JP2012032780A - Pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct a process capable of safely forming a negative tone pattern.SOLUTION: A pattern is formed by applying a resist composition comprising: a (meth)acrylate polymer having a repeating unit a having a carboxyl group substituted with an acid labile group represented by the formula (1) and a repeating unit b having a lactone ring, an acid generator, and an organic solvent onto a substrate to form a resist film; exposing the resist film with high-energy radiation after heating treatment; and performing development with a solution containing 50 mass% or more of 2-heptanone as a developing solution after heating treatment. (Where, R2 is an acid labile group.)

Description

  The present invention relates to a pattern forming method for obtaining a negative pattern in which an unexposed portion is dissolved by development with a specific organic solvent after exposure, and an unexposed portion is dissolved by development with a specific organic solvent.

In recent years, with the higher integration and higher speed of LSIs, there is a demand for finer pattern rules. In light exposure currently used as a general-purpose technology, the intrinsic resolution limit derived from the wavelength of the light source Is approaching. As exposure light used for forming a resist pattern, light exposure using g-ray (436 nm) or i-line (365 nm) of a mercury lamp as a light source was widely used in the 1980s. As a means for further miniaturization, the method of shortening the exposure wavelength is effective, and mass production after 64 Mbit (process size is 0.25 μm or less) DRAM (Dynamic Random Access Memory) in the 1990s In the process, a KrF excimer laser (248 nm) having a short wavelength was used as an exposure light source instead of i-line (365 nm). However, in order to manufacture DRAMs with a density of 256M and 1G or more that require finer processing technology (processing dimensions of 0.2 μm or less), a light source with a shorter wavelength is required, and an ArF excimer has been used for about 10 years. Photolithography using a laser (193 nm) has been studied in earnest. Initially, ArF lithography was supposed to be applied from 180 nm node device fabrication, but KrF lithography is extended to 130 nm node device mass production, and full-scale application of ArF lithography is from the 90 nm node. Further, a 65 nm node device is being studied in combination with a lens whose NA is increased to 0.9. For the next 45 nm node device, the exposure wavelength has been shortened, and F ₂ lithography with a wavelength of 157 nm was nominated. However, the cost of the scanner is increased by using a large amount of expensive CaF ₂ single crystal for the projection lens, the optical system is changed due to the introduction of the hard pellicle because the durability of the soft pellicle is extremely low, and the etching resistance of the resist film is reduced. Due to various problems, the development of F ₂ lithography was discontinued and ArF immersion lithography was introduced.

  In ArF immersion lithography, water with a refractive index of 1.44 is inserted between the projection lens and the wafer by a partial fill method, thereby enabling high-speed scanning, and mass production of 45 nm node devices is possible with NA1.3 class lenses. Has been done.

  As a lithography technique for the 32 nm node, vacuum ultraviolet light (EUV) lithography with a wavelength of 13.5 nm is cited as a candidate. Problems with EUV lithography include high laser output, high resist film sensitivity, high resolution, low edge roughness, defect-free MoSi laminated mask, and low reflection mirror aberrations. Are piled up.

  Another candidate for high refractive index immersion lithography for the 32 nm node was developed because of the low transmittance of LUAG, which is a high refractive index lens candidate, and the liquid refractive index did not reach the target of 1.8. Canceled.

  Recently, a double patterning process in which a pattern is formed by the first exposure and development, and a pattern is formed just between the first pattern by the second exposure has attracted attention recently. Many processes have been proposed as a double patterning method. For example, the first exposure and development form a photoresist pattern with 1: 3 line and space spacing, the lower hard mask is processed by dry etching, and another hard mask is laid on the first hard mask. In this exposure method, a line pattern is formed by exposure and development of a photoresist film in a space portion of the exposure, and a hard mask is processed by dry etching to form a line-and-space pattern that is half the pitch of the initial pattern. Also, a photoresist pattern having a space and line spacing of 1: 3 is formed by the first exposure and development, a hard mask in the lower layer is processed by dry etching, and a photoresist film is applied thereon to form a hard mask. The remaining space pattern is exposed to the remaining portion and the hard mask is processed by dry etching. In either case, the hard mask is processed by two dry etchings.

It is difficult to make a hole pattern finer than a line pattern. If a hole pattern mask is combined with a positive resist film in order to form a fine hole by a conventional method, an exposure margin becomes extremely narrow. Therefore, a method has been proposed in which a hole having a large size is formed and the hole after development is shrunk by a thermal flow, a RELACS ^™ method or the like. However, there is a problem that the difference between the pattern size after development and the size after shrinking is large, and the control accuracy decreases as the shrink amount increases. In the hall shrink method, the hole size can be reduced, but the pitch cannot be reduced.

  A positive resist film is used to form a line pattern in the X direction by dipole illumination, the resist pattern is cured, a resist composition is again applied thereon, and the line pattern in the Y direction is exposed by dipole illumination to form a lattice pattern. A method of forming a hole pattern from a gap between line patterns has been proposed (Non-patent Document 1: Proc. SPIE Vol. 5377, p. 255 (2004)). A hole pattern can be formed with a wide margin by combining X and Y lines by high-contrast dipole illumination, but it is difficult to etch the line pattern combined vertically with high dimensional accuracy. On the other hand, there has been proposed a method of forming a hole pattern by exposing a negative resist film by combining a Levenson type phase shift mask for X direction lines and a Levenson type phase shift mask for Y direction lines (Non-patent Document 2: IEEE). IEDM Tech.Digest 61 (1996)). However, the bridged negative resist film has a drawback that the resolution is lower than that of the positive resist film because the limit resolution of the ultrafine holes is determined by the bridge margin.

  The hole pattern formed by exposing the X-direction line and the Y-direction line to a double exposure and combining it with a negative pattern by image inversion can be formed by using a high-contrast line pattern light. Therefore, it is possible to open fine holes with a narrower pitch than the conventional method. However, in this case, since it is necessary to perform the exposure twice while exchanging the mask, a decrease in throughput due to this and a positional deviation between the two exposures become problems.

Non-Patent Document 3 (Proc. SPIE Vol. 7274, p.72740N (2009)) reports the production of a hole pattern by image inversion by the following three methods.
That is, a method of forming a dot pattern by double exposure of a double dipole of X and Y lines of a positive resist composition, forming an SiO ₂ film thereon by LPCVD, and inverting the dots into holes by O ₂ -RIE A dot pattern is formed in the same way using a resist composition that becomes alkali-soluble and solvent-insoluble by heating, and a phenol-based overcoat film is applied thereon, and the image is inverted by alkali development to form a hole pattern. And a method of forming holes by double dipole exposure using a positive resist composition and image reversal by organic solvent development. This also has the problem of double exposure as described above.

  In recent years, organic solvent development has attracted attention again. In order to resolve a very fine hole pattern that cannot be achieved by positive tone by negative tone exposure, a negative pattern is formed by organic solvent development using a positive resist composition having high resolution. Further, studies are being made to obtain double resolution by combining two developments, alkali development and organic solvent development.

As an ArF resist composition for negative tone development using an organic solvent, a conventional positive ArF resist composition can be used, and Patent Documents 1 to 6 (JP 2008-281974 A, JP 2008-281975 A). JP-A-2008-281980, JP-A-2009-53657, JP-A-2009-25707, and JP-A-2009-25723) show pattern forming methods.
In these applications, hydroxyadamantane methacrylate is copolymerized, norbornane lactone methacrylate is copolymerized, or a methacrylate in which acidic groups such as carboxyl group, sulfo group, phenol group, and thiol group are substituted with two or more acid labile groups. There have been proposed a resist composition for developing an organic solvent obtained by copolymerizing a methacrylate having a cyclic acid-stabilized ester and a pattern forming method using the same.

A pattern forming method for applying a protective film on a resist film in an organic solvent development process is disclosed in Japanese Patent Application Laid-Open No. 2008-309878.
In an organic solvent development process, as a resist composition, a pattern forming method without using a top coat by using an additive that aligns on the surface of a resist film after spin coating and improves water repellency is disclosed in Patent Document 8 (Japanese Patent Application Laid-Open (JP-A) 2008). -309879).

