JP4347209B2 - Method for forming resist pattern - Google Patents

Description

  The present invention relates to a resist pattern forming method.

In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, pattern miniaturization has been rapidly progressing due to advances in 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 at present, mass production of semiconductor elements using a KrF excimer laser or an ArF excimer laser has started. Further, F ₂ excimer laser having a shorter wavelength than these excimer lasers, electron beams, also consider such extreme ultraviolet radiation and X-rays have been made.
In addition, as one of the resist materials that satisfy the high resolution conditions that can reproduce patterns with fine dimensions, it contains a base resin whose alkali solubility changes due to the action of acid and an acid generator that generates acid upon exposure. A chemically amplified resist composition is known. The chemically amplified resist composition includes a negative type containing an alkali-soluble resin, an acid generator and a cross-linking agent, and a positive type containing a resin whose acid solubility is increased by the action of an acid and an acid generator. .

  For example, as a resist base resin used in ArF excimer laser lithography or the like, a resin (acrylic resin) having a structural unit derived from (meth) acrylic acid is mainly used because of excellent transparency near 193 nm. (Patent Document 1 etc.).

And when forming a resist pattern using such a chemically amplified resist composition, for example, a step of forming a resist layer on a substrate using a resist composition, a step of selectively exposing the resist layer, A post-exposure heat treatment (PEB treatment) step and a step of developing the resist layer to form a resist pattern are performed.
In forming a resist pattern, for example, when forming a pattern such as a line or hole on a single substrate, a dense pattern with a narrow interval between adjacent patterns and a sparse pattern with a wide interval between adjacent patterns May form.

In recent years, with the increasing complexity and density of devices, it is required to form such different patterns with high accuracy on a single substrate.
However, the conventional resist pattern formation has a problem that the depth of focus (DOF) when forming a sparse pattern tends to be narrower than the DOF when forming a dense pattern.

Therefore, in Patent Document 2, for example, a second resist layer (upper layer) is stacked on a first resist layer (lower layer) on which a dense pattern is formed, and the dense pattern is embedded, and then the dense pattern is embedded in the upper layer. A technique is disclosed in which a pattern different from the pattern is formed so that a part of the dense pattern in the lower layer is exposed and the remaining dense pattern is embedded. That is, the upper layer pattern is formed so as to embed a part of the dense pattern formed in the lower layer.
For example, the upper layer pattern is formed in a larger size than the pattern formed in the lower layer. For example, when hole patterns are formed in the upper and lower layers, a pattern larger than the diameter of holes formed in the lower dense pattern is formed in the upper layer, and the hole patterns in the upper and lower layers are connected. Then, in the range where the upper hole pattern is formed, the lower dense pattern can be exposed. And in the range which does not remove an upper layer, it will be in the state where a part of dense pattern of the lower layer was embedded.
In this way, a sparse pattern composed of a pattern formed in the lower layer and a pattern formed in the upper layer continuous with the pattern is formed on a part of the substrate. That is, since this pattern uses a dense pattern formed in the lower layer, a lower layer pattern in contact with the substrate is formed in a desired size, and a sparse pattern satisfying the DOF characteristics can be obtained.
In this way, a resist pattern in which a dense pattern and a sparse pattern are mixed can be formed on one substrate.
As a result, problems due to variations in the DOF characteristics between the dense pattern and the sparse pattern can be suppressed.
JP 2003-167347 A US Publication No. US2003-0104319A1

  However, in the resist pattern forming method in which a dense pattern is formed in the lower layer and a pattern different from the lower layer is formed in the upper layer, there is a problem that mixing occurs at the interface between the upper and lower layers. Mixing refers to a phenomenon in which both resist layers are dissolved.

  The present invention has been made in view of the above circumstances, and provides a resist pattern forming method capable of suppressing mixing in a resist pattern forming method in which a dense pattern is formed in a lower layer and a pattern different from the lower layer is formed in an upper layer. This is the issue.

In order to achieve the above object, the present invention employs the following configuration.
A first aspect is a resist pattern forming method in which a dense pattern is formed in a lower first resist layer, and a pattern different from the lower layer is formed in an upper second resist layer,
Steps (i) to (ii) below (i) A first resist layer is formed on a substrate using a first positive resist composition, selectively exposed to form a first resist layer. Step (ii) forming a latent image portion of a dense pattern After applying a second positive resist composition on the first resist layer to form a second resist layer and selectively exposing, Simultaneously developing the first resist layer and the second resist layer to remove a part of the latent image portion of the dense pattern and to expose a part of the dense pattern;
As the first positive resist composition, a positive resist composition comprising (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid upon exposure. Use
As the second positive resist composition, (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid by exposure, an alcohol solvent is included, dissolved in an organic solvent which does not dissolve the first resist layer, and the component (a ') is the use of a positive resist composition containing an alicyclic group having a fluorinated hydroxyalkyl group A feature is a method of forming a resist pattern.
The second aspect is a resist pattern forming method in which a dense pattern is formed in a lower first resist layer, and a pattern different from the lower layer is formed in an upper second resist layer,
Steps (i ′) to (ii ′) below (i ′) A first resist layer is formed on a substrate using a first positive resist composition, selectively exposed, developed, and then developed. Step (ii ′) of forming a dense pattern on the first resist layer A second positive resist composition is applied on the first resist layer to embed the dense pattern and form a second resist layer And selectively exposing and developing to remove a part of the second positive resist composition embedded in the dense pattern and to expose a part of the dense pattern,
As the first positive resist composition, a positive resist composition comprising (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid upon exposure. Use
As the second positive resist composition, (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid by exposure, an alcohol solvent is included, dissolved in an organic solvent which does not dissolve the first resist layer, and the component (a ') is the use of a positive resist composition containing an alicyclic group having a fluorinated hydroxyalkyl group A feature is a method of forming a resist pattern.
A third aspect is a resist pattern forming method in which a dense pattern is formed in a lower first resist layer, and a pattern different from the lower layer is formed in an upper second resist layer,
Steps (i) to (ii) below
(I) A step of forming a first resist layer on a substrate using a first positive resist composition and selectively exposing to form a latent image portion having a dense pattern on the first resist layer.
(Ii) A second positive resist composition is applied onto the first resist layer to form a second resist layer, and after selective exposure, the first resist layer and the second resist layer Simultaneously developing the resist layer to remove part of the latent image portion of the dense pattern and exposing part of the dense pattern
Including
The first positive resist composition includes (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid upon exposure, ') A positive resist in which the component contains a structural unit (a1') derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group and a structural unit (a2) derived from an acrylate ester having a lactone ring Using the composition,
As the second positive resist composition, (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid by exposure, the first resist layer And the component (A ′) comprises a structural unit (a1 ′) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group, and a fluorinated hydroxyalkyl group. A positive resist composition comprising a structural unit (a2 ′) containing an alicyclic group having a resist pattern forming method is used.
A fourth aspect is a resist pattern forming method in which a dense pattern is formed in a lower first resist layer, and a pattern different from the lower layer is formed in an upper second resist layer,
The following steps (i ′) to (ii ′)
(I ′) a step of forming a first resist layer on the substrate using the first positive resist composition, selectively exposing, and developing to form a dense pattern in the first resist layer
(Ii ′) A second positive resist composition is applied on the first resist layer to embed the dense pattern, and a second resist layer is formed, selectively exposed, and developed. Removing a part of the second positive resist composition embedded in the dense pattern to expose a part of the dense pattern
Including
The first positive resist composition includes (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid upon exposure, ') A positive resist in which the component contains a structural unit (a1') derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group and a structural unit (a2) derived from an acrylate ester having a lactone ring Using the composition,
As the second positive resist composition, (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid by exposure, the first resist layer And the component (A ′) comprises a structural unit (a1 ′) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group, and a fluorinated hydroxyalkyl group. A positive resist composition comprising a structural unit (a2 ′) containing an alicyclic group having a resist pattern forming method is used.

  Note that the term “exposure” includes not only light irradiation but also general irradiation of radiation such as electron beam irradiation.

  The present invention can provide a resist pattern forming method capable of suppressing mixing in a resist pattern forming method in which a dense pattern is formed in a lower layer and a pattern is formed in an upper layer.

