqueous methylammonium hydroxide (TMAH) solution.
In the present invention, since the second resist film 2 is formed from a positive resist composition, when alkali development is performed, the exposed portion is removed, while the unexposed portion remains on the first resist film. Then, a positive resist pattern (a rough pattern 2 ′ made of the second resist film 2) is formed.
The wavelength used for exposure is not particularly limited, and includes KrF excimer laser, ArF excimer laser, F ₂ excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), EB (electron beam), X-ray, soft X-ray, etc. Can be done using radiation.

As the photomask, for example, a binary mask (Binary-Mask) in which the transmittance of the light shielding portion is 0% or a halftone phase shift mask (HT-Mask) in which the transmittance of the light shielding portion is 6% can be used.
The binary mask is generally formed by forming a chromium film, a chromium oxide film or the like as a light shielding portion on a quartz glass substrate.
As the halftone phase shift mask, generally, a quartz glass substrate on which a MoSi (molybdenum silicide) film, a chromium film, a chromium oxide film, a silicon oxynitride film, or the like is formed as a light shielding portion is used. .

At this time, the selective exposure of the second resist film may be normal exposure (dry exposure) performed in an inert gas such as air or nitrogen, or may be performed by immersion exposure.
In immersion exposure, as described above, the portion between the lens, which has been filled with an inert gas such as air or nitrogen, and the resist film on the wafer at the time of exposure is refracted larger than the refractive index of air. The exposure is performed in a state filled with a solvent having a high rate (immersion medium).
More specifically, the immersion exposure is a solvent (immersion medium) having a refractive index larger than the refractive index of air between the resist film obtained as described above and the lowermost lens of the exposure apparatus. And in this state, exposure (immersion exposure) is performed through a desired mask pattern.
As the immersion medium, a solvent having a refractive index larger than the refractive index of air and smaller than the refractive index of the resist film exposed by immersion exposure is preferable. The refractive index of such a solvent is not particularly limited as long as it is within the above range.
Examples of the solvent having a refractive index larger than the refractive index of air and smaller than the refractive index of the resist film include water, a fluorine-based inert liquid, a silicon-based solvent, and a hydrocarbon-based solvent.
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 etc. are mentioned. The fluorine-based inert liquid preferably has a boiling point of 70 to 180 ° C, more preferably 80 to 160 ° C. It is preferable that the fluorine-based inert liquid has a boiling point in the above range since the medium used for immersion can be removed by a simple method after the exposure is completed.
As the fluorine-based inert liquid, a perfluoroalkyl compound in which all hydrogen atoms of the alkyl group are substituted with fluorine atoms is particularly preferable. Specific examples of the perfluoroalkyl compound include a perfluoroalkyl ether compound and a perfluoroalkylamine compound.
More specifically, examples of the perfluoroalkyl ether compound include perfluoro (2-butyl-tetrahydrofuran) (boiling point 102 ° C.). Examples of the perfluoroalkylamine compound include perfluorotributylamine ( Boiling point of 174 ° C.).

[Dense pattern formation process]
Low exposure of the first resist film (Eth ₁₎ large exposure amount than (Dose _1), with respect to said first resist film is exposed through a coarse pattern. The exposure can be open frame exposure (exposure not through a mask). The exposure amount (Dose ₁ ) is larger than the minimum exposure amount (Eth ₂ ) of the second resist film and larger than the minimum exposure amount (Eth ₁ ) of the first resist film. In addition, since the rough pattern is formed from the second resist film derived from the second positive resist composition, the entire rough pattern is exposed by this exposure, and the first resist film has a rough pattern. A non-exposed portion corresponding to the vicinity of the side wall and an exposed portion to which light other than the portion corresponding to the vicinity of the side wall of the rough pattern 2 ′ is formed, and the exposed portion is exposed.
In the first resist film, the reason why an unexposed portion is generated in a portion corresponding to the vicinity of the side wall of the rough pattern 2 ′ is not clear, but irregular reflection occurs on the side wall of the rough pattern 2 ′, and light does not reach. In addition, in the portion corresponding to the vicinity of the side wall of the coarse pattern 2 ′, the light that directly reaches without a mask and the light that passes through the coarse pattern 2 ′ cancel each other with an optical path difference of about half a wavelength. Therefore, it is presumed that an unexposed part is generated.

In the present invention, since the first resist film 1 is formed from a positive resist composition, for example, baking (PEB (post-exposure heating)) is performed under the same conditions as in the rough pattern forming step. Then, when alkali development is performed, the exposed portion is removed, while the unexposed portion remains on the support 10 as it is, and a positive resist pattern (a dense pattern made of the first resist film 1) finer than the rough pattern is left. Pattern 1 ′) is formed.
The process of dissolving and removing the coarse pattern that has been exposed to light and becomes soluble in the developer can be performed separately from the process of developing the first resist film, but for the development of the first resist film. It is preferable that the developer used is the same as the developer used for developing the second resist film because both operations can be performed simultaneously in one step.
Thus, according to the resist pattern forming method of the present invention, it is possible to form a resist pattern with a narrower pitch than in the case of the resist pattern forming method in which selective exposure is performed once, for example.

Further, after the dense pattern forming step, the support 10 may be etched using the formed dense pattern 1 ′ as a mask.
Thus, a semiconductor device etc. can be manufactured by etching support bodies, such as a board | substrate.

A known method can be used as an etching method. For example, dry etching is preferable for etching an organic film. In particular, oxygen plasma etching or etching using CF ₄ gas or CHF ₃ gas is preferable from the viewpoint of high resistance to etching and production efficiency, and oxygen plasma etching is particularly preferable.
Etching using a halogen gas is preferable for etching the substrate, etching using a fluorocarbon-based gas is preferable, and etching using CF ₄ gas or CHF ₃ gas is particularly preferable.

[Resist composition (pattern forming material)]
The first positive resist composition and the second positive resist composition may be non-chemically amplified resist compositions or chemically amplified resist compositions. A chemically amplified resist composition is preferred.

  Examples of the non-chemically amplified resist composition include a main chain decomposition type positive resist composition in which the main chain in the base material component is decomposed by exposure to increase the solubility in a developer, and the base material component is exposed by exposure. A positive resist composition which changes to alkali-soluble can be mentioned.

The chemically amplified resist composition includes a base material component (A) whose solubility in an alkaline developer is changed by the action of an acid (hereinafter referred to as “component (A)”) and an acid generator component that generates an acid upon exposure ( B) (hereinafter referred to as “component (B)”) is generally dissolved in organic solvent (S) (hereinafter referred to as “component (S)”).
Here, the “base material component” is an organic compound having a film forming ability, and an organic compound having a molecular weight of 500 or more is preferably used. When the molecular weight of the organic compound is 500 or more, the film-forming ability is improved and a nano-level resist pattern is easily formed.
The organic compound having a molecular weight of 500 or more is roughly classified into a low molecular weight organic compound having a molecular weight of 500 to 2000 (hereinafter referred to as a low molecular compound) and a high molecular weight resin having a molecular weight of more than 2000 (polymer). Is done. As the low molecular weight compound, a non-polymer is usually used. In the case of a resin (polymer), a polystyrene-reduced weight average molecular weight by GPC (gel permeation chromatography) is used as the “molecular weight”. Hereinafter, the term “resin” simply means a resin having a molecular weight of more than 2000.
The component (A) may be a low-molecular compound whose solubility in an alkali developer is changed by the action of an acid, or may be a resin whose solubility in an alkali developer is changed by the action of an acid. It may be a mixture of

As the component (A), organic compounds that are usually used as base components for chemically amplified resists can be used alone or in combination of two or more.
The component (A) of the chemically amplified resist composition used in the present invention preferably has a hydrophilic group.
The hydrophilic group in the component (A) includes a hydroxyl group, a carboxy group, a carbonyl group (—C (O) —), an ester group (ester bond; —C (O) —O—), an amino group, and an amide group. One or more selected from the group consisting of Among these, a hydroxyl group (particularly an alcoholic hydroxyl group or a phenolic hydroxyl group), a carboxy group, and an ester group are more preferable.
Among these, a carboxy group, an alcoholic hydroxyl group, and a phenolic hydroxyl group are preferable because they can form a resist pattern having a small line edge roughness (unevenness on the pattern side wall) at the nano level.