  In Japanese Patent Application Laid-Open No. 2008-281974, as a developing solution, examples of an organic developing solution that can be used for negative development include ketone solvents, ester solvents, alcohol solvents, amide solvents, ether solvents. Polar solvents such as solvents and hydrocarbon solvents are shown. Specifically, ketone solvents include 1-octanone, 2-octanone, 1-nonanone, 2-nonanone, acetone, 4-heptanone, 1-hexanone, 2 -Hexanone, diisobutyl ketone, cyclohexanone, methylcyclohexanone, phenylacetone, methylethylketone, methylisobutylketone, acetylacetone, acetonylacetone, ionone, diacetonyl alcohol, acetylcarbinol, acetophenone, methylnaphthylketone, isophorone, propylene carbonate, e Tellurium solvents include methyl acetate, butyl acetate, ethyl acetate, isopropyl acetate, amyl acetate, propylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl-3-ethoxypropio Nate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, methyl formate, ethyl formate, butyl formate, propyl formate, ethyl lactate, butyl lactate, propyl lactate, alcohol solvents include methyl alcohol, ethyl alcohol , N-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, Alcohols such as sobutyl alcohol, n-hexyl alcohol, n-heptyl alcohol, n-octyl alcohol, n-decanol, glycol solvents such as ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, propylene glycol monomethyl Glycol ether solvents such as ether, ethylene glycol, propylene glycol, diethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and methoxymethylbutanol, ether solvents include the above glycol ether solvents, dioxane, tetrahydrofuran, amide solvents N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide , Hexamethylphosphoric triamide, 1,3-dimethyl-2-imidazolidinone, hydrocarbon solvents include aromatic hydrocarbon solvents such as toluene and xylene, aliphatics such as pentane, hexane, octane, and decane A hydrocarbon-based solvent is shown.

  Of these, many organic solvents are exemplified, but in reality, not all of them can be used, and some of them do not dissolve in the space part and the pattern is not formed at all. There are some that are remarkable. In addition, there is a developer whose flash point is too low to be practically used from the viewpoint of safety.

  In these applications, hydroxyadamantane methacrylate is copolymerized, norbornane lactone methacrylate is copolymerized, or a methacrylate in which acidic groups such as carboxyl group, sulfo group, phenol group, and thiol group are substituted with two or more acid labile groups. There have been proposed a resist composition for developing an organic solvent obtained by copolymerizing a methacrylate having a cyclic acid-stabilized ester and a pattern forming method using the same.

The production of negative patterns by organic solvent development is a technique that has been used for a long time. The cyclized rubber-based resist composition uses an alkene such as xylene as a developer, and the initial chemically amplified resist composition based on poly-t-butoxycarbonyloxystyrene has a negative pattern using anisole as a developer. It was.
In Patent Document 9 (Japanese Patent No. 4445860), calixarene is drawn by EB and developed with n-butyl acetate or ethyl lactate to obtain a negative pattern.

JP 2008-281974 A JP 2008-281975 A JP 2008-281980 A JP 2009-53657 A JP 2009-25707 A JP 2009-25723 A JP 2008-309878 A JP 2008-309879 A Japanese Patent No. 4445860

Proc. SPIE Vol. 5377, p. 255 (2004) IEEE IEDM Tech. Digest 61 (1996) Proc. SPIE Vol. 7274, p. 72740N (2009)

It is necessary to develop an optimum developer having a high dissolution contrast and high safety for performing negative development with an organic solvent.
An object of the present invention is to provide a pattern forming method in which an optimum developer and a resist composition for performing negative tone development using an organic solvent are combined.

  As the aforementioned organic solvent developer, butyl acetate is preferred from the viewpoint of dissolution contrast. However, since the flash point of butyl acetate is as low as 28 ° C., an explosion-proof device is required to use it safely in a coater developer, leading to an increase in the cost of the device. There is a need for an organic solvent developer that has a flash point of 40 ° C. or higher and can provide a dissolution contrast equivalent to or higher than that of butyl acetate.

  An amyl acetate having more carbon atoms than butyl acetate has a flash point of 45 ° C., which is preferable from the viewpoint of safety, but the dissolution rate of the unexposed area is lowered. Amyl formate having the same number of carbon atoms as butyl acetate can obtain the same degree of dissolution contrast, but has a flash point of 25 ° C. and is more flammable than butyl acetate. An ester solvent having a carbon number less than that of butyl acetate further lowers the flash point, and the solubility is too high to reduce the remaining film of the exposed portion of the resist pattern after development.

Therefore, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ethylene glycol such as ethylene glycol monomethyl ether, hydroxy group-substituted propylene glycol, ethyl lactate, cyclohexanone, etc. are so soluble that they can be used alone as a resist agent. Therefore, the resist pattern after development does not remain. The alcohol solvent is so low in solubility of the resist that it is used as a solvent for the top coat, and the space pattern of the unexposed portion after development is not dissolved.
Development of a developer having a flash point of 40 ° C. or higher and a high dissolution contrast is desired.

  As a result of intensive studies to meet such demands, the present inventor has developed a resist film formed by using a chemically amplified positive resist composition having repeating units a and b in the following general formula (1). When developing with a developer containing heptanone as a main component, the exposed portion of the resist film does not dissolve, and a negative tone pattern is formed in which the non-exposed portion dissolves, and the dissolution contrast can be increased. It has been found that a fine hole pattern can be formed by exposure and development using a mask pattern having a shape, and the present invention has been made.

Accordingly, the present invention provides the following pattern forming method.
Claim 1:
A (meth) acrylate polymer containing both a repeating unit a having a carboxyl group substituted with an acid labile group represented by the following general formula (1) and a repeating unit b having a lactone ring, an acid generator, A resist composition containing an organic solvent is applied onto a substrate to form a resist film, and after the heat treatment, the resist film is exposed with a high energy beam, and after the heat treatment, contains 50% by mass or more of 2-heptanone as a developer. The pattern formation method characterized by performing image development with the solution to do.

(In the formula, R ¹ and R ³ represent a hydrogen atom or a methyl group, but they may be the same or different. R ² is an acid labile group. X and Y are a single bond or —C (═O ) —O—R ⁹ —, wherein R ⁹ is a linear, branched or cyclic alkylene group having 1 to 10 carbon atoms, and the alkylene group has an ether group, an ester group, a lactone ring or a hydroxy group. R ⁴ , R ⁶ , R ⁷ , R ⁸ may be a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, or a trifluoromethyl group. , Or a cyano group, R ⁵ is a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, a carboxyl group, a substituted or unsubstituted alkoxycarbonyl group having 1 to 12 carbon atoms, or a cyano group And Z is a methylene group, an oxygen atom or a sulfur atom. Are 0 <a <1.0, 0 <b <1.0, and 0 <a + b ≦ 1.0.)
Claim 2:
In addition to 2-heptanone, the developer is 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methyl acetophenone, propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, butenyl acetate, isoamyl acetate, phenyl acetate , Propyl formate, butyl formate, isobutyl formate, amyl formate, isoamyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, amyl lactate, 2. The pattern forming method according to claim 1, wherein at least one selected from lactic acid isoamyl ester is mixed at a ratio of less than 50% by mass.
Claim 3:
3. The pattern forming method according to claim 1, wherein the exposure with the high energy beam is immersion lithography using an ArF excimer laser having a wavelength of 193 nm or EUV lithography having a wavelength of 13.5 nm.
Claim 4:
4. The light-irradiated portion is not dissolved in the developer, the unexposed portion is dissolved in the developer, and the pattern after development becomes a negative tone. Pattern forming method.
Claim 5:
The pattern forming method according to claim 1, wherein a trench pattern is formed after development.
Claim 6:
In immersion lithography using an ArF excimer laser with a wavelength of 193 nm, a post-development hole pattern is formed at the intersection of a lattice-like shifter grating using a halftone phase shift mask on which a lattice-like shifter pattern is arranged The pattern formation method of any one of Claims 1 thru | or 4.
Claim 7:
7. The pattern forming method according to claim 6, wherein the lattice pattern is a halftone phase shift mask having a transmittance of 3 to 15%.
Claim 8:
Phase shift in which a lattice-shaped first shifter having a line width of half pitch or less and a second shifter having a dimension on the wafer that is 2 to 30 nm thicker than the line width of the first shifter are arranged on the first shifter 8. The pattern forming method according to claim 6, wherein a hole pattern is formed only where the thick shifters are arranged using a mask.
Claim 9:
A grid-shaped first shifter having a line width of half pitch or less and a second shifter having a dot pattern that is 2 to 100 nm thicker on the wafer than the line width of the first shifter are arranged on the first shifter. 8. The pattern forming method according to claim 6, wherein a hole pattern is formed only where the thick shifters are arranged using the phase shift mask.

