JP2015200796A - Lower layer film forming composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lower layer film forming composition suitable for patterning by photolithography using extreme ultraviolet rays.SOLUTION: A lower layer film forming composition comprises a cyano group-containing polymer and a crosslinking agent, or a polymer comprising a cyano group and a crosslinking group. The composition also comprises an acid generator and a solvent.

Description

  The present invention relates to a composition for forming an underlayer film used when forming a pattern by lithography using a photoresist, and a method for forming an underlayer film using the composition. The present invention also relates to a compound used in the composition for forming an underlayer film.

In the manufacturing process of a semiconductor device, microfabrication by lithography using a photoresist is generally performed. The microfabrication was obtained by forming a thin film of photoresist on a semiconductor substrate such as a silicon wafer, irradiating it with actinic rays such as ultraviolet rays through a mask pattern on which a device pattern was drawn, and developing it. This is a processing method in which fine irregularities corresponding to the pattern are formed on the surface of the substrate by etching the substrate using the photoresist pattern as a protective film. However, in recent years, the degree of integration of devices has increased, and it has become very much like KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm), or extreme ultraviolet light (wavelength 13.5 nm, hereinafter sometimes referred to as EUV). Light with a short wavelength tends to be used for exposure. However, it has been difficult to form a sufficiently good rectangular resist pattern only by adjusting the exposure apparatus and the resist material in the lithography technique using light having a short wavelength, particularly EUV. Specifically, there is a tendency that an ideal rectangular shape cannot be obtained because the cross-sectional shape of the pattern is skirted or trapezoidal, pattern sidewall roughness is increased, and critical dimension uniformity is deteriorated. Therefore, in the EUV lithography process, it is desired to develop a resist underlayer film for EUV lithography that can reduce these adverse effects and form a good resist pattern.
Various underlayer film forming compositions have been studied for the purpose of solving such problems. For example, Patent Documents 1 to 4 disclose compositions containing a polymer having a benzene ring, a naphthalene ring, an anthracene ring, or the like. However, according to the applicant's examination, it is considered that there is room for further improvement in these compositions.

International Patent Publication No. 2012/107823 International Patent Publication No. 2011/074494 Specification International Patent Publication No. 2010/061774 JP 2011-150023 A

  The present invention has been made in view of the above circumstances, and when used in EUV lithography, the cross-sectional shape of the pattern is rectangular, and pattern sidewall roughness and critical dimension uniformity (hereinafter sometimes referred to as CDU). An object of the present invention is to provide a composition capable of forming a superior underlayer film.

  The composition for forming an underlayer film according to the present invention comprises a cyano group-containing polymer, a crosslinking agent, an acid generator, and a solvent.

  Another underlayer film forming composition according to the present invention comprises a polymer having a cyano group and a crosslinking group, an acid generator, and a solvent.

  Further, the underlayer film according to the present invention is obtained by applying the above composition for forming an underlayer film on a substrate and heating it.

Furthermore, the pattern forming method according to the present invention includes:
Applying the composition for forming an underlayer film described above on a semiconductor substrate and baking to form an underlayer film;
Forming a photoresist layer on the lower layer film;
It comprises a step of exposing the semiconductor substrate covered with the lower layer film and the photoresist layer, and a step of developing with a developer after the exposure.

（式中、
Ｘはハロゲン原子であり、
ｎは１〜５の数である）
で表される繰り返し単位を含むことを特徴とするものである。 Also, the compound according to the present invention has the following general formula:

(Where
X is a halogen atom,
n is a number from 1 to 5)
It is characterized by including the repeating unit represented by these.

  When used in EUV lithography, an underlayer film excellent in pattern sidewall roughness and critical dimension uniformity can be formed by using the underlayer film forming composition according to the present invention. And when this resist film is coated thereon with a resist composition, there is little peeling of the film due to the resist solvent, and it can be developed and removed at the same time as the photoresist in the development process. It exhibits excellent characteristics.

  Hereinafter, embodiments of the present invention will be described in detail as follows.

<First composition for forming an underlayer film>
[Cyano group-containing polymer]
The first underlayer film forming composition according to the present invention (hereinafter sometimes simply referred to as “composition”) comprises a cyano group-containing polymer as a film forming component. The structure of this polymer is not particularly limited as long as it contains a cyano group. Therefore, it can be set as the polymer containing the cyano group in this invention by introduce | transducing a cyano group into the arbitrary film-forming polymer conventionally known.

  Various polymers are used in conventional compositions for forming an underlayer film, and examples thereof include vinyl polymers, acrylic polymers, methacrylic polymers, and polyesters. In the present invention, in the polymer having such a main chain structure, it is preferable that at least one repeating unit contains a cyano group.