[First embodiment]
A first aspect is a resist pattern forming method in which a dense pattern is formed in a lower first resist layer, and a pattern different from the lower layer is formed in an upper second resist layer,
Steps (i) to (ii) below (i) A first resist layer is formed on a substrate using a first positive resist composition, selectively exposed to form a first resist layer. Step (ii) forming a latent image portion of a dense pattern After applying a second positive resist composition on the first resist layer to form a second resist layer and selectively exposing, Simultaneously developing the first resist layer and the second resist layer to remove a part of the latent image portion of the dense pattern and to expose a part of the dense pattern;
As the first positive resist composition, a positive resist composition comprising (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid upon exposure. Use
As the second positive resist composition, (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid by exposure, an alcohol solvent is included, dissolved in an organic solvent which does not dissolve the first resist layer, and the component (a ') is the use of a positive resist composition containing an alicyclic group having a fluorinated hydroxyalkyl group A feature is a method of forming a resist pattern.
[Third Aspect]
A third aspect is a resist pattern forming method in which a dense pattern is formed in a lower first resist layer, and a pattern different from the lower layer is formed in an upper second resist layer,
Steps (i) to (ii) below
(I) A step of forming a first resist layer on a substrate using a first positive resist composition and selectively exposing to form a latent image portion having a dense pattern on the first resist layer.
(Ii) A second positive resist composition is applied onto the first resist layer to form a second resist layer, and after selective exposure, the first resist layer and the second resist layer Simultaneously developing the resist layer to remove part of the latent image portion of the dense pattern and exposing part of the dense pattern
Including
The first positive resist composition includes (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid upon exposure, ') A positive resist in which the component contains a structural unit (a1') derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group and a structural unit (a2) derived from an acrylate ester having a lactone ring Using the composition,
As the second positive resist composition, (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid by exposure, the first resist layer And the component (A ′) comprises a structural unit (a1 ′) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group, and a fluorinated hydroxyalkyl group. A positive resist composition comprising a structural unit (a2 ′) containing an alicyclic group having a resist pattern forming method is used.

Here, the dense pattern indicates that the interval between adjacent patterns is narrow when a pattern such as a line shape or a hole shape is formed. Specifically, for example, in the cross section of the pattern, the ratio of the distance to the adjacent pattern with respect to the width of the pattern is preferably 1 or less, particularly preferably 0.9 or less, and even 0.8 or less. . The lower limit is substantially 0.5 or more. Note that the width of the pattern in the hole-shaped pattern indicates a range in which the resist layer is removed, for example, the diameter of the hole in the hole pattern. The pattern width in the line pattern indicates the width of the line.
The sparse pattern has a larger interval between adjacent patterns than the dense pattern. Specifically, for example, in the pattern cross section, the ratio of the spacing between adjacent patterns to the pattern width is preferably 2 or more, particularly preferably 3 or more, and even 5 or more. The upper limit value is substantially 10 or less.
The width and interval of the pattern indicate the size near the interface between the substrate and the resist layer.

  FIG. 1A shows a flow of an example of the procedure of the first aspect (hereinafter referred to as process 1). FIG. 2 is an explanatory diagram (cross-sectional view) of the process 1. FIG. 4 is a plan view showing a state after forming a dense pattern and a sparse pattern through a process.

In the process 1, the following steps are sequentially performed.
(I-1) First positive resist composition coating step An acid generator component (hereinafter also referred to as “acid generator”) that generates an acid by exposure on the substrate 1 using a coating apparatus. A chemical amplification type positive resist composition (first positive resist composition) is applied (see FIG. 2A).

(I-2) PAB (Pre-Bake) Step The applied resist film is heated to form the first resist layer 2 (see FIG. 2A).
The heating conditions are, for example, about 80 to 150 ° C. and 40 to 120 seconds (preferably 60 to 90 seconds).
The thickness of the first resist layer 2 is, for example, about 0.05 to 1.0 μm, and preferably 0.1 to 0.5 μm.

(I-3) Exposure Step By selectively exposing the first resist layer 2, a latent image portion (exposed portion) 2a ′ having a dense pattern is formed on the first resist layer. (See FIG. 2 (a)). The “latent image portion” means an exposed range.
That is, the first resist layer 2 is selectively exposed using a dense pattern mask (reticle) 3.
FIG. 2A shows an example in which the hole pattern is exposed to form a dense pattern in which the pattern width D ¹ and the interval L ¹ are formed with a size of about 1: 1.
That is, as shown in FIG. 4, the first resist layer 2, is selectively exposed to form a dense pattern in which a plurality of holes 2a in the width D ¹ of the pattern is closely spaced L ¹ facilities Is done.
The wavelength used for exposure is not particularly limited, and includes ArF excimer laser, KrF excimer laser, F ₂ excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), EB (electron beam), X-ray, soft X-ray, etc. Although it can be performed using radiation, an ArF excimer laser is preferable (the same applies to the following exposure steps).

(I-4) PEB (post-exposure heat treatment) step The first resist layer 2 subjected to selective exposure is subjected to heat treatment, and an acid component generated from the acid generator in the first resist layer 2 is appropriately adjusted. By diffusing, the acid dissociable, dissolution inhibiting group of the base material component of the positive resist composition is eliminated. However, some acid dissociable, dissolution inhibiting groups may be eliminated by exposure alone. Therefore, the PEB process is not always necessary.
The heating conditions are, for example, about 80 to 150 ° C. and 40 to 120 seconds (preferably 60 to 90 seconds).

(Ii-1) Application Step of Second Positive Resist Composition Using a coating apparatus, a chemically amplified positive resist composition containing a acid generator on the first resist layer 2 (second positive resist composition) (Type resist composition) is applied (see FIG. 2B).
The first positive resist composition and the second positive resist composition are a positive resist composition that forms the first resist layer 2 and a positive resist that forms the second resist layer 12. It is a term used to distinguish the composition from the convenience.

(Ii-2) PAB (Pre-Bake) Step The applied resist film is heated to form the second resist layer 12 (see FIG. 2B).
The heating conditions are, for example, about 80 to 150 ° C. and 40 to 120 seconds (preferably 60 to 90 seconds).
The thickness of the second resist layer 12 is, for example, about 0.05 to 1.0 μm, and preferably 0.1 to 0.5 μm.

(Ii-3) Exposure Step The second resist layer 12 is selectively exposed.
That is, when the second resist layer 12 is selectively exposed using a desired mask (reticle) 13, a latent image portion (exposed portion) 12a ′ is formed (see FIG. 2B).
FIG. 2B shows an example in which the hole pattern is exposed to form a sparse pattern in which the pattern width D ² and the interval L ² are formed with a size of about 1: 2.
That is, as shown in FIG. 4, in the drawing, the region 21 located at the left and right ends is exposed as a whole, and in the region 22 sandwiched between them, the pattern of the pattern is formed on the second resist layer 12. hole 12a of width D ² is subjected to a selective exposure using a mask 13 such as are arranged at intervals L ^2.
Incidentally, as shown in FIG. 2 (b), FIG. 2 (c), the Figure 4, ^{D 2} (width of the pattern) diameter sparse pattern of holes 12a are holes 2a formed in the first resist layer 2 ( It is designed larger than the diameter (pattern width) D ¹ of the latent image portion 2a '). The hole 12a (latent image portion 12a ′) is formed in a range including the hole 2a (latent image portion 2a ′) formed immediately below.

(Ii-4) PEB (post-exposure heat treatment) step The second resist layer 12 subjected to the selective exposure is subjected to a heat treatment so that an acid component generated from the acid generator in the second resist layer 12 is appropriately treated. Spread (see FIG. 2B). As a result, the acid dissociable, dissolution inhibiting group of the base component of the positive resist composition is eliminated. However, some acid dissociable, dissolution inhibiting groups may be eliminated by exposure alone. Therefore, the PEB process is not always necessary.
The heating conditions are, for example, about 80 to 150 ° C. and 40 to 120 seconds (preferably 60 to 90 seconds).

(Ii-5) Development process of first resist layer and second resist layer The laminate of the first resist layer 2 and the second resist layer 12 is developed. For the development processing, for example, a TMAH aqueous solution (tetramethylammonium hydroxide aqueous solution) having a concentration of 0.1 to 10% by mass (preferably 2.38% by mass) is used.
When the development process is performed, in the region 22 shown in FIG. 4, the exposed portion (latent image portion 12a ′) of the second resist layer 12 is first removed as shown in FIG. Is formed. Then, the developer entering from the hole 12a comes into contact with the first resist layer 2 constituting the bottom surface of the hole 12a, so that the exposed portion (latent image portion 2a ′) of the first resist layer 2 becomes. Developed, removed and exposed. That is, the latent image portion 2a ′ of the first resist layer 2 is patterned. As a result, a hole 2a immediately below the hole 12a is formed. As a result, a sparse hole pattern in which the holes 2a and the holes 12a are continuous is formed.
On the other hand, in the region 21, the entire second resist layer 12 in the region 21 is developed with a developer and removed because light is applied to the entire region during selective exposure. Then, the dense pattern exposure portion (latent image portion 2a ′) formed in the first resist layer 2 is developed to form a hole 2a.

That is, in the region 22, the hole 2 a is formed in a dense pattern that can ensure a wide DOF characteristic, and thus can be accurately formed in a desired size. The sparse holes 12 a are formed on a part of the holes 2 a of the dense pattern formed in the first resist layer 2.
That is, in this method, a part of the wide DOF dense pattern formed in the first resist layer 2 as a lower layer is exposed and patterned by development, and used as a sparse pattern.
Even if a sparse pattern is formed in the lower first resist layer 2 from the beginning, a wide DOF characteristic cannot be secured, but a sparse pattern having a wide DOF characteristic can be obtained through the above-described steps. it can.
The DOF characteristics of the upper second resist layer 12 are not required to be as high as the pattern formed in the lower layer (first resist layer 2). This is because the hole 2a in the lower layer 2 is important in a sparse hole pattern in which the holes 2a and 12a are continuous. This is because the pattern of the lower layer 2 is transferred when the substrate is etched (depending on the pattern of the lower layer 2 when transferred to the substrate).