  By using the developer of the present invention, a process capable of safely forming a negative tone pattern can be constructed. The developer of the present invention is a copolymer of (meth) acrylate having an acid labile group having a feature capable of suppressing acid diffusion and a (meth) acrylate having a specific bridged cyclic lactone as an adhesive group In particular, it is possible to increase the dissolution contrast with respect to a resist composition based on the above, and it is possible to form a fine hole pattern by exposure and development using a lattice-like mask pattern.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a patterning method according to the present invention, where (A) is a cross-sectional view of a state where a photoresist film is formed on a substrate, (B) is a cross-sectional view of a state where the photoresist film is exposed, and (C) is an organic It is sectional drawing of the state developed with the solvent. An optical image of an X-direction line having a NA1.3 lens using an ArF excimer laser with a wavelength of 193 nm, dipole illumination, a 6% halftone phase shift mask, a pitch of 90 nm with s-polarized light, and a line size of 45 nm is shown. The optical image of the Y direction line is shown. 4 shows a contrast image in which optical images of the Y direction line in FIG. 3 and the X direction line in FIG. 2 are superimposed. The mask on which a grid pattern is arranged is shown. It is an optical image of a lattice-like line pattern with a pitch of 90 nm and a width of 30 nm in NA 1.3 lens, cross pole illumination, 6% halftone phase shift mask, and azimuthally polarized illumination. This is a mask in which an NA1.3 lens, a cross-pole illumination, a 6% halftone phase shift mask, a square dot pattern having a pitch of 90 nm and a width of 60 nm in an azimuthally polarized illumination is arranged. It is an optical image contrast in the mask. A mask in which a thick cross line of a cross is arranged at a portion where a dot is to be formed on a 20 nm line grid pattern at a pitch of 90 nm is shown. 10 shows a contrast image of an optical image in the mask of FIG. A mask is shown in which a thick dot is arranged at a portion where a dot is to be formed on a lattice pattern of 15 nm line at a pitch of 90 nm. 12 shows a contrast image of an optical image in the mask of FIG. The mask in which the grid pattern is not arranged is shown. The contrast image of the optical image in the mask of FIG. 13 is shown. It is a graph which shows the relationship between the exposure amount in Example 1-1, and Comparative Example 1-1, and a film thickness. The lattice mask used by ArF exposure patterning evaluation (2) is shown. The mask of the pattern by which the dot is arrange | positioned on the grid | lattice shape used by ArF exposure patterning evaluation (3) is shown. The mask of the pattern by which a thick grating | lattice is arrange | positioned on the grating | lattice form used by ArF exposure patterning evaluation (4) is shown.

  As described above, the present invention provides a photoresist composition based on a copolymer of (meth) acrylate having an acid labile group and a (meth) acrylate having a specific bridged cyclic lactone as an adhesive group. Coating, removing unnecessary solvent by pre-baking to form a resist film, exposing to high energy rays, heating after exposure, and pattern formation to obtain a negative pattern by developing an organic solvent containing 50% by mass or more of 2-heptanone A method is proposed.

As a repeating unit of a copolymer of (meth) acrylate having an acid labile group and a (meth) acrylate having a specific bridged cyclic lactone as an adhesive group, the repeating unit a in the following general formula (1): And b.

(In the formula, R ¹ and R ³ represent a hydrogen atom or a methyl group, but they may be the same or different. R ² is an acid labile group. X and Y are a single bond or —C (═O ) —O—R ⁹ —, wherein R ⁹ is a linear, branched or cyclic alkylene group having 1 to 10 carbon atoms, and the alkylene group has an ether group, an ester group, a lactone ring or a hydroxy group. R ⁴ , R ⁶ , R ⁷ , R ⁸ may be a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, or a trifluoromethyl group. Or a cyano group, R ⁵ is a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, a carboxyl group, an unsubstituted alkoxy group having 1 to 12 carbon atoms substituted with a fluorine atom, etc. Or a cyano group, Z is a methylene group, oxygen atom or sulfur atom A and b are ranges of 0 <a <1.0, 0 <b <1.0, and 0 <a + b ≦ 1.0.)

The monomer Ma for obtaining the repeating unit a is shown below.

(Wherein R ¹ represents a hydrogen atom or a methyl group, R ² represents an acid labile group, X represents a single bond or —C (═O) —O—R ⁹ —, and R ⁹ represents the number of carbon atoms. 1 to 10 linear, branched or cyclic alkylene groups which may have an ether group, an ester group, a lactone ring or a hydroxy group, or a naphthylene group.)

Specific examples of the structure in which the X of the repeating monomer Ma is changed can be exemplified below. Here, R ¹ and R ² are as described above.

In the general formula (1), various acid labile groups represented by R ² are selected, and conventionally known acid labile groups are used. Particularly, in the following formulas (AL-10) and (AL-11) And a tertiary alkyl group represented by the following formula (AL-12), an oxoalkyl group having 4 to 20 carbon atoms, and the like.

In the formulas (AL-10) and (AL-11), R ⁵¹ and R ⁵⁴ are monovalent hydrocarbon groups such as linear, branched or cyclic alkyl groups having 1 to 40 carbon atoms, particularly 1 to 20 carbon atoms. Yes, it may contain heteroatoms such as oxygen, sulfur, nitrogen and fluorine. R ⁵² and R ⁵³ are each a hydrogen atom or a monovalent hydrocarbon group such as a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, and includes heteroatoms such as oxygen, sulfur, nitrogen and fluorine. Alternatively, a5 is an integer of 0 to 10, particularly 1 to 5. R ⁵² and R ⁵³ , R ⁵² and R ⁵⁴ , or R ⁵³ and R ⁵⁴ are bonded to each other to form a ring having 3 to 20 carbon atoms, particularly 4 to 16 carbon atoms, together with the carbon atom or carbon atom and oxygen atom to which they are bonded, An alicyclic ring may be formed.

R ⁵⁵ , R ⁵⁶ , and R ⁵⁷ are each a monovalent hydrocarbon group such as a linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms, and include heteroatoms such as oxygen, sulfur, nitrogen, and fluorine. But you can. Alternatively, R ⁵⁵ and R ⁵⁶ , R ⁵⁵ and R ⁵⁷ , or R ⁵⁶ and R ⁵⁷ are combined to form a ring having 3 to 20 carbon atoms, particularly 4 to 16 carbon atoms, particularly an alicyclic ring, together with the carbon atom to which they are bonded. May be.

  Specific examples of the compound represented by the formula (AL-10) include tert-butoxycarbonyl group, tert-butoxycarbonylmethyl group, tert-amyloxycarbonyl group, tert-amyloxycarbonylmethyl group, 1-ethoxyethoxycarbonyl. Examples include a methyl group, 2-tetrahydropyranyloxycarbonylmethyl group, 2-tetrahydrofuranyloxycarbonylmethyl group and the like, and substituents represented by the following general formulas (AL-10) -1 to (AL-10) -10. .

In the formulas (AL-10) -1 to (AL-10) -10, R ⁵⁸ is the same or different linear, branched or cyclic alkyl group having 1 to 8 carbon atoms, aryl having 6 to 20 carbon atoms. Group or a C7-20 aralkyl group is shown. R ⁵⁹ represents a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms. R ⁶⁰ represents an aryl group having 6 to 20 carbon atoms or an aralkyl group having 7 to 20 carbon atoms. a5 is as described above.

  Examples of the acetal compound represented by the formula (AL-11) are (AL-11) -1 to (AL-11) -44.

  Examples of the acid labile group include groups represented by the following general formula (AL-11a) or (AL-11b), and the base resin may be intermolecularly or intramolecularly crosslinked by the acid labile group. Good.

In the above formula, R ⁶¹ and R ⁶² represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms. Alternatively, R ⁶¹ and R ⁶² may be bonded to each other to form a ring together with the carbon atom to which they are bonded, and when forming a ring, R ⁶¹ and R ⁶² are linear or A branched alkylene group is shown. R ⁶³ is a linear, branched or cyclic alkylene group having 1 to 10 carbon atoms, b5 and d5 are 0 or an integer of 1 to 10, preferably 0 or an integer of 1 to 5, and c5 is an integer of 1 to 7. It is. A represents a (c5 + 1) -valent aliphatic or alicyclic saturated hydrocarbon group having 1 to 50 carbon atoms, an aromatic hydrocarbon group or a heterocyclic group, and these groups are heteroatoms such as oxygen, sulfur and nitrogen. Or a part of hydrogen atoms bonded to the carbon atom may be substituted with a hydroxyl group, a carboxyl group, a carbonyl group or a fluorine atom. B represents —CO—O—, —NHCO—O— or —NHCONH—.