（式中、
Ｒ^ａおよびＲ^ｃは、それぞれ独立に水素およびアルキル基からなる群から選択される基であり、好ましくは水素またはメチル基であり、
Ｌ^ａ、Ｌ^ｂ、Ｌ^ｃ１およびＬ^ｃ２はそれぞれ独立に、単結合または脂肪族炭化水素鎖であり、前記脂肪族炭化水素鎖は、末端又は中間にエーテル結合、チオエーテル結合、アミド結合、またはカルボニル結合、カルボン酸エステル結合を含んでいてもよく
Ａｒ^ｂおよびＡｒ^ｃは、それぞれ独立に１個以上のベンゼン環を含む芳香族骨格であり、前記芳香族基は、アルキル、ハロゲン原子、アルコキシ、アルキルスルファニル、カルボン酸エステル、およびシアノからなる群から選択される置換基で置換されていてもよく、ハロゲン原子で置換されていることがより好ましく、
ｐ２およびｐ３は１または２である。） Examples of such repeating units containing a cyano group include the following.

(Where
R ^a and R ^c are each independently a group selected from the group consisting of hydrogen and an alkyl group, preferably hydrogen or a methyl group,
L ^a , L ^b , L ^c1 and L ^c2 are each independently a single bond or an aliphatic hydrocarbon chain, and the aliphatic hydrocarbon chain has an ether bond, a thioether bond, an amide bond, or a carbonyl at the terminal or in the middle. Ar ^b and Ar ^c each independently represent an aromatic skeleton containing one or more benzene rings, and the aromatic group is an alkyl, halogen atom, alkoxy, alkyl It may be substituted with a substituent selected from the group consisting of sulfanyl, carboxylic acid ester, and cyano, more preferably substituted with a halogen atom,
p2 and p3 are 1 or 2. )

  Since the repeating units (1b) and (1c) contain an aromatic ring, the amount of absorption of extreme ultraviolet rays is increased, and among them, the repeating unit in which a halogen atom is bonded to the aromatic ring is particularly preferable.

L ^a , L ^b , L ^c1 and L ^c2 are groups that fix a cyano group by directly or indirectly connecting it to the polymer main chain. These are generally a single bond or an aliphatic hydrocarbon chain, but the aliphatic hydrocarbon group may have an arbitrary substituent as a side chain within a range not impairing the effects of the present invention, The methylene group may be substituted with any linking group. Specific examples of L ^a , L ^b , L ^c1 or L ^c2 include a single bond, — (CH ₂ ) _m —, —O— (CH ₂ ) _m —, —C (═O) —O— (CH ₂ ) _M- , -S- (CH ₂ ) _m- , -NH- (CH ₂ ) _m- , (CH ₂ ) _m -O- (CH ₂ ) _n- , -O- (CH ₂ ) _m -CH ( CN)-and the like. L ^a , L ^b , L ^c1 and L ^c2 may have a branched structure, or may have a cyano group in the side chain. Examples of those having such a branched _{structure, -N [(CH 2) m} CN] [CH 2] n -, - CH [(CH 2) m CN] [CH 2] n - , and the like.

  Here, m and n are each independently an arbitrary number, but are selected so that the proportion of the cyano group contained in the polymer is appropriate, as will be described later.

Among such repeating units, the following are particularly preferable.

（式中、
Ｒ^２は、水素およびアルキル基からなる群から選択される基であり、好ましくは水素またはメチル基であり、
Ｚは、Ｒ^３ＣＯＯＲ^４、およびＲ^３ＯＲ^４からなる群から選択される基であり、
ここで、
Ｒ^３は、単結合、酸素、および炭素数１以上、好ましくは炭素数１〜６、のフッ素で置換されていてもよい直鎖アルキレンおよび分岐アルキレンならびに芳香環からなる群から選択される連結基であり、
Ｒ^４は、水素、置換炭化水素基および非置換炭化水素基からなる群から選択される基である。） The polymer used in the composition according to the present invention may contain only the repeating units (1a) to (1c) described above or may be a combination of these repeating units. Moreover, you may contain the repeating unit which does not contain a cyano group other than that. Examples of the repeating unit not containing a cyano group include those represented by the following formula (2).

(Where
R ² is a group selected from the group consisting of hydrogen and an alkyl group, preferably hydrogen or a methyl group,
Z is a group selected from the group consisting of R ³ COOR ⁴ and R ³ OR ⁴ ;
here,
R ³ is a single bond, oxygen, and a linking group selected from the group consisting of linear alkylene and branched alkylene which may be substituted with fluorine having 1 or more carbon atoms, preferably 1 to 6 carbon atoms, and an aromatic ring. And
R ⁴ is a group selected from the group consisting of hydrogen, a substituted hydrocarbon group and an unsubstituted hydrocarbon group. )

Such a polymer can be produced by polymerizing monomers corresponding to each repeating unit. For example, the following polymer can be mentioned as an example of the polymer which combined the repeating unit (1a) and the repeating unit (2).