  In the present specification, “structural unit” and “unit” mean a monomer unit constituting a resin (polymer).

As the component (A) of the positive resist composition, a substrate component having an acid dissociable, dissolution inhibiting group and increasing the solubility in an alkali developer by the action of an acid is used.
Such a positive resist composition is hardly soluble in an alkali developer before exposure. When an acid is generated from the component (B) by exposure at the time of resist pattern formation, an acid dissociable, dissolution inhibiting group is generated by the action of the acid. Dissociates, and the component (A) becomes soluble in an alkaline developer. Therefore, in the formation of a resist pattern, when selective exposure is performed on a resist film obtained by applying the positive resist composition on a substrate, the exposed portion turns soluble in an alkali developer, Since the unexposed portion remains hardly soluble in the alkali developer, it does not change, so that alkali development can be performed.

As the (A) component of the positive resist composition, those having a hydrophilic group and an acid dissociable, dissolution inhibiting group are preferred, and the following (A-1) component and / or (A-2) component are more preferred.
The hydrophilic group may also serve as an acid dissociable, dissolution inhibiting group.
Component (A-1): a resin having a hydrophilic group and an acid dissociable, dissolution inhibiting group.
Component (A-2): a low molecular compound having a hydrophilic group and an acid dissociable, dissolution inhibiting group.
Hereinafter, preferred embodiments of the component (A-1) and the component (A-2) will be described more specifically.

[(A-1) component]
As the component (A-1), a resin having a structural unit having a hydrophilic group and a structural unit having an acid dissociable, dissolution inhibiting group is preferable.
The proportion of the structural unit having the hydrophilic group in the resin is preferably 20 to 80 mol%, more preferably 20 to 70 mol%, based on the total amount of all the structural units constituting the resin. 20 to 60 mol% is more preferable.
The proportion of the structural unit having the acid dissociable, dissolution inhibiting group in the resin is preferably 20 to 80 mol% with respect to the total amount of all structural units constituting the resin. Is more preferable, and 30 to 60 mol% is more preferable.
Preferably, the structural unit having a hydrophilic group is a structural unit having a carboxy group, an alcoholic hydroxyl group or a phenolic hydroxyl group, more preferably an acrylic acid, methacrylic acid or an alcoholic hydroxyl group (α-lower alkyl). A unit derived from an acrylate ester and hydroxystyrene.

More specifically, the component (A-1) is derived from a novolak resin having a hydrophilic group and an acid dissociable, dissolution inhibiting group, a hydroxystyrene resin, an (α-lower alkyl) acrylate resin, or hydroxystyrene. And a copolymer resin containing a structural unit derived from an (α-lower alkyl) acrylate ester are preferably used.
In this specification, “(α-lower alkyl) acrylic acid” refers to one or both of acrylic acid (CH ₂ ═CH—COOH) and α-lower alkylacrylic acid.
α-Lower alkyl acrylic acid refers to one in which a hydrogen atom bonded to a carbon atom to which a carbonyl group in acrylic acid is bonded is substituted with a lower alkyl group. “(Α-Lower alkyl) acrylic acid ester” is an ester derivative of “(α-lower alkyl) acrylic acid” and represents one or both of acrylic acid ester and α-lower alkyl acrylic acid ester.
The “structural unit derived from (α-lower alkyl) acrylic acid ester” is a structural unit formed by cleavage of an ethylenic double bond of (α-lower alkyl) acrylic acid ester. -Lower alkyl) acrylate structural unit. “(Α-lower alkyl) acrylate” refers to one or both of acrylate and α-lower alkyl acrylate.
The “structural unit derived from hydroxystyrene” is a structural unit formed by cleaving an ethylenic double bond of hydroxystyrene or α-lower alkylhydroxystyrene, and may hereinafter be referred to as a hydroxystyrene unit. “Α-lower alkylhydroxystyrene” indicates that the lower alkyl group is bonded to the carbon atom to which the phenyl group is bonded.
In the “structural unit derived from an α-lower alkyl acrylate ester” and the “structural unit derived from an α-lower alkylhydroxystyrene”, the lower alkyl group bonded to the α-position has 1 to 5 carbon atoms. An alkyl group, preferably a linear or branched alkyl group, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group Etc. Industrially, a methyl group is preferable.
In the lower alkyl group, part or all of the hydrogen atoms may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable.

The resin component suitable as the component (A-1) is not particularly limited. For example, a unit having a phenolic hydroxyl group such as the following structural unit (a1), the following structural unit (a2) and the following structural unit A structural unit having at least one acid dissociable, dissolution inhibiting group selected from the group consisting of the unit (a3), and poorly soluble in an alkali developer such as the structural unit (a4) used as necessary. The resin component which has a structural unit of (Hereinafter, it may be called (A-11) component.).
In the component (A-11), cleavage occurs in the structural unit (a2) and / or the structural unit (a3) by the action of the acid generated from the acid generator upon exposure. On the other hand, in a resin that is hardly soluble, the solubility in an alkali developer increases. As a result, a chemically amplified positive pattern can be formed by exposure and development.

..Structural unit (a1)
The structural unit (a1) is a unit having a phenolic hydroxyl group, and is preferably a unit derived from hydroxystyrene represented by the following general formula (I).

（式中、Ｒは水素原子または低級アルキル基を示す。）

(In the formula, R represents a hydrogen atom or a lower alkyl group.)

R is a hydrogen atom or a lower alkyl group. The lower alkyl group is as described above, and a hydrogen atom or a methyl group is particularly preferable. The description of R is the same below.
The bonding position of —OH to the benzene ring is not particularly limited, but the position 4 (para position) described in the formula is preferred.
The structural unit (a1) is contained in the component (A-11) in an amount of 40 to 80 mol%, preferably 50 to 75 mol%, from the viewpoint of forming a resist pattern. By setting it to 40 mol% or more, solubility in an alkali developer can be improved, and an effect of improving the resist pattern shape can also be obtained. The balance with other structural units can be taken by setting it as 80 mol% or less.
Moreover, from the point that a coating film is formed on the pattern, the structural unit (a1) is preferably contained in the component (A-11) in an amount of 50 mol% or more, more preferably 60 mol% or more. More preferably, it is 75 mol% or more. Although an upper limit is not specifically limited, It is 80 mol% or less. Within the above range, due to the presence of the phenolic hydroxyl group, a good coating film can be formed on the pattern, and a pattern with a good shape can be obtained. In addition, the adhesion between the pattern and the coating film is improved.

..Structural unit (a2)
The structural unit (a2) is a structural unit having an acid dissociable, dissolution inhibiting group, and is represented by the following general formula (II).

（式中、Ｒは上記と同じであり、Ｘは酸解離性溶解抑制基を示す。）

(In the formula, R is the same as above, and X represents an acid dissociable, dissolution inhibiting group.)

The acid dissociable, dissolution inhibiting group X is an alkyl group having a tertiary carbon atom, and the tertiary carbon atom of the tertiary alkyl group is bonded to the ester group [—C (O) O—]. Examples thereof include acid-dissolving dissolution inhibiting groups, cyclic acetal groups such as a tetrahydropyranyl group and a tetrahydrofuranyl group.
As such an acid dissociable, dissolution inhibiting group X, for example, those other than the above can be arbitrarily used from among those used in a chemically amplified positive resist composition.

  As the structural unit (a2), for example, those represented by general formula (III) shown below are preferred.