  In this case, A is preferably a divalent to tetravalent C1-C20 linear, branched or cyclic alkylene group, alkanetriyl group, alkanetetrayl group, or C6-C30 arylene group. These groups may have intervening heteroatoms such as oxygen, sulfur, nitrogen, etc., and some of the hydrogen atoms bonded to the carbon atoms are substituted by hydroxyl groups, carboxyl groups, acyl groups or halogen atoms. Also good. C5 is preferably an integer of 1 to 3.

  Specific examples of the crosslinked acetal group represented by the general formulas (AL-11a) and (AL-11b) include those represented by the following formulas (AL-11) -45 to (AL-11) -52.

  Next, examples of the tertiary alkyl group represented by the formula (AL-12) include tert-butyl group, triethylcarbyl group, 1-ethylnorbornyl group, 1-methylcyclohexyl group, 1-ethylcyclopentyl group, tert Examples thereof include an amyl group and the like, or groups represented by the following general formulas (AL-12) -1 to (AL-12) -16.

In the above formula, R ⁶⁴ represents the same or different linear, branched or cyclic alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, A ring having 3 to 20 carbon atoms, particularly 4 to 16 carbon atoms, particularly an alicyclic ring may be formed together with carbon atoms to which R ⁶⁴ are bonded to each other. R ⁶⁵ and R ^{67 each} represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms. R ⁶⁶ represents an aryl group having 6 to 20 carbon atoms or an aralkyl group having 7 to 20 carbon atoms.

Further, examples of the acid labile group include groups represented by the following formulas (AL-12) -17 and (AL-12) -18, and the acid containing R ⁶⁸ which is a divalent or higher valent alkylene group or an arylene group. The base resin may be intramolecularly or intermolecularly cross-linked by an unstable group. In the formulas (AL-12) -17 and (AL-12) -18, R ⁶⁴ represents the same as described above, and R ⁶⁸ represents a linear, branched or cyclic alkylene group having 1 to 20 carbon atoms, or an arylene group. And may contain a hetero atom such as an oxygen atom, a sulfur atom or a nitrogen atom. b6 is an integer of 1 to 3.

R ⁶⁴ , R ⁶⁵ , R ⁶⁶ , R ⁶⁷ described above may have a heteroatom such as oxygen, nitrogen, sulfur, etc., specifically, the following formulas (AL-13) -1 to (AL— 13) -7.

In particular, the acid labile group represented by R ² is preferably one having an exo structure represented by the following formula (AL-12) -19.

(In the formula, R ⁶⁹ represents a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms or an optionally substituted aryl group having 6 to 20 carbon atoms. R ^{70 to} R ⁷⁵ and R ^78. , R ⁷⁹ is each independently a monovalent hydrocarbon group, a hydrogen atom or an alkyl group that may contain a hetero atom having 1 to 15 carbon atoms, R ^76, R ⁷⁷ is a hydrogen atom. Alternatively, the R ⁷⁰ R ⁷¹ , R ⁷² and R ⁷⁴ , R ⁷² and R ⁷⁵ , R ⁷³ and R ⁷⁵ , R ⁷³ and R ⁷⁹ , R ⁷⁴ and R ⁷⁸ , R ⁷⁶ and R ⁷⁷ , or R ⁷⁷ and R ⁷⁸ are bonded to each other. A ring (particularly an alicyclic ring) may be formed together with the carbon atom to which they are bonded, and in this case, those involved in the formation of the ring are divalent such as an alkylene group which may contain a hetero atom having 1 to 15 carbon atoms. a hydrocarbon group. Further R ⁷⁰ and R ^79, R ⁷⁶ and R ^79, or R ⁷² and R ⁷⁴ is nothing through in between those bonded to the adjacent carbon Bind without, may form a double bond. The formula also represents enantiomer.)

Here, the following repeating unit having an exo-body structure represented by the general formula (AL-12) -19

JP-A-2000-327633 discloses an ester monomer for obtaining the above. Specific examples include the following, but are not limited thereto. R ¹ is as described above.

Furthermore, examples of the acid labile group used for R ² include an acid labile group having a furandiyl group, a tetrahydrofurandiyl group or an oxanorbornanediyl group represented by the following formula (AL-12) -20. .

(In the formula, R ⁸⁰ and R ⁸¹ each independently represent a monovalent hydrocarbon group such as a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, or R ⁸⁰ and R ⁸¹ are bonded to each other. And an aliphatic hydrocarbon ring having 3 to 20 carbon atoms, together with the carbon atom to which they are bonded, R ⁸² represents a divalent group selected from a frangyl group, a tetrahydrofurandiyl group or an oxanorbornanediyl group. R ⁸³ represents a monovalent hydrocarbon group such as a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms which may contain a hydrogen atom or a hetero atom.)

A repeating unit substituted with an acid labile group having the following furandyl group, tetrahydrofurandiyl group or oxanorbornanediyl group

Examples of the monomer for obtaining the are as follows. R ¹ is as described above. In the following formulae, Me represents a methyl group, and Ac represents an acetyl group.

  As the acid labile group, the tertiary ester type (AL-12) has a high dissolution contrast in organic solvent development and is preferably used. Among tertiary esters, acid labile groups listed in (AL-12) -1 to (AL-12) -16, (AL-12) -19 are most preferably used.

The monomer used for the repeating unit b is specifically exemplified below. Here, R ³ is as described above.

  As the adhesive group, those having a lactone are preferably used. In the case of an adhesive group of lactone, there is a feature that not only the dissolution contrast is high when 2-heptanone is used as a developer, but also acid diffusion can be suppressed. Among lactones, a lactone having a structure represented by the repeating unit b is excellent in terms of improving dissolution contrast and controlling acid diffusion. Among them, those in which Y in the repeating unit b of the general formula (1) is a single bond are excellent from the viewpoint of acid diffusion control.

The polymer compound serving as the base of the resist composition used in the pattern forming method of the present invention must have the repeating unit a and the repeating unit b of the general formula (1). A repeating unit c derived from a monomer having an adhesive group such as a group, a carbonyl group, an ester group, an ether group, a lactone ring, a carboxyl group, or a carboxylic anhydride group may be copolymerized.
Specific examples of the monomer for obtaining the repeating unit c include the following.

Furthermore, any of the sulfonium salts d1 to d3 represented by the following general formula may be copolymerized.

(Wherein R ²⁰ , R ²⁴ and R ²⁸ are a hydrogen atom or a methyl group, R ²¹ is a single bond, a phenylene group, —O—R ³³ —, or —C (═O) —Y—R ³³ —. Y is an oxygen atom or NH, R ³³ is a linear, branched or cyclic alkylene group having 1 to 6 carbon atoms, an alkenylene group or a phenylene group, a carbonyl group (—CO—), an ester group (—COO) -), An ether group (-O-) or a hydroxy group, R ²² , R ²³ , R ²⁵ , R ²⁶ , R ²⁷ , R ²⁹ , R ³⁰ , R ³¹ may be the same or different. 1 to 12 linear, branched or cyclic alkyl group, which may contain a carbonyl group, an ester group or an ether group, or an aryl group having 6 to 12 carbon atoms or an aralkyl having 7 to 20 carbon atoms Z ₀ represents a single bond, a methylene group, an ethylene group, a phenyl group, or a thiophenyl group. Rene group, fluorinated phenylene group, —O—R ³² —, or —C (═O) —Z ₁ —R ³² —, wherein Z ₁ is an oxygen atom or NH, and R ³² has 1 to 6 carbon atoms. A linear, branched or cyclic alkylene group, an alkenylene group or a phenylene group, which may contain a carbonyl group, an ester group, an ether group or a hydroxy group, and M ⁻ represents a non-nucleophilic counter ion. .)