  The polymerization method for obtaining the cyano group-containing polymer can be carried out in a suitable solvent using a radical polymerization initiator or an ionic polymerization initiator using the above-mentioned monomer as a raw material. In addition, the cyano group-containing polymer used in the present invention can have various configurations such as a random copolymer and a block copolymer, and the polymerization conditions can be selected according to the various configurations.

  Specific examples of the reaction initiator for carrying out the polymerization reaction include 2,2′-azobis (isobutyronitrile) (AIBN), 2,2′-azobis-dimethyl- (2-methylpropinate), 2, 2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2-cyclopropylpropionitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethylpentanenitrile), 1,1′-azobis (cyclohexanecarbonitrile), benzoyl peroxide, t-butylperoxybenzoate, di-t-butyldiperoxyphthalate, t -Butylperoxy-2-ethylhexanoate, t-butylperoxypivalate, t-amylperoxypivalate, butyllithium From the viewpoint of safety and availability, 2,2′-azobis (isobutyronitrile) (hereinafter sometimes referred to as AIBN) or 2,2′-azobis-dimethyl- (2-methylpropinate) ) Is preferred. Moreover, it is preferable that the usage-amount is 1 to 10 weight% with respect to the total weight of all the monomers.

  Preferable solvents for carrying out the polymerization reaction include toluene, tetrahydrofuran, benzene, methyl amyl ketone, dimethylformamide, dimethyl sulfoxide, ethyl lactate, propylene glycol monomethyl ether acetate (PGMEA) and the like. These solvents may be used alone or in combination of two or more. Moreover, it is preferable that the usage-amount is 1-10 times amount with respect to the weight of all the monomers.

  The polymerization temperature for carrying out the polymerization reaction is usually 50 to 200 ° C, preferably 60 to 150 ° C, more preferably 80 to 120 ° C.

  The molecular weight of the cyano group-containing polymer used in the present invention is not particularly limited. However, the weight average molecular weight of the polymer is preferably in the range of 1,000 to 30,000 daltons as measured by gel permeation chromatography (GPC) using polystyrene as a standard. In consideration of film formability, solubility, and thermal stability, those of 1,500 to 20,000 daltons are more preferable.

  The content of the cyano group-containing polymer in the composition of the present invention is not particularly limited as long as each component is uniformly dissolved. However, in order to fully exhibit the effects of the present invention, the content of the cyano group-containing polymer is not limited. The rate is preferably 20% by weight or more, more preferably 60% or more, based on the total weight of the composition. On the other hand, from the viewpoint of controlling the film thickness to be formed, the content of the cyano group-containing polymer is preferably 90% by weight or less, more preferably 80% by weight or less, based on the total weight of the composition.

  The composition according to the present invention is required to contain the cyano group-containing polymer, but two or more cyano group-containing polymers having different structures may be combined. In addition, the composition according to the present invention may contain a polymer that does not contain a cyano group as long as the effects of the present invention are not impaired. In any case, it is preferable that the number of cyano groups contained in the entire polymer is a certain number or more in order to sufficiently exhibit the effects of the present invention. Specifically, the weight of the cyano group relative to the total weight of the polymer is preferably 1% or more, and more preferably 3% or more. On the other hand, in order to maintain the film-forming property of the composition, it is preferably below a certain level. Specifically, the weight of the cyano group relative to the total weight of the polymer is preferably 30% or less, and more preferably 20% or less.

[Crosslinking agent]
The first composition according to the present invention comprises a crosslinking agent. A cross-linking agent is used to prevent the lower layer film to be formed from being mixed by an upper layer film such as a resist. As the crosslinking agent, any compound can be used as long as it is a compound that acts on the terminal hydroxy group of the dendrimer compound to form a crosslinked structure when exposed. Specific examples of such a crosslinking agent include hexamethylmelamine, hexamethoxymethylmelamine, 1,2-dihydroxy-N, N′-methoxymethylsuccinimide, 1,2-dimethoxy-N, N′-methoxymethylsuccinimide, 1 , 3,4,6-tetrakis (methoxymethyl) glycoluril, 4,5-dimethoxy-1,3-bis (methoxyethyl) imidazolidin-2-one, 1,1,3,3-tetramethoxyurea, Examples include tetramethoxymethyl glycoluril and N, N′-methoxymethylurea.