In the formula, R is the same as above, and R ¹¹ , R ¹² , and R ¹³ may each independently be a lower alkyl group (either linear or branched. Preferably, it has 1 to 5 carbon atoms. .) Or, among R ¹¹ , R ¹² and R ¹³ , R ¹¹ may be a lower alkyl group, and R ¹² and R ¹³ may be bonded to form a monocyclic or polycyclic aliphatic cyclic group. . The aliphatic cyclic group preferably has 5 to 12 carbon atoms.
When R ¹¹ , R ¹² and R ¹³ do not have an aliphatic cyclic group, for example, it is preferable that R ¹¹ , R ¹² and R ¹³ are all methyl groups.
In the case where any of R ¹¹ , R ¹² and R ¹³ has an aliphatic cyclic group, when the aliphatic cyclic group is a monocyclic aliphatic cyclic group, as the structural unit (a2), for example, cyclopentyl And those having a cyclohexyl group are preferred.
When the aliphatic cyclic group is a polycyclic alicyclic group, preferred examples of the structural unit (a2) include those represented by the following general formula (IV).

［式中、Ｒは上記と同じであり、Ｒ^１４は低級アルキル基（直鎖状、分岐鎖状のいずれでもよい。好ましくは、炭素数は１〜５である。）］

[Wherein, R is the same as above, and R ¹⁴ is a lower alkyl group (which may be linear or branched. Preferably, it has 1 to 5 carbon atoms)]

  Moreover, what is represented by the following general formula (V) is preferable as what has an acid dissociable dissolution inhibiting group containing a polycyclic aliphatic cyclic group.

［式中、Ｒは上記と同じであり、Ｒ^１５、Ｒ^１６は、それぞれ独立に低級アルキル基（直鎖状、分岐鎖状のいずれでもよい。好ましくは、炭素数は１〜５である。）である。］

[Wherein, R is the same as defined above, and R ¹⁵ and R ¹⁶ each independently represent a lower alkyl group (which may be linear or branched. Preferably, it has 1 to 5 carbon atoms. ). ]

  In the component (A-11), the proportion of the structural unit (a2) is preferably 5 to 50 mol%, more preferably 10 to 40 mol%, and still more preferably 10 to 35 mol%.

..Structural unit (a3)
The structural unit (a3) is a structural unit having an acid dissociable, dissolution inhibiting group, and is represented by the following general formula (VI).

（式中、Ｒは上記と同じであり、Ｘ’は酸解離性溶解抑制基を示す。）

(In the formula, R is the same as above, and X ′ represents an acid dissociable, dissolution inhibiting group.)

Examples of the acid dissociable, dissolution inhibiting group X ′ include tertiary alkyloxycarbonyl groups such as tert-butyloxycarbonyl group and tert-pentyloxycarbonyl group; tert-butyloxycarbonylmethyl group, tert-butyloxycarbonylethyl group Tertiary alkyloxycarbonylalkyl groups such as: tertiary alkyl groups such as tert-butyl and tert-pentyl groups; cyclic acetal groups such as tetrahydropyranyl and tetrahydrofuranyl groups; ethoxyethyl groups and methoxypropyl groups And alkoxyalkyl groups.
Among these, a tert-butyloxycarbonyl group, a tert-butyloxycarbonylmethyl group, a tert-butyl group, a tetrahydropyranyl group, and an ethoxyethyl group are preferable.
As the acid dissociable, dissolution inhibiting group X ′, those other than those described above can be arbitrarily used from among those used in, for example, chemically amplified positive resist compositions.
In the general formula (VI), the bonding position of the group (—OX ′) bonded to the benzene ring is not particularly limited, but the position 4 (para position) shown in the formula is preferable.

  The structural unit (a3) is in the range of 5 to 50 mol%, preferably 10 to 40 mol%, more preferably 10 to 35 mol% in the component (A-11).

..Structural unit (a4)
The structural unit (a4) is a unit that is hardly soluble in an alkali developer and is represented by the following general formula (VII).

（式中、Ｒは上記と同じであり、Ｒ^４’は低級アルキル基を示し、ｎ’は０または１〜３の整数を示す。）

(In the formula, R is the same as above, R ^{4 ′} represents a lower alkyl group, and n ′ represents 0 or an integer of 1 to 3).

The lower alkyl group for R ^{4 ′} may be either linear or branched, and the carbon number is preferably 1 to 5.
n ′ represents 0 or an integer of 1 to 3, and is preferably 0.

  In the component (A-11), the proportion of the structural unit (a4) is preferably 1 to 40 mol%, more preferably 5 to 25 mol%. By setting it to 1 mol% or more, the effect of improving the shape (particularly, improving film loss) is enhanced, and by setting it to 40 mol% or less, it is possible to balance with other structural units.

In the component (A-11), while the structural unit (a1) and at least one selected from the group consisting of the structural unit (a2) and the structural unit (a3) are essential, the structural unit (a4) is arbitrarily selected. May be included. In addition, a copolymer having all these units may be used, or a mixture of polymers having one or more of these units may be used. Or you may combine these.
Further, the component (A-11) can optionally contain components other than the structural units (a1), (a2), (a3), and (a4), but the total ratio of these structural units is 80. It is preferably at least mol%, more preferably at least 90 mol%, most preferably 100 mol%.

As the component (A-11), in particular, “any one of the copolymers having the structural units (a1) and (a3), or a mixture of two or more of the copolymers” or “configuration An embodiment in which any one of the copolymers having units (a1), (a2) and (a4), or a mixture of two or more of the copolymers is used or mixed, has lithography characteristics, heat resistance It is most preferable because of its excellent properties.
In particular, a mixture of polyhydroxystyrene protected with a tertiary alkyloxycarbonyl group and polyhydroxystyrene protected with a 1-alkoxyalkyl group is preferred. When such mixing is performed, the mixing ratio (mass ratio) of each polymer (polyhydroxystyrene protected with a tertiary alkyloxycarbonyl group / 1-polyhydroxystyrene protected with 1-alkoxyalkyl group) is, for example, 1/9 to The ratio is 9/1, preferably 2/8 to 8/2, and more preferably 2/8 to 5/5.

In addition to the component (A-11), examples of the resin component suitable as the component (A-1) include (α-lower alkyl) acrylate resin (hereinafter referred to as component (A-12)).
As the component (A-12), a resin having a structural unit (a5) derived from an (α-lower alkyl) acrylic acid ester containing an acid dissociable, dissolution inhibiting group is preferable. The α-lower alkyl group is the same as described above.
The acid dissociable, dissolution inhibiting group of the structural unit (a5) has an alkali dissolution inhibiting property that makes the entire component (A-12) before exposure difficult to dissolve in an alkali developer, and at the same time, the component (B) after exposure. It is a group that is dissociated by the action of the acid generated from, and changes the entire component (A-12) to be soluble in an alkali developer.
In the component (A-12), when the acid dissociable, dissolution inhibiting group in the structural unit (a5) is dissociated by the acid generated from the component (B), a carboxylic acid is generated.

As the acid dissociable, dissolution inhibiting group, for example, a resin for resist compositions of ArF excimer laser can be appropriately selected and used from among many proposed ones. In general, a group that forms a cyclic or chain tertiary alkyl ester with a carboxy group of (α-lower alkyl) acrylic acid, or a cyclic or chain alkoxyalkyl group is widely known.
Here, the “group forming a tertiary alkyl ester” is a group that forms an ester by substituting a hydrogen atom of a carboxy group of acrylic acid. That is, it shows a structure in which the tertiary carbon atom of a chain-like or cyclic tertiary alkyl group is bonded to the terminal oxygen atom of the carbonyloxy group [—C (O) —O—] of the acrylate ester. . In this tertiary alkyl ester, when an acid acts, a bond is cut between an oxygen atom and a tertiary carbon atom.
The tertiary alkyl group is an alkyl group having a tertiary carbon atom.
Examples of the group that forms a chain-like tertiary alkyl ester include a tert-butyl group and a tert-pentyl group.
Examples of the group that forms a cyclic tertiary alkyl ester include those exemplified in the “acid dissociable, dissolution inhibiting group containing an alicyclic group” described later.

The “cyclic or chain alkoxyalkyl group” forms an ester by substituting a hydrogen atom of a carboxy group. That is, a structure is formed in which the alkoxyalkyl group is bonded to the terminal oxygen atom of the carbonyloxy group [—C (O) —O—] of the acrylate ester. In such a structure, the bond between the oxygen atom and the alkoxyalkyl group is broken by the action of the acid.
Examples of such cyclic or chain alkoxyalkyl groups include 1-methoxymethyl group, 1-ethoxyethyl group, 1-isopropoxyethyl, 1-cyclohexyloxyethyl group, 2-adamantoxymethyl group, 1-methyladamant Examples thereof include a xymethyl group, a 4-oxo-2-adamantoxymethyl group, a 1-adamantoxyethyl group, and a 2-adamantoxyethyl group.