  In this way, a so-called sparse / dense mixed pattern in which both a dense pattern region 21 and a sparse pattern region 22 having the same DOF characteristic are formed on one substrate can be obtained.

  In the method of the present invention, a specific positive resist composition is used as the second positive resist composition. Since the material of the resist composition is the same as that of the second aspect, it will be described collectively after explaining the process example of the second aspect.

[Second embodiment]
The second aspect is a resist pattern forming method in which a dense pattern is formed in a lower first resist layer, and a pattern different from the lower layer is formed in an upper second resist layer,
Steps (i ′) to (ii ′) below (i ′) A first resist layer is formed on a substrate using a first positive resist composition, selectively exposed, developed, and then developed. Step (ii ′) of forming a dense pattern on the first resist layer A second positive resist composition is applied on the first resist layer to embed the dense pattern and form a second resist layer And selectively exposing and developing to remove a part of the second positive resist composition embedded in the dense pattern and to expose a part of the dense pattern,
As the first positive resist composition, a positive resist composition comprising (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid upon exposure. Use
As the second positive resist composition, (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid by exposure, an alcohol solvent is included, dissolved in an organic solvent which does not dissolve the first resist layer, and the component (a ') is the use of a positive resist composition containing an alicyclic group having a fluorinated hydroxyalkyl group A feature is a method of forming a resist pattern.
[Fourth aspect]
A fourth aspect is a resist pattern forming method in which a dense pattern is formed in a lower first resist layer, and a pattern different from the lower layer is formed in an upper second resist layer,
The following steps (i ′) to (ii ′)
(I ′) a step of forming a first resist layer on the substrate using the first positive resist composition, selectively exposing, and developing to form a dense pattern in the first resist layer
(Ii ′) A second positive resist composition is applied on the first resist layer to embed the dense pattern, and a second resist layer is formed, selectively exposed, and developed. Removing a part of the second positive resist composition embedded in the dense pattern to expose a part of the dense pattern
Including
The first positive resist composition includes (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid upon exposure, ') A positive resist in which the component contains a structural unit (a1') derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group and a structural unit (a2) derived from an acrylate ester having a lactone ring Using the composition,
As the second positive resist composition, (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid by exposure, the first resist layer And the component (A ′) comprises a structural unit (a1 ′) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group, and a fluorinated hydroxyalkyl group. A positive resist composition comprising a structural unit (a2 ′) containing an alicyclic group having a resist pattern forming method is used.

  FIG. 1B shows a flow of an example of the procedure of the second aspect (hereinafter referred to as process 2). FIG. 3 is an explanatory diagram (cross-sectional view) of the process 2. FIG. 4 is a plan view showing a state after forming a dense pattern and a sparse pattern through a process.

In the process 2, the following steps are sequentially performed.
(I′-1) First positive resist composition coating step The same as (i-1) in the first embodiment (see FIG. 3A).
(I′-2) PAB (pre-baking) step This is the same as (i-2) in the first embodiment (see FIG. 3A).
(I′-3) Exposure Step This is the same as (i-3) in the first aspect (see FIG. 3A).
(I′-4) PEB (post-exposure heat treatment) step This is the same as (i-4) in the first embodiment (see FIG. 3A).

(I′-5) First resist layer development step The first resist layer 2 is developed. For the development processing, for example, a TMAH aqueous solution (tetramethylammonium hydroxide aqueous solution) having a concentration of 0.1 to 10% by mass (preferably 2.38% by mass) is used.
When the development process is performed, the exposed portion is removed as shown in FIG. 3B, and the first resist layer 2 is designed with a pattern width D ¹ and a distance L ^{1 of} about 1: 1. A dense pattern having a plurality of holes 2a is obtained.
That is, as shown in FIG. 4, the first resist layer 2 entirely, hole 2a of the width D ¹ of the pattern is dense patterns are densely arranged at intervals L ¹ is formed.

(Ii'-1) Application process of second positive resist composition As shown in FIG. 3C, acid is generated on the first resist layer 2 on which a dense pattern is formed, using an application apparatus. A chemically amplified second positive resist composition containing an agent is applied.
The first positive resist composition and the second positive resist composition are a positive resist composition that forms the first resist layer 2 and a positive resist that forms the second resist layer 12. It is a term used to distinguish the composition from the convenience.
Then, the hole 2a is filled with the second positive resist composition, the hole 2a is buried, a resist film is formed thereon, and the first resist layer 2 on which the dense pattern is formed is formed by the resist film. Covered.

(Ii′-2) PAB (Pre-Bake) Step The applied resist film is heat-treated to form the second resist layer 12 (see FIG. 3C).
The heating temperature is, for example, about 80 to 150 ° C. and 40 to 120 seconds (preferably 60 to 90 seconds).
The thickness of the second resist layer 12 (the length from the surface of the first resist layer 2 to the surface of the second resist layer 12) is, for example, about 0.05 to 1.0 μm, preferably 0.1. About 0.5 μm.

(Ii′-3) Exposure Step The second resist layer 12 is selectively exposed.
In other words, the second resist layer 12 is selectively exposed using a desired mask (reticle) 13.
FIG. 3C shows an example in which the hole pattern in FIG. 3C is exposed to form a sparse pattern in which the pattern width D ² and the interval L ² are formed with a size of about 1: 2. is there.
That is, also in this example, the same area is exposed using the same mask as in the first aspect, and as shown in FIG. 4, the entire region 21 is exposed, and in the region 22, the second resist layer 12 is exposed. the, by conducting selective exposure as a hole 12a of a width D ² of the pattern are arranged at intervals L ^2, the latent image portion (exposed portion) 12a 'is formed.
As shown in FIGS. 3D and 4, the diameter (pattern width) D ² of the sparsely patterned holes 12 a is the diameter (pattern width) of the holes 2 a formed in the first resist layer 2. D is designed larger than ^1. The hole 12a is formed in a range including the hole 2a formed immediately below the hole 12a.

(Ii′-4) PEB (post-exposure heat treatment) step The second resist layer 12 subjected to selective exposure is subjected to a heat treatment to moderately generate an acid component generated from the acid generator in the second resist layer 12. To dissociate the acid dissociable, dissolution inhibiting group of the base component of the positive resist composition. (See FIG. 3C).
However, some acid dissociable, dissolution inhibiting groups may be eliminated by exposure alone. Therefore, the PEB process is not always necessary.
The heating temperature is, for example, about 80 to 150 ° C. and 40 to 120 seconds (preferably 60 to 90 seconds).

(Ii′-5) Development Step of Second Resist Layer When the laminate of the first resist layer 2 and the second resist layer 12 is developed, the region 22 shown in FIG. 4 is shown in FIG. Similarly, the exposed portion (latent image portion 12a ′) of the second resist layer 12 is removed to form a sparsely patterned hole 12a.
As a result, in the region 22, a sparse hole pattern in which the holes 12a and the holes 2a immediately below are continuous is formed. In addition, in the selective exposure, the entire region 21 is exposed to light. Therefore, the entire second resist layer 12 in the region 21 is developed with a developer, and the first resist layer is densely formed. The second positive resist composition in which the pattern is embedded is also removed at the same time, and a hole 2a is formed.

That is, this method embeds a wide DOF dense pattern formed in the first resist layer 2 with the second resist layer 12, selectively exposes and develops, and removes a part of the second resist layer 12. By exposing a part of the dense pattern formed on the first resist layer 2, this dense pattern is used as a sparse pattern. Note that, in the dense pattern, a portion where the second resist layer 12 is not removed is buried with the second resist layer 12.
Although a wide DOF characteristic cannot be ensured even if a sparse pattern is formed on the first resist layer 2 as a lower layer from the beginning, a wide DOF sparse pattern can be obtained through the above-described steps.

Note that the DOF characteristics of the upper second resist layer 12 are not required to be as high as those of the pattern formed in the first resist layer (lower layer) 2. This is because the hole 2a in the lower layer 2 is important in a sparse hole pattern in which the holes 2a and 12a are continuous. This is because the pattern of the lower layer 2 is transferred when the substrate is etched (depending on the pattern of the lower layer when transferred to the substrate).
In this way, as shown in FIG. 4, a so-called sparse / dense mixed pattern in which both a dense pattern region 21 and a sparse pattern region 22 are formed on one substrate is obtained.

Process 2 has an advantage that scum after development is less likely to occur.
In addition, since the first resist layer is once developed and then the second resist layer is formed, the second resist layer is not affected by the acid generator in the first resist layer, and is more accurate. There is also an advantage that the pattern can be formed.

  In the method of the present invention, a specific positive resist composition is used as the second positive resist composition used for forming the second resist layer 12. The materials such as the resist composition are the same as those in the first aspect, and will be described below.

[Second positive resist composition]
The positive resist composition contains (A ′) a resin component that contains a structural unit derived from an acrylate ester and increases alkali solubility by the action of an acid, and (B) acid generation that generates an acid upon exposure. What dissolved the agent component in the organic solvent is preferable.
The second positive resist composition used in the present invention is characterized by dissolving these components in a specific organic solvent.

Organic Solvent In the second positive resist composition, an organic solvent that does not dissolve the first resist layer is used. Thereby, mixing can be suppressed.
As such an organic solvent, any solvent which is not compatible with the first resist layer can be used.
The fact that the first resist layer is not dissolved preferably means, for example, that after forming a first resist layer having a thickness of 0.2 μm under a condition of 23 ° C. and immersing it in an organic solvent, after 60 minutes It shows that the film thickness does not vary.

Examples of such a solvent 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 the alcohol solvent include n-amyl alcohol (boiling point 138.0 ° C.), s-amyl alcohol (boiling point 119.3 ° C.), t-amyl alcohol (101.8 ° C.), isoamyl alcohol (boiling point 130.degree. C.). 8 ° C), isobutanol (also called isobutyl alcohol or 2-methyl-1-propanol) (boiling point 107.9 ° C), isopropyl alcohol (boiling point 82.3 ° C), 2-ethylbutanol (boiling point 147 ° C), neopentyl Alcohol (boiling point 114 ° C), n-butanol (boiling point 117.7 ° C), s-butanol (boiling point 99.5 ° C), t-butanol (boiling point 82.5 ° C), 1-propanol (boiling point 97.2 ° C) , N-hexanol (boiling point 157.1 ° C.), 2-heptanol (boiling point 160.4 ° C.), 3-heptanol (boiling point 156.2) ), 2-methyl-1-butanol (boiling point 128.0 ° C.), 2-methyl-2-butanol (boiling point 112.0 ° C.), 4-methyl-2-pentanol (boiling point 131.8 ° C.) and the like. It is done. In particular, isobutanol (2-methyl-1-propanol), 4-methyl-2-pentanol, n-butanol and the like are preferable. Of these, isobutanol and n-butanol are preferred.

Examples of the fluorine-based solvent include perfluoro-2-butyltetrahydrofuran.
The organic solvent can be used alone or in combination.

As long as the first resist layer is not dissolved, an organic solvent other than an alcohol solvent, a fluorine solvent, or the like may be used as the organic solvent. It is preferable to use 100% by mass.
As the other organic solvent, one or two or more kinds of conventionally known solvents for chemically amplified resists can be appropriately selected and used.
For example, lactones such as γ-butyrolactone, ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate Polyhydric alcohols such as dipropylene glycol or dipropylene glycol monoacetate monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether and derivatives thereof, cyclic ethers such as dioxane, Methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, pyruvate Le, methyl methoxypropionate, esters such as ethyl ethoxypropionate can be exemplified.

  Although the amount of the organic solvent used is not particularly limited, it is a concentration that can be applied to a substrate and the like, and is appropriately set according to the coating film thickness. In general, the solid content concentration of the resist composition is 2 to 20 mass. %, Preferably 5-15% by mass.

(A ′) Resin component, (B) Acid generator component that generates acid upon exposure, and other optional components that can be added are not particularly limited and have been proposed as materials for conventional positive resist compositions. Can be used as appropriate.
In view of the influence of the second positive resist composition coming into contact with the first resist layer 2, it is desirable that the second positive resist composition has high sensitivity.
Preferred examples include the following.

In the following description of examples of positive resist compositions, the meanings of terms are as follows. “Structural unit” refers to a monomer unit constituting a polymer (resin).
“Structural unit derived from acrylic acid” means a structural unit formed by cleavage of an ethylenic double bond of acrylic acid.
The “structural unit derived from an acrylate ester” means a structural unit constituted by cleavage of an ethylenic double bond of an acrylate ester.
The “structural unit derived from an acrylate ester” is a concept that includes those in which the hydrogen atom at the α-position is substituted with another substituent such as a halogen atom, an alkyl group, or a halogenated alkyl group. In the “structural unit derived from acrylic acid” and “structural unit derived from acrylate ester”, the term “α-position (α-position carbon atom)” means that a carboxy group is present unless otherwise specified. It is a bonded carbon atom.
The “structural unit derived from acrylic acid” is a structural unit in which a hydrogen atom bonded to a carbon atom at the α-position is substituted with another substituent such as a halogen atom, an alkyl group, or a halogenated alkyl group, The concept includes a structural unit derived from an acrylate ester in which a hydrogen atom is bonded to a carbon atom at the position.
Further, the “alkyl group” includes a linear, cyclic or branched alkyl group unless otherwise specified.

(A ′) Resin Component The (A ′) component of the second positive resist composition contains (A ′) a structural unit derived from an acrylate ester, and increases alkali solubility by the action of an acid. It is preferable to use a resin component.
The component (A ′) contains a structural unit (a1 ′) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group and an alicyclic group having a fluorinated hydroxyalkyl group ( a2 ′) is more preferable.
In the second positive resist composition, by using a resin component having a structural unit (a2 ′) containing an alicyclic group having a fluorinated hydroxyalkyl group, the solubility in an alcohol-based organic solvent is improved. It is preferable because it is good.

A structural unit derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group (a1 ′)
In the structural unit (a1 ′), a hydrogen atom, a halogen atom, a halogenated lower alkyl group, or a lower alkyl group is bonded to the α carbon atom.
The lower alkyl group is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and includes a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, and pentyl. Group, isopentyl group, neopentyl group and the like. Industrially, a methyl group is preferable.
The halogenated lower alkyl group is preferably a linear or branched halogenated alkyl group having 1 to 5 carbon atoms, preferably a linear or branched fluorinated lower alkyl group having 1 to 5 carbon atoms. And most preferably a trifluoromethyl group.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferable.
Of these, a hydrogen atom or a methyl group is preferred.

The acid dissociable, dissolution inhibiting group of the structural unit (a1 ′) has an alkali dissolution inhibiting property that renders the entire component (A ′) before exposure insoluble in alkali, and at the same time, an acid generated from the acid generator (B) after exposure. It is a group that dissociates by the action of and changes the entire component (A ′) to alkali-soluble.
As the acid dissociable, dissolution inhibiting group, for example, a resin for resist composition of ArF excimer laser can be appropriately selected from those proposed in large numbers. In general, a group that forms a cyclic or chain tertiary alkyl ester with a carboxy group of acrylic acid and a group that forms a cyclic or chain alkoxyalkyl are widely known.

The cyclic or chain alkoxyalkyl ester forms an ester by replacing the hydrogen atom of the carboxy group with an alkoxyalkyl group, and the terminal of the carbonyloxy group (—C (O) —O—) is formed. This shows a structure in which the alkoxyalkyl group is bonded to an oxygen atom, and this alkoxyalkyl ester group is cleaved between the oxygen atom and the alkoxyalkyl group when an acid acts. 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 and a 4-oxo-2-adamantoxymethyl group.
Examples of the acid dissociable, dissolution inhibiting group that forms a chain-like tertiary alkyl ester include a t-butyl group and a tert-amyl group.
In addition, as the structural unit (a1 ′), a structural unit including a cyclic group, in particular, an “acid dissociable, dissolution inhibiting group containing an alicyclic group” is preferable. The alicyclic group may be monocyclic or polycyclic, and can be appropriately selected and used from among many proposed, for example, ArF resists. Are preferred. The alicyclic group is preferably a hydrocarbon group and is preferably saturated.
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.
Specific examples of the monocyclic group include a cyclopentyl group and a cyclohexyl group. Examples of the polycyclic 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, and tetracyclo A tetracyclododecanyl group obtained by removing one hydrogen atom from dodecane is preferred industrially.

  More specifically, the structural unit (a1 ′) is preferably at least one selected from the following general formulas (I ′) to (III ′).

［式中、Ｒ^０は水素原子、ハロゲン原子、ハロゲン化低級アルキル基、または低級アルキル基であり、Ｒ^２１は低級アルキル基である。］

[Wherein, R ⁰ represents a hydrogen atom, a halogen atom, a halogenated lower alkyl group, or a lower alkyl group, and R ²¹ represents a lower alkyl group. ]

［式中、Ｒ^０は水素原子、ハロゲン原子、ハロゲン化低級アルキル基、または低級アルキル基であり、Ｒ^２２及びＲ^２３はそれぞれ独立に低級アルキル基である。］

[Wherein, R ⁰ is a hydrogen atom, a halogen atom, a halogenated lower alkyl group, or a lower alkyl group, and R ²² and R ²³ are each independently a lower alkyl group. ]

［式中、Ｒ^２４は第３級アルキル基である。］

[Wherein R ²⁴ represents a tertiary alkyl group. ]

R ⁰ is a hydrogen atom, a halogen atom, a halogenated lower alkyl group, or a lower alkyl group. The lower alkyl group is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and includes a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, and pentyl. Group, isopentyl group, neopentyl group and the like. Industrially, a methyl group is preferable.
The halogenated lower alkyl group is a group in which some or all of the hydrogen atoms of the lower alkyl group are substituted with halogen atoms. In the halogenated lower alkyl group, examples of the halogen atom substituted with a hydrogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable.
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.
And as ^R0 , a hydrogen atom or a methyl group is preferable among these.
R ²¹ is preferably a lower linear or branched alkyl group having 1 to 5 carbon atoms, and is a methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, pentyl group, isopentyl group. And neopentyl group. Among these, a methyl group and an ethyl group are preferable because they are easily available industrially.