  Further, as the crosslinking agent, a polymer having the structure of the crosslinking agent as described above can also be used. More preferably, a polymer comprising a repeating unit similar to the above-described cyano group-containing polymer and a repeating unit containing a crosslinking group corresponding to the above-described crosslinking agent can be used as the crosslinking agent. Here, the repeating unit containing a crosslinking group may be any as long as it contains the structure of the crosslinking agent as described above, but it functions as a crosslinking group. The polymer containing such a crosslinking group can be selected from polymers containing a cyano group and a crosslinking group used in the second underlayer film forming composition described later.

[Acid generator]
The first composition according to the present invention comprises an acid generator. This acid generator functions as an auxiliary agent that promotes crosslinking of the lower layer film to be formed.

  Such an acid generator is roughly classified into a thermal acid generator and a photoacid generator. Since the composition according to the present invention crosslinks the polymer by heat to form an underlayer film, it is essential to contain a thermal acid generator. However, both a thermal acid generator and a photoacid generator can be included. These acid generators can be selected from any conventionally known ones.

  Specific examples of the thermal acid generator that can be used in the underlayer film forming composition of the present invention include various aliphatic sulfonic acids and salts thereof, various aliphatic carboxylic acids such as citric acid, acetic acid, and maleic acid and salts thereof. , Benzoic acid, phthalic acid and other aromatic carboxylic acids and their salts, aromatic sulfonic acids and their ammonium salts, various amine salts, aromatic diazonium salts, phosphonic acids and their salts, salts and esters that generate organic acids Etc. Among the thermal acid generators used in the present invention, a salt composed of an organic acid and an organic base is preferable, and a salt composed of a sulfonic acid and an organic base is more preferable.

  Preferred thermal acid generators containing sulfonic acid include p-toluenesulfonic acid, benzenesulfonic acid, p-dodecylbenzenesulfonic acid, 1,4-naphthalenedisulfonic acid, methanesulfonic acid, and the like. These acid generators can be used in combination of two or more.

  Specific examples of the photoacid generator that can be used in the first composition according to the present invention include onium salt compounds, crosslinkable onium salt compounds, sulfomaleimide derivatives, and disulfonyldiazomethane compounds.

  Specific examples of the onium salt compound include, for example, diphenyliodonium hexafluorophosphate, diphenyliodonium trifluoromethanesulfonate, diphenyliodonium nonafluoro-normal butanesulfonate, diphenyliodonium perfluoro-normaloctanesulfonate, diphenyliodonium camphorsulfonate, bis (4- iodonium salt compounds such as tert-butylphenyl) iodonium camphorsulfonate and bis (4-tert-butylphenyl) iodonium trifluoromethanesulfonate, and triphenylsulfonium hexafluoroantimonate, triphenylsulfonium nonafluoro-normal butanesulfonate, triphenylsulfonium Camphorsulfone And sulfonium salt compounds such as triphenylsulfonium trifluoromethanesulfonate, and bis (4-hydroxyphenyl) (phenyl) sulfonium trifluoromethanesulfonate, bis (4-hydroxyphenyl) (phenyl) sulfonium-1,1,2,2, 3,3,4,4,4-nonafluorobutane-1-sulfonate, phenylbis (4- (2- (vinyloxy) ethoxy) phenyl) sulfonium-1,1,2,2,3,3,4,4 -Octafluorobutane-1,4-disulfonate, tris (4- (2- (vinyloxy) ethoxy) phenyl) sulfonium-1,1,2,2,3,3,4,4-octafluorobutane-1, Although crosslinkable onium salt compounds, such as 4-disulfonate, are mentioned, It is not limited to them.

  Specific examples of the sulfomaleimide derivatives include, for example, N- (trifluoromethanesulfonyloxy) succinimide, N- (nonafluoro-normalbutanesulfonyloxy) succinimide, N- (camphorsulfonyloxy) succinimide, and N- (trifluoromethanesulfonyloxy). And naphthalimide.

  Specific examples of the disulfonyldiazomethane compound include, for example, bis (trifluoromethylsulfonyl) diazomethane, bis (cyclohexylsulfonyl) diazomethane, bis (phenylsulfonyl) diazomethane, bis (p-toluenesulfonyl) diazomethane, and bis (2,4- Dimethylbenzenesulfonyl) diazomethane, and methylsulfonyl-p-toluenesulfonyldiazomethane. In the composition for forming a lower antireflection film of the present invention, these photoacid generators can be used in combination of two or more.