As the structural unit (a5), a structural unit containing an acid dissociable, dissolution inhibiting group containing a cyclic group, particularly an aliphatic cyclic group, is preferred.
Here, “aliphatic” and “aliphatic cyclic group” are as defined above.
The aliphatic cyclic group may be monocyclic or polycyclic, and can be appropriately selected and used from among many proposed, for example, ArF resists. From the viewpoint of etching resistance, a polycyclic alicyclic group is preferred. The alicyclic group is preferably a hydrocarbon group, and particularly preferably a saturated hydrocarbon group (alicyclic group).
Examples of the monocyclic alicyclic group include groups in which one hydrogen atom has been removed from a cycloalkane. Examples of the polycyclic alicyclic group include groups in which one hydrogen atom has been removed from bicycloalkane, tricycloalkane, tetracycloalkane and the like.
Specifically, examples of the monocyclic alicyclic group include a cyclopentyl group and a cyclohexyl group. Examples of the polycyclic alicyclic group include groups in which one hydrogen atom has been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.
Among these, an adamantyl group obtained by removing one hydrogen atom from adamantane, a norbornyl group obtained by removing one hydrogen atom from norbornane, a tricyclodecanyl group obtained by removing one hydrogen atom from tricyclodecane, tetra A tetracyclododecanyl group obtained by removing one hydrogen atom from cyclododecane is industrially preferred.

More specifically, the structural unit (a5) is preferably at least one selected from the following general formulas (I ′) to (III ′).
And a unit derived from an (α-lower alkyl) acrylate ester having a cyclic alkoxyalkyl group as described above, specifically 2-adamantoxymethyl group, 1-methyladamant Aliphatic polycyclic alkyloxy lower alkyl (α which may have a substituent such as xymethyl group, 4-oxo-2-adamantoxymethyl group, 1-adamantoxyethyl group, 2-adamantoxyethyl group, etc. -Lower alkyl) It is preferably at least one selected from units derived from acrylic acid esters.

［式（Ｉ’）中、Ｒは上記と同じであり、Ｒ^１は低級アルキル基である。］

[In the formula (I ′), R is the same as above, and R ¹ is a lower alkyl group. ]

［式（ＩＩ’）中、Ｒは上記と同じであり、Ｒ^２及びＲ^３はそれぞれ独立に低級アルキル基である。］

[In formula (II ′), R is as defined above, and R ² and R ³ each independently represents a lower alkyl group. ]

［式（ＩＩＩ’）中、Ｒは上記と同じであり、Ｒ^４は第３級アルキル基である。］

[In the formula (III ′), R is the same as above, and R ⁴ is a tertiary alkyl group. ]

In formulas (I ′) to (III ′), the hydrogen atom or lower alkyl group of R is the same as described above for the hydrogen atom or lower alkyl group bonded to the α-position of the acrylate ester.
The lower alkyl group for R ¹ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, Examples include isobutyl group, pentyl group, isopentyl group, neopentyl group and the like. Among these, a methyl group and an ethyl group are preferable because they are easily available industrially.
The lower alkyl group for R ² and R ³ is preferably each independently a linear or branched alkyl group having 1 to 5 carbon atoms. Among them, when R ² and R ³ are both methyl groups is preferred industrially. Specific examples include structural units derived from 2- (1-adamantyl) -2-propyl acrylate.

R ⁴ is a chain-like tertiary alkyl group or a cyclic tertiary alkyl group. Examples of the chain-like tertiary alkyl group include a tert-butyl group and a tert-pentyl group, and the tert-butyl group is industrially preferable.
The cyclic tertiary alkyl group is the same as that exemplified in the aforementioned “acid dissociable, dissolution inhibiting group containing an aliphatic cyclic group”, and includes a 2-methyl-2-adamantyl group, 2-ethyl- A 2-adamantyl group, 2- (1-adamantyl) -2-propyl group, 1-ethylcyclohexyl group, 1-ethylcyclopentyl group, 1-methylcyclohexyl group, 1-methylcyclopentyl group and the like can be mentioned.
The group —COOR ⁴ may be bonded to the 3 or 4 position of the tetracyclododecanyl group shown in the formula, but the bonding position cannot be specified. Similarly, the carboxy group residue of the acrylate structural unit may be bonded to the position 8 or 9 shown in the formula.

The structural unit (a5) can be used alone or in combination of two or more.
In the component (A-12), the proportion of the structural unit (a5) is preferably 20 to 60 mol% with respect to the total of all the structural units constituting the component (A-12), and is preferably 25 to 50 mol. % Is more preferable, and 30 to 45 mol% is most preferable. A resist pattern can be obtained by setting it to the lower limit value or more, and a balance with other structural units can be achieved by setting the upper limit value or less.

In the first positive resist composition and the second positive resist composition, the component (A-12) is derived from an acrylate ester having a lactone ring in addition to the structural unit (a5). It is preferable to have a unit (a6). The structural unit (a6) is effective in increasing the adhesion of the resist film to the substrate and increasing the hydrophilicity with the developer.
In the structural unit (a6), a lower alkyl group or a hydrogen atom is bonded to the α-position carbon atom. The lower alkyl group bonded to the α-position carbon atom is the same as described for the structural unit (a5), and is preferably a methyl group.
Examples of the structural unit (a6) include a structural unit in which a monocyclic group consisting of a lactone ring or a polycyclic cyclic group having a lactone ring is bonded to the ester side chain portion of the acrylate ester. At this time, the lactone ring refers to one ring containing the —O—C (O) — structure, and this is counted as the first ring. Therefore, here, when only the lactone ring is present, it is referred to as a monocyclic group, and when it has another ring structure, it is referred to as a polycyclic group regardless of the structure.
Examples of the structural unit (a6) include a monocyclic group obtained by removing one hydrogen atom from γ-butyrolactone and a polycyclic group obtained by removing one hydrogen atom from a lactone ring-containing bicycloalkane. It is done.
More specifically, the structural unit (a6) is preferably at least one selected from, for example, the following general formulas (IV ′) to (VII ′).

［式（ＩＶ’）中、Ｒは上記と同じであり、Ｒ^５、Ｒ^６は、それぞれ独立に、水素原子または低級アルキル基である。］

[In formula (IV ′), R is the same as defined above, and R ⁵ and R ⁶ each independently represent a hydrogen atom or a lower alkyl group. ]

［式（Ｖ’）中、Ｒは上記と同じであり、ｍは０または１である。］

[In the formula (V ′), R is the same as described above, and m is 0 or 1. ]

［式（ＶＩ’）中、Ｒは上記と同じである。］

[In the formula (VI ′), R is the same as above. ]

［式（ＶＩＩ’）中、Ｒは上記と同じである。］

[In the formula (VII ′), R is the same as above. ]

In formula (IV ′), R ⁵ and R ⁶ are each independently a hydrogen atom or a lower alkyl group, preferably a hydrogen atom. In R ⁵ and R ⁶ , the lower alkyl group is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, Examples thereof include an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. Industrially, a methyl group is preferable.

Among the structural units represented by the general formulas (IV ′) to (VII ′), the structural unit represented by (IV ′) is inexpensive and industrially preferable, and among the structural units represented by (IV ′) , R is a methyl group, R ⁵ and R ⁶ are hydrogen atoms, and the position of the ester bond between the methacrylic ester and γ-butyrolactone is α-position on the lactone ring is α-methacryloyloxy-γ-butyrolactone Most preferably it is.
The structural unit (a6) can be used alone or in combination of two or more.
In the first positive resist composition, the proportion of the structural unit (a6) in the component (A-12) is 20 to 70 mol% with respect to the total of all the structural units constituting the component (A-12). Is preferable, 35-65 mol% is more preferable, and 40-60 mol% is the most preferable. Lithographic properties are improved by setting it to the lower limit value or more, and balance with other structural units can be achieved by setting the upper limit value or less.
In the second positive resist composition, the proportion of the structural unit (a6) in the component (A-12) is 10 to 50 mol% with respect to the total of all the structural units constituting the component (A-12). Is preferable, 10 to 45 mol% is more preferable, and 15 to 40 mol% is most preferable. Lithographic properties are improved by setting it to the lower limit value or more, and balance with other structural units can be achieved by setting the upper limit value or less.