  In the repeating units a, b, c, d1, d2, and d3, the ratio of the repeating units is 0 <a <1.0, 0 <b <1.0, 0 <a + b ≦ 1.0, 0 ≦ c <. 1.0, 0 ≦ d1 <0.2, 0 ≦ d2 <0.2, 0 ≦ d3 <0.2, preferably 0.1 ≦ a ≦ 0.9, 0.1 ≦ b ≦ 0.9 0.2 ≦ a + b ≦ 1.0, 0 ≦ c ≦ 0.9, 0 ≦ d1 ≦ 0.15, 0 ≦ d2 ≦ 0.15, 0 ≦ d3 ≦ 0.15, more preferably 0.15 ≦ a ≦ 0.8, 0.15 ≦ b ≦ 0.8, 0.25 ≦ a + b ≦ 1.0, 0 ≦ c ≦ 0.8, 0 ≦ d1 ≦ 0.12, 0 ≦ d2 ≦ 0.12 , 0 ≦ d3 ≦ 0.12. Note that a + b + c + d1 + d2 + d3 = 1.

  Here, for example, a + b = 1 indicates that in the polymer compound containing the repeating units a and b, the total amount of the repeating units a and b is 100 mol% with respect to the total amount of all the repeating units. <1 indicates that the total amount of the repeating units a and b is less than 100 mol% with respect to the total amount of all the repeating units and has other repeating units c and the like in addition to a and b.

  The polymer compound serving as the base resin of the resist composition used in the pattern forming method of the present invention has a polystyrene-reduced weight average molecular weight of 1,000 to 500,000, particularly 2,000 to 4,000 by gel permeation chromatography (GPC). 30,000 is preferred. If the weight average molecular weight is too small, film loss tends to occur at the time of organic solvent development, and if it is too large, the solubility in the organic solvent decreases, and the trailing phenomenon may easily occur after pattern formation.

  Furthermore, in the high molecular compound used as the base resin of the resist composition used in the pattern forming method of the present invention, when the molecular weight distribution (Mw / Mn) is wide, there is a low molecular weight or high molecular weight polymer. Thereafter, foreign matter may be seen on the pattern or the shape of the pattern may be deteriorated. Therefore, since the influence of such molecular weight and molecular weight distribution tends to increase as the pattern rule becomes finer, a multi-component copolymer to be used is used to obtain a resist composition suitably used for fine pattern dimensions. The molecular weight distribution of is preferably 1.0 to 2.0, particularly 1.0 to 1.5, and is narrowly dispersed.

It is also possible to blend two or more polymers having different composition ratios, molecular weight distributions, and molecular weights, or to blend with a polymer not containing a hydroxy group substituted with an acid labile group.
It is also possible to blend a polymer compound having a repeating unit in which a hydroxy group is substituted with an acid labile group and a polymer compound having a repeating unit in which a carboxyl group is substituted with an acid labile group. A polymer compound having both a repeating unit substituted with an labile group and a repeating unit having a carboxyl group substituted with an acid labile group is blended with a polymer compound having a repeating unit having a hydroxy group substituted with an acid labile group. Alternatively, a polymer compound having a repeating unit in which a carboxyl group is substituted with an acid labile group can be blended.

  In order to synthesize these polymer compounds, one method is to heat a monomer having an unsaturated bond to obtain repeating units a, b, c, d1, d2, and d3 in an organic solvent by adding a radical initiator. There is a method of performing polymerization, whereby a polymer compound can be obtained. Examples of the organic solvent used at the time of polymerization include toluene, benzene, tetrahydrofuran, diethyl ether, dioxane and the like. As polymerization initiators, 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl 2,2-azobis (2-methylpropionate) ), Benzoyl peroxide, lauroyl peroxide and the like, and preferably polymerized by heating to 50 to 80 ° C. The reaction time is 2 to 100 hours, preferably 5 to 20 hours. As the acid labile group, those introduced into the monomer may be used as they are, or they may be protected or partially protected after polymerization.

  As described above, the positive resist composition is applied on a substrate to form a resist film, and after heat treatment, a high energy ray is irradiated and exposed to a desired portion of the resist film. Using a developer, the unexposed portion of the resist film is dissolved by negative development with an organic solvent to form a negative pattern such as a trench pattern or a hole pattern.

  The resist composition used in the pattern forming method of the present invention comprises an organic solvent, a compound that generates an acid in response to high energy rays (acid generator), and if necessary, a dissolution controller, a basic compound, and a surfactant. Other components can be contained.

  The resist composition used in the pattern forming method of the present invention may contain an acid generator, particularly for functioning as a chemically amplified positive resist composition, for example, a compound that generates an acid in response to actinic rays or radiation. (Photoacid generator) may be contained. In this case, the compounding amount of the photoacid generator is preferably 0.5 to 30 parts by mass, particularly 1 to 20 parts by mass with respect to 100 parts by mass of the base resin. The component of the photoacid generator may be any compound that generates an acid upon irradiation with high energy rays. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, oxime-O-sulfonate type acid generators, and the like. Although described in detail below, these may be used alone or in combination of two or more.

  Specific examples of the acid generator are described in paragraphs [0122] to [0142] of JP-A-2008-111103. When a polymerizable acid generator selected from the repeating units d1, d2, and d3 is copolymerized, it is not always necessary to add the acid generator.

  The resist composition used in the pattern forming method of the present invention may further contain any one or more of an organic solvent, a basic compound, a dissolution controller, a surfactant, and acetylene alcohols.

  Specific examples of the organic solvent include ketones such as cyclohexanone and methyl-2-n-amyl ketone described in paragraphs [0144] to [0145] of JP-A-2008-111103, 3-methoxybutanol, 3-methyl- Alcohols such as 3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether , Ethers such as diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, pyruvic acid Esters such as chill, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, propylene glycol mono tert-butyl ether acetate, lactones such as γ-butyrolactone, and the like Examples of basic compounds include primary, secondary, and tertiary amine compounds described in paragraphs [0146] to [0164], particularly hydroxy groups, ether groups, ester groups, lactone rings, and cyano. And an amine compound having a sulfonic acid ester group or a compound having a carbamate group described in Japanese Patent No. 3790649. The surfactant is described in paragraphs [0165] to [0166], the dissolution control agent is described in paragraphs [0155] to [0178] of JP-A-2008-122932, and the acetylene alcohols are described in paragraphs [0179] to [0182]. Things can be used.

  A polymer compound for improving the water repellency of the resist surface after spin coating can also be added. This additive can be used in immersion lithography without a topcoat. Such an additive has a 1,1,1,3,3,3-hexafluoro-2-propanol residue having a specific structure, and is disclosed in JP-A-2007-297590, JP-A-2008-111103, Examples are Japanese Unexamined Patent Application Publication No. 2008-122932, Japanese Unexamined Patent Application Publication No. 2009-98638, and Japanese Unexamined Patent Application Publication No. 2009-276363. The water repellency improver added to the resist composition must be dissolved in the organic solvent of the developer. The above-mentioned water repellent improver having a specific 1,1,1,3,3,3-hexafluoro-2-propanol residue has good solubility in a developer. As a water-repellent additive, a polymer compound copolymerized with amino groups or amine salts as a repeating unit has a high effect of preventing the evaporation of an acid in PEB and preventing a defective opening of a hole pattern after development. A resist composition to which a water-repellent polymer compound copolymerized with an amino group is added is disclosed in JP 2009-31767 A, and a copolymer of sulfonic acid amine salt is disclosed in JP 2008-107443 A. As the copolymerized amine salt, those described in JP-A-2008-239918 can be used. The addition amount of the water repellency improver is 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the base resin of the resist composition.

  In addition, it is preferable that the compounding quantity of an organic solvent shall be 100-10,000 mass parts with respect to 100 mass parts of base resins, especially 300-8,000 mass parts. Moreover, it is preferable that the compounding quantity of a basic compound shall be 0.0001-30 mass parts with respect to 100 mass parts of base resins, especially 0.001-20 mass parts.