[solvent]
As the solvent used in the first underlayer film forming composition according to the present invention, any solvent can be selected and used as long as it can dissolve each of the above components. Specific examples of the solvent include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene Glycol propyl ether acetate, toluene, xylene, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, 2-hydroxy-3-methylbutane Acid methyl, methyl 3-methoxypropionate, -Ethyl methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate, methyl pyruvate, ethyl pyruvate, ethyl acetate, butyl acetate, ethyl lactate, butyl lactate, N, N-dimethylformamide, N, N -Dimethylacetamide, N-methylpyrrolidone, etc. can be used. These solvents can be used alone or in combination of two or more. Furthermore, high boiling point solvents such as propylene glycol monobutyl ether and propylene glycol monobutyl ether acetate can be mixed and used.

[Other ingredients]
The composition for forming an underlayer antireflection film according to the present invention can contain other components as required. For example, a surfactant, a smoothing agent and the like can be mentioned. These components should be used without impairing the effects of the present invention.

[First composition for forming an underlayer film]
The first composition for forming an underlayer film according to the present invention is prepared by mixing and uniformly dissolving the above-described components. The amount of each component is not particularly limited, but is appropriately adjusted according to the purpose.

  For example, in the first composition according to the present invention, the content of the crosslinking agent is preferably 5 to 40 parts by weight, more preferably 10 to 30 parts by weight with respect to 100 parts by weight of the total weight of the polymer. .

  The total content of the polymer is preferably 1 to 10% by weight, preferably 1 to 3% by weight, based on the total weight of the composition.

  Furthermore, the content of the photoacid generator is preferably 0.01 to 20 parts by weight, and more preferably 0.02 to 5 parts by weight with respect to 100 parts by weight of the polymer. By adding a photoacid generator, it is possible to control the shape of the photoresist. The reason is not completely elucidated, but this is thought to be because the acidity of the lower layer film is adjusted by the addition of the photoacid generator. That is, by adding a photoacid generator, a more preferable rectangular photoresist pattern can be formed.

  The underlayer film composition obtained by mixing each component is preferably used after being filtered using a filter having a pore size of about 0.2 to 0.05 μm. The underlayer resin composition thus prepared is excellent in long-term storage stability at room temperature.

<Second composition for forming the lower layer film>
The second composition for forming an underlayer film according to the present invention is characterized in that, instead of the cyano group-containing polymer and the crosslinking agent, the first composition contains a polymer containing a cyano group and a crosslinking group. In other words, it can be said that the crosslinking agent in the first composition is embedded in the cyano group-containing polymer.

  Accordingly, the polymer used in the second composition according to the present invention comprises the same repeating unit as the polymer used in the first composition and the repeating unit containing a crosslinking group. Here, the repeating unit containing a crosslinking group may be any as long as it contains the structure of the crosslinking agent described in the section of the first composition as it is, but it must function as a crosslinking group. That is, when the polymer includes the above-described structure of the crosslinking agent, at least one crosslinkable functional group needs to be included in an unreacted state.

（式中、
Ｘはハロゲン原子であり、
Ｒは、それぞれ独立に水素、メチル基、エチル基、ｎ−プロピル基およびｉ−プロピル基からなる群から選ばれる基であり
ｎは１〜５の数である） For this reason, it is preferable that a crosslinking group originates in a crosslinking agent with higher functionality. Specifically, among the aforementioned crosslinking agents, 1,3,4,6-tetrakis (methoxymethyl) glycoluril having four functional groups, 4,5-dimethoxy-1,3-bis (methoxyethyl) imidazolidine Polymers having repeating units derived from 2-one, 1,1,3,3-tetramethoxymethylurea and the like are preferred. Examples of the polymer having such a cyano group and a crosslinking group include those represented by the following formula.

(Where
X is a halogen atom,
R is independently a group selected from the group consisting of hydrogen, methyl group, ethyl group, n-propyl group and i-propyl group, and n is a number from 1 to 5)

Of these, the polymer represented by the following formula is particularly preferred.

  Even if the cyano group-containing polymer has a crosslinking group, the molecular weight is not particularly limited. However, the weight average molecular weight of the polymer is preferably in the range of 1,000 to 30,000 daltons as measured by gel permeation chromatography (GPC) using polystyrene as a standard. In consideration of film formability, solubility, and thermal stability, those of 1,500 to 20,000 daltons are more preferable.

  In the second composition according to the present invention, the same additives as those in the first composition can be used for the components other than the specific polymer and the crosslinking agent, and the blending amounts are also the same. The second composition according to the present invention may contain a cyano group described in the first underlayer film-forming composition and a polymer not containing a crosslinking group or a crosslinking agent, if necessary. Good.

<Method for Forming Lower Layer Film and Method for Forming Pattern>
The underlayer film forming method and pattern forming method according to the present invention will be described as follows.