The component (A-12) is derived from an acrylate ester containing a polar group-containing polycyclic group in addition to the structural unit (a5) or in addition to the structural units (a5) and (a6). It is preferable to have a structural unit (a7).
By the structural unit (a7), the hydrophilicity of the entire component (A-12) is increased, the affinity with the developer is increased, the solubility in the alkaline developer in the exposed area is improved, and the resolution is improved. Contribute.
In the structural unit (a7), a lower alkyl group or a hydrogen atom is bonded to the α-position carbon atom. The lower alkyl group bonded to the α-position carbon atom is the same as described for the structural unit (a5), and is preferably a methyl group.
Examples of the polar group include a hydroxyl group, a cyano group, a carboxy group, and an amino group, and a hydroxyl group is particularly preferable.
As the polycyclic group, among the aliphatic cyclic groups exemplified in the “acid dissociable, dissolution inhibiting group containing an aliphatic cyclic group” which is the structural unit (a5), a polycyclic group is appropriately selected. It can be selected and used.
The structural unit (a7) is preferably at least one selected from the following general formulas (VIII ′) to (X ′).

［式（ＶＩＩＩ’）中、Ｒは上記と同じであり、ｎは１〜３の整数である。］

[In the formula (VIII ′), R is the same as described above, and n is an integer of 1 to 3. ]

R in the formula (VIII ′) is the same as R in the above formulas (I ′) to (III ′).
Among these, those in which n is 1 and the hydroxyl group is bonded to the 3-position of the adamantyl group are preferable.

［式（ＩＸ’）中、Ｒは上記と同じであり、ｋは１〜３の整数である。］

[In formula (IX ′), R is the same as above, and k is an integer of 1 to 3. ]

  Among these, those in which k is 1 are preferable. Moreover, it is preferable that the cyano group has couple | bonded with 5-position or 6-position of the norbornyl group.

［式（Ｘ’）中、Ｒは上記と同じであり、ｔ’は１〜３の整数であり、ｌは１〜５の整数であり、ｓは１〜３の整数である。］

[In formula (X ′), R is the same as above, t ′ is an integer of 1 to 3, l is an integer of 1 to 5, and s is an integer of 1 to 3. ]

  Among these, t ′ is preferably 1. l is preferably 1. s is preferably 1. These preferably have a 2-norbornyl group or a 3-norbornyl group bonded to the terminal of the carboxy group of acrylic acid. The fluorinated alkyl alcohol is preferably bonded to the 5th or 6th position of the norbornyl group.

The structural unit (a7) can be used alone or in combination of two or more.
In the first positive resist composition, the proportion of the structural unit (a7) in the component (A-12) is 10 to 50 mol% based on the total of all the structural units constituting the component (A-12). Is preferable, 10 to 40 mol% is more preferable, and 15 to 35 mol% is most preferable. Lithographic properties are improved by setting it to the lower limit value or more, and balance with other structural units can be achieved by setting the upper limit value or less.
In the second positive resist composition, the proportion of the structural unit (a7) in the component (A-12) is 20 to 70 mol% with respect to the total of all the structural units constituting the component (A-12). Is preferable, 35-65 mol% is more preferable, and 40-60 mol% is the most preferable. Lithographic properties are improved by setting it to the lower limit value or more, and balance with other structural units can be achieved by setting the upper limit value or less.
In particular, since the solubility in organic solvents (S ₂ ) such as alcohol solvents and fluorine solvents described later is good, the second positive resist composition has a configuration represented by the above general formula (X ′). It is preferable to contain a copolymer having units.

  In the component (A-12), the total of these structural units (a5) to (a7) is 70 to 100 mol% with respect to the total of all the structural units constituting the component (A-12). Preferably, it is 80-100 mol%.

The component (A-12) may contain a structural unit (a8) other than the structural units (a5) to (a7).
The structural unit (a8) is not particularly limited as long as it is another structural unit that is not classified into the structural units (a5) to (a7).
As the structural unit (a8), for example, a structural unit containing a polycyclic aliphatic hydrocarbon group and derived from an (α-lower alkyl) acrylate ester is preferable. The polycyclic aliphatic hydrocarbon group is appropriately selected from, for example, polycyclic ones among the aliphatic cyclic groups exemplified in the aforementioned “acid dissociable, dissolution inhibiting group containing an aliphatic cyclic group”. Can be used. In particular, at least one selected from a tricyclodecanyl group, an adamantyl group, a tetracyclododecanyl group, a norbornyl group, and an isobornyl group is preferable in terms of industrial availability. The structural unit (a8) is most preferably a non-acid dissociable group.
Specific examples of the structural unit (a8) include the following structures (X) to (XII).

（式中、Ｒは上記と同じである。）

(In the formula, R is the same as above.)

（式中、Ｒは上記と同じである。）

(In the formula, R is the same as above.)

（式中、Ｒは上記と同じである。）

(In the formula, R is the same as above.)

  In the case of having the structural unit (a8), the proportion of the structural unit (a8) in the component (A-12) is 1 to 25 mol% based on the total of all the structural units constituting the component (A-12). Preferably, 5 to 20 mol% is more preferable.

  In the first positive resist composition and the second positive resist composition, the component (A-12) as the component (A) includes at least the structural units (a5), (a6), and (a7). A polymer is preferred. Examples of such a copolymer include a copolymer composed of the structural units (a5), (a6) and (a7), and a copolymer composed of the structural units (a5), (a6), (a7) and (a8). A polymer etc. can be illustrated.

  The component (A-1) can be obtained by polymerizing the monomer related to the structural unit by a known method. For example, the monomer related to each structural unit can be obtained by polymerizing by a known radical polymerization using a radical polymerization initiator such as azobisisobutyronitrile (AIBN).

The component (A-1) is preferably 30000 or less, more preferably 20000 or less, and preferably 12000 or less, in terms of mass average molecular weight (Mw, polystyrene-converted mass average molecular weight by gel permeation chromatography, the same shall apply hereinafter). More preferably. The lower limit may be more than 2000, and is preferably 4000 or more, and more preferably 5000 or more in terms of suppressing pattern collapse and improving resolution.
Further, the dispersity (Mw / Mn) is not particularly limited, but is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5. . In addition, Mn shows a number average molecular weight.

[(A-2) component]
The component (A-2) has a molecular weight of 500 or more and 2000 or less, has a hydrophilic group, and has an acid dissociable, dissolution inhibiting group X or X as exemplified in the description of the component (A-1). Low molecular weight compounds having 'are preferred.
Specifically, those in which a part of the hydrogen atoms of the hydroxyl group of the compound having a plurality of phenol skeletons are substituted with the acid dissociable, dissolution inhibiting group X or X ′ can be mentioned.
The component (A-2) contains, for example, a part of the hydrogen atom of the hydroxyl group of a low molecular weight phenol compound known as a sensitizer or heat resistance improver for non-chemically amplified g-line or i-line resists. Those substituted with a dissociable, dissolution inhibiting group are preferred and can be arbitrarily used.