The patterning method according to the present invention is shown in FIG. In this case, as shown in FIG. 1A, in the present invention, a positive resist composition is applied on the substrate 20 to be processed formed on the substrate 10 directly or via the intermediate intervening layer 30. A resist film 40 is formed. The thickness of the resist film is preferably 10 to 1,000 nm, particularly 20 to 500 nm. This resist film is heated (pre-baked) before exposure, and as this condition, it is preferable to carry out at 60 to 180 ° C., particularly 70 to 150 ° C. for 10 to 300 seconds, and particularly 15 to 200 seconds.
As the substrate 10, a silicon substrate is generally used. Examples of the substrate 20 to be processed include SiO ₂ , SiN, SiON, SiOC, p-Si, α-Si, TiN, WSi, BPSG, SOG, Cr, CrO, CrON, MoSi, a low dielectric film, and an etching stopper film thereof. It is done. Examples of the intermediate intervening layer 30 include hard masks such as SiO ₂ , SiN, SiON, and p-Si, a lower layer film made of a carbon film, a silicon-containing intermediate film, and an organic antireflection film.

  Next, exposure 50 is performed as shown in FIG. Here, high energy rays having a wavelength of 140 to 250 nm and EUV having a wavelength of 13.5 nm can be used as the exposure, and among these, exposure at 193 nm with an ArF excimer laser is most preferably used. The exposure may be a dry atmosphere in the air or a nitrogen stream, or may be immersion exposure in water. In ArF immersion lithography, pure water or an alkane or the like having a refractive index of 1 or more and a highly transparent liquid at the exposure wavelength is used as an immersion solvent. In immersion lithography, pure water or other liquid is inserted between a pre-baked resist film and a projection lens. As a result, a lens with an NA of 1.0 or more can be designed, and a finer pattern can be formed. Immersion lithography is an important technique for extending the life of ArF lithography to the 45 nm node. In the case of immersion exposure, pure water rinsing (post-soak) after exposure to remove the water droplet residue remaining on the resist film may be performed, and elution from the resist film is prevented, and the surface lubricity of the film is prevented. In order to increase the thickness, a protective film may be formed on the resist film after pre-baking. As a material for forming a resist protective film used in immersion lithography, for example, it has a 1,1,1,3,3,3-hexafluoro-2-propanol residue that is insoluble in water and soluble in an alkaline developer. A material based on a polymer compound and dissolved in an alcohol solvent having 4 or more carbon atoms, an ether solvent having 8 to 12 carbon atoms, or a mixed solvent thereof is preferable. In this case, the protective film-forming composition may be obtained from a monomer such as a repeating unit having a 1,1,1,3,3,3-hexafluoro-2-propanol residue. Although the protective film needs to be dissolved in an organic solvent developer, the polymer compound composed of a repeating unit having a 1,1,1,3,3,3-hexafluoro-2-propanol residue is the above-mentioned organic solvent. Dissolve in developer. In particular, 1,1,1,3,3,3-hexafluoro exemplified in JP2007-25634A, JP2008-3569A, JP2008-81716A, and JP2008-111089A1. The solubility of the protective film material having a 2-propanol residue in an organic solvent developer is high.

  After the photoresist film is formed, pure water rinsing (post-soak) may be performed to extract an acid generator or the like from the resist film surface or to wash out particles, or to remove water remaining on the film after exposure. Rinse (post-soak) may be performed.

It is preferable to expose so that the exposure amount in exposure is about 1 to 200 mJ / cm ² , preferably about 10 to 100 mJ / cm ² . Next, post-exposure baking (PEB) is performed on a hot plate at 60 to 150 ° C. for 1 to 5 minutes, preferably 80 to 120 ° C. for 1 to 3 minutes.

  Furthermore, as shown in FIG. 1C, using an organic solvent developer, the immersion method (dip), paddle method, spray (0.1-3 minutes, preferably 0.5-2 minutes) The negative pattern 40a in which the unexposed portion is dissolved is formed on the substrate by development by a conventional method such as a spray method. As a developer at this time, an organic solvent developer contains 50 mass% or more of 2-heptanone, and in addition to 2-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methyl acetophenone Ketones, propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, butenyl acetate, isoamyl acetate, phenyl acetate, propyl formate, butyl formate, isobutyl formate, amyl formate, isoamyl formate, methyl valerate, methyl pentenoate, crotonic acid One or more solutions selected from methyl, ethyl crotonate, methyl lactate, ethyl lactate, purpyl lactate, butyl lactate, isobutyl lactate, amyl lactate, and isoamyl lactate ester may be mixed in a proportion of less than 50% by mass. Absent.

  2-heptanone has a flash point higher than that of butyl acetate of a conventional developer, and has not only excellent safety but also high dissolution contrast after development. That is, after development, γ (contrast curve slope) is high, and film loss in the exposed area is small.

  At the end of development, rinse is performed. As the rinsing liquid, a solvent which is mixed with the developer and does not dissolve the resist film is preferable. As such a solvent, alcohols having 3 to 10 carbon atoms, ether compounds having 8 to 12 carbon atoms, alkanes having 6 to 12 carbon atoms, alkenes, alkynes, and aromatic solvents are preferably used.

Specifically, as the alkane having 6 to 12 carbon atoms, hexane, heptane, octane, nonane, decane, undecane, dodecane, methylcyclopentane, dimethylcyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, cycloheptane, cyclooctane, cyclononane. Is mentioned. Examples of the alkene having 6 to 12 carbon atoms include hexene, heptene, octene, cyclohexene, methylcyclohexene, dimethylcyclohexene, cycloheptene, cyclooctene, alkyne having 6 to 12 carbon atoms, hexyne, heptin, octyne and the like. As the alcohol of several 3 to 10, n-propyl alcohol, isopropyl alcohol, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, tert-amyl alcohol, neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, 3- Xanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 2-methyl-1-pentanol, 2 -Methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1- Examples include pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol, cyclohexanol, and 1-octanol.
Examples of the ether compound having 8 to 12 carbon atoms include di-n-butyl ether, diisobutyl ether, di-sec-butyl ether, di-n-pentyl ether, diisopentyl ether, di-sec-pentyl ether, and di-t-amyl. One or more kinds of solvents selected from ether and di-n-hexyl ether are exemplified.
In addition to the aforementioned solvents, aromatic solvents such as toluene, xylene, ethylbenzene, isopropylbenzene, t-butylbenzene, mesitylene and the like can also be used.

  When a hole pattern is formed by negative tone development, it is possible to use light having the highest contrast when exposure is performed by dipole illumination of two line patterns in the X and Y directions. If s-polarized illumination is added to the dipole illumination, the contrast can be further increased.

FIG. 2 shows an optical image of an X-direction line having a NA1.3 lens using an ArF excimer laser with a wavelength of 193 nm, dipole illumination, a 6% halftone phase shift mask, a pitch of 90 nm with s-polarized light, and a line size of 45 nm.
FIG. 3 shows an optical image of an NA 1.3 lens using an ArF excimer laser with a wavelength of 193 nm, dipole illumination, a 6% halftone phase shift mask, a pitch of 90 nm with s-polarized light, and a Y-direction line with a line size of 45 nm. The darker one is the light-shielding portion, the white one is the light-intensive region, and the contrast difference between white and black is clear, indicating that there is a particularly strong light-shielding portion.
FIG. 4 is a contrast image in which the optical image of the X direction line is superimposed on the Y direction line. The combination of X and Y lines seems to produce a lattice-like image, but the pattern of the black part where light is weak is circular. When the size of the circle is large, it is easy to connect to the adjacent pattern with a rhombus shape, but it is shown that the smaller the size of the circle, the better the degree of circle and there is a small circle that is strongly shielded from light.

The exposure that combines X and Y direction lines with two dipole illuminations and polarized illumination is certainly high contrast, but there is a drawback that the throughput is greatly reduced by the two exposures and the exchange of the mask between them. . Therefore, a method has been proposed in which exposure is performed twice with dipole illumination in the X and Y directions using a mask having a lattice pattern (Non-Patent Document 1). In this case, since the mask does not need to be replaced, the throughput is slightly improved because two consecutive exposures are required. However, two exposures using an expensive immersion scanner lead to a decrease in throughput and cost, and there is a problem that the position of the hole deviates from the original position due to misalignment of the two exposures. ing.
Here, by using a lattice pattern mask and combining X and Y polarized illumination and cross-pole illumination, a hole pattern can be formed in a single exposure, and a considerable improvement in throughput is expected. In addition, the problem of misalignment due to double exposure is avoided. If such a mask and illumination are used, a hole pattern of 40 nm class can be formed at a practical cost.

  In the mask on which the grid pattern shown in FIG. 5 is arranged, the intersection of the grid is strongly shielded from light, and as shown in FIG. 6, a black spot with very high light shielding properties appears. FIG. 6 is an optical image of a lattice-like line pattern with a pitch of 90 nm and a width of 30 nm in NA 1.3 lens, cross pole illumination, 6% halftone phase shift mask, and azimuthally polarized illumination. A fine hole pattern can be formed by performing exposure using a mask having such a pattern and developing with an organic solvent accompanied by positive / negative reversal.

  Optical image contrast in the mask shown in FIG. 7 in which a square dot pattern with a pitch of 90 nm and a side width of 60 nm is arranged with NA 1.3 lens, cross pole illumination, 6% halftone phase shift mask, and azimuthally polarized illumination. Is shown in FIG. In this case, it can be seen that the area of the circle of the strong light-shielding portion is smaller than that of FIG. 6, and the contrast is lower than that of the mask having the lattice pattern.

  It is difficult to form a fine hole pattern in which pitches and positions are randomly arranged. The dense pattern can be improved in contrast by super-resolution technology combining a phase shift mask and polarized light with oblique incidence illumination such as dipole and cross pole, but the contrast of the isolated pattern is not improved so much.

  When the super-resolution technique is used for a dense repetitive pattern, a coarse / dense (proximity) bias with an isolated pattern becomes a problem. The stronger the super-resolution technology is used, the higher the resolution of the dense pattern, but the resolution of the isolated pattern does not change, so the density bias increases. The increase in the density bias in the hole pattern accompanying the miniaturization is a serious problem. In order to suppress the density bias, generally, a bias is applied to the dimension of the mask pattern. Since the density bias varies depending on the characteristics of the photoresist composition, that is, dissolution contrast and acid diffusion, the density bias of the mask varies depending on the type of the photoresist composition. Masks with different density biases are used for each type of photoresist composition, increasing the burden of mask production. Therefore, only the dense hole pattern is resolved with strong super-resolution illumination, a negative resist film of an alcohol solvent that does not dissolve the first positive resist pattern is applied on the pattern, and unnecessary hole portions are exposed. There has been proposed a method (Pack and unpack; PAU method) in which both a dense pattern and an isolated pattern are produced by blocking by development (Proc. SPIE Vol. 5753 p171 (2005)). Problems with this method include misalignment between the first exposure and the second exposure, and the author of the literature points out this point. Further, a hole pattern that is not blocked by the second development is developed twice, and a dimensional change due to this is also a problem.

In order to form a hole pattern with a random pitch by organic solvent development with positive / negative reversal, a mask in which a lattice-like pattern is arranged on the entire surface and the width of the lattice is increased only at a place where a hole is to be formed is used.
As shown in FIG. 9, thick cross lines with a cross are arranged on a lattice pattern of 20 nm lines at a pitch of 90 nm, as shown in FIG. The black part of the color is the halftone shifter part. A thicker line (40 nm in FIG. 9) is arranged in the isolated portion, and a line having a width of 30 nm is arranged in the dense part. A thick line is used because an isolated pattern has a lower light intensity than a dense pattern. Since the intensity of light also slightly decreases at the end portion of the dense pattern, a line of 32 nm that is slightly wider than the center of the dense portion is assigned.
A contrast image of the optical image of the mask of FIG. 9 is shown in FIG. A hole is formed in the black light-shielding part by positive / negative reversal. Black spots can be seen in places other than where the holes are to be formed, but since the size of the black spots is small, practically little transfer is performed. It is possible to prevent unnecessary hole transfer by further optimization such as narrowing the width of the grid lines of unnecessary portions.

  Similarly, a mask in which grid-like patterns are arranged on the entire surface and thick dots are arranged only at the positions where holes are formed can be used. As shown in FIG. 11, thick dots are arranged on a grid pattern of 15 nm lines at a pitch of 90 nm, as shown in FIG. The black part of the color is the halftone shifter part. A dot having a larger size (a side of 90 nm in FIG. 11) is arranged as it is isolated, and a square dot having a side of 55 nm is arranged in a dense part. The shape of the dot may be a regular square, a rectangle, a rhombus, a pentagon, a hexagon, a heptagon, an octagon or more polygon, and a circle. FIG. 12 shows a contrast image of the optical image in the mask of FIG. Compared to FIG. 10, there is a black light shielding portion that is almost equivalent, and it is shown that holes are formed by positive / negative reversal.

  When a mask in which a grid pattern is not arranged as shown in FIG. 13 is used, a black light shielding portion does not appear as shown in FIG. In this case, it is difficult to form a hole, or even if it can be formed, the contrast of the optical image is low, and as a result, the variation in the mask size largely reflects the variation in the size of the hole.

  EXAMPLES Hereinafter, although a synthesis example, an Example, and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example etc. In addition, a weight average molecular weight (Mw) shows the polystyrene conversion weight average molecular weight by GPC.

[Synthesis example]
As a polymer compound used in the resist composition, the respective monomers are combined and subjected to a copolymerization reaction in a tetrahydrofuran solvent, crystallized in methanol, further washed with hexane, isolated and dried, and the composition shown below Polymer compounds (Polymers 1 to 14 and Comparative Polymers 1 and 2) were obtained. The composition of the obtained polymer compound was confirmed by ¹ H-NMR, and the molecular weight and dispersity were confirmed by gel permeation chromatography.

Resist polymer 1
Molecular weight (Mw) = 8,900
Dispersity (Mw / Mn) = 1.79

Resist polymer 2
Molecular weight (Mw) = 8,300
Dispersity (Mw / Mn) = 1.75

Resist polymer 3
Molecular weight (Mw) = 7,500
Dispersity (Mw / Mn) = 1.86

Resist polymer 4
Molecular weight (Mw) = 8,300
Dispersity (Mw / Mn) = 1.80

Resist polymer 5
Molecular weight (Mw) = 8,300
Dispersity (Mw / Mn) = 1.77

Resist polymer 6
Molecular weight (Mw) = 7,500
Dispersity (Mw / Mn) = 1.79

Resist polymer 7
Molecular weight (Mw) = 8,730
Dispersity (Mw / Mn) = 1.77

Resist polymer 8
Molecular weight (Mw) = 6,500
Dispersity (Mw / Mn) = 1.79

Resist polymer 9
Molecular weight (Mw) = 9,100
Dispersity (Mw / Mn) = 1.95

Resist polymer 10
Molecular weight (Mw) = 8,300
Dispersity (Mw / Mn) = 1.77

Resist polymer 11
Molecular weight (Mw) = 8,500
Dispersity (Mw / Mn) = 1.75

Resist polymer 12
Molecular weight (Mw) = 8,800
Dispersity (Mw / Mn) = 1.78

Resist polymer 13
Molecular weight (Mw) = 8,800
Dispersity (Mw / Mn) = 1.79

Resist polymer 14
Molecular weight (Mw) = 8,300
Dispersity (Mw / Mn) = 1.69

Comparative resist polymer 1
Molecular weight (Mw) = 8,600
Dispersity (Mw / Mn) = 1.88

Comparative resist polymer 2
Molecular weight (Mw) = 8,900
Dispersity (Mw / Mn) = 1.93

Each composition in the following table is as follows.
Acid generator: PAG1, PAG2 (see structural formula below)

Water repellent polymer 1
Molecular weight (Mw) = 9,100
Dispersity (Mw / Mn) = 1.83

Water repellent polymer 2
Molecular weight (Mw) = 7,300
Dispersity (Mw / Mn) = 1.54

Basic compounds: Quencher1, Quencher2 (see structural formula below)

Organic solvent: PGMEA (propylene glycol monomethyl ether acetate)
CyH (cyclohexanone)

ArF exposure patterning evaluation (1)
A resist composition prepared with the composition shown in Table 1 below was spin-coated on a silicon wafer with an anti-reflective film manufactured by Nissan Chemical Industries, Ltd. having a thickness of 80 nm, and heated at 100 ° C. using a hot plate. The resist film was baked for 60 seconds to a thickness of 160 nm.
This was subjected to open frame exposure with an ArF excimer laser scanner (Nikon Corporation, NSR-305B, NA 0.68, σ 0.73) while changing the exposure amount in 0.2 mJ / cm ² steps. After exposure, baking (PEB) at 110 ° C. for 60 seconds, paddle development with the organic solvent shown in Table 2 for 60 seconds, rinsing at 500 rpm with the organic solvent shown in Table 2, and spin drying at 2,000 rpm Then, baking was performed at 100 ° C. for 60 seconds to evaporate the rinsing solvent, and negative development was performed.
The film thickness after PEB and the film thickness after organic solvent development were measured, and the relationship between the exposure amount and the film thickness (contrast curve) was determined. The results are shown in FIG.
Further, the difference in film thickness after development was obtained from the slope γ of the contrast curve and the PEB film thickness at the exposed portion. The results are shown in Table 2.

ArF exposure patterning evaluation (2)
A resist composition prepared with the composition shown in Table 3 below was applied to a silicon wafer with a spin-on carbon film ODL-50 (carbon content of 80% by mass) manufactured by Shin-Etsu Chemical Co., Ltd. having a thickness of 200 nm and silicon-containing spin-on hard. A mask SHB-A941 (silicon content: 43 mass%) was spin-coated on a substrate for a trilayer process having a film thickness of 35 nm, and baked at 100 ° C. for 60 seconds using a hot plate to form a resist film The thickness was set to 100 nm. This is an ArF excimer laser immersion scanner (manufactured by Nikon Corporation, NSR-610C, NA 1.30, σ0.98 / 0.78, cross pole opening 20 degrees, azimuthally polarized illumination, 6% halftone phase shift mask, wafer The upper dimensions are 90 nm pitch and the grid width of the layout shown in FIG. 16 is used. The exposure is performed while changing the exposure amount. After the exposure, baking is performed at the temperature shown in Table 4 for 60 seconds (PEB). Then, the developer shown in Table 4 was discharged from the developing nozzle while rotating at 30 rpm for 3 seconds, followed by static paddle development for 27 seconds, rinsed with diisoamyl ether, spin-dried, and baked at 100 ° C. for 20 seconds. The rinse solvent was evaporated.

  The dimensions of 50 hole patterns obtained by reversing the image of the solvent development were measured with TDSEM (S-9380) manufactured by Hitachi High-Technologies Corporation to determine the dimensional variation of 3σ. The results are shown in Table 4.

ArF exposure patterning evaluation (3)
Resist compositions (resist 2-1 and 2 and comparative resists 2-1 and 2) prepared with the compositions shown in Table 3 above were applied to a silicon wafer on a spin-on carbon film ODL-50 (manufactured by Shin-Etsu Chemical Co., Ltd.). The spin-on hard mask SHB-A940 (silicon content is 43% by mass) having a film thickness of 35 nm is spin-coated on a substrate for a trilayer process. Then, the resist film was baked at 100 ° C. for 60 seconds using a hot plate to make the thickness of the resist film 100 nm. This is an ArF excimer laser immersion scanner (manufactured by Nikon Corporation, NSR-610C, NA 1.30, σ0.98 / 0.78, cross pole opening 20 degrees, azimuthally polarized illumination, 6% halftone phase shift mask, wafer The exposure is performed while changing the exposure amount and the focus position using a mask of a pattern in which dots are arranged on a lattice pattern shown in FIG. 17 having a pitch of 90 nm and a line width of 15 nm as shown in FIG. Bake (PEB) at the temperature shown in Table 5 for 60 seconds, discharge 2-heptanone from the developing nozzle while rotating at 30 rpm for 3 seconds, then perform stationary paddle development for 27 seconds, rinse with diisoamyl ether, spin Dry and bake at 100 ° C. for 20 seconds to evaporate the rinse solvent.

  The dimension of the hole pattern in which the image of the solvent development was reversed was measured with TDSEM (S-9380) manufactured by Hitachi High-Technologies Corporation, and the focus margin (DoF) of 40 nm ± 5 nm was obtained. The dimensions of 50 holes in the same exposure shot and the same focus shot were measured to obtain a 3σ dimensional variation. The results are shown in Table 5.

ArF exposure patterning evaluation (4)
Resist compositions (resist 2-1 and 2 and comparative resists 2-1 and 2) prepared with the compositions shown in Table 3 above were applied to a silicon wafer on a spin-on carbon film ODL-50 (manufactured by Shin-Etsu Chemical Co., Ltd.). The spin-on hard mask SHB-A940 (silicon content is 43% by mass) having a film thickness of 35 nm is spin-coated on a substrate for a trilayer process. Then, the resist film was baked at 100 ° C. for 60 seconds using a hot plate to make the thickness of the resist film 100 nm. This is an ArF excimer laser immersion scanner (manufactured by Nikon Corporation, NSR-610C, NA 1.30, σ0.98 / 0.78, cross pole opening 20 degrees, azimuthally polarized illumination, 6% halftone phase shift mask, wafer The exposure is performed while changing the exposure amount using a mask having a pattern in which a thick lattice is arranged on the lattice shape of the layout shown in FIG. Baked for 60 seconds (PEB), and discharged 2-heptanone from the developing nozzle while rotating at 30 rpm for 3 seconds, followed by stationary paddle development for 27 seconds, rinsed with diisoamyl ether, spin-dried, and 100 ° C. The rinse solvent was evaporated by baking for 20 seconds.

  The dimensions of the holes at the positions A and B on the mask of the hole pattern obtained by reversing the image of the solvent development were measured with a TDSEM (S-9380) manufactured by Hitachi High-Technologies Corporation. The results are shown in Table 6.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

10 Substrate 20 Substrate 30 Intervening Layer 40 Resist Film 40a Resist Pattern

Claims (9)

A (meth) acrylate polymer containing both a repeating unit a having a carboxyl group substituted with an acid labile group represented by the following general formula (1) and a repeating unit b having a lactone ring, an acid generator, A resist composition containing an organic solvent is applied onto a substrate to form a resist film, and after the heat treatment, the resist film is exposed with a high energy beam, and after the heat treatment, contains 50% by mass or more of 2-heptanone as a developer. The pattern formation method characterized by performing image development with the solution to do.

(In the formula, R ¹ and R ³ represent a hydrogen atom or a methyl group, but they may be the same or different. R ² is an acid labile group. X and Y are a single bond or —C (═O ) —O—R ⁹ —, wherein R ⁹ is a linear, branched or cyclic alkylene group having 1 to 10 carbon atoms, and the alkylene group has an ether group, an ester group, a lactone ring or a hydroxy group. R ⁴ , R ⁶ , R ⁷ , R ⁸ may be a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, or a trifluoromethyl group. , Or a cyano group, R ⁵ is a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, a carboxyl group, a substituted or unsubstituted alkoxycarbonyl group having 1 to 12 carbon atoms, or a cyano group And Z is a methylene group, an oxygen atom or a sulfur atom. Are 0 <a <1.0, 0 <b <1.0, and 0 <a + b ≦ 1.0.)   In addition to 2-heptanone, the developer is 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methyl acetophenone, propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, butenyl acetate, isoamyl acetate, phenyl acetate , Propyl formate, butyl formate, isobutyl formate, amyl formate, isoamyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, amyl lactate, 2. The pattern forming method according to claim 1, wherein at least one selected from lactic acid isoamyl ester is mixed at a ratio of less than 50% by mass.   3. The pattern forming method according to claim 1, wherein the exposure with the high energy beam is immersion lithography using an ArF excimer laser having a wavelength of 193 nm or EUV lithography having a wavelength of 13.5 nm.   4. The light-irradiated portion is not dissolved in the developer, the unexposed portion is dissolved in the developer, and the pattern after development becomes a negative tone. Pattern forming method.   The pattern forming method according to claim 1, wherein a trench pattern is formed after development.   In immersion lithography using an ArF excimer laser with a wavelength of 193 nm, a post-development hole pattern is formed at the intersection of a lattice-like shifter grating using a halftone phase shift mask on which a lattice-like shifter pattern is arranged The pattern formation method of any one of Claims 1 thru | or 4.   7. The pattern forming method according to claim 6, wherein the lattice pattern is a halftone phase shift mask having a transmittance of 3 to 15%.   Phase shift in which a lattice-shaped first shifter having a line width of half pitch or less and a second shifter having a dimension on the wafer that is 2 to 30 nm thicker than the line width of the first shifter are arranged on the first shifter 8. The pattern forming method according to claim 6, wherein a hole pattern is formed only where the thick shifters are arranged using a mask.   A grid-shaped first shifter having a line width of half pitch or less and a second shifter having a dot pattern that is 2 to 100 nm thicker on the wafer than the line width of the first shifter are arranged on the first shifter. 8. The pattern forming method according to claim 6, wherein a hole pattern is formed only where the thick shifters are arranged using the phase shift mask.