  A composition for forming an underlayer film according to the present invention on a semiconductor substrate (for example, a silicon / silicon dioxide coated substrate, a silicon nitride substrate, a silicon wafer substrate, a glass substrate and an ITO substrate) by an appropriate coating method such as a spinner or a coater. Apply. After coating, the lower layer film is formed by further baking. As the conditions for firing, the firing temperature is generally appropriately selected from the range of 80 ° C. to 250 ° C., preferably 100 ° C. to 250 ° C., and the firing time is generally 0.3 to 5 minutes, preferably 0.5 to 2 minutes. The By this firing, a curing reaction proceeds in the lower film layer to form a lower film.

  For example, a positive photoresist composition is applied on the lower layer film thus formed. Here, the positive type photoresist means a substance that reacts when irradiated with light and has increased solubility in a developer. The photoresist used is not particularly limited, such as a positive photoresist, a negative photoresist, and a negative tone development (NTD) photoresist that are sensitive to light used for exposure for pattern formation. it can.

  Next, exposure is performed through a predetermined mask. Although the wavelength of the light used for exposure is not specifically limited, It is preferable to expose with the light whose wavelength is 13.5-248 nm. Specifically, a KrF excimer laser (wavelength 248 nm), an ArF excimer laser (wavelength 193 nm), extreme ultraviolet light (wavelength 13.5 nm), or the like can be used, and exposure with extreme ultraviolet light is particularly preferable.

In general, in the case of pattern formation using extreme ultraviolet rays, the amount of acid generated is reduced because the photoacid generator has a low absorbance for extreme ultraviolet rays. For this reason, in order to effectively use the optical energy of extreme ultraviolet rays, a material that easily generates secondary electrons is used, secondary electrons are generated by absorption of extreme ultraviolet rays, and the secondary electrons generate photoelectron generators. Increasing the amount of acid generated is being studied. For this reason, conventionally, polymers in which an aromatic ring or a halogen atom is introduced into the polymer have been studied. Compared to such a conventionally used polymer, the composition according to the present invention can be further improved by using a cyano group-containing polymer.
The reason why an excellent resist pattern can be formed by the composition according to the present invention is presumed as follows.

  The light emitted from the currently used extreme ultraviolet exposure machine is often insufficient in terms of intensity. If the light intensity is insufficient at the time of exposure, many secondary electrons are generated above the exposed resist layer, and as a result, more acid is released from the photoacid generator. However, sufficient light does not reach the lower part of the resist layer, and the amount of acid released is small. As a result, the cross-sectional shape of the pattern has a footing shape with a skirt. However, the lower layer film formed by the composition according to the present invention has a dielectric constant improved by a cyano group and more secondary electrons exist, so even if the light intensity is the same, it is lower than that of a conventional lower layer film. More secondary electrons are present, and more acid is generated. As a result, it is considered that the bottom of the pattern hardly remains, and as a result, a rectangular shape is achieved. Therefore, the composition according to the present invention is preferably used when a pattern is formed by exposure to extreme ultraviolet rays.

  After exposure, post-exposure bake can be performed as necessary. The post-exposure heating temperature is appropriately selected from 80 ° C. to 150 ° C. and the baking time is appropriately selected from 0.3 to 5 minutes. Preferably they are 100 to 140 degreeC and 0.5 to 2 minutes.

  Next, development is performed with a developer. As a result, the exposed positive photoresist layer is removed by development, and a photoresist pattern is formed.

  Developers used for development in the above pattern formation method include aqueous solutions of alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, tetrahydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide and choline. Examples include aqueous solutions of quaternary ammonium and alkaline aqueous solutions such as aqueous amine solutions such as ethanolamine, propylamine, and ethylenediamine. In particular, a 2.38 wt% TMAH aqueous solution that is widely used as a developing solution can be used. By using such a developing solution, the lower layer film can be easily dissolved and removed at room temperature. Further, a surfactant or the like can be added to these developers.

  The temperature of the developer is generally 5 ° C. to 50 ° C., preferably 25 to 40 ° C., and the development time is generally appropriately selected from 10 to 300 seconds, preferably 30 to 60 seconds.

  The following examples serve to illustrate the present invention more specifically. The present invention is not limited to these examples.