R ²² and R ²³ are each independently preferably a linear or branched lower alkyl group having 1 to 5 carbon atoms. Among them, it is industrially preferable that both R ²² and R ²³ are methyl groups, and specific examples include structural units derived from 2- (1-adamantyl) -2-propyl acrylate.

R ²⁴ is preferably a chain-like tertiary alkyl group or a cyclic tertiary alkyl group. The chain-like tertiary alkyl group is, for example, a tert-butyl group or a tert-amyl group, and the case where it is a tert-butyl group is industrially preferable. The tertiary alkyl group is an alkyl group having a tertiary carbon atom.
The cyclic tertiary alkyl group is the same as that exemplified in the aforementioned “acid dissociable, dissolution inhibiting group containing an alicyclic group”, and includes a 2-methyl-2-adamantyl group, 2-ethyl-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.
Further, the group —COOR ²⁴ 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, but the bonding position cannot be specified.

The structural unit (a1 ′) can be used alone or in combination of two or more.
The structural unit (a1 ′) is 20 to 60 mol%, preferably 30 to 50 mol%, most preferably 35 to 45 mol%, based on the total of all structural units in the component (A ′). preferable. A pattern can be obtained by setting it to the lower limit value or more, and balancing with other structural units can be achieved by setting it to the upper limit value or less.

.Structural unit (a2 ′) containing an alicyclic group having a fluorinated hydroxyalkyl group
By having the structural unit (a2 ′), an effect of improving the solubility in an alcohol-based solvent can be obtained.

.. Alicyclic group having a fluorinated hydroxyalkyl group In the structural unit (a2 ′), the alicyclic group has a fluorinated hydroxyalkyl group.
The fluorinated hydroxyalkyl group is an alkyl group having a hydroxy group in which part or all of the hydrogen atoms of the alkyl group are substituted with fluorine. In the group, the hydrogen atom of the hydroxyl group is easily liberated by fluorination.
In the fluorinated hydroxyalkyl group, the alkyl group is linear or branched, and the number of carbon atoms is not particularly limited, but is, for example, 1 to 20, preferably 4 to 16. The number of hydroxyl groups is not particularly limited, but is usually one.
In particular, in the alkyl group, a fluorinated alkyl group and / or a fluorine atom is bonded to the α-position carbon atom to which the hydroxy group is bonded (in this case, the α-position carbon atom of the hydroxyalkyl group). Those are preferred. In the fluorinated alkyl group bonded to the α-position, it is preferable that all of the hydrogen atoms of the alkyl group are substituted with fluorine.

  The alicyclic group may be monocyclic or polycyclic, but is preferably a polycyclic group. Moreover, an alicyclic hydrocarbon group is preferable. Moreover, it is preferable that it is saturated. Moreover, it is preferable that carbon number of an alicyclic group is 5-15.

Specific examples of the alicyclic group include the following.
That is, examples of the monocyclic group include groups in which one hydrogen atom has been removed from a cycloalkane. Examples of the polycyclic group include groups in which one or two hydrogen atoms have been removed from bicycloalkane, tricycloalkane, tetracycloalkane or the like.
More specifically, examples of the monocyclic group include groups in which one or two hydrogen atoms have been removed from cyclopentane or cyclohexane, and two hydrogen atoms have been removed from cyclohexane.
Examples of the polycyclic group include groups in which one or two hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane.
Such a polycyclic group is appropriately selected from among many that have been proposed as constituting an acid dissociable, dissolution inhibiting group in a resin for a positive photoresist composition for ArF excimer laser process, for example. Can be used.
Of these, groups in which two hydrogen atoms have been removed from cyclohexane, adamantane, norbornane, and tetracyclododecane are preferred because they are readily available in the industry.
Of these exemplified monocyclic groups and polycyclic groups, groups in which two hydrogen atoms have been removed from norbornane are particularly preferred.

  The structural unit (a2 ′) is preferably a structural unit derived from acrylic acid, and has a structure (carboxy group) in which the alicyclic group is bonded to the ester group [—C (O) O—] of the acrylate ester. In which the hydrogen atom is substituted with the above alicyclic group).

  As the structural unit (a2 ′), more specifically, those represented by the following general formula (1) are preferable.

（式中、Ｒは水素原子、アルキル基、フッ素化アルキル基またはフッ素原子であり、ｍ、ｎ、ｐはそれぞれ独立して１〜５の整数である。）

(In the formula, R is a hydrogen atom, an alkyl group, a fluorinated alkyl group or a fluorine atom, and m, n and p are each independently an integer of 1 to 5.)

R is a hydrogen atom, an alkyl group, a fluorinated alkyl group or a fluorine atom.
The alkyl group is preferably a lower alkyl group having 5 or less carbon atoms. For example, a methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group A methyl group is preferable.
The fluorinated alkyl group is preferably a group in which one or more hydrogen atoms of a lower alkyl group having 5 or less carbon atoms are substituted with fluorine atoms. Specific examples of the alkyl group are the same as described above. The hydrogen atoms substituted with fluorine atoms may be part or all of the hydrogen atoms constituting the alkyl group.
In R, a hydrogen atom or an alkyl group is preferable, a hydrogen atom or a methyl group is particularly preferable, and a hydrogen atom is most preferable.
N, m, and p are each preferably 1.

  Among those represented by the general formula (1), the structural unit derived from the monomer corresponding to m in the following [Chemical Formula 14] is effective and can be easily synthesized and has high etching resistance. Is also preferable.

As the structural unit (a2 ′), one type or a mixture of two or more types can be used.
The structural unit (a2 ′) is 10 to 65 mol%, preferably 20 to 60 mol%, most preferably 25 to 55 mol%, based on the total of all structural units in the component (A ′). preferable. By setting the lower limit value to the upper limit value, it is possible to balance with other structural units.

  In addition to the structural unit (a1 ′) and the structural unit (a2 ′), the component (A ′) is further a structural unit (a2) derived from an acrylate ester containing a lactone-containing monocyclic or polycyclic group. It is preferable to have.

・ Structural unit (a2)
When the lactone-containing monocyclic or polycyclic group of the structural unit (a2) is used in the formation of a resist film, the component (A ′) increases the adhesion of the resist film to the substrate, or is hydrophilic with the developer. It is effective in improving the sex.
Here, the lactone-containing monocyclic or polycyclic group refers to a cyclic group containing one ring (lactone ring) containing an —O—C (O) — structure. The lactone ring is counted as the first ring, and when it is only the lactone ring, it is called a monocyclic group, and when it has another ring structure, it is called a polycyclic group regardless of the structure.

As the structural unit (a2), any structural unit can be used without particular limitation as long as it has both such a lactone structure (—O—C (O) —) and a cyclic group.
Specifically, examples of the lactone-containing monocyclic group include groups in which one hydrogen atom has been removed from γ-butyrolactone. Examples of the lactone-containing polycyclic group include groups in which one hydrogen atom has been removed from a bicycloalkane, tricycloalkane, or tetracycloalkane having a lactone ring. In particular, a group obtained by removing one hydrogen atom from a lactone-containing tricycloalkane having the following structural formula is advantageous in that it is easily available industrially.

  More specifically, examples of the structural unit (a2) include structural units represented by general formulas (a2-1) to (a2-5) shown below.

［式中、Ｒ^０は水素原子、ハロゲン原子、ハロゲン化低級アルキル基、または低級アルキル基であり、Ｒ’は水素原子、低級アルキル基、または炭素数１〜５のアルコキシ基であり、ｍ’は０または１の整数である。］

[Wherein, R ⁰ is a hydrogen atom, a halogen atom, a halogenated lower alkyl group, or a lower alkyl group, R ′ is a hydrogen atom, a lower alkyl group, or an alkoxy group having 1 to 5 carbon atoms; Is an integer of 0 or 1. ]

The lower alkyl group for R ⁰ and R ′ in formulas (a2-1) to (a2-5) is the same as the lower alkyl group for R ⁰ in the structural unit (a1).
In general formulas (a2-1) to (a2-5), R ′ is preferably a hydrogen atom in view of industrial availability.

  Among these, it is preferable to use at least one selected from general formulas (a2-1) to (a2-5), and at least one selected from general formulas (a2-1) to (a2-3). It is preferable to use more than one species.

As the structural unit (a2), one type may be used alone, or two or more types may be used in combination.
The proportion of the structural unit (a2) in the component (A ′) is preferably 5 to 60 mol%, more preferably 10 to 50 mol%, based on the total of all structural units constituting the component (A ′). 20-50 mol% is more preferable. By setting it to the lower limit value or more, the effect of containing the structural unit (a2) can be sufficiently obtained, and by setting the upper limit value or less, it is possible to balance with other structural units.

・ Structural unit (a3)
The component (A ′) may have a structural unit (a3) derived from an (α-lower alkyl) acrylate ester containing a polar group-containing aliphatic hydrocarbon group. By having the structural unit (a3), the hydrophilicity of the component (A ′) is increased, the affinity with the developer is increased, the alkali solubility in the exposed area is improved, and the resolution is improved. .
Examples of the polar group include a hydroxyl group, a cyano group, a carboxy group, and a hydroxyalkyl group in which a part of hydrogen atoms of an alkyl group is substituted with a fluorine atom. A hydroxyl group is particularly preferable.
Examples of the aliphatic hydrocarbon group include a linear or branched hydrocarbon group having 1 to 10 carbon atoms (preferably an alkylene group) and a polycyclic aliphatic hydrocarbon group (polycyclic group). . As the polycyclic group, for example, a resin for a resist composition for ArF excimer laser can be appropriately selected from among many proposed ones.
Among them, an aliphatic polycyclic group containing a hydroxyalkyl group in which a part of hydrogen atoms of a hydroxyl group, a cyano group, a carboxy group, or an alkyl group is substituted with a fluorine atom, and (α-lower alkyl) acrylic A structural unit derived from an acid ester is more preferred. Examples of the polycyclic group include groups in which one or more hydrogen atoms have been removed from bicycloalkane, tricycloalkane, tetracycloalkane, or the like. Specific examples include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane. Such a polycyclic group can be appropriately selected and used from among many proposed polymers (resin components) for resist compositions for ArF excimer lasers. Among these polycyclic groups, there are groups in which two or more hydrogen atoms have been removed from adamantane, groups in which two or more hydrogen atoms have been removed from norbornane, and groups in which two or more hydrogen atoms have been removed from tetracyclododecane. Industrially preferable.

  As the structural unit (a3), when the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a linear or branched hydrocarbon group having 1 to 10 carbon atoms, (α-lower alkyl) acrylic acid A structural unit derived from hydroxyethyl ester is preferred, and when the hydrocarbon group is a polycyclic group, a structural unit represented by the following formula (a3-1), a structural unit represented by (a3-2) Is preferable.

（式中、Ｒ^０は前記に同じであり、ｊは１〜３の整数であり、ｋは１〜３の整数である。）

(In the formula, R ⁰ is the same as above, j is an integer of 1 to 3, and k is an integer of 1 to 3.)

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When j is 2, it is preferable that the hydroxyl group is bonded to the 3rd and 5th positions of the adamantyl group. When j is 1, it is preferable that the hydroxyl group is bonded to the 3-position of the adamantyl group.
j is preferably 1, and a hydroxyl group bonded to the 3rd position of the adamantyl group is particularly preferred.

  In formula (a3-2), k is preferably 1. The cyano group is preferably bonded to the 5th or 6th position of the norbornyl group.

As the structural unit (a3), one type may be used alone, or two or more types may be used in combination.
When the component (A ′) has the structural unit (a3), the proportion of the structural unit (a3) in the component (A ′) is 5 to 50 mol with respect to all the structural units constituting the component (A ′). %, More preferably 15 to 45 mol%, and most preferably 15 to 35 mol%.

・ Structural unit (a4)
The component (A ′) is a group consisting of the structural units (a1 ′), (a2) ′, (a2), and (a3) (hereinafter referred to as “configuration” as long as the effects of the present invention are not impaired. Other structural units (a4) other than those not included in the “unit group” may be included.
The structural unit (a4) is not particularly limited as long as it is another structural unit that is not classified into the above-mentioned “structural unit group”, such as for ArF excimer laser, for KrF positive excimer laser (preferably for ArF excimer laser), etc. Many things conventionally known as what is used for resin for resists can be used.
As the structural unit (a4), for example, a structural unit containing an acid non-dissociable aliphatic polycyclic group and derived from an acrylate ester is preferable. Examples of the polycyclic group include those similar to those exemplified for the structural unit (a1 ′). For ArF excimer laser, for KrF positive excimer laser (preferably ArF excimer laser) A large number of hitherto known materials can be used for the resin component of the resist composition.
In particular, at least one selected from a tricyclodecanyl group, an adamantyl group, a tetracyclododecanyl group, an isobornyl group, and a norbornyl group is preferable in terms of industrial availability. These polycyclic groups may be substituted with a linear or branched alkyl group having 1 to 5 carbon atoms.
Specific examples of the structural unit (a4) include those represented by the following general formulas (a4-1) to (a4-5).

（式中、Ｒ^０は前記と同じである。）

(Wherein R ⁰ is the same as described above.)

  The structural unit (a4) is preferably contained in an amount of 1 to 30 mol%, preferably 10 to 20 mol% of the structural unit (a4) based on the total of all the structural units constituting the component (A ′).

The component (A ′) can be obtained by polymerizing a monomer for deriving each structural unit by a known radical polymerization using a radical polymerization initiator such as azobisisobutyronitrile (AIBN). .
In addition, for the component (A ′), in the polymerization, a chain transfer agent such as HS—CH ₂ —CH ₂ —CH ₂ —C (CF ₃ ) ₂ —OH is used in combination, -C terminated _{(CF 3)} may be introduced 2 -OH group. As described above, a copolymer introduced with a hydroxyalkyl group in which a part of hydrogen atoms of the alkyl group is substituted with a fluorine atom reduces development defects and LER (line edge roughness: uneven unevenness of line side walls). It is effective in reducing

The component (A ′) can be obtained, for example, by radical polymerization of a monomer for deriving each structural unit by a conventional method.
(A ') A component can be used 1 type or in mixture of 2 or more types.

-Mass average molecular weight (A ') The mass average molecular weight (polystyrene conversion mass average molecular weight by gel permeation chromatography, the same shall apply hereinafter) of the component is, for example, 30000 or less, preferably 20000 or less, and preferably 12000 or less. Is more preferable, and most preferably 10,000 or less.
The lower limit is not particularly limited, but is preferably 4000 or more, and more preferably 5000 or more, from the viewpoint of suppressing pattern collapse and improving resolution.

Also,
What is necessary is just to adjust content of (A ') component according to the resist film thickness to form.

(B) Acid generator component that generates acid by exposure The component (B) can be used without particular limitation from known acid generators used in conventional chemically amplified resist compositions.
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, iminosulfonate acid generators, disulfone acid generators, and the like.

  Specific examples of the onium salt-based acid generator include diphenyliodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, bis (4-tert-butylphenyl) iodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, and triphenylsulfonium trifluoromethane. Sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, tri (4-methylphenyl) sulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, dimethyl (4-hydroxynaphthyl) sulfonium trifluoromethane Sulfonate, its heptafluoropropane sulphonate or its Nafluorobutane sulfonate, trifluoromethane sulfonate of monophenyldimethylsulfonium, heptafluoropropane sulfonate or nonafluorobutane sulfonate thereof, trifluoromethane sulfonate of diphenyl monomethylsulfonium, heptafluoropropane sulfonate or nonafluorobutane sulfonate thereof, (4- Trifluoromethanesulfonate of methylphenyl) diphenylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, trifluoromethanesulfonate of (4-methoxyphenyl) diphenylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, tri (4 -Tert-bu Le) trifluoromethanesulfonate triphenylsulfonium, its like heptafluoropropane sulfonate or nonafluorobutane sulfonates.

  Specific examples of the oxime sulfonate acid generator include α- (methylsulfonyloxyimino) -phenylacetonitrile, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (trifluoromethylsulfonyloxyimino)- Phenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (ethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (propylsulfonyloxyimino) -p-methylphenylacetonitrile, α- (methylsulfonyloxyimino) -p-bromophenylacetonitrile and the like can be mentioned. Of these, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile is preferred.

Among diazomethane acid generators, specific examples of bisalkyl or bisarylsulfonyldiazomethanes include bis (isopropylsulfonyl) diazomethane, bis (p-toluenesulfonyl) diazomethane, bis (1,1-dimethylethylsulfonyl) diazomethane, Examples include bis (cyclohexylsulfonyl) diazomethane, bis (2,4-dimethylphenylsulfonyl) diazomethane, and the like.
Examples of poly (bissulfonyl) diazomethanes include 1,3-bis (phenylsulfonyldiazomethylsulfonyl) propane (compound A) and 1,4-bis (phenylsulfonyldiazomethylsulfonyl) having the following structure. Butane (compound B), 1,6-bis (phenylsulfonyldiazomethylsulfonyl) hexane (compound C), 1,10-bis (phenylsulfonyldiazomethylsulfonyl) decane (compound D), 1,2-bis (cyclohexylsulfonyl) Diazomethylsulfonyl) ethane (compound E), 1,3-bis (cyclohexylsulfonyldiazomethylsulfonyl) propane (compound F,), 1,6-bis (cyclohexylsulfonyldiazomethylsulfonyl) hexane (compound G), 1,10 -Bis (cyclohe Such Sil diazomethylsulfonyl) decane (compound H) can be mentioned.