Examples of such low molecular weight phenol compounds include the following.
Bis (4-hydroxyphenyl) methane, bis (2,3,4-trihydroxyphenyl) methane, 2- (4-hydroxyphenyl) -2- (4′-hydroxyphenyl) propane, 2- (2,3,3) 4-trihydroxyphenyl) -2- (2 ′, 3 ′, 4′-trihydroxyphenyl) propane, tris (4-hydroxyphenyl) methane, bis (4-hydroxy-3,5-dimethylphenyl) -2- Hydroxyphenylmethane, bis (4-hydroxy-2,5-dimethylphenyl) -2-hydroxyphenylmethane, bis (4-hydroxy-3,5-dimethylphenyl) -3,4-dihydroxyphenylmethane, bis (4- Hydroxy-2,5-dimethylphenyl) -3,4-dihydroxyphenylmethane, bis (4-hydroxy-3-methylphenol) Nyl) -3,4-dihydroxyphenylmethane, bis (3-cyclohexyl-4-hydroxy-6-methylphenyl) -4-hydroxyphenylmethane, bis (3-cyclohexyl-4-hydroxy-6-methylphenyl) -3 , 4-dihydroxyphenylmethane, 1- [1- (4-hydroxyphenyl) isopropyl] -4- [1,1-bis (4-hydroxyphenyl) ethyl] benzene, phenol, m-cresol, p-cresol or xylenol And 2,3,4 nuclei of formalin condensates of phenols and the like. Of course, it is not limited to these.
The acid dissociable, dissolution inhibiting group is not particularly limited, and examples thereof include those described above.

<(B) component>
As the component (B), any conventionally known acid generator for chemically amplified resists can be appropriately selected and used. Examples of such acid generators include onium salt acid generators such as iodonium salts and sulfonium salts, oxime sulfonate acid generators, bisalkyl or bisarylsulfonyldiazomethanes, poly (bissulfonyl) diazomethanes, and the like. There are various known diazomethane acid generators, nitrobenzyl sulfonate acid generators, imino sulfonate acid generators, disulfone acid generators, and the like.

  Specific examples of the onium salt acid generator include diphenyliodonium trifluoromethanesulfonate, (4-methoxyphenyl) phenyliodonium trifluoromethanesulfonate, bis (p-tert-butylphenyl) iodonium trifluoromethanesulfonate, and triphenylsulfonium trifluoromethanesulfonate. (4-methoxyphenyl) diphenylsulfonium trifluoromethanesulfonate, (4-methylphenyl) diphenylsulfonium nonafluorobutanesulfonate, (p-tert-butylphenyl) diphenylsulfonium trifluoromethanesulfonate, diphenyliodonium nonafluorobutanesulfonate, bis (p -Tert-Butylphenyl) iodonium nonafluorobutans Honeto include triphenylsulfonium nonafluorobutanesulfonate. Of these, onium salts having a fluorinated alkyl sulfonate ion as an anion are preferable.

  Examples of oxime sulfonate compounds include α- (methylsulfonyloxyimino) -phenylacetonitrile, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) -phenyl. Acetonitrile, α- (trifluoromethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (ethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (propylsulfonyloxyimino) -p-methylphenylacetonitrile, α -(Methylsulfonyloxyimino) -p-bromophenylacetonitrile and the like. Among these, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile is preferable.

  Specific examples of the diazomethane acid generator include bis (isopropylsulfonyl) diazomethane, bis (p-toluenesulfonyl) diazomethane, bis (1,1-dimethylethylsulfonyl) diazomethane, bis (cyclohexylsulfonyl) diazomethane, bis (2, 4-dimethylphenylsulfonyl) diazomethane and the like.

As the component (B), one type of acid generator may be used alone, or two or more types may be used in combination.
(B) The usage-amount of a component becomes like this. Preferably it is 1-20 mass parts with respect to 100 mass parts of (A) component, More preferably, you may be 2-10 mass parts. By setting it to be equal to or higher than the lower limit value of the above range, sufficient pattern formation is performed.
Moreover, the sensitivity of each positive resist composition can be adjusted by adjusting the compounding quantity of (B) component. For example, if the blending amount of the component (B) in the second positive resist composition is larger than that in the first positive resist composition, the sensitivity of the second positive resist composition is increased (minimum). It is possible to adjust the exposure amount (Eth ₂ ) and the optimum exposure amount (Eop ₂ ).
The sensitivity can also be adjusted by adjusting the blending amount of the following component (D).

<Optional component>
The positive resist composition may further contain a nitrogen-containing organic compound (D) (hereinafter referred to as “component (D)”) as an optional component in order to improve the pattern shape, stability over time, and the like. it can.
Since a wide variety of components (D) have been proposed, any known one may be used, but amines, particularly secondary lower aliphatic amines and tertiary lower aliphatic amines are preferred. .
Here, the lower aliphatic amine means an alkyl or alkyl alcohol amine having 5 or less carbon atoms. Examples of the secondary and tertiary amines include trimethylamine, diethylamine, triethylamine, and di-n-propylamine. , Tri-n-propylamine, tripentylamine, diethanolamine, triethanolamine, triisopropanolamine and the like, and tertiary alkanolamines such as triethanolamine and triisopropanolamine are particularly preferable.
These may be used alone or in combination of two or more.
(D) component is normally used in 0.01-5.0 mass parts with respect to 100 mass parts of (A) component.
If the blending amount of the component (D) in the second positive resist composition is less than that in the first positive resist composition, the sensitivity of the second positive resist composition is increased (minimum). It is possible to adjust the exposure amount (Eth ₂ ) and the optimum exposure amount (Eop ₂ ).
When adjusting the sensitivity of each positive resist composition, both the blending amount of the component (B) and the blending amount of the component (D) may be adjusted, or only one of them may be adjusted.

Further, in the positive resist composition, deterioration of sensitivity due to the blending with the component (D) is prevented, and an organic carboxylic acid or Phosphorus oxo acid or derivative thereof (E) (hereinafter referred to as component (E)) can be contained. In addition, (D) component and (E) component can also be used together, and any 1 type can also be used.
As the organic carboxylic acid, for example, malonic acid, citric acid, malic acid, succinic acid, benzoic acid, salicylic acid and the like are suitable.
Phosphorus oxoacids 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, phosphonic acid- Like 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.
(E) A component is normally used in the ratio of 0.01-5.0 mass parts per 100 mass parts of (A) component.

  If desired, the positive resist composition may further contain miscible additives such as an additional resin for improving the performance of the coating film of the resist composition, a surfactant for improving the coating property, and a dissolution agent. An inhibitor, a plasticizer, a stabilizer, a colorant, an antihalation agent and the like can be appropriately contained.

[(S) component]
As the component (S), any component can be used as long as it can dissolve each component to be used to form a uniform solution. Conventionally, any one or two of known solvents for resist compositions can be used. More than one species can be appropriately selected and used.
Specific examples include lactones such as γ-butyrolactone; ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl isopentyl ketone, and 2-heptanone; ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene Polyhydric alcohols such as glycol monoacetate, propylene glycol monomethyl ether acetate (PGMEA), dipropylene glycol, or monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether of dipropylene glycol monoacetate and derivatives thereof Cyclic ethers such as dioxane; methyl lactate, ethyl lactate (EL), acetic acid Can chill, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, and the like esters such as ethyl ethoxypropionate. Furthermore, the alcohol solvent mentioned later, a fluorine-type solvent, etc. are mentioned.

Among these, as the component (S) used in the first positive resist composition, propylene glycol monomethyl ether acetate (PGMEA), ethyl lactate (EL), and propylene glycol monomethyl ether (PGME) are preferable. These (S) components may be used independently and may be used as 2 or more types of mixed solvents. Among these, a combination of propylene glycol monomethyl ether acetate (PGMEA) and a polar solvent is preferable. The blending ratio (mass ratio) may be appropriately determined in consideration of the compatibility between PGMEA and the polar solvent, but is preferably in the range of 1: 9 to 9: 1. 2: 8 to 8 : More preferably within the range of 2.
More specifically, when EL is blended as a polar solvent, the mass ratio of PGMEA: EL is preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2. Moreover, when mix | blending PGME as a polar solvent, the mass ratio of PGMEA: PGME becomes like this. Preferably it is 1: 9-9: 1, More preferably, it is 2: 8-8: 2, More preferably, it is 3: 7-7: 3.

In the present invention, as the component (S) used in the second positive resist composition, the base material of the second positive resist composition is dissolved, and the base material of the first positive resist composition is used. It is preferable to use an organic solvent (S ₂ ) that does not dissolve.
Examples of such organic solvents (S _2), both of which are available as long as the solvent does not have a first resist film and the compatibility of the lower layer side.
Here, “does not dissolve the substrate of the first positive resist composition” means that the first positive resist composition is applied on a support and dried, and the film thickness is 0.2 μm under the condition of 23 ° C. When the first resist film is formed and immersed in an organic solvent, the film thickness does not vary even after 60 minutes.

Examples of such an organic solvent (S ₂ ) include alcohol solvents and fluorine solvents. These can be used alone or in combination.
Among these, alcohol solvents are preferable from the viewpoint of applicability and solubility of materials such as resin components. Therefore, the organic solvent preferably contains an alcohol solvent.
The alcohol solvent is more preferably a monohydric alcohol. Among them, although depending on the number of carbons, a primary or secondary monohydric alcohol is preferable, and a primary monohydric alcohol is most preferable.
The boiling point is preferably 80 to 160 ° C., more preferably 90 to 150 ° C., and preferably 100 to 135 ° C., coating properties, stability of composition during storage, and heating in the PAB process and PEB process. Most preferable from the viewpoint of temperature.
Here, the monohydric alcohol means a case where the number of hydroxy groups contained in the alcohol molecule is 1, and does not include a dihydric alcohol, a trihydric alcohol, or a derivative thereof.

  Specific examples of alcohol solvents include n-amyl alcohol, s-amyl alcohol, t-amyl alcohol, isoamyl alcohol, isobutanol (also called IBA, isobutyl alcohol or 2-methyl-1-propanol), isopropyl alcohol, 2 -Ethylbutanol, neopentyl alcohol, n-butanol, s-butanol, t-butanol, 1-propanol, n-hexanol, 2-heptanol (boiling point 160.4 ° C), 3-heptanol, 2-methyl-1-butanol 2-methyl-2-butanol, 4-methyl-2-pentanol and the like. Of these, isobutanol (IBA), 4-methyl-2-pentanol, n-butanol and the like are preferable. Isobutanol (IBA) is particularly preferred.

Examples of the fluorine-based solvent include perfluoro-2-butyltetrahydrofuran.
The organic solvent can be used alone or in combination.
The amount of component (S) used is not particularly limited. Usually, an amount is used in which the chemically amplified resist composition becomes a liquid having a concentration that can be applied onto the support.

[Organic film forming material]
In the first resist film forming step described above, the organic film forming material for forming the organic film that may be formed on the substrate as the support 10 is an electron beam or light like a resist film. Sensitivity is not necessarily required. Commonly used resists and resins can be used in the manufacture of semiconductor elements and liquid crystal display elements.
In addition, the organic film forming material can be formed by etching the organic film using the dense pattern formed by the resist pattern forming method of the present invention so that the dense pattern can be transferred to the organic film and the organic film pattern can be formed. Is preferably a material capable of forming an organic film that can be etched, particularly dry-etched.
In particular, a material capable of forming an organic film capable of etching such as oxygen plasma etching is preferable.
Such an organic film forming material may be a material conventionally used for forming an organic film such as an organic BARC. Examples include the ARC series manufactured by Brewer Science, the AR series manufactured by Rohm and Haas, and the SWK series manufactured by Tokyo Ohka Kogyo.
In particular, as described above, when oxygen plasma etching is used in the etching process, the organic film can be easily etched by oxygen plasma etching, and a fluorine gas such as halogen gas, specifically CF ₄ gas or CHF ₃ gas. It is preferable to use a material having a relatively high resistance to gas.
Further, an organic film containing at least one resin component selected from the group consisting of novolac resin, acrylic resin and soluble polyimide may be formed between the organic BARC and the substrate.
These materials are suitable for the present invention because they are easy to perform etching such as oxygen plasma etching and have high resistance to fluorocarbon gases. That is, in general, etching of a substrate or the like is performed using a halogen gas such as a fluorocarbon-based gas. Therefore, by forming an organic film from such a material, oxygen plasma etching is used when forming an organic film pattern. Etching resistance can be improved in a subsequent process using a halogen gas such as a fluorocarbon gas for etching a substrate or the like.
These resin components may be used individually by 1 type, and 2 or more types may be mixed and used for them.

Among the above, a novolak resin and an acrylic resin having an alicyclic moiety or an aromatic ring in the side chain are preferably used because they are inexpensive and widely used and have excellent resistance to dry etching using a fluorocarbon-based gas. Used.
As the novolac resin, those generally used in positive resist compositions can be used, and i-line and g-line positive resists containing novolac resin as a main component can also be used.

The novolac resin is, for example, a resin obtained by addition condensation of an aromatic compound having a phenolic hydroxyl group (hereinafter simply referred to as “phenols”) and an aldehyde under an acid catalyst.
Examples of phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-butylphenol, m-butylphenol, p-butylphenol, 2, 3 -Xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol , P-phenylphenol, resorcinol, hydroquinone, hydroquinone monomethyl ether, pyrogallol, phloroglicinol, hydroxydiphenyl, bisphenol A, gallic acid, gallic acid ester, α-naphthol, β-naphthol and the like.
Examples of aldehydes include formaldehyde, furfural, benzaldehyde, nitrobenzaldehyde, acetaldehyde and the like.
The catalyst for the addition condensation reaction is not particularly limited. For example, hydrochloric acid, nitric acid, sulfuric acid, formic acid, oxalic acid, acetic acid and the like are used as the acid catalyst.
As the novolak resin, a commercially available product can be used.

The lower limit of the mass average molecular weight (Mw) of the novolak resin is preferably 3000 or more, more preferably 5000 or more, more preferably 6000 or more, and further preferably 7000 or more. As an upper limit, 50000 or less is preferable, 30000 or less is more preferable, 10,000 or less is further more preferable, and 9000 or less is the most preferable.
When Mw is 3000 or more, it is difficult to sublime when baked at a high temperature, and the device or the like is hardly contaminated. Further, it is preferable to set Mw to 5000 or more because etching resistance against a fluorocarbon gas or the like is excellent.
Further, when Mw is 50000 or less, good embedding characteristics with respect to a substrate having fine irregularities are excellent, and when it is 10,000 or less, dry etching tends to be easy, which is preferable.

As the novolak resin, in particular, the content of low nuclei having a Mw of 5000 to 50000, preferably 8000 to 30000, and a molecular weight of 500 or less, preferably 200 or less, is gel permeation chromatography ( A novolak resin having a GPC) method of 1% by mass or less, preferably 0.8% by mass or less is preferred. The content of the low nucleus is preferably as small as possible, and is desirably 0% by mass.
In the novolak resin having Mw within the above range, the content of the low nucleus having a molecular weight of 500 or less is 1% by mass or less, so that the embedding characteristic with respect to the substrate having fine irregularities is improved. Although the reason why the embedding property is improved by reducing the content of the low nuclei is not clear, it is presumed that the degree of dispersion becomes small.
Here, the “low molecular weight having a molecular weight of 500 or less” is detected as a low molecular fraction having a molecular weight of 500 or less when analyzed by GPC using polystyrene as a standard. “Low molecular weight less than 500 molecular weight” includes monomers that have not been polymerized and those that have a low degree of polymerization, such as those in which 2 to 5 molecules of phenols are condensed with aldehydes, depending on the molecular weight. .
The content (mass%) of the low nuclei having a molecular weight of 500 or less is graphed by taking the analysis result by the GPC method with the fraction number on the horizontal axis and the concentration on the vertical axis. It is measured by determining the percentage (%) of the area under the curve of the low molecular fraction.

As the acrylic resin, those generally used in positive resist compositions can be used. For example, a structural unit derived from a polymerizable compound having an ether bond and a polymerizable compound having a carboxy group can be used. Mention may be made of acrylic resins containing derived structural units.
Examples of the polymerizable compound having an ether bond include 2-methoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (meth) acrylate, phenoxypolyethylene glycol (meta And (meth) acrylic acid derivatives having an ether bond and an ester bond such as acrylate, methoxypolypropylene glycol (meth) acrylate, and tetrahydrofurfuryl (meth) acrylate. These compounds can be used alone or in combination of two or more. In the present specification, (meth) acrylate indicates one or both of acrylate and methacrylate.
Examples of the polymerizable compound having a carboxy group include monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; 2-methacryloyloxyethyl succinic acid, and 2-methacryloyloxyethyl. Examples include maleic acid, 2-methacryloyloxyethylphthalic acid, 2-methacryloyloxyethylhexahydrophthalic acid and other compounds having a carboxy group and an ester bond, and acrylic acid and methacrylic acid are preferred. These compounds can be used alone or in combination of two or more.
A soluble polyimide is a polyimide that can be made liquid by an organic solvent.

The organic film-forming material further contains miscible additives as desired, for example, additional resins for improving the performance of organic films, surfactants for improving coating properties, dissolution inhibitors, plasticizers, Stabilizers, colorants, antihalation agents and the like can be appropriately contained.
The organic film forming material can be manufactured by dissolving the above-described materials such as the resin component in an organic solvent. As an organic solvent, the thing similar to what was illustrated as (S) component of the chemically amplified resist composition mentioned above can be used.

According to the resist pattern forming method of the present invention, a fine resist pattern can be formed using an existing exposure apparatus or an existing chemical amplification resist composition.
The resist pattern forming method of the present invention forms a fine resist pattern by performing, for example, one patterning of the second resist film on the upper layer side and one patterning of the first resist film on the lower layer side. Can do. Thereby, the number of steps can be reduced as compared with the double patterning method in which the patterning needs to be performed at least twice and the etching of the substrate or the like needs to be performed at least twice.

  Examples of the present invention will be described below, but the scope of the present invention is not limited to these examples.

(Example 1)
In the following procedure, a resist pattern was formed by the same process as that shown in FIG.
That is, an organic antireflection film composition “ARC29A” (trade name, manufactured by Brewer Science Co., Ltd.) is applied onto an 8-inch silicon wafer using a spinner, and baked on a hot plate at 205 ° C. for 60 seconds to be dried. Thereby, an organic antireflection film having a thickness of 77 nm was formed.
A first chemically amplified positive resist composition shown in Table 1 is applied on the organic antireflection film using a spinner, and prebaked (PAB) at 110 ° C. for 60 seconds on a hot plate. The first resist film 1 having a film thickness of 150 nm was formed by performing treatment and drying.
Next, a chemically amplified second positive resist composition shown in Table 1 is applied onto the first resist film 1 using a spinner, and prebaked at 110 ° C. for 60 seconds on a hot plate. By performing (PAB) treatment and drying, a second resist film 2 having a film thickness of 150 nm was formed.

Each abbreviation in Table 1 has the following meaning. Moreover, the numerical value in [] is a compounding quantity (mass part).
(A) -1: a copolymer represented by the following formula (A) -1.
(A) -2: a copolymer represented by the following formula (A) -2.
(B) -1: di (1-naphthyl) phenylsulfonium nonafluorobutanesulfonate (B) -2: triphenylsulfonium nonafluorobutanesulfonate (D) -1: tri-n-pentylamine (S) -1: propylene Glycol monomethyl ether acetate (PGMEA) / propylene glycol monomethyl ether (PGME) mixed solvent (6/4)
(S) -2: Isobutanol (IBA)

（質量平均分子量１００００、Ｍｗ／Ｍｎ＝１．５）

(Mass average molecular weight 10,000, Mw / Mn = 1.5)

（質量平均分子量１００００、Ｍｗ／Ｍｎ＝１．５）

(Mass average molecular weight 10,000, Mw / Mn = 1.5)

Here, the first resist film 1 on the lower layer side is dissolved as the resist solvent ((S) -2) of the second positive resist composition used when forming the second resist film 2 on the upper layer side. Isobutanol (IBA) was selected as the non-solvent. Moreover, resin (A) -2 containing many fluorinated alcohol units was selected as a copolymer which melt | dissolves with respect to isobutanol (IBA).
The minimum exposure (Eth ₁ ) of the first resist film 1 on the lower layer side was about 5 mJ / cm ² . Therefore, specifically, the blending of the component (D) is performed so that the minimum exposure amount (Eth ₂ ) and the optimum exposure amount (Eop ₂ ) of the second resist film 2 on the upper layer side are smaller than 5 mJ / cm ^2. The amount is adjusted to 0.1 parts by mass and less than the case of the first positive resist composition so that the optimum exposure amount (Eop ₂ ) of the second resist film 2 is 1.2 mJ / cm ^2. did.

Using an ArF exposure apparatus NSR-S302 (Nikon Corporation; NA (numerical aperture) = 0.60, σ = 0.75) and an ArF excimer laser (193 nm) as a photomask, “line width 180 nm, line width : Space width = 1: 1 ”was selectively irradiated through a halftone mask (manufactured by Dai Nippon Printing Co., Ltd .; transmittance 6%) (exposure amount (Dose ₂ ) 1.2 mJ / cm ² ).
Thereafter, PEB treatment was performed at 110 ° C. for 60 seconds, and further developed with an aqueous 2.38 mass% tetramethylammonium hydroxide (TMAH) solution at 23 ° C. for 30 seconds, and then rinsed with pure water for 20 seconds. Then, it was shaken and dried.

  A line-and-space (1: 1) resist pattern (coarse pattern 2 ′) in which a line pattern having a line width of 180 nm made of the second resist film is arranged at equal intervals (pitch 360 nm) without changing the first resist film. ) Was formed.

Using the above exposure apparatus NSR-S302 (manufactured by Nikon; NA (numerical aperture) = 0.60, σ = 0.75), an open frame exposure (exposure not through a mask) is performed with an ArF excimer laser (193 nm). (Exposure amount 24 mJ / cm ² ).
Thereafter, PEB treatment was performed at 110 ° C. for 60 seconds, and further developed with an aqueous 2.38 mass% tetramethylammonium hydroxide (TMAH) solution at 23 ° C. for 30 seconds, and then rinsed with pure water for 20 seconds. Then, it was shaken and dried.
Thereafter, the film is heated at 100 ° C. for 60 seconds (post-bake treatment) and dried to form a resist film (2) having an L / S pattern (dense pattern 1 ′) having a line width of 90 nm and a pitch of 180 nm (double pitch of 360 nm). I was able to.

  By the resist pattern forming method of Example 1 according to the present invention, it can be confirmed that a high-resolution resist pattern can be formed by a novel pattern forming method capable of reducing the number of steps without going through a plurality of etching treatment steps. It was.

It is a schematic process drawing explaining the preferable embodiment of the resist pattern formation method of this invention. It is a schematic process drawing explaining an example of the conventional double patterning method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... 1st resist film, 1 '... Dense pattern, 2 ... 2nd resist film, 2' ... Coarse pattern, 10 ... Support body, 101 ... Substrate, 102 ... Underlayer film, 103 ... Hard mask, 104 ... Resist Pattern, 105 ... mask, 106 ... resist pattern.

Claims (4)

A first positive resist composition is applied on a support to form a first resist film;
A second positive resist composition is applied onto the first resist film, and the second resist composition has a minimum exposure (Eth ₂ ) smaller than the minimum exposure (Eth ₁ ) of the first resist film. Forming a resist film,
Minimum exposure amount of said first resist film (Eth ₁₎ minimum exposure amount of small and said second resist film than larger exposure amount than _{(Eth 2) (Dose 2)} , the said second resist film Selectively exposed and developed to form a rough pattern of the second resist film,
Minimum exposure amount of said first resist film (Eth ₁₎ large exposure amount than in (Dose _1), with respect to said first resist film was exposed through a crude pattern, and developed, crude pattern And forming a dense pattern made of the first resist film. The resist pattern forming method according to claim ₁ , wherein an optimum exposure amount (Eop ₂ ) of the _second resist film is smaller than a minimum exposure amount (Eth ₁ ) of the first resist film. The second positive resist composition includes an organic solvent (S ₂ ) that dissolves the base material of the _second positive resist composition and does not dissolve the base material of the first positive resist composition. The resist pattern formation method of Claim 1 or 2 containing.   The resist pattern forming method according to claim 1, wherein a developing solution used for developing the first resist film and a developing solution used for developing the second resist film are the same.

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