[Synthesis of Polymer P1]
3-Iodophenol (1.0 part) and 4-bromobutanenitrile (1.2 parts) under a nitrogen atmosphere using a reactor equipped with a stirrer, condenser, heating device, nitrogen inlet tube and temperature controller And potassium carbonate (3.0 parts) and acetone (7.6 parts) were added and stirred. The reaction mixture was held at 50 degrees for 18 hours. After cooling the reaction mixture to room temperature, methyl-tert-butyl ether (hereinafter sometimes referred to as MTBE) (30000 parts) and pure water (30000 parts) were added to extract the MTBE solution. Next, magnesium sulfate (200 parts) was added to the MTBE solution and stirred. Thereafter, filtration was performed to remove magnesium sulfate, and the MTBE solution was concentrated by distillation under reduced pressure. The obtained reaction mixture was purified by column chromatography (methylene chloride), whereby monomer M1 was obtained in a yield of 52%.

  1,3,4,6-tetrakis (methoxymethyl) glycoluril (1.94 parts) (formula) under a nitrogen atmosphere in a reactor equipped with a stirrer, a condenser, a heating device, a nitrogen introduction tube and a temperature control device MX-270 (trade name), monomer M1 (1.00 parts), p-toluenesulfonic acid monohydrate (0.035 parts), and propylene glycol monomethyl ether acetate (5.33 parts, manufactured by Sanwa Chemical Co., Ltd.) ) And THF (12.43 parts) were added and stirred. The reaction mixture was held at 80 degrees for 8 hours. The reaction mixture was added with triethylamine (0.35 parts) to stop the reaction, cooled to room temperature, and slowly added to vigorously stirred pure water (30000 parts) to precipitate a polymer. The polymer was filtered and then dried under reduced pressure at 50 ° C. to obtain the target polymer P1 in a yield of 34%. The obtained polymer P1 had Mw = 1460 and PDI = 1.90. The relative dielectric constant is measured by forming a polymer film with a thickness of 20 nm on a silicon wafer using a spin coater (Mark-8 (trade name), manufactured by Tokyo Electron Ltd.), and a non-contact CV measuring device (FAaSt, Semilab). The relative dielectric constant (k value) was measured at 5 points in the diameter direction using SDI), and the average value was obtained.

[Synthesis of Polymer R1]
For the synthesis method of polymer P1, polymer R1 was obtained in the same manner except that 4-bromobutanenitrile was not used. The obtained polymer P1 had Mw = 1,040, PDI = 1.60, and dielectric constant = 5.38. Moreover, it was 33.26 when the dielectric constant of the film formed from the polymer P1 was measured.

[Synthesis of Polymer P2]
3-acryloyloxypropionitrile (1.00 part) (manufactured by Tokyo Chemical Industry Co., Ltd.) and acrylic under nitrogen atmosphere in a reactor equipped with a stirrer, condenser, heating device, nitrogen inlet tube and temperature control device Ethyl acid (0.33 parts) (manufactured by Tokyo Chemical Industry Co., Ltd.), hydroxypropyl methacrylate (0.33 parts) (manufactured by Tokyo Chemical Industry Co., Ltd.) and 2,2′-azobis (methyl isobutyrate) (0. 085 parts) (Wako Pure Chemical Industries, Ltd.) and dipropylene glycol monomethyl ether (6.14 parts) were added and stirred. The reaction mixture was held at 85 degrees for 5 hours. After cooling to room temperature, it was slowly added to pure water (30000 parts) that was vigorously stirred to precipitate the polymer. The polymer was filtered and then dried under reduced pressure at 50 ° C. to obtain the target polymer P2 in a yield of 64%. The obtained polymer P2 had Mw = 29,498, PDI = 4.08, and dielectric constant = 39.18.

[Synthesis of Polymer R2]
For the synthesis method of polymer P2, polymer R2 was obtained in the same manner except that 3-acryloyloxypropionitrile was not used. The obtained polymer R2 had Mw = 21,515, PDI = 3.46, and dielectric constant = 29.55.

[Examples 1-7 and Comparative Examples 1-2]
The polymer and the crosslinking agent were blended in the proportions shown in Table 1 to obtain a polymer mixture. As the crosslinking agent, 1,3,4,6-tetrakis (methoxymethyl) glycoluril (manufactured by Sanwa Chemical Co., Ltd., MX-270 (trade name)) was used. To this mixture (1.00 parts by weight), 4-n-dodecylbenzenesulfonic acid triethylamine salt as the thermal acid generator 1, nonafluoro-1-butanesulfonic acid triethylamine salt as the thermal acid generator 2, and triethylamine as the photoacid generator. Phenylsulfonium salt (hereinafter referred to as TPS) and propylene glycol monomethyl ether acetate as a solvent were mixed and stirred at room temperature for 30 minutes to prepare the underlayer film forming composition of each example. The thermal acid generator 1, thermal acid generator 2, and photoacid generator were 0.01 parts by weight, 0.005 parts by weight, and 0.02 parts by weight, respectively, based on the solid content weight in the composition. . The concentration of the composition was such that the total solid content was 0.5% by weight based on the total weight of the composition.
The prepared composition was applied onto a silicon microchip wafer by spin coating, and heated on a vacuum hot plate at 200 ° C. for 60 seconds to cause a crosslinking reaction to obtain an underlayer film.