  As the component (B), the following general formula (b-1) or (b-2)

［式中、Ｘは、少なくとも１つの水素原子がフッ素原子で置換された炭素数２〜６のアルキレン基を表し；Ｙ、Ｚは、それぞれ独立に、少なくとも１つの水素原子がフッ素原子で置換された炭素数１〜１０のアルキル基を表し；Ｒ^１１〜Ｒ^１３は、それぞれ独立に、アリール基またはアルキル基を表し、Ｒ^１１〜Ｒ^１３のうち少なくとも１つはアリール基を表す］で表される構成単位からなる群から選ばれる少なくとも１種のスルホニウム化合物も好ましい。

[Wherein X represents an alkylene group having 2 to 6 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom; Y and Z each independently represents at least one hydrogen atom substituted with a fluorine atom; R ^{11 to} R ¹³ each independently represents an aryl group or an alkyl group, and at least one of R ^{11 to} R ¹³ represents an aryl group]. Also preferred are at least one sulfonium compound selected from the group consisting of:

In the formulas (b-1) and (b-2), X is a linear or branched alkylene group in which at least one hydrogen atom is substituted with a fluorine atom, and the alkylene group has, for example, 2 carbon atoms. -6, preferably 3-5, most preferably 3 carbon atoms.
Y and Z are each independently a linear or branched alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, and the alkyl group has, for example, 1 to 10 carbon atoms, preferably 1 -7, more preferably 1-3.
The smaller the number of carbon atoms of the alkylene group of X or the number of carbon atoms of the alkyl groups of Y and Z, the better the solubility in the resist solvent, which is preferable.
In addition, in the alkylene group of X or the alkyl group of Y and Z, the greater the number of hydrogen atoms substituted by fluorine atoms, the stronger the acid, and the transparency to high energy light and electron beams of 200 nm or less Is preferable. The proportion of fluorine atoms in the alkylene group or alkyl group, that is, the fluorination rate is preferably 70 to 100%, more preferably 90 to 100%, and most preferably all hydrogen atoms are substituted with fluorine atoms. A perfluoroalkylene group or a perfluoroalkyl group.

R ^{11 to} R ¹³ each independently represents an aryl group or an alkyl group.
At least one of R ^{11 to} R ¹³ represents an aryl group. Of R ^{11 to} R ¹³ , two or more are preferably aryl groups, and most preferably all of R ^{11 to} R ¹³ are aryl groups.
There is no restriction | limiting in particular as an aryl group of R < ¹¹ > -R < ¹³ >, For example, it is a C6-C20 aryl group, Comprising: It may be substituted by the alkyl group, the alkoxy group, the halogen atom, etc. Good phenyl group and naphthyl group can be mentioned. An aryl group having 6 to 10 carbon atoms is preferable because it can be synthesized at low cost.
The alkyl group of R ¹¹ to R ^13, not particularly limited, for example, a straight, include alkyl groups such as branched or cyclic. It is preferable that it is C1-C5 from the point which is excellent in resolution. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group, and a decanyl group. A methyl group is preferable because it is excellent in resolution and can be synthesized at low cost.
Among these, it is most preferable that all of R ^{11 to} R ¹³ are phenyl groups.

  These sulfonium compounds may be used alone or in combination of two or more.

Especially, it is preferable to use the onium salt which uses a fluorinated alkylsulfonic acid ion as an anion as (B) component.
In the positive resist composition described later, it is preferable to use an onium salt having a fluorinated alkyl sulfonate ion as an anion.
As the component (B), one type of acid generator may be used alone, or two or more types may be used in combination.

  The content of the component (B) is 0.5 to 30 parts by mass, preferably 1 to 10 parts by mass with respect to 100 parts by mass of the component (A ′). By setting it as the said range, pattern formation can fully be performed. Moreover, since a uniform resist solution is obtained and storage stability becomes favorable, it is preferable.

(D) Nitrogen-containing organic compound In the positive resist composition, a nitrogen-containing organic compound (D) (hereinafter referred to as (D)) is further added as an optional component in order to improve the resist pattern shape, stability over time and the like. Component)).
Since a wide variety of components (D) have been proposed, any known one may be used, but aliphatic amines, particularly secondary aliphatic amines and tertiary aliphatic amines are preferred. .
Examples of the aliphatic amine include amines (alkyl amines or alkyl alcohol amines) in which at least one hydrogen atom of ammonia NH ₃ is substituted with an alkyl group or hydroxyalkyl group having 12 or less carbon atoms. Specific examples thereof include monoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine; diethylamine, di-n-propylamine, di-n-heptylamine, Dialkylamines such as di-n-octylamine and dicyclohexylamine; trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine, tri-n-pentylamine, tri-n-heptyl Trialkylamines such as amine, tri-n-octylamine, tri-n-nonylamine, tri-n-decanylamine, tri-n-dodecylamine; diethanolamine, triethanolamine, diisopropanolamine, triisopropanolamine, di-n -Ok Noruamin, alkyl alcohol amines such as tri -n- octanol amine.
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. Among these, alkyl alcohol amines and trialkyl amines are preferable, and alkyl alcohol amines are most preferable. Of the alkyl alcohol amines, alkyl alcohol amines such as triethanolamine and triisopropanolamine are most preferred.

(E) Component For the purpose of preventing sensitivity deterioration due to the blending with the (D) component, and improving the resist pattern shape, retention stability, etc., as an optional component, an organic carboxylic acid or an oxo acid of phosphorus or its A derivative (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 derivatives thereof, phosphinic acids such as phosphinic acid, phenylphosphinic acid and their esters Among these, phosphonic acid is particularly preferable.
The component (E) is used in a proportion of 0.01 to 5.0 parts by mass per 100 parts by mass of the component (A ′).

Other optional components In the positive resist composition, if necessary, there are miscible additives such as an additional resin for improving the performance of the resist film, a surfactant for improving the coating property, and a dissolution inhibitor. , Plasticizers, stabilizers, colorants, antihalation agents, dyes, and the like can be added as appropriate.

[First positive resist composition]
As the first positive resist composition, for example, the same one as the second positive resist composition can be used. Among these, (A ′) contains a resin component that contains a structural unit derived from an acrylate ester and increases alkali solubility by the action of an acid, and (B) an acid generator component that generates an acid upon exposure. A positive resist composition is preferable, and the component (A ′) is composed of a structural unit (a1 ′) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group and an acrylate ester having a lactone ring. Those containing the derived structural unit (a2) are most preferred.
However, in the first positive resist composition, there is no restriction that an organic solvent that does not dissolve the first resist layer 2 is used unlike the second positive resist composition.
Therefore, it is also possible to use an organic solvent other than the organic solvent described in the second positive resist composition.
For example, the organic solvent only needs to dissolve each component to be used to form a uniform solution. Conventionally, any one of known solvents for chemically amplified resists may be used. Two or more types can be appropriately selected and used.
For example, ketones such as γ-butyrolactone, acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate, dipropylene glycol Or polyhydric alcohols such as 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, lactic acid Ethyl (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methoxy Methyl propionate, esters such as ethyl ethoxypropionate can be exemplified.

These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.
A mixed solvent obtained by mixing 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, preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2. It is preferable to be within the range.
More specifically, when EL is blended as a polar solvent, the mass ratio of PGMEA: EL is preferably 2: 8 to 8: 2, more preferably 3: 7 to 7: 3.
In addition, as the organic solvent, a mixed solvent of at least one selected from PGMEA and EL and γ-butyrolactone is also preferable. In this case, the mixing ratio of the former and the latter is preferably 70:30 to 95: 5.

A preferred component (A ′) as the resin component of the first positive resist composition is a structural unit (a1 ′) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group, and an acrylate ester having a lactone ring What contains the structural unit (a2) induced | guided | derived from is preferable. Further, it is most preferable to include a structural unit (a3) derived from an acrylate ester containing a polar group-containing polycyclic group in addition to the structural unit (a1 ′) and the structural unit (a2).
The component (A ′) preferable as the resin component of the second positive resist composition includes a structural unit (a1 ′) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group and a fluorinated hydroxyalkyl group. And a structural unit (a2 ′) containing an alicyclic group.

  The component (A ′) of the first positive resist composition is composed of a copolymer represented by the following chemical formula (A′-1) and a copolymer represented by the following chemical formula (A′-2). It is preferable that either of them is included, and further, a mixture of these copolymers is particularly preferable. The mixing ratio (mass ratio) is preferably 9: 1 to 1: 9, more preferably 8: 2 to 2: 8, and most preferably 6: 4 to 4: 6.

（式中、Ｒ^０については上記と同じである。）

(In the formula, R ⁰ is the same as above.)

（式中、Ｒ^０については上記と同じである。） The component (A ′) of the second positive resist composition preferably contains a copolymer represented by the following chemical formula (A′-3).

(In the formula, R ⁰ is the same as above.)

  In the resist pattern forming method of the present invention, as described above, a specific positive resist composition is used as the second positive resist composition, whereby a dense pattern is formed in the lower layer and a pattern is formed in the upper layer. In the method for forming a resist pattern, mixing can be suppressed, and a method for forming a resist pattern having a good shape can be provided.

[Reference Example 1]
(Adjustment of positive resist composition used for second resist layer)
As resin components, 100 parts by mass of resin 1 represented by the following chemical formula (mass ratio 1: 1), 5.0 parts by mass of triphenylsulfonium nonafluorobutanesulfonate as an acid generator, and triethanolamine as a nitrogen-containing organic compound Was dissolved in isobutanol using 0.45 parts by mass as an organic solvent to obtain a positive resist composition having a solid concentration of 6% by mass.

樹脂１（質量平均分子量９８００、分散度（質量平均分子量／数平均分子量）１．４、ｌ／ｍ＝／４８／５２（モル比））

Resin 1 (mass average molecular weight 9800, dispersity (mass average molecular weight / number average molecular weight) 1.4, l / m = / 48/52 (molar ratio))

[Reference Example 2]
(Adjustment of positive resist composition used for first resist layer)
As a resin component, 100 parts by mass (mass ratio 1: 1) of a mixture of resin 1 and resin 2 represented by the following chemical formula, 3.0 parts by mass of triphenylsulfonium nonafluorobutane sulfonate as an acid generator, nitrogen-containing organic Propylene glycol monomethyl ether acetate and ethyl lactate using 0.15 parts by weight of triethanolamine as a compound and 0.1 parts by weight of a surfactant (R-08: manufactured by Dainippon Ink & Chemicals, Inc.) as other components. And a positive resist composition having a solid content concentration of 10% by mass.

樹脂１（分子量１００００、分散度２．０、ｌ／ｍ／ｎ＝４／４／２（モル比））

Resin 1 (molecular weight 10,000, dispersity 2.0, l / m / n = 4/4/2 (molar ratio))

樹脂２（分子量１００００、分散度２．０、ｌ／ｍ／ｎ＝３／５／２（モル比））

Resin 2 (molecular weight 10,000, dispersity 2.0, l / m / n = 3/5/2 (molar ratio))

An organic antireflective coating composition “ARC-29” (trade name, manufactured by Brewer Science) is applied onto an 8-inch silicon wafer using a spinner, and baked on a hot plate at 215 ° C. for 60 seconds to be dried. Thereby, an organic antireflection film having a thickness of 77 nm was formed.
Then, the first positive resist composition prepared in Reference Example 2 is applied onto the antireflection film using a spinner, prebaked (PAB) at 115 ° C. for 60 seconds on a hot plate, and dried. Thus, a 300 nm-thick resist layer was formed.
Next, ArF excimer laser (193 nm) was selectively irradiated through the mask pattern by an ArF exposure apparatus NSR-S302 (manufactured by Nikon Corporation; NA (numerical aperture) = 0.60, σ = 0.75).
Then, PEB treatment at 100 ° C. for 60 seconds, paddle development with a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. for 60 seconds, followed by washing with water for 20 seconds and drying to a 140 nm 1: 1 dense A hole pattern was formed.
Next, on the formed dense hole pattern, the second positive resist composition prepared in Reference Example 1 was applied using a spinner, and prebaked (PAB) at 115 ° C. for 60 seconds on a hot plate, By drying, a 200 nm thick resist layer was formed. At that time, mixing with the lower resist layer was not generated. Next, ArF excimer laser (193 nm) was selectively irradiated through the mask pattern by an ArF exposure apparatus NSR-S302 (manufactured by Nikon Corporation; NA (numerical aperture) = 0.60, σ = 0.75).
Then, PEB treatment at 100 ° C. for 60 seconds, paddle development with a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. for 60 seconds, followed by washing with water for 20 seconds and drying to a 140 nm 1: 1 dense A dense / dense mixed pattern having both a (dense) contact hole pattern and a sparse pattern with a hole width of 140 nm could be formed.

  Thus, in the example according to the present invention, mixing could be prevented and a practical resist pattern could be formed.

FIG. 1A is an explanatory diagram showing a flow of an example procedure (process 1) of the first aspect, and FIG. 1B is an explanatory diagram showing a flow of an example procedure (process 2) of the second aspect. Figure. Explanatory drawing (sectional drawing) of the process 1. FIG. Explanatory drawing (sectional drawing) of the process 2. FIG. The top view which showed the state after forming a dense pattern and a sparse pattern through the process 1 or 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... 1st resist layer (lower layer), 2a ... Hole, 2a '... Latent image part (exposure part), 12 ... 2nd resist layer (upper layer) , 12a ... holes, 12a '... latent image part (exposure part), 3, 13 ... mask

Claims (7)

A resist pattern forming method in which a dense pattern is formed in a lower first resist layer, and a pattern different from the lower layer is formed in an upper second resist layer,
Steps (i) to (ii) below (i) A first resist layer is formed on a substrate using a first positive resist composition, selectively exposed to form a first resist layer. Step (ii) forming a latent image portion of a dense pattern After applying a second positive resist composition on the first resist layer to form a second resist layer and selectively exposing, Simultaneously developing the first resist layer and the second resist layer to remove a part of the latent image portion of the dense pattern and to expose a part of the dense pattern;
As the first positive resist composition, a positive resist composition comprising (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid upon exposure. Use
As the second positive resist composition, (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid by exposure, an alcohol solvent is included, dissolved in an organic solvent which does not dissolve the first resist layer, and the component (a ') is the use of a positive resist composition containing an alicyclic group having a fluorinated hydroxyalkyl group A method for forming a resist pattern. A resist pattern forming method in which a dense pattern is formed in a lower first resist layer, and a pattern different from the lower layer is formed in an upper second resist layer,
Steps (i ′) to (ii ′) below (i ′) A first resist layer is formed on a substrate using a first positive resist composition, selectively exposed, developed, and then developed. Step (ii ′) of forming a dense pattern on the first resist layer A second positive resist composition is applied on the first resist layer to embed the dense pattern and form a second resist layer And selectively exposing and developing to remove a part of the second positive resist composition embedded in the dense pattern and to expose a part of the dense pattern,
As the first positive resist composition, a positive resist composition comprising (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid upon exposure. Use
As the second positive resist composition, (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid by exposure, an alcohol solvent is included, dissolved in an organic solvent which does not dissolve the first resist layer, and the component (a ') is the use of a positive resist composition containing an alicyclic group having a fluorinated hydroxyalkyl group A method for forming a resist pattern. 3. The method of forming a resist pattern according to claim 1 , wherein the alcohol solvent is isobutanol and / or n-butanol. The component (A ′) of the first positive resist composition is derived from a structural unit (a1 ′) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group and an acrylate ester having a lactone ring. The resist pattern formation method as described in any one of Claims 1-3 containing the structural unit (a2). The component (A ′) of the second positive resist composition has an alicyclic ring having a structural unit (a1 ′) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group and a fluorinated hydroxyalkyl group. The resist pattern formation method as described in any one of Claims 1-4 containing the structural unit (a2 ') containing a formula group. A resist pattern forming method in which a dense pattern is formed in a lower first resist layer, and a pattern different from the lower layer is formed in an upper second resist layer,
  Steps (i) to (ii) below
(I) A step of forming a first resist layer on a substrate using a first positive resist composition and selectively exposing to form a latent image portion having a dense pattern on the first resist layer.
(Ii) A second positive resist composition is applied onto the first resist layer to form a second resist layer, and after selective exposure, the first resist layer and the second resist layer Simultaneously developing the resist layer to remove part of the latent image portion of the dense pattern and exposing part of the dense pattern
Including
  The first positive resist composition includes (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid upon exposure, ') A positive resist in which the component contains a structural unit (a1') derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group and a structural unit (a2) derived from an acrylate ester having a lactone ring Using the composition,
  As the second positive resist composition, (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid by exposure, the first resist layer And the component (A ′) comprises a structural unit (a1 ′) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group, and a fluorinated hydroxyalkyl group. A positive resist composition comprising a structural unit (a2 ′) containing an alicyclic group having a resist pattern forming method. A resist pattern forming method in which a dense pattern is formed in a lower first resist layer, and a pattern different from the lower layer is formed in an upper second resist layer,
  The following steps (i ′) to (ii ′)
(I ′) a step of forming a first resist layer on the substrate using the first positive resist composition, selectively exposing, and developing to form a dense pattern in the first resist layer
(Ii ′) A second positive resist composition is applied on the first resist layer to embed the dense pattern, and a second resist layer is formed, selectively exposed, and developed. Removing a part of the second positive resist composition embedded in the dense pattern to expose a part of the dense pattern
Including
The first positive resist composition includes (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid upon exposure, ') A positive resist in which the component contains a structural unit (a1') derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group and a structural unit (a2) derived from an acrylate ester having a lactone ring Using the composition,
  As the second positive resist composition, (A ′) a resin component whose alkali solubility is increased by the action of an acid, and (B) an acid generator component which generates an acid by exposure, the first resist layer And the component (A ′) comprises a structural unit (a1 ′) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group, and a fluorinated hydroxyalkyl group. A positive resist composition comprising a structural unit (a2 ′) containing an alicyclic group having a resist pattern forming method.

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