[EUV exposure test]
A resist underlayer film was formed by spin-coating the underlayer film forming composition solution of each example on a silicon wafer and heating at 200 ° C. for 1 minute. The resist underlayer film is spin-coated with an EUV resist solution (polyhydroxystyrene), heated, and exposed using an EUV exposure apparatus (Albany MET) under the conditions of NA = 0.36 and σ = 0.93. did. After the exposure, the film was heated after the exposure, cooled to room temperature on the cooling plate, developed and rinsed, and a resist pattern was formed on the silicon wafer. Sensitivity and critical dimension uniformity (CDU) were evaluated.

[Evaluation of pattern cross-sectional shape]
The cross section of each resist underlayer film was observed with an electron microscope and evaluated according to the following criteria.
A: Rectangular shape with the photoresist side face perpendicular to the substrate surface B: The photoresist side face is not perpendicular to the substrate surface and is slightly inclined but has no practical problem Level C: The photoresist side face is on the substrate surface For footing shape

[Evaluation of critical dimension uniformity (CDU) (unit: nm):]
When observing a 30 nm one-to-one contact hole resolved at the optimum exposure amount from the top of the pattern, measure the pattern width at 100 points at any point and make the 3 sigma value (variation) of the measured value uniform to the critical dimension. Sex (CDU).

[Evaluation of sensitivity (unit: mJ / cm ² ):]
The exposure amount (mJ / cm ² ) formed in a one-to-one contact hole with a width of 30 nm through a mask of a one-to-one contact hole with a dimension of 30 nm is defined as the optimum exposure amount. cm ² ) was defined as “sensitivity”.

Solvent resistance evaluation:
A film thickness reduction test of the lower layer film was performed with ethyl lactate (hereinafter referred to as EL), propylene glycol monomethyl ether acetate (hereinafter referred to as PGMEA), and propylene glycol monomethyl ether (hereinafter referred to as PGME). The evaluation criteria were as follows.
A: The lower layer film is practically excellent because it is insoluble in any of EL, PGMEA, and PGM. B: Although the lower layer film is slightly dissolved in either EL, PGMEA, or PGME, Level C with no problem in practical use: Level in which the lower layer film is dissolved in any or all of EL, PGMEA, and PGME and has no practicality

The obtained results were as shown in Table 1.

Claims (10)

  A composition for forming an underlayer film comprising a cyano group-containing polymer, a crosslinking agent, an acid generator, and a solvent. The cyano group-containing polymer has the following formulas (1a) to (1c):

(Where
R ^a and R ^c are each independently a group selected from the group consisting of hydrogen and an alkyl group;
L ^a , L ^b , L ^c1 and L ^c2 are each independently a single bond or an aliphatic hydrocarbon chain, and the aliphatic hydrocarbon chain has an ether bond, a thioether bond, an amide bond, or a carbonyl at the terminal or in the middle. Ar ^b and Ar ^c each independently represent an aromatic skeleton containing one or more benzene rings, and the aromatic group is an alkyl, halogen atom, alkoxy, alkyl Optionally substituted with a substituent selected from the group consisting of sulfanyl, carboxylic acid ester, and cyano,
p2 and p3 are 1 or 2. )
The composition of Claim 1 which contains any repeating unit of these. The repeating unit is the following (1a-1) or (1b-1):

The composition of Claim 2 which is represented by these.   A composition for forming an underlayer film comprising a polymer having a cyano group and a crosslinking group, an acid generator, and a solvent. The polymer having a cyano group and a crosslinking group is represented by the following formula:

(Where
X is a halogen atom,
n is a number from 1 to 5)
The composition of Claim 4 represented by these.   The composition of any one of Claims 1-5 whose weight of the cyano group with respect to the total weight of a polymer is 8% or more and 50% or less.   An underlayer film obtained by applying the composition for forming an underlayer film according to any one of claims 1 to 6 on a substrate and heating the composition. Applying the composition for forming an underlayer film according to any one of claims 1 to 6 on a semiconductor substrate and baking to form an underlayer film;
Forming a photoresist layer on the lower layer film;
A pattern forming method comprising the steps of: exposing the semiconductor substrate covered with the lower layer film and the photoresist layer; and developing with a developer after the exposure.   The pattern formation method according to claim 7, wherein the exposure is performed with light having a wavelength of 13.5 to 248 nm. Following formula:

(Where
X is a halogen atom,
n is a number from 1 to 5)
A compound represented by the